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.
About 0 people in these 2 cities breathed unhealthy air on an average day over the last 30 days.
Ranked by people: each city's population times its share of unhealthy days, those with a daily mean over 35.4 µg/m³ (US AQI 101+). That is how many people living there breathed unhealthy air on an average day. Only cities measured at 2 or more places at least 3 km apart are ranked: one monitor shouldn't speak for a whole city. Population is the city itself, not its wider metro area.
- 1Wilmington 0
- 2Newark 0
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.
| City | 7-day estimate |
|---|---|
| Middletown | ≈ 5 µg/m³ |
Bad-air episodes in Delaware
- Northern United States and Canada, July 202614 to 21 July 2026, 8 days327 cities548 µg/m³peak, Superior
- North-eastern United States and Canada, 14 to 19 February 20266 days108 cities54 µg/m³peak, Lancaster
- North-eastern United States and Canada, 29 July to 9 August 202512 days292 cities112 µg/m³peak, Marquette
- Northern United States and Canada, June 202510 to 14 June 2025, 5 days134 cities71 µg/m³peak, Wilmington
- Pennsylvania and Delaware, United States, January 202523 to 24 January 2025, 2 days14 cities35 µg/m³peak, New Holland
- United States and Canada, July 202314 to 19 July 2023, 6 days322 cities202 µg/m³peak, Edmonton
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.
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.