Median AQI
43
Good
Maryland · County air quality · 2025
Baltimore (City) County, Maryland
Median AQI 43 (Good). 68.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 43
- Median AQI
- 68.1%
- Good-air days
- 0
- Unhealthy days
- 28%
- Cleaner than US counties
Baltimore (City) County's 2025 annual median AQI is 43 (Good), with 68.1% Good days
According to the U.S. EPA Air Quality System, Baltimore (City) County, Maryland posted a 2025 median AQI of 43 (Good) across 364 monitored days, with 68.1% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Baltimore (City) County's 68.1% Good-day share places it cleaner than 28% of US counties in 2025.
- Closest median-AQI peer
- Ashtabula County (81.2% Good, median AQI 43) is the closest nationwide median-AQI peer to Baltimore (City) County.
- 2020–2025 trend
- Baltimore (City) County's floor-qualifying Good-day share is worsening from 2020 to 2025 (80.7% → 68.1%).
- Median AQI
- Median AQI: 43
The verdict
According to EPA Air Quality System monitoring data, Baltimore (City) County's air is good on balance, more polluted than the median US county, a median AQI of 43 with 68.1% of 364 monitored days in the Good band, driven mainly by PM2.5.
- 43
- median AQI · Good
- 68.1%
- days rated Good
- PM2.5
- main pollutant
- 28%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 136.
Annual release change
What changed in the 2025 EPA annual release
- Baltimore (City) County's Good-day share fell from 70.7% to 68.1% between the 2024 and 2025 EPA annual releases, a change of -2.6 percentage points.
- Baltimore (City) County's peak single-day AQI rose from 112 to 136 between the 2024 and 2025 EPA annual releases, a change of +24 points.
Data updated August 2026
- Good · 248 d · 68.1%
- Moderate · 114 d · 31.3%
- USG · 2 d · 0.5%
How did Baltimore (City) County's air break down in 2025?
Across 364 monitored days, 248 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 136 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 364 days monitored. Median AQI: 43 (Good).
Insights: Baltimore (City) County, Maryland. EPA monitors recorded a median Air Quality Index of 43 across 364 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 248 (68%) fell in the Good band (AQI 0–50), 114 (31%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 64, while the worst single-day peak hit 136 (USG). Residents averaged about 20.4 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (191 days), Ozone (162 days), NO2 (11 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -12.6 points and the median AQI moved +5 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 136, usg but never Unhealthy. Nearby counties show comparable readings: Anne Arundel (87.6% good, AQI 40); Baltimore (64.7% good, AQI 45); Calvert (94.6% good, AQI 38); Carroll (90.3% good, AQI 38); Cecil (79.8% good, AQI 41); Charles (92.4% good, AQI 38).
Air Quality Summary
Good Days
68.1%
248 of 364 monitored days
-6.9pp vs 75% target
Max AQI Recorded
136
USG
Health Grade
Moderate
90th-pct AQI 64
Baltimore (City) County, Good days share 68.1%
National avg
Share of monitored days at AQI 0-50 (Good band).
Baltimore (City) County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 364 monitored days across EPA AQI categories.
Good
248
68%
Moderate
114
31%
USG
2
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Baltimore (City) County.
- PM2.5 · 191 days · 52.5%
- Ozone · 162 days · 44.5%
- NO₂ · 11 days · 3.0%
Health Impact Assessment
Moderate
Baltimore (City) County's air quality is rated Moderate based on 68.1% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 68.1% of monitored days in 2025, with a median AQI of 43. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 191 of 364 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Baltimore (City) County. Highest Good-day share: 2020 (80.7%, 293 of 363 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 293 | 70 | 0 | 0 | 38 | 97 |
| 2021 | 243 | 121 | 0 | 0 | 43 | 93 |
| 2022 | 242 | 109 | 2 | 0 | 44 | 112 |
| 2023 | 242 | 116 | 4 | 3 | 44 | 192 |
| 2024 | 258 | 101 | 6 | 0 | 42 | 112 |
| 2025 | 248 | 114 | 2 | 0 | 43 | 136 |
How does Baltimore (City) County compare?
How Baltimore (City) County compares
Good-day share worse than typical
Baltimore (City) County 68.1%
Ashtabula County, Ohio 81.2%
Typical US county 76.0%
Median AQI worse than typical
Baltimore (City) County 43
Ashtabula County, Ohio 43
Typical US county 39
Unhealthy days / yr better than typical
Baltimore (City) County 0
Ashtabula County, Ohio 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Baltimore (City) County (43), not geographic neighbors.
Ashtabula County, Ohio
Median AQI 43 · 81.2% Good-day share
Bartholomew County, Indiana
Median AQI 43 · 72.6% Good-day share
Berks County, Pennsylvania
Median AQI 43 · 68.2% Good-day share
Bolivar County, Mississippi
Median AQI 43 · 71.9% Good-day share
Brewster County, Texas
Median AQI 43 · 74.7% Good-day share
Broward County, Florida
Median AQI 43 · 73.4% Good-day share
Same primary pollutant: PM2.5
PM2.5 led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Randolph County, Illinois
68.1% Good-day share · median AQI 43
Josephine County, Oregon
68.2% Good-day share · median AQI 33
Edgefield County, South Carolina
68.0% Good-day share · median AQI 43
Snohomish County, Washington
68.0% Good-day share · median AQI 41
Hamilton County, Illinois
67.9% Good-day share · median AQI 42
McHenry County, Illinois
67.9% Good-day share · median AQI 42
Maryland counties on the map
Geographic containment only, other monitored counties in Maryland, independent of AQI or pollutant match.
What Baltimore (City) County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 43 means for exposure. Health guidance
- See how Baltimore (City) County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Baltimore (City) County with its Maryland neighbours before drawing a conclusion about the region. All of Maryland
Based on 364 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Baltimore (City) County, Maryland? ▼
Baltimore (City) County has a median Air Quality Index (AQI) of 43, rated "Good." 68.1% of monitored days (248 out of 364) had good air quality in 2025.
What is the main pollutant in Baltimore (City) County? ▼
The primary pollutant in Baltimore (City) County is Fine Particles (PM2.5), which was the main AQI driver on 191 days (52% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Baltimore (City) County have? ▼
In 2025, Baltimore (City) County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 136.
Is the air quality in Baltimore (City) County getting better or worse? ▼
Air quality in Baltimore (City) County 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 80.7% (293 of 363 days). Lowest qualifying Good-day share: 2023 at 66.3% (242 of 365 days).
What does AQI 43 mean for health? ▼
Baltimore (City) County's median AQI of 43 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Baltimore (City) County compare to other counties in Maryland? ▼
Baltimore (City) County has 68.1% good air days. Nearby counties in Maryland: Anne Arundel (87.6% good), Baltimore (64.7% good), Calvert (94.6% good), Carroll (90.3% good), Cecil (79.8% good), Charles (92.4% good).
What is the 90th percentile AQI in Baltimore (City) County? ▼
The 90th percentile AQI for Baltimore (City) County is 64, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 136 (USG).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Baltimore (City) County, Maryland · 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.