From today's paper in Rochester:

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"For many years, Kodak was a global leader in cameras as well as film. And not a few of its cameras came with lenses that made Geiger counters chatter.
As much as 30 percent of these lenses consisted of thorium, a naturally occurring radioactive metal. Added to glass, it improves the ability of a lens to refract light, or change its direction, so that it can be focused.
Other companies used thoriated glass in lenses, but the process was developed by a Kodak consultant, George W. Morey, and first patented by the company in the United States in 1936. Kodak later developed a thorium lens coating to achieve the same effect.
The use of thoriated glass ended in the 1980s."