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Navigating the Meaning of “Hazardous” in the Regulatory Universe – Part 2

February 9, 2024

The terms “hazardous substances” and “hazardous waste” sound so similar, but in the regulatory world, the implications and financial liability can be very different. This understanding becomes even more critical when considering emerging federal regulations related to per- and polyfluoroalkyl substances (PFAS). In Part 1 of this two-part series, we took a close look at the term “hazardous substances.” Now, we are taking a closer look at “hazardous waste” and the potential challenges and liabilities associated with it.  

What is a RCRA Hazardous Waste? 

While the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) focuses on the cleanup and remediation of contaminated sites, the Resource Conservation and Recovery Act (RCRA) focuses on waste management and prevention to minimize contamination. Unlike CERCLA, RCRA hazardous waste must first be classified as solid waste. Therefore, the  term “hazardous waste” is also more limited in scope than what federal law deems a “hazardous substance.” 

RCRA gives EPA, “the authority to control hazardous waste from cradle to grave,” which includes the generation of the waste as well as its transportation, treatment, storage, and disposal. Therefore, RCRA hazardous waste carries a more comprehensive regulatory burden than CERCLA hazardous substances.  

Specifically, RCRA defines “hazardous waste” as “a solid waste, or combination of solid wastes, which because of its quantity, concentration, or physical, chemical, or infectious characteristics may cause, or significantly contribute to, an increase in mortality or an increase in serious irreversible, or incapacitating reversible, illness; or pose a substantial present or potential hazard to human health or the environment when improperly treated, stored, transported, or disposed of, or otherwise managed” (42 USC § 6903(5)).  

Waste from certain industrial processes is automatically considered hazardous (40 CFR § 261). If the waste does not appear on a RCRA hazardous waste list, it may be classified as hazardous if it has one of four properties: ignitability, corrosivity, reactivity, and/or toxicity. The waste might also reach hazardous status if it mixes with a hazardous waste or a hazardous constituent. 

Hazardous constituents include heavy metals (such as lead, mercury, and cadmium), certain organic compounds, pesticides, and other toxic substances. The presence of these hazardous constituents in waste when above the regulatory level listed in 40 CFR 261.24 Table 1 or waste containing any of the toxic constituents listed in Appendix VIII of 40 CFR 261) puts the waste into the RCRA hazardous waste category. 

Currently, PFAS compounds are not specifically listed as hazardous waste under RCRA. But in October 2021, EPA announced its intention to designate four PFAS (PFOA, PFOS, PFBS, and GenX) as RCRA hazardous constituents, which would trigger cleanup authority and give EPA further authority to regulate the generation, transportation, treatment, storage, and disposal of PFAS. The proposed rule is expected to be published before the end of 2023. 

Knowing whether waste is considered hazardous and how that particular waste is classified will determine a facility’s obligations under RCRA. What rules apply depends on the amount and type of waste generated, stored, or transported.  

Example: Designating PFAS as hazardous constituents would increase facilities’ reporting obligations. Currently, facilities that use and store certain PFAS must submit annual reports to EPA’s Toxics Release Inventory (TRI) program. However, in the future, they might also need to file a report every two years documenting their hazardous waste operations under RCRA. 

Where Is There Overlap?  

People sometimes use the terms hazardous substance and hazardous waste interchangeably because there is significant overlap between these definitions. 

CERCLA hazardous substances always include RCRA hazardous wastes. However, because RCRA only governs hazardous solid waste CERCLA hazardous substances are not automatically subject to RCRA regulation. Under RCRA, the term “solid waste” includes solid materials, liquids, and contained gasses. But, depending on how it is classified, a CERCLA hazardous substance may also become a RCRA-regulated waste, which carries additional regulatory obligations. 


Understanding the distinctions between hazardous substances and hazardous waste is crucial for companies to successfully navigate current and future regulatory frameworks. Given the potential financial liability associated with compliance and noncompliance within each regulatory scheme, particularly as applied to PFAS, it is imperative for businesses to identify the applicable laws and stay informed about emerging regulations. By doing so, industrial and commercial facilities can understand their compliance responsibilities and potential liability under federal law and prepare for future regulatory challenges. 

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