Air Date: 8-14-2020|Episode 596
Understanding fungi, bacteria, and chemicals in the indoor environment.
According to Karen C. Dannemiller, PhD (Assistant Professor at The Ohio State University) she has always been interested in human exposures. She started by studying exposure to formaldehyde and then added microorganism exposures.
Nuggets mined from today’s episode:
What is the best way to measure environmental fungal communities when trying to determine the potential for health outcomes? We need to find the “thing” to measure that has the best associations with human health outcomes of interest. Right now, qualitative measures like visual inspection and detection of moldy odor have the strongest associations with health. We still need to identify something quantitative that is more strongly associated with health. It’s still a big question- requiring an interdisciplinary approach to determine what to quantitatively measure to find the best associations with health.
Dannemiller, K.C., J., Leaderer, B., and Peccia, J. “Influence of housing characteristics on bacterial and fungal communities in homes of asthmatic children’ Indoor Air. 26 (2), 179-192. DOI: 10.1111/ina.12205
We looked at housing factors previously identified as associated with asthma outcomes: urban versus rural, single family versus multi family, and presence of: pets, visible mold, water damage. Takeaways: building conditions affect microbial communities. These factors influenced: diversity (richness) and what microbes are present.
Dust from the housing analysis came from the STAR study: https://www.niehs.nih.gov/research/supported/cohort/resources/cohort755412.cfm
There are thousands of organisms in the DNA data base. The cost of DNA sequencing is coming down. Figure out what to measure, what measurements best associate with human health outcomes, then measure and then analyze. Subjective indicators: visible mold, water stains and musty odor have the closest association with health. The comparative concentration of total fungal and bacterial species found indoors is pretty even. Significantly associated according to statistical analysis.
Richness is the number of species present.
Volutella, a turf grass pathogen, was associated with increased asthma severity in atopic children. However, more studies are needed to confirm this association.
Cryptococcus species may affect asthma severity. Cryptococcus can be hard to culture in the lab. Of the 304 species, about 30 species of Cryptococcus are commonly found indoors.
Exposure matters. Exposure can be complicated: type and quantity.
Indoor microbial communities influence asthma. Allergic people respond to presence of allergens while nonallergic people are irritated by high levels. Examine both microbial communities and asthma sub-types (allergic/nonallergic)
Recommend a really nice review on indoor fungal measurements and associations with health. Respiratory and Allergic Respiratory and Allergic Health Effects of Dampness, Mold, and Dampness-Related Agents: A Review of the Epidemiologic Evidence by Mark Mendell et al.
Chemicals affect microorganisms indoors. Microorganisms interact with chemicals indoors.
What is the most important thing to measure to find health outcomes? The current conclusion is using more subjective inspection for: visible fungal growth, water staining, and moldy odors is most closely tied to health.
Moisture control indoors improves health outcomes.
Dannemiller, K.C., Wechler, C.J., and Peccia, J. 2016. “Fungal and bacterial growth in floor dust at elevated relative humidity levels” Indoor Air. 27 (2), 354-363. DOI:10.1111/ina.12313
We measured microbial growth in carpet because carpeting has high dust re-suspension rate. Often, we think of microbes in the indoor environment as inactive. However, in our study we found that elevated relative humidity is sufficient to support microbial growth. At 100% RH there is 27 times more fungi compared to the original dust.
“Our material balance model predicts that the growth due to 100% relative humidity exposure for a week, the re-suspension of microbes grown in carpet dust may account for 75% of the fungal and 21% of the bacterial load in the air.”
We also studied microbial function in house dust. Microbial function in dust increases secondary metabolic diversity at higher ERHs.
Relative humidity indoors varies between different points within rooms.
She is looking for stronger information before recommending changing field inspection and sampling methods. Some reasons why we have trouble finding an association between measured fungi and health outcomes include: measurement errors, measuring non-casual factors- effects may change over time (age) interaction effects from multiple exposures. Statistically very complicated.
Dust picks up moisture very quickly!
Working on a more realistic condition study with variable RHs throughout the day.
Bridget Hegarty, Karen C. Dannemiller, and Jordan Peccia. 2018 “Gene expression of indoor fungal communities under damp building conditions: Implications for human health.”Indoor Air. Doi: 10.1111/ina.12459
We have the capability of looking at all microbial function of organisms through gene expression.
At Yale, Bridget Hegerty worked with Jordan Peccia to do the analysis on sequenced RNA. This involves generating large files of data, processing the data using the Trinity Program and forming a map of genes expressed at different RHs- carbohydrates, amino acids, energy, nucleotide, lipids and TCA cycle.
What is the microbial function? Looking at RNA when genes are expressed in dust samples at high RH.
Omics is looking at many molecules how they relate on a large scale to structure and microbial communities.
Metatranscriptomics- looks at all the genes expressed in the “entire community” to measure overall microbial function. Is the spore different depending on how grown? At 50% RH some genes are expressed of primary metabolic process showing that the organism is waiting for water, at 85% RH increase in gene expression of primary metabolic processes, 100% RH especially secondary metabolic processes are expressed in diverse ways.
Allergens, endotoxins are often found in secondary metabolic processes, and were more highly expressed at 100% RH.
The Last Word:
Pay attention to moisture indoors. Thank her team, the Alfred Sloan Foundation, co-authors of studies, study participants, welcomes hearing from industry pros.
Z-Man signing off
Questions: Who insisted on the addition of the word “The” to Ohio University?
Answer: to separate the institution from other Ohio colleges, President Edward Orton insisted on adding The.