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Can you heat up Styrofoam? What you need to know to keep yourself safe

Find out if you can microwave Styrofoam

Styrofoam coffee cups
Pighurska Valentyna/Shutterstock

Sure, you may love to cook delicious, gourmet meals that your friends and family salivate over, but sometimes, throwing something in the microwave is just easier. Whether you’re heating up yesterday’s leftovers or reheating lukewarm takeout, the microwave can be the busy homeowner’s best friend. But do you need to take the food out of that convenient Styrofoam container first? Can you heat up Styrofoam or is it unsafe to do so?

Microwaves are easy to use, but that doesn’t mean every type of food container belongs in them. Depending on what you’re using to reheat food, you may need to transport it to a microwave-safe plate. Metal-based materials, for instance, can’t go in the microwave since the waves can’t penetrate metal. With a few exceptions, most glass and ceramic dishes are microwave-safe containers, as are some forms of Tupperware, but they may not be practical for transporting or storing foods. Styrofoam is a commonly used food container, but can you microwave Styrofoam or even heat Styrofoam at all?

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Keep reading to find out more about putting your Styrofoam bowls, cups, or plates in the microwave.

Person holding two Styrofoam containers

What is Styrofoam?

Trademarked by The Dow Chemical Company, the term ‘Styrofoam’ actually refers to a type of polystyrene foam commonly used in the building industry. Over the years, the term has often been misused when referring to an expanded polystyrene foam that’s injected into molds to make disposable plates, cups, and takeout containers. 

Polystyrene containers are cheap to manufacture and are excellent at keeping foods and beverages warm, making them a popular choice in the food industry. But over the past several years, there has been a growing backlash against single-use polystyrene containers due to environmental and potential health concerns. Indeed, many states, cities, and local governments have banned the use of polystyrene in recent years.

It can take about 50 years for a Styrofoam coffee cup to decompose; sadly, Styrofoam and other plastics make up about 30% of all landfill volume in the United States. 

From a health perspective, Styrofoam-based products contain a compound called styrene, which has been linked to cancers in animal and human studies. There is an increased risk of styrene leaking into foods when containers are microwaved. This is especially true for fatty foods.

Microwave on a shelf with dishes

Can you safely microwave or heat Styrofoam cups or other food containers?

Food-use Styrofoam containers, made from expanded polystyrene, are not oven safe. These Styrofoam containers will begin to soften at 212 degrees Fahrenheit and actually melt at 464 degrees. They are, however, safe to use for storing food in the refrigerator but never to cook or reheat in the oven. 

The Food and Drug Administration regulates plastic and polystyrene containers, cups, and plates and tests their safety and use in microwave ovens, making sure that the amount of chemicals that leach out isn’t higher than 100 to 1,000 times lower than the amount that has proven to hurt lab animals. Any container that achieves that can be outfitted with a microwave-safe label indicating they have been tested for safety in the microwave. Look for the microwave-safe labeling on any Styrofoam containers before putting them into the microwave.

Person holding two Styrofoam carry-out containers

What are Styrofoam alternatives?

To reduce landfill items and to ensure what you are reheating is safe, glass and ceramic are generally safe for microwave use. Sure, it’s not as convenient as taking your food straight from the fridge in the Styrofoam container, but knowing you aren’t putting any harsh or unsafe chemicals into your body is worth the extra step.

Man looking into microwave oven
ryuhei shindo / Getty Images

A few more things regarding microwave reheating and safety

  • If you can’t verify that your Styrofoam container is microwave safe, transfer the food to a glass or ceramic container labeled microwave safe.
  • If you want to cover foods while reheating in the microwave, use wax paper, parchment, or even paper towels. Don’t allow plastic wrap to contact food while microwaving, as it may melt during heating.
  • Those plastic tubs that hold yogurt, cream cheese, mayonnaise, and other foods may be tempting to use as extra food storage in the fridge, but they aren’t microwave-safe containers.
  • Any plastic containers that are cracked, scratched, or microwaved many times can begin to leach harmful plastic into your food. 
  • If you aren’t sure if you have a microwave-safe container, you can always transfer the food to a pot or pan and reheat it on the stove or in the oven.

Microwaves and Styrofoam containers are products born out of modern needs for convenience but are they safe together? As a general rule, if you are unsure of your food containers’ microwave safety, don’t use them. But by being diligent, reading labels, and following the tips above,  you’ll be able to enjoy the convenience of microwave heating while still keeping you and your family safe.

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Kim Renta
Former Digital Trends Contributor
Kim has written for Bloomingdales, Movado, and various e-commerce wine sites. When she's not writing about wine and…
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