School children's exposure to indoor fine particulate matter

Assessing the exposure of children to indoor fine particulate matter (PM_2.5) is important because children spend about one third of their day inside early learning microenvironments. Children are more vulnerable to air pollution due to a number of physiological reasons and, therefore, it is crucial to explore the factors that affect indoor (and outdoor) PM_2.5 levels in these locations to determine appropriate measures to reduce children's exposure to air pollution. To provide health policy guidance about how to reduce indoor air pollution in schools, this study systematically reviewed the associations between environmental factors and classroom characteristics with indoor PM_2.5 concentrations or indoor/outdoor (I/O) PM_2.5 in early learning microenvironments using a PRISMA framework. The systematic literature search reviewed studies that: monitored indoor PM_2.5 levels in at least one early learning microenvironment; measured outdoor PM_2.5 levels; and, analysed the influence of relevant factors on PM_2.5 concentrations or I/O relationships. From an initial search of 1282 results, 66 studies were included in the final review. Overall, these studies showed a lack of robust statistical analyses being performed, inconsistent application of methodological approaches and considerable variation in results. Consequently, these studies demonstrated weak evidence of significant and consistent associations between seasonal, meteorological, activity-based, site-based and ventilation rate variables with indoor PM_2.5 concentrations. Further large-scale and statistically robust analyses are needed to accurately quantify these associations, with particular attention needed as to how associations between influential variables and indoor PM_2.5 concentrations or I/O relationships change with seasonal and other factors, and whether these associations vary spatially. Once identified, these factors and relationships could be used to inform policy decisions that would enable better protection of the health of children in early learning microenvironments from chronic and acute exposure to air pollution.