"People should take steps to minimize radiation exposure when using cell phones, including reducing the amount of time spent using a cell phone and using speaker mode or a headset to place more distance between one’s head and the cell phone." - The US. Dept. of Health and Human Services
The World Health Organization classifies cell phone radiation as a "Class 2b. Known Carcinogen" in the same category of Lead, Asbestos, and Engine Exhaust.