Close the toilet lid when you flush

As a father of 5 daughters, I have been sufficiently instructed in leaving the toilet seat – and lid – down.

But is it important to close the lid before flushing?

It’s a random question that came out of nowhere, but Schaffner provided a link to a possible answer.

Caroline Picard of Good Housekeeping writes that with one little flick of the lever, the swirling water whisks away your business … down into the sewer but also up into the air, all over your counters, and even in your towels and toothbrushes. Yuck.

In the field of science (yep, there’s science about this!), it’s called the “toilet plume,” a.k.a. the germs and fecal matter that get shot upwards — up to 15 feet high! — with the force created by the sudden gush of water.

The first foray into this poop-tastic piece of physics happened during the ’50s, with a particularly groundbreaking (and skin-crawling) piece of research emerging in 1975, when Charles P. Gerba published a study in the journal Applied Microbiology. Gerba found that a single flush sent E. coli airborne and viable for at least four to six hours later. That means your 7-year-old could flush the toilet with the lid up after he gets home from school and harmful bacteria would still be floating around your bathroom at dinnertime.

Today’s low-flow toilets might not produce such gag-inducing results, but a 2013 review of studies done on the topic still came to a pretty horrifying conclusion. “Research suggests that this toilet plume could play an important role in the transmission of infectious diseases for which the pathogen is shed in feces or vomit,” the scientists wrote in the American Journal of Infection Control. “The possible role of toilet plume in airborne transmission of norovirus, SARS, and pandemic influenza is of particular interest.”

One 2012 study found that leaving the lid up versus down led to 12 times as much diarrhea-inducing bacterium Clostridium difficile in the air.

Lifting the lid on toilet plume aerosol: A literature review with suggestions for future research

David L. Johnson, PhDa,*, Kenneth R. Mead, PhDb, Robert A. Lynch, PhDa, and Deborah V.L. Hirst, PhDb
aDepartment of Occupational and Environmental Health, University of Oklahoma College of Public Health, Oklahoma City, OK

Division of Applied Research and Technology, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, OH

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.


Aerosol; Droplet nuclei; Airborne infection; Bioaerosol

An association between inhalable bioaerosols produced from disturbed sewage and the transmission of infectious disease has been proposed for over 100 years. However, little study has been devoted to characterizing the potential risks posed by the “toilet plume”

*Address correspondence to David L. Johnson, PhD, Department of Occupational and Environmental Health, University of Oklahoma College of Public Health, P.O. Box 26901, Room 431, Oklahoma City, OK 73126-0901. (D.L. Johnson).

Conflicts of interest: None to report.

The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health. Mention of company names and/or products does not constitute endorsement by the Centers for Disease Control and Prevention.