What is the role of organochlorine exposure in the etiology of breast cancer?

Updated: Dec 26, 2019
  • Author: Graham A Colditz, MD, DrPH; Chief Editor: Chandandeep Nagi, MD  more...
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Answer

Organochlorines are among the potential environmental factors of greatest concern as causes of breast cancer. Epidemiologic studies of breast cancer and environmental exposures to synthetic chemicals have concentrated on biologically persistent organochlorines. This class of compounds includes pesticides, eg, 2,2-bis(p -chlorophenyl)-1,1,1-trichloromethane (DDT), chlordane, hexachlorocyclohexane (HCH, lindane), hexachlorobenzene (HCB), kepone, and mirex; industrial chemicals, eg, polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs); and dioxins (polychlorinated dibenzofurans [PCDFs] and polychlorinated dibenzodioxin [PCDDs]), produced as combustion byproducts of PCBs or contaminants of pesticides.

Many of these chemicals are weak estrogens and may act as estrogenic agents in breast tissue, thereby hypothesized to increase breast cancer risk by mimicking endogenous estradiol. Other compounds, specifically the dioxins and some PCB congeners, exhibit antiestrogenic activity and may be protective against breast cancer.

Studies of occupational exposure to organochlorines have not supported an association with increased breast cancer risk. Fewer cases were observed than expected in studies of women occupationally exposed to phenoxyl herbicides and PCBs. However, these studies are limited by few workers exposed and difficulties of exposure assessment.

The results of small case-control studies of organochlorine levels and breast cancer risk have been mixed. However, the large case-control study conducted on Long Island, New York, observed no association with breast cancer risk for blood levels of dichlorodiphenyldichloroethane (DDE), chlordane, dieldrin, or common PCB congeners. [83]

Several prospective studies have also used stored blood samples collected prior to diagnosis to evaluate the relationship between DDE and total PCBs with breast cancer. A pooled study reanalyzing data from the 5 large studies in the northeast found no association between PCBs and DDE levels and breast cancer risk when comparing the highest and lowest quintiles. [84] Based on this body of evidence, organochlorines appear unlikely to be an important breast cancer risk factors or an explanation for breast cancer trends over time.


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