Short-term effect of fine particulate matter (PM 2.5) on daily mortality due to diseases of the circulatory system in Madrid (Spain).

Introduction: Owing to their small size, fine particles, i.e., those having a diameter ≤ 2.5 μm (PM(2.5)), have a high alveolar penetration capacity, thereby triggering a local inflammatory process with circulatory repercussion. Despite being linked to respiratory and cardiovascular morbidities, there is limited evidence of an association between this type of particulate matter and short-term increases in mortality.

Objective: The aim of this study was to analyse and quantify the short-term impact of PM(2.5) on daily mortality due to diseases of the circulatory system, registered in Madrid from 1 January 2003 to 31 December 2005.

Methods: An ecological longitudinal time-series study was conducted, with risks being quantified by means of Poisson regression models. As a dependent variable, we took daily mortality registered in Madrid from 1 January 2003 to 31 December 2005, attributed to all diseases of the circulatory system as classified under heads I00-I99 of the International Classification of Diseases-10th revision (ICD-10) and broken down as follows: I21, acute myocardial infarction (AMI); I20, I22-I25, other ischemic heart diseases; and I60-I69, cerebrovascular diseases. The independent variable was daily mean PM(2.5) concentration. The other variables controlled for were: chemical pollution (PM(10), O(3), SO(2), NO(2) and NO(x)); acoustic and biotic pollution; influenza; minimum and maximum temperatures; seasonalities; trend; and autocorrelation of the series.

Results: A linear relationship was observed between PM(2.5) levels and mortality due to diseases of the circulatory system. For every increase of 10 μg/m(3) in daily mean PM(2.5) concentration, the relative risks (RR) were as follows: for overall circulatory mortality, associations were established at lags 2 and 6, with RR of 1.022 (1.005-1.039) and 1.025 (1.007-1.043) respectively; and for AMI mortality, there was an association at lag 6, with an RR of 1.066 (1.032-1.100). The corresponding attributable risks percent (AR%) were 2.16%, 2.47% and 6.21% respectively. No statistically significant association was found with other ischemic heart diseases or with cerebrovascular diseases.

Conclusion: PM(2.5) concentrations are an important risk factor for daily circulatory-cause mortality in Madrid. From a public health point of view, the planning and implementation of specific measures targeted at reducing these levels constitute a pressing need.