Airborne bacteria, fungi, and endotoxin levels in residential microenvironments: a case study

Abstract

Limited data are currently available on the concentrations of airborne bacteria, fungi, and endotoxins in indoor environments. The levels of aerial bacteria and fungi were measured at several microenvironments within a well-ventilated residential apartment in Singapore including the living room, kitchen, bedroom, toilet, and at a workplace environment by sampling indoor air onto culture medium plates using the 6-stage Andersen sampler. Total microbial counts were determined by collecting the air samples in water with the Andersen sampler, staining the resultant extracts with a fluorescent dye, acridine orange, and counting the microbes using a fluorescent microscope. The levels of airborne endotoxins were also determined by sampling the airborne microorganisms onto 0.4 lm polycarbonate membrane filter using the MiniVol sampler at 5 l/min for 20 h with a PM 2.5 cut-off device. The aerial bacterial and fungal concentrations were found to be in the ranges of 117-2,873 CFU/m 3 and 160-1,897 CFU/m 3 , respectively. The total microbial levels ranged from 49,000 to 218,000 microbes/m 3 . The predominant fungi occurring in the apartment were Aspergillus and Penicillium while the predominant bacterial strains appeared to be Staphylococcus and Micrococcus. The average indoor endotoxin level was detectable in the range of 6-39 EU/m 3 . The amount of ventilation and the types of human activities carried out in the indoor environment appeared to be important factors affecting the level of these airborne biological contaminants.

Impact of dwelling characteristics on concentrations of bacteria, fungi, endotoxin and total inflammatory potential in settled dust

“…However, the observation contrasts with the more transient observation that more spores are aerosolised from many different common indoor fungi at high air velocity if the fungal colonised area is dried out [20,23]. High relative humidity has also been shown as a factor to increase fungal concentrations in other continents and cultures [5,45] were present. This difference was not significant in this study, however.…”

The short-term effect of residential home energy retrofits on indoor air quality and microbial exposure: a case-control study

“…Previous studies have shown that indoor concentrations of bacteria range from 10 1 to 10 3 colony forming units per m 3 of air with conflicting size distributions (57-59). Our average bacteria concentration of 200 16S gene copies per m 3 air is within the range found in previous research (58, 59). Unlike previous studies, we found that airborne bacteria concentration was relatively uniform throughout all size bins ( S3 Fig ).…”

Exposure of Workers of Municipal Landfill Site to Bacterial and Fungal Aerosol

“…All the above species produce harmful secondary metabolites and cause allergic and fungal diseases [42][43][44]. However, qualitative studies of bacteria present in the air at the municipal landfill site in Toru n indicate that Gramnegative bacteria, the source of endotoxins (lipopolysaccharides) as a component of their cell walls constituted only a small percentage (1.8%) of all isolated bacterial strains.…”