Adding new fuel to the debate over cell phone safety, three European research groups in separate studies have found an increased risk of brain tumors in people who have used the phones for 10 years or more.
Two of the studies found a correlation between the tumor's location and the side of the head where people reported they held the phone. One also suggests the greatest risk is in people who began using the phones before age 20, but researchers said the study group was small and more research should be done.
Two of the studies, one in England and one in Germany, are part of the 13-nation Interphone Study, an effort sanctioned by the World Health Organization to assess possible health risks from the radiation emitted by cell phones.
Both studies found an increased risk of glioma, an often deadly brain cancer, in people who had used cell phones 10 years or more.
An earlier Interphone study, reported in October 2004 by researchers at the Karolinska Institute in Sweden, found an increased risk for a non-cancerous brain tumor called acoustic neuroma after 10 years of cell phone use, but not for glioma. "When you put the three large Interphone results together -- the German, English and Swedish -- they tell a story, and it begs for attention," said Louis Slesin, publisher of Microwave News, who has been reporting on the health effects of such radiation for two decades.
John Walls, vice president of public affairs for CTIA, The Wireless Association, a cell phone industry trade group in Washington, D.C., said the increase in glioma in people who had used the phones more than 10 years was "statistically insignificant," and said there is no cause for concern.
The German study, conducted by Joachim Schuz and colleagues at the University of Mainz, was published online by the American Journal of Epidemiology. The researchers compared a group of 749 brain tumor patients with 1,494 similar people who had not used cell phones and found a doubling of the risk of gliomas after 10 years of use.
They said numbers of people in the study who had used the phones for 10 years was small, and the findings need to be confirmed by other studies.
The British researchers compared a group of 966 brain tumor patients with a group of 1,716 healthy patients who had not used cell phones. They found a 20 percent increase in cancers among long-term users, but no overall increased risk in people who used cell phones.
The study, funded largely by the cell phone industry and published online by the British Medical Journal, found a significantly increased risk for tumors that developed on the same side of the head where patients said they most often held the phone. But lead researcher Patricia McKinney said that finding probably was due to many patients not accurately recalling which ear they'd used most of the time.
Critics said conclusions drawn by the researchers were "highly misleading" and might give cell phone users a false sense of security.
George Carlo, who headed the American cell phone industry's 1990s research program, said the findings indicate a 24 percent increase in tumors among people who used the phone on the same side as the tumor.
Alasdair Philips, director of Powerwatch, an independent watchdog group in England, also said the claim of no association of risk is unjustified because the study excluded half the people who developed gliomas because they died before they could be interviewed.
McKinney, an epidemiologist at the Leeds Institute of Genetics, Health and Therapeutics, said "we have no reason to believe the findings were affected by the [exclusion of half the cases]."
In an e-mail to the South Florida Sun-Sentinel, she defended the decision to discount the high number of cases reported on the same side of the head where the phone was held.
A third study, in the February edition of International Journal of Oncology, found an increased risk of acoustic neuromas in long-term users. Dr. Lennart Hardell and colleagues at Orebro University in Sweden analyzed the cases of 1,254 people diagnosed with benign brain tumors between 1997 and 2003, and compared them with a similar group of 2,162 people who had not used cell phones.
They found that people who used analog cell phones starting 15 years before diagnosis developed acoustic neuromas at a rate almost four times higher than the comparison group.
Walls, of the CTIA, said he had not seen the Swedish study, but questioned the validity of the findings and the researchers' study design.
An analysis late last year by Dr. Henry Lai, who heads the Bioelectromagnetics Research Laboratory at the University of Washington in Seattle, said of 271 laboratory or clinical studies done in recent years, about 60 percent have shown a biological effect in cells or animals exposed to radio frequency radiation.
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