Study calls for changes to public toilet design

The study looked at the contribution toilet plume particles play on cross-contamination in indoor environments and recommended that public toilets should be designed with antimicrobial surfaces, should optimise ventilation and should introduce timely disinfection protocols. In doing so, the spread of infections including of C. difficilе infection, influenza and Norovirus could be curtailed.

Researchers investigated the factors contributing to increased bioaerosol exposure following flushing and developed a realistic model for predicting when and where there is a greater risk of spreading airborne disease.

In a statement, Elizabeth Paddy, a doctoral researcher from the University’s School of Architecture, Building and Civil Engineering, said: “When a toilet is used and flushed, the turbulence caused by the mixture of water and waste in the toilet bowl creates a plume. This releases tiny droplets into the air called bioaerosols – which can contain bacteria, viruses and other microorganisms. Depending on the nature of organisms, the bioaerosols can stay in the air for a while, and they can be inhaled by people using the toilet or, alternatively, they can settle on surfaces that people then touch. People who have poor hand washing habits can go on to ingest them, and then this potentially leads to the spread of diseases.

“We must consider a holistic approach when it comes to limiting the spread of infectious diseases – not just a single intervention. Public toilets are everywhere and one of the main places where people can catch infections, so I think it’s important that policymakers, public health officials, facility managers and other relevant government stakeholders take note.”

The study saw the construction of a bespoke indoor toilet cubicle in a microbiological laboratory to replicate the appearance of a toilet commonly found in healthcare or hospitality environments.

Certain elements were taken into consideration, including whether to include a window or jet air dryer. 

Paddy said: “Traditionally, windows are positioned high on the public toilet walls to address privacy and security concerns and, in Britain, are usually required to provide light rather than any substantial ventilation. Not including a window ensured the findings of this study can be applied to a wide range of indoor environments where natural ventilation is limited. We balanced this out by equipping the room with an air purifier – which goes further in eliminating bioaerosols.

“We also decided to exclude jet air dryers from this study – choosing to equip the cubicle with paper towels for hand drying. The powerful airflow caused by these dryers play a huge part in dispersing bioaerosols during the cleaning process so including them would have made it impossible to accurately measure what pathogens are caused by the flushing toilet.”

Elizabeth Paddy's research was supervised by the University’s Dr Oluwasola Afolabi, senior lecturer in Water and Environmental Engineering, and Professor M. Sohail, Professor of Sustainable Infrastructure. 

Dr. Afolabi said: “This is something groundbreaking as it allows us to understand, perhaps for the first time, the many ways in which bioaerosols are transmitted and distributed. Elizabeth has been able to transfer a very critical engineering methodology into a public health space and this is something we’ve not really seen before.

“The study highlights the role mechanical ventilation can play in reducing bioaerosol viability and reducing the associated health risks by maintaining humidity at safe levels. A move towards this, alongside promoting strategic facility design and rigorous cleaning protocols can go a long way to safeguarding public health.”