Short-term effect of fine particulate matter (PM2.5) on daily mortality due to diseases of the circulatory system in Madrid (Spain) Original Research Article

Introduction Owing to their small size, fine particles, i.e., those having a diameter ≤ 2.5 μm (PM2.5), 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 PM2.5 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 PM2.5 concentration. The other variables controlled for were: chemical pollution (PM10, O3, SO2, NO2 and NOx); acoustic and biotic pollution; influenza; minimum and maximum temperatures; seasonalities; trend; and autocorrelation of the series. Results A linear relationship was observed between PM2.5 levels and mortality due to diseases of the circulatory system. For every increase of 10 μg/m3 in daily mean PM2.5 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 PM2.5 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.