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Wi-Fi critics are cooking up a health scare

Dave Bailey’s article on the health risks of Wi-Fi (Wi-Fi health risks are clouded by static, 14 May) highlighted a major psychological aspect of the debate - the word “microwave” is loaded through its association with an unnatural kitchen device that can burn your dinner without the plate getting hot.

People are aware of warnings about keeping microwave oven doors sealed: these ovens and their radiation are clearly highly dangerous! Campaigners against Wi-Fi play on this. However, microwave ovens don’t actually have to work at 2.45GHz, they simply commonly do so because licence-free spectrum is available worldwide and because it’s easy and cheap to mass produce components at this frequency. Microwave ovens could work anywhere between about 1GHz and 5GHz, maybe higher.

The old hospital treatment known as diathermy, which employed deep tissue heating, operated at 27MHz. Crumbs, didn’t they use that for CB radio too?

I was taught that microwaves begin at 1GHz but US sources seem to prefer the VHF/UHF boundary at 300MHz. Nothing special happens at either point, and the word itself just means “tiny waves” - which they are, in the context of radio broadcasting. Compared with infrared or light waves, they’re enormous. It’s all a matter of perspective.

Martin Nicholson

May 21, 2007 in Science | Permalink


The public anxiety about cellphones and Wi-Fi is largely due to the (often deliberate) misuse of the word "radiation". Radiation is associated in the public mind with radioactivity, which is indeed dangerous even at low doses. However it really means "anything that is radiated". This includes the whole of the electromagnetic spectrum, right the way from hard gamma rays (very dangerous) through X-rays, ultraviolet, visible light, infra-red, microwaves, broadcast radio, down to radio waves with frequencies too low to measure. It also includes alpha-rays, beta-rays, and other more esoteric things. From the point of view of harmfulness to humans or other animals, the critical parameter for electromagnetic waves is the energy per photon. If this is enough to disrupt your cell chemistry, it can cause cancer. The energy per photon is proportional to the frequency, and the threshold for damage to cells is somewhere in the near ultraviolet. So anything between hard gamma rays and near ultraviolet can cause cancer, and anything with a lower frequency (light, microwaves, etc.) can't. As far as real injury from electromagnetic waves are concerned, the major problem is melanoma (a kind of skin cancer). 90% of melanomas are caused by the ultraviolet rays in sunlight. In the USA (for which I was able to find statistics on the Web), there are about 50,000 melanoma diagnoses per year, leading to just under 8,000 deaths. The other mechanism by which electromagnetic waves can harm you is by the heating effect of very high intensities: this is the source of the risk from inadequately shielded microwave ovens.
The low GHz energy from cellphones and Wi-Fi has much too low a per-photon energy (much lower than visible light) to cause cell damage, and far too low an intensity to cause any measurable heating effect. Of course it is impossible to prove something is absolutely safe, so it is theoretically possible that there is some as yet unknown mechanism by which low intensity microwaves could harm people, but it seems very improbable given that human beings evolved on a planet which has continuously been bathed in the cosmic microwave background radiation since it was formed. If low intensity microwaves were anything like as dangerous as sunlight, we would be seeing a huge excess of cancer deaths among cellphone owners. In short, if you're worried about the risks from electromagnetic waves, stay indoors and communicate with your friends by cellphone!

Posted by: Richard Parkins | 22 May 2007 14:26:05

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