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Background levels of fungi in NYC - white paper

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9 Seasonal concentrations Both outdoor and indoor results were grouped into quarters – March through May (spring), June through August (summer), September through November (fall), and December through February (winter). For the outdoor air samples, the highest average fungal spore concentrations were encountered in the fall and summer months, and the lowest in the winter and spring. Total average spore levels for the different seasons ranged from 105 to 407 CFU/m 3 . For the indoor air samples, there was virtually no difference in the average fungal spore concentrations between the various seasons, with the results ranging from 29 to 32 CFU/m 3 . DISCUSSION The sampling data indicated that for each fungal group, indoor air concentrations were lower than those found outdoors. The five major fungal groups identified both indoors and outdoors were Cladosporium, Penicillium, Aspergillus, basidiomycetes and yeasts. These results are similar to those identified in prior studies involving non-residential buildings located in various states throughout the U.S. and the District of Columbia (20,21,22,23,24,25) Overall, the ratio for total indoor fungal concentrations versus those found outdoors was 0.22, a level which is also comparable to those found in a previous study (26) and lower than those identified in a limited study conducted in Tennessee. (27) Since there are no generally accepted indoor air quality guidelines for fungi and bacteria, comparison with reference samples is the most useful approach. Reference samples are usually outdoor samples and samples that have been collected from "non-complaint" areas. In general, indoor fungal types and concentrations should be similar to those found outdoors and in non-complaint areas. (28) If there are differences in the types or levels of fungi found indoors versus those found outdoors, this may indicate that moisture problems and indoor amplification of the fungi may be occurring. (29) Caution must be exercised, however, because even when using sampling quantitative devices, there can be significant variations (up to 1000-fold) between essentially identical samples. (30) Additionally, the concentrations and variety of species detected can vary substantially depending upon which sampling equipment, techniques and/or types of agar plates are used. (31,32,33,34) Protocols involving the collection of multiple samples from both suspect problem locations and control areas must be developed and followed in order to properly evaluate sample results. (35) Additionally, several field studies have shown that the fungal spore concentration in problem buildings is not necessarily higher than those found in non-problem ones. (36,37,38,39) These results suggests that airborne fungal spores may not be the only agents contributing to the health effects often encountered in damp indoor environments. (40)

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