AUTHORS: M. Feychting et al.
Epidemiology. 1994:5(5) p. 501-509.
STUDY DESIGN: A case-control design nested in a cohort of adults living within 300 meters of 220 or 400 kilovolt power lines (the power line corridor) in Sweden was used to investigate the hypothesis that exposure to magnetic fields generated by high-voltage power lines is associated with increased leukemia and cancer of the central nervous system in adults. Study participants had to live in the power line corridor at some time between 1960 and 1985. Three hundred and twenty-five (325) leukemia cases and 223 cases of central nervous system tumors were identified. Controls were randomly chosen from the cohort with two matched controls for most cases. Exposure assessment was conducted by combining contemporaneous spot measurements in homes with calculations of the historical magnetic fields generated by the power lines. These data were used to assign estimated levels of average exposure for each year spent residing in the power line corridor. Cumulative exposure was determined by summing exposure for each of 15 years preceding diagnosis.
CONCLUSIONS: While relative risks were elevated for exposures of calculated magnetic fields of 2 mG or greater in the time period closest to the time of diagnosis, none were statistically significant. For instance, the relative risk for acute myeloid leukemia was 1.7, but the 95% confidence interval included values less than one (95% CI=0.8-3.5); the same was true for chronic myeloid leukemia (RR=1.7, 95% CI=0.7-3.8). Even for the highest category of cumulative exposure a relative risk of 2.3 was seen for acute myeloid leukemia with 95% confidence intervals including one (95% CI=1.0-4.6); again, the same non- statistically significant relationship was observed for chronic myeloid leukemia (RR=2.1, 95% CI=0.9-4.7). No association was observed for central nervous system tumors or chronic lymphatic leukemia.
LIMITATIONS: A major limitation of this study is that it ignores all sources of exposure except living in the power line corridor. With adults, the other sources of exposure could be significant, especially with regard to the occupational setting.