Abstracts: ISEE 22nd Annual Conference, Seoul, Korea, 28 August-1 September 2010: Air Pollution - Sand Dust and Coarse Particles
Short-term effects of airborne particulate matter (PM10) on mortality have been consistently reported, especially for fine particles (PM2.5), which are thought to contain the more harmful components of PM10. However, recent evidences have put new insight into the adverse effects of coarse particles (PM10–2.5). In order to further explore the relative role of the 2 size fractions, we investigated the temporal pattern of their effects on short-term mortality in 9 French cities during the 2000–2004 period.
Data from background monitoring stations measuring both PM10 and PM2.5 levels were used to compute daily mean levels of PM2.5 and PM10–2.5. For each city, the temporal distribution of the effects of both fractions of PM10 on daily number of deaths (for nontraumatic, cardiovascular and cardiac causes) up to 15 days following exposure was estimated using polynomial distributed lag within Poisson regression models. City-specific results were combined using random effects models.
The temporal patterns of the effect of the 2 size fractions were clearly different: the effect of PM2.5 decreased slowly from the day of exposure to 5 days after exposure. No excess risk was observed after then. For PM10–2.5, the decrease was sharper, and risks became negative between lags 5 and 10, showing some evidence of mortality displacement. Overall, the excess risks of mortality associated with PM2.5 doubled when considering the cumulated effect over the 15 days following exposure compared to the average effect over the 2 days following exposure, whereas the cumulated effect of PM10–2.5 was lower than the effects at lags 0–1.
Our results suggest that, while the levels of both fine and coarse particles are associated with very short-term increases in mortality, the effect of PM2.5 persists over 15 days, while the effect of PM10–2.5 appears to be attenuated. Chemical composition and pathways of both fractions could explain those differences.