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Brain cancer and occupational exposure to magnetic fields among men: results from a Canadian population-based case-control study

^a Environmental Risk Assessment and Case Surveillance Division, Labora-tory Centre for Disease Control, Health Canada, Ottawa, Ontario, CanadaK1A 0L2.
^b Department of Epidemiology and Community Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5.
^c Department of Public Health Sciences, University of Toronto, 12 Queen's Park Crescent, Toronto, Ontario, Canada M5S 1A8.
^d The Canadian Cancer Registries Epidemiology Research Group comprises a Principal Investigator from each of the Provincial Cancer Registries involved in the National Enhanced Cancer Surveillance System: Bertha Paulse, Newfoundland Cancer Foundation; Ron Dewar, Nova Scotia Cancer Registry; Dagny Dryer, Prince Edward Island Cancer Registry; Nancy Kreiger, Cancer Care Ontario; Erich Kliewer, Cancer Care Manitoba; Diane Robson, Saskatchewan Cancer Foundation; Shirley Fincham, Division of Epidemiology, Prevention and Screening, Alberta Cancer Board; and Nhu Le, British Columbia Cancer Agency.

Dr Paul Villeneuve, Department of Epidemiology and Community Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5.

Abstract

Background The relationship between occupational exposure to magnetic fields and brain cancer in men was investigated using population-based case-control data collected in eight Canadian provinces. Emphasis was placed on examining the variations in risk across different histological types.

Methods A list of occupations was compiled for 543 cases and 543 controls that were individually matched by age. Occupations were categorized according to their average magnetic field exposure through blinded expert review (<0.3, 0.3–<0.6, and 0.6 µT). In total, 133 cases (14%) and 123 controls (12%) were estimated to have at least one occupation whereby magnetic field exposures exceeded 0.3 µT. Odds ratios (OR) were generated using conditional logistic regression, and were adjusted for suspected occupational risk factors for brain cancer.

Results A non-significantly increased risk of brain cancer was observed among men who had ever held a job with an average magnetic field exposure >0.6 µT relative to those with exposures <0.3 µT (OR = 1.33, 95% CI : 0.75–2.36). A more pronounced risk was observed among men diagnosed with glioblastoma multiforme (OR = 5.36, 95% CI : 1.16–24.78). Moreover, a cumulative time weighted index score of magnetic field exposure was significantly related to glioblastoma multiforme (P = 0.02). In contrast, magnetic field exposures were not associated with astrocytoma or other brain cancers.

Conclusions Our findings support the hypothesis that occupational magnetic field exposure increases the risk of glioblastoma multiforme.

Keywords Magnetic fields, brain cancer, occupation

Accepted 2 August 2001