Respiratory effects of inhaled sulfuric acid on senior asthmatics and nonasthmatics.

The objective of this study was two-fold: (1) to investigate the response of asthmatic subjects who were 60 to 75 y of age to inhaled sulfuric acid, and (2) to compare that response to findings from healthy subjects in the same age group. Nine subjects who had asthma and eight healthy subjects participated. Each subject was exposed to clean air, an inert ammonium sulfate aerosol, or 70 micrograms/m3 sulfuric acid during a 40-min exposure period composed of 30 min at rest and 10 min of light exercise on a treadmill. The sulfuric acid was delivered twice, one preceded by a lemonade drink to neutralize oral concentrations of ammonia. Exposures were separated by at least 1 wk. Oral ammonia levels and pulmonary function parameters (forced expiratory volume in one second, forced vital capacity, and total respiratory resistance) were measured before and after each exposure. None of the functional parameters in either group showed significant changes. However, total respiratory resistance changes from baseline after sulfuric acid exposure were significantly higher (+16%) in the asthmatic subjects, compared with the healthy subjects (-6%). These data suggest that older subjects are not at increased risk for adverse respiratory effects from inhalation of sulfuric acid by virtue of age alone, and older subjects with asthma are slightly more vulnerable than are their healthy peers.