PITTSBURGH -- Nearly a dozen countries have expressed concern about kids and cell phones. Some are asking children to limit their use and France is about to make it illegal to market cell phones to kids under 12.

Pittsburgh Doctor Sounding Cell Phone Warning Bells

The radiation and nuclear safety authority in Finland has now issued a warning that allowing kids to use cell phones could put them at risk.

They said because a child's brain absorbs the phone's radiation much more deeply than an adult brain, children are more vulnerable to its effects.

"I'm very concerned as a mother and grandmother about what this will mean for our children, who are growing up with much higher uses of these things than any of us ever had before," said Dr. Devra Davis.

Davis is the Director of the UPMC center for Environmental Oncology. She said alerts and warnings around the world should make us pay attention here at home. Not just for ourselves, but for kids who are using cell phones at a young age when their brains are still growing.

"We know children's brains double in the first two years of life. They continue to mature, hopefully, throughout their early teenage years and hopefully throughout their early teenage years. And it won't surprise many parents to learn that children's brains don't finish maturing until the mid-20s," Davis said.

That immature brain is what worries Davis and other researchers in about a dozen countries.

"A child's brain, seen right here, gets a lot more absorption than that of an adult," Davis said.

Davis showed Channel 4 Action News' Marcie Cipriani a model of a brain, demonstrating how far a cell signal reaches in a 5-year-old's brain compared to an adult brain. The model comes from one-time use and is based on a University of Utah study that Davis said took place over 30 years.

"That's why the Finnish Nuclear Radiation and Safety Authority issued an advisory recommending that children limit their use of cell phones. That's why it's illegal to sell a cell phone in Mangalore, India to a child under the age of 16. And that's why many national authorities have now advised that children not use cell phones or they use them only for very limited purposes. Text messaging is much safer," Davis said.

Davis said there is no definitive proof that the cell signal actually causes brain tumors, but she said by the time there is concrete evidence, it may be too late. Davis is not suggesting people stop using cell phones. Rather, as the Finnish safety authority is suggesting, Davis recommends limiting cell phone use by children and encouraging them, if they need to talk on a cell, to use the speaker phone or an earpiece.