Female Breast Cancer and Electrical Manufacturing: Results of a Nested Case-control Study

Background: A previous explorative record-linkage study suggested a putative role of employment in electrical manufacturing in increasing female breast cancer risk in the Province of Milan (Italy). We deepened the understanding of this possible association in a single large electrical manufacturing plant located in Lombardy in the Province of Milan. Methods: We carried out a nested case-control study within a cohort of women employed in a large electrical manufacturing plant. All incident cases during 2002 to 2009 of female breast cancer in individuals who worked at least a 1 year in the factory and resided in Lombardy, Italy, were selected. Controls were randomly sampled from all women who worked in the same plant and resided in Lombardy as of December 31, 2005. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated using multiple logistic regression models, taking into consideration only female workers as ever/never exposed to physical/chemical agents and their longest occupational period. ORs were adjusted for several potential confounders, namely, other known risk factors. Results: The ORs for female breast cancer were significantly increased for exposure to chlorinated solvents (OR 1.65, 95% CI 1.04-2.62), and there was a twofold increase (OR 2.10, 95% CI 1.21-3.66) among women exposed for at least 10 years. We found no other significantly increased OR by exposure or job title. Conclusions: Our results suggest an increased risk of breast cancer after exposure to chlorinated solvents among women employed in the electrical manufacturing industry.