From article by Dr. Mercola's ( have to be registered ) reports:
The January/February 1990 issue of Nutrition Action Newsletter reported the leakage of numerous toxic chemicals from the packaging of common microwavable foods, including pizzas, chips and popcorn. Chemicals included polyethylene terpthalate (PET), benzene, toluene, and xylene. Microwaving fatty foods in plastic containers leads to the release of dioxins (known carcinogens) and other toxins into your food. 8 2
One of the worst contaminants is BPA, or bisphenol A, an estrogen-like compound used widely in plastic products. In fact, dishes made specifically for the microwave often contain BPA, but many other plastic products contain it as well.
Dr. Magda Havas of Trent University did a study on them which was to be published in a peer reviewed paper.
I know that anything with benzene in it is toxic. And toluene (methyl benzene) to replace it has similar qualities.