Credit NIOSH
#15,315
A number of times over the past decade we've looked at cases studies, and laboratory experiments, that suggest that the flushing of toilets may create an aerosolized `toilet plume', which can potentially spread viruses or bacteria through the air.
Back in 2012, in Norovirus: The Gift That Keeps On Giving, we looked at an outbreak of norovirus that was believed due to just such an event, when a reusable open top grocery bag stored in a hotel bathroom became contaminated by one infected individual, and ended up spreading the virus to the other members of a girls soccer team.The incident was described in the Journal of Infectious Diseases (see A Point-Source Norovirus Outbreak Caused by Exposure to Fomites by Kimberly K. Repp, and William E. Keene), where the authors wrote:
Aerosolization of vomit and feces has been demonstrated to be of major importance in norovirus outbreaks [13]. Even viruses aerosolized from flushing a toilet can contaminate surfaces throughout a bathroom [14]. Once a fomes is contaminated, transfer to hands and other animate objects can readily occur [15]. The more confined the space (eg, most bathrooms), the more intense would be the “fallout” [13].
It’s not a new idea, and in fact Mythbusters did a segment on this very early on in their series. In 2013, NIOSH and the University of Oklahoma produced a literature review on the topic.
Lifting the lid on toilet plume aerosol: a literature review with suggestions for future research.
Johnson-DL; Mead-KR; Lynch-RA; Hirst-DVL
Am J Infect Control 2013 Mar; 41(3):254-258
http://dx.doi.org/10.1016/j.ajic.2012.04.330
NIOSHTIC No. 20042357
Abstract
BACKGROUND: The potential risks associated with "toilet plume" aerosols produced by flush toilets is a subject of continuing study. This review examines the evidence regarding toilet plume bioaerosol generation and infectious disease transmission.
METHODS: The peer-reviewed scientific literature was searched to identify articles related to aerosol production during toilet flushing, as well as epidemiologic studies examining the potential role of toilets in infectious disease outbreaks.
RESULTS: The studies demonstrate that potentially infectious aerosols may be produced in substantial quantities during flushing. Aerosolization can continue through multiple flushes to expose subsequent toilet users. Some of the aerosols desiccate to become droplet nuclei and remain adrift in the air currents. However, no studies have yet clearly demonstrated or refuted toilet plume-related disease transmission, and the significance of the risk remains largely uncharacterized.
CONCLUSION: Research suggests that toilet plume could play a contributory role in the transmission of infectious diseases. Additional research in multiple areas is warranted to assess the risks posed by toilet plume, especially within health care facilities.We revisited the topic in 2015, with NIOSH Video: Adventures In Toilet Plume Research, after researchers at NIOSH and the University of Oklahoma completed a build (see photo at top of blog) that allowed them to test the amount of aerosols generated at different flush rates.
Not only was this approach flushed with success, they showed that high powered flushing units – such as those commonly used in hospital settings – gave off more aerosols than standard toilets. Something for nursing staff to think about the next time they are charged with emptying an emesis basin or bedpan from a suspected infectious patient.Then entire 6 minute video is well worth watching, including briefly revisiting the soccer team norovirus story mentioned above, at the link below.
Three years later, in Toilet Bowl Sunday, we looked at research published in BMC Antimicrobial Resistance & Infection Control called Bioaerosol concentrations generated from toilet flushing in a hospital-based patient care setting by Samantha D. Knowlton, Corey L. Boles, Eli N. Perencevich, Daniel J. Diekema, Matthew W. Nonnenmann and CDC Epicenters Program that quantified the number of particles and bioaerosols produced from flushing a hospital toilet during routine patient care.
All of which brings us to a new study, published in the CDC's EID Journal, that examines two genetically similar healthcare-associated Legionnaires’ infections linked to a common toilet - 5 months apart.It shouldn't be lost on anyone that if Legionnaires' disease and norovirus can be spread via mechanical aerosolization from a flush toilet, that the same could easily hold true for SARS-CoV-2 (see JAMA NETWORK Air, Surface Environmental, and Personal Protective Equipment Contamination by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) From a Symptomatic Patient).
I've only posted some excerpts from the study, so follow the link to read it in its entirety. I'll have a postscript when you return.
Dispatch
Transmission of Legionnaires’ Disease through Toilet Flushing
Jeanne Couturier, Christophe Ginevra, Didier Nesa, Marine Adam, Cyril Gouot, Ghislaine Descours, Christine Campèse, Giorgia Battipaglia, Eolia Brissot, Laetitia Beraud, Anne-Gaëlle Ranc, Sophie Jarraud, and Frédéric Barbut
Abstract
We describe 2 cases of healthcare-associated Legionnaires’ disease in patients in France hospitalized 5 months apart in the same room. Whole-genome sequencing analyses showed that clinical isolates from the patients and isolates from the room’s toilet clustered together. Toilet contamination by Legionella pneumophila could lead to a risk for exposure through flushing.
Legionella pneumophila is a gram-negative bacterium usually found in small amounts in water in both nature and built environments. In larger amounts, it can be responsible for a severe pneumonia known as Legionnaires’ disease (LD). Transmission usually occurs when someone inhales contaminated aerosols from showers, cooling towers, faucets, or fountains. Person-to-person transmission is extremely rare (1). Researchers have evocated a variety of other uncommon sources of contamination, such as windshield washer fluid (2) or dental unit waterlines (3). LD transmission through flushing toilets has also been suspected (4) but not demonstrated. We report 2 cases of LD in immunocompromised patients in France, potentially caused by L. pneumophila transmission through flushing toilets.
(SNIP)
Conclusions
We describe 2 cases in which LD was probably caused by L. pneumophila transmitted through contaminated toilet water that became aerosolized during flushing. We reached this conclusion because we found little to no detectable difference between whole genomes in isolates obtained from 2 patients hospitalized 5 months apart in the same room and those from the toilet in that room. The other commonly suspected sources, in this case the shower and the sink, tested negative for L. pneumophila.
This investigation suggests that transmission of L. pneumophila through toilet flushing should be considered when investigating a LD case. However, as previously suggested, there remains a need for a laboratory-based study to explore whether flushing toilets can generate and spread contaminated aerosols (8,9).
Dr. Couturier is a medical biologist at the Saint-Antoine Hospital, and a teaching assistant at the René Descartes Faculty of Pharmacy, Paris, France. Her research interests include microbiology and hospital hygiene.
(Continue . . . )
We've one more (relatively recent) study on point that suggests closing the lid may reduce, but not eliminate, the aerosols generated by a flush toilet.
ACCESS MICROBIOLOGY
Volume 2, Issue 2
Meeting Report
Open Access
Real-time Monitoring of Aerosols Generated from Toilet Flushing
Mehael Fennelly1,2, Stig Hellebust1, John Sodeau1, Michael Prentice2,3
First Published: 28 February 2020
https://doi.org/10.1099/acmi.fis2019.po0192
Flushing toilets generate visible droplets from turbulent flow, but also produce numerous smaller airborne droplets (∼micrometres in size) through atomisation. Flushing may aerosolise pathogens from stool or urine, spreading disease. This study continuously monitored aerosols in a shared office lavatory over a week using a biological particle detector, the Wideband Integrated Bioaerosol Sensor (WIBS). This instrument monitors individual particle sizes and numbers and identifies fluorescent particles likely to be droplets containing bacteria.
The toilet was a standard wash-down design, (Armitage Shanks), with a lid. No statistically significant variation between fluorescent particle counts was found between periods prior to flushing. Fluorescent particle numbers and intensity increased with toilet flushing, remaining above background for 5 minutes post-flushing on average.
Placing the toilet lid down significantly (P < 0.001) reduced total and fluorescent particle counts during and after flushing by 30-50%. Lid usage significantly increased (P < 0.001) particle diameter from 1.5 μm to 2.1 μm and increased particle fluorescence intensity (P < 0.001) during flushing and after flushing, intensity remaining above background for 16 minutes.
This suggests standard lid usage reduces but does not eliminate flush-related bioaerosols. Lid-use changes their characteristics and apparently prolongs their residence time in room air. The aerosol change could represent particle agglomeration by a pressure-related Kelvin effect or particle re-aerosolisation from different surfaces in the toilet rather than exclusively originating from droplet generation. Previous studies reporting the effect of toilet lids have found that they prevent the spread of visible droplets on flushing, however the effect on smaller particles is less clear cut.
Published Online: 28/02/2020
I understand that toilet lids are viewed as unhygienic - and with no lid there is one less surface to touch - but that is something that can be readily solved by rigorous hand washing. Other issues frequently cited are that they add to the cleaning routine, and in public toilets they are frequently damaged.
But if the act of flushing makes breathing - or touching other surfaces in the bathroom - more hazardous, then any infection control advantages derived from eliminating toilet lids would seem suspect.Given the costs of HAIs (Hospital Acquired Infections), the impact of norovirus outbreaks on cruise ships and in schools, and our struggles with the current COVID-19 pandemic, it seems like it should be time to close the lid on this topic once and for all.
