Airborne Microorganisms at a Senior High School in Chang-Hua County, Taiwan

Abstract

Bioaerosols are a type of suspended sediments that contribute to poor air quality in Taiwan. Bioaerosols include allergens such as fungi, bacteria, actinomycetes, arthropods, and protozoa, as well as microbial products such as mycotoxins, endotoxins and glucans. When allergens and microbial products are suspended in the air, local air quality is adversely influenced. In addition, when the particle size is small enough to pass through the human respiratory tract, the health of the local population is also threatened. The classroom is where students spend a large portion of weekday time and thus could play an important role in student's exposure to potential threatening bioaerosols. The purpose of this study was to understand the airborne bacteria and fungi concentrations at a sampling classroom (with the windows opened and closed) from a senior high school in Chang-Hua County, Taiwan. The results indicate that the total average bacterial concentrations were 2.2 × 103, 1.7 × 103, 7.8 × 102, 1.2 × 103, 7.4 × 102 and 7.6 × 102 cfu/m3 using tryptic soy agar (TSA)-medium incubated for 48 hr under various sampling conditions in the morning, afternoon, and evening with windows closed and opened, respectively (i.e., morning with windows closed [MC], afternoon with windows closed [AC], evening with windows closed [EC], morning with windows opened [MO], afternoon with windows opened [AO], and evening with windows opened [EO]) at the sampling classroom. Moreover, the total average fungi concentrations were 1.1×103, 7.3×102, 6.3×102, 7.4×102, 5.8×102, and 6.2×102 cfu/m3 using malt extract agar (MEA) medium incubated for 96 hr under the same various sampling conditions (MC, AC, EC, MO, AO, and EO). The total average bacterial and fungi concentrations were higher with windows closed than with windows opened during any sampling period. Ventilation is the possible reason for the above finding. The highest average bacterial or fungi concentrations was found in the particle size of 0.53 mm (average bioaerosol size was in the range of 2.1–3.3 μm) for any sampling condition. These findings may be relevant in a forensic investigation related to a potential bioattack, since it provides baseline information of bioaerosols composition (e.g., before an attack is initiated) within the tested environment.