Scientists say the study is important, because it is the first of its kind to focus on children.
The study's authors compared the cellphone habits of nearly 1,000 children in Western Europe, including 352 with brain tumors and 646 without. Kids who used cellphones were no more likely to develop a brain tumor than others, according to the study of children ages 7 to 19, published online Wednesday in the Journal of the National Cancer Institute.
Scientists have been eagerly awaiting these results, says Martha Linet, a doctor with the National Cancer Institute who wasn't involved in the study. "It's very reassuring," Linet says.
Researchers, led by Denis Aydin of the Swiss Tropical and Public Health Institute, looked at their data in several ways, searching for possible trends with long-term use. They found no increase in brain tumors among children who had used cellphones for five years or more, according to the study, funded by European health agencies.
Some scientists and consumers have been concerned about cellphones' health effects, especially on developing children, because cellphones emit energy close to the brain.
In the study, Aydin and colleagues note that radio frequency electromagnetic fields created by cellphones penetrate deeper into children's brains than adults' brains, mainly because kids' skulls are smaller, the study says. Recent studies have suggested that small children's brains absorb about twice as much mobile phone energy as adults' brains.
But authors also point out that this energy — unlike the radiation given off by X-rays or CT scans — isn't strong enough to damage DNA, cause mutations and lead to cancer. And while many people are concerned about cellphones, no one has ever come up with a way to explain how the devices might cause cancer, Linet says.
If cellphones caused brain tumors, researchers might expect to find those tumors on the side of the head where kids hold their phones. In the new study, however, children had the lowest risk of tumors in the part of the brain exposed to the most cellphone energy, write scientists John Boice and Robert Tarone in an accompanying editorial. They note that there has been no increase in brain tumors — among kids or adults — since cellphones came into widespread use in the 1990s. In their editorial, they note that there were 285 million cellphone subscribers in 2009 in the USA alone. If cellphones really did cause brain tumors, doctors would likely have noticed this by now, they write.
But the study also produced some mixed signals.
In a subset of children, researchers found a higher risk of brain tumors in children whose cellphone subscriptions had begun more than 2.8 years ago.
Overall, however, parents should find these results reassuring, says pediatrician Rachel Vreeman, of the Indiana University School of Medicine, who summarizes recent cellphone research in her book, Don't Cross Your Eyes… They'll Get Stuck That Way!: And 75 Other Health Myths Debunked.
"This is a good piece of evidence that parents don't need to be panicked about cellphones and cancer," Vreeman says.
Concerns about cellphones were renewed last month, when a branch of the World Health Organization, the International Agency for Research on Cancer, reversed its previous position. In the past, the agency had said there was "no conclusive evidence" linking cellphones to brain tumors. Now, the agency classifies cellphones as "possibly carcinogenic" based on "limited evidence," acknowledging that the few links between cellphones and cancer could be due to chance.
The "possibly carcinogenic" category includes a number of staples of everyday life, however, such as coffee, pickles and styrofoam, Vreeman says.
"Scientific evidence has overwhelmingly indicated that wireless devices do not pose a public health risk for adults or children," said John Walls of CTIA-The Wireless Association, in a statement.
Consumers who remain concerned can take a number of steps to reduce their exposure to cellphone energy, such as using a hands-free device or a speakerphone, the American Cancer Society says.