http://www.sciencedaily.com/releases/2002/08/020823063221.htm
"news from a U.S. government sponsored study that he participated
in which shows that the 28,000 nuclear shipyard workers with the
greatest radiation doses, when compared to 32,500 shipyard workers
who had no on-the-job radiation, had significantly less cancer
and a 24 percent lower death rate from all causes."
When we lived in Germany there were Europeans who used to flock
to Radon caves for health reasons... Probably some more "lost knowledge"
gained through years and years of empirical data, just not written
down...