Research Projects

The projects completed under this contract permit the following conclusions:

1. Inhalation of dense (38 g/m3) aerosols through a mouthpiece during moderate exercise for a brief period (10 minutes) can cause cough and mild bronchoconstriction in subjects with asthma (Project 1). There were no significant differences between the bronchoconstrictor effects of the 3 acid aerosols studied (H2SO4, HNO3, and a 1:1 mixture of H2SO4 and HN03) and that of neutral saline.

2. In relatively large (5 to 6 microns) particle hypoosmolar aerosols of extremely high LWC (up to 87 g/ma3) inhaled through a mouthpiece, the most important bronchoconstrictor effect of acidity is potentiation of the bronchoconstrictor effect of hypoosmolarity (Project 2).

3. Clinically significant bronchoconstriction did not occur in subjects with mild-moderate asthma exposed to H2SO4-containing fogs for one hour in a chamber during intermittent exercise (Project 3). The H2SO4 concentrations administered in this study are at least an order of magnitude higher than those that are likely to occur in the environment.

4. The lack of a dose-response effect with regard to LWC in the exposure chamber study (Project 3) suggests that the density of a fog, at least in the range of what has been measured in the environment, is not an important factor in terms of its bronchoconstrictor potency.