TSCA Work Plan Chemical

Problem Formulation and Initial Assessment

1,4-Dioxane

CASRN: 123-91-1

April 2015

United States

Environmental Protection Agency

EPA Document# 740-R1-5003

April 2015

Office of Chemical Safety and 

Pollution Prevention
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TABLE OF CONTENTS

TABLE OF CONTENTS.........................................................................................................................2

AUTHORS / CONTRIBUTORS / ACKNOWLEDGEMENTS .......................................................................4

ABBREVIATIONS................................................................................................................................5

EXECUTIVE SUMMARY ......................................................................................................................7

1 INTRODUCTION........................................................................................................................10

1.1 SCOPE OF THE ASSESSMENT ............................................................................................................................11

1.2 REGULATORY AND ASSESSMENT HISTORY..........................................................................................................12

2 PROBLEM FORMULATION ........................................................................................................14

2.1 PHYSICAL AND CHEMICAL PROPERTIES ..............................................................................................................14

2.2 PRODUCTION AND USES .................................................................................................................................15

2.3 FATE AND TRANSPORT ...................................................................................................................................19

2.4 EXPOSURES ..................................................................................................................................................21

2.4.1 Releases to the Environment................................................................................................................ 21

2.4.2 Presence in the Environment................................................................................................................ 21

2.4.3 Occupational Exposure......................................................................................................................... 23

2.4.4 General Population Exposure............................................................................................................... 25

2.4.5 Consumer Exposure.............................................................................................................................. 27

2.5 HAZARD ENDPOINTS......................................................................................................................................28

2.5.1 Environmental Hazard.......................................................................................................................... 28

2.5.2 Human Health Hazard.......................................................................................................................... 28

2.6 RESULTS OF PROBLEM FORMULATION ..............................................................................................................30

2.6.1 Conceptual Model ................................................................................................................................ 30

2.6.2 Analysis Plan ........................................................................................................................................ 33

2.6.3 Uncertainties and Data Gaps............................................................................................................... 34

REFERENCES....................................................................................................................................35

APPENDICES 40

Appendix A Regulatory and Assessment History............................................................................40

Appendix B Summary of Uses and End Products............................................................................43

Appendix C Occupational Exposure Data.......................................................................................44

Appendix D Ecological Hazard Studies ...........................................................................................46

D-1 ACUTE TOXICITY TO AQUATIC ORGANISMS ..................................................................................................... 46

D-2 CHRONIC TOXICITY TO AQUATIC ORGANISMS .................................................................................................. 48

D-3 TERRESTRIAL PLANTS TOXICITY...................................................................................................................... 49

D-4 SOIL INVERTEBRATE AND AVIAN TOXICITY ....................................................................................................... 49

Appendix E Human Health Hazard Studies ....................................................................................50

E-1 ACUTE TOXICITY STUDIES ............................................................................................................................. 50
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E-2 REPEATED-DOSE TOXICITY STUDIES ............................................................................................................... 50

E-3 REPRODUCTIVE AND DEVELOPMENTAL TOXICITY STUDIES.................................................................................. 51

E-4 SKIN IRRITATION AND SENSITIZATION STUDIES................................................................................................. 51

E-5 GENOTOXICITY AND CANCER STUDIES ............................................................................................................ 51

LIST OF TABLES

Table 2-1: Physical and Chemical Properties of 1,4-Dioxane. .................................................................. 15

Table 2-2: 1986-2012 National Production Volume Data for 1,4-Dioxane (Millions of Pounds). ............ 15

Table 2-3: CDR Industrial and Consumer Use Data. ................................................................................. 18

Table 2-4: Environmental Fate Endpoints for 1,4-Dioxane. ..................................................................... 20

Table 2-5: Exposure Concentrations for Occupational Scenarios in European Industrial and Laboratory 

Facilities. ................................................................................................................................................... 24

Table 2-6: Preliminary Data from the EPA UCMR 3 (January 2015)......................................................... 26

Table A 1: History of Regulatory and Assessment Actions in the U.S. and Internationally ......................39

Table B-1: Summary of All Uses of 1,4-Dioxane and End Products.......................................................... 43

Table C-1: Summary of 1,4 Dioxane Occupational Monitoring Data for Process Operators in the 

Synthesis Area from an ACC Member Company where 1,4-Dioxane is Produced as a Byproduct in its 

Manufacturing Process.........................................................................................................................................43

Table C-2: 1,4-Dioxane - OSHA Chemical Exposure Health Data, 1997 - 2011.............................................45

Table D-1: Aquatic Toxicity Data for 1,4-Dioxane - Acute Toxicity.................................................................47

Table D-2: Aquatic Toxicity Data for 1,4-Dioxane - Chronic Toxicity.............................................................48

Table E-1: Human Health Endpoints for 1,4-Dioxane......................................................................................53

LIST OF FIGURES

Figure 2-1: Chemical structure of 1,4-dioxane. ........................................................................................ 14

Figure 2-2: Conceptual Model of Potential Exposure Pathways for 1,4-Dioxane. ................................... 31
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AUTHORS / CONTRIBUTORS / ACKNOWLEDGEMENTS

This report was developed by the United States Environmental Protection Agency (US EPA),

Office of Chemical Safety and Pollution Prevention (OCSPP), Office of Pollution Prevention and

Toxics (OPPT). The Work Plan Chemical Problem Formulation for 1,4-dioxane was prepared based on 

currently available data. Mention of trade names does not constitute endorsement by EPA.

EPA Assessment Team

Leads:

Katherine Anitole, OPPT/Risk Assessment Division (RAD)

Susan A. Laessig, OPPT/RAD

Team Members:

Nishkam Agarwal, OPPT/ Chemistry, Economics and Sustainable Strategies Division (CESSD)

Christina Cinalli (retired), OPPT/RAD

Ana Corado, OPPT/Environmental Assistance Division (EAD)

Joe Ford, OPPT/RAD

Amuel Kennedy, OPPT/RAD

Scott Prothero, OPPT/RAD

Teresa Washington, OPPT/RAD

Management Leads:

Yvette Selby-Mohamadu, OPPT/RAD

Todd Stedeford, OPPT/RAD

Contract Support

Technical support for portions of this document was provided by Abt Associates, Inc. under EPA 

Contract No. EP-W-08-010.

Docket

Please visit the public docket (www.regulations.gov; Docket: EPA-HQ-OPPT-2015-0078) to view 

supporting information.
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ABBREVIATIONS

ACC American Chemistry Council

ACGIH American Conference of Government Industrial Hygienists

AEGL Acute Exposure Guideline Level

AES Alkyl ethoxy sulphates

ATSDR Agency for Toxic Substances and Disease Registries

BCF Bioconcentration factor

CAA Clean Air Act

CASRN Chemical Abstract Service Registry Number

CBI Confidential Business Information

CCL Candidate Contaminant List

CDR Chemical Data Reporting

CPSC Consumer Product Safety Commission

CSF Cancer Slope Factor

EC European Commission

ECHA European Chemicals Agency

EPA Environmental Protection Agency

EU European Union

EUSES European System for the Evaluation of Substances

FDA Food and Drug Administration

HEAA -hydroxyethoxy acetic acid

Hg Mercury

HHS Department of Health and Human Services

HPV High Production Volume

IARC International Agency for Research on Cancer

IRIS Integrated Risk Information System

IUR Inventory Update Reporting Rule; Inhalation Unit Risk

kg Kilogram(s)

KOW Octanol:Water partition coefficient

lb Pound

LOEC Lowest Observed Effect Concentration

LOEL Lowest Observed Effect Level

Log KOW Logarithmic Octanol:Water partition coefficient

MATC Maximum Acceptable Toxicant Concentration

mg Milligram(s)

MOE Margin of Exposure

MRL Minimal Risk Level

NIOSH National Institute of Occupational Safety and Health

NOEC No Observed Effect Concentration

NOAEL No Observed Adverse Effect Level

NPL National Priorities List

NTP National Toxicology Program
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OAR Office of Air and Radiation

OCSPP Office of Chemical Safety and Pollution Prevention

OECD Organisation for Economic Co-operation and Development

OPPT Office of Pollution Prevention and Toxics

OSHA Occupational Safety and Health Administration

OSWER Office of Solid Waste and Emergency Response

OW Office of Water

PBPK Physiologically Based Pharmacokinetic

PBT Persistent, Bioaccumulative, Toxic

PDE Permitted Daily Exposure

PEC Predicted Environmental Concentration

PEL Permissible Exposure Level

ppb Parts per billion

ppm Parts per million

PV Production Volume

PWS Public Water System

RA Risk Assessment

RAR Risk Assessment Report

REACH Registration, Evaluation, Authorisation and Restriction of Chemicals

REL Recommended Exposure Level

RfC Reference Concentration

RfD Reference Dose

TCA 1,1,1-trichloroethane

TLV Threshold Limit Value

TRI Toxic Release Inventory

TSCA Toxic Substances Control Act

UCMR Unregulated Contaminant Monitoring Rule

US United States

WHO World Health Organisation

WWTP Wastewater Treatment Plant

Yr Year
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EXECUTIVE SUMMARY

As part of EPA’s comprehensive approach to enhance the Agency’s management of existing 

chemicals, in March 2012 EPA/OPPT identified a work plan of chemicals for further assessment 

under the Toxic Substances Control Act (TSCA)1. Chemical risk assessments will be conducted if, 

as a result of scoping and problem formulation, there are exposures of concern, identified 

hazards and sufficient data for quantitative analysis. If an assessment identifies unreasonable

risks to humans or the environment, EPA will pursue risk management. This document presents 

the problem formulation and initial assessment for 1,4-dioxane as part of the TSCA Work Plan

program.

The conclusions from this problem formulation and initial assessment are that:

 EPA/OPPT will further assess potential risks to workers exposed during product 

formulation and use as a cleaning agent.

 EPA/OPPT will further assess potential risks to workers and consumers exposed during 

the use of TSCA-use products that contain 1,4-dioxane as a contaminant, such as paints, 

varnishes, adhesives, cleaners and detergents.

 Risk to the general population through inhalation exposure to ambient air emissions is 

estimated to be low. 

 An assessment of risk from exposure through drinking water is not needed at this time 

because 1,4-dioxane is currently being monitored and EPA will determine whether or 

not regulatory action is needed as part of EPA’s Regulatory Determination process.

 Based on the low hazard profile for 1,4-dioxane to aquatic organisms, risks to these 

organisms are expected to be low. Lack of hazard data for sediment and soil organisms 

precludes determination of risk to these environmental compartments. Therefore, 

further analysis of environmental risk is not planned.

1,4-Dioxane is an industrial solvent used in the production of a wide variety of products, as a 

laboratory reagent, a chemical intermediate, an extraction medium for fats and oils, and as part 

of a polymerization catalyst. Other uses of 1,4-dioxane are in commercial and consumer 

products such as lacquers, varnishes, paint strippers, dyes, greases, cleaners and detergents, 

adhesives, cosmetics and deodorants. 1,4-Dioxane is also present as an unintended byproduct 

in cosmetics, detergents, and shampoos. Historically, 90% of all 1,4-dioxane was used as a 

stabilizer in chlorinated solvents such as 1,1,1-trichloroethane (TCA). Use of 1,4-dioxane has 

decreased since 1,1,1-trichloroethane was phased out by the Montreal Protocol in 1996 for all 

uses except a few select applications. In the 1980’s and early 1990’s, 10 to 50 million pounds 

were manufactured yearly and from 1994 to 2006, the yearly U.S. production volume of 1,4-

 

1

http://www.epa.gov/oppt/existingchemicals/ 
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dioxane has been 1 to 10 million pounds. Recent data show that 1.1 million pounds is released 

to the environment. 

During scoping and problem formulation, EPA/OPPT reviewed previous risk assessments and 

additional published studies on the fate, exposure and hazard of 1,4-dioxane. EPA/OPPT

examined likely exposure and hazard scenarios based on current production, use, and fate 

information to identify scenarios amenable to risk analysis. The scenarios considered were:

 Workers potentially exposed during manufacturing and formulation of 1,4-dioxane or in 

industrial or laboratory facilities where 1,4-dioxane is used.

 Workers and consumers potentially exposed during the use of products that contain 

1,4-dioxane as a contaminant. 

 The general population potentially exposed via inhalation of ambient air receiving

emissions from manufacturing/formulating facilities, as well as incineration of waste 

streams/products. 

 The general population potentially exposed to 1,4-dioxane through contaminated 

drinking water.

The routes of potential human exposure to 1,4-dioxane are inhalation, ingestion and dermal 

contact. Dermal exposures are not addressed due to high volatilization, low absorption and lack 

of dermal toxicity studies. Potential human health effects from inhalation and ingestion include 

cancer and noncancer outcomes (liver, kidney and nasal effects) in workers, consumers and the 

general population. 

EPA/OPPT reviewed the ecological hazards of 1,4-dioxane and determined that acute and 

chronic hazard is low for aquatic species. There are no sediment or soil toxicity data to assess 

the hazard to organisms in these environmental compartments. A conceptual model was not 

developed for environmental health and further analysis of environmental risk is not planned.

The results of problem formulation as illustrated in the conceptual model for human health and 

described under the assessment questions indicate that:

 A 2002 European assessment found potential risk to workers for occupational exposures via 

the dermal and inhalation routes during product formulation and the use of 1,4-dioxane as 

a cleaning agent. Availability of EPA’s recently updated benchmarks for human health 

suggest that human health risks should be reassessed. While US data on occupational 

exposures are limited, EPA/OPPT will further assess the risk to workers from inhalation of 

1,4-dioxane during manufacture, formulation and use of products using available data or 

modeled exposures in the absence of data.

 Workers and consumers may be exposed to 1,4-dioxane present as a contaminant in 

products such as personal care products, paints, adhesives, varnishes, cleaners and 

detergents. Risk assessments in Canada and Europe concluded that levels of contamination 

do not pose concerns for human health. While personal care products are regulated by the 
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FDA, uses in paints, adhesives, varnishes, cleaners and detergents fall under TSCA authority. 

Availability of EPA’s recently updated benchmarks for human health suggest that human 

health risks should be reassessed. Therefore, EPA/OPPT plans to further assess potential 

risks posed to consumers by 1,4-dioxane in products covered under TSCA.

 The general population may be exposed from inhalation to ambient levels of 1,4-dioxane in 

air. Regulations for air pollution are in place through the Clean Air Act (CAA). 1,4-Dioxane is

short lived in the environment and historical ambient air levels of 1,4-dioxane are

considered low. Risk assessments in Canada and Europe concluded that there are no risks of 

concern from exposure to 1,4-dioxane in ambient air. Given that 1,4-dioxane is regulated 

under the CAA as a hazardous air pollutant (US EPA, 2000) and EPA/OPPT’s comparison of 

historical air concentrations of 1,4-dioxine against the recent EPA IRIS benchmarks (RfC and 

IUR) indicate these concentrations are below levels of concern, assessment of general 

population exposure to 1,4-dioxane in ambient air will not be further analyzed by EPA/OPPT 

under TSCA.

 The general population may be exposed to 1,4-dioxane in contaminated drinking water. 

EPA’s Office of Water is currently monitoring public drinking water systems in order to 

evaluate the risk to defined populations. Potential source contributions to drinking water 

are uncertain. Since 1,4-dioxane is being monitored through December 2015, decisions as to 

whether or not to regulate the contaminant in drinking water will be considered as part of

the EPA’s Regulatory Determination process.

In summary, as a result of problem formulation, EPA/OPPT plans to conduct additional risk

analysis on potential worker and consumer exposures under the TSCA Existing Chemicals 

Program using existing data and methods. EPA/OPPT plans to carefully review and evaluate the 

results of previous exposure assessments and health benchmarks. EPA will develop margins of 

exposure and cancer risk estimates to evaluate the potential risks from worker and consumer 

exposure to 1,4-dioxane. EPA does not have risk concerns for the general population through 

inhalation exposure to ambient air emissions.
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1 INTRODUCTION

As a part of EPA’s comprehensive approach to enhance the Agency’s management of existing 

chemicals, in March 2012 EPA/OPPT identified a work plan of chemicals for further assessment 

under the Toxic Substances Control Act (TSCA)2. After gathering input from stakeholders, 

EPA/OPPT developed criteria used for identifying chemicals for further assessment3. The 

criteria focused on chemicals that meet one or more of the following factors: (1) potentially of 

concern to children’s health (for example, because of reproductive or developmental effects); 

(2) neurotoxic effects; (3) persistent, bioaccumulative and toxic (PBT); (3) probable or known 

carcinogens; (4) used in children’s products; or (5) detected in biomonitoring programs. Using 

this methodology, EPA/OPPT identified a TSCA Work Plan of chemicals as candidates for risk 

assessment in the next several years. In the prioritization process, 1,4-dioxane was identified 

for assessment based on classification as a probable human carcinogen, wide use in consumer 

products, high reported releases to the environment, and presence in groundwater, ambient air 

and indoor environments.

EPA/OPPT is performing risk assessments on chemicals in the work plan. If an assessment 

identifies unacceptable risks to humans or the environment, EPA will pursue risk management. 

The target audience for the final risk assessment is primarily EPA risk managers; however, it 

may also be of interest to the broader risk assessment community as well as US stakeholders 

interested in 1,4-dioxane. The information presented in the risk assessment may be of 

assistance to other federal, state and local agencies as well as to members of the general public 

who are interested in understanding whether there are risks from exposure to 1,4-dioxane. 

The initial step in the EPA/OPPT risk assessment development process, which is distinct from 

the initial prioritization exercise, includes planning, scoping and problem formulation. During 

these steps EPA/OPPT may review currently available data and information, including but not 

limited to, assessments conducted by others (e.g., authorities in other countries), published or 

readily available reports and published scientific literature. The problem formulation data 

review could result in refinement of pathways of interest previously identified in the initial 

prioritization.

This document includes the results of scoping, problem formulation, and initial assessment for 

1,4-dioxane. In the scoping stage, EPA/OPPT determined which chemical(s) to include and what 

uses to consider in the assessment. During problem formulation, EPA/OPPT identified available

fate, exposure and hazard data, and characterized potential exposures, receptors and effects. 

EPA/OPPT developed a conceptual model and an analysis plan as a result of problem 

formulation.

 

2

http://www.epa.gov/oppt/existingchemicals/pubs/workplans.html

3

http://www.epa.gov/oppt/existingchemicals/pubs/wpmethods.pdf
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1.1 Scope of the Assessment

The TCSA Work Plan chemical 1,4-dioxane is a high production volume chemical (up to 10 

million lbs/yr, based on publicly available information), has a variety of industrial uses and may 

be present in both consumer and commercial products. 1,4-Dioxane is used as an industrial 

solvent in the production of a wide variety of products, as a laboratory reagent, a chemical 

intermediate, an extraction medium for fats and oils and as part of a polymerization catalyst 

(ATSDR, 2012). 1,4-dioxane is also used in commercial and consumer products such as lacquers, 

varnishes, paint strippers, dyes, greases, cleaners and detergents, adhesives, cosmetics and 

deodorants (European Chemicals Bureau, 2002; US EPA, 2014d). In addition, 1,4-dioxane is 

present as a contaminant in consumer cosmetics/toiletries, household detergents,

pharmaceuticals, foods, agricultural and veterinary products and ethylene glycol-based 

antifreeze coolants, because it is a byproduct of certain ethoxylated substances (ATSDR, 2012).

Workers, consumers and the general population may be exposed to 1,4-dioxane by inhalation, 

ingestion and dermal routes. Because 1,4-dioxane is not intentionally added to consumer 

products, only workers are exposed to products which intentionally contain 1,4-dioxane. 

Inhalation is expected to be the predominant route of exposure due to the high vapor pressure 

and volatility of 1,4-dioxane. Workers and consumers may be exposed to products that contain 

1,4-dioxane as an unwanted byproduct or an intermediate that is not fully reacted and the 

concentrations of 1,4-dioxane in these cases are lower, usually measured in parts per million or 

less. The general population may be exposed environmentally from air or water containing 1,4-

dioxane.

Absorption of 1,4-dioxane occurs readily through the lungs and gastrointestinal system and 

poorly through the skin. After absorption, 1,4-dioxane is rapidly eliminated from the body and 

does not accumulate. EPA classifies 1,4-dioxane as “likely to be carcinogenic to humans” by all 

routes of exposure based on liver tumors in rats and mice following chronic drinking water 

exposure (US EPA, 2013b). Nasal tumors were observed in rats following chronic inhalation or 

drinking water exposure. Short-term exposure may result in irritation of the eyes and throat 

(ATSDR, 2012) and chronic exposure may result in dermatitis, eczema, drying and cracking of 

skin, and liver and kidney damage (ATSDR, 2012). 

In the environment, 1,4-dioxane partitions to water and is highly mobile in soil. 1,4-Dioxane is 

highly volatile, has a short residence time in air and does not readily biodegrade in water. 

Toxicity to aquatic organisms is not expected based on low hazard values.

Given the common use, widespread exposure and potential human health hazards of 1,4-

dioxane, EPA/OPPT conducted a problem formulation and evaluation of readily available data 

and information to determine the exposures and hazards of interest for risk assessment. 

Available data were used including chemical structure, physical chemistry, production volume, 
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reported uses and toxicological information from existing assessments to develop a conceptual 

model and an analysis plan.

1.2 Regulatory and Assessment History

EPA/OPPT reviewed and considered the regulatory and assessment history of 1,4-dioxane 

(Appendix A: Regulatory and Assessment History).

National (U.S.)

1,4-Dioxane is a known animal carcinogen according to the National Toxicology Program (NTP)

(NTP, 2014). The US Department of Health and Human Services (DHHS) considers 1,4-dioxane 

as reasonably anticipated to be a human carcinogen (US DHHS, 1993). EPA has determined that 

1,4-dioxane is likely to be carcinogenic to humans (US EPA, 1999).

Occupational exposure limits have been set by federal agencies and organizations in the US

(OSHA, NIOSH, ACGIH) and are summarized in Appendix A. A recent Toxicological Profile for 1,4-

dioxane (ATSDR, 2012) provided a detailed analyses of available hazard data. The data were 

used to derive minimal risk levels (MRLs), exposure levels posing minimal risk to humans, for 

inhalation and oral exposures. The EPA Integrated Risk Information System (IRIS) Program 

recently updated the assessment of 1,4-dioxane, including the results of a two-year inhalation 

bioassay (US EPA, 2013b). IRIS developed cancer and non-cancer reference values for inhalation 

and drinking water exposure. Acute Exposure Guideline Levels (AEGLs) for 1,4-dioxane have 

been established (NAS/COT Subcommittee for AEGLs, 2005). The MRLs, IRIS benchmarks and 

AEGLs are provided in Appendix A.

The Food and Drug Administration (FDA) does not require 1,4-dioxane to be listed on labels of 

personal care products and considers it a contaminant. FDA has indicated that the levels of 1,4-

dioxane found in their monitoring of cosmetics do not present a hazard to consumers and

recommended a level of 3.8 mg/day (380 ppm) as the “permitted daily exposure (PDE)” for 1,4-

dioxane that is an acceptable intake of residual solvents in drugs and dietary supplements (US 

FDA, 2011). FDA limits 1,4-dioxane levels in glycerides and polyglycerides of hydrogenated 

vegetable oils used as a food additive to 10 mg/kg.

Industries manufacturing, processing or using 1,4-dioxane are legally required to report 

releases to EPA’s Toxic Release Inventory (TRI) if they manufacture or process more than 

25,000 pounds of a TRI-listed chemical or otherwise use more than 10,000 pounds of a listed 

chemical in a given year. 

The EPA Office of Water (OW) has included 1,4-dioxane on the third Candidate Contaminant 

List (CCL3). No federal drinking water standards have been established for 1,4-dioxane and it is 

being monitored in public water systems as part of the Unregulated Contaminant Monitoring 

Rule 3 (UCMR3) list. OW is conducting a three-year (2013-2015) monitoring program of public 

water systems to collect data for contaminants suspected to be present in finished drinking 
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water including 1,4-dioxane (USEPA, 2013). Information about UCMR3 and 1,4-dioxane 

monitoring in Public Water Systems (PWS) can be found at: 

http://water.epa.gov/lawsregs/rulesregs/sdwa/ucmr/data.cfm.

EPA’s Office of Air and Radiation (OAR) regulates 1,4-dioxane as a Hazardous Air Pollutant 

(http://www.epa.gov/ttn/uatw/hlthef/dioxane.html). EPA’s Office of Solid Waste and 

Emergency Response (OSWER) regulates the Superfund sites that are historically a source of 

1,4-dioxane in ground water around those sites. 1,4-Dioxane has been reported at 32 National 

Priorities List (NPL) sites (http://www.atsdr.cdc.gov/SPL/index.html). Examples include sites in 

New Hampshire (http://www.epa.gov/region1/removal-sites/NH14DioxaneSite.html) and 

Massachusetts (http://www.epa.gov/region1/superfund/sites/graceacton/507061.pdf). 

States

1,4-Dioxane is listed on California’s Proposition 65 list because it is known to cause cancer (CA 

EPA OEHHA, 2007, 2014). The action level under California Proposition 65 for 1,4-dioxane in 

personal care products is above 10 ppm. California also lists 1,4-dioxane on the Informational 

“Initial” Candidate Chemicals List and the Informational Candidate Chemicals List under 

California’s Safer Consumer Products regulations (State of California, 2010). Further, Minnesota 

and Washington classify 1,4 dioxane as a chemical of high concern (Minnesota Department of 

Health (MDH), 2013; Washington State, 2013). 

International

The International Agency for Research on Cancer (IARC) has determined that 1,4-dioxane is 

possibly carcinogenic to humans (IARC, 1976) based on inadequate evidence in humans and 

sufficient evidence in experimental animals.

A Canadian screening assessment (Environment Canada and Health Canada, 2010) evaluated 

the risk of 1,4-dioxane to human health. Ecological risks were not assessed since 1,4-dioxane 

did not meet the criteria for bioaccumulation and inherent toxicity to aquatic organisms. 

Exposures to the general population from intake from air, water, soil, diet, use of personal care 

products and household products were estimated. The report concluded that 1,4-dioxane is not 

entering the environment in a quantity or concentration or under conditions that constitute or 

may constitute a danger in Canada to human life or health. 

The European Union Risk Assessment Report (EU RAR, 2002) concluded that there is no concern 

for human safety with regard to repeated-dose toxicity, carcinogenicity and reproductive 

toxicity. The assessed risk concern was low for the general population (inhalation and drinking 

water), direct and indirect consumer exposures in cosmetic/toiletries and household 

detergents, pharmaceuticals, foods, agricultural and veterinary products, and ethylene glycolbased antifreeze coolants and ecological exposures. A potential risk concern for workers was 

found for occupational exposures via the dermal and inhalation routes during product 

formulation and the use of cleaning agents containing 1,4-dioxane. 
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2 PROBLEM FORMULATION

Problem formulation aims to determine the major factors to be considered in an assessment, 

including exposure pathways, receptors and health endpoints (US EPA, 1998, 2014b). 

Accordingly, this problem formulation summarizes the exposure pathways, receptors and 

health endpoints that EPA/OPPT considered to determine whether to conduct further risk 

analysis and what exposure/hazard scenarios to include in a potential risk assessment. To make 

this determination, EPA/OPPT conducted a preliminary data review to identify available fate, 

exposure and hazard data and determine its likely suitability for quantitative analysis and to 

identify exposure pathways, receptors and health endpoints for quantitative analysis. 

The outcome of this evaluation is summarized in a conceptual model (Figure 2-2) that illustrates

the exposure pathways, receptors and effects that were considered for potential risk 

assessment. An analysis plan is developed if the results of problem formulation indicate the 

need for further analysis.

2.1 Physical and Chemical Properties

1,4-Dioxane is a clear liquid at room temperature. The cyclic structure (Figure 2-1) has oxygen 

molecules attached at the first and fourth bonds, each with free electrons (US EPA, 2006b). 1,4-

Dioxane is expected to volatilize from dry soil surfaces based on its high vapor pressure (40 mm 

Hg at 25 °C) (US EPA, 2009). 1,4-Dioxane has a Log Kow value of -0.27, which indicates that this 

chemical is hydrophilic, readily miscible in water (US EPA, 2009). A summary of the physical and 

chemical properties of 1,4-dioxane are listed in Figure 2-1.

Figure 2-1: Chemical structure of 1,4-dioxane.
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Table 2-1: Physical and Chemical Properties of 1,4-Dioxane.

Property Value References

Molecular Weight 88.1 g/mol (Howard, 1990)

Melting Point 11.85 °C (measured) (Lide, 2008-2009)

Boiling Point 101.1 °C (measured) (O'Neil et al., 2006)

Vapor Pressure 40 mm Hg at 25 °C (Lewis, 2000)

Water Solubility ˃ 8.00 × 102g/L (Yalkowsky and He, 2003)

Log KOW -0.27 (Hansch et al., 1995)

Henry’s Law Constant 4.8 × 10-6atm-m

3

/mol at 25 °C (Howard, 1990)

2.2 Production and Uses 

The EPA’s Inventory Update Reporting (IUR) and 2012 Chemical Data Reporting (CDR) databases

were searched to identify the uses and associated production volumes of 1,4-dioxane. Some 

information was claimed as Confidential Business Information (CBI) and is not included in this 

report. Additional information on uses and specific end products that may contain 1,4-dioxane 

can be found in Appendix B: Summary of Uses and End Products.

Production

In 2006, the U.S. production volume of 1,4-dioxane was between 1 million and 10 million 

pounds, including both imports and domestic manufacture (US EPA, 2010). Data from the 2012 

CDR for reporting years 2010 and 2011 were claimed as CBI and indicate only domestic 

manufacture of 1,4-dioxane (US EPA, 2014c). The non-confidential U.S. production volumes of 

1,4-dioxane, as submitted by companies under the IUR or CDR for 1986 to 2012, are given in 

Table 2-2.

Table 2-2: 1986-2012 National Production Volume Data for 1,4-Dioxane (Millions of Pounds).

Uses

1,4-Dioxane is currently used as both an industrial and a commercial solvent. As a result of 

chemical ethoxylation of surfactants, 1,4-dioxane can be formed as a byproduct and may be 

present as a contaminant in commercial and consumer products. Historically, the main use of 

1986 IUR 1990 IUR 1994 IUR 1998 IUR 2002 IUR 2006 IUR 2012 CDR

10-50 10-50 1-10 1-10 1-10 1-10 Withheld

Source: (US EPA, 2006a, 2010, 2012b)
Page 16 of 54

1,4-dioxane (90 percent) was as a stabilizer in chlorinated solvents such as 1,1,1-

trichloroethane (TCA). Use of TCA was phased out under the 1995 Montreal Protocol and the 

use of 1,4-dioxane as a stabilizer is no longer significant (European Chemicals Bureau, 2002; 

NTP, 2014). 

Industrial Uses. At present, 1,4-dioxane is used as an industrial solvent in the manufacture of 

chemicals because it is capable of solubilizing most organic and many inorganic compounds

(ATSDR, 2012; Ullman's, 2012). As an industrial solvent, 1,4-dioxane is used as:

 a processing solvent

 a reaction medium solvent

 an industrial solvent with an unspecified function in the production of various end 

products (ATSDR, 2012; US EPA, 2006a)

Other industrial uses include:

 as an extraction medium

 an inert (chemically inactive) ingredient in pesticides and fumigants

 a chemical intermediate

 a polymerization catalyst

 a dehydrating agent

 a wetting and dispersing agent

 a degreasing agent (ATSDR, 2012; US EPA, 2006a)

Appendix B lists examples of end products for each of these industrial uses. Table 2-3 provides 

the industrial use data as reported in the 2012 CDR database4. 

Commercial and Consumer Uses. As an industrial processing solvent or chemical intermediate, 

1,4-dioxane has previously been reported to be used in the production of products that may 

have commercial or consumer applications such as paints, adhesives, detergents, and pesticides 

(ATSDR, 2012; US EPA, 2006a, 2014c). In the most recent CDR database, no consumer uses were 

reported for 1,4-dioxane in the US (Table 2-3). Additional US sources do not differentiate 

between consumer and commercial products (ATSDR, 2012; US EPA, 2006a). EPA was unable to 

identify any US sources that definitively stated the chemical is used in the production of 

consumer products. A European risk assessment stated that the chemical is used as a solvent in 

the production of several products that may be used by consumers (European Chemicals 

Bureau, 2002). 

Contaminant in Consumer Products. 1,4-dioxane may be present as a contaminant in 

consumer cosmetics/toiletries, household detergents, pharmaceuticals, foods, agricultural and 

veterinary products and ethylene glycol-based antifreeze coolants. It is formed as a byproduct 

 

4

The manufacturer submitted a correction to EPA to revise the 2012 CDR to reflect that 1,4-dioxane is not used for 

the categories ‘Paints and Coatings’ and ‘Laundry and Dishwashing Products’. The correction was received and is 

not yet indicated in the CDR public database.
Page 17 of 54

during the manufacture of ethoxylated surfactants. Manufacturers can remove most of the 1,4-

dioxane in consumer products through a vacuum stripping process (ATSDR, 2012), although the 

extent that this occurs is unknown. 
Page 18 of 54

Table 2-3: CDR Industrial and Consumer Use Data.

Manufacturing 

Site

Parent 

Company 

Industrial Use Data Consumer and Commercial Use Data

Sector Function 

Category Industrial Use

Percent of 

Production 

Volume

Product 

Category*

Commercial or 

Consumer Use

Percent of 

Production 

Volume

Novolyte 

Performance 

Materials

111 West Irene 

Road

Zachary, LA 

70791

BASF

All Other Basic

Organic Chemical 

Manufacturing

Processing 

aids, not 

otherwise 

listed

Use-nonincorporative 

activities*

CBI

Paints and 

Coatings Commercial CBI

Laundry and 

Dishwashing 

Products

Commercial CBI

Note: Use in non-incorporative activities would include uses such as chemical processing aids or chemical manufacturing aids, where the chemical is not intended to remain in or 

become part of the final product, or ancillary activities where a chemical is used at a facility for purposes other than aiding chemical processing or manufacturing (e.g. 

degreasers or cleaners). 

Source: The public 2012 CDR Database; updated June 11, 2014 (US EPA, 2012b). 

*A correction was received that is not yet indicated in the CDR public database.
Page 19 of 54

2.3 Fate and Transport

Environmental fate properties are summarized in Table 2-4.

Based on available environmental fate data, 1,4-dioxane is expected to volatilize readily from 

dry surfaces, reside in water and soil compartments if released to the environment, and have 

high persistence and low bioaccumulation potential in the environment. 1,4-Dioxane is not 

readily biodegradable under normal environmental conditions.

1,4-Dioxane is expected to volatilize from dry surfaces and dry soil due to its high vapor 

pressure. It reacts with hydroxyl radicals (OH) in the atmosphere where the estimated 

atmospheric photooxidation half-life of 1,4-dioxane is 4.6 hours (US EPA, 2013a). 1,4-Dioxane is 

not expected to be susceptible to direct photolysis under environmental conditions since this 

compound lacks functional groups that absorb light at visible-UV light wavelengths (Lyman et 

al., 1982; NIH, 2006). 1,4-dioxane will not hydrolyze in water because it does not have 

functional hydrolyzable groups (ATSDR, 2012). 

Due to a high water solubility of > 8.00 × 102g/L (Yalkowsky and He, 2003) and a low Henry’s 

Law constant of 4.8 × 10-6atm-m

3

/mol at 25 °C (Howard, 1990; US EPA, 2009), 1,4-dioxane is 

expected to be only slightly volatile from water surfaces and moist soil. Once it enters the 

environment, 1,4-dioxane is expected to have high mobility in soil based on its negligible Koc 

value of 0.4 (US EPA, 2013a). 1,4-dioxane is not expected to significantly sorb to suspended 

solids and sediment and, therefore, may migrate rapidly to surface waters and groundwater. 

In a ready biodegradation test, following OECD Guideline 301 F (Manometric Respirometry 

Test), reported by the European Chemicals Agency (ECHA), 1,4-dioxane was degraded less than 

10 percent in 29 days (ECHA, 2014a). In another ready biodegradation test following OECD 

Guideline 310 (Headspace Test) 1,4-dioxane was degraded less than 5 percent in 60 days

(ECHA, 2014b). 1,4-dioxane is considered to be not readily biodegradable.

In a soil microcosm study which analyzed the potential for bacteria to degrade 1,4-dioxane, 

1,4-dioxane was not biodegraded during a 120 day period by indigenous bacteria. During the 

next 6 months, the bacteria removed about 60% of the added 1,4-dioxane. The reason for the 

delayed biodegradation was not clear (Kelley et al., 2001).

In a bioaccumulation test using the common carp (Cyprinus carpio) following OECD Test 

Guideline 305, measured bioconcentration factor (BCF) values of 0.3-0.7 at a concentration of 

10 mg/L, and 0.2-0.6 at a concentration of 1 mg/L were reported (ECHA, 2014c). These values 

indicate that bioaccumulation 1,4-dioxane is low. 

Using the environmental fate estimation model EPISuiteTM (Estimation Program Interface Suite 

for Microsoft Windows) v 4.11, a level III fugacity model with equal releases of 1,4-dioxane to 
Page 20 of 54

air, water, soil, and sediment, estimates that 1,4-dioxane will tend to partition mostly to soil 

(52.6%), and water (44.7%) (US EPA, 2013a) (Table 2-4).

Table 2-4: Environmental Fate Endpoints for 1,4-Dioxane.

Endpoint Environmental Fate Data References

Photodegradation 

Half-life

4.579 hours

(estimated rate constant of 2.8 × 10-11 cm3/molec-sec

1.5 × 106 hydroxyl radicals per cm3

12-hour day) 

(US EPA, 2013a)

Hydrolysis Half-life Does not undergo hydrolysis (ATSDR, 2012)

Biodegradation <10% in 29 days (OECD 301F)

<5% in 60 days (OECD 310)

0% after 120 days in soil microcosms; 60% after 300 days

(ECHA, 2014a)

(ECHA, 2014b)

(Kelley et al., 2001)

Bioconcentration BCF = 0.2 – 0.6 (measured in carp at 1 mg/L)

BCF = 0.3 – 0.7 (measured in carp at 10 mg/L)

(ECHA, 2014c)

Log Koc 0.4 (estimated) (US EPA, 2013a)

Fugacity

(Level III Model)

Air (%)

Water (%)

Soil (%)

Sediment (%)

2.65

44.7

52.6

0.0868

(The input values for this estimation are the melting 

point, boiling point, vapor pressure, water solubility, Log 

KOW and Henry’s Law constant values provided in Table 

2.1 above, and the following SMILES notation: 

O(CCOC1)C1)

(US EPA, 2013a)
Page 21 of 54

2.4 Exposures

The exposure data identified and considered during problem formulation and used to construct 

the conceptual model and pose assessment questions is summarized. Use and exposure 

scenarios were selected for inclusion in the conceptual model by the identification of high 

volume uses that are known or likely to be associated with significant exposures.

Releases to the environment were assessed to determine potential pathways of exposure for

both human and ecological receptors. Exposures to workers, consumers and the general 

population were evaluated to determine the potential exposure to 1,4-dioxane during

manufacturing, formulation and use of products. Environmental exposure of the general 

population to 1,4-dioxane in air or water was also considered. 

2.4.1 Releases to the Environment

Environmental releases of 1,4-dioxane to air and water may contribute to ecological and 

general population exposures. The potential for release of 1,4-dioxane to air is high due to the 

high vapor pressure of 1,4-dioxane and disposal through incineration. Industrial and 

commercial use of 1,4-dioxane and presence in consumer products suggest releases to water 

are possible. Readily available sources of information for environmental releases that may lead 

to exposures were reviewed including the EPA Toxic Release Inventory (TRI) database (US EPA, 

2012c).

An analysis of TRI data from 1988 to 2007 indicates that total on-site releases of 1,4-dioxane 

are generally decreasing. During this period, the high was 1,234,968 pounds in 1993 and the 

low was 182,338 pounds in 2007; 69% of the 2007 total releases from 45 facilities were to air

(ATSDR, 2012). Data from the most recent TRI indicate that 82% of the total on- and off-site 

releases of 106,300 pounds from 39 sites (including the manufacturing site) were to air (on-site 

fugitive and point sources) and 18% were to surface water. An additional 1,035,300 pounds 

were reported released from two additional sites that primarily inject 1,4-dioxane in 

underground wells (on-site and off-site) or send to waste brokers (US EPA, 2012c). Releases to 

these wells and to waste brokers are not usually a concern for human exposures. Facilities that 

release less than 25,000 pounds are not required to report data to the TRI.

The EPISuiteTM model (Table 2-4) indicates that following release, 1,4-dioxane will partition 

predominantly to water and moist soil. Likely exposure pathways are by atmospheric 

deposition and runoff into surface water and leaching into groundwater.

2.4.2 Presence in the Environment
Page 22 of 54

EPA/OPPT reviewed available information on the presence of 1,4-dioxane in the environment

from the 2002 EU Risk Assessment Report (RAR), a leachate study from two landfills, a 

groundwater plume study and two WWTP studies.

The EU RAR included predicted environmental concentrations (PECs) for wastewater effluent 

and surface water and a limited number of measured data of 1,4-dioxane in surface water, 

drinking water, wastewater effluent and leachate from the vicinity of landfills (European 

Chemicals Bureau, 2002). Site-specific and generic location emission data were used to

generate estimated regional release values to surface water and WWTPs and develop the PECs. 

The PECs in surface water were based on estimated regional releases to water of 434 kg/d and 

the estimated regional release via WWTP was 304 kg/d (European Chemicals Bureau, 2002). 

PECs of 1,4-dioxane in wastewater effluent ranged from 0.002 – 183 mg/L based on life cycle 

stages or scenarios. PECs in surface water during an emission episode ranged from 0.001 mg/L 

(contaminated alkyl ethoxy sulphates) to 18.3 mg/L (processing pharmaceuticals and pesticides)

(European Chemicals Bureau, 2002).

In the EU RAR, surface water data in a Dutch study were compared to the predicted regional 

environmental concentration of 1.3 g/L and was within the study values of 1-10 g/L. The 

measured data for the WWTP effluent from unintentional release from a PET plant was much 

higher (100 mg/L) than the PEC of 0.01 – 6.9 mg/L for site-specific emission data for various 

unintentional 1,4-dioxane releases. However, the EU RAR noted that the source of the 

measured 100 mg/L value used may be unreliable (European Chemicals Bureau, 2002).

The primary method of disposal of 1,4-dioxane is by incineration (ATSDR, 2012). In a study, that

investigated 1,4-dioxane in landfill leachate, extremely high levels of 1,4-dioxane (89 and 340 

mg/L) were detected in the leachate from two landfill sites. Analysis of leachate and 

measurement of 1,4-dioxane in incineration residues suggest that the most likely source of 1,4-

dioxane in the leachate is the fly ash produced by municipal solid waste incinerators (Fujiwara 

et al., 2008).

Groundwater beneath the city of Ann Arbor, Michigan is currently contaminated with 1,4-

dioxane after it was used as an industrial solvent and the contaminated waste water was stored 

in unlined wastewater lagoons between 1976 and 1986 (City of Ann Arbor, 2015). Since then, 

the chemical has seeped through the soil and entered the groundwater in the Ann Arbor area. 

Concentrations up to 7,000 ppb have been detected in the plume at the source. The maximum 

concentration of 1,4-dioxane detected at an off-site monitoring well near the center of the 

plume was 3,788 ppb (Pall Corporation, 2004). In 2004, concentrations of 1,4-dioxane in 

influent and effluent were measured in a WWTP in Ann Arbor, MI. In February, April and June, 

raw wastewater influent concentrations were 3, 2 and 3 g/L, respectively. Treated effluent 

concentrations were 3, 1 and 3 for those same months (Skadsen, 2004). The similar influent and 

effluent values suggest that 1,4-dioxane is not readily removed and passes through a municipal 

WWTP. 
Page 23 of 54

Samples of waste water effluent were collected from 40 municipal WWTPs that receive 

predominantly domestic wastewater from households. Sampling took place in 2010 and 

included WWTPs at select sites in 15 states. Of the WWTPs effluents samples, two had 1,4-

dioxane concentrations below the LOQ (<0.30 g/L) and 38 samples had concentrations 

between 0.30 and 3.30 g/L (Simonich et al., 2013). 

2.4.3 Occupational Exposure

Occupational exposure data from three sources were reviewed: the 2002 EU RAR, the OSHA 

Chemical Exposure Health Data database, and a data set provided by an American Chemistry 

Council (ACC) member company. 

Manufacturing sites produce 1,4-dioxane in liquid form at 90 percent concentration or higher. 

Workers may be exposed by inhalation and skin contact when they work with 1,4-dioxane. The 

high vapor pressure of 1,4-dioxane causes a high potential for air releases and associated 

worker inhalation exposure. Dermal exposure may occur, but due to a low rate of absorption 

through the skin and rapid volatilization, inhalation is considered the predominant route of 

exposure.

Occupational exposure limits can affect the handling and processing of chemicals, thereby

reducing the potential for exposures. The US has several regulatory and non-regulatory 

exposure limits for 1,4-dioxane (ACGIH, 2009): an Occupational Safety and Health 

Administration (OSHA) Permissible Exposure Limit (PEL) of 100 ppm 8-hour time-weighted 

average (TWA) (360 mg/m3) with a skin notation, a National Institute of Occupational Safety 

and Health (NIOSH) Recommended Exposure Limit (REL) of 1 ppm (3.6 mg/m3) as a 30 minute 

ceiling, and an American Conference of Government Industrial Hygienists (ACGIH) Threshold 

Limit Value (TLV) of 20 ppm TWA (72 mg/m3). 

Public CDR information (US EPA, 2012c) indicates there is one domestic manufacturing site, 25 

to 99 industrial processing sites and two commercial/ consumer product categories (Paints and 

Coatings and Laundry and Dishwashing Products) for this chemical5. Information on current 

domestic processing and use of 1,4-dioxane that may result in exposures is limited. 1,4-dioxane

has been potentially formulated into specialized products for industries in Europe with no

expected consumer uses. Also, some processes to make other chemicals produce 1,4-dioxane

as a reaction byproduct (e.g., ethoxylation reactions), and these chemicals have a variety of 

uses that may result in worker and consumer exposures.

 

5

The manufacturer submitted a correction to EPA to revise the 2012 CDR to reflect that 1,4-dioxane is not used for 

the categories ‘Paints and Coatings’ and ‘Laundry and Dishwashing Products’. The correction was received and is 

not yet indicated in public database.
Page 24 of 54

In the US, limited worker inhalation monitoring data for this chemical were found in the OSHA 

Chemical Exposure Health Data database (OSHA, 2014). During the most recent 15 year period 

(1997 - 2011), 21 samples were taken from 6 sites, with 2 detects of 0.21 and 0.22 ppm and 19 

non-detects. Worker monitoring data specific to an American Chemistry Council (ACC) member 

company facility where 1,4-dioxane is produced as a byproduct in its manufacturing process 

were collected from 2001 to 2003 (Franz, 2014). All of the 21 samples taken at this facility were 

below analytical detection limits, which ranged from 0.044 to 0.9 ppm (0.16 to 3.24 mg/m3).

The two sets of data are too limited to consider representative of potential exposures that may 

occur throughout the US (Appendix C: Occupational Exposure Data).

Estimates of worker exposure in Europe are provided in the EU RAR (European Chemicals 

Bureau, 2002) for 1,4-dioxane. Inhalation concentrations and dermal doses for worker 

exposures in five “Worker Use Activity” scenarios (Table 2-5) were estimated: production, 

formulation and three end uses (cleaning agents in industries such as metal fabrication; paints 

and varnishes in the production of precision and optical instruments, watches and clocks; and 

lab solvents). All of these scenarios were relevant primarily to industrial and laboratory 

facilities. 

Table 2-5: Exposure Concentrations for Occupational Scenarios in European Industrial and Laboratory 

Facilities.

Worker Use Activity Reasonable Worst-case 

inhalation concentration

(mg/m3, TWA)

Typical inhalation 

concentration

(mg/m3, TWA)

Manufacturing 10 (measured) 0.2 (measured)

Processing/ formulating 180 (modeled) 40 (modeled)

Use of cleaning agent 50 (measured) 15 (measured)

Use of paint 11 (modeled) 2 (modeled)

Use of solvent in lab 25 (calc. from measured values) 5 (measured)

Table Note: “It is not clear whether the chemical is still used in cleaning agents.” Source: Table 4-4 in 

(European Chemicals Bureau, 2002).

Comparing the concentrations of 1,4-dioxane estimated for worker inhalation in Europe (Table 

2-5) to US limits and recommended action levels, exposures did not exceed the OSHA 

Permissible Exposure Limit (PEL), but typically exceeded the NIOSH Recommended Exposure 

Limit (REL). EPA/OPPT could not determine whether the worker exposures estimated in the EU 

assessment are similar to those in the US.

The European report did not estimate worker exposures for processes that produce 1,4-dioxane

as a reaction byproduct (e.g., ethoxylation reactions). Concentrations of 1,4-dioxane as a

contaminant in detergents and paints are expected to be lower than the estimated 

concentrations of 1,4-dioxane in processed formulations. Formulations typically contain 10 

weight percent or higher handled by workers in the assessed European scenarios. Worker 

exposures to commercial products (such as detergents and paints) containing 1,4-dioxane as a 
Page 25 of 54

contaminant could therefore be orders of magnitude below the EU RAR estimated exposure 

concentrations.

No information was found regarding the current total number of workers exposed to 1,4-

dioxane. Historical estimates from the 1970s and 1980s indicate that the number of workers 

potentially exposed to 1,4-dioxane could have been up to 466,000 individuals (ATSDR, 2012). Of 

those workers, significant numbers were estimated to have been exposed as a result of the use 

of 1,4-dioxane as a stabilizer in TCA. While there is no data on current worker populations, the 

numbers are expected to be much lower assuming production of 1,4-dioxane has been 

reduced, particularly for use as a stabilizer in 1,1,1-trichloroethane (TCA).

In conclusion, workers in the US may be exposed to 1,4-dioxane. Several very limited worker 

monitoring data sets for US workers showed exposures to be below both the OSHA PEL and the 

NIOSH REL, but these data are very limited and may not be representative of exposures in the 

US. Worker exposure estimates in the EU could be a reasonable starting point for assessing 

exposures in the US. In order to better characterize worker exposures to 1,4-dioxane in the US, 

information on current uses and volumes, processes used during production/formulation, 

worker activities and measurements of exposure levels are needed.

2.4.4 General Population Exposure

General population exposures were identified and considered during problem formulation. A 

review of available data and assessments for 1,4-dioxane revealed that potential general 

population exposure can occur from ingesting contaminated drinking water and inhaling 1,4-

dioxane in the air. Exposures to 1,4-dioxane in food and cosmetics are outside the scope of 

TSCA, have been addressed by other organizations such as FDA and are not addressed in this 

assessment.

Exposure in Air

Air releases of 1,4-dioxane have decreased notably due to the ban of TCA according to historical 

data. The TRI data indicate that air is the media with the greatest releases (ATSDR, 2012; US 

EPA, 2012c). TRI data is summarized in Section 2.4.1 Releases to the Environment.

Exposure in Drinking Water

Recent actions from the State of California (CSWRCB, 2014) have labeled 1,4-dioxane as an 

emerging contaminant because of its increased presence in drinking water. The California 

Department of Public Health’s Drinking Water Program measured 1,4-dioxane levels in drinking 

water systems from 2000 to 2013. The program reported a mean concentration of 0.0042 

mg/L; a median of 0.003 mg/L; and maximum concentration of 0.053 mg/L in the 2,592 samples 

taken. 
Page 26 of 54

High concentrations of 1,4-dioxane have been found in runoff ditches around Superfund sites 

and nearby drinking water wells have been contaminated at levels above concern for health 

effects (ATSDR, 2012).

EPA/OW’s three year monitoring program (i.e. UCMR) of public water systems (PWS) tests for 

1,4-dioxane and other chemicals in finished drinking water (US EPA, 2014e). Samples are 

collected at entry points to the distribution system (i.e., the point at which water is discharged 

into the distribution system from a well, storage tank, pressure tank or water treatment plant). 

Source water (i.e., ambient surface or ground water) is not measured as part of the UCMR. 

Monitoring data from PWSs during the first two years of the UCMR program as of January 2015

are summarized in Table 2-6. The results include 243 PWSs representing 708 samples with 

results greater than the 10-6cancer reference concentration (0.35 g/l) and no PWSs with 

detections above the 10-4cancer reference concentration level (35 ppb). It is unknown whether 

additional monitoring data will result in higher occurrence or detection levels of 1,4-dioxane in 

PWSs. Since 1,4-dioxane is being monitored through December 2015, decisions as to whether 

or not to regulate the contaminant in drinking water will be considered as part of the EPA’s 

Regulatory Determination process (US EPA, 2014e). The reference concentrations used for 1, 4-

dioxane are based on publically-available health information found in the 2012 Drinking Water 

Standards and Health Advisory (US EPA, 2012a) and range from 0.35 to 35 g/l, based on 

cancer risk of 10-6to 10-4, respectively. The draft reference concentration does not represent an 

“action level”; EPA requires no particular action based simply on the fact that UCMR monitoring 

results exceed draft reference concentrations, nor should the draft reference concentration be 

interpreted as any indication of EPA’s intent to establish a future drinking water regulation for 

the contaminant at this or any other level (US EPA, 2014e). 

Table 2-6: Preliminary Data from the EPA UCMR 3 (January 2015).

Contaminant MRL

1 Reference

Conc. 1,2

Total #

of results

# of

results

≥MRL

# of

results

> Ref.

Conc.2

% of total 

results

> Ref.

Conc.2

Total 

number

of PWSs

with 

results

# of 

PWSs

with 

results

≥MRL

# of PWSs

with 

results

>Ref.

Conc. 2

% of PWSs

with results

>Ref.

Conc. 2

1,4-dioxane 0.07 0.35 / 35 22,611 6132 708 / 0 3.1% / 0% 5873 727 243 / 0 6.8% / 0%

(http://water.epa.gov/lawsregs/rulesregs/sdwa/ucmr/upload/epa815s15001.pdf

1Measured in μg/L (ppb)

2Where two reference concentrations are listed, the first number is associated with a 10-6

cancer risk; the 

second number a 10-4cancer risk. Where two results are presented the first number is associated with the first 

reference concentration; the second number is associated with the second reference concentration.
Page 27 of 54

2.4.5 Consumer Exposure

The primary route of consumer exposure to 1,4-dioxane is by inhalation and dermal contact 

with contaminated consumer products containing ethoxylated surfactants such as personal 

care products, soaps and detergents. Limited data on concentrations in consumer products 

exist. Currently, manufacturers may voluntarily 1) minimize the formation of the 1,4-dioxane as 

by-product during manufacture of alkyl ethoxy sulfates (AES), or 2) remove 1,4-dioxane by 

stripping the AES paste before formulation of ethoxylated surfactants into consumer cosmetics 

and household products. The extent to which manufacturers use these practices is uncertain. 

Cosmetics and personal care products are regulated by FDA. FDA has estimated consumer 

exposure to 1,4-dioxane to be low (US FDA, 2007). FDA reported that levels of 1,4-dioxane 

present in products such as shampoo and body wash do not pose a significant risk to consumers 

since products do not remain in contact with the skin for a long period of time (US FDA, 2007). 

FDA does not consider concentrations of 1,4-dioxane measured in cosmetics and toiletries to be 

a risk of concern (ATSDR, 2012). These uses are outside the jurisdiction of TSCA regulatory 

authority.

EPA/OPPT reviewed limited data on measured concentrations of 1,4-dioxane in products. Levels 

of 1,4-dioxane in cosmetics are reported from two sources as 6-34 ppm (Black, 2001) and nondetectable to 487 ppm (European Chemicals Bureau, 2002). When used as a chemical 

intermediate, 1,4-dioxane concentrations are 100-380 ppm in pharmaceuticals and 1.0 to 2.8% 

w/w% in household adhesives (ATSDR, 2012). Unintentional contamination levels of 1,4-

dioxane in products are < 10 ppm in food (European Chemicals Bureau, 2002), 6-160 ppm in 

household detergents (ATSDR, 2012) and 0.1 – 22 ppm in antifreeze and deicing products 

(European Chemicals Bureau, 2002). An analysis of consumer products by the Campaign for 

Safe Cosmetics found 1,4-dioxane in 32 out of 48 personal care products and cosmetics tested 

(67%) at levels ranging from 0.27 to 35 ppm. The Organic Consumers Association tested 100 

organic and natural consumer products and found detectable levels of 1,4-dioxane in 47 

products. In a study of household products (soaps, shampoos, cleaners and detergents) in 

Japan, 1,4-dioxane was detected in 40 out of 51 products at concentrations from 0.05 to 33 

mg/kg with a mean of 2.7 mg/kg (Tanabe and Kawata, 2008).

The European risk assessment evaluated risk of exposure to several consumer products: 

shampoos, baby lotion and hand dishwashing liquid via dermal and inhalation routes using 

ConsExpo, a well-documented exposure model for substances from consumer products

(European Chemicals Bureau, 2002). The worst case scenario yielded a combined total internal 

dose of 3.3 μg/kg-bw/day and the “very worst case” combined total internal dose was 10 

μg/kg-bw/day (European Chemicals Bureau, 2002). The margins of safety for consumer 

inhalation and dermal exposure scenarios for the three product categories ranged from greater 

than 1000 to greater than 10,000 using health benchmarks available at the time.

The Canadian risk assessment presented aggregate exposure estimates for various age groups 

including infants, children and adults (Environment Canada and Health Canada, 2010). Adult 
Page 28 of 54

women were considered the highest exposed demographic group due to the use of cosmetics 

and well as other consumer products. The estimated aggregate intake of 1,4-dioxane for daily 

use of hair conditioner, hair shampoo, skin moisturizer (body cream) and body wash was 1.2 

μg/kg-bw per day. The margins of safety for daily intake (dermal and inhalation) for aggregate 

exposure of the general population and consumers ranged from 7620 to 50,000 using the same 

point of departure (Kociba et al., 1974) as used to derive the oral IRIS RfD.

EPA/OPPT concludes that exposure to consumers can result from the use of soaps and 

detergents and other products that contain 1,4-dioxane as a contaminant. Adult women who 

use multiple cosmetics and cleaning products are likely the most exposed population as 

determined in the Canada assessment. The EU RAR and Canada separately assessed aggregate 

risks from exposure to several consumer products and found no risk of concern. However, the 

assumptions used in those assessments may differ from EPA risk assessment guidelines, and 

EPA IRIS recently published an updated review of health benchmarks for non-cancer and cancer 

endpoints that includes new studies not considered in the previous assessments.

2.5 Hazard Endpoints

2.5.1 Environmental Hazard

The available ecotoxicity studies for 1,4-dioxane on fish, aquatic invertebrates and aquatic 

plants are summarized in Appendix D. There are no studies for 1,4-dioxane on sediment, soil or 

terrestrial organisms. 

The hazard of 1,4-dioxane to aquatic organisms is low. The hazard of 1,4-dioxane is expected to 

be low for soil organisms due to its high potential to volatilize from soil surfaces and low for 

sediment-dwelling organisms due to its low adsorption potential to sediment. 

2.5.2 Human Health Hazard

A detailed summary of human health studies is in Appendix E-1 and additional information can 

be found in the EPA IRIS Toxicological Review of 1,4-Dioxane (with Inhalation Update) available 

at: http://www.epa.gov/IRIS/toxreviews/0326tr.pdf. 

Several national and international organizations have evaluated the human health hazard of 

1,4-dioxane. Previous assessments were reviewed to identify potential hazard concerns of 1,4-

dioxane including a 2013 IRIS review (US EPA, 2013b), a 2012 ATSDR Toxicological Profile 

(ATSDR, 2012), a Canadian screening assessment (Environment Canada and Health Canada, 

2010) and the EU RAR (European Chemicals Bureau, 2002).

Moderate to high hazard concerns for repeated exposures are based on subchronic and chronic 

oral and inhalation studies. In subchronic studies, the primary target organs are the liver, 
Page 29 of 54

kidney and nasal/respiratory epithelium. Chronic studies have reported an apparent 

progression to tumor formation at these sites that appears to be independent of genotoxicity.

Physiologically based pharmacokinetic models (PBPK) models have been developed for 1,4-

dioxane in rats, mice, humans and lactating women (US EPA, 2013b). Animal studies indicate 

1,4-dioxane is readily absorbed via oral and inhalation exposures, with less absorption through 

the skin (ATSDR, 2012). No data are available on the distribution of 1,4 dioxane in humans, and 

no data on distribution are available in animals via oral or inhalation routes. Metabolism of 1,4-

dioxane in humans and experimental animals is extensive. Rats were shown to metabolize 

inhaled 1,4-dioxane to β-hydroxyethoxy acetic acid (HEAA). Elimination of 1,4-dioxane in

humans and rats is via the urine in the form of HEAA. 

Mortality was observed in multiple acute high-dose studies in rats, mice and rabbits. The acute 

oral, dermal and inhalation toxicity of 1,4-dioxane is low in rats, mice and rabbits. Repeateddose toxicity studies in rats via oral administration with 1,4-dioxane at mid- and high-dose, 

showed variable degrees of kidney and liver changes and mortality. Liver and nasal carcinomas 

were observed in rats via the inhalation route.

Delayed ossification of the sternebrae and reduced fetal body weights were observed in a 

prenatal developmental toxicity study with 1,4-dioxane. No reproductive toxicity studies have 

been performed with 1,4-dioxane; however, no histopathological changes were reported in the 

reproductive organs of male and female rats/mice exposed in subchronic and chronic studies. 

The high dose at which developmental effects occurred suggests a low hazard for 

developmental and reproductive toxicity.

The genotoxic potential of 1,4-dioxane has been evaluated using in vitro and in vivo assay 

systems. The majority of in vitro assays with 1,4-dioxane were nongenotoxic. Fifty-percent of in 

vivo studies with 1,4-dioxane were positive. EPA (US EPA, 2013b) concluded that 1,4-dioxane is 

nongenotoxic or weakly genotoxic based on the IRIS review.

No treatment-related effects were observed in a single dose dermal irritation assay in rats. In a

90-day inhalation study, no gross or microscopic alterations were reported in the skin of rats.

However, this study was conducted via inhalation and does not provide an adequate 

representation of dermal toxicity.

Evidence of carcinogenicity in animals (liver and nasal tumors, mesotheliomas of the 

peritoneum in male rats and an increase in mammary gland adenomas in female rats) indicates 

that 1,4-dioxane is “likely to be carcinogenic to humans” (US EPA, 2013b). A cancer slope factor 

(CSF) of 0.1 (mg/kg/day)

-1 was derived from the tumor incidence data for nasal squamous cell 

carcinomas in mice and gall bladder carcinomas in guinea pigs. A new two-year inhalation 

bioassay in rats was used to calculate an inhalation unit risk (IUR) of 5 x 10-6(μg/m3)

-1

(US EPA, 

2013b). 
Page 30 of 54

2.6 Results of Problem Formulation

The results of problem formulation are a conceptual model, key assessment questions and an 

analysis plan for human health (US EPA, 2014b). A conceptual model was not developed for 

environmental health due to the low ecotoxicity hazard values reported from standard acute 

and chronic ecological toxicity tests.

2.6.1 Conceptual Model

The following conceptual model (Figure 2-2) illustrates the sources and potential pathways

(arrows) of 1,4-dioxane from chemical manufacture and formulation, releases to the 

environment and potential exposure pathways for human (workers, consumer and general 

population) receptors. The blue solid and dotted blue lines in the conceptual model represent 

pathways from potential sources, and the red solid and dotted lines represent potential 

exposure pathways via inhalation or ingestion for human receptors. Dermal exposures are not 

addressed due to a low rate of absorption, high volatilization and lack of dermal toxicity studies. 

Potential human health effects include cancer (progression of tumor formation) and noncancer 

outcomes (liver, kidney and nasal effects) in workers, consumers and the general population. 

The source-exposure-receptor pathways, labeled numerically in the conceptual model, are 

described as follows:

1. Workers may be potentially exposed from inhalation exposures during manufacturing 

and formulation of 1,4-dioxane or in industrial or laboratory facilities where 1,4-dioxane 

is used. 

2. Workers and consumers may be potentially exposed by inhalation during the use of 

products that contain 1,4-dioxane as a contaminant. 

3. Inhalation exposures may occur to the general population as a result of emissions 

from manufacturing/formulating/use facilities, as well as incineration of waste 

streams/products. 

4. Oral exposures to the general population may occur from drinking contaminated 

water. 1,4-Dioxane in surface water or ground water may travel through public drinking 

water treatment plants (DWTPs) and private wells to the “tap”. The source 

contributions to drinking water are uncertain and may originate from wastewater 

effluent, leaching from landfills and disposal sites to groundwater and surface water.
Page 31 of 54

Figure 2-2: Conceptual Model of Potential Exposure Pathways for 1,4-Dioxane.

Solid blue lines represent potential source pathways; solid red lines represent exposure pathways to 

receptors; dotted blue lines indicate pathways with limited data to assess.

Four key assessment questions were developed from the Conceptual Model:

1. Are there risks to workers exposed during manufacturing and formulation of 1,4-

dioxane or in industrial or laboratory facilities where 1,4-dioxane is used? 

A 2002 European assessment found potential risk to workers for occupational exposures via the 

dermal and inhalation routes during product formulation and the use of 1,4-dioxane as a 

cleaning agent. Comparing the estimates of worker inhalation in Europe to US limits and 

recommended action levels, exposures did not exceed the OSHA Permissible Exposure Limit 

(PEL), but typically exceeded the NIOSH Recommended Exposure Limit (REL). Exceeding the 

NIOSH REL may indicate potential exposure concerns. The few US data on worker exposure 

were below the NIOSH REL. However, EPA’s recently updated IRIS cancer and non-cancer

benchmarks for human health suggest that human health risks should be reassessed. 

2. Are there risks to workers and consumers potentially exposed by inhalation during the 

use of products that contain 1,4-dioxane as a contaminant?

Workers and consumers may be exposed to 1,4-dioxane present as a contaminant in products 

such as personal care products, paints, adhesives, varnishes, cleaners and detergents. Previous

risk assessments in Canada and Europe concluded that levels of contamination do not pose 

concerns for human health. However, the assumptions used in those assessments may differ 

from EPA risk assessment guidelines. EPA’s recently updated IRIS benchmarks for non-cancer 
Page 32 of 54

and cancer human health endpoints, including new studies, were not considered in the 

previous assessments. EPA/OPPT should reassess risks to workers and consumers from 

products. While personal care products are regulated by the FDA, uses in paints, adhesives, 

varnishes, cleaners and detergents fall under TSCA authority. 

3. Are air emissions of 1,4-dioxane a potential risk to the general population from 

inhalation exposure?

EPA/OPPT considered the exposure of the general population to ambient air levels of 1,4-

dioxane. Minimal data on 1,4-dioxane uses and releases to the environment exist for estimating 

the ambient levels of 1,4-dioxane in air and recent monitoring data is unavailable. TRI data (US 

EPA, 2012c) indicate that there are 39 sites reporting the release of 106,300 pounds of 1,4-

dioxane to on- and off-site releases with 82% of these air releases to onsite fugitive and point 

sources and 18% to surface water. There was an additional 1,035,300 pounds from two sites 

with almost all going to underground injection wells (on-site and off-site) and waste brokers. 

Since phasing out of the use of 1,4-dioxane as a stabilizer in chlorinated solvents except for 

select uses, air releases of 1,4-dioxane have decreased as can be seen in the TRI data (Section 

2.4.1). Air monitoring data from urban areas in the 1980s and 1990s showed significant 

decreases in 1,4-dioxane over the period covering the phase out. Since the 1990’s, the 

reduction seems to have leveled off. The latest TRI data indicate that air releases continue to 

occur.

During problem formulation, EPA/OPPT considered that 1,4-dioxane is: 1) regulated under the 

CAA as a hazardous air pollutant (US EPA, 2000); 2) photooxidized in the environment with a t1/2

of 1-3 days; and, 3) historical levels of 1,4-dioxane range from 0.0001 to 0.0004 mg/m3(i.e., 0.1 

μg/m3to 0.4 μg/m3) (ATSDR, 2012). Canada assessed the exposure of the general population to 

1,4-dioxane in air and concluded that there is no risk of concern (Environment Canada and 

Health Canada, 2010). Compared to the IRIS Reference Concentration (RfC) (US EPA, 2013b) for 

noncancer effects (0.03 mg/m3), the historical levels are 75 to 300 times lower than the RfC.

Calculation of lifetime cancer risk using the IRIS IUR (5 × 10-6(μg/m3)

-1

) (US EPA, 2013b)

indicates that risks associated with historical 1,4-dioxane levels range from 5 × 10-7to 2 × 10-6, 

which are below EPA’s target risk range of 1 × 10-6to 1 × 10-4.

4. Are there risks to the general population from drinking water contaminated with 1,4-

dioxane? 

Data being generated by EPA’s OW show that the general population may be exposed to 1,4-

dioxane from contamination of finished drinking water. Groundwater may also be a source of 

general population exposures especially around Superfund sites. However, based on the limited 

data, it may be premature for EPA/OPPT to conduct a TSCA risk assessment of the drinking 

water pathway because there is too much uncertainty to adequately characterize source 

contributions of 1,4-dioxane in drinking water from TSCA uses. EPA’s OW is currently 

monitoring for 1,4-dioxane as part of the UCMR 3 monitoring program until December 2015. 
Page 33 of 54

EPA will determine whether or not regulatory action is needed as part of the EPA’s Regulatory 

Determination process.

2.6.2 Analysis Plan

Based on Problem Formulation, EPA/OPPT plans to use available data to evaluate:

1. Potential occupational risks of exposure to 1,4-dioxane during manufacturing and 

formulation of 1,4-dioxane or in industrial or laboratory facilities where 1,4-dioxane is 

used.

2. Potential risks to workers and consumers exposed by inhalation during the use of 

products that contain 1,4-dioxane as a contaminant.

For the exposure assessment, EPA/OPPT plans to use the following data and information to 

estimate worker exposures:

 Physico-chemical data on 1,4-dioxane

 Production volume and use information (non-confidential) 

 Data on concentrations of 1,4-dioxane in commercial products from published literature 

or provided by industry or consumer groups

 Data and information on production, formulation and use processes

 Data from the OSHA Chemical Exposure Health Data database or provided by industry

 Measured and modeled data and information from exposure scenarios considered in 

the Canadian and European assessments.

For the hazard assessment, EPA/OPPT plans to carefully review the existing human health 

benchmarks established by OSHA, NIOSH, ATSDR and EPA IRIS (Appendix B). EPA/OPPT will 

select the relevant benchmarks according to the relevant route of exposure. The exposure 

estimates will be corrected for expected duration and frequency in agreement with the hazard 

assessment.

For the risk characterization, EPA/OPPT will compare measured or estimated exposures to the 

selected hazard benchmarks and calculate cancer risk estimates and non-cancer margins of 

exposure for workers and consumers exposed to 1,4-dioxane through inhalation.

Given the limited amount of exposure data identified during problem formulation, EPA/OPPT 

will search for additional data and information on current uses and production volumes, 

processes used during production/formulation, worker activities, concentrations in products 

and measurements of exposure levels.

Following review of comments and consideration of any additional data or information 

EPA/OPPT may receive, EPA/OPPT plans to publish a final assessment for 1,4-dioxane.
Page 34 of 54

2.6.3 Uncertainties and Data Gaps

The industrial and commercial use data as reported in the 2012 CDR database indicate no 

current consumer uses (US EPA, 2012b). The 2012 CDR does not give a complete picture of all 

uses because only manufacturers of more than 25,000 pounds of a chemical at a single site are 

required to report. Downstream industrial, consumer and commercial use data are reported 

only if they manufactured more than 100,000 pounds of a chemical during a particular year. 

Processing and use is often not under the control of the manufacturers and they may have 

incomplete knowledge of these activities (US EPA, 2014a). As a result of these factors, the 

processing and use information in the CDR public database presents only a limited picture of 

the actual processing and use situation in the United States (US EPA, 2014a). Recent production 

volume and use data are claimed confidential by the manufacturer. EPA was unable to identify 

any US sources that definitively stated the chemical is used in the production of consumer 

products, and therefore assumes there are no current consumer uses. As a contaminant, data 

on the concentrations of 1,4-dioxane in consumer products are limited.

Data to understand the sources and pathways by which 1,4-dioxane enters the environment 

are limited. The total actual releases from facilities that formulate or use 1,4-dioxane have 

some uncertainties. For example, these releases may be higher than the total reported since

facilities that release less than 25,000 pounds are not required to report data to the TRI. Legacy 

contamination, wastewater effluent and non-point sources may also contribute to releases of 

1,4-dioxane into the environment. Recent ambient air data are needed to better understand 

current worker exposures.

EPA/OPPT is uncertain whether worker exposures to 1,4-dioxane in the US may be similar to 

those estimated in the EU RAR (European Chemicals Bureau, 2002). EPA/ OPPT is also uncertain 

whether the limited 1,4-dioxane inhalation monitoring data for US workers are representative 

of occupational exposures in the US. Also, the historical total numbers of workers exposed to 

1,4-dioxane is expected to be much higher than the current total, which is unknown.

Information on current uses and volumes, processes used during production/formulation, 

worker activities and measurements of exposure levels are not available. The extent to which 

manufacturers use processes to reduce the contamination of 1,4-dioxane in products is 

unknown.

In the human health hazard assessment, EPA IRIS noted uncertainties in the development of 

the cancer risk values including the use of low-dose extrapolation, dose metric, cross-species 

scaling, alternative bioassays, species/gender combination, human relevance to mouse tumor 

data and human population variability in metabolism and response/sensitive subpopulations. 

There is a data gap in human health hazard since no multigeneration reproductive toxicity 

studies are available for 1,4-dioxane.
Page 35 of 54

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http://www.ecy.wa.gov/programs/swfa/cspa/chcc.html (accessed on July 10, 2014).
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Yalkowsky, S., and Y. He. 2003. Handbook of Aqueous Solubility Data (Pp 117). Boca Raton, FL: 

CRC Press.

APPENDICES

Appendix A Regulatory and Assessment History

Table A-1: History of Regulatory and Assessment Actions in the U.S. and Internationally.

COUNTRY REGULATORY/ASSESSMENT ACTION

UNITED STATES

Occupational Exposure 

Limits

Occupational exposure limits are established:

 1989 OSHA PEL: 25 ppm (90 mg/m3) TWA

 1994 NIOSH REL: 1 ppm (3.6 mg/m3) 30-minute ceiling, [skin]

 1993-1994 ACGIH TLV: 25 ppm (90 mg/m3) TWA

UNITED STATES

ATSDR Minimal Risk Levels 

(MRLs) 2013

Inhalation MRLs:

 Acute-duration inhalation exposure (14 days or less) = 7.2 mg/m3(2 ppm) was 

derived from a NOAEL of 72 mg/m3(20 ppm) for eye and respiratory irritation 

and pulmonary function effects in humans.

 Intermediate-duration inhalation exposure (15 to 364 days) = 0.72 mg/m3(0.2 

ppm) was derived from a BMCL10 of 101 mg/m3(27.99 ppm) (subsequently 

adjusted for duration) for increased incidence of nasal lesions in rats.

 Chronic-duration inhalation exposure (365 days or more) = 0.11 mg/m3(0.03 

ppm) was derived from a LOAEL of 180 mg/m3(50 ppm) (subsequently 

adjusted for duration) for increased incidence of nasal lesions in rats (Kasai et 

al, 2009).

Oral MRLs:

 Acute-duration oral exposure (14 days or less) = 5 mg/kg-bw/day was derived 

from a NOAEL of 516 mg/kg-bw/day for developmental and maternal effects 

in rats.

 Intermediate-duration oral exposure (15 to 364 days) = 0.5 mg/kg-bw/day was 

derived from a NOAEL of 52 mg/kg-day for liver effects in rats.

 Chronic-duration oral exposure (365 days or more) = 0.1 mg/kg-bw/day was 

derived from a NOAEL of 9.6 mg/kg-day for liver effects in rats (Kociba et al, 

1974).

UNITED STATES

IRIS Cancer and Noncancer Benchmarks 2013

 Cancer Slope Factor: 0.1 (mg/kg/day)

-1

(based on Kano et al, 2009)

 Drinking Water Unit Risk: 2.9 × 10-6μg/L

 Inhalation Unit Risk: 5 × 10-6(μg/m3)

-1

 RfD = 0.03 mg/kg-day based on degenerative liver effects as the most 

sensitive endpoint observed in a chronic bioassay; point of departure = 9.6 

mg/kg-day (Kociba et al, 1974)

 RfC = 3.0 × 10-2 mg/m3(0.0083 ppm) based on co-critical effects of olfactory 
Page 41 of 54

COUNTRY REGULATORY/ASSESSMENT ACTION

epithelium atrophy and respiratory metaplasia in rats exposed for 2 years via 

inhalation; point of departure = 32.2 mg/m3(Kasai et al, 2009).

 http://www.epa.gov/iris/subst/0326.htm

UNITED STATES

Drinking Water Limits 

2012

 Health advisory levels for 1,4-dioxane in drinking water: 4 mg/L (one-day, 10-

kg child), 0.4 mg/L (ten-day, 10-kg child), 1 mg/L (DWEL), 0.2 mg/L (Life-time), 

and 0.035 mg/L at 10-4cancer risk. (USEPA, 2012) 

 On the EPA Unregulated Contaminant Monitoring Rule 3 (UCMR3) list. 

UNITED STATES

Cancer Classification

 EPA - classified as B2- Probable human carcinogen (EPA 2003) - “1,4-dioxane is 

‘likely to be carcinogenic to humans’ based on evidence of carcinogenicity in 

several 2-year bioassays conducted in four strains of rats, two strains of mice, 

and guinea pigs.

 The National Toxicology Program concluded that 1,4-dioxane is 'reasonably 

anticipated to be a human carcinogen' (NTP 2005).

 IARC classifies 1,4-dioxane as 'possibly carcinogenic to humans' (IARC 1999

UNITED STATES

Hazardous Air Pollutant

 Listed as a hazardous air pollutant under the Clean Air Act (CAA)

UNITED STATES

Wastes, Releases, and 

Remediation

 May be regulated as hazardous waste when used as a solvent stabilizer 

 Reportable quantity of 100 pounds has been established under CERCLA

 Facilities manufacturing, processing, or otherwise using 1,4-dioxane are 

required to report releases to EPA’s Toxic Release Inventory (TRI). 

UNITED STATES

Food and Drugs

 FDA set limits of 10 ppm in approving glycerides and polyglycerides for use in 

dietary supplements, and for spermicides.

EUROPEAN UNION

2002

The European Union Risk Assessment Report (EU RAR) concluded that: 

 Environmental risk, risk to consumers, and risk to general populations are not 

expected. 

 Risks are expected to workers due to: (i) skin effects during production, 

formulation and use of the substance or the product containing the 

substance, and (ii) systemic toxicity and carcinogenicity due to dermal 

exposure from the use of the substance as cleaning agent, and due to 

inhalation during formulation of the substance. 

CANADA

2010

 Environment Canada (2010) assessed risks to human health based on 

potential exposure and carcinogenicity and concluded that 1,4-dioxane is not 

entering the environment in a quantity or concentration or under conditions 

that constitute or may constitute a danger in Canada to human life or health.

Australia

1998

 Priority existing chemical, report published in 1998. 

 The occupational risk assessment concluded that, for known Australian work 

situations, 1,4-dioxane is unlikely to cause acute or chronic adverse effects, 

including inhalation and dermal exposure. However, estimated exposure 

based on modeled data to workers involved in optical lens manufacture 

indicate a potential risk. 

 The public health risk assessment concluded there are no significant health 

risks to the general public from the only source of potential exposure 
Page 42 of 54

COUNTRY REGULATORY/ASSESSMENT ACTION

(consumer products containing 1,4-dioxane as impurity). 

 The environmental risk assessment indicated that the majority of 1,4-dioxane 

will be released to wastewater, and that the chemical does not present a 

significant risk of adverse effects to the Australian aquatic environment.

Japan  Priority Assessment Chemical Substance (PACS). PACS are substances whose 

long-term toxicity to humans or to flora and fauna in the human living 

environment is unclear, that have been found, or are expected to be found, 

inconsiderable amounts over a substantially extensive area of the 

environment. These substances are designated as chemicals that require a 

priority assessment to assess the risk they may pose.)
Page 43 of 54

Appendix B Summary of Uses and End Products 

Table B-1: Summary of All Uses of 1,4-Dioxane and End Products.

Use End Product(s)

Processing solvent  Waxes 

 Fats 

 Lacquers and varnishes 

 Cleaning and detergent preparations 

 Adhesives 

 Cosmetics*

 Deodorant fumigants 

 Emulsions and polishing compositions

 Wood pulp

Reaction medium solvent  Organic chemicals

Industrial solvent with an unspecified 

function

 Fluid for scintillation counter (radiation detector) samples

 Specific applications in biological procedures (histology)

 Cellulose acetate membranes used as filters

 Dye baths

 Lacquers and paints 

 Waxes 

 Varnishes and stains 

 Printing compositions 

 Paint and varnish removers

 Laboratory reagent (e.g., mobile phase in chromatography)

Extraction medium  Animal and vegetable oils

Inert ingredient  Pesticides and fumigants

Chemical intermediate  Pharmaceuticals 

 PET plastic

 Rubber

 Insecticides and herbicides 

 Cements

 Deodorant fumigants

 Magnetic tape 

 Adhesives

Polymerization catalyst  Plastics (unspecified plastic type) 

Dehydrating agent  Unknown

Wetting and dispersing agent  Textiles

Degreasing agent  Unknown

Unintentional Impurity  Food (as a result of food additives or pesticides)

 Cosmetics

 Agricultural/veterinary products

 Industrial detergents

 Household detergents

 Pharmaceuticals

 Antifreeze and deicing products

*As listed in ECHA, 2002 and not confirmed by US sources.

Sources: EPA, 2006; ASTDR, 2012; ECHA, 2002; FDA, 2007; Environment Canada, 2010
Page 44 of 54

Appendix C Occupational Exposure Data

Appendix C contains US occupational exposure inhalation data from two sources.

Table C-1: Summary of 1,4 Dioxane Occupational Monitoring Data for Process Operators in the 

Synthesis Area from an ACC Member Company where 1,4-Dioxane is Produced as a Byproduct in its 

Manufacturing Process.

Sample Date Activity Results (ppm, 8-hour TWA)

10/29/01 Emptying & Boiling out Vessel LT 0.044

10/29/01 Emptying & Boiling out Vessel LT 0.054

10/29/01 Emptying & Boiling out Vessel LT 0.045

10/29/01 Emptying & Boiling out Vessel LT 0.045

10/29/01 Emptying & Boiling out Vessel LT 0.046

10/29/01 Emptying & Boiling out Vessel LT 0.043

10/29/01 Emptying & Boiling out Vessel LT 0.046

07/11/02 Running PO and EO into 

[Product] batch LT 0.1

05/29/03 Drumming [Product] LT 0.9

06/03/03 Drumming [Product] LT 0.3

06/09/03 Sampling and Drumming 

[Product] LT 0.3

06/09/03 Adding [Raw Material] to 

[Product] LT 0.3

06/11/03 Drumming [Product] LT 0.3

06/13/03 Drumming [Product] LT 0.3

06/16/03 Sampling and Drumming 

[Product] LT 0.3

06/19/03 Drumming [Product] LT 0.4

06/23/03 Sampling [Product] LT 0.3

07/02/03 Sampling and Drumming 

[Product] LT 0.3

07/06/03 Dumping P2O5 into [Product] LT 0.3

07/09/03 Drumming [Product] LT 0.3

07/14/03 Drumming [Product] LT 0.3

Source: Franz, 2014.

Key: LT = Less than (the value provided is the limit of detection (LOD)).

TWA = time weighted average over an 8-hour period
Page 45 of 54

Table C-2: 1,4-Dioxane - OSHA Chemical Exposure Health Data, 1997 – 2011.

Establishment City State Zip Date SIC NAICS Type Time 

(minutes)

Result 

(ppm)

Peter Cremer North 

America, Lp

Cincinnati OH 45204 15-

May-08

2869 325199 

D46774

P 15 ND

Peter Cremer North 

America, Lp

Cincinnati OH 45204 15-

May-08

2869 325199 

D46775

P 19 ND

Peter Cremer North 

America, Lp

Cincinnati OH 45204 15-

May-08

2869 325199 

D46773

P 15 ND

Crystal, Inc. - Pmc Lansdale PA 19446 16-Jun002841 0 E77374 P 32 ND

Crystal, Inc. - Pmc Lansdale PA 19446 16-Jun002841 0 E77370 P 65 ND

Crystal, Inc. - Pmc Lansdale PA 19446 16-Jun002841 0 E77372 P 30 ND

Crystal, Inc. - Pmc Lansdale PA 19446 16-Jun002841 0 E77368 P 60 ND

Crystal, Inc. - Pmc Lansdale PA 19446 16-Jun002841 0 E77369 P 84 0.2117

Crystal, Inc. - Pmc Lansdale PA 19446 16-Jun002841 0 E77371 P 50 0.2242

Crystal, Inc. - Pmc Lansdale PA 19446 16-Jun002841 0 E77373 P 60 ND

Tex-Tube, Inc. Houston TX 77024 13-Jul983498 0 E65998 P 18 ND

Raytheon Aircraft 

Company

Wichita KS 67206 2-Apr983721 0 E63443 A 75 ND

Raytheon Aircraft 

Company

Wichita KS 67206 2-Apr983721 0 E63444 A 40 ND

Raytheon Aircraft 

Company

Wichita KS 67206 2-Apr983721 0 E63441 A 75 ND

Raytheon Aircraft 

Company

Wichita KS 67206 2-Apr983721 0 E63440 A 75 ND

Raytheon Aircraft 

Company

Wichita KS 67206 2-Apr983721 0 E63442 A 75 ND

Raytheon Aircraft 

Company

Wichita KS 67206 2-Apr983721 0 E63439 A 75 ND

Yellow Freight 

Systems, Inc.

Columbus OH 43228 9-Mar984231 0 J61640 P 17 ND

Yellow Freight 

Systems, Inc.

Columbus OH 43228 9-Mar984231 0 J61642 B 0 ND

Yellow Freight 

Systems, Inc.

Columbus OH 43228 9-Mar984231 0 J61639 P 25 ND

Baker Petrolite Sand 

Springs

OK 74063 17-Feb982869 0 P 225 ND

Source: https://www.osha.gov/opengov/healthsamples.html accessed 3/7/14

Key: SIC = Standard Industrial Classification; NAICS = North American industrial Classification System; ND = Not 

Detected; Types: P = Personal, A = Area, B = Bulk

The detection limits for samples labeled as ND are not given.
Page 46 of 54

Appendix D Ecological Hazard Studies

The ecological hazard summary of 1,4-dioxane is based on available hazard data. In addition, an 

updated literature survey was conducted to identify articles on ecological toxicity published 

between 2003 and 2014. The search terms included freshwater and saltwater fish, aquatic 

invertebrates, and aquatic plants; pelagic and benthic organisms; acute and chronic sediment 

toxicity in freshwater and saltwater and terrestrial toxicity to soil organisms, birds, and 

mammals. The test species, test conditions, toxicity endpoints, statistical significance, and 

strengths/limitations of the study were evaluated for data quality. 

1,4-dioxane has been tested for acute and chronic aquatic toxicity. In order to characterize the 

effects of 1,4-dioxane to the environment, a hazard rating was assigned based on EPA 

methodology for existing chemical classification (US EPA, 2009). Included in this assessment are 

eight acute aquatic toxicity studies and three chronic aquatic toxicity studies. There is one study 

that characterizes the toxicity of 1,4-dioxane for aquatic plants. Acute and chronic toxicity data 

for 1,4-dioxane exist for freshwater and saltwater fish, daphnia, and green algae. There are no 

available sediment, soil, or avian toxicity studies found in literature for 1,4-dioxane. Also, 

EPA/OPPT agrees with the classification of studies previously reviewed in the EU RAR (European 

Chemicals Bureau, 2002). The European Chemicals Agency (ECHA) database on 1,4-dioxane 

contains updated hazard studies that were used to supplement the EU RAR. 

A summary of the available ecotoxicity data for 1,4-dioxane is provided below. The data show 

that there is a low acute and chronic ecotoxicity for fish, aquatic invertebrates and aquatic 

plants Hazard to soil and sediment organisms are expected to be low based on the lack of 

partitioning to and persistence in these environmental compartments. The EU RAR (European 

Chemicals Bureau, 2002) also concluded low hazard for soil and sediment organisms.

D-1 Acute Toxicity to Aquatic Organisms

Acute aquatic toxicity studies considered for this assessment are summarized in Table D-1.

Based on the available studies, fish, invertebrates and algae, 1,4-dioxane exhibits low acute 

toxicity for aquatic species.
Page 47 of 54

Table D-1: Aquatic Toxicity Data for 1,4-Dioxane - Acute Toxicity.

Test Species Fresh/ Salt 

Water Duration Endpoint

Conc.

(mg/L)

Test 

Analysis Effect References

Fish

Bluegill sunfish (Lepomis 

macrochirus)

Fresh 96-hour LC50 >1,000 Nominal Mortality

Dawson et al. 

(1977) as cited 

in Verschueren, 

(2010) 

Fathead minnow 

(Pimphales promelas)

Fresh 96-hour LC50

1,080 to

9,850 Measured Mortality Geiger, et al. (1990)

Fathead minnow 

(Pimphales promelas)

Fresh 96-hour LC50 9,872 Measured Mortality Brooke (1987)

Fathead minnow

(Pimphales promelas)

Fresh 96-hour LC50 12,326 Nominal Mortality Brooke (1987)

Fathead minnow 

(Pimphales promelas) Fresh 96-hour LC50 >100 Nominal Mortality

Dow (1991) as 

cited in the EU 

RAR (2002)

Inland Silversides

(Menidia beryllina)

Salt 96-hour LC50 67,000 Nominal Mortality Dawson et al. 

(1977)

Aquatic Invertebrates

Water flea 

(Daphnia magna) Fresh 48-hour EC50 >1,000 Nominal Immobilization

ECHA 

Assessment 

Report (2014)

Water flea 

(Ceridodaphnia dubia) Fresh 48-hour EC50 >299 Nominal Immobilization

Dow (1989) as 

cited in the 

2002 EU RAR

Acute Toxicity to Aquatic Invertebrates

For this assessment, there are two studies on the acute ecotoxicity to aquatic invertebrates. 

The water flea (Daphnia magna) were exposed to unspecified concentrations of 1,4-dioxane for 

48-hours under semi-static conditions. The highest concentration tested was 1,000 mg/L. No 

effects were seen at the highest concentration of 1,000 mg/L. A 48-hour EC50 of >1,000 mg/L 

was reported (European Chemicals Bureau, 2002). In the other study, Ceridodaphnia dubia was 

tested under the same conditions. A 48-hour EC50 of >299 mg/L was reported (Dow Chemical, 

1989). These values show that the acute toxicity of 1,4-dioxane to aquatic invertebrates is low.

Acute Toxicity to Fish

The acute 96-hour LC50 values ranges from >100 mg/L for fathead minnows (Pimephales 

promelas) to 67,000 mg/L for the Inland Silversides (Menidia beryllina). Overall, the acute 

toxicity of 1,4-dioxane to fish is low (European Chemicals Bureau, 2002).

 

 
Page 48 of 54

D-2 Chronic Toxicity to Aquatic Organisms

Table D-2: Aquatic Toxicity Data for 1,4-Dioxane - Chronic Toxicity.

Test Species

Fresh/ 

Salt 

Water

Duration Endpoint

Conc.

(mg/L) Test Analysis Effect References

Aquatic Plants

Green algae 

(Pseudokirchnerella 

subcapitata)

Fresh 72-hour EC50

580

unspecified

growth ECHA 

Assessment 

Report, 2014 1,000 biomass

Aquatic Invertebrates

Water flea 

(Daphnia magna) Fresh 21-day NOEC >1,000 Unspecified Reproduction

ECHA 

Assessment 

Report, 2014

Fish

Medaka (Oryzias latipes)

Fresh 28-day NOEC 565 Measured Not Reported

Johnson et al. 

(1993) as cited 

in EPA’s 

Ecotox 

Database, 

2014

Fathead minnow (Pimphales 

promelas) Fresh 32-day MATC 145 Measured

Development, 

Hatching, 

Survival

TSCATS, (1989) 

as cited in the 

EU RAR (2002)

Toxicity to Aquatic Plants

Only one adequate study is available to characterize the toxicity of 1,4-dioxane to aquatic 

plants. Green algae (Pseudokirchnerella subcapitata) were exposed to unspecified 

concentrations of 1,4-dioxane for 72-hours under static conditions. No effects were observed 

on growth rate or biomass at 1,000 mg/L, the highest concentration tested. A 72-hour EC50

(growth rate and biomass) of > 1,000 mg/L (growth rate) was reported. A NOEC of 580 mg/L 

(biomass) and a NOEC of 1,000 mg/L were reported (ECHA Assessment Report, 2014). This 

study indicates the toxicity of 1,4-dioxane to aquatic plants is low.

Chronic Toxicity to Aquatic Invertebrates

One study is available that characterizes the chronic toxicity of 1,4-dioxane to aquatic 

invertebrates. Water fleas (D. magna) were exposed to unspecified concentrations of 1,4-

dioxane in a 21 day reproduction test. The exposure conditions were not reported. The highest 

exposure concentration tested was 1,000 mg/L. No effects on reproduction, survival or growth 

were reported. A 21-day NOEC of >1,000 mg/L was reported (ECHA Assessment Report, 2014). 

The reported NOEC indicates the chronic effects of 1,4-dioxane to aquatic invertebrates is low.

There are no available studies on the toxicity of 1,4-dioxane to sediment-dwelling organisms. EPA/OPPT

agrees with the EU RAR (European Chemicals Bureau, 2002) that there is low potential of 1,4-dioxane to 

adsorb to sediment and elevated levels are not expected in sediments.
Page 49 of 54

Chronic Toxicity to Fish

There are three available studies that characterize the chronic toxicity of 1,4-dioxane to 

freshwater fish. Medaka (Oryzias latipes) were exposed to measured concentrations of 1,4-

dioxane ranging from 565 to 6,933 mg/L for 28 days under flow-through conditions. The effects 

on growth and survival were reported (Johnson et al., 1993). No effects were seen. A no 

observed effect concentration (NOEC) of 565 mg/L was reported. In another study, fathead 

minnows (P. promelas) were exposed to mean measured concentrations of 27.6, 40.3, 65.3, 

99.7, and 145 mg/L of 1,4-dioxane to observe the effects of the chemical on hatching, 

development and survival for 32 days under flow-through conditions. 1,4-dioxane had no 

significant effects on embryo development, hatching, larvae survival or larvae weight. A NOEC 

of >103 and a maximum acceptable toxicant concentration (MATC) of >145 mg/L were reported 

(European Chemicals Bureau, 2002).

D-3 Terrestrial Plants Toxicity

One study was found that characterizes the hazard of 1,4-dioxane to terrestrial plants. Lettuce 

(Actuca sativa) was exposed to 1,4-dioxane in a germination/root elongation toxicity test for 3-

days. An EC50 of 1,450 mg/L was reported for germination (Reynolds, 1989). This is a nonguideline study. Currently, EPA has no available hazard criteria that applies to this endpoint.

D-4 Soil Invertebrate and Avian Toxicity

There are no available acute or chronic toxicity studies that characterize the hazard of 1,4-

dioxane to soil or terrestrial organisms. However, the toxicity of 1,4-dioxane is expected to be 

low in these environments based on the chemical’s high vapor pressure and it’s propensity to 

volatilize from soil. 1,4-dioxane is slightly volatile from water surfaces and moist soil due to its 

high water solubility. No toxicity data are available for 1,4-dioxane to birds. 
Page 50 of 54

Appendix E Human Health Hazard Studies

The human health studies summarized here and in Table E- are referenced in the EPA IRIS 

Toxicological Review of 1,4-Dioxane (with Inhalation Update) available at: 

http://www.epa.gov/IRIS/toxreviews/0326tr.pdf. 

E-1 Acute Toxicity Studies

Mortality was observed in multiple acute high-dose studies in rats, rabbits, and mice via the 

oral, dermal, or inhalation route. The oral LD50 values calculated for rats ranged from 5,170 –

7,339 mg/kg-bw; the dermal LD50 in rabbits is equal to 7,885 mg/kg-bw, and the inhalation LC50

in mice is equal to 36,700 mg/m3and ranged from 46,000 – 52,000 mg/m3in rats.

E-2 Repeated-Dose Toxicity Studies

Oral Toxicity

A 90-day oral repeated-dose toxicity study in male and female F344 rats and BDF1-mice with 

1,4-dioxane in drinking water (Kano et al, 2008) showed a dose-depended increase in the 

relative weights of the kidney and lung in rats and mice with a relative liver weight increase 

only in rats. A no-observed-adverse-effect level (NOAEL) was determined at 170 mg/kg-bw/day 

in mice and 52 mg/kg-bw/day in rat.

Kociba et al (1974), conducted a study in which Sherman rats were administered 1,4-dioxane in 

drinking water for up to 716 days. No treatment-related effects were observed at the lowest 

dose tested for either sex. Both sexes that were treated at the mid-dose, showed variable 

degrees of renal and hepatic degenerative changes with no occurances of tumors. 

Hepatocellular and renal degenerative changes, and hepatocellular and nasal carcinomas 

observed at the highest dose were considered equivalent to previous reported study results. A 

LOAEL of 94 mg/kg-bw/day and a NOAEL of 9.6 mg/kg-bw/day were determined.

Dermal Toxicity

The 90-day study conducted by Kasai et al (2008) via inhalation does not provided appropriated 

details of the dermal toxicity of 1,4-dioxane.

Inhalation Toxicity

A 90-day repeated-dose toxicity study with F344 with vaporized 1,4-dioxane for 6 hours/day 

and 5/days/week as reported by Kasai (2008), showed mortality at the highest dose tested. 

Histopathological changes in the liver, kidney, nasal epithelium, and lung were observed at 360 

mg/m3. A LOAEC of 360 mg/m3 is based on histopathological changes in the liver, kidney, nasal 

epithelium, and lung.
Page 51 of 54

E-3 Reproductive and Developmental Toxicity Studies

No reproductive toxicity studies have been performed; however, no histopathological changes 

were reported in the reproductive organs of male and female rats/mice exposed to 1,4-dioxane 

in subchronic and chronic studies, which suggests a low concern for reproductive toxicity.

Pregnant female Sprague Dawley rats given 1,4-dioxane by oral gavage in water on gestation 

days 6-15, showed decreases in maternal body weight gain at 1000 mg/kg-bw/day (Giavini et. 

al., 1985). A slight decrease in fetal weight and ossification of the sternebrae was also observed 

at 1000 mg/kg-bw/day.

E-4 Skin Irritation and Sensitization Studies

Clark et al (1994) conducted a dermal irritation assay where male (COBS/Wister rats (number 

not stated) were shaved on specific areas of the back and flank then exposed to a single dose of 

1,4-dioxane at 8,300 mg/kg and observed for 14 days. No treatment-related effects were 

observed. 

The 90-day study conducted by Kasai et al (2008) via inhalation does not provide appropriate 

details of the dermal toxicity of 1,4-dioxane.

E-5 Genotoxicity and Cancer Studies

The genotoxic potential of 1,4-dioxane has been evaluated using in vitro and in vivo assay 

systems. The majority of in vitro assays with 1,4-dioxane were nongenotoxic. Fifty-percent of in 

vivo studies with 1,4-dioxane were positive. EPA’s IRIS program concluded that 1,4-dioxane is 

nongenotoxic or weakly genotoxic based on reviewed gene mutation and chromosome 

aberration studies.

In the Kociba et al (1974) repeated-dose oral drinking water study in rats previously mentioned, 

1,4-dioxane increased tumor progression in the liver via the oral route.

Kasai et al (2009) conducted a two-year bioassay in male F344 rats exposed to 1,4-dioxane via

vapor inhalation at various concentrations for 6 hours/day, 5/days/week. Mortality was 

observed at the mid- and high dose. A statistically significant dose-dependent increase in nasal 

squamous cell carcinomas, hepatocellular adenomas, and peritoneal mesotheliomas were 

observed predominantly at the high dose. Renal cell carcinomas, mammary gland 

fibroadenomas, and adenomas were observed in a dose-dependent manner. Nasal cavity and 

liver preneoplastic lesions were observed at all doses. At 50 ppm, nonneoplastic lesions, 

nuclear enlargement, atrophy, and respiratory metaplasia in the nasal cavity were significantly 

increased. 1,4-Dioxane increased the incidence of tumors in rats.
Page 52 of 54

The IRIS cancer slope factor (CSF) was based on the development of liver tumors in female mice 

(Kano et al, 2009). In this study, male and female F344/DuCrj rats and Crj:BDF(1) mice were 

exposed up to 5000 ppm (rats) and 8000 ppm in mice of 1,4-dioxane in the drinking water for 2 

years. A significant induction of nasal squamous cell carcinomas (females), hepatocellular 

adenomas and carcinomas (males and females), peritoneal mesotheliomas (males), and 

mammary gland adenomas (females) were observed. Mice showed a significant induction of 

hepatocellular tumors in males and females. 

In a supporting study (NCI, 1978), Osborne-Mendel rats (0, 240, and 530 mg/kg-bw/day- males; 

0, 350 and 640 mg/kg-bw/day-females) and B6C3F1 mice (0, 720, and 830 mg/kg-bw/daymales; 0, 380, and 860 mg/kg-bw/day-females) were exposed to 1,4-dioxane (v/v) via drinking 

water for 2-years. 1,4-Dioxane induced squamous-cell carcinomas of the nasal turbinates in 

treated rats and hepatocellular carcinomas in treated mice.
Page 53 of 54

Table E-1: Human Health Endpoints for 1,4-Dioxane.

Endpoint Hazard Determination References

(all are as cited in (US EPA, 2013b))

Acute Oral Toxicity

 LD50 (mg/kg-bw) 5,170 – 7,339 (rat)

Laug et al. (1939); Smyth et al. (1941); 

Nelson (1951); Pozzani et al. (1959); JBRC 

(1998)

Acute Dermal Toxicity

 LD50 (mg/kg-bw) 7,885 (rabbit) Clark et al. (1984)

Acute Inhalation Toxicity

 LC50 (mg/L) 36,700 (mouse)

Fairley et al. (1934); Wirth and Klimmer 

(1936)

46,00 – 52,000 (rat) Failey et al. (1934); Nelson (1951); 

Pozzani et al. (1959)

Repeated-Dose Toxicity

 

Oral (mg/kg-bw/day)

 

 

 Inhalation (mg/L/day)

NOAEL = 170 mg/kg-bw/day (mice); NOAEL = 52 mg/kg-bw/day 

(rat)

Moderate hazard via the oral route based on histopathological 

changes in the liver, kidney and bronchial epithelium

Kano et al. (2008 and 2009)

LOAEL = 94 mg/kg-bw/day; NOAEL = 9.6 mg/kg-bw/day (rat)

High hazard based on degeneration and necrosis of renal cells and 

hepatocytes (non-cancer)

Kociba et al (1974). 

Endpoint used as the point of departure 

(POD) for the IRIS Reference Dose (RfD).

NOAEC = 360 mg/m3(rat)

Moderate hazard via the inhalation route based on 

histopathological changes in the liver, kidney, nasal epithelium, 

and lung

Kasai et al. (2008)

Developmental Toxicity NOAEL = 500; LOAEL = 1,000 mg/kg-bw/day

Low hazard based on delayed ossification of the sternebrae and 

reduced body weights in rats

Giavini et al. (1985)

Reproductive Toxicity No specific reproductive studies have been performed

Low hazard based on no histopathological changes in reproductive 

organs of male and female mice in subchronic and chronic studies.

Giavini et al. (1985)

Genetic Toxicity, gene 

mutation

 In vitro

Nongenotoxic 

Low hazard based on available in vitro studies

Morita and Hayashi (1998); Stott et al. 

(1981); Hellmer and Bolcsfoldi (1992); 

Zimmerman et al. (1985)
Page 54 of 54

Endpoint Hazard Determination References

(all are as cited in (US EPA, 2013b))

 In vivo

Nongenotoxic or weakly genotoxic

Low hazard based on available in vitro and in vivo studies

Roy et al. (2005); Morita and Hayashi 

(1998); Stott et al. (1981)

Genetic Toxicity, 

chromosomal aberrations 

 In vitro

In vivo

Nongenotoxic

Low hazard based on available in vitro studies

Galloway et al. (1987); Morita and 

Hayashi (1998)

Nongenotoxic or weakly genotoxic

Low hazard based on available in vitro and in vivo studies

Miyagawa et al. (1999); Goldsworthy et 

al. (1991); Stott et al. (1981)

Chronic (Non-Cancer)

 Oral

Inhalation

NOAEL = 9.6; LOAEL = 94 mg/kg-bw/day

NOAEL = 170; LOAEL = 387 mg/kg-bw/day

Kociba et al. (1974); Giavini et al. (1985); 

Kano et al. (2008) 

NOAEC = 360 mg/m3

Kasai et al. (2008)

Endpoint used as the POD for IRIS 

Reference Concentration (RfC)

Carcinogenicity

 Oral

 Inhalation

“Likely to be carcinogenic to humans based on evidence of 

carcinogenicity in several 2-year bioassays”

High hazard base on tumor progression in the liver via the oral 

route 

Kociba et al (1974); Kano et al (2009); NCI 

(1978)

“Likely to be carcinogenic to humans based on evidence of 

carcinogenicity in several 2-year bioassays”

High hazard base on tumor progression tumor progression at 

multiple sites via 

inhalation

Kasai et al. (2009)

Dermal Irritation Not irritating Clark et al (1994)

Skin Sensitization No Data Kasai et al. (2008)

Respiratory Sensitization Positive for Sensitization Kasai et al. (2009)