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Lab Research Put Mobile Phones Under New Scrutiny
The safety of mobile phones is under fresh scrutiny following the discovery that their emissions have an unexpected effect on living creatures. The finding throws out the strongest challenge yet to the widely held belief that heating from mobile phone signals is their only potential threat to brain cells.
In lab tests, British scientists have found that microwave emissions typical of mobile phones make a type of worm more fertile. Why this happens is unclear and there's no suggestion that human fertility could be affected. But the research is important because it reveals, for the first time, that biological effects are possible without any warming of tissues.
Until now, regulations designed to protect people from microwave radiation - from mobile phones, microwave ovens and radar systems - have been based purely on avoiding heating from the microwave radiation. There is no evidence that cellphone emissions have harmed people's health.
William Stewart, head of the British government's "independent expert group" on mobile phones is taking the results seriously. "These results are very important and potentially far-reaching," he told New Scientist. "Independent confirmation is crucial and we need this quickly."
De Pomerai's team found that exposing nematode worms to microwaves at frequencies and energies similar to those emitted by a cellphone, increased the number of worms that go on to produce eggs. This is significant, says de Pomerai, because even mild heating makes most larvae infertile as adults. "It would be difficult to explain this effect in terms of heating," he says.
In previous experiments, the Nottingham team tested the effect of microwaves on nematodes which had been chosen because their cell function is very well understood. The worms had been genetically modified to produce a heat-shock protein when exposed to other stresses besides heat.
These tests showed that prolonged exposure produced the stress proteins, even though there appeared to be no heating (New Scientist, 10 April 1999, p 20). In addition, these worms grew to be about 10 per cent larger than worms not exposed to radiation. Difficulties in measuring the temperatures of the tiny worms meant the team couldn't be sure that they were not being heated. But the latest experiments rule this out.
"What's needed first is to establish a mechanism," de Pomerai says. One theory suggests that water molecules agitated by the microwaves could be attracted to water-seeking areas on a protein's surface, influencing its ability to fold into its proper, functional shape. This could explain the heat-shock response, says de Pomerai, which is usually triggered by this kind of activity.
De Pomerai concedes there is a possible get-out for those doubtful that cellphones can have non-thermal effects: the controversial theory that microwaves could cause localised "hot spots" within cells. This could conceivably trigger stress proteins without raising the overall temperature of cell or tissue.
But he accepts that research cannot totally rule out the idea that heat is responsible for microwaves' effects. "I think it will always be an explanation of last resort," he says.
The latest results are unlikely to have an immediate impact on guidelines designed to safeguard cellphone users. "The guidelines can't be changed on the basis of one experiment," says Michael Clark, spokesman for the National Radiological Protection Board. "However good it is, it needs to be replicated elsewhere."
Journal reference: Enzyme and Microbial Technology (vol 30, p 73)