Review and Assessment of Chlorine Mammalian Lethality Data and the Development of a Human Estimate R-1

New human estimates for chlorine inhalation lethality as a function of exposure duration (for a healthy subpopulation and the general population) were derived via a review and statistical analysis of existing mammalian lethality data. Median lethal dosage and quantal response data were found and analyzed for eight species (mouse, rat, guinea pig, rabbit, cat, dog, goat and sheep) and for durations (T) from 8 min to 235 min. Resulting human estimates were expressed via the toxic load model, L(CnT)50 = k, where n = 2.75 and k = 6.79 x 1010 (military) or 2.58 x 1010 (general), with C in mg/m3 and T in minutes. For 2-min exposures, LCT50 equals 13,500 and 9500 mg-min/m3, for military and general population, respectively. The base 10 probit slope (concentration) was estimated to equal 8.0 (military) and 6.0 (general). Previous human estimates were reviewed, and one study identified as corresponding to the lower confidence limit for the new estimate. The impact of the new estimate was evaluated through a series of transport and dispersion modeling runs using the general population estimate. The predicted downwind hazard distances were consistent with what has been witnessed historically. The original document contains color images.