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Radon in Pennsylvania well water, by county

By the Tested Water teamLab data from the USGS and EPA Water Quality Portal, 2000 to 2023Updated November 8, 2026

Radon is widespread, over the limit in 15% or more of tested wells, in 1 of the 18 Pennsylvania counties with 10 or more tested wells. A county's share tells you how likely a problem is nearby. Only a test of your own well tells you what's in it.

Find a radon in water test See every county

How Pennsylvania compares with the rest of the country

Across Pennsylvania, about 1 in 15 tested wells had radon in water over 4,000 pCi/L, a level the EPA proposed (59 of 904). Across all tested wells in the US it's about 1 in 24. So radon in water turns up somewhat more often in Pennsylvania than in the country as a whole. Check your county below.

Why it matters: It escapes into the air when you shower or run the tap, and breathing it raises the risk of lung cancer.

Radon is a gas given off by uranium in granite and similar rock.

Radon in tested wells, county by county

Share of each county's tested wells with at least one result over 4,000 pCi/L, a level the EPA proposed. Counties need 10 or more tested wells to be listed. Widespread means 15% or more, worth checking 5 to 15%, rare under 5%.

CountyWells testedWells over the limitLevel
Chester County 71
28% 20 of 71
 Widespread
Wayne County 127
13% 16 of 127
 Worth checking
Sullivan County 21
10% 2 of 21
 Worth checking
Lancaster County 22
9% 2 of 22
 Worth checking
Northampton County 11
9% 1 of 11
 Worth checking
Union County 11
9% 1 of 11
 Worth checking
Dauphin County 36
8% 3 of 36
 Worth checking
Bucks County 17
6% 1 of 17
 Worth checking
Cumberland County 18
6% 1 of 18
 Worth checking
Pike County 95
4% 4 of 95
 Rare
Lycoming County 82
2% 2 of 82
 Rare
Bradford County 78
1% 1 of 78
 Rare
Clinton County 59
0% 0 of 59
 Rare
Potter County 48
0% 0 of 48
 Rare
Lebanon County 16
0% 0 of 16
 Rare
Berks County 14
0% 0 of 14
 Rare
Centre County 12
0% 0 of 12
 Rare
York County 11
0% 0 of 11
 Rare

39 more Pennsylvania counties have 1 to 9 tested wells for radon in water, too few to rate.

Download this table (CSV) ยท Free to reuse under CC BY 4.0

Where to get your well tested for radon in water in Pennsylvania

1

Your county health department

Pennsylvania doesn't run a statewide free testing program that we know of. Some county health departments test wells or sell kits, so call yours first.

Pennsylvania's private well page
3

A mail-in kit

Fill the bottles at your kitchen tap and mail them back. We mark the kits that include radon in water.

Compare kits

Keep reading about wells in Pennsylvania

Questions people ask about radon in water in Pennsylvania

Is there radon in water in Pennsylvania well water?

Radon is widespread, over the limit in 15% or more of tested wells, in 1 of the 18 Pennsylvania counties with 10 or more tested wells. Across Pennsylvania, about 1 in 15 tested wells had radon in water over 4,000 pCi/L, a level the EPA proposed (59 of 904). Across all tested wells in the US it's about 1 in 24. So radon in water turns up somewhat more often in Pennsylvania than in the country as a whole. Check your county below.

Where can I get my well tested for radon in water in Pennsylvania?

Use a lab certified by Pennsylvania for drinking water, or a mail-in kit that includes radon in water from a certified lab. Some county health departments test wells too, so call yours first.

See Pennsylvania's list of certified labs (a PDF list), or compare mail-in kits.

Where these numbers come from

  • Lab tests: Water Quality Portal (USGS and EPA), well samples since 2000. A well counts as over if any of its tests was over 4,000 pCi/L, a level the EPA proposed. Wells tested for studies and monitoring, not a random sample of homes.
  • Likely overstated: our own check of who tested the wells, when and where. How we check.
  • State programs and links: Department of Environmental Protection.