For more information, please visit these credible sites

www.radon.com
www.epa.gov
www.health.state.mn.us
http://www.aarst.org
http://www.neha.org
www.csbsju.edu/MNradon/default.shtm
http://state-radon.info
http://mn-radon.info/MN_countries.html

These Downloads might be helpful in your research about Radon:

Consumer’s Guide to Radon Reduction
EPA Citizen’s Guide to Radon
EPA Home Buyer’s and Seller’s Guide to Radon