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Is Cancer A Call Away?
The safety of mobile phones is in doubt again, as a new study suggests a link with brain cancer.
Concerns have been raised once again that mobile phones might be linked to brain and head cancers and, once again, an entirely satisfactory assessment of the dangers, if any, remains frustratingly elusive.
The health effects of mobile phones are far from obvious, so the risks cannot be large. But that does not mean they must be insignificant: with more than 44 million cellphones used in Britain and approaching one billion worldwide, even a small risk would have devastating ramifications.
This month, during a debate at the British Association's science festival in Glasgow, an important new study was cited. Probably its most significant conclusion is a dose response relationship that links the duration of phone use and tumour risk. The study found that use of mobile phones for up to 10 years increased the risk of brain cancer by 26 per cent, but the risk jumped to 77 per cent for more than a decade's use.
The tumours were significantly more likely to be on the side of the head where the cellphone was held - 2.5 times greater for temporal brain tumours and 3.7 times greater for acoustic neurinoma tumours, which involves the auditory nerve and begins in the ear canal. Although benign, the latter tumours can cause facial paralysis and become life-threatening if they exert too much pressure inside the skull.
Although several previous studies have suggested that mobile phones might have detrimental effects, this study shifts the balance of evidence, challenging the conclusions of a major inquiry that was published last year.
The radiation watchdog, the National Radiological Protection Board (NRPB), said it will not comment until this work is published in a peer-reviewed journal. But the study has already gained credence because of the size of its sample (1,617 cancer patients and a control of the same number) and its duration (more than a decade of epidemiological data).
The good news, if such, was that the epidemiological data used applied to analogue mobile phones, which were phased out in 1997. The bad news was that although the digital GSM system currently in use emits less radiation, its pulsed nature might make it more damaging.
"We will have to wait several more years, probably at least until 2005, before we can see the health effects of digital phones," said Lennart Hardell, author of the study and professor of oncology at Orebro University in Sweden. In the meantime, he added, users should exercise caution.
The findings fuelled the row over the use of mobile phones by children. It grew in intensity at the science festival debate when Sir William Stewart, president of the Royal Society of Edinburgh and chairman of the Government's independent expert group on mobile phones, condemned mobile phone companies for encouraging young people to use them.
For parents worried by the the gadget their children clutch to their ears, often for hours at a time, it was the latest in a long line of inconclusive and contrary reports. Driven by the rising tide of parental concerns and cranks peddling bogus science on microwave radiation, the Department of Health set up an inquiry in 1999.
Sir William's expert group on mobile phones concluded in May last year that the balance of evidence then available did not suggest that emissions from handsets or masts put the health of the general population at risk - a finding broadly echoed by the health directorate in France, among others. But still the issue was not settled. Sir William made recommendations that suggested the jury was still out. There was scientific evidence suggesting the kind of microwave radiation that mobile phones emit might have biological effects, even at exposures below NRPB guidelines. And he said the effects could be beneficial or adverse.
"We recommend that a precautionary approach to the use of mobile phone technologies be adopted until much more detailed and scientifically robust information on any health effects becomes available," Sir William advised.
In particular, he recommended that children, whose skull bones are less developed than adults and who will probably use mobile phones for more of their lifetimes, should not use cellphones more than necessary.
The expert group also suggested the guidelines of the International Commission on Non-Ionising Radiation Protection on exposure to radiation should be adopted in Britain (although no detailed scientific evidence was provided to justify the commission's recommendation that maximum exposure levels for the public should be about five times lower than the NRPB guidelines). Crucially, Sir William said that guidelines are set to minimise tissue heating and take no account of so-called non-thermal effects.
Since then, a new research programme costing pounds 7.5 million has been commissioned, half of it sponsored by the industry and half by the Department of Health, which will be reviewed by a panel under Sir William's chairmanship. Funding is only now being allocated.
There have also been delays in responding to the Stewart report. He recommended that the specific absorption rate of the radio waves given out by phones should be displayed on their packaging, so people can select the lowest values (these can vary by up to 50 times between models). It is yet to happen, though the industry promises labelling will start next month.
Sir William has also been concerned by a pounds 2.5 billion secure radio system - the Terrestrial Trunked Radio (Tetra) digital radio system - already under test by police in Lancashire, which looks likely to be adopted by the emergency services and the Ministry of Defence.
The system is modulated at close to 16 pulses a second (Hz), a frequency his report said should be avoided as a precaution because old research seemed to suggest it might affect the release of calcium from brain tissue. Neurons are sensitive to calcium, which carries out signalling, regulates secretions and other tasks, though the Stewart report said there was as yet no evidence of what consequences this had for health.
Little work has been conducted on the calcium effect since the early Eighties, although a recent study on rats reported to the Bioelectromagnetics Society by Dr John Tattersall of the Defence science and technology laboratory failed to show any unusual effect from one type of 16Hz modulation on brain cell function.
However, another study by Dr Tattersall, published a few weeks ago in the journal Brain Research, showed that radio frequency radiation can affect brain cell signalling at intensities well below those that cause heating. "We don't know what this means at the moment," Dr Tattersall said. "The effects we have found could be hazardous - they could even be beneficial."
A Tetra report for the NRPB was mostly reassuring, though it did call, among other things, for studies of the calcium effect, research on volunteers, and efforts to see if there is a link with epileptic fits. Co-author Prof Colin Blakemore of Oxford University said that, in some circumstances, Tetra could breach existing NRPB safety guidelines and added that Dr Tattersall's Brain Research study meant that a new effect on brain cells of low-level radio waves has been discovered.
"This is the first direct evidence I know of that very low-intensity radio frequency radiation can directly affect the potential difference [voltage] across nerve membranes," Prof Blakemore said. "There does seem to be something going on.
"Personally, I am not worried, but this is the best-documented example of a non-thermal effect on nerve cells This issue needs to be pinned down once and for all by additional research."
Like mobile phones, Tetra seems destined to be a victim of the adage that it is impossible to prove safety. Unless incontrovertible hard evidence of a health risk emerges, we will have to continue to wonder about the health effects of our love affair with the mobile telephone.
A study by the National Cancer Institute, published last spring in the New England Journal of Medicine, found no association between cellphone users and certain types of brain tumours.
There is no correlation between phone use and brain or nervous system cancers, according to a study of 420,000 Danish cell phone users conducted by the Danish Cancer Society and published in the Journal of the National Cancer Institute this year.
Researchers at the University Neurology Clinic in Freiburg, Germany, found mobile phones increased blood pressure. The rise was small but could be harmful to people with high pressure levels, they said.
An expert panel report prepared under the direction of the Royal Society of Canada could find no conclusive evidence of adverse health effects from radio frequency exposure. However, like the Stewart report, it recognised that documented biological effects existed at even low levels, that those effects might have adverse health effects and called for more research.
A study of 11,000 mobile phone users conducted by Dr Kjell-Hansson Mild at the National Institute of Working Life in Umea, Sweden, suggested that regular use of mobiles phones could lead to fatigue, headaches and skin irritation.
Scientists led by David de Pomerai at the University of Nottingham found that tiny nematode worms grow faster but wriggle less when given a dose of low-intensity microwaves.
Henry Lai at the University of Washington in Seattle found rats exposed to microwaves produce endorphins and were more likely to binge on alcohol or react strongly to morphine and barbiturates.
In 1994, Dr Leif Salford showed a breakdown in the blood-brain barrier of rats when they were exposed to radio waves, possibly impairing the blood-brain barrier's ability to protect the brain.
A team at the University of Essen in Germany concluded that people who regularly used a mobile phone were three times more likely to develop cancer of the eye.