Sulfur dioxide (SO2) is one of a group of highly reactive gases called sulfur oxides (SOX). SO2 is colorless and has a sharp, irritating odor. It reacts easily with other substances to form harmful compounds, such as sulfuric acid, sulfurous acid and sulfate particles. About 99% of the sulfur dioxide in air comes from human sources. The main source of SO2 in the air is industrial activity that processes materials that contain sulfur, such as the generation of electricity from coal, oil or gas. Sulfur dioxide is also present in motor vehicle emissions, as the result of fuel combustion. SO2 adversely affects the respiratory system, causing irritation of the eyes and the respiratory tract. This could result in coughing, mucus secretion, as well
