State-of-the-Art vs. Current TechnologyLast summer, a tsunami struck the fungal sampling coastlands of USA…but hardly created a splash.  The tsunami quietly seeped into the wetlands when the US EPA announced the development of ERMI…the acronym for Environmental Relative Moldiness Indexsm on August, 2006.  The mold community welcomed ERMI with a yawn and raised eye brow.  While a handful of laboratories have been promoting ERMI since last fall, its acceptance into the industrial hygiene and fungal detection disciplines has been tepid at best, and relegated to the more esoteric, high-end projects such as litigation support and celebrity cases where cost is less valued than precision and accuracy.  It has grown at the glacial pace of Stachybotrys in Arizona.

What is ERMI?
That’s not an easy question to answer…  First, ERMI is not an analytical method.  It is a sophisticated statistical method by which to compare and interpret environmental fungal data using state-of-the-art DNA test methods.  For those of you that have been around for a few years, it is to mold what TEM (transmission electron microscopy) was to asbestos.  If you remember, when asbestos first became the designer contaminant of the 1980’s, industrial hygienists used a method called PCM (phase contrast microscopy) to detect asbestos fibers in air…actually…it didn’t detect only asbestos, it measured all fibers with a certain morphology and aspect ratio.  PCM parallels our modern day spore trap analysis in the sense that it requires microscopic examination; spore traps are unable to discern between viable and non-viable fungi, they have wide variability and are relatively inexpensive…similar to PCM.

So when TEM burst onto the scene in the early 1980’s most IHs thought they finally had an accurate, true measure of asbestos airborne concentrations…until they saw the price tag…$450/sample!!  Fortunately, when EPA promulgated the Asbestos AHERA Standard for schools, they integrated TEM analysis as a requirement for clearance testing.   Until then TEM was largely a research tool used by PhD types.  This legal mandate became the impetus for IHs to use TEM as an invaluable tool to measure actual asbestos concentrations.  Now the street price for TEM is closer to $70/sample 20 years later.

Unfortunately, ERMI does not have this luxury…yet.  No state or federal standards to date require the use of ERMI during mold inspection activities….leaving this extremely sensitive, highly accurate tool on the side lines.  Coupled with the fact that it’s not well understood, most field investigators are comfortable with the use and interpretation of spore traps and tape lift samples, and its substantially more expensive ($325/sample), there’s not a compelling reason to switch to ERMI…until now.

Steve Parkhurst, CIH, CSP, LIH, CIAQC has well over 25 years experience in the area of industrial hygiene and environmental consulting.  Mr. Parkhurst currently serves as the Senior Certified Industrial Hygienist for Clean Air Labs and Infrared Consultants, both of which are members of The Chiodo Companies:  a diversified family of Global Service Corporations, with interests in Real Estate, Financial Services, Retail, Wholesale, Concierge Services, Holistic Health, and Environmental Health and Safety. 

With ERMI, none of this matters…ERMI is a historic bulk dust sample collected via a vacuum pump.  According to EPA protocols, a specialized sampling cassette is attached to the end of a high volume vacuum pump.  A composite sample is obtained by taping a rectangular area 3’x6’ (18 ft2) in two different primary rooms of the home, bedroom and living room.  Each area is vacuumed for 5 minutes creating the composite sample.  A composite sample is preferred because EPA discovered that over time, mold spores accumulate in a relatively homogenous manner due to their size and ease of distribution via air currents and ventilation systems.  An investigator can take a sample out of one single room if needed, but the standard protocol is the composite approach.

Bulk dust samples are preferred since environmental fungal spores accumulate over time providing a historic sample of the water intrusion event, rather than singular moment in time that spore traps provide.  Anyone who has been deposed as an expert witness has been confronted with the diminishing question, “Aren’t spore traps simply a glimpse, a snap shot into the air quality conditions, and isn’t it true that spore concentrations may have changed dramatically before or after the sampling period?”  We always sheepishly admit, “yes…” since most of our reports carry those ominous disclaimers.  If you’re testifying, which would you rather have…a couple of sketchy black and white photographs or a full length color video to win your case?  The answer, of course, is rhetorical.

You might wonder if a home has been recently cleaned if this would impact the historic dust bulk sample.  To be honest, it could; however, I’ve never found a home or office building where I couldn’t find some dust accumulation…on top of the refrigerator, in a corner, above cabinets, on book shelves or in a closet.  Remember, you only need a 5 milligram (mg) dust sample to attain sensitivity down to a single spore.  Even a visually clean floor will have invisible spores accumulating on its surface.  Next the sample is capped and shipped using your favorite shipping method…no ice or shipping precautions necessary as with culturable samples.

As with spore traps, the investigator’s powers of observation, moisture readings, and understanding of the water impact scenario are critical to giving the sampling results context and developing coherent recommendations.  ERMI does not replace the investigator but adds another powerful tool in their evidence collecting tool belt.

Samples are analyzed using Mold Specific Quantitative Polymerase Chain Reaction.  Don’t bother trying to remember all that…just remember DNA.  MSQPCR is a highly accurate and sensitive molecular technique for the detection and quantification of molds.  It is objective and specific because it is a detection system based on unique DNA sequences.2  Just as humans have unique DNA sequences that provide statistical probabilities of 1,000,000,000:1 odds, so do environmental fungi.  The DNA sequence for Aspergillus fumigatus is uniquely different from A. flavus and A. versicolor.  As popularized by the criminal forensics program CSI, “DNA doesn’t lie.”  It’s as close to the statistical truth as possible with an accuracy of 99.99%.

Spore trap and tape lift analyses depend on microscopic examination which are fully dependent on the experience of the microscopist, the level of debris and the concentrations of other organisms overshadowing organisms of lesser concentrations in the sample.  And, yes, while the AIHA accreditation process has raised the bar on laboratory performances and quality control, the accuracy and precision of microscopic examination will never equal that of MSQPCR analysis.  Furthermore, how many times have you collected a sample to have a depressing value of OL (overload) appear in the sample report, or have a high debris rating (5) meaning the value of the data is diminished.  Not possible with ERMI.  No overloads, no interferences, no occlusions, no ambiguities…only irrefutable, bulletproof certainty.

We’ve all encountered the ubiquitous result “Aspergillus/Penicillium-like” (A/P) in both spore trap and tape lift samples.  In talking with Dr. Ed Sobek, Laboratory Director at Clean Air Labs in Oak Ridge, Tennessee, he explained that… “These A/P spores under the microscope appear as small 1-3 micrometer (um) unremarkable spheres.  Unfortunately, many spores have a similar appearance.  Unless you culture these spores, there’s no way of knowing via microscopic examination if they are Aspergillus, Penicillium or perhaps some other genera of mold.”

The implications behind this statement are astounding and substantial…both from a medical perspective and a practical perspective.  Aspergillus contains 160 different species, 16 of which have been documented as etiological agents of human disease but rarely occur in individuals with normally functioning immune systems.3  Approximately 200 different Penicillium species have been isolated causing medical issues ranging from a type I & III allergen to hypersensitivity pneumonitis and allergic alveolitis in susceptible individuals.  It can cause other infections such as keratitis, penicilliosis, and otomycosis.3

In other words, when you see the laboratory designation Aspergillus/Penicillium-like in a lab report, this represents at least 360 different species of molds that cause highly variable medical maladies which in many instances are highly species dependent.  I don’t know about you, but the uncertainty and ambiguities that accompany this relatively crude analytical method, in my opinion, is grossly inadequate and has just become obsolete by ERMI/DNA.

We all make decisions ranging from a few thousand dollars upwards toward millions of dollars based on these A/P-like results, primarily because these genera are common water impact molds with intermediate water activities (Aw – 0.8-0.9).  However, even trained microscopists cannot ascertain if these are truly Aspergillus or Penicillium spores.  The only real value in this is that if these same spherical spores are not appear in the outside or control sample, there exists a discrepancy or dissimilarity between the inside and outside samples.  Not much to go on when recommending thousands of dollars be spent for remediation, or trying to determine whether an environment is conducive to a disease.  Even culturable/viable samples can’t provide the level of precision and accuracy that ERMI/DNA offer plus they require 7-10 days to culture…ERMI/DNA….24 hours.  Furthermore, culturables are agar specific so certain molds require certain agars before detection is possible.

ERMI Data Interpretation
Every environment has some mold and no method can quantify all molds present.  Therefore EPA selected indicator molds for water damage and non-water damaged conditions.  Group 1 mold species are the 26 indicator molds occurring in water-damaged, atypical homes; and Group 2 mold species are the 10 indicator molds potentially found in all homes, even without water-damage.4

Examples of Group 1 molds include A. flavus, A. fumigatus, A. sydowii, Aureobasidium pullulans, Chaetomium globosum, Penicillium brevicompactum, P. spinulosum, Stachybotrys chartarum, Trichoderma viride, Wallemia sebi and 16 others.  Group 2 molds include Acremonium strictum, Alternaria alternata, A. ustus, Cladosporium cladosporioides (Types 1 and 2), P. chrysogenum Type 2 and 4 others.

In 2006, HUD carried-out the American Healthy Home Survey of a statistically representative sample of approximately 1100 homes across the US and analyzed the dust with the ERMI analysis. For each sample, the mold concentration of each species (spores/mg of dust) is converted to its algebraic log then summed for the respective groups.  The sum of logs of Group 2 molds is subtracted from the sum of logs of Group 1 molds to arrive at an ERMI score.  This log transformation adjusts for magnitudinal variance in spore concentrations associated with region (Florida vs. Arizona) and season (winter vs. summer).  The subtraction of Group 2 mold from Group 1 mold normalizes the data to account for variation in cleaning habits and growth substrate (building materials).   The 1100 values for the homes were assembled from lowest to highest to create the ERMI scale from -10 to 20 or even higher (Figure 1).  These homes were then divided into four quartiles (25% lowest, 25% highest etc.) based on the percentage of homes in each (Figure 1).  Now any home sampled and analyzed in the same way can be placed on the ERMI, to determine its relative moldiness compared to the U.S.5

Figure 1. ERMI values for homes from 2006 HUD American Healthy Home Survey assembled from lowest to highest and divided by percentiles. (reprint with permission of the American College of Occupational and Environmental Medicine).

With ERMI, no more comparing inside to outside spore concentrations, no more wondering what does A/P-like really mean, no more aborted studies due to inclement weather conditions and open windows, far more clarity regarding whether a home is mold impacted, and far more accurate and comprehensive analyses.  So not only can it be used on initial mold investigations but also on post-remediation verification studies, wall cavity checks, on property damage water-impact claims, on property transfers, and potentially on personal injury suits.  Soon, every home will have an ERMI value determined prior to the real estate transaction.  It will be like checking your cholesterol level…

This is the future…it only makes sense.  DNA doesn’t lie…

Stayed tuned for part 2.

Table 1.  Comparative Table of Various Analytical Testing Techniques to Identify and Quantify Indoor Air Fungal Concentrations

References
1) “Bioaerosols:  Assessment and Control”, ACGIH, 1999; Section 7.4.2.1, p.7-6.

2) Vesper, M, S. Vesper, et. al.; “Mold-Specific Quantitative PCR:  The Emerging Standard in Mold Analysis”, American Laboratory, January 2005, p.10.

3) Aerotech/PK Website, www.aerotechpk.com; Microbial Glossary, Aspergillus and Penicillium.

4) Vesper, S., et. al., “Specific Molds Associated With Asthma in Water-Damaged Homes”, Journal of Occupational and Environmental Medicine, Vol. 48, No. 8, August 2006: 853-858.

5) Vesper SJ, McKinstry, C., Haugland RA, Wymer L, Ashley P, Cox D, DeWalt G, Friedman W., Development of an Environmental Relative Moldiness Indexsm for homes in the U.S.  Journal of Occupational and Environmental Medicine. In Press. 2007

6) Tucker, J., “Selecting an Air Sampler for Bioaerosol Collection”, EMS Inc, 2005.

7) Bartlett, K., et. al., “Evaluating Indoor Air Quality:  Test Standards for Bioaerosols”, 99FS-64, rev. July 2003:23.

ERMI/DNA Laboratory Analysis
ERMI samples are prepped by EPA licensed laboratories of which there are only 14 world-wide (see http://www.epa.gov/nerlcwww/moldtech.htm).  AIHA does not have an ERMI accreditation process to date but may undertake this project within the next 1-2 years.  Meanwhile, the EPA has an extremely rigorous licensing process, so look for the EPA license number before utilizing an ERMI laboratory.

 How ERMI Works…
Imagine as an environmental investigator you pull up to a home or building, walk inside to meet the client only to discover all the windows of the residence are open…despite your notice to close all windows at least 24 hours prior to the study.  Or, you arrive on site only to have a storm develop causing concern whether it’s worth collecting outside samples since a down pour likely reduces airborne spore levels.  Or, you live in a northern state where snow cover and temperatures below 40°F persist for days if not months are common.  Even the ACGIH Bioaerosols book (the Bible for us fungal followers) recognizes that these issues confound the data interpretation process.1  Not only are they frustrating, but they add additional expense and uncertainty to the sample collection and data interpretive processes.  Now imagine if none of this mattered.  How much time and expense it would save in re-scheduling studies and questioning data validity and ambiguities.