AUTHORS: G. Theriault et al.
American Journal of Epidemiology. 1994:139(6) p. 550-572.
STUDY DESIGN: A case-control study was nested within three cohorts of male workers at the following electric utilities: Electricite de France-Gaz de France (170,000); Ontario Hydro (31,543) and Hydro-Quebec (21,749) to determine if occupational exposure to magnetic fields of 50- 60 Hz was associated with cancer. Exposure was estimated using personal dosimetry on 2,066 workers performing similar tasks. During the period of observation (1970-1989), incident cases of cancer were recorded and studied. Controls were other employees from the same utility matched with the case on year of birth.
CONCLUSIONS: Workers exposed to higher fields (based on median cumulative exposure to magnetic fields) had an increased risk of developing acute nonlymphoid leukemia (OR=2.41, CI=1.07-5.44). An increased risk for developing acute myeloid leukemia, a subtype of acute nonlymphoid leukemia, (OR=3.15, CI=1.20-8.27) was also observed. A non- statistically significant elevated risk was observed for astrocytoma for workers in the 90th percentile exposure group, but this observation was based on small numbers. No association was observed for male breast cancer, skin melanoma or prostate cancer.
LIMITATIONS: Despite careful exposure assessments, improper classification of exposure status was unavoidable. Information of smoking status was available for only one utility, limiting the ability to control for confounding across all groups. Each utility differed in method of employee follow-up at employee termination which could be responsible for the variation across utilities with regard to leukemia.