Environmental Exposures and Breast Cancer on Long Island

Erin O'Leary, Ph.D. Stony Brook University (funded through the grant "Environmental and Genetic Determinants of Breast Cancer")

Dr. Erin O'Leary, while at the University of Buffalo, conducted a nested, case-control study to determine if residence in close proximity to hazardous waste sites, toxic release inventory sites, prior land use (for example, farm land), and exposure to various chemicals in drinking water may be associated with breast cancer on Long Island.

The study population was selected from a cohort of New York State residents in 1980, established by investigators at the University at Buffalo, who had lived at least 18 years in their current residences and had completed a mailed questionnaire. Within the cohort, 3,097 women from Long Island answered the questionnaire. From this Long Island group, data on 105 women who had been diagnosed with breast cancer (cases) between 1980 and 1992 were compared to data on 210 randomly selected Long Island women who did not have breast cancer (controls), and who were age and race matched to cases.

Because there is no proven way to measure an individual's historical environmental exposure to most chemicals in the environment, Dr. O'Leary relied on proxies to estimate exposure. She linked data on each woman's residence with data on historical land use, drinking water, and proximity to hazardous waste sites and toxic release inventory sites, and estimated historical exposures to organochlorine and carbamate pesticides, solvents or volatile organic compounds (VOCs) (for example, tetrachloroethylene, trichloroethylene, and 1,1,1-trichloroethane), nitrates, and metals (cadmium, chromium, and arsenic). Geographic information software was used to calculate the distance between residences and the point sources of pollution.

Findings from this exploratory study are:

• Women who lived within 1 mile of hazardous waste sites containing organochlorine pesticides were found to have an increased risk for breast cancer, after adjusting for known risk factors. No association was found between breast cancer and pesticides detected in drinking water or residence on or near agricultural land. Women who lived on or near agricultural land and who were nulliparous (never given birth) or had an older age at first birth had an increased breast cancer risk, compared to women who did not live on or near agricultural land and who had a younger age at first birth. The small sample size limited the study power, and the confidence intervals were wide, which means the findings could be due to change. These findings suggest the need for additional research on the topic.
• No association was found between increased risk for breast cancer and exposure to VOCs in drinking water, or residing in close proximity to hazardous waste sites and toxic release inventory sites containing these compounds. A recent hypothesis suggests that VOCs may be transformed in the breast fat tissue, excreted into the ductular systems, and may initiate or promote breast carcinogenesis.
• No association was found between increased risk for breast cancer and levels of nitrates or metals in drinking water. None of the wells in the water districts studied exceeded the maximum contaminant levels for these compounds allowed by the U.S. Environmental Protection Agency. Also, risk for breast cancer was not associated with living within 1 mile of hazardous waste or toxic release inventory sites containing metals. (Nitrates were studied because they have been linked to other cancers, but not specifically to breast cancer. One occupational study indicated a slightly increased risk for breast cancer in women exposed to metals. In another study, the metal cadmium was found to increase the growth of human breast cancer lines in cell culture and may have estrogenic activity. Results of a recent study show that cadmium has estrogen-like activity in rats (in vivo).)

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