(HealthDay News) — Occupational exposure to solvents before first full-term birth may be associated with an increased risk of breast cancer in certain settings, according to a study published in the June 1 issue of Cancer Research.

Christine C. Ekenga, M.P.H., Ph.D., from the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., and colleagues examined the correlation between occupational exposure to solvents and breast cancer in a prospective study involving 47,661 women from the Sister Study cohort. Occupational solvent exposure was classified according to baseline data relating to self-reported job-specific solvent use.

During follow-up, 1,798 women were diagnosed with breast cancer, including 1,255 invasive cases. The researchers observed no correlation between the risk of invasive breast cancer and lifetime exposure to solvents (hazard ratio [HR], 1.04; 95 percent confidence interval [CI], 0.88 to 1.24). The risk of estrogen receptor-positive invasive breast cancer was increased for parous women who worked with solvents before the first full-term birth, compared with women who never worked with solvents (HR, 1.39; 95 percent CI, 1.03 to 1.86). Among clinical laboratory technologists and technicians, there was an increased risk of estrogen receptor-positive invasive breast cancer associated with solvent exposure (HR, 2.00; 95 percent CI, 1.07 to 3.73).

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“Occupational exposure to solvents before first birth, a critical period of breast tissue differentiation, may result in increased vulnerability for breast cancer,” the authors write. “Our findings suggest a need for future studies in this area to focus on exposure time windows and solvent types in different occupational setting.”

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