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VISUALLY OBSERVED MOLD AND MOLDY ODOR VERSUS QUANTITATIVELY MEASURED MICROBIAL EXPOSURE IN HOMES
Citation:
Reponen, T., U. Singh, C. Schaffer, S. J. VESPER, E. Johansson, A. Adhikari, S. A. Grinshpun, R. Indugula, P. Ryan, L. Levin, AND G. LeMasters. VISUALLY OBSERVED MOLD AND MOLDY ODOR VERSUS QUANTITATIVELY MEASURED MICROBIAL EXPOSURE IN HOMES. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier Science Ltd, New York, NY, 408(22):5565-5574, (2010).
Impact/Purpose:
The analysis of mold populations in homes has historically been completed by some type of capturing or collection of a sample, most often from the air but sometimes from dust or building material (e.g. dry wall), and the microscopic enumeration, either directly by observing the spores/cells/fragments or by culturing from the sample collected. The Department of Housing and Urban Development (HUD) in its Report to Congress described the resulting situation succinctly (HUD 2005). “Standard approaches to mold testing include: (1) viable count methods that involve collecting spores in air and dust samples or through direct contact with the mold, then culturing the spores on nutrient media and counting the number of colonies that grow and classifying them by species: and (2) spore counts that involve counting the number of mold spores in air or dust samples and, if possible, identifying individual species or groups. These techniques are time consuming and require considerable technical expertise. Another problem is the difficulty in interpreting test results, since mold spores are ubiquitous and there is no consensus among experts regarding what constitutes acceptable indoor spore concentrations in indoor air or house dust, or which species are most problematic.” As a result of the situation described by HUD above, EPA guidance to consumers has been not to test for mold but rather remove all molds and eliminate the underlying water source (US EPA 2002). However, as HUD also noted (HUD 2005): “Yet even now there are situations where reliable test methods are needed, including the identification of hidden mold problems and …to better define mold-related hazards based on significant association with adverse health effects in residents.” In addition, one of the major recommendations espoused by the Institutes of Medicine report (IOM 2004) regarding mold, moisture and health was the need for the development of a molecular based method of mold analysis.
Description:
The main study objective was to compare different methods for assessing mold exposure in conjunction with an epidemiologic study on the development of children's asthma. Homes of 184 children were assessed for mold by visual observations and dust sampling at child's age 1 (Year 1). Similar assessment supplemented with air sampling was conducted in Year 7. Samples were analyzed for endotoxin, (1-3)-β-D-glucan, and fungal spores. the mold specific Quantitative Polymerase Chain Reaction assay was used to analyze 36 mold species in dust samples, and the Environmental Relative Moldiness Index (ERMI) was calculated. Homes were categorized based on three criteria: 1) visible mold damage, 2) moldy odor, and 3) ERMI. Even for homes where families had not moved, Year 7 endotoxin and (1-3)-β-D-glucan exposures were significantly higher than those in Year 1 (p<0.001), whereas no difference was seen for ERMI (p=0.78). Microbial concentrations were not consistently associated with visible mold damage categories, but were consistently higher in homes with moldy odor and in homes that had high ERMI. Low correlations between results in air and dust samples indicate different types or durations of potential microbial exposures from dust vs. air. Future analysis will indicate which, if any, of the assessment methods is associated with the development of asthma.