title: Effect of atmospheric mixing layer depth variations on urban air quality and daily mortality during Saharan dust outbreaks.
abstract: Several epidemiological studies have shown that the outbreaks of Saharan dust over southern European countries can cause negative health effects. The reasons for the increased toxicity of airborne particles during dust storms remain to be understood although the presence of biogenic factors carried by dust particles and the interaction between dust and man-made air pollution have been hypothesized as possible causes. Intriguingly, recent findings have also demonstrated that during Saharan dust outbreaks the local man-made particulates can have stronger effects on health than during days without outbreaks. We show that the thinning of the mixing layer (ML) during Saharan dust outbreaks, systematically described here for the first time, can trigger the observed higher toxicity of ambient local air. The mixing layer height (MLH) progressively reduced with increasing intensity of dust outbreaks thus causing a progressive accumulation of anthropogenic pollutants and favouring the formation of new fine particles or specific relevant species likely from condensation of accumulated gaseous precursors on dust particles surface. Overall, statistically significant associations of MLH with all-cause daily mortality were observed. Moreover, as the MLH reduced, the risk of mortality associated with the same concentration of particulate matter increased due to the observed pollutant accumulation. The association of MLH with daily mortality and the effect of ML thinning on particle toxicity exacerbated when Saharan dust outbreaks occurred suggesting a synergic effect of atmospheric pollutants on health which was amplified during dust outbreaks. Moreover, the results may reflect higher toxicity of primary particles which predominate on low MLH days.
authors: Institute of Environmental Assessment and Water Research (IDAEA-CSIC), c/Jordi-Girona 18-26, 08034 Barcelona, Spain. Electronic address: marco.pandolfi@idaea.csic.es.
authors: M
authors: M
authors: Pandolfi
authors: Institute of Environmental Assessment and Water Research (IDAEA-CSIC), c/Jordi-Girona 18-26, 08034 Barcelona, Spain.
authors: A
authors: A
authors: Tobias
authors: Institute of Environmental Assessment and Water Research (IDAEA-CSIC), c/Jordi-Girona 18-26, 08034 Barcelona, Spain.
authors: A
authors: A
authors: Alastuey
authors: Centre for Research in Environmental Epidemiology (CREAL), c/Doctor Aiguader 88, 08003 Barcelona, Spain; Pompeu Fabra University, Plaça de la Mercè 10-12, 08002 Barcelona, Spain.
authors: J
authors: J
authors: Sunyer
authors: Department of Environmental Health, Harvard School of Public Health, 677 Huntington Avenue, 02115 Boston, MA, USA.
authors: J
authors: J
authors: Schwartz
authors: Department of Astronomy and Meteorology, University of Barcelona (UB), c/Martí i Franquès 1, 08028 Barcelona, Spain.
authors: J
authors: J
authors: Lorente
authors: Institute of Environmental Assessment and Water Research (IDAEA-CSIC), c/Jordi-Girona 18-26, 08034 Barcelona, Spain; Aix-Marseille Université, CNRS, LCE FRE 3416, 13331 Marseille, France.
authors: J
authors: J
authors: Pey
authors: Institute of Environmental Assessment and Water Research (IDAEA-CSIC), c/Jordi-Girona 18-26, 08034 Barcelona, Spain.
authors: X
authors: X
authors: Querol
mesh_terms: D000352:Africa, Northern; D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data*; D001272:Atmosphere / Q000737:chemistry*; D002318:Cardiovascular Diseases / Q000401:mortality; D004196:Disease Outbreaks; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D005060:Europe / Q000453:epidemiology; D009026:Mortality; D052638:Particulate Matter / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter
keywords: Health effect; Mixing layer depth; Saharan dust outbreaks