Which U.S. state has the greatest concentration of radon? Utah has the greatest concentration of radon. In Utah, 1 out of every 3 homes tested have elevated radon levels. By ProMatcher Staff Updated: 08/08/2016 Next Question Source: National Safety Council Next Question Find Local Pros Free Actuaries Cost Estimates Related Questions What is the second leading cause of lung cancer? Where is radon typically found in the U.S.? How many homes have elevated radon levels? How many lung cancer deaths are related to radon? How Much Does It Cost to Get Rid of Radon?