SmogRank / World / United States / Massachusetts / 2024
Most polluted cities in Massachusetts, United States, 2024
14 cities in Massachusetts, United States ranked by their average PM2.5 over the 366 days; 12 above the WHO annual guideline (5.0 µg/m³). Worst: Lexington at 6.8 µg/m³, #1,506 of 2,052 cities in the world. Cleanest: Ware at 4.3. A city needs measurements on 70% of the days to be ranked.
OpenAQ's archive, where our readings come from, has almost none for one of these days. Cities in the United States and Europe have it from the EPA's and the European Environment Agency's own records of the same monitors; elsewhere a city's average is over its other days. Why.
OpenAQ's archive, where our readings come from, has almost none from the United States for March 20, 2024: cities in the United States have it from the EPA's own records of the same monitors. Why.
About 622 people in these 3 cities breathed unhealthy air on an average day of 2024.
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.
Low-cost sensors: consumer units, counted only in cities with no government-grade monitor; they read close to reference monitors on the whole, but 15 to 25% high in humid air. How we use them.
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
All cities in the world, 2024 · All cities in United States, 2024 · Massachusetts now
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SmogRank, most polluted cities in Massachusetts, United States, PM2.5, 2024, smogrank.com/us/region/massachusetts/history/2024 (accessed 6 Oct 2026).
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.