One in every 25 Britons believes they are sensitive to electromagnetic radiation.Addstyle

There is no evidence that short-term exposure to signals from mobile telephone masts causes illness, say British researchers who have carried out a trial involving dozens of people who claim to be sensitive to the signals.

Participants in the study could not tell whether or not they were being exposed to an electromagnetic field.

The results suggest that the many health problems attributed to mobile phone transmitters — including nausea, headache and flu-like symptoms — are probably caused by something else, says Elaine Fox, a psychologist at the University of Essex in Colchester, who led the research. She suggests that the problems may well be psychological.

Sensitive tests

Roughly 4% of Britons claim to be affected by radio waves from sources such as telephone transmitters and other electrical equipment.

Fox and her colleagues tested 44 people who claimed to suffer various illnesses as a result of exposure to mobile telephone signals, and 114 people who did not. They used a laboratory set-up containing a replica transmitter broadcasting both conventional and '3G' telephone signals.

When told that the transmitter was switched on for 50 minutes, 'sensitive' individuals reported higher anxiety, discomfort and tension. But when asked to tell whether the transmitter was on or off, only two of the 44 'sensitive' volunteers were correct six times out of six. Five of the controls were equally successful.

And the severity of symptoms reported by the volunteers, as well as their heart rate and levels of sweating, did not depend on whether the transmitter was switched on or off, the researchers report in the journal Environmental Health Perspectives¹.

This suggests that although peoples' symptoms are genuine, they may be triggered by the knowledge that they are near a telephone mast, rather than being an effect of the electromagnetic waves themselves.

That makes sense, given that humans, unlike some other animals such as sharks, have no sensory cells that can detect electromagnetic waves. As Fox and her colleagues point out, there is no established mechanism by which telephone signals can cause illness.

Psychological trigger

"At least under short-term exposure there don't seem to be any adverse health effects," says Fox. She admits, however, that more research is needed to rule out long-term health effects for those living or working near telephone masts.

Fox also says that several 'electrosensitive' people dropped out of the study before they could complete the testing, meaning that the number of volunteers was lower than the researchers had hoped. But she says that 44 volunteers are enough to statistically rule out adverse health effects.

"I had great hopes that this study would find something, and I was surprised it didn't," says Alasdair Philips of Powerwatch, a campaign group based near Cambridge that lobbies on behalf of 'electrosensitive' people. He admits that psychological triggering is a possible mechanism, but adds that "many electrosensitive people get panicked by phones, but that doesn't mean the effect isn't real in the first place".

"It's probably time now to start really looking at what is causing this," Fox says. "Many of these people genuinely have a very poor quality of life. If people are convinced that it is electromagnetic fields then they don't look at other possibilities."

Psychological triggering remains the most plausible mechanism. "If we have a headache on the train and we see someone with a mobile phone, you can make a connection. It's quite a natural thing," Fox adds.

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• References

  1. Eltiti, S. et al. Env. Health Perspect. doi:10.1289/ehp.10286 (2007).