Magnetic fields and leukaemia risks in UK electricity supply workers

Aims: To investigate whether leukaemia risks are related to occupational exposure to low-frequency magnetic fields.

Methods: Leukaemia risks experienced by 73 051 employees of the former Central Electricity Generating Board of England and Wales were investigated for the period 1973–2010. All employees were hired in the period 1952–82 and were employed for at least 6 months with some employment in the period 1973–82. Detailed calculations had been performed by others to enable an assessment to be made of exposures to magnetic fields. Poisson regression was used to calculate relative risks (rate ratios) of developing leukaemia or leukaemia subtypes for categories of lifetime, distant (lagged) and recent (lugged) exposure.

Results: Findings for all leukaemias combined were unexceptional; risks were close to unity for all exposure categories and there was no suggestion of risks increasing with cumulative (or recent or distant) magnetic field exposures. There were no statistically significant dose–response effects shown for acute myeloid leukaemia, chronic myeloid leukaemia or chronic lymphocytic leukaemia. There was a significant positive trend for acute lymphocytic leukaemia (ALL), but this was based, in the main, on unusually low risks in the lowest exposure category.

Conclusions: This study found no convincing evidence to support the hypothesis that exposure to magnetic fields is a risk factor for leukaemia, and the findings are consistent with the hypotheses that both distant and recent magnetic field exposures are not causally related to the generality of leukaemia. The limited positive findings for ALL may well be chance findings.