Air quality · Maryland
Air quality in Maryland
Across the 5 Maryland ZIPs with EPA county air-quality data, the median day is Good in all 5 (median AQI 39–43). No day in those counties reached Unhealthy in 2025. This is a 2025 county annual summary, not a live reading.
Last verified 2026-09-24 · methodology
Air quality by ZIP code in Maryland
EPA's 2025 annual summary for each ZIP's county. Median AQI is the typical day; lower is cleaner.
| ZIP | Median AQI | Good days | Unhealthy or worse |
|---|---|---|---|
| 21201BaltimoreBaltimore (city) | 43 Good | 248 of 364 | 0 |
| 20850RockvilleMontgomery County | 39 Good | 299 of 360 | 0 |
| 21401AnnapolisAnne Arundel County | 40 Good | 227 of 259 | 0 |
| 21202BaltimoreBaltimore City | 43 Good | 248 of 364 | 0 |
| 20815Chevy ChaseMontgomery County | 39 Good | 299 of 360 | 0 |
County-level figures from EPA Air Quality System (AQS), annual county summary, joined to each ZIP by county. None of them is a measurement at a specific address.
What lands here
Pages show the 2025 median AQI category (Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, Hazardous) for the ZIP's county, plus the year's max/90th-percentile AQI and day-count breakdown by category.
Source & refresh
EPA Air Quality System (AQS), annual county summary. Refreshed annual (epa aqs publication). Primary source →
Maryland top concern
Chesapeake flood, lead pipes
Maryland has dense FEMA NFHL coverage along Chesapeake Bay tributaries. Baltimore City has extensive LCRR lead-service-line obligations and flagged EPA SDWIS compliance history. Radon Zone 1-2 across most counties.
See Maryland state page for the full state-level rollup across all 12 dimensions.
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