www.7plus7.com

 

Cancer cell study revives cellphone safety fears

The safety of cellphones has been brought into question once again by research that suggests radio waves from the devices could promote the growth of tumours. Paradoxically, the study suggests that the radiation makes tumours grow more aggressively by initially killing off cancer cells.

Cell biologist Fiorenzo Marinelli and his team at the National Research Council in Bologna, Italy, decided to investigate whether radio waves had any effect on leukaemia cells after previous studies indicated that the disease might be more common among mobile phone users. The life cycle of leukaemia cells is well understood, making it relatively easy to spot changes in behaviour.

The team exposed leukaemia cells in the lab to 900-megahertz radio waves at a power level of 1 milliwatt, and then looked at the activity of a gene that triggers cell suicide. Many European mobile networks operate at 900 megahertz, and maximum power outputs are typically 2 watts, although they regularly use only one-tenth of this power.

After 24 hours of continuous exposure to the radio waves, the suicide genes were turned on in far more leukaemia cells than in a control population that had not been exposed. What is more, 20 per cent more exposed cells had died than in the controls.

But after 48 hours exposure, the apparently lethal effect of the radiation went into reverse. Rather than more cells dying, Marinelli found that a survival mechanism kicked in. Three genes that trigger cells to multiply were turned on in a high proportion of the surviving cells, making them replicate ferociously. The cancer, although briefly beaten back, had become more aggressive.

DNA damage?

Marinelli presented his results this month at the International Workshop on Biological Effects of Electromagnetic Fields on the Greek island of Rhodes. While the results do not show a direct health threat from mobile phones, they provide fresh evidence that radiation from such devices could play an important role in activating genes that might help cancer cells thrive.

"We don't know what the effects would be on healthy human cells," says Marinelli. "But in leukaemia cells the response is always the same." Marinelli suspects the radiation may initially damage DNA, and that this interferes with the cells' biochemical signals in a way that ultimately triggers a defensive mechanism.

Many scientists believe that because radiation from cellphones does not have enough energy to break chemical bonds, it cannot damage cells. The only way damage could occur, they say, is if the radio waves heated tissues up.

But British research earlier in 2002, by molecular toxicologist David de Pomerai at the University of Nottingham, showed that radio waves can cause biological effects that are not due to heating. He found that nematode worms exposed to radio waves showed an increase in fertility - the opposite effect from what would be expected from heating (New Scientist print edition, 9 February).

"Confused field"

Marinelli's study is intriguing, says de Pomerai. "But I'm far from convinced that these authors are looking at any reproducible and real phenomena," he says. Other studies have shown mobile phone radiation to have no effect on cell death, de Pomerai adds.

An inquiry in April 2000 by the British government found no evidence of any health risks from mobile phones. But it still recommended that people take a precautionary approach until further evidence emerged. In particular, it suggested children, whose brains are still developing, should not use mobile phones excessively.

"It's a very confused field," admits Colin Blakemore, a physiologist at the University of Oxford and a member of the British National Radiological Protection Board's advisory group on non-ionising radiation. People should place more reliance on animal studies than lab-based experiments on cells, he says.

But de Pomerai insists that a consensus is emerging that non-ionising radiation can indirectly damage DNA by affecting its repair system. If the DNA repair mechanism does not work as well as it should, mutations in cells could accumulate, with disastrous consequences. "Cells with unrepaired DNA damage are likely to be far more aggressively cancerous," he says.