Outdoor air quality refers to the condition of air outdoors, with a focus on pollutants that impact human health. Outdoor air pollution results from human activities like burning fossil fuels, and from natural sources like smoke and dust. Poor outdoor air quality can cause both short- and long-term harm to our airways and lungs, and impact other important organs and systems in our bodies.
What causes poor outdoor air quality?
Emissions from cars and trucks, manufacturing and power plants, homes and businesses, and fumes from fuel and chemical manufacturing are the primary sources of human-made air pollution. Smoke from wildfires and blowing dust during times of drought can also result in poor air quality.
Local emissions, such as traffic-related air pollutants and burning oil and gas for home heating, contribute to poor local air quality. Air pollution may also blow in from other regions of the US and Canada.
Extreme heat events in Massachusetts can result in high concentrations of ozone, pollen, and particles in the air like dust, dirt, smoke, or liquid droplets (particulate matter) that are so small they can be inhaled and cause serious health problems.
How is outdoor air quality a public health concern?
Poor outdoor air quality events are associated with reduced lung function, asthma, cardiac problems, emergency department visits, and hospital admissions. Health studies also associate long-term exposure to poor outdoor air quality with heart disease, stroke, lung disease, lung cancer, diabetes and reduced life expectancy. Chronic exposure to poor outdoor air quality can interfere with proper lung growth and development in children.
What are outdoor air quality hazards in Massachusetts?
In 1970, the federal Clean Air Act required the U.S. Environmental Protection Agency (U.S. EPA) to set limits called National Ambient Air Quality Standards (NAAQS) to protect public health, including the health of "sensitive" populations. These standards specify limits for six air pollutants across the United States. These criteria air pollutants include:
- Carbon Monoxide (CO)
- Lead (Pb)
- Nitrogen Dioxide (NO2)
- Sulfur Dioxide (SO2)
- Ozone (O3), and
- Particulate Matter (e.g., PM10 and PM2.5).
Poor outdoor air quality in Massachusetts may involve local exposure to any of several hundred additional toxic chemicals, such as benzene or other industrial solvents. MassDEP maintains an updated list of these regulated chemicals.
In Massachusetts, particulate matter and ozone are the most commonly monitored outdoor air pollutants. These primarily result from fossil fuel combustion for transportation, heating, and power generation. Particulate matter exposure may reach extreme levels during wildfire smoke events and summertime heat waves.
How are people exposed to poor outdoor air quality?
Outdoor air quality impacts the air we breathe outdoors and indoors, too. People are most heavily exposed to outdoor air pollution during outdoor activities, such as working, driving, commuting, and exercising. Poor outdoor air quality may also affect indoor air quality when it comes in through open windows, air infiltration through walls, and unfiltered ventilation systems.
Who is most at risk from poor outdoor air quality?
Some people may be more at risk because of where they live, their access to official government information, availability of resources to prepare and respond, and whether they already have health problems. These people include:
- Children under 5 and people over 65
- Pregnant people
- People with disabilities
- People with pre-existing medical conditions such as heart disease, asthma, lung disease and respiratory allergies
- People of color due to systemic racism (e.g., emissions from major highways, industrial areas in neighborhoods)
- People who speak little or no English, and who may not receive emergency messages in their native language
- People that live in areas with heavy traffic
- People that work or exercise outdoors
How can you protect your health from outdoor air pollution?
Illness and death due to poor air quality can be prevented. Here are some tips for protecting health from poor air quality:
- Be aware of the air quality around you - check your community’s Air Quality Index
- Reduce common asthma triggers at home, such as secondhand smoke, dust, pet hair and dander, and mold
- Use portable air filters or air conditioning if you have it
- Use high-efficiency (HEPA) air filters in heating and cooling systems
- Close windows and vents in homes and vehicles during air quality alerts and wildfire smoke events
- Maintain humidity levels between 30-50% indoors with air conditioners, fans, or dehumidifiers
- Ask your doctor about how to recognize seasonal allergy symptoms and reactions to air pollution and wildfire smoke and use appropriate medications
- Limit time outside on days with poor air quality or high pollen counts
- Ask schools and camps to reduce children’s exposure to common asthma triggers such as exposure to idling vehicles in pick-up and drop-off lines
- Walk or bike or take public transportation when possible
- When using a car, do not idle your vehicle for any longer than necessary
- Plan to move outdoor activities indoors during wildfire smoke events
- Learn how to create a clean air room in your home using a box fan
To learn more visit the National Institutes of Environmental Health Science’s Air Pollution and Your Health webpage, the CDC’s About Air Quality and How Wildfire Smoke Affects Your Body webpages. The Massachusetts Department of Public Health has downloadable factsheets for Poor Outdoor Air Quality and Wildfire Smoke Events available in 16 languages.
Why is MA EPHT tracking Outdoor Air Quality?
Ambient air quality monitoring data provide the best available information on the concentration of pollutant levels in the outdoor air at a given time and location.
Modeled air quality data for particulate matter and ozone from the EPA and CDC Downscaler model combines AQS monitoring measurements with air pollution predictions from the Community Multi-Scale Air Quality Model (CMAQ). These data fill in the substantial time and geography gaps that exist in the monitored data. In counties where monitors exist, the combined “monitored and modeled” pollutant dataset is useful for understanding pollution trends that may occur at the local and community levels.
Both outdoor air quality monitored and modeled data provide historical information on air quality in Massachusetts, such as the frequency of poor air quality events.
Where can I find additional information on Outdoor Air Quality?
More information is available from the websites listed here: Related Links for Outdoor Air Quality
In Massachusetts, the MassDEP Air Assessment Branch (AAB) operates an ambient air quality monitoring network of 22 monitoring stations located in 17 cities and towns in Massachusetts. The Wampanoag Tribe of Gay Head operates an ozone monitoring site on Martha’s Vineyard (Dukes County). Monitoring sites are chosen to meet U.S. EPA’s national monitoring objectives and siting criteria. For example, some sites are selected because they are probable “hot spots” for high levels of certain air pollutants while others are chosen to provide data that are representative of a wider area. The MassDEP provides a map of the “Air Quality Index” (AQI) that tells you how clean or polluted your air is and what associated health effects might be a concern for you to consider. (For more information, connect to: MassDEP Air Quality Online).
MassDEP submits quality-assured monitoring data to a central U.S. EPA repository database system called the Air Quality System (AQS), which is accessible to the public. The outdoor air quality measures for environmental public health tracking are based on monitoring data extracted from the U.S. EPA's AQS.
Additionally, MassDEP maintains around 200 additional small area monitors for PM2.5 and Ozone in rural areas and environmental justice areas. Current readings for these monitors may be viewed on AirNow’s Fire and Smoke Map, and with other personal and community-owned small area monitors on Purple Air.
Available Data on Outdoor Air Quality
Use the Explore Maps & Tables link on this page to access the following measures for outdoor air quality for your community:
- Monitored Ozone (O3), and Particulate Matter (PM2.5) – county only
- Modeled Ozone (O3), and Particulate Matter (PM2.5) – county, community, census tract
- Combined monitored and modeled Ozone (O3), and Particulate Matter (PM2.5) – county only
The most current available data will be shown. Be sure to check the site periodically as new data are added each year.