Sulfur Dioxide and Exercise: Relationships between Response and Absorption in Upper Airways

Higher ventilation rates and decreased time of contact with upper airway surfaces occurring during exercise appear to result in delivery of greater doses of gases such as SO2 to sensitive target sites within the respiratory system. In human clinical studies, the effects of SO2 on pulmonary function are indeed enhanced during exercise. A mathematical model has been developed from measurable anatomical, physiological and physicochemical parameters as well as from controlled experiments with humans and laboratory animals. The model takes into account minute ventilation, partitioning between oral and nasal breathing, and differences in pollutant scrubbing in oral and nasal airways. The model has been tested on apparently divergent experimental results from two different laboratories and has resolved differences between results of clinical SO2 exposures of resting and exercising people.