Abstract

Air pollution is considered as one of the major causes of environmental health problems. Young children and infants are more susceptible than adults due to age and higher sensitivity to environmental hazards. The aim of the present study was to an investigation of indoor/outdoor, regional and seasonal variations of airborne bacteria and PM concentrations of six randomly selected child day-care centers (DCCs) in greater Ahvaz. bio-aerosol sampling, PM measurement, and meteorological parameters data capture were performed monthly in DCCs of industrial, high traffic and residential regions during autumn, winter, and spring. The results revealed that the highest and the lowest of indoor and outdoor of mean concentrations of airborne bacteria were observed in the DCCs in the high traffic regions and residential area, respectively. The monthly highest and the lowest mean of culturable bacteria was determined in February (812 CFU/m3) and November (188 CFU/m3), respectively. There is a positive correlation between concentrations of PM and airborne bacteria in the DCCs during the study. The highest mean concentrations of airborne bacteria in indoor air samples were measured in winter season in high traffic and residential regions with 789 CFU/m3 and 646 CFU/m3, respectively, this value for outdoor samples was determined in spring and winter seasons at industrial and residential regions with 335.41 CFU/m3 and 306.34 CFU/m3, respectively. The highest and the lowest indoor/outdoor (I/O) ratio of mean concentrations of bacteria were determined in the autumn and spring at the industrial region with I/O ratio of 23.17 and 1.37, respectively. In the indoor and outdoor conditions of all DCCs, the Gram-positive bacteria were the dominant species which shows higher concentration than Gram-negative bacteria. The dominant bacterial genera were Bacillus spp. and Staphylococcus spp. in air samples. The results of the present study suggest strongly that instead of natural ventilation using windows, use of artificial ventilation and air conditioning systems could improve indoor air quality (IAQ) in the DCCs. Facial air filters and air treatment devices are recommended particularly at the time of dust event days in cities like Ahvaz. © 2019 Elsevier Ltd