Occupational exposure to electromagnetic fields and female breast cancer

grantor: University of TorontoThe present study was designed to examine the association between occupational exposure to electromagnetic fields (EMF) and female breast cancer, The study design was case control, within the study population of the National Breast Screening Study (NBSS) of Canada. The sample included 1156 cases and 3468 matched controls (3 controls were matched for each case). The NBSS epidemiologic questionnaire included the title of the most recently held occupation. Classification of the case and control subjects into the exposure categories were made by an expert. Conditional logistic regression modelling using PHREG procedure was used to estimate the relative risks and their related confidence intervals. The results of the study suggest that women whose occupation entails exposure above the general population level are at higher risk for breast cancer. Analysis of data for younger (40-49 years) and older women (50-59 years) suggests a more than double increase in the risk for both age groups which is significant for the older subjects but below the significance level for the younger subjects. This study also shows that there is a significant interaction between EMF exposure and regularity of periods. The risk of breast cancer associated with exposure to electromagnetic fields increases when periods are regular, but a smaller sample of women whose periods are irregular show a protective effect. The present study found that women who had undergone mammography prior to the NBSS, were at higher risk for breast cancer. A dose-response relation for the number of prior mammographies was found. (Abstract shortened by UMI.)M.Sc