Sponsor
This project was funded by National Institute of Environmental Health Sciences (NIEHs) with grant number P30ES030287 via the Pacific Northwest Center for Translational Environmental Health Research.
Published In
Journal of Exposure Science & Environmental Epidemiology
Document Type
Article
Publication Date
11-23-2022
Subjects
VOC Emission -- Testing, Indoor Spaces -- Air Quality
Abstract
Background
Several studies suggest that far-field transmission (>6 ft) explains a significant number of COVID-19 superspreading outbreaks.
Objective
Therefore, quantifying the ratio of near- and far-field exposure to emissions from a source is key to better understanding human-to-human airborne infectious disease transmission and associated risks.
Methods
In this study, we used an environmentally-controlled chamber to measure volatile organic compounds (VOCs) released from a healthy participant who consumed breath mints, which contained unique tracer compounds. Tracer measurements were made at 0.76 m (2.5 ft), 1.52 m (5 ft), 2.28 m (7.5 ft) from the participant, as well as in the exhaust plenum of the chamber.
Results
We observed that 0.76 m (2.5 ft) trials had ~36–44% higher concentrations than other distances during the first 20 minutes of experiments, highlighting the importance of the near-field exposure relative to the far-field before virus-laden respiratory aerosol plumes are continuously mixed into the far-field. However, for the conditions studied, the concentrations of human-sourced tracers after 20 minutes and approaching the end of the 60-minute trials at 0.76 m, 1.52 m, and 2.28 m were only ~18%, ~11%, and ~7.5% higher than volume-averaged concentrations, respectively.
Significance
This study suggests that for rooms with similar airflow parameters disease transmission risk is dominated by near-field exposures for shorter event durations (e.g., initial 20–25-minutes of event) whereas far-field exposures are critical throughout the entire event and are increasingly more important for longer event durations.
Rights
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
Locate the Document
DOI
10.1038/s41370-022-00499-6
Persistent Identifier
https://archives.pdx.edu/ds/psu/38799
Citation Details
Parhizkar, H., Fretz, M., Laguerre, A. et al. A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields; implications for the spread of respiratory viruses. J Expo Sci Environ Epidemiol (2022). https://doi.org/10.1038/s41370-022-00499-6