SmogRank / World / North America / United States / Connecticut
Most polluted cities in Connecticut, United States
6 measured cities, this year; 6 above the WHO annual guideline. Worst: Bridgeport at 7.5 µg/m³, #2,036 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.
- 1Danbury 1%
- 2Bridgeport 1%
- 3New Haven 1%
- 4Waterbury 1%
- 5Hartford 1%
- 6New London 1%
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
Connecticut 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 |
|---|---|
| Stamford | ≈ 5 µg/m³ |
| North Stamford | ≈ 6 µg/m³ |
| Norwalk | ≈ 6 µg/m³ |
| East Norwalk | ≈ 5 µg/m³ |
| New Britain | ≈ 6 µg/m³ |
| West Hartford | ≈ 6 µg/m³ |
| Bristol | ≈ 6 µg/m³ |
| Meriden | ≈ 6 µg/m³ |
| Hamden | ≈ 5 µg/m³ |
| Fairfield | ≈ 5 µg/m³ |
| West Haven | ≈ 5 µg/m³ |
| Milford | ≈ 5 µg/m³ |
| Stratford | ≈ 5 µg/m³ |
| City of Milford (balance) | ≈ 5 µg/m³ |
| East Hartford | ≈ 6 µg/m³ |
| Middletown | ≈ 6 µg/m³ |
| Enfield | ≈ 6 µg/m³ |
| Southington | ≈ 6 µg/m³ |
| Shelton | ≈ 5 µg/m³ |
| Norwich | ≈ 5 µg/m³ |
| Trumbull | ≈ 5 µg/m³ |
| West Torrington | ≈ 4 µg/m³ |
| Torrington | ≈ 4 µg/m³ |
| Glastonbury | ≈ 6 µg/m³ |
| Naugatuck | ≈ 5 µg/m³ |
| Manchester | ≈ 5 µg/m³ |
| Newington | ≈ 6 µg/m³ |
| Cheshire | ≈ 6 µg/m³ |
| Branford | ≈ 5 µg/m³ |
| East Haven | ≈ 5 µg/m³ |
| Windsor | ≈ 5 µg/m³ |
| Wethersfield | ≈ 6 µg/m³ |
| Mansfield City | ≈ 5 µg/m³ |
| Westport | ≈ 5 µg/m³ |
| Farmington | ≈ 6 µg/m³ |
| South Windsor | ≈ 5 µg/m³ |
| North Haven | ≈ 5 µg/m³ |
| Windham | ≈ 5 µg/m³ |
| Guilford | ≈ 5 µg/m³ |
| Bloomfield | ≈ 5 µg/m³ |
Bad-air episodes in Connecticut
- 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, January 202618 January 2026, 1 day16 cities37 µg/m³peak, New Holland
- North-eastern United States and Canada, 29 July to 9 August 202512 days292 cities112 µg/m³peak, Marquette
- North-eastern United States and Canada, 24 to 28 July 20255 days113 cities88 µg/m³peak, Sorel-Tracy
- South-eastern Canada and United States, December 202426 to 29 December 2024, 4 days27 cities48 µg/m³peak, Nepean
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 Connecticut, United States, PM2.5, this year to 6 Oct 2026, 22:00 UTC, smogrank.com/us/region/connecticut?w=year.
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.