The hidden health hazard lurking in your office microwave

Wafts of reheated fish might seem like the most toxic landmine in the office kitchen, but there are actually bigger hazards waiting in the microwave.

Experts say to beware of the office break room, and the microwave in particular, which may seem harmless but could actually get you sick.

“By 2 p.m., food debris from breakfast and lunch has built up inside, creating an invisible layer of contamination,” Sarah Jeffries, an instructor at Emergency First Aid at Work Course, said.

“At this point, the warmth and moisture make it a breeding ground for bacteria, meaning anyone reheating their meal is at a higher risk of foodborne illness.”

A 2012 study collected nearly 5,000 individual swabs from office buildings containing more than 3,000 employees and found that the dirtiest areas were break rooms and kitchens. 

“People assume that bathrooms have the most germs,” Dr. Charles Gerba, a professor of virology at the University of Arizona, told Forbes.

“A lot of studies have been done about the desktop work area, but the break room has been overlooked. Usually the break room is a germ transfer point in the workplace; people eat lunches there,” he said. “You are dealing with an unregulated restaurant in a lot of ways.”

Additionally, a 2024 study found that microwaves in shared environments such as office break rooms often contain bacteria commonly found on human skin, like staphylococcus. 

Other bacteria frequently found in office microwaves include salmonella and E. coli. While all of this bacteria should be killed in high temperatures, uneven heating — a notorious issue with microwaves — can leave some areas of the food dangerously undercooked.

To minimize the health risks, Jeffries suggests doing the following when using the office microwave.

Avoid reheating food after 2 p.m. 

If you can eat earlier in the day, do so. Otherwise just grab a snack or something that doesn’t need to be heated. 

Cover your food 

Covering your food with a microwave-safe lid or paper towel can reduce the spread of food splatters. Make sure you use microwave-safe containers.

Stir and rotate halfway through heating

Stir your food midway through to avoid cold spots where bacteria can thrive. If the microwave doesn’t have a rotating turntable, pause periodically to rotate the container manually.

Make sure it’s the right temperature 

Your food should be reaching an internal temperature of at least 165°F (74°C), which is the temperature recommended by the USDA to kill most harmful bacteria.

Wipe it down before you use it 

Giving the microwave — including the door handle, buttons and inside walls — a quick clean with disinfectant wipes will get rid of germs and, as an upside, probably endear you to your colleagues. 

Avoid high-risk foods 

Be careful when reheating raw or partially cooked foods, seafood or eggs, which are more prone to bacterial growth if not heated thoroughly.

Post a reminder

Finally, while no one wants to be “that person,” you can encourage your office to implement a regular cleaning schedule or post a sign reminding your colleagues of best practices. 

As Jeffries said, “Most people assume the office microwave is harmless, but without proper cleaning and safe reheating practices, it can quickly become a hidden health risk.”