"I've been telling friends and family members to seriously consider switching to CDMA if they're using GSM cellphones," Joel Moskowitz, director of the Center for Family and Community Health at the University of California, Berkeley, told Natalie Wolchover of Life's Little Mysteries.
CDMA is used by Verizon, Sprint and U.S. Cellular, while GSM is used by AT&T and T-Mobile. See the complete list here.
CDMA phones, on average, emit a fraction of their maximum radiation output, otherwise referred to as specific absorption rate (SAR), whereas GSM phones emit half the maximum rate, explained Moskowitz. GSM phones go to peak power, and then the power is ratcheted down to a lower level. But CDMA phones transmit at the lowest possible level all the time.
If you use your smart phone for web browsing or downloading MP3s, you might be better off with a CDMA phone, because it uses better data transfer technology. But if you do a lot of business traveling overseas, you may want to stick with your GSM phone because the European Union mandates the sole use of GSM.
Either way, you can take some basic precautions to minimize radiation risks, like avoiding using bluetooth and not speaking on the phone when reception is weak. (For the 9 ways to be safer, go here.)