What EPA's radon map says about Gratiot County

EPA places Gratiot County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts Gratiot County in the 20th percentile nationally for radon potential — higher than 20% of the counties EPA has rated.

Where Gratiot County sits nationally

About 41,372 people live in Gratiot County, Michigan, spread over 568.382 square miles. That works out to roughly 73 people per square mile. Among counties sharing Gratiot County's EPA zone, it outranks 62% of them by population. Gratiot County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Gratiot County's Zone 3 prediction undercuts the roughly 1.3 pCi/L most US homes average, nowhere near EPA's 4 pCi/L threshold for recommending mitigation. Don't read Zone 3 as a pass for Gratiot County — EPA's guidance to test every home makes no exception for counties predicted low.

If Gratiot County tests above the action level

Mitigation cost doesn't depend on Gratiot County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Michigan's state radon program

Gratiot County's test kit answers today; a Airthings radon monitor keeps answering for Gratiot County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 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. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.