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Air Quality Control Keywords
The following list of keywords will help to familiarize you with Air Quality Control.

VOC'c (Volatile Organic Compound)
includes many organic chemicals that vaporize easily, such as those found in gasoline and solvents. They are emitted from many sources, including gasoline stations, motor vehicles, trains, airplanes, boats, petroleum storage tanks and oil refineries. Other major sources include biogenic or natural emissions from trees and plants.
NOx (Nitrogen Oxide)
produced almost entirely as a by-product of high-temperature combustion. Common sources include automobiles, trucks, and marine vessels, construction equipment, power generation, industrial processes and natural gas furnaces
Ozone
Ozone is a gas that occurs both in the Earth's upper atmosphere and at ground level. Ozone can be "good" or "bad" for people's health and for the environment, depending on its location in the atmosphere
Good Ozone
The stratosphere or "good" ozone layer extends upward from about 6 to 30 miles and protects life on Earth from the sun's harmful ultraviolet (UV) rays.
Bad Ozone
The layer closest to the Earth's surface is the troposphere. Here, ground-level or "bad" ozone is an air pollutant that is harmful to breathe and it damages crops, trees and other vegetation. It is a main ingredient of urban smog. The troposphere generally extends to a level about 6 miles up, where it meets the second layer, the stratosphere
Air Quality Index (AQI)
an index for reporting daily air quality. It tells you how clean or polluted your air is and what associated health effects might be a concern for you.

Think of the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern. For example, an AQI value of 50 represents good air quality with little potential to affect public health, while an AQI value over 300 represents hazardous air quality.

An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. AQI values below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is considered to be unhealthy-at first for certain sensitive groups of people, then for everyone as AQI values get higher.
Nonattainment area
geographic area that fails to meet a NAAQS. An area must be officially designated by the EPA, under procedures set forth by the Federal Clean Air Act, in order to be classified in nonattainment. An area that complies with a NAAQS is generally known as an “attainment area,” although that is not an official classification under the Federal Clean Air Act.
One-hour ozone standard
The former indicator of air quality acceptability as it pertains to ground-level ozone. This indicator involves taking an average 1-hour concentration of pollutants. The current threshold is 0.12 parts per million (ppm). An area meets the ozone National Ambient Air Quality Standard if the monitored ozone level does not exceed the standard more than three times over a consecutive three-year period.
Eight-hour ozone standard
The new indicator of air quality acceptability as it pertains to ground-level ozone. The current threshold value for this standard is 0.08 ppm, measured as maximum daily eight-hour average concentrations. To attain the ozone National Ambient Air Quality Standard, the three-year average of the annual fourth-highest daily maximum eight-hour ozone concentration must not exceed 0.08 ppm.
State Implementation Plan (SIP)
It is a specific plan required by the Clean Air Act to achieve the national air quality standards in all non-attainment areas. The SIPs are developed by the states (with local inputs) and submitted to U.S.EPA for approval. After approval, the SIPs and all associated control measures are enforceable at both the state and federal levels.
Air Pollution
the presence of substances, both gases and particles, in the air in amounts that are harmful to the health or comfort of humans or animals, or cause damage to plants or materials. Although there are natural sources of air pollution, such as volcanic eruptions, forest fires and wind-blown dust, significant air pollution is usually the result of human activities, like industrial processes and motor vehicle use.
Clean Air Act (1970)
geographic area that fails to meet a NAAQS. An area must be officially designated by the EPA, under procedures set forth by the Federal Clean Air Act, in order to be classified in nonattainment. An area that complies with a NAAQS is generally known as an “attainment area,” although that is not an official classification under the Federal Clean Air Act.
National Ambient Air Quality Standards (NAAQS)
federal standards that are intended, based on the latest scientific knowledge, to protect public health and welfare
Carbon Monoxide (CO)
a colorless, odorless gas, that is emitted during the combustion of gasoline, wood, natural gas and other fuel. Emission of CO increases significantly from improperly tuned engines.
Sulfur Dioxide (SO2)
a colorless, odorless gas at low concentration, but has a pungent odor at higher concentrations. In Texas, SO2 is emitted primarily by power plants that burn coal that contains sulfur, petroleum refineries and sulfuric acid plants. SO2 can harm vegetation, impair visibility by the formation of sulfates, and contribute to acid rain, in addition to its effects on health
Nitrogen Dioxide (NO2)
a yellow-brown gas that is part of the family of pollutants referred to as nitrogen oxides (NOx). Nitrogen oxides are formed almost entirely by high-temperature combustion, such as the burning of fuels in power generation plants, industrial boilers, cars, trucks, furnaces and cooking stoves
Lead (Pb)
a toxic metal that was previously used in gasoline and most paints. Lead is emitted into the air by lead battery manufacturing plants, lead battery recovery plants, smelter operations, and the combustion of coal that contains lead. In the US, lead has been phased out of gasoline, paint and other consumer products because of its undesirable health effects and because lead in gasoline damaged catalytic converters. Levels of lead in the air have since decreased significantly.
Air Toxics
Air toxics are defined primarily by their effects. Exposure to air toxics increase a person’s risk of developing cancer, as well as increase the risk of birth defects in children. Although the term “air toxics” cam be used to refer to any hazardous chemical or metal, the term is usually reserved for the 189 chemicals and metals named in Title III of the 1990 Clean Air Act Amendments as Hazardous Air Pollutants (HAPs). These chemicals and metals include: benzene, toluene, vinyl chloride, perchloroethylene, asbestos, arsenic, mercury, chlordane, chromium, 1,3-butadiene, formaldehyde and xylene.
Mercury
Mercury contamination primarily comes from coal burned in power plants. Mercury pollution has become an increasing problem because mercury, first released as air pollution from factories and plants, eventually ends up in bodies of water where it bio-accumulates up the food chain. Most human exposure comes from eating contaminated fish. Large fish that feed on smaller aquatic species generally have the highest levels. Mercury pollution can result in serious neurological and reproductive problems.



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