This paper discusses the status and application of Computational Fluid Dynamics (CFD) models to address environmental engineering challenges for more detailed understanding of air pollutant source emissions, atmospheric dispersion and resulting human exposure. CFD simulations provide a number of unique opportunities for expanding and improving capabilities for modeling environmental flows. The application of CFD for detailed modeling of environmental flow requires tools for complex geometry creation and meshing, advanced physical models and parallel computing capabilities. Unlike most currently used models, CFD simulations are able to account rigorously for topographical details such as terrain variations and structures in urban areas as well as local aerodynamics and turbulence. These features can be influential in determining local human exposures to environmental pollution. CFD simulations of complex distributions of pollutant concentrations within microenvironments of human exposure are feasible using today's high performance computing. Through further research, validation and testing, CFD modeling has the potential to become a reliable tool for estimating pollutant concentrations for situations that today have no reliable modeling method.