Radon levels in York County, PA

What are radon levels by ZIP code in York County?

Radon levels in York County range from a median of 8.80 pCi/L in Windsor to 1.80 in York, so start with your own ZIP code rather than the county figure. The county average of 10.75 pCi/L is a useful headline and a poor guide to any particular street, because the range inside York County is wide.

No York County ZIP code matches that. Only ZIP codes with at least 300 recorded tests are listed, so a very small area may not appear.

The table is sorted and banded on the median, because that is what a normal house in the area measures. Bands are ours rather than official: below the line is a median under 4 pCi/L, elevated is 4 to 6, and high is 6 and above. The only official threshold is the EPA action level of 4 pCi/L.

Both columns are here because they disagree. Averages are dragged upward by a small number of extreme results, so New Cumberland averages 7.78 while its median is 3.20. Ten of the 34 ZIP codes below have a median under the action level and an average well above it. Read the median for what is normal, the average for how heavy the tail is, and the last column for how many households face a decision.

How much do radon levels vary inside York County?

Radon levels vary about 4.9 times inside York County. Windsor at a median of 8.80 pCi/L and York at 1.80 sit in the same county, on the same fractured limestone and shale, about 4.9 times apart. On averages the same two are 8.9 times apart. Either way the gap is the whole argument against treating a county map as an answer.

The heaviest readings sit in the rural south and west. Windsor, Felton, Dallastown, Seven Valleys and Airville all have medians at or above 7 pCi/L, and Glenville follows at 6.90. The lightest sit to the north along the Susquehanna, around York Haven, Wellsville and Dover, where medians run between 2.8 and 3.3 and half the houses test below the action level.

The genuine surprise is downtown. ZIP code 17401, the oldest and densest part of York city, averages 2.83 pCi/L with only 22.1 percent of tests at or above the action level, which makes it the lowest reading area in the county. That runs against the usual assumption that older housing means more radon, and it is a reminder that what matters is the ground and the foundation rather than the age of the building. The rest of York city reads very differently: 17404 averages 7.00 and 17403 and 17406 both sit above 11.

None of which tells you what is under your own slab. Two identical houses on one street can differ several times over, because entry depends on the cracks in your particular foundation and how your particular house is heated. The neighborhood figure tells you whether testing is worth doing, and outside 17401 the answer in every York County ZIP code is a clear yes.

How should you read York County radon data?

Read York County radon data as a guide rather than a measurement of your house: owners chose the tests, most were taken in basements over forty years, and houses that were already mitigated are not flagged. Four things about this dataset are worth knowing before you lean on it.

1. These are tests people chose to take. Not a random sample of houses. Testing clusters around property sales and around people who already suspect a problem, which can pull an area's average in either direction.
2. Most readings are basement readings. Of the York County tests recording a floor level, 82.8 percent were taken in a basement, which is the highest point of any house. Your first floor bedroom will normally read lower than the figure here.
3. Mitigated houses are not flagged. The field that would tell us whether a system was already installed is recorded as not collected for every York County row, so some of these readings are from houses that had already been fixed. That pulls averages slightly down rather than up.
4. The record spans forty years. Tests run from October 1986 to June 2026, across charcoal canisters, continuous monitors, liquid scintillation and electret detectors. Methods and practice changed over that period.

None of this makes the figures useless. It makes them what they are: a very large, imperfect, real measurement of the ground under York County, which is a great deal more than a predicted zone.

What radon level is safe?

No radon level is known to be safe, according to the EPA, which recommends fixing a house at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L. In York County 71.3 percent of recorded tests reach 2 pCi/L and 52.5 percent reach the 4 pCi/L action level.

Most of these are basement readings. A basement test in York County averages 11.79 pCi/L against 5.84 on a first floor, so the same house can land in a different band depending on where the device stood. Where to place a test is covered on the page about radon testing in York County.

Source: EPA action level guidance; shares computed from the PA DEP radon test dataset, retrieved 21 September 2026.

Is the EPA radon zone map enough for York County?

No. The EPA county map places York County in Zone 1, its highest predicted category. That is correct and it is also nearly useless on its own, because Zone 1 covers a large share of Pennsylvania and says nothing about the difference between 8.80 and 1.80 pCi/L inside one county.

Live monitor maps have the opposite problem. They show real readings from real devices, but from whichever handful of monitors happen to be nearby and switched on, which is a sample of a few rather than thousands. Several of the national pages ranking for York radon queries carry no York figure at all, only a state median.

The figures here come from the same place the state uses: certified test results reported to DEP by the laboratories and testers who ran them.

What should you do with your own radon reading?

Compare your own radon reading with the 4 pCi/L action level rather than with your ZIP code average. Four pCi/L is the number that triggers action, and it applies to your house regardless of what the neighborhood averages.

If you do not have a result yet, that is the only real next step, and a short term test kit is the cheapest way to get one. Whatever this page says about your area, the reading that matters is the one from your own basement.

If you are buying or selling in York County, an elevated reading is normally settled with a credit rather than a canceled sale, and the page on buying or selling a house with radon covers how that works.

If your result is at or above 4, the pages on how a radon mitigation system works and what mitigation costs in York County cover what happens next, and the list of certified York County contractors covers who can do it.

Common questions about radon levels in York County