I thought about writing this note for a long time, but I was not sure if this was the best place to post it. Every once a while I would hear about mold in buildings, along with the common refrain “Mold is everywhere. We’re always breathing in mold.” Since many people here tend to enjoy learning, I decided to write this up. This is not meant to be a rigorous review of the subject, but I hope it introduces some interesting research literature.

Mold is everywhere. This is strictly true, but also a simplification of a vast field of study that is relatively new. Mold gets most of the attention when it comes to buildings, but there is a whole microbiome associated with the built environment that can affect human health, and we did not begin surveying it using more precise genetic identification methods until 2004. The first such genetic survey noted the presence of several opportunistic pathogens on shower curtains. Many broader surveys have since followed, showing that the microbiome of a particular study site varies with its surroundings, i.e. buildings in urban sites tend to be dominated by microorganisms of human origin, but rural and agricultural buildings tend to have more species that come from their immediate outdoor environments (1).

So, fungi, bacteria, and viruses are everywhere. But the composition of these communities and their distribution matters. Shower curtains can be thrown away and replaced. Moving homes or replacing building materials is a much more difficult and expensive process. 

There is scientific consensus that mold and dampness affect human health. We know this from high quality epidemiology studies that show exposures from dampness and mold have been associated with increased risks for respiratory symptoms, asthma, general and hypersensitive immune response-related respiratory tissue inflammation, and respiratory infections. We have also performed intervention studies that support these findings (2, 3, 4).

We have also documented that the microbiome of human airways interacts with both airway tissue and environmental factors such as particulate pollution, and these interactions can have health effects. Species from the airway microbiome are also found in building materials (5, 6, 1). We are also learning that the impact of these species is influenced by climate change (7).

So, it’s true: mold is everywhere. But it is also true that mold and other microorganisms directly affect us, they can interact with other environmental factors to amplify the impact of those factors and themselves, and their effects may be increasing with climate change.

I hope in the future as an industry we can begin to understand that there are many facets to this subject. And not all of them are negative. As we are discovering with diet and nutrition, we may eventually discover ways to build buildings that supplement and reinforce human health in the face of unavoidable climate change by influencing the human microbiome. Some might say we have already been doing this in the way we produce cellar-aged products like wine (8).

Note: if you cannot access these journal articles, try contacting the author(s) directly by email or via ResearchGate, and they will gladly share their work.

1. https://www.nature.com/articles/s41579-018-0065-5

2. https://link.springer.com/article/10.1007/s00253-014-6178-5 

3. https://www.osti.gov/servlets/purl/924852 

4. https://journals.asm.org/doi/epub/10.1128/AEM.01973-06?src=getftr 

5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7218407/ 

6. https://www.nature.com/articles/s41591-023-02424-2 

7. https://onlinelibrary.wiley.com/doi/full/10.1111/all.14476#all14476-bib-0038  

8. https://buildingscience.com/documents/insights/bsi-010-wine-cellars