The radiation level about three feet from the these lenes is barely above the ambient, background radiation level.
Thorium in finder glass surfaces (especially eye pieces) is another story. Those levels are significant (similar to dental X-Rays or numerous trans-continental air plane trips).
Thorium-232 emits primarily alpha radiation. Alpha particles barely make it through scotch tape, let alone a lens cap. Measure the radiation level from an alpha emitter with and without scotch tape over the source was one of the first experiments we did back in 1968 during training at Oak Ridge Associated Universities. The point was to show alpha particles are easily absorbed by the first material they hit.
But many people do not care about scientific evidence. They hear the word radioactive and after that it's all over.
So I underscore X-Ray's point with two simple questions.
Has anyone ever heard of photographic film being damaged when stored in a camera fitted with lens containing thorium glass?
If the film is not exposed to significant amounts of radioactivity, how would a photographer be exposed to significant amounts of radioactivity?
PS Thanks for sharing your good news X-Ray. A close friend is in a serious caner battle right now, so it's wonderful to learn of a positive result.