Outdoor air quality refers to how healthy the air is to breathe. It focuses on pollutants that impact human health. Outdoor air pollution results from human activities like burning fossil fuels and natural sources like smoke and dust. Poor outdoor air quality can cause both short- and long-term harm to our airways and lungs, as well as impact other important organs in our bodies.
What causes poor outdoor air quality?
Primary sources of human-made air pollution include:
- Emissions from cars and trucks
- Manufacturing and power plants
- Homes and businesses
- Fumes from fuel and chemical manufacturing
Important natural sources of air pollution include wildfire smoke and dust from drought.
Nearby emissions from traffic and burning of oil and gas for home heat can cause poor air quality. Air pollution can also blow in from other regions of the U.S. and Canada.
Extreme heat events can increase air pollutants like ozone, pollen, and particulate matter (PM). Particulate matter is a mix of solid particles and liquid droplets in the air, like dust, dirt, and smoke. They are so small they can be inhaled and cause serious health problems.
How is outdoor air quality a public health concern?
Short and long-term exposure to poor outdoor air quality can contribute to:
- Heart disease and cardiac problems
- Stroke
- Reduced lung function, lung disease, and lung cancer
- Asthma
- Diabetes
- Emergency department visits and hospitalizations
- Reduced life expectancy
Long-term exposure can also impact lung growth and development in children.
How is outdoor air quality measured in Massachusetts?
In Massachusetts, the Massachusetts Department of Environmental Protection’s (MassDEP) Air Assessment Branch operates an ambient air quality monitoring network. It has 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.
Monitoring sites are chosen to meet the U.S. Environmental Protection Agency’s (EPA) national monitoring criteria. For example, some sites are selected because they are probable “hot spots” for high levels of certain air pollutants. Others are chosen to provide data that is representative of a wider area.
MassDEP uses the monitoring data to provide a map of the “Air Quality Index” (AQI). The map tells you how clean or polluted your air is and what associated health effects might be a concern.
MassDEP also submits monitoring data to an EPA database system called the Air Quality System (AQS). This system is accessible to the public. The outdoor air quality measures for MA EPHT are based on monitoring data from the EPA's AQS.
Additionally, MassDEP has around 200 small area monitors for PM2.5 and ozone in rural areas and environmental justice areas1. Current readings for these monitors may be viewed on AirNow’s Fire and Smoke Map along with other personal and community-owned small area monitors.
Why is MA EPHT tracking outdoor air quality?
Outdoor air quality monitoring gives us data on the concentration of pollutants. This data is the best available information at a given time and location. However, not all locations have monitors.
Modeled air quality data exists for particulate matter and ozone. The EPA and the U.S. Centers for Disease Control and Prevention (CDC) use the downscaler model to combine measurements from the EPA's Air Quality System (AQS) with predictions from the Community Multi-Scale Air Quality Model (CMAQ). These data fill in the gaps that exist in the monitored data.
In counties with monitors, the combined “monitored and modeled” pollutant dataset is used to look at pollution trends at the local and community levels.
The combination of monitored and modeled data allows us to look at the frequency of poor air quality events and historical trends. This understanding can inform future estimates and forecasts of air quality conditions.
What outdoor air quality hazards are expected in Massachusetts?
The federal Clean Air Act requires the U.S. Environmental Protection Agency (EPA) to set limits on air pollutants to protect public health, including the health of sensitive populations. These national standards set limits for six air pollutants (called criteria air pollutants):
- Carbon Monoxide (CO)
- Lead (Pb)
- Nitrogen Dioxide (NO2)
- Sulfur Dioxide (SO2)
- Ozone (O3), and
- Particulate Matter (e.g., PM10 and PM2.5)
In Massachusetts, particulate matter and ozone are the most monitored outdoor air pollutants. Both come from fossil fuel combustion for transportation, heating, and power generation. Particulate matter may reach extreme levels during wildfire smoke events and summertime heat waves. Ozone levels may become dangerous on hot days and days when pollutants are “trapped” near the ground by the weather. Poor outdoor air quality may also 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 (called air toxics).
How are people exposed to poor outdoor air quality?
Outdoor air quality affects the air we breathe both outdoors and indoors. People are most exposed during outdoor activities, such as working, driving, commuting, and exercising. Poor outdoor air quality may also affect indoor air quality by blowing in through open windows, filtering through walls, or being pulled in by an unfiltered ventilation system.
Who is most at risk from poor outdoor air quality?
Some people may be more at risk of health problems due to poor air quality 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
- People that live in areas with heavy traffic
- People that work or exercise outdoors
- People who speak little or no English, and who may not receive emergency messages or outdoor air quality alerts in their native language
- People with disabilities
- People with medical conditions such as heart disease, asthma, lung disease and respiratory allergies or are pregnant
Massachusetts has a history of racially discriminatory housing policies, such as racial housing covenants and redlining. These still affect the availability and quality of housing for people of color who are more likely to have homes close to roads with heavy traffic and live in neighborhoods with air pollution from major highways and/or industrial areas. All this can increase the chance of health impacts from poor outdoor air quality.
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 your health from poor outdoor 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 the difference between seasonal allergies and reactions to poor air quality. Also ask about appropriate medications for each.
- 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 to inside spaces during days with poor air quality or wildfire smoke events
- Learn how to create a clean air room in your home using a box fan
Available data
Use the Explore outdoor air quality data link on this page to access the following measures:
- Monitored Ozone (O3) and Particulate Matter (PM2.5)
- Modeled Ozone (O3) and Particulate Matter (PM2.5)
- Combined monitored and modeled Ozone (O3) and Particulate Matter (PM2.5)
Measures are available at the county level, with modeled ozone and PM2.5 available at the community and census tract levels. The most current available data will be shown. Be sure to check the site periodically as new data are added.
Related links
Additional resources
Massachusetts
- DPH fact sheets on poor outdoor air quality: Learn about climate and poor outdoor quality. Available in 16 languages
- MassDEP MassAir Online: Current air quality data and information for Massachusetts
- MassDEP - Criteria air pollutants: Learn about six common air pollutants that are found everywhere and emitted from a range of sources: homes, motor vehicles, industry, power plants, and more
- MassDEP - Air pollutants and toxics: Information on criteria and toxics air pollutants, greenhouse gases, haze, and acid rain among other air quality topics
- MassDEP - Annual air quality reports: Annual reports prepared by MassDEP based on representative samples of ambient air for several pollutants at monitoring stations located across the Commonwealth
- MassDEP - Air quality topics: Links to air quality-related information
National
- CDC - National Environmental Public Health Tracking on outdoor air quality: CDC’s National Environmental Public Health Tracking website
- CDC - About air quality: Information on the Air Quality Index and other helpful resources
- National Institutes of Environmental Health Science’s air pollution and your health: Information for the public and educators on the health hazards of air pollution and research studies on population groups who are most affected
- EPA Integrated Compliance Information System (ICIS) for air: Data on regulated Clean Air Act stationary sources and their compliance records
- AirNow: Air quality forecasts for the United States
- EPA - National air quality report: Interactive report on air quality trends of key air pollutants
- EPA - Ambient monitoring technology information center: Information on ambient air quality monitoring programs and methods, quality assurance and control procedures, and federal regulations
- EPA - Clean air act: Overview of the Clean Air Act and air pollution
- EPA - National air quality and emissions trends report: Current emissions trends data
- EPA's report on the environment: Report on the status of and trends in the quality of the nation’s environment, including air
- EPA - Tribal air quality: Information on air quality on tribal land along with resources
- EPA - Urban strategy: Framework for addressing emissions of air toxics in urban areas