Q. My wife doesn�t like it when I microwave food in plastic containers and says she can taste the difference when I do. Is there really any harm from doing this? I can�t detect any difference.
A. While there is no argument over whether harmful substances migrate from plastic when food is microwaved (they do), the plastics industry and the Food and Drug Administration say the amounts are too small to be harmful. Some consumer groups present a different view and warn that any amount of chemical contamination of our food is dangerous. Very likely the risk of harm depends on how sensitive a particular individual is to chemical exposure.
The major concern with microwaved plastic appears to be the additive (called DEHA) that keeps plastics flexible, so plastic wrap is probably worse than the solid plastic containers that are marked “microwave safe.” This doesn’t mean the solid containers do not contribute some chemicals to the food, but just that they are less likely to warp or crack from the heat. Everyone agrees that the container that food is in when you purchase it is not suitable for heating in a microwave unless it is marked for microwave use, and even then it is good for only one use.
The amount of DEHA that migrates from plastic wrap to food is indeed small. The FDA considers 0.00005 parts per million a safe limit, since experiments indicate 1,800 parts per million have almost no ill effects on rats. A much-celebrated experiment by a high school girl named Claire Nelson, in which microwaved olive oil accumulated DEHA at 500 parts per million, attracted a lot of attention a few years ago, although this level is still far below an amount that would worry the FDA.
DEHA is considered a weak carcinogen, but there are other chemicals – substances that act like estrogen – that migrate into food from plastic wrap. These estrogen mimics are linked to falling sperm counts in men and to breast cancer in women, so should definitely be minimized.
For someone really sensitive to chemicals, as your wife appears to be, even food packaged in plastic might be a problem. In today’s supermarkets we find meat and poultry on Styrofoam trays, cheese and margarine in plastic cartons, and deli sandwiches and vegetables swathed in plastic wrap. Every day most of us eat food that has come into contact with plastic. Some plastic packaging inevitably leaves a residue of chemicals on foods stored in it for long periods of time. The FDA has approved all plastics that have contact with food, but little research has been done on the migration or leaching of chemicals from plastics into food. Someone whose personal experience indicates an extraordinary sensitivity to chemicals should avoid even these plastics, in addition to microwaved plastics. Harmful chemicals do migrate from plastic containers into food cooked in the microwave, and the risks are under-studied. Certainly some people are more sensitive to chemical exposure than others and may have a more serious reaction.
To lower exposure to these chemicals, if plastic wrap is used at all, do not let it touch foods during microwaving. Wax paper, parchment paper, or microwave-safe paper towels can substitute, and glass containers are probably the safest option.
This article appears in June 11 • 2004.