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Air Toxics: Also known as toxic air pollutants or hazardous air pollutants, these are chemicals that cause or may cause serious effects in humans, and may be emitted into the air in quantities that are large enough to cause those adverse health effects. These effects cover a wide range of conditions from lung irritation to birth defects to cancer. Health concerns may be associated with both short and long term exposures to these pollutants. Many are known to have respiratory, neurological, immune or reproductive effects, particularly for more susceptible sensitive populations such as children. 188 air toxics are listed as "Hazardous Air Pollutants" in the 1990 Clean Air Act.

Area Sources: Small sources of air pollution which by themselves may not emit very much, but when their emissions are added together they may account for a sizable portion of the total emissions of air toxics. In NATA, USEPA refers to this category as "area and other sources," and includes small industrial sources that fall below the "major souce" threshold. Included in this category are: consumer products (personal care products, household products, adhesives and sealants, automotive products, coatings); residential heating and fuel use; pesticide use; fires; gasoline stations; dry cleaners; chromium electroplating; surface coating of cans and paper; metal parts cleaning; metal recycling; small chemical manufacturing plants; and bakeries, among others.

Background Concentration: The pollutant levels that are found throughout the continental United States even in "clean air locations," areas where no man-made air toxic emissions would be expected. They are a result of past emissions of persistent pollutants, long-range transport of recent emissions, and widespread man-made sources.

Carcinogen: A chemical that has been shown to cause cancer, either in people or animals.

CEP: USEPA's Cumulative Exposure Project for 1990.

Chronic: long duration or frequent recurrence.

Emissions Inventory: A list of activity categories that emit pollutants and an estimate of how much is emitted by each.

Exposure: Contact with a substance through inhalation, ingestion or some other means for a specific period of time.

HAP: Hazardous air pollutant. In general, an "air toxic." Specifically, this also refers to one of the 188 specific pollutants listed in the 1990 Clean Air Act amendments.

Health Benchmark: The chemical-specific air concentration below which there should be no significant harm to human health. For a carcinogen (cancer-causing chemical), the health benchmark is set at the air concentration that over a lifetime would cause no more than a one in a million increase in the likelihood of getting cancer. For a noncarcinogen, the health benchmark is the air concentration which is likely to cause no harm, even if exposure occurs on a daily basis for a lifetime.

MACT: Maximum Achievable Control Technology.

Major Sources: Defined in the Clean Air Act as a facility that emits at least 10 tons per year of one HAP, or 25 tons per year of a combination of HAPs. See also point source.

Mobile Sources: A source of air pollution which can move from place to place. In NATA, mobile sources are separated into on-road sources (cars, trucks, buses, motorcycles) and non-road sources (airplanes, trains, construction equipment, lawnmowers, boats, dirt bikes, etc.).

NATA: National-Scale Air Toxics Assessment. A project undertaken by USEPA in which they estimate exposure to air toxics nationwide for 1996. It consists of an inventory of air toxics emissions from point, area, and mobile sources; dispersion modeling of those emissions to estimate ambient air concentrations; and estimates of the resulting risk to the population nationwide.

NJDEP: New Jersey Department of Environmental Protection

Noncarcinogen: A pollutant that can cause adverse health effects other than cancer.

Ozone: an air pollutant that is produced from other air pollutants and sunlight. Unhealthy levels can occur during the summer in New Jersey. Studies have shown that ozone causes asthma attacks. For more information click here.

PAH: Polycyclic aromatic hydrocarbons. 7 chemicals that are part of a class of compounds called polycyclic organic matter (POM). They are: benz[a]anthracene; benzo[b]fluoranthene; benzo[k]fluoranthene; benzo[a]pyrene; chrysene; dibenz[a,h]anthracene; and indeno[1,2,3-cd]pyrene. They are all probable human carcinogens.

Particulate matter: small particles suspended in the air that are respiratory irritants. Some studies have associated particulate matter with asthma attacks.

Particulates: Fine liquid or solid particles such as dust, smole, mist, fumes or smog, found in the air or emissions.

Point Sources: A stationary facility or process that emits a significant amount of air pollution during manufacturing, power generation, heating, incineration, or other such activity. In NATA, USEPA used the term major source and included in it just those sources which emit at least 10 tons per year of any one hazardous air pollutant (HAP), or at least 25 tons per year total of any HAPs.

Pollutants: Unwanted chemicals or other materials found in the air. Pollutants can harm health, the environment and property. Many air pollutants occur as gases or vapors, but some are very tiny solid particles: dust, smoke or soot.

POM: Polycyclic organic matter. A broad class of compounds that is formed primarily from combustion, and is present in the air in particulate form. Sources are diverse and include vehicle exhaust, fires, and hazardous waste sites. Because of limited emissions data, for NATA, POM has been separated into two categories. 7-PAH consists of 7 species of POM (identified above and evaluated separately in NATA).

Reference Concentration: (RfC) - An estimate (with uncertainty spanning about an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of harmful effects during a lifetime. It can be derived from various types of human or animal data, with uncertainty factors generally applied to reflect limitations of the data used.

Risk Ratio: The comparison of the measured or estimated air concentration of a specific chemical to its health benchmark to determine either the magnitude of the risk of developing cancer or of some noncancer health effect. If the risk ratio for a chemical is less than one, the air concentration does not pose a health risk. If it greater than one, it may be of concern. The risk ratio shows just how much higher the air concentration is than the health benchmark.

TRI: Toxic Release Inventory. This is a database of information about releases of more than 650 toxic chemicals from manufacturing facilities throughout the United States.

Unit Risk Factor: The upper-bound excess lifetime cancer risk estimated to result from continuous exposure to a chemical at a concentration of 1 µg/m3 in air. For example, if the Unit Risk Factor = 2 x 10-6 /µg/m3, then a person exposed daily for a lifetime to 1 µg of the chemical in 1 cubic meter of air would have an increased risk of cancer equal to 2 in a million.

USEPA: United States Environmental Protection Agency.

Volatile Organic Compounds (VOCs): Organic chemicals all contain the element carbon(C); organic chemicals are the basic chemicals found in living things and in products derived from living things, such as coal, petroleum and refined petroleum products. Many of the organic chemicals we use do not occur in Nature, but were synthesized by chemists in laboratories. Volatile chemicals produce vapors readily; at room temperature and normal atmospheric pressure, vapors escape easily from volatile liquid chemicals. Volatile Organic chemicals include gasoline, industrial chemicals such as benzene, solvents such as toluene and xylene, and tetrachloroethylene (perchloroethylene, the principal dry cleaning solvent). Many volatile organic chemicals are also hazardous air pollutants; for example, benzene causes cancer.

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