An ecological study of the association of environmental chemicals on breast cancer incidence in Texas

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Abstract
Purpose. To investigate the role of environment in breast cancer development, we conducted an ecological study to examine the association of releases for selected industrial chemicals with breast cancer incidence in Texas. Methods. During 1995–2000, 54,487 invasive breast cancer cases were reported in Texas. We identified 12 toxicants released into the environment by industry that: (1) were positively associated with breast cancer in epidemiological studies, (2) were Environmental Protection Agency (EPA) Toxics Release Inventory (TRI) chemicals designated as carcinogens or had estrogenic effects associated with breast cancer risk, and (3) had releases consistently reported to EPA TRI for multiple Texas counties during 1988–2000. We performed univariate, and multivariate analyses adjusted for race and ethnicity to examine the association of releases for these toxicants during 1988–2000 with the average annual age-adjusted breast cancer rate at the county level. Results. Univariate analysis indicated that formaldehyde, methylene chloride, styrene, tetrachloroethylene, trichloroethylene, chromium, cobalt, copper, and nickel were positively associated with the breast cancer rate. Multivariate analyses indicated that styrene was positively associated with the breast cancer rate in women and men (β = 0.219, p =0.004), women (β = 0.191, p=0.002), and women ≥ 50 years old (β = 0.187, p=0.002). Conclusion. Styrene was the most important environmental toxicant positively associated with invasive breast cancer incidence in Texas, likely involving women and men of all ages. Styrene may be an important breast carcinogen due to its widespread use for food storage and preparation, and its release from building materials, tobacco smoke, and industry.