Are Your Plastic Takeout Containers Safe to Reuse?

Reusing plastic takeout containers seems like an easy, eco-friendly way to cut down on waste, but beneath the good intention is a question that keeps swirling: What happens when that plastic is reused or reheated? As concerns over microplastics continue to grow, that everyday habit is getting a much closer look.

While research continues to uncover the full health impacts of microplastics, many people are seeking practical ways to minimize their exposure. To determine whether plastic takeout containers are safe to reuse (and reheat), we consulted three microplastics experts to break down everything you need to know. 

Is it safe to reuse plastic containers in the microwave?

Short answer: It depends. Many people assume all plastics are the same, but that actually isn’t the case, as indicated by the different recycling numbers on containers, says Robert Glowacki, PhD, a microbiologist, immunologist, and assistant professor of biology at Hope College. Reusing single-use containers — such as clamshells, tubs, and bowls used for salads and sandwiches — is discouraged because these containers are typically made from less durable materials that break down more easily than those designed for long-term storage, he explains.  

By contrast, Tupperware and related products are generally made of sturdier plastics designed for repeated use, including microwaving and dishwashing. Given this, if a takeout container is specifically labeled for reuse and marketed as microwave- and/or dishwasher-safe, the likelihood of microplastics leaching into food is low, says Chris DeArmitt, PhD, a polymer scientist and founder of the Plastics Research Council. 

“As a PhD chemist, I wouldn’t do it unless it was safe, but I reheat food that way myself,” says DeArmitt. “The word ‘microplastic’ is new in the public perception, but we have thousands of studies spanning over 50 years from the FDA and European Food Safety Authority that have looked into this in detail and found no cause for concern because any exposure is extremely low.”

Of course, plastic can degrade over time, so Glowacki advises regularly checking containers for signs of deterioration, such as cracks, pitting, or discoloration (often appearing as a cloudy or foggy haze), which typically signal the end of a container’s usable life. “I’m not aware of any specific guidelines or a number of times that plastic containers can be reused, but brands like Tupperware that are made specifically for the purpose of reheating and storing food, are going to be safer than single-use takeout containers,” he says. 

What are microplastics, exactly?

According to Victoria Fulfer, PhD, a microplastics scientist at The 5 Gyres Institute, microplastics are plastic particles less than five millimeters in diameter and vary widely in shape, size, and chemical composition. Many are thinner than a human hair and invisible to the naked eye, making them virtually impossible to clean up or eradicate once in the environment.

Unlike ordinary “dust,” microplastics include microfibers from textiles, tire wear from cars, microbeads in personal care products, plastic pellets, and fragments from larger plastic items as they break down, Fulfer explains. Because they continually fragment into smaller pieces, microplastics accumulate in the environment and move through multiple food chains, Glowacki says — for example, from ocean waters to fish and ultimately to people.

Microplastic ingestion is known to harm mice, fish, and other organisms, causing behavioral and physiological changes, oxidative stress (an imbalance in free radicals and antioxidants that can lead to cell damage), and reduced growth, Fulfer says. To date, there have been no comprehensive studies conclusively linking microplastics to a specific disease or medical condition in humans; however, research suggests that similar effects may be associated with oxidative stress and inflammation, including links to endocrine disorders, cardiovascular disease, reproductive issues, and dementia. Growing evidence also shows that microplastics can disrupt gut bacteria and trigger intestinal inflammation, which is associated with infections, poor nutrient absorption, and an increased risk of gastrointestinal cancers, Glowacki adds. 

That said, because we’re exposed to microplastics through the air we breathe, the food we eat, the water we drink, and the clothes we wear, direct human studies on the health impacts of microplastics are difficult to conduct, Fulfer says, because true control groups don’t exist. As a result, many questions about long-term and cumulative health effects remain unanswered.