EPA Supplemental TSCA Analysis Spurs Renewed Discussion over 1,4-Dioxane Regulation

December 08, 2020

The EPA’s supplemental analysis includes certain consumer exposures, as well as surface/ambient water exposures, to 1,4-dioxane.

The US Environmental Protection Agency (EPA) released an expanded risk evaluation for 1,4-dioxane under the Toxic Substances Control Act (TSCA) on November 19, 2020 (the Supplemental Analysis). In its original draft risk evaluation, released in June 2019, EPA preliminarily found unreasonable risks in certain circumstances for workers, but no unreasonable risks to the environment or occupational nonusers. The Supplemental Analysis expands the scope of the review to include certain consumer exposures, as well as surface/ambient water exposures. EPA initiated its Supplemental Analysis following public comments and peer review feedback to the initial draft risk evaluation.

1,4-dioxane is one of the first 10 chemicals evaluated by EPA pursuant to the 2016 amendments to the TSCA[1] (which directed EPA to select the first 10 chemicals for evaluation from the 2014 update of the TSCA Work Plan). EPA is supposed to finalize all of the first 10 risk evaluations by the end of 2020, but so far it does not appear to be on track to meet this deadline.

1,4-dioxane is classified by EPA as a likely human carcinogen that is often used as a stabilizer in greases, waxes, paint strippers, antifreeze, and chlorinated solvents. It is also used in some consumer products, such as deodorant, cosmetics, and shampoo, where it typically results as a byproduct from ethoxylation, a process used to make the products less harsh to consumers.

Industry groups had advocated for the expansion to the risk evaluation in the hopes of preempting state rules that are set to come into effect, including most notably rules in California and New York. New York, for example, recently amended its environmental conservation law to place maximum allowable concentrations of 1,4-dioxane in cosmetics, personal care, and household cleaning products. Under the New York legislation, household cleaning products and personal care products will be subject to a limit of 1,4-dioxane of 2 parts per million (ppm) starting on December 31, 2022, and 1 ppm starting December 31, 2023, and cosmetic products will be subject to a maximum concentration of 10 ppm starting on December 31, 2022. If EPA issues a final decision that the chemicals present no unreasonable risk, states would be preempted under the TSCA from regulating 1,4-dioxane under the conditions of use the agency evaluated.

In its Supplemental Analysis, EPA found that the presence of 1,4-dioxane as a byproduct in certain consumer products does not pose an unreasonable risk subject to TSCA regulations. The consumer products analyzed were surface cleaners, antifreeze, dish soap, dishwater detergent, laundry detergent, paint and floor lacquer, textile dye, and spray polyurethane foam.

The Supplemental Analysis also considered recreational activities in ambient/surface water, and also made a no-risk finding for those uses. Notably, the Supplemental Analysis did not evaluate exposures to 1,4-dioxane in drinking water, which was separately reviewed by EPA as part of the Safe Drinking Water Act (SDWA) UCMR3 earlier this year, and was not advanced by EPA at that time for a preliminary determination. EPA has not promulgated a maximum contaminant level (MCL) for 1,4-dioxane in drinking water, and declined to do so in March 2020. The contaminant is currently on the EPA’s fourth contaminant candidate list (CCL).

The Supplemental Analysis drew immediate criticism from environmentalists as a result of its 20-day comment period, which is unprecedented under the TSCA for its brevity. Environmental groups pressed EPA to grant a public comment extension, as well as additional peer review by the Science Advisory Committee on Chemicals.

EPA’s choice to review ambient/surface water levels has also been the subject of recent criticism by the Association of Metropolitan Water Agencies (AMWA), which, in a November 30 letter to EPA, questioned why EPA has deferred to the SDWA findings but seeks to evaluate surface/ambient water exposures under the TSCA and not the Clean Water Act. And in its November 24 letter to EPA, the Association of State Drinking Water Administrators (ASDWA) also argued for additional time (seeking a 40-day extension) to review and comment on the Supplemental Analysis, particularly in light of the increased number of coronavirus (COVID-19) cases and the timing of the comment period over the Thanksgiving holiday.

As of the date of this writing, EPA has not extended the comment period, which is currently set to expire on December 10, 2020.


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Ella Foley Gannon

Washington, DC
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Glen Stuart 

[1] 2016 Frank R. Lautenberg Chemical Safety Act for the 21st Century Act amendments to federal Toxic Substances Control Act.