On November 20, 2020, the U.S. Environmental Protection Agency (EPA) issued a supplemental analysis to the draft risk evaluation of 1,4-dioxane under the Toxic Substances Control Act. The supplemental analysis was developed in response to public and peer review comments to the draft risk evaluation, which our blog previously reported on here.
The EPA’s risk evaluation states that 1,4-dioxane is a “likely human carcinogen” that is “highly mobile” and “does not readily biodegrade in the environment.” However, the draft risk evaluation notes “(n)o unreasonable risks to occupational non-users …” and “no unreasonable risk to the environment.” However, the EPA did acknowledge some danger of exposure to 1,4-dioxane, as it found “unreasonable risks to workers in certain circumstances.”
As a refresher, 1,4-dioxane is likely present at many sites contaminated with certain chlorinated solvents because of its widespread use as a stabilizer for those chemicals. The EPA says that 1,4-dioxane is used in “paint strippers, dyes, greases, varnishes and waxes,” as well as consumer products like shampoos, deodorants, cleaning detergents, and cosmetics. Other products that may use 1,4-dioxane include building materials like cement, roofing, siding, and insulation, and children’s toys. The EPA considers 1,4-dioxane “a likely human carcinogen” because there are studies that indicate that it may be toxic to the liver, kidney, and central nervous system. It also may be toxic to aquatic plants and invertebrates.
The EPA’s supplemental analysis concerned six separate categories of potential exposure; for each of those categories, the EPA found no unreasonable risk of injury to health for either consumers or bystanders. The categories studied were (1) arts, crafts and hobby materials (textile dye); (2) automotive care products (antifreeze); (3) cleaning and furniture care products (surface cleaner); (4) laundry and dishwashing products (dish soap, dishwasher detergent, laundry detergent); (5) paints and coatings (paint and floor lacquer); and (5) spray polyurethane foam. The EPA concluded that “the risk estimates, the health effects of 1,4-dioxane, the exposures, and consideration of uncertainties support EPA’s determination that there is no unreasonable risk of injury to health (consumers and bystanders) from the consumer use of 1,4-dioxane.”
The EPA also evaluated the human health risks of potential acute and chronic incidental exposures via oral and dermal routes from recreational swimming, determining that these risks are not unreasonable. In addition, because 1,4-dioxane has low bioaccumulation potential, the EPA determined that the human health risks from fish ingestion are not unreasonable.
The EPA did not assess exposures from ambient air, drinking water, and sediment pathways because they fall under the jurisdiction of other environmental statutes administered by EPA (i.e., CAA, SDWA, RCRA, and CERCLA). In particular, 1,4-dioxane does not currently have established water quality criteria to protect human health under the CWA Section 304(a).
The complete draft supplemental analysis can be found here.