On November 13, 2024, the Environmental Protection Agency (EPA) released its revised Unreasonable Risk Determination and the final Supplement to the Risk Evaluation for 1,4- dioxane. The updates incorporated additional exposure pathways for the general public and from 1,4-dioxane generated as a byproduct.
The EPA has determined that this chemical poses an unreasonable risk of injury to human health for both workers and the general population. The risk evaluation concluded that 1,4-dioxane can cause cancer, liver toxicity, and adverse effects on nasal tissue.
1,4-Dioxane is used primarily as a solvent in a variety of industrial and commercial applications, including chemical manufacturing and processing as well as laboratory use. As a byproduct of various manufacturing processes, 1,4 -dioxane may be found as an unintentional contaminant in consumer products, such as dish soaps and laundry detergents.
The EPA found that of the 26 industrial and commercial conditions of use evaluated, 22 “significantly contribute to the unreasonable risk to workers.” They include those listed below.
- Manufacturing (including domestic manufacture and import)
- Processing (such as repackaging, recycling, and as a byproduct and reactant)
- Applications in adhesives, sealants, paints and coatings, and cleaning products
- Laboratory use as a solvent
The complete list of conditions of use can be found in EPA’s November 13, 2024 notice.
In the workplace, the EPA determined that there was an unreasonable risk based on both inhalation and dermal contact for employees that handle 1,4-dioxane or are otherwise exposed. EPA also found an unreasonable risk to the general population, primarily from ingestion of 1,4-dioxane in contaminated drinking water.
Under the Toxic Substances Control Act (TSCA), Section 6(a), the EPA is required to take action to address chemicals that pose an unreasonable risk to human health or the environment. They are currently beginning the risk management process to address the unreasonable risk posed by 1,4-dioxane. Under TSCA, the EPA must release a proposed rule for public comment no later than one year after the date on which the final risk evaluation is published (November 2025). A final rule is required no later than two years after the publication date of the risk evaluation (November 2026).
There are various possible restrictions on 1,4 dioxane use that the EPA might consider in their proposed rule including those listed below.
- Prohibit or otherwise restrict, or limit the manufacture, processing, or distribution in the marketplace
- Require adequate minimum warnings and instructions with respect to its use, distribution in commerce, or disposal
- Require recordkeeping, monitoring, or testing by manufacturers and processors
- Prohibit or regulate the manner or method of commercial use
One potential outcome of the rulemaking is that 1,4-dioxane may be banned from many applications but for certain “highly industrialized” purposes such as laboratory use, the chemical wouldn’t be banned but rather the EPA could impose a requirement for a Workplace Chemical Protection Program (WCPP) or the equivalent. This was the outcome of the EPA’s Risk Management Rule for methylene chloride as we discussed in a recent blog, EPA Finalizes Ban on Methylene Chloride. However, it’s too soon to know if this is the direction the EPA will be going in for 1,4-dioxane.
There will be opportunities for public comment and stakeholder engagement as the EPA works on the proposed and final versions of the 1,4-Dioxane Risk Management Rule. For additional information on the recently published Unreasonable Risk Determination and the final Supplement to the Risk Evaluation on 1,4-dioxane, please contact us.
This blog was written by Beth Graham, Safety Partners’ Director of Quality, Research, and Training
