In the 60s and 70s, there were quite a few lenses made which had one or more lens elements containing radioactive glass. In some cases it might have been due to Thorium-contaminated Lanthanum glass, in a few cases it was deliberate usage of Thorium glass.

Some of those lenses have attained "legendary" status, as the optical performance was miles ahead of anything else available at the time. So after 40 years those lenses are still legendary - and still radioactive.

SInce then the use of Lanthanum glasses has become a lot more common, but the refining technique has progressed to the point where the lenses are no longer radioactive. There is good reason to believe that most high-performance lenses made today contain one or more Lanthanum-glass elements, but they are not emphasised to the same degree due to the unfortunate association with radioactivity in the minds of many photographers (and lens reviewers).