EnviroNearby

Union County, Arkansas air quality history

Daily Air Quality Index summaries from EPA monitors in Union, Arkansas, 1989–2025.

42%
Good days in 2025
52
Median daily AQI, 2025
0
Days above 100 in 2025
122
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Union, Arkansas on 122 days. 51 of those days (42%) were in the Good range, and the median daily AQI was 52. That median is higher than the typical monitored county in Arkansas (median 46 across 11 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 122 days. Across the years with fuller monitoring, the share of Good days rose: an average of 48% in 2010–2014 versus 51% in 2020–2025.

EPA did not report an AQI for every day of 2025 here (122 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

Years with fewer than 120 monitored days (2011, 2012, 2015, 2021, 2022, 2023…) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%1989: Good 32 of 34 days1989: Moderate 2 of 34 days19891990: Good 56 of 56 days1991: Good 59 of 60 days1991: Moderate 1 of 60 days1992: Good 57 of 60 days1992: Moderate 3 of 60 days1993: Good 55 of 56 days1993: Moderate 1 of 56 days1994: Good 58 of 58 days19941995: Good 56 of 57 days1995: Moderate 1 of 57 days1996: Good 54 of 55 days1996: Moderate 1 of 55 days1997: Good 53 of 54 days1997: Moderate 1 of 54 days1999: Good 4 of 25 days1999: Moderate 21 of 25 days2000: Good 19 of 97 days2000: Moderate 77 of 97 days2000: Unhealthy for Sensitive Groups 1 of 97 days20002001: Good 27 of 92 days2001: Moderate 64 of 92 days2001: Unhealthy for Sensitive Groups 1 of 92 days2002: Good 34 of 112 days2002: Moderate 77 of 112 days2002: Unhealthy for Sensitive Groups 1 of 112 days2003: Good 37 of 102 days2003: Moderate 65 of 102 days2004: Good 41 of 108 days2004: Moderate 67 of 108 days2005: Good 26 of 108 days2005: Moderate 79 of 108 days2005: Unhealthy for Sensitive Groups 3 of 108 days20052006: Good 39 of 112 days2006: Moderate 73 of 112 days2007: Good 34 of 108 days2007: Moderate 74 of 108 days2008: Good 42 of 105 days2008: Moderate 63 of 105 days2009: Good 48 of 102 days2009: Moderate 54 of 102 days2010: Good 38 of 120 days2010: Moderate 82 of 120 days20102011: Good 34 of 116 days2011: Moderate 82 of 116 days2012: Good 48 of 114 days2012: Moderate 66 of 114 days2013: Good 66 of 120 days2013: Moderate 54 of 120 days2014: Good 69 of 121 days2014: Moderate 52 of 121 days2015: Good 73 of 119 days2015: Moderate 46 of 119 days20152016: Good 66 of 122 days2016: Moderate 56 of 122 days2017: Good 164 of 365 days2017: Moderate 201 of 365 days2018: Good 189 of 365 days2018: Moderate 173 of 365 days2018: Unhealthy for Sensitive Groups 3 of 365 days2019: Good 135 of 241 days2019: Moderate 106 of 241 days2020: Good 74 of 121 days2020: Moderate 47 of 121 days20202021: Good 66 of 116 days2021: Moderate 50 of 116 days2022: Good 65 of 115 days2022: Moderate 50 of 115 days2023: Good 59 of 119 days2023: Moderate 59 of 119 days2023: Unhealthy for Sensitive Groups 1 of 119 days2024: Good 62 of 121 days2024: Moderate 59 of 121 days2025: Good 51 of 122 days2025: Moderate 71 of 122 days2025
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501001989: 90th percentile AQI 441990: 90th percentile AQI 401991: 90th percentile AQI 351992: 90th percentile AQI 391993: 90th percentile AQI 351994: 90th percentile AQI 361995: 90th percentile AQI 431996: 90th percentile AQI 331997: 90th percentile AQI 311999: 90th percentile AQI 792000: 90th percentile AQI 802001: 90th percentile AQI 792002: 90th percentile AQI 692003: 90th percentile AQI 722004: 90th percentile AQI 732005: 90th percentile AQI 822006: 90th percentile AQI 722007: 90th percentile AQI 752008: 90th percentile AQI 682009: 90th percentile AQI 632010: 90th percentile AQI 662011: 90th percentile AQI 662012: 90th percentile AQI 672013: 90th percentile AQI 652014: 90th percentile AQI 612015: 90th percentile AQI 602016: 90th percentile AQI 592017: 90th percentile AQI 622018: 90th percentile AQI 632019: 90th percentile AQI 592020: 90th percentile AQI 572021: 90th percentile AQI 602022: 90th percentile AQI 612023: 90th percentile AQI 632024: 90th percentile AQI 622025: 90th percentile AQI 621989: Median AQI 231990: Median AQI 221991: Median AQI 191992: Median AQI 201993: Median AQI 201994: Median AQI 221995: Median AQI 201996: Median AQI 201997: Median AQI 191999: Median AQI 592000: Median AQI 592001: Median AQI 562002: Median AQI 542003: Median AQI 542004: Median AQI 542005: Median AQI 612006: Median AQI 542007: Median AQI 562008: Median AQI 532009: Median AQI 522010: Median AQI 552011: Median AQI 542012: Median AQI 542013: Median AQI 472014: Median AQI 462015: Median AQI 432016: Median AQI 472017: Median AQI 522018: Median AQI 492019: Median AQI 462020: Median AQI 452021: Median AQI 482022: Median AQI 472023: Median AQI 512024: Median AQI 492025: Median AQI 5219891994200020052010201520202025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Fine particles (PM2.5)122100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202512251710000526273PM2.5
202412162590000496293PM2.5
2023119595910005163102PM2.5
2022115655000004761100PM2.5
202111666500000486074PM2.5
202012174470000455790PM2.5
20192411351060000465999PM2.5
201836518917330004963122PM2.5
20173651642010000526292PM2.5
201612266560000475974PM2.5
201511973460000436077PM2.5
201412169520000466173PM2.5
201312066540000476599PM2.5
201211448660000546790PM2.5
201111634820000546689PM2.5
201012038820000556696PM2.5
200910248540000526379PM2.5
200810542630000536880PM2.5
2007108347400005675100PM2.5
200611239730000547284PM2.5
2005108267930006182115PM2.5
200410841670000547387PM2.5
200310237650000547282PM2.5
2002112347710005469125PM2.5
200192276410005679102PM2.5
200097197710005980101PM2.5
1999254210000597980PM2.5
1997545310000193151PM10
1996555410000203351PM10
1995575610000204356PM10
1994585800000223644PM10
1993565510000203554PM10
1992605730000203964PM10
1991605910000193559PM10
1990565600000224047PM10
1989343220000234453PM10

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in Arkansas with a similar median AQI in 2025

All monitored counties in Arkansas

Source: U.S. EPA AirData, “Annual AQI by County” files for 1989–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem