Environmental, biological and cognitive monitoring of children in European primary schools: LEARN crossover study protocol

Abstract

Poor indoor air quality (IAQ) in schools is of particular concern as it can negatively impact children's cognitive development, health, and well-being. Measuring IAQ-related parameters, assessing children's internal and external exposures, and developing solutions for reducing exposure are therefore critical to protecting children's health. The use of air purifiers can be a good mitigation strategy to improve IAQ in classrooms, but their association with health effects and cognitive outcomes in children remains unclear. The LEARN crossover study protocol aims to address this gap by evaluating the impact of a novel air purification intervention on IAQ, biomarkers of exposure, clinical health parameters, and cognitive performance in primary school children (n = 450). In this single-blinded (teachers/students blinded) crossover study conducted in primary school classrooms in Belgium, Denmark, and Greece, the participating classrooms are cluster-randomized via a computer-generated sequence to the order of receiving the intervention and the sham intervention (air purifiers operated with or without filters), with a washout period between study phases. Active and passive measurements of volatile organic compounds (VOCs) and aldehydes, active measurements of polycyclic aromatic hydrocarbons (PAHs), as well as monitoring of particles (PM10, PM2.5, ultrafine particles, black carbon) and microclimate parameters are performed. At pre-defined timepoints, urine samples, blood samples, and skin swabs are collected and assessed for exposure biomarkers and health parameters. To ensure cross-site comparability, children's cognitive performance is evaluated using Danish, Greek, and Dutch versions of standardized tests: the Continuous Performance Test, Symbol Digit Modalities Test, Memory Span Task, STROOP Task, and Signal Detection Test. Additional health assessments include anthropometric and blood pressure measurements, and psychological well-being questionnaires. Statistical analyses include mixed models to explore exposure-response relationships between children's external and internal exposures, health, and cognitive outcomes. This protocol presents a comprehensive approach to assess indoor air exposures and the impact on children's health and cognition, as well as the effectiveness of the air purification strategy. The results of this study can provide a reference for novel IAQ remediation strategies in schools and help promote the application of human biomonitoring in risk assessment of children's indoor exposure.