Metro area air quality · 2024

St. Marys, PA

Median AQI 34 (Good). 95.8% of monitored days rated Good across this metro's EPA monitoring network.

34
Median AQI
95.8%
Good-air days
0
Unhealthy days
94%
Cleaner than US metros

Aggregated from EPA Air Quality System (2024), 358 monitored days. EPA AQS → · NOAA →

Insights: St. Marys, PA metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 34 over 358 measured days in 2024, which corresponds to a Good band and a Excellent metro-wide health grade. The monitored-day split lands at 343 Good days (96%), 15 Moderate (4%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 46 while the highest single-day reading hit 67 (Moderate). Metro residents averaged roughly 28.7 clean-air days per 30-day window across the reporting year.

Across the 2020–2024 trend window, good days shifted by -13 and the median AQI moved +0 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 Clarksburg, WV (80.5% good, AQI 34); Kinston, NC (95.8% good, AQI 34); New Castle, IN (78.1% good, AQI 34).

Air Quality Summary

Median AQI

34

Good

Good Days

95.8%

343 of 358 days

Max AQI

67

Moderate

Health Grade

Excellent

90th pct: 46

AQI Day Breakdown (2024)

Distribution of 358 monitored days across EPA AQI categories.

Good

343

96%

Moderate

15

4%

USG

0

0%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Excellent

The St. Marys, PA metro area's air quality is rated Excellent based on 95.8% good air days. No unhealthy air days were recorded in 2024.

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

How does the St. Marys, PA metro compare?

How St. Marys, PA compares

Good-day share better than US avg
St. Marys, PA 95.8%
Clarksburg, WV 80.5%
US average 70.2%
Median AQI better than US avg
St. Marys, PA 34
Clarksburg, WV 34
US average 41
Unhealthy days / yr better than US avg
St. Marys, PA 0
Clarksburg, WV 0
US average 1

5-Year Air Quality Trend

Air quality is worsening in the St. Marys, PA metro. Best year: 2020 (356 good days).

Year Good Moderate Unhealthy Median AQI
2020 356 2 0 34
2021 340 18 0 34
2022 353 9 0 35
2023 343 20 0 35
2024 343 15 0 34

Metros with Similar Air Quality

Metro areas across the US with a similar median AQI to St. Marys, PA.

Clarksburg, WV

AQI 34 · 80.5% good

34

Kinston, NC

AQI 34 · 95.8% good

34

New Castle, IN

AQI 34 · 78.1% good

34

Sioux Falls, SD

AQI 34 · 81.4% good

34

Arkadelphia, AR

AQI 35 · 93.3% good

35

Atlantic City-Hammonton, NJ

AQI 35 · 82.5% good

35

More Air Quality Data

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Air Quality Guides

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Health Effects of Air Pollution

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Frequently Asked Questions

What is the air quality in the St. Marys, PA metro area? ▼
The St. Marys, PA metro area has a median Air Quality Index (AQI) of 34, rated "Good." 95.8% of monitored days (343 out of 358) had good air quality in 2024.
How many unhealthy air days does St. Marys, PA have? ▼
In 2024, the St. Marys, PA metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 67.
Is air quality in St. Marys, PA getting better or worse? ▼
Air quality in the St. Marys, PA metro is worsening based on 5-year trends (2020-2024). Best year: 2020 with 356 good days. Worst year: 2021 with 340 good days.
What does AQI 34 mean for health? ▼
An AQI of 34 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 St. Marys, PA? ▼
The 90th percentile AQI for the St. Marys, PA metro area is 46, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 67 (Moderate).
How does St. Marys, PA compare to other metro areas? ▼
The St. Marys, PA metro has 95.8% good air days. Similar metros: Clarksburg, WV (80.5% good), Kinston, NC (95.8% good), New Castle, IN (78.1% good).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset, 2020–2024. The AQS collects ambient air monitoring data from state, local, and tribal monitoring agencies across the United States.

Metrics: Air Quality Index (AQI) is calculated using EPA-standard breakpoints for six criteria pollutants: PM2.5, PM10, Ozone, NO2, CO, and SO2. Median AQI, max AQI, and 90th percentile AQI are computed from daily measurements. Good days percentage reflects days with AQI 0–50.

Coverage: 501 metro areas (Core Based Statistical Areas). Only metros with active monitoring stations are included. Unmonitored areas are not represented.

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

Source: U.S. EPA, AirNow / AQS Air Quality Index readings and pollutant concentrations · 2025