I am wondering about this too and whether to get a smart phone or use a land line.

The research I’ve read seems to be inconclusive about this. I think generally trying to keep your cell phone away from your body (not in a pocket), and using a headset instead of holding directly to your head is probably a safer bet, but we may not know more for some time as we continue to study the long term effects of our use, which shows no sign of slowing.