Median AQI
42
Good
West Virginia · County air quality · 2025
Greenbrier County, West Virginia
Median AQI 42 (Good). 89.3% of monitored days rated Good, direct from EPA Air Quality System stations.
- 42
- Median AQI
- 89.3%
- Good-air days
- 0
- Unhealthy days
- 74%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Greenbrier County's air is good on balance, cleaner than the median US county, a median AQI of 42 with 89.3% of 121 monitored days in the Good band, driven mainly by Ozone.
- 42
- median AQI · Good
- 89.3%
- 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 77.
Data updated July 2026
- Good · 108 d · 89.3%
- Moderate · 13 d · 10.7%
How did Greenbrier County's air break down in 2025?
Across 121 monitored days, 108 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 77 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 121 days monitored. Median AQI: 42 (Good).
Insights: Greenbrier County, West Virginia. EPA monitors recorded a median Air Quality Index of 42 across 121 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 108 (89%) fell in the Good band (AQI 0–50), 13 (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 77 (Moderate). Residents averaged about 26.8 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (121 days). Across the 2020–2025 trend window, good days shifted by -124 and the median AQI moved +8 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 77, moderate but never Unhealthy. Nearby counties show comparable readings: Berkeley (81.1% good, AQI 40); Brooke (79.3% good, AQI 35); Cabell (74.0% good, AQI 41); Hancock (74.6% good, AQI 42); Harrison (73.3% good, AQI 32); Kanawha (79.6% good, AQI 40).
Air Quality Summary
Good Days
89.3%
108 of 121 monitored days
14.3pp vs 75% target
Max AQI Recorded
77
Moderate
Health Grade
Good
90th-pct AQI 51
Greenbrier County, Good days share 89.3%
National avg
Share of monitored days at AQI 0-50 (Good band).
Greenbrier 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 121 monitored days across EPA AQI categories.
Good
108
89%
Moderate
13
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 Greenbrier County.
- Ozone · 121 days · 100.0%
Health Impact Assessment
Good
Greenbrier County's air quality is rated Good based on 89.3% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 89.3% 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 121 of 121 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Greenbrier County. Best year: 2022 (236 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 232 | 2 | 0 | 0 | 34 | 54 |
| 2021 | 223 | 8 | 0 | 0 | 37 | 64 |
| 2022 | 236 | 4 | 0 | 0 | 34 | 71 |
| 2023 | 227 | 15 | 0 | 0 | 38 | 87 |
| 2024 | 234 | 9 | 0 | 0 | 40 | 64 |
| 2025 | 108 | 13 | 0 | 0 | 42 | 77 |
How does Greenbrier County compare?
How Greenbrier County compares
Good-day share better than US avg
Greenbrier County 89.3%
Berkeley County, West Virginia 81.1%
US average 76.5%
Median AQI worse than US avg
Greenbrier County 42
Berkeley County, West Virginia 40
US average 38
Unhealthy days / yr about average
Greenbrier County 0
Berkeley County, West Virginia 0
US average 0
Other Counties in West Virginia
Air quality comparison for nearby counties in West Virginia.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Greenbrier 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 Greenbrier 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 Greenbrier County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Greenbrier County with its West Virginia neighbours before drawing a conclusion about the region. All of West Virginia
Based on 121 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 Greenbrier County, West Virginia? ▼
Greenbrier County has a median Air Quality Index (AQI) of 42, rated "Good." 89.3% of monitored days (108 out of 121) had good air quality in 2025.
What is the main pollutant in Greenbrier County? ▼
The primary pollutant in Greenbrier County is Ozone (O3), which was the main AQI driver on 121 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Greenbrier County have? ▼
In 2025, Greenbrier County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 77.
Is the air quality in Greenbrier County getting better or worse? ▼
Air quality in Greenbrier County is worsening based on 5-year trends (2020-2025). Best year: 2022 with 236 good days. Worst year: 2025 with 108 good days.
What does AQI 42 mean for health? ▼
Greenbrier 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 Greenbrier County compare to other counties in West Virginia? ▼
Greenbrier County has 89.3% good air days. Nearby counties in West Virginia: Berkeley (81.1% good), Brooke (79.3% good), Cabell (74.0% good), Hancock (74.6% good), Harrison (73.3% good), Kanawha (79.6% good).
What is the 90th percentile AQI in Greenbrier County? ▼
The 90th percentile AQI for Greenbrier County is 51, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 77 (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.