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SEPA
PUBLIC RELEASE DRAFT
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EPA Document# EPA-740-D-24-016
November 2024
United States Office of Chemical Safety and
Environmental Protection Agency Pollution Prevention
Draft Risk Evaluation for
1,3-Butadiene
CASRN: 106-99-0
h2c^^
November 2024
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34 TABLE OF CONTENTS
3 5 ACKNOWLEDGEMENTS 7
36 EXECUTIVE SUMMARY 8
37 1 INTRODUCTION 11
38 2 SCOPE OF THE RISK EVALUATION 12
39 2.1 Life Cycle and Production Volume 12
40 2.2 Conditions of Use Included in the Risk Evaluation 14
41 2.2,1 Occupational Scenarios 17
42 2.2.2 Conceptual Models 24
43 2.2,3 Populations 27
44 2.2,4 Potentially Exposed or Susceptible Subpopulations 27
45 2.3 Systematic Review 27
46 2.4 Organization of the Risk Evaluation 28
47 3 CHEMISTRY AND FATE AND TRANSPORT OF 1,3-BUTADIENE 30
48 3.1 Summary of Chemistry and Environmental Fate and Transport 30
49 3.2 Weight of Scientific Evidence Conclusions for Chemistry, Fate, and Transport 31
50 4 RELEASES AND CONCENTRATIONS OF 1,3-BUTADIENE IN THE
51 ENVIRONMENT 33
52 4.1 Summary of Environmental Releases 33
53 4,1,1 Industrial and Commercial 33
54 4.1.1.1 Summary of Daily Environmental Release Estimates 33
55 4.1.1.2 Weight of Scientific Evidence Conclusions for Environmental Releases from
56 Industrial and Commercial Sources 38
57 4.2 Summary of Concentrations of 1,3-Butadiene in the Environment 39
58 4.2.1 Environmental Exposure Scenarios 39
59 4.2.1.1 Air Pathway 39
60 4.2.1.2 Surface Water and Sediment Pathway 40
61 4.2.1.3 Drinking Water Pathway 40
62 4.2.1.4 Land Pathway 40
63 4.2,2 Weight of Scientific Evidence Conclusions for Environmental Concentrations 41
64 5 HUMAN HEALTH RISK ASSESSMENT 42
65 5.1 Summary of Human Exposures 44
66 5.1.1 Occupational Exposures 44
67 5.1.1.1 Summary of Occupational Exposure Assessment 44
68 5.1.1.2 Weight of Scientific Evidence Conclusions for Occupational Exposure 47
69 5.1,2 Consumer Exposures 49
70 5.1.2.1 Summary of Consumer Exposure Assessment 49
71 5.1.3 General Population Exposures to Environmental Releases 49
72 5.1.3.1 Summary of General Population Exposure Assessment 49
73 5.1.3.2 Weight of Scientific Evidence Conclusions for General Population Exposure 50
74 5.2 Summary of Human Health Hazard 50
75 5,2.1 Weight of Scientific Evidence Conclusions for Human Health Hazard 51
76 5.3 Human Health Risk Characterization 52
77 5,3,1 Risk Assessment Approach 52
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5.3.1.1 Non-cancer Risk Calculations 53
5.3.1.2 Cancer Risk Calculations 54
5.3.2 Risk Estimates for Workers 55
5.3.3 Risk Estimates for Consumers 81
5.3.4 Risk Estimates for General Population Exposed to Environmental Releases 81
5.3.4.1 Inhalation Margin of Exposures by Discrete Distances 82
5.3.4.2 Inhalation Cancer Risks by Discrete Distances 82
5.3.4.3 Inhalation Cancer Risks by Census Blocks 85
5.3.4.4 Inhalation Cancer Risks Estimated by Previous EPA Assessments 87
5.3.5 Risk Characterization for Potentially Exposed or Susceptible Subpopulations 99
5.3.6 Risk Characterization for Aggregate Exposures 102
5.3.7 Overall Confidence and Remaining Uncertainties in Human Health Risk Characterization....
102
5.3.7.1 Occupational Risk Characterization 102
5.3.7.2 General Population Risk Characterization 103
6 ENVIRONMENTAL RISK ASSESSMENT 104
6.1 Summary of Environmental Exposures 104
6.1.1 Summary of Exposures to Aquatic Species 104
6.1.2 Summary of Exposures to Terrestrial Species 105
6.1.3 Weight of Scientific Evidence Conclusions for Environmental Exposures 105
6.2 Environmental Risk Characterization 105
6.2.1 Risk Assessment Approach 105
6.2.2 Risk Estimates for Aquatic Species 106
6.2.3 Risk Estimates for Terrestrial Species 106
6.2.4 Overall Confidence and Remaining Uncertainties in Environmental Risk Characterization....
107
7 UNREASONABLE RISK DETERMINATION 108
7.1 Unreasonable Risk to Human Health 110
7.1.1 Populations and Exposures EPA Assessed to Determine Unreasonable Risk to Human
Health 110
7.1.2 Summary of Human Health Effects Ill
7.1.3 Basis for Unreasonable Risk to Human Health Ill
7.1.4 Workers 113
7.1.5 Consumers 118
7.1.6 General Population Including Fenceline Communities 118
7.2 Unreasonable Risk to the Environment 122
7.2.1 Populations and Exposures EPA Assessed for the Environment 122
7.2.2 Summary of Environmental Effects 122
7.2.3 Basis for Risk of Injury to the Environment 123
7.3 Additional Information Regarding the Basis for the Unreasonable Risk Determination 123
REFERENCES 131
APPENDICES 137
Appendix A KEY ABBREVIATIONS AND ACRONYMS 137
Appendix B REGULATORY AND ASSESSMENT HISTORY 139
B. 1 Federal Laws and Regulations 139
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B.2 State Laws and Regulations 142
B.3 International Laws and Regulations 142
B.4 Government Assessment History 143
Appendix C LIST OF TECHNICAL SUPPORT DOCUMENTS 145
Appendix D UPDATES TO THE 1,3-BUTADIENE CONDITIONS OF USE TABLES 149
Appendix E CONDITIONS OF USE DESCRIPTIONS 152
E. 1 Manufacturing - Domestic Manufacturing 152
E.2 Manufacturing - Importing 152
E.3 Processing - Reactant - Intermediate in: Adhesive Manufacturing; All Other Basic Organic
Chemical Manufacturing; Fuel Binder for Solid Rocket Fuels; Organic Fiber Manufacturing;
Petrochemical Manufacturing; Petroleum Refineries; Plastic Material and Resin
Manufacturing; Propellant Manufacturing; Synthetic Rubber Manufacturing; Paint and
Coating Manufacturing, Wholesale and Retail Trade 152
E.4 Processing - Reactant - Monomer Used in Polymerization Process in: Synthetic Rubber
Manufacturing; Plastic Material and Resin Manufacturing 154
E.5 Processing - Incorporation into a Formulation, Mixture, or Reaction Product - Processing
Aids, Not Otherwise Listed in: Petrochemical Manufacturing 154
E.6 Processing - Incorporation into a Formulation, Mixture, or Reaction Product - Other:
Adhesive Manufacturing, Paint and Coating Manufacturing, Petroleum Lubricating Oil and
Grease Manufacturing, and All Other Chemical Product and Preparation Manufacturing 155
E.7 Processing - Incorporation into Article - Other: Polymer in: Rubber and Plastic Product
Manufacturing 155
E.8 Processing - Repackaging- Intermediate in: Wholesale and Retail Trade; Monomer in:
Synthetic Rubber 155
E.9 Processing - Recycling 156
E.10 Distribution in Commerce 156
E,11 Industrial Use - Adhesives and Sealants, Including Epoxy Resins 156
E.12 Commercial Use - Fuels and Related Products 156
E. 13 Commercial Use - Other Articles with Routine Direct Contact During Normal Use
Including Rubber Articles; Plastic Articles (Hard); Toys Intended for Children's Use (and
Child Dedicated Articles), Including Fabrics, Textiles, and Apparel; or Plastic Articles
(Hard); Synthetic Rubber (e.g., Rubber Tires); Furniture & Furnishings Including Stone,
Plaster, Cement, Glass and Ceramic Articles; Metal Articles; Or Rubber Articles; Packaging
(Excluding Food Packaging), Including Rubber Articles; Plastic Articles (Hard); Plastic
Articles (Soft) 157
E.14 Commercial Use - Automotive Care Products 157
E.15 Commercial Use - Other Use - Laboratory Chemicals 158
E.16 Commercial Use - Lubricants and Lubricant Additives 158
E.17 Commercial Use -Paint and Coatings 158
E.18 Commercial Use - Adhesives and Sealants 158
E, 19 Consumer Use - Other Articles with Routine Direct Contact During Normal Use Including
Rubber Articles; Plastic Articles (Hard); Toys Intended for Children's Use (and Child
Dedicated Articles), Including Fabrics, Textiles, and Apparel; or Plastic Articles (Hard);
Synthetic Rubber (e.g., Rubber Tires); Furniture & Furnishings Including Stone, Plaster,
Cement, Glass and Ceramic Articles; Metal Articles; or Rubber Articles; Packaging
(Excluding Food Packaging), Including Rubber Articles; Plastic Articles (Hard); Plastic
Articles (Soft) 158
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E.20 Disposal 159
Appendix F OCCUPATIONAL EXPOSURE VALUE DERIVATION AND ANALYTICAL
METHODS USED TO DETECT 1,3-BUTADIENE 160
F.l Occupational Exposure Value Calculations 161
F.2 Summary of Air Sampling Analytical Methods Identified 163
F.3 Short-Term Occupational Exposure Value Derivation 163
Appendix G POTENTIALLY EXPOSED OR SUSCEPTIBLE SUBPOPULATIONS
CONSIDERED IN RISK EVALUATIONS 165
Appendix H GENERAL POPULATION RISK 166
H. 1 HEM Estimated 1,3-Butadiene Cancer Risks across Discrete Distances 166
H.2 General Population Cancer Risk Maps Based on HEM Modeled Census Blocks 172
LIST OF TABLES
Table 2-1. Categories and Subcategories of Conditions of Use Included in the Draft Risk Evaluation ..15
Table 2-2. Crosswalk of Conditions of Use to Occupational Exposure Scenarios Assessed 18
Table 2-3. Description of the Function of 1,3-Butadiene for each OES 21
Table 4-1. Summary of Environmental Releases by Occupational Exposure Scenarios 35
Table 4-2. Summary of the Weight of Scientific Evidence Ratings for Environmental Releases 38
Table 5-1. Summary of Occupational Inhalation Exposure Results by Occupational Exposure Scenarios
45
Table 5-2. Summary of the Weight of Scientific Evidence Ratings for Occupational Exposures 48
Table 5-3. Use Scenarios, Populations of Interest, and Toxicological Endpoints Used for Risk
Estimation 53
Table 5-4. Occupational Risk Summary Table 59
Table 5-5. General Population Cancer Risk Summary Table at 100 to 1,000 m from Facility Releases
Based on HEM Modeled Concentrations 83
Table 5-6. Inhalation Cancer Risk Population Count Based on HEM Modeling Results Using 2020
Census Blocks for TRI2016-2021 Releases 89
Table 5-7. Human Exposure Model (HEM) Demographic Cancer Risk Results Nationwide 97
Table 5-8. Summary of PESS Factors Incorporated into Risk Estimates 100
Table 7-1. Supporting Basis for the Draft Unreasonable Risk Determination for Human Health
(Occupational COUs, Inhalation Exposure Route) 124
Table 7-2. Supporting Basis for the Draft Unreasonable Risk Determination for Human Health
(Consumer COUs, Inhalation Exposure Route) 130
LIST OF FIGURES
Figure 1-1. TSCA Existing Chemical Risk Evaluation Process 11
Figure 2-1. 1,3-Butadiene Life Cycle Diagram 13
Figure 2-2. Percentage of 1,3-Butadiene Production Volume by Use 14
Figure 2-3. 1,3-Butadiene Conceptual Model for Industrial and Commercial Activities and Uses:
Potential Exposure and Hazards 25
Figure 2-4. 1,3-Butadiene Conceptual Model for Environmental Releases and Wastes: Environmental
and General Population Hazards 26
Figure 2-5. Diagram of the Systematic Review Process 28
Figure 2-6. Document Map of Draft Risk Evaluation for 1,3-Butadiene 29
Figure 3-1. Transport, Partitioning, and Degradation of 1,3-Butadiene in the Environment 31
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Figure 4-1. An Overview of How EPA Estimated Daily Releases for Each OES 33
Figure 5-1. Map of Contiguous United States with HEM Model Results for Cancer Risks Aggregated
and Summarized by Census Block for the 2021 TRI Reporting Year 85
Figure 5-2. Southern United States Close-Up 86
LIST OF APPENDIX TABLES
Table_Apx B-l. Federal Laws and Regulations 139
Table_Apx B-2. State Laws and Regulations 142
Table_Apx B-3. International Laws and Regulations 142
TableApx B-4. Assessment History of 1,3-Butadiene 144
TableApx D-l. Additions and Name Changes to Categories and Subcategories of Conditions of Use
Based on CDR Reporting and Stakeholder Engagement 149
TableApx F-l. Limit of Detection (LOD) and Limit of Quantification (LOQ) Summary for Air
Sampling Analytical Methods Identified 163
Table Apx F-2. Comparison between Occupational Exposure Values for 1,3-Butadiene 164
Table Apx G-l. PESS Factors Considered in the Risk Evaluation 165
Table Apx H-l. 1,3-Butadiene Cancer Risks Based on HEM 95th Percentile Modeled Concentrations
from 10 to 50,000 Meters 166
Table Apx H-2. 1,3-Butadiene Cancer Risks Based on HEM 50th Percentile Modeled Concentrations
from 10 to 50,000 Meters 168
Table Apx H-3. 1,3-Butadiene Cancer Risks Based on HEM 10th Percentile Modeled Concentrations
from 10 to 50,000 Meters 170
LIST OF APPENDIX FIGURES
FigureApx H-l. Map of Contiguous United States with HEM Model Results for Cancer Risks
Aggregated and Summarized by Census Block for the 2020 TRI Reporting Year 172
Figure Apx H-2. Map of Contiguous United States with HEM Model Results for Cancer Risks
Aggregated and Summarized by Census Block for the 2018 TRI Reporting Year 173
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ACKNOWLEDGEMENTS
The Assessment Team gratefully acknowledges the participation, input, and review comments from U.S.
Environmental Protection Agency (EPA or the Agency) Office of Pollution Prevention and Toxics
(OPPT) and Office of Chemical Safety and Pollution Prevention (OCSPP) senior managers and science
advisors. The Agency is also grateful for assistance from EPA contractors ICF (Contract No.
68HERC23D0007), ERG (Contract No. 68HERD20A0002 and GS-00F-079CA), and SRC, Inc.
(Contract No. 68HERH19D0022). Special acknowledgement is given for the contributions of technical
experts Leonid Kopylev and Thomas Bateson from EPA's Office of Research and Development (ORD)
for supporting cancer dose-response analysis. Additional expert support for cancer dose-response
analysis was provided by Dr. Dana Loomis and Dr. Leslie Elliott from the University of Reno-Nevada
through the SRC contract.
Docket
Supporting information can be found in the public docket, Docket ID: EPA-HQ-QPPT-2024-0425.
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: Kiet Ly and Aderonke Adegbule, Assessment Leads, Sheila Healy, Management Lead,
Melody Bernot, Marcy Card, Ann Huang, Keith Jacobs, Abhilash Sasidharan, Kelley Stanfield, Michael
Stracka, and Catherine Taylor.
Contributors: Leonid Kopylev, Thomas Bateson, Bryan Groza, and Grant Goedjen
Technical Support: Mark Gibson, Hillary Hollinger, Grace Kaupas, S. Xiah Kragie, and Cory Strope.
This draft risk evaluation was reviewed and cleared for release by OPPT and OCSPP leadership.
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EXECUTIVE SUMMARY
Background and Preliminary Risk Determination
The U.S. Environmental Protection Agency (EPA or the Agency) has evaluated the health and
environmental risks of the chemical 1,3-butadiene under section 6 of the Toxic Substances Control Act
(TSCA). EPA designated 1,3-butadiene as a high priority substance for risk evaluation in December
2019 and followed with the Final Scope of the Risk Evaluation for 1,3-Butadiene; CASRN106-99-0
(I 3c). In alignment with the Final Scope's Analysis Plan, the Agency evaluated all
reasonably available physical and chemical properties, environmental fate, and environmental release
data and determined that air is the major exposure pathway. Following public comment and independent
peer review, EPA will issue a risk evaluation that includes its determination as to whether 1,3-butadiene
presents unreasonable risk of injury to health or the environment under its conditions of use (COUs; also
called TSCA COUs).
1,3-Butadiene is used primarily as a chemical intermediate and monomer in the manufacture of
polymers such as synthetic rubbers and elastomers. Domestic manufacturers report 1,3-butadiene
production volumes through the TSCA Chemical Data Reporting (CDR) rule under CAS Registry
Number (CASRN) 106-99-0. The U.S. production volume for 1,3-butadiene in 2016 ranged from 1 to 5
billion pounds (lb) and remained unchanged in 2019, based on the latest 2020 CDR data. EPA describes
production volumes as a range to protect confidential business information. 1,3-Butadiene has been
assessed by multiple national and international governmental organizations and is broadly regulated by
EPA, various states, and other countries (Appendix B).
The Agency chose to evaluate 1,3-butadiene because both laboratory animal and human data show that
it may be harmful to people if they are exposed to enough of it over a long enough period of time. The
kinds of health effects that 1,3-butadiene is associated with include harm to pregnant women and their
fetuses, blood and immune system disease, and cancer. In particular, lymphomas seen in laboratory mice
were consistent with human epidemiology studies linking workers' exposure to 1,3-butadiene to
increases in lymphatic and hematopoietic cancers.
EPA evaluated the risks to people from being exposed to 1-3-butadiene at work and outdoors. Given the
environmental fate properties of 1,3-butadiene, an in-depth analysis of releases to water or land and
associated environmental exposures was not conducted. When it is manufactured or used to make
products, 1,3-butadiene is mainly released into the air due to its volatility, with relatively small releases
to land or water. If released into water or land, 1,3-butadiene will quickly volatilize from water and land
surfaces. 1,3-Butadiene breaks down in the air within a few hours by reacting with hydroxyl or nitrate
radicals in the atmosphere. Additional sources of 1,3-butadiene exposure come from vehicle exhaust,
tobacco smoke, burning wood, and forest fires. Consistent with these properties, the Agency for Toxic
Substances and Disease Registry (ATSDR (2012)) concluded that inhalation is the predominant route
for human exposures and 1,3-butadiene has not been quantified by any other routes.
Workers may be exposed to 1,3-butadiene when using 1,3-butadiene in the workplace. The general
population—specifically, people who reside near facilities that manufacture or process 1,3-butadiene—
may be exposed when those facilities release 1,3-butadiene into the air. In determining whether 1,3-
butadiene presents an unreasonable risk of injury to human health, EPA incorporated the following
potentially exposed and susceptible subpopulations (PESS) into its assessment: females of reproductive
age, males of reproductive age, pregnant females, infants, children and adolescents, people exposed to
1,3-butadiene in the workplace, and populations who reside near 1,3-butadiene-releasing facilities.
These subpopulations are PESS because some have greater exposure to 1,3-butadiene or exhibit greater
biological susceptibility than the general population.
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Appendix Bin this draft risk evaluation, EPA only evaluated risks resulting from exposure to 1,3-
butadiene from facilities that use, manufacture, or process 1,3-butadiene under industrial and/or
commercial COUs subject to TSCA and the products that result from such manufacture and processing.
Human or environmental exposure to 1,3-butadiene from other sources (e.g., vehicle exhaust, tobacco
smoke, woodburning) were not quantitatively evaluated for risk characterization by EPA in reaching its
preliminary determination of unreasonable risk to injury of human health.
EPA's assessment preliminarily determined that 1,3-butadiene presents an unreasonable risk of injury to
human health because of risks to workers and the general population (including fenceline communities)
from inhalation exposure. The risks are highest in areas along the Gulf Coast region from Texas to
Louisiana, near 1,3-butadiene-releasing facilities.
Based on the assessment of consumer risk and related risk factors, the Agency preliminarily determined
that consumer COUs do not significantly contribute to the unreasonable risk of 1,3-butadiene.
Based on the pathways evaluated in this draft risk evaluation, EPA preliminarily determines that risk to
the environment does not significantly contribute to the unreasonable risk determination for 1,3-
butadiene.
Summary, Considerations, and Next Steps
EPA evaluated a total of 28 TSCA COUs for 1,3-butadiene detailed in Section 2.2 with subsequent
exposures and risk characterizations for human health and to environmental species in Sections 5 and 6,
respectively.
The Agency preliminarily determines that the following COUs, considered singularly or in combination
with other exposures, significantly contribute to the unreasonable risk to human health:
• Manufacturing - domestic manufacturing;
• Manufacturing - import;
• Processing - processing as a reactant - intermediate (adhesive manufacturing; all other basic
organic chemical manufacturing; fuel binder for solid rocket fuels; organic fiber manufacturing;
petrochemical manufacturing; petroleum refineries; plastic material and resin manufacturing;
propellant manufacturing; synthetic rubber manufacturing; paint and coating manufacturing;
wholesale and retail trade);
• Processing - processing as a reactant - monomer used in polymerization process (synthetic
rubber manufacturing; plastic material and resin manufacturing);
• Processing - incorporation into formulation, mixture, or reaction product - processing aids, not
otherwise listed (petrochemical manufacturing; monomers used in: plastic product
manufacturing; synthetic rubber manufacturing);
• Processing - incorporation into formulation, mixture, or reaction product - other (adhesive
manufacturing, paint and coating manufacturing, petroleum lubricating oil and grease
manufacturing, and all other chemical product and preparation manufacturing);
• Processing - incorporation into article - other (polymer in: rubber and plastic product
manufacturing);
• Processing - repackaging - intermediate (wholesale and retail trade; monomer in: synthetic
rubber manufacturing);
• Processing - recycling;
• Commercial use - other use - laboratory chemicals; and
• Disposal
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EPA preliminarily determines that the following COUs do not contribute significantly to the
unreasonable risk:
• Industrial use - adhesives and sealants, including epoxy resins;
• Commercial use - fuels and related products;
• Commercial use - other articles with routine direct contact during normal use including rubber
articles; plastic articles (hard);
• Commercial use - toys intended for children's use (and child dedicated articles), including
fabrics, textiles, and apparel; or plastic articles (hard);
• Commercial use - synthetic rubber (e.g., rubber tires);
• Commercial use - furniture & furnishings including stone, plaster, cement, glass and ceramic
articles; metal articles; or rubber articles;
• Commercial use - packaging (excluding food packaging), including rubber articles; plastic
articles (hard); plastic articles (soft);
• Commercial use - automotive care products;
• Commercial use - lubricants and lubricant additives, including viscosity modifier;
• Commercial use - paints and coatings, including aerosol spray paint;
• Commercial use - adhesives and sealants, including epoxy resins;
• Consumer use - other articles with routine direct contact during normal use including rubber
articles; plastic articles (hard);
• Consumer use - toys intended for children's use (and child dedicated articles), including fabrics,
textiles, and apparel; or plastic articles (hard);
• Consumer use - synthetic rubber (e.g., rubber tires);
• Consumer use - furniture & furnishings including stone, plaster, cement, glass and ceramic
articles; metal articles; or rubber articles;
• Consumer use - packaging (excluding food packaging), including rubber articles; plastic articles
(hard); plastic articles (soft); and
• Distribution in commerce.
This draft risk evaluation has been released for public comment and will be peer reviewed by the
Science Advisory Committee on Chemicals (SACC) in February 2025. EPA will issue a finalized 1,3-
butadiene risk evaluation after considering input from the public and recommendations received from
the SACC. If the Agency determines that 1,3-butadiene presents unreasonable risk to human health or
the environment in the finalized risk evaluation, EPA will initiate regulatory action to mitigate those
risks.
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1 INTRODUCTION
EPA has evaluated 1,3-butadiene (CASRN 106-99-0) under the Toxic Substances Control Act (TSCA).
1,3-Butadiene is a colorless gas with a total production volume (PV) in the United States between 1 and
5 billion pounds (lb). 1,3-Butadiene is produced from petrochemical processing and is also used to aid in
petrochemical manufacturing, but is primarily used as a monomer to produce plastic and rubber
products. This involves polymerization of 1,3-butadiene with itself or with other monomers, which are
then incorporated into various rubber and plastic articles. These synthetic rubbers, resins, and latex are
used to manufacture tires, other rubber components and plastic materials. 1,3-Butadiene polymers are
also used as viscosity agents in several formulations for adhesives, lubricants, and paints and coatings.
These polymerization products which are a polymer form of 1,3-butadiene are also referred to as 1,3-
butadiene by some chemical safety data sheets (SDSs). This draft risk assessment covers only the
monomer form of 1,3-butadiene.
Figure 1-1 describes the major inputs, phases, and outputs/components of the TSCA risk evaluation
process, from scoping to releasing the final risk evaluation. Sections 2, 2.1, and 2.2 provide the scope of
the risk evaluation, including PV, life cycle diagram (LCD), conditions of use (COUs; also called TSCA
COUs), and conceptual models used for 1,3-butadiene; Section 2.3 includes an overview of the
systematic review process; and Section 2.4 presents the organization of this draft risk evaluation.
Inputs
Phase
Outputs
Existing Laws, Regulations,
and Assessments
Use Document
Public Comments
Draft Scope
Document
4
Public Comments on
Draft Scope Document
Conditions of use, exposure, hazardsand
potentially exposed or susceptible
subpopulations(PESS)
Analysis of conditions of use ->
Lifecycle Diagram
• Initial Conceptual Models
Industrial/Commercial uses
Environmental releases
• Preliminary analysis plan
Final Scope
Document
Analysis Plan
Systematic Review
Data Evaluation Process
Data Integration
£
%
\7
Refined Conceptual
Models
Refined Analysis Plan
Public Comments on
Draft RE
Peer Review Comments
on Draft RE
Draft Risk
1 \
Final Risk
Evaluation
1 ^
Evaluation
Draft Risk
Determination
Final Risk
Determination
—
\7
Risk Management
Process
Figure 1-1. TSCA Existing Chemical Risk Evaluation Process
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2 SCOPE OF THE RISK EVALUATION
EPA designated 1,3-butadiene as a high priority substance for risk evaluation in December 2019 and
followed with the Final Scope of Risk Evaluation for 1,3-Butadiene; CASRN106-99-0 (also called "final
scope document") (U.S. EPA. 2020c). In alignment with the Scope's Analysis Plan, EPA evaluated all
reasonably available physical and chemical properties, environmental fate, and environmental release
data and determined that air is the major exposure pathway. The Agency evaluated risk to human and
environmental populations for 1,3-butadiene. Specifically for human populations, EPA quantitatively
evaluated risk to (1) workers and occupational non-users (ONUs) via the inhalation route described in
Section 5.3.2, and (2) the general population via inhalation route in Section 5.3.4. Additionally, EPA
considered PESS in Section 5.3.5. For environmental populations, the Agency qualitatively assessed
risks via water, sediment, and air to aquatic and terrestrial species in Sections 6.2.2 and 6.2.3,
respectively.
EPA identified literature with human health hazards via the inhalation route of exposure. Furthermore,
as expected based on the determination of air as the major pathway of exposure, the Agency did not
identify literature on human health hazards via the oral or dermal routes of exposure. EPA also did not
find literature reporting hazards to aquatic or terrestrial organisms. OPPT identified several inhalation
epidemiological studies describing a single cohort of styrene-butadiene rubber occupational workers.
Some of the studies that used this occupational cohort study were included in the 2002 EPA Integrated
Risk Information System (IRIS) Health Assessment of 1,3-Butadiene (U.S. EPA. 2002b). Using the
occupational cohort data, OPPT re-evaluated and revised the inhalation unit risk for cancer which was
published by IRIS in 2002.
EPA used reasonably available information, defined in 40 CFR 702.33, in a fit-for purpose approach to
develop a risk evaluation that relies on the best available science and is based in the weight of scientific
evidence. EPA evaluated the quality of methods and reporting or results of the individual studies using
the evaluations strategies described in the Draft Systematic Review Protocol Supporting TSCA Risk
Evaluations for Chemical Substances ( )21 a) and Draft Systematic Review Protocol for 1,3-
Butadiene ( lac), or as otherwise noted in the relevant technical support documents
(TSDs; see also Appendix C).
2.1 Life Cycle and Production Volume
The life cycle diagram (LCD) in Figure 2-1 depicts the COUs that are within the scope of this draft risk
evaluation during various life cycle stages, including manufacture and import, processing, distribution,
use industrial, commercial, consumer), and disposal. The LCD has been updated since its original
inclusion in the final scope document. A complete list of updates and explanations of the updates made
to COUs for 1,3-butadiene from the final scope document to this draft risk evaluation is provided in
Appendix D.
The LCD is a graphical representation of the various life stages of the industrial, commercial, and
consumer use categories included within the scope of this draft risk evaluation. The information in the
life cycle diagram is grouped according to the Chemical Data Reporting (CDR) processing codes and
use categories (including functional use codes for industrial uses and product categories for industrial,
commercial, and consumer uses). The CDR Rule under TSCA section 8(a) (see 40 CFR part 711)
requires U.S. manufacturers (including importers) who manufactured/imported 25,000 lb or more of a
relevant chemical for commercial purposes during any calendar year, to provide EPA with information
on the chemicals they manufacture or import into the United States. The Agency collects CDR data
approximately every 4 years with the latest collections occurring in 2020. The Risk Evaluation for 1,3-
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Butadiene CASRN: 106-99-0, Supplemental Information on Environmental Releases and Occupational
Exposure Assessment (U.S. EPA. 2024y) contains additional descriptions (e.g., process descriptions,
worker activities, process flow diagrams) for each manufacturing, processing, use, and disposal
category.
MFG/IMPORT
PROCESSING
INDUSTRIAL, COMMERCIAL USE RELEASES and WASTE DISPOSAL
Manufacture
(Including
Import)
Processing as Reactant
(Intermediate in: Adhesive manufacturing; All
other basic organic chemical manufacturing;
Organicfiber manufacturing; Petrochemical
manufacturing; Petroleum refineries; Plastic
material and resin manufacturing; Synthetic
rubber manufacturing; Monomer in: Plastics
material and resin manufacturing; Synthetic
rubber manufacturing, fuel binder for rocket
propellant;)
Incorporation into Formulation,
Mixture, or Reaction Product (Processing
aids: Petrochemical manufacturing; Other:
Adhesive manufacturing, paints and coatings
manufacturing, petroleum lubricatingoiland
grease manufacturing, and all other chemical
product and preparation manufacturing)
Incorporation into Article
(Polymer in: Rubber and plastic product
manufacturing)
Repackaging
Recycling
Adhesive and Sealants1
(e.g. epoxy resins)
Automotive Care Products1
Fuel and Related Products1
Laboratory Chemicals1
Lubricants and lubricant additives1
(e.g., viscosity modifier)
Paints and Coatings1
(e.g., Aerosol spray paint)
Plastic and Rubber Products1,2
(e.g., rubber tires)
~
~
~
See Conceptual Model for
Environmental Releases and
Wastes
Manufacture(lncluding Import)
Processing
Uses.
1. Industrial and/or commercial
Figure 2-1. 1,3-Butadiene Life Cycle Diagram
Activities related to distribution were assessed as part of each relevant use; for example, loading and
unloading that occurs at a manufacturing site will be addressed with the manufacturing use. For any
distribution in commerce activities not associated with another use, EPA assessed releases and
exposures by reviewing incident reports related to 1,3-butadiene distribution within the U.S. Department
of Transportation (DOT) and National Response Center (NRC) databases.
The PV for 1,3-butadiene in 2016 ranged between 1 billion and 5 billion lb (U.S. EPA. 2020a) and
remained unchanged in 2019 based on the latest 2020 CDR data. EPA described PV as a range to protect
data claimed as confidential business information (CBI). For the 2016 and 2020 CDR cycles, collected
data included the company name, volume of each chemical manufactured/imported, the number of
workers at each site, and information on whether the chemical was used in the commercial, industrial,
and/or consumer sector(s).
1,3-Butadiene is a monomer that is primarily used in the production of a wide range of polymers and
copolymers. It is also used as an intermediate in the production of several chemicals. Due to a large
majority of the total manufacturing and import volume being indicated as CBI by reporting sites, EPA
did not have the ability to specify the percent of PV for each occupational exposure scenario (OES)
based on CDR but instead relied on industry submitted data from the American Chemistry Council
(ACC) to estimate relative percentages of use for 1,3-butadiene. ACC reported in 2022 (Figure 2-2) that
roughly 63 to 69 percent of 1,3-butadiene PV goes toward the production of polymers and copolymers,
such as polybutadiene and styrene-butadiene rubber, and roughly 26 to 32 percent of 1,3-butadiene PV
goes toward the production of intermediate chemicals, such as adiponitrile and chloroprene. The "Other"
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category comprised all remaining uses of 1,3-butadiene, which may include use in formulations or as a
laboratory chemical. Due to the limitations in reporting, these estimates may not fully reflect actual use
and each OES may make up a smaller or larger percentage of the overall PV of 1,3-butadiene.
Polychloroprene
Nitrile
ABS
Thermoplastic Elastomers (e.g., SBCs)
5%
Styrene Butadiene Latexes
7%
Polybutadien«
33%
Styrene Butadiene Rubbers
21%
Source: American Chemistry Council analysis, S&P Global (formerly IHS Markit)
Figure 2-2. Percentage of 1,3-Butadiene Production Volume by Use
2.2 Conditions of Use Included in the Risk Evaluation
The Final Scope of the Risk Evaluation for 1,3-Butadiene; CASRN106-99-0 (U.S. EPA. 2020b)
identified and described the life cycle stages, categories, and subcategories that comprise TSCA COUs
that EPA planned to consider in the draft risk evaluation. 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 identifies COUs for chemicals during the scoping phase and presents them in the
Scoping Document, though the COUs presented may change between the scope document and the risk
evaluation itself as the assessment is conducted and more information about the chemical is gathered.
EPA only evaluated risks resulting from exposure to 1,3-butadiene from facilities that use, manufacture,
or process 1,3-butadiene under industrial and/or commercial COUs subject to TSCA and the products
resulting from such manufacture and processing. Human or environmental exposure to 1,3-butadiene
from other sources (e.g., vehicle exhaust, tobacco smoke, woodburning) were not evaluated or taken into
account by EPA in reaching its preliminary determination of unreasonable risk to injury of human health
(see Section 7 for further information). Each COU has a unique combination of lifestyle stage, category,
and subcategory that describes the chemical's use. EPA has identified a total of 28 TSCA COUs for 1,3-
butadiene. All COUs for 1,3-butadiene included in this draft risk evaluation are presented in Table 2-1
below.
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526 Table 2-1. Categories and Subcategories of Conditions of Use Included in the Draft Risk
527 Evaluation
Life Cycle Stage"
Category''
Subcategory'
Reference(s)
Manufacture
Domestic
manufacturing
Domestic manufacturing
U.S. EPA (2019a)
Importing
Importing
U.S. EPA (2019a)
Processing
Processing as a
reactant
Intermediate in: adhesive manufacturing;
all other basic organic chemical
manufacturing; fuel binder for solid
rocket fuels; organic fiber manufacturing;
petrochemical manufacturing; petroleum
refineries; plastic material and resin
manufacturing; propellant manufacturing;
synthetic rubber manufacturing; paint and
coating manufacturing; wholesale and
retail trade
322a. 2019a)
Monomer used in polymerization process
in: synthetic rubber manufacturing; plastic
material and resin manufacturing
U.S. EPA (2019a):EPA-
HO-OPPT-2018-
0004
Processing -
incorporation into
formulation,
mixture, or reaction
product
Processing aids, not otherwise listed in:
petrochemical manufacturing; monomers
used in: plastic product manufacturing;
synthetic rubber manufacturing
322a)
Other: adhesive manufacturing, paint and
coating manufacturing, petroleum
lubricating oil and grease manufacturing,
and all other chemical product and
preparation manufacturing
EPA-HO-OPPT-2018-
)3: EPA-HO-
OPPT-2018-i >05:
EPA-HO-OPPI-2018-
)9; EPA-HO-
'22
Processing -
incorporation into
article
Other: polymer in: rubber and plastic
product manufacturing
il
Repackaging
Intermediate in: wholesale and retail
trade; monomer in: synthetic rubber
manufacturing
U.S. EPA (2022a)
Recycling
Recycling
U.S. EPA (2019a. 2019e)
Distribution in
Commerce^
Distribution in
commerce
Distribution in commerce (e.g., sold to a
trader; sold to re-sellers for petroleum fuel
and petrochemical industry in:
petrochemical manufacturing)
il
Industrial Use
Adhesives and
sealants
Adhesives and sealants, including epoxy
resins
EPA-HO-OPPT-2018-
)3: EPA-HO-
OPPT-2018-i >05;
EPA-HO-OPPT-2018-
)9: EPA-HO-
'22
Commercial Use
Fuels and related
products
Fuels and related products
i)
Other articles with
routine direct
contact during
Other articles with routine direct contact
during normal use including rubber
articles; plastic articles (hard)
U.S. EPA (2022a)
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Life Cycle Stage"
Category''
Subcategory'
Reference(s)
normal use
including rubber
articles; plastic
articles (hard)
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)
U.S. EPA (2022a)
Synthetic rubber
Synthetic rubber (e.g., rubber tires)
U.S. EPA (2022a)
Commercial Use
Furniture &
furnishings
including stone,
plaster, cement,
glass and ceramic
articles; metal
articles; or rubber
articles
Furniture & furnishings including stone,
plaster, cement, glass and ceramic
articles; metal articles; or rubber articles
322a)
Packaging
(excluding food
packaging),
including rubber
articles; plastic
articles (hard);
plastic articles
(soft)
Packaging (excluding food packaging),
including rubber articles; plastic articles
(hard); plastic articles (soft)
U.S. EPA (2022a)
Automotive care
products
Automotive care products
U.S. EPA (2019a)
Other use
Laboratory chemicals
Siema-Aldricli (2024)
Lubricants and
lubricant additives
Lubricant additives, including viscosity
modifier
EPA-HO-OPPT-2018-
)3; EPA-HO-
>22
Paints and coatings
Paints and coatings, including aerosol
spray paint
EPA-HO-OPPT-2018-
)5; EPA-HO-
>22
Adhesives and
sealants
Adhesives and sealants, including epoxy
resins
EPA-HO-OPPT-2018-
)3; EPA-HO-
OPPT-2018-i >09:
EPA-HO-OPPT- 2019-
12
Consumer Use
Other articles with
routine direct
contact during
normal use
including rubber
articles; plastic
articles (hard)
Other articles with routine direct contact
during normal use including rubber
articles; plastic articles (hard)
322a)
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Life Cycle Stage"
Category''
Subcategory'
Reference(s)
Consumer Use
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)
U.S. EPA (2022a)
Synthetic rubber
Synthetic Rubber (e.g., rubber tires)
U.S. EPA (2022a)
Furniture &
furnishings
including stone,
plaster, cement,
glass and ceramic
articles; metal
articles; or rubber
articles
Furniture & furnishings including stone,
plaster, cement, glass and ceramic
articles; metal articles; or rubber articles
322a)
Packaging
(excluding food
packaging),
including rubber
articles; plastic
articles (hard);
plastic articles
(soft)
Packaging (excluding food packaging),
including rubber articles; plastic articles
(hard); plastic articles (soft)
U.S. EPA (2022a)
Disposal
Disposal
Disposal
In this draft risk evaluation, EPA made updates to the COUs listed in the final scope document. These
updates reflect EPA's improved understanding of the COUs based on further outreach, public
comments, and updated industry code names under the CDR for 2020. Updates included (1) additions
and clarification of COUs based on new reporting in the CDR for 2020 or information received from
stakeholders, and (2) correction of typos or edits for consistency. A complete list of updates and
explanations of the updates made to COUs for 1,3-butadiene from the final scope document to this draft
risk evaluation is provided in Appendix D. EPA may further refine the COU descriptions for 1,3-
butadiene included in the draft risk evaluation when the completed risk evaluation for 1,3-butadiene is
published, based upon further outreach, peer-review comments, and public comments. Table 2-1
presents the revised COUs that were included and evaluated in this draft risk evaluation and Appendix E
contains descriptions of each COU.
2.2.1 Occupational Scenarios
EPA assessed environmental releases and occupational exposures for the COUs described in Table 2-1.
Each COU for 1,3-butadiene was assigned an OES that characterizes its release and exposure potential.
Although named for their utility when assessing occupational exposure, these scenarios are also used
when assessing environmental releases from industrial and commercial facilities. OES is a term that is
intended to describe the grouping or segmenting of COUs for assessment of releases and exposures. For
example, EPA may assess a group of multiple COUs together as one OES due to similarities in release
and exposure sources, worker activities, and use patterns. Alternatively, EPA may assess multiple OESs
for one COU because there are different release and exposure potentials within a given COU. OES
determinations are largely driven by the availability of data and modeling approaches to assess
occupational releases and exposures. For example, even if there are similarities between multiple COUs,
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if there is sufficient data to separately assess releases and exposures for each COU, EPA would not
group them into the same OES. For each OES, environmental releases and occupational exposure results
are provided and are expected to be representative of the entire population of workers and sites involved
for the given OES in the United States. These results can be found in the Draft Environmental Release
and Occupational Exposure Assessment for 1,3-Butadiene ( 24y).
Table 2-2 shows the mapping between the COUs from Table 2-1 and the OESs assessed. For 1,3-
butadiene, EPA mapped OESs to COUs based on data and information gathered during systematic
review, industry outreach, and public comments. Several of the condition of use categories and
subcategories were grouped and assessed together in a single OES due to similarities in the processes or
lack of data to differentiate between them, for example Importing and Intermediate in wholesale and
retail trade were both assessed under the Repackaging OES. This grouping minimized repetitive
assessments. In one case, the condition of use subcategory was further delineated into multiple OESs
based on expected differences in process equipment and associated releases or exposure potentials
between facilities. This case was Disposal, which was delineated into Waste handling, treatment, and
disposal and Recycling. Fifteen unique OESs were identified.
Table 2-2. Crosswalk of Conditions of Use to Occupational Exposure Scenarios Assessed
Life Cycle
Stage"
Category''
Subcategory'
Occupational Exposure
Scenario
Manufacture
Domestic manufacturing
Domestic manufacturing
Domestic manufacturing
Importing
Importing
Repackaging
Processing
Processing as a reactant
Intermediate in: adhesive
manufacturing; all other basic
organic chemical manufacturing; fuel
binder for solid rocket fuels; organic
fiber manufacturing; petrochemical
manufacturing; petroleum refineries;
plastic material and resin
manufacturing; propellant
manufacturing; synthetic rubber
manufacturing; paint and coating
manufacturing; wholesale and retail
trade
Processing as a reactant
Monomer used in polymerization
process in: synthetic rubber
manufacturing; plastic material and
resin manufacturing
Plastics and rubber
compounding
Processing -
incorporation into
formulation, mixture, or
reaction product
Processing aids, not otherwise listed
in: petrochemical manufacturing;
monomers used in: plastic product
manufacturing; synthetic rubber
manufacturing
Processing - incorporation
into formulation, mixture,
or reaction product
Other: adhesive manufacturing, paint
and coating manufacturing,
petroleum lubricating oil and grease
manufacturing, and all other
chemical product and preparation
manufacturing
Processing - incorporation
into formulation, mixture,
or reaction product
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Life Cycle
Stage"
Category''
Subcategory'
Occupational Exposure
Scenario
Processing -
incorporation into
article
Other: polymer in: rubber and plastic
product manufacturing
Plastics and rubber
converting
Processing
Repackaging
Intermediate in: wholesale and retail
trade; monomer in: synthetic rubber
manufacturing
Repackaging
Recycling
Recycling
Processing as a reactant
Use of plastics and rubber
products®
Distribution in
Commerce
Distribution in
commerce
Distribution in commerce (e.g., sold
to a trader; sold to re-sellers for
petroleum fuel and petrochemical
industry in: petrochemical
manufacturing)
Distribution in commerce^
Industrial Use
Adhesives and sealants
Adhesives and sealants, including
epoxy resins
Application of adhesives
and sealants
Fuels and related
products
Fuels and related products
Fuels and related products
Other articles with
routine direct contact
during normal use
including rubber
articles; plastic articles
(hard)
Other articles with routine direct
contact during normal use including
rubber articles; plastic articles (hard)
Use of plastics and rubber
products®
Commercial Use
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)
Synthetic rubber
Synthetic Rubber (e.g., rubber tires)
Furniture & furnishings
including stone, plaster,
cement, glass and
ceramic articles; metal
articles; or rubber
articles
Furniture & furnishings including
stone, plaster, cement, glass and
ceramic articles; metal articles; or
rubber articles
Packaging (excluding
food packaging),
including rubber
articles; plastic articles
(hard); plastic articles
(soft)
Packaging (excluding food
packaging), including rubber articles;
plastic articles (hard); plastic articles
(soft)
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Life Cycle
Stage"
Category''
Subcategory'
Occupational Exposure
Scenario
Automotive care
products
Automotive care products
Use of plastics and rubber
products®
Other use
Laboratory chemicals
Use of laboratory
chemicals
Commercial Use
Lubricants and lubricant
additives
Lubricant additives, including
viscosity modifier
Use of lubricants and
greases®
Paints and coatings
Paints and coatings, including
aerosol spray paint
Application of paints and
coatings
Adhesives and sealants
Adhesives and sealants, including
epoxy resins
Application of adhesives
and sealants
Other articles with
routine direct contact
during normal use
including rubber
articles; plastic articles
(hard)
Other articles with routine direct
contact during normal use including
rubber articles; plastic articles (hard)
WAf
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)
Consumer Use
Synthetic rubber
Synthetic rubber (e.g., rubber tires)
Furniture & furnishings
including stone, plaster,
cement, glass and
ceramic articles; metal
articles; or rubber
articles
Furniture & furnishings including
stone, plaster, cement, glass and
ceramic articles; metal articles; or
rubber articles
Packaging (excluding
food packaging),
including rubber
articles; plastic articles
(hard); plastic articles
(soft)
Packaging (excluding food
packaging), including rubber articles;
plastic articles (hard); plastic articles
(soft)
Disposal
Disposal
Disposal
Waste handling, treatment,
and disposal
Recycling
a 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.
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Life Cycle
Stage"
Category''
Subcategory'
Occupational Exposure
Scenario
- "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 conditions of use appear in the Life Cycle Diagram, reflect CDR codes, and broadly represent
conditions of use of 1,3-butadiene in industrial and/or commercial settings.
c These subcategories reflect more specific conditions of use of 1,3-butadiene.
- "Incorporation into article - polymer in rubber product manufacturing," as reported to the 2016 CDR, is a
condition of use that EPA considered as manufacturing of articles involving butadiene-derived polymers,
including plastics such as acrylonitrile butadiene styrene made using polybutadiene rubber.
- "Monomer used in polymerization process," as reported to the 2016 CDR under commercial use, indicates
processing of 1,3-butadiene for a polymerization reaction. This reported use was evaluated under processing as a
reactant.
d EPA considers the activities of loading and unloading of chemical product part of distribution in commerce,
however these activities were assessed as part of each use's OES. EPA's current approach for quantitively assessing
releases and exposures for the remaining aspects of distribution in commerce consists of searching Department of
Transportation (DOT) and National Response Center (NRC) data for incident reports pertaining to 1,3-butadiene
distribution.
'' Though these uses were identified during scoping, upon further investigation EPA made the decision to not
quantitatively assess these uses of 1,3-butadiene. For a description of the rationale for not performing a quantitative
assessment, and details for each decision, see Section 5.14 of the Draft Environmental Release and Occupational
Exposure Assessment for 1,3-Butadiene (U.S. EPA. 2024y).
' Consumer uses are not assigned to an OES as they are not part of the occupational assessment. See Section 5.1.2 for
information on the consumer exposure assessment.
569
570 After identifying those OESs that will be assessed, the next step was to describe the function of 1,3-
571 butadiene within each OES (Table 2-3). This would be utilized in mapping release and exposure data to
572 an OES as well as applying release modeling approaches. The table below is a summary; for more
573 information on each OES, see the corresponding process description in the Draft Environmental Release
574 and Occupational Exposure Assessment for 1,3-Butadiene (U.S. EPA. 2024y).
575
576 Table 2-3. Description of the Function of 1,3-Butadiene for each OES
OES
Role/Function of 1,3-Butadiene
Manufacturing
This OES captures the Domestic manufacture COU category.
1,3-Butadiene can be produced by three processes: steam cracking of paraffinic
hydrocarbons (the ethylene coproduct process), catalytic dehydrogenation of n-butane and
n-butene (the Houndry process), and oxidative dehydrogenation of n-butene (the Oxo-D or
O-X-D process). The predominant method of the three processes is the steam cracking
process, which accounts for greater than 91% of the world's butadiene supply
Repackaging
This OES captures the Importing and Repackaging COU categories.
Import and repackaging sites are expected to distribute 1,3-butadiene to various
downstream uses. Liquefied butadiene is shipped by pipelines, ships, barges, rail tank cars,
tank trucks and bulk liquid containers. A portion of the 1,3-butadiene manufactured is also
expected to be repackaged into smaller containers for commercial laboratory use.
Processing as a
reactant
This OES captures the Processing as an Intermediate COU subcategory and part of the
Recycling COU category.
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OES
Role/Function of 1,3-Butadiene
Processing as a reactant or intermediate is the use of 1,3-butadiene as a feedstock in the
production of another chemical via a chemical reaction in which 1,3-butadiene is consumed
to form the product. 1,3-Butadiene is used in the production of intermediate chemicals
which are then used to make nylon and neoprene rubber among other products. 1,3-
Butadiene is also processed as a reactant in propellant manufacturing by the United States
Department of Defense. Also included in this OES is when ethylene manufacturers have
excess butadiene supply, they can recycle the butadiene as a feedstock to produce ethylene.
Processing -
incorporation into
formulation,
mixture, or
reaction product
This OES captures the Processing -incorporation into formulation, mixture, or reaction
product COU category.
Incorporation into a formulation, mixture or reaction product refers to the process of
mixing or blending of several raw materials to obtain a single product or preparation. 1,3-
Butadiene may be used during lubricant manufacturing as a viscosity improver, as well as
in paints, coatings, and adhesive manufacturing as a binder.
Plastic and rubber
compounding
This OES captures the Processing as a Monomer COU subcategory.
1,3-Butadiene is used as a monomer in polymerization processes, often to produce rubbers
and plastics such as styrene-butadiene, polybutadiene, acrylonitrile-butadiene-styrene, and
nitrile rubber. This is the most common use of 1,3-butadiene.
Plastics and rubber
converting
This OES captures the Processing -incorporation into article COU category.
After the compounding process that occurs during the plastic and rubber compounding
OES briefly described above, compounded plastic and rubber resins are converted into
solid articles.
Distribution in
commerce
This OES captures the Distribution in Commerce COU category.
1,3-Butadiene is expected to be distributed in commerce for the purposes of each
processing, industrial, and commercial use of 1,3-butadiene. EPA expects 1,3-butadiene to
be transported from manufacturing sites to downstream processing and repackaging sites.
Use of laboratory
chemicals
This OES captures the Laboratory chemicals COU subcategory.
1,3-Butadiene uses as a laboratory chemical may include demonstration of Diels Alder
reactions, synthesis of thermoplastic resins, and synthesis of disilylated dimers by reacting
with chlorosilanes.
Application of
paints and
coatings
This OES captures the Paints and coatings COU category.
1,3-Butadiene was identified as possibly being present in multiple paint and coating
products, including aerosol propellants, architectural paints and coatings, latex paints,
electro-dipping coatings, and automotive primers. The application procedure depends on
the type of paint or coating formulation and the type of substrate, but may involve
application via brush, spray, roll, dip, curtain, or syringe or bead.
Application of
adhesives and
sealants
This OES captures the Industrial use of adhesives and sealants, as well as the Commercial
use of adhesives and sealants COU categories.
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OES
Role/Function of 1,3-Butadiene
1,3-Butadiene was identified in multiple adhesive and sealant products, including aerosol
propellants, epoxy resins (incorporated for their tensile and elastomeric properties), and
adhesives for electrical and circuit boards. The application procedure depends on the type
of adhesive or sealant formulation and the type of substrate but may involve application via
brush, spray, roll, dip, curtain, or syringe or bead.
Fuels and related
products
This OES captures the Fuels and related products COU category.
1,3-Butadiene may be used at industrial sites for fueling purposes. This use of 1,3-
butadiene is addressed in the Recycling OES. EPA did not find evidence that 1,3-butadiene
in its monomer form is used as an additive to fuel, however it was found that 1,3-butadiene
is present in butane. This use is discussed, but no release or exposure estimates provided.
Recycling
This OES captures part of the Disposal COU categories.
There are multiple ways 1,3-butadiene can be recycled during its life cycle. When finished
1,3-butadiene does not meet commercial specifications, it is often combined with crude
streams for energy recovery. This is examined in this OES.
Waste handling,
treatment, and
disposal
This OES captures part of the Disposal COU category.
Each of the OESs may generate waste streams of 1,3-butadiene that are collected and
transported to third-party sites for disposal or treatment, and these cases are assessed under
this OES. Also handled under this OES are cases of 1,3-butadiene produced as a byproduct
or impurity in an industrial setting and burned.
Use of plastics and
rubber products
This OES captures the five plastic and rubber COU categories detailed in the Commercial
use life cycle stage as well as the automative care products and part of the Recycling COU
categories.
1,3-Butadiene may be present within rubber tires and articles produced with synthetic
rubber. In addition, plastics containing 1,3-butadiene were identified in electronic
appliances, furniture and furnishings, toys and recreational products, housewares,
packaging, automotive parts, building materials, and 3D-printing filament.
Plastic and rubber products may be recycled mechanically (injection molding, extrusion,
rotational molding, and compression molding) into newly shaped products. Tires may also
be recycled into tire crumbs for use on synthetic turf fields.
Most automotive applications of 1,3-butadiene pertain to tires, tire products, and coatings
and thus falls under plastic and rubber products described above.
It was determined that butadiene is present in rubber products at no greater amounts that
6.6 ppm, and after polymerization occurs it is nearly impossible to break the polymer chain
back into individual units of 1,3-butadiene. No release or exposure numbers are provided
for this OES.
Use of lubricants
and greases
This OES captures the Lubricants and lubricant additive COU category.
1,3-Butadiene has been identified in automotive lubricants and aircraft lubricants. 1,3-
Butadiene monomer is present at very low levels within the finished styrene-butadiene
copolymer product. Further, due to lack of evidence otherwise, it was determined that 1,3-
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OES
Role/Function of 1,3-Butadiene
butadiene is not present within lubricants and greases for any purpose other than the
amount that may be residual within the styrene-butadiene copolymer. No release or
exposure numbers are provided for this OES.
2.2.2 Conceptual Models
Figure 2-3 presents the conceptual model for exposure pathways, exposure routes, and hazards to human
populations from industrial and commercial activities and uses of 1,3-butadiene. There is potential for
exposures to workers and/or ONUs via inhalation. EPA evaluated activities resulting in exposures
associated with distribution in commerce (e.g., loading, unloading) throughout the various life cycle
stages and COUs (e.g., Manufacturing, Processing, Industrial use, Commercial use, Disposal), as well as
qualitatively through a single distribution scenario.
Figure 2-4 presents the conceptual model for general population exposure pathways and hazards from
environmental releases and wastes, and ecological exposures and hazards from environmental releases
and wastes.
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Industrial and Commercial Exposure Pathway Exposure Route Populations Hazards
Activities / Uses"
590 Figure 2-3.1,3-Butadiene Conceptual Model for Industrial and Commercial Activities and Uses: Potential Exposure and Hazards
591 11 Some products are used in both industrial and commercial applications. See Table 2-1 for categories and subcategories of COUs.
592 h Fugitive air emissions are emissions that are not routed through a stack and include fugitive equipment leaks from valves, pump seals, flanges,
593 compressors, sampling connections and open-ended lines; evaporative losses from surface impoundment and spills; and releases from building ventilation
594 systems.
595 Solid lines represent a quantitative assessment while broken lines represent a qualitative assessment.
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INITIAL CONCEPTUAL MODEL FOR ENVIRONMENTAL RELEASES AND WASTES: HUMAN AND ECOLOGICAL RECEPTOR EXPOSURES/EFFECTS a
RELEASES AND WASTES FROM PATHWAY EXPOSURE ROUTE RECEPTORS EFFECTS
INDUSTRIAL / COMMERCIAL / CONSUMER USES
597 Figure 2-4.1,3-Butadiene Conceptual Model for Environmental Releases and Wastes: Environmental and General Population
598 Hazards
599 The conceptual model presents the exposure pathways, exposure routes, and hazards to human and ecological populations from releases and wastes from
600 industrial and commercial uses of 1,3-butadiene.
601 Solid lines represent a quantitative assessment while broken lines represent a qualitative assessment.
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2.2.3 Populations
Based on the conceptual models presented in Section 2.2.2, EPA evaluated risk to environmental and
human populations. Environmental exposure and risks were qualitatively evaluated for aquatic and
terrestrial species in Section 6. Human health risks were evaluated for all exposure scenarios, as
applicable based on reasonably available exposure and hazard data as well as the relevant populations
for each. Human populations assessed included
• workers and ONUs, including average adults and women of reproductive age; and
• general population exposed to environmental releases, including infants, children, youth, and
adults.
2.2.4 Potentially Exposed or Susceptible Subpopulations
TSCA section 6(b)(4)(A) requires that risk evaluations "determine whether a chemical substance
presents an unreasonable risk of injury to health or the environment, without consideration of costs or
other non-risk factors, including an unreasonable risk to a potentially exposed or susceptible
subpopulation identified as relevant to the risk evaluation by the Administrator, under the conditions of
use." TSCA section 3(12) states that "the term 'potentially exposed or susceptible subpopulation'
(PESS) means a group of individuals within the general population identified by the Administrator who,
due to either greater susceptibility or greater exposure, may be at greater risk than the general population
of adverse health effects from exposure to a chemical substance or mixture, such as infants, children,
pregnant women, workers, or the elderly."
This draft risk evaluation considers PESS throughout the human health risk assessment (Section
5.3.5)—including throughout the exposure assessment, hazard identification, and dose-response analysis
supporting this assessment. In addition, see Section 9.2 inth q Draft Human Health Hazard Assessment
for 1,3-Butadiene ( 2024f) for more details on how EPA considered evidence of greater
susceptibility among subpopulations.
2.3 Systematic Review
EPA/OPPT applies systematic review principles in the development of risk evaluations under the
amended TSCA. TSCA section 26(h) requires EPA to use scientific information, technical procedures,
measures, methods, protocols, methodologies, and models consistent with the best available science and
base decisions under section 6 on the weight of scientific evidence.
To meet the TSCA section 26(h) science standards, EPA used the TSCA systematic review process
described in the Draft Systematic Review Protocol Supporting TSCA Risk Evaluations for 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. 2021a) and in the Draft
Systematic Review Protocol for 1,3-Butadiene ( 2024ac). Systematic review supports the risk
evaluation in that data searching, screening, evaluation, extraction, and evidence integration are used to
develop the exposure and hazard assessments based on reasonably available information. EPA defines
"reasonably available information" to mean information that the Agency possesses or can reasonably
obtain and synthesize for use in risk evaluations, considering the deadlines for completing the evaluation
(40 CFR 702.33).
The systematic review process is briefly described in Figure 2-5 below. Additional information
regarding these steps is provided in the Draft Systematic Review Protocol ( 021a) and the
Draft Systematic Review Protocol for 1,3-Butadiene (U, 2024ac). The latter provides additional
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information on the steps in the systematic review process—including literature inventory trees and
evidence maps for each discipline (e.g., human health hazard) containing results of the literature search
and screening, as well as sections summarizing data evaluation, extraction, and evidence integration.
• Based on the
approach
described in the
Literature
Search Strategy
documents.
• Title/abstractand
full-text screening
based on pre-
defined
inclusion/exclusion
criteria.
• Evaluateand
document the
quality of studies
based on pre-
defined criteria.
Data Search
~
Data Screen
¦Jg)
Data
~ —
Evaluation
~ —
~ —
~ —
Figure 2-5. Diagram of the Systematic Review Process
• Extract relevant
information based
on pre-defined
templates.
Data
Extraction
=1
• Evaluate results
both within and
across evidence
streams to develop
weight of the
scientific evidence
conclusions.
Evidence
Integration
The Agency also identified key assessments not identified from systematic review, conducted by other
EPA programs and other U.S. and international organizations. Depending on the source, these
assessments may include information on COUs (or the equivalent), hazards, exposures, and potentially
exposed or susceptible subpopulations. For more details, see the Draft Systematic Review Protocol for
1,3-Butadiene (U.S. EPA. 2024ac).
2.4 Organization of the Risk Evaluation
Figure 2-6 illustrates the organization the draft risk evaluation and related TSDs for 1,3-butadiene (see
also Appendix C). This draft risk evaluation for 1,3-butadiene includes five additional major sections
and several appendices:
• Section 3 summarizes basic physical and chemical characteristics as well as the fate and
transport of 1,3-butadiene.
• Section 4 includes an overview of releases and concentrations of 1,3-butadiene in the
environment.
• Section 5 presents the human health risk assessment, including the exposure, hazard, and risk
characterization based on the COUs. It includes a discussion of PESS based on both greater
exposure and/or susceptibility, as well as a description of aggregate and sentinel exposures. The
section also discusses assumptions and uncertainties and how they potentially impact the strength
of the evidence of the draft risk evaluation.
o Section 5.3.5 provides considerations for potentially exposed or susceptible
subpopulations.
• Section 6 provides a discussion and analysis of the environmental risk assessment, including the
environmental exposure and risk characterization based on the COUs for 1,3-butadiene. It also
discusses assumptions and uncertainties and how they potentially impact the strength of the
evidence of the draft risk evaluation.
• Section 7 presents EPA's proposed determination of whether the chemical presents an
unreasonable risk to human health or the environment as a whole-chemical approach and under
the assessed COUs.
• Appendix A provides a list of key abbreviations and acronyms used throughout this draft risk
evaluation.
• Appendix B provides a summary of the federal, state, and international regulatory history of 1,3-
butadiene.
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• Appendix C includes a list and citations for all TSDs and supplemental files included in the draft
risk evaluation for 1,3-butadiene.
• Appendix D provides a summary of updates made to COUs for 1,3-butadiene from the final
scope document to this draft risk evaluation.
• Appendix E provides descriptions of the 1,3-butadiene COUs evaluated by EPA.
• Appendix F provides the draft occupational exposure value for 1,3-butadiene that was derived by
EPA.
• Appendix H provides additional tables and figures for general population risks.
1,3-butadiene systematic review protocol and data extraction files
TSDs outlined in green; shaded boxes indicate qualitative narrative in main RE without separate TSD
Figure 2-6. Document Map of Draft Risk Evaluation for 1,3-Butadiene
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3 CHEMISTRY AND FATE AND TRANSPORT OF 1,3-BUTADIENE
Physical and chemical properties determine the behavior and characteristics of a chemical that inform its
conditions of use, environmental fate and transport, potential toxicity, exposure pathways, routes, and
hazards. Environmental fate and transport includes environmental partitioning, accumulation,
degradation, and transformation processes. Environmental transport is the movement of the chemical
within and between environmental media, such as air, water, soil, and sediment. Thus, understanding the
environmental fate of 1,3-butadiene informs the specific exposure pathways, and potential human and
environmental exposed populations that EPA considered in this draft risk evaluation. This section
summarizes the physical and chemical properties, and environmental fate and transport of 1,3-butadiene.
3.1 Summary of Chemistry and Environmental Fate and Transport
1,3-Butadiene is a colorless gas with a mildly aromatic or gasoline-like odor (Rumble. 2018b; N.LM.
2003). It is moderately soluble in aqueous systems, with a water solubility of 735 mg/L (NLM. 2003). It
is a highly volatile organic compound, with a -4.54 °C boiling point and a vapor pressure of 1,900 mm
Hg (HIST. 2022; National Toxicology Program (NTP). 1993).
With greater than 90 percent of 1,3-butadiene released to air as reported by EPA's Toxics Release
Inventory Program (TRI; see Draft Environmental Release and Occupational Exposure Assessment for
1,3-Butadiene ( 2024y)). EPA expects air to be the major environmental compartment for 1,3-
butadiene. 1,3-Butadiene will degrade in air rapidly (half-life of 1.6-2.6 hours) by reaction with
photochemically produced hydroxyl radicals in the atmosphere during the day to form formaldehyde and
acrolein (Khaled et ai. 2019; Vimal. 2008; Klann h")l">3). It will also react more slowly with nitrate
radicals and ozone in the atmosphere, with half-lives of 3 to 9 hours and 34 hours, respectively (U.S.
Zhao et ai. 2011; Andersson and Liungstrom. 1989). Based on an estimated octanol-air
partition coefficient (Km) of 3 1.5 to 33.7 ( 012b). 1,3-butadiene is not expected to associate
strongly with airborne particulates; hence, it is not expected to undergo dry deposition. Overall, 1,3-
butadiene in the atmosphere is expected to remain largely in the vapor phase, where it is not expected to
persist or undergo long-range transport.
TRI reported very low releases of 1,3-butadiene to water ( 2024y). Based on a Henry's Law
constant of 0.076 atm nrVmol at 25 °C (Rumble. 2018a) and a vapor pressure of 1,900 mm Hg at 20 °C
(National Toxicoloj ixam (NTP). 1993). volatilization from water surfaces is expected to be a
significant process for 1,3-butadiene, thus mitigating its persistence in aquatic environments. 1,3-
Butadiene is not expected to bioaccumulate in aquatic organisms given an estimated BCF of 9.55 L/kg
( 2012b). Overall, 1,3-butadiene is primarily released to and will generally partition to air
where it has low persistence potential. A detailed description of the selected physical and chemical and
fate values and other fate analyses are contained in th q Draft Physical Chemistry and Fate Assessment
for 1,3-Butadiene ( 2024z). The graphic summary of the fate assessment is shown in Figure
3-1.
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Emissions
from
Source
Dry Deposition
Dispersal
Wet Deposition
Air ~
-- " / \ x
Vapor pressure:
1900 mm Hg
V \
Photolysis i
t,a= 1.6-9 h J
/ '
I
! Wastewater facility /
i Indirect/Direct discharge '
' Henry's Law Constant:
0.076 atm-m3/mol
Aerobic Biodegradation
Rate = 7-28 d
" T ~
I
I
l
1
| Surface Water
Aqueous
Photolysis j
Rate = Negligible '\
/ \ Aerobic
/' v \ Biodegradation
I V 1 70 \ Rate = 7"28 d
, Log Koc = 1 73 ^
Bioconcentration
BCF = 9.55 L/Kg
Rate = Negligible Sediment/
Pnrp Watpi
Anaerobic
Biodegradation
Rate = low
Pore Water
Groundwater
Figure Legend
~ Negligible
(H Partitioning/transportation
Transformation/degradation
Wastewater facility
indirect/direct discharge
Figure 3-1. Transport, Partitioning, and Degradation of 1,3-Butadiene in the Environment
The diagram depicts the distribution (grey arrows), transport, and partitioning (black arrows), as well as
the transformation and degradation (white arrows) of 1,3-butadiene in the environment. The width of the
arrow is a qualitative indication of the likelihood that the indicated partitioning will occur or the rate at
which the indicated degradation will occur (i.e., wider arrows indicate more likely partitioning or more
rapid degradation).
3.2 Weight of Scientific Evidence Conclusions for Chemistry, Fate, and
Transport
The general confidence in the physical and chemical properties for 1,3-butadiene is robust. Measured
data were identified from high-quality studies for all physical and chemical properties. Evaluation of the
weight of scientific evidence for the fate and transport of 1,3-butadiene is shown below and is based on
categorization described in the Draft Systematic Review Protocol (J.S. EPA. 2021a).
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Given consistent results from numerous high-quality studies, there is robust confidence that 1,3-
butadiene will
• photodegrade rapidly in air to yield formaldehyde and acrolein;
• not partition to organic matter in water; and
• not hydrolyze significantly in water.
Given limited results from high-quality studies, there is moderate confidence that 1,3-butadiene will
• biodegrade rapidly in aerobic river water or wetland sediment;
• biodegrade rapidly in aerobic soil;
• not sorb to soil/sediment particles;
• not biodegrade rapidly in anaerobic sediment;
• be degraded by methane-utilizing bacteria to form 1,2-epoxybutene; and
• not bioaccumulate in fish.
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4 RELEASES AND CONCENTRATIONS OF 1,3-BUTADIENE IN
THE ENVIRONMENT
EPA estimated environmental releases and concentrations of 1,3-butadiene. Section 4.1 summarizes the
approach and methodology for estimating release and presents estimates of environmental releases.
Section 4.2 summarizes the approach and methodology for estimating environmental concentrations as
well as a summary of concentrations of 1,3 butadiene in the environment. Complete descriptions of
these analyses are presented in the Draft Environmental Releases and Occupational Exposure
Assessment for 1,3-Butadiene (U.S. EPA. 2024y).
4.1 Summary of Environmental Releases
4.1.1 Industrial and Commercial
EPA's first source of information to estimate releases from each OES is programmatic databases. These
databases provide annual facility releases, from which daily release estimates are obtained by dividing
the annual release by the number of expected release days. Once these data are obtained from the
databases, each facility is mapped to one of the OESs described in Section 4.1.1. After mapping is
complete, each OES may have release data from multiple facilities. These data are considered together
to inform the releases that are expected to occur due to the OES. There are cases when there are few or
no facilities mapped to a given OES. In these cases, gaps are filled with release modeling. For 1,3-
butadiene, only one OES (Application of adhesives and sealants) required the use of release modeling
due to lack of programmatic data.
The other important components of the environmental release assessment are number of release days
and the number of facilities. Number of release days may be obtained through literature or through
assumptions based on generic industry information, often from Emission Scenario Documents (ESDs) or
Generic Scenarios (GS). Number of facilities may be obtained through programmatic data, literature, or
through assumptions and modeling based on Bureau of Labor Statistics (BLS)1 and Statistics of U.S.
Businesses (SUSB)2 data.
4.1.1.1 Summary of Daily Environmental Release Estimates
Figure 4-1 shows an overview for how the different assessment components and data sources feed into
the Daily Release Estimates for each OES.
Figure 4-1. An Overview of How EPA Estimated Daily Releases for Each OES
1 https://www.bls. gov/.
2 https://www.census.gov/programs-surveYs/susb.html.
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In Table 4-1, EPA provides a summary for each of the occupational exposure scenarios (OESs) by
indicating the type of release and number of facilities. EPA provides high-end and central tendency daily
and annual release estimates. A majority of releases of 1,3-butadiene were to air, with land and water
releases occurring at vastly fewer sites. The OES with the highest expected releases were
Manufacturing, Plastic and rubber compounding, and Application of adhesives and sealants. For more
detail on these procedures for estimating environmental releases, see the Draft Environmental Releases
and Occupational Exposure Assessment for 1,3-Butadiene ( 24y).
Releases were not quantified from Commercial Use in Fuels and related products, which includes 1,3-
butadiene used as a fuel binder for solid rocket fuels, and 1,3-butadiene's presence in liquid petroleum
gas (LPG) used as a fuel. Releases were not quantified for this COU because, in the case of the use as a
fuel binder, this is not a use of 1,3-butadiene monomer but rather polymers created from 1,3-butadiene
and other monomers. Although residual 1,3-butadiene monomer has the potential to be present in these
polymers, the concentration of residual 1,3-butadiene would be minimal. Thus, the release of 1,3-
butadiene from this use is negligible. With respect to LPG, these releases were not quantified due to (1)
uncertainty in the amount of 1,3-butadiene in LPG product; (2) dispersed use of LPG product across
domestic, industrial, and commercial applications; (3) inability to determine a reasonable number of use
sites; and (4) predicted minimal or unquantifiable releases from connecting equipment/cylinder leaks
and due to the high combustion efficiency of LPG fuel.
Releases were also not quantitatively assessed for the commercial COUs covered by the OES of Use of
plastics and rubber products and Use of lubricants and greases. Reasonably available evidence suggests
that 1,3-butadiene monomer does not exist at concentrations above 6.6 ppm in rubber products or above
quantifiable levels in lubricants and greases. In EPA's investigations, any 1,3-butadiene indicated in
SDSs or other product reports referred either to upstream steps or to reacted polymeric forms.
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Table 4-1. Summary of Environmental Releases by Occupational Exposure Scenarios
Estimated Annual Release
Estimated Daily Release
Occupational Exposure
Scenario (OES)
Range across Sites
(kg/site-yr)
Type of Discharge
Air Emission c, or
Range across Sites
(kg/site-day)''
Number of
Facilities
Source(s)
Central
Tendency
High-End"
Transfer for Disposal''
Central
Tendency
High-End
2.3
371
Surface water
6.5E-03
1.1
4
TRI
7,500
2.1E04
WWT
22
59
3
TRI
360
8,419
Fugitive air
1.0
24
37
TRI
Manufacturing
649
7,139
Fugitive air
1.9
20
45
NEI
1,142
3.3E04
Stack air
3.3
95
39
TRI
665
1.7E04
Stack air
2.0
46
45
NEI
0.45
120
Land
1.3E-03
0.34
9
TRI
2.3
4.3
Surface water
6.5E-03
1.2E-02
1
TRI
18
3,559
Fugitive air
5.1E-02
10
22
TRI
Repackaging
1.6
999
Fugitive air
4.6E-03
2.8
89
NEI
21
1,970
Stack air
5.9E-02
5.6
24
TRI
23
1,127
Stack air
7.4E-02
3.2
89
NEI
2.3
6.8
Land
6.5E-03
1.9E-02
2
TRI
2.3
21
Surface water
6.5E-03
6.0E-02
4
TRI
1.2
6.3
POTW
3.5E-03
1.8E-02
3
TRI
0.5
0.5
WWT
1.3E-03
1.3E-03
1
TRI
Processing as a reactant
64
1,778
Fugitive air
0.18
5.08
54
TRI
49
2,986
Fugitive air
0.13
8.2
70
NEI
94
4,419
Stack air
0.27
13
53
TRI
54
3,632
Stack air
0.15
10
70
NEI
0.69
207
Land
2.0E-03
0.59
13
TRI
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Occupational Exposure
Scenario (OES)
Estimated Annual Release
Range across Sites
(kg/site-yr)
Type of Discharge b,
Air Emission or
Transfer for Disposal''
Estimated Daily Release
Range across Sites
(kg/site-day)''
Number of
Facilities
Source(s)
Central
Tendency
High-End"
Central
Tendency
High-End
Processing - incorporation into
formulation, mixture, or reaction
product
7.7
8.8
Surface water
3.1E-02
3.5E-02
2
TRI
1.4
2.5
POTW
5.4E-03
1.0E-02
2
TRI
79
120
WWT
0.32
0.48
1
TRI
10
712
Fugitive air
4.0E-02
2.8
47
TRI
3.9
282
Fugitive air
1.5E-02
0.89
153
NEI
56
1,349
Stack air
0.22
5.4
49
TRI
12
455
Stack air
3.7E-02
1.2
153
NEI
27
1.0E04
Land
0.11
40
4
TRI
Plastics and rubber compounding
22
51
Surface water
7.5E-02
0.17
4
TRI
2.3
266
WWT
7.6E-03
0.89
3
TRI
635
8,385
Fugitive air
2.1
28
31
TRI
453
8,048
Fugitive air
1.7
22
65
NEI
903
1.7E04
Stack air
3.0
56
33
TRI
142
9,294
Stack air
0.43
33
65
NEI
49
366
Land
0.16
1.2
7
TRI
Plastics and rubber converting
113
215
Fugitive air
0.38
0.72
1
TRI
0.57
18
Fugitive air
1.9E-03
7.3E-02
76
NEI
113
215
Stack air
0.38
0.72
2
TRI
6
46
Stack air
1.9E-02
0.14
76
NEI
113
113
Land
0.38
0.38
1
TRI
Use of laboratory chemicals
6.4E-02
6.3
Fugitive air
2.6E-04
2.5E-02
5
NEI
37
53
Stack air
0.1
0.14
5
NEI
Application of paints and coatings
0.2
31
Fugitive air
5.7E-04
0.12
28
NEI
13
370
Stack air
4.4E-02
1.1
28
NEI
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Occupational Exposure
Scenario (OES)
Estimated Annual Release
Range across Sites
(kg/site-yr)
Type of Discharge
Air Emission or
Transfer for Disposal''
Estimated Daily Release
Range across Sites
(kg/site-day)''
Number of
Facilities
Source(s)
Central
Tendency
High-End"
Central
Tendency
High-End
Application of adhesives and sealants
108
108
Stack air
0.41
0.43
1
NEI
19
205
Fugitive or stack air
0.11
1.0
2-299,581
generic sites
Environ-
mental
release
modeling
589
2,878
Incineration or landfill
2.7
15
2.7E04
1.2E05
Air, incineration, or
landfill
124
631
Recycling
5.2
11
Surface water
1.5E-02
3.1E-02
2
TRI
20
160
Fugitive air
5.8E-02
0.46
9
TRI
20
183
Fugitive air
5.8E-02
1.3E-02
7
NEI
13
475
Stack air
3.6E-02
1.4
11
TRI
3.9
459
Stack air
1.3E-02
1.3
7
NEI
1.6E-04
1.6E-04
Land
4.6E-07
4.6E-07
1
TRI
Waste handling, disposal, and
treatment
4.5E-02
3.6
Fugitive air
1.8E-04
1.4E-02
6
TRI
0.54
20
Fugitive air
1.5E-03
7.8E-02
282
NEI
1.7E-01
113
Stack air
6.9E-04
0.45
6
TRI
1.4E-03
0.42
Stack air
5.4E-06
1.7E-03
282
NEI
5,781
6,226
Land
23
25
2
TRI
Distribution in Commerce
NM/
" "High-end" are defined as 95th percentile releases
b Direct discharge to surface water and indirect discharges to WWT or POTW are included
c Emissions via fugitive air; stack air; or treatment via incineration
''Transfer to surface impoundment, land application, or landfills
e Where available, EPA used peer-reviewed literature (e.g., Generic Scenarios (GSs) or Emission Scenario Documents (ESDs) to provide a basis to estimate the number
of release days of 1,3-butadiene within an OES.
' While EPA considers distribution of commerce activities such as loading and unloading as part of each use' OES, EPA also reviewed NRC data and DOT data for the
2016-2021 calendar vears for incident reports oertainine to distribution of 1.3-butadiene (DOT Hazmat Incident RcdoiI Data. (NRCe. 2009V).
g TRI data from years 2016-2021, and NEI data from years 2017 and 2020
818
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819 4.1.1.2 Weight of Scientific Evidence Conclusions for Environmental Releases from
820 Industrial and Commercial Sources
821 Table 4-2 summarizes the weight of scientific evidence ratings for each media of release for each OES.
822 For more detail, see the Draft Environmental Releases and Occupational Exposure Assessment for 1,3-
823 Butadiene ( 2024vY
824
825 Table 4-2. Summary of the Weight of Scientific Evidence Ratings for Environmental Releases
Occupational
Exposure
Scenario (OES)
Release Media
Reported
Data"
Data Quality
Ratings for
Reported Data
Modeling
Data Quality
Ratings for
Modeling''
Weight of
Scientific
Evidence
Conclusion
Manufacturing
Surface water
H
X
N/A
Moderate to
Robust
Fugitive air (NEI)
M
X
N/A
Fugitive air (TRI)
H
X
N/A
Stack air (NEI)
M
X
N/A
Stack air (TRI)
H
X
N/A
Land
H
X
N/A
Repackaging
Surface water
H
X
N/A
Moderate to
Robust
Fugitive air (NEI)
M
X
N/A
Fugitive air (TRI)
H
X
N/A
Stack air (NEI)
M
X
N/A
Stack air (TRI)
H
X
N/A
Land
H
X
N/A
Processing as a
reactant
Surface water
H
X
N/A
Moderate to
Robust
Fugitive air (NEI)
M
X
N/A
Fugitive air (TRI)
H
X
N/A
Stack air (NEI)
M
X
N/A
Stack air (TRI)
H
X
N/A
Land
H
X
N/A
Processing -
incorporation into
formulation,
mixture, or
reaction product
Surface water
H
X
N/A
Moderate to
Robust
Fugitive air (NEI)
M
X
N/A
Fugitive air (TRI)
H
X
N/A
Stack air (NEI)
M
X
N/A
Stack air (TRI)
H
X
N/A
Land
H
X
N/A
Plastics and rubber
compounding
Surface water
H
X
N/A
Moderate to
Robust
Fugitive air (NEI)
M
X
N/A
Fugitive air (TRI)
H
X
N/A
Stack air (NEI)
M
X
N/A
Stack air (TRI)
H
X
N/A
Land
H
X
N/A
Plastics and rubber
converting
Surface water
H
X
N/A
Moderate to
Robust
Fugitive air (NEI)
M
X
N/A
Fugitive air (TRI)
H
X
N/A
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Occupational
Exposure
Scenario (OES)
Release Media
Reported
Data"
Data Quality
Ratings for
Reported Data
Modeling
Data Quality
Ratings for
Modeling''
Weight of
Scientific
Evidence
Conclusion
Stack air (NEI)
M
X
N/A
Stack air (TRI)
H
X
N/A
Land
H
X
N/A
Use of laboratory
chemicals
Fugitive air (NEI)
M
X
N/A
Moderate
Stack air (NEI)
M
X
N/A
Application of
paints and coatings
Fugitive air (NEI)
M
X
N/A
Moderate
Stack air (NEI)
M
X
N/A
Application of
adhesives and
sealant
Stack air (NEI)
M
y^
N/A
Moderate
Fugitive or stack
air
3c
N/A
y^
M
Incineration or
landfill
3c
N/A
y^
M
Air, incineration,
or landfill
3C
N/A
y^
M
Recycling
Surface Water
H
X
N/A
Moderate to
Robust
Fugitive Air (NEI)
M
X
N/A
Fugitive Air (TRI)
H
X
N/A
Stack Air (NEI)
M
X
N/A
Stack Air (TRI)
H
X
N/A
Land
H
X
N/A
Waste handling,
disposal, and
treatment
Surface water
-
-
Moderate to
Robust
Fugitive Air (NEI)
M
X
N/A
Fugitive Air (TRI)
H
X
N/A
Stack Air (NEI)
M
X
N/A
Stack Air (TRI)
H
X
N/A
Land
H
X
N/A
a Reported data includes data obtained from EPA databases (i.e., TRI, NEI).
h Data quality ratings for models include ratings of underlying literature sources used to select model approaches and input
values/distributions such as a GS/ESD used in tandem with Monte Carlo modeling.
826
827 4.2 Summary of Concentrations of 1,3-Butadiene in the Environment
828 4.2.1 Environmental Exposure Scenarios
829 4.2.1.1 Air Pathway
830 EPA searched peer-reviewed literature for air monitoring and environmental sampling studies, as well as
831 databases to obtain concentrations of 1,3-butadiene in air. EPA found measured data on 1,3-butadiene in
832 ambient air, indoor air, landfill gas and personal exposure monitoring samples from peer reviewed
833 studies through systematic review. For ambient air, concentrations from five U.S. studies ranged from
834 0.01 to 1.91 |ig/m3. In addition, monitoring data were extracted from EPA's Ambient Monitoring
Page 39 of 173
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835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
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PUBLIC RELEASE DRAFT
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Technology Information Center (AMTIC) database where 24-hour concentrations ranged from 0.0 to
122.8 |ig/m3. For more details, s qq Draft Environmental Media Concentrations for 1,3-Butadiene (U.S.
E 24p). Based on the physical and chemical properties, and concentrations reported from
databases and scientific literature, a quantitative exposure assessment was conducted for the ambient air
pathway for general population. See Section 5.1.3.1 for more details.
4.2.1.2 Surface Water and Sediment Pathway
The Water Quality Portal (WQP) ( ) is a publicly available resource which integrates
water quality data from the USGS National Water Information System (NWIS) (TISGS. ) and the
EPA Water Quality Exchange (WQX) Data Warehouse ( ;). The NWIS database
contains current and historical water data from more than 1.5 million sites across the nation. The WQX
is the EPA's repository of water quality monitoring data collected by water resource management groups
across the country. The complete set of 1,3-butadiene monitoring results for surface water stored in the
Water Quality Portal (WQP) (NWQMC. 2022) was retrieved in January 2024. Without exception, all
surface water samples reported 1,3-butadiene concentrations below the minimum detection limit (MDL).
Based on the low reported releases to surface water (see Draft Environmental Release and Occupational
Exposure Assessment for 1,3-Butadiene ( !4y)). the low solubility in water of 735 mg/L
(NLM. 2003). high volatility from water, low estimated organic carbon:water partition coefficient (Koc)
value of 54 ( ) and WQP data reporting 1,3-butadiene concentrations for all surface
water samples below the minimum detection limit (MDL), EPA has decided not to conduct a
quantitative assessment of exposure for surface water or sediment. For more details, see Draft
Environmental Media Concentrations for 1,3-Butadiene ( 024p) and Draft Water Quality
Portal (WQP) Monitoring Data 2011 to 2023for 1,3-Butadiene ( !024ad).
4.2.1.3 Drinking Water Pathway
Public water systems (PWSs) are regulated under the Safe Drinking Water Act (SDWA)3 to enforce
common standards for drinking water across the country. To assess concentrations of 1,3-butadiene in
water known to be distributed as drinking water, monitoring data collected by PWSs were evaluated.
Concentrations of 1,3-butadiene found in finished {i.e., treated) drinking water were collected from the
EPA's published Third Unregulated Contaminant Monitoring Rule (UCMR3)4 data set, which includes
samples collected between 2013 to 2015 ( ). Based on the physical and chemical
properties of 1,3-butadiene {i.e., its low water solubility and high tendency to volatilize from water as
well as UCMR3 data showing that 1,3-butadiene is not detected in drinking water), EPA has decided not
to conduct a quantitative assessment of exposure for drinking water. For more details, see Draft
Environmental Media Concentrations for 1,3-Butadiene ( 024p).
4.2.1.4 Land Pathway
The complete set of 1,3-butadiene monitoring results for groundwater stored in the Water Quality Portal
(WQP) (NWQMC. 2022) was retrieved in January 2024. The WQP data indicated less than 1 percent
detection frequency in groundwater. Based on the low volume of releases to land (see Draft
Environmental Release and Occupational Exposure Assessment for 1,3-Butadiene (U.S. EPA. 2024y)).
the low risk of failure of the predominant release scenario (see Draft Environmental Media
Concentrations for 1,3-Butadiene ( '24p)). the physical and chemical properties of 1,3-
butadiene (see Draft Chemistry, Fate and transport Assessment for 1,3-Butadiene (U.S. EPA. 2024z)) as
well as monitoring data indicating less than 1 percent detection frequency in groundwater (NWQMC.
2022). EPA did not perform a quantitative analysis for the land pathway because exposure to the general
population is not expected to occur. For more details, see Draft Environmental Media Concentrations
3 See https://www.epa.gov/sdwa for more information.
4 See https://www.epa.gov/dwucmr/third-unregulated-contaminant-monitoring-rule for more information.
Page 40 of 173
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879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
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PUBLIC RELEASE DRAFT
November 2024
for 1,3-Butadiene ( 2Q24p). Draft Chemistry, Fate and transport Assessment for 1,3-
Butadiene (I v «« \ 2024z) and Draft Water Quality Portal (WOP) Monitorins Data 2011 to 2023 for
1,3-Butadiene (U.S. EPA. 2024adY
4.2,2 Weight of Scientific Evidence Conclusions for Environmental Concentrations
Based on the physical and chemical properties of 1,3-butadiene {i.e., high volatility, low solubility, and
low sorption tendencies) ( 2024z), the low release volume to land and water (U.S. EPA.
2024y) and the minimal detection of 1,3-butadiene in surface and groundwater, EPA has robust
confidence that air is the major pathway of exposure for 1,3-butadiene, and that contributions to
exposure from the land and water pathways will be infrequent and at low levels. As a result, air is the
only pathway that will be assessed quantitatively.
For regions where monitoring data are available, EPA has robust confidence in the overall
characterization of environmental media concentrations for 1,3-butadiene as it relies upon standard
reporting databases with strictly regulated monitoring requirements, such as AMTIC, WQP, and UCMR,
and extracted data from peer-reviewed literature that received medium to high-quality ratings from
EPA's systematic review process. In addition, states with a concentration of facilities releasing 1,3-
butadiene are included in the monitoring databases. Due to the presence of 1,3-butadiene releasing
facilities, these states would be expected to have the largest 1,3-butadiene releases. Therefore, EPA has
robust confidence in the representativeness of the databases.
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898 5 HUMAN HEALTH RISK ASSESSMENT
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l,3-l$ul;i
-------
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
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November 2024
5.1 Summary of Human Exposures
5.1,1 Occupational Exposures
5.1.1.1 Summary of Occupational Exposure Assessment
EPA's general approach for estimating occupational exposures and the specific basis for each estimate is
discussed in the Draft Environmental Releases and Occupational Exposure Assessment for 1,3-
Butadiene ( E024y). Table 5-1 summarizes the occupational inhalation exposure results for
each OES. EPA used inhalation monitoring data to evaluate acute, intermediate, and chronic exposures
to workers and ONUs for each OES. Where no monitoring data existed relevant to certain OESs,
analogous monitoring data were used. Analogous monitoring data refer to data from the same chemical
but for a different yet similar activity or OES. Inhalation exposures to 1,3-butadiene from most
industrial and commercial OESs are expected to be rather low, except for the repackaging and laboratory
use OES. Dermal exposure was not assessed for 1,3-butadiene due to the volatility and transport method
of the chemical.
Exposures were not quantified for commercial use of fuels and related products. Occupational exposures
from liquid petroleum gas connections, cylinder leaks, and incomplete combustion are expected to be
minimal. Exposures were also not quantitatively assessed for the commercial COUs covered by the OES
of Use of plastics and rubber products and Use of lubricants and greases. Reasonably available evidence
suggests that 1,3-butadiene monomer does not exist at concentrations above 6.6 ppm in rubber products
or above quantifiable levels in lubricants and greases. Any 1,3-butadiene indicated in SDSs or other
product reports likely referred either to upstream steps or to reacted polymeric forms.
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922 Table 5-1. Summary of Occupational Inhalation Exposure Results by Occupational Exposure
923 Scenarios
Occupational
Exposure
Scenario
(OES)
Worker
Description
Exposure
Davs
Worker Inhalation
Estimates (ppm)
ONU
Inhalation
Estimates (ppm)
Sources/Notes
(dav/yr)
High-
End
Central
Tendency
High-
End
Central
Tendency
Infrastructure/
distribution
operations
250
0.45
2.5E-02
Instrument and
electrical
250
0.16
2.0E-02
Laboratory
technician
250
0.24
2.5E-02
ToxStrateeies (2021) data for
manufacturing and processing
facilities
Manufacturing
Machinery and
specialists'
group
250
0.28
6.0E-03
1.7E-02
8.0E-03
Maintenance
technician
250
0.23
0.15
Operations
onsite
250
0.2
2.0E-02
Safety, health,
and engineering
250
0.36
3.8E-02
Processing -
repackaging
26-128
15
1.1
1.1
Used analogous data from
loading/unloading during
manufacturing and processing.
ONU data not available; used
the central tendency from
worker estimates.
Infrastructure/
distribution
operations
250
0.45
2.5E-02
Instrument and
electrical
250
0.16
2.0E-02
Laboratory
technician
250
0.24
2.5E-02
ToxStrateeies (2021) data for
manufacturing and processing
facilities
Processing as a
reactant
Machinery and
specialists'
group
250
0.28
6.0E-03
1.7E-02
8.0E-03
Maintenance
technician
250
0.23
0.15
Operations
onsite
250
0.2
2.0E-02
Safety, health,
and engineering
250
0.36
3.8E-02
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Occupational
Exposure
Scenario
(OES)
Worker
Description
Exposure
Davs
(day/yr)
Worker Inhalation
Estimates (ppm)
ONU
Inhalation
Estimates (ppm)
Sources/Notes
Hiuh-
End
Central
Tendency
Hi^h-
Eml
Central
Tendency
Processing -
incorporation
into
formulation,
mixture, or
reaction product
Infrastructure/
distribution
operations
250
0.45
2.5E-02
1.7E-02
8.0E-03
ToxStrateeies (2021) data for
manufacturing and processing
facilities
Instrument and
electrical
250
0.16
2.0E-02
Laboratory
technician
250
0.24
2.5E-02
Machinery and
specialists'
group
250
0.28
6.0E-03
Maintenance
technician
250
0.23
0.15
Operations
onsite
250
0.2
2.0E-02
Safety, health,
and engineering
250
0.36
3.8E-02
Plastics and
rubber
compounding
250
0.3
3.0E-02
3.0E-02
Based on NIOSH/OSHA data.
ONU data not available; used
the central tendency from
worker estimates.
Plastics and
rubber
converting
"
250
0.3
2.0E-02
2.0E-02
Based on NIOSH/OSHA data.
Use of
laboratory
chemicals
Laboratory
technician
174-250
9.0E-02
6.0E-02
1.7E-02
8.0E-03
Used analogous data from
manufacturing/processing
(laboratory technicians).
Application of
paints, coatings,
adhesives, and
sealants
250
9.0E-02
5.0E-02
5.0E-02
Based on NIOSH/OSHA data.
All values were below the
LOD. Used LOD for the HE
and LOD/2 for CT. ONU data
not available; used the central
tendency from worker
estimates.
Recycling
250
1.3
0.23
0.23
Used analogous data from
waste handling activities
during manufacturing /
processing. ONU data not
available; used the central
tendency from worker
estimates.
Waste handling,
treatment, and
disposal
250
1.3
0.23
0.23
Used analogous data from
waste handling activities
during manufacturing /
processing. ONU data not
available; used the central
tendency from worker
estimates.
NIOSH = National Institute for Occupational Safety and Health; OSHA = Occupational Safety and Health Administration
Page 46 of 173
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924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
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5.1.1.2 Weight of Scientific Evidence Conclusions for Occupational Exposure
EPA used 1,3-butadiene monitoring data that were either directly applicable to each scenario or from
another comparable scenario as analogous. The use of monitoring data is preferable to other assessment
approaches such as modeling or the use of occupational exposure limits (OELs). EPA used personal
breathing zone (PBZ) air concentration data to assess inhalation exposures, with the data source for the
data used in the majority of scenarios having a high data quality rating from the systematic review
process (ToxStrategies. 2021).
The primary limitations to these data include: the uncertainty of the representativeness of the data for
scenarios to which the data is used as analogous, and the fact that much of the data for both workers and
ONUs from the source were reported as below the LOD. EPA also assumed 250 exposure days per year
in each case. Exposure days are assumed to be the same as operating days, but with a maximum of 250
days because EPA assumed that a single worker would not work more than 250 days per year. However,
it is uncertain whether this captures actual worker schedules and exposures.
In Table 5-2, EPA summarizes the weight of scientific evidence ratings for the occupational exposures
for each OES. The Agency has the highest confidence (moderate to robust) in Manufacturing and
processing (for which most of the monitoring data was based) along with Plastic and rubber converting.
The lowest confidence is for Application of paints/coatings and Application of adhesives/sealants (slight
to moderate), for which all monitored values fell below the LOD. Other OESs were moderate and
primarily used analogous data from manufacturing/processing. For more detail, see the Draft
Environmental Releases and Occupational Exposure Assessment for 1,3-Butadiene (U.S. EPA. 2024y).
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Table 5-2. Summary of the Weight of Scientific Evidence Ratings for Occupational Exposures
Occupational
Exposu rc
Scenario (OES)
Inhalation Exposure
1,3-Butadicnc Monitoring
Analogous Monitoring"
Modeling
WOSE
Conclusion
Worker
# Data
Points
ONU
# Data
Points
Overall
Quality
Determin.
Worker
# Data
Points
ONU
# Data
Points
Overall
Quality
Determin.
Worker
ONU
Manufacturing
V
3,532
V
39
H
X
N/A
X
N/A
N/A
X
X
Moderate to
Robust
Repackaging
X
N/A
X
N/A
N/A
V
158
X
0
H
X
X
Moderate
Processing as a
reactant
V
3,532
V
39
H
X
N/A
X
N/A
N/A
X
X
Moderate to
Robust
Processing -
incorporation into
formulation,
mixture, or reaction
product
V
3,532
V
39
H
X
N/A
X
N/A
N/A
X
X
Moderate to
Robust
Plastic and rubber
compounding
X
N/A
X
N/A
N/A
V
53
X
0
M-H
X
X
Moderate
Plastic and rubber
converting
V
53
X
0
M-H
X
N/A
X
N/A
N/A
X
X
Moderate to
Robust
Use of lab
chemicals
X
N/A
X
N/A
N/A
V
215
V
39
H
X
X
Moderate
Application of
paints and coatings
V
43
X
0
M
X
N/A
X
N/A
N/A
X
X
Slight to
Moderate
Application of
adhesives and
sealants
V
43
X
0
M
X
N/A
X
N/A
N/A
X
X
Slight to
Moderate
Recycling
X
N/A
X
N/A
N/A
V
10
X
0
H
X
X
Moderate
Waste handling,
disposal, and
treatment
X
N/A
X
N/A
N/A
V
10
X
0
H
X
X
Moderate
WOSE = weight of scientific evidence
" "Analogous data" refers to data from the same chemical and similar OESs.
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5.1,2 Consumer Exposures
5.1.2.1 Summary of Consumer Exposure Assessment
According to reports in the 2016 CDR, the use of plastic and rubber products, including synthetic
rubbers, were identified as consumer conditions of use for 1,3-butadiene. EPA qualitatively assessed
whether consumers using or disposing of plastic and rubber products may be exposed to 1,3-butadiene
through vapor emissions which may lead to inhalation exposure, given its volatility at room temperature.
And, in addition, whether bystanders present during the consumer use or disposal of 1,3-butadiene
plastic and rubber products may also be exposed to vapor emissions leading to an inhalation exposure.
Based on product searches and data identified from systematic review ( )24ac. 2Q19d\ EPA
has determined that 1,3-butadiene, a monomer used in polymer-derived consumer products such as
synthetic rubbers, is stable in these products and not expected to degrade and expose the consumer to the
1,3-butadiene monomer. These polymers include but are not limited to, acrylonitrile-butadiene-styrene
(ABS) resins and styrene-butadiene rubber (SBR).
Residual butadiene concentrations in polymers and downstream concentrations are very low and often
not detectable. Processing of synthetic polymers into rubber or plastic products further reduces any
remaining residual butadiene resulting in minimal to no potential end-user exposures (EPA-HQ-OPPT-
2018-0451-0041). Also, since 1,3-butadiene is a highly volatile vapor at room temperature, oral and
dermal exposures to 1,3-butadiene during consumer use of plastic and rubber products are not expected
(ECHA. 2019). Based on this, consumer products or articles containing 1,3-butadience are not
quantitatively assessed in this draft risk evaluation.
5.1.3 General Population Exposures to Environmental Releases
EPA expects the ambient air pathway to be the predominant human exposure pathway to 1,3-butadiene
in the outdoor environment. 1,3-Butadiene is released from industrial facilities as uncontrolled fugitive
releases (e.g., process equipment leaks, process vents, building windows, building doors, roof vents) and
stack releases that may be either uncontrolled (e.g., direct releases out a stack) or controlled with a
pollution control device (e.g., baghouse, scrubber, thermal oxidizer). Once released to the ambient air,
1,3-butadiene may move off-site into the surrounding areas where the general population may be
exposed through inhalation.
5.1.3.1 Summary of General Population Exposure Assessment
Based on the fate assessment for 1,3-butadiene, the monitored concentrations from the AMTIC database
(I 2b), and the measured concentrations identified through systematic review (U.S. EPA.
2024p). EPA conducted a quantitative assessment for ambient air exposure to the general population.
Ambient air concentrations of 1,3-butadiene based on facility releases from the TRI2016-2021 reporting
years were modeled using a tiered approach with the Integrated Indoor-Outdoor Air calculator (IIOAC)
as a screening tool and followed by the HEM for refined modeling. EPA assumed that the general
population is exposed to modeled ambient air concentrations 24 hours a day, 365 days a year over a
lifetime. Therefore, exposure concentrations were equal to ambient air concentrations.
The 95th percentile modeled results from IIOAC for ambient concentrations living near industrial
facilities (within 100-1,000 m [0.062-0.62 miles]) releasing 1,3-butadiene to the ambient air ranged
from 0.0 to 109.5 |ig/m3, with the highest concentrations modeled at 100 m from facility releases. Since
IIOAC 95th and 50th modeled concentrations resulted in corresponding risk estimates at or above the
cancer risk benchmark at 1,000 m from facility releases, EPA proceeded with refined modeling using
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the HEM. The 95th percentile modeled results from HEM ranged from 0.0 to 91.2 |ig/m3 for populations
living within 100 to 1,000 m (0.062-0.62 miles) from industrial facilities releasing 1,3-butadiene. For all
distances modeled with HEM (10-50,000 m, or 0.006 to 31.06 miles), the 95th percentile modeled
concentration ranged from 0.0 to 383.4 |ig/m3 with the highest concentrations modeled within the first
30 to 60 m away from facility releases. See the Draft General Population Exposures for 1,3-Butadiene
( 2024r) for the assessment.
5.1.3.2 Weight of Scientific Evidence Conclusions for General Population Exposure
EPA has robust confidence in the overall characterization of exposures for this ambient air exposure
assessment as it relies upon direct reported releases from databases that received a high-quality rating
from EPA's systematic review process and peer-reviewed models to estimate ambient concentrations at
distances from releasing facilities. Use of additional peer-reviewed models (AirToxScreen and HEM)
along with monitoring data (AMTIC) to further contextualize ambient air concentrations of 1,3-
butadiene, provide added strength and confidence to the approaches and methods used in this draft
ambient air exposure assessment. EPA acknowledges that the assumptions made for the general
population being exposed to modeled ambient air concentrations 24 hours a day, 365 days a year, over a
lifetime contributes uncertainty to the estimates.
The use of reported release data across multiple years of data provides a more comprehensive ambient
air exposure assessment and ensure higher release years are not missed. Furthermore, use of actual
reported releases minimizes uncertainties around estimated releases using theoretical distributions and
provides added confidence that modeled concentrations and exposures are actual and not based in
modeling apart from EPA estimated releases for the Adhesives and sealants OES.
5.2 Summary of Human Health Hazard
In alignment with Section 4.2, EPA quantitatively evaluated hazards via the inhalation route; oral and
dermal exposure is not expected. Inhalation hazards were assessed through systematic review of
reasonably available evidence, which included human epidemiology, laboratory animal toxicology, and
mechanistic data (including in vitro studies). EPA refined the systematic approach for 1,3-butadiene by
reviewing previous authoritative reviews by federal agencies to better target the assessment. To this end,
EPA utilized the IRIS Health Assessment of 1,3-Butadiene (2002a) and AT SDR Toxicological Profile
for 1,3-Butadiene (. ) to identify the primary hazards and key studies. Key studies from these
assessments were supplemented with both literature that was "filtered" based on whether it was
informative for dose-response analysis.
1,3-Butadiene is readily absorbed through the lungs and distributed throughout the body, with higher
partitioning to adipose tissue. The primary metabolites are reactive mono- or di-epoxides, which can
interact with biomolecules and induce toxicity. Qualitatively, metabolic pathways are identical between
mice, rats, and humans. However, they are quantitatively different, with mice producing much greater
levels of metabolites, especially di-epoxides. 1,3-Butadiene is primarily eliminated through exhalation,
with additional excretion via urination, and individual urinary metabolites corresponding to specific
epoxy metabolites and/or pathways. These metabolites are considered to be the source of toxicity, so
species-specific toxicokinetic differences can largely influence relative species sensitivity.
EPA began the assessment by focusing on the endpoints and studies considered for deriving hazard
values in ( 002a) and (ATSDR. 2012). Ovarian atrophy was the basis of the chronic
reference concentration (RfC) in 0 v H* \ -°02a) while (ATSDR. 201 J) elected not to derive an
inhalation minimum risk level (MRL) due to uncertainty in how to accurately extrapolate the mouse data
to humans. Following a mode of action (MO A) analysis, EPA concluded that ovarian atrophy observed
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in mice is not appropriate for quantitative use in human health risk assessment due to evidence
suggesting greatly increased susceptibility in mice and difficulty in confidently quantifying cross-
species differences. Instead, EPA determined that three other critical hazard outcomes were appropriate
for dose-response analysis. These non-cancer health outcomes were (1) maternal and related
developmental toxicity, (2) male reproductive system and resulting developmental toxicity, and (3)
hematological and immune effects. 1,3-Butadiene is a potent multi-organ carcinogen in laboratory
animals, notably inducing lymphomas in mice and exhibiting greater carcinogenic potential in mice than
rats. Epidemiological evidence consistently links occupational 1,3-butadiene exposure to increased
mortality from lymphatic and hematopoietic cancers. EPA determined that 1,3-butadiene "is
carcinogenic to humans", based primarily on robust human, animal, and mechanistic evidence for
lymphohematopoietic cancers, although varying evidence for other cancer types was also identified.
Further, the weight of scientific evidence supports a mutagenic mode of action for carcinogenicity.
A hazard value was not derived for acute exposures because it is unlikely any adverse effects will result
following a single exposure at concentrations relevant to human exposures. Candidate endpoints for an
acute point of departure (POD) from repeat-dose studies were considered but have substantial
uncertainties as to whether they are relevant to acute exposures and were also found to be less protective
than the intermediate/chronic POD. EPA performed dose-response analysis for multiple repeated-dose
non-cancer endpoints under each hazard domain. Decreased fetal weight associated with other
developmental toxicity outcomes was selected as the most sensitive and robust human-relevant endpoint
for use in risk characterization of intermediate and chronic exposures, with a human equivalent
concentration (HEC) of 2.5 ppm (5.5 mg/m3) derived from benchmark dose modeling following
dichotomization of male mouse fetal weight data. All other candidate PODs (germ cell mutation and
anemia) were within 2 to 4 times of this value.
EPA used an occupational epidemiological cohort with 50+ years of follow-up and subsequent exposure
estimate updates to derive inhalation hazard values for leukemia applicable to general population and
occupational exposures. Due to an identified mutagenic mode of action for cancer, EPA applied an age-
dependent adjustment factor (ADAF) to the unit risk (UR) for leukemia for the general population to
yield the IUR; that is, risk scenarios where children or adolescents under 16 years old may be exposed
(I )b). The IUR for general population risk estimation is 0.0098 per ppm (4.4><10~6 per
|ig/m3) and the chronic unit risk for occupational scenarios applied to adolescent and adult workers 16
years or older is 0.0062 per ppm (2.8xl0~6 per |ig/m3)5.
EPA has robust overall confidence in the assessments and associated hazard values for
maternal/developmental toxicity and leukemia, which will be used for risk estimation. These confidence
ratings were based on the weight of scientific evidence considering evidence integration, selection of the
critical endpoint and study, relevance to exposure scenarios, dose-response considerations, and
incorporation of PES S.
Full details are provided in the Draft Human Health Hazard Assessment for 1,3-Butadiene (U.S. EPA.
2024t).
5.2.1 Weight of Scientific Evidence Conclusions for Human Health Hazard
EPA evaluated the confidence for human health hazard conclusions based on the following factors:
evidence integration conclusions, selection of the most critical endpoint and study, relevance to
5 The occupational unit risk was corrected as described 1,3-Butadiene: Corrected lifetable analyses for leukemia and bladder
cancer (U.S. EPA. 202431. The corrected occupational unit risk = 0.0049 per ppm (2.2x 10~6 per ng/m3) ( see also Table 5-3).
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exposure scenarios, dose-response considerations, and incorporation of PESS. More details on how EPA
evaluated these factors are provided in Section 6 of the Draft Human Health Hazard Assessment for 1,3-
Butadiene (U.S. EPA. 2024tY
Based on comparison of results from short term studies with intermediate-duration studies, EPA has
only indeterminate to slight confidence in any potential health effects following a single exposure at
relevant human exposure levels. Intermediate PODs are expected to be protective of acute exposures.
Therefore, EPA did not derive an acute POD.
EPA has robust overall confidence for the evidence integration, study/endpoint selection, exposure
scenario applicability, dose-response, and PESS sensitivity of the conclusions and PODs for
maternal/developmental toxicity, including the POD based on reduced fetal weight that will be used for
risk estimates.
There is robust human, animal, and mechanistic evidence associating leukemia and other
lymphohematopoietic cancers with 1,3-butadiene exposure. An IUR for leukemia was derived from a
study incorporating years of updates to a large occupational cohort covering more than 60 years of
follow up and a novel lifetable analysis was performed to account for extra risk relative to background
population rates. Both men and women were included in the analysis, and an ADAF was applied to
incorporate elevated childhood susceptibility due to the mutagenic mode of action and in accordance
with EPA guidance ( )05b). Based on the above factors, the Agency has robust overall
confidence in the hazard assessment for leukemia. EPA did not combine cancer risks from leukemia and
bladder due to inconsistent results across publications and concern for smoking as a confounder in the
association between bladder cancer and 1,3-butadiene exposure; however, total cancer risk may be
underestimated without incorporating other tumor sites.
5.3 Human Health Risk Characterization
5.3,1 Risk Assessment Approach
EPA calculated non-cancer and cancer risk estimates for occupational and general population exposures
following intermediate, chronic, and lifetime exposures. Risks were not estimated for acute exposures
because sensitive organ-level endpoints are unlikely to result from a single exposure at concentrations
relevant to human exposures (see Section 5.2 and the Draft Human Health Hazard Assessment for 1,3-
Butadiene ( It)). Table 5-3 presents the scenarios, populations, assumptions, and hazard
values used for risk estimation.
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Table 5-3. Use Scenarios, Populations of Interest, and Toxicological Endpoints Used for Risk
Estimation
Population of Interest and
Exposure Scenario
Workers and Occupational Non-users (ONUs)
EPA estimated risks to workers and ONUs >16 years old via inhalation only following
intermediate and chronic exposures.
General Population Exposed to Environmental Releases
EPA estimated risks to the general population of any lifestage living near facilities
releasing 1,3-butadiene into the environment via inhalation only following chronic or
lifetime exposure. a
Health Effects, Hazard
Values and Uncertainty
Factors
Non-cancer POD for Intermediate and Chronic Risk Estimates
HEC = 2.5 ppm (5,500 ng/m3) based on decreased fetal weight
• Adjusted for continuous exposure (24 hr/day, 7 days/week)
Benchmark MOE = 30 (3x UFa x IOx UFh)
Cancer Hazard Values for Chronic and Lifetime Cancer Risk Estimates
Occupational unit risk = 0.0062 per ppm (2.8* 10 " per (ig/m:,)/' lor leukemia
• Adjusted lor continuous (24 hr/day. 7 days/week) exposure and resting breathing
rate (20 m Vday): Used lor estimating risks to workers >16 years old.
General population IUR (ADAF-adjusted) = 0.0098 per ppm (4.4x 10 " per ng/nv1)
• Only lor estimating risks to the general population where individuals <16 years
old may be exposed.
UFa = interspecies uncertainly factor: UFn = intraspccics uncertainty factor.
" EPA conservatively assumes that the general population may be exposed for the entirely of their lifetime. Therefore, general
population chronic and lifetime exposures arc equivalent.
b The occupational unit risk was corrected as described in 1,3-Butadiene: Corrected Lifetable Analyses for Leukemia and
Bladder Cancer ( ). The corrected occupational unit risk = 0.0049 per ppm (2.2 x 10 ' per fig/m')
5.3.1.1 Non-cancer Risk Calculations
EPA used a margin of exposure (MOE) approach to estimate non-cancer risks. The MOE is the ratio of
the non-cancer hazard value (or POD) divided by a human exposure dose. The chronic MOEs for non-
cancer inhalation risks were calculated using Equation 5-1
Equation 5-1. Margin of Exposure Calculation
Non — cancer Hazard Value (POD)
M0E= Human Exposure
Where:
MOE = Margin of exposure for intermediate or chronic
risk estimation (unitless)
Non-cancer Hazard Value (POD) = Human equivalent concentration (HEC, |ig/m3)
Human Exposure = Exposure estimate (|ig/m3)
MOE risk estimates are compared to benchmark MOEs. Benchmark MOEs are the product of all
uncertainty factors for each non-cancer POD. The MOE estimate is interpreted as a human health risk of
concern if the MOE estimate is less than the benchmark MOE (i.e., the total uncertainty factor). The
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larger the MOE, the more unlikely it is that a non-cancer adverse effect will occur. When determining
whether a chemical substance presents unreasonable risk to human health or the environment, calculated
risk estimates are not "bright-line" indicators of unreasonable risk, and EPA has the discretion to
consider other risk-related factors in addition to risks identified in the risk characterization.
Non-cancer hazard values were based on data from laboratory animal toxicology studies. The POD,
reduced fetal body weight, is protective of other non-cancer endpoints, particularly germ cell mutations
(target organ: spermatids and spermatozoa) and anemia which yielded similar POD values, after 10 and
40 weeks of exposure, respectively. In deriving HECs, EPA adjusted for dosimetry and continuous
exposure duration in accordance with guidance documents ( , 1994). The dosimetric
impact of relative breathing rate was also considered when calculating risk estimates because increased
breathing rate results in elevated internal dose/ concentration. Therefore, occupational exposure was
adjusted upward based on the relative ratio of occupational vs. general population breathing rates. The
default breathing rate is 0.6125 m3/hr (based on the average of mean long-term inhalation rates for adult
males and females combined aged 21-81 years), while the occupational breathing rate is 1.25 m3/hr
(corresponding to light activity level) from (\ v H \ IVI I). Occupational exposures were then
adjusted as time-weighted averages (TWAs) over continuous exposure (30 days for intermediate, 365
days for chronic) for direct comparison to the HEC.
5.3.1.2 Cancer Risk Calculations
Extra cancer risks for repeated exposures to a chemical were estimated using Equation 5-2.
Equation 5-2. Extra Lifetime Cancer Risk Calculation
Lifetime Cancer Risk = Human Exposure x IUR/UR
Where:
Human Exposure = Exposure estimate (LADC in ppm or |ig/m3; LADD in mg/kg-day)
IUR/UR = Inhalation or Occupational Unit Risk; risk per unit of exposure
(ppm or |ig/m3)
Consistent with NIOSH guidance , under TSCA EPA typically applies a 1 x 10~4 benchmark for
occupational scenarios in industrial and commercial work environments subject to OSHA requirements.
EPA typically considers the general population and consumer benchmark for cancer risk to be within the
range of 1 x 10~4 to 1 / 10 6, Again, it is important to note that these benchmarks are not bright lines and
EPA has discretion to find unreasonable risks based on other risk-related considerations based on
analysis. Exposure-related considerations (e.g., duration, magnitude, population exposed) can affect
EPA's estimates of the excess lifetime cancer risk.
The general population IUR was adjusted for continuous ambient exposure by the default occupational
ventilation rate and for the intermittent work week schedule ( ). Because the IUR was
derived from an occupational cohort study, the value was adjusted for continuous exposure by the
general population (10 m3/day and 240 days/year to 20 m3/day and 365 days/year). The general
population IUR was applied to general population risks because populations living near a release site
may be exposed from birth. The chronic occupational unit risk is the cancer hazard value derived from
the study cohort without ADAF applied because workers and ONUs are assumed to be at least 16 years
old. As with non-cancer risks, occupational exposures were adjusted as time-weighted averages over
continuous exposure (365 days, 78 years for lifetime exposures) for direct comparison to the UR.
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5.3,2 Risk Estimates for Workers
Occupational risk estimates utilized monitoring exposure measurements from workplace inhalation
monitoring data collected by government agencies such as OSHA and NIOSH, monitoring data found in
published literature {i.e., personal exposure monitoring data and area monitoring data), and monitoring
data submitted via public comments 053. Studies were evaluated using the
evaluation strategies laid out in the Draft Systematic Review Protocol Supporting TSCA Risk
Evaluations for Chemical Substances ( )21a) and Draft Systematic Review Protocol for 1,3-
Butadiene ( lac). These data provided measurements at the level of individual worker
populations, or similarly exposed groups (SEGs). This granularity allowed EPA to differentiate even
within OESs among different types of activities and frequencies. The majority of occupational exposure
sampling data points, collected primarily from ACC's monitoring report (ToxStrateeies. 2021) as well
as existing OSHA or NIOSH data, were not quantifiable values but were identified as being below the
limit of detection (LOD). For data sets including exposure data that were reported as below the LOD,
EPA estimated the exposure concentrations for these data, following EPA's Guidelines for Statistical
Analysis of Occupational Exposure Data. Based on these guidelines, EPA used the LOD value as the
high-end estimate and half the LOD as central tendency. As stated above, calculated risk estimates are
not "bright-line" indicators of unreasonable risk relative to benchmarks, and EPA has the discretion to
consider other risk-related factors in addition to risks identified in the risk characterization. Therefore,
EPA is summarizing the range of non-cancer and cancer risk estimates for each COU across all
respective OESs and SEGs without declaring any conclusions on unreasonable risk.
Sensitive organ-level endpoints are unlikely to result from a single exposure at concentrations relevant
to human exposures (Section 5.2 and the Draft Human Health Hazard Assessment for 1,3-Butadiene
(U.S. EPA. 2024t)). Therefore, low risks from all COUs are expected from acute occupational
exposures. Similarly, measurable dermal exposures are not expected due to the low boiling point,
volatility, and transport method of 1,3-butadiene (see Section5.1.1 and Draft Environmental Releases
and Occupational Exposure Assessment for 1,3-Butadiene ( 24y)). so low risks from all
COUs are expected from occupational dermal exposure. Additionally, inhalation exposures were not
quantified for Commercial Use of Fuels and related products as well as Commercial COUs covered by
the OES of Use of plastics and rubber products and Use of lubricants and greases. Exposures are
expected to be primarily minimal/negligible and risk is expected to be low for these COUs. See Sections
3.11 and 3.14 in the Draft Environmental Releases and Occupational Exposure Assessment for 1,3-
Butadiene ( E024y) for more information.
Although both intermediate and chronic exposures were measured, only intermediate non-cancer risks
are summarized below because they are protective of chronic exposures for the same health endpoint.
All risk estimates are presented in Table 5-4. See Appendix F for derivation of the existing chemical
occupational exposure value, which summarizes the occupational exposure scenario and sensitive health
endpoints into a single value, as well as the LOD for available governmental air sampling analytical
methods. Non-routine laboratory technician activities which can include line sampling presented the
greatest non-cancer risk estimates with an MOE of 0.24 for 12-hour shifts for both central tendency and
high end. This is often more than 10-fold higher than other activities within life cycle stage/categories
(Table 5-4). In such cases, this SEG was excluded in ranges reported below. EPA notes that the
occupational UR was corrected late in the draft risk evaluation process ( 024a). The
corrected UR is 0.0049 per ppm (2.2x 10~6 per |ig/m3), down from 0.0062 per ppm. The values below
and in Table 5-4 do not reflect the corrected occupational UR. Table 5-4 will be corrected to reflect the
lower occupational UR in the Risk Evaluation for 1,3-Butadiene.
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1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
PUBLIC RELEASE DRAFT
November 2024
Note that in cases where there were no ONU exposure data available, it was assumed that ONU
exposure is equal to the central tendency worker exposure. In these cases, ONUs may have only a single
MOE.
Manufacture — Domestic Manufacturing, Processing -as a Reactant (Intermediate), Processing —
Incorporation into Formulation, Mixture, or Reaction Product, and Processing—Recycling
• Excluding risk from non-routine laboratory technician activity, non-cancer MOEs (benchmark =
30) from central tendency exposure ranged from 22 (highest risk) for 12-hour shifts of
maintenance activities to 984 (lowest risk) for 8-hour shifts of turnaround of machinery and
specialists.
• Excluding risk from non-routine laboratory technician activity, non-cancer MOEs (benchmark =
30) from high end exposure ranged from 1.1 (highest risk) for 12-hour shifts of maintenance
turnaround activities to 656 (lowest risk) for 8-hour shifts of turnaround of machinery and
specialists.
• Extra cancer risks from central tendency exposure ranged from 1 .Ox 10 3 (highest risk) for 12-
hour shifts of non-routine laboratory technician activities to 2.5 xl0~7 (lowest risk) for 8-hour
shifts of turnaround of machinery and specialists.
• Extra cancer risks from high end exposure ranged from 1.3x 10 3 (highest risk) for 12-hour shifts
of non-routine laboratory technician activities to 4.9x10 7 (lowest risk) for 8-hour shifts of
turnaround of machinery and specialists.
Manufacture — Importing and Processing — Repackaging
• Non-cancer MOEs (benchmark = 30) from central tendency exposure were 4.6 for 8-hour shifts
of both workers and ONUs.
• Non-cancer MOEs (benchmark = 30) from high end exposure ranged from 0.33 (highest risk) for
8-hour shifts of workers to 4.6 (lowest risk) for 8-hour shifts of ONUs.
• Extra cancer risks from central tendency exposure were 6.4 x 10~4 for 8-hour shifts of both
workers and ONUs.
• Extra cancer risks from high end exposure ranged from 1.1 x 10~2 (highest risk) for 8-hour shifts
of workers to 8.3 x 10~4 (lowest risk) for 8-hour shifts of ONUs.
Processing -as a Reactant (Polymerization)
• Non-cancer MOEs (benchmark = 30) from central tendency exposure ranged from 22 (highest
risk) for 12-hour shifts of both workers and ONUs to 173 (lowest risk) for 8-hour shifts of both
workers and ONUs.
• Non-cancer MOEs (benchmark = 30) from high end exposure ranged from 12 (highest risk) for
12-hour shifts of workers to 173 (lowest risk) for 8-hour shifts of ONUs.
• Extra cancer risks from central tendency exposure ranged from 7.9x 10~5 (highest risk) for 12-
hour shifts of both workers and ONUs to 1.7 xl0~5 (lowest risk) for 8-hour shifts of both workers
and ONUs.
• Extra cancer risks from high end exposure ranged from 2.Ox 10~4 (highest risk) for 8-hour and 12-
hour shifts of workers to 2.2x 10 ~5 (lowest risk) for 8-hour shifts of ONUs.
Processing — Incorporation into Article
• Non-cancer MOEs (benchmark = 30) from central tendency exposure ranged from 37 (highest
risk) for 12-hour shifts of workers and ONUs to 202 (lowest risk) for 8-hour shifts of workers
and ONUs.
Page 56 of 173
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1273
1274
1275
1276
1211
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
PUBLIC RELEASE DRAFT
November 2024
• Non-cancer MOEs (benchmark = 30) from high end exposure ranged from 12 (highest risk) for
12-hour shifts of workers to 202 for (lowest risk) for 8-hour shifts of ONUs.
• Extra cancer risks from central tendency exposure ranged from 5.1 x 10~5 (highest risk) for 12-
hour shifts of workers and ONUs to 1.4x10 5 (lowest risk) for 8-hour shifts of workers and
ONUs.
• Extra cancer risks from high end exposure ranged from 2.2x 10~4 (highest risk) for 8-hour shifts
of workers to 1,4x 10 ~5 for (lowest risk) for 8-hour shifts of ONUs.
Commercial Use — Other Use
• Excluding risk from non-routine laboratory technician activity, non-cancer MOEs (benchmark =
30) from central tendency exposure ranged from 134 (highest risk) for 12-hour shifts of
laboratory technician activities to 295 (lowest risk) for 8-hour shifts of ONUs.
• Excluding risk from non-routine laboratory technician activity, non-cancer MOEs (benchmark =
30) from high end exposure ranged from 2.6 (highest risk) for 12-hour shifts of ONUs to 21
(lowest risk) for 8-hour shifts of laboratory technicians.
• Extra cancer risks from central tendency exposure ranged from 1,0x 10 3 (highest risk) for 12-
hour shifts of non-routine laboratory technician activities to 9,6 x ] 0 6 (lowest risk) for 12-hour
shifts of ONUs.
• Extra cancer risks from high end exposure ranged from 1.3 x 10 3 (highest risk) for 12-hour shifts
of non-routine laboratory technician activities to 1.7xl0~4 (lowest risk) for 12-hour shifts of
laboratory technicians.
Commercial Use — Paints and Coatings—Adhesives and Sealants; Industrial Use—Adhesives and
Sealants
• Non-cancer MOEs (benchmark = 30) from central tendency exposure were 111 for 8-hour shifts
of both workers and ONUs.
• Non-cancer MOEs (benchmark = 30) from high end exposure ranged from 55 (highest risk) for
8-hour shifts of workers to 111 (lowest risk) for 8-hour shifts of ONUs.
• Extra cancer risks from central tendency exposure were 2.6x 10~5 for 8-hour shifts of both
workers and ONUs.
• Extra cancer risks from high end exposure ranged from 6.8x 10~5 (highest risk) for 8-hour shifts
of workers to 3.4x 10 ~5 (lowest risk) for 8-hour shifts of ONUs.
Disposal — Disposal
• Non-cancer MOEs (benchmark = 30) from central tendency exposure were 22 for all SEGs.
• Non-cancer MOEs (benchmark = 30) from high end exposure ranged from 3.9 (highest risk) for
workers to 22 (lowest risk) for ONUs.
• Extra cancer risks from central tendency exposure were 1.3 x 10~4 for all SEGs.
• Extra cancer risks from high end exposure ranged from 9.8x 10~4 (highest risk) for workers to
1.7x10 4 (lowest risk) for ONUs.
Although risk estimates were found to be excessive at high-end for most OESs and SEGs, several OESs
were also found to have risk at central tendency exposures. Among these OESs were non-routine
laboratory technicians, which showed non-cancer risk estimates approximately two orders of magnitude
below benchmark and cancer risk estimates 7 to 10 in 10,000, even at central tendency exposures. This
SEG represented the highest risk across all COUs. Maintenance SEGs from 12-hour shifts also
demonstrated non-cancer risk estimates below 30 at both exposure levels. Among COUs with OES-
specific worker SEGs, both workers and ONUs from 12-hour shifts of plastics and rubber compounding
demonstrated potential non-cancer risk relative to benchmark at both exposure levels. Both workers and
Page 57 of 173
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PUBLIC RELEASE DRAFT
November 2024
1318 ONUs from (1) recycling; (2) waste handling, treatment, and disposal; and (3) repackaging OES
1319 demonstrated potential non-cancer and cancer risk relative to benchmark at both exposure levels.
1320 Repackaging demonstrated the second highest non-cancer risk (and the highest cancer risk for workers
1321 at high-end exposures) compared to non-routine laboratory technician activities.
1322
1323 All risk estimates are presented below in Table 5-4. Colored shading and bold values indicate scenarios
1324 where risk estimates were below (for non-cancer) or above (for cancer) benchmarks. The Draft Risk
1325 Calculator for Occupational Exposures for 1,3-Butadiene ( )24aa) contains all calculations,
1326 exposure values, and exposure factors, used for risk estimation.
Page 58 of 173
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PUBLIC RELEASE DRAFT
November 2024
1327 Table 5-4. Occupational Risk Summary Table
Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
lilt (14)«
Infrastructure/
Distribution
Operations
Inhalation
8-hour
TWA
Central
Tendency
200
206
1.5E-05
High-End
11
11
3.4E-04
Infrastructure/
Distribution
Inhalation
8-hour
TWA
Central
Tendency
60
725
4.2E-06
Operations -
No n routine
High-End
28
342
1.1E-05
Instrument and
Inhalation
8-hour
TWA
Central
Tendency
251
258
1.2E-05
Manufacture/
Domestic
Domestic
manufacture
Manufacturing
(8-hour shift)
Electrical
High-End
31
32
1.2E-04
Manufacturing
Instrument and
Electrical -
No n routine
Inhalation
8-hour
TWA
Central
Tendency
490
2,064
1.5E-06
High-End
245
1,073
3.6E-06
Instrument and
Electrical -
Turnaround
Inhalation
8-hour
TWA
Central
Tendency
463
5,636
5.3E-07
High-End
57
689
5.6E-06
Laboratory
Technician
Inhalation
8-hour
TWA
Central
Tendency
200
206
1.5E-05
High-End
21
22
1.8E-04
Page 59 of 173
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PUBLIC RELEASE DRAFT
November 2024
Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Laboratory
Technician -
Nonroutine
Inhalation
8-hour
TWA
Central
Tendency
0.37
4.5
6.7E-04
High-End
0.37
4.5
8.7E-04
Machinery and
Specialists
Inhalation
8-hour
TWA
Central
Tendency
835
860
3.5E-06
High-End
18
19
2.1E-04
Machinery and
Specialists -
Turnaround
Inhalation
8-hour
TWA
Central
Tendency
984
1.2E04
2.5E-07
High-End
656
7,984
4.9E-07
Maintenance
Inhalation
8-hour
TWA
Central
Tendency
33
34
8.9E-05
High-End
21
22
1.8E-04
Maintenance -
Nonroutine
Inhalation
8-hour
TWA
Central
Tendency
65
787
3.8E-06
High-End
36
433
9.0E-06
272
3,304
9.1E-07
Page 60 of 173
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PUBLIC RELEASE DRAFT
November 2024
Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Inhalation
8-hour
TWA
Central
Tendency
Maintenance -
Turnaround
High-End
1.6
19
2.0E-04
Operations
Inhalation
8-hour
TWA
Central
Tendency
251
258
1.2E-05
Onsite
High-End
25
26
1.5E-04
Operations
Onsite -
Nonroutine
Inhalation
8-hour
TWA
Central
Tendency
689
8,384
3.6E-07
High-End
165
2,002
1.9E-06
Operations
Onsite -
Turnaround
Inhalation
8-hour
TWA
Central
Tendency
281
3,422
8.8E-07
High-End
131
1,597
24E-06
Safety Health
and
Engineering
Inhalation
8-hour
TWA
Central
Tendency
132
136
2.2E-05
High-End
14
14
2.7E-04
ONU
Inhalation
8-hour
TWA
Central
Tendency
626
645
4.7E-06
High-End
295
303
1.3E-05
Page 61 of 173
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PUBLIC RELEASE DRAFT
November 2024
Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
lill (14)"
Manufacture/
Domestic
Manufacturing
Domestic
manufacture
Manufacturing
(12-hour shift)
Infrastructure/
Distribution
Operations
Inhalation
12-hour
TWA
Central
Tendency
134
214
14E-05
High-End
7.4
12
3.3E-04
Infrastructure/
Distribution
Operations -
No n routine
Inhalation
12-hour
TWA
Central
Tendency
40
483
6.2E-06
High-End
19
228
1.7E-05
Instrument and
Electrical
Inhalation
12-hour
TWA
Central
Tendency
167
268
1.1E-05
High-End
21
33
1.2E-04
Instrument and
Electrical -
No n routine
Inhalation
12-hour
TWA
Central
Tendency
327
1,376
2.2E-06
High-End
163
715
54E-06
Instrument and
Electrical -
Turnaround
Inhalation
12-hour
TWA
Central
Tendency
309
3,757
8.0E-07
High-End
38
460
8.5E-06
Laboratory
Technician
Inhalation
12-hour
TWA
Central
Tendency
134
214
14E-05
High-End
14
23
1.7E-04
Page 62 of 173
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PUBLIC RELEASE DRAFT
November 2024
Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Laboratory
Technician -
Nonroutine
Inhalation
12-hour
TWA
Central
Tendency
0.24
3.0
1.0E-03
High-End
0.24
3.0
1.3E-03
Machinery and
Inhalation
12-hour
TWA
Central
Tendency
557
892
34E-06
Specialists
High-End
12
19
2.0E-04
Machinery and
Specialists -
Turnaround
Inhalation
12-hour
TWA
Central
Tendency
656
7,984
3.8E-07
High-End
438
5,323
7.3E-07
Maintenance
Inhalation
12-hour
TWA
Central
Tendency
22
35
8.6E-05
High-End
14
23
1.7E-04
Maintenance -
Inhalation
12-hour
TWA
Central
Tendency
43
524
5.7E-06
Nonroutine
High-End
24
289
1.3E-05
Maintenance -
Turnaround
Inhalation
12-hour
Central
Tendency
181
2,203
14E-06
TWA
High-End
1.1
13
3.0E-04
Page 63 of 173
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November 2024
Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Operations
Onsite
Inhalation
12-hour
TWA
Central
Tendency
167
268
1.1E-05
High-End
17
27
1.5E-04
Operations
Onsite -
Nonroutine
Inhalation
12-hour
TWA
Central
Tendency
459
5,589
5.4E-07
High-End
110
1,335
2.9E-06
Operations
Onsite -
Turnaround
Inhalation
12-hour
TWA
Central
Tendency
188
2,281
1.3E-06
High-End
88
1,065
3.7E-06
Safety Health
and
Engineering
Inhalation
12-hour
TWA
Central
Tendency
88
141
2.1E-05
High-End
9.2
15
2.6E-04
ONU
Inhalation
12-hour
TWA
Central
Tendency
418
669
4.5E-06
High-End
197
315
1.2E-05
Processing /
Repackaging
Intermediate
in: wholesale
and retail trade;
Repackaging
Worker
Inhalation
8-hour
TWA
Central
Tendency
4.6
4.7
6.4E-04
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Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
lilt (14)"
Manufacture /
Importing
monomer in:
synthetic
rubber
manufacturing
Importing
High-End
0.33
0.34
1.1E-02
ONU
Inhalation
8-hour
TWA
Central
Tendency
4.6
4.7
6.4E-04
High-End
4.6
4.7
8.3E-04
Processing/As a
Reactant
Intermediate
in: adhesive
manufacturing;
all other basic
organic
chemical
manufacturing;
fuel binder for
solid rocket
fuels; organic
fiber
manufacturing;
petrochemical
manufacturing;
petroleum
refineries;
plastic material
and resin
manufacturing;
propellant
manufacturing;
synthetic
rubber
manufacturing;
paint and
coating
Processing as a
reactant
(8-hour shift)
Infrastructure/
Distribution
Operations
Inhalation
8-hour
TWA
Central
Tendency
200
206
1.5E-05
High-End
11
11
3.4E-04
Infrastructure/
Distribution
Operations -
No n routine
Inhalation
8-hour
TWA
Central
Tendency
60
725
4.2E-06
High-End
28
342
1.1E-05
Instrument and
Electrical
Inhalation
8-hour
TWA
Central
Tendency
251
258
1.2E-05
High-End
31
32
1.2E-04
Instrument and
Electrical -
No n routine
Inhalation
8-hour
TWA
Central
Tendency
490
2,064
1.5E-06
High-End
245
1,073
3.6E-06
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Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Processing /
Recycling
manufacturing;
Wholesale and
retail trade
Instrument and
Electrical -
Turnaround
Inhalation
8-hour
TWA
Central
Tendency
463
5,636
5.3E-07
Recycling
High-End
57
689
5.6E-06
Laboratory
Inhalation
8-hour
TWA
Central
Tendency
200
206
1.5E-05
Technician
High-End
21
22
1.8E-04
Laboratory
Technician -
No n routine
Inhalation
8-hour
TWA
Central
Tendency
0.37
4.5
6.7E-04
High-End
0.37
4.5
8.7E-04
Machinery and
Inhalation
8-hour
TWA
Central
Tendency
835
860
3.5E-06
Specialists
High-End
18
19
2.1E-04
Machinery and
Specialists -
Turnaround
Inhalation
8-hour
TWA
Central
Tendency
984
1.2E04
2.5E-07
High-End
656
7,984
4.9E-07
Maintenance
Inhalation
8-hour
TWA
Central
Tendency
33
34
8.9E-05
High-End
21
22
1.8E-04
Page 66 of 173
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Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Maintenance -
Inhalation
8-hour
TWA
Central
Tendency
65
787
3.8E-06
Nonroutine
High-End
36
433
9.0E-06
Maintenance -
Inhalation
8-hour
TWA
Central
Tendency
272
3,304
9.1E-07
Turnaround
High-End
1.6
19
2.0E-04
Operations
Inhalation
8-hour
TWA
Central
Tendency
251
258
1.2E-05
Onsite
High-End
25
26
1.5E-04
Operations
Onsite -
Nonroutine
Inhalation
8-hour
TWA
Central
Tendency
689
8,384
3.6E-07
High-End
165
2,002
1.9E-06
Operations
Onsite -
Turnaround
Inhalation
8-hour
TWA
Central
Tendency
281
3,422
8.8E-07
High-End
131
1,597
2.4E-06
Safety Health
and
Engineering
Inhalation
8-hour
TWA
Central
Tendency
132
136
2.2E-05
Page 67 of 173
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Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
High-End
14
14
2.7E-04
ONU
Inhalation
8-hour
TWA
Central
Tendency
626
645
4.7E-06
High-End
295
303
1.3E-05
Processing/As a
Reactant
Intermediate
in: adhesive
manufacturing;
Processing as a
reactant
(12-hour shift)
Infrastructure/
Distribution
Operations
Inhalation
12-hour
TWA
Central
Tendency
134
214
14E-05
all other basic
organic
chemical
manufacturing;
fuel binder for
solid rocket
fuels; organic
High-End
7.4
12
3.3E-04
Infrastructure/
Distribution
Inhalation
12-hour
TWA
Central
Tendency
40
483
6.2E-06
fiber
manufacturing;
petrochemical
Operations -
Nonroutine
High-End
19
228
1.7E-05
manufacturing;
petroleum
refineries;
plastic material
and resin
manufacturing;
propellant
Instrument and
Inhalation
12-hour
TWA
Central
Tendency
167
268
1.1E-05
Electrical
High-End
21
33
1.2E-04
manufacturing;
synthetic
rubber
manufacturing;
paint and
coating
manufacturing;
Instrument and
Electrical -
Nonroutine
Inhalation
12-hour
TWA
Central
Tendency
327
1,376
2.2E-06
High-End
163
715
54E-06
309
3,757
8.0E-07
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November 2024
Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Processing/
Recycling
Wholesale and
retail trade
Instrument and
Inhalation
Central
Tendency
Recycling
Electrical -
Turnaround
12-hour
TWA
High-End
38
460
8.5E-06
Laboratory
Inhalation
12-hour
TWA
Central
Tendency
134
214
14E-05
Technician
High-End
14
23
1.7E-04
Laboratory
Technician -
No n routine
Inhalation
12-hour
TWA
Central
Tendency
0.24
3.0
1.0E-03
High-End
0.24
3.0
1.3E-03
Machinery and
Inhalation
12-hour
TWA
Central
Tendency
557
892
34E-06
Specialists
High-End
12
19
2.0E-04
Machinery and
Specialists -
Turnaround
Inhalation
12-hour
TWA
Central
Tendency
656
7,984
3.8E-07
High-End
438
5,323
7.3E-07
Maintenance
Inhalation
12-hour
TWA
Central
Tendency
22
35
8.6E-05
High-End
14
23
1.7E-04
Page 69 of 173
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November 2024
Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Maintenance -
Inhalation
12-hour
TWA
Central
Tendency
43
524
5.7E-06
Nonroutine
High-End
24
289
1.3E-05
Maintenance -
Inhalation
12-hour
TWA
Central
Tendency
181
2,203
14E-06
Turnaround
High-End
1.1
13
3.0E-04
Operations
Inhalation
12-hour
TWA
Central
Tendency
167
268
1.1E-05
Onsite
High-End
17
27
1.5E-04
Operations
Onsite -
Nonroutine
Inhalation
12-hour
TWA
Central
Tendency
459
5,589
54E-07
High-End
110
1,335
2.9E-06
Operations
Onsite -
Turnaround
Inhalation
12-hour
TWA
Central
Tendency
188
2,281
1.3E-06
High-End
88
1,065
3.7E-06
Safety Health
and
Engineering
Inhalation
12-hour
TWA
Central
Tendency
88
141
2.1E-05
Page 70 of 173
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November 2024
Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
High-End
9.2
15
2.6E-04
ONU
Inhalation
12-hour
TWA
Central
Tendency
418
669
4.5E-06
High-End
197
315
1.2E-05
Processing/
Incorporation
into
Processing
aids, not
otherwise listed
Processing -
incorporation
into
Infrastructure/
Distribution
Operations
Inhalation
8-hour
TWA
Central
Tendency
200
206
1.5E-05
formulation,
mixture, or
reaction product
in:
petrochemical
manufacturing;
monomers used
in: plastic
product
manufacturing;
formulation,
mixture, or
reaction
product
(8-hour shift)
High-End
11
11
3.4E-04
Infrastructure/
Distribution
Inhalation
8-hour
TWA
Central
Tendency
60
725
4.2E-06
synthetic
rubber
manufacturing
Operations -
Nonroutine
High-End
28
342
1.1E-05
Other: adhesive
manufacturing,
paints and
coatings
manufacturing,
petroleum
lubricating oil
and grease
manufacturing.
Instrument and
Inhalation
8-hour
TWA
Central
Tendency
251
258
1.2E-05
Electrical
High-End
31
32
1.2E-04
Instrument and
Electrical -
Nonroutine
Inhalation
8-hour
TWA
Central
Tendency
490
2,064
1.5E-06
and all other
chemical
product and
preparation
manufacturing
High-End
245
1,073
3.6E-06
463
5,636
5.3E-07
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Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Instrument and
Inhalation
Central
Tendency
Electrical -
Turnaround
8-hour
TWA
High-End
57
689
5.6E-06
Laboratory
Inhalation
8-hour
TWA
Central
Tendency
200
206
1.5E-05
Technician
High-End
21
22
1.8E-04
Laboratory
Technician -
No n routine
Inhalation
8-hour
TWA
Central
Tendency
0.37
4.5
6.7E-04
High-End
0.37
4.5
8.7E-04
Machinery and
Inhalation
8-hour
TWA
Central
Tendency
835
860
3.5E-06
Specialists
High-End
18
19
2.1E-04
Machinery and
Specialists -
Turnaround
Inhalation
8-hour
TWA
Central
Tendency
984
1.2E04
2.5E-07
High-End
656
7,984
4.9E-07
Maintenance
Inhalation
8-hour
TWA
Central
Tendency
33
34
8.9E-05
High-End
21
22
1.8E-04
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Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Maintenance -
Inhalation
8-hour
TWA
Central
Tendency
65
787
3.8E-06
Nonroutine
High-End
36
433
9.0E-06
Maintenance -
Inhalation
8-hour
TWA
Central
Tendency
272
3,304
9.1E-07
Turnaround
High-End
1.6
19
2.0E-04
Operations
Inhalation
8-hour
TWA
Central
Tendency
251
258
1.2E-05
Onsite
High-End
25
26
1.5E-04
Operations
Onsite -
Nonroutine
Inhalation
8-hour
TWA
Central
Tendency
689
8,384
3.6E-07
High-End
165
2,002
1.9E-06
Operations
Onsite -
Turnaround
Inhalation
8-hour
TWA
Central
Tendency
281
3,422
8.8E-07
High-End
131
1,597
2.4E-06
Safety Health
and
Engineering
Inhalation
8-hour
TWA
Central
Tendency
132
136
2.2E-05
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Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
High-End
14
14
2.7E-04
ONU
Inhalation
8-hour
TWA
Central
Tendency
626
645
4.7E-06
High-End
295
303
1.3E-05
Processing/
Incorporation
into
Processing
aids, not
otherwise listed
Processing -
incorporation
into
Infrastructure/
Distribution
Operations
Inhalation
12-hour
TWA
Central
Tendency
134
214
14E-05
formulation,
mixture, or
reaction product
in:
petrochemical
manufacturing;
monomers used
in: plastic
product
manufacturing;
synthetic
rubber
manufacturing
formulation,
mixture, or
reaction
product
(12-hour shift)
High-End
7.4
12
3.3E-04
Infrastructure/
Distribution
Inhalation
12-hour
TWA
Central
Tendency
40
483
6.2E-06
Operations -
Nonroutine
High-End
19
228
1.7E-05
Other: adhesive
manufacturing.
Instrument and
Inhalation
12-hour
TWA
Central
Tendency
167
268
1.1E-05
paints and
coatings
manufacturing,
petroleum
lubricating oil
Electrical
High-End
21
33
1.2E-04
Central
327
1,376
2.2E-06
and grease
manufacturing.
Instrument and
Electrical -
Nonroutine
Inhalation
12-hour
TWA
Tendency
and all other
chemical
product and
High-End
163
715
54E-06
309
3,757
8.0E-07
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Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
preparation
manufacturing
Instrument and
Inhalation
Central
Tendency
Electrical -
Turnaround
12-hour
TWA
High-End
38
460
8.5E-06
Laboratory
Inhalation
12-hour
TWA
Central
Tendency
134
214
14E-05
Technician
High-End
14
23
1.7E-04
Laboratory
Technician -
No n routine
Inhalation
12-hour
TWA
Central
Tendency
0.24
3.0
1.0E-03
High-End
0.24
3.0
1.3E-03
Machinery and
Inhalation
12-hour
TWA
Central
Tendency
557
892
34E-06
Specialists
High-End
12
19
2.0E-04
Machinery and
Specialists -
Turnaround
Inhalation
12-hour
TWA
Central
Tendency
656
7,984
3.8E-07
High-End
438
5,323
7.3E-07
Maintenance
Inhalation
12-hour
TWA
Central
Tendency
22
35
8.6E-05
High-End
14
23
1.7E-04
Page 75 of 173
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November 2024
Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Maintenance -
Inhalation
12-hour
TWA
Central
Tendency
43
524
5.7E-06
Nonroutine
High-End
24
289
1.3E-05
Maintenance -
Inhalation
12-hour
TWA
Central
Tendency
181
2,203
14E-06
Turnaround
High-End
1.1
13
3.0E-04
Operations
Inhalation
12-hour
TWA
Central
Tendency
167
268
1.1E-05
Onsite
High-End
17
27
1.5E-04
Operations
Onsite -
Nonroutine
Inhalation
12-hour
TWA
Central
Tendency
459
5,589
54E-07
High-End
110
1,335
2.9E-06
Operations
Onsite -
Turnaround
Inhalation
12-hour
TWA
Central
Tendency
188
2,281
1.3E-06
High-End
88
1,065
3.7E-06
Safety Health
and
Engineering
Inhalation
12-hour
TWA
Central
Tendency
88
141
2.1E-05
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Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
High-End
9.2
15
2.6E-04
ONU
Inhalation
12-hour
TWA
Central
Tendency
418
669
4.5E-06
High-End
197
315
1.2E-05
Processing /
Processing as a
reactant
Monomer used
in
polymerization
process in:
synthetic
rubber
manufacturing;
plastic material
and resin
manufacturing
Plastics and
rubber
compounding
Worker
Inhalation
8-hour
TWA
Central
Tendency
173
178
1.7E-05
High-End
18
19
2.0E-04
ONU
Inhalation
8-hour
TWA
Central
Tendency
173
178
1.7E-05
High-End
173
178
2.2E-05
Worker
Inhalation
12-hour
TWA
Central
Tendency
24
38
7.9E-05
High-End
12
19
2.0E-04
ONU
Inhalation
12-hour
TWA
Central
Tendency
24
38
7.9E-05
High-End
24
38
1.0E-04
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Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
Processing/
Incorporation
into article
Other: polymer
in: rubber and
plastic product
Plastics and
rubber
converting
Worker
Inhalation
8-hour
TWA
Central
Tendency
202
208
1.4E-05
manufacturing
High-End
17
18
2.2E-04
ONU
Inhalation
8-hour
TWA
Central
Tendency
202
208
14E-05
High-End
202
208
1.9E-05
Worker
Inhalation
12-hour
TWA
Central
Tendency
37
59
5.1E-05
High-End
12
19
2.1E-04
ONU
Inhalation
12-hour
TWA
Central
Tendency
37
59
5.1E-05
High-End
37
59
6.6E-05
Commercial
Use/ Other use
Laboratory
chemicals
Use of
laboratory
chemicals
Laboratory
Inhalation
8-hour
TWA
Central
Tendency
200
206
1.5E-05
Technician
High-End
21
22
1.8E-04
Laboratory
Technician -
No n routine
Inhalation
8-hour
TWA
Central
Tendency
0.37
4.5
6.7E-04
High-End
0.37
4.5
8.7E-04
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Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
ONU
Inhalation
8-hour
Central
Tendency
295
303
9.9E-06
TWA
High-End
3.9
4.0
9.8E-04
Laboratory
Inhalation
12-hour
TWA
Central
Tendency
134
214
14E-05
Technician
High-End
14
23
1.7E-04
Laboratory
Technician -
No n routine
Inhalation
12-hour
TWA
Central
Tendency
0.24
3.0
1.0E-03
High-End
0.24
3.0
1.3E-03
ONU
Inhalation
12-hour
TWA
Central
Tendency
197
315
9.6E-06
High-End
2.6
4.1
9.4E-04
Commercial Use
/ Paints and
Coatings /
Paints and
coatings,
including
Paints,
coatings,
adhesives, and
Worker
Inhalation
8-hour
TWA
Central
Tendency
111
114
2.6E-05
Adhesives and
sealants
aerosol spray
paint
sealants
High-End
55
57
6.8E-05
Industrial Use /
Adhesives and
Sealants
Adhesives and
sealants.
ONU
Inhalation
8-hour
TWA
Central
Tendency
111
114
2.6E-05
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November 2024
Life Cycle
Stage/Category
Subcategory
Occupational
Exposure
Scenario
Population/
SEG
Exposure
Route and
Duration
Exposure
Level
Intermediate Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Chronic Non-
cancer
(HEC = 2.5 ppm,
Benchmark = 30)
Cancer
(Benchmark
HII (14)"
including
epoxy resins
High-End
111
114
3.4E-05
Disposal
Disposal
Recycling
Worker
Inhalation
8-hour
TWA
Central
Tendency
22
22
1.3E-04
High-End
3.9
4.0
9.8E-04
ONU
Inhalation
8-hour
TWA
Central
Tendency
22
22
1.3E-04
High-End
22
22
1.7E-04
Disposal
Disposal
Waste
handling,
treatment, and
disposal
Worker
Inhalation
8-hour
TWA
Central
Tendency
22
22
1.3E-04
High-End
3.9
4.0
9.8E-04
ONU
Inhalation
8-hour
TWA
Central
Tendency
22
22
1.3E-04
High-End
22
22
1.7E-04
" The occupational unit risk was corrected as described in 1,3-Butadiene: Corrected Li fetable Analyses for Leukemia and Bladder Cancer (U.S. EPA. 2024a). The
corrected occupational unit risk = 0.0049 per ppm (2.2 x 10~6 per ng/m3). The cancer estimates herein do not reflect the 20 percent reduction in occupational UR.
1328
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November 2024
5.3.3 Risk Estimates for Consumers
The consumer COUs and associated disposal for 1,3-butadiene do not have quantitative risk estimates.
However, EPA has qualitatively evaluated the COUs by assessing the possibility of 1,3-butadiene
monomer exposure from polymer consumer use in Section 5.1.2 and concluded limited potential for
exposure. Based on this analysis, no appreciable risks are expected from consumer COUs for the 1,3-
butadiene monomer assessed in this risk evaluation.
5.3.4 Risk Estimates for General Population Exposed to Environmental Releases
As detailed in Section 4.2.1, EPA decided to conduct a quantitative exposure assessment for only the air
pathway in order to evaluate non-cancer and cancer risks for the general population. As part of a tiered
approach, EPA used the IIOAC model to estimate 1,3-butadiene ambient air concentrations across
discrete distances between 100 to 1,000 m from TRI2016 to 2021 reported facility releases and
presented a range of modeled concentrations across all reporting years for each facility. The ambient air
concentrations modeled with IIOAC were used for the risk calculations found in Section 5.3.1 for
chronic non-cancer MOEs and inhalation cancer risks. Based on the results from IIOAC, non-cancer
risks were not expected for the general population (Section 5.3.4.1). However, there were potential
screening-level risk estimates at or above the cancer risk benchmark up to 1,000 m. Therefore, EPA
used the HEM to refine 1,3-butadiene ambient air concentrations across discrete distances between 10 to
50,000 m from TRI facility releases and calculated inhalation cancer risks (Section 5.3.4.2).
EPA focused on modeled air concentrations for the following distances: 100 m, 100 to 1,000 m, and
1,000 m. These distances are also consistent with the community populations living near facilities as
described in the fenceline methodology (Draft Screening Level Approach for Assessing Ambient Air
and Water Exposures to Fenceline Communities Versio ).
In addition to modeling ambient air concentrations at discrete distances, HEM also models annual-
averaged concentrations and estimates cancer risks at census blocks within 50,000 m from TRI facility
releases. Census block-based results are aggregated across facilities; that is, if a census block is within
proximity to more than one TRI facility release, then the modeled concentrations, and in turn, the
estimated cancer risks, from each facility release are added together for that census block.
Sensitive organ-level endpoints are unlikely to result from a single exposure at concentrations relevant
to human exposures (Section 5.2 and the Draft Human Health Hazard Assessment for 1,3-Butadiene
(I ft). Therefore, EPA expects low risks to the general population from acute exposures for
all COUs. EPA evaluated chronic non-cancer risk for general population chronic exposure using the
HEC of 2.5 ppm (5,500 |ig/m3) for reduced fetal weight with a benchmark MOE of 30. EPA evaluated
lifetime cancer risk using the general population IUR of 0.0098 per ppm (4,4/ 10 6 per |ig/m3). See
Section 5.2 and the Draft Human Health Hazard Assessment for 1,3-Butadiene ( 2024f) for
more details on the human health hazard values. If the calculated lifetime cancer risk was above the
cancer risk benchmark of 1 in a million, or 1 x 10~6, then potential risk was identified and further
characterized.
There is uncertainty in underlying parameters required for accurately estimating releases for cases where
1,3-butadiene is present in LPG, and only minimal monomer 1,3-butadiene is expected to be released
from final use products. As a result, EPA did not quantify releases and resulting general population
exposures from Commercial use in fuels and related products or the Commercial COUs covered by the
OES of Use of plastics and rubber products and Use of lubricants and greases. Risks from these COUs
are expected to be low.
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As the Agency incorporates refined or additional release data received during the public comment period
and SACC review of the draft risk evaluation, it is possible that the risk estimates for specific COUs
could change.
5.3.4.1 Inhalation Margin of Exposures by Discrete Distances
As part of a tiered analysis, EPA calculated ambient air concentrations and associated MOEs using
Equation 5-1 at radial distances of 100, 100 to 1,000 and 1,000 m from TRI releases of 1,3-butadiene
using IIOAC. No calculated MOE was below the benchmark of 30 for any IIOAC modeled
concentrations from 100 to 1,000 m across all TRI facilities. The highest concentration and therefore
lowest corresponding MOE was calculated for a facility corresponding with the Processing - plastics
and rubber compounding COU/OES, at an MOE of 60, which is twice the benchmark of 30. Therefore,
based on the MOE over the benchmark for the highest estimated concentrations from this assessment,
non-cancer risks are not expected for the general population from inhalation of 1,3-butadiene from
environmental releases and no further refinements were conducted. See the Draft General Population
Exposures for 1,3-Butadiene (U. 2024r) for more details on the IIOAC modeling and results.
5.3.4.2 Inhalation Cancer Risks by Discrete Distances
Although the tiered analysis with IIOAC 95th percentile modeled concentrations resulted in no
expectation for non-cancer risks, estimated cancer risks based on IIOAC 95th percentile and mean
modeled concentrations were at or above the 1 in a million benchmark up to 1,000 m from facility
releases. Since the risk estimates derived using IIOAC results were above this benchmark, EPA utilized
HEM to conduct a more geographically refined analysis of ambient air concentrations using localized
meteorological data and site-specific days of operation. Using 95th, 50th, and 10th percentile modeled
concentrations from HEM, EPA calculated the lifetime cancer risks using Equation 5-2 and are
summarized by OESs and associated COUs across the 100, 100 to 1,000 and 1,000 m distances in Table
5-5. Based on the 95th percentile modeled concentrations, cancer risks ranged from 1.9xl0-13 to
4.1ExlO~4 from 100, 100 to 100 m and 1,000 m distances across all TRI 2016 to 2021 reporting years.
Processing - plastics and rubber compounding COU/OES resulted in the highest risks while
Manufacture - manufacturing COU/OES is associated with the furthest distance showing risk above the
1 x 10~6 benchmark at 5,000 m. Summary tables for cancer risks based on the 95th, 50th, and 10th
percentile modeled from HEM across all distances by OESs and associated COUs across all distances
from 10 to 50,000 m are presented in Appendix H. 1.
For all TRI 2016 to 2021 modeled exposure concentrations and calculated MOEs and cancer risks for all
distances from 10 to 50,000 m, see the supplemental file: Draft Human Exposure Model (HEM) TRI
2016-2021 Exposure and Risk Analysis for 1,3-Butadiene (U.S. EPA. 2024s).
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1411 Table 5-5. General Population Cancer Risk Summary Table at 100 to 1,000 m from Facility Releases Based on HEM Modeled
1412 Concentrations"bcd
Population
Exposure
Route-
Life Cycle
Stage
Category
Subcategory
Exposure
Scenario
Facility
Count
Facility Count
Within
Benchmark
Range
Exposure
Concentration
Statistic
100 m
100-1,000 m
1,000 m
General
Population
Air
Inhalation
Manufacture
Domestic
manufacturing
Domestic
manufacturing
Manufacturing
40
30
95th percentile
3.5E-04
6.0E-05
2. IE—05
23
50 th percentile
1.4E-04
1.3E-05
7.5E-06
22
10th percentile
6.6E-05
4.6E-06
3.3E-06
Processing
Processing as a
reactant
Other: monomer used
in polymerization
process in: plastic
material and resin
manufacturing;
manufacturing
synthetic rubber and
plastics
Plastics and
Rubber
Compounding
33
29
95th percentile
4. IE—04
3.2E-05
9.4E-06
22
50 th percentile
1.2E-04
6.6E-06
3.6E-06
18
10th percentile
7. IE—05
2.9E-06
1.9E-06
Processing
Processing -
incorporation
into article
Other: polymer in:
rubber and plastic
product
manufacturing
Plastics and
Rubber
Converting
1
0
95th percentile
2.3E-12
6.5E-13
1.9E-13
0
50 th percentile
9.0E-13
2.4E-13
1.6E-13
0
10th percentile
5.9E-13
1.6E-13
1.4E-13
Processing
Processing -
incorporation
into formulation,
mixture, or
reaction product
Processing aids, not
otherwise listed in:
petrochemical
manufacturing
Processing -
Incorporation
into
Formulation,
Mixture, or
Reaction
Product
53
16
95th percentile
7.6E-05
2.9E-05
1.4E-05
9
50 th percentile
1.7E-05
1.6E-06
1.3E-06
6
10th percentile
5.8E-06
3.6E-07
2.3E-07
Processing
Processing as a
reactant
Intermediate in:
adhesive
manufacturing; all
other basic organic
chemical
manufacturing; Fuel
binder for solid rocket
Processing as a
Reactant
57
31
95th percentile
1.4E-04
1.3E-05
3.5E-06
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Population
Exposure
Route-
Life Cycle
Stage
Category
Subcategory
Exposure
Scenario
Facility
Count
Facility Count
Within
Benchmark
Range
Exposure
Concentration
Statistic
100 m
100-1,000 m
1,000 m
fuels; organic fiber
manufacturing;
petrochemical
manufacturing;
petroleum refineries;
plastic material and
resin manufacturing;
propellant
manufacturing;
synthetic rubber
16
50 th percentile
4.5E-05
2.1E-06
1.1E-06
General
Air
manufacturing; paint
and coating
manufacturing;
wholesale and retail
trade
14
10th percentile
2.2E-05
8.0E-07
5.3E-07
Population
Inhalation
Recycling
3
95th percentile
3. IE—06
3.8E-07
9.8E-08
11
1
50 th percentile
1.4E-06
6.3E-08
3.4E-08
0
10th percentile
6.3E-07
3.3E-08
2.3E-08
Disposal
Disposal
Disposal
Waste
Handling,
Disposal,
Treatment, and
Recycling
0
95th percentile
7.9E-07
9.2E-08
3. IE—08
7
0
50 th percentile
7.8E-08
2.0E-08
1.1E-08
0
10th percentile
3.0E-08
5.7E-09
3.7E-09
Manufacture
Import
Import
Repackaging
6
95th percentile
9.0E-05
1.1E-05
2.3E-06
23
5
50 th percentile
3.7E-05
1.9E-06
9.9E-07
Processing
Repackaging
Intermediate in:
wholesale and retail
trade
3
10th percentile
2.3E-05
7.5E-07
5. IE—07
"Cancer endpoint = leukemia (U.S. EPA, 20240
4 IUR = [9.8E-03] per ppm; [4.4E-06] per |ig/m3
c Maximum cancer risk
d Cancer Risk = Human Exposure x IUR (Benchmark =
1E-06 to 1E-04)
1413
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5.3.4.3 Inhalation Cancer Risks by Census Blocks
EPA aggregated and summarized cancer risk estimates from HEM based on TRI2016-2021 ambient air
releases at the facility and census block levels. Further description of the modeling procedures and
details on how cancer risks are calculated is available in the Draft General Population Exposures for
1,3-Butadiene (U.S. EPA. 2024r) as well as the HEM User Guides (SC&A. 2023). As an illustrative
example, Figure 5-1 shows the cancer risk results for census blocks based on the most recent 2021 TRI
reporting year. Figures for the other reporting years are presented in Appendix H.2. Elevated cancer
risks are concentrated in areas along the Gulf Coast region from Texas to Louisiana, primarily between
Houston and Baton Rouge shown in the zoomed-in map (Figure 5-2). Across the 2016 to 2021 TRI
reporting years, the calculated cancer risks at census block centroids ranged from 0 to 1.3x10 4; that is,
some facilities are predicted to have no risk at any census blocks within 50 km, up to a facility with
cancer risk as high as 1.3 in 10,000. The highest cancer risk estimated was based on 2017 TRI releases
from the Ineos USA LLC - Chocolate Bayou Plant (TRI ID 77511MCCHM2MISO), a 1,3-butadiene
manufacturing facility located in Alvin, TX (in the greater Houston area). Upon further investigation, it
was determined that the latitude and longitude coordinates for this facility were erroneously reported in
the TRI database for the 2016, 2017 and 2019 reporting years. Releases from this facility and associated
ambient air concentrations were remodeled using the correct coordinates. After correction of the location
of the Ineos USA LLC - Chocolate Bayou Plant facility, associated cancer risks in surrounding census
blocks were reduced (updated maps for the 2016, 2017 and 2019 reporting years will be included in the
final risk evaluation). The highest cancer risk was then determined to be associated with the Total
Energies Petrochemical and Refining USA Inc. facility (TRI ID 77640FNLNDHIGHW), a 1,3-
butadiene processing facility located in Port Arthur, TX (part of the greater Houston-Beaumont area).
2016 TRI releases from this facility resulted in an estimated cancer risk of 7.4><10~5, or 7.4 in 100,000.
Modeled Maximum
Individual Risk from
TRI Releases by Census Block
<1E - 06
1E-06 - 1E-05
• 1E-05 - 1E-04
• >lE-04
. ,, Tribal Lands
I I States
Figure 5-1. Map of Contiguous United States with HEM Model Results for Cancer Risks
Aggregated and Summarized by Census Block for the 2021 TRI Reporting Year
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1447
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Modeled Maximum
Individual Risk from
TRI Releases by Census Block
<1E - 06
1E-06 - 1E-05
• 1E-05 - 1E-04
• >lE-04
Y// Tribal Lands
I I States
Figure 5-2. Southern United States Close-Up
Based on the general population IUR of 4.4><10"6 risk per |ig/m3, exposure concentrations of 0.227
|ig/m3 (1.03xl0-4 ppm), 2.27 |ig/m3 (1.03><10"3 ppm) and 22.7 |ig/m3 (1.03><10"2 ppm) or greater, will
result in risk at or above the 1 in a million (lxlO-6), 1 in 100,000 (lxlO-5) and 1 in 10,000 (lxlO-4)
benchmarks, respectively. For all census blocks modeled, HEM utilizes population counts within each
census block to calculate a total estimated population count; that is, number of people exposed, to 1,3-
butadiene in ambient air that would result in cancer risk at each benchmark. Table 5-6 tabulates the
number of modeled facilities, the range of census block cancer risks for all the modeled facilities, the
total estimated population summed from all census blocks exposed above each benchmark value, and
the number of facilities (N) attributed to the population count and is categorized by OESs and associated
COUs for the 2016 to 2021 TRI reporting years. Updated results with the corrected location for the
Ineos USA LLC - Chocolate Bayou Plant are noted with an italicized, superscripted "a" (t?) for the years
that this facility reported TRI releases in 2016, 2017, and 2019.
As an excerpt from Table 5-6, based on the 2021 TRI reporting year, there were a total of 37
manufacturing facilities that reported 1,3-butadiene releases. Cancer risks were estimated for the census
blocks around those 37 manufacturing facilities. The estimated cancer risks across all of the census
blocks around the 37 manufacturing facilities ranged from 6.5 xlO-11 to 8.9xl0~5. For the census blocks
that had estimated cancer risks at or above the 1 in a million, 1 in 100,000, and 1 in 10,000 benchmarks,
the population counts from each census block were summed together to show the total population count
exposed at or above each benchmark. Of the 37 manufacturing facilities, releases from 15 facilities
resulted in 80,461 people exposed to cancer risks at or above the 1 in a million benchmark and releases
from 3 facilities resulted in 1,721 people exposed to cancer risks at or above the 1 in 100,000
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1500
1501
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benchmark. There were no populations exposed to cancer risk at or above the 1 in 10,000 benchmark.
The 1 in a million benchmark is defined as 1 additional case of cancer expected to develop per 1 million
people if exposed daily to 0.227 |ig/m3 (1.03xl0-4 ppm) over a lifetime. 80,461 people with an estimated
risk at or above 1 in a million but below the 1 in 100,000 benchmark results in 0.08 to 0.8 additional
cases expected for the 80,461 people if exposed daily over a lifetime while 1,721 people with an
estimated risk at or above 1 in 100,000 and an estimated maximum risk of 8.9x 10-5 results in 0.017 to
0.15 additional cases expected for the 1,721 people if exposed daily over a lifetime. Altogether, based on
the 2021 TRI reporting year for 1,3-butadiene releases from manufacturing facilities, there is range of
0.097 to 0.95 additional cases expected for that population if exposed daily over a lifetime.
Across the 2016 to 2021 TRI reporting years, the estimated cancer risks across all census blocks ranged
from 0 to 7.4x 10~5; that is some census blocks within 50 km of facilities have no estimated risk of
cancer from exposure to 1,3-butadiene while other census blocks have estimated cancer risk as high as
7.4 in 10,000. The total number of people across all OESs and associated COUs with an estimated
cancer risk at or above the 1 in a million-benchmark ranged from 79,907 to 156,303 people. The
Manufacture - manufacturing COU-OES is identified as the highest contributor among all the COUs-
OESs, followed by Processing - incorporation into formulation, mixture, or reaction product and then
Processing - plastics and rubber compounding and Processing as a reactant COUs-OESs. The census
block with highest estimated risk (ID 66001009) has a population of 3 people exposed to risk of
7.4><10~5 (7.4 in 100,000). This census block is located within 1,000 m from the Total Energies
Petrochemical and Refining USA Inc. facility.
Table 5-7 shows the demographic breakdown nationwide and for all census blocks within 50,000 m
from TRI facilities along with average cancer risk based on populations categorized by racial and ethnic
groups, age, and other sociodemographic factors. Average cancer risk estimates ranged from 0.008 to
0.03 in a million across all demographic categories; that is, 0.008 to 0.03 additional cases expected per 1
million people if exposed daily over a lifetime.
A source of uncertainty in these analyses is the assumption that the TRI-reported emissions from each
facility are from a standardized stack of 10 m in height and ground-level area source of 10 by 10 m as
described in the Draft Environmental Releases and Occupational Exposure Assessment for 1,3-
Butadiene ( |y). This assumption is a source of uncertainty for large multi-acre facilities
with disperse sources and could bias results either to more or less risk based on the relation between the
assumed point of release and the exposed population. In other words, if the actual releases are more
dispersed and farther from the exposed populations then modeled, the results would be an overestimate
of risk. However, if the actual releases are closer to the edge of the facility boundaries or upwind of
population centers then the estimates could be an underestimate. As a check on the direction of
uncertainty, EPA cross walked the cancer risk estimates with previous assessments, described below, of
the same facilities with more refined analyses of emissions processes.
5.3.4.4 Inhalation Cancer Risks Estimated by Previous EPA Assessments
As described in Appendix B, 1,3-butadiene is a hazardous air pollutant (HAP) subject to Clean Air Act
(CAA) sections 112(d) and 112(f). As a result, most of the highest-emitting facilities for 1,3-butadiene
are subject to regular risk and technology reviews (RTR) by applicable source category, including
residual risk reviews. Emissions of all HAPs from a modeled facility are generally estimated at the
process level for the source category and aggregated with all other HAPs for a whole-facility estimate of
attributable risk.
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While the objective of these RTRs serves a different purpose, the underlying modeling to estimate
ambient air concentrations are comparable to the HEM census block modeling of same facilities
reporting to TRI. The RTRs have relied on the IRIS Health Assessment of 1,3-Butadiene (2002a) with
an IUR of 3 x 10~5 per |ig/m3, compared to the less potent IUR of 4.4x 10~6 per |ig/m3, described above in
Section 5.3. Thus, the RTRs would be expected to show approximately 7 times higher risks for the same
lifetime exposures. Other differences include the underlying population analysis, this evaluation relied
on 2020 census data while the recent RTRs used 2010 census data with adjustments for maximum
individual risk.
The facilities identified in this risk evaluation analysis with the highest associated cancer risks at
downwind census blocks were cross walked with the most recent RTR whole facility assessments which
estimated risks from HAP emissions, including 1,3-butadiene. Similarly, the facilities with the highest
maximum individual risk attributable to 1,3-butadiene in the most recent and relevant RTR, the Residual
Risk Assessment for the Synthetic Organic Chemical Manufacturing Industry (SOCMI) Source (U.S.
E 24ah) were also cross-walked with the highest cancer risks estimated in this risk evaluation.
Most of the 1,3-butadiene facilities associated with the highest census block risks were evaluated in the
SOCMI RTR with the exception of the following three facilities which were most recently covered by
the Polymer and Resin Group 1 source category: Firestone Polymers (TRI ID 70602FRSTNLA108),
Lion Elastomers Orange (TRI ID 77630FRSTNFARMR), and Arlanxeo (TRI ID 77631PLYSRFM100).
For all facilities, the maximum individual risk attributable to 1,3-butadiene from each facility in the
SOCMI RTR were found to be similar or lower than the highest census block risk estimates from this
evaluation after correcting for the updated IUR. Therefore, EPA is confident that the uncertainty
associated with modeling TRI-reported emissions from standardized stack and area sources is health
protective and the cancer risk estimates do not underestimate risks to proximate communities.
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1538 Table 5-6. Inhalation Cancer Risk Population Count Based on HEM Modeling Results Using 2020 Census Blocks for TRI2016-2021
1539 Releases
Year
Lite Cycle
Stage
Category
Subcategory
OES
Facility
Count
(N)
Cancer Risk Range
for all Census Blocks
within 50 km
Number
People
Exposed to >
1 in 1,»»»,»»»
Risk (1E—06)
N
Number
People
Exposed to >
1 in 1 ()(),()(>()
Risk (1E-05)
N
Number
People
Exposed to
>1 in 1 (),()()()
Risk (1E-04)
N
Min
Max
2016
Manufacturing
Domestic
manufacturing
Domestic manufacturing
Manufacturing
38
0.0E00
1.1E-04
(1.2E-05)"
67,291
(43,839)"
13
1,655
(32)"
2(1)°
80
(0)°
1
(0)°
Processing
Processing as a
reactant
Other: monomer used in
polymerization process in:
plastic material and resin
manufacturing;
manufacturing synthetic
rubber and plastics
Plastics and
rubber
compounding
29
7.9E-09
1.8E-05
5,231
10
184
3
0
0
Processing
Processing -
incorporation
into
formulation,
mixture, or
reaction product
Processing aids, not
otherwise listed in:
petrochemical
manufacturing
Processing -
incorporation
into
formulation,
mixture, or
reaction
product
46
0.0E00
7.4E-05
41,314
1
1,179
1
0
0
Processing
Processing as a
reactant
Intermediate in: adhesive
manufacturing; all other
basic organic chemical
manufacturing; fuel
binder for solid rocket
fuels; organic fiber
manufacturing;
petrochemical
manufacturing; petroleum
refineries; plastic material
and resin manufacturing;
propellant manufacturing;
synthetic rubber
manufacturing; wholesale
and retail trade
Processing as a
reactant
53
0.0E00
4.3E-06
128
4
0
0
0
0
Disposal
Disposal
Disposal
Recycling
10
1.4E-10
4.5E-07
0
0
0
0
0
0
Manufacturing
Import
Import
Repackaging
16
5. IE—11
3.1E-06
273
1
0
0
0
0
Processing
Repackaging
Intermediate in:
Wholesale and retail trade
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Year
Lite Cycle
Stage
Category
Subcategory
OES
Facility
Count
(N)
Cancer Risk Range
for all Census Blocks
within 50 km
Number
People
Exposed to >
1 in 1,»»»,»»»
Risk (IE—06)
N
Number
People
Exposed to >
1 in 100,000
Risk (1E-05)
N
Number
People
Exposed to
>1 in 10,000
Risk (1E-04)
N
Min
Max
Disposal
Disposal
Disposal
Waste
handling,
disposal,
treatment, and
recycling
4
1.8E-11
1.8E-07
0
0
0
0
0
0
Grand Total
196
114,237
(90785)"
29
3,018
(1395)a
6
(5 y
80
(0)"
1
(0)"
2017
Manufacturing
Domestic
Manufacturing
Domestic manufacturing
Manufacturing
38
0.0E00
1.3E-04
(1.1E-05)"
70,555
(42,125)"
14
2,588
(28)"
2(1 y
80
(0)°
1 (0)"
Processing
Processing as a
reactant
Other: monomer used in
polymerization process in:
plastic material and resin
manufacturing;
manufacturing synthetic
rubber and plastics
Plastics and
rubber
compounding
29
8.2E-10
1.4E-05
7172
13
170
2
0
0
Processing
Processing -
incorporation
into
formulation,
mixture, or
reaction product
Processing aids, not
otherwise listed in:
petrochemical
manufacturing
Processing -
incorporation
into
formulation,
mixture, or
reaction
product
44
0.0E00
6.4E-05
33977
1
877
1
0
0
Processing
Processing as a
reactant
Intermediate in: adhesive
manufacturing; all other
basic organic chemical
manufacturing; fuel
binder for solid rocket
fuels; organic fiber
manufacturing;
petrochemical
manufacturing; petroleum
refineries; plastic material
and resin manufacturing;
propellant manufacturing;
synthetic rubber
manufacturing; wholesale
and retail trade
Processing as a
reactant
52
0.0E00
3.6E-06
525
7
0
0
0
0
Disposal
Disposal
Disposal
Recycling
11
3.6E-10
4.9E-07
0
0
0
0
0
0
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Year
Lite Cycle
Stage
Category
Subcategory
OES
Facility
Count
(N)
Cancer Risk Range
for all Census Blocks
within 50 km
Number
People
Exposed to >
1 in 1,»»»,»»»
N
Number
People
Exposed to >
1 in 100,000
N
Number
People
Exposed to
>1 in 10,000
N
Min
Max
Risk (IE—06)
Risk (1E-05)
Risk (1E-04)
Manufacturing
Import
Import
Processing
Repackaging
Intermediate in: wholesale
and retail trade
Repackaging
10
3.0E-09
2.9E-06
1,813
2
0
0
0
0
Disposal
Disposal
Disposal
Waste
handling,
disposal,
treatment, and
recycling
3
1.4E-12
8. IE—08
0
0
0
0
0
0
Grand Total
187
114,042
(85,612)a
37
3,635
(l,075)a
5
(4)"
80
1
Manufacturing
Domestic
manufacturing
Domestic manufacturing
Manufacturing
37
1.2E-10
7.3E-05
80,424
13
1308
2
0
0
Processing
Processing as a
reactant
Other: monomer used in
polymerization process in:
plastic material and resin
manufacturing;
manufacturing synthetic
rubber and plastics
Plastics and
rubber
compounding
28
3.2E-10
9.3E-06
1,346
12
0
0
0
0
Processing
Processing -
incorporation
into article
Other: polymer in: Rubber
and plastic product
manufacturing
Plastics and
rubber
converting
1
8.0E-13
8.0E-13
0
0
0
0
0
0
2018
Processing
Processing -
incorporation
into
formulation,
mixture, or
reaction product
Processing aids, not
otherwise listed in:
petrochemical
manufacturing
Processing -
incorporation
into
formulation,
mixture, or
reaction
product
41
0.0E00
2.4E-06
10
1
0
0
0
0
Processing
Processing as a
reactant
Intermediate in: adhesive
manufacturing; all other
basic organic chemical
manufacturing; fuel
binder for solid rocket
fuels; organic fiber
manufacturing;
petrochemical
manufacturing; petroleum
Processing as a
reactant
51
0.0E00
2.2E-06
522
6
0
0
0
0
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Year
Lite Cycle
Stage
Category
Subcategory
OES
Facility
Count
(N)
Cancer Risk Range
for all Census Blocks
within 50 km
Number
People
Exposed to >
1 in 1,»»»,»»»
N
Number
People
Exposed to >
1 in 1 ()(),()(>()
N
Number
People
Exposed to
>1 in 10,000
N
Min
Max
Risk (IE—06)
Risk (1E-05)
Risk (1E-04)
refineries; plastic material
and resin manufacturing;
propellant manufacturing;
synthetic rubber
manufacturing; wholesale
and retail trade
Disposal
Disposal
Disposal
Recycling
11
4.0E-10
7.7E-07
0
0
0
0
0
0
Manufacturing
Import
Import
Repackaging
13
3.0E-09
1.4E-06
1,480
2
0
0
0
0
Processing
Repackaging
Intermediate in: wholesale
and retail trade
Disposal
Disposal
Disposal
Waste
handling,
disposal,
treatment, and
recycling
4
2.0E-12
9.2E-08
0
0
0
0
0
0
Grand Total
186
83,782
34
1,308
2
0
0
2019
Manufacturing
Domestic
Manufacturing
Domestic Manufacturing
Manufacturing
36
1.3E—10
1.0E-04
(2.3E-05)"
172,773
(150,547)"
15
3,450(1827)
4(3)"
80
(0)°
1 (0)"
Processing
Processing as a
reactant
Other: monomer used in
polymerization process in:
plastic material and resin
manufacturing;
manufacturing synthetic
rubber and plastics
Plastics and
rubber
compounding
28
3.2E-10
1.1E-05
1,986
11
161
1
0
0
Processing
Processing -
incorporation
into
formulation,
mixture, or
reaction product
Processing aids, not
otherwise listed in:
petrochemical
manufacturing
Processing -
incorporation
into
formulation,
mixture, or
reaction
product
47
0.0E00
2.5E-06
0
0
0
0
0
0
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Year
Lite Cycle
Stage
Category
Subcategory
OES
Facility
Count
(N)
Cancer Risk Range
for all Census Blocks
within 50 km
Number
People
Exposed to >
1 in 1,»»»,»»»
N
Number
People
Exposed to >
1 in 1 ()(),()(>()
N
Number
People
Exposed to
>1 in 10,000
N
Min
Max
Risk (IE—06)
Risk (1E-05)
Risk (1E-04)
Processing
Processing as a
reactant
Intermediate in: Adhesive
manufacturing; All other
basic organic chemical
manufacturing; Fuel
binder for solid rocket
fuels; Organic fiber
manufacturing;
Petrochemical
manufacturing; Petroleum
refineries; Plastic material
and resin manufacturing;
Propellant manufacturing;
Synthetic rubber
manufacturing; Wholesale
and retail trade
Processing as a
Reactant
51
6. IE—11
9.4E-06
2,670
7
0
0
0
0
Disposal
Disposal
Disposal
Recycling
11
5.IE—10
2.9E-07
0
0
0
0
0
0
Manufacturing
Import
Import
Repackaging
14
0.0E00
2.2E-06
1,100
2
0
0
0
0
Processing
Repackaging
Intermediate in:
Wholesale and retail trade
Disposal
Disposal
Disposal
Waste
Handling,
Disposal,
Treatment, and
Recycling
4
1.6E-12
9.2E-08
0
0
0
0
0
0
Grand Total
191
178,529
(156,303)"
35
3,611
(1,988)"
5
(4)"
80
(0)"
1
(0)"
2020
Manufacturing
Domestic
Manufacturing
Domestic Manufacturing
Manufacturing
38
1.3E-10
8.4E-05
74,858
13
1,288
1
0
0
Processing
Processing as a
reactant
Other: Monomer used in
polymerization process in:
Plastic material and resin
manufacturing;
Manufacturing synthetic
rubber and plastics
Plastics and
Rubber
Compounding
29
7.7E-10
2.4E-05
3,724
11
162
2
0
0
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November 2024
Year
Lite Cycle
Stage
Category
Subcategory
OES
Facility
Count
(N)
Cancer Risk Range
for all Census Blocks
within 50 km
Number
People
Exposed to >
1 in 1,»»»,»»»
N
Number
People
Exposed to >
1 in 100,000
N
Number
People
Exposed to
>1 in 10,000
N
Min
Max
Risk (IE—06)
Risk (IE—05)
Risk (1E-04)
Processing
Processing -
incorporation
into
formulation,
mixture, or
reaction product
Processing aids, not
otherwise listed in:
Petrochemical
manufacturing
Processing -
incorporation
into
formulation,
mixture, or
reaction
product
43
0.0E00
2.7E-06
0
0
0
0
0
0
Processing
Processing as a
reactant
Intermediate in: Adhesive
manufacturing; All other
basic organic chemical
manufacturing; Fuel
binder for solid rocket
fuels; Organic fiber
manufacturing;
Petrochemical
manufacturing; Petroleum
refineries; Plastic material
and resin manufacturing;
Propellant manufacturing;
Synthetic rubber
manufacturing; Wholesale
and retail trade
Processing as a
Reactant
52
0.0E00
1.1E-05
781
7
1
0
0
Disposal
Disposal
Disposal
Recycling
11
1.5E-10
2.7E-07
0
0
0
0
0
0
Manufacturing
Import
Import
Repackaging
12
0.0E00
2.9E-06
544
3
0
0
0
0
Processing
Repackaging
Intermediate in:
Wholesale and retail trade
Disposal
Disposal
Disposal
Waste
Handling,
Disposal,
Treatment, and
Recycling
4
3.5E-12
8.3E-08
0
0
0
0
0
0
Grand Total
189
79,907
34
1,451
3
0
0
2021
Manufacturing
Domestic
Manufacturing
Domestic Manufacturing
Manufacturing
37
6.5E-11
8.9E-05
80,461
15
1,721
3
0
0
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Year
Lite Cycle
Stage
Category
Subcategory
OES
Facility
Count
(N)
Cancer Risk Range
for all Census Blocks
within 50 km
Number
People
Exposed to >
1 in 1,»»»,»»»
N
Number
People
Exposed to >
1 in 1 ()(),()(>()
N
Number
People
Exposed to
>1 in 10,000
N
Min
Max
Risk (IE—06)
Risk (1E-05)
Risk (1E-04)
Processing
Processing as a
reactant
Other: Monomer used in
polymerization process in:
Plastic material and resin
manufacturing;
Manufacturing synthetic
rubber and plastics
Plastics and
Rubber
Compounding
31
6.4E-10
3.2E-05
40,86
13
161
1
0
0
Processing
Processing -
incorporation
into
formulation,
mixture, or
reaction product
Processing aids, not
otherwise listed in:
Petrochemical
manufacturing
Processing -
incorporation
into
formulation,
mixture, or
reaction
product
41
0.0E00
2.7E-06
0
0
0
0
0
0
Processing
Processing as a
reactant
Intermediate in: Adhesive
manufacturing; All other
basic organic chemical
manufacturing; Fuel
binder for solid rocket
fuels; Organic fiber
manufacturing;
Petrochemical
manufacturing; Petroleum
refineries; Plastic material
and resin manufacturing;
Propellant manufacturing;
Synthetic rubber
manufacturing; Wholesale
and retail trade
Processing as a
Reactant
49
0.0E00
1.1E-05
812
7
1
1
0
0
Disposal
Disposal
Disposal
Recycling
11
1.7E-10
2.4E-07
0
0
0
Manufacturing
Import
Import
Repackaging
12
0.0E00
6.4E-06
1,356
3
0
0
0
0
Processing
Repackaging
Intermediate in:
Wholesale and retail trade
Disposal
Disposal
Disposal
Waste
Handling,
Disposal,
Treatment, and
Recycling
3
3.5E-12
9.2E-08
0
0
0
0
0
0
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PUBLIC RELEASE DRAFT
November 2024
Year
Lite Cycle
Stage
Category
Subcategory
OES
Facility
Count
(N)
Cancer Risk Range
for all Census Blocks
within 50 km
Number
People
Exposed to >
1 in 1,»»»,»»»
Risk (IE—06)
N
Number
People
Exposed to >
1 in 1 ()(),()(>()
Risk (1E-05)
N
Number
People
Exposed to
>1 in 10,000
Risk (1E-04)
N
Min
Max
Grand Total
184
86,715
38
1,883
5
0
0
" Denotes updated results with corrected location for Inoes Chocolate Bayou Plant
1540
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1541 Table 5-7. Human Exposure Model (HEM) Demographic Cancer Risk Results Nationwide
Distribution of Cancer Risk lor Racial mid Ethnic Groups, Age Groups, Adults without a High School Diploma, People Living in Low Income Households, mid People Living in Linguistic Isolation - 50 km
Study Area Radius
Veil r
Descriptor
Total
Population
White
People of
C ,'olor'
African
American
Native
Amcricmi
Other mid
Multi-
racial
Ilispanic
or Latino ¦'
Age
(years)
0-17
Age (vea rs)
18-64
Age
(years)
>65
People
Living
Below the
Poverty
Level
People
Living
lielow
Twice the
Poverty
Level
Total
Number
>25 Years
Old
Number >25
Years Old
without a
High School
Diploma
People
Living in
Linguistic
Isolation
All
Nationwide demographic breakdown
Total
population1
329.824.950
196.283.090
133.541.860
39.997.867
2.076.003
28.894.345
62.573.645
73.907.898
202.887.029
53.030.023
42.311.284
99.653.072
225.188.926
26.087.112
17.242.818
Percentage of
total
59.5%
40.5%
12.1%
0.6%
8.8%
19.0%
22.4%
61.5%
16.1%
12.8%
30.2%
68.3%
11.6%
5.2%
2016
Proximity results
Total
population
within 50 km
of any facility
110.900.368
58.474.444
52.425.924
15.892.328
431.730
12.872.392
23.229.473
24.612.214
69.557.736
16.730.418
13.739.964
31.167.722
76.311.023
9.165.100
6.91 8.769
Percentage of
total
52.7%
47.3%
14.3%
0.4%
11.6%
20.9%
22.2%
62.7%
15.1%
12.4%
28.1%
68.8%
12.0%
6.2%
Average risk
(in one
million) "
0.02
0.01
0.02
0.02
0.008
0.01
0.03
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
2017
Proximity results
Total
population
within 50 km
of any facility
99.416.428
52.232.582
47.183.846
14.443.744
398.265
12.010.455
20.331.383
21.874.530
62.351.960
15.189.937
12.457.100
28.032.826
68.620.325
8.266.315
6.365.954
Percentage of
total
52.5%
47.5%
14.5%
0.4%
12.1%
20.5%
22.0%
62.7%
15.3%
12.5%
28.2%
69.0%
12.0%
6.4%
Average risk
(in one
million)
0.02
0.02
0.03
0.03
0.01
0.01
0.04
0.03
0.02
0.02
0.03
0.03
0.02
0.03
0.03
2018
Proximitv results
Total
population
within 50 km
of any facility
105.570.626
56.289.137
49.281.489
14.696.118
432.512
13.143.845
21.009.014
23.151.403
66.342.311
16.076.912
12.996.068
29.283.747
72.999.660
8.572.772
6.635.136
Percentage of
total
53.3%
46.7%
13.9%
0.4%
12.5%
19.9%
21.9%
62.8%
15.2%
12.3%
27.7%
69.1%
11.7%
6.3%
Average risk
(in one
million) e
0.02
0.01
0.02
0.02
0.008
0.009
0.04
0.02
0.02
0.01
0.02
0.02
0.02
0.03
0.03
2019
Proximity results
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Distribution of (,'ancer Risk for Racial mid Ktlinic Groups,
Age Groups, Adults without a High School Diploma, People Living in Low Income Households,
and People Living in Linguistic Isolation
- 50 km
Study Area Radius
Vcu r
Descriptor
Total
Population
White
People of
C ,'olor'
African
American
Native
American
Other and
Multi-
Ilispanic
or Latino ''
Age
(years)
Age (yea rs)
18-64
Age
(years)
People
Living
lielow the
People
Living
lielow
Twice the
Poverty
Level
Total
Number
>25 Years
Old
Number >25
Years Old
without a
People
1 jiving in
Linguistic
Isolation
racial
0-17
>65
Poverty
High School
Level
Diploma
Total
106,339,741
57,371,278
48,968,463
14,957,553
434,080
12,533,118
21,043,712
23,343,102
66,858,003
16,138,635
13,106,134
29,533,562
73,513,418
8,629,228
6,623,056
population
within 50 km
of any facility
Percentage of
54.0%
46.0%
14.1%
0.4%
11.8%
19.8%
22.0%
62.9%
15.2%
12.3%
27.8%
69.1%
11.7%
6.2%
total
Average risk
0.02
0.02
0.03
0.03
0.009
0.01
0.04
0.02
0.02
0.02
0.03
0.03
0.02
0.03
0.03
(in one
million) e
Proximity results
Tolal
103.238.135
55.055.508
48.182.627
14.879.280
410.928
12.196.430
20.695.990
22.674.417
64.895.383
15.668.335
12.810.913
28.813.070
71.328.812
8.466.056
6.531.694
population
within 50 km
2020
of any facility
Percentage of
total
53.3%
46.7%
14.4%
0.4%
11.8%
20.0%
22.0%
62.9%
15.2%
12.4%
27.9%
69.1%
11.9%
6.3%
Average risk
0.02
0.01
0.02
0.02
0.008
0.01
0.04
0.02
0.02
0.01
0.02
0.02
0.02
0.03
0.03
(in one
million) e
Proximily results
Tolal
104.974.141
56.348.397
48.625.744
14.835.396
377.634
12.463.647
20.949.067
23.018.202
66.027.341
15.928.598
12.929.561
29.133.736
72.585.658
8.535.192
6.599.365
population
within 50 km
2021
of any facility
Percentage of
total
53.7%
46.3%
14.1%
0.4%
11.9%
20.0%
21.9%
62.9%
15.2%
12.3%
27.8%
69.1%
11.8%
6.3%
Average risk
0.02
0.01
0.03
0.02
0.01
0.01
0.04
0.02
0.02
0.02
0.03
0.03
0.02
0.03
0.03
(in one
million) e
" Total nationwide population includes all 50 states plus Puerto Rico.
Distributions by race, ethnicity, age, education, income, and linguistic isolation are based on demographic information at the census block group level. Risks from UpdatedUIR AddedREs 2016R emissions are modeled at
the census block level.
' Modeled risks are for a 70-year lifetime, based on the predicted outdoor concentration and not adjusted for exposure factors.
c The People of Color population includes people identifying as African American, Native American, Other and Multiracial, or Hispanic/Latino. Measures are taken to avoid double counting of people identifying as both
Hispanic/Latino and a racial minority.
d In order to avoid double counting, the "Hispanic or Latino" category is treated as a distinct demographic category for these analyses. A person is identified as one of five racial/ethnic categories above: White, African
American, Native American, Other and Multiracial, or Hispanic/Latino.
e The population-weighted average risk takes into account risk levels at all populated block receptors in the modeled domain for the entire source category.
1542
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1543
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1546
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1548
1549
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PUBLIC RELEASE DRAFT
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5,3.5 Risk Characterization for Potentially Exposed or Susceptible Subpopulations
For the 1,3-butadiene risk evaluation, EPA considered information that could support increased
exposure or biological susceptibility compared to the general population (see Appendix D for full list of
factors). EPA was able to incorporate considerations for multiple PESS factors into risk estimates, as
presented in Table 5-8. EPA considered these PESS factors through the use of exposure factors,
uncertainty factors, PESS group-specific data. In some cases, information on PESS factors may have
supported the weight of scientific evidence for a particular hazard or exposure value. For the non-cancer
health endpoint, EPA performed dose-response analysis for multiple repeat-dose non-cancer endpoints
under each hazard domain. Decreased fetal weight associated with other developmental toxicity
outcomes was selected as the most sensitive and robust human-relevant endpoint for use in risk
characterization of intermediate and chronic exposures. For the cancer health endpoint, EPA used an
occupational epidemiological cohort, comprised of both male and female workers, with more than 50
years of follow-up and subsequent exposure estimate updates to derive inhalation hazard values for
leukemia applicable to general population and occupational exposures. Due to an identified mutagenic
mode of action for cancer, EPA applied an age-dependent adjustment factor (ADAF) for the general
population to account for elevated childhood susceptibility. The combination of using the most sensitive
endpoint protective of the pregnant worker, robust evidence from a large, highly exposed occupational
human cohort tracked over many decades along with the application of an ADAF, allows the derived
hazard values used for non-cancer and cancer risk characterizations to fully account for potentially
exposed or susceptible subpopulations. Full details on all available information relating to biological
susceptibility are presented in Section 7.2 of the Draft Human Health Hazard Assessment for 1,3-
Butadiene ( It)—including PESS factors with only indirect evidence or otherwise
insufficient information to incorporate into hazard or risk values.
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Table 5-8. Summary of PESS Factors Incorporai
ted into Risk Estimates
PESS Factor
Potential Increased Exposures
Incorporated into Exposure
Assessment
Sources of Uncertainty for
Exposure Assessment
Potential Sources of
Biological Susceptibility
Incorporated into Hazard
Assessment
Sources of Uncertainty for
Hazard Assessment
Lifestage
• Lifestage-specific exposures were
not incorporated into the risk
evaluation.
• Exposures were quantified as air
concentrations and not internal
dose. However, UFH is expected to
account for any toxicokinetic
differences (US. EPA. 2012a).
• Direct evidence of a
developmental effect was the
basis for the
intermediate/chronic POD used
for risk estimation.
• Increased susceptibility of
children to cancer was
addressed by incorporation of an
ADAF into the general
population IUR.
• EPA expects that this PESS
factor is sufficiently
accounted for in risk
estimates.
Pre-existing
Disease
Not applicable
Not applicable
• Application of a 10 x UFH to
account for human variability.
• Especially susceptible
individuals may not be
accounted for by standard
approaches.
Occupational and
Consumer
Exposures
• Occupational exposure sampling
data was broken down into subsets
of worker roles that identify higher
exposure activities.
• Worker exposures and hazard
values incorporated adjustments for
relative breathing rate per day of
exposed workers compared to the
general population.
• The majority of occupational
exposure sampling data points used
in generating estimates of
occupational exposure were not
quantifiable values but were
identified as being below the limit
of detection (LOD).
• Exposure factors change over time
and differing assumptions may
result in risk estimates varying by
up to 30%.
Not applicable
Not applicable
Geography/Site-
specific
• Populations who reside nearby
facility releases of 1,3-butadiene
were taken into consideration with
modeled exposure concentrations
by distance
• The estimates of risks via ambient
air are dependent on inputs and
assumptions described in Section 2
of the Draft General Population
Exposures for 1,3-Butadiene (U.S.
EPA, 2024r) and calculations based
on census data and equations from
the Human Exposure Model
(HEM) as detailed in the HEM
User's Guides
Not applicable
Not applicable
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PESS Factor
Potential Increased Exposures
Incorporated into Exposure
Assessment
Sources of Uncertainty for
Exposure Assessment
Potential Sources of
Biological Susceptibility
Incorporated into Hazard
Assessment
Sources of Uncertainty for
Hazard Assessment
Sociodemographic
Status
• Cancer risks were estimated for
racial and ethnic groups, age
groups, poverty and linguistically
isolated areas
• The estimates of risks via ambient
air are dependent on inputs and
assumptions described in Section 2
of the Draft General Population
Exposures for 1,3-Butadiene (U.S.
EPA, 2024r) and calculations based
on census data and equations from
the Human Exposure Model
(HEM) as detailed in the HEM
User's Guides
• EPA utilized the most sensitive
sex from rodent assays for non-
cancer dose-response modeling
and incorporated data from both
sexes in cancer modeling.
• EPA was unable to quantify
sociodemographic
differences other than sex.
Genetics/
Epigenetics
Not applicable
Not applicable
• Application of a linear low-dose
cancer dose-response model
should account for varying
susceptibility across
populations.
• Application of a 1 Ox UFH to
account for human variability.
• Hazard values are based on
wild-type rodents and a
broad occupational
population and may
underestimate risks for
populations with sensitizing
mutations.
Aggregate
Exposures
• Cancer risks were estimated based
on aggregate modeled exposure
concentrations at census blocks
• The estimates of exposure via
ambient air are dependent on inputs
and assumptions described in
Section 2 of the Draft General
Population Exposures for 1,3-
Butadiene (U.S. EPA. 2024ri
Not applicable
Not applicable
1567
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1568
1569
1570
1571
1572
1573
1574
1575
1576
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5.3.6 Risk Characterization for Aggregate Exposures
Section 2605(b)(4)(F)(ii) of TSCA requires EPA, as a part of the Risk Evaluation, to describe whether
aggregate or sentinel exposures under the conditions of use were considered and the basis for their
consideration. Further, in the final RE framework rule, EPA codified at 720.39(d)(8), a requirement that
"EPA will consider aggregate exposures to the chemical substance, and, when supported by reasonably
available information, consistent with the best available science and based on the weight of scientific
evidence, include an aggregate exposure assessment in the risk evaluation, or will otherwise explain in
the risk evaluation the basis for not including such an assessment."
EPA quantified risk estimates for TRI-reporting facilities. The highest risk estimates based on modeled
air concentrations were focused along the Texas and Louisiana Gulf Coast (Figure 5-2). AMTIC
monitoring stations report air concentrations of ambient 1,3-butadiene from all sources, including fuel
combustion. Monitoring data provide an indication of the aggregate risk from all sources contributing to
ambient air concentrations of 1,3-butadiene, which may be present in the real world and provide context
for risks from individual TSCA COUs. The modeled and monitored air concentrations (AMTIC) are
with an order of magnitude along the Texas and Louisiana Gulf Coast, indicating that the modeled
numbers used for risk evaluation capture aggregate 1,3-butadiene exposure in the region of the United
States showing highest risk estimates. Additionally, EPA incorporated aggregation of environmental
exposures from multiple facilities to the general population within a given census track; modeled
numbers reflect aggregation of facilities within 50 km of each other.
5.3.7 Overall Confidence and Remaining Uncertainties in Human Health Risk
Characterization
There is robust confidence in the human health hazard values for both non-cancer and cancer endpoints
(see Section 6 of the Draft Human Health Hazard Assessment for 1,3-Butadiene ( 24t)).
The non-cancer HEC is supported by multiple effects observed at similar doses across studies at relevant
exposure durations and despite large differences in metabolism across species, maternal-developmental
effects were observed in both mice and rats (Sections 4.2.1.2 and 4.2.2.2.3 of ( !24t)). The
general population cancer IUR/chronic occupational UR is based on a large occupational human cohort
tracked over many decades with robust evidence for the leukemia endpoint (Sections 5.3.1.1 and 5.3.2 of
(I ft)). As mentioned in Section 5.2.1 however, cancer risk estimates may underestimate
total cancer risk due to not incorporating bladder cancer risk, of which EPA is uncertain.
5.3.7.1 Occupational Risk Characterization
For the 1,3-butadiene risk evaluation, EPA has robust confidence in the inhalation exposure data.
Several OES studies of 1,3-butadiene exposure were directly applicable and used to estimate inhalation
exposures. Additionally, inhalation exposure data collected during OSHA enforcement activities
provided additional sampling data across several industries and conditions of use. The primary strength
of this data is the use of personal and applicable data that received a high rating during systematic
review and data used in enforcement proceedings.
The primary limitations to these data include the uncertainty of the representativeness of the exposures
in specific industries, uncertainty in the representativeness of the data towards the true distribution of
inhalation concentrations in this scenario, that the data come primarily from one industry source, and
that much of the data for both workers and ONUs from the source were reported as below the LOD.
When reported monitoring data was a non-detect, EPA applied the submitter's methodology of using the
LOD as the high-end estimate and V2 the LOD as the central tendency. These standard conservative
assumptions were applied consistent with EPA's Guidelines for Statistical Analysis of Occupational
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Exposure Data). EPA also assumed 250 exposure days per year for routine 8-hour shifts based on 1,3-
butadiene exposure each working day for a typical worker schedule consistent with the OSHA PEL and
other occupational exposure limits; it is uncertain whether this captures actual worker schedules and
exposures. While for many COUs the majority of monitored values were non-detects, high-end
(95%tile) values were typically based on measured, recorded values above the LOD. Central tendency
estimates incorporated both measured values and statistical adjustments for non-detects. Exposure
values are based on single-day measurements that are extrapolated to represent average daily
concentrations over the specified duration. Therefore, high-end exposures and risk estimates are most
appropriate for consideration of shorter-duration exposures (i.e., intermediate) while central tendency
values are more representative for chronic and lifetime exposures.
Based on these strengths and limitations, EPA has concluded that the weight of scientific evidence for
the occupational exposure assessment overall is moderate and provides a plausible estimate of exposures
in consideration of the strengths and limitations of reasonably available data. There is reduced
confidence in conclusions of potential risks when risks relative to benchmark are indicated only at
higher-end exposures. As stated above, this is especially true for cancer, which is based on average
exposure across a lifetime, in contrast with intermediate exposures for which higher-end measurements
are more applicable. Additionally, for these scenarios there is robust confidence when high-end
exposures did not indicate risk relative to benchmarks. For example, EPA had the lowest confidence for
exposure estimates from application of paints, coatings, adhesives, and sealants because all associated
datapoints were below the LOD. However, potential risk was not identified for this OES even at high-
end exposure set equivalent to the LOD, and therefore EPA has robust confidence that risk is not
associated with this COU/OES.
There is moderate to robust confidence in the risk estimates relative to benchmarks for the two
OES/SEGs with the highest exposure: non-routine laboratory technician and repackaging. Risk estimates
for these scenarios were 1 to 2 orders of magnitude away from benchmarks, suggesting that any
refinements to the monitoring sensitivity or other consideration would be highly unlikely to change the
conclusions. Details for confidence in the exposure assessment for other OES are summarized in Section
5.1.1.2. For more detail, see the Draft Environmental Releases and Occupational Exposure Assessment
for 1,3-Butadiene (U.S. EPA. 2024y).
5.3.7.2 General Population Risk Characterization
Based on the weight of scientific evidence for general population exposures detailed in Section 5.1.3.2
and for human health hazard in Section 5.2.1: the high-rated quality of environmental release data
combined with peer-reviewed models to assess general population exposure and the robust human,
animal, and mechanistic evidence associating leukemia and other lymphohematopoietic cancers with
1,3-butadiene exposure, EPA has robust confidence in the general population risk characterization. The
use of HEM risk results based on census block information, incorporating population count and
sociodemographic data as well as providing geospatial visualizations, allows for a representative
estimation of exposure concentrations and risk for the general population. However, EPA acknowledges
that the assumptions made for the general population being exposed to modeled ambient air
concentrations 24 hours a day, 365 days a year, over a lifetime contributes uncertainty to the estimates.
There is also uncertainty as to whether risk is underestimated or overestimated due to photodegradation
of 1,3-butadiene (See Section 3.1) not being accounted for in this risk evaluation.
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6 ENVIRONMENTAL RISK ASSESSMENT
1.3-ISiil:i(lienc — Knvironinonliil Risk Assessment (Section 6):
Kev Points
l-l\\ c\alualcd the reasonably ii\ ailablc information for cn\ironmenlal exposures lo 1..^-hLilatlicne
key points of i lie en\ ironmenlal e\pusii res aiicl ha/arcls assessmeiil a re summarized below
Allhouuh I ..'-butadiene may be released lo wilier, kind, nnd air. 1.3-bulacliene concentrations
were nol modeled for the surface water and kind palhwa\ s because I ..'-butadiene is priniariI\
released as a uas lo air ll is nol expected to persist in soil and water based on physical and
chemical properties and cn\ironmenlal late and transport characteristics
l-l\\ t|ualitali\ely assessed en\ironmenlal exposures of I..'-butadiene in water and soil
I ..'-liuladicnc is not expected to be present in surface water ui\en minimal releases to
surface water, rapid biodcuradalion. and \ olatilization. Additionally. I ..'-butadiene has
low sorption potential and is not expected to be present in sediment
I..'-liuladicnc is not released to soil and air to soil deposition is not expected due lo the
physical and chemical properties (hiuh \olalilily and reacli\ il\ and low sorption lo
organic material)
I .3-liuladicnc releases in air are expected to be the predominant pathway of cn\ ironmenlal
exposure
l'xtensi\e ambient air monilorinu dala are mailable lor I ..'-butadiene and confirms that
air is the primary exposure pathway
Allhouuh these dala demonstrate I ..'-butadiene concentrations in ambient air. the source
is unknown Concentrations of I ..'-butadiene in ambient air are likely from a
combination of TSCA and oilier sources forest Hres. mobile exhaust, etc )
l-l\\ summarizes a\ ailablc I ..'-butadiene ambient air monilorinu data in this draft
assessment
There is no risk to aquatic oruanisms as I ..'-butadiene is not appreciably released to. and does
not persist in. surface water and exposure is nol expected
There is no risk lo terrestrial oruanisms through soil exposure as I ..'-butadiene does not
partition, deposit, or persist in or on land and exposure is not expected
Allhouuh exposure of I ..'-butadiene to terrestrial oruanisms is expected \ia ambient air.
exposures will be transient due lo the rcacli\c nature of I ..'-butadiene further. I ..'-butadiene
exposure in ambient air cannot be attributed to a specific TSC A use Thus. cn\ ironmenlal risk to
terrestrial oruanisms \ia ambient air was not <.|iianlilali\ely assessed
6.1 Summary of Environmental Exposures
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1,3-Butadiene is not expected to be present in surface water due to its physical and chemical properties
(gas form under ambient conditions, high volatility and reactivity, low sorption potential {Draft Physical
Chemistry and Fate Assessment ( I4z)). 1,3-Butadiene releases to surface water are
minimal {Draft Environmental Release and Occupational Exposure Assessment for 1,3-Butadiene (U.S.
>24vV). Additionally, monitoring results from WQP indicate all surface water samples (n = 231)
were below detection limits for 1,3-butadiene (0.04 |_ig/L) {Draft Environmental Media Concentrations
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for 1,3-Butadiene ( 2024p)). Thus, multiple lines of evidence demonstrate 1,3-butadiene will
not be present in surface water and aquatic organisms will not be exposed to 1,3-butadiene.
6.1.2 Summary of Exposures to Terrestrial Species
Releases of 1,3-butadiene to land make up less than one percent of 1,3-butadiene releases to the
environment, and most land releases are to class I underground injection wells {Draft Environmental
Release and Occupational Exposure Assessment for 1,3-Butadiene (U.S. EPA. 2024y)). Class I wells are
typically drilled thousands of feet below any drinking water aquifers and are constructed to contain
injected waste streams and prevent movement into water systems or soil. Terrestrial organisms will not
be exposed to 1,3-butadiene via the land pathway (soil, biosolids) based on the low volume of releases
to land, the low risk of failure of class I injection wells, the physical and chemical properties of 1,3-
butadiene (i.e., low sorption potential) as well as monitoring data indicating less than one percent
detection frequency (see Draft Physical Chemistry and Fate Assessment for 1,3-Butadiene and Draft
Environmental Media Concentrations for 1,3-Butadiene (U.S. EPA. 2024p. z)).
Extensive ambient air data, both measured data and monitoring data, are available for 1,3-butadiene and
confirm that air is the primary exposure pathway. Terrestrial organisms are likely exposed to 1,3-
butadiene in air; however, the sources of 1,3-butadiene in ambient air are a combination of TSCA and
other sources (e.g., forest fires, mobile exhaust, etc.). EPA summarizes available 1,3-butadiene ambient
air measured concentrations and monitoring data in Draft Environmental Media Concentrations for 1,3-
Butadiene ( 2024|»).
6.1.3 Weight of Scientific Evidence Conclusions for Environmental Exposures
EPA uses several considerations when weighing the scientific evidence to determine confidence in the
draft environmental risk assessment. These considerations include the quality of the database,
consistency, strength, and precision, biological gradient/dose response, and relevance. This approach is
consistent with the Draft Systematic Review Protocol Supporting TSCA Risk Evaluations for Chemical
Substances (U.S. EPA. 2021a). EPA has robust confidence in this environmental exposure assessment.
The 1,3-butadiene data from the WQP has a strong bias of samples collected from California, New
York, Texas, Georgia, North Carolina, and Florida (which represents >39% of the U.S. population)
relative to other areas and was missing data from Alaska, Delaware, Rhode Island, Hawaii, and Vermont
(<2% of the U.S. population). The states with a higher number of data points are states where a higher
percentage of the U.S. population resides. In addition, states with a concentration of facilities releasing
1,3-butadiene, such as Texas and Louisiana, are included in the monitoring database. Due to the
presence of 1,3-butadiene releasing facilities, these states would be expected to have the largest 1,3-
butadiene releases. Because data reflects that 1,3-butadiene is typically not detected above the detection
limit in water, EPA has robust confidence that in areas with lower releases, 1,3-butadiene will not be in
the water. In addition, based on the physical and chemical properties of 1,3-butadiene and low release
quantities to water and land, EPA has confidence that the WQP data is representative of the entire
United States. Notably, the WQP data is not specific to only TSCA COUs. Therefore, EPA has robust
confidence in this environmental exposure assessment.
6.2 Environmental Risk Characterization
6.2,1 Risk Assessment Approach
EPA determined that, based on the fate properties of 1,3-butadiene (see Section 3 and Draft Physical
Chemistry and Fate Assessment for 1,3-Butadiene ( 2024z)), an in-depth analysis of releases
to water or land and associated exposures from those releases were not needed for the water or land
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pathways since 1,3-butadiene does not persist in either medium. EPA used information from all
reasonably available sources to characterize exposure, hazard, and risk posed from 1,3-butadiene to
aquatic and terrestrial organisms.
6.2.2 Risk Estimates for Aquatic Species
1,3-Butadiene rapidly biodegrades in aerobic aquatic environments and rapidly volatilizes from water to
air, and is therefore not expected to persist in water (see Section 3 and Draft Physical Chemistry and
Fate Assessment for 1,3-Butadiene ( 024zV). Given (1) the physical and chemical properties
governing the environmental fate of 1,3-butadiene in water, (2) limited release of 1,3-butadiene directly
to surface water, and (3) available monitoring data demonstrating 1,3-butadiene was not detected in
water, EPA does not expect that 1,3-butadiene will persist in surface water or groundwater. Therefore,
EPA concludes there is no expected risk to aquatic organisms for all COUs due to no 1,3-butadiene
exposure in water or sediment.
1,3-Butadiene is not expected to sorb to suspended solids based on its physical and chemical properties.
As such, terrestrial exposures via soil and sediment are not expected and, therefore, are not quantified.
Environmental fate and transport data indicate 1,3-butadiene does not bioaccumulate (see Section 3 and
Draft Physical Chemistry and Fate Assessment for 1,3-Butadiene ( 24zV). Thus, there is no
dietary exposure of 1,3-butadiene from aquatic organisms to terrestrial organisms and no risk is
expected for all COUs.
6.2.3 Risk Estimates for Terrestrial Species
1,3-Butadiene does not sorb or bind to soil or sediment and does not persist on land (due to volatility and
reactivity) (see Section 3 and Draft Physical Chemistry and Fate Assessment for 1,3-Butadiene (U.S.
E 24zV). The predominant environmental release of 1,3-butadiene to land is disposal via
underground injection into wells. Therefore, there are no appreciable direct releases to land (see Section
3 and Draft Physical Chemistry and Fate Assessment for 1,3-Butadiene ( 2024z)).
Considering these lines of evidence, 1,3-butadiene is not expected to persist in or on land. Therefore,
EPA concludes there is no expected risk from any COU to terrestrial organisms via the land pathway
due to no 1,3-butadiene exposure in soils. There is no expected risk from any COU via dietary exposure
to terrestrial organisms is expected as 1,3-butadiene does not bioaccumulate (see Section 3 and Draft
Physical Chemistry and Fate Assessment for 1,3-Butadiene ( )24zV).
Environmental fate and release data indicate that there is no expected risk to terrestrial organisms via
soil exposure is expected. Specifically, 1,3-butadiene rapidly volatilizes, has low sorption potential, and
has an estimated half-life of 7 to 28 days in soil. Further, environmental release of 1,3-butadiene to land
accounts for less than one percent of total environmental releases.
Terrestrial organisms may be exposed to 1,3-butadiene via ambient air and extensive ambient air
monitoring data are available. These data show that 1,3-butadiene is prevalent in ambient air and
confirms that air is a major 1,3-butadiene exposure pathway. Although these data represent actual 1,3-
butadiene concentrations in ambient air, the source is unknown and likely a combination of TSCA and
other sources (e.g., forest fires, mobile exhaust).
A potential terrestrial 1,3-butadiene exposure scenario may involve a fugitive or stack 1,3-butadiene
release to ambient air from a TSCA COU that is inhaled by terrestrial organisms located in proximity to
the release facility. Many terrestrial organisms are transient in the environment. As such, the
aforementioned exposure scenario is most applicable to local and non-transient organisms such as
plants. However, there are no available plant hazard data for 1,3-butadiene, and there is uncertainty in
attributing exposure to a TSCA source. Therefore, risk to terrestrial plants cannot be determined.
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6.2,4 Overall Confidence and Remaining Uncertainties in Environmental Risk
Characterization
EPA used several considerations when weighing the scientific evidence to determine confidence in the
draft environmental risk assessment. These considerations include the quality of the database,
consistency, strength and precision, biological gradient/dose response, and relevance. This approach is
consistent with the Draft Systematic Review Protocol Supporting TSCA Risk Evaluations for Chemical
Substances (U.S. EPA. 2021a). EPA has robust confidence in this environmental risk assessment.
The Agency has robust confidence in the conclusion that there is no expected risk to aquatic organisms
resulting from TSCA COUs. Multiple lines of evidence support this conclusion. Environmental fate and
transport data indicate 1,3-butadiene is expected to have negligible persistence in water {Draft Physical
Chemistry and Fate Assessment for 1,3-Butadiene ( 2024z)). There are also limited releases of
1,3-butadiene directly to surface water due to TSCA COUs and available monitoring data demonstrate
that 1,3-butadiene has not been detected in water.
EPA has robust confidence in the conclusion that there is no expected risk to terrestrial organisms due to
TSCA COUs via the land pathway. Multiple lines of evidence support this conclusion. Environmental
fate and transport data indicate 1,3-butadiene does not sorb or bind to soil or sediment and has negligible
persistence on land (due to volatility and reactivity) (see Section 3 and Draft Physical Chemistry and
Fate Assessment for 1,3-Butadiene ( 024zV). Furthermore, 1,3-butadiene is reactive and
volatile. There are also limited releases of 1,3-butadiene to land (see Section 3 and Draft Physical
Chemistry and Fate Assessment for 1,3-Butadiene ( 2024z)). These chemical and fate
properties support a robust confidence conclusion.
EPA also has robust confidence that there is no expected risk to terrestrial organisms due to TSCA
COUs via the dietary pathway. Environmental fate and transport data indicate 1,3-butadiene does not
bioaccumulate (see Section 3 and Draft Physical Chemistry and Fate Assessment for 1,3-Butadiene
( |z)). As 1,3-butadiene is also not expected to persist in the water and land pathways, the
potential for dietary exposure is limited. These qualities support a robust confidence conclusion.
Risk to terrestrial organisms (e.g., plants, mammals, birds) due to TSCA COUs via the air pathway
cannot be determined. Concentrations of 1,3-butadiene in ambient air are due to TSCA and other
sources. Additional factors which can impact EPA's ability to attribute exposure for a specific terrestrial
organism to a specific TSCA COU are the transient nature of most terrestrial organisms, and the absence
of specific activity pattern data of such organisms in or around a particular industrial process which
could be attributed to a TSCA COU. Further, there are no relevant hazard data available to assess
potential risk to terrestrial organisms.
Additional details on overall confidence and remaining uncertainties are described in the following
technical support documents: Draft Physical Chemistry and Fate Assessment for 1,3-Butadiene (US
E 24z), Draft Environmental Media Concentrations for 1,3-Butadiene ( 24p\ and
Draft Environmental Release and Occupational Exposure Assessment for 1,3-Butadiene (
2024vY
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7 UNREASONABLE RISK DETERMINATION
TSCA section 6(b)(4) requires EPA to conduct a risk evaluation to determine whether a chemical
substance presents an unreasonable risk of injury to health or the environment, without consideration of
costs or other non-risk factors, including an unreasonable risk to a PESS identified by EPA as relevant to
the risk evaluation, under the TSCA COUs.
EPA is preliminarily determining that 1,3-butadiene presents an unreasonable risk of injury to human
health under the COUs. Based on the pathways evaluated in the draft risk evaluation for 1,3-butadiene,
the Agency is preliminarily determining that risk of injury to the environment does not significantly
contribute to EPA's preliminary determination of unreasonable risk. This draft unreasonable risk
determination is based on the information in previous sections of this draft risk evaluation, the TSDs that
support this draft risk evaluation, and their appendices in accordance with TSCA section 6(b). It is also
based on (1) the best available science (TSCA section 26(h)); (2) weight of scientific evidence standards
(TSCA section 26(i)); and (3) relevant implementing regulations in 40 CFR part 702, including the
amendments to the procedures for chemical risk evaluations under TSCA finalized in May of 2024 (89
FR 37028; Mav 3. 2024Y
As noted in the EXECUTIVE SUMMARY, 1,3-butadiene is primarily used as a chemical intermediate
and as a monomer in the manufacture of polymers such as synthetic rubbers and elastomers. This
involves polymerization of 1,3-butadiene with itself or with other monomers, then this polymerization
product is incorporated into various rubber and plastic articles. Workers may be exposed to 1,3-
butadiene when making these products or otherwise using it in the workplace. When it is manufactured
or used to make products, 1,3-butadiene is mainly released into the air due to its volatility, with
relatively small releases to land or water. If released into water or land, 1,3-butadiene will quickly
volatilize from water and land surfaces. 1,3-Butadiene in air will photodegrade within a few hours by
reacting with hydroxyl or nitrate radicals in the atmosphere. Therefore, EPA quantitatively evaluated
hazards only via the inhalation route. Consistent with these properties, existing assessments (OEHHA.
2013; ATSDR. 2012; Grant et al.. JO 10; I c< « i1 \ 2002a) also concluded that inhalation is the
predominant route for human exposures and 1,3-butadiene exposure has not been quantified by any
other routes. Additional sources of 1,3-butadiene exposure come from vehicle exhaust, tobacco smoke,
burning wood, and forest fires.
Following EPA's Guidelines for Carcinogen Risk Assessment ( )5a), EPA determined that
1,3-butadiene is Carcinogenic to Humans with robust evidence across all evidence streams for
lymphohematopoietic cancers, and the weight of scientific evidence supports a mutagenic mode of
action for lymphohematopoietic cancers (Section 5.3 of Draft Human Health Assessment). Further, the
non-cancer chronic POD is based on decreased fetal weight and was selected as the most robust, human
relevant and protective endpoint for use in risk characterization of intermediate and chronic exposures,
with a human equivalent concentration (HEC) of 2.5 ppm (5.5 mg/m3) derived from benchmark dose
modeling following dichotomization of mouse fetal weight data. All other representative PODs were
within a few fold of this value.
Whether EPA makes a determination of unreasonable risk for a particular chemical substance under
amended TSCA depends upon risk-related factors beyond exceedance of benchmarks. These include the
endpoint under consideration, the reversibility of the effect, exposure-related considerations (e.g.,
duration, magnitude, or frequency of exposure, or population exposed), and the confidence in the
information used to inform the hazard and exposure values.
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To determine whether an occupational COU significantly contributes to unreasonable risk, EPA
compares the risk estimates of the occupational exposure scenario (OES) used to evaluate the COUs and
considered whether the risk from the COU was best represented by the central tendency or high-end risk
estimates.
EPA is preliminarily determining that the following COUs, considered singularly or in combination with
other exposures, significantly contribute to the unreasonable risk:
• Manufacturing - domestic manufacturing;
• Manufacturing - import;
• Processing - processing as a reactant - intermediate (adhesive manufacturing; all other basic
organic chemical manufacturing; fuel binder for solid rocket fuels; organic fiber manufacturing;
petrochemical manufacturing; petroleum refineries; plastic material and resin manufacturing;
propellant manufacturing; synthetic rubber manufacturing; paint and coating manufacturing;
wholesale and retail trade);
• Processing - processing as a reactant - monomer used in polymerization process (synthetic
rubber manufacturing; plastic material and resin manufacturing);
• Processing - incorporation into formulation, mixture, or reaction product - processing aids, not
otherwise listed (petrochemical manufacturing; monomers used in: plastic product
manufacturing; synthetic rubber manufacturing);
• Processing - incorporation into formulation, mixture, or reaction product - other (adhesive
manufacturing, paint and coating manufacturing, petroleum lubricating oil and grease
manufacturing, and all other chemical product and preparation manufacturing);
• Processing - incorporation into article - other (polymer in: rubber and plastic product
manufacturing);
• Processing - repackaging - intermediate (wholesale and retail trade; monomer in: synthetic
rubber manufacturing);
• Processing - recycling;
• Commercial use - other use - laboratory chemicals; and
• Disposal
EPA is preliminarily determining that the following COUs do not contribute significantly to the
unreasonable risk:
• Industrial use - adhesives and sealants, including epoxy resins;
• Commercial use - fuels and related products;
• Commercial use - other articles with routine direct contact during normal use including rubber
articles; plastic articles (hard);
• Commercial use - toys intended for children's use (and child dedicated articles), including
fabrics, textiles, and apparel; or plastic articles (hard);
• Commercial use - synthetic rubber (e.g., rubber tires);
• Commercial use - furniture & furnishings including stone, plaster, cement, glass and ceramic
articles; metal articles; or rubber articles;
• Commercial use - packaging (excluding food packaging), including rubber articles; plastic
articles (hard); plastic articles (soft);
• Commercial use - automotive care products;
• Commercial use - lubricant additives, including viscosity modifier;
• Commercial use - paints and coatings, including aerosol spray paint;
• Commercial use - adhesives and sealants, including epoxy resins;
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• Consumer use - other articles with routine direct contact during normal use including rubber
articles; plastic articles (hard);
• Consumer use - toys intended for children's use (and child dedicated articles), including fabrics,
textiles, and apparel; or plastic articles (hard);
• Consumer use - synthetic rubber (e.g., rubber tires);
• Consumer use - furniture & furnishings including stone, plaster, cement, glass and ceramic
articles; metal articles; or rubber articles;
• Consumer use - packaging (excluding food packaging), including rubber articles; plastic articles
(hard); plastic articles (soft); and
• Distribution in commerce.
7.1 Unreasonable Risk to Human Health
Calculated risk estimates (MOEs6 or cancer risk estimates) can, when considered together, provide a risk
profile of 1,3-butadiene by presenting a range of estimates for different health effects for different
COUs. When characterizing the risk to human health from occupational exposures during risk
evaluation under TSCA, EPA conducts assessments of risk and makes its determination of unreasonable
risk from a scenario that does not assume use of respiratory protection or other personal protective
equipment (PPE)7. A calculated MOE that is less than the benchmark MOE, in consideration of other
risk-related factors, generally supports a determination of unreasonable risk of injury to health, based on
non-cancer effects. Similarly, a calculated cancer risk estimate that is greater than the cancer benchmark
generally supports a determination of unreasonable risk of injury to health from cancer. It is important to
emphasize that these calculated risk estimates alone are not bright-line indicators of unreasonable risk.
7.1.1 Populations and Exposures EPA Assessed to Determine Unreasonable Risk to
Human Health
EPA evaluated risk to workers, including occupational non-users (ONUs), consumers, bystanders, and
the general population, using reasonably available monitoring and modeling data for inhalation
exposures, as applicable. The Agency evaluated risk from inhalation exposure of 1,3-butadiene to
workers, including ONUs, for relevant COUs. EPA has quantitatively assessed the commercial use of
laboratory chemicals, paints and coatings, and adhesives and sealants. All other commercial/consumer
uses were qualitatively assessed. As mentioned in Section 0, based on product searches and systematic
review data, EPA has determined that 1,3-butadiene, a monomer used in polymer-derived products such
as synthetic rubbers, is stable in these products and not expected to degrade and expose workers or
consumers to the 1,3-butadiene monomer. For the general population, EPA has evaluated risk from
chronic inhalation exposure from ambient air. No dermal or oral exposure is expected based on physico-
chemical properties of 1,3-butadiene.
Descriptions of the data used for human health exposure and human health hazards are provided in
Sections 0 and 5.2, respectively, in this draft risk evaluation. Uncertainties for overall exposures and
hazards are presented in this draft risk evaluation and TSDs—including the Draft General Population
Exposure Assessment for 1,3-Butadiene, the Draft Environmental Media and General Population
Screening for 1,3-Butadiene, and the Draft Environmental Release and Occupational Exposure
6 EPA derives non-cancer MOEs by dividing the non-cancer POD (HEC [mg/m3] or HED [mg/kg-day]) by the exposure
estimate (mg/m3 or mg/kg-day). Section 5.3.1 has additional information on the risk assessment approach for human health.
7 It should be noted that, in some cases, baseline conditions may reflect certain mitigation measures, such as engineering
controls, in instances where exposure estimates are based on monitoring data at facilities that have engineering controls in
place.
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Assessment for 1,3-Butadiene —and all are considered in this preliminary unreasonable risk
determination.
7.1.2 Summary of Human Health Effects
EPA is preliminarily determining that the unreasonable risk presented by 1,3-butadiene is due to
• non-cancer effects and cancer in workers from inhalation exposures; and
• cancer in the general population, including fenceline communities, from inhalation exposure.
With respect to health endpoints upon which EPA is basing this preliminary unreasonable risk
determination for non-cancer effects, the Agency has robust overall confidence in the proposed POD
based on decreased fetal weight for intermediate and chronic exposure scenarios. Similarly, for cancer,
EPA has robust overall confidence in the proposed POD based on leukemia for chronic exposures.
These confidence ratings were based on the weight of scientific evidence considering evidence
integration, selection of the critical endpoint and study, relevance to exposure scenarios, dose-response
considerations, and consideration of PESS. The confidence in the PODs is described in Section 5.2.
The health risk estimates for workers, including ONU's, consumers, and the general population are
presented in Section 5.3. Specifically for human populations, the Agency quantitatively evaluated risk to
(1) workers including ONUs via the inhalation route in Section 5.3.2; and (2) the general population via
inhalation route in Section 5.3.4. Additionally, EPA considered PESS as discussed in Section 5.3.5.
For more information regarding EPA's approach for developing risk estimates for 1,3-butadiene, see the
following supplement files: Draft Human Health Hazard Assessment for 1,3-Butadiene (U.S. EPA.
2024t), Draft Environmental Releases and Occupational Exposure Assessment for 1,3-Butadiene (U.S.
EP \ _ *24y). Draft Human Exposure Model (HEM) TRI 2016-2021 Exposure and Risk Analysis for
1,3-Butadiene ( 2024s). and Draft General Population Exposure Assessment for 1,3-
Butadiene ( E024r). The Draft Risk Calculator for Occupational Exposures for 1,3-Butadiene
( 2024aa) contains all calculations, exposure values, and exposure factors for workers and
ONUs.
7.1.3 Basis for Unreasonable Risk to Human Health
In developing the exposure and hazard assessments for 1,3-butadiene, EPA analyzed reasonably
available information to ascertain whether some human populations may have greater exposure and/or
susceptibility than the general population to the hazard posed by 1,3-butadiene. For the 1,3-butadiene
draft risk evaluation, EPA accounted for the following PESS: females of reproductive age, males of
reproductive age, pregnant females, infants, children and adolescents, people exposed to 1,3-butadiene
in the workplace, populations who reside near 1,3-butadiene-releasing facilities, and racial/ethnic
groups. Additionally, the Agency identified a list of specific PESS factors that contribute to a group
having increased exposure or biological susceptibility, such as lifestage in the basis for the
intermediate/chronic POD, occupational exposures, nutrition, and lifestyle activities. EPA was able to
incorporate considerations for multiple PESS factors into risk estimates, as presented in Section 5.3.5.
Full details on all available information relating to biological susceptibility are presented in Section 9.2
of the Draft Human Health Hazard Assessment for 1,3-Butadiene ( 24t), including PESS
factors with only indirect evidence or otherwise insufficient information to incorporate into hazard or
risk values. Full details on all available information relating to biological susceptibility are presented in
Section 7.2 of the Draft Human Health Hazard Assessment for 1,3-Butadiene ( 324s).
including PESS factors with only indirect evidence or otherwise insufficient information to incorporate
into hazard or risk values.
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For 1,3-butadiene, the use of either central-tendency or high-end risk estimates is, in part, due to the
amount of information available. For 1,3-butadiene, the occupational exposure estimates are based off a
statistical distribution of multiple single day measurements. EPA assumes that these results are generally
applicable to all working days; however, the uncertainty in this assumption increases as the single-day
results are extrapolated to longer durations. Therefore, EPA generally used high-end estimates for
workers in its preliminary risk determination for shorter term inhalation exposures {i.e., intermediate
non-cancer risk covering average exposures over one month) because the measured high-end exposures
are more realistically consistent over shorter time periods, while central tendency estimates are used for
longer term exposures {i.e., several decades for chronic non-cancer and cancer). Central tendency is used
for EPA's preliminary risk determination for chronic non-cancer and lifetime cancer estimates since
longer-term average exposure {e.g., 250 days per working years or 78 years for cancer estimates) would
bias toward central tendency {i.e., the more common risk estimates) vs. higher-end values {i.e., less
common risk estimates or 95th percentile or value at which 95% of all measurements fall below it). In
the case of all occupational COUs to which EPA is preliminary determining significantly contributes to
unreasonable risk, there is risk indicated for intermediate non-cancer using high-end estimates. This use
of high-end for the intermediate duration is protective of PESS, because the sensitive endpoint for 1,3-
butadiene is a developmental effect based on being exposed during a period of pregnancy and this
timeframe is more representative of the exposure period of concern for this population.
In addition, risk estimates have been provided for both an 8- and a 12-hour TWA for certain
manufacturing and processing conditions of use. These both represent real scenarios and shift lengths for
workers exposed to 1,3-butadiene; therefore, EPA considered both shift lengths in its preliminary risk
determination. For example, for two activities under the domestic manufacturing COU, Manufacturing -
instrument and electric manufacturing and Manufacturing - maintenance - turnaround, unreasonable
risks were found only for the 12-hour TWA and not the 8-hour TWA. The 12-hour TWA is associated
with higher risk for intermediate non-cancer due to the number of shifts in a 30-day period working 12
hours/day compared to the 8-hour TWA {i.e., the worker's hours may be condensed due to longer shift
lengths in a given month, resulting in higher exposure). EPA is preliminarily determining that both of
those activities significantly contribute to the unreasonable risk of 1,3-butadiene due to the unreasonable
risk identified for the 12-hour TWA.
Risk estimates were not quantified for commercial or consumer uses of plastics, rubber, lubricants, and
fuels since reasonably available evidence suggests that 1,3-butadiene monomer only exists at trace
concentrations in these products and articles and is stable and not expected to depolymerize and expose
the commercial/consumer user to the 1,3-butadiene monomer. For general population exposures,
including exposures to fenceline communities, EPA modeled air concentrations from facilities, focusing
on the distances of 100 m, 100 to 1,000 m, and 1,000 m from release points, and aggregated exposures
from multiple facilities from all releasing facilities within a 50,000-meter radius to the general
population within a given census block based on 2020 census data. EPA estimated cancer risks to the
general population of any lifestage {i.e., EPA derived an IUR which incorporates an ADAF to account
for increased susceptibility to cancer from early life exposure to 1,3-butadiene) via lifetime inhalation
exposure. For occupational risks, EPA estimated risks to workers and ONUs via inhalation only
following intermediate, chronic, or lifetime exposure. As stated in Section 5.3.1, occupational risks were
not estimated for acute exposures because effects observed in the toxicology animal database could not
be attributed to a single-dose and are unlikely to result from a single exposure at concentrations relevant
to humans. The non-cancer intermediate and chronic non-cancer POD is protective of susceptible
populations; specifically, maternal/developmental toxicity resulting in decreased fetal weight. In
addition, the POD, reduced fetal body weight, is protective of other non-cancer endpoints, particularly
germ cell mutation (target organ: spermatids and spermatozoa) and anemia which yielded similar POD
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values. The UF of 10 for human variability that EPA has applied to the non-cancer intermediate and
chronic MOE accounts for increased susceptibility of populations, such as children and elderly
populations.
For cancer, EPA derived risk estimates based on a human, occupational exposure which reflects sentinel
exposure and variability in the population. More information on how EPA characterized sentinel and
aggregate risks is provided in Section 5.3.6 and the Draft Human Health Hazard Assessment for 1,3-
Butadiene ( ft).
7,1,4 Workers
Based on the occupational risk estimates and related risk factors, EPA is preliminarily determining that
the non-cancer and cancer effects from worker intermediate inhalation exposure and chronic inhalation
exposure to 1,3-butadiene in occupational settings for all COUs with quantified risk estimates, except
for two commercial uses, to the unreasonable risk presented by 1,3-butadiene. These two are:
Commercial use -paints and coatings - paints and coatings, including aerosol spray paint and
Commercial use - adhesives and sealants - adhesives and sealants, including epoxy resins, significantly
contribute. The risk estimates for non-cancer and cancer effects for workers can be found in Section
5.3.2. However, the cancer risk estimates have been changed for occupational exposure as described in
1,3-Butadiene: Corrected lifetable analyses for leukemia and bladder cancer (U.S. EPA. 2024a).
Although Table 5-4 does not reflect this change, EPA's preliminary risk determination described below
accounts for this correction and the approximately 20 percent reduction in occupational unreasonable risk
as a result. As discussed in Section 5.1.1.1, due to the volatility and transport methods of 1,3-butadiene,
EPA did not evaluate routine dermal exposure to workers.
As stated in Section 5.3, occupational risk estimates utilized monitoring exposure measurements from
workplace inhalation monitoring data collected by government agencies such as OSHA and NIOSH,
monitoring data found in published literature {i.e., personal exposure monitoring data and area
monitoring data), and monitoring data submitted via public comments. Studies were evaluated using the
evaluation strategies laid out in the Draft Systematic Review Protocol Supporting TSCA Risk
Evaluations for Chemical Substances ( )21a). For manufacturing and processing of 1,3-
butadiene, EPA was also provided inhalation monitoring data by ACC. The ACC report includes 5,676
full-shift PBZ samples for workers and ON Us collected from 2010 to 2019 (ToxStrateeies. 2021). The
report includes a compilation and analyses of existing air concentrations of 1,3-butadiene from 47
consortium member facilities. These data were also able to be used to characterize worker exposure for
some 1,3-butadiene's OESs beyond manufacturing and processing (such as laboratory use and waste
handling) using the worker descriptions accompanying the data. This data set provided measurements at
the level of individual worker populations, or similarly exposed groups (SEGs). This granularity allowed
EPA to differentiate even within OES among different types of activities and frequencies. See Table 2-3
for descriptions of the function of 1,3-butadiene for each OES.
The majority of occupational exposure sampling data points, collected from OSHA, NIOSH, and ACC's
monitoring report (ToxStrateeies. 2021). were not quantifiable values but were identified as being below
the limit of detection (LOD) which according to the sampling methods may range from approximately
0.0036 to 0.09 ppm for full shift sampling depending on individual sample conditions. In such cases, in
accordance with EPA's Guidelines for Statistical Analysis of Occupational Exposure Data the data were
scored as half the LOD value and incorporated into the overall distribution. To make a preliminary risk
determination, the Agency analyzed the individual COUs by the Population/SEG to determine if the
COU was best represented by central tendency or high-end estimates for workers and ONUs based on
the description of the COU and the parameters and assumptions used in the occupational exposure
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scenarios. If an activity significantly contributed to the unreasonable risk for non-cancer or cancer for
any Population/SEG within the COU, EPA preliminarily determined there was unreasonable risk to that
activity within that COU.
There were COUs with MOEs below the benchmark of 30 at the high-end estimates for intermediate
inhalation exposure for worker populations. As discussed previously, because of the robust data set
associated with 1,3-butadiene in occupational settings, EPA is generally using high-end estimates for
workers in its preliminary risk determination for shorter term exposures (i.e., intermediate non-cancer
risk or 30-day durations). However, EPA is generally using central tendency for longer term exposures
(i.e., chronic non-cancer and cancer) due to the effect of averaging this larger set of data over the longer
period of time. Central tendency is generally used for EPA's preliminary risk determination for chronic
non-cancer and cancer estimates for 1,3-butadiene since longer-term average exposure would bias
toward central tendency (i.e., the more common risk estimates) vs. higher-end values (i.e., less common
risk estimates or 95th percentile). In addition, risk estimates have been provided for both an 8- and a 12-
hour TWA for certain manufacturing and processing conditions of use. Because these both represent real
scenarios and shift lengths for workers exposed to 1,3-butadiene, EPA considered both shift lengths in
its preliminary determination.
As previously mentioned, these calculated risk estimates alone are not bright-line indicators of
unreasonable risk and EPA has the discretion to consider other risk-related factors in addition to risks
identified in the risk characterization. There are estimated risks for workers associated with activities
and COUs that approach or border the benchmark, including the maintenance activities which occur
under three COUs: the domestic manufacturing; processing as a reactant - intermediate in various
manufacturing industries; and processing - incorporation into formulation, mixture, or reaction product.
The risk estimates for the maintenance activity are the same across the COUs. This is because the data
associated with this activity are the used for each corresponding COU, with differing estimates for the 8-
and 12-hour TWA due to the days exposed per year (i.e., 250 days for 8-hour TWA and 167 days for 12-
hour TWA). The high-end estimates for intermediate non-cancer for the maintenance activity at both
timeframes are well below the benchmark MOE of 30 (i.e., 21 for the 8-hour TWA and 14 for the 12-
hour TWA). In addition, the estimates for the central tendency are borderline for intermediate non-
cancer at the 8-hour TWA (i.e., 33) and below the benchmark MOE for the 12-hour TWA for
intermediate non-cancer (i.e., 22). The central tendency estimates for chronic non-cancer for the
maintenance activity at both timeframes are above the benchmark MOE of 30 (i.e., 34 for the 8-hour
TWA and 35 for the 12-hour TWA), but both well below for the high-end estimates (i.e., 22 and 23 for
the 8-hour TWA and the 12-hour TWA, respectively. Lastly, the cancer risk estimates are above a 1 in
10,000 risk for the high-end estimates at both the 8- and the 12-hour TWA, but well below 1 in 10,000
for workers using the central tendency.
As previously stated, there is increased uncertainty for longer-term timeframes due to the extrapolation
of single-day results to longer durations. Because the distribution of the monitoring data associated with
the maintenance activity indicates less of a range, we can assume less uncertainty over longer durations
and that the high-end and central tendency estimates both appropriately represent risk for this activity
for chronic non-cancer. Considering the indication of risk across the two timeframes, because the MOEs
for both the intermediate and chronic non-cancer are close, indicating not a large range in the data for
this activity, and because the central tendency borders the benchmark MOE, EPA is preliminarily
determining the intermediate and chronic non-cancer significantly contribute to the unreasonable risk.
EPA is preliminarily determining that the activities listed below associated with domestic manufacturing
significantly contribute to the unreasonable risk to workers presented by 1,3-butadiene, see Table 5-4 for
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occupational risk estimates. For two of those activities under the domestic manufacturing COU,
Manufacturing - instrument and electric manufacturing and Manufacturing - maintenance - nonroutine,
risks were indicated for the 12-hour TWA but not for the 8-hour TWA. However, as stated previously,
EPA is considering both timeframes when preliminarily determining unreasonable risk and therefore, is
finding that those two also significantly contribute to the unreasonable risk. The remaining activities
significantly contribute at both the 8- and 12-hour TWA.
The following activities significantly contribute to the unreasonable risk to the domestic manufacturing
COU based on the non-cancer and cancer effects from worker intermediate inhalation and chronic
inhalation exposure to 1,3-butadiene in occupational settings:
• Manufacturing - Infrastructure/ Distribution Operations*
• Manufacturing - Infrastructure/ Distribution Operations - Nonroutine*
• Manufacturing - Instrument and Electrical* (12-hour TWA)
• Manufacturing - Laboratory Technician*
• Manufacturing - Laboratory Technician - Nonroutine**
• Manufacturing - Machinery and Specialists*
• Manufacturing - Maintenance*
• Manufacturing - Maintenance - Nonroutine* (12-hour TWA)
• Manufacturing - Maintenance - Turnaround*
• Manufacturing - Operations Onsite*
• Manufacturing - Safety Health and Engineering*
*= intermediate non-cancer only
**= non-cancer (intermediate and chronic) and cancer
EPA is preliminarily determining that all activities associated with Import and processing - repackaging
significantly contribute to the unreasonable risk presented by 1,3-butadiene. EPA understands that
import and repackaging sites are distributing to various downstream uses. Liquefied butadiene is shipped
by pipelines, ships, barges, rail tank cars, tank trucks and bulk liquid containers. A portion of the 1,3-
butadiene manufactured is also expected to be repackaged into smaller containers for commercial
laboratory use. The following activities significantly contribute to the unreasonable risk based on the
non-cancer and cancer effects from worker intermediate inhalation exposure and chronic inhalation
exposure to 1,3-butadiene in occupational settings for both the 8- and 12-hour TWA:
• Manufacturing - Import - Worker* *
• Manufacturing - Import - ONU* *
• Processing - Repackaging - Worker* *
• Processing - Repackaging - ONU* *
**= non-cancer (intermediate and chronic) and cancer
EPA is preliminarily determining that the activities listed below associated with Processing - processing
as a reactant - intermediate and Processing - processing as a reactant - monomer used in polymerization
process significantly contribute to the unreasonable risk presented by 1,3-butadiene, see Table 5-4 for
occupational risk estimates. For two of those activities under the processing as a reactant COU,
Processing - processing as a reactant - instrumental and electrical and Processing - processing as a
reactant - maintenance - nonroutine, risks were found only for the 12-hour TWA. The remaining
activities significantly contribute at both the 8- and 12-hour TWA. The following activities significantly
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contribute to the unreasonable risk based on the non-cancer and cancer effects from worker intermediate
inhalation exposure and chronic inhalation exposure to 1,3-butadiene in occupational settings:
Processing - Processing as a Reactant - Intermediate - Infrastructure/ Distribution Operations*
Processing - Processing as a Reactant - Intermediate - Infrastructure/ Distribution Operations -
Nonroutine*
Processing - Processing as a Reactant - Intermediate - Instrumental and Electrical* (12-hour
TWA)
Processing - Processing as a Reactant - Intermediate - Laboratory Technician*
Processing - Processing as a Reactant - Intermediate - Laboratory Technician - Nonroutine**
Processing - Processing as a Reactant - Intermediate - Machinery and Specialists*
Processing - Processing as a Reactant - Intermediate - Maintenance*
Processing - Processing as a Reactant - Intermediate - Maintenance - Nonroutine* (12-hour
TWA)
Processing - Processing as a Reactant - Intermediate - Maintenance - Turnaround*
Processing - Processing as a Reactant - Intermediate - Operations Onsite*
Processing - Processing as a Reactant - Intermediate - Safety Health and Engineering*
Processing - Processing as a Reactant - Monomer used in polymerization process - Worker*
Processing - Processing as a Reactant - Monomer used in polymerization process - ONU* (12-
hr TWA)
*= intermediate non-cancer only
**= non-cancer (intermediate and chronic) and cancer
EPA is preliminarily determining that the activities listed below associated with Processing -
incorporation into formulation, mixture, or reaction product significantly contribute to the unreasonable
risk presented by 1,3-butadiene, see Table 5-4 for occupational risk estimates. For two of those activities
under the incorporation into formulation, mixture, or reaction product COU, Processing - incorporation
into formulation, mixture, or reaction product - instrument and electrical and Processing - incorporation
into formulation, mixture, or reaction product - maintenance - nonroutine, risks were found only for the
12-hour TWA. The remaining activities significantly contribute at both the 8- and 12-hour TWA. The
following activities significantly contribute to the unreasonable risk based on the non-cancer and cancer
effects from worker intermediate inhalation exposure and chronic inhalation exposure to 1,3-butadiene
in occupational settings:
• Processing - Incorporation into Formulation, Mixture, or Reaction Product - Infrastructure/
Distribution Operations*
• Processing - Incorporation into Formulation, Mixture, or Reaction Product - Infrastructure/
Distribution Operations - Nonroutine*
• Processing - Incorporation into Formulation, Mixture, or Reaction Product - Instrument and
Electrical * (12-hour TWA)
• Processing - Incorporation into Formulation, Mixture, or Reaction Product - Laboratory
Technician*
• Processing - Incorporation into Formulation, Mixture, or Reaction Product - Laboratory
Technician - Nonroutine**
• Processing - Incorporation into Formulation, Mixture, or Reaction Product - Machinery and
Specialists*
• Processing - Incorporation into Formulation, Mixture, or Reaction Product - Maintenance*
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• Processing - Incorporation into Formulation, Mixture,
Nonroutine*(12-hour TWA)
• Processing - Incorporation into Formulation, Mixture,
Turnaround*
• Processing - Incorporation into Formulation, Mixture,
• Processing - Incorporation into Formulation, Mixture,
Engineering*
*= intermediate non-cancer only
**= non-cancer (intermediate and chronic) and cancer
EPA is preliminarily determining that the activities listed below associated with Processing -
Incorporation into Article - Plastics and Rubber Compounding significantly contributes to the
unreasonable risk based on the non-cancer effects from worker intermediate inhalation exposure
presented by 1,3-butadiene in occupational settings:
• Processing - Incorporation into Article - Other: Polymer in: Rubber and plastic product
manufacturing (Worker)*
*= intermediate non-cancer only
EPA is preliminarily determining that all activities associated with Processing - recycling, commercial
use - other use - laboratory chemicals, and Disposal significantly contribute to the unreasonable risk
presented by 1,3-butadiene based on the non-cancer and cancer effects from worker intermediate
inhalation exposure and chronic inhalation exposure to 1,3-butadiene in occupational settings. For one
of those activities under the Commercial use -laboratory chemicals COU, Laboratory Technician -
Nonroutine, risks for cancer effects were found only for the 12-hour TWA and non-cancer for both the
8- and 12-hour TWA.
The following occupational COUs do not have quantitative risk estimates for workers. However, EPA
has qualitatively evaluated the COUs by integrating additional reasonably available information. The
qualitative analyses are a best estimate of what EPA expects given the weight of scientific evidence (see
Section 5.1.1):
• Distribution in commerce: EPA expects 1,3-butadiene to be transported in sealed containers from
import sites to downstream processing and use sites, or for final disposal of 1,3-butadiene. EPA
preliminarily expects, under standard operating procedures, that exposures and releases could
occur during distribution in commerce but would not significantly contribute to the unreasonable
risk presented by 1,3-butadiene because inhalation exposure is not expected.
• Commercial use - fuels and related products: Exposures were not quantitatively assessed for the
commercial COUs covered by the OES of "Fuels and related products", which includes 1,3-
butadiene used as a fuel binder for solid rocket fuels, and 1,3-butadiene's presence in liquid
petroleum gas (LPG) used as a fuel. In the case of the use as a fuel binder, EPA understands this
is not a use of 1,3-butadiene monomer, but rather polymers created from 1,3-butadiene and other
monomers. EPA found evidence of 1,3-butadiene at small concentrations (less than 0.1%) in
LPG. Occupational exposures from LPG connections, cylinder leaks, and incomplete combustion
are expected to be minimal.
• Commercial use - lubricants and lubricant additives: Exposures were not quantitatively assessed
for the commercial COUs covered by the OES of "Use of lubricants and greases." Reasonably
or Reaction Product - Maintenance -
or Reaction Product - Maintenance -
or Reaction Product - Operations Onsite*
or Reaction Product - Safety Health and
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available evidence suggests that 1,3-butadiene monomer does not exist at concentrations above
reporting thresholds in lubricants and greases. Based on conversations with companies who have
listed 1,3-butadiene in their SDS, EPA believes 1,3-butadiene indicated in SDS or other products
refer either to upstream steps or to reacted polymeric forms.
• Commercial use - other articles with routine direct contact during normal use including rubber
articles; plastic articles (hard); Commercial use - Toys intended for children's use (and child
dedicated articles), including fabrics, textiles, and apparel; or plastic articles (hard); Commercial
use - Synthetic Rubber; Commercial use - Furniture & furnishings including stone, plaster,
cement, glass and ceramic articles; metal articles; or rubber articles; Commercial use -
Packaging (excluding food packaging), including rubber articles; plastic articles (hard); plastic
articles (soft); Commercial use - Automotive care products: Exposures were also not
quantitatively assessed for the commercial COUs covered by the OES of "Use of plastics and
rubber products." Reasonably available evidence suggests that 1,3-butadiene monomer does not
exist at concentrations above 6.6 ppm in rubber products and that 1,3-butadiene is stable in these
products and not expected to degrade. Any 1,3-butadiene indicated in SDSs or other product
reports likely referred either to upstream steps or to reacted polymeric forms. The Agency
expects these articles to pose no significant risk for inhalation exposures to commercial workers
who use articles in a similar fashion to consumers for these COUs. Thus, EPA is preliminarily
determining that these COUs do not significantly contribute to the unreasonable risk presented
by 1,3-butadiene.
7.1.5 Consumers
Based on the assessment of consumer risk and related risk factors, EPA is preliminarily determining that
no consumer conditions of use significantly contribute to the unreasonable risk of 1,3-butadiene. The
consumer COUs and associated disposal do not have quantitative risk estimates. EPA has qualitatively
evaluated the consumer COUs by integrating reasonably available information demonstrating that
butadiene polymer-derived consumer products, such as synthetic rubbers, are not expected to degrade
and expose the consumer to the 1,3-butadiene monomer. The qualitative analyses are a best estimate of
what the Agency expects given the weight of scientific evidence (see Section 5.1.2).
• Consumer use - Other articles with routine direct contact during normal use including rubber
articles; plastic articles (hard); Toys intended for children's use (and child dedicated articles),
including fabrics, textiles, and apparel; or plastic articles (hard); Synthetic Rubber (e.g., rubber
tires); Furniture & furnishings including stone, plaster, cement, glass and ceramic articles; metal
articles; or rubber articles; and Packaging (excluding food packaging), including rubber articles;
plastic articles (hard); plastic articles (soft): Residual butadiene concentrations in polymers and
downstream chemicals used to create these plastic and rubber articles are very low and often not
detectable. Further, processing of synthetic polymers into rubber or plastic products reduces any
remaining residual butadiene resulting in minimal to no potential end-user exposures. Therefore,
EPA has determined this COU does not significantly contribute to the unreasonable risk to
consumers presented by 1,3-butadiene.
• Disposal: Based on product searches and systematic review data, EPA has determined that 1,3-
butadiene is stable in these products and not expected to degrade and expose the consumer to the
1,3-butadiene monomer from the use or disposal of these products.
7.1.6 General Population Including Fenceline Communities
EPA employed a qualitative, screening level approach for general population exposures to 1,3-butadiene
for the land, surface water, sediment, and drinking water pathways. The Agency identified the ambient
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air pathway to be the predominant human exposure pathway to 1,3-butadiene in the outdoor
environment and quantitatively assessed the risk of 1,3-butadiene to the general population, including
fenceline communities. For further information see Section 4.2. EPA preliminarily finds that ambient air
exposure from releases of 1,3-butadiene significantly contributes to the unreasonable risk from 1,3-
butadiene for the sub-populations living near facilities manufacturing and processing 1,3-butadiene.
Land Pathway
EPA evaluated the complete set of monitoring data from EPA's Water Quality Portal, which includes
380 million water quality data records from 900 federal, state, tribal and other partners, in assessing
exposures via the land pathway, as well as the surface water and sediment pathways, and drinking water
pathway. 1,3-Butadiene is not released to soil, and air to soil deposition is not expected due to the
physical and chemical properties of 1,3-butadiene (high volatility and reactivity and low sorption to
organic material). Based on the low volume of releases to land, the low risk of failure of the
predominant release scenario, the physical and chemical properties of 1,3-butadiene as well as
monitoring data indicating less than 1 percent detection frequency, the land pathway is not considered a
pathway of concern for exposure to the general population. As such, EPA preliminarily determines this
pathway does not significantly contribute to unreasonable risk of 1,3-butadiene to the general population
from the land pathway. For further information see Section 4.2.1.4.
Surface Water and Sediment Pathways
Based on the physical and chemical properties of 1,3-butadiene's; that is, it's low water solubility, high
volatility from water, and low estimated Koc value, as well as the low reported releases to surface water
and monitoring data showing no detection of 1,3-butadiene, EPA does not expect general population
exposure to 1,3-butadiene to occur via the surface water or sediment pathways. As such, the Agency
preliminarily determines this pathway does not significantly contribute to unreasonable risk of 1,3-
butadiene to the general population from the surface water or sediment pathways. For further
information see Section 4.2.1.2.
Drinking Water Pathway
Based on the physical and chemical properties of 1,3-butadiene; that is, its low water solubility and high
tendency to volatilize from water, as well as the monitored data showing that 1,3-butadiene is not
detected in drinking water, EPA does not expect general population exposure to 1,3-butadiene from
drinking water. As such, EPA preliminarily determines this pathway does not significantly contribute to
unreasonable risk of 1,3-butadiene to the general population from drinking water. For further
information see Section 4.2.1.3.
Ambient Air Pathway
Recognizing the ubiquity of 1,3-butadiene in ambient air is due to contributions from many different
sources, EPA considered and presented measured and modeled concentrations of 1,3-butadiene from
multiple lines of evidence, data, and analyses in this ambient air exposure assessment to evaluate and
contextualize 1,3-butadiene exposures in ambient air due to TSCA COUs. Based on the physical and
chemical properties, and concentrations reported from databases and scientific literature, a quantitative
exposure assessment was conducted for the ambient air pathway for the general population. 1,3-
butadiene in the atmosphere is expected to remain largely in the vapor phase, where it is not expected to
persist or undergo long-range transport. As such, EPA estimated risks to the general population of any
lifestage living near facilities releasing 1,3-butadiene into the environment via inhalation only following
chronic or lifetime exposure.
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To evaluate non-cancer and cancer risks for general population, EPA modeled air concentrations for the
following distances: 100 m, 100 to 1,000 m, and 1,000 m. These distances are also consistent with the
community populations living near facilities as described in the fenceline methodology (Draft Screening
Level Approach for Assessing Ambient Air and Water Exposures to Fenceline Communities Version
L0).
For non-cancer risks, no calculated MOE was below the benchmark of 30 for all Draft Integrated Indoor
Outdoor Air Calculator (IIOAC) modeled concentrations from 100 to 1,000 m across all TRI facilities.
The highest concentration was calculated for a facility corresponding with the Processing - plastics and
rubber compounding COU/OES, at an MOE of 60, which is twice the benchmark of 30. Therefore, EPA
preliminarily determined that non-cancer risks from ambient air do not significantly contribute to the
unreasonable risk from exposure to 1,3-butadiene for any COU.
For cancer risks, EPA is preliminarily determining that the ambient air pathway significantly contributes
to the unreasonable risk from inhalation exposure to 1,3-butadiene. When the cancer risk estimates
derived using IIOAC results, based on 95th percentile and mean modeled concentrations, were at or
above the 1 in a million benchmark up to 1,000 m from facility releases, EPA utilized HEM to conduct a
more geographically refined analysis of ambient air concentrations using localized meteorological data
and site-specific parameters (when available). EPA calculated lifetime cancer risk using the lifetime
average daily concentration (LADC) based on the 95th modeled annual air concentration and the general
population IUR. of 0.0098 per ppm (4.4/ 10 6 per |ig/m3). See Section 5.2 and the Draft Human Health
Hazard Assessment for 1,3-Butadiene ( )24f)) for more details on the human health hazard
values. As an example, from Table 5-6, for the 2021 TRI reporting year, for the manufacturing COU,
there were a total of 37 manufacturing facilities that reported 1,3-butadiene releases, and cancer risks
were estimated for the census blocks around those facilities. The estimated cancer risks across all of the
census blocks around the 37 manufacturing facilities ranged from 6.5xlO-11 to 8.9x10 5.
As the Agency incorporates refined or additional release data received during the public comment period
and SACC review of the draft risk evaluation, it is possible that the specific COUs preliminarily
determined to significantly contribute to unreasonable risk could change.
The following COUs significantly contribute to unreasonable risk of cancer to fenceline communities in
the general population due to inhalation of 1,3-butadiene:
• Manufacturing - domestic manufacturing: Even at the modeled distance of 1,000 m for both the
50th percentile and the 95th percentile, the risk estimates indicate cancer risk above the
benchmark of 1 in a million (see Table 5-5), with risk estimates for the 95th percentile estimates
for this COU at 1,000 m being 2.1 x 10~5. In addition, the HEM risk estimates based on census
block information indicates that there are populations exposed above this benchmark for the TRI
reporting years 2016 to 2021, with some even above the 10 in a million. Based on EPA's robust
confidence in the general population risk estimates, the radial distance modeling showing risk
above the 1 in a million benchmark, and the census block data showing populations exposed for
all six years, EPA is preliminarily determining that this COU significantly contributes to
unreasonable risk to fenceline communities in the general population.
• Processing - processing as a reactant - monomer used in polymerization process in: synthetic
rubber manufacturing; plastic material and resin manufacturing: Similarly to the domestic
manufacturing COU, at both the 50th and 95th percentile for the highest modeled radial distance
{i.e., 1,000 m) the risk estimates are above the benchmark of 1 in a million, with the highest at
1,000 m being 9,4x 10 6, Census block information indicates that there are populations exposed
above 1 in a million risk for all reported years and above 10 in a million risk for all years except
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2018 where there was no reporting for those facilities. Again, based on EPA's robust confidence
in the general population risk estimates, the radial distance modeling showing risk above the 1 in
a million benchmark, and the census block data showing populations exposed for all six years,
EPA is preliminarily determining that this COU significantly contributes to unreasonable risk to
fenceline communities in the general population.
• Processing - incorporation into formulation, mixture, or reaction product - processing aids, not
otherwise listed in: petrochemical manufacturing: Similarly to the previously discussed COUs, at
both the 50th and 95th percentile for the highest modeled radial distance {i.e., 1,000 m) the risk
estimates are above the benchmark of 1 in a million, with the highest at the 95th percentile for
1,000 m being 1.4X10~5. Fifty-three facilities reported to TRI during the 2016 to 2021 reporting
years for this use. The risk estimates above 1 in a million are associated with two facilities. One
facility (TRI ID: 77640FNLNDHIGHW) reported in 2016 to 2019 but releases indicated risk
above the benchmark for only years 2016 and 2017. This facility's reporting indicates a decline
in releases and therefore a decrease in the number of people exposed during the six reporting
years and indicates that there are no populations exposed for the most recent four reported years
{i.e., 2021, 2020, 2019, 2018) above 1 in a million. The second facility (TRI ID:
77641TXCCHGATE2) reported for all 6 years {i.e., 2016-2021) but releases indicated risk
above the benchmark for only 2018. However, unlike the other facility, the reported release data
does not indicate a decline. Based on the radial distance modeling showing risk above the 1 in a
million benchmark, and the census block data showing populations exposed, EPA is
preliminarily determining that this COU significantly contributes to unreasonable risk to
fenceline communities in the general population.
The following COUs are above 1 in a million risk but do not significantly contribute to unreasonable
risk of cancer to fenceline communities in the general population:
• Processing as a reactant - intermediate in: adhesive manufacturing; all other basic organic
chemical manufacturing; fuel binder for solid rocket fuels; organic fiber manufacturing;
petrochemical manufacturing; petroleum refineries; plastic material and resin manufacturing;
propellant manufacturing; synthetic rubber manufacturing; wholesale and retail trade: The risk
estimates at the 50th for the highest modeled radial distance {i.e., 1,000 m) borders the 1 in a
million benchmark {i.e., l.lxio-6) and is above for the 95th (3.5xl0~6). EPA's model
conservatively assumes the general population is being exposed to modeled ambient air {i.e.,
outdoor) concentrations 24 hours a day, 365 days a year, over a lifetime. In addition, the
estimates reflect the highest modeled concentration across all reported facilities {i.e., the 50th
percentile risk at 1,000 m represents the risk based on the highest 50th percentile modeled
concentration at 1,000 m across all 57 processing facilities). Given these conservative
assumptions, EPA is using the 50th percentile {i.e., l.lxio-6) and in addition, based on the
census block data, for all five reporting years, little to no people are above the 10 in a million
risk and the range of people exposed based on reporting year varies for the 1 in a million
benchmark. EPA is preliminary determining that this COU does not significantly contribute to
unreasonable risk to fenceline communities in the general population.
For the other COUs, not previously listed and where EPA conducted a quantitative assessment, risk
estimates did not indicate risk and none were above a 1 in a million risk. EPA does not expect risk for
those COUs where EPA has conducted a qualitative assessment. In addition, EPA expects that general
population inhalation exposures from distribution in commerce would be even lower than those for
workers. Therefore, the Agency is preliminarily determining that distribution in commerce does not
contribute significantly to the unreasonable risk of 1,3-butadiene due to the injury to health.
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EPA has robust confidence in the overall characterization of environmental media concentrations for
1,3-butadiene as it relies upon databases that are publicly available and reviewed with quality control
and assurance protocols. The Agency also has robust confidence in the overall characterization of
exposures for the ambient air exposure assessment as it relies upon direct reported releases from
databases that received a high-quality rating from EPA's systematic review process and peer-reviewed
models to derive exposure concentrations at distances from releasing facilities where individuals reside
for many years. Furthermore, use of actual reported releases minimizes uncertainties around estimated
releases using theoretical distributions and provides added confidence that modeled concentrations and
exposures are real and not hypothetical apart from EPA estimated releases for adhesives and sealants
OES. The greatest uncertainty is associated with the contribution of 1,3-butadiene to the total ambient
monitoring data due to non-attributable sources related to fuel use, combustion, and mobile
emissions. Another source of uncertainty in is the assumption that the TRI-reported emissions from each
facility are from a standardized stack of 10 m in height and ground-level area source of 10 by 10 m as
described in the Draft Environmental Releases and Occupational Exposure Assessment for 1,3-
Butadiene ( E024y).
7.2 Unreasonable Risk to the Environment
Based on the pathways evaluated in the draft risk evaluation for 1,3-butadiene, EPA preliminarily
determines that risk to the environment does not significantly contribute to the unreasonable risk
determination for 1,3-butadiene. Given the fate properties of 1,3-butadiene, an in-depth analysis of
releases to water or land and associated exposures from those releases were not conducted. The
environmental risk characterization for 1,3-butadiene involved a review of release and monitoring data
which demonstrated limited release and that 1,3-butadiene was not detected in water. In addition, EPA
does not expect that 1,3-butadiene will persist in surface water or groundwater or adsorb to soil or
sediment and does not persist on land, due to its physical and chemical properties {i.e., gas form under
ambient conditions, high volatility and reactivity, low sorption potential). Extensive ambient air
monitoring data are available for 1,3-butadiene, which shows that 1,3-butadiene is prevalent in ambient
air and confirms that air is a major 1,3-butadiene exposure pathway. However, EPA did not conduct a
quantitative analysis on this pathway for aquatic or terrestrial species.
7.2.1 Populations and Exposures EPA Assessed for the Environment
EPA quantitatively determined 1,3-butadiene concentrations for ambient air pathway based on the
physical and chemical properties, and concentrations reported from databases and scientific literature for
the general population. Furthermore, the Agency qualitatively assessed environmental exposures for
surface water and sediment pathway as well as drinking water and soil. This qualitative analysis was
based on the low amounts of releases and high frequencies of non-detects reported in databases and
scientific literature. EPA has robust confidence in the overall characterization of environmental media
concentrations for 1,3-butadiene as it relies upon databases that are publicly available and reviewed with
quality control and assurance protocols, such as AMTIC, WQP, and UCMR, and extracted data from
peer-reviewed literature that received medium to high-quality ratings from EPA's systematic review
process.
7.2.2 Summary of Environmental Effects
EPA qualitatively assessed environmental exposures of 1,3-butadiene in air, water, and soil. Based on
these assessments, the preliminary findings are as follows:
• 1,3-Butadiene releases in air are expected to be the predominant pathway of environmental
exposure.
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• 1,3-Butadiene is not expected to be present in surface water given minimal releases to surface
water, rapid biodegradation, and volatilization. Additionally, 1,3-butadiene has low sorption
potential and is not expected to be present in sediment.
• 1,3-Butadiene is not released to soil, and air to soil deposition is not expected due to the physical
and chemical properties (high volatility and reactivity and low sorption to organic material).
Extensive ambient air monitoring data are available for 1,3-butadiene and confirms that air is the
primary exposure pathway. Although these data demonstrate 1,3-butadiene concentrations in ambient
air, the sources are unknown. Concentrations of 1,3-butadiene in ambient air is likely from a
combination of non-point sources (e.g., forest fires, mobile exhaust).
7.2.3 Basis for Risk of Injury to the Environment
Based on the pathways evaluated in the draft risk evaluation for 1,3-butadiene, EPA did not identify risk
of injury to the environment that would contribute significantly to the unreasonable risk determination
for 1,3-butadiene. EPA is preliminarily determining that there is no significant risk of injury to the
environment to aquatic organisms as 1,3-butadiene is not appreciably released to, and does not persist in,
surface water and exposure is not expected based on the physical and chemical properties of 1,3-
butadiene. Additionally, EPA is preliminarily determining that there is no significant risk of injury to the
environment to terrestrial organisms through soil exposure as 1,3-butadiene does not partition, deposit,
or persist in or on land and exposure is not expected. Although exposure of 1,3-butadiene to terrestrial
organisms is expected via ambient air, exposures will be transient due to the reactive nature of 1,3-
butadiene. Because 1,3-butadiene exposure in ambient air cannot be attributed to a specific TSCA use
and there is no available hazard data for 1,3-butadiene in terrestrial organisms, environmental risk to
terrestrial organisms via ambient air was not assessed and a preliminary risk cannot be determined for
this pathway.
7.3 Additional Information Regarding the Basis for the Unreasonable Risk
Determination
Table 7-1 summarizes the basis for this draft unreasonable risk determination of injury to human health
for occupational COUs, presented in this draft risk evaluation for those COUs with a qualitative
evaluation. Table 7-2 summarizes the basis for this draft unreasonable risk determination of injury to
human health for consumer COUs, presented in this draft risk evaluation. In these tables, a checkmark
(/) indicates how the COU significantly contributes to the unreasonable risk by identifying the type of
effect (e.g., non-cancer for human health). Inhalation was the only exposure route assessed. Dermal
exposures are not expected due to the volatility and transport method of the chemical. As explained in
Section 7, for this draft unreasonable risk determination, EPA considered the effects of 1,3-butadiene to
human health at the central tendency and high-end.
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2538 Table 7-1. Supporting Basis for the Draft Unreasonable Risk Determination for Human Health (Occupational COUs, Inhalation
2539 Exposure Route)
Life Cycle
Stage
Category
Subcategory
Population/SEG
Intermediate
Non-cancer
Chronic
Non-cancer
Cancer
Infrastructure/ Distribution
~
—
—
Operations
Infrastructure/ Distribution
•/
-
-
Operations - Nonroutine
Instrument and Electrical
-
-
Instrument and Electrical -
—
-
-
Nonroutine
Instrument and Electrical -
—
-
-
Turnaround
Laboratory Technician
V
-
-
Laboratory Technician -
S
•/
Domestic manufacturing
Domestic manufacturing
Nonroutine
Manufacturing
Machinery and Specialists
V
-
-
Machinery and Specialists -
Turnaround
—
—
—
Maintenance
s
•/
Maintenance - Nonroutine
V
-
-
Maintenance - Turnaround
V
-
-
Operations Onsite
s
-
-
Operations Onsite - Nonroutine
-
-
-
Operations Onsite -
Turnaround
—
—
—
Safety Health and Engineering
-
-
ONU
-
-
-
Importing
Importing
Worker
•/
V
•/
ONU
V
V
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Life Cycle
Stage
Category
Subcategory
Population/SEG
Intermediate
Non-cancer
Chronic
Non-cancer
Cancer
Infrastructure/ Distribution
•/
—
—
Operations
Infrastructure/ Distribution
-
-
Operations - Nonroutine
Instrument and Electrical
•/
-
-
Instrument and Electrical -
—
-
-
Intermediate in: adhesive
manufacturing; all other basic
organic chemical manufacturing;
fuel binder for solid rocket fuels;
organic fiber manufacturing;
petrochemical manufacturing;
petroleum refineries; plastic
Nonroutine
Instrument and Electrical -
Turnaround
—
-
-
Laboratory Technician
V
-
-
Processing as a reactant
Laboratory Technician -
Nonroutine
V
~
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Life Cycle
Stage
Category
Subcategory
Population/SEG
Intermediate
Non-cancer
Chronic
Non-cancer
Cancer
Infrastructure/ Distribution
•/
—
—
Operations
Infrastructure/ Distribution
-
-
Operations - Nonroutine
Instrument and Electrical
•/
-
-
Instrument and Electrical -
—
-
-
Nonroutine
Instrument and Electrical -
—
-
-
Turnaround
Laboratory Technician
V
-
-
Processing -incorporation into
Processing aids, not otherwise
listed in: petrochemical
Laboratory Technician -
Nonroutine
V
~
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Life Cycle
Stage
Category
Subcategory
Population/SEG
Intermediate
Non-cancer
Chronic
Non-cancer
Cancer
Laboratory Technician -
Nonroutine
•/
V
•/
Machinery and Specialists
-
-
Other: adhesive manufacturing,
paints and coatings
manufacturing, petroleum
lubricating oil and grease
manufacturing, and all other
chemical product and preparation
Machinery and Specialists -
Turnaround
—
—
—
Processing - incorporation into
formulation, mixture, or
reaction product
Maintenance
•/
Processing
Maintenance - Nonroutine
S
-
-
Maintenance - Turnaround
S
-
-
Operations Onsite
s
-
-
manufacturing
Operations Onsite - Nonroutine
-
-
-
Operations Onsite -
Turnaround
—
—
—
Safety Health and Engineering
-
-
ONU
-
-
-
Processing - incorporation into
Other: polymer in: rubber and
Worker
•/
-
-
article
plastic product manufacturing
ONU
-
-
-
Intermediate in: wholesale and
Worker
s
V
•/
Repackaging
retail trade; monomer in:
synthetic rubber manufacturing
ONU
s
V
•/
Infrastructure/ Distribution
s
—
—
Operations
Infrastructure/ Distribution
V
—
—
Operations - Nonroutine
Processing
Instrument and Electrical
s
-
-
Instrument and Electrical -
Nonroutine
-
-
-
Recycling
Recyling
Instrument and Electrical -
Turnaround
—
—
—
Laboratory Technician
s
-
-
Laboratory Technician -
Nonroutine
•/
Machinery and Specialists
s
-
-
Machinery and Specialists -
Turnaround
-
-
-
Maintenance
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Life Cycle
Stage
Category
Subcategory
Population/SEG
Intermediate
Non-cancer
Chronic
Non-cancer
Cancer
Processing
Recycling
Recyling
Maintenance - Nonroutine
•/
-
-
Maintenance - Turnaround
•/
-
-
Operations Onsite
-
-
Operations Onsite - Nonroutine
-
-
-
Operations Onsite -
Turnaround
—
-
-
Safety Health and Engineering
-
-
ONU
-
-
-
Distribution in
Ccommerce
Distribution in commerce
Distribution in commerce (e.g.,
Sold to a trader; Sold to re-sellers
for petroleum fuel and
petrochemical industry in:
petrochemical manufacturing)
Worker
-
-
-
ONU
Industrial Use
Adhesives and sealants
Adhesives and sealants,
including epoxy resins
Worker
-
-
-
ONU
-
-
-
Commercial
Use
Fuels and related products
Fuels and related products
Worker
-
-
-
ONU
-
-
-
Other articles with routine
direct contact during normal
use including rubber articles;
plastic articles (hard)
Other articles with routine direct
contact during normal use
including rubber articles; plastic
articles (hard)
Worker
-
-
-
ONU
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)
Worker
-
-
-
ONU
Synthetic Rubber
Synthetic Rubber (e.g., rubber
tires)
Worker
-
-
-
ONU
-
-
-
Furniture & furnishings
including stone, plaster,
cement, glass and ceramic
articles; metal articles; or
rubber articles
Furniture & furnishings
including stone, plaster, cement,
glass and ceramic articles; metal
articles; or rubber articles
Worker
-
-
-
ONU
Packaging (excluding food
packaging), including rubber
Packaging (excluding food
packaging), including rubber
Worker
-
-
-
ONU
-
-
-
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Life Cycle
Stage
Category
Subcategory
Population/SEG
Intermediate
Non-cancer
Chronic
Non-cancer
Cancer
Commercial
Use
articles; plastic articles (hard);
plastic articles (soft)
articles; plastic articles (hard);
plastic articles (soft)
Automotive care products
Automotive care products
Worker
-
-
-
ONU
-
-
-
Other use
Laboratory chemicals
Laboratory Technician
•/
-
-
Laboratory Technician -
Nonroutine
•/
•/
ONU
-
-
Paints and coatings
Paints and coatings, including
aerosol spray paint
Worker
-
-
-
ONU
-
-
-
Adhesives and sealants
Adhesives and sealants, including
epoxy resins
Worker
-
-
-
ONU
-
-
-
Disposal
Disposal
Disposal
Worker
s
V
•/
ONU
s
V
•/
2540
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2541 Table 7-2. Supporting Basis for the Draft Unreasonable Risk Determination for Human Health (Consumer COUs, Inhalation
2542 Exposure Route)
Life Cycle
Stage
Category
Subcategory
Population/SEG
Intermediate
Non-cancer
Chronic Non-
cancer
Cancer
Consumer Use
Other articles with routine direct
contact during normal use
including rubber articles; plastic
articles (hard)
Other articles with routine direct
contact during normal use including
rubber articles; plastic articles (hard)
Worker
-
-
-
ONU
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)
Worker
-
-
-
ONU
Synthetic Rubber
Synthetic rubber (e.g., rubber tires)
Worker
-
-
-
ONU
-
-
-
Furniture & furnishings
including stone, plaster, cement,
glass and ceramic articles; metal
articles; or rubber articles
Furniture & furnishings including
stone, plaster, cement, glass and
ceramic articles; metal articles; or
rubber articles
Worker
-
-
-
ONU
Packaging (excluding food
packaging), including rubber
articles; plastic articles (hard);
plastic articles (soft)
Packaging (excluding food
packaging), including rubber articles;
plastic articles (hard); plastic articles
(soft)
Worker
-
-
-
ONU
2543
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(U.S. Environmental Protection Agency). (Draft Adhesives and Sealants Release Model for
1,3-Butadiene. Washington, DC: Office of Pollution Prevention and Toxics.
https://www.reeiilations.eov/docket/EPA-HQ-OPPT-2024-0425
(U S Environmental Protection Agency). ( Draft Air Releases (NEI2017) for 1,3-Butadiene.
Washington, DC: Office of Pollution Prevention and Toxics.
https://www.reeiilations.eov/docket/EPA-HQ-QPPT-2024-0425
(U.S. Environmental Protection Agency). Draft Ambient Monitoring Technology Information
Center (AMTIC) Monitoring Data 2016 to 2021 for 1,3-Butadiene. Washington, DC: Office of
Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). ( Draft Benchmark Dose Modeling Results for 1,3-
Butadiene. Washington, DC: Office of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). ( Draft Data Extraction Information for General
Population, Consumer, and Environmental Exposure for 1,3-Butadiene. Washington, DC: Office
of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). ( Draft Data Extraction Information for Human
Health Hazard Animal Toxicology and Epidemiology for 1,3-Butadiene. Washington, DC:
Office of Pollution Prevention and Toxics.
Fate and Transport for 1,3-Butadiene. Washington, DC: Office of Pollution Prevention and
Toxics.
(U.S. Environmental Protection Agency). (Release and Occupational Exposure for 1,3-
Butadiene. Washington, DC: Office of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). (Physical and Chemical Properties for 1,3-
Butadiene. Washington, DC: Office of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). ( Draft Data Quality Evaluation Information for
General Population, Consumer, and Environmental Exposure for 1,3-Butadiene. Washington,
DC: Office of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). (Animal Toxicology for 1,3-Butadiene.
Washington, DC: Office of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). (Epidemiology for 1,3-Butadiene. Washington, DC:
Office of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). ( Draft Environmental Media Concentrations for
1,3-Butadiene. Washington, DC: Office of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). ( Draft Further Filtering Results for Human Health
Hazard Animal Toxicology and Epidemiology for 1,3-Butadiene. Washington, DC: Office of
Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). ( Draft General Population Exposure for 1,3-
Butadiene. Washington, DC: Office of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). ( Draft Human Exposure Model (HEM) TRI2016-
2021 Exposure and Risk Analysis for 1,3-Butadiene. Washington, DC: Office of Pollution
Prevention and Toxics.
(U.S. Environmental Protection Agency). ( Draft Human Health Hazard Assessment for 1,3-
Butadiene. Washington, DC: Office of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). ( Draft Integrated Indoor Outdoor Air Calculator
(IIOAC) TRI 2016-2021 Exposure and Risk Analysis for 1,3-Butadiene. Washington, DC:
Office of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). (Draft Land Releases for 1,3-Butadiene.
Washington, DC: Office of Pollution Prevention and Toxics.
https://www.reeiilations.eov/docket/EPA-HQ-QPPT-2024-0425
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Draft Lifetable Analysis of Leukemia and Bladder Cancer for 1,3-Butadiene. Washington,
DC: Office of Pollution Prevention and Toxics.
(U.S. Environmental Protection Agency). ( Draft Number of Sites for 1,3-Butadiene.
Washington, DC: Office of Pollution Prevention and Toxics.
https://www.reeiilations.eov/docket/EPA-HQ-OPPT-2024-0425
( Residual risk assessment for the Synthetic Organic Chemical Manufacturing Industry
(SOCMI) source category in support of the 2024 Risk and Technology Review Final Rule.
Office of Air Quality Planning and Standards, Office of Air and Radiation.
https://www.epa.gov/svstem/files/documents/2024-
04/socmi sk assessment report wappendices 21mar2024.pdf
LISGS (U.S. Geological Survey). (2013). National Water Information System (NWIS) [Database],
Retrieved from http://waterdata.usgs.gov/nwis
Vimal P. (2008) Laboratory investigations of the hydroxyl radical-initiated oxidation of atmospheric
volatile organic compounds. (Doctoral Dissertation). Indiana University, Bloomington, IN.
Whittaker. C; Ri Vlckernan. L; Dankovic. D; Lentz. T; Macmahon. K; Kuempel. E; Zumwalde. R;
Schulte. P. (2016). Current Intelligence Bulletin 68: NIOSH Chemical Carcinogen Policy. US
Department of Health and Human Services.
https://ntrl.ntis.eov/NTRL/dashboard/searchResults/titleDetail/PB: html
WHO. (2001). 1,3-Butadiene: Human health aspects. (RISKLINE/2001120004). World Health
Organization.
Zhao. Z; Husainy. S: Smith. GD. (2011). Kinetics studies of the gas-phase reactions of N03 radicals
with series of 1-alkenes, dienes, cycloalkenes, alkenols, and alkenals. J Phys Chem A 115:
12161-12172. hut;
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2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
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2847
2848
2849
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APPENDICES
Appendix A KEY ABBREVIATIONS AND ACRONYMS
ABS
Acrylonitrile butadiene styrene resin plastics
ACC
American Chemistry Council
ACGM
American Conference of Governmental Industrial Hygienists
ADAF
Age-Dependent Adjustment Factor
AEGL
Acute Exposure Guideline Level
ATSDR
Agency for Toxic Substances and Disease Registry
BCF
Bioconcentration factor
CAA
Clean Air Act
CASRN
Chemical Abstracts Service Registry Number
CBI
Confidential Business Information
CCL
Contaminant Candidate List
CDR
Chemical Data Reporting
CEPA
Canadian Environmental Protection Act
CERCLA
Comprehensive Environmental Response, Compensation and Liability Act
CFR
Code of Federal Regulations
COU
Condition of use
CSCL
Chemical Substances Control Law
ECB
European Chemicals Bureau
ECHA
European Chemicals Agency
EPA
Environmental Protection Agency
EPCRA
Emergency Planning and Community Right-to-Know Act
ESD
Emission Scenario Document
GACT
Generally Available Control Technology
ECEL
Existing Chemical Exposure Limit
EU
European Union
EV
Exposure Value
GS
Generic Scenario
HAP
Hazardous Air Pollutant
HEC
Human Equivalent Concentration
IIOAC
Integrated Indoor-Outdoor Air Calculator
IMAP
Inventory Multi-Tiered Assessment and Prioritization
(I)UR
(Inhalation) Unit Risk
IRIS
Integrated Risk Information System
ISHA
Industrial Safety and Health Act
Koa
Octanol: Air partition Coefficient
Koc
Organic Carbon: Water Partition Coefficient
Kow
Octanol: Water partition Coefficient
LADC
Lifetime Average Daily Concentration
LCD
Life Cycle Diagram
MACT
Maximum Achievable Control Technology
MOA
Mode of action
MOE
Margin of exposure
NAICS
North American Industry Classification System
NEI
National Emissions Inventory
NICNAS
National Industrial Chemicals Notification and Assessment Scheme (Australia)
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2859
NIOSH
National Institute for Occupational Safety and Health
2860
NPL
National Priorities List
2861
NPRI
National Pollutant Release Inventory
2862
NTP
National Toxicology Program
2863
OCSPP
Office of Chemical Safety and Pollution Prevention
2864
OECD
Organisation for Economic Co-operation and Development
2865
OEL
Occupational exposure limits
2866
OES
Occupational exposure scenario
2867
ONU
Occupational non-user
2868
OPPT
Office of Pollution Prevention and Toxics
2869
OSHA
Occupational Safety and Health Administration
2870
PBZ
Personal breathing zone
2871
PEL
Permissible Exposure Limit
2872
PECO
Populations, exposures, comparators, and outcomes
2873
PESS
Potentially exposed or susceptible subpopulations
2874
POD
Point of departure
2875
POTW
Publicly owned treatment works
2876
PV
Production volume
2877
PWS
Public water system
2878
REACH
Registration, Evaluation, Authorisation and Restriction of Chemicals (European Union)
2879
SARA
Superfund Amendments and Reauthorization Act
2880
SBR
Styrene-butadiene rubber
2881
SDS
Safety data sheet
2882
SDWA
Safe Drinking Water Act
2883
SEG
Similarly exposed group
2884
STEL
Short-Term Exposure Limit
2885
TSCA
Toxic Substances Control Act
2886
TLV
Threshold limit value
2887
TRI
Toxics Release Inventory
2888
TWA
Time-weighted average
2889
UCMR
Unregulated Contaminants Monitoring Rule
2890
UF
Uncertainty factor
2891
VOC
Volatile organic compound
2892
WWT
Wastewater treatment
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2893 Appendix B REGULATORY AND ASSESSMENT HISTORY
2894 The chemical substance, 1,3-butadiene, is subject to federal and state laws and regulations in the United
2895 States (Sections B. 1 and B.2). Regulatory actions by other governments, tribes, and international
2896 agreements applicable to 1,3-butadiene are listed in Sections B.3 and the governmental assessment
2897 history is presented in Section B.4.
2898 B.1 Federal Laws and Regulations
2899
2900 Table Apx B-l. Federal Laws and Regulations
Statutes/Regulations
Description of Authority/Regulation
Description of Regulation
Toxic Substances
Control Act (TSCA) -
Section 6(b)
EPA is directed to identify high-priority
chemical substances for risk evaluation; and
conduct risk evaluations on at least 20 high
priority substances no later than three and
one-half years after the date of enactment of
the Frank R. Lautenberg Chemical Safety for
the 21st Century Act.
1,3-Butadiene is one of the 20
chemicals EPA designated as a High-
Priority Substance for risk evaluation
under TSCA (84 FR 71924. December
30, 2019). Designation of 1,3-
butadiene as a high-priority substance
constitutes the initiation of the risk
evaluation on the chemical.
Toxic Substances
Control Act (TSCA) -
Section 8(a)
The TSCA section 8(a) CDR Rule requires
manufacturers (including importers) to give
EPA basic exposure-related information on
the types, quantities, and uses of chemical
substances produced domestically and
imported into the United States.
1,3-Butadiene manufacturing
(including importing), processing, and
use information is reported under the
CDR rule (85 FR20122. April 2.
2020).
Toxic Substances
Control Act (TSCA) -
Section 8(b)
EPA must compile, keep current, and publish
a list (the TSCA Inventory) of each chemical
substance manufactured (including imported)
or processed in the United States.
1,3-Butadiene was on the initial TSCA
Inventory and therefore was not
subject to EPA's new chemicals
review process under TSCA section 5
(60 FR 16309. March 29. 1995).
Toxic Substances
Control Act (TSCA) -
Section 8(e)
Manufacturers (including importers),
processors, and distributors must immediately
notify EPA if they obtain information that
supports the conclusion that a chemical
substance or mixture presents a substantial
risk of injury to health or the environment.
20 risk reports received for 1,3-
butadiene (2017, 2011, 2008-2007,
2005, 2002-1997, 1995-1994, 1992,
1990) (U.S. EPA. ChemView.
Accessed April 8, 2019).
Emergency Planning
and Community
Right-to-Know Act
(EPCRA) - Section
313
Requires annual reporting from facilities in
specific industry sectors that employ 10 or
more full-time equivalent employees and that
manufacture, process or otherwise use a TRI-
listed chemical in quantities above threshold
levels. A facility that meets reporting
requirements must submit a reporting form for
each chemical for which it triggered reporting,
providing data across a variety of categories,
including activities and uses of the chemical,
releases and other waste management (e.g.,
quantities recycled, treated, combusted) and
1,3-Butadiene is a listed substance
subject to reporting requirements under
40 CFR 372.65. effective as of Januarv
01, 1987.
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Statutes/Regulations
Description of Authority/Regulation
Description of Regulation
pollution prevention activities (under Section
6607 of the Pollution Prevention Act). These
data include on- and off-site data as well as
multimedia data (i.e., air, land and water).
Clean Air Act (CAA)
- Section 112(b)
Defines the original list of 189 hazardous air
pollutants (HAPs). Under 112(c) of the CAA,
EPA must identify and list source categories
that emit HAPs and then set emission
standards for those listed source categories
under CAA Section 112(d). CAA Section
112(b)(3)(A) specifies that any person may
petition the Administrator to modify the list of
HAPs by adding or deleting a substance.
Since 1990, EPA has removed two pollutants
from the original list leaving 187 at present.
1,3-Butadiene is listed as a HAP (42
^ I* - 4e Sectio.s ML').
Clean Air Act (CAA)
- Section 112(d)
Directs EPA to establish, by rule, NESHAPs
for each category or subcategory of listed
major sources and area sources of HAPs
(listed pursuant to Section 112(c)). For major
sources, the standards must require the
maximum degree of emission reduction that
EPA determines is achievable by each
particular source category. This is generally
referred to as maximum achievable control
technology (MACT). For area sources, the
standards must require generally achievable
control technology (GACT) though may
require MACT.
EPA has established NESHAPs for a
number of source categories that emit
1,3-butadiene to air.
Clean Air Act (CAA) -
Sections 112(d) and
112(f)
Risk and technology review (RTR) of Section
112(d) national emission standards for
hazardous air pollutants (NESHAP). Section
112(f)(2) requires EPA to conduct risk
assessments for each source category subject
to Section 112(d) NESHAP that require
maximum achievable control technology
(MACT), and to determine if additional
standards are needed to reduce remaining
risks. Section 112(d)(6) requires EPA to
review and revise the emission standards, as
necessary, taking into account developments
in practices, processes and control
technologies.
EPA has promulgated a number of
RTR NESHAP and will do so, as
required, for the remaining source
categories with NESHAP.
Clean Air Act (CAA) -
Section 183(e)
Section 183(e) requires EPA to list the
categories of consumer and commercial
products that account for at least 80% of all
VOC emissions in areas that violate the
National Ambient Air Quality Standards
(NAAQS) for ozone and to issue standards for
these categories that require "best available
controls." In lieu of regulations, EPA may
1,3-Butadiene is listed under the
National Volatile Organic Compound
Emission Standards for Aerosol
Coatings ("40 CFR Dart 59. subpart EV
1,3-Butadiene has a reactivity factor of
13.58 g03/g VOC.
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Statutes/Regulations
Description of Authority/Regulation
Description of Regulation
issue control techniques guidelines if the
guidelines are determined to be substantially
as effective as regulations.
Safe Drinking Water
Act (SDWA) -
Section 1412(b)
Every 5 years, EPA must publish a list of
contaminants that: (1) are currently
unregulated, (2) are known or anticipated to
occur in public water systems (PWSs) and (3)
may require regulations under SDWA. EPA
must also determine whether to regulate at
least five contaminants from the list every 5
years.
1,3-Butadiene was identified on both
the Third (2009) and Fourth (2016)
Contaminant Candidate Lists (CCL)
(Mi;;* October 8, 2009) (81
! K SK«>9, November 17, 2016).
Safe Drinking Water
Act (SDWA) -
Section 1445(a)
Every 5 years, EPA must issue a new list of
no more than 30 unregulated contaminants to
be monitored by PWSs. The data obtained
must be entered into the National Drinking
Water Contaminant Occurrence Database.
1,3-Butadiene was identified in the
Third Unregulated Contaminant
Monitoring Rule (UCMR3), issued in
2012 (77 FR 26071. Mav 2. 2012).
Comprehensive
Environmental
Response,
Compensation and
Liability Act
(CERCLA) - Sections
102(a) and 103
Authorizes EPA to promulgate regulations
designating as hazardous substances those
substances which, when released into the
environment, may present substantial danger
to the public health or welfare or the
environment.
EPA must also promulgate regulations
establishing the quantity of any hazardous
substance the release of which must be
reported under Section 103.
Section 103 requires persons in charge of
vessels or facilities to report to the National
Response Center if they have knowledge of a
release of a hazardous substance above the
reportable quantity threshold.
1,3-Butadiene is a hazardous substance
under CERCLA. Releases of 1,3-
butadiene in excess of 10 lb must be
reported (40 CFR 302.4).
Superfund
Amendments and
Reauthorization Act
(SARA)
Requires the Agency to revise the hazardous
ranking system and update the National
Priorities List of hazardous waste sites,
increases state and citizen involvement in the
superfund program and provides new
enforcement authorities and settlement tools.
1.3-Butadiene is listed on SARA, an
amendment to CERCLA and the
CERCLA Priority List of Hazardous
Substances. This list includes
substances most commonly found at
facilities on the CERCLA National
Priorities List (NPL) that have been
deemed to pose the greatest threat to
public health.
Oilier federal slalules ivijukilions
Occupational Safety
and Health Act
(OSHA)
Requires employers to provide their workers
with a place of employment free from
recognized hazards to safety and health, such
as exposure to toxic chemicals, excessive
noise levels, mechanical dangers, heat or cold
stress or unsanitary conditions (29 U.S.C
Section 651 et seq.).
OSHA established a PEL for 1,3-
butadiene of 1 ppm / 5 ppm short-term
exposure limit (STEL) as an 8-hour,
TWA (29 CI ).
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Statutes/Regulations
Description of Authority/Regulation
Description of Regulation
Under the Act, OSHA can issue occupational
safety and health standards including such
provisions as Permissible Exposure Limits
(PELs), exposure monitoring, engineering and
administrative control measures, and
respiratory protection.
2901 B.2 State Laws and Regulations
2902
2903 Table Apx B-2. State Laws and Regulations
State Actions
Description of Action
State Air Regulations
Allowable Ambient Levels: New Hampshire (Env-A 1400: Regulated Toxic Air
Pollutants). Rhode Island (Air Pollution Regulation No. 22).
State PELs
California ("PEL of 1 ppm and a STEL of 5) (Cal Code Rees. Title 8. § 5155)
Hawaii PEL: 1 ppm ("Hawaii Administrative Rules Section 12-60-50).
State Right-to-Know
Acts
Massachusetts (105 Code Mass. Rees. § 670.000 Appendix A). New Jersev ("N.J.A.C.
) and Pennsylvania ( Jo. 159 and 34 Pa. Code § 323).
Chemicals of High
Concern to Children
Two states have adopted reporting laws for chemicals in children's products containing
1.3-butadiene, including Maine (38 MRS A Chapter 16-D) and Minnesota (Toxic Free
Kids Act Minn. Stat. 116.9401 to 116.9407).
Other
California listed 1,3-butadiene on Proposition 65 in 1998 due to cancer, and in 2004 due
to developmental toxicity and female/male reproductive toxicity (Cal Code Rees. Title
27. § 27001).
1,3-Butadiene is listed as a Candidate Chemical under California's Safer Consumer
Products Program established under Health and Safety Code § 25252 and 25253
(California. Candidate Chemicals List. Accessed April 15. 2019).
California lists 1,3-butadiene as a designated priority chemical for biomonitoring under
criteria established bv California SB 1379 (Biomonitorine California, Priority
Chemicals. February 2019).
1.3-Butadiene is on the MA Toxic Use Reduction Act (TURA) list of 2019 ( dR
)).
2904
2905
2906
B.3 International Laws and Regulations
Table Apx B-3. International
Laws and Regulations
Country/ Tribe/ Organization
Requirements and Restrictions
Canada
1.3-Butadiene is on the (CEPA 1999
Schedule 1).
Other regulations include:
Canada's National Pollutant Release Inventory (NPRI) Part 1A as a VOC.
European Union
1,3-Butadiene is registered for use in the EU with no restrictions
CoRAP (Final).
1,3-Butadiene was evaluated under the 2014 Community rolling action plan
(CoRAP) under regulation European Commission (EC) Nol907/2006. -
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Country/ Tribe/ Organization
Requirements and Restrictions
REACH (Registration, Evaluation, Authorisation and Restriction of
Chemicals). European Chemical Agencv (ECHA) database. Accessed April
10, 2019.
Australia
1,3-Butadiene was assessed under Human Health Tier II of the Inventory
Multi-Tiered Assessment and Prioritisation (IMAP). Uses reported include:
• Producing synthetic rubber (used to manufacture automotive tires and tire
products);
• Producing plastics such as acrylics, high impact polystyrene and
acrylonitrile butadiene styrene (ABS) resin plastics, nylon and neoprene;
• Producing resins;
• Processing petroleum;
• As a chemical intermediate in producing some fungicides; and
• In manufacturing latex adhesives and paints
fNICNAS. 2013. Human Health Tier II assessment for 1.3-butadiene.
Accessed April 16, 2019).
Japan
1,3-Butadiene is regulated in Japan under the following legislation:
Act on the Evaluation of Chemical Substances and Regulation of Their
Manufacture, etc. ("Chemical Substances Control Law; CSCL)
Act on Confirmation, etc. of Release Amounts of Specific Chemical
Substances in the Environment and Promotion of Improvements to the
Management Thereof
Industrial Safety and Health Act (ISHA)
Air Pollution Control Law
(Accessed April 10, 2019.)
Basel Convention
Solid Plastic Waste is listed as a cateaorv of waste under the Basel
Convention. Although the United States is not currently a partv to the Basel
Convention, this treaty still affects U.S. importers and exporters.
Australia, Austria, Belgium,
Canada, Denmark, European
Union, Finland, France,
Germany, Hungary, Ireland,
Latvia, New Zealand,
People's Republic of China,
Poland, Romania, Singapore,
South Korea, Spain, Sweden,
Switzerland, The
Netherlands, United Kingdom
Occupational exposure limits for 1,3-butadiene (GESTIS International limit
values for chemical aaents (Occupational exposure limits. OELs database.
Accessed April 16, 2019).
2907 B.4 Government Assessment History
2908 Only governmental assessments published since 2000 are included in the below table. This list
2909 represents prominent assessments referenced either directly or indirectly by this risk evaluation or
2910 supporting documents and others identified through the systematic review process. It does not include
2911 private organizational or academic assessments and may not be inclusive of every single national or
2912 international governmental assessment.
2913
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2914 Table Apx B-4. Assessment History of 1,3-Butadiene
Authoring Organization
Publication
LIW puhlicliIions
L .S. LIW Office of Pollution Pre\eiition and Toxics
(OPPT)
TSCA Work Plan for Chemical Assessments. 2U14
Update (U.S. EPA. 2014b)
U.S. EPA, Office of Research and Development (ORD)
Health Assessment of 1.3-Butadiene (U.S. EPA,
2002b)
Oilier I S
agencies
Agency for Toxic Substances and Disease Registry
(ATSDR)
Toxicoloaical Profile for 1.3-Butadiene (ATSDR.
2012)
I S. States
California, California Environmental Protection
Agency, Office of Environmental Health Hazard
Assessments
1.3-Butadiene Reference Exposure Levels (OEHHA,
2013)
Texas, Texas Commission on Environmental Quality
A Chronic Reference Value for 1,3-Butadiene Based
on an Updated Noncancer Toxicitv Assessment (Grant
et ah. 2010)
International
Australia, Australian Department of Health, National
Industrial Chemicals Notification and Assessment
Scheme (NICNAS)
1,3-Butadiene. Human health tier 11 assessment
(NICNAS. 2013)
International Agency for Research on Cancer (IARC),
IARC monograph
Chemical agents and related occupations: A review of
human carcinogens (IARC, 2012)
Netherlands, National Institute for Public Health and
the Environment
Environmental risk limits for 1.3-butadiene (RIVM,
2009)
European Union, European Chemicals Bureau, Institute
for Health and Consumer Protection
European Union risk assessment report: 1,3-Butadiene
(ECB. 2002)
World Health Organization (WHO)
1.3-Butadiene: Human health aspects (WHO, 2001)
Canada, Environment Canada, Health Canada
Priority Substances List Assessment Report: 1,3-
Butadiene (Health Canada, 2000)
2915
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Appendix C LIST OF TECHNICAL SUPPORT DOCUMENTS
The below list indicates all technical support documents associated with this risk evaluation. These
include discipline-specific assessments, systematic review results, risk calculations, modeling outputs,
public communication documents, etc. Files are numbered corresponding with the filenames uploaded to
the docket: https://www.reeulations.gov/docket/1 Q-OPPT-2024-0425
2. Draft Charge Questions to the SACC for 1,3-Butadiene
Associated Technical Support Documents - Provide additional details and information on physical
chemistry, fate, exposure, hazard, and risk assessments.
3. Draft Physical Chemistry, Fate, and Transport Assessment for 1,3-Butadiene (U.S. EPA. 2024z)
4. Draft Environmental Release and Occupational Exposure Assessment for 1,3-Butadiene (U.S.
EPA. 2024v)
5. Draft Environmental Media Concentrations for 1,3-Butadiene ( 2024p)
6. Draft General Population Exposure for 1,3-Butadiene ( J024r)
7. Draft Human Health Hazard Assessment for 1,3-Butadiene ( 24t)
Associated Systematic Review Protocol and Data Quality Evaluation and Data Extraction
Documents - Provide additional detail and information on systematic review methodologies used as
well as the data quality evaluations and extractions criteria and results.
8. Draft Systematic Review Protocol for 1,3-Butadiene ( 24ac) - In lieu of an update to
the Draft Systematic Review Protocol Supporting TSCA Risk Evaluations for Chemical Substances,
also referred to as the "2021 Draft Systematic Review Protocol" (I. c. < i1 \ 2021a), this systematic
review protocol for the Draft Risk Evaluation for 1,3-Butadiene describes some clarifications and
different approaches that were implemented than those described in the 2021 Draft Systematic
Review Protocol in response to (1) SACC comments, (2) public comments, or (3) to reflect
chemical-specific risk evaluation needs. This supplemental file may also be referred to as the "1,3-
Butadiene Systematic Review Protocol."
9. Draft Data Quality Evaluation and Data Extraction Information for Physical and Chemical
Properties for 1,3-Butadiene ( 41) - Provides a compilation of tables for the data
extraction and data quality evaluation information for 1,3-butadiene. Each table shows the data
point, set, or information element that was extracted and evaluated from a data source that has
information relevant for the evaluation of physical and chemical properties. This supplemental file
may also be referred to as the "1,3-Butadiene Data Quality Evaluation and Data Extraction
Information for Physical and Chemical Properties."
10. Draft Data Quality Evaluation and Data Extraction Information for Environmental Fate and
Transport for 1,3-Butadiene ( 2024D - Provides a compilation of tables for the data
extraction and data quality evaluation information for 1,3-butadiene. Each table shows the data
point, set, or information element that was extracted and evaluated from a data source that has
information relevant for the evaluation for Environmental Fate and Transport. This supplemental file
may also be referred to as the "1,3-Butadiene Data Quality Evaluation and Data Extraction
Information for Environmental Fate and Transport."
11. Draft Data Quality Evaluation and Data Extraction Information for Environmental Release and
Occupational Exposure for 1,3-Butadiene ( 024k) - Provides a compilation of tables for
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the data extraction and data quality evaluation information for 1,3-butadiene. Each table shows the
data point, set, or information element that was extracted and evaluated from a data source that has
information relevant for the evaluation of environmental release and occupational exposure. This
supplemental file may also be referred to as the "1,3-Butadiene Data Quality Evaluation and Data
Extraction Information for Environmental Release and Occupational Exposure."
12. Draft Data Quality Evaluation Information for General Population, Consumer, and
Environmental Exposure for 1,3-Butadiene ( 2024m) - Provides a compilation of tables
for the data extraction for 1,3-butadiene. Each table shows the data point, set, or information element
that was extracted from a data source that has information relevant for the evaluation of general
population, consumer, and environmental exposure. This supplemental file may also be referred to as
the "1,3-Butadiene Data Extraction Information for General Population, Consumer, and
Environmental Exposure."
13. Draft Data Extraction Information for General Population, Consumer, and Environmental
Exposure for 1,3-Butadiene ( 024h) - Provides a compilation of tables for the data
quality evaluation information for 1,3-butadiene. Each table shows the data point, set, or information
element that was evaluated from a data source that has information relevant for the evaluation of
general population, consumer, and environmental exposure. This supplemental file may also be
referred to as the "1,3-Butadiene Data Quality Evaluation Information for General Population,
Consumer, and Environmental Exposure."
14. Draft Data Further Filtering Results for Human Health Hazard Animal Toxicology and
Epidemiology for 1,3-Butadiene ( 2024q) - Provides a compilation of tables for study-
wide summary information for 1,3-butadiene human health hazard studies. This information was
used to "filter" studies that met PECO criteria to determine which studies should undergo data
evaluation and extraction based on whether they could potentially support dose-response analysis.
This supplemental file may also be referred to as the "1,3-Butadiene Further Filtering Results for
Human Health Hazard."
15. Draft Data Quality Evaluation Information for Human Health Hazard Epidemiology for 1,3-
Butadiene ( ) - Provides a compilation of tables for the data quality evaluation
information for DIDP. Each table shows the data point, set, or information element that was
evaluated from a data source that has information relevant for the evaluation of epidemiological
information. This supplemental file may also be referred to as the "1,3-Butadiene Data Quality
Evaluation Information for Human Health Hazard Epidemiology."
16. Draft Data Quality Evaluation Information for Human Health Hazard Animal Toxicology for
1,3-Butadiene ( 2024m) - Provides a compilation of tables for the data quality evaluation
information for 1,3-butadiene. Each table shows the data point, set, or information element that was
evaluated from a data source that has information relevant for the evaluation of human health hazard
animal toxicity information. This supplemental file may also be referred to as the "1,3-Butadiene
Data Quality Evaluation Information for Human Health Hazard Animal Toxicology."
17. Draft Data Extraction Information for Human Health Hazard Animal Toxicology and
Epidemiology for 1,3-Butadiene ( 2024i) - Provides a compilation of tables for the data
extraction for 1,3-butadiene. Each table shows the data point, set, or information element that was
extracted from a data source that has information relevant for the evaluation human health hazard
animal toxicology and epidemiology information. In contrast with other risk evaluations, this file
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contains dose-response information for every assessed endpoint within each animal toxicology
study. This supplemental file may also be referred to as the "1,3-Butadiene Data Extraction
Information for Environmental Hazard and Human Health Hazard Animal Toxicology and
Epidemiology."
Associated Quantitative Analysis Supplemental Documents:
18. Draft EPI Suite Modeling Results Supporting Fate Assessment for 1,3-Butadiene (
2024af)
19. Draft Ambient Monitoring Technology Information Center (AMTIC) Monitoring Data 2016 to
2021 for 1,3-Butadiene ( )24f)
20. Draft Water Quality Portal (WOP) Monitoring Data 2011 to 2023for 1,3-Butadiene (U.S. EPA.
2024ad)
21. Draft Land Releases for 1,3-Butadiene ( I024v)
22. Draft Water Releases for 1,3-Butadiene ( 2024ae)
23. Draft Air Releases (TRI) for 1,3-Butadiene ( 2024e)
24. Draft Air Releases (NEI2017) for 1,3-Butadiene (1 c< } V \ JO- I.)
25. Draft Air Releases (NEI 2020) for 1,3-Butadiene ( 024d)
26. Draft Adhesive s and Sealants Release Model for 1,3-Butadiene ( 024b)
27. Draft Number of Sites for 1,3-Butadiene ( 24x)
28. Draft Benchmark Dose Modeling Results for 1,3-Butadiene ( 024e)
29. Draft Lifetable Analysis of Leukemia and Bladder Cancer for 1,3-Butadiene ( 24w)
30. Modified Lifetable Analysis of Leukemia and Bladder Cancer for 1,3-Butadiene (
2024ae)
31. Draft Risk Calculator for Occupational Exposures for 1,3-Butadiene ( 24aa)
32. Draft Integrated Indoor Outdoor Air Calculator (IIOAC) TRI 2016-2021 Exposure and Risk
Analysis for 1,3-Butadiene ( )24u)
33. Draft Human Exposure Model (HEM) TRI 2016-2021 Exposure and Risk Analysis for 1,3-
Butadiene (U.S. EPA. 2024s)
34. 1,3-Butadiene: Corrected Lifetable Analyses for Leukemia and Bladder Cancer (U.S. EPA.
2024a)
35. Draft Supplemental Information on the Human Exposure Modeling Results for 1,3-Butadiene
( A. 2024ab)
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3063 36. Draft Nontechnical Summary for 1,3-Butadiene
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3064 Appendix D UPDATES TO THE 1,3-BUTADIENE CONDITIONS OF
3065 USE TABLES
3066 After the final scope, EPA received updated submissions under the 2020 Chemical Data Reporting
3067 (CDR) reported data. Therefore, EPA is amending the description of certain 1,3-butadiene COUs based
3068 on the new submissions, expanding subcategories to accurately represent EPA's understanding of the
3069 use, and consolidating categories already covered in the COU table. Also, EPA is amending an error to a
3070 COU in the final scope document.
3071
3072 TableApx D-l. Additions and Name Changes to Categories and Subcategories of Conditions of
3073 Use Based on CDR Reporting and Stakeholder Engagement
Life Cycle
Stage and
Category
Original Subcategory
in the Final Scope
Document
Occurred Change
Revised Subcategory in the 2024 Draft
Risk Evaluation
Processing;
incorporation
into
formulation,
mixture, or
reaction product
Other: Paints and
coatings manufacturing
Expanded category and
associated subcategory to
more accurately represent
EPA's understanding of the
use and based on public
comments. Added
"Intermediate in: Paint and
coating manufacturing"
Processing - Incorporation into
formulation, mixture, or reaction product -
Other (paint and coating manufacturing)
And
Processing - Processing as a reactant -
Intermediate (paint and coating
manufacturing)
Processing;
repackaging
N/A
Added subcategory to reflect
updates from 2020 CDR
reporting cycle.
Processing - Repackaging - Monomer
(synthetic rubber manufacturing)
Industrial Use;
Processing aids,
specific
to petroleum
production
Hydraulic fracturing
fluids
Removed "Hydraulic
fracturing fluids" 1,3-
butadiene is not used for
hydraulic fracturing for oil
and gas.
N/A
Commercial
Use
Plastic and rubber
products not covered
elsewhere, including
rubber tires
Replaced "plastic and rubber
products not covered
elsewhere" with new
subcategories based on
updates to CDR reporting
and the 2020 CDR reporting
cycle.
Commercial use - Other articles with
routine direct contact during normal use
including rubber articles; plastic articles
(hard);
Commercial use - Toys intended for
children's use (and child dedicated
articles), including fabrics, textiles, and
apparel; or plastic articles (hard);
Commercial use - Synthetic Rubber (e.g.,
rubber tires);
Commercial use - Furniture & furnishings
including stone, plaster, cement, glass and
ceramic articles; metal articles; or rubber
articles;
And
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Life Cycle
Stage and
Category
Original Subcategory
in the Final Scope
Document
Occurred Change
Revised Subcategory in the 2024 Draft
Risk Evaluation
Commercial use - Packaging (excluding
food packaging), including rubber articles;
plastic articles (hard); plastic articles (soft)
Commercial
Use
Other: Monomer used in
polymerization process
Consolidated category and
associated subcategory under
"Processing as a reactant;
Intermediate" EPA believes
this use is already covered,
this is not a commercial use,
and is consolidating to avoid
duplication.
Processing - Processing as a reactant -
Intermediate
Consumer Use
Plastic and rubber
products not covered
elsewhere
Replaced "plastic and rubber
products not covered
elsewhere" with new
subcategories based on
updates to CDR reporting
and the 2020 CDR reporting
cycle.
Consumer Use - Other articles with routine
direct contact during normal use including
rubber articles; plastic articles (hard);
Consumer Use - Toys intended for
children's use (and child dedicated
articles), including fabrics, textiles, and
apparel; or plastic articles (hard);
Consumer Use - Synthetic Rubber (e.g.,
rubber tires);
Consumer Use - Furniture & furnishings
including stone, plaster, cement, glass and
ceramic articles; metal articles; or rubber
articles;
And
Consumer Use - Packaging (excluding
food packaging), including rubber articles;
plastic articles (hard); plastic articles (soft)
As indicated in the Table Apx D-l, the changes are based on close examination of the CDR reports,
including the 2020 CDR reports that were received after the scope was completed, additional research
on the conditions of use, additional comments from stakeholders, and overall systematic review of the
use information.
In addition, EPA did further analysis of the following conditions of use, which resulted in the changes
presented on the table which warrant further explanation because these COUs were changed
significantly between the final scope and the draft risk evaluation:
• "Processing; Processing as a reactant - Intermediate in: Paint and coating manufacturing" -
EPA expanded this paint and coating manufacturing use to include both "incorporation into
formulation, mixture, or reaction product" and "processing as a reactant." The original COU
represented in the scope document, "incorporation into formulation, mixture, or reaction
product," was included based on public comments. A commenter stated that manufacturers note
residual amounts of 1,3-butadiene in architectural paints and coatings (EPA-HQ-OPPT-2018-
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0451-0005) However, "processing as a reactant - Intermediate in: paint and coating
manufacturing" more accurately represent 1,3 butadiene's function in these uses. Although 1,3-
butadiene monomer is not directly incorporated into paints and coatings, rather a 1,3-butadiene
polymer, residual 1,3-butadiene may be present.
• "Industrial Use - Processing aids, specific to petroleum production - Hydraulic fracturing
fluids"- Hydraulic Fracturing was added to the COU table in response to a public comment
EPA- HQ-2019-0131-0036. The commenters stated that since 1,3-butadiene is listed in EPA's
Hydraulic fracturing for oil and gas: Impacts from the hydraulic fracturing water cycle on
drinking water resources in the United States, 1,3-butadiene should be included in the COU table
in the scope. On checking the source from EPA's hydraulic fracturing report, FracFocus, 1,3-
butadiene is not listed, instead a different chemical, Benzene, ethenyl-, polymer with 2-methyl-
1,3-butadiene, hydrogenated (CASRN 68648-89-5) was listed in the report. The 2020 CDR data
also did not report the use of 1,3-butadiene in hydraulic fracturing fluid. As a result, hydraulic
fracturing was removed from the COU table.
• "Consumer Use; Plastic and rubber products not covered elsewhere " - EPA updated the table
to reflect the most recent CDR reporting codes. These COUs are broken up into five
subcategories: "Other articles with routine direct contact during normal use including rubber
articles; plastic articles (hard);" "Toys intended for children's use (and child dedicated articles),
including fabrics, textiles, and apparel; or plastic articles (hard);" "Synthetic Rubber (e.g., rubber
tires);" "Furniture & furnishings including stone, plaster, cement, glass and ceramic articles;
metal articles; or rubber articles;" and "Packaging (excluding food packaging), including rubber
articles; plastic articles (hard); plastic articles (soft)." In addition, these COUs were reported in
2020 CDR as commercial use, but not all were reported as consumer use. However, EPA is
assuming that if these products are in commercial use they could also be available for consumer
use.
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Appendix E CONDITIONS OF USE DESCRIPTIONS
The following descriptions are intended to include examples of uses, so as not to exclude other activities
that may also be included in the COUs of the chemical substance. To better describe the COU, EPA
considered CDR submissions from the last two CDR cycles for 1,3-butadiene (CASRN 106-99-0) and
the COU descriptions reflect what EPA identified as the best fit for that submission.
E.l Manufacturing - Domestic Manufacturing
Domestic manufacture means to produce 1,3-butadiene within the United States. For purposes of the
1,3-butadiene risk evaluation, this includes the extraction of 1,3-butadiene from a previously existing
chemical substance or complex combination of chemical substances, and loading/unloading and
repackaging (but not transport) associated with the manufacturing and production of 1,3-butadiene.
1,3-Butadiene can be produced by three processes: catalytic dehydrogenation of n-butane and n-butene,
oxidative dehydrogenation of n-butene, and in the process of the steam cracking of hydrocarbon streams
for ethylene production. The most common method is as a co-product during ethylene production (Sun
and Wristers. 2002). The process can use a variety of hydrocarbon feedstocks, the heavier fractions
generally giving a higher yield of 1,3-butadiene/amount of ethylene produced (Miller and Villaume.
1978).
Examples of CDR Submissions
In the 2016 CDR, nine companies reported domestic manufacturing of 1,3-butadiene with all
manufacturers producing a liquid or a gas/vapor. In the 2020 CDR, eight companies reported importing
of 1,3-butadiene with all manufacturers producing a liquid or a gas/vapor.
E.2 Manufacturing - Importing
Import refers to the import of 1,3-butadiene into the customs territory of the United States. In general,
chemicals may be imported into the United States in bulk via water, air, land, and intermodal shipments,
and loading and repackaging (but not transport) associated with the import of 1,3-butadiene. These
shipments take the form of oceangoing chemical tankers, railcars, tank trucks, and intermodal tank
containers (U.S. EPA. 2021b). 1,3-Butadiene is primarily shipped in pressurized containers via railroads
or tankers (Sun and Wristers. 2002). Other forms of transport include pipeline and barge (National
Toxicolov \ PiovMin fNTPl 1999).
Examples of CDR Submissions
In the 2016 CDR, nine companies reported importing of 1,3-butadiene with all importing a liquid or
gas/vapor. In the 2020 CDR, nine companies reported importing of 1,3-butadiene with all importing a
liquid or gas/vapor.
E.3 Processing - Reactant - Intermediate in: Adhesive Manufacturing; All
Other Basic Organic Chemical Manufacturing; Fuel Binder for Solid
Rocket Fuels; Organic Fiber Manufacturing; Petrochemical
Manufacturing; Petroleum Refineries; Plastic Material and Resin
Manufacturing; Propellant Manufacturing; Synthetic Rubber
Manufacturing; Paint and Coating Manufacturing, Wholesale and
Retail Trade
Processing as a reactant includes the polymerization of 1,3-butadiene with itself or with other monomers
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(Sun and Wristers. 2002). Some of the common polymers derived from the use of 1,3-butadiene as a
monomer feedstock are:
• Polybutadiene
• Hydroxyl-terminated polybutadiene
• Styrene-butadiene rubber
• Styrene-butadiene latex
• Acrylonitrile-butadiene-styrene polymer
The general process at polymerization sites is unloading of 1,3-butadiene, a washing or purification step
to remove polymerization inhibitors, then the different monomers are added to the reactor. After
completion of reaction, the content of unreacted monomer may vary depending on the reactions and
additives used. Typically, this may be followed with a butadiene monomer recovery system to recycle
1,3-butadiene back to feed into the reactor. Polymer production can be done either via emulsion
polymerization or solution polymerization depending on the end product use. The final polymer
products may be packaged to sale to downstream users ( 96). This polymerization product
is incorporated into various rubber and plastic articles.
EPA received information on ways 1,3-butadiene is used as a chemical intermediate (EPA-HQ-OPPT-
2018-0451-0021). One use is in the production of Nylon. In this process, 1,3-butadiene is subjected to
direct hydrocyanation to form pentenitrile compounds and adiponitrile, which are further hydrocyanated
to form hexamethylenediamine. This compound is polymerized to manufacture nylon resins. Another
process in which 1,3-butadiene is used as a chemical intermediate is in the production of neoprene
rubber which involves 1,3-butadiene being chlorinated to form chloroprene, which is then polymerized
to form neoprene. 1,3-Butadiene is also used to produce 1,4-hexadiene (used to create ethylene-
propylene terpolymer), sulfolane (an extraction solvent), and 1,5,9-cyclodecatriene (used in the
production of nylon fibers and resins). Interagency and intra-agency comments indicate that 1,3-
butadiene is also processed as a reactant in propellant manufacturing by the United States Department of
Defense (DOD).
The CDR product category code for fuels and related products includes cooking and heating fuels, fuel
additives, and vehicle and appliance fuels. EPA did not identify information on how 1,3-butadiene is
used in fuels and related products. The National Library of Medicine's Hazardous Substance Databank
(HSDB) confirms that polybutadiene (a polymer formed from the polymerization of 1,3-butadiene) is
used as a matrix for rocket propellant as a binder, rather than the 1,3-butadiene monomer itself (NLM.
2003).
Examples of CDR Submissions
In the 2016 CDR, 13 companies reported processing as a reactant of 1,3-butadiene as an intermediate in:
adhesive manufacturing, all other basic organic chemical manufacturing, fuel binder for solid rocket
fuels; organic fiber manufacturing, petrochemical manufacturing, petroleum refineries, plastic material
and resin manufacturing, propellant manufacturing, synthetic rubber manufacturing, and wholesale and
retail trade. In the 2020 CDR, 10 companies for 1,3-butadiene reported processing as a reactant as an
intermediate: for all other basic organic chemical manufacturing, organic fiber manufacturing,
petrochemical manufacturing, petroleum refineries, plastic material and resin manufacturing, and
synthetic rubber manufacturing. EPA is aware of one company reporting use of 1,3-butadiene as an
"intermediate in non-incorporative activities: intermediate in wholesale and retail trade" in the 2020
CDR data. EPA is aware it was reported differently from the 2016 CDR data. However, based on EPA's
understanding of 1,3-butadiene's use, EPA is keeping this COU as a reactant rather than an intermediate
in non-incorporative activities.
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E.4 Processing - Reactant - Monomer Used in Polymerization Process in:
Synthetic Rubber Manufacturing; Plastic Material and Resin
Manufacturing
As discussed previously, processing as a reactant includes the polymerization of 1,3-butadiene with
itself or with other monomers (Sun and Wristers. 2002). 1,3-Butadiene is most commonly used as a
monomer in polymerization processes, often to produce rubbers and plastics such as styrene-butadiene,
polybutadiene, acrylonitrile-butadiene-styrene, and nitrile rubber (Sun and Wristers. 2002). During this
process, dry solvent, initiator, other monomers, and 1,3-butadiene are loaded into a reactor until all
monomers are depleted. Then, the chain ends are terminated, and the resulting polymer solution is
pumped to a blend tank. These processes can be run in batch or continuous operation (EPA-HQ-OPPT-
2018-0451-0022).
These polymers, such as acrylonitrile butadiene styrene (ABS), polybutadiene, and styrene-butadiene,
are manufactured using 1,3-butadiene, and are often involved in compounding processes to produce
final plastic and rubber products. Copolymers of styrene and butadiene containing over 45 percent 1,3-
butadiene possess rubber like properties and copolymers containing over 45 percent styrene having
plastic or latex like qualities (IJ..S J.'!1A Unreacted 1,3-butadiene monomer is recovered and
recycled during the process and according to public comments, synthetic rubber such as butadiene
rubber (BR) and solution styrene butadiene rubber (SSBR) polymers contain less than 50 ppb of residual
1,3-butadiene monomer (EPA-HQ-OPPT-2018-0451-0027).
Examples of CDR Submissions
In the 2016 CDR, four companies reported processing as a reactant of 1,3-butadiene as a monomer used
in polymerization process. In the 2020 CDR, six companies reported processing as a reactant of 1,3-
butadiene as a monomer used in polymerization process. EPA is aware of one company reporting use of
1,3-butadiene as "Incorporation into a formulation, mixture, or reaction product - Monomers used in
plastic product manufacturing; Synthetic rubber Manufacturing" in the 2020 CDR data. EPA is aware it
was reported differently from the 2016 CDR data. However, based on EPA's understanding of 1,3-
butadiene's chemical properties, EPA is keeping this COU as a reactant.
E.5 Processing - Incorporation into a Formulation, Mixture, or Reaction
Product - Processing Aids, Not Otherwise Listed in: Petrochemical
Manufacturing
This COU refers to the preparation of a product; that is, the incorporation of 1,3-butadiene into a
formulation, mixture, or a reaction product which occurs when a chemical substance is added to a
product (or product mixture) after its manufacture, for distribution in commerce. 1,3-Butadiene is used
as processing aids and butadiene polymers are used in several petrochemical manufacturing operations
(I M-
Examples of CDR Submissions
In the 2016 CDR, two companies reported use of 1,3-butadiene as a processing aid, not otherwise listed
in petrochemical manufacturing. In the 2020 CDR, one company reported use of 1,3-butadiene as a
processing aid, not otherwise listed in petrochemical manufacturing.
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E.6 Processing - Incorporation into a Formulation, Mixture, or Reaction
Product - Other: Adhesive Manufacturing, Paint and Coating
Manufacturing, Petroleum Lubricating Oil and Grease
Manufacturing, and All Other Chemical Product and Preparation
Manufacturing
This COU refers to the preparation of a product; that is, the incorporation of 1,3-butadiene into a
formulation, mixture, or a reaction product, which occurs when a chemical substance is added to a
product (or product mixture) after its manufacture, for distribution in commerce. 1,3-Butadiene is used
as a processing aid and butadiene polymers are used in several petrochemical manufacturing operations,
adhesives, lubricants and in formulated paints and coatings (EPA-HQ-OPPT-2018-0451-0003; EPA-
HQ-OPPT-2018-0451 -0005; EPA-HQ-OPPT-2018-0451 -0009; EPA-HQ-OPPT-2019-0131 -0022).
This use was not reported to EPA in the 2016 or 2020 CDR reporting cycles.
E.7 Processing - Incorporation into Article - Other: Polymer in: Rubber
and Plastic Product Manufacturing
This COU refers to the preparation of an article; that is, the incorporation of 1,3-butadiene into articles,
meaning 1,3-butadiene becomes a component of the article, after its manufacture, for distribution in
commerce. 1,3-Butadiene is used as a monomer or co-monomer in the manufacture of synthetic rubbers.
These synthetic rubbers and latex are used to manufacture tires, other rubber components and plastic
materials ( b). In plastic manufacturing, the final plastic article is produced in a
conversion process that forms the compounded plastic into the finished products ( .;
OECD. 2009). The converting process is different depending on whether the plastic is a thermoplastic or
a thermosetting material (OECD. 2009). Thermoplastics converting involves the melting of the plastic
material, forming it into a new shape and then cooling it ( a; OECD. 2009). The
converting of thermoplastics may involve extrusion, injection molding, blow molding, rotational
molding or thermoforming ( i; OECD. 2009).
Examples of CDR Submissions
In the 2016 CDR, one company reported incorporation into article - Other: Polymer in: Rubber and
plastic product manufacturing. This use was not reported to the 2020 CDR reporting cycle.
E.8 Processing - Repackaging - Intermediate in: Wholesale and Retail
Trade; Monomer in: Synthetic Rubber
Repackaging refers to the preparation of 1,3-butadiene for distribution in commerce in a different form,
state, or quantity than originally received or stored by various industrial sectors, including chemical
product and preparation manufacturing, wholesale and retail trade, and laboratory chemicals
manufacturing. This COU includes the transferring of 1,3-butadiene from a bulk container into smaller
containers. This COU would not apply to the relabeling or redistribution of a chemical substance
without removing the chemical substance from the original container it was supplied in.
Examples of CDR Submissions
This use was not reported to the 2016 CDR reporting cycle. In the 2020 CDR, one company reported
repackaging 1,3-butadiene as an intermediate in wholesale and retail trade and one company reported
repackaging 1,3-butadiene as monomer in synthetic rubber manufacturing.
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E.9 Processing - Recycling
This COU refers to the process of treating generated waste streams {i.e., which would otherwise be
disposed of as waste), containing 1,3-butadiene, that are collected, either on-site or transported to a third-
party site, for commercial purpose. Recovery and recycling of unreacted 1,3-butadiene from the various
synthetic rubber manufacturing operations are common. 1,3-Butadiene and other monomers (such as
styrene) are recovered and reused in rubber manufacturing to the extent possible (ECB. 2002). EPA
notes that although 1,3-butadiene was not reported for recycling in the 2016 or 2020 CDR reporting
periods, EPA is assuming that recycling waste streams could contain 1,3-butadiene.
There are multiple ways 1,3-butadiene can be recycled during its life cycle. First, when finished 1,3-
butadiene does not meet commercial specifications, it is often combined with crude streams for energy
recovery. Similarly, when ethylene manufacturers have excess butadiene supply, they can recycle the
butadiene as a feedstock for the production of ethylene. In polymer production, unreacted butadiene-
containing monomers are recycled back to the reactors to improve the process yield.
E.lODistribution in Commerce
For purposes of assessment in this risk evaluation, distribution in commerce consists of the
transportation associated with the moving of 1,3-butadiene or 1,3-butadiene-containing products
between sites manufacturing, processing, or recycling 1,3-butadiene or 1,3-butadiene-containing
products, or to final use sites, or for final disposal of 1,3-butadiene or 1,3-butadiene-containing products.
More broadly under TSCA, "distribution in commerce" and "distribute in commerce" are defined under
TSCA section 3(5).
E.ll Industrial Use - Adhesives and Sealants, Including Epoxy Resins
This COU refers to 1,3-butadiene as it is used in various industrial sectors as a component of adhesive or
sealant mixtures, meaning the use of 1,3-butadiene after it has already been incorporated into an
adhesive and/or sealant product or mixture, as opposed to when it is used upstream, {e.g., when 1,3-
butadiene is processed into the adhesive and sealant formulation). Examples of applications for adhesive
and sealant products that are used in aerospace industrial uses include: adhesives critical to electrical and
circuit boards and pre-impregnated fiberglass or carbon reinforced fabrics and tapes, space vehicle
propellants, and epoxy resin adhesive systems for bonding and sealing of glass to metal components
(EP A-HQ-OPPT-2018-0451 -0009).
Examples of CDR Submissions
In the 2016 CDR, one company reported use of 1,3-butadiene as an intermediate in adhesive
manufacturing. This use was not reported to the 2020 CDR reporting cycle.
E.12 Commercial Use - Fuels and Related Products
This COU is referring to the commercial use of 1,3-butadiene in fuels and related products. 1,3
Butadiene is a byproduct in the refining process and in liquified petroleum gas as a result of butane
contamination. The CDR product category code for fuels and related products includes cooking and
heating fuels, fuel additives, and vehicle and appliance fuels. EPA did not identify information on how
1,3-butadiene is used in fuels and related products. Evidence was found, however, of 1,3-butadiene's
presence within butane liquified petroleum gas (LPG) product, which is used as a fuel . The safety data
sheet (SDS) for butane LPG states the product "is intended for use as a fuel in devices designed for
combustion of butane, or for use in industrial processes." LPG can be used for the same domestic,
commercial, and industrial applications as natural gas, with the largest market for LPG is the
domestic/commercial market. Further, one of the main LPG uses is in rural areas for domestic cooking
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and heating. For commercial and industrial settings, LPG is used as a primary or backup fuel in small
boilers and space heating equipment and is used to generate heat and process steam. Pressurized cylinder
sizes will vary depending on the application {i.e., larger cylinders would be used for industrial
applications vs. smaller cylinders for consumer cooking).
Examples of CDR Submissions
In the 2016 CDR, one company reported use of 1,3-butadiene as commercial use in fuels and related
products. In the 2020 CDR, one company reported the use of 1,3-butadiene as sold to re-sellers for
petroleum fuel and petrochemical industry.
E.13Commercial Use - Other Articles with Routine Direct Contact During
Normal Use Including Rubber Articles; Plastic Articles (Hard); Toys
Intended for Children's Use (and Child Dedicated Articles), Including
Fabrics, Textiles, and Apparel; or Plastic Articles (Hard); Synthetic
Rubber (e.gRubber Tires); Furniture & Furnishings Including Stone,
Plaster, Cement, Glass and Ceramic Articles; Metal Articles; Or
Rubber Articles; Packaging (Excluding Food Packaging), Including
Rubber Articles; Plastic Articles (Hard); Plastic Articles (Soft)
This COU is referring to the commercial use of 1,3-butadiene already incorporated in plastic and rubber
products not covered elsewhere. EPA understands examples of this COU could include tires, auto parts,
the medical industry, footwear, industrial goods, the construction industry, appliances, lubricants,
fabrics, wires and cables, and synthetic rubber in toys (EPA-HQ-OPPT-2018-0451-0003, EPA-HQ-
OPPT-2019-0131-0012).
Examples of CDR Submissions
In the 2016 CDR, four companies reported commercial use of 1,3-butadiene in plastic and rubber
products not covered elsewhere. After updates to the 2020 CDR reporting cycle, the subcategories
changed from the 2016 CDR reporting cycle. In the 2020 CDR, three companies reported commercial
use of 1,3-butadiene as other articles with routine direct contact during normal use including rubber
articles; plastic articles (hard); one company reported commercial use of 1,3-butadiene in toys intended
for children's use (and child dedicated articles), including fabrics, textiles, and apparel; or plastic articles
(hard); one company reported commercial use of 1,3-butadiene in synthetic rubber (e.g., rubber tires);
one company reported commercial use of 1,3-butadiene in furniture & furnishings including stone,
plaster, cement, glass and ceramic articles; metal articles; or rubber articles; one company reported
commercial use of 1,3-butadiene in packaging (excluding food packaging), including rubber articles;
plastic articles (hard); plastic articles (soft).
E.14 Commercial Use - Automotive Care Products
This COU is referring to the commercial use of 1,3-butadiene in automotive care products. Meaning the
use of 1,3-butadiene in automotive care products in a commercial setting, such as an automotive parts
business or a worker driving a vehicle, as opposed to upstream use of 1,3-butadiene (e.g., when 1,3-
butadiene-containing products are used in the manufacturing of the automotive product) or use in an
industrial setting. EPA understands that 1,3-butadiene has been used as part of a thermoplastic or as an
elastomer/elastomeric compound and production parts of an automobile, such as console assembly, air
brake valves, or seat set (EPA-HQ-OPPT-2019-0131-0022).
Examples of CDR Submissions
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In the 2016 CDR, two companies reported commercial use of 1,3-butadiene in automotive care products.
This use was not reported to the 2020 CDR reporting cycle.
E.15Commercial Use - Other Use - Laboratory Chemicals
This COU is referring to the commercial use of 1,3-butadiene in laboratory chemicals. EPA understands
1,3-butadiene could be used as a product in analytical chemistry, research, equipment calibration, and
sample preparation applications, including reference sample for analysis of terrestrial and extraterrestrial
material samples. Additionally, 1,3-butadiene could be as a component of resin products that are used in
research (EPA-HQ-OPPT-2018-0451 -0039).
This use was not reported to EPA in the 2016 or 2020 CDR reporting cycles.
E.16Commercial Use - Lubricants and Lubricant Additives
This COU is referring to the commercial use of 1,3-butadiene based polymers in lubricants and lubricant
additives, including for use as lubricant additives and viscosity modifiers (EPA-HQ-OPPT-2018-
0451 -0003; EP A-HQ-OPPT-2019-0131 -0022)
This use was not reported to EPA in the 2016 or 2020 CDR reporting cycles.
E.17Commercial Use - Paint and Coatings
This COU is referring to the commercial use of 1,3-butadiene in paints and coatings. EPA understands
1,3-butadiene to be present in architectural paints and coatings (EPA-HQ-OPPT-2018-0451-0005).
This use was not reported to EPA in the 2016 or 2020 CDR reporting cycles.
E.18Commercial Use - Adhesives and Sealants
This COU is referring to the commercial use of 1,3-butadiene in adhesives and sealants, including epoxy
resins (EP A-HQ-OPPT-2018-0451-0003; EP A-HQ-OPPT-2018-0451-0009; EPA-HQ-OPPT- 2019-
0131-0022).
This use was not reported to EPA in the 2016 or 2020 CDR reporting cycles.
E.19 Consumer Use - Other Articles with Routine Direct Contact During
Normal Use Including Rubber Articles; Plastic Articles (Hard); Toys
Intended for Children's Use (and Child Dedicated Articles), Including
Fabrics, Textiles, and Apparel; or Plastic Articles (Hard); Synthetic
Rubber (e.gRubber Tires); Furniture & Furnishings Including
Stone, Plaster, Cement, Glass and Ceramic Articles; Metal Articles; or
Rubber Articles; Packaging (Excluding Food Packaging), Including
Rubber Articles; Plastic Articles (Hard); Plastic Articles (Soft)
This COU is referring to the consumer use of 1,3-butadiene in plastic rubber products not covered
elsewhere, including rubber tires. It is estimated that more than 3 million metric tons of natural and
synthetic rubber are used annually. Half of this use volume is expected to be from the use of styrene-
butadiene-rubber (SBR). Half of this SBR is used to make tires (Burgess. 1991). In addition, plastics
containing 1,3-butadiene were identified in electronic appliances, furniture and furnishings, toys and
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recreational products, housewares, packaging, automotive parts, building materials, and 3D-printing
filament (Steinle. 2016; Pfaffli and Saamanen. 1993).
Examples of CDR Submission
In the 2016 CDR, two companies reported consumer use of 1,3-butadiene in plastic and rubber products
not covered elsewhere. This use was not reported to the 2020 CDR reporting cycle.
E.20Disposal
Each of the COUs of 1,3-butadiene may generate waste streams of the chemical. For purposes of the
1,3-butadiene risk evaluation, this COU refers to the 1,3-butadiene in a waste stream that is collected
from facilities and households and are unloaded at and treated or disposed at third-party sites. This COU
also encompasses 1,3-butadiene contained in wastewater or other wastes generated by consumer or
occupational users and discharged to a POTW or other, non-public treatment works for treatment. TRI
data indicate 1,3-butadiene may be land disposed, deep-well injected, or discharged to water following
pretreatment ( 2). Disposal may also include destruction and removal by incineration.
Streams containing 1,3-butadiene may be combined with crude streams for energy recovery when
finished 1,3-butadiene does not meet commercial specifications. Recycling of 1,3-butadiene and 1,3-
butadiene-containing products is considered a different COU. Environmental releases from industrial
sites are assessed in each COU.
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Appendix F OCCUPATIONAL EXPOSURE VALUE DERIVATION
AND ANALYTICAL METHODS USED TO DETECT
1,3-BUTADIENE
EPA has calculated an 8-hour time-weighted average (TWA) existing chemical occupational exposure
value to summarize the occupational exposure scenario and sensitive health endpoints into a single
value. This calculated value may be used to support risk management efforts for 1,3-butadiene under
TSCA section 6(a), 15 U.S.C. 2605. EPA calculated the value rounded to 0.14 ppm (0.31 mg/m3) for
inhalation exposures to 1,3-butadiene as an 8-hour TWA and for consideration in workplace settings
(see Appendix F. 1 below) based on the chronic occupational unit risk (UR) for leukemia.
TSCA requires risk evaluations to be conducted without consideration of cost and other non-risk factors,
and thus this most sensitive occupational exposure value represents a risk-only number. If risk
management for 1,3-butadiene is implemented following the final risk evaluation, EPA may consider
cost and other non-risk factors, such as technological feasibility, the availability of alternatives, and the
potential for critical or essential uses. Any existing chemical exposure limit (ECEL) used for
occupational safety risk management purposes could differ from the occupational exposure value
presented in this appendix based on additional consideration of exposures and non-risk factors consistent
with TSCA section 6(c).
This calculated value for 1,3-butadiene represents the exposure concentration below which exposed
workers and occupational non-users are not expected to exhibit any appreciable risk of adverse
toxicological outcomes. This value accounts for PESS. The value is derived based on the most sensitive
human health effect {i.e., leukemia) supported by the weight of scientific evidence. This value is
expressed relative to benchmarks and standard occupational scenario assumptions of 8 hours per day, 5
days per week exposures for a total of 250 days exposure per year, and a 40-year working life.
All hazard values used in these calculations are based on the non-cancer intermediate POD and chronic
occupational cancer UR from the Draft Human Health Hazard Assessment for 1,3-Butadiene (U.S. EPA.
2024t).
EPA expects that at the occupational exposure value of 0.14 ppm (0.31 mg/m3) for lifetime exposure,
workers and occupational non-users also would be protected against non-cancer health effects for acute,
intermediate, and chronic durations. EPA has not separately calculated a short-term occupational
exposure value (STEV) for 1,3-butadiene (see Section F.3 for details).
Of the identified occupational monitoring data for 1, 3-butadiene, there have been measured workplace
air concentrations below the calculated exposure value. A summary table of available monitoring
methods from the Occupational Safety and Health Administration (OSHA) and the National Institute for
Occupational Safety and Health (NIOSH) is included in Appendix F.2. The table presents validated
methods from governmental agencies and is not intended to be a comprehensive list of available air
monitoring methods for 1,3-butadiene. The calculated occupational exposure value is above the limit of
detection (LOD) and limit of quantification (LOQ) using at least one of the monitoring methods
identified.
The Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit (PEL)
as an 8-hour TWA for 1,3-butadiene of 1 ppm and a short-term exposure limit (STEL) of 5 ppm at a
duration of 15 minutes. However, as noted on OSHA's website, "OSHA recognizes that many of its
permissible exposure limits (PELs) are outdated and inadequate for ensuring protection of worker
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health. Most of OSHA's PELs were issued shortly after adoption of the Occupational Safety and Health
(OSH) Act in 1970 and have not been updated since that time." In addition, OSHA's PEL must undergo
both risk assessment and feasibility assessment analyses before selecting a level that will substantially
reduce risk under the Occupational Safety and Health Act. EPA's calculated exposure value is a lower
value and is based on newer information and analysis from this risk evaluation.
Other governmental agencies and independent groups have also set recommended exposure limits
established for 1, 3-butadiene. The American Conference of Governmental Industrial Hygienists
(ACGIH) has set a Threshold Limit Value (TLV) at 2 ppm TWA. While this chemical does not have a
NIOSH Recommended Exposure Limit (REL), NIOSH notes and identifies 1, 3-butadiene as a
carcinogen and lists the following guidance: "reduce exposures to lowest feasible concentrations".
F.l Occupational Exposure Value Calculations
This section presents the calculations used to estimate the occupational exposure values using inputs
derived in this risk evaluation. Multiple values are presented below for hazard endpoints based on
different exposure durations. For 1,3-butadiene, the most sensitive occupational exposure value is based
on cancer following lifetime exposure and the resulting 8-hour TWA is rounded to 0.14 ppm. The
human health hazard values (HECs, UR) used in the equations are derived in the risk evaluation draft
risk evaluation and Draft Human Health Hazard Assessment for 1,3-Butadiene ( 2024t).
Most Sensitive Occupational Exposure Value (Lifetime Cancer)
The EVcancer is the concentration at which the extra cancer risk is equivalent to the benchmark cancer
risk of lxlO"4: EPA notes that the occupational UR was corrected late in the draft risk evaluation process
( 2024a). The corrected UR is 0.0049 per ppm (2.2x 10"6 per |ig/m3), down from 0.0062 per
ppm. The value below does not reflect the corrected occupational UR. The value for EVcancer will be
corrected to reflect the lower occupational UR in the Risk Evaluation for 1,3-Butadiene.
rj.h 365d _q m3
— BenchmarkCancer ATIUR ^resting _ 1X10~4 T y * y 125|^ _ r\ -i a nnTV1
cancer UR ED*£F*wy IRworkers 6 2xl0"3 per ppm 8i—*40y 1252^ '
a y hr
9
™j f ms\ EVppm*MW 0.14 ppm*54.0916^ mg
k"cancer 1 ~ / = ~ = l = 0-31 ~
\m / Molar Volume 24.45— rn
mol
Where:
Molar Volume = 24.45 L/mol, the volume of a mole of gas at 1 atm and 25 °C
MW = Molecular weight of 1,3-butadiene (54.0916 g/mole)
Acute Non-cancer Occupational Exposure Value
EPA did not derive an acute POD for 1,3-butadiene. Therefore, no corresponding occupational exposure
value is calculated.
Intermediate Non-cancer Occupational Exposure Value
The intermediate occupational exposure value (EVintermediate) was calculated as the concentration at
which the intermediate MOE would equal the benchmark MOE for intermediate occupational exposure
using the following equation:
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EV;
HECjntej-jnedjate
intermediate
Benchmark MOEinfermediate
AThec intermediate* IRresting
ED*EF IRworkers
2.5 ppm 24/i/d*30d 0.6125 m3/hr
¦ * * ¦
30
EV;
intermediate
8h/d * 22d
&) =
1.25 m3/hr
0.17 ppm
EV ppm *MW
Molar Volume
3
0.17 ppm*54.0916—
? ^ = 0.38 -f
24.45 —
mol
m
ATur
Chronic Non-cancer Occupational Exposure Value
The hazard value (an HEC of 2.5 ppm) is the same for the intermediate and chronic occupational
exposure scenarios. The chronic occupational exposure value (EVchronic) can be calculated as the
concentration at which the chronic MOE would equal the benchmark MOE for exposures. However,
EPA has determined that because the same critical health effect applies to both intermediate and chronic
exposure contexts, the relevant averaging time should be considered equivalent across both exposure
scenarios. Therefore, the resulting EVchronic would be the same as the EVintermediate based on intermediate
exposures and EPA is presenting only the EVintermediate.
The parameters used in the above equations are described here. Numerical values chosen for the
parameters are described in relevant sections of this draft risk evaluation and Draft Human Health
Hazard Assessment for 1,3-Butadiene ( )24t).
Where:
A THECintermediate = Averaging time for the POD/HEC used for evaluating non-cancer,
intermediate occupational risk, based on study conditions and/or any
HEC adjustments (24hrs/day for 30 days)
= Averaging time for the cancer UR, based on study conditions and any
adjustments (24 hrs/day for 365 days/yr) and averaged over a lifetime
(78 yrs)
BenchmarkMOEintermediate = Intermediate non-cancer benchmark margin of exposure, based on the
total uncertainty factor of 30
= Benchmark for excess lifetime cancer risk
= Draft occupational exposure value based on reduced fetal body weight
= Draft occupational exposure value based on reduced fetal body weight
= Draft occupational exposure value based on excess cancer risk
= Exposure duration (8 hrs/day)
= Exposure frequency 22 days/yr for intermediate, 250 days/yr for
lifetime]
= Human equivalent concentration for acute, intermediate, or chronic
occupational exposure scenarios
= Occupational unit risk (per mg/m3 and per ppm)
= Inhalation rate (default is 1.25 m3/hr for workers and 0.6125 m3/hr for
the general population at rest)
= Working years per lifetime at the 95th percentile (40 yrs)
= 24.45 L/mol, the volume of a mole of gas at 1 atm and 25 °C
= Molecular weight of 1,3-butadiene (54.0916 g/mole)
Benchmarkcancer
EVintermediate
EVchronic
EVcancer
ED
EF
HEC intermediate
UR
IR
WY
Molar Volume
MW
Unit conversion:
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1 ppm = 2.2 mg/m3 (based on the molecular weight of 54.0916 g/mol for 1,3-butadiene)
F.2 Summary of Air Sampling Analytical Methods Identified
EPA conducted a search to identify relevant NIOSH, OSHA, and EPA analytical methods used to
monitor for the presence of 1,3-butadiene in air (see TableApx F-l). This table presents validated
methods from governmental agencies and is not intended to be a comprehensive list of available air
monitoring methods for 1,3-butadiene. The sources used for the search included the following:
1) NIOSH Manual of Analytical Methods (NMAM); 5th Edition
URL: https://www.cdc.eov/niosh/nmam/default.html
2) NIOSH NMAM 4th Edition
URL: https://www.cdc.gov/niosh/docs/2003-154/defaiilt.html
3) OSHA Index of Sampling and Analytical Methods
URL: https://www.osha.eov/dts/sltc/methods/
4) EPA Environmental Test Method and Monitoring Information
URL: https://www.epa.eov/measurements-modeline/index-epa4est-methods
Table Apx F-l. Limit of Detection (LOD) and Limit of Quantification (LOQ) Summary for Air
Sampling Analytical Methods Identified
Air Sampling
Analytical Methods
Year
Published
LOD"
LOQ
Notes
Source
NIOSH Method
1994
(issue 2)
0.2-0.6
(ig/sample
(3.6-90
ppb)
N/A
NIOSH Method 1024 reports the LOD
as 0.2 |_ig per sample and provides
procedures for collecting air samples
between 5 and 25 L with a flow rate of
0.01 to 0.5 L/min. Multiple media
change- outs will be required in order
to achieve the minimum LOD based on
a maximum sampling volume of 25L.
OSHA Method 56 recommends an air
sample volume of 3L and lists a
detection limit of the overall
procedure as 90 ppb, which would
make the LOD 0.6 (ig per sample.
OSHA Index
10246
of Sampling
0 [ethod 56
and Analytical
Methods
NIOSH
NMAM
4th Edition
ppm = parts per million; ppb = parts per billion; ppt = parts per trillion
a These sources cover a range of LODs both below and above the most sensitive occupational exposure value.
This method provides the LOD based on sample size. For a sample size range of 0.5L to 15L, the LOD would be
0.67 mg/m3 to 20 mg/m3. However, the LOD listed in the table can be achieved through changes of media across
an 8-hour period.
b It is common for laboratories to acquire updated equipment from the equipment used by NIOSH to develop Method
1003. Modern equipment can offer dramatically greater performance compared with the equipment available when
NIOSH 1003 was published. This can result in significantly lower LOQ/LODs. However, NIOSH does not
necessarily continually update the method because the labs are using the same general procedures with just
modified/better equipment. Therefore, the lab is permitted to report their method as "modified NIOSH Method
1003". The lab will include a record of how it modifies the method in their results.
F.3 Short-Term Occupational Exposure Value Derivation
According to Current Intelligence Bulletin 69: NIOSH Practices in Occupational Risk Assessment
(NIOSH. 2020). a short-term occupational exposure value (described as a short-term exposure limit
(STEL) in (NIOSH. 2020)) should be derived if there is a concern for effects following short-term
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exposure at 15-min concentrations. The 8-hour TWA most sensitive occupational exposure value would
prevent 15-min exposures above 32x that value (based on 32 15-min periods in 8 hours), assuming only
a single 15-min chemical exposure in one day. Therefore, if short-term health effects are expected and
can be quantified with a derived short-term occupational exposure value (STEV) lower than 32x the
most sensitive EV, implementing a short-term exposure value could be justified.
EPA did not derive an acute non-cancer hazard value for 1,3-butadiene because any options would have
low confidence and be less protective than existing exposure limits. Therefore, EPA would default to the
AEGL-1 value for determination of a STEV. The AEGL-1 value for 1,3-butadiene based on difficulty to
focus is 670 ppm (NAC/AEGL. 2009). This value is significantly higher than the 15-min TWA
occupational exposure equivalent value (Table Apx F-2), and therefore the most sensitive occupational
exposure value is already protective of any hazards specific to short-term exposure.
Table Apx F-2. Comparison between Occupational Exposure Values for 1,3-Butadiene
Value Type
Most Sensitive
Occupational Exposure
Value
(8-hour TWA)
Possible Short-term
Occupational Exposure
Value
(15-minute value)
Most Sensitive
Occupational Exposure
Value
(15-minute TWA)
Health Effect
Cancer
Difficulty to focus
Cancer
Exposure Value (ppm)
0.14
670
4.5
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Appendix G POTENTIALLY EXPOSED OR SUSCEPTIBLE
SUBPOPULATIONS CONSIDERED IN RISK
EVALUATIONS
Considerations related to PESS can influence the selection of relevant exposure pathways, the sensitivity
of derived hazard values, the inclusion of particular human populations, and the discussion of
uncertainties throughout the assessment. Evaluation of the qualitative and quantitative evidence for
PESS begins as part of the systematic review process, where any available relevant published studies
and other data are identified. If adequate and complete, this evidence informs the derivation of exposure
estimates and human health hazard endpoints/values that are protective of PESS.
EPA has identified a list of specific PESS factors that may contribute to a group having increased
exposure or biological susceptibility, such as lifestage, occupational exposures, nutrition, and lifestyle
activities. For 1,3-butadiene, the Agency identified how the risk evaluation addressed these factors as
well as any remaining uncertainties in Section 5.3.5. The full list of PESS factors and representative
examples of each are presented below in Table Apx G-l.
Table Apx G-l. PESS Factors Considered in the Risk Evaluation
PESS Factor
Examples"
Lifestage
Embryo/fetus, pregnant females, children, older adults
Pre-existing Disease
Obesity, cardiovascular disease, diabetes
Lifestyle Activities
Smoking, alcohol consumption, physical activity
Occupational Exposures
High end duration and frequency workers/ONUs;
Geography/Site-specific
Fenceline, residence/school location, historical releases
Sociodemographic Status
Race/ethnicity, socioeconomic status, sex/gender, education
Nutrition
Diet, malnutrition, subsistence fishing
Genetics/Epigenetics
Genetic polymorphisms
Unique Activities
Open burning, sweat lodge/purification ceremonies (tribal)
Aggregate Exposures
Multiple routes, multiple pathways, multiple COUs
Other Chemical and Non-
chemical stressors
Stress, adverse childhood experiences, built environment,
chemical co-exposures
ONU = occupational non-user
a Examples are not intended to be exhaustive but are illustrative of considerations for the risk evaluation.
Page 165 of 173
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3629 Appendix H GENERAL POPULATION RISK
3630 H.1 HEM Estimated 1,3-Butadiene Cancer Risks across Discrete Distances
3631
3632 Table Apx H-l. 1,3-Butadiene Cancer Risks Based on HEM 95th Percentile Modeled Concentrations from 10 to 50,000 Meters
Life ( Vcle
Stii fje
( iitejjoi'V
Subcategory
OES
1 kl 1'iieilities
I'.stitniitcil (,'nncer Risk using \I;iximum (,'onceiitriition Across Kneilities within OI'.S by Distance from All Sourees (in)
(ISased on 95th Percentile Modeled Concentrations)
Total
Risk
Above
11-06
10
30
30-60
60
100
100-1,000
1,000
2,500
5,000
1,0000
15,000
25,000
50,000
Manufacturing
Domestic
manufacturing
Domestic
manufacturing
Manufacturing
40
32
5.3E-04
9.1E-04
7.2E-04
5.1E-04
3.5E-04
6.0E-05
2.1E-05
6.1E-06
2.4E-06
9.0E-07
5.0E-07
2.4E-07
8.7E-08
Processing
Processing as a
reactant
Other: monomer
used in
polymerization
process in: plastic
material and resin
manufacturing;
manufacturing
synthetic rubber
and plastics
Plastics and
rubber
compounding
33
29
1.3E-03
1.7E-03
1.2E-03
8.4E-04
4.1E-04
3.2E-05
9.4E-06
2.2E-06
7.4E-07
2.5E-07
1.3E-07
5.8E-08
1.9E-08
Processing
Processing -
incorporation
into article
Other: polymer in:
rubber and plastic
product
manufacturing
Plastics and
rubber
converting
1
0
1.3E-17
1.3E-12
1.6E-12
1.8E-12
2.3E-12
6.5E-13
1.9E-13
8.3E-14
3.7E-14
1.6E-14
9.1E-15
4.4E-15
1.6E-15
Processing
Processing -
incorporation
into
formulation,
mixture, or
reaction
product
Processing aids,
not otherwise
listed in:
petrochemical
manufacturing
Processing -
incorporation
into
formulation,
mixture, or
reaction
product
53
25
6.8E-05
1.7E-04
1.5E-04
1.1E-04
7.6E-05
2.9E-05
1.4E-05
3.8E-06
1.5E-06
5.3E-07
2.9E-07
1.3E-07
4.9E-08
Page 166 of 173
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PUBLIC RELEASE DRAFT
November 2024
Life C Vcle
Stii fje
( iitejjoi'V
Subcategory
OES
1 kl 1'iieilities
Estimated (,'ancer Risk using Maximum Concentration Across Facilities within OI'.S by Distanee from All Sourees (in)
(ISased on 95th Percentile Modeled (,'onccntratioiis)
Total
Risk
Above
11 '.-06
10
30
30-60
60
100
100-1,000
1,000
2,500
5,000
1,0000
15,000
25,000
50,000
Processing
Processing as a
reactant
Intermediate in:
adhesive
manufacturing; all
other basic
organic chemical
manufacturing;
fuel binder for
solid rocket fuels;
organic fiber
manufacturing;
petrochemical
manufacturing;
petroleum
refineries; plastic
material and resin
manufacturing;
propellant
manufacturing;
synthetic rubber
manufacturing;
wholesale and
retail trade
Processing as
a reactant
57
43
3.7E-04
5.5E-04
4.9E-04
3.2E-04
1.4E-04
1.3E-05
3.5E-06
8.1E-07
2.7E-07
9.4E-08
5.0E-08
2.2E-08
8.1E-09
Disposal
Disposal
Disposal
Recycling
11
6
6.0E-06
1.0E-05
8.7E-06
6.4E-06
3.1E-06
3.8E-07
9.8E-08
2.4E-08
9.2E-09
3.2E-09
1.6E-09
6.6E-10
2.4E-10
Manufacturing
Import
Import
Repackaging
23
13
2.75E-04
4.14E-04
2.94E-04
1.87E-0
4
9.03E-0
5
1.08E-05
2.28E-06
5.35E-07
1.83E-07
6.35E-08
3.37E-08
1.53E-08
5.27E-09
Processing
Repackaging
Intermediate in:
wholesale and
retail trade
Disposal
Disposal
Disposal
Waste
handling,
disposal,
treatment, and
recycling
7
1
2.2E-06
3.2E-06
2.7E-06
1.7E-06
7.9E-07
9.2E-08
3.1E-08
8.9E-09
3.4E-09
1.2E-09
6.4E-10
3.0E-10
1. IE 10
Total
225
149
3633
Page 167 of 173
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PUBLIC RELEASE DRAFT
November 2024
3634 Table Apx H-2.1,3-Butadiene Cancer Risks Based on HEM 50th Percentile Modeled Concentrations from 10 to 50,000 Meters
Life ( ycli'
Stii
C iltMIOIT
Subrutcgorv
TRI l iitil itits
Ol.S
Total
Risk
Above
II '.-06
Kstimuted ( iiilet'r Risk using Maximum Concentration across 1'acilitics within OKS In Distance from All Sources (m)
(ISased on 50th Percentile Modeled Concentrations)
10
30
30-60
60
100
100-1,000
1,000
2,500
5,000
1,0000
15,000
25,000
50,000
Manufacturing
Domestic
Manufacturing
Domestic
Manufacturing
Manufacturing
40
29
2.1E-04
5.1E-04
3.5E-04
2.6E-04
1.4E-04
1.3E-05
7.5E-06
2.4E-06
9.1E-07
3.5E-07
1.9E-07
9.6E-
3.5E-
Processing
Processing as
a reactant
Other:
monomer used
in
polymerization
process in:
plastic material
and resin
manufacturing;
manufacturing
synthetic rubber
and plastics
Plastics and
rubber
compounding
33
28
2.7E-04
4.7E-04
3.3E-04
2.4E-04
1.2E-04
6.6E-06
3.6E-06
9.2E-07
3.2E-07
1.2E-07
6.2E-
2.9E-
1.0E-
Processing
Processing -
incorporation
into article
Other: polymer
in: rubber and
plastic product
manufacturing
Plastics and
rubber
converting
6.7E-18
1.5E-14
2.8E-13
4.4E-13
9.0E-13
2.4E-13
1.6E-13
5.1E-14
1.9E-14
7.9E-15
3.9E-15
1.5E-15
5.8E-16
Processing
Processing -
incorporation
into
formulation,
mixture, or
reaction
product
Processing aids,
not otherwise
listed in:
petrochemical
manufacturing
Processing -
incorporation
into
formulation,
mixture, or
reaction
product
53
15
3.1E-05
6.2E-05
4.3E-05
3.3E-05
1.7E-05
1.6E-06
1.3E-06
5.5E-07
2.4E-07
9.1E-
5.0E-
2.3E-
8.2E-09
Processing
Processing as
a reactant
Intermediate in:
adhesive
manufacturing;
all other basic
organic
chemical
manufacturing;
fuel binder for
solid rocket
fuels; organic
fiber
manufacturing;
petrochemical
manufacturing;
petroleum
refineries;
plastic material
and resin
manufacturing;
Propellant
Processing as
a reactant
57
30
8.8E-05
2.5E-04
1.6E-04
1.0E-04
4.5E-05
2.1E-06
1.1E-06
3.4E-07
1.3E-07
4.9E-
2.7E-
1.2E-
4.4E-09
Page 168 of 173
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PUBLIC RELEASE DRAFT
November 2024
Life ( Vcle
Stii fje
C iitejioiT
Subcategory
OES
TKI Facilities
Estimated (,'aneer Risk using Maximum Concentration aei'oss Laeilities within OES In Distanee from All Sourees (m)
(ISased on 50th Percentile Modeled C ,'onccntratioiis)
Total
Risk
Above
1E-06
10
30
30-60
60
100
100-1,000
1,000
2,500
5,000
1,0000
15,000
25,000
50,000
manufacturing;
Synthetic
rubber
manufacturing;
Wholesale and
retail trade
Disposal
Disposal
Disposal
Recycling
11
3
1.7E-06
5.8E-06
4.7E-06
3.4E-06
1.4E-06
6.3E-08
3.4E-08
7.8E-09
2.6E-09
8.7E-10
4.6E-10
2.1E-10
7.4E-11
Manufacturing
Import
Import
Repackaging
23
8
6.55E-05
1.51E-04
1.05E-0
4
7.78E-05
3.75E-05
1.92E-06
9.93E-07
2.43E-07
8.32E-08
2.9E-08
1.53E-08
7.05E-09
2.56E-09
Processing
Repackaging
Intermediate in:
Wholesale and
retail trade
Disposal
Disposal
Disposal
Waste
handling,
disposal,
treatment, and
recycling
7
0
6.0E-08
1.8E-07
1.2E-07
8.4E-08
7.8E-08
2.0E-08
1.1E-08
3.5E-09
1.4E-09
5.4E-10
3.0E-10
1.4E-10
4.8E-11
Total
225
113
3635
3636
Page 169 of 173
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PUBLIC RELEASE DRAFT
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3637 Table Apx H-3.1,3-Butadiene Cancer Risks Based on HEM 10th Percentile Modeled Concentrations from 10 to 50,000 Meters
1 KI 1'iieilities
Estimated (,'ancer Risk using Maximum Concentration aei'oss Facilities within OI'.S In Distanee from All Sources (in)
Life C vcle
C ,'ategoiy
Subcategory
OES
(ISased on 10th Percentile Modeled Concentrations)
Stage
Total
Risk
Above
1E-06
10
30
30-60
60
100
100-1,000
1,000
2,500
5,000
1,0000
15,000
25,000
50,000
Manufacturing
Domestic
Manufacturing
Domestic
Manufacturing
Manufact-
uring
40
24
5.6E-05
2.4E-04
1.8E-04
1.4E-04
6.6E-05
4.6E-06
3.3E-06
9.6E-07
3.8E-07
1.5E-07
8.5E-08
4.2E-08
1.7E-08
Processing
Processing as a
reactant
Other:
monomer used
in
polymerization
process in:
plastic material
and resin
manufacturing;
manufacturing
synthetic rubber
and plastics
Plastics
and rubber
compound
-ing
33
24
1.3E-04
2.7E-04
2.0E-04
1.4E-04
7.1E-05
2.9E-06
1.9E-06
5.2E-07
1.9E-07
6.5E-08
3.5E-08
1.7E-08
5.7E-09
Processing
Processing -
incorporation
into article
Other: Polymer
in: Rubber and
plastic product
manufacturing
Plastics
and rubber
converting
1
0
4.4E-19
6.9E-15
4.3E-14
3.1E-13
5.9E-13
1.6E-13
1.4E-13
4.1E-14
1.5E-14
4.3E-15
2.6E-15
1.0E-15
3.9E-16
Processing
Processing -
incorporation
into
formulation,
mixture, or
reaction product
Processing aids,
not otherwise
listed in:
Petrochemical
manufacturing
Process-
ing -
Incorporat
ion into
formul-
ation,
mixture,
or reaction
product
53
7
5.8E-06
2.3E-05
1.6E-05
1.2E-05
5.8E-06
3.6E-07
2.3E-07
8.3E-08
3.7E-08
1.5E-08
8.4E-09
3.4E-09
1.3E-09
Processing
Processing as a
reactant
Intermediate in:
adhesive
manufacturing;
all other basic
organic
chemical
manufacturing;
fuel binder for
solid rocket
fuels; organic
fiber
manufacturing;
petrochemical
manufacturing;
petroleum
refineries;
plastic material
Process-
ing as a
reactant
57
22
1.3E-05
8.4E-05
5.9E-05
4.5E-05
2.2E-05
8.0E-07
5.3E-07
1.9E-07
7.5E-08
2.9E-08
1.6E-08
7.6E-09
2.8E-09
Page 170 of 173
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PUBLIC RELEASE DRAFT
November 2024
Life C,'ycle
Stage
C ,'atcgoiy
Subcategory
OES
1 KI 1- acil ities
Estimated Cancer Risk using Maximum Concentration across Facilities within OI'.S by Distance from All Sources (m)
(ISased on 10th Percentile Modeled Concentrations)
Total
Risk
Above
11'-06
10
30
30-60
60
100
100-1,000
1,000
2,500
5,000
1,0000
15,000
25,000
50,000
and resin
manufacturing;
propellant
manufacturing;
synthetic rubber
manufacturing;
wholesale and
retail trade
Disposal
Disposal
Disposal
Recycling
11
2
1.1E-07
4.1E-06
3.1E-06
2.4E-06
6.3E-07
3.3E-08
2.3E-08
5.4E-09
1.7E-09
5.3E-10
2.8E-10
1 .IE—10
4.1E-11
Manufacturing
Import
Import
Repack-
aging
23
4
2.56E-06
9.84E-05
6.23E-05
5.03E-05
2.28E-05
7.54E-07
5.06E-07
1.16E-07
3.85E-08
1.27E-08
6.66E-09
2.98E-09
1.08E-09
Processing
Repackaging
Intermediate in:
wholesale and
retail trade
Disposal
Disposal
Disposal
Waste
handling,
disposal,
treatment,
and
recycling
7
0
3.0E-09
5.3E-08
3.6E-08
2.7E-08
3.0E-08
5.7E-09
3.7E-09
1.3E-09
5.2E-10
1.9E-10
1 .IE—10
5.3E-11
2.1E-11
Total
225
83
3638
Page 171 of 173
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PUBLIC RELEASE DRAFT
November 2024
3639 H.2 General Population Cancer Risk Maps Based on HEM Modeled
3640 Census Blocks
Modeled Maximum
Individual Risk from
TRI Releases by Census Block
<1E - 06
1E-Q6 - 1E-05
• 1E-05 - 1E-04
• >lE-04
Tribal Lands
i States
0 250 500 km
3642
3643
3644
FigureApx H-l. Map of Contiguous United States with HEM Model Results for Cancer Risks
Aggregated and Summarized by Census Block for the 2020 TRI Reporting Year
Page 172 of 173
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November 2024
3645
3646 FigureApx H-2. Map of Contiguous United States with HEM Model Results for Cancer Risks
3647 Aggregated and Summarized by Census Block for the 2018 TR1 Reporting Year
Modeled Maximum
Individual Risk from
TRI Releases by Census Block
<1E - 06
1E-06 - 1E-05
• 1E-05 - 1E-04
• >lE-04
V/A Tribal Lands
I I States
Page 173 of 173
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