Can Styrofoam Be Microwaved? (Safety and Risks)

February 5, 2024
Microwave Repair

Is heating food in the microwave in Styrofoam cups, plates, and other containers safe? And, is microwaving polystyrene products safe in general?

That’s what we’ll be answering today. But before we start, it’s important to clarify one thing:

Styrofoam and expanded polystyrene (EPS) foam are not the same. Styrofoam is an extruded polystyrene foam (XPS), mainly used as a building material for insulation and not for the cups and plates we are discussing here, as these are made of expanded polystyrene foam.

However, since these terms are used interchangeably in the USA and Canada, this article will look at expanded polystyrene foam products and refer to them as “Styrofoam”, even though this is technically incorrect.

Can You Microwave Styrofoam?

It’s recommended that you don’t microwave Styrofoam products unless they are clearly marked as microwave-safe. That’s because polystyrene contains a compound called styrene, which has been linked to cancer in animal and human studies.

There’s a chance this styrene can leach out into the food or drink you are heating up, potentially posing a health risk if consumed. It’s also possible that substances used during the polystyrene manufacturing process may leak into the food.

However, it must be said that polystyrene products labeled as microwave-safe are fine to use. That’s because the Food and Drug Administration (FDA) regulates these polystyrene containers and tests their safety for microwave oven use.

So, in summary, it’s best to avoid microwaving polystyrene without microwave-safe labels, as there are some safety concerns. However, you can microwave polystyrene containers if they are labeled microwave-safe.

You can usually find the microwave-safe label on the bottom or sides of a polystyrene container; the symbol is typically a microwave with some wavy lines.

Tips for Microwaving Food Safely

Here are some tips for microwaving food in polystyrene containers safely: 

  • Always check for the microwave-safe label on polystyrene cups, plates, and containers.
  • Transfer the food to a container made from Pyrex, ceramic, or glass if you’re unsure if the Styrofoam container is microwave-safe.
  • Do not microwave polystyrene containers that are old, damaged, or cracked, as they may leak chemicals.
  • Be careful removing a microwave-safe polystyrene container after heating, and wear oven gloves to protect your hands from burns.
  • Open the container lid slightly or vent it to allow steam to escape. This will prevent pressure buildup that could cause the polystyrene container to explode.

Alternatives to Microwaving in Styrofoam

As mentioned, although the risk is low, there are potential health concerns with using non-microwave-safe Styrofoam containers in the microwave. However, there are also environmental concerns since polystyrene is non-biodegradable, pollutes our land and seas, and has a low recycling rate. 

For all these reasons, you may wish to opt for an alternative to microwaving in Styrofoam. Here are some to consider:

  • Glass Containers: Reusable and recyclable, glass is a more environmentally friendly option than Styrofoam. Plus, it’s microwave-safe and doesn’t release any dangerous chemicals. 
  • Ceramic Containers: These are also reusable, and as long as they don’t have a metallic glaze, they’re microwave-safe. 
  • Silicone Containers: Food-grade silicone containers are durable and versatile, making them great for heating food in the microwave and storing food in the fridge or freezer.
  • Paper Plates: Microwave-safe paper plates and bowls are another more environmentally friendly option, especially if you opt for paper containers that are compostable and biodegradable.
  • Wax and Parchment Paper: Heat-resistant wax and parchment paper are other versatile options since you can use them in the oven, microwave, air fryer, or freezer.
  • Cookware: Another option is to avoid the microwave altogether and opt for the oven, air fryer, or stove instead by transferring the food to pots, pans, or baking trays. 

What Else Should You Avoid Microwaving?

Polystyrene that’s not labeled microwave-safe isn’t the only thing you should avoid putting in the microwave. For your safety, you should also avoid the following.  

Non-Microwave Safe Containers

Using non-microwave-safe containers in the microwave could lead to melting, the release of harmful chemicals, sparks, or even a fire. This includes plastic containers not labeled microwave-safe, such as old yogurt or margarine tubs.

Metal Containers or Utensils

Metal reflects the microwaves a microwave emits, causing sparks and creating a fire risk. Therefore, you should not put any metal containers, utensils, foil, ceramics with a metallic glaze, or anything else containing metal in the microwave.

Brown Paper Bags

While microwave-safe paper is fine to use in the microwave, brown paper bags are not. Due to how they’re made and their physical structure, these bags can easily catch fire and release toxic fumes when microwaved.  


Don’t put Styrofoam containers in the microwave unless they are clearly marked with a microwave-safe label since they could leak styrene—a substance that studies show has been linked to cancer—into the food.

You can find the microwave-safe label on the bottom or sides of polystyrene cups, plates, and containers; it usually looks like a microwave with wavy lines inside.

Polystyrene containers with a microwave-safe label should be fine since they’re regulated by the FDA and tested to ensure their safety in microwaves. They don’t pose the same styrene-related risks.

However, if you’re ever unsure whether a Styrofoam container is microwave-safe or not, always err on the side of caution and use a ceramic, glass, or another microwave-safe container instead. Not only are these alternatives often safer, but they’re also reusable and more environmentally friendly.


Leave a Reply