- Scientists used lasers to show what really happens when you flush the toilet.
- Images showed a tall plume of tiny drops of toilet water being blasted into the air.
- It’s not clear whether the plumes could carry dangerous microbes, an expert said.
Scientists showed how water spews from the toilet bowl after a flush, using powerful lasers to illustrate what we normally can’t see.
Scientists have known for some time that tiny, invisible drops of water escape the toilet bowl after each flush. But this is the first time scientists have shown this happening in real-time with lasers.
The video below shows droplets shining green as the laser bounces off of them. A cloud of smaller drops, called aerosols, floats further through the air, carrying the toilet water across the lab.
A side-by-side view of the effect shows that these water drops are invisible to the naked eye.
The results of their observations were published in the peer-reviewed journal Scientific Reports on Thursday.
“The very first time we did it, our jaws just dropped,” John Crimaldi, a study author and professor of engineering at the University of Colorado, told Insider.
He said his team “had no idea and no reason to expect” the plumes would go as high and as far as they did.
There may be more than just bad smells in the spray
For now, there’s no reason to be unduly concerned. People go to the bathroom without getting sick all the time.
It’s possible the spray is ferrying microbes around, Joshua Santarpia, a microbiologist at the University of Nebraska Medical Center, told Insider in an email.
The problem is that we just don’t know.
“It is actually incredibly difficult to demonstrate the mode of transmission, much less the source, in most cases,” said Santarpia, who studies the transmission of disease by aerosols.
Scientists think there is good reason to assume toilet plumes could be involved in some outbreaks. But the evidence doesn’t show definitively that toilet water spritzing into the air has caused anyone to get sick.
Lasers reveal aerosols leaving the toilet after every flush.
Until that question is answered, there are simple steps that not only protect you from any potential bad stuff but could improve your bathroom manners.
If there is a lid on the toilet, close it. This limits the height and spread of the larger droplets, Santarpia and Crimaldi said. A fringe benefit is that it should limit the spread of any odors.
Wearing a mask in a public bathroom is also “advisable for a variety of reasons,” said Santarpia.
“Public bathrooms can be confined spaces with highly variable air change rates, so masking protects against human-to-human aerosol transmission, which is more likely in a small, poorly ventilated room, as well as contact with any potentially infectious aerosols from toilet flushing,” he said.
Designing a spray-free toilet
Crimaldi hopes his study will help people rethink toilet design, ventilation, and disinfection.
“If it ain’t broke, why fix it?” Crimaldi said.
“You go to the bathroom, you flush the handle, the stuff disappears, you’re like: ‘boom, works great!’ Then you look at the videos that we took and you’re like: ‘oh, maybe not so great!’,” he said.
The video could also help raise public awareness about this issue so it can be taken more seriously.
For instance, a lot of public buildings in the US don’t have lids on their toilets.
“I can tell you this is fundamentally changed my relationship with toilets. I look at them suspiciously now,” said Crimaldi.
“I can sort of see in my mind’s eye these aerosol clouds that are filling that whole room.”