Is Lincoln County, SD a radon risk area?

EPA places Lincoln County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Nationally, Lincoln County ranks higher in radon potential than 93% of rated counties (the 93rd percentile).

Lincoln County by the numbers

About 75,244 people live in Lincoln County, South Dakota, spread over 577.293 square miles. Population density there runs about 130 people per square mile. Rank 235 by population within its EPA zone puts Lincoln County at the 78th percentile among zone peers. Lincoln County falls in EPA Radon Region 8, one of 291 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Lincoln County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Being in Zone 1 raises the odds Lincoln County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

If Lincoln County tests above the action level

Nothing about Lincoln 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 South Dakota's state radon program

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

Lincoln County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.