Asthma prevalence and mortality due to asthma have been increasing dur
ing the last decade, and both the rates and the increases in rates hav
e been higher for blacks than whites and higher for children than adul
ts. Whether environmental factors such as air pollution contribute to
these increases is unknown. The purpose of this study was to examine t
he relationship between emergency visits to a hospital for childhood a
sthma and exposure to ozone in an indigent, predominantly black popula
tion. Data were collected by abstracting clinical records for all chil
dren with asthma or reactive airway disease in one public hospital dur
ing the summer of 1990. From June 1, 1990, to August 31, 1990, 609 vis
its were made by children aged 1 to 16 years to an emergency clinic fo
r treatment of asthma or reactive airway disease. Monitoring data indi
cated that maximum ozone levels equalled or exceeded 0.11 ppm on 6 day
s during the study period. The average number of visits for asthma or
reactive airway disease was 37% higher on the days after those 6 days
(from 6:00 PM to 6:00 PM the next day) than on other days (95% CI, RR
= 1.02-1.73). The results of the study suggest that among black childr
en from low-income families, asthma may be exacerbated following perio
ds of high ozone pollution. (C) 1994 Academic Press, Inc.