Chronic air pollution and social deprivation as modifiers of the association between high temperature and daily mortality Tarik Benmarhnia 1, 2, Youssef Oulhote 2, Claire Petit 1, 3, Annabelle Lapostolle 4, 5, Pierre Chauvin 4, 5, Denis Zmirou-Navier 1, 3, 6, Séverine Deguen 1, 3 (1) EHESP School of Public Health, Rennes, Sorbonne-Paris Cité, France; (2) Montréal University, DSEST, Montréal, QC, Canada; (3) INSERM U1085 (IRSET), Rennes, France; (4) INSERM UMRS707, DS3, Paris, France;(5) UPMC University Paris 06, UMRS 707, Paris, France; (6) Lorraine University Medical School, Vandœuvre-les-Nancy, France Background An increase in daily summer temperatures is associated with an increase in daily mortalities Daily air pollution has been documented as an effect modifier in the relation between temperature and mortality as well as the social deprivation. However, chronic air pollution has never been studied in the relationship between heat and mortality as well as the double interaction with social deprivation Figure 1: Spatial distribution of deaths attributable to mean temperature by chronic air pollution exposure (A) and by summer by social deprivation (B) in Paris, France, (period ) Figure 2: Number of deaths attributable to mean temperature by summer with double stratification To identify whether the effect of daily temperature on all-cause mortality is modified by chronic exposure to NO 2 (representing urban traffic) and social deprivation, and a combination of these two factors. Objectives Methods Daily mortality and daily mean temperature in the City of Paris (France) over the period 2004 to 2009 Estimates of chronic exposure to NO 2 concentrations and social deprivation at the census block were split into three strata. Stratified Poisson regression controlling for daily NO 2 and relative humidity. Heterogeneity test of the regression coefficients in different strata. Deaths due to ambient temperature were calculated from attributable fractions. Results Conclusion – Perspectives Our results may have important implications considering chronically polluted areas as vulnerable in heat actions plans (especially including adapted surveillance and warning systems) and in the long-term measures to reduce the burden of heat stress (as building regulations, urban planning or land-use changes), especially in the context of climate change. However, it is necessary to determine whether a consistent finding could be found in other settings. A B (a) Low chronic exposure/ Low Social Deprivation; (b) Low chronic exposure/ Medium Social Deprivation; (c) Low chronic exposure/ High Social Deprivation; (d) High chronic exposure/ Low Social Deprivation; (e) High chronic exposure/ Medium Social Deprivation; (f) High chronic exposure/ High Social Deprivation. Figure 1 Chronic air pollution modifies the relation between daily summer temperatures and mortality. Social deprivation modifies also the summer mortality – temperature relationship. Figure 2 There is a potential combined effect modification of social deprivation and chronic exposure to NO 2 in the mortality- temperature relationship.