Many of the risks and control measures are outlined in a fascinating new research paper, titled “Can a toilet promote virus transmission? From a fluid dynamics perspective” – from the journal Physics of Fluids. This assesses that if someone is infected with the virus, when the toilet is flushed and the lid is not placed down, what are the transmission risks? This is something of relevance not only to viral transmission but also in terms of the transmission of fecal bacteria, and hence a general public health measure.
The data, based on computer models designed to simulate water and air flows in a flushing toilet and the resulting droplet cloud, reveals that between 1,000 to 10,000 particles are typically ejected upon flushing, with an average range of 1.5 metres, if a facility is used without the lid being closed. The activity of flushing a toilet creates a large amount of turbulence in the water and air. The particles will not all be viral and will include some enteric bacteria. The assessment is based upon some neat equations looking at the dynamics of fluids and different force, based around how waste and water is drawn out of a toilet.
When a lid is closed prior to flushing the rate and number of ejected particles decreases substantially. The paper also indicates the importance of flushing a toilet regularly, and with cleaning and disinfecting toilets located in public rest areas (ideally after each use but this is not always practicable). This is because coronaviruses have been found to bind to porcelain, so they remain across several lavatorial uses and can potentially be ejected.
The authors make the fairly obvious recommendations for using public conveniences, but they are worth noting given the number of toilet facilities that are located with restrooms which do not have lids:
1. Put the toilet lid down before flushing, which can basically prevent virus transmission.
2. Clean the toilet seat before using it, since floating virus particles could have settled on its surface.
3. Wash hands carefully after flushing, since virus particles may be present on the flush button and door handle.
The paper also seeks to enlighten toilet manufacturers and prompt them to produce better designed toilets in which the lid is automatically put down before flushing and cleaned before and after flushing.
