Saharan dust and association between particulate matter and case-specific mortality: a case-crossover analysis in Madrid (Spain)

Julio Díaz,Cristina Linares,Aurelio Tobías

doi:10.1186/1476-069x-11-11

Abstract

BackgroundSaharan dust intrusions are a common phenomenon in the Madrid atmosphere, leading induce exceedances of the 50 μg/m3- EU 24 h standard for PM10.MethodsWe investigated the effects of exposure to PM10 between January 2003 and December 2005 in Madrid (Spain) on daily case-specific mortality; changes of effects between Saharan and non-Saharan dust days were assessed using a time-stratified case-crossover design.ResultsSaharan dust affected 20% of days in the city of Madrid. Mean concentration of PM10 was higher during dust days (47.7 μg/m3) than non-dust days (31.4 μg/m3). The rise of mortality per 10 μg/m3 PM10 concentration were always largely for Saharan dust-days. When stratifying by season risks of PM10, at lag 1, during Saharan dust days were stronger for respiratory causes during cold season (IR% = 3.34% (95% CI: 0.36, 6.41) versus 2.87% (95% CI: 1.30, 4.47)) while for circulatory causes effects were stronger during warm season (IR% = 4.19% (95% CI: 1.34, 7.13) versus 2.65% (95% CI: 0.12, 5.23)). No effects were found for cerebrovascular causes.ConclusionsWe found evidence of strongest effects of particulate matter during Saharan dust days, providing a suggestion of effect modification, even though interaction terms were not statistically significant. Further investigation is needed to understand the mechanism by which Saharan dust increases mortality.

Highlights

Saharan dust intrusions are a common phenomenon in the Madrid atmosphere, leading induce exceedances of the 50 μg/m3- EU 24 h standard for PM10
The aim of this study is to evaluate the effect of Saharan dust on the association between particulate matter and daily case-specific mortality in Madrid
Case specific mortality was distributed between Saharan dust and non-dust days

Summary

Introduction

Saharan dust intrusions are a common phenomenon in the Madrid atmosphere, leading induce exceedances of the 50 μg/m3- EU 24 h standard for PM10. The increased levels of particulate matter in a given geographical area are mainly influenced by the intrusion of natural origin such as those related to the advection of dust from the desert [1]. In the case of the Saharan desert, Southern European countries are largely influenced by dust intrusions [2]. Saharan dust events can contribute to exceedances of PM10 daily European Union Limit of 50 μg/m3 [2,4]. These particles can carry biological material that makes them potentially harmful to health [5]

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