[FlyingAvatar]

I don't really buy the comparison. If you're really unlucky, you can get cancer from a "safe dose" of radiation.

Low exposures of both things are statistically less likely to hurt you than large doses. We pick a line to call "safe", but completely safety in either case is not guaranteed.

[nkmnz]

There is a natural level of radioactivity which the body is used to compensate. Small additional doses of radioactivity can therefor be neglected. This is not true for stuff like abestos.

[jojobas]

There is even the "hormesis hypothesis" which posits that low levels above background might be beneficial for human health.

[userbinator]

There are actually naturally occurring asbestos fibers in the air, caused by weathering of asbestos-containing rocks.