Adventures in Wonderlab

Adventures in Wonderlab

Fun science adventures for all ages!

Do I Have to Use Sanitizing Wipes on my Shopping Cart?

Most grocery stores offer sanitizing wipes as an option to wipe down your cart before starting your grocery shopping. I really do appreciate the opportunity to decontaminate my shopping cart. After all, I have read that shopping carts are one of the germiest things we touch in public… When you think about it, diaper-aged kiddos sit in the cart… Add in any kind of meat juices, plus any germs from the previous cart pusher…. YEEESH.

shopping cart

Shopping Cart Study

In 2012, University of Arizona microbiologist Charles Gerba, PhD, sometimes called “Dr. Germ” conducted a study on total numbers of bacteria on grocery shopping cart handles and seats. This study was conducted to determine the general sanitation of shopping carts with regard to bacteria. The results of this study found the shopping cart seats and handles to be bacteria-laden, and suggested the need for improved sanitation of shopping cards/baskets.

This study was conducted 5 years ago. After 5 years of wiping down shopping carts, and many parents using blankets/cloth seat protectors for their kids, I wondered if shopping cart conditions have improved. And truthfully, I really dislike using those wipes. I don’t like getting my hands all wet, and it seems to take forever for the cleaning solution to dry on the handle.

So, I decided to bring my own agar plates and sterile cotton swabs to the grocery store, and test out the handles of shopping carts myself (I did not test the seats).

Background

Agar Plates and Growing Bacteria

I purchased some luria broth agar plates, which are used to grow environmental bacteria, including E. coli. Other types of agar plates are used to grow pathogenic bacteria- I did not want to grow any of those in our home! I should also note here that only bacteria can be grown on agar plates – no viruses.

Petri dishes

Heating lamp and thermometer on the left (for our incubator), and agar plates are stacked on the right.

Incubator

When it is time to grow the bacteria, I placed the agar plates in an upside-down position in a homemade incubator with a temperature between 85 and 100 degrees F. For the homemade incubator, I used a plastic bin, a thermometer, and a heating light bulb as a heat source.

Homemade incubator

Growing bacteria

After 1-2 days in the incubator, I watched for the appearance of small bacterial colonies (usually white or yellow dots) on the surface of the agar plates. You need millions of bacteria in one spot just to see one dot on the agar plate.

My Sampling Method

I went to two different Meijer stores, and sampled 4 different carts on 4 separate shopping trips. Meijer stores have Purell sanitizing wipes available for use next to the shopping cart corral, so I used Purell sanitizing wipes in this experiment..

So that my results would be fair, my comparison of wiped/unwiped cart handles were performed on the same cart – I used a Purell wipe on 1/2 of the shopping cart handle, and left the other 1/2 untreated. I scrubbed 1/2 of each cart handle thoroughly with the Purell wipe, and waited until it was dry before using my sterile cotton swab to test the surface of the handle, and then applied the swab to my agar plate. I left the other half of the handle untreated, and carefully swabbed the untreated 1/2 as well. Then, I put the plates in an incubator for 1-2 days to grow bacteria.

Purell Sanitizing Wipes

All about Purell Sanitizing Wipes:

“These wipes sanitize hands and clean surfaces while doing no harm. They contain benzalkonium chloride, which is strong enough to effectively kill germs and food-borne pathogens, and a plant derived cleanser that does not harm vinyl, plastic, metal or rubber surfaces. PURELL wipes also contain glycerin, a skin conditioner that helps protect skin from dryness, but with no sticky residue.”

Purell wipes

Shopping Cart Handle Results

I was surprised to find that overall, the shopping cart handles were pretty clean!

Shopping cart results

The top half of each plate, labeled “W” for Purell “wipe”, were swabs from the wiped shopping cart handles. The bottom half of each plate were swabbed with shopping cart handles NOT wiped with Purell. The arrows are pointing to the colonies of bacteria.

My results from 4 different shopping trips provided 7 total colonies of bacteria (not much) from unsanitized shopping cart handles vs. 1 colony from handles treated with Purell. And on one sampling day, I was unable to grow any bacteria from the shopping cart handle – sanitized or not – it had been raining for about 24 hours, and I wonder if the rain helped to make this cart extra clean (my cart was dry when I got it, but it could have been rinsed off with rain and already dried).

Conclusion

So, should I use the sanitizing wipes? Sure. They do a good job of killing most bacteria. I was only able to grow 1 colony of bacteria from all 4 of my sanitizing wipe samples. Also, remember that I only focused on bacteria – the ingredients in Purell wipes are also effective in killing certain viruses.

But do I have to? If you are like me, and don’t really love the wipes, I think it’s okay to skip them. In lieu of the wipes,  I use hand sanitizer when I get into my car after a grocery trip. And, as soon as I get home but before I put my groceries away, I always wash my hands with soap and water. *See our hand washing study here*

The best solution for your cart-riding child? I would never take any risks with a baby/small child. I would not use the sanitizing wipes and assume that your child is safe from all bacteria and viruses. Instead, make sure that they do not touch the shopping cart handle at all – ensure that the area that your baby rides in is covered with a blanket or shopping cart cover. Even years ago, I always used a cloth grocery cart cover when shopping with my kids, and washed it when we returned home from a shopping trip. Totally worth it!


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