Is It Safe to Microwave Food in Styrofoam Containers? 

Last night's take-out can be a convenient lunch for today, but you might want to remove it from the Styrofoam to-go container before reheating.

man holding styrofoam take-out containers
Photo: twinsterphoto/Getty Images

Suppose last night's dinner was take-out from your favorite local food place, delivered right to your door in a handy Styrofoam package after a busy day. The leftovers went into the fridge and now it's the next day, and you're looking for lunch. That chicken from dinner last night sounds like a good idea, but can you microwave the Styrofoam container the food is in for another meal?

There's no easier meal than taking leftovers straight from the refrigerator to the microwave for a quick nuking. That's the magic of the microwave after all, piping hot food in just a few minutes.

Some items like aluminum foil and plastic wrap are not considered to be "microwave-safe" and should not go in this reliable kitchen appliance. But what about Styrofoam?

What Is Styrofoam?

Let's start with the name, "Styrofoam."

You probably refer to the plastic foam take-out food containers and to-go coffee cups as Styrofoam products. However, they are actually not made with real Styrofoam. Styrofoam is a trademarked brand name for a specific type of building product made by the Dow Chemical Company. It's made from extruded polystyrene foam.

The foam-like food containers we think of are constructed from a product made with expanded polystyrene foam, also known as EPS. This commonly used material is about 95% air, which is what makes it incredibly lightweight but durable for packaging purposes.

The styrene used to make the foam food containers associated with take-out deliveries and the to-go cups meals are manufactured with products derived from petroleum and natural gas.

Is Styrofoam Safe for Food Storage?

According to The U.S. Food and Drug Administration (FDA), the polystyrene food containers used to package hot and cold food items are safe to use.

When it comes to storing leftovers in the refrigerator, you want to make sure the container is resealed properly to avoid leaks in the refrigerator and to prevent air from entering the container, making contamination a concern.

food in styrofoam containers
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Can You Microwave Styrofoam?

When it is time for reheating leftover food in the microwave, not all foam containers are created equal. This can easily be confirmed with a quick check of the packaging.

Take a look at your foam container and see if it has a symbol depicting the outline of a microwave with a series of wavy lines. This is a visual indication that the container is microwavable. The symbol means the FDA has approved the container for safe use in the microwave; however, if you do not see this symbol, you should not microwave the container. Instead, transfer your food to a microwave-safe vessel before reheating.

Foam containers are convenient for keeping food and drink at hot or cold temperatures, but all in all, they really aren't the best options when it comes to reheating food.

The chemicals from the styrene can leach into the food when the foam container is heated and this can be a cause for concern. The styrene has been classified as a cancer-causing ingredient and there is also a danger for containers to catch fire or melt (especially if heated too long) if they aren't marked as safe-to-use in the microwave. This also applies to Styrofoam plates used in the microwave to heat up food.

So, the Styrofoam containers can get your food delivery to your door and safely hold the contents in the fridge for later use, but after they serve these purposes — you may want to play it safe and retire them. Take the extra step to transfer any leftover food items to a microwave-safe container for reheating in the convenient countertop appliance or use a dish that is made for oven use and warm the contents by baking at a gentle temperature.

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