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Does evidence support measuring spore counts to identify dampness or mold in buildings? A literature review



To identify dampness or mold (D/M) in buildings, investigators generally inspect for observable D/M indicators, the presence of which justifies remediation. Investigators may also use microbiological measurement and interpretation strategies with uncertain scientific support.


We assessed available evidence supporting uses of spore counts, the microbiological measurement most commonly used to assess D/M.


We reviewed published studies assessing relationships between spore counts and observable D/M, across buildings with different observable D/M levels.


Penicillium/Aspergillus counts were consistently elevated in damp vs. reference (dry or outdoor) locations. Total spore counts provided a weaker, less consistent signal. The most detailed published analysis could distinguish groups of damp homes but not individual damp homes.


Evidence did not validate current interpretations of spore count data for identifying single damp homes. Thus, such interpretations rest primarily on professional judgment. An additional series of informative but ineligible articles demonstrated an unconventional, more powerful “statistically based” comparison of multiple indoor vs. outdoor spore counts for identifying elevated indoor spores (and assumed D/M). Findings suggest that validation of enhanced spore trap approaches, including more samples indoors and outdoors plus statistically based comparisons of specific fungal groups, may allow evidence-based microbial identification of probable dampness in individual buildings.

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Fig. 1: Results reported by Baxter et al. [13], in Figure 3 in that article, showing that the interquartile range for indoor spore counts in moldy homes completely exceeded the interquartile ranges for both clean homes and outdoors.
Fig. 2


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We wish to thank Ian Cull for comments on our draft manuscript, Daniel Baxter for permission to reproduce a figure from his prior publication, and R. C. Spicer for discussions about his methods. This research was supported entirely by the California Department of Public Health.

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MJM contributed to the original concept of this article, helped conduct the literature review, synthesized the findings, and was the primary writer. RIA contributed to the original concept of this article, conducted the literature review, contributed to writing the initial draft, and reviewed the final drafts.

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Correspondence to Mark J. Mendell.

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Mendell, M.J., Adams, R.I. Does evidence support measuring spore counts to identify dampness or mold in buildings? A literature review. J Expo Sci Environ Epidemiol 32, 177–187 (2022).

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  • Fungi
  • Moisture
  • Water damage
  • Housing
  • Indoor air pollution
  • Spore traps


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