Tips to Reduce Risk From Plastic in the Microwave

How safe are those plastic containers in the microwave? Because everyone has them, here’s a primer on what’s safe and what’s not.

The first warnings the public received on plastics was to avoid microwaving any at all, for fear of what was lurking (or leaching) beneath the surface. But that ignores the science behind some plastics and some good common sense as well.

According to a report from Harvard Medical School, there’s a really good reason to no microwave plastics: They could release chemicals called dioxins into your food. Trouble is, dioxins are created when plastics (along with other materials such as wood and metal) are burned or incinerated. Although this is not going on in the average microwave, this information was not widely disseminated and little was done to calm jittery nerves when plastic was involved.

Today’s worries stem from bisphenol-A and phthalates, substances in plastics that can leach into food and wreak havoc with hormones. These “plasticizers” serve to make plastic clear and hard, and soft and flexible, respectively.

Fortunately, the FDA closely regulates plastic containers and materials that come into contact with food, and designates which are “microwave safe.”

The tests are stringent: Some measure chemicals leaching at temperatures the container or wrap is likely to encounter during ordinary use. For approval, the FDA estimates the ratio of plastic surface area to food, how long the container is likely to be in the microwave, how often a person is likely to eat from the container, and how hot the food can be expected to get during microwaving. That’s a lot to swallow.

There’s independent reporting too: A Good Housekeeping study microwaved food in 31 plastic containers, lids, and wraps, and found almost none of the food contained plastic additives.

And containers not labeled microwave-safe aren’t necessarily unsafe; they just may not have been tested by the time of purchase. That said, Harvard suggests these some common sense approaches to keeping the peace between your microwave and your plastics:

• If no amount of research suits you, simply use glass or ceramic containers labeled for use in microwaves. That means no plastic.
• Keep plastic wrap away from food during microwaving. This prevents any mingling in the event the wrap melts. Use alternatives like wax paper or white paper towels.
• Single use is just that. Microwavable takeout dinner trays are for one-time use only and they say so on the package.
• Throw away old containers. Scratched, cracked, broken containers may leach out those pesky plasticizers.
• Most takeout containers, water bottles, and plastics that margarine, yogurt, whipped topping, and cream cheese, mayonnaise, and mustard come in are not generally microwave safe.
• Those plastic bags from the grocery store? Unless specifically tagged, they’re not microwave friendly.
• Leave a vent on your container before microwaving. That allows steam to escape and avoids pressure that could superheat or erupt.

The bottom line? Some plastics in the microwave are just fine, as research bears out. But if none suits you, follow your intuition.