It is a matter of concern for some people that the carrier waves used by Bluetooth´s transmitters use the same frequency range as microwave Owens (Bluetooth uses 2.402 GHz to 2.480 GHz). What does it feel like to get in the path of such waves?
Actually, the transmitting power is far too weak to be noticeable for humans. Moreover, the radiation is not concentrated in a beam, but dispersed more or less in all directions. When using a wireless phone or a Bluetooth device, some of the emitted RF energy is absorbed by the body. The penetration depth is about 1.5 cm at 2450 MHz (about 2.5 cm at 900 MHz), which means that the absorption is very superficial. The main absorption mechanism is field induced rotation of polar molecules (for example H2O), which generates heat through molecular "friction".
Heating by means of radio frequencies is possible over a broad frequency range. This is taken advantage of in microwave ovens at 2450 MHz using very high power levels (up to 1,000,000 times the power used by Bluetooth devices). However, 2450 MHz is not a resonance frequency of water. But does exposure to Bluetooth RF emission heat the human body? No it does not. The output power of a Bluetooth-enabled device is far too low to cause any detectable temperature increase. Again, in comparison, the maximum increase from handheld cellular phones is less than 0.1°C.
There is, however, another side to this; some people are demonstrably over-sensitive to electromagnetic radiations. Long exposure to strong fields makes some individuals so sensitive, after a few years that they can no longer be near such fields without considerable discomfort. Bluetooth fits into a general development pattern where antennas for GSM-transmission and other sources of electromagnetic radiations become more and more prevalent in our cities. The future will show whether this is a healthy development.
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