The U.S. Environmental Protection Agency (EPA) announced on August 6, 2025, the availability of the draft Toxic Substances Control Act (TSCA) risk evaluations for the phthalates butyl benzyl phthalate (BBP) and diisobutyl phthalate (DIBP) for public comment. 90 Fed. Reg. 37855. According to EPA, the purpose of TSCA risk evaluations is to determine whether a chemical substance presents an unreasonable risk of injury to health or the environment under the conditions of use (COU), including unreasonable risk to potentially exposed or susceptible subpopulations identified as relevant to the risk evaluation by EPA, and without consideration of costs or non-risk factors. EPA states that it used the best available science to prepare the draft risk evaluations and to determine preliminarily, based on the weight of scientific evidence, that BBP and DIBP pose unreasonable risk to health and the environment driven primarily by certain COUs analyzed in the draft risk evaluations. Comments are due October 6, 2025.

EPA seeks “specific input on each section of the draft risk evaluation for each chemical,” particularly on the following questions:

• Whether and how personal protective equipment (PPE) and engineering controls are used during the manufacture, processing, and use of BBP and DIBP for each COU;
• Information that could be used to refine upper-bound or screening level assumptions for BBP and DIBP, particularly for the COUs that may significantly contribute to unreasonable risk;
• Information on environmental releases of BBP and DIBP, including media of environmental release (i.e., air, land, water, or incineration), facility-specific receiving water bodies, and the use of wastewater treatment;
• Information on inhalation occupational exposure to BBP and DIBP under the COUs, including monitoring or personal breathing zone data and exposure to respirable particles (i.e., data on particle formation or size);
• Input on the dermal occupational exposure scenarios used to assess BBP and DIBP, including the use of a flux-limited approach to estimate dermal absorption and any supporting data to inform assumptions regarding duration and surface area of exposure;
• Information to inform the assessment of dermal and inhalation exposures to BBP and DIBP for occupational non users (ONU);
• Information on the extent to which spray applications of BBP and DIBP are used in industrial and commercial COUs and the volumes of BBP and DIBP that may be used;
• Information to inform assumptions of inhalation of dust/particulate matter in the consumer exposure assessment of BBP;
• Approaches used to estimate chemical migration rate for ingestion via mouthing in the BBP and DIBP consumer exposure assessments;
• Selection of human health and environmental hazard endpoints used in the BBP and DIBP risk characterizations;
• Integration of its cumulative risk assessment approach within individual risk evaluations, derivation of relative potency factors (RPF), and individual BBP and DIBP points of departure (POD); and
• Any other information that may inform the assumptions used for exposure modeling used to assess the COUs for BBP and DIBP.