Indoor Air Quality and Bioaerosols in Spanish University Classrooms

Abstract

A comprehensive study assessed indoor air quality parameters, focusing on relevant air pollutants such as particulate matter (PM₁₀ and PM_2.5), gaseous compounds (CO, CO₂, formaldehyde, NO₂) and volatile/semi-volatile organic chemicals, as well as respiratory viruses (including SARS-CoV-2), fungi and bacteria in Spanish university classrooms. Non-target screening strategies evaluated the presence of organic pollutants inside and outside the classrooms. Saliva samples from teachers and students were collected to explore correlations between respiratory viruses in the air and biological samples. Indoor results revealed the punctual exceedance of recommended guidelines for CO₂, formaldehyde (HCHO), volatile organic compounds (TVOCs) and PM in the least naturally ventilated classrooms. Significant differences occurred between the classes, with the least ventilated one showing higher average concentrations of CO₂, HCHO, NO₂, PM₁₀ and PM_2.5. A respiratory virus (rhinovirus/enterovirus) was detected in the medium naturally ventilated classroom, although saliva samples tested negative. Suspect screening tentatively identified 65 substances indoors and over 200 outdoors, with approximately half reporting a high toxicological risk based on the Cramer rules. The study provides a comprehensive overview of indoor air quality, respiratory viruses and organic pollutants in university classrooms, highlighting the variations and potential health risks associated with ventilation differences.

Keywords: classrooms; indoor air quality; non-target screening; respiratory viruses; saliva; university.

Figure 1

Boxplots for the assessed pollutants in each classroom: (A) CO₂ (ppm), (B) HCHO (mg m⁻³), (C) NO₂ (ppm), (D) PM₁₀ (mg m⁻³), (E) PM_2.5 (mg m⁻³) and (F) TVOCs (ppm). Boxplots show the median, minimum and maximum values.

Figure 2

Boxplots for (A) TSA bacteria (CFU m⁻³), (B) SBD fungi (CFU m⁻³) in the assessed classrooms.