Electrical sources like power cables emit alternating electromagnetic fields at very low frequencies. For many years there was no special concern that these might be associated with cancer. However, in 1979 an epidemiological study was published by Drs Wertheimer and Leeper suggesting that children who lived within a short distance of alternating electromagnetic fields were at increased risk of some cancers. This observation has generated a vast amount of discussion, research and investment in research into the possible harmful effects of electromagnetic fields. The work is incomplete and it is hard to draw conclusions. Indeed, our colleague Professor Ray Cartwright, in an article in the British Journal of Cancer, concluded ‘it is not surprising that some confusion exists in the minds of the scientific community and the general public as to the reality of these risks’.
Briefly, most of the scientific evidence, although not yet conclusive, suggests that the risk, if it exists, is small. The energy emitted by these low-frequency electrical sources is at the low end of the electromagnetic (EM) spectrum, much below that of radio waves or ultraviolet rays. Electromagnetic fields are not ionizing and do not even produce heat. There has not been much work in the laboratory, but such work as has been done does not show any consistent evidence of cancer causation by electromagnetic irradiation from electrical sources. Wertheimer and Leeper produced the only evidence which causes concern. They looked at the incidence of childhood leukaemia in relation to electromagnetic fields and said that it was higher in children who had a high exposure to EM fields. Since then, studies have looked at occupations where there is believed to be an excess of exposure to electrically generated electromagnetic irradiation. Such occupations include those of linesmen, power-station workers, telecommunication workers, electrical engineers, nuclear-shipyard electricians, radio and television repairers and assembly-line workers. On balance, the studies suggest there may be a small excess risk of leukaemia in these workers but it is difficult to link this conclusively to electromagnetic irradiation. There is no good, conclusive evidence that they are actually exposed to more electromagnetic irradiation than the general population and it is quite possible that they are exposed to other leukaemagens (leukaemia-inducing agents) such as chemicals in the workplace. Studies which have attempted to reproduce the observations of a link between childhood leukaemia and overhead power cables have, in general, been unconvincing but are continuing. The results of these investigations are very difficult to interpret because the studies are small and the documentation of the actual exposure to electromagnetic irradiation as a result of the power lines is rather imprecise.
Those currently investigating this problem in North America and Europe will try even harder to tease out the answers. This will take years, and will cost the power industry and government large sums of money. There will be much more speculation but. at present, the scientific evidence seems to point to the following conclusion drawn by Ray Cartwright in his recent article: ‘We are thus looking forward to many more years of speculation surrounding the supposed adverse health effects of electromagnetic fields at very low frequencies with respect to leukaemia, despite the fact that our present scientific knowledge points at the very best to a minute risk of electromagnetic fields verging on the point of non-existence.’
*83\194\4*

CANCER AND RADIATION HAZARDS: ELECTROMAGNETIC FIELDSElectrical sources like power cables emit alternating electromagnetic fields at very low frequencies. For many years there was no special concern that these might be associated with cancer. However, in 1979 an epidemiological study was published by Drs Wertheimer and Leeper suggesting that children who lived within a short distance of alternating electromagnetic fields were at increased risk of some cancers. This observation has generated a vast amount of discussion, research and investment in research into the possible harmful effects of electromagnetic fields. The work is incomplete and it is hard to draw conclusions. Indeed, our colleague Professor Ray Cartwright, in an article in the British Journal of Cancer, concluded ‘it is not surprising that some confusion exists in the minds of the scientific community and the general public as to the reality of these risks’.Briefly, most of the scientific evidence, although not yet conclusive, suggests that the risk, if it exists, is small. The energy emitted by these low-frequency electrical sources is at the low end of the electromagnetic (EM) spectrum, much below that of radio waves or ultraviolet rays. Electromagnetic fields are not ionizing and do not even produce heat. There has not been much work in the laboratory, but such work as has been done does not show any consistent evidence of cancer causation by electromagnetic irradiation from electrical sources. Wertheimer and Leeper produced the only evidence which causes concern. They looked at the incidence of childhood leukaemia in relation to electromagnetic fields and said that it was higher in children who had a high exposure to EM fields. Since then, studies have looked at occupations where there is believed to be an excess of exposure to electrically generated electromagnetic irradiation. Such occupations include those of linesmen, power-station workers, telecommunication workers, electrical engineers, nuclear-shipyard electricians, radio and television repairers and assembly-line workers. On balance, the studies suggest there may be a small excess risk of leukaemia in these workers but it is difficult to link this conclusively to electromagnetic irradiation. There is no good, conclusive evidence that they are actually exposed to more electromagnetic irradiation than the general population and it is quite possible that they are exposed to other leukaemagens (leukaemia-inducing agents) such as chemicals in the workplace. Studies which have attempted to reproduce the observations of a link between childhood leukaemia and overhead power cables have, in general, been unconvincing but are continuing. The results of these investigations are very difficult to interpret because the studies are small and the documentation of the actual exposure to electromagnetic irradiation as a result of the power lines is rather imprecise.Those currently investigating this problem in North America and Europe will try even harder to tease out the answers. This will take years, and will cost the power industry and government large sums of money. There will be much more speculation but. at present, the scientific evidence seems to point to the following conclusion drawn by Ray Cartwright in his recent article: ‘We are thus looking forward to many more years of speculation surrounding the supposed adverse health effects of electromagnetic fields at very low frequencies with respect to leukaemia, despite the fact that our present scientific knowledge points at the very best to a minute risk of electromagnetic fields verging on the point of non-existence.’*83\194\4*

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