WEAK magnetic fields from electric appliances or power lines might cause cancer by interfering with the checks cells make before dividing. The finding could explain the limited evidence for a link between pylons and childhood leukaemia, but not everyone is convinced.
The US National Institute of Environmental Health Sciences lists low–frequency magnetic fields as a “possible human carcinogen”. This circumspect classification reflects the weakness of evidence of any link. Some population studies have found leukaemia clusters around power lines (91av, 9 August 1997, p 16), but the effect has proved impossible to replicate in the lab.
Also, there is no obvious mechanism by which these fields could cause permanent damage to DNA. Low–energy, low–frequency fields only induce a small electrical current in body tissues.
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Now Brian Heaton’s work at the University of Aberdeen suggests that these magnetic fields make cells more slapdash when they are dividing. His team bombarded cell cultures with gamma radiation and then exposed some to a low–frequency magnetic field. Normally, cells stressed with gamma radiation delay division while they repair the damage, but to the team’s surprise, those subjected to the magnetic field didn’t pause. In fact, 12 out of 20 cultures exposed to the field actually divided faster than those exposed to radiation alone they report in Cancer Cell International’s online edition.
Heaton thinks magnetic fields interfere with the repair processes that normally delay division. So exposure may increase the chances of cancer even though the fields aren’t directly damaging DNA.
But Michael Rapacholi, a World Health Organization expert on the effects of electromagnetic fields on health, is sceptical. “The effect is too small to be very convincing,” he says. He also points out that the magnetic field was a thousand times stronger than that from a power line.
