Boston, MA Air Quality & Smog

Dominant pollutants, when smog is worst, notable historical episodes, and local agency resources for Boston, MA — plus how to check the current AQI. For real-time readings, the free Smog Report iOS app pulls live air quality from EPA AirNow.

Dominant pollutants

ozone (summer), PM2.5 (transport + heating).

Seasonal pattern: when smog is worst

Boston has cleaner baseline air than the New York-DC corridor, but summer ozone elevates during hot stagnant days, especially in the South Shore where pollution transported up the I-95 corridor accumulates. Winter PM2.5 from heating + the I-93 / Big Dig corridor.

A recent or notable event

June 8, 2023 — Boston briefly entered AQI 200+ from Canadian wildfire smoke.

Local agencies and resources

MassDEP runs the AirNow monitors. The Boston Public Health Commission coordinates local advisories.

• Massachusetts DEP
• Boston Public Health Commission

How to check air quality in Boston

The EPA's AirNow.gov publishes the canonical reading from the nearest regulatory monitor. For glanceable iPhone access — including widgets, Live Activities, Siri voice queries, and Apple Watch — install Smog Report. It's free, requires no account, and pulls from the same AirNow API.

For Boston-specific advisories and alerts that go beyond the federal AirNow feed, check the agency pages above directly.

Common questions about Boston air quality

Why does Boston have air-quality and smog problems?

Boston has cleaner baseline air than the New York-DC corridor, but summer ozone elevates during hot stagnant days, especially in the South Shore where pollution transported up the I-95 corridor accumulates. Winter PM2.5 from heating + the I-93 / Big Dig corridor.

What are the main air pollutants in Boston?

Boston's dominant pollutants are ozone (summer), PM2.5 (transport + heating). The AQI on any given day is usually driven by whichever of these is highest.

Has Boston had a major air-quality or smog event?

June 8, 2023 — Boston briefly entered AQI 200+ from Canadian wildfire smoke.

How can I check Boston's air quality right now?

The EPA's AirNow.gov publishes the official reading from the nearest regulatory monitor. For live AQI on your iPhone — with home-screen widgets, Lock Screen Live Activities, Siri, and Apple Watch — the free Smog Report app pulls from the same AirNow feed. No account is required.

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