Mass.gov logo
Icon of a home and lettering for EOHHS
MA EPHT Logo with Tree Link to DPH Website Link to DPH Environmental Public Health Link to Main MA EPHT landing page

Air Quality

Picture Mom, Dad and two children holding hands on a beach.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 such as asthmatics, children, and the elderly. 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).

State, local, and tribal air quality agencies operate and maintain a wide variety of ambient monitoring systems across the United States to determine compliance with the NAAQS. Environmental contaminants in outdoor air are monitored by the Massachusetts Department of Environmental Protection (MassDEP).

Air quality monitoring networks serve multiple environmental objectives including determining compliance with national air standards, informing the public about how clean or polluted the outdoor air is, forecasting daily pollution levels for the public, and tracking progress in reducing air pollution from major sources including automobiles, trucks, and industrial sources (e.g., power plants, chemical manufacturing facilities).

In Massachusetts, the MassDEP Air Assessment Branch (AAB) operates an ambient air quality monitoring network of 28 monitoring stations located in 20 cities and towns in Massachusetts. The Wampanoag Tribe of Gay Head operates an ozone monitoring site on Martha’s Vineyard (Dukes County). U.S. EPA New England also operates a monitoring station at their laboratory in Chelmsford, MA (Middlesex 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 network has two types of monitoring systems: one system is designed to determine compliance with the NAAQS and the monitors are referred to as Federal Reference Method (FRM) monitors.

 

The other type of monitoring system measures daily air pollution levels.  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 On-line).

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 air quality measures for environmental public health tracking are based on monitoring data extracted from the U.S. EPA's AQS.

The map below shows Massachusetts communities where air monitors were located during 2011.

 

Ambient monitoring data provide the best available information on the concentration of pollutant levels in the outdoor air at a given time and location. One disadvantage of using the ambient monitoring data is that there are a limited number of monitors that can be sited and maintained. This limitation creates gaps in coverage across the state in areas that do not have ambient monitoring sites. However, the U.S. EPA has been working with the EPHT program to develop models that will predict air pollution concentrations in counties without monitors. Predicted air quality data for Massachusetts may be accessed at the following U.S. EPA webpage: http://www.epa.gov/heasd/research/cdc.html.

Fine Particles (PM2.5)

Picture of three-lane highway congested with cars and trucks, which pertains to air quality indicators for fine particulate matter."Particulate matter," also known as particle pollution or PM, is a complex mixture of extremely small particles and liquid droplets made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals, soil or dust particles, and allergens (such as fragments of pollen or mold spores). The size of particles is directly linked to their potential for causing health problems. Particulate matter less than 10 micrometers in diameter pose the greatest problems because these particles can deposit deep into the lungs.

The National Ambient Air Quality Standards (NAAQS) listed below for particulate matter address two categories of particle pollutions: "inhalable coarse particles" (PM10) or "fine particles" (PM2.5). Inhalable coarse particles (PM10) are those that are larger than 2.5 micrometers but smaller than 10 micrometers in diameter (PM10) and is associated primarily with road dust. Fine particles are those that are 2.5 micrometers in diameter or less (PM2.5) and are generated from residential wood burning and fossil fuel combustion.

Pollutant Measure Standards
Pollutant
Averaging Time
NAAQS
PM10
24-hour
150 µg/m3
PM2.5
Annual Arithmetic Mean
12 µg/m3
PM2.5
24-hour
35 µg/m3

There are a large number of health studies that link exposure to fine particles (i.e., PM2.5) at levels measured in the ambient air with a variety of heart and respiratory diseases. Long-term exposures, such as those experienced by people living in areas with high particle levels for many years, have been associated with problems such as reduced lung function and the development of chronic bronchitis and even premature death. Short-term exposures to particles (hours or days) can aggravate lung disease, causing asthma attacks and acute bronchitis, and may also increase susceptibility to respiratory infections. In people with heart disease, short-term exposures have been linked to heart attack and arrhythmias. Healthy children and adults have not been reported to suffer serious effects from short-term exposures, although they may experience temporary minor irritation when particle levels are elevated. However, people with heart or lung disease, older adults, and children are considered at greater risk from particles than other people, especially when they are physically active. Exercise and physical activity cause people to breathe faster and more deeply and therefore take more particles into their lungs.

Did You Know?
Fine particles (PM2.5) are the main cause of reduced visibility (haze) in parts of the United States.

In addition to providing annual average PM2.5 concentrations for each county where monitors are located, the air quality measures provide information on the percent of statewide population exposed to PM2.5 levels exceeding the NAAQS. The daily measures include percent of days exceeding the daily PM2.5 NAAQS as well as information on the number of people exposed to high levels of PM2.5 pollution. When comparing across counties, the highest number of person-days indicates areas with both a large exposed population and a large number of high pollution days.

The air quality measures for fine particles identifies counties that may be at higher risk of adverse health effects due to exposure to fine particles

Data Considerations

There are important limitations to consider when evaluating the air quality measures for PM2.5 in your community:

  • Monitoring data are available for certain counties where monitors are located
  • Variations in pollutant concentrations within a county will likely exist but will not necessarily be captured by the monitoring network.
  • In counties with multiple monitoring sites, the air quality measures are based on the maximum concentration measured in the county.
  • Personal exposure and related health risks depend on such factors as the amount of time and level of activity outdoors and cannot be determined solely from air quality measures.

For additional information, please read the FAQ

Available Data on Air Quality Measures for Fine Particles (PM2.5)

Click the Explore Data link on this page to access the following measures for Fine Particles (PM2.5) in your community. The most current available data will be shown. Be sure to check the site periodically as new data are added each year. To protect privacy, no information is shown that could identify an individual.

  • Annual average PM2.5 concentration by county
  • Percent of monitored days that PM2.5 24-hour concentration exceeds daily NAAQS by county
  • Number of person-days that PM2.5 24-hour concentration exceeds daily NAAQS by county

Ground-Level Ozone

Picture of smokestacks emitting smoke, which pertain to the air quality indicators for ozone.Ozone is a colorless gas pollutant found in the air we breathe. It is a major part of urban smog. There are two types of ozone:

  • Ozone that occurs naturally in the sky about 10 to 30 miles above the earth's surface forms a layer that protects life on earth from the sun's harmful rays.
  • Ground-level ozone, is an odorless, colorless gas that is created by a chemical reaction when pollutants that come from cars, power plants, and other sources come in contact with each other in the presence of heat and sunlight.

Breathing air containing ground-level ozone can reduce lung function, and aggravate asthma or other respiratory ailments. Ozone exposure has also been linked with more respiratory infections, medicine use by asthmatics, doctors' visits, emergency department visits, and hospital admissions. Ozone exposure also may contribute to premature death in people with heart and lung disease. People with lung disease, children, older adults, and people who are active outdoors can be affected when ozone levels are unhealthy.

Substantial evidence exists to show links with a wide range of health effects (e.g., lung function decrements, pulmonary inflammation) and prolonged exposures (i.e., 6- to 8-hr) to ozone at levels measured in the ambient air. The current National Ambient Air Quality Standards (NAAQS) for ozone is an 8-hour average ozone concentration of 0.075 ppm. Concentrations above the NAAQS are considered unhealthy, particularly for sensitive groups including people with lung disease, children, older adults, and people who are active outdoors. The air quality measures for all years are based on the current NAAQS of 0.075 ppm.

Did You Know?
Ozone can reach unhealthy levels typically on hot, sunny days. People with lung disease, children, older adults, and people who are active outdoors may be particularly sensitive to ozone.

The air quality measures for ozone include the number of days in a county that the maximum 8-hour average ozone concentration exceeds the NAAQS during the year and over multiple years (trends) as well as the number of people potentially exposed to levels over the NAAQS. The person-days measure provides information on the number of people exposed to high levels of ozone pollution. When comparing across counties, the highest number of person-days indicates areas with both a large exposed population and a large number of high pollution days. The number of days when ozone concentrations exceed the NAAQS also provides an indication of short-term "spikes" in ozone concentrations.

The air quality measures for ozone identifies counties that may be at higher risk of adverse health effects due to exposure to ozone.

Data Considerations

When reviewing and interpreting air quality ozone data, it is important to take into consideration the following:

  • Air quality measures are available for certain counties where monitors are located.
  • Ozone is likely to reach unhealthy levels on hot sunny days. Therefore, the ozone monitoring network operates from April-September.
  • Variation in pollutant concentrations within a county will likely exist but will not necessarily be captured by the monitoring network.
  • In counties with multiple monitoring sites, the daily air quality measures are based on the maximum 8-hour average concentration measured in the county.
  • Personal exposure and related health risks depend on such factors as the amount of time and level of activity outdoors and cannot be determined solely from air quality measures.

For additional information, please read the FAQ

Available Data on Air Quality Measures for Ozone

Click the Explore Data link on this page to access the following measures for Ozone in your community. The most current available data will be shown. Be sure to check the site periodically as new data are added each year. To protect privacy, no information is shown that could identify an individual.

  • Number of days that highest daily maximum 8-hour ozone concentration exceeds NAAQS by county
  • Number of person-days that highest daily maximum 8-hour ozone concentration exceeds NAAQS by county
     ©   Commonwealth of Massachusetts
Click to download Adobe Reader
Site Policies   Helpdesk