Ultrafine particle and lung deposited particle surface area concentrations and daily cause-specific mortality in the Ruhr Area in Western Germany 2009-2014

Abstract

Introduction: Evidence on health effects of air pollution metrics other than particulate matter (PM) is rare and mostly based on short or discontinuous time series. We analysed the association of different air pollution metrics with cause-specific daily mortality, using number concentrations of particles with an electric mobility diameter <100 and 100-750 nm (PNC<100 and PNC100-750), lung deposited particle surface area concentrations (PSC), PM10 (aerodynamic diameter <10µm). Methods: We used a time series (2009-14) of daily natural, cardiovascular and respiratory mortality (NM, CVM, RM) in 3 adjacent cities in the German Ruhr Area. Particle metrics were measured at a central monitoring site. We used Poisson regression models to estimate %-change in daily mortality (95%-confidence interval) per interquartile range (IQR) increase, using single lags 0-7 and moving averages of lags 0-1, 2-3 and 4-7, adjusting for time trend, temperature, humidity, flu epidemic, population dynamics, holidays, weekday and rainfall. Results: Mean(IQR) daily concentrations for PNC<100, PNC100-750, PSC and PM10 were 10,320(4,892) #/cm3, 1,657(1,114) #/cm3, 41(23) μm2/m³ and 24(13.5) µg/m3. Air pollution metrics correlated heterogeneously, ranging from 0.2 to 0.9 for PNC<100 with PM10 and PNC100-750 with PSC. Mean±SD NM, CVM and RM were 32±6, 12±4 and 3±2 deaths/day. First results show a pattern of delayed associations for PNC<100 and CVM with -1.2%(-3.8, 1.4), 1.1%(-1.3, 3.7) and 2.5%(-0.2, 5.3) for lag01, lag23 and lag47, while no clear pattern was seen for NM or RM. PNC100-750, PSC and PM10 showed similar patterns for NM and CVM, with clear acute and delayed associations, e.g. for NM: 1.2%(0, 2.4), 0.1%(-1, 1.3) and 1.4%(0.3, 2.5) for lag01, lag23 and lag47. No clear pattern was observed for RM. Conclusion: Our results suggest more pronounced delayed associations of UFPs with CVM, while other particle metrics showed clear similar acute and delayed associations for NM and CVM.