How much is Covid 19 Spread by AIR in washrooms

• Virus’ and germs travel by air. Silently, unseen and undetected.

• They emerge at speed from our mouths, noses and waste excretions

• Washrooms have the most dangerous of air environments to manage.

• Flushing sends up a mushroom cloud of aerosolised droplets

• Anything and everything you smell is an aerosolised particle – especially in toilets

They are the headlines and for those wanting more detail – read on

An aerosol is essentially a very small droplet of water. They are so tiny that gravity does not act on them allowing them to be suspended in the air. (Wells, 1934) These droplets are thrown into the air when someone coughs, sneezes or even just speaks and they can remain airborne for long periods of time. this year a study (Doremalen et al., 2020) found that aerosolised 2020 Coronavirus (SARS-CoV-2) remained viable in the air and infectious for hours, and then on surfaces for days!! These aerosols are generated by just talking and breathing, also meaning the spread of virus’ by people without symptoms is not just possible, but probable (Yan et al., 2018). Just ten minutes of speaking at a normal volume with some people was shown to emit an aerosol cloud of up to 6,000 particles (Asadi et al., 2019).

Early studies in the 1930s and 1940 demonstrated that aerosolised particles can stay in the air for longer than a week (Wells, 1934) (Wells and Stone, 1934) (Duguid, 1946). This is compounded by the fact that these airborne particles have been measured 20m from their source (depending on environmental factors such as pressure and humidity) (Nuyttens et al., 2008).

Social trends and our reliance on indoor air means that maintaining the quality and safety of this air is a huge public health issue (Sattar et al., 1999) (Yang and Marr, 2011). It has become clear in recent years that viruses, bacteria and fungal spores from an infectious source are able to disperse over very great distances by air currents and infect individuals who have had no contact with the source (Riley et al., 1959) (Bloch, Orenstein and Ewing, 1985) (Coronado et al., 1993).

Of most concern in washrooms is the quality of the air affected by flushing toilets and expulsion of air by infected individuals. Aerosol particles containing viruses are generated and spread high into the air and then onto surfaces in the bathroom. More flushes and more spread (Barker and Jones, 2005). This mode of transmission is a vital one to consider when we take into account that the 2003 SARS outbreak at the Amoy Gardens apartment complex in Hong Kong was likely spread via sewage-related bio-aerosols (Yu et al., 2004) (Hong Kong Special Administrative Unit Department of Health 2011).

Now given what we now know, the next question we have to ask is how infectious are these aerosol particles? This is dependent on two main factors- the size of the particle and the amount of water that has been removed already (Cole and Cook, 1998). Larger particles usually mean a higher number/load of the organism and hence greater virulence of the dose (Cole and Cook, 1998). Some pathogens for example need only a tiny amount to come into contact with a human in order to begin a full-blown infection (Tuberculosis, Influenza etc) (Blachere et al., 2009). Now, we do not yet know the minimum amount of this new Coronavirus virus it takes to initiate a Covid 19 infection, however studies on another viral respiratory illness have shown that just one single virus can cause infection (Nicas, Nazaroff and Hubbard 2005).

Hong Kong Special Administrative Unit Department of Health. 2011. Outbreak of Sever Acute Respiratory Syndrome (SARS) at Amoy Gardens, Kowloon Bay, , Hong Kong: Main Findings of the Investigation.

F. M. Blachere, W. G. Lindsley, T. A. Pearce et al., “Measurement of airborne in�uenza virus in a hospital emergency department,” Clinical Infectious Diseases, vol. 48, no. 4, pp. 438–440, 2009.

D. Nuyttens, M. De Schampheleire, K. Baetens, D. Dekeyser, and B. Sonck, “Direct and indirect dri assessment means. Part 3: �eld dri experiments,” Communications in Agricultural and Applied Biological Sciences, vol. 73, no. 4, pp. 763–767, 2008.

W. Wells and W. Stone, “On air-borne Infection,” American Journal of Hygiene, vol. 20, pp. 619–627, 1934.

P. H. Gregory, The Microbiology of the Atmosphere, Wiley, New York, NY, USA, 1973.

A. B. Bloch, W. A. Orenstein, and W. M. Ewing, “Measles outbreak in a pediatric practice: airborne transmission in an office setting,” Pediatrics, vol. 75, no. 4, pp. 676–683, 1985.