Cancer rise linked to power lines

The pylon debate has raged for decades

By Alex Kirby, BBC News Online environment correspondent and presenter of Costing the Earth

UK researchers claim to have found sharply higher cancer rates in people living close to overhead power lines.

If their findings apply nationally, it would suggest premature deaths on the scale of the annual road accident toll.

The researchers say the excess cancers are found only in people living downwind of the lines.

And they say this is strong evidence to support one theory of how electric fields may damage health.

But their work, described in BBC Radio Four's environment programme Costing the Earth, has been rejected by the National Grid, the company that operates the power lines.

Ionising effect

The research appears to vindicate a theory developed by Professor Denis Henshaw, of the physics department at Bristol University in the west of England.

He has found that a power line ionises the surrounding air, and believes this makes wind-borne pollution much more dangerous.

Professor Denis Henshaw put forward the aerosol hypothesis

"It splits the air up into positive and negative electrical charges, which are blown away from the power line by the wind," he says.

"They attach themselves to particles of pollution in the air and put an electrical charge on to them. When you inhale these small particles, they have a much higher probability of sticking in the lung."

Professor Henshaw stresses that his work deals with the electrical effects of power lines, not their magnetic fields. It is experimental and so far unproven.

But the new research findings appear to bear him out. The head of the research team is Dr Alan Preece, an epidemiologist in the oncology department of Bristol University medical centre.

Large excess

Dr Preece told the programme: "We're assessing the relative cancer risk within 400 metres of the lines. We looked at the postcodes of all the diagnoses of the different sorts of cancer for the whole of South West England.

"We found an excess, particularly of lung cancer, in that group of people who had been living within 400m of a line at the time of diagnosis.

The industry says the balance of evidence has yet to show the cables are a cancer risk

"You are likelier to get cancer there, but only if you live downwind, which is almost proof, or very strong supporting evidence, for the effect of the aerosols driven by the wind."

Dr Preece's own work is yet to be published officially. But a conference in Germany earlier this year of the Bioelectromagnetics Society heard that it suggested an average increase in the cancer risk of 29% over the expected rate.

Across the country, this could mean more than 3,000 premature deaths annually, roughly the number of people killed every year on the UK's roads.

Asked how confident he was of his findings, Dr Preece said: "I'm amazed at how robust they appear to be.

"Being cautious, I would love to repeat the study in another area of England, to see if we've got the same effect. It would be very easy to do."

Sceptical note

Studies of electricity industry workers in Canada and elsewhere support the hypothesis that electric fields are involved in the cancer process as a tumour promoter.

But the National Grid, which owns the UK's power lines, says it is "sympathetic but unconvinced" by Professor Henshaw and Dr Preece.

The Grid's scientific adviser, and spokesman for the UK Electricity Association, Dr John Swanson, said the industry had spent perhaps half a billion dollars worldwide over the last 20 years researching the effects of power lines.

"We have never said in a categorical way that power lines are safe," he said.

"What we have always said is that when you look at the totality of studies, then you come to the conclusion that the balance of evidence is that power lines and the fields they produce do not have an effect on health."

Costing the Earth is broadcast on BBC Radio Four at 2100 BST on 21 September.