Plastic is made of petroleum, and therefore has the disadvantage of being flammable. In order to make it less flammable, flame retardants composed of chlorine, bromine and other halogen compounds, and nitrogen and phosphor compounds are added. There is currently a trend towards restricting the use of some of these flame retardants owing to the fact that they may cause environmental pollution, and work is currently underway to establish a good balance between the retardants that are required for household appliances and automobile parts and measures to cope with environmental issues. Some retardants contain aluminum hydroxide and magnesium hydroxide, which produce water as a result of decomposition.