Our latest preprint on COVID-19 and aerosol transmission: “A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields” is available!
The public has been told for the majority of the pandemic that we need to keep our distance to prevent the spread of COVID-19, and while social distancing is important, distance only goes so far.
To make public health decisions, we need better evaluation of airborne pathogen transmission, and our team has been working on estimating disease transmission risk indoors and specifically measuring the differences between exposures within the 6-foot range (near-field) and beyond the 6-foot range (far-field) to get a better assessment of how distance impacts exposure risk.
Our recent study shows that social distancing indoors, that is staying 6-feet or more away from others, has a relatively lower risk of rebreathing infectious aerosols compared to the immediate field (within 2.5 ft), but after 20 minutes (in a room similar to the study chamber), as the air blends within a space, the concentration of virus-laden particles in the near field may not be that much greater than that of the far-field. Therefore, the impact of social distancing starts to diminish as duration increases.
Excited to share our new preprint “A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields” @mark_fretz J.Stenson @LaguerreAurelie @CorsIAQ @Wymelenberg @etgall @UO_Research @UO_IHBE @MaseehCollege @UCDavisCOE https://t.co/1MvsxgB5IG
— Hooman Parhizkar (@HoomanParhizkar) March 12, 2022
Read the full abstract below:
Several studies suggest that far-field transmission (> 6 ft) explains the significant number of COVID-19 superspreading outbreaks. Therefore, quantitative evaluation 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. 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 2.5 ft, 5 ft, 7.5 ft from the participant, as well as in the exhaust plenum of the chamber. We observed that 2.5 ft trials had substantially (~36-44%) higher concentrations than other distances during the first 20 minutes of experiments, highlighting the importance of the near-field 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 2.5 ft, 5 ft, and 7.5 ft were only ~18%, ~11%, and ~7.5% higher than volume-averaged concentrations, respectively. Our findings highlight the importance of far-field transmission of airborne pathogens including SARS-CoV-2, which need to be considered in public health decision making.