Respiratory damage caused by long-term inhalation of high concentration of sulphur-dioxide in dogs.

It has been tried in this study to produce chronic obstructive bronchitis in dogs by exposing them to high concentrations of SO2. The study was extended to 175 days and during that period the animals were exposed to 300-500 ppm SO2 for a total of 435 h. None of the three dogs developed serious respiratory damage. Most of the symptoms were transitory. Histological examinations showed increased number of goblet cells in trachea, main- and lobar bronchi and a slight alteration of the bronchial glands.