Sulfur oxides are all around us. Some of them are naturally occurring (for instance in volcanic eruptions), and relatively harmless; some, however, can be man-made as a byproduct of industrial processing, and are extremely toxic.
Sulfur oxides can be any of several compounds formed by sulfur and oxygen. The most common are sulfur dioxide (SO2) and sulfur trioxide (SO3). Sulfur dioxide is a very poisonous gas that can occur both naturally or anthropogenically; it is colorless and smells like a match that has just been struck. Sulfur trioxide is also highly poisonous, highly reactive and very corrosive.
Sulfur dioxide can be used for several things:
Sulfur dioxide is a common pollutant in most civilized countries, from industrial processing plants (coal, oil, cement, metal, wood, copper, electric power plants etc.). It can cause various serious health problems, especially with long-term exposure, exposure to critical levels, exposure in children or in people with preexisting heart and lung conditions: