As the issue gradually shoulders its way up the media agenda - a BBC Panorama at the beginning of this year, a feature in a leading woman's magazine - more and more parents are becoming anxious. There have been more than 5,000 inquiries so far this year to the electricity industry's electromagnetic fields unit, more than ever before.
People hunger for straightforward, simple answers to the question 'Is this a danger to my children or myself?' and for advice they can follow. Alas, these are not going to be available for years. The following is about as near as one can get to the truth. Several recent childhood cancer studies 'do not establish that exposure to electromagnetic fields is a cause of cancer but, taken together, they do provide some evidence to suggest that the possibility exists. The risks, if any, however, would be small'.
Those plodding clauses were carefully chosen earlier this year by the National Radiological Protection Board's expert panel chaired by Sir Richard Doll, the leading epidemiologist who established the link between smoking and cancer.
One reason why it is so difficult to prove a link is that childhood cancer is fairly rare and a low proportion of children developing it are exposed to high-strength EMFs. This leaves the epidemiologists with very small numbers of cases to work with.
More significantly, out of hundreds of studies in which laboratory animals, cells, tissues and even people have been exposed to powerful EMFs none has produced any good evidence of a cancer-causing effect. Professor Ray Cartwright, a senior Leukaemia Research Fund epidemiologist, says: 'We haven't found any really convincing way in which these fields could cause cancer.'
Epidemiological studies outside the laboratory look at real cancer cases and try to show if EMF exposure is involved. These have become bigger, better and more expensive since the first such study from Denver, Colorado claimed to show a link 15 years ago, but there has been little pay off in strengthening or clarifying this connection. 'We continue to find this link but it remains murky,' says Dr David Savitz, from the University of North Carolina, a leading EMFs epidemiologist.
If high EMFs can contribute to the onset of childhood leukaemia (where the link appears strongest) then they appear to increase the risk by between 1.5 and three times the risk every child runs of developing the disease. By way of comparison, smokers increase their lifetime risk of lung cancer about twentyfold above non-smokers.
Leukaemia is the most common chidlhood cancer and the risk of developing it between birth and age 15 is one in 1,900. Although much progress has been made in treatment, it still kills about a quarter of its victims. Thus if the child lives close to high-voltage lines or another powerful EMF source the risk of becoming ill could - if there is a link - grow to higher than than one in 1,000 and risks of death to more than one in 4,000.
Are those unacceptable odds? Definitely, says Martin Day of lawyers Leigh, Day and Co, the only firm so far to represent alleged victims of EMFs. He points to a report from the Royal Society, which suggests that any involuntary risk of death or serious disability greater than one in 10,000 may be regarded as unacceptable. 'Most parents are less willing to take risks with their children's health and lives than with their own,' he says.
He acts for eight sets of parents who believe their children developed leukaemia or brain tumours because of EMFs and are seeking compensation from the power industry. Among them are Simon Studholme's mother and father from Radcliffe, north Manchester, who have obtained legal aid.
Simon, who died from leukaemia at the age of 13, lived next to an electricity sub-station and two buried high-voltage cables but, more significantly, he also slept with his head inches away from the household's electricity meter on the other side of the bedroom wall. He was exposed to an EMF about 15 times stronger than three milligauss - the level at which the childhood cancer risk might begin to increase, according to some epidemiological studies.
Mr Day argues that the regional electricity companies and the National Grid should at least warn all households exposed to high EMFs that there could be a risk. The industry says it is doing enough in tracking the research, responding to public inquiries and offering free surveys of the strength of electromagnetic fields inside homes.
The Government also says there is no need to do anything for now, apart from further research. Ministers say their expert advisers tell them there is no need for a policy of 'prudent avoidance', which would include measures such as forbidding the construction of houses and schools next to high- voltage lines.
Further studies may establish or disprove the link in a few years' time.
High hopes are being pinned on Britain's five-year childhood cancer study, which aims to look in detail at every one of the 1,000 cases expected each year. For each sick child, two healthy, matched 'control' children from the same locality and social background will also be studied; exposure to EMFs is one of the factors under investigation. We will have to wait three years or more for the results - about how long it will take Simon Studholme's case and others to come to trial in the High Court.
Meanwhile, the press coverage, the uncertainty and fear will continue. As a news story it has plenty to recommend it; the 'sinister' quality of EMFs which, like radiation, can never be seen, smelt or touched, the fact that the victims are children and the 'villains' large and powerful companies.
Professor Cartwright says that if EMFs do cause chilhood cancer, as some epidemiological studies suggest, then they are responsible for only about six extra cases in Britain each year. That will comfort every parent, apart from those living almost directly above or below high-voltage cables (any further than 50 metres away and the power lines make little difference to the earth's background electromagnetic field). For them, the options, all unenviable, are to move or cling on to the fact that the risk to their children is relatively small and the link, so far, unproven.
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