EnviroNearby

Delaware County, Indiana air quality history

Daily Air Quality Index summaries from EPA monitors in Delaware, Indiana, 1989–2025.

65%
Good days in 2025
43
Median daily AQI, 2025
2
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 Delaware, Indiana on 365 days. 236 of those days (65%) were in the Good range, and the median daily AQI was 43. That median is about the same as the typical monitored county in Indiana (median 41 across 33 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 197 days. Across the years with fuller monitoring, the share of Good days rose: an average of 44% in 2001–2003 versus 70% in 2023–2025.

Years with fewer than 120 monitored days (1989, 1990, 1999, 2000) 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 23 of 28 days1989: Moderate 5 of 28 days19891990: Good 26 of 27 days1990: Moderate 1 of 27 days1999: Good 10 of 24 days1999: Moderate 14 of 24 days2000: Good 20 of 113 days2000: Moderate 91 of 113 days2000: Unhealthy for Sensitive Groups 2 of 113 days2001: Good 98 of 230 days2001: Moderate 107 of 230 days2001: Unhealthy for Sensitive Groups 23 of 230 days2001: Unhealthy 2 of 230 days2002: Good 103 of 238 days2002: Moderate 102 of 238 days2002: Unhealthy for Sensitive Groups 23 of 238 days2002: Unhealthy 10 of 238 days20022003: Good 110 of 233 days2003: Moderate 110 of 233 days2003: Unhealthy for Sensitive Groups 10 of 233 days2003: Unhealthy 3 of 233 days2004: Good 129 of 237 days2004: Moderate 105 of 237 days2004: Unhealthy for Sensitive Groups 3 of 237 days2005: Good 82 of 216 days2005: Moderate 110 of 216 days2005: Unhealthy for Sensitive Groups 21 of 216 days2005: Unhealthy 3 of 216 days2006: Good 132 of 240 days2006: Moderate 102 of 240 days2006: Unhealthy for Sensitive Groups 6 of 240 days2007: Good 95 of 333 days2007: Moderate 219 of 333 days2007: Unhealthy for Sensitive Groups 18 of 333 days2007: Unhealthy 1 of 333 days20072008: Good 142 of 233 days2008: Moderate 91 of 233 days2009: Good 148 of 242 days2009: Moderate 93 of 242 days2009: Unhealthy for Sensitive Groups 1 of 242 days2010: Good 135 of 234 days2010: Moderate 97 of 234 days2010: Unhealthy for Sensitive Groups 2 of 234 days2011: Good 154 of 242 days2011: Moderate 85 of 242 days2011: Unhealthy for Sensitive Groups 3 of 242 days2012: Good 126 of 240 days2012: Moderate 106 of 240 days2012: Unhealthy for Sensitive Groups 8 of 240 days20122013: Good 174 of 239 days2013: Moderate 65 of 239 days2014: Good 184 of 240 days2014: Moderate 55 of 240 days2014: Unhealthy for Sensitive Groups 1 of 240 days2015: Good 185 of 236 days2015: Moderate 50 of 236 days2015: Unhealthy for Sensitive Groups 1 of 236 days2016: Good 170 of 230 days2016: Moderate 59 of 230 days2016: Unhealthy for Sensitive Groups 1 of 230 days2017: Good 225 of 280 days2017: Moderate 54 of 280 days2017: Unhealthy for Sensitive Groups 1 of 280 days20172018: Good 301 of 361 days2018: Moderate 56 of 361 days2018: Unhealthy for Sensitive Groups 4 of 361 days2019: Good 299 of 352 days2019: Moderate 53 of 352 days2020: Good 303 of 365 days2020: Moderate 62 of 365 days2021: Good 299 of 362 days2021: Moderate 63 of 362 days2022: Good 303 of 359 days2022: Moderate 55 of 359 days2022: Unhealthy for Sensitive Groups 1 of 359 days20222023: Good 287 of 363 days2023: Moderate 71 of 363 days2023: Unhealthy for Sensitive Groups 5 of 363 days2024: Good 240 of 366 days2024: Moderate 126 of 366 days2025: Good 236 of 365 days2025: Moderate 127 of 365 days2025: Unhealthy for Sensitive Groups 2 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 year0501001501989: 90th percentile AQI 551990: 90th percentile AQI 331999: 90th percentile AQI 662000: 90th percentile AQI 842001: 90th percentile AQI 1012002: 90th percentile AQI 1152003: 90th percentile AQI 872004: 90th percentile AQI 802005: 90th percentile AQI 1032006: 90th percentile AQI 802007: 90th percentile AQI 932008: 90th percentile AQI 672009: 90th percentile AQI 692010: 90th percentile AQI 742011: 90th percentile AQI 692012: 90th percentile AQI 842013: 90th percentile AQI 612014: 90th percentile AQI 612015: 90th percentile AQI 592016: 90th percentile AQI 602017: 90th percentile AQI 572018: 90th percentile AQI 582019: 90th percentile AQI 562020: 90th percentile AQI 552021: 90th percentile AQI 572022: 90th percentile AQI 542023: 90th percentile AQI 622024: 90th percentile AQI 612025: 90th percentile AQI 631989: Median AQI 251990: Median AQI 181999: Median AQI 532000: Median AQI 622001: Median AQI 572002: Median AQI 542003: Median AQI 512004: Median AQI 482005: Median AQI 602006: Median AQI 492007: Median AQI 592008: Median AQI 452009: Median AQI 462010: Median AQI 482011: Median AQI 442012: Median AQI 482013: Median AQI 412014: Median AQI 412015: Median AQI 382016: Median AQI 422017: Median AQI 402018: Median AQI 362019: Median AQI 362020: Median AQI 352021: Median AQI 372022: Median AQI 382023: Median AQI 402024: Median AQI 442025: Median AQI 431989200220072012201720222025
  • 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)19754%
Ozone16846%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536523612720004363108PM2.5
20243662401260000446197PM2.5
20233632877150004062121Ozone
20223593035510003854115Ozone
2021362299630000375797Ozone
2020365303620000355597Ozone
2019352299530000365671Ozone
20183613015640003658129Ozone
20172802255410004057112Ozone
20162301705910004260115Ozone
20152361855010003859105Ozone
20142401845510004161130Ozone
2013239174650000416188Ozone
201224012610680004884136Ozone
20112421548530004469112Ozone
20102341359720004874108Ozone
20092421489310004669101Ozone
2008233142910000456790Ozone
200733395219181005993154PM2.5
200624013210260004980126Ozone
2005216821102130060103182Ozone
200423712910530004880133Ozone
2003233110110103005187182Ozone
200223810310223100054115182Ozone
2001230981072320057101174Ozone
2000113209120006284134PM2.5
19992410140000536690PM2.5
1990272610000183355PM10
1989282350000255560PM10

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 Indiana with a similar median AQI in 2025

All monitored counties in Indiana

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