Wildfires, Air Quality, and Health


Several factors driven by climate change are increasing the intensity and duration of wildfires throughout North America, including Eastern Canada. Smoke from wildfires can travel long distances, affecting air quality far from the location of the fires.

Wildfire smoke contains several air pollutants, including particulate matter (smoke particles), and hydrocarbons. The source of these pollutants (trees) results in many types of plant-based, sticky particles.

Vulnerable Groups

Poor air quality, including that caused by wildfire smoke can negatively affect health, especially for people with certain medical conditions and other risk factors. Groups who are especially vulnerable include:

  • Children;
  • People with Asthma and Chronic Obstructive Pulmonary Disease (COPD);
  • People with Heart Disease or Circulatory Disease;
  • Older Adults;
  • Pregnant People and Infants; and
  • Outdoor Workers, including delivery, building trades, and landscaping.

Residents are encouraged to take precautions and limit some outdoor activities as air quality worsens. It is especially important for vulnerable groups to follow guidelines related to exposure to air pollutants.

Air Quality Index

The US Environmental Protection Agency (EPA) and its partners developed the Air Quality Index, or AQI, to make information available about local air quality. Residents can check current air quality in Cambridge and available forecasts by visiting the site www.AirNow.gov and entering their zip code.

The EPA’s AQI rates air quality using six levels, ranging from Good to Hazardous. More information about this rating scale and recommendations for activity at each level can be found here: Air Quality Guide. The guide explains when to avoid certain outdoor activities due to air quality concerns.

Residents should be aware that air quality can change quickly based on wind patterns, precipitation and other factors. The AQI tells you when air pollution is likely to reach levels that could be harmful. Checking the AQI in the morning will give you the most accurate information about local air quality and can help you plan your outdoor activities. (Note: While there are many different air quality scales available, CPHD recommends AirNow.gov, a partnership of several federal, state and local agencies.)

Protect Yourself and Your Family

The good news is there’s a lot you can do to protect yourself and your family from the health effects caused by air pollution.


When air quality is not good, take steps to limit the amount of air you breathe in while you’re outside. The basics:

  • Think about spending more time indoors, where particle pollution levels are usually lower.
  • Choose easier outdoor activities (like walking instead of running) so you don’t breathe as hard.
  • Avoid busy roads and highways where pollutants are usually worse because of emissions from cars and trucks.
  • Wear a high-quality mask when the air quality is very poor, especially if vulnerable/sensitive to poor air quality. A N95 mask is your best option, but a KN95 works as well.


Take steps to keep indoor air as clean as possible.

  • If smoke levels are high, try to avoid using anything that burns, such as wood fireplaces, gas logs, gas stoves – and even candles!
  • Don’t vacuum. That stirs up particles already inside your home.
  • Don’t smoke inside. Smoking puts even more pollution in your lungs, and in the lungs of people around you.
  • Run your air conditioner if you have one. Be sure to keep the fresh air intake closed and the filter clean to prevent bringing additional smoke inside.
  • Use HEPA air filters or MERV-13 filters or higher in your HVAC system.
  • Use a portable air cleaner designed to reduce particles indoors. Follow guidance size or # of units (or size of units) needed per area. Capacity to filter an area is important.
  • Note: If you don’t have an air conditioner, staying inside with the windows closed may be dangerous in extremely hot weather. In these cases, seek alternative shelter. Libraries, malls, and other air conditioned buildings are good options. In some extreme heat situations, the City of Cambridge may also set up cooling shelters.

If you have heart or lung disease, if you are an older adult, or if you have children, talk with your doctor about whether and when you should leave the area. When smoke is heavy for a prolonged period of time, fine particles can build up indoors, even though you may not be able to see them.

Updated May 21, 2024