It is possible to become ill from inhaling tiny airborne particles containing fecal matter, a concept known as fecal aerosol transmission. These invisible fecal aerosols are a recognized route for various pathogens to move from contaminated waste into the air where they can be subsequently breathed in. Understanding how these particles become airborne and the types of microbes they carry is important for mitigating the risks associated with this indirect exposure.
The Mechanics of Fecal Aerosolization
Fecal matter becomes airborne primarily through the “toilet plume,” which is the cloud-like dispersal of potentially infectious particles generated during flushing. The mechanical force of the flushing water creates numerous droplets from the contents of the toilet bowl. This aerosolization is intensified in high-energy flushing systems, such as flushometer toilets often found in public restrooms, which can produce over 145,000 droplets per flush.
The resulting plume contains droplets of varying sizes, with the majority being less than five micrometers in diameter. These small particles can remain suspended in the air for extended periods, sometimes for tens of minutes, and travel on air currents throughout a room. The smallest particles can even evaporate into droplet nuclei, which are light enough to be inhaled deep into the lungs. While the toilet plume is the most well-studied source, the disturbance of dried fecal dust from contaminated surfaces can also contribute to infectious aerosols.
Specific Pathogens Transmitted by Inhaled Particles
The inhalation of fecal aerosols can lead to infection by viruses, bacteria, and protozoa shed in the feces and vomit of an infected person. One frequently implicated pathogen in aerosol transmission is Norovirus, a highly contagious agent responsible for acute gastroenteritis. Norovirus is shed in extremely high concentrations, with an infected person potentially shedding up to 5 billion infectious doses per gram of feces.
The infectious dose for Norovirus is low, estimated to be as few as 18 viral particles, making it highly transmissible through aerosol exposure. Inhaling these airborne viral particles can bypass the body’s initial defenses, leading to symptoms like diarrhea, vomiting, and stomach pain, which typically resolve in one to three days. Bacteria such as Escherichia coli (E. coli) and Salmonella can also survive in these aerosols and contaminate surfaces.
Other microbes shed in feces, including Clostridium difficile (C. difficile) and the SARS coronavirus, have been shown to survive aerosolization. The ability of these pathogens to survive on surfaces for weeks or months after aerosol deposition extends the window of transmission risk. The combination of high pathogen shedding, low infectious dose, and microbial stability makes the inhalation route a significant factor in disease outbreaks, particularly in crowded or poorly ventilated settings.
Practical Strategies for Reducing Exposure
The most direct action to reduce the risk of fecal aerosol exposure from flushing is to close the toilet lid before flushing. Closing the lid significantly reduces the total number of particles released into the air and deposited on surrounding surfaces. While a lid may not completely eliminate the escape of the smallest viral particles, it substantially suppresses the overall plume dispersion.
Improving ventilation in bathrooms is an important environmental control measure, as air movement helps remove suspended aerosols from the immediate area. Utilizing exhaust fans during and shortly after flushing can mitigate particle accumulation, especially in heavily used public or shared restrooms. Frequent and thorough cleaning of bathroom surfaces with appropriate disinfectants is necessary to eliminate pathogens that settle from the air. This includes high-touch areas like the toilet seat, handle, and sink fixtures.
Personal hygiene practices, particularly proper handwashing with soap and water for at least twenty seconds, remain a foundational defense against the hand-to-mouth transfer of aerosolized pathogens. Keeping personal items, such as toothbrushes, stored away from the toilet area limits the potential for surface contamination. These combined efforts create layers of protection against inhaling and ingesting pathogens shed in fecal matter.