Flushing the Toilet Can Propel Germs High Enough to Reach Your ‘Breathing Zone’

Previous studies have shown that toilet flushing generates aerosols and bioaerosols (airborne biological particles, including microorganisms). The new research review provides a “clearer picture of how far these aerosols can travel, how small they can be, and what factors may increase their generation,” says lead author Lira Adiyani, a PhD candidate at Flinders University in Adelaide, Australia.

“The evidence shows that toilet-generated aerosols can disperse beyond the immediate area of the toilet, and some are small enough to be inhaled and potentially enter the respiratory tract,” she says.

What Actually Happens When You Flush a Toilet?

Toilet flushing is a “surprisingly energetic process,” says John Crimaldi, PhD, a professor of hydrology, water resources, and environmental fluid mechanics at the University of Colorado Boulder. Dr. Crimaldi was not involved with the latest study, but he has researched the aerosol plumes from flushing toilets.

When you flush, jets of water enter the toilet bowl, collide with the water (and waste), and produce a “fairly violent ejection of aerosol particles,” he explains. These aerosol plumes move quickly over large areas and are invisible to the naked eye.

Toilet Aerosols Can Be Small Enough to Reach Our Lungs

The new review, published in Science of the Total Environment, examined 22 studies focusing on factors influencing toilet aerosols and bioaerosols, including toilet design, target microorganisms, and air sampling methods.

Researchers found that toilet flushing can “generate aerosols that disperse beyond the immediate area of the toilet,” Adiyani says.

Across the studies, aerosols were detected up to 163 centimeters (more than 5 feet) above the floor level and up to 150 centimeters (just under 5 feet) away from the toilet. Some studies reported aerosol particles as tiny as 3 micrometers or less, small enough to potentially be inhaled and enter the respiratory tract.

The review also found that the amount of germs in toilet aerosol plumes increased when toilet bowls themselves were dirtier. The water volume in the toilet affected how many germs ended up in the air, too, with aerosol and bioaerosol levels increasing about 1.3-fold for each additional liter of water used per flush.

“These findings help us better understand toilet flushing as a potential pathway for exposure to microorganisms and provide useful evidence for future quantitative microbial risk assessments to better determine the potential risk of infection associated with this exposure,” Adiyani says.

Should You Worry About Germs From Flushing Your Toilet?

“Toilets unquestionably spew large amounts of aerosols into the air,” Crimaldi says, but it’s unclear whether this poses a health risk. “There’s a very big difference between exposure and transmission.”

It’s important to be aware that aerosols from a flushed toilet can reach as high as your nose and mouth and potentially be inhaled, but it doesn’t mean an illness or infection will happen, Adiyani says, only that there’s the potential for exposure to microorganisms.

“The actual risk depends on several factors, including the type and concentration of microorganisms present, the amount of exposure, and a person’s susceptibility to infection,” she says. This may be particularly relevant for people with weakened immune systems.

How to Make Toilet Flushing More Hygienic

It may be difficult to prevent toilet aerosol plumes from circulating in your bathroom, but there are some ways to minimize the impact:

• Close the toilet lid before flushing. However, Crimaldi says plumes can still escape through gaps between the lid and the top of the toilet.
• Use the bathroom exhaust fan to improve ventilation.
• Wash your hands after using the bathroom.
• Clean your toilet and surrounding surfaces regularly. It’s important to note that the study didn’t determine a specific cleaning frequency.