Is McLean County, ND a radon risk area?

McLean County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. That puts McLean County in the 75th percentile nationally for radon potential — higher than 75% of the counties EPA has rated.

How McLean County compares

About 9,845 people live in McLean County, North Dakota, spread over 2,110.272 square miles. Averaged across its land area, McLean County runs about 5 people per square mile. Rank 768 by population within its EPA zone puts McLean County at the 28th percentile among zone peers. McLean County falls in EPA Radon Region 8, one of 291 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in McLean County

McLean County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. A Zone 1 rating means testing is worth doing sooner rather than later, but it is still county-wide average, not a reading for any single house — some homes in McLean County will test well under the action level, and EPA's guidance is to test regardless of zone.

If McLean County tests above the action level

Nothing about McLean County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find North Dakota's state radon program

McLean County's test kit answers today; a Airthings radon monitor keeps answering for McLean County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. Whatever zone McLean County carries, the zone explainer covers what it does and doesn't tell you about any one house.