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| 23 June 2005 |
| Pylons and Childhood Leukaemia: The Draper Report Following recent press coverage of scientific findings showing a correlation between the occurrence of childhood leukaemia and the proximity of high voltage electricity pylons, this bulletin provides details of the purpose, scope and outcome of the study. The Draper Report, named after its principal researcher and author, Gerald Draper, was first published in the British Medical Journal on 3 June 2005. This is the largest study of its kind ever undertaken, involving double the number of cases than the next largest study, conducted by Feychting and Ahlbom in 1993.
Background to the Report The Draper report suggests that there may be some association between an individual's proximity to high voltage power lines at birth and the occurrence of childhood leukaemia. This suggestion is not revolutionary. Previous research has also indicated a similar relationship. In Wertheimer and Leeper’s report of 1979, concerns were first raised of a possible connection between low frequency electric and magnetic fields and the occurrence of cancer. A series of studies in 2000 pooled their results for an analysis of magnetic fields and childhood leukaemia, revealing that the risk is doubled for those living in areas where the average magnetic field equals or exceeds 0.4µT. In 2001, the International Agency for Research on Cancer considered the scientific evidence strong enough to categorise low frequency magnetic fields as ‘possibly carcinogenic’.
Parameters and method The aim of the Draper report was to look at where children diagnosed with cancer lived at birth and whether a disproportionate number of these locations were close to high voltage power lines. The study identified 33,000 cases of children aged 0-14 born and diagnosed with cancer between the years 1962 and 1995, representing most of the period that the National Grid has existed. Of the 33,000 cases identified, information of the location of their residence at birth was only available for 31,000. After matching each cancer case to an appropriate non-cancer control case, selected from birth registers with matching sexes, dates of birth and registration districts, the final group of cancer cases eligible for the study was 29,081, with a corresponding number of non-cancer control cases. Of these, 9,700 were cases of leukaemia, with the remainder being other forms of cancer. The study then established the locations of all 400kV and 275kV overhead power lines, and a ‘small fraction’ of 132kV overhead power lines in the United Kingdom. All cases that were living within 1km of such power lines at birth were subsequently identified.
Outcome The study revealed that 3.4% of all leukaemia cases lived within 600 metres of a high voltage power line at birth. Of the corresponding non-cancer control cases, 2.7% lived within the same proximity of such power lines at birth. Closer examination of the results approximately showed a correlation with the incidences of childhood leukaemia the closer the child’s residence at birth was to the high voltage power lines. The report concludes that the ‘relative risk’ of childhood leukaemia at up to 199 metres from the power lines is 1.67 times than at 600+ metres from the power lines. This ‘relative risk’ drops to 1.23 when the distance is between 200 and 599 metres. Significantly, the increased risk associated with proximity to high voltage power lines is only revealed in the results for childhood leukaemia cases. All other forms of childhood cancer failed to show any similar trend. In fact, the results for cases of Central Nervous System and brain tumours show a reduced risk in areas between 0 and 199 metres from high voltage power lines compared to that at 600+ metres.
Potential explanations The study considers various factors that may naturally explain the apparent trend, other than there being some causative effect of nearby high voltage power lines on childhood leukaemia. There is an established connection between affluence and the risk of being diagnosed with leukaemia. Using previous research, the study made appropriate adjustments for the socio-economic status of each case, but this failed to have any impact on the results. The report concludes, therefore, that socio-economic factors do not explain the increased risk. The study also considered the proposal that potentially damaging electrically charged particles are blown by the wind from the power lines, hence affecting the area around the power lines. However, when prevailing wind directions were analysed, the predicted affected area was shown not to be represented by the results. The report concludes that this is not the root of the increased risk of childhood cancer around high voltage power lines. The report considered the possibility that the increased magnetic field created by high voltage power lines may be the underlying cause of the increased risk of childhood leukaemia. Unlike the other explanations that the report explores, there is no evidence enabling such an explanation to be discounted. However, the report does not examine the effect of an increased magnetic field, rather it suggests that, on the strength of current scientific research, this is the most plausible explanation for the increased risk of childhood leukaemia. The report makes clear that it does not establish a link between proximity of high voltage power lines at birth and increased incidences of childhood leukaemia. However, it does offer the suggestion that irrespective of the cause, approximately 5 of the 400-420 cases of childhood leukaemia diagnosed each year will be ‘associated with’ high voltage power lines.
Conclusions While making no claims as to causation, the study does focus on the effect of high voltage power lines on the magnetic field of the surrounding area. There is little doubt that the magnetic field is increased in the immediate vicinity of a high voltage power line, however, other studies have shown that such an effect is usually obscured at 200 metres from the power line by the normal background magnetic fields created in the home. Hence the report repeatedly expresses its surprise at the extent of the distance from the power lines that it concludes there to be an increased risk of childhood leukaemia. Already, the Draper report has drawn some critical responses from various academics and industry experts, highlighting the apparently positive effect high voltage power lines have in reducing the risk of brain tumours, as well as the statistical inaccuracies that the report’s failure to consider other geographical features around power lines will inevitably create. Whilst a number of media articles following the Draper report led with some alarming headlines, the report does not claim to establish a causal connection between childhood leukaemia and the proximity of high voltage power lines at birth. Rather it merely highlights the as yet inexplicable fact that a slightly disproportionate number of childhood leukaemia cases occur in children living within 600 metres of high voltage power lines at birth.
The content of this article does not constitute legal advice and should not be relied on as such. Specific advice should be sought about your specific circumstances. Herbert Smith LLP, Gleiss Lutz and Stibbe are three independent firms that have a formal alliance. © Herbert Smith LLP 2005
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