Sunday, February 04, 2018

Toilet Bowl Sunday

2015 NIOSH Video


Since this is super-spreading Sunday (correction: Super Bowl Sunday), and we won't know the epidemiological impact (if any) of the thousands of football gatherings across our flu-drenched country for another week or longer, today seems like a good day to look at a new study - and some older research - on another suspected way to share germs with friends, families, and complete strangers. 
The modern flush toilet. Making this - at least here at AFD - Toilet Bowl Sunday.
It's not a new idea, of course. The TV show Mythbusters did a segment on this very early on in their series.  And five years ago, 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


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.


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.

Two years later, in NIOSH Video: Adventures In Toilet Plume Research we looked at an experimental `build' (see graphic at top of blog) that allowed researchers from NIOSH and the University of Oklahoma to measure the amount of aerosols generated at different flush rates. 
Tests 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 norovirus, flu, C. diff, or MERS patient. All of which are known to spread particularly well in hospital environments.

In 2015, in CID Study: Airborne Norovirus In Healthcare Facilities, we looked at a study that looked for - and found - norovirus in ambient air samples taken from 8 hospitals, both inside and outside of an infected patient’s room.
While the act of vomiting (see Vomiting Larry And His Aerosolized Norovirus) may fully account for this airborne infusion, the usual receptacle is a toilet, followed by a power flush.
Going back even further, in 2012's The Flight Of The Bacterial Intruder, we looked at potential for airborne spread of bacterial pathogens (including C. diff & MRSA) in a hospital environment (see Leeds University Superbugs ride air currents around hospital wards). 
Regarding airborne MRSA and C. Difficile the Journal of The Royal Society published a review in 2009 called:
Airborne transmission of disease in hospitals

I. Eames, J. W. Tang,Y. Li and P. Wilson


MRSA can survive on surfaces or skin scales for up to 80 days and spores of Clostridium difficile may last even longer. MRSA can be transmitted in aerosol from the respiratory tract but commonly attaches to skin scales of various sizes. The distance of travel depends on the size of the scale, the larger falling to the floor within 1–2 m, the smaller travelling the entire length of the ward.


Clostridium difficile spores are thought to spread in the air and can be found near a patient carrying the organism (Roberts et al. 2008). However, unlike MRSA, they are rarely isolated from air samples.

Again in 2012, the Journal of Hospital Infection published Potential for aerosolization of Clostridium difficile after flushing toilets: the role of toilet lids in reducing environmental contamination risk, which found:
C. difficile was recoverable from air sampled at heights up to 25 cm above the toilet seat. The highest numbers of C. difficile were recovered from air sampled immediately following flushing, and then declined 8-fold after 60 min and a further 3-fold after 90 min. Surface contamination with C. difficile occurred within 90 min after flushing, demonstrating that relatively large droplets are released which then contaminate the immediate environment. The mean numbers of droplets emitted upon flushing by the lidless toilets in clinical areas were 15-47, depending on design. C. difficile aerosolization and surrounding environmental contamination occur when a lidless toilet is flushed.

Lidless conventional toilets increase the risk of C. difficile environmental contamination, and we suggest that their use is discouraged, particularly in settings where CDI is common.
While coughing, sneezing, vomiting, and aerosolizing procedures (BiPAP and CPAP, endotracheal intubation, airway suction, nebulizer treatments, etc.) undoubtedly contribute heavily to the airborne spread of pathogens, attention continues to be focused on the contributions from toilet flushing.

All of which brings us to a new open access study, published last week in BMC Antimicrobial Resistance & Infection Control called:
Bioaerosol concentrations generated from toilet flushing in a hospital-based patient care setting

Samantha D. Knowlton, Corey L. Boles, Eli N. Perencevich, Daniel J. Diekema, Matthew W. Nonnenmann and CDC Epicenters Program
Antimicrobial Resistance & Infection Control20187:16
© The Author(s). 2018
Received: 25 July 2017 Accepted: 11 January 2018 Published: 26 January 2018 +


In the United States, 1.7 million immunocompromised patients contract a healthcare-associated infection, annually. These infections increase morbidity, mortality and costs of care. A relatively unexplored route of transmission is the generation of bioaerosols during patient care. Transmission of pathogenic microorganisms may result from inhalation or surface contamination of bioaerosols. The toilet flushing of patient fecal waste may be a source of bioaerosols. To date, no study has investigated bioaerosol concentrations from flushing fecal wastes during patient care.


Particle and bioaerosol concentrations were measured in hospital bathrooms across three sampling conditions; no waste no flush, no waste with flush, and fecal waste with flush. Particle and bioaerosol concentrations were measured with a particle counter bioaerosol sampler both before after a toilet flushing event at distances of 0.15, 0.5, and 1 m from the toilet for 5, 10, 15 min.


Particle concentrations measured before and after the flush were found to be significantly different (0.3–10 μm). Bioaerosol concentrations when flushing fecal waste were found to be significantly greater than background concentrations (p-value = 0.005). However, the bioaerosol concentrations were not different across time (p-value = 0.977) or distance (p-value = 0.911) from the toilet, suggesting that aerosols generated may remain for longer than 30 min post flush. Toilets produce aerosol particles when flushed, with the majority of the particles being 0.3 μm in diameter. The particles aerosolized include microorganisms remaining from previous use or from fecal wastes. Differences in bioaerosol concentrations across conditions also suggest that toilet flushing is a source of bioaerosols that may result in transmission of pathogenic microorganisms.

This study is the first to quantify particles and bioaerosols produced from flushing a hospital toilet during routine patient care. Future studies are needed targeting pathogens associated with gastrointestinal illness and evaluating aerosol exposure reduction interventions.
        (Continue . . . )

While this study confirms the creation of bioaerosols from the flushing of toilets (and even from the subsequent `clean' flushing of a previously used toilet) - and suggests this may result in the transmission of pathogenic aerosols - it doesn't quantify the risk to human health.
It does suggest that closing the lid before, or stepping away quickly after flushing might be worth considering. At least until we learn more about the potential risks involved.
And if all of this isn't enough for this Toilet Bowl Sunday, last December, a paper was published on concerns over the aerosolization of pathogens, especially Legionella pneumophila, from using reclaimed water for toilet flushing, irrigation, and cooling towers. 
Water Research
13 December 2017
Health risks from exposure to Legionella in reclaimed water aerosols: Toilet flushing, spray irrigation, and cooling towers

T. Hamiltonb William Johnsonc PatrickJ jembac ZiaBukharic Mark Le Chevallierc Charles N. Haasa

• Legionella risks for toilet models exceeded drinking water benchmarks in some cases.
• Legionella risks are non-trivial at potentially large distances for long range models.
• Concentration of Legionella was the most influential model parameter in all models.
• Other management practices can be applied to reduce theoretical setback distances needed. 

While it may be surprising to some that in 2018 we still don't have solid answers as to the health risk from - or the best ways to mitigate - toilet plume aerosols, the same can be said about ubiquitous respiratory viruses like colds and flus.

Last October, in EID Journal: Evidence-Based Options for Controlling Respiratory Virus Transmission, we looked at a paper by some of the top scientists in the field, who wrote:
Surprisingly, little is known about the mechanisms by which these viruses are transmitted; much of what is believed to be known is based on dogma. Such knowledge gaps include the relative importance of contact, fomite, and airborne (large droplet versus small droplet) spread; how environmental factors affect different modes of transmission; the aerobiology of virus transmission; the role of viral “quasi-species” and fitness landscape in transmission (6); and viral and host determinants of adaptation of animal viruses for transmission in humans (7,8). 
For those of us who have been forced to make do with less modern conveniences, the flush toilet is a wonderful device, but it isn't without its drawbacks.

Or blow backs, for that matter.

1 comment:

Anonymous said...

Great post! The research findings are not surprising for anyone who has used a hospital toilet (some at the top hospitals of the nation are so strong that they spray not only aerosols, but water into the room...). I've often wondered why hospital toilets, in particular don't include lids.