Can You Microwave Plastic?
Plastic is a synthetic or semi-synthetic material that’s durable, lightweight, and flexible.
These properties allow it to be made into a variety of products, including medical devices, automotive parts, and household goods like food storage containers, beverage containers, and other dishes.
However, you may wonder whether you can safely microwave plastic to prepare food, warm up your favorite beverage, or reheat leftovers.
This article explains whether you can safely microwave plastic.
Plastic is a material comprised of long chains of polymers, which contain several thousand repeating units called monomers (1).
While they’re typically made from oil and natural gas, plastics can also be made from renewable materials like wood pulp and cotton linters (1).
At the base of most plastic products, you will find a recycling triangle with a number — the resin identification code — ranging from 1 to 7. The number tells you what type of plastic it’s made of (2).
The seven types of plastic and products produced from them include (2, 3):
- Polyethylene terephthalate (PET or PETE): soda drink bottles, peanut butter and mayonnaise jars, and cooking oil containers
- High density polyethylene (HDPE): detergent and hand soap containers, milk jugs, butter containers, and protein powder tubs
- Polyvinyl chloride (PVC): plumbing pipes, electrical wiring, shower curtains, medical tubing, and synthetic leather products
- Low density polyethylene (LDPE): plastic bags, squeeze bottles, and food packaging
- Polypropylene (PP): bottle caps, yogurt containers, food storage containers, single-serve coffee capsules, baby bottles, and shaker bottles
- Polystyrene or Styrofoam (PS): packing peanuts and disposable food containers, plates, and disposable cups
- Other: includes polycarbonate, polylactide, acrylic, acrylonitrile butadiene, styrene, fiberglass, and nylon
Some plastics contain additives to achieve the desired properties of the finished product (3).
These additives include colorants, reinforcements, and stabilizers.
Plastic is made primarily from oil and natural gas. There are several types of plastic that have a variety of applications.
The main concern with microwaving plastic is that it can cause additives — some of which are harmful — to leach into your foods and beverages.
The primary chemicals of concern are bisphenol A (BPA) and a class of chemicals called phthalates, both of which are used to increase the flexibility and durability of plastic.
These chemicals — especially BPA — disrupt your body’s hormones and have been linked to obesity, diabetes, and reproductive harm (4, 5, 6, 7).
BPA is found mostly in polycarbonate (PC) plastics (number 7), which have been widely used since the 1960s to make food storage containers, drinking glasses, and baby bottles (8).
The BPA from these plastics can leach into foods and beverages over time, as well as when the plastic is exposed to heat, such as when it’s microwaved (9, 10, 11).
However, today, some manufacturers of food preparation, storage, and serving products have swapped PC plastic for BPA-free plastic like PP.
The Food and Drug Administration (FDA) also prohibits the use of BPA-based materials in infant formula packaging, sippy cups, and baby bottles (8).
Still, studies have shown that even BPA-free plastics can release other hormone-disrupting chemicals like phthalates, or BPA alternatives like bisphenol S and F (BPS and BPF), into foods when microwaved (12, 13, 14, 15).
Therefore, it’s generally a good idea to avoid microwaving plastic, unless — according to the FDA — the container is specifically labeled safe for microwave use (16).
Microwaving plastic can release harmful chemicals like BPA and phthalates into your foods and drinks. Therefore, you should avoid microwaving plastic, unless it’s labeled for this specific use.
While microwaving plastic accelerates the release of BPA and phthalates, it’s not the only way these chemicals can end up in your food or drinks.
Other factors that can increase chemical leaching include (14, 17):
- placing foods in plastic containers that are still hot
- scrubbing containers using abrasive materials, such as steel wool, that can cause scratching
- using containers for an extended period of time
- exposing containers to the dishwasher repeatedly over time
As a general rule, plastic containers that are cracked, pitting, or show signs of wear, should be replaced with new BPA-free plastic containers or containers made from glass.
Today, many food storage containers are made from BPA-free PP.
You can identify containers made from PP by looking on the bottom for the PP stamp or a recycling sign with the number 5 in the middle.
Plastic food packaging like clingy plastic wrap can also contain BPA and phthalates (18).
As such, if you need to cover your food in the microwave, use wax paper, parchment paper, or a paper towel.
Plastic containers that are scratched, damaged, or excessively worn, pose a higher risk of chemical leaching.
Plastics are materials made primarily from oil or petroleum, and they have a variety of applications.
While many food storage, preparation, and serving products are made from plastic, microwaving them can accelerate the release of harmful chemicals like BPA and phthalates.
Therefore, unless the plastic product is deemed microwave safe, avoid microwaving it, and replace worn plastic containers with new ones.