40 CFR 261: EPA Hazardous Waste Identification

Regulatory citation: 40 CFR Part 261, Identification and Listing of Hazardous Waste

What Is EPA's Hazardous Waste Identification Rule?

40 CFR Part 261 sets out how to decide whether a material is a solid waste and, if so, whether it is a hazardous waste under RCRA. A waste is hazardous if it is not excluded and either shows one of four characteristics in Subpart C or appears on one of the lists in Subpart D.

Generators make this determination for each waste stream they produce. The answer controls which waste codes apply, how the waste must be stored and shipped, and how it can be treated and disposed of.

Why Hazardous Waste Identification Matters

Missing a hazardous waste means it may be stored, shipped or disposed of without the controls the law requires. That can lead to fires, chemical exposure, contaminated soil and groundwater, and enforcement action against the generator.

Core Requirements

1. Decide Whether It Is a Solid Waste (261.2)

A solid waste is any discarded material that is not excluded. Discarded means abandoned, recycled in certain ways, inherently waste-like, or a military munition identified as a solid waste. Abandoned includes disposal, burning or incineration, and accumulating or treating material before or instead of disposal. Sham recycling is treated as discard. Materials used as ingredients or effective substitutes, or returned to the original process, are generally not solid wastes.

2. Check the Exclusions (261.4)

Some materials are not solid wastes at all. Examples include domestic sewage and mixtures passing through a sewer to a publicly owned treatment works, and industrial wastewater discharges permitted under Clean Water Act section 402. Other solid wastes are not hazardous wastes, such as household waste, certain agricultural wastes returned to the soil, and fly ash and other wastes generated primarily from burning coal or other fossil fuels.

3. Test for Ignitability and Corrosivity (261.21–261.22)

A liquid waste is ignitable (D001) if its flash point is below 60 °C (140 °F). Ignitable compressed gases, oxidizers and some non-liquids that can cause fire through friction, moisture or spontaneous change also qualify. An aqueous waste is corrosive (D002) if its pH is 2 or less, or 12.5 or more. A liquid waste is also corrosive if it corrodes SAE 1020 steel at more than 6.35 mm (0.250 inch) per year at 55 °C (130 °F).

4. Test for Reactivity and Toxicity (261.23–261.24)

Reactive wastes (D003) include materials that are normally unstable, react violently with water, can detonate, or are cyanide- or sulfide-bearing and can release toxic gas. Toxicity (D004–D043) is measured with the Toxicity Characteristic Leaching Procedure, Method 1311. A waste fails if its extract meets or exceeds the regulatory level in Table 1, for example 5.0 mg/L for lead, 0.2 mg/L for mercury and 0.5 mg/L for benzene.

5. Check the F and K Lists (261.31–261.32)

The F list covers wastes from common processes in many industries. It includes spent halogenated and non-halogenated solvents (F001–F005) and electroplating wastewater treatment sludges (F006). The K list covers wastes from specific industries, such as wood preserving, petroleum refining, iron and steel production and pesticide manufacturing.

6. Check the P and U Lists (261.33)

The P and U lists cover discarded commercial chemical products, off-specification products, container residues and spill cleanup residues of the listed chemicals. P-listed wastes are acute hazardous wastes. They count toward the lower acute hazardous waste quantity limits in the generator rules.

7. Apply the Mixture and Derived-From Rules (261.3)

Mixing a listed hazardous waste with a solid waste generally makes the whole mixture hazardous, with limited exceptions. Wastes generated from treating, storing or disposing of a hazardous waste, such as sludge, spill residue, ash or leachate, are also hazardous. A hazardous waste stays hazardous until it meets the conditions in 261.3(d) or is delisted.

8. Know When a Container Is Empty (261.7)

A container that held non-acute hazardous waste is empty when all waste has been removed by common practices and no more than 2.5 cm (1 inch) of residue remains. Alternatively, no more than 3% by weight may remain in containers of 119 gallons or less, or 0.3% in larger containers. A container that held acute hazardous waste must be triple rinsed or cleaned by an equivalent method.

Common Compliance Approaches

Build a Waste Stream Inventory

List every waste each process produces, along with its source, the determination made and the codes assigned.

Use Testing and Process Knowledge Together

Use safety data sheets and process knowledge to screen wastes, and send samples for flash point, pH or TCLP testing where the answer is unclear.

Review After Process Changes

Redo determinations when raw materials, chemicals or processes change, and keep the records with your generator files.

Example: Hazardous Waste Identification in Practice

A metal parts manufacturer reviews its waste streams. Spent degreasing solvent containing trichloroethylene is coded F001. Rinse water from a parts washer tests at pH 1.8 and is coded D002. A sludge from the paint line is sent for TCLP testing and passes for lead, so it is not D008. Unused, expired cans of a P-listed chemical are counted as acute hazardous waste. The environmental coordinator records each result and updates the inventory when a new coating is introduced.

Related regulations: EPA Hazardous Waste Generators, EPA Land Disposal Restrictions, EPA Universal Waste Rule.

Note: This summary reflects federal EPA requirements. Many states run these programs under EPA authorization and may have additional or more stringent requirements. Always check the current regulation text and any state rules that apply to you.

Frequently Asked Questions

What are the four hazardous waste characteristics?

Ignitability (D001), corrosivity (D002), reactivity (D003) and toxicity (D004–D043). They are defined in 40 CFR 261.21 to 261.24.

What is the difference between P-listed and U-listed wastes?

Both cover discarded commercial chemical products, off-specification products and spill or container residues of listed chemicals. P-listed wastes are acute hazardous wastes and are subject to lower quantity limits in the generator rules.

Is household waste a hazardous waste?

No. Household waste, meaning material derived from households, is excluded from the definition of hazardous waste under 40 CFR 261.4(b)(1).