Electromagnetic fields in homes carry leukaemia risk for children, WHO agency says
Electromagnetic fields, in particular the 50- or 60-Hz magnetic fields generated by household appliances, are possibly carcinogenic to children, WHO's International Agency for Research on Cancer (IARC) has concluded after a review of dozens of studies conducted over the past two decades. Children with the highest exposure experienced a twofold risk for leukaemia, but no significant association between electromagnetic fields and other childhood or adult cancers was found. Nor was there evidence of an increased risk to children living near high-tension power lines.
The review was conducted by an IARC scientific working group, which examined data from hundreds of laboratory and animal studies conducted since 1979, when the first scientific reports appeared suggesting a link between cancer in children and exposure to residential magnetic fields. Dr Robert Baan, who coordinated the group's deliberations, said that the research does not prove that low-level electromagnetic fields actually cause leukaemia. ''One of the intriguing problems with this evaluation is that there is no scientific explanation for the association between magnetic fields and childhood leukaemia,'' he said.
But the group did find that two recent analyses provided consistent evidence of an increased leukaemia risk. The most convincing study, published last year in the British Journal of Cancer, pooled data from nine studies on a total of 3247 leukaemia cases and 10 400 controls. Children exposed daily to magnetic fields higher than 0.4 microtesla showed a twofold risk of leukaemia. However, less than 1% of the children with cancer were in this group. Such high levels only occur in households with ''considerably higher than average'' electri-city use, Baan said. (Magnetic fields are measured in tesla. The general population is exposed to an average of about 0.1 microtesla, according to a recent study conducted by Germany's Federal Office for Radiation Safety in 2000 people across a range of occupations and lifestyles.) The other study, published last year in Epidemiology, reviewed data from 15 less rigorous studies and found a relative risk of 1.7 for children exposed to more than 0.3 microtesla.
Appliances like hair dryers, vacuum cleaners, radios and refrigerators generate magnetic fields that diminish quickly with distance. For instance, a portable radio generating a field of 20 microtesla at 1 cm produces less than 0.01 microtesla at a range of 1 m. According to the IARC review, such wide ranges make logging and measuring daily exposure difficult. The reviewed studies could be biased by these and other methodological quirks, the group believed, but they concluded that the mass of evidence outweighed such concerns.
Another IARC working group will review data from studies of high radiofrequency electromagnetic fields produced, for example, by radio and television transmitters, cell phones, and radar equipment, after publication of long-term studies in three or four years.
Brian Vastag, Bethesda, Maryland, USA