Richard Denison, Ph.D., is a Lead Senior Scientist.

On Friday, the Environmental Defense Fund (EDF) filed extensive comments on a draft risk evaluation for the likely human carcinogen 1,4-dioxane EPA issued on July 1.  While the formal public comment period runs until August 30, Friday was the deadline EPA set for comments if submitters want them to be considered by the Scientific Advisory Committee on Chemicals (SACC), which will be conducting peer review of the draft risk evaluations for this chemical and another, the flame retardant hexabromocyclododecane (HBCD), next week.

In its draft risk evaluation for 1,4-dioxane, the Environmental Protection Agency (EPA) has grossly understated the risks that workers and the environment face from exposure to the chemical.  EPA has also abdicated its responsibility under the Toxic Substances Control Act (TSCA) to identify and evaluate the risks the chemical presents to consumers and the general population by excluding from its risk evaluation conditions of use and exposures that are known or reasonably foreseen.  EPA has not met its mandatory duty under TSCA to identify and evaluate the risks to vulnerable subpopulations, falsely asserting there is no evidence that certain subpopulations are or may be more susceptible to adverse effects from exposure to the chemical.  EPA has utterly failed to utilize the enhanced authorities Congress granted it in 2016 to ensure that it has or obtains robust information on 1,4-dioxane’s uses, hazards and exposures, resulting in serious information and analytic gaps and deficiencies that severely undermine the scientific quality of its risk evaluation.

EDF’s comments raised numerous major concerns with EPA’s draft.  Among them are the following (see the noted section of the full comments for the details):

• EPA has ignored evidence that some subpopulations are or may be more susceptible to 1,4-dioxane exposures than the general population (see section 1.A).
• EPA has distorted OSHA requirements and over-relied on personal protective equipment, ignoring its real-world limitations (see section 1.B).
• EPA has, without scientific basis, sought to sow doubt on the use of a linear, non-threshold model for 1,4-dioxane’s carcinogenicity, an approach that reflects longstanding agency policy and consensus in the scientific community (see section 1.D).
• EPA has dismissed the liver tumors observed in female mice in the key oral cancer study it uses to extrapolate dermal cancer risks. Its insufficient rationale ignores the IRIS program’s basis for including these tumors and its determination that they are the most sensitive endpoint, which has been affirmed through peer review.  As a result, cancer risk is significantly understated, a concern also noted by the New Jersey Department of Environmental Protection. (See section 1.E.ii.)
• EPA has excluded all exposures and risks to consumers (and to workers from at least one use), based on 1,4-dioxane’s presence in such products as a byproduct rather than being intentionally used, a distinction without any basis in science (see section 2.A).
• EPA has excluded from its risk evaluation all general population exposures to 1,4 dioxane, based on EPA’s unsupported assertion that existing regulatory programs under other statutes EPA administers have addressed or are in the process of addressing potential risks of 1,4-dioxane in all media pathways (see section 2.B).
• In several instances, EPA’s decisions are inconsistent with Agency guidelines (see section 4.B.i).
• EPA fails to consider combined exposures to workers from different routes and sources (see section 4.B.ii).
• EPA has significantly understated the extent of risks to workers it has identified (see section 5).
• EPA’s “expectation” of compliance with existing laws and standards as a basis for not finding unreasonable risk is unwarranted (see section 6.A).
• EPA finds no unreasonable risk even when the high-end risk exceeds relevant benchmarks, an approach that is not adequately protective (see section 6.B).
• EPA’s allowance of a 1 in 10,000 cancer risk for workers is a major and unwarranted deviation from longstanding agency policy and practice to regulate upon finding cancer risks on the order of 1 in 1 million (see section 6.C).
• EPA’s systematic review to support the risk evaluation is flawed and not reflective of best practices (see section 7).