CHILDREN'S INDIVIDUAL DOSE AND EXPOSURE TO ULTRAFINE PARTICLES

Epidemiologic evidence indicates a relationship between particle pollution exposure and adverse respiratory and cardiovascular health effects, including decreased lung function, asthma, myocardial infarction and all-cause mortality (Brunekreef and Holgate, 2002). In general, the smaller the particle size, the greater its ability to penetrate into the lungs and thus to produce adverse effects on human health. For this reason, sub-micrometer particles and even more UFPs (diameter < 0.1 µm), show higher health care interest than other particle sizes. Anyway, while there is considerable toxicological evidence of potential harmful effect of UFPs on human health, epidemiological studies are still not sufficient for conclusions on the dose-response relationship concerning this aerosol fraction (WHO, 2005). This study, which falls within the UPTECH international project, deals with the children's personal exposure assessment to UFPs and black carbon. BC was used as an indicator of exposure to diesel exhausts whose negative health effects (short and long-term cardiovascular, respiratory and neurodegenerative health effects) were reported in Baja et al., 2010; McCracken et al., 2010. We considered children because they represent the most vulnerable group with regard to harmful effects of airborne particles exposure. This is due to: i) the higher dose of UFPs as function of the children lung size compared to adult one; ii) their developing organs and immunological system. Air quality can be measured at four different spatial scales: i) “city scale”, the broadest and most common scale used to characterize air quality across several city blocks using remote measurements; ii) “outdoor scale”, representative of outside building grounds particle exposure; iii) “indoor scale”, within building rooms reflecting indoor-based exposure; iv) “personal scale”, using hand-held instruments carried as a personal monitor in order to assess their actual exposure. The daily overall children exposure is dominated by particle concentration levels in three main microenvironments: home, school, and transport mode. Therefore, children attending the same school, can receive different doses. In the present work personal exposure measurements were performed on a sample of about one hundred children aged 8 to 11 years who attend three schools (S1, S2, S3) in Cassino (Italy). S1 is a primary school located on traffic urban street; S2 is a secondary school close to intersection of moderate and heavily trafficked urban street; S3 is a primary school located in a rural area far away from urban traffic. The personal exposure was monitored through: two hand-held particle counters (NanoTracer, Philips) and one BC monitor (Aethalometer-microAeth Model AE51, MageeScientific). These monitors have a high temporal resolution (1÷16 s for NanoTracer, 1 s ÷ 5 min for Aethalometer), are small and portable (750 g and 250 g, respectively) and do not require special training to use. NanoTracer, which works by diffusion charging, is able to provide number concentration (in the range 10-300 nm), average particle diameter, and lung deposited surface area concentration measurements. An electrometer measures the current induced by previously charged particles collected on a filter inside a Faraday cage. The device is also able to evaluate the different fractions of the lung deposited surface area through a semi-empiric algorithm implemented by Marra et al., 2010. The Aethalometer detects the changing optical absorption of light transmitted through an internal small teflon-coated borosilicated glass fiber filter where BC-particles are captured. We monitored children for 24-h, they also filled in a diary reporting the main indoor and outdoor activities (such as studying, eating, transportation, sleeping), also indicating the length of each activity. From data collected by NanoTracers it was found that school contribution on daily exposure to UFPs is about 15%-20%, with an average particle number concentration in the range 1.5×104 – 5.3×104 part. cm-3. The highest exposure intensity was measured during lunch time with a contribution of about 20% and particle number concentrations in the range 4.2×104-1.9×105 part. cm-3. For BC, as expected, the most contributing activity to personal exposure is transport with an average exposure of 12.4 μg m-3, while lowest average exposure was found at home (4.4 μg m-3).