As you may know, cell phones emit significant radiation (source: http://reviews.cnet.com/4520-6602_7-5020355-1.html). Fortunately for us consumers and the general public, the …government has regulations of somewhere around 1.6 SAR, which is a measure of radiation..
I was watching a news article from CNN, which you should be able to find on their website. Wearing a bluetooth headset emits significantly less radiation, about 100x less. However, there is still radiation, and it's still bad because you have it right next to your head, perhaps for long periods of time..
If you still plan to use your bluetooth, which I don't suggest, you should switch it from your left ear and your right ear so that the radiation is evenly distributed. I personally have an iPhone 3G, which has smart headphones. Headphones emit no radiation, though some people think that radiation runs from your phone to up the cord. You can buy special cords for that though, which contain an element that eats up the radiation..
Hope this answers your question!.