Dose response functions and the harvesting effect

Much of the existing literature on air pollution and mortality deals only with the short-term effects of air pollution. Policy on the other hand needs to know when, whether and to what extent pollution-induced increases in mortality counts are reversed. This involves modelling the entire infinite distributed-lag effect of air pollution on mortality counts.Using an ARMAX modelling strategy this paper illustrates how distributed lag effects can be parsimoniously but plausibly estimated in the context of a time-series study into the relationship between ambient levels of air pollution and daily mortality counts for Manchester. The analysis reveals that maximum 1-h ozone levels are strongly associated with daily mortality counts and that a significant harvesting effect is present. The mortality cost of peak 1-h ozone concentrations for Greater Manchester with a population of 2.6 million is estimated to be £572 million annually. This accounts for the fact that some of the deaths associated with maximum 1-h O₃ concentrations have been advanced only by a short period of time.