Saharan Dust Transport and Daily Mortality

Abstract

ISEE-0292 Background and Objective: A recent study in Barcelona evaluated the effects of Saharan dust on mortality. In this study, the authors showed that increases of both fine and coarse particles were associated with greater effects on mortality in Saharan dust days than in non Saharan dust ones. We study this relationship in Emilia-Romagna, a region in the north-east of Italy. In this region the meteorological and air quality station of Mt. Cimone (2165 a.s.l.) is located, one of the first high mountains that is passed by the Saharan air masses and where measurements of their chemical composition has been regularly carried out since 2002. Methods: The identification of Saharan dust episodes was done analysing the hourly number concentration of coarse particles at Mt. Cimone. Additional information on dust episodes was obtained from the analysis of background trajectories and satellite images. Exposure of study population to particulate matter was defined through the monitored level of PM10 in urban areas. We studied all subjects at least 75 years of age who died of natural causes in the main cities of the region from 2002 to 2006. The association of daily concentrations of PM10 with daily mortality was investigated using a case-crossover design. Conditional logistic regression was used to estimate percent increase in the risk of dying for an increase of 10 μg/m3 in PM10 (lag 1). Chemical composition of particles was also analyzed. Results: Natural mortality risk increased by 3.8% (95% Confidence Intervals, CI, 0.2-7.5) during non Saharan dust days and by 5.7% (CI, −3.0-15.2%) during Saharan dust days in summer period. Other analyses have been done by age, sex and cause of death. Conclusion: The apparent increase in mortality associated with Saharan dust raises concern over possible underestimation of toxicity from coarse particles when they come from desert sources.