nants and, if possible, to develop EEGLs and CEGLs for selected chemicals that do not have existing or proposed levels. The committee was also asked to identify data gaps and to make recommendations for future research. Specifically, the Navy asked the committee to review guidance levels for acetaldehyde, hydrogen chloride, hydrogen fluoride, hydrogen sulfide, and propylene glycol dinitrate. See Appendix B for a verbatim statement of task.

POPULATION CHARACTERISTICS

An estimated 30,000 submariners are on active duty in the U.S. Navy (Cassano 2003). Permanent crew members on U.S. submarines are all male and are 18-48 years old. Before entry into the submarine service, candidates receive comprehensive physical and psychologic examinations and are rejected if any major medical problems—such as heart disease, asthma, or chronic bronchitis—are noted (U.S. Navy 1992, 2001). Submariners are also required to undergo a complete physical examination every 5 years (Capt. D. Molé, U.S. Navy, personal commun., May 28, 2003); they may be disqualified from submarine duty if any medical problems are noted at that time or during active duty (Cassano 2003). Thus, the population that serves on U.S. submarines is, in general, quite healthy.

Studies that have evaluated mortality patterns in U.S. submariners support the conclusion that submariners are healthy. Charpentier et al. (1993) examined a cohort of 76,160 submariners who served on U.S. nuclear-powered submarines during the period 1969-1982. They compared mortality in the submariners with that in the general adult male population of the United States and found that the standardized mortality ratio (SMR) for total mortality was significantly less than 1.1 The SMR was also significantly lower than that expected in a military population. The SMRs for specific causes of mortality were also less than 1. SMRs exceeded 1 for only two causes: malignant neoplasms of the central nervous system (SMR, 1.03) and motor-vehicle accidents (SMR, 1.06). The results reported by the study authors were supported by a study of Royal Navy submariners, who must meet stringent physical requirements similar to those of the U.S. Navy (Inskip et al. 1997).

Morbidity patterns in U.S. Navy submariners also indicate a healthy population. Thomas et al. (2000) evaluated the rates of medical events in crews on 136 submarine patrols over 2 years (1997-1998). Injury was the most common medical-event category, followed by respiratory illness (primarily upper respiratory infections) and then skin problems, such as minor infections and ingrown toenails. Other medical events included ill-defined symptoms, infectious diseases, digestive disorders, ear and eye complaints, and musculoskeletal condi-

1

An SMR indicates whether mortality in a given population is greater (SMR > 1) or less (SMR < 1) than that in a comparison population.



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