WASHINGTON, D.C. — Environmental Protection Agency Deputy Administrator David Fotouhi issued an internal memo directing EPA offices and external entities to review and phase out the use of Integrated Risk Information System chemical toxicity assessments, ending the program. The memo tasks the offices that craft regulations with conducting toxicity assessments going forward.

The IRIS program, created by the EPA in 1985 as the nation's clearinghouse for information on the toxicity of chemicals, maintains a library of more than 500 chemical assessments that quantify the highest safe level of exposure to a chemical before it triggers health effects, including cancer. The agency had previously kept the program separate from the offices that craft regulation to protect its science from industry influence.

Fotouhi sharply criticized the program in the memo, directed EPA offices that have used IRIS chemical assessments to review them, advised external entities to consider similar reviews, and cautioned against using IRIS assessments in future regulations. The memo said the EPA would add disclaimer language to the IRIS website stating that its toxicity findings are not necessarily meant to be used in regulation.

"When many conservative assumptions are stacked on top of each other, the cumulative effect can produce an estimated 'safe' exposure level that is orders of magnitude below naturally occurring levels in the environment," Fotouhi wrote in the memo. Before his appointment to the EPA, he worked as a lawyer representing companies accused of causing toxic pollution.

The directive could allow weakening of hundreds of efforts to protect people from harmful chemicals at the state and federal level, extending to standards for allowable arsenic levels in drinking water and lead levels in paint and soil. EPA offices have routinely relied on IRIS assessments to set allowable emission amounts for particular chemicals, and states use them to decide which chemicals deserve immediate attention and to calculate limits in rules and regulations.

"Anybody who wants to ignore a regulation, permit or enforcement action can now just point to this memo and say the IRIS number it was based on wasn't valid," attorney Robert Sussman said. "It's a huge setback for the process of protecting people from chemicals."

In a statement defending the directive, an EPA spokesperson said, "Science is at the heart of the Agency's work, and this memo reaffirms that point clearly and unequivocally." The Heritage Foundation's Project 2025 called for the elimination of the IRIS program on the grounds that it often sets safe levels based on questionable science and that its reviews result in billions in economic costs.

Last year, congressional Republicans introduced industry-backed legislation that would prevent the EPA from using IRIS assessments in rules, regulations, enforcement actions and permits, but the bills were not put to a vote. Over the past year, the EPA reassigned most of the scientists who worked in the IRIS program to other parts of the agency, and the EPA refused to publish a report on perfluorononanoic acid completed by IRIS in April 2025.

IRIS updated its assessment of ethylene oxide in 2016 and found that the chemical was a more potent carcinogen than previously believed. The updated cancer risk estimate set off concern and lawsuits in communities with high exposure and led the Biden administration to issue more protective regulations. Companies that use or manufacture ethylene oxide complained to the EPA and questioned the science. Under the Trump administration, the EPA paused efforts to protect the public from ethylene oxide.