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How Bad Is It to Microwave a Plastic Container?

How Bad Is It to Microwave a Plastic Container?

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Here’s what you should know before reheating those leftovers.

It’s common knowledge that you should avoid microwaving anything with metal—if you’ve ever accidentally zapped a dish with a scrap of aluminum foil still attached, you know why.

A lot of info out there also warns against the use of microwaving plastic containers, using scary terms like BPA to scare us into transferring our leftovers into a glass dish before reheating them. Yet it gets confusing when you look at items like frozen dinners, which come in plastic containers with specific instructions to reheat them in the microwave. So, what gives?

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“In general, any food contact material that is made to transport, package or deliver food to a consumer—including plastic—is regulated by the FDA,” says Tamika D. Sims, PhD, director of food technology communications at International Food Information Council Foundation, an organization focused on communicating science-based information on health, nutrition and food safety to the public.

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The FDA has used toxicological, chemical, and environmental data to evaluate the safety of any food contact material before it reaches the consumer level since 1997, when new procedures were implemented in the FDA’s Modernization Act. So if you toss a package of plastic containers into your shopping cart at the grocery store in anticipation of Thanksgiving leftovers, you don’t have to worry about them containing BPA or other harmful chemicals that could leach into your food.

“What people have to realize is that any food contact substance has already been tested for how much migration is possible,” says Dr. Sims, noting that all food contact substances have some migration properties—even things like frying pans, for example—that aren’t unsafe.

As a rule of thumb, you should pay attention to what the package says, and use any container only as the manufacturer instructs you to do. If it says “do not reuse” or “do not put in dishwasher,” you shouldn’t. But if you break the rule once in a while, it doesn't mean you’re destined for sickness, says Dr. Sims.

The reason manufacturers include instructions like “do not microwave” is because the integrity of the product can start to break down at a certain temperature. While you won’t be causing illness by doing so, you could burn yourself, melt the container, or even harm your microwave. The same holds true for other plastics, like plastic wrap (which begins to break down in the microwave, potentially melting into your food) or plastic cutlery (which can bend and break when it gets too warm).

The bottom line? For things that need a quick reheat, using a plastic container that says it can be microwaved is fine, says Dr. Sims, and you won’t be making yourself sick if you have to heat up your lunch this way every now and then. But if you aren’t pressed for time, it’s worth it to skip the microwave in general and warm up your food in another way.

“Try reheating it with foil in an oven,” says Dr. Sims. “[Doing so] helps things like pizza get crispy, and makes it taste better [than a microwave], too.”

That Plastic Container You Microwave In Could Be Super-Toxic

If your idea of meal preparation is microwaving leftovers in the plastic takeout container they came in, here’s some bad news: Several chemicals in pliable plastic can leach into your food when you heat it, and even if you’re diligent enough to transfer the food to a bowl or plate labeled “microwave-safe,” you still may not be protected. By and large, that label means they won’t melt or break when heated𠅋ut it doesn’t mean they’re safe.

The two components in plastics that experts are most concerned about arephthalates and bisphenol-A (BPA), which are often referred to as endocrine disruptors because of their ability to affect estrogen and testosterone levels in humans. They also appear to have the potential to impact the development of the brain and reproductive organs in developing fetuses.

Exposure to phthalates, which make plastic flexible (and also turn up in perfume—see Is Perfume Bad for Me? for more on that), has been associated with reduced sperm quality in men and shorter distances between the anus and the scrotum in male fetuses. A shorter anogenital area is considered 𠇊 marker for future reproductive and fertility issues,” says Dr. Sheela Sathyanarayana, associate professor at the University of Washington.

Exposure to BPA when a fetus is developing, meanwhile, has been associated with prematurity, changes in breast and prostate cells, early puberty, obesity, diabetes, and heart disease according to the Pediatric Environmental Health Specialist Unit. After growing concern from public health groups over the potential health risks of BPA, the FDA banned its use in baby bottles and sippy cups in 2012.

Doctors typically advise minimizing exposure to these chemicals �sed on a strong body of evidence in animal literature and a good body of literature supporting what has been seen in animal studies in human studies,” says to Dr. Maida Galvez, Associate Professor in the Department of Preventive Medicine and Pediatrics at the Icahn School of Medicine at Mount Sinai.

So what to do? To reduce unnecessary risk, experts advise everyone to microwave food in glass or ceramic and replace plastic housewares labeled “microwave-safe” if they have been scratched or if the color has changed. “That means a certain area designed not to come in contact with food is coming in contact with food and potentially more chemicals present in that container will migrate into food,” says Rolf Halden, Director of the Center for Environmental Security at the Biodesign Institute at Arizona State University.

If food must be covered, then use paper towel, not plastic wrap. Condensation underneath the plastic wrap, which could contain phthalates, could cause fluid to drip down into the food, Halden says.

If microwaving food in plastics is unavoidable, then pay attention to the recycling codes at the bottom of the container. Those codes say something about the type of plastic used𠅊void any that have the code 3 or 7. The USDA Food Safety and Inspection Service advises Americans not to reuse margarine tubs, take-out containers, whipped topping bowls, and other one-time use containers, which are more likely to melt and cause chemicals to leach into food.

And it’s not just some plastic containers it’s most. An analysis of 455 common plastic products, including supposedly BPA-free ones, found that 70% tested positive for estrogenic activity that number went up to 95% when the plastics were microwaved.

Some scientists also worry that the chemicals replacing controversial ones may not be safer. A review of existing research on BPA replacements found they’re “hormonally active in ways similar to BPA,” and a pair of studies linked high blood pressure and insulin resistance to DINP and DIDP, which are designed to replace DEHP, a chemical in consumer plastics that the EPA deemed a probable human carcinogen.

“What ends up happening is one chemical will get a lot of scrutiny, so a company will use one that’s very similar because it has the same properties,” says Sathyanarayana.

In the end, as Mount Sinai‘s Galvez sums up the dilemma: “It’s really hard to be a smart shopper when you don’t necessarily know what’s in a given product, so ideally the legislation and labeling would be in place so that this wouldn’t be a concern.”

A microwave-safe container shouldn't be heated significantly by the microwave (only by conduction from the food it contains). So, it should be fine, so long as the food is, and as long as the food doesn't exceed its allowable temperature.

You can test fairly easily—put the container, partially filled with some water, in the microwave for a few minutes. Does the container heat up, possibly more so than the water—especially where its not in contact with the water? If so, I'd be reluctant to use it in the microwave for that long.

Some containers are microwave safe, but only for heating to maybe 160°F or so. A common example is LDPE (often used for plastic wrap). Some can't take boiling for more than a short time (e.g., HDPE). Polypropylene should be fine, even with boiling. Go any hotter (e.g., filled with oil, which is probably insane) and most will fail. If you're lucky, the container will have a resin ID code on it, LDPE is #4, HDPE is #2, polypropylene is #5.

Your microwave may not be fine with 40 minutes of strait microwaving, or with the steam buildup. You should probably check its manual.

I assume also you've read Jay's comment about converting recipes, and that you're doing something where 40 minutes won't result in charcoal.

Microwave Covers: Are They Safe?

Q: At work, we're supposed to use plastic covers to keep the microwave clean. Are they safe?

A: Microwave covers are inexpensive, and they're dishwasher-safe and reusable, which makes them even cheaper (and green). Some are just a flat sheet of plastic, while others are dome-shaped. Most brands come in several sizes to fit different plates and dishes. Many are made of plastic that the FDA has approved for microwave use.

Plastic microwave covers are meant to replace the plastic wrap that many people cover their food with in the microwave to keep it from splattering. The FDA says plastic wrap labeled "microwave safe" is indeed safe. But if plastic wrap -- even microwave-safe plastic wrap -- touches food, especially food with high fat content, it can melt, as well as cause steam burns when unwrapped.

Chemicals can also leach into the food if plastic wrap or plastic covers make contact with the food being heated. The FDA says those chemicals aren't dangerous. But your safest bet is to check labels carefully and use only the plastic wrap and covers that are specifically approved for microwaves.

Want an easier solution? Cover your food with a ceramic plate or with a piece of biodegradable wax paper or paper towel.

Microwaving Plastic Honey Container?

My husband takes the honey in the plastic bear and microwaves the whole plastic container every time he wants to use a little honey. Is this healthy or safe to microwave it so often in this plastic container?

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A lot of people are saying that it isn't safe to microwave plastic. It is fine. You see, plastic is made from petroleum based sources. Over time, it out-gasses, making it brittle. The gasses that it releases aren't the greatest, but they are going to be released whether or not you microwave them. Microwaving it won't hurt anymore than leaving the honey in the container. It would take a very very very long time for it to have a negative effects.

I am guilty of doing this myself. Never thought about safety issues of microwaving the plastic. My problem was that the plastic bottle got too warm and went out of shape--it listed to one side and the bottom was no longer flat--it wouldn't stand upright.

Problem solved--I transferred the honey to an empty glass jelly jar. No more worries about the plastic container. Do the same thing and your husband can microwave all he likes.

Certain plastics are indeed carcinogenic when heated in the microwave so you probably should find out what kind of plastic container the honey is in and do a little research about it.

My other thought is that heating and reheating is 'cooking' the honey over and over again and is probably depleting the honey of nutritional value.
Might be best to just transfer the honey in to a large mouth glass jar and scoop out with a spoon.

If you have the plastic that is hard/brittle, misshapen, you have the kind of plastic advised NOT to do this with. If the plastic stays soft and pliable, it is safer. Again, to keep using the microwave, just jar it. Infact, find a bee keeper and get it FRESH. A whole different favor.

One more info about plastic. There was the recall on certain plastics containing the chemicals that are harmful. As with anything, there are different kinds of plastic. Even baby bottle of certain kinds were found to contain the harmful chemicals.

I myself would think that just squirting out a portion into a glass measuring cup and then microwaving would be better. That's what I do with pure maple syrup on pancake morning. I buy it in a fairly large container that stays in the frig. I just pour some into my small pyrex measuring cup and heat that way.

Pour the honey into a glass syrup or vinegar carafe and then the plastic wont be an issue. Reheating honey over and over might cause it to crystallize eventually (like cooking sugar or syrup, I'm guessing) but glass is better all around if you ask me.

I also agree that microwaving that bear container is fine. Of course, if it is melting the container, that is not fine, but more for the mess factor than any other reason.

If the honey has been pasteurized, the reheating in the microwave is not going to make any difference to the honey, except to make it liquid.

If the honey has not been pasteurized, heating might destroy some natural "stuff" in the honey, but I personally wouldn't be overly concerned with this.

If he does it too often or too long he's going to melt your little bear! Believe me. my poor little bear died that way.

No, it is toxic. Try plunging bottle in hot water first. Any plastic microwaved is very toxic.

Don't do it! All the research on cancer sites tell you never to microwave anything in plastic as it releases toxins into your food.

Plastic plus microwave seems like a bad idea to me, we all get enough toxins. I'd put it into a mason jar if it were my honey er guy er both. If you don't have the squeeze thing around then no arguments can ensue. :o)

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How Do Microwaves Work?

The magic box takes your food and returns it warm, in exchange you get cancer 20 years later (totally kidding, I promise). According to the USDA, a microwave takes electric power from a wall socket and with a magnetron (magical device) converts the power to very short radio waves (aka micro waves, get it?). These radio waves are absorbed by water, fats, and sugars, which makes the molecules vibrate very fast and creates heat.

Contrary to popular belief, microwaves don't cook food inside out. The radio waves actually only penetrate food 1 to 1.5 inches into the food. In thick pieces of food, the radio waves don't reach the center, but instead of heated up by conduction of heat, which is the transfer of heat via direct contact.

Inorganic materials in the microwave work differently than food. Non-reactive and non-metal containers such as ceramic, glass, or plastic don't absorb the radio waves at that frequency. They don't heat up like your food does. On the other hand, metal reflects the micro waves of energy, and your microwave is lined with sheets of metal so that the waves are only in the tiny magic box cooking your food and not in the kitchen.

Harvard researchers are warning against microwaving food in plastic

If we had a dime for every time we’ve heated up our food in a plastic takeaway container, let’s just say we𠆝 be rollin’ in cash.

But according to a new Harvard Medical School study, plastic containers can leak toxins when they’re reheated, which can have hazardous health effects. Oh crap.

The research explained that the trusty Chinese takeout containers can contain dangerous phthalates from the plasticisers, which are used to make them flexible and last longer.

And when the plastic is heated up in a microwave, the amount of phthalates that seep out is increased.

But it doesn’t just stop there. For the kind souls out there who wash and re-use their plastic-containers to protect the environment, you’re unfortunately not benefiting your health in anyway.

The article said reusing plastic takeaway containers that are “scratched, or cracked, or those that have been microwaved many times, may leach out more plasticisers.”

But what can cause more harm to your health is actually the food you’re heating up.

Higher fat foods such as meats and cheese are prone to leaching, where the phthalates can cause damage to the reproductive system, liver, kidneys and lungs if ingested.

How is this possible? The chemical works as an endocrine disruptor, which mimics the body’s natural hormones and causes health problems.

While the winter season might be over for this year, we know you’re reading this and silently panicking about having to eat cold leftover casserole and soup come next year.

The study advised that before you heat up your food, make sure the container has a “microwave safe” logo and ensure you vent the container either by leaving the lid ajar or lifting the edge of the cover. If it doesn’t have a “microwave safe” logo, simply transfer it into a microwave safe container or bowl.

And if you’re also guilty of sticking your food in the microwave with a piece of flimsy plastic wrap tossed on top, that’s also another habit you need to break ASAP.

𠇍on’t let plastic wrap touch food during microwaving because it may melt,” the researchers advised.

“Wax paper, kitchen parchment paper, white paper towels, or a domed container that fits over a plate or bowl are better alternatives.”

Can you microwave food in plastic containers?

The next time you use a plastic container to zap leftovers in the microwave, you may want to consider what heated plastic does to your food. And, more importantly, what that food is doing to your body.

The problem with plastic is that it’s not all the same. The term plastic refers to a range of materials, with substances added to shape or stabilize it. The two most common stabilizers are:

  • Bisphenol A (BPA): Used to make plastic harder
  • Phthalates: Used to make plastic stronger and more flexible

“It’s important to avoid substances that interfere with hormones,” says Dr. Neelima Chu, a board-certified endocrinologist and internal medicine doctor with Sharp Rees-Stealy. “These substances can lead to infertility thyroid disease early puberty leukemia breast, uterine and prostate cancers neurobehavioral issues obesity and metabolic dysfunction.”

So is it time to toss your plastic storage collection? Not necessarily. While all the above sounds a bit scary, consider the following:

  1. The FDA regulates plastic. The FDA makes certain determinations when it comes to plastic, such as how much of a chemical you can consume during your lifetime with little to no risk. While this doesn’t necessarily prevent some substances from being included in plastic, it ensures the amounts are within an estimated safe range.

Is That Plastic Container Safe?

The two best-studied offenders are bisphenol A (BPA) and phthalates. BPA mimics estrogen and has been shown to disrupt hormone and reproductive system function in animals. Research by the National Toxicology Program found a moderate level of concern about its "effects on the brain, behavior and prostate gland in fetuses, infants and children." Phthalates have been shown to disrupt the endocrine system and have led to malformations in the male reproductive system in animals. Studies in humans have found associations between high phthalate exposure and a variety of health concerns including low sperm quality, high waist circumference and insulin resistance.

Researchers are still debating whether phthalates and BPA actually cause these health problems and, if so, how much exposure is necessary to trigger them. While these issues are being figured out, some experts recommend taking a preventive approach: "Minimize contact of food with problematic plastics as a precautionary measure to protect your health," suggests Rolf Halden, PhD, adjunct associate professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health. Here are six simple tips for reducing your exposure to the potentially harmful chemicals in plastics.

1. Know the code. Look on the bottom of your plastic to find the recycling symbol (a number between 1 and 7 enclosed in a triangle of arrows). The code indicates the type of plastic you are using and can give you important clues about safety. "We generally say 1, 2, 4 and 5 are considered to be the safest," says Sonya Lunder, senior analyst at the Environmental Working Group. Try to avoid using plastics with 3 or 6, as these leach chemicals that may be harmful. Number 7 is an "other" category that includes BPA-containing plastics called polycarbonates. These plastics, which you should avoid, will have the letters PC printed underneath the 7.

2. Reconsider the microwave. Heat can increase the rate at which chemicals like BPA leach from plastic. Containers labeled "microwave safe" have been tested by the Food and Drug Administration (FDA) and found to leach extremely small amounts, which the FDA has determined to be safe. However, some experts advise people to keep plastic out of the microwave altogether. "I don't microwave anything in plastic," says Lunder. "It's really easy and fast to put my food into a ceramic or glass container and heat it that way." And never put plastic wrap on top of your food in the microwave, since it can melt. Use wax paper or a paper towel instead.

3. Use it for its intended purpose. Plastics that are designed for single use should only be used once. "Plastic breaks down over time," Lunder explains. "Some aren't designed to withstand heating and cooling." Most plastics with recycling code number 1 are intended for single use, such as disposable water bottles. And that takeout container from six months ago? Toss it. In general they're fine for refrigerating leftovers, but aren't designed for heat exposure or long-term use.

4. Wash by hand. Only put plastics into the dishwasher if they have a dishwasher safe label. If you want to be extra-cautious, wash all plastics by hand or use only glass and ceramic plates and dishes. In the dishwasher, plastics are exposed to detergents and heat, which may accelerate the leaching of BPA from food containers.

5. Do not freeze. Only put plastics in the freezer if they have a freezer-safe label. Freezer temperatures can cause plastics to deteriorate, which increases the leaching of chemicals into the food when you take containers out of the freezer to thaw or reheat.

6. Don't panic. Cutting down on exposure to potentially harmful chemicals in plastics can benefit your health. But as Dr. Halden reminds us, "Many things in your life pose a much higher risk than exposure to plastics, such as smoking, poor diet and even driving a car."


If you have had success using Tupperware in the microwave, then it&rsquos easy to continue along the same path. However, even though the products may be labeled &ldquosafe for microwave use,&rdquo can you really trust the descriptions?

After diving into the subject a little further, I believe that glass and ceramic microwave safe containers are better alternatives to use rather than microwaving plastic Tupperware.

Covered food heats up quicker and more consistently. Consider using a microwave food cover to expedite the reheating process and evenly distribute the heat.

Although Tupperware has developed new products over the past few years, they have provided very strict instructions that must be accurately followed when using microwavable Tupperware:

  • Do not cut or scratch the plastic
  • Pop the vent
  • Reheat food only
  • Use medium heat
  • 3 minutes or less
  • Do not exceed fill-line

Don&rsquot use old or damaged plastic containers in the microwave because they may have exceeded the microwave ability. Doing so also puts the food at risk for encountering toxic release, so throw away old Tupperware or use them for purposes other that food storage.

In addition, Tupperware made before 2010 most likely contains BPA in the plastic compound.

When it comes to the cooking and food storage products that you have, it&rsquos important to understand the uses and misuses.

If you understand the symbols and are confident using microwave safe Tupperware, then I don&rsquot think you should have anything to worry about. However, if you find yourself at all uncertain, then stick with glass or ceramic and simply avoid using all plastics in the microwave.


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