In order to investigate indoor airborne microbial contamination in school classrooms, air samples were collected with six-stage Andersen samplers in classrooms at a kindergarten, a primary school, a middle school and a university in Nanjing, Jiangsu. Ten classrooms in each school were randomly selected. Among the four types of school surveyed, the kindergarten classrooms were found to have the maximum concentration of airborne bacteria and fungi. The mean concentrations of bacteria and fungi were 605CFU/m3 and 648CFU/m3, respectively, which were much higher than that in the other three schools. The size distributions of indoor airborne bacteria and fungi were similar cross all four types of school, with the peak at the stage 5 (1.1~2.1μm). The correlation between indoor environmental parameters and airborne microorganisms was only found to be significant in university classrooms. The daily inhalation doses of airborne bacteria and fungi for kindergarten students were highest at 150.2CFU/kg and 160.9CFU/kg respectively. The study provided some evidence data to evaluate the risk of airborne microbial contamination in schools.
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