ERMI (sm) is the acronym for Environmental Relative Moldiness Index. ERMI (sm) is a scale created from a National database of approximately 1100 homes sampled by Housing and Urban Development (HUD) during the 2006 American Healthy Home Survey and then analyzed by Qualitative Polymerase Chain Reaction (QPCR).
ERMI (sm) was developed by scientists at the USEPA to provide a straightforward, objective and standardized way to obtain results for mold investigations in homes as well as a tool used to evaluate the potential risk of indoor mold growth and associated health effects. Traditionally, mold analysis is done by either the microscopic observation of air samples and direct samples which is not standardized and can’t identify most species; or plate culturing of mold spores on various media – not all molds grow on the same medium.
The ERMI (sm) method involves the analysis of a single sample of dust from a home. Using Mold Specific Qualitative Polymerase Chain Reaction (MSQPCR), one can determine the presence of deoxyribonucleic acid (DNA) sequences that are unique to a particular mold species – DNA-based detection and quantification of molds to the species level.
How was ERMI (sm) 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). For the calculation of the ERMI (sm) all concentrations are log-transformed and the sum of group 2 is subtracted from the sum of group 1.
The Collection Process
The sample could be dust from the carpets in the house (providing historical data) and the primary method used for ERMI (sm). Carpet dust acts as a reservoir for mold spores and is more representative of mold levels over a period of time versus short term air samples. Other applications could be flour from a mill where the level of aflatoxin producing mold is critical. Dust from the window drapes, office furniture and even from the HVAC duct work can be collected (although this process has not been totally formalized as of this writing)
ERMI (sm) Advantages
ERMI (sm) is based on standardized sample and machine based analysis which takes the human element out of the process (as much as possible)Accurate identification down to the speciesSensitive detection at low levels of sporesAbility to detect total cellsProvides simple interpretation of resultsFast – QPCR takes 24 hours turnaround timeWhat ERMI (sm) is NotThe ERMI is a mold index, not a health index. Each person responds differently to mold exposure due to genetics, pre-existing health conditions, age, etc. Medical questions about mold are for the Health Professionals to address