Coal plants release vastly more radioactive material than a nuclear power plant is even permitted to release.
That says less about coal than about the government regulations on atomic energy, though.
As for radiation - it's everywhere. Natural gas from your stove contains radioactive bits, and even the human body on average contains 7000 Bq worth, about three times that of a kilogram of coal ash. A becquerel is one atomic decay per second.
Check out
http://www.uic.com.au/ral.htm