Is it true that these cellular pphones can cause brain tumor?

There was a lot of media attention about this kind of thing in the past, and it meant that I did not get a cell phone for much longer than I would have done if there had not been this kind of attention. I think that there is a chance that mobile phones could cause things like this, because there is some kind of radiation if you hold it to your ear the whole time. However, a lot of mobile phones now come with things like hands free kits and that means that you don't have to put your phone anywhere near your head and you can still talk to people, so there are ways in which you can reduce your risks.