Nerve agents occupational exposure

Airborne Exposure Limits (AEL) The permissible airborne exposure concentration for VX for an 8-hour workday of a 40-hour work week is an 8-hour time weighted average (TWA) of 0.00001 mg/m3. This value can be found in DA Pam 40-8, Occupational Health Guidelines for the Evaluation and Control of Occupational Exposure to Nerve Agents GA, GB, GD, and VX. To date, however, the Occupational Safety and Health Administration (OSHA) has not promulgated a permissible exposure concentration for VX. 

U.S. Army. 1990. Occupational Health Guidelines for the Evaluation and Control of Occupational Exposure to Nerve Agents GA, GB, GD and VX. Pamphlet 40-8, December. Washington D.C. U.S. Army Medical Services. 

OPs have been in use for several decades as important chemicals for the control of crop pests. With their chemical and biochemical reactions, OPs have been well established as extremely poisonous chemicals. This classification is due to the inhibition of the marker enzyme ChE, which is produced in the liver. Blood enzymes provide an estimate of tissue enzyme activity. After acute exposure to OPs or a nerve agent, the erythrocyte enzyme activity most closely reflects the activity of the tissue enzyme. Once the OPs inhibit the tissue enzyme, it cannot hydrolyze ACh, and the accumulation stimulates the affected organ. Based on the manner of exposure (dose and duration) to different OPs, a series of toxicity signs and symptoms set in the organism, leading to death. These are important aspects to be closely monitored among pest control operators and occupational workers exposed to OPs. 

Department of the Army (DA) (1990a). Occupational health guidelines for evaluation and control of occupational exposure to nerve agents GA, GB, GD and VX. DA Pam 40-8. US Department of the Army, Headquarters, Washington, DC. 

Historically, the inhibition of BuChE in plasma has been used to monitor exposure to nerve agents using the classical Ellman colorimetric method (Ellman et al, 1961), or modifications thereof (Woreketal., 1999). This method is used routinely in occupational health monitoring, and could be used to rapidly screen casualties. Its disadvantages are that detection of low-level exposure requires previous baseline measurements, and the assay is non-specific with regard to the inhibitor. 

Willems JL, Nicaise M, DeBisschop HC Delayed neuropathy by the organophosphorus nerve agents soman and tabun. Arch Toxicol 55 76-77, 1984 Xintaras C, Burg JR, Tanaka S, et al NIOSH Health Survey of Velsicol Pesticide Workers Occupational Exposure to Leptophos and Other Chemicals. Cincinnati, OH, U.S. Department of Health, Education, and Welfare, 1978 Zwiener RJ, Ginsburg CM Organophosphate and carbamate poisoning in infants and children. Pediatrics 81 121-126, 1988... 

Ion Mobility Spectrometry (IMS) technology is used to detect nerve, vesicant, and blood agents. The Chemical Agent Monitor (CAM) uses ion mobility spectrometry to provide a portable, hand-held point detection instrument for monitoring nerve or vesicant agent vapors. Minimum levels detectable are about 100 times the acceptable exposure limit (AEL) for the nerve agents and about 50 times the AEL for vesicants. This insensitivity to low concentrations limits the utility of this instrument to check the efficacy of decontamination efforts or in occupational exposure measurements. 

The ability to detect very low concentrations of agents will always be desirable, if for no other reason than to ensure long-term exposure in a previously contaminated environment wiU not have consequences. For example, one of the initial symptoms of low-concentration exposure to nerve agent vapor is affected vision. This may have disastrous consequences for occupations such as fighter pilots. Nanoscale sensors have been demonstrated to detect single moieties but, thus far, only when those moieties can be delivered to a very small detection volume. ... 

Concern about effects of low doses of nerve agents are foimded in part on observations in populations, such as agricultural workers, with chronic occupational exposure to OP compounds, such as pesticides. Many reports relate neurologic changes to these exposmes, and relevant biochemical alterations have been described in these subjects, including changes in antioxidant status (Lopez et al., 2007). Other investigators have shown... 

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