Airborne Endotoxins and Airborne Gram-Negative Bacteria in a Residential Neighborhood

Ambient outdoor concentrations of airborne endotoxins and airborne gram-negative bacteria were measured in a residential area. Further, the species composition of the airborne gram-negative bacterial flora was investigated. The results demonstrated that humans and other mammals are exposed to airborne endotoxins in the outdoor air, but at levels where a development of adverse health effects is unlikely. The total amount of inhalable endotoxins ranged from <3.0 EU/m³ to 27.8 EU/m³. Airborne gram-negative bacteria were detected only at low concentrations (maximum 7.9 cfu/m³). Most gram-negative bacterial isolates belonged to the family Enterobacteriaceae and Pseudomonadaceae. Furthermore, the results of this study suggest that soil and vegetation are potential sources of airborne endotoxins and airborne gram-negative bacteria in the outdoor air of this environment.