“Think of the children!” was the underlying message of a recent documentary by the BBC’s Panorama, claiming that widely used wi-fi transmitters could pose a health risk that had been insufficiently studied.
Wi-fi networks are proliferating worldwide, especially in commercial centres, but also in schools, where laptop computers are becoming as common as exercise books and wireless LANs (local area networks) are used to allow students and teachers to communicate.
Tests conducted by Panorama at one British school suggested that “the height of signal strength to be three times higher in the school classroom using wi-fi than the main beam of radiation intensity from a mobile phone mast”.
This should be of concern, the documentary said, because children’s skulls are thinner and still forming, and therefore they absorb more radiation than adults.
The claims found support from some scientists and medical experts, but many others dismissed the whole matter as a scare story, and said the methods used to measure radiation from a wi-fi transmitter were unscientific.
In New Zealand, the National Radiation Laboratory deals with radiation emitted by electronic devices and possible health issues. Spokesman Martin Gledhill, who has 16 years’ experience in the field and contributed to the national guidelines on radiation, describes the Panorama story as “a bit overblown”. He’s carried out radiation tests on wireless LANs and should know what he’s talking about.
The NRL tests found that the wi-fi transmitter’s emissions were just a few nanowatts per square centimetre. A nanowatt is a measure of the amount of power from a transmitter that would impact on a particular area. Think of a light bulb, in a room where you’re reading a book. The further away you are from the bulb, the less light falls on the book. The radiation emitted by a wi-fi transmitter dissipates in the same way.
The level of radiation from a wi-fi transmitter, measured in nanowatts, is about 100,000 lower than the exposure limit recommended for the public.
“That safety limit itself is 50 times lower than where you might actually start to see anything happening,” Gledhill says.
The real issue being debated here is not so much the amount of energy being generated, as the rate at which the human body absorbs it.
“Part of the problem is, you can never prove something is safe,” Gledhill explains. “You’re dealing with fairly complex systems - the body, an experimental animal, a test tube full of cells, etc. - and so it’s always difficult to try to isolate one particular influence and determine what effect that influence is having on your experimental system. In any field you can get results which may or may not agree with the bulk of of the work that’s gone before. The science is to be able to look at the whole wide range of work that’s been done and assess it on its strengths and weaknesses and say ‘What is the picture that’s coming out of it?’”
The consensus of worldwide scientific studies is that radiation emitted by wireless transmitters is very low and diminishes over distances. Think of how the signal from a city-based radio station on your car radio starts to break up as you drive out into the country. We’re surrounded by radiation emitted by all manner of popular devices and gadgets, but no one has produced evidence of any direct health risks – warnings about spending long periods with a mobile phone clamped to your ear notwithstanding.
“We’ve had it for 100 years or more, ever since radio transmitting started,” Gledhill says. “Even for people working in an area with a wireless network, I would expect that generally they get higher exposures from other radio transmitters – the FM radio, the AM radio, TV stations, and so on.”
As for the risk to children, studies carried out by the World Health Organisation do not support claims that they’re more susceptibla than adults. Gledhill tested a wi-fi transmitter at one local school, at a parent’s request, and found the level of exposure to be even lower than the previously mentioned public limit. He also points out that you only get exposure when the network is transmitting, and schools are unlikely to be constantly sending large packets of data. While New Zealand complies with international standards for wireless equipment, Gledhill is currently arranging to carry out further tests at schools with wi-fi transmitters “so we’ve got a broader base of information when we respond to queries”.
The Panorama story:
tinyurl.com/2bbvgr
A scientific response:
tinyurl.com/3dmyn4
Radiation information
Ministry of Health/NRL guidelines:
tinyurl.com/24bfxa
Mobile phones and cell towers:
tinyurl.com/29hsuk
Points to ponder:
Mobile phones conserve battery life by transmitting a weaker signal into the air (and therefore also your head) the closer they are to the tower. Still unhappy about that cell tower in your neighbourhood?
That friend who swears wireless signals are to blame for their headaches/lethargy/skin rashes, etc. probably has another medical problem entirely. Provocation tests (done without the person knowing whether they’re near a wireless signal or not) have shown no correlation between these signals and physical illness.