Exposure to power-frequency magnetic fields and the risk of childhood cancer. UK Childhood Cancer Study Investigators

BACKGROUND: Previous studies have suggested an association between exposure to power-frequency electromagnetic fields (EMF) and the development of childhood malignant disease, especially leukaemia and tumours of the central nervous system. We investigated the relation between all childhood cancer and exposure to power-frequency magnetic fields. METHODS: The UK Childhood Cancer Study was a population case-control study covering the whole of England, Wales, and Scotland. All children with a confirmed malignant disorder were potentially eligible. For each case, we matched two controls on date of birth and sex, randomly chosen from the list of the Family Health Services Authority in England and Wales or Health Board in Scotland. In the main study, 3838 cases and 7629 controls were interviewed. The EMF part of the study included only one control per case, and household EMF measurements and school measurements where relevant were taken on 2226 matched pairs. These measurements, adjusted for historical line load and appliance fields, were used to estimate average exposure in the year before the date of diagnosis, or an equivalent date for controls. Analyses were by conditional logistic regression, incorporating a census-derived deprivation index used as a measure of socioeconomic status. FINDINGS: For children with mean exposures of more than 0.2 microT compared with children with mean exposures of less than 0-1 microT, the adjusted odds ratios were 0.92 (95% CI 0.47-1.79) for acute lymphoblastic leukaemia, 0.90 (0.49-1.63) for all leukaemia, 0.46 (0.11-1.86) for central-nervous-system tumours, 0.97 (0.46-2.05) for other malignant disease, and 0.87 (0.56-1.35) for all malignant disease combined. Higher exposures (>0.4 microT) were recorded for only 17 (