Sir William Stewart, chairman of the Health Protection Agency, has called for a review of the health risks of wireless technology after an investigation into its effects on children.

The BBC’s investigative programme Panorama claims that wi-fi networks in schools can give off three times as much signal radiation as phone masts.

Current government advice says that phone masts should not be sited near schools without consulting parents and teachers, because children are thought to be more vulnerable to radio-frequency radiation.

The programme-makers measured radiation levels from a wi-fi-enabled laptop in a classroom in Norwich. It found that the signal strength was three times higher than that of a typical phone mast. Wi-fi, or wireless fidelity, allows a computer user to connect to the internet at broadband speeds without cables.

More than two thirds of secondary schools and nearly half of primary schools have wi-fi. Panoramaspoke to nearly 50 schools and only one had been alerted to possible health risks. Others had been told that there was no risk.The Government says that wi-fi poses no health risks, citing advice from the World Health Organisation.

In 2000 Sir William produced a report on the impact of mobile phone masts on health. He found that: “There may be changes, for example in cognitive function . . . There were some indications that there may be cancer inductions . . . There was some molecular biology changes within the cell. . . ”

The levels of radiation found in the Norwich classroom were 600 times lower than the levels deemed dangerous by the Government. It uses data from the International Commission on NonIonizing Radiation Protection, which bases exposure limits on a thermal effect. In other words, the radiation has to be strong enough to cause a heat effect before it is restricted.

Dr Olle Johansson, of the Karolinska Institute in Sweden, has carried out experiments on radiation similar to or lower than wi-fi and found biological implications. Asked if the commission was right to set limits based on thermal effect, he said: “That’s just rubbish. You cannot put emphasis on such guidelines.”

— Panorama: Wi-Fi – A Warning Signal is tonight at 8.30pm.

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