The regulating agency can estimate the concentrations of pollutants from a source to which a community is exposed by performing mathematical dispersion modeling if they know the rate at which the pollutants are being released. They can also model the ACL backwards to establish the maximum allowable rate of release at the pollutant source.
The EPA has guidelines for using the most popular models (U.S. EPA 1986). Models are available for various meteorological conditions, terrains, and sources. Meteorological data are often difficult to obtain but crucial for accurate results from mathematical models.
The NAAQSs in Table 4.1.1 are ACLs derived from the best available data. State and local regulators have also used an array of ACLs for regulating toxic air pollutants. Examples are shown in Table 4.1.2.
Was this article helpful?