Rigid Plastic #6 (Polystyrene) Put in Garbage Foam Plastic #6 Is Not the Same Foam plastic #6 is a different material than rigid plastic #6, so it has different disposal options. Whereas rigid plastic #6 is smooth and glossy, foam plastic #6 is porous and dull. Find out how to dispose of foam plastic #6. Did You Know? Plastic in Our Bodies Styrene, a component of polystyrene, has been found in 100 percent of human fat tissue samples dating back to 1986. It is known to cause cancer in animals, and suspected to be both cancerous for humans as well.