The U.S. Environmental Protection Agency (EPA) announced on April 10, 2026, that it is advancing its review of four chemicals under the Toxic Substances Control Act (TSCA) — 1,3,4,6,7,8-Hexahydro-4,6,6,7,8,8-hexamethylcyclopenta [g]-2-benzopyran (HHCB), phthalic anhydride, o-dichlorobenzene (oDCB), and p-dichlorobenzene (pDCB) — by releasing draft documents related to the review of these chemicals and convening a Science Advisory Committee on Chemicals (SACC) peer review meeting. According to EPA, these chemicals are found in fragrances, paints, coatings, cleaners, and industrial processes, “meaning decisions in these cases can directly affect the air we breathe at work and at home.” EPA released the draft risk evaluations for HHCB and phthalic anhydride and the draft hazard assessments and supporting documents for oDCB and pDCB for public comment and independent scientific peer review — “two essential steps in ensuring the integrity, radical transparency, and quality of EPA’s chemical safety assessments.” On June 8-12, 2026, EPA will hold a virtual public meeting of SACC to review the draft risk evaluations for HHCB and phthalic anhydride and technical support documents for pDCB and oDCB. EPA will also hold a preparatory virtual public meeting on May 26, 2026, for SACC and the public to consider and ask questions regarding the scope and clarity of the draft charge questions that will be used in the peer review meeting. To have comments on the draft risk evaluations, draft hazard assessments, and technical support documents considered by SACC, comments must be submitted by May 29, 2026. 91 Fed. Reg. 19131. Comments on the draft risk evaluations for HHCB and phthalic anhydride are due to EPA by June 15, 2026. 91 Fed. Reg. 19134.
Draft Risk Evaluation for HHCB
According to EPA, HHCB is a liquid used as an odor agent in fragrances, such as air care and cleaning products. EPA states that its draft risk evaluation found that HHCB does not present an unreasonable risk of injury to human health or the environment under the conditions of use (COU), including manufacture, processing, commercial and consumer use, and disposal. EPA notes that its preliminary determination of no unreasonable risk applies to workers, consumers, and the general population (including subsistence fishers and Tribal populations), as well as aquatic and terrestrial ecological receptors.
EPA states that the draft risk evaluation uses both real world monitoring data and modeling to assess potential risks for workers from inhalation exposure via dust or vapor, inhalation exposure to consumers via continuous action air fresheners, and to the general population from fish and water consumption. According to EPA, “[t]he combination of screening-level approaches and refined analysis resulted in the very conservative evaluation and a preliminary finding of no unreasonable risks.” EPA notes that this conclusion is also supported by the European Union (EU) and the Australian National Industrial Chemicals Notification and Assessment Scheme (NICNAS, which has since been replaced by the Australian Industrial Chemicals Introduction Scheme (AICIS)).
Draft Risk Evaluation for Phthalic Anhydride
EPA states that phthalic anhydride is a white solid used as a reactant for producing adhesives, laboratory chemicals, and various paints, coatings, and plastic materials. According to EPA, once in the environment, phthalic anhydride can react with water or moisture in the air to become phthalic acid, and therefore the Agency also evaluated risks from exposure to phthalic acid for its assessment of risks to the general population and risks to the environment. Phthalic anhydride is a strong respiratory sensitizer and dermal sensitizer. In contrast, phthalic acid is not.
According to EPA, the draft risk evaluation found that phthalic anhydride presents an unreasonable risk for workers and from dermal and inhalation exposure across manufacturing, processing, industrial, and commercial COUs. The draft risk evaluation also found unreasonable risk to consumers from dermal and inhalation exposure in certain uses of solvent-based paints, coatings, adhesives, and sealants. EPA notes that the draft risk evaluation did not identify unreasonable risk to the general population or the environment.
Technical Support Documents for pDCB and oDCB
EPA is releasing draft human health and environmental hazard assessments for pDCB and oDCB. According to EPA, these assessments “present a robust review of available studies related to potential harm to human health and the environment.” The assessments compile and evaluate reasonably available evidence, calculate the levels at which these chemicals may cause harm to human health and the environment, and will inform the forthcoming draft risk evaluations that integrate hazard and exposure to characterize risk.
Along with these draft hazard assessments, EPA is also releasing an assessment of the use of New Approach Methods (NAM) related to both chemicals. EPA states that in support of Administrator Lee Zeldin’s commitment to end animal testing at EPA, it “used new scientific techniques and approaches to screen for health effects, including transcriptomics, to develop conservative risk estimates.”
According to EPA, pDCB is a colorless to white crystalline solid with a strong, pungent odor, used to manufacture plastics and other chemicals, and as an odor agent. EPA states that non-cancer hazards associated with pDCB exposure include respiratory system, liver, and kidney toxicity, as well as neurotoxicity and developmental and reproductive toxicity. For pDCB, EPA’s draft assessment shows this chemical is not likely to cause cancer in humans. EPA notes that this conclusion “is based on long-term studies showing that while pDCB causes mice to develop liver tumors, due to the differences in how our bodies work, exposures of humans to pDCB will not result in liver tumors.”
EPA states that oDCB is a colorless liquid with a pleasant, aromatic odor, used in the manufacture of dyes, paints, and pigments, and in products used for cleaning, degreasing, and painting. For oDCB, EPA used transcriptomics to screen for gene expression. According to EPA, using this approach allowed it to develop conservative and protective inhalation, oral, and dermal risk estimates and fill in gaps found in existing studies. EPA notes that non-cancer hazards associated with oDCB exposure include respiratory system, liver, and kidney toxicity. Using the Rethinking Carcinogenicity Assessment for Agrochemicals Project (ReCAAP) framework, a weight of evidence (WOE) framework, EPA determined a quantitative cancer assessment is not warranted.
EPA intends to release the draft risk evaluations for pDCB and oDCB prior to the June 2026 SACC meeting. EPA states that because of the unique and novel scientific approaches used in the human health and environmental assessments for these chemicals, it is seeking peer review from SACC on the draft technical documents released on April 10, 2026. According to EPA, it “anticipates that the reminder of the draft risk evaluations for these chemicals will use scientific approaches and techniques the SACC has previously commented on; therefore, EPA does not expect the need for an additional peer review of the forthcoming risk evaluations for pDCB and oDCB.” EPA will use the feedback from SACC to inform its final risk evaluations.
Commentary
These actions are yet another vital step forward for EPA in meeting its requirements under a 2024 consent decree and court-ordered schedule to complete risk evaluations for 20 high-priority chemicals. EPA has made significant progress toward meeting these requirements, including publishing nine of 20 final risk evaluations to date. The four chemicals discussed in this memorandum are part of the remaining 11 chemicals that require final, complete risk evaluations by February 2027.
In the announcement for these actions, EPA emphasized its commitment to “using the best available science and adhering to rigorous, gold standard scientific practices throughout the evaluation process,” including systematic review of available information and additional data from NAMs. EPA, for example, cites to novel use of transcriptomic analysis for measuring differences in gene expression for adverse health effects, and computational approaches to integrate data from in chemico studies and in vitro studies in human tissues. EPA also noted collaborations with other government and non-governmental organizations.
Of particular interest is the HHCB draft evaluation. Despite HHCB being a high-volume chemical and its use in a wide range of consumer products, EPA’s preliminary conclusion in the draft evaluation is that HHCB does not present an unreasonable risk. If the conclusion remains in the final determination, it will be the first instance of a “no unreasonable risk” finding for a chemical under TSCA Section 6 in the program’s history. While EPA has previously found that certain individual uses of chemicals did not present unreasonable risk, those findings were all eventually overturned in favor of a single risk determination on “the chemical substance,” sometimes referred to as the “whole chemical” approach. The whole chemical approach has been the subject of significant industry scrutiny, has been raised as an issue in several pending legal challenges, and slated for elimination in EPA’s 2025 proposed update to the procedural framework rule. Ironically, many, including some within Bergeson & Campbell, P.C. (B&C®), have argued that the “whole chemical” approach would result in EPA finding unreasonable risk in every instance because EPA would always “foresee” problematic COUs — a theory the draft HHCB evaluation proves wrong.
EPA notes that its conclusion for HHCB was the result of a “very conservative evaluation” that relied on both real-world monitoring data and modeling to assess risks to workers, consumers, and the general population. B&C agrees with the scope of EPA’s evaluation, but has not yet found EPA’s rationale for concluding that other uses are not foreseeable, a key consideration for the boundaries of COUs. B&C does note that EPA cites to Chemical Data Reporting for the basis for the uses that are “intended” and “known,” but EPA does not state that those represent the totality of the COUs.
Nonetheless, given that HHCB was listed in EPA’s 2014 TSCA Work Plan because of its characteristics for persistence and bioaccumulation, widespread consumer use, and high releases to the environment, the draft risk evaluation is sure to be the subject of robust public comment and debate.
