Residential proximity to electricity transmission and distribution equipment and risk of childhood leukemia, childhood lymphoma, and childhood nervous system tumors: systematic review, evaluation, and meta-analysis.

In 1979, Wertheimer and Leeper reported an increased risk of cancer mortality among children living near 'electrical wiring configurations' suggestive of high current flow. Since then, numerous, often inconclusively small, investigations with conflicting results have studied the possible association between exposure to electric and magnetic fields (EMF) and health effects. The high prevalence of exposure to EMF has drawn attention to the issue of carcinogenesis. We report here the results of a meta-analysis of 13 epidemiologic studies of residential proximity to electricity transmission and distribution equipment and risk of childhood leukemia, lymphoma, and nervous system tumors. The combined relative risks for leukemia, lymphoma, and nervous system tumors are 1.49 (95 percent confidence interval [CI] = 1.11-2.00); 1.58 (CI = 0.91-2.76); and 1.89 (CI = 1.34-2.67) respectively. The reports of the primary studies were evaluated for epidemiologic quality and adequacy of exposure assessment. We found no statistically significant relation between combined relative risk estimates and 15 indicators of epidemiologic quality. Assessment of EMF exposure in the primary studies was found to be imperfect and imprecise. Additional high quality epidemiologic research, incorporating comprehensive assessments of EMF exposure collected concurrently with surrogate measures of exposure, is needed to confirm these results.