Parental occupational exposure to magnetic fields and childhood cancer (Sweden)

Objectives: To test the hypothesis that parental occupational exposure to m agnetic fields before conception and during pregnancy increases the risk of cancer in the offspring. Methods: The study is designed as a cohort study based on a population of 2 35,635 children born shortly after two different censuses in Sweden. The ch ildren were followed from birth to 14 years and cases of cancer were identi fied in the Swedish cancer registry. The parents' occupational titles in th e censuses were linked to a job-exposure matrix with information about magn etic field levels in different occupations. The cancer incidence among the exposed was compared to that among the unexposed using Cox proportional haz ards modeling. Results: There was no association between childhood cancer and maternal occ upational magnetic field exposure. Paternal exposure was associated with an increased risk of childhood leukemia, with a relative risk of 2.0 (95% CI 1.1-3.5) for exposures greater than or equal to 0.30 mu T. A decreased risk was found for brain tumors (RR = 0.5; 95% CI 0.3-1.0). Conclusions: The results do not support previous findings of an increased r isk of childhood brain tumors associated with paternal occupational exposur e to magnetic fields. The finding for childhood leukemia has to be interpre ted with caution.