LONDON (AP) — Danish researchers can offer some
reassurance if you're concerned about your cellphone: Don't worry. Your device
is probably safe.
The biggest study ever to examine the possible
connection between cellphones and cancer found no evidence of any link,
suggesting that billions of people who are rarely more than a few inches from
their phones have no special health concerns.
The Danish study of more than 350,000 people
concluded there was no difference in cancer rates between people who had used a
cellphone for about a decade and those who did not.
Last year, a separate large study found no clear
connection between cellphones and cancer. But it showed a hint of a possible
association between very heavy phone use and glioma, a rare but often deadly
form of brain tumor. However, the numbers of heavy users was not sufficient to
make the case.
That study of more than 14,000 people in multiple
countries, in addition to animal experiments, led the International Agency for
Research on Cancer to classify electromagnetic energy from cellphones as
"possibly carcinogenic," adding it to a list that also includes
things such as coffee and gasoline engine exhaust.
But that designation does not mean the phones
necessarily pose a risk. Cellphones do not emit the same kind of radiation as
that used in some medical tests or found in other sources such as radon in
soil.
Two U.S. agencies — the Food and Drug
Administration and the Federal Communications Commission — have found no
evidence that cellphones are linked to cancer.
Yet fears of a link persist, despite the fact that
cancer rates have not risen since cellphones were introduced.
In the latest research, published online Thursday
in the journal BMJ, researchers updated a previous study examining 358,403
cellphone users aged 30 and over in Denmark from 1990 to 2007. They found cellphone
users did not have a higher cancer risk compared with those without cellphones.
Cancer rates in people who used cellphones for
about 10 years were similar to rates in people without a cellphone. Cellphone
users were also no more likely to get a tumor in the part of the brain closest
to where phones are usually held against the head. The study was paid for by
the government's Danish Strategic Research Council.
"Our study provides little evidence for a
causal association, but we cannot rule out a small to moderate increase in risk
for subgroups of heavy users," said Patrizia Frei, of the Institute of
Cancer Epidemiology in Copenhagen, Denmark, one of the paper's authors.
"This is encouraging news, but it doesn't mean
we're at the end of the road," said Hazel Nunn, head of Health Evidence
and Information at Cancer Research U.K., which was not linked to the study.
About three-quarters of the world's population,
more than 5 billion people, use a cellphone. That makes it difficult for
scientists to compare cancer incidence in people who use the devices versus
those who do not.
Others disputed the Danish study's findings. The
advocacy group MobileWise, which believes cellphones pose a health risk, said
the study wasn't long enough to consider the long-term risk, since brain tumors
can take decades to develop.
In an accompanying editorial in BMJ, Anders Ahlbom
and Maria Feychting of Sweden's Karolinska Institute wrote that one of the
study's strengths was its use of objective data from cellphone records. Previous
studies have been criticized for relying on people to recall their cellphone
habits from decades earlier.
In about 30 other studies done in Europe, New
Zealand and the U.S., patients with brain tumors have not reported using their
cellphones more often than unaffected people.
The editorial writers pointed out that research on
cellphones and cancer was not sparked by any evidence of a connection, but from
concerns that something about the relationship between radio frequency fields
and human physiology had been "overlooked or misunderstood." Research
into the safety of cellphones is now "extensive," they wrote.
Nunn said studies with longer-term data were still
needed and that there was little information on children's exposure to
cellphones.
There was no biological evidence for how cellphones
might cause cancer, unlike, for example, the proof that tobacco is
carcinogenic, she added.
Cellphones send signals to nearby towers via radio
waves, a form of energy similar to microwaves. But the radiation produced by
cellphones cannot directly damage DNA and is different from stronger types of
radiation like X-rays or ultraviolet light. At very high levels, radio
frequency waves from cellphones can heat up body tissue, but that is not
believed to damage human cells.
Nunn said people should not change their cellphone
habits based on the current evidence, except perhaps for limiting their kids'
use of the devices.
"There are a lot more worrying things in the
world than mobile phones," she said.
Copyright 2011 The Associated Press.
(AP Photo/Seth Wenig, File)
