A study has found that pathogens spread into the air when flushing toilets. Fortunately, using an exhaust fan can significantly reduce this risk.
Researchers from the China University of Geosciences noted on the 18th in the international journal "Risk Analysis" that "the concentration of Escherichia coli and Staphylococcus aureus released into the air after toilet use exceeds the acceptable level set by the Centers for Disease Control and Prevention (CDC) in the United States."
The researchers conducted experiments in two restrooms located in office buildings in China. One had a squat toilet, while the other was equipped with a bidet toilet. They measured the emission of bacteria-laden aerosols based on the flushing method and ventilation conditions.
According to the analysis, both types of toilets released bacterial aerosols, with the squat toilet releasing more than the bidet toilet. The squat toilet emitted 42%-62% more Staphylococcus aureus and 16%-27% more Escherichia coli compared to the bidet. Professor Kim Jae-yeol of Chungang University stated, "It is known that closing the lid is advisable due to aerosols generated when flushing the toilet," adding, "The squat toilet appears to spread bacteria more easily since it lacks a lid."
The researchers also confirmed that the credit entry affects the concentration of bacteria. When flushing without a credit entry, the levels of Staphylococcus aureus were found to be 25%-43% lower, and Escherichia coli levels were 16%-27% lower compared to when a credit entry was present.
To prevent pathogen release, it is advisable to close the lid before flushing. Researchers noted that using an exhaust fan could be a solution. According to the researchers, operating the exhaust fan reduces the risk of aerosol release by one tenth. Wajid Ali, a researcher at the China University of Geosciences, said, "Improving the ventilation system in public restrooms can effectively reduce exposure to bacterial aerosols."
Professor Kim Jae-yeol advised that using an exhaust fan at home could also be effective. He said, "Home restrooms are mostly small and poorly ventilated, which may pose an even greater risk," adding, "Using an exhaust fan in home restrooms can help reduce bacterial aerosols."
References
Risk Analysis (2025), DOI: https://doi.org/10.1111/risa.70000