The broad waste categories frequently used in waste statistics, such as municipal, industrial and hazardous waste, combine many waste materials into categories based on the similarity of their collection, treatment and disposal. The amount of waste generated can be estimated with high reliability when the waste management system is well developed and covers all waste. Hazardous waste is a special group of waste that, due to its toxic or other hazardous character, requires special management and is controlled by law in many countries.