Late October 2013: a friend shared this on facebook:
This was my comment in reply:
You'd get the same sort of thermographic image after drying your hair with a hair dryer: all it's showing is that your head is a bit warmer! In the case of the mobile phone the warmth is probably mostly because you've had your hand (holding the phone) to your head preventing it from losing heat naturally: the phone itself doesn't produce much heat. As for the radiation it produces, it's the same sort of radiation you get from a candle (but at a wavelength we can't see, like the invisible infra-red warmth from a candle).
To get a risk of causing cancer we have to go to shorter wavelengths like the deep ultra-violet in sunlight that can cause skin cancer, and beyond to X-rays and gamma rays because at these wavelengths electromagnetic radiation has enough energy to break up molecules and damage cells in our bodies (which is why X-rays are used in radiotherapy to kill cancer cells).
There's quite a good explanation of the various possible effects of radiation on our bodies in Sense About Science's booklet at http://www.senseaboutscience.org/data/files/resources/8/MSofRadiation.pdf
A few years ago the International Agency for Research into Cancer did classify mobile phone radiation as possibly causing cancers but Cancer Research UK point out that although there is some evidence linking them it is too weak to draw strong conclusions from, and that "the vast majority of existing studies have not found a link between phones and cancer, and if such a link exists, it is unlikely to be a large one”.
Because people get cancers anyway, and we all do so many different things in our lives, if you do enough studies on anything you can probably find a correlation between anything and cancer in some group of people even if whatever-it-is doesn't actually cause cancer: this can be because there's some other cause (e.g. with mobile phones it might be that mobile users tend to have more stressful lives and the stress could be a factor) or it could be pure chance. I bet if you did enough studies of hair-dryer users you'd find some who have more cancers than normal!