SmogRank / World / North America / United States / Maryland

Most polluted cities in Maryland, United States

10 measured cities, last 30 days; 0 above the WHO 24-hour guideline. Worst: Baltimore at 5.5 µg/m³, #2,007 in the world.

Ranked by unhealthy days: the share of each city's measured days with a daily mean over 35.4 µg/m³ (US AQI 101+), Unhealthy for Sensitive Groups or worse on the US EPA's scale. Ties go to the higher average.

Pennsylvania: 36 measured citiesVirginia: 14 measured citiesDistrict of Columbia: 1 measured cityMaryland: 10 measured citiesDelaware: 7 measured citiesNew Jersey: 19 measured citiesWest Virginia: 4 measured cities#10 Rockville: 2.5 µg/m³#9 Cambridge: 2.9 µg/m³#8 Oxon Hill-Glassmanor: 3.2 µg/m³#6 Frostburg: 3.6 µg/m³#7 South Laurel: 3.6 µg/m³#5 Halfway: 4.4 µg/m³#4 Edgewood: 4.6 µg/m³#2 Hunt Valley: 4.9 µg/m³#3 Scaggsville: 4.9 µg/m³#1 Baltimore: 5.5 µg/m³
Each dot is a measured city, coloured by its PM2.5; tap a dot to open the city.
← Baltimore 0% 0.75%0
Every measured city in Maryland, United States, one column each, ranked by unhealthy days: height is the share of its measured days that were unhealthy, colour its average. Point at it to read a city; tap to open it.
  1. 1Baltimore 0%
  2. 2Hunt Valley 0%
  3. 2Scaggsville 0%
  4. 4Edgewood 0%
  5. 5Halfway 0%
  6. 6Frostburglast full day 3 Oct 0%
  7. 6South Laurel 0%
  8. 8Oxon Hill-Glassmanor 0%
  9. 9Cambridge 0%
  10. 10Rockville 0%
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales

Estimated: cities without a monitor

Maryland cities we can't measure, with model estimates for the last 7 days. Listed by population, not ranked: estimates aren't precise enough to rank. Model estimates from the Copernicus Atmosphere Monitoring Service (CAMS), adjusted to measured cities nearby where there are any. Adjusted, a single day lands within ×1.5 of what a monitor would read about two times in three; unadjusted, it can be off by half or double. Treat them as a guide, not a measurement.

City7-day estimateBand
Columbia≈ 5 µg/m³Good
Germantown≈ 5 µg/m³Good
Silver Spring≈ 6 µg/m³Good
Frederick≈ 4 µg/m³Good
Waldorf≈ 5 µg/m³Good
Glen Burnie≈ 5 µg/m³Good
Gaithersburg≈ 5 µg/m³Good
Ellicott City≈ 5 µg/m³Good
Dundalk≈ 5 µg/m³Good
Bethesda≈ 6 µg/m³Good
Bowie≈ 5 µg/m³Good
Towson≈ 5 µg/m³Good
Aspen Hill≈ 5 µg/m³Good
Wheaton≈ 5 µg/m³Good
Bel Air South≈ 6 µg/m³Good
Gwynn Oak≈ 5 µg/m³Good
Potomac≈ 5 µg/m³Good
Severn≈ 5 µg/m³Good
North Bethesda≈ 5 µg/m³Good
Catonsville≈ 5 µg/m³Good
Annapolis≈ 4 µg/m³Good
Hagerstown≈ 5 µg/m³Good
Hanover≈ 5 µg/m³Good
Woodlawn≈ 5 µg/m³Good
Severna Park≈ 5 µg/m³Good
Odenton≈ 5 µg/m³Good
Saint Charles≈ 5 µg/m³Good
Clinton≈ 5 µg/m³Good
Olney≈ 5 µg/m³Good
Suitland-Silver Hill≈ 5 µg/m³Good
Chillum≈ 5 µg/m³Good
St. Charles≈ 5 µg/m³Good
Salisbury≈ 4 µg/m³Good
Randallstown≈ 6 µg/m³Good
College Park≈ 5 µg/m³Good
Montgomery Village≈ 5 µg/m³Good
Pikesville≈ 5 µg/m³Good
Parkville≈ 5 µg/m³Good
Owings Mills≈ 5 µg/m³Good
Bel Air North≈ 6 µg/m³Good

Bad-air episodes in Maryland

Times when many cities around here had PM2.5 at twice their usual or more on the same days.

Use this board

SmogRank, most polluted cities in Maryland, United States, PM2.5, last 30 days to 6 Oct 2026, 23:00 UTC, smogrank.com/us/region/maryland?w=30d.

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.

Updated 2026-10-06 23:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.