Comprehensive air quality assessment including non-targeted approaches in primary schools from Spain

This work aims to establish a strategy to comprehensively assess the indoor air quality in schools including the analysis of chemical pollutants, bio-aerosols like fungi, bacteria and respiratory viruses and the identification of volatile and semi-volatile organic compounds applying non-targeted approaches. For this, a pilot study was performed in four primary schools from Spain, located in different urban and rural areas during different seasons. Common indoor pollutants, like CO_2, NO₂, O₃, CO, particulate matter (PM₁₀, PM_2.5), ultrafine particles (UFP), total volatile organic compounds (TVOCs), and formaldehyde (HCHO), were assessed in terms of maximum recommended levels, daily variations, seasonality, and school location. Additionally, fungi and bacteria were studied indoors and they were always found at adequate levels. The most prevalent fungal genera were Aspergillus, Penicillium, and Cladosporium. Seventeen respiratory viruses were measured in the air of the assessed classrooms and none were detected. Volatile and semivolatile organic compounds were identified indoors and outdoors using non-targeted approaches based on GC-HRMS and UHPLC-HRMS. High-confidence identified compounds were classified according to their chemical and toxicological characteristics, revealing that 44% and 26% of them presented a high toxicological risk in outdoor and indoor environments, respectively. This study provides a new strategy to assess comprehensively the IAQ in schools, and expands the knowledge about contaminants present in these environments, giving rise to future research.