Mobile phone masts are safe, and people claiming to suffer health problems from them should look elsewhere for relief from their symptoms, according to a three-year study at the University of Essex.

The study found that people who claimed to suffer ill-effects from mobile phone masts would report those effects, whether or not they had experienced mast radiation. It also could find no measurable symptoms linked to the radiation. Anti-mast campaigners are hunting for objections to the study, which used double-blind methods to eliminate bias, and is available online at Environmental Health Perspectives.

The study tested 158 people, 44 of whom had reported symptoms such as anxiety, tension and tiredness, which they claimed were caused by emissions from phone masts. The tests simulated radiation received 20 to 30 metres from a 2G/3G mast, telling the subjects when it was turned on at first, and then keeping both experimenters and subjects in the dark - the classic double-blind method.

Over three years the study found there were no changes in heart rate, blood pressure and skin conductance when the radiation was switched on, and nor could the sensitive subjects detect when the radiation was there (in fact, two of them guessed right, which was the same proportion in the control group statistically as what you would expect from chance).

Despite this, the sensitives were more, well, "sensitive," reporting more symptoms regardless of radiation.

Blaming phone masts is actually preventing these people getting any real help, according to principal investigator professor Elaine Fox: "It is clear that sensitive individuals are suffering real symptoms and often have a poor quality of life. It is now important to determine what other factors could be causing these symptoms, so appropriate research studies and treatment strategies can be developed."

There have now been at least 31 blind and double-blind studies, and the overall result is a clean bill of health, according to Dr James Rubin, of the Mobile Phones Research Unit at Kings College London: 'The Essex study is one of the largest and most detailed of these experiments and its findings, that mobile phone signals are not responsible for the symptoms that some people describe, are in line with those from most other previous experiments."

Anti-phone mast activists scrabbling for a flaw in the study have seized on the fact that twelve "sensitive" volunteers dropped out at an early stage, with campaigners Mast Sanity saying the study's integrity was "completely breached" according to the Guardian newspaper.

In fact, none of the dropouts detected radiation in the first double blind trial, but Professor Fox concedes the reduced sample does increase the statistical chance that some small real effect has been missed (to about 30 percent).

The study was funded by the MTHR (Mobile Telecommunications and Health Research) programme, which is paid for by the industry and government.