| Human-Toxicity Estimates for GB | |||||
|---|---|---|---|---|---|
| Toxicity Type | Route and Form of Exposure | Existing Estimates | CDEPAT's Proposed Estimates | Subcommittee's Evaluation of Proposed Estimates for GB | Rationale for Subcommittee's Evaluation |
| LCt50a | Percutaneous, vapor | 15,000 mg-min/m3 | 10,000 mg-min/m3 | Proposed estimate is scientifically valid | Proposed estimate supported by studies in monkeys and humans |
| Inhalation, vapor | 70 mg-min/m3 | 35 mg-min/m3 | Proposed estimate should be lowered | Estimate too high because human studies show 100% lethality at 40 mg-min/m3 | |
| ECt50b | |||||
| Threshold effects | Percutaneous, vapor | None | 1,200 mg-min/m3 | Proposed estimate is scientifically valid | Estimate supported by studies of ChE inhibition in humans; further research recommended |
| Severe effects | Inhalation, vapor | 35 mg-min/m3 | 25 mg-min/m3 | Proposed estimate should be lowered | ECt50/LCt50 ratio of 0.7 used to develop estimate; LCt50 for this route of exposure was lowered; therefore, ECt50 should be lowered correspondingly; further research recommended |
| Mild effects | Inhalation, vapor | 2 mg-min/m3 | 0.5 mg-min/m3 | Proposed estimate should be raised | No effects in humans at 0.5 mg-min/m3; effects begin to appear at  2 mg-min/m3; further research recommended |
| LD50c | Percutaneous, liquid | 1,700 mg for 70-kg man | 1,700 mg for 70-kg man | Low confidence in proposed estimate; proposed estimate should serve as interim value | Estimate based on a ratio of ChE inhibition in rabbits and humans; however, human data concerning the relation between ChE inhibition and adverse effects are inconsistent; further research recommended |
| ED50d | |||||
| Severe effects | Percutaneous, liquid | None | 1,000 mg for 70-kg man | Proposed estimate should serve as interim value | In the absence of adequate data on GB for this effect, CDEPAT assumed that the ratio of ID50e/LD50 is 0.6 and used that to estimate the ED50 values; further research recommended |
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.
ECt50: Percutaneous vapor exposure or inhalation vapor exposure causing a defined effect (e.g., incapacitation, severe effects, mild effects, threshold effects).
LD50: Liquid dose causing lethality in 50% of the exposed animals.
ED50: Liquid dose causing a defined effect in 50% of the exposed animals.
ID50: Liquid dose causing incapacitation in 50% of the exposed population.
From: 3, Review of Acute Human-Toxicity Estimates for GB (Sarin)
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