Simple inverse-square-law considerations should tell you that you don't have anything to worry about.

Oh right. Should have listened harder at school.

Thanks for your answers. I was slightly concerned that I was in effect strapping two mobile phones to my head for several hours a day. And yes - not proven yet as you say. I just want to make sure I won't be the one to prove it.

I shall listen in total reasurance from now on.

Cheers

Paul