The U.S. Environmental Protection Agency (EPA) announced on June 14, 2023, that it is accepting public comments on candidates under consideration for selection as ad hoc reviewers to assist the Science Advisory Committee on Chemicals (SACC) with its review of the 2023 draft supplement to the 1,4-dioxane risk evaluation under the Toxic Substances Control Act (TSCA). EPA states that after it published the final risk evaluation for 1,4-dioxane in December 2020, it determined a supplement was needed to consider critical exposure pathways not previously assessed.

According to EPA, the supplement includes evaluation of additional conditions of use in which 1,4-dioxane is present as a byproduct in industrial processes and commercial products, and it evaluates risks from general population exposures to 1,4-dioxane released to ambient surface water and groundwater, ambient air, and land. EPA notes that to evaluate these additional exposure pathways, it used new methods and novel applications of existing methods. EPA seeks review of these new methods because they have not been the subject of public comment or peer review for applications in TSCA risk evaluations. EPA will consider feedback from this review in the development of the final supplement to the 1,4-dioxane risk evaluation. EPA plans to release the risk evaluation documents for public comment by the end of June 2023. Comments on the candidates are due June 29, 2023. If selected, candidates will serve as peer reviewers for the draft supplement, which SACC plans to review at a four-day virtual public meeting September 12-15, 2023. EPA will post registration instructions for the meeting on the SACC website in mid-August 2023.