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January 13, 2021

Final Risk Evaluation for 1,4-Dioxane Finds Unreasonable Risk to Workers for Certain Uses

The ACTA Group

On January 8, 2021, the U.S. Environmental Protection Agency (EPA) released the final risk evaluation for 1,4-dioxane. 86 Fed. Reg. 1495. The final risk evaluation identifies unreasonable risk to workers for 13 out of 24 conditions of use. EPA states that it found no unreasonable risk to the general population and the environment. EPA notes that it also published a supplemental analysis to the draft risk evaluation that evaluated eight additional conditions of use for 1,4-dioxane present as a byproduct in consumer products. According to EPA, after “carefully considering” public comments on the supplemental analysis, it found no unreasonable risk for these consumer uses.

EPA’s next step in the process required by the Toxic Substances Control Act (TSCA) is to develop a plan to reduce or eliminate the unreasonable risks found in the final risk evaluation. EPA states that it “is now moving immediately to risk management for 1,4-dioxane.” The potential actions that EPA could take to address these risks include regulating how 1,4-dioxane is used or limiting or prohibiting the manufacture, processing, distribution in the marketplace, use, or disposal of 1,4-dioxane, as applicable.


TSCA Section 6, as amended by the Frank R. Lautenberg Chemical Safety for the 21st Century Act (Lautenberg Act), requires EPA to conduct risk evaluations to “determine whether a chemical substance presents an unreasonable risk of injury to health or the environment, without consideration of costs or other nonrisk factors, including an unreasonable risk to a potentially exposed or susceptible subpopulation identified as relevant to the risk evaluation by the Administrator, under the conditions of use.” The statute identifies the minimum components EPA must include in all risk evaluations. For each risk evaluation, EPA must publish a document that outlines the scope of the risk evaluation to be conducted, which includes the hazards, exposures, conditions of use, and the potentially exposed or susceptible subpopulations that EPA expects to consider. Each risk evaluation must also: (1) integrate and assess available information on hazards and exposure for the conditions of use of the chemical substance, including information on specific risks of injury to health or the environment and information on relevant potentially exposed or susceptible subpopulations; (2) describe whether aggregate or sentinel exposures were considered and the basis for that consideration; (3) take into account, where relevant, the likely duration, intensity, frequency, and number of exposures under the conditions of use; and (4) describe the weight of the scientific evidence for the identified hazards and exposure. The risk evaluation must not consider costs or other nonrisk factors. A detailed summary and analysis of the final risk evaluation rule is available in our June 26, 2017, memorandum, “EPA Issues Final TSCA Framework Rules.”

Risk Evaluation for 1,4-Dioxane

EPA evaluated the following conditions of use: manufacturing; processing; industrial and commercial use in functional fluids in open and closed systems, laboratory chemicals, adhesives and sealants (professional film cement), spray polyurethane foam, printing and printing compositions, and dry film lubricant; consumer use in arts, crafts, and hobby materials (textile dye), automotive care products (antifreeze), cleaning and furniture care products (surface cleaner), laundry and dishwashing products (dish soap, dishwasher detergent, laundry detergent), paints and coatings (paint and floor lacquer), and other uses (spray polyurethane foam); and disposal of waste materials containing 1,4-dioxane. The final risk evaluation states that EPA has exercised its authority in TSCA Section 6(b)(4)(D) to exclude from the scope of the risk evaluation conditions of use associated with 1,4-dioxane generated as a byproduct in manufacturing, industrial, and commercial uses. EPA notes that while use of 1,4-dioxane as a process solvent and as an intermediate in the manufacture of pharmaceuticals was included in the problem formulation and draft risk evaluation, upon further analysis of the details of these processes, EPA determined that these uses fall outside TSCA’s definition of “chemical substance.” Under TSCA Section 3(2)(B)(vi), the definition of “chemical substance” does not include any food, food additive, drug, cosmetic, or device (as such terms are defined in section 201 of the Federal Food, Drug, and Cosmetic Act) when manufactured, processed, or distributed in commerce for use as a food, food additive, drug, cosmetic, or device. According to the final risk evaluation, EPA concluded that 1,4-dioxane use as a process solvent and an intermediate during pharmaceutical manufacturing falls outside TSCA’s definition of a chemical substance when used for these purposes. As a result, the use of 1,4-dioxane as a process solvent and an intermediate during pharmaceutical manufacturing are not included in the scope of this risk evaluation.

The final risk evaluation notes that EPA did not identify any “legacy uses” (i.e., circumstances associated with activities that do not reflect ongoing or prospective manufacturing, processing, or distribution) or “associated disposal” (i.e., future disposal from legacy uses) of 1,4-dioxane. Therefore, EPA did not add any such uses or disposals to the scope of the risk evaluation for 1,4-dioxane following the issuance of the opinion in Safer Chemicals, Healthy Families v. EPA. The final risk evaluation states that EPA did not evaluate “legacy disposal” (i.e., disposals that have already occurred) in the risk evaluation “because legacy disposal is not a ‘condition of use’ under Safer Chemicals.”

EPA made the following risk evaluation findings. EPA stated that in making these unreasonable risk determinations, it considered the hazards and exposure, magnitude of risk, exposed population, severity of the hazard, uncertainties, and other factors.

  • EPA found no unreasonable risks to the environment from any conditions of use. EPA assessed the impact of 1,4-dioxane on aquatic vertebrates and invertebrates, and aquatic plants, in surface waters. After reviewing these data, EPA found no unreasonable risk to the environment;
  • EPA found no unreasonable risks to consumers or bystanders from any conditions of use. EPA did not identify any direct consumer uses of this chemical. EPA notes that 1,4-dioxane may be found as an impurity in consumer products such as soaps and detergents when 1,4-dioxane is created as a byproduct during the manufacture of other chemicals that are used to make certain consumer products, however. After reviewing eight consumer uses of surface cleaners, laundry/dishwashing detergents, and paint/floor lacquer where 1,4-dioxane is present as an impurity, EPA found no unreasonable risks;
  • EPA found no unreasonable risks to the general population. EPA assessed exposure to the general population from 1,4-dioxane in surface water and found no unreasonable risks; and
  • EPA found unreasonable risks to workers from 13 conditions of use of 1,4-dioxane and unreasonable risks to ONUs from most industrial and commercial uses of 1,4-dioxane. EPA found unreasonable risks to workers from 13 commercial uses of 1,4-dioxane in the following categories: manufacture; processing; industrial/commercial use; and disposal. Additionally, EPA found unreasonable risks from most commercial uses of 1,4-dioxane to ONUs. According to EPA, common commercial uses include in the manufacture of other chemicals, as a processing aid, in laboratory chemicals, and in adhesives and sealants. Unreasonable risks to workers and ONUs can come from both short- and long-term inhalation and dermal exposure.


As EPA has now issued the final risk evaluation for 1,4-dioxane, risk management efforts will commence covering the conditions of use for which EPA found unreasonable risk. A final Section 6(a) regulation is required to be issued within three and one half years, including potentially available extensions. In addition, for the conditions of use that were determined not to present an unreasonable risk, these decisions, which EPA issued by order under Section 6(i)(1) of TSCA, represent final agency actions that are subject to legal challenge. Generally consistent with the other risk evaluations issued to date, EPA did not evaluate certain hazards or exposures to the general population and non-human species in the risk evaluation (e.g., from ambient air, drinking water, on-site release to land, and disposal pathways) where those exposures fall under the jurisdiction of other environmental statutes administered by EPA. As a result, the unreasonable risk determinations for the relevant conditions of use do not account for these exposures. Considering the legal challenges filed to date on the Section 6(i)(1) orders issued as part of the final risk evaluations on methylene chloride and the cyclic aliphatic bromide cluster (HBCD), legal challenges to the order may arise for the conditions of use that EPA determined do not present an unreasonable risk for reasons including EPA’s exclusion of certain exposure pathways.

Among the conditions of use, the most significant source of unreasonable risk is dermal exposure in industrial and commercial settings. EPA’s margins of exposure exceed cancer and non-cancer benchmarks without and, in a number of cases, with glove use. If unreasonable risks cannot be mitigated with highly protective gloves, the possible risk management options narrow significantly.

One of the most significant changes from the draft risk evaluation is that EPA decided to include the impurity condition of use in its risk evaluation. 1,4-dioxane is a common impurity in products that contain surfactants, such as hard surface cleaners, detergents, and many other products, including personal care products (shampoo, body wash). 1,4-dioxane is formed during the manufacture of these surfactants and low levels remain in final products. EPA did not identify any unreasonable risks from consumer uses. This outcome will test the preemption provisions of TSCA as several states have taken action to limit the levels of 1,4-dioxane in consumer products. It remains to be seen if EPA’s no unreasonable risk in consumer products will lead to the preemption of any state action.

Under TSCA Section 6(b)(4), EPA has three years to complete a risk evaluation, extendable for an additional six months; the deadline for the issuance of the risk evaluations for the “first ten” chemicals selected for risk evaluation under Section 6(b)(2)(A), as extended by six months by EPA, was June 19, 2020. EPA has to date completed risk evaluations on eight of the “first ten” chemicals selected for risk evaluation under Section 6(b)(2)(A): methylene chloride, 1-bromopropane, HBCD, carbon tetrachloride, trichloroethylene, perchloroethylene, n-methyl pyrrolidone, and now, 1,4-dioxane. EPA has also completed part 1 of the risk evaluation on asbestos; it covers the chrysotile form of asbestos but does not cover legacy uses and associated disposal. Part 2 of the risk evaluation for asbestos will focus on legacy uses and associated disposals (i.e., conditions of use for which manufacture (including import), processing, and distribution in commerce no longer occur, but where use and disposal are still known, intended, or reasonably foreseen to occur (e.g., asbestos in older buildings)) of chrysotile as well as other asbestos fiber types. Additionally, the final risk evaluation for Colour Index (C.I.) Pigment Violet 29 is currently under development.