Sponges and Scrubbing Pads: Your Secret Weapon for Disinfecting

You’ll be a bit horrified to read here in an excerpt from 4 Weeks to Maximum Immunity about the pathogens found on sponges and scrubbing pads. Who knew they could be so contaminated? Although I don’t use microwaves for heating food (and I won’t until someone can prove to me that microwaves don’t kill food enzymes), I can see following these directions for using microwaves for disinfecting kitchen cleaning utensils.

Even the cleanest-looking kitchen can be crawling with nasty germs such as E. coli and salmonella. It’s easy to unwittingly spread these pathogens by using the same sponges and dishcloths to wipe down counters, stove tops, tabletops, and other surfaces. Because sponges and dishcloths contain the two essential elements to sustain microbial life–water and nutrients–they’re ideal habitats for viruses, bacteria, and other microorganisms.

You can disinfect dishcloths by regularly laundering them with hot water. But what can you do about sponges and plastic scrubbers?

To find out, researchers from the University of Florida in Gainesville conducted a novel experiment, the results of which were published in a 2006 issue of the Journal of Environmental Health. The researchers soaked sponges and scrubbing pads in a raw wastewater containing a witch’s brew of viruses, fecal bacteria, protozoan parasites, and bacterial spores, including one especially hard-to-kill spore: Bacillus cereus. Then they tested the ability of the common microwave oven to destroy these pathogens.

The results were unambiguous: Just two minutes of microwaving damp sponges and scrubbing pads at full power was enough to inactivate more than 99 percent of the pathogens. But 4 minutes of microwaving was required to inactivate Bacilus cereus, which is similar to the protozoan cysts and oocysts that cause giardiasis, a common gastrointestinal infection.

“People often put their sponges and scrubbers in the dishwasher, but if they really want to decontaminate them and not just clean them, they should use the microwave,” says lead researcher Gabriel Bitton, Ph.D. “The microwave is a very powerful and inexpensive tool for sterilization.” He recommends microwaving sponges according to how often you cook, with every other day being a good rule of thumb.

After the study was published, some consumers complained that microwaving caused sponges and scrubbers to catch fire, which ruined their microwave ovens and stunk up their homes for several hours. As it turned out, the consumers had nuked sponges and scrubbers when they were dry. This prompted the University of Florida to issue the following advisory: “To guard against the risk of fire, people who wish to sterilize their sponges at home must ensure (that) the sponge is completely wet. Two minutes of microwaving is sufficient for most sterilization. Sponges should have no metallic content.”

Adapted from 4 Weeks to Maximum Immunity, by the editors of Prevention (Rodale, 2008).