Effects of Exercise on Dose and Dose Distribution of Inhaled AutomotivePollutants

摘要

The study evaluated how changes in ventilation rate and the entry route of airpollutants into the respiratory tract (nose versus mouth breathing) affect the respiratory tract uptake and penetration of inhaled gaseous and particle pollutants in automobile emissions. Beagle dogs were exposed at rest or while exercising to nitrogen dioxide (1 and 5 ppm), formaldehyde (2 and 10 ppm), and an aerosol of ammonium nitrate particles (0.3 micro MMAD at 1 mg/m). Total respiratory system uptake and effects on breath time expired tidal volume, fractional expiration time, minute ventilation, respiratory gas exchange, ventilation equivalents for oxygen and carbon dioxide, and dynamic pulmonary resistance and compliance were measured. Regional penetration of pollutants through oral and nasal airways and pollutant uptake in the lung were measured in a separate group of six tracheostomized dogs. Dogs exposed to 5 ppm nitrogen at rest tended to breathe more rapidly and more shallowly than dogs exposed to purified air. Rapid-shallow breathing was not observed when the dogs were exposed during exercise to 5 ppm nitrogen dioxide. Dogs exposed to a mixture of 10 ppm formaldehyde and 1 mg/m 3 ammonium nitrate particles during exercise showed a shift to larger tidal volume breathing. The total respiratory system uptake of formaldehyde in the mixture was larger than that measured for 10 ppm of formaldehyde alone in another exercise and exposure study. In tracheostomized dogs exposed at rest, formaldehyde was rapidly removed from inspired air by the upper airways and penetrated to the trachea, whether breathing was by nose or mouth. Nitrogen dioxide penetrated the upper airways more readily. For both gases, penetration was greater during mouth breathing than during nose breathing, and penetration increased with increased ventilation.