THERE is fresh concern about the safety of mobile phones after further evidence emerged that low levels of microwaves can affect cells. The findings add weight to claims that cellphone radiation could cause headaches, tiredness and even the growth of tumours.
Dariusz Leszczynski at the Radiation and Nuclear Safety Authority in Helsinki has found that an hour鈥檚 exposure to mobile phone radiation affects numerous proteins in human cells grown in culture and makes the cells shrink.
While this does not necessarily mean mobiles are a health threat, Leszczynski says the changes he discovered could affect the blood-brain barrier that protects brain cells from toxins and infection. They could also affect a cell鈥檚 ability to self-destruct when damaged, a process called apoptosis. 鈥淲hile this would not induce a tumour or mutation, it would support the development of one, by preventing the cell from dying,鈥� he says. Human studies are now urgently needed.
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Two years ago, Britain鈥檚 former chief scientist William Stewart led a government inquiry into the health effects of mobile phones. It concluded that although there was no evidence of any risk to health, we should adopt a precautionary attitude until further evidence was available. 鈥淚 advocate that even more strongly now than two years ago, because of the evidence that has been coming out since then,鈥� Stewart told 快猫短视频.
Leszczynski will tell the Bioelectromagnetic Society meeting in Quebec this week that he has traced a chain of events that leads to changes in cell function. It鈥檚 the first evidence that mobile phone radiation can affect human cells without heating them, he says.
Such non-thermal effects have only been seen in nematode worms before (快猫短视频, 9 February, p 4). And these worm studies, done by David de Pomerai of the University of Nottingham, didn鈥檛 imply there was any health risk.
Leszczynski found phone radiation affected hundreds of proteins, but he focused on the finding that it both activates and increases production of one stress protein called HSP27. This protein is known to inhibit some of the proteins involved in apoptosis.
HSP27 is also thought to help regulate the permeability of the blood-brain barrier through its effect on the fibres that maintain the shape of the cells lining the brain鈥檚 blood vessels. Leszczynski used fluorescent dyes to show that these fibres did indeed change after cells were exposed to radiation.
And if cells in the blood-brain barrier shrink as a result, unwanted molecules could creep into the brain. 鈥淚f the blood-brain barrier is even temporarily affected by mobile phone radiation it might have long-term health effects,鈥� he says. Other studies on the effects of radiation on the blood-brain barrier have produced conflicting results.
De Pomerai says Leszczynski鈥檚 work is 鈥渟ignificant鈥�, but it does not reveal exactly how mobile phone radiation causes these changes. 鈥淯ntil you can demonstrate a mechanism and demonstrate that it is not a heat-activated process people will dismiss it.鈥� Leszczynski is now working backwards from the effects he鈥檚 seen to try to identify the point at which radiation is interacting with the cell.
But Michael Repacholi of the World Health Organization still questions whether heating effects could be entirely ruled out because of the methods Leszczynski used to regulate the cells鈥� temperature. 鈥淭here are much more effective ways of doing this,鈥� he says.
The bulk of evidence so far suggests that mobiles don鈥檛 give you cancer, adds Repacholi. 鈥淭he implications here for health are zero,鈥� he says. Indeed, a team at the Washington University School of Medicine in Missouri reported this week that rats exposed to mobile phone radiation for four hours a day for two years didn鈥檛 get cancer.
Whether or not there are non-thermal effects is significant because mobile phone regulations are based solely on avoiding the heating effect of microwave radiation. Most scientists believe heating is the only way microwaves could possibly damage cells because they don鈥檛 have enough energy to break even weak chemical bonds.
Mays Swicord at Motorola鈥檚 Florida Research Labs, for instance, says he has spent 30 years looking for a possible mechanism for non-thermal effects and has yet to see any reproducible evidence. 鈥淚t鈥檚 difficult for me to believe that non-thermal effects exist,鈥� he says.
But Stewart says you can鈥檛 yet rule out non-thermal effects. What鈥檚 important is to find out if there are any health risks at all, he says. 鈥淚 don鈥檛 care if it鈥檚 non-thermal or thermal, what I鈥檓 worried about is whether there are effects.鈥�