A Background concentrations: is In this context, EPA uses background concentrations to mean the contributions to outdoor Air Toxics concentrations resulting from natural sources, persistence in the environment of past years' emissions and long-range transport from distant sources. Background concentrations could be levels of pollutants that would be found in 1996 even if there had been no recent manmade emissions. To accurately estimate outdoor concentrations, it is necessary to account for the background concentrations by adding them to the modeled concentrations. In this assessment, except for diesel PM, background concentrations are based on values identified in the Cumulative Exposure Project (study which estimated 1990 ambient concentrations of air toxics). From that study, EPA used background concentration values reported in the technical literature for 13 of the air toxic pollutants, and for the rest, EPA assumed a value of zero. For diesel PM, instead of using monitored air quality data to estimate background concentrations, a modeling-based approach was used. For more detailed information, see Background Concentrations.

Related Articles

Ambient ■■■■■■■■■
An ambient is pertaining to the Current Environmental condition. It means surrounding, or on all sides. . . . Read More
Aerodynamics ■■■■■■
Aerodynamics in the environmental context refers to the study of how air moves around objects, including . . . Read More
Chemistry ■■■■■■
Chemistry is the scientific study of the properties, composition, and behavior of matter. In the context . . . Read More
Diesel ■■■■■■
Diesel is a petroleum-based fuel which is burned in engines ignited by compression rather than sparkcommonly . . . Read More
Calve ■■■■■■
A Calve is Giving birth to a calf. Same as parturition. Other definition is following: In the context . . . Read More
Criteria Pollutants ■■■■■
Criteria Pollutants are the 1970 amendments to the Clean Air Act required EPA to set National Ambient . . . Read More
National Ambient Air Quality Standards (NAAQS): ■■■■■
National Ambient Air Quality Standards: National Ambient Air Quality Standards (NAAQS): : A National . . . Read More
Criteria ■■■■■
A Criteria is Descriptive factors taken into account by EPA in setting standards for various pollutants. . . . Read More
Chemical Compound ■■■■■
A Chemical Compound is a distinct and pure substance formed by the union or two or more elements in definite . . . Read More
Power plant ■■■■■
A Power plants is a facility (plant) that produce energy. In the context of the environment, "power plants" . . . Read More