Microwaving food in plastic: Dangerous or
If you use e-mail, chances are you’ve received an urgent “PLEASE
READ THIS!” message about the dangers of microwaving food in
plastic containers or plastic wrap. The message warns that chemicals
can leach out of the plastic and into the food, causing cancer, reproductive
problems, and other ills. Is there any truth to this, or is it just
another Internet-fueled “urban legend”? As is often the
case with alarmist e-mails, this one contains a small kernel of truth — and
a lot of misinformation.
When food is wrapped in plastic or placed in a plastic container and microwaved, substances used in manufacturing the plastic (plasticizers) may leak into the food. In particular, fatty foods such as meats and cheeses cause a chemical called diethylhexyl adipate to leach out of the plastic. This certainly sounds scary, so it’s little wonder that a warning is making its way across the Web.
But here’s what the e-mails don’t mention. The FDA, recognizing the potential for small amounts of plasticizers to migrate, closely regulates plastic containers and materials that come into contact with food. The FDA requires that manufacturers test these containers and that those tests meet FDA standards and specifications. It then review the test data before approving a container.
Some of these tests measure the migration of chemicals at temperatures that the container or wrap is likely to encounter during ordinary use. For microwave approval, the agency 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. The scientists then measure the chemicals that leach out and the extent to which they migrate to different kinds of foods. The maximum allowable amount is 100–1,000 times less per pound of body weight than the amount shown to harm laboratory animals over a lifetime of use. Only containers that pass this test can display a microwave-safe icon, the words “microwave safe,” or words to the effect that they’re approved for use in microwave ovens.
What about containers without a microwave-safe label? Only those containers labeled “microwave safe” have been tested and found safe for that purpose. A container that’s not labeled safe for microwave use isn’t necessarily unsafe; the FDA simply hasn’t determined whether it is or not.
Is Styrofoam microwave safe?
Contrary to popular belief, some Styrofoam and other polystyrene
containers can safely be used in the microwave. Just follow
the same rule you follow for other plastic containers: Check
The bottom line
Here are some things to keep in mind when using the microwave:
- Most takeout containers, water bottles, and plastic tubs or jars
made to hold margarine, yogurt, whipped topping, and foods such as
cream cheese, mayonnaise, and mustard are not microwave-safe.
- Microwavable takeout dinner trays are formulated for one-time use
only and will say so on the package.
- Don’t microwave plastic storage bags or plastic bags from the
- Before microwaving food, be sure to vent the container: Leave the
lid ajar, or lift the edge of the cover.
- Don’t allow plastic wrap to touch food during microwaving because
it may melt. Wax paper, kitchen parchment paper, or white paper towels
- If you’re concerned about plastic wraps or containers in the
microwave, transfer food to glass or ceramic containers labeled for
microwave oven use.
July 2006 update
Back to Previous