Sponsor
The author(s) declare that financial support was received for the research and/or publication of this article. This project was supported, in part, by a 2020 Wood Innovations Program Grant (#20-11-062765-736) from the USDA U.S. Forest Service.
Published In
Frontiers in Microbiomes
Document Type
Article
Publication Date
4-9-2025
Subjects
Indoor air quality, Air purifier -- Clean air delivery rate, Carbon dioxide -- Environmental aspects
Abstract
IntroductionHumans have used wood as a construction material throughout history. Currently, mass timber products, such as cross-laminated timber (CLT), are becoming more popular as a structural material, since they are renewable and have a lower carbon footprint than concrete or steel. Nonetheless, some building types, such as healthcare, veterinary, and food manufacturing, avoid using structural mass timber due to concerns about microbial growth in the event of wetting. One solution is to use protective coatings on mass timber products to increase moisture resistance, although the coatings themselves may generate concerns about volatile organic compound (VOC) emissions. Natural uncoated wood also produces VOCs, some of which may have intrinsic antimicrobial effects.MethodsIn this study, we inoculated coated and uncoated cross- laminated timber (CLT) blocks with a mock microbial community and isolated each block within individual sealed microcosms. We characterized VOCs and surface microbial communities from the CLT blocks before, during, and after wetting periods of varying durations. VOC concentration and emission rate were analyzed with chromatography-mass spectrometry (GC-MS), while microbial community abundance, diversity, and composition were analyzed through qPCR and shotgun metagenomics.ResultsVOC emissions were elevated immediately after inoculation, then decreased through the remainder of the experiment, except for a plateau during the wetting period. VOCs from uncoated CLT blocks were primarily terpenes, while coated blocks emitted VOCs associated with coatings, plastics, and industrial solvents, as well as terpenes. One VOC—acetoin (3-hydroxy, 2-butanone)—was present at high levels across all samples immediately after microbial inoculation. Bacteria comprised 99.54% of the identified microbial sequences. The plastic control microcosm (not containing a CLT block) had higher abundance of viable bacteria for the majority of the study, but there was no difference in abundance between coated and uncoated blocks. Prior to wetting periods, microbial composition was driven primarily by sampling day, whereas surface type played a larger role during and after wetting periods.
Rights
Copyright © 2025 Mhuireach, Collins, Dietz, Horve, Laguerre, Northcutt, Stenson, Wymelenberg, Gall and Fretz. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Locate the Document
DOI
10.3389/frmbi.2025.1395519
Persistent Identifier
https://archives.pdx.edu/ds/psu/43256
Publisher
Frontiers Media SA
Citation Details
Mhuireach, G. Á., Collins, S., Dietz, L., Horve, P. F., Laguerre, A., Northcutt, D., Stenson, J., Wymelenberg, K. V. D., Gall, E., & Fretz, M. (2025). Effects of wetting events on mass timber surface microbial communities and VOC emissions: implications for building operation and occupant well-being. Frontiers in Microbiomes, 4.
