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)

Jackson County had the highest share of days unhealthy for sensitive groups or worse (US EPA AQI) of 23 counties in 2015, at 7.9%. Douglas County had the lowest, at 0.3%. The median was 1.6%. Source: EPA.

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Highest7.9Jackson County
Lowest0.3Douglas County
Median1.623 counties

Map of counties, 2015

Baker County: 2.7 %Benton County: 0.5 %Clackamas County: 1.8 %Columbia County: 0.3 %Crook County: 2.2 %Deschutes County: 1.6 %Douglas County: 0.3 %Grant County: 2.5 %Harney County: 0.8 %Jackson County: 7.9 %Jefferson County: 4.3 %Josephine County: 1.6 %Klamath County: 3.6 %Lake County: 0.8 %Lane County: 4.1 %Linn County: 1.4 %Marion County: 0.8 %Multnomah County: 0.5 %Umatilla County: 2.5 %Union County: 3 %Wallowa County: 2.5 %Wasco County: 0.6 %Washington County: 0.5 %
  • Under 0.5
  • 0.5 to 1.3
  • 1.3 to 2.3
  • 2.3 to 2.9
  • 2.9 and over
  • No data
%, 2015. 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, 2015

Jackson County: 7.9 %Jackson County7.9Jefferson County: 4.3 %Jefferson County4.3Lane County: 4.1 %Lane County4.1Klamath County: 3.6 %Klamath County3.6Union County: 3 %Union County3Baker County: 2.7 %Baker County2.7Grant County: 2.5 %Grant County2.5Umatilla County: 2.5 %Umatilla County2.5Wallowa County: 2.5 %Wallowa County2.5Crook County: 2.2 %Crook County2.2Clackamas County: 1.8 %Clackamas County1.8Deschutes County: 1.6 %Deschutes County1.6Josephine County: 1.6 %Josephine County1.6Linn County: 1.4 %Linn County1.4Harney County: 0.8 %Harney County0.8Lake County: 0.8 %Lake County0.8Marion County: 0.8 %Marion County0.8Wasco County: 0.6 %Wasco County0.6Benton County: 0.5 %Benton County0.5Multnomah County: 0.5 %Multnomah County0.5Washington County: 0.5 %Washington County0.5Columbia County: 0.3 %Columbia County0.3Douglas County: 0.3 %Douglas County0.3Jackson County: 7.9 %Jackson County7.9Jefferson County: 4.3 %Jefferson County4.3Lane County: 4.1 %Lane County4.1Klamath County: 3.6 %Klamath County3.6Union County: 3 %Union County3Baker County: 2.7 %Baker County2.7Grant County: 2.5 %Grant County2.5Umatilla County: 2.5 %Umatilla County2.5Wallowa County: 2.5 %Wallowa County2.5Crook County: 2.2 %Crook County2.2Clackamas County: 1.8 %Clackamas County1.8Deschutes County: 1.6 %Deschutes County1.6Josephine County: 1.6 %Josephine County1.6Linn County: 1.4 %Linn County1.4Harney County: 0.8 %Harney County0.8Lake County: 0.8 %Lake County0.8Marion County: 0.8 %Marion County0.8Wasco County: 0.6 %Wasco County0.6Benton County: 0.5 %Benton County0.5Multnomah County: 0.5 %Multnomah County0.5Washington County: 0.5 %Washington County0.5Columbia County: 0.3 %Columbia County0.3Douglas County: 0.3 %Douglas County0.3
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2015 (%)Change on 2014
1Jackson County7.9+7.4 pts
2Jefferson County4.3+1.9 pts
3Lane County4.1-0.6 pts
4Klamath County3.6+2.5 pts
5Union County3+1.3 pts
6Baker County2.7+2.7 pts
7Grant County2.5+1.9 pts
7Umatilla County2.5+2.5 pts
7Wallowa County2.5+1.7 pts
10Crook County2.2-0.5 pts
11Clackamas County1.8+0.4 pts
12Deschutes County1.6+1.3 pts
12Josephine County1.6+1.1 pts
14Linn County1.4+0.9 pts
15Harney County0.8-0.6 pts
15Lake County0.8-2.8 pts
15Marion County0.8+0.5 pts
18Wasco County0.6+0.3 pts
19Benton County0.5+0.2 pts
19Multnomah County0.5+0.2 pts
19Washington County0.50 pts
22Columbia County0.3+0.3 pts
22Douglas County0.3+0.3 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 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: 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), 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: 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), 2015. 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=2015. 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), 2015. 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=2015.

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), 2015 [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=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: 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), 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/unhealthy-air-quality-days-share/oregon-counties?period=2015. 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), 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/unhealthy-air-quality-days-share/oregon-counties?period=2015
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/unhealthy-air-quality-days-share/oregon-counties?period=2015.
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)?

Jackson County, with 7.9% in 2015, according to EPA.

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

Douglas County, with 0.3% 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: 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 2015 and are not ranked.

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

Counties in Oregon: more rankings