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June 01, 2022
Compliance Tip: Characteristic hazardous waste

A hazardous waste characteristic is a property which, when present in a waste, indicates that the waste poses a sufficient enough threat to human health or the environment to deserve regulation as hazardous. The U.S. Environmental Protection Agency (EPA) has established four hazardous waste characteristics: ignitability, corrosivity, reactivity, and toxicity. A waste is a “characteristic waste” if a “representative sample” exhibits one or more of these four identified characteristics.

Each waste produced by a generator must be checked for hazardous characteristics even if the waste has been designated by the EPA as a “listed waste”. A listed waste must still be checked for hazardous waste characteristics in order to ensure that the generator complies with the land disposal because a listed waste may still have hazardous characteristics that are not indicated by the listed waste’s hazard code.

The hazardous characteristic must be measurable by an available standardized test method that is reasonably within the capability of generators’ private sector laboratories to apply or the characteristic can be reasonably detected by generators through their knowledge of their waste.

As with listed wastes, each of the four characteristic wastes is assigned an EPA hazardous waste number (code). These waste numbers (i.e., the waste’s identification number) should be used unless the waste is listed and, therefore, already assigned a waste code number. EPA hazardous waste numbers are needed to comply with several hazardous waste regulations, such as notification requirements, recordkeeping, and reporting.

Ignitability. Ignitable wastes are those that are capable of causing or intensifying a fire during routine handling. A substance is ignitable if it displays any of these properties:

  • A liquid with a flash point of less than 60°C (140°F);
  • A nonliquid that is capable, under standard temperature and pressure, of causing fire through friction, absorption of moisture, or spontaneous chemical changes and, when ignited, burns so vigorously and persistently that it creates a hazard;
  • An ignitable compressed gas; or
  • An oxidizer (such as a chlorate or peroxide).

Waste that exhibits the characteristic of ignitability has the EPA Hazardous Waste Number D001. See 40 CFR 261.21 for detailed information about ignitable waste, including suggested test methods for determining ignitability.

Corrosivity. Corrosivity describes those wastes that might be capable of corroding metal containers and escaping to contaminate the environment. They include wastes that are highly acidic or highly alkaline and those capable of corroding metal tanks, containers, drums, and barrels. A substance is corrosive if it displays any of these properties:

  • An aqueous material with a pH less than or equal to 2 or greater than or equal to 12.5, or
  • A liquid that corrodes steel at a rate of at least 0.25 inches per year at 55°C (130°F).

Note: A waste that is not aqueous and contains no liquid falls outside the EPA definition of corrosivity.
Waste that exhibits the characteristic of corrosivity has the EPA Hazardous Waste Number D002.

Reactivity. Reactive wastes are those that are particularly unstable and likely to explode or react violently during transportation, storage, or disposal. A substance is reactive if it displays any of these properties:

  • Normally unstable and readily undergoes violent change without detonating;
  • Reacts violently with water;
  • Forms potentially explosive mixtures with water;
  • When mixed with water, generates toxic gases, vapors, or fumes in a quantity sufficient to present a danger to human health or the environment;
  • A cyanide or sulfide-bearing waste that can generate fumes in a quantity sufficient to present a danger to human health or the environment;
  • Capable of detonation; or
  • A forbidden explosive.

Waste that exhibits the characteristic of reactivity has the EPA Hazardous Waste Number D003.There are no test methods for determining reactivity.

Toxicity. Toxic wastes are harmful or fatal when ingested or absorbed and may be able to leach from the waste into water systems. A substance is toxic if it exceeds the concentrations for contaminants listed in the Maximum Concentration of Contaminants for the Toxicity Characteristic Table.

A specific test, the Toxicity Characteristic Leaching Procedure (TCLP), must be conducted to determine if the waste is classified as toxic. TCLP testing is required before land disposal of a hazardous waste. This testing procedure extracts the toxic constituents from a solid waste in a manner that simulates the natural leaching action that occurs in landfills and is designed to determine the mobility of both organic and inorganic contaminants present in liquid, solid, and multiphasic wastes. It is the only reliable method for determining whether toxicity concentration (TC) levels are met.

Waste with a toxicity characteristic have EPA hazardous waste numbers D004 through D043.

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