There are 300 million cell phones in America -- almost as many phones as people. But there's still some concern about their safety. A study of users under the age of 20 out today found no link between cell phone use and an increased risk for brain cancer. CBS News medical correspondent Dr. Jon LaPook has more on that.
With a generation of kids connected to each other through cell phones, doctors like Keith Black of Cedars-Sinai Medical Center in Los Angeles have concerns about safety.
"What we know is that the microwave radiations from cell phones may penetrate deeper into the child's brain," said Black. "More of the radiation goes into their brain because their scalp is thinner -- their skull is thinner."
In today's study, researchers compared cell phone use in healthy children and 352 brain tumor patients between the ages of 7 and 19. Cell phone use did not significantly increase the risk of a brain tumor.
The research comes out just two months after the World Health Organization categorized cell phones as "possibly carcinogenic."
Seventy-five percent of teenagers now have a cell phone, up from 45 percent in 2004, so a clearer picture of safety will only come from long-term studies.
"What we're really concerned about," said Black, "the child that begins using the cell phone at seven or 12, when they become an adult after 20 or 30 years of using the cell phone for, is that risk higher? That is not answered by this study.'
Long-term studies are currently being done.