Paul Matthews blogs:
In terms of Electromagnetic Fields (EMFs), the debate is actually around intensity; the evidence is clear that high strength EMFs – massively higher than wifi signal strength – can be harmful to people. But what is high and low, and can prolonged exposure to very low levels of EMFs also be harmful?
This low vs high intensity question is the same in many other radiation contexts as well. For example, exposure to sunlight in moderation is not considered harmful, however too much of it can cause burning and lead to skin cancer. So where does wifi sit on that spectrum?
Let’s first consider just how strong a signal we’re talking about here. Jonathan Brewer’s Inside Telecommunications blog has a great summary of EMFs and electromagnetic radiation, including the following table (Hat tip @shiftygeek):
Type of Radiation Power Level Potential to be Harmful (heat can be felt) 200W/kg Maximum Permitted in New Zealand 4.00W/kg Highest Radiation Cell Phones (Avg of 20) 1.43W/kg 50 Watt Cell Phone Transmitter at 10m distance 0.365W/kg Lowest Radiation Cell Phones (Avg of 20) 0.32W/kg Wi-Fi Device Average between 0.5 and 2m distance 0.0057W/kg
Have a look at those numbers. WiFi is at one 35,000th of the level where it has the potential to be harmful.
The Te Horo School should be ashamed for giving in to hysteria. Matthew concludes:
In short, the science is clear and credible. Following very comprehensive and ongoing research,there is absolutely no evidence of a link between exposure to wifi transmission and adverse health effects. It would appear to make no more sense banning wifi in schools as banning electricity, and neither is supported by the evidence.
Maybe the school should also ban the dangerous dihydrogen monooxide.