EnviroNearby

Hamilton County, Ohio air quality history

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

34%
Good days in 2025
54
Median daily AQI, 2025
13
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 Hamilton, Ohio on 365 days. 125 of those days (34%) were in the Good range, and the median daily AQI was 54. That median is higher than 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 263 days. Across the years with fuller monitoring, the share of Good days fell: an average of 44% in 1980–1982 versus 38% 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 145 of 366 days1980: Moderate 142 of 366 days1980: Unhealthy for Sensitive Groups 51 of 366 days1980: Unhealthy 17 of 366 days1980: Very Unhealthy 11 of 366 days19801981: Good 191 of 365 days1981: Moderate 134 of 365 days1981: Unhealthy for Sensitive Groups 32 of 365 days1981: Unhealthy 8 of 365 days1982: Good 150 of 365 days1982: Moderate 147 of 365 days1982: Unhealthy for Sensitive Groups 50 of 365 days1982: Unhealthy 15 of 365 days1982: Very Unhealthy 3 of 365 days1983: Good 118 of 365 days1983: Moderate 104 of 365 days1983: Unhealthy for Sensitive Groups 103 of 365 days1983: Unhealthy 31 of 365 days1983: Very Unhealthy 9 of 365 days1984: Good 157 of 366 days1984: Moderate 169 of 366 days1984: Unhealthy for Sensitive Groups 26 of 366 days1984: Unhealthy 13 of 366 days1984: Very Unhealthy 1 of 366 days1985: Good 177 of 365 days1985: Moderate 155 of 365 days1985: Unhealthy for Sensitive Groups 27 of 365 days1985: Unhealthy 5 of 365 days1985: Very Unhealthy 1 of 365 days19851986: Good 187 of 365 days1986: Moderate 124 of 365 days1986: Unhealthy for Sensitive Groups 44 of 365 days1986: Unhealthy 8 of 365 days1986: Very Unhealthy 2 of 365 days1987: Good 164 of 365 days1987: Moderate 135 of 365 days1987: Unhealthy for Sensitive Groups 35 of 365 days1987: Unhealthy 26 of 365 days1987: Very Unhealthy 5 of 365 days1988: Good 195 of 366 days1988: Moderate 110 of 366 days1988: Unhealthy for Sensitive Groups 22 of 366 days1988: Unhealthy 30 of 366 days1988: Very Unhealthy 9 of 366 days1989: Good 185 of 365 days1989: Moderate 140 of 365 days1989: Unhealthy for Sensitive Groups 23 of 365 days1989: Unhealthy 16 of 365 days1989: Very Unhealthy 1 of 365 days1990: Good 206 of 365 days1990: Moderate 126 of 365 days1990: Unhealthy for Sensitive Groups 25 of 365 days1990: Unhealthy 6 of 365 days1990: Very Unhealthy 2 of 365 days19901991: Good 210 of 365 days1991: Moderate 118 of 365 days1991: Unhealthy for Sensitive Groups 22 of 365 days1991: Unhealthy 10 of 365 days1991: Very Unhealthy 5 of 365 days1992: Good 251 of 366 days1992: Moderate 107 of 366 days1992: Unhealthy for Sensitive Groups 7 of 366 days1992: Unhealthy 1 of 366 days1993: Good 243 of 365 days1993: Moderate 96 of 365 days1993: Unhealthy for Sensitive Groups 22 of 365 days1993: Unhealthy 4 of 365 days1994: Good 252 of 365 days1994: Moderate 82 of 365 days1994: Unhealthy for Sensitive Groups 17 of 365 days1994: Unhealthy 14 of 365 days1995: Good 234 of 365 days1995: Moderate 93 of 365 days1995: Unhealthy for Sensitive Groups 22 of 365 days1995: Unhealthy 14 of 365 days1995: Very Unhealthy 2 of 365 days19951996: Good 214 of 366 days1996: Moderate 109 of 366 days1996: Unhealthy for Sensitive Groups 34 of 366 days1996: Unhealthy 9 of 366 days1997: Good 210 of 365 days1997: Moderate 125 of 365 days1997: Unhealthy for Sensitive Groups 21 of 365 days1997: Unhealthy 9 of 365 days1998: Good 186 of 365 days1998: Moderate 132 of 365 days1998: Unhealthy for Sensitive Groups 38 of 365 days1998: Unhealthy 8 of 365 days1998: Very Unhealthy 1 of 365 days1999: Good 54 of 365 days1999: Moderate 259 of 365 days1999: Unhealthy for Sensitive Groups 42 of 365 days1999: Unhealthy 9 of 365 days1999: Very Unhealthy 1 of 365 days2000: Good 39 of 366 days2000: Moderate 293 of 366 days2000: Unhealthy for Sensitive Groups 31 of 366 days2000: Unhealthy 3 of 366 days20002001: Good 41 of 365 days2001: Moderate 276 of 365 days2001: Unhealthy for Sensitive Groups 42 of 365 days2001: Unhealthy 6 of 365 days2002: Good 34 of 365 days2002: Moderate 283 of 365 days2002: Unhealthy for Sensitive Groups 28 of 365 days2002: Unhealthy 18 of 365 days2002: Very Unhealthy 2 of 365 days2003: Good 40 of 365 days2003: Moderate 294 of 365 days2003: Unhealthy for Sensitive Groups 25 of 365 days2003: Unhealthy 6 of 365 days2004: Good 60 of 366 days2004: Moderate 283 of 366 days2004: Unhealthy for Sensitive Groups 23 of 366 days2005: Good 176 of 365 days2005: Moderate 138 of 365 days2005: Unhealthy for Sensitive Groups 39 of 365 days2005: Unhealthy 11 of 365 days2005: Very Unhealthy 1 of 365 days20052006: Good 193 of 365 days2006: Moderate 141 of 365 days2006: Unhealthy for Sensitive Groups 28 of 365 days2006: Unhealthy 3 of 365 days2007: Good 88 of 365 days2007: Moderate 219 of 365 days2007: Unhealthy for Sensitive Groups 50 of 365 days2007: Unhealthy 8 of 365 days2008: Good 150 of 366 days2008: Moderate 182 of 366 days2008: Unhealthy for Sensitive Groups 30 of 366 days2008: Unhealthy 4 of 366 days2009: Good 80 of 365 days2009: Moderate 277 of 365 days2009: Unhealthy for Sensitive Groups 8 of 365 days2010: Good 23 of 365 days2010: Moderate 311 of 365 days2010: Unhealthy for Sensitive Groups 28 of 365 days2010: Unhealthy 3 of 365 days20102011: Good 104 of 365 days2011: Moderate 230 of 365 days2011: Unhealthy for Sensitive Groups 26 of 365 days2011: Unhealthy 5 of 365 days2012: Good 46 of 366 days2012: Moderate 293 of 366 days2012: Unhealthy for Sensitive Groups 22 of 366 days2012: Unhealthy 5 of 366 days2013: Good 65 of 365 days2013: Moderate 296 of 365 days2013: Unhealthy for Sensitive Groups 4 of 365 days2014: Good 62 of 365 days2014: Moderate 292 of 365 days2014: Unhealthy for Sensitive Groups 11 of 365 days2015: Good 119 of 365 days2015: Moderate 240 of 365 days2015: Unhealthy for Sensitive Groups 5 of 365 days2015: Unhealthy 1 of 365 days20152016: Good 118 of 366 days2016: Moderate 236 of 366 days2016: Unhealthy for Sensitive Groups 12 of 366 days2017: Good 118 of 365 days2017: Moderate 242 of 365 days2017: Unhealthy for Sensitive Groups 5 of 365 days2018: Good 97 of 365 days2018: Moderate 260 of 365 days2018: Unhealthy for Sensitive Groups 7 of 365 days2018: Unhealthy 1 of 365 days2019: Good 99 of 365 days2019: Moderate 260 of 365 days2019: Unhealthy for Sensitive Groups 6 of 365 days2020: Good 105 of 366 days2020: Moderate 254 of 366 days2020: Unhealthy for Sensitive Groups 7 of 366 days20202021: Good 109 of 365 days2021: Moderate 251 of 365 days2021: Unhealthy for Sensitive Groups 5 of 365 days2022: Good 125 of 365 days2022: Moderate 236 of 365 days2022: Unhealthy for Sensitive Groups 3 of 365 days2022: Unhealthy 1 of 365 days2023: Good 129 of 365 days2023: Moderate 217 of 365 days2023: Unhealthy for Sensitive Groups 17 of 365 days2023: Unhealthy 2 of 365 days2024: Good 164 of 366 days2024: Moderate 191 of 366 days2024: Unhealthy for Sensitive Groups 11 of 366 days2025: Good 125 of 365 days2025: Moderate 227 of 365 days2025: Unhealthy for Sensitive Groups 12 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 1431981: 90th percentile AQI 1051982: 90th percentile AQI 1191983: 90th percentile AQI 1541984: 90th percentile AQI 1021985: 90th percentile AQI 1001986: 90th percentile AQI 1151987: 90th percentile AQI 1431988: 90th percentile AQI 1591989: 90th percentile AQI 1011990: 90th percentile AQI 931991: 90th percentile AQI 1011992: 90th percentile AQI 671993: 90th percentile AQI 841994: 90th percentile AQI 931995: 90th percentile AQI 1051996: 90th percentile AQI 1051997: 90th percentile AQI 931998: 90th percentile AQI 1101999: 90th percentile AQI 1122000: 90th percentile AQI 1002001: 90th percentile AQI 1122002: 90th percentile AQI 1222003: 90th percentile AQI 972004: 90th percentile AQI 882005: 90th percentile AQI 1152006: 90th percentile AQI 972007: 90th percentile AQI 1192008: 90th percentile AQI 992009: 90th percentile AQI 802010: 90th percentile AQI 972011: 90th percentile AQI 972012: 90th percentile AQI 932013: 90th percentile AQI 772014: 90th percentile AQI 802015: 90th percentile AQI 772016: 90th percentile AQI 772017: 90th percentile AQI 722018: 90th percentile AQI 762019: 90th percentile AQI 772020: 90th percentile AQI 712021: 90th percentile AQI 772022: 90th percentile AQI 712023: 90th percentile AQI 772024: 90th percentile AQI 712025: 90th percentile AQI 711980: Median AQI 581981: Median AQI 501982: Median AQI 541983: Median AQI 751984: Median AQI 541985: Median AQI 521986: Median AQI 501987: Median AQI 541988: Median AQI 501989: Median AQI 501990: Median AQI 471991: Median AQI 471992: Median AQI 441993: Median AQI 431994: Median AQI 431995: Median AQI 421996: Median AQI 471997: Median AQI 461998: Median AQI 501999: Median AQI 712000: Median AQI 682001: Median AQI 682002: Median AQI 652003: Median AQI 642004: Median AQI 632005: Median AQI 532006: Median AQI 482007: Median AQI 622008: Median AQI 552009: Median AQI 582010: Median AQI 712011: Median AQI 592012: Median AQI 612013: Median AQI 612014: Median AQI 612015: Median AQI 552016: Median AQI 552017: Median AQI 552018: Median AQI 572019: Median AQI 572020: Median AQI 552021: Median AQI 562022: Median AQI 542023: Median AQI 542024: Median AQI 522025: Median AQI 541980198519901995200020052010201520202025
  • 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)26372%
Ozone9626%
Nitrogen dioxide (NO₂)62%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025365125227121005471154PM2.5
2024366164191110005271140PM2.5
2023365129217172005477193PM2.5
202236512523631005471151PM2.5
202136510925150005677140PM2.5
202036610525470005571126PM2.5
20193659926060005777119PM2.5
20183659726071005776159PM2.5
201736511824250005572129PM2.5
2016366118236120005577140PM2.5
201536511924051005577151PM2.5
201436562292110006180143PM2.5
20133656529640006177112PM2.5
201236646293225006193182PM2.5
2011365104230265005997179PM2.5
201036523311283007197172PM2.5
20093658027780005880133PM2.5
2008366150182304005599169Ozone
2007365882195080062119187PM2.5
2006365193141283004897182Ozone
200536517613839111053115208NO2
200436660283230006388150PM2.5
200336540294256006497197PM2.5
20023653428328182065122213PM2.5
2001365412764260068112200PM2.5
2000366392933130068100187PM2.5
1999365542594291071112209PM2.5
19983651861323881050110203NO2
1997365210125219004693200NO2
19963662141093490047105187NO2
19953652349322142042105216NO2
1994365252821714004393192NO2
199336524396224004384197NO2
199236625110771004467166NO2
199136521011822105047101219NO2
1990365206126256204793209NO2
198936518514023161050101205NO2
198836619511022309050159222NO2
198736516413535265054143236NO2
19863651871244482050115205NO2
19853651771552751052100210NO2
198436615716926131054102202NO2
1983365118104103319075154227NO2
198236515014750153054119218NO2
19813651911343280050105190NO2
1980366145142511711058143223NO2

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