Median AQI
53
Moderate
Ohio · County air quality · 2025
Franklin County, Ohio
Median AQI 53 (Moderate). 40.3% of monitored days rated Good, direct from EPA Air Quality System stations.
- 53
- Median AQI
- 40.3%
- Good-air days
- 1
- Unhealthy days
- 3%
- Cleaner than US counties
Franklin County's 2025 annual median AQI is 53 (Moderate), with 40.3% Good days
According to the U.S. EPA Air Quality System, Franklin County, Ohio posted a 2025 median AQI of 53 (Moderate) across 365 monitored days, with 40.3% rated Good and 1 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Franklin County's 40.3% Good-day share places it cleaner than 3% of US counties in 2025.
- Closest median-AQI peer
- Cook County (40.8% Good, median AQI 53) is the closest nationwide median-AQI peer to Franklin County.
- 2020–2025 trend
- Franklin County's floor-qualifying Good-day share is worsening from 2020 to 2025 (63.4% → 40.3%).
- Median AQI
- Median AQI: 53
The verdict
According to EPA Air Quality System monitoring data, Franklin County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 53 with 40.3% of 365 monitored days in the Good band, driven mainly by PM2.5.
- 53
- median AQI · Moderate
- 40.3%
- days rated Good
- PM2.5
- main pollutant
- 3%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 156.
Annual release change
What changed in the 2025 EPA annual release
- Franklin County's peak single-day AQI rose from 118 to 156 between the 2024 and 2025 EPA annual releases, a change of +38 points.
- Franklin County's Unhealthy-category days rose from 0 to 1 between the 2024 and 2025 EPA annual releases, a change of +1 days.
Data updated August 2026
- Good · 147 d · 40.3%
- Moderate · 213 d · 58.4%
- USG · 4 d · 1.1%
- Unhealthy · 1 d · 0.3%
How did Franklin County's air break down in 2025?
Across 365 monitored days, 147 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 156 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 365 days monitored. Median AQI: 53 (Moderate).
Insights: Franklin County, Ohio. EPA monitors recorded a median Air Quality Index of 53 across 365 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 147 (40%) fell in the Good band (AQI 0–50), 213 (58%) registered Moderate readings, and 4 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 74, while the worst single-day peak hit 156 (Unhealthy). Residents averaged about 12.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (263 days), Ozone (92 days), PM10 (9 days), NO2 (1 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -23.1 points and the median AQI moved +8 points, placing the multi-year trajectory at worsening. The annual record contains 1 day at Unhealthy or worse. On that day, the EPA recommends that sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Allen (67.0% good, AQI 42); Ashtabula (81.2% good, AQI 43); Athens (83.4% good, AQI 31); Belmont (63.0% good, AQI 42); Butler (33.1% good, AQI 55); Clark (61.4% good, AQI 45).
Air Quality Summary
Good Days
40.3%
147 of 365 monitored days
-34.7pp vs 75% target
Max AQI Recorded
156
Unhealthy
Health Grade
Poor
90th-pct AQI 74
Franklin County, Good days share 40.3%
National avg
Share of monitored days at AQI 0-50 (Good band).
Franklin County, Unhealthy-or-worse share 2.7%
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 365 monitored days across EPA AQI categories.
Good
147
40%
Moderate
213
58%
USG
4
1%
Unhealthy
1
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Franklin County.
- PM2.5 · 263 days · 72.1%
- Ozone · 92 days · 25.2%
- PM10 · 9 days · 2.5%
- NO₂ · 1 days · 0.3%
Health Impact Assessment
Poor
Franklin County's air quality is rated Poor based on 40.3% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 4 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 156. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is PM2.5, driving AQI on 263 of 365 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Franklin County. Highest Good-day share: 2020 (63.4%, 232 of 366 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 232 | 132 | 2 | 0 | 45 | 102 |
| 2021 | 170 | 195 | 0 | 0 | 52 | 100 |
| 2022 | 206 | 157 | 2 | 0 | 48 | 143 |
| 2023 | 136 | 218 | 7 | 3 | 54 | 210 |
| 2024 | 151 | 211 | 4 | 0 | 53 | 118 |
| 2025 | 147 | 213 | 4 | 1 | 53 | 156 |
How does Franklin County compare?
How Franklin County compares
Good-day share worse than typical
Franklin County 40.3%
Cook County, Illinois 40.8%
Typical US county 76.0%
Median AQI worse than typical
Franklin County 53
Cook County, Illinois 53
Typical US county 39
Unhealthy days / yr about typical
Franklin County 1
Cook County, Illinois 5
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Franklin County (53), not geographic neighbors.
Cook County, Illinois
Median AQI 53 · 40.8% Good-day share
Cuyahoga County, Ohio
Median AQI 53 · 43.3% Good-day share
Dallas County, Texas
Median AQI 53 · 40.5% Good-day share
Lake County, Indiana
Median AQI 53 · 41.6% Good-day share
Montgomery County, Texas
Median AQI 53 · 39.1% Good-day share
Nueces County, Texas
Median AQI 53 · 40.5% Good-day share
Same primary pollutant: PM2.5
PM2.5 led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Marion County, Indiana
40.0% Good-day share · median AQI 54
Union County, Arkansas
41.8% Good-day share · median AQI 52
Kent County, Michigan
41.9% Good-day share · median AQI 52
Orange County, California
37.8% Good-day share · median AQI 53
Bibb County, Georgia
42.7% Good-day share · median AQI 52
Bexar County, Texas
43.3% Good-day share · median AQI 52
Ohio counties on the map
Geographic containment only, other monitored counties in Ohio, independent of AQI or pollutant match.
What Franklin County's air means for you
On most days the air here is fine, but PM2.5 drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 53 means for exposure. Health guidance
- See how Franklin County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Franklin County with its Ohio neighbours before drawing a conclusion about the region. All of Ohio
Based on 365 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Franklin County, Ohio? ▼
Franklin County has a median Air Quality Index (AQI) of 53, rated "Moderate." 40.3% of monitored days (147 out of 365) had good air quality in 2025.
What is the main pollutant in Franklin County? ▼
The primary pollutant in Franklin County is Fine Particles (PM2.5), which was the main AQI driver on 263 days (72% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Franklin County have? ▼
In 2025, Franklin County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 156.
Is the air quality in Franklin County getting better or worse? ▼
Air quality in Franklin County is worsening across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2020 at 63.4% (232 of 366 days). Lowest qualifying Good-day share: 2023 at 37.4% (136 of 365 days).
What does AQI 53 mean for health? ▼
Franklin County's median AQI of 53 falls in the "Moderate" category. See the AQI category guide for what each range means for health.
How does Franklin County compare to other counties in Ohio? ▼
Franklin County has 40.3% good air days. Nearby counties in Ohio: Allen (67.0% good), Ashtabula (81.2% good), Athens (83.4% good), Belmont (63.0% good), Butler (33.1% good), Clark (61.4% good).
What is the 90th percentile AQI in Franklin County? ▼
The 90th percentile AQI for Franklin County is 74, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 156 (Unhealthy).
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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Franklin County, Ohio · 2020–2025
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Every figure on PlainAirData 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.