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Star Bulletin Alan Titchenal & Joannie Dobbs Health Options
Alan Titchenal
 & Joannie Dobbs
                   Monday, July 7, 2003


Microwave warnings mix fact and fiction

If "scaremail" is not in the new edition of the Merriam-Webster Collegiate Dictionary, it will likely make the next one. Anyone with an e-mail address likely has received some form of scaremail forwarded by well-intentioned friends. Warning messages about microwave cooking dangers, for example, started up more than a year ago and continue to be recycled. Many contain a mixture of fact and fiction, making it difficult to decipher the truth.

Claim: Microwaving food in plastic containers or with plastic wrap causes cancer by contaminating food with dioxin.

Fact: The U.S. Food and Drug Administration requires manufacturers of containers or plastic wraps intended for microwave use to obtain approval that they are safe. This includes testing to verify that they will not melt with normal use or release toxic chemicals into food.

Claim: All plastic containers are safe for microwave cooking.

Fact: Dr. Aurora Saulo, food scientist at the University of Hawaii, recommends using only containers labeled "for microwave oven use." Other plastic containers may release undesirable chemical compounds (not dioxin), and the container may melt. Some disposable containers are meant only for one-time microwave use and should not be reused.

Dr. Saulo also recommends that plastic wraps not touch food during microwave cooking, even if the food wrap is microwave-safe. This is to prevent any chance of the plastic melting into the food.

For additional information, see Dr. Saulo's article on "Safe Cooking with Microwaves" listed under "free publications" at

Claim: Microwaving water in a cup can result in boiling water exploding out of the cup.

Fact: Although "exploding" may be an exaggeration, overheated water can unexpectedly erupt into a vigorous boil. When water is heated too long in a smooth, clean container, the water can become "superheated" to a temperature that exceeds its boiling point, but without breaking into a boil. Once the cup is moved or something like instant coffee or sugar is added to the cup, the water can erupt into a violent boil and bubble out of the cup.

To avoid overheating, follow the manufacturer's instructions for the length of time to heat water, leave the cup in the microwave for a short time to allow the heated water to cool slightly and do not add anything to the water right away.

Before acting on your well-intentioned urge to forward scaremail, check out the validity of the message. A simple Web search with some of the key words and the word "hoax" will typically bring up reliable sources of information. Two that are especially helpful:



Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S.
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa.
Dr. Dobbs also works with the University Health Service

© 2003 Honolulu Star-Bulletin --

Human Nutrition, Food & Animal Sciences · University of Hawai`i at Mānoa
1955 East-West Road · Honolulu, HI 96822
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