Direction régionale des affaires sanitaires et sociales de Bretagne, Cellule interrégionale d’épidémiologie Ouest, 20, rue d’Isly, CS 84224, 35042 Rennes cedex, Institut de veille sanitaire (InVS), Département santé environnement, 12, rue du Val d’Osne, 94415 Saint-Maurice cedex, école nationale de la santé publique (ENSP), Avenue du Pr. Léon Bernard, CS74312, 35043 Rennes cedex
Background: When French regional planning for air quality first began, exposure-response functions from time-series studies were used to assess the short-term health impact of urban air pollution. The World Health Organisation also suggests that exposure-response functions from cohort studies be taken into account to evaluate the effects of chronic exposure and to quantify the prematurity of deaths related to chronic exposure to air pollution. This work characterises the long-term effects of air pollution in Nantes by considering years of life lost as well as the number of attributable deaths. Methods: The study population is classified in birth cohorts. For each cohort, 2 survival curves are built based on current mortality conditions: the first is built for current exposure to air pollution and the second for exposure to a lower reference level of air pollution. The area between the 2 curves represents years of life lost attributable to urban air pollution. Results: The estimated number of premature deaths due to air pollution is approximately 56, or about 2.0% of the deaths of those older than 30 years. The health impact on the Nantes population is estimated at 27.2 years of life lost attributable to urban air pollution in 1999 and 2,388.1 years of life lost for the 1999-2008 period. This amounts to a decrease of roughly 4 months in the life expectancy of those aged 30 years. Conclusion: This study, which also identifies and discusses relevant errors and uncertainty, confirmed that air pollution in Nantes has significant health effects and that chronic exposure plays an essential role in this impact. The number of years of life lost and the reduction in life expectancy provide new reasons to reject the assumption that health effects are limited to the premature deaths of terminally-ill people. The expected health gains in Nantes associated with reduced although still moderate air pollution levels are on the same scale as, and possibly better than, those found in 9 other French cities for similar air pollution decreases.