EnviroNearby

Jefferson County, Kentucky air quality history

Daily Air Quality Index summaries from EPA monitors in Jefferson, Kentucky, 1980–2025.

52%
Good days in 2025
49
Median daily AQI, 2025
10
Days above 100 in 2025
365
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Jefferson, Kentucky on 365 days. 188 of those days (52%) were in the Good range, and the median daily AQI was 49. That median is higher than the typical monitored county in Kentucky (median 39 across 25 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 213 days. Across the years with fuller monitoring, the share of Good days rose: an average of 28% in 1980–1982 versus 45% in 2023–2025.

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%1980: Good 84 of 366 days1980: Moderate 154 of 366 days1980: Unhealthy for Sensitive Groups 64 of 366 days1980: Unhealthy 39 of 366 days1980: Very Unhealthy 25 of 366 days19801981: Good 104 of 365 days1981: Moderate 199 of 365 days1981: Unhealthy for Sensitive Groups 49 of 365 days1981: Unhealthy 8 of 365 days1981: Very Unhealthy 5 of 365 days1982: Good 119 of 365 days1982: Moderate 196 of 365 days1982: Unhealthy for Sensitive Groups 37 of 365 days1982: Unhealthy 9 of 365 days1982: Very Unhealthy 4 of 365 days1983: Good 115 of 365 days1983: Moderate 172 of 365 days1983: Unhealthy for Sensitive Groups 38 of 365 days1983: Unhealthy 26 of 365 days1983: Very Unhealthy 14 of 365 days1984: Good 156 of 366 days1984: Moderate 147 of 366 days1984: Unhealthy for Sensitive Groups 34 of 366 days1984: Unhealthy 22 of 366 days1984: Very Unhealthy 7 of 366 days1985: Good 244 of 365 days1985: Moderate 87 of 365 days1985: Unhealthy for Sensitive Groups 25 of 365 days1985: Unhealthy 8 of 365 days1985: Very Unhealthy 1 of 365 days19851986: Good 207 of 365 days1986: Moderate 126 of 365 days1986: Unhealthy for Sensitive Groups 22 of 365 days1986: Unhealthy 8 of 365 days1986: Very Unhealthy 2 of 365 days1987: Good 200 of 365 days1987: Moderate 112 of 365 days1987: Unhealthy for Sensitive Groups 43 of 365 days1987: Unhealthy 9 of 365 days1987: Very Unhealthy 1 of 365 days1988: Good 215 of 366 days1988: Moderate 94 of 366 days1988: Unhealthy for Sensitive Groups 32 of 366 days1988: Unhealthy 20 of 366 days1988: Very Unhealthy 5 of 366 days1989: Good 268 of 365 days1989: Moderate 76 of 365 days1989: Unhealthy for Sensitive Groups 16 of 365 days1989: Unhealthy 5 of 365 days1990: Good 243 of 365 days1990: Moderate 106 of 365 days1990: Unhealthy for Sensitive Groups 15 of 365 days1990: Unhealthy 1 of 365 days19901991: Good 279 of 365 days1991: Moderate 62 of 365 days1991: Unhealthy for Sensitive Groups 16 of 365 days1991: Unhealthy 8 of 365 days1992: Good 290 of 366 days1992: Moderate 72 of 366 days1992: Unhealthy for Sensitive Groups 3 of 366 days1992: Unhealthy 1 of 366 days1993: Good 256 of 365 days1993: Moderate 80 of 365 days1993: Unhealthy for Sensitive Groups 20 of 365 days1993: Unhealthy 7 of 365 days1993: Very Unhealthy 2 of 365 days1994: Good 202 of 365 days1994: Moderate 114 of 365 days1994: Unhealthy for Sensitive Groups 33 of 365 days1994: Unhealthy 15 of 365 days1994: Very Unhealthy 1 of 365 days1995: Good 230 of 365 days1995: Moderate 94 of 365 days1995: Unhealthy for Sensitive Groups 27 of 365 days1995: Unhealthy 14 of 365 days19951996: Good 263 of 366 days1996: Moderate 68 of 366 days1996: Unhealthy for Sensitive Groups 26 of 366 days1996: Unhealthy 8 of 366 days1996: Very Unhealthy 1 of 366 days1997: Good 248 of 365 days1997: Moderate 76 of 365 days1997: Unhealthy for Sensitive Groups 29 of 365 days1997: Unhealthy 12 of 365 days1998: Good 222 of 365 days1998: Moderate 88 of 365 days1998: Unhealthy for Sensitive Groups 38 of 365 days1998: Unhealthy 15 of 365 days1998: Very Unhealthy 2 of 365 days1999: Good 54 of 365 days1999: Moderate 234 of 365 days1999: Unhealthy for Sensitive Groups 57 of 365 days1999: Unhealthy 19 of 365 days1999: Very Unhealthy 1 of 365 days2000: Good 39 of 366 days2000: Moderate 285 of 366 days2000: Unhealthy for Sensitive Groups 36 of 366 days2000: Unhealthy 6 of 366 days20002001: Good 50 of 365 days2001: Moderate 263 of 365 days2001: Unhealthy for Sensitive Groups 49 of 365 days2001: Unhealthy 3 of 365 days2002: Good 32 of 365 days2002: Moderate 284 of 365 days2002: Unhealthy for Sensitive Groups 31 of 365 days2002: Unhealthy 18 of 365 days2003: Good 49 of 365 days2003: Moderate 291 of 365 days2003: Unhealthy for Sensitive Groups 23 of 365 days2003: Unhealthy 2 of 365 days2004: Good 69 of 366 days2004: Moderate 289 of 366 days2004: Unhealthy for Sensitive Groups 7 of 366 days2004: Unhealthy 1 of 366 days2005: Good 50 of 365 days2005: Moderate 268 of 365 days2005: Unhealthy for Sensitive Groups 44 of 365 days2005: Unhealthy 3 of 365 days20052006: Good 70 of 365 days2006: Moderate 276 of 365 days2006: Unhealthy for Sensitive Groups 18 of 365 days2006: Unhealthy 1 of 365 days2007: Good 65 of 365 days2007: Moderate 255 of 365 days2007: Unhealthy for Sensitive Groups 38 of 365 days2007: Unhealthy 7 of 365 days2008: Good 85 of 366 days2008: Moderate 267 of 366 days2008: Unhealthy for Sensitive Groups 13 of 366 days2008: Unhealthy 1 of 366 days2009: Good 278 of 365 days2009: Moderate 81 of 365 days2009: Unhealthy for Sensitive Groups 6 of 365 days2010: Good 207 of 365 days2010: Moderate 132 of 365 days2010: Unhealthy for Sensitive Groups 23 of 365 days2010: Unhealthy 3 of 365 days20102011: Good 130 of 365 days2011: Moderate 210 of 365 days2011: Unhealthy for Sensitive Groups 22 of 365 days2011: Unhealthy 3 of 365 days2012: Good 77 of 366 days2012: Moderate 261 of 366 days2012: Unhealthy for Sensitive Groups 22 of 366 days2012: Unhealthy 5 of 366 days2012: Very Unhealthy 1 of 366 days2013: Good 68 of 365 days2013: Moderate 297 of 365 days2014: Good 90 of 365 days2014: Moderate 271 of 365 days2014: Unhealthy for Sensitive Groups 3 of 365 days2014: Unhealthy 1 of 365 days2015: Good 113 of 365 days2015: Moderate 243 of 365 days2015: Unhealthy for Sensitive Groups 5 of 365 days2015: Unhealthy 4 of 365 days20152016: Good 121 of 366 days2016: Moderate 230 of 366 days2016: Unhealthy for Sensitive Groups 14 of 366 days2016: Unhealthy 1 of 366 days2017: Good 133 of 365 days2017: Moderate 228 of 365 days2017: Unhealthy for Sensitive Groups 4 of 365 days2018: Good 125 of 365 days2018: Moderate 232 of 365 days2018: Unhealthy for Sensitive Groups 6 of 365 days2018: Unhealthy 2 of 365 days2019: Good 124 of 365 days2019: Moderate 239 of 365 days2019: Unhealthy for Sensitive Groups 2 of 365 days2020: Good 151 of 366 days2020: Moderate 208 of 366 days2020: Unhealthy for Sensitive Groups 7 of 366 days20202021: Good 138 of 365 days2021: Moderate 221 of 365 days2021: Unhealthy for Sensitive Groups 6 of 365 days2022: Good 147 of 365 days2022: Moderate 211 of 365 days2022: Unhealthy for Sensitive Groups 7 of 365 days2023: Good 123 of 365 days2023: Moderate 226 of 365 days2023: Unhealthy for Sensitive Groups 15 of 365 days2023: Unhealthy 1 of 365 days2024: Good 186 of 366 days2024: Moderate 168 of 366 days2024: Unhealthy for Sensitive Groups 11 of 366 days2024: Unhealthy 1 of 366 days2025: Good 188 of 365 days2025: Moderate 167 of 365 days2025: Unhealthy for Sensitive Groups 9 of 365 days2025: Unhealthy 1 of 365 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 year0501001502001980: 90th percentile AQI 1771981: 90th percentile AQI 1221982: 90th percentile AQI 1121983: 90th percentile AQI 1541984: 90th percentile AQI 1361985: 90th percentile AQI 1001986: 90th percentile AQI 971987: 90th percentile AQI 1121988: 90th percentile AQI 1331989: 90th percentile AQI 711990: 90th percentile AQI 781991: 90th percentile AQI 791992: 90th percentile AQI 621993: 90th percentile AQI 871994: 90th percentile AQI 1081995: 90th percentile AQI 1081996: 90th percentile AQI 971997: 90th percentile AQI 1051998: 90th percentile AQI 1191999: 90th percentile AQI 1332000: 90th percentile AQI 1052001: 90th percentile AQI 1052002: 90th percentile AQI 1192003: 90th percentile AQI 912004: 90th percentile AQI 852005: 90th percentile AQI 1062006: 90th percentile AQI 902007: 90th percentile AQI 1052008: 90th percentile AQI 872009: 90th percentile AQI 642010: 90th percentile AQI 932011: 90th percentile AQI 872012: 90th percentile AQI 872013: 90th percentile AQI 722014: 90th percentile AQI 802015: 90th percentile AQI 742016: 90th percentile AQI 802017: 90th percentile AQI 672018: 90th percentile AQI 772019: 90th percentile AQI 712020: 90th percentile AQI 642021: 90th percentile AQI 742022: 90th percentile AQI 712023: 90th percentile AQI 812024: 90th percentile AQI 712025: 90th percentile AQI 671980: Median AQI 831981: Median AQI 661982: Median AQI 641983: Median AQI 631984: Median AQI 551985: Median AQI 431986: Median AQI 471987: Median AQI 481988: Median AQI 461989: Median AQI 421990: Median AQI 431991: Median AQI 381992: Median AQI 381993: Median AQI 411994: Median AQI 481995: Median AQI 431996: Median AQI 421997: Median AQI 421998: Median AQI 431999: Median AQI 682000: Median AQI 662001: Median AQI 692002: Median AQI 652003: Median AQI 632004: Median AQI 612005: Median AQI 662006: Median AQI 622007: Median AQI 632008: Median AQI 592009: Median AQI 402010: Median AQI 452011: Median AQI 552012: Median AQI 582013: Median AQI 582014: Median AQI 582015: Median AQI 552016: Median AQI 542017: Median AQI 542018: Median AQI 542019: Median AQI 542020: Median AQI 522021: Median AQI 542022: Median AQI 532023: Median AQI 552024: Median AQI 502025: Median AQI 491980198519901995200020052010201520202025
  • 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)21358%
Ozone14740%
Nitrogen dioxide (NO₂)51%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536518816791004967153PM2.5
2024366186168111005071156PM2.5
2023365123226151005581171PM2.5
202236514721170005371136PM2.5
202136513822160005474126PM2.5
202036615120870005264115PM2.5
201936512423920005471136PM2.5
201836512523262005477166PM2.5
201736513322840005467112PM2.5
2016366121230141005480151PM2.5
201536511324354005574174PM2.5
20143659027131005880169PM2.5
2013365682970000587297PM2.5
201236677261225105887202PM2.5
2011365130210223005587177PM2.5
2010365207132233004593177Ozone
20093652788160004064150Ozone
200836685267131005987159PM2.5
2007365652553870063105182PM2.5
200636570276181006290159PM2.5
2005365502684430066106164PM2.5
20043666928971006185169PM2.5
200336549291232006391177PM2.5
20023653228431180065119197PM2.5
2001365502634930069105155PM2.5
2000366392853660066105192PM2.5
19993655423457191068133202PM2.5
19983652228838152043119218Ozone
19973652487629120042105200Ozone
199636626368268104297202Ozone
19953652309427140043108197Ozone
199436520211433151048108221NO2
199336525680207204187206Ozone
19923662907231003862151Ozone
199136527962168003879195Ozone
1990365243106151004378154CO
198936526876165004271197CO
19883662159432205046133225Ozone
19873652001124391048112222Ozone
1986365207126228204797205NO2
1985365244872581043100223Ozone
198436615614734227055136234CO
1983365115172382614063154237CO
19823651191963794064112222CO
19813651041994985066122222CO
198036684154643925083177245CO

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 Kentucky with a similar median AQI in 2025

All monitored counties in Kentucky

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem