Interesting. Now I have a question about that video, and I think I'm more likely to get a good answer from someone here than in the comments there, so here goes:

Tom says that because that's the only radon cave that can turn the flow of radon on and off at will, it's the only place where you could (in theory) run a double-blind experiment on radon exposure therapy.

My question is: would it not be just as possible to do that in a laboratory setting? Surely there are already lab facilities in the world that are set up for double blind "exposure" experiments of that sort, with easy control of dosages, flow rates, etc. Is the problem that radon gas too expensive to harvest or store safely? Why is that cave the only feasible option?

EDIT: It now occurs to me that the answer could be "because the half life of radon is to short to transport it, so you would basically have to generate it in the lab by getting an enormous amount of uranium in one place and letting it decay and find some way of filtering the byproducts to isolate the radon in a way that putting it under a huge layer of bedrock does naturally." Sounds plausible to me, but does anyone know if that's the case?