Using MSQPCR technology to analyze the dust sample from each of the homes in the AHHS resulted in the creation of the ERMI scale. This scale estimates the mold burden in homes by identifying the diversity as well as the quantity of mold cells in the dust sample.
The ERMI assessment was in agreement with the inspection and/or occupant’s answers about mold and moisture in 48% of fourth quartile homes. But neither of these human assessments indicated a moisture or mold problem in the other 52% of fourth quartile homes. Yet the population of the 26 water-damage indicator molds was statistically indistinguishable in any of these fourth quartile homes; In these cases, the “walk-through” inspections and questionnaires missed hidden mold problems.
On the other hand, the ERMI values were low in 18 (7%) of first quartile homes where the inspector reported mold or musty smell. But none of the 26 water-damage indicator molds in these 18 homes were similar to the population of these molds in fourth quartile homes. In these homes, the human assessments overestimated the mold burden. This demonstrates that human assessments are hard to standardize. But many mold assessments are based on just such a visual/olfactory inspection during a “walk-through” and by questioning the occupants. These assessments cannot be carried out in an objective and quantitative manner because they rely on human perceptions.
The collaboration of EPA and HUD researchers resulted in the development of the ERMI scale. The ERMI scale allows homes to be ranked in terms of relative water damage and mold growth and allows homes to be divided on the relative basis of rank order statistics using quartiles. The standard dust sample protocol combined with a DNA-based method of analysis makes this approach more objective and quantitative than the human assessment methods used.
What can we learn about homes in an epidemiological study using the ERMI scale? Epidemiological studies of asthmatic children’s homes have demonstrated an association between higher ERMI values and increased risk of asthma or asthma related symptoms.
In conclusion, analysis of the 36 molds that make up the ERMI provided a more objective way to describe the mold burdens in homes. The ERMI is not designed to eliminate the investigator or inspection but to serve as another tool, like the infra-red camera or moisture meter, to help the inspector understand and describe hidden mold and moisture problems.
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