Although the National Cancer Institute states that no scientific data has conclusively linked cell phone use to cancer, many owners have concerns about mobile devices and radiation. A wired headphone reduces radiation exposure significantly; a Bluetooth earpiece may lower it even further.
Cell Phones and Radiation
All cell phones are tiny transmitters that produce radiation in the form of radio waves. As you talk on the phone, your head and brain absorb a small amount of this radiation. The amount of exposure falls off greatly with distance, however, and Bluetooth accessories or headphones let you put distance between your head and the phone.
Note that, unlike X-rays and other kinds of radiation, the radio waves from your cell phone are considered much too weak to directly affect your health.
In tests, scientists use a number called the Specific Absorption Rate to measure radiation exposure from cell phones. A higher SAR means the head absorbs more radiation from radio waves. Among other factors, SAR takes into account that only part of the radio waves from a cell phone are absorbed by the human body; the rest goes into the air with a small portion reaching the cell tower.
According to the Swiss Federal Office of Public Health, using a wired headset lowers SAR values by 8 to 22 times. The wire that connects the phone to the earpiece acts as an antenna, carrying a small part of the radio energy to the head; when the cable is lying next to the body, much of the radiation goes into the body where its effects are less harmful than to the head. A small metal device called a ferrite bead can lower the SAR factor even more. When slipped onto the wire, the bead traps some of the radiation before it reaches the earpiece.
A Bluetooth headset replaces a wired connection to a mobile device with a tiny radio signal. In addition to eliminating wire tangles, Bluetooth reduces SAR because its radio waves carry minuscule amounts of power. As with a wired headset, you get the most benefit from a Bluetooth accessory when the phone is away from your body. Tests have measured a reduction in SAR for Bluetooth headsets up to 34 times compared to holding the phone to your ear. The exact SAR reduction depends on the accessory itself and the conditions under which it is used.