Metro area air quality · 2025

Marietta, OH

Median AQI 41 (Good). 86.7% of monitored days rated Good across this metro's EPA monitoring network.

41
Median AQI
86.7%
Good-air days
0
Unhealthy days
78%
Cleaner than US metros

Aggregated from EPA Air Quality System (2025), 211 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 41 with 86.7% of 211 monitored days in the Good band.

41
median AQI · Good
86.7%
days rated Good
78%
cleaner than US metros
105
worst single reading

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

Insights: Marietta, OH metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 41 over 211 measured days in 2025, which corresponds to a Good band and a Good metro-wide health grade. The monitored-day split lands at 183 Good days (87%), 26 Moderate (12%), and 2 Unhealthy-for-Sensitive-Groups (1%). The 90th-percentile AQI finished at 61 while the highest single-day reading hit 105 (USG). Metro residents averaged roughly 26.0 clean-air days per 30-day window across the reporting year.

Across the 2020–2025 trend window, good days shifted by -50 and the median AQI moved +3 points, which classifies the multi-year trajectory as worsening. 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 Adrian, MI (77.3% good, AQI 41); Altoona, PA (71.9% good, AQI 41); Ann Arbor, MI (76.0% good, AQI 41).

Air Quality Summary

Median AQI

41

Good

Good Days

86.7%

183 of 211 days

Max AQI

105

USG

Health Grade

Good

90th pct: 61

AQI Day Breakdown (2025)

Distribution of 211 monitored days across EPA AQI categories.

Good

183

87%

Moderate

26

12%

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 86.7% 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 US avg
Marietta, OH 86.7%
Adrian, MI 77.3%
US average 71.3%
Median AQI about average
Marietta, OH 41
Adrian, MI 41
US average 41
Unhealthy days / yr better than US avg
Marietta, OH 0
Adrian, MI 0
US average 1

5-Year Air Quality Trend

Air quality is worsening in the Marietta, OH metro. Best year: 2020 (233 good 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 183 26 0 41

Metros with Similar Air Quality

Metro areas across the US with a similar median AQI to Marietta, OH.

Adrian, MI

AQI 41 · 77.3% good

41

Altoona, PA

AQI 41 · 71.9% good

41

Ann Arbor, MI

AQI 41 · 76.0% good

41

Bowling Green, KY

AQI 41 · 81.2% good

41

Charlottesville, VA

AQI 41 · 77.9% good

41

Clarksville, TN-KY

AQI 41 · 76.8% good

41

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 41, rated "Good." 86.7% of monitored days (183 out of 211) 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 based on 5-year trends (2020-2025). Best year: 2020 with 233 good days. Worst year: 2025 with 183 good days.
What does AQI 41 mean for health? ▼
An AQI of 41 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 61, 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 86.7% good air days. Similar metros: Adrian, MI (77.3% good), Altoona, PA (71.9% good), Ann Arbor, MI (76.0% 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.