The first results of the EMF part of the case-control UK Childhood Cancer Study (UKCCS) were published in 19991. The main conclusion of the analysis was that there was no evidence that exposure to magnetic fields associated with the electricity supply in the UK augments risk for childhood leukaemia, cancers of the central nervous system, or any other childhood cancer. Recently an important subsidiary analysis has been carried out which focuses on the relationship between childhood cancer and living near to power lines2. The results, published in the British Journal of Cancer, are consistent with those based on measurements in the first analysis. There was no evidence that either residential proximity to electrical installations, or the magnetic field levels they produce, is associated with increased risk of childhood leukaemia or any other cancer.
The UKCCS was set up in the early 1990s at a time when previous studies had suggested an association between exposure to power frequency electromagnetic fields (EMF) and the development of childhood malignant disease, especially leukaemia and cancers of the central nervous system3. The main analysis1 was based on residential and school measurements of magnetic flux density. Exposure was estimated for the year preceding the date of diagnosis (or an equivalent date for controls) by weighting the measurements by the time spent in bed, at school and elsewhere, as determined during interview. Exposure estimates were adjusted for appliance and power line historical fields as necessary. The study found no association between measured power-frequency magnetic field exposure and risk for any malignancy1.
Several previous epidemiological studies have used distance from power lines as a crude marker of exposure4. Some have shown associations with childhood cancer; others have not. A recent view put forward is that either distance is a more stable surrogate for historical magnetic field exposure or that it may be a proxy measure for some unknown ‘causal exposure’ factor, less closely related to average measured magnetic fields4. During the course of the original study, details of external sources such as high voltage lines, underground cables, substations and some types of distribution circuits, were collected for the homes of most cases and one control per case. Home addresses and grid references were provided on questionnaires sent to electricity companies, masked with respect to case-control status. The details have provided study investigators with the opportunity to examine the postulated association between disease and distance. The effect of magnetic fields calculated from power lines alone has also been examined, using categories selected beforehand to be the same as those used for the measured analysis1.
The results are consistent with the previously reported results based on measured magnetic fields1. The study found no evidence that proximity to electrical installations, or the magnetic field levels they produce, is associated with increased risk of childhood leukaemia or any other cancer3. All homes with external source information were examined, giving 3380 cases and 3390 controls, as compared to the 2226 case-control pairs in the measurement based analysis1. The proximity study included the great majority of eligible households (85% of interviewed cases) so the possible effect of participation bias was small. Restricting the analysis to those children who had lived in the same home for all the year of interest (approximately 90% of study subjects) made little difference to the results.
NRPB Response Statement R3/00
14 November 2000
Last updated 14th November 2000