Why It Isn’t Safe to Microwave Styrofoam

A closeup view of a styrofoam cup of macaroni and cheese
A closeup view of a styrofoam cup of macaroni and cheese

Ever since the microwave was invented in 1945 by engineer Percy Spencer, people worldwide have been using it as a convenient way to cook and heat up foods. A meal that may take 30 minutes on the stovetop to cook or warm up takes just a fraction of that time in the microwave.

The microwave is an incredibly convenient tool that allows the user to simply place something on a plate or in a bowl, press a few buttons, and receive perfectly warm food in minutes. 

However, there can be drawbacks to using a microwave—especially regarding what containers can be placed in one.

Everyone should know that you can’t put a metal container in a microwave. Some may not be as aware that another questionable material is Styrofoam—a familiar container used for fast food, takeout, leftovers, and grocery store food and drinks. So the question is, “Can I just heat up the food in its styrofoam container?”

Some sources say “Yes” for 30 seconds or less. Others say “No, not at all.” In this article we will look at that question and provide information to help you answer that question.

First, we will discuss the various chemicals that make up Styrofoam. This will lead us to talking about why it isn’t safe to microwave it. We will also mention some microwave-safe containers that can be used instead of styrofoam and some others you shouldn’t use in the microwave. 

What Makes Up Styrofoam?

Before we talk about the consequences and risks of microwaving Styrofoam, it may be helpful to first understand the chemical makeup of styrofoam.

Did you know that Styrofoam was actually discovered by accident? In 1954, Dow Chemical Company chemist Ray McIntire was trying to create an electrical insulator when he created Styrofoam instead.

At its most basic chemical makeup, Styrofoam is a plastic. More specifically, it is a plastic called polystyrene. Polystyrene is commonly found in two forms: solid and foam. Polystyrene foam is used today with many different containers, including Styrofoam plates, Styrofoam cups, Styrofoam takeout containers, and more. 

It became popular over the years because of its attractive chemical properties. Polystrene is lightweight, resistant to moisture, versatile, and durable. It is most commonly used in the food space, but has many other applications besides cookware and storage.

Risks and Consequences to Microwaving Styrofoam

There are many risks and consequences in microwaving Styrofoam, whether it is just one time or multiple times. Even though it may be convenient, here are some reasons why you shouldn’t microwave Styrofoam.

Risk of Fire

One of the first risks to microwaving Styrofoam—even Styrofoam that’s advertised as microwave safe—is that it can cause burning or fire. 

Styrofoam starts to soften at 212 degrees Fahrenheit. However, the polystyrene plastics in Styrofoam begin to decompose far earlier in the heating process. This is all fine and dandy, except microwaves heat up to 212 degrees Fahrenheit. This poses numerous fire hazards and safety hazards.

Even if you only need to microwave your food or drink for 30 seconds, we recommend against using Styrofoam for this reason alone. The last thing you want to happen is to ignite a spark in your already hot microwave and have that spark explode into flames.

It can be difficult to stop microwave fires because they spread so quickly. Styrofoam can ignite from a single spark, so all it needs is one flame to start a fire that could cause severe damage.

microwave oven on fire

Styrofoam May Melt

Another related consequence of microwaving styrofoam is that it can melt in the microwave. The longer the styrofoam is heated, the more likely it is to start melting.

There are multiple downsides to this. First, you run the risk of making a mess all over the inside of your microwave (which is never fun to clean). Not only will the Styrofoam container melt, but the food or drink in it could spill everywhere and possibly ruin your microwave.

You Could Ingest Toxic Chemicals In Food or Drink

Another downside to microwaving styrofoam is that chemicals from Styrofoam containers can leech into your food or drink and/or released into the air when the container is heated. The most prominent chemical in styrofoam cookware, styrene, gives off toxic chemical gasses and can become fixed into the food or drink you’re warming up. 

In addition to the numerous health hazards this poses, it can also make your food or drink taste different than normal. There’s nothing worse than looking forward to a meal or drink and not being able to stomach it because it doesn’t taste right.

What matters most is your safety and the well-being of others around you.

If you are wondering, “Well, I’m only going to use the microwave for 10 seconds, so can I microwave Styrofoam,” the answer is still “No.” As silly or inconvenient as it may seem, even 10 seconds in the microwave is 10 seconds too long.

Now let’s consider some health concerns associated with inhaling or ingesting Styrofoam.

Potential Health Problems

The biggest concern about microwaving Styrofoam is the health problems it can cause. Following are some of those risks.

Neurotoxic Side Effects

neurotoxic reaction or side effect is one that modifies the normal activity of our nervous system. Many neurotoxic side effects can be caused when individuals microwave Styrofoam.

In their report, “Styrofoam: More Harmful Than Helpful,” Drs. Adrienne Miller, Sheila Mohazzebi, Samantha Pasewark, and Julie M. Fagan of Rutgers University wrote, “Long-term exposure to small quantities of styrene can cause neurotoxic (fatigue, nervousness, difficulty sleeping)… effects.” 

This means that even the 40 seconds to microwave your takeout leftover from last night can pose irreversible and harmful side effects to your body. Constantly feeling tired and nervous/anxious can seriously affect one’s physical and mental health. Add difficulty sleeping to those issues and you may have a hard time completing many daily activities that used to be so easy.

If this were the only reason to avoid microwaving Styrofoam containers, we believe it would be enough.  Unfortunately, it isn’t the only one.

senior man rubbing eyes as if they're irritated or he's tired

Carcinogenic Effects

Carcinogenic side effects are some of the most dangerous risks  that can occur by microwaving Styrofoam. As noted earlier, heating styrofoam can cause gasses and hazardous chemicals to leech into the air and into your food or drink.

Carcinogens are cancer-causing substances. Cancer is a condition where the body’s cells grow uncontrollably and spread. Carcinogens can cause cells to divide too fast or change the DNA in cells.

Even small amounts of heated polystyrene exposure can cause these carcinogenic side effects over time.

Acute Health Effects

In addition to the more serious side effects of inhaling or ingesting Styrofoam, there are also acute side effects that can affect you immediately after inhalation or ingestion. These side effects can include eye irritation, headaches, temporary hearing loss, and stomach irritation. Even though these effects are not long-lasting, your body’s reaction to the incident is its way of telling you “Don’t do that again!”

Gastrointestinal Effects

Another possible risk from heating styrofoam are gastrointestinal side effects that can harm your esophagus, stomach, and intestines. Things such as upset stomach, nausea, and vomiting can be common with repeated exposure to heated Styrofoam. Other serious side effects include difficulty swallowing or going to the bathroom.

If after heating Styrofoam in your microwave you experience any side effects mentioned in this article, take that as a strong hint to switch to a non-toxic alternative container. If health problems persist even after you make that switch, immediately consult a doctor to get medical help as soon as possible.

Microwave-Safe Styrofoam Alternatives

After reviewing reports and evidence concerning the risk of heating Styrofoam in the microwave, we have concluded the risks far outweigh the convenience. In an abundance of caution, we would caution readers not to use even Styrofoam containers that are advertised as being microwaveable.

Instead, we recommend any microwaved food or drink be in one of the following safe alternatives.


Glassware is one of the best alternatives to Styrofoam for microwave use. Glass can withstand extremely high temperatures and won’t spark like how Styrofoam might. The only way that you could possibly burn glass would be if you heated it to 2,500 degrees Fahrenheitwell beyond the capability of your kitchen microwave.

Many people prefer glass over styrofoam for a few reasons. It is resistant to staining and won’t release toxic fumes into the air. Although you have to clean it, it is 100% reusable.

Two things to consider when using glass cookware. First, be careful when handling it. The glass could be hot coming out of the microwave, so use those potholders for the purpose they were made. Besides blisters on your fingers, a dropped dish can leave shards of glass all over the floor.

The other thing is to make sure the glass container does not have any metal on it because metal and microwaves are a dangerous combination

a woman putting a glass bowl of vegetables into the microwave

Tupperware and Other Plastics

While Styrofoam is a plastic that can be harmful when heated, there are many plastic options that aren’t harmful and can be microwaved. One of these types of plastics is Tupperware containers. Tupperware is BPA-free, meaning it won’t release harmful chemicals into the air or melt into your food. 

When trying to identify plastics that are safe to put into the microwave, you should look for the microwave-friendly emblem that is embossed on microwavable containers. This emblem looks like a microwave with squiggly lines going across it. Many of these safe containers will also state that they are microwave-friendly.

If you have any doubts about the microwavability of the container, use a different dish that you have no doubts about. It is always better to be safe rather than sorry.

The only potential downside to using Tupperware or other plastics in the microwave is that they may be permanently stained by certain foods. Dark sauces or foods that are dense with oil can stain even darker colored plastics. For this reason, we recommend using Tupperware and other plastic containers you wouldn’t care get stained.

Paper Plates (many options) 

Another alternative to using Styrofoam in the microwave is paper plates. Plain paper plates are safe to use in the microwave and won’t catch fire or dispense harmful chemicals into the air.

One of the biggest reasons why people use paper plates in the microwave is because they’re both safe and disposable, so you won’t have to worry about cleaning another dish.

However, there are some paper plate options that aren’t safe to use in the microwave. These plates often have a plastic film on them or other types of coating. They may have specific designs or letting on them. Many paper plates that can’t be used in the microwave will have a warning on their package to let consumers know they are not microwave-safe.

We recommend double and triple checking to be sure a plate is safe to use in the microwave before using it. That way, both you and your food will remain unharmed.

closeup of someone holding a stack of biodegradable paper plates

Paper Towels

Paper towels have many uses besides wiping up spills. One of those is for microwaving food. The paper towel can cover food so it doesn’t make a mess in the microwave, wrap food up for quick heating or serve as a quick “plate” to put the food on while heating.

Another advantage to this option is that cleanup is simple. All you have to do is throw the paper towel away after it has served its purpose. Many paper towel options are made without harsh chemicals or additives, which also makes them environmentally friendly. 

Certain Ceramic Pieces

Ceramic plates, bowls, or cups can also be heated in the microwave. In fact, they are one of the safest options to use in the microwave because of their heat resistance and sturdiness. Much mass-made cookware is created using ceramic with a smooth coating added on top for easy cleaning. 

If you are going to use a ceramic piece in the microwave, double check to make sure it is microwave safe. Most ceramic pieces are safe, but those that are homemade or contain metal pieces or flammable materials are not. 

To find out whether your ceramic dish is safe to microwave, either contact the seller, perform an internet search, or look for the microwave-friendly emblem on the bottom of the dish.

Another thing to consider with ceramics is to avoid heating a cracked piece. Heating in the microwave could cause it to crack further or shatter. So if your favorite ceramic mug has a hairline fracture, it would be best to retire it to the china cabinet for display and heat up your hot chocolate in a newer cup.

Don’t Use These Alternatives in the Microwave

When you make the decision to avoid Styrofoam in the microwave, be careful not to choose an option that might also cause problems. Just as there are many safe options to use in the microwave, there are also others that are unsafe. Here are a few options to avoid.

Anything With Metal

As noted a few times previously, never ever put anything in the microwave that has metal on it. Metal sparks instantly, especially when it is heated, so metal in the microwave is a serious risk of fire—not to mention ruining your food. 

lasagna in a disposable foil pan

Single-Use Plastics

Single-Use plastics that are used to store things such as cottage cheese, yogurt, and other similar food items should also never go in the microwave. These containers tend to melt easily and may contain toxic chemicals that are released when heated. They should not be used or reused as very cheap Tupperware. They aren’t.

Check the package for the microwave-friendly emblem on the bottom of the container or just play it safe and put the food to be heated in one of the aforementioned safe types of containers.

Aluminum Foil

Aluminum foil is a very thin sheet of metal. That being the case, do not put it in the microwave. It can spark easily, causing potential harm to you, your food, or your microwave. If you’re looking for something to cover your food, you can use a microwave-safe lid or a paper towel alternative.

Want to heat up last night’s baked potato? Wrap it in aluminum foil if it is going in the oven, but use a paper towel if it is going in the microwave.

partially unwound roll of aluminum foil against black background

Recycled Paper Materials

Recycled paper materials include things such as grocery bags, takeout bags, newspapers, and other similar things. It is nearly impossible to know what is in the container besides just paper. Many containers made with recycled paper contain a wax film or plastic coating to help preserve the life of the container. Instead, use a paper plate that can still be thrown away when finished.

In Summary

We get it. Styrofoam is a very convenient way to store food that can be easily disposed of once you’re done using it. Unfortunately, it is not safe to use in a microwave. The risks far outweigh the benefits.

However, not all hope is lost! There are many microwave-safe alternatives available so you don’t have to choose between eating cold spaghetti or firing up the stove burner for a quick lunch.

We hope this guide provided you with information you can use to make safer choices in using your microwave and why many experts warn against using styrofoam to heat up your food and drink.

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