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

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.

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.

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.

Some elevated ORs were observed in the present study, but the results are based on small numbers and no firm conclusions can be drawn.