National Radiation Laboratory comment on BMJ study

Media Release

3 June 2005

National Radiation Laboratory comment on BMJ study

Further material was added to the long-running debate about a possible link between power lines and leukemia in children by a study published today in the British Medical Journal (BMJ).

The latest study was carried out by the Childhood Cancer Research Group at Oxford University and looked at 35,000 cases of childhood leukemia and other cancers between 1962 and 1995. The researchers examined whether risk of childhood leukemia was related to distance from high voltage transmission lines at birth.

The results suggest a slightly higher chance of children developing leukemia when living within 600 metres of high voltage overhead lines. Children who lived within 200m of high voltage power lines at birth appeared to have a 70% raised risk of leukemia compared with those who lived beyond 600m. There was a 23% increased risk for those living 200-600m from the lines at birth.

No excess risk was found for other childhood cancers. The authors emphasise that these results may be due to chance and further research is needed to find out whether there really is a link. If they do indicate a true cause and effect relationship, they estimate that residence near power lines could account for around 1% of childhood leukemia cases reported in the UK.

National Radiation Laboratory senior science advisor Martin Gledhill said about the study: ``Rather than help resolve the debate, if anything, it further confuses it.

``To date, debate on possible associations between transmission lines and childhood leukemia has largely focused on whether the extremely low frequency (ELF) magnetic fields produced around the line may be responsible. Magnetic fields could not explain an effect occurring up to 600 metres from the line, as they would have little or no influence on overall exposures beyond about 100 metres. While a large pooled analysis of previous studies did find an apparent association between exposure to ELF magnetic fields and increased risk of childhood leukemia, a study in New Zealand found that none of the cases of childhood leukemia reported over a four-year period was exposed to high field levels. Laboratory work does not suggest that magnetic fields at these levels could gave any effect on cancer.''

An accompanying editorial by Heather Dickinson from the University of Newcastle Tyne in the same issue agrees that, even if the effect is causal, it could account for only a tiny proportion of cases. She comments that we don't yet fully understand the aetiology of childhood leukemia, but that it may be triggered by delayed exposure to infection after prenatal damage to DNA.

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