Assessment of Personal PM Exposure in the PM-CARE Project

The present exposure assessment is directed at investigating associations between both seasonal and individual activity-related variations in urban air particulate exposure and a series of clinical parameters, measured continuously and at end-24h-sessions in 79 non-smoking elderly subjects, grouped into three panels according to their clinical history. Individual exposures to ultrafine (UFP: <0,1µm), fine (0,1-2,5µm) and coarse (>2,5µm) fractions of particulate matter (PM) were measured during subjects' habitual activities in Summer 2005 (July to September) and Winter 2005/2006 (December to March) with selective air-monitoring devices mounted onto a trolley (25kg; 0,12m3) carried along by the subjects during their indoor and outdoor displacements. PM sampling techniques spaced from 24h gravimetric determination, using a multistage cascade impactor, to continuous optical particle counting of the ultrafine, fine and coarse fractions. In addition, gas-phase contaminants were continuously monitored (CO, O3) and determined by 24h passive sampling (NO2). Continuous reading of temperature and relative humidity completed the monitoring cycle. Preliminary results of the daily average mass particulate concentrations (PM10) during the summer [winter] session was 44µg/m3 [71µg/m3]; of this, 74% [87%] of the mass was below 2.5µm in aerodynamic diameter, 63% [78%] was below 1µm and 55% [71%] was below 0.5µm, with the last fraction (<0.5µm) still containing more than 99% of the concentration based on particle number. Average number concentrations were about 1.8x104#/cm3 [2.7x104#/cm3]. Significant increases of UFP levels were associated with flame-cooking activities and subjects' outdoor displacements and consistent with increases in carbon monoxide (CO) levels. Estimated UFP peak exposures depended on the examined averaging period, ranging from about 1,5x105#/cm3 (outdoor displacement) to 3x105#/cm3 (flame-cooking) at two minutes. In general, outdoor displacements determined particle loads (all PM fractions) one to two orders of magnitude higher than those observed during home - at rest activities. CO average concentrations were 1,2mg/m3 [1,8mg/m3], with time averaged maxima ranging from 8mg/m3 (flame-cooking) to 12mg/m3 (outdoor displacement) at two minutes. Sufficient reason exist to believe that UFPs are important because when compared with larger particles, they have order of magnitudes higher particle number concentration and surface area and could therefore have larger concentrations of adsorbed or condensed air pollutants per unit mass. Final results of this assessment are still awaiting and are expected to offer a valuable support to the PM-CARE project, aimed at investigating the pathogenetic mechanisms of cardio-respiratory effects produced by changes in personal PM exposure.