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ERMI – It’s Not About the Score

There is a discrepancy with the ERMI score because the calculation used to determine the score is incapable of accounting for the toxicity of specific mold species. Additionally, many are using the ERMI score as the be all, end all to decipher how impacted a home is. This leaves many people with a false sense of security that their home is without issues.

Another common misstep is how often individuals are using the ERMI score to write their remediation protocols. This is problematic because in the same way that an air sample collected in the middle of a room can’t tell you where source areas of mold are located, an ERMI cannot be used to pinpoint source areas of contamination.

Remediation must be focused on source removal in order to properly reduce the fungal load. Interestingly, in the last several years, many in the Indoor Environmental Industry have stated that ERMI is not a valid test. They cite this EPA document which states:

“The ERMI scale for estimating mold contamination was developed for use in research studies related to mold exposure and health impacts. ERMI has been peer reviewed for research purposes but has not been validated for non-research purposes. For this reason, EPA does not recommend the routine public use of ERMI in homes, schools, or other buildings.”

However, we are going to show you that saying an ERMI is not valid is short sighted and equivalent to throwing out the baby with the bathwater.

With all that said, we are going to look at why an ERMI was developed, what it is, and the proper way to use it.

Why an ERMI Was Developed and What is it?

The Institute of Medicine’s 2004 report, “Damp Indoor Spaces and Health,” recommended the development of “more rapid measurement methods for specific microorganisms that use DNA-based and other technology.”

As a result, the EPA developed the ERMI (Environmental Relative Moldiness Index) in an attempt to provide a straightforward, objective, sensitive, and standardized way to assess mold and indoor air quality investigations. ERMI also known as MSQPCR (Mold Specific Polymerase Chain Reaction) is a DNA sequencing methodology that is highly sensitive. As such this sampling methodology is the most sensitive form for detecting mold and its various species.

Based on widely published data from EPA researcher’s 2006 HUD American Healthy Home Survey, the test has been developed as a tool to evaluate the potential risk of indoor mold growth and associated health effects to occupants. The original ERMI was a sampling methodology that used a vacuum to collect five minute samples in two separate rooms from a 3′ x 6′ area in each room. The sensitive nature of the ERMI enables us to identify these molds down to the species level. It also tells us two very critical pieces of information: the species of molds and the concentration levels.

All About the ERMI Score and the Proper Way to Use an ERMI

ERMI uses a weighted logarithmic scale to come up with the ERMI Score. It uses a panel of 36 molds that are characterized into two separate groups:

Group 1 — contains 26 molds related to water damage
Group 2 — contains 10 molds typically found outdoors

The way the ERMI score is calculated is by subtracting, “Group 1 sum of logs,” from, “Group 2 sum of logs.”

Each ERMI Score is rated for moldiness against the 1096 homes tested by the EPA during the 2006 HUD American Healthy Home Survey. The black curved line in the chart below represents the ERMI values of homes tested rated from lowest to highest.

It is the use of this exact ERMI score that has individuals up in arms about its value and worthiness. We wholeheartedly agree with this sentiment and that is why we believe it isn’t about the score. Instead, the value of an ERMI is in the data it provides specific to the types of mold species and concentration levels of those species.

During a comprehensive inspection, the proper way to use an ERMI is to first assess the types of species, concentration levels, and then combine those findings with other supporting environmental labs (i.e. mycotoxins, wall cavity air samples, swabs of mold growth). This is how we determine the overall mold burden in a home.

However, if you yourself want to collect an ERMI it can help you determine if water damage and mold growth are occurring in your home by paying attention to the types of species and concentration levels.

In the ERMI report below you will see how misleading the score is when we compare the score against the types of species and concentration levels. If you subtract “Group 1 Sum of Logs” from “Group 2 Sum of Logs” that will give you an ERMI score of negative -1.2. This would fall into quadrant 1 (Q1) which is interpreted as, “Low Relative Moldiness Index.”

It is suggested that, “further investigation is not needed to determine the sources of the mold.”

However, when you analyze the species of molds in, “Group 1 Water Damage Molds,” the following four molds were detected in high concentrations (well above the average mean seen in the 2006 HUD study).

The asterisk specifically denotes how much higher the mold count was when compared to the average mean.

Aspergillus unguis*** (1,000 fold higher than normal)
Chaetomium globosum** (100 fold higher than normal)
Penncillium brevicompactum* (10 fold higher than normal)

Penicillium crustosum** (100 fold higher than normal)

Furthermore, the three molds that were detected have the ability to produce the following potent mycotoxins that are harmful to both humans and animals:

Chaetomium globosum** — produce chaetoglobosins A and C
Penicillium brevicompactum * — produces mycophenolic acid (MPA)
Penicillium crustosum** — produces potent neurotoxins

The “Group 2 molds” detected the following three common outdoor molds in high concentration well above the average mean noted in the 2006 HUD study. Typically, high concentrations of molds is most often an indication of mold growth.

Apergillus ustus ** (100 fold higher than normal)
Mucor amphibiorum ** (100 fold higher than normal)
Penicillium chrysogenum ** (100 fold higher than normal)

Practitioners of all kinds are erroneously using the ERMI score to determine if it is ok for their patients to stay in their home after testing for suspected water damaged or move back into their home after remediation. An ERMI score of 2 or less, in general, is the score that most practitioners are using to advise their patients whether or not a home is safe for them.

Again, this is a concern because in this example, a -1.2 ERMI falls into quadrant 1 (Q1), low relative moldiness index. This score states that it doesn’t warrant any further investigation to determine the sources of the mold.

However, when the data within an ERMI report is properly used, it is a powerful and reliable tool to keep in your tool box. It can help you flesh out mold problems that could otherwise have been missed.

A Few Other Considerations

Paying attention to species types is important, especially if you are sick. Knowing you have mold is one thing, but determining the type of species is critical. All molds in themselves are known allergens, others can be pathogenic and/or toxigenic (producing mycotoxins).

Mold is very elusive.

Most of the time you don’t see it. It is inside and behind walls, cabinets, under carpet, and in the HVAC ventilation system. There are two types of mold contamination. The first source is the physical growth of the mold itself. Sometimes you see it, but most of the time you don’t.

The secondary source is the byproducts of the mold which are the spores, fragments, and toxins. Hair is 100 microns, spores are 2–4 microns, and mycotoxins are 0.1 microns. As you can imagine, these ultrafine byproducts are extremely small, ultralight, and easily become airborne with the slightest bit of movement.

Once airborne, they can traverse through the home over long distances and easily enter peoples’ breathing zones. Eventually, the contaminants settle throughout the home’s dust reservoirs. Dust is ultimately the #1 enemy as it harbors all of the contaminants (spores, fragments, and toxins).

A home is a living breathing system. All buildings are pressurized. This pressure creates air movement that travels through the home and through its interstitial spaces. Mold spores and its byproducts are carried through the air from the lowest to the highest level of the home, including its interstitial spaces such as wall cavities, attics, basements, and crawlspaces.

As the HVAC system is being utilized, the ultralight dust carrying the contaminants are pulled into the system and redistributed back into the home’s living space. Mold and biotoxins can infiltrate the ventilation system and perpetually send contaminants throughout the home. When the spores, fragments, and toxins settle throughout the home in the dust, this is how mold cross contaminates your home and impacts everything inside of it (i.e., furniture, clothes and all your personal contents).

So, what is the best way to test your home to determine if you have a systemic mold problem?

Many people hire a mold inspector who comes out and takes ambient air samples in the middle of select rooms. Then they will compare it to the outdoor baseline levels to determine if a home has been impacted. However, the problem with these types of air samples is that they are only a snapshot in time.

Typically, five to ten minutes minutes is the collection time. Air samples are
extremely variable. Air flow is dynamic and it is constantly changing. What you may capture at the point of collection time will be different from other collection times. Additionally, some molds are more dominant than others and/or lighter, causing them to be suspended in the air longer. Which means other molds that are heavier, denser, or stickier can be overshadowed or just not captured.

This is another way one can be given a false sense of security on what is actually circulating throughout the home.

By using an ERMI to test the dust reservoirs in the home, you can get a historical perspective on the types of molds and species that are in the home. The best way to determine a home’s holistic mold burden is through the collection of dust.

How the HERTSMI Score Hurts You!

Another form of measurement that is being used is the HERTSMI-2 score (Health Effects Roster of Type-Specific Formers of Mycotoxins and Inflammagens-2nd Version). HERTSMI-2 Testing focuses on the five most toxigenic water damage mold species verses the ERMI that looks at thirty-six mold species.

The HERTSMI is often used as an alternative in lieu of the ERMI for some of the most vulnerable and chronically ill populations who often cannot afford an ERMI. It is supposed to also serve as an indicator on whether or not it is safe for a mold injured individual to occupy their home without recurrence of symptoms.

In this second example, we will look at another ERMI report along with the HERTSMI-2 score. By the end you will see that using this additional HERTSMI-2 score is just another way to give yourself a false sense of security.

The ERMI test showed 23 out of 26 water damage molds were present in this home! This many mold species, in and of itself, establishes that mold is an issue in this home, regardless of any score.

Aspergillus flavus/oryzae
Aspergillus fumigatus *
Aspergillus niger * *
Aspergillus ochraceus
Aspergillus penicillioides
Aspergillus sclerotiorum
Aureobasidium pullulans
Chaetomium globosum
Cladosporium sphaerospermum

Eurotium (Asp.) amstelodami
Paecilomyces variotii *
Penicillium brevicompactum * *
Penicillium corylophilum *
Penicillium crustosum *
Penicillium purpurogenum* *
Penicillium Spinulosum
Penicillium variabile
Scopulariopsis brevicaulis/fusca
Scopulariopsis chartarum
Stachybotrys chartarum
Trichoderma viride
Wallemia sebi

Furthermore, the following thirteen mold species have the ability to produce potent mycotoxins.

Aspergillus flavus/oryzae
Aspergillus fumigatus *
Aspergillus niger * *
Aspergillus ochraceus
Chaetomium globosum
Eurotium (Asp.) amstelodami
Paecilomyces variotii *
Penicillium brevicompactum * *
Penicillium corylophilum *
Penicillium crustosum *
Stachybotrys chartarum
Trichoderma viride
Wallemia sebi

Now let’s look at the HERTSMI-2 score.

If we had only purchased a HERTSMI-2 score for this home, you would have received a HERTSMI-2 score of (4). You will see that the interpretation
the lab provides states the following:

In only 1.7% of cases, re-occupancy of building following mold remediation has led to relapse of CIRS-WDB symptoms.

The false sense of security provided by this HERTSMI-2 is a common occurrence. We simply don’t recommend using the HERTSMI-2.

In conclusion, we believe the ERMI-like collection that uses swiffers is a valid testing methodology when used correctly. We always encourage incorporating the highly sensitive technology as MSQPCR (ERMI) to your sampling plan to help determine the settlement of mold spores and its byproducts throughout your home.

It’s important to understand that all sampling methods have limitations. Using only one sampling method cannot determine the impact of mold in your home.

The first step is always to find out and understand the the history of the home, previous water events, current water damage conditions, and to utilize additional technologies like moisture meters and infrared cameras. Then after completing the thorough investigation, a comprehensive sampling plan can be developed which will often include the following types of testing:

Source Identification Samples — Air is collected from inside wall, floor, ceiling cavities, and small isolated areas. Swabs are collected from any area where there is visible mold growth. These types of samples enable us to develop the part of the remediation plan that focuses on source removal (Air & Swab testing).

Dispersion Samples — These samples enable us to set the appropriate protocols for cleaning the home. Dispersion samples test for the various bi-products dispersed throughout a home during the mold’s life cycle. They are collected from settled dust in/on the ventilation, heating systems, duct work, contents, and/or specific rooms. (ERMI & Mycotoxin).

Progressive Samples — Mold is the main culprit, but for many additional bacterial and chemical contaminants can also contribute to an unhealthy environment. (Actinobacteria, Endotoxin, Formaldehyde, & VOC testing).

Writers: Mark Levy — Founder and President, The Mold Guy

Betsy Maldonado — Director of Operations and Education, The Mold Guy

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