ACC and 1,4-dioxane: Its “late hit” tactics are just more of the same

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

The American Chemistry Council (ACC) was up to all of its old tricks yesterday at the first day of the Environmental Protection Agency’s (EPA) panel that is conducting a peer review of EPA’s draft risk evaluation of the likely human carcinogen, 1,4-dioxane.  We blogged last week about the extensive comments EDF submitted to the peer review panel on this flawed assessment.

Yesterday ACC rolled out the same game plan the industry has used for years to slow down, derail, or obfuscate chemical assessments conducted by EPA’s Information Risk Information System (IRIS), and more recently, the last Administration’s effort, now aborted by the Trump EPA, to restrict high-risk uses of the highly toxic chemical trichloroethylene (TCE).

In the public comment period yesterday afternoon, ACC Senior Director Steve Risotto revealed to the peer review panel that ACC has sponsored a new “study” that he says – lo and behold – supports all of the positions downplaying 1,4-dioxane’s carcinogenicity that ACC has espoused for years.

The aim of this is to get EPA to set the level of exposure to 1,4-dioxane that would be deemed acceptable well above the level EPA would set if 1,4-dioxane is assumed to pose a risk at any level of exposure.  (Briefly, if EPA determines that 1,4-dioxane does not have a safe threshold, it must extrapolate exposures to zero to set acceptable risk levels in its risk evaluation. If, as ACC wants, EPA finds that there is a threshold below which exposure poses no risk, then the Agency’s risk calculations will be much less conservative.)

So, where is ACC’s new study?  Well, it’s not public.  It hasn’t been provided to the peer review panel.  It hasn’t been published by ACC.  There’s no indication it’s been peer-reviewed. 

Almost as an aside, Risotto mentioned yesterday that ACC had done a webinar for EPA staff on the study, walking them through a Powerpoint presentation.  Yet neither the webpages nor the dockets for the 1,4-dioxane draft risk evaluation or this peer review panel makes any mention of this meeting between ACC and EPA or provides the Powerpoint or any other materials provided at that meeting.  EPA makes no mention of this study in its draft risk evaluation.

In comments posted last week to the docket, ACC has stated “the results of this recently completed study will be provided to EPA as part of ACC’s supplemental comments.”

This tactic of “late hits” is classic ACC:  Step 1: Claim industry has a new study that answers all questions and that it will be available shortly.  Step 2: Describe the conclusions in settings that provide no ability for the public or peer reviewers to independently assess what is being said.  Step 3: Then (maybe) provide the study at a time too late for others to comment on or thoroughly evaluate.

ACC’s “new study” seeks to find support for its claim that 1,4-dioxane has a “safe threshold” below which there is no risk of cancer.  ACC has been on this tack for a long time.  It and other industry commenters yesterday repeatedly cited industry-funded work done by Dr. Michael Dourson that has pushed this notion.

The arguments in Dourson’s 2014 and 2017 papers, both published in the chemical industry’s go-to journal, Regulatory Toxicology and Pharmacology, have been roundly rejected by a number of state agencies and thoroughly rebutted by scientists at the New Jersey Department of Environmental Protection, who argue that EPA and other regulators should continue to rely on a no-safe-threshold approach to 1,4-dioxane’s carcinogenicity.  See NJDEP’s rebuttals on pp. 11-17 here (2014) and pp. 79-88 here (2018).

One other note of irony must be added here.  As we blogged about back in 2017, it is this very same Steve Risotto of ACC who worked hand-in-hand, if clandestinely, with Dourson in his earlier efforts to convince certain states to press EPA to weaken health standards for chemicals such as TCE and – you guessed it – 1,4-dioxane.



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  1. Posted August 1, 2019 at 8:06 am | Permalink

    Dear Dr. Dennison

    I appreciate reference to my two publications on dioxane.* They were developed with help or endorsement from colleagues of 7 different governments, 3 consulting firms, 1 university and 2 industries over a period of 4 years. The second publication was done under the auspices of the Alliance for Risk Assessment (ARA) shepherded by a Steering Group of government, university and NGO members. This work is now being cited by Health Canada to support its assessment of dioxin’s cancer findings using a threshold approach, which the new findings clearly show for liver tumors. I expect that this research will assist EPA and others in their deliberations on the re-assessment of this chemical, which otherwise is two ethanol molecules joined together in a ring.

    As an aside, I was surprised at your reference to Regulatory Toxicology and Pharmacology as an industry “go to” journal. I have published in this journal extensively, as have many of my government colleagues, since it is unique in its focus on risk assessment manuscripts. For example, my two most cited papers, with about 500 citations each, were written when I was an EPA employee. These papers are still being cited today.


    Michael Dourson

    * Dourson, M; Reichard, J; Nance, P; Burleigh-Flayer, H; Parker, A; Vincent, M; McConnell, EE; (2014). Mode of Action Analysis for Liver Tumors from Oral 1,4-Dioxane Exposures and Evidence-Based Dose Response Assessment. Reg. Toxicol. Pharmacol. Volume 68, Issue 3, April 2014, Pages 387–401

    Michael L. Dourson, Jeri Higginbotham, Jeff Crum, Heather Burleigh-Flayer, Patricia Nance, Norman D. Forsberg, Mark Lafranconi, John Reichard. 2017. Update: Mode of action (MOA) for liver tumors induced by oral exposure to 1,4-dioxane. Regulatory Toxicology and Pharmacology 88:45-55.

    • Posted August 5, 2019 at 10:51 am | Permalink

      Dear readers:

      I’m afraid Dr. Dourson is up to his same old tricks again. Recall that he was forced to withdraw his nomination to head EPA’s toxic office after the extent of his conflicts of interest and efforts to mask them were brought to light.

      Despite his assertions about the authorship and sources of support for his 2014 and 2017 papers on 1,4-dioxane, the papers themselves show they were co-written mainly by Dourson and colleagues at his consulting firm, TERA, and other industry consulting firms, as well as by PPG Industries, which has a major financial stake in the outcome of risk assessments of the chemical. See the authors’ affiliations for yourself here and here. (Note that for a brief time during and around 2017, TERA was housed at the University of Cincinnati.)

      The work reported on in the papers was bankrolled by PPG and, for the second paper, also Waste Management, Inc. See the conflict of interest statement and acknowledgments following the text of the papers at the links above.

      As to Dourson’s statement about the high frequency of his publishing his work in the industry-favoring journal, Regulatory Toxicology and Pharmacology: My point exactly. In fact, I blogged about that very thing here. Regulatory Toxicology and Pharmacology has a longstanding reputation of being the go-to journal for both tobacco and chemical industry-friendly paper publishing. See these blog posts here and here for more detail.