RESUMEN
A time-series study was carried out in Paris from January 1 to December 31, 1988 with the aim of investigating the association between urban air pollution and daily emergency room visits for asthma in a pediatric hospital. Levels of black smoke, sulfur dioxide, nitrogen dioxide, and ozone were monitored throughout the study area, and meteorological data were collected. Influenza epidemics and pollen periods were identified. Health data were collected from a pediatric hospital emergency room. Case definition of asthma attacks was based on clinical diagnosis. Children were included in the study if: 1) they were 1 to 15 years old; 2) they had doctor-diagnosed asthma and were followed in our asthma outpatient clinic; and 3) they were residents in the Paris region. The relation between daily asthma visit counts and air pollution levels was assessed, using a multiple linear regression model and taking into account temporal variations and autocorrelation in the data. A thousand and twenty visits for asthma were observed during the study period. A positive statistical association was found between daily asthma visits and daily variations of ozone levels (1 day after exposure, relative risk = 1.52 [95% confidence interval: 1. 06-2.19]) after controlling for monthly and weekly variations, influenza epidemics, periods of pollen exposure, and daily mean temperature (2 days' lag). This study underlines the significant role of ozone as a trigger for asthma attacks in children.