Data / Rankings / Median Air Quality Index (US EPA) / Counties in Pennsylvania

Counties in Pennsylvania by median Air Quality Index (US EPA)

Lancaster County had the highest median Air Quality Index (US EPA) of 38 counties in 2023, at 58. Wyoming County had the lowest, at 27. The median was 44. Source: the U.S. Environmental Protection Agency.

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Highest58Lancaster County
Lowest27Wyoming County
Median4438 counties

Map of counties, 2023

Adams County: 50 indexAllegheny County: 56 indexArmstrong County: 44 indexBeaver County: 52 indexBerks County: 48 indexBlair County: 43 indexBradford County: 40 indexBucks County: 39 indexCambria County: 46 indexCentre County: 45 indexChester County: 45 indexCumberland County: 44 indexDauphin County: 52 indexDelaware County: 50 indexElk County: 35 indexErie County: 42 indexFayette County: 44 indexFranklin County: 39 indexGreene County: 44 indexIndiana County: 41 indexLackawanna County: 44 indexLancaster County: 58 indexLawrence County: 34 indexLebanon County: 47 indexLehigh County: 43 indexLycoming County: 38 indexMercer County: 44 indexMonroe County: 34 indexMontgomery County: 44 indexNorthampton County: 46 indexPhiladelphia County: 58 indexSomerset County: 35 indexSusquehanna County: 28 indexTioga County: 41 indexWashington County: 51 indexWestmoreland County: 42 indexWyoming County: 27 indexYork County: 48 index
  • Under 38
  • 38 to 42
  • 42 to 44
  • 44 to 46
  • 46 to 50
  • 50 and over
  • No data
index, 2023. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2023

Lancaster County: 58 indexLancaster County58Philadelphia County: 58 indexPhiladelphia County58Allegheny County: 56 indexAllegheny County56Beaver County: 52 indexBeaver County52Dauphin County: 52 indexDauphin County52Washington County: 51 indexWashington County51Adams County: 50 indexAdams County50Delaware County: 50 indexDelaware County50Berks County: 48 indexBerks County48York County: 48 indexYork County48Lebanon County: 47 indexLebanon County47Cambria County: 46 indexCambria County46Northampton County: 46 indexNorthampton County46Centre County: 45 indexCentre County45Chester County: 45 indexChester County45Armstrong County: 44 indexArmstrong County44Cumberland County: 44 indexCumberland County44Fayette County: 44 indexFayette County44Greene County: 44 indexGreene County44Lackawanna County: 44 indexLackawanna County44Mercer County: 44 indexMercer County44Montgomery County: 44 indexMontgomery County44Blair County: 43 indexBlair County43Lehigh County: 43 indexLehigh County43Erie County: 42 indexErie County42Westmoreland County: 42 indexWestmoreland County42Indiana County: 41 indexIndiana County41Tioga County: 41 indexTioga County41Bradford County: 40 indexBradford County40Bucks County: 39 indexBucks County39Franklin County: 39 indexFranklin County39Lycoming County: 38 indexLycoming County38Elk County: 35 indexElk County35Somerset County: 35 indexSomerset County35Lawrence County: 34 indexLawrence County34Monroe County: 34 indexMonroe County34Susquehanna County: 28 indexSusquehanna County28Wyoming County: 27 indexWyoming County27Lancaster County: 58 indexLancaster County58Philadelphia County: 58 indexPhiladelphia County58Allegheny County: 56 indexAllegheny County56Beaver County: 52 indexBeaver County52Dauphin County: 52 indexDauphin County52Washington County: 51 indexWashington County51Adams County: 50 indexAdams County50Delaware County: 50 indexDelaware County50Berks County: 48 indexBerks County48York County: 48 indexYork County48Lebanon County: 47 indexLebanon County47Cambria County: 46 indexCambria County46Northampton County: 46 indexNorthampton County46Centre County: 45 indexCentre County45Chester County: 45 indexChester County45Armstrong County: 44 indexArmstrong County44Cumberland County: 44 indexCumberland County44Fayette County: 44 indexFayette County44Greene County: 44 indexGreene County44Lackawanna County: 44 indexLackawanna County44Mercer County: 44 indexMercer County44Montgomery County: 44 indexMontgomery County44Blair County: 43 indexBlair County43Lehigh County: 43 indexLehigh County43Erie County: 42 indexErie County42Westmoreland County: 42 indexWestmoreland County42Indiana County: 41 indexIndiana County41Tioga County: 41 indexTioga County41Bradford County: 40 indexBradford County40Bucks County: 39 indexBucks County39Franklin County: 39 indexFranklin County39Lycoming County: 38 indexLycoming County38Elk County: 35 indexElk County35Somerset County: 35 indexSomerset County35Lawrence County: 34 indexLawrence County34Monroe County: 34 indexMonroe County34Susquehanna County: 28 indexSusquehanna County28Wyoming County: 27 indexWyoming County27
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2023
index		Change on 2022
1Lancaster County58-1
1Philadelphia County58+6
3Allegheny County560
4Beaver County52+1
4Dauphin County52+4
6Washington County51-1
7Adams County50+3
7Delaware County50+1
9Berks County48+4
9York County48+1
11Lebanon County47+1
12Cambria County46-6
12Northampton County46+1
14Centre County45+1
14Chester County450
16Armstrong County44-4
16Cumberland County440
16Fayette County44+1
16Greene County44+2
16Lackawanna County44+1
16Mercer County44+4
16Montgomery County440
23Blair County43-1
23Lehigh County43+1
25Erie County42+4
25Westmoreland County42+1
27Indiana County41-1
27Tioga County41+2
29Bradford County400
30Bucks County39-2
30Franklin County390
32Lycoming County38-2
33Elk County350
33Somerset County35+1
35Lawrence County34-3
35Monroe County34-5
37Susquehanna County28-5
38Wyoming County27-7

Other periods

About this ranking

Median of the daily Air Quality Index (AQI) values of a US county over the days of the year with an AQI, from the EPA AirData annual summaries.

More on how it is measured
  • The daily county AQI is the highest AQI among the monitors and pollutants reported that day (ozone, PM2.5, PM10, carbon monoxide and nitrogen dioxide).
  • Lower is cleaner: 0 to 50 is good, 51 to 100 moderate and above 100 unhealthy for sensitive groups.

United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. 6 counties with data in other periods have no value for 2023 and are left out rather than filled from another source. Equal values share a rank.

How to cite

U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: median daily AQI (Counties in Pennsylvania by median Air Quality Index (US EPA), 2023) [Data set]. Retrieved October 12, 2026, from https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual

MLA 9

EPA AirData annual AQI by county: median daily AQI, Counties in Pennsylvania by median Air Quality Index (US EPA), 2023. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/median-air-quality-index/pennsylvania-counties?period=2023. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Counties in Pennsylvania by median Air Quality Index (US EPA), 2023. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/median-air-quality-index/pennsylvania-counties?period=2023.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Counties in Pennsylvania by median Air Quality Index (US EPA), 2023 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/median-air-quality-index/pennsylvania-counties?period=2023 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_pennsylvania_by_2023,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Counties in Pennsylvania by median Air Quality Index (US EPA), 2023}},
  year = {2026},
  howpublished = {Data set},
  url = {https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/pennsylvania-counties?period=2023. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download\_files.html\#Annual. Retrieved 2026-10-12.},
}
RIS
TY  - DATA
AU  - U.S. Environmental Protection Agency
TI  - EPA AirData annual AQI by county: median daily AQI: Counties in Pennsylvania by median Air Quality Index (US EPA), 2023
PY  - 2026
DA  - 2026/07/13
PB  - U.S. Environmental Protection Agency
DB  - Invokely
UR  - https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual
L2  - https://invokely.ai/rankings/median-air-quality-index/pennsylvania-counties?period=2023
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/pennsylvania-counties?period=2023.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Rank Counties in Pennsylvania by median Air Quality Index (US EPA) using official data, and cite the source.
rank_places {"indicator":"aqi_median","level":"province","within":"Pennsylvania","limit":10}
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Questions

Which county has the highest median Air Quality Index (US EPA)?

Lancaster County, with 58 in 2023, according to the U.S. Environmental Protection Agency.

Which county has the lowest median Air Quality Index (US EPA)?

Wyoming County, with 27 in 2023.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12. 6 counties have no value for 2023 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Pennsylvania: more rankings