Breast cancer, occupation, and exposure to electromagnetic fields among Swedish men

Background Investigations of breast cancer among men may provide clues for environmental and occupational risk factors that may be difficult to study in women, because of confounding or effect modification from reproductive f emale characteristics. The objective was to estimate occupation-specific ri sks of male breast cancer and to assess the effect of occupational exposure to extremely low-frequency magnetic fields (ELFMF). Methods Standardized incidence ratios were computed for the period 1971-198 9 among Swedish men who were 25-59 years of age at start of follow-up and g ainfully employed in 1970. Log-linear Poisson models were fitted to adjust for geographical area. A job exposure matrix was used to classify occupatio nal ELFMF exposure. Results A marked and consistent excess risk was found for machinery repaire rs. Increased relative risks based on few cases were also noted for librari ans/archivists/curators, bank employees, non-specified clerical workers, me tal processing workers, tanners/fur dressers, policemen, and custom surveil lance officials. The relative risk among subjects with an estimated ELFMF e xposure above the first quartile (0.12 muT) was 1.31 (95% confidence interv al = 0.94-1.81), without a clear exposure-response pattern. Indications of an exposure-response relationship were found in workers with intermittent E LFMF exposure. Conclusion The findings give no clear evidence for an etiological role of E LFMF in the development of breast cancer in men, but suggest that large var iations in exposure over the work-day may be associated with an increased r isk. (C) 2001 Wiley-Liss, Inc.