Radon and home risks by county

Radon in Pennsylvania

49 of Pennsylvania's 67 counties are in EPA's highest radon zone, home to about 77% of the state's residents. Radon zones describe an area's potential; EPA recommends testing every home regardless of zone.

Zone 1 counties
49
high radon potential
Zone 2 counties
16
moderate potential
Zone 3 counties
1
low potential
Counties with water violations
65
since 2016; 31 with unresolved ones

Tap water reports for Pennsylvania cities

Philadelphia1,573,916 residents · PFAS, lead, violations

Find your county by ZIP

Zone 1: high potential (49 counties)

CountyResidentsWater systemsHealth violations since 2016Unresolved
Adams County107,91435131
Allegheny County1,231,81439772
Armstrong County63,67922640
Beaver County165,54030635
Bedford County47,64325500
Berks County439,11777690
Blair County120,26925121
Bradford County59,6992270
Bucks County650,13170742
Butler County199,34140412
Cameron County4,348230
Carbon County65,74329625
Centre County159,80543290
Chester County560,745671080
Clarion County36,85514202
Clearfield County78,13217250
Clinton County37,86516270
Columbia County66,01218173
Cumberland County275,51627271
Dauphin County293,02928600
Delaware County584,8825160
Franklin County159,28530280
Fulton County14,452320
Huntingdon County43,3592190
Indiana County82,95317910
Juniata County23,39513160
Lackawanna County216,85933631
Lancaster County563,29398940
Lebanon County145,31930160
Lehigh County385,65542150
Luzerne County331,37974415
Lycoming County113,23632784
Mifflin County45,935630
Monroe County166,523681573
Montgomery County879,19038220
Montour County18,115220
Northampton County322,98946513
Northumberland County90,0271130
Perry County46,81625281
Schuylkill County144,52340260
Snyder County39,62716190
Sullivan County5,927480
Susquehanna County38,10022212
Tioga County40,69822401
Union County42,159631
Venango County49,47625301
Westmoreland County350,93517170
Wyoming County25,77130496
York County471,24045500

Zone 2: moderate potential (16 counties)

CountyResidentsWater systemsHealth violations since 2016Unresolved
Cambria County130,108361441
Crawford County82,08943401
Elk County30,1248240
Erie County267,75041572
Fayette County123,94119619
Greene County33,9603180
Jefferson County43,36711230
Lawrence County84,2331890
McKean County39,47817521
Mercer County108,14033468
Pike County62,37642691
Potter County15,9939160
Somerset County72,13434410
Warren County37,37315391
Washington County210,4349792
Wayne County51,419408910

Zone 3: low potential (1 county)

CountyResidentsWater systemsHealth violations since 2016Unresolved
Philadelphia County1,573,916100

EPA's radon map has no zone for Forest County.

How to read this table

Water systems counts community systems that list the county in their service area; one system can serve several counties. Health violations are breaches of a legal limit or treatment rule recorded by EPA since January 2016, not paperwork lapses. A violation stays unresolved until the state records it as fixed.

Other states

Sources: EPA Map of Radon Zones, EPA ECHO Safe Drinking Water Act data (2026Q3, published October 2026), US Census Bureau Vintage 2024 estimates. See the methodology.