File:Submarine Air Quality Monitoring 1988.pdf

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~ j• r .... ~ :a,.. -. .. t .;" .. """ Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 44 leader. or supervisory personnel, the direct reading device is used to determine exact concentrations. This ability to quickly determine the nature and extent of a toxic gas release helps avoid unnecessary disruption of plant operations." Many small hand-held, battery-operated instruments are available, reliable, and accurate. They are capable of giving a continuous readout when needed. Such devices would be superior to detector tubes as a CAMS backup. Alternative portable, battery-operated instruments of reasonable reliability and accuracy are described (ACGIH, 1983). Some. such as the Bacharach H~ detector. are diffusion instruments that do not require a pump. Others, such as the Ecolyser CO instrument. operate on the electrochemical oxidation principle and require a battery-operated pump. Small hand-held instruments that measure oxygen and combustible vapors are available from a number of manufacturers. ACGIH has listed and described all portable, battery-operated. direct-reading instruments for airborne gases and vapors. Improved protocols for the use of detector tubes on submarines should be prepared for the guidance of users, and improved instructions should be issued, to assist in interpreting the implications of detector-tube readings for human health effects. Special attention needs to be given to the quality-assurance aspects of detector-tube freshness. reading correctness. storage. and use conditions. When available and as soon as possible. more accurate and more reliable instruments should be substituted for detector tubes for performing routine measurements, and simple methods for checking zero and span readings should be built into each newly adopted instrument. In the long term, the air monitors of choice might be yet-to-be-developed biosensors. The Navy should follow future developments in this field. METHODS FOR MEASUREMENT OF DIVER'S AIR Submarine air from the air banks that is used to prepare diver's air is monitored for hydrazine, CO • CO. FC-12. FC-114, total hydrocarbons. and other compounds before use by divers in accordance with procedures outlined in Chapter 3. The current method for monitoring CO2 for diver's air involves the periodic use of Submarine Air . Qualily CAMS-I. The CO2 concentration that is safe for diver's air is lower than the safe concentration on the submarine at I AT A. and the reading on the CAMS-I for CO for diver's air is close to the detection limit of the CAMS-I. The ability to monitor CO2 continuously for diver's air is necessary. To ensure greater precision, the measurements should be midrange. 0.01- 2.0% (not at the detection limit of the instrument). APPLICATION OF MONITORING PROCEDURES The ultimate effectiveness of monitoring on the submarine is tied to the training of personnel. the careful execution of established procedures. and good judgment. The Panel observed that training in the use and function of the monitoring and control equipment is concentrated at the enlisted level. The responsibility for operating the equipment is distributed among several persons. The Panel recommends that methods of instruction of personnel be reviewed and updated. The Panel also recommends that the command level be given additional specific training in physiology and in the operation of the air monitoring and control equipment. The Submarine Atmosphere Control Manual (U.S. Naval Sea Systems command, 1979) does not contain detailed instruction on the use of the monitoring equipment immediately after an emergency. particularly as to which gas readings are most important to monitor. The Panel recommends that methods for determining the safe conclusion of an emergency situation be established in terms of instrumentation and setting of all-clear standards (e.g .• the concentrations of HCN, HCI, CO, and NO• after a fire might be used as indexes of air punty). The Submarine Atmosphere Control Manual does not contain information on the probable consequences of exceeding the guidelines, for various extents of excess exposure, or on the actions that should be taken for various exposures. The Panel recommends that the Submarine Atmosphere Control Manual be revised to contain usable toxicologic information on the consequences of exceeding recommended concentration limits. Three levels of air control needs were recognized by the Panel: Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/Measurement of Air Quality • Category I substances (0 2, CO2, and CO) should be monitored continuously. • Category Ila substances (NO , HF, HCI, Cl2, NH3, HCN, 0 3, H2, FC-12, Ft-114, acrolern, tobacco-smoke constituents, total aromatics, and total aliphatics) should be monitored routinely. These are normal-release substances, in contrast with category Db substances (fire products, spill products, monoethanola45 mine, and total hydrocarbons), which might result Crom abnormal release. Category Ilb substances should be monitored according to need. • Category III substances (toxic or possibly toxic substances) should be measured at set intervals, until a sufficient data base exists to determine the appropriate Crequency and substances for monitoring. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. CHAPTERS CONCLUSIONS AND RECOMMENDATIONS ATMOSPHERIC SURVEY AND CONTROL 1. Results of full analysis of the submarine atmosphere were not available to the Panel, and apparently no such analysis has been done in recent years. Therefore, the Panel was limited in its ability to answer fully the questions put to it. Without such information, detailed conclusions and recommendations that reflect the current environment cannot be offered. The Panel recommends that the Navy thoroughly survey various classes of submarines for trace contaminants and particulate matter. Carefully controlled sampling procedures should be established to collect samples quantitatively with such sorbents as Tenex and have them analyzed in on-shore laboratories. Other techniques should be used for inorganic and small organic substances. Compounds of concern that have been detected or are suspected, but for which no concentrations are available, should be measured. 2. Studies have shown that cigarette smoking accounts for large amounts of particulate matter, CO, and some of the hydrocarbons in the submarine atmosphere. The health hazard of sidestream smoke and other problems associated with passive smoking have been discussed in recent National Research Council reports. Elimination of smoking would have a great impact on air quality in submarines under normal oper47 ations. Contaminants introduced by smoking decrease performance efficiency and increase the load on air control equipment; a result is an additional service rate for air monitoring and other equipment. (Smoking is prohibited on French submarines.) The Panel recommends that smoking be eliminated to improve air quality under normal operations. 3. The minute-by-minute status of the performance of the air control equipment is not known. Failures of the control equipment are detected by measuring an increase in the average concentration of a gas in the atmosphere. Air monitoring can provide a late indication of an equipment failure, because of the large volume of submarine air. The air entering and leaving the control equipment is not monitored routinely on submarines (it is done with jumper hoses and only for trouble-shooting). The Panel recommends that the number of air sampling ports going to the CAMS-I be increased to provide continuous information on the performance of the air control equipment. 4. Two-stage electrostatic precipitators are installed in the ventilation equipment. It was not clear to the Panel whether the electrostatic precipitators have adequate efficiency, whether the airflow through them is sufficient, and whether they are maintained adequately. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 48 The Panel recommends that the effectiveness of the electrostatic precipitator system be addressed. S. Nontoxic paints have been the subject of research for a number of years, but the Panel is not aware that any have been adopted for use on the submarine. The Panel recommends that nontoxic paints be developed and used on board submarines with due consideration for the potential for biologic growth on such painted surfaces. INSTRUMENTS FOR MONITORING 6. A consensus method of satisfactorily monitoring hydrocarbons has not been established. New methods for monitoring hydrocarbons have been suggested, but no consensus method has been established. Also, new monitors might be required after further identification of additional specific contaminants in the submarine atmosphere. The CAMS-II will be used to monitor aliphatic and aromatic hydrocarbons as a group. The Panel recommends that the Navy develop a stable photoionization instrument that is capable of continuous monitoring and can be moved about to establish the source of a leak. 7. Adequate monitoring equipment is not available for the analysis of many trace contaminants, especially inorganic substances. Many compounds with DDS limits cannot be monitored with the CAMS-I or CAMS-II. Detector tubes are not suitable for real-time at-sea monitoring. The Panel recommends that monitors be used in place of detector tubes for the analysis of specific trace contaminants, such as oxides of nitrogen, hydrogen chloride, sulfur dioxide, and ozone. Additional monitoring equipment is needed for acrolein, mercury, and lithium salts. 8. The Panel concludes that current practice for monitoring submarine air quality is incomplete in that contaminant concentrations of physiologic importance might be outside the capability of the equipment. CAMS-II is not Submari11e Air Quality more effective than CAMS-I for the currently monitored substances at low concentrations, because the lower limit of detection of the two instruments is the same. CAMS-II can detect more substances than CAMS-I, but does not add capability for trace contaminants, in that most information on additional substances will be collected on tape (no direct readout) and accessible only to personnel on shore. The Panel recommends that monitors be developed to detect lower concentrations of gases that pose a hazard at very low concentrations (possibly Fourier-tranf orm infrared spectroscopy [FTIR] or other instrumentation that meets performance specifications). Additional instrumentation should be used to identify various contaminant sources (e.g., nonspecific portable photoionization detectors to replace detector tubes, and a portable fluorocarbon monitor in place of current industrial leak detector). 9. Direct air sampling of submarines is needed to identify previously unrecognized contaminants that might pose health problems. The current method of analyzing spent charcoal filters provides only qualitative, not quantitative, information. The Panel recommends that evacuated canisters and organic sorbent traps, such as Tenex, be used to make quantitative measurements of air contaminants in nuclear submarines routinely. A plan should be put in place to look periodically at the archived data from the CAMS-II. 10. Airborne particulate matter is not monitored, and it is not possible to ensure that filtration is adequate. The Panel recommends that equipment be provided to measure particulate matter on submarines in real time and periodically by detailed shore-based methods. 11. Oxygen is routinely monitored with the CAMS-I. The instrument to back up the CAMS-I for monitoring 0 2 is the Beckman D2, which lacks sensitivity. The Panel recommends that the Navy develop alternative monitoring instruments Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/Conclusions and Recommendations that have greater sensitivity and reliability than the Beckman D-2. DIVER'S AIR 12. Diver's air passes through a LiOH scrubber and an 18-µm filter. There is no method for monitoring particulate matter. The Panel is concerned that diver's air is not filtered adequately to remove respirable particulate matter (<10 µm). The Panel recommends that the Navy ensure that diver's air is filtered adequately to remove respirable particulate matter and that limits for total particulate matter be established for diver's air on submarines. The S mg/m3 limit should be adhered to until new studies suggest otherwise. 13. The current method for monitoring diver's air for CO..2.. involves the periodic use of the CAMS-I. The level of CO2 concentration that is safe for diver's air is lower than the concentration that is safe on the submarine at I AT A, and the CO2 reading on the CAMS-I for diver's air is close to the detection limit of the CAMS1. The Panel recommends that capability be developed for continuously monitoring diver's air for CO2 more precisely to ensure the quality of diver's air. The measurements should be midrange (0.01-2.0% ), so that concentrations well below the safe concentrations are detectable. INFORMATION, TRAINING, AND RESEARCH NEEDS 14. The Panel notes that categories of atmospheric gases can be established according to hazard potential. The Panel recommends the following air monitoring categories: •Category I substances (0 2, CO2, and CO), for which continuous monitoring is essential for life support. •Category Ila substances (NO , HF, HC I, Cl 2, NH3, HCN, 0 3, H2, FC-12, if=-114, acrolein, tobacco-smoke constituents, total aromat49 ics, and total aliphatics), which are commonly or occasionally released and should be monitored routinely, in contrast with category Jib substances (fire products, spill products, monoethanolamine, and total hydrocarbons), which might result from abnormal release and should be monitored according to needs. • Category Ill substances (toxic or possibly toxic substances), which should be measured at set intervals, until a sufficient data base exists to determine the appropriate frequency and substances for monitoring. IS. The deep-fat fryer used for food preparation on submarines is a source of atmospheric contaminants with possible health consequences. The deep-fat fryer adds to the burden on the atmosphere control equipment and is a fire hazard. The Panel recommends that the Navy evaluate the impact of the deep-fat fryer in the submarine atmosphere and consider eliminating it from submarines if necessary in order to eliminate this source of atmospheric contaminants. 16. The current Submarine Atmosphere Control Manual does not contain information on the probable consequences of exceeding the guidelines for various extents of excess exposure or on the action that should be taken in the event of various exposures. The Panel recommends that the Submarine Atmosphere Control Manual contain usable toxicologic information on the consequences of exceeding recommended exposure concentration limits. 17. The NRC Committee on Toxicology (COT) has been updating exposure guidance levels for atmospheric contaminants since 1984. The values reported are emergency exposure guidance levels (EEGLs) for 1- and 24-hour exposures and continuous exposure guidance levels (CEGLs) for 90-day (24-hour/day) exposures. The Panel recommends that current COT EEGLs and CEGLs be cited in the Submarine Atmosphere Control Manual. 18. The Panel concludes that information on the concentration of contaminants in submarine air is incomplete. The Navy conducts tests on Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 50 the air-pollution consequences of materials that might be used on the submarine and catalogs the resulting information according to whether the materials are permitted, restricted, etc. This procedure is time-consuming and has not kept up with all new products as soon as they are introduced. The Panel recommends that work on the screening of materials be continued and that the permitted-substance list for products that can be used without restrictions be expanded and kept current. Emissions under both use and storage conditions should be considered. 19. Current guidance for the use of detector tubes is incomplete. For example, instructions contained in the Submarine Atmosphere Control Manual on detector tubes are not sufficiently quantitative (e.g. "store in a cool, dry location"). Also, the quality assurance of detector tubes is provided currently by the manufacturer with no agency oversight. The Panel considers detector tubes to be less reliable than stated in the Submarine Atmosphere Control Manual(± SO% vs± 30%). The Panel recommends that improved protocols for the use of detector tubes on submarines be prepared for the guidance of users and that improved instructions be issued to assist in interpreting the implications of detector-tube readings for human health effects . Special attention needs to be given to quality assurance, with regard to detector-tube freshness, reading correctness, and storage and use conditions. High priority should be given to substitution of more accurate and more reliable instruments to replace detector tubes for routine measurements . Simple methods are needed for calibration . Span readings should be built into each instrument. 20. Carbon canisters are used to collect and store hydrocarbons from the submarine atmosphere as part of the atmosphere control system. The retention of hydrocarbons on carbon depends on temperature, pressure, and competition for adsorption sites on the surface of the charcoal. Changes in the pressure and adsorption of more strongly held compounds could result in the release of previously stored hydrocarbons to the atmosphere. Submarine Air Quality The Panel recommends that retention of hydrocarbons on carbon be investigated, to provide information on adsorption and release of toxic contaminants in a broad range of conditions . The arrangement of the carbon in the bed should be examined and optimized, to decrease breakthrough. Methods for regenerating the beds might be explored for emergency use. 21. Removal of hydrocarbons from the submarine atmosphere by carbon beds is incomplete, and operation of the CO-H 2 burner at temperatures high enough to oxidize additional hydrocarbons is undesirable, because of the simultaneous conversion of fluorocarbons (FCs) to acid gases. The Panel recommends that the Navy undertake research on the selective removal of contaminants with techniques other than the use of carbon beds and the CO- !"1.2 burner, including gas separation. Methods for improving efficiency of carbon beds might also be investigated. 22. The Panel observes that training in the use and function of the monitoring and control equipment is concentrated at the enlisted level. The responsibility for operating the equipment is distributed among several persons. The Panel recommends that methods of instruction of personnel be reviewed and updated. The Panel also recommends that the command level be given appropriate training in physiology and in the operation of air monitoring and control equipment. 23. The enclosed environment of the submarine constitutes a unique controlled environment for study of toxicologic, physiologic, and epidemiologic relationships involving prolonged exposure of submariners to atmospheric contaminants. The Panel recommends that monitoring on submarines provide complete analysis of submarine air and data on exposure of personnel to contaminants to provide a basis for further retrospective epidemiologic health-effects studies that might be desired. 24. The British Royal Navy has set maximal permissible exposure concentrations and Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/Conclusions and RecommendaJions established a monitoring protocol for many substances for which no limits are set and for which no monitoring is done on U.S. submarines. The Panel recommends that the U.S. Navy explore with the British Royal Navy the reasons for the different strategies and determine whether additional exposure limits and monitoring for additional substances are necessary on U.S. submarines. EMERGENCIES 25. The Submarine Atmosphere Control Manual does not contain detailed instructions on the use of monitoring equipment during and immediately after an emergency and in particular on whether readings of some gases might be more important than readings of others. 51 The Panel recommends that methods be established for determining the safe conclusion of an emergency situation, with respect to instrumentation and setting of all-clear standards (e.g., concentrations of HCN, HCl, CO, and NOx might be used after a fire as indexes of air purity). 26. Emergency situations that release large quantities of contaminants to the submarine atmosphere can place a large burden on the air monitoring and control equipment. The Panel recommends that the Navy consider the design, development, and testing of an air-cleaning scrubber system for use in purifying the air after an emergency. such as a fire. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. REFERENCES Alexander, A. L., and V. R. Piatt, Eds. 1967. The Present Status of Chemical Research in Atmosphere Purification and Control on Nuclear-Powered Submarines: Fifth Annual Progress Report. NRL Report 6491. Washington, D.C.: U.S. Naval Research Laboratory. (ACGllI) American Conference of Governmental Industrial Hygienists. 1983. Air Sampling Instruments for Evaluation of Atmospheric Contaminants, 6th ed. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists. Anderson, W. L. 1961. Aerosols in nuclear submarines, pp. 114-120. In V. R. Piatt and E. A. Ramskill, Eds. 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Emergency and Continuous Exposure Guidance Levels for Selected Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 56 Airborne Contaminants. Vol. 5. Washington, D.C.: National Academy Press. National Research Council, Committee on Passive Smoking. 1986a. Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects. Washington, D.C.: National Academy Press. National Research Council, Committee on Airliner Cabin Air Quality. 1986b. The Airliner Cabin Environment Air Quality and Safety. Washington, D.C.: National Academy Press. National Research Council, Committee on Toxicology. 1986c. Emergency and Continuous Exposure Guidance Levels for Selected Airborne Contaminants. Vol. 6. Benzene and Ethylene Oxide. Washington, D.C.: National Academy Press. National Research Council, Committee on Toxicology. 1987. Emergency and Continuous Exposure Guidance Levels for Selected Airborne Contaminants. Vol. 7. Ammonia, Hydrogen Chloride, Lithium Bromide, and Toluene. Washington, D.C.: National Academy Press. (NIOSH) National Institute for Occupational Safety and Health. 1980. The Certified Equipment List. DHHS (NIOSH). Pub. No. 80-144, U.S. Government Printing Office, Washington, D.C. Ostfeld, A. M., P. A. Charpentier, and 0. Hadjimichael. 1985. Out-of-Service Mortality among Submariners, 1969-82. New Haven, Ct.: Yale University School of Medicine, Department of Epidemiology and Public Health. 171 pp. Paulose M . M., and S. S. Chang. 1978. Chemical Reactions Involved in the Deep-Fat Frying of Foods: VIII. Characterization of Nonvolatile Decomposition Products of Trilinolein. J. Amer. Oil Chem. Soc. 55:375-380. Paulose M. M., and S. · S. Chang . 1973. Chemical Reactions Involved in Deep-Fat Frying of Foods: IV. Characterization of Nonvolatile Decomposition Products of Trilinolein. J. Amer. Oil Chem. Soc. 50:147-154. Submarine Air Quality Piatt, V. R., and J. C. White, Eds. 1962. The Present Status of Chemical Research in Atmosphere Purification and Control on NuclearPowered Submarines: Second Annual Progress Report. NRL Report 5814. Washington, D.C.: U.S. Naval Research Laboratory. Piatt, V. R., and E. A. Ramskill, Eds. 1970. Chemical Research in Nuclear Submarine Atmosphere Purification: Progress Report. NRL Report 7037. Washington, D.C.: U.S. Naval Research Laboratory. Piatt, V. R., and E. A. Ramskill, Eds. 1961. The Present Status of Chemical Research in Atmosphere Purification and Control on Nuclear-Powered Submarines: Annual Progress Report. NRL Report 5630. Washington, D.C.: U.S. Naval Research Laboratory. Purer, A., G. A. Deason, and R. J. Taylor. 1983. Total Halogenated Hydrocarbons in Divers' Breathing Air. NCSC TR 383-83. Panama City, Fla.: Naval Coastal Systems Center. 19 pp. Reddy, B. R., K. Yasuda, R. G. Krishnamurthy, and S. S. Chang. 1968. Chemical Reactions Involved in the Deep-Fat Frying of Foods: V. Identification of Nonacidic Volatile Decomposition Products of Hydrogenated Cottonseed Oil. J. Amer. Oil Chem. Soc. 45:629-631. Rossier, R. N. 1984. Trident Atmosphere Control Sea Trial Final Report. Contract No. N000- 24-73-C-0232. Groton, Conn.: General Dynamics Electric Boat Division. 49 pp. Saalfeld, F. E., F. W. Williams, and R. A. Saunders. 1971. Identification of Trace Contaminants in Enclosed Atmospheres. Am. Lab. (July):8-15. Saalfeld, F. E., and J. R. Wyatt. 1976. NRL's Central Atmosphere Monitor Program. NRL Memorandum Report 3432. Washington, D.C.: U.S. Naval Research Laboratory . Saunders, R. A., and F. E. Saalfeld. 1965. Improved Methods for the Detailed Analysis of Trace Contaminants in Submarine Atmosphere. In L. B. Lockhart, Jr., and V. R. Piatt, Eds. The Present Status of Chemical Research in Atmosphere Purification and Control on Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ References Nuclear-Powered Submarines: Fourth Annual Progress Report. NRL Report 6251. Washington, D.C.: U.S. Naval Research Laboratory. Shibamoto, T., and G. F. Rusell. 1976. Study of Meat Volatiles Associated With Aroma Generated in a d-Glucose-Hydrogen SulfideAmmonia Model System. J. Agric. Food Chem. 24:843-846. Shigematsu, H., T. Kurata, H. Kato, and M. Fujimaki. 1972. Volatile Compounds Formed on Roasting DL-a-Alanine with d-Glucose . Agric . Biol. Chem. 36:1631-1637. Smith, W. D., F. J. Woods, and M. E. Umstead. 1965. Submarine Atmosphere Studies Aboard the USS SCAMP. NRL Report 6312. Washington, D.C.: U.S. Naval Research Laboratory. Spain, D., J. J. DeCorpo, and J. R. Holtzclaw. 1980. Use of a Photoionization Detector as a Hydrocarbon Trace Gas Analyzer. NRL Memorandum Report 4239. Washington, D.C.: U.S. Naval Research Laboratory . Thompson, J. A., W. A. May, M. M. Paulose, R. J. Peterson, and S. S. Chang. 1978. Chemical Reactions Involved in the Deep-Fat Frying of Foods: VII. Identification of Volatile Decomposition Products of Trilinolein . J. Amer. Oil Chem. Soc. 55:897-901. Thompson, G. 1973. Trident Submarine Summary of Shipboard Aerosol Testing for Trident Design . Groton, Ct.: General Dynamics Electric Boat Division. Umstead, M., W. Smith, and J. Johnson. 1964. Submarine Atmosphere Studies Aboard USS SCULPIN. NRL Report 6074. Washington, D.C.: U.S. Naval Research Laboratory. U.S. Naval Sea Systems Command. 1986. Interim Air Purity Guidelines for Dry Deck Shelter (DDS) Operations. Enclosure to letter 10560, Ser 00C3/2101, 16 July, 1986. Washington, D.C. U.S. Naval Sea Systems Command. 1985. U.S. Navy Diving Manual, Vol. 1, Air Diving. Revision 1. Washington, D.C.: U.S. Government Printing Office. 57 U.S. Naval Sea Systems Command. 1979. Submarine Atmosphere Control Manual. NA VSEA S 9510-AB-A TM-010/(C), unclassified section provided to the National Research Council's Committee on Toxicology. USS Cavalla. 1986. Air Sampling Procedures and Results during Diving Operations Aboard USS Cavalla (unpublished report) from Commander, Naval Special Warf are Group 2, Norfolk, Virginia, 17 November, 1986. USS Michigan. 1986. Submarine log. (Unpublished data) USS Daniel Webster. 1986. Submarine log. (Unpublished data) USS Kamehameha. 1975. Analysis of samples. (Unpublished data) Watkins, H. M. S. 1970. Epidemiologic Investigations in Polaris Submarines, pp. 9-53. In I. H. Silver, Ed. Aerobiology: Proceedings of the Third International Symposium on Aerobiology, University of Sussex, England, Sept. 1969. New York: Academic Press. Weathersby, P. K., R. S. Lillo, and E.T. Flynn. 1987. Air Purity in Diving from Submarines. I. Review and Preliminary Analyses. NMRI 87- 62. Bethesda, Md .: U.S. Naval Medical Research Institute. Weathersby, P. K., R. S. Lillo, E. T. Flynn, J. R. Wyatt, and W. D. Dorko. 1986. Trace Chemical Contaminants in a New Human Pressure Chamber. NMRI 86-54. Bethesda, Md.: Naval Medical Research Institute. 17 pp. Wells, W. F. 1955. Airborne Contagion and Air Hygiene; An Ecological Study of Droplet Inf ections. Cambridge, Mass.: Harvard University Press. 423 pp. Williams, F. W., and J. E. Johnson. 1970. Atmospheric Contamination with a Cleaning Solvent, pp. 6-10. In V. R. Piatt and E. A. Ramskill, Eds. Chemical Research in Nuclear Submarine Atmosphere Purification: Progress Report . NRL Report 7037. Washington, D.C.: U.S. Naval Research Laboratory. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 58 Williams, F.W., and J. E. Johnson. 1968. Halogenated Hydrocarbons in the Atmospheres of Submarines in Squadron Fifteen. NRL Report 6708. Washington, D.C.: U.S. Naval Research Laboratory. Wyatt, J. R. 1984. CAMS-II Technical Evaluation Phase-I. NRL Memorandum Report 5309. Washington, D.C.: U.S. Naval Research Laboratory. Submarine Air Quality Yasuda, K., B. R. Reddy, and S. S. Chang. 1968. Chemical Reactions Involved in the Deep-Fat Frying of Foods: IV. Identification of Acidic Volatile Decomposition Products of Hydrogenated Cotton Seed Oil. J. Amer. Oil Chem. Soc. 45:625-628. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. APPENDIX A CONTAMINANTS PRESENT IN AIR Awareness of the possibility that some substances in submarine air have been overlooked as constituting a potential health hazard led to compilation of analytic data from various sources as Table A-1. This information was obtained from reports of substances recorded in submarine logs, of the use of adsorbents in submarines, of air exhaled by submarine personnel, and of accidents. 59 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 60 Substance Acetaldehyde Acetic acid Acetone Acetonitrile Acetylene Aerosolsb Aliphatics C8 Aliphatics C9 Aliphatics C10 Aliphatics C11 Aliphatics c12 Aliphatics C13 Aliphatics straight chain C14 Aliphatics straight chain C15 Aliphatics branched chain ~ 9-C 13 Ammonia Aromatics C9 Aromatics C10 Aromatics C14 (tertiary) Arsine Asbestos Benzene Submarine Air Quality TABLE A-1 Contaminants Potentially Present in Submarine Air Concentration or Partial Pressure• NR NR NR ND NR NR NR NR 57-218 µ.g/m3 0.05-0.2 ppm 0.2 ppm 0.2-0.5 ppm 3.6 ppm 0.2-0.5 ppm 0.7 ppm 0.2-0.5 ppm 0.2-0.5 ppm 0.2-0.5 ppm 0.05-0.2 ppm 0.05-0.2 ppm 0.05-0.2 ppm ND 2 ppm NR NR NR 0.015 ppm < OSHA PEL ND <0.01 ppm ND 0.1 ppm ND NR NR References Saalf eld et al., 1971 Kagarise and Saunders, 1962 Kagarise and Saunders, 1962 USS Cavalla, 1986 Saalf eld et al., 1971 Kagarise and Saunders, 1962 Saalf eld et al., 1971 Kagarise and Saunders, 1962 Rossier, 1984 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 USS Cavalla, 1986 Johnson, 1963 Saalfeld et al., 1971 Saalfeld et al., 1971 Saalf eld et al., 1971 Johnson, 1963 DeCorpo, pers. comm., 1986 Rossier, 1984 Wyatt, pers. comm., 1986 USS Cavalla, 1986 Johnson et al., 1964 Weathersby et al., 1987 Saalf eld et al., 1971 Kagarise and Saunders, 1962 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix A. 61 TABLE A-1 (contd) Concentration or S11bstaoce Partial Pressure• BeCereoces C3-benzene 0.4 ppm Wyatt. pers. comm.. 1986 0.05-0 .2 ppm Wyatt. pers. comm.. 1986 C4-benzene 0.6 ppm Wyatt. pers. comm.. 1986 0.7 ppm Wyatt. pers. comm .• 1986 0.8 ppm Wyatt. pers. comm .• 1986 0.9 ppm Wyatt. pers. comm.. 1986 I.I ppm Wyatt. pers. comm .• 1986 Butane ND Weathersby et al .• 1987 2-Butene (trans) NR Kagarise and Saunders. 1962 2-Butene (cis) NR Kagarise and Saunders, 1962 Butylacetate NR Saalf eld et al .• 1971 Butylalcohol NR Saalfeld et al .• 1971 Butylbenzene NR Saunders and Saalf eld. 1965 Carbon dioxide NR Thompson. 1973 2.1-3.6 Torrb USS Michigan. 1986 2.3-7.1 Torrb USS Daniel Webster. 1986 0.3% USS Cavalla. 1986 <0.01 to 0.59% Weathersby et al .• 1987 0.35% Rossier. 1984 1% Johnson. 1963 NR Kagarise and Saunders. 1962 Carbon disulfide NR Saalfeld et al .• 1971 Carbon monoxide 1-9 milliTorrb USS Michigan, 1986 2-9 milliTorrb USS Daniel Webster. 1986 1-3 ppm Weathersby et al .• 1987 1-5 milliTorrb Rossier, 1984 7 ppm Bondi. 1978 30ppm Johnson. 1963 NR Kagarise and Saunders. 1962 <10 ppm USS Cavalla. 1986 9ppm USS Kamehameha. 1975 Chlorine ND USS Cavalla, 1986 1 ppm Johnson, 1963 Chlorobenzene NR Saalfeld et al .• 1971 Chloroform <0.1 ppm Williams and Johnson. 1968 Cigarette smoke NR Thompson. 1973 Cyclohexane NR Saalf eld et al., 1971 Cyclopentene NR Saalfeld et al .• 1971 n-Decane NR Saunders and Saalf eld. 1965 Dichlorobenzene NR Saalfeld et al.. 1971 Difluorodichloromethane NR Saalf eld et al .• 1971 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 62 Substaoce Difluorochloromethane Dimethylheptane 2,3-Dimethylpentane Dimethyl sulfide Dioxane Dodecane n-Dodecane Ethane Ethylacetate Ethylalcohol Ethylbenzene Ethylene Ethylene glycol Ethyl nitrile Auorocarbon TF Auorocarbon 11 Auorocarbon 12 Auorocarbon 113 Auorocarbon 114 Submarine Air Quality TABLE A-1 (contd) Concentration or Partial Pressure• NR 2ppm 3 ppm NR NR 0.4 ppm NR ND to 0.18 ppm NR NR NR NR NR S ppm NR 0.3 ppm NR NR NR NR NR 0-26,S00 ppm NR ND 5-52 ppm 1-16 milliTorrb 40-100 ppm 8-50 ppm 0.5-12 ppm 26 ppm and 30 ppm 1-8 ppm NR 5-38 milliTorrb 0.2-2.4 ppm <0.1-3 ppm 4 ppm and IO g pm 1-11 milliTorr <0.1 to 14.2 ppm 52 ppm and 60 ppm 1-19 milliTorrb 0-21 milliTorrb NR Kefeceoces Saalfeld et al., 1971 U~ Kamehameha, 1975 U~ Kamehameha, 1975 Saalfeld et al., 1971 Saalf eld et al., I 971 Wyatt, pers. comm., 1986 Kagarise and Saunders, 1962 Weathersby et al., 1987 Kagarise and Saunders, 1962 Kagarise and Saunders, 1962 Saalfeld et al., 1971 Saalfeld et al., 1971 Kagarise and Saunders, 1962 U~ Kamehameha, 1975 Saalfeld et al., 1971 Wyatt, pers. comm., 1986 Johnson et al., 1964 Saalf eld et al., 1971 Kagarise and Saunders, 1962 Saalfeld et al., 1971 Saalfeld et al., 1971 Eaton, 1970 Williams and Johnson, 1968 Weathersby et al., 1987 Williams and Johnson, 1968 U~ Michigan, 1986 Smith et al., 1965 Umstead et al., 1964 Weathersby et al., 1987 U~ Kamehameha, 1975 Rossier, 1984 Kagarise and Saunders, 1962 U~ Daniel Webster, 1986 Williams and Johnson, 1968 Weathersby et al., 1987 U~ Daniel Webster, 1986 U~ Daniel Webster, 1986 Weathersby et al., 1987 U~ Kamehameha, 1975 Rossier, 1984 U~ Michigan, 1986 Kagarise and Saunders, 1962 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix A Substance Fluorocarbon l 14B2 Fluorocarbon 22 Fluorodichloromethane Fluorotrichloromethane Furan n-Heptane n-Hexane Hydrazine Hydrocarbons, total (excluding methane) Hydrogen Hydrogen chloride Hydrogen cyanide Hydrogen fluoride lndene Isobutane Isobutene lsopentane lsoprene lsopropyl alcohol Isopropylbenzene Mercury Methane Methoxy acetic acid Methyl alcohol TABLE A-1 (contd) Concentration or Partial Pressure• <0.1 ppm ND NR NR NR NR ND to 0.13 ppm NR O.S ppm 10-20 ppm lS-49 ppm 0.01 - 0.03% 0.33% (battery room during charge) 0.35% 0.1-3.3 Torrb 0.1-1.0 Torrb ND NR 0.3 ppm NR NR NR NR NR NR NR NR NR NR ND 10-30 ppm S-60 ppm 2-12 ppm NR 2S ppm NR NR 6 ppm NR BeCerences Williams and Johnson, 1968 Weathersby et al., 1987 Saalfeld et al., 1971 Saalfeld et al., 1971 Saalfeld et al., 1971 Kagarise and Saunders, 1962 Weathersby et al., 1987 Saalfeld et al., 1971 U~ Cavalla, 1986 Wyatt, pers. comm., 1986 Rossier, 1984 Rossier, 1984 Rossier, 1984 Johnson, 1963 U~ Michigan, 1986 U~ Daniel Webster, 1986 U~ Cavalla, 1986 Thompson, 1973 Johnson, 1963 Saalfeld et al., 1971 Kagarise and Saunders, 1962 Kagarise and Saunders, 1962 Kagarise and Saunders, 1962 Saalfeld et al., 1971 Kagarise and Saunders, 1962 Saalfeld et al., 1971 Kagarise and Saunders, 1962 Johnson et al., 1964 Kagarise and Saunders, 1962 Rossier, 1984 Smith et al., l 96S Umstead et al., 1964 Weathersby et al., 1987 Kagarise and Saunders, 1962 U~ Kamehameha, 1975 Saalfeld et al., 1971 Saalf eld et al., 1971 Johnson, 1963 Kagarise and Saunders, 1962 63 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Substance Methyl acetate Methyl chloroform Methyl cyclohexane Methyl cyclopentane 2-Methyl-3-heptanol Methyl ethyl benzene Methyl ethyl ketone Methyl isobutyl ketone Monoethanolamine Naphthalene Nitrogen dioxide n-Nonane Octane n-Octane Oil smoke Oxides of nitrogen Oxygen Ozone Pentane n-Pentane Pentylbenzene 1-Pentene Phenol Propane Propylbenzene Propyl nitrite Propylene sec-Butyl alcohol Submarine Air Quality TABLE A-I (contd) Concentration or Partial Pressure• NR 0.9 ppm 4-6 ppm NR ND 6ppm 0.0S-0.2 ppm NR I ppm NR NR NR NR NR <l ppm NR I.S ppm NR 0.8 ppm 0.2 ppm NR NR 0.03S - 0.2 ppm 20% 18.6-20.9% NR Trace 0.003-0.0 IO ppm 0.0S ppm ND to 0.12 ppm NR NR NR NR NR ND to 0.06 ppm NR NR 0.2 ppm NR NR NR References Saalf eld et al., 1971 Wyatt, pers. comm., 1986 Williams and Johnson, 1968 Saalf eld et al., 1971 Weathersby et al., 1987 Johnson, 1963 Wyatt, pers. comm., 1986 Saalf eld et al., 1971 U~ Kamehameha, 197S Johnson et al., 1964 Saalf eld et al., 1971 Kagarise and Saunders, 1962 Saalf eld et al., I 971 Kagarise and Saunders, 1962 Johnson, 1963 Saunders and Saalf eld, 196S U~ Cavalla, 1986 Kagarise and Saunders, 1962 Wyatt, pers. comm., 1986 Wyatt, pers. comm., 1986 Kagarise and Saunders, 1962 Thompson, 1973 Bondi et al., 1983 Johnson, 1963 U~ Daniel Webster, 1986 Thompson, I 973 U~ Cavalla, 1986 Rossier, 1984 Johnson, 1963 Weathersby et al., 1987 Saalfeld et al., 1971 Kagarise and Saunders, 1962 Saunders and Saalf eld, 196S Saalf eld et al., 1971 Saunders and Saalf eld, 196S Weathersby et al., 1987 Kagarise and Saunders, 1962 Kagarise and Saunders, 1962 Wyatt, pers. comm., 1986 Saalf eld et al., 1971 Saalf eld et al., 1971 Saalf eld et al., 1971 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix A Substaoc:e Silicone Sulfur dioxide Stibene Tar-like aerosol Tetrachloroethylene Tetramethylpentane Toluene Trichloroethylene Trifluorotrichloroethane Trimethylbenzene 2,2,3-Trimethylbutane Trimethylfluorosilane Trimethylheptanes Trimethylhexene Undecane Vinylidene chloride Xylene TABLE A-1 (contd) Concentration or Partial Pcessnre• 0.5 ppm 1.1 ppm NR ND NR 0.01 ppm NR NR 0.2-0.4 ppm 2ppm 0.2-0.5 ppm ND ND 1.5 ppm and 10 ppm NR NR NR 0.01-15 .2 ppm 5 ppm and 8 ppm NR NR 5 ppm NR NR 2 ppm 1 ppm 1.0 ppm NR 0.2-0.4 ppm NR 2 ppm 0.7 ppm 0.2-0.5 ppm NR ND 10 ppm NR NR BeCeamces Wyatt, pers. comm.. 1986 Wyatt, pers. comm., 1986 Saalfeld et al .• 1971 USS Cavalla, 1986 Saalfeld et al .• 1971 Johnson, 1963 Thompson, 1973 Saalf eld et al., 1971 Williams and Johnson, 1968 USS Kamehameha, 1975 Wyatt, pers. comm.. 1986 USS Cavalla, 1986 Weathersby et al., 1987 USS Kamehameha, 1975 Saalfeld et al., 1971 Kagarise and Saunders, 1962 Johnson et al., 1964 Williams and Johnson, 1968 USS Kamehameha, 1975 Saalf eld et al., 1971 Saalfeld et al., 1971 USS Kamehameha, 1975 Saalf eld et al., 1971 Saalfeld et al., 1971 USS Kamehameha, 1975 USS Kamehameha, 1975 Wyatt, pers. comm., 1986 Saunders and Saalf eld, 1965 Williams and Johnson, 1968 Saalf eld et al., 1971 Johnson, 1963 Wyatt, pers. comm .• 1986 Wyatt, pers. comm.. 1986 Johnson et al., 1964 Weathersby et al., 1987 USS Kamehameha, 1975 Saalf eld et al., 1971 Kagarise and Saunders, 1962 8NR, chemical cited in reference, but no concentration or pressure given. 65 ND, chemical not detectable . bAerosol concentration cannot be converted to ppm as the molecular weight is unknown; torr and millitorr values were not converted to ppm because variation can be due to fluctuations in total pressure. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. APPENDIXB BRITISH ROYAL NAVY DATA TABLE B-1 Compounds Detected in British Royal Navy Submarines• Aromatic Compounds; 2-Methylfuran (Sylvan) Benzene Thiophene 2-Ethylfuran Toluene Chlorobenzene Ethyl benzene m-,p-Xylene Styrene o-Xylene Isopropylbenzene ( cumene) n-Propylbenzene m-,p-Ethyltoluene 1,3,5-Trimethylbenzene (mesitylene) o-Ethyltoluene 1,2,4-Trimethylbenzene (pseudocumene) tert-Butylbenzene Benzofuran Isobutylbenzene p-Dichlorobenzene sec-Butylbenzene 1,2,3-Trimethylbenzene (hemimellitene) p-Isopropyltoluene (p-cumene) 2,3-Dihydroindene (indan) Indene Diethylbenzene (all 3 isomers) n-Butylbenzene Dimethylethylbenzene (5 of 6 isomers) 2-Phenyl-2-propanol 1,2,4,5-Tetramethylbenzene (durene) 1,2,3,5-Tetramethylbenzene (isodurene) 1,2,3,4-Tetramethylbenzene (prebnitene) l ;2,3,4-Tetrahydronaphthalene (tetralin) Naphthalene Methyltetralin (2 of 4 isomers) Benzothiazole 2-Methylnaphthalene 1-Methylnaphthalene 2-Ethylnaphthalene 1-Ethylnaphthalene 67 Boiling Point, ·c 63 80 84 92-3 110 132 136 138-9 144 146 152 157 161-2 164 165 169 169 174 173 174 173 176 177 178 183 181-4 183 184-8 202 197 198 205 208 216 220-2 231 241 245 258 259 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 68 Aromatic Compounds; Dimethylnaphthalene (5 of 10 isomers) Phenanthrene Aliphatic Hydrocarbons; Methane Ethane 2-Methylbutane (isopentane) n-Pentane 2-Methylpentane 3-Methylpentane n-Hexane Methylcyclopentane Cyclohexane 2-Methylhexane 3-Methylhexane 2,2,4-Trimethylpentane n-Heptane Methylcyclohexane Ethylcyclopentane Dimethylcyclohexane (all 7 isomers) 2-Methylheptane n-Octane Ethylcyclohexane 4-Methyloctane 2-Methyloctane 3-methyloctane n-Nonane lsopropylcyclohexane a-Pinene n-Propylcyclohexane Butylcyclopentane 8-Pinene 5-Methylnonane 4-Methylnonane 2-Methylnonane 3-Methylnonane n-Decane TABLE B-1 (contd) l-Methyl-4-isopropenylcyclohexene (limonene) n-Butylcyclohexane trans-Decahydronaphthalene (trans-decalin) 5-Methyldecane 4-Methyldecane 2-Methyldecane 3-Methyldecane n-Undecane 6-Methylundecane 5-Methylundecane Submarine Air Quality Boiling Point, ·c 263-8 336 Boiling Point, ·c 36 60 63 69 72 80 90 92 99 100 101 103-4 119-130 118 126 130 142 143 143 151 154-5 156 157 165 165 166 167 168 174 178 181 187 189 188 196 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix B TABLE B-1 (contd) Aliphatic Hydrocarbons: 4-Methylundecane 2-Methylundecane 3-Methylundecane n-Dodecane 6-Methyldodecane 5-Methyldodecane 4-Methyldodecane 2-Methyldodecane 3-Methyldodecane n-Tridecane n-Tetradecane n-Pentadecane n-Hexadecane (cetane) n-Heptadecane 2,6,10,14-Tetramethylpentadecane (pristane) n-Octadecane ~.4-Dimethylhexane ~.3-Dimethylhexane ~.4-Dimethylheptane ~.S-Dimethylheptane ~.3-Dimethylheptane ~.6-Dimethyloctane ~-Methyl-3-ethylheptane ~.3- Dimethyloctane ~.6-Dimethylnonane bJ, 7-Dimethylnonane ~-Methyl-6-ethyloctane ~.6-Dimethyldecane ~.6-Dimethylundecane ~.2,6-Trimethyloctane ~.2,6-Trimethyldecane ~.6, 11-Trimethyldodecane ~.2,4,6,6-Pentamethylheptane ~.2,6,6-Tetramethyl-4-ethylheptane Compounds Containing Halogen; 1, 1-Dichloroethylene ( vinylidene chloride) Dichlorodifluoromethane (Freon 12; Halon 12) Fluorotrichloromethane (Freon 11; Halon 11) Bromoethane (ethyl bromide) I, 1,2-Trichlorotrifluoroethane (Freon 113; Halon 113) Dichloromethane (methylene chloride) trans-1,2-Dichloroethylene I, 1-Dichloroethane cis-1,2-Dichloroethylene Chloroform Bromochloromethane Boiling Point, ·c 218 234 2S4 271 287 316 110-11 113 133-4 136 140-1 160-1 165 - 37 - 30 24 38 46 40 47-8 57 60 62 68 69 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 70 TABLE B-1 (contd) Compounds Containing Halogen: I, I, I -Trichloroethane (methylchlorof orm) 1,2-Dichloroethane Tetrachloromethane (carbon tetrachloride) Trichloroethylene 1,2-Dibromoethane (ethylene dibromide) Tetrachloroethylene (perchloroethylene) Chlorobenzene l, I ,2,2-Tetrachloroethane p-Dichlorobenzene Compounds Containing Oxygen: Ethanol Acetone 2-Methyl-2-propanol (tert-butanol) 2-Methylfuran 2-Methyl-1-propanol (isobutanol) 1-Butanol (n-butanol) Ethyl acetate 2-Ethylfuran 2-Ethoxyethanol 4-Methyl-2-pentanone (isobutylmethylketone) lsobutyl acetate n-Butyl acetate Furf ural (furancarboxaldehyde) Cyclohexanol 2-Butanoxyethanol 2-Ethoxyethylacetate Benzofuran 2-Phenyl-2-propanol 4,6,6-Trimethylbicyclo[3,l, l]hept-3-en-2-one Compounds Containing Other Elements: Carbon disulfide Thiophene Dimethyldisulfide Benzothiazole 8Data provided by British Royal Navy. ~ass spectral assignment only; not verified with standard compound . Submarine Air Quality Boiling Point, ·c 72 83-4 76 87 131 121 132 146 174 78-9 S6 82 63 108 117 77 92-3 13S 117 117 126 162 161 174 202 227-9 38 84 110 231 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix B TABLE B-2 Compounds for Which Maximal Permissible Concentrations in British Royal Navy Submarines Are Set• Acetonitrile Acetylene Ammonia Antimony Beryllium Butanolamine Beryllium Cadmium Carbon dioxide Carbon monoxide Chlorine Chromium Cobalt Copper Diethyltriamine (DET A) Ethylbenzene Fluorocarbon-12 Fluorocarbon-114 Fluorocarbon-1301 Hydrazine Hydrogen Hydrogen cyanide Hydrogen fluoride Hydrogen sulfide Iron Lead Manganese Mercury Methane Methyl chloroform Molybdenum Monoethanolamine Nickel 8Data from British Royal Navy. Nitric acid vapor Nitrogen dioxide Otto fuel Oxygen Ozone Phosgene Sulfur dioxide Tin Toluene Total aerosols Total aliphatics Total aromatics Total organics Triaryl phosphate Unsymmetrical dimethyl hydrazine Vanadium Vinyl chloride Xylenes 71 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. APPENDIXC AIR CONTAMINANT SOURCE DATA TABLE C-1 General Physicochemical Characteristics of Cigarette Smoke• Characteristic Peak temperature, •c pH No. particles/ cigarette Particle size, µm Particle mean diameter, µm Total particulate matter, µg/cigarette Gas concentration vol.% co CO2 ~ 2 Mainstream Smoke 900 6.0-6 .2 10.5 X 1012 0.1-1.0 0.4 100-40,000 3-5 8-11 12-16 3-15 8Data from National Research Council, 1986a. 73 Sidestream Smoke 600 6.4-6.6 3.5 X 1012 0.01-0.8 0.32 130-76,000 2-3 4-6 1.5-2 0.8-1.0 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 74 Submarine ..4ir Quality TABLE C-2 Chemicals in Nonfilter-Cigarette Undiluted Mainstream and Diluted Sidestream Smoke• Substance Vapor Phase: Carbon monoxide Carbon dioxide Carbonyl sulfide Benzene Toluene Formaldehyde Acrolein Acetone Pyridine 3-Methylpyridine 3-Vinylpyridine Hydrogen cyanide Hydrazine Ammonia Methylamine Dimethylamine Nitrogen oxides N-Nitrosodimethylamine N-Nitrosodiethylamine N-Nitrosopyrrolidine Formic acid Acetic acid Methyl chloride Particulate Phase: Particulate matter Nicotine Anatabine Phenol Catechol Hydroquinone Aniline Concentration in Mainstream Smoke, ug/cigarette 10,000-23,000 20,000-40,000 18-42 12-48 100-200 70-100 60-100 100-250 16-40 12-36 11-30 400-500 0.032 50-130 11.5-28.7 7.8-10 100-600 0.01-0.04 0-0.025 0.006-0.03 210-490 330-810 150-600 15,000-40,000 1,000-2,500 2-20 60-140 100-360 110-300 0.36 Sidestream-toMainstream Concentration Ratio 2.5-4.7:1 8-11:1 0.03-0.13: 1 5-10:1 5.6-8.3:1 0.1-50:1 8-15:1 2-5:1 6.5-20:1 3-13:1 20-40:1 0.1-0.25:1 3:1 40-170:1 4.2-6.4:1 3.7-5.1:1 4-10:1 20-100:1 <40:1 6-30:1 1.4-1.6:1 1.9-3.6:1 1.7-3.3:1 1.3-1.9:1 2.6-3.3:1 <0.1-0.5:1 1.6-3.0:1 0.6-0.9:1 0.7-0.9:1 30:1 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix C TABLE C-2 (contd) Substance 2-Toluidine 2-Naphthylamine 4-Aminobiphenyl Benz[a]anthracene Benzo[a)pyrene Cholesterol "'(-Butyrolactone Quinoline Hannanb N-Nitrosonornicotine NNKC N-Nitrosodiethanolamine Cadmium Nickel Zinc Polonium-210 Benzoic acid Lactic acid Glycolic acid Succinic acid Concentration in Mainstream Smoke, us/cigarette 0.16 0.0017 0.0046 0.02-0.07 0.02-0.04 22 10-22 O.S-2 1.7-3.1 0.2-3 0.1-1 0.02-0.07 0.1 0.02-0.08 0.06 0.04-0.l pCi 14-28 63-174 37-126 ll0-140 Sidestream-toMainstream Concentration Ratio 19:l 30:l 31:l 2-4:l 2.5-3.5:l 0.9:l 3.6-5.0:l 8-11:l 0.7-1.7:l 0.5-3:l 1-4:l 1-2:l 7.2:l 13-30:l 6.7:l 1-4:l 0.67-0.95:l 0.5-0.7:l 0.6-0.95:1 0.43-0.62: l 1From National Research Council (1986a). bl-methyl 9H-pyrido [3,4-b]indole. c4-(N-methyl-N-nitrosoamino)-l-(3-pyridal)-l-butanone. 75 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 76 Submarine ..4ir Quality TABLE C-3 Chemicals in Undiluted Mainstream Smoke from High-, Medium-, and Low-Tar Nonfilter Cigarettes• Concentration, Concentration, Substance ug/cigareue Substance us /cigarette Methyl butene 0.2-14 2,3-Dimethyl-l-butene 0.08 Acetaldehyde + isoprene 1.5-107 3,3-Dimethyl-1-butene Cyclopentene 0.08-6 cis-2-Butene 29 Hexene 0.05-5 trans-2-Butene 41 Dimethylhexane 0.05-4 2-Methyl-2-butene 68 Cyclopentadiene 0.06-7 trans-2-Pentene 15 Methylpentene 0.01-1 cis-2-Pentene 10 Acetone 0.40-52 1-Hexene 0.4 Methylpentadiene 0.01-1 trans-2-Hexene 0.12 Acrolein 0.09-12 Acetylene 26 Methylacetate 0.02-14 Methylacetylene 7 Methylpentadiene 0.02-13 Ethylacetylene Cyclohexane 0.02-24 Cyclopentane 1 Cyclohexadiene(s) 0.04-19 Methylcyclopentane 2 Methylfuran 0.07-86 Cyclohexene 0.01 Methyl cyclopentadiene 0.02-6 P-Pinene 3 Methyl ethyl ketone 0.03-131 4-Isopropyltoluene 7-14 Methyl vinyl ketone 0.02-44 I-Methyl styrene 1 Benzene 0.05-94 3-Methyl styrene 2 Methyl isopropyl ketone 0.03-52 Methyl alcohol 180 Butanedione 0.01-60 Acetonitrile 140 Dimethyl furan 0.02-34 n-Propanol 4 Isobutyronitrile 0.01-46 n-Butanol 5 Methyl propyl ketone <0.01-26 Isobutanol <6 Nonane <0.01-5 sec-Butanol <4 Toluene 0.10-126 Glyoxal Methyl butyl ketone <0.01-6 l-Penten-3-one 45 Ethyl benzene <0.01-14 Isopropylformate 6 p-Xylene <0.01-8 Formic acid 0.42 m-Xylene <0.01-20 Acetic acid 117-322 o-Xylene <0.005-10 Propionic acid 100-300 Styrene <0.005-13 Hexanoic acid 500 Limonene <0.005-34 Isohexanoic acid 700 Methane -1,000 Furf uryl alcohol Ethane -500 Anisole 5 Propane 250 o-Methoxyphenol 15-25 Butane 70 n-Capronitrile 1 2-Methylpentane 6 Methacrylanitrile 3 3-Methylpentane 1 Methyl nitrite 19-91 Ethylene 240 Hydrogen sulfide 12 Propene 240 Carbonyl sulfide Butene 6.2 3-Ethylpyridine 1.9 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix C TABLE C-3 (contd) Concentration, Substance ug/cigarette 2-Methyl-1-butene 24 3-Methyl-1-butene 1 Methylisocyanate 0.55 2,6-Dimethylpyridine 5 Propionaldehyde 40 Propionitrile 30 Crotonaldehyde 16 Methacrolein 8 Pivaldehyde 4 Ethyl alcohol 2 Tetrahydropyran 2 Substance 3-Butenenitrile Pyrrole Sulfur dioxide Vinyl pyridine Methyl formate lsovaleraldehyde Isobutyraldehyde n-Valeraldehyde Methylacrylate Thiophene lsoprene Concentration, ug/cigarette 4 -3 28 30 20 12 8 3 2 630 77 'Data from: Elmenhorst and Schultz, 1968; Grob, 1966; Grob, 1963; Grob and Vollmin, 1969; Higgins et al., 1984; Higgins et al., 1983; Klus and Kubn, 1982. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 78 TABLE C-4 Materials for Certification by Naval Sea Systems•,b Adhesives Cleaning agents and detergents Coatings and sealants Deck coverings Duplicating products Dye penetrants Electric components Deck finishes and waxes Insulation materials Lubricants Office supplies Paints and varnishes Personal hygiene items Pesticides and insecticides Photographic supplies Polishes Preservatives/anticorrosion agents Solvents Miscellaneous items Solders, soldering fluxes, and cleanen Water treatment products Plastic/polymeric materials Packaging and packing materials Submarine ..4ir Quality 8Data from Demas and Greenberg (I 986). !>substances are categorized according to restrictions on their use--permitted, limited, restricted, or prohibited. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix C TABLE C-S Coating Material Components• Chemical l , l , 1-Trichloroethane l, l ,2-Trichloro-1,2,2-trifluoroethane l ,4-Epoxy-1,3-butadiene 1-Butanol 1-Propanol 2,4-Hexadienal 2-Butanal 2-Butanol 2-Butanone 2-Butoxyethyl alcohol 2-Ethoxy-1-ethanol 2-Ethoxyethyl ethanoate 2-Hexanone 2-Methoxyethanol 2-Methyl-1-propanol 2-Propanol 2-Propanone 4-Methyl-2-pentanone 4-Methyl-3-penten-2-one Acetaldehyde Acrolein Ammonia n-Butanal C10-C12 saturated and unsaturated aliphatics C5 alcohols C5 aldehydes C6 aldehydes C6 ketones C6 saturated and unsaturated aliphatics C7 aldehydes C7 esters C7 ketones C7 saturated and unsaturated aliphatics Ca esters Ca saturated and unsaturated aliphatics C9 aromatics C9 saturated and unsaturated aliphatics Cyclohexanone Dichloromethane Ethanol Ethylacetate Maximal Estimated Emission-- mg/m2/min CNo, Materials Iestedl 12 (4) 41 (7) 32 (12) 1,000 (47) 2,759 (9) 6 (3) 12 (3) 1,325 (6) 3,329 (170) 120 (4) 620 (12) 1,577 (54) 307 (3) 960 (4) 100 (19) 1,590 (72) 6,022 (115) 3,900 (60) 489 (16) 460 (79) 19 (4) 120 (10) 7,871 (26) 3,000 (26) 1,325 (8) 310 (27) 120 (26) 30 (4) ss (12) 10 (4) 97 (4) 6 (4) 160 (22) 2.S (2) 91 (16) 145 (17) I0S (13) 2,800 (IS) 21 (6) 590 (SI) 85 (17) 79 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 80 Submarine Air Quality TABLE C-S (contd) Chemical Ethylf ormate Methanol Methylacetate Methylformate Toluene Propane Propene Siloxane tetramer Siloxane trimer Styrene Trimethylbenzene Xylenes n-Butylacetate n-Butylf ormate n-Butyraldehyde n-Propylacetate 8 From NASA Materials Testing Data Base, 1986. Maximal Estimated Emission-- mg/m2/min {No. Materials Jested} 200 (13) 9,999 (S6) 20 (6) 31 (8) 1,178 (78) 7S (12) 12 (8) 40 (2) 9.6 (4) 40 (6) 100 (2) 1,600 (92) s.ooo (25) 3.9 (4) 37 (2) 2,400 (9) Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix C TABLE C-6 Vapor Emissions from Rubber Products• Chemical l, l, 1-Trichloroethane 1, l ,2-Trichloro-1,2,2-trifluoroethane 1-Butanol 2-Butanone 2-Methyl-2-propanol 2-Propanol 2-Propanone Acetaldehyde Acetic acid Carbon bisulfide Carbon oxysulfide Ethanol Hexamethylcyclotrisiloxane Methanol Toluene Octamethylcyclotetrasiloxane Siloxane tetramer Siloxane trimer Xylenes 'From NASA Materials Testing Data Base, 1986. Maximal Estimated Emission-- mg/m2/min CNo, Materials Jested} 41 (4) 23 (IS) 92 (3) 160 (12) 520 (13) 770 (15) 110 (18) S (4) IS (3) 11 (19) 14 (20) 330 (16) IS (3) 1,200 (18) 2,000 (16) 12 (4) so (15) 21 (10) 11 (4) 81 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 82 Submarine Air Quality TABLE C-7 Vapor Emissions from Plastics and Insulation• Chemical I, I, I-Trichloroethane l, l ,2-Trichloro-l ,2,2-trifluoroethane 1-Butanol 2-Butanol 2-Butanone 2-Methyl-2-propanol 2-Propanol 2-Propanone sec-Butyl acetate 1From NASA Materials Testing Data Base, 1986. Maximal Estimated Emission-- mg/m2/min <No, Materials Tested} 1.9 (2) 25 (S) 1.4 (I) 64 (16) 632 (21) 400 (18) 38 (IS) 24 (9) 58 (10) Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix C Chemical l, l, 1-Trichloroethane FC-113 Xylenes 1-Pentanol 2-Methyl-2-propanol 2-Propanol Hexamethylcyclotrisiloxane Octamethylcyclotetrasiloxane TABLE C-8 Vapor Emissions from Wire, Cables• Maximal Estimated Emission-- mg/m2/min <No, Materials Tested} 1.8 (1) 37 (2) 29 (3) 17 (1) 14 (3) 180 (2) 115 (1) 35 (3)

• From NASA Materials Testing Data Base, 1986.

83 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 84 Chemical 2-Butanone 2-Methyl-2-propanol 2-Propanol Acetaldehyde Ethanol Ethyl acetate Methanol TABLE C-9 Vapor Emissions from Penonal Items• Maximal Estimated Emission-- mg/m2/min CNo. Materials Dated} 15 (3) 51 (4) 3,600 (12) 67 (5) 9,999 (4) 330 (2) 12 (5) 8From NASA Materials Testing Data Base, 1986. Submarine Air Quality Examples Creams Deodorants Wipes and leather Creams and deodorants Creams and deodorants Creams Creams Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix C 85 TABLE C-10 Volatile Decomposition Products of Triglycerides During Simulated Deep-Fat Frying• Relative Amouot o{ Com12owid Corn Hydrogenated CQmoouod Qil_ couonseed Oil Irilioolein Jriolein I. Acidic Products A. Saturated acids Acetic s Propanoic s M Butanoic s s M Pentanoic L s M L Hexanoic XL s XL L Heptanoic L s L M Octanoic L s M XL Nonanoic L s M XL Decanoic s s M L Undecanoic s XS M Dodecanoic s s M Tridecanoic L s Tetradecanoic M s Pentadecanoic XS Hexadecanoic XL Heptadecanoic XS Octadecanoic L B. Unsaturated acids trans-2-Butenoic s trans-2-Pentenoic L trans-2-Hexenoic s trans-2-Heptenoic s XL trans-2-0ctenoic M s s M trans-2-Noneonic M XS XL M trans-2-Decenoic XL M trans-2-Undecenoic s L trans-2-Dodecenoic s trans-2-Tridecenoic s cis-2-Heptenoic s cis-2-Nonenoic L cis-2-Decenoic s trans-3-Pentenoic M trans-3-Nonenoic L trans-3-Decenoic s s XS cis-3-Heptenoic s cis-3-0ctenoic s M cis-3-Nonenoic s s cis-3-Decenoic L M s XS cis-3-Undecenoic S(tent.) Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 86 Submarine Air Quality TABLE C-10 (contd) Reliuive Ama1101 a( Cam12a11od Corn Hydrogenated Camoound Qil_ CanaNHdOH Jrilinatein Jriglein cis-3-Dodecenoic M cis-4-Nonenoic S(tent.) Hexenoic s L 6-Heptenoic XS L L 7-0ctenoic s s L I 0- U ndecenoic XS Palmitoleic XS Elaidic s M Oleic XL Linoleic L Linolenic XS cis-2-trans-4-0ctadienoic M S(tent.) trans-2-cis-4-Decadienoic M trans-2-trans-4-Decadienoic M C. Hydroxy acids 3-Hydroxyhexanoic s s 2-Hydroxyheptanoic s M 2-Hydroxyoctanoic s 3-Hydroxyoctanoic S(tent.) S-Hydroxyoctanoic XS(tent.) S-Hydroxydecanoic XS(tent.) I 0-Hydroxy-cis-8- XS(tent.) hexadecenoic D. Aldehydo acids Octanedioic acid XS s semialdehyde Nonanedioic acid XS semialdehyde Decanedioic acid XS semialdehyde Undecanedioic acid XS semialdehyde Tetradecanedioic XS acid semialdehyde E. Keto acids 4-0xohexanoic M(tent.) 4-0xoheptanoic S(tent.) XS(tent.) S(tent.) 4-0xooctanoic S(tent.) 4-0xononanoic XS(tent.) 4-0xo-trans-2-octenoic L 4-0xo-trans-2-nonenoic M 4-0xo-trans-2-undecenoic s 4-0xo-cis-2-decenoic XS(tent.) Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix C 87 TABLE C-10 (contd) Ri2l1iivi2 Amsn1ni g[ C2m122:uo'1 Corn Hydrogenated C2mmn,10'1 Oil C2U2D~i2i2'1 Oil I[ilio2li2iD Id2li2iD F. Dibasic acids Hexanedioic s s Heptanedioic s XS XS Octanedioic M XS s s Nonanedioic L XS M Decanedioic XS U ndecanedioic XS 4-Oxoheptanedioic XS(tent.) II. Nonacidic Products A. Saturated hydrocarbons Hexane XS Heptane s M Octane s s s Nonane M s XL Decane L M M M Undecane M M s Dodecane s s L Tridecane s XS Tetradecane s s s Pentadecane s XS Hexadecane s XS Heptadecane s Octadecane XS B. Unsaturated hydrocarbons 1-0ctene s M 2-Nonene s M 1-Decene s 1-Undecene XS trans-2-0ctene s s cis-2-0ctene s trans-Undecene s trans-Dodecene M XS s trans- Tridecene XS s trans-Tetradecene s XS trans-Hexadecene s trans-Heptadecene S(tent.) trans-1,3-0ctadiene S(tent.) trans-1,3-Nonadiene S(tent.) trans,trans-Tetradecadiene S(tent.) trans,cis-Tetradecadiene S(tent.) Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 88 Submarine Air Quality TABLE C-10 (contd) B,elaiixe Amo:uui o[ Q2mwu1nd Corn Hydrogenated Comoo:und Oil Cottouseed OjJ Icilinolein Triolein C. Alcohols Ethanol M 1-Propanol L 1-Butanol s M L M 1-Pentanol XL L XL 1-Hexanol s M s L 1-Heptanol L s L 1-0ctanol XL M L L 1-Decanol s 1-U ndecanol M 1-Dodecanol s 2-Hexanol XS(tent.) 2-0ctanol M 3-0ctanol XL s 1-Penten-3-ol L 1-0cten-3-ol XL L XL D. Saturated aldehydes Propanal L Butanal s M Pentanal XL M XL Hexanal XL L XL M Heptanal XL L XL L Octanal M XL M XL Nonanal XL XL s XL Decanal M M M M Undecanal s L Dodecanal XS XS M Tridecanal XS Tetradecanal XS Pentadecanal XS 3.4.S-Trimethyl- L(tent.) M(tent.) heptanal 4-Methoxy-3.3- S(tent.) S(tent.) dimethylbutanal E. Unsaturated aldehydes trans-2-Hexenal M M M s trans-2-Heptenal XL XL XL M trans-2-0ctenal XL XL XL M trans-2-Nonenal XL XL M L Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix C 89 TABLE C-10 (contd) Relative Ams2110i <>I C<>m12<>11od Corn Hydrogenated C<>moound Oil C<>U<>nseed Oil Icilio<>lein Jri<>lein trans-2-Decenal XL XS M XL trans-2-Undecenal s s XL cis-2-Heptenal s cis-2-0ctenal s cis-2-Nonenal XS cis-3-Hexenal M(tent.) trans-4-Hexenal s S(tent.) trans-3-Decenal s M S-Hexenal M 6-Heptenal M 7-0ctenal L S-Methyl-4-hexenal S(tent.) 4-Oxo-trans-2-octenal L(tent.) trans-2-cis-4-Heptadienal M trans-2-cis-4-Nonadienal s L M M trans-2-trans-4-Nonadienal L M XL trans-2-trans-6-Nonadienal XL trans-2-cis-4-Decadienal s L XS trans-2-trans-4-Decadienal XL L XL F. Ketones 2-Heptanone s L s 2-0ctanone , s M 2-Nonanone XS s M 2-Decanone s s L 2-Undecanone M 2-Dodecanone s XS 3-Heptanone s s 3-0ctanone XS s s 3-Nonanone s s 3-Decanone M 3-Dodecanone XS(tent.) 4-0ctanone M 4-Undecanone M XS 4-Dodecanone s l-Octen-3-one S(tent.) 2-Methyl-3-octen-S-one S(tent.) S(tent.) trans-3-Nonen-2-one XL S(tent.) trans-3-Undecen-2-one S(tent.) Nonenone XS(tent.) XS(tent.) Dodecenone XS(tent.) l-Methoxy-3-hexanone M(tent.) L(tent.) Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 90 Submarine Air Qualily TABLE C-10 (contd) Rel111ive Ama11ni a( Cgmmnuu1 Corn Hydrogenated Cgmoguod Oil CgugmM<J Oil Jrilinakin G. Esters Ethyl acetate XL XL XL Butyl acetate s s Hexyl formate XS Ethyl hexanoate s H. Lactones 4-Hydroxypentanoic s M 4-Hydroxyhexanoic L s 4-Hydroxyheptanoic s XS 4-Hydroxyoctanoic L M 4-Hydroxynonanoic s s 4-Hydroxydecanoic s s 5-Hydroxyhexanoic S(tent.) 5-Hydroxydecanoic s 6-Hydroxyhexanoic s 4-Hydroxy-2-hexenoic M 4-Hydroxy-2-heptenoic s XS 4-Hydroxy-2-octenoic XS 4-Hydroxy-2-nonenoic L XL 4-Hydroxy-2-decenoic s 4-Hydroxy-3-octenoic 4-Hydroxy-3-nonenoic XL(tent.) S-Hydroxy-2-nonenoic M(tent.) I. Aromatic compounds Toluene s Butyl benzene s Isobutylbenzene M Hexylbenzene s s Phenol L Benzaldehyde s XS M Acetophenone S(tent.) 4-Phenylbutanal M(tent.) XS 5-Phenylpentanal S(tent.) s J. Miscellaneous compounds 2-Pentylfuran XL L XL 1,4-Dioxane L •Data from Chang et al., 1978. XS, extra small gas chromatographic peaks; S, small peaks; M, medium peaks; L, large peaks; XL, extra large peaks. Triglein XL L XS s M s XS(tent) M S(tent.) Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Monitoring/ Appendix C Cbfmi~al Methanethiol Dimethyl sulfide Diethyl sulfide Thiophene Methyl isothiocyanate (tentative) 2,3-Pentanedione 2-Methylthiophene 3-Methylthiophene 2,5-Dimethylthiophene 2-Ethylthiophene 2,4-Dimethylthiophene 2,3-Dimethylthiophene (tentative) Thiazole 2-Formylthiophene (tentative) 5-Methylthiazole 4-Methylthiazole 5-Methyl-2-formylthiophene (tentative) 2-Ethylthiazole 2-Ethyl-4,5- dihydrothiophene (tentative) 4,5-Dimethylthiazole (tentative) Furfural Methyl furfuryl sulfide 2-Acetylfuran (Furyl-2)-1- propanone-2 Methyl 2-ethyl f uryl sulfide Methyl thiof uroate 5-Methylf urfural Ethyl 2-furyl ketone 2-Furylmethanethiol (tentative) TABLE C-11 Chemicals Identified ind-Glucose-Hydrogen Sulfide-Ammonia Model System• Area, ~ 0.62 7.45 10.14 10.19 3.56 0.45 24.92 4.41 6.35 0.28 0.51 0.28 0.28 0.23 1.95 I.IO 0.23 0.11 0.11 0.06 10.67 0.06 I 1.18 0.40 0.06 0.09 0.52 0.39 0.03 Occurrence in Foods Onion, leek, garlic, beef Onion, garlic, beef Cabbage Coffee Cabbage, sprouts, cauliflower Coffee, filberts Chicken, beef Beef Beef, onion Pressure-cooked beef Onion Beef Peanuts, popcorn Coffee, filberts, beef (Cysteine-pyruvaldehyde) Peanuts Coffee, popcorn (Cysteine-pyruvaldehyde) (Thiamine) Bread, chicory, popcorn Coffee Chicory, coffee, popcorn Coffee Coffee Coffee, popcorn, filberts Coffee Coffee 8Modified from Shibamoto and Russell (1976). 91 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 92 TABLE C-12 Compounds Identified in Volatiles Formed in Roasting of di-a-Alanine with d-Glucose• 2-Acetyl-1-ethylpyrrole 2-Acetyl-S-methylfuran 2-Acetylfuran 2-Acetylpyrrole Acylpyrrole Alkylpyrazine Alkylpyrrole 2,S-Dimethyl-1-ethylpyrrole 2,5-Dimethyl-3-ethylpyrazine 2,6-Diethyl-3-methylpyrazine Diethylmethylpyrazine 3-Ethyl-S-methylpyrazine l-Ethyl-S-methylpyrrole-2-aldehyde Ethylmethylpyrrole 1-Ethylpyrrole I -Ethylpyrrole-2-aldehyde 2-Furaldehyde 1-(f-Methyl-2' -furfuryl)-pyrrole 5-Methyl-2-furfurylalcohol Methylpyrazine 5-Methylpyrrole-2-aldehyde Oxazoline derivative Pyrazine derivative •Data from Shigematsu et al. (1972). Submarine Air Qualily Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. HEALTH EFFECfS IN DIVERS OF BREATHING SUBMARINE AIR UNDER HYPERBARIC CONDITIONS REPORT OF THE PANEL ON HYPERBARICS AND MIXTURES Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. CHAPTER 1 INTRODUCTION This report assesses the health effects of breathing submarine air and especially the potential use of submarine air at increased pressure for submarine-based divers. The pressure inside the submarine is generally I atmosphere absolute ( I AT A). Fluctuations can result from venting of pneumatic devices into the interior of the submarine, the periodic reduction of pressure by pumping of air into flasks, and snorkeling operations that, although infrequent, can cause fluctuations of as much as ISO torr. Temperature and humidity in the submarine are rigidly controlled to ensure crew comfort and reliability of electronic components. The atmosphere of the nuclear-powered submarine is artificial. Oxygen generated from water is used to replenish oxygen consumed by the crew. Carbon dioxide, carbon monoxide, hydrogen, trace contaminants, and particles are partially removed from the atmosphere. From the early 1960s to the late 1970s, atmosphere control equipment on nuclear submarines was substantially improved. Ambient carbon monoxide during patrol was reduced from about 44 ppm in 1961 to 7-8 ppm by 1977, and ambient carbon dioxide was decreased from 1.2-1.5% to 0.85% (Tansey et al., 1979). Carbon dioxide is currently regulated not to exceed 0.8%. Submarine personnel are generally semisedentary, and both work and recreation take place in warm well-lighted spaces. Divers operate in a very different environment. The ambient pressure for divers can vary from I A TA (sometimes less) to 30 A TA. The diving 95 environment is dark, generally cold, and relatively weightless. The physical activity of divers can be light, but is more commonly strenuous, sometimes maximal. The biomedical problems confronting the submariner are principally toxicologic, nutritional, chronobiologic (circadian), and those related to a sedentary life style. The main biomedical concerns in diving are related to cold exposure, narcosis, carbon dioxide, toxic effects of oxygen, decompression sickness, and the effects of the diving environment on respiratory and central nervous system function. Toxicologic problems are generally not important in diving, because such diving typically takes place at shallow depths and for short periods. As a consequence, purity standards for diver's air have been at best rudimentary extrapolations of existing standards for industrial and submarine atmospheres. The submarine can serve as an ideal platform for diving operations. It is mobile and can launch divers underwater, where they cannot be observed. The advantages of submarines and other submersible vehicles for launching divers have been recognized for some years by the scientific, commercial, and military communities. Although a number of systems aboard these vessels lend themselves to the support of diving operations, the diver's breathing gas is usually stored in and supplied from sources separate from those used by the vehicles. Use of compressed air from submarine air banks as a breathing medium for divers was not intended by the original designers. For example, the Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 96 oxygen concentration in a nuclear submarine is 140-160 torr (18.4-21.1%) (U.S. Naval Sea Systems Command, 1979). U.S. Navy standard air decompression schedules have been developed for use with a constant oxygen content of 21% (U.S. Naval Sea Systems Command, 198S). Atmospheric concentrations of carbon dioxide in nuclear submarines are about 0.7-0.8%. Divers breathing such compressed air at S AT A would therefore be breathing the equivalent of Submarine Air .Quality about 4% carbon dioxide, which is unacceptable. To circumvent this problem, before compressed air from submarine air banks is used for divers, carbon dioxide needs to be removed by passing the air through lithium hydroxide scrubbers. Submarine atmospheres have also been shown to contain hundreds of volatile organic compounds; it is reasonable to suspect that the trace contaminants of submarine air can ~ome harmful at increased pressures. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. CHAPTER2 PHYSICS OF THE HYPERBARIC ENVIRONMENT In an environment of compressed air, gas volumes, density, and partial pressures are drastically affected, and increased amounts of gases are dissolved in body fluids. Each of these consequences deserves careful consideration. Alterations in ambient pressure are the hallmark of the diving environment, so engineers, biomedical scientists, and operators associated with the operations need to become comfortable with the multiplicity of units for expressing pressure. The following equivalents illustrate the more common units of pressure (with commonly used approximations shown in parentheses): I ATA • 10.08 (10) m of seawater • 33.07 (33) ft of seawater • 33.90 (34) ft of fresh water • 760 mm Hg • 760 torr • 1.103 bars • 1.033 kg/cm 2 • 14.696 (14.7) lb/in 2• In the simplest conception, a gas is postulated to consist of a large number of very small, elastic particles in continuous motion in all directions. The pressure exerted by a gas is considered to result from the collisions of particles with the walls of the containing vessel. Anything that increases the number of impacts or the velocity of movement will increase the gas pressure. Several laws of gases (CRC, 1984) describe the relationships among the factors concerned with total and partial pressures of 97 gases and are pertinent to the hyperbaric environment. PRE~URE AND VOLUME Boyle's law states that, as a contained gas is compressed at constant temperature, its volume varies inversely with the pressure exerted on it. That statement and its converse are of obvious importance during the changes in pressure that occur in the hyperbaric environment. The change from one pressure and volume to a second pressure and volume is expressed as follows, for an ideal gas under isothermal conditions: P1V1 • P2V2. Thus, IO L of gas at sea level ( I AT A) will be compressed to 5 Lat 2 ATA and to 2 Lat 5 ATA. Volume changes are greatest near the surface. Going from the surface to 33 ft (2 AT A), the volume change is 5 L, and going to 165 ft (6 ATA), the volume is 1.7 L, a change of 3.3 L. TEMPERATURE AND VOLUME Charles' law states that, if pressure is constant, the volume of a contained gas is proportional to the absolute temperature. (The absolute temperature is approximately 273° more Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 98 than the Celsius temperature). A useful expression of this law is the following: V1/T 1 • Vz1T2 • Boyle's and Charles' laws may be used together if temperature and pressure both change. The combined laws can be expressed as the universal gas equation: PARTIAL PRESSURE OF GASES IN GAS MIXTURES Dalton's law states that, in a gas mixture, the pressure exerted by each gas in a space is independent of the pressures of other gases in the mixture. Each gas behaves as though it were the only gas in a space and distributes itself uniformly, so total gas pressure is the sum of the partial pressures of each of the individual gases present. For example, in the pulmonary alveoli: total pressure• PH O + P00 + PN + P0 . 2 2 2 2 The partial pressure (P) of one gas in the mixture is therefore equal to the product of the percentage of the gas in the mixture and the total pressure of the gas mixture. Thus, oxygen partial pressure in a dry gas mixture containing 20.94% oxygen at a pressure of 1.0 atmosphere (760 torr) is: (0.2094)(760) • 159.l torr. In the calculation of partial pressure of a gas in a mixture, water vapor if present must be Submarine Air .Quality considered as one of the gases. To determine the partial pressure of a gas in the lungs, where alveolar gas is saturated with water vapor, one must subtract the partial pressure of alveolar water vapor from the total ambient pressure to obtain the total pressure of dry gases. The saturation pressure of water vapor is a function of temperature and at normal body temperature is assumed to be 47 torr. For example, if the air is at S.0 AT A and contains 0.8% carbon dioxide: P co • (0.008)((5 x 760) - 47] torr • 30 torr; 2 P0 • (0.2094)((5 x 760) - 47] torr• 786 torr. 2 PARTIAL PRESSURES OF GASES IN LIQUIDS Henry's law states that the degree to which a gas enters into physical solution in a fluid is in direct proportion to the partial pressure of the gas to which the fluid is exposed. At equilibrium, the fluxes of gas passing into and out of solution are equal. At sea level (I AT A), a diver's body fluids contain about 1 L of gaseous nitrogen in solution. If he dives to 99 ft and thus breathes air at 4 AT A, he eventually reaches equilibrium again and has 4 times as much nitrogen in solution in his body. The time taken to reach a new equilibrium depends on the solubility of the gas in a given tissue and the rate of gas delivery to each tissue. When the total pressure is reduced, gas can pass out of solution. If a rapid and large drop in total pressure occurs, a tissue might contain more gas than it can hold in solution. In that situation, bubbles can form and cause decompression sickness. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. CHAPTER3 SUBMARINE AIR HANDLING SYSTEM The following section provides a general overview of submarine atmosphere control and air quality as they might affect SCUBA (selfcontained underwater breathing apparatus) divers who are based on submarines and who breathe compressed air from submarine air banks. Equipment and procedures vary with submarine size, type, age, and mission; therefore, details of this outline will not be universally applicable (it is based in part on information obtained by panel members on a visit to the USS Philadelphia, SSN 690). Most of what is presented here is well known among submariners, but the operating routines and descriptions of relevant equipment in part I of this report, Monitoring the Air in Submarines, should be helpful to readers of the report who are not submariners. We outline here general features of submarine atmospheres and their management and then comment on the following separate systems: high-pressure air, burners, carbon filters, electrostatic filters, carbon dioxide scrubbers, oxygen generators, central air monitoring system, and diver's air. Table 11 summarizes various air handling devices on submarines. We have included comments on potential sampling sites throughout the air handling system because of the need for additional data on the components of submarine air, as outlined in part I. Submarines have "floodable volumes" of around I 00,000 ft3 and contain air near I AT A. Oxygen is removed and carbon dioxide is added by the crew's metabolism and by other processes of smaller magnitude. Contaminants have many 99 sources within the boat despite restriction of materials allowed on submarines. The submarine atmosphere is periodically renewed by exchanging it with exterior air while the boat is at the surf ace or at periscopic depth. Two terms are used to describe this process (unfortunately, they are inconsistently defined). "Ventilating" refers to the use of pumps to draw air into and simultaneously eject it from the submarine. The boat's diesel engines might or might not be operating during ventilation. The "snorkeling" procedure (the exchange of interior submarine air via the gas intake called the snorkel), is generally used in connection with operation of the diesel engines, which draw large volumes of air from the boat's interior. Because of the possibility of taking in contaminants, the high-pressure air banks are not usually charged during operation of the diesel engines (or during or after a fire or when there have been battery or refrigerant leaks). If the air intake becomes submerged during ventilating or snorkeling, it shuts, but air continues to be removed from the boat. Boat pressure can fall by as much as I SO torr within 1-S min, and stay low for perhaps 1-1 S min. Such pressure decrements might increase the risk of decompression sickness for divers recently returned to the boat. Even the routine variations in boat pressure (± SO torr) might be undesirable at such times. Such pressure variations can be largely avoided, if the crew is aware of the need to avoid them during diving operations. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. TABLE 11 .... <:::, Submarine Atmosphere Devices <:::, Device Number Location Inlet Outlet Sampling Sites CAMS MKI I Variable Fan room and NA Inlet filter paper other Sites Main air banks Several Often outside Air tower Many sites Liquids via drain on each bank pressure hull gases via high-pressure outlets Compressors 2-3 high Varies with sub- High-room location High-air tower Inlet filters I low marine class low-variable low-multiple Air tower 1 With compressor High pressure Main air banks At each point in air tower Moisture separator air compressors sampling sites are available CUNO filter Prefilter Dryer After filter Oxygen generator 1-2 Varies with class Distilled water Oxygen banks (from seawater) Oxygen banks Several May be outside Oxygen 2-03 o2 bleed stations pressure hull generator blee stations CO2 scrubbers 2 Varies with class Room location Fan room Monoethanolamine before and after CO2 absorption Silica-gel filters Burners 1-2 Varies with class Room location CO2 scrubber Condensate collection jug and or fan room LiOH scrubber particles Air-conditioners Several Fan room, and other Room location Multiple Multiple I compartments ~ s· Activated-carbon Several Fan room, galley, Room location Ventilation Spent carbon Ill filters wash room, water system • :;· closets, sanitary le:) tanks s -.... Electrostatic Several Within ventilation Room location Ventilation Second-stage collector ~ precipitators system system Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/Submarine A.ir Handling System The boat is sometimes isolated from exterior air for relatively long periods, so its atmosphere must be maintained artificially. Continuous circulation of air is usually maintained by blowers that distribute air through a system of ducts originating in a plenum chamber ("fan room") and leading throughout the boat; air is returned through ducts and through the spaces of the boat itself. The system allows choices of flow routing for different conditions (with variation among boat classes). Each compartment has local fan circulation through chillers and heaters. Such circulation minimizes local variations in air composition in the boat. HIGH-PRESSURE AIR Compressed air has many uses in submarines. It powers a multitude of pneumatic devices, fewer of them in newer classes of submarine and few (if any) oil-lubricated; they exhaust into the submarine's interior. It is also used to displace seawater from ballast tanks to control buoyancy. U oder some circumstances, large quantities of air at very high pressure are needed for surfacing. Less commonly, compressed air is used in operating the escape trunks, where it serves both for displacing water and as breathing air. Finally, compressed air is used for breathing in two other ways: first, an emergency air breathing (EAB) system with outlets throughout the boat provides compressed air to demand-valve masks for use (nominally at I AT A) if the submarine's interior air becomes unbreathable; second, SCUBA tanks are occasionally used and can be recharged from the boat's high-pressure system. Some boats are used for more extensive diving operations, and there the quality of diver's air (in SCUBA tanks, etc.) is of greater concern. Compresson A submarine has two or three high-pressure compressors (up to about 4,500 psi) and one low-pressure compressor (1 SO psi). The lowpressure compressor can draw air from any compartment. High-pressure compressors draw air through only a coarse mesh filter from the compartments that house them. They are oillubricated, multistage, air-cooled devices that operate at or below about 350°F ( I 77°C). They discharge air through an air cleaning system (air tower) and charge the high-pressure air banks. 101 During submergence, they are run periodically to keep the boat's interior pressure from exceeding the desired range (ordinarily near I AT A) because of the addition of exhaust gas into the boat from pneumatic devices and from the emergency air breathing system (which is used periodically for training). Air Tower The air tower is a cluster of devices that process air from the high-pressure compressors. A submarine has one air tower. Compressed air first traverses a moisture separator (drier), an upright cylindrical chamber in which water and other substances condense; samples for analyses could easily be collected here. Next, it passes through a 5-µm rigid polystyrene particle filter; the 3 x 12-in. cylindrical filter is replaced periodically and could easily be collected for analysis. The next steps include passage through a mesh-screen prefilter, a gas drier, and an after-filter; samples could also probably be collected from these items. From the air tower, air enters a high-pressure manifold that runs the length of the boat and connects with the air banks. Air Banks A boat has about five high-pressure air banks, distributed, for example, two aft and three forward. Each bank is made up of some five steel air bottles about 2 ft in diameter and IO ft long. Each bottle has a drain; the drains are manifolded to a petcock, one per air bank. The petcocks are opened at intervals ranging from daily on some classes of submarine, to as infrequently as monthly on others. On some boats little or no discharge (except air) is found; on others, tea-spoon quantities of water or other liquid effluent is found and could easily be sampled for analysis. Once they are put into service, the air banks are not emptied--except during complete overhauls of the boat (up to 12 years apart), at which time they are carefully cleaned according to detailed specifications that include Freon rinsing and analysis of residual gases. The use of air banks is based on the vital importance of compressed air for surfacing in emergency circumstances. A central tenet seems to be that the air banks will all be completely full (about 4,500 psi) at all times, except Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 102 for one (not always the same one) that is used for daily operations. In the daily-use air bank, the pressure may be allowed to cycle as low as 2,000 psi. During submerged operations, this bank receives much of its air from the submarine's interior after processing in the air tower; like the other air banks, it may also be charged with fresh air from the surface. Thus, the composition of the air in a bank depends on the composition of the air that it receives, on reactions within it, and on what is removed from it. The air in a particular bank can have a history that is long, undocumented, complex, and quite different from the histories of other banks. The composition of air in individual banks can, of course, be measured with the central air monitoring system, but no routine sampling connections or procedures exist. The need for such an operation arises only when the air is to be used by divers. 'BURNERS Burners are used to remove some oxidizable contaminants from the boat's atmosphere. Air from a compartment is drawn through a filter, then through a heat exchanger and heater, and then over a catalyst at 600°F (316°C), where hydrogen, carbon monoxide, hydrocarbons (including oil mists), and other substances are oxidized. · The products of oxidation are handled in three ways. Condensed water and other substances drain into a plastic jug for periodic disposal; samples could easily be collected from the jug. Acids (such as hydrofluoric acid and hydrochloric acid) are removed by a lithium carbonate scrubber operating at 140°F (60°C) or less; again, samples could easily be collected from the scrubber. Carbon dioxide is discharged into the submarine or directly to the CO2 scrubber. Heavy metals (residue from burning oil mists) are deposited on the catalyst; samples could be collected. Complex reactions probably take place in the burners; effluent air from the burners has been sampled, but such sampling is not routine. CARBON FILTERS Activated carbon is used to remove some organic contaminants and odors near their site of generation. The filters (cotton bats halffilled with activated carbon) are in the fan Submarine Air Quality room, galley, washroom, and water closets and above sanitary tanks. The carbon is changed on a schedule, and spent carbon has been collected and studied (in the 1960s), although apparently this is no longer done. ELECTROSTATIC FILTERS Two-stage electrostatic precipitators at several sites in the ventilation system are used to collect particulate contaminants. The first stage charges the incoming particles, and they are collected by the second stage, which could be sampled. Examination of these particles showed that half (by mass) were generated by cigarettes; other sources of particles are cooking and machine lubrication oils. CARBON DIOXIDE SCRUBBERS There are two high-capacity carbon dioxide (CO2) scrubbers on a boat. They provide for exctiange of CO2 between cocurrent flows of air and aqueous monoethanolamine (MEA) spray (which absorbs CO2), draining through and over Goodloe woven mesh (an arrangement that presents a large surf ace area). The MEA is then circulated to, and continuously regenerated in, a heater that evolves CO2 to be pumped overboard. "Rich" and "poor" samples of the amine are easily collected. The air is drawn from a compartment, processed, chilled to condense MEA vapor, passed through a silica gel filter (the "bag," which is periodically replaced and easily sampled) to remove suspended MEA and discharged into the fan room, still containing MEA at 1-2 ppm. The scrubbers remove only about 70-80% of the CO2 from the air presented to them. The cocurrent design probably contributes to the relative inefficiency of the scrubbers. Backup CO removal uses lithium hydroxide (LiOH) granufes, which absorb and react with CO2, in canisters with circulating fans. In emergencies, the LiOH may be spread on surfaces open to the submarine's interior. The granules tend to pulverize during handling, and the dust is irritating if inhaled. A supply of LiOH adequate for at least 3 d (often twice as that) is carried on a submarine. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/Submarine Air Handling System OXYGEN GENERATORS Electrolysis of distilled water provides 0 2• The production rate is adjusted to maintain a pressure of about 2, I 00 psi in a line connected to one of several 0 2 storage banks. 0 2 from it is independently bled to the boat in two or more locations at a rate adjusted to maintain the desired 0 2 fraction in the boat's atmosphere. Other 0 2 tanks are kept closed and fully charged at about 3,000 psi. Total 0 2 storage is a nominal S-d supply. Hydrogen produced by the electrolysis is discharged overboard. Traces that enter the submarine's air are burned; permissible limits are determined on the basis of fire considerations, not biologic considerations. There appear to be no other airborne contaminants as byproducts of the electrolysis. Backup 0 2 generation uses chlorate candles, which give off irritant smoke that contains chlorine and CO. CENTRAL ATMOSPHERE MONITORING SYSTEM The Central Atmosphere Monitoring System (CAMS) is a mass spectrometer that draws gas samples through a selector valve from any of about eight sample lines, then through a pickup head with filter paper at its inlet (the filters could easily be collected). The system runs continuously, usually sampling from the fan room, except when another site (of about eight) is selected. The CAMS monitors concentrations of 0 2, N2! CO2!.. CO (by infrared absorption), H2, and three nuorocarbons--FC-11, FC-12, 103 and FC-114. Sampling sites could be added (e.g., air banks, diver's tanks, dry deck shelters, and inlet and outlet air of devices described above). Hourly readings are logged, and the system activates an alarm when a limit is exceeded. The next generation of equipment will provide continuous records. Backup monitoring for additional substances is provided by sets of indicator tubes and by portable instruments for sampling 0 2, FCs, and hydrocarbons. DIVER'S AIR Most submarines carry only two or three divers. SCUBA tanks can be filled directly from a high-pressure line on board, but the line does not include a CO2 scrubber. SCUBA tanks are usually brought aboard filled and rarely used, and the on-board filling system is almost never used. It is not clear that divers know of the potential problems associated with breathing air with 0.S-0. 7% CO2 (as would be expected in gas taken from a submarine's main air banks) at S-6 ATA. Some submarines are equipped for more extensive and specialized diving activities, for example, dry deck shelter (DDS) operations. In these submarines, diver's air from the banks is passed through CO2 scrubbers before (at least) some uses, reducing the COi to an acceptable fraction, around 0.1%. Agam, it is not clear that all Navy divers know of the potential problems associated with breathing air with 0.S-0.7% CO2 at S-6 ATA. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. CHAPTER4 EFFECTS OF BREATHING MAJOR GASES AT UP TO 6 ATMOSPHERES ABSOLUTE This chapter considers the acute effects on submarine-based SCUBA divers of breathing clean air at pressures up to 6 atmospheres absolute {ATA) for up to 12 h, at rest and during bursts of violent activity. There is·wide experience with SCUBA diving from the surface using air that was compressed from the atmosphere. The literature is large and readily available (Bennett and Elliott, 1982; Edmonds et al., 1976; Flynn et al., 1981; Lanphier, 1964; Miller, 1979; Strauss, 1976; U.S. Naval Sea Systems Command, 1985). For readers unfamiliar with diving, this chapter introduces basic issues in diving and then discusses differences between surface-based and submarine-based diving. BASIC ISSUES IN DIVING During a dive, N2 narcosis impairs higher brain functions, anci increased gas density impedes breathing; during emergence, decompression sickness can occur. These phenomena are related to each other and to cold, immersion, dehydration, stress, and fatigue (Bennett and Elliott, 1982; Shilling et al., 1976). Other issues, not addressed here (for example, oxygen toxicity and exposure to hypoxic gas mixtures) are not related to the subjects of this report. 105 Nitrogen Narcosis Nitrogen has narcotic effects (Bennett, 1982) that increase with its partial pressure (PN2), calculated as the product of its fraction m the respired gas (about 0.79 in air) and the total pressure . Thus, during air breathing, PN2 increases in proportion to absolute pressure, 1 A-; A at the surface (sea level) and I AT A more for each 33 ft of seawater. Narcosis does not occur when one breathes air at I AT A; at 6 ATA, there are appreciable decrements in judgment and problem-solving and measurable, although probably unimportant, effects on other nervous system functions. The associated sensations are similar to those of mild intoxication with alcohol or mild hypoxia . Individual responses vary, and some experienced people believe that they can compensate fairly well; but task performance and especially safety suffer enough for conservative practice to limit compressed-air diving to 5 AT A ( 132 ft of seawater). Onset and remission of N 2 narcosis depend on N2 delivery to and removal from the brain, an approximately exponential process with a time constant (time required to achieve 63% of the change from one state to another after a stepchange in respired PN2) of about 2 min (Bennett, 1982); thus, for ordinary rates of change of depth, narcosis varies almost directly with depth (pressure). Hypercapnia (high CO2 concentration in blood) potentiates N2 narcosis (Hesser et al., I 971). Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 106 Breathin1 or Dense Gases The breathing of dense gases increases airway resistance and the work of breathing and decreases maximal expiratory flow rates; therefore, maximal achievable ventilation might be less than the ventilation required for heavy exercise (Lanphier and Camporesi, 1982). The added mechanical load also influences the control of breathing, so, for example, the ventilatory response to exercise is diminished. Effects on the gas-transport and gas-exchange functions of lung are negligible at pressures up to 6 ATA. Airway Resistance Increased gas density (at pressures up to 6 AT A) adds only negligibly to the work of inspiration at rest, but becomes significant during exercise with three consequences. Added inspiratory resistance causes a reflex increase in ventilatory drive and breathing effort, with an associated increase in the sense of effort. The increase in effort is not enough to off set the increase in mechanical load (Pengelly et al., 1974), so the ventilatory response to exercise is diminished; the resulting hypoventilation allows CO2 to increase to above normal in the body. An increase in the work of breathing leads to early fatigue of the breathing muscles (Hesser et al., 1981; Roussos and Macklem, 1985), decreasing the capacity for sustained hyperpnea and introducing a limit to sustained aerobic exercise that is not usually present at I A TA. All three--increased sense of effort, hypercapnia, and inspiratory-muscle fatigue--are involved in the control of breathing and probably contribute to unpleasant breathing sensations that play a role in exercise intolerance at depth. Maximal Expiratory Flow Rates The maximal expiratory flow rate that can be achieved is determined by an effort-independent mechanism that depends on elasticity of lung and airways, lung volume, tissue characteristics, and the density of gases breathed (Hyatt, 1986). This physical mechanism is independent of conscious and reflex mechanisms controlling breathing. The smaller the lung volume and the denser the gases, the lower the maximal flow rate. The decrease in maxiSubmarine Air.Qualily mal flow rate caused by breathing dense gases forces extreme hyperpnea to take place at high lung volumes--an effect that becomes more pronounced as gas density increases (Wood and Bryan, I 969; Hesser at al., 198 I), particularly during hyperpnea induced by exercise. There are several adverse consequences: the elastic work of breathing increases markedly and that creates a load that falls on the inspiratory muscles; and the inspiratory muscles work with disadvantageous lengths and mechanical arrangements, which require increased effort and oxygen and contribute to early fatigue of inspiratory muscles, dyspnea, and exercise intolerance. Reduced maximal expiratory flow rates combine with reduced inspiratory flow rates (due to increased inspiratory resistance) to reduce maximal voluntary ventilation (MV't), for example, from around 200 L/min at I AT A to 95 L/min at 6 AT A (Hesser et al., 1981 ). This pulmonary function test is a I S-s ventilatory "sprint" that cannot be sustained; yet at depth, even this briefly achievable maximum is well below the I SO L/min that is required for intense aerobic exercise . Under these circumstances, an unusual and little-studied phenomenon can occur: exertion of modest severity can quickly elicit an intense air hunger of a terrifying quality never before experienced and slow to recede. One can speculate that a high inspired fraction of CO2 would make it worse. Control or Breathin1 The effects described above lead to decreased ventilation during submaximal exercise, with slightly higher than usual CO2 concentrations in blood and tissues, despite increased breathing effort. These higher concentrations might contribute to unpleasant sensations and decreased exercise tolerance. Gas Transport Complex coupling of convective and diffusive mechanisms influences the transport of gases and thus the distribution of gases in the lung (Engel, 1983; Pedley et al., 1977). These phenomena, which depend in part on gas density, have not been well studied in hyperbaric states; but pressures up to 6 AT A do not appear to have biologically important effects on them. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/Ef/ects of Breathing Major Gases Gas Exchan1e Gas exchange in the lung depends in part on uniform regional distributions (i.e., matching) of alveolar ventilation and capillary blood flow. No significant impairment in gas exchange is known to be caused by pressures up to 6 AT A. Decompression Sickness During air diving, the PN2 in alveolar gas is higher than usual, so N2 passes into solution in blood and tissues. The amounts are substantial --in a long dive, 1-1.S L (measured at standard temperature and pressure) for each ATA. During ascent, the process is reversed, with an important limitation: if the total pressure (that is, depth) is reduced too fast, dissolved nitrogen forms bubbles and causes decompression sickness (the bends). To avoid that, diver's ascent is carefully regulated with decompression tables that take the depth and duration of the dive into account. Standard tables assume that the dive starts and ends at sea level, with the diver breathing air. If either assumption is violated, the risk of decompression sickness might be increased, so special tables are used. Most of the clinical manifestations of decompression sickness are thought to result from mechanical effects of bubbles that distort tissues and obstruct vessels. Bubbles also constitute a foreign surface in body tissues and fluids. Deleterious effects result from the interaction of this foreign surface with blood constituents (Lee and Hairston, 1971 ). Intravascular bubbles can cause serious alterations in the secondary and tertiary structure of globular plasma proteins (Philp et al., 1972). Effects on lipoproteins result in the release of free phospholipids, cholesterol, triglycerides, and free fatty acids. Coalescence of released lipids into globules can occur, and the globules can contribute to embolic vascular obstruction. It is thought that bubbles formed during decompression can damage vascular endothelium and that the damage can promote platelet aggregation and adhesion and fibrin deposition. Increased number of circulating endothelial cells have been observed after decompression stress. Histologic studies of saccular endothelium after decompression have shown areas of endothelial cell loss (Philp et al. 1972). Experimental animals with decompression sickness have shown endothelial cells trapped in capillary beds. The damaged endothelium is the site 107 for platelet aggregation and adhesion, fibrin deposition, and eventually clot formation. In addition to platelet aggregation, stimulation of the coagulation and fibrinolytic systems and activation of the complement and kinin systems can occur in decompression sickness (Hallenbeck and Andersen, 1982). The roles of all these phenomena have not been thoroughly delineated, but experimental work has shown that bubbles activate Hageman factor and accelerate clotting of both whole blood and cellf ree plasma (Hallenbeck et al., 1973 ). Platelet aggregation, the initial event in arterial thrombosis and a component of venous clotting, promotes thrombin generation and fibrin formation and releases serotonin. Red blood cells clump because of coating with denatured plasma proteins. Such aggregation increases blood viscosity and stasis and increases the tendency for blood to clot. The consequences of the phenomena noted above in decompression sickness might be as follows. Serotonin, bradykinin, and histamine provoke pain. Serotonin and histamine cause increased vascular permeability by forming interendothelial gaps of 1,000-8,000 A. Kinins also increase capillary permeability, as do the complement anaphylatoxins C3a and CSa. Increased viscosity and sludging of venular blood cause both capillary stasis and a local transcapillary loss of plasma. This further increases stress forces of venular blood. The disturbance leads to fibrin deposition in areas of stasis, which reinforces and perpetuates a vascular obstruction that is initiated by bubbles, platelet aggregates, and red-cell aggregates. The resulting tissue ischemic damage results in the synthesis of various eicosanoids, some of which can cause vasoconstriction, increased capillary permeability, and further platelet aggregation. As a consequence of the tissue damage and the derangement of regional tissue perfusion, progressive impairment of microvascular perfusion develops and can extend the ischemic damage. When ambient pressure decreases, gas in the lungs (and other cavities) expands. On rare occasions, the lungs become overdistended and rupture; gas can then enter the pleural spaces and the systemic arterial circulation. If those effects occur in decompression, they usually lead, respectively, to tension pneumothorax and cerebral air embolism, both of which are likely to be lethal unless treated immediately. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 108 Cold Cold is pervasive in the diving environment. Even in warm water, however, heat loss from the body is rapid. Thermal protective suits and heating systems off er some protection, but commonly allow mild heat loss. Body cooling, as occurs in diving with protective gear, leads to a number of effects. The first phase--and the only one germane here--is excitation (Reuter, 1978), which occurs at core temperatures between 34• and 37°C. During excitation, hypothalamic stimulation results in shivering and increased metabolic heat production. Shivering is maximal at a core temperature of 35°C. Intense peripheral vasoconstriction and adrenal release of cortisol and cathecholamines lead to increases in heart rate, blood pressure, cardiac output, central blood volume, and respiratory minute ventilation . Diuresis and natriuresis secondary to atrial distention ensue and are mediated by decreases in plasma antidiuretic hormone and aldosterone and an increase in natriuretic factor. Diuresis ultimately leads to a decrease in plasma volume and to hemoconcentration. Hyperglycemia is common and results from a decrease in pancreatic insulin release, peripheral insulin blockade, and the combined influence of increases in plasma epinephrine and cortisol. Free fatty acids and glycerol increase, and mild ketosis is often present. Decrements in diver performance due to distraction are common during the excitation phase (Webb et al., 1976) and are caused by the aggravating effects of the cold water. Reaction time, symbol processing, target detection, navigation problem-solving, and memory are impaired by exposure to cold before significant core cooling has occurred. At body temperatures of 35.5- 360C, recall is significantly affected. In 6-h simulated missions in 6°C water, well-trained divers omitted important procedural steps for mission requirements (Vaughn, 1975). Horvath ( 1981) reviewed the Ii terature on the ability of humans to exercise in a cold environment. Tolerance of cold-water exposure is limited by the extent to which loss of body heat exceeds heat production when core temperature cannot be maintained (and is decreasing at an increasing rate). Once core temperature reaches 35°C, heat production decreases, respiratory and circulatory irregularities appear, and death can follow. Exercise in cold water places a more severe thermal load on the body than exercise in air at the equivalent temperature. During exerSubmarine Air Qualily cise in cold water, core temperature can be reduced enough (to 35°C) to result in interference with normal muscular activity, and maximal aerobic capacity is reduced under these conditions, so the cost of performing submaximal work will be increased. Shivering, an inefficient method of increasing heat production, diminishes the ability to perform tasks that require dexterity. The lowered skin temperature of the extremities has an influence on the ability to exert hand strength; it might be reduced by up to 50%. The increased metabolic costs of being in cold water, whether one is active or inactive, will result in reduction of the possible duration of the exposure, because available tank air will be used faster . It is quite evident that the placement of divers outside the submarine environment has consequences beyond those directly related to the quality of the air in their tanks. The degree and duration of projected activity will influence performance. As mentioned, the diver must contend at least with the inconvenience of having to work with markedly reduced blood flow to his extremities. Schmidt and Vandervoort (1987) have stated that the only means of heating divers in the field is via a hotwater umbilical line from the surf ace. Combat swimmers and divers operating from SEAL (sea, air, and land) delivery vehicles have inadequate heating. Diver-suit insulation (passive insulation) has improved, but remains inadequate to provide the thermal protection necessary for optimal performance. At first glance, it might appear that exercise during cold-water immersion would enable a diver to increase heat production enough to prevent a reduction in core temperature. However, Keatinge (1969) showed that, below a critical water temperature of 25°C, rectal temperature of swimmer decreased faster if subjects performed moderate exercise than if they remained at rest. A large amount of body fat has some protective value. Pugh and Edholm (1955) showed that, although a fat man was easily able to maintain his rectal temperature while swimming in 16°C water, his thin companion showed a larger decrease in rectal temperature during exercise than when immersed at rest. In general, the presence of body fat sufficient to provide a protective effect will reduce one's capability to perform as desired. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/E/feclS of Breathing Major Gases Interactions The effects of N2 narcosis are potentiated by many factors, such as alcoholic-beverage consumption (Jones et al., 1979; Fowler et al., 1986), fatigue and exertion (Adolfson, 1964, 1965), apprehension and anxiety (Davis et al., 1972), and increases in exogenous or endogenous carbon dioxide (Hesser et al., 1971, 1978). Exercise tolerance and ventilatory responses to exercise are presumably influenced by those factors and by dehydration, fear, and perhaps inanition. Conditions and responses are so variable, and the interactions so little studied, that it is not possible to provide guidelines for reliable predictions. DIFFERENCES BETWEEN SURF ACEBASED AND SUBMARINE-BASED DIVING We consider here four factors that make diving from a submarine different from surface-based diving: • Total pressure in the submarine can vary from SSO to 850 torr. • The N2 fraction in the submarine can vary from 0.789 to 0.816. • The 0 2 fraction in the submarine can vary from 0.184 to 0.211. • The CO2 fraction in the submarine is always high, averaging 0.6%. Total Pressure To the extent that total pressure in the submarine departs from 1 A TA, divers can be saturated with N2 at PN2 other than the usual value of 600 torr (0.79 x 760 torr) before dives and return to pressures other than 1 AT A after dives. The potential problems after a dive are of two kinds: if total pressure is low, the probability of bubble formation is increased; and if the PN2 is high, the rate at which N2 is washed out of the body can be decreased. The difficulties are similar to those of diving at altitude: the variable conditions make it hard to establish appropriate decompression schedules, increase the risk of decompression sickness, and complicate repetitive diving and decompression schedules. If the pressure swings are small (say, 109 1.S%•), or do not occur within 24 h of a dive, they can probably be ignored. Nitro1en Fraction In the submarine, the product of N2 fraction and total pressure determines the inspired PN2• Variations in the N2 fraction influence predive N2 saturation and postdive N2 washout, as outlined above. They also determine the inspired PN2 during a dive. If the N2 fraction in the diver's tank is higher than 0.79, then both N2 narcosis and N2 uptake will be greater than expected at any depth. The latter will make decompression schedules more difficult and presumably increase the risk of the bends. The difficulties are similar to those of mixed-gas (e.g., SO% N2 and SO% 0 2) diving: divers will have to be aware of their equivalent air depth (EAD), and not just gauge depth. However, if the N2 fraction in submarines and their air banks IS held within narrow limits, these issues can probably be ignored. Oxy1en Fraction Within the currently allowable range, variations in the O fraction in submarines and diver's tank wilf not lead to significant Qi toxicity when the air is breathed at 1-6 A TA for up to 12 h. Such variations can probably therefore be ignored. Carbon Dioxide Fraction Carbon dioxide is a major issue for submarine-based SCUBA divers, so we discuss it here in detail. The CO2 in inspired (atmospheric) air is ordinarily negligible, about 0.03% by volume. Multiplying the inspired fraction by the total •standard U.S. Navy dive tables are used without making allowances for changes in barometric pressure. Barometric pressure at sea level rarely varies by more than 3% (Yarkin, NOAA, personal communication), so pressure swings half as great should be safe for divers from submarines. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. JJO pressure gives the inspired partial pressure; at sea level, 0.0003 x 760 gives an inspired PCO2 of about 0.2 torr. CO2 is produced by aerobic metabolism in amounts averaging about 80% of the volume of 0 2 consumed, ranging from 0.2 L/min in adult humans at rest to over 5 L/min in extreme exercise. A person consuming 3,000 kcal/d in his diet produces CO at about 500 L/d (0.35 L/min); it constitutes a1t,out 3% of his expired air (at I AT A, and if inspired air is free of CO2). The partial pressure of CO~ in alveolar gas (thus in the body as a whole) is ordinarily regulated by adjusting alveolar ventilation (~ A) to be about 20 times the CO2 production (~CO 2). Thus, the normal alveolar CO2 fraction is about 5.6%, and the alveolar PCOz. is about 40 torr . Departures can occur--l"or example, when ~ A/~CO is low (hypoventilation). Some of the effec& are outlined below. The CO2 exhaled into a submarine's environment has to be removed by chemical scrubbers to prevent its accumulation. Assuming that the scrubbers remove all the CO2 from gas passing through them ( 100% efficiency), the steady fraction of CO2 in the boat's environment is, in principle, equal to the ratio of CO2 input (summed crew ~CO 2) to scrubber flow. That is, the boat's air can be maintained as nearly free of CO2 as desired, at the cost of geometric increases in scrubber flow . The practical compromise between that cost and the undesirable effects of long exposure to high inspired PCO2 is now struck at a 90-d threshold limit value (TL V) of 0.8% (about 6 torr) (U.S. Naval Sea Systems Command, 1979). Current scrubbers are only about 70% efficient, so a continuous scrubber flow of about 60 L/min (2 cfm) for each man is implied. A CO2 concentration range of 0. 7-1 .0% during Polaris patrols was reported in 1979 (Schaefer, 1979); more recent averages are around 0.6% (Weathersby et al., 1987), implying a scrubber flow of around 3 cfm per man. The inspired PCO2 for submarine crews is higher than usual, about 6 torr. That tends to raise alveolar and arterial PC~ in submariners, with several consequences (Consolazio et al., 1947; Guillerm and Radziszewski, 1979; Schaefer, 1975, 1979). Breathing is stimulated, so resting ventilation increases by approximately 20% and the alveolar PCO2 rises by about 2 torr (Schaefer, 1979). This very mild chronic respiratory acidosis is partially offset by a normal renal compensatory response. Such compensation is incomplete, so there is a slight residual acidemia; that is, the blood is slightly less than Submarine Air Quality normally alkaline, with an arterial blood pH that is about 0.03 below its normal value of 7 .40. But these are small changes, within the range of normal variation for humans, which are functionally insignificant or nearly so. They may be compared with larger abnormalities tolerated for months or years by diseased humans; for example, arterial PCO2 over SO torr is not uncommon in advanced chronic obstructive pulmonary diseases (COPD). Inspired CO2 concentrations of 3% (21 torr) were "long regarded as suitable in the U.S. Navy" (Behnke and Lanphier, 1965) before the advent of nuclear submarines . Those were shorter exposures, however, and those with higher CO2 concentrations were associated with significant symptoms and impaired function. There is more to the subject than the above simple summary indicates. First, a great deal is known about chronic CO2 exposures on submarines. Acid-base state varies with time over periods of days to weeks, and there are measurable effects in several organ systems (Schaefer, 1979). Second, a great deal is uncertain and unknown about such exposures. What happens to the ventilatory responses to exercise and to exercise tolerance of people acclimated to, and breathing, inspired CO2 at a partial pressure of 6 torr? What if they are acclimated to that PCO2, but exercising with higher or lower PCO? wien gas is compressed and used by divers at pressures greater than I AT A, the inspired CO2 fraction is unchanged, but its partial pressure increases with the absolute pressure at which the gas is breathed. At 6 AT A, surface air (0.03% CO2) has a CO2 partial pressure of 0.0003 x 760 x 6, or 1.4 torr. If gas from a submarine containing I% CO2 were breathed at 6 ATA, the inspired PCO would be 0.01 x 760 x 6, or 46 torr--greater tfian the normal alveolar PCO . During acute exposures under those con~tions, alveolar PCO2 might rise to 55 torr or more, and there wouht be distressing symptoms, including headache and breathlessness at rest, with marked impairment of exercise and other performance (Consolazio et al., 1947; Schaefer, 1975, 1979). If 6 torr is an acceptable inspired PCO2 in acute hyperbaric states, as in chronic normobaric states, then at 6 AT A the compressed gas must be no more than 0.13% CO2, i.e., one sixth of the value now accepted in submarine atmospheres . We found no satisfactory basis for specifying this or any other inspired PCO2 greater than zero as acceptable during violent Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/Effects of Breathing Major Gases exertion at pressures up to 6 AT A, but it is clear that submarine air must be further scrubbed of CO if it is to be used by divers (Weathersby et af., 1987). That should be done by passing divers' air through a lithium hydroxide scrubber as their tanks are filled from the boat's air banks (U.S. Naval Sea Systems Command, 1986), reducing the CO2 fraction to around 0. I%. Divers will presumably be acclimated to the submarine atmosphere and thus display the respiratory, acid-base, and other effects of chronic mild hypercapnia. We do not know the effect, if any, of that background on the performance of divers; we think it is worth study. 111 Ideally, all CO2 should be removed from the gas to be breathec:1 by SCUBA divers. Variations of up to about 1.5% in PN2 (around 600 torr) and in total pressure (around I AT A) in submarines are probably insignificant for submarine-based SCUBA divers. •Larger variations might increase the risk of decompression sickness. Research is needed to see whether chronic adaptation to mild hypercapnia affects the performance of SCUBA divers while they are breathing gas free of CO2 or containing some CO2• •standard U.S. Navy dive tables are used without making allowances for changes in barometric pressure. Barometric preuure at sea level rarely varies by more than 3% (Yarkin, NOAA, personal communication), so preuure swings half as great should be safe for <liven from submarines. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. CHAPTERS EFFECTS OF BREATHING SUBMARINE AIR CONTAMINANTS AT UP TO 6 ATA Submarine air contains not only major gases (0 2 and N2), but also contaminants that result from emission from human activities, from structural materials, and from equipment required to operate the submarine and complete its military missions. This chapter discusses the potential health effects of two major submarine air contaminants--carbon monoxide and cigarette smoke--and of trace contaminants, with reference to the use of the submarine air for divers operating at up to 6 AT A. CARBON MONOXIDE Carbon monoxide (CO) on submarines has various sources, including incomplete combustion of cooking, smoking, and engine operations. The 90-d continuous exposure guidance level recommended by the National Research Council Committee on Toxicology for CO is set at 20 ppm or 1 S.2 millitorr (National Research Council, 1984a). CO in submarines undergoing sea trials has been reported at 1-5 millitorr (up to 6.6 ppm) (Rossier, 1984). Smokers would, of course, be exposed to higher concentrations (see the next section on tobacco smoke). CO in inhaled air binds to hemoglobin (Hb) and forms carboxyhemoglobin (COHb) after passing through the alveolar membrane. The ratio of Hb affinity for CO to its affinity for 0 2 is approximately 235: I. The principal mechanism by which CO exerts its toxic effect in 113 mammals is commonly accepted to be by the reduction in blood O -carrying capacity (Coburn, 1979). Althougl research on environmentally relevant CO exposure remains to be done, it is also possible that CO itself is cytotoxic (Piantadosi et al., 1985, 1987). Pharmacoklnetlcs The formation of COHb has been described by Coburn et al. (1965) with a differential equation. On the basis of that equation, Figure 4 has been constructed to depict the formation of COHb (in percent saturation) for various CO concentrations as a function of time. The Coburn et al. equation was also used to predict COHb formation and elimination at I and S AT A with exposure at 25 ppm. The 5- A TA results are appropriate to the case in which normobaric air containing CO at 25 ppm is compressed to 5 AT A. The results for COHb formation are shown in Figures 5 and 6 and for elimination in Figures 7 and 8. The figures must be interpreted with caution, because they are predictions based on a model that has not been tested in this context. The provisional conclusion that can be drawn from the figures is that increased atmospheric pressure increases the rate of COHb formation, but does not change the asymptotic concentration (Figures 5 and 6) and increases the rate of elimination (Figures 7 and 8). That holds true only if the -- - Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. CHAPTERS EFFECTS OF BREATHING SUBMARINE AIR CONTAMINANTS AT UP TO 6 ATA Submarine air contains not only major gases (0 2 and N2), but also contaminants that result from emission from human activities, from structural materials, and from equipment required to operate the submarine and complete its military missions. This chapter discusses the potential health effects of two major submarine air contaminants--carbon monoxide and cigarette smoke- -and of trace contaminants, with reference to the use of the submarine air for divers operating at up to 6 ATA. CARBON MONOXIDE Carbon monoxide (CO) on submarines has various sources, including incomplete combustion of cooking, smoking, and engine operations. The 90-d continuous exposure guidance level recommended by the National R Council Committee on Toxicology for at 20 ppm or 15.2 millitorr Council, 1984a). CO sea trials to6.6 mammals is commonly accepted to be by ~he reduction in blood O -carrying cap~cJty (Coburn, 1979). Althougfi research on_environmentally relevant CO exposure ~emai~s to be done, it is also possible that CO itself is cytotoxic (Piantadosi et al., 1985, 1987). I I I I • , . , . . . , • , . • I , . , • I J ,, • • • , , . , , . . . ' ';.t s, o- ect. 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0.0 ,, s::i ., ~- 0 100 200 300 400 500 600 700 800 "' :i... MINUTES :;· I<::) s ~-- FIGURE 4 Projected COHb formation as function of time for CO exposures. Projections generated. by use of Coburn et al. (1965) equation. For alveolar ventilation of IO L/min at I A TA. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/Effects of Breathing Submarine Air Contaminants at Up to 6 ATA ll5 \\ \ \ \ \ 8 \ \ II) \ \ \ \\ \ ' \ \ \\ I 8 \ \ 'O' e C. \ \ C. "' \ \ \ N ... OS \ \ -.&! 0 It) u \ \ \ - ... u, 0 . 8 w '- C: .... \' \ ... «> e " :) e- z ·;: ..J \ \ :i '-0 ON ~} ~~' C: I o"' ?~ ?o\ ••«.. t,o ~\ ~,, C: (II

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0 0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0,5 ,o \J~(\ ----- ---~ _.,,..::;...- _____ ,__--=- - / ~ ""- .,,,---- -----------· ~ ~~ ---- ~ .. , ---- ~ ,J ,JI!':-;,,,, ft. \J~(\ ,, ,,-- / , "" ,,-' // ,, .... / /// ,,,,,"·' // ,,/' I I ,, I ,, ~/ / ,, / ,,11 ll ,' t~I fl/ ,, 0.0 -W• W w i W a • w w • t W w WWW W • WW I W w WW I a i WU I• W • * • i W **I WU i • WW WW• • *•* i 1 * 9 c I i 0 100 200 300 MINUTES FIGURE 6 Projected COHb formation as function of time for CO at 25 ppm in air, compressed to 5 ATA at alveolar ventilation rates of 5-20 L/min. 400 500 600 .... .... °' i ~ i' i)i,,. ~- i ~-- Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/E//ects of Breathing Submarine Air Contaminants at Up to 6 ATA .,., q .,, .,,; C) 1ft .. c-; c-; N ~ II? q .,, 0 ... .,.. C) C) (%)qHOO 117 8 N g ... C) C: ·e -..J 0 N I c.. "' 0 § OS .. C .9 ... ~ - -C G) > .. OS 0 G) > (U .. ~ .. ·; 0 ·t: OS .0 0 e .. 0 C .5 C .9 - OS C: ·e ... "i> .0

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" ' .........._ ......... -.._ 1S•• VltJ/11 --------------. 0 0 -I I C U U U C U U • • • I V i U U I U ........... __ 201.1n,i;-----------=== ~- -- ----•-- w u I u u w I u u o u e ........ . . . . . .. - W I i C V W W U o W U I u W i • I W ... 0 100 200 300 MINUTES 400 500 FIGURE 8 Projected COHb elimination at 5 AT A pressure for alveolar ventilation rates of 5-20 L/min. 600 .... .... 0o ~ ~ i" ~ .... ., lO §. ~- Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/E/fects of Breathing Submarine Air Contaminants at Up to 6 ATA JJ9 PCO-to-PO 2 ratio remains constant. Data published by Rose et al. (1970) support the prediction that asymptotic COHb concentrations are not changed by increased pressure, but no data on COHb formation rate are available. If those predictions regarding COHb formation under pressure are verified, then, at least for purposes of studying COHb pharmacokinetics, the asymptotic COHb concentration is not a function of PCO, but of the ratio, PCO/PO2• This is because CO competes with O for binding sites on hemoglobin. It remains true, however, that, for exposure periods that are shorter than one time constant (time to reach 63% of equilibrium value) for COHb formation, more COHb would be formed under high pressure than would be formed with the same CO concentration at normal pressure; the reason is the predicted pressure-associated increase in the rate of COHb formation. Other mechanisms have been postulated whereby CO could reduce 0 2 transport. Carbon monoxide can bind to intracellular hemoproteins, such as myoglobin and cytochrome oxidase and binding depends on the relationship of 02 tension (P02) and CO tension (PCO) to CO bmding constants (Coburn, 1979). The affinity of cytochrome oxidase for CO is similar to that for 0 2• This is in marked contrast to the much higher affinity for CO over 0 2 exhibited by myoglobin (30-50x) and hemoglobin (235x). Thus, cytochrome oxidase is less likely to be responsible for impairing diffusion of 02 to the mitochondria than are proteins with high CO/O2 affinity ratios. However, if steep 0 2 tension gradients exist between the extracellular and intracellular environments, then the PO2 surrounding the mitochondrial terminal oxidase would be low enough for increased binding with CO. That hypothesis was tested by Coburn (1979) in studies on isolated vascular smooth muscle. He concluded that significant CO binding to cytochrome oxidase was unlikely to be an in vivo mechanism of CO toxicity in that tissue. Myoglobin binding was also unlikely, because it is absent or present in only low concentrations. Carbon monoxide might bind to hemoproteins other than hemoglobin, to myoglobin, or to cytochrome oxidase. Cytochrome P-450, tryptophan deoxygenase, and tryptophan catalase all have high enough binding affinities for CO in specific tissues to be considered as possible candidates (Coburn, 1979). The binding of CO to myoglobin in heart and skeletal muscle might be high enough to reduce intracellular oxygen transport in those tissues (Coburn, 1979; Agostoni et al., 1980). Using a computer simulation of a three-compartment model (arterial blood, venous capillary blood, and tissue myoglobin), Agostoni et al. (1980) predicted that conditions would be favorable for formation of carboxymyoglobin at COHb concentrations of 5-10%, particularly where the PO2 was low in normal physiologic conditions (e.g., in subendocardium) and when hypoxia, ischemia, or increased metabolic demand was present. This model for formation of carboxymyoglobin could provide theoretical support for experimental evidence of myocardial ischemia, such as electrocardiographic irregularities and decrements in work capacity (discussed later). However, it is not known whether binding of CO to myoglobin could cause health effects (e.g., decreases in maximal oxygen consumption during exercise) at COHb concentrations as low as about 4-5%. Additional research is needed for this possibility to be more definitively evaluated. Neurobehavioral Effects Brain Energetics Blood O2-carrying capacity is reduced in proportion to the hemoglobin available for 0 2 binding, but the presence of COHb in the blooci or the reduction in 0 2 supply triggers a compensatory increase in cerebral blood flow (CBF) (HAggendal et al., 1966; Paulson, 1977; Traystman and Fitzgerald, 1977; Doblar et al., 1977; Traystman, 1978). The adequacy of compensatory CBF responses can be judged by the tissue partial pressure of 0 2 (PtQ2) or, as a surrogate, the venous partial pressure of 0 2 (PVO ). From such measurements and calculations ~Paulson, 1973; Zorn, 1972; Miller and Wood, 1974; Forster, 1970; Permutt and Farhi, 1969), it appears that PtO2 falls by about half the amount that would be expected if no compensatory action were occurring. Apparently, the compensatory increase in CBF is not adequate to prevent the fall of PtO2 due to increased COHb. However, the amount of 0 2 consumption in the brain, as measured by Traystman and Fitzgerald ( 1977) and Traystman (1978) as a function of COHb in anesthetized dogs, did not change significantly until concentrations exceeded 30%. The latter findings could be used to argue that the compensatory mechanisms of increased CBF were adequate. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 120 The issue of adequacy of compensatory mechanisms remains to be resolved. Central Nervous System Functional Effects The literature on the motor, sensory, and vigilance effects of increased COHb is large and internally inconsistent. No neurobehavioral data were reported on CO effects at increased pressures. Despite the lack of consistency, it appears that COHb as low as 5% at normal pressures will sometimes deleteriously affect some aspect of motor coordination, visual sensitivity in dim light, and possibly alertness. Many references are available to document that conclusion, as follows. Motor Effects. Accuracy in various target tracking tasks appears to be decreased by COHb of 5% (Putz et al., 1976; Putz, 1979; Benignus et al., 1987; Wright et al., 1973; Rummo and Sarlanis, 1974), although other tracking tasks were not affected (O'Donnell et al., 197 la; Forbes et al., 1937; Weir and Rockwell, 1973; McFarland, 1973). Task complexity seems to increase the effects of CO (Bender et al., 1971, 1972). Other kinds of motor behavior seem not to be affected (Stewart et al., 1970, 1975; Wright et al., 1973; Fodor and Winneke, 1972; O'Donnell et al., 1971 a). Sensory Effects. Small but reliable concentration-related decreases in visual sensitivity were reported by McFarland et al. ( 1944) and Halperin et al. ( 1959) when COHb was increased to values ranging from 4.5 to 19.7%. Critical flicker fusion was decreased at similar concentrations (Seppanen et al., 1977). Many other sensory abilities seem to be unaffected by COHb up to 26% (Stewart et al., 1970; Wright et al., 1973; Ramsey, 1972, 1973; Fodor and Winneke, 1972; Guest et al., 1970; Lilienthal and Fugitt, 1946; O'Donnell et al., 1971 b; Vollmer et al., 1946; Von Post-Lingen, 1964). Beard and Wertheim (1967) reported that timeduration judgments were affected by COHb, but others have been unable to confirm that ( O'Donnell et al., 1971 b; Stewart, 197 5; Stewart et al., 1973; Otto et al., 1979; Mikulka et al., 1970). Vigilance Effects. Impairment of vigilance might be among the effects of COHb up to 6% (Horvath et al., 1971; Fodor and Winneke, 1972; Submarine Air .Quality Beard and Grandstaff, 1970), but some have failed to show such impairment (Christensen et al., 1977; Winneke, 1974; Roche et al., 1981; Benignus et al., 1977). Pulmonary Function and Exercise Maximal Work The work of Chiodi et al. ( 1941) and Roughton and Darling (1944) indicated that work capacity is reduced to zero when COHb approaches 50%. Goldsmith (1970) reported that competitive swimmers' performance is impaired when events are conducted in atmospheres containing CO at 30 ppm. Oxygen Uptake and Heart Rate The presence of COHb does not appear to affect 0 2 uptake during submaximal work (Brinkhouse, 1977; Chevalier et al., 1966; Ekblom and Huot, 1972; Ekblom et al., 1975; Gliner et al., 1975; Nielsen, 1971; Pirnay et al., 1971; Vogel and Gieser, 1972); Chevalier et al. (1966) and Klein et al. (1977) studied men with a light workload and reported that, although 0 2 uptake was not affected by COHb of 4%, there was a significant increase in 0 2 debt in relation to total 0 2 uptake. Klausen et al. ( 1968) found no differences in energy expenditure related to CO. Vogel and Gieser (1972), Pirnay et al. (1971), and Gliner et al. (1975) reported higher heart rates at submaximal workloads and increased ventilation per unit of 0 2 uptake with COHb of 15-20%. Aerobic Capacity In short-term maximal exercise of several minutes, in which capacity for effort depends mainly on aerobic metabolism, it is reasonable to predict that maximal aerobic capacity would be diminished approximately in proportion to the concentration of COHb. Such diminution in VO x when COHb is 7-33% has been observed by ~ppanen (1977) and Ekblom et al. (1975). There is a linear decline in VO2max. as COHb ranges from 4 to 33% (Horvath, 1981 ). Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/Elfects of Breathing Submarine Air Contaminants at Up to 6 ATA 121 Cardiovascular System People in constant contact with CO are reported to develop ECG evidence of left ventricular hypertrophy and conduction system abnormalities (Zenkevic, 1973; Ejam-Berdyev, 1973; Komatsu, 1959). Davies and Smith (1980) studied subjects living continuously in a closedenvironment chamber for 18 d. During the middle 8 d, they were continuously exposed at CO concentrations of SO ppm, IS ppm, or 0 ppm (control). P-wave changes were observed in 6 of IS subjects at SO ppm and 13 of IS subjects at IS ppm, but in none of 14 subjects at 0 ppm. COHb concentrations were 0.4, 2.4, and 7.0% for exposure concentrations at 0, IS, and SO ppm, respectively. At higher ambient CO concentrations (75 ppm), 7 of 10 subjects had significant ECG changes. Effect of Hiah Pressure Other than the pharmacokinetic considerations mentioned earlier, no data on human CO effects under hyperbaric conditions are available. If the pharmacokinetic predictions prove correct, however, the effects of CO exposure at high atmospheric pressure should be the same as at normal pressure, except that the onset should be earlier because COHb is formed more rapidly. Rose et al. (1970) reported that the lethality of CO exposure was not increased by high atmospheric pressure, as long as the PCO:PO2 ratio remained constant. The latter finding supports the prediction that the effect of COHb would not increase at high pressure, although lethality is not a sensitive measure of adverse effects. More research is required to discover the interaction of COHb and hyperbaric conditions, in that the predictions were based on the idea that CO effects are due to hypoxia resulting from COHb formation. No account was taken of the possibility of cytotoxicity of CO in either normobaric or hyperbaric conditions. Summary The principal effect of CO appears to be hypoxia due to COHb formation, although CO cytotoxicity itself is also possible. COHb formation and elimination are predicted to be more rapid as atmospheric pressure increases, but the asymptotic concentration of COHb appears to be independent of pressure as long as the PCO/PO2 remains constant. Such neurobehavioral variables as motor coordination, visual sensitivity, and vigilance appear to be decreased when COHb is greater than 5%. The effects seem to depend heavily on the circumstances in which measurements are made. When COHb is as high as 5%, aerobic capacity is reduced in proportion to COHb. Oxygen uptake at COHb up to 20% is not affected during short exposures. Chronic CO poisoning may cause a myocarditis and in some cases myocardial infarction. Severity of these disorders increases with increasing CO blood levels (Graziani and Rossi, 1959). TOBACCO SMOKE Tobacco-smoking, which is permitted on U.S. Navy submarines, produces effects both in smokers and, via air pollution, in others (National Research Council, 1986a,b). The extent of tobacco-related pollution in submarine air is not known, and estimates are difficult to make, because tobacco smoke has so many components and their longevity is not known. Furthermore, the components might be removed, to an unknown extent, either by active "scrubbing" or as a side effect of compression of air in the air banks. Rossier ( 1984 ), in a report on the atmospheric control in a Trident submarine during a sea trial, noted an aerosol generation rate from cigarettes of 2.S g/h in the submarine. The cigarette-smoke generation rates were calculated on the basis of crew distribution in the submarine and 42.9 mg of aerosol produced per cigarette. A medical survey indicated that 40% of the 177 crew members were smokers, and an average of 77 packs of cigarettes were smoked per day (Rossier, 1984). This information indicates that cigarette smoke was a major source of aerosols in the submarine, but the report did not include analyses of other tobacco-smoke components. Despite the lack of estimates of tobaccosmoke components in submarine air, effects on smokers themselves are known. Cigarettesmoking induces a significant rise in the incidence of carcinoma of the lung and of coronary arterial disease (U.S. Surgeon General, 1964, 1982; Astrup and Kjeldsen, 1974; Kjeldsen, 1975). A recent National Research Council (1986a) report on environmental tobacco smoke Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 122 suggested that, although cigarette-smoking increases the risk of lung cancer in smokers by over 1,000%, the risk in nonsmokers frequently exposed to environmental cigarette smoke may increase as much as 30%. These diseases are long-term effects of smoking and would not be of immediate concern in connection with the shorter exposures expected in submarine duty, even in prolonged underwater patrols of 6-8 months. However, cigarette-smoking can be documented to have immediate effects that can alter performance, and these should be considered in relation to the environment of the submarine. Irritation Nonsmokers experience irritation of the nose, eyes, and throat when subjected to a smoky environment, and conventional air-cleaning systems often do not filter the irritating substances (National Research Council, 1986a,b), such as phenols, aldehydes, acids, and oxides of nitrogen. In industrial settings, high ventilation rates--perhaps over 50 ft3 /min per occupant-- are necessary to make room air acceptable to most nonsmoking adults when people are smoking cigarettes in the environment (National Research Council, 1986a). Some of the symptoms of irritation might be allergic reactions to constituents of the smoke, tearing of eyes, and complaints of noxious odors. Cardiovascular Effects Physiologic and Clinical Studies It has been noted for a number of years that cigarette-smoking increases the risk of coronary arterial disease (U.S. Surgeon General, 1983; U.S. Centers for Disease Control, 1986; Astrup and Kjeldsen, 1974; Kjeldsen, 1975). The mechanism of the increased risk is not clear, but it has been documented in a large national trial, the Coronary Artery Surgery Study (Kennedy et al., 1982). In that study, the risk of coronary arterial disease was significantly higher in males and females who smoked cigarettes than in nonsmokers. Cigarette-smoking can also produce a more acute effect on blood vessels than the development of disease in the coronary arteries. A recent article demonstrated that the risk of stroke was 2-3 times higher in male Submarine Air Quality cigarette-smokers than in nonsmokers (Abbott et al., 1986). Effects on Coronary and Other Arteries Studies on the effects of cigarette smoke on blood vessels can be divided into those based on isolated arteries or the intact heart and those based on clinical observations. Cox and coworkers (1984) used isolated segments of carotid and femoral arteries from dogs subjected to the smoking of 12 cigarettes/d for 2 years. They compared their data with data from unexposed controls and demonstrated a small increase in passive artery stiffness in the smoking animals. Active force generation in arterial smooth muscle was reduced in the smoking animals' arteries, and their arteries were less sensitive to the constricting effects of potassium. That study in isolated blood vessels demonstrated a direct effect of chronic cigarettesmoking on the blood vessels of smoking dogs. The model, in which carotid and femoral arteries were studied, suggested that arteries throughout the body can be affected by chronic cigarette-smoking. Studies of skin circulation in humans have demonstrated reduced blood flow in the presence of cigarette-smoking (Waeber et al., 1984)--evidence of an acute vasoconstrictor effect. Recent human studies that examined myocardial perfusion suggested that smoking causes coronary vasoconstriction (Winniford et al., 1986, 1987; Maouad et al., 1984; Deanfield et al., 1986). In studies by Winniford and co-workers (Winniford et al., 1986, 1987; Deanfield et al., 1986), cigarettesmoking induced coronary vasoconstriction and a change in myocardial perfusion in patients with coronary arterial disease. Other studies have demonstrated a rise in blood pressure associated with cigarette-smoking (Richards et al., 1986; Martin et al., 1984). Additional Smoking Studies in Animals Human studies involving vasoreactivity and effects of cigarette-smoking on blood vessels are based on the results of numerous animal studies that have shown alterations in vasoreactivity and myocardial function during or after cigarette-smoking. A study by Piascik and coworkers (Piascik et al., 1985) showed that 23 weeks of exposure to cigarette smoke in rats caused an increase in coronary vasoreactivity Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/E/fects of Breathing Submarine Air Contaminants at Up to 6 ATA 123 responses to angiotensin-induced vasoconstriction. As in human studies, Gillespie and co-workers (Gillespie et al., 1985) found that nicotine exaggerated release of norepinephrine from hearts of atherosclerotic rabbits. That result supported several clinical observations and suggested that smoking affects coronary and other vessels through the sympathetic nervous system. Studies of nicotine alone, which has actions like those of acetylcholine, have demonstrated changes in the heart directly related to its action. Fenton and Dobson (1985) demonstrated that nicotine augments cardiac contractility and oxygen consumption independently of sympathetic influences and increases the release of adenosine in the coronary circulation. In a study of chronically smoking dogs, cigarettesmoking led to an increase in myocardialinfarct size (Sridharan et al., 1985). The combination of nicotine and alcohol reduced cardiac contractility in dogs given both cigarettes and alcohol for 18 months (Ahmed et al., 1985). Some of the cardiovascular effects of smoking might be related to high CO in cigarette smoke. However, the contribution of CO has not been isolated from the contributions of other smoke constituents. CO effects on the cardiorespiratory system have been reviewed (Turino, 1981; Ahmed et al., 1980). In a study by Lough (1978), guinea pigs were exposed to the smoke of eight cigarettes/d, 5 d/week for 12-15 weeks. The heart rate of the smoking animals was found to be significantly increased. Toxic changes associated with edema, increased lipids, and increased lysosomal activity were noted in the myocardial mitochondria. The investigator suggested that the cardiomyopathy probably caused by CO from cigarette smoke resembles the changes of chronic intermittent hypoxia. Wanstrup and co-workers (1969) demonstrated that the endothelial surface of arteries can be damaged by prolonged exposure to CO. Endothelial cells play a major role in maintaining normal coronary vasoregulatory tone (Brum et al., 1984), and regulatory mechanisms can be damaged by inhalation of CO in cigarette smoke. Results of studies by Astrup and co-workers (Astrup et al., 1967) indicated that chronic CO exposure of cholesterol-fed rabbits augmented the development of atherosclerosis. Castro de Souza and co-workers (1977) showed that nicotine causes release of vasopressin, a potent vasoconstrictor. Studies that attempted to separate the effects of nicotine from those of other constituents of cigarette smoke in dogs demonstrated a slight reduction in left ventricular performance and an increase in blood pressure, but no myocardial hypertrophy or ultrastructural abnormalities (Ahmed et al., 1976). Interstitial fibrosis was evident in animals given both cigarette smoke and nicotine and led the authors to conclude that the cardiovascular abnormalities depended on the nicotine in cigarettes. Reece and Ball (1972) examined the effects of cigarette smoke on treadmill exercise in dogs; they found a rapid reduction in exercise capacity when animals were exposed to cigarette smoke while exercising. Summers and coworkers (1971) noted that cigarette-smoking increased the excretion of lactate by the heart in patients with severe coronary atherosclerosis. Other data show that cigarette-smoking can damage blood vessels in the heart. Auerbach and co-workers (1971) demonstrated that myocardial arterioles increased in thickness in dogs exposed chronically to cigarette smoke and in smokers who died from unrelated causes. In summary, reports of animal studies of the effects of cigarette smoke or nicotine on the cardiovascular system confirm that cigarette smoke causes vasoconstriction of blood vessels. Apparently, cigarette smoke can directly augment the reactivity of blood vessels in the presence of such vasoconstrictors as vasopressin and angiotensin. Carbon monoxide in cigarette smoke alters endothelial function in animals, and both CO and cigarette smoke accelerate atherosclerosis in experimental models. Cigarette smoke appears to affect the myocardium directly (Klein et al., 1983). That is a long-term effect; it is manifested by reductions in cardiac contractile performance and apparent structural anatomic changes, such as fibrosis in large animals and damage to mitochondria in small animals. In addition, cigarette-smoking can increase myocardial-infarct size in experimental animals, can lower the threshold of fibrillation in response to ventricular tachycardia in acute myocardial infarction in animals and accelerate atherosclerosis, and can result in acute vasoconstriction of coronary and other blood vessels. Those characteristics suggest that the effects of cigarette-smoking in the submarine environment deserve more attention; longterm effects, such as carcinoma of the lung and increased incidence of atherosclerosis, are clearly not the only major health factors associated with cigarette-smoking in this enclosed environment. The fact that cigarette-smoking alters exercise performance, can produce Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 124 ischemia in patients with coronary arterial disease. and is known to affect pulmonary function indicates that smokers are likely to perform suboptimally, especially when strenuous physical activity is required. Neurobehavloral Effects A short-term decrement in performance of a critical task by a person exposed to tobacco smoke can have immediate effects on many other persons. Such immediate effects could produce consequences as important as chronic health effects. Effects of environmental tobacco smoke on neural and behavioral variables have not been studied, except for sensory measures. such as odor and irritation. An important body of literature does. however. exist on neurobehavioral effects of smoking in smokers themselves (Thornton. 1978; Emley and Hutchinson. 1984; Wesnes and Warburton, 1983b; Benningfield, 1984). Effects of tobacco-smoking on military task performance were recently reviewed extensively by Dyer (1986). Others have also reviewed the neurobehavioral effects of tobacco-smoking. This section reviews the effects of mainstream smoke and attempts to generalize them to the effects of environmental tobacco smoke at up to 6 AT A. Mainstream Smoke Of the approxima~ely 3,800 compounds identified in tobacco smoke (National Research Council, 1986a). few are present in sufficient quantities to rank as important contributors to acute neurobehavioral effects. The two outstanding exceptions are CO and nicotine. Motor tremor appears to increase with increased tobacco-smoking. Hull (1924) reported increased tremor. heart rate. and blood pressure after pipe-smoking. Habitual smokers showed greater effects than nonsmokers. Similar results were reported by others (Edwards. 1948; Frankenhaueser and Myrsten. 1968; Frankenhaueser et al.. 1970; Smith et al.. 1977; Lippold et al., 1980; Shiff man et al.. 1983; Heimstra et al.. 1967). Simple reaction time is reportedly decreased by smoking in persons habituated to cigarettesmoking (Heimstra et al., 1967; Smith et al., 1977; Wesnes and Warburton. 1983a. 1984). Comparison of habituated smokers with nonsmokers (Heimstra et al.. 1967) indicated that Submarine Air Quality smokers had the shortest reaction time while smoking. nonsmoking habituated smokers the longest reaction time. and nonsmokers reaction time between them. Cotten et al. (1971) studied habituated smokers and reported that the decrease in reaction time after smoking was only temporary and was followed by a "rebound" during which reaction-times were longer than normal. Thus. the improved performance in reaction-time tasks after smoking in habituated smokers is temporary and comes at the price of a later decrement when there is no smoking. as during diving. In persons habituated to cigarette-smoking. smoking appears to improve performance of tasks that involve vigilance (Hull. 1924; Tarriere and Hartemann. 1964; Heimstra et al., 1967; Frankenhaueser et al., 1971; Myrsten et al., 1972; Wesnes and Warburton. 1983b; Wesnes et al.. 1983; Tong et al.. 1980; Williams. 1980). In general. the vigilance performance of habituated smokers while smoking declined least as a function of time. that of habituated smokers not permitted to smoke declined most. and that of nonsmokers (when included) declined to a degree between those. Again, it is noteworthy that the nonsmoking habituated smoker is worse in vigilance performance than the nonsmoker in the same circumstances. Thus. for habituated smokers. the improvement in vigilance and reaction time is temporary and comes at a cost in performance during times when smoking is not going on. Combined Effects of Mainstream Smoke and Other Substances The combined effects of smoking and exposure to other substances on neurobehavioral variables are only rarely reported. Smith et al. (1977) studied effects of smoking and caffeine administration in habitual smokers. Effects of smoking and ethanol administration on vigilance in habitual smokers were studied by Tong et al. ( 1980). They studied the eff ec\J of smoking and ethanol on two-flash discrimination. In most instances. the results indicated additive effects in the directions expected from the drugs used. For example, the effects of a stimulant and a depressant usually nullified each other. and the effects of two stimulants were additive. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/Ef/ects of Breathing Submarine Air Contaminants at Up to 6 ATA 125 Neurobehavioral Effects of Environmental Tobacco Smoke from Systemic Uptake Limited studies are available on the neurobehavioral effects of environmental tobacco smoke, such as those related to odor or irritation. However, some informed speculation can be made about such effects from knowledge of effects of environmental tobacco smoke and observations of body burdens of some smoking products in nonsmokers. Such findings may be compared with those in active smokers, and the effects of mainstream smoke may be extended (with caution) to possible (or likely) effects of exposure to environmental tobacco smoke. Exposure to environmental tobacco smoke has been reported to produce no increase in COHb in nonsmokers (Foliart et al., 1983). It has also been reported to produce an increase comparable with that in a smoker who has just consumed one cigarette (Jarvis et al., 1983). Unless specific conditions are known or in situ measurements of COHb are made, the neurobehavioral importance of environmental tobacco smoke is difficult to estimate. In most studies of the concentrations of nicotine and cotinine (a metabolite of nicotine) in the blood of nonsmokers exposed to environmental tobacco smoke, the values were only a few percent of those of smokers (National Research Council, 1986a). In the worst reported case (Hoffmann et al., 1984), blood nicotine contents of exposed nonsmokers were no more than 6% of those of smokers. Thus, at these concentrations, nicotine appears not to be neurobehaviorally important in nonsmokers exposed to environmental tobacco smoke. It can be conjectured that, when environmental tobacco smoke becomes neurobehaviorally important, it is COHb that is the variable of concern for nonsmokers. This conjecture implies that some of the neurobehavioral effects of environmental tobacco smoke exposure in nonsmokers should be similar to those of CO exposure (as discussed earlier in this chapter). Also, cigarette smoke can be a potent source of irritants, such as phenols, acids, and oxides of nitrogen. Summary An important source of particulate and volatile organic contaminants in submarine air is cigarette smoke. Cigarette-smoking adversely affects pulmonary function and exercise performance; increases the risk of lung cancer, heart disease, and several other diseases; and increases motor tremor. Recent reports and extrapolations indicate potential adverse effects of cigarette smoke on nonsmokers in the same enclosed space. In nonsmokers, environmental tobacco smoke can be acutely irritating to eyes and upper airways. It also produces noxious odors. The nonsmoking habituated smoker is less vigilant and has slower reactions than a nonsmoker in the same circumstances. Obviously, a diver cannot smoke while diving. TRACE CONTAMINANTS In addition to consideration of the effects of high pressure on breathing 0 2, CO2, N2, and CO, one must consider the potential toxic effect of the many trace contaminants found in submarine atmospheres. The objectives of this consideration are as follows: • To determine which contaminants normally found on submarines might pose the greatest hazards if such atmospheres were used as breathing gases for divers at 1-6 AT A for missions lasting up to 12 h. • To determine exposure criteria for trace contaminants at these pressures and for these durations of exposure. • To determine whether exposure to multiple trace contaminants at high pressure might have additive or synergistic effects. The first two objectives are addressed in this chapter; the third is the subject of Chapter 6. Toxicity of Contaminants Careful perusal of the data on concentrations of trace contaminants (Table A-1, pp. 60-65) found in submarine atmospheres and on emergency and continuous exposure guidance levels for atmospheric contaminants (National Research Council, l 984a,b,c, l 985a,b, 1986c, 1987a) and exposure limits recommended by other agencies (Table 12) reveals that the contaminants of greatest concern are in four toxicologically functional categories: those which produce central nervous system depression; those which affect the cardiovascular system; those which produce irritation of eye, nose, throat, and respiratory system; and those which are known or suspected human Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 126 Submarine Air Quality TABLE 12 Exposure Limits for Airborne Contaminants (Limits are in ppm Unless Otherwise Noted) OSHA8 ACGIHb Navyc NRC8 NRC1 8-h 8-h 90-d DDSd 90-d EEGLs Compound TWA ILY-TWA Limi1 TWA CEGL ~ 1=h_ Acetaldehyde 200 100 0.01 so Acetonitrile 40 40 10 Acrolein 0.1 0.1 0.1 0.025 0.01 0.01 0.05 Ammonia so 25 25 12.S so 100 100 Arsine 0.05 o.os 0.01 0.0125 0.1 1.0 Benzene9 10 10 1 0.25 2 so Bromine 0.1 0.1 0.025 Butyl cellosolve so 25 12.S Carbon dioxide S,000 S,000 8,000 1,250 Carbon disulfide 20 10 0.25 so Carbon monoxide so so IS 12.S 20 so 400 Carbon tetrachloride 10 s 2.S Chlorine l(C) 1 0.1 0.25 0.1 o.s 3 Chlorobenzene 75 75 19 Chlorodiphenyl (PCB) l h th o.2sh ( 42% chlorine) Chlorodiphev.yl (PCB) 0.Sh 0.5h o.12sh (54% chlorine) Chlo roe thane 1,000 1,000 250 Chloroform 9 S0(C) 10 12.S 1 30 100 Cumene so so 12.S Cyclohexane 300 300 75 1,2-Dichloroethylene 200 200 so Dimethyl formamide 10 10 2.S Dioxane 100 25 25 Di-sec-octyl 5h 5h l.2Sh phthalate Ethyl acetate 400 400 100 Ethyl benzene 100 100 25 Ethylene dichloride so 10 12.S Ethylene glycol S0(C) 12.S 4 20 40 FC ll 1,000 l,0OO(C) s 250 100 soo 1,500 FC 12 1,000 1,000 200 250 100 1,000 10,000 FC 113 1,000 1,000 250 100 500 l,S00 FC 114 1,000 1,000 200 250 100 1,000 10,000 Formaldehyde' 3 1 o.s 0.75 Heptane soo 400 125 Hexane 500 so 125 Hydrazine 9 l 0.1 0.25 0.25 o.oos 1 0.121 Hydrogen chloride S(C) S(C) 1 1.25 o.s 20 20 Hydrogen fluoride 3 3(C) 0.1 0.75 Isopropanol 400 400 so 100 200 400 Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/E//ects of Breathing Submarine Air Contaminants at Up to 6 ATA Compound Methanol Methyl acetate Methyl bromide Methyl cellosolve Methyl chloride Methyl chloroform Methylene chloride" Methyl ethyl ketone Methyl isobutyl ketone Naphthalene Nitrogen dioxide Nonane Octane Ozone Perchloroethylene Phenol Phosgene Styrene Sulfur dioxide Toluene I , I ,2-Trichloroethane Trichloroethylene Trimethyl benzene Vinyl chloride" Vinylidene chloride Xylene OSHA8 8-h DA 200 200 20(C) 2S 100 3SO soo 200 100 10 S(C)J soo 0.1 s 0.1 100 s 200 10 100 s IO 100 TABLE 12 ( contd) ACGIHb Navyc 8-h 90-d ILY-TWA Limi1 200 200 s s so 3SO so 200 so 10 3 200 300 0.1 so s 0.1 so 2 100 10 so 2S s s 100 10 2.S o.s 0.02 1.2S I so 2S I 2 so DDSd TWA so so s 6.2 2S 88 12S so 2S 2.S o.2sJ so 12S 0.02S 12.S 1.2S 0.02S 2S I.2S so 2.S 2S 6.2S I.2S 2.S 2S NRC- NRCf 90-d EEGLs CEGL ~ .1=h.... 0.02 0.01 I 20 O.IS so 10 0.041 0.1 0.02 s 100 10 100 200 1.0 0.2 10 200 200 127 80ccupational Safety and Health Administration (OSHA) 8-h TWA. C • ceiling. Many of the TW As were proposed in 1968 and have not been revised. bAmerican Conference of Governmental Industrial Hygienists (ACGIH) (1986) recommended Threshold Limit Values-Time Weighted Average (TLV-TWA) for 8-h workday. C • ceiling. ~avy 90-d limits (U.S. Naval Sea System Command 1979). dory Deck Shelter recommendations (U.S. Naval Sea Systems Command, 1986) for exposure limits for diver's air based on dividing OSHA TWA by 4. ~ational Research Council's recommended 90-d continuous exposure guidance levels (CEGLs) ~National Research Council, 1984a,b,c, 198Sa,b, 1986c, 1987a). National Research Council's recommendations for 1-h and 24-h emergency exposure guidance levels (EEGLs) (National Research Council, 1984a,b,c, 198Sa,b, 1986c, 1987a). "Carcinogen or suspected carcinogen. hconcentrations in ma/m 3• 1Short-Term Public Emergency Guidance Levels (SPEGLs) (National Research Council, 1985a,b). lNIOSH has a I ppm ceiling (15 min) for nitrogen dioxide. This is the limit listed in the U.S. Navy Interim Air Purity Guidelines for Dry Deck Shelter (DDS) Operations and is the basis for the 0.25 ppm limit for the DDS (U.S. Naval Sea Systems Command, 1986). Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 128 carcinogens. CNS depressant activity can result from overexposure to alcohols, straight-chain hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons. Cardiovascular effects are due primarily to the halocarbons, nicotine, and CO. Irritants in submarine air include ammonia, ethanolamine, aldehydes, acrolein from cooking, and the acid gases, such as HC l, HF, HBr, the nascent halogens, and NO2 from catalytic burners. The carcinogens or suspected carcinogens that have been detected in submarine air are benzene, chloroform, hydrazine, and vinyl chloride. Central Nenous System Effects Of the various CNS depressants found in operational submarines under normal conditions- -i.e., without spills--the halogenated hydrocarbons appear to reach the highest airborne concentrations. Those compounds are used primarily as refrigerants and solvents or are contaminants released from paints and coatings. Pharmacologically important exposure of humans to the compounds, whether by design or by accident, is usually by inhalation, inasmuch as most have relatively high vapor pressures. The halogenated hydrocarbons, especially the haloalkanes, readily diffuse through cell membranes, because of their lipid solubility. Availability to the alveolar membrane, coupled with lipid solubility, results in the potential for substantial pulmonary absorption. In general, the haloalkanes are not pulmonary irritants, and acute exposure to relatively low concentrations is not an unpleasant experience, nor does prolonged exposure result in pathologic changes in the respiratory tract or lungs (Back and Van Stee, 1977). Acute exposure to the compounds is not considered to be very toxic, in that the LC5a5 are calculated in percent concentrations and not in parts per million (Back and Van Stee, 1977). For instance, rats, guinea pigs, dogs, and cats can be exposed to 60% trifluorobromomethane for 70 h without observable effects, and the reported LC5.D for chlorobromomethane is about 2.9% (29,0oo ppm) in mice (Back and Van Stee, 1977). The pharmacodynamic effects of those compounds are in part associated with their lipid solubility. Their solvent power ranges from poor (the highly fluorinated compounds) to fairly good (those containing less fluorine). Halogenated hydrocarbons are typical nonpolar liquids and, as such, are good solvents for other Submarine Air Quality non polar materials and poor solvents for highly polar materials. Generally, the better solvents are also the more lipid-soluble. The most important toxic effects of the haloalkanes are on the CNS and the cardiovascular system (Van Stee, 1974). The neurologic effects are manifested as alterations of perception, increased reaction time, and impaired ability to concentrate on complex intellectual tasks. At greater exposures, more obvious end points might be drowsiness, drunkenness, and anesthesia, depending on the compound. As with most compounds producing CNS effects closely allied to anesthesia, lipid solubility is important. The relative solubilities of three halogenated hydrocarbons have been studied with respect to accumulation in brain tissue of animal models and extent of CNS depression. The relative lipid solubilities of the compounds are CBrF3 < CBrClF 2 < CH ClBr, and their relative biologic activities are 30:6: I. That is, the concentration of CBrF that can be tolerated is about S times that of CBrClF 2, the concentration of CBrCIF2 that can be tolerated is about 6 times that or CH2CIBr, and the concentration of CBrF3 that can be tolerated is about 30 times that of CH CIBr (Van Stee, 1974). Clinically important CNS effects almost always appear in response to smaller exposures than clinically important cardiovascular effects. That relationship to dose has been found in both animals and humans for a number of the haloalkanes. For instance, men exposed to CBrF3 at 5% for 25 min showed no performance decrement, whereas those exposed at 7-12% evinced drowsiness, decreases in judgment, disturbances in equilibrium, and failure to perform neuromuscular skills without cardiovascular effects. Electrocardiographic changes--such as flattening of the T wave, premature ventricular beats, and tachycardia--with decreased blood pressure were elicited at concentrations of 15% (Hine et al., 1968). Many volatile organic compounds, especially solvents, can depress the central nervous system and decrease performance. These substances might interact with cold and N2 narcosis to decrease performance. Cardio.ascular Effects The cardiovascular effects of halogenated hydrocarbons are manifested as changes in cardiovascular dynamics and electric activity of the heart. Typically, these can include a decrease Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/E/fects of Breathing Submarine Air Contaminants at Up to 6 ATA 129 in blood pressure via reductions in total peripheral resistance as a consequence of autonomic ganglionic blockade, and cardiac arrhythmias with concurrent negative inotropism (Back and Van Stee, 1977). In the mid-1970s, a body of literature suggested that sudden death could be related to fluorocarbon-containing aerosols (Frank, 1975; Aviado, 1975; Aviado and Belej, 1975). Studies on the effects of fluorocarbons on the cardiac conduction system ( Grabowski and Payne, 1983) suggested that those agents might have direct effects on cardiac conduction tissue. Cardiotoxic effects of CBrF3 (FC-1301) have recently been reviewed (National Research Council, 1984c), and some deaths after shipboard exposure to halocarbons have been reported (Clark et al., 1985). Lessard and Paulet (1985) described alterations in cardiac membrane activity in the presence of CF2Cl (FC-12). These reports support the clinical observations of a decade earlier that CF 2CI2 and other fluorocarbons can stimulate cardiac arrhythmias. Halocarbons have been shown to increase the frequency of cardiac arrhythmias in the presence of excess catecholamines (Fogel, 1976; Carlson and White, 1983; Steadman et al., 1984). Although studies in this field are controversial, it is generally accepted that the combination of adrenergic stimulation of the myocardium and halocarbon exposure increases the incidence of cardiac arrhythmias. Adrenergic stimulation is not required, however, for the production of cardiac arrhythmias. Indeed, blood pressure, blood pH, and carotid sinus reflexes can influence arrhythmogenic activity (Back and Van Stee, 1977). Carlson and White (1983) demonstrated that aromatic hydrocarbons also can be arrhythmogenic. Steadman et al. ( 1984) reported deaths of several adolescents who inhaled fluorocarbons from fire extinguishers. Halogenated alkanes, such as fluorocarbons, have been shown to sensitize the heart to the arrhythmogenic effect of endogenous epinephrine. During cold stress, a generalized increase in sympathetic tone results from epinephrine release. Moreover, moderate to heavy exercise causes large increases in catecholamine release. Thus, a heavily working, mildly hypothermic diver might be especially susceptible to the cardiac effects of fluorocarbons in his breathing medium. Irritation The submarine atmosphere can contain irritants that affect the mucous membranes of the eye, nose, mouth, and respiratory tract. Possible irritants include ammonia, ethanolamine, acrolein, carbon disulfide, hydrazines, ozone, phosgene, SO2, NO2, HCI, HF, and HBr. For the most part, irritant gases--such as acrolein, formaldehyde, HF, HBr, HCl, NO2, and ammonia--have not been found in submarines, in greater than trace amounts. Ozone has been found at 3-50 ppb, and hydrazine at 0.5 ppm (Table A-1, pp. 60-65). The acute effects of irritants depend in part on the dose delivered to various parts of the respiratory tract. Reactive gases with high water solubility--such as S02, HCI, HF, and formaldehyde--are largely absorbed as soon as they enter the respiratory tract, mainly in the nose. Reactive gases of lower water solubility, such as NO2 and ozone, penetrate deeper into the respiratory tract and, at high concentrations, cause pulmonary edema. Some gases--such as SO2, ammonia, and formaldehyde--are known sensory irritants and cause an intense burning sensation in the nose and upper airways that leads to a reduction in respiration rate. Sulfur dioxide and ammonia also cause bronchoconstriction. Some pulmonary irritants, such as NO2 and ozone, result in a sensation of dyspnea or breathlessness, rather than pain, and cause an increase in respiration rate. Lowry and Schuman (1956) and Grayson ( 1956) reported that NO -induced pneumonia in silage workers resulted from inhalation of silage gas, which contains a high concentration of NO . Bronchiolitis fibrosa obliterans was a sequefa. The exposure concentrations that caused this condition were much higher than the contaminant concentrations that might occur on a submarine. More relevant to low concentrations of NO and ozone is the finding that these gases can re~uce resistance to infection. Lowering of mouse resistance to bacteria has been observed at exposure to NO as low as 0.5 ppm for 6 months for 6 h/d (Etrlich and Henry, I 968) and to ozone at as low as 0.08 ppm for 3 h (Miller et al., 1978). Speizer et al. (I 980) reported a greater incidence of respiratory illness before age 2 in children in homes with gas stoves (and peak concentration of NO2 of 0.5 ppm) than in children in homes with electric stoves (and lower NO concentration). Frampton et al. (1987) and2i<:uue et al. (1987) reported reduced resistance to viral infections in humans exposed Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 130 to NO2 at 0.6 ppm for 3.5 h (Frampton et al., 1987) or at 1-2 ppm for 2 h/d for 3 d (Kulle et al., 1987). Carcinogenesis Some compounds that are known or suspected human carcinogens have been detected in submarine air. They include benzene, chloroform, vinyl chloride, and hydrazine. The National Research Council Committee on Toxicology does not recommend 90-d exposure guidance levels for carcinogens, and such compounds should be removed from submarine air to the greatest extent possible with charcoal filters or the best technique available. Removal is necessary for both divers and personnel on the submarine. Effects of Particles Two types of aerosols make up the majority of the particles found in submarine air: oil mist or smoke from the engines and particulate material from smoking tobacco (Rossier, 1984). In the early 1960s, aerosol concentrations were often as high as 500 µ,g/m3• Since then, the addition of more electrostatic precipitators has lowered shipboard aerosols to 150-200 µ,g/m3 (General Dynamics 1972). Approximately half the aerosol particles have been reported to have aerodynamic diameters less than 0.4 µ,m in the engine room and approximately 70% of the particles less than 0.4 µ,m in the forward compartment. In a recent sea trial of a Trident nuclear submarine, aerosol concentrations were approximately 100-200 µ,g/m3, except for spaces where electronic equipment was kept, where concentrations of 20-40 µ,g/m3 were maintained with high-efficiency particle-absorbing (HEPA) filters (Rossier, 1984). The presence of particles in submarine air that is to be compressed for use by divers poses several potential problems. Particles in the air would be concentrated under hyperbaric conditions to the same extent as gases, because the volume in which the particles are suspended would be decreased in proportion to the increase in pressure. At the high pressures used to compress submarine air for storage, physicochemical interactions of particles with vapors and gases might result in the association of slowly desorbed toxicants with the particles. Information on the extent to which that occurs Submarine Air Quality is not available. The effect of dense gases on the deposition of inhaled particles is also unknown. Increased pressure would change submicrometer particle behavior through the corresponding decrease in the mobility of these particles. The lower mobility might decrease respiratory tract deposition that is due to Brownian diffusion mechanisms. Changes in breathing patterns due to breathing of dense gases could also alter the pattern of deposition. The solution to any anticipated problems with particle-contaminated air is to filter the air before use. It would be best to filter particles out of the air breathed by divers, both for health reasons and to prevent fouling of breathing equipment. EFFECT OF HIGH PRESSURE ON TOXICITY OF CONTAMINANTS Given the same absolute concentration, will the toxic or pharmacologic effects of a contaminant be the same at 6 ATA as at 1 ATA? It is important to distinguish between relative or fractional units, parts per million and percent, and absolute units, such as partial pressures and milligrams per cubic meter. Values expressed as parts per million or percent are relative to the total number of moles of gas in a given volume and are independent of pressure. A value given as partial pressure or milligrams per cubic meter indicates the absolute amount of a gas in a given volume and is directly proportional to the total pressure of the system. For toxicity concerns, the absolute units (i.e., the partial pressures of the volatile organic compounds or the concentrations of particles) are of interest. On the basis of the physical laws governing the characteristics of ideal gases, one would expect an increase in the toxicity of a compound proportional to an increase in its partial pressure. At pressures up to 6 AT A, one would not expect deviations from the ideal-gas laws (Smith, 1959). An increase in pressure will cause an equivalent increase in the partial pressure of each gas in the atmosphere (in accordance with Dalton's law) and, within limits, one would expect the dose-response relationship to vary linearly with partial pressures. The question is whether a compound at a given absolute concentration (partial pressure) would be more toxic at a higher pressure than it is at 1 AT A, especially if an exposed person is working under stressful conditions of low temperature and increased exercise. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/Elfects of Breathing Submarine Air Contaminants at Up to 6 ATA 131 Very little research has been done on the effect of high environmental pressure on the uptake, disposition, and toxic effects of inhaled gases. Rose et al. (1970) reported that the LC5~ of CO in guinea pigs, rats, and mice were not changed by high pressures (25, 50, 75, and I 00 psig), as long as P0 2 remained normal; i.e., CO exposures were at 2. 7, 4.4, 6.1, and 7 .8 AT A, and PO was held at about 158 mm Hg. Carter et ~ - (1970) studied the effects of CBrF3 on operant behavior of monkeys at normal pressure. Monkeys exposed to CBrF3 at 20-25% had significant decrements in operant behavior with no visible signs of CNS depression. Higher concentrations produced complete loss of function with catatonic states. In addition, Van Stee and Back (1969) recorded spontaneous cardiac arrhythmias when dogs and monkeys were exposed to CBrF3 at concentrations of 40% or more at 14.7 ps1a. Greenbaum et al. (1972) exposed cats to 5% CBrF3 at a simulated depth of 165 ft (6 ATA) and showed the same cardiovascular effects, namely, hypotension and altered cardiac rhythmicity. At 6 ATA, 5% CBrF has a partial pressure of 228 mm Hg or 30~. which is 5% more than that used by Carter et al. (1970) to show performance decrement. The results are compatible and lend credence to the idea that the partial pressure of the gas, rather than the overall environmental pressure, is the important characteristic to relate to untoward effects . Some studies have been conducted at low pressures. McNerney and MacEwen (1965) reported similar toxic effects of exposure to carbon tetrachloride at the same absolute concentration inhaled at ambient pressure or reduced pressure (258 mm Hg). The study was done in mice, rats, dogs, and monkeys, and serum enzymes were used to monitor liver damage. Similar studies in the same species exposed to ozone or NO2 at ambient or reduced pressure (but with the toxic gases at constant absolute concentration) produced no evidence of an effect of pressure on the toxicity of the gases (MacEwen et al., 1967; MacEwen and Geekier, 1968). Rats exposed to CBrF3 at constant absolute concentration at reduced pressures indicated no effect of the pressure changes on the toxicity of the compound (Call, 1972, 1973). Reduction in pressure was not found to alter the toxicity of methylisobutylketone (MacKenzie, 1971 ). Similarly, ozone, NO2, and methylisobutylketone have shown the same degree of toxicity at low pressure, as long as the partial pressure of the compound remained equivalent (Small and Friess, 1975). As long as the P0 2 does not exceed 380 mm Hg, there is little chance of marked pathologic effect that has been shown many times at low, normal, and high pressures. Research on the effect of high and low pressures on the action of pharmaceuticals is of interest, because it can provide information on potential interactive effects of pressure and exogenous chemicals. Such studies were included in the review by Small and Friess (197S), who concluded that, although there were some inconsistent reports, pressure seemed to have little effect on the action of the drugs examined. The small amount of information on the action of gases in hyperbaric environments suggests that toxicity of gases is not changed by increases in ambient pressure . The data indicate that the partial pressure of the gas, rather than the total environmental pressure, is the important characteristic in determining effects . Additional research is needed to determine the effect of high pressure on the toxicity of inhaled organic compounds . Not all compounds can be studied under all conditions. Recent advances in physiologic modeling allow extrapolations between compounds and between species to elucidate the disposition and fate of inhaled gases (Fiserova-Bergerova et al., 1980, I 984; Andersen, I 98 I; Fiserova-Bergerova, 1983, l 98S; Clewell and Andersen, 1987). A model developed for one compound in one species can be adjusted for the physiologic characteristics appropriate for another compound in another species. Such quantities as body weight, alveolar ventilation, blood flow rates, tissue volumes, blood-air partition coefficients, tissue-blood partition coefficients, maximal reaction rate (V max>• and the Michaelis constant (substrate concentration at half the maximal reaction rate) can be used to scale from one compound or species to another (Ramsey and Andersen, 1984). That approach should be useful in the research required to estimate the effect of high pressure on the toxicity of inhaled volatile submarine air contaminants . SETTING LIMITS OF EXPOSURE The manual Interim Air Purity Guidelines for Dry Deck Shelter Operations (U.S. Naval Sea Systems Command, 1986) bases acceptable limits for gaseous contaminants in submarine air compressed for use as diver's breathing air on Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 132 the 8-h time-weighted average (TWA) established by the Occupational Safety and Health Administration (OSHA). At greater than l A TA, the applicable limit for a contaminant is the OSHA limit divided by the pressure in atmospheres absolute. That is based on the idea that the toxicity of the compound increases in direct proportion to its partial pressure. It remains to be determined whether that approach is valid. There is little information on the effect of high pressure on the toxicity of airborne gases and aerosols. Results of the research that has been done indicate no effect of pressure up to 6 AT A on the toxic properties of gases. There is no information on the effect of breathing dense gases on the deposition and potential toxicity of aerosols inhaled as contaminants. Therefore, the conceptual approach described in Interim Air Purity Guidelines for Dry Deck Sheller Operations appears to be acceptable for pressures of 1-6 AT A. An additional question is what guideline should be used for the air pollutants at l AT A. Several sets of guidelines are available on permissible concentrations of air pollutants (Table 12). One is the OSHA set of legal standards or limits. which are 8-h TWAs designed to regulate atmospheres in occupational settings where the workday is 8 h. The Navy is using these standards divided by 4 (on the basis of the assumed pressure of 4 A TA for divers) to set the limits for the Dry Deck Shelter (U.S. Naval Sea Systems Command. 1986). Most of the OSHA TW As have not been reviewed for many years. Another set of guidelines is published by the American Conference of Governmental Submarine Air Quality Industrial Hygienists (ACGIH) ( 1987) and consists of- voluntary guidelines, including 8-h TW As similar to those of OSHA. The ACGIH values are reviewed more often than the OSHA rules. A third set of guidelines consists of the emergency and continuous exposure guidance levels (EEGLs and CEGLs) recommended by the Committee on Toxicology of the National Research Council (l984a,b,c, 198Sa,b, 1986c, 1987a). The CEGLs are designed for situations in which personnel will be continuously exposed to an atmosphere for 90 d. The EEGLs are for situations in which personnel will be exposed rarely and for only a short period (l h up to 24 h) and must be able to continue their work during the exposure. EEGLs and CEGLs have been developed for only a relatively few compounds. The 8-h TWA values designed for occupational settings appear to be the most appropriate for divers because divers work for several hours at a time and do so repeatedly. Where OSHA or ACGIH standards have not been reviewed within the past l S years, they should be carefully evaluated before their incorporation. The most recent (usually more conservative) value of the OSHA and ACGIH guidelines should be used as the basis for calculations for the DDS air, from which diver's air will come. Although the use of TW As is appropriate, it should be noted that submarine air is already regulated by the Navy 90-d limits (Table 12). That should further reduce problems of toxicity to divers breathing the air at 6 ATA~ in that the 90-d limits are no more than one-fourth the TWA limits set by OSHA and recommended by ACGIH. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. CHAPTER6 INTERACTIONS OF SUBMARINE AIR CONTAMINANTS ATUPTO 6ATA Concepts of interactions are central to the understanding of toxicology. A toxic response is usually considered to be the result of an interaction between a target and an exogenous chemical or toxic agent. This interaction presumably results in an alteration (or toxic effect) in the target and often is accompanied by an alteration in the toxic chemical itself. Such a toxic effect is assumed to be related to the dose at the site of action. The biologically effective dose usually is not known, but is assumed to be related to the amount to which the organism is exposed (National Research Council, 1987b,c, 1988 ). Exposure commonly can be measured, or at least approximated; the dose at the site of action is commonly not known. The more knowledge that is available on absorption, solubility, transport mechanisms, etc., the more accurate and reliable are the estimates of dose at the site of action. TYPES OF INTERACTIONS Two circumstances are required for a toxic episode to occur: there must be an exposure, and the exposure must elicit some effect. An exposure that results in a dose that does not elicit an effect is considered to be below the threshold for the effect in question, and an effect in the absence of an exposure might not be a toxic response at all. Toxicologic interactions can occur in two forms: the quantity of an active form of a chemical available for interac133 tion at the target can be altered by the presence (or past presence) of another chemical, or the reactivity of the target with the toxicant can be altered. Exposures to submarine atmospheres, either normobaric or hyperbaric, are actually exposures to mixtures of chemicals. Problems and uncertainties associated with exposures to mixtures are not new (Fairchild, 1983; Murphy, 1980, 1983; National Research Council, 1980, 1988; WHO, 1981). A toxicologic interaction is usually considered to be a condition in which exposure to two or more chemicals results in a biologic response qualitatively or quantitatively different from what would be predicted for exposure to a single chemical (Murphy, 1980). For the purposes of predicting the potential sequelae of exposing divers to compressed air from a nuclear submarine's air banks, it is necessary to expand any definition of potential sources of interaction to include consideration of the stress of physical activity and physiologic adaptation, as well as the effects of exposure to an abnormal environment. The potential for interactions involving pressure, the total gaseous environment, and a toxic agent has been recognized (Doull, 1980). CHEMICAL INTERACTIONS Interactions among chemicals can occur in the exposure environment itself. Interactions can also occur between the airborne materials Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 134 and the container through which they are circulated and in which they are compressed. The environment of a nuclear submarine is dynamic, and the identity and concentrations of contaminants are changing constantly. Contaminants can interact with components of and contaminants in atmosphere purification systems that are not working at optimal efficiency, thereby creating new and different contaminants. For example, l, 1-dichloroethylene (vinylidene chloride) can be generated from methyl chloroform that was originally leached from adhesives; fluorocarbon refrigerants can decompose to hydrogen chloride and hydrogen fluoride (Davies, 1975); and the degreasing agent trichloroethylene can generate dichloroacetylene (Saunders, 1967; Siegel et al., 1971 ). INTERACTIONS Wim THE ORGANISM Various pathologic and physiologic states can affect the metabolism (and therefore the effect) of drugs and other exogenous chemicals (Kato, 1977). If several contaminants are present at the same time and the effect of each is determined by the amount (dose) that reaches the target, the usual concepts of toxic-chemical interaction--such as synergism, antagonism, and potentiation--can be assumed to apply. Such interactions can occur at sites of absorption, sites of elimination, sites of biotransformation, and sites of storage, as well as at sites of action, or targets (National Research Council, 1980). The interpretations of those interactions usually imply some knowledge of the mechanisms of the effects of the toxicants and an ability to measure the effects. INTERACTIONS Wim mE ENVIRONMENT The effects of the environment itself on an organism exposed to a toxic chemical must be considered. Divers work in environments that are usually not addressed in the science of toxicology. In an ordinary occupational or community setting, the environment in which an exposure occurs is usually considered to be constant. In the case of diving, an abnormal or nonconstant environment and the effects of that environment on the persons exposed cannot be overlooked, because it is known that the environment can exert substantial effects on biologic responses to toxic chemicals (Doull, 1972; Submarine Air Quality Fouts, 1976; Hayes, 1975; Sanvordeker and Lambert, 1974). Many environment-induced effects are mediated through the microsomal enzyme system (Vesell et al., 1976; National Research Council, 1980), although changes in absorption, diffusion, quantity and rate of tissue distribution (Fuller et al., 1972; Setnikar and Temelcou, 1962), and effect on endogenous catecholamines (Muller and Vemikos-Danellis, 1970) can be important independently, as well as for their effects on metabolism. Thus, alterations in the dose delivered to a site of action and in the sensitivity (or threshold) of the target can come about as a result of interactions between environmental stressors and an organism exposed to those stressors in combination with toxic chemicals. Most experimental knowledge of the effects (and mechanisms of effects) of chemicals has been gathered from organisms exposed in a "normal" physical environment. In fact, in most animal experimentation, the investigator goes to a great deal of trouble to keep the temperature, lighting cycle, humidity, and many other physical characteristics constant (Lang and Vesell, 1976; Vesell et al., 1976), so that they will not complicate the experiment being done. Because many observable toxic effects are either biochemical or physiologic, environmental stressors that also affect those biochemical or physiologic processes must be considered for their contribution to interactions between chemicals and organism. MIXED STRESSES Divers breathing an air mixture might be exposed to several stresses at the same time. For example, the exposure will be under hyperbaric conditions. There is some information on the effects of exposure of experimental animals to inhaled toxicants, such as CO (Rose et al., 1970), and drugs (Small and Friess, 1975) at increased atmospheric pressure. The results suggest that there is some continuity in the case of exposure to a gas when the gas is considered in terms of its partial pressure. The toxic effects must be interpreted in the light of the physiologic state of the animal when it is at a pressure of several atmospheres. The physical environmental factors that are most likely to result in interactions that should be considered for divers are temperature (Burn, 1961; Cremer and Bligh, 1969; Fuller et al., Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/lnteractions of Submarine Air Contaminanls at Up to 6 ATA JJ5 1972; Keplinger et al., 1959; Muller and Vernikos-Danellis, 1970; Nomiyama et al .• 1980; Setnikar and Temelcou, 1962; Weihe, 1973) and pressure (Rose et al., 1970; Small and Friess, 1975). More information is available on the effect of temperature on toxic response than on the effect of pressure. There is virtually no information on the effect of combination of temperature and pressure on toxicity, the combination that divers are most likely to be exposed to. The diving environment also exposes subjects to cold and the attendant alterations in physiologic status. Thus, the potential for interactions between toxic chemicals and targets must be interpreted in the light of the knowledge of adaptation to cold under pressure. It is unlikely that divers will be exposed for the entire duration of their submersion in a constant state of physical activity. For example, there will probably be periods of inactivity interspersed with periods of extreme activity. Adaptation to cold induces two major physiologic protective mechanisms--increased metabolism and marked peripheral vasoconstriction (Horvath, 1981), both of those can affect the vascular transport and hepatic metabolism of exogenous chemicals. Exposure to cold has an effect on the secretion of endogenous catecholamines (WHO, 1981). Some of the low-molecular-weight chlorinated hydrocarbons affect the myocardium and can result in fatal arrhythmia (A viado, 1978; Balazs et al., 1986; Cornish, 1980). Some have been implicated in reducing heart rate, contractility. and conduction and are thought to act by sensitizing the heart to the arrhythmogenic effect of endogenous epinephrine (Balazs et al., 1986). The combination of excess catecholamines and some halocarbons probably increases the incidence of cardiac arrhythmia, so the potential for interaction between the toxic-chemical stress and the cold stress should be looked into. Furthermore, because bursts of physiologic and physical activity are likely, it is important to know whether the adaptations to cold and physiologic effects of chemicals will interact so as to affect cardiac function. Such interactions could shift the threshold at which toxic effects of chlorinated hydrocarbons occur or change the slope of the expected dose-response curve. Any such interactions must be anticipated and interpreted in the context of the maximal physical activity that the heart must respond to. The potential for interactions with the physiologic sequelae of psychologic stress must also be considered. The use of mathematical models is increasingly popular in toxicology. In general, models are often useful for extending experimental observations, particularly in species-to-species extrapolation needed for risk assessment . They also have utility in addressing some of the unknowns for estimating the potential for toxic interactions associated with exposure to multiple chemicals (Jenkins et al., 1977; National Research Council, 1980, 1988). Few data are available on the descriptive toxicology or mechanisms of toxicity of many (or most) of the co11taroinants of submarine air banks. Derivation of experimental data from laboratory animals on the myriad responses to a mixed-stress environment is extremely difficult, expensive, and time-consuming, because of the complexity of experimental equipment and protocols. Many approaches, however, are available through the use of mathematical models of both the physiologic adaptations to the environment and the kinetic distribution of toxicants introduced into the body. Much of the early work in deriving physiologically based toxicokinetic models of the interaction between the body and toxic chemicals was developed as part of the Navy's nuclear submarine habitability program (Andersen et al., 1980). One of the original goals of the program was the development of concepts and information that would enable realistic permissible exposure limits to be set while eliminating or minimizing the use of safety factors that are necessary when serious data gaps exist. Many physiologic models of the hyperbaric environment have been developed in the Navy's hyperbaric medicine and physiology programs. Conceptually. those models could be combined and provide much better definitions of the physiologically based criteria that must be considered as integral parts of any exposure-effect predictions. Pharmacokinetic models accept physical constants related to the solubility of a given chemical in an aqueous medium. Because perfusion is a major parameter, the combination of solubility of an inhaled toxicant in blood with such physiologic information as organ and tissue blood flow and perfusion during adaptation to a physiologic stress can provide information on delivered dose. Models can then be manipulated to combine physiologic and toxicologic parameters and aid in predicting toxicity (National Research Council, 1987b). Vinylidene chloride is a known contaminant of both nuclear submarines and spacecraft. The Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 136 induction of microsomal metabolism in rat liver increased the hepatic toxicity of vinylidene chloride delivered orally or intraperitoneally. That was not the case, however. when the animal was exposed to vinylidene chloride by inhalation. The use of a physiologically based toxicokinetic model indicated that the increase in hepatotoxicity depended on both microsomal induction and the delivery of sufficient vinylidene chloride to the liver. The model showed that, in the case of inhalation, delivery of vinylidene chloride to the liver by the systemic circulation was a rate-limiting step, because of the solubility of vinylidene chloride; metabolism was therefore •saturabte• (Andersen et al., 1979a,b). Models based on hyperbaric, thermal, and exercise (work) physiology, which consider organ blood flow and perfusion, could be combined with the toxicokinetic models to estimate the probability of altered organ perfusion in response to delivery of toxic substances to a particular organ. That sort of operation, coupled with the derivation of some descriptive and dose-response data in the toxicology research laboratory. could improve the prediction of the effects of exposures to toxic chemiSubmarine Air Quality cats under the mixed-stress conditions to be encountered when divers breathe air from submarine's air banks. STANDARD-SETTING One of the more demanding (and useful) things that modem toxicology is being asked to assist in is quantitative risk assessment. The utility of using physiologically based pharmacokinetic models in this endeavor has been shown (Andersen et al., 1987). Much of the effort expended to date has been in attempting to quantify the risks of exposure to carcinogens, but models can be adapted and modified to address the quantitative risk of almost any untoward event. Improvement in the physiologically based kinetic models, with addition of parameters related to the physiologic adaptation to the hostile environment in which exposures are likely to take place, should be important in setting realistic standards for exposure. Standards thus set can serve the double purpose of protecting the health of service members and assisting in ensuring the reliability of military missions. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. CHAPTER 7 CONCLUSIONS AND RECOMMENDATIONS TOXICITY OF AIR CONTAMINANTS AT HIGH PRESSURE In hyperbaric as in normobaric states. the effects of air contaminants depend on their absolute concentration; i.e .• under hyperbaric conditions. the toxicity of a substance increases in direct proportion to its partial pressure. I . Recommendation: The proposed approach of the U.S. Navy to setting limits for contaminants in diver's air by dividing current Occupational Safety and Health Administration (OSHA) 8-h TW As by the pressure (in atmospheres) at which the air will be breathed is reasonable . The OSHA or American Conference of Governmental Industrial Hygienists (ACGIH) exposure limits are based on moderate activity; commanders must use judgment in adjusting the exposure limits downward for increased air intake during strenuous activity (except in the case of CO--see below). The most recent limits proposed by ACGIH and OSHA should be used for the calculations. 2. Recommendation: Additional research is needed to determine the potential for formation of toxic products during compression of the air and the behavior of particles in dense gases. in terms of deposition in the respiratory tract and interactions with compressed gases. 3. Recommendation: Additional research is required to determine whether hyperbaric conditions have any unexpected effects on toxicity 137 of inhaled contaminants in gaseous atmospheres . PHYSIOLOGIC GASES A CO2 fraction (e.g .• 0.8%) that is acceptable at I AT A may be unacceptable at 6 AT A. because the partial pressure of CO2 increases with absolute pressure. CO2 fractions in diver's air should be zero. but fractions up to about 0.1 % are considered acceptable. 4. Recommendation: Air in high-pressure submarine air banks should be checked for CO2 content. to ensure acceptably low values before use by divers, and if the CO2 concentration is higher than 0.1 %, it should 6e passed through an effective CO2 scrubber before being used. The gas that has passed through the scrubber should be checked with a real-time monitor for CO2• Divers based on submarines will presumably be adapted to inspired CO2 at up to 0.8%. The effects of such acclimation on diving performance are not known. S. Recommendation: Exercise tolerance and other aspects of diving performance should be studied at increased FICO2 (fraction of CO2 in inspired air). These stuaies should be conducted at atmospheric conditions that might reasonably be encountered in submarines and at pressures up to 6 AT A in humans already Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 138 acclimated to inspired CO2 at up to 0.8% at I ATA. Human responses to higher than normal inspired CO fractions vary with time and are incomplelely known. Thus, the physiologic states of divers acclimated to submarine atmosphere are not well known and might vary in unknown ways during the course of a cruise. 6. Recommendation: Responses of experimental animals and possibly humans to chronic CO2 exposure needs to be experimentally determined with inspired CO2 at up to 2% for up to 3 months. Marked variations in total pressure and therefore partial pressure of N in the submarine atmosphere pose risks for divers based in submarines. Some variations on submarines occur during routine submarine operations and in accidents. 7. Recommendation: During diving operations, whenever possible, the pressure in the submarine should be maintained at I AT A, to reduce risk to divers. CARBON MONOXIDE The mechanism by which CO exerts its principal toxic effects is reduction of the oxygencarrying capacity of the blood. Because CO competes with O for binding sites on hemoglobin, the toxicily of CO depends on the ratio PCO:PO2 in the blood and is independent of the absolute pressure. Carbon monoxide might have a cytotoxic effect as well. Any direct cytotoxicity that is not related to the competitive binding of CO to hemoglobin can be expected to depend on PCO. Mathematical modeling of the binding of CO to hemoglobin at different absolute pressures predicts that increased absolute pressure will increase the rate of carboxyhemoglobin (COHb) formation and elimination. For periods shorter than one time constant for COHb formation (less than approximately 8 h), the model predicts that more COHb will be formed under high pressure than at the same CO concentration under normal pressure. The maximal COHb concentration (in such models) is, however, not affected by pressure. Submarine Air Quality 8. Recommendation: The proposed approach of the U.S. Navy to setting limits for CO in diver's air by dividing the OSHA limits by the pressure (in atmospheres) at which the air will be breathed is a reasonable and conservative approach and should be more than adequate to prevent CO toxicity. 9. Recommendation: Research on the rates of COHb formation and elimination under hyperbaric conditions should be performed, to test the prediction of current mathematical models that these rates will be increased by high pressures. I 0. Recommendation: Research should be conducted on the effects of hyperbaric conditions on the relative binding of CO to hemoglobin and myoglobin at sites in the body where PCO remains high while PO2 falls (peripheral tissues, tissue capillary blood, venous blood and arterial blood, when there is venous admixture). CARCINOGENS Trace amounts of substances that are known human carcinogens (such as vinyl chloride and benzene) or suspected human carcinogens (such as chloroform and hydrazine) or that are highly toxic (such as vinylidene fluoride) have been detected in submarine air. For carcinogens, there are no recommended 90-d NRC guidance levels or the recommended guidance levels are below the detection limit of the monitoring system. Therefore, carcinogenic compounds. obviously of concern for their long-term health effects, are not of immediate concern in the submarine environment, excepting where associated with other acute short-term effects. 11. Recommendation: The above type of compounds should be removed from submarine air to the greatest extent possible using available techniques. Potential sources of these compounds should be restricted from submarines when possible. SMOKING An important source of particles and volatile organic contaminants is cigarette smoke. Residues from cigarette smoke contaminate electronic equipment and f out surfaces throughout the submarine. Cigarette-smoking adversely Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. Hyperbarics/Conclusions and Recommendalions affects pulmonary function and exercise performance. Environmental tobacco smoke produces irritation of eyes and upper airways; it also produces noxious odors. There is evidence that the habituated smoker who is unable to smoke is less vigilant and has slower reactions than a nonsmoker in the same circumstances . A diver who is a habituated smoker is unable to do so when diving and his performance may be impeded. The long-term effects of cigarette smoking include increased risk of lung cancer and cardiovascular disease. Recent reports indicate adverse effects on nonsmokers exposed to environmental tobacco smoke. Although the long-term effects are not of immediate concern in the submarine environment, they cannot be ignored when considering the overall health of those who serve on submarines. 12. Recommendation: Cigarette-smoking is an important source of air contaminants in submarine air. The Navy should eliminate or curtail smoking on submarines. l.J9 INTERACTIONS In addition to hyperbaric conditions, divers are exposed to other stress factors, such as cold, darkness, and extreme exercise . Those factors might induce physiologic changes that influence the disposition and fate of inhaled contaminants. 13. Recommendation: Physiologic research is required to provide information on the interaction of breathing compressed gases (nitrogen, oxygen, and endogenous and exogenous carbon dioxide) in air at up to 6 AT A. cold, and extreme exercise. Such research would provide data for use in physiologically based toxicokinetic and hyperbaric models for predicting interactions between the hostile environment and toxic effects of breathing compressed submarine air. Submarine Air Quality: Monitoring the Air in Submarines: Health Effects in Divers of Breathing Submarine Air Under Hyperbaric Conditions Copyright National Academy of Sciences. All rights reserved. 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Description

This source is identified as a National Research Council report from 1988 titled "Submarine Air Quality" [33, 34]. The provided excerpts are limited but include publication information and references potentially related to submarine atmosphere studies and the health effects of air contaminants like nitrogen dioxide [35].

Abstract

This document is a report on Submarine Air Quality published by the National Research Council in 1988 [33, 34].