Indoor/outdoor air quality in primary schools in Luanda

Despite the numerous studies on particulate matter and gaseous pollutants in school environments in developed countries, air quality in African schools has been largely neglected. In this work, the atmospheric concentrations of particulate matter (PM₁₀) were evaluated in various classrooms and outdoor courtyards of four primary schools in Luanda, Angola, using photometric monitors and gravimetric samplers. Comfort parameters, carbon oxides (CO and CO₂) and total volatile organic compounds (TVOCs) were measured in real time. Passive sampling was also used to assess the levels of various gaseous pollutants: benzene, toluene, ethylbenzene, and xylenes (BTEX), ozone (O₃), nitrogen dioxide (NO₂), and carbonyl compounds. The daily PM₁₀ concentrations (62.0 ± 37.0 μg/m³) exceeded the WHO guideline value on 68% of the days. Indoor PM₁₀ levels were usually lower than outdoors, except at one school with poor structural conditions and unpaved roads in the vicinity. Average temperature and relative humidity levels consistently exceeded recommended standards, potentially impacting academic performance. CO₂ and TVOCs levels followed occupancy patterns, with elevated concentrations exceeding international standards in just one classroom due to poor ventilation. NO₂ concentrations in the classrooms were very similar to those recorded outdoors, whereas BTEX levels slightly exceeded those measured in the courtyards. These compounds were primarily attributed to emissions from road traffic. O₃ levels in the classrooms were, on average, 2.3 times lower than those outdoors. For most carbonyl compounds, indoor concentrations were 1.8–3.8 times higher than those measured outdoors, suggesting the presence of active emission sources indoors. Butyraldehyde, formaldehyde, and hexaldehyde were the most abundant carbonyl compounds. While BTEX, O₃, and NO₂ levels in Luanda aligned with those reported for European schools, formaldehyde concentrations were lower, likely due to better natural ventilation supported by the milder climate.