Metro area air quality · 2025

Boston-Cambridge-Newton, MA-NH

Median AQI 44 (Good). 71.0% of monitored days rated Good across this metro's EPA monitoring network.

44
Median AQI
71.0%
Good-air days
0
Unhealthy days
47%
Cleaner than US metros

Boston-Cambridge-Newton, MA-NH posted a 2025 median AQI of 44 (Good) with 71.0% Good days

According to the U.S. EPA Air Quality System, the Boston-Cambridge-Newton, MA-NH CBSA recorded a median AQI of 44 across 365 monitored days in 2025, with 71.0% rated Good and 0 unhealthy or worse. This is an annual metro comparison, not a live advisory.

Data source EPA Air Quality System (AQS)

Cleaner than US metros
The Boston-Cambridge-Newton, MA-NH CBSA's 71.0% Good-day share places it cleaner than 47% of US metros in 2025.
Closest median-AQI peer
Bartlesville, OK (68.0% Good, median AQI 44) is the closest nationwide median-AQI peer to Boston-Cambridge-Newton, MA-NH.
2020–2025 Good-day shift
Boston-Cambridge-Newton, MA-NH's Good-day share moved +18.7 points from 2020 to 2025 (median AQI -5).
Median AQI
Median AQI: 44

Aggregated from EPA Air Quality System (2025), 365 monitored days. EPA AQS →

The verdict

Boston-Cambridge-Newton, MA-NH's peak reading 150 is in the upper max-AQI tercile among CBSA metros here. On the EPA scale the metro runs good, more polluted than the median US metro, with a median AQI of 44 and 71.0% of 365 monitored days in the Good band.

44
median AQI · Good
71.0%
days rated Good
47%
cleaner than US metros
150
worst single reading

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

Annual release change

What changed in the 2025 EPA annual release

2024 → 2025
  • Boston-Cambridge-Newton, MA-NH metro's peak single-day AQI fell from 1513 to 150 between the 2024 and 2025 EPA annual releases, a change of -1363 points.
  • Boston-Cambridge-Newton, MA-NH metro's Unhealthy-category days fell from 2 to 0 between the 2024 and 2025 EPA annual releases, a change of -2 days.
  • Boston-Cambridge-Newton, MA-NH metro's Good-day share rose from 70.5% to 71.9% between the 2024 and 2025 EPA annual releases, a change of +1.4 percentage points.

Compared against 363 monitored days in 2024 and 360 in 2025. These are arithmetic differences between two stored EPA annual summaries, not a cause claim or a live advisory.

National release changes Two-year CSV

Boston-Cambridge-Newton, MA-NH's peak reading 150 is in the upper max-AQI tercile among CBSA metros here. Signature read: peak AQI 150 (high tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 44 over 365 measured days in 2025 (Good / Moderate). The monitored-day split lands at 259 Good (71%), 101 Moderate (28%), and 5 Unhealthy-for-Sensitive-Groups (1%). The 90th-percentile AQI finished at 64; the highest single-day reading hit 150 (USG).

Across 2020–2025, Good-day share shifted +18.7 points and median AQI moved -5 (improving). No Unhealthy-tier days appear in this annual dataset. Metros with comparable AQI profiles include Bartlesville, OK (68.0% good, AQI 44); Berlin, NH-VT (81.5% good, AQI 44); Bloomington, IL (66.0% good, AQI 44).

Health effects of air pollution →

Air Quality Summary

Median AQI

44

Good

Good Days

71.0%

259 of 365 days

Max AQI

150

USG

Health Grade

Moderate

90th pct: 64

AQI Day Breakdown (2025)

Distribution of 365 monitored days across EPA AQI categories.

Good

259

71%

Moderate

101

28%

USG

5

1%

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 71.0% 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 about typical
Boston-Cambridge-Newton, MA-NH 71.0%
Bartlesville, OK 68.0%
Typical US metro 70.6%
Median AQI worse than typical
Boston-Cambridge-Newton, MA-NH 44
Bartlesville, OK 44
Typical US metro 41
Unhealthy days / yr better than typical
Boston-Cambridge-Newton, MA-NH 0
Bartlesville, OK 1
Typical US metro 1

5-Year Air Quality Trend

Air quality is improving in the Boston-Cambridge-Newton, MA-NH metro. Highest Good-day share: 2025 (71.9%, 259 of 360 monitored 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 259 101 0 44

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Boston-Cambridge-Newton, MA-NH (44).

Bartlesville, OK

Median AQI 44 · 68.0% Good-day share

44

Berlin, NH-VT

Median AQI 44 · 81.5% Good-day share

44

Bloomington, IL

Median AQI 44 · 66.0% Good-day share

44

Bridgeport-Stamford-Norwalk, CT

Median AQI 44 · 64.7% Good-day share

44

Buffalo-Cheektowaga-Niagara Falls, NY

Median AQI 44 · 63.8% Good-day share

44

Cedar City, UT

Median AQI 44 · 74.7% Good-day share

44

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Boston-Cambridge-Newton, MA-NH's 0 (independent of median AQI).

Aberdeen, SD

0 unhealthy-or-worse days · median AQI 27

27

Aberdeen, WA

0 unhealthy-or-worse days · median AQI 22

22

Adrian, MI

0 unhealthy-or-worse days · median AQI 41

41

Akron, OH

0 unhealthy-or-worse days · median AQI 45

45

Albany, GA

0 unhealthy-or-worse days · median AQI 46

46

Albany, OR

0 unhealthy-or-worse days · median AQI 27

27

Frequently Asked Questions

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 64, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 150 (USG).
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 150.
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." 71.0% of monitored days (259 out of 365) had good air quality in 2025.
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 across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2025 at 71.9% (259 of 360 days). Lowest qualifying Good-day share: 2023 at 53.1% (190 of 358 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.
How does Boston-Cambridge-Newton, MA-NH compare to other metro areas? ▼
The Boston-Cambridge-Newton, MA-NH metro has 71.0% good air days. Similar metros: Bartlesville, OK (68.0% good), Berlin, NH-VT (81.5% good), Bloomington, IL (66.0% good).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Boston-Cambridge-Newton, MA-NH, 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, Boston-Cambridge-Newton, MA-NH · 2020–2025