Agency for Toxic Substances and Disease Registry
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Learning Objectives |
Upon completion of this section, you should be able to
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Cancer Risks |
Generally, organophosphorus compounds are not thought to be carcinogenic, although there is some controversy about this. (Poisindex Editorial Staff 2005) Although a number of studies have concluded that pesticide exposure increased the risk of some childhood cancers, these studies suffered from significant methodological problems. These have included:
Note: One study of Gulf War Veterans exposed to sarin and cyclosarin from the 1991 explosion of the Khamisiyah chemical munitions cache in Iraq found an almost 2-fold increase in subsequent brain cancer deaths. In this study, exposure was assessed using plume modeling and the location of the soldier’s company at the time of the explosion. However, the investigators noted that neither sarin nor cyclosarin are known carcinogens, so the cancer deaths could have been due to other chemicals released in the explosion. (Bullman, Mahan et al. 2005) |
Fetal Effects |
Some organophosphorus compounds have been shown to cross the placenta in animals. However, there is a lack of evidence that fetal toxicity has occurred in the absence of maternal toxicity. The few reported cases in humans where pregnant women were poisoned were managed successfully with standard treatment. (Arbuckle and Sever 1998; Erdman 2004) Currently, there is a lack of convincing evidence that cholinesterase inhibitors cause birth defects or adverse effects on the reproductive system in humans. Although many studies have been carried out, they suffer from serious methodological problems. There are human case reports on third trimester exposures that did not result in birth defects. Animal data are conflicting. While some animal studies suggest that birth defects could result from exposure to cholinesterase inhibitors, others do not. Thus, the possibility that birth defects could occur has neither been confirmed nor ruled out. (Minton and Murray 1988; Sever 1997; Shaw, Wasserman et al. 1999; Erdman 2004) Experience with oxime treatment of pregnant patients is almost non-existent. Only six cases have been published describing the findings in pregnant victims of organophosphate poisoning. In only 3 cases did these patients receive oxime treatment. One mother, who received obidoxime, elected to have an abortion. The findings in the aborted fetus were not reported. The other two patients were at 16 weeks and 36 weeks of gestation at the time of exposure, and were treated with 2-PAM and atropine. Both delivered normal term infants. (Bailey 1997) |
Gulf War I Illness |
An extensive review of the literature carried out by the RAND Corporation came to the following conclusions about the association between cholinesterase inhibitors and Gulf War I illness (Cecchine, Golomb et al. 2000)
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Immune System Effects |
There are a multitude of physiological processes that lead to effective immune system function, and the immunotoxic disruption of any one of them may not necessarily alter host resistance. Studies in laboratory animals have documented immunotoxic effects of organophosphorus compounds, and in some cases have even linked them with altered disease resistance. However, there is a lack of clear-cut evidence to show that exposure to these compounds alters overall immune function in humans. (Galloway and Handy 2003) |
Key Points |
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Progress Check |