Sulfur mustard as a carcinogen: application of relative potency analysis to the chemical warfare agents H, HD, and HT.

A relative potency method for assessing potential human health effects from exposures to relatively untested chemicals is presented and documented. The need for such a method in evaluating the carcinogenic potential of the chemical warfare agent sulfur mustard (agent HD) from a limited data base is specifically addressed. The best-estimate potency factor for sulfur mustard relative to benzo[a]pyrene is 1.3, with an interquartile range of 0.6 to 2.9. The method is applied to (1) the estimated fence-boundary air concentrations of mustard during operation of a proposed agent incinerator at Aberdeen Proving Ground (APG), Maryland, and (2) the current approved general population exposure level of 1 X 10(-4) mg HD/m3 and the occupational exposure level of 3 X 10(-3) mg HD/m3. Maximum estimates of excess lifetime cancer risk for individuals at sites along the APG boundary range between 3 X 10(-8) and 1 X 10(-7). Lifetime cancer risk estimates less than or equal to 10(-6) are not now regulated by the U.S. Environmental Protection Agency or the Food and Drug Administration. Maximum estimates of excess lifetime cancer risk assuming daily exposure to the approved standards during the proposed 5 years of incinerator operation are on the order of 10(-5) for the general public and 10(-4) for the worker population. These values are considered upper limit estimates.