Final answer:
The two largest classes of hazardous wastes are listed wastes and characteristic wastes.
Step-by-step explanation:
The two largest classes of hazardous wastes are listed wastes and characteristic wastes.
Listed hazardous wastes are materials specifically identified as hazardous wastes and are listed in the Code of Federal Regulations. These wastes can come from non-specific sources, specific sources, or discarded chemical products.
Characteristic hazardous wastes are materials that exhibit certain characteristic properties, such as being toxic, corrosive, flammable, or reactive. These wastes are categorized based on their physical and chemical properties.