摘要：Indoor air quality is associated with academic performance and harmful health effects on students and teachers who participate in the classroom. Outdoor sources always contribute to classroom air quality. This study aims to estimate the amounts of indoor and outdoor pollutants and the influence of outdoor sources on open-air classrooms in a school located in the city. A health risk assessment was applied to assess the non-carcinogenic risk to students and teachers from exposure to the pollutants in the classroom. The concentrations of indoor NO<sub>2</sub> ranged between 46.40 and 77.83 µg/m<sup>3</sup>, which is about 0.8 times that of outdoor NO<sub>2</sub>. A strong correlation and a high indoor/outdoor (I/O) ratio (>0.5) without a source, indicated that indoor NO<sub>2</sub> is significantly influenced by outdoor sources. The range of indoor PM<sub>2.5</sub> concentrations was 1.66 to 31.52 µg/m<sup>3</sup> which was influenced by meteorological conditions. The indoor PM<sub>2.5</sub> concentrations were affected by both indoor and outdoor sources. Although the level of indoor air pollutants met the official standard, the young children were exposed to indoor air pollutants which were above the recommended limits to human health with regard to the hazard index (HI) of 1.12. Instant measures such as regularly cleaning the classrooms, zoning the students, and installation of solid and vegetation barriers are recommended to reduce the daily dose of pollutants affecting students in open-air classrooms.
