The potential carcinogenicity of electric and magnetic fields encountered in “electrical occupations” has been of concern to researchers and the public for nearly 20 years. Increasingly complex methods of occupational epidemiology have been applied to this issue, culminating in a series of reports in the past decade from studies that are large, apply intricate methods of exposure assessment, and use complex statistical analyses. The article by Sorahanet al 1 examining mortality from brain cancer among over 80 000 employees of the former Central Electricity Generating Board is a methodologically strong addition to these publications.

As was found among southern Californian Edison workers in the United States2 and Danish electric utility workers,3the British workers show no indications whatsoever of an association between measures of exposure to magnetic fields and mortality from brain cancer. By contrast, the study of French and Canadian utility workers provided sporadic positive findings for astrocytomas and benign tumours,4 with a suggestion of electric fields conferring increased risk among the French workers in that study.5The cohort of several United States electric utility company employees yielded a clear positive association between exposure to magnetic fields and brain cancer, including a dose-response gradient, particularly for recent exposure.6 …