Median AQI
39
Good
South Carolina · County air quality · 2025
Aiken County, South Carolina
Median AQI 39 (Good). 89.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 39
- Median AQI
- 89.1%
- Good-air days
- 0
- Unhealthy days
- 74%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Aiken County's air is good on balance, cleaner than the median US county, a median AQI of 39 with 89.1% of 229 monitored days in the Good band, driven mainly by Ozone.
- 39
- median AQI · Good
- 89.1%
- days rated Good
- Ozone
- main pollutant
- 74%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 71.
Data updated July 2026
- Good · 204 d · 89.1%
- Moderate · 25 d · 10.9%
How did Aiken County's air break down in 2025?
Across 229 monitored days, 204 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 71 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 229 days monitored. Median AQI: 39 (Good).
Insights: Aiken County, South Carolina. EPA monitors recorded a median Air Quality Index of 39 across 229 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 204 (89%) fell in the Good band (AQI 0–50), 25 (11%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 51, while the worst single-day peak hit 71 (Moderate). Residents averaged about 26.7 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (229 days). Across the 2020–2025 trend window, good days shifted by -54 and the median AQI moved +7 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 71, moderate but never Unhealthy. Nearby counties show comparable readings: Anderson (90.0% good, AQI 41); Berkeley (92.2% good, AQI 36); Charleston (59.0% good, AQI 47); Chesterfield (61.2% good, AQI 46); Darlington (87.3% good, AQI 42); Edgefield (68.1% good, AQI 44).
Air Quality Summary
Good Days
89.1%
204 of 229 monitored days
14.1pp vs 75% target
Max AQI Recorded
71
Moderate
Health Grade
Good
90th-pct AQI 51
Aiken County, Good days share 89.1%
National avg
Share of monitored days at AQI 0-50 (Good band).
Aiken 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 229 monitored days across EPA AQI categories.
Good
204
89%
Moderate
25
11%
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 Aiken County.
- Ozone · 229 days · 100.0%
Health Impact Assessment
Good
Aiken County's air quality is rated Good based on 89.1% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 89.1% 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 229 of 229 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Aiken County. Best year: 2021 (259 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 258 | 1 | 0 | 0 | 32 | 71 |
| 2021 | 259 | 23 | 0 | 0 | 36 | 84 |
| 2022 | 246 | 25 | 0 | 0 | 37 | 87 |
| 2023 | 252 | 23 | 0 | 0 | 39 | 80 |
| 2024 | 238 | 29 | 0 | 0 | 39 | 84 |
| 2025 | 204 | 25 | 0 | 0 | 39 | 71 |
How does Aiken County compare?
How Aiken County compares
Good-day share better than US avg
Aiken County 89.1%
Anderson County, South Carolina 90.0%
US average 76.5%
Median AQI worse than US avg
Aiken County 39
Anderson County, South Carolina 41
US average 38
Unhealthy days / yr about average
Aiken County 0
Anderson County, South Carolina 0
US average 0
Other Counties in South Carolina
Air quality comparison for nearby counties in South Carolina.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Aiken County.
Ada County, Idaho
AQI 39 · 80.6% 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
Boyd County, Kentucky
AQI 39 · 82.8% good
What Aiken 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 Aiken County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Aiken County with its South Carolina neighbours before drawing a conclusion about the region. All of South Carolina
Based on 229 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 Aiken County, South Carolina? ▼
Aiken County has a median Air Quality Index (AQI) of 39, rated "Good." 89.1% of monitored days (204 out of 229) had good air quality in 2025.
What is the main pollutant in Aiken County? ▼
The primary pollutant in Aiken County is Ozone (O3), which was the main AQI driver on 229 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Aiken County have? ▼
In 2025, Aiken County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 71.
Is the air quality in Aiken County getting better or worse? ▼
Air quality in Aiken County is worsening based on 5-year trends (2020-2025). Best year: 2021 with 259 good days. Worst year: 2025 with 204 good days.
What does AQI 39 mean for health? ▼
Aiken 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 Aiken County compare to other counties in South Carolina? ▼
Aiken County has 89.1% good air days. Nearby counties in South Carolina: Anderson (90.0% good), Berkeley (92.2% good), Charleston (59.0% good), Chesterfield (61.2% good), Darlington (87.3% good), Edgefield (68.1% good).
What is the 90th percentile AQI in Aiken County? ▼
The 90th percentile AQI for Aiken County is 51, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 71 (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.