Chromium VI

EPA regulates chromium and its compounds under a variety of statutes that include the Clean Air Act; Clean Water Act; Comprehensive Environmental Response, Compensation, and Liability Act; Resource Conservation and Recovery Act; Emergency Planning and Community Right-to-Know Act of 1986; Federal Insecticide, Fungicide, and Rodenticide Act; Safe Drinking Water Act; and Toxic Substances Control Act. Besides directly regulating chromium and its compounds in different industrial and environmental settings, the main impact of these statutes on CERCLA activities is the requirement under the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) to consider them as potential applicable or relevant and appropriate requirements (ARARs).

Clean Air Act. Under 40 CFR PART 61—National Emission Standards for Hazardous Air Pollutants— chromium is a designated hazardous air pollutant. An air emissions permit obtained for thermal desorption and destruction of a co-contaminating organic constituent would also have to address the potential for the chromium in the soil to vaporize.

Clean Water Act. A number of chromium compounds have been designated as hazardous substances by regulations (40 CFR PART 116—Designation of Hazardous Substances) promulgated under the Clean Water Act. These compounds have been assigned reportable quantities under 40 CFR PART 117. The list of hazardous substances and their reportable quantities developed under CERCLA (40 CFR 302) incorporated those developed under the CWA. 40 CFR 131 provides for the development of water quality standards for each water body in the country. The standards are usually developed by the state and are directly applicable to Superfund cleanups that involve surface waters. Chromium: Water Quality Standards Criteria Summaries: A Compilation of State/Federal Criteria (EPA/440/5-88/026) while dated, is the most up-to-date treatment of chromium, and the National Recommended Water Quality Criteria provides a current list of federally recommended criteria. When conducting a cleanup action, the state regulations should be consulted to determine if any of these criteria have changed. Finally the Clean Water Act creates the National Pollutant Elimination System (40 CFR 125) which governs the point source discharge of chemicals into surface water bodies. Any cleanup action taken at a site that involves the discharge of treated water to a surface water body should comply with the state discharge regulations for the specific water body with regard to chromium and any other regulated material that might remain in the effluent after treatment.

Safe Drinking Water Act. The Safe Drinking Water Act provides for the setting of maximum contaminant limits for chemicals found to be hazardous and in the water supply (40 CFR 141). The National Oil and Hazardous Substances Pollution Contingency Plan, which is the implementing document for Superfund, specifically names MCLs as Superfund ARARs. The federal MCL for chromium does not address hexavalent chromium as a separate entity and sets a limit of 100 µg/L for total chromium. General drinking water standards and policies are available on the EPA website. Note that state drinking water standards are also ARARs and can be different from the federal standards. For example, California has an MCL for total chromium of 50 µg/L and is in the process of developing a separate MCL for hexavalent chromium. The Safe Drinking Water Act also regulates the injection of fluids into the ground (40 CFR 144). The program is usually administered by the state and permission is generally required to return treated water to an aquifer or apply in situ chemical oxidation or flushing.

Resource Conservation and Recovery Act. RCRA governs the treatment, storage, and disposal of chemicals or process wastes that have been designated by the government to be hazardous. There are some 23 waste or process waste streams that are specifically named (40 CFR 261.31 and 40 CFR 261.32) as hazardous under RCRA because of potential total or hexavalent chromium content. In addition any material that contains chromium that will leach 5 mg/L total chromium under the Toxicity Characteristic Leaching Procedure (40 CFR 191) is considered a characteristic RCRA hazardous waste. These sections of RCRA are Superfund ARARs and have the potential to govern on-site treatment requirements and offsite disposal of chromium containing wastes and contaminated soils.

Federal Insecticide, Fungicide, and Rodenticide Act. Controls the use of pesticides through registration or licensing. The primary pesticide containing chromium is copper chromated arsenic (CCA) a wood preservative.

Toxic Substances Control Act. Under the Toxic Substances Control Act (TOSCA) the administrator of EPA has the authority to set controls on any chemical hazard that the administrator determines cannot be controlled better under other authorities. 40 CFR 749.68 exercises this authority for hexavalent chromium-based water treatment chemicals in cooling systems by prohibiting their use in systems that have comfort cooling towers. Since the operation of comfort cooling towers is not related to CERCLA activities this regulation would not be an ARAR. However, as 40 CFR Part 761 that regulates polychlorinated biphenyls and is a CERCLA ARAR demonstrates, there is the potential in the future for TOSCA to cover hexavalent chromium.

Comprehensive Environmental Response, Compensation, and Liability Act. Chromium compounds are listed as hazardous substances under CERCLA (40 CFR 302) and have associated reportable release quantities. In addition, all the RCRA D, F, and K code wastes are included in the CERCLA hazardous substance list. However, treatment and disposal requirements under RCRA are still ARARs.

Emergency Planning and Community Right-to-Know Act. This Act contains a citizen's right to know section which requires manufacturer's that handle hazardous substances to report any release of these substances to the environment. In many cases these releases involve fugitive emissions and permitted releases such as discharge permits issued under the CWA. EPA keeps the information gathered by this requirement in its Toxics Release Inventory. The data, which can be displayed by facility, are presented as chromium and chromium compounds in the database. For specific chromium releases see the Toxics Release Inventory (TRI) Program.

Guidance documents specifically addressing hexavalent chromium policy under CERCLA were not found. The soil screening guidance listed below is useful for estimating cleanup levels at specific sites that have chromium contamination. Also, the EPA Region 9 Preliminary Remediation Goals website provides some guidance on chromium cleanup levels for various use scenarios .

For Further Information

The Scenarios Approach to Attenuation-Based Remedies for Inorganic and Radionuclide Contaminants
Truex, M., P. Brady, C. Newell, M. Rysz, M. Denham, and K. Vangelas.
SRNL-STI-2011-00459, 111 pp, Aug 2011

This document was developed as a technical resource to guide interested parties through the process of evaluating attenuation-based remedies for sites contaminated with inorganic or radionuclide contaminants. The six scenarios are based on aquifer geochemical properties: oxidation-reduction potential, cation exchange capacity, and ferric iron oxide content. Section 1 steps the reader through using the scenarios approach, including how to choose a scenario, the parameters on which the scenarios are based, and worksheets to organize data. Section 2 discusses specific attenuation processes affecting contaminant mobility, shows how to use a scenario to develop a site conceptual model, discusses how to apply MNA and EA to specific scenarios, and ties the scenarios approach to U.S. EPA's four tiers of evidence for demonstrating MNA. Section 3 provides detail on attenuation mechanisms and development of conceptual models, discusses the EPA four-tiered approach in more detail, and includes additional information on geochemical reactions, monitoring, remediation, and costs. Appendix B contains a synopsis of mercury chemistry.

Soil Screening Guidance: A User's Guide
U.S. Environmental Protection Agency
EPA 540/R-96/018, Office of Solid Waste and Emergency Response, 1996
Contact: David Cooper, cooper.davide@epa.gov

Attachments A-D