The iris is the part of the eye that controls how much light enters into it. In doing so, and through working with the other parts of the eye, it helps us to see and navigate the world around us.
A U.S. EPA program by the same name helps us see in a different way. First created under President Ronald Reagan in 1985, IRIS, short for “Integrated Risk Information System,” provides EPA with critical scientific data about the toxicity of chemicals. While IRIS does not itself issue regulations about these chemicals, it is one aspect of EPA that enables the Agency to perform a broader risk assessment for a given chemical and, ultimately, propose risk management options to minimize harms to human health.
For example, IRIS assessments provide information about whether a chemical may cause cancer, and under what level of exposure or dose. In other words, and much like its anatomical namesake, the IRIS program works with the rest of EPA—which considers a variety of additional social, legal, economic, technical, and political factors—to ensure that Americans aren’t in the dark when it comes to toxics.
The role of IRIS in risk assessment is twofold: hazard identification and dose-response assessment. In the hazard identification process, scientists first determine potential health hazards associated with a chemical. Then, in the dose-response assessment, they investigate the relationship between the dose—for example, how much of a chemical is inhaled—and each hazard. This latter assessment is used to derive toxicity.
How do these assessments play out in practice? IRIS procedures have evolved over the years in response to periodic reviews of the program by the National Academies of Sciences (NAS). Comments from the NAS have been used to improve transparency and clarity in the process and methodology of the IRIS program, which now follows a 7-step framework. This process begins with problem formulation and assessment drafting, followed by reviews by internal agency experts, public comment, and external peer review, before an assessment is finalized.
Some, however, maintain that IRIS leaves much to be desired. The chemical industry has long critiqued the program as lacking transparency and being out of line with the best available science. In early 2025, the American Chemistry Council—the major trade group for U.S. chemicals companies—sent a letter to EPA Administrator Lee Zeldin, sharing concerns about the Agency’s reliance on IRIS science when conducting risk assessments and advocating for its disbandment.
Similar concerns have been raised by members of Congress, which most recently have been reflected through a pair of bills termed the “No Industrial Restrictions in Secret” or “No IRIS” Act. Sen. John Kennedy (R-La.) and Rep. Glenn Grothman (R-Wis.) introduced the bills in the Senate and House, respectively, arguing that IRIS-backed regulations are overly cautious and unduly restrict business across a wide range of sectors, including computer chips, national defense, and healthcare. This is all taking place in the backdrop of larger plans to restructure EPA, which could involve dissolving the Office of Research and Development that houses the IRIS program and shifting EPA’s scientific and research efforts into a newly established “Office of Applied Science and Environmental Solutions.”
Regardless of the uncertainty in what may come from Congress or EPA, closing our eyes to the health issues caused by toxic pollution won’t make these issues disappear. In Senator Kennedy’s home state of Louisiana exists an 85-mile stretch of land that contains about 200 fossil fuel and petrochemical operations, now commonly known as “Cancer Alley” due to the elevated rates of cancer borne by its predominantly impoverished and Black residents compared to the national average. Scientists have linked these high cancer rates to air pollution from industry, and the United Nations Special Rapporteur on Human Rights and the Environment called this area a “sacrifice zone,” noting that Cancer Alley contains 7 of the 10 census tracts in the United States with the highest risk of cancer due to air pollution according to 2014 EPA data.
In Cancer Alley and across the United States, the need to confront toxic pollution with science-based regulations is a matter of life and death. It isn't clear how that will happen without a program like IRIS. We just might be left in the dark.