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 37 counties in 2015, at 58. Bradford County had the lowest, at 32. The median was 51. Source: the U.S. Environmental Protection Agency.

Keep it in a collection in your library.
Highest58Allegheny County
Lowest32Bradford County
Median5137 counties

Map of counties, 2015

Adams County: 51 indexAllegheny County: 58 indexArmstrong County: 53 indexBeaver County: 51 indexBerks County: 54 indexBlair County: 52 indexBradford County: 32 indexBucks County: 53 indexCambria County: 54 indexCentre County: 46 indexChester County: 55 indexClearfield County: 38 indexCumberland County: 54 indexDauphin County: 56 indexDelaware County: 55 indexElk County: 36 indexErie County: 44 indexFranklin County: 34 indexGreene County: 37 indexIndiana County: 37 indexLackawanna County: 51 indexLancaster County: 56 indexLawrence County: 33 indexLebanon County: 52 indexLehigh County: 34 indexLuzerne County: 34 indexLycoming County: 34 indexMercer County: 53 indexMonroe County: 42 indexMontgomery County: 47 indexNorthampton County: 56 indexPhiladelphia County: 56 indexSomerset County: 34 indexTioga County: 44 indexWashington County: 55 indexWestmoreland County: 52 indexYork County: 55 index
  • Under 34
  • 34 to 44
  • 44 to 51
  • 51 to 53
  • 53 to 55
  • 55 and over
  • No data
index, 2015. 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, 2015

Allegheny County: 58 indexAllegheny County58Dauphin County: 56 indexDauphin County56Lancaster County: 56 indexLancaster County56Northampton County: 56 indexNorthampton County56Philadelphia County: 56 indexPhiladelphia County56Chester County: 55 indexChester County55Delaware County: 55 indexDelaware County55Washington County: 55 indexWashington County55York County: 55 indexYork County55Berks County: 54 indexBerks County54Cambria County: 54 indexCambria County54Cumberland County: 54 indexCumberland County54Armstrong County: 53 indexArmstrong County53Bucks County: 53 indexBucks County53Mercer County: 53 indexMercer County53Blair County: 52 indexBlair County52Lebanon County: 52 indexLebanon County52Westmoreland County: 52 indexWestmoreland County52Adams County: 51 indexAdams County51Beaver County: 51 indexBeaver County51Lackawanna County: 51 indexLackawanna County51Montgomery County: 47 indexMontgomery County47Centre County: 46 indexCentre County46Erie County: 44 indexErie County44Tioga County: 44 indexTioga County44Monroe County: 42 indexMonroe County42Clearfield County: 38 indexClearfield County38Greene County: 37 indexGreene County37Indiana County: 37 indexIndiana County37Elk County: 36 indexElk County36Franklin County: 34 indexFranklin County34Lehigh County: 34 indexLehigh County34Luzerne County: 34 indexLuzerne County34Lycoming County: 34 indexLycoming County34Somerset County: 34 indexSomerset County34Lawrence County: 33 indexLawrence County33Bradford County: 32 indexBradford County32Allegheny County: 58 indexAllegheny County58Dauphin County: 56 indexDauphin County56Lancaster County: 56 indexLancaster County56Northampton County: 56 indexNorthampton County56Philadelphia County: 56 indexPhiladelphia County56Chester County: 55 indexChester County55Delaware County: 55 indexDelaware County55Washington County: 55 indexWashington County55York County: 55 indexYork County55Berks County: 54 indexBerks County54Cambria County: 54 indexCambria County54Cumberland County: 54 indexCumberland County54Armstrong County: 53 indexArmstrong County53Bucks County: 53 indexBucks County53Mercer County: 53 indexMercer County53Blair County: 52 indexBlair County52Lebanon County: 52 indexLebanon County52Westmoreland County: 52 indexWestmoreland County52Adams County: 51 indexAdams County51Beaver County: 51 indexBeaver County51Lackawanna County: 51 indexLackawanna County51Montgomery County: 47 indexMontgomery County47Centre County: 46 indexCentre County46Erie County: 44 indexErie County44Tioga County: 44 indexTioga County44Monroe County: 42 indexMonroe County42Clearfield County: 38 indexClearfield County38Greene County: 37 indexGreene County37Indiana County: 37 indexIndiana County37Elk County: 36 indexElk County36Franklin County: 34 indexFranklin County34Lehigh County: 34 indexLehigh County34Luzerne County: 34 indexLuzerne County34Lycoming County: 34 indexLycoming County34Somerset County: 34 indexSomerset County34Lawrence County: 33 indexLawrence County33Bradford County: 32 indexBradford County32
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2015
index		Change on 2014
1Allegheny County580
2Dauphin County56+2
2Lancaster County56-5
2Northampton County56+3
2Philadelphia County56-3
6Chester County55+3
6Delaware County55-1
6Washington County55-4
6York County55+3
10Berks County54+1
10Cambria County54+1
10Cumberland County540
13Armstrong County530
13Bucks County53-1
13Mercer County53-2
16Blair County52-1
16Lebanon County52-3
16Westmoreland County520
19Adams County51+6
19Beaver County51-2
19Lackawanna County51+1
22Montgomery County470
23Centre County46-5
24Erie County44-9
24Tioga County44+6
26Monroe County42-4
27Clearfield County38+6
28Greene County37-2
28Indiana County37-1
30Elk County360
31Franklin County34-4
31Lehigh County34-1
31Luzerne County340
31Lycoming County34-1
31Somerset County34-2
36Lawrence County33-2
37Bradford County32+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. 7 counties with data in other periods have no value for 2015 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), 2015) [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), 2015. 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=2015. 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), 2015. 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=2015.

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), 2015 [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=2015 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_pennsylvania_by_2015,
  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), 2015}},
  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=2015. 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), 2015
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=2015
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/pennsylvania-counties?period=2015.
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 58 in 2015, according to the U.S. Environmental Protection Agency.

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

Bradford County, with 32 in 2015.

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. 7 counties have no value for 2015 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Pennsylvania: more rankings