Viewers of BBC1 experienced some unpleasant revelations on Monday night. We discovered that, in the comfort of our own living rooms, we are being bombarded by invisible electromagnetic waves, which have the potential to penetrate the brain, altering our minds irrevocably.

Admittedly, the transmission of Panorama lasted only half an hour, but perhaps scientists should be worried about what the long-term health effects of being exposed to such a programme might be.

If you were lucky enough to miss Wi-Fi - A Warning Signal, let me summarise. The Panorama "investigation" (one bloke with a radiation meter) visited a school where said bloke discovered that if he stood within a metre of a laptop connected to a wireless (wi-fi) computer network, he received a dose of radiation which was (occasionally) "three times higher" than when he stood 100m away from a mobile-phone mast nearby.

The radiation looked very frightening - it made some bright spiky yellow lines on the meter and also a loud crackly noise. So why, asked Panorama, are schools exposing our children to wi-fi? Why is our government not banning schools from using wireless networks?

Well, first of all, the levels of radiation were still 600 times lower than present safety limits. But activists claim this limit is meaningless because it is based only on "thermal" affects. "Radiation does not have to cook you to harm you", they say, and they may conceivably be correct.

In that case, however, where is the evidence of the other, non-thermal harmful effects that wi-fi is having on your child's brain? Alas, Panorama did not present a single scientific study that found wi-fi can harm your kids. Not one. Presumably because there are none. Instead there were a couple of scientists who expressed "fears". These fears were based on subjective experiences from a few people who work in wi-fi environments and became ill, so they claim, because of "electrosensitivity".

So we met a woman who is so sensitive to "electromagnetic smog" that she has wrapped her entire house in protective foil. To see if she was "imagining it", the woman took part in a blindfolded scientific study (unpublished), which found that she could tell if a mobile phone was on "66% of the time".

This, of course, means that 33% of the time she thought the phone was on when it was in fact off. Hardly conclusive proof that she can sense radiation, let alone that the radiation itself is harmful.

Admittedly, there is growing evidence that a very small number of people are in fact sensitive to radiation from mobile-phone masts, just as a small number of people are intolerant to certain foods. But for every one who has a genuine intolerance to wheat, there are 10 more who have swallowed so many scare stories about food "allergies" that they feel sick every time they eat pasta. The anxiety leads to stress, releasing stress hormones which can cause genuine physical symptoms such as headaches, nausea and lack of sleep exactly the symptoms that many people who live close to phone masts experience.

Returning to wi-fi, in the absence of any clear evidence, what should we tell our schools? The UK government takes the line of the World Health Organisation and correctly advises that there is no evidence that wi-fi is harmful to our health. But why, said Panorama, should we believe this when the WHO's chief scientific adviser "used to work for the telecommunications industry"?

Well, hang on: what about the bloke who carried out the scary yellow readings? He was from Powerwatch, an anti-radiation lobby group which sells radiation meters to worried parents. Does this mean we can't trust him either? Of course not.

Instead of conducting personal witch-hunts, health policy on wi-fi must be based on objective scientific enquiry - studies whose findings have been reproduced time and time again.

Sir William Stewart, head of the Health Protection Agency, has called for further studies into wi-fi. Until then, he says, it might be wise to adopt a precautionary approach. Maybe so. But perhaps we should apply the same health warning to watching Panorama.