Nerve agents occupational

Occupational Safety and Health Administration, National Institute for Occupational Safety and Health. Interim Guidance on Personal Protective Equipment Selection for Emergency Responders Nerve Agents, August 30, 2004 (http //www.osha.gov/SLTC/... 

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. 

For the purposes of occupational medicine, the determination of cholinesterases in the blood of workers intoxicated with OP is obhgatory. However, the normal values varied within the laboratories depending on the method of determination. Systematic monitoring of workers with nerve agents was performed at our department from 1962 to 1963 however, the results presented contain determinations during 40 years (1964-2004). Because of the large number of results, the results are limited to RBC AChE only although plasma BuChE aetivity was also determined. 

Recovery from the ChE inhibition produced by chemical warfare nerve agents or other OP compounds is not a simple matter, however. The recovery of CNS ChE does not parallel the recovery of plasma ChE, with plasma ChE often recovering much more rapidly than RBC-AChE, which more closely parallels the recovery of brain AChE (McDonough et al., 1983 Russell et al., 1986) Thus, these and other tolerance studies (Clement 1989, 1991) suggest that behavior has often recovered to near baseline, while AChE is still significantly lowered. This has been noted clinically and Sidell (1992) cautions, Analysis of blood for ChE is useful for occupational monitoring, but in an exposed patient, one treats the patient, not the ChE activity. ... 

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. 

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