EnviroNearby

Clark County, Ohio air quality history

Daily Air Quality Index summaries from EPA monitors in Clark, Ohio, 1980–2025.

61%
Good days in 2025
45
Median daily AQI, 2025
2
Days above 100 in 2025
363
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Clark, Ohio on 363 days. 223 of those days (61%) were in the Good range, and the median daily AQI was 45. That median is about the same as the typical monitored county in Ohio (median 43 across 36 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 222 days. Across the years with fuller monitoring, the share of Good days fell: an average of 75% in 1980–1982 versus 60% 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 269 of 351 days1980: Moderate 51 of 351 days1980: Unhealthy for Sensitive Groups 24 of 351 days1980: Unhealthy 7 of 351 days19801981: Good 268 of 331 days1981: Moderate 34 of 331 days1981: Unhealthy for Sensitive Groups 19 of 331 days1981: Unhealthy 7 of 331 days1981: Very Unhealthy 3 of 331 days1982: Good 195 of 294 days1982: Moderate 54 of 294 days1982: Unhealthy for Sensitive Groups 28 of 294 days1982: Unhealthy 14 of 294 days1982: Very Unhealthy 3 of 294 days1983: Good 244 of 342 days1983: Moderate 41 of 342 days1983: Unhealthy for Sensitive Groups 32 of 342 days1983: Unhealthy 20 of 342 days1983: Very Unhealthy 5 of 342 days1984: Good 262 of 329 days1984: Moderate 49 of 329 days1984: Unhealthy for Sensitive Groups 18 of 329 days1985: Good 291 of 360 days1985: Moderate 50 of 360 days1985: Unhealthy for Sensitive Groups 15 of 360 days1985: Unhealthy 4 of 360 days19851986: Good 231 of 314 days1986: Moderate 51 of 314 days1986: Unhealthy for Sensitive Groups 25 of 314 days1986: Unhealthy 5 of 314 days1986: Very Unhealthy 2 of 314 days1987: Good 119 of 237 days1987: Moderate 62 of 237 days1987: Unhealthy for Sensitive Groups 34 of 237 days1987: Unhealthy 21 of 237 days1987: Very Unhealthy 1 of 237 days1988: Good 125 of 228 days1988: Moderate 45 of 228 days1988: Unhealthy for Sensitive Groups 25 of 228 days1988: Unhealthy 16 of 228 days1988: Very Unhealthy 17 of 228 days1989: Good 116 of 213 days1989: Moderate 62 of 213 days1989: Unhealthy for Sensitive Groups 26 of 213 days1989: Unhealthy 6 of 213 days1989: Very Unhealthy 3 of 213 days1990: Good 138 of 214 days1990: Moderate 39 of 214 days1990: Unhealthy for Sensitive Groups 27 of 214 days1990: Unhealthy 10 of 214 days19901991: Good 109 of 214 days1991: Moderate 63 of 214 days1991: Unhealthy for Sensitive Groups 31 of 214 days1991: Unhealthy 10 of 214 days1991: Very Unhealthy 1 of 214 days1992: Good 157 of 214 days1992: Moderate 44 of 214 days1992: Unhealthy for Sensitive Groups 11 of 214 days1992: Unhealthy 2 of 214 days1993: Good 138 of 214 days1993: Moderate 56 of 214 days1993: Unhealthy for Sensitive Groups 17 of 214 days1993: Unhealthy 3 of 214 days1994: Good 112 of 214 days1994: Moderate 60 of 214 days1994: Unhealthy for Sensitive Groups 31 of 214 days1994: Unhealthy 9 of 214 days1994: Very Unhealthy 2 of 214 days1995: Good 103 of 214 days1995: Moderate 65 of 214 days1995: Unhealthy for Sensitive Groups 37 of 214 days1995: Unhealthy 8 of 214 days1995: Very Unhealthy 1 of 214 days19951996: Good 115 of 214 days1996: Moderate 59 of 214 days1996: Unhealthy for Sensitive Groups 27 of 214 days1996: Unhealthy 11 of 214 days1996: Very Unhealthy 2 of 214 days1997: Good 111 of 214 days1997: Moderate 75 of 214 days1997: Unhealthy for Sensitive Groups 20 of 214 days1997: Unhealthy 7 of 214 days1997: Very Unhealthy 1 of 214 days1998: Good 87 of 214 days1998: Moderate 80 of 214 days1998: Unhealthy for Sensitive Groups 31 of 214 days1998: Unhealthy 15 of 214 days1998: Very Unhealthy 1 of 214 days1999: Good 113 of 214 days1999: Moderate 53 of 214 days1999: Unhealthy for Sensitive Groups 34 of 214 days1999: Unhealthy 14 of 214 days2000: Good 112 of 234 days2000: Moderate 106 of 234 days2000: Unhealthy for Sensitive Groups 12 of 234 days2000: Unhealthy 3 of 234 days2000: Very Unhealthy 1 of 234 days20002001: Good 109 of 259 days2001: Moderate 127 of 259 days2001: Unhealthy for Sensitive Groups 20 of 259 days2001: Unhealthy 3 of 259 days2002: Good 98 of 263 days2002: Moderate 108 of 263 days2002: Unhealthy for Sensitive Groups 35 of 263 days2002: Unhealthy 21 of 263 days2002: Very Unhealthy 1 of 263 days2003: Good 129 of 264 days2003: Moderate 117 of 264 days2003: Unhealthy for Sensitive Groups 15 of 264 days2003: Unhealthy 1 of 264 days2003: Very Unhealthy 2 of 264 days2004: Good 126 of 265 days2004: Moderate 124 of 265 days2004: Unhealthy for Sensitive Groups 14 of 265 days2004: Unhealthy 1 of 265 days2005: Good 102 of 262 days2005: Moderate 131 of 262 days2005: Unhealthy for Sensitive Groups 24 of 262 days2005: Unhealthy 5 of 262 days20052006: Good 128 of 265 days2006: Moderate 123 of 265 days2006: Unhealthy for Sensitive Groups 13 of 265 days2006: Unhealthy 1 of 265 days2007: Good 112 of 264 days2007: Moderate 131 of 264 days2007: Unhealthy for Sensitive Groups 19 of 264 days2007: Unhealthy 2 of 264 days2008: Good 130 of 263 days2008: Moderate 122 of 263 days2008: Unhealthy for Sensitive Groups 10 of 263 days2008: Unhealthy 1 of 263 days2009: Good 151 of 264 days2009: Moderate 105 of 264 days2009: Unhealthy for Sensitive Groups 8 of 264 days2010: Good 123 of 350 days2010: Moderate 217 of 350 days2010: Unhealthy for Sensitive Groups 10 of 350 days20102011: Good 140 of 365 days2011: Moderate 210 of 365 days2011: Unhealthy for Sensitive Groups 15 of 365 days2012: Good 110 of 363 days2012: Moderate 231 of 363 days2012: Unhealthy for Sensitive Groups 21 of 363 days2012: Unhealthy 1 of 363 days2013: Good 157 of 365 days2013: Moderate 202 of 365 days2013: Unhealthy for Sensitive Groups 6 of 365 days2014: Good 175 of 365 days2014: Moderate 189 of 365 days2014: Unhealthy for Sensitive Groups 1 of 365 days2015: Good 183 of 365 days2015: Moderate 175 of 365 days2015: Unhealthy for Sensitive Groups 7 of 365 days20152016: Good 200 of 363 days2016: Moderate 157 of 363 days2016: Unhealthy for Sensitive Groups 6 of 363 days2017: Good 209 of 365 days2017: Moderate 154 of 365 days2017: Unhealthy for Sensitive Groups 2 of 365 days2018: Good 170 of 362 days2018: Moderate 188 of 362 days2018: Unhealthy for Sensitive Groups 4 of 362 days2019: Good 147 of 362 days2019: Moderate 213 of 362 days2019: Unhealthy for Sensitive Groups 2 of 362 days2020: Good 218 of 343 days2020: Moderate 124 of 343 days2020: Unhealthy for Sensitive Groups 1 of 343 days20202021: Good 169 of 365 days2021: Moderate 196 of 365 days2022: Good 212 of 338 days2022: Moderate 125 of 338 days2022: Unhealthy for Sensitive Groups 1 of 338 days2023: Good 187 of 365 days2023: Moderate 170 of 365 days2023: Unhealthy for Sensitive Groups 5 of 365 days2023: Unhealthy 3 of 365 days2024: Good 239 of 363 days2024: Moderate 121 of 363 days2024: Unhealthy for Sensitive Groups 3 of 363 days2025: Good 223 of 363 days2025: Moderate 138 of 363 days2025: Unhealthy for Sensitive Groups 2 of 363 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 901981: 90th percentile AQI 871982: 90th percentile AQI 1291983: 90th percentile AQI 1291984: 90th percentile AQI 741985: 90th percentile AQI 871986: 90th percentile AQI 1011987: 90th percentile AQI 1501988: 90th percentile AQI 1771989: 90th percentile AQI 1261990: 90th percentile AQI 1291991: 90th percentile AQI 1221992: 90th percentile AQI 841993: 90th percentile AQI 1001994: 90th percentile AQI 1221995: 90th percentile AQI 1261996: 90th percentile AQI 1331997: 90th percentile AQI 1191998: 90th percentile AQI 1431999: 90th percentile AQI 1362000: 90th percentile AQI 932001: 90th percentile AQI 1002002: 90th percentile AQI 1362003: 90th percentile AQI 932004: 90th percentile AQI 872005: 90th percentile AQI 1052006: 90th percentile AQI 872007: 90th percentile AQI 972008: 90th percentile AQI 842009: 90th percentile AQI 742010: 90th percentile AQI 842011: 90th percentile AQI 802012: 90th percentile AQI 872013: 90th percentile AQI 712014: 90th percentile AQI 712015: 90th percentile AQI 712016: 90th percentile AQI 672017: 90th percentile AQI 662018: 90th percentile AQI 692019: 90th percentile AQI 672020: 90th percentile AQI 612021: 90th percentile AQI 682022: 90th percentile AQI 632023: 90th percentile AQI 712024: 90th percentile AQI 632025: 90th percentile AQI 651980: Median AQI 311981: Median AQI 311982: Median AQI 421983: Median AQI 371984: Median AQI 331985: Median AQI 361986: Median AQI 381987: Median AQI 501988: Median AQI 471989: Median AQI 491990: Median AQI 441991: Median AQI 501992: Median AQI 421993: Median AQI 451994: Median AQI 501995: Median AQI 511996: Median AQI 491997: Median AQI 491998: Median AQI 581999: Median AQI 502000: Median AQI 512001: Median AQI 542002: Median AQI 582003: Median AQI 512004: Median AQI 522005: Median AQI 602006: Median AQI 522007: Median AQI 542008: Median AQI 512009: Median AQI 472010: Median AQI 572011: Median AQI 542012: Median AQI 562013: Median AQI 522014: Median AQI 512015: Median AQI 502016: Median AQI 482017: Median AQI 472018: Median AQI 522019: Median AQI 532020: Median AQI 442021: Median AQI 522022: Median AQI 462023: Median AQI 502024: Median AQI 452025: Median AQI 451980198519901995200020052010201520202025
  • 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)22261%
Ozone14139%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536322313820004565126PM2.5
202436323912130004563133PM2.5
202336518717053005071196PM2.5
202233821212510004663129PM2.5
202136516919600005268100PM2.5
202034321812410004461108PM2.5
201936214721320005367105PM2.5
201836217018840005269140PM2.5
201736520915420004766105PM2.5
201636320015760004867119PM2.5
201536518317570005071133PM2.5
201436517518910005171105PM2.5
201336515720260005271112PM2.5
2012363110231211005687172PM2.5
2011365140210150005480140PM2.5
2010350123217100005784136PM2.5
200926415110580004774119Ozone
2008263130122101005184161Ozone
2007264112131192005497177Ozone
2006265128123131005287164Ozone
20052621021312450060105177Ozone
2004265126124141005287156Ozone
2003264129117151205193216Ozone
20022639810835211058136214Ozone
20012591091272030054100166Ozone
2000234112106123105193209Ozone
19992141135334140050136200Ozone
1998214878031151058143214Ozone
1997214111752071049119201Ozone
19962141155927112049133204Ozone
1995214103653781051126208Ozone
1994214112603192050122207Ozone
1993214138561730045100200Ozone
199221415744112004284179Ozone
19912141096331101050122203Ozone
19902141383927100044129200Ozone
1989213116622663049126227Ozone
198822812545251617047177230Ozone
19872371196234211050150204Ozone
1986314231512552038101218Ozone
198536029150154003687166Ozone
198432926249180003374147Ozone
19833422444132205037129206Ozone
19822941955428143042129214Ozone
198133126834197303187217Ozone
198035126951247003190200Ozone

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 Ohio with a similar median AQI in 2025

All monitored counties in Ohio

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