Metro area air quality · 2025

Durham-Chapel Hill, NC

Median AQI 43 (Good). 71.5% of monitored days rated Good across this metro's EPA monitoring network.

43
Median AQI
71.5%
Good-air days
0
Unhealthy days
48%
Cleaner than US metros

Durham-Chapel Hill, NC posted a 2025 median AQI of 43 (Good) with 71.5% Good days

According to the U.S. EPA Air Quality System, the Durham-Chapel Hill, NC CBSA recorded a median AQI of 43 across 365 monitored days in 2025, with 71.5% 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 Durham-Chapel Hill, NC CBSA's 71.5% Good-day share places it cleaner than 48% of US metros in 2025.
Closest median-AQI peer
Ashtabula, OH (81.2% Good, median AQI 43) is the closest nationwide median-AQI peer to Durham-Chapel Hill, NC.
2020–2025 Good-day shift
Durham-Chapel Hill, NC's Good-day share moved +16.0 points from 2020 to 2025 (median AQI -5).
Median AQI
Median AQI: 43

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

The verdict

Durham-Chapel Hill, NC's peak reading 77 stays in the lower max-AQI tercile on this extract. On the EPA scale the metro runs good, more polluted than the median US metro, with a median AQI of 43 and 71.5% of 365 monitored days in the Good band.

43
median AQI · Good
71.5%
days rated Good
48%
cleaner than US metros
77
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
  • Durham-Chapel Hill, NC metro's Good-day share rose from 46.2% to 71.5% between the 2024 and 2025 EPA annual releases, a change of +25.3 percentage points.
  • Durham-Chapel Hill, NC metro's median AQI fell from 51 to 43 between the 2024 and 2025 EPA annual releases, a change of -8 points.
  • Durham-Chapel Hill, NC metro's peak single-day AQI fell from 97 to 77 between the 2024 and 2025 EPA annual releases, a change of -20 points.

Compared against 366 monitored days in 2024 and 365 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

Durham-Chapel Hill, NC's peak reading 77 stays in the lower max-AQI tercile on this extract. Signature read: peak AQI 77 (low tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 43 over 365 measured days in 2025 (Good / Moderate). The monitored-day split lands at 261 Good (72%), 104 Moderate (28%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 57; the highest single-day reading hit 77 (Moderate).

Across 2020–2025, Good-day share shifted +16.0 points and median AQI moved -5 (improving). No Unhealthy-tier days appear in this annual dataset. Metros with comparable AQI profiles include Ashtabula, OH (81.2% good, AQI 43); Bloomington, IN (67.7% good, AQI 43); Champaign-Urbana, IL (65.8% good, AQI 43).

Understanding AQI →

Air Quality Summary

Median AQI

43

Good

Good Days

71.5%

261 of 365 days

Max AQI

77

Moderate

Health Grade

Moderate

90th pct: 57

AQI Day Breakdown (2025)

Distribution of 365 monitored days across EPA AQI categories.

Good

261

72%

Moderate

104

28%

USG

0

0%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Moderate

The Durham-Chapel Hill, NC metro area's air quality is rated Moderate based on 71.5% 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 Durham-Chapel Hill, NC metro compare?

How Durham-Chapel Hill, NC compares

Good-day share better than typical
Durham-Chapel Hill, NC 71.5%
Ashtabula, OH 81.2%
Typical US metro 70.6%
Median AQI worse than typical
Durham-Chapel Hill, NC 43
Ashtabula, OH 43
Typical US metro 41
Unhealthy days / yr better than typical
Durham-Chapel Hill, NC 0
Ashtabula, OH 0
Typical US metro 1

5-Year Air Quality Trend

Air quality is improving in the Durham-Chapel Hill, NC metro. Highest Good-day share: 2025 (71.5%, 261 of 365 monitored days).

Year Good Moderate Unhealthy Median AQI
2020 203 163 0 48
2021 159 205 1 52
2022 208 157 0 47
2023 162 196 2 52
2024 169 197 0 51
2025 261 104 0 43

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Durham-Chapel Hill, NC (43).

Ashtabula, OH

Median AQI 43 · 81.2% Good-day share

43

Bloomington, IN

Median AQI 43 · 67.7% Good-day share

43

Champaign-Urbana, IL

Median AQI 43 · 65.8% Good-day share

43

Cleveland, MS

Median AQI 43 · 71.9% Good-day share

43

Columbus, IN

Median AQI 43 · 72.6% Good-day share

43

Elizabethtown-Fort Knox, KY

Median AQI 43 · 73.4% Good-day share

43

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Durham-Chapel Hill, NC'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 Durham-Chapel Hill, NC? ▼
The 90th percentile AQI for the Durham-Chapel Hill, NC metro area is 57, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 77 (Moderate).
How many unhealthy air days does Durham-Chapel Hill, NC have? ▼
In 2025, the Durham-Chapel Hill, NC metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 77.
What is the air quality in the Durham-Chapel Hill, NC metro area? ▼
The Durham-Chapel Hill, NC metro area has a median Air Quality Index (AQI) of 43, rated "Good." 71.5% of monitored days (261 out of 365) had good air quality in 2025.
Is air quality in Durham-Chapel Hill, NC getting better or worse? ▼
Air quality in the Durham-Chapel Hill, NC 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 71.5% (261 of 365 days). Lowest qualifying Good-day share: 2021 at 43.6% (159 of 365 days).
What does AQI 43 mean for health? ▼
An AQI of 43 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 Durham-Chapel Hill, NC compare to other metro areas? ▼
The Durham-Chapel Hill, NC metro has 71.5% good air days. Similar metros: Ashtabula, OH (81.2% good), Bloomington, IN (67.7% good), Champaign-Urbana, IL (65.8% good).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Durham-Chapel Hill, NC, 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, Durham-Chapel Hill, NC · 2020–2025