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