Sulfur dioxide ( SO2) is primarily produced from the burning of fossil fuels (coal and oil) and the smelting of mineral ores that contain Sulphur. Exposure to SO2 affects the respiratory system and the function of the lungs, and causes irritation of the eyes. Inflammation of the respiratory tract from SO2 can aggravate asthma and chronic bronchitis, as well as increases the risk of infection, leading to increased hospital admissions and visits to emergency rooms. SO2 also combines with water in the air to form sulfuric acid - the main component of acid rain.


Sulfur dioxide

Time-weighted average

730 (0.28) - 365 (0.14) - 80 (0.03) µg/Nm3 (ppm)

Averaging time

1 hour - 24 hour - Annual

Time –weighted average Averaging Time Number of allowable exceedances
280 ppb 1-hour 2 times per annum
140 ppb 24-hour 1 time per annum
30 ppb annually None
Number of allowable exceedances

2 times per annum - 1 time per annum - N/A