I just checked the EPA website, and there are more questions than answers. Rathr frightening to think that some granite CC, depending on their origin, could be emitting radon, linked to breast cancer.
Do a search and you will find this discussed to pieces.
Here is a link that might be useful: radon threads
Here we go - another Corian salesman :-)
thanks, all. It seemed silly to me, like junk science, but I've read the other links and feel able to answer questions on this topic.