In understanding the possible health effects of wi-fi, research into the effects of living near a mobile phone mast is of special relevance. Phone masts emit microwave radiation at a similar frequency and modulation to wi-fi. Because they do so at a far higher strength than wi-fi, it is often thought that wi-fi radiation is insignificant and safe. The signals emitted by phone masts and wi-fi certainly do differ greatly in strengthbut that is only part of the story.
When we compare the strength of wi-fi radiation and phone mast radiation, an important distinction needs to be made: between point of emission and point of exposure (i.e. where the person subject to the radiation is). At the point of emission, wi-fi signals are obviously much weaker than phone mast signals. However, we are concerned with the radiation a person is actually exposed to.
At the point of exposure, someone using a laptop with wi-fi is exposed to microwave radiation similar in strength to that of radiation from a phone mast 100 or 200 metres away. Often the exposure figures for wi-fi are even higher than those for phone masts.
This is because signal strength falls off in proportion to the square of the distance from the point of emission, i.e. very rapidly. Distance from a phone mast is generally measured in hundreds of metres. But from a wi-fi node (antenna) it is a matter of metresand from the antenna in a laptop, centimetres. (The wi-fi node is for example fixed to the classroom wall, and the laptop is on a child’s desk, a few centimetres from the child.) It is these huge differences in distance that, at the point of exposure, make the strength of wi-fi and phone mast signals comparable.
For example, the exposure levels measured in the Panorama programme referred to above were as follows: 50
100 metres from phone mast: 0.7 V/m (volts per metre, peak reading) 51
0.5 metres from laptop: 1.7 V/m (volts per metre, peak reading)
Studies of the health effects of microwave radiation from mobile phone masts are thus directly applicable in understanding the possible health effects of microwave radiation from wi-fi. We may note here that adverse health reactions have been reported at exposure levels down to 0.05 V/m. 52 In Salzburg, the public exposure guideline is 0.02 V/m inside houses. 53 (Compare the exposure at 0.5 metres of someone using a laptop of 1.7 V/m.)