EPA Finalizes Solvent 1,4-Dioxane TSCA Risk Evaluation

Released November 13, 2024

Today, the U.S. Environmental Protection Agency (EPA) released its final supplement to the risk evaluation and final risk determination for the solvent 1,4-dioxane under the Toxic Substances Control Act (TSCA). EPA has determined that this chemical poses an unreasonable risk of injury to human health. 1,4-Dioxane has the potential to cause cancer and harm the liver and nasal tissue.

Although 1,4-dioxane was one of the first ten chemicals to be reviewed under amended TSCA, EPA’s 2020 risk evaluation did not evaluate general population exposures to 1,4-dioxane in drinking water or air, did not evaluate all the ways people could be exposed to 1,4-dioxane as a byproduct, did not evaluate the potential for simultaneous exposure to more than one source of 1,4-dioxane (aggregate risk) and did not evaluate potential exposures to fenceline communities. These omissions led several Scientific Advisory Committee on Chemicals members to say that EPA’s “failure to assess 1,4-dioxane exposure in the general population may leave substantial portions of the population at risk. This is particularly concerning for drinking water.” The final supplement to the 1,4-dioxane risk evaluation addresses these concerns and provides the public with a more complete understanding of the risks presented by 1,4-dioxane. 

Uses and Risks Associated with 1,4-Dioxane

1,4-Dioxane is a solvent used in a variety of commercial applications, such as in a laboratory, or in dish soap or laundry detergent used by cleaning services or laundromats, and industrial applications, such as the manufacture or processing of other chemicals (e.g., adhesives, sealants). It is also generated 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 which contribute to its presence in surface water when these products are washed down the drain.

People may be exposed to 1,4-dioxane at work or through consumer products. If industrial or commercial facilities release 1,4-dioxane into the air, people may breathe it in. Additionally, people may be exposed to 1,4-dioxane in water. Water can be contaminated with 1,4-dioxane through industrial or commercial sources, or when consumer and commercial products that contain 1,4-dioxane are washed down the drain or disposed of in landfills. 

EPA found that 1,4-dioxane presents unreasonable risk to workers and the general population, including fenceline communities. Ingesting or breathing 1,4-dioxane can cause cancer, liver toxicity, and adverse effects to nasal tissue. 

EPA found unreasonable risk based on both inhalation and dermal exposures to workers who handle 1,4-dioxane in manufacturing and industrial applications and from commercial products containing 1,4-dioxane as a byproduct. Twenty-two out of 26 industrial and commercial conditions of use of 1,4-dioxane significantly contribute to the unreasonable risk to workers.

EPA found unreasonable risk to the general population, including potentially exposed or susceptible subpopulations such as people living in communities near release sites (i.e., fenceline communities) and people who may be more susceptible to 1,4-dioxane due to age, underlying heath conditions, and other factors. These groups may be exposed to 1,4-dioxane in drinking water in areas where drinking water is sourced from smaller or slow-flowing streams and industrial discharges have contaminated the water with 1,4-dioxane, or large numbers of people living nearby have washed 1,4-dioxane in consumer products down the drain, or some combination of those circumstances. The sources of 1,4-dioxane in drinking water that contribute to unreasonable risk include industrial discharges of 1,4-dioxane resulting from manufacturing and processing of chemicals, including the production of detergents and plastics, and down-the-drain releases of commercial and consumer products that contain 1,4-dioxane as a contaminant, such as dish soap, dishwasher detergent, laundry detergent, surface cleaner, and paint and floor lacquer. 

1,4-Dioxane does not pose an unreasonable risk to the environment. 

Next Steps

EPA must begin risk management to address the unreasonable risk presented by 1,4-dixoane.  EPA will release a proposed rule under TSCA section 6 to protect people from the identified risks.

Additionally, TSCA section 9(b) requires EPA to coordinate TSCA actions with actions taken under other Agency authorities. EPA has begun to consider possible risk management options and has determined that, in addition to TSCA, regulatory actions under the Safe Drinking Water Act (SDWA) may be appropriate for 1,4-dioxane. EPA’s Office of Chemical Safety and Pollution Prevention (OCSPP) and Office of Water (OW) have agreed to coordinate actions to address the risks from 1,4-dioxane contamination in drinking water through both OCSPP actions under TSCA section 6(a) and OW consideration of remaining risk and appropriate action under SDWA. 

Read the final supplement to the risk evaluation.

Additional Information

Conditions of Use that Significantly Contribute to the Unreasonable Risk (based on the 2020 risk evaluation and 2024 supplement):

• Manufacture (including domestic manufacture and import)
• Processing (including repackaging, recycling, non-incorporative, as a reactant, and as a byproduct (including ethoxylation processing and polyethylene terephthalate (PET) manufacturing))
• Industrial/commercial use: Intermediate
• Industrial/commercial use: Processing aid
• Industrial/commercial use: Functional fluids (open and closed system): Metalworking fluid, cutting and tapping fluid, polyalkylene glycol fluid, hydraulic fluid
• Industrial/commercial use: Laboratory chemicals 
• Industrial/commercial use: Adhesives and sealants: Film cement 
• Industrial/commercial use: Other uses: Spray polyurethane foam 
• Industrial/commercial use: Other uses: Printing and printing compositions 
• Industrial/commercial use: Other uses: Dry film lubricant 
• Industrial/commercial use: Other uses: Hydraulic fracturing 
• Industrial/commercial use: Arts, crafts, and hobby materials: Textile dye 
• Industrial/commercial use: Cleaning and furniture care products: Surface cleaner 
• Industrial/commercial use: Laundry and dishwashing products: Dish soap 
• Industrial/commercial use: Laundry and dishwashing products: Dishwasher detergent 
• Industrial/commercial use: Laundry and dishwashing products: Laundry detergent 
• Industrial/commercial use: Paints and coatings: Paint and floor lacquer 
• Consumer use: Cleaning and furniture care products: Surface cleaner 
• Consumer use: Laundry and dishwashing products: Dish soap 
• Consumer use: Laundry and dishwashing products: Dishwasher detergent  
• Consumer use: Laundry and dishwashing products: Laundry detergent 
• Consumer use: Paints and coatings: Paint and floor lacquer 
• Disposal

Conditions of Use that Do Not Significantly Contribute to the Unreasonable Risk

• Distribution in commerce 
• Commercial use of automobile antifreeze 
• Consumer use of textile dyes 
• Consumer use of automobile antifreeze 
• Consumer use of spray polyurethane foam