Short-term effects of ambient particles on mortality in Italy - a national approach

Abstract

Background. Short-term exposure to particulate matter (PM) has been related to mortality worldwide. Most evidence comes from studies conducted in major cities, while little is known on the effects of low concentrations of PM and in less urbanized areas. We aim to investigate the relationship between PM and all-cause mortality at national level in Italy.Methods. Daily numbers of all-cause mortality were collected for all 8,092 municipalities of Italy, from 2006 to 2015. A satellite-based spatiotemporal model was developed to estimate daily PM10 (inhalable particles) and PM2.5 (fine particles) concentrations at 1-km resolution. Multivariate Poisson regression models were fit to estimate the association between daily PM and mortality at province level, then results were pooled with a random-effects meta-analysis. Associations were estimated by age, sex and degree of urbanization of the municipalities. Flexible functions were estimated to explore the shape of the associations at low PM concentrations.Results. We analyzed 6,552,257 deaths (40% among subjects older than 85 years, 55% occurring outside the main urban areas). National daily mean (interquartile range) PM10 and PM2.5 concentrations were 23 (12) μg/m3 and 17 (9) μg/m3, respectively. Relative increases of mortality, per 10 μg/m3 variation in lag 0-5 (average of last six days since death) PM10 and PM2.5, were 0.80% (95% Confidence Intervals [CI]: 0.58%, 1.01%) and 0.72% (0.34%, 1.09%) respectively. Associations were highest among elderly and women, similar between rural and urbanized areas, and were present even at low concentrations, e.g. below WHO guidelines. Conclusions. Air pollution was robustly associated with peaks in daily all-cause mortality in Italy, both in large cities and in less urbanized areas of Italy. Current WHO Air Quality Guidelines for PM10 and PM2.5 are not sufficient to protect public health.