Organochlorine Residues and Breast Cancer

Publisher Website
Google Scholar
Abstract
Hunter et al. (Oct. 30 issue)1 report that there is no significant correlation between breast cancer and plasma levels of 1,1'-dichloro-2,2-bis( p-chlorophenyl)ethylene (p,p'-DDE) and polychlorinated biphenyls (PCBs) two to three years before diagnosis, but estrogenic chemicals in pesticides, plastics, and other products that could contribute significantly to the burden of environmental estrogens in the body were not examined. Hunter et al. state, “The blood levels of DDE and PCBs we measured reflect exposure that occurred over a period of many years.” Although parent 2,2-bis( p-chlorophenyl )-1,1,1-trichloroethane (DDT) and PCB mixtures show estrogenic activity, persistent residues in plasma measured years after exposure to parent mixtures do not show a similar net estrogenic activity. Although p,p'-DDE is the highly persistent in vivo metabolite of DDT, it acts primarily as an antiandrogen.2 The most active estrogenic contaminant in commercial DDT is o,p'-DDT, but neither o,p'-DDT nor its in vivo metabolite is detected years after exposure. Only a small proportion of the 209 PCB congeners have been tested. Many of the estrogenic PCBs (and their more active in vivo metabolites) are not persistent and would also not be present in plasma years after exposure. Some persistent PCB metabolites typically found in plasma actually antagonize estrogenic actions.3,4 The interaction of these chemicals with components of the endocrine system was thus not accurately described. Persistent PCB residues and p,p'-DDE are often measured, because the analysis is relatively inexpensive, and they are always detected in human plasma. The analogy is looking under the nearest lamppost for lost keys because that is where there is light.