Glossary of Terms

Attainment - To achieve air quality pollutant concentrations below the National Ambient Air Quality Standard. For ozone, this means allowing no more than average of one exceedance of the NAAQS per year in any three consecutive year period.

Biogenic Emissions - Emissions from soil and vegetation.

CASAC - Clean Air Science Advisory Committee; An independent advisory committee housed within USEPA’s Science Advisory Board that reports directly to the USEPA administrator. CASAC reviews the periodic reevaluations of the NAAQS.

Clean Air Act of 1990 - Enacted to establish and enforce air quality standards that protect the public within an adequate margin of safety. The Clean Air Act requires EPA, states and cities to implicate a series of programs that will further reduce emissions of VOCs and NOX from cars, fuels, industrial and chemical facilities, power plants, and consumer and commercial products among other sources. Cleaner cars and fuels, new kinds of gasoline nozzles, enhanced vehicle inspection, and other programs will be phased in over the next decade. The act does not require a cost/benefit analysis to guarantee that Americans will actually be better off.

Criteria Document - A report prepared by USEPA that summarizes all of the relevant science on the sources, chemistry, effects, etc., of air pollutants.

Difference Plot - An exhibit that compares the ozone concentrations in a scenario being modeled to ozone concentrations in a base case to assess the impact of the modeled scenario on ozone and ozone precursor transport.

Domain - The region or area being modeled.

Isopleth - A line connecting points of equal ozone concentrations.

NAAQS - National Ambient Air Quality Standards; There are two types of NAAQS: primary and secondary.

NARSTO-NE - North American Research Strategy on Tropospheric Ozone - Northeast; NARSTO-NE is a field study being conducted in the northeastern U.S. associated with NARSTO.

NOx - Nitrogen oxides; ozone precursors that are found in emissions from automobiles, electric generating plants, lawn mowers and tractors. NOx react with VOCs during summer days to form ozone when there is a combination of high temperatures, low humidity and stagnant air.

OTAG - Ozone Transport Assessment Group; An advisory group to the EPA made up of environmental and clean air directors from the 37 easternmost states and the District of Columbia. The stated group of the goal is: "To develop a thoughtful assessment and a consensus agreement for reducing ground-level ozone and the pollutants that cause ground-level ozone."

Ozone - Ozone is a product of chemical reactions in the air involving volatile organic compounds (VOCs), nitrogen oxides (NOx) and sunlight. There are two types of ozone: stratospheric ozone and tropospheric or ground-level ozone.

Primary NAAQS - These NAAQS are set to protect public health with an adequate margin of safety. A cost/benefit analysis is not considered when determining the appropriate level of a primary standard.

SAQM - San Joaquin Air Quality Model.

Secondary NAAQS - These NAAQS are set to protect against adverse welfare effects which include protection of plants, animals, ecosystems, visibility, etc. A cost/benefit analysis can be considered when determining the appropriate level of a secondary standard.

Staff Paper - A report that contains USEPA’s recommendations for the range and form of the NAAQS along with the justifications for the recommendations that are drawn from material contained in the Criteria Document.

Stratospheric Ozone - Located 10 to 30 kilometers (6 to 18 miles) above the surface of the earth, it is considered "good" ozone because it blocks harmful ultraviolet (UV) radiation from the sun.

SOS - Southern Oxidants Study; SOS is a field study examining ozone and ozone precursors in the southeastern U.S.

Trophospheric Ozone - Located from the surface to 10 kilometers above the earth, it is considered "bad" ozone because high concentrations can cause adverse health effects.

UAM - Urban Airshed Model; UAM divides the modeling domain into small boxes or grid cells in both the horizontal and vertical planes to better account for the physical processes occurring in the atmosphere.

VOCs - Volatile organic compounds; ozone precursors that are found in emissions from automobiles, chemical plants and other industrial facilities and evaporating gasoline and solvents. Biogenic emissions, such as emissions from trees and other vegetation, are also a large source of VOCs. VOCs react with NOx during summer days to form ozone when there is a combination of high temperatures, low humidity and stagnant air.

| About MOG | News | Press Releases | Briefing Documents |
| Other Resources | Regional Haze | Search MOG |
| Members Only | Home |

Contact The Midwest Ozone Group at:
mog@citynet.net