Toxic Air Pollutants

Also known as air toxics, these are pollutants that at sufficient concentrations and exposure are known or suspected to cause cancer, other serious health problems, or damage to the environment.

About Air Toxics

There are three main types of air toxics:

  • Gases. These include benzene, toluene, and xylenes, which are all found in gasoline.
  • Liquid Aerosols. Perchloroethylene, a dry cleaning agent, and methylene chloride, an industrial solvent, are among these.
  • Particles. Examples include heavy metals such as cadmium, chromium, lead and mercury, and polycyclic aromatic hydrocarbons from the burning of fossil fuels and waste.

Generally, the toxic air pollutants of greatest concern are those released in amounts large enough to create a risk to human health or in areas where many people are likely to be exposed.

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Health & Environmental Effects

Short-term exposure can lead to eye irritation, nausea, or difficulty in breathing. Long-term exposures may result in damage to the respiratory, nervous, or reproductive systems, birth and developmental defects, and other serious health problems.

While everyone is at risk from exposure to air toxics, many factors determine how seriously any pollutant will affect a person or at-risk population. These include the level, duration, and frequency of exposure, the toxicity of the pollutant, and the overall health of people who are exposed.

Some air toxic, such as mercury, can deposit onto soils or surface waters, where they are taken up by plants, ingested by animals and fish, and work their way up the food chain. Like people, animals may experience health problems if exposed to sufficient quantities of air toxics over time.

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Federal Standards & State Guidelines

The U.S. Environmental Protection Agency (EPA) has established health-based National Emission Standards for Hazardous Air Pollutants (NESHAPs) addressing more than 180 air toxics.

In Massachusetts, meanwhile, the Department of Environmental Protection (MassDEP) has developed recommended Ambient Air Exposure Limits (AALs) and Threshold Effects Exposure Limits (TELs) for air toxics. In the some instances, these are more stringent than NESHAPs.

See below to learn more.

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Long-Term Trends

MassDEP operates a National Air Toxics Trends Station (NATTS) in Boston that is designed to collect and quantify a number of toxic air pollutants including carbonyls, black carbon, metals, volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs).

Data from this site are compared with information collected by a network of similar sites positioned across the country to identify transport, trends and site-specific characteristics of these pollutants.

MassDEP also monitors toxic VOCs in Lynn, which serves as a downwind background site for the NATTS in Boston.

EPA conducts a periodic National Air Toxics Assessment (NATA) focused on air toxics that are of greatest concern to public health.

According to NATA, air toxics found at unhealthy levels in specific Massachusetts locations include formaldehyde, acrolein, and benzene. There also are unhealthy levels of mercury in fish in some Massachusetts lakes and ponds, primarily due to deposition of mercury in the air from sources both within and outside of our state.

See below to learn more.

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