Median AQI
38
Good
Indiana · County air quality · 2025
Boone County, Indiana
Median AQI 38 (Good). 86.9% of monitored days rated Good, direct from EPA Air Quality System stations.
- 38
- Median AQI
- 86.9%
- Good-air days
- 0
- Unhealthy days
- 69%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Boone County's air is good on balance, cleaner than the median US county, a median AQI of 38 with 86.9% of 260 monitored days in the Good band, driven mainly by Ozone.
- 38
- median AQI · Good
- 86.9%
- days rated Good
- Ozone
- main pollutant
- 69%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 112.
Data updated July 2026
- Good · 226 d · 86.9%
- Moderate · 31 d · 11.9%
- USG · 3 d · 1.2%
How did Boone County's air break down in 2025?
Across 260 monitored days, 226 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 112 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 260 days monitored. Median AQI: 38 (Good).
Insights: Boone County, Indiana. EPA monitors recorded a median Air Quality Index of 38 across 260 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 226 (87%) fell in the Good band (AQI 0–50), 31 (12%) registered Moderate readings, and 3 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 54, while the worst single-day peak hit 112 (USG). Residents averaged about 26.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (260 days). Across the 2020–2025 trend window, good days shifted by -104 and the median AQI moved +6 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 112, usg but never Unhealthy. Nearby counties show comparable readings: Allen (58.2% good, AQI 45); Bartholomew (69.2% good, AQI 44); Brown (94.5% good, AQI 37); Carroll (87.8% good, AQI 37); Clark (59.7% good, AQI 46); Delaware (63.4% good, AQI 44).
Air Quality Summary
Good Days
86.9%
226 of 260 monitored days
11.9pp vs 75% target
Max AQI Recorded
112
USG
Health Grade
Good
90th-pct AQI 54
Boone County, Good days share 86.9%
National avg
Share of monitored days at AQI 0-50 (Good band).
Boone County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 260 monitored days across EPA AQI categories.
Good
226
87%
Moderate
31
12%
USG
3
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Boone County.
- Ozone · 260 days · 100.0%
Health Impact Assessment
Good
Boone County's air quality is rated Good based on 86.9% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 86.9% of monitored days in 2025, with a median AQI of 38. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 260 of 260 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Boone County. Best year: 2021 (337 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 330 | 20 | 2 | 0 | 32 | 101 |
| 2021 | 337 | 27 | 1 | 0 | 33 | 101 |
| 2022 | 331 | 30 | 1 | 0 | 36 | 115 |
| 2023 | 307 | 46 | 8 | 1 | 37 | 185 |
| 2024 | 313 | 46 | 0 | 0 | 36 | 93 |
| 2025 | 226 | 31 | 3 | 0 | 38 | 112 |
How does Boone County compare?
How Boone County compares
Good-day share better than US avg
Boone County 86.9%
Allen County, Indiana 58.2%
US average 76.5%
Median AQI about average
Boone County 38
Allen County, Indiana 45
US average 38
Unhealthy days / yr about average
Boone County 0
Allen County, Indiana 0
US average 0
Other Counties in Indiana
Air quality comparison for nearby counties in Indiana.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Boone County.
Adams County, Illinois
AQI 38 · 94.4% good
Anoka County, Minnesota
AQI 38 · 82.1% good
Atlantic County, New Jersey
AQI 38 · 79.6% good
Avery County, North Carolina
AQI 38 · 93.9% good
Barnstable County, Massachusetts
AQI 38 · 92.5% good
Bay County, Michigan
AQI 38 · 71.8% good
What Boone County's air means for you
The air here stays in the breathable range year-round, with Ozone the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 38 means for exposure. Health guidance
- See how Boone County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Boone County with its Indiana neighbours before drawing a conclusion about the region. All of Indiana
Based on 260 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Boone County, Indiana? ▼
Boone County has a median Air Quality Index (AQI) of 38, rated "Good." 86.9% of monitored days (226 out of 260) had good air quality in 2025.
What is the main pollutant in Boone County? ▼
The primary pollutant in Boone County is Ozone (O3), which was the main AQI driver on 260 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Boone County have? ▼
In 2025, Boone County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 112.
Is the air quality in Boone County getting better or worse? ▼
Air quality in Boone County is worsening based on 5-year trends (2020-2025). Best year: 2021 with 337 good days. Worst year: 2025 with 226 good days.
What does AQI 38 mean for health? ▼
Boone County's median AQI of 38 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Boone County compare to other counties in Indiana? ▼
Boone County has 86.9% good air days. Nearby counties in Indiana: Allen (58.2% good), Bartholomew (69.2% good), Brown (94.5% good), Carroll (87.8% good), Clark (59.7% good), Delaware (63.4% good).
What is the 90th percentile AQI in Boone County? ▼
The 90th percentile AQI for Boone County is 54, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 112 (USG).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.