Is Delta County, MI a radon risk area?

EPA places Delta 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. Nationally that's the 19th percentile for radon potential — Delta County outranks 19% of every county EPA has rated.

Delta County by the numbers

About 36,687 people live in Delta County, Michigan, spread over 1,171.094 square miles. Population density there runs about 31 people per square mile. Rank 430 by population within its EPA zone puts Delta County at the 58th percentile among zone peers. Delta County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Delta County

Delta 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. A Zone 3 rating means Delta County's county-wide average is predicted low, but EPA is explicit that a meaningful share of homes in low-potential zones still test above the action level — a low zone is not a reason to skip testing.

Testing and mitigation in Delta County

Nothing about Delta 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 Michigan's state radon program

Delta County's test kit answers today; a Airthings radon monitor keeps answering for Delta 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

The methodology guide shows exactly which EPA and Census sources feed Delta County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.