sulfur dioxide is formed by the combustion of fossil fuels
sulfur_dioxide is dioxide. combustion_gas is gas. sulfur_dioxide is inorganic_substance. sulfur_dioxide is chemical_compound. sulfur_dioxide is gas. combustion_of_fossil_fuels is common_source_of_air_pollution. internal_combustion is burning. sulfur_dioxide is pollutant. sulfur_dioxide is oxide. internal_combustion is combustion.