Behavior and Exposure of Chalk Dust during Classroom Teaching

• Main Authors: Chang-Jin Ma, Gong-Unn Kang, Mei Hamada
• Format: Article
• Language: English
• Published: Asian Association for Atmospheric Environment 2019-12-01
• Series: Asian Journal of Atmospheric Environment
• Subjects: chalk dust; classroom; exposure; dose; children; pm2.5
• Online Access: http://asianjae.org/_common/do.php?a=full&b=11&bidx=1801&aidx=22236

It is meaningful to estimate the chalk dust behavior and its exposure for school-aged children and teachers who spend a lot of time in the classroom. In the present study, model classes were designed to characterize temporal and spatial variations of chalk dust in a classroom and indoor exposure dose to children and teachers. For about 20% of the entire class time, the PM2.5 level greatly exceeded that of ambient PM2.5 daily standard (35 μg m-3). Meanwhile, there was no apparent elevation of PM2.5 during the control experiment carried out using a whiteboard and a dry erase marker with the same teaching behavior. The largest quantity of chalk dust was deposited in the front of the classroom when a cleaner of the blackboard eraser was operated. A SEM image revealed that chalk particles have random shape in a broad range (mainly in the diameter range of 2.0 to 5.0 μm) of their size. The calculated chalk PM2.5 deposition dose, DosePM2.5 (μg), in the alveolar interstitial region revealed the highest level during the period from operating a cleaner of the chalkboard eraser to the end of the class. The DosePM2.5 (μg) in that period was 3.86, 18.95, and 15.79 μg for 10y male/female students, male teacher, and female teacher, respectively.