Radon Risk in Missouri

Missouri's statewide average radon level is 3.9 pCi/L, which falls below the EPA's action level of 4 pCi/L. That's a reasonable baseline, but statewide averages can mask significant county-to-county variation. Some parts of Missouri run considerably higher than others.

Looking at the zone breakdown: 11 of Missouri's 115 counties are EPA Zone 1 (high risk), 97 are Zone 2 (moderate), and 7 are Zone 3 (low). That means 10% of the state falls into the highest risk category, counties where the EPA predicts average indoor levels above 4 pCi/L. Use the county list below to find your area and see the most specific data available.

Within Missouri, the spread is notable. Sullivan County has the highest measured average in the state at 12.9 pCi/L. Mississippi County sits at the other end with 0.8 pCi/L. 50 counties have a measured average above 4 pCi/L. Remember: these are averages. Individual homes can test significantly higher or lower than their county average depending on construction, foundation type, and ventilation.

Tipper's recommendation for Missouri residents: if you haven't tested your home, start there. A short-term test kit costs around $15 and gives you a result in 48 hours. If your home tests at or above 4 pCi/L, a professional mitigation system (typically $800–$2,000 depending on your foundation and home size) will reliably bring levels down.