Networking

Peter Cochrane's Blog: Protestors clueless on wireless health risks

Please build more base station masts near our schools…

Written in the bar of a London hotel and dispatched via a free wi-fi service from Canary Wharf in the capital's docklands.

Scare stories about mobile phones cooking our brains come and go as regularly as the seasons. Irrational and unexplained results are periodically hailed by the media as the death knell for the mobile industry.

Schools, colleges and universities advise against - or even ban - the use of wi-fi, and services are closed down as a potential health risk.

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There are many protest groups actively campaigning against wireless in any form because of some unknown and unquantified potential risk to health. These groups include those preventing base station towers being erected close to their schools or in the middle of their communities.

Unfortunately their lack of understanding actually has an inverse reality impact. If they understood the basic physics involved they would be asking for more towers and not fewer. Living really close to a mobile phone base station tower is the safest place to be.

Here is what is happening. The mobile phone pressed close to your ear adjusts its transmit power according to the distance from the base station.

That means the further from the tower the lower the power received by a mobile and the higher the power transmitted back as a result.

So if you get really close to a base station your mobile sees lots of signal and therefore transmits back a minimal amount in turn. Interesting, isn't it? That is the inverse perception of the protestors.

The detailed physics is also interesting. Near-field emissions - those that are mainly magnetic field coupling - fall away at a rate of 1/d^6 while the far-field radiation - that is, electro-magnetic waves - die at the slower rate of 1/d^2 where d is the distance from a transmitter.

These inverse distance laws lead to the situation whereby the power entering the human head from a tower is generally less than 1,000 times smaller than that produced by a mobile.

Hence, to reduce the exposure to radiation to a minimum it is always better to be really close to the base station to ensure the mobile is emitting a minimum energy.

And what of wi-fi and WiMax? Various emission limits and active control systems, plus deployment methods generally render these systems less power aggressive than mobile networks. And of course the same inverse distance/power laws apply.

And now for the really good news. The radiation from mobile devices, base stations, wi-fi and WiMax equipment is non-ionising. That is, it can only jiggle cells and warm them up. To do any real lasting damage, very high powers are required - microwave oven-style.

Radio emissions are not at all like ionising x-rays that can blow cells apart. So, as adequately demonstrated by our overall survival and ability to live with electromagnetic radiation for almost 100 years, there isn't a real problem with wireless radiation anyway.

How can we be really sure there isn't an unknown risk? How about all the troops in WWII exposed to radar emissions as they sat on the deck of troop ships, aircrews on bombers and night-time interceptors, or the thousands exposed to the headlong radiation from military and civil walkie-talkies during the same period and up to the introduction of mobile phones some 25 years ago?

All these pieces of equipment emitted far greater powers than today's mobiles and used frequencies that spanned, high to low, all our current mobile and wi-fi bands.

Will any of this change the minds of the protestors? Perhaps - but most likely not. They are bound up in a belief system and lamentably their lack of mathematical and physical knowledge will see them continuing to campaign for the most illogical of scenarios for a non-threatening technology.

In the mean time I'm off to install my own mobile base station so I can increase the power level to my handset and minimise the non-risk in my life.

About Peter Cochrane

Peter Cochrane is an engineer, scientist, entrepreneur, futurist and consultant. He is the former CTO and head of research at BT, with a career in telecoms and IT spanning more than 40 years.

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