A Note on Radiation Hormesis
People who live in the Rocky Mountain area (“…where the scenery's attractive and the air is radioactive…”—Tom Lehrer) tend to have a low lung cancer mortality rate. That can mean only one thing: Radioactivity makes people stop smoking.
Seriously, when data is about barely-detectable phenomena, confounding factors mean we can't trust the conclusions that might be derived. Maybe low levels of radioactivity are dangerous and maybe they're beneficial. We have no good basis for either conclusion.
In other words, we also have no good reason to believe low levels of radioactivity are dangerous.