Cellphone masts do not cause harmful short-term health effects, according to a study of people who say they experience symptoms when they are close to them. The study dealt another blow to the notion that low-level electromagnetic fields from cellphones or base stations are dangerous.
The researchers looked at second generation (2G) and the more recent 3G phone masts in a laboratory setting where neither the participants nor researchers knew whether the equipment was turned on. The set-up was designed to mimic the output from a phone mast at 20m to 30m from the subject. ‘It looks like there was pretty good evidence that people couldn’t detect the signals,†said Elaine Fox at Essex University, England, who led the study, published this week in the journal, Environmental Health Perspectives.
Of the 159 people who took part in the experiment 44 said they were sensitive to electronic equipment. At first the participants were told when the electric field was turned on during the test. Under these conditions, the electrosensitive participants reported unpleasant symptoms such as headaches and nausea. In three further tests the researchers subjected them to 2G radiation, 3G radiation or no radiation under ‘double blind†conditions, meaning that no one involved knew whether the equipment was switched on. Under these conditions two of the electrosensitive group and five of the control group correctly identified whether the electricity was on every time — no better than you would expect by chance alone.
The team also measured heart rate, blood volume pulse (a measure of pressure) and the sweatiness of the subject’s skin. All of these should go up when the participants are experiencing unpleasant symptoms or anxiety.
The electrosensitive individuals had generally higher scores than the control group for all three, but they did not change when the 2G or 3G radiation was switched on.
Anti-phone-mast campaigners said the results were skewed by the fact that 12 volunteers who claimed to be sensitive to electronic equipment dropped out. ‘Even a child can see that by eliminating 12 of the original 56 electrosensitive volunteers — over 20% of the group — the study integrity has been completely breached,†the campaign group Mast Sanity said. It argued that these people were presumably the ones most sensitive to the radiation.
Fox counters that her team was still able to test 44 people.
Of the dropouts none was able to identify correctly when the radiation was on or off in the first double blind test. The reduced numbers do mean that the statistical power of the experiment was compromised, though. Fox estimated that there was a 30% chance that the experiment was less effective because of the smaller numbers.
Some anti-mast campaigners have been impressed by the study. ‘The Essex team have carried out one of the best-designed and executed studies to date,†said campaign group Powerwatch.
Fox said that scientists and sufferers should now concentrate on finding the real cause of the symptoms. ‘If people are convinced that they are suffering because of cellphone masts, they don’t investigate other causes,†she said.
Of those who claim to be sensitive to electronic equipment many experience flu-like symptoms such as headache, streaming eyes or a burning sensation and for some these are so bad they opt to shield their homes with foil-lined wallpaper, or even move to the country. —