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

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

Lane County had the highest median Air Quality Index (US EPA) of 25 counties in 2011, at 46. Yamhill County had the lowest, at 18. The median was 31. Source: the U.S. Environmental Protection Agency.

Keep it in a collection in your library.
Highest46Lane County
Lowest18Yamhill County
Median3125 counties

Map of counties, 2011

Baker County: 31 indexBenton County: 21 indexClackamas County: 30 indexColumbia County: 29 indexCoos County: 32 indexCrook County: 28 indexDeschutes County: 36 indexDouglas County: 27 indexGrant County: 41 indexHarney County: 37 indexJackson County: 43 indexJefferson County: 28 indexJosephine County: 28 indexKlamath County: 36 indexLake County: 28 indexLane County: 46 indexLinn County: 34 indexMarion County: 34 indexMultnomah County: 37 indexUmatilla County: 39 indexUnion County: 29 indexWallowa County: 23 indexWasco County: 23 indexWashington County: 35 indexYamhill County: 18 index
  • Under 28
  • 28 to 29
  • 29 to 34
  • 34 to 37
  • 37 and over
  • No data
index, 2011. 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, 2011

Lane County: 46 indexLane County46Jackson County: 43 indexJackson County43Grant County: 41 indexGrant County41Umatilla County: 39 indexUmatilla County39Harney County: 37 indexHarney County37Multnomah County: 37 indexMultnomah County37Deschutes County: 36 indexDeschutes County36Klamath County: 36 indexKlamath County36Washington County: 35 indexWashington County35Linn County: 34 indexLinn County34Marion County: 34 indexMarion County34Coos County: 32 indexCoos County32Baker County: 31 indexBaker County31Clackamas County: 30 indexClackamas County30Columbia County: 29 indexColumbia County29Union County: 29 indexUnion County29Crook County: 28 indexCrook County28Jefferson County: 28 indexJefferson County28Josephine County: 28 indexJosephine County28Lake County: 28 indexLake County28Douglas County: 27 indexDouglas County27Wallowa County: 23 indexWallowa County23Wasco County: 23 indexWasco County23Benton County: 21 indexBenton County21Yamhill County: 18 indexYamhill County18Lane County: 46 indexLane County46Jackson County: 43 indexJackson County43Grant County: 41 indexGrant County41Umatilla County: 39 indexUmatilla County39Harney County: 37 indexHarney County37Multnomah County: 37 indexMultnomah County37Deschutes County: 36 indexDeschutes County36Klamath County: 36 indexKlamath County36Washington County: 35 indexWashington County35Linn County: 34 indexLinn County34Marion County: 34 indexMarion County34Coos County: 32 indexCoos County32Baker County: 31 indexBaker County31Clackamas County: 30 indexClackamas County30Columbia County: 29 indexColumbia County29Union County: 29 indexUnion County29Crook County: 28 indexCrook County28Jefferson County: 28 indexJefferson County28Josephine County: 28 indexJosephine County28Lake County: 28 indexLake County28Douglas County: 27 indexDouglas County27Wallowa County: 23 indexWallowa County23Wasco County: 23 indexWasco County23Benton County: 21 indexBenton County21Yamhill County: 18 indexYamhill County18
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2011
index		Change on 2010
1Lane County46-1
2Jackson County43+4
3Grant County41+8
4Umatilla County39-1
5Harney County37+4
5Multnomah County37+1
7Deschutes County36+2
7Klamath County36+1
9Washington County35+2
10Linn County340
10Marion County34+3
12Coos County32n/a
13Baker County31-2
14Clackamas County30+3
15Columbia County290
15Union County29-4
17Crook County28+1
17Jefferson County28-5
17Josephine County28-1
17Lake County280
21Douglas County27-1
22Wallowa County23-3
22Wasco County23-2
24Benton County21+1
25Yamhill County18-3

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. 1 counties with data in other periods have no value for 2011 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), 2011) [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), 2011. 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=2011. 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), 2011. 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=2011.

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), 2011 [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=2011 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_oregon_by_2011,
  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), 2011}},
  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=2011. 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), 2011
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=2011
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/oregon-counties?period=2011.
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)?

Lane County, with 46 in 2011, according to the U.S. Environmental Protection Agency.

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

Yamhill County, with 18 in 2011.

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. 1 counties have no value for 2011 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Oregon: more rankings