Is It Safe to Microwave Food in Plastic Containers? A Scientist Settles the Debate

For many years we have been warned about overexposure to microplastics and toxic chemicals found in everything from tea bags to fish and even chicken breasts. It seems no matter how much we try to dodge microplastics, we simply can’t avoid exposure when they’re literally in our drinking water. But we’ve also been told by some manufacturers and some researchers that plastic storage containers are safe and you can even microwave them to reheat your leftovers. To get a better understanding of the safety of microwaving plastic storage containers, I dug into the research and reached out to Lisa Yakas, a microbiologist and senior account manager of product certification at NSF, an independent organization that tests, audits and certifies an array of products, including food storage products, for her opinion on the subject. As is the case with most seemingly controversial topics, the answer is fairly straightforward, though a bit nuanced. A good rule of thumb is to check the manufacturer’s directions.

What Are Plastic Storage Containers Made Of?

Plastic is a relatively general term and may contain a variety of different chemicals, though it is typically made from an assortment of organic polymers. Research has found that of the more than 13,000 chemicals associated with plastics and plastic production across a wide range of applications, 10 groups of chemicals have major concern due to high toxicity and potential to migrate or be released from the plastic itself.

When looking at plastic used for packaging, a study identified nearly 1,000 different chemicals likely associated with plastic packaging—and 148 of those have significant human toxicity. In addition, 63 of those chemicals rank highest for human health hazards and 68 for environmental hazards.

This is not to demonize plastics or turn a blind eye to their widely positive impact on modern society. After all, plastic has been around for more than 100 years and is used in nearly all aspects of life today. Modern storage containers are quite different from what was produced at the turn of the 20th century. Around the 1950s and onward, plastic started to be relatively cheap and easy to make. Over the next several decades, the use of plastics exploded. Today, Yakas explained, manufacturers are developing new, more durable and flexible plastic products.

Are Plastic Containers Safe to Use in the Microwave?

Not all plastic storage containers are created equally. This may seem obvious, but it’s an important point when trying to discern the relative safety of heating plastic containers in the microwave. 

As a former line cook, my body is likely part bionic with regular consumption of hot coffee sipped from a plastic deli container. Seriously, those deli containers were used for everything, and not just makeshift cups: storing sauces and clarified butter or sending customers home with hot soup. These types of containers are not intended for repeat use, Yakas explained, so it’s best to use them once, then recycle them or use them for storing nonfood items.

“Always check the manufacturer’s directions to see if your plastic food storage container is microwave-safe,” said Yakas. “If not, the container may carry a risk of leaching harmful chemicals into the food.” Some companies, like Rubbermaid and Tupperware, make plastic storage containers without bisphenol A (BPA), which has been linked to possible health concerns like cardiovascular disease and type 2 diabetes.

But it’s hard to know exactly what chemicals are in all plastic storage containers. “For example, while it may be tempting to reheat leftovers in takeout containers, these containers are usually not designed for multiple uses,” says Yakas. NSF recommends reheating food stored in a plastic container on a different plate or bowl. “One best practice is to transfer food to another microwave-safe bowl or plate before using the microwave,” Yakas said. “This can minimize risks and support the durability of your plastic food storage containers.” 

Tips for Upgrading Your Food Storage Containers

If you are going to use plastic containers, look for NSF’s “Certified for Home Use” mark on the product label or the bottom of the product itself, Yakas said. This certification, NSF Protocol P386: Food Storage Containers for Home Use, ensures that containers (glass, ceramic, metal, plastic and rubber) are easily cleanable and produced from home-safe materials.

Even if your container is certified for home use, you may need to replace it. “If a container has a persistent stain, throw it away, as deep stains and scratches may harbor bacteria and retain odors,” Yakas said. “Stains can also indicate that the plastic has absorbed food components, which can increase the risk of chemical leaching, especially when used in the microwave.” 

When you are ready to upgrade your plastic containers, consider nontoxic alternatives like Rubbermaid’s Brilliance line, OXO’s Good Grips line of glass storage containers or Caraway’s ceramic-coated containers.

While I may be opposed to ditching all our plastic storage containers (I have young kids, so they get plenty of use keeping small toys and art supplies in one place), several years ago I upgraded our food storage to glass. Aside from not having the health concerns associated with microwaving plastic, glass has the unique advantage of serious durability. You don’t need to rush out and buy new containers if your plastic is in good shape, but consider a plastic-free option when it’s time to upgrade. 

The Bottom Line

Many plastic containers are not safe for use in the microwave, as they can leach toxic chemicals into your food. Always check the manufacturer’s directions to see if the container is microwave-safe. If you’re unsure or just want to be safe, transfer food to a microwave-safe bowl or plate before microwaving. Because using plastic containers can also increase your exposure to microplastics, if you can, upgrade your plastic containers to those made with glass or ceramic.