Schoolchildren's exposure to PM2.5: a student club-based air quality monitoring campaign using low-cost sensors

To assess schoolchildren's exposure to outdoor/indoor air pollution and identify those at a higher risk, it is desirable to conduct personal-level air quality monitoring. This paper documents a 2-month voluntary monitoring campaign with students attending the environmental club of the Spring Valley High School in urban Las Vegas, Nevada. The students wore low-cost sensors to log their exposure to PM2.5 (particulate matter with aerodynamic diameters < 2.5 mu m) at 5-min temporal resolution throughout the school hours. Calibrations of these sensors as well as concurrent outdoor monitors were traceable to the official air monitoring network. On a daily basis, the collective exposure among the students generally tracked the outdoor PM2.5 levels (r(2) = 0.55), but the ratio of personal over outdoor exposure (P/O ratio) varied by student, ranging from 1.1 +/- 0.6 to 1.9 +/- 1.2, consistent with the indoor/outdoor (I/O) ratios for naturally-ventilated classrooms with substantial indoor sources. The personal exposure showed impacts of short-term, acute events, which were not observed outdoors and likely resulted from resuspension of particles due to students' movements, particularly during class breaks. Such indoor sources could have dominated PM2.5 exposure when outdoor air is clean. Improving air filtration and surface cleaning for the classrooms are recommended to lower students' exposure to particulate air pollution. The personal monitoring protocol established in this study may be expanded to different pollutants and integrated into many schools' science curricula to generate much-needed exposure data and increase air quality awareness among schoolchildren.