Understanding the Four Characteristics of Hazardous Waste

Author: admin
Date: February 3, 2024

The first step in managing your hazardous waste is determining that it is, in fact, a waste (as defined by the EPA). If your waste really is a waste, the next step is to determine if the waste is produced from certain non-specific sources (F list waste) or certain specific sources (K list waste), or if it is a listed as an unused commercial chemical product (U list) or an acutely hazardous unused commercial chemical product (P list).

Even if you determine your waste is not a listed waste, you are not done! The final step is to determine if your waste exhibits one of four hazardous waste “characteristics.” According to the EPA, “A hazardous waste characteristic is a property which, when present in a waste, indicates that the waste poses a sufficient threat to merit regulation as hazardous.” The four federal hazardous waste characteristics are ignitability (40 CFR 261.21), corrosivity (40 CFR 261.22), reactivity (40 CFR 261.23) and toxicity (40 CFR 261.24). Certain states, including California and Washington, have established their own state-specific requirements and have expanded on the EPA hazard characteristic definitions.

We will briefly review each of these below. In future posts, we will look at each of them more closely.

Ignitability (flammable material), EPA Waste Code D001

A liquid with the flashpoint of less than 140 degrees Fahrenheit (60 degrees Celsius) is considered “ignitable” (or flammable). Remember: Flashpoint is not the temperature at which a liquid would burst into flames (that’s the auto-ignition temperature); flashpoint is the temperature at which a liquid would ignite if there were an ignition source. Flammable solids (solids that are readily ignitable through friction, moisture or chemical reaction and that burn vigorously), as well as ignitable compressed gases and certain oxidizers, are also considered ignitable. Examples include organic solvents used in painting or cleaning parts, as well as waste gasoline or kerosene.

Corrosivity (material that can rust or decompose), EPA Waste Code D002

Corrosive materials can attack and destroy tissue or metal (including steel containers). Liquid wastes with a pH less than or equal to 2, or greater than or equal to 12.5, are considered corrosive, as are liquid wastes that corrode steel at greater than ¼” (6.35 mm) per year. The EPA definition of characteristic corrosivity does not include solids (the EPA does not recognize corrosive solids). However, certain states (including California) include corrosive solids in state-specific definitions. Examples of corrosive wastes include battery acid, rust removers and caustic hot-tank waste.

Reactivity (explosive material), EPA Waste Code D003

Reactive wastes are unstable under normal conditions and may react violently with air or water, may be capable of detonation or explosion, or are capable of releasing toxic gases or vapors. The EPA uses a “narrative” definition for characteristic reactivity that describes the hazards but does not reference specific test methods. Instead, it is up to the generator to determine if the waste exhibits characteristic reactivity, based on their knowledge or on similar definitions from OSHA (explosive, self-reactive, pyrophoric, self-heating, chemicals that emit flammable gases in contact with water), DOT (Division 1.1, 1.2, 1.3 Explosives, Division 4.2 Spontaneously Combustible, Division 4.3 Dangerous When Wet) or other authorities. Many cyanide and sulfide compounds are classified as reactive due to their potential to release toxic gases. Examples of reactive wastes include certain organic peroxides, cyanide-plating wastes, damaged lithium batteries and waste-concentrated bleaches.

Toxicity (poisonous material), EPA Waste Codes D004–D043

Toxic wastes are harmful to the environment when released to soil, air or groundwater. For hazardous waste purposes, characteristic toxicity is based on the presence of a listed substance above threshold levels when tested according to the “Toxicity Characteristic Leaching Procedure” (TCLP). Listed substances include certain metals, pesticides and other substances that are likely to persist in the environment. Note that the EPA definition of “toxicity” is based on the potential to cause environmental harm and is much more limited than the OSHA GHS health hazards, which are based on the potential to cause harm to workers. In addition, many states, including Washington and California, have additional state-specific definitions of characteristic toxicity. Examples of toxic wastes include painting wastes containing certain metal-based pigments, and certain solvents.

Evaluating hazardous waste characteristics

Most hazardous waste generators understand their waste, either based on professional knowledge or personal experience. For example, if you operate a plating shop, you understand the waste from your etch tank is corrosive, and if you operate a paint booth, you know your solvent waste is flammable. This “generator knowledge” can be used to determine if your waste is “hazardous” based on the characteristics described above. In some cases, laboratory testing may be required, where the answer isn’t clear or to show a waste does not exhibit a characteristic. Technical definitions for hazard characteristics are found in the applicable regulations, and additional information on waste testing is found in EPA publication SW-846 “Test Methods for Evaluating Solid Waste.”

In addition to being a critical part of your hazardous waste management plan, the information you use to determine if your waste has any of the four characteristics is a required part of the Hazardous Waste Profile. This is an internal document used by hazardous waste brokers to document physical properties, characteristics, process information and other information required to classify the waste and manage it for disposal. There is typically an approval process for new wastes streams, and profiles are reviewed periodically to ensure the waste classification remains accurate.

If you have any questions about hazardous waste — from testing to management to disposal — ACT has the resources to help. Please e-mail us at [email protected]. We’re happy to help!

James Kapin is Principal Advisor for safety, health and environmental compliance for ACTenviro.  Jim is a Certified Industrial Hygienist (CIH) and a Certified Safety Professional (CSP) with over 25 years of workplace safety and environmental protection experience.   Do you have any hazardous waste questions for Jim?  Or any other workplace safety or environmental compliance questions?  Let us know at [email protected]


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