Median AQI
40
Good
Virginia · County air quality · 2025
Arlington County, Virginia
Median AQI 40 (Good). 84.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 40
- Median AQI
- 84.8%
- Good-air days
- 0
- Unhealthy days
- 66%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Arlington County's air is good on balance, cleaner than the median US county, a median AQI of 40 with 84.8% of 283 monitored days in the Good band, driven mainly by Ozone.
- 40
- median AQI · Good
- 84.8%
- days rated Good
- Ozone
- main pollutant
- 66%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 140.
Data updated July 2026
- Good · 240 d · 84.8%
- Moderate · 41 d · 14.5%
- USG · 2 d · 0.7%
How did Arlington County's air break down in 2025?
Across 283 monitored days, 240 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 140 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 283 days monitored. Median AQI: 40 (Good).
Insights: Arlington County, Virginia. EPA monitors recorded a median Air Quality Index of 40 across 283 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 240 (85%) fell in the Good band (AQI 0–50), 41 (14%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 56, while the worst single-day peak hit 140 (USG). Residents averaged about 25.4 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (216 days), PM2.5 (43 days), NO2 (24 days). Across the 2020–2025 trend window, good days shifted by -92 and the median AQI moved +6 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 140, usg but never Unhealthy. Nearby counties show comparable readings: Albemarle (77.9% good, AQI 41); Bristol City (78.3% good, AQI 33); Caroline (96.2% good, AQI 37); Carroll (100.0% good, AQI 9); Charles (88.6% good, AQI 38); Chesterfield (77.2% good, AQI 42).
Air Quality Summary
Good Days
84.8%
240 of 283 monitored days
9.8pp vs 75% target
Max AQI Recorded
140
USG
Health Grade
Good
90th-pct AQI 56
Arlington County, Good days share 84.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Arlington 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 283 monitored days across EPA AQI categories.
Good
240
85%
Moderate
41
14%
USG
2
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Arlington County.
- Ozone · 216 days · 76.3%
- PM2.5 · 43 days · 15.2%
- NO₂ · 24 days · 8.5%
Health Impact Assessment
Good
Arlington County's air quality is rated Good based on 84.8% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 84.8% of monitored days in 2025, with a median AQI of 40. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 216 of 283 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Arlington County. Best year: 2020 (332 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 332 | 34 | 0 | 0 | 34 | 90 |
| 2021 | 306 | 56 | 3 | 0 | 38 | 115 |
| 2022 | 325 | 40 | 0 | 0 | 37 | 100 |
| 2023 | 302 | 58 | 3 | 2 | 38 | 181 |
| 2024 | 309 | 53 | 4 | 0 | 36 | 115 |
| 2025 | 240 | 41 | 2 | 0 | 40 | 140 |
How does Arlington County compare?
How Arlington County compares
Good-day share better than US avg
Arlington County 84.8%
Albemarle County, Virginia 77.9%
US average 76.5%
Median AQI worse than US avg
Arlington County 40
Albemarle County, Virginia 41
US average 38
Unhealthy days / yr about average
Arlington County 0
Albemarle County, Virginia 0
US average 0
Other Counties in Virginia
Air quality comparison for nearby counties in Virginia.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Arlington County.
Amador County, California
AQI 40 · 84.8% good
Anne Arundel County, Maryland
AQI 40 · 87.2% good
Bergen County, New Jersey
AQI 40 · 71.1% good
Berkeley County, West Virginia
AQI 40 · 81.1% good
Billings County, North Dakota
AQI 40 · 80.3% good
Bossier County, Louisiana
AQI 40 · 86.5% good
What Arlington 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 40 means for exposure. Health guidance
- See how Arlington County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Arlington County with its Virginia neighbours before drawing a conclusion about the region. All of Virginia
Based on 283 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 Arlington County, Virginia? ▼
Arlington County has a median Air Quality Index (AQI) of 40, rated "Good." 84.8% of monitored days (240 out of 283) had good air quality in 2025.
What is the main pollutant in Arlington County? ▼
The primary pollutant in Arlington County is Ozone (O3), which was the main AQI driver on 216 days (76% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Arlington County have? ▼
In 2025, Arlington County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 140.
Is the air quality in Arlington County getting better or worse? ▼
Air quality in Arlington County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 332 good days. Worst year: 2025 with 240 good days.
What does AQI 40 mean for health? ▼
Arlington County's median AQI of 40 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 Arlington County compare to other counties in Virginia? ▼
Arlington County has 84.8% good air days. Nearby counties in Virginia: Albemarle (77.9% good), Bristol City (78.3% good), Caroline (96.2% good), Carroll (100.0% good), Charles (88.6% good), Chesterfield (77.2% good).
What is the 90th percentile AQI in Arlington County? ▼
The 90th percentile AQI for Arlington County is 56, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 140 (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.