Sulfur dioxide, a respiratory tract irritant, even if ingested.

Sulfur dioxide (SO2) is a well-known atmospheric pollutant and respiratory tract irritant. Inhalation of trace quantities may result in the rapid development of laryngeal and bronchial spasm, excessive bronchial secretions, and pulmonary edema. It has been suggested that the increasing incidence of asthma and chronic bronchitis in urban areas may be attributable to the rising SO2 content of the air owing to the combustion of high sulfur-containing fuels. Sulfur dioxide is also widely used as a preservative in certain common foodstuffs, i.e., dried fruits.