Metro area air quality · 2025

Marietta, OH

Median AQI 40 (Good). 88.4% of monitored days rated Good across this metro's EPA monitoring network.

40
Median AQI
88.4%
Good-air days
0
Unhealthy days
83%
Cleaner than US metros

Marietta, OH posted a 2025 median AQI of 40 (Good) with 88.4% Good days

According to the U.S. EPA Air Quality System, the Marietta, OH CBSA recorded a median AQI of 40 across 242 monitored days in 2025, with 88.4% 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 Marietta, OH CBSA's 88.4% Good-day share places it cleaner than 83% of US metros in 2025.
Closest median-AQI peer
Altoona, PA (76.9% Good, median AQI 40) is the closest nationwide median-AQI peer to Marietta, OH.
2020–2025 Good-day shift
Marietta, OH's Good-day share moved -6.3 points from 2020 to 2025 (median AQI +2).
Median AQI
Median AQI: 40

Aggregated from EPA Air Quality System (2025), 242 monitored days. EPA AQS →

The verdict

The Marietta, OH metro runs good on the EPA scale, cleaner than most US metros, a median AQI of 40 with 88.4% of 242 monitored days in the Good band.

40
median AQI · Good
88.4%
days rated Good
83%
cleaner than US metros
105
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
  • Marietta, OH metro's Good-day share rose from 86.9% to 89.2% between the 2024 and 2025 EPA annual releases, a change of +2.3 percentage points.
  • Marietta, OH metro's peak single-day AQI rose from 90 to 105 between the 2024 and 2025 EPA annual releases, a change of +15 points.

Compared against 244 monitored days in 2024 and 240 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

Insights: Marietta, OH metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 40 over 242 measured days in 2025, which corresponds to a Good band and a Good metro-wide health grade. The monitored-day split lands at 214 Good days (88%), 26 Moderate (11%), and 2 Unhealthy-for-Sensitive-Groups (1%). The 90th-percentile AQI finished at 54 while the highest single-day reading hit 105 (USG). Metro residents averaged roughly 26.5 clean-air days per 30-day window across the reporting year.

Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -6.3 points and the median AQI moved +2 points, which classifies the multi-year trajectory as worsening. The metro recorded no Unhealthy-tier days in this annual dataset. Metros with comparable AQI profiles include Altoona, PA (76.9% good, AQI 40); Beaver Dam, WI (72.3% good, AQI 40); Bismarck, ND (76.7% good, AQI 40).

Air Quality Summary

Median AQI

40

Good

Good Days

88.4%

214 of 242 days

Max AQI

105

USG

Health Grade

Good

90th pct: 54

AQI Day Breakdown (2025)

Distribution of 242 monitored days across EPA AQI categories.

Good

214

88%

Moderate

26

11%

USG

2

1%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Good

The Marietta, OH metro area's air quality is rated Good based on 88.4% 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 Marietta, OH metro compare?

How Marietta, OH compares

Good-day share better than typical
Marietta, OH 88.4%
Altoona, PA 76.9%
Typical US metro 70.6%
Median AQI better than typical
Marietta, OH 40
Altoona, PA 40
Typical US metro 41
Unhealthy days / yr better than typical
Marietta, OH 0
Altoona, PA 0
Typical US metro 1

5-Year Air Quality Trend

Air quality is worsening in the Marietta, OH metro. Highest Good-day share: 2020 (95.5%, 233 of 244 monitored days).

Year Good Moderate Unhealthy Median AQI
2020 233 11 0 38
2021 222 23 0 39
2022 222 23 0 39
2023 206 32 0 42
2024 212 32 0 41
2025 214 26 0 40

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Marietta, OH (40).

Altoona, PA

Median AQI 40 · 76.9% Good-day share

40

Beaver Dam, WI

Median AQI 40 · 72.3% Good-day share

40

Bismarck, ND

Median AQI 40 · 76.7% Good-day share

40

Cape Coral-Fort Myers, FL

Median AQI 40 · 76.4% Good-day share

40

College Station-Bryan, TX

Median AQI 40 · 68.5% Good-day share

40

Fallon, NV

Median AQI 40 · 85.2% Good-day share

40

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Marietta, OH'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

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 Marietta, OH metro area? ▼
The Marietta, OH metro area has a median Air Quality Index (AQI) of 40, rated "Good." 88.4% of monitored days (214 out of 242) had good air quality in 2025.
How many unhealthy air days does Marietta, OH have? ▼
In 2025, the Marietta, OH metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 105.
Is air quality in Marietta, OH getting better or worse? ▼
Air quality in the Marietta, OH metro is worsening across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2020 at 95.5% (233 of 244 days). Lowest qualifying Good-day share: 2023 at 86.6% (206 of 238 days).
What does AQI 40 mean for health? ▼
An AQI of 40 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 Marietta, OH? ▼
The 90th percentile AQI for the Marietta, OH metro area is 54, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 105 (USG).
How does Marietta, OH compare to other metro areas? ▼
The Marietta, OH metro has 88.4% good air days. Similar metros: Altoona, PA (76.9% good), Beaver Dam, WI (72.3% good), Bismarck, ND (76.7% 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

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Every figure on PlainAirData 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.