There are also a large number of compounds which have been determined to be hazardous which are called air toxics. Sources There are many sources of emissions. Point sources include things like factories and electric power plants . Mobile sources include cars and trucks, of course, but also lawn mowers, airplanes and anything else that moves and puts pollution into the air. Biogenic sources include trees and vegetation, gas seeps, and microbial activity.
Area sources consist of smaller stationary sources such as dry cleaners and degreasing operations.
Since then additional laws and regulations have been added including the 1990 Amendments to the Clean Air Act. In order to make improvements in the air quality, the amount of pollutants in the air must be measured. The Emissions Measurement Center develops standards and evaluates testing methods so that regulations can be developed and enforced. An emission factor is a relationship between the amount of emissions that are released and the activity of the producer. Emission factors are used to predict emission levels fordifferent industries.