Is Union County, PA a radon risk area?

EPA places Union 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. Union County sits at the 88th percentile nationally for radon potential — above 88 of every 100 rated counties.

Union County by the numbers

About 42,159 people live in Union County, Pennsylvania, spread over 315.957 square miles. Averaged across its land area, Union County runs about 133 people per square mile. Rank 363 by population within its EPA zone puts Union County at the 66th percentile among zone peers. EPA's geology-based Region 3 groups Union County with 244 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Union 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. Being in Zone 1 raises the odds Union 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.

Next steps for a home in Union County

Nothing about Union 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 Pennsylvania's state radon program

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

The methodology guide shows exactly which EPA and Census sources feed Union County's numbers. Whatever zone Union County carries, the zone explainer covers what it does and doesn't tell you about any one house.