Polystyrene is all around us, in coffee cups and egg cartons, meat and produce trays, soup and salad bowls, in CD jewel boxes, and the packing "peanuts" and molded foam that protect new appliances and electronics. It is the lightweight packaging and insulating material that helps prevent damage to products in transit. Polystyrene is also used in building materials, electrical appliances, in light switches and plates, and many other household items.
Dow Chemical Company introduced and trademarked StyrofoamÒ, a form of polystyrene foam insulation, in the U.S. in 1954. The scientific name for Styrofoam is polystyrene foam. According to the industry, that coffee you drank from a foam cup this morning was not Styrofoam; it was polystyrene foam.
Like all traditional plastics, polystyrene is made from petroleum, which is a non-sustainable source of major environmental pollution. Additionally, Ethylene and Benzene are chemical precursors in the manufacture of polystyrene and large amounts of hazardous waste are generated in the manufacturing process. Solid at room temperature, polystyrene is a thermoplastic substance; a plastic that melts when heated and becomes solid again when cooled. There are many kinds of polystyrene foams in use, one of which is used for food packaging.
The styrene in polystyrene cups has been shown to migrate into beverages. One single use may leach as much as .025 percent. If that doesn’t seem like much, consider that if you drink from polystyrene cups 4 times a day over 3 years, you may have consumed a foam cup's worth of styrene. That’s just a few cups of coffee or tea a day. The Environmental Justice Network reports that styrene is absorbed through the skin, lungs and intestines and is known to indiscriminately attack the body’s tissue and nervous system.
The migration of styrene is also influenced by the fat content of the food or beverage in the polystyrene container. Foods with a higher fat content will draw a higher degree of styrene into the food. Some beverages, such as alcohol or the acids in "tea with lemon," may also raise the rate of styrene migration. Styrene also appears to migrate more quickly when the food or beverages are hot.
Plastics that get into our food are now referred to as, "Food Contact Substances" by the US Food and Drug Administration (FDA), however before April 2002, they were called "Indirect Food Additives." The FDA changed the name with the intention of removing the implication that plastic was indeed migrating into the food. 
To complicate matters, mountains of polystyrene packaging from food service, is piling up in landfills. Not only do the puffed up foam containers take up more space than paper, they are not presently recycled because it is not economically sustainable. Non-food service packaging is not contaminated with food and other wastes like the clamshells and beverage cups from fast food restaurants.
It would be pretty difficult to avoid polystyrene altogether, however as consumers we do have many choices. We can choose to avoid fast food takeout and eat unprocessed whole foods as much as possible. We can keep non-disposable cups and flatware at our desk. At the very least, disposable paper cups and plates are a better choice; they are biodegradable and not damaging to your health.
 Styrene and Ethylbenzene Migration from Polystyrene into Dairy Products by Dynamic Purge-and-Trap Gas Chromatography J. EHRET-HENRY, V. DUCRUET, A. LUCIANI, A. FEIGENBAUMJournal of Food Science. Volume 59, Issue 5 , Pages990 – 992
1994 by the Institute of Food Technologists
 Guidance for Industry: Preparation of Food Contact Notifications and Food Additive Petitions for Food Contact Substances: Chemistry Recommendations FINAL GUIDANCE U.S. Food and Drug Administration, Center for Food Safety & Applied Nutrition, Office of Food Additive Safety April 2002 http://www.cfsan.fda.gov/~dms/opa2pmnc.html