Mycotoxin & ERMI Testing
Mycotoxins and ERMI — What the Tests Actually Measure
Mycotoxin testing and ERMI (Environmental Relative Moldiness Index) analysis are two of the most frequently requested and most frequently misunderstood mold testing methods. Both are legitimate scientific tools with specific, well-defined applications. Both are also promoted far beyond those applications in ways that can lead to unnecessary expense and inaccurate conclusions. This page explains what each test actually measures, what the science supports, and when each method is genuinely useful.
What mycotoxins are
Mycotoxins are secondary metabolites — toxic chemical compounds produced by certain mold species as byproducts of their metabolic activity. They are distinct from the mold spores themselves: a building can have elevated mold spore counts without significant mycotoxin concentrations, and in some scenarios mycotoxins may be present in settled dust even after active mold growth has been remediated.
Not all molds produce mycotoxins. Not all strains of mycotoxin-producing species produce them under all conditions. Production depends on the specific strain, the substrate the mold is growing on, temperature, competing organisms, and the growth stage of the colony. The major mycotoxin-producing genera relevant to indoor environments are:
Genus
Primary mycotoxins
Notes
Stachybotrys
Trichothecenes (satratoxins, verrucarin)
Only ~1/3 of strains produce. Requires sustained high moisture. Less common than feared.
Aspergillus
Aflatoxins (A. flavus), ochratoxin A (A. ochraceus, A. niger)
Multiple species, variable. Aflatoxins primarily dietary concern. Indoor production possible under certain conditions.
Penicillium
Ochratoxin A, citrinin, patulin
Nephrotoxic at high exposure levels. Common post-water-damage genera in South FL homes.
Fusarium
Fumonisins, deoxynivalenol (DON), trichothecenes
Not black — illustrates why color does not indicate toxicity. Found on water-damaged textiles.
Chaetomium
Chaetoglobosins, sterigmatocystin
Strong water-damage indicator. Common South FL post-hurricane finding. Distinctive musty odor.
Alternaria
Alternariol, tenuazonic acid (under specific conditions)
Primary concern is allergenicity, not mycotoxin production at typical indoor levels.
How mycotoxin testing works
Mycotoxin testing analyzes samples — typically settled dust collected from surfaces, HVAC filters, or specific building materials — for the chemical presence of specific toxic compounds. The two primary analytical methods used in accredited laboratories are:
- ELISA (Enzyme-Linked Immunosorbent Assay) — An immunological method that detects specific mycotoxins using antibody reactions. Faster and less expensive than LC-MS/MS. Can have cross-reactivity issues where structurally similar compounds trigger a positive result for the wrong mycotoxin.
- LC-MS/MS (Liquid Chromatography-Tandem Mass Spectrometry) — The gold standard for mycotoxin analysis. Highly specific, able to identify and quantify individual mycotoxin compounds with high accuracy. More expensive and requires specialized laboratory instrumentation.
An important limitation: Urine mycotoxin tests marketed to individuals as evidence of mycotoxin exposure from building environments are not FDA-approved diagnostic tests and have not been validated for that specific application. The Institute of Medicine 2004 report noted that available evidence does not support inhaled mycotoxins from building interiors as a primary health risk pathway compared to dietary exposure. If you have health concerns potentially related to mold exposure, consult a board-certified allergist, pulmonologist, or occupational medicine physician who follows evidence-based guidelines.
When mycotoxin testing is genuinely useful
- Post-remediation verification in a building with confirmed Stachybotrys or significant Aspergillus contamination, where documentation that mycotoxin-producing materials have been removed is needed for insurance or legal purposes
- Buildings where standard mold assessment and remediation have been completed but occupants continue to report symptoms, and a physician is investigating whether residual mycotoxin burden in dust may be a contributing factor
- Legal proceedings where establishing the presence of specific mycotoxins in building materials is part of the evidentiary record
- Research or industrial hygiene investigations where comprehensive environmental characterization is required
What ERMI testing is and how it works
ERMI stands for Environmental Relative Moldiness Index. It was developed by researchers at the U.S. Environmental Protection Agency as a research tool to characterize the mold burden in buildings more comprehensively than standard air sampling.
ERMI analyzes settled house dust collected from carpeting or other floor surfaces. The dust sample is analyzed using quantitative PCR (polymerase chain reaction) — a DNA-based method that identifies and quantifies 36 specific mold species. Those 36 species are divided into two groups:
- Group 1 (26 species): Molds associated with water-damaged buildings — species like Stachybotrys chartarum, Chaetomium globosum, and Aspergillus versicolor that are significantly more prevalent in buildings with moisture problems
- Group 2 (10 species): Common indoor molds found in both water-damaged and non-water-damaged buildings — Cladosporium species, Aspergillus niger, and others
The ERMI score is calculated from the log-transformed concentrations of Group 1 and Group 2 species. Higher scores indicate greater relative moldiness compared to a national reference dataset.
What ERMI does and does not tell you
ERMI captures information that standard air sampling does not. Because it analyzes settled dust rather than current airborne concentrations, ERMI reflects the accumulated mold history of a building — what has grown there over time, even if active growth has been remediated and current air concentrations are normal. A building with a history of water damage and mold that appears “clean” in air sampling may still have elevated ERMI scores because the spore burden in dust reflects past contamination.
This makes ERMI particularly useful for:
- Characterizing buildings where occupants have persistent health concerns despite prior remediation
- Long-term monitoring of buildings following remediation to track whether the mold burden in settled dust is declining over time
- Screening buildings with unknown water damage history as part of pre-purchase due diligence
- Research and epidemiological studies on building-related illness
ERMI does not replace standard assessment. It does not identify where mold is currently growing, what the moisture source is, or what remediation is needed. It also has not been validated as a standalone clinical diagnostic tool for attributing health symptoms to specific building environments. AIHA has published guidance on the appropriate use of ERMI that emphasizes its research origins and cautions against its use as a stand-alone health determination.
Our position at Coastal Air Assessments: We do not offer ERMI testing or mycotoxin testing as client services. ERMI was developed as a research tool and the science does not yet support its use as a reliable clinical assessment instrument for individual properties. Mycotoxin testing for building exposure attribution is not scientifically validated for the conclusions it is often marketed to support. Our job is to evaluate buildings — using the instruments and laboratory methods that the published science supports. When the science catches up, our services will too.
At Coastal Air Assessments, we discuss whether ERMI, mycotoxin testing, or other specialized analytical methods are warranted for your specific situation. These are not default add-ons — they are tools applied when the specific circumstances call for them.
Frequently Asked Questions
Do I need mycotoxin testing if mold is found in my home?
Not necessarily. Standard mold assessment with spore trap air sampling and surface sampling identifies what mold species are present and at what concentrations. If findings indicate significant contamination by mycotoxin-producing species — particularly Stachybotrys or Aspergillus — and if there are health concerns or legal documentation needs, mycotoxin-specific testing may be appropriate as a next step. For most residential assessments, standard sampling methodology provides the information needed to scope and execute remediation. We assess whether specialized testing is warranted based on your specific findings and situation.
What is the ERMI score range and what does a high score mean?
ERMI scores are based on a national reference dataset from EPA researchers. Scores are expressed on a continuous scale, with higher scores indicating greater relative moldiness compared to the reference population of U.S. homes. Generally: scores below 0 are in the lower moldiness range, scores between 0 and 5 are in the mid-range, and scores above 5 are in the higher moldiness range. However, ERMI score interpretation requires context — building age, climate, and occupant history all affect what a given score means. ERMI is not a pass/fail test; it is one data point in a broader building assessment.
Can mycotoxin testing prove that a building made me sick?
Mycotoxin testing documents whether specific toxic compounds are present in building materials or dust. It cannot establish medical causation between building exposure and specific health outcomes. The IOM 2004 report found insufficient evidence to support a causal relationship between mycotoxin inhalation at building exposure levels and specific health syndromes. If you have health concerns potentially related to mold exposure, a board-certified physician — typically an allergist, pulmonologist, or occupational medicine specialist — is the appropriate professional to evaluate health causation. Our role is to document the environmental conditions accurately.
What does ERMI testing cost and how is a sample collected?
ERMI testing requires a settled dust sample collected from carpeting or flooring surfaces using a specified protocol. The laboratory analysis is typically in the $200-$300 range. When ERMI is appropriate for your situation, we discuss collection methodology and coordinate with the laboratory directly. ERMI is added to an assessment when the circumstances warrant it — it is not a default component of every assessment.
