Microwave Ovens, Plastic Wrap and Dioxin - Analysis
Update: A more recent revision of this text makes the additional claim that freezing water in plastic bottles can cause the release of cancer-causing dioxin. Read more...
Update: Similar allegations about dioxin dangers from heating foods in plastic containers and/or with cling wrap have been added to a viral text warning consumers of purported health hazards from drinking water in disposable plastic bottles. Read more...
Analysis: While some of the claims made in these forwarded messages are questionable at best, food safety experts do agree that consumers should take the following precautions when using plastic wrap or plastic containers in a microwave oven:
- Only plastic containers or packaging labeled "Microwave Safe" should be used in microwave ovens.
- If plastic wrap is used when microwaving, it should not be placed in direct contact with food.
According to the U.S. Food and Drug Administration, chemical components can indeed "migrate" from plastics into food at microwaving temperatures. However, there is scant evidence to date, says the agency, that such contaminants pose a serious threat to human health.
Dioxin in plastic wrap?
Dioxins and dioxin-related compounds are pollutants that mainly enter the environment (and food supply) as industrial by-products. Particular dioxin compounds are considered to be highly toxic, with known health hazards ranging from birth defects to cancer.
Studies have shown that dioxins may be released into the atmosphere when chlorinated plastics such as polyvinyl chloride (PVC) which is a component of some plastic wraps and food packaging are incinerated at high temperatures, but there is no research demonstrating that dioxins are produced when the same plastics are heated in a microwave oven.
(Saran Wrap, which is mentioned by name in the email, has been reformulated by its manufacturer, S.C. Johnson & Son, such that the product no longer contains PVC or any other chlorinated substance which could release dioxin.)
DEHA is a "plasticizer" a softening compound added to plastic products to make them more pliable. Studies - including the one initiated by high school student Claire Nelson (mentioned in one of the email texts above) have shown that DEHA, when present, can migrate into food at high temperatures. Though it is not contained in Saran Wrap, it has been, and may still be, an ingredient in some other brands of plastic wrap.
At issue is whether or not or to what degree it is toxic to human beings. The current scientific consensus is that it is not, at least not in the minute amounts resulting from migration from plastics into foods.
Even though DEHA has long been regarded as a possible human carcinogen, the U.S. Environmental Protection Agency removed it from its list of toxic chemicals in the late 1990s after concluding, based on a review of the scientific evidence, that "it cannot reasonably be anticipated to cause cancer, teratogenic effects, immunotoxicity, neurotoxicity, gene mutations, liver, kidney, reproductive or developmental toxicity or other serious or irreversible chronic health effects."
It must be noted that while the plastics industry and government health agencies in both the U.S. and Europe currently maintain that chemicals migrating into food from plastic wraps and containers pose no human health threat, consumer and environmental groups say otherwise. Both sides support their case by citing a lack of concrete evidence. The FDA argues that no studies have yet demonstrated toxic effects on humans; consumer advocates argue that not enough studies have been done.
Virtually all sources do agree on one important point: Consumers can and should protect themselves when using plastic products in the microwave by following the basic precautions stated above.
Sources and further reading:
Cooking with Plastics
Johns Hopkins Bloomberg School of Public Health, 3 December 2004
Use Your Microwave Safely
FDA fact sheet, 12 April 2013
Cooking Safely in the Microwave Oven
USDA fact sheet, 24 May 2011
Microwaving Food in Plastic
Harvard Medical School Family Health Guide, July 2006
A Bad Wrap for Microwaving Food?
Seattle Post-Intelligencer, 8 Jan 2002
Saran Wrap FAQ
Product information from S.C. Johnson & Son, Inc.
Does Freezing Water in Plastic Bottles Release Dioxin?
Urban legends, 8 December 2004
AP article on high school researcher Claire Nelson, 28 April 2000
Last updated: 05/06/13