Health study ranks the most germ-infested everyday items

Being a physician, infection control measures are probably second nature to you. As COVID-19 sweeps the world, you are probably more than aware of the importance of these measures when it comes to public places, hospitals, your office environment, and in interactions with your patients. But, do you realize that even in the safety of your home, infection control measures should come into play?

Your home is full of dirty places and dirty things, harboring bacteria where you’d least expect it. Researchers from NSF International, an independent public health organization, did a study to find out where germs lurk in the average home. They swabbed 30 common items in the households of 22 volunteer families. The news was not good:

Coliform bacteria—including Salmonella and Escherichia coli—are harbingers of potential fecal contamination and were found in 81% of households. Yeast and mold, which can have negative impacts on health, were present in 31% of households. Finally, researchers found Staphylococcus aureus in over 5% of households.

Here’s a list of some common household items you touch each day that—if not properly sanitized—are veritable hotbeds of germs and pathogens: 

Kitchen sponge/rag. According to NSF International, the germiest thing in your house isn’t the toilet—or anything else in the bathroom, for that matter. It’s something you probably touch several times a day, and even use to clean: your kitchen sponge. Of the 81% of families that had coliform bacteria in their homes, over 75% had the bacteria on their dish sponges or rags. But, that’s not all that’s lurking there. Of the 31% households in which yeast and mold were present, 86% had sponges that held these fungi. And, in homes where S. aureus was found, 18% had the bacteria on their dish sponge/rags. Shockingly, the researchers found 363,631,038 average normalized microorganisms per gram of sponge!

These study findings support those from another study, in which researchers found that as many as 200 million bacteria could be living in just 1 square inch of a sponge! The warm, moist environment your sponge provides is a breeding ground for germs. Add that to all the nooks and crannies that make a sponge—well—a sponge, and your kitchen sponge is literally a condominium for germs.

Kitchen hand towels. For much the same reasons sponges are breeding grounds for all sorts of microorganisms, dish towels are another of the dirtiest things you touch every day. Researchers collected 82 kitchen hand towels from households in 5 major cities in the United States and Canada. They found coliform bacteria in 89.0% and E. coli in 25.6% of towels. The E. coli presence, they noted, was related to the frequency (or infrequency) of washing the towels.

Kitchen sink. Next to kitchen sponges and hand towels, the kitchen sink is one the dirtiest places in a home. Kitchen sinks were found to house 11,381,285 average normalized microorganisms per 10 square cm. Coliform bacteria were found in nearly one-half (45%) of kitchen sinks in homes where coliforms were present. Yeast and mold were also found in 27% of kitchen sinks. The only good news is that S. aureus was found in none of them.

Coffee machine. Believe it or not, the inside of your coffee machine—the reservoir, specifically—is one of the germiest places, and can play host to 548,270 normalized microorganisms per 10 square cm. It gets warm and stays damp—the perfect environment for yeast and mold. In NSF International’s study, yeast and mold were found in 50% of the coffee reservoirs and coliforms in 9%.

All the water that runs through the coffee maker also leaves mineral deposits inside where germs can grow. According to NSF International, it’s not as dirty as your pet bowl but dirtier than the handle of your bathroom faucet, in fact. Imagine how exponentially dirtier the office coffee machine is. Gross!

Toothbrush holder. Moving on to the bathroom, you may be surprised to learn that one of its germiest locales is your toothbrush holder. That’s pretty disgusting considering it holds something you put in your mouth a few times a day—your toothbrush. Although researchers didn’t find as many coliforms in the bathroom as in the kitchen, 27% of toothbrush holders did test positive for them. That’s kind of surprising—and good news—considering the close proximity of the household toilet.

But, almost one-third of homes had yeast and mold present, with 64% harboring them in the toothbrush holder. And, S. aureus—present in the over 5% of homes—was found in 14% of toothbrushes, with 2,465,876 average normalized microorganisms per 10 square cm.

Pet bowls and pet toys. Your beloved family pet’s bowl is the fourth germiest thing in your house, with 1,476,612 average normalized microorganisms per 10 square cm, according to NSF International. S. aureus was found in the pet bowls of 14% of households, coliforms in 18%, and yeast and mold in 45%. And although E. coli was found in less than 1% of all surfaces sampled in the study, it was present in the pet bowls of two families. Pet toys are also notoriously dirty, and researchers found that 55% of families had yeast and mold on their pet toys, 23% had S. aureus, and 23% had coliforms.

Money. No list of germiest items would be complete without mentioning money. Did you know that the average dollar bill in New York City is home to hundreds of species of microorganisms? These include dermal bacteria, vaginal bacteria, oral microbes, pet DNA, viruses, and even drugs, according to researchers of a recent study. They swabbed circulating $1 bills from an NYC bank and used shotgun metagenomic sequencing to profile the microorganisms on their surfaces.

“Our results suggest that money amalgamates DNA from sources inhabiting the human microbiome, food, and other environmental inputs, some of which can be recovered as viable organisms. These monetary communities may be maintained through contact with human skin, and DNA obtained from money may provide a record of human behavior and health. Understanding these microbial profiles is especially relevant to public health as money could potentially mediate interpersonal transfer of microbes,” concluded the authors.

Think of that next time you pull out your wallet!

Use this list to arm yourself against infectious pathogens—even in your home. Pay particular attention to the cleanliness of these items, and monitor (and sanitize!) them regularly. The outside world is not the only place where you can be exposed to germs and bacteria that could cause illnesses.