Spatiotemporal variation of ambient bioaerosols in a large and industrialized metropolis of Iran and their association with PM2.5 and meteorological factors

The presence of bioaerosols in the airborne fine particulate matters (PM2.5) has raised public concern due to their pathogenic effects on human. The objective of this study was to investigate the levels of airborne bacteria and fungi and their association with PM2.5 and meteorological parameters in Isfahan. Air samples were collected from seven different locations of Isfahan city using SKC pumps connected to glass impingers containing a buffer solution and analyzed by the cell culture method. The meteorological variables were obtained from the provincial meteorological office, and the data of atmospheric PM2.5 were taken from the Department of Environment. The highest and the lowest bacterial levels were found at station 7 (114.4 (40-254.2) CFU/m(3)) and station 3 (39.6 (12-67.5) CFU/m(3)), respectively. While, the highest and the lowest fungal levels were observed at station 5 (61.1 (22.5-117)) and station 4 (26.9 (0-50)) CFU/m(3), respectively. The most predominant bacteria were Gram-positive bacilli, and that for fungi were Dematiaceous and Yeast. The microbial levels varied between various months and the mean concentration of 76 CFU/m(3) for bacteria and 46 CFU/m(3) for fungi were obtained. The average of airborne PM2.5 concentrations was 25 mu g/m(3), with mean maximum occurring in the cold season. A positive association between PM2.5 and bioaerosols levels were observed, while the correlation between PM2.5 and meteorological parameters was not significant (P < 0.05). Air temperature significantly impacted both the airborne bacterial and fungal concentration (P < 0.05). Also, there was a strong correlation between the bacteria level and wind speed (P < 0.05).