U.S. EPA Seeks Public Comment on Updated Draft Formaldehyde Risk Calculation Memorandum to Inform Risk Evaluation under the Toxic Substance Control Act

On December 3, 2025, the United States Environmental Protection Agency (U.S. EPA or Agency) announced availability of and solicitation for public comment on an Updated Draft Risk Calculation Memorandum (Risk Calculation Memo) for formaldehyde (HCHO) under the Toxic Substances Control Act (TSCA). The purpose of the notice and the Risk Calculation Memo is to provide the rationale for why the Agency is considering a revised acute inhalation point of departure (POD), revised uncertainty factors, and corresponding revised margin of exposure (MOE) calculations. Following this public comment period, the Agency will determine if the proposed revisions to the Risk Calculation Memo warrant updating the Agency’s December 2024 TSCA HCHO risk evaluation that found an unreasonable risk of injury to human health through acute inhalation and dermal exposures under 63 conditions of use (COU). If the revisions to the Risk Calculation Memo are finalized as proposed, the Agency’s revised HCHO risk evaluation would remove unreasonable risk determinations for acute inhalation exposure to workers under the following COU:

• Oxidizing/reducing agents and processing aids (not otherwise listed);
• Lawn and garden products;
• Adhesives and sealant chemicals in wood product manufacturing, plastic material (including structural and fireworthy aerospace interiors), construction (including roofing materials), and paper manufacturing;
• Recycling; and
• Laboratory chemicals.

Formaldehyde TSCA Unreasonable Risk Determination and Scientific Peer Review

In December 2024, the U.S. EPA released the final risk evaluation under TSCA for HCHO titled “Unreasonable Risk Determination of the Risk Evaluation for Formaldehyde TSCA Risk Evaluation.” In the risk evaluation, the Agency determined that HCHO presents an unreasonable risk to injury of human health under 63 COU for formaldehyde‑containing products and articles subject to TSCA that include composite wood articles, plastics, paints, adhesives, and sealants.

When the Agency makes a determination of unreasonable risk for a particular chemical substance under TSCA, it evaluates risk-related factors, such as the endpoint under consideration, the reversibility of the effect, exposure-related considerations (e.g., duration, magnitude, frequency of exposure, population exposed), and the confidence in the information used to inform the hazard and exposure values. The December 2024 HCHO risk evaluation focused on sources involved in the manufacturing, processing, distribution in commerce, use, and disposal of HCHO using aggregated findings from a series of U.S. EPA assessments:

• HCHO Environmental Risk Assessment comprised of:
  • Environmental Exposure Assessment, and
  • Environmental Hazard Assessment
• HCHO Human Health Risk Assessment comprised of:
  • Integrated Risk Information System (IRIS) Assessment,
  • Human Health Hazard Assessment, and
  • Human Exposure Assessments for:
    • Occupational,
    • Consumer,
    • Indoor Air, and
    • Ambient Air.

Following the risk evaluation’s publication, two independent federal science advisory bodies, the Human Studies Review Board (HSRB) and the Scientific Advisory Committee on Chemicals (SACC), called into question whether the IRIS assessment complied with the TSCA requirement to use “best available science” and “weight of scientific evidence” with respect to interpretation to various studies, integration of evidence, and Mechanism/Mode of Action (MOA) analysis. Both the HSRB and SACC provided independent critiques of toxicology and epidemiology studies, hazards identified, uncertainty/extrapolation factors, and provided recommendations for alternative POD and hazard identification approaches. HSRB and SACC were critical of the Agency using observational studies in the draft IRIS toxicological assessment to derive a quantitative POD. Instead, the federal advisory bodies recommended the use of the acute sensory irritation studies performed in the clinical setting for deriving or providing qualitative support for a POD.

After review of the comments raised during the scientific peer review process, U.S. EPA is reconsidering the use of certain hazard values in the formaldehyde risk evaluation that did not consider a portal-of-entry threshold MOA for inhalation exposures or sensory irritation as the most sensitive endpoint that is protective of effects (including carcinogenic effects) for all exposure durations.

Proposed Revisions to the Risk Calculation Memo

Given the concerns raised by the HSRB and SACC on the Agency’s scientific interpretations of MOA, dose response, and health outcome information in the IRIS assessment, U.S. EPA’s Office of Chemical Safety and Pollution Prevention (OCSPP) revisited the use of the IRIS chronic reference concentration (RfC) and cancer inhalation unit risk (IUR) values for purposes of the Agency’s TSCA risk evaluation of HCHO. Based on evaluation of the best available science, and multiple independent peer review records, the Risk Calculation Memo no longer relies on the IRIS RfC or IUR values for HCHO risk estimates. The Risk Calculation Memo now includes updated risk estimates developed by the OCSPP for acute inhalation exposures based on controlled human exposure studies.

Proposed revisions to the Risk Calculation Memo do not change the U.S. EPA’s overall conclusion that HCHO presents unreasonable risk under numerous COU. Instead, the updates to the Risk Calculation Memo provide the rationale for an updated acute occupational exposure value (OEV) of 300 parts per billion (ppb) that utilizes an acute inhalation POD of 300 ppb for sensory irritation with an uncertainty factor of 1 (UF =1) for workers, consumers, and the general population. The updated OEV is intended to protect workers and occupational non-users against sensory irritation effects resulting from acute occupational exposures. The Agency also concludes that managing risks from acute sensory irritation endpoint will be protective against other health effects, including cancer; therefore, it is not necessary to prepare a separate quantitative cancer assessment.

60-Day Public Comment Period [12/3/2025 – 2/3/2026]

U.S. EPA is seeking comments on all aspects of the Risk Calculation Memo including additional information, specific to how formaldehyde is manufactured and used, which may inform the risk management of formaldehyde. The public comment period runs from December 3, 2025, through February 3, 2026. You can review the full docket and submit public comments at the links below:

• Federal Register Link: https://www.federalregister.gov/d/2025-21776
• Comments can be submitted in docket EPA-HQ-OPPT-2018-0438 at regulations.gov.

The docket includes the Risk Calculation Memo and redline versions of the Revised Draft Human Health Hazard Assessment, Revised Draft Human Health Risk Assessment, Revised Draft Executive Summary, and Revised Draft Unreasonable Risk Determination to show the impact of the revisions on the overall evaluation and its components, if the Risk Calculation Memo were finalized. The materials included in the docket provide the science and science policy basis for determining how the revised draft inhalation POD impacts the corresponding draft MOE estimates and the risk determination for HCHO under TSCA.

Because the Agency is not changing its conclusion that HCHO poses unreasonable risk of injury to human health, U.S. EPA must still initiate risk management regulation(s) for HCHO under Section 6(a) of TSCA that address all COU that significantly contribute to the unreasonable risk finding. The Risk Calculation Memo specifically states the updated acute OEV “may be used to support risk management efforts for formaldehyde under TSCA section 6(a), 15 U.S.C §2605.”

If the revisions to Risk Calculation Memo are finalized and considered in the revised HCHO risk evaluation as proposed, the five COU identified in the opening section of this article would not be subject to future TSCA Section 6(a) risk management requirements based on the acute OEV of 300 ppb. Instead, the five COU removed from the unreasonable risk determination would be subject to the existing Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) of 750 parts per billion (ppb) for an 8-hour time weighted average (TWA). Additionally, the risk estimate for the general population inhalation exposure COU was revised to a value below the Benchmark MOE of 1; therefore, the Agency determined there is no unreasonable risk from acute inhalation of HCHO via ambient air to the general population. Because no acute inhalation risk was identified (i.e., COU risk estimate > Benchmark MOE), U.S. EPA now concludes HCHO does not present a chronic or cancer inhalation risk to the general population.

ALL4 continues to track TSCA-related rulemaking impacting the chemical sector and beyond including recently released U.S. EPA TSCA risk evaluations for:

• 1,3-Butadiene [EPA Document# EPA-740-R-25-054]
• Butyl Benzyl Phthalate (BBP) [EPA Document# EPA-740-R-25-023]
• Dibutyl Phthalate (DBP) [EPA Document# EPA-740-R-25-031]
• Dicyclohexyl Phthalate (DCHP) [EPA Document# EPA-740-R-25-038]
• Diethylhexyl Phthalate (DEHP) [EPA Document# EPA-740-R-25-062]
• Diisobutyl Phthalate (DIBP) [EPA Document# EPA-740-R-25-027]

If you have any questions on how the Risk Memo or recently released TSCA risk evaluations could impact your organization, please contact Stewart McCollam at smccollam@all4inc.com.