How to heat food or soften butter in seconds instead of minutes? There is no better choice than a microwave oven. The convenience of the microwave oven made it popular among American households in the mid-1970s.

It is well known that materials such as metals (including aluminum foil) and most plastics are not meant to be microwaved and they are potentially harmful to one’s health.

So, can you microwave Styrofoam? Check this guide carefully before you put your Styrofoam bowls, cups, or plates into the microwave.

What Is Styrofoam?

Styrofoam is a term that’s trademarked by The Dow Chemical Company, which refers to a type of polystyrene foam commonly used in the building industry.

However, in some countries, such as the United States and Canada, the term is often incorrectly used to refer to a type of expanded polystyrene foam that is injected into a mold to make disposable plates, cups, and take-out containers.

These containers are popular because they are cheap and act as good insulators, which means they can keep foods and beverages warm. Thus, they have become a popular choice in the food industry.

However, in the past few years, there has been a growing backlash against disposable polystyrene containers due to environmental and potential health issues.

From a health point of view, products based on polystyrene foam contain a compound called styrene, which has been linked to cancer in animal and human studies. When the container is heated by a microwave oven, the risk of styrene leaking into the food increases.

From the perspective of environmental protection, the container is not easy to decompose and difficult to recycle. A Styrofoam coffee cup may actually take about 50 years to decompose.

Types of Styrofoam

Traditional Styrofoam

One of the main chemical components traditional Styrofoam is Polystyrene, which contains toxic molecules of styrene and benzene. They are chemicals that with potential carcinogenicity, neurotoxicity, and other detrimental side effects.

The National Institute of Standards and Technology (NIST) have published many reviews that indicate polystyrene starts to show signs of decomposition around 200 degrees Celsius and showed small trace amounts of polystyrene being released.

The most frightening thing is that around 224 degrees Celsius, polystyrene begins to decompose. For pure Styrene, the temperature is about 175 degrees.

Microwave-safe Styrofoam

The Food and Drug Administration (FDA) does regulate plastic and polystyrene containers, cups, and plates, and test their safety and use in microwave ovens.

Those polystyrene containers deemed qualified will receive a microwave oven safety label indicating that they have been tested for safety in the microwave oven. This alternative material consists of safer materials and lower levels of harmful compounds, and it has higher stability when heated.

How to Tell If Styrofoam Is Microwave-safe?

Before putting any Styrofoam or polystyrene container into the microwave, check if there is a clear microwave-safe sign on the container. Since Styrofoam products are produced all over the world, the standard symbols may be different. Therefore, you need to look for a symbol similar to the image below.

If you can’t verify that your Styrofoam container is microwave safe, transfer the food to a glass or ceramic container labeled microwave safe.

How to Safely Heat Food?

Here are some tips to help you microwave food safely:

  1. Check to see if it has a microwave-safe label, scratches, or cracks if you are using a Styrofoam container.
  2. Transfer the food into a glass or ceramic container labeled microwave-safe before microwaving.
  3. Vent the container before heating it to prevents pressure from forming, causing food inside the container to explode.
  4. Reheat the food in your conventional oven using an oven-safe container covered with foil or transfer the food into a pot or pan to heat on the stovetop.
  5. After heating, use insulated gloves to take out the container and place it on the baking mats for oven.

Can You Microwave Styrofoam?

While some types of Styrofoam containers are labeled as microwave-safe, we don’t recommend using them for reheating food in a microwave oven since there is almost no data showing that it is completely safe.

For your health, please transfer your food into a microwave-safe ceramic, glass, or Pyrex container prior to heating it.


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