Breast cancer and occupational exposures in women in Finland

Background: The etiology of breast cancer is not fully under-stood. Environmental and occupational exposures may contribute to breast cancer risk. Methods: We linked 324 job titles from the 1970 census of 892,591 Finnish women with incidence of breast cancer (23,638 cases) during 1971-1995. We converted job titles to 31 chemical and two ergonomic agents through a measurement-based, period-specific, national job-exposure matrix. Poisson regression models were fit to the data, with adjustment for birth cohort, follow-up period, socioeconomic status, mean number of children, mean age at first delivery, and turnover rate. Results: For premenopausal breast cancer;. medium/high level of occupational exposure to ionizing:radiation was; associated with a standardized incidence ratio (SIR) of 1.3 (95% confidence interval (CI) 0.7-2.5; trend P = 0.03). For postmenopausal breast cancel; we found art SIR of 1.2 (1.1-1.3)for low level and 1.4 (1.1-1.8)for medium/high level of ionizing radiation (trend P = 0.001); and an SIR 1.3 (1.1-1.7)for medium/high levels of both asbestos and map-made vitreous fibers. Aromatic hydrocarbon solvents showed a significant trend for a modest excess of postmenopausal breast cancer. Conclusions:Our study indicates that occupational exposure to ionizing radiation may be associated with an increased risk of female breast cancer High-quality studies on environmental and occupational etiology of breast cancer are needed for further elucidation of risk factors.:Am. J. Ind. Med. 36:48-53, 1999. (C) 1999 Wiley-Liss, Inc.