Influence of the PM10 measurement techniques on the assessment of the short-term mortality impacts of PM10

Abstract

Background and aims: In France, before 2007, particulate matter (PM) was measured with Tapered Element Oscillating Microbalance (TEOM). This method systematically under-estimated PM concentrations compared to the gravimetric reference method. Since 2007, concentrations are measured with TEOMs equipped with a Filter Dynamics Measurement System (TEOM-FDMS), which correct for the loss of semi-volatile compounds, and provide values consistent with the gravimetric method. We investigate how this change in measurement techniques influenced the estimates of the impacts of PM10 on mortality. Methods: The analysis was performed in nine French urban areas, for the period 2000-2006 (using TEOM data) and 2007-2010 (using TEOM-FDMS). The associations between PM10 and non-accidental, cardiovascular and respiratory mortality were investigated in each city using a generalized additive Poisson regression model. The mean levels of PM10 observed during the current and the previous day were introduced as a linear term. The percent increase in the mortality rate was estimated for a 10 ?g/m3 increase in PM10 levels for the whole year and by season. City specific results were combined using random effect models. Results: PM10 were consistently higher during 2007-2010 (+5.9 ?g/m3 on average) with strong seasonal variations. Estimates of the mortality increase for a 10 ?g/m3 increase in PM10 were similar between the two periods, with the largest estimates observed during summer (e.g. non-accidental mortality: +3.2% [1.8:4.7] for 2000-2006 and +2.0% [0.8:3.3] for 2007-2010), and the lowest during winter. The main difference was observed for respiratory mortality during summer (-0.5% [-6.3:5.8] for 2000-2006 and +3.8% [-1.9:9.2] for 2007-2010). Conclusions: Despite large differences in the PM10 concentrations reported between 2000-2006 and 2007-2010 due to different measurement techniques, the concentration-response functions were similar across the two periods. This suggests that the semi-volatile part of PM10 have a similar impact on mortality.