Flushing public toilets could be more dangerous than you think; study reveals shocking health risks

Ever wondered what happens when you flush a public restroom toilet? Turns out, it's not just water swirling down the drain, it's also sending a cloud of invisible bacteria into the air. A recent study reveals that each flush releases germ-laden droplets that could pose health risks, and some toilet designs make it even worse. (Also read: Stop infections before they start: Must-know safety tips for women using public restrooms )

How toilets spread airborne bacteria

Researchers from China University of Geosciences investigated how different toilets and ventilation systems impact the spread of airborne bacteria. They focused on two common culprits, Staphylococcus aureus, often found on the skin and in airways, and E. coli, a bacteria that normally lives in the intestines. The findings might just make you rethink your next restroom visit.

A study in Risk Analysis compared squat toilets to bidet-style ones, finding that squat toilets spread more bacteria—2.6 times more S. aureus and 1.4 times more E. coli. The design of squat toilets, with their lower height and smaller bowl walls, allows more droplets to escape. Surprisingly, a second flush can release even more bacteria—1.8 times more S. aureus and 1.4 times more E. coli—suggesting multiple flushes may increase, rather than decrease, exposure to harmful germs.

Why size of particles and ventilation matters

The size of these airborne water droplets plays a key role in health risks. Researchers found that most bacteria-laden droplets were under 4.7 micrometres, tiny enough to stay suspended in the air and be inhaled deep into the lungs. Around 55-70% of S. aureus and 52-62% of E. coli droplets fell into this concerning category.

Ventilation proved to be a game-changer. Running exhaust fans reduced airborne bacteria by up to 2.2 times, highlighting the importance of airflow in public restrooms. Alarmingly, in many scenarios, bacterial concentrations exceeded WHO safety guidelines, posing infection risks, especially for those with weaker immune systems. However, with proper ventilation, these risks dropped significantly.

Simple changes can reduce health risks

Since public restrooms experience heavy foot traffic, even small changes could significantly cut down health risks.

• Swapping squat toilets for bidet-style options could reduce bacterial spread.
• Keeping ventilation systems in top shape can dramatically lower airborne bacteria.
• Rethinking the habit of multiple flushes might prevent unnecessary bioaerosol release.

Lead author Wajid Ali, a PhD student in environmental studies at China University of Geosciences, emphasizes the risks: " “Enhancing ventilation systems by optimizing exhaust fan efficiency and air exchange rates can effectively reduce bioaerosol concentrations and exposure risks for the public.”

How to stay safe in public restroom

If you’re using a public restroom, the study suggests a few easy precautions to minimize exposure:

• Pick a stall with good ventilation if possible.
• Avoid multiple flushes unless absolutely necessary.
• Wait a few moments before entering a stall if someone just flushed.

This research highlights how even routine actions, like flushing, can have unexpected health risks. As public spaces continue to evolve, recognising and addressing these invisible hazards is key to keeping everyone safe.

Note to readers: This article is for informational purposes only and not a substitute for professional medical advice. Always seek the advice of your doctor with any questions about a medical condition.