Wi-fi is one of those technologies that has captured the popular imagination so quickly that it is already hard to remember what life was like without it. Where internet access once relied on a fixed telephone line, the advent of wireless hotspots in coffee shops, airports and hotels means that we can use a laptop to surf on demand. One adult in five owns a wi-fi computer, and 80 per cent of secondary schools have a network.

Media enthusiasm for wi-fi, however, has given way to a backlash of late, with much speculation about its effects on health. Wireless networks have been suggested as a cause of ailments from headaches to cancer. A group called Powerwatch, run by a man who makes a living selling devices that block electromagnetic radiation, has even claimed that classroom wi-fi is causing bad behaviour.

Some schools have dismantled networks and a teaching union has called for a moratorium. The Independent on Sunday is running a “Danger on the Airwaves” campaign, and the Daily Telegraph last week proclaimed a “Warning over wi-fi health risk to children”. A new health scare is germinating.

It is true that little research has yet been conducted into the health effects of wi-fi. That, though, does not mean that it is anything to be afraid of. There is no evidence that wireless networks present any special hazards beyond those posed by existing technology. The hotspot in your local Starbucks, indeed, should cause less concern than the mobile phone in your pocket.

That is not to say that mobiles are dangerous. The large studies conducted during the first decade of widespread use are almost universally reassuring. Though a longer-term risk of cancer cannot yet be ruled out, the evidence indicates that any danger is likely to be small.

If any such effect does exist, it is certain to be more significant than anything that wi-fi might cause. That is because the two technologies rely on similar electromagnetic waves to transmit data, but expose users to very different levels of radiation. Mobile phones are designed to work hundreds of metres from the nearest base station. Wireless equipment has a much shorter reach, so the power it requires is much less. A computer terminal is used at arm’s length, while a mobile handset is placed next to the head. Exposure differs by a factor of 200.

There may still be some sense in taking precautions. Lawrie Challis, who chairs the Government’s Mobile Telecommunications Health Research programme, suggested in the recent Telegraph story that children avoid using laptops on their laps: this brings the wi-fi receiver closer to the body and thus raises exposure closer to mobile phone levels.

Such advice scarcely justifies “health warning” headlines. There is really no need for panic. Even if wi-fi is all but certain to be safe, though, the Government should still consider sponsoring research. That is because of the way these fears reflect the psychology of risk.

People will always perceive risks they elect consciously to take on differently from risks that may be much smaller but over which they have no choice. To use a mobile is an active decision. Wi-fi networks, however, emit radiation to which people are exposed whether they use the technology or not. And a feeling of powerlessness can promote fears that are quite irrational from a purely scientific standpoint.

This does not justify any kind of wi-fi ban, but it does make a case for a limited study. It might be unlikely to reveal anything that is not already known, but that is not necessarily the point.

Unlikely risks do not always need detailed investigation and should never be pursued at ridiculous expense, as they were in the MMR fiasco. When they are not optional, however, a little research can do much to reassure.

Mark Henderson is Science Editor of The Times

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