Polystyrene (PS) is processed into different forms: Pure polystyrene (brittle plastic) and expanded polystyrene (light, insulating, waterproof plastic). The hard and transparent type is used in things like plastic forks and yoghurt pots and the softer variety is used in foamy takeaway packaging, Styrofoam and some types of insulation. Many foods are sold in Polystyrene cups and trays, although Polystyrene synthesis requires Benzene, a known carcinogen, to form the monomer Styrene. Polystyrene is usually not recyclable in normal Local Authority collections.