Experts Weigh In On Whether You Should Flush The Toilet With The Seat Up Or Down

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A recent study published on January 24 in the American Journal of Infection Control suggests that closing the toilet lid before flushing does not decrease the spread of viral particles.

Instead, researchers found that the most effective method for reducing viral particles involves disinfection the toilet, toilet water, and surrounding surfaces.

However, does this imply that closing the lid before flushing serves no purpose? Not necessarily. Charles P. Gerba, PhD, a senior author and professor virology at the University of Arizona in Tucson, suggests that while closing the lid may not mitigate viral transmission, it could potentially hinder the spread of bacteria.

What Exactly Happens When You Flush?

When a toilet is flushed, millions of aerosolized particles, invisible to the naked eye, are rapidly propelled into the air, creating what scientists refer to as a “toilet plume.” These particles can be launched upward and outward from the bowl, reaching distances of five feet or more. If an individual is sick and contagious germs land in the toilet bowl, flushing can disperse these germs onto various surfaces within the bathroom, including floors, walls, sinks, and other nearby areas, as outlined by the study authors.

Closing the Lid Before Flushing Doesn’t Reduce the Spread of Viral Pathogens, Says Researchers

While previous research has shown that closing the toilet lid can reduce the spread of bacteria, it has remained uncertain whether the same effect applies to viral pathogens, which are typically smaller than bacteria. To address this question, investigators conducted experiments to analyze the spread of viral particles during flushing, with both open and closed toilet lids. They utilized a non-harmful virus as a stand-in for more dangerous pathogens, seeding toilets with varying concentrations of the virus and subsequently collecting samples from the toilet bowl water and surfaces on the toilet, floor, and walls.

Additionally, the effectiveness of disinfecting the toilet with a disinfectant was assessed through an analysis involving samples collected from the toilet bowl brush and its caddy. While the study encompassed both household and public toilets, the impact of toilet lid closure could only be evaluated with household toilets, as public toilets typically lack lids.

Results from the experiments conducted with household toilets revealed no significant difference in the amount of virus collected from surfaces on the toilet or the surrounding floor, regardless of whether the toilet lid was open or closed during flushing. Minimal viral contamination was observed on the surrounding walls in both scenarios, with the toilet seat emerging as the most contaminated surface. Similar patterns of contamination were observed in the analysis of public toilets.

Interestingly, closing the toilet lid during flushing appeared to alter the direction of the aerosol plume. In instances of closed-lid flushing, floor surfaces located in front of and to the left of the toilet exhibited higher levels of contamination, while those to the right of the toilet were less contaminated compared to flushing with an open lid.

Why Do Viral Particles Escape the Toilet Lid But Bacterial Don’t?

Many wonder why it is that viral particles escape the toilet lid, however bacterial ones do not. According to researcher and professor at UW Medicine in Seattle, Ferric Fang, MD, who was not involved in the study, said “Bacteria are much larger than viruses and tend to be associated with larger droplets, which do not remain airborne as long or travel as far. Basically, viruses aerosolize more readily than bacteria.”

Researchers also investigated the impact of toilet cleaning methods, comparing those with and without disinfectant. Using only the brush for cleaning resulted in considerable contamination residue, whereas employing a disinfectant alongside the brush markedly decreased the presence of virus particles in the toilet.

Furthermore, the introduction of disinfectant into the toilet bowl prior to flushing or utilizing disinfectant dispensers within the toilet rank proved to be effective strategies for minimizing contamination caused by flushing. According to the study’s findings, employing a combination of disinfectant and brush led to a reductio in viral contamination on the toilet by over 99.99 percent and on the brush by 97.64 percent.

How Often Should You Clean Your Toilet?

According to the authors, these findings can also be sued to lessen the spread of nasty germs in the home. “We found that cleaning and disinfecting the toilet twice a week is best to limit the spread of viral particles,” Dr. Fang says.

However, Dr. Gerba explains that if someone in the household is sick, specifically those with gastroenteritis – otherwise known as stomach flu – cleaning and disinfecting one to two times a day is a good idea.

“We also recommend using disinfecting wipes on the toilet seat and flush handle, as these surfaces will get contaminated after flushing,” he adds.

How Often Does Illness Caused by Pathogens from Toilet Flushing Occur?

Dr. Fang says that knowing how often pathogens from toilet flushing make people sick is difficult to pinpoint.

“There have been some outbreaks of viral gastroenteritis associated with planes or ships in which using a bathroom was a risk factor for acquiring infection. Also, a cluster of SARS cases in a Hong Kong apartment complex in 2003 was attributed to the generation of toilet aerosols that were carried to other apartments by the ventilation system,” he says.

Dr. Fang state that the role of toilet aerosols in public bathrooms as a significant pathway for COVID-19transmissions remains uncertain. However, simulations have demonstrated that toilet plumes can transport viruses recently excreted in stool, such as SARS-CoV-2, norovirus, and influenza.

Advice from Experts on Lessening the Risk of Infection from Toilet Plume Germs 

As per Dr. Fang, viruses that cause diarrhea have to be swallowed, not inhaled.

“Flushing the toilet can spread these viruses to bathroom surfaces, where they can be picked up on your hands and transferred to your mouth. Disinfecting bathroom environmental surfaces and careful handwashing with soap and water after using the toilet can prevent this from happening,” he says.

Meanwhile, when it comes to COVID-19 concerns, Dr. Fang also explains that getting the most recent vaccine, face mask wearing, proper handwashing, abstinence from cellphone use while in the restroom and spending the least amount of time in the bathroom will help minimize the risk of infection.

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