The U.S. Environmental Protection Agency’s Integrated Risk Information System (IRIS) program develops human health toxicity assessments of chemicals released into the environment by a wide range of industries. These assessments are used by EPA, states, and others to inform regulatory, permitting, cleanup, and emergency response decisions.
Yet, IRIS is characterized by one member of Congress as “the most destructive EPA program you’ve never heard of”. The IRIS program is targeted by Project 2025. The Competitive Enterprise Institute has called for eliminating IRIS. The American Chemistry Council “applauds” the introduction of the “No IRIS Act”, federal legislation to prevent EPA from using its own toxicity assessments to inform decisions.
The IRIS program was created in 1985, during the Reagan administration, as an efficiency measure to “foster consistency in the evaluation of chemical toxicity across the Agency.” The program produces scientific assessments focused on identifying hazards, such as cancer, to human health from a given chemical, and quantifying the relationship between dose and adverse health response.
IRIS assessments are developed for chemicals relevant to EPA regulatory offices (e.g., air, water, land and chemical offices), EPA regional offices, states, and Tribes. These assessments are developed independently, to assure scientific integrity, by an interdisciplinary team that serves the entire agency to avoid duplication of resources. State and Tribal environmental agencies, which typically lack resources to develop their own toxicity assessments, look to EPA as a reliable source of toxicity data.
IRIS assessments address two of the four main components of a risk assessment. Thus, IRIS assessments are not complete risk assessments. Decisions informed by IRIS assessments incorporate other scientific input on exposure and risk.
Furthermore, IRIS assessments are not policies: they do not set a standard or benchmark for what may constitute acceptable risk. Policy decisions informed in part by IRIS take into account judgments regarding acceptable risk, and – depending on the statute that provides authority for the decision – other factors such as the balance between control costs and benefits of avoided adverse health effects.
In 2024, the U.S. District Court for the District of Columbia dismissed a lawsuit by the American Chemistry Council (ACC) v. National Academy of Sciences (NAS), et al., affirming that the IRIS “database by itself has no preclusive effect.” Furthermore, the court noted that regulations informed by IRIS dose-response relationship values, and other scientific assessments, must “go through notice-and-comment, at which time ACC and its members could provide their input on the value (as they have done in the past).”
Some industry stakeholders and others argue that IRIS is not mandated by statute. However, it is funded through annual appropriations that are approved by Congress. Furthermore, multiple statutes, as interpreted by federal courts, require that EPA use best available science. IRIS meets the requirements for best available science for toxicity.
Many critics of the IRIS program point to a 2011 National Academy of Sciences (NAS) report that peer reviewed a draft toxicity assessment of formaldehyde and was highly critical of the IRIS program as a whole at that time. NASEM recommended that EPA bolster IRIS by adopting systematic review methods, an emerging best practice for identifying, reviewing, and interpreting scientific literature, as well as other improvements.
EPA has addressed the National Academy’s 2011 advice. EPA’s 2020 draft IRIS Handbook received a favorable NAS external peer review for its adoption of systematic review methods. After a pause on the formaldehyde assessment during the first Trump Administration, EPA completed a revised draft in 2022 that was favorably reviewed by NAS in 2023 and finalized in 2024.
IRIS assessments are developed transparently according to best scientific practices that adhere to tenets of information quality, peer review, and scientific integrity. A program outlook gives advance notice of upcoming assessments, followed by sequential public releases of an assessment plan, a systematic review protocol, and an external review draft. The external review draft undergoes inter-agency science consultation, public comment, and external independent scientific expert peer review.
The Government Accountability Office (GAO) includes the IRIS program on its list of “high risk” programs, but not for reasons claimed by critics. GAO states that the EPA “needs to address capacity issues”, not fraud, waste, or abuse. A key implication is that more, not fewer, resources should be made available from Congress to the IRIS program to enable it to meet partner needs.
Some critics contend that IRIS assessments fail to consider various scientific issues, such as consideration of alternative “modes of action”, which are the mechanisms by which a toxic substance causes harm, or uncertainty in dose-response relationships. The 2022 IRIS handbook specifically addresses consideration of multiple hypothesized modes of action and improvements in uncertainty characterization.
Because science is a search for evidence-based inference and objectivity, science is inherently self-correcting, if and as needed, via the research and peer review process. The evolution of scientific methods that underpin the EPA IRIS program is a case in point. The most stable, effective, efficient, and credible way to develop science that informs policy decisions is to allow scientists to do science, and to do so as part of an integrated team that continues to adopt and advance scientific practices and to deliver best available science.
H. Christopher Frey is a professor of environmental engineering at North Carolina State University. He served as Assistant Administrator of the Office of Research and Development at the U.S. Environmental Protection Agency from 2022 to 2024. He has over 30 years of experience in development and translation of science to inform policy. The views do not necessarily reflect those of NC State.