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The primary responses of the lung to exercise are an increase in and a redistribution of ventilation and perfusion. In the presence of environmental pollutant gases, these changes will have a direct effect on the internal distribution of pollutant concentration and absorption in the lower airways. In the conducting airways, higher ventilation rates promote turbulence and increase gas phase mass transfer coefficients, and this can accelerate the absorption of pollutant by bronchial tissue. Also, the larger tidal volumes associated with exercise increase alveolar ventilation, resulting in higher pollutant exposure levels in the respiratory air spaces.
Uptake of sparingly soluble, slowly reacting pollutants into the pulmonary circulation depends on the relationship between ventilation and perfusion. Moreover, the spatial distribution of the ventilation/perfusion ratio VA/Q, has an influence on pollutant concentration in the intervening parenchymal tissue. During exercise, regional distributions of VA/Q become more uniform, implying a more homogeneous distribution of pollutant exposure between different lung regions. On the other hand, intraregional VAQ distributions become less uniform, so that pollutant exposure within a lung segment is expected to be more heterogeneous.
pollutant exposure, lung dosimetry, exercise, lower airways, pulmonary ventilation, pulmonary diffusion, pulmonary perfusion, ventilation-perfusion ratio, lung mass transfer coefficients
Professor, Pennsylvania State University, University Park, PA