Data / Share of days unhealthy for sensitive groups or worse (US EPA AQI) / Union County

Share of days unhealthy for sensitive groups or worse (US EPA AQI) in Union County

Share of days unhealthy for sensitive groups or worse (US EPA AQI) in Union County was 0% in 2025, according to EPA. That is down 0.5 pts from 2024.

20250%
Change on 2024-0.5 pts
Series high32006
Series low01984

Next release: Tuesday, 13 July 2027, estimated by Invokely from past publication dates (low confidence), not announced by the publisher. Release calendar

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Share of days unhealthy for sensitive groups or worse (US EPA AQI) in Union County, 1984 to 2025

0123198419901996200220082014202020251984: 0 %1985: 0 %1986: 0 %1987: 0 %1988: 1.5 %1989: 0.6 %1990: 0.3 %1991: 0.3 %1992: 0 %1993: 0 %1994: 1.1 %1995: 0 %1996: 0 %1997: 0 %1998: 0 %1999: 0 %2000: 0.3 %2001: 0 %2002: 0.6 %2003: 0 %2004: 0.3 %2005: 1.4 %2006: 3 %2007: 0 %2008: 0 %2009: 0 %2010: 0.3 %2011: 1.4 %2012: 0.5 %2013: 1.4 %2014: 1.7 %2015: 3 %2016: 0 %2017: 3 %2018: 1.7 %2019: 0 %2020: 2.5 %2021: 1.9 %2022: 1.1 %2023: 0 %2024: 0.5 %2025: 0 %012319841998201220251984: 0 %1985: 0 %1986: 0 %1987: 0 %1988: 1.5 %1989: 0.6 %1990: 0.3 %1991: 0.3 %1992: 0 %1993: 0 %1994: 1.1 %1995: 0 %1996: 0 %1997: 0 %1998: 0 %1999: 0 %2000: 0.3 %2001: 0 %2002: 0.6 %2003: 0 %2004: 0.3 %2005: 1.4 %2006: 3 %2007: 0 %2008: 0 %2009: 0 %2010: 0.3 %2011: 1.4 %2012: 0.5 %2013: 1.4 %2014: 1.7 %2015: 3 %2016: 0 %2017: 3 %2018: 1.7 %2019: 0 %2020: 2.5 %2021: 1.9 %2022: 1.1 %2023: 0 %2024: 0.5 %2025: 0 %
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12, published 2026-07-13.
All 42 values
Period%
20250
20240.5
20230
20221.1
20211.9
20202.5
20190
20181.7
20173
20160
20153
20141.7
20131.4
20120.5
20111.4
20100.3
20090
20080
20070
20063
20051.4
20040.3
20030
20020.6
20010
20000.3
19990
19980
19970
19960
19950
19941.1
19930
19920
19910.3
19900.3
19890.6
19881.5
19870
19860
19850
19840

Union County compared with nearby places

Baker County: 0 %Clackamas County: 0.6 %Columbia County: 0 %Crook County: 0.5 %Deschutes County: 0.8 %Grant County: 0 %Harney County: 0 %Jackson County: 0.5 %Jefferson County: 0 %Josephine County: 2.2 %Klamath County: 0.8 %Lake County: 0.3 %Lane County: 1.6 %Linn County: 0.3 %Marion County: 0 %Multnomah County: 0 %Umatilla County: 0 %Union County: 0 %Wallowa County: 0 %Wasco County: 0 %Washington County: 0 %
  • Under 0.3
  • 0.3 to 0.6
  • 0.6 and over
  • No data
Share of days unhealthy for sensitive groups or worse (US EPA AQI), 2025, %. Union County is outlined. Same source and period for every area shown. Source: U.S. Environmental Protection Agency. Boundaries: U.S. Census Bureau cartographic boundary files.

Rankings

Definition

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.

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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 (Share of days unhealthy for sensitive groups or worse (US EPA AQI), Union County, 1984 to 2025) [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, Share of days unhealthy for sensitive groups or worse (US EPA AQI), Union County, 1984 to 2025. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/en/unhealthy-air-quality-days-share/union-county-oregon. 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. Share of days unhealthy for sensitive groups or worse (US EPA AQI), Union County, 1984 to 2025. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/en/unhealthy-air-quality-days-share/union-county-oregon.

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, Share of days unhealthy for sensitive groups or worse (US EPA AQI), Union County, 1984 to 2025 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/unhealthy-air-quality-days-share/union-county-oregon (Accessed: 12 October 2026).

BibTeX
@misc{environmental_share_of_days_unhealthy_2025,
  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: Share of days unhealthy for sensitive groups or worse (US EPA AQI), Union County, 1984 to 2025}},
  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/en/unhealthy-air-quality-days-share/union-county-oregon. 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: Share of days unhealthy for sensitive groups or worse (US EPA AQI), Union County, 1984 to 2025
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/en/unhealthy-air-quality-days-share/union-county-oregon
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/unhealthy-air-quality-days-share/union-county-oregon.
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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Questions

What is the share of days unhealthy for sensitive groups or worse (US EPA AQI) in Union County?

Share of days unhealthy for sensitive groups or worse (US EPA AQI) in Union County was 0% in 2025, according to EPA. That is down 0.5 pts from 2024.

Where does this figure come from?

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 by Invokely on 2026-10-12.

What was the highest share of days unhealthy for sensitive groups or worse (US EPA AQI) in Union County?

3% in 2006, the highest value since 1984 in this series.

Related statistics for Union County

All statistics for Union County | Union County in figures