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You are here: Home / Publications / Periodicals / Natural Outlook / Spring 2010 / Terms Used in the Spring 2010 Issue of Natural Outlook

Terms Used in the Spring 2010 Issue of Natural Outlook

Definitions of terms used in this issue of Natural Outlook. (Natural Outlook, Spring 2010)

Attainment area
A geographic area that complies with a NAAQS under the Federal Clean Air Act.

Attainment demonstration
A plan to demonstrate how a nonattainment area expects to meet the NAAQS by a given deadline.

Area source
A source of air pollutant emissions not attributable to a specific location.

Control strategies
Measures to deal with air pollution.

Design value
A statistic that describes the air quality status of a given area relative to the level of the NAAQS. It is calculated from observed pollutant concentrations and is used as an indicator for the air pollution level of a particular pollutant.

8-hour ozone standard
An indicator of air quality acceptability as it pertains to ground-level ozone.

Ground-level ozone
Ground-level ozone is formed through chemical reactions between natural and man-made emissions of volatile organic compounds (VOC) and nitrogen oxides (NOx) in the presence of sunlight. These gaseous compounds mix in the air, and when they interact with sunlight, ground-level ozone is formed. Sources of these pollutants include automobiles, gas-powered mowers, refineries, chemical manufacturing plants, solvents used in dry cleaners and paint shops, and wherever natural gas, gasoline, diesel fuel, kerosene, and oil are used as fuel.

NAAQS (National Ambient Air Quality Standards)
The Clean Air Act requires the EPA to set two types of NAAQS for criteria air pollutants: primary standards to protect public health with an adequate margin of safety, including the health of sensitive populations such as asthmatics, children, and the elderly; and secondary standards to protect public welfare from adverse effects, including visibility impairment and effects on the environment (e.g., vegetation, soils, water, and wildlife). The criteria pollutants are ozone, particulate matter, carbon monoxide, lead, nitrogen oxides, and sulfur dioxide.

Nonattainment area
A 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.

PM2.5
Particles with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers.

PM10
Particles with an aerodynamic diameter less than or equal to a nominal 10 micrometers.

Point source
A single, identifiable source of air pollutant emissions that meets the reporting requirements of 30 TAC 101.10.

SIP (State Implementation Plan)
The Federal Clean Air Act (CAA) requires states with areas that fail to meet the NAAQS prescribed for criteria pollutants to develop a State Implementation Plan (SIP). The SIP describes how the state will reduce and maintain air pollution emissions in order to comply with the federal standards.

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