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 39 counties in 2018, at 58. Lycoming County had the lowest, at 31. The median was 42. Source: the U.S. Environmental Protection Agency.

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Highest58Allegheny County
Lowest31Lycoming County
Median4239 counties

Map of counties, 2018

Adams County: 44 indexAllegheny County: 58 indexArmstrong County: 42 indexBeaver County: 52 indexBerks County: 44 indexBlair County: 42 indexBradford County: 37 indexBucks County: 33 indexCambria County: 44 indexCentre County: 44 indexChester County: 44 indexClearfield County: 33 indexCumberland County: 48 indexDauphin County: 44 indexDelaware County: 56 indexElk County: 34 indexErie County: 44 indexFayette County: 42 indexFranklin County: 32 indexGreene County: 39 indexIndiana County: 35 indexLackawanna County: 41 indexLancaster County: 52 indexLawrence County: 32 indexLebanon County: 47 indexLehigh County: 43 indexLuzerne County: 32 indexLycoming County: 31 indexMercer County: 43 indexMonroe County: 36 indexMontgomery County: 41 indexNorthampton County: 48 indexPhiladelphia County: 54 indexSomerset County: 33 indexSusquehanna County: 32 indexTioga County: 37 indexWashington County: 52 indexWestmoreland County: 40 indexYork County: 45 index
  • Under 33
  • 33 to 38
  • 38 to 42
  • 42 to 44
  • 44 to 48
  • 48 and over
  • No data
index, 2018. 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, 2018

Allegheny County: 58 indexAllegheny County58Delaware County: 56 indexDelaware County56Philadelphia County: 54 indexPhiladelphia County54Beaver County: 52 indexBeaver County52Lancaster County: 52 indexLancaster County52Washington County: 52 indexWashington County52Cumberland County: 48 indexCumberland County48Northampton County: 48 indexNorthampton County48Lebanon County: 47 indexLebanon County47York County: 45 indexYork County45Adams County: 44 indexAdams County44Berks County: 44 indexBerks County44Cambria County: 44 indexCambria County44Centre County: 44 indexCentre County44Chester County: 44 indexChester County44Dauphin County: 44 indexDauphin County44Erie County: 44 indexErie County44Lehigh County: 43 indexLehigh County43Mercer County: 43 indexMercer County43Armstrong County: 42 indexArmstrong County42Blair County: 42 indexBlair County42Fayette County: 42 indexFayette County42Lackawanna County: 41 indexLackawanna County41Montgomery County: 41 indexMontgomery County41Westmoreland County: 40 indexWestmoreland County40Greene County: 39 indexGreene County39Bradford County: 37 indexBradford County37Tioga County: 37 indexTioga County37Monroe County: 36 indexMonroe County36Indiana County: 35 indexIndiana County35Elk County: 34 indexElk County34Bucks County: 33 indexBucks County33Clearfield County: 33 indexClearfield County33Somerset County: 33 indexSomerset County33Franklin County: 32 indexFranklin County32Lawrence County: 32 indexLawrence County32Luzerne County: 32 indexLuzerne County32Susquehanna County: 32 indexSusquehanna County32Lycoming County: 31 indexLycoming County31Allegheny County: 58 indexAllegheny County58Delaware County: 56 indexDelaware County56Philadelphia County: 54 indexPhiladelphia County54Beaver County: 52 indexBeaver County52Lancaster County: 52 indexLancaster County52Washington County: 52 indexWashington County52Cumberland County: 48 indexCumberland County48Northampton County: 48 indexNorthampton County48Lebanon County: 47 indexLebanon County47York County: 45 indexYork County45Adams County: 44 indexAdams County44Berks County: 44 indexBerks County44Cambria County: 44 indexCambria County44Centre County: 44 indexCentre County44Chester County: 44 indexChester County44Dauphin County: 44 indexDauphin County44Erie County: 44 indexErie County44Lehigh County: 43 indexLehigh County43Mercer County: 43 indexMercer County43Armstrong County: 42 indexArmstrong County42Blair County: 42 indexBlair County42Fayette County: 42 indexFayette County42Lackawanna County: 41 indexLackawanna County41Montgomery County: 41 indexMontgomery County41Westmoreland County: 40 indexWestmoreland County40Greene County: 39 indexGreene County39Bradford County: 37 indexBradford County37Tioga County: 37 indexTioga County37Monroe County: 36 indexMonroe County36Indiana County: 35 indexIndiana County35Elk County: 34 indexElk County34Bucks County: 33 indexBucks County33Clearfield County: 33 indexClearfield County33Somerset County: 33 indexSomerset County33Franklin County: 32 indexFranklin County32Lawrence County: 32 indexLawrence County32Luzerne County: 32 indexLuzerne County32Susquehanna County: 32 indexSusquehanna County32Lycoming County: 31 indexLycoming County31
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2018
index		Change on 2017
1Allegheny County580
2Delaware County56+4
3Philadelphia County54-2
4Beaver County52-2
4Lancaster County52-3
4Washington County52-3
7Cumberland County48+5
7Northampton County48-8
9Lebanon County47-9
10York County45-2
11Adams County44-1
11Berks County44-5
11Cambria County44-11
11Centre County44-7
11Chester County44-10
11Dauphin County44-3
11Erie County44+1
18Lehigh County43-1
18Mercer County43-12
20Armstrong County42-8
20Blair County42-3
20Fayette County42n/a
23Lackawanna County41-4
23Montgomery County41-6
25Westmoreland County40-15
26Greene County39-3
27Bradford County37-5
27Tioga County37-16
29Monroe County36-6
30Indiana County35-3
31Elk County34-1
32Bucks County33-1
32Clearfield County33-3
32Somerset County33-3
35Franklin County32-1
35Lawrence County32-2
35Luzerne County32-1
35Susquehanna County32n/a
39Lycoming County31-2

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. 5 counties with data in other periods have no value for 2018 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), 2018) [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), 2018. 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=2018. 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), 2018. 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=2018.

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), 2018 [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=2018 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_pennsylvania_by_2018,
  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), 2018}},
  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=2018. 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), 2018
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=2018
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/pennsylvania-counties?period=2018.
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)?

Allegheny County, with 58 in 2018, according to the U.S. Environmental Protection Agency.

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

Lycoming County, with 31 in 2018.

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. 5 counties have no value for 2018 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Pennsylvania: more rankings