EnviroNearby

Union County, North Carolina air quality history

Daily Air Quality Index summaries from EPA monitors in Union, North Carolina, 1999–2025.

91%
Good days in 2025
40
Median daily AQI, 2025
0
Days above 100 in 2025
245
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Union, North Carolina on 245 days. 223 of those days (91%) were in the Good range, and the median daily AQI was 40. That median is about the same as the typical monitored county in North Carolina (median 39 across 33 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 245 days. Across the years with fuller monitoring, the share of Good days rose: an average of 54% in 1999–2001 versus 87% in 2023–2025.

EPA did not report an AQI for every day of 2025 here (245 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.

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%1999: Good 95 of 188 days1999: Moderate 53 of 188 days1999: Unhealthy for Sensitive Groups 27 of 188 days1999: Unhealthy 13 of 188 days19992000: Good 130 of 198 days2000: Moderate 51 of 198 days2000: Unhealthy for Sensitive Groups 14 of 198 days2000: Unhealthy 3 of 198 days2001: Good 96 of 206 days2001: Moderate 70 of 206 days2001: Unhealthy for Sensitive Groups 39 of 206 days2001: Unhealthy 1 of 206 days20012002: Good 100 of 214 days2002: Moderate 65 of 214 days2002: Unhealthy for Sensitive Groups 34 of 214 days2002: Unhealthy 13 of 214 days2002: Very Unhealthy 2 of 214 days2003: Good 140 of 207 days2003: Moderate 56 of 207 days2003: Unhealthy for Sensitive Groups 10 of 207 days2003: Very Unhealthy 1 of 207 days20032004: Good 151 of 214 days2004: Moderate 50 of 214 days2004: Unhealthy for Sensitive Groups 13 of 214 days2005: Good 117 of 212 days2005: Moderate 67 of 212 days2005: Unhealthy for Sensitive Groups 27 of 212 days2005: Unhealthy 1 of 212 days20052006: Good 89 of 166 days2006: Moderate 61 of 166 days2006: Unhealthy for Sensitive Groups 14 of 166 days2006: Unhealthy 2 of 166 days2007: Good 90 of 199 days2007: Moderate 86 of 199 days2007: Unhealthy for Sensitive Groups 20 of 199 days2007: Unhealthy 3 of 199 days20072008: Good 133 of 213 days2008: Moderate 63 of 213 days2008: Unhealthy for Sensitive Groups 16 of 213 days2008: Unhealthy 1 of 213 days2009: Good 168 of 210 days2009: Moderate 40 of 210 days2009: Unhealthy for Sensitive Groups 2 of 210 days20092010: Good 139 of 221 days2010: Moderate 75 of 221 days2010: Unhealthy for Sensitive Groups 7 of 221 days2011: Good 133 of 209 days2011: Moderate 62 of 209 days2011: Unhealthy for Sensitive Groups 14 of 209 days20112012: Good 165 of 214 days2012: Moderate 44 of 214 days2012: Unhealthy for Sensitive Groups 4 of 214 days2012: Very Unhealthy 1 of 214 days2013: Good 182 of 205 days2013: Moderate 23 of 205 days20132014: Good 166 of 214 days2014: Moderate 46 of 214 days2014: Unhealthy for Sensitive Groups 2 of 214 days2015: Good 153 of 209 days2015: Moderate 55 of 209 days2015: Unhealthy for Sensitive Groups 1 of 209 days20152016: Good 165 of 209 days2016: Moderate 41 of 209 days2016: Unhealthy for Sensitive Groups 3 of 209 days2017: Good 204 of 236 days2017: Moderate 31 of 236 days2017: Unhealthy for Sensitive Groups 1 of 236 days20172018: Good 143 of 189 days2018: Moderate 43 of 189 days2018: Unhealthy for Sensitive Groups 3 of 189 days2019: Good 175 of 235 days2019: Moderate 57 of 235 days2019: Unhealthy for Sensitive Groups 3 of 235 days20192020: Good 242 of 242 days2021: Good 209 of 244 days2021: Moderate 34 of 244 days2021: Unhealthy for Sensitive Groups 1 of 244 days20212022: Good 218 of 244 days2022: Moderate 26 of 244 days2023: Good 201 of 245 days2023: Moderate 43 of 245 days2023: Unhealthy for Sensitive Groups 1 of 245 days20232024: Good 212 of 245 days2024: Moderate 33 of 245 days2025: Good 223 of 245 days2025: Moderate 22 of 245 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 year0501001501999: 90th percentile AQI 1332000: 90th percentile AQI 902001: 90th percentile AQI 1122002: 90th percentile AQI 1432003: 90th percentile AQI 932004: 90th percentile AQI 902005: 90th percentile AQI 1082006: 90th percentile AQI 1002007: 90th percentile AQI 1082008: 90th percentile AQI 972009: 90th percentile AQI 712010: 90th percentile AQI 802011: 90th percentile AQI 872012: 90th percentile AQI 712013: 90th percentile AQI 512014: 90th percentile AQI 712015: 90th percentile AQI 712016: 90th percentile AQI 672017: 90th percentile AQI 582018: 90th percentile AQI 672019: 90th percentile AQI 642020: 90th percentile AQI 442021: 90th percentile AQI 582022: 90th percentile AQI 512023: 90th percentile AQI 672024: 90th percentile AQI 542025: 90th percentile AQI 501999: Median AQI 502000: Median AQI 442001: Median AQI 542002: Median AQI 542003: Median AQI 452004: Median AQI 412005: Median AQI 472006: Median AQI 492007: Median AQI 512008: Median AQI 472009: Median AQI 422010: Median AQI 452011: Median AQI 452012: Median AQI 402013: Median AQI 382014: Median AQI 442015: Median AQI 442016: Median AQI 442017: Median AQI 432018: Median AQI 442019: Median AQI 452020: Median AQI 312021: Median AQI 422022: Median AQI 412023: Median AQI 432024: Median AQI 412025: Median AQI 4019992001200320052007200920112013201520172019202120232025
  • 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
Ozone245100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025245223220000405090Ozone
2024245212330000415497Ozone
20232452014310004367101Ozone
20222442182600004151100Ozone
20212442093410004258101Ozone
202024224200000314450Ozone
20192351755730004564105Ozone
20181891434330004467122Ozone
20172362043110004358115Ozone
20162091654130004467108Ozone
20152091535510004471101Ozone
20142141664620004471115Ozone
2013205182230000385184Ozone
20122141654440104071206Ozone
201120913362140004587126Ozone
20102211397570004580115Ozone
20092101684020004271133Ozone
200821313363161004797161Ozone
200719990862030051108177Ozone
200616689611420049100177Ozone
2005212117672710047108159Ozone
200421415150130004190133Ozone
200320714056100104593201Ozone
20022141006534132054143212Ozone
200120696703910054112177Ozone
200019813051143004490154Ozone
1999188955327130050133187Ozone

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 North Carolina with a similar median AQI in 2025

All monitored counties in North Carolina

Source: U.S. EPA AirData, “Annual AQI by County” files for 1999–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem