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EPA Document# EPA-740-R1-8007
November 2020
Office of Chemical Safety and Pollution Prevention
Environmental Protection Agency
Draft Supplemental Analysis to the
Draft Risk Evaluation for 1,4-Dioxane
CASRN: 123-91-1
November 2020
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TABLE OF CONTENTS
26 TABLE OF CONTENTS 2
27 EXECUTIVE SUMMARY 3
28 1 INTRODUCTION 7
29 1.1 Scope of this Draft Supplemental Analysis to the Draft Risk Evaluation 7
30 1.1,1 Conditions of Use Included in the Supplemental Analysis to the Draft Risk Evaluation 8
31 1,1,2 Conceptual Models 9
32 1.2 Systematic Review 11
33 1.2.1 Data and Information Collection 12
34 2 EXPOSURES 15
35 2.1 Environmental Releases 15
36 2.1.1 Environmental Releases to Water 15
37 2.4 Human Exposures 26
38 2.1,2 General Population Exposure 26
39 2.1,3 Consumer Exposures 33
40 3 HAZARDS (EFFECTS) 57
41 3.1.1 Summary of Human Health Hazards 57
42 4 RISK CHARACTERIZATION 59
43 4.1 Human Health Risk 59
44 4.1.1 Risk Estimate for Exposures from Incidental Exposure to 1,4-Dioxane in Surface Water... 59
45 4.1.2 Risk Estimates for Exposures from Consumer Use of 1,4-Dioxane 62
46 4.2 Risk Conclusions 65
47 4.2.1 Summary of Human Health Risk 65
48 5 RISK DETERMINATION 70
49 5.1 Overview 70
50 5,1,1 Human Health 70
51 5.2 Detailed Draft Unreasonable Risk Determinations by Condition of Use 72
52 5,2,1 Consumer use - Arts, crafts and hobby materials - Textile dye 72
53 5.2.2 Consumer use - Automotive care products - Antifreeze 73
54 5.2,3 Consumer use - Cleaning and furniture care products Surface cleaner 73
55 5.2,4 Consumer use - Laundry and dishwashing products - Dish soap 74
56 5.2.5 Consumer use - Laundry and dishwashing products - Dishwasher detergent 75
57 5.2.6 Consumer use - Laundry and dishwashing products - Laundry detergent 75
58 5.2,7 Consumer use - Paints and coatings - Paint and floor lacquer 76
59 5.2.8 Consumer use - Other uses - Spray Polyurethane Foam 77
60 5.2,9 General Population 77
61 6 REFERENCES 79
62 APPENDICES 82
63
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EXECUTIVE SUMMARY
This Draft Supplemental Analysis to the Draft Risk Evaluation for 1.4-Dioxane was developed in
response to public and peer review comments on the draft risk evaluation, and includes additional
conditions of use for 1,4-dioxane present as a byproduct in consumer products, as well as an analysis of
recreational activities in ambient/surface water as an exposure pathway under all conditions of use
included in the draft risk evaluation and this draft supplemental analysis. EPA plans to incorporate this
Draft Supplemental Analysis to the draft risk evaluation into the final risk evaluation. The Frank R.
Lautenberg Chemical Safety for the 21st Century Act amended the Toxic Substances Control Act
(TSCA), the Nation's primary chemicals management law, in June 2016. Under the amended statute,
EPA is required, under TSCA § 6(b), to conduct risk evaluations to determine whether a chemical
substance presents unreasonable risk of injury to health or the environment, under the conditions of use,
without consideration of costs or other non-risk factors, including an unreasonable risk to potentially
exposed or susceptible subpopulations (PESS), identified as relevant to the risk evaluation. Also, as
required by TSCA § (6)(b), EPA established, by rule, a process to conduct these risk evaluations.
Procedures for Chemical Risk Evaluation Under the Amended Toxic Substances Control Act (82 FR
6) (Risk Evaluation Rule). This Draft Supplemental Analysis is in conformance with TSCA § 6(b),
and the Risk Evaluation Rule, and is to be used to inform risk management decisions. In accordance
with TSCA Section 6(b), if EPA finds unreasonable risk from a chemical substance under its conditions
of use in any final risk evaluation, the Agency will propose actions to address those risks within the
timeframe required by TSCA. However, any proposed or final determination that a chemical substance
presents unreasonable risk under TSCA Section 6(b) is not the same as a finding that a chemical
substance is "imminently hazardous" under TSCA Section 7. The preliminary conclusions, findings, and
determinations in this Draft Supplemental Analysis document will be integrated into the Final Risk
Evaluation for 1,4-Dioxane for the purpose of identifying whether the chemical substance presents
unreasonable risk or no unreasonable risk under the conditions of use, in accordance with TSCA Section
6, and are not intended to represent any findings under TSCA Section 7.
TSCA § 26(h) and (i) require EPA, when conducting risk evaluations, to use scientific information,
technical procedures, measures, methods, protocols, methodologies and models consistent with the best
available science and to base its decisions on the weight of the scientific evidence.1 To meet these TSCA
§ 26 science standards, EPA used the TSCA systematic review process described in the Application of
Systematic Review in TSCA Risk Evaluations document (U.S. EPA. 2018). The data collection, data
evaluation and data integration stages of the systematic review process are used to develop the exposure,
fate and hazard assessments for risk evaluations.
Approach
EPA used reasonably available information (defined in 40 CFR 702.33 in part as "information that EPA
possesses, or can reasonably obtain and synthesize for use in risk evaluations, considering the deadlines
. . .for completing the evaluation . . . "), in a fit-for-purpose approach, to develop a risk evaluation that
relies on the best available science and is based on the weight of the scientific evidence. EPA used
previous analyses as a starting point for identifying key and supporting studies to inform the exposure,
fate and hazard assessments. EPA also evaluated other studies that were published since these reviews.
EPA reviewed reasonably available information and evaluated the quality of the methods and reporting
1 Weight of the scientific evidence means a systematic review method, applied in a manner suited to the nature of the
evidence or decision, that uses a pre-established protocol to comprehensively, objectively, transparently, and consistently
identify and evaluate each stream of evidence, including strengths, limitations, and relevance of each study and to integrate
evidence as necessary and appropriate based upon strengths, limitations, and relevance.
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of results of the individual studies using the evaluation strategies described in Application of Systematic
Review in TSCA Risk Evaluations (U.S. EPA. 2018). To satisfy requirements in TSCA Section 26(j)(4)
and 40 CFR 702.51(e), EPA has provided a list of studies considered in carrying out the risk evaluation
and the results of those studies are in Appendix C and several supplemental files.
In the problem formulation and draft risk evaluation, EPA identified the conditions of use and presented
two conceptual models and an analysis plan. These have been updated in this Supplemental Analysis
where EPA has quantitatively evaluated the risk to the environment and human health, using both
monitoring data and modeling approaches, for new conditions of use (identified in Section 1.4.1).2 In
this Draft Supplemental Analysis, EPA evaluated the risk to consumers from acute and chronic
exposures to 1,4-dioxane in consumer products as a byproduct., as well as the risk to bystanders from
acute exposures to 1,4-dioxane in consumer products as a byproduct. The Draft Supplemental Analysis
also includes an evaluation of general population exposures to 1,4-dioxane in ambient surface water by
comparing the estimated exposures to acute human health hazards.
Several of the points of departure (PODs) for evaluating human health risks from acute and chronic
dermal and inhalation exposure were revised in response to peer review and public comment. The PODs
identified through dose-response analysis in the draft risk evaluation are summarized below. These
revised PODs are the basis for risk estimates presented in the risk characterization section.
Risk Characterization
This Draft Supplemental Analysis presents risk estimates for acute dermal and inhalation exposures to
the general population that may occur from incidental contact with surface water. Calculated margin of
exposure (MOE) values below the benchmark MOE (300) would indicate a potential safety concern.
Risks from acute oral exposure through incidental ingestion of surface water are shown in Table 4-1 and
risks from acute dermal exposure through swimming in surface water are shown in Table 4-2. This Draft
Supplemental Analysis also presents human health risk estimates for acute and chronic dermal and
inhalation exposures to consumers and acute dermal and inhalation exposures to bystanders following
consumer use of products containing 1,4-dioxane as a byproduct.
Potentially Exposed or Susceptible Subpopulations
TSCA § 6(b)(4) requires that EPA conduct a risk evaluation to "determine whether a chemical
substance presents an unreasonable risk of injury to health or the environment, without consideration of
cost 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 § 3(12) defines the term "potentially exposed or susceptible subpopulation" as "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."
2 EPA did not identify any "legacy uses" (i.e., circumstances associated with activities that do not reflect ongoing or
prospective manufacturing, processing, or distribution) or "associated disposal" (i.e., future disposal from legacy uses) of 1,4-
dioxane, as those terms are described in EPA's Risk Evaluation Rule, 82 FR 33726, 33729 (July 20, 2017). Therefore, no
such uses or disposals were added to the scope of the risk evaluation for 1,4-dioxane following the issuance of the opinion in
Safer Chemicals, Healthy Families v. EPA, 943 F.3d 397 (9th Cir. 2019). EPA did not evaluate "legacy disposal" (i.e.,
disposals that have already occurred) in the risk evaluation, because legacy disposal is not a "condition of use" under Safer
Chemicals, 943 F.3d 397.
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In developing the risk evaluation, the EPA analyzed the reasonably available information to ascertain
whether some human receptor groups may have greater exposure or greater susceptibility than the
general population to the hazard posed by a chemical. The results of the reasonably available human
health data for all routes of exposure evaluated (i.e., dermal and inhalation) indicate that there is no
evidence of increased susceptibility for any single group relative to the general population. However,
there is limited data on reproductive and developmental toxicity and a lack of quantitative information
on how genetics, pre-existing disease, or other factors may contribute to increased susceptibility. For
consideration of the most highly exposed groups in this Draft Supplemental Analysis, EPA considered
1,4-dioxane exposures to be higher amongst consumers and bystanders that are exposed through the use
of consumer products containing 1,4-dioxane as a byproduct as compared to the general population
based on greater exposure.
Unreasonable Risk Determination
This Draft Supplemental Analysis to the Draft Risk Evaluation for 1,4-Dioxane presents draft
unreasonable risk determinations for eight consumer conditions of use. This document also presents
draft unreasonable risk determinations for all conditions of use for the general population. This draft
unreasonable risk determination for the general population includes the consumer conditions of use in
this Draft Supplemental Analysis as well as the conditions of use presented in the Draft Risk Evaluation.
Unreasonable Risks of Injury to Health: EPA's draft determination of unreasonable risk for specific
conditions of use of 1,4-dioxane listed below are based on health risks to consumers, bystanders, and the
general population. For acute exposures to consumers and bystanders, EPA evaluated unreasonable risks
for adverse non-cancer effects based on liver toxicity. For chronic exposures to consumers and
bystanders, EPA evaluated unreasonable risks of cancer.
Unreasonable Risk of Injury to Health of the General Population: 1,4-Dioxane exposures to the general
population may occur from the conditions of use due to releases to air, water or land. During the course
of the risk evaluation process for 1,4-dioxane, EPA worked closely with the offices within EPA that
administer and implement regulatory programs under the Clean Air Act (CAA), the Safe Drinking
Water Act (SDWA), the Clean Water Act (CWA), the Resource Conservation and Recovery Act
(RCRA), and the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA). EPA believes it is both reasonable and prudent to tailor TSCA risk evaluations when other
EPA offices have expertise and experience to address specific environmental media, rather than attempt
to evaluate and regulate potential exposures and risks from those media under TSCA. EPA believes that
coordinated action on exposure pathways and risks addressed by other EPA-administered statutes and
regulatory programs is consistent with the statutory text and legislative history, particularly as they
pertain to TSCA's function as a "gap-filling" statute, and also furthers EPA aims to efficiently use
Agency resources, avoid duplicating efforts taken pursuant to other Agency programs, and meet the
statutory deadlines for completing risk evaluations. EPA has therefore tailored the scope of the risk
evaluation for 1,4-dioxane using authorities in TSCA Sections 6(b) and 9(b)(1). EPA did not evaluate
unreasonable risk to the general population from ambient air, drinking water, and sediment pathways for
any conditions of use in this risk evaluation, and the draft unreasonable risk determinations do not
account for exposures to the general population from ambient air, drinking water, and sediment
pathways.
As part of this Draft Supplemental Analysis, EPA evaluated acute and chronic incidental exposures via
oral and dermal routes from recreational swimming in ambient water and preliminarily determined that
this activity presents no unreasonable risk to the general population from all conditions of use. In
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addition, because 1,4-dioxane has low bioaccumulation potential, EPA has preliminarily determined that
fish consumption does not present an unreasonable risk to the general population from any of the
conditions of use.
Unreasonable Risk of Injury to Health of Consumers: 1,4-Dioxane may be found as a contaminant in
consumer products. It is present as a result of byproduct formation during manufacture of ethoxylated
chemicals that are subsequently formulated into products. In the draft risk evaluation, EPA did not
evaluate exposures to consumers and bystanders from byproduct or contaminant exposure, explaining
that EPA's intention was to consider 1,4-dioxane byproduct and contaminant uses in the scope of any
risk evaluation of ethoxylated chemicals. In response to peer review and public comments, in this draft
Supplemental Analysis, EPA evaluated eight consumer uses of products that contain 1,4-dioxane as a
contaminant to preliminarily determine if there was unreasonable risk of injury to consumers' health.
For each of the eight uses, EPA evaluated non-cancer effects to consumers from acute inhalation and
dermal exposures. For four of the products, based on the exposure assessment, EPA also evaluated
cancer risks to consumers from chronic inhalation and dermal exposures. A full description of EPA's
draft unreasonable risk determination for each condition of use is in Section 5.
Unreasonable Risk of Injury to Health of Bystanders (from consumer uses): Because this supplemental
evaluation includes an evaluation of hazards and exposures for consumers, EPA evaluated hazards and
exposures for bystanders to consumer uses. Specifically, EPA evaluated non-cancer effects to bystanders
from acute inhalation exposures from eight consumer uses of products that contain 1,4-dioxane as a
contaminant to preliminarily determine if there was unreasonable risk of injury to bystanders' health.
EPA did not estimate chronic inhalation exposures to bystanders because bystanders would be exposed
to lower levels than the user based on the model bystander placement in the home during the product's
use. EPA also did not evaluate non-cancer effects from dermal exposures to bystanders because
bystanders are not dermally exposed to 1,4-dioxane. A full description of EPA's draft unreasonable risk
determination for each condition of use is in Section 5.
Based on the Draft Supplemental Analysis, EPA has preliminarily determined that the following
conditions of use of 1,4-dioxane do not present an unreasonable risk of injury to health or the
environment. The details of these determinations are in Section 5.2.
Conditions of I so llisit Do Not Present sin I nre;ison:ihle Risk
Consumer use: Arts, crafts, and hobby materials - Textile dye
Consumer use: Automotive care products - Antifreeze
Consumer use: Cleaning and furniture care products - Surface cleaner
Consumer use: Laundry and dishwashing products - Dish soap
Consumer use: Laundry and dishwashing products - Dishwasher detergent
Consumer use: Laundry and dishwashing products - Laundry detergent
Consumer use: Paints and coatings - Paint and floor lacquer
Consumer use: Other uses - Spray polyurethane foam
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1 INTRODUCTION
This document presents a Draft Supplemental Analysis to the Draft Risk Evaluation that will be
incorporated into the Final Risk Evaluation for 1,4-Dioxane under the Frank R. Lautenberg Chemical
Safety for the 21st Century Act. The Frank R. Lautenberg Chemical Safety for the 21st Century Act
amended the Toxic Substances Control Act, the Nation's primary chemicals management law, in June
2016. In this Draft Supplemental Analysis, EPA evaluated the risk to consumers and bystanders from
1,4-dioxane in consumer products, and the general population exposed to 1,4-dioxane in ambient surface
water by comparing the estimated exposures to acute and chronic human health hazards.
The Agency published the Scope of the Risk Evaluation for 1,4-dioxane (EPA. 2017) in June 2017, and
the problem formulation in June, 2018 (TP_\_ which represented the analytical phase of risk
evaluation in which "the purpose for the assessment is articulated, the problem is defined, and a plan for
analyzing and characterizing risk is determined" as described in Section 2.2 of the Framework for
Human Health Risk Assessment to Inform Decision Making. The EPA received comments on the
published problem formulation and draft risk evaluation for 1,4-dioxane and has considered the
comments specific to 1,4-dioxane, as well as more general comments regarding the EPA's chemical risk
evaluation approach for developing the risk evaluations for the first 10 chemicals the EPA is evaluating.
This Draft Supplemental Analysis document is structured such that the Introduction presents a
background on uses, conditions of use and conceptual models, with emphasis on any changes since the
publication of the draft risk evaluation. This section also includes a discussion of the systematic review
process utilized in this Supplemental Analysis. The exposures section provides a discussion and analysis
of the human exposures expected based on the conditions of use for 1,4-dioxane evaluated in this Draft
Supplemental Analysis. The hazards section summarizes the human health hazards of 1,4-dioxane. The
risk characterization section integrates and assesses reasonably available information on human health
hazards and exposures, as required by TSCA (15 U.S.C 2605(b)(4)(F)). The risk determination section is
included, in which the agency presents the draft determinations of whether risk posed by the chemical
substance under the conditions of use is unreasonable as required under TSCA (15 U.S.C. 2605(b)(4)).
EPA is providing the opportunity for public comment on this Draft Supplemental Analysis to the Draft
Risk Evaluation for 1.4-Dioxane. The final risk evaluation may change in response to public comments
received and/or in response to peer review on the draft risk evaluation, as well as in response to public
comments received on this Draft Supplemental Analysis. The draft supplemental analysis is not being
peer reviewed for the sake of expediency to finalize the first ten risk evaluations. The EPA will respond
to public and peer review comments received on the draft risk evaluation and further public comments
received on this Draft Supplemental Analysis when it issues the final risk evaluation.
1.1 Scope of this Draft Supplemental Analysis to the Draft Risk
Evaluation
This document presents updated sections of the Draft Risk Evaluation for 1.4-Dioxane. appendices, and
supplemental files that have been developed based on additional COUs for 1,4-dioxane as a byproduct in
consumer products. In addition, the document presents an exposure analysis to the general population
from recreational activities (i.e., swimming) in ambient/surface water.
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1.1.1 Conditions of Use Included in the Supplemental Analysis to the Draft Risk
Evaluation
TSCA (15 U.S.C. § 2602(4)) defines "conditions of use" as "the circumstances, as determined by the
Administrator, under which a chemical substance is intended, known, or reasonably foreseen to be
manufactured, processed, distributed in commerce, used, or disposed of." The conditions of use are
described below in Table 1.
As explained in the scope document for 1,4-dioxane, EPA anticipates the production of 1,4-dioxane as a
byproduct from ethoxylation of other chemicals and presence as a contaminant in industrial, commercial
and consumer products. In particular, 1,4-dioxane may be produced as a reaction byproduct in chemicals
produced through ethoxylation, including alkyl ether sulphates (AES, anionic surfactants) and other
ethoxylated substances, such as alkyl, alkylphenol and fatty amine ethoxylates; polyethylene glycols and
their esters; and sorbitan ester ethoxylates. 1,4-Dioxane may also be present at residual concentrations in
commercial and consumer products that contain ethoxylated chemicals. Examples of products
potentially containing 1,4-dioxane as a residual contaminant are paints, coatings, lacquers, ethylene
glycol-based antifreeze coolants, spray polyurethane foam, household detergents, cosmetics/toiletries,
textile dyes, foods, agricultural and veterinary products ("ATSDR. 2012; Canada. .'Mi', ^ U \ .007;
ECJRC. 2002). In the Draft Risk Evaluation for 1.4-Dioxane. the manufacture of 1,4-dioxane as a
byproduct from ethoxylation of other chemicals, use and disposal of 1,4-dioxane at residual
concentrations in industrial, commercial and consumer products containing ethoxylated chemicals were
excluded from the scope of the risk evaluation. In response to peer review and public comments, in this
Draft Supplemental Analysis, EPA evaluated eight consumer uses of products that contain 1,4-dioxane
as a contaminant to determine if there was unreasonable risk of injury to consumers' and bystanders'
health. For each of the eight uses, EPA evaluated non-cancer effects to consumers from acute inhalation
and dermal exposures. For four of the products, based on the exposure assessment, EPA also evaluated
cancer risks to consumers from chronic inhalation and dermal exposures.
In the draft risk evaluation, general population exposures were not evaluated for any condition of use.
The exposures to general population via drinking water, ambient air and sediment pathways fall under
the jurisdiction of other environmental statutes administered by EPA, i.e., CAA, SDWA, CERCLA, and
RCRA. EPA believes it is both reasonable and prudent to tailor TSCA risk evaluations when other EPA
offices have expertise and experience to address specific environmental media, rather than attempt to
evaluate and regulate potential exposures and risks from those media under TSCA. However, because
there is no nationally recommended Ambient Water Quality Criteria under the CWA, EPA included
exposures to the general population via ambient surface water in this supplemental analysis. EPA did
evaluate hazards or exposures to the general population from ambient surface water for the conditions of
use in the draft risk evaluation (see Table 1-2), and the draft unreasonable risk determinations for
relevant conditions of use account for exposures to the general population via surface water (EPA.
2018bY
Table 1-1 includes the additional conditions of use included in this supplemental analysis covering
consumer exposure pathways for products containing 1,4-dioxane as a byproduct.
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Table 1-1 Additional Categories and Subcategories of Conditions of Use Included in the
Supplemental Analysis to the Draft Risk Evaluation
Life Cycle Stage
Category
Subcategory
References
Consumer uses
Paints and Coatings
1. Latex Wall Paint or Floor
Lacquer
TSCA Work Plan
Chemical Problem
Cleaning and Furniture
Care Products
2. Surface Cleaner
Formulation and
Initial Assessment:
1.4-Dioxane CCASRN
123-91-1H2015)
Laundry and
Dishwashing Products
3. Dish Soap
4. Dishwasher Detergent
5. Laundry Detergent
Arts, Crafts and Hobby
Materials
6. Textile Dye
Automotive Care
Products
7. Antifreeze
Other Consumer Uses
8. Spray Polyurethane Foam
(SPF)
The draft risk evaluation included worker and ONU exposures for Occupational Exposure Scenarios
(OES) but did not include associated environmental releases to surface water, which are included in this
supplemental analysis for the OES in Table 1-2. These releases to surface water are used in the
evaluation of general population exposures via the ambient water pathway and reflect additional
pathways of exposure for conditions of use that were presented in the Draft Risk Evaluation.
Table 1-2 Existing Conditions of Use Included in the Supplemental Analysis to the Draft Risk
OES
References
Manufacturing
Draft Risk Evaluation for 1.4-
Import and Repackaging
Dioxane
Recycling
Industrial Uses
Functional Fluids (Open-System)
Laboratory Chemical Use
Film Cement
Spray Foam Application
Printing Inks (3D)
Dry Film Lubricant
Disposal
1.1.2 Conceptual Models
The conceptual models for this draft supplemental analysis to the draft risk evaluation are shown in
Figure 1-1 and Figure 1-2. EPA considered the potential for hazards to consumers from inhalation and
dermal routes and to bystanders from the inhalation route via use of household products containing 1,4-
dioxane as a byproduct and hazards from incidental exposure to the general population via releases to
ambient water as shown in the conceptual models.
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CONSUMER
ACTIVITIES / USES EXPOSURE PATHWAY EXPOSURE ROUTE RECEPTORS3 HAZARDS
Paints and Coatings
e.g. Latex Wall Paint or Floor
Lacquer
Cleaning and Furniture Care
Products
e.g. Surface Cleaner
Laundry and Dishwashing
Products
e.g. Dish Soap, Dishwasher
Detergent, Laundry Detergent
Arts, Crafts and Hobby
Materials
e.g. Textile Dye
Automotive Care Products
e.g. Antifreeze
Other Consumer Uses
e.g. Spray Polyurethane Foam,
Antifreeze
340 Figure 1-1 1,4-Dioxane Conceptual Model for Consumer Activities and Uses: Consumer
341 Exposures and Hazards
342 The conceptual model presents the exposure pathways, exposure routes and hazards to human
343 receptors from consumer activities and uses of 1,4-dioxane in the draft risk evaluation and this
344 supplemental analysis to the draft risk evaluation.
345 a Receptors include potentially exposed or susceptible subpopulations.
Dermal
Hazards Potentially
Associated
with Acute and/or Chronic
Exposures
Liquid Contact
Inhalation
Bystanders
Vapor/Mist
KEY:
Pathways and receptors that were not
further analyzed
>
Pathways that were not further analyzed.
Pathways that were not further analyzed.
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RELEASES AND WASTES FROM EXPOSURE PATHWAY EXPOSURE ROUTE RECEPTORS HAZARDS
INDUSTRIAL / COMMERCIAL USES
discharge
Water/
Sediment
Aquatic
Species
Indirect discharge
Biosolids
Land D sposal
Soil
General
Population
Liquid Wastes 3
Incidental Oral,
Dermal
Industrial WWT
Industrial Pre-
Hazards Potentially
Associated with Acute
and Chronic Exposures
Hazards Potentially
Associated with Acute
Exposures
Figure 1-2.1,4-Dioxane Conceptual Model for Environmental Releases and Wastes:
Potential Exposures and Hazards
The conceptual model presents the exposure pathways, exposure routes and hazards to human
and environmental receptors from environmental releases and wastes of 1,4-dioxane in the draft
risk evaluation and this supplemental analysis to the draft risk evaluation.
a Industrial wastewater or liquid wastes could be treated on-site and then released to surface
water (direct discharge), or pre-treated and released to POTW (indirect discharge).
1.2 Systematic Review
TSCA requires EPA to use scientific information, technical procedures, measures, methods, protocols,
methodologies and models consistent with the best available science and base decisions on the weight of
the scientific evidence. Within the TSCA risk evaluation context, the weight of the scientific evidence is
defined as "a systematic review method, applied in a manner suited to the nature of the evidence or
decision, that uses a pre-established protocol to comprehensively, objectively, transparently, and
consistently identify and evaluate each stream of evidence, including strengths, limitations, and
relevance of each study and to integrate evidence as necessary and appropriate based upon strengths,
limitations, and relevance" (40 C.F.R. 702.33).
To meet the TSCA § 26(h) science standards, EPA used the TSCA systematic review process described
in the Application of Systematic Review in TSCA Risk Evaluations document (U.S. EPA. 2018). The
process complements the risk evaluation process in that the data collection, data evaluation and data
integration stages of the systematic review process are used to develop the exposure and hazard
assessments based on reasonably available information. EPA defines "reasonably available information"
to mean information that EPA possesses, or can reasonably obtain and synthesize for use in risk
evaluations, considering the deadlines for completing the evaluation (40 CFR 702.33).
EPA is implementing systematic review methods and approaches within the regulatory context of the
amended TSCA. Although EPA is adopting as many best practices as practicable from the systematic
review community, EPA expects modifications to the process to ensure that the identification, screening,
evaluation and integration of data and information can support timely regulatory decision making under
the aggressive timelines of the statute.
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411
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413
414
1.2.1 Data and Information Collection
For the risk evaluation, EPA planned and conducted a comprehensive literature search based on
chemical descriptors and key words related to the different discipline-specific evidence supporting the
risk evaluation (e.g., environmental fate and transport; engineering releases and occupational exposure;
exposure to general population, consumers and environmental exposure; and environmental and human
health hazard). EPA then developed and applied inclusion and exclusion criteria during the title and
abstract screening to identify information potentially relevant for the risk evaluation process. The
literature and screening strategy as specifically applied to 1,4-dioxane is described in the Strategy for
Conducting Literature Searches for 1,4-Dioxane: Supplemental File for the TSCA Scope Document and
the results of the title and abstract screening process were published in the 1, 4-Dioxane (CASRN123-
91-1) Bibliography: Supplemental File for the TSCA Scope Document (U.S. EPA. 2017a). EPA
subsequently conducted full-text screening using inclusion/exclusion criteria within population,
exposure, comparator, outcome (PECO) or similar statements that are included in Appendix F of
Problem Formulation of the Risk Evaluation for 1,4-Dioxane (EPA... 2018c).
For the current supplemental analysis, EPA performed an supplemental literature search of peer
databases to identify studies related to consumer exposure. EPA conducted a new comprehensive
literature search of peer databases based on chemical name and CAS related to exposure to general
population, consumers and environmental exposure. EPA filtered the new literature search results of 1,4-
dioxane for consumer specific references using Structured Query Language (SQL) querying shown in
Table 1-2.
Table 1-2 Categorical Term Sets used in SQL Querying for 1,4-Dioxane Supplemental Consumer
Analysis
carpet|Drapery|curtain|upholstery|furniture|rug|Suede|cleaner|leather|water proofing| starch
anti-static|candle|matches|bleach|laundry|detergent|Insect repellent|litter|Charcoal|briquettes|lighter fluid|Drain
cleaner|Dishwasher|dishwashing|dishes|soap|Fabric
dye|softener|Oven cleaner|home|pet|collar|Fertilizer|garden|Fire extinguisher|floor|metal|silver|Food packaging|packaged
food
deodorizer|freshener|disinfectant|spot remover|stain remover| Scouring pad|Toilet|Herbicide|patio|Water treatment
chemicals|Insecticide|swimming pool|Paint|varnish|remover|thinner|interior|spray|house
exterior|polyurethane|stain|Ceiling|tile|patching|plaster|caulk|sealer|filler|Dry
wall|Roofing|Refinishing|wall|wallpaper|Insulation|automobile|car|truck|cycle|van
Antifreeze|Motor oil|Radiator|additives|Automotive paint|Gasoline|diesel
fuel|vehicle|Windshield|washer|Clothes|clothing|shoe|Sheets|towels|diaper|games|toys|chew|ingest|jewelry|colorprint|newsp
rint|newspaper|photograph|consumer|emission
Categorical term sets were derived from the Exposure Factors Handbook. This included Household Furnishings, Garment
Conditioning Products, Household Maintenance Products, Home Building & Improvement Products, Automobile-Related
Products, and Personal Materials. Cosmetic Hygiene Products, insecticide, food packaging terminology was excluded for
the purposes of this assessment per TSCA section 3(2).
Next, a machine learning model was employed to rank how similar the filtered references were to a pre-
determined set of consumer references (positive seeds), and how unsimilar the filtered references were
to a pre-determined set of non-consumer references (negative seeds). References that ranked above a
relevancy cut-off (0.4 for references with abstracts, 0.1 for references with just titles) were included for
data screening. These approaches reduced the number of references from 21,373 to 239. The revised
literature flow diagram (Table 3) includes the additional SQL querying and machine learning steps that
were used for the consumer assessment.
In addition to the peer database search, EPA utilized previous assessments and performed an additional
gray literature search for the supplemental consumer analysis. Previous assessments that were identified
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422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
in support of the development of EPA's 2015 TSCA Work Plan Chemical Problem Formulation and
Initial Assessment of 1,4-Dioxane (U.S. EPA... 2015). were screened and evaluated for use in the
supplemental consumer assessment. EPA conducted an additional consumer gray literature search to
identify references with consumer information related to 1,4-dioxane. Previous assessments and results
of the additional gray literature search for consumer uses resulted in 34 data sources. The revised
literature flow diagram (Table 3) includes the previous assessments, as well as the additional gray
literature results that were used for the consumer assessment.
The 239 references as a result of the machine learning efforts and the 34 references from previous
assessments and the additional gray literature search underwent data screening. These sources are listed
in the Supplemental Analysis File [ Consumer References, Data Screening].
For the consumer supplemental analysis, EPA modified the inclusion and exclusion criteria for title and
abstract screening and full text screening to identify consumer information potentially relevant for the
risk evaluation process. The revised PECO is presented in Table 1-3.
Table 1-3 PECO Statement 1,4-Dioxane Consumer Exposure Assessment (September 2020)
PECO Element
Evidence
Population
Human: Consumers and bystanders, including children. Targeted human Domilation srouDS
may be exposed to 1,4-dixoane.
Ecological: None.
Exposure
Exncctcd Primarv Exposure Sources. Pathwavs, Routes
Source: Consumer use of products containing 1.4 dioxanc as a byproduct, and associated air
emissions and dermal contact.
Pathwav: Indoor air. contact with products.
Routes: Indoor (inhalation), dermal (contact with products)
Comparator
(Scenario)
Human: Consider use/source specific exposure scenarios as well as which receptors are and are not
reasonably exposed across the projected exposure scenarios.
Ecological: None.
Outcomes for
Exposure
Concentration or
Dose
Human: A wide range of effects following acute and chronic exposure doses ma/ka/dav and
concentrations mg/ml
Ecological: None.
The results of the data screening efforts resulted in 37 references that were sent to data evaluation, and
17 references that were evaluated qualitatively. The results of the data evaluation are included in the
Supplemental Analysis File [Data Quality Evaluation on Data Sources on Consumer and Environmental
Exposure] and the list of references evaluated qualitatively are included in the Supplemental Analysis
File [Consumer References, Data Screening]. Following data evaluation, 30 references were sent
forward for data extraction/integration. The process is depicted below in Figure 1-3.
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443
444
445
446
447
448
449
450
451
452
Data Extraction/Data Integration (n = 30)
Data Evaluation (n = 37)
Data Screening (n = 545)
Raw Literature Search Results
(n =85,379)
Consumer Search Results after SQL
Query (n =8,077)
Consumer Search Results after Machine
Learning (n =239)
Literature Search Results (n = 21,373)
Gray literature and previous
assessments
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457
458
459
460
461
462
463
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475
476
477
478
479
480
481
482
483
484
2 EXPOSURES
2.1 Environmental Releases
Releases to the environment from conditions of use (e.g., industrial and commercial processes) are one
component of potential exposure and may be derived from reported data that are obtained through direct
measurement, calculations based on empirical data and/or assumptions and models.
Under the Emergency Planning and Community Right-to-Know Act (EPCRA) Section 313, 1,4-dioxane
has been a Toxics Release Inventory (TRI)-reportable substance since 1987. The TRI database includes
information on disposal and other releases of 1,4-dioxane to air, water, and land, in addition to how it is
being managed through recycling, treatment, and burning for energy recovery.
2.1.1 Environmental Releases to Water
EPA categorized the conditions of use (COUs) listed in Section 1.4.1 into 12 Occupational Exposure
Scenarios (OES). For each OES, a daily water release was estimated based on annual releases, release
days, and the number of facilities (Figure 2-1). In this section, EPA describes its approach and
methodology for estimating daily water releases, and for each OES provides a summary of release days,
number of facilities, and daily water releases (Table 2-1).
Release
Days
Annual
Releases
Number of
Facilities
OES
Daily Release
Estimate
ESD, GS,
Assumptions
TRI, DMR, ESD,
GS
TRI, CDR, DMR,
Census, ESD,
GS*
Figure 2-1. An Overview of How EPA Estimated Daily Water Releases for Each OES
* TRI: Toxics Release Inventory; DMR: Discharge Monitoring Report; ESD: Emission Scenario Document; GS: Generic
Scenario
2.1.1.1 Results for Daily Release Estimate
EPA combined its estimates for annual releases, release days, and number of facilities to estimate a
range for daily water releases for each OES. A summary of these ranges across facilities is presented in
Table 2-1. The examples of certain OES where water releases are not expected follows.
Laboratory Uses: EPA expects that releases of 1,4-dioxane from laboratory uses are to air (through
volatile releases into the indoor laboratory air and/or through laboratory fume hoods to atmospheric
air) and liquid wastes of 1,4-dioxane are handled as hazardous waste. EPA expects commercial and
university laboratories to handle their wastes as hazardous waste and not discharge wastes to POTW
via pouring the wastes down the drain.
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485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
Printing Inks (3D): EPA does not expect water releases from 3D printing ink uses. EPA expects
spent printing ink containers, shavings or fragments, or waste scraps to be disposed of as solid waste.
There is some uncertainty as to whether and how much 1,4-dioxane may remain in 3D printed
products and waste scraps. However, due to the volatility of 1,4-dioxane, EPA expects 1,4-dioxane
to evaporate from any printed object, shavings or fragments, or other printed material deposited to
the floor or work surface prior to it being cleaned and disposed of as solid waste.
Film Cement: EPA assessed no wastewater discharges for this OES. EPA expects the small glue
bottles to be disposed of as solid waste without rinsing them in a sink. There is some uncertainty as
to whether and how much 1,4-dioxane may remain in the small glue bottles when disposed.
However, due to the small quantities of the glue and high volatility of the 1,4-dioxane, EPA expects
any residual 1,4-dioxane to evaporate to the air or remain in the solid waste stream.
Table 2-1. Summary of EPA's Daily Water Release Estimates for Each OES and EPA's Overall
Confidence in these Estimates
Occnp;ilioiiiil r.xpoMiiv
SiTiisirio (OI'.S)
llsliiiiiilod 1
K.
Ami!
(kii/si
Mini in ii m
);iil\ Koloiiso
ii lie
«s Silos
li'-(l;i\)
M;i\iimi in
Uokiiso
Dsijs per
Yi-sir
Kcli'sisi*
Miuliii
0\i*r:ill
(on lidence
Nolcs
Manufacturing
0
2.48
250
Surface
Water
M
Estimates based
on TRI and DMR
data.
Import and Repackaging
0
0
0
N/A
M
Estimates based
on TRI and DMR
data.
Recycling
-
-
-
-
-
EPA evaluated
recycling as part
of the industrial
uses OES.
Industrial Uses
0
67.7
250
Surface
Water,
POTW,
and Non-
Public
WWT
M
Estimates based
on TRI and DMR
data.
Functional Fluids (Open-
System)
9.92E-4
3.79E-2
247
Surface
Water and
POTW
M
EPA estimates
releases for three
sites reported in
DMR and for
additional,
unknown sites
not captured in
DMR or TRI
using the
Emission
Scenario
Document on the
Use of
Metalworking
Fluids.
Laboratory Chemical Use
N/A
N/A
N/A
N/A
H
1,4-Dioxane
could be released
to air; and wastes
disposed of as
-------
Occnp;ilioiiiil r.xpoMiiv
Sccn;irio (OI'.S)
I'.sliiiiiilod l);iil\ Rolen so
Uiiniic
Across Silos
(kii/si(e-d;ij)
Uokiiso
Dsijs per
Year
Role;ise
Miuliii
()\or;ill
(on lideiice
Soles
Mini in ii in
M;i\iimi in
hazardous waste
fortius OES.
Film Cement
N/A
N/A
N/A
N/A
H
EPA expects
releases of 1,4-
dioxane to be to
air and wastes
disposed of as
solid waste for
this OES.
Spray Foam Application
3.59E-3
260
Surface
Water or
POTW
M
Modeled using
the Application
of Spray
Polyurethane
Foam Insulation
Generic
Scenario.
Printing Inks (3D)
N/A
N/A
N/A
N/A
H
EPA expects
releases of 1,4-
dioxane to be to
air and wastes
disposed of as
solid waste for
this OES.
Dry Film Lubricant
N/A
N/A
N/A
N/A
H
Based on
conversations
with the only
known user, EPA
expects wastes to
be drummed and
sent to a waste
handler with
residual wastes
releasing to air or
being disposed to
landfill.
Disposal
0
0.12
250
Surface
Water
M
Estimates based
on TRI and DMR
data.
N/A: Not applicable. EPA does not expect 1,4-dioxane releases to water from this OES.
POTW = Publicly owned treatment works
WWT = wastewater treatment
500 2.1,1.2 Approach and Methodology
501 2.1.1.2.1 Water Release Estimates
502 Where available, EPA used 2018 TRI ( ) and 2018 DMR ( ) data to
503 provide a basis for estimating releases. Facilities are only required to report to TRI if the facility has 10
504 or more full-time employees, is included in an applicable NAICS code, and manufactures, processes, or
505 uses the chemical in quantities greater than a certain threshold (25,000 pounds for manufacturers and
506 processors of 1,4-dioxane and 10,000 pounds for users of 1,4-dioxane). Due to these limitations, some
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509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
sites that manufacture, process, or use 1,4-dioxane may not report to TRI and are therefore not included
in these datasets.
For the 2018 Discharge Monitoring Report (DMR) ( ), EPA used the Water Pollutant
Loading Tool within EPA's Enforcement and Compliance History Online (ECHO) to query all 1,4-
dioxane point source water discharges in 2018. DMR data are submitted by National Pollutant
Discharge Elimination System (NPDES) permit holders to states or directly to the EPA according to the
monitoring requirements of the facility's permit. States are only required to load major discharger data
into DMR and may or may not load minor discharger data. The definition of major versus minor
discharger is set by each state and could be based on discharge volume or facility size. Due to these
limitations, some sites that discharge 1,4-dioxane may not be included in the DMR dataset.
Where releases are expected but TRI and DMR data were not reasonably available or where EPA
determined TRI and DMR data did not sufficiently represent releases of 1,4-dioxane to water for a
condition of use, releases were estimated using data from literature, relevant Emission Scenario
Documents (ESDs), and Generic Scenarios (GSs).
2.1.1.2.2 Estimates of Number of Facilities
Where available, EPA used 2018 TRI ( ), and 2018 DM R ( ) data to
provide a basis to estimate the number of sites using 1,4-dioxane within a condition of use. Generally,
information for reporting sites in CDR was sufficient to accurately characterize each reporting site's
condition of use. However, information for determining the condition of use for reporting sites in TRI
and DMR is typically more limited.
In TRI, sites submitting a Form R indicate whether they perform a variety of activities related to the
chemical, including, but not limited to whether they: produce the chemical; import the chemical; use the
chemical as a reactant; use the chemical as a chemical processing aid; and ancillary or other use. In TRI,
sites submitting Form A are not required to designate an activity. For both Form R and Form A, TRI
sites are also required to report the primary North American Industry Classification System (NAICS)
code for their site. For each TRI site, EPA used the reported primary NAICS code and activity indicators
to determine the condition of use at the site. For instances where EPA could not definitively determine
the condition of use because: 1) the reported NAICS codes could include multiple conditions of use; 2)
the site reported multiple activities; and/or 3) the site did not report activities due to submitting a Form
A, EPA made an assumption on the condition of use to avoid double counting the site. For these sites,
EPA supplemented the NAICS code and activity information with information from company websites,
satellite images, and industry data to determine a "most likely" or "primary" condition of use.
In DMR, the only information reported on condition of use is each site's Standard Industrial
Classification (SIC) code. EPA could not determine each reporting site's condition of use based on SIC
code alone; therefore, EPA supplemented the SIC code information with the same supplementary
information used for the TRI.
Where the number of sites could not be determined using CDR/TRI/DMR or where these data sources
were determined to insufficiently capture the number of sites within a condition of use, EPA
supplemented the available data with U.S. economic data using the following method:
Identify the North American Industry Classification System (NAICS) codes for the industry sectors
associated with these uses.
Estimate total number of sites using the U.S. Census' Statistics of US Businesses (SUSB) (U.S.
Census Bureau. 2015) data on total establishments by 6-digit NAICS.
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555
556
557
558
559
560
561
562
563
564
565
566
567
568
Review available ESDs and GSs for established facility estimates for each occupational exposure
scenario.
Combine the data generated in Steps 1 through 3 to produce an estimate of the number of sites using
1,4-dioxane in each 6-digit NAICS code, and sum across all applicable NAICS codes for the
condition of use, augmenting as needed with data from the ESDs and GSs, to arrive at a total
estimate of the number of sites within the condition of use.
Table 2-2. Summary of EPA's Estimates for the Number of Facilities for Each PES
Occiipiilioiiiil r.\|)osiiiv
Number of
Smiiirio (OI'.S)
I'iicililk's
Noles
Manufacturing
2
Based on CDR and TRI reporting (see Appendix G.6.1)
Import and Repackaging
3 to 18
Based on TRI and CDR reporting (see Appendix G.6.2)
Recycling
-
Evaluated as a part of Industrial Uses.
Industrial Uses
24
Based on TRI and DMR data (see Appendix G.6.3)
Functional Fluids (Open-System)
89,000
Based on TRI reporting and bounding estimate from the
2011 OECD Emission Scenario Document on the Use of
Metalworking Fluids (see Appendix G.6.4)
Laboratory Chemicals
6,844
Bounding estimate based on CDR, and U.S. Census
Bureau data for NAICS code 541380, Testing Laboratories
(see Appendix G.6.5)
Film Cement
211
Bounding estimate based on U.S. Census Bureau data for
NAICS code 512199, Other Motion Picture and Video
Industries (see Appendix G.6.6)
Spray Foam Application
1,553,559
Bounding estimate based on U.S. Census Bureau data for
NAICS code 238310, Drywall and Insulation Contractors
and the 2018 EPA generic scenario Application of Spray
Polyurethane Foam Insulation (see Appendix G.6.7)
Printing Inks (3D)
10,767
Bounding estimate based on U.S. Census Bureau data for
NAICS code 339113, Surgical Appliance and Supplies
Manufacturing (see Appendix G.6.8)
Dry Film Lubricant
8
Based on conversations with the Kansas City National
Security Campus, which is a manufacturer and user (see
Appendix G.6.9)
Disposal
14
Based on TRI and DMR data (see Appendix G.6.10)
2.1.1.2.3 Estimates of Release Days
EPA referenced Emission Scenario Documents (ESDs) or needed to make assumptions when estimating
release days for each OES. A summary along with a brief explanation is presented in Table 2-3 below.
Table 2-3. Summary of EPA's Estimates for Release Days Expected for Each PES
Occiipiilioiiiil l.\|)oNurc
SiTiisirio (OI'.S)
Ki'li'.isi* l);i\s
Noll's
Manufacturing
250
Assumed five days per week and 50 weeks per year with
two weeks per year for shutdown activities.
Import and Repackaging
250
Assumed five days per week and 50 weeks per year with
two weeks per year for shutdown activities.
Recycling
-
Evaluated as a part of Industrial Uses.
Industrial Uses
250
Assumed five days per week and 50 weeks per year with
two weeks per year for shutdown activities.
Functional Fluids (Open-System)
247
2011 OECD Emission Scenario Document on the Use of
Metalworking Fluids
Laboratory Chemicals
250
Assumed five days per week and 50 weeks per year with
two weeks per year for shutdown activities.
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569
570
571
572
573
574
575
576
577
578
579
580
Occupational Exposure
Scenario (Or.S)
Ki'lcasc l)a\s
Noll's
Film Cement
250
Assumed five days per week and 50 weeks per year with
two weeks per year for shutdown activities.
Spray Foam Application
260
Based on the 2018 EPA generic scenario Application of
Spray Polyurethane Foam Insulation, estimated average of
3 days spent/year at each work site.
Printing Inks (3D)
250
Assumed five days per week and 50 weeks per year with
two weeks per year for shutdown activities.
Dry Film Lubricant
56
Facility provided dry film lubricant manufacture and
application frequency.
Disposal
250
Assumed 5 days per week and 50 weeks per year.
Table 2-4 shows site-specific 1,4-dioxane releases as per 2018 TRI and DMR documents. For each
Occupational Exposure Scenario (OES), annual releases, release media, the type of water body, and
water use are also tabulated. These releases were reported to the 2018 TRI or DMR, and these data
represent a snapshot in time. Several reported water releases to TRI and DMR are estimated only.
Facilities below a requisite size are not required to report in TRI or DMR and therefore this map is likely
not representative of all the releases in the U.S. for 2018. There were no releases reported to TRI or
DMR for facilities in Alaska or Hawaii during this time period. Additional information available in
Supplemental Analysis File [Exposure Modeling Inputs, Results, and Risk Estimates for Incidental
Ambient Water Exposure],
Table 2-4.1,4-Dioxane re
eases in TRI and DMR
(2018)
Company
Name
City, State
OES
Annual
Release
(kg/yr)
NPDES Permit
Number1
Release
Media
Sub-Watershed
or Waterbody
Name1
Recreational /
Aquatic Life
Use1
BASF Corp.
Zachary, LA
Manufacturing
620.06
LA0004057
Surface
Water
Tchefuncta
River: Savannah
Branch
Yes / Yes
INEOS Oxide
Plaquemine,
LA
Industrial Uses
721.70
LAO 115100
Non-
POTW
WWT
Bayou
Bourbeaux
No/No
Microdyn-
Nadir Corp
Goleta, CA
Industrial Uses
24.04
CAZ482715
POTW
None Listed
No/No
Union Carbide
Industrial Uses
Surface
Water
Corp:
St Charles
Hahnville, LA
828.26
LA0000191
Bayou Fortier
No/No
Operations
Suez Wts
Solutions
USA Inc
Minnetonka,
MN
Industrial Uses
16920.83
MN0059013
POTW
South Fork
Ninemile Creek
No/No
The Dow
Chemical Co -
Louisiana
Operations
Plaquemine,
LA
Industrial Uses
647.73
LAG530436
Surface
Water
Bayou
Bourbeaux
No/No
Union Carbide
Corp: Institute
Facility
Institute, WV
Industrial Uses
3818.80
WVG611765
Surface
Water
Rocky Fork
Yes / Yes
Union Carbide
Corp:
Seadrift Plant
Seadrift, TX
Industrial Uses
503.49
None
Surface
Water
Private Surface
Water
No/No
BASF Corp.
Monaca, PA
Industrial Uses
2.98
PA0092223
Surface
Water
Sixmile Run-
Ohio River -
Raccoon Creek
No/No
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582
583
584
585
586
587
588
589
590
591
592
593
594
Company
Name
City, State
OES
Annual
Release
(kg/yr)
NPDES Permit
Number1
Release
Media
Sub-Watershed
or Waterbody
Name1
Recreational /
Aquatic Life
Use1
Cherokee
Pharmaceutica
Is LLC
Riverside, PA
Industrial Uses
1.66
PA0008419
Surface
Water
Susquehanna
River
No/No
Dak Americas
LLC
Fayetteville,
NC
Industrial Uses
7965.95
NC0003719
Surface
Water
Locks Creek-
Cape Fear River
Yes / Yes
Institute Plant
Institute, WV
Industrial Uses
6132.57
WV0000086
Surface
Water
Tyler Creek-
Kanawha River
- Rocky Fork
Yes / Yes
Kodak Park
Division
Rochester, NY
Industrial Uses
63.88
NY0001643
Surface
Water
Round Pond
Creek, Paddy
Hill Creek
Yes / Yes
Pharmacia &
Upjohn
(Former)
North Haven,
CT
Industrial Uses
1.05
CT0001341
Surface
Water
Quinnipiac
River
No/No
Philips
Electronics
Plant
Parker County,
TX
Industrial Uses
0.06
TX0113484
Surface
Water
Rock Creek
No/No
Sanderson
Gulch
Drainage
Improvements
Denver, CO
Industrial Uses
0.03
COG315474
Surface
Water
Bolden Gulch-
Muddy Creek
Yes / Yes
Ametek Inc.
U.S. Gauge
Division
Sellersville, PA
Open System
Functional Fluid
2.64
PA0056014
Surface
Water
East Branch
Perkiomen
Creek
No/No
Lake Reg
Med/Collegev
ille
Collegeville,
PA
Open System
Functional Fluid
0.24
PA0042617
Surface
Water
Lower
Perkiomen
Creek - Donny
Brook
No/No
Pall Life
Sciences Inc
Ann Arbor, MI
Open System
Functional Fluid
5.42
MI0048453
Surface
Water
Honey Creek
Yes / Yes
Beacon
Heights
Landfill
Beacon Falls,
CT
Disposal
30.06
CTMIU0161
Surface
Water
Bladens River-
Naugatuck
River
No/No
Ingersoll
Rand/Torringt
on Facility
Walhalla, SC
Disposal
11.49
SC0049093
Surface
Water
Cane Creek-
Little River
No/No
'Further detail on water releases and media of release are available at httos://echo.eoa.gov/
2,1.1,3 Assumptions and Key Sources of Uncertainty for Environmental Releases
EPA estimated water releases using reported discharges from the 2018 TRI and the 2018 DMR. TRI and
DMR data were determined to have a "medium" confidence rating through EPA's systematic review
process. Due to reporting requirements for TRI and DMR, the number of sites for a given OES may be
underestimated. It is uncertain the extent to which sites not captured in these databases discharge
wastewater containing 1,4-dioxane and whether any such discharges would be to surface water, POTW,
or non-POTW WWT.
In addition, information on the use of 1,4-dioxane at facilities in TRI and DMR is limited; therefore,
there is uncertainty as to whether the number of facilities estimated for a given OES do in fact represent
that specific OES. If sites were categorized under a different OES, the annual wastewater discharges for
each site would remain unchanged; however, average daily discharges may change depending on the
release days expected for the different OES.
-------
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
Facilities reporting to TRI and DMR only report annual discharges; to assess daily discharges, EPA
estimated the release days and averaged the annual releases over these days. There is uncertainty that all
sites for a given OES operate for the assumed duration; therefore, the average daily discharges may be
higher if sites have fewer release days or lower if they have greater release days. TRI-reporting facilities
are required to submit their "best available data" to EPA for TRI reporting purposes. Some facilities are
required to measure or monitor emissions or other waste management quantities due to regulations
unrelated to the TRI Program (e.g., permitting requirements), or due to company policies. These
existing, readily available data are often used by facilities for TRI reporting purposes, as they represent
the best available data. When monitoring or direct measurement data are not readily available or are
known to be non-representative for TRI reporting purposes, the TRI regulations require that facilities
determine release and other waste management quantities of TRI-listed chemicals by making reasonable
estimates. These reasonable estimates may be obtained through various Release Estimation Techniques,
including mass-balance calculations, the use of emission factors, and engineering calculations. There
may be greater uncertainty in data resulting from estimates compared to monitoring measurements.
Furthermore, 1,4-dioxane concentrations in wastewater discharges at each site may vary from day-to-
day such that on any given day the actual daily discharges may be higher or lower than the estimated
average daily discharge.
In some cases, the number of facilities for a given OES was estimated using data from the U.S. Census.
In such cases, the average daily release calculated from sites reporting to TRI or DMR was applied to
the total number of sites reported in (U.S. Census Bureau. 2015). It is uncertain how accurate this
average release is to actual releases at these sites; therefore, releases may be higher or lower than the
calculated amount.
2.1.1.3.1 Summary of Overall Confidence in Release Estimates
Table 2-5 provides a summary of EPA's overall confidence in its release estimates for each of the
Occupational Exposure Scenarios assessed.
Table 2-5. Summary of Overall Confidence in Release Estimates by OES
Occiipiilioiiiil
r.\|)ONIMY
Scenario (OI'.S)
()\cr;ill Confidence' in Kcloiisc l.sliniiik's
Manufacturing
Wastewater discharges are assessed using reported discharges from the 2018 TRI for two sites. TRI
data were determined to have a "medium" confidence rating through EPA's systematic review
process. Facilities reporting to TRI only report annual discharges; to assess daily discharges, EPA
assumed 250 days/yr. of operation and averaged the annual discharges over the operating days.
There is some uncertainty that all sites manufacturing 1,4-dioxane will operate for this duration;
therefore, the average daily discharges may be higher if sites operate for fewer than 250 days/yr. or
lower if they operate for greater than 250 days/yr. Furthermore, 1,4-dioxane concentrations in
wastewater discharges at each site may vary from day-to-day such that on any given day the actual
daily discharges may be higher or lower than the estimated average daily discharge. Based on this
information, EPA has a medium confidence in the wastewater discharge estimates for the two sites
in the 2018 TRI.
Import and
Repackaging
Wastewater discharges are assessed using reported discharges from the 2018 TRI and the 2018
DMR. TRI and DMR data were determined to have a "medium" confidence rating through EPA's
systematic review process. Due to reporting requirements for TRI and DMR, the number of sites in
this OES may be underestimated. It is uncertain the extent that sites not captured in these databases
discharge wastewater containing 1,4-dioxane and whether any such discharges would be to surface
-------
Occiipiilioiiiil
r.\|)ONIMY
Scenario (OI'.S)
()\cr;ill ( oillidenco in Kcloiisc l.sliniiik'N
water, POTW, or non-POTW WWT. Additionally, information on the conditions of use of 1,4-
dioxane at facilities in TRI and DMR is limited; therefore, there is some uncertainty as to whether
all the sites assessed in this section are performing repackaging (of imported or domestically
manufactured volumes) rather than a different OES. If the sites were categorized under a different
OES, the annual wastewater discharges for each site would remain unchanged; however, average
daily discharges may change depending on the number of operating days expected for the OES.
Facilities reporting to TRI and DMR only report annual discharges; to assess daily discharges, EPA
assumed 250 days/year of operation and averaged the annual discharges over the operating days.
There is some uncertainty that all sites importing or repackaging 1,4-dioxane will operate for this
duration; therefore, the average daily discharges may be higher if sites operate for fewer than 250
days/yr. or lower if they operate for greater than 250 days/yr. Furthermore, 1,4-dioxane
concentrations in wastewater discharges at each site may vary from day-to-day such that on any
given day the actual daily discharges may be higher or lower than the estimated average daily
discharge. Based on this information, EPA has a medium confidence in the wastewater discharge
estimates.
Recycling
Assessed as part of industrial uses.
Industrial Uses
Wastewater discharges are assessed using reported discharges from the 2018 TRI and the 2018
DMR. TRI and DMR data were determined to have a "medium" confidence rating through EPA's
systematic review process. Due to reporting requirements for TRI and DMR, the number of sites in
this OES may be underestimated. It is uncertain the extent that sites not captured in these databases
discharge wastewater containing 1,4-dioxane and whether any such discharges would be to surface
water, POTW, or non-POTW WWT. Additionally, information on the conditions of use of 1,4-
dioxane at facilities in TRI and DMR is limited; therefore, there is some uncertainty as to whether
all the sites assessed in this section are using 1,4-dioxane in an industrial use capacity rather than a
different OES. If the sites were categorized under a different OES, the annual wastewater
discharges for each site would remain unchanged; however, average daily discharges may change
depending on the number of operating days expected for the OES.
Facilities reporting to TRI and DMR only report annual discharges; to assess daily discharges, EPA
assumed 250 days/yr. of operation and averaged the annual discharges over the operating days.
There is some uncertainty that all sites using 1,4-dioxane for industrial uses will operate for this
duration; therefore, the average daily discharges may be higher if sites operate for fewer than 250
days/yr. or lower if they operate for greater than 250 days/yr. Furthermore, 1,4-dioxane
concentrations in wastewater discharges at each site may vary from day-to-day such that on any
given day the actual daily discharges may be higher or lower than the estimated average daily
discharge. Based on this information, EPA has a medium confidence in the wastewater discharge
estimates.
Functional Fluids
(Open-System)
Wastewater discharges are assessed using reported discharges from the 2018 TRI and the 2018
DMR. TRI and DMR data were determined to have a "medium" confidence rating through EPA's
systematic review process. Due to reporting requirements, the number of sites reflected in TRI and
DMR is assessed as an underestimate. EPA included the estimated 89,000 metal products and
machinery facilities estimated by the ESD on the Use of Metalworking Fluids as a conservative
bounding estimate for the possible range of sites. It is uncertain the extent that sites not captured in
the TRI and DMR databases discharge wastewater containing 1,4-dioxane and whether any such
discharges would be to surface water, POTW, or non-POTW WWT. Additionally, information on
the conditions of use of 1,4-dioxane at facilities in TRI and DMR is limited; therefore, there is
some uncertainty as to whether all the sites assessed in this section are using 1,4-dioxane in an open
system functional fluids capacity rather than a different OES. If the sites were categorized under a
different OES, the annual wastewater discharges for each site would remain unchanged; however,
-------
Occiipiilioiiiil
r.\|)ONIMY
Scenario (OI'.S)
()\cr;ill ( oillidenco in Kcloiisc l.sliniiik'N
average daily discharges may change depending on the number of operating days expected for the
OES.
Facilities reporting to TRI and DMR only report annual discharges; to assess daily discharges, EPA
assumed 247 days/yr. of operation and averaged the annual discharges over the operating days.
There is some uncertainty that all sites using 1,4-dioxane for open system functional fluids will
operate for this duration; therefore, the average daily discharges may be higher if sites operate for
fewer than 247 days/yr. or lower if they operate for greater than 247 days/yr. Furthermore, 1,4-
dioxane concentrations in wastewater discharges at each site may vary from day-to-day such that on
any given day the actual daily discharges may be higher or lower than the estimated average daily
discharge. Based on this information, EPA has a medium confidence in the wastewater discharge
estimates.
Laboratory Chemicals
Water releases from laboratory uses are unlikely as laboratories collect and track spent and unspent
chemicals prior to hazardous waste disposal. The releases of 1,4-dioxane from laboratory uses are
to air (through volatile releases into the indoor laboratory air and/or through laboratory fume hoods
to atmospheric air) and liquid wastes of 1,4-dioxane are handled as hazardous waste. The
commercial analytical laboratories and university laboratories handle their wastes as hazardous
waste and they are not allowed to discharge wastes to POTW via pouring the wastes down the
drain.
The number of laboratories assessed is based on the U.S. Census Bureau data for NAICS code
541380, Testing Laboratories. This NAICS code was chosen based on the main use of 1,4-dioxane
in the laboratory setting: as a reference standard for determination of analytes in bulk
pharmaceuticals. There are other types of laboratories, such as university laboratories and analytical
laboratories, that may use 1,4-dioxane that are not represented in this NAICS code. However, it is
unknown how many of laboratories within each of these categories use 1,4-dioxane. Thus, it is
possible that the inclusion of only NAICS code 541380 could overrepresent the number of
laboratories that use 1,4-dioxane. The direction of bias, whether the 6,844 number of sites is an
underestimate or overestimate of the number of laboratories using 1,4-dioxane, is unknown.
However, EPA has high confidence in the assessment of no or negligible releases to water or
POTWs. This high confidence in no releases of water mitigates the uncertainties in the estimate of
number of sites. Based on this information, EPA has a high confidence in the wastewater discharge
estimates.
Film Cement
EPA assessed no wastewater discharges for this OES. The small glue bottles could be disposed of
as solid waste without rinsing them in a sink. There is some uncertainty as to whether and what
quantity of 1,4-dioxane could remain in the small glue bottles when disposed. However, due to the
small quantities of the glue and high volatility of the 1,4-dioxane, EPA expects any residual 1,4-
dioxane to evaporate to the air or remain in the solid waste stream. Small amount of film cement
could inadvertently be spilled inside a facility, but due to the higher viscosity and small quantities
of the substance, it will likely be cleaned up via wiping and disposed of as solid waste. Based on
this information, EPA has a high confidence in the release assessment.
Spray Foam
Application
Wastewater discharges are assessed using EPA's container residual model. EPA defined operating
days, operating days per site, foam thickness, and mass fraction of B-side in final formulation from
the Generic Scenario for Application of Spray Polyurethane Foam Insulation. The parameters for
average roofing area were defined from homeadvisor.com and houselogic.com. The parameters for
density and mass fraction of the 1,4-dioxane in the B-side formulation were defined from a spray
foam producer's technical fact sheet. This EPA model addresses residual spray polyurethane foam
in the container only and is based on industry averages, such as roof size. As a result of the model
limitations and uncertainties due to various activities including container cleaning and product
handling could vary dramatically on a site-by-site basis. It is uncertain to the extent these water
releases are over- or underestimated.
-------
Occiipiilioiiiil
r.\|)ONIMY
Scenario (OI'.S)
()\cr;ill ( oillidenco in Kcloiisc l.sliniiik'N
EPA determined that there were 17,857 establishments that fell into NAICS code 238310, for
Drywall and Insulation Contractors. The GS estimates that a contractor spends three days at a job
site before moving to the next job site and further estimates that a contractor works 260 days per
year. Assuming a contractor works at only a single job site at a time, EPA calculates that a
contractor works at approximately 87 job sites per year (260 working days divided by three days
per job site). EPA multiplied the number of contractors by 87 to determine a bounding limit for the
number of job sites in a year at which all contractors could potentially discharge container residuals
down a drain to a POTW or directly on the ground, which could eventually reach surface waters.
Based on this information, EPA has a low confidence in the release assessment.
Printing Inks (3D)
EPA assessed no wastewater discharges for this OES. EPA expects spent printing ink containers,
shavings or fragments, or waste scraps to be disposed of as solid waste. There is some uncertainty
as to whether and how much 1,4-dioxane may remain in 3D printed products and waste scraps.
However, due to the volatility of 1,4-dioxane, EPA expects 1,4-dioxane to evaporate from any
printed object, shavings or fragments, or other printed material deposited to the floor or work
surface prior to it being cleaned and disposed of. EPA acknowledges that some 3D printing inks
may be inadvertently spilled inside a facility prior to printing and some quantities may not be
properly captured through spill containment techniques, resulting in printing ink being discharged
to POTW (through floor or sink drains. Due to the high volatility of 1,4-dioxane, EPA expects any
spilled printing ink not captured by spill containment materials to primarily be released to air.
Based on this information, EPA has a high confidence in the release assessment.
Dry Film Lubricant
EPA assessed no wastewater discharges for this OES based on conversations with the only known
facility to use the product. All dry film lubricant materials are mixed and handled in a laboratory
setting underneath a fume hood. The material is sprayed onto components in a spray booth with
ventilation. Wastes are containerized and handled as wastes for removal by a waste handler. There
is some uncertainty as to whether and how much 1,4-dioxane may be deposited on the floor or other
surfaces as a result of overspray or spills. However, due to the volatility of 1,4-dioxane and
expected spill clean-up methods of the laboratory setting, EPA expects deposited overspray or
spilled 1,4-dioxane to evaporate to the air or be contained in spill containment materials and
handled as waste. Based on this information, EPA has a high confidence in the release assessment.
Disposal
Wastewater discharges are assessed using reported discharges from the 2018 TRI and the 2018
DMR. TRI and DMR data were determined to have a "medium" confidence rating through EPA's
systematic review process. Due to reporting requirements for TRI and DMR, the number of sites in
this OES may be underestimated. It is uncertain the extent that sites not captured in these databases
discharge wastewater containing 1,4-dioxane and whether any such discharges would be to surface
water, POTW, or non-POTW WWT. Additionally, information on the conditions of use of 1,4-
dioxane at facilities in TRI and DMR is limited; therefore, there is some uncertainty as to whether
all the sites assessed in this section are using 1,4-dioxane in a disposal capacity rather than a
different OES. If the sites were categorized under a different OES, the annual wastewater
discharges for each site would remain unchanged; however, average daily discharges may change
depending on the number of operating days expected for the OES.
Facilities reporting to TRI and DMR only report annual discharges; to assess daily discharges, EPA
assumed 250 days/yr. of operation and averaged the annual discharges over the operating days.
There is some uncertainty that all sites using 1,4-dioxane for disposal will operate for this duration;
therefore, the average daily discharges may be higher if sites operate for fewer than 250 days/yr. or
lower if they operate for greater than 250 days/yr. Furthermore, 1,4-dioxane concentrations in
wastewater discharges at each site may vary from day-to-day such that on any given day the actual
daily discharges may be higher or lower than the estimated average daily discharge. Based on this
information, EPA has a medium confidence in the wastewater discharge estimates.
625
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626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
2.4 Human Exposures
2.1.2 General Population Exposure
1,4-Dioxane does not currently have established water quality criteria to protect human health under the
CWA Section 304(a). Therefore, in this evaluation, EPA considers potential general population
exposures via the ambient water pathway through evaluating incidental oral and dermal exposures
related to recreational activities such as swimming. 1,4-Dioxane is not expected to accumulate in fish
tissues; therefore, exposures to the general population via fish ingestion are not expected. The EPI
Suite BCFBAF model estimates 1,4-dioxane's bioaccumulation factor (BAF) to be 0.9. The BAF
indicates the concentration in fish tissues relative to the surrounding water, with concentrations in fish
tissues resulting from partitioning from water and dietary sources and reduced by metabolism. A BAF <
1 indicates that concentrations in fish tissues are expected to be lower than aqueous concentrations and
supports the expectation that fish ingestion is not a primary pathway of human exposure for 1,4-dioxane.
This is consistent with human and rat toxicokinetic data suggesting a short half-life (approximately 1
hour) for 1,4-dioxane following uptake. Given its hydrophilic properties and short half-life, 1,4-dioxane
is not expected to accumulate in tissue .
2.1.2.1 General Population Exposure Approach
Both estimated {i.e., modeled) and measured levels of 1,4-dioxane in ambient water/surface water, were
used to estimate incidental oral and dermal exposures during recreational activities such as swimming.
Based on the incidental nature of such exposures, this supplemental analysis focuses on only acute
exposures.
2.1.2.1.1 Modeling Surface Water Concentrations
In Section 2.2.1, Environmental Releases to Water, EPA estimates annual releases, release days, and
number of facilities to provide a range of daily water releases for each OES based on 2018 TRI and
DMR. Some OES had no predicted releases to surface water (see Table 2-1). Therefore, included in this
evaluation of general population exposures via ambient water include discharging sites involved in the
following OES: manufacturing, industrial uses, functional fluids (open-system), spray foam application,
and disposal. Table 2-1 shows the range of surface water release estimates across these OES; however,
site-specific discharges are provided and used in this exposure analysis (see Supplemental File
[Exposure Modeling Inputs, Results, and Risk Estimates for Incidental Ambient Water Exposure]).
Using the described site-specific water release information (kg/site/day) and days of release based on
OES categories and assumptions, environmental modeling was conducted using EPA's Exposure and
Fate Assessment Screening Tool (E-FAST 2014) to predict surface water concentrations in near-facility
ambient water bodies (U.S. EPA.: ). For more on the operation and inputs of the E-FAST model,
refer to the Estimating Surface Water Concentrations Section of Appendix E and the E-FAST 2014
Documentation Manual (U.S. EPA. 2007).
In this evaluation, site-specific stream flows were applied within E-FAST, where available, and no
wastewater treatment removal was applied. E-FAST does not incorporate degradation or volatilization
once released and estimates concentrations at the point of release (not downstream).
Modeled Surface Water Concentrations
Table 2-6 displays the modeled surface water concentrations obtained from E-FAST, as well as the site-
specific water release inputs. Refer to the Supplemental Files {Exposure Modeling Inputs, Results, and
-------
670 Risk Estimates for Incidental Ambient Water Exposure and Ambient Water Exposure Modeling Output
671 from E-FAST].
672
673 Table 2-6. Modeled Surface Water Concentrations
Occupational
Exposure
Scenario (OES)
Facility
SIC Code or
NPDES1
Daily Release
(kg/site/day)
Days of
Release
30Q52 Surface
Water
Concentration
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674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
Occupational
Exposure
Scenario (OES)
Facility
SIC Code or
NPDES1
Daily Release
(kg/site/day)
Days of
Release
30Q52 Surface
Water
Concentration
(HS/L)
Pall Life Sciences Inc
MI0024066
0.02
247
4.30E-02
Modeled Release
Estimates
Industrial POTW
0.038
247
2.85E+00
Spray Foam
Application
Modeled Release
Estimates
Industrial POTW
0.00
260
2.70E-01
Disposal
Beacon Heights
Landfill
CT0101061
0.12
250
5.30E-01
Ingersoll
Rand/Torrington Fac
Industrial POTW
0.05
250
3.46E+00
1 Some of the site-specific OES release estimates were unable to be associated with a specific NPDES code and receiving
water body within the E-FAST model. These sites were modeled using a generic, sector-specific SIC code.
2 Predicted 30Q5 surface water concentrations are the concentrations predicted using a 30Q5 stream flow. The 30Q5
stream flow is the lowest 30-day mean stream flow for a recurrence interval of five years. For sites modeled using a
generic SIC code, the values in this column correspond to concentrations predicted using the low-end (i.e., 10th percentile)
of the 30Q5 stream flow distribution for that SIC code. Receiving stream flow distributions for direct discharges within a
given SIC code are used to apply the 10th percentile flow. The 30Q5 concentrations are used in this evaluation over the
mean or 7Q10 concentrations based on alignment with the E-FAST guidance for assessing acute drinking water exposures;
this is noted to be consistent with EPA's Office of Water Technical Support Document for Water Quality-Based Toxics
Control (U.S. Km.
2.1.2.1.2 Measured Surface Water Concentrations
Surface water monitoring data were discussed and submitted during the public comment for 1,4-
dioxane. These submitted sources are briefly summarized below and were utilized in this evaluation of
general population exposures via ambient water.
A report from the North Carolina Department of Environmental Quality identified 1,4-dioxane in
surface water in the Deep, Haw, and Cape Fear Rivers at levels as high as 1,030 ug/L (mean 42.6-350.5
ug/L) (EPA-HO-OF* I M<_ 0238-0042; EPA-H.O-OPPT-2019-0238-0060; EPA-Ht M "j T-2019-
0238-0061). Sun et al. ( ) reported detections in North Carolina's Cape Fear watershed of 154 to
1,405 (J,g/L. The Minnesota Department of Environmental Quality reported 1,4-dioxane in state surface
waters at levels ranging from 0.05 to 4.4 (J,g/L (EPA-HQ-QPPT-2019-0238-0043). The upper ends of
these ranges were also used to estimate incidental oral and dermal exposures from swimming.
2.1.2.1.3 Estimating Incidental Oral Exposures from Swimming
Predicted stream concentrations were used to estimate incidental acute incidental oral exposure from
swimming. Predicted surface water concentrations range from 2.63E-03 |ig/L to 5.09E+03 |ig/L (see
Table 2-6); this range of predicted concentrations encompasses the full range of the surface water
monitoring data submitted during the public comment period.
Additional inputs/exposure factors used to estimate these acute oral exposures are included in
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695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
Table 2-7. Supplemental Analysis File [Exposure Modeling Inputs, Results, and Risk Estimates for
Incidental Ambient Water Exposure] for additional details on inputs and assumptions. This evaluation
focused on children 11-15 years, as they present most conservative conditions when considering the age-
specific ingestion rate, body weight, and duration of exposure.
Table 2-7 Incidental Oral Exposure Factors
Description
Value
Notes
Age Class
11-15
Selected based on having highest incidental oral ingestion rate during
swimming from the Exposure Factors Handbook, Table 3-7 (EPA, 2019b)
Incidental Ingestion
Rate
152 mL/hr
Upper-percentile hourly incidental ingestion rate from the Exposure Factors
Handbook, Table 3-7 CEP A. 2019b)
Body Weight
56.8 kg
Recommended, mean body weight for children 11-15 from the Exposure
Factors Handbook Table 8-1 (IIS. EPA. 2011)
Duration of
Exposure
2 hrs/day
High-end default short-term duration default from EPA Swimmer Exposure
Assessment Model (SWIMODEL): based on competitive swimmers in the
child 11-15 age class ( 15)
Daily Incidental
Ingestion Rate
0.304 L/day
0.152 L/day * 2 hrs
The equation used to estimate the acute daily dose rate (ADR) for incidental oral ingestion is shown below (U.S.
EPA. 2007s):
ADR
Where,
SWC = Surface water concentration (|ig/L)
IR = Daily ingestion rate (L/day)
CF = 0.001 mg/|ig
BW = Body weight (kg)
2.1.2.1.4 Estimating Dermal Exposures from Swimming
Predicted stream concentrations were used to estimate incidental acute and incidental dermal exposure
from swimming. Predicted surface water concentrations ranges from 2.63E-03 |ig/L to 5.09E+03 |ig/L
(see Table 2-6). Additional inputs/exposure factors used to estimate these acute dermal exposures are
included in
Table 2-8. Supplemental Analysis File [Exposure Modeling Inputs, Results, and Risk Estimates for
Incidental Ambient Water Exposure] for additional details on inputs and assumptions. This evaluation
focused on the adult age class, as they present the most conservative exposure conditions when
considering the age-specific surface area to body weight ratio and duration of exposure. Default
parameterization from OPP's SWIMODEL were utilized for most inputs as shown in Table 2-8 (EPA.
2015V
Table 2-8 Dermal Exposure Factors
Description
Value
Notes
Age Class
Adult
Selected based on having highest dose based on permeability-based dermal
exposure eanation used in SWIMODEL. considering exposed surface area,
duration, and body weight
Skin Surface Area
19,500 cm2
Default dermal contact surface area for the adult age class in
SWIMODEL(EPA. 2015)
Body Weight
80 kg
Recommended, mean body weight for adult age class (EFH. Table 8-1)
SWxIRx CF
BW
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724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
Description
Value
Notes
Exposure Duration
3 hrs/day
High-end, short-term default duration from EPA Swimmer Exposure
Assessment Model (SWIMODEL): based on competitive swimmers in the
adult age class (EPA. 2015)
Permeability
Coefficient (Kp)
5.05E-04
cm/hr
Estimated usins IHSkinPerm© for 1.4-dioxane dermallv absorbed into the
stratum corneum from water
The equation used to estimate the acute daily dose rate for dermal exposure from swimming shown below ("EPA.
2015):
CW x Kp x SA x ET x CF
ADR = w
Where,
CW = Chemical concentration in water (mg/L)
Kp = Permeability coefficient (cm/hr)
SA = Skin surface area exposed (cm2)
ET = Exposure time (hrs/day)
CF = Conversion factor (0.001 L/cm3)
BW = Body Weight (kg)
2.1.2.2 General Population Exposure Results
Estimated acute incidental oral exposures range from 1.41E-08 to 2.73E-02 mg/kg/day, while estimated
acute dermal exposures range from 9.71E-10 to 1.88E-03 mg/kg/day. The highest doses are associated
with releases from the industrial uses OES. This range of exposure estimates cover acute oral and
dermal doses estimated using both modeled and measured surface water concentrations. Refer to the
Supplemental File [Exposure Modeling Inputs, Results, and Risk Estimates for Incidental Ambient Water
Exposure] and Section 4.2.2 for the full set of results for all releasing sites and submitted monitoring
data.
2.1.2.3 Assumptions and Key Sources of Uncertainty Uncertainties for General Population
Exposure
EPA's approach recognizes the need to include uncertainty analysis. One important distinction for such
an analysis is variability versus uncertainty - both aspects need to be addressed. Variability refers to the
inherent heterogeneity or diversity of data in an assessment. It is a quantitative description of the range
or spread of a set of values and is often expressed through statistical metrics, such as variance or
standard deviation, that reflect the underlying variability of the data. Uncertainty refers to a lack of data
or an incomplete understanding of the context of the risk evaluation decision. Variability cannot be
reduced, but it can be better characterized. Uncertainty can be reduced by collecting more or better data.
Quantitative methods to address uncertainty include non-probabilistic approaches such as sensitivity
analysis and probabilistic or stochastic methods. Uncertainty can also be addressed qualitatively, by
including a discussion of factors such as data gaps and subjective decisions or instances where
professional judgment was used. Uncertainties associated with approaches and data used in the
evaluation of general population exposures are described below.
Modeling Inputs and Assumptions
Releases modeled using E-FAST 2014 were predicted based on engineering site-specific estimates based
on DMR and TRI reporting databases. These data that form the basis for engineering estimates are self-
reported by facilities subject to minimum reporting thresholds; therefore, they may not capture releases
from certain facilities not meeting reporting thresholds {i.e., environmental releases may be
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underestimated). These release estimates, however, are described as having a medium level of
confidence in Section 2.2.1.3.1.
E-FAST 2014 estimates surface water concentrations at the point of release, without accounting for
post-release environmental fate or degradation processes such as volatilization, biodegradation,
photolysis, hydrolysis, or partitioning. Additionally, E-FAST does not estimate stream concentrations
based on the potential for downstream transport and dilution. These considerations tend to lead to higher
predicted surface water concentrations. Dilution is incorporated, but it is based on the stream flow
applied. Therefore, there is uncertainty regarding the level of 1,4-dioxane that would be predicted
downstream of a releasing facility or after accounting for potential volatilization from the water surface,
which is dependent on the degree of mixing in a receiving water body.
The ambient water analysis assumes that members of the general population are incidentally exposed via
swimming in ambient waters, but there is uncertainty surrounding the likelihood that such recreation and
contact would occur at or near the point of release. If such activities occurred further from the point of
release, this analysis may overestimate the water concentrations that swimmers would be exposed to.
EPA's SWIMODEL was used as the source for exposure duration. This model is intended to assess
exposure from swimming in pools, not ambient water bodies, so there is uncertainty about the
application of swimming pool duration data in this analysis.
Aggregate Exposure
Background levels of 1,4-dioxane from other sources are not considered or aggregated in this analysis;
therefore, there is a potential for underestimating exposures, particularly for populations living near a
facility emitting 1,4-dioxane or living in a home with other sources of 1,4-dioxane, such as other 1,4-
dioxane-containing products stored and/or used in the home such as personal care products that are not
covered under TSCA. Similarly, there was no aggregation of incidental oral and dermal exposures from
swimming, which would be expected to be concurrent.
2.1.2.4 Confidence in General Population Exposure Estimates
Confidence ratings for general population ambient water exposure scenarios are informed by
uncertainties surrounding inputs and approaches used in modeling surface water concentrations and
estimating incidental oral and dermal doses. In Section 2.2.1.3.1, confidence ratings are assigned to
these estimated daily releases (kg/site-day) on a per occupational exposure scenario (OES) basis and
reflect moderate confidence.
Other considerations that impact confidence in the ambient water exposure scenarios include the model
used (E-FAST 2014) and its associated default and user-selected values and related uncertainties. As
described, there are uncertainties related to the ability of E-FAST 2014 to incorporate downstream fate
and transport. Of note, as stated on the EPA's E-FAST : ebsite. "modeled estimates of
concentrations and doses are designed to reasonably overestimate exposures, for use in an exposure
assessment in the absence of or with reliable monitoring data." Regarding the assumption that members
of the general population could reasonably be expected to swim at or near the point of release, there is
relatively low confidence due to uncertainty.
EPA utilized the SWIMODEL default duration parameters to estimate incidental dermal and oral
exposures to the general population from swimming in ambient water bodies. The model's default
duration inputs were based on swimming pool use patterns rather than freshwater bodies, so there is low
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to moderate confidence that these parameters accurately reflect the ambient water body recreation
activities covered in this supplemental analysis.
There are surface water monitoring data available that reflect ambient water exposure levels in the
United States (see Section 2.4.2.3). These data were submitted from only two states (NC and MN) and
may reflect multiple sources of 1,4-dioxane in surface water that may or may not be related to within-
scope occupational exposure scenarios. Because these monitoring data reflect surface water conditions
at specific sampling sites during a specific sampling period, they may not reflect current levels of 1,4-
dioxane in surface water. The modeled surface water concentration ranges obtained from E-FAST
modeling (2.63E-03 - 5.09E+03 |ig/L) encompass the full range of the surface water monitoring data
submitted during public comment period.
Based on the above considerations, the general population ambient water exposure assessment scenarios
have an overall low to moderate confidence.
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2.1.3 Consumer Exposures
As explained in the scope document, 1,4-dioxane may be found as a contaminant in consumer
products that are readily available for public purchase.
2.1.3.1 Consumer Conditions of Use and Routes of Exposure Evaluated
Eight consumer conditions of use are evaluated based on the uses identified in EPA's 2015
TSCA Work Plan Chemical Problem Formulation and Initial Assessment of 1,4-Dioxane (U.S.
LI). An additional systematic review effort was undertaken for consumer exposures to
identify, screen, and evaluate relevant data sources. These conditions of use include surface
cleaner, antifreeze, dish soap, dishwasher detergent, laundry detergent, paint and floor lacquer,
textile dye, and spray polyurethane foam (SPF). 1,4-Dioxane may be found in these products at
low levels (0.0009 to 0.02%) based on its presence as a byproduct of other formulation
ingredients, i.e., ethoxylated chemicals.
Inhalation exposures to 1,4-dioxane are estimated for household consumers {i.e., product users -
receptors who use a product directly) and bystanders {i.e., receptors who are a non-user that may
be incidentally exposed to the product). Acute inhalation exposures are presented for all
conditions of use, while chronic inhalation exposures are only presented for conditions of use
that are reasonably expected to involve daily use intervals {i.e., surface cleaner, dish soap,
dishwasher detergent, and laundry detergent). Other conditions of use {i.e., SPF, antifreeze,
textile dye, and paint and floor lacquer) are not evaluated over chronic exposure durations based
on expected infrequent and intermittent use frequencies.
Dermal exposures to 1,4-dioxane are estimated for household consumers, or users. Users are
assumed to include adults (21+ years) and children (11-20 years). As with inhalation, acute
dermal exposures are presented for all conditions of use, while chronic inhalation exposures are
only presented for conditions of use that are reasonably expected to involve daily use intervals
{i.e., surface cleaner, dish soap, dishwasher detergent, and laundry detergent). Other conditions
of use {i.e., SPD, antifreeze, textile dye, and paint and floor lacquer) are not evaluated over
chronic exposure durations based on expected infrequent and intermittent use frequencies.
Generally, individuals that have contact with liquid 1,4-dioxane would be users and not
bystanders. Therefore, direct dermal exposures are not expected for bystanders and are only
estimated for users.
2.1.3.2 Potentially Exposed or Susceptible Subpopulations
Consumers and bystanders are potentially exposed or susceptible subpopulations (PESS) due to
their greater exposure. Additionally, high-intensity users {i.e., those using consumer products for
longer durations or in great amounts) are evaluated. Consumers are considered to include
children and adults, ages 11 and up, while bystanders in the home exposed via inhalation could
include children and adults of all ages.
2.1.3.3 Consumer Exposure Modeling Approach
Modeling was conducted to estimate exposure from the identified consumer conditions of use.
Exposures via inhalation and dermal contact to consumer products were estimated using EPA's
Consumer Exposure Model (CEM) Version 2.1 (U.S. EPA. 2019a). along with consumer
behavioral pattern data {i.e., use patterns) and product-specific inputs. An older version of CEM,
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available within E-FAST 2014, was used to estimate chronic inhalation exposures and obtain
lifetime average daily concentration outputs (U.S. EPA. 2014c). EPA's Multi-Chamber
Concentration and Exposure Model (MCCEM) was used to estimate inhalation exposures related
to use of SPF based on the availability of measured emission rate data for that scenario (EPA.
2010). Table 2-9 displays the models used to estimate inhalation and dermal exposures across the
consumer conditions of use.
Table 2-9 Models Used Across Consumer Conditions of Use and Routes of
Exposure
Consumer Condition
Acute Inhalation
Chronic Inhalation
Acute Dermal
Chronic Dermal
of Use
Exposure
Exposure
Exposure
Exposure
Surface Cleaner
CEM 2.1
CEM
CEM 2.1
CEM 2.1
Antifreeze
CEM 2.1
CEM 2.1
Dish Soap
CEM 2.1
CEM
CEM 2.1
CEM 2.1
Dishwasher Detergent
CEM 2.1
CEM
CEM 2.1
CEM 2.1
Laundry Detergent
CEM 2.1
CEM
CEM 2.1
CEM 2.1
Paint and Floor Lacquer
CEM 2.1
CEM 2.1
Textile Dye
CEM 2.1
CEM 2.1
SPF
MCCEM
CEM 2.1
Emission data were identified and evaluated through systematic review. For some conditions of
use, emission data were used to support estimated exposures and to model emissions of SPF (see
Appendix A. 1.2.1).
2.1.3 .3 .1 Modeling Air Concentrations and Inhalation Exposure
Consumer Exposure Model
CEM 2.1 and CEM predict indoor air concentrations from consumer product use by
implementing a deterministic, mass-balance calculation utilizing an emission profile determined
by applying appropriate emission scenarios. The model uses a two-zone representation of the
building of use (e.g., residence, school, office), with Zone 1 representing the room where the
consumer product is used (e.g., a utility room) and Zone 2 being the remainder of the building.
The product user is placed within Zone 1 for the duration of use, while a bystander is placed in
Zone 2 during product use. Otherwise, product users and bystanders follow prescribed activity
patterns throughout the simulated period.
For acute exposure scenarios, emissions from each incidence of product usage are estimated over
a period of 72 hours using the following approach that accounts for how a product is used or
applied, the total applied mass of the product, the weight fraction of the chemical in the product,
and the molecular weight and vapor pressure of the chemical. Time weighted averages (TWAs)
were then computed based on these user and bystander concentration time series per available
human health hazard data. For 1,4-dioxane, 8-hour TWAs were quantified for use in risk
evaluation based on alignment of relevant acute human health hazard endpoints. For additional
details on CEM 2.l's underlying emission models, assumptions, and algorithms, please see the
User Guide Section 3: Detailed Descriptions of Models within CEM 2.1 (U.S. EPA. ), also
summarized in Appendix A. The emission models used have been compared to other model
results and measured data; see Appendix D: Model Corroboration of the User Guide Appendices
for the results of these analyses ( 1019b).
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For chronic exposure scenarios, CEM within E-FAST 2014 was used to obtain lifetime average
daily concentrations (LADCs) for the scenarios involving chronic exposures. Emissions are
estimated over a period of 60 days. For cases where the evaporation time estimated exceeds 60
days, the model will truncate the emissions at 60 days. Conversely, for cases where the
evaporation time is less than 60 days, emissions will be set to zero between the end of the
evaporation time and 60 days. For more information on this version of CEM and its chronic
inhalation estimates, refer to the E-FAST 2014 Documentation Manual (U.S. EPA. 2007).
The general steps of the calculation engine within the CEM 2.1 and CEM models include:
Introduction of the chemical {i.e., 1,4-dioxane into the room of use (Zone 1) through
two possible pathways: (1) overspray of the product or (2) evaporation from a thin
film;
Transfer of the chemical to the rest of the house (Zone 2) due to exchange of air
between the different rooms;
Exchange of the house air with outdoor air; and
Compilation of estimated air concentrations in each zone as the modeled occupant
{i.e., user or bystander) moves about the house per prescribed activity patterns.
Multi-Chamber Concentration and Exposure Model
The Multi-Chamber Concentration and Exposure Model (MCCEM) estimated indoor air
concentrations of chemicals released from household products (EPA.! ). It uses air
infiltration and interzonal air flow rates with user-input emission rates to calculate time-varying
concentrations in several zones or chambers within a residence. Four types of source models are
available in MCCEM - constant, single exponential, incremental, and data entry. For additional
details, see the MCCEM User Guide (EPA. 2019c).
Within MCCEM, the incremental source model is specifically designed for products that are
applied to a surface (as SPF is) rather than products that are placed in an environment {e.g., an
air freshener). This distinction is important because the incremental source model considers the
time or duration of application or use in its calculations of emissions and concentrations, while
the single exponential source model does not. The incremental model assumes a constant
application rate over time, coupled with an emission rate for each instantaneously applied
segment that declines exponentially.
The incremental model can be populated using data derived from the experimental data and
proposed model of emission rates in Karlovich et al. (2011). See Appendix A for details on the
underlying equations and applying these data to estimate the emission rate for this scenario.
2.1.3 .3 .2 Modeling Dermal Exposure
CEM 2.1 contains dermal modeling components that estimate absorbed dermal doses resulting
from dermal contact with chemicals found in consumer products: P_DER2a: Dermal Dose from
a Product Applied to Skin, Fraction Absorbed Model and P_DER2b: Dermal Dose from Product
Applied to Skin, Permeability Model. The selection of the appropriate dermal model was based
on whether an evaluated condition of use is expected to involve dermal contact with impeded or
unimpeded evaporation. For scenarios that are more likely to involve dermal contact with
impeded evaporation {e.g., wiping or cleaning with a chemical soaked rag), the permeability
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model is applied. In contrast, for scenarios less likely to involve impeded evaporation, the
fraction absorbed model is applied. For acute exposure scenarios, dermal acute dose rates
(ADRs) are estimated and, for chronic exposure scenarios, lifetime average daily doses (LADDs)
are estimated. See Appendix A for a more detailed comparison of these dermal models.
The permeability model estimates the mass of a chemical absorbed and dermal flux based on a
permeability coefficient (Kp) and is based on the ability of a chemical to penetrate the skin layer
once contact occurs. It assumes a constant supply of chemical directly in contact with the skin
throughout the exposure duration. Kp is a measure of the rate of chemical flux through the skin.
The parameter can either be specified by the user (if measured data are reasonably available) or
be estimated within CEM using a chemical's molecular weight and octanol-water partition
coefficient (Kow). The permeability model does not inherently account for evaporative losses
(unless the available flux or Kp values are based on non-occluded, evaporative conditions),
which can be considerable for volatile chemicals in scenarios where evaporation is not impeded.
While the permeability model does not explicitly represent exposures involving such impeded
evaporation, the model assumptions make it the preferred model for an such a scenario. For 1,4-
dioxane, an estimated aqueous dermal permeability coefficient (Kp, 5.05E-04 cm/hr) is used,
based on IHSkinPerm© predictions. For additional details on this model, please see Appendix A
and the CEM User Guide Section 3: Detailed Descriptions of Models within CEM (U.S. EPA.
2019aY
The fraction absorbed model estimates the mass of a chemical absorbed through the applicational
of a fractional absorption factor to the mass of chemical present on or in the skin following a use
event. The initial dose or amount retained on the skin is determined using a film thickness
approach. A fractional absorption factor is then applied the initial dose to estimate absorbed
dose. The fraction absorbed is essentially the measure of two competing processes, evaporation
of the chemical from the skin surface and penetration deeper into the skin. It can be estimated
using an empirical relationship based on Frasch and Bunge (2015). Due to the model's
consideration of evaporative processes, it was considered more representative of dermal
exposure under unimpeded exposure conditions. For additional details on this model, please see
Appendix A and the CEM User Guide Section 3: Detailed Descriptions of Models within CEM
(I >019aY
2,1,3,4 Consumer Exposure Scenarios and Modeling Inputs
Based on the combination of high-end and central tendency inputs, modeling results are
presented for "high-intensity users" or "moderate-intensity users." High-intensity user scenarios
are characterized by high-end {i.e., 95th percentile or maximum) inputs governing key user
behavior pattern inputs (duration of use, mass of product used). Moderate-intensity user
scenarios are characterized by central tendency {i.e., 50th percentile) inputs governing the key
user behavior pattern inputs of duration of use and mass of product used. Although key inputs
represent high-end or central tendencies, this was a deterministic assessment and exposure
results are not reflective of a distribution.
For acute exposure scenarios, only high-intensity user scenarios that incorporate high-end mass,
duration, and weight fraction inputs are presented. For chronic exposure scenarios, both high-end
and moderate-intensity user scenarios are presented based on model documentation and the
understanding that central tendency parameters may more accurately represent lifetime
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exposures. CEM and CEM 2.1 are designed to use central tendency inputs for mass, duration,
use frequency, and weight fraction when estimating lifetime exposures ( ^ \ 1 v
EPA. 2019a). Chronic high-intensity user scenarios, unlike the acute high-intensity user
scenarios, utilize central tendency weight fraction inputs, where possible.
Some modeling inputs such as the room of use {i.e., Zone 1 volume) and surface area to body
weight ratio exposed in dermal exposure scenarios were held constant across the multiple
iterations of a single product scenario but differed across product scenarios based on their
product-specific nature. Other parameters such as chemical properties, building volume, air
exchange rate, interzonal ventilation rate, and user and bystander activity patterns {i.e.,
movements around the home) were held constant across all exposure scenarios and reflect central
tendency inputs {i.e., median or mean values; see Table 2-10).
For details on default modeling inputs and a sensitivity analysis, see Appendix B and Appendix
C, respectively, of the CEM 2.1 user guide appendices (U.S. EPA. 2019b). The sensitivity
analysis is also summarized in Appendix A.
Table 2-10 Default Modeling In
put Parameters
Parameter Type
Modeling
Parameter
Default Value Modeled
Value
Characterization
Reference
Building
Characteristic1
Building Volume
(m3)
492
Central Tendency
(Mean)
(U.S. EPA. 2011)
Air Exchange Rate
(hr1)
0.45
Central Tendency
(Median)
(U.S. EPA. 2011)
Interzonal
Ventilation Rate2
(m3/hr)
107
NA
Defaults tU.S. EPA. 2019a. b)
Emission
Characteristics
Background Air
Concentration
(mg/m3)
0
Minimum
Gas Phase Mass
Transfer
Coefficient (m/hr)
Based on chemical properties and estimated
within CEM (for SPF scenario modeled with
MCCEM, see Appendix A)
Emission Factor
(ug/m2/hr)
Saturation
Concentration in
Air (mg/m3)
1.89E+05
Based on chemical
properties and
estimated within
CEM
Use Patterns and
Exposure Factors
Receptor Activity
Pattern
Stay at home3
NA
Default (U.S. EPA. 2019a. b)
Use Start Time
9 AM4
NA
NA
Frequency of Use
1 event per day
NA
Defaults (U.S. EPA. 2019a. b)
Acute Exposure
Duration
1 day
NA
Page 37 of 93
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Acute Averaging
Time
1 day
NA
Chronic Exposure
Duration
57 years
NA
Chronic Averaging
Time
78 years
NA
Surface Area to
Face, Hands, Arms
Body Weight Ratio
Adult (21+): 15.8
Central tendency
Children (16-20): 14.9
(mean)
Children (11-15): 16.4
Both Hands
Adult (21+): 12.4
Central tendency
Children (16-20): 11.6
(mean)
Children (11-15): 12.7
Inside of One Hand
Adult (21+): 3.10
Central tendency
Children (16-20): 2.90
(mean)
Children (11-15): 3.17
10% of Hands
Adult (21+): 1.24
Central tendency
Children (16-20): 1.16
(mean)
Children (11-15): 1.27
1 An overall residential building volume of 492 m3 is used to calculate air concentrations in Zone 2 and room volume is
used to calculate air concentrations in Zone 1. The volume of the near-field bubble in Zone 1 was assumed to be 1 m3 in
all cases, with the remaining volume of Zone 1 comprising the far-field volume.
2 The default interzonal air flows are a function of the overall air exchange rate and volume of the building, as well as the
"openness" of the room itself. Kitchens, living rooms, garages, schools, and offices are considered more open to the rest
of the home or building of use; bedrooms, bathrooms, laundry rooms, and utility rooms are usually accessed through one
door and are considered more closed.
3 The activity pattern (i.e., zone location throughout the simulated exposure period) for user and bystander was the
default "stay-at-home" resident, which assumes the receptors are primarily in the home (in either Zone 1 or 2)
throughout the day. These activity patterns in CEM were developed based on Consolidated Human Activity Database
(CHAD) data of activity ratterns (Isaacs. 2014).
4 Product use was assumed to start at 9 AM in the morning; as such, the user was assumed to be in the room of use (Zone
1) at that time, regardless of the default activity pattern at 9 AM.
1019
1020 Key product scenario-specific modeling inputs for inhalation modeling are shown in Table 2-11.
1021 For scenarios with both acute and chronic exposure estimates, the table includes both high-end
1022 and central tendency inputs for duration, mass, and frequency of use. Please refer to the
1023 Supplemental Analysis File [Consumer Exposure Assessment Modeling Input Parameters] for a
1024 detailed listing of all inputs and associated sources.
1025
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1026 Table 2-11 Key Product-Specific Inputs for Inha
Consumer
Product
Scenario
Form
Range of
Product Cone,
(ppm)
Max 1
Weight
Fraction
Room of
Use
(volume,
m3)
Duration
of Use
(min)
Mass of
Product
Used
(g)
Frequency
of Use
(days/year)
Surface
Cleaner
Liquid
0.36-9
9.00E-06
Bathroom
(15)
30
300
365
15
200
300
Antifreeze
Liquid
0.01-86
8.60E-05
Garage
(90)
15
150
NA
Dish Soap
Liquid
0.7-204
2.04E-04
Kitchen
(24)
20
84
365
10
48
300
Dishwasher
Detergent
Liquid/
Gel
0.86-9.7
9.70E-06
50
40
365
45
20
300
Laundry
Detergent
Liquid
0.05 - 14
1.40E-05
Utility
Room
(20)
50
60
365
45
40
300
Paint and
Floor
Lacquer
Liquid
0.02-30
3.00E-05
Bedroom
(36)
810
26025
NA
Textile Dye
Aqueous
NA
4.70E-06
Utility
Room
(20)
20
100
NA
SPF2
Foam
500 3
5.00E-04
Attic
(123)
360
4.5 4
NA
Basement
(246)
4.5 4
Garage
(118)
180
2.2 4
1 The use of "Max" (/'. e., maximum) here does not indicate use of a theoretical maximum or upper limit but refers to
the highest identified weight fraction for a given product type based on the available data. Mean weight fractions
were used, where possible, for chronic exposure estimates. See the Supplemental Analysis File [Consumer
Exposure Assessment Modeling Input Parameters].
2 The SPF scenario was modeled using MCCEM to estimate inhalation exposures. Please refer to the Supplemental
Analysis File [Consumer Exposure Assessment Modeling Input Parameters] for additional, distinct modeling inputs
for this scenario.
3 The applied 500 ppm concentration aligns with the related OES, which assumed 50% blending (parts A and B).
4 Mass of use was not an input in MCCEM as it was in the CEM model. These masses instead reflect the total mass
of chemical released in each exposure setting. These were estimated using loading ratios, application surface areas,
emission rate per square inch, and decay rate per hour. Please refer to the Supplemental Analysis File [Consumer
Exposure Assessment Modeling Input Parameters1 and Appendix A for more details.
ation Modeling
1027
1028
1029
1030
1031
1032
Key product scenario-specific modeling inputs for dermal modeling are shown in Table 2-12.
For scenarios with both acute and chronic exposure estimates, the table includes both high-end
and central tendency inputs for duration, mass, and frequency of use. Please refer to the
Supplemental Analysis File [Consumer Exposure Assessment Modeling Input Parameters] for a
detailed listing of all inputs and associated sources.
Page 39 of 93
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1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
Table 2-12 Key Proc
uct-Specific Inputs
'or Dermal Modeling
Consumer
Product
Scenario
Form
Max 1
Weight
Fraction
Exposed
Surface
Area
Duration
of Use2
(min)
Absorption
Fraction3
Film
Thickness
(cm)
Permeability
Coefficient
(Kp, cm/hr)
Frequency
of Use
(days/year)
Surface
Cleaner
Liquid
9.00E-06
Inside of
one hand
30
0.32
0.00214
5.05E-04
365
15
0.26
300
Antifreeze
Liquid
8.60E-05
15
0.26
0.00655
NA
Dish Soap
Liquid
2.04E-04 4
Both
hands
20
0.29
0.00655
365
10
0.21
300
Dishwasher
Detergent
Liquid/
Gel
9.70E-06
10% of
hands
1
0.038
0.00655
365
300
Laundry
Detergent
Liquid
1.40E-05 4
Both
hands
20
0.29
0.00655
365
10
0.21
300
Paint and
Floor
Lacquer
Liquid
3.00E-05
Face,
hands,
arms
810
0.34
0.00981
NA
Textile
Dye
Aqueou
s
4.70E-06 4
Both
hands
20
0.29
0.00655
NA
SPF
Foam
5.00E-04
Face,
hands,
arms
Attic
360
0.34
0.01
NA
Basement
360
Garage
180
1 The use of "Max" (i.e., maximum) here does not indicate use of a theoretical maximum or upper limit but refers to the
highest identified weight fraction for a given product type based on the available data. See the Supplemental Analysis File
[Consumer Exposure Assessment Modeling Input Parameters].
2 Durations of use were adjusted for dermal exposure for two scenarios: dishwashing detergent and laundry detergent. The
model default durations listed in Table 2-11 above are based on machine run times and would not be appropriate for dermal
contact duration.
3 Absorption fractions are estimated using duration of exposures; therefore, distinct absorption fractions are estimated and
applied for high-end vs. central tendency durations. This term is only used in estimation of dose using the fraction absorbed
model.
4 Dilution fractions were applied to three scenarios: dish soap (3%), laundry detergent (1.6%), and textile dye (10%). See
the Supplemental Analysis File [Consumer Exposure Assessment Modeling Input Parameters] for details.
2.1.3.5 Consumer Exposure Results
Estimated inhalation and dermal exposures are presented below for all consumer conditions of
use. Scenarios that involve frequent {i.e., daily) exposure intervals present acute and chronic
exposure estimates for consumer users and acute exposure estimates for users and bystanders.
Scenarios that involve intermittent or infrequent exposure intervals present acute exposure
estimates only for users and bystanders.
2.1.3 .5 .1 Surface Cleaner
Acute and chronic inhalation and dermal exposures to 1,4-dioxane present as a byproduct in
surface cleaner were evaluated. Concentrations of 1,4-dioxane in surface cleaners range from
0.36 to 9 ppm (up to 0.0009%). CEM 2.1 default inputs for all-purpose liquid cleaner were used
as the basis for duration of use and mass of product used. The room of use (Zone 1) is a
bathroom and the dermal surface area reflects the inside of one hand. This scenario assumes
Page 40 of 93
-------
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
dermal contact during wiping/cleaning activities and may involve inhibited evaporation from the
skin surface.
Inhalation exposure estimates are presented below. See the Supplemental Analysis File
[.Exposure Modeling Results and Risk Estimates for Consumer Exposures] for exposure results
and associated risk estimates.
Table 2-13 Esl
imated Inhalation Exposure: Surface Cleaner
Scenario
Description
Duration of Use
(min)
Weight
Fraction
Mass Used
(g)
Product User
or Bystander
8-hr Max
TWA
(mg/m3)
LADC
(mg/m3)
Acute
High-Intensity
User
High End
(30)
Max
(9.0E-06)
High End
(300)
User
5.0E-03
Bystander
9.5E-04
Chronic
High-Intensity
User
High End
(30)
Max 1
(9.0E-06)
High End
(300)
User
1.0E-03
Moderate-
Intensity User
Central Tendency
(15)
Max
(9.0E-06)
Central
Tendency
(200)
User
5.6E-04
Although, generally, mean weight fractions were utilized in all chronic modeling (high-intensity and moderate-
intensity user scenarios), a mean could not be estimates for this scenario based on source information.
Dermal exposure estimates are presented below and are based on the permeability model within
CEM 2.1. See the Supplemental Analysis File [Exposure Modeling Results and Risk Estimates
for Consumer Exposures] for exposure results and associated risk estimates, including those
based on the fraction absorbed model within CEM 2.1.
Page 41 of 93
-------
1061
1062 Table 2-14 Estimated Dermal Exposure: Surface Cleaner
Scenario Description
Duration of Use
(min)
Weight
Fraction
(%)
Receptor
ADR
(mg/kg/day)
LADD
(mg/kg/day)
Acute
High-Intensity User
High End
(30)
Max
(9.0E-06)
Adult (>21 years)
7.7E-06
Children (16-20 years)
7.2E-06
Children (11-15 years)
7.9E-06
Chronic
High-Intensity User
High End
(30)
Max1
(9.0E-06)
Adult (>21 years)
5.6E-06
Moderate-Intensity
User
Central Tendency
(15)
Max
(9.0E-06)
Adult (>21 years)
2.3E-06
Although, generally, mean weight fractions were utilized in all chronic modeling (high-intensity and moderate-
intensity user scenarios), a mean could not be estimates for this scenario based on source information.
1063
1064 2.1.3.5.2 Antifreeze
1065 Acute inhalation and dermal exposures to 1,4-dioxane present as a byproduct in antifreeze were
1066 evaluated. Concentrations of 1,4-Dioxane in antifreeze range from 0.01 to 86 ppm (up to
1067 0.0086%). CEM 2.1 default inputs for anti-freeze liquid were used as the basis for duration of
1068 use and mass of product used. The room of use (Zone 1) is a garage and the dermal surface area
1069 reflects the inside of one hand. This scenario assumes dermal contact during pouring activities
1070 and is not expected to involve inhibited evaporation from the skin surface.
1071
1072 Inhalation exposure estimates are presented below. See the Supplemental Analysis File
1073 [.Exposure Modeling Results and Risk Estimates for Consumer Exposures] for exposure results
1074 and associated risk estimates.
1075
Table 2-15 Estimated Inhalation Exposure: Ant
ifreeze
Scenario
Description
Duration of Use
(min)
Weight
Fraction
Mass Used
(g)
Product User
or Bystander
8-hr Max
TWA
(mg/m3)
Acute
High-Intensity
User
High End
(15)
Max
(8.6E-05)
High End
(150)
User
1.6E-02
Bystander
4.0E-03
1077
1078 Dermal exposure estimates are presented below and are based on the fraction absorbed model
1079 within CEM 2.1. See the Supplemental Analysis File [.Exposure Modeling Results and Risk
1080 Estimates for Consumer Exposures] for exposure results and associated risk estimates, including
1081 those based on the permeability model within CEM 2.1.
1082
Page 42 of 93
-------
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
Table 2-16 Estimated Dermal Exposure: Antifreeze
Scenario Description
Duration of Use
(min)
Weight
Fraction
(%)
Receptor
ADR
(mg/kg/day)
Acute
High-Intensity User
High End
(15)
Max
(150)
Adult (>21 years)
5.12E-04
Children (16-20 years)
4.80E-04
Children (11-15 years)
5.24E-04
2.1.3.5.3 Dish Soap
Acute and chronic inhalation and dermal exposures to 1,4-dioxane present as a byproduct in dish
soap were evaluated. Concentrations of 1,4-dioxane in dish soap range from 0.7 to 204 ppm (up
to 0.02%). CEM 2.1 default inputs for hand dishwashing soap/liquid serves as the basis for
duration of use and an American Cleaning Institute exr
document serves as the basis for mass of product used during hand dishwashing. The room of
use (Zone 1) is a kitchen and the dermal surface area reflects both hands. A 0.7% dilution factor
is applied. This scenario assumes immersive dermal contact in the 0.7% dish soap solution
during washing activities and may involve inhibited evaporation from the skin surface.
Inhalation exposure estimates are presented below. See the Supplemental Analysis File
[.Exposure Modeling Results and Risk Estimates for Consumer Exposures] for exposure results
and associated risk estimates.
Table 2-17 Estimated Inhalation Exposure: Dish Soap
Scenario
Description
Duration of Use
(min)
Weight
Fraction
Mass Used
(g)
Product
User or
Bystander
8-hr Max
TWA
(mg/m3)
LADC
(mg/m3)
Acute
High-Intensity
User
High End
(20)
Max
(2.04E-04)
High End
(84)
User
3.0E-02
Bystander
5.4E-03
Chronic
High-Intensity
User
High End
(20)
Central
Tendency
(2.40E-05)
High End
(84)
User
7.1E-04
Moderate-
Intensity User
Central Tendency
(10)
Central
Tendency
(2.40E-05)
Central
Tendency
(48)
User
3.3E-04
Dermal exposure estimates are presented below and are based on the permeability model within
CEM 2.1. See the Supplemental Analysis File [Exposure Modeling Results and Risk Estimates
for Consumer Exposures] for exposure results and associated risk estimates, including those
based on the fraction absorbed model within CEM 2.1.
Page 43 of 93
-------
1105 Table 2-18 Estimated Dermal Exposure: Dish Soap
Scenario Description
Duration of Use
(min)
Weight
Fraction
(%)
Receptor
ADR
(mg/kg/day)
LADD
(mg/kg/day)
Acute
High-Intensity User
High End
(20)
Max
(2.04E-04)
Adult (>21 years)
3.1E-06
Children (16-20 years)
2.9E-06
Children (11-15 years)
3.1E-06
Chronic
High-Intensity User
High End
(20)
Central
Tendency
(2.40E-05)
Adult (>21 years)
2.6E-07
Moderate-Intensity
User
Central Tendency
(10)
Central
Tendency
(2.40E-05)
Adult (>21 years)
1.1E-07
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
2.1.3.5.1 Dishwashing Detergent
Acute and chronic inhalation and dermal exposures to 1,4-dioxane present as a byproduct in
dishwashing detergent were evaluated. Concentrations of 1,4-dioxane in dishwashing detergent
range from 0.86 to 9.7 ppm (up to 0.001%). CEM 2.1 default inputs for on machine dishwashing
detergent (liquid/gel) were used as the basis for duration of use and mass of product used. The
room of use (Zone 1) is a kitchen and the dermal surface area reflects 10% of hands. This
scenario assumes brief dermal contact during loading activities and is not expected to involve
inhibited evaporation from the skin surface.
Inhalation exposure estimates are presented below. See the Supplemental Analysis File
[.Exposure Modeling Results and Risk Estimates for Consumer Exposures] for exposure results
and associated risk estimates.
Table 2-19 Estimated Inhalation Exposure: Dishwasher Detergent
Scenario
Description
Duration of Use
(min)
Weight
Fraction
Mass Used
(g)
Product
User or
Bystander
8-hr Max
TWA
(mg/m3)
LADC
(mg/m3)
Acute
High-Intensity
User
High End
(50)
Max
(9.7E-06)
High End
(40)
User
6.9E-04
Bystander
1.2E-04
Chronic
High-Intensity
User
High End
(50)
Central
Tendency
(5E-06)
High End
(40)
User
7.1E-05
Moderate-
Intensity User
Central Tendency
(45)
Central
Tendency
(5E-06)
Central
Tendency
(20)
User
2.9E-05
1120
Page 44 of 93
-------
1121
1122
1123
1124
1125
1126
Dermal exposure estimates are presented below and are based on the fraction absorbed model
within CEM 2.1. See the Supplemental Analysis File [Exposure Modeling Results and Risk
Estimates for Consumer Exposures'] for exposure results and associated risk estimates, including
those based on the permeability model within CEM 2.1.
Table 2-20 Estimated Dermal Exposure: Dishwasher Detergent
Scenario Description
Duration of Use 1
(min)
Weight
Fraction
(%)
Receptor
ADR
(mg/kg/day)
LADD
(mg/kg/day)
Acute
High-Intensity User
(1)
Max
(9.7E-06)
Adult (>21 years)
3.2E-06
Children (16-20 years)
3.0E-06
Children (11-15 years)
3.3E-06
Chronic
High-Intensity User2
(1)
Central
Tendency
(5E-06)
Adult (>21 years)
1.2E-06
Moderate-Intensity
User2
(1)
Central
Tendency
(5E-06)
Adult (>21 years)
9.9E-07
1 The exposure duration applied for dermal exposures to dishwashing detergent were adjusted to 1 minute, as the
scenario default exposure duration is based on the run time of a dishwasher, not on expected dermal contact time.
2 For this scenario, the distinct chronic dermal estimates are a result of a difference in frequency of use (365 days/yr
for high-intensity users and 300 days/yr for moderate-intensity users).
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
2.1.3 .5.2 Laundry Detergent
Acute and chronic inhalation and dermal exposures to 1,4-dioxane present as a byproduct in
laundry detergent were evaluated. Concentrations of 1,4-dioxane in laundry detergent range from
0.05 to 14 ppm (up to 0.0014%). CEM 2.1 default inputs for laundry detergent (liquid) were used
as the basis for duration of use and mass of product used. The room of use (Zone 1) is a utility
room and the dermal surface area reflects both hands. A 1.6% dilution factor is applied. This
scenario assumes immersive dermal contact in the 1.6% laundry detergent solution during hand
washing activities and may involve inhibited evaporation from the skin surface.
Inhalation exposure estimates are presented below. See the Supplemental Analysis File
[.Exposure Modeling Results and Risk Estimates for Consumer Exposures] for exposure results
and associated risk estimates.
Table 2-21 Estimated Inhalation Exposure: Laundry Detergent
Scenario
Description
Duration of Use
(min)
Weight
Fraction
Mass Used
(g)
Product
User or
Bystander
8-hr Max
TWA
(mg/m3)
LADC
(mg/m3)
Acute
High End
Max
High End
User
1.5E-03
Page 45 of 93
-------
Scenario
Description
Duration of Use
(min)
Weight
Fraction
Mass Used
(g)
Product
User or
Bystander
8-hr Max
TWA
(mg/m3)
LADC
(mg/m3)
High-Intensity
User
(50)
(1.4E-05)
(20)
Bystander
2.7E-04
Chronic
High-Intensity
User
High End
(50)
Central
Tendency
(6E-06)
High End
(20)
User
1.3E-04
Moderate-
Intensity User
Central Tendency
(45)
Central
Tendency
(6E-06)
Central
Tendency
(10)
User
7.1E-05
1142
1143 Dermal exposure estimates are presented below and are based on the permeability model within
1144 CEM2.1. Seethe Supplemental Analysis File [Exposure Modeling Results and Risk Estimates
1145 for Consumer Exposures] for exposure results and associated risk estimates, including those
1146 based on the fraction absorbed model within CEM 2.1.
1147
Table 2-22 Estimated Dermal Exposure: Launt
ry Detergent
Scenario Description
Duration of Use 1
(min)
Weight
Fraction
(%)
Receptor
ADR
(mg/kg/day)
LADD
(mg/kg/day)
Acute
High-Intensity User
High End
(20)
Max
(1.4E-05)
Adult (>21 years)
4.8E-07
Children (16-20 years)
4.5E-07
Children (11-15 years)
4.9E-07
Chronic
High-Intensity User
High End
(20)
Central
Tendency
(6E-06)
Adult (>21 years)
1.5E-07
Moderate-Intensity
User
Central Tendency
(10)
Central
Tendency
(6E-06)
Adult (>21 years)
6.2E-08
1 The exposure duration applied for dermal exposures to laundry detergent were adjusted to equal the default exposures
times for dish soap, as this dermal exposure scenario is intended to approximate dermal contact from hand washing of
clothing, whereas the default exposure durations for the laundry detergent scenario are based on run times of the
washing machine.
1149
1150 2.1.3.5.3 Paints and Floor Lacquer
1151 Acute inhalation and dermal exposures to 1,4-dioxane present as a byproduct in paints or floor
1152 lacquer were evaluated. Concentrations of 1,4-dioxane in paints and floor lacquer range from
1153 0.02 to 30 ppm (up to 0.003%). Westat Survey data on latex paint were used as the basis for
1154 duration of use and mass of product used. The room of use (Zone 1) is a bedroom and the dermal
1155 surface area reflects the face, hands, and arms. This scenario assumes dermal contact during
1156 painting activities and is not expected to involve inhibited evaporation from the skin surface.
1157
Page 46 of 93
-------
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
Inhalation exposure estimates are presented below. See the Supplemental Analysis File
[.Exposure Modeling Results and Risk Estimates for Consumer Exposures] for exposure results
and associated risk estimates.
Table 2-23 Estimated Inhalation Exposure: Paints and Floor Lacquer
Scenario
Description
Duration of Use
(min)
Weight
Fraction
Mass Used
(g)
Product User
or Bystander
8-hr Max
TWA
(mg/m3)
Acute
High-Intensity
User
95th Percentile
(810)
Max
(3E-05)
95th Percentile
(26025)
User
2.0E-02
Bystander
7.5E-03
Dermal exposure estimates are presented below and are based on the fraction absorbed model
within CEM 2.1. See the Supplemental Analysis File [Exposure Modeling Results and Risk
Estimates for Consumer Exposures'] for exposure results and associated risk estimates, including
those based on the permeability model within CEM 2.1.
Table 2-24 Estimated Dermal Exposure: Paints and Floor Lacquer
Scenario Description
Duration of Use
(min)
Weight
Fraction
(%)
Receptor
ADR
(mg/kg/day)
Acute
High-Intensity User
95th Percentile
(810)
Max
(3E-05)
Adult (>21 years)
1.96E-03
Children (16-20 years)
1.85E-03
Children (11-15 years)
2.03E-03
2.1.3.5.4 Textile Dye
Acute inhalation and dermal exposures to 1,4-dioxane present as a byproduct in textile dye were
evaluated. An identified concentration of 1,4-dioxane in textile dye is 4.7 ppm (up to 0.00047%).
CEM 2.1 default inputs for textile and fabric dyes were used as the basis for duration of use and
mass of product used. The room of use (Zone 1) is a utility room and the dermal surface area
reflects both hands. A 10% dilution factor is applied. This scenario assumes immersive dermal
contact in the 10% dye solution during dyeing activities and may involve inhibited evaporation
from the skin surface.
Inhalation exposure estimates are presented below. See the Supplemental Analysis File
[.Exposure Modeling Results and Risk Estimates for Consumer Exposures] for exposure results
and associated risk estimates.
Page 47 of 93
-------
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
Table 2-25 Estimated Inhalation Exposure: Textile Dye
Scenario
Description
Duration of Use
(min)
Weight
Fraction
Mass Used
(g)
Product User
or Bystander
8-hr Max
TWA
(mg/m3)
Acute
High-Intensity
User
High End
(20)
Max
(4.7E-06)
High End
(100)
User
8.5E-04
Bystander
1.5E-04
Dermal exposure estimates are presented below and are based on the permeability model within
CEM 2.1. See the Supplemental Analysis File [Exposure Modeling Results and Risk Estimates
for Consumer Exposures] for exposure results and associated risk estimates, including those
based on the fraction absorbed model within CEM 2.1.
Table 2-26 Estimated Dermal Exposure: Textile I
>ye
Scenario Description
Duration of Use
(min)
Weight
Fraction1
(%)
Receptor
ADR
(mg/kg/day)
Acute
High-Intensity User
High End
(20)
Max
(4.7E-06)
Adult (>21 years)
6.4E-07
Children (16-20 years)
6.0E-07
Children (11-15 years)
6.5E-07
2.1.3.5.5 Spray Polyurethane Foam
Acute inhalation and dermal exposures to 1,4-dioxane present as a byproduct in SPF were
evaluated. Concentrations of 1,4-dioxane in SPF range from <0.5 to 500 ppm (up to 0.05% in
mixed SPF) and the selected weight fraction aligns with that used in the occupational exposure
assessment. Three rooms of use (Zone 1) were assumed: the basement, the attic, and the garage.
The dermal surface area reflects the face, hands, and arms. Duration of use is based on loading
rate and application surface area, but it aligns well with the durations assumed in the
occupational exposure assessment (see Appendix A for more details). This scenario assumes
dermal contact during application activities and are not expected to involve inhibited evaporation
from the skin surface.
While application of SPF insulation products may primarily be occupational, a "do it yourself'
or DIY installation of SPF is possible. There are consumer products available that may expose
consumers (users and bystanders) to 1,4-dioxane.
Inhalation exposure estimates are presented below. See the Supplemental Analysis File
[.Exposure Modeling Results and Risk Estimates for Consumer Exposures] for exposure results
and associated risk estimates.
Page 48 of 93
-------
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
Table 2-27 Estimated Inhalation Exposure: SPF
Scenario
Description
Duration of Use
(min)
Weight
Fraction
Mass Used
(g)
Product User
or Bystander
8-hr Max
TWA
(mg/m3)
Acute
Basement1
(360)2
Max
(5.0E-04)
4.5 3
User
8.9E-01
Bystander
7.4E-01
Attic1
(360)2
Max
(5.0E-04)
4.5 3
User
1.9E-01
Bystander
7.1E-02
Garage1
(180)2
Max
(5.0E-04)
2.5 3
User
1.6E-01
Bystander
1.2E-01
1 SPF scenarios are not described in the same manner as the other product scenarios, as they are based on home
application areas: basement, attic, and garage, each with distinct air exchange rates and interzonal ventilation
rates.
2 Durations of use are not described as "high-end" in these scenarios because they are not based on a
distribution; however, they are based on loading rates and application surface areas and align with occupational
exposure scenario durations (excluding time for set-up and without considering multiple jobs per day).
3 Mass of use was not an input in MCCEM as it was in the CEM model. These masses instead reflect the total
mass of chemical released in each exposure setting. These were estimated using loading ratios, application
surface areas, emission rate per square inch, and decay rate per hour. Please refer to the Supplemental Analysis
File \Consumer Exposure Assessment Modeling Input Parameters] for more details.
Dermal exposure estimates are presented below and are based on the fraction absorbed model
within CEM 2.1. See the Supplemental Analysis File [Exposure Modeling Results and Risk
Estimates for Consumer Exposures'] for exposure results and associated risk estimates, including
those based on the permeability model within CEM 2.1.
Table 2-28 Estimated Dermal Exposure: SPF
Scenario Description
Duration of Use
(min)
Weight
Fraction
(%)
Receptor
ADR
(mg/kg/day)
Acute
Basement, Attic,
Garage1
(360, 360, 180)2
Max
(5.0E-04)
Adult (>21 years)
1.0E-03
Children (16-20 years)
9.7E-04
Children (11-15 years)
1.0E-03
1 SPF scenarios are not described in the same manner as the other product scenarios, as they are based on
home application areas: basement, attic, and garage, each with distinct air exchange rates and interzonal
ventilation rates. For dermal exposures, there is no difference across these scenarios, as the maximum
fraction absorbed is estimated and applied for either duration (360 or 180 minutes).
2 Durations of use are not described as "high-end" in these scenarios because they are not based on a
distribution; however, they are based on loading rates and application surface areas and align with
occupational exposure scenario durations (excluding time for set-up and without considering multiple
jobs per day).
2.1.3.6 Assumptions and Key Sources of Uncertainty for Consumer Exposures
EPA's approach recognizes the need to include uncertainty analysis. One important distinction
for such an analysis is variability versus uncertainty - both aspects need to be addressed.
Page 49 of 93
-------
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
Variability refers to the inherent heterogeneity or diversity of data in an assessment. It is a
quantitative description of the range or spread of a set of values and is often expressed through
statistical metrics, such as variance or standard deviation, that reflect the underlying variability
of the data. Uncertainty refers to a lack of data or an incomplete understanding of the context of
the risk evaluation decision. Variability cannot be reduced, but it can be better characterized.
Uncertainty can be reduced by collecting more or better data. Quantitative methods to address
uncertainty include non-probabilistic approaches such as sensitivity analysis and probabilistic or
stochastic methods. Uncertainty can also be addressed qualitatively, by including a discussion of
factors such as data gaps and subjective decisions or instances where professional judgment was
used. Uncertainties associated with approaches and data used in the evaluation of consumer
exposures are described below.
Deterministic vs. Stochastic
With deterministic approaches like the one applied in this evaluation of consumer exposure, the
output of the model is fully determined by the choices of parameter values and initial conditions.
Stochastic approaches feature inherent randomness, such that a given set of parameter values and
initial conditions can lead to an ensemble of different model outputs.
Aggregate Exposure
Background levels of 1,4-dioxane in indoor and outdoor air are not considered or aggregated in
this analysis; therefore, there is a potential for underestimating consumer inhalation exposures,
particularly for populations living near a facility emitting 1,4-dioxane or living in a home with
other sources of 1,4-dioxane, such as other 1,4-dioxane-containing products stored and/or used in
the home such as personal care products that are not covered under TSCA. Similarly, inhalation
and dermal exposures were evaluated on a product-specific basis and are based on use of a single
product type within a day, not multiple products. There was no aggregation of dermal and
inhalation exposure to single products either.
Dermal Exposure Approach
For dermal exposure scenarios using the permeability model that may involve dermal contact
with impeded evaporation based on professional considerations of the formulation type and
likely use pattern, there is uncertainty surrounding the application of exposure durations for such
scenarios. The exposure durations modeled are based on reported durations of product use,
unless otherwise specified, and may not reflect reasonable durations of dermal contact with
impeded evaporation. The exposure duration modeled could exceed a reasonable duration of
such dermal contact with a wet rag, for example.
For scenarios using the absorption fraction model that are less likely to involve dermal contact
with impeded evaporation, there is uncertainty surrounding the assumption that the entire mass
present in the thin film is absorbed and retained in the stratum corneum following a use event.
The fractional absorption factor estimated based on Frasch and Bunge (2015) is intended to be
applied to the mass retained in the stratum corneum after exposure; it does not account for
evaporation from the skin surface during the exposure event. Therefore, the assumption that the
entire amount of chemical present in the thin film on the skin surface is retained in the stratum
corneum may lead to uncertainty in the absorbed dose estimate.
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1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
Product Concentration Data
The products evaluated are largely based on EPA's 2015 TSCA Work Plan Chemical Problem
Formulation and Initial Assessment of 1,4-Dioxane (U.S. EPA. 2015). EPA conducted an
additional systematic review focused on identifying data on 1,4-dioxane presence in consumer
products and associated exposures and/or emissions. Because 1,4-dioxane is present in consumer
products as a byproduct and not as an ingredient, there is more uncertainty than typical when
identifying and using concentration information. Unlike other chemicals that are ingredients in
consumer products with readily available reported concentration ranges in SDSs for each product
category, 1,4-dioxane concentrations have been sourced from a variety of primary and secondary
sources such as governmental risk assessments, SDSs, literature reviews, emission studies, etc.
There are limited reasonably available data and they are not necessarily complete or consistently
updated and general internet searches cannot guarantee entirely comprehensive product
identification. Therefore, it is possible that the entire universe of products that contain 1,4-
dioxane as a byproduct may not have been identified, or that certain changes in the universe of
products may not have been captured, due to market changes or research limitations. Maximum
identified weight fractions were used in acute high-intensity user scenarios and mean weight
fractions were used in chronic high-intensity and moderate-intensity user scenarios, where
possible. While weight fractions are described as "maximum" in tables, these reflect only the
maximum levels identified from available literature and other sources and may not capture the
true maximum in specific products or batches. There is uncertainty about how these means and
maximums broadly reflect typical products and there is also uncertainty about whether the true
upper end is captured in the ranges identified through the available sources. For the range of
weight fractions identified, see the Supplemental Analysis File [Consumer Exposure Assessment
Modeling Input Parameters].
Emission Rate
The higher-tier Multi-Chamber Concentration and Exposure Model (MCCEM) is used in the
estimation of inhalation exposures from SPF application only. For other product scenarios, key
data (i.e., chamber emission data) were not reasonably available. Therefore, the model used
(CEM 2.1) estimates emission rate based on chemical properties and emission profiles matching
the formulation type and use method.
The emission rate data derived from Karlovich et al. (2011) is based on occupational-grade
products, so there is some uncertainty surrounding the application to consumers. The product for
which 1,4-dioxane emission data were collected is an open-cell foam. The initial emission rate
and decay constant estimates were based on a modeled relationship, as measured emission data
were not available during application.
Dilution Factor
For most product scenarios, the dilution factor is not considered. For dish soap, laundry
detergent, and textile dye, all of which are expected to be used in aqueous solutions during hand
washing or dyeing activities, dilution factors are incorporated. For dish soap, a dilution factor of
0.7% is applied based on assuming a mass of 28 g (~1 oz) is used in one gallon of water for hand
washing of dishes. For laundry detergent, a dilution factor of 1.6% is applied based on assuming
Page 51 of 93
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1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
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1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
a high-end mass of 60 g (oz) is used in one gallon of water for hand washing of laundry. These
estimations incorporate a conservative water use assumption.
Chronic Exposure Estimations
Chronic (lifetime) inhalation and dermal exposures were estimated for four product scenarios:
surface cleaner, dish soap, dishwasher detergent, and laundry detergent. The inclusion of lifetime
exposure estimates for these conditions of use is based on the anticipated daily or near-daily use
of these products. This differs from expected intermittent exposure pattern associated with the
other evaluated consumer conditions of use. Lifetime exposure estimates are calculated assuming
the exposure event occurs for 365 or 300 days per year for high-end or central tendency
frequencies, respectively, for 57 years. The exposure scenarios still assume one exposure event
per day and therefore may not capture users that continuously use products throughout the day.
This exposure is averaged over a period of 78 years. The models employed (CEM 2.1 and CEM)
typically utilize central tendency inputs for weight fraction, duration, frequency, and mass when
estimating lifetime exposures (U.S. EPA. 2.019a; 07). Central tendency inputs for
weight fraction were used in estimating chronic exposures, across high- and moderate-intensity
user scenarios.
2.1.3,7 Confidence in Consumer Exposure Estimates
The considerations and overall confidence ratings for the inhalation consumer exposure
scenarios are displayed in Table 2-29. Ratings are based on the strength of the models employed,
as well as the quality and relevance of the modeling parameterization. CEM, CEM 2.1, and
MCCEM are peer reviewed, publicly available, and were designed to estimate inhalation and
dermal exposures from household uses of products and articles.
Systematic review identified several studies reporting emission rates or chamber concentrations
of 1,4-dioxane from spray foam and paint products and findings as they relate to the current
evaluation are summarized in Appendix A.3. Although measured chamber or test room
concentrations are not directly comparable to the 8-hr TWAs estimated for the various consumer
exposure scenarios, on the whole, these emission studies bolster confidence in the predicted air
concentrations for the SPF and paint and floor lacquer conditions of use.
The predicted 8-hr TWAs for SPF range from 160 to 890 |ig/m3 for users. These predicted
estimates fall within the range predicted in Karlovich et al. (2011) for samples measured at four
and 12 hours. Peppendieck et al. Q ) also reported measured air concentrations that
encompass the modeled consumer exposure estimates, with concentrations from non-ideal
closed-cell spray foam ranging from 500 to 1,000 |ig/m3 over the first 48 hours. Won et al.
(2014) reported levels of 1,4-dioxane well below the CEM 2.1 predictions, from 0.25 to 44.68
|ig/m3 at six hours for various insulation products including foam board and two-component
open- and closed-cell spray foams.
The predicted 8-hr TWAs for paint and floor lacquer is 20 |ig/m3 for users, which is roughly one
order of magnitude greater than concentrations measured in Won et al. (2014) (0.8 - 1.74 |ig/m3
at six hours), but aligns with the measured air concentration five hours after application of the
two-component epoxy floor paint (21 |ig/m3). The predicted TWA also falls within the range of
air concentrations taken five hours after application in the Danish EPA's 2020 Follow-Up study,
which reported levels from 7 to 460 |ig/m3 at five hours.
Page 52 of 93
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Table 2-29 Overall Confidence Ratings for Consumer Inhalation Exposure Estimates
Consumer Product
Scenario
Overall Confidence
Acute
Overall Confidence
Chronic
Scenario-Specific Considerations
Overarching Considerations
Surface Cleaner
Moderate to High
Moderate
Duration and mass inputs obtained from
the Westat Survey from its solvent-type
cleaning fluids and degreasers category.
Weight fraction range obtained from
few sources.
There is uncertainty
regarding how the maximum
and mean from identified
weight fraction sources
reflects the existing range or
Antifreeze
Moderate to High
NA
Duration and mass inputs obtained from
CEM 2.1 scenario-specific defaults.
Weight fraction range obtained from
few sources.
captures actual maximum
concentrations.
Use of CEM (not CEM 2.1)
to estimate lifetime inhalation
Dish Soap
Moderate to High
Moderate
Duration and mass inputs obtained from
CEM 2.1 scenario-specific defaults.
Weight fraction range obtained from
several sources.
exposures (LADCs) did not
estimate exposure to
bystanders; however,
bystanders would be exposed
Dishwasher Detergent
Moderate to High
Moderate
Duration and mass inputs obtained from
CEM 2.1 scenario-specific defaults.
Exposure duration assumes user is in the
room of use (kitchen) during the
machine's run time (50 min).
Weight fraction range obtained from
several sources.
to lower levels than the
presented user exposures
based on their placement in
the home during use (Zone
2).
Use of central tendency
weight fractions for chronic
exposure scenarios bolsters
confidence, as it does not
assume use of the highest
identified concentration daily
or near-daily intervals over
57 years.
Laundry Detergent
Moderate to High
Moderate
Duration and mass inputs obtained from
CEM 2.1 scenario-specific defaults.
Exposure duration assumes user is in the
room of use (utility) during the
machine's runtime (50 min).
Weight fraction range obtained from
several sources.
Paint and Floor
Lacquer
High
NA
Duration and mass inputs obtained from
the Westat Survey from its latex paint
category.
Weight fraction data obtained from
American Coatings Association public
submission (Nekoomaram and
Wieroniev. 2015).
Measured emission data align with 8-hr
TWA for users.
Page 53 of 93
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Consumer Product
Scenario
Overall Confidence
Acute
Overall Confidence
Chronic
Scenario-Specific Considerations
Overarching Considerations
Textile Dye
Moderate
NA
Duration and mass inputs obtained from
CEM 2.1 scenario-specific defaults.
Single weight fraction source.
SPF
High
NA
Initial emission rate and decay constant
are based on a modeled relationship.
No emission or concentration data were
available for 1,4-dioxane during
application.
Emission data on 1,4-dioxane from
Karlovich et al (2012) is from open cell
foam.
Duration inputs based on the SPF
occupational exposure assessment.
Application area specific air exchange
rates and ventilation rates applied.
Product and chemical specific emission
rate applied.
Used higher-tier MCCEM model to
estimate air concentrations.
Weight fraction based on occupational
exposure assessment.
Measured and predicted emission data
encompass predicted range of 8-hr
TWAs for users.
The considerations and overall confidence ratings for the dermal consumer exposure scenarios are displayed in Table 2-30. Ratings
are based on the strength of the models employed, as well as the quality and relevance of the modeling parameterization. CEM 2. lis
peer reviewed, publicly available, and was designed to estimate inhalation and dermal exposures from household uses of products and
articles.
Page 54 of 93
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Table 2-30 Overall Confidence Ratings for Consumer Dermal Exposure Estimates
Consumer Product
Scenario
Overall Confidence
Acute
Overall Confidence
Chronic
Scenario-Specific Considerations
Overarching Considerations
Surface Cleaner
Moderate
Low to Moderate
Duration input obtained from the Westat
Survey from its solvent-type cleaning
fluids and degreasers category.
Exposure duration assumes dermal
contact may occur during the entire
activity duration.
Weight fraction range obtained from
few sources.
There is uncertainty
regarding how the maximum
and mean from identified
weight fraction sources
reflects the existing range or
captures actual maximum
concentrations.
An estimated permeability
Antifreeze
Moderate
NA
Duration input obtained from CEM 2.1
scenario-specific defaults.
Exposure duration assumes dermal
contact may occur during the entire
activity duration.
Weight fraction range obtained from
few sources.
coefficient is used in dermal
modeling.
There are uncertainties
associated with both dermal
models applied (see Section
2.4.3.6).
Use of central tendency
Dish Soap
Moderate
Low to Moderate
Duration input obtained from CEM 2.1
scenario-specific defaults.
Dilution fraction of 3% may be a
conservative assumption.
Weight fraction range obtained from
several sources.
weight fractions for chronic
exposure scenarios bolsters
confidence, as it does not
assume use of the highest
identified concentration daily
or near-daily intervals over
57 years.
Dishwasher Detergent
Moderate
Low to Moderate
Duration input obtained from CEM 2.1
scenario-specific defaults.
Exposure duration adjusted to one
minute to approximate contact time
during loading of liquid detergent.
Weight fraction range obtained from
several sources.
Laundry Detergent
Moderate
Low to Moderate
Duration input obtained from CEM 2.1
scenario-specific defaults.
Exposure duration adjusted to equal dish
soap exposure durations to approximate
contact time during hand washing of
laundry.
Page 55 of 93
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Consumer Product
Scenario
Overall Confidence
Acute
Overall Confidence
Chronic
Scenario-Specific Considerations
Overarching Considerations
Chronic exposure scenario assumes
hand washing of laundry daily or near
daily.
Weight fraction range obtained from
several sources.
Paint and Floor
Lacquer
Moderate
NA
Duration and mass inputs obtained from
the Westat Survey from its latex paint
category.
Exposure duration assumes dermal
contact may occur during the entire
activity duration.
Weight fraction data obtained from
American Coatings Association public
comment submission (Nekoomaram and
Wieroniev. 2015).
Textile Dye
Moderate
NA
Duration and mass inputs obtained from
CEM 2.1 scenario-specific defaults.
Dilution fraction of 10% likely a
conservative assumption.
Single weight fraction source.
SPF
Moderate
NA
Duration inputs based on the SPF
occupational exposure assessment.
Exposure duration assumes dermal
contact may occur during the entire
activity duration.
Weight fraction based on occupational
exposure assessment.
Page 56 of 93
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3 HAZARDS (EFFECTS)
Several of the points of departure (PODs) for human health hazard presented in the draft risk evaluation were revised in response to
peer review and public comment. The PODs identified through dose-response analysis in the draft risk evaluation are summarized
below. These revised PODs are the basis for risk estimates presented in the risk characterization section.
3.1.1 Summary of Human Health Hazards
The results of the hazard identification and dose-response are summarized in Table 3-1.
Table 3-1. Summary of Hazard Identification and Dose-Response Values
l'l\|)OMIIV
Kuiilc
I'lmlpoini
Tj po
llii/iii'd
POD/I ll.( /Slope
l-iicloi"1
Value
I nils
benchmark
M()i:h
Basis for Soled inn
Kej Siuclj
Inhalation
Short-term
Acute inhalation
PODhec
283.5
mg/m3
300
(UFL= 10; UFa =
3;UFH= 10)
Systemic liver effect; Study duration
relevant to worker short-term exposures
(Mattie et
aL 2012)
Dermal
Short-term
Acute dermal PODhed
extrapolated from an
inhalation study
35.4
mg/kg/day
300
(UFL= 10; UFa =
3;UFh= 10)
Inhalation
Non-Cancer
Human Equivalent
Concentration (HEC)
12.8
mg/m3
30
(UFa3=3;UFh
= 10)
POD relevant for olfactory epithelium
effects (i.e., metaplasia and atrophy)
(Kasai et aL.
2009)
Cancer
Inhalation Unit Risk
(IUR)
1.18E-06
(Hg/m3)"1
N/A
Result of combined cancer modeling for
male rats (including liver)
(Kasai et aL.
2009)
1.03E-06
(Hg/m3)"1
N/A
Result of combined cancer modeling for
male rats (excluding liver)
(Kasai et aL.
2009)
Page 57 of 93
-------
l'l\|)OMIIV
Rouk'
I'.nripoini
Tj pe
llii/iinl
POD/MIX /Slope
l-iicloi-1
Value
I nils
lienehniiirk
MOF.1'
liiisis for Selection
Koj Sliulj
Dermal
Non-Cancer
Human Equivalent Dose
(HED) extrapolated from
an inhalation study
1.6
mg/kg/day
30
(UFa = 3; UFh =
10)
POD for systemic effects in the nasal ca\ n\
(respiratory metaplasia of the olfactory
epithelium) in male rats
( >ciba
a.L 1974)
(Kasai et aL
2009)
Human Equivalent Dose
(HED) extrapolated from
oral studies
2.6
mg/kg/day
30
(UFA =3; UFH
= 10)
PODs for hepatocellular and renal toxicity
(degeneration and necrosis of renal tubular
cells and hepatocytes; hepatocellular mixed
cell foci) following drinking water exposure
in male rats0
(Kano et aL
2009);
Kociba et al.
(1974)
Cancer
Cancer Slope Factor
(CSF) extrapolated from
an oral study
1.2E-01
(mg/kg-d)"1
N/A
Cancer model for liver tumors in female
mice (the most sensitive sex/species);
(Kano et al.
2009)
Cancer Slope Factor
(CSF) extrapolated from
an inhalation study
1.4E-02
(mg/kg-d)"1
N/A
Result of combined cancer modeling for
male rats (including liver)
(Kasai et al.
2009)
1.2E-02
(mg/kg-d)"1
N/A
Result of combined cancer modeling for
male rats (excluding liver)
(Kasai et al.
2009)
11 HECs are adjusted from the study conditions as described above in Section 3.2.6
bUFs = subchronic to chronic UF; UFa = interspecies UF; UFh = intrasDecies UF; UFt. = LOAEL to NOAEL UF (IIS. EPA. 2002)
0 Data from both drinking water studies independently arrived at the same POD for liver effects
N/A is shown in the benchmark MOE column for cancer endpoints because EPA did not use MOEs for cancer risks, see Section 3.2.6 for more information.
Page 58 of 93
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4 RISK CHARACTERIZATION
4.1 Human Health Risk
4.1.1 Risk Estimate for Exposures from Incidental Exposure to 1,4-Dioxane in
Surface Water
The following sections present the risk estimates for acute dermal and inhalation exposures that
may occur from incidental contact with surface water. Calculated MOE values below the
benchmark MOE (300) would indicate a potential safety concern.
Risks from acute oral exposure through incidental ingestion of surface water are shown in Table
4-1. and risks from acute dermal exposure through swimming in surface water are shown in
Table 4-2.
Table 4-1. Risk from Acute Oral Exposure Through Incidental Ingestion of Water;
Benchmark MOE = 300
OES
Facility/Data Source
Surface Water
Concentration
(Hg/L)
Drinking Water
Acute Dose,
Child 11-15
(mg/kg/day)a
MOE
(Oral POD 35.4
mg/kg/day)
Siie-Specil'ic Modeling- r.Mimaled Surface Wilier ( oncon 1 r;itions
Manufacturing
BASF
9.7E+01
5.2E-04
6.8E+04
Industrial Uses
Ineos Oxide
2.2E+02
1.2E-03
3.0E+04
Industrial Uses
Microdyn-Nadir Corp
7.2E+00
3.9E-05
9.1E+05
Industrial Uses
St Charles Operations
(Taft/Star) Union
Carbide Corp
1.1E-02
5.9E-08
6.0E+08
Industrial Uses
SUEZ Water
Technologies &
Solutions
5.1E+03
2.7E-02
1.3E+03
Industrial Uses
The Dow Chemical
Co - Louisiana
Operations
8.7E-03
4.7E-08
7.6E+08
Industrial Uses
Union Carbide Corp
Institute Facility
3.3E+00
1.8E-05
2.0E+06
Industrial Uses
Union Carbide Corp
Seadrift Plant
2.4E+01
1.3E-04
2.7E+05
Industrial Uses
BASF Corp
3.4E-01
1.8E-06
2.0E+07
Industrial Uses
Cherokee
Pharmaceuticals LLC
2.6E-03
1.4E-08
2.5E+09
Industrial Uses
DAK Americas LLC
2.8E+01
1.5E-04
2.4E+05
Industrial Uses
Institute Plant
5.3E+00
2.8E-05
1.3E+06
Page 59 of 93
-------
OES
Facility/Data Source
Surface Water
Concentration
(Mg/L)
Drinking Water
Acute Dose,
Child 11-15
(mg/kg/day)a
MOE
(Oral POD 35.4
mg/kg/day)
Industrial Uses
Kodak Park Division
1.7E-01
9.1E-07
3.9E+07
Industrial Uses
Pharmacia & Upjohn
(Former)
2.7E-02
1.5E-07
2.4E+08
Industrial Uses
Philips Electronics
Plant
1.0E-01
5.4E-07
6.6E+07
Industrial Uses
Sanderson Gulch
Drainage
Improvements
1.0E-02
5.4E-08
6.6E+08
Open System
Functional Fluids
Ametek Inc. U.S.
Gauge Div
4.0E-01
2.1E-06
1.7E+07
Open System
Functional Fluids
Lake Reg
Med/Collegeville
1.3E-02
7.0E-08
5.1E+08
Open System
Functional Fluids
Pall Life Sciences Inc
4.3E-02
2.3E-07
1.5E+08
Open System
Functional Fluids
Modeled Release
Estimates
2.9E+00
1.5E-05
2.3E+06
Spray Foam
Application
Modeled Release
Estimates
2.7E-01
1.5E-06
2.5E+07
Disposal
Beacon Heights
Landfill
5.3E-01
2.8E-06
1.3E+07
Disposal
Ingersoll
Rand/Torrington Fac
3.5E+00
1.9E-05
1.9E+06
Nigh-liml of Sub milled Monitoring l);il;i- Measured Surface \\ aler C oiicon I r;il ions
STORET
1.0E+02
5.4E-04
6.6E+04
Sunetal. 2016
1.4E+03
7.5E-03
4.7E+03
North Carolina
Department of
Environmental
Quality
1.0E+03
5.5E-03
6.4E+03
Minnesota
Department of
Environmental
Quality
4.4E+00
2.4E-05
1.5E+06
aDose is based on high end incidental intake rate
Page 60 of 93
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Table 4-2. Risk from Acute Dermal Exposure from Swimming; Benchmark MOE = 300
OES
Facility/Data Source
Surface Water
Concentration
(Mg/L)
Dermal Acute
Dose, Adult
(mg/kg/day)
MOE
(Dermal POD
35.4 mg/kg/day)
Siie-Spccil'ic Modeling- r.Mimaled Surface Wilier ( oncon 1 r;itions
Manufacturing
BASF
9.7E+01
3.6E-05
9.9E+05
Industrial Uses
Ineos Oxide
2.8E+02
8.0E-05
4.4E+05
Industrial Uses
Microdyn-Nadir Corp
7.2E+00
2.7E-06
1.3E+07
Industrial Uses
St Charles Operations
(Taft/Star) Union
Carbide Corp
1.1E-02
4.1E-09
8.6E+09
Industrial Uses
SUEZ Water
Technologies &
Solutions
5.1E+03
1.9E-03
1.9E+04
Industrial Uses
The Dow Chemical
Co - Louisiana
Operations
8.7E-03
3.2E-09
1.1E+10
Industrial Uses
Union Carbide Corp
Institute Facility
3.3E+00
1.2E-06
2.9E+07
Industrial Uses
Union Carbide Corp
Seadrift Plant
2.4E+01
8.9E-06
4.0E+06
Industrial Uses
BASF Corp
3.4E-01
1.3E-07
2.8E+08
Industrial Uses
Cherokee
Pharmaceuticals LLC
2.6E-03
9.7E-10
3.6E+10
Industrial Uses
DAK Americas LLC
2.8E+01
1.0E-05
3.4E+06
Industrial Uses
Institute Plant
5.3E+00
2.0E-06
1.8E+07
Industrial Uses
Kodak Park Division
1.7E-01
6.3E-08
5.6E+08
Industrial Uses
Pharmacia & Upjohn
(Former)
2.7E-02
1.0E-08
3.5E+09
Industrial Uses
Philips Electronics
Plant
1.0E-01
3.7E-08
9.6E+08
Industrial Uses
Sanderson Gulch
Drainage
Improvements
1.00E-02
3.7E-09
9.6E+09
Open System
Functional Fluids
Ametek Inc. U.S.
Gauge Div
4.0E-01
1.5E-07
2.4E+08
Open System
Functional Fluids
Lake Reg
Med/Collegeville
1.3E-02
4.8E-09
7.3E+09
Open System
Functional Fluids
Pall Life Sciences Inc
4.3E-02
1.6E-08
2.2E+09
Open System
Functional Fluids
Modeled Release
Estimates
2.9E+00
1.1E-06
3.4E+07
Spray Foam
Application
Modeled Release
Estimates
2.7E-01
10.0E-08
3.6E+08
Page 61 of 93
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OES
Facility/Data Source
Surface Water
Concentration
(Mg/L)
Dermal Acute
Dose, Adult
(mg/kg/day)
MOE
(Dermal POD
35.4 mg/kg/day)
Disposal
Beacon Heights
Landfill
5.3E-01
2.0E-07
1.8E+08
Disposal
Ingersoll
Rand/Torrington Fac
3.5E+00
1.3E-06
2.8E+07
Nigh-lind of Sub milled Monitoring l);K;i- Measured Surface \\ aler ( oncenlralions
...
STORET
1.0E+02
3.7E-05
9.6E+05
...
Sunet al. 2016
1.4E+03
5.2E-04
6.8E+04
North Carolina
Department of
Environmental
Quality
1.0E+03
3.8E-04
9.3E+04
Minnesota
Department of
Environmental
Quality
4.4E+00
1.6E-06
2.2E+07
4,1.2 Risk Estimates for Exposures from Consumer Use of 1,4-Dioxane
The following sections present risk estimates for acute and chronic dermal and inhalation
exposures following consumer use of products containing 1,4-dioxane.
4,1,2.1 Risk Estimation for Inhalation Exposures to 1,4-Dioxane as a byproduct in
Consumer Products
Risks from acute and chronic inhalation exposure to 1,4-dioxane in consumer products are
shown in Table 4-3., and Table 4-4, respectively.
EPA evaluated risk from acute inhalation exposure using a POD of 283.5 mg/m3 based on liver
toxicity reported in Mattie et al. (2012). Calculated MOE values below the benchmark MOE of
300 would indicate a consumer safety concern for acute exposures.
Table 4-3. Risks from Acute Inhalation Exposure to 1,4-Dioxane in Consumer Products;
Benchmark MOE= 300
Consumer Condition of Use
Scenario
Receptor
8 hr Max
TWA (mg/m3)
MOE
Surface Cleaner
High-Intensity User
User
5.0E-03
5.7E+04
Bystander
9.5E-04
3.0E+05
Antifreeze
High-Intensity User
User
1.6E-02
1.8E+04
Bystander
4.0E-03
7.2E+04
Dish Soap
High-Intensity User
User
3.0E-02
9.3E+03
Bystander
5.4E-03
5.2E+04
Page 62 of 93
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Dishwasher Detergent
High-Intensity User
User
6.9E-04
4.1E+05
Bystander
1.2E-04
2.3E+06
Laundry Detergent
High-Intensity User
User
1.5E-03
1.9E+05
Bystander
2.7E-04
1.1E+06
Paint and Floor Lacquer
High-Intensity User
User
2.1E-02
1.4E+04
Bystander
7.5E-03
3.8E+04
Textile Dye
High-Intensity User
User
8.5E-04
3.3E+05
Bystander
1.5E-04
1.9E+06
Spray Polyurethane Foam
Basement
User
8.9E-01
317
Bystander
7.4E-01
384
Attic
User
1.9E-01
1.5E+03
Bystander
7.1E-02
4.0E+03
Garage
User
1.6E-01
1.7E+03
Bystander
1.2E-01
2.5E+03
For consumer products that are used regularly, EPA also evaluated chronic cancer risks. EPA
evaluated cancer risk from chronic inhalation exposure using an inhalation unit risk of 1.0E-06
((ig/m3)"1. Calculated MOE values for chronic exposure above the cancer benchmark for
consumers (1 x 10"6) would indicate a consumer safety concern.
Table 4-4. Risks from Chronic Inhalation Exposure to 1,4-Dioxane in Consumer Products.
Benchmark Cancer Risk = 1 x 10"6
Consumer
Condition of Use
Scenario
Lifetime Average Daily
Concentration
(LADC, mg/m3)
Cancer Risk
Surface Cleaner
High-Intensity User
1.0E-03
1.0E-06
Moderate-Intensity User
5.6E-04
5.6E-07
Dish Soap
High-Intensity User
7.1E-04
7.1E-07
Moderate-Intensity User
3.3E-04
3.3E-07
Dishwasher
Detergent
High-Intensity User
7.1E-05
7.1E-08
Moderate-Intensity User
2.9E-05
2.9E-08
Laundry Detergent
High-Intensity User
1.3E-04
1.3E-07
Moderate-Intensity User
7.1E-05
7.1E-08
Bold: Cancer risk exceeds the benchmark of 1 x 10 s.
4,1,2,2 Risk Estimation for Dermal Exposure to 1,4-Dioxane in Consumer Products
Risks from acute and chronic dermal exposure to 1,4-dioxane in consumer products are shown in
Table 4-5., and Table 4-6, respectively.
Page 63 of 93
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EPA evaluated risk from acute dermal exposure using a POD of 35.4 mg/kg/day based on liver
toxicity reported in Mattie et al. (2012). Calculated MOE values below the benchmark MOE of
300 would indicate a consumer safety concern for acute exposures.
Table 4-5. Risks from Acute Dermal Exposure to 1,4-Dioxane in Consumer Products;
Benchmark MOE=300
Consumer Condition
of Use
Scenario
Receptor
Acute Dose Rate
(mg/kg/day)
MOE
Surface Cleaner
High-Intensity User
Adult (>21 years)
7.7E-06
4.6E+06
Child (16-20 years)
7.2E-06
4.9E+06
Child (11-15 years)
7.9E-06
4.5E+06
Antifreeze
High-Intensity User
Adult (>21 years)
5.1E-04
6.9E+04
Child (16-20 years)
4.8E-04
7.4E+04
Child (11-15 years)
5.2E-04
6.8E+04
Dish Soap
High-Intensity User
Adult (>21 years)
3.1E-06
1.2E+07
Child (16-20 years)
2.9E-06
1.2E+07
Child (11-15 years)
3.1E-06
1.1E+07
Dishwasher Detergent
High-Intensity User
Adult (>21 years)
3.2E-06
1.1E+07
Child (16-20 years)
3.0E-06
1.2E+07
Child (11-15 years)
3.3E-06
1.1E+07
Laundry Detergent
High-Intensity User
Adult (>21 years)
4.8E-07
7.4E+07
Child (16-20 years)
4.5E-07
7.9E+07
Child (11-15 years)
4.9E-07
7.2E+07
Paint and Floor
Lacquer
High-Intensity User
Adult (>21 years)
2.0E-03
1.8E+04
Child (16-20 years)
1.9E-03
1.9E+04
Child (11-15 years)
2.0E-03
1.7E+04
Textile Dye
High-Intensity User
Adult (>21 years)
6.4E-07
5.6E+07
Child (16-20 years)
6.0E-07
5.9E+07
Child (11-15 years)
6.5E-07
5.4E+07
Spray Polyurethane
Foam
Basement, Attic or
Garage
Adult (>21 years)
1.0E-03
3.5E+04
Child (16-20 years)
9.7E-04
3.7E+04
Child (11-15 years)
1.1E-03
3.3E+04
For consumer products that are used regularly, EPA also evaluated chronic cancer risks. EPA
evaluated cancer risk from chronic inhalation exposure using a dermal cancer slope factor of
0.12 (mg/kg-d)1. Calculated MOE values for chronic exposure above the cancer benchmark for
consumers (1 x 10-6) would indicate a consumer safety concern.
Page 64 of 93
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Table 4-6. Risks from Chronic Dermal Exposure to 1,4-Dioxane in Consumer Products.
Benchmark Cancer I
lisk = 1 x 10"6
Consumer Condition of
Use
Scenario
Lifetime Average Daily
Dose
(mg/kg/day)
Cancer Risk (Cancer
Slope Factor = 0.12)
Surface Cleaner
High-Intensity User
5.6E-06
6.7E-07
Moderate-Intensity User
2.3E-06
2.8E-07
Dish Soap
High-Intensity User
2.6E-07
3.2E-08
Moderate-Intensity User
1.1E-07
1.3E-08
Dishwasher Detergent
High-Intensity User
1.2E-06
1.4E-07
Moderate-Intensity User
9.9E-07
1.2E-07
Laundry Detergent
High-Intensity User
1.5E-07
1.8E-08
Moderate-Intensity User
6.2E-08
7.4E-09
4.2 Risk Conclusions
4,2.1 Summary of Human Health Risk
4.2.1.1 Summary of Risk for the General Population
EPA considered reasonably available information to characterize general population exposures
and risk.
Table 4-7. summarizes potential risks from acute exposures from incidental ingestion of or
dermal contact with 1,4-dioxane in surface water. Calculated MOE values below the benchmark
MOE (300) would indicate a potential safety concern. None of the surface water concentration
estimates indicate risks from acute exposures to the general population. EPA did not identify
releases to surface waters from OESs that are not included in this table (including for
import/repackaging, recycling, film cement, printing inks, dry film lubricants, and laboratory
chemical use).
Table 4-7. Summary of Human Health Risks from Incidental Exposure to 1,4-Dioxane in
Surface Waters
OES
Facility/Data Source
Acute MOE
Oral Exposure
Benchmark= 300
Acute MOE
Dermal Exposure
Benchmark = 300
Siie-Specific Modeling - I'.slimaled Surface Waler ( oiicenlralions
Manufacturing
BASF
6.8E+04
9.9E+05
Industrial Uses
Ineos Oxide
3.0E+04
4.4E+05
Industrial Uses
Microdyn-Nadir Corp
9.1E+05
1.3E+07
Industrial Uses
St Charles Operations (Taft/Star) Union
Carbide Corp
6.0E+08
8.6E+09
Industrial Uses
SUEZ Water Technologies & Solutions
1.3E+03
1.9E+04
Page 65 of 93
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OES
Facility/Data Source
Acute MOE
Oral Exposure
Benchmark= 300
Acute MOE
Dermal Exposure
Benchmark = 300
Industrial Uses
The Dow Chemical Co - Louisiana
Operations
7.6E+08
1.1E+10
Industrial Uses
Union Carbide Corp Institute Facility
2.0E+06
2.9E+07
Industrial Uses
Union Carbide Corp Seadrift Plant
2.7E+05
4.0E+06
Industrial Uses
BASF Corp
2.0E+07
2.8E+08
Industrial Uses
Cherokee Pharmaceuticals LLC
2.5E+09
3.6E+10
Industrial Uses
DAK Americas LLC
2.4E+05
3.4E+06
Industrial Uses
Institute Plant
1.3E+06
1.8E+07
Industrial Uses
Kodak Park Division
3.9E+07
5.6E+08
Industrial Uses
Pharmacia & Upjohn (Former)
2.4E+08
3.5E+09
Industrial Uses
Philips Electronics Plant
6.6E+07
9.6E+08
Industrial Uses
Sanderson Gulch Drainage Improvements
6.6E+08
9.6E+09
Open System
Functional Fluids
Ametek Inc. U.S. Gauge Div
1.7E+07
2.4E+08
Open System
Functional Fluids
Lake Reg Med/Collegeville
5.1E+08
7.3E+09
Open System
Functional Fluids
Pall Life Sciences Inc
1.5E+08
2.2E+09
Open System
Functional Fluids
Modeled Release Estimates
2.3E+06
3.4E+07
Spray Foam
Application
Modeled Release Estimates
2.5E+07
3.6E+08
Disposal
Beacon Heights Landfill
1.3E+07
1.8E+08
Disposal
Timci'siill Rand'Toi'i iimkiii Fac
i <>i: o(>
:si: u"
Ili'Ji-l.nri of Sub milled Monitoring l);il;i- Measured Surface \\ aler C oiicon I r;il ions
STORET
6.6E+04
9.6E+05
Sunetal. 2016
4.7E+03
6.8E+04
North Carolina Department of
Environmental Quality
6.4E+03
9.3E+04
Minnesota Department of Environmental
Quality
1.5E+06
2.2E+07
4.2.1.2 4.6.2.2 Summary of Risk for Consumer Users and Bystanders
Table 4-8. summarizes risk estimates for inhalation and dermal exposures for all consumer
exposure scenarios. Risk estimates that indicate potential risk {i.e., MOEs less than the
benchmark MOE or cancer risks greater than the cancer risk benchmark) are highlighted by
holding the number and shading the cell in gray. The consumer exposure assessment and risk
characterization are described in more detail in Sections 2.4.3 and 4.2.3, respectively.
Page 66 of 93
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Table 4-8. Summary of Human
health Risks from Consumer Exposures
Category
Assessed
Condition of Use
Scenario
Descriptor
Receptor
Dermal Risk Estimates
Inhalation Risk Estimates
Acute MOE
Benchmark =
300
Chronic
Cancer
Risk3
Benchmark
= 1E-06
Acute MOE
HEC = 284
mg/m3
Benchmark =
300
Chronic
Cancer Risk3
Benchmark =
1E-06
Paints and
Coatings
Paint and Floor
Lacquer
High-Intensity User
Adult
(>21 years)
1.8E+04
NA
1.4E+04
NA
High-Intensity User
Child
(16-20 years)
1.9E+04
NA
NA
NA
High-Intensity User
Child
(11-15 years)
1.7E+04
NA
NA
NA
High-Intensity User
Bystander
NA
NA
3.8E+04
NA
Cleaning and
Furniture Care
Products
Surface Cleaner
High-Intensity User
Adult
(>21 years)
4.6E+06
6.7E-07
5.7E+04
1.0E-06
Moderate-Intensity
User
Adult
(>21 years)
NA
2.8E-07
NA
5.6E-07
High-Intensity User
Child
(16-20 years)
4.9E+06
NA
NA
NA
High-Intensity User
Child
(11-15 years)
4.5E+06
NA
NA
NA
High-Intensity User
Bystander
NA
NA
3.0E+05
NA
Laundry and
Dishwashing
Products
Dish Soap
High-Intensity User
Adult
(>21 years)
1.2E+07
3.2E-08
9.3E+03
7.1E-07
Moderate-Intensity
User
Adult
(>21 years)
NA
1.3E-08
NA
3.3E-07
High-Intensity User
Child
(16-20 years)
1.2E+07
NA
NA
NA
High-Intensity User
Child
(11-15 years)
1.1E+07
NA
NA
NA
High-Intensity User
Bystander
NA
NA
5.2E+04
NA
Dishwasher
Detergent
High-Intensity User
Adult
(>21 years)
1.1E+07
1.4E-07
4.1E+05
7.1E-08
Page 67 of 93
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Dermal Risk Estimates
Inhalation Risk Estimates
Category
Assessed
Condition of Use
Scenario
Descriptor
Receptor
Acute MOE
Benchmark =
300
Chronic
Cancer
Risk3
Benchmark
Acute MOE
HEC = 284
mg/m3
Benchmark =
Chronic
Cancer Risk"
Benchmark =
1E-06
= 1E-06
300
Moderate-Intensity
User
Adult
(>21 years)
NA
1.2E-07
NA
2.9E-08
High-Intensity User
Child
(16-20 years)
1.2E+07
NA
NA
NA
High-Intensity User
Child
(11-15 years)
1.1E+07
NA
NA
NA
High-Intensity User
Bystander
NA
NA
2.3E+06
NA
Laundry Detergent
High-Intensity User
Adult
(>21 years)
7.4E+07
1.8E-08
1.9E+05
1.3E-07
Moderate-Intensity
User
Adult
(>21 years)
NA
7.4E-09
NA
7.8E-08
High-Intensity User
Child
(16-20 years)
7.9E+07
NA
NA
NA
High-Intensity User
Child
(11-15 years)
7.2E+07
NA
NA
NA
High-Intensity User
Bystander
NA
NA
1.1E+06
NA
Arts, Crafts,
and Hobby
Textile Dye
High-Intensity User
Adult
(>21 years)
5.6E+07
NA
3.4E+05
NA
Materials
High-Intensity User
Child
(16-20 years)
5.9E+07
NA
NA
NA
High-Intensity User
Child
(11-15 years)
5.4E+07
NA
NA
NA
High-Intensity User
Bystander
NA
NA
1.9E+06
NA
Other
Consumer Uses
Spray Polyurethane
Foam
Basement
Adult
(>21 years)
3.5E+04
NA
317
NA
Bystander
NA
NA
384
NA
Child
(16-20 years)
3.7E+04
NA
NA
NA
Page 68 of 93
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Dermal Risk Estimates
Inhalation Risk Estimates
Category
Assessed
Condition of Use
Scenario
Descriptor
Receptor
Acute MOE
Benchmark =
300
Chronic
Cancer
Risk3
Benchmark
Acute MOE
HEC = 284
mg/m3
Benchmark =
Chronic
Cancer Risk"
Benchmark =
1E-06
= 1E-06
300
Child
(11-15 years)
3.3E+04
NA
NA
NA
Attic
Adult
(>21 years)
3.5E+04
NA
1.5E+03
NA
Bystander
NA
NA
4.0E+03
NA
Child
(16-20 years)
3.7E+04
NA
NA
NA
Child
(11-15 years)
3.3E+04
NA
NA
NA
Garage
Adult
(>21 years)
3.5E+04
NA
1.7E+03
NA
Bystander
NA
NA
2.5E+03
NA
Child
(16-20 years)
3.7E+04
NA
NA
NA
Child
(11-15 years)
3.3E+04
NA
NA
NA
Antifreeze
High-Intensity User
Adult
(>21 years)
6.9E+04
NA
1.8E+04
NA
High-Intensity User
Child
(16-20 years)
7.4E+04
NA
NA
NA
High-Intensity User
Child
(11-15 years)
6.8E+04
NA
NA
NA
High-Intensity User
Bystander
NA
NA
7.2E+04
NA
NA= Not Applicable
" Risks from chronic exposure were evaluated only for consumer products that are used regularly
Page 69 of 93
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5 RISK DETERMINATION
5.1 Overview
In each risk evaluation under TSCA Section 6(b), EPA determines whether a chemical substance
presents an unreasonable risk of injury to health or the environment, under the conditions of use. These
determinations do not consider costs or other non-risk factors. In making these determinations, EPA
considers relevant risk-related factors, including, but not limited to: the effects of the chemical substance
on health and human exposure to such substance under the conditions of use (including cancer and non-
cancer risks); the effects of the chemical substance on the environment and environmental exposure
under the conditions of use; the population exposed (including any potentially exposed or susceptible
subpopulations (PESS)); the severity of hazard (including the nature of the hazard, the irreversibility of
the hazard); and uncertainties. EPA takes into consideration the Agency's confidence in the data used in
the risk estimate. This includes an evaluation of the strengths, limitations, and uncertainties associated
with the information used to inform the risk estimate and the risk characterization.
This section describes the draft unreasonable risk determinations for the conditions of use in this
supplemental analysis.
5.1.1 Human Health
EPA identified cancer and non-cancer adverse effects from acute and chronic inhalation and dermal
exposure to 1,4-dioxane from the conditions of use described in this supplemental analysis. The health
risk estimates for the conditions of use in this supplemental analysis are in Section 4 (Table 4.8).
For this supplemental analysis, EPA identified as Potentially Exposed or Susceptible Subpopulations:
consumers and bystanders, including men, women, and children of any age.
EPA evaluated exposures to consumer users and bystanders using reasonably available modeling data of
inhalation and dermal exposures, as applicable. For example, EPA assumed that bystanders do not have
direct contact with 1,4-dioxane; therefore, non-cancer effects and cancer from dermal exposures to 1,4-
dioxane are not expected and were not evaluated for bystanders. Also, EPA did not estimate chronic
inhalation exposures to bystanders; however, bystanders would be exposed to lower levels than the user
based on the model bystander placement in the home during the product's use. The description of the
data used for human health exposure is in Section 2. Uncertainties in the analysis are discussed above
and are considered in the draft unreasonable risk determination for each condition of use presented
below.
EPA considered reasonably available information and environmental fate properties to characterize
general population exposure from surface water via the oral and dermal routes. EPA does not expect
general population exposure from fish consumption. EPA's draft unreasonable risk determination for the
general population is presented below. EPA did not evaluate risks to the general population from
ambient air, drinking water, and sediment pathways for any conditions of use, and the draft unreasonable
risk determinations do not account for exposures to the general population from ambient air, drinking
water, and sediment pathways.
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5.1.1.1 Non-Cancer Risk Estimates
The risk estimates of non-cancer effects (MOEs) refers to adverse health effects associated with health
endpoints other than cancer, including to the body's organ systems, such as reproductive/developmental
effects, cardiac and lung effects, and kidney and liver effects. The MOE is the point of departure (POD)
(an approximation of the no-observed adverse effect level (NOAEL) or benchmark dose level (BMDL))
for a specific health endpoint divided by the exposure concentration for the specific scenario of concern.
The MOEs are compared to a benchmark MOE. The benchmark MOE accounts for the total uncertainty
in a POD. The benchmark MOE for 1,4-dioxane for acute exposures is 100 (accounting for interspecies
and intraspecies variability and LOAEL-to-NOAEL uncertainty), while the benchmark MOE for chronic
exposures is 30 (accounting for interspecies and intraspecies variability).
5.1.1.2 Cancer Risk Estimates
Cancer risk estimates represent the incremental increase in probability of an individual in an exposed
population developing cancer over a lifetime (excess lifetime cancer risk (ELCR)) following exposure to
the chemical. Standard cancer benchmarks used by EPA and other regulatory agencies are an increased
cancer risk above benchmarks ranging from 1 in 1,000,000 to 1 in 10,000 (i.e., lxlO"6 to lxlO"4)
depending on the subpopulation exposed. For this supplemental analysis, EPA used lxlO"6 as the
benchmark for the cancer risk to consumers from consumer use of cleaning and furniture care products
and laundry and dishwashing products.
The benchmark of lxlO"6 is not a bright line and EPA has discretion to make unreasonable risk
determinations based on other benchmarks as appropriate.
5.1.1.3 Determining Unreasonable Risk to Injury Health
Calculated risk estimates (MOEs or cancer risk estimates) can provide a risk profile by presenting a
range of estimates for different health effects for different conditions of use. A calculated MOE that is
less than the benchmark MOE 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 supports a determination of unreasonable risk of injury to health from cancer. Whether EPA
makes a determination of unreasonable risk depends upon other risk-related factors, such as the endpoint
under consideration, the reversibility of 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.
EPA may make a determination of no unreasonable risk for conditions of use where the substance's
hazard and exposure potential, or where the risk-related factors described previously, lead the Agency to
determine that the risks are not unreasonable.
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107
108
5.2 Detailed Draft Unreasonable Risk Determinations by Condition of
Use
Table 5-1. Categories and Subcategories of Conditions of Use Included in the Supplemental
Analysis
Life Cycle Stage
Category"
Subcategory b
Unreasonable Risk
Consumer uses
Arts, Crafts, and
Hobby Materials
Textile dye
No
Automotive care
products
Antifreeze
No
Cleaning and furniture
care products
Surface cleaner
No
Laundry and
dishwashing products
Dish soap
No
Dishwasher detergent
No
Laundry detergent
No
Paints and coatings
Paint and floor lacquer
No
Other uses
Spray polyurethane foam
No
5.2,1 Consumer use - Arts, crafts and hobby materials - Textile dye
Section 6(b)(4)(A) unreasonable risk determination for the consumer use of 1.4-dioxane in textile dye:
Does not present an unreasonable risk of injury to health (consumers and bystanders).
For consumers, EPA found that there was no unreasonable risk of non-cancer effects (liver toxicity)
from acute inhalation or dermal exposures at the high-intensity use. For bystanders, EPA found that
there was no unreasonable risk of non-cancer effects (liver toxicity) from acute inhalation exposures at
the high intensity use.
EPA's determination that the consumer use of 1,4-dioxane in textile dye does not present an
unreasonable risk is based on the comparison of the risk estimates for non-cancer effects to the
benchmarks (Table 4.8) and other considerations. As explained in Section 5.1., EPA considered the
health effects of 1,4-dioxane, the exposures from the condition of use, and the uncertainties in the
analysis (Section 4):
Chronic exposures were not evaluated for this condition of use because daily use intervals are
not reasonably expected to occur.
Inhalation exposures to consumers and bystanders were evaluated with the Consumer Exposure
Model Version 2.1 (CEM 2.1). The magnitude of inhalation exposures to consumers and
bystanders depends on several factors, including the concentration of 1,4-dioxane in products
used, use patterns (including frequency, duration, amount of product used, room of use, and
local ventilation), and application method.
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Dermal exposures to consumers were evaluated with the CEM (Fraction Absorbed). Dermal
exposures to consumers result from dermal contact not involving impeded evaporation while
using the product. The magnitude of dermal exposures depends on several factors, including
skin surface area, film thickness, concentration of 1,4-dioxane in product used, dermal exposure
duration, and estimated fractional absorption.
In summary, the risk estimates, the health effects of 1,4-dioxane, the exposures, and consideration of
uncertainties support EPA's determination that there is no unreasonable risk of injury to health
(consumers and bystanders) from the consumer use of 1,4-dioxane in textile dye.
5.2.2 Consumer use - Automotive care products - Antifreeze
Section 6(b)(4)(A) unreasonable risk determination for the consumer use of 1,4-dioxane in antifreeze:
Does not present an unreasonable risk of injury to health (consumers and bystanders).
For consumers, EPA found that there was no unreasonable risk of non-cancer effects (liver toxicity)
from acute inhalation or dermal exposures at the high-intensity use. For bystanders, EPA found that
there was no unreasonable risk of non-cancer effects (liver toxicity) from acute inhalation exposures at
the high intensity use.
EPA's determination that the consumer use of 1,4-dioxane in antifreeze does not present an
unreasonable risk is based on the comparison of the risk estimates for non-cancer effects to the
benchmarks (Table 4.8) and other considerations. As explained in Section 5.1., EPA considered the
health effects of 1,4-dioxane, the exposures from the condition of use, and the uncertainties in the
analysis (Section 4):
Chronic exposures were not evaluated for this condition of use because daily use intervals are
not reasonably expected to occur.
Inhalation exposures to consumers and bystanders were evaluated with the Consumer Exposure
Model Version 2.1 (CEM 2.1). The magnitude of inhalation exposures to consumers and
bystanders depends on several factors, including the concentration of 1,4-dioxane in products
used and use patterns (including frequency, duration, amount of product used, and local
ventilation).
Dermal exposures to consumers were evaluated with the CEM (Fraction Absorbed). Dermal
exposures to consumers result from dermal contact not involving impeded evaporation while
using the product. The magnitude of dermal exposures depends on several factors, including
skin surface area, film thickness, concentration of 1,4-dioxane in product used, dermal exposure
duration, and estimated fractional absorption.
In summary, the risk estimates, the health effects of 1,4-dioxane, the exposures, and consideration of
uncertainties support EPA's determination that there is no unreasonable risk of injury to health
(consumers and bystanders) from the consumer use of 1,4-dioxane in antifreeze.
5.2.3 Consumer use - Cleaning and furniture care products -- Surface cleaner
Section 6(b)(4)(A) unreasonable risk determination for the consumer use of 1,4-dioxane in general
purpose cleaners: Does not present an unreasonable risk of injury to health (consumers and bystanders).
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For consumers, EPA found that there was no unreasonable risk of non-cancer effects (liver toxicity)
from acute inhalation or dermal exposures or of cancer from chronic inhalation or dermal exposures at
the high intensity use. For bystanders, EPA found that there was no unreasonable risk of non-cancer
effects (liver toxicity) from acute inhalation exposures at the high intensity use.
EPA's determination that the consumer use of 1,4-dioxane in surface cleaner does not present an
unreasonable risk is based on the comparison of the risk estimates for non-cancer effects and cancer to
the benchmarks (Table 4.8) and other considerations. As explained above, EPA considered the health
effects of 1,4-dioxane, the exposures from the condition of use, and the uncertainties in the analysis
(Section 4):
Inhalation exposures to consumers and bystanders were evaluated with the Consumer Exposure
Model Version 2.1 (CEM 2.1). The magnitude of inhalation exposures to consumers and
bystanders depends on several factors, including the concentration of 1,4-dioxane in products
used and use patterns (including frequency, duration, amount of product used, and local
ventilation).
Dermal exposures to consumers were evaluated with the CEM (Fraction Absorbed). Dermal
exposures to consumers result from dermal contact not involving impeded evaporation while
using the product. The magnitude of dermal exposures depends on several factors, including
skin surface area, film thickness, concentration of 1,4-dioxane in product used, dermal exposure
duration, and estimated fractional absorption.
In summary, the risk estimates, the health effects of 1,4-dioxane, the exposures, and consideration of
uncertainties support EPA's determination that there is no unreasonable risk of injury to health
(consumers and bystanders) from the consumer use of 1,4-dioxane in surface cleaner.
5,2.4 Consumer use - Laundry and dishwashing products - Dish soap
Section 6(b)(4)(A) unreasonable risk determination for the consumer use of 1,4-dioxane in dish soap:
Does not present an unreasonable risk of injury to health (consumers and bystanders).
For consumers, EPA found that there was no unreasonable risk of non-cancer effects (liver toxicity)
from acute inhalation or dermal exposures or of cancer from chronic inhalation or dermal exposures at
the high intensity use. For bystanders, EPA found that there was no unreasonable risk of non-cancer
effects (liver toxicity) from acute inhalation exposures at the high intensity use.
EPA's determination that the consumer use of 1,4-dioxane in dish soap does not present an
unreasonable risk is based on the comparison of the risk estimates for non-cancer effects and cancer to
the benchmarks (Table 4.8) and other considerations. As explained above, EPA considered the health
effects of 1,4-dioxane, the exposures from the condition of use, and the uncertainties in the analysis
(Section 4):
Inhalation exposures to consumers and bystanders were evaluated with the Consumer Exposure
Model Version 2.1 (CEM 2.1). The magnitude of inhalation exposures to consumers and
bystanders depends on several factors, including the concentration of 1,4-dioxane in products
used and use patterns (including frequency, duration, amount of product used, and local
ventilation).
Dermal exposures to consumers were evaluated with the CEM (Fraction Absorbed). Dermal
exposures to consumers result from dermal contact not involving impeded evaporation while
using the product. The magnitude of dermal exposures depends on several factors, including
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skin surface area, film thickness, concentration of 1,4-dioxane in product used, dermal exposure
duration, and estimated fractional absorption.
In summary, the risk estimates, the health effects of 1,4-dioxane, the exposures, and consideration of
uncertainties support EPA's determination that there is no unreasonable risk of injury to health
(consumers and bystanders) from the consumer use of 1,4-dioxane in dish soap.
5.2. 5 Consumer use - Laundry and dishwashing products - Dishwasher detergent
Section 6(b)(4)(A) unreasonable risk determination for the consumer use of 1,4-dioxane in dishwasher
detergent: Does not present an unreasonable risk of injury to health (consumers and bystanders).
For consumers, EPA found that there was no unreasonable risk of non-cancer effects (liver toxicity)
from acute inhalation or dermal exposures or of cancer from chronic inhalation or dermal exposures at
the high intensity use. For bystanders, EPA found that there was no unreasonable risk of non-cancer
effects (liver toxicity) from acute inhalation exposures at the high intensity use.
EPA's determination that the consumer use of 1,4-dioxane in dishwasher detergent does not present an
unreasonable risk is based on the comparison of the risk estimates for non-cancer effects and cancer to
the benchmarks (Table 4.8) and other considerations. As explained above, EPA considered the health
effects of 1,4-dioxane, the exposures from the condition of use, and the uncertainties in the analysis
(Section 4):
Inhalation exposures to consumers and bystanders were evaluated with the Consumer Exposure
Model Version 2.1 (CEM 2.1). The magnitude of inhalation exposures to consumers and
bystanders depends on several factors, including the concentration of 1,4-dioxane in products
used and use patterns (including frequency, duration, amount of product used, and local
ventilation).
Dermal exposures to consumers were evaluated with the CEM (Fraction Absorbed). Dermal
exposures to consumers result from dermal contact not involving impeded evaporation while
using the product. The magnitude of dermal exposures depends on several factors, including
skin surface area, film thickness, concentration of 1,4-dioxane in product used, dermal exposure
duration, and estimated fractional absorption.
In summary, the risk estimates, the health effects of 1,4-dioxane, the exposures, and consideration of
uncertainties support EPA's determination that there is no unreasonable risk of injury to health
(consumers and bystanders) from the consumer use of 1,4-dioxane in dishwasher detergent.
5.2.6 Consumer use - Laundry and dishwashing products - Laundry detergent
Section 6(b)(4)(A) unreasonable risk determination for the consumer use of 1,4-dioxane in laundry
detergent: Does not present an unreasonable risk of injury to health (consumers and bystanders).
For consumers, EPA found that there was no unreasonable risk of non-cancer effects (liver toxicity)
from acute inhalation or dermal exposures or of cancer from chronic inhalation or dermal exposures at
the high intensity use. For bystanders, EPA found that there was no unreasonable risk of non-cancer
effects (liver toxicity) from acute inhalation exposures at the high intensity use.
EPA's determination that the consumer use of 1,4-dioxane in laundry detergent does not present an
unreasonable risk is based on the comparison of the risk estimates for non-cancer effects and cancer to
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the benchmarks (Table 4.8) and other considerations. As explained in Section 5.1., EPA considered the
health effects of 1,4-dioxane, the exposures from the condition of use, and the uncertainties in the
analysis (Section 4):
Inhalation exposures to consumers and bystanders were evaluated with the Consumer Exposure
Model Version 2.1 (CEM 2.1). The magnitude of inhalation exposures to consumers and
bystanders depends on several factors, including the concentration of 1,4-dioxane in products
used and use patterns (including frequency, duration, amount of product used, and local
ventilation).
Dermal exposures to consumers were evaluated with the CEM (Fraction Absorbed). Dermal
exposures to consumers result from dermal contact not involving impeded evaporation while
using the product. The magnitude of dermal exposures depends on several factors, including
skin surface area, film thickness, concentration of 1,4-dioxane in product used, dermal exposure
duration, and estimated fractional absorption.
In summary, the risk estimates, the health effects of 1,4-dioxane, the exposures, and consideration of
uncertainties support EPA's determination that there is no unreasonable risk of injury to health
(consumers and bystanders) from the consumer use of 1,4-dioxane in laundry detergent.
5,2,7 Consumer use - Paints and coatings - Paint and floor lacquer
Section 6(b)(4)(A) unreasonable risk determination for the consumer use of 1,4-dioxane in paint and
floor lacquer: Does not present an unreasonable risk of injury to health (consumers and bystanders).
For consumers, EPA found that there was no unreasonable risk of non-cancer effects (liver toxicity)
from acute inhalation or dermal exposures at the high-intensity use. For bystanders, EPA found that
there was no unreasonable risk of non-cancer effects (liver toxicity) from acute inhalation exposures at
the high intensity use.
EPA's determination that the consumer use of 1,4-dioxane in paint and floor lacquer does not present
an unreasonable risk is based on the comparison of the risk estimates for non-cancer effects to the
benchmarks (Table 4.8) and other considerations. As explained in Section 5.1., EPA considered the
health effects of 1,4-dioxane, the exposures from the condition of use, and the uncertainties in the
analysis (Section 4):
Chronic exposures were not evaluated for this condition of use because daily use intervals are
not reasonably expected to occur.
Inhalation exposures to consumers and bystanders were evaluated with the Consumer Exposure
Model Version 2.1 (CEM 2.1). The magnitude of inhalation exposures to consumers and
bystanders depends on several factors, including the concentration of 1,4-dioxane in products
used and use patterns (including frequency, duration, amount of product used, and local
ventilation).
Dermal exposures to consumers were evaluated with the CEM (Fraction Absorbed). Dermal
exposures to consumers result from dermal contact not involving impeded evaporation while
using the product. The magnitude of dermal exposures depends on several factors, including
skin surface area, film thickness, concentration of 1,4-dioxane in product used, dermal exposure
duration, and estimated fractional absorption.
In summary, the risk estimates, the health effects of 1,4-dioxane, the exposures, and consideration of
uncertainties support EPA's determination that there is no unreasonable risk of injury to health
(consumers and bystanders) from the consumer use of 1,4-dioxane in paint and floor lacquer.
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5.2.8 Consumer use - Other uses - Spray Polyurethane Foam
Section 6(b)(4)(A) unreasonable risk determination for the consumer use of 1.4-dioxane in spray
polyurethane foam: Does not present an unreasonable risk of injury to health (consumers and
bystanders).
For consumers, EPA found that there was no unreasonable risk of non-cancer effects (liver toxicity)
from acute inhalation and dermal exposures at the high-intensity use. For bystanders, EPA found that
there was no unreasonable risk of non-cancer effects (liver toxicity) from acute inhalation exposures at
the high intensity use.
EPA's determination that the consumer use of 1,4-dioxane in spray polyurethane foam does not present
an unreasonable risk is based on the comparison of the risk estimates for non-cancer effects to the
benchmarks (Table 4.8) and other considerations. As explained in Section 5.1., EPA considered the
health effects of 1,4-dioxane, the exposures from the condition of use, and the uncertainties in the
analysis (Section 4):
Chronic exposures were not evaluated for this condition of use because daily use intervals are
not reasonably expected to occur.
Inhalation exposures to consumers and bystanders were evaluated with the Consumer Exposure
Model Version 2.1 (CEM 2.1). The magnitude of inhalation exposures to consumers and
bystanders depends on several factors, including the concentration of 1,4-dioxane in products
used and use patterns (including frequency, duration, amount of product used, and local
ventilation).
Dermal exposures to consumers were evaluated with the CEM (Fraction Absorbed). Dermal
exposures to consumers result from dermal contact not involving impeded evaporation while
using the product. The magnitude of dermal exposures depends on several factors, including
skin surface area, film thickness, concentration of 1,4-dioxane in product used, dermal exposure
duration, and estimated fractional absorption.
In summary, the risk estimates, the health effects of 1,4-dioxane, the exposures, and consideration of
uncertainties support EPA's determination that there is no unreasonable risk of injury to health
(consumers and bystanders) from the consumer use of 1,4-dioxane in spray polyurethane foam.
5.2.9 General Population
Section 6(b)(4)(A) unreasonable risk determination from any of the conditions of use of !.¦4-dioxane:
Does not present an unreasonable risk of injury to health (general population). EPA did not assess
exposures from ambient air, drinking water, and sediment pathways because they fall under the
jurisdiction of other environmental statutes administered by EPA, i.e., CAA, SDWA, RCRA, and
CERCLA. However, EPA has not developed recommended ambient water quality criteria for the
protection of human health for 1,4-dioxane. Exposure to the general population via surface water can
occur through recreational activities (e.g., swimming) and through consuming fish. EPA considered
reasonably available information and environmental fate properties to characterize general population
exposure through the surface water pathway. EPA evaluated the human health risks of potential acute
and chronic incidental exposures via oral and dermal routes from recreational swimming and
determined that these risks are not unreasonable. In addition, because 1,4-dioxane has low
bioaccumulation potential, EPA has determined that the human health risks from fish ingestion are not
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341 unreasonable. This unreasonable risk determination does not account for exposures to the general
342 population from ambient air, drinking water, and sediment pathways.
343
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1 r j * \ (2018). Application of systematic review in TSCA risk evaluations. (740-P1-8001).
Washington, DC: U.S. Environmental Protection Agency, Office of Chemical Safety and
Pollution Prevention, https://www.epa.gov/sites/production/files/2018-
06/documents/final application of sr in tsc
U.S. EPA. (2019a). Consumer Exposure Model (CEM) 2.1 User Guide. (EPA Contract # EP-W-12-
010). Washington, DC.
U.S. EPA. (2019b). Consumer Exposure Model (CEM) 2.1 User Guide - Appendices. (EPA Contract #
EP-W-12-010). Washington, DC.
Won. DNoGYaWCoP. (2014). Material Emissions Testing: VOCs from Wood, Paint, and Insulation
Materials. National Research Council of Canada.
http://dx.doi.Org/https://doi.oii 24/23002015
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APPENDICES
Appendix A CONSUMER EXPOSURES
For additional consumer modeling support files, please see the following supplemental documents:
Supplemental Analysis to the Draft Risk Evaluation for 1,4-Dioxane - Consumer Exposure Assessment
Model Input Parameters; Supplemental Analysis to the Draft Risk Evaluation for 1,4-Dioxane -
Exposure Modeling Results and Risk Estimates for Consumer Exposures.
A,1 Consumer Inhalation Exposure
A.1.1 CEM 2.1 and CEM
The Consumer Exposure Models (CEM 2.1 and CEM within E-FA.ST 2.014) predict indoor air
concentrations from consumer product use by implementing a deterministic, mass-balance calculation
utilizing an emission profile determined by implementing appropriate emission scenarios. The model
uses a two-zone representation of the building of use (e.g., residence, school, office), with Zone 1
representing the room where the consumer product is used (e.g., a utility room) and Zone 2 being the
remainder of the building. The product user is placed within Zone 1 for the duration of use, while a
bystander is placed in Zone 2 during product use. Otherwise, product users and bystanders follow
prescribed activity patterns throughout the simulated period. Each zone is considered well-mixed.
Product users are exposed to airborne concentrations estimated within the near-field during the time of
use and otherwise follow their prescribed activity pattern. Bystanders follow their prescribed activity
pattern and are exposed to far-field concentrations when they are in Zone 1. Background concentrations
can be set to a non-zero concentration if desired.
The general steps of the calculation engine within the CEM models include:
Introduction of the chemical (i.e., 1,4-dioxane) into the room of use (Zone 1) through two possible pathways:
(1) overspray of the product or (2) evaporation from a thin film;
Transfer of the chemical to the rest of the house (Zone 2) due to exchange of air between the different rooms;
* Exchange of the house air with outdoor air; and
* Compilation of estimated air concentrations in each zone as the modeled occupant (i.e., user or bystander)
moves about the house per prescribed activity patterns.
For acute exposure scenarios, emissions from each incidence of product usage are estimated over a
period of 72 hours using the following approach that accounts for how a product is used or applied, the
total applied mass of the product, the weight fraction of the chemical in the product, and the molecular
weight and vapor pressure of the chemical. Time weighted averages (TWAs) were then computed based
on these user and bystander concentration time series per available human health hazard data. For 1,4-
dioxane, 8-hour TWAs were quantified for use in risk evaluation based on alignment of relevant acute
human health hazard endpoints. For additional details on CEM 2.1's underlying emission models,
assumptions, and algorithms, please see the User Guide Section 3: Detailed Descriptions of Models
within CEM 2.1 ( a). The emission models used have been compared to other model
results and measured data; see Appendix D: Model Corroboration of the User Guide Appendices for the
results of these analyses (U.S. EPA. 2.019b).
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For chronic exposure scenarios, CEM within E-FAST 2014 was used to obtain lifetime average daily
concentrations (LADCs) for the scenarios involving chronic exposures. Emissions are estimated over a
period of 60 days. For cases where the evaporation time estimated exceeds 60 days, the model will
truncate the emissions at 60 days. Conversely, for cases where the evaporation time is less than 60 days,
emissions will be set to zero between the end of the evaporation time and 60 days. For more information
on this version of CEM and its chronic inhalation estimates, refer to the imentation
Manual (U.S. EPA. 2007).
Emission Models in CEM 2.1
Based on the suite of product scenarios developed to evaluate the 1,4-dioxane consumer conditions of
use, the specific emission models applied for the purposes of this evaluation include: El: Emission from
Product Applied to a Surface Indoors Incremental Source Model and E4: Emission from Product Added
to Water.
Product Scenarios in CEM
Based on the suite of product scenarios developed to evaluate the 1,4-dioxane consumer conditions of
use, the specific models applied for the purposes of this evaluation include: Product Applied to Surface
- Incremental Source Model and Product Added to Water - Constant Rate Model.
CEM 2.1's El model and CEM's Product Applied to Surface - Incremental Source Model are analogous
and are generally applicable for liquid products applied to a surface such as cleaners. These emission
models assume a constant application rate over a user-specified duration of use and an emission rate that
declines exponentially over time, at a rate that depends on the chemical molecular weight and vapor
pressure.
CEM 2.1's E4 model and CENM's Product Added to Water - Constant Rate Model assume emission at
a constant rate over a duration that depends on the chemical's molecular weight and vapor pressure. If
this estimated duration is longer than the user-specified duration of use, chemical emissions are
truncated at the end of the product use period and the remaining chemical mass is assumed to go down
the drain. These emission models are applied for use scenarios such as laundry and dishwashing
detergent, dish soap, and textile dye.
A.1.2 MCCEM
The Multi-Chamber Concentration and Exposure Model (MCCEM) estimates indoor air concentrations
of chemicals released from household products ( 010). It uses air infiltration and interzonal air
flow rates with user-input emission rates to calculate time-varying concentrations in several zones or
chambers within a residence. Four types of source models are available in MCCEM - constant, single
exponential, incremental, and data entry. For additional details, see the MCCEM User Guide (EPA.
2019c).
Within MCCEM, the incremental source model is specifically designed for products that are applied to a
surface (as SPF is) rather than products that are placed in an environment (e.g., an air freshener). This
distinction is important because the incremental source model considers the time or duration of
application or use in its calculations of emissions and concentrations, while the single exponential
source model does not. The incremental model assumes a constant application rate over time, coupled
with an emission rate for each instantaneously applied segment that declines exponentially. The equation
for the time-varying emission rate resulting from the combination of constant application and
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exponentially declining emissions (Evans. 1996) utilized in the single exponential incremental model is
shown below. This is a simplification of the overall incremental model in MCCEM that considers two
emission decay constants and rates to capture emissions from both the evaporation and diffusion phases.
However, the SPF scenario is better modeled by a single decay constant after application.
ER(t) =
MxWFxCF
x [(l e~fc(t_tstart)) ((l e~k(-t~(-tstart+ta^) x //(t))]
Where:
ER(t)
M
WF
CF
Emission rate at time t (mg/min)
Mass of product used (g)
Weight fraction of chemical in product (unitless)
Conversion factor (1000 mg/g)
tstart = Time of start of application (min)
ta = Application time (min)
k = First-order rate constant for emissions decline (min1)
t = Time (min)
H (t) = 0/1 value used to indicate if product is actively in use
= 0 if t - (tstart + ta)< 0
= 1 if t - (tstart + ta) > 0
The incremental model can be populated using experimental data and proposed model of emission rates
in Karlovich et al. Q ). In this study, the authors measured air concentrations of 1,4-dioxane after
taking samples from an open-cell SPF product applied to a cardboard box and placed in a small-scale
environmental chamber. These concentrations were used to develop a mathematical relationship
between the emission factor and loading factor based on the volume and airflow of the chamber.
Where:
EF
^chamber
LF
ACH
EF =
-chamber
LF X ACH
Emission Factor (|ig/m2-hr)
Chamber concentration (|ig/m3)
Loading factor (m2/m3)
air changes per hour
Based on the chamber air flow rate, foam sample surface area, and indoor air assumptions, the above
equation can be reworked to find predicted air concentrations:
-air, predicted
EF x 0.5
03
The concentration data can be used to determine decay rates by fitting the data to a time series
concentration function associated with MCCEM's incremental model. The general mass-balance
equation for a test chamber can be integrated assuming an initial concentration of zero to the following:
C(t)=^-x(e~kt-eZrt)
V{v~k)
Where:
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C(t)
Concentration (|ig/m3)
E0
Initial emission rate (ng/hr)
V
= Volume of the chamber (m3)
Q
Airflow rate into and out of the chamber (m3/hr)
k
First-order rate constant (hr1)
t
= Time (hr)
Karlovich et al. (2011) collected air samples 4, 12, 24, and 48 hours after placing the sample in the
chamber. Predicted indoor air concentrations (1,479, 663, 201, and 40 |ig/m3, respectively) were fitted to
the concentration equation above to identify the initial emission rate and decay constant, 73.868 |ig/hr
and 0.1 hr"1, respectively. The emission rate was normalized to the applied surface area of SPF in the
study (25 square inches) to find an emission rate per square inch of SPF applied, 2.955 |ig/in2/hr. This
initial emission rate and decay constant can then be scaled appropriately to find the total mass applied in
each application setting (attic, basement, and garage).
A.1,2.1 MCCEM Inputs for SPF Scenario
Product and Exposure Settings
The suggested values for house volume (492 m3) and air exchange rate (0.45 ACH) are central values
from the Exposure Factors Handbook (EPA. ). A two-story house is assumed for all cases. The attic
volume is assumed to be half the volume of one story, or 123 m3. The basement volume is assumed to be
the volume of one story, or 246 m3. The assumed garage volume (118 m3) is the average volume of one-
and two-car garages in 15 single-family homes with attached garages, as reported by Batterman et al.
2007. The attic and garage are assumed to be outside of the standard house volume as they are not
modeled to be conditioned or finished.
For the attic scenario, interzonal airflow rates were applied based on measured air change rates at a
variety of temperatures and wind speeds for vented and unvented attics (Walker et al. 2005). The
central measured value at wind speeds of 2-3 m/s was about 1.5 air changes per hour (ACH) for the
unvented attic and about 6.0 ACH for the vented. The latter case is used in this scenario as most US
homes are assumed to have vented attics. When multiplied by the volume of the attic, this 6.0 ACH
rate corresponds to an interzonal airflow rate of 738 m3/hr between the attic and outdoors. Walker et
al. also considered the airflow between unconditioned attics and the remainder of the houses,
measuring an average of about 0.125 ACH at standard temperatures of 20-25°C. This corresponds
to an interzonal airflow rate of 61.5 m3/hr between the attic and the rest of the house (ROH). The
suggested value of 0.45 ACH was applied for the rest of the house and outdoors, corresponding to
an interzonal airflow rate of 221.4 m3/hr.
For the basement scenario, interzonal airflow rates were applied using an algorithm developed in a
study estimating the distributions for residential air exchange rates (Koomtz and Rector. 2005). The
estimated interzonal airflow rate between both basements and garages is estimated at 109 m3/hr.
The suggested value of 0.45 ACH was applied for the rest of the house and outdoors, corresponding
to an interzonal airflow rate of 110.7 m3/hr.
For the garage scenario, interzonal airflow rates were informed by the results of a study measuring
the airtightness of garages on a variety of homes under induced pressurized conditions (Emmerich
et al. 2003). The average airtightness measured with the blower door was 48 ACH at 50 Pa, which
corresponds to an air exchange rate of about 2.5 ACH and 295 m3/hr under normal conditions. The
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suggested value of 0.45 ACH was applied for the rest of the house and outdoors, corresponding to
an interzonal airflow rate of 221.4 m3/hr.
A typical floor or ceiling loading ratio of 0.41 m2/ m3 (i.e., for a ceiling height of 2.44 m; EPA, 2011),
when multiplied by the upstairs volume of 246 m3, gives an estimated attic floor area of 100.9 m2 (1086
sq. feet or 156,384 sq. inches). The same ratio applies to the garage ceiling, giving an estimated area of
48.4 m2 (521 sq. feet or 75,024 sq. inches) when multiplied by the garage volume of 118 m3. The
basement volume (246 m3) and ceiling height (2.44 m) indicate a floor area of 100.8 m2, corresponding
to dimensions of 7.9 m by 12.8 m. The wall area is 2.44 m x (7.9 m x 2 + 12.8 m x 2) = 101 m2 or 1087
sq. ft. or 156,528 sq. inches. These areas of application surface were multiplied by the emission rate per
square inch over the decay rate per hour to determine the total mass of 1,4-dioxane released in each
setting: 4523.752659 mg in the attic, 4527.918177 mg in the basement, and 2170.234931 mg in the
garage.
Use Patterns and Exposure Factors
An installation rate of 3 sq. ft. An in or 180 sq. ft./hour is assumed, based on an instructional video for
DIY spray foam insulation installation. Corresponding estimates for the duration of installation are 6
hours for the attic floor, 6 hours for basement walls, and 3 hours for the garage ceiling. Each application
was modeled to start at 9 AM. It is assumed that the user would be in the room of use during the time of
application and in the rest of the house for the remainder of the model run. This assumption of staying at
home produces a conservative estimate of exposure. Bystander exposure is based on the assumption that
the bystander is home during the application period but spends the entire time in the rest of the house
and no time in the room of use.
In MCCEM, a breathing rate of 15.083 m3/day was estimated based on the recommended mean long-
term exposure inhalation values in the 2011 Exposure Factors Handbook (EPA. 2011).
A.2 Consumer Dermal Exposure
Two models were used to evaluate consumer dermal exposures, the Fraction Absorbed model (P_DE2a
within CEM) and the Permeability model (P_DER2b within CEM). A brief comparison of these two
dermal models through the calculation of acute dose rates (ADRs) is provided below. They have been
applied to distinct exposure conditions, with the permeability model applied to scenarios likely to
involve occluded dermal contact where evaporation may be inhibited and the fraction absorbed model
applied to scenarios less likely to involve occluded dermal contact.
The dermal models described below were run for all consumer conditions of use to provide a
comparison between the two results while recognizing each model is unique in its approach to
estimating dermal exposure and may not be directly comparable. Keeping these limitations in mind, the
full suite of exposure results from both models is shown for all conditions of use in Supplemental
Analysis to the Draft Risk Evaluation for 1,4-Dioxane - Exposure Modeling Results and Risk Estimates
for Consumer Exposures.xlsx.
Because neither model considers the mass of chemical as an input in the absorbed dose equations, both
have the potential to overestimate the dermal absorption by modeling a mass which is larger than the
mass used in a scenario. Therefore, when utilizing either of the CEM models for dermal exposure
estimations, a mass check is necessary outside of the CEM model to make sure the mass absorbed does
not exceed the typical mass used for a given scenario.
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CEM Absorption Fraction Model (P_DER2a)
The fraction absorbed model estimates the mass of a chemical absorbed through the applicational of a
fractional absorption factor to the mass of chemical present on or in the skin following a use event. The
initial dose or amount retained on the skin is determined using a film thickness approach. A fractional
absorption factor is then applied to estimate the absorbed dose from the initial dose. The fraction
absorbed is essentially the measure of two competing processes, evaporation of the chemical from the
skin surface and penetration deeper into the skin. It can be estimated using an empirical relationship
based on Frasch and Bunge (2015). Due to the model's consideration of evaporative processes, dermal
exposure under unimpeded exposure conditions was considered to be more representative. For
additional details on this model, please see Appendix A and the CEM User Guide Section 3: Detailed
Descriptions of Models within CEM (U.S. EPA. 2019a).
The acute form of the absorption fraction model is given below:
ADR =¦
SA
AR X Fabs x x FQac x Dil xWFx EDac x CF1
ATac
Where:
ADR
= Acute daily dose rate (mg/kg-day)
AR
= Amount retained in the skin (g/cm2, film thickness [cm] multiplied by product density)
F abs
= Absorption fraction (see below)
Dac
= Duration of use (min/event)
SA/BW
= Surface area to body weight ratio (cm2/kg)
FQac
= Frequency of use (events/day, 1 for acute exposure scenarios)
Dil
= Product dilution fraction (unitless)
WF
= Weight fraction of chemical in product (unitless)
EDac
= Exposure duration (1 day for acute exposure scenarios)
CFI
= Conversion factor (1,000 mg/g)
ATcr
= Averaging time (1 day for acute exposure scenarios)
The fraction absorbed (Fabs) term is estimated using the ratio of evaporation from the stratum corneum to
the dermal absorption rate through the stratum corneum, as informed by gas phase mass transfer
coefficient, vapor pressure, molecular weight, water solubility, real gas constant, and permeability
coefficient.
3 + X
FRabs =
Dn
1 exp(a t acrc )
hagXCFiJ
3(1+*)
Where:
X
a
Dac
tlag
CFi
= Ratio of the evaporation rate from the stratum corneum (SC) to the dermal absorption rate
= Constant (2.906)
= Duration of use (min/event)
= Lag time for chemical transport through SC (hr)
= Conversion factor (60 min/hr)
The chronic form of the dermal absorption fraction model is given below:
LADD =
SA
AR x Fabs x -y x FQcr x Dil x WF x EDcr x CF1
ATcr x CF2
Where:
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LADD = Lifetime average daily dose (mg/kg-day)
Dcr = Duration of use (min/event)
FQcr = Frequency of use (events or days/year)
EDCr = Exposure duration (57 years)
CF2 = Conversion factor (365 days/yr)
ATCr = Averaging time (78 years)
CEM Permeability Model (P_DER2b)
The permeability model estimates the mass of a chemical absorbed and dermal flux based on a
permeability coefficient (Kp) and is based on the ability of a chemical to penetrate the skin layer once
contact occurs. It assumes a constant supply of chemical directly in contact with the skin throughout the
exposure duration. Kp is a measure of the rate of chemical flux through the skin. The parameter can
either be specified by the user (if measured data are reasonably available) or be estimated within CEM
using a chemical's molecular weight and octanol-water partition coefficient (Kow). The permeability
model does not inherently account for evaporative losses (unless the available flux or Kp values are
based on non-occluded, evaporative conditions), which can be considerable for volatile chemicals in
scenarios where evaporation is not impeded. While the permeability model does not explicitly represent
exposures involving such impeded evaporation, the model assumptions make it the preferred model for
an such a scenario. For additional details on this model, please see Appendix A and the CEM User
Guide Section 3: Detailed Descriptions of Models within CEM (U.S. EPA. 2019a).
The acute form of the dermal permeability model is given below:
SA
K x Dac x p x w x FQac x Dil xWFx EDac x CF1
ADR = -
ATac X CF2
Where:
ADR = Potential acute dose rate (mg/kg-day)
Kp = Permeability coefficient (cm/hr)
Dac = Duration of use (min/event)
p = Density of formulation (g/cm3)
SA/BW = Surface area to body weight ratio (cm2/kg)
FQac = Frequency of use (events/day, 1 for acute exposure scenarios)
Dil = Product dilution fraction (unitless)
WF = Weight fraction of chemical in product (unitless)
EDac = Exposure duration (1 day for acute exposure scenarios)
CF1 = Conversion factor (1,000 mg/g)
CF2 = Conversion factor (60 min/hr)
ATac = Averaging time (1 day for acute exposure scenarios)
The chronic form of the dermal permeability model is given below:
C/l
Kv x Dcr x p x -nTjT x FQcr x Dil x WF x EDcr x CF1
LADD =
A I'cr X C. /* 2 X CF%
Where:
LADD = Lifetime average daily dose (mg/kg-day)
DCT = Duration of use (min/event)
FQcr = Frequency of use (events or days/year)
EDCT = Exposure duration (57 years)
CF3 = Conversion factor (365 days/yr)
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ATCr = Averaging time (78 years)
A.3 Measured Emission Data
Systematic review identified several studies reporting emission rates or chamber emission
concentrations of 1,4-dioxane from spray foam and paint samples. These emission data are summarized
below. These data are not directly comparable to the predicted 8-hr TWAs presented for consumer
exposure scenarios, as the 8-hr TWAs are zone-integrated to account for the activity patterns of the user
or bystander (i.e., the presented TWAs account for a user or bystander's movement throughout the house
- Zones 1 and 2 - for the 8-hr period).
As described above, Karlovich et al. ( ) identified 1,4-dioxane in emissions from a two-component
open-cell SPF hours and days after application. Chamber concentrations and emission factors were
calculated from these sampling results. The emission factors were then used to predict indoor air
concentrations (1,479, 663, 201, and 40 |ig/m3 for samples measured at 4, 12, 24, and 48 hours,
respectively).
Naldzhiev et al. (2.019) analyzed volatile organic compound presence in and emissions from three spray
foam insulation products. Authors measured 1,4-dioxane in a two-component closed-cell SPF product,
both in the raw material (i.e., mixed spray foam, pre-application) and in the headspace from the cured
foam. Air concentrations were not reported, but findings confirm 1,4-dioxane's presence in closed-cell
SPF products. 1,4-Dioxane was not detected in the other two products tested including a commercially
available, two-component closed-cell spray foam and a commercially available, one-component spray
foam.
Poppendieck et al. ( ) reported concentrations of 1,4-dioxane in micro-chamber air sampling of a
high-pressure closed-cell spray foam. Initial concentrations (i.e., at sampling time 0) were just above
100 |ig/m3 and fell below 50 |ig/m3 after roughly 48 hours of sampling. In the authors' related final
report (Poppendieck. 2017). additional 1,4-dioxane chamber concentrations were reported for a "non-
ideal" closed-cell spray foam. The non-ideal foam samples were submitted by the Consumer Product
Safety Commission (CPSC) to reflect non-ideal preparation or application conditions such as off-ratio
mixing of two-component foams, low substrate temperature, and incorrect nozzle pressure or
temperature. Chamber concentrations measured from the non-ideal closed-cell foam were higher, falling
between 500 and 1,000 |ig/m3 at sampling time 0, -500 |ig/m3 at 48 hours, and falling below 250 |ig/m3
around 175 hours.
Won et al. (2014) tested 30 building materials for 121 VOCs and reported measured chamber
concentrations and emission factors for 1,4-dioxane in two of the product types covered in this consumer
evaluation: foam insulation and paint. Chamber concentrations of 1,4-dioxane from various insulation
products ranged from 0.25 to 44.68 |ig/m3 at six hours, with the highest level measured from a two-
component, closed-cell foam. Chamber concentrations of 1,4-dioxane from various paint products
ranged from 0.80 to 1.74 |ig/m3 at six hours, with the highest level measured from an interior latex paint.
Study authors cite mean emission rates of 15.72 |ig/m2/hr and 1.97 |ig/m2/hr for insulation and paint,
respectively.
The Danish EPA's 2018 Survey and Risk Assessment of Chemical Substances in Chemical Products
Used for "Do-It-Yourself' Projects in the Home (EPA. 2.018a) measured respiratory zone concentrations
during a realistic use of specific products in a test room and then measured subsequent emissions in a
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climate chamber after five hours, three days, and 28 days. During application of water-based, two-
component epoxy floor paint, respiratory zone levels of 1,4-dioxane were 220 |ig/m3. At five hours,
levels decreased to 21 |ig/m3. In a 2020 follow-up survey, the Danish EPA (2019a) tested additional
products and reported chamber concentrations of 1,4-dioxane from two-component paint and lacquer
ranging from 7 to 460 |ig/m3 at five hours. Following application of floor polish, levels of 1,4-dioxane
were measured at 68-70 |ig/m3 at five hours.
Although measured chamber or test room concentrations are not directly comparable to the 8-hr TWAs
estimated for the various consumer exposure scenarios, on the whole, these emission studies bolster
confidence in the predicted air concentrations for the SPF and paint and floor lacquer conditions of use.
The predicted 8-hr TWAs for SPF range from 160 to 890 |ig/m3 for users. These predicted estimates fall
within the range predicted in Karlovich et al., (2011) for samples measured at four and 12 hours.
Peppendieck et al. (2017) also reported measured air concentrations that encompass the modeled
consumer exposure estimates, with concentrations from non-ideal closed-cell spray foam ranging from
500 to 1,000 |ig/m3 over the first 48 hours. Won et al. (2014) reported levels of 1,4-dioxane well below
the CEM 2.1 predictions, from 0.25 to 44.68 |ig/m3 at six hours for various insulation products including
foam board and two-component open- and closed-cell spray foams.
The predicted 8-hr TWA for paint and floor lacquer is 20 |ig/m3 for users, which is roughly one order of
magnitude greater than concentrations measured in Won et al. (2014) (0.8 - 1.74 |ig/m3 at six hours), but
aligns with the Danish EPA's measured air concentration five hours after application of the two-
component epoxy floor paint (21 |ig/m3) (EPA. 2018a). The predicted TWA also falls within the range
of air concentrations taken five hours after application in the Danish EPA's 2020 Follow-Up study,
which reported levels from 7 to 460 |ig/m3 at five hours.
A.4 CEM Model Sensitivity Analysis Summary
The CEM 2.1 developers conducted a detailed sensitivity analysis for CEM, as described in Appendix C
of the CEM User Guide ( b). The CEM developers included results of model
corroboration analysis in Appendix D of the CEM User Guide (U.S. EPA. 2019b).
In brief, the analysis was conducted on continuous variables and categorical variables that were used in
CEM emission or dermal models. A base run of different CEM models using various product or article
categories, along with CEM defaults, was used. Individual variables were modified, one at a time, and
the resulting Acute Dose Rate (ADR) and Chronic Average Daily Dose (CADD) were compared to the
corresponding results for the base run. Benzyl alcohol, a VOC, was used as an example for product
models such as those applied in this evaluation of 1,4-dioxane.
The tested model parameters were increased by 10%. The measure of sensitivity for continuous
variables such as mass of product used, weight fraction, and air exchange rate was "elasticity," defined
as the ratio of percent change in each result to the corresponding percent change in model input. A
positive elasticity indicates that an increase in the model parameter resulted in an increase in the model
output, whereas a parameter with negative elasticity is associated with a decrease in the model output.
For categorical variables such as receptor activity pattern {i.e., work schedule) and room of use, the
percent difference in model outputs for different category pairs was used as the measure of sensitivity.
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The results are summarized below for the inhalation and dermal models used to evaluate consumer
exposures to 1,4-dioxane (i.e., emission models El and E3 and the dermal permeability model
P_DER2b. For full results and additional background, refer to Appendix C of the CEM User Guide
(U.S. EPA. 2017b).
A.4.1 Continuous Variables
For acute exposures generated from emission model El, WF (weight fraction) and M acute (mass of
product used) have the greatest positive elasticities of the tested parameters. The next most sensitive
parameters demonstrate negative elasticity and include: VolBuilding (building volume); AER_Zone2
(air exchange rate in Zone 2); AERZonel (air exchange rate in Zone 1); VolZonel (room of use, or
Zone 1 volume). Inhalation exposures from liquid products applied to surface such as surface cleaner
were modeled using El.
El Elasticity for ADR and CADD
WF
VP*
VP
Vol_Zonel
VolBuilding
Q_zl2
MW*
MW
M_Chronic
M_Acute
AER_Zone2
AER Zonel
-0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Elasticity (% change in dose/% change in variable)
¦ ADR Negative ¦ ADR Positive II CADD Negative ~ CADD Positive
FigureApx A-l. Elasticities (> 0.05) for Parameters Applied in El
For acute exposures generated from emission model E4, WF (weight fraction), M acute (mass of
product used), VP (vapor pressure), and MW (molecular weight) have the greatest positive elasticities of
the tested parameters. The next most sensitive parameters demonstrate negative elasticity and include:
Vol Zonel (room of use volume); Qzl2 (interzonal ventilation rate); Vol Building (building volume);
AER_Zone2 (air exchange rate in Zone 2); AER Zonel (air exchange rate in Zone 1). Inhalation
exposures from products added to water such as laundry detergent and dish soap were modeled using
E4.
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E4 Elasticity for ADR and CADD
=¦ WF
VP*
J VP
i VolZonel
VolBuilding
. Q_zl2
MW*
MW
^^MChronic
, MAcute
DurationChronic
i DurationAcute
AER_Zone2
AERZonel
-0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2
Elasticity (% change in dose/% change in variable)
¦ ADR Negative ¦ ADR Positive ~ CADD Negative ~ CADD Positive
FigureApx A-2. Elasticities (> 0.05) for Parameters Applied in E4
For acute exposures generated from the dermal permeability model, the chemical properties that inform
absorption rate, or absorption rate estimates, have the greatest elasticities. For 1,4-dioxane, dermal
exposures from consumer product formulations were modeled using a measured Kp (permeability
coefficient). Therefore, LogKow (octanol/water partition coefficient) and MW (molecular weight) were
not used to estimate skin penetration.
LogKow*
Kp_g
-2.0 -1.0 0.0 1.0 2.0 3.0
Elasticity (% change in dose/% change in variable)
¦ ADR Megative ¦ ADR Positive ~ CADD Negative ~ CADD Positive
Figure Apx A-3. Elasticities (> 0.05) for Parameters Applied in P_DER2b
A.4.2 Categorical Variables
For categorical variables there were multiple parameters that affected other model inputs. For example,
varying the room type changed the ventilation rates, volume size and the amount of time per day that a
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person spent in the room. Thus, each modeling result was calculated as the percent difference from the
base run. Among the categorical variables, the most sensitive parameters included receptor type (adult
vs. child), room of use (Zone 1) selection, and application of the near-field bubble within Zone 1.
However, these types of variables were held constant within a given product modeling scenario and
were applied using consistent assumptions across all modeling scenarios.
Supplemental Analysis and Systematic Review Files:
Consumer Exposure:
Supplemental Systematic Review to the Draft Risk Evaluation for 1,4-Dioxane: Data Quality Evaluation
for Data Sources on Consumer Exposure
Supplemental Analysis to the Draft Risk Evaluation for 1,4-Dioxane: Exposure Modeling Results
and Risk Estimates for Consumer Exposures
Supplemental Information File: Consumer Exposure Assessment Modeling Input Parameters
General Population/Ambient Water Exposure:
Supplemental Analysis to the Draft Risk Evaluation for 1,4-Dioxane: Ambient Water Exposure
Modeling Outputs from E-FAST
Supplemental Analysis to the Draft Risk Evaluation for 1,4-Dioxane: Modeling Inputs, Results, and Risk
Estimates for Incidental Ambient Water Exposures
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