Data / Rankings / Share of days unhealthy for sensitive groups or worse (US EPA AQI) / Counties in Oregon

Counties in Oregon by share of days unhealthy for sensitive groups or worse (US EPA AQI)

Jefferson County had the highest share of days unhealthy for sensitive groups or worse (US EPA AQI) of 23 counties in 2017, at 9.8%. Benton County had the lowest, at 0.6%. The median was 3.3%. Source: EPA.

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Highest9.8Jefferson County
Lowest0.6Benton County
Median3.323 counties

Map of counties, 2017

Baker County: 1.6 %Benton County: 0.6 %Clackamas County: 5.6 %Columbia County: 1.2 %Crook County: 4.5 %Deschutes County: 7.7 %Douglas County: 1.9 %Grant County: 3.4 %Harney County: 2.2 %Jackson County: 8.5 %Jefferson County: 9.8 %Josephine County: 5.8 %Klamath County: 7.2 %Lake County: 5 %Lane County: 8.2 %Linn County: 2.5 %Marion County: 2.5 %Multnomah County: 1.6 %Umatilla County: 3.3 %Union County: 3 %Wallowa County: 2.5 %Wasco County: 4.4 %Washington County: 3.3 %
  • Under 2
  • 2 to 2.9
  • 2.9 to 4.4
  • 4.4 to 6.6
  • 6.6 and over
  • No data
%, 2017. Hatched areas have no value for this period. Source: Invokely calculation with data from EPA. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2017

Jefferson County: 9.8 %Jefferson County9.8Jackson County: 8.5 %Jackson County8.5Lane County: 8.2 %Lane County8.2Deschutes County: 7.7 %Deschutes County7.7Klamath County: 7.2 %Klamath County7.2Josephine County: 5.8 %Josephine County5.8Clackamas County: 5.6 %Clackamas County5.6Lake County: 5 %Lake County5Crook County: 4.5 %Crook County4.5Wasco County: 4.4 %Wasco County4.4Grant County: 3.4 %Grant County3.4Umatilla County: 3.3 %Umatilla County3.3Washington County: 3.3 %Washington County3.3Union County: 3 %Union County3Linn County: 2.5 %Linn County2.5Marion County: 2.5 %Marion County2.5Wallowa County: 2.5 %Wallowa County2.5Harney County: 2.2 %Harney County2.2Douglas County: 1.9 %Douglas County1.9Baker County: 1.6 %Baker County1.6Multnomah County: 1.6 %Multnomah County1.6Columbia County: 1.2 %Columbia County1.2Benton County: 0.6 %Benton County0.6Jefferson County: 9.8 %Jefferson County9.8Jackson County: 8.5 %Jackson County8.5Lane County: 8.2 %Lane County8.2Deschutes County: 7.7 %Deschutes County7.7Klamath County: 7.2 %Klamath County7.2Josephine County: 5.8 %Josephine County5.8Clackamas County: 5.6 %Clackamas County5.6Lake County: 5 %Lake County5Crook County: 4.5 %Crook County4.5Wasco County: 4.4 %Wasco County4.4Grant County: 3.4 %Grant County3.4Umatilla County: 3.3 %Umatilla County3.3Washington County: 3.3 %Washington County3.3Union County: 3 %Union County3Linn County: 2.5 %Linn County2.5Marion County: 2.5 %Marion County2.5Wallowa County: 2.5 %Wallowa County2.5Harney County: 2.2 %Harney County2.2Douglas County: 1.9 %Douglas County1.9Baker County: 1.6 %Baker County1.6Multnomah County: 1.6 %Multnomah County1.6Columbia County: 1.2 %Columbia County1.2Benton County: 0.6 %Benton County0.6
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2017 (%)Change on 2016
1Jefferson County9.8n/a
2Jackson County8.5+8.5 pts
3Lane County8.2+7.9 pts
4Deschutes County7.7+7.7 pts
5Klamath County7.2+7.2 pts
6Josephine County5.8+5.8 pts
7Clackamas County5.6+5.1 pts
8Lake County5+4.4 pts
9Crook County4.5+4.2 pts
10Wasco County4.4+4.4 pts
11Grant County3.4+3.4 pts
12Umatilla County3.3+3 pts
12Washington County3.3+3.3 pts
14Union County3+3 pts
15Linn County2.5+2.5 pts
15Marion County2.5+2.5 pts
15Wallowa County2.5+2.5 pts
18Harney County2.2+1.9 pts
19Douglas County1.9+1.9 pts
20Baker County1.6+1.6 pts
20Multnomah County1.6+1.3 pts
22Columbia County1.2+1.2 pts
23Benton County0.6+0.6 pts

Other periods

About this ranking

Days with a daily Air Quality Index above 100 (unhealthy for sensitive groups, unhealthy, very unhealthy or hazardous) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; the counts are stored with each value.

Use the share rather than the number of days to compare counties, since the days with an AQI differ. 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 2017 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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts. 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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts (Counties in Oregon by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2017) [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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts, Counties in Oregon by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2017. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/unhealthy-air-quality-days-share/oregon-counties?period=2017. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts. Counties in Oregon by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2017. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/unhealthy-air-quality-days-share/oregon-counties?period=2017.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts, Counties in Oregon by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2017 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/unhealthy-air-quality-days-share/oregon-counties?period=2017 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_oregon_by_2017,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts: Counties in Oregon by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2017}},
  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/unhealthy-air-quality-days-share/oregon-counties?period=2017. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts. 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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts: Counties in Oregon by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2017
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/unhealthy-air-quality-days-share/oregon-counties?period=2017
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/unhealthy-air-quality-days-share/oregon-counties?period=2017.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Rank Counties in Oregon by share of days unhealthy for sensitive groups or worse (US EPA AQI) using official data, and cite the source.
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Questions

Which county has the highest share of days unhealthy for sensitive groups or worse (US EPA AQI)?

Jefferson County, with 9.8% in 2017, according to EPA.

Which county has the lowest share of days unhealthy for sensitive groups or worse (US EPA AQI)?

Benton County, with 0.6% in 2017.

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: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts. Retrieved 2026-10-12. 3 counties have no value for 2017 and are not ranked.

Share of days unhealthy for sensitive groups or worse (US EPA AQI): other rankings

Counties in Oregon: more rankings