* No apparent cancer risk, but concern about heaviest users
* Study's findings unclear, methodology has weaknesses
* Experts say phone use now much higher so more work needed
(Adds reaction from representatives of mobile phone industry)
By Kate Kelland, Health and Science Correspondent
LONDON, May 16 Experts who studied almost 13,000
cell phone users over 10 years, hoping to find out whether the
mobile devices cause brain tumours, said on Sunday their
research gave no clear answer.
A study by the World Health Organisation's International
Agency for Research on Cancer (IARC), the largest ever to look
at possible links between mobile phones and brain cancer, threw
up inconclusive results but researchers said suggestions of a
possible link demanded deeper examination.
"The results really don't allow us to conclude that there is
any risk associated with mobile phone use, but... it is also
premature to say that there is no risk associated with it," the
IARC's director Christopher Wild told Reuters.
The results of the study have been keenly awaited by mobile
phone companies and by campaign groups who have raised concerns
about whether mobile phones cause brain tumours.
Years of research have failed to establish a connection.
The British-based GSM Association, which represents
international cell phone firms, said IARC's findings echoed "the
large body of existing research and many expert reviews that
consistently conclude that there is no established health risk".
The Australian-based Mobile Manufacturers Forum also
welcomed the study and backed "the need for ongoing research".
Wild said part of the problem with this study, which was
launched in 2000, was that rates of mobile phone usage in the
period it covered were relatively low compared with today.
It was also based on people searching their memories to
estimate how much time they spent on their cell phones, a method
that can throw up inaccuracies.
European scientists last month launched what will now become
the biggest ever study into the effects of mobile phone use on
long-term health. It aims to track at least a quarter of a
million of people in five European countries for up to 30 years.
This kind of study, called a prospective study, is
considered more accurate because it does not require people to
remember their cell phone use later but tracks it in real time.
SUGGESTION OF A RISK?
Data from the IARC study showed that overall, mobile
telephone users in fact had a lower risk of brain cancer than
people who had never used one, but the 21 scientists who
conducted the study said this finding suggested problems with
the method, or inaccurate information from those who took part.
Other results showed high cumulative call time may slightly
raise the risk, but again the finding was not reliable.
"We can't just conclude that there is no effect," said
Elisabeth Cardis of the Centre for Research in Environmental
Epidemiology in Barcelona, Spain, who led the study.
"There are indications of a possible increase. We're not
sure that it is correct. It could be due to bias, but the
indications are sufficiently strong... to be concerned."
Because of this, and because cell phone use is rising all
the time, more research was needed, the scientists said.
The 21 scientists were part of a group known as the
Interphone International Study Group which was funded in part by
money from mobile phone companies. The study was published in
the International Journal of Epidemiology.
Mobile phone use has increased dramatically since its
introduction in the early-to-mid 1980s. About 5 billion mobile
phones are currently in use worldwide.
The researchers said the majority of people covered in their
study "were not heavy mobile phone users by today's standards".
The average lifetime cumulative call time for those who took
part was around 100 hours, with an average of 2 to 2-1/2 hours
of reported use a month. The heaviest 10 percent of users had
clocked up an average of 1,640 hours of phone use spread over 10
years, which corresponds to about half an hour a day.
"Today, mobile phone use has become much more prevalent and
it is not unusual for young people to use mobile phones for an
hour or more a day," the researchers wrote.
But increasing use is tempered by generally lower radiation
emissions from modern phones and greater use of texting and
hands-free sets that keep the phone away from the head, they
The study received 19.2 million euros ($24.4 million) in
funding, around 5.5 million euros of which came from industry
sources. It analysed data from interviews with 2,708 people with
a type of brain cancer called glioma and 2,409 with another type
called meningioma, plus around 7,500 people with no cancer.
Participants were from Australia, Canada, Denmark, Finland,
France, Germany, Israel, Italy, Japan, New Zealand, Norway,
Sweden and Britain.
(Editing by Mark Trevelyan and Reed Stevenson)