At the end of 2025, the U.S. Environmental Protection Agency (EPA) completed a review of 1,3-butadiene, finding potential unreasonable health risks for workers who breathe in this chemical at their jobs in 11 specific industrial settings. These include factories that make or use 1,3-butadiene to create rubber, plastics, and other products. Specifically, one condition that the EPA determined contributed to "unreasonable risk of injury to human health for workers due to inhalation exposure" was the industrial use "processing as a reactant — intermediate in various industries such as adhesive manufacturing and synthetic rubber manufacturing."

The agency reports that the use of personal protective equipment, which is often used in industrial workplaces, will help mitigate these risks. EPA did not find unreasonable risks to the environment for consumers and to the general population including people living near facilities.  

As required by law under the Toxic Substances Control Act (TSCA), EPA will now develop rules to protect workers from the risks that the agency identified. The process will include consideration of health effects, exposure levels, economic impacts, and benefits of use, with extensive stakeholder engagement to ensure the resulting rules are both protective and practical.  

According to EPA, the agency improved its risk evaluation by incorporating real-world data and refining some conservative assumptions from its first draft. For example, EPA switched to a more detailed database (NEI) that includes specific details like how tall stacks are, what angle they release emissions at, and emission temperatures, which are not reported in TRI. The agency claims that this allowed its evaluation to move away from defaults to more accurate, facility-specific conditions. The NEI database also provides exact coordinates of where emissions are actually released, rather than just general facility locations. This geographic precision gives a more accurate picture of actual exposure risks.  

EPA also took into account additional feedback from peer reviewers recommending that the agency adds together the risks from bladder cancer and leukemia. This resulted in a higher overall cancer risk estimate used in the risk evaluation.

1,3-butadiene is a colorless gas essential for manufacturing products Americans use every day, including car tires, adhesives and sealants, paints and coatings, and automotive care products. Consumer products only contain tiny, safe amounts less than 0.001 percent. Unreasonable risks are found in industrial settings where workers could be exposed to much higher levels that could lead to health risks which may include reduced birthweight pregnancies, anemia, leukemia, and bladder cancer.