2024 No Characteristics of air pollutants inside and outside a primary school classroom in Beijing and respiratory health impact on children https://doi.org/10.1016/j.envpol.2019.113147 Zhang, Lulu Asia Exposure Students Elementary (K-5) Particulate Matter (PM) Particulate matter (PM) Trace gases Water-soluble ions Carbonaceous compounds Lower respiratory infections In a Beijing primary school, indoor and outdoor monitoring showed PM2.5, PM10, and O₃ exposure—mainly from traffic and coal—posed respiratory risks to children. Results support dual indoor-outdoor air quality controls near schools. 2019