Characteristic and Concentration Distribution of Culturable Airborne Bacteria in Residential Environments in Beijing, China

The present investigation was conducted to assess the culturable concentration and distribution characteristics of airborne bacteria in 31 homes with children aged from 1 to 10 years in Beijing, China. The results showed that the concentration of culturable airborne bacteria in these homes ranged from 47 colony forming units (CFU)/m(3) to 12341 CFU/m(3), with a mean and a median of 1821 and 877 CFU/m3, respectively. A total of 632 bacterial isolates from the air in homes in different regions and different seasons were identified and distributed across 43 genera and 136 species of bacteria. Micrococcus (26.74%), Bacillus (14.56%), Kocuria (12.66%), and Staphylococcus (12.03%) were determined as the most common culturable airborne bacteria, and the dominant bacterial species were Micrococcus luteus (14.56%), Kocuria roseus (8.39%), Bacillus megaterium (4.75%), Staphylococcus cohnii (3.63%), and Micrococcus lylae (3.01%). Data analysis revealed that bacterial concentrations in homes with a male child were significantly higher than those with a female child (**P < 0.01), and a negative correlation was found between bacterial concentration and living area per person in the homes (**P < 0.01). Additionally, the mean bacterial concentration was highest in Spring, followed by Summer and Autumn, and lowest in Winter (**P < 0.01) in homes with child. The results provide an exposure database of airborne bacteria in family homes in Beijing, and suggest that the sex of children and living area per person in homes have a significant influence on the bacterial concentration in the air.