Parents building registries may notice an unusual item in the ever-growing list of "must have"s for baby: a shopping cart cover.
Cart covers are advertised as a way to protect children from germs coating the average shopping cart, which, according to some recent studies, plays host to more bacteria than a public toilet. But how much health risk is actually posed by a shopping cart? And can a cart cover minimize that risk?
Targeting shopping cart handles
Shopping cart handles began earning a reputation when they made an appearance in a four-year study of environmental surfaces conducted by researchers at the University of Arizona. Bacteria was not the main focus of the study, which mostly tested surfaces in public places (daycare, offices, grocery stores, etc.) for protein and biochemical markers. In other words, the researchers were mainly looking to find bodily substances and viruses that transmit through those substances. But the researchers also took 200 samples from various environmental surfaces and tested them for coliforms, a subgroup of bacteria types generally present in the intestines that are generally good indicators of possible fecal contamination, in addition to protein and biochemical markers. One of these surfaces was shopping cart handles. The study determined that one shopping cart handle out of twenty contained coliforms.
That first study, published in 2005, appears to have inspired other studies of shopping carts. Other researchers began testing environmental surfaces for bacteria commonly found in raw meat and surveying the various ways children might be exposed to it. A 2007 survey of parents whose infants had been infected with campylobacter (the most likely culprit of human diarrheal illnesses) found that children who rode in shopping carts were more likely to be infected with campylobacter than children who had not ridden in carts.
In another study published in 2010, researchers surveyed parents whose children had tested positive for salmonella. Children who had been riding in the back of the cart were more likely to be infected than children who were riding in the front of the cart. Only 10% of the parents surveyed responded that their children had been directly exposed to raw meat, suggesting that the carts themselves might be the site of infection for many kids infected with salmonella.
"More fecal matter than on the toilet"
After these multi-site contamination studies identified shopping carts as a potential hazard, researchers began devoting entire studies to shopping carts alone. A 2012 study of 85 randomly-sampled grocery carts in California found that 72% of the handles contained coliform bacteria. 18 of those cart handles tested positive for the most well-known coliform bacteria, E. coli.
That finding led to headlines like "E. coli found on 50% of shopping carts," which is an overstatement of both the finding and its impact. The "50%" refers to 18 out of 35 cart handles that were given additional testing. It's more reasonable to say that E. coli was found on 50% of carts contaminated with coliforms. The sample size may be too small to know whether or not it is representative of all shopping carts as a whole. Furthermore, the study's authors note that one of the types of tests they attempted did not identify E. coli in any of the samples. They explain that one test may not have detected E. coli because the amount of bacteria was too low. In other words, if one of the tests they conducted found bacteria while another test found none, there might not be sufficient quantities of bacteria to be medically concerning.
The author of that panic-inducing news article actually quotes one of the authors of the California cart-sampling study, Charles Gerba, who explained why shopping cart handles tend to have more bacteria than public restrooms: “That’s because they use disinfecting cleaners in the restrooms. Nobody routinely cleans and disinfects shopping carts.”
What's on the bottom of the cover is on the whole cover
Many parents, understandably panicked by the fear-inducing reports of so many multi-syllabic bacteria, have opted to purchase fabric shopping cart covers in order to protect their children from all of the bacteria reported in the news.
There are two major problems with this approach.
First, there is the problem of installing the cover in the first place. Imagine you are trying to cover a shopping cart while also carrying a child. You are inevitably going to touch the shopping cart in the process. During the trip through the store, you are probably going to touch your child, say, to give them the snack you promised yourself you wouldn't open until you got out of the checkout. So, even though the cover is there, from the moment you touched the cart to install it, you've picked up and transmitted bacteria to the cart cover, to yourself, to the snack, and, therefore, to your child's mouth.
Second, even if you managed not to touch a single square inch of the cart, the bottom of the cover will touch the cart. If the cart is covered in bacteria, so is the bottom of the shopping cart cover. And if bacteria is on the bottom of the cart cover, it'll be on the top eventually.
Although there haven't been any widely-reported studies of bacteria present on cart covers, there have been studies of another object that frequently travels in shopping carts: purses. In 2013, one study of women's purses led to flurry of news articles about purses carry more bacteria than public toilets.
The medical community uses the word "fomite," which comes from the Latin for "tinder," to refer to a non-living object that can carry and readily transmit infectious organisms. Like the shopping cart handles in the previous examples, purses are also fomites that can transport bacteria from bathrooms to shopping carts to cars to kitchen counters.
It's likely that cart covers are also good fomites, because it's likely that they, like purses, are infrequently washed.
Fecal matter is everywhere
Before giving into fear of our purses and shopping carts, it's important to step back and consider the funding sources of these studies. Gerba's work at the University of Arizona has been funded at least in part by Clorox, a company so tied to the concept of germ-fighting that its name is synonymous with bleach. The study in the UK that launched so many reports about 1 in 5 purses harboring dangerous levels of bacteria? The organization behind it was Initial Hygeine, a company that sells different sanitation devices, among them bathroom cleaning equipment.
The organizations supporting these studies don't make the resulting research invalid, but they do suggest that these organizations had something to gain from public perception that our shopping carts and purses are carrying dangerous levels of bacteria. Such studies have inspired not just cart covers, but also patents for shopping cart sanitizing machines, shopping cart handles that repel bacteria, and countless forms of sanitizing wipes. The questions that these studies do not answer is whether those objects are necessarily more dangerous than any other items.
Yes, that cart has more fecal matter on it than a public toilet. Yes, your diaper bag is harboring burgeoning colonies of bacteria.
But so is everything else.
A recent Huffington Post article summarizes the issue nicely by reminding readers that "there's fecal matter on practically everything." The article quotes Kelly Reynolds, a professor of Public Health and the main author of the paper that initiated the concern over bacteria-laden shopping carts. “Given that we all produce and excrete feces," Reynolds says, "fecal matter in the environment is pretty common." Reynolds' advice to those concerned about bacteria is simple: wash your hands and wash your surfaces. That's it. There's no mention of protective devices to ward off bacteria.
The average human body has roughly 30 trillion cells, as well as 40 trillion bacteria. Bacteria is everywhere, and we tend to think about it only when its presence is advertised, as when we read a newspaper report about bacteria-coated purses. If you go looking for bacteria, you're going to find it. But that doesn't mean you are likely to get sick from it.
Bacteria is present on shopping cart handles, and yes, in quantities larger than you'd expect to find in a public restroom. But that's because public restrooms are regularly cleaned, while shopping carts are not. Using a sanitizing wipe before touching the cart handle can bring your cart to bathroom or even better-than-bathroom levels. And even if your kid licks a dirty shopping cart handle, most of the resulting bacteria are relatively safe. Remember that E. coli, common fixture of news terror though it may be, already exists in our intestines and is in many cases harmless.
If you've bought that shopping cart cover because you want to protect your kid's adorable clothes from whatever the last kid left behind, it may work as a stain protector. If your cover is full of distractions to help you shop in peace, fine. If you just want a little extra padding so your child will lay back and snooze in the cart, it's also a fine option. But a piece of infrequently-washed cloth isn't going to do much in the way of disease prevention.
This piece originally appeared on Parent.co.