A PARTICIPATORY APPROACH TO ASSESS CHILDREN PERSONAL EXPOSURE TO BLACK CARBON IN AN URBAN ENVIRONMENT: SPATIAL ANALYSIS, PERSONAL MEASUREMENTS, AND POSSIBLE MITIGATION ACTIONS.

Introduction: According to the World Health Organization (WHO), ambient and household air pollution are currently a major cause of death and disease globally. However, air pollution does not affect the whole population in the same way. In particular, a larger impact is reported being linked to the most susceptible subgroups of the population, such as children. To effectively tackle this public health threat, strengthen actions to protect the most vulnerable ones are needed, as well as environmental education interventions aiming to effectively raise awareness among the public. This is especially true for the city of Milan, which is located in one of the most polluted areas in Europe. Moreover, since a multitude of new evidences shows up on the relation between air pollution and health outcomes, reducing exposure misclassification in epidemiological studies remains an important challenge in the framework of exposure science. The aim of this dissertation is to present a novel participatory approach to assess schoolchildren exposure to air pollution with different approaches and to find possible exposure-mitigation actions. The common thread of the whole research process is black carbon (BC), an important component of particulate matter, a well-known indicator of traffic-related air pollution, linked with both long- and short-term health outcomes. In this process, some of the newest approaches in the framework of the exposure science are experienced. Methods: A four-step research project was set up. In the first part, BC was monitored on fixed sites during two seasons in a school catchment area. The monitoring sites were identified by involving the school, schoolchildren parents and the residents of the neighborhood. The spatial distribution of the contaminant was studied and modelled as well, focusing in particular on the morning rush hour. In the second part, a two-module environmental education intervention was carried out with a participatory and experienced-based approach. In the third part, more than 100 schoolchildren were involved in a two-season personal monitoring campaign to identify the weight of different microenvironments (MEs) on the overall daily personal exposure to BC. Finally, a validation of the previously developed spatial model focused on morning rush hour was conducted by using personal BC concentration, measured during home-to-school paths in order to assess the effectiveness of the tool in the identification of the cleanest routes. Results and conclusions: The two seasonal fixed-sites monitoring campaigns showed that the cold season is the most critical period for BC concentrations, while the morning rush hour is the most critical daily time-window. In general, according to our data, increasing concentrations are linked to the period during which people move, whether they go to work or to school (weekly morning rush hour), or spend time in the city for leisure activities (weekend nighttime). These findings especially highlight the need for actions to mitigate personal exposure during weekly morning rush hours, the time during which children go to school. The six developed spatial models show that traffic variables are the main factors that explain BC distribution inside the school catchment area, suggesting that traffic mitigation actions can be useful to lower BC concentrations. In the second part of the project, 128 schoolchildren were involved in a multitude of ludical activities on air pollution, raising their awareness and their level of engagement in the research process. This participatory approach helped to recruit volunteers for the following step: the two-season personal monitoring campaigns. The measured personal concentrations of BC, matched with time-activity diaries and GPS data, showed that indoor MEs are the most relevant source of personal exposure. Moreover, although it accounts only for 5-10% of the overall daily personal exposure, transportation-related exposure is actually the most intense, i.e. it exposes schoolchildren to the highest peaks of concentration in a very short period. Among the others, home-to-school commuting period is confirmed as the highest critical time-window for personal exposure for both warm- and cold-season. Furthermore, the comparison between spatial model estimates and personal exposure data collected during the home-to-school routes shows moderate to good agreement, suggesting that a modelling approach is a valuable choice to identify and predict the cleanest routes to school. Moreover, although the model tends to a systematic underestimation of personal measured concentrations, this can be a valuable starting point toward more refined tools for lowering exposure misclassification bias in the framework of environmental epidemiology studies. In summary, starting from the analysis and the spatial modelling of a selected air pollutant, passing by the personal exposure assessment, to the validation of the model with personal exposure data, this dissertation confirms that a participatory approach is a valuable choice that can add social value to the research project without losing in scientific quality.