Persistent Organic Pollutants and Breast Cancer Risk: Chemicals, Old and New

Persistent organic pollutants (POPs) are a class of synthetic, lipophilic, bioaccumulative compounds, many of which were first introduced during the post WWII industrial boom. Most notable among these older POPs are dichlorodiphenyl trichloroethane (DDT) and polychlorinated biphenyls (PCBs), which were banned in the 1970s in the U.S. due to concerns over widespread human exposures and potential adverse health effects in wildlife and humans. Because of their persistent and bioaccumulative nature, however, exposure to these compounds continues decades later with detectable levels prevalent in human tissue today. Polybrominated diphenyl ethers (PBDEs) are a newer class of POPs, introduced into the marketplace in the late 1970s as flame retardant additives to consumer and building products.   Owing to their similar molecular structure and toxicological properties to PCBs, in combination with the ubiquity of exposure, it appears PBDEs are poised to become the PCBs of the 21st century. In response to recent regulatory action that banned the use of two of the three primary commercial PBDE formulations in the U.S., replacement brominated flame retardants (BFRs) have recently emerged and are in widespread use. 

Interest in the role of POPs in breast cancer etiology stems largely from the well-documented endocrine disrupting properties of these compounds. Despite considerable research on the older POPs, which has primarily focused on PCBs and DDT, evidence supporting a link between exposures to these compounds and breast cancer risk is quite mixed. Meanwhile the association between the newer POPs and breast cancer risks remains completely unexplored.  This proposal capitalizes on the vast and unique resources available from the California Teachers Study (CTS), an on-going prospective study of breast cancer, to evaluate the risk of breast cancer associated with both the older and newer POPs, addressing many of the key limitations common to the studies of PCBs and DDT. In addition to providing the opportunity to conduct the first large-scale investigation into the risk of breast cancer associated with the PBDEs and replacement BFRs, the current proposal also will provide critical information on disparities in and determinants of PBDE/BFR human exposures. This information is essential to optimizing the design of future epidemiologic studies on this topic as well as informing public health practices and regulatory action to curb exposures to these compounds. 

CPIC Principal Investigators: Peggy Reynolds, Ph.D.; David Nelson, Ph.D; Pamela Horn-Ross, Ph.D.

Collaborators:  Myrto Petreas, Ph.D. (CalEPA); Katie Henderson, Ph.D. (City of Hope); Hoda Anton-Culver, Ph.D. (University of California, Irvine)

Funding Sources: California Breast Cancer Research Program (CBCRP)

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