Another view of plastics in microwaves

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FAQs: Using Plastics in the Microwave --> Because plastics serve so many

purposes in the kitchen, many consumers get confused about which products are

right for the microwave. This list of FAQs will help you decide which plastics

to use and how to use them properly.

How can I know if a plastic container is okay to use in the microwave oven?

Are other plastic items unsafe to use in the microwave?

Can knowing the type of plastic something is made from help me decide whether

I should?

What should I know about microwaving with plastic wrap?

Is it okay to use plastic wrap with high-fat foods in the microwave?

Is it safe to reheat leftovers in takeout containers or reused containers,

such as empty butter tubs or dessert topping containers?

I got an e-mail from s Hopkins alleging that microwaving food in plastic

containers releases dioxin. Is this true?

Resources and Links

How can I know if a plastic container is okay to use in the microwave oven?

Many of today’s plastic containers, packages and wraps are specially designed to

withstand microwave temperatures. To make sure yours is one of them, check the

item or its packaging label and follow any instructions. If neither the item nor

the package is marked, it’s best to use a different container.

Some products may use the term “Microwave Safe.” This is the manufacturer’s way

of letting consumers know that a product has been designed to withstand

microwave heat without melting or warping under normal use conditions. Other

products may carry a microwave symbol or simply provide instructions for proper

microwave use. Either of these is an indication that a product is suitable for

microwaving when used in accordance with the directions provided.

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Are other plastic items unsafe to use in the microwave?

All plastics intended for food use — whether designed for microwaving or not —

must meet stringent U.S. Food and Drug Administration (FDA) safety standards

before they are allowed on the market. When manufacturers develop individual

plastic packaging products, they often conduct additional testing based on a

product’s intended use. Choosing to microwave with a plastic item not labeled

for microwave suitability isn’t necessarily “unsafe,” but you won’t have the

assurance of knowing the item was tested and evaluated for this purpose.

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Can knowing the type of plastic something is made from help me decide whether

I should use a plastic container or package in the microwave?

Many plastic food packages are marked with a symbol that identifies a particular

type of plastic for recycling purposes. This symbol is not intended to provide

guidance on safe or recommended uses. The only way to know if a particular item

is suitable for microwave use is to check the label.

For example, frozen meals are often packaged in microwavable trays made of PET,

a type of plastic also used to make cold storage jars and beverage bottles.

While microwavable PET trays are specially fabricated for high heat resistance,

other packages made with PET could warp if subject to high heat.

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What should I know about microwaving with plastic wrap?

Plastic wrap, placed loosely over bowls or dishes during reheating, can help

retain moisture to allow foods to cook more evenly and thoroughly and prevent

splattering. As with any plastic packaging, it’s best to use plastic wrap that

is labeled for microwave use or includes microwave cooking instructions. Because

microwaves heat foods more quickly than plastic, most manufacturers recommend

leaving at least an inch between the food and the wrap covering the dish. This

is to prevent the plastic wrap from melting, which could result from contact

with extremely hot foods.

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Is it okay to use plastic wrap with high-fat foods in the microwave?

Yes, it is okay to use plastic wrap with high-fat foods in accordance with the

manufacturer’s instructions. Plastic wrap is not heated by microwave energy, but

it can be heated by contact with hot foods. Normally, foods in a microwave oven

do not become hot enough to bring the wrap to its melting point. However,

because certain foods with high fat content (such as butter) can become very hot

in a microwave oven, most manufacturers recommend leaving an inch of air space

between the food and the wrap or turning back a corner for ventilation. The

instructions on various plastic wraps may vary, so again, it’s always a good

idea to check the label.

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Is it safe to reheat leftovers in takeout containers or reused containers,

such as empty butter tubs or dessert topping containers?

It is not likely that microwaving with these containers presents any health

risk, but if used inappropriately, accidental burns could occur. So, unless a

container is marked that it is suitable for microwave use, there may be a risk

that it will melt or deform if exposed to high heat. If your container isn’t

marked for microwave use, it’s best to choose one that is.

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I got an e-mail from s Hopkins alleging that microwaving food in plastic

containers releases dioxin. Is this true?

No. This is an e-mail hoax that has been circulating the Internet for years.

Dioxins are a group of compounds that can be produced by combustion at very high

temperatures. The vast majority of plastics used in food wraps and packaging do

not contain the chemical constituents needed to form dioxins. And dioxins form

at very high temperatures, typically above 700 degrees Fahrenheit — much higher

than the temperatures that would be generated by microwave cooking. You also may

hear claims that using plastic containers in the freezer can “release” dioxins —

which is also untrue. According to the FDA, which regulates food packaging,

“With regard to dioxins, we have seen no evidence that plastic containers or

films contain dioxins and know of no reason why they would.”

The e-mail and its alleged ties to s Hopkins University or Walter Army

Medical Center (depending on which version you receive) are part of the hoax,

and both organizations have publicly disavowed the claims.

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