Iowa has the highest average indoor radon levels of any U.S. state. The Iowa Department of Public Health estimates that approximately 71% of Iowa homes test above the EPA action level of 4.0 pCi/L, and Iowa’s statewide average indoor radon level of roughly 8.5 pCi/L is the highest in the nation. Every county in Iowa is designated EPA Radon Zone 1.
EPA Radon Zone Designation
Iowa is predominantly EPA Radon Zone 1. All 99 Iowa counties are Zone 1 — the highest radon potential designation — reflecting the state’s geology of uranium-rich glacial deposits, black shale, and granite-derived soils across the entire state.
Radon Contractor Licensing in Iowa
Iowa requires radon contractors to hold certification from NRPP or NRSB to legally conduct radon measurement and mitigation work. Iowa’s radon program enforces contractor certification requirements and maintains a list of certified professionals. Performing radon mitigation without certification in Iowa may violate state public health regulations. Verify any contractor’s current certification status through the Iowa Department of Public Health radon program website before hiring.
Radon Disclosure Requirements in Iowa
Iowa requires sellers of real property to disclose known radon test results. The Iowa disclosure requirement applies to residential real estate transactions and directs sellers to disclose whether the property has been tested for radon and the results of any such test. Iowa also requires that buyers be provided information about radon and its health risks. Given that 71% of Iowa homes exceed the EPA action level, radon contingencies and testing are standard practice in Iowa real estate transactions.
Radon-Resistant New Construction (RRNC) in Iowa
Iowa mandates radon-resistant new construction features for new residential construction. As a Zone 1 state with the nation’s highest average radon levels, Iowa’s building code requirements include RRNC provisions for new homes. Builders constructing new homes in Iowa should confirm current RRNC requirements with their local building department, as specific requirements have evolved and local adoption varies. EPA strongly recommends full RRNC per AARST-ANSI RRNC-2022 for all new Iowa construction.
Highest-Radon Counties and Areas in Iowa
All 99 Iowa counties are Zone 1. The counties with historically highest average radon measurements include Linn, Polk, Johnson, Scott, and Black Hawk — the state’s most populous counties — as well as the geological formation areas in north-central and northeastern Iowa where glacial deposits are thickest. Iowa State University Extension and IDPH have documented elevated radon across the entire state, with rural counties in northern Iowa showing some of the highest averages.
Testing Resources for Iowa Residents
The Iowa Department of Public Health administers the state radon program and provides resources for homeowners including lists of certified contractors, low-cost or free test kit programs (availability varies by year and funding), and technical guidance on radon mitigation. Contact the state radon program directly for the most current contractor list, any available test kit distribution programs, and jurisdiction-specific requirements that may have changed since this page was last updated.
Frequently Asked Questions
Is Iowa a high-radon state?
Iowa is the highest-radon state in the U.S. by average indoor concentration. Approximately 71% of Iowa homes test above the EPA action level of 4.0 pCi/L, and Iowa’s statewide average of roughly 8.5 pCi/L exceeds all other states. Testing is essential for every Iowa home.
Are radon contractors required to be licensed in Iowa?
Yes. Iowa requires radon measurement and mitigation contractors to hold current NRPP or NRSB certification. Verify contractor credentials through the Iowa Department of Public Health radon program before hiring.
Does Iowa require radon disclosure when selling a home?
Yes. Iowa sellers must disclose known radon test results to buyers. Given that the majority of Iowa homes exceed the EPA action level, radon testing and disclosure are standard components of Iowa real estate transactions.
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