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The safety of cell
phones has been brought into question once again by research
that suggests radio waves from the devices could promote the
growth of tumors. Paradoxically, the study suggests that the
radiation makes tumors 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 leukemia cells after previous studies indicated
that the disease might be more common among mobile phone users.
The life cycle of leukemia cells is well understood, making
it relatively easy to spot changes in behavior.
The team exposed
leukemia 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 leukemia cells than in a control
population that had not been exposed. What is more, 20 percent
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 leukemia 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 cell phones 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.
"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-ionizing
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-ionizing 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.
New
Scientist October 24, 2002
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