Breast cancer risk higher in non-white women who worked with PCBs.

Silver, SR, EA Whelan, JA Deddens, NK Steenland, NB Hopf, MA Waters, AM Ruder, MM Prince, LC Yong, MJ Hein and EM Ward. 2009. Occupational exposure to polychlorinated biphenyls and risk of breast cancer. Environmental Health Perspectives 117:276–282.

Researchers observed a difference in breast cancer risk between minority and white women exposed to PCBs between the 1930s and late 1970s while on the job at manufacturing plants that made electrical capacitors.

In non-white women, as exposure to PCBs increased, so did their risk for breast cancer onset. White women working in the same plants had no relationship between PCB exposures and breast cancer onset, a finding that is consistent with previous studies.

Many studies have examined and found no relationship between PCBs and breast cancer risk. However, recent results suggest that sensitive populations may be at risk of increased breast cancer due to PCB exposure.

Here and elsewhere, race can represent both differences in exposures to PCBs and differences in genetic responses to PCBs. Studies find that women with both PCBs exposure and a specific "breast cancer gene" have a higher risk of breast cancer.

Polychlorinated biphenyls, called PCBs, are long-lived chemicals that were used in the US as coolants and insulators in electrical capacitors and in other products before their ban in the late 1970s. Today, exposure to the pollutants occurs mainly through food and is linked to reproductive, immune and skin and liver problems.

This retrospective study involved 5,752 women who worked at three capacitor manufacturing plants in the United States.

Of those, 69 percent returned questionnaires. The forms in English, Spanish and Portuguese were used to determine diagnoses of breast cancer, risk factors for breast cancer such as family history, as well as demographic information, such as ethnicity and education. Breast cancer cases were also identified through death certificates, medical records and cancer registries maintained by the states where the capacitor manufacturing plants are located.

The age, demographic, smoking history and other circumstances of the women were taken into account in the research.

Only 282 members of the study were identified as nonwhite, so the risk for each ethnic group was not possible. Of the 145 breast cancer cases, only 14 of these cases were nonwhite. Although statistically significant, this low number makes it difficult to know how accurate the risk of breast cancer due to PCB exposure is for this population and more followup is needed, the authors report.

Capacitor plant workers are generally exposed to higher levels of PCB compared to the general US population. Exposure to PCBs in this study was determined by ranking study participants relative to one another. While the authors validated ranks with a subset of real PCB measurements, it is not possible to directly compare exposures in this study to other studies.