When it comes to minimizing your potential exposure to radio-frequency electromagnetic-field (RF EMF) emissions, the type of network that your cellular-service provider operates makes a difference.
A U.S.-Swiss research team published a study in 2010 in Journal of Exposure Science and Environmental Epidemiology that measured the average power output of cellphones that operate on the four modulation systems that have been used since cellphones were introduced. The output directly correlates with RF EMF exposure; the higher the output, the higher the exposure of RF EMF.
The researchers found that now-defunct analog networks posed by far the highest exposure risk for consumers. The next highest were Time-Division Multiple Access (TDMA) networks, which rapidly are being phased out.
Of the two remaining modulation types, researchers found that Code-Division Multiple Access (CDMA) has lower power output levels than does Global System for Mobile Communications (GSM). Sprint and Verizon use CDMA network technology. AT&T and T-Mobile use GSM technology. Outside of the United States, GSM is the predominant modulation system.
Here are the results: