Currents of Death?
Twenty-five years of research has rubbished claims of a link between childhood cancer and overhead power lines. So why do new studies keep appearing?
A new epidemiological study suggesting a link between childhood cancer and overhead power lines was launched at a press conference yesterday, 2 June. The study, which appears in the British Medical Journal with an accompanying editorial, immediately generated considerable media interest (1).
Over 29,000 children with cancer, including 9,700 with leukaemia, were included in the study. The children were aged 0-14 years and were born in England and Wales between 1962 and 1995. They were compared with a control group of children individually matched for sex, approximate date of birth, and birth registration district. The distance of each child’s home address at birth from the nearest high voltage power line was calculated. Children who lived within 200m of high voltage power lines at birth appeared to have a 70 per cent raised risk of leukaemia compared with those who lived beyond 600m. There was also a slightly increased risk for those living 200 to 600m from the lines at birth.
The press release is at pains to emphasise that the results should be treated with caution, and even if there were some role played by these so-called power frequencies (or what is known by the usual acronym ELF – extremely low frequency fields), this could only explain a very small number of childhood leukaemias. Usefully, the press release explains the scale of the possible association: ‘To put these risks into perspective, about five of the 400-420 cases of childhood leukaemia that occur annually in England and Wales may be associated with power lines.’
The authors add that the effect could be simply down to chance or another cause. The most important so-called ‘confounding factor’ (all the other influences that equally might explain any association found between one factor and another) in this case has long been recognised to be the fact that neighbourhoods with heavy concentrations of power lines are typically poor, congested and polluted – all of which are risk factors for cancer.
This is particularly relevant with this study. As the Institute of Electrical Engineers points out in its press release, also published on 2 June, the elevated rates are found some 600 metres from the power lines. It explains: ‘At these distances, the magnetic fields in homes due to the lines are negligible compared to background levels.’ Given that it is generally accepted that it could only be the magnetic fields generated by power lines that might cause a problem, it must be something other than the power lines themselves that explains the results.
With such a tiny possible problem identified, and with such heavy qualification provided, one is left to wonder why this study was deemed worthy of such attention. Given that the research was not stimulated by an evident problem – notably any increased incidence of leukaemia among children – one might also ask why the study was carried out in the first place. This is particularly the case given that the anxiety over a potential link between power lines and childhood leukaemia dates back over 25 years, and has already generated a large amount of research. So why do the researchers’ conclude that even more research is needed? Not only is it questionable whether such a tiny association merits further investigation in itself, but the enormous quantity of previous research in this area has effectively ruled out any such need.
Like other such ‘microwave anxieties’, the power line issue is American in origin and it is instructive to look at its history. The issue was brought to prominence by a single individual, Paul Brodeur. He was a writer for the New Yorker magazine who turned his attention to environmental health issues in the late 1960s. Through a series of articles and a subsequent book, Brodeur first of all made a name for himself by suggesting that microwaves such as in microwave ovens could cause harm – despite their acknowledged inability to damage DNA, the key effect of cancer-inducing agents.
As the subsequent microwave panic subsided, Brodeur turned his attention to power lines. In scientific terms, grounds for concern were laid by a small study of childhood leukaemia patients in Denver carried out by Nancy Wertheimer and Ed Leeper in 1979. They suggested that children from homes near power lines were three times more likely to develop leukaemia. At such a low frequency (around 60 Hz) at one end of the electromagnetic spectrum, there is not even the heating effect created by microwaves. The only concern was that the effect of the alternating magnetic fields created by power lines might somehow interfere with our cancer defences. The accumulated evidence conclusively suggests that they do not.
When Brodeur turned his attention to the issue some years later, however, power lines became a major focus for anxiety within American society. In 1989 he wrote a series of articles for the New Yorker that drew upon his earlier attack on microwaves, but this time focused attention upon power lines. Brodeur made a massive media impact with his articles and subsequently produced a book, Currents of Death.
Single-handedly Brodeur stimulated a massive research programme into this highly improbable threat. Although only one seriously-regarded study seemed to confirm the possibility of such an association, power lines became a major concern in the early 1990s – even making an appearance in Eddie Murphy’s 1992 film The Distinguished Gentleman. Besides Brodeur’s efforts, probably most important in raising anxiety was a preliminary report by the American Environmental Protection Agency in 1990, which suggested a ‘probable’ link between power lines and cancer – a wording that was subsequently corrected to ‘possible’ after the media damage had already been done.
The high profile created for the power line issue ensured that an enormous amount of research resources were dedicated to it. A 1994 study, for example, that typically found no overall increased cancer risk, looked at 223,000 Canadian and French electrical workers over four years. A similar American study the following year had an even larger population and found that the cancer rate among electrical workers is lower than the general population.
The renowned physicist Robert Park, in his book, Voodoo Science, identifies two decisive moments in what he calls ‘slamming the door shut’ on the controversy (2). The first was the so-called Stevens report by the (American) National Academy of Sciences (NAS) in 1996, which concluded definitively that ‘the current body of evidence does not show that exposure to these fields presents a human health hazard’. Significantly, and unlike the single study released today, the NAS report was based upon a review of all the relevant research literature published to date – some 500 studies. According to its review, any link was too weak to detect or to be concerned about.
In the face of such growing evidence Brodeur became increasingly conspiratorial; a subsequent series of articles was also turned into a book, this time called The Great Power-Line Cover Up. But a further blow was struck in the year following the NAS review. In 1997, the prestigious National Cancer Institute (NCI) announced the results of its exhaustive seven-year investigation into the purported childhood leukaemia/power line connection. The NCI study found no association at all, effectively establishing that the link suggested by earlier research was just an artefact of earlier statistical analysis. As Park wrote, ‘As is so often the case with voodoo science, with every improved study the effect had gotten smaller. Now, after 18 years, it was gone completely’.
In the wake of these findings, and the realisation of just how many resources had been spent on a fruitless scientific quest initiated by an enterprising journalist, there was sober reflection within the American scientific community. The White House Science Committee calculated that $25 billion had been spent – including relocating people from their houses. The Department of Energy closed down the EMF Research and Public Information Dissemination (RAPID) programme created by Congress in 1992. As Park points out in Voodoo Science, this didn’t prevent another committee defining Electro-Magnetic Fields (EMF) as a ‘possible carcinogen’ only a year later.
Yet the press release for the study released yesterday keeps the controversy going, by pointing out that the International Agency for Research on Cancer (IARC) defines ELF as ‘possibly carcinogenic’. But we should recognise that ‘possibly’ has very little meaning, and represents less a simple scientific judgement than an attempt to play cautious science politics. Given the highly cautious way in which science politics has subsequently progressed, it was widely recognised that the IARC would be unwilling to dismiss any cancer risk and would opt for the much safer definition of ‘possible’.
By contrast, an editorial in the prestigious New England Journal of Medicine following the release of the NCI study in 1997 remains admirably clear: ‘It is sad that hundreds of millions of dollars have gone into studies that never had much promise of finding a way to prevent the tragedy of cancer in children. The many inconclusive and inconsistent studies have generated worry and fear and have given peace of mind to no one. The 18 years of research have produced considerable paranoia, but little insight and no prevention. It’s time to stop wasting our resources. We should redirect them to research that will be able to discover the true biologic causes of the leukemic clones that threaten the lives of children.’
In The Rise and Fall of Modern Medicine, the doctor and medical writer James LeFanu suggested that closing down all the epidemiology departments in the country would, at a stroke, greatly minimise health anxiety within society (3). When it comes to the presentation of power lines as ‘currents of death’, I’m inclined to agree.
Adam Burgess is lecturer in sociology at the University of Kent and author of Cellular Phones, Public Fears and a Culture of Precaution (New York: Cambridge University Press, 2004)
(1) ‘Is there a link between childhood cancer and overhead power lines? Childhood cancer in relation to distance from high voltage power lines in England and Wales: a case-control study’, British Medical Journal, Volume 330, pp 1290-2; and ‘Science commentary: Power to confuse’, British Medical Journal, Volume 330, p 1293. ‘Editorial: The causes of childhood leukaemia’ British Medical Journal, Volume 330, pp 1279-80
(2) Robert Parks, Voodoo Science (Oxford University Press, 2000)
(3) James LeFanu, The Rise and Fall of Modern Medicine (London: Abacus, 1999)