A major study into the safety of mobile phones has concluded that they may affect the health of people who use them.
Research carried out by scientists in Finland suggests radiation from mobile phones causes changes in the brain.
It is the first time that scientists have looked at the effects of mobile phone radiation on human cells rather than those of rats.
The two-year study concluded that even low-level emissions from handsets are damaging.
Scientists from the Radiation and Nuclear Safety Authority found that exposing human cells to mobile phone radiation damaged the blood-brain barrier – a safety barrier in the body that stops harmful substances in blood from entering the brain.
They discovered that the exposure caused the cells in blood vessel walls to shrink which enabled molecules to pass into brain tissue.
Professor Darius Leszcynski, who carried out the study, said the results came from laboratory tests on human cells and that further research was needed to see if the same effect actually happened in humans.
But speaking to BBC News Online, he said: “The blood-brain barrier has been shown to be affected by radiation in animal studies.
“There is a lot of uncertainty about whether this happens in humans. We have shown some biological effects.”
Prof Leszcynski said these changes could have a serious impact on a person’s health if they were found to happen in humans.
“If it did happen it could lead to disturbances, such as headaches, feeling tired or problems with sleeping. A study by a Swedish research group even suggested it could lead to Alzheimer’s disease.”
However, he added: “It is important to remember that our study has been done in the laboratory where we can detect even the smallest changes.
“We cannot say whether it happens in humans. We need further study looking at real people to see if the blood-brain barrier is affected.
“What is happening in the human brain is an absolute enigma. We don’t know at all.”
Prof Leszcynski said mobile phones were still safe to use.
“At the moment, there is no scientific support for introducing any sort of limitation either on use of mobile phones or setting new safety limits.
“There is no need because we don’t have any science to support it. All the guidelines in place at the moment are fine.”
Prof Leszcynski will present his findings at a conference in Quebec, Canada, next week.
He said a study by French scientists, which will also be presented at the conference, found similar results in rats.
Dr Michael Clark, science spokesman at the National Radiological Protection Board, said the research did not show any impact on people’s health.
“This is demonstrating a biological effect in cells in the lab.”
Speaking to the BBC, he said: “It doesn’t relate to a health effect. You can’t go from a biological effect in a Petri dish to say that’s a health effect.”
He added: “The authors themselves are saying that this doesn’t mean that mobile phones are unsafe or the guidelines are wrong.”
The Consumers’ Association said there was still insufficient evidence to say whether or not mobile phones were safe.
A spokesman said: “At the moment, it’s too soon to reach a definitive verdict on health risks from mobile phones, but neither has research given it the all clear.”
The National Consumers’ Council said mobile phone users were reaching their own conclusions about the risks.
“The people who feel that mobile phones are very important and essential in their lives would attach less weight to this new information than those who are already concerned about the risk,” said a spokeswoman.
More than 40 million people in Britain have mobile phones, many of them children.
Two years ago a government inquiry led by Sir William Stewart concluded that mobile phones posed no provable health risk.
But its report urged caution over the use of mobile phones by children until more was known about their impact on health.
In January, a new £7.4 million research programme was announced, backed by the government and the mobile phone industry, to be managed by an international committee of experts led by Sir William.
The programme includes 15 studies which will seek clear conclusions about the health hazards of mobile phones, in particular fears of an association between mobile phone radiation and brain cancer.
The main purpose of the research will be to see whether “subtle biological changes” already known to be caused by mobile phones pose a risk.
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