Sulfur dioxide (SO2) is the gas with the highest concentration in the air of the sulfur oxides group (SOx) and it is used as the indicator for the whole group.
The largest source of SO2 emissions is fossil fuel combustion at power plants and other industrial facilities.
Short-term exposures to SO2 can make breathing difficult, especially in people with asthma and children. SOx can react with other compounds in the atmosphere to form small particles that can penetrate deeply into the lungs and cause severe problems to the respiratory system.