Guidelines for Chemical Warfare Agents in Military Field Drinking Water (1995) / Chapter Skim
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3 GUIDELINES FOR ORGANOPHOSPHORUS NERVE AGENTS
3 GUIDELINES FOR ORGANOPHOSPHORUS NERVE AGENTS
Pages 19-28
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From page 19... ...
compiled a detailed review of the properties and fate of organophosphorus nerve agents and their health effects in animals and humans. Because of its volatility, GB is an effective toxicant by He inhalation route, whereas the relatively low volatility of VX makes it more effective following dermal exposures.
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From page 20... ...
Toxic effects observed in humans and animals acutely exposed to organophosphorus nerve agents are excessive bronchial, salivary, ocu
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From page 21... ...
However, data are insufficient to predict the risk accurately in humans exposed to Tow doses of these nerve agents, and since most investigators use AChE inhibition as a measure of exposure rather than more direct measures, there are multiple sources of uncertainty. The World Health Organization reports that a 50-70% reduction of plasma or red-blood-cell-AChE activity in workers exposed to organophosphate pesticides justifies the removal of workers from furler exposure (V/HO, 19751.
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From page 22... ...
In addition, any military field drinking-water standard must be more conservative than the standards applied in industry and agriculture because the nature of the chemicals and their potential use as chemical warfare agents is in direct contrast with the goals and objectives of a workplace hygiene program. For example, AChE monitoring in agriculture is designed to protect workers from excessive exposure and AChE monitoring in the military is designed to protect against impaired performance by personnel in a situation that might already be life-threaten~ng.
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From page 23... ...
MPCs assume a 70-kg person consuming field drinking water at 5 L/day or 15 L/day for up to 7 days. The MPC:s for 25 % inhibition of AChE are advocated as standards at this time based on the limited dose-response data available and on the likelihood that AChE inhibitions adversely affecting performance are smaller than previously thought.
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From page 24... ...
For comparative purposes, inhalation exposures are considered more analogous to intravenous exposures than to ingestion or dermal contact (Somani, 1992~. With respect to route and rate of exposure, absorption of organophosphorus nerve agents from the gastrointestinal tract is expected to be intermittent during waking hours.
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From page 25... ...
suggested that concurrent biomonitoring of AChE activity and urinary metabolites could yield a complimentary analysis of the status of persons exposed to organophosphorus chemicals. Measurements of AChE inhibition are indicative of
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From page 26... ...
It should be noted that the lowest level of statistical reliability in measuring AChE changes is approximately 20%; changes that are less than 20% cannot be detected reliably. Based on the available data, the subcommittee recommends that the 25 % AChE inhibition level be used as the basis for the field drinkingwater guidelines for organophosphorus nerve agents and recommends the following guidelines for the organophosphorus nerve agents: GA, 22.5 ~g/L and 70.0 ,ug/~; GB, 4.6 and 13.S ,ug/~; GD, 2.0 and 6.0 Ago; and VX, 2.5 and 7.5 ,ug/I, assuming a water consumption of 15
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From page 27... ...
Based on that review, only the most conservative field drinking-water standards are acceptable pending development of more dose-response data directly relating the toxicity of organophosphorus nerve agents to exposure. Extensive studies during the past 15 years with structurally related methyl and ethyl organophosphate insecticides have shown the corresponding dialky!
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From page 28... ...
. However, performance criteria for military personnel operating complicated equipment, including aircraft, weapons systems, and heavy machinery, are critical to the subcommittee's recommendation that field drinking-water guidelines based on 25 % AChE inhibition be adopted for the entire class of organophosphorus nerve agents.
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