Background: To support environmental policies aiming to tackle air pollution, quantitative health impact assessments (HIAs) stand out as one of the best decision-making tools. However, no risk assessment studies have quantified or mapped the health and equity impact of air pollution reduction at a small spatial scale. Objectives: We developed a small-area analysis of the impact of air pollution on "premature" death among an adult population over 30 years of age to quantify and map the health and equity impact related to a reduction of air pollution. Methods: All-cause mortality data of an adult population (>30 years) from January 2004 to December 2009 were geocoded at the residential census block level in Paris. Each census block was assigned socioeconomic deprivation levels and annual average ambient concentrations of NO₂, PM10, and PM2.5. HIAs were used to estimate, at a small-area level, the number of "premature" deaths associated with a hypothetical reduction of NO₂, PM10, and PM2.5 exposure. In total, considering global dose response function for the three pollutants and socioeconomic deprivation specific dose response function, nine HIAs were performed for NO₂ and six and four HIAs for PM10 and PM2.5, respectively. Finally, a clustering approach was used to quantify how the number of "premature" deaths could vary according to deprivation level. Results: The number of deaths attributable to NO₂, PM10, and PM2.5 exposure were equal to 4301, 3209, and 2662 deaths, respectively. The most deprived census blocks always appeared as one of the groups most impacted by air pollution. Our findings showed that "premature" deaths attributable to NO₂ were not randomly distributed over the study area, with a cluster of excess "premature" deaths located in the northeastern area of Paris. Discussion: This study showed the importance of stratifying an environmental burden of disease study on the socioeconomic level, in order to take into consideration the modifier effect of socioeconomic status on the air pollution-mortality relationship. In addition, we demonstrated the value of spatial analysis to guide decision-making. This shows the need for tools to support priority-setting and to guide policymakers in their choice of environmental initiatives that would maximize health gains and reduce social inequalities in health.
Keywords: AirQ; environmental inequalities; equity impact; health impact; health impact assessments; premature death; reduction of air pollution; small area; spatial analysis.