A team of University of Florida Engineering researchers have come to the conclusion that as long as proper safety precautions are observed, microwaving kitchen sponges on full power can destroy practically 100% of the bacteria and viruses, parasites or spores collected on them.
More than 90% Americans using microwaves in their kitchens have what Gabriel Bitton leader of the study calls, “a very powerful and an inexpensive tool for sterilization."
Bitton, an environmental engineering professor, remarked that if people really wanted to sanitize their sponges and scrubbers they should use the microwave rather than the dishwasher which only cleans them.
In their report in the Journal of Environmental Health, Bitton and his co authors, UF professor of anesthesiology, Richard Melker, and UF biomedical engineering doctoral student Dong Kyoo Park described how they immersed scrubbing pads and sponges in untreated wastewater teeming with fecal bacteria like E. coli, protozoan parasites, salmonella, viruses and bacterial spores. (The spores included Bacillus cereus, that stood in for food-borne viruses responsible for diseases such as noroviruses and hepatitis A.)
The sponges and scrub pads were then 'cooked' in an ordinary domestic microwave oven for varying lengths of time. They were wrung out and the microbial load of the water was determined for each test. The findings were compared with water from control sponges and pads not placed in the microwave.
The results were telling. Every contaminant but the spores were killed after two minutes. The spores took a little longer, between four to ten minutes to be exterminated as they are difficult to kill, being resistant to radiation, heat and lethal chemical substances.
Bitton believed that the heat, and not the microwave radiation, most likely put paid to the pathogens. He further advises that as the microwave functions by stimulating water molecules, microwaving wet rather than dry sponges or scrub pads is preferable.
The UF paper divulged that earlier studies have proved that sponges and scrubbers are common carriers of germs mainly because they are often damp for long periods of time, and this helps the germs survive and flourish.
The U.S. Center for Disease Control and Prevention has estimated that millions of Americans fall sick each year due to contaminated food. The statistics are even direr with about five to six thousand people dying from them. The sponge should always be wet before heating in the microwave according to advice from the University.
Seeing that the germs contaminating the food are food borne, it follows that most of these illnesses have their sources in the kitchen.
On further experimentation the researchers discovered another use for microwaves-that of sterilizing syringes albeit that it takes up to 12 minutes to annihilate Bacillus cereus spores.
They then found the time required for sterilization could be shortened by placing the syringes in ceramic bowls that trap heat.
The scientists also revealed that their studies suggested the usefulness of microwaves in destroying bioterrorism pathogens such as anthrax.
However, more research is needed to confirm that this approach works against actual anthrax spores, Bitton said.
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Following the University the report a British Fire Service has issued a warning covering the dangers of microwaving sponges: http://news.bbc.co.uk/2/hi/health/6293735.stm
