Put simply, a hazardous waste is waste that poses substantial or potential threats to public health or the environment and generally exhibits one or more of these characteristics:
• ignitable (i.e., flammable)
U.S. environmental laws (see Resource Conservation and Recovery Act) additionally describe a "hazardous waste" as a waste (usually a solid waste) that has the potential to:
• cause, or significantly contribute to an increase in mortality (death) or an increase in serious irreversible, or incapacitating reversible illness; or
• pose a substantial present or potential hazard to human health or the environment when improperly treated, stored, transported, or disposed of, or otherwise managed.
The term "hazardous waste" comprises all toxic chemicals, radioactive materials, and biologic or infectious waste. These materials threaten workers through occupational exposure and the general public in their homes, communities, and general environment. Exposure to these materials can occur near the site of generation, along the path of its transportation, and near their ultimate disposal sites. Most hazardous waste results from industrial processes that yield unwanted byproducts, defective products, and spilled materials. The generation and disposal of hazardous wastes is controlled through a variety of international and national regulations.
Hazardous waste was formerly known as 'special' waste
 Resource Conservation and Recovery Act (RCRA)
Modern hazardous waste regulations in the U.S. began with the Resource Conservation and Recovery Act (RCRA) which was enacted in 1976. The primary contribution of RCRA was to create a "cradle to grave" system of record keeping for hazardous wastes. Hazardous wastes must be tracked from the time they are generated until their final disposition.
RCRA's record keeping system helps to track the life cycle of hazardous waste...