Is radon high in Bethlehem, Pennsylvania?

Moderate. Averaging the model's ZIP-code predictions across Bethlehem (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 2.4 pCi/L - about 1.3× the US average of 1.8 and close to the Pennsylvania average of 2.3. That is in the 2-4 pCi/L range where the EPA says to consider fixing. Bethlehem ranks 4 of 12 Pennsylvania cities on this site.

What do actual radon tests show around Bethlehem?

Pennsylvania Department of Environmental Protection publishes results for Northampton County (not the city alone) covering 1988-2026 (52,343 tests): an average of 8.3 pCi/L, a median of 3.6, 46.7% of results at or above the 4 pCi/L action level. These are voluntary home tests, so they skew toward basements and toward homes where radon was suspected; the model's predicted basement average for Bethlehem is 2.4 pCi/L.

Which Bethlehem ZIP codes have the highest radon?

Predictions for the 3 modeled ZIP codes in Bethlehem range from 2.1 to 2.8 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 100% at or above 2. The city is fairly uniform, so the city-wide number is a reasonable guide for any neighborhood.

Should I test for radon in Bethlehem?

Yes, soon. With a predicted basement average of 2.4 pCi/L, a meaningful share of Bethlehem homes will test above the 4 pCi/L action level. Start with a short-term kit; if it reads 2 or higher, confirm with a long-term test or a continuous monitor before paying for mitigation.

What does EPA Radon Zone 1 mean for Bethlehem?

Bethlehem sits mainly in Northampton County, which the EPA classifies as Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and covers whole counties. The newer model's city average of 2.4 pCi/L does not line up with Zone 1, which is common - the EPA itself says high-radon homes exist in every zone. Neither replaces a test of your own home.

Radon levels in Bethlehem, Pennsylvania

ModerateEPA Zone 1

Predicted long-term basement average of 2.4 pCi/L (model estimate) across the 3 modeled ZIP codes in Bethlehem - about 1.3× the US average of 1.8, close to the Pennsylvania average of 2.3. Ranked #4 of 12 Pennsylvania cities on this site. Most of the city lies in Northampton County (its ZIPs also reach into 1 other county).

Test Bethlehem, PA - the EPA says "consider fixing" in this range

The predicted basement average here is 2.4 pCi/L, in the 2-4 pCi/L band where the EPA recommends considering mitigation. Plenty of individual homes in a moderate area test above 4. Start with a short-term test; if it comes back at 2 or higher, follow up with a long-term test or a continuous monitor.

Get a short-term test kit →Or track it with a continuous monitor

Already tested at 4 pCi/L or higher? Find a certified mitigation professional (EPA). A mitigation system typically runs $800-$2,500 installed.

We may earn a commission from Amazon at no extra cost to you.

Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. Measured state test results are shown separately below, labeled with their source and years. How the numbers work.

2.4 ± 0.09

pCi/L predicted basement mean (model SD)

1.8 ± 0.07

pCi/L predicted upstairs (above-ground) mean

2.1-2.8

range of ZIP-level basement predictions in the city

of Bethlehem ZIPs predicted ≥ 4 pCi/L (100% ≥ 2)

Measured radon tests in Northampton County (Pennsylvania Department of Environmental Protection, 1988-2026)

Actual results from home radon tests reported to the state, separate from the model estimate above. Coverage: 1988-2026.

Measured mean: 8.3 pCi/L
Measured median: 3.6 pCi/L
Results ≥ 4 pCi/L: 46.7%
Results ≥ 2 pCi/L: 68.4%
Basement tests, mean: 8.9 pCi/L
Sample: 52,343 tests

Figure	Model (predicted)	State tests (measured)
Mean, pCi/L	2.6 basement	8.3 (8.9 basement)
Share ≥ 4 pCi/L	not a model output	46.7%

The measured mean runs 5.7 pCi/L above the model because state test data is voluntary and skews toward basements, winter, and homeowners who already suspected a problem, while the model estimates the long-term average across all homes.

Source: Radon Test Results September 1986 - Current Annual County Environmental Protection, Pennsylvania Department of Environmental Protection, Bureau of Radiation Protection. Public Domain (as stated on data.pa.gov). Method and download.

What this means for Bethlehem

The typical Bethlehem home is predicted in the 2-4 pCi/L band. The EPA's guidance for this range is to consider fixing, because there is no known safe level and a meaningful minority of homes in a moderate area will test above 4.

The city figure is not a separate estimate: it is the mean of the model's ZIP-code predictions, weighted by the share of the city's land in each ZIP (Census 2020 ZCTA-to-place relationship file). Note that the EPA classifies Northampton County as Zone 1 while the newer model predicts 2.4 pCi/L for Bethlehem; where they disagree, we grade on the model but show both.

Comparable Pennsylvania cities: Reading (2.3), Allentown (2.3), Harrisburg (2.6), Lancaster (2.8).

ZIP codes in Bethlehem

ZIPs that overlap the city, largest share of its land first. Predicted basement and upstairs means are model estimates; ZIPs the model does not cover show a dash.

ZIP	Share of city	Basement	Upstairs	Grade
18015	37%	2.1 ± 0.11	1.6	Moderate
18017	36%	2.8 ± 0.08	2.3	Moderate
18018	27%	2.2 ± 0.08	1.5	Moderate

Testing help in Pennsylvania

Pennsylvania's radon program page is at www.pa.gov; it lists testing and certified-mitigator guidance. EPA state radon contacts page. If a test comes back at 4 pCi/L or higher, mitigation typically costs $800-$2,500 installed; use EPA find-a-professional and read the mitigation guide.

Bethlehem radon questions

Is radon high in Bethlehem, Pennsylvania?: Moderate. Averaging the model's ZIP-code predictions across Bethlehem (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 2.4 pCi/L - about 1.3× the US average of 1.8 and close to the Pennsylvania average of 2.3. That is in the 2-4 pCi/L range where the EPA says to consider fixing. Bethlehem ranks 4 of 12 Pennsylvania cities on this site.
What do actual radon tests show around Bethlehem?: Pennsylvania Department of Environmental Protection publishes results for Northampton County (not the city alone) covering 1988-2026 (52,343 tests): an average of 8.3 pCi/L, a median of 3.6, 46.7% of results at or above the 4 pCi/L action level. These are voluntary home tests, so they skew toward basements and toward homes where radon was suspected; the model's predicted basement average for Bethlehem is 2.4 pCi/L.
Which Bethlehem ZIP codes have the highest radon?: Predictions for the 3 modeled ZIP codes in Bethlehem range from 2.1 to 2.8 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 100% at or above 2. The city is fairly uniform, so the city-wide number is a reasonable guide for any neighborhood.
Should I test for radon in Bethlehem?: Yes, soon. With a predicted basement average of 2.4 pCi/L, a meaningful share of Bethlehem homes will test above the 4 pCi/L action level. Start with a short-term kit; if it reads 2 or higher, confirm with a long-term test or a continuous monitor before paying for mitigation.
What does EPA Radon Zone 1 mean for Bethlehem?: Bethlehem sits mainly in Northampton County, which the EPA classifies as Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and covers whole counties. The newer model's city average of 2.4 pCi/L does not line up with Zone 1, which is common - the EPA itself says high-radon homes exist in every zone. Neither replaces a test of your own home.

← All Pennsylvania counties and cities · Northampton County · How to test · Methodology