[ekianjo]

You'll have to explain me why it's OK to live in Colorado then where the natural levels of radioactivity are about 6 times higher than in other places in the country.

There's very clearly a threshold effect, just like in many natural phenomenons. Political nonsense is what is causing confusion, not the scientific basis. And most of the "science" trying to prove otherwise is based on too few numbers to be statistically significant. (the cases of reported leukemias, for example, is very often misleading when you look at the ACTUAL numbers and not just the percentages.)

If you use "no-threshold" for planning purpose then you can't technically live on Earth anywhere, since there's natural radioactivity all around us and cosmic rays as well through the atmosphere.

The regulatory limits for radiations are based on No Science whatsoever. Currently, at least. We know radiations kill with certainty at very high levels, there is no debate about that, but at low levels it's just a political issue more than anything else.