Median AQI
42
Good
Alabama · County air quality · 2025
DeKalb County, Alabama
Median AQI 42 (Good). 78.6% of monitored days rated Good, direct from EPA Air Quality System stations.
- 42
- Median AQI
- 78.6%
- Good-air days
- 0
- Unhealthy days
- 48%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, DeKalb County's air is good on balance, more polluted than the median US county, a median AQI of 42 with 78.6% of 243 monitored days in the Good band, driven mainly by Ozone.
- 42
- median AQI · Good
- 78.6%
- days rated Good
- Ozone
- main pollutant
- 48%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 93.
Data updated July 2026
- Good · 191 d · 78.6%
- Moderate · 52 d · 21.4%
How did DeKalb County's air break down in 2025?
Across 243 monitored days, 191 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 93 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 243 days monitored. Median AQI: 42 (Good).
Insights: DeKalb County, Alabama. EPA monitors recorded a median Air Quality Index of 42 across 243 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 191 (79%) fell in the Good band (AQI 0–50), 52 (21%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 55, while the worst single-day peak hit 93 (Moderate). Residents averaged about 23.6 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (156 days), PM2.5 (87 days). Across the 2020–2025 trend window, good days shifted by -141 and the median AQI moved +5 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 93, moderate but never Unhealthy. Nearby counties show comparable readings: Baldwin (72.2% good, AQI 42); Clay (85.4% good, AQI 32); Elmore (97.2% good, AQI 32); Etowah (63.5% good, AQI 45); Jefferson (36.8% good, AQI 53); Lawrence (100.0% good, AQI 23).
Air Quality Summary
Good Days
78.6%
191 of 243 monitored days
3.6pp vs 75% target
Max AQI Recorded
93
Moderate
Health Grade
Good
90th-pct AQI 55
DeKalb County, Good days share 78.6%
National avg
Share of monitored days at AQI 0-50 (Good band).
DeKalb 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 243 monitored days across EPA AQI categories.
Good
191
79%
Moderate
52
21%
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 DeKalb County.
- Ozone · 156 days · 64.2%
- PM2.5 · 87 days · 35.8%
Health Impact Assessment
Good
DeKalb County's air quality is rated Good based on 78.6% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 78.6% of monitored days in 2025, with a median AQI of 42. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 156 of 243 monitored days.
5-Year Air Quality Trend
Air quality is worsening in DeKalb County. Best year: 2020 (332 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 332 | 32 | 0 | 0 | 37 | 91 |
| 2021 | 315 | 46 | 0 | 0 | 37 | 84 |
| 2022 | 323 | 41 | 0 | 0 | 38 | 97 |
| 2023 | 212 | 151 | 2 | 0 | 48 | 133 |
| 2024 | 277 | 89 | 0 | 0 | 43 | 87 |
| 2025 | 191 | 52 | 0 | 0 | 42 | 93 |
How does DeKalb County compare?
How DeKalb County compares
Good-day share better than US avg
DeKalb County 78.6%
Baldwin County, Alabama 72.2%
US average 76.5%
Median AQI worse than US avg
DeKalb County 42
Baldwin County, Alabama 42
US average 38
Unhealthy days / yr about average
DeKalb County 0
Baldwin County, Alabama 0
US average 0
Other Counties in Alabama
Air quality comparison for nearby counties in Alabama.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to DeKalb County.
Adams County, Pennsylvania
AQI 42 · 73.8% good
Anderson County, Tennessee
AQI 42 · 91.0% good
Andrew County, Missouri
AQI 42 · 84.3% good
Armstrong County, Pennsylvania
AQI 42 · 68.1% good
Baldwin County, Alabama
AQI 42 · 72.2% good
Belmont County, Ohio
AQI 42 · 63.0% good
What DeKalb 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 42 means for exposure. Health guidance
- See how DeKalb County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare DeKalb County with its Alabama neighbours before drawing a conclusion about the region. All of Alabama
Based on 243 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 DeKalb County, Alabama? ▼
DeKalb County has a median Air Quality Index (AQI) of 42, rated "Good." 78.6% of monitored days (191 out of 243) had good air quality in 2025.
What is the main pollutant in DeKalb County? ▼
The primary pollutant in DeKalb County is Ozone (O3), which was the main AQI driver on 156 days (64% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does DeKalb County have? ▼
In 2025, DeKalb County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 93.
Is the air quality in DeKalb County getting better or worse? ▼
Air quality in DeKalb County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 332 good days. Worst year: 2025 with 191 good days.
What does AQI 42 mean for health? ▼
DeKalb County's median AQI of 42 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 DeKalb County compare to other counties in Alabama? ▼
DeKalb County has 78.6% good air days. Nearby counties in Alabama: Baldwin (72.2% good), Clay (85.4% good), Elmore (97.2% good), Etowah (63.5% good), Jefferson (36.8% good), Lawrence (100.0% good).
What is the 90th percentile AQI in DeKalb County? ▼
The 90th percentile AQI for DeKalb County is 55, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 93 (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.