A new study published in the Journal of the Royal Society Interface has found that preadolescent children release fewer droplets and aerosols compared to adults.

Researchers compared the particle emission rates during various vocal tasks in 15 children, aged 8-10 years, with the emission rates in 15 children using a laser particle counter in four test settings: breathing at rest, speaking, singing and shouting. The participants were asked to speak and sing at a moderate loudness. The volume of particles emitted over time were also assessed.

Compared to adults, children were found to emit particles at a lower rate and at a lower volume during breathing, speaking and singing. But, no significant variations were noted in the volume of particles released between the two groups on shouting. Particle emission rates (P_M) were measured as particles per second and the emitted particle volume rates (PVR) were measured in mL per second.

The median cumulative P_M of all examined children at rest was 8 (PVR 4.4 × 10−11). For speaking, singing and shouting, the median P_M were 24, 118 and 1083, respectively (PVRs of 5.6 × 10⁻¹⁰, 1.9 × 10⁻⁸ and 1.8 × 10⁻⁷). Among all adults examined, the median cumulative P_M at rest was 20 (PVR 2.8 × 10⁻¹⁰). And for speaking, singing and shouting, the median P_M were 204, 1640 and 1295, respectively (PVRs of 1.5 × 10⁻⁸, 1.1 × 10⁻⁷ and 1.5 × 10⁻⁷). The P_M decreased from adults to children for breathing at rest, speaking, singing and shouting by factors of 2.5, 8.7, 13.9 and 1.2, respectively. The PVR also decreased from adults to children for breathing at rest, speaking and singing by a factor of 6.4, 26.5 and 6.0.

Covid-19 spreads through droplets containing the SARS-CoV-2 virus that are produced during coughing, sneezing, singing and even speaking. The virus can also spread through the air as aerosols. A person in close proximity to the infected person can get infected by breathing in the aerosols and droplets.

This study has shown a decline in the rates of particle emission including volume of particles in children compared to adults. The shorter vocal folds in children and “shorter contact times during the oscillation cycles of a child’s vocal register” may explain the differences in emission rates.

The participants were not infected with SARS-CoV-2. Extrapolating these findings to the ongoing Covid pandemic would mean that children emit fewer respiratory droplets and aerosols than adults and may be less likely to transmit the infection. According to the researchers, these findings may help in making decisions about risk management in schools now that schools have mostly reopened. However, the authors caution that there may be high inter-individual variability in particle emission rates and viral loads, which must be taken into account.

Reference

1. Fleischer M, et al. Pre-adolescent children exhibit lower aerosol particle volume emissions than adults for breathing, speaking, singing and shouting. J R Soc Interface. 2022 Feb;19(187):20210833. doi: 10.1098/rsif.2021.0833.