What Is ERMI? The Environmental Relative Moldiness index (ERMI) was developed by the U.S. Environmental Protection Agency, Office of Research and Development (ORD) as a research tool to investigate mold contamination in homes. The methodology is based on using mold-specific quantitative polymerase chain reaction (MSQPCR) to quantify 36 molds and calculate an index number for comparison with a database of reference homes. Eurofins EMLab P&K was one of the first collaborators to help establish the reference database and continues to offer this service to clients for the identification of mold problems in some buildings.
Disclaimer: The EPA has not endorsed or validated any tools or methods to determine mold burden in homes including MSQPCR and ERMI. The EPA licensed this test to laboratories including Eurofins EMLab P&K. However, the transfer of this technology under the Federal Technology Transfer Act cannot be used to make any claims suggesting that the ERMI is an EPA-approved or validated test. (Source: EPA, Office of Inspector General: Public May Be Making Indoor Mold Cleanup Decisions Based on EPA Tool Developed Only for Research Applications)
How Does ERMI Work?
The ERMI test involves the analysis of a single sample of dust from a home. The sample is analyzed using mold-specific quantitative polymerase chain reaction (MSQPCR), a highly specific DNA-based method for quantifying mold species. A simple algorithm is used to calculate a ratio of water damage-related species to common indoor molds and the resulting score is called the Environmental Relative Moldiness Index or ERMI. The ERMI value is typically between -10 and 20.
National Relative Moldiness Index Values
In order to most effectively use this new tool, the ERMI must be compared to a national database. Indices were determined using this method for 1,096 homes across the U.S. as part of the 2006 HUD American Healthy Home Survey. Individual indices, ranked from lowest to highest were used to create a national Relative Moldiness Index (RMI) Scale.
How Was ERMI Developed?
In initial studies by the EPA, the concentrations of different mold species in “moldy homes” (homes with visible mold growth or a history of water damage) and “reference homes” (homes with no visible mold) were compared. Based on those results, mold species were selected and grouped into those with higher concentrations in moldy homes (group 1) and those with lower concentrations (group 2). To calculate the ERMI, all concentrations are log-transformed and the sum of group 2 is subtracted from the sum of group 1.
What Are The Advantages of ERMI Testing?
In addition to the simplicity of taking only one sample, the ERMI offers several advantages over traditional mold screening methods. Carpet dust acts as a reservoir for mold spores and is more representative of mold levels over time versus short-term air samples. The use of MSQPCR for this test allows for increased precision as it is based on a biochemical assay using calibrated instrumentation. Further research is being conducted and published that will link the ERMI assessing health risks for susceptible individuals. This information along with the national database will be invaluable in providing an objective and standardized method for screening homes for mold.
When Should I Use The ERMI Test?
The ERMI test can be used for evaluating “moldiness” in indoor environments. Molds are found in every home but not all molds are always present. The ERMI helps to make an assessment if a home is more or less likely to have “unhealthy” mold conditions. Especially residents sensitive to molds should consider using the ERMI to evaluate their indoor environment. Also home buyers can use this tool to predict if their new home is likely to have a history of water damage.
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