Metro area air quality · 2025

Boston-Cambridge-Newton, MA-NH

Median AQI 44 (Good). 68.3% of monitored days rated Good across this metro's EPA monitoring network.

44
Median AQI
68.3%
Good-air days
0
Unhealthy days
41%
Cleaner than US metros

Aggregated from EPA Air Quality System (2025), 274 monitored days. EPA AQS →

The verdict

The Boston-Cambridge-Newton, MA-NH metro runs good on the EPA scale, more polluted than the median US metro, a median AQI of 44 with 68.3% of 274 monitored days in the Good band.

44
median AQI · Good
68.3%
days rated Good
41%
cleaner than US metros
136
worst single reading

No day crossed into the Unhealthy tier across the metro's monitors in 2025.

Insights: Boston-Cambridge-Newton, MA-NH metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 44 over 274 measured days in 2025, which corresponds to a Good band and a Moderate metro-wide health grade. The monitored-day split lands at 187 Good days (68%), 82 Moderate (30%), and 5 Unhealthy-for-Sensitive-Groups (2%). The 90th-percentile AQI finished at 67 while the highest single-day reading hit 136 (USG). Metro residents averaged roughly 20.5 clean-air days per 30-day window across the reporting year.

Across the 2020–2025 trend window, good days shifted by -8 and the median AQI moved -5 points, which classifies the multi-year trajectory as improving. The metro avoided any Unhealthy-tier days entirely, an outcome that typically reflects favorable wind patterns, lower industrial density, or effective regional emission controls. Metros with comparable AQI profiles include Athens-Clarke County, GA (66.7% good, AQI 44); Bartlesville, OK (65.6% good, AQI 44); Bloomington, IL (64.1% good, AQI 44).

Air Quality Summary

Median AQI

44

Good

Good Days

68.3%

187 of 274 days

Max AQI

136

USG

Health Grade

Moderate

90th pct: 67

AQI Day Breakdown (2025)

Distribution of 274 monitored days across EPA AQI categories.

Good

187

68%

Moderate

82

30%

USG

5

2%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Moderate

The Boston-Cambridge-Newton, MA-NH metro area's air quality is rated Moderate based on 68.3% good air days. No unhealthy air days were recorded in 2025.

Air quality is generally acceptable. Unusually sensitive people should monitor real-time conditions at AirNow.gov during high-pollution events.

How does the Boston-Cambridge-Newton, MA-NH metro compare?

How Boston-Cambridge-Newton, MA-NH compares

Good-day share worse than US avg
Boston-Cambridge-Newton, MA-NH 68.3%
Athens-Clarke County, GA 66.7%
US average 71.3%
Median AQI worse than US avg
Boston-Cambridge-Newton, MA-NH 44
Athens-Clarke County, GA 44
US average 41
Unhealthy days / yr better than US avg
Boston-Cambridge-Newton, MA-NH 0
Athens-Clarke County, GA 0
US average 1

5-Year Air Quality Trend

Air quality is improving in the Boston-Cambridge-Newton, MA-NH metro. Best year: 2024 (256 good days).

Year Good Moderate Unhealthy Median AQI
2020 195 171 0 49
2021 206 154 1 48
2022 197 162 0 49
2023 190 168 0 50
2024 256 105 2 43
2025 187 82 0 44

Metros with Similar Air Quality

Metro areas across the US with a similar median AQI to Boston-Cambridge-Newton, MA-NH.

Athens-Clarke County, GA

AQI 44 · 66.7% good

44

Bartlesville, OK

AQI 44 · 65.6% good

44

Bloomington, IL

AQI 44 · 64.1% good

44

Bridgeport-Stamford-Norwalk, CT

AQI 44 · 66.8% good

44

Buffalo-Cheektowaga-Niagara Falls, NY

AQI 44 · 61.3% good

44

Casper, WY

AQI 44 · 85.6% good

44

More Air Quality Data

Explore EPA air quality rankings and guides across U.S. metros and counties.

Cleanest Metro Areas

U.S. metros ranked by their share of Good air-quality days.

Worst Air Quality

Counties and metros with the most unhealthy air days.

All Metro Areas

Annual AQI by CBSA for every monitored U.S. metro area.

Best and Worst City Air

What drives urban air quality and how metro areas compare.

Air Quality Guides

Frequently Asked Questions

What is the air quality in the Boston-Cambridge-Newton, MA-NH metro area? ▼
The Boston-Cambridge-Newton, MA-NH metro area has a median Air Quality Index (AQI) of 44, rated "Good." 68.3% of monitored days (187 out of 274) had good air quality in 2025.
How many unhealthy air days does Boston-Cambridge-Newton, MA-NH have? ▼
In 2025, the Boston-Cambridge-Newton, MA-NH metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 136.
Is air quality in Boston-Cambridge-Newton, MA-NH getting better or worse? ▼
Air quality in the Boston-Cambridge-Newton, MA-NH metro is improving based on 5-year trends (2020-2025). Best year: 2024 with 256 good days. Worst year: 2025 with 187 good days.
What does AQI 44 mean for health? ▼
An AQI of 44 is "Good", air quality is satisfactory and poses little or no health risk. This is the best category on the EPA's AQI scale.
What is the 90th percentile AQI for Boston-Cambridge-Newton, MA-NH? ▼
The 90th percentile AQI for the Boston-Cambridge-Newton, MA-NH metro area is 67, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 136 (USG).
How does Boston-Cambridge-Newton, MA-NH compare to other metro areas? ▼
The Boston-Cambridge-Newton, MA-NH metro has 68.3% good air days. Similar metros: Athens-Clarke County, GA (66.7% good), Bartlesville, OK (65.6% good), Bloomington, IL (64.1% good).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset, 2020–2025. See our methodology for how AQI, median, and coverage figures are computed.

Read our methodology , how this data is sourced, computed, and verified.

Source: U.S. EPA Air Quality System (AQS) Annual AQI by CBSA summary files (metro-level) · 2020–2025

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.