Median AQI
39
Good
Kentucky · County air quality · 2025
Oldham County, Kentucky
Median AQI 39 (Good). 95.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 39
- Median AQI
- 95.1%
- Good-air days
- 0
- Unhealthy days
- 90%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Oldham County's air is good on balance, among the cleanest 10% of US counties, a median AQI of 39 with 95.1% of 122 monitored days in the Good band, driven mainly by Ozone.
- 39
- median AQI · Good
- 95.1%
- days rated Good
- Ozone
- main pollutant
- 90%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 105.
Data updated July 2026
- Good · 116 d · 95.1%
- Moderate · 5 d · 4.1%
- USG · 1 d · 0.8%
How did Oldham County's air break down in 2025?
Across 122 monitored days, 116 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 105 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 122 days monitored. Median AQI: 39 (Good).
Insights: Oldham County, Kentucky. EPA monitors recorded a median Air Quality Index of 39 across 122 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 116 (95%) fell in the Good band (AQI 0–50), 5 (4%) registered Moderate readings, and 1 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 48, while the worst single-day peak hit 105 (USG). Residents averaged about 28.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (122 days). Across the 2020–2025 trend window, good days shifted by -102 and the median AQI moved +1 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 105, usg but never Unhealthy. Nearby counties show comparable readings: Bell (63.5% good, AQI 43); Boone (95.1% good, AQI 38); Boyd (82.8% good, AQI 39); Bullitt (92.7% good, AQI 39); Campbell (78.5% good, AQI 39); Carter (89.8% good, AQI 36).
Air Quality Summary
Good Days
95.1%
116 of 122 monitored days
20.1pp vs 75% target
Max AQI Recorded
105
USG
Health Grade
Excellent
90th-pct AQI 48
Oldham County, Good days share 95.1%
National avg
Share of monitored days at AQI 0-50 (Good band).
Oldham 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 122 monitored days across EPA AQI categories.
Good
116
95%
Moderate
5
4%
USG
1
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 Oldham County.
- Ozone · 122 days · 100.0%
Health Impact Assessment
Excellent
Oldham County's air quality is rated Excellent based on 95.1% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 95.1% of monitored days in 2025, with a median AQI of 39. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 122 of 122 monitored days.
5-Year Air Quality Trend
Air quality is improving in Oldham County. Best year: 2022 (221 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 218 | 21 | 0 | 0 | 38 | 97 |
| 2021 | 216 | 27 | 1 | 0 | 39 | 105 |
| 2022 | 221 | 22 | 2 | 0 | 41 | 112 |
| 2023 | 195 | 46 | 1 | 0 | 42 | 105 |
| 2024 | 194 | 43 | 5 | 0 | 43 | 136 |
| 2025 | 116 | 5 | 1 | 0 | 39 | 105 |
How does Oldham County compare?
How Oldham County compares
Good-day share better than US avg
Oldham County 95.1%
Bell County, Kentucky 63.5%
US average 76.5%
Median AQI worse than US avg
Oldham County 39
Bell County, Kentucky 43
US average 38
Unhealthy days / yr about average
Oldham County 0
Bell County, Kentucky 0
US average 0
Other Counties in Kentucky
Air quality comparison for nearby counties in Kentucky.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Oldham County.
Ada County, Idaho
AQI 39 · 80.6% good
Aiken County, South Carolina
AQI 39 · 89.1% good
Albany County, New York
AQI 39 · 67.4% good
Alexander County, North Carolina
AQI 39 · 92.4% good
Ashland County, Wisconsin
AQI 39 · 85.6% good
Bennington County, Vermont
AQI 39 · 82.9% good
What Oldham 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 39 means for exposure. Health guidance
- See how Oldham County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Oldham County with its Kentucky neighbours before drawing a conclusion about the region. All of Kentucky
Based on 122 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 Oldham County, Kentucky? ▼
Oldham County has a median Air Quality Index (AQI) of 39, rated "Good." 95.1% of monitored days (116 out of 122) had good air quality in 2025.
What is the main pollutant in Oldham County? ▼
The primary pollutant in Oldham County is Ozone (O3), which was the main AQI driver on 122 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Oldham County have? ▼
In 2025, Oldham County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 105.
Is the air quality in Oldham County getting better or worse? ▼
Air quality in Oldham County is improving based on 5-year trends (2020-2025). Best year: 2022 with 221 good days. Worst year: 2025 with 116 good days.
What does AQI 39 mean for health? ▼
Oldham County's median AQI of 39 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 Oldham County compare to other counties in Kentucky? ▼
Oldham County has 95.1% good air days. Nearby counties in Kentucky: Bell (63.5% good), Boone (95.1% good), Boyd (82.8% good), Bullitt (92.7% good), Campbell (78.5% good), Carter (89.8% good).
What is the 90th percentile AQI in Oldham County? ▼
The 90th percentile AQI for Oldham County is 48, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 105 (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.