Micro-biophysical characterization of respiration aerosols (µResp) and their role in airborne transmission of infectious diseases
Medical Physics, Biomedical Technology
Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
Final Report Abstract
The characterisation of the size and concentration of particles exhaled by humans is essential to understanding the source of particles that contribute to airborne transmission of infections. Not only is the prediction of any model of infection transmission critically dependent on these characteristics, but the efficacy of non-pharmaceutical interventions can only be quantitatively evaluated if the source of infectious particles is known as accurately as possible. Most importantly, samples must be collected under extremely controlled conditions that preclude contamination of the sample by ambient aerosols or other human particle sources. Exhaled particles also span a wide size spectrum from nanometers to millimeters, making it difficult to accurately characterize them. To meet these stringent requirements, particles from exhaled air are sampled in a clean room laboratory using state-of-the-art aerosol spectrometers, inline holography, and size-resolved Lagrangian particle tracking systems. We have characterized the size and concentration of exhaled particles during various breathing activities, such as singing and playing wind instruments. By performing specific respiratory activities, we were also able to determine the contribution of different regions in the human respiratory tract to particle production. In addition, we performed size-resolved particle tracking velocimetry and demonstrated that respiratory particles can reach velocities of up to 20-30 m s^−1 during vocalisations, regardless of their size. We have also investigated the assumption of a well-mixed room in large indoor spaces and quantitatively demonstrated that near-field trasnmision is dominant in such environments. Finally, we integrated all these findings into an easy-to-use and free web app that can be used by the public, researchers, and policy makers. The results of our research have already been published and are freely available to all. Another manuscript is to be published in the near future. This completes all funded tasks set out in µResp.
