Comparison of airborne bacteria and fungi in different built environments in selected cities in five climate zones of China.

Bioaerosols in different built environments and climate zones have unique effects on occupant health, which demands comparisons of their characteristics to make targeted control measures. This study investigated bioaerosol distribution in five different climate zones across China with four building types (n = 686 rooms). The results showed significant disparities in bioaerosol concentrations among various buildings and climate zones. The bacterial concentrations in residences (536 ± 647 CFU/m) were significantly higher than in schools, offices, and hospitals owing to different built environments and human activities. The highest mean value of fungal concentration was found in schools (826 ± 955 CFU/m) due to their greater landscaping area. The bacterial concentrations in the cold zone (307 ± 506 CFU/m) and the hot summer and cold winter zone (214 ± 180 CFU/m) were significantly lower than in the other three climate zones. The fungal concentrations in the severe cold zone (709 ± 900 CFU/m) and the hot summer and warm winter zone (1094 ± 832 CFU/m) were significantly higher than in the other three climate zones; the lower the indoor temperature (T) and the higher the air exchange rate, the lower the indoor airborne bacterial concentration; the lower the relative humidity (RH), the lower the indoor airborne fungi. In addition, a higher air exchange rate could also reduce the effect of occupant density on indoor bacterial concentration. The results of this study provide valuable data on bioaerosol profiles in various built environments and climate zones and highlight the significance of T, RH, and air exchange rate on indoor bioaerosol concentrations.