A toilet plume is the dispersal of microscopic particles as a result of flushing a toilet. Normal use of a toilet by healthy individuals is considered unlikely to be a major health risk. However this dynamic changes if an individual is fighting an illness and currently shedding out a virulent pathogen in their urine, feces or vomitus. There is indirect evidence that specific pathogens such as norovirus or SARS coronavirus could potentially be spread by toilet aerosols, but as of 2015, no direct experimental studies had clearly demonstrated or refuted actual disease transmission from toilet aerosols. It has been hypothesized that dispersal of pathogens may be reduced by closing the toilet lid before flushing, and by using toilets with lower flush energy.

Possible effects on disease transmission

A video discussing research on the health hazards of aerosol toilet plumes

There is indirect evidence that toilet aerosol can be a vector for diseases that involve acute gastroenteritis with the shedding of large numbers of pathogens through feces and vomit, with normal use of a toilet unlikely to be a major health risk.[1] For example, some epidemiological studies indicate transmission of norovirus in passenger airplanes[2] and ships,[3] and SARS coronavirus through a contaminated building sewage system,[4] via contaminated toilets rather than other routes.[5] The feces and vomit of infected people can contain high concentrations of pathogens, many of which are known to survive on surfaces for weeks or months, and toilets may continue to produce contaminated toilet plumes over multiple successive flushes. Some other pathogens speculatively identified as being of potential concern for these reasons include gram-positive MRSA, Mycobacterium tuberculosis, and the pandemic H1N1/09 virus commonly known as "swine flu".[5]

There is no direct experimental evidence on disease transmission by toilet aerosols. Whether or not aerosols can contain norovirus, SARS coronavirus, or other pathogens has not been directly measured as of 2015.[5][6] The combination of cleaning and disinfecting surfaces is usually effective at removing contamination, although some pathogens such as norovirus[7] have an apparent resistance to these techniques.[5]

Mechanism

Aerosol droplets produced by flushing the toilet can mix with the air of the room,[6] larger droplets will settle on a surface before they can dry,[5][8] and can contaminate surfaces such as the toilet seat and handle, which can then be contacted by hands.[1] Smaller aerosol particles can become droplet nuclei as a result of evaporation of the water in the droplet; these have negligible settling velocity and are carried by natural air currents.[8] Disease transmission through droplet nuclei is not a concern for many pathogens, because they are not excreted in feces or vomit, or are susceptible to drying.[5] The critical size dividing these dispersal modes depends on the evaporation rate and vertical distance between the toilet and the surface in question.[8]

Experiments to test bioaerosol production usually involve seeding a toilet with bacteria or virus particles,[5] or fluorescent microparticles,[8] and then testing for their presence on nearby surfaces and in the air, after varying amounts of time.[5][8] The amount of bioaerosol varies with the type of flush toilet. Older wash-down toilet designs produce more bioaerosol than modern siphoning toilets.[5] Among modern toilets, bioaerosol production increases as qualitative flush energy increases, from low-flush gravity-flow toilets common in residences, to pressure-assisted toilets, to vigorous flushometer toilets often found in public restrooms.[8]

One study found that lowering the toilet lid prevented dispersion of large droplets, and reduced the airborne bacteria concentrations by a factor of 12. The study recommended discouraging the use of lidless toilets, and thus contradicts the US Uniform Plumbing Code specifications for public toilets.[5][9]

History

Experiments on the bioaerosol content of toilet plumes were first performed in the 1950s.[5] A 1975 study by Charles P. Gerba popularized the concept of disease transmission through toilet plumes.[10] The term "toilet plume" was in use before 1999.[11]

References

  1. ^ a b Barker, J.; Jones, M. V. (2005). "The potential spread of infection caused by aerosol contamination of surfaces after flushing a domestic toilet". Journal of Applied Microbiology. 99 (2): 339–347. doi:10.1111/j.1365-2672.2005.02610.x. ISSN 1364-5072. PMID 16033465. S2CID 25625899.
  2. ^ Widdowson, Marc-Alain; Glass, Roger; Monroe, Steve; Beard, R. Suzanne; Bateman, John W.; Lurie, Perrianne; Johnson, Caroline (20 April 2005). "Probable transmission of norovirus on an airplane". JAMA. 293 (15): 1859–1860. doi:10.1001/jama.293.15.1859. ISSN 1538-3598. PMID 15840859.
  3. ^ Ho, Mei-Shang; Monroe, Stephan S.; Stine, Sarah; Cubitt, David; Glass, Roger I.; Madore, H. Paul; Pinsky, Paul F.; Ashley, Charles; Caul, E.O. (21 October 1989). "Viral Gastroenteritis Aboard a Cruise Ship". The Lancet. 334 (8669): 961–965. doi:10.1016/s0140-6736(89)90964-1. ISSN 0140-6736. PMID 2571872. S2CID 29429652.
  4. ^ "Outbreak of Severe Acute Respiratory Syndrome (SARS) at Amoy Gardens, Kowloon Bay, Hong Kong: Main Findings of the Investigation" (PDF). Hong Kong Special Administrative Region Department of Health. 29 March 2011. Archived (PDF) from the original on 20 April 2017.
  5. ^ a b c d e f g h i j k Johnson, David L.; Mead, Kenneth R.; Lynch, Robert A.; Hirst, Deborah V.L. (March 2013). "Lifting the lid on toilet plume aerosol: A literature review with suggestions for future research". American Journal of Infection Control. 41 (3): 254–258. doi:10.1016/j.ajic.2012.04.330. PMC 4692156. PMID 23040490.
  6. ^ a b Jones, RM; Brosseau, L. M. (May 2015). "Aerosol transmission of infectious disease". Journal of Occupational and Environmental Medicine. 57 (5): 501–8. doi:10.1097/JOM.0000000000000448. PMID 25816216. S2CID 11166016.
  7. ^ Barker, J.; Vipond, I. B.; Bloomfield, S. F. (1 September 2004). "Effects of cleaning and disinfection in reducing the spread of Norovirus contamination via environmental surfaces". The Journal of Hospital Infection. 58 (1): 42–49. doi:10.1016/j.jhin.2004.04.021. ISSN 0195-6701. PMID 15350713.
  8. ^ a b c d e f Johnson, David; Lynch, Robert; Marshall, Charles; Mead, Kenneth; Hirst, Deborah (1 September 2013). "Aerosol Generation by Modern Flush Toilets". Aerosol Science and Technology. 47 (9): 1047–1057. Bibcode:2013AerST..47.1047J. doi:10.1080/02786826.2013.814911. ISSN 0278-6826. PMC 4666014. PMID 26635429. Archived from the original on 15 April 2017.
  9. ^ Best, E. L.; Sandoe, J. a. T.; Wilcox, M. H. (1 January 2012). "Potential for aerosolization of Clostridium difficile after flushing toilets: the role of toilet lids in reducing environmental contamination risk". The Journal of Hospital Infection. 80 (1): 1–5. doi:10.1016/j.jhin.2011.08.010. ISSN 1532-2939. PMID 22137761.
  10. ^ Ray, C. Claiborne (26 November 2012). "Does Flushing a Toilet Release Germs Into the Air?". The New York Times. ISSN 0362-4331. Archived from the original on 23 June 2016. Retrieved 15 July 2016.
  11. ^ Adams, Cecil (15 April 1999). "The Straight Dope". Chicago Reader. Archived from the original on 20 April 2017. Retrieved 20 April 2017.
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