MAGNETIC-FIELDS AND BREAST-CANCER IN SWEDISH ADULTS RESIDING NEAR HIGH-VOLTAGE POWER-LINES

We conducted a case-control study to test the hypothesis that resident ial magnetic field exposures increase the incidence of breast cancer. The study was based on people who had lived within 300 m of 220- or 40 0-kV power lines in Sweden at any time between 1960 and 1985. We ident ified 699 cases of breast cancer in women and 9 cases in men. One matc hed control per female case and eight per male case were selected at r andom. Estrogen receptor information was available for a subset of fem ale cases. We assessed magnetic field exposure through calculations of the magnetic fields generated by the power lines before diagnosis. Fo r calculated magnetic field levels greater than or equal to 0.2 microt esla (mu T) closest in time before diagnosis, we estimated the relativ e risk to be 1.0 [95% confidence interval (CI) = 0.7-1.5] for women an d 2.1 (95% CI = 0.3-14.1) for men. Women younger than 50 years of age at diagnosis had a relative risk of 1.8 (95% CI = 0.7-4.3). For women with estrogen receptor positive breast cancer, the relative risk was e stimated at 1.6 (95% CI = 0.6-4.1), using the exposure cutoff point gr eater than or equal to 0.1 mu T. Among estrogen receptor-positive wome n younger than 50 years at diagnosis, the relative risk increased to 7 .4 (95% CI = 1.0-178.1).