Accurate information on contributing sources to ambient air pollution in a location is the foremost requirement for development of efƒcient air quality management strategies. The top-down approach using emission inventories alone or combined with air quality dispersion modeling is usually used as a tool to generate information on source contributions to ambient air pollution. The dispersion modeling approach requires accurate emission input data to predict ambient air pollutant concentrations; hence, the lack of these data introduces much uncertainty to the top-down approach results. Besides, the source emission inventory usually does not include fugitive releases or provide direct information on secondary air pollutants that are formed in the atmosphere; thus, it is insufƒcient for air quality management in several situations.