Microwaving food in plastic containers or wrapped in plastic cling wrap releases harmful chemicals into the food.

See the email here.

Maybe, but it's complicated.

Widely forwarded email is a poor source of information, especially health and medical advice. It often glosses over issues of active scientific dispute or research in delivering a dire warning.

Let's step back for a second and look at the issues involved:

• Exposure to Substance X correlates with adverse health effects.
• Substance X is proven to have deleterious health effects under certain conditions.
• Common household item contains Substance X and thus constitutes a health risk.

Often in medical science it is a big enough challenge to show a statistical correlation between exposure to a substance and health effects. The human body is complex. It's often a much greater challenge to show precisely how a substance damages the body.

The email makes two specific claims:

• Di(2-ethylhexyl)adipate (DEHA) contained in plastics can contaminate food heated in a microwave.
• Dioxins in plastics can contaminate food heated in a microwave.

Let's look at DEHA first.

DEHA is a phthalate, one of many types of 'plasticizers' commonly added to plastics. Most types of plastic, such as polyvinyl chloride, are rigid or brittle, not very useful if you are trying to make cling wrap or tupperware. Plasticizers make plastic malleable and flexible.

Plasticizers in general, and DEHA in particular, don't form a chemical bond with the plastic. While they are not soluble in water, other substances, like oils and fats, can dissolve phthalates out of the plastic. Heating phthalates can turn them into a gas or vapor.

Some types of phthalates have been shown to have health effects, including cancer. Some studies in the late 1990s linked exposure to high levels of phthalates to various health problems in rats and mice. In response to these studies, the Environment Protection Agency in the US and European Union environmental health agencies classified some phthalates, including DEHA, as possible carcinogens.

Recent studies of DEHA and some other phthalates have not shown a link between phthalates and cancer. As a result of these studies, the EPA and EU agencies has reclassified DEHA as not a suspected carcinogen.

Does this mean DEHA is safe? By the current lights of science it is. Of course, DEHA may be found to have health effects on further study.

What's not in dispute is that under some conditions, DEHA can leach out of plastic and into food. Oils and heat can dissolve DEHA into food.

What about dioxins?

Unlike phthalates, the health threats of dioxins are well known and documented. Dioxins cause a wide variety health problems, including cancer.

There is no question that dioxins are nasty, but are they present in plastics?

A major source of dioxins in our environment comes from the burning of plastics, especially polyvinyl chloride. But the Urban Legend Zeitgeist could find no scientific study that suggested that dioxins are formed in plastics heated by microwaves.

It's not implausible that heating plastic in a microwave could form dioxins, however, no scientific research shows it happening.

One thing to note, the suggestion in the email to use paper towels instead of plastic may not be without risk either. Dioxins are often formed through bleaching, something paper products often undergo. Paper may contain trace amounts of dioxins.

So what's a prudent consumer to do? The USDA recommends:

• Only use cookware that is specially manufactured for use in the microwave oven. Glass, ceramic containers, and all plastics should be labeled for microwave oven use.
• Plastic storage containers such as margarine tubs, take-out containers, whipped topping bowls, and other one-time use containers should not be used in microwave ovens. These containers can warp or melt, possibly causing harmful chemicals to migrate into the food.
• Microwave plastic wraps, wax paper, cooking bags, parchment paper, and white microwave-safe paper towels should be safe to use. Do not let plastic wrap touch foods during microwaving.
• Never use thin plastic storage bags, brown paper or plastic grocery bags, newspapers, or aluminum foil in the microwave oven.

So where did this email come from?

Yes, Claire Nelson and Dr. Edward Fujimoto are real people.

The portion of the email on Claire Nelson is extracted from an Associated Press article by Chris Lehourites that appeared in April 2000.

Not to slight Claire Nelson's accomplishments, but the article's claim that Nelson came up with the idea of testing plastic wrap in microwaves is not true. In the late 1990s, the European Union was considering regulations on the acceptable levels of phthalates and a number of studies were done on how phthalates can contaminate food, including exposing plastic wraps to oil and heat and measuring much DEHA leached out.

Dr. Edward Fujimoto did appear on a morning news health blurb on KHON in Hawaii in January 2002. Dr. Fujimoto's TV spot inspired some anonymous author to send out an email warning about microwaves dioxins. One thing to note, Dr. Fujimoto is not a medical doctor, he's a PhD serving as director of the Wellness and Lifestyle Medicine Department at Castle Medical Center in Hawaii.

Sometime in June 2002, another anonymous author prepended the redacted Claire Nelson article with the Fujimoto blurb and a new scaremail was born.

• Science phenom: Girl finds cancer-causing particles from plastic wrap seeping into food from CNews
• Cooking Safely in the Microwave Oven from the US Food and Drug Administration
• Questions and Answers about Dioxins from the US Food and Drug Administration
• Dioxins and Furans: Where They Come From from the Academy of Natural Sciences
• Di(2-ethylhexyl)Phthalate (DEHP) from the Agency for Toxic Substances and Disease Registry (Centers for Disease Control)
• DEHP Confirmed as Non-Carcinogenic: International Agency for Research on Cancer (IARC) reclassifies DEHP as Non-Carcinogenic to Humans from the European Council for Plasticisers and Intermediates
• Health Studies On DEHA Show That DEHA Used Properly In Food Wrap Does Not Pose A Health Hazard from the American Plastics Council

Got a new legend?
Got a question?
Send it to ulz@tafkac.org