US EPA

Before the U.S. Environmental Protection Agency issued the 1988 Guidelines for Estimating Exposures, it published proposed guidelines in the Federal Register for public review and comment. he guidelines are intended to give risk analysis a basic framework and the tools they need to conduct human and nonhuman exposure assessments for specific pollutants. our areas requiring further research were identified during the review process. ne of the areas identified was the selection criteria for mathematical models used in exposure assessments. his document presents criteria for selecting the most appropriate mathematical model(s) to use in an exposure assessment related to air contamination. art I contains general guidelines and principles for model selection and a step-by-step approach to identifying the appropriate model(s) to use in a specific application. he scale, land use of the setting, time scale, and type of terrain; source characteristics; and emission characteristics. ost exposure assessment scenarios call for assessing human exposure as a result of near-filed releases of nonreactive contaminants from point or area sources over flat terrain in either an urban or rural setting. aussian models, which are applicable to most exposure assessment situations, are discussed in relation to selected applications. he model selection process is illustrated through three typical exposure assessment scenarios. art II presents assumptions, limitations, and uncertainties associated with Gaussian plume models; discusses dispersion coefficients typically used in Gaussian models; and provides typical source parameters for hazardous waste management facilities. art III characterizes indoor sources of emissions; describes the general mass-balance equation for indoor air quality, which incorporates the five major determinants of indoor air pollutant levels; and discusses how dispersion models can be applied to model indoor air concentration.

U.S. EPA. Selection Criteria for Mathematical Models Used in Exposure Assessments: Atmospheric Dispersion Models. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/8-91/038 (NTIS PB94114725).

Project Officer: ichard Walentowicz