“Styrofoam” is the commonly used brand name for Expanded Polystyrene Foam (EPS), a material composed of about 98% air and 2% plastic. While generally safe for cold-storage or non-food applications, EPS poses a low-level risk to human health when exposed to heat or specific food types. The primary concern centers on the chemical building block used to create the plastic polymer, which can migrate into food or drinks. The safety profile of EPS changes dramatically based on how it is handled and used by the consumer.
Understanding Polystyrene Foam
The material commonly called Styrofoam is technically expanded polystyrene (EPS), a foam made from the polymer polystyrene. This polymer is created by linking together units of a chemical called styrene monomer. The finished EPS foam is mostly air, which provides its insulating and lightweight properties.
A key chemical concern is the trace amount of unreacted styrene monomer that remains trapped within the polymer structure after manufacturing. Styrene is classified as a volatile organic compound (VOC), meaning it can easily become a vapor or leach into substances it contacts. This residual styrene forms the basis of most health concerns regarding EPS food containers.
Consumer Risks from Heat Exposure
The risk of chemical exposure for the general public is predominantly linked to thermal exposure. When EPS containers are used for hot food or beverages, or especially when microwaved, the heat increases the rate at which residual styrene monomer leaches from the plastic matrix. This chemical migration contaminates the food or drink, leading to ingestion of the compound.
The presence of fat, oil, or acidic substances in food also significantly increases this leaching risk. Styrene is a fat-soluble compound, meaning hot, oily foods like curries or soups accelerate the breakdown of the polymer bond, drawing the styrene out of the foam. Acidic substances, such as tomato sauces or citrus juices, can also enhance this migration process.
Consumers should never microwave food in EPS containers unless they are explicitly certified as microwave-safe. Even placing very hot liquids, such as coffee or tea, into EPS cups can cause styrene to migrate into the beverage. To avoid potential chemical ingestion, consumers should transfer hot food to glass or ceramic dishes before heating or eating.
Chronic and Occupational Health Considerations
Styrene’s regulatory status reflects a potential for chronic health effects, which is separate from acute consumer exposure. The International Agency for Research on Cancer (IARC) has classified styrene as a Group 2A carcinogen, meaning it is “probably carcinogenic to humans.” This classification is based on limited evidence in humans but strong evidence from animal studies.
The greatest risk of exposure is not to the average consumer but to workers who handle the chemical in large quantities. Occupational exposure occurs primarily through the inhalation of styrene vapor in manufacturing or recycling facilities. Workers involved in producing the raw monomer or the finished EPS foam are exposed to higher concentrations over long periods.
Chronic exposure in the workplace has been linked to effects on the central nervous system, including symptoms like headaches, fatigue, and minor impacts on kidney function. The IARC classification is particularly relevant for these occupational settings, requiring safety protocols to limit the inhalation of the volatile organic compound.
Practical Alternatives for Food Service
Given the potential for chemical leaching under heat and environmental concerns, many food service providers are moving toward safer, more sustainable alternatives to EPS.
Molded fiber, often made from sugarcane byproducts called bagasse, is a popular choice. It is compostable, offers thermal resistance, and can handle hot, wet, and greasy foods, making it sturdy for takeout applications.
Paper-based products, such as heavy-duty paperboard containers with grease-resistant coatings, provide another practical option suitable for hot and cold foods. Polypropylene (PP) is a common plastic substitute for packaging requiring durability, as it is considered more heat-resistant and safer for microwaving than EPS. These alternatives help reduce the risk of chemical migration while addressing demand for environmentally responsible packaging.