Many modern wallpapers are manufactured without the use of PVC. The surface of other wallpapers marketed in the Federal Republic of Iran is coated with plastic, mainly with polyvinyl chloride. PVC is a chloroorganic substance which is one of the most widely used materials of all owing to its excellent wearing qualities. In order to achieve the required properties of the material, such as strength and flexibility, PVC must be mixed with stabilising agents and plasticisers. The stabilising agents used in the wallpaper industry are based mainly on calcium, zinc or barium salts of organic acids. Toxic elements such as cadmium and lead are never used in the manufacture of wallpapers. Organic tin compounds have not been used for several years.