Missouri has significant radon risk across much of the state, with an estimated 35–40% of Missouri homes testing above the EPA action level of 4.0 pCi/L. Missouri’s geology — including limestone and dolomite formations in the Ozark plateau, granite in the St. Francois Mountains, and glacial till in northern Missouri — creates varied but often elevated radon potential. The Missouri Department of Health and Senior Services administers the state radon program.
EPA Radon Zone Designation
Missouri counties range from Zone 1 in portions of northern and central Missouri to Zone 2 in the Ozark plateau and Zone 2-3 in the Mississippi lowlands of southeastern Missouri (“Bootheel”). The highest-radon areas include northern Missouri glaciated counties (Adair, Linn, Macon, Shelby, Knox, Lewis, Marion, Ralls, Pike, and Monroe counties), the St. Francois Mountains counties (St. Francois, Iron, Reynolds, Shannon), and the St. Louis metropolitan area (St. Louis County, St. Charles County).
Radon Contractor Requirements in Missouri
Missouri requires radon contractors to hold NRPP or NRSB national certification. Missouri’s radon program is administered through the Missouri Department of Health and Senior Services. Missouri does not have a separate state radon contractor licensing statute beyond national certification requirements. Verify contractor credentials at nrpp.info or nrsb.org before hiring.
Radon Disclosure in Missouri
Missouri’s Seller’s Disclosure Statement requires sellers to disclose known material defects. Missouri does not have a radon-specific disclosure statute, but known elevated radon conditions are material information that sellers should disclose under the general duty. Radon testing is recommended during the inspection period for all Missouri real estate transactions, particularly in northern and central Missouri and the St. Louis metro area.
Frequently Asked Questions
Is the St. Louis area high in radon?
St. Louis County and St. Charles County are in Zone 1 or Zone 2 with meaningful radon risk. Radon testing is recommended for all St. Louis metro homes. Older homes in the area with block foundations or basements should be prioritized.
Does Missouri require radon contractor certification?
NRPP or NRSB national certification is required. No separate Missouri licensing statute. Verify credentials at nrpp.info or nrsb.org before hiring.
What parts of Missouri have the highest radon?
Northern Missouri glaciated counties and the St. Francois Mountain counties of southeastern Missouri have the highest potential. The Kansas City and St. Louis metropolitan areas have significant radon risk. The Bootheel counties of extreme southeastern Missouri have generally lower levels.
Kansas City Metro Radon Risk
The Kansas City metropolitan area — which spans both Missouri and Kansas — has significant radon risk on the Missouri side. Jackson County (Kansas City proper) and the surrounding Missouri suburbs including Clay, Platte, Cass, and Ray counties show Zone 1 to Zone 2 radon levels. The Missouri side of the metro has glaciated geology in the north (Clay, Platte, Ray) transitioning to limestone and shale geology southward. Kansas City’s extensive older housing stock — particularly the bungalow and ranch-style homes with basements built throughout the post-WWII era — represents a significant untested population.
St. Louis Metro Radon
St. Louis County and St. Charles County on the Missouri side of the St. Louis metropolitan area are Zone 1 to Zone 2. The St. Francis Mountains geology (St. Francois County) — ancient Precambrian granite exposed at the surface — creates particularly high radon potential in Missouri’s Lead Belt region southeast of St. Louis. Jefferson County (south St. Louis suburbs) shows elevated readings. The city of St. Louis (independent city, Zone 2) has lower average levels than suburban St. Louis County but still warrants testing in older housing.
Missouri Testing Resources
The Missouri Department of Health and Senior Services (MDHSS) Radon Program provides certified contractor lists, county-level radon data from the Missouri Residential Radon Survey, and educational resources. Missouri participates in EPA’s SIRG program. The Missouri Geological Survey has published radon potential maps that provide more granular geological risk assessment than EPA’s county-level zone designations. Contact MDHSS for the current certified contractor list and test kit availability.
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