NYC-WTC_000232813

NYC 9/11 Public Portal Document

highest count for any one species being 500 CFU/in^ and a total sum of 1,600 Cf l /in ’.

Mold

Interpretation of these results cannot be completed using standard practices. The standard practice for determining if an indoor environment is being impacted by mold is to compare the species and concentration of indoor mold samples to outdoor mold samples that were collected during the same sampling event, however, based on the data received it appears that there were no outdoor samples collected for comparison. Using an approach that is less desired than the standard practice, the following conclusions can be drawn from the data. Although there are no specific standards, the general rule of thumb for interpreting mold data usually considers concentrations greater than 10,000 CFU/in^ to be the low end of the spectrum for beginning additional mold investigation, and concentrations greater than 100,000 to signify “mold contamination”. The concentrations for each individual species, as well as the total sum for all species was well below 10,000 CFU/in‘. In addition, the fungi species observed are the most frequent species identified and are ubiquitous in the environment, both outdoors and indoors. This leads to an overall conclusion that the concentration and species of mold present are typical of an indoor environment. In general, mold contamination is identified by finding visible mold growth that covers an area greater than 1 square meter. More information can be obtained from the American Industrial Hygiene Association at http://www.aiha.org/GovemmentAffairs-PRZhtml/oomold.htm.

Bacteria

The interpretation of the bacteria results has the same limitations as discussed above for mold, namely that indoor concentrations should be compared to outdoor concentrations. There is less information about indoor concentrations of bacteria than there is for mold, however one report http://www.atsdr.cdc.gov/HAC/PHA/franklinfungi/ief pThtml from the Agency for Toxic Substances and Disease Registry (ATSDR) reports that concentrations of Bacillus at 1,000 CFU/in2 and Staphylococcus at 2,400 CFU/in2 are low and most likely are a normal part of the bacterial load. The concentrations reported from 114 Liberty are much lower than these values. Therefore, even though there was not an appropriate outdoor sample collected for comparison, it can be concluded that the bacterial concentrations reported from the one indoor sample that was collected are typical of an indoor environment.

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