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Suggested Citation:"CONCLUSIONS AND RECOMMENDATIONS." National Research Council. 1997. Review of Acute Human-Toxicity Estimates for Selected Chemical-Warfare Agents. Washington, DC: The National Academies Press. doi: 10.17226/5825.
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Page 64
Suggested Citation:"CONCLUSIONS AND RECOMMENDATIONS." National Research Council. 1997. Review of Acute Human-Toxicity Estimates for Selected Chemical-Warfare Agents. Washington, DC: The National Academies Press. doi: 10.17226/5825.
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Page 65
Suggested Citation:"CONCLUSIONS AND RECOMMENDATIONS." National Research Council. 1997. Review of Acute Human-Toxicity Estimates for Selected Chemical-Warfare Agents. Washington, DC: The National Academies Press. doi: 10.17226/5825.
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Page 66

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REVIEW OF ACUTE HUMAN-TOXICITY ESTIMATES FOR HD 64 CONCLUSIONS AND RECOMMENDATIONS The subcommittee's conclusions concerning the scientific validity of CDEPAT's proposed estimates for HD are summarized in Table 7-1. Of the 10 human-toxicity estimates for HD proposed by CDEPAT, the subcommittee concludes that seven of the estimates are appropriate for protecting soldiers and are scientifically valid. The subcommittee recommends that two estimates serve as interim values estimates until further research is conducted and one estimate be lowered. In general, the subcommittee agrees that most of CDEPAT's proposed estimates for HD are reasonable and based on sound scientific judgments of the available data. The subcommittee is concerned that the estimates were central values and calculated without uncertainty factors. Such an approach might not be protective of all members of the military forces. Thus, the subcommittee recommends that further research be conducted to establish the estimates with a greater degree of confidence.

TABLE 7-1 Evaluation of Human-Toxicity Estimates for HD Human-Toxicity Estimates for HD Toxicity Route and Existing CDEPAT's Subcommittee's Rationale for Subcommittee's Evaluation Type Form of Estimates Proposed Evaluation of Proposed Exposure Estimates Estimates for HD LCt50 a Percutaneous, 10,000 mg- 5,000 mg- Proposed estimate should Estimate might be too high because data from the most- vapor min/m3 min/m3 be lowered sensitive species (rats and mice) not used; further research recommended Inhalation, 1,500 mg- 900 mg-min/ Proposed estimate is CDEPAT averaged LCT50 data in several animal vapor min/m3 m3 scientifically valid species; in the absence of data on humans, that approach is reasonable ECt50 b Threshold Percutaneous, None 50 mg-min/ Proposed estimates In the absence of details on studies on value; which effects vapor m3 (moderate should serve as interim estimates were based, proposed estimate should be temperature); values considered interim further research recommended 25 mg-min/ m3 (hot temperature) REVIEW OF ACUTE HUMAN-TOXICITY ESTIMATES FOR HD Severe Percutaneous, 2000, mg- 500 mg-min/ Proposed estimated are Estimates based on human studies effects vapor min/ m3 m3 (moderate scientifically valid (moderate temperature); temperature <200 mg- 1000 mg- min/m3 (hot min/ m3 (hot temperature) temperature 65

Human-Toxicity Estimates for HD Toxicity Route and Form Existing CDEPAT's Subcommittee's Rationale for Subcommittee's Evaluation Type of Exposure Estimates Proposed Evaluation of Proposed Estimates Estimates for HD Severe Inhalation 200 mg-min-/ 100 mg-min/ Proposed estimate is Proposed estimated supported by human data effects vapor m3 (moderate m3 moderate scientifically valid temperature) temperature) Mild Inhalation, >50 mg-min/ 25 mg-min/ Proposed estimate is Proposed estimate supported by human data effects vapor m3 m3 scientifically valid LD50 c Percuataneous, 7,000 mg for 1,400 mg for Proposed estimate is Proposed estimate supported by a study in dogs liquid 70-kg man 70-kg man scientifically valid ED50 d Severe Percutaneous, None 610 mg for Proposed estimate is Proposed estimate supported by human data effects liquid 70-kg man scientifically valid; however, it should be rounded to 600 mg for a 70-kg man to avoid appearance of precision REVIEW OF ACUTE HUMAN-TOXICITY ESTIMATES FOR HD that is not there a LCt : Vapor exposure that produces lethality in 50% of the exposed animals. Ct refers to the product of concentration (c) and exposure time (t). Note that Ct is not 50 necessarily a constant. b ECt : Percutaneous vapor exposure or inhalation vapor exposure causing a defined effect (e.g., incapacitation, severe effects, mild effects, threshold effects). 50 c LD : Liquid dose causing lethality in 50% of the exposed animals. 50 d ED : Liquid dose causing a defined effect in 50% of the exposed animals. 50 66

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No reliable acute-exposure1 standards have been established for the particular purpose of protecting soldiers from toxic exposures to chemical warfare (CW) agents. Some human-toxicity estimates are available for the most common CW agents--organophosphorus nerve agents and vesicants; however, most of those estimates were developed for offensive purposes (that is, to kill or incapacitate the enemy) and were intended to be interim values only. Because of the possibility of a chemical attack by a foreign power, the Army's Office of the Surgeon General asked the Army's Chemical Defense Equipment Process Action Team (CDEPAT) to review the toxicity data for the nerve agents GA (tabun), GB(sarin), GD (soman), GF, and VX, and the vesicant agent sulfur mustard (HD) and to establish a set of exposure limits that would be useful in protecting soldiers from toxic exposures to those agents. This report is an independent review of the CDEPAT report to determine the scientific validity of the proposed estimates.

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