Many firms have extensive experience modeling individual industrial facilities to support permit applications. The true challenge for a modeler is to address the analysis on an urban-scale, model all quantifiable source categories in a metropolitan area, and determine how realistic the assessment is relative to measured air quality data.

Since the first major EPA urban-scale air toxics study conducted in 1981, the staff of Sullivan Environmental Consulting, INC. was responsible for developing methods for EPA to address urban-scale air toxics exposures. The methodology was developed and refined in the EPA Integrated Environmental Management Project (IEMP), which was one of the key components used by EPA to address air toxics in the 1980s.

EPA urban scale studies generally involve establishing air toxics monitoring networks in the selected metropolitan area, compiling available point source emissions data, conducting pollutant apportionment as necessary into individual species, and addressing the general area source terms such as mobile sources, home heating, and solvent use. Dispersion modeling methods are then used to link the emissions and measured air quality data to determine the strengths and weaknesses in the exposure assessments. After an evaluation of these assessments, a more obvious picture emerges of where risks were found in terms of both pollutant species and source categories. These urban-scale studies were performed for metropolitan areas in the U.S. and also in Eastern Europe based on the same fundamental principles as applied in the earlier IEMP studies.

Highlights of this Work Include: