Beware! The EPA mold scale ERMI© is misleading

Charles and Danielle Dobbs

ERMI testingIn part 1 of “Is ERMI Testing Reliable To Test A Home For Mold?” we explained the research behind ERMI testing, now here are the flaws:

Improper sample selection of “moldy” and “non-moldy” homes
First, the homes were classified as either “moldy” or “non-moldy” based on the following criteria.  The paper states:

“A “moldy home” (MH) had at least one of the following: water damage history, visible mold/water damage, or moldy odor.  A “non-moldy” home (NMH) had none of these.”

Any experienced mold inspector knows that a visual mold inspection is not enough to assess a home for mold, and we cannot rely on our nose to establish whether a mold problem is present.  We must also collect air samples.  By taking several air samples we can find out 1) how many spores are in the air in a particular room and 2) the types (genera) of mold spores that are present and their respective amounts.  That tells us right away whether there is a mold problem and where.

We certainly cannot rely on a “nose test” because an air test may indicate a mold problem even though neither the occupants nor us could detect a “moldy odor”.  Alternatively, on several occasions we have been called to homes because the occupants smelled an odor that they attributed to mold.  Our tests revealed normal levels of mold spores, but volatile organic compounds (VOCs) found in new building materials, such as cabinetry or carpet were the culprits, and produced an odor.

We conclude that the samples in that study were improperly selected.  Assessing the air quality with air tests would have established scientifically beforehand whether homes had a mold problem or not.  Also, the study does not say whether the visual inspections were conducted by “home inspectors” or “mold inspectors.”  It only says that the on-site visits were performed by “trained two-person teams.”

If Plan A does not work, go to plan B

“The Wilcoxon test performed on the mold concentrations for homes grouped by the inspection process into NMH versus MH showed that no species was significantly different in concentration between these two groups of homes.”
“ … homes were reclassified into “more moldy homes” (MMHs) and “less moldy homes” (LMHs).

It is improper to choose different groups half way through the study and massage the data with statistics to come up with something meaningful simply because the two original groups, non-moldy homes and moldy homes, did not work out.

The ERMI© scale seems to have been derived solely with less moldy and more moldy homes.
Referring to the y-coordinate of ERMI© scale “Percent of Homes in the US”, are we to believe that the data representing homes in the US came only from “less moldy homes” and “more moldy homes”?  If so, this scale is not representative of homes in the U.S.

Improper control of variables of homes with smokers and non-smokers.  The  researchers state:

“. . . major mold/water damage was observed through home inspection and survey in only 5% of the homes, yet 19.6% of the infants developed wheezing and 49% developed rhinitis at age one.  Therefore, most cases of illness were not predictable on the basis of a home inspection.  These predictions could have been complicated by other exposures, such as smokers living in the home.”

Indeed, it has long been recognized that children are affected by cigarette smoke.  This variable should have been taken into account by selecting only homes with non-smokers.

The researchers added:

“ . . . an immediate and obvious improvement to predicting risk of respiratory illness would be to include additional information to the RMI in the predictive model like smoking in the home, pets, dust mites, or other indicators that could be taken from the home survey.  Adding these factors to the logistic model might improve the prediction of illness even more.”

Why didn’t they think of that prior to conducting this $5 million study?

The study was biased – The introduction of the research paper indicates that a parallel study of air tests was conducted but the body of the paper hardly mentioned the comparative results.  It states

“A parallel study did not find any associations between the total mold spores count and rhinitis or allergen sensitization. However several associations emerged when mold species were identified.  . . .  However, the methods used in that study are very time consuming and not highly standardized.”

We certainly agree that individual species (or genus) (along with the total spore count) should be taken into account as well as their individual amounts of spores and their ratios to be compared to levels found in an outside sample.  In addition, the research paper fails to say that air tests are both qualifying (identification of genera) and quantifying (amount of spores).

Researchers made a biased judgment by saying that collecting air tests are “very time consuming and not highly standardized”.  We disagree – air test results can be obtained immediately in a lab if you live near a laboratory or as little as one day if the samples are sent overnight to a laboratory.  It takes a minimum of five to ten days to get the results from an ERMI© test dust sample.  It certainly would have been nice if researchers could have also included the results of air samples as comparison.  And, what do the researchers mean by “highly standardized”?  They talk about “standardization” when their research is flawed!

Questionable molds found in both moldy and non-moldy homes
Table 1 found in “Relative Moldiness Index as Predictor of Childhood Respiratory Illness” shows Stachybotrys and Chaetomium mold to be present in both “Moldy homes” and “Non-moldy homes”.

We have recapped their information in the following table to show the average of mold concentrations for
Stachybotrys and Chaetomium:

Moldy homes

Non-moldy homes







It is known that Stachybotrys mold grows in a wet environment and Chaetomium mold grows on, among other things, drywall that is wet or has been wet!  Both types of mold are often found together in a home with a mold problem.  How can the researchers explain this?

If we poked around further into the study we would, no doubt, find other flaws.  The study does look impressive with all kinds of statistical analyses, but if you read it carefully there are many holes.  With statistics all kinds of things can be derived, but massaging the data is not proper.  By removing the group of “Non-moldy homes” (NMHs) and then using two groups “More moldy homes” (MMHs) and “Less moldy homes” (LMHs), researchers found something to report.  At a score of -4.29 they found a correlation between the incidence of illness in a home with (enough) mold between the “less moldy” and the “more moldy homes.”  Give us a break!!!  There is no doubt that this study will impress many people because it is based on DNA analysis and many people will accept it at face value and not read it carefully.  With all its bells and whistles, we say that ERMI© dust sample testing is flawed.

Until a better tool comes along we will continue to use the traditional method of collecting air samples in different parts of the home with an outside control, and collecting surface samples if mold-like substance is visible.  Air samples are not perfect, and things can always be improved but, in our opinion, they give us a better picture than one or two dust samples that are supposed to be representative of the entire home.  ERMI© testing does not tell us precisely if and where a mold problem exists.  Air tests can.  If you had a score of 5 or 10 that would tell you that there is a serious mold problem somewhere (pardon me “high mold burden”).  But, we would have to go back to the house and guess what . . . we would have to collect air samples to find the location of the problem.  So, why not collect air samples in the first place?  Besides, spore trap analysis is very fast, and you could get same day results if you wanted to, while dust sample analysis takes five to 10 days.  Clients do not have money to waste on some fancy DNA testing that does not tell them whether a mold problem exists in their house and if so, the location of mold contamination.

EPA researchers are in their ivory tower and do not have a clue of real situations or budgetary concerns of the average homeowner.

Clients want to know three things from a mold inspector:

1) Do I have a mold problem?  2) If so where is it?   3) How do I get rid of it?

This ERMI© scale was designed for a specific study.  In our opinion the application of the ERMI© test should not be extrapolated and touted as the “latest technology” to evaluate a home or building for mold.  Several U.S. laboratories now perform this analysis, and novice and unaware mold inspectors started performing the test for clients.  ERMI© testing appears “scientific” because it involves DNA analysis, and thus it sounds impressive for the majority of people.  It can identifies the species of mold, such as “Aspergillus penicillioides” or “Cladosporium cladosporioides”, or “Cladosporium herbarum” while an air test identifies the genus “Penicillium/Aspergillus”, or Cladosporium.  We say that knowing the genus of mold is usually enough to assess a home for mold, knowing the species does not necessarily add anything to the testing.

Dr. Shoemaker, M.D. who treats patients who have been exposed to mold thinks highly of the ERMI© testing, but he warns:  “No sampling can replace the skill of the experience mold inspector in investigating mold problems.”  What Dr. Shoemaker does not know is that the best mold inspector could miss a mold problem by performing only a visual mold inspection.  It is essential to collect air samples in different parts of a home.  Then the laboratory results will tell us the amount of mold spores per cubic meter and the genera compared to spores found in an outside sample.  With this information we get a picture of what’s going on and where.  Like air testing, the ERMI© test is a tool to detect a mold problem, but the dust test gives less practical information than the traditional air tests.  The score representing the “mold burden” is too vague.  If the ERMI© score is elevated, it does not tell the client the location of the problem.  Consequently more testing would be required, specifically air tests in various rooms, which would increase the overall cost of testing for the client.

If researchers come up with better testing that give us more information than air testing in terms of pin-pointing the location of a hidden mold problem (that wall, rather than the other three), and quick turn around analysis, we will jump on it.  In the meantime, we feel that the so-called “new technology” of ERMI© testing makes us go backward.  It gives us less practical information, it is vague, and it ends up being more costly to homeowners than air tests.  Finally, because the meaning of the ERMI© score is vague, it has the potential of implicating mold inspectors in lawsuits. When mold inspectors get sued because it is found later that a serious mold problem was developing at the time of ERMI© testing, researchers will be far away in their ivory towers and mold inspectors will be by themselves fighting lawsuits.

Another bit of interesting information about ERMI testing.  Taxpayers paid for the EPA study, then the EPA obtained a patent on taxpayers’ dime, and after that, laboratories around the country are required to pay the EPA royalties for performing the sample dust analysis!  How about that!!!

ABOUT THE AUTHORS: Charles and Danielle Dobbs are professional mold assessors, expert witnesses, authors of several books on mold.  Feel free to contact us for questions pertaining to this article.

Lin, K. T., Shoemaker, R.C. Inside Indoor Air Quality: Environmental Relative Moldiness Index (ERMI©). Filtration News May/June 2007: 32-36.

PRWEB. EPA Relative Mold Index (ERMI©) – A Powerful New Standardized Investigation Tool for Screening Homes for Mold Contamination. 2/2007.

Vesper. S.J., McKinstry C., Haughland R.A., Iossifova Y., Lemasters G., Levin L., Khurana Hershey, G.K., Villareal M., Bernstein D.L., Lockey J., Reponen T. Relative Moldiness Index as Predictor of Childhood Respiratory Illness.  Journal of Exposure Science and Environmental Epidemology 2007: 88-94.

Written by Charles & Danielle Dobbs – Professional mold assessors, expert witnesses, authors of several books on mold, and mold education bloggers

Charles & Danielle Dobbs - Professional mold assessors, expert witnesses, authors of several books on mold, and mold education bloggers