A preliminary study on microbial air contamination in select schools in Doha, Qatar

Available data of the indoor airborne culturable bacteria and fungi at schools’ environments is very limited in the peninsula of Qatar. This study aims to determine the microbial load in indoor and outdoor air at three schools utilizing two types of air sampling methods: (i) six-stage Andersen cascade impactor for cultivable microbes and (ii) air filtration method for non-cultivable microbes. The maximum levels of airborne culturable bacteria were 971 CFU/m 3 in indoor and 334 CFU/m 3 in outdoor air samples in the morning in a private (international) school. Lower concentrations of airborne culturable bacteria were recorded in indoor (348 CFU/m 3 ) and outdoor areas (261 CFU/m 3 ) in the afternoon. High CFU numbers (971 CFU/m 3 ) were observed at the food court area during breakfast time, exceeding the WHO indoor air quality limit value. The size distribution of the bacteria had maximum in the 1.1 - 2.3 μm size bin. The most frequently isolated fungal genera were Aspergillus and Penicillium , and their concentration was higher during winter. The prevalence and concentration of airborne microbes were altering spatially (indoors versus outdoors), temporally (morning versus afternoon) and seasonally (winter versus summer). The results indicate that airborne bacterial and fungal spores must be considered as important biological pollutants. Our findings might contribute to the implementation of preventative public health programs and creation of recommendations aimed at providing healthier school environments.