York County Radon Levels

Updated September 2026

Here is what is actually published, publicly, about radon in York County, Pennsylvania -- with the source for every number. We also say plainly where the data stops, rather than filling the gap with an estimate presented as fact.

York County's EPA radon zone

The U.S. EPA rates York County as Radon Zone 1, its highest radon-potential classification, where the predicted average indoor screening level is above 4 picocuries per liter (pCi/L) -- the level at which the EPA recommends fixing a home. This comes from the EPA's county-by-county radon zone map, a federal planning tool. The EPA's own documentation notes the map was developed in 1993 and "should not be used to determine if a home in a given zone should be tested" -- elevated levels have been found in every zone, so Zone 1 status is a reason to test your specific home, not a substitute for testing it.

Pennsylvania's statewide numbers

The PA Department of Environmental Protection states that approximately 40% of homes tested in Pennsylvania have radon levels above the EPA's 4 pCi/L action guideline -- one of the more serious statewide radon pictures in the country. That figure is statewide, not broken out by county. DEP's own guidance: test in the basement or lowest lived-in level, preferably during the heating season when the house is sealed up tightest, and if a result comes back at or above 4 pCi/L, do a second test to confirm before moving to mitigation.

What DEP does not publish

DEP's only location-specific radon lookup is a tool called RadonZip, which returns results for one ZIP code at a time when you search it directly -- it is not a downloadable dataset, and DEP does not publish a York County average, a municipality breakdown, or a bulk ZIP-code table anywhere on its site. If you have tested your own home, or your ZIP code's RadonZip result, that is real, specific data about your address -- a countywide "average" assembled from a handful of ZIP codes and presented as representative of the whole county is not something DEP publishes, and should be read skeptically wherever you see it.

The geology worth knowing about

York County sits on a mix of geology, and the most specific, sourced finding relevant to radon comes from a USGS study of Pennsylvania groundwater: the Peters Creek Schist, a geologic formation running through southern York, Lancaster, and Chester counties, was found to have the highest potential radon exposure from both groundwater and indoor air of any unit studied -- and that same area has the highest concentration of private well users in the state, which matters because radon can enter a home through well water as well as through soil gas. If you are in southern York County on a private well, that combination is worth knowing about specifically.

What this means for testing

None of the above substitutes for testing your own home. A Zone 1 rating and a 40% statewide exceedance figure describe the broad picture; only a test of your specific address tells you your specific number. If you have not tested, DEP's guidance -- basement or lowest level, heating season, and a $20 to $30 kit from most hardware stores -- is the place to start.