Bluetooth uses the 2.4GHz spectrum (along with a lot of other stuff) which is non-ionising, the main side effect is heating but bluetooth transmitters have tiny

Bluetooth uses the 2.4GHz spectrum (along with a lot of other stuff) which is non-ionising, the main side effect is heating but bluetooth transmitters have tiny power output so any heating effect would be unmeasurable. Your body is constantly bombarded by radio sources both natural and artificial, honestly I wouldn't worry about it.