Review of Acute Human-Toxicity Estimates for Selected Chemical-Warfare Agents (1997)
Chapter: CONCLUSIONS AND RECOMMENDATIONS
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
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Human-Toxicity Estimates for HD |
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Toxicity Type |
Route and Form of Exposure |
Existing Estimates |
CDEPAT's Proposed Estimates |
Subcommittee's Evaluation of Proposed Estimates for HD |
Rationale for Subcommittee's Evaluation |
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LCt50a |
Percutaneous, vapor |
10,000 mg-min/m3 |
5,000 mg-min/m3 |
Proposed estimate should be lowered |
Estimate might be too high because data from the most-sensitive species (rats and mice) not used; further research recommended |
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Inhalation, vapor |
1,500 mg-min/m3 |
900 mg-min/m3 |
Proposed estimate is scientifically valid |
CDEPAT averaged LCT50 data in several animal species; in the absence of data on humans, that approach is reasonable |
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ECt50b |
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Threshold effects |
Percutaneous, vapor |
None |
50 mg-min/m3 (moderate temperature); 25 mg-min/m3 (hot temperature) |
Proposed estimates should serve as interim values |
In the absence of details on studies on value; which estimates were based, proposed estimate should be considered interim further research recommended |
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Severe effects |
Percutaneous, vapor |
2000, mg-min/ m3 (moderate temperature 1000 mg-min/ m3 (hot temperature |
500 mg-min/m3 (moderate temperature); <200 mg-min/m3 (hot temperature) |
Proposed estimated are scientifically valid |
Estimates based on human studies |
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Human-Toxicity Estimates for HD |
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Toxicity Type |
Route and Form of Exposure |
Existing Estimates |
CDEPAT's Proposed Estimates |
Subcommittee's Evaluation of Proposed Estimates for HD |
Rationale for Subcommittee's Evaluation |
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Severe effects |
Inhalation vapor |
200 mg-min-/ m3 (moderate temperature) |
100 mg-min/m3 moderate temperature) |
Proposed estimate is scientifically valid |
Proposed estimated supported by human data |
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Mild effects |
Inhalation, vapor |
>50 mg-min/m3 |
25 mg-min/m3 |
Proposed estimate is scientifically valid |
Proposed estimate supported by human data |
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LD50c |
Percuataneous, liquid |
7,000 mg for 70-kg man |
1,400 mg for 70-kg man |
Proposed estimate is scientifically valid |
Proposed estimate supported by a study in dogs |
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ED50d |
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Severe effects |
Percutaneous, liquid |
None |
610 mg for 70-kg man |
Proposed estimate is scientifically valid; however, it should be rounded to 600 mg for a 70-kg man to avoid appearance of precision that is not there |
Proposed estimate supported by human data |
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a LCt50: 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 necessarily a constant. b ECt50: Percutaneous vapor exposure or inhalation vapor exposure causing a defined effect (e.g., incapacitation, severe effects, mild effects, threshold effects). c LD50: Liquid dose causing lethality in 50% of the exposed animals. d ED50: Liquid dose causing a defined effect in 50% of the exposed animals. |
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