I am in the chemical field of things, wont elaborate due to privacy concerns but basically ANY product that contains plastics (silicon is not a plastic btw, it is produced via a few chemical reactions from ordinary beach sand or can be mined as a metal or metal salt) plastic are hydrocarbons bonded to other chemicals, usually oxygen, sulfur, chlorine, fluorine and nitrogen. If you look at the middle 3, very toxic in even small amounts it can cause damage. Plastics decompose very gradually and so, release most of these chemicals and other organic molecules from the plastic. This is also why you dont heat foods in plastics which have not been designed to handle heat.
toxiclover, you are correct in saying that... that is why they do not use Styrofoam as packaging for fast foods, and any other warm foods for that matter, because the heat will a molecule to form that is very similar in chemical stucture and nature to estrogen, the female hormone.
This is a short version and a very simplistic version of the chemistry of plastics, actually very complex. But it boils down to the fact that plastics are not really that good for human health due to the the toxicity of the chemicals and other organic materials that might be gradually "break off" from the main body of plastic.
Hope this helps to some extent, even if this not a science forum but one dedicated to sex and many forms of it.