Investigating the Synergistic Effects Between Meteorological Variables and Air Pollutants: Results from the European PHEWE, EUROHEAT and CIRCE Projects

ISEE-0929 Backgroundand Objectives: In the past 20 years, extensive scientific evidence demonstrated and quantified the short-term effects of air pollution and weather extremes on health. However, the studies formally addressing synergy between pollutants and meteorological variables are relatively few. Within the multi-centre European projects PHEWE, EUROHEAT and CIRCE we have investigated the interaction between the effects of air pollutants and meteorological variables on mortality. Methods: We used data from 22 cities in Europe and around the Mediterranean, including daily values for total and cause-specific mortality, air pollutants concentrations (PM10, NO2, O3, SO2, CO) and meteorological variables (apparent temperature, wind speed and direction, “heat-waves”). A GEE modeling approach was applied assuming a Poisson distribution on the outcome variable. Results: We found evidence for an interaction between high temperatures and high ozone and PM10 concentrations. This was particularly evident for “heat-wave” days. For the age group 75–84 years, the estimated heat wave effect is 54% larger on high ozone days. During high PM10 days the heat-wave effects on mortality, for both the 75–84 and the 85+ years age groups, are significantly larger. Differences between cities in Northern Europe, Southern Europe and non-European cities around the Mediterranean were also investigated. It was noted that failure to adjust for air pollution when estimating the temperature effects on mortality may lead to overestimation of the heat and heat-wave effects by up to 30%. Conclusions: The effects of heat-wave days on mortality are larger during high ozone and PM10 days. For ozone this is more evident for those aged 75–84 years compared to those older than 85. In contrast, the interaction with PM10 appears to affect the elderly to a larger extent, probably due to the high penetration of PM indoors. There was no evidence for interaction between heat-wave days and the concentrations of NO2, SO2 and CO.