Am. J. Respir. Crit. Care Med., Vol 152, No. 3, 09 1995, 885-891.
Controlled exposures of young asthmatics to mixed oxidant gases and acid aerosol
WS Linn, KR Anderson, DA Shamoo, SA Edwards, TL Webb, JD Hackney and H Gong Jr
Environmental Health Service, Rancho Los Amigos Medical Center, Downey, CA 90242, USA.
To help assess short-term respiratory responses to summertime air
pollution, we exposed 24 asthmatic volunteers aged 11-18 in a chamber to
respirable acid aerosol (mass median aerodynamic diameter 0.66 micron) plus
0.3 ppm nitrogen dioxide (NO2) plus 0.2 ppm ozone (O3). The aerosol
contained available hydrogen ions (H-) at an average concentration of 2.6
mumol/m-, equivalent to 127 micrograms/m3 sulfuric acid (H2SO4); some H+
probably was in NH4HSO4 rather than H2SO4. The volunteers were exposed
separately to O3/NO2 without acid and to clean air. Exposures lasted 90
min, including three 15-min exercise sessions with ventilation averaging 32
L/min, at 21 degrees C and 50% relative humidity. Asthma medications were
withheld before and during exposures. Subjects gargled lemonade to minimize
acid neutralization by oral ammonia (NH3). Exercise-induced bronchospasm
was evident in all exposures. Differences in group mean lung function
response among H2SO4/O3/NO2, O3/NO2, and clean-air exposures were not
statistically significant. Individuals' measured oral NH3 concentrations or
estimated inhaled doses of H2SO4 did not significantly predict their lung
function changes. A few subjects showed unfavorable function changes during
pollutant exposures, which might be chance occurrences or might indicate
the existence of an acid-pollution-susceptible subgroup among young
asthmatic subjects.
