Mechanisms of Airway Responses to Inhaled Sulfur Dioxide

The bronchomotor effect of sulfur dioxide (SO₂) in subjects with asthma is greatly potentiated if the pollutant is inhaled during exercise. These observations did provide an experimental system in which to examine the mechanism(s) by which inhalation of sulfur dioxide causes an increase in airflow resistance. Several studies have examined the effects of acute inhalation of SO₂ on normal human subjects. In general, SO₂ has not acutely caused direct lower respiratory injury in animals unless it was inhaled in high concentrations. Over the past 30 years, these epidemiologic observations have stimulated a series of laboratory studies examining the effects of this ubiquitous pollutant on the airways of animals and of human subjects. The observation that dermal sensitivity to sulfite could be passively transferred via the serum of one affected patient is consistent with a humoral immune mechanism of response.