Healthy home

时间:2019-03-07 08:10:05166网络整理admin

By Andy Coghlan MAGNETIC fields generated indoors by household wiring and electrical appliances don’t cause childhood cancers—at least not in Europe. So say researchers in Britain who last week presented results of the world’s largest ever investigation into the health effects of electromagnetic fields. But despite its size, the study is not the last word on the subject. It cannot rule out possible harmful effects of the more powerful magnetic fields generated in North American homes. And studies from the same researchers into the magnetic fields generated by overhead power cables—which are up to ten times as strong as those generated indoors—have yet to be completed. Electric fields generated indoors are also under investigation. As part of the UK Childhood Cancer Study, a £12.5-million project sponsored by government, industry and cancer charities, researchers led by Nick Day of the University of Cambridge spent eight years collecting data on childhood cancer cases. They visited 2226 children with cancer and measured the magnetic fields to which they were exposed while in bed, around the house and in school or nursery. From this, they worked out the average fields to which the children were exposed in the year preceding their diagnosis. They repeated the exercise for healthy children matched so that they were the same age and sex as each child with cancer. The team found there were no differences in the fields experienced by the two groups (see Table). As many healthy children as cancer cases had been exposed to fields above 0.2 microteslas, which previous research had suggested might be dangerous. “The fields to which children are exposed do not give rise to excess risk of childhood leukaemia or any other childhood cancers,” says Day. However, the results for higher doses were less reliable statistically, because only 2 per cent of the children studied by the team experienced fields averaging 0.2 microteslas or more. This is typical for Europe, but 11.4 per cent of children in the US and 15.4 per cent in Canada are exposed to these stronger fields. In North America, electricity is delivered to homes at half the European voltage but at double the current, which in turn doubles the strength of the magnetic field. In an editorial accompanying the paper from Day’s team, published in The Lancet, Michael Repacholi of the WHO in Geneva stresses this limitation. American epidemiologists agree. “The biggest problem is the scarcity of exposures in the upper brackets,” says David Savitz of the University of North Carolina at Chapel Hill. However,