Polystyrene is made by linking together large numbers of styrene molecules. After the polymerization process, polystyrene can be processed as a solid, film, or foam. Post-processed polystyrene is perhaps best recognized as the material used in disposable food and beverage containers and packing peanuts.
On July 28, 2014, however, the National Research Council report, Review of the Styrene Assessment in the National Toxicology Program 12th Report on Carcinogens, listed styrene as a probable human carcinogen. Additionally, the report said that human epidemiological and animal testing evidence identified styrene as a risk factor for lymphomas and leukemias and possibly for pancreatic, kidney, and esophageal cancers. See also: Cancer (medicine); Computational environmental toxicology; Data-mining and informatics approaches for environmental contaminants; Environmental toxicology; Epidemiology; Film (chemistry); Foam; Food manufacturing; Leukemia; Lymphoma; Oncology; Plastics processing; Polymer; Polymerization; Polystyrene resin; Styrene; Toxicology
In terms of risk, styrene exposure is mainly an occupational hazard for workers producing polystyrene. Polystyrene, the material with which most of the population has experience, contains only low levels of styrene. The U.S. Food and Drug Administration (FDA) considers polystyrene safe, as long as it contains less than one percent styrene. In the United States, the estimated daily intake of styrene from food sources in contact with polystyrene is 6.6 micrograms per person, while the FDA considers up to 90,000 micrograms per person per day safe. See also: Personal chemical exposure informatics; Tools to assess community-based cumulative risk and exposures
The properties that make polystyrene foam a good insulator—its 95 percent air content by volume and its stability to breakdown—also account for its problems for the environment. Although it is recyclable, most polystyrene foam ends up in landfills because it is expensive to transport a product that is virtually air to recycling plants. And because polystyrene does not readily biodegrade, once it enters a landfill or the environment, including the ocean, it will likely remain there for a very long time. See also: Recycling technology
On July 29, 2014, Washington D.C. mayor Vincent Gray signed a bill that will ban the use of polystyrene food containers, adding the city to a growing list of others in the United States that have already done so. As a result of this movement, more sustainable materials are replacing polystyrene in a variety of products, including biodegradable starch-based packing peanuts and recyclable, biodegradable, and compostable food and beverage containers made from biopolymers, such as poly(lactic acid), and paper. See also: Biopolymer; Paper; Polymer recycling and degradation; Polymers from renewable resources