Influence of advections of particulate matter from biomass combustion on specific-cause mortality in Madrid in the period 2004–2009

Approximately, 20 % of particulate and aerosol emissions into the urban atmosphere are of natural origin (including wildfires and Saharan dust). During these natural episodes, PM₁₀and PM₂.₅levels usually exceed World Health Organisation (WHO) health protection thresholds. This study sought to evaluate the possible effect of advections of particulate matter from biomass fuel combustion on daily specific-cause mortality among the general population and the segment aged ≥75 years in Madrid. Ecological time-series study in the city of Madrid from January 01, 2004 to December 31, 2009. The dependent variable analysed was daily mortality due to natural (ICD-10:A00-R99), circulatory (ICD-10:I00-I99), and respiratory (ICD-10:J00-J99) causes in the population, both general and aged ≥75 years. The following independent and control variables were considered: a) daily mean PM₂.₅and PM₁₀concentrations; b) maximum daily temperature; c) daily mean O₃and NO₂concentrations; d) advection of particulate matter from biomass combustion (http://www.calima.ws/), using a dichotomous variable and e) linear trend and seasonalities. We conducted a descriptive analysis, performed a test of means and, to ascertain relative risk, fitted a model using autoregressive Poisson regression and stratifying by days with and without biomass advection, in both populations. Of the 2192 days analysed, biomass advection occurred on 56, with mean PM₂.₅and PM₁₀values registering a significant increase during these days. PM₁₀had a greater impact on organic mortality with advection (RRall ages = 1.035 [1.011–1.060]; RR ≥ 75 years = 1.066 [1.031–1.103]) than did PM₂.₅without advection (RRall ages = 1.017 [1.009–1.025]; RR ≥ 75 years = 1.012 [1.003–1.022]). Among specific causes, respiratory—though not circulatory—causes were associated with PM₁₀on days with advection in ≥75 year age group. PM₁₀, rather than PM₂.₅, were associated with an increase in natural cause mortality on days with advection of particulate matter from biomass combustion, particularly in the ≥75 year age group.