EPA Publishes Revised 1,4-Dioxane Determination


At the end of last month, the U.S. Environmental Protection Agency released a revised risk determination for 1,4-dioxane through the Toxic Substances Control Act, evaluating it as a whole chemical substance.

According to the release, the draft revised risk determination presents a “more complete picture” of the unreasonable risk presented by 1,4-dioxane. The agency is now seeking comment on several areas to inform the final risk determination. 

1,4-dioxane is a solvent used in a variety of commercial and industrial applications to manufacture other chemicals, including adhesives and sealants, as well as a processing aid or laboratory chemical. It can also be a byproduct in several manufacturing processes.

About the Changes

Previously, the EPA’s published risk determination found that 13 out of 24 conditions of use of 1,4-dioxane presented unreasonable risks to workers and occupationally exposed non-users as part of the 2020 Risk Evaluation.

Among the changes, the EPA has preliminarily determined that the better way to characterize the unreasonable risk from 1,4-dioxane is as a whole chemical, rather than condition-of-use-specific risk determinations.

Additionally, the EPA proposes that the risk determination should not assume, as the 2020 risk determination did, that workers always and appropriately wear personal protective equipment (PPE), even though some facilities might use PPE as one way to reduce workers’ exposure.

Based on this year’s Draft Supplement to the risk evaluation, several additional conditions of use would also contribute to the unreasonable risk determination due to worker inhalation and dermal risks from exposure to 1,4-dioxane as a byproduct, the agency explains.

Finally, the EPA proposes, based on its evaluation of air-related and drinking water-related risks to the general population and fenceline communities from 1,4-dioxane, that drinking water sourced from surface water contaminated with 1,4-dioxane contributes to the unreasonable risk from 1,4-dioxane.

The proposed changes to the determination include:

  • Two additional conditions of use in addition to the original 13 conditions of use from the 2020 Risk Evaluation would contribute to the unreasonable risk from 1,4-dioxane;
  • Several additional conditions of use from the 2023 Draft Supplement, which were not assessed in 2020, would also contribute to the unreasonable risk due to worker inhalation and dermal risks; and
  • Overall, based on the revised risk determination, EPA’s preliminary findings include that worker exposure to 1,4-dioxane from all but four occupational conditions of use contribute to the unreasonable risk from 1,4-dioxane. 

However, the agency notes that it understands that there could be occupational safety protections in place at some workplace locations, including personal protective equipment.

Before finalization of the risk determination, the EPA is specifically seeking public comment on several aspects of the 2023 draft unreasonable risk determination, including the EPA’s finding that general population exposure to 1,4-dioxane in drinking water contributes to the determination that 1,4-dioxane presents an unreasonable risk, and whether the risks to the general population from drinking water exposure can be attributed to specific conditions of use of 1,4-dioxane.

Written comments on the draft revised risk determination will be accepted through Sept. 8 upon publication in the Federal Register.

TSCA Regulation Amendments

In May, the EPA released proposed amendments to the review of new chemicals under the Toxic Substances Control Act. The updated regulations would reportedly improve efficiency, as well as align with the 2016 TSCA amendments under the Frank R. Lautenberg Chemical Safety for the 21st Century Act. 

According to the release, the latest proposal eliminates eligibility for exemptions from the full safety review process for new per- and polyfluoroalkyl substances (PFAS) and other persistent, bioaccumulative and toxic (PBT) chemicals.

Additionally, the reforms are anticipated to advance the EPA’s PFAS Roadmap, which outlines actions over the next three years, including steps to control PFAS at its sources, hold polluters accountable, ensure science-based decision making and address the impacts on disadvantaged and disproportionately impacted communities.

The proposed amendments the following provisions:

  • Align federal regulations with existing law;
  • Eliminate certain exemptions for PFAS and PBTs; and
  • Improve the efficiency of EPA’s review of new chemical submissions to foster innovation.

Previous TSCA Updates

In March last year, the EPA announced a new research program under the TSCA with the goal of modernizing the process and bringing innovative science to the review of new chemicals before they enter the market.

According to the EPA, the OCSPP is proposing the development and implementation of a multi-year collaborative research program in partnership with the Agency’s Office of Research and Development (ORD) and other federal entities focused on approaches for performing risk assessments on new chemical substances under TSCA.

Through the partnership, the program aims to bring innovative science to new chemical reviews, modernize the approaches used and increase the transparency of the human health and ecological risk assessment process.

The multi-year research program will refine existing approaches and develop and implement new approach methodologies (NAMs) to ensure the best available science is used in TSCA new chemical evaluations.

Recent chemicals impacted by the TSCA regulations included trichloroethylene (TCE)perchloroethylene (PCE)formaldehyde in composite wood products and methylene chloride.


Tagged categories: Adhesive; Coating Materials - Commercial; Construction chemicals; Environmental Protection; Environmental Protection Agency (EPA); EPA; Good Technical Practice; Government; Health and safety; NA; North America; Program/Project Management; Regulations; Solvents

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