What type of waste is classified as hazardous waste?

Hazardous waste is specifically characterized by its potential to be harmful to human health or the environment. Xylene is a chemical solvent commonly used in laboratories and industries, making it fall under the category of hazardous waste due to its toxic properties. It can pose serious health risks through inhalation or skin contact, and when improperly disposed of, it can contaminate soil and water, leading to environmental hazards.

In contrast, the other options do not meet the criteria for hazardous waste. Used paper towels, while potentially contaminated, are generally classified as regular waste unless they are contaminated with specific hazardous materials. Plastic wrap and plastic bags are typical materials that can be recycled or disposed of as regular waste. Human and animal parts, while they may sound hazardous, are typically classified and managed under specific biomedical waste protocols rather than as hazardous waste unless they are contaminated with a hazardous substance. Thus, xylene is clearly the choice that is recognized as a hazardous waste due to its inherent chemical properties.