In a more comprehensive report, Lembke & Kniseley (1985) addressed the numbersand types of airborne micro-organisms indoors at the Ames municipal solid wasterecovery system. Air sampling locations included the tipping floor where the solid wasteswere received and stored until they were processed and the processing area, where thesolid wastes were shredded, ferrous metals removed, and the waste was sorted accordingto density by an air classifier. One of the most notable observations was the extremevariability among the airborne microbial densities. For example, the numbers of totalaerobes in 96 samples from the tipping floor ranged from 190 to 110,000 cfu m-3 with amean of 22,000 cfu m-3. Similarly, the numbers of total aerobes in 189 samples fromthe processing area ranged from 1000 to > 3,700,000 cfu m-3 with a mean of210,000 cfu m-;. In addition to the variability of counts, there was a high degree ofvariability of microbial types among samples. The predominant bacteria recovered were Bacillus spp. and these comprised between 50 and 80% of the airborne bacterial counts.The average numbers of airborne fungi were lower than the numbers of airbornebacteria. Aspergillus spp. were the most prevalent fungi. Lembke & Kiseley (1985) statedthat there was no evidence that the airborne micro-organisms produced adverse healtheffects on the workers.Rahkonen et al. (1987) surveyed the concentrations of bioaerosols and dust at fivesanitary landfills in Finland during the summer and autumn. Total bacterial densitiesobserved outside ranged from 50 to 17,000 cfu m - and mesophilic fungal densitiesranged from 500 to 5600 cfu m-3. In each case, the mean values in the summer werehigher than those in the autumn. Dust concentrations ranged from < 0.1 to 5.4 mg m-3and were highest in warm windy weather in August.
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