EPA Moves to Dismantle the IRIS Centralized Chemical Risk Assessment

U.S. Environmental Protection Agency (EPA) Deputy Administrator David Fotouhi on April 27, 2026, issued an internal memorandum titled "Future Development and Use of Risk Assessments" that directs the agency to add disclaimer language to the Integrated Risk Information System (IRIS) website. The memorandum is a way to address limitations to the IRIS approach to risk assessment and stakeholder criticism.

Background

Since its establishment in 1985, the IRIS program has functioned as the federal government's principal repository of chemical-specific human health toxicity values. Although IRIS does not itself promulgate regulations, IRIS assessments serve as the foundational basis for a wide range of health-based standards, regulations and screening levels.

For example, IRIS values have historically served as the presumptive basis for human health risk assessments at Superfund sites and for the derivation of EPA Regional Screening Levels. They also underpin residual risk and technology reviews for hazardous air pollutants under Section 112 of the Clean Air Act, inform Maximum Contaminant Level Goals under the Safe Drinking Water Act and guide corrective action risk evaluations under the Resource Conservation and Recovery Act.

IRIS' influence extends beyond EPA. State environmental agencies routinely incorporate IRIS values into cleanup standards and air toxics programs, and other federal agencies and international regulators have relied on IRIS determinations as benchmarks. Therefore, IRIS assessments directly affect the regulated community by shaping the stringency of cleanup obligations, permit limits, Toxic Substances Control Act (TSCA) risk management measures and broader product stewardship considerations across environmental programs.

Criticism of IRIS

The IRIS program has faced significant criticism from a wide range of stakeholders, including congressional proposals to eliminate the program, which has no specific basis in statute. The April 27, 2026, memorandum identifies several issues with the IRIS program that led to the issuance of the memorandum and, presumably, the usefulness of the IRIS risk information, including:

• Fit-for-Purpose. IRIS assessments are meant to have general applicability. Therefore, the assessments are not tailored to specific statutory programs. Science policy judgements (e.g., uncertainty factors, dose-response modeling choices, population selection) are better made by the regulatory programs that will use the risk information.
• Conservative Assumptions. IRIS has historically stacked conservative assumptions (e.g., uncertainty factors) on top of each other, leading to "safe" exposure levels that are orders of magnitude below naturally occurring levels in the environment or human body.
• Failure to Consider All Available Science. In some cases, assessments are old, and new information has not been applied. In others, newer information that might affect dose-response values has been excluded (e.g., mode of action data, mechanistic data).

The Memorandum

The memorandum affirms that each EPA program office is "in the best position to make determinations about how best to conduct all elements of risk assessments that can be used to implement programmatic objectives and inform regulatory actions." This direction aligns with the "fit-for-purpose" critique of IRIS noted above. The memorandum also directs several immediate operational changes to address these concerns:

1. Add disclaimer language to the IRIS website "to remind users that IRIS values represent only the first two steps of the four-step risk assessment process and are not necessarily intended for use as regulatory levels."
2. "Before relying on IRIS values, users should ensure that the IRIS assessments and values are fit for their intended purpose and that the values are consistent with the most current scientific literature."
3. Each EPA program office that has relied on IRIS is directed to review how that information was used and consider whether the IRIS information is fit-for-purpose, represents best available science, was developed in a manner consistent with statutory and regulatory obligations, and meets current standards for transparency, impartiality, reliability and credibility.
4. External stakeholders are encouraged to evaluate their use of IRIS values "to ensure any decision or reliance was accurate and properly implemented."

These directives coincide with the elimination of the Office of Research and Development and reflect a broader structural shift away from centralized chemical risk assessment toward decentralized, program-specific development of toxicity values. (See Holland & Knight's previous alerts, "EPA Announces Deregulatory Initiative to 'Power the Great American Comeback,'" March 17, 2025, and EPA Proposes Significant Budget Reduction for Fiscal Year 2026, June 5, 2025.)

The memorandum does not create a new methodology or replacement body of toxicity values. However, the memorandum highlights the newly created Office of Applied Science and Environmental Solutions (OASES), housed within the Office of the Administrator, as the coordinating body intended to support program offices and agency partners in developing fit-for-purpose risk assessments. It is expected that OASES will play a critical role in ensuring coordination and helping the program offices articulate the rationale to the extent there are differing risk assessment approaches.

As OASES steps into that coordinating role, companies currently engaged in Superfund cleanups, permit negotiations or TSCA risk evaluations will no doubt raise an immediate practical question: Which toxicity values should govern pending decisions where IRIS values have historically been the default? Indeed, given the memorandum's emphasis on fit-for-purpose, the use of different models, approaches and assumptions within risk assessment is likely to introduce a degree of uncertainty as to what risk assessment elements should be used as EPA stands up its new regime. 

Conclusions

EPA's April 27, 2026, memorandum identifies and aims to address several long-standing criticisms of the IRIS program, largely through devolution of the previous risk assessment process to the program offices.

This solution has the potential to create divergent standards, benchmarks and risk models within the agency, which is expected to be managed by OASES. It raises questions on how other regulators (e.g., states, Tribes, other federal agencies) will react to this new approach. 

Members of the regulated community will need to track federal and state regulatory changes as chemical risk assessments are integrated into new rules, benchmarks and standards. The response to these changes will need to be tailored to each company's specific position. For example, one compliance strategy for a company doing business in states that diverge from EPA may involve adoption of the most conservative approach to allow for production and distribution efficiency. Other companies may elect to challenge new or existing standards to address one or more of the deficiencies identified in the April 27, 2026, memorandum.

Holland & Knight is tracking the ripple effect of the memorandum and will provide additional analysis. A forthcoming companion alert will address how the U.S. Supreme Court's decision in Loper Bright Enterprises v. Raimondo, 603 U.S. 369 (2024), and other deference doctrines affect the legal vulnerability of existing regulations, standards and determinations built on the IRIS-derived toxicity values and litigation strategies that are likely to emerge.

For more information or questions, please contact the authors.

Information contained in this alert is for the general education and knowledge of our readers. It is not designed to be, and should not be used as, the sole source of information when analyzing and resolving a legal problem, and it should not be substituted for legal advice, which relies on a specific factual analysis. Moreover, the laws of each jurisdiction are different and are constantly changing. This information is not intended to create, and receipt of it does not constitute, an attorney-client relationship. If you have specific questions regarding a particular fact situation, we urge you to consult the authors of this publication, your Holland & Knight representative or other competent legal counsel.