The safety of microwaving Styrofoam containers and their potential health risks, particularly concerning cancer, is a common concern. These containers are widely used for takeout and reheating leftovers. This article explores the science behind microwaving Styrofoam and offers guidance for safer practices.
Understanding Styrofoam and Its Composition
While “Styrofoam” is a brand name for extruded polystyrene foam (XPS) primarily used in building insulation, disposable food containers commonly called “Styrofoam” are actually made from expanded polystyrene (EPS) foam. Polystyrene is a synthetic polymer created from styrene monomers, which are aromatic hydrocarbons. Polystyrene foam is lightweight and provides good insulation, making it a popular choice for food packaging, such as disposable cups, plates, and takeout containers. This material consists of approximately 95-98% air, giving it its characteristic lightness and insulating properties. While generally stable at room temperature, its composition becomes a concern when exposed to heat.
Chemical Leaching During Microwaving
Microwaving food in polystyrene containers, especially those not labeled “microwave safe,” can lead to the transfer of chemicals like styrene into the food. Styrene, a component of polystyrene, is a primary chemical of concern that can leach into food during this process. Microwaves heat food by causing water and fat molecules to vibrate, which generates heat from the inside out. This uneven heating can create “hot spots” within the food, causing parts of the container to reach temperatures that promote chemical leaching. The presence of fats and oils in food can further accelerate the leaching of these fat-soluble chemicals from the plastic. Repeated heating of polystyrene containers also increases the likelihood and extent of chemical migration.
Health Implications of Leached Chemicals
The International Agency for Research on Cancer (IARC) has classified styrene as “possibly carcinogenic to humans” (Group 2B). It means styrene is capable of causing cancer, but this classification does not account for the probability of causing cancer given the level of exposure. The U.S. Food and Drug Administration (FDA) regulates food-contact packaging materials, including polystyrene. The FDA considers polystyrene safe for its intended use, stating that the minor amounts of styrene and ethylbenzene that may migrate from food-contact styrenic polymers do not pose a health risk under normal use conditions. Products explicitly labeled as “microwave safe” have been tested to meet FDA standards for microwave use, meaning they are designed to withstand microwave temperatures without releasing excessive amounts of chemicals. However, some studies suggest that even with “microwave safe” labels, the label primarily means the container will not melt or warp, not that no chemicals will leach.
Safe Practices and Alternatives
To minimize any potential risks, it is advisable to avoid microwaving food in polystyrene containers unless they are explicitly labeled “microwave safe.” A “microwave safe” label typically indicates that the material can withstand temperatures of at least 250 degrees Fahrenheit without deforming or leaching excessive chemicals. This label might appear as wavy lines or a microwave icon on the container.
If a polystyrene container lacks a “microwave safe” label, transferring food to alternative dishes before heating is a safer practice. Recommended alternatives for microwaving include glass, ceramic, or specific microwave-safe plastic containers. Polypropylene (PP), often identified by the recycling symbol “5,” is generally considered microwave-safe due to its high melting point and resistance to chemical leaching. These materials are more stable when exposed to microwave energy and are less likely to transfer chemicals into your food.