Comparison of Responses and Deposition Following Human Exposures Via Oral or Nasal Inhalation of Sulphuric Acid Aerosols.

Controlled human exposure studies with inhaled air pollutants frequently utilise mouth breathing. To determine the extent that the route of inhalation influences airway responses to particulate pollutants, we examined pulmonary responses of asthmatics breathing sulphuric acid (H2SO4) aerosols by oral or nasal inhalation. Asthmatics were exposed to H2SO4 aerosols in a 45 m3 chamber for one hour including 10 minutes of exercise or via a mouthpiece for 16 minutes during resting ventilation. We produced aerosols in concentrations of 100 //g/m3 and 450 //g/m3. We measured before and immediately after all exposures FVC, FEV1, and specific airway conductance (SGaw). At the 450 /ig/m3 concentration, there were remarkable similarities in airway responses despite the different exposure routes. Although the exposures were not strictly comparable in duration, we calculated tracheobronchial (TB) deposition for the two modes of aerosol administration and utilized contemporary models for deposition in explaining the lack of qualitative and quantitative distinctions in the pattern of response. [ABSTRACT FROM PUBLISHER]