Sorry this is lengthy. The e-mail that Mo's aunt got bothered me, because the language used is not what one would expect for an e-mail originating from John Hopkins. Accordingly, I went to Snopes.com since they do a very good job in debunking (or supporting) urban myths. Here's what they had to say:
Claim: Research shows that microwaving foods in plastic containers releases cancer-causing agents into the foods.
Status: False.
Example: [Collected via e-mail, 2002]
Info for the Health Conscious
Dioxin Carcinogens causes cancer. Especially breast cancer. Don't freeze your plastic water bottles with water as this also releases dioxin in the Plastic.
On Channel 2 this morning. They had a Dr. Edward Fujimoto from Castle Hospital on the program. He is the manager of the Wellness Program at the hospital. He was talking about dioxins and how bad they are for us. He said that we should not be heating our food in the microwave using plastic containers. This applies to foods that contain fat. He said that the combination of fat, high heat and plastics releases dioxins into the food and ultimately into the cells of the body. Dioxins are carcinogens and highly toxic to the cells of our bodies. Instead, he recommends using glass, Corning Ware, or ceramic containers for heating food. You get the same results without the dioxins. So such things as TV dinners, instant saimin and soups, etc. should be removed from the container and heated in something else.
Paper isn't bad but you don't know what is in the paper. Just safer to use tempered glass, Corning Ware, etc. He said we might remember when some of the fast food restaurants moved away from the foam containers to paper. The dioxin problem is one of the reasons.
Pass this on to your family and friends.
Variations:
In early 2004 the following paragraph was added to the beginning of the message quoted above:
Johns Hopkins Newsletter
Johns Hopkins has recently sent this out in their newsletters. This information is being circulated At Walter Reed Army Medical Center. Dioxin Carcinogens cause cancer. Especially breast cancer. Don't freeze plastic water bottles with water in them as this also releases dioxin from the plastic. Dr. Edward from Castle hospital was on a TV program explaining this health hazard. He is the manager....
In November 2004, this message was combined with another piece about the purported dangers of lead-containing lipstick.
Origins: This "health alert" began appearing in people's inboxes in February 2002; the "Channel 2" reference indicates it was someone's summarization of a short morning news health segment aired on KHON-TV in Hawaii on 23 January 2002, which was then forwarded all over the Internet as "important health information." One- or two-minute health spots on local news programs are not ideal sources of medical information, however. While important basic information can be imparted in such a format, trying to explicate complex medical topics in a minute or two can easily mislead or confuse viewers, many of whom come away believing absolutely whatever they've heard (or think they've heard) because "a doctor on TV said it was true"  in this case an unshakeable belief that using plastic containers in microwave ovens causes
cancer.
That a doctor (or, more accurately, someone bearing the title "Dr.") appears on TV does not mean he's a leading practitioner in his field; it generally means only that he has something to say that a news director considers newsworthy, accurate or not. (We point out here that the "Dr. Edward Fujimoto" identified in this piece is not a staff physician from "Castle Hospital" or a medical doctor; he's a PhD serving as director of the Center for Health Promotion at Castle Medical Center in Kailua, Hawaii.) What TV news covers is dictated by ratings, not importance, and sensational claims get better ratings than straightforward, mundane information, even if the latter is more valuable to the viewing audience. It's a pretty good assumption that if using plastic containers in microwaves  as millions of people have been doing for decades  posed a significant risk of cancer, you'd be hearing about it somewhere other than an e-mail forward of an anonymous summary of a morning news spot on a Hawaiian television station.
Is there really something to the central claim of this e-mail, that heating plastic in microwaves releases a cancer-causing agent into the food? It's within the realm of possibility, but it must be stressed the FDA does impose stringent regulations on plastics meant for microwaving. Also, if there are dioxins lurking in the plastic containers we heat food in and the process of warming those receptacles looses those nasties into our ingestibles, we've yet to locate the studies that prove this. However, because most dioxins are dangerous compounds we want to have as little to do with as possible, many people are cautious about using anything associated with them. So, if you're one of the concerned, be sure that when you cover a dish you intend to microwave with ordinary plastic wrap you do not let the covering touch the food, because some of the plasticizer in the wrap  which may contain toxic chemicals, as opposed to does contain toxic chemicals  could migrate to what you're cooking, especially foods high in fat. Alternatively, use waxed paper for this purpose. Those who are very, very cautious about the potential for dioxin contamination might choose to adopt the central point of the e-mail's advice, which is to decant all items into glass or ceramic containers before microwaving.
But how real is this concern? According to Dr. George Pauli, a leading Food and Drug Administration scientist, not very. He acknowledged that some plasticizers do migrate into foods, particularly those containing a lot of fat, oil, or sugars. But research has found no ill effects from consumption of plasticizers in FDA-approved plastic wraps or from freezing or re-using plastic water bottles. Even so, others remain unconvinced, and those on both sides of the issue recommend not letting plastic wrap touch food during microwaving.
Several months after this piece began to circulate, it was merged with a similar item describing a seventh-grade student's science project:
As a seventh grade student, Claire Nelson learned that di-ethyl-hexyl-adepate (DEHA), considered a carcinogen, is found in plastic wrap. She also learned that the FDA had never studied the effect of microwave cooking on plastic-wrapped food. Claire began to wonder: "Can cancer-causing particles seep into food covered with household plastic wrap while it is being microwaved?"
Three years later, with encouragement from her high school science teacher, Claire set out to test what the FDA had not. Although she had an idea for studying the effect of microwave radiation on plastic-wrapped food, she did not have the equipment. Eventually, Jon Wilkes at the National Center for Toxicological Research in Jefferson, Arkansas, agreed to help her. The research center, which is affiliated with the FDA, let her use its facilities to perform her experiments, which involved microwaving plastic wrap in virgin olive oil. Claire tested four different plastic wraps and "found not just the carcinogens but also xenoestrogen was migrating [into the oil]...." Xenoestrogens are linked to low sperm counts in men and to breast cancer in women.
Throughout her junior and senior years, Claire made a couple of trips each week to the research center, which was 25 miles from her home, to work on her experiment.
An article in Options reported that "her analysis found that DEHA was migrating into the oil at between 200 parts and 500 parts per million. The FDA standard is 0.05 parts per billion." Her summarized results have been published in science journals. Claire Nelson received the American Chemical Society's top science prize for students during her junior year and fourth place at the International Science and Engineering Fair (Fort Worth, Texas) as a senior. "Carcinogens-At 10,000,000 Times FDA Limits" Options May 2000. Published by People Against Cancer, 515-972-4444.
To add to this: Saran wrap placed over foods as they are nuked, with the high heat, actually drips poisonous toxins into the food. Use a paper towel instead.
This gist of this latter addition is true in that a student named Claire Nelson did perform the experiment described for a school science fair project back in 1997 (she came up with the idea for the project while she was in seventh grade, but as noted, she didn't actually conduct the experiment until three years later) by working with an FDA-affiliated laboratory. Like the Fujimoto piece, however, the claims made in this version tend towards the alarmist: the results of the experiment described tended to indicate that diethylhexyl adipate (DEHA) and xenoestrogens could migrate from plastic wraps into microwaved food (specifically olive oil, the "food" used in the experiment), but only with some brands of plastic wrap (primarily ones not sold as "microwave-safe") and only when the plastic wrap was in direct contact with the food being heated; moreover, no research has yet demonstrated that DEHA poses a significant cancer risk to humans at the levels noted here (even though they exceed FDA standards) or that xenoestrogens are a direct cause of breast cancer in women or reduced sperm counts in men.
Additional information:
Cooking Safely in the Microwave Oven
(USDA)
Cooking with Plastics
(Johns Hopkins University)
Last updated: 31 December 2005
Here's the link for the above article.
