Tracheal mucous transport in Beagles after long-term exposure to 1 ppm sulfur dioxide

Tracheal mucous velocity was determined in eight purebred beagle dogs exposed intermittently to 1 ppm sulfur dioxide for 12 months. Three control dogs were also studied. Teflon disks filmed at constant speed through a bronchofiberscope served as indicators of mucous motion. An average of 16 disks were analyzed in each dog. Although there was no significant difference in average velocity for controls and the SO-2-exposed animals, the frequency distribution curve of individual disk velocities in SO-2-exposed dogs revealed significant slowing. No significant differences in mechanics of breathing and gas exchange were found between the two groups. It appears that long-term exposure to low levels of SO-2 produces an impairment of mucociliary activity as one of the first signs of pulmonary dysfunction.