Microwaving with Plastics: Myths vs. Facts

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Plastic is a synthetic or semi-synthetic substance characterized by its resilience, low weight, and pliability. Due to these characteristics, it can be fashioned into a wide range of commodities, encompassing domestic items such as food storage containers, beverage containers, and additional dishes, as well as medical devices and automotive components.

However, you may be unsure as to whether plastic can be microwaved safely in order to reheat leftovers, prepare food, or preheat your preferred beverage.

This article clarifies the misconceptions and presents the facts regarding microwaving plastic.

Understanding Plastics and Microwaves

food in containers

In the 1970s, the time microwave ovens began heating and operating in homes, they transformed lives. Microwaves, the cross-country runner of the conventional oven, accelerated the preparation and reheating of meals, thereby increasing the opportunity for leisure over labor and saving time. From its inception, the microwave’s mechanics remained shrouded in mystery. It appears to be a magical metal box that rotates and heats food through invisible means, as opposed to the conventional method of heating the air and surroundings via conduction from a flame.

Unexpectedly, foods are cooked in microwave appliances via the injection of microwaves—a form of energy. These electromagnetic waves, which are shorter in wavelength than infrared waves, are imperceptible to the human vision. They are positioned between the two. A magnetron, located within the workings of a microwave, directs electron flow from an electrical inlet to a heated filament, thereby generating an electrical current. This electron flow then transmits microwaves into the cooking chamber via an antenna. By settling in water, fats, and carbohydrates, microwaves induce radiation heating—the excitation of molecules within an object—and thereby heat food by bouncing around the chamber. Due to the limited distance that microwaves can penetrate an object before losing momentum, denser foods have their exteriors heated by microwaves before the interiors are subsequently heated through the conduction of heat from the exteriors.

The molecules of frigid water move at a slower rate. When water is subjected to heat, the water molecules collide. Heat is generated as a result of the collisions’ energy. To preheat food, therefore, it is necessary to stir the water molecules contained within the food. At this point, the microwave becomes useful. Microwaves are special electric and magnetic pulses that are emitted by a microwave oven. The passage of these microwaves through the food induces a collision between the water molecules present in the food. As a result, the food becomes heated.

The indisputable utility of plastic in our everyday existence stands in contrast to the numerous criticisms leveled against it. This is most evident in the residence, where numerous commodities and products are constructed from plastic. The kitchen is one location where an abundance of plastic products are typically present. Plastic kitchenware consists of plates, bowls, knives, forks, utensils, and other implements that are utilized in the culinary domain and have the potential to come into contact with food.

Generally, there are 7 types of plastic, these are:

  • PET or PETE (Polyethylene Terephthalate Ethylene)
  • HDPE (High-density polyethylene)
  • PVC (Polyvinyl chloride)
  • LDPE (Low-density polyethylene)
  • PP (Polypropylene)
  • PS (Polystyrene)
  • Other (an all-encompassing category)
  • PET is a non-leaching plastic that has been given approval for use in direct food contact. It can be recycled alongside the other plastics.

You’ve probably observed that plastics are frequently used as containers for food and drink. Carbonated beverage containers, water bottles, food storage containers, jars of peanut butter, and even frozen food are all packaged in PET.

Myths vs. Facts

Myth 1: All plastics are the same when microwaved.

Fact: A critical aspect of plastics is that they are composed of compounds that have the potential to cause acute and chronic harm to individuals. Additionally, keep in mind that there are various types of plastics, and making the incorrect selection can have severe consequences for both the individual’s life and their microwave.

Primary applications for high-density polyethylene (HDPE) include beverages and potable liquids. This plastic is frequently encountered in juice and milk containers. It transforms from –40 to 266 degrees Fahrenheit in temperature. Additionally, it has numerous benefits that make it ideal for storing liquids.

PP, or polypropylene, is frequently employed in the production of utensils, forks, and food containers. Having a resistance to temperatures of 230 degrees Fahrenheit, it is ideal for preparing dishes in the microwave.

Myth 2: Any plastic container is safe if it doesn’t melt.

Fact: Prominent contributors to hazardous plastics are synthetic compounds known as phthalates and bisphenol A (BPA), which are frequently incorporated into plastic in order to impart flexibility and maintain its form. Excessive quantities of these substances have been associated with a variety of adverse health effects, such as disruptions in hormone balance, respiratory complications, and cardiovascular ailments. Children and pregnant women may be more susceptible to adverse effects. Heating plastics (e.g., by microwaving) can increase the likelihood that these substances will transfer to food. Additionally, subjecting plastic containers to the high temperature of the dishwasher may induce chemical leaching, which is something to be avoided. 

The process by which a substance is extracted from a solid material dissolved in a liquid is known as leaching. 

Myth 3: If a container survives the microwave once, it’s always safe.

Fact: Plastic polymers are more susceptible to degradation when subjected to high temperatures in the oven or microwave than metals and ceramics. However, the degree and mechanism of degradation are contingent upon the polymer’s chemical structure and the quantity of additional substances (additives) that are present. The plastic container is weakened by heating and radiation, which facilitates the escape of additives and ingredients that could contaminate the food.

Leaks of the chemical into your food may result in cancer, reproductive ailments, and other health complications. The quantity of chemical leakage is contingent upon the heating time, temperature, and frequency of use of the plastic container.

Myth 4: “Microwave-safe” means completely free of chemical leaching.

Fact: What does it imply that an item is safe for use in the microwave? Does “safe for containers” and “safe for people” have the same meaning?

It indicates that a plastic container bearing the label “microwave safe” will not dissolve or bubble when placed in the microwave. It guarantees that molten plastic contained within will ignite on whoever handles the container.

There are undulating lines on your container, which indicates that it is microwave safe. The symbol may undergo substantial changes in appearance, at different times depicting a dish or a microwave emitting radiation waves; however, the undulating lines will consistently remain. The presence of undulating lines on the label signifies that the product can be reheated without difficulty.

Myth 5: Microwaving plastics is the biggest health concern in kitchens.

Fact: Equipment used for food preparation, physical handling, the manner in which stock is stored, and the general cleanliness of the environment are frequently the sources of hazards in commercial kitchens. But the reality is that individuals are the cause of the vast majority of risks, if not all of them.

Kitchens are known for both their heat and their level of activity as places of employment. Even in the kitchens of residential homes, hazards can be found, therefore it is important to exercise caution to avoid getting hurt or having an accident.

In the kitchen, you run the risk of getting burned by hot equipment, cutting yourself on sharp blades, and contaminating food with pathogens. Due to the inherent nature of the activity, it is impossible to eliminate all risks entirely; nevertheless, these dangers can be managed and reduced to a tolerable level through comprehensive training, regular staffing, and rigorous housekeeping.

Safety Standards and Regulations

microwave on countertop

Standards for the safe production and storage of food, beverages, and pharmaceuticals were established by the Food and Drug Administration (FDA). In addition to establishing rigorous standards for consumable products, they conduct thorough examinations of packaging materials and preparation equipment, including plastic.

“FDA compliant” denotes that a substance satisfies every FDA regulation pertaining to direct, secure contact with food. It is essentially an official designation that a substance is “food grade.” An FDA-compliant material must possess the capacity to endure the environment in which it will be utilized. A plastic conveyor belt that is utilized to transport food through an exceedingly high-temperature oven for the purpose of heating, for instance, must not deform physically under the influence of such temperatures. Additionally, it must be able to withstand rigorous cleansing and sanitizing cycles, if relevant. Lastly, it must be chemical-compatible with the food it will come into contact with; for instance, if a food has a high moisture content, is acidic like tomato sauce, or is acidic, it must not discharge any chemicals.

An electron tube known as a magnetron generates microwaves without leaving the furnace. The microwaves are absorbed by the food after being reflected within the metal interior of the oven. Water molecules in food are vibrated by microwaves, generating heat that prepares the food. Hence, raw vegetables, which possess a high water content, can be prepared for a shorter cooking time compared to other foods. As the food absorbs the microwave energy, it is converted to heat; therefore, the food is not rendered “radioactive” or “contaminated.”

Despite the direct generation of heat within the food, microwave appliances do not facilitate “inside-out” cooking. When dense foods are prepared, the exterior layers are predominantly heated and cooked using microwaves, whereas the interior is predominantly cooked through the conduction of heat from the hot exterior layers.

Microwave cookery utilizes containers made of glass, paper, ceramic, or plastic due to the conductivity of microwaves through these substances. While these containers are impermeable to microwave heating, the heat generated by the food during cooking may cause them to warm. Because certain plastic containers are susceptible to melting when exposed to the heat of the food inside, they should not be used in a microwave. In general, metal pans and aluminum foil should not be utilized in a microwave oven due to the reflection of microwaves that could potentially damage the oven and result in inconsistent cooking of food. The recommended containers for use in each microwave oven are specified in the accompanying instructions. In addition, they describe the procedure for determining whether a container can be utilized in a microwave appliance.

Two standards have been imposed by Thailand on specific food contact plastic materials and microwave oven-ready items.

TIS 2493 Part 1-2554 (2011) ‘Part 1 of plastic food containers designed for reheating. The stipulations of this standard pertain to the marking, labeling, packaging, and conformity of polypropylene (PP), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), and polymethyl pentene (PMP).

TIS 2493 Part 2-2556 (2013) “Part 2: Microwave-safe plastic food containers for single reheating.” The requirements for PP, PET, and polystyrene (PS) are outlined in this standard, which encompasses aspects such as temperature resistance, marking, labeling, packaging, and conformity.

Health Implications of Microwaving Plastics

You may be exposed to numerous plastic products on a daily basis, depending on where you reside and work. Plastic containers for food and beverages, certain disposable dishes, and bottles for toiletries are all composed of chemicals. All plastics may discharge chemicals when scratched or heated, according to research. Furthermore, substantial research indicates that certain levels of exposure to certain compounds found in these products, including bisphenol A (BPA), may potentially induce cancer in humans.

Chemicals made from plastics that have been heated in the microwave may migrate into food. Plastic is ubiquitous. Various containers, including bowls, wraps, bottles, and bags, are utilized to store delicacies and beverages. But in recent years, an increasing number of individuals have questioned the safety of exposing ourselves and our food to so much plastic.

Certain compounds contained in plastic have been found to leach into the food and beverages we consume, according to studies. A number of these chemicals have been associated with adverse health effects, including decreased fertility and metabolic disorders (including obesity). Exposure of plastic to heat can accelerate and amplify the rate of this leakage. By microwaving leftovers in a plastic container, you may be exposing them to an even greater concentration of potentially hazardous compounds.

One primary issue associated with the use of microwaved plastic is the potential for additives, including those that are hazardous, to leach into food and beverages.

The compounds that are of principal concern are phthalates (a class of substances including bisphenol A) and BPA, which are both employed in plastic to enhance its flexibility and durability.

These chemicals, particularly BPA, have been associated with obesity, diabetes, and reproductive damage, as well as hormone disruption.

Polycarbonate (PC) plastics, which have been extensively utilized in the production of food storage containers, drinking glasses, and infant bottles since the 1960s, are the primary sources of BPA. BPA may gradually infiltrate into foods and beverages from these plastics, in addition to occurring when the plastic is heated, as in the case of microwaving.

Presently, however, certain food preparation, storage, and serving product manufacturers have replaced PC plastic with PP or another BPA-free plastic. Additionally, the use of BPA-based materials in infant formula packaging, sippy containers, and baby bottles is prohibited by the Food and Drug Administration (FDA).

However, research has indicated that microwave cooking can cause the release of hormone-disrupting chemicals such as phthalates, as well as BPA alternatives like bisphenol S and F (BPS and BPF), from even BPA-free plastics into food. 

In light of this, it is generally prudent to refrain from microwaving plastic containers, unless the FDA specifies otherwise on the label. 

Best Practices for Microwaving with Plastics

Plastics are indispensable components of our appliances. There are numerous daily instances in which our food comes into contact with plastic, ranging from storage to service. The substances and compounds used in the production of certain types of plastic can leak into food when heated in the microwave, according to Robert J. George, DO, an osteopathic family physician from Bradenton, Florida. Ingestion of this plastic residue may give rise to health concerns, particularly among infants and expectant women.

Prior to its utilization in food preparation, each plastic container is subjected to rigorous testing standards established by the Food and Drug Administration (FDA). In the event that the safety of a plastic product for microwave operation is ascertained, written instructions or a microwave-safe symbol will be displayed on the product. The numbering system that appears on plastics is for recycling purposes only and does not provide information regarding the plastic’s suitability for heating.

Dr. George cautions, nevertheless, that not every microwave-safe product can be utilized in the microwave in the exact same manner.

Although specific varieties of plastic wrap have been labeled microwave-safe by the FDA, it may melt and discharge some of its contents into the food if it comes into direct contact with hot food (especially fatty foods) in the microwave, according to him. Hence, it is advisable to maintain a minimum distance of one inch between food and plastic wrap prior to reheating, or substitute suitable materials such as white paper towels, parchment paper, or wax paper.

Remember the following:

  • Oven bags, wax paper, and plastic wrap from the shop can all be used safely in the microwave if you know what you’re doing. The food must not come into contact with the plastic wrap.
  • Oven bags, wax paper, and plastic wrap should not be reused.
  • Fat and sugar-rich foods may cause plastic to melt if used together. This warning is printed on the majority of plastic packaging.
  • The manufacturer may not have meant for foam insulated trays to be cooked, and if they melt while in touch with hot meals, chemicals from the container or plastic covers could potentially leach into the food.
  • Plastic wrapping from grocery store purchases and Styrofoam containers should not be heated in a microwave. Take food out of its packaging to prevent chemical migration.
  • Do not heat food in plastic containers, such as restaurant takeout containers or margarine tubs. The containers could perhaps melt or distort.
  • Discard containers that store prepared microwavable meals after you use them because they are meant for one-time use, unless they say that they are reusable.
  • Microwave-safe plastic wrap should be placed loosely over food to allow steam to escape, as recommended by the Food and Drug Administration. There should be at least an inch of space between the plastic and the food when microwaving in a microwave, according to the labeling on some plastic wraps.
  • Don’t ever heat up anything in a plastic bag, a supermarket bag, a newspaper, or aluminum foil.

Alternatives to Microwaving with Plastics

Although it is unlikely that any individual will completely abstain from plastic, it is feasible for all to substantially diminish their plastic consumption, especially with regard to their dietary choices, which constitute the primary route of BPA exposure for the majority of people. If you’re considering a break from plastic, consider the following alternatives to food storage that we’ve discovered:

Glass

Glass, being chemically inert, ensures that no hazardous substances or toxins will permeate into food, irrespective of the temperature it attains. In addition to being suitable for use in the microwave and dishwasher, this material will not absorb odors from food due to its impermeable structure. Furthermore, its exceptional sustainability is attributed to its construction entirely of organic materials, including sand, soda ash, calcium carbonate, and recycled glass. What could be disliked?

Beeswax Wraps

Microwave-safe beeswax coverings, which are constructed from jojoba oil and organic cotton infused with beeswax, can also be used to shield food items. After each use, these pliable, reusable wraps may be laundered with cool water and mild detergent. As a result of the composition of these coverings, we consider them a secure substitute for plastic microwave covers.

Ceramic Plates

When placing food to be prepared in a microwave, one of the most secure methods is to employ a ceramic plate or soup plate that is supported by another ceramic flat plate. Conversely, if you are reheating a meal in a bowl or a ceramic soup plate, utilize a flat plate as a cover. This approach is also the most cost-effective, given that soup dishes are readily available in every kitchen.

Environmental Considerations

Regarding environmental impact, many of us intuitively recognize that reuse is preferable to single-use.  Furthermore, scientific evidence supports this claim. Although it may be disheartening to acknowledge that alternatives to single-use plastic, such as compostable and recyclable products, aluminum, or paper, frequently fail to provide environmental benefits, there is a viable solution that can be implemented.

Although plastic bags are recyclable, this practice is uncommon. Presently, only 6% of flexible plastic packaging is recycled in the United Kingdom, as collection is restricted to supermarkets (Wrap). The remainder are discarded as debris or in landfills, where they degrade into microplastics that contaminate our air, water, and soils, or cause harm to wildlife and ecosystems.

Reusable products, food ware, and packaging produce fewer greenhouse gas emissions (GHGs) throughout their entire life cycle in comparison to their disposable counterparts.

We can surmount the worldwide predicament posed by single-use plastics through adjustments to our way of life, inventive resolutions, and political determination. Individuals, organizations, and governments will, however, need to reconsider the methods by which we manufacture, utilize, and dispose of plastic products. Wasteful and superfluous plastics must be reduced to an absolute minimum and eventually eliminated for the sake of human and environmental health. The cumulative effect of many small actions will be to establish a circular economy.

The kitchen is where the majority of households discard single-use plastic. Fortunately, plastic-free alternatives exist for the vast majority of single-use plastic items; all that is required is the proper equipment to convert your kitchen into an oasis devoid of plastic, toxins, and dirt. 

Plastic packaging is present on pulses, grains, and other grocery items sold at your local supermarket. However, in close proximity to it, you will also discover them available for purchase in unstructured form. They are individually packaged in paper sacks in the desired quantity. Considering that product packaging comprises the majority of plastic waste generated by households, purchasing in volume and loose can significantly contribute to the reduction of plastic waste produced.

Glass containers should be utilized when placing remains in the refrigerator. They are hermetic, long-lasting, and produce little environmental waste. Additionally, the visibility of the food item contained within them reduces the likelihood of wastage.

Likewise, cling films that serve as substitutes for lids—the largest source of plastic debris in the kitchen—can be avoided. In many cases, a standard steel lid will suffice; however, for an airtight closure, reusable silicone lid covers that are compatible with bowls of various sizes can be utilized.

To Summarize

Foods that are microwaved are generally safe to consume. However, there is a correlation between microwaving in plastic containers and increased leaching, which is the transfer or leakage of chemicals into food. It is important to note that a vacuum-sealed plastic container does not necessarily mean that the contents will not dissolve.  Notably, there are both high-quality and low-quality plastics. There are plastics that are more secure than others. Completely avoid BPA products, and examine the symbol for recycling that appears at the bottom.

The utilization of plastic containers and covers bearing the Food and Drug Administration’s (FDA) “microwave-safe” label is, in fact, risk-free and has not been scientifically proven to induce cancer. You are not exposing yourself to dioxins by burning food in a microwave or utilizing containers that are not designed for microwave operation, which may melt and release chemicals into food.

References: 

  1. Microwave Ovens. FDA Guidelines https://www.fda.gov/radiation-emitting-products/resources-you-radiation-emitting-products/microwave-ovens Content current as of: 10/12/2023 
  2. What are FDA approved plastics for food contact? https://www.acplasticsinc.com/informationcenter/r/fda-approved-plastics-for-food-contact.
  3. Ten tips for using plastics when microwave cooking.  Jeannie Nichols https://www.canr.msu.edu/news/ten_tips_for_using_plastics_when_microwave_cooking Michigan State University Extension – June 19, 2014
  4. Does the Use of Plastic Containers in the Microwave Cause Cancer? Kim Polacek, APR, CPRC https://endeavor.moffitt.org/archive/does-the-use-of-plastic-containers-in-the-microwave-cause-cancer  .May 29, 2018
  5. Hardgoods. https://www.sgs.com/en/news/2022/06/safeguards-07122-thailand-mandates-two-standards-for-microwavable-food-contact-plastic-containers. June 08, 2022
  6. https://www.breastcancer.org/risk/risk-factors/exposure-to-chemicals-in-plastic 
  7. Is plastic a threat to your health? .https://www.health.harvard.edu/staying-healthy/is-plastic-a-threat-to-your-health . December 1, 2019

Can you microwave plasric?. Gavin Van De Walle, MS, RD . Medically reviewed by Natalie Olsen, R.D., L.D., ACSM EP-C https://www.healthline.com/nutrition/can-you-microwave-plastic . June 4, 2020

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