| July 30, 2013

It's not like anybody believes their shopping carts are clean. Most supermarkets place a dispenser of sanitizing wipes nearby, as if to hint at the exact opposite.

But in case you were on the fence, yes, they're gross.

A study of 85 random shopping carts conducted by Dr. Charles P. Gerba found that 50 percent carried E. coli, while 72 percent contained coliform bacteria. "The exceptionally high level of coliform bacteria suggests that fecal material may be involved in cart contamination," the report further stated.

In other words, your cart most likely harbors bathroom germs.

According to Donna Duberg, an assistant professor of clinical laboratory science at Saint Louis University, these pathogens find their way into our carriages through a number of avenues. "Certainly children can be a source of the germs," she explains, as toddlers often ride in carts when accompanying their parents, but Duberg doesn't downplay the role of the consumers either. "We may bring in germs with our hands," she adds.

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Depending on our immune systems, many of these pathogens have the potential to make us sick, too. "Especially the fecal coliforms," notes Elizabeth Scott, an assistant professor of biology at Simmons University in Boston. "The concern is that we can pick up pathogens from the cart that can be transmitted directly to our mouths or to other foodstuffs."

Is this really that big of a concern, though? Germs are everywhere, from cell phones to computer keyboards. They're always going to be present, so how bad could a shopping cart be?

Duberg cites Gerba's findings for the answer: "[There are] 138,00 total bacteria per square inch of a shopping cart — an amount which exceeds the number of bacteria in the average public restroom," she says. "These are fecal bacteria capable of causing illness."

Unfortunately, fecal germs aren't the only bacteria to be wary of. "There are bacteria capable of causing food-borne illnesses such as Salmonella, Shigella, Listeria, and, of course, E. coli O157H7 that may be hiding in the food we are purchasing, especially the fruits and vegetables and raw meats," says Duberg. "You can tell by doing a quick scan of food recalls," such as these online safety alerts posted by the FDA, she adds.

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Taking both fecal and food-borne pathogens into account, it's no wonder there are disinfecting wipes in almost every supermarket. But as it turns out, they may not be as effective as we think.

"In theory, it's a good idea, but rather hard to achieve," explains Scott. "Where do you apply the disinfectant? How effective is the disinfectant? It's much better to practice careful hand hygiene and use alcohol hand sanitizer and hand washing."

Duberg adds that most of the wipes are utilizing benzalkonium chloride — and not bleach or alcohol — a disinfecting agent. This means that in order to sanitize, shoppers should be thoroughly wetting the surface areas (handles, grates, coffee cup holders) with the wipes. But if a shopper wanted to disinfect, Duberg says most brands of benzalkonium chloride recommend you leave the surfaces wet for up to four minutes.

The good news, she adds, is that if you thoroughly wet the surfaces with a benzalkonium chloride wipe, "you’re going to get way over 99 percent" of the germs.

Or, if you'd rather skip that step, you can just grab a hand-held basket instead. Baskets might contain the same pathogenic bacteria as a cart, but as Scott says, "If it's baskets vs. carts, at least baskets aren't used to carry kids."

But just to be safe, you should probably make time to wipe down the basket, too.