Can You Safely Microwave Plastic Food Storage Containers?

The rules around safely reheating food in plastic containers are confusing, but we can help.

Woman heating leftovers in plastic container in microwave
Photo: BRETT STEVENS/Getty Images

Whether you're a meal-prepper or simply a lover of leftovers, food storage containers are a staple in most Americans' arsenal of home cooking tools. The most common of these are made of plastic, many of which are marketed with claims that they are safe for the microwave or free of certain chemicals. But are they really safe for microwaving? The answer is complicated.

Are Plastic Containers Microwave Safe?

As a general rule of thumb, plastic containers should not be microwaved. The amount of risk associated with heating plastic varies depending on the type of plastic, but in order to avoid all possible negative repercussions on one's health, it's best to reheat in glass or ceramic as much as possible. Heating plastic, like in the microwave, increases the probability for leaching — which is the transfer of chemical compounds (such as Phthalates and BPA) into the contents of the containers; in this case, food. When you eat food that has been heated in a plastic container, any chemicals that have leached out of the plastic are being put into your body. Over the course of a lifetime, those chemicals can build up and lead to adverse health effects.

What Does 'Microwave Safe' Even Mean?

The FDA does not regulate the term "microwave safe," which means different companies use the phrase in different ways. When you see the term "microwave safe" in association with food storage containers, you can be certain that it means those containers will not warp or melt in the microwave. Beyond that, it's best to do your own research about the type of plastic being used in storage sets that are marketed as microwave safe. Certain plastics, like those labeled with numbers 2,4, and 5, are more safe in the face of heat than other types of plastic, but not without some risk. Plastics labeled with numbers 1, 3, 6, or 7 should never go into the microwave; in fact, it's best to avoid putting these plastic containers through the dishwasher as well.

What Does 'BPA-Free' Mean?

BPA stands for bisphenol A, which is a stabilizer used to make plastic harder. It's unsafe for consumption because it is an endocrine disruptor, which can impact your own body's natural hormone production. Obviously, this is not something you want leaching into your leftover pasta. If a plastic food storage container is labeled "BPA-Free," you know that this particular stabilizer hasn't been used in manufacturing the container. Other common stabilizers include phthalates, which are also endocrine disruptors and should be avoided as much as possible.

Is Tupperware Microwave Safe?

All Tupperware products sold in the United States since 2010 is BPA-free, so they're safer than they used to be. However, if you're using Tupperware containers that are older than that, it's definitely worth considering disposing of those older containers and replacing them with newer, BPA- and phthalate-free containers — or simply opting for glass or ceramic lidded containers instead. The more years and use a plastic container has under its belt, the greater the risk of leaching.

Should You Microwave a Plastic Container With the Lid On?

If you're going to microwave food in a plastic container, it's best not to use the plastic lid. The concentration of steam that will be produced in a covered container raises the internal temperature of the container even further, which can lead to more leaching of chemicals into your food. The moisture that gathers on the lid in particular can be concentrated with any chemicals that are leaching out of the plastic. If the food needs to be covered, consider using a glass or ceramic plate as a loose fitting lid, or even use a damp paper towel to cover the dish.

Tips for Microwaving Food In Plastic Containers

Plastic containers are a standard part of many of our lives – they're super convenient for lots of reasons. If you do decide to use them for food storage and re-heating, there are ways to minimize the risk.

When storing food, let it cool completely before transferring it to a plastic container. This reduces the risk of prompting leaching as the food cools down. Try to use medium heat in the microwave and avoid setting it to run for more than 3 minutes. Instead, reheat food a minute at a time, stirring in between to distribute the heat and avoid super-high temperatures. And if you're looking to replace your food storage containers with something that's more appropriate for reheating food, glass containers are likely your best bet.

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