As I said, I understand people's opinion on radiation may be different, but I personally would rather avoid exposure as much as possible. I do own some radioactive lenses, therefore the less I own the better. Just wanted to clarify though, on a quick search, an Am-241 smoke detector appears to give a dose to a normal home owner of 10-50 nSv in a year. A single Yashica lens, at around 1 meter, and according to camerapedia, is 762 nSv in just one hour.
Quick edit: I just realised that is probably not fair to compare different radiation sources since they may decay differently etc. and the type of emmisions may be different. But as a biologist, I think people should be a bit more aware of trying to minimise radiation sources to the minimum when possible. There is a very good video on the topic on Simon's utak channel on youtube, nevertheless I don't think we should stray away from the topic of this post too much.