Study: Flushing Toilets Release Pathogen-Laden Aerosols Into Breathing Zone; Closing Lid May Not Fully Prevent Escape

The researchers found that higher levels of microbes in the water and stronger turbulence during flushing increased the volume of suspended particles. However, the effects of bathroom ventilation and whether the lid was up or down were unclear. Despite this uncertainty, lead author and PhD student Lira Adiyani said she would still recommend closing the toilet lid after use as a precautionary measure, while recognizing that it does not completely prevent aerosols from escaping.

In their report, the researchers wrote that the impact of indoor aerosols has been understudied despite the risk of infection. They said this has important implications for risk assessment, building design and infection control, particularly in an era of water security pressures and emerging infectious diseases. Indoor aerosols can penetrate deep into the respiratory tract when inhaled, providing a direct exposure pathway, they added.

Co-author and environmental health professor Harriet Whiley said people should not be worried in their own homes unless someone there is immunocompromised. She said the team is working on protecting the most vulnerable through good design in places such as hospitals and aged care environments. The researchers are increasingly concerned about opportunistic pathogens that can be present in recycled or rainwater, which do not affect healthy people but can be fatal for immunocompromised individuals. Whiley emphasized the need for an effective flush with less volume and less turbulence.

Lotti Tajouri, an associate professor in molecular genetics at Bond and Murdoch universities who was not involved in the study, said bathroom dangers go well beyond the toilet. He warned that every surface in the bathroom, including the door, floor and taps, can be contaminated. He also noted that studies show between 50% and 80% of people use mobile phones in the toilet, with the share nearly 100% among younger generations, and doing so can transfer fecal microorganisms such as salmonella and campylobacter to hands and phones. His advice is to minimize contact with bathroom surfaces.