Answering the radiation question
(New Scientist Via Thomson Dialog NewsEdge)IT STARTED with a Larry King show in 1993. Larry's guest, widower David Reynard, was suing several phone companies because his wife, who used a cellphone, died of a brain tumour. While the case was eventually dismissed due to lack of scientific evidence, many more followed.
By 1998, the number of mobile phone owners had skyrocketed, and the UK's National Radiation Protection Board was being inundated with calls about the safety of the phones and the masts. Rumours of microwaves frying the brain, and children who lived near phone masts getting cancer all added fuel to the frenzy.
If any of these rumours were to prove true, the implications would be truly terrifying: this year the number of mobile phone users worldwide is expected to top 2 billion. But the jury is still divided over the issue of mobile phone safety. Last month British researchers published their part of the Interphone study an international project involving 13 countries, which since 1998 has been investigating trends in mobile phone use in people with brain tumours. It suggested that regular mobile phone users were at no greater risk of developing brain tumours than less frequent users.
Meanwhile Gunther Speit and his colleagues at the University of Ulm in Germany have replicated the results of an earlier international study called REFLEX, which suggested that radiation from mobile phones could damage DNA in cells.
So what is the real story behind mobile phones, and just how safe are they? Repeating the REFLEX study has added weight to the argument that radio-frequency (RF) radiation does at least have some effect on living cells. "For me, there is no doubt that electromagnetic fields can cause DNA strand breaks and genotoxic effects," says Franz Adlkofer, who led the original REFLEX study. Whether they produce a similar effect in people is a different matter, but he believes that the evidence is convincing enough to justify caution in using mobile phones, such as following the advice of the UK's Mobile Telecommunications and Health Research Programme (MTHR) not to give cellphones to children under 9 years old.
Others are less convinced. Even if Speit's results do stand up to scrutiny, it doesn't guarantee that radiation is causing the DNA breaks, says Primo Schaer at the University of Basel in Switzerland, who is also trying to replicate the results. Some also point out that DNA breaks and changes in gene expression do not necessarily indicate damage, and even if there is damage that doesn't necessarily equate to health problems.
It is no wonder that we are all so confused. Scientists can't even agree on how mobile phones might be damaging our bodies, if indeed they are. While many think that accidental heating from RF radiation might be to blame, others say that the radiation from mobile phones is not powerful enough to cause significant heating, and suspect an alternative, non-thermal effect.
David De Pomerai of the University of Nottingham, UK, was the first to convincingly report such a phenomenon when his work in nematode worms suggested that RF radiation could cause cells to produce heat shock proteins a measure of cellular stress even though there appeared to be no heating. But after recalibrating his equipment, he detected small temperature fluctuations of around 0.1 to 0.2 C, and found that if you reduced this "trivial" heating you could also eliminate the heat-shock response. It remains unclear how important these tiny temperature fluctuations are.
Other researchers believe that even if overall levels of heating are very small, it is possible that hotspots could be forming within brain tissue. "I think we need to ask whether it is conceivable that there are some areas where more energy is being dumped, and whether some areas of the brain are being heated up more than we would like," says Lawrie Challis of the MTHR. "I think it's unlikely, but we need to rule it out".
The MTHR is planning to do a series of microdosimetry studies in the next phase of its programme, to establish how low-level radiation affects specific areas of tissue in the head, but as yet no one has managed to devise an experiment that would categorically rule out the possibility that RF radiation is causing hotspots.
Even if low doses of radiation from mobile phones can damage DNA, the big question remains: does it actually make any difference to human health?
Research published in the British Medical Journal
last month suggests not. British Interphone researchers interviewed nearly 1000 people who had developed a glioma, one of the most common types of brain tumour, as well as more than 1700 healthy people. They found no increased risk of glioma in the medium term (DOI: 10.1136/bmj.38720.687975.55).
For a clearer picture we need the rest of the Interphone results, says Elisabeth Cardis from the International Agency for Research on Cancer in France, who is carrying out the final Interphone analysis. "It's one of the largest studies on brain tumours ever conducted," she says, and it is only when all the results are analysed and published that we should finally be able to draw some definitive conclusions about mobile phone safety, at least in the short to medium term.
With all the data now in, the final analysis could be published in just a few months. In the meantime, expect further chaos and confusion as the remaining Interphone countries race to publish their results, especially if different groups draw different conclusions. This happened last week when German Interphone researchers published their results online in the American Journal of Epidemiology
, suggesting that although there was no increased risk of glioma among mobile phone users overall, long-term users might incur some increased risk (DOI: 10.1093/aje/kwj068).
Even when the full Interphone study is published, it will be difficult to draw conclusions about long-term safety because people have only really been using mobile phones for about a decade, and some cancers take many years to develop. "We won't be able to rule out any effects in the long term, say 20 or 30 years or so," says Cardis.
The only real hope of this lies with a massive international cohort study being organised by the World Health Organization, due to begin this year, which will monitor around 200,000 light, medium and heavy-use mobile phone users over at least a decade, and ideally for the rest of their lives. What makes this study so different, apart from the sheer scale, is that unlike Interphone and other studies it does not rely on subjects having to recall their mobile phone use memories being prone to bias. "With this we talk to people before they are sick, which is a much better way of doing things," says Paul Elliott at Imperial College, London, who is heading the British part of the new study. But it could be many years before results emerge.
And what about the dangers of mobile phone masts? Parents have been increasingly concerned about the growing number of masts being erected near schools and on other public buildings such as shopping centres, following mixed media reports of an increased risk of cancer and other illnesses in people living near mobile phone base stations.
Elliott's team has now begun a long-term study plotting all UK cancer cases in childen up to 4 years old onto a map, and looking at their proximity to mobile phone masts, in order to establish whether there is a link between childhood cancer and radiation from these masts. The study is likely to be completed later this year and will be published in 2007.
Despite the lack of any conclusive evidence about the safety of mobile phones and phone masts, the benefits of mobile phones appear to be enough for most people to keep on using them, whether or not there is any risk. And with worldwide mobile phone sales continuing to rise, by the time we know if there is a health risk, will any of us actually be able to imagine life without them?
Urban myths and phone truthsCaroline Williams Duncan Graham-Rowe 1. Radio waves, microwaves, electromagnetic radiation, RF radiation. What's the difference and can they all fry the brain?
Media scare stories often hopelessly jumble these terms. They are actually all the same thing. Microwaves are simply electromagnetic radio-frequency (RF) waves with frequencies in the microwave band, which stretches from about 800 megahertz to 30 gigahertz. With wavelengths in the range of tens of centimetres, the fear is that microwaves may set up electrical resonances in the human body because our body parts are on that scale. The microwaves used by mobile phones are very low-power, but if they cause molecules in our bodies to vibrate and generate heat, there may be health effects. However, it is still too early to say what, if any, these are.
2. Does living next to a phone mast increase your exposure to radiation?
Not necessarily. A mast is designed to serve areas at least 50 metres away, so if you live very close to a mast the powerful main beam is likely to be directed over your head. Fifty to 200 metres away, you may be hit by the beam, but the intensity of the radiation will be greatly reduced.
3. Will I be exposed to more radiation if I use a mobile phone closer to a phone mast or further away?
Mobile phones only use as much power as is necessary to link to the nearest base station. The further away from a mast you are, the harder the phone has to work and the higher the total radiation you will be exposed to from the phone and the mast combined. So a phone call in the middle of nowhere will expose you to more radiation than if you were using your phone in the city.
4. Regardless of whether heating comes from the battery or radio waves, surely it is still a worry?
Heat from the battery tends to stay at the surface of the skin, and is mostly dissipated by surface blood flow. The concern with radio waves is that they could penetrate deep into the brain and be absorbed by brain tissue, and that any heating might be concentrated in a small area. There are also worries about radio waves being absorbed by the eyes one study suggested that mobile phone use could trigger cataracts.
5. Can a ferrite bead attached to your hands-free kit absorb radiation and make talking on the phone safer?
Some studies suggest that hands-free kits amplify the electric field the brain is exposed to by allowing the mobile phone signal to travel up through the headset wire. Ferrite beads were developed to block such signals. Lawrie Challis, chair of the UK's Mobile Telecommunications and Health Research Programme, believes that any reduction in radiation exposure must be a good thing. But Mays Swicord, Motorola's director of electromagnetic research, says that such devices are probably unnecessary. "You're talking about taking a hands-free kit which already reduces exposure by a factor of 10 and now you want to reduce it more?"
6. Are there other sources of microwave radiation besides phones?
Microwave radiation sources in our environment have swelled thanks to the ever wider use of an open frequency band called the Industrial Scientific and Medical (ISM) microwave band. Centred at 2.4 GHz, the ISM is used by Wi-Fi internet links for computers, by DECT digital cordless phones and by the Bluetooth short-range radio data link. But these operate at power levels hundreds of times lower than cellphones. More microwave sources are on the way: ultra-wideband (UWB) links and WiMAX, a long range version of Wi-Fi, will also harness microwaves. No-one yet knows what power level will ultimately be deemed acceptable.
Additional reporting by Paul Marks
Electromagnetic hypersensitivity syndromeCaroline Williams Duncan Graham-Rowe For people claiming to suffer from Electromagnetic Hypersensitivity Syndrome (EHS), the question of whether mobile phones can have a negative impact on human health is a no-brainer. EHS sufferers complain of a wide range of symptoms, from headaches, confusion and fatigue to skin rashes and muscular pain when exposed to any form of electromagnetic field (EMF), including those from mobile phones.
Some sceptics doubt whether the condition exists at all, while others claim that EHS is a psychosomatic illness. Indeed, in the vast majority of lab studies, it has been impossible to pin the symptoms experienced by EHS sufferers on RF radiation specifically. With one exception a study by the Netherlands Organisation for Applied Scientific Research found that radiation from a mobile phone mast increased dizziness, headaches and nausea in both EHS sufferers and healthy controls. The study is being repeated in Switzerland and Germany, and the largest EHS study to date is now under way at the University of Essex, UK, led by Riccardo Russo and his colleagues. They aim to work out whether these symptoms have anything to do with RF radiation, or are more closely linked to stress or other lifestyle factors.
Russo's team has begun testing about 100 people who claim to be hypersensitive to EMF and 100 others both in the presence of an electromagnetic field similar to that of a mobile phone base-station, as well as when the field is turned off. While these numbers may seem small, there are great difficulties in recruiting volunteers for this sort of study one reason why so little literature on EHS exists.
Part of the problem is that many EHS sufferers simply don't like travelling because it involves exposing themselves to radiation outdoors. But this is only half the battle. "The nature of the experiment is that people have to expose themselves to EMF," says Russo, which may make people reluctant to volunteer.
Several theories have been put forward to explain EHS. The most controversial is that radio waves could be jamming the brain's electrical frequencies, causing the grey matter equivalent of white noise. Nerve impulses in the brain vary from 2 hertz to 500Hz, well outside of the range of early analogue mobile phones, whose range was 800 to 900 MHz, but GSM mobile phones, which make up the majority of mobile phones in use today, package signals in 217-Hz pulses. So could these interfere with the brain?
Stuart Butler of the Burden Neurological Institute in Bristol, UK, isn't convinced. "The only thing that is clear so far is that there are no consistently repeatable positive findings of any effect of pulsed digital microwave radiation on behaviour, on the electrical activity of the brain, or on health or feelings of well-being."
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