MadSci Network: Biochemistry

Re: VRD - dangers of cooking with styrofoam

Date: Thu May 11 09:27:33 2000
Posted By: Carl Custer, Staff, Office Public Health & Science, Scientific Research Oversight Staff , USDA FSIS OPHS
Area of science: Biochemistry
ID: 956784680.Bc

Well, you know. I was ready to list the dangerous chemicals that would leach out into your food. So I did a search for a list of those nasty compounds and found:
at using the argument: +Styrofoam +microwave +cancer wsjendo.htm and Where a similar question was asked:
"What containers are not safe to use in a microwave? I am particularly concerned about Styrofoam containers as I use them to make TV dinners for my family. Is it OK to heat directly in these containers?" And a better answer than I could cobble up:
"The two critical issues with containers in a microwave are (1) that they do not absorb or reflect microwaves and (2) that they tolerate high temperatures. Concerning the first issue, a container that absorbs microwaves will become extremely hot and may be damaged or destroyed. Most plastics (including Styrofoam) don't absorb microwaves and are fine. Glazed water-free ceramics and glasses are usually also fine, as long as they don't have any metallic trim. Metal dishes are a poor choice because they reflect microwaves and lead to uneven heating. Unglazed ceramics absorb water and will overheat.

Concerning the second issue, many plastics melt or soften below the temperature of boiling water. Polystyrene, the plastic from which Styrofoam is made, has a glass transition temperature of almost exactly 212 Fahrenheit (100 Celsius). That means that it will begin to soften at just about the temperature of boiling water. While pure water will boil without much problem in Styrofoam, water containing dissolved solids such as sugar or salt will boil at a higher temperature and may melt the Styrofoam. You'll know when this's not really a health issue, just a potential for a messy oven. I've only encountered the problem once myself, when a Polystyrene gravy separator melted in the microwave and let the gravy spill."

Bottom line: there are plastics (including wraps) that SHOULD NOT BE USED in a microwave because heat will cause risky compounds to leach into the food. Those plastics that are safe, will say they are "Microwave Safe" on the container or on the box. Evidently styrofoam is not a plastic that leaches nasty chemicals -- but it isn't labeled "microwave safe" and it will melt.

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