EPA Releases Draft Revised TSCA Risk Determination for 1,4-Dioxane
Released July 25, 2023
Additional conditions of use and exposure pathways support unreasonable risks to human health
Today, the U.S. Environmental Protection Agency (EPA) released for public comment the draft revised TSCA 2023 Draft Revised Risk Determination for 1,4-Dioxane (pdf) . The draft revised risk determination evaluates 1,4-dioxane as a whole chemical substance to make one overall risk determination rather than evaluating each condition of use separately and making individual risk determinations. This draft risk determination incorporates the occupational and consumer exposures from EPA’s 2020 Final Risk Evaluation for 1,4-Dioxane (pdf) , as well as additional exposure pathways to the general public (including fenceline communities) and from 1,4-dioxane generated as a byproduct from the recently released 2023 2023 Draft Supplement to the 2020 Risk Evaluation for 1,4-Dioxane (pdf) . The draft revised risk determination released today presents a more complete picture of the unreasonable risk presented by 1,4-dioxane, and the Agency is specifically 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 such as the manufacture of other chemicals (e.g., adhesives, sealants) or as a processing aid or laboratory chemical. It is also produced as a byproduct in several manufacturing processes, resulting in its presence as a contaminant in commercial and consumer products like dish soaps and laundry detergents and its presence in surface water. Health effects of concern for 1,4-dioxane include risks of cancer and risks of adverse effects to the liver and nasal tissue.
EPA’s previously 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.
In the draft revised 2023 risk determination for 1,4-dioxane, EPA proposes some important changes to the 2020 risk determination. First, 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. Second, 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. Third, based on the 2023 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. Fourth, 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. Many conditions of use contribute to general population or fenceline communities’ exposures to 1,4-dioxane in surface water, including industrial releases from a range of conditions of use (including where 1,4-dioxane is produced as a byproduct).
Worker Risks:
EPA’s proposed changes to the risk 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.
- 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.
EPA understands that there could be occupational safety protections in place at some workplace locations, including PPE. However, not assuming use of PPE in its risk determination reflects EPA’s recognition that certain subpopulations of workers exist that may be highly exposed because:
- They are not covered by OSHA standards (e.g., self-employed individuals and public sector workers who are not covered by a state plan);
- Their employers are out of compliance with OSHA standards; or
- OSHA’s permissible exposure limit (PEL) for 1,4-dioxane was adopted in the 1970s and OSHA has described those early PELs as being “outdated and inadequate for ensuring protection of worker health.”
Consumer Risks:
In the 2020 Risk Evaluation, EPA evaluated risks to consumers from eight conditions of use and found that the use of the evaluated products did not present an unreasonable risk to consumers or bystanders. In the 2023 draft revised unreasonable risk determination, EPA does not propose to identify the consumer conditions of use as contributing to the unreasonable risk determination from 1,4-dioxane. However, EPA notes that the manufacture of those consumer products, and, in some cases, the commercial use of similar products, does contribute to the unreasonable risk determination, due to worker risks of cancer and non-cancer effects from inhalation and dermal exposures and risk to fenceline communities from exposures to drinking water sourced from surface water contaminated with 1,4-dioxane discharged from industrial facilities.
General Population and Fenceline Community Risks:
In the 2023 Draft Supplement, EPA evaluated exposures via ingestion of drinking water sourced from surface water or groundwater contaminated with 1,4-dioxane from facility-specific releases, down-the-drain releases of consumer and commercial products that contain 1,4-dioxane as a byproduct, hydraulic fracturing releases, and leaching from landfills. EPA proposes to include the risks to the general population and fenceline communities from drinking water sourced from surface water contaminated with 1,4-dioxane that is discharged from industrial facilities (including where it is produced as a byproduct) as contributing to the unreasonable risk determination.
Before finalization of the risk determination, EPA is specifically seeking public comment on several aspects of the 2023 draft unreasonable risk determination, including 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.
Upon publication of the Federal Register notice, written comments on the draft revised risk determination will be accepted until September 8 through www.regulations.gov (Docket No. EPA-HQ-OPPT-2016-0723).