Indoor and outdoor airborne bacterial and fungal air quality in kindergartens: Seasonal distribution, genera, levels, and factors influencing their concentration

Kindergartens in developing countries are sensitive places for children owing to exposure to bioaerosols that promote a range of infections. This work aimed to determine the concentration of culturable bacteria and fungi aerosols in indoor and outdoor air of twelve kindergartens in Rasht, Iran. The mean concentrations of fungi versus bacteria in indoor air of kindergartens were 7 +/- 6 CFU/plate/hr versus 42 +/- 29 CFU/plate/hr, respectively, while the mean concentrations of fungi versus bacteria in outdoor air of the same kindergartens were 12 +/- 8 CFU/plate/hr versus 24 +/- 18 CFU/plate/hr, respectively. The findings revealed that 33% of the concentration of indoor bioaerosols (bacteria and fungi) and 8% of the concentration of outdoor bioaerosols in kindergartens were higher than the recommended value (40-84 CFU/plate/hr), indicating medium risk. The main bacteria species detected in indoor and outdoor air in kindergartens were Bacillus spp., Staphylococcus aureus, Micrococcus spp., Staphylococcus epidermidis, Staphylococcus saprophyticus, Enterococcus spp., and Streptococcus spp. The predominant genera of the airborne fungi isolated from indoor and outdoor air in kindergartens were Aspergillus terreus, Aspergillus flavus, Cladosporium spp., Penicillium spp., Rhodotorula spp., Ulocladium spp., and Alternaria spp. Indoor air quality of kindergartens qualified as posing a medium risk level, and strategies should be considered to remove bioaerosol emissions in these susceptible places. Hence, to reduce negative health effects of bioaerosols on children, it is important to have proper ventilation, air conditioning systems, minimal furniture and textile materials, and application of disinfectants.