Personal exposure to fine particles (PM2.5) of the Grenoble population: the European EXPOLIS study

Background: The aim of this article is to describe PM2.5 personal exposures within the Grenoble population and to identify the implications of such me asurements on epidemiological or risk assessment studies of air quality. Methods: Non smoking adult volunteers, selected in summer 1996 (n=40), in w inter 1997 (n=40) and in summer 1998 (n=20), carried a case containing 2 PM 2.5 personal monitors. One of the monitors was running continuously for 48h . (cumulative exposures), the other one was running only while indoors (ind oor exposure). PM2.5 masses were determined by reflectometry (black smoke m ethod) and by deionised weighting (Mettler MT5 micro-balance; gravimetric m ethod). Results: Cumulative PM2.5 personal exposures ranged on average from 21.9 in summer to 36.7 mu g/m(3) in winter (arithmetic mean), using the gravimetri c results; the dispersion of these personal exposures was greatest in winte r (s.d.=23.1 mu g/m(3)) than in summer (s.d.=10.4 mu g/m(3)). There was a g ood correlation (R=0.7) between the reflectometry and weighting results in winter, bur not in summer. Outdoor personal exposures, determined by differ ence between the cumulated and indoor masses, were slightly higher than the cumulative personal exposures: the geometric means was 49.6 mu g/m(3) (geo metric standard deviation=2.7 mu g/m(3)) in summer and 55.1 mu g/m(3) (3.7 mu g/m(3)) in winter (gravimetric results). Due to these greater outdoor co ncentrations, the fraction of outdoor exposure was high (25%) relative to t he small amount of time spent outdoors (less than 10%). Conclusion: These descriptive data, consistent with the literature, show th e importance of "expology" studies aiming at characterizing PM2.5 personal measurements across the year. This would lead, in the future, to optimizing the use of "ecological" estimates of exposures from ambient air concentrat ions provided by the ambient air quality networks for the characterization of exposure in epidemiological or risk assessment studies.