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

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

Harney County had the highest median Air Quality Index (US EPA) of 24 counties in 2019, at 44. Benton County had the lowest, at 22. The median was 32. Source: the U.S. Environmental Protection Agency.

Keep it in a collection in your library.
Highest44Harney County
Lowest22Benton County
Median3224 counties

Map of counties, 2019

Baker County: 31 indexBenton County: 22 indexClackamas County: 31 indexColumbia County: 27 indexCoos County: 25 indexCrook County: 30 indexDeschutes County: 26 indexDouglas County: 32 indexGrant County: 41 indexHarney County: 44 indexJackson County: 41 indexJefferson County: 29 indexJosephine County: 34 indexKlamath County: 39 indexLake County: 25 indexLane County: 44 indexLinn County: 37 indexMarion County: 37 indexMultnomah County: 36 indexUmatilla County: 40 indexUnion County: 26 indexWallowa County: 29 indexWasco County: 31 indexWashington County: 37 index
  • Under 27
  • 27 to 31
  • 31 to 36
  • 36 to 39
  • 39 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

Harney County: 44 indexHarney County44Lane County: 44 indexLane County44Grant County: 41 indexGrant County41Jackson County: 41 indexJackson County41Umatilla County: 40 indexUmatilla County40Klamath County: 39 indexKlamath County39Linn County: 37 indexLinn County37Marion County: 37 indexMarion County37Washington County: 37 indexWashington County37Multnomah County: 36 indexMultnomah County36Josephine County: 34 indexJosephine County34Douglas County: 32 indexDouglas County32Baker County: 31 indexBaker County31Clackamas County: 31 indexClackamas County31Wasco County: 31 indexWasco County31Crook County: 30 indexCrook County30Jefferson County: 29 indexJefferson County29Wallowa County: 29 indexWallowa County29Columbia County: 27 indexColumbia County27Deschutes County: 26 indexDeschutes County26Union County: 26 indexUnion County26Coos County: 25 indexCoos County25Lake County: 25 indexLake County25Benton County: 22 indexBenton County22Harney County: 44 indexHarney County44Lane County: 44 indexLane County44Grant County: 41 indexGrant County41Jackson County: 41 indexJackson County41Umatilla County: 40 indexUmatilla County40Klamath County: 39 indexKlamath County39Linn County: 37 indexLinn County37Marion County: 37 indexMarion County37Washington County: 37 indexWashington County37Multnomah County: 36 indexMultnomah County36Josephine County: 34 indexJosephine County34Douglas County: 32 indexDouglas County32Baker County: 31 indexBaker County31Clackamas County: 31 indexClackamas County31Wasco County: 31 indexWasco County31Crook County: 30 indexCrook County30Jefferson County: 29 indexJefferson County29Wallowa County: 29 indexWallowa County29Columbia County: 27 indexColumbia County27Deschutes County: 26 indexDeschutes County26Union County: 26 indexUnion County26Coos County: 25 indexCoos County25Lake County: 25 indexLake County25Benton County: 22 indexBenton County22
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2019
index		Change on 2018
1Harney County44+5
1Lane County440
3Grant County41-4
3Jackson County41-7
5Umatilla County40+4
6Klamath County39-10
7Linn County37+1
7Marion County37+2
7Washington County37+1
10Multnomah County36-1
11Josephine County34-13
12Douglas County32+3
13Baker County31-1
13Clackamas County31-6
13Wasco County31-6
16Crook County30-4
17Jefferson County29-20
17Wallowa County29+1
19Columbia County27-1
20Deschutes County26-1
20Union County26-6
22Coos County25n/a
22Lake County25-9
24Benton County220

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. 2 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 Oregon 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 Oregon 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/oregon-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 Oregon 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/oregon-counties?period=2019.

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

BibTeX
@misc{environmental_counties_in_oregon_by_2019,
  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), 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/oregon-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 Oregon 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/oregon-counties?period=2019
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/oregon-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 Oregon by median Air Quality Index (US EPA) using official data, and cite the source.
rank_places {"indicator":"aqi_median","level":"province","within":"Oregon","limit":10}
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Questions

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

Harney County, with 44 in 2019, according to the U.S. Environmental Protection Agency.

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

Benton County, with 22 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. 2 counties have no value for 2019 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Oregon: more rankings