Skip to main content

EPA Releases Draft Risk Evaluations for Two More of the "First Ten Chemicals" - 1,4 Dioxane and Cyclic Aliphatic Bromide Cluster (HBCD)

On July 1, 2019, the U.S. Environmental Protection Agency (EPA) released draft risk evaluations for 1,4-Dioxane and a cluster of Cyclic Aliphatic Bromide flame retardants, including Hexabromocyclododecane (collectively, HBCD).  The draft risk evaluations and associated support documents are open for public comment for 60 days (until August 30, 2019) and will undergo peer review by EPA’s Science Advisory Committee on Chemicals (SACC) beginning July 29, 2019.  Click here to read the Federal Register notice. 


Section 6 of the Toxic Substances Control Act (TSCA), as amended by the 2016 Frank R. Lautenberg Chemical Safety for the 21st Century Act (LCSA), requires EPA to prioritize and perform risk evaluations on existing chemicals to determine whether the chemicals pose an “unreasonable risk” of injury to human health or the environment.  EPA commenced its first ten risk evaluations in December 2016 and must complete each of them by December 2019.   The ten substances (or groups) currently under review are:

  • Asbestos
  • 1-Bromopropane
  • Carbon Tetrachloride
  • 1,4-Dioxane
  • the Cyclic Aliphatic Bromide Cluster
  • Methylene Chloride
  • N-Methylpyrrolidone
  • Perchloroethylene
  • Pigment Violet 29, and
  • Trichloroethylene

In June 2018, EPA published problem formulation documents and opened public dockets for these ten chemicals. To date, EPA has released only one other draft risk evaluation for substances in this group --  C.I. Pigment Violet 29, which has been heavily criticized.  EPA is expected to release draft risk evaluations for each of the remaining seven substances in the coming weeks.

Draft Risk Evaluations for HBCD and 1,4-Dioxane

The draft risk evaluations for HBCD and 1,4-Dioxane review the chemistry and physical and chemical properties of these substances, assess their environmental and human exposures and ecological and human health hazards, characterize the risks they present, and present EPA’s proposed determinations whether the risks they present to different relevant sectors are unreasonable and warrant regulation. 

1, 4-Dioxane

In the draft risk evaluation for 1,4 dioxane, for all conditions of use considered, EPA found no unreasonable risks to the environment and no unreasonable risks to occupational non-users . 

For domestic manufacturing, certain processing uses (processing as a reactant, non-incorporative use, recycling), certain industrial uses (intermediate use, use as a processing aid, laboratory chemicals, adhesives and sealants, printing and printing compositions) and disposal, EPA preliminarily determined that these uses present an unreasonable risk to workers. 

However, for import, repackaging, distribution and certain industrial uses (functional fluids in an open system, spray polyurethane foam compositions, dry film lubricant)  EPA initially determined that these uses do not present an unreasonable risk of injury to workers.  

For the industrial use of 1,4-dioxane as a functional fluid in a closed system, EPA determined that this use is “not a condition of use” due to lack of evidence supporting its use in closed system functional fluids.  Therefore, EPA did not assess occupational exposures for this use.

EPA explains that potential health effects of 1,4-dioxane exposure found in its literature review include “effects on the liver, kidneys, respiratory system, neurological endpoints, and cancer.” For domestic manufacture and processing (processing as a reactant, non-incorporative use, recycling), industrial use (as an intermediate, processing aid and laboratory chemicals) and disposal, EPA preliminarily found an unreasonable risk of cancer from chronic dermal occupational exposure and “noncancer portal of entry effects resulting from chronic inhalation occupational exposure.”  EPA preliminarily found cancer risks from chronic dermal occupational exposure for industrial uses in adhesives and sealants and in printing and printing compositions.  However, these assessments assumed PPE was not used.  When the protective effect of PPE was considered, EPA did not find the risks to be unreasonable.


In the draft risk evaluation for HBCD, EPA has preliminarily found no unreasonable risks under any conditions of use to the general population, consumers, exposed and non-exposed  workers, or to the environment.  EPA explains that there are no unreasonable risks for the uses evaluated for HBCD because “there is no evidence that domestic manufacturing or import of HBCD is occurring” in the United States.

Peer Review

The draft risk evaluations for HBCD and 1,4-Dioxane and associated support documents will undergo peer review by the TSCA SACC.  The peer review will include a 3-hour preparatory virtual meeting for the panel to consider the scope of the draft charge questions, and then a 5-day, in-person meeting of the SACC to consider the draft risk evaluations.  The meetings will be held as follows:

  • July 10, 2019: Preparatory virtual meeting.
  • July 29 - August 2, 2019:  In-person meeting.


Comments on the draft risk evaluations and underlying support documents are due by August 30, 2019.

Written comments for consideration during the TSCA SACC preparatory virtual meeting, or requests to make oral comments during the virtual meeting, are due by July 9, 2019. Written comments and requests to make oral comments during the TSCA SACC in-person meeting must be submitted by July 19, 2019.

For additional information regarding EPA’s draft risk evaluation for HBCD:

For additional information regarding EPA’s draft risk evaluation for 1,4-Dioxane:

For questions or assistance in preparing comments on the draft risk evaluations please contact us:

Herbert Estreicher, Ph.D.,
Thomas C. Berger,
James G. Votaw,