Sulfur Dioxide (SO2)
Sulfur dioxide is a colourless gas with a pungent odour that irritates skin and the tissues and mucus membranes of the eyes, nose and throat. It mainly affects the upper respiratory tract and bronchi.
The World Health Organisation recommends a concentration of no greater than 0.5 ppm over 24 hours for maximum exposure. Immediate irritation of the nose and throat occurs with 6-12 ppm concentration, 20 ppm causes eye irritation and 10,000 ppm will irritate moist skin within minutes.
An active volcano emits between 20 and 10,000,000 tonnes per day according to the style of volcanic activity and type and volume of magma involved.