ERMI – Environmental Relative Moldiness Index

What is the ERMI test?

ERMI is a research tool developed by EPA scientists for estimating mold contamination. In using this tool, researchers analyze the DNA from mold found in dust samples collected from a home, and then compare the sample to the ERMI’s scale, which is based on a national database of molds found in homes across the country. The ERMI scale for estimating mold contamination was developed for use in research studies related to mold exposure and health impacts. The EPA’s fact sheet can be found here.

What We Like About the ERMI Test

ERMI test interpretation provides a straightforward, objective, sensitive and standardized way to assess mold and indoor air quality investigations. It also provides a long-term picture of the potential exposure to mold in a home. Finally, the ERMI test was designed to inform physicians about the living condition of a home. This will inform a physician about the daily exposure to mold that you may experience.

Challenges With the ERMI Test

We all have different cleaning habits, some people dust and or vacuum daily, others monthly. Sample quality and consistency can be difficult. Where one residence may not have enough dust, another may have dust months or years old.

One of the strengths of the ERMI test is also one of its weaknesses. By comparing the dust in your home to a national database, regional differences in mold spore count and specie distribution are averaged out. Specie distribution and spore counts can vary quite substantially regionally and seasonally, so the picture painted by the data might not be particularly relevant to the local conditions in which you live.

Finally, despite being held in high regard by the medical community, the EPA states that the ERMI is a research tool and is not recommended for use except as a research tool. Furthermore, we question the strength of the connection between settled dust and health effects in the research.

Recommended Practice

We’re concerned primarily with breathable air in habitable spaces; therefore, we recommended traditional mold air samples be taken concurrently with ERMI testing. This provides better snapshot in time of the mold level exposure. Because of the costs involved, we also recommend holding the ERMI samples at the lab until the air samples are analyzed. If elevated mold spore counts are found in the air, then the ERMI dust samples can be analyzed at the lab. With all the data from the lab in addition to our visual inspection, we can arm physicians with more information to help identify health problems and give remediation professionals guidance for successfully removing the mold.