Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
REVIEW OF ACUTE HUMAN-TOXICITY ESTIMATES FOR GA (TABUN) 24 mate could be greater than 0.5 mg-min/m3. At concentrations of 0.7 mg-min/m3 and exposure periods ranging from 2 to 10 min, GA could be detected by smell (Udhe and Moore 1945). However, the number of volunteers detecting the odor was not specified. Tightness of the chest was also observed at exposures of 0.7 mg-min/m3 (Udhe and Moore 1945). In the same study, tightness of the chest and miosis, with impaired vision, occurred at doses ranging from 3.2 to 30 mg-min/m 3 (Udhe and Moore 1945). At higher vapor doses, those effects were accompanied by severe eye pain, headaches, nausea, and vomiting. On the basis of the review of the available data, the subcommittee concludes that CDEPAT's proposed estimate of 0.5 mg-min/m3 can be raised. The subcommittee recommends that further research be conducted to establish the ECt50 estimate with a greater degree of confidence. PERCUTANEOUS LIQUID EXPOSURE Lethal Effects (LD50) CDEPAT's proposed LD50 for percutaneous exposure to GA liquid on bare skin is 1,500 mg for a 70-kg man. The proposed LD50 estimate does not differ from the existing estimate (CDEPAT 1994). LD50 values reported for animals ranged from 1 mg/kg for mice to 30 to 50 mg/kg for dogs. However, it is difficult to use those data for predicting the human LD50 estimate because many of the animal studies involved the use of depilated animals (animals whose hair was removed chemically, thus making them more susceptible to toxic effects of chemicals) and others tested only crude material. The proposed LD50 estimate for men was based on animal data without the use of uncertainty factors to account for inter-species variability. Thus, the subcommittee concludes that the proposed LD50 value for humans is not scientifically defensible because it is based on the use of limited animal data without the use of uncertainty factors. The subcommittee recommends that the proposed estimate be lowered until further research is conducted on GA to establish an LD50 estimate With a greater degree of confidence. ED50 for Severe Effects CDEPAT's proposed estimate for the ED50 for severe effects (that is,
