Residential and occupational exposure to 50 Hz magnetic fields and hematological cancers in Norway.

ABSTRACT

OBJECTIVE: The aim of this nested case-control study was to test the hypothesis that exposure to electromagnetic fields from high-voltage power lines increases the incidence of hematological cancers in adults. Data from an occupational exposure matrix was also used. METHODS: The study population comprised subjects aged 16 and above who had lived in a residence situated in a broad corridor around a high-voltage power line in 1980, or one of the years from 1986 to 1996. The cases were incident cases diagnosed 1980-1996. Two controls were matched to each case by year of birth, sex, municipality and first year entering the cohort. Time-weighted average exposure to residential magnetic fields generated by the power lines was calculated for the exposure follow-up from January 1, 1967 until diagnosis using cut-off points at 0.05 and 0.20 microT. In addition, job titles and industrial branch was classified as categories of hours per week in a magnetic field above background (0.1 microT). Subjects exposures were cumulated over occupationally active years for the exposure follow-up January 1, 1955 until diagnosis. RESULTS: When residential magnetic fields are evaluated, the two upper residential time weighted average magnetic field categories showed non-significant elevated odds ratios (ORs) for all leukemia combined (OR 1.3, 95% confidence interval (CI) 0.7-2.5 and OR 1.5, 95% CI 0.8-3.0). The increased risk was confined to chronic lymphocytic leukemia, acute lymphocytic and acute myeloid leukemia. Lymphoma showed a non-significant lower OR in the upper exposure category. Multiple myeloma showed non-significant elevated ORs. Occupational exposure showed no significant association to exposure for any site. CONCLUSIONS: Some elevated ORs were observed in the present study, but the results are based on small numbers and no firm conclusions can be drawn.