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

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

Allegheny County had the highest median Air Quality Index (US EPA) of 40 counties in 2019, at 59. Lawrence County had the lowest, at 31. The median was 43. Source: the U.S. Environmental Protection Agency.

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Highest59Allegheny County
Lowest31Lawrence County
Median4340 counties

Map of counties, 2019

Adams County: 45 indexAllegheny County: 59 indexArmstrong County: 43 indexBeaver County: 50 indexBerks County: 44 indexBlair County: 46 indexBradford County: 41 indexBucks County: 35 indexCambria County: 45 indexCentre County: 49 indexChester County: 46 indexClearfield County: 33 indexCumberland County: 51 indexDauphin County: 44 indexDelaware County: 51 indexElk County: 35 indexErie County: 39 indexFayette County: 42 indexFranklin County: 36 indexGreene County: 38 indexIndiana County: 38 indexLackawanna County: 39 indexLancaster County: 52 indexLawrence County: 31 indexLebanon County: 46 indexLehigh County: 43 indexLuzerne County: 34 indexLycoming County: 37 indexMercer County: 44 indexMonroe County: 34 indexMontgomery County: 40 indexNorthampton County: 44 indexPhiladelphia County: 49 indexSomerset County: 36 indexSusquehanna County: 32 indexTioga County: 37 indexWashington County: 51 indexWestmoreland County: 41 indexWyoming County: 38 indexYork County: 44 index
  • Under 36
  • 36 to 38
  • 38 to 43
  • 43 to 44
  • 44 to 49
  • 49 and over
  • No data
index, 2019. 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, 2019

Allegheny County: 59 indexAllegheny County59Lancaster County: 52 indexLancaster County52Cumberland County: 51 indexCumberland County51Delaware County: 51 indexDelaware County51Washington County: 51 indexWashington County51Beaver County: 50 indexBeaver County50Centre County: 49 indexCentre County49Philadelphia County: 49 indexPhiladelphia County49Blair County: 46 indexBlair County46Chester County: 46 indexChester County46Lebanon County: 46 indexLebanon County46Adams County: 45 indexAdams County45Cambria County: 45 indexCambria County45Berks County: 44 indexBerks County44Dauphin County: 44 indexDauphin County44Mercer County: 44 indexMercer County44Northampton County: 44 indexNorthampton County44York County: 44 indexYork County44Armstrong County: 43 indexArmstrong County43Lehigh County: 43 indexLehigh County43Fayette County: 42 indexFayette County42Bradford County: 41 indexBradford County41Westmoreland County: 41 indexWestmoreland County41Montgomery County: 40 indexMontgomery County40Erie County: 39 indexErie County39Lackawanna County: 39 indexLackawanna County39Greene County: 38 indexGreene County38Indiana County: 38 indexIndiana County38Wyoming County: 38 indexWyoming County38Lycoming County: 37 indexLycoming County37Tioga County: 37 indexTioga County37Franklin County: 36 indexFranklin County36Somerset County: 36 indexSomerset County36Bucks County: 35 indexBucks County35Elk County: 35 indexElk County35Luzerne County: 34 indexLuzerne County34Monroe County: 34 indexMonroe County34Clearfield County: 33 indexClearfield County33Susquehanna County: 32 indexSusquehanna County32Lawrence County: 31 indexLawrence County31Allegheny County: 59 indexAllegheny County59Lancaster County: 52 indexLancaster County52Cumberland County: 51 indexCumberland County51Delaware County: 51 indexDelaware County51Washington County: 51 indexWashington County51Beaver County: 50 indexBeaver County50Centre County: 49 indexCentre County49Philadelphia County: 49 indexPhiladelphia County49Blair County: 46 indexBlair County46Chester County: 46 indexChester County46Lebanon County: 46 indexLebanon County46Adams County: 45 indexAdams County45Cambria County: 45 indexCambria County45Berks County: 44 indexBerks County44Dauphin County: 44 indexDauphin County44Mercer County: 44 indexMercer County44Northampton County: 44 indexNorthampton County44York County: 44 indexYork County44Armstrong County: 43 indexArmstrong County43Lehigh County: 43 indexLehigh County43Fayette County: 42 indexFayette County42Bradford County: 41 indexBradford County41Westmoreland County: 41 indexWestmoreland County41Montgomery County: 40 indexMontgomery County40Erie County: 39 indexErie County39Lackawanna County: 39 indexLackawanna County39Greene County: 38 indexGreene County38Indiana County: 38 indexIndiana County38Wyoming County: 38 indexWyoming County38Lycoming County: 37 indexLycoming County37Tioga County: 37 indexTioga County37Franklin County: 36 indexFranklin County36Somerset County: 36 indexSomerset County36Bucks County: 35 indexBucks County35Elk County: 35 indexElk County35Luzerne County: 34 indexLuzerne County34Monroe County: 34 indexMonroe County34Clearfield County: 33 indexClearfield County33Susquehanna County: 32 indexSusquehanna County32Lawrence County: 31 indexLawrence County31
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2019
index		Change on 2018
1Allegheny County59+1
2Lancaster County520
3Cumberland County51+3
3Delaware County51-5
3Washington County51-1
6Beaver County50-2
7Centre County49+5
7Philadelphia County49-5
9Blair County46+4
9Chester County46+2
9Lebanon County46-1
12Adams County45+1
12Cambria County45+1
14Berks County440
14Dauphin County440
14Mercer County44+1
14Northampton County44-4
14York County44-1
19Armstrong County43+1
19Lehigh County430
21Fayette County420
22Bradford County41+4
22Westmoreland County41+1
24Montgomery County40-1
25Erie County39-5
25Lackawanna County39-2
27Greene County38-1
27Indiana County38+3
27Wyoming County38n/a
30Lycoming County37+6
30Tioga County370
32Franklin County36+4
32Somerset County36+3
34Bucks County35+2
34Elk County35+1
36Luzerne County34+2
36Monroe County34-2
38Clearfield County330
39Susquehanna County320
40Lawrence County31-1

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. 4 counties with data in other periods have no value for 2019 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), 2019) [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), 2019. 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=2019. 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), 2019. 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=2019.

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), 2019 [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=2019 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_pennsylvania_by_2019,
  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), 2019}},
  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=2019. 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), 2019
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=2019
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/pennsylvania-counties?period=2019.
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.
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Questions

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

Allegheny County, with 59 in 2019, according to the U.S. Environmental Protection Agency.

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

Lawrence County, with 31 in 2019.

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. 4 counties have no value for 2019 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Pennsylvania: more rankings