Ambient ozone and acute health effects: evidence from daily data

This paper reports on the results of a detailed epidemiological investigation of daily acute health effects in adults and children associated with daily exposure to ozone and other air pollutants. Using a Markov process model of health effects, we find statistically significant and robust effects of ambient ozone concentrations on daily reported respiratory symptoms among healthy nonsmoking adults but not among smokers or children. We also estimate a model in which ozone is allowed to affect individuals who are already ill differently from individuals who are not, and find that ozone is negatively correlated with additional illness. This result is consistent with avoidance behavior. Assuming a 10% ozone reduction, the health improvements predicted using our study are of the same order of magnitude as those predicted using two other, more problematic epidemiological studies.