Power cables – what risk?
The current panic over power cables is typical of the contradictory nature of health scares. A risk is either small or it is significant. It cannot be both.
‘High-voltage power cables have been officially linked to cancer for the first time’, reported The Sunday Times (London) on 4 March 2001. ‘A study shows that children living near them run a small but significant increased risk of falling victim to the disease.’
With this story, the Sunday Times report heralded a new escalation in government-sponsored scaremongering. The source of the story was Sir Richard Doll, whose name is always followed in press accounts by the description ‘the epidemiologist who discovered the link between smoking and lung cancer in the 1960s’.
In fact, that significant discovery was largely down to Sir Bradford Hill, a great proponent of statistical rigour. After the death of Hill, his colleague Doll rather went off the rigorous rails and launched into some of the greater excesses of the subject that its practitioners call epidemiology – and many real scientists call a bad joke. He achieved his apotheosis with a notorious book called The Causes of Cancer, written with Sir Richard Peto.
As medical journalist James LeFanu has pointed out, the whole of Doll’s thesis – that cancer is caused by diet – is based on a deliberate bit of deception. This involved ignoring by far the most important factor in cancer – age. The offence was compounded by the proliferation of tables purporting to show elaborate corrections for age factors, but in fact doing nothing of the sort. This technique is known among stage magicians as misdirection.
The opening paragraph from The Sunday Times, quoted above, is typical of the self-contradictory nature of health scares like the current scare over power cables. A risk is either small or it is significant. It cannot be both.
The whole fiasco of modern epidemiology is based on the quotation of risk ratios that are unacceptable in real science, together with many other techniques of obfuscation – like the way it ignores what are known as confounding factors. A favourite technique for generating papers in journals of epidemiology is ‘cluster spotting’, which is the basis of this renewed scare.
Another member of the committee issuing the scare over power cables is Professor Colin Blakemore. Professor Blakemore famously promoted the panic about mobile phones, ignoring the blatant fact that with 60 percent of the population using the devices, there is no sign of an epidemic of any sort.
But a clearer picture of the power cables issue emerges from the media response to the full report given by the National Radiological Protection Board (NRPB), on 6 March 2001. Significantly, this more measured (indeed dismissive) account was largely ignored by the media.
The report claims that the overall risk of leukaemia, which in all children is 1 in 1400, becomes elevated to 1 in 700 for those exposed to magnetic fields of 0.4microTesla or more (about 0.5 percent of children). This is a risk ratio of 2, which is considered unacceptable in all branches of science except epidemiology. In actual numbers, however, it represents about one extra case of leukaemia every two years as a result of exposure to magnetic fields – this, out of a total number of 500 cases per year.
Even if such a phenomenon were to exist, it would generally be considered to be undetectable by available statistical methods. There are many other questions that occur: for example, why 0.4microTesla? How much exposure and for how long? What other phenomena correlate with power lines? (For example, do rich people live under them?) These questions, however, are dwarfed by the minuscule nature of the numbers involved.
Another curiosity about the report is its concentration on magnetic fields, for which no known disease-causing mechanism has been advanced. Electric fields, on the other hand, cause corona, especially in damp weather, which has highly active by-products such as ozone and oxides of nitrogen. Although this risk is still somewhat implausible, it is far more acceptable than the magnetic hypothesis.
The next act in this artificial drama will no doubt feature the compensation lawyers, who have so far been frustrated in their efforts to build up a nice little earner out of power cables.
John Brignell is author of Sorry, Wrong Number!. He resigned a chair in Industrial Instrumentation in order to concentrate on writing about the abuse of measurement in the media and politics, and is currently working on a book about the epidemiologists.
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