Median AQI
47
Good
South Carolina · County air quality · 2025
Charleston County, South Carolina
Median AQI 47 (Good). 59.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 47
- Median AQI
- 59.0%
- Good-air days
- 0
- Unhealthy days
- 13%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Charleston County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 47 with 59.0% of 273 monitored days in the Good band, driven mainly by PM2.5.
- 47
- median AQI · Good
- 59.0%
- days rated Good
- PM2.5
- main pollutant
- 13%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 105.
Data updated July 2026
- Good · 161 d · 59.0%
- Moderate · 111 d · 40.7%
- USG · 1 d · 0.4%
How did Charleston County's air break down in 2025?
Across 273 monitored days, 161 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). 273 days monitored. Median AQI: 47 (Good).
Insights: Charleston County, South Carolina. EPA monitors recorded a median Air Quality Index of 47 across 273 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 161 (59%) fell in the Good band (AQI 0–50), 111 (41%) registered Moderate readings, and 1 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 59, while the worst single-day peak hit 105 (USG). Residents averaged about 17.7 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (172 days), Ozone (100 days), PM10 (1 days). Across the 2020–2025 trend window, good days shifted by -103 and the median AQI moved +4 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 105, usg but never Unhealthy. Nearby counties show comparable readings: Aiken (89.1% good, AQI 39); Anderson (90.0% good, AQI 41); Berkeley (92.2% good, AQI 36); Chesterfield (61.2% good, AQI 46); Darlington (87.3% good, AQI 42); Edgefield (68.1% good, AQI 44).
Air Quality Summary
Good Days
59.0%
161 of 273 monitored days
-16.0pp vs 75% target
Max AQI Recorded
105
USG
Health Grade
Moderate
90th-pct AQI 59
Charleston County, Good days share 59.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Charleston 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 273 monitored days across EPA AQI categories.
Good
161
59%
Moderate
111
41%
USG
1
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 Charleston County.
- PM2.5 · 172 days · 63.0%
- Ozone · 100 days · 36.6%
- PM10 · 1 days · 0.4%
Health Impact Assessment
Moderate
Charleston County's air quality is rated Moderate based on 59.0% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 59.0% of monitored days in 2025, with a median AQI of 47. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 172 of 273 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Charleston County. Best year: 2024 (269 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 264 | 101 | 1 | 0 | 43 | 117 |
| 2021 | 197 | 168 | 0 | 0 | 48 | 93 |
| 2022 | 209 | 156 | 0 | 0 | 47 | 84 |
| 2023 | 212 | 153 | 0 | 0 | 47 | 93 |
| 2024 | 269 | 97 | 0 | 0 | 43 | 77 |
| 2025 | 161 | 111 | 1 | 0 | 47 | 105 |
How does Charleston County compare?
How Charleston County compares
Good-day share worse than US avg
Charleston County 59.0%
Aiken County, South Carolina 89.1%
US average 76.5%
Median AQI worse than US avg
Charleston County 47
Aiken County, South Carolina 39
US average 38
Unhealthy days / yr about average
Charleston County 0
Aiken 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 Charleston County.
Beaver County, Pennsylvania
AQI 47 · 54.3% good
Bell County, Texas
AQI 47 · 61.3% good
Bowie County, Texas
AQI 47 · 57.3% good
Bronx County, New York
AQI 47 · 56.6% good
Butte County, California
AQI 47 · 66.1% good
Calcasieu County, Louisiana
AQI 47 · 61.5% good
What Charleston 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 47 means for exposure. Health guidance
- See how Charleston County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Charleston County with its South Carolina neighbours before drawing a conclusion about the region. All of South Carolina
Based on 273 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 Charleston County, South Carolina? ▼
Charleston County has a median Air Quality Index (AQI) of 47, rated "Good." 59.0% of monitored days (161 out of 273) had good air quality in 2025.
What is the main pollutant in Charleston County? ▼
The primary pollutant in Charleston County is Fine Particles (PM2.5), which was the main AQI driver on 172 days (63% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Charleston County have? ▼
In 2025, Charleston County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 105.
Is the air quality in Charleston County getting better or worse? ▼
Air quality in Charleston County is worsening based on 5-year trends (2020-2025). Best year: 2024 with 269 good days. Worst year: 2025 with 161 good days.
What does AQI 47 mean for health? ▼
Charleston County's median AQI of 47 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 Charleston County compare to other counties in South Carolina? ▼
Charleston County has 59.0% good air days. Nearby counties in South Carolina: Aiken (89.1% good), Anderson (90.0% good), Berkeley (92.2% good), Chesterfield (61.2% good), Darlington (87.3% good), Edgefield (68.1% good).
What is the 90th percentile AQI in Charleston County? ▼
The 90th percentile AQI for Charleston County is 59, 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.