SEASONAL EFFECT OF PM2.5 ON MORTALITY: A CASE-CROSSOVER ANALYSIS IN NINE FRENCH CITIES

Background and aims: Short-term effects of airborne particulate matter on mortality have been consistently reported, especially for fine particles (PM2.5), which are thought to contain the most harmful components. Recently, several studies in Europe and North America have suggested that the greatest effect of particles was observed during warm seasons. We examined the seasonal changes in the effects of PM2.5 on mortality in nine French cities during the 2000-2006 period. Methods: Data from urban air monitoring stations measuring PM2.5 with TEOM were used to compute daily means of PM2.5. For each city, we analysed by season the association between daily PM2.5 and daily number of non-accidental deaths, using a time-stratified case-crossover design, adjusting on daily mean temperature at lags 0 and 1-7. We also used a temperature-stratified case-crossover design to assess changes in the association by temperature quartiles. Analyses were carried out with and without adjustment on daily 8h-maximum levels of o...