For what its worth... There have been several questions about older lenses with glass containing radioactive constituents (e.g., thorium and lanthanum) used to improve index of refraction properties. The concern promtped me to put a quest ion to the Health Physics Society's "Ask an Expert" forum. Their response is gi ven in:
http://www.hps.org/publicinformation/ate/q1356.html.
Hope this helps others understand the issues and risks.
Dave Erb
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