SmogRank / World / North America / United States / Delaware

Most polluted cities in Delaware, United States

7 measured cities, last 30 days; 0 above the WHO 24-hour guideline. Worst: Dover at 5.4 µg/m³, #2,057 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 citiesMaryland: 10 measured citiesDelaware: 7 measured citiesNew Jersey: 19 measured cities#7 Newark: 4.3 µg/m³#5 Glasgow: 4.4 µg/m³#6 Seaford: 4.4 µg/m³#4 Claymont: 4.5 µg/m³#3 Bear: 4.8 µg/m³#2 Wilmington: 4.9 µg/m³#1 Dover: 5.4 µg/m³
Each dot is a measured city, coloured by its PM2.5; tap a dot to open the city.
← Dover 0% 0.75%0
Every measured city in Delaware, 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. 1Dover 0%
  2. 2Wilmington 0%
  3. 3Bear 0%
  4. 4Claymontlast full day 3 Oct 0%
  5. 5Glasgowlast full day 3 Oct 0%
  6. 5Seaford 0%
  7. 7Newark 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

Delaware 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
Middletown≈ 5 µg/m³Good

Bad-air episodes in Delaware

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

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SmogRank, most polluted cities in Delaware, United States, PM2.5, last 30 days to 6 Oct 2026, 22:00 UTC, smogrank.com/us/region/delaware?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 22:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.