In the interests of recycling, it's tempting to reuse long lasting plastic materials, like the polystyrene cups that are commonly known as styrofoam cups. Scientists and environmentalists warn that such reuse has dangers.
In her paper "Reusing Food Packaging . . .Is It Safe?", M. Susan Brewer of the University of Illinois at Urbana-Champaign points out that expanded polystyrene foams, such as styrofoam, are porous. The material has air spaces where food can become trapped and microorganisms can grow.
According to the Earth Resource Foundation, toxic chemicals leech out of styrofoam and into the food it contains. Heating foods in this material, especially in a microwave oven, intensifies the problem and can release chemicals, such as styrene and benzene, that are known human health and reproductive hazards. Hot foods, alcohol, oils and certain acidic foods break down styrene, a suspected carcinogen and neurotoxin, making it easier to be absorbed into the blood stream.
Drinks like tea with lemon, coffee with cream and fruit juice can release styrene from styrofoam. In the presence of heat, materials that contain vitamin A decompose to release toluene, a substance that can further degrade styrofoam. A cup used for carrot juice, for example, could leave microscopic traces that would interact with hot coffee in a subsequent reuse.