This paper describes a simplified method, the Smeared Concentration Approximation, developed to characterize air pollution dispersion for use in models concerned with long-term policy analysis at the regional level. The methodology centers around the urban scale. The main assumptions behind the approximation are described and the SCA Dispersion Parameter is defined. Development of the SCA Dispersion parameter, using detailed air pollution despersion models, is described. Illustrations of the use of this methodology in regional energy/environment analysis are presented and some conclusions concerning the use of the method are given.