e has diminished sharply during the past 29 years. Since 1975, the concentration of lead has decreased by more than 90%, which can be directly linked to the elimination of lead from gasoline. The following table shows that huge drop. TABLE 2 Gas Another primary group of pollutants consists of the surfur oxides(Sox), and the major contributor is SO2, a sulfur dioxide. This is generated whenever sulfur is burned, most often where fuel with a high sulfur content is used. Coal can have very high sulfur concentrations, as can some oil. Overall, coal and oil are the major sources for sulfur oxide pollution. The vast majority of this type of air pollution comes from generation of heat and electricity. These stationary sources account about 80% of all sulfur oxides. Transportation's contribution is minor, about 5%. The rest comes from industry. Sulfur dioxides cause damage to vegetation and material. Plants lose their chlorophyll which is the plants food factory. But the most damage appears when sulfur oxides combine with other substances. Because of its solubility, sulfur dioxide becomes a major contributor to acid deposition. Leaves are bleached and show damage. Tree growth is stunted and vegetation dies. Damage to vegetation occurs at concentrations lower than what is harmful to people. Carbon monoxide (CO) Carbon monoxide is colorless, odorless , tasteless,non-corrosive, highly poisonous gas of about the same density as that of air. It is very flammable, burns in air with bright blue flame. Its melting point is at-205.0 C and boiling point is at -191.5 C. There is no way to know if it is around, except we may no feel so well. When a fire burns in an enclosed space, oxygen is gradually depleted and carbon dioxide is increased. The changes in both of the these gases increasingly cause the combustion process to change from one of complete combustion to one of incomplete combustion, resulting in the release of increasing amounts of CO. Thus, ev...
