Radon webpage Environmental Protection Agency
https://www.epa.gov/radon/health-risk-radon#main-content
https://www.epa.gov/radon/health-risk-radon#main-content
https://www.cdc.gov/nceh/radiation/brochure/profile_radon.htm
https://www.cdc.gov/healthywater/drinking/private/wells/disease/radon.html
https://sosradon.org/water-testing
https://archive.epa.gov/water/archive/web/html/basicinformation-2.html