Air quality in Boston has been bad lately mainly because of a mix of local pollution (cars, buildings, and wood burning), regional wildfire smoke, and weather patterns that trap dirty air near the ground.

What’s making Boston’s air quality worse?

  • Wood burning and fireplaces. A recent study found that smoke from wood burning now makes up about 35% of Boston’s fine particle pollution, meaning that a big share of the tiny particles you breathe on “bad air” days is from wood stoves, fire pits, and similar sources.
  • Wildfire smoke blowing in. In recent years, smoke from large wildfires in other parts of North America has periodically drifted over New England, causing hazy skies and AQI spikes even when local emissions haven’t changed much.
  • Traffic and buildings. Exhaust from cars, trucks, and buses, plus emissions from heating and cooling buildings, adds ozone-forming gases and particulate matter to the air, especially on hot or stagnant days.
  • Weather and heat waves. Heat waves and still air let pollutants build up instead of being dispersed, leading to “Moderate” to “Unhealthy” Air Quality Index readings on some days.

In simple terms: Boston’s air gets dirty when pollution from cars, buildings, and wood smoke gets trapped by the weather, and wildfire smoke drifting in from far away can turn an average day into a bad-air one.

Is this a new or growing problem?

  • Reports in 2024–2025 flagged that ozone smog and particle pollution in the Boston metro area had worsened, with wildfire smoke episodes being a key reason.
  • Local tracking shows that most days are still in the “Good” or “Moderate” range, but there are more days than before when sensitive people (kids, older adults, people with asthma) can feel the effects.

What it means for you day to day

  • On days with higher AQI (over about 100), people with asthma, heart or lung disease, children, and older adults may notice coughing, throat irritation, or breathing discomfort if they spend a lot of time outside.
  • Even when AQI is only “Moderate,” some very sensitive people report throat scratchiness or chest tightness, especially during visible haze or when there’s strong wood smoke in certain neighborhoods.

Example: Someone in Boston might wake up to a hazy sky, check AQI around “Moderate to Unhealthy for Sensitive Groups,” and feel a scratchy throat after a walk near a neighborhood with lots of wood stoves—this doesn’t mean the air is the worst in the world, but it’s polluted enough to cause symptoms for some people.

Quick tips if the air looks or feels bad

  • Check a reputable AQI app or site a few times a day, especially in summer or when you smell smoke.
  • If AQI is high, limit long or intense outdoor exercise and close windows during the worst hours.
  • If you’re sensitive, a well‑fitting mask (like N95/KN95) and an air purifier indoors can reduce exposure to fine particles from smoke and traffic.

TL;DR: The air quality in Boston is bad on some days because wood smoke, traffic, building emissions, and imported wildfire smoke combine with heat and stagnant weather to trap more pollution where people breathe.