persistent in the environment. Odor thresholds of 1 mg·min/m3, 0.15 mg/m3, and 0.6 mg/m3 have been reported. Among various U.S. Army facilities, there are currently approximately 17,018.1 tons of sulfur mustard (agent HD) awaiting disposal.

Exposure to sulfur mustard vapor may result in irritation and damage to the eyes, respiratory tract, and skin. The toxic effects of sulfur mustard are temperature- and humidity-dependent; for a given exposure, the effects could be greater with increasing temperature and humidity. An exposure-dependent latency period of hours to days is documented and is relevant for all routes of exposure but may be shorter for ocular and upper respiratory tract effects than for dermal and systemic responses. Both human and animal data indicate that the eyes are the most sensitive organ/tissue; deaths resulting from sulfur mustard exposure are more often the result of respiratory tract involvement. Because the toxic effects of sulfur mustard (at least for short time periods) appear to be a linear function of exposure duration and exposure concentration, most of the available exposure-response data are expressed as cumulative exposures (Ct).

Minor ocular irritation (conjunctival injection in the absence of irritation) occurs in humans following exposure at 12–30 mg·min/m3. More severe effects develop at 60–75 mg·min/m3 (conjunctivitis, irritation, photophobia) and at 100 mg·min/m3 (severe ocular irritation). Vapor inhalation LCt50 estimates for humans range from 900 mg·min/m3 to 1,500 mg·min/m3.

Animal lethality following acute exposure to sulfur mustard occurs at cumulative exposures ranging from approximately 600 mg·min/m3 to 1,500 mg·min/m3. Nonlethal effects were similar to those observed in humans and included effects on the eyes, respiratory tract, and skin. Long-term exposure of dogs, rats, and guinea pigs to concentrations at 0.03 mg/m3 produced only minor signs of ocular and respiratory tract irritation. One-hour (h) exposure of mice to concentrations up to 16.9 mg/m3 resulted in notable effects on respiratory parameters, and acute exposures of rabbits (20 minutes [min]) to 12 h) to concentrations ranging from 58 mg/m3 to 389 mg/m3 (Ct ≥2,300 mg·min/m3) resulted in severe respiratory tract damage.

Because exposure-response data were unavailable for all of the AEGL-specific exposure durations, temporal extrapolation was used in development of values for the AEGL-specific time periods. The concentration-exposure time relationship for many irritant and systemically acting vapors and gases may be described by Cn×t=k, where the exponent n ranges from 0.8 to 3.5 (ten Berge et al. 1986). Data regarding AEGL-1-type ef-



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