EPA
EPA Document# EPA-740-R1-7003
June 2017
United States Office of Chemical Safety and
Environmental Protection Agency Pollution Prevention
Scope of the Risk Evaluation for
1,4-Dioxane
CASRN: 123-91-1
O
June 2017
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS 5
ABBREVIATIONS 6
EXECUTIVE SUMMARY 8
1 INTRODUCTION 11
1.1 Regulatory History 13
1.2 Assessment History 14
1.3 Data and Information Collection 15
2 SCOPE OF THE EVALUATION 18
2.1 Physical and Chemical Properties 18
2.2 Conditions of Use 19
2.2.1 Data and Information Sources 19
2.2.2 Identification of Conditions of Use 19
2.3 Exposures 26
2.3.1 Fate and Transport 26
2.3.2 Releases to the Environment 27
2.3.3 Presence in the Environment and Biota 29
2.3.4 Environmental Exposures 30
2.3.5 Human Exposures 30
2.3.5.1 Occupational Exposures 30
2.3.5.2 Consumer Exposures 31
2.3.5.3 General Population Exposures 31
2.3.5.4 Potentially Exposed or Susceptible Subpopulations 32
2.4 Hazards (Effects) 33
2.4.1 Environmental Hazards 33
2.4.2 Human Health Hazards 33
2.4.2.1 Non-Cancer Hazards 33
2.4.2.2 Genotoxicity and Cancer Hazards 34
2.4.2.3 Potentially Exposed or Susceptible Subpopulations 34
2.5 Initial Conceptual Models 35
2.5.1 Initial Conceptual Model for Industrial and Commercial Activities and Uses: Potential
Exposures and Hazards 35
2.5.2 Initial Conceptual Model for Consumer Activities and Uses: Potential Exposures and
Hazards 37
2.5.3 Initial Conceptual Model for Environmental Releases and Wastes: Potential Exposures and
Hazards 37
2.6 Initial Analysis Plan 39
2.6.1 Exposure 39
2.6.1.1 Environmental Releases 39
2.6.1.2 Environmental Fate 39
2.6.1.3 Environmental Exposures 40
2.6.1.4 Occupational Exposures 40
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2.6.1.5 Consumer Exposures 40
2.6.1.6 General Population 41
2.6.2 Hazards (Effects) 41
2.6.2.1 Environmental Hazards 41
2.6.2.2 Human Health Hazards 41
2.5.3 Risk Characterization 42
REFERENCES 43
APPENDICES 47
Appendix A REGULATORY HISTORY 47
A.l Federal Laws and Regulations[[[ 47
A.2 State Laws arid Regulations[[[ 53
A3 International Laws and Regulations[[[ 53
Appendix B PROCESS, RELEASE AND OCCUPATIONAL EXPOSURE INFORMATION 55
B.l Process Information............................ 55
B.l.l Manufacture (Including Import) 55
B.l.2 Processing and Distribution 56
B.l.2.1 Processing as a Reactant/lntermediate 56
B.l.2.2 Processing - Non-lncorporative 56
B.l.2.3 Repackaging 56
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LIST OF TABLES
Table 1-1. Assessment History of 1,4-Dioxane 14
Table 2-1. Physical and Chemical Properties of 1,4-Dioxane 18
Table 2-2. Production Volume of 1,4-Dioxane in Chemical Data Reporting (CDR) Reporting Period (2012
to 2015) 20
Table 2-3. Categories and Subcategories of Conditions of Use of 1,4-Dioxane 23
Table 2-4. Environmental Fate Characteristics of 1,4-Dioxane 26
Table 2-5. Summary of 1,4-Dioxane TRI Production-Related Waste Managed in 2015 (lbs) 28
Table 2-6. Summary of 1,4-Dioxane TRI Releases to the Environment in 2015 (lbs) 28
LIST OF FIGURES
Figure 2-1. Initial 1,4-Dioxane Life Cycle Diagram 22
Figure 2-2. Initial 1,4-Dioxane Conceptual Model for Industrial and Commercial Activities and Uses:
Potential Exposures and Hazards 36
Figure 2-3. Initial 1,4-Dioxane Conceptual Model for Environmental Releases and Wastes: Potential
Exposures and Hazards 38
LIST OF APPENDIX TABLES
Table_Apx A-l. Federal Laws and Regulations 47
Table_Apx A-2. State Laws and Regulations 53
Table_Apx A-3. Regulatory Actions by other Governments and Tribes 53
Table_Apx B-l. Summary of Industry Sectors with 1,4-Dioxane Personal Monitoring Air Samples
Obtained from OSHA Inspections Conducted Between 2002 and 2016 58
LIST OF APPENDIX FIGURES
Figure_Apx B-l: General Process Flow Diagram for 1,4-Dioxane Manufacturing 55
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ACKNOWLEDGEMENTS
This report was developed by the United States Environmental Protection Agency (U.S. EPA), Office of
Chemical Safety and Pollution Prevention (OCSPP), Office of Pollution Prevention and Toxics (OPPT).
Acknowledgements
The OPPT Assessment Team gratefully acknowledges participation or input from EPA's Office of
General Counsel, Office of Research and Development and assistance from EPA contractors CSRA LLC
(Contract No. CIO-SP3, HHSN316201200013W), ERG (Contract No. EP-W-12-006), ICF (Contract No.
EP-C-14-001) and SRC (Contract No. EP-W-12-003).
Docket
Supporting information can be found in public docket: IE PA-HQ-Oil" F 1" u.'n- u ' 3.
Disclaimer
Reference herein to any specific commercial products, process or service by trade name, trademark,
manufacturer or otherwise does not constitute or imply its endorsement, recommendation or favoring
by the United States Government.
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ABBREVIATIONS
°C Degrees Celsius
AAL Allowable Ambient Level
ACGIH American Conference of Government Industrial Hygienists
AEGL Acute Exposure Guideline Level
AES Alkyl Ethyl Sulphates
AQS Ai r Qua I ity Syste m
atm Atmosphere(s)
ATSDR Agency for Toxic Substances and Disease Registries
BAF Bioaccumulation Factor
BCF Bioconcentration Factor
BSER Best System of Emission Reduction
CAA Clean Air Act
CASRN Chemical Abstracts Service Registry Number
CBI Confidential Business Information
CCL Candidate Contaminant List
CDR Chemical Data Reporting
CERCLA Comprehensive Environmental Response, Compensation and Liability Act
cm3 Cubic Centimeter(s)
COC Concentration of Concern
cP Centipoise
CPCat Chemical and Product Categories
CSCL Chemical Substances Control Law
EC European Commission
EPA Environmental Protection Agency
EPCRA Emergency Planning and Community Right-to-Know Act
EU European Union
FDA Food and Drug Administration
FFDCA Federal Food, Drug and Cosmetic Act
g Gram(s)
GACT Generally Available Control Technology
HAP Hazardous Air Pollutant
HPV High Production Volume
IARC International Agency for Research on Cancer
IRIS Integrated Risk Information System
ISHA Industrial Safety and Health Act
kg Kilogram(s)
kPa Kilopascal(s)
L Liter(s)
lb Pound
Log Koc Logarithmic Soil Organic Carbon:Water Partitioning Coefficient
Log Kow Logarithmic OctanokWater Partition Coefficient
m3 Cubic Meter(s)
MACT Maximum Achievable Control Technology
mg Milligram(s)
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ng
Microgram(s)
mmHg
Millimeter(s) of Mercury
MSDS
Material Safety Data Sheet
NAC
National Advisory Committee
NAICS
North American Industry Classification System
NATA
National Air Toxics Assessment
NCEA
National Center for Environmental Assessment
NEI
National Emissions Inventory
NESHAP
National Emission Standards for Hazardous Air Pollutants
NICNAS
National Industrial Chemicals Notification and Assessment Scheme
NIH
National Institute of Health
NIOSH
National Institute of Occupational Safety and Health
NOAEL
No-Observed-Adverse-Effect Level
NPRI
National Pollutant Release Inventory
NSPS
New Source Performance Standards
NTP
National Toxicology Program
OCSPP
Office of Chemical Safety and Pollution Prevention
OECD
Organisation for Economic Co-operation and Development
OPPT
Office of Pollution Prevention and Toxics
OSHA
Occupational Safety and Health Administration
PBPK
Physiologically Based Pharmacokinetic
PEL
Permissible Exposure Limit
PET
Polyethylene Terephthalate
POD
Point of Departure
POTW
Publicly Owned Treatment Works
PPm
Part(s) per Million
PWS
Public Water System
RCRA
Resource Conservation and Recovery Act
REL
Recommended Exposure Level
SDS
Safety Data Sheet
SDWA
Safe Drinking Water Act
SIDS
Screening Information Data Set
TCA
1,1,1-Trichloroethane
TCCR
Transparent, Clear, Consistent and Reasonable
TLV
Threshold Limit Value
TRI
Toxics Release Inventory
TSCA
Toxic Substances Control Act
TWA
Time-Weighted Average
UCMR
Unregulated Contaminant Monitoring Rule
U.S.
United States
UV
Ultraviolet
VCCEP
Voluntary Children's Chemical Evaluation Program
VOC
Volatile Organic Compound
WHO
World Health Organisation
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EXECUTIVE SUMMARY
TSCA § 6(b)(4) requires the United States Environmental Protection Agency (U.S. EPA) to establish a
risk evaluation process. In performing risk evaluations for existing chemicals, EPA is directed to
"determine whether a chemical substance presents an unreasonable risk of injury to health or the
environment, without consideration of costs or other non-risk factors, including an unreasonable risk
to a potentially exposed or susceptible subpopulation identified as relevant to the risk evaluation by
the Administrator under the conditions of use." In December of 2016, EPA published a list of
10 chemical substances that are the subject of the Agency's initial chemical risk evaluations (81 FR
91927). as required by TSCA § 6(b)(2)(A). 1,4-Dioxane was one of these chemicals.
TSCA § 6(b)(4)(D) requires that EPA publish the scope of the risk evaluation to be conducted, including
the hazards, exposures, conditions of use and potentially exposed or susceptible subpopulations that
the Administrator expects to consider. This document fulfills the TSCA § 6(b)(4)(D) requirement for 1,4-
dioxane.
This document presents the scope of the risk evaluation to be conducted for 1,4-dioxane. If a hazard,
exposure, condition of use or potentially exposed or susceptible subpopulation has not been discussed,
EPA, at this point in time, is not intending to include it in the scope of the risk evaluation. As per the
rulemaking, Procedures for Chemical Risk Evaluation Under the Amended Toxic Substances Control Act
(TSCA), with respect to conditions of use in conducting a risk evaluation under TSCA, EPA will first
identify "circumstances" that constitute "conditions of use" for each chemical. While EPA interprets
this as largely a factual determination—i.e., EPA is to determine whether a chemical substance is
actually involved in one or more of the activities listed in the definition—the determination will
inevitably involve the exercise of some discretion.
In the case of 1,4-dioxane, EPA anticipates that production of 1,4-dioxane as a by-product from
ethoxylation of other chemicals and presence as a contaminant in industrial, commercial and
consumer products will be excluded from the scope of the risk evaluation. These 1,4-dioxane activities
will be considered in the scope of the risk evaluation for ethoxylated chemicals. EPA believes its
regulatory tools under TSCA section 6(a) are better suited to addressing any unreasonable risks that
might arise from these activities through regulation of the activities that generate 1,4-dioxane as an
impurity or cause it to be present as a contaminant than they are to addressing them through direct
regulation of 1,4-dioxane.
To the extent practicable, EPA has aligned this scope document with the approach set forth in the risk
evaluation process rule; however, the scope documents for the first 10 chemicals in the risk evaluation
process differ from the scope documents that EPA anticipates publishing in the future. Time
constraints have resulted in scope documents for the first 10 chemicals that are not as refined or
specific as future scope documents are anticipated to be.
Because there was insufficient time for EPA to provide an opportunity for comment on a draft of this
scope document, as it intends to do for future scope documents, EPA will publish and take public
comment on a problem formulation document which will refine the current scope, as an additional
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interim step, prior to publication of the draft risk evaluation for 1,4-dioxane. This problem formulation
is expected to be released within approximately 6 months of publication of the scope.
In 2015, EPA/OPPT published a Problem Formulation and Initial Assessment for 1,4-Dioxane (EPA,
2015) and received public comments. As part of this scope, EPA developed an initial life cycle diagram
and initial conceptual models for 1,4-dioxane that reconsidered all information under the amended
law.
Historically, 90% of 1,4-dioxane production was used as a stabilizer in chlorinated solvents such as
1,1,1-trichloroethane (TCA). Use of 1,4-dioxane has decreased since TCA was phased out by the
Montreal Protocol in 1996. 1,4-Dioxane is currently used in industrial processes and for industrial and
commercial uses. Industrial processing uses include use as a processing aid and in functional fluids in
closed systems. 1,4-Dioxane has uses as a laboratory chemical reagent, in adhesives and sealants and
several other identified uses. Based on data from the 2016 Chemical Data Reporting (CDR), the current
production volume is approximately 1 million pounds per year (U.S. EPA. 2016b). The most recent data
on environmental releases, according to the Toxics Release Inventory (TRI), indicate that approximately
675,000 pounds of 1,4-dioxane were released to the environment in 2015 (U.S. EPA. 2017c). Releases
are reported to all types of environmental media: air, water and land. The environmental fate of 1,4-
dioxane is characterized by partitioning to the atmosphere, surface water and groundwater, and
degradation by atmospheric oxidation or biodegradation. It is expected to be moderately persistent in
the environment and have a low bioaccumulation potential.
The initial conceptual models presented in Section 2 identify conditions of use; exposure pathways
(e.g., media); exposure routes (e.g., inhalation, dermal, oral); potentially exposed populations,
including potentially exposed or susceptible subpopulations; and hazards EPA expects to evaluate
based on the inherent hazards of the chemical.
This document presents the occupational scenarios in which workers and occupational non-users may
be exposed to 1,4-dioxane during conditions of use, such as manufacturing, processing, repackaging
and recycling. For 1,4-dioxane, EPA believes that workers and bystanders as well as certain other
groups of individuals may experience greater exposures than the general population. EPA will evaluate
whether other groups of individuals within the general population may be exposed via pathways that
are distinct from the general population due to unique characteristics (e.g., life stage, behaviors,
activities, duration) or have greater susceptibility than the general population, and should therefore be
considered relevant potentially exposed or susceptible subpopulations for purposes of this risk
evaluation.
Exposures to workers and/or the general population may occur from industrial releases and industrial
and commercial uses. Environmental releases of 1,4-dioxane are reported in the Toxics Release
Inventory to air, water or land. 1,4-Dioxane is stable under environmental conditions and does not
degrade or react to any appreciable extent in the environment.
1,4-Dioxane has been the subject of several health hazard and risk assessments, based on data in
animal studies. Any existing assessments will be a starting point as EPA will conduct a systematic
review of the literature, including new literature since the existing assessments, as available in 1,4-
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Dioxane (CASRN 123-91-1) Bibliography: Supplemental File for the TSCA Scope Document (EPA-IHQ-
0 16-0723). EPA expects to consider human health hazards of 1,4-dioxane including acute
toxicity, non-cancer effects and cancer. Non-cancer effects include irritation of the eyes and
respiratory tract, liver toxicity and kidney toxicity. Animals exposed to 1,4-dioxane by inhalation and
oral exposure have developed multiple types of cancer.
The initial analysis plan describes EPA's plan for conducting systematic review of readily available
information and identification of assessment approaches to be used in conducting the risk evaluation
for 1,4-dioxane. The initial analysis plan will be used to develop the problem formulation and final
analysis plan for the risk evaluation of 1,4-dioxane.
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1 INTRODUCTION
This document presents the scope of the risk evaluation to be conducted for 1,4-dioxane. If a condition
of use has not been discussed, EPA, at this point in time, is not intending to include that condition of
use in the scope of the risk evaluation. Moreover, during problem formulation EPA may determine that
not all conditions of use mentioned in this scope will be included in the risk evaluation. Any condition
of use that will not be evaluated will be clearly described in the problem formulation document.
On June 22, 2016, the Frank R. Lautenberg Chemical Safety for the 21st Century Act, which amended
the Toxic Substances Control Act (TSCA), the Nation's primary chemicals management law, was signed
into law. The new law includes statutory requirements and deadlines for actions related to conducting
risk evaluations of existing chemicals.
TSCA § 6(b)(4) requires the United States Environmental Protection Agency (U.S. EPA) to establish a
risk evaluation process. In performing risk evaluations for existing chemicals, EPA is directed to
"determine whether a chemical substance presents an unreasonable risk of injury to health or the
environment, without consideration of costs or other non-risk factors, including an unreasonable risk
to a potentially exposed or susceptible subpopulation identified as relevant to the risk evaluation by
the Administrator under the conditions of use."
In December of 2016, EPA published a list of 10 chemical substances that are the subject of the
Agency's initial chemical risk evaluations (81 FR 91927), as required by TSCA § 6(b)(2)(A). These
10 chemical substances were drawn from the 2014 update of EPA's TSCA Work Plan for Chemical
Assessments, a list of chemicals that EPA identified in 2012 and updated in 2014 (currently totaling
90 chemicals) for further assessment under TSCA. EPA's designation of the first 10 chemical substances
constituted the initiation of the risk evaluation process for each of these chemical substances, pursuant
to the requirements of TSCA § 6(b)(4).
TSCA § 6(b)(4)(D) requires that EPA publish the scope of the risk evaluation to be conducted, including
the hazards, exposures, conditions of use and potentially exposed or susceptible subpopulations that
the Administrator expects to consider. On February 14, 2017, EPA convened a public meeting to
receive input and information to assist the Agency in its efforts to establish the scope of the risk
evaluations under development for the ten chemical substances designated in December 2016 for risk
evaluations pursuant to TSCA. EPA provided the public an opportunity to identify information, via oral
comment or by submission to a public docket, specifically related to the conditions of use for the ten
chemical substances. EPA used this information in developing this scope document, which fulfills the
TSCA § 6(b)(4)(D) requirement for 1,4-dioxane.
As per the rulemaking, Procedures for Chemical Risk Evaluation Under the Amended Toxic Substances
Control Act (TSCA), in conducting a risk evaluation under TSCA EPA will first identify "circumstances"
that constitute "conditions of use" for each chemical. While EPA interprets this as largely a factual
determination —i.e., EPA is to determine whether a chemical substance is actually involved in one or
more of the activities listed in the definition—the determination will inevitably involve the exercise of
some discretion. Based on legislative history, statutory structure and other evidence of Congressional
intent, EPA has determined that certain activities may not generally be considered to be conditions of
use. In exercising its discretion, for example, EPA would not generally consider that a single
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unsubstantiated or anecdotal statement (or even a few isolated statements) on the internet that a
chemical can be used for a particular purpose would necessitate concluding that this represented part
of the chemical substance's "conditions of use." As a further example, although the definition could be
read literally to include all intentional misuses (e.g., inhalant abuse), as a "known" or "reasonably
foreseen" activity in some circumstances, EPA does not generally intend to include such activities in
either a chemical substance's prioritization or risk evaluation. In addition, EPA interprets the mandates
under section 6(a)-(b) to conduct risk evaluations and any corresponding risk management to focus on
uses for which manufacture, processing, or distribution in commerce is intended, known to be
occurring, or reasonably foreseen (i.e., is prospective or on-going), rather than reaching back to
evaluate the risks associated with legacy uses, associated disposal, and legacy disposal, and interprets
the definition of "conditions of use" in that context. For instance, the conditions of use for purposes of
section 6 might reasonably include the use of a chemical substance in insulation where the
manufacture, processing or distribution in commerce for that use is prospective or on-going, but would
not include the use of the chemical substance in currently installed insulation, if the manufacture,
processing or distribution for that use is not prospective or on-going. In other words, EPA interprets
the risk evaluation process of section 6 to focus on the continuing flow of chemical substances from
manufacture, processing and distribution in commerce into the use and disposal stages of their
lifecycle. That said, in a particular risk evaluation, EPA may consider background exposures from legacy
use, associated disposal, and legacy disposal as part of an assessment of aggregate exposure or as a
tool to evaluate the risk of exposures resulting from non-legacy uses.
Furthermore, in exercising its discretion under section 6(b)(4)(D) to identify the conditions of use that
EPA expects to consider in a risk evaluation, EPA believes it is important for the Agency to have the
discretion to make reasonable, technically sound scoping decisions in light of the overall objective of
determining whether chemical substances in commerce present an unreasonable risk. Consequently,
EPA may, on a case-by case basis, exclude certain activities that EPA has determined to be conditions
of use in order to focus its analytical efforts on those exposures that are likely to present the greatest
concern meriting an unreasonable risk consideration. For example, EPA intends to exercise discretion
in addressing circumstances where the chemical substance subject to scoping is unintentionally
present as an impurity in another chemical substance that is not the subject of the pertinent scoping,
in order to determine which risk evaluation the potential risks from the chemical substance should be
addressed in. As an additional example, EPA may, on a case-by-case basis, exclude uses that EPA has
sufficient basis to conclude would present only "de minimis" exposures. This could include uses that
occur in a closed system that effectively precludes exposure, or use as an intermediate. During the
scoping phase, EPA may also exclude a condition of use that has been adequately assessed by another
regulatory agency, particularly where the other agency has effectively managed the risks.
The situations identified above are examples of the kinds of discretion that EPA will exercise in
determining what activities constitute conditions of use, and what conditions of use are to be included
in the scope of any given risk evaluation. See the preamble to Procedures for Chemical Risk Evaluation
Under the Amended Toxic Substances Control Act (TSCA) for further discussion of these issues.
To the extent practicable, EPA has aligned this scope document with the approach set forth in the risk
evaluation process rule; however, the scope documents for the first 10 chemicals in the risk evaluation
process differ from the scope documents that EPA anticipates publishing in the future. The first
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10 chemical substances were not subject to the prioritization process that will be used in the future in
accordance with amendments to TSCA. EPA expects to collect and screen much of the relevant
information about chemical substances that will be subject to the risk evaluation process during and
before prioritization. The volume of data and information about the first 10 chemicals that is available
to EPA is extremely large and EPA is still in the process of reviewing it, since the Agency had limited
ability to process the information gathered before issuing the scope documents for the first
10 chemicals. As a result of the statutory timeframes, EPA had limited time to process all of the
information gathered during scoping for the first 10 chemicals within the time provided in the statute
for publication of the scopes after initiation of the risk evaluation process. For these reasons, EPA's
initial screenings and designations with regard to applicability of data (e.g., on-topic vs. off-topic
information and data) may change as EPA progresses through the risk evaluation process. Likewise, the
Conceptual Models and Analysis Plans provided in the first 10 chemical scopes are designated as
"Initial" to indicate that EPA expects to further refine them during problem formulation.
The aforementioned time constraints have resulted in scope documents for the first 10 chemicals that
are not as refined or specific as future scope documents are anticipated to be. In addition, there was
insufficient time for EPA to provide an opportunity for comment on a draft of this scope document, as
it intends to do for future scope documents. For these reasons, EPA will publish and take public
comment on a problem formulation document which will refine the current scope, as an additional
interim step, prior to publication of the draft risk evaluations for the first 10 chemicals. This problem
formulation is expected to be released within approximately 6 months of publication of the scope.
1.1 Regulatory H istory
EPA conducted a search of existing domestic and international laws, regulations and assessments
pertaining to 1,4-dioxane. EPA compiled this summary from data available from federal, state,
international and other government sources, as cited in Appendix A. EPA may evaluate and consider
the impact of these existing laws and regulations in the problem formulation step to determine what, if
any further analysis might be necessary as part of the risk evaluation.
Federal Laws and Regulations
1,4-Dioxane is subject to federal statutes or regulations, other than TSCA, that are implemented by
other offices within EPA and/or other federal agencies/departments. A summary of federal laws,
regulations and implementing authorities is provided in Appendix A.l.
State Laws and Regulations
1,4-Dioxane is subject to state statutes or regulations implemented by state agencies or departments.
A summary of state laws, regulations and implementing authorities is provided in Appendix A.2.
Laws and Regulations in Other Countries and International Treaties or Agreements
1,4-Dioxane is subject to statutes or regulations in countries other than the United States and/or
international treaties and/or agreements. A summary of these laws, regulations, treaties and/or
agreements is provided in Appendix A.3.
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1.2 Assessment History
EPA has identified assessments conducted by other EPA Programs and other organizations (see Table
1-1). Depending on the source, these assessments may include information on conditions of use,
hazards, exposures and potentially exposed or susceptible subpopulations—information useful to EPA
in preparing this scope for risk evaluation. Table 1-1 shows the assessments that have been conducted
In addition to using this information, EPA intends to conduct a full review of the data collected (see
1,4-Dioxane (CASRN123-91-1) Bibliography: Supplemental File for the TSCA Scope Document, EPA-HQ-
QPPT-2016-0723) using the literature search strategy (see Strategy for Conducting Literature Searches
for 1,4-Dioxane: Supplemental File for the TSCA Scope Document, EPA-HQ-QPPT-2016-0723) to ensure
that EPA is considering information that has been made available since these assessments were
conducted.
In 2015, EPA/OPPT published a Problem Formulation and Initial Assessment for 1,4-Dioxane (EPA,
2015) and received public comments. As part of this scope, EPA developed an initial life cycle diagram
and initial conceptual models for 1,4-dioxane that re-considered all information under the amended
law.
Table 1-1. Assessment History of 1,4-Dioxane
Authoring Organization
Assessment
EPA assessments
EPA, Office of Chemical Safety and Pollution
Prevention (OCSPP), Office of Pollution Prevention
and Toxics (OPPT)
TSCA Work Plan Chemical Problem Formulation
and Initial Assessment: 1,4-Dioxane (CASRN 123-
91-1) (2015b)
EPA, National Center for Environmental
Assessment (NCEA)
Toxicological Review of 1,4-Dioxane (With
Inhalation Update) (CASRN 123-91-1) (2013)
EPA, NCEA
Toxicological review of 1,4-Dioxane (CAS No. 123-
91-1) (2010)
EPA, Office of Water (OW)
Drinking Water Health Advisory (U.S. EPA, 2012a)
Other U.S.-based organizations
National Toxicology Program (NTP)
Report on Carcinogens, Fourteenth Edition, 1,4-
Dioxane (2016)
Agency for Toxic Substances and Disease Registry
(ATSDR)
Toxicological Profile for 1,4-Dioxane (2012)
National Advisory Committee for Acute Exposure
Guideline Levels for Hazardous
Substances (NAC/AEGL Committee)
Interim Acute Exposure Guideline Levels (AEGL)
for 1,4-Dioxane (CAS Reg. No. 123-91-1) (2005b)
International
International Cooperation on Cosmetics
Regulation
Report of the ICCR Working Group:
Considerations on Acceptable Trace Level of 1.4-
Dioxane in Cosmetic Products (2017)
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Authoring Organization
Assessment
International Agency for Research on Cancer
(IARC)
IARC Monographs on the Evaluation of
Carcinogenic Risks to Humans Volume 71 (1999)
Government of Canada, Environment Canada,
Health Canada
Screening Assessment for the Challenge. 1,4-
Dioxane. CASRN 123-91-1 (2010)
Research Center for Chemical Risk Management,
National Institute of Advanced Industrial Science
and Technology, Japan
Estimating Health Risk from Exposure to 1,4-
Dioxane in Japan (2006)
World Health Organisation (WHO)
1,4-Dioxane in Drinking-water (2005)
Employment, Social Affairs, and Inclusion,
European Commission (EC)
Recommendation from the Scientific Committee
on Occupational Exposure Limits for 1,4-dioxane
(2004)
European Chemicals Bureau, Institute for Health
and Consumer Protection
European Union Risk Assessment Report. 1,4-
dioxane. CASRN 123-91-1. EINECS No: 204-661-8.
(2002)
National Industrial Chemicals Notification and
Assessment Scheme (NICNAS), Australian
Government
1,4-Dioxane. Priority Existing Chemical No. 7. Full
Public Report (1998)
Organisation for Economic Co-operation and
Development (OECD), Screening Information Data
Set (SIDS)
1,4-Dioxane. SIDS initial assessment profile (1999)
1.3 Data and Information Collection
EPA/OPPT generally applies a process and workflow that includes: (1) data collection, (2) data
evaluation and (3) data integration of the scientific data used in risk assessments developed under
TSCA. Scientific analysis is often iterative in nature as new knowledge is obtained. Hence, EPA/OPPT
expects that multiple refinements regarding data collection will occur during the process of risk
evaluation.
Data Collection: Data Search
EPA/OPPT conducted chemical-specific searches for data and information on: physical and chemical
properties; environmental fate and transport; conditions of use information; environmental exposures,
human exposures, including potentially exposed or susceptible subpopulations; ecological hazard,
human health hazard, including potentially exposed or susceptible subpopulations.
EPA/OPPT designed its initial data search to be broad enough to capture a comprehensive set of
sources containing data and/or information potentially relevant to the risk evaluation. Generally, the
search was not limited by date and was conducted on a wide range of data sources, including but not
limited to: peer-reviewed literature and gray literature (e.g., publicly-available industry reports, trade
association resources, government reports). When available, EPA/OPPT relied on the search strategies
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from recent assessments, such as EPA Integrated Risk Information System (IRIS) assessments and the
NTP Report on Carcinogens, to identify relevant references and supplemented these searches to
identify relevant information published after the end date of the previous search to capture more
recent literature. Strategy for Conducting Literature Searches for 1,4-Dioxane: Supplemental File for the
TSCA Scope Document (EPA-HQ-QPPT-2016-0723) provides details about the data sources and search
terms that were used in the initial search.
Data Collection: Data Screening
Following the data search, references were screened and categorized using selection criteria outlined
in the Strategy for Conducting Literature Searches for 1,4-Dioxane: Supplemental File for the TSCA
Scope Document (EPA-HQ-QPPT-2016-0723). Titles and abstracts were screened against the criteria as
a first step with the goal of identifying a smaller subset of the relevant data to move into the
subsequent data extraction and data evaluation steps. Prior to full-text review, EPA/OPPT anticipates
refinements to the search and screening strategies, as informed by an evaluation of the performance
of the initial title/abstract screening and categorization process.
The categorization scheme (or tagging structure) used for data screening varies by scientific discipline
(i.e., physical and chemical properties; environmental fate and transport; chemical use/conditions of
use information; environmental exposures, human exposures, including potentially exposed or
susceptible subpopulations identified by virtue of greater exposure; human health hazard, including
potentially exposed or susceptible subpopulations identified by virtue of greater susceptibility; and
ecological hazard), but within each data set, there are two broad categories or data tags: (1) on-topic
references or (2) off-topic references. On-topic references are those that may contain data and/or
information relevant to the risk evaluation. Off-topic references are those that do not appear to
contain data or information relevant to the risk evaluation. The Strategy for Conducting Literature
Searches for 1,4-Dioxane: Supplemental File for the TSCA Scope Document (EPA-HQ-QPPT-2016-0723)
discusses the inclusion and exclusion criteria that EPA/OPPT used to categorize references as on-topic
or off-topic.
Additional data screening using sub-categories (or sub-tags) was also performed to facilitate further
sorting of data/information. For example, identifying references by source type (e.g., published peer-
reviewed journal article, government report); data type (e.g., primary data, review article); human
health hazard (e.g., liver toxicity, cancer, reproductive toxicity); or chemical-specific and use-specific
data or information. These sub-categories are described in Strategy for Conducting Literature Searches
for 1,4-Dioxane: Supplemental File for the TSCA Scope Document (EPA-HQ-OtT ll_ u 11 v 3) and will be
used to organize the different streams of data during the stages of data evaluation and data
integration steps of systematic review.
Results of the initial search and categorization results can be found in the 1,4-Dioxane
(CASRN123-91-1) Bibliography: Supplemental File for the TSCA Scope Document (EPA-HQ-OPPT-2
0723). This document provides a comprehensive list (bibliography) of the sources of data identified by
the initial search and the initial categorization for on-topic and off-topic references. Because systematic
review is an iterative process, EPA/OPPT expects that some references may move from the on-topic to
the off-topic categories, and vice versa. Moreover, targeted supplemental searches may also be
conducted to address specific needs for the analysis phase (e.g., to locate specific data needed for
Page 16 of 58
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modeling); hence, additional on-topic references not initially identified in the initial search may be
identified as the systematic review process proceeds.
Page 17 of 58
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2 SCOPE OF THE EVALUATION
As required by TSCA, the scope of the risk evaluation identifies the conditions of use, hazards,
exposures and potentially exposed or susceptible subpopulations that the Administrator expects to
consider. To communicate and visually convey the relationships between these components, EPA is
including an initial life cycle diagram and initial conceptual models that describe the actual or potential
relationships between 1,4-dioxane and human and ecological receptors. An initial analysis plan is also
included which identifies, to the extent feasible, the approaches and methods that EPA may use to
assess exposures, effects (hazards) and risks under the conditions of use of 1,4-dioxane. As noted
previously, EPA intends to refine this analysis plan during the problem formulation phase of risk
evaluation.
2.1 Physical and Chemical Properties
Physical-chemical properties influence the environmental behavior and the toxic properties of a
chemical, thereby informing the potential conditions of use, exposure pathways and routes and
hazards that EPA intends to consider. For scope development, EPA considered the measured or
estimated physical-chemical properties set forth in Table 2-1.
Table 2-1. Physical and Chemical Properties of 1,4-Dioxane
Property
Valuea
References
Molecular formula
C4H8O2
Molecular weight
88.1 g/mole
Howard (1990)
Physical form
Clear liquid
(O'Neil etal.. 2001)
Melting point
11.75°C
(Havnes, 2014)
Boiling point
101.1°C
O'Neil etal. (2006)
Density
1.0329 g/cm3
(O'Neil etal.. 2001)
Vapor pressure
40 mm Hg at 25°C
Lewis (2000)
Vapor density
3.03 (relative to air)
(Lewis. 2012)
Water solubility
>8.00 x 102 g/L
(Yalkowskv et al., 2010)
Octanol:water partition
coefficient (log Kow)
-0.27
Hansch et al. (1995)
Henry's Law constant
4.8 x 10"6 atm-m3/mole at 25°C
4.93 X 10"4 atm-m7mole at 40°C
(Sander, 2017)
Howard (1990)
Atkins (1986)
Flash point
18.3°C (open cup)
(Lewis. 2012)
Autoflammability
Not readily available
Viscosity
0.0120 cP at25°C
(O'Neil. 2013)
Refractive index
1.4224 at 20°C
(Havnes, 2014)
Page 18 of 58
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Property
Valuea
References
Dielectric constant
2.209
Bruno and PDN (2006)
a Measured unless otherwise noted
2.2 Conditions of Use
TSCA § 3(4) defines the conditions of use as "the circumstances, as determined by the Administrator,
under which a chemical substance is intended, known, or reasonably foreseen to be manufactured,
processed, distributed in commerce, used, or disposed of."
2.2.1 Data and Information Sources
As the first step in preparing these scope documents, EPA identified, based on reasonably available
information, the conditions of use for the subject chemicals. As further described in this document,
EPA searched a number of available data sources (e.g. Use and Market Profile for 1,4-Dioxane, (EPA-
HQ-QPPT-2016-0723). Based on this search, EPA published a preliminary list of information and
sources related to chemical conditions of use (see Preliminary Information on Manufacturing,
Processing, Distribution, Use, and Disposal: 1,4-Dioxane, EPA-HQ-QPPT-2017-0723-0003) prior to a
February 2017 public meeting on scoping efforts for risk evaluation convened to solicit comment and
input from the public. EPA also convened meetings with companies, industry groups, chemical users
and other stakeholders to aid in identifying conditions of use and verifying conditions of use identified
by EPA. The information and input received from the public and stakeholder meetings has been
incorporated into this scope document to the extent appropriate, as indicated in Table 2-3. Thus, EPA
believes the manufacture, processing, distribution, use and disposal activities identified in these
documents constitute the intended, known, and reasonably foreseen activities associated with the
subject chemicals, based on reasonably available information. The documents do not, in most cases,
specify whether activity under discussion is intended, known, or reasonably foreseen, in part due to
the time constraints in preparing these documents.
2.2.2 Identification of Conditions of Use
As part of the scope, an initial life cycle diagram is provided (Figure 2-1) depicting the conditions of use
that are within the scope of the risk evaluation during various life cycle stages including manufacturing,
processing, distribution, use (industrial, commercial, consumer; when distinguishable) and disposal.
The information is grouped according to CDR processing codes and use categories (including functional
use codes for industrial uses and product categories for industrial, commercial and consumer uses), in
combination with other data sources (e.g., published literature and consultation with stakeholders) to
provide an overview of conditions of use. EPA notes that some subcategories of use may be grouped
under multiple CDR categories.
For the purposes of this scope, use categories include the following: "industrial use" means use at a
site at which one or more chemicals or mixtures are manufactured (including imported) or processed.
"Commercial use" means the use of a chemical or a mixture containing a chemical (including as part of
an article) in a commercial enterprise providing saleable goods or services. "Consumer use" means the
use of a chemical or a mixture containing a chemical (including as part of an article, such as furniture or
clothing) when sold to or made available to consumers for their use (U.S. EPA. 2016b).
Page 19 of 58
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To understand conditions of use relative to one another and associated potential exposures under
those conditions of use, the life cycle diagram includes the production volume associated with each
stage of the life cycle, as reported in the 2016 CDR reporting (U.S. EPA. 2016b). when the volume was
not claimed confidential business information (CBI). The 2016 CDR reporting data for 1,4-dioxane are
provided in Table 2-2 for 1,4-dioxane from EPA's CDR database (U.S. EPA. 2016b).
Table 2-2. Production Volume of 1,4-Dioxane in Chemical Data Reporting (CDR) Reporting Period
(2012 to 2015)a
Reporting Year
2012
2013
2014
2015
Total Aggregate
Production Volume (lbs)
894,505
1,043,627
474,331
1,059,980
aThe CDR data for the 2016 reporting period is available via ChemView (https://iava.eoa.gov/chemview) (U.S. EPA.
2016b). Because of an ongoing CBI substantiation process reauired bv amended TSCA. the CDR data available in the scope
document is more specific than currently in ChemView.
Figure 2-1 depicts the initial life cycle diagram of 1,4-dioxane from manufacture to the point of
disposal. The total volume (in lbs) of 1,4-dioxane manufactured (including imported) in the U.S. from
2012 to 2015 indicates that production has varied over that time period. Historically, the main use
(90%) of 1,4-dioxane was as a stabilizer of chlorinated solvents such as 1,1,1 trichloroethane (TCA)
(ATSDR. 2012). Use of TCA was phased out under the 1995 Montreal Protocol and the use of
1,4-dioxane as a solvent stabilizer was terminated (NTP. 2016; ECJRC. 2002). Lack of recent reports for
other previously reported uses (Sapphire Group. 2007) suggest that many other industrial, commercial
and consumer uses were also stopped.
Descriptions of the industrial, commercial and consumer use categories identified from the 2016 CDR
and included in the life cycle diagram are summarized below (U.S. EPA. 2016b). The descriptions
provide a brief overview of the use category; Appendix B contains more detailed descriptions (e.g.,
process descriptions, worker activities, process flow diagrams, equipment illustrations) for each
manufacture, processing, use and disposal category. The descriptions provided below are primarily
based on the corresponding industrial function category and/or commercial and consumer product
category descriptions from the 2016 CDR and can be found in EPA's Instructions for Reporting 2016
TSCA Chemical Data Reporting (U.S. EPA. 2016a).
As reflected in the initial life cycle diagram (Figure 2-1), intended, known and reasonably foreseen uses
of 1,4-dioxane are primarily associated with industrial and commercial activities. Manufacturing sites
produce 1,4-dioxane in liquid form at >90% concentration [EPA-HQ-QPPT-2016-0723-0012 (BASF.
2017)1.1,4-Dioxane is currently used in industrial processes and for industrial and commercial uses.
Industrial processing uses include use as a processing aid during wood pulping, pharmaceutical
manufacture and etching of fluoropolymers and in functional fluids in closed systems. 1,4-Dioxane
uses as a laboratory chemical reagent and in adhesives and sealants may occur in either industrial
and/or commercial settings. A search for products containing 1,4-dioxane found several identified
laboratory reference materials or standards containing 1,4-dioxane. In addition, two products with >5%
of 1,4-dioxane: a professional film cement and a chemiluminescent laboratory reagent were identified.
Other uses identified include use in fuels and fuel additives; spray polyurethane foam; and printing and
printing compositions.
Page 20 of 58
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No consumer uses for 1,4-dioxane were reported in the U.S. in the 2016 CDR (U.S. EPA. 2016b). EPA did
not identify any other U.S. sources that stated that 1,4-dioxane is currently used in the production of
consumer products and, therefore, assumes that it is not. Other information sources do not
differentiate between use of consumer and commercial products (ATSDR, 2012; U.S. EPA. 2006). A
European risk assessment stated that 1,4-dioxane is used as a solvent in the production of several
products that may be used by consumers like pharmaceuticals, pesticides, magnetic tape and
adhesives (ECJRC, 2002). Public comments submitted by an industry coalition group (Public Comment,
EPA-1 0012) assert that 1,4-dioxane is not an intentionally added ingredient in any
consumer products in the U.S.
1,4-Dioxane may be produced as a reaction by-product, particularly in chemicals which are produced
by ethoxylation. These include alkyl ether sulphates (AES, anionic surfactants) and other ethoxylated
substances, such as alkyl, alkylphenol and fatty amine ethoxylates; polyethylene glycols and their
esters; and sorbitan ester ethoxylates. Therefore, 1,4-dioxane may be present at residual
concentrations in commercial and consumer products that contain ethoxylated chemicals. Examples of
products potentially containing 1,4-dioxane as a residual contaminant are paints, coatings, lacquers,
ethylene glycol-based antifreeze coolants, spray polyurethane foam, household detergents,
cosmetics/toiletries, textile dyes, pharmaceuticals, foods, agricultural and veterinary products (ATSDR.
2012; Health Canada. 2010; FDA. 2007; ECJRC, 2002). Manufacturers can apply controls to minimize
the formation of 1,4-dioxane or remove most of the 1,4-dioxane present in these products through a
vacuum stripping process (Public Comment, EPA-HQ-QPPT-2016-0723-0007) (ATSDR. 2012). The extent
that manufacturers or processors apply controls or processes to minimize or remove 1,4-dioxane in
surfactants during manufacture or before formulation in consumer products is unknown and likely
varies by sector (ICCR, 2017).
1-4-Dioxane produced as a by-product of reactions in the production of other chemicals is excluded
from the scope of the risk evaluation. EPA anticipates that 1,4-dioxane by-product and contaminant
issues will be considered in the scope of any risk evaluation of ethoxylated chemicals.
Page 21 of 58
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MFG/IMPORT
Manufacture
(Includes Import)
(1 million lbs.)
PROCESSING
INDUSTRIAL, COMMERCIAL, CONSUMER USES a
Processing as a
Reactant/lntermediate
(Not reported in 2016 CDR)
Repackaging
(270,000 lbs.)
Non-lncorporative
Activities
(270,000 lbs.)
Recycling
Processing Aids, Not Otherwise
Listed
(270,000 lbs.)
e.g., wood pulping, pharmaceutical
manufacture, etching of fluoropolymers
Functional Fluids (closed system)
(<150,000 lbs.)
e.g., hydraulic fluid
Laboratory Chemicals
(<150,000 lbs.)
e.g., laboratory reagent
Adhesives and Sealants
e.g., film cement
Other Uses
Fuels and Fuel Additives; Spray
Polyurethane Foam; Printing and
Printing Compositions
RELEASES and WASTE DISPOSAL
Emissions to Air
Wastewaterb
Liquid Wastes'3
Solid Wastes
See Figure 2-3 for Environmental
Releases and Wastes
I I Manufacture (Includes Import) I I Processing ~ Industrial uses of 1,4-dioxane.
1 | Industrial and/or commercial uses of 1,4-dioxane
Figure 2-1. Initial 1,4-Dioxane Life Cycle Diagram
The initial life cycle diagram depicts the conditions of use that are within the scope of the risk evaluation during various life cycle stages
including manufacturing, processing, use (industrial or commercial) and disposal. The production volumes shown are for reporting year
2015 from the 2016 CDR reporting period (u .. EPA, 2016b). Activities related to distribution (e.g., loading, unloading) will be considered
throughout the 1,4-dioxane life cycle, rather than using a single distribution scenario.
aSee Table 2-3 for additional uses not mentioned specifically in this diagram.
b Wastewater: combination of water and organic liquid, where the organic content is <50%. Liquid Wastes: combination of water and organic liquid, where the organic
content is >50%.
Page 22 of 58
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Table 2-3 summarizes each life cycle stage and the corresponding categories and subcategories of
conditions of use for 1,4-dioxane that EPA expects to consider in the risk evaluation. Using the 2016
CDR, EPA identified industrial processing or use activities, industrial function categories and
commercial use product categories. EPA identified the subcategories by supplementing CDR data with
other published literature and information obtained through stakeholder consultations. For risk
evaluations, EPA intends to consider each life cycle stage (and corresponding use categories and
subcategories) and assess relevant potential sources of release and human exposure associated with
that life cycle stage.
Table 2-3. Categories and Subcategories of Conditions of Use of 1,4-Dioxane
Life Cycle Stage
Categorya
Subcategory b
References
Manufacture
Domestic
manufacture
Domestic manufacture
Use document, EPA-
HQ-OPPT-2016-0723-
0003; Public Comment,
EPA-HQ-OPPT-2016-
0723-0012
Import
Import
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Processing
Processing as a
reactant
Pharmaceutical intermediate
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Polymerization catalyst
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Non-incorporative
Pharmaceutical and medicine
manufacturing
Public Comment, EPA-
HQ-OPPT-2016-0723-
(process solvent)
0012
Basic organic chemical
manufacturing
Public Comment, EPA-
HQ-OPPT-2016-0723-
(process solvent)
0012
Repackaging
Bulk to packages, then
distribute
Public Comment, EPA-
HQ-OPPT-2016-0723-
0012
Recycling
Recycling
U.S. EPA (2017c)
Distribution in
Distribution
Distribution in commerce
commerce
Industrial use
Intermediate use
Agricultural chemical
intermediate
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Page 23 of 58
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Life Cycle Stage
Categorya
Subcategory b
References
Plasticizer intermediate
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Catalysts and reagents for
anhydrous acid reactions,
brominations and
sulfonations
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Processing aids, not
otherwise listed
Wood pulping
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Extraction of animal and
vegetable oils
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Wetting and dispersing agent
in textile processing
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Polymerization catalyst
Use document. EPA-HQ-
OPPT-2016-0723-0003
Purification of
pharmaceuticals
Use document. EPA-HQ-
OPPT-2016-0723-0003
Etching of fluoropolymers
Public Comment, EPA-
HQ-OPPT-2016-0723-
0012
Functional fluids
(closed system)
Polyalkylene glycol lubricant
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Synthetic metalworking fluid
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Cutting and tapping fluid
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Hydraulic fluid
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Industrial use,
potential commercial
use
Laboratory chemicals
Chemical reagent
Use document, EPA-
HQ-OPPT-2016-0723-
0003; Public Comment,
EPA-HQ-OPPT-2016-
0723-0009
Page 24 of 58
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Life Cycle Stage
Categorya
Subcategory b
References
Reference material
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Spectroscopic and
photometric measurement
Use document, EPA-
HQ-OPPT-2016-0723-
0003; Public Comment,
EPA-HQ-OPPT-2016-
0723-0009
Liquid scintillation counting
medium
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Stable reaction medium
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Cryoscopic solvent for
molecular mass
determinations
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Preparation of histological
sections for microscopic
examination
Use document, EPA-
HQ-OPPT-2016-0723-
0003
Adhesives and
sealants
Film cement
Use document, EPA-
HQ-OPPT-2016-0723-
0003; Public Comment,
EPA-HQ-OPPT-2016-
0723-0021
Other uses
Fuels and fuel additives
Spray polyurethane foam
Printing and printing
compositions
Use document, EPA-
HQ-OPPT-2016-0723-
0003; Public Comment,
EPA-HQ-OPPT-2016-
0723-0012
Disposal
Emissions to air
Air
U.S. EPA (2017c)
Wastewater
Industrial pre-treatment
Industrial wastewater
treatment
Publicly owned treatment
works (POTW)
Underground injection
Solid wastes and
liquid wastes
Municipal landfill
Hazardous landfill
Page 25 of 58
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Life Cycle Stage
Categorya
Subcategory b
References
Other land disposal
Municipal waste incinerator
Hazardous waste incinerator
Off-site waste transfer
aThese categories of conditions of use appear in the initial life cycle diagram (Figure 2-1), reflect CDR codes and broadly
represent conditions of use of 1,4-dioxane in industrial and/or commercial settings.
bThese subcategories reflect more specific uses of 1,4-dioxane.
2.3 Exposures
For TSCA exposure assessments, EPA expects to evaluate exposures and releases to the environment
resulting from the conditions of use applicable to 1,4-dioxane. Post-release pathways and routes will
be described to characterize the relationship or connection between the conditions of use of 1,4-
dioxane and the exposure to human receptors, including potentially exposed or susceptible
subpopulations, and ecological receptors. EPA will take into account, where relevant, the duration,
intensity (concentration), frequency and number of exposures in characterizing exposures to 1,4-
dioxane.
2.3.1 Fate and Transport
Environmental fate includes both transport and transformation processes. Environmental transport is
the movement of the chemical within and between environmental media. Transformation occurs
through the degradation or reaction of the chemical with other species in the environment. Hence,
knowledge of the environmental fate of the chemical informs the determination of the specific
exposure pathways and potential human and environmental receptors EPA expects to consider in the
risk evaluation. Table 2-4 provides environmental fate data that EPA has identified and considered in
developing the scope for 1,4-dioxane.
Table 2-4. Environmental Fate Characteristics of 1,4-Dioxane
Property or Endpoint
Valuea
References
Direct photodegradation
Not expected to undergo direct photolysis
U.S. EPA (2015b)
Indirect photodegradation
4.6 hours (estimated for atmospheric
degradation)
U.S. EPA (2015b)
Hydrolysis half-life
Does not undergo hydrolysis
U.S. EPA (2015b)
Biodegradation
<10% in 29 days (aerobic in water, OECD 301F)
<5% in 60 days (aerobic in water, OECD 310)
0% in 120 days, 60% in 300 days (aerobic in soil
microcosm)
U.S. EPA (2015b)
Bioconcentration factor
(BCF)
0.2-0.7 (OECD 305C)
U.S. EPA (2015b)
Page 26 of 58
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Property or Endpoint
Valuea
References
Bioaccumulation factor
(BAF)
0.93 (estimated)
U.S. EPA (2012b)
Organic carbon:water
partition coefficient (log Koc)
0.4 (estimated)
U.S. EPA (2015b)
a Measured unless otherwise noted.
1,4-Dioxane is expected to volatilize from dry surfaces and dry soil due to its vapor pressure of 40 mm
Hg at 25°C (Table 2-1). It reacts with hydroxyl radicals (OH*) in the atmosphere with an estimated
indirect photolysis half-life on the order of hours. 1,4-Dioxane is not expected to be susceptible to
direct photolysis under environmental conditions since this compound lacks functional groups that
absorb light at visible-ultraviolet (UV) light wavelengths.
Due to its water solubility (>800 g/L; Table 2-1) and Henry's Law constant (4.8 x 10"6 atm-m3/mole at
25°C; Table 2-1), 1,4-dioxane is expected to be slightly volatile from water surfaces and moist soil. Once
it enters the environment, 1,4-dioxane is expected to be mobile in soil based on its organic carbon
partition coefficient (estimated log Koc = 0.4) and may therefore migrate to surface waters and
groundwater. 1,4-Dioxane will not hydrolyze in water because it does not have functional hydrolyzable
groups.
In experimental studies, 1,4-dioxane has been demonstrated to be not readily biodegradable and was
subject to biodegradation after acclimation in a soil microcosm. Measured bioconcentration factors for
1,4-dioxane are 0.7 or below and the estimated bioaccumulation factor is 0.93. Therefore, 1,4-dioxane
has low bioaccumulation potential.
2.3.2 Releases to the Environment
Releases to the environment from conditions of use (e.g., industrial and commercial processes,
commercial or consumer uses resulting in down-the-drain releases) are one component of potential
exposure and may be derived from reported data that are obtained through direct measurement,
calculations based on empirical data and/or assumptions and models.
A source of information that EPA expects to consider in evaluating exposure are data reported under
the Toxics Release Inventory (TRI) program. Under the Emergency Planning and Community Right-to-
Know Act (EPCRA) Section 313 rule, 1,4-Dioxane is a TRI-reportable substance effective January 1,
1987.
Table 2-5 provides production-related waste managed data (also referred to as waste managed) for
1,4-dioxane reported by industrial facilities to the TRI program for 2015. Table 2-6 provides more
detailed information on the quantities released to air or water or disposed of on land.
Page 27 of 58
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Table 2-5. Summary of 1,4-Dioxane TRI Production-Related Waste Managed in 2015 (lbs)
Number of
Energy
Total Production
Facilities
Recycling
Recovery
Treatment
Releasesa,b,c
Related Waste
49
4,292
1,591,064
1,923,623
705,691
4,224,670
Data source: 2015 TRI Data (updated March 2017) U.S. EPA (2017c).
aTerminology used in these columns may not match the more detailed data element names used in the TRI public data
and analysis access points.
b Does not include releases due to one-time event not associated with production such as remedial actions or
earthquakes.
c Counts all releases including release quantities transferred and release quantities disposed of by a receiving facility
reporting to TRI.
Facilities are required to report if they manufacture (including import) or process more than 25,000
pounds of 1,4-dioxane, or if they otherwise use more than 10,000 pounds of 1,4-dioxane. In 2015, 49
facilities reported a total of 4.2 million pounds of 1,4-dioxane waste managed. Of this total, over 4
thousand pounds were recycled, 1.6 million pounds were recovered for energy, 1.9 million pounds
were treated and 700 thousand pounds were released to the environment.
Of the almost 700 thousand pounds of total releases, there were both stack and fugitive air releases,
water releases, Class I underground injection, release to Resource Conservation and Recovery Act
(RCRA) Subtitle C landfills and other land disposal (Table 2-6).
Table 2-6. Summary of 1,4-Dioxane TRI Releases to the Environment in 2015 (
Number
of
Facilities
Air Releases
Water
Releases
Land Releases
Other
Releasesa
Total
Releasesbc
Stack
Air
Releases
Fugitive
Air
Releases
Class 1
Under-
ground
Injection
RCRA
Subtitle C
Landfills
All other
Land
Disposala
Subtotal
46,219
16,377
563,976
13,376
49
Totals
49
62,596
35,402
577,400
0
675,399
Data source: 2015 TRI Data (updated March 2017) U.S. EPA (2017c).
3 Terminology used in these columns may not match the more detailed data element names used in the TRI public data and analysis access points.
b These release quantities include releases due to one-time events not associated with production such as remedial actions or earthquakes.
c Counts release quantities once at final disposition, accounting for transfers to other TRI reporting facilities that ultimately dispose of the chemical
waste.
bs)
While production-related waste managed shown in Table 2-5 excludes any quantities reported as
catastrophic or one-time releases (TRI section 8 data), release quantities shown in Table 2-6 include
both production-related and non-routine quantities (TRI section 5 and 6 data). As a result, release
quantities may differ slightly and may further reflect differences in TRI calculation methods for
reported release range estimates (U.S. EPA. 2017c).
One source EPA will use to quantify releases of 1,4-dioxane is EPA's AP-42, Compilation of Air Pollutant
Emission Factors. AP-42 section 6.13 on pharmaceuticals production provides general process and
emissions information and the ultimate disposition of 1,4-dioxane (air, sewer, incineration, solid waste,
product) by pharmaceutical manufacturers. Other sources of information provide evidence of releases
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of 1,4-dioxane, including National Emission Standards for Hazardous Air Pollutants (NESHAPs)
promulgated under the Clean Air Act (CAA) or other EPA standards and regulations that set legal limits
on the amount of 1,4-dioxane that can be emitted to a particular media. EPA expects to consider these
and other available data in conducting the exposure assessment component of the risk evaluation for
1,4-dioxane.
2.3.3 Presence in the Environment and Biota
Monitoring studies or a collection of relevant and reliable monitoring studies provide(s) information
that can be used in an exposure assessment. Monitoring studies that measure environmental
concentrations or concentrations of chemical substances in biota provide evidence of exposure.
Monitoring data were identified in EPA's data search for 1,4-dioxane.
Monitoring data (measured) from EPA's Air Quality System (AQS) and the open literature, as well as
modeled estimates based on the National Air Toxics Assessment (NATA) and TRI emissions data
suggest that 1,4-dioxane is present in ambient air. Monitored and modeled air concentrations from
these sources suggest that many air concentrations may be low (i.e., <1 |-ig/m3) and appear to have
been higher in the past, possibly reflecting past uses (U.S. EPA. 2015a, 2011).
Indoor air monitoring data are available. One recent study reported annual average concentrations of
1,4-dioxane ranging from 0.01 to 0.11 |-ig/m3 in several hundred homes in Germany (Wissenbach et al.,
2016). Older indoor air monitoring studies are summarized in the U.S. EPA Voluntary Children's
Chemical Evaluation Program (VCCEP) submission and report slightly higher concentrations, possibly
reflecting past uses (Sapphire Group. 2007).
EPA's third Unregulated Contaminant Monitoring Rule (UCMR 3), published in 2012, required
monitoring for 1,4-dioxane, along with 29 other contaminants. Over 28,000 drinking water samples
were collected for chemicals suspected to be present in drinking water that lack health-based
standards under the Safe Drinking Water Act.
Reported levels of 1,4-dioxane in groundwater range from 3 to 31,000 ng/L (ATSDR. 2012; USGS, 2002).
Such instances of ground water contamination with 1,4-dioxane are documented in the states of
California and Michigan. These data provide a basis for including groundwater in the scope of the
1,4-dioxane risk evaluation from manufacturing, processing, distribution and use unless otherwise
regulated or managed.
There are relatively fewer data available on 1,4-dioxane levels in surface water, though some studies of
groundwater contamination also reported levels in nearby surface water. 1,4-Dioxane is released into
surface water and some studies have examined 1,4-dioxane levels in sewage treatment or chemical
plant effluent, combined collection treatments from apartment homes, and in river basin systems
(ATSDR. 2012). 1,4-Dioxane has also been detected in landfill leachate. These data are consistent with
including releases to surface water within the scope of 1,4-dioxane.
1,4-Dioxane has not been measured and is unlikely to be present in sediment, sludge, soil or dust,
based on its physical and chemical properties. 1,4-Dioxane has a low bioaccumulation potential for
accumulation in aquatic organisms and is short-lived in humans and few biomonitoring data are
available.
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2.3.4 Environmental Exposures
The manufacturing, processing, use and disposal of 1,4-dioxane can result in releases to the
environment. EPA expects to consider exposures to the environment and ecological receptors that
occur via the exposure pathways or media shown in Figure 2-3 in conducting the risk evaluation for
1,4-dioxane.
2.3.5 Human Exposures
EPA expects to consider three broad categories of human exposures: occupational exposures,
consumer exposures and general population exposures. Subpopulations within these exposure
categories will also be considered as described herein.
2.3.5.1 Occupational Exposures
EPA expects to consider worker activities where there is a potential for exposure under the various
conditions of use described in Section 2.2. In addition, EPA expects to consider exposure to
occupational non-users, who do not directly handle the chemical but perform work in an area where
the chemical is present. When data and information are available to support the analysis, EPA also
expects to consider the effect(s) that engineering controls and/or personal protective equipment have
on occupational exposure levels.
Workers and occupational non-users may be exposed to 1,4-dioxane when performing activities
associated with the conditions of use described in Section 2.2, including, but not limited to:
• Unloading and transferring 1,4-dioxane to and from storage containers to process vessels.
• Using 1,4-dioxane in process equipment.
• Cleaning and maintaining equipment.
• Sampling chemical, formulations or products containing 1,4-dioxane for quality control.
• Repackaging chemicals, formulations or products containing 1,4-dioxane.
• Handling, transporting and disposing waste containing 1,4-dioxane.
• Performing other work activities in or near areas where 1,4-dioxane is used.
Based on these activities, EPA expects to consider inhalation exposure to vapors and mists and dermal
exposure, including skin contact with vapors, liquids and mists for workers and occupational non-users.
EPA also expects to consider potential worker exposure through mists that deposit in the upper
respiratory tract and are swallowed.
The United States has several regulatory and non-regulatory exposure limits for 1,4-dioxane: An
Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) of 100 ppm
8-hour time-weighted average (TWA) (360 mg/m3) with a skin notation, a National Institute of
Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL) of 1 ppm (3.6 mg/m3) as a
30-minute ceiling and an American Conference of Government Industrial Hygienists (ACGIH) Threshold
Limit Value (TLV) of 20 ppm TWA (72 mg/m3) (OSHA. 2005). The influence of these exposure limits on
occupation exposures will be considered in the occupational exposure assessment.
Key data that inform occupational exposure assessment and which EPA expects to consider
include: the OSHA Chemical Exposure Health Data (CEHD) and NIOSH Health Hazard Evaluation (HHE)
program data. OSHA data are workplace monitoring data from OSHA inspections. The inspections can
be random or targeted, or can be the result of a worker complaint. OSHA data can be obtained through
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the OSHA Integrated Management Information System (IMIS) at
https://www.osha.gov/oshstats/index.html. Table_Apx B-l in Appendix B.2 provides a summary of
industry sectors with 1,4-dioxane personal monitoring air samples obtained from OSHA inspections
conducted between 2002 and 2016. NIOSH HHEs are conducted at the request of employees, union
officials, or employers and help inform potential hazards at the workplace. HHEs can be downloaded at
https://www.cdc.gov/niosh/hhe/. During the problem formulation, EPA will review these data and
evaluate their utility in the risk evaluation.
2.3.5.2 Consumer Exposures
No consumer uses for 1,4-dioxane were reported to EPA (U.S. EPA. 2017a, 2016b). 1,4-Dioxane may be
found as a contaminant in consumer products and/or commercial products that are readily available
for public purchase. However, it is present as a result of by-product formation during manufacture of
ethoxylated chemicals that are subsequently formulated into products.
EPA does not expect to consider exposures to consumers and bystanders from by-product or
contaminant exposure in the risk evaluation for 1,4-dioxane. Rather, EPA anticipates that 1,4-dioxane
by-product and contaminant issues will be considered in the scope of any risk evaluation of
ethoxylated chemicals.
2.3.5.3 General Population Exposures
Wastewater/liquid wastes, solid wastes or air emissions of 1,4-dioxane could result in potential
pathways for oral, dermal or inhalation exposure to the general population. EPA expects to consider
each media, route and pathway to estimate general population exposures.
Inhalation
There is inhalation exposure potential to 1,4-dioxane by breathing ambient air and indoor air. Ambient
air exposures may occur from releases from industrial/commercial sources. Indoor air exposures may
occur from infiltration from ambient air or emissions from tap water during activities such as
showering and bathing. Based on the relatively high water solubility and relatively low Henry's law
constant for 1,4-dioxane, 1,4-dioxane is only slightly volatile from water, though water temperature
can also influence volatilization.
Based on these potential sources and pathways of exposure, EPA expects to consider inhalation
exposures of the general population to 1,4-dioxane in air that may result from the conditions of use of
1,4-dioxane.
Oral
The general population may ingest 1,4-dioxane via contaminated drinking water. Based on reported
uses, down-the-drain sources may contribute to surface water and drinking water levels. Therefore,
there is potential oral exposure to 1,4-dioxane by ingestion of drinking water from surface water and
ground water sources.
Based on these potential sources and pathways of exposure, EPA expects to consider oral exposures to
the general population that may result from the conditions of use of 1,4-dioxane.
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Dermal
Dermal exposure via water could occur through contact, such as washing and bathing, with tap water
containing 1,4-dioxane. The source of the contaminated water could either be contaminated surface or
ground waters.
Based on these potential sources and pathways of exposure, EPA expects to consider dermal exposures
to the general population that may result from the conditions of use of 1,4-dioxane.
2.3.5.4 Potentially Exposed or Susceptible Subpopulations
TSCA requires that the determination of whether a chemical substance presents an unreasonable risk
include consideration of unreasonable risk to "a potentially exposed or susceptible subpopulation
identified as relevant to the risk evaluation" by EPA. TSCA § 3(12) states that "the term 'potentially
exposed or susceptible subpopulation' means a group of individuals within the general population
identified by the Administrator who, due to either greater susceptibility or greater exposure, may be at
greater risk than the general population of adverse health effects from exposure to a chemical
substance or mixture, such as infants, children, pregnant women, workers, or the elderly."
In this section, EPA addresses the potentially exposed or susceptible subpopulations identified as
relevant based on greater exposure. EPA will address the subpopulations identified as relevant based
on greater susceptibility in the hazard section.
Of the human receptors identified in the previous sections, EPA identifies the following as potentially
exposed or susceptible subpopulations due to their greater exposure that EPA expects to consider in
the risk evaluation:
• Workers and occupational non-users.
• Other groups of individuals within the general population who may experience greater
exposures due to their proximity to conditions of use identified in Section 2.2 that result in
releases to the environment and subsequent exposures (e.g., individuals who live or work near
manufacturing, processing, distribution, use or disposal sites).
In developing exposure scenarios, EPA will evaluate available data to ascertain whether some human
receptor groups may be exposed via exposure pathways that may be distinct to a particular
subpopulation or lifestage (e.g., children's crawling, mouthing or hand-to-mouth behaviors) and
whether some human receptor groups may have higher exposure via identified pathways of exposure
due to unique characteristics (e.g., activities, duration or location of exposure) when compared with
the general population (U.S. EPA. 2006).
In summary, in the risk evaluation for 1,4-dioxane, EPA expects to consider the following potentially
exposed groups of human receptors: workers and occupational non-users. As described above, EPA
may also identify additional potentially exposed or susceptible subpopulations that will be considered
based on greater exposure.
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2.4 Hazards (Effects)
For scoping, EPA conducted comprehensive searches for data on hazards of 1,4-dioxane, as described
in Strategy for Conducting Literature Searches for 1,4-Dioxane: Supplemental File for the TSCA Scope
Document (IE PA- IH Q-0 IP PT-2016-0723). Based on initial screening, EPA expects to consider the hazards
of 1,4-dioxane identified in this scope document. However, when conducting the risk evaluation, the
relevance of each hazard within the context of a specific exposure scenario will be judged for
appropriateness. For example, hazards that occur only as a result of chronic exposures may not be
applicable for acute exposure scenarios. This means that it is unlikely that every hazard identified in
the scope will be considered for every exposure scenario.
2.4.1 Environmental Hazards
For scoping purposes, EPA consulted the following sources of environmental hazard data for
1,4-dioxane: Health Canada (2010): OECD (1999): ECJRC(2002): NO 38). However, EPA also
expects to consider other studies (e.g., more recently published, alternative test data) that have been
published since these reviews, as identified in the literature search conducted by the Agency for 1,4-
dioxane [1,4-Dioxane (CASRN 123-91-1) Bibliography: Supplemental File for the TSCA Scope Document,
IE IP A- H Q-0 IP PT-2016-07231. The OECD's High Production Volume (HPV) Chemicals program assessed
environmental hazards from 1,4-dioxane to fish, aquatic invertebrates and aquatic plants exposed
under acute and chronic exposure conditions. Exposure to 1,4-dioxane indicated acute toxicity to
aquatic invertebrates, based on mortality and immobilization, chronic toxicity to aquatic invertebrates
(growth and reproduction) and toxicity to aquatic plants (growth rate). No chronic effects occurred in
fish exposed to 1,4-dioxane.
EPA expects to consider the hazards of 1,4-dioxane to aquatic organisms including fish, aquatic
invertebrates and algae exposed to relevant media under acute and chronic exposure conditions. EPA
does not expect to consider the hazards of 1,4-dioxane to sediment invertebrates and terrestrial
organisms including soil invertebrates, birds and mammals because the physical and chemical
properties and high mobility in soil make presence in these media unlikely (see Section 2.3.1).
2.4.2 Human Health Hazards
1,4-Dioxane has an existing EPA IRIS Assessment (U.S. EPA. 2013, 2010), ATSDR Toxicological Profile
(ATSDR, 2012), Canada Screening Assessment (Health Canada. 2010), European Union (EU) Risk
Assessment Report (EQRC, 2002) and Interim AEGL (U.S. EPA. 2005b): hence, many of the hazards of
1,4-dioxane have been previously compiled and reviewed. EPA has relied heavily on these
comprehensive reviews in preparing this scope. EPA also expects to consider other studies (e.g., more
recently published, alternative test data) that have been published since these reviews, as identified in
the literature search conducted by the Agency for 1,4-dioxane [1,4-Dioxane (CASRN 123-91-1)
Bibliography: Supplemental File for the TSCA Scope Document, IE PA-IH Q-0 IP PT-2016-07231. EPA expects
to consider all potential hazards associated with 1,4-dioxane. Based on reasonably available
information, the following are the hazards that have been identified in previous government
documents and that EPA currently expects will likely be the focus of its analysis.
2.4.2.1 Non-Cancer Hazards
Acute Toxicity
Effects following acute exposures were evaluated (U.S. EPA. 2005b). The Interim AEGLs (U.S. EPA.
2005b) evaluated acute toxicity and irritation and concluded that, in animals, acute toxic effects of 1,4-
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dioxane include central nervous system depression, kidney and liver damage and irritation. Humans
acutely exposed to 1,4-dioxane experienced irritation of the eyes, nose and throat, nausea and
vomiting, coma and death. Also, 1,4-dioxane can cause narcosis in animals inhaling very high
concentrations (U.S. EPA. 2005b).
Irritation
Acute inhalation studies in human volunteers noted irritation of the eyes, nose and throat (U.S. EPA.
2005b). In rats, 2 years of inhalation exposure to 1,4-dioxane, resulted in metaplasia, hyperplasia,
atrophy, hydropic change, vacuolic change and preneoplastic cell proliferation in the nasal cavity (U.S.
EPA. 2013).
Liver Toxicity
In subchronic and chronic repeated exposure studies conducted in rats and mice by the oral (via
drinking water) and inhalation routes, evidence shows that 1,4-dioxane is toxic to the liver (U.S. EPA.
2013). Chronic administration of 1,4-dioxane via the drinking water resulted in hepatocellular
degeneration and preneoplastic changes. Inhalation exposure to 1,4-dioxane resulted in necrosis of the
centrilobular region and preneoplastic changes in the liver.
Kidney Toxicity
In subchronic and chronic repeated exposure studies conducted in rats and mice by the oral (via
drinking water) and inhalation routes, evidence shows that 1,4-dioxane is toxic to the kidney (U.S. EPA.
2013). Kidney damage following drinking water exposure to 1,4-dioxane includes degeneration of
cortical tubule cells, necrosis with hemorrhage and glomerulonephritis.
2.4.2.2 Genotoxicity and Cancer Hazards
U.S. EPA (2013) concluded that overall, the available literature indicates that 1,4-dioxane is
nongenotoxic or weakly genotoxic. Per EPA's Cancer Guidelines (U.S. EPA. 2005a), EPA concluded that
"there is insufficient biological support for potential key events and to have reasonable confidence in
the sequence of events and how they relate to the development of nasal tumors following exposure to
1,4-dioxane". The mode of action by which 1,4-dioxane produces liver, nasal, peritoneal
(mesotheliomas) and mammary gland tumors was not conclusive, and the available data did not
support any hypothesized carcinogenic mode of action for 1,4-dioxane.
EPA evaluated the weight of the evidence for cancer in humans and animals and concluded that
1,4-dioxane is "likely to be carcinogenic to humans" based on evidence of carcinogenicity in several
2-year bioassays (oral and inhalation) conducted in four strains of rats, two strains of mice and in
guinea pigs (U.S. EPA. 2013). Human occupational studies into the association between 1,4-dioxane
exposure and increased cancer risk are inconclusive because they are limited by small cohort size and a
small number of reported cancer cases.
2.4.2.3 Potentially Exposed or Susceptible Subpopulations
TSCA requires that the determination of whether a chemical substance presents an unreasonable risk
include consideration of unreasonable risk to "a potentially exposed or susceptible subpopulation
identified as relevant to the risk evaluation" by EPA. TSCA § 3(12) states that "the term 'potentially
exposed or susceptible subpopulation' means a group of individuals within the general population
identified by the Administrator who, due to either greater susceptibility or greater exposure, may be at
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greater risk than the general population of adverse health effects from exposure to a chemical
substance or mixture, such as infants, children, pregnant women, workers, or the elderly." In
developing the hazard assessments, EPA will evaluate available data to ascertain whether some human
receptor groups may have greater susceptibility than the general population to the chemical's
hazard(s).
The IRIS assessment for 1,4-dioxane U.S. EPA (2013) found no direct evidence that certain populations
and lifestages may be more susceptible to 1,4-dioxane. Information on induction of liver enzymes,
genetic polymorphisms and gender differences was inadequate to quantitatively assess toxicokinetic or
toxicodynamic differences in 1,4-dioxane hazard between animals and humans and the potential
variability in human susceptibility.
2.5 Initial Conceptual Models
A conceptual model describes the actual or predicted relationships between the chemical substance
and receptors, either human or environmental. These conceptual models are integrated depictions of
the conditions of use, exposures (pathways and routes), hazards and receptors. As part of the scope for
1,4-dioxane, EPA developed three conceptual models, presented here.
2.5.1 Initial Conceptual Model for Industrial and Commercial Activities and Uses:
Potential Exposures and Hazards
Figure 2-2 presents the initial conceptual model for human receptors from industrial and commercial
activities and uses of 1,4-dioxane. EPA expects that workers and occupational non-users may be
exposed to 1,4-dioxane via dermal and inhalation routes during manufacturing, processing,
distribution, use and disposal of 1,4-dioxane. EPA also expects to consider potential worker exposure
through mists that deposit in the upper respiratory tract and are swallowed.
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INDUSTRIAL AND COMMERCIAL EXPOSURE PATHWAY EXPOSURE ROUTE RECEPTORS41 HAZARDS
ACTIVITES / USES a
Manufacture
(Including import)
Liquid Contact
Dermal
Hazards Potentially Associated
with Acute and/or Chronic
Exposures
See Section 2.4.2
Processing :
• Processing as a
reacta nt/intcr med i ate
• Repackaging
• Non-incorporative
activities
Vapor/ Mist
Fugitive
missions11
Outdoor Air
(See Figure 2 3 tor Air
I missions)
Recycling
Processing Aids, Not
Otherwise Listed
Stack
I missions
Air Pollution Control
Functional I luids
{Closed System)
Laboratory Chemicals
Other Industrial or
Commercial Uses
Workers e,
Occupational
Non-users
Liquid Contact, Vapor
-» Dermal, Inhalation
Wastewater, Liquid Wastes, Solid Wastes
(Sec Figure 2-3)
Figure 2-2. Initial 1,4-Dioxane Conceptual Model for Industrial and Commercial Activities and Uses: Potential Exposures and Hazards
The conceptual model presents the exposure pathways, exposure routes and hazards to human receptors from industrial and commercial
activities and uses of 1,4-dioxane.
a Additional uses of 1,4-dioxane are included in Table 2-3.
b Stack air emissions are emissions that occur through stacks, confined vents, ducts, pipes or other confined air streams. Fugitive air emissions are those that are not
stack emissions, and include fugitive equipment leaks from valves, pump seals, flanges, compressors, sampling connections, open-ended lines; evaporative losses from
surface impoundment and spills; and releases from building ventilation systems.
c Exposure may occur through mists that deposit in the upper respiratory tract and are swallowed.
d Receptors include potentially exposed or susceptible subpopulations.
e When data and information are available to support the analysis, EPA also considers the effect that engineering controls and/or personnel protective equipment have
on occupational exposure levels.
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2.5.2 Initial Conceptual Model for Consumer Activities and Uses: Potential
Exposures and Hazards
As shown in the 1,4-dioxane initial life cycle diagram (Figure 2-1), no uses of 1,4-dioxane in consumer
products have been identified.
2.5.3 Initial Conceptual Model for Environmental Releases and Wastes: Potential
Exposures and Hazards
Figure 2-3 illustrates exposure pathways for human and ecological receptors from environmental
releases and waste disposal activities.
As shown in Figure 2-3, the potential pathways from industrial and commercial activities and waste
streams reflect the possible exposures to human and ecological receptors. EPA expects the general
populations living near industrial and commercial facilities using 1,4-dioxane will be exposed via
inhalation of outdoor air. General populations may also be exposed via ingestion of contaminated
drinking water, dermal and inhalation exposure from showering/bathing with contaminated drinking
water, and inhalation exposure from the migration of vapor in air, soil, or ground water to air. Aquatic
and terrestrial life may be exposed to 1,4-dioxane via contaminated surface water.
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RELEASES AND WASTES FROM EXPOSURE PATHWAY EXPOSURE ROUTE RECEPTORS6 HAZARDS
INDUSTRIAL / COMMERCIAL USES
Direct
Discharge
Water,
Sediment
Aquatic
Species
Indirect
Discharge
Biosolids
General
Population
Ground
water
Soil
Waste Transport
Air
Terrestrial
Species
Human Health Pathway
Emissions to Air
POTW
Wastewater or
Liquid Wastes*
Off-site Waste
Transfer
Underground
injection
Inhalation d
Oral, Dermal,
Inhalation c
Recycling, Other
Treatment b
Liquid Wastes
Solid Wastes
Industrial Pre-
Treatment or
Industrial WWT
Incinerators
(Municipals
Hazardous Waste)
Municipal,
Hazardous Landfill
or Other Land
Disposal
Hazards Potentially Associated with Acute
and/or Chronic Exposures:
See Section 2.4.1
Hazards Potentially Associated with Acute
and/or Chronic Exposures:
See Section 2.4.1
Hazards Potentially Associated with Acute
and/or Chronic Exposures:
See Section 2.4.2
Ecological Pathway
Figure 2-3. Initial 1,4-Dioxane Conceptual Model for Environmental Releases and Wastes: Potential Exposures and Hazards
The conceptual model presents the exposure pathways, exposure routes and hazards to human and environmental receptors from
environmental releases and wastes of 1,4-dioxane,
a Industrial wastewater or liquid wastes may be treated on-site and then released to surface water (direct discharge), or pre-treated and released to POTW (indirect
discharge). Drinking water will undergo further treatment in drinking water treatment plants. Ground water may also be a source of drinking water.
b Additional releases may occur from recycling and other waste treatment.
d Volatilization from or liquid contact with tap water in the home during showering, bathing, washing, etc. represents another potential in-home exposure pathway.
e Presence of mist is not expected; dermal and oral exposure are negligible.
f Receptors include potentially exposed or susceptible subpopulations.
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2.6 Initial Analysis Plan
The initial analysis plan will be used to develop the eventual problem formulation and final analysis
plan for the risk evaluation. While EPA has conducted a search for readily available data and
information from public sources as described in Section 1.3, EPA encourages submission of additional
existing data, such as full study reports or workplace monitoring from industry sources, that may be
relevant for refining conditions of use, exposures, hazards and potentially exposed or susceptible
subpopulations.
The analysis plan outlined here is based on the conditions of use of 1,4-dioxane, as described in Section
2.2 of this scope. The analysis plan may be refined as EPA proceeds with the systematic review of the
information in the 1,4-Dioxane (CASRN123-91-1) Bibliography: Supplemental File for the TSCA Scope
Document (E IP A- IH Q-Q P PT-2016-0723]. EPA will be evaluating the weight of the scientific evidence for
both hazard and exposure. Consistent with this approach, EPA will also use a systematic review
approach. As such, EPA will use explicit, pre-specified criteria and approaches to identify, select, assess,
and summarize the findings of studies. This approach will help to ensure that the review is complete,
unbiased, reproducible, and transparent.
2.6.1 Exposure
2.6.1.1 Environmental Releases
EPA expects to consider and analyze releases to environmental media as follows:
1) Review reasonably available published literature or information on processes and activities
associated with the conditions of use to evaluate the types of releases and wastes generated.
2) Review reasonably available chemical-specific release data, including measured or estimated
release data (e.g., data collected under the TRI and National Emissions Inventory [NEI]
programs).
3) Review reasonably available measured or estimated release data for surrogate chemicals that
have similar uses, volatility, chemical and physical properties.
4) Understand and consider regulatory limits that may inform estimation of environmental
releases.
5) Review and determine applicability of OECD Emission Scenario Documents and EPA Generic
Scenarios to estimation of environmental releases.
6) Evaluate the weight of the evidence of environmental release data.
7) Map or group each condition(s) of use to a release assessment scenario.
2.6.1.2 Environmental Fate
EPA expects to consider and analyze fate and transport in environmental media as follows:
1) Review reasonably available measured or estimated environmental fate endpoint data
collected through the literature search.
2) Using measured data and/or modeling, determine the influence of environmental fate
endpoints (e.g., persistence, bioaccumulation, partitioning, transport) on exposure pathways
and routes of exposure to human and environmental receptors.
3) Evaluate the weight of the evidence of environmental fate data.
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2.6.1.3 Environmental Exposures
EPA expects to consider the following in developing its environmental exposure assessment of
1,4-dioxane:
1) Review reasonably available environmental and biological monitoring data for all media
relevant to environmental exposure.
2) Review reasonably available information on releases to determine how modeled estimates of
concentrations near industrial point sources compare with available monitoring data. Available
exposure models will be evaluated and considered alongside available monitoring data to
characterize environmental exposures. Modeling approaches to estimate surface water
concentrations, sediment concentrations and soil concentrations generally consider the
following inputs: release into the media of interest, fate and transport and characteristics of the
environment.
3) Review reasonably available biomonitoring data. Consider whether these monitoring data could
be used to compare with species or taxa-specific toxicological benchmarks.
4) Determine applicability of existing additional contextualizing information for any monitored
data or modeled estimates during risk evaluation. Review and characterize the spatial and
temporal variability, to extent data are available, and characterize exposed aquatic and
terrestrial populations.
5) Evaluate the weight of evidence of environmental occurrence data and modeled estimates.
6) Map or group each condition(s) of use to environmental assessment scenario(s).
2.6.1.4 Occupational Exposures
EPA expects to consider and analyze both worker and occupational non-user exposures as follows:
1) Review reasonably available exposure monitoring data for specific condition(s) of use. Exposure
data to be reviewed may include workplace monitoring data collected by government agencies
such as OSHA and the NIOSH, and monitoring data found in published literature (e.g., personal
exposure monitoring data (direct measurements) and area monitoring data (indirect
measurements).
2) Review reasonably available exposure data for surrogate chemicals that have uses, volatility
and chemical and physical properties similar to 1,4-dioxane.
3) For conditions of use where data are limited or not available, review existing exposure models
that may be applicable in estimating exposure levels.
4) Review reasonably available data that may be used in developing, adapting or applying
exposure models to the particular risk evaluation.
5) Consider and incorporate applicable engineering controls and/or personal protective
equipment into exposure scenarios.
6) Evaluate the weight of the evidence of occupational exposure data.
Map or group each condition of use to occupational exposure assessment scenario(s).
2.6.1.5 Consumer Exposures
EPA does not expect to consider and analyze consumer exposures in the risk evaluation (see Section
2.3.5.2).
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2.6.1.6 General Population
EPA expects to consider and analyze general population exposures as follows:
1) Review reasonably available environmental and biological monitoring data for media to which
general population exposures are expected.
2) For exposure pathways where data are not available, review existing exposure models that may
be applicable in estimating exposure levels.
3) Consider and incorporate applicable media-specific regulations into exposure scenarios or
modeling.
4) Review reasonably available data that may be used in developing, adapting or applying
exposure models to the particular risk evaluation. For example, existing models developed for a
chemical assessment may be applicable to another chemical assessment if model parameter
data are available.
5) Review reasonably available information on releases to determine how modeled estimates of
concentrations near industrial point sources compare with available monitoring data.
6) Review reasonably available population- or subpopulation-specific exposure factors and activity
patterns to determine if potentially exposed or susceptible subpopulations need be further
defined.
7) Evaluate the weight of the evidence of general population exposure data.
8) Map or group each condition of use to general population exposure assessment scenario(s).
2.6,2 Hazards (Effects)
2.6.2.1 Environmental Hazards
EPA expects to conduct an environmental hazard assessment of 1,4-dioxane as follows:
1) Review reasonably available environmental hazard data, including data from alternative test
methods (e.g., computational toxicology and bioinformatics; high-throughput screening
methods; data on categories and read-across; in vitro studies).
2) Conduct hazard identification (the qualitative process of identifying acute and chronic
endpoints) and concentration-response assessment (the quantitative relationship between
hazard and exposure) for all identified environmental hazard endpoints.
3) Derive concentrations of concern (COC) for all identified ecological endpoints.
4) Evaluate the weight of the evidence of environmental hazard data.
5) Consider the route(s) of exposure, available biomonitoring data and available approaches to
integrate exposure and hazard assessments.
2.6.2.2 Human Health Hazards
EPA expects to consider and analyze human health hazards as follows:
1) Review reasonably available human health hazard data, including data from alternative test
methods (e.g., computational toxicology and bioinformatics; high-throughput screening
methods; data on categories and read-across; in vitro studies; systems biology).
2) In evaluating reasonably available data, determine whether particular human receptor groups
may have greater susceptibility to the chemical's hazard(s) than the general population.
3) Conduct hazard identification (the qualitative process of identifying non-cancer and cancer
endpoints) and dose-response assessment (the quantitative relationship between hazard and
exposure) for all identified human health hazard endpoints.
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4) Derive points of departure (PODs) where appropriate; conduct benchmark dose modeling
depending on the available data. Adjust the PODs as appropriate to conform (e.g., adjust for
duration of exposure) to the specific exposure scenarios evaluated.
5) Evaluate the weight of the evidence of human health hazard data.
6) Consider the route(s) of exposure (oral, inhalation, dermal), available route-to-route
extrapolation approaches, available biomonitoring data and available approaches to correlate
internal and external exposures to integrate exposure and hazard assessment.
2,6,3 Risk Characterization
Risk characterization is an integral component of the risk assessment process for both ecological and
human health risks. EPA will derive the risk characterization in accordance with EPA's Risk
Characterization Handbook (U.S. EPA. 2000). As defined in EPA's Risk Characterization Policy, "the risk
characterization integrates information from the preceding components of the risk evaluation and
synthesizes an overall conclusion about risk that is complete, informative and useful for decision
makers." Risk characterization is considered to be a conscious and deliberate process to bring all
important considerations about risk, not only the likelihood of the risk but also the strengths and
limitations of the assessment, and a description of how others have assessed the risk into an
integrated picture.
Risk characterization at EPA assumes different levels of complexity depending on the nature of the risk
assessment being characterized. The level of information contained in each risk characterization varies
according to the type of assessment for which the characterization is written. Regardless of the level of
complexity or information, the risk characterization for TSCA risk evaluations will be prepared in a
manner that is transparent, clear, consistent and reasonable (TCCR) (U.S. EPA. 2000). EPA will also
present information in this section consistent with approaches described in the Risk Evaluation
Framework Rule.
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APPENDICES
Appendix A REGULATORY HISTORY
A.l Federal Laws and Regulations
Table_Apx A-l. Federal Laws and Regulations
Statutes/Regulations
Description of
Authority/Regulation
Description of Regulation
EPA Regulations
TSCA - Section 6(b)
EPA is directed to identify and
begin risk evaluations on 10
chemical substances drawn from
the 2014 update of the TSCA
Work Plan for Chemical
Assessments.
1,4-Dioxane is on the initial list of
chemicals to be evaluated for risk
under TSCA (81 FR 91927, December
19, 2016).
TSCA - Section 8(a)
The TSCA section 8(a) CDR Rule
requires manufacturers
(including importers) to give EPA
basic exposure-related
information on the types,
quantities and uses of chemical
substances produced
domestically and imported into
the United States.
1,4-Dioxane manufacturing (including
importing), processing distribution
and use information is reported under
the CDR rule information about
chemicals in commerce in the United
States.
TSCA - Section 8(b)
EPA must compile, keep current
and publish a list (the TSCA
Inventory) of each chemical
substance manufactured or
processed in the United States.
1,4-Dioxane was on the initial TSCA
Inventory and therefore was not
subject to EPA's new chemicals review
process.
TSCA - Section 8(e)
Manufacturers (including
importers), processors and
distributors must immediately
notify EPA if they obtain
information that supports the
conclusion that a chemical
substance or mixture presents a
substantial risk of injury to
health or the environment.
Ten substantial risk reports from 1989
to 2004 (US EPA, ChemView. Accessed
April 13, 2017).
EPCRA - Section 313
Requires annual reporting from
facilities in specific industry
1,4-Dioxane is a listed substance
subject to reporting requirements
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Statutes/Regulations
Description of
Authority/Regulation
Description of Regulation
sectors that employ 10 or more
full time equivalent employees
and that manufacture, process
or otherwise use a TRI-Iisted
chemical in quantities above
threshold levels.
under 40 CFR 372.65 effective as of
January 01,1987.
Federal Food, Drug, and
Cosmetic Act (FFDCA) -
Section 408
FFDCA governs the allowable
residues of pesticides in food.
Section 408 of the FFDCA
provides EPA with the authority
to set tolerances (rules that
establish maximum allowable
residue limits) or exemptions
from the requirement of a
tolerance, for all residues of a
pesticide (including both active
and inert ingredients) that are in
or on food. Prior to issuing a
tolerance or exemption from
tolerance, EPA must determine
that the tolerance or exemption
is "safe." Sections 408(b) and (c)
of the FFDCA define "safe" to
mean the Agency has reasonable
certainty that no harm will result
from aggregate exposures to the
pesticide residue, including all
dietary exposure and all other
exposure (e.g., non-occupational
exposures) for which there is
reliable information. Pesticide
tolerances or exemptions from
tolerance that do not meet the
FFDCA safety standard are
subject to revocation. In the
absence of a tolerance or an
exemption from tolerance, a
food containing a pesticide
residue is considered
adulterated and may not be
distributed in interstate
commerce.
In 1998,1,4-dioxane was removed
from the list of pesticide product inert
ingredients because it was no longer
being used in pesticide products.
1,4-Dioxane is also no longer exempt
from the requirement of a tolerance
(the maximum residue level that can
remain on food or feed commodities
under 40 CFR Part 180, Subpart D).
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Statutes/Regulations
Description of
Authority/Regulation
Description of Regulation
CAA-Section 111(b)
Requires EPA to establish new
source performance standards
(NSPS) for any category of new
or modified stationary sources
that EPA determines causes, or
contributes significantly to, air
pollution, which may reasonably
be anticipated to endanger
public health or welfare. The
standards are based on the
degree of emission limitation
achievable through the
application of the best system of
emission reduction (BSER) which
(taking into account the cost of
achieving reductions and
environmental impacts and
energy requirements) EPA
determines has been adequately
demonstrated.
1,4-Dioxane is subject to the NSPS for
equipment leaks of volatile organic
compounds (VOCs) in the synthetic
organic chemicals manufacturing
industry for which construction,
reconstruction or modification began
after 1/5/1981 and on or before
11/7/2006 (40 CFR Part 60, Subpart
VV).
CAA-Section 112(b)
Defines the original list of 189
hazardous air pollutants (HAP).
Under 112(c) of the CAA, EPA
must identify and list source
categories that emit HAP and
then set emission standards for
those listed source categories
under CAA section 112(d). CAA
section 112(b)(3)(A) specifies
that any person may petition the
Administrator to modify the list
of HAP by adding or deleting a
substance.
1,4-Dioxane is listed as a HAP under
section 112 (42 U.S.C. § 7412) of the
CAA.
CAA-Section 112(d)
Section 112(d) states that the
EPA must establish (NESHAPs for
each category or subcategory of
major sources and area sources
of HAPs [listed pursuant to
Section 112(c)]. The standards
must require the maximum
degree of emission reduction
that the EPA determines to be
There are a number of source-specific
NESHAPs that are applicable to 1,4-
dioxane, including:
Organic Hazardous Air Pollutants
from the Synthetic Organic
Chemical Manufacturing Industry
(40 CFR Part 63, Subpart F),
Organic Hazardous Air Pollutants
from the Synthetic Organic
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Statutes/Regulations
Description of
Authority/Regulation
Description of Regulation
achievable by each particular
source category. Different
criteria for maximum achievable
control technology (MACT) apply
for new and existing sources.
Less stringent standards, known
as generally available control
technology (GACT) standards,
are allowed at the
Administrator's discretion for
area sources.
Chemical Manufacturing Industry
for Process Vents, Storage Vessels,
Transfer Operations, and
Wastewater (40 CFR Part 63,
Subpart G)
Off-Site Waste and Recovery
Operations (40 CFR Part 63, Subpart
DD),
Wood Furniture Manufacturing
Operations (40 CFR Part 63, Subpart
JJ),
Pharmaceuticals Production (40 CFR
Part 63, Subpart GGG),
Group IV Polymers and Resins
(thermoplastic product
manufacturing) (40 CFR Part 63,
Subpart JJJ),
Organic Liquids Distribution (Non-
gasoline) (40 CFR Part 63, Subpart
EEEE),
Miscellaneous Organic Chemical
Manufacturing (40 CFR Part 63,
Subpart FFFF),
Rubber Tire Manufacturing (40 CFR
Part 63, Subpart XXXX),
Site Remediation (40 CFR Part 63,
Subpart GGGGG), and
Miscellaneous Coating
Manufacturing (40 CFR Part 63,
Subpart HHHHH).
Comprehensive
Environmental Response,
Compensation and Liability
Act (CERCLA) - Sections
102(a) and 103
Authorizes EPA to promulgate
regulations designating as
hazardous substances those
substances which, when
released into the environment,
may present substantial danger
to the public health or welfare or
the environment. EPA must also
promulgate regulations
establishing the quantity of any
hazardous substance the release
1,4-Dioxane is a hazardous substance
under CERCLA. Releases of 1,4-
dioxane in excess of 100 pounds must
be reported (40 CFR 302.4).
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Statutes/Regulations
Description of
Authority/Regulation
Description of Regulation
of which must be reported under
Section 103.
Section 103 requires persons in
charge of vessels or facilities to
report to the National Response
Center if they have knowledge of
a release of a hazardous
substance above the reportable
quantity threshold.
Safe Drinking Water Act
(SDWA) - Section 1412(b)
Every 5 years, EPA must publish
a list of contaminants that: (1)
are currently unregulated, (2)
are known or anticipated to
occur in public water systems
(PWSs) and (3) may require
regulations under SDWA. EPA
must also determine whether to
regulate at least five
contaminants from the list every
5 years.
1,4-dioxane was identified on both the
Third (2009) and Fourth (2016)
Contaminant Candidate List (CCL) (74
FR 51850, October 8, 2009) (81 FR
81099, November 17, 2016).
SDWA-Section 1445(a)
Every 5 years, EPA must issue a
new list of no more than
30 unregulated contaminants to
be monitored by PWSs. The data
obtained must be entered into
the National Drinking Water
Contaminant Occurrence
Database.
1,4-dioxane was identified in the third
UCMR, issued in 2012 (77 FR 26072,
May 2, 2012).
RCRA - Section 3001
Directs EPA to develop and
promulgate criteria for
identifying the characteristics of
hazardous waste, and for listing
hazardous waste, taking into
account toxicity, persistence,
and degradability in nature,
potential for accumulation in
tissue and other related factors
such as flammability,
corrosiveness, and other
hazardous characteristics.
In 1980,1,4-dioxane became a listed
hazardous waste in 40 CFR 261.33 -
Discarded commercial chemical
products, off-specification species,
container residues, and spill residues
thereof (U108) (45 FR 33084).
Other federal regulations
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Statutes/Regulations
Description of
Authority/Regulation
Description of Regulation
FFDCA
Provides the U.S. Food and Drug
Administration (FDA) with
authority to oversee the safety
of food, drugs and cosmetics.
FDA established a limit of 10 mg/kg on
the amount of 1,4-dioxane that can be
present in the food additive glycerides
and polyglycides of hydrogenated
vegetable oils (21 CFR 172.736 and 71
FR 12618, March 13, 2006).
Occupational Safety and
Health Act
Requires employers to provide
their workers with a place of
employment free from
recognized hazards to safety and
health, such as exposure to toxic
chemicals, excessive noise levels,
mechanical dangers, heat or cold
stress or unsanitary conditions.
Under the Act, OSHA can issue
occupational safety and health
standards including such
provisions as PELs, exposure
monitoring, engineering and
administrative control measures
and respiratory protection.
In 1989, OSHA established a PEL for
1,4-dioxane of 100 ppm or 360 mg/m3
as an 8-hour, TWA (29 CFR
1910.1001).
While OSHA has established a PEL for
1,4-dioxane, OSHA has recognized
that many of its PELs are outdated and
inadequate for ensuring the
protection of worker health. 1,4-
Dioxane appears in OSHA's annotated
PEL tables, wherein OSHA
recommends that employers follow
the California OSHA limit of 0.28 ppm,
the NIOSH REL of 1 ppm as a 30-
minute ceiling or the ACGIH TLV of
20 ppm (8-hour TWA).
Atomic Energy Act
The Atomic Energy Act
authorizes the Department of
Energy to regulate the health
and safety of its contractor
employees
10 CFR 851.23, Worker Safety and
Health Program, requires the use of
the 2005 ACGIH TLVs if they are more
protective than the OSHA PEL.
Federal Hazardous
Materials Transportation
Act
Section 5103 of the Act directs
the Secretary of Transportation
to:
Designate material (including
an explosive, radioactive
material, infectious
substance, flammable or
combustible liquid, solid or
gas, toxic, oxidizing or
corrosive material and
compressed gas) as
hazardous when the
Secretary determines that
transporting the material in
The Department of Transportation
(DOT) has designated 1,4-dioxane as a
hazardous material, and there are
special requirements for marking,
labeling and transporting it (49 CFR
Part 171, 40 CFR 173.202 and 40 CFR
173.242).
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Statutes/Regulations
Description of
Authority/Regulation
Description of Regulation
commerce may pose an
unreasonable risk to health
and safety or property.
Issue regulations for the safe
transportation, including
security, of hazardous
material in intrastate,
interstate and foreign
commerce.
A.2 State Laws and Regulations
Table_Apx A-2. State Laws and Regulations
State Actions
Description of Action
State PELs
California PEL: 0.28 ppm (Cal Code Regs. Title 8, § 5155).
State Right-to-Know Acts
New Jersey (8:59 N.J. Admin. Code § 9.1), Pennsylvania (34 Pa.
Code § 323).
State air regulations
Allowable Ambient Levels (AAL): New Hampshire (RSA 125-1:6,
ENV-A Chap. 1400), Rhode Island (12 R.I. Code R. 031-022).
State drinking/ground water limits
Massachusetts (310 Code Mass. Regs. § 22.00), Michigan (DEQ
2016).
Chemicals of high concern to
children
Several states have adopted reporting laws for chemicals in
children's products that include 1,4-dioxane, such as Oregon
(Toxic-Free Kids Act, Senate Bill 478, 2015) Vermont (Code Vt. R. §
13-140-077) and Washington State (Wash. Admin. Code § 173-
334-130).
Other
In California, 1,4-dioxane was added to the Proposition 65 list in
1988 (Cal. Code Regs, title 27, § 27001).
A.3 International Laws and Regulations
Table_Apx A-3. Regulatory Actions by other Governments and Tribes
Country/Organization
Requirements and Restrictions
Canada
1,4-Dioxane is on the Cosmetic Ingredient Hotlist as a substance
prohibited for use in cosmetics. 1,4-Dioxane is also included in
Canada's National Pollutant Release Inventory (NPRI), the publicly-
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Country/Organization
Requirements and Restrictions
accessible inventory of pollutants released, disposed of and sent for
recycling by facilities across the country (Government of Canada,
2010.1,4-Dioxane. Accessed April 18, 2017).
Australia
In 1994, 1,4-dioxane was assessed. A workplace product containing
more than 0.1% 1,4-dioxane is classed as a hazardous substance.
1,4-Dioxane is in Class 3, (Packing Group II) under the Australian
Dangerous Goods Code (National Industrial Chemicals Notification
and Assessment Scheme, NICNAS, 2013, Dioxane (1,4-Dioxane).
Accessed April, 18 2017).
Japan
1,4-dioxane is regulated in Japan under the following legislation:
• Act on the Evaluation of Chemical Substances and Regulation
of Their Manufacture, etc. (Chemical Substances Control
Law; CSCL)
• Act on Confirmation, etc. of Release Amounts of Specific
Chemical Substances in the Environment and Promotion of
Improvements to the Management Thereof
• Industrial Safety and Health Act (ISHA)
• Air Pollution Control Law
• Water Pollution Control Law
(National Institute of Technology and Evaluation (NITE) Chemical
Risk Information Platform (CHIRP), Accessed April 18, 2017).
Republic of Korea
The Ministry of the Environment recently adopted a provisional
water quality standard for human health of 50 |ag/L 1,4-dioxane in
drinking water (An et al, 2014).
Australia, Austria, Belgium,
Canada, Denmark, European
Union (EU), Finland, France,
Germany, Hungary, Ireland,
Italy, Japan, Latvia, New
Zealand, People's Republic of
China, Poland, Singapore, South
Korea, Spain, Sweden,
Switzerland, The Netherlands,
Turkey, United Kingdom
Occupational exposure limits for 1,4-dioxane (GESTIS International
limit values for chemical agents (Occupational exposure limits, OELs)
database. Accessed April 18, 2017).
WHO
Established a tolerable daily intake of 16 |ag 1,4-dioxane/kg body
weight based on a no-observed-adverse-effect level (NOAEL) of 16
mg/kg body weight per day for hepatocellular tumors observed in a
long-term drinking-water study in rats. The WHO water quality
guideline is 0.05 mg/L 1,4-dioxane in drinking water (WHO 2005).
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Appendix B PROCESS, RELEASE AND OCCUPATIONAL EXPOSURE
INFORMATION
This appendix provides information and data found in preliminary data gathering for 1,4-dioxane.
B.l Process Information
Process-related information potentially relevant to the risk evaluation may include process diagrams,
descriptions and equipment. Such information may inform potential release sources and worker
exposure activities for consideration.
B.l.l Manufacture (Including Import)
The primary method for industrial production of 1,4-dioxane involves an acid-catalyzed conversion of
ethylene glycol (mono-, di-, tri- and polyethylene glycol may be used) by ring closure in a closed
system. The process is carried out at a temperature between 266 and 392°F (130 and 200°C) and a
pressure between 0.25 and 1.1 atm (25 and 110 kPa). The synthesis step is performed in a heated
vessel. The raw 1,4-dioxane product is then moved to a distillation column to start the purification
process. Multiple steps are used to purify the 1,4-dioxane, including separation from water and volatile
by-products by extractive distillation, heating with acids, salting out with NaCI, CaCh or NaOH, and fine
subsequent distillation (EGRC. 2002). The 1,4-dioxane manufacturing plant in Zachary, Louisiana
produces 1,4-dioxane using this reaction with diethylene glycol and concentrated sulfuric acid.
Figure_Apx B-l shows a process flow diagram for the process used by the manufacturer [EPA-HQ-
QPPT-2016-0723-0012 (BASF. 2017)1.
Components
Reaction
~isolation NeuVa Nation
D'stillafcn
F nal PioJuct
Fsed
Tank
DiSillajui
Colimr
Figure_Apx B-l: General Process Flow Diagram for 1,4-Dioxane Manufacturing
Source: EPA-HQ-QPPT-2016-0723-0012 (BASF. 2017).
Two other reactions can be used to make 1,4-dioxane, but they are primarily used to make substituted
dioxanes and not known to be used for industrial 1,4-dioxane production (ECJRC. 2002).
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B.1.2 Processing and Distribution
B.1.2.1 Processing as a Reactant/Intermediate
1,4-Dioxane can be used as a chemical reactant in the production of pharmaceuticals, polyethylene
terephthalate (PET) plastics, rubber, insecticides and pesticides, cement, deodorant fumigant,
magnetic tape and adhesives [EPA-HQ-QPPT-201 ¦ 0 1 3-0003 (U.S. EPA. 201?b)1. Exact process
operations involved in the use of 1,4-dioxane as a chemical reactant are dependent on the final
product that is being synthesized. For the use of 1,4-dioxane as a chemical reactant, operations would
typically involve unloading 1,4-dioxane from transport containers and feeding the 1,4-dioxane into a
reaction vessel(s), where the 1,4-dioxane would react either fully or to a lesser extent. Following
completion of the reaction, the produced substance may or may not be purified further, thus removing
unreacted 1,4-dioxane (if any exists). Reacted 1,4-dioxane is assumed to be destroyed and is thus not
expected to be released or cause potential worker exposures.
B.1.2.2 Processing - Non-Incorporative
1,4-Dioxane is used as a process solvent during the manufacturing of cellulose acetate, resins, waxes
and fats [EPA-HQ-OPPT-2Q \ __0 -3-0003 (U.S. EPA. 201?b)1.
B.1.2.3 Repackaging
Typical repackaging operations involve transferring of chemicals into appropriately sized containers to
meet customer demands/needs.
B.1.2.4 Recycling
1,4-Dioxane is used as a solvent in several applications. In this capacity, 1,4-dioxane can be
regenerated and recycled for reuse.
B.1.3 Uses
B.1.3.1 Processing Aids, Not Otherwise Listed
Processing aids are chemical substances used to improve the processing characteristics or the
operation of process equipment or to alter or buffer the pH of the substance or mixture, when added
to a process or to a substance or mixture to be processed. Processing agents do not become a part of
the reaction product and are not intended to affect the function of a substance or article created (U.S.
EPA. 2016a). 1,4-Dioxane is used in a number of industrial processes as a processing aid. These
processes include wood pulping, extraction of animal and vegetable oils, textile processing,
polymerization, pharmaceutical purification and etching of fluoropolymers [EPA-HQ-Q1 17-0723-
0003 (U.S. EPA. 2017b): EPA-HQ-QPPT-20 U. 0 23-0012 (BASF. 2017)1. Exact process operations
involved in the use of 1,4-dioxane as a processing aid are dependent on the final product that is being
synthesized.
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B.l.3.2 Functional Fluids (Closed System)
Functional fluids are liquid or gaseous chemical substances used for one or more operational
properties (U.S. EPA. 2016a). 1,4-Dioxane is used in polyalkylene glycol lubricants, synthetic
metalworking fluids, cutting and tapping fluids and hydraulic fluids [EPA-HQ-QPPT-2017-0723-0003
(U.S. EPA. 2017b)1. Exact operations involved in the use of 1,4-dioxane as a functional fluid are
dependent on the final product.
B.l.3.3 Laboratory Chemicals
1,4-Dioxane is used in laboratories as a chemical reagent, reference material, stable reaction medium,
liquid scintillation counting medium, spectroscopic and photometric measurement, cryoscopic solvent
and histological preparation rEPA~HQ~OPPT~2017~0723~0003 (U.S. EPA. 2017b)l. Laboratory procedures
are generally done within a fume hood, on a bench with local exhaust ventilation or under general
ventilation.
B.l.3.4 Adhesives and Sealants
1,4-Dioxane is found in film cement and as a residual contaminant in two-component glues and
adhesives [Eka-hu-ui-'i- i-zui/-u/za-uuua (u,5, tm, zui/p)1. The application procedure depends on
the type of adhesive and the type of substrate. After the adhesive is received by the user, it may be
diluted or mixed prior to application. The formulation is then loaded into the application reservoir or
apparatus and applied to the substrate via spray, roll, curtain or syringe or bead application.
Application may be manual or automated. After application, the adhesive or sealant is allowed to dry,
usually at ambient temperature, such that the solvent completely evaporates and a bond is formed
between the substrates (OECD, 2015).
B.l.3.5 Other Uses
Other conditions of use where 1,4-dioxane may be formulated into a product or used as part of
another process may include use in fuels and fuel additives rEPA-HQ-OPPT-2 '23-0012 (BASF.
2017)1, spray polyurethane foam and in printing and printing compositions [EPA-HQ-QPPT-2017-0723-
0003 (U.S. EPA. )].
B.1.4 Disposal
1,4-Dioxane is disposed of to a variety of environmental media: land, water and air. Land disposals
include Class I underground injection, RCRA Subtitle C landfills and to other uncategorized land points.
1,4-Dioxane is sometimes discharged to water. Wastewater treatment may or may not precede these
water releases. Additionally, 1,4-dioxane is also commonly incinerated (U.S. EPA. 2017c).
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B.2 Occupational Exposure Data
EPA presents below an example of occupational exposure-related information from the preliminary
data gathering. EPA will consider this information and data in combination with other data and
methods for use in the risk evaluation.
Table_Apx B 1 summarizes OSHA CEHD data by North American Industry Classification System (NAICS)
code (OSHA. 2017a. b).
Table_Apx B-l. Summary of Industry Sectors with 1,4-Dioxane Personal Monitoring Air Samples
Obtained from OSHA Inspections Conducted Between 2002 and 2016
NAICS
NAICS Description
315225
Men's and Boys' Cut and Sew Work Clothing Manufacturing
325199
All Other Basic Organic Chemical Manufacturing
334418
Printed Circuit Assembly (Electronic Assembly) Manufacturing
336399
All Other Motor Vehicle Parts Manufacturing
926150
Regulation, Licensing, and Inspection of Miscellaneous Commercial Sectors
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