Science Inventory

Geographic Distribution of Environmental Relative Moldiness Index (ERMI) in U.S. Homes


VESPER, S. J., J. Wakefield, P. Ashley, D. Cox, G. Dewalt, AND W. Friedman. Geographic Distribution of Environmental Relative Moldiness Index (ERMI) in U.S. Homes. JOURNAL OF ENVIRONMENTAL AND PUBLIC HEALTH. Hindawi Publishing Corporation, New York, NY, 2011(Article ID 2424):1-11, (2011).


Approximately 9% of children have asthma. The medical costs of asthma are approximately $15 billion per year in the US alone and asthma results in about 2,000 deaths per year (Fisk et al. 2007). Lost school and work days run into the millions each year. The IOM’s expert committee (2004) concluded that exposure to moldy, damp indoor environments was associated with asthma. A subsequent review (Sahakian et al. 2008) of more recent publications also linked dampness to mold and asthma/asthma symptoms. The World Health organization has come to the same conclusion and suggest that exposure to molds should be “minimized” (WHO 2009). A meta-analysis of studies associating mold contamination with adverse health effects demonstrated that building dampness and mold were associated with approximately a 30 to 50% increase in a variety of respiratory and asthma-related health outcomes (Fisk et al. 2007). Therefore, it is critical that mold assessments are accurate and meaningful. US EPA researchers developed a DNA-based method of mold analysis called MSQPCR which is sensitive, specific and accurate. The US EPA in conjunction with HUD developed a simple, standard method of sampling homes for mold populations and created a scale called the ERMI to compare the mould burden in homes across the US (Vesper et al. 2007). In four epidemiological studies, higher ERMI values in homes were associated with increased risk of asthma in children. Remediating the water-damage and mould in asthmatics homes resulted in a statistically significant improvement in the child’s health and a reduction in the need for hospitalizations and emergency room visits (Kercsmar et al. 2006). Although these results are from a limited number of studies and have not been corroborated independently by other research groups, they are suggestive of the conclusions that mold problems are not always obvious. Furthermore, discovering hidden mold is possible using the ERMI analysis and subsequently correcting a mold problem may reduce asthma’s costs to the US by reducing hospitalizations and emergency room visits.


The objective of this study was to quantify and describe the distribution of the 36 settled dust molds that make up the Environmental Relative Moldiness Index (ERMI). Materials and Methods. As part of the 2006 American Healthy Homes Survey, settled dust samples were analyzed by mold specific quantitative PCR (MSQPCR) for the 36 ERMI molds. The 1096 survey homes were grouped into 82 sampling locales on the basis of latitude and longitude. The 36 mold populations were divided into disjoint clusters on the basis of their standardized concentrations and First Principal Component (FPC) scores which were calculated for each locale. Results and Conclusions. Disjoint variable clustering resulted in seven mold clusters. The population distribution of the FPC scores for these clusters suggests that co-occurrence of molds may have some regional selection. However, the ERMI values themselves were found to be heterogeneously distributed across the United States (US).

Record Details:

Product Published Date: 10/01/2011
Record Last Revised: 05/24/2012
OMB Category: Other
Record ID: 227212