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EPA Document# EPA-740-D-25-001
January 2025
United States Office of Chemical Safety and
Environmental Protection Agency Pollution Prevention
Draft Scope of the Risk Evaluation for Vinyl Chloride
(Ethene, chloro-)
CASRN 75-01-4
ci/^>ch2
January 2025
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27 TABLE OF CONTENTS
28 ACKNOWLEDGMENTS 6
29 EXECUTIVE SUMMARY 7
30 1 INTRODUCTION 10
31 1.1 Regulatory History 10
32 1.2 Assessment History 10
33 1.3 Reasonably Available Information 10
34 2 SCOPE OF THE RISK EVALUATION 12
35 2.1 Physical and Chemical Properties 12
36 2.2 Conditions of Use 13
37 2.2.1 Data and Information Sources 13
38 2.2.2 Categories and Subcategories of Conditions of Use Included in the Scope of the Risk
39 Evaluation 13
40 2.2.3 Activities Excluded from the Scope of the Risk Evaluation 16
41 2.2.4 Production Volume 17
42 2.2.5 Overview of Conditions of Use and Lifecycle Diagram 18
43 2.3 Exposures 20
44 2.3.1 Releases to the Environment 20
45 2.3.2 Fate and Transport 20
46 2.3.2.1 Intermedia Transport and Partitioning Behavior of Vinyl Chloride 20
47 2.3.2.2 Preliminary Media Assessments to Inform Fit-for-Purpose Analysis Plan 21
48 2.3.2.3 Air and Atmosphere 21
49 2.3.2.4 Aquatic Environments 21
50 2.3.2.5 Terrestrial Environments 22
51 2.3.2.6 BioaccumulationPotential 24
52 2.3.2.7 Vinyl Chloride as a Transformation Product 24
53 2.3.3 Environmental Exposures 25
54 2.3.4 Human Exposures 25
55 2.3.4.1 Occupational Exposures 25
56 2.3.4.2 Consumer Exposures 26
57 2.3.4.3 General Population Exposures 27
58 2.3.4.3.1 Inhalation 27
59 2.3.4.3.2 Oral 28
60 2.3.4.3.3 Dermal 29
61 2.3.4.4 Potentially Exposed or Susceptible Subpopulations: Exposure Considerations 29
62 2.4 Hazards 30
63 2.4.1 Environmental Hazards 30
64 2.4.2 Human Health Hazards 30
65 2.4.2.1 Non-cancer Hazards 30
66 2.4.2.1.1 Liver Toxicity 31
67 2.4.2.1.2 Neurotoxicity 31
68 2.4.2.1.3 Immunotoxicity 31
69 2.4.2.1.4 Developmental Toxicity 31
70 2.4.2.1.5 Other Hazards 32
71 2.4.2.2 Genotoxicity and Cancer Hazards 32
72 2.4.2.2.1 Cancer 32
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73 2.4.2.2.2 Genotoxi city/Mutagenicity and Other Mechanisms of Carcinogenicity 32
74 2.4.2.3 Potentially Exposed or Susceptible Subpopulations: Hazard Considerations 33
75 2.5 Conceptual Models 33
76 2.5.1 Conceptual Model for Industrial and Commercial Activities and Uses 33
77 2.5.1.1 Pathways EPA Plans to Quantitatively Analyze in the Risk Evaluation 36
78 2.5.1.2 Pathways EPA Plans to Qualitatively Analyze in the Risk Evaluation 36
79 2.5.2 Conceptual Model for Consumer Activities and Uses 36
80 2.5.2.1 Pathways EPA Plans to Quantitatively Analyze in the Risk Evaluation 38
81 2.5.2.2 Pathways EPA Plans to Qualitatively Analyze in the Risk Evaluation 38
82 2.5.3 Conceptual Model for Environmental Releases and Wastes 38
83 2.5.3.1 Pathways EPA Plans to Quantitatively Analyze in the Risk Evaluation 40
84 2.5.3.2 Releases, Pathways, Routes, and Populations That EPA Plans to Qualitatively
85 Analyze in the Risk Evaluation 40
86 2.5.3.2.1 Surface Water and Sediment 40
87 2.5.3.2.2 Landfill Leachate and Groundwater 40
88 2.5.3.2.3 Drinking Water 41
89 2.5.3.2.4 Soil 41
90 2.5.3.2.5 Land-Applied Biosolids Pathway 42
91 2.5.3.2.6 Aquatic Species 42
92 2.5.3.2.7 Terrestrial Species 43
93 2.5.3.2.8 Oral and Dermal 43
94 2.6 Analysis Plan 43
95 2.6.1 Exposure 43
96 2.6.1.1 Releases to the Environment 43
97 2.6.1.2 Fate and Transport 45
98 2.6.1.3 Environmental Exposures 46
99 2.6.1.4 Occupational Exposures 46
100 2.6.1.5 Consumer Exposures 48
101 2.6.1.6 General Population Exposures 49
102 2.6.2 Hazards 52
103 2.6.2.1 Environmental Hazards 52
104 2.6.2.2 Human Health Hazards 53
105 2.6.3 Risk Characterization 56
106 2.7 Peer Review 56
107 REFERENCES 58
108 APPENDICES 65
109 Appendix A ASSESSMENT HISTORY 65
110 Appendix B EVIDENCE MAPS OF VINYL CHLORIDE INFORMATION 67
111 B.l Fate and Transport 67
112 B.2 Occupational Exposure and Environmental Release 68
113 B.3 General Population, Consumer, and Environmental Exposure 69
114 B.4 Environmental Hazard 70
115 B. 5 Human Health Hazard 71
116 Appendix C ENVIRONMENTAL FATE PROPERTIES OF VINYL CHLORIDE 72
117
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LIST OF TABLES
Table 2-1. Physical and Chemical Properties of Vinyl Chloride 12
Table 2-2. Conditions of Use of Vinyl Chloride 14
Table 2-3. 1986 to 2019 National Aggregate Production Volume Data for Vinyl Chloride 18
LIST OF FIGURES
Figure 2-1. Preliminary Life Cycle Diagram for Vinyl Chloride 19
Figure 2-2. Reductive Dechlorination Pathway via Biodegradation in Anaerobic Environments 24
Figure 2-3. AirToxScreen Modeling Results for Vinyl Chloride, Based on 2020 NEI Data 28
Figure 2-4. Vinyl Chloride Conceptual Model for Industrial and Commercial Activities and Uses:
Worker and ONU Exposures and Hazards 35
Figure 2-5. Vinyl Chloride Conceptual Model for Consumer Activities and Uses: Consumer
Exposures and Hazards 37
Figure 2-6. Vinyl Chloride Conceptual Model for Environmental Releases and Wastes:
Environmental and General Population Exposures and Hazards 39
LIST OF APPENDIX TABLES
Table_Apx A-l. Assessment History 65
Table_Apx C-l. Environmental Fate Properties of Vinyl Chloride 72
LIST OF APPENDIX FIGURES
FigureApx B-l. Evidence Map of Environmental Fate and Transport Properties for Vinyl Chloride... 67
FigureApx B-2. Evidence Map of Occupational Exposure and Environmental Release Information
for Vinyl Chloride 68
Figure Apx B-3. Evidence Map of Consumer, General Population, and Environmental Exposure
Information for Vinyl Chloride 69
Figure Apx B-4. Evidence Map of Environmental Hazard Information for Vinyl Chloride 70
Figure Apx B-5. Evidence Map for Human Health Hazard Information for Vinyl Chloride 71
KEY ABBREVIATIONS AND ACRONYMS
ATSDR
Agency for Toxic Substances and Disease Registry
ANSI
American National Standards Institute
BAF
Bioaccumulation factor
BCF
Bioconcentration factor
CASRN
Chemical Abstracts Service Registry Number
CDR
Chemical Data Reporting
CEM
Consumer Exposure Model
CFR
Code of Federal Regulations
COU
Condition of use
DMR
Discharge Monitoring Report
EPA
(U.S.) Environmental Protection Agency (or the Agency)
ESD
Emission scenario document
FFDCA
Federal Food, Drug, and Cosmetic Act
FIFRA
Federal Insecticide, Fungicide, and Rodenticide Act
IRIS
Integrated Risk Information System
Koc
Organic carbon:water partition coefficient
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MCL
Maximum contaminant level
MOA
Mode of action
MRL
Minimal risk level
NEI
National Emissions Inventory
NIOSH
National Institute for Occupational Safety and Health
NSF
National Sanitation Foundation
OCSPP
Office of Chemical Safety and Pollution Prevention (EPA)
OECD
Organization for Economic Cooperation and Development
ONU
Occupational non-user
OPPT
Office of Pollution Prevention and Toxics (EPA)
ORD
Office of Research and Development (EPA)
OSHA
Occupational Safety and Health Administration
PCE
Perchloroethylene
PEL
Permissible exposure limit
PESS
Potentially exposed or susceptible subpopulation
POD
Point of departure
POTW
Publicly owned treatment works
PPE
Personal protective equipment
PVC
Polyvinyl chloride
SDWA
Safe Drinking Water Act
SDS
Safety data sheets
TCE
T ri chl oroethy 1 ene
TRI
Toxics Release Inventory
TSCA
Toxic Substances Control Act
U.S.
United States
VOC
Volatile organic compound
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ACKNOWLEDGMENTS
This draft scope and associated supplemental documents were developed by the United States
Environmental Protection Agency (EPA or the Agency), Office of Chemical Safety and Pollution
Prevention (OCSPP), Office of Pollution Prevention and Toxics (OPPT). The Assessment Team
gratefully acknowledges the participation, input, and review comments from OPPT and OCSPP senior
managers and science advisors. This draft scope was also reviewed by Agency colleagues in the Office
of Research and Development (ORD) and Office of Air and Radiation (OAR).
Docket
Supporting information can be found in the public docket, Docket ID: EPA-HQ-QPPT-2018-0448.
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.
Authors: Marcy Card (Scope Lead), Kesha Forrest (Management Lead and Branch Supervisor), Lillie
Marie Barnett, Albana Bega, Judith Brown, Emily Griffin, Franklyn Hall, Keith Jacobs, Kara Koehrn,
Catherine Ngo, Haley Skinner, and Olivia Wrightwood.
Collaborators: Amber Aranda and Bridget Eklund.
Technical Support: Mark Gibson and Hillary Hollinger.
This draft scope document was reviewed and cleared for release by OPPT and OCSPP leadership.
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EXECUTIVE SUMMARY
In December 2024, EPA designated vinyl chloride (CASRN 75-01-4)—a colorless gas at room
temperature and pressure—as a high-priority substance for risk evaluation following the prioritization
process as required by section 6(b) of the Toxic Substances Control Act (TSCA) and implementing
regulations (40 CFR Part 702) (Docket ID: EPA-HQ-QPPT-2018-0448). The first step of the chemical
risk evaluation process is the development of the draft scope document. Following its publication, EPA
will provide a 45-day comment period on the draft scope per 40 CFR 702.43(a). The Agency will
consider information received during the public comment period to both inform the finalization of the
scope document and the subsequent development of the draft risk evaluation for vinyl chloride. This
draft scope for vinyl chloride includes the conditions of use (COUs; also called TSCA COUs),
potentially exposed or susceptible subpopulations (PESS), hazards, and exposures that EPA expects to
consider in the risk evaluation—along with a description of the reasonably available information,
conceptual models, analysis plan and science approaches, and plan for peer review.
General Information
Vinyl chloride is listed on the TSCA Inventory with the name "ethene, chloro-." Vinyl chloride has total
production volume in the United States of between 10 and less than 20 billion pounds (lb) per year.
Reasonably Available Information
EPA leveraged the data and information sources already described in the Proposed Designation of Vinyl
Chloride as a High-Priority Substance for Risk Evaluation (U.S. EPA. 2024c) to inform the
development of this draft scope document. As described in the proposed designation document, EPA
applied systematic review methods to identify and screen reasonably available information across
multiple evidence streams (i.e., chemistry, fate, release and engineering, exposure, and hazard) for
consideration in the risk evaluation. This information includes the hazards, exposures, PESS, and TSCA
COUs that may help inform the risk evaluation for vinyl chloride. EPA has focused on the data
collection phase (consisting of data search and screening) during prioritization and preparation of this
draft scope; in contrast, the data extraction, evaluation, and integration stages will occur during the
development of the draft risk evaluation and thus are not part of the scoping activities described in this
document. EPA plans to consider additional information identified following release of the draft and
final scope, as appropriate, in developing the draft risk evaluation—including Chemical Data Reporting
(CDR) information that the Agency received in November 2024.
Conditions of Use
Vinyl chloride COUs are presented in Section 2.2. EPA plans to evaluate manufacturing (including
importing); processing; distribution in commerce; industrial, commercial, and consumer uses; and
disposal of vinyl chloride in the risk evaluation. Vinyl chloride is manufactured domestically and
imported into the United States. The chemical is processed as a reactant; incorporated into a
formulation, mixture, or reaction product; incorporated into articles; and used in other industrial and
commercial processes. The identified processing activities also include the repackaging and recycling of
vinyl chloride. All of the identified industrial, commercial, and consumer uses are related to vinyl
chloride serving as a monomer in plastics—primarily polyvinyl chloride (PVC)—and other polymers.
EPA identified these COUs from information reported to the Agency through CDR, public comments,
and other publicly available data sources, including emissions databases, safety data sheets (SDSs),
published literature, and company websites.
Conceptual Model
The conceptual models for vinyl chloride are presented in Section 2.5. These are graphical depictions of
the actual or predicted relationships of COUs, exposure pathways (e.g., media), exposure routes (e.g.,
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inhalation, dermal, oral), hazards, and populations throughout the life cycle of the chemical. EPA
considered reasonably available information, including public comments, in considering the exposure
pathways, exposure routes, and hazards the Agency expects to evaluate in the risk evaluation.
Furthermore, EPA's plan for evaluating exposure in the scope of the risk evaluation considers major or
minor exposure pathways and routes based on physical and chemical information (Section 2.1), release
information (Section 2.3.1), fate and transport properties (Section 2.3.1.1), and other information such as
industry standards in PVC production. The Agency expects to focus the risk evaluation for vinyl
chloride on the exposures and hazards listed below, with a fit-for-purpose approach determining the
level and types of analysis (i.e., quantitative or qualitative) conducted for each exposure route, pathway,
and population (40 CFR 702.37(a)(4)):
• Exposures (Pathways and Routes), Populations, and PESS: EPA plans to evaluate releases to the
environment as well as both human and environmental exposures resulting from vinyl chloride
COUs that the Agency expects to consider in the risk evaluation. Exposures to vinyl chloride are
discussed in Section 2.3. Vinyl chloride is a gas at room temperature (Section 2.1), more than 98
percent of vinyl chloride releases are to air (Section 2.3.1), and vinyl chloride is not expected to
significantly partition from air into other environmental media (Section 2.3.1.1). Thus, EPA
plans to quantitatively assess inhalation exposures in occupational settings, to consumers and
bystanders, and to the general population. The Agency also plans also to qualitatively assess
other exposures to vinyl chloride (Section 2.5). Additional information gathered through
systematic review searches will also inform expected exposures.
EPA considered reasonably available information and comments received on the proposed
designation document for vinyl chloride in determining the relevancy of human and
environmental exposure pathways, routes, populations, and PESS for inclusion in this draft
scope. The Agency expects to evaluate the following human and environmental exposure
pathways, routes, populations, and PESS in the scope of the risk evaluation:
- Occupational Exposure: EPA plans to quantitatively evaluate exposures to workers and
occupational non-users (ONUs) via the inhalation route and to qualitatively assess
exposures only to workers—not ONUs—via the dermal route associated with the
manufacturing, processing, distribution, use, and disposal of vinyl chloride.
- Consumer and Bystander Exposure: EPA plans to quantitatively evaluate inhalation
exposures to vinyl chloride vapor for consumers and bystanders during use of products
containing vinyl chloride. The Agency further plans to qualitatively assess oral and
dermal exposures to consumer products and articles containing residual vinyl chloride
monomer.
- General Population Exposure: EPA plans to quantitatively evaluate general population
exposures to vinyl chloride from inhalation of ambient air and to qualitatively assess
exposures via other media.
- PESS: EPA plans to include children, women of reproductive age (i.e., developmental
exposures), workers, populations who live near a facility releasing vinyl chloride, and
consumers as PESS in the risk evaluation due to the potential for increased exposure
and/or susceptibility to vinyl chloride in these groups.
- Environmental Exposures: EPA plans to qualitatively evaluate exposure to vinyl chloride
for aquatic and terrestrial organisms.
• Hazards: Hazards for vinyl chloride are discussed in Section 2.4. EPA completed preliminary
reviews of information (e.g., U.S. and international government chemical assessments,
databases, and information obtained through systematic review) to identify potential
environmental and human health hazards for vinyl chloride as part of the prioritization process
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(U.S. EPA, 2024c). The information received through public comments and collected during
prioritization informed determination of the broad categories of environmental and human health
hazard effects to be evaluated in the draft risk evaluation.
EPA plans to evaluate all potential environmental and human health hazard effects identified for
vinyl chloride in Sections 2.4.1 and 2.4.2, respectively. The Agency identified limited
environmental hazard information for vinyl chloride during prioritization due to its volatility
from water and surfaces (including food), which are the exposure pathways included in most
ecological toxicity tests. EPA plans to qualitatively assess hazards and risks to environmental
organisms, as described in Sections 2.5.3.2.2 and 2.5.3.2.3. The following human health hazards
were identified for vinyl chloride: liver toxicity, neurotoxicity, immunotoxicity, developmental
toxicity, genotoxicity and cancer, and other hazards. EPA plans to quantitatively assess human
health hazards. As the Agency continues to evaluate reasonably available and relevant hazard
information identified through systematic review, EPA may update the potential environmental
and human health hazards considered in the risk evaluation. The Agency plans to evaluate PESS
due to factors that potentially increase susceptibility to vinyl chloride toxicity—including early-
life and prenatal exposures (e.g., infants, children, pregnant women), sex, comorbidities, genetic
polymorphisms, and other lifestyle factors (e.g., consuming certain drugs, alcohol, and high-
calorie diets).
Analysis Plan
The analysis plan for vinyl chloride is presented in Section 2.6. It outlines the general science
approaches that EPA plans to use for the various evidence streams (i.e., releases, fate, engineering,
exposure, and hazard) supporting the risk evaluation. The analysis plan is based on EPA's knowledge of
vinyl chloride to date that includes a review of identified information as described in Section 1.3. Should
additional data or approaches become reasonably available, the Agency plans to consider them for the
draft risk evaluation.
Peer Review
The draft risk evaluation for vinyl chloride will be peer reviewed as required by the TSCA Risk
Evaluation Rule (89 FR 37028). Peer review will be conducted in accordance with relevant and
applicable methods for chemical risk evaluations, including using EPA's Peer Review Handbook (U.S.
EPA. 2015a) and other methods consistent with section 26 of TSCA (40 CFR 702.41).
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1 INTRODUCTION
This document presents the draft scope of the risk evaluation to be conducted for vinyl chloride under
the Frank R. Lautenberg Chemical Safety for the 21st Century Act, which amended the Toxic
Substances Control Act (TSCA) on June 22, 2016. The law includes statutory requirements and
deadlines for actions related to conducting risk evaluations of existing chemicals.
Under TSCA section 6(b), EPA must designate chemical substances as high-priority substances for risk
evaluation or low-priority substances for which risk evaluations are not warranted at the time, and upon
designating a chemical substance as a high-priority substance, initiate a risk evaluation on the substance.
TSCA section 6(b)(4) directs EPA to conduct risk evaluations for existing chemicals to "determine
whether a chemical substance presents an unreasonable risk of injury to health or the environment,
without consideration of costs or other nonrisk factors, including an unreasonable risk to a potentially
exposed or susceptible subpopulation [PESS] identified as relevant to the risk evaluation by the
Administrator under the conditions of use" (COUs; also called TSCA COUs).
TSCA section 6(b)(4)(D) and the implementing regulation (40 CFR 702.43) require EPA to publish the
scope of the risk evaluation to be conducted, including the hazards, exposures, COUs, and PESS that the
Administrator expects to consider within 6 months after the initiation of a risk evaluation. In addition, a
draft scope is to be published pursuant to 40 CFR 702.43(a). In December 2024, EPA published a list of
five chemical substances, including vinyl chloride, that have been designated high-priority substances
for risk evaluation (see Docket ID: EPA-HQ-QPPT-2018-0448. December 18, 2024), which initiated the
risk evaluation process for those chemical substances. The Agency is now releasing this draft scope for
the risk evaluation of vinyl chloride.
1.1 Regulatory History
In addition to federal and state laws and regulations, vinyl chloride is also subject to various regulatory
actions by other governments, tribes, and international agreements as described in the Proposed
Designation of Vinyl Chloride as a High-Priority Substance for Risk Evaluation (U.S. EPA. 2024c).
1.2 Assessment History
The Agency identified previous assessments of vinyl chloride conducted by EPA programs and other
organizations (Table Apx A-l). The Agency may also look to consider these assessments or portions of
assessments conducted by other federal, state, or international authoritative bodies. EPA may consider
whether these existing assessments or reviews represent the best available science as required under
TSCA and use pertinent portions of them to directly inform a risk evaluation. Depending on the source,
these assessments may include information on COUs, hazards, exposures, and PESS—information
useful to EPA in preparing this draft scope for the risk evaluation of vinyl chloride. In addition to using
information from prior assessments, the Agency is reviewing data recently collected through systematic
literature review (Section 1.3).
1.3 Reasonably Available Information
As described in the Proposed Designation of Vinyl Chloride as a High-Priority Substance for Risk
Evaluation (U.S. EPA, 2024c), EPA's OPPT applies systematic review methods in the identification and
review of reasonably available information in a manner that is objective, unbiased, and transparent for
the purpose of assessing the risks associated with each high-priority substance under its COUs. EPA
uses scientific information that is consistent with the best available science as required by the scientific
standards in TSCA section 26(h) (15 U.S.C. 2625[h])). The Agency also used the systematic review
process described in the Draft Systematic Review Protocol Supporting TSCA Risk Evaluations for
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Chemical Substances, Version 1.0: A Generic TSCA Systematic Review Protocol with Chemical-Specific
Methodologies (also called the "Draft Systematic Review Protocol") (U.S. EPA. 20211 incorporating
recommendations from the Scientific Advisory Committee on Chemicals (SACC), to identify relevant
information to inform the prioritization considerations set forth in 40 CFR 702.9.
The chemical-specific systematic review process being employed by EPA to identify and screen
reasonably available information for vinyl chloride is described in the Proposed Designation of Vinyl
Chloride as a High-Priority Substance for Risk Evaluation (U.S. EPA. 2024c); the search of reasonably
available information on vinyl chloride, title and abstract screening, and full-text screening were
conducted to inform the designation of vinyl chloride as a High-Priority Substance (HPS) during
prioritization. Since the designation of vinyl chloride as an HPS, additional PDFs of the identified
potentially relevant data sources for vinyl chloride were acquired and underwent full-text screening.
During the two 90-day public comment periods, additional data sources were also identified, and if
relevant, were considered for inclusion in this draft scope of the risk evaluation for vinyl chloride. EPA
is in the process of incorporating all potentially relevant data sources identified for vinyl chloride and
respective disciplines into visuals such as the evidence maps, available in Appendix B, which depict
discipline-specific data elements identified in data sources that meet screening criteria during full-text
screening.
Relevant information submitted with public comments on the draft scope document will be considered
for use in the draft risk evaluation of vinyl chloride. EPA has completed data quality evaluation and data
extraction of data sources containing physical and chemical property information identified during the
prioritization process and is currently evaluating and extracting environmental fate and transport
information. The chemistry and fate information collected to date was used to inform the fit-for-purpose
analysis described in this draft scope document. During the risk evaluation phase, EPA will conduct data
extraction and evaluation for information sources related to the pathways, routes, and populations that
will receive quantitative assessment, and will conduct evidence integration for all components that are in
scope for vinyl chloride. Chemical-agnostic data extraction, data evaluation, and evidence integration
approaches are described in the Draft Systematic Review Protocol (U.S. EPA. 2021). The exposure
routes, pathways, and populations that EPA expects to quantitatively assess are described in Sections 2.5
and 2.6. The Agency may update the analysis plan based on additional relevant information received or
identified.
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2 SCOPE OF THE RISK EVALUATION
As required by TSCA, the scope of the risk evaluation identifies the COUs, hazards, exposures, and
PESS that the Administrator expects to consider. To communicate and visually convey the relationships
between these components, EPA included in the Proposed Designation of Vinyl Chloride as a High-
Priority Substance for Risk Evaluation (U.S. EPA. 2024c) an initial life cycle diagram and initial
conceptual models that describe the actual or potential relationships between vinyl chloride and human
and ecological populations. This draft scope document additionally presents conceptual models that
were revised to illustrate which components of the risk evaluation (i.e., exposure pathways and routes,
ecological organisms, and human populations) EPA is proposing to quantitatively assess. An initial
analysis plan is also included that identifies, to the extent feasible, the approaches and methods that EPA
may use to assess exposures, effects (hazards), and risks under the TSCA COUs of vinyl chloride.
2.1 Physical and Chemical Properties
EPA reviewed databases and previously conducted assessments to identify information for physical and
chemical properties to characterize the potential for vinyl chloride to persist in the environment or
bioaccumulate. The physical and chemical property values selected preliminarily and for use in this draft
scope are given in Table 2-1. Detailed information on the draft physical and chemical assessment of
vinyl chloride is available in the Draft Chemistry and Fate Technical Support Document: Physical and
Chemical Property and Fate and Transport Assessment for Vinyl Chloride (U.S. EPA, 2025a).
Table 2-1. Physical and Chemical Properties of Vinyl Chloride
Property
Selected Value"
Reference(s)
Molecular formula
C2H3CI
NLM (2023b)
Molecular weight
62.498 g/mole
Rumble (2023)
Physical form
Colorless gas at room
temperature and pressure; mild,
sweet odor
NLM (2023b): RSC (2023): U.S. EPA (2000b)
Melting point
-153.84 °C
PhvsProp (2023): Rumble (2023)
Boiling point
-13.9 °C
NLM (2023b): Reaxvs (2023): U.S. EPA (2023a)
Density
0.9106 g/cm3 at 20 °C
ATSDR (2023): RSC (2023): Rumble (2023):
OECD (2001)
Vapor pressure
2,550 mm Hg at 20 °C
ECHA (2023a)
Vapor density
2.21 (relative to air = 1)
NLM (2023b)
Water solubility
9,150 mg/L at 20.5 °C
ECHA (2023a): Reaxvs (2023)
Octanol: water partition
coefficient (log Kow)
1.38
ATSDR (2023): ECHA (2023b): Rumble (2023)
Octanol:air partition
coefficient (log Koa)
\324b
EPI Suite™ (KOAWIN)
Henry's Law constant
0.0278 atm-m3/mol at 24.8 °C
PhvsProp (2023)
Flash point
-78 °C (closed cup)
NLM (2023b): RSC (2023)
Autoflammability
472 °C
NLM (2023b)
Viscosity
0.01072 cP at 20 °C
NLM (2023b)
UV-Vis absorption
Chemical is a gas that does not
absorb wavelengths >218 nm
ATSDR (2023): OECD (2001)
"Measured unless otherwise noted
b Information was estimated using EPI Suite™ (U.S. EPA. 2012c).
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2.2 Conditions of Use
TSCA section 3(4) defines COUs 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.'" EPA will not exclude COUs from the scope of the risk
evaluation, but a fit-for-purpose approach may result in varying types and levels of analysis and
supporting information for certain COUs. The extent to which the Agency will refine its evaluations for
one or more COUs in any risk evaluation will vary as necessary to determine whether a chemical
substance presents an unreasonable risk of injury to human health or the environment.
2.2.1 Data and Information Sources
EPA identified COUs based on Chemical Data Reporting (CDR) provided in 2016 (U.S. EPA. 2016)
and 2020 (U.S. EPA, 2020a)—as well as other publicly available data sources such as the Toxics
Release Inventory (TRI), Discharge Monitoring Reports (DMRs), National Emissions Inventory (NEI)
(U.S. EPA. 2020b). safety data sheets (SDSs), Chemical Exposure Knowledgebase (ChemExpo), EPA
Chemical and Product Categories (CPCat) data (U.S. EPA. 2019). and the High Priority Chemicals Data
System (HPCDS). EPA consulted a variety of other sources, including published literature, company
websites, and government and commercial trade databases and publications, to identify additional
readily available information regarding the use of vinyl chloride {Use Report for Vinyl Chloride (CASRN
75-01-4), (U.S. EPA. 2025b)). The Agency also received public comments that can be found in docket
ID numbers EPA-HQ-OPPT-2018-0448 and EPA-HQ-OPPT-2023-0601. which contain potentially
relevant information regarding the use of vinyl chloride. COUs determined based on these sources are
summarized below in Table 2-2.
2.2.2 Categories and Subcategories of Conditions of Use Included in the Scope of the Risk
Evaluation
Most reported COUs in CDR for vinyl chloride have remained unchanged between the 2016 and 2020
reporting periods, although some changes have been identified. Guidance regarding the reporting of
categories and subcategory information was updated between the 2016 and 2020 reporting periods for
CDR. This makes it difficult to discern whether there were significant changes in vinyl chloride COUs
based on reported information to CDR during that period. This update may have resulted in the use
information being reported differently in 2020 compared to 2016, possibly leading to inaccurate
implications that some uses may have commenced or ceased in recent years.
In the 2016 reporting period, vinyl chloride was reported as a reactant intermediate in adhesive and
industrial gas manufacturing. It was also reported in repackaging as an intermediate in plastic material
and resin manufacturing as well as a laboratory chemical in chemical product and preparation
manufacturing. One consumer use was reported in plastic and rubber products not covered elsewhere.
None of these uses were reported again in 2020, so they may no longer be occurring or are not occurring
at a threshold requiring CDR reporting; however, they are included in Table 2-2. In the 2020 reporting
period, vinyl chloride was newly reported as a reactant as an intermediate in petrochemical
manufacturing; as a monomer in plastic material and resin manufacturing; and as being incorporated into
formulation, mixture, or reaction product as a binder in plastics material and resin manufacturing.
Commercial uses as a binder and intermediate in plastic and rubber products were also reported. These
may be new uses for vinyl chloride since the 2016 reporting cycle or uses that increased since the 2016
reporting cycle and therefore meet CDR reporting thresholds or reporting discrepancies. EPA is seeking
comment to understand if these uses are ongoing.
Information presented in the Proposed Designation of Vinyl Chloride as a High-Priority Substance for
Risk Evaluation CASRN 75-01-4 (U.S. EPA. 2024c) and in public comments indicates the presence of
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489 vinyl chloride in commercial and consumer products and articles as an impurity. Consistent with the
490 Procedures for Chemical Risk Evaluation Under the Toxic Substances Control Act (TSCA) rule (89 FR
491 37028), EPA expects to conduct risk evaluations in a fit-for-purpose manner, tailoring the level of
492 analysis based on factors such as the substance's physical-chemical properties; environmental fate and
493 transport properties; the likely duration, intensity, frequency, and number of exposures under the COU;
494 reasonably available information about the release to the environment; and other relevant considerations
495
496 Table 2-2. Conditions of Use of Vinyl Chloride
Life Cycle Stage"
Category6
Subcategoryc
Reference(s)
Manufacture
Domestic manufacture
Domestic manufacture
U.S. EPA
(2020a. 2016)
Import
Import
U.S. EPA
(2020a. 2016)
Processing
Processing as a reactant
Intermediate in: adhesive manufacturing;
industrial gas manufacturing; plastic material
and resin manufacturing
U.S. EPA
(2020a. 2016);
EPA-HQ-OPPT-
2018-0448-0021
Intermediate in petrochemical manufacturing
U.S. EPA
(2020a)
Other basic inorganic chemical manufacturing
U.S. EPA
(2022b)
Monomer in plastic material and resin
manufacturing
U.S. EPA
(2020a); U.S.
EPA (2022b)
Processing -incorporating
into formulation, mixture,
or reaction product
Intermediate in petrochemical manufacturing
U.S. EPA
(2020a. 2016)
Solvent
U.S. EPA
(2020b)
Cleaning agent
U.S. EPA
(2020b)
Binder in plastics material and resin
manufacturing
U.S. EPA
(2020a)
Processing - incorporating
into articles
Wire and cable in primary metal
manufacturing
U.S. EPA
(2020a. 2016)
Repackaging
Intermediate in plastic material and resin
manufacturing
U.S. EPA (2016)
Other
Industrial process - pulp and paper
(U.S. EPA.
2020b)
HFC production
EPA-HQ-OPPT-
2018-0448-0025
Industrial process - non-ferrous metals;
industrial process - ferrous metals
(U.S. EPA.
2020b)
Laboratory chemical
2016 CDR; EPA-
HQ-OPPT-2018-
0448-0025
Recycling
Recycling
U.S. EPA
(2020a. 2016)
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Life Cycle Stage"
Category6
Subcategoryc
Reference(s)
Distribution in
Commerce
Distribution in commerce
Distribution in commerce
Commercial Use
Construction and building
materials covering large
surface areas, including
paper articles; metal
articles; stone, plaster,
cement, glass and ceramic
articles
Construction and building materials, including
roof sheets, drinking water pipes, sewer pipes,
cable and wire
U.S. EPA
(2020a. 2016);
EPA-HQ-OPPT-
2018-0448-0018
Petrochemical
manufacturing
Intermediate
U.S. EPA
(2020a. 2016);
EPA-HQ-OPPT-
2018-0448-0018
Other articles with routine
direct contact during
normal use including
rubber articles; plastic
articles (hard)
Binder
U.S. EPA
(2020a. 2016);
EPA-HQ-OPPT-
2018-0448-0016
Intermediate
U.S. EPA
(2020a. 2016);
EPA-HQ-OPPT-
2018-0448-0016
Other
Automotive components, including instrument
and door panels, convertible tops, upholstery
EPA-HQ-OPPT-
2018-0448-0018
Consumer Use
Furniture & furnishings
including plastic articles
(soft); leather articles
Furniture & furnishings including plastic
articles (soft); leather articles
EPA-HQ-OPPT-
2018-0448-0018
Construction and building
materials covering large
surface areas including
stone, plaster, cement,
glass and ceramic articles;
fabrics, textiles, and
apparel
Construction and building materials including
roof sheets, drinking water pipes, sewer pipes,
cable and wire, fabrics, textiles, and apparel
U.S. EPA
(2024a); EPA-
HQ-OPPT-2018-
0448-0014; EPA-
HQ-OPPT-2018-
0448-0018
Two-component caulks
Two-component caulks
IC2 (2024); U.S.
EPA (2024a)
Water-based paint
Water-based paint
IC2 (2024); U.S.
EPA (2024a)
Single-component glues
and adhesives
Single-component glues and adhesives
https: //www .hom
cdcDot.com/D/Su
Dcr-Glue-1 -fl-oz-
Vinvl-Leather-
Mender-12-Pack-
T-VL/202806522
Solvent-based paint
Solvent-based paint
IC2 (2024); U.S.
EPA (2024a)
Other
Textiles, synthetic fibers and blends
IC2 (2024)
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Life Cycle Stage"
Category6
Subcategoryc
Reference(s)
Consumer Use
Packaging (Excluding
rubber articles; plastic
articles (hard); plastic
articles (soft)
Packaging (Excluding rubber articles; plastic
articles (hard); plastic articles (soft)
EPA-HQ-OPPT-
2018-0448-0016
Plastic and rubber products
not covered elsewhere
Plastic and rubber products not covered
elsewhere
U.S. EPA (2016)
Toys intended for
children's use (and child
dedicated articles),
including fabrics, textiles,
and apparel; or plastic
articles (hard)
Toys intended for children's use (and child
dedicated articles), including fabrics, textiles,
and apparel; or plastic articles (hard)
EPA-HQ-OPPT-
2018-0448-0018;
EPA-HQ-OPPT-
2018-0448-0021;
https://hpcds.thei
c2.ors/Search;
Disposal
Disposal
Disposal
" Life cycle stage use definitions (40 CFR 711.3)
"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.
Although EPA has identified both industrial and commercial uses here for purposes of distinguishing scenarios in
this document, the Agency interprets the authority over "any manner or method of commercial use" under TSCA
section 6(a)(5) to reach both.
b These categories of COUs appear in the preliminary life cycle diagram, reflect CDR codes, and broadly represent
conditions of use of vinyl chloride in industrial and/or commercial settings. For categories of conditions of use reported
in CDR where there might be overlaps or misidentification of conditions of use. If those issues arise, EPA plans to
address them in the preparation of the draft risk evaluation.
c These subcategories reflect CDR codes and represent more specific conditions of use of vinyl chloride. For
subcategories of conditions of use reported in the CDR there might be overlaps or misidentification of conditions of
use. If those issue arise, EPA plans to address them in the preparation of the draft risk evaluation.
Note: Byproducts can be formed during the manufacture of vinyl chloride, including 1,1-dichloroethane (CASRN 75-
34-3); 1,1,2-trichloroethane (79-00-5); trans-1.2-dichlorocthylcnc (156-60-5); trichloroethylene (79-01-6);
perchloroethylene (127-18-4); methylene chloride (75-09-2); and carbon tetrachloride (56-23-5). Additionally, vinyl
chloride may contain residual feedstocks including hydrochloric acid (7647-01-0) and 1,2-dichloroethane (107-06-2).
EPA plans to assess byproducts and residual feedstocks of vinyl chloride manufacture during the risk evaluation phase.
497 2.2.3 Activities Excluded from the Scope of the Risk Evaluation
498 TSCA section 6(b)(4)(D) requires EPA, during scoping, to identify COUs of a chemical substance the
499 Administrator expects to consider in a risk evaluation.
500
501 In accordance with TSCA section 3(4)'s definition of COUs, EPA determines the circumstances
502 appropriately considered to be COUs for a particular chemical substance.1 TSCA section 3(2) excludes
1 Chemical substance means any organic or inorganic substance of a particular molecular identity, including any combination
of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature, and any element or
uncombined radical. Chemical substance does not include (1) any mixture; (2) any pesticide (as defined inFIFRA) when
manufactured, processed, or distributed in commerce for use as a pesticide; (3) tobacco or any tobacco product; (4) any
source material, special nuclear material, or byproduct material (as such terms are defined in the Atomic Energy Act of 1954
and regulations issued under such Act); (5) any article the sale of which is subject to the tax imposed by section 4181 of the
Internal Revenue Code of 1954 (determined without regard to any exemptions from such tax provided by section 4182 or
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from the definition of "chemical substance," among other things, "any food, food additive, drug,
cosmetic, or device (as such terms are defined in section 201 of the Federal Food, Drug, and Cosmetic
Act [FFDCA] [21 U.S.C. 321]) when manufactured, processed, or distributed in commerce for use as a
food, food additive, drug, cosmetic, or device" as well as "any pesticide (as defined in the Federal
Insecticide, Fungicide, and Rodenticide Act [FIFRA] [7 U.S.C. 136 et seq.]) when manufactured,
processed, or distributed in commerce for use as a pesticide."
Cosmetics
EPA determined that vinyl chloride was historically used in cosmetics, including hair sprays that meet
the definition of cosmetics under Section 201 of the Federal Food, Drug and Cosmetics Act, 21 U.S.C.
321. Therefore, these uses are excluded from the definition of "chemical substance" in TSCA section
3(2)(B)(vi) and are not included in Table 2-2. Activities and releases associated with the use of such
cosmetics are therefore not "conditions of use" (defined as circumstances associated with "a chemical
substance," TSCA section 3(4)) and will not be evaluated during the risk evaluation of vinyl chloride.
Food Additives
The U.S. Food and Drug Administration lists vinyl chloride as an optional substance to be used in food
packaging materials. Food packaging materials meet the definition for a "food additive" described in
section 201 of FFDCA, 21 U.S.C. 321. Therefore, use of vinyl chloride in food packaging is excluded
from the definition of "chemical substance" in TSCA section 3(2)(B)(vi) and is not included in Table
2-2. Activities and releases associated with the use of such food packaging materials are therefore not
"conditions of use" (defined as circumstances associated with "a chemical substance," TSCA section
3(4)) and will not be evaluated during risk evaluation.
Intentional Misuse
EPA will not include within the scope of a risk evaluation any exposures associated with intentional
misuse or acts of terror (82 FR 33729-1; 89 FR 37028; S.Rept. 114-67, 2015). As expressed by the U.S.
Senate, the term "conditions of use" is intended to describe the context in which EPA will assess a
chemical substance and apply the TSCA standard in making risk determinations and taking risk
management action. Intentional misuse of a chemical substance was one example identified by the
Senate as not a condition of use (82 FR 33729-1; 89 FR 37028; S.Rept. 114-67, 2015). EPA believes acts
of terror are comparable to intentional misuse and thus generally not a condition of use.
Catastrophic Accidents, Extreme Weather Events, and Other Natural Disasters
EPA generally does not include in the scope of the risk evaluation catastrophic accidents, extreme
weather events, and other natural disasters if such events do not lead to regular and predictable
exposures associated with a given condition of use. However, such a determination requires a fact-
specific, chemical-by-chemical analysis (EPA-HQ-OPPT-2023-0496-0431). Thus, EPA would consider
including such events (e.g., catastrophic accidents, extreme weather events, and other natural disasters)
in the scope of the risk evaluation if the Agency receives information indicating regular and predictable
changes in exposures associated with these events (88 FR 74292).
2.2.4 Production Volume
EPA considered current volume or significant changes in volume of vinyl chloride using information
reported by manufacturers (including importers). EPA assembled reported information for years 1986
through 2019 on the production volume reported under the CDR rule, formerly known as the Inventory
4221 or any other provision of such Code); and (6) any food, food additive, drug, cosmetic, or device (as such terms are
defined in section 201 of the FFDCA) when manufactured, processed, or distributed in commerce for use as a food, food
additive, drug, cosmetic, or device (TSCA section 3(2)).
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Update Rule (IUR) (40 CFR Part 711).
The national aggregate production volume, which is presented as a range to protect individual site
production volumes that are confidential business information, is presented in Table 2-3. Since 1986, the
national aggregate production volume of vinyl chloride has been consistently over 1 billion lb. In 2011,
over 16 billion lb were reported and since 2012 production volume has been reported between 10 and 20
billion lb.
Table 2-3.1986 to 2019 National Aggregate
Production Vo
ume Data for Vinyl Chloride
Year
Production Volume
(Billions of lb)
1986
>1
1990
>1
1994
>1
1998
>1
2002
>1
2006
>1
2011
16,713,648,476
2012
10 to <20
2013
10 to <20
2014
10 to <20
2015
10 to <20
2016
10 to <20
2017
10 to <20
2018
10 to <20
2019
10 to <20
2.2.5 Overview of Conditions of Use and Lifecycle Diagram
Figure 2-1 provides the preliminary life cycle diagram for vinyl chloride, which is a graphical
representation of the various life stages of the industrial, commercial, and consumer use categories of
vinyl chloride. The preliminary life cycle diagram includes functional use codes for industrial uses and
product categories for commercial and consumer uses. There might be overlaps or misidentification of
COUs for categories and subcategories of uses reported in CDR. If those issues arise, EPA plans to
address them in the preparation of the draft risk evaluation. Figure 2-1 duplicates and is identical to the
preliminary life cycle diagram presented in the Proposed Designation of Vinyl Chloride as a High-
Priority Substance for Risk Evaluation (U.S. EPA. 2024c).
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MFG/1MPORT
PROCESSING
INDUSTRIAL, COMMERCIAL, CONSUMER USES
WASTE DISPOSAL
Manufacture
(Including
Import)
567
568
569
570
571
572
Processing as a Reactant
(Intermediate in adhesive
manufacturing, industrial gas
manufacturing, plastic material and
resin manufacturing; Monomer in
plastic material and resin
manufacturing)
Incorporated Into
Formulation, Mixture, or
Reaction Product
(Intermediate in petrochemical
manufacturing; Binder in plastics
material and resin manufacturing)
Incorporated into Articles
(Wire and cable in primary metal
manufacturing)
Repackaging
(Intermediate in plastic material and
resin manufacturing and laboratory
chemical in all other chemical
product and preparation
manufacturing)
I
Building/Construction Materials Not Covered
Elsewhere1
(e.g. cable and wire manufacturing)
Petrochemical Manufacturing1
(e.g. intermediate)
Plastic and Rubber Products Not Covered
Elsewhere1,2
(e.g. binder; intermediate)
Recycling
t
See Conceptual Model for
Environmental Releases
and Wastes
Uses:
1. Industrial and/or
Commercial
2. Consumer
Figure 2-1. Preliminary Life Cycle Diagram for Vinyl Chloride
Distribution in commerce is not explicitly included in the life cycle diagram because its activities are associated with other COUs. Unloading and loading
activities are associated with other COUs. The information in the preliminary life cycle diagram is grouped according to the 2016 and 2020 CDR
processing codes and use categories from Table 2-2.
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2.3 Exposures
EPA expects to assess human and environmental exposures and releases to the environment resulting
from COUs within the scope of the risk evaluation of vinyl chloride. This section describes the physical
and chemical properties, environmental fate and transport properties, releases to the environment, and
potential human and environmental exposures from COUs and from other possible or known sources.
EPA plans to consider, where relevant, the duration, intensity (concentration), frequency and number of
exposures in characterizing exposures to vinyl chloride.
2.3.1 Releases to the Environment
Chemical releases to the environment from COUs are considered in identifying potential exposure and
may be derived from reported data obtained through direct measurement, calculations based on
empirical data, or assumptions and models. Preliminary information on releases to the environment, as
reported in TRI, NEI, and DMR are presented in thq Proposed Designation of Vinyl Chloride as a High-
Priority Substance for Risk Evaluation (U.S. EPA, 2024c). In summary, of the more than 5 million lb of
vinyl chloride disposed of or otherwise released to the environment during the TRI reporting years 2013
to 2022, more than 98 percent was released onsite to air. Eighty-four percent of NEI-reported air
emissions are from industrial processes for chemical manufacturing or waste disposal. The majority of
offsite releases reported to TRI were to wastewater treatment facilities other than publicly-owned
treatment works (e.g., industrial wastewater treatment). In DMR, less than 20 percent of the facilities
with water discharge monitoring requirements reported a vinyl chloride discharge in 2023. Of those
discharges, nearly 90 percent were from two industry sectors (516 kg from 5 facilities in total),
miscellaneous plastics products and rolling, drawing, and extruding of nonferrous metals.
Appendix B.2 summarizes the types of information used to inform environmental releases of vinyl
chloride.
2.3.2 Fate and Transport
EPA reviewed databases and previously conducted assessments (see Section 3.2 of the Updated Search
Strategies Used to Identify Potentially Relevant Discipline-Specific Information (U.S. EPA, 2024d)) to
identify information on fate endpoints for vinyl chloride that inform the fit-for-purpose analysis plan.
Specifically, this information was analyzed to characterize transport and partitioning pathways, identify
environmental persistence potential, and assess bioaccumulation potential of vinyl chloride. Appendix
B.l summarizes the types of information identified for environmental fate and transport properties of
vinyl chloride. Table Apx C-l provides the identified and selected environmental fate properties for
vinyl chloride considered in this draft scope. Detailed information on the draft fate and transport
assessment of vinyl chloride is available in the Draft Chemistry and Fate Assessment for Vinyl Chloride
(U.S. EPA. 2025a).
2.3.2.1 Intermedia Transport and Partitioning Behavior of Vinyl Chloride
The magnitude of the partitioning coefficients identified for vinyl chloride suggest that vinyl chloride
will exist primarily in air and water in the environment. Vinyl chloride has a vapor pressure of 2,550
mmHg at 20 °C (ECHA. 2023a). indicating that vinyl chloride will exist predominantly as a free gas in
the atmosphere. Therefore, dry deposition is unlikely to be a common process. This is consistent with
the estimated octanokair partition coefficient of 25.4 (U.S. EPA. 2012c).
Vinyl chloride has a considerable water solubility (9,150 mg/L at 20.5 °C (ECHA, 2023a; Reaxys,
2023)). consistent with its polarity and small molecular size. However, with a Henry's Law constant of
0.0278 atmm3/mol at 24.8 °C (PhysProp. 2023). volatilization from surface waters is expected to be
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rapid and a dominant process for vinyl chloride. (ECHA, 2023a; Reaxys, 2023)Sorption to organics
present in sediment and suspended and dissolved solids present in water is unlikely to be a dominant
pathway given the range of log Koc values identified to date (TableApx C-l). Vinyl chloride's
solubility along with its low tendency to sorb to organics present in solids suggest that in soil it will
exhibit mobility and might be transported through the vadose zone to groundwater.
2.3.2.2 Preliminary Media Assessments to Inform Fit-for-Purpose Analysis Plan
Preliminary media assessments were conducted to (1) inform the fit-for-purpose analysis plan for the
risk evaluation of vinyl chloride, and (2) to identify major and minor media in which vinyl chloride is
expected to occur given that its physical and chemical properties drive its ready partitioning to air.
Furthermore, because the vast majority (see more below) of vinyl chloride TRI releases are reported to
air (Section 2.3.1), the air compartment is expected to be a major compartment of interest. Surface water
and soil media are expected to hold minor importance; that is, vinyl chloride that remains in each of
these media is expected to show moderate to high persistence moderated by biodegradation that is
highly variable and dependent on environmental conditions (e.g., electron donors, oxygen levels,
minerality). However, occurrences of vinyl chloride in surface water and soil are expected to be minimal
as supported by monitoring and TRI release data, as well as the expected rapid volatilization of vinyl
chloride from both wet and dry surfaces. Biosolids, sediments, groundwater, and biota are expected to
be minor compartments in the evaluation of vinyl chloride due to negligible releases and/or negligible
partitioning to these media. The following subsections summarize the preliminary media assessments for
this draft scope.
2.3.2.3 Air and Atmosphere
Based on its release information, physical and chemical properties, as well as fate properties, vinyl
chloride in the environment is expected to primarily be present in air. Vinyl chloride is a gas at room
temperature and most environmentally relevant temperatures (boiling point -13.9 °C or 7 °F). According
to the reporting to TRI, greater than 98 percent of reported vinyl chloride releases are to air.
Additionally, it is expected that vinyl chloride released to surface water and wastewater treatment plants
will rapidly volatilize to the air compartment. Vinyl chloride reacts with hydroxyl radicals (*OH) with
transformation rates reported between 3.95><10~12 and 8.40><10~12 cm3/mole-sec (ATSDR. 2024; ECHA.
2023a; NIST. 2023; NLM. 2023a; OECD. 2001). Assuming a *OH concentration of 1.5xlO6 •OH/cm3
and 12 hours of sunlight, the half-life of vinyl chloride may range from 1.27 to 2.71 days, with a mean
of 1.84 days (Sections 3.3.2.1 and 3.4.1.1 inth q Draft Chemistry and Fate Assessment for Vinyl
Chloride (U.S. EPA. 2025a)). Thus, in the atmosphere, vinyl chloride is expected to have low to high
persistence (i.e., half-life [ti 2] > 2 days; 64 FR 692; January 5, 1999).
In indoor air, vinyl chloride in gas phase is expected to be more persistent as compared to in outdoor
environments. Indoor environments have fewer physical transport drivers (e.g., advection by wind and
atmospheric flows) as well as less sunlight and subsequently lower concentrations of hydroxyl radicals.
Therefore, vinyl chloride transformation rates are expected to be slower in indoor air than in the
atmosphere. However, vapor intrusion is not expected to be a dominant pathway introducing vinyl
chloride to indoor environments (Section 3.4.1.2 in the Draft Chemistry and Fate Assessment for Vinyl
Chloride (U.S. EPA. 2025a)).
2.3.2.4 Aquatic Environments
Monitoring data from the Water Quality Portal indicate minimal occurrence of vinyl chloride in surface
waters (Section 3.4.2 in the Draft Chemistry and Fate Assessment for Vinyl Chloride U.S. EPA. 2025a)).
Vinyl chloride may enter surface waters through direct release (approximately 0.01% of releases
reported to TRI in the period 2013-2022), migration of landfill leachate, and releases from spills and
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leaks. Vinyl chloride is not expected to undergo wet or dry deposition (Section 3.4.1.1 in the Draft
Chemistry and Fate Assessment for Vinyl Chloride (U.S. EPA. 2025a)). Vinyl chloride may also form in
anaerobic media from the reductive dehalogenation of more highly chlorinated ethylenes such as
perchloroethylene (PCE) and trichloroethylene (TCE); Section 3.3.4.5 in the Draft Chemistry and Fate
Assessment for Vinyl Chloride (U.S. EPA. 2025a)).
Although vinyl chloride present in surface water is expected to volatilize appreciably, some fractions
may remain dissolved in the aqueous phase and to a lesser extent adsorbed to organics found in
suspended solids, as indicated by the log Koc values presented in Table Apx C-l. Of the small amount
of vinyl chloride that may remain in surface water, dissolved and sorbed fractions are expected to have
moderate to high persistence (characterized by tm of 60-179 days, and >180 days, respectively).
Because hydrolysis of vinyl chloride is unlikely, transformation of vinyl chloride in water is expected to
be primarily mediated by biodegradation processes, as discussed below.
One ready biodegradability test (Organization for Economic Cooperation and Development [OECD] test
protocol 301D) indicates vinyl chloride is not readily biodegradable, reporting a degradation rate of 16
percent over 28 days (ECHA. 2023a; NITE. 2023; NLM. 2023a). One additional CO2 evolution study
employing a municipal activated sludge inoculum, reported a mineralization rate of 21.5 percent over 5
days (ECHA, 2023a; OECD, 2001). Anaerobic biodegradation rates range from a half4ife of 70 days
with groundwater inoculum to 10 percent over 106 days in water under methanogenic conditions
following a 50-day lag period (ECHA. 2023a; NLM. 2023a; Reaxys. 2023). The degree of vinyl
chloride biodegradation in aqueous systems is therefore expected to vary with microbial community and
environmental conditions. Despite not being readily biodegradable, vinyl chloride is not widely or
frequently detected in aquatic environments, likely due to minimal releases to water and its tendency to
volatilize rapidly.
No empirical data on vinyl chloride adsorption to sediment were identified. Based on empirical soil log
Koc values, vinyl chloride sorption to organics in particulate matter and sediments might occur.
Although is not expected to be a dominant process, vinyl chloride can also be transported by diffusion
and advection processes to sediment pore water. Given the range of anaerobic biodegradation rates
identified in water, vinyl chloride is expected to have high persistence in natural, non-adapted sediments
(Section 3.4.2.2 in the Draft Chemistry and Fate Assessment for Vinyl Chloride (U.S. EPA. 2025a)).
However, aqueous vinyl chloride concentrations resulting from COUs are expected to be negligible
based on water release and discharge information identified to date (see Section 2.3.1 and Section 3.2.2
in the Draft Chemistry and Fate Assessment for Vinyl Chloride (U.S. EPA. 2025a)).
2.3.2.5 Terrestrial Environments
Vinyl chloride can enter terrestrial environments via the disposal of industrial processing wastes, the
degradation of more highly-chlorinated ethylenes (Section 3.3.4.5 in the Draft Chemistry and Fate
Assessment for Vinyl Chloride (U.S. EPA. 2025a)). and incidental spills and leaks. Because the majority
of reported releases are to air (Section 3.2.2 in the Draft Chemistry and Fate Assessment for Vinyl
Chloride (U.S. EPA, 2025a) and releases to soil media are expected to volatilize rapidly, terrestrial
environments and processes are not expected to be significant to the evaluation of vinyl chloride.
However, understanding the terrestrial fate of vinyl chloride is important to inform exposure potential
from incidental releases; for example, by spills and leaks during regular manufacturing, processing, and
handling activities.
Vinyl chloride may be subject to several competing processes dictating its fate in soil, including (1)
volatilization from both wet and dry soil, (2) migration to groundwater, (3) limited sorption to organic
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solid fractions, and (4) aerobic and anaerobic biodegradation. Two sources were identified reporting
measured log Koc values for vinyl chloride. The first reported a log Koc value of 1.75, but without
additional detail on materials or methods (NLM. 2023a; OECD. 2001). The second is an empirical study
following OECD 106 guidelines that investigated seven low-organic content, natural clayey till soils
from Denmark, reporting log Koc values ranging from 2.38 to 2.95 (mean 2.70) (ATSDR. 2024).
Because of vinyl chloride's tendency to volatilize from soil and to have moderate to rapid migration to
groundwater, only a small portion of vinyl chloride is likely to be subject to biodegradation in soil. As
discussed above, biodegradation rates can vary greatly depending on the conditions and microbial
species present. Given the anticipated transport and biodegradation in soil systems alongside low
historical releases to land, vinyl chloride is not expected to persist in soil environments.
Vinyl chloride present in groundwater systems is likely to be primarily due to the reductive
dehalogenation of chlorinated ethylenes. Vinyl chloride in groundwater may be subject to both
anaerobic biodegradation and abiotic reductive dehalogenation. The degree of susceptibility of vinyl
chloride to abiotic dehalogenation relies on the minerality of the anaerobic system, with estimated half-
lives ranging from 1.25 to 12.6 days (Reaxys. 2023). Despite the short half-lives achieved in laboratory
reductive dehalogenation studies, vinyl chloride has been detected in groundwater in several U.S.
locations (ATSDR. 2024) and might be fed by the degradation of chloroethylene (CE) plumes.2
Volatility of vinyl chloride is expected to drive its removal in wastewater treatment plants (WWTPs).
Results from the STPWIN Model of EPI Suite™ v4.11 predict that approximately 89 percent of vinyl
chloride will be removed via losses to air stripping assuming negligible removal due to biodegradation
(U.S. EPA. 2012c). Negligible amounts of vinyl chloride are expected to partition to sludge during
wastewater treatment; therefore, vinyl chloride transport to terrestrial environments from the application
of municipal biosolids is not expected to be a significant pathway (Section 3.4.3.1 in the Draft
Chemistry and Fate Assessment for Vinyl Chloride (U.S. EPA. 2025a)).
Articles containing vinyl chloride-based polymers (namely polyvinyl chloride [PVC]) may be disposed
of in municipal landfills. However, information gathered to-date suggests that typical conditions in
landfill environments will tend not to drive vinyl chloride monomer release from PVC products. For
example, Mersiowsky et al. (2001) performed lysimeter experiments over 4 years to track the release of
organics from PVC wiring and flooring under simulated landfill conditions and found no detectable
degradation of the PVC polymer (based on molecular weight distribution) and no vinyl chloride
monomer in lysimeter biogas. These results are consistent with the low expected concentration of
residual vinyl chloride monomer in PVC (Section 2.3.4).
Vinyl chloride may also occur in landfills from the biological reductive dehalogenation of more highly-
chlorinated ethylenes (e.g., PCE, TCE), especially in deep anaerobic landfill layers. Kromann et al.
(1998) demonstrated that vinyl chloride formed from chlorinated ethylenes can be degraded within the
time frame of weeks-to-months in landfill leachate, although is highly dependent on landfill
characteristics (e.g., organic content). Vinyl chloride in gas form can also diffuse upwards in landfill
soils and might degrade in the presence of methane and oxygen—conditions characteristic of topsoil
layers in landfills with methanogenic activity (Scheutz and Kieldsen. 2005). The fate of vinyl chloride in
a landfill was modeled and its removal was found to occur primarily through volatilization/gas flow and
biodegradation (contingent upon the presence of appropriate microbial consortia and conditions), with
minimal (<1%) remaining in the landfill after 5 years (Kieldsen and Christensen, 2001). Fractions of
2 Note that vinyl chloride as a transformation product was addressed by the recently finalized risk management actions for
PCE or TCE, or will be addressed in future risk evaluations for other chlorinated ethylenes; see also Section 2.3.2.7).
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vinyl chloride that are not degraded in the landfill will likely volatilize and may cause areas of elevated
atmospheric concentrations above landfill surfaces (ATSDR. 2024; Molton et al.. 1987). Because the
majority of the vinyl chloride in landfills is expected to originate from sources outside of scope, and
leaching of vinyl chloride from polymers is likely to be minimal, the Agency expects to assess landfill
pathways qualitatively in subsequent risk analyses. Section 3.4.3.3 in the Draft Chemistry and Fate
Assessment for Vinyl Chloride (U.S. EPA. 2025a) provides additional detail on the behavior of vinyl
chloride in landfills.
2.3.2.6 Bioaccumulation Potential
Vinyl chloride is not expected to significantly bioconcentrate, bioaccumulate, or undergo trophic
transfer. Two empirical bioconcentration factors (BCFs) were identified: a BCF of 40 was found in
green algae (Chlorellafused) (ATSDR. 2024; ECHA. 2023a; NLM. 2023a; OECD. 2001) and a BCF of
less than 10 in golden ide (Lend sens idus melanotus) (ATSDR. 2024; ECHA. 2023 a; NLM. 2023 a;
OECD. 2001). Supporting evidence from empirical BCFs, bioaccumulation factors (BAFs) of 2.59,
2.80, 3.63 L/kg were obtained for lower, middle, and upper trophic levels, respectively, using the Arnot-
Gobas method of the BCFBAF model (U.S. EPA. 2012c). EPA identified no bioaccumulation or
bioconcentration data for terrestrial organisms from databases or previously conducted assessments.
2.3.2.7 Vinyl Chloride as a Transformation Product
Vinyl chloride has been reported as a transformation product (i.e., resulting from biotic or abiotic
degradation of other substances) of other chlorinated organic compounds; therefore, some instances of
vinyl chloride in the environment may be due to the uses of those parent chemicals rather than direct
uses of vinyl chloride. PCE and TCE are two of the most commonly reported precursors of vinyl
chloride; in anaerobic environments, more highly-chlorinated ethylenes can undergo sequential
reductive dehalogenation following the pathway:
2 H HCl 2 H HCl 2 H HCl 2 H HCl
C2Cl4——»C2HCl3—^ > C2H2CI2 ^ » C2H3Cl^-^C2H4
perchloroethylene trichloroethylene dichloroethylenes vinyl chloride ethene
(PCE) (TCE) (1,1-DCE, (VC) (ETH)
cis-l,2-DCE,
trans-l,2-DCE)
Figure 2-2. Reductive Dechlorination Pathway via Biodegradation in Anaerobic Environments
Adapted from (Eklund et al.. 2022; Freedman and Gossett. 1989; Molton etal.. 1987).
The relative rates of dechlorination proceed such that the half-lives of PCE and TCE are much shorter
than those of 1,1- and 1,2-dichloroethylenes (DCEs) and vinyl chloride. Wood et al. (1985) reported
half-lives of 34, 43, and 53 days for PCE, TCE, and 1,1-DCE, respectively, while there was no
detectable reduction of 1,2-DCEs and vinyl chloride. Historically, this has led to accumulation and
presence of DCEs and vinyl chloride in groundwater where only PCE and/or TCE were known to have
been released (Lee et al.. 2015; Hunkeler et al.. 2011; Milde et al.. 1988). This is consistent with
observations that the vinyl chloride-to-ethene reduction is the rate-limiting step during complete
dechlorination in controlled systems (Freedman and Gossett, 1989).(Freedman and Gossett, 1989). The
composition of microbial communities and redox conditions also dictate the kinetics and extent to which
the degradation pathway illustrated in Figure 2-2 might proceed (Lee et al.. 2015; Hunkeler et al.. 2011).
Dechlorination of more highly-chlorinated ethylenes yielding vinyl chloride has also been reported as an
important source of vinyl chloride in landfills (Molton et al.. 1987). While vinyl chloride can accumulate
in anaerobic environments (e.g., groundwater or landfills) as a result of anaerobic biodegradation of
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parent substances, the concentration of vinyl chloride appears generally to be orders of magnitude lower
than that of the parent chemical and the relative concentration of vinyl chloride to the parent chemical
varies depending on factors such as the age of the plume and local conditions (e.g., Hunkeler et al.
(2011). Leeetal. (2015)).
Because of this formation route, environmental concentrations of vinyl chloride from monitoring data—
especially in areas of known chloroethylene contamination—may not be reliably attributable to direct
sources or uses of vinyl chloride. Related uncertainties will be accounted for when considering the use
of monitoring data during the evaluation of environmental concentrations and exposures. Exposures and
risks related to vinyl chloride as a transformation product will be assessed in future risk evaluations of
parent substances or will be addressed by the recently finalized risk management actions for PCE
(Docket ID: EPA-HQ-QPPT-2019-0502) or TCE (Docket ID: EPA-HQ-QPPT-2019-0500). Given these
regulations for PCE and TCE have been finalized, EPA will not be re-evaluating these chemicals.
23.3 Environmental Exposures
The manufacturing, processing, distribution, use, and disposal of vinyl chloride can result in releases to
the environment and exposure to aquatic and terrestrial organisms (biota). Environmental exposures to
biota are informed by releases into the environment, overall persistence, degradation, and
bioaccumulation within the environment, as well as partitioning across different media. Concentrations
of chemical substances in biota provide evidence of exposure. EPA expects to consider reasonably
available fate information (Section 2.3.1.1; Appendix B.l) and environmental monitoring data for vinyl
chloride—including the identified studies monitoring for vinyl chloride in groundwater (68 studies),
ambient air (26 studies), soil (13 studies), sediment (5 studies), and other media, and in biota (aquatic
species, 1 study; and terrestrial species, 3 studies). These are summarized in Appendix B.3.
2.3.4 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.
All human populations that EPA expects to be assessed in the vinyl chloride risk evaluation may be
exposed to vinyl chloride as a residual monomer in plastics made from PVC and related polymers.
However, due to regulatory and industry standards, the concentration of residual vinyl chloride
monomer in plastic products is expected to be low. In the most common PVC production process, 90
percent of the vinyl chloride monomer is consumed to make PVC resin (small particles that are later
melted and mixed with additives to make PVC products), while excess monomer is removed and
retained for reuse. PVC resin is stripped of excess vinyl chloride monomer using pressure and steam and
then may be dried, depending on the type of PVC resin. Final concentrations of residual vinyl chloride
monomer in PVC resin are generally < 3 ppm (Borrelli et al.. 2005). Due to its boiling point (-13.9 °C),
vapor pressure (2,550 mm Hg at 20 °C), and Henry's Law constant (0.0278 atm-m3/mol at 24.8 °C),
vinyl chloride will volatilize from wet or dry surfaces that are exposed to the atmosphere. Thus, the
residual vinyl chloride in PVC resin and products is expected to be entrapped within the matrix of PVC
polymer but, depending on factors such as the density and porosity of the PVC, might leach out of the
material by diffusion over time (e.g., Walter et al. (2011)).
2.3.4.1 Occupational Exposures
EPA plans to evaluate worker activities where there is a potential for exposure under the various COUs
(manufacturing, processing, industrial/commercial uses and disposal) described in Section 2.2. The
Agency plans to evaluate exposure to both workers (i.e., employees who handle the chemical substance)
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and occupational non-users (ONUs; i.e., employees who do not directly handle the chemical but perform
work in an area where the chemical is present). Although EPA generally does not assume the use of
personal protective equipment (PPE), where information is reasonably available, EPA expects to
consider the availability of engineering controls and/or PPE as part of the risk evaluation.
Examples of worker activities associated with COUs within the scope of the risk evaluation for vinyl
chloride that EPA may analyze include, but are not limited to the following:
• unloading and transferring vinyl chloride to and from storage containers to process vessels;
• handling and disposing of waste containing vinyl chloride;
• cleaning and maintaining equipment;
• sampling chemicals, formulations, or products containing vinyl chloride for quality control;
• repackaging chemicals, formulations, or products containing vinyl chloride; and
• performing other work activities in or near areas where vinyl chloride is used.
Several commercial uses in Section 2.2 are reported to be downstream uses of PVC and other polymers
produced using vinyl chloride monomer. According to regulatory and industry standards currently in
place (Section 2.3.4), residual vinyl chloride monomer in plastic products is required to be abated
through process operations. Subsequently, occupational exposures for the commercial use of these
products may be low. Additional key data that EPA expects will inform occupational exposure
assessment include Occupational Safety and Health Administration (OSHA), Chemical Exposure Health
Data (CEHD), and National Institute for Occupational Safety and Health (NIOSH) Health Hazard
Evaluation (HHE) program data.
Vinyl chloride is a gas with a vapor pressure of 2,550 mmHg at 20 °C (ECHA. 2023a); hence, inhalation
exposure is expected to be a significant route of exposure for workers and ONUs. Vinyl chloride has an
OSHA standard (29 CFR 1910.1017; established in 1974) Permissible Exposure Limit (PEL) of 1 part
per million (ppm) over an 8-hour work day by time-weighted average (TWA), and a Short-Term
Exposure Limit (STEL) of 5 ppm over 15 minutes (OSHA. 2019). NIOSH labels vinyl chloride a
potential carcinogen and recommends that both exposure to carcinogens be limited to the lowest feasible
concentration, and that workers exposed to measurable concentrations of vinyl chloride should wear
respirators (assigned protection factor [APF] = 10,000) (NIOSH 2020; Whittaker. 2017).
EPA generally does not evaluate occupational exposures through the oral route. In some cases, workers
and ONUs may inadvertently ingest inhaled particles that deposit in the upper respiratory tract.
Additionally, workers may transfer chemicals from their hands to their mouths. However, because vinyl
chloride is a gas at room temperature and highly volatile (Section 2.1), these exposures are not expected
to be significant for vinyl chloride.
EPA plans to evaluate dermal exposure to workers for particular COUs based on expected handling
practices as identified through the Agency's systematic review process. ONUs do not directly handle
vinyl chloride; therefore, direct liquid contact with vinyl chloride is not expected.
Appendix B.2 summarizes the types of information identified for occupational exposures to vinyl
chloride.
2.3.4.2 Consumer Exposures
Information presented in the Proposed Designation of Vinyl Chloride as a High-Priority Substance for
Risk Evaluation CASRN 75-01-4 (U.S. EPA. 2024c) indicates the potential presence of vinyl chloride in
consumer products and articles: plastic and rubber products, adhesives and sealants, paints and coatings,
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furniture and furnishings, floor coverings, apparel, toys, and fabrics. These products and articles often
contain PVC, of which approximately 99 percent of global vinyl chloride is used to produce. Residual
vinyl chloride monomer can leach from PVC-containing products, potentially resulting in exposures to
consumers, but the concentration of residual vinyl chloride monomer in plastic products is expected to
be low due to regulatory and industry standards (Section 2.3.4). EPA plans to review the reported
concentrations of residual vinyl chloride monomer in and potential to leach from PVC products during
the risk evaluation phase. Appendix B.3 summarizes the types of information identified for consumer
exposures to vinyl chloride.
Based on reasonably available information on consumer COUs, inhalation of vinyl chloride may occur
through inhalation of vapor during product use. During the risk evaluation phase EPA plans to
investigate the plausibility of inhalation exposures to products containing vinyl chloride monomer. Dust-
or mist-mediated pathways are not expected because vinyl chloride will predominantly exist as a gas at
room temperature and not partition to particulates in air. Thus, exposure pathways that are not expected
include inhalation of indoor dust or mist, incidental ingestion of dust or mist containing vinyl chloride,
and dermal contact with dust or mist deposition onto the skin. Other potential oral exposure pathways
for consumers are ingestion during product use via transfer from hand to mouth or mouthing of articles.
Other possible dermal pathways are direct dermal contact with articles containing vinyl chloride.
2.3.4.3 General Population Exposures
Environmental releases of vinyl chloride from certain COUs such as but not limited to
manufacturing, processing, distribution, use, and disposal may lead to general population exposure.
General population may be exposed via oral, dermal, or inhalation routes. Appendix B.3 summarizes the
types of information identified for general population exposures to vinyl chloride.
2.3.4.3.1 Inhalation
There is inhalation exposure potential to vinyl chloride by breathing indoor air and ambient air. Indoor
air exposures can occur from infiltration from ambient air, where less sunlight and lower concentrations
of hydroxyl radicals retard indirect photolysis (Section 2.3.2.2). Although vapor intrusion is another
possible source of vinyl chloride in indoor air, it is not expected to be a significant one because (1)
degradation of vinyl chloride in the vadose zone is expected to be faster than its upward diffusion into
buildings, and (2) its occurrence in groundwater and soil from COUs is negligible (Sections 2.5.3.2.2
and 2.5.3.2.4).
Ambient air exposures may occur from releases from industrial or commercial sources. More than 98
percent of vinyl chloride disposed of or otherwise released to the environment is released onsite to air
according to TRI data for 2013 through 2022 (Section 2.3.1 and (U.S. EPA, 2024c)). As a preliminary
screening step, EPA used existing modeled data from the 2020 AirToxScreen Assessment to evaluate
the range of vinyl chloride concentrations in ambient air from nonpoint sources, point sources, and all
sources (Figure 2-3). The 2020 AirToxScreen uses the Community Multiscale Air Quality (CMAQ)
chemical transport model and the AERMOD dispersion model to estimate annual average outdoor
ambient air concentrations across the United States using release data from the 2020 NEI database. The
maximum vinyl chloride concentration in the AirToxScreen modeling results is approximately 3.2
|ig/m3 (equivalent to -0.0012 ppm), which falls below the acute (0.5 ppm) and intermediate Minimal
Risk Levels (MRLs; 0.02 ppm) reported by the Agency for Toxic Substances and Disease Registry
(ATSDR) (2024). The sources of vinyl chloride included in Figure 2-3 may include non-TSCA uses;
during risk evaluation, EPA plans to assess general population inhalation exposures specific to COUs
resulting in point and nonpoint sources of vinyl chloride in ambient air.
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10 1
10°
10"'
10"'
10~31
10
_J0
n
E
SjMO"4'
C.
2 10"
*00
© 10 "
o
c
O 10^
10'W
10'"
10'"
10'3
10'14
10"5
Source
Non-Point Sources
^ Point Sources
9 Total Concentration
Non-Point Sources
Point Sources
Sources of Vinyl Chloride
Total Concentration
Figure 2-3. AirToxScreen Modeling Results for Vinyl Chloride, Based on 2020 NEX Data
2.3.4.3.2 Oral
The general population may be exposed to chemical substances via processes such as incidental
ingestion of surface water during recreational activities like swimming; ingestion of contaminated
drinking water, soil, or fish exposed to water or sediment containing the chemical; or incidental
ingestion of consumer products containing the chemical. Based on its physical and chemical properties,
fate properties, and release patterns, none of these exposure pathways are expected to be significant for
vinyl chloride (Section 2.5.3.2).
The fourth cycle (2012-2019) of the Six-Year Review of National Primary Drinking Water Regulations
under the Safe Drinking Water Act (SDWA) showed that less than 0.001 percent of drinking water
systems (1 system serving 45 people out of 52,021 systems in the United States collectively serving
274.5 million people) exceeded the current maximum contaminant level (MCL) for average vinyl
chloride concentrations in drinking water ( J.S. EPA, 2024b). ATSDR (2024 also concluded that the
majority of U.S. drinking water supplies do not contain detectable levels of vinyl chloride based on their
review of existing monitoring data, which includes those collected under previous SDWA 6-Year
Reviews.
The majority of PVC produced in the United States is used in the manufacture of pipes such as
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drinking water distribution pipes and sewer pipes, and there is evidence that residual vinyl chloride
monomer can leach into water carried in PVC pipes (e.g., Walter et al. (2011)). State and local
authorities establish requirements for plumbing materials via building and plumbing codes. EPA
has supported the development of independent, third-party testing standards for plumbing
materials under NSF International and American National Standards Institute (ANSI) Standard 61.
which has been incorporated into many state and local codes. NSF/ANSI requires analysis of
chemicals that leach from a material into drinking water and a toxicological evaluation of leached
concentrations to ensure that they are below levels that might cause potential adverse human health
effects. The toxicological evaluation criteria are based on lifetime exposure to the concentration of
contaminants in drinking water.
Compliance of drinking water system components with NSF/ANSI 61 is required in legislation,
regulation, or policies in 49 U.S. states (National Sanitation Foundation, 2019). NSF/ANSI 61 requires
that PVC and chlorinated PVC materials be tested for several analytes, including residual vinyl chloride
monomer, and that materials meet the standard if residual vinyl chloride monomer concentrations are
below 3.2 mg vinyl chloride monomer/kg PVC. NSF set the limit for water distribution pipes at 3.2
mg/kg using a diffusion model and maximum leached vinyl chloride content in water set to 10 percent
of the drinking water MCL level of 2 ppb (Borrelli et al.. 2005).
Most U.S. drinking water monitoring data are collected at the entry point into the distribution system,
before the water may be exposed to PVC pipes. However, one study evaluated the concentration of vinyl
chloride in tap water in homes with a variety of types of PVC pipes (Walter et al.. 2011). In that study,
vinyl chloride concentrations were less than or equal to 25 ng/L after 101 hours of exposure to new PVC
and chlorinated PVC (CPVC) pipes, compared to the vinyl chloride drinking water MCL of 2,000 ng/L.
2.3.4.3.3 Dermal
Dermal exposure to a chemical substance can occur through incidental contact with contaminated water
during recreation, use of contaminated drinking water for washing or bathing, contact with soil, or
contact with products and materials containing the chemical. No measured information related to dermal
exposures have yet been identified (Section B.3).
2.3.4.4 Potentially Exposed or Susceptible Subpopulations: Exposure Considerations
TSCA section 6(b)(4) requires EPA to determine whether a chemical substance presents an
unreasonable risk to "a potentially exposed or susceptible subpopulation identified as relevant to the risk
evaluation." In 40 CFR 702.33 states that "potentially exposed or susceptible subpopulation means a
group of individuals within the general population identified by EPA 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, the elderly, or overburdened communities." General population is "the total of individuals
inhabiting an area or making up a whole group" and hereafter refers to the U.S. general population (U.S.
EPA. 2011a).
EPA identified and plans to evaluate the relevancy of exposure pathways for the following PESS based
on CDR information and previous assessments: children; pregnant women and people of reproductive
age; workers; ONUs; communities living near industrial facilities where vinyl chloride is manufactured
or used; and consumers, including users and bystanders. The Agency plans to review reasonably
available population- or subpopulation-specific exposure factors and activity patterns to determine if
PESS need to be further defined (e.g., early life and/or puberty as a potential critical window of
exposure).
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2.4 Hazards
2.4.1 Environmental Hazards
EPA used the Agency's ECOTOXicology Knowledgebase (ECOTOX) and previous assessments to
identify reasonably available information that may be relevant for characterizing potential
environmental hazard resulting from exposure to vinyl chloride. For scoping purposes, the Agency
consulted previous assessments of environmental hazard data for vinyl chloride (NICNAS. 2014a;
OECD. 2001; IPCS. 1999). EPA also expects to consider publicly available peer-reviewed literature,
gray literature, and other relevant information submitted to the Agency not covered by these assessments
using the TSCA systematic review process as described in the Proposed Designation of Vinyl Chloride
as a High-Priority Substance for Risk Evaluation CASRN 75-01-4 (U.S. EPA. 2024c). Appendix B.4
summarizes the types of information identified for environmental hazards of vinyl chloride.
Based on data collected through ECOTOX and previous assessments, exposure to vinyl chloride might
cause acute toxicity to aquatic vertebrates (mortality, growth, and behavior) and invertebrates (mortality,
reproduction, behavior), chronic toxicity to aquatic vertebrates (mortality) and chronic toxicity to
aquatic invertebrates (reproduction and growth/development), and toxicity to algae (growth inhibition).
No environmental hazard information for terrestrial organisms were identified in previous assessments.
Data gathered within the ECOTOX database identified environmental hazard information for terrestrial
invertebrates (mortality, reproduction, and growth/development). As EPA continues to evaluate
reasonably available and relevant hazard information identified through systematic review, the Agency
may update the list of potential hazard effects to be analyzed in the risk evaluation. In the case of
inhalation, which is a potential exposure route for terrestrial wildlife, the relative contribution to total
exposure risk is considered to be negligible in most situations. Inhalation exposure risk results both from
inhalation of airborne particulates and from inhalation of volatile organic compounds (VOCs). The
fraction of dust that cannot be inhaled is considered non-respirable and is accounted for in published soil
ingestion rates. Data to quantify the dust fraction that is respirable to wildlife are species-specific and
very limited (U.S. EPA. 1993).
2.4.2 Human Health Hazards
Vinyl chloride has been previously assessed by EPA and other authoritative bodies (ATSDR. 2024; CA
DTSC. 2022; NTP. 2021; NICNAS. 2014a. b; Health Canada. 2013; IARC. 2012; NRC. 2012; OEHHA.
2011; OECD. 2001; IRIS. 2000; U.S. EPA. 2000b; IPCS. 1999; CARB. 1990a. b, c; ORD. 1975); thus,
many of the hazards of vinyl chloride have been previously compiled and reviewed. EPA plans to use
these previous assessments to identify reasonably available epidemiological, animal toxicity, and
mechanistic information relevant for characterizing potential human health hazards resulting from
exposure to vinyl chloride—with a particular focus on (ATSDR)'s Toxicological Profile for Vinyl
Chloride (ATSDR. 2024) and EPA's Integrated Risk Information System (IRIS) assessment (IRIS.
2000). In addition to previous assessments, the Agency plans to evaluate publicly available, peer-
reviewed literature, gray literature, and other relevant information submitted to EPA and not covered by
these assessments using the TSCA systematic review process described in the Proposed Designation of
Vinyl Chloride as a High-Priority Substance for Risk Evaluation CASRN 75-01-4 (U.S. EPA. 2024c).
Appendix B.5 shows the human health hazard literature, organized by hazard domain, which EPA
identified through systematic review.
2.4.2.1 Non-cancer Hazards
EPA expects to consider all potential hazards associated with vinyl chloride. Based on reasonably
available information from ATSDR (2024) and from the Agency's systematic review process, the
Agency plans to focus its risk assessment on the non-cancer human health hazards detailed below. As
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EPA continues to evaluate reasonably available and relevant hazard information identified through
systematic review, the Agency may update the potential human health hazards considered in the risk
evaluation.
2.4.2.1.1 Liver Toxicity
ATSDR (2024) concluded that hepatic effects are "a presumed health effect for humans" based on
evidence of fibrosis, cirrhosis, and steatohepatitis in vinyl chloride workers following chronic-duration
inhalation exposures. Evidence of hepatic effects in animals includes increased liver weight and
histopathological liver lesions in rats and mice following intermediate- and chronic-duration inhalation
and chronic-duration oral exposure. No studies on liver toxicity resulting from dermal exposure were
identified, and EPA will determine whether this data gap can be supplemented through systematic
review of the available literature.
Previous risk assessments derived quantitative endpoints based on liver effects in rodents. Specifically,
ATSDR selected liver toxicity as the endpoint on which it based MRLs for intermediate inhalation and
chronic oral exposures (ATSDR. 2024). Additionally, EPA also selected liver toxicity as the endpoint on
which it based the Reference Concentration/Dose (RFC/RFD) in its IRIS assessment (IRIS. 2000).
2.4.2.1.2 Neurotoxicity
ATSDR (2024) concluded that neurological effects are "a presumed health effect for humans" based on
limited epidemiological and animal evidence. This includes neurological symptom reporting (e.g.,
dizziness, headache, nausea, ataxia, neurasthenia), peripheral neuropathy, and other peripheral nervous
system symptoms in vinyl chloride workers following inhalation exposure and in volunteers after acute
and intermediate inhalation exposure. There is a moderate level of evidence in animal studies based on
clinical signs in multiple acute-duration inhalation studies in rats, mice, and guinea pigs as well as a
chronic-duration oral study in rats. No studies on neurotoxicity resulting from dermal exposure were
identified, and EPA will determine whether this data gap can be supplemented through systematic
review of the available literature.
2.4.2.1.3 Immunotoxicity
ATSDR (2024) concluded that immunological effects are "a suspected health effect for humans" based
on increased circulating immune complexes, immunoglobulins, complement factors, and levels of
inflammatory cytokines in vinyl chloride workers. Limited evidence in animal studies includes increases
in spleen weight in rats after chronic duration inhalation exposure, increased thymus weight in
immunized rabbits, and spontaneous and mitogen-stimulated lymphocyte proliferation in mice and
immunized rabbits after intermediate duration inhalation exposure. No studies on immunotoxicity
resulting from oral or dermal exposure were identified, and EPA will determine whether this data gap
can be supplemented through systematic review of the available literature.
2.4.2.1.4 Developmental Toxicity
ATSDR (2024) concluded that developmental effects are a "suspected health effect for humans" based
on evidence from studies in mice and rabbits that were exposed via inhalation during gestation. Human
data were limited to a small number of ecological and case-control studies that did not report
developmental effects. No studies on developmental toxicity resulting from oral or dermal exposure
were identified, and EPA will determine whether this data gap can be supplemented through systematic
review of the available literature.
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Previous risk assessments derived quantitative endpoints based on developmental toxicity in rodents.
Specifically, ATSDR (2024) selected developmental toxicity as the endpoint on which they based an
MRL for acute inhalation.
2.4.2.1.5 Other Hazards
EPA identified the following additional potential non-cancer human health hazards and related
information that may be considered for the risk evaluation: cardiovascular, gastrointestinal, skin and eye
irritation, respiratory, mortality, musculoskeletal, nutritional and metabolic, ocular and sensory, renal,
reproductive, sensitization, skin/connective tissue, and thyroid. As EPA continues to evaluate reasonably
available and relevant hazard information identified through systematic review, the Agency may update
the potential human health hazards considered in the risk evaluation.
2.4.2.2 Genotoxicity and Cancer Hazards
2.4.2.2.1 Cancer
Carcinogenicity classifications for vinyl chloride in previous assessments range from "May Cause
Cancer" (NICNAS. 2014b) to "Known Human Carcinogen" (ATSDR. 2024; IRIS. 2000) or
"Carcinogenic to Humans" (NTP. 2021; NICNAS. 2014b; Health Canada. 2013; IARC. 2012; IRIS.
2000; CARES. 1990a). EPA previously evaluated the weight of evidence for cancer in humans and
animals (IRIS. 2000) and concluded that vinyl chloride is "a known human carcinogen by the inhalation
route of exposure, and by analogy, the oral route because of positive animal bioassay data and
pharmacokinetic data allowing dose extrapolation across routes." The Agency further concluded that
vinyl chloride is also considered "highly likely to be carcinogenic by the dermal route." These findings
are based on a large body of epidemiological and animal evidence described below.
Occupational inhalation exposure to vinyl chloride was associated with liver cancer (including
angiosarcoma, hepatocellular carcinoma, and cholangiocellular carcinoma) in male workers, and this
provides the most compelling evidence of the carcinogenicity of vinyl chloride. Although other cancers
were previously reported in vinyl chloride workers—including brain cancer, lung cancer, soft tissue
cancers, lymphatic/hematopoietic cancers, and malignant melanoma—more recent follow-up studies and
pooled and meta-analysis studies do not demonstrate a consistent association between vinyl chloride
exposure and tumor formation in these organs (ATSDR. 2024). Studies in non-occupational settings and
in women are limited, with one study associating occupational exposure with leukemia or lymphoma in
women, and another associating increased breast cancer risk with exposure to vinyl chloride as a
hazardous air pollutant in California (ATSDR. 2024).
Evidence of the carcinogenicity of vinyl chloride in animals is available from inhalation studies in rats,
mice, and hamsters and from oral studies in rats. No studies are currently available for dermally exposed
animals. Chronic inhalation studies report liver angiosarcomas, mammary gland carcinomas, Zymbal
gland carcinomas, neuroblastomas, nephroblastomas, lung tumors, melanomas, acoustical duct epithelial
tumors, and leukemias in rats, mice, and hamsters—with species-specific variation in the target organs
that developed tumors. Notably, liver angiosarcomas were reported in all tested species. Studies in orally
exposed rats found increased neoplastic nodules of the liver, hepatocellular carcinoma, hepatic
angiosarcoma, and increased incidence of Zymbal gland tumors.
2.4.2.2.2 Genotoxicity/Mutagenicity and Other Mechanisms of Carcinogenicity
EPA (2000b) previously concluded that vinyl chloride carcinogenicity occurs via a well-understood
genotoxic mode of action. Vinyl chloride is metabolized to a reactive metabolite, probably 2-
chloroethylene oxide, which is believed to be the ultimate carcinogenic metabolite of vinyl chloride.
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This metabolite binds to DNA, forming DNA adducts that, if not repaired, ultimately lead to mutations
and tumor formation.
Several lines of evidence indicate that vinyl chloride metabolites are genotoxic; that is, interacting
directly with DNA. Occupational exposure to vinyl chloride has resulted in chromosome aberrations,
micronuclei, and sister chromatid exchanges (SCEs); response levels were correlated with exposure
levels, and reversibility of chromosome damage has been reported following a cessation or reduction of
exposure to vinyl chloride. DNA adducts were identified in rats following inhalation exposure to vinyl
chloride and have been shown to generate mainly base pair substitution mutations (ATSDR. 2024).
Vinyl chloride is mutagenic in the Salmonella typhimurium reverse mutation assay, with the mutagenic
activity decreased or eliminated in the absence of exogenous metabolic activation (Bartsch and
Montesano, 1975; Rannug et al., 1974). The vinyl chloride metabolites 2-chloroethylene oxide and 2-
chloroacetaldehyde are both mutagenic in the Salmonella assay; however, 2-chloroethylene oxide was
shown to be the more potent mutagen and might be the ultimate carcinogenic metabolite. Mutations in
specific genes (i.e., ras oncogenes and p53 tumor suppressor gene) have also been identified in vinyl
chloride-induced liver tumors in rats and humans (ATSDR. 2024).
2.4.2.3 Potentially Exposed or Susceptible Subpopulations: Hazard Considerations
In developing the hazard assessments, EPA will evaluate available data to ascertain whether some
human subpopulations may have greater susceptibility than the general population to the chemical's
hazard(s). ATSDR (2024) identified the following factors that might increase susceptibility to adverse
health effects from vinyl chloride exposure based on direct evidence in humans and/or animals: early-
life and prenatal exposures; sex; comorbidities (obesity, liver disease, irregular heart rhythms, impaired
peripheral circulation, and systemic sclerosis); genetic polymorphisms (HLA-DR5, HLA-DR3, and B8
alleles); and other lifestyle factors (exposure to organochlorine pesticides, consuming high-calorie diets,
ethanol, Antabuse, and barbiturates).
2.5 Conceptual Models
In this section, EPA presents the conceptual models describing the identified exposures (pathways and
routes), populations, and hazards associated with COUs of vinyl chloride. Pathways and routes of
exposure associated with workers and ONUs are described in Section 2.5.1 and consumers in Section
2.5.2. Pathways and routes of exposure associated with environmental releases and wastes are discussed
and depicted in the conceptual model shown in Section 2.5.3.
Except where noted, the pathways, routes, and populations illustrated in these conceptual models are the
same as those in the preliminary conceptual models presented in the Proposed Designation of Vinyl
Chloride as a High-Priority Substance for Risk Evaluation (U.S. EPA. 2024c). The conceptual models
presented in Sections 2.5.1, 2.5.2, and 2.5.3 have been modified to depict those pathways, routes, and
populations for which EPA expects to conduct quantitative assessments (bold lines) and those for which
EPA expects to conduct qualitative assessments (dashed lines). Pathways, routes, and populations
labeled here as not receiving quantitative assessment will be reconsidered for quantitative assessment if
additional reasonably available information is identified.
2.5.1 Conceptual Model for Industrial and Commercial Activities and Uses
The conceptual model in Figure 2-4 illustrates the pathways of exposure from industrial and commercial
activities and uses of vinyl chloride that EPA expects to include in the draft risk evaluation. There is
potential for exposures to workers and ONUs via inhalation routes and exposures to workers via dermal
routes. Due to vinyl chloride's high vapor pressure, it is expected that inhalation exposure to vapor is the
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1186 most likely exposure pathway. In addition, workers at waste management facilities might be exposed via
1187 inhalation and dermal routes during waste handling, treatment, and disposal. EPA expects to evaluate
1188 activities resulting in exposures associated with distribution in commerce (e.g., loading, unloading)
1189 throughout the various lifecycle stages and COUs (e.g., manufacturing, processing, industrial use,
1190 commercial use, disposal) rather than a single distribution scenario.
1191
1192 For each COU identified in Table 2-2, a determination was made as to whether EPA plans to evaluate
1193 each combination of exposure pathway, route, and populations in the risk evaluation.
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INDUSTRIAL AND COMMERCIAL ACTIVITIES/USES EXPOSURE PATHWAY EXPOSURE ROUTE POPULATIONS HAZARDS
1195 Figure 2-4. Vinyl Chloride Conceptual Model for Industrial and Commercial Activities and Uses: Worker and ONU Exposures and
1196 Hazards
1197 This conceptual model presents the exposure pathways, exposure routes, and hazards to humans from industrial and commercial activities and uses of
1198 vinyl chloride. Bold lines indicate pathways, routes, populations, and hazards that EPA plans to quantitatively assess (Section 2.5.1.1) while dashed lines
1199 indicate those that the Agency plans to include but not quantitatively assess (Section 2.5.1.2).
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2.5.1.1 Pathways EPA Plans to Quantitatively Analyze in the Risk Evaluation
As described in Section 2.3.2.2, air is the primary exposure pathway for vinyl chloride. In industrial
settings, vinyl chloride is transported and stored as a liquefied compressed gas, but when released to
ambient pressure it rapidly expands and converts to gaseous form. Thus, inhalation is expected to be a
significant route of occupational exposure for workers and ONUs. EPA plans to quantitatively assess
concentration of vinyl chloride vapors in industrial and commercial settings and inhalation exposures of
workers and ONUs to those vapors.
2.5.1.2 Pathways EPA Plans to Qualitatively Analyze in the Risk Evaluation
EPA plans to evaluate dermal exposure to workers for particular COUs based on expected handling
practices as identified through the Agency's systematic review process. Vinyl chloride is a gas at room
temperature and is transported and stored as a liquid under pressure. Because contact with rapidly
vaporizing liquid vinyl chloride can cause frostbite, sustained or routine dermal exposure to liquid vinyl
chloride is not expected.
Residual vinyl chloride monomer can be present in PVC resin and products, but the concentration of
vinyl chloride in PVC is generally low (Section 2.3.4). Workers do not handle PVC resin until it has
been stripped of excess vinyl chloride monomer, and in some cases (depending on the type of resin),
dried. Overall, because dermal exposure to liquid vinyl chloride and residual vinyl chloride in PVC resin
is expected to be low to negligible, workers' dermal exposure to vinyl chloride is expected to be low.
ONUs do not directly handle vinyl chloride; therefore, dermal contact with vinyl chloride is not
expected for any COU expected to be assessed. Overall, EPA does not plan to quantitatively assess
occupational dermal exposures to vinyl chloride for workers or ONUs. Barring identification of
information that indicates that further qualitative or quantitative assessment of occupational dermal
exposure to vinyl chloride is warranted, the Agency does not plan to further assess occupational dermal
exposure beyond that which is presented in this draft scope document.
2.5.2 Conceptual Model for Consumer Activities and Uses
The conceptual model in Figure 2-5 presents the exposure pathways, exposure routes, and hazards to
humans from consumer activities and uses of vinyl chloride. EPA expects inhalation to be the primary
route of exposure and plans to quantitatively evaluate inhalation exposures to vinyl chloride vapor for
consumers and bystanders during use and disposal of products containing vinyl chloride. Oral exposures
were added to this conceptual model following the publication of the Proposed Designation of Vinyl
Chloride as a High-Priority Substance for Risk Evaluation (U.S. EPA. 2024c) based on reports that
residual vinyl chloride monomer may be present in plastic consumer products, including toys (U.S.
EPA. 2025b).
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CONSUMER ACTIVITIES / USES
EXPOSURE PATHWAY
EXPOSURE ROUTE
POPULATIONS
HAZARDS
Wastewater, Liquid Wastes, and Solid Wastes
(See Environmental Release Conceptual
Models)
Figure 2-5. Vinyl Chloride Conceptual Model for Consumer Activities and Uses: Consumer Exposures and Hazards
The conceptual model presents the exposure pathways, exposure routes, and hazards to humans from consumer activities and uses of vinyl chloride. Bold
lines indicate pathways, routes, populations, and hazards that EPA plans to quantitatively assess (Section 2.5.2.1) while dashed lines indicate those that the
Agency plans to include but not quantitatively assess (Section 2.5.2.2).
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2.5.2.1 Pathways EPA Plans to Quantitatively Analyze in the Risk Evaluation
As described in Section 2.3.2.2, air is the primary exposure pathway for vinyl chloride; thus, EPA
expects to quantitatively evaluate all consumer articles and products that could lead to inhalation
exposure. Two consumer COUs (Adhesives and sealants, Paints and coatings) include consumer
products that can contain vinyl chloride monomer ranging from trace levels to up to 15.4 percent. In
addition, many consumer products made with PVC and related polymers may contain residual vinyl
chloride monomer, which may volatilize from consumer products and lead to inhalation exposure. These
include home and office furnishings, clothing, sporting goods, as well as children's toys and other
products (U.S. EPA. 2023b). However, some of the SDSs that indicate the presence of vinyl chloride in
consumer products do not report a weight fraction, likely because it is below the 0.1 percent reporting
threshold for carcinogens like vinyl chloride.
2.5.2.2 Pathways EPA Plans to Qualitatively Analyze in the Risk Evaluation
EPA does not plan to quantitatively evaluate oral exposure from Adhesives and sealants as well as
Paints and coatings—even though these two consumer COUs contain consumer products reporting
concentrations up to 15.4 percent. Consumers are unlikely to ingest these products during use. Other
COUs that have consumer products containing PVC might lead to oral and dermal exposure. As
described in Section 2.3.4, the concentration of residual vinyl chloride monomer in plastic products is
expected to be low, and based on that assessment, EPA expects to conduct a qualitative assessment of
oral and dermal exposure to vinyl chloride via consumer products that contain PVC or related polymers.
Taking all of the above into account, the Agency does not plan to further assess this pathway beyond
that which is presented in this draft scope document. However, consideration of reasonably available
information on the concentration of vinyl chloride monomer in consumer products is underway and will
inform whether further qualitative assessment or a quantitative assessment of consumer exposure to
vinyl chloride via ingestion or dermal contact is appropriate for the fit-for-purpose risk assessment.
2^.3 Conceptual Model for Environmental Releases and Wastes
The conceptual model in Figure 2-6 illustrates the potential exposure pathways, exposure routes, and
hazards to general population and environmental organisms from releases and waste streams associated
with industrial, commercial, and consumer uses of vinyl chloride.
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RELEASES AND WASTES FROM EXPOSURE PATHWAYS EXPOSURE ROUTES POPULATIONS HAZARDS
INDUSTRIAL / COMMERCIAL / CONSUMER USES
1269
1270 Figure 2-6. Vinyl Chloride Conceptual Model for Environmental Releases and Wastes: Environmental and General Population
1271 Exposures and Hazards
1272 The conceptual model presents the exposure pathways, exposure roLites, and hazards to humans and ecological species from environmental releases and
1273 wastes resulting from uses of vinyl chloride. Bold lines indicate pathways, routes, populations, and hazards that EPA plans to quantitatively assess
1274 (Section 2.5.2.1) while dashed lines indicate those that the Agency plans to include but not quantitatively assess (Section 2.5.2.2).
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2.5.3.1 Pathways EPA Plans to Quantitatively Analyze in the Risk Evaluation
Air is the primary exposure pathway for vinyl chloride because it is a gas at room temperature (boiling
point -13.9 °C; Section 2.1), greater than 98 percent of releases are to air (Section 2.3.1), and vinyl
chloride releases to the air are not expected to partition into other media (Section 2.3.2.2). Thus,
inhalation is expected to be a significant route of exposure for the general population and ecological
species. EPA plans to quantitatively assess concentrations of vinyl chloride in ambient air.
2.5.3.2 Releases, Pathways, Routes, and Populations That EPA Plans to Qualitatively
Analyze in the Risk Evaluation
2.5.3.2.1 Surface Water and Sediment
Vinyl chloride in surface water or sediment can occur from direct releases of industrial processes
(including leaks and spills) or transport from groundwater through sediment layers at aquifer-fed bodies
of water. TRI data for 2013 to 2022 report an average of 0.12 percent of vinyl chloride releases each
year going to water on-site and publicly-owned treatment works (POTW) or non-POTW wastewater
treatment (U.S. EPA. 2024c). Monitoring data from the Water Quality Portal report minimal occurrence
of vinyl chloride in surface waters with most tests results being non-detects, which is expected because
most vinyl chloride that does enter surface water will likely volatilize (Section 2.3.2.3). EPA's
systematic review process identified about 30 monitoring studies published prior to January 2023 that
investigated the presence of vinyl chloride in surface water. A preliminary title and abstract screen of
these studies indicate low levels of vinyl chloride in the surface water and co-occurrence of highly
chlorinated ethylenes (e.g., TCE) that can degrade into vinyl chloride (Section 2.3.2.7), which may
explain the presence of vinyl chloride in the water. Taking the above information into account, barring
identification of information that indicates that further qualitative or quantitative assessment of surface
water or sediment is warranted, EPA does not plan to further assess this pathway beyond that which is
presented in this draft scope document. Potential exposure to vinyl chloride through ingestion of surface
water used as a source of drinking water is discussed in Section 2.5.3.2.3.
2.5.3.2.2 Landfill Leachate and Groundwater
Vinyl chloride found in landfill leachate and subsequent groundwater can come from a variety of
sources—particularly the transformation of more highly-chlorinated ethylenes (e.g., TCE, PCE; see
Sections 2.3.2.7) following their disposal. As of January 2025, EPA's systematic review process has
identified 94 monitoring studies published prior to January 2023 that investigated the presence of vinyl
chloride in groundwater and 3 studies that assessed vinyl chloride in landfill leachate (Section B.3). A
preliminary title and abstract screen indicated that almost all studies reported a co-occurrence of vinyl
chloride with more highly chlorinated compounds, which can transform into vinyl chloride in anaerobic
environments (Section 2.3.2.7). or investigated groundwater in or near a contaminated site with known
use of those compounds.
Multiple waste streams, including consumer, residential, industrial, and municipal waste, can also be a
source of vinyl chloride in landfills. They may not be direct sources but rather a result of residual vinyl
chloride monomer leaching from PVC-containing products. The release of residual vinyl chloride
monomer into landfill leachates might be limited for various reasons. PVC products, such as pipes and
plastic materials from consumer products, often contain low concentrations of residual vinyl chloride
monomer. During these products' useful lifetimes, residual vinyl chloride is expected to evaporate or
leach from the surface prior to disposal. When they are disposed of in landfills, vinyl chloride can be
removed through volatilization/gas flow (e.g., diffusion upwards toward landfill soil) or biodegradation
(Section 2.3.1.1)—both of which further limit the concentration of vinyl chloride in landfill leachate.
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For the reasons discussed above, release of vinyl chloride into landfill leachate is unlikely to occur from
TSCA COUs {i.e., vinyl chloride present in landfill leachate is more likely to be present as a
transformation product of other substances; see Section 2.3.2.7). Therefore, EPA does not plan to
quantitatively evaluate this exposure pathway unless the ongoing review of existing literature or new
information that becomes available during the risk evaluation process warrant reconsideration.
Very small quantities of vinyl chloride are expected to be directly released to groundwater. As presented
in the Proposed Designation of Vinyl Chloride as a High-Priority Substance for Risk Evaluation U.S.
EPA. 2024c). almost all the vinyl chloride released to the environment is released to air (average
>99.8% per year since 2019; average 448,000 lb per year released to air). Releases to other media,
which includes off-site transfers for treatment or disposal, average 630 lb per year across 10 states,
primarily Louisiana (56%) and Texas (27%). Because the vinyl chloride released to air is not expected
to be transported to groundwater and vinyl chloride released to water or land is expected to largely
partition to air, these relatively small releases to other media represent the upper bound of potential
direct releases of vinyl chloride to groundwater.
Overall, concentrations of vinyl chloride in groundwater as a result of releases of vinyl chloride (as
opposed to parent compounds that degrade to vinyl chloride in anaerobic environments) are expected to
be very low. Considering the information above, EPA does not plan to conduct further assessment of
landfill leachate and groundwater beyond that which is presented in this draft scope document unless
information is identified that indicates that further qualitative or quantitative assessment is necessary.
2.5.3.2.3 Drinking Water
Vinyl chloride concentrations in drinking water are regulated by SDWA, with an MCL of 2 ppb (2
|ig/L) allowed in finished drinking water, measured at the point where the water leaves the drinking
water treatment plant and enters the distribution system. Under SDWA, EPA also set a Maximum
Contaminant Level Goal (MCLG) of 0 ppb for vinyl chloride. Further, vinyl chloride concentrations are
regulated in some drinking water source water (i.e., water that is collected to be routed to drinking water
treatment plants) under the Clean Water Act. Under the Clean Water Act section 304(a), EPA
recommends that (1) vinyl chloride concentrations be limited to 0.022 |ig/L for "Human Health for the
consumption of Water + Organism" based on 10 6 carcinogenicity risk (U.S. EPA. 2022a); and (2) vinyl
chloride be labeled as a toxic contaminant and thus subject to effluent controls (40 CFR 413.02(i)).
Due to standard industry practice that limits residual vinyl chloride monomer concentrations in PVC,
widespread building codes that set limits on vinyl chloride monomer concentrations in drinking water-
grade PVC pipes, as well as low detected concentrations of vinyl chloride in drinking water at the
distribution entry point (Section 2.3.4 and Section 2.3.4.3.2), EPA plans to qualitatively evaluate
potential exposure through drinking water—including direct consumption or incidental ingestion during
showering. Taking the above information into account, unless information is identified which indicates
that further qualitative or quantitative assessment of drinking water is warranted, the Agency does not
plan to conduct further assessment beyond that which is presented in this scope document.
2.5.3.2.4 Soil
As described in Section 2.3.2.4, EPA expects that vinyl chloride released to soil will rapidly volatize or
leach into groundwater. No on-site releases to land have been reported to TRI since 2018, so off-site
transfers for treatment or disposal (0.13% of total vinyl chloride releases) are the only potential releases
to land. ATSDR (2024) reports 140 lb of vinyl chloride released to land from 38 manufacturing facilities
in 2021, which amounts to 0.03 percent of total environmental releases. Vinyl chloride that is released to
air (>98% of TRI releases) is not expected to significantly partition to soil through wet or dry deposition.
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Based on low releases to land and limited expected partitioning from other environmental media into
soil, EPA expects that vinyl chloride concentrations in soil are negligible and therefore does not plan to
quantitatively assess exposures via soil. Considering the information above, barring identification of
information that indicates that further qualitative or quantitative assessment of soil is necessary, the
Agency does not plan to conduct further assessment beyond that which is presented in this scope
document.
2.5.3.2.5 Land-Applied Biosolids Pathway
EPA does not plan to quantitatively analyze vinyl chloride releases to terrestrial environments from
biosolids application to soil and subsequent human exposure during risk evaluation. This is not expected
to be a significant pathway because stripping of volatile organics in WWTP processes and industrial
settings is expected to dominate the removal of vinyl chloride. Vinyl chloride sorbed to solids in
biosolids is also expected to desorb readily and not be persistent in receiving areas based on its water
solubility and relatively low affinity for organic solids (Section 2.3.1). Therefore, biosolids are generally
expected to be a minor compartment due to negligible releases as supported by TRI data and/or
negligible partitioning to this media.
Monitoring data, albeit limited, also indicate the negligible occurrence of vinyl chloride in biosolids.
EPA identified three studies that investigated the presence of vinyl chloride in biosolids or sludge in its
comprehensive search of reasonably available literature published before January 2023. Parrish et al.,
(1991) evaluated the emissions of metals and organics from four wastewater sludge incineration
processes presumably in the United States (i.e., authors did not specify sampling location). Vinyl
chloride was not detected in any of the four feed sludges. The authors noted the formation of vinyl
chloride due to incomplete combustion of other VOCs but did not describe possible chemical formation
routes. Lu et al., (2017) investigated the use of a bacterial biomarker of organohalides' presence in waste
streams; however, vinyl chloride was not measured in sludge but in sediment as a transformation
product of PCE. The sampling location was not indicated. Lastly, EPA (1982) measured either
negligible (<1 (J,g/L) or non-detectable concentrations of vinyl chloride in sludge collected from a U.S.
POTW for 30 consecutive days. Based on physical and chemical properties and monitoring data, EPA
does not expect the land application of biosolids leading to incidental soil exposure through dermal
uptake or ingestion to be a pathway of concern. Taking the above information into account, EPA does
not plan to conduct further assessment of land-applied biosolids beyond that which is presented in this
draft scope document unless additional information is identified which indicates that further assessment
is warranted.
2.5.3.2.6 Aquatic Species
Vinyl chloride has a low potential for bioconcentration, bioaccumulation, and trophic transfer in aquatic
species, as discussed in Section 2.3.1 and previous assessments by ATSDR (2024) and other
authoritative sources (NICNAS. 2014a; Health Canada. 2013; OECD. 2001). EPA also did not identify
any biomonitoring studies reporting vinyl chloride concentrations in fish tissue in its comprehensive
search of reasonably available literature published before January 2023. Taken together with the
minimal releases to surface water as supported by TRI data (Section 2.3.1) and its high volatility
(Section 2.3.2.3), exposure of aquatic species to vinyl chloride via surface water, sediment, or diet are
not expected to be pathways of concern and humans nor are they expected to be exposed via
consumption of aquatic species. Considering the information above, barring identification of
information that indicates that further qualitative or quantitative assessment of aquatic species is
necessary, EPA does not plan to conduct further assessment beyond that which is presented in this scope
document.
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2.5.3.2.7 Terrestrial Species
Vinyl chloride has low bioaccumulation and trophic transfer potential (Section 2.3.2.6) so (1) terrestrial
species are not expected to be exposed to vinyl chloride through their diet, and (2) humans are not
expected to be exposed via consumption of terrestrial species. Furthermore, vinyl chloride is not
expected to be present in surface water or soil at significant concentrations (Sections 2.5.3.2.1 and
2.5.3.2.4); thus, terrestrial organisms are expected to be exposed to vinyl chloride primarily through the
air.
Because at least 95 percent of vinyl chloride is used in production of PVC and related copolymers and
vinyl chloride have a low persistence potential in air (Section 2.3.2.2), the ecological organisms most
exposed to vinyl chloride are those that live near vinyl chloride and/or PVC manufacturing facilities.
However, with few exceptions, environmental risk assessments typically do not quantitatively address
inhalation hazards posed by VOCs such as vinyl chloride (Markwiese et al.. 2008; Spring et al.. 2004;
Carl sen. 1996) (Section 2.4.1).
Taking the above information into account, unless information is identified which indicates that further
qualitative or quantitative assessment of terrestrial species is warranted, EPA does not plan to conduct
further assessment beyond that which is presented in this scope document.
2.5.3.2.8 Oral and Dermal
Vinyl chloride is expected to be present in drinking water at concentrations below the MCL, even after
passing through PVC water distribution pipes (Section 2.5.3.2.3). Therefore, oral or dermal (e.g.,
bathing) exposures via drinking water are expected to be limited. Vinyl chloride also has a low potential
for bioconcentration and bioaccumulation (Section 2.3.2.6) and exposure from consumption of aquatic
or terrestrial species is expected to be negligible. Considering the information above, barring
identification of information that indicates that further qualitative or quantitative assessment of the
drinking water or fish ingestion pathways is necessary (e.g., empirical fish tissue data), EPA does not
plan to conduct further assessment beyond that which is presented in this scope document.
2.6 Analysis Plan
The analysis plan is based both on EPA's knowledge of vinyl chloride resulting from review of previous
assessments and screening of reasonably available information as described in Proposed Designation of
Vinyl Chloride as a High-Priority Substance for Risk Evaluation (U.S. EPA. 2024c). The Agency
encourages submission of additional existing data such as full study reports or workplace monitoring
from industry sources that may be relevant to EPA's evaluation of COUs, exposures, hazards, and PESS
during risk evaluation. As discussed in the Draft Systematic Review Protocol (U.S. EPA. 2021). targeted
supplemental searches during the analysis phase may be necessary to identify additional information for
the risk evaluation of vinyl chloride. For any additional data needs identified during the risk evaluation,
EPA may use the Agency's TSCA authorities under sections 4, 8, or 11, as appropriate.
2.6.1 Exposure
EPA plans to quantitatively analyze exposures via vapors in indoor and outdoor air and to qualitatively
assess exposures via other pathways (Section 2.5). Exposures can be characterized through a
combination of reasonably available monitoring data and estimated concentrations from modeling
approaches. EPA plans to analyze scenario-specific exposures based on sources (uses), exposure
pathways, and exposed populations.
2.6.1.1 Releases to the Environment
EPA plans to analyze releases to environmental media as described below.
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1. Review reasonably available published literature and other reasonably available
information on processes and activities associated with the COU to analyze the types of
releases and wastes generated.
EPA will review reasonably available information as described in the Draft Systematic Review Protocol
(U.S. EPA. 2021). EPA plans to continue to review data sources identified, including potential sources
such as:
• EPA TRI Data,
• EPA Generic Scenarios,
• EPA National Emissions Inventory,
• OECD Emission Scenario Documents,
• EU Risk Assessment Reports, and
• DMR surface water discharge data for vinyl chloride from National Pollutant Discharge
Elimination System (NPDES)-permitted facilities.
2. Review reasonably available chemical-specific release data, including measured or
estimated release data (e.gdata from risk assessments by other environmental agencies).
EPA has reviewed key release data sources including TRI, as summarized in Section 2.3.1. The Agency
plans to consider additional reasonably available information and will evaluate it during development of
the risk evaluation as well as match identified data to applicable COUs (Section 2.2) and identify COUs
where no data are found. EPA also plans to address data gaps identified as described in Steps 3 and 4
below by considering potential surrogate data and models.
Additionally, for COUs where no measured data on releases are reasonably available, EPA may use a
variety of methods including release estimation approaches and assumptions in the Chemical Screening
Tool for Exposures and Environmental Releases (ChemSTEER) (U.S. EPA. 2013).
3. Review reasonably available measured or estimated release data for surrogate chemicals
that have similar uses and physical properties.
EPA plans to review literature sources identified, and if surrogate data are found, these data will be
matched to applicable COUs for potentially filling data gaps.
4. Review reasonably available data that may be used in developing, adapting, or applying
exposure models to the particular risk evaluation.
This step will be performed after completion of Steps 2 and 3 above. EPA plans to evaluate relevant data
to determine whether the data can be used to develop, adapt, or apply models for specific COUs (and
corresponding release scenarios). The Agency has identified information from various EPA sources,
including, for example, regulatory limits, reporting thresholds, or disposal requirements that may be
relevant to consider for release estimation and environmental response. EPA also plans to further
consider relevant regulatory requirements in estimating releases during risk evaluation.
5. Review and determine applicability of OECD Emission Scenario Documents (ESDs) and
EPA Generic Scenarios to estimation of environmental releases.
EPA will identify potentially relevant OECD ESDs and EPA Generic Scenarios (GSs) that correspond to
COUs of vinyl chloride. If ESDs and GSs are not available, other methods may be considered. The
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Agency may perform additional supplemental targeted searches of peer-reviewed or gray literature to
understand those COUs that may inform identification of release scenarios. The Agency may also need
to perform supplemental targeted searches for applicable models and associated parameters that the
Agency may subsequently use to estimate releases for certain COUs. Additionally, for COUs where no
measured data on releases are available, EPA may use a variety of methods, including the application of
default assumptions.
6. Map or group each COU to a release assessment scenario(s).
EPA plans to map release scenarios to relevant COUs based on a variety of factors, such as process
equipment and handling, magnitude of production volume used, release sources and usage rates of vinyl
chloride, polymer products, and formulations containing vinyl chloride, corresponding to COUs using
reasonably available information. The Agency may perform supplemental targeted searches of peer-
reviewed or gray literature to better understand certain COUs to further develop release scenarios.
7. Evaluate the weight of scientific evidence of environmental release data.
During risk evaluation, EPA plans to evaluate and integrate the exposure evidence identified in the
literature inventory using the methods described in the Draft Systematic Review Protocol (U.S. EPA,
2021). Based on data quality and relevance (including strengths and limitations) and synthesis and
integration of the evidence, EPA will determine the weight of scientific evidence related to
environmental releases of vinyl chloride.
2.6.1.2 Fate and Transport
EPA plans to refine the analysis presented in the Draft Chemistry and Fate Assessment for Vinyl
Chloride (U.S. EPA. 2025a) on the physical and chemical properties and environmental fate and
transport of vinyl chloride according to the steps below. EPA will consider all reasonably available
information on vinyl chloride for inclusion in the risk evaluation.
1. Review reasonably available measured or estimated physical and chemical properties and
environmental fate endpoint data.
EPA plans to evaluate data and information collected through the systematic review process and public
comments about the physical and chemical properties (Table 2-1) and fate endpoints (Table Apx C-l).
The Agency plans to evaluate and integrate identified information according to the procedures and
metrics described in EPA's Draft Systematic Review Protocol (U.S. EPA, 2021). Where experimentally
measured values for chemical properties are not reasonably available or of sufficiently high-quality,
values will be estimated using chemical parameter estimation models as appropriate. Model-estimated
fate properties will be reviewed for applicability and quality. Newly identified and evaluated data will be
used to update and refine the preliminarily identified and selected physical and chemical properties and
environmental fate endpoints presented in this draft scope.
2. Use the updated dataset to revise the influence of physical and chemical properties and
environmental fate endpoints (e.gpersistence, bioaccumulation, partitioning, transport)
on exposure pathways and routes of exposure to human and environmental populations.
Measured data and, where necessary, model predictions of physical and chemical properties and
environmental fate endpoints will be used to update characterizations of the persistence and movement
of vinyl chloride within and across environmental media. As discussed in the Draft Chemistry and Fate
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Assessment for Vinyl Chloride (U.S. EPA, 2025a), fate characteristics of particular importance to vinyl
chloride include volatilization, solubility and transport in aqueous phases, atmospheric photolysis rates,
aerobic and anaerobic biodegradation rates, and abiotic reductive dehalogenation rates. EPA plans to use
these finalized endpoint data in exposure calculations.
3. Using the updated physical and chemical properties, environmental fate endpoints, and
associated analyses, refine the identification of major and minor pathways.
This will likely include rerunning the Level III fugacity model and assessing the long-range transport
potential of vinyl chloride—especially in the atmosphere—using finalized endpoint data as model
inputs. EPA plans to perform more granular, quantitative analyses on the preliminarily identified major
media and pathways highlighted in Section 2.5; media and pathways contributing less to vinyl chloride
exposure potential will receive qualitative assessment.
4. Conduct a weight of scientific evidence evaluation of physical and chemical properties and
environmental fate data, including qualitative and quantitative sources of information.
The Agency plans to evaluate the weight of scientific evidence for fate and transport information as
described in the Draft Systematic Review Protocol (U.S. EPA, 2021).
2.6.1.3 Environmental Exposures
EPA does not plan to quantitatively analyze environmental exposures to aquatic or terrestrial
environmental species (Sections 2.5.3.2.2 and 2.5.3.2.3). The Agency expects that vinyl chloride
concentrations in ambient air, especially close to industrial sites where vinyl chloride is produced or
used, may be significant. However, EPA generally does not assess inhalation hazards to environmental
species because environmental risk assessments, including those in TSCA risk evaluations, typically do
not quantitatively address inhalation hazards posed by VOCs (Markwiese et al„ 2008; Spring et al.,
2004; Carlsen, 1996). Based on release patterns and chemical and fate properties, vinyl chloride
concentrations in all other environmental media are expected to be negligible; therefore, exposure in
aquatic organisms and exposure by pathways other than inhalation in terrestrial organisms are expected
to be negligible.
2.6.1.4 Occupational Exposures
EPA plans to analyze worker and ONU exposures as described below.
1. Review reasonably available exposure monitoring data for specific COUs.
EPA plans to review exposure data including workplace monitoring data collected by government
agencies such as OSHA and NIOSH as well as monitoring data found in published literature. These
workplace monitoring data include personal exposure monitoring data (direct exposures) and area
monitoring data (indirect exposures).
OSHA has established a PEL for vinyl chloride of 1 ppm 8-hour TWA and a STEL of 5 ppm (OSHA,
2019). EPA plans to consider the influence of these regulatory limits on occupational exposures in the
occupational exposure assessment.
2. Review reasonably available exposure data for surrogate chemicals that have uses,
volatility, and physical and chemical properties similar to vinyl chloride.
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EPA plans to review literature sources identified and if surrogate data are found, these data will be
matched to applicable COUs for potentially filling data gaps.
3. Map or group each condition of use to occupational exposure assessment scenario(s).
EPA plans to conduct mapping or grouping of occupational exposure scenarios based on factors (e.g.,
process equipment and handling, magnitude of production volume used, exposure/release sources)
corresponding to COUs. The Agency may perform supplemental targeted searches of peer-reviewed or
gray literature to better understand certain COUs to further develop exposure scenarios. The mapping
will be completed in accordance with engineering assessment predictability tables that present the
assessment approaches used for each COU and occupational exposure scenario combination from past
risk evaluations. These tables provide insight into how various uses of a chemical may be assessed and
the type of data needed for the assessment.
4. For COUs where data are limited or not reasonably available, review existing exposure
models that may be applicable in estimating exposure levels.
EPA plans to identify relevant OECD ESDs and EPA GSs corresponding to COUs, and to critically
review these ESDs and GSs to determine their applicability to the COUs. If the Agency is not able to
identify ESDs or GSs for all COUs, it may conduct industry outreach or perform supplemental targeted
searches of peer-reviewed or gray literature to understand those COUs that may inform identification of
applicable exposure scenarios. EPA may also need to perform targeted supplemental searches to identify
applicable models that the Agency may subsequently use to estimate exposures for certain COUs.
5. Review reasonably available data that may be used in developing, adapting, or applying
exposure models to a particular risk evaluation scenario.
Based on information developed during Steps 2 and 3 above, EPA plans to evaluate relevant data to
determine whether the data can be used to develop, adapt, or apply models for specific COUs (and
corresponding exposure scenarios). The Agency may utilize existing, peer-reviewed exposure models
developed by EPA or other government agencies or that are reasonably available in the scientific
literature. Alternatively, the Agency may elect to develop additional models to assess specific COUs.
Inhalation exposure models may be simple box models or two-zone (near-field/far-field) models.
6. Consider and incorporate applicable engineering controls and/or PPE into exposure
scenarios.
EPA plans to review potentially relevant data sources on engineering controls and PPE to determine
their applicability and incorporation into exposure scenarios during risk evaluation. OSHA recommends
employers utilize the hierarchy of controls to address hazardous exposures in the workplace. The
hierarchy of controls strategy outlines, in descending order of priority, the use of elimination,
substitution, engineering controls, administrative controls, and lastly PPE. EPA plans to assess worker
exposure pre- and post-implementation of engineering controls using reasonably available information
on available control technologies and control effectiveness. For example, the Agency may assess worker
exposure in industrial use scenarios before and after implementation of local exhaust ventilation.
7. Evaluate the weight of scientific evidence of occupational exposure data, which may include
qualitative and quantitative sources of information.
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During risk evaluation, EPA plans to evaluate and integrate the exposure evidence identified in the
literature inventory using the methods described in the Draft Systematic Review Protocol (U.S. EPA.
2021). The Agency plans to rely on the weight of scientific evidence when evaluating and integrating
occupational data. EPA also plans to use systematic review methods to assemble the relevant data,
evaluate the data for quality and relevance including strengths and limitations, and synthesize and
integrate the evidence.
2.6.1.5 Consumer Exposures
EPA plans to analyze exposures for consumers using a consumer product and bystanders to a consumer
using the product as described below.
1. Group COUs to consumer exposure assessment scenarios.
2. Review available hazard and exposure information to determine whether oral and dermal
exposure routes will be quantitatively assessed.
EPA currently plans to qualitatively assess oral and dermal exposures via consumer products (Section
2.5.2.2). If information is identified (e.g., as data extraction and evaluation proceed [Section 1.3] or
public comments are received) that indicates that these exposure routes should be quantitatively
assessed, oral and/or dermal information will be included in subsequent steps of the consumer exposure
assessment.
3. Construct exposure scenarios.
EPA plans to consider all reasonably available information in developing the relevant exposure
pathways and in constructing consumer exposure scenarios. The following are important parameters to
construct consumer exposure scenarios:
• COU and type of consumer product specific to the exposed population (e.g., adults, children,
infants);
• Duration, frequency, and magnitude of exposure;
• Weight fraction of chemical in products: When weight fractions are not specified, such as several
plastic products containing PVC, EPA will assume a concentration equal to the SDS reporting
threshold. For carcinogens including vinyl chloride, that weight fraction is 0.1 percent;
• Amount of chemical used; and
• Use patterns of the consumer product.
If oral and dermal exposure routes are to be quantitatively assessed, additional route-specific parameters
include mouthing duration for oral exposure or absorption values for dermal exposure. These values will
be estimated based on peer-reviewed literature or modeling if no empirical data are available.
4. Evaluate existing indoor exposure models that may be applicable in estimating indoor air
concentrations.
Vinyl chloride is a VOC that is expected to volatilize readily from the surface of liquid and solid
consumer goods to air. Once emitted, partitioning to airborne dust and particulates is likely negligible
because it exists predominantly in the gas phase. Two models may be required to estimate exposure to
vinyl chloride via inhalation: (1) the Consumer Exposure Model (CEM), and (2) the Indoor
Environmental Concentrations in Buildings with Conditioned and Unconditioned Zones (IECCU)
Model. CEM can estimate exposure during use of liquid and paste products (e.g., paint). However, it
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was designed to model exposures to semi-volatile organic compounds (SVOCs), and its equations for
emissions of chemicals from solid articles contain simplifying assumptions specific to SVOCs that
undermines its suitability for use for VOCs. For inhalation exposure to solid articles, the IECCU model
may be more appropriate.
Both the CEM and IECCU Models consider physical and chemical properties (e.g., vapor pressure,
molecular weight), product-specific properties (e.g., weight fraction of the chemical in the product), use
patterns (e.g., duration and frequency of use), user environment (e.g., room of use, ventilation rates), and
characteristics of the exposed population (e.g., exposure factors, activity patterns).
Additional methods may be employed if oral and dermal exposures to vinyl chloride from consumer
products are to be quantitatively assessed.
5. Review reasonably available empirical data that may be used in developing, adapting, or
applying exposure models to each exposure scenario.
To the extent that previous assessments have already modeled a vinyl chloride consumer exposure
scenario using TSCA-relevant products, EPA plans to evaluate those modeled estimates along with their
underlying parameters and assumptions and compare to our modeled consumer exposure results. The
Agency also plans to compare its modeled estimates of indoor air concentrations from use of consumer
products with monitoring data reporting vinyl chloride in indoor air.
6. Review reasonably available population- or subpopulation-specific exposure factors and
activity patterns to determine if PESS need to be further refined.
EPA plans to both evaluate exposure scenarios that involve PESS and consider age-specific behaviors,
activity patterns, and exposure factors unique to those subpopulations. For some exposure scenarios
related to consumer uses, the Agency also plans to consider whether exposures for adults may differ
from those of children due to different activities (e.g., children who mouth certain products) or exposure
factors (e.g., inhalation rates).
7. Evaluate the weight of scientific evidence of consumer exposure estimates based on
different approaches.
EPA plans to rely on the weight of scientific evidence when evaluating and integrating data related to
consumer exposure. The weight of the scientific evidence may include qualitative and quantitative
sources of information. EPA also plans to use systematic review methods to assemble the relevant data,
evaluate the data for quality and relevance including strengths and limitations, and synthesize and
integrate the evidence.
2.6.1.6 General Population Exposures
EPA plans to analyze general population exposures to vinyl chloride in ambient air as described below.
1. Review reasonably available ambient air data collected through systematic review and
public comments.
a. Releases from COUs: EPA will use industry-specific releases from COUs, to be assessed
as described in Section 2.6.1.1, as evidence of presence of vinyl chloride in ambient air.
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b. Monitoring data: EPA will use monitoring data as (1) evidence of presence of vinyl
chloride in ambient air, and (2) to determine how modeled estimates of concentrations
near industrial point sources compare with reasonably available monitoring data. The
monitoring data EPA plans to use are the following:
i. Ambient Monitoring Technology Information Center (AMTIC) archive
ii. Literature. Literature data provides context but rarely if ever temporally or
spatially aligned with releases from COUs, and
iii. Other federal (including data collected from industry by other EPA offices), state,
or local monitoring data.
b. Previous assessments: To the extent other organizations have already modeled a vinyl
chloride general population exposure scenario, EPA plans to evaluate their monitored or
modeled estimates, along with their underlying parameters and assumptions, and compare
published exposure findings to exposure results.
2. Apply a tiered approach to estimate inhalation exposures from releases to ambient air.
The first-tier analysis is based on data that is reasonably available without a significant number of
additional inputs or assumptions. The results of first-tier analyses inform whether scenarios require more
refined analysis. Refined analyses will be iterative and require careful consideration of variability and
uncertainty.
a. Tier 1
i. Use the single highest release value within industries and sectors within the
reporting period (i.e., max kg/site-yr) as determined by the process described in
Section 2.6.1.1.
ii. Industry-specific data from TRI will be used in Tier 1.
iii. Use Integrated Indoor/Outdoor Air Calculator (IIOAC) Model. IIOAC estimates
high-end and central tendency (mean) exposures at 100, 100 to 1,000, and 1,000
m from a releasing point. Uses the most conservative (health protective) exposure
scenario: a facility that operates year-round (365 days per year, 24 hours per day,
7 days per week), a South Coastal meteorologic region, and a rural topography
setting.
iv. Use provisional inhalation point of departures (PODs) from prior assessments
(Section 2.4.2).
If there is no risk above Agency benchmark(s), EPA does not plan to further analyze the ambient air
pathway. If there is risk at or above Agency benchmark(s), EPA plans to conduct a Tier 2 analysis.
b. Tier 2
i. Use highest release for each industry or sector within the reporting period (i.e.,
max kg/site-yr for each industry/sector) as determined by the process described in
Section 2.6.1.1.
ii. Facility-specific data from TRI will be used in Tier 2.
iii. Use IIOAC Model.
iv. Use provisional inhalation PODs from prior assessments (Section 2.4.2).
If there is no risk at or above Agency benchmark(s) for a given industry or sector, EPA does not plan to
further analyze the ambient air pathway for that industry or sector. For any industries or sectors for
which there is risk at or above Agency benchmark(s), EPA plans to conduct a Tier 3 analysis.
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c. Tier 3
i. Use facility-specific releases and NEI data.
ii. Use Human Exposure Model (HEM).
iii. Use inhalation PODs as determined in the TSCA risk evaluation for vinyl
chloride.
3. Compare modeled estimates of concentrations near industrial point sources with available
monitoring data.
4. Evaluate the weight of scientific evidence of ambient air exposure estimates.
EPA plans to rely on the weight of scientific evidence when evaluating and integrating data related to
general population exposures. The weight of scientific evidence may include qualitative and quantitative
sources of information. EPA plans to use systematic review methods to assemble the relevant data,
evaluate the data for quality and relevance including strengths and limitations, and synthesize and
integrate the evidence.
For the non-air pathways, EPA expects to analyze general population exposure as follows:
1. Review reasonably available monitoring and source information collected through
systematic review and public comments.
The Agency plans to consider all identified information according to the procedures and metrics
described in EPA's Draft Systematic Review Protocol (U.S. EPA, 2021). It is not possible to source
apportion between TSCA and non-TSCA sources using monitoring data. However, this review will
inform assessment of potential vinyl chloride concentrations in these media and determination of
whether media other than air will be quantitatively analyzed.
2. Using the updated data following the completion of systematic review, revise the fit-for-
purpose assessment plans for human exposure pathways and routes.
As discussed in the Draft Chemistry and Fate Assessment for Vinyl Chloride (U.S. EPA. 2025a). fate
characteristics of particular importance to vinyl chloride include volatilization, solubility and transport
in aqueous phases, atmospheric photolysis rates, aerobic and anaerobic biodegradation rates, and abiotic
reductive dehalogenation rates. If the physical and chemical properties and environmental fate endpoints
are revised following review of reasonably available data, and further review of monitoring data support
the presence of vinyl chloride in other media, EPA plans to consider conducting quantitative analyses
for oral and dermal exposure to vinyl chloride from other environmental media (e.g., surface and
drinking water).
If these pathways are evaluated quantitatively, EPA plans to follow a similar approach as the ambient air
pathway. The Agency also plans to evaluate a variety of data types to determine which types are most
appropriate when assessing exposure scenarios. Environmental monitoring data, biomonitoring data,
modeled estimates, experimental data, epidemiological data, and survey-based data can all be used to
quantify exposure scenarios. Not all data types will be relevant to each pathway, although, for example,
experimental data will not be applicable to estimating exposure scenarios for drinking water ingestion.
After developing exposure scenarios, EPA plans to quantify concentrations and/or doses for these
scenarios using a tiered approach. The approaches will vary by the pathway being assessed. For
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example, the surface water pathway's Tier 1 approach may involve use of a simple dilution-based model
known as Exposure and Fate Assessment Screening Tool, version 2014 (E-FAST 2014) ("Versar. 2014).
A higher-tiered model may not be needed because partitioning of vinyl chloride to sediment and
suspended and dissolved solids in water is unlikely given its range of log Koc values identified to date.
Modeled estimates of concentrations will be compared with reasonably available monitoring data
including the Water Quality Portal, EPA's Safe Drinking Water's Six-Year Review, state databases, or
peer-reviewed literature obtained through systematic review. The Agency will plan to reply on the
weight of scientific evidence when evaluating and integrating data related to population exposures.
2.6.2 Hazards
2.6.2.1 Environmental Hazards
EPA expects to conduct an environmental hazard assessment as described below.
1. Review reasonably available environmental hazard data, including data from alternative
test methods (e.gcomputational toxicology and bioinformatics; high-throughput screening
methods; data on categories and read-across; in vitro studies).
EPA plans to qualitatively consider the hazards of vinyl chloride to aquatic and terrestrial organisms—
including vertebrates, invertebrates, and plants and/or algae across exposure durations and conditions if
potential environmental hazards are identified through systematic review and public comments.
Additional types of environmental hazard information may also be considered (e.g., analog and read-
across data) when characterizing the potential hazards of vinyl chloride to aquatic organisms.
EPA also plans to evaluate environmental hazard data using the evaluation strategies laid out in the
Draft Systematic Review Protocol (U.S. EPA. 2021). The study evaluation results will be documented in
the risk evaluation phase and data from acceptable studies will be extracted and integrated in the risk
evaluation process.
2. Derive hazard thresholds.
EPA plans to qualitatively consider the hazards of vinyl chloride to aquatic and terrestrial organisms and
does not plan to derive quantitative hazard thresholds.
3. Evaluate the weight of scientific evidence of environmental hazard data.
During risk evaluation, EPA plans to evaluate and integrate the environmental hazard evidence
identified in the literature inventory using the methods described in the Draft Systematic Review
Protocol (U.S. EPA. 202IV
4. Consider the route(s) of exposure, based on reasonably available monitoring and modeling
data, and other available approaches to integrate exposure and hazard assessments.
EPA also plans to qualitatively consider aquatic (e.g., water and sediment exposures) and terrestrial
(e.g., soil) pathways in the vinyl chloride conceptual model.
5. Consider a persistence, bioaccumulation, and toxicity assessment of vinyl chloride.
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Vinyl chloride is not expected to persist in environmental media. EPA plans to consider the reasonably
available studies collected from the systematic review process relating to bioaccumulation and
bioconcentration (e.g., BAF, BCF) of vinyl chloride. Detailed information on the draft physical and
chemical assessment of vinyl chloride, including a discussion of preliminary-available bioconcentration
information, is available in the Draft Chemistry and Fate Assessment for Vinyl Chloride U.S. EPA.
2025a). Additional bioconcentration data that becomes available through systematic review or through
public comment will also be considered. EPA also plans to qualitatively consider environmental hazard
endpoint values (e.g., LC50, lowest-observed-effect concentration [LOEC]) if sufficient data is available
and exposure concentrations (e.g., surface water concentrations, tissue concentrations) for vinyl chloride
with the fate parameters (e.g., BAF, BCF, biomagnification factor, trophic magnification factor) in the
environmental risk characterization.
2.6.2.2 Human Health Hazards
EPA expects to evaluate human health hazards as follows. The steps described below are iterative and
may not necessarily occur in the prescribed order based on data availability and evolving fit-for-purpose
analysis during the evaluation stage.
1. Review reasonably available epidemiological, animal toxicology, and mechanistic studies
including data from alternative test methods (e.gcomputational toxicology and
bioinformatics; high-throughput screening methods; data on categories and read-across; in
vitro studies; systems biology).
EPA plans to review epidemiological, animal toxicology, and mechanistic studies using the strategies
described in the Draft Systematic Review Protocol (U.S. EPA. 2021). During prioritization, the Agency
searched and screened publicly available peer-reviewed literature, gray literature including previous
assessments from other regulatory agencies, and other relevant information submitted to EPA to identify
literature pertinent to understanding the potential human health hazards of vinyl chloride. Next, the
Agency will produce literature inventory trees and evidence tables to summarize the extent and nature of
the evidence that meets the human health hazard screening criteria. EPA will then evaluate the quality of
key studies and extract information containing relevant data for dose-response analysis. In identifying
key studies for data evaluation and extraction, the Agency will prioritize studies used to derive hazard
values in the ATSDR (2024) and EPA IRIS (2000) assessments, in addition to any other studies
identified in EPA's systematic review of the reasonably available literature that were not covered by
these assessments. The Agency's review of the literature will additionally focus on identifying data on
toxicokinetics, mode of action, and factors that increase biological susceptibility to vinyl chloride to
support the PESS analysis.
2. Conduct hazard identification (the qualitative process of identifying non-cancer and cancer
endpoints) and evidence integration (evaluating the evidence supporting those endpoints
across all evidence streams) that may include mode of action analysis for target
organs/critical effects, especially for cancer.
To identify human health hazards from acute, intermediate, and chronic exposures, EPA will consider
conclusions from previous assessments (discussed in Sections 2.4.2.1 and 2.4.2.2) in addition to
epidemiological, animal toxicology, and mechanistic data identified during the TSCA systematic review
process (U.S. EPA. 2021). The Agency will integrate these separate bodies of evidence to draw an
overall judgement for each potential health effect. The evidence integration strategy will be designed to
be fit-for-purpose in which EPA will use systematic review methods to assemble the relevant data;
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evaluate the data for quality and relevance, including strengths and limitations; followed by synthesis
and integration of the evidence; and considering principles of Bradford-Hill criteria. The results of
evidence integration will inform which endpoints are considered for dose-response analysis. Refer to
Section 7 in the Draft Systematic Review Protocol (U.S. EPA. 2021) for more information on the
general process for evidence integration.
The cancer mode of action (MOA) determines how cancer risks can be quantitatively evaluated. EPA
will evaluate information on genotoxicity and other information informing the MOA for cancer to
determine the appropriate dose-response approach for quantitative cancer assessment in accordance with
the U.S. EPA Guidelines for Carcinogen Risk Assessment (U.S. EPA. 2005a). Based on an initial review
of the literature, including previous assessments (discussed in Section 2.4.2.2), vinyl chloride appears to
have a mutagenic MOA. MOA analysis will also be performed for non-cancer endpoints when
appropriate for informing dosimetry, human relevance, or other dose-response considerations.
3. Conduct dose-response analysis, including selection of key studies and hazard endpoints.
Identify what types of hazard values (e.ginhalation unit risk [IUR], cancer slope factor
[CSF], no-observed-adverse-effect concentration or level [NOAEC/NOAEL], benchmark
concentration or dose limit [BMCL/BMDL]) are appropriate for the assessment and what
adjustments are required. Adjustments may include dosimetry for extrapolating across
species or routes, duration adjustments to consistently match a given human exposure
scenario, and modeling to refine the precision of hazard values. Determine appropriate
uncertainty factors required to account for adjustments that could not be accurately
quantified.
EPA will evaluate whether cancer and non-cancer hazard values need to be updated from prior
assessments or derived de novo. In cases where the Agency must derive updated/new hazard values,
non-cancer dose-response assessment will be performed in accordance with the following EPA guidance
to derive hazard values:
• U.S. EPA Guidelines for Carcinogen Risk Assessment (U.S. EPA. 2005a)
• Methods for Derivation of Inhalation Reference Concentrations and Application of Inhalation
Dosimetry (U.S. EPA. 1994)
• Exposure Factors Handbook: 2011 Edition (U.S. EPA, 201 la)
• Recommended Use of Body Weight 3/4 as the Default Method in Derivation of the Oral
Reference Dose (U.S. EPA. 201 lb)
• Benchmark Dose Technical Guidance (U.S. EPA. 2012b)
• A Review of the Reference Dose and Reference Concentration Processes (U.S. EPA. 2002b)
• Advances in Inhalation Gas Dosimetry for Derivation of a Reference Concentration (RfC) and
Use in Risk Assessment (U.S. EPA. 2012a).
Consistent with EPA's Benchmark Dose Technical Guidance Document (U.S. EPA. 2012b). non-cancer
hazard data will be evaluated to determine whether benchmark dose modeling is applicable to derive a
benchmark dose lower 95th percentile estimate (BMDL). Where benchmark dose modeling is not
feasible, NOAELs and lowest-observed-adverse-effect levels (LOAELs) will be identified.
To derive cancer hazard values, dose-response assessment will be performed in accordance with EPA's
Guidelines for Carcinogen Risk Assessment (U.S. EPA. 2005a). The Agency will determine whether a
linear or threshold-based approach is appropriate depending on the cancer MOA for vinyl chloride.
Based on an initial review of the literature, including previous assessments (discussed in Section
2.4.2.2), vinyl chloride appears to have a mutagenic MOA; therefore, EPA expects to perform linear
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modeling. In accordance with EPA's Supplemental Guidance for Assessing Susceptibility from Early-
Life Exposures to Carcinogens (U.S. EPA. 2005b). and based on the determination in previous
assessments that vinyl chloride is carcinogenic through a mutagenic MO A, EPA plans to apply age-
dependent adjustment factors when calculating cancer risk for specific COUs that involve potential early
life exposure to vinyl chloride.
EPA will evaluate whether the available physiologically-based pharmacokinetic (PBPK) and empirical
kinetic models for vinyl chloride are adequate for interspecies extrapolation of hazard values, or for
extrapolation of the hazard values to standard exposure durations (e.g., lifetime continuous exposure). If
application of the PBPK Model is not possible, oral hazard values may be adjusted by body weight
(BW)3/4 scaling in accordance with (U.S. EPA. 2011b) and inhalation hazard values may be adjusted by
exposure duration and chemical properties in accordance with (U.S. EPA. 2012a. 2002b. 1994).
Studies from all available routes will be considered for hazard values and route-to-route extrapolation
will be performed as needed. For vinyl chloride, EPA will consider whether the oral toxicological
studies are adequate for use in dose-response due to uncertainties in the method of administration (e.g.,
entrained in PVC powder). There may be uncertainties both in the accurate quantification of vinyl
chloride monomer and additionally whether the PVC powder itself may be inducing any toxicological
responses. In such cases where data are either limited or unavailable for a given exposure route, EPA
will consider whether route-to-route extrapolation is valid based on portal of entry effects, first pass
metabolism, method of exposure administration, and the relevance of that exposure route given vinyl
chloride's COUs and physical-chemical properties. Without an adequate PBPK Model, considerations
regarding the adequacy of data for route-to-route extrapolation are described in (U.S. EPA. 2012a.
2002b. 1994). EPA may use these considerations when determining whether to extrapolate from the oral
to the inhalation route of exposure. Similar approaches for oral-to-dermal route extrapolation are
described in EPA's Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation
Manual (Part E, Supplemental Guidance for Dermal Risk Assessment) (U.S. EPA. 2004).
Uncertainty factors (UFs) are used to account for potential uncertainty in estimating a human exposure
that will not result in any adverse health effects. EPA will apply UFs in the human health hazard dose-
response assessment according to previously published guidance (U.S. EPA. 2002b. 1994). In summary,
the Agency will determine whether any of the following UFs is appropriate depending on the
uncertainties, variability, or absence of human health hazard data for vinyl chloride: An interspecies UF
(UFa) to account for uncertainty related to extrapolating from experimental animals to humans; an
intraspecies UF (UFh) to account for variation in sensitivity among the human population; a LOAEL-to-
NOAEL UF (UFl) to account for use of a LOAEL rather than a NOAEL or BMDL value; a subchronic-
to-chronic UF (UFs) to account for uncertainty in extrapolating effects observed in a short-term
exposure study to potential effects for a longer exposure duration; and a database UF (UFd) to account
for deficiencies in the toxicological database that might lead to a lower POD.
4. Identify factors that increase biological susceptibility and determine whether these groups
were addressed in the risk assessment.
Reasonably available human health hazard data will be evaluated to ascertain whether some human
populations may have greater susceptibility than the general population to vinyl chloride hazard(s).
Susceptibility of particular human populations to vinyl chloride will be determined by evaluating
information on factors such as life stage, pre-existing diseases or disorders, lifestyle activities,
sociodemographic status, nutrition, genetics, and other chemical and nonchemical stressors.
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5. Evaluate the weight of scientific evidence and overall confidence for human health hazard
conclusions.
EPA will evaluate the weight of the scientific evidence supporting the human health hazard assessment.
This evaluation may separately consider distinct aspects such as evidence integration, dose-response,
and incorporation of PESS. The Agency EPA will then describe overall confidence in human health
hazard conclusions based on these considerations.
2J5.3 Risk Characterization
Risk characterization is an integral component of the risk assessment process for both ecological and
human health risks. The Agency will derive the risk characterization in accordance with EPA's Risk
Characterization Handbook (U.S. EPA. 2000a). More specifically, EPA will consider for each COU and
exposure scenario whether risks should be quantified or qualitatively described based on a fit-for-
purpose assessment. Risks which are quantified will be compared to various benchmarks. These
benchmarks are not "bright-lines" for determination of unreasonable risk but provide context for where a
risk concern may exist. EPA expects to only qualitatively describe environmental risk. For human health
non-cancer effects, an MOE approach is used where the value of the POD divided by the exposure
estimate is compared to a benchmark MOE that incorporates relevant uncertainty factors. Cancer risk
will be estimated by multiplying the cancer hazard value by the lifetime average daily
dose/concentration (for tumors following a linear model, as is expected for vinyl chloride). For all risk
calculations, assumptions, exposure durations, and exposure factors will be coordinated across hazard
and exposure considerations. EPA may additionally qualitatively describe some risks through
comparative narrative or using pilot examples. Tier-based approaches may also be used, whereby a
conservative screening estimate is followed by a more detailed analysis if risk concerns are indicated.
Risk characterization at EPA assumes different levels of complexity depending on the nature of the risk
assessment being characterized. 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. 2000a). EPA will also present information in this section
consistent with approaches described in the Procedures for Chemical Risk Evaluation Under the Toxic
Substances Control Act (TSCA) Rule (EPA). 2024). For instance, in the risk characterization summary,
EPA will further carry out the obligations under TSCA section 26; for example, by identifying and
assessing uncertainty and variability in each step of the risk evaluation, discussing considerations of data
quality such as the reliability, relevance and whether the methods utilized were reasonable and
consistent, explaining any assumptions used, and discussing information generated from independent
peer review. The Agency will also be guided by EPA's Information Quality Guidelines (U.S. EPA.
2002a) as it provides guidance for presenting risk information. Consistent with those guidelines, in the
risk characterization, EPA will also identify (1) each population addressed by an estimate of applicable
risk effects; (2) the expected upper end risk or central estimate of risk, including consideration of any
potentially exposed or susceptible subpopulations affected; (3) each significant uncertainty identified as
part of the risk assessment how these uncertainties might lead to over- or underestimation of risk; and
(4) all reasonably available information known to the Agency that support, are directly relevant to, or
fail to support any estimate of risk effects and the methodology used to reconcile inconsistencies in the
scientific information.
2.7 Peer Review
Peer review will be conducted in accordance with EPA's regulatory procedures for chemical risk
evaluations, including using the Procedures for Chemical Risk Evaluation under the Toxic Substances
Control Act (TSCA); Final Rule (May 3, 2024; 89 FR 37028), preamble to the TSCA Risk Evaluation
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2078 Rule (89 FR 37041-37042),), EPA's Peer Review Handbook (U.S. EPA, 2015a), and other methods
2079 consistent with Section 26 of TSCA (40 CFR 702.41). As explained in the TSCA Risk Evaluation Rule,
2080 the purpose of peer review is for the independent review of the science underlying the risk assessment.
2081 Peer review will therefore address aspects of the underlying science as outlined in the charge to the peer
2082 review panel such as hazard assessment, assessment of dose-response, exposure assessment, and risk
2083 characterization. The draft risk evaluation for vinyl chloride will be peer reviewed with the appropriate
2084 scope and type of peer review consistent with the applicable peer review policies, procedures, and
2085 methods in guidance promulgated by the Office of Management and Budget and EPA, and in
2086 accordance with 15 U.S.C. 2625(h) and (i).
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75-01-4). Washington, DC: Office of Pollution Prevention and Toxics.
Versar. (2014). Exposure and Fate Assessment Screening Tool (E-FAST 2014) - Documentation
manual. Washington, DC: U.S. Environmental Protection Agency, https://www.epa.gov/tsca-
screening-tools/e-fast-exposure-and-fate-assessment-screening-tool-version-2014
Walter. RK; Lin. PH; Edwards. M; Richardson. RE. (2011). Investigation of factors affecting the
accumulation of vinyl chloride in polyvinyl chloride piping used in drinking water distribution
systems. Water Res 45: 2607-2615. http://dx.doi.Org/10.1016/i.watres.2011.02.016
Whittaker. C. (2017). Current Intelligence Bull. 68, NIOSH Chemical Carcinogen Policy at 20.
Cincinnati, OH: National Institute of Occupational Safety and Health.
https://www.cdc.gov/niosh/docs/2017-100/pdf/2017-10Q.pdf
WHO (World Health Organization). (2004). Vinyl Chloride in Drinking-Water. Background document
for development of WHO Guidelines for Drinking-water Quality. (WHO/SDE/WSH/03.04/119).
Geneva, Switzerland, https://cdn.who.int/media/docs/default-source/wash-documents/wash-
chemicals/vinvlchloride.pdf?sfvrsn=8el9c6cd 4
Wood, PR; Lang, RF; Payan, IL. (1985). Anaerobic transformation, transport, and removal of volatile
Page 63 of 75
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2381 chlorinated organics in ground water. In GW Ward Ch (Ed.), Ground water quality (pp. 493-
2382 511). New York, NY: John Wiley and Sons.
2383 https://search.proquest.com/docview/19041334?accountid=171501
2384
2385
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2386 APPENDICES
2387
2388 Appendix A ASSESSMENT HISTORY
2389 Table Apx A-l. Assessment History
Authoring Organization
Title or Description
Reference
EPA
Integrated Risk Information
System (IRIS)
Toxicological Review of Vinyl Chloride
U.S. EPA (2000b)
IRIS
IRIS Chemical Assessment Summary:
Vinyl Chloride CASRN 75-01-4
IRIS (2000)
Office of Research and
Development (ORD)
Scientific and Technical Assessment
Report on Vinyl Chloride and Polyvinyl
Chloride
ORD (1975)
Office of Water
Update of Human Health Ambient
Water Quality Criteria: Vinyl Chloride
75-01-4
U.S. EPA (2015b)
Office of Water
Vinyl Chloride Health Advisory Draft
U.S. EPA (1987)
Office of Water
Drinking Water Criteria Document for
Vinyl Chloride (Final Draft)
U.S. EPA (1985)
Other U.S.-Based Organizations
ATSDR
Toxicological Profile for Vinyl
Chloride: Draft for Public Comment
ATSDR (2024)
ATSDR
Interaction Profile for Chloroform, 1,1-
Dichloroethvlene, Trichloroethvlene,
and Vinyl Chloride [Draft]
ATSDR (2007)
ATSDR
Toxicological Profile for Vinyl
Chloride
ATSDR (2006)
California Air Resources
Board (CARB)
Proposed Identification of Vinyl-
Chloride as a Toxic Air Contaminant
CARB (1990a)
CARB
Proposed Identification of Vinyl-
Chloride as a Toxic Air Contaminant:
Technical Support Document, Part A:
Public Exposure to. Sources, and
Emissions of Vinyl Chloride in
California
CARB (1990b)
CARB
Proposed Identification of Vinyl-
Chloride as a Toxic Air Contaminant:
Technical Support Document, Part B:
Health Effects of Airborne Vinyl
Chloride
CARB (1990c)
California Environmental
Protection Agency
Human Health Risk Assessment Note 3
- DTSC-Modified Screening Levels
(DTSC-SLs), June 2020, Revised
Update
CA DTSC (2022)
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Authoring Organization
Title or Description
Reference
California Environmental
Protection Agency
Technical Support Document for
Cancer Potency Values, Appendix B:
Chemical-Specific Summaries of the
Information Used to Derive Unit Risk
and Cancer Potency Values
OEHHA (2011)
California Environmental
Protection Agency
Technical Support Document for
Noncancer RELs, Appendix D2: Acute
RELs and Toxicity Summaries Using
the Previous Version of the Hot Spots
Risk Assessment Guidelines (OEHHA
1999)
OEHHA (2008)
National Research Council
(now the National
Academies of Sciences,
Engineering, and Medicine)
Vinyl Chloride: Acute Exposure
Guideline Levels, in Acute Exposure
Guideline Levels for Selected Airborne
Chemicals
NRC (2012)
National Toxicology
Program
Vinyl Halides (Selected), in Report on
Carcinogens
NTP (2021)
International Organizations
Australia: National
Industrial Chemicals
Notification and Assessment
Scheme (NICNAS)
Ethene, Chloro-: Environment Tier II
Assessment
NICNAS (2014a)
Australia: NICNAS
Ethene, Chloro-: Human Health Tier II
Assessment
NICNAS (2014b)
Canada: Health Canada
Guidelines for Canadian Drinking
Water Quality: Guideline Technical
Document - Vinyl Chloride
Health Canada (2013)
International Agency for
Research on Cancer
Vinyl Chloride, in Chemical Agents and
Related Occupations: A Review of
Human Carcinogens
IARC (2012)
OECD
SIDS Initial Assessment Report for
SIAM13: Vinyl Chloride
OECD (2001)
World Health Organization
Vinyl Chloride in Drinking-Water.
Background Document for
Development o f Who Guidelines for
Drinking-Water Quality
WHO (2004)
World Health Organization:
International Program on
Chemical Safety
Environmental Health Criteria (EHC)
215: Vinyl Chloride
IPCS (1999)
2390
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2391 Appendix B EVIDENCE MAPS OF VINYL CHLORIDE
2392 INFORMATION
2393 B.l Fate and Transport
2394
Distinct count of Hero ID
1
Media
Endpoints
Air
Sediment
Soil
Wastewater/
biosolids
Water
Other
Grand Total
Atmospheric Cycling/Transport
3
1
1
2
5
Bioconcentration
1
3
1
5
5
Biodegradation
4
29
17
9
90
30
118
Drinking Water Treatment
1
3
2
3
Hydrolysis
1
2
1
4
4
Incineration
1
1
Photolysis
10
1
3
2
7
1
16
Reductive Dehalogenation
1
7
3
22
5
27
Sorption
1
4
1
4
1
5
Transformation Products
7
7
2
2
17
9
31
Vapor Intrusion
1
1
1
2
Volatilization
2
1
3
1
7
2
8
Wastewater Treatment
2
1
7
8
1
11
Other
3
3
2
1
22
38
38
Grand Total
21
32
20
10
101
38
147
2395
2396 FigureApx B-l. Evidence Map of Environmental Fate and Transport Properties for Vinyl
2397 Chloride
2398 View the interactive evidence map in HAWC. Data in this figure represent the references obtained from the
2399 publicly available databases and gray literature references searches that were included in systematic review as of
2400 December 11, 2024. Additional data may be added to the interactive version as they become available.
2401
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2402 B.2 Occupational Exposure and Environmental Release
Distinct count of Hero ID
41 ¦ 146
Data Type Evidence Tag
References
COU Disposal
30
Distribution in Commerce
5
Industrial/Commercial Use
37
Manufacture - Domestic manufacture
101
Manufacture-Import
7
Processing - Processing - repackaging
5
Processing - Processing as a reactant
113
Processing - Processing incorporation into formulation, mixture, or reaction product
94
Processing - Processing- incorporation into articles
87
Processing - Recycling
4
COU Other
60
Total
303
Environmental Accidental releases/spills
4
Release Description of the release source
66
Environmental release media
52
Release frequency
17
Release or emission factors
56
Release quantity
42
Waste treatment and pollution control
44
Total
85
General Chemical Concentration
25
Engineering Life cycle Description
11
Number of sites
45
Process description
121
Production, Import, or Use Volume
50
Throughput
19
Total
164
Occupational Area sampling data
129
Exposure Dermal exposure data
12
Engineering control
44
Exposure duration
82
Exposure frequency
45
Exposure route
105
Number of workers
115
Particle size characterization
4
Personal protective equipment
31
Personal sampling data
108
Physical form
55
Sampling and analytical methodology
60
Worker Activity description
146
Total
225
Grand Total
303
The column totals, row totals, and grand totals indicate total numbers of distinct references. The various shades of color v isually represent the distinct number of relevant re ferences
2403 identified by data type or engineering evidence tag. The darker the color, the more references are available for a given data type or engineering ev idence tag.
2404 Figure Apx B-2. Evidence Map of Occupational Exposure and Environmental Release
2405 Information for Vinyl Chloride
2406 View the interactive evidence map in HAWC. Data in this figure represent the references obtained from the
2407 publicly available databases and gray literature references searches that were included in systematic review as of
2408 December 19, 2024. Additional data may be added to the interactive version as they become available.
Page 68 of 75
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2409 B.3 General Population, Consumer, and Environmental Exposure
Distinct count of Hero ID
1IH
Sludv type
Media
Completed
Assessment
Database
Experimental
Modeling
Monitoring
Survey
Grand Total
Ambient (Outdoor) Air
12
8
1
17
44
72
Aquatic Species
1
2
2
5
Biosolids Sludge
1
4
5
Building Material
2
1
2
Consumer Product or Article
2
1
8
2
2
12
Dietary/Food
5
1
2
2
7
15
Drinking Water
10
3
3
2
18
33
Dust (Indoor)
1
1
Groundwater
9
3
1
9
94
III
Human Biomonitoring - Blood
I
2
1
3
Human Biomonitoring - Dermal
1
1
Human Biomonitoring - Milk
1
1
Human Biomonitoring - Tissues, Other
1
1
1
2
Human Biomonitoring - Urine
1
1
2
Indoor Air
4
2
6
3
10
22
Leachate
1
2
3
6
Other Media
3
1
5
7
22
33
Personal Inhalation
2
1
3
6
Precipitation
1
1
1
Sediment
3
1
1
8
12
Soil
5
3
1
3
18
27
Surface Water
9
4
2
24
37
Terrestrial Species
1
1
3
5
Wastewater
5
1
1
11
18
Grand Total
21
11
17
34
176
0
238
The column totals, row totals, and grand totals indicate total numbers of distinct references. The various shades of color visually represent the distinct
number of relevant references identified by study type or media tag. The darker the color, the more references are available for a given study type or
2410 media tag-
2411 Figtire Apx B-3. Evidence Map of Consumer, General Population, and Environmental Exposure
2412 Information for Vinyl Chloride
2413 View the interactive evidence map in HAWC. Data in this figure represent the references obtained from the
2414 publicly available databases and gray literature references searches that were included in systematic review as of
2415 January 6, 2025. Additional data may be added to the interactive version as they become available.
2416
Page 69 of 75
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2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
PUBLIC RELEASE DRAFT
January 2025
B.4 Environmental Hazard
Distinct count of Hero ID
Ecosystem / Taxonomic group
Aquatic
Terrestrial
Health outcome
. , _ t > Vegetation and
Invertebrate Vertebrate „
rungi
. , ,, , Vegetation and
Invertebrate Vertebrate _
rungi
Grand Total
Accumulation/ADM E
0
Behavior
1 1
2
Biochemical/Biochemistry, Enzyme(s), Hormone(s)
1
1
Biomarkers
1 ~1
I ~1
2
| Cancer/Carcinogenesis
0
Cell signaling/function
1
1
Computation toxicology and data integration
0
| Cytotoxicity
0
| Development
1
1
2
| Ecosystem processes
0
Enhanced adipogenesis
0
| Epigenetics
0
Cienotoxicity
4
4
Growth
1 1 1
3
| Histology
0
Immobilization
0
Morphology
1
1
| Mortality
2
3
5
Oxidative stress
1
1
Photosynthesis/Respiration
0
Physiology/organ function
0
| Population
0
Receptor binding/regulation of receptor activity
0
Reproduction
1
3
4
Grand Total
2 2 1
5 0 0
9
The column totals, row totals, and grand totals indicate total numbers of distinct references. The various shades of color visually represent the distinct number of relevant
references identified by taxonomic group or health outcome tag. The darker the color, the more references are available for a given taxonomic group or health outcome tag...
FigureApx B-4. Evidence Map of Environmental Hazard Information for Vinyl Chloride
View the interactive evidence map in HAWC. Data in this figure represent all references obtained from the
publicly available databases and gray literature reference searches that were included in systematic review as of
December 19, 2024. Additional data may be added to the interactive version as they become available. The left
side of the evidence map depicts references obtained for aquatic ecosystems while the right side depicts references
obtained for terrestrial ecosystems. The column and row grand totals indicate total number of distinct references.
The various shades of color represent the number of relevant references identified for each health outcome-
taxonomic group pair. Darker colors indicate a higher number of references available for a given health outcome-
taxonomic group pair. In cases where a given reference reported the same health outcome for multiple taxonomic
groups and/or multiple health outcomes for a single taxonomic group, the number of references within the table
may appear higher than the grand totals.
Page 70 of 75
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2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
PUBLIC RELEASE DRAFT
January 2025
B.5 Human Health Hazard
Distinct count of Hero ID
Exposure type
Health
outcome
Animal toxicity
Epidemiology
Inhalation
Oral
Dermal
Drinking
water
Food
Inhalation
Ocular/Eye
Teeth or
denial patient
Grand Total
Caneer/Carcinogenesis
28
7
68
4
2
31
124
Cardiovascular
20
4
33
2 1
38
17
61
Gastrointestinal
6
4
15
1
19
9
28
Hepatic/Liver
56
8
41
4
2
51
20
113
Immune 11 ematologtcal
28
5
28
4
3
37
13
1
69
Irritation(skin, eye)
3
3
3
3
Lung/Respiratory
24
5
30
2 1
38
19
65
Mortality
33
6
26
1 1
32
13
69
Musculoskeletal
5
2
7
I
9
4
16
Neurological/Behavioral
19
6
16
2 1
26
10
48
Nutritional/Metabolic
39
7
7 1 1
9
4
53
Ocular/Sensory
4
2
4
9
3
14
Other
28
7
44
1
64
24
97
Renal/Kidney
25
5
13 1 1
18
8
46
Reproductive/Developmental
25
5
9 1 1
15
4
44
Sensitization
5
5
Skin/Connective Tissue
5
2
10
1
2
14
7
1
20
Thyroid
5
3
1
9
Grand Total
90
9
129
9
4
176
65
1
272
The column totals, row totals, and grand totals indicate total numbers of distinct references. The various shades of color visually represent the distinct
number of relevant references identified by exposure type or health outcome tag. The darker the color, the more references are available for a given expos..
FigureApx B-5. Evidence Map for Human Health Hazard Information for Vinyl Chloride
View the interactive evidence map m HAWC. Data in this figure represent all references obtained from the
publicly available databases that were included in systematic review as of December 19, 2024. Additional data
may be added to the interactive version as they become available. The X-axis lists exposure types:
oral/food/drinking water, dermal, inhalation, and ocular. The Y-axis lists health outcomes described for each
appropriate exposure type The column totals, row totals, and grand totals indicate total numbers of distinct
references. The vanous shades of color visually represent the distinct number of relevant references identified for
each health outcome-taxonomic group pair. Darker colors indicate a higher number of references available for a
given health outcome-exposure pair.
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2442 Appendix C ENVIRONMENTAL FATE PROPERTIES OF
2443 VINYL CHLORIDE
2444
2445 Table Apx C-l. Environmental Fate Properties of Vinyl Chloride
Property or Endpoint
Value"
Reference(s)
Does not absorb light at wavelengths >218
ATSDR (2024)
Direct photodegradation
(air)
nm
0.09 s_1 determined in static system, xenon
lamp irradiation at 2.7 kW;
Reaxvs(2023)
Section 3.3.2.1''
0.047 s_1 determined from flow experiments
with 16-second residence time, xenon lamps
at 3.7 kW
Direct photodegradation
(water)
0% over 90 hours in water at 10 mg/L test
substance concentration irradiated with >300
OECD (2001)
Section 3.3.2.2d
nm; absorption in water was <218 nm
•OH-mediated: ti/2 range = 1.27 to 2.71 days
(n = 9; based on »OH rate constants of
OECD (2001). ECHA (2023a).
NLM (2023a). NIST (2023).
3.95E10-12 to 8.40E10-12 cm3/mole-sec
ATSDR (2024)
and a 12-hour day with 1.5E6 OH/cm3)
Indirect
photodegradation (air)
NCh-mediated: ti/2 range = 155 to 478 days (n
= 6; based on NO3 rate constants of 1.40E-16
to 4.30E-16 cm3/mole-sec and a 12-hour day
ECHA (2023a). NIST (2023)
Section 3.3.2.1''
with 2.40E08 NO;,/cm3)
Os-mediated: ti/2 range = 91.3 to 93.6 days (n
= 2; based on O3 rate constant of 2.45E-19 to
ECHA (2023a). NLM (2023a)
2.51E-19 cm3/mole-sec and a 12-hour day
with 7.0E11 Os/cm3)
No decomposition over 20 hours at 10 mg/L
test substance concentration in unfiltered
OECD (2001)
Oconee River and Okefenokee Swamp water
with 20 mg/L commercial humic acid
Indirect
80% over 3 hours at 10 mg/L test substance
OECD (2001)
photodegradation
concentration, and H2O2 as a photosensitizer
(water)
Not readily degraded at 10 mg/L test
substance concentration, with 1.0E-04M
OECD (2001)
Section 3.3.2.2d
methylene blue (singlet) and irradiation at
578 nm
Rapid decomposition at 10 mg/L test
substance concentration, with 10% vol.
OECD (2001)
acetone and UV irradiation at 313 nm
Hydrolysis half-life
(water)
Section 3.3.1''
ti/2 > 9.91 years at 25 °C and pH 7
ti/2 > 107 years at 10 °C and pH 7
NLM (2023a)
ti/2 > 1 year at both pH 4 and 6.1
OECD (2001)
No degradation observed in water after 12
hours at 85 °C, at 20 mg/L test substance
concentration; saturated with molecular
oxygen
ATSDR (2024)
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Property or Endpoint
Value"
Reference(s)
<10 years at 25.5 °C and pH 4.3-9.4
(estimated)
OECD (2001). ATSDR (2024)
Abiotic reductive
dehalogenation (water,
soil)
Section 3.3.3d
<0.002 d_1 with zero-valent Fetb, and 0.59 to
0.76 d_1 with zero-valent FeBH
Reaxvs(2023)
0.055, 0.323, 0.537, and 0.555 d_1 with
Silawa loamy sand, montmorillonite,
vermiculite, and biotite, respectively, in the
presence of Fe(II) at 22 °C and pH 7-7.2
Reaxvs(2023)
0.247, 0.355, and 0.358 d_1 with
montmorillonite, vermiculite, and biotite,
respectively, at 22°C and pH 7
Reaxvs(2023)
0.15 d_1 with Silawa loamy sand and
dithionite at pH 7.2
Reaxvs(2023)
0.94 d 1 with green rust sulfate in Tris buffer
at 22 °C and pH8.1
Reaxvs(2023)
Aerobic biodegradation
(water)
Section 3.3.4.1d
21.5% over 5 days (CO2 evolution) at 0.05
mg/L test substance concentration,
with municipal activated sludge inoculum,
adaptation not specified
OECD (2001). ECHA (2023a)
16% over 28 days (OECD 30ID) at 2.04
mg/L test substance concentration;
with sludge inoculum, adaptation not
specified
NITE (2023). ECHA (2023a).
NLM (2023a)
Aerobic biodegradation
(sediment)
Section 3.3.4.2d
Complete dehalogenation within 28 days in a
freshwater river sediment microcosm,
following a 7-day lag period; non-adapted
Atashsahi et al. (2013)
Aerobic biodegradation
(groundwater
microcosms)
Section 3.3.4.4d
22-39% over 84 hours (mineralization) at
-1.13 mg/L test substance concentration in
natural aquifer microcosm; some adaptation
from chlorinated solvent and vinyl chloride
contamination
Reaxvs (2023). ATSDR (2024)
>99% over 57 days, and >99% over 204 days
at 330 (ig/L test substance concentration, in
groundwater/sediment batch microcosms;
adaptation likely due to media exposure to
vinyl chloride
NLM (2023a)
Aerobic biodegradation
(soil)
Section 3.3.4.3d
>99% over 108 days (transformation) and
65% over 108 days (mineralization) at 1
mg/L test substance concentration in a natural
shallow aquifer soil/groundwater microcosm,
adaptation not specified
OECD (2001). ATSDR (2024)
ECHA (2023a)
1.456 j_ig/g soil/hour biodegradation in gas
phase, incubated with soil from a landfill
under methane oxidizing conditions,
adaptation not specified
NLM (2023a)
Anaerobic
biodegradation (water)
10% over 106 days following a 50-day lag at
2.6E-04 mg/L test substance concentration in
groundwater containing Fb and acetate, under
Reaxvs(2023)
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Property or Endpoint
Value"
Reference(s)
Section 3.3.4.1d
methanogenic conditions; adaptation likely
due to media exposure to vinyl chloride
ti/2 = 70 days at 0.4 mg/L test substance
concentration, with groundwater bacteria
inoculum, adaptation not specified
ECHA (2023a). NLM (2023a)
ti/2 = 110 days; study details not specified
NLM (2023a)
5-44% over 37 days and 8-100% over 37
days (mineralization) at 0.013 to 3.79 mg/L
test substance concentration, in natural creek
bed microcosm under methanogenic and
Fe(III)-reducing conditions, respectively;
some adaptation from former drum disposal
area
Reaxvs (2023). ATSDR (2024)
Anaerobic
biodegradation (sedime
nt)
Section 3.3.4.2d
50% over 25 days and 100% over 19 days
with 0.02 and 0.1 mg/L dissolved oxygen,
respectively, at 0.65 mg test substance; vinyl
chloride-oxidizing culture inoculum in
microcosm with media from contaminated
site; adapted
ATSDR (2024)
98% and 21% over 70 days in Naval Air
Station, and Naval Weapons Industrial
Reserve Plant sediment microcosms,
respectively; under methanogenic conditions;
some adaptation with preexposure of media
to chlorinated solvents
ECHA (2023a)
40% over 20 hours at 31.2 mg/L test
substance concentration, in brackish sediment
microcosm supplemented with methanol;
adaptation not specified
Reaxvs(2023)
40% over 20 hours at 28.7 mg/L test
substance concentration, in brackish sediment
microcosm supplemented with H2; adaptation
not specified
Reaxvs(2023)
Complete dehalogenation within 28 days in a
freshwater river sediment microcosm,
following a 7-day lag period; non-adapted
Atashsahi et al. (2013)
100% over 15 days in aquifer microcosm
supplemented with methanol and C2CI4;
adaptation not specified
Reaxvs(2023)
Anaerobic
biodegradation (ground
water microcosms)
100% over 14 weeks, and <20% over 14
weeks with and without supplemented
electron donors/ respectively, in aquifer
microcosm; some adaptation with media from
vinyl chloride-contaminated site
Reaxvs(2023)
Section 3.3.4.4d
100% over >100 days at 39 mg/L test
substance concentration in groundwater with
sediment microcosm under Fe- and SO4 -
reducing conditions; some adaptation with
media from contaminated site
Reaxvs(2023)
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Property or Endpoint
Value"
Reference(s)
15-34% over 84 hours and 2.8-4.6% over 84
hours (mineralization) at ~1.13 mg/L test
substance concentration, in natural aquifer
microcosm, amended with Fe(III) and
unamended, respectively; some adaptation
from media exposure to chlorinated solvents
and vinyl chloride
Reaxvs (2023). ATSDR (2024)
Anaerobic
biodegradation (soil)
Section 3.3.4.3d
ti/2 = 4 weeks at 0.4 mg/L test substance
concentration, in sand/water microcosm;
adaptation not specified
ECHA (2023a). NLM (2023a)
Bioconcentration factor
BCF <10 in Golden Ide (Leuciscus idus
melanotus)
OECD (2001). ATSDR (2024).
NLM (2023a). ECHA (2023a)
(BCF)
(L/kg wet weight [ww])
BCF = 40 in green algae (Chlorella fiiisca)
OECD (2001). ATSDR (2024).
NLM (2023a). ECHA (2023a)
Section 3.6d
Upper Trophic Level: 3.168
Middle Trophic Level: 2.482
Lower Trophic Level: 2.310
EPI Suite™ (BCFBAF, Arnot-
Gobas method)h
Bioaccumulation factor
(BAF)
(L/kg ww, unless noted)
Upper Trophic Level: 3.168
Middle Trophic Level: 2.482
Lower Trophic Level: 2.310
EPI Suite™ (BCFBAF, Arnot-
Gobas method)h
Section 3.6d
Organic carbon:water
partition coefficient (log
Koc) (soil)
2.38-2.95 in seven natural clayey till soil
samples
ATSDR (2024)
1.75
OECD (2001). NLM (2023a)
Section 3.2. ld
Removal in wastewater
treatment
Section 3.5.3d
Total removal: 91.54%
Losses to stripping: -89%
EPI Suite™ (STPWIN, with
default biodegradation ti/2S =
10,000 h)b
"Measured unless otherwise noted.
b Information was estimated using EPI Suite™ (U.S. EPA. 2012c).
0H2, formate, acetate, pyruvate, lactate, fumarate, glycerol, glucose, molasses, or whey
''Respective accompanvine section of the Draft Chemistry and Fate Assessment for Vinvl Chloride (U.S. EPA.
2025a)
2446
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