Inhalation route effects on exposure to 2. 0 parts per million sulfur dioxide in normal subjects

To investigate possible changes in nasal resistance due to sulfur dioxide (SO{sub 2}) exposure, 14 subjects, healthy non-smokers, between the ages of 20 and 46 years, were exposed for 30 minutes to filtered air while free breathing and to 2.0 ppm SO{sub 2} with either free breathing, forced oral or forced nasal breathing with continuous exercise at a workload 300 kg{center dot}m/min below the workload which initiated cross-over from nasal to oral/nasal breathing in a preliminary incremental workload test. An incremental work test under the ambient conditions was performed immediately following the 30-minute exercise to ascertain any change in the cross-over ventilation. Pre- and post-measures of pulmonary functions were obtained to ascertain any changes in these parameters due to the exposure. There was a significant difference in the workload at which cross-over occurred following forced oral breathing in 2.0 ppm sulfur dioxide. The nasal ventilation prior to cross-over and the nasal component of ventilation were significantly smaller for this exposure condition, indicating a possible change in nasal dynamics following the 30 minutes of forced oral breathing in 2.0 ppm SO{sub 2}. Lack of concomitant changes in pulmonary function tests including airway resistance suggests that breathing 2.0 ppm SO{sub 2} does not affect normal subjects whether administration is by free, forced oral or forced nasal breathing.