For decades, a small program at the Environmental Protection Agency has performed the painstaking scientific work of assessing the toxicity of chemicals.
As it is commonly known, the calculations made by IRIS scientists underpin a vast array of chemical regulations, permits, and other environmental regulations in the United States and abroad.
Now, the Trump administration has indicated that its library of more than 500 chemical assessments is unreliable, opening the door to undermining hundreds of efforts to protect people from harmful chemicals at the state and federal level. Environmental scientists say long-established standards, such as the amount of arsenic allowed in drinking water and the amount of lead allowed in paint and soil, could be reconsidered.
In an internal memo obtained by ProPublica, the agency’s deputy administrator, David Fotouhi, harshly criticized IRIS this week and directed EPA offices that used chemical assessments produced by the program to review their assessments. He also advised “external parties” that used IRIS assessments to consider conducting similar reviews and warned them against using them for future regulation.
The six-page memo states that the EPA plans to add a “disclaimer” to the program’s website, called the Integrated Risk Information System, stating that its toxicity findings are not necessarily intended to be used in regulation.
“This creates an opportunity for polluting companies to push back on rules and regulations they don’t like,” said Robert Sussman, an attorney who has worked for the EPA as well as chemical companies and environmental groups. “Anyone who wants to ignore regulations, permits, and enforcement actions can point to this memo and say that the IRIS number on which it was based is invalid. This is a major setback to the process of protecting people from chemicals.”
Fotouhi’s memo echoes industry criticism that the program’s scientists are too conservative in assessing the toxicity of chemicals. Before President Donald Trump appointed him as the EPA’s second-highest-ranking official, Fotouhi worked as a lawyer representing companies accused of creating toxic pollution.
The EPA Press Office said in an emailed statement that Fotouhi has complied with all applicable government ethics obligations and that his instructions do not put people at risk or disregard environmental regulations. The Secretariat noted that any revisions to permitting or regulatory standards must go through a process that includes public participation.
“Science is at the heart of the Office of Science’s work, and this memo clearly and unequivocally reaffirms that point,” the news agency wrote.
EPA established IRIS in 1985 as the national clearinghouse for information on chemical toxicity. That assessment often quantifies the safest level of exposure to a chemical before it causes health effects such as cancer. The agency previously prided itself on the impartiality of its programs, intentionally separating them from the agency’s offices that set regulations to protect science from industry influence.
The memorandum now requires those offices to conduct toxicity assessments, ending a program that has advanced EPA’s efforts to protect people from harmful chemicals.
IRIS has a reputation for being very detailed and having been reviewed multiple times by many scientists. The EPA office routinely relied on them to set the amounts of certain chemicals that industrial facilities were allowed to emit. Countries use IRIS assessments to determine which chemicals require immediate attention and to calculate limits for rules and regulations. And IRIS reports guide environmental regulations in countries that don’t have the resources to fund their own scientists to study chemicals.
This memo is the latest attack on the program. The Heritage Foundation’s Project 2025 called for IRIS to be abolished, saying it “often sets ‘safety levels’ based on questionable science” and that its review would result in “billions in economic costs.” And last year, Republicans in Congress introduced an industry-backed bill that would block the EPA from using IRIS assessments in environmental rules, regulations, enforcement actions, and permits. (The bill was not voted on.)
IRIS has been criticized from time to time by independent scientific bodies. For example, more than a decade ago, the National Academies of Sciences, Engineering, and Medicine raised questions about the organization, length, and clarity of the IRIS review. A more recent report from the same group found that IRIS had made “significant progress” in addressing the problem.
Still, in a world where much of the science around toxic chemicals is funded by companies with vested interests, IRIS’s work stood out. Research shows that industry-funded science tends to be biased in favor of the sponsor’s products.
Over the past year, EPA effectively shut down IRIS by reassigning most of the dozens of scientists who worked on the program to other parts of the agency. And the administration has refused to release a report completed by IRIS in April 2025 on the “forever chemical” known as PFNA.
But to date, EPA has not challenged the science in its evaluation of IRIS. This memo changes that. The agency will continue to post the documents on its website, but has questioned the validity of the toxicity levels calculated in the IRIS report, saying they are overly cautious and do not include the perspectives of all “stakeholders.”
According to Fotouhi, this approach creates values that are more protective than necessary. “The cumulative effect of many conservative assumptions can be to cause estimated ‘safe’ exposure levels to be orders of magnitude lower than levels that occur naturally in the environment,” he wrote.
Mr. Fotouhi specifically singled out ethylene oxide, a chemical used to sterilize medical equipment and used by Medline, a company he once represented as an attorney at Gibson, Dunn & Crutcher, according to financial statements he filed, which are included in ProPublica’s database of disclosures by Trump administration officials. IRIS updated its assessment of ethylene oxide in 2016 after reviewing the medical literature and finding the chemical to be a more potent carcinogen than previously thought.
The EPA’s latest cancer risk estimates have sparked a wave of concern and lawsuits in communities across the country where people are highly exposed to the chemical. And that prompted the Biden administration to impose further protective regulations. Companies that use or produce ethylene oxide and their representatives have filed complaints with the EPA, questioning the science behind so much money.
The agency, which championed industry under the Trump administration, has already suspended efforts to protect the public from ethylene oxide. But Maria Doerr, an Environmental Defense Fund scientist who has worked on chemical regulation at the EPA for more than 20 years, said this latest move threatens to destabilize the health protections built on hundreds of IRIS assessments and benefits countless companies that emit a wide variety of toxic chemicals.
“This is EPA adopting an industry argument,” Doa said. “And a lot of people are going to be at risk.”
