THE WORLD'S biggest investigation of childhood cancers has failed to find a link be- tween the magnetic fields created by electricity power lines and leukaemia.
The authors of the study, which was published in The Lancet, said the findings were so unequivocal that any possible role of electromagnetic fields in causing cancer could now be eliminated.
But the findings are unlikely to end the controversy over the possible health risks of overhead electricity cables as a second, smaller study claims to have established a possible route by which power lines can cause cancer. Professor Denis Henshaw, of Bristol University, said his research, published in the International Journal of Radiation Biology, demonstrates how it is theoretically possible for high-voltage cables to increase the dosage of cancer-causing pollutants to people living near by.
The authors of the Lancet study dismissed Professor Henshaw's findings as "irrelevant" yesterday because his research had not established any association between electricity cables and a cancer risk.
Professor Nick Day, an epidemiologist at Cambridge University who led the Lancet research, said the study should reassure parents who were concerned about living near power lines. "This is a very powerful study for the levels of exposure found in the UK," Professor Day said. "No other study has investigated so many causes of cancer in children over such a long period of time."
The scientists measured the magnetic fields in the homes and schools of 2,226 cancer patients under the age of 14 and compared the results with a group of healthy children. "We found no evidence that there is an association between the level of magnetic field to which a child is exposed and the risk of leukaemia or other malignancy," Professor Day said.
Sir Richard Doll, who chairs the scientific committee overseeing the UK Childhood Cancer Study, said the findings lay to rest any suggestion of a link: "The magnetic component of electromagnetic fields has been under suspicion for some time, but this study provides firm evidence that exposure to the levels of magnetic fields found in the UK does not augment risk for childhood cancer."
But the issue is not resolved completely. In addition to magnetic fields generated as a result of strong electric currents, power lines also create electric fields because of high voltages, which is the area of concern raised by Professor Henshaw's study. The Bristol research found that the electric fields of power lines increased the amount of pollutants deposited on the surface of dummies to 10 times the normal rate. Professor Henshaw suggested that the electrically charged particles created by power lines could enter the body to increase the internal dose of cancer-causing pollutants up to 500 metres away from a pylon.
The government's watchdog on radiation safety, the National Radiological Protection Board, acknowledged Professor Henshaw's study as interesting but said it was hard to envisage how charged particles could enter the bone marrow of the body to cause leukaemia.
Professor Doll said that scientists now have to look at other possible causes of childhood leukaemia. "Childhood cancer is a distressing disease and, despite improving survival rates, it is imperative that we discover its root causes."
Professor Day said that the next stage of the ongoing investigation would be published next spring.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies