After ten days of discussions to consider evidence from studies all over the world, a 28-member panel of the prestigious National Institutes of Health (NIH) voted by 19 to nine that electric fields such as those around power lines should be considered possible human carcinogens. Only one of the nine dissenting panel members thought the evidence was against a link; the other eight said the conflicting evidence left them undecided.
Professor Denis Henshaw, a British scientist who first suggested a possible mechanism by which overhead high-voltage cables could cause cancer, said yesterday that the decision will be important for the 23,000 people in the UK who live within 50 metres of a pylon. "The question becomes one of whether power companies owe a duty of care to people who are affected by them. We should look to countries like Sweden which have a policy of avoidance of putting homes next to pylons."
But Dr Michael Clark, a spokesman for the National Radiological Protection Board, the Government's radiation adviser, said the evidence was not convincing: "We continue to support research in this area, but our view is that there is no firm evidence of a cancer risk."
Last autumn a number of legal cases filed by Britons who live near pylons and have developed cancers were thrown out of court. That decision was based on a US National Research Council report, in which a different panel of scientists evaluated about 500 studies on the health effects of high- voltage power lines and found "no conclusive and consistent evidence" that electric and magnetic fields cause any human disease.
However, in 1996 Professor Henshaw led a team which found that the electric fields emanating from high-voltage power lines concentrate car and industrial fumes into clusters of dangerous gases which increase the risk of cancer. They reported that carcinogenic pollutants were attracted to power lines "like bees round a honey pot".
Alasdair Philips, director of consumer watchdog Powerwatch, said the authorities should at least accept that there was "reasonable doubt" over the safety of pylons and take necessary precautions.
"I think we should stop building new housing near electricity pylons and stop putting up the pylons near residential areas," he said.
Professor Henshaw reckons that the "danger zone", in which the electric field is particularly strong, extends about 50 metres from any overhead pylon or unshielded substation. "Two hundred metres is too far away to be worth worrying about," he said. The electric field falls off rapidly with distance: it would be 16 times less at 200 metres than 50 metres. Also, people are not at risk while inside a house, because the fields cannot penetrate building materials.
The National Grid Company, which owns the power lines, said last night: "Other studies have found that there is no likely link between electric fields and human health. Far more studies have found no link that those which have."