Nearly everything you find in nature has such low levels of radioactivity that handling them isn't dangerous.
It's only when you start refining and enriching natural things that they become really risky. Unfortunately thats what Curie did.
It's only when you start refining and enriching natural things that they become really risky. Unfortunately thats what Curie did.
It’s a big factor, but not only. You don’t need to refine or enrich anything to have radon poisoning, for example.
Tunnels and caves could still be problematic though there’s a lot of gasses that can cause problems in such environments.