University of Aberdeen's Brian Heeston and colleagues may have discovered why cancer clusters have been found near overhead power lines.

When a cell is damaged it usually stops dividing into more cells until that damage is repaired. If it did not, the risk of cancer developing would be very high. When Brian and his team exposed cells which had been deliberately damaged with gamma radiation to electromagnetic fields, not only did the cells start dividing, the rate of division actually sped up. Electromagnetic fields appeared to interfere with the body's anti-cancer mechanisms.

The finding would be convincing were it not for the fact that the strength of electromagnetic field used by the team was a thousand times more than that emitted by the average overhead power line. Further tests using power line strength fields are needed.

The biggest ever UK Government-funded study into a possible link between high-voltage power lines and child cancer [1] suggested that living within 100 metres of a high voltage power lines can double leukaemia in children aged under 15. The risk to children aged five and under is likely to be even higher because their skulls are thinner and bodies still developing.

These " preliminary results" were known in 2001 and formally presented to the UK Department of Health in 2003 but the Government never made them public. Suspecting a cover up, Powerwatch UK Director Alasdair Phllips finally leaked the findings in 2004. "It is likely to be a definitive finding on whether UK power lines can cause childhood leukaemia", he commented.

Ed.- (i) Is melatonin involved?
Bristol University’s Professor Denis Henshaw is the UK’s principal investigator of the link between overhead power lines and child cancers. At the 2004 Children with Leukaemia conference, he suggested that the electromagnetic fields emitted from power lines cause leukaemia because they disrupted the pineal gland’s nocturnal production of melatonin. He supported his hypothesis with the following research findings from other researchers:

• Exposure to EMFs of strengths experienced underneath power lines can disrupt the body’s nocturnal production of melatonin [1]

• Melatonin is an antioxidant and mops up free radicals much more effectively than either vitamins C or E [2]

• Melatonin protects the blood from genetic damage by free radicals and carcinogens [3]

• Melatonin is also highly protective of the foetus. There is compelling evidence that acute lymphoblastic leukaemia starts in the womb [4]

(ii) The Government study correlated 33 years of data on 35,000 children diagnosed with cancer with the distance they lived from the nearest high voltage overhead power line. Its finding of a double risk of leukaemia corresponds well with earlier generally accepted international studies that prolonged exposures to electromagnetic fields (EMFs) above 0.4 microtesla in strength double the risk of childhood leukaemia. EMFs below power lines are usually much higher.

(iii) In March 2004 the UK's National Radiological Protection Board reduced the national official 'safe' magnetic field strength exposure guidelines from 1,600 microtesla to 100 microtesla.