Just come across these YouTube videos and it would be kind of surprise that old camera glass are not only containing toxic lead, but also more harmful radioactive substance!
So, don't come near the lenses, nor use them in SLRs and view through the lens! But only just Rangefinder! ;-D
Following the discussions under each YouTube page and these are quite interesting (and useful).. (Just don't worry, I'm just kidding above. The radiation level is negligible! :->)
(http://www.youtube.com/watch?v=oL3D7FQTHXo)
(http://www.youtube.com/watch?v=1GPCIKvdRYA)
(http://www.youtube.com/watch?v=OWgYhQnRcWM)