Magnetic fields of high voltage power lines and risk of cancer in Finnish adults: nationwide cohort study

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Abstract
Objective: To investigate the risk of cancer in association with magnetic fields in Finnish adults living close to high voltage power lines. Design: Nationwide cohort study. Subjects: 383 700 people who lived during 1970–89 within 500 metres of overhead power lines of 110–400 kV in a magnetic field calculated to be >/=0.01 μT. Study subjects were identified by record linkages of nationwide registers. Main outcome measures: Numbers of observed and expected cases of cancer, standardised incidence ratios, and incidence rate ratios adjusted for sex, age, calendar year, and social class—for example, by continuous cumulative exposure per 1 μT year—with 95% confidence intervals from multiplicative models for all cancers combined and 21 selected types. Results: Altogether 8415 cases of cancer were observed (standardised incidence ratio 0.98; 95% confidence interval 0.96 to 1.00) in adults. All incidence rate ratios for both sexes combined were non-significant and between 0.91 and 1.11. Significant excesses were observed in multiple myeloma in men (incidence rate ratio 1.22) and in colon cancer in women (1.16). Conclusions: Typical residential magnetic fields generated by high voltage power lines do not seem to be related to the risk of overall cancer in adults. The previously suggested associations between extremely low frequency magnetic fields and tumours of the nervous system, lymphoma, and leukaemia in adults and breast cancer in women were not confirmed. The present population based cohort study among Finnish adults with 8500 observed cancer cases found no increase in the risk of overall cancer in adults exposed to magnetic fields of high voltage power lines The previously suggested associations between magnetic fields and tumours of the nervous system, lymphoma, leukaemia, and breast cancer in women were not confirmed The results of the present study suggest strongly that typical residential magnetic fields generated by high voltage power lines are not related to cancer in adults The possibility of an increase in risk at higher magnetic field levels, or in more specific cancer subtypes, cannot be excluded on the basis of this study