Bluetooth headset is better to use than phones directly to the ear

The wireless technology known as Bluetooth is popular for connecting cell phones with cordless headsets. Research has proved that holding phones close to your ear (hence head/brain) increases health risks. There is a possibility of developing brain tumors. Electromagnetic radiation emitted from cell phones affect the body's cells, brain and immune system. A wide range of diseases, from cancer to Alzheimer's, may develop due to such harmful exposures.

This is not surprising. While a phone needs to transmit with enough power to reach a base station antenna that may be a couple of miles away, Bluetooth has a nominal range of 30 feet. Radio energy dissipates at a rate proportional to the square of the distance, the transmit power of a Bluetooth radio can be orders of magnitude lower than that of the phone itself. And except when you are actually using the headset for a conversation, the Bluetooth radio is idle nearly all the time.

Bluetooth headset contains radio frequency so its not harmful for your health infact. Somewhere I read over the net that, Davis said. carrying a cell phone in a pocket or clipped to a belt means, you are just roasting your bone marrow by time.

Few tips while on mobile calls:
Use the speakerphone
Use a wired headset with a ferrite bead
Use a Bluetooth earpiece
Use a "hollow tube" earpiece
Get a phone with less radiation