Nobody knows for sure. Personally, I would rather not take the risk. I keep a mobile for essential use only - and I don't condsider walking down the street chatting to friends, as many people seem to do, essential use. I prefer to make most calls using my 'phone at home.
if you ring one mobile phone with another mobile phone and place them ten inches appart and put a raw agg in the middle - the egg will be hard boiled in 20 minutes.... enough said.