• Even if the waste does not appear on one of the four lists of hazardous wastes, it may still exhibit a hazardous characteristic.
• There are four basic hazardous waste characteristics: ignitability, corrosivity, reactivity, and toxicity.

Even if the waste does not appear on one of the four lists of hazardous wastes, it may still exhibit a hazardous characteristic.

The Resource Conservation and Recovery Act (RCRA) Part 261, Subpart C describes four basic hazardous waste characteristics.

• Ignitability (I): Ignitable wastes can create fires under certain conditions and have a flash point of <140°F. Any waste material that, after testing, exhibits the characteristic of ignitability, but is not a listed waste, is assigned the Environmental Protection Agency (EPA) hazardous waste number D001.
• Corrosivity (C): Corrosive wastes are acids or bases that are capable of corroding metal containers, such as storage tanks, drums, and barrels and have a pH of ≤2 or ≥12.5. Any waste material that, after testing, exhibits the characteristic of corrosivity, but is not a listed waste, is assigned the EPA hazardous waste number D002.
• Reactivity (R): Reactive wastes are unstable under “normal” conditions, and can cause explosions, toxic fumes, gases, or vapors when heated, compressed, or mixed with water. Any waste material that, after testing, exhibits the characteristic of reactivity, but is not a listed waste, is assigned the EPA hazardous waste number D003.
• Toxicity (E): Toxic wastes are harmful or fatal when ingested or absorbed, such as poisons. When toxic wastes are land disposed, contaminated liquid may leach from the waste and pollute ground water. Any waste material that, after testing, exhibits the characteristic of toxicity, but is not a listed waste, is assigned an EPA hazardous waste number from D004 to D043. The number will correspond to the identified toxic contaminant. The numbers and contaminants are found in 40 CFR 261.24.

All waste must be considered hazardous until proven otherwise, and generators are responsible for determining if a waste is hazardous because of a hazardous characteristic.