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Comparison of ERMI results for dust collected from homes by an electrostatic cloth and by the standard vacuum method

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Pages 423-429 | Published online: 21 Jul 2021


The Environmental Relative Moldiness Index (ERMI) is a scale used to compare mold contamination levels in U.S. homes. To create the ERMI scale, a nationally representative set of U.S. homes was selected (n = 1,096). From each of these homes, a standard vacuum-dust sample was collected and then 36 common molds, the 26 Group 1 and 10 Group 2 molds, as grouped for forming the ERMI metric, were quantified using quantitative PCR assays. However, in investigations of mold in homes, it is not always practical or even possible to collect dust using the standard vacuum method. Therefore, we performed a comparative study of dust samples collected in the same homes (n = 151) by the standard vacuum method and by an electrostatic cloth (EC) method. First, floor dust was collected by vacuuming a 2 m2 area in the living room and a 2 m2 area in a bedroom, directly adjacent to the sofa or bed, for 5 min each with a Mitest sampler-fitted vacuum. Second, immediately after the collection of the vacuum dust sample, an EC dust sample was collected by wiping above-floor horizontal surfaces in the living room and bedroom. Then, the ERMI analysis of each sample was performed by a commercial laboratory. The results showed the average concentrations of 33 of the 36 ERMI molds were not significantly different in the vacuum and EC samples. Also, the average summed logs of the Group 1 molds, Group 2, or ERMI values were significantly (p < 0.001) correlated between the vacuum and EC samples. Logistic regression indicated that an EC sample could identify homes in the highest ERMI quartile 96% of the time by using the same ERMI value cutoff as vacuum sample ERMI value cutoff and 35% of samples proved to be false positives. When it is not practical to obtain the standard vacuum-dust sample, an EC sample can provide a useful practical alternative for ERMI analyses.


We are grateful to the homeowners and occupants who took part in AHHS II.

Conflicts of interest

There are no additional conflicts to declare.


The United States Environmental Protection Agency through its Office of Research and Development funded and managed the research described here. It has been subjected to the Agency’s administrative review and approved for publication. AHHS II and the collection of the dust samples were funded by the U.S. Department of Housing and Urban Development (HUD). The findings and conclusions in this manuscript are those of the authors and do not necessarily represent the official positions of HUD. Mention of trade names or commercial products does not constitute, for either EPA or HUD, endorsement or recommendation for use.

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