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

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

Jackson County had the highest median Air Quality Index (US EPA) of 23 counties in 2015, at 49. Benton County had the lowest, at 22. The median was 37. Source: the U.S. Environmental Protection Agency.

Keep it in a collection in your library.
Highest49Jackson County
Lowest22Benton County
Median3723 counties

Map of counties, 2015

Baker County: 31 indexBenton County: 22 indexClackamas County: 35 indexColumbia County: 33 indexCrook County: 32 indexDeschutes County: 37 indexDouglas County: 26 indexGrant County: 42 indexHarney County: 35 indexJackson County: 49 indexJefferson County: 42 indexJosephine County: 37 indexKlamath County: 42 indexLake County: 28 indexLane County: 44 indexLinn County: 31 indexMarion County: 37 indexMultnomah County: 39 indexUmatilla County: 41 indexUnion County: 38 indexWallowa County: 26 indexWasco County: 27 indexWashington County: 40 index
  • Under 29
  • 29 to 35
  • 35 to 37
  • 37 to 42
  • 42 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

Jackson County: 49 indexJackson County49Lane County: 44 indexLane County44Grant County: 42 indexGrant County42Jefferson County: 42 indexJefferson County42Klamath County: 42 indexKlamath County42Umatilla County: 41 indexUmatilla County41Washington County: 40 indexWashington County40Multnomah County: 39 indexMultnomah County39Union County: 38 indexUnion County38Deschutes County: 37 indexDeschutes County37Josephine County: 37 indexJosephine County37Marion County: 37 indexMarion County37Clackamas County: 35 indexClackamas County35Harney County: 35 indexHarney County35Columbia County: 33 indexColumbia County33Crook County: 32 indexCrook County32Baker County: 31 indexBaker County31Linn County: 31 indexLinn County31Lake County: 28 indexLake County28Wasco County: 27 indexWasco County27Douglas County: 26 indexDouglas County26Wallowa County: 26 indexWallowa County26Benton County: 22 indexBenton County22Jackson County: 49 indexJackson County49Lane County: 44 indexLane County44Grant County: 42 indexGrant County42Jefferson County: 42 indexJefferson County42Klamath County: 42 indexKlamath County42Umatilla County: 41 indexUmatilla County41Washington County: 40 indexWashington County40Multnomah County: 39 indexMultnomah County39Union County: 38 indexUnion County38Deschutes County: 37 indexDeschutes County37Josephine County: 37 indexJosephine County37Marion County: 37 indexMarion County37Clackamas County: 35 indexClackamas County35Harney County: 35 indexHarney County35Columbia County: 33 indexColumbia County33Crook County: 32 indexCrook County32Baker County: 31 indexBaker County31Linn County: 31 indexLinn County31Lake County: 28 indexLake County28Wasco County: 27 indexWasco County27Douglas County: 26 indexDouglas County26Wallowa County: 26 indexWallowa County26Benton County: 22 indexBenton County22
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2015
index		Change on 2014
1Jackson County49+4
2Lane County44-5
3Grant County420
3Jefferson County42-2
3Klamath County420
6Umatilla County41+4
7Washington County40+5
8Multnomah County39+3
9Union County38+4
10Deschutes County370
10Josephine County37+6
10Marion County37+3
13Clackamas County35+1
13Harney County35-2
15Columbia County33+4
16Crook County32+1
17Baker County31+1
17Linn County31-2
19Lake County28-1
20Wasco County27+3
21Douglas County26-1
21Wallowa County26+3
23Benton County22+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. 3 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 Oregon 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 Oregon 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/oregon-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 Oregon 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/oregon-counties?period=2015.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Counties in Oregon 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/oregon-counties?period=2015 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_oregon_by_2015,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Counties in Oregon 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/oregon-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 Oregon 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/oregon-counties?period=2015
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/oregon-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 Oregon 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)?

Jackson County, with 49 in 2015, according to the U.S. Environmental Protection Agency.

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

Benton County, with 22 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. 3 counties have no value for 2015 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Oregon: more rankings