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Background levels of fungi in NYC - white paper

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3 the interior and exterior surfaces of the sampler were wiped with 70% isopropyl alcohol. Collection of microorganisms was made using sterile 100mm x 15mm polystyrene petri dishes that contained 2% malt extract agar (MEA). The sampling media were prepared by mixing 20 g of malt extract broth and 20 g of bacto-agar in 1,000 ml of distilled water and then autoclaving the mixture for 15 minutes. The same microbiology laboratory that prepared the sampling media also performed the analysis of the samples. After sampling, the covers of the petri dishes were sealed with masking tape, and then shipped to the laboratory via overnight courier. No attempt was made to refrigerate the samples during shipping. Upon arrival at the laboratory, the MEA plates were incubated at room temperature (25 o C) and examined every other day for a period of seven to ten days. Following incubation, the samples were then examined at 100-1000x magnification utilizing stereo and compound microscopy techniques. Fungal colonies were identified to the genus level based on colony morphology and spore formation, size and shape; major taxonomical references were used to assist in identification. The actual plate counts were then used to calculate the number of colony forming units per cubic meter of air. (19) Data from these samples was not adjusted relative to the positive hole conversion. Analysis of all samples was performed by an AIHA-certified environmental microbiology laboratory. Data Analysis The data from the indoor and outdoor samples were analyzed using descriptive statistics, including mean, median, frequency of occurrence, and 95 th percentiles. Qualitative and quantitative results were then compared by season, as well as indoor air versus outdoor air. For this study, the seasons were defined as spring (March, April and May), summer (June, July and August), fall (September, October and November) and winter (December, January and February). RESULTS Overall Concentrations Evaluation of the 533 indoor air fungi samples revealed that a total of twenty five (25) different genera/groups were identified, with six of those found more than 10% of the time (Table 1). Indoor fungal concentrations ranged from <7 CFU/m 3 to 415 CFU/m 3 , with an average concentration of 31 CFU/m 3 . Ninety five percent of those samples had total concentrations of less than 118 CFU/m 3 , with over thirty percent of all the samples having no fungal colonies detected. Cladosporium was isolated from 28.9% of the samples with an average concentration of 9 CFU/m 3 , followed by Penicillium (27.4%, 7 CFU/m 3 ) and Aspergillus (16.9%, 3 CFU/m 3 ). Other frequently identified fungi in descending order of frequency included yeasts, basidiomycetes, non-sporulating fungi, and

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