No abstract

Microbes are present everywhere in outdoor air. However, the general characterization of outdoor air mycobiota and bacterial flora is incomplete. In this study, seasonal variations in outdoor air microbial concentrations and differences between a landfill, urban and rural sites were compared. Samples were collected monthly for a period of one year. Airborne dust samples were collected onto polyvinyl chloride filters. Filter samples were analyzed for ergosterol, and 14 species or assay groups of fungi and for the bacterial genus Streptomyces by using quantitative PCR. Viable bacteria and fungi were collected with a cascade impactor twice each month from the three sampling sites. The concentrations in the different sampling sites varied depending on the species. The concentrations of Penicillium and Aspergillus species were significantly higher in the waste center compared with the other sites, while the concentration of Cladosporium spp. was highest in the rural area. The highest concentrations of Streptomyces and Cladosporium species were observed in warmer weather periods. Similar observations were made for ergosterol. Group and species seasonal variation was less distinct for Penicillium and Aspergillus. According to the present results, both season and environment are determinants of microbial communities in outdoor air.

We investigated the immunotoxicological activity of airborne particles in three different environments during 11 months. Specifically, we analyzed the relation of the immunotoxicological activity to microbial concentrations. During the study period, samples from a landfill, an urban and a rural site were collected on filters once a month. The immunotoxicological characteristics of collected particle samples were studied by exposing mouse macrophages (RAW264.7), and measuring the viability and production of inflammatory mediators i.e. nitric oxide (NO), tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 after 24 hours. In addition, the results were compared to corresponding microbial concentrations measured with quantitative polymerase chain reaction (qPCR) in the same sites. The particles collected from the landfill caused significantly more toxicity and inflammatory responses than the particles from other sites. The immunotoxicological activity of the samples changed according to the season, being the lowest in all study sites in the winter. In the rural and urban sites the responses peaked during the spring, whereas at the landfill the highest responses were detected towards the fall. All immunotoxic responses correlated strongly with airborne microbial concentrations at the landfill, whereas on the other sites the correlations were weaker. These results indicate that the overall immunotoxicological activity of the particles is increased in waste handling area with a heavy microbial load. The activity of the samples collected from different sites changes according to the season being at their lowest at wintertime. At the waste center, the immunotoxicological responses are related with concentrations of microbes, whereas at rural area and city center other factors seem to govern the toxicity of the sample.

Microbial particles can readily be released into the air from different types of man-made sources such as waste operations. Microbiological emissions from different biological sources and their dispersion may be an issue of concern for area planning and for nearby residents. This study was designed to determine the concentrations and diversity of microbiological emissions from four different man-made source environments: waste center with composting windrows, sewage treatment plant, farming environment, and cattle manure spreading. Samples of airborne particles were collected onto polyvinyl chloride filters at three distances along the prevailing downwind direction, from each source environment during a period of approximately 1 week. These samples were analyzed for 13 species or assay groups of fungi, bacterial genus Streptomyces, and Gram-positive and -negative bacteria using quantitative polymerase chain reaction (PCR). Samples for determining the concentrations of viable fungi and bacteria were collected from all environments using a six-stage impactor. The results show that there were variations in the microbial diversity between the source environments. Specifically, composting was a major source for the fungal genera Aspergillus and Penicillium, particularly for Aspergillus fumigatus, and for the bacterial genus Streptomyces. Although the microbial concentrations in the sewage treatment plant area were significantly higher than those at 50 or 200 m distance from the plant area, in the farming environment or cattle manure spreading area, no significant difference was observed between different distances from the source. In summary, elevated concentrations of microbes that differ from background can only be detected within a few hundred meters from the source. This finding, reported earlier for culturable bacteria and fungi, could thus be confirmed using molecular methods that cover both culturable and nonculturable microbial material.