Since cellphone radiation is non ionising it cannot be measured in microsieverts (and there's no evidence that non-ionising radiation can harm you) but for comparison - eating a banana will give you about 0.1 microsieverts of radiation.

I actually looked up all the numbers the other day (yes, this is the kind of thing I do for fun)... before you can get a dangerous dose of ionising radiation (which is the stuff you get from nuclear weapons and such) by eating bananas you would rupture your gutt 222-thousand times over. You need to eat about half a million bananas to get what US occupational-safety standards consider a dangerous annual dose. And you have to do it in one sitting (because the radioactive potassium-40 is is exreted) - and the average stomach can only hold about 5l of food before bursting (22 and half average bananas worth).

And phones have less radiation than that - and not even the dangerous ionising kind.