INTERPRETING MOLD RESULTS

Since there are no established threshold limits for mold in an indoor environment, much care and consideration must given to the interpretation of testing results. When taking air samples, a sample or samples from outdoors should be taken to serve as a reference for comparison with indoor air. It may also be helpful to take samples from non-complaint areas to serve as indoor references.

In general, the concentration of organisms in indoor air should be lower than that of outdoor air samples. Also, the concentration of organisms from non-complaint areas should be lower than that of complaint areas. Generally, the same types of organisms should be found indoors and outdoors. If there is a difference in the microbial diversity between indoor and outdoor samples, this may be an indication of indoor amplification. It should also be noted if the presence of indicator organisms is detected. These are organisms that are associated with water-damaged materials or high humidity. Some indicator organisms include: Acremonium sp., Aspergillus (some species), Chaetomium sp., Eurotium sp., Fusarium sp., Memnoniella sp., Penicillium (some species), Stachybotrys chartarum (synonym S. atra), Trichoderma sp., Ulocladium sp., and Wallemia sp.

The confirmed presence of Stachybotrys chartarum in an indoor environment requires urgent risk management decisions to be made due to the potential high toxicity of this organism. For further information on the handling of this organism consult "Guidelines on Assessment and Remediation of Fungi in Indoor Environments" (available through the New York City Department of Health web site at: http://home2.nyc.gov/html/doh/html/epi/moldrpt1.shtml). Also, careful consideration should be given to organisms that are known to cause disease, especially in immunocompromised individuals: Aspergillus fumigatus, A. flavus, A. niger, A. versicolor and Fusarium moniliforme as well as some of the Zygomycetes. These should be given special attention in hospital settings or areas occupied by individuals with impaired immune system function.