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Friday, 3 December, 1999, 01:15 GMT
Battle lines drawn in pylon debate
The pylon health debate started in the 1980s

After a week filled with conflicting scientific evidence over the health risks of living near power lines, BBC News Online examines what the latest figures mean.

Whether it was sheer coincidence or not, the publication of two, entirely contradictory, studies relating to power line safety in the same week will leave consumers rightly feeling confused and concerned.

On Thursday, Professor Denis Henshaw, of the University of Bristol, released the results of a large-scale investigation involving tests taken under and around thousands of pylons.

And on Friday, the world's largest statistical analysis of childhood cancer hit the pages of The Lancet.

These two are only the latest of a series of studies designed to test the theory - first put forward in the 1980s - that the electromagnetic fields (EMFs) generated by the transmission of electricity through power lines could somehow produce cancerous changes, particularly in the very young.

EMF Studies: Conflicting evidence
Sweden - slightly increased risk
Norway - no link
Finland/Denmark - studies too small
US - no increased risk
Canada - no increased risk
Germany - possible link
New Zealand - possible link
UK (1999) - no link
And it seems unlikely that either will prove the definitive answer to the question, regardless of the claims of the authors concerned.

Professor Henshaw's work suggests a mechanism which might explain any increased risk of leukaemia near the pylons.

He says that the electrical field affects particles in the atmosphere, drawing them into the area around the pylons.

These particles include those linked with cancer, such as benzene or the radioactive gas radon.

Therefore, people close to power lines may have an increased exposure to such particles, which might increase the risk of developing cancers, he said.

The latest survey compared cancer sufferers with healthy children
This theory was first aired a year ago following a small-scale study, and was ridiculed by the National Radiological Protection Board, the watchdog on health issues involving radiation and electromagnetic fields.

They described it "implausible and highly speculative".

This time around, Professor Henshaw has carried out thousands more tests to back his theory - but other physicists still dispute that the dangerous particles can reach the body's internal organs.

However, it is estimated that more than 20,000 families live near or under power lines in the UK.

If Professor Henshaw is right, his theory would be backed by epidemiological evidence - an analysis of every childhood cancer case would show more cases than expected living in these conditions.

So the UK Childhood Cancer Survey, headed by Sir Richard Doll, effectively debunks the Bristol team's work - or at least as far as the UK is concerned.

In the largest study of its kind, researchers looked at every case of childhood cancer - and found no association whatsoever with EMFs, whether created by power lines or simply by wiring arrangements in the home.

Previous studies

So, should people living near the lines feel reassured?

In the UK, the answer is yes. The Doll study is larger than every single previous study combined, and the answer is unequivocal.

However, its main weakness is a lack of cases at the highest exposure levels. While it shows that exposure to the lowest levels (0.2 micro-Tesla or less) is not linked to cancer, it has precious few cases above this level.

In the US and Canada, the lower voltage of the national grid (110v as opposed to 240v or more), means far more intense electromagnetic fields, with potential exposures well over the 0.4 micro-Tesla level.

Studies, have been carried out in the US and Canada, but on a much smaller scale, which renders them less than conclusive.

So, while the UK can sleep more soundly, much of the rest of the world must wait for a similarly-scaled study of the highest exposure levels before their fears are answered.

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See also:
02 Dec 99 |  Health
Pylons 'treble cancer particles'
03 Dec 99 |  Health
Pylons safe, says 'definitive' research

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