The extended use of fuels with high sulfur content (fuel oil) in the electric power industry represents one of the biggest concerns on air quality currently in Mexico. The organic sulfur compounds in the fuel oil are oxidized as SOx during combustion, causing high concentration at the surface level near the releasing point. Shifting towards cleaner energy is crucial, however natural gas (NG) production is currently scarce and substantial investment is required to assure the NG supply to replace the fuel oil. Large investments should be made by the public and private sectors to replace heavy fuel oil use by NG. In order to support decision takers, this work assess the air quality impact due to cleaner energy use and determine the optimal NG and fuel oil mixture required to reduce substantially the SO2, concentration. The dispersion model was applied to compare, against a base case, a set of artificial emissions scenarios with different fuel oil and NG mixtures. The model was previously validated against SO2 field measurements performed at an Industrial Corridor, Mexico. The results show that increasing 40% the NG consumption, the SO2, concentration in the air is reduced in 90%, therefore not further NG increasing is needed. (c) 2005 Elsevier B.V. All rights reserved.