B.6 CONCLUSIONS FROM THE HEALTH RISK ASSESSMENT
The results of the health risk assessment suggest the possibility that some troops were exposed to concentrations of pesticide active ingredients which exceeded reasonable risk-based levels of concern. However, the majority of veterans probably were not exposed above the levels of concern. The HRA alone does not prove either that overexposures occurred during deployment, or that any connection exists between pesticide exposures and chronic health effects months or years after exposure. Conversely, the HRA also provides no support for eliminating pesticides as potential causative or contributory agents. One important result of the HRA is the identification and prioritization of a small number of pesticides of potential concern (POPCs), and the elimination of the many pesticides which posed little or no risk. This will help focus future work.
Investigators employed two different approaches to characterize risk for noncarcinogenic effects: a toxicological approach, using reference doses (RfDs) based mainly on laboratory animal data, and an epidemiological approach, using benchmarks based on human data. The results of the toxicological approach identified more cases where estimated doses exceeded levels of concern; however, using the epidemiological approach, the estimated doses were well below the benchmarks in the majority of cases. Under the present circumstances, the toxicological approach is more thorough and reliable in terms of establishing levels of concern. Many of the RfDs have been verified by EPA, or are based on values verified by EPA. The human benchmarks, while noteworthy for perspective, are not verified values for the most part, they are not necessarily associated with the most sensistive endpoints, and values for many chemical, exposure duration, and route combinations were not available.
The investigators believe the biological indices used and the assumptions made to establish the likelihood of exceeding risk-based levels are conservative. The probability that exceeding the levels of concern defined gives rise to any of the symptoms associated with the undiagnosed illnesses in Gulf War veterans remains unknown at the present time. For example, even if some veterans were exposed to pesticide active ingredients at the highest levels estimated, and even if biological changes such as mild to moderate suppression of cholinesterase occurred, it is unknown if such changes could be associated with any long-term health problems, particularly given that so few serious acute reactions to pesticide products were documented.
The HRA drew from a number of sources along with the balance of this Environmental Exposure Report (EER) to provide the most comprehensive analysis to date of pesticide exposures during the Gulf War. The HRA concludes that some troops may have been exposed to concentrations of pesticide active ingredients which exceeded conservatively-derived risk-based levels of concern. While not providing evidence that acute effects actually resulted during deployment, the latter finding may be useful when considered along with information in Part A, the tabs, and other studies, regarding a potential for acute and chronic adverse health effects.
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