Shopper’s Guide to Plastics & Food: Microwave Ovens

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Shopper’s Guide to Plastics & Food: Microwave Ovens

Allison Sloan and Pamela Lundquist
The Green Guide #88/89
Last Updated: Tuesday, July 24, 2007

A “microwave-safe” label does not guarantee that containers don’t leach chemicals into foods when heated.

Is it safe to microwave food in plastics?

A "microwave-safe" or "microwavable" label on plastic containers only means that they shouldn’t melt, crack or fall apart when used in the microwave. These labels do not guarantee that containers don’t leach chemicals into foods when heated; the U.S. Food and Drug Administration does not regulate these labels and has not developed any standards for them. As a precaution, toxicologist Lisa Lefferts always avoids using plastic in her microwave. "Plastic plus hot plus fat is the worst combination," she advises. "That's because most chemicals that leach from plastic are lipophilic (they love fat) and high temperature speeds up the leaching process into the fat."

For safety’s sake, it’s best not to heat foods in plastics. Ceramic or oven-proof glass (such as Pyrex) dishes with lids provide safe and effective substitutes. To ensure thorough heating (which kills harmful microbes), be sure to use lids. Never microwave food in margarine tubs, yogurt cups or other containers, such as styrofoam.