Critical Evaluation of Dichlorvos’ Breast Cancer Risk

Abstract Dichlorvos was once a very popular and commonly used organophosphate pesticide. Dichlorvos applications were not restricted to agriculture. It was widely used as an insecticide in public places and in homes. Its many different non-agricultural applications created the potential for widespread exposure. Dichlorvos use was restricted in response to concerns about its cancer causing potential. For this report, we have used a modification of the International Agency for Research on Cancer (IARC) approach to conduct a detailed evaluation of any direct or related evidence of cancer risk from exposure to dichlorvos, with a focus on breast cancer risk. We have critically evaluated al I the available human, experimental animal, and cancer-related molecular and mechanistic studies on dichlorvos. Chemical and up-to-date regulatory information is included, as well as a discussion of dichlorvos’ environmental fate and potential for human exposure. We have classified dichlorvos in Group 3. In the Program on Breast Cancer and Environmental Risk Factor's (BCERF) breast cancer risk classification scheme (see Appendix B), this group represents chemicals that are not classifiable for breast cancer risk in humans. However, studies in experimental animals provide enough evidence to suggest that dichlorvos exposure can increase cancer risk at other sites.