Comparing respiratory aerosol emissions between children and adults during sustained phonation

Abstract

Respiratory aerosols arise due to bronchial fluid film bursting within the pulmonary tract, the vibration of the vocal folds during phonation, and articulation of the tongue/lips/teeth. We expect respiratory aerosol emission rates to be lower in children than adults due to the smaller size of their laryngeal structure, reduced sub-glottal pressure created during speech, and reduced number of alveoli. However, few studies have evaluated respiratory aerosols for children. We recruited 50 participants from three age categories: children aged 6–11 years, children aged 12–18 years, and adults (>18 years). We investigated particle emissions for three different 5 s sustained vocalizations of /a/ or /pa/ at 262 Hz, as well as for running speech and breathing. The particle generation rate ranged from 0 to 488 particles/s. Children aged 6–11 years produced fewer particles (mean 12 $\pm$ SD 9 particles/s) than children aged 12–18 years (23 $\pm$ $19 \text{particles/s}$) and adults (70 $\pm$ $73 \text{particles/s}$). Taking a deep breath before vocalizing /a/ resulted in higher aerosol emission rates than the baseline case. The particle number size distributions for all vocalizations and age groups consistently showed two modes at ≈0.6 μm and $\approx 2 \mu \mathrm{m}.$ Children had a slightly smaller primary mode location and larger secondary mode location than adults. Superemitters (statistical outliers) were found in all groups. Experiments repeated over time revealed large intrapersonal variability indicating additional variables (e.g., environmental, physiological, behavioral) may significantly influence emission rates. The lower respiratory aerosol emission rates for children indicate a need to consider population demographics when predicting airborne disease transmission risks.

Copyright © 2023 American Association for Aerosol Research

Graphical Abstract

EDITOR:

• Shanna Ratnesar-Shumate

Author contributions

All authors contributed to the article and approved the submitted version. MSR: Writing – original draft, data curation, formal analysis, visualization, coding. MA: Writing – original draft, data curation, formal analysis, visualization, coding. TA: Data curation, visualization. BDE: Supervision, conceptualization, validation, editing, and project administration. DS: Formal analysis, visualization, coding. SM: Statistical methodology, validation, editing. ARF: Supervision, conceptualization, validation, editing, and project administration.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Science Foundation [CBET:2029548] and the Clarkson University COVID-19 Special Solicitation.