Your Office Microwave Could Be Crawling With Bacteria, According to a Recent Study

Microwaves have become indispensable tools in modern kitchens, praised for their ability to quickly heat food and eliminate harmful bacteria through the application of high temperatures and radiation. However, could these very appliances, designed to combat microbes, actually serve as habitats for bacterial communities uniquely adapted to harsh environments? 

According to a recent study published in Frontiers in Microbiology, researchers from the University of Valencia in Spain showed that microwaves can harbor unexpected microbial passengers. Additionally, home microwaves may host different bacteria than those found in microwaves shared in offices or laboratories. 

The researchers aimed to illuminate the types of bacteria that may flourish inside microwaves and their effects on human hygiene and food safety. They focused on whether microwave radiation affects bacteria or if food and user habits are more influential. To investigate this, they examined 30 microwaves from homes, shared spaces, and labs to identify the bacteria present and understand how usage patterns shape these bacterial communities. Their sampling revealed 101 distinct bacterial strains, with common types like Bacillus, Micrococcus, and Staphylococcus found in all microwaves, including those used solely at home. Certain bacteria were specific to particular environments, such as those in domestic microwaves or shared-use ones in labs, emphasizing the impact of usage on microbial variety.

Unsurprisingly, many of the bacteria found in domestic microwaves originated from human skin, food residues, or both, reflecting typical household use. However, laboratory microwaves, which are not used for cooking but rather for heating scientific materials, have different bacteria that are better adapted to harsh conditions like high heat and dryness— including bacteria known for their extraordinary survival skills, even in extreme environments such as solar panels or radioactive waste. Certain bacteria, like cyanobacteria, were more prevalent in the shared microwave group (like those found in shared office spaces) compared to domestic (non-shared) microwaves. Cyanobacteria can be concerning because some species are capable of producing harmful toxins that may cause illnesses after exposure, depending on the type of toxin and the method of exposure. 

What’s so bad about using the microwave at work?

According to the study, all microwaves appear to harbor bacteria. But using the microwave at work may be riskier than nuking your meal at home, explained Dr. Darin Detwiler, Food safety expert, author, and professor at Northeastern University.

“Unlike at home, where you control the cleanliness of your appliances, office microwaves are the Wild West of food safety,” Detweiler explained. “Between shared responsibilities, absent-minded co-workers, and those brave souls reheating questionable leftovers from last Friday’s meeting, your lunch break becomes a gamble.”

“At home, you and your family are already sharing many bacteria,” explained Dr. Bryan Quoc Le, food scientist, food industry consultant, and author of the book 150 Food Science Questions Answered. “There are far fewer people using the microwave at any one time, and you’re more likely to be heating similar foods. You can also more easily control the cleanliness of your own home microwave compared to one at work.”

Beyond bacteria, Detweiler explained that allergens are another concern when using a shared microwave in an office. “If your coworker reheats shrimp pasta in the microwave and doesn’t wipe it down afterward, residues can linger on the interior, triggering reactions in allergy-sensitive individuals,” he explained.

So how can I microwave safely?

While you may want to toss your shared microwave out the window and stick to cold PB and J sandwiches at work, the authors of the study highlight that regular cleaning of microwaves is essential to reduce possible health risks from bacteria carried in on food or skin. Beyond that, Dr. Detweiler suggests that we don’t have to do without reheating our food using a shared microwave altogether. 

“Certainly it’s best to use a microwave that is routinely cleaned to remove food residues,” says Quoc Le. “Microwaves with lingering residues that have molded are a very bad sign that the microwave is contaminated.”. According to the U.S. Food and Drug Administration, users should use water and mild detergent to regularly clean the oven cavity, the outer edge of the cavity, and the door. Do not use scouring pads, steel wool, or other abrasives, as they can damage the interior of the microwave and potentially leave metal particles behind.

“Microwaves used for research purposes, such as those used in microbiological laboratories, should not be used for heating food due to the possibility of cross-contaminating with highly virulent microorganisms,” Quoc Le added.