What is Considered Hazardous Waste?

Posted On: January 8, 2020
Classifying hazardous waste
As you know, hazardous waste is very dangerous. Therefore, it's heavily regulated. But before any regulations can be created to keep humans and the environment safe, someone needs to identify what counts as hazardous material. And that someone is the Environmental Protection Agency (EPA). The EPA is in charge of categorizing and assigning rules for how to handle hazardous wastes per the Resource Conservation and Recovery Act (RCRA) of 1976. No matter if the potential harm could be immediate (think burns or illness), or have prolonged effects (like birth defects), the EPA classifies all hazardous wastes using the same system. When the EPA is determining whether or not they should classify waste as hazardous, they use the following set of questions known as the Hazardous Waste Identification Process.

Question 1: Is the Material a Solid Waste? 

This question can be confusing because the EPA isn't actually determining if a waste is physically solid. In fact, hazardous wastes can be liquid, semi-solid, gaseous, or solid. Also, according to the EPA, a material is considered solid waste if it's abandoned, inherently waste-like, discarded military munitions, or recycled in specific ways.

Question 2: Is the Material Excluded From the Definition of a Solid or Hazardous Waste? 

Although the material might typically be included in the solid or hazardous waste categories, there are certain exclusions to the categorizations. Specific materials can be excluded for a variety of reasons, including public policy, economic impact, regulation by other laws, and impracticality of regulations. While there are dozens of hazardous waste exclusions, some of the broader categories include:
  • Sewage
  • Irrigation return flow
  • Radioactive waste
  • Agricultural waste
  • Fossil fuel combustion waste
  • Oil waste

Question 3: Is the Waste a Listed or Characteristic Waste?

An easy way to determine if a material should be considered hazardous waste is if it's already been identified as a listed or characteristic waste. As the name implies, a listed waste is one that is specifically listed in section 261 of the Code of Federal Regulations. Examples include: 
  • Solvent wastes
  • Dioxin bearing wastes
  • By-products of wood preservation, petroleum refinery, and pesticide manufacturing
On the other hand, there are four main hazardous waste characteristics.


Reactive materials are those that can suddenly change or transform when exposed to a variety of different conditions. They're extremely unstable and can often explode or release toxic gases when mixed with water.


The ignitability category encompasses any waste that could be flammable. Examples of flammable wastes include liquids with a flashpoint of 140 degrees Fahrenheit, solids that can spontaneously catch on fire, and oxidizers. Alcohol, gasoline, and acetone are all included in this category.


Waste with a pH level of 2 or less or greater than 12.5 is considered corrosive. Corrosive liquids can breakdown containers and metals and leak harmful materials. Examples of corrosive wastes are hydrochloric acid, nitric acid, sulfuric acid, battery acid, and rust removers.


This category includes any material that can poison the environment, water, or humans. The EPA uses a testing method called the Toxicity Characteristic Leaching Procedure to determine if a substance is toxic. Testing includes examining each potentially toxic material against the EPA's current list of 60 toxic contaminants. Toxicity is different from the other three characteristic wastes because toxic materials can cause long-term negative health effects. In contrast, ignitable, corrosive, and reactive wastes are immediately dangerous.

Question 4: Is the Waste Delisted?

As the name suggests, delisting refers to the removal of a hazardous waste from the list of hazardous wastes in the Code of Federal Regulations. The waste generator can petition to have their waste removed from the RCRA's listing if the waste does not have dangerous properties. If the waste has been delisted, the EPA cannot categorize it as a hazardous waste. Once EPA has reviewed the above four questions, they will determine if a substance should be classified as a hazardous waste under the RCRA. If the material is considered hazardous, extra precautions and regulations must be put in place to protect the handlers and the environment, especially during the waste disposal process.

Learn More About Hazardous Waste in HAZWOPER Training

While we hope this introductory post has been helpful in your understanding of hazardous wastes, but it's not a substitution for formal training. For a more in-depth overview of hazardous wastes, take our HAZWOPER training course!

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