Aerosol generation in public restrooms

TL;DR

This study quantifies aerosol generation from flushing toilets and urinals in public restrooms, revealing significant droplet production that may contribute to disease transmission, emphasizing the importance of ventilation and design improvements.

Contribution

It provides empirical measurements of aerosolized droplets from restroom fixtures, highlighting design factors influencing aerosol spread and potential mitigation strategies.

Findings

Large number of droplets generated in 0.3μm to 3μm range

Covering toilets reduces but does not eliminate aerosols

Aerosol levels increase with multiple flushes

Abstract

Aerosolized droplets play a central role in the transmission of various infectious diseases, including Legionnaire's disease, gastroenteritis-causing norovirus, and most recently COVID-19. Respiratory droplets are known to be the most prominent source of transmission for COVID-19, however, alternative routes may exist given the discovery of small numbers of viable viruses in urine and stool samples. Flushing biomatter can lead to the aerosolization of microorganisms, thus, there is a likelihood that bioaerosols generated in public restrooms may pose a concern for the transmission of COVID-19, especially since these areas are relatively confined, experience heavy foot traffic, and may suffer from inadequate ventilation. To quantify the extent of aerosolization, we measure the size and number of droplets generated by flushing toilets and urinals in a public restroom. The results indicate that the particular designs tested in the study generate a large number of droplets in the size range 0.3$\mu m$ to 3$\mu m$, which can reach heights of at least 1.52m. Covering the toilet reduced aerosol levels but did not eliminate them completely, suggesting that aerosolized droplets escaped through small gaps between the cover and the seat. In addition to consistent increases in aerosol levels immediately after flushing, there was a notable rise in ambient aerosol levels due to the accumulation of droplets from multiple flushes conducted during the tests. This highlights the need for incorporating adequate ventilation in the design and operation of public spaces, which can help prevent aerosol accumulation in high occupancy areas and mitigate the risk of airborne disease transmission.