We're constantly bathed in an electric soup of RF emissions. Is there anything to fear, or is fear itself the most damaging consequence of our increasingly wireless lives?
Four years ago, the Russian newspaper Komsomolskaya Pravda claimed its journalists had managed to cook an egg in just over an hour by sitting it between two mobile phones. Tapping into fears about the effects of ambient RF radiation, people enthusiastically forwarded the article around the Internet, even though no one could replicate what the journalists said they had done.
In an attempt to counter the report, the Australian radio authority ARPANSA stepped in with its own experiments, even putting an egg next to a small cellular basestation, well inside the exclusion limits that service engineers are meant to obey when working near the equipment. The eggs remained uncooked.
The UK television show 'Brainiac' tried a similar experiment with 100 mobile phones, and achieved the same (lack of) effect. An earlier take on the egg-cooking claim by Charlie Ivermee, published on a website for the fictional village of Wymsey, was meant to draw attention to the hysteria around mobile phone emissions but took on a life of its own as evidence of the 'effect'. The egg-cooking myth has proved far more persistent than the raw reality.
Mobile communications currently take the brunt of criticisms about the potential dangers of man-made RF emissions. A Eurobarometer survey by the European Commission found that worries about mobile basestations exceeded those about mobile phones, even though the handsets can expose the body to higher levels of RF while they are being used.
TV and radio broadcasts have at times faced similar criticisms, as have the cathode ray tubes used in televisions before we switched to flat panels. The only consistent concern for decades has been the very low-frequency emissions from power lines, which rate as slightly more worrying than basestations on the Eurobarometer survey.
Professor Kenneth Foster of the University of Pennsylvania says: 'I first became involved in this field in 1971 when, as a new PhD and newly minted naval officer, I was assigned to a medical research lab to study the health effects of RF energy. Apart from occupational health concerns, the military was responding to citizens' fears about the safety of emissions from its radar and communications transmitters.
'I found the same arguments that were made in 1971 are being made now. Activists would put together lists of the reported bio-effects of RF fields and claim that low-level exposure to RF energy posed serious health risks.'
What was missing, he says, was any conclusive proof.
'In the 1980s, funding levels for RF bioeffects research declined, because very little had emerged from the research, other than the clear hazards from excessive heating [from very high RF power levels].'
The arrival of mobile communications reawakened concerns over RF and focused attention on the microwave end of the spectrum. This was even though the dosage from a TV station 10km away could be as high as that from a basestation 100m away, according to Graham Barber, principal policy adviser at the IET.
'We are irradiated all the time across most of the non-ionising spectrum,' says Barber, in much the same way as we are also irradiated with visible light.
Research on basestation emissions from 60 sites around Australia by ARPANSA's Michael Bangay and Stuart Henderson confirmed a spread of radiation at similar levels from a variety of sources. But the focus remains on mobile.
'More recently, many studies have been done in communications bands. No doubt this has focused attention on possible health risks at these frequencies. This approach, focusing research on frequency bands of actual public exposure, is clearly reasonable,' says Foster.
Although it may be possible to separate out the effects of a phone used at close range, Georg Neubauer, a researcher at the Austrian Institute of Technologies, says the presence of other RF emissions makes it difficult to predict the effect of specific frequencies. 'It makes no sense to consider basestations alone. This is one of the challenges of performing studies: everybody has been exposed.'
However, exposure levels for the overwhelming majority of the public have been way below the limits given by organisations such as the International Commission on Non-ionizing Radiation Protection (ICNIRP), which are used by many governments around the world.
With the rise of ambient wireless sources such as Wi-Fi, Bluetooth, digital broadcasting as well as cellular communications, it is easy to believe that we are being bathed in RF at unprecedented levels. However, measurements in one study of metropolitan Wi-Fi deployment in the US, the ambient RF levels were below 1 per cent of ICNIRP levels and below that of the leakage from a microwave oven at a distance of a metre or so.
Digital modulation schemes could make a difference as the approach is more pulse-like than analogue modulation techniques. Studies are underway to investigate this but have shown, so far, no significant differences to experiments using continuous waves.
There could even be a positive trade off, since digital modulation potentially offers a way to reduce transmission levels thanks to increased error correction. However, other factors come into play. A team from research company IMST took 'before' and 'after' measurements at more than 300 points around Munich and Nürnberg as DVB-T transmissions were introduced to the region. In some cases there was a clear increase in exposure; in others the exposure fell because of the way that digital TV was being rolled out in Germany. The introduction of digital audio broadcasting (DAB) saw a fall in RF exposure relative to the FM transmissions it was meant to replace, but the researchers reckoned this difference would decrease as broadcasters boosted DAB transmission power to improve indoor reception.
Levels of ambient RF have clearly increased since the 20th century began - the few milliwatts per square metre of black-body radiation are now supplemented by a variety of sources operating in the microwatt to milliwatt per square centimetre range, representing a relative increase of five or more orders of magnitude, though from very low levels. But some of these sources have been operating for most of a century - a far longer period in which to recognise any potential health effects than the working lifetime of relative newcomers such as cellular radio and Wi-Fi. That has yet to be reflected in public perception of the risks of RF radiation - if there are any.