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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 47
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.
×
Page 48
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 49

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REVIEW OF ACUTE HUMAN-TOXICITY ESTIMATES FOR GF 47 (Cullumbine et al. 1954). The subcommittee believes that, in the absence of adequate data, the use of this assumption is a reasonable approach. The subcommittee recommends that CDEPAT's estimate of 350 mg for a 70-kg man be considered an interim estimate until further research on GF is conducted to establish this estimate with a greater degree of confidence. ED50 for Severe Effects CDEPAT's proposed ED50 estimate for severe effects from percutaneous liquid exposure to GF is 200 mg for a 70-kg man, assuming exposure durations of 2 to 10 min and moderate temperatures. There is no existing ED50 estimate (CDEPAT 1994). In the absence of adequate human and animal data on the severe effects following percutaneous exposure to GF liquid, CDEPAT (1994) assumed that GD and GF are equipotent. The subcommittee concludes that the approach used by CDEPAT (1994) to derive the ED50 is reasonable and recommends that the proposed estimate be considered an interim value until further research on GF is conducted to establish this estimate with a greater degree of confidence. CONCLUSIONS AND RECOMMENDATIONS The subcommittee's conclusions concerning CDEPAT's proposed estimates for GF are summarized in Table 5-1. Of the seven acute human-toxicity estimates for GF proposed by CDEPAT (1994), the subcommittee agrees that the estimates are not scientifically valid or appropriate for protecting soldiers. Four estimates are recommended to serve as interim values until further research is conducted, one estimate should be raised, and two estimates should be lowered. The subcommittee recommends that further research be conducted to establish estimates with a greater degree of confidence.

TABLE 5-1 Evaluation of Human-Toxicity Estimates for GF Human-Toxicity Estimates for GF 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 GF LCt50 a Percutaneous, 15,000 mg- 2,500 mg- Proposed estimate should Rationale for the CDEPAT estimate not supported by vapor min/m3 min/m3 serve as an interim value data; further research recommended Inhalation, None 35 mg-min/ Proposed estimate should In the absence of adequate data, proposed estimate based vapor m3 be lowered on assumption that GF, GD, and GB are equipotent; approach is reasonable; because LCt50 for GB was recommended to be lowered, proposed value for GF should be lowered correspondingly; further research recommended ECt50 b Threshold Percutaneous, None 300 mg-min/ Proposed estimate should Proposed estimate based on assumption that GF and GD effects vapor m3 serve as an interim value are equipotent; approach is reasonable; further research recommended Severe Inhalation, None 25 mg-min/ Proposed estimate should In the absence of adequate data, proposed estimate based REVIEW OF ACUTE HUMAN-TOXICITY ESTIMATES FOR GF effects vapor m3 be lowered on assumption that GF, GD, and GB are equipotent; approach is reasonable, because ECt50 s for severe effects for GB and GD were recommended to be lowered, proposed value for GF should be lowered correspondingly; further research recommended 48

Human-Toxicity Estimates for GF 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 GF Mild Inhalation, None 0.2 mg-min/ Proposed estimate should In the absence of adequate human or animal data, the effects vapor m3 be raised proposed estimate based on assumption that GF and GD are equipotent; approach is reasonable; because ECt50 for mild effects for GD was recommended to be raised, proposed value for GF should be raised correspondingly; further research recommended LD50 c Percutaneous, None 350 mg for Proposed estimate should In the absence of adequate human or animal data, liquid 70-kg man serve as an interim value proposed estimate based on assumption that GF and GD are equipotent; approach is reasonable; further research recommended ED50 d Severe Percutaneous, None 200 mg for Proposed value should In the absence of adequate human or animal data, the effects liquid 70-kg man serve as an interim value proposed estimate based on assumption that GF and GD are equipotent; approach is reasonable; further research REVIEW OF ACUTE HUMAN-TOXICITY ESTIMATES FOR GF recommended 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 49

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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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