Or they're completely harmless. It depends which physicist or epidemiologist you ask, which research you cite, and even which section of a particular study you believe.
It's enough to keep you awake at night. (That insomnia, by the way, probably has nothing to do with yakking away on the phone before bedtime. Then again, it might, according to one study).
"The solution here is not hard. This is not rocket science. Just keep it away from your brain," said epidemiologist Devra Davis, author of "Disconnect: The Truth About Cell Phone Radiation, What the Industry Has Done to Hide It, and How to Protect Your Family," due out next month.
Davis, who argues that the $153 billion wireless industry is blocking Americans' access to reliable information on cell-phone radiation, said that consumers should change their habits now - even if the science is inconclusive - to prevent a "catastrophe" years down the road.
"In my professional opinion, there are a number of cases of people with brain tumors today for which cell-phone radiation was a major contributing cause," she said.
Experts who believe that the radiation could be harmful recommend using a speaker phone or a hands-free device - preferably a wired headset - instead of holding the phone to your ear, and texting instead of talking.
"A Bluetooth [hands-free device] does reduce your exposure significantly," Davis said. "But if you have the Bluetooth on all the time and the phone is in your front pocket where it's radiating your gonads, that really is not a good idea. You want to keep the phone off of your body."
Bruce Stutz, whose report in Yale Environment 360 last week examined a decade of peer-reviewed studies, said it's difficult to assess the dangers of cell phones because brain cancers are slow-growing and the use of wireless devices is evolving.
