(Photo courtesy of porkfork6) A microwave-safe TV dinner tray. (Creative Commons Attribution-ShareAlike 3.0 License.)
Plastics and Microwave Oven Safety
Delicious Reddit

FEBRUARY 01, 2010
April Holladay, HappyNews Columnist

Q: Do the recycle numbers assigned to plastic containers indicate if they are safe to use for heating food in a microwave oven?
Lanney, Sandia Park, New Mexico, USA
A: This seemed a simple question when I first read it and it actually is. But it took time to spot a recycle myth and realize the answer is just: NO. I can easily say what plastics are microwave safe — any that the label says is safe — but the recycle numbers don't help.
At first, I tried to make a connection between the recycling numbers and microwave safety. The Internet was all too happy to help. I found charts merrily connecting recycling numbers (those raised numbers we find on the bottom of plastic containers) with food safety.
"It ain't necessarily so," as the character Sportin' Life (a drug dealer) sung in Porgy and Bess.
As I constructed a similar table of my own, I ran into big problems. For example, I found frozen-food manufacturers routinely package their TV dinners in plastic trays they label as "microwavable." The plastic trays are made out of a plastic called PET, which has a recycle code of #1. So far, so good.
But manufacturers of cold-storage jars and 2-liter soft-drink bottles also use PET plastic with, of course, the same recycle number, #1. These cold-storage bottles could warp if placed in the microwave and used for reheating something. A warped or melted plastic is not safe. I scratched my head. How to resolve this?
The American Chemistry Council (representing hundreds of companies in the business of chemistry, such as, DuPont) set me straight: "[The recycling symbol] is not intended to provide guidance on safe or recommended uses." Well, no wonder, I thought.
Health Canada and the US Food and Drug Administration (FDA) go to much trouble determining what plastics are safe to use in a microwave oven. If a manufacturer labels its plastic product as "microwavable," or "microwave safe" then it is. If the product isn't so labeled, it likely is not safe. Don't put it in the microwave! That's the bottom line.
I redid the table to summarize my findings. See below.
By the way, "...we have read the article and agreed with the 'Comments,'" says Christelle Legault of Health Canada.
Plastic Containers and their Use in Microwave Ovens: Always check the label.
The table summarizes information from publications written by Health Canada and FDA
----- LABEL ----- Container ----- Comments
- NO LABEL ----- Most restaurant takeout Styrofoam containers, water and two-liter soft-drink bottles, and plastic tubs or jars containing margarine, yogurt, whipped topping, and foods such as cream cheese, mayonnaise, and mustard. Also plastic bags (such as flimsy produce bags from grocery stores). ----- These containers are not microwave safe. The heated food may melt them.
- "MICROWAVE DIRECTIONS" or similar wording. ----- Plastic storage bags (such as ZipLoc bags). ----- These bags are not microwave safe. Hot food may melt them.
- "ONE-TIME USE ONLY" ----- Any plastic container with the "one-time use only" label, for example, frozen TV dinner trays. ----- The FDA approves them only for one time use.
- MICROWAVE SAFE ----- Plastic cling wrap ----- OK to microwave, but don't allow the wrap to touch the food during micro-waving because the hot food may melt the plastic wrap.
- MICROWAVE SAFE ----- Any plastic with the microwave-safe label (except be careful with plastic cling wrap, see above). ----- These plastic containers are safe to heat food in the microwave oven.
More exploring
How the FDA tests plastic chemicals for safety, WonderQuest.com
Further Reading:
Microwave Ovens and Food Safety, Health Canada, July 2005
Microwaving food in plastic: Dangerous or not? Health Harvard newsletter, July 2006
PLASTICS AND THE MICROWAVE, FDA Consumer magazine, Nov-Dec 2002
Cooking Safely in the Microwave Oven, FDA Fact sheet, 3 April 2006
FAQs: Using Plastics in the Microwave, Plastics Info, American Chemistry Council, 2007
Leslie Beck (Globe and Mail columnist) nukes the microwave myths, CTV global media, 10 Sep. 2008