Food Poisoning Health Center

Microwave Kills Germs in Sponges

Jan. 24, 2007 -- Your microwave may be a powerful weapon in protecting your family against disease-causing germs.

A new study shows zapping sponges and plastic scrubbing pads in the microwave can kill bacteria, such as E. coli, that can cause illness.

"Basically, what we find is that we could knock out most bacteria in two minutes," says researcher Gabriel Bitton, professor of environmental engineering at the University of Florida, in a news release. "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."

Researchers say disease-causing bacteria and germs from uncooked eggs, meat, and vegetables often work their way onto countertops and cleaning tools, and the dampness of sponges, dish cloths, and scrubbers provide an ideal breeding ground for the bugs.

Microwave Sterilizes Sponges

In the study, published in the Journal of Environmental Health, researchers evaluated the effects of zapping sponges and plastic scrubbing pads in the microwave on bacteria and viruses.

The sponges and scrubbing pads were soaked in wastewater containing a dangerous mix of fecal bacteria, E. coli, and bacterial spores. Bacterial spores are more difficult to kill.

The results showed that two minutes in the microwave at full power killed or inactivated more than 99% of all the living germs and the bacterial spores in the sponges and pads, including E. coli.

After an additional two minutes -- a total of four -- none of the bacterial spores survived.

Before you zap your sponges in the microwave, researchers offer the following advice:

• Microwave only sponges or plastic scrubbers that do not contain steel or other metals.
• Make sure the sponge or scrubber is wet, not dry.
• Two minutes should be enough to kill most disease-causing germs.
• Be careful in removing the sponge from the microwave because it will be hot and should not be handled immediately after zapping.

Bitton recommends that people microwave their sponges according to how often they cook, with every other day being a good rule of thumb.