Why Your Clean Kitchen Sponge Is Still Growing and Spreading Millions of Germs

We’ve been told microwaving or boiling our kitchen sponges gets rid of the germs growing in them. But a new study published in Science Reports says it’s not that simple.

An Incubator for Germs

Think of kitchen sponges as hotspots for microbiology, researchers urge. The way we use sponges bears an uncanny resemblance to how a scientist uses a Petri dish to grow specimens. As if following instructions from a textbook, we dampen the sponge with water, then add germs (wipe it across contaminated kitchen counters, appliances and dining room tables). Then we feed the germs nutrients (clean up meat juices, fruit and vegetable residues and spilled drinks). And finally, we leave it undisturbed at room temperature for a period of time. We repeat the process several times a day.

Scientists say our sponges serve as the perfect incubator for growing germs by the millions. In fact, studies show that kitchens play host to more microbes than toilets.

A Mobile Home for Germs

Not only are our sponges serving as nurseries for germs, but as taxis as well.  We wipe up a drip of chicken juice on the stovetop and transfer it to the countertop by using the same sponge to sop up water from a colander. Later we rest a serving spoon on the contaminated countertop while removing the casserole from the oven.

Between all the wiping and wringing, researchers say, we are re-contaminating and cross-contaminating every surface in our kitchen with close relatives to bacteria that cause pneumonia and meningitis. Some of the microbes can cause infections in people with weak immune systems and are responsible for making the laundry stink.

Population Explosion of the Survivors

In a most disturbing discovery, the study found that while cleaning or sanitizing sponges did temporarily reduce the microbiology, it didn’t kill all the germs, and the ones left behind actually increased significantly in population. Scientists speculate this may happen because when certain germs were destroyed, the remaining ones found more room and nutrients to spread out and fill in the empty cavities.

Researchers found bacteria could be packed in a single cubic centimeter of sponge at about the same density as seven times the number of people inhabiting the Earth. “Such bacterial densities are found only in feces,” says the write-up in Science magazine. The study recommends throwing out sponges once a week.

Tips for Managing Kitchen Germs

Follow these recommendations by the USDA and FoodSafety.gov to help reduce germs in the kitchen:

• Use paper towels. Wipe up spills on counter surfaces with throwaway paper products. If you do use cloths, wash them frequently in the hot cycle of your washing machine.
• Rinse and wring out dish cloths or sponges between uses. Never leave cloths in water in the sink, even soapy water. Let them dry completely between uses.
• Use a dishwasher. Place sponges in the dishwasher on the longest and hottest cycle. Finish with the dry cycle. Use dishwashers to sanitize as many kitchen tools as possible.
• Microwave wet sponges. A sponge can be at least partially cleaned by wetting it and placing it in the microwave for two minutes. Let it cool before handling.
• Throw it away. Pick up cheap throwaways at discount stores. After a week, recycle them as garage or shop rags before sending them to the trash can.