Median AQI
37
Good
Massachusetts · County air quality · 2025
Dukes County, Massachusetts
Median AQI 37 (Good). 95.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 37
- Median AQI
- 95.2%
- Good-air days
- 1
- Unhealthy days
- 90%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Dukes County's air is good on balance, among the cleanest 10% of US counties, a median AQI of 37 with 95.2% of 210 monitored days in the Good band, driven mainly by Ozone.
- 37
- median AQI · Good
- 95.2%
- days rated Good
- Ozone
- main pollutant
- 90%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 151.
Data updated July 2026
- Good · 200 d · 95.2%
- Moderate · 8 d · 3.8%
- USG · 1 d · 0.5%
- Unhealthy · 1 d · 0.5%
How did Dukes County's air break down in 2025?
Across 210 monitored days, 200 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 151 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 210 days monitored. Median AQI: 37 (Good).
Insights: Dukes County, Massachusetts. EPA monitors recorded a median Air Quality Index of 37 across 210 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 200 (95%) fell in the Good band (AQI 0–50), 8 (4%) registered Moderate readings, and 1 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 46, while the worst single-day peak hit 151 (Unhealthy). Residents averaged about 28.6 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (206 days), PM2.5 (4 days). Across the 2020–2025 trend window, good days shifted by -145 and the median AQI moved +0 points, placing the multi-year trajectory at stable. Residents and visitors experienced 1 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Barnstable (92.5% good, AQI 38); Berkshire (71.6% good, AQI 41); Bristol (77.8% good, AQI 41); Essex (77.0% good, AQI 42); Franklin (72.8% good, AQI 40); Hampden (72.2% good, AQI 41).
Air Quality Summary
Good Days
95.2%
200 of 210 monitored days
20.2pp vs 75% target
Max AQI Recorded
151
Unhealthy
Health Grade
Excellent
90th-pct AQI 46
Dukes County, Good days share 95.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
Dukes County, Unhealthy-or-worse share 0.5%
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 210 monitored days across EPA AQI categories.
Good
200
95%
Moderate
8
4%
USG
1
0%
Unhealthy
1
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Dukes County.
- Ozone · 206 days · 98.1%
- PM2.5 · 4 days · 1.9%
Health Impact Assessment
Excellent
Dukes County's air quality is rated Excellent based on 95.2% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 1 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 151. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is Ozone, driving AQI on 206 of 210 monitored days.
5-Year Air Quality Trend
Air quality is stable in Dukes County. Best year: 2020 (345 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 345 | 11 | 1 | 0 | 37 | 126 |
| 2021 | 329 | 27 | 0 | 0 | 36 | 100 |
| 2022 | 338 | 20 | 1 | 0 | 37 | 126 |
| 2023 | 332 | 25 | 6 | 0 | 38 | 133 |
| 2024 | 331 | 25 | 1 | 0 | 37 | 108 |
| 2025 | 200 | 8 | 1 | 1 | 37 | 151 |
How does Dukes County compare?
How Dukes County compares
Good-day share better than US avg
Dukes County 95.2%
Barnstable County, Massachusetts 92.5%
US average 76.5%
Median AQI better than US avg
Dukes County 37
Barnstable County, Massachusetts 38
US average 38
Unhealthy days / yr worse than US avg
Dukes County 1
Barnstable County, Massachusetts 0
US average 0
Other Counties in Massachusetts
Air quality comparison for nearby counties in Massachusetts.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Dukes County.
Alachua County, Florida
AQI 37 · 90.1% good
Beltrami County, Minnesota
AQI 37 · 88.8% good
Benewah County, Idaho
AQI 37 · 74.6% good
Brevard County, Florida
AQI 37 · 89.7% good
Brown County, Indiana
AQI 37 · 94.5% good
Brown County, Wisconsin
AQI 37 · 79.0% good
What Dukes County's air means for you
On most days the air here is fine, but Ozone drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 37 means for exposure. Health guidance
- See how Dukes County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Dukes County with its Massachusetts neighbours before drawing a conclusion about the region. All of Massachusetts
Based on 210 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 Dukes County, Massachusetts? ▼
Dukes County has a median Air Quality Index (AQI) of 37, rated "Good." 95.2% of monitored days (200 out of 210) had good air quality in 2025.
What is the main pollutant in Dukes County? ▼
The primary pollutant in Dukes County is Ozone (O3), which was the main AQI driver on 206 days (98% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Dukes County have? ▼
In 2025, Dukes County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 151.
Is the air quality in Dukes County getting better or worse? ▼
Air quality in Dukes County is stable based on 5-year trends (2020-2025). Best year: 2020 with 345 good days. Worst year: 2025 with 200 good days.
What does AQI 37 mean for health? ▼
Dukes County's median AQI of 37 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 Dukes County compare to other counties in Massachusetts? ▼
Dukes County has 95.2% good air days. Nearby counties in Massachusetts: Barnstable (92.5% good), Berkshire (71.6% good), Bristol (77.8% good), Essex (77.0% good), Franklin (72.8% good), Hampden (72.2% good).
What is the 90th percentile AQI in Dukes County? ▼
The 90th percentile AQI for Dukes County is 46, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 151 (Unhealthy).
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.