Defining Hazardous Waste: Introduction to RCRA and Hazardous Waste

Wherever you work, chances are pretty high that there is a hazardous material or two nearby. The modern workplace is filled with materials that can be harmful to human health or the environment, a fact that is especially true for those who work in industrial, laboratory or healthcare settings. Learning how to identify these materials and how they are regulated when they become waste can help you and your company avoid costly mistakes for your business, community and environment as the result of imporoper management.

Definition of a Hazardous Waste

Before we can discuss the proper handling and disposal of hazardous wastes, we must first define a hazardous waste. In 1976 the EPA was empowered by congress to regulate the generation, storage, transportation and disposal of hazardous waste with the passage of the Resource Conservation and Recovery Act (RCRA). The resulting waste management regulations can be found in title 40 of the Code of Federal Regulations (CFR), with hazardous waste being defined in 40 CFR 261.3.

Informed readers will clock that I haven't mentioned solid waste yet. This is already a going to be a boring read, so I'll spare the details. Put simply, a solid waste is any solid, liquid or compressed gas that is being disposed of. For a waste to be a hazardous waste, it must be a solid waste. Some specific wastes are excluded from regulation as a solid waste, but these exclusions are so specific they don't really belong in this article. If you happen to be reading this at night and are having difficulty falling asleep, you can read the full text of Part 261 for more information.

Chracteristics of Hazardous Waste

The EPA identifies four distinct characteristics of a hazardous waste. These characteristics are as follows: Ignitability (given the waste code D001), Corrosivity (D002), Reactivity (D003) and Toxicity (D004-D043). Each characteristic is identified on hazardous waste manifests, labels, etc. by the waste codes D001-D043 (known as characteristic codes, or D-codes). These waste codes help disposal facilities know what standards to treat the waste to.

Ignitable waste (D001) is defined as:

• any liquid having a flash point below 140 F
• any non-liquid capable of burning vigorously under normal temperatures and pressures through friction, absorption of water, or spontaneous chemical changes
• any compressed gas which is ignitable
• oxidizers (chemicals which produce oxygen when burned)

Corrosive wastes (D002) are defined as any aqueous liquid with a pH below 2 or above 12.5, or any liquid capable of corroding steel at a rate greater than 6.35 mm per year at 130 F. Notice that both definitions require the waste be a liquid. Corrosive solids such as sodium hydroxide pellets are not considered hazardous wastes. I guess the EPA doesn't think it rains on landfills.

A waste is reactive (D003) if:

• It is normally unstable and readily undergoes violent change without detonating.
• It reacts violently with water.
• It forms potentially explosive mixtures with water.
• When mixed with water, it generates toxic gases, vapors or fumes in a quantity sufficient to present a danger to human health or the environment.
• It is a cyanide or sulfide bearing waste which, when exposed to pH conditions between 2 and 12.5, can generate toxic gases, vapors or fumes in a quantity sufficient to present a danger to human health or the environment.
• It is capable of detonation or explosive reaction if it is subjected to a strong initiating source or if heated under confinement.
• It is readily capable of detonation or explosive decomposition or reaction at standard temperature and pressure.
• It is explosive (defined by the PHMSA in 49 CFR 173.50, 173.53 and 173.54)

Characteristically toxic wastes can carry hazardous waste codes D004-D043, each corresponding to a specific toxic constituent which, if present in the simulated leachate of a waste above a defined concentration, cause the waste to be characteristically toxic according to the law. Refer to the table in 40 CFR 261.24 for these limits. Note that it is possible for these constituents to be present in a waste in concentrations larger than the regulated limit and still not be a hazardous waste. Notice I said "present in the simulated leachate of a waste". When testing for the toxicity of a waste, the TCLP (Toxicity Chartacteristic Leaching Proceedure) method is used to simulate landfill leachate.

Listed Hazardous Wastes

In addition to defining hazardous wastes based on their hazardous characteristics, the EPA also specifically lists certain chemcials that it has deemed hazardous. There are four lists we are interested in, and they are broken into two different categories: spent wastes and virgin wastes. Just like with the characteristics of hazardous waste, each listed hazardous waste is assigned a waste code. Wastes are listed because they exhibit a hazardous characteristic, meaning that many listed wastes would also meet the definition of a characteristic waste code. When it comes to reporting and characterizing waste, listed waste codes will take priority over characteristic codes. In most cases, the listed code will cover the treatment requirements of the characteristic code, except for cases where a listed waste is mixed with other constituents that make the waste hazardous for a characteristic other than what the listed waste was listed for. This is more common with listed spent wastes, but does rarely occur with virgin listed wastes as well (such as in a spill clean up). Still with me? So let's take a look at these lists.

The four lists are as follows:

• F-List: Spent Wastes from non-specific sources (example: Spent solvents)
• K-List: Spent Wastes from specific source (example: Wastewater treatment sludge from the production of zinc yellow pigments)
• U-List: Virgin Wastes listed as a hazardous waste for their hazardous characteristics
• P-List: Virgin Wastes listed as a hazardous waste for their acute hazardous characterics

So, to summarize, the two lists for spent wastes are the F and K lists, with the operative difference being that F-Codes assigend to wastes used in more general processes while K-Codes are assigned to wastes involved in very specific processes. Confusingly, there are some F-Codes that get pretty specific. It just is what it is. The two lists for virgin wastes are the P and U list, with the operative difference being tha P-listed wastes are considered acutely hazardous (or, more immediately dangerous). There are some greater regulatory considerations involved when it comes to handling of P-list material which we will discuss in later posts about the management of hazardous waste.

Conclusion