Kitchen Warning After Scientists Discover ‘Unexpected’ Health Risk From Microwaves

How often do you clean your microwave? Probably not enough.

It’s easy to assume that the powerful radiation in a microwave oven is enough to kill any lurking bacteria, but according to new research, that’s not true at all.

In a study published in the journal Frontiers in Microbiology, Scientists from biotech startup Darwin Bioprospecting Excellence and the University of Valencia in Spain sampled microbes from inside 30 different microwaves to explore which, if any, bacterial colonies were able to grow in their extreme interior.

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“We hypothesize that microwaves are actually selecting for bacteria in the air and surfaces that are resistant to radiation,” said microbiologist Manuel Borcar, CEO of Darwin BioProspecting Excellence. Newsweek.

In total, the researchers found 747 different groups of bacteria, the most common of which were Firmicutes, Actinobacteria, and Proteobacteria.

The researchers also compared the microbial colonies found in home microwave ovens to those in their laboratories and found that while laboratory microwaves mostly contain harmless bacteria, those in home microwave ovens may pose a greater risk to human health.

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“The bacteria in home microwaves can be pathogenic, although not more than those found elsewhere in the kitchen,” Borkar said.

According to U.S. Census data, microwaves can be found in 90 percent of U.S. homes, and most sources recommend cleaning them once a week. However, according to YouGov surveys, one in three Americans doesn’t meet that goal.

“We need to clean the microwave as much as any other surface in the kitchen, because our work shows that microwaves do not remove microbial contamination at all, which is somewhat unexpected,” Borkar said.

In a statement, co-author Daniel Torrent added: “For both the general public and laboratory workers, we recommend regularly disinfecting microwave ovens with a diluted bleach solution or a commercially available disinfectant spray.

“In addition, it is important to wipe the interior surfaces with a damp cloth after each use to remove any residue and clean up spills immediately to prevent bacteria growth.”

Beyond the health implications of these findings, the researchers hope their discovery will lead to new biotechnological applications where particularly robust strains of bacteria are needed to support industrial processes.

“To find microbial biodiversity, you don’t need to travel to exotic locations, you need to find exotic microbial environments that can be very close to us,” Borkar said.

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References

Torrent et al., (2024), Microwave bacteria: the biodiversity of household and laboratory microwave ovens, Frontiers in Microbiology http://dx.doi.org/10.3389/fmicb.2024.1395751