Assumptions in Setting Air Quality Standards for Naval Undersea Environments. P. K. Weathersby, Gales Ferry, CT 06335; and R. S. Lillo, Naval Medical Research Institute, Bethesda, MD 20889
Military operations are subject to different sets of regulations than civilian and industrial activities, but pose similar risk analysis and management requirements. Like other agencies, the U.S. Navy defines exposure limits for its undersea environments despite having less than complete data, and must insert default assumptions when necessary.
In nuclear submarines, air near one atmosphere pressure can be recirculated continuously up to 90 days. Many of the substances found in a small city can be trace components of the air. Safe exposure levels to many substances are set based on chronic toxicity with guidance from the Committee on Toxicology of the National Academy of Sciences. A population of healthy adult males is assumed.
Navy divers can breathe air compressed to seven atmospheres, and helium-oxygen mixtures to 30 atmospheres. Toxicity is assumed proportional to substance partial pressure (even for carbon monoxide, where mechanistic counter arguments can be made). Thus, as diver working depth is increased, contaminant limits for diving gas become more stringent, and more difficult to monitor.
We are developing guidelines for safe use of a submarine source recirculated air that is compressed for diving use, an application that combines both of the above aspects (submarine contaminants and high pressure exposure). Exposure distribution data are now being sought to improve monitoring strategies so that on-site verification of gas safety can be assured immediately prior to use. Choice of compounds to monitor depends on both probability of occurrence and degree of toxicity.
Supported by Naval Medical Research and Development Command work unit 63713N M0099.01C-1506.