There is a frequently repeated statistic on the internet: your cell phone is 10 times dirtier than a toilet seat. It’s all over the web, and it’s commonly attributed to “scientists at the University of Arizona.”
I decided to find the source of this claim. It sounded like misinformation, but it deserves an investigation.
Is a toilet seat even a valid measure of dirtiness? As a microbiome scientist, I know that the presence of bacteria isn’t a dangerous sign on their own. I suspect that this fact is scaremongering, disseminated in part to sell phone disinfecting gadgets.
To figure out where these claims even started, we turn to the Internet Archive, which saves old snapshots of websites — even after the original page is deleted. A lot of these sources aren’t publicly available today.
Important missing context from the original quote
A number of sources of this “dirty cell phone” claim attribute it to research from scientists at Arizona. (Sometimes it’s University of Arizona, sometimes, it’s Arizona State University — these are different places.) Most of the sources don’t provide any further context nor any names nor links to any source material.
The original claim actually came from Charles P. Gerba, a professor of environmental science at the University of Arizona. He made a statement about this in a small article for a defunct site called MyHealthNewsDaily, published Sept. 15, 2012.
(The original article is no longer available — nor does MyHealthNewsDaily exist any longer. It’s only viewable through the Wayback Machine on the Internet Archive.)
But Gerba goes on to add critical additional context:
However, the amount of germs on a phone isn’t a problem — it’s the sharing of phones between people. Without sharing, each phone carries just one set of germs, and won’t get its owner sick[.]
There’s no study cited, so I reached out to Gerba to see if he could provide context. He told me that this “10x the germs” came from some research that never ended up being published, looking at bacterial tests of 200 cell phones from members of the general public.
The comparison of cell phone germ counts was to a 1998 study, “Reduction of faecal coliform, coliform and heterotrophic plate count bacteria in the household kitchen and bathroom by disinfection with hypochlorite cleaners,” which measured bacterial levels on different surfaces in the house. That study was originally focused on the effectiveness of cleaning agents.
Gerba didn’t have exact counts of how many bacteria were on the cell phones, but other studies, such as this one looking at the phones of high school students, do identify bacteria that are present.
Do these bacteria actually matter?
Given my line of work, I’m very aware that just about every surface we touch is coated with bacteria. There are bacteria floating in the air around us, on our skin, in our mouths. There is no escaping from bacteria.
But most of these bacteria don’t pose an immediate threat. And as Prof. Gerba noted, re-exposing yourself to the same bacteria that you’re carrying with you anyway won’t make you sick.
For most of us, this is also the case with our phones. You touch your phone, you touch your mouth, you touch the sandwich you’re eating… you’re not introducing new germs.
However, as studies have noted, there are a couple of caveats:
- Food preparation. If you’re working with ingredients that can carry disease-causing bacteria (like raw chicken or raw flour), you might be touching your phone to keep checking the recipe. This can transfer dangerous germs like Salmonella or Listeria to your phone.
- In the bathroom. Yes, you can get sick from your own poop; bacteria that are fine in your intestines can cause illness if they spread to other areas like the mouth or an open cut or wound. And it’s also an environment where you can be exposed to other peoples’ bacteria. You might wash your hands, but your phone could carry bacteria out from the bathroom.
But oddly enough, toilet seats can be… surprisingly clean.
Toilet seats are, in many cases, cleaned more often than other household objects (like doorknobs or computer keyboards), and their slick surface doesn’t provide a good home for germs to stick around. One estimate suggests that a typical toilet seat only has about 50 bacteria per square inch.
(And do you know who provided that estimate? That’s right, Professor Charles Gerba! It all comes back around.)
Should I sterilize my phone?
Phone sanitization has always been a thing, but it was pushed to new heights in the early days of COVID-19. The FCC’s guide to phone sanitization suggests it may help prevent the spread of COVID, but that page was last updated in May 2020. It was months later before evidence demonstrated that COVID was mainly spread through the air, not from touching surfaces.
A lot of search results say you “should sanitize your phone,” but they also tend to cite unnamed “experts” and are light on actual studies. A July 2020 study searched for documented cases of COVID transmission via phone and came up empty: there were zero documented cases since the pandemic began at the start of the year.
Overall, sanitizing your phone is recommended if you:
- Work around food, such as in a kitchen
- Work in a hospital or other medical setting
- Interact regularly with individuals with compromised immune systems
- Regularly share your phone or let others handle it
But for most of us, sanitizing a phone won’t significantly reduce our rates of getting sick. We also touch our phones so frequently that even daily sanitization wouldn’t prevent all opportunities for disease transmission. It’s much better to wash your hands than your phone.
Bacterial counts can make for a scary number, but “more bacteria on a surface” does not translate directly into an increased likelihood of getting sick. Yes, your phone has far more bacteria on it than your toilet seat, but so does that cutting board in your kitchen — 200x more (versus only 10x more on your phone), and you eat food from there!
If it helps you feel better, you could get a UV device to sanitize your phone, but it’s likely not going to make a big difference in keeping you from getting sick. Germs are spread through the air and when you transfer germs to your food from dirty hands.
Instead of committing to sanitizing your phone, grab a mask for when you’re in public — or just make sure to wash your hands after every bathroom visit.