Median AQI
48
Good
South Carolina · County air quality · 2025
Greenville County, South Carolina
Median AQI 48 (Good). 53.9% of monitored days rated Good, direct from EPA Air Quality System stations.
- 48
- Median AQI
- 53.9%
- Good-air days
- 0
- Unhealthy days
- 9%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Greenville County's air is good on balance, among the most polluted counties nationally, a median AQI of 48 with 53.9% of 273 monitored days in the Good band, driven mainly by PM2.5.
- 48
- median AQI · Good
- 53.9%
- days rated Good
- PM2.5
- main pollutant
- 9%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 93.
Data updated July 2026
- Good · 147 d · 53.8%
- Moderate · 126 d · 46.2%
How did Greenville County's air break down in 2025?
Across 273 monitored days, 147 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). 273 days monitored. Median AQI: 48 (Good).
Insights: Greenville County, South Carolina. EPA monitors recorded a median Air Quality Index of 48 across 273 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 147 (54%) fell in the Good band (AQI 0–50), 126 (46%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 64, while the worst single-day peak hit 93 (Moderate). Residents averaged about 16.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (145 days), Ozone (128 days). Across the 2020–2025 trend window, good days shifted by -87 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 93, moderate 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); Charleston (59.0% good, AQI 47); Chesterfield (61.2% good, AQI 46); Darlington (87.3% good, AQI 42).
Air Quality Summary
Good Days
53.9%
147 of 273 monitored days
-21.1pp vs 75% target
Max AQI Recorded
93
Moderate
Health Grade
Moderate
90th-pct AQI 64
Greenville County, Good days share 53.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Greenville 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
147
54%
Moderate
126
46%
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 Greenville County.
- PM2.5 · 145 days · 53.1%
- Ozone · 128 days · 46.9%
Health Impact Assessment
Moderate
Greenville County's air quality is rated Moderate based on 53.9% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 53.9% of monitored days in 2025, with a median AQI of 48. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 145 of 273 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Greenville County. Best year: 2020 (234 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 234 | 131 | 1 | 0 | 44 | 116 |
| 2021 | 180 | 184 | 1 | 0 | 51 | 101 |
| 2022 | 179 | 186 | 0 | 0 | 51 | 97 |
| 2023 | 167 | 196 | 2 | 0 | 52 | 126 |
| 2024 | 198 | 165 | 0 | 0 | 48 | 99 |
| 2025 | 147 | 126 | 0 | 0 | 48 | 93 |
How does Greenville County compare?
How Greenville County compares
Good-day share worse than US avg
Greenville County 53.9%
Aiken County, South Carolina 89.1%
US average 76.5%
Median AQI worse than US avg
Greenville County 48
Aiken County, South Carolina 39
US average 38
Unhealthy days / yr about average
Greenville 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 Greenville County.
Black Hawk County, Iowa
AQI 48 · 56.6% good
Box Elder County, Utah
AQI 48 · 60.0% good
Brookings County, South Dakota
AQI 48 · 53.0% good
Clear Creek County, Colorado
AQI 48 · 64.4% good
Coconino County, Arizona
AQI 48 · 62.5% good
Columbia County, Florida
AQI 48 · 56.4% good
What Greenville 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 48 means for exposure. Health guidance
- See how Greenville County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Greenville 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 Greenville County, South Carolina? ▼
Greenville County has a median Air Quality Index (AQI) of 48, rated "Good." 53.9% of monitored days (147 out of 273) had good air quality in 2025.
What is the main pollutant in Greenville County? ▼
The primary pollutant in Greenville County is Fine Particles (PM2.5), which was the main AQI driver on 145 days (53% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Greenville County have? ▼
In 2025, Greenville County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 93.
Is the air quality in Greenville County getting better or worse? ▼
Air quality in Greenville County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 234 good days. Worst year: 2025 with 147 good days.
What does AQI 48 mean for health? ▼
Greenville County's median AQI of 48 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 Greenville County compare to other counties in South Carolina? ▼
Greenville County has 53.9% good air days. Nearby counties in South Carolina: Aiken (89.1% good), Anderson (90.0% good), Berkeley (92.2% good), Charleston (59.0% good), Chesterfield (61.2% good), Darlington (87.3% good).
What is the 90th percentile AQI in Greenville County? ▼
The 90th percentile AQI for Greenville County is 64, 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.