Median AQI
39
Good
Kentucky · County air quality · 2025
Boyd County, Kentucky
Median AQI 39 (Good). 82.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 39
- Median AQI
- 82.8%
- Good-air days
- 0
- Unhealthy days
- 60%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Boyd County's air is good on balance, cleaner than the median US county, a median AQI of 39 with 82.8% of 186 monitored days in the Good band, driven mainly by PM2.5.
- 39
- median AQI · Good
- 82.8%
- days rated Good
- PM2.5
- main pollutant
- 60%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 88.
Data updated July 2026
- Good · 154 d · 82.8%
- Moderate · 32 d · 17.2%
How did Boyd County's air break down in 2025?
Across 186 monitored days, 154 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 88 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 186 days monitored. Median AQI: 39 (Good).
Insights: Boyd County, Kentucky. EPA monitors recorded a median Air Quality Index of 39 across 186 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 154 (83%) fell in the Good band (AQI 0–50), 32 (17%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 54, while the worst single-day peak hit 88 (Moderate). Residents averaged about 24.8 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (94 days), Ozone (86 days), PM10 (5 days), NO2 (1 days). Across the 2020–2025 trend window, good days shifted by -131 and the median AQI moved -2 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 88, moderate but never Unhealthy. Nearby counties show comparable readings: Bell (63.5% good, AQI 43); Boone (95.1% good, AQI 38); Bullitt (92.7% good, AQI 39); Campbell (78.5% good, AQI 39); Carter (89.8% good, AQI 36); Christian (78.3% good, AQI 41).
Air Quality Summary
Good Days
82.8%
154 of 186 monitored days
7.8pp vs 75% target
Max AQI Recorded
88
Moderate
Health Grade
Good
90th-pct AQI 54
Boyd County, Good days share 82.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Boyd 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 186 monitored days across EPA AQI categories.
Good
154
83%
Moderate
32
17%
USG
0
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Boyd County.
- PM2.5 · 94 days · 50.5%
- Ozone · 86 days · 46.2%
- PM10 · 5 days · 2.7%
- NO₂ · 1 days · 0.5%
Health Impact Assessment
Good
Boyd County's air quality is rated Good based on 82.8% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 82.8% 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 PM2.5, driving AQI on 94 of 186 monitored days.
5-Year Air Quality Trend
Air quality is improving in Boyd County. Best year: 2020 (285 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 285 | 81 | 0 | 0 | 41 | 89 |
| 2021 | 231 | 128 | 1 | 0 | 44 | 102 |
| 2022 | 252 | 113 | 0 | 0 | 43 | 80 |
| 2023 | 226 | 133 | 2 | 2 | 46 | 159 |
| 2024 | 275 | 90 | 0 | 0 | 42 | 93 |
| 2025 | 154 | 32 | 0 | 0 | 39 | 88 |
How does Boyd County compare?
How Boyd County compares
Good-day share better than US avg
Boyd County 82.8%
Bell County, Kentucky 63.5%
US average 76.5%
Median AQI worse than US avg
Boyd County 39
Bell County, Kentucky 43
US average 38
Unhealthy days / yr about average
Boyd 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 Boyd 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 Boyd County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 39 means for exposure. Health guidance
- See how Boyd County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Boyd County with its Kentucky neighbours before drawing a conclusion about the region. All of Kentucky
Based on 186 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 Boyd County, Kentucky? ▼
Boyd County has a median Air Quality Index (AQI) of 39, rated "Good." 82.8% of monitored days (154 out of 186) had good air quality in 2025.
What is the main pollutant in Boyd County? ▼
The primary pollutant in Boyd County is Fine Particles (PM2.5), which was the main AQI driver on 94 days (51% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Boyd County have? ▼
In 2025, Boyd County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 88.
Is the air quality in Boyd County getting better or worse? ▼
Air quality in Boyd County is improving based on 5-year trends (2020-2025). Best year: 2020 with 285 good days. Worst year: 2025 with 154 good days.
What does AQI 39 mean for health? ▼
Boyd 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 Boyd County compare to other counties in Kentucky? ▼
Boyd County has 82.8% good air days. Nearby counties in Kentucky: Bell (63.5% good), Boone (95.1% good), Bullitt (92.7% good), Campbell (78.5% good), Carter (89.8% good), Christian (78.3% good).
What is the 90th percentile AQI in Boyd County? ▼
The 90th percentile AQI for Boyd County is 54, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 88 (Moderate).
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.