For decades, a small program at the Environmental Protection Agency has conducted careful scientific work evaluating the toxicity of chemicals.
Calculations made by IRIS scientists, as it is commonly known, underlie many of the chemical regulations, permits and other environmental rules in the United States and abroad.
Now the Trump administration is suggesting that its library of more than 500 chemical assessments is unreliable, opening the door to weakening hundreds of efforts to protect people from harmful chemicals at the state and federal levels. The challenges could even extend to long-established standards, environmental scientists said, such as the amount of arsenic allowed in drinking water and the amount of lead acceptable in paint and soil.
In an internal memo obtained by ProPublica, David Fotouhi, the agency’s deputy administrator, sharply criticized IRIS this week and ordered EPA offices that used any of the chemical assessments produced by the program to review them. It also advised “external entities” that have used IRIS assessments to consider undertaking similar reviews and warned against their use in future regulations.
The six-page memo stated that the EPA would add a “disclaimer” to the program’s website – the Integrated Risk Information System — specifying that its toxicity results are not necessarily intended for use in regulations.
“This creates the opportunity for companies that pollute to push back against rules and regulations they don’t like,” said Robert Sussman, a lawyer who has worked for chemical companies and environmental groups as well as the EPA. “Anyone who wants to ignore a regulation, permit or enforcement action can now simply point to this memo and say that the IRIS number it was based on was invalid. This is a huge setback to the process of protecting people from chemicals.”
Fotouhi’s memo echoes industry criticism that the program’s scientists are far too conservative in assessing the toxicity of chemicals. Before President Donald Trump named him the EPA’s second-highest official, Fotouhi worked as an attorney representing companies accused of causing toxic pollution.
In an emailed statement, the EPA press office wrote that Fotouhi had complied with all applicable government ethical obligations and said his directive would not put people at risk or allow anyone to ignore environmental regulations. Any revision to permits or regulatory standards must go through a process that includes public participation, the office noted.
“Science is at the heart of the Agency’s work, and this memo reaffirms this point clearly and unequivocally,” the press service wrote.
The EPA established IRIS in 1985 as a national clearinghouse for chemical toxicity information. Its assessments quantify the highest level of safe exposure to a chemical before it triggers health effects, including, in many cases, cancer. The agency previously prided itself on the program’s impartiality and, in an effort to protect its science from industry influence, deliberately kept the program separate from the agency offices that develop the regulations.
The memo now directs these offices to conduct toxicity assessments and ends the program that fueled the EPA’s efforts to protect people from harmful chemicals.
IRIS assessments have gained a reputation for being extremely detailed and subject to numerous rounds of review by many scientists. EPA offices routinely rely on it to set the amount of a particular chemical that industrial facilities are allowed to emit. States use IRIS assessments to decide which chemicals deserve their immediate attention and to calculate limits in rules and regulations. And IRIS reports guide environmental regulation in countries that don’t have the resources to fund their own scientists to examine chemicals.
The memo is the latest attack on the program. The Heritage Foundation’s Project 2025 called for the elimination of IRIS on the grounds that it “often sets ‘safe levels’ based on questionable science” and that its reviews result in “billions in economic costs.” And last year, Congressional Republicans introduced industry-backed legislation this would prevent EPA from using IRIS assessments in environmental rules, regulations, enforcement actions, and permits. (The bills were not put to a vote.)
IRIS has sometimes been criticized by independent scientific organizations. More than a decade ago, for example, the National Academies of Sciences, Engineering, and Medicine challenged the organization, length, and clarity of the IRIS journals; a more recent report from the same group found that IRIS had made “significant progress” in resolving the issues.
Still, IRIS’s work stood out in a world where much of the science on toxic chemicals is funded by companies with vested interests in those products. Studies have shown that industry-funded science tends to be biased in favor of the sponsor’s products.
Over the past year, the EPA has virtually shut down IRIS by reassigning most of the dozens of scientists who worked in the program to other parts of the agency. And the administration refused to publish a report on a “forever chemical” known as PFNAwhich was completed by IRIS in April 2025.
But until now, the EPA has not challenged the science behind the IRIS assessments. The memo changes that. Although the agency will continue to publish the documents on its website, it questions their validity, arguing that the toxicity levels calculated in the IRIS reports are too conservative and do not take into account the views of all “stakeholders.”
This approach produces values that are more protective than they should be, according to Fotouhi. “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 lower than natural levels in the environment,” he wrote.
Fotouhi specifically pointed to ethylene oxide, a chemical used to sterilize medical equipment — and used by Medline, a company he represented as an attorney at the firm Gibson, Dunn & Crutcher, according to financial statements he filed that are contained in ProPublica. database of disclosures from 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 updated cancer risk estimate has sparked waves of concern — and lawsuits — in communities across the country where people are heavily exposed to the chemical. And that led the Biden administration to issue more protective regulations. Companies that use or manufacture ethylene oxide and their representatives have complained to the EPA and questioned the science that cost them so much.
Under Trump, the agency, which defends the industry, has already suspended its efforts to protect the public from ethylene oxide. But this latest step, which threatens to destabilize health protections based on hundreds of IRIS assessments, is a boon for countless companies emitting a wide variety of toxic chemicals, according to Maria Doa, an Environmental Defense Fund scientist who spent more than 20 years working on chemical regulation at the EPA.
“This is the EPA adopting industry talking points,” Doa said. “And that’s going to put a lot of people at risk.”
