• When a determination is made to regulate a substance under the CAA, CWA, RCRA, or TSCA, it automatically becomes a CERCLA hazardous substance.

Hazardous substance is defined in the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) 101(14) to include a compilation of substances listed in accordance with the Clean Air Act (CAA), Clean Water Act (CWA), Resource Conservation and Recovery Act (RCRA), and Toxic Substances Control Act (TSCA). The term also includes any element, compound, mixture, solution, or substance designation pursuant to CERCLA section 102(a), meaning the substance may present a substantial danger to the public health or welfare or the environment when released into the environment.

When a determination is made to regulate a substance under the CAA, CWA, RCRA, or TSCA, it automatically becomes a CERCLA hazardous substance and will be added to the Table 302.4 found at 40 CFR 302.4. When a substance is delisted from the CAA, CWA, RCRA, or TSCA lists, the substance remains on the hazardous substance list unless the Environmental Protection Agency (EPA) determines that there is no independent basis for retaining the hazardous substance listing. Regarding CAA-, CWA-, RCRA-, and TSCA-listed chemicals, CERCLA grants EPA the authority to automatically add new substances to the list of hazardous substances codified in Table 302.4 found at 40 CFR 302.4. In a nutshell, 40 CFR 302.4 offers a list of covered hazardous substances.

On the other hand, when a determination is made to regulate a substance under CERCLA section 102, it too is added to Table 302.4 found in 40 CFR 302.4. To find these, look for Statutory Code ‘‘5’’ in Table 302.4. The code indicates that a hazardous substance is designated under section 102(a) of CERCLA. Note that a May 8, 2024, final rule designates perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), including their salts and structural isomers, as CERCLA hazardous substances, effective July 8, 2024.

In addition, according to 302.4, the release of a material that exhibits one or more characteristics (identified at 40 CFR 261.20 through 261.24) of hazardous waste, but is not specifically listed on Table 302.4, is reportable provided the material becomes a waste upon release and the amount released meets the reportable quantity (RQ).