TOXICOLOGICAL PROFILE FOR 

1,4-DIOXANE 

April 2012 
 

 

1,4-DIOXANE ii 

DISCLAIMER 

Use of trade names is for identification only and does not imply endorsement by the Agency for Toxic 

Substances and Disease Registry, the Public Health Service, or the U.S. Department of Health and Human 

Services. 
 

 

 

 

 

 

1,4-DIOXANE iii 

UPDATE STATEMENT 

A Toxicological Profile for 1,4-Dioxane, Draft for Public Comment was released in October 2007. This 

edition supersedes any previously released draft or final profile. 

Toxicological profiles are revised and republished as necessary. For information regarding the update 

status of previously released profiles, contact ATSDR at: 

Agency for Toxic Substances and Disease Registry
	

Division of Toxicology and Environmental Medicine/Applied Toxicology Branch 

1600 Clifton Road NE
	

Mailstop F-62 

Atlanta, Georgia 30333
	
1,4-DIOXANE iv 

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1,4-DIOXANE v 

FOREWORD
	 

This toxicological profile is prepared in accordance with guidelines* developed by the Agency for Toxic 

Substances and Disease Registry (ATSDR) and the Environmental Protection Agency (EPA). The 

original guidelines were published in the Federal Register on April 17, 1987. Each profile will be revised 

and republished as necessary. 

The ATSDR toxicological profile succinctly characterizes the toxicologic and adverse health effects 

information for the toxic substances each profile describes. Each peer-reviewed profile identifies and 

reviews the key literature that describes a substance's toxicologic properties. Other pertinent literature is 

also presented but is described in less detail than the key studies. The profile is not intended to be an 

exhaustive document; however, more comprehensive sources of specialty information are referenced. 

The profiles focus on health and toxicologic information; therefore, each toxicological profile begins with 

a public health statement that describes, in nontechnical language, a substance's relevant toxicological 

properties. Following the public health statement is information concerning levels of significant human 

exposure and, where known, significant health effects. A health effects summary describes the adequacy 

of information to determine a substance's health effects. ATSDR identifies data needs that are significant 

to protection of public health. 

Each profile: 

(A) Examines, summarizes, and interprets available toxicologic information and 

epidemiologic evaluations on a toxic substance to ascertain the levels of significant human 

exposure for the substance and the associated acute, subacute, and chronic health effects; 

(B) Determines whether adequate information on the health effects of each substance is 

available or being developed to determine levels of exposure that present a significant risk to 

human health of acute, subacute, and chronic health effects; and 

(C) Where appropriate, identifies toxicologic testing needed to identify the types or levels of 

exposure that may present significant risk of adverse health effects in humans. 

The principal audiences for the toxicological profiles are federal, state, and local health professionals; 

interested private sector organizations and groups; and members of the public. 

This profile reflects ATSDR’s assessment of all relevant toxicologic testing and information that has been 

peer-reviewed. Staff of the Centers for Disease Control and Prevention and other federal scientists also 

have reviewed the profile. In addition, this profile has been peer-reviewed by a nongovernmental panel 

and was made available for public review. Final responsibility for the contents and views expressed in 

this toxicological profile resides with ATSDR. 

Christopher J. Portier, Ph.D. 

Assistant Administrator
	

Agency for Toxic Substances and Disease Registry
	
 

 

 

 

 

1,4-DIOXANE vi 

*Legislative Background 

The toxicological profiles are developed under the Comprehensive Environmental Response, 

Compensation, and Liability Act of 1980, as amended (CERCLA or Superfund). CERCLA section 

104(i)(1) directs the Administrator of ATSDR to “...effectuate and implement the health related 

authorities” of the statute. This includes the preparation of toxicological profiles for hazardous 

substances most commonly found at facilities on the CERCLA National Priorities List and that pose the 

most significant potential threat to human health, as determined by ATSDR and the EPA. Section 

104(i)(3) of CERCLA, as amended, directs the Administrator of ATSDR to prepare a toxicological profile 

for each substance on the list. In addition, ATSDR has the authority to prepare toxicological profiles for 

substances not found at sites on the National Priorities List, in an effort to “...establish and maintain 

inventory of literature, research, and studies on the health effects of toxic substances” under CERCLA 

Section 104(i)(1)(B), to respond to requests for consultation under section 104(i)(4), and as otherwise 

necessary to support the site-specific response actions conducted by ATSDR. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE vii 

QUICK REFERENCE FOR HEALTH CARE PROVIDERS 

Toxicological Profiles are a unique compilation of toxicological information on a given hazardous 

substance. Each profile reflects a comprehensive and extensive evaluation, summary, and interpretation 

of available toxicologic and epidemiologic information on a substance. Health care providers treating 

patients potentially exposed to hazardous substances will find this information helpful for fast answers to 

often-asked questions. 

Primary Chapters/Sections of Interest 

Chapter 1: Public Health Statement: The Public Health Statement can be a useful tool for educating 

patients about possible exposure to a hazardous substance. It explains a substance’s relevant 

toxicologic properties in a nontechnical, question-and-answer format, and it includes a review of 

the general health effects observed following exposure. 

Chapter 2: Relevance to Public Health: The Relevance to Public Health Section evaluates, interprets, 

and assesses the significance of toxicity data to human health. 

Chapter 3: Health Effects: Specific health effects of a given hazardous compound are reported by type 

of health effect (death, systemic, immunologic, reproductive), route of exposure, and length of 

exposure (acute, intermediate, and chronic). In addition, both human and animal studies are 

reported in this section. 

NOTE: Not all health effects reported in this section are observed in the clinical setting. Please 

refer to the Public Health Statement to identify general health effects observed following 

exposure. 

Pediatrics: Four new sections have been added to each Toxicological Profile to address child health 

issues: 

Section 1.6 How Can (Chemical X) Affect Children?
 

Section 1.7 How Can Families Reduce the Risk of Exposure to (Chemical X)?
 

Section 3.7 Children’s Susceptibility
 

Section 6.6 Exposures of Children
 

Other Sections of Interest: 

Section 3.8 Biomarkers of Exposure and Effect 

Section 3.11 Methods for Reducing Toxic Effects 

ATSDR Information Center 

Phone: 1-800-CDC-INFO (800-232-4636) or 1-888-232-6348 (TTY) Fax: (770) 488-4178 

E-mail: cdcinfo@cdc.gov Internet: http://www.atsdr.cdc.gov 

The following additional material can be ordered through the ATSDR Information Center: 

Case Studies in Environmental Medicine: Taking an Exposure History—The importance of taking an 

exposure history and how to conduct one are described, and an example of a thorough exposure 

history is provided. Other case studies of interest include Reproductive and Developmental 

Hazards; Skin Lesions and Environmental Exposures; Cholinesterase-Inhibiting Pesticide 

Toxicity; and numerous chemical-specific case studies. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE viii 

Managing Hazardous Materials Incidents is a three-volume set of recommendations for on-scene 

(prehospital) and hospital medical management of patients exposed during a hazardous materials 

incident. Volumes I and II are planning guides to assist first responders and hospital emergency 

department personnel in planning for incidents that involve hazardous materials. Volume III— 

Medical Management Guidelines for Acute Chemical Exposures—is a guide for health care 

professionals treating patients exposed to hazardous materials. 

Fact Sheets (ToxFAQs) provide answers to frequently asked questions about toxic substances. 

Other Agencies and Organizations 

The National Center for Environmental Health (NCEH) focuses on preventing or controlling disease, 

injury, and disability related to the interactions between people and their environment outside the 

workplace. Contact: NCEH, Mailstop F-29, 4770 Buford Highway, NE, Atlanta, 

GA 30341-3724 • Phone: 770-488-7000 • FAX: 770-488-7015. 

The National Institute for Occupational Safety and Health (NIOSH) conducts research on occupational 

diseases and injuries, responds to requests for assistance by investigating problems of health and 

safety in the workplace, recommends standards to the Occupational Safety and Health 

Administration (OSHA) and the Mine Safety and Health Administration (MSHA), and trains 

professionals in occupational safety and health. Contact: NIOSH, 200 Independence Avenue, 

SW, Washington, DC 20201 • Phone: 800-356-4674 or NIOSH Technical Information Branch, 

Robert A. Taft Laboratory, Mailstop C-19, 4676 Columbia Parkway, Cincinnati, OH 45226-1998 

• Phone: 800-35-NIOSH. 

The National Institute of Environmental Health Sciences (NIEHS) is the principal federal agency for 

biomedical research on the effects of chemical, physical, and biologic environmental agents on 

human health and well-being. Contact: NIEHS, PO Box 12233, 104 T.W. Alexander Drive, 

Research Triangle Park, NC 27709 • Phone: 919-541-3212. 

Referrals 

The Association of Occupational and Environmental Clinics (AOEC) has developed a network of clinics 

in the United States to provide expertise in occupational and environmental issues. Contact: 

AOEC, 1010 Vermont Avenue, NW, #513, Washington, DC 20005 • Phone: 202-347-4976 

• FAX: 202-347-4950 • e-mail: AOEC@AOEC.ORG • Web Page: http://www.aoec.org/. 

The American College of Occupational and Environmental Medicine (ACOEM) is an association of 

physicians and other health care providers specializing in the field of occupational and 

environmental medicine. Contact: ACOEM, 25 Northwest Point Boulevard, Suite 700, Elk 

Grove Village, IL 60007-1030 • Phone: 847-818-1800 • FAX: 847-818-9266. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE ix 

CONTRIBUTORS 

CHEMICAL MANAGER(S)/AUTHOR(S): 

Sharon Wilbur, M.A.
	

Dennis Jones, D.V.M.
	

John F. Risher, Ph.D
	

Jewell Crawford, M.D.
	

Brian Tencza, M.S.
	

ATSDR, Division of Toxicology and Environmental Medicine, Atlanta, GA
	

Fernando Llados, Ph.D
	

Gary L. Diamond, Ph.D
	

Mario Citra, Ph.D.
	

Mark R. Osier, Ph.D
	

Larry O. Lockwood, Ph.D
	

SRC, Inc., North Syracuse, NY
	

THE PROFILE HAS UNDERGONE THE FOLLOWING ATSDR INTERNAL REVIEWS: 

1. Health Effects Review. The Health Effects Review Committee examines the health effects 

chapter of each profile for consistency and accuracy in interpreting health effects and classifying 

end points. 

2. Minimal Risk Level Review. The Minimal Risk Level Workgroup considers issues relevant to 

substance-specific Minimal Risk Levels (MRLs), reviews the health effects database of each 

profile, and makes recommendations for derivation of MRLs. 

3. Data Needs Review. The Applied Toxicology Branch reviews data needs sections to assure 

consistency across profiles and adherence to instructions in the Guidance. 

4. Green Border Review. Green Border review assures the consistency with ATSDR policy. 
1,4-DIOXANE x 

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1,4-DIOXANE xi 

PEER REVIEW
	

A peer review panel was assembled for 1,4-dioxane. The panel consisted of the following members: 

1. Dr. George Alexeeff, Deputy Director for Scientific Affairs, Office of Environmental Health 

Hazard Assessment, CAL/EPA, Oakland, California; 

2. Dr. Phillip Leber, Consultant in Toxicology, Akron, Ohio; 

3. Dr. Raghubir Sharma, Emeritus Fred C. Davison Distinguished Chair in Toxicology, Department 

of Physiology and Pharmacology, University of Georgia College of Veterinary Medicine, Athens, 

Georgia; and 

4. Dr. Alan Stern, Chief, Bureau for Risk Analysis, Division of Science and Research, Bureau for 

Risk Assessment, New Jersey Department of Environmental Protection, Trenton, New Jersey. 

These experts collectively have knowledge of 1,4-dioxane’s physical and chemical properties, 

toxicokinetics, key health end points, mechanisms of action, human and animal exposure, and 

quantification of risk to humans. All reviewers were selected in conformity with the conditions for peer 

review specified in Section 104(I)(13) of the Comprehensive Environmental Response, Compensation, 

and Liability Act, as amended. 

Scientists from the Agency for Toxic Substances and Disease Registry (ATSDR) have reviewed the peer 

reviewers' comments and determined which comments will be included in the profile. A listing of the 

peer reviewers' comments not incorporated in the profile, with a brief explanation of the rationale for their 

exclusion, exists as part of the administrative record for this compound. 

The citation of the peer review panel should not be understood to imply its approval of the profile's final 

content. The responsibility for the content of this profile lies with the ATSDR. 
1,4-DIOXANE xii 

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1,4-DIOXANE xiii 

CONTENTS
	

DISCLAIMER .............................................................................................................................................. ii
	

UPDATE STATEMENT .............................................................................................................................iii
	

FOREWORD ................................................................................................................................................ v
	

QUICK REFERENCE FOR HEALTH CARE PROVIDERS....................................................................vii
	

CONTRIBUTORS....................................................................................................................................... ix
	

PEER REVIEW ........................................................................................................................................... xi
	

CONTENTS............................................................................................................................................... xiii
	

LIST OF FIGURES .................................................................................................................................. xvii
	

LIST OF TABLES..................................................................................................................................... xix
	

1. PUBLIC HEALTH STATEMENT.......................................................................................................... 1
	

1.1 WHAT IS 1,4-DIOXANE? ............................................................................................................ 1
	

1.2 WHAT HAPPENS TO 1,4-DIOXANE WHEN IT ENTERS THE ENVIRONMENT? ............... 2
	

1.3 HOW MIGHT I BE EXPOSED TO 1,4-DIOXANE? ................................................................... 2
	

1.4 HOW CAN 1,4-DIOXANE ENTER AND LEAVE MY BODY?................................................. 3
	

1.5 HOW CAN 1,4-DIOXANE AFFECT MY HEALTH?.................................................................. 3
	

1.6 HOW CAN 1,4-DIOXANE AFFECT CHILDREN?..................................................................... 4
	

1.7 HOW CAN FAMILIES REDUCE THEIR EXPOSURE TO 1,4-DIOXANE?............................. 5
	

1.8 IS THERE A MEDICAL TEST TO DETERMINE WHETHER I HAVE BEEN 

EXPOSED TO 1,4-DIOXANE? .................................................................................................... 5
	

1.9 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? ................................................................................................... 6
	

1.10 WHERE CAN I GET MORE INFORMATION? .......................................................................... 7
	

2. RELEVANCE TO PUBLIC HEALTH ................................................................................................... 9
	

2.1 BACKGROUND AND ENVIRONMENTAL EXPOSURES TO 1,4-DIOXANE IN THE
	

UNITED STATES ......................................................................................................................... 9
	

2.2 SUMMARY OF HEALTH EFFECTS........................................................................................... 9
	

2.3 MINIMAL RISK LEVELS (MRLs) ............................................................................................ 14
	

3. HEALTH EFFECTS.............................................................................................................................. 29
	

3.1 INTRODUCTION........................................................................................................................ 29
	

3.2 DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE ..................................... 29
	

3.2.1 Inhalation Exposure .............................................................................................................. 31
	

3.2.1.1 Death.............................................................................................................................. 31
	

3.2.1.2 Systemic Effects............................................................................................................. 32
	

3.2.1.3 Immunological and Lymphoreticular Effects................................................................ 52
	

3.2.1.4 Neurological Effects ...................................................................................................... 52
	

3.2.1.5 Reproductive Effects...................................................................................................... 53
	

3.2.1.6 Developmental Effects................................................................................................... 53
	

3.2.1.7 Cancer............................................................................................................................ 54
	

3.2.2 Oral Exposure........................................................................................................................ 54
	

3.2.2.1 Death.............................................................................................................................. 54
	

3.2.2.2 Systemic Effects............................................................................................................. 79
	

3.2.2.3 Immunological and Lymphoreticular Effects................................................................ 85
	

3.2.2.4 Neurological Effects ...................................................................................................... 85
	

3.2.2.5 Reproductive Effects...................................................................................................... 86
	

3.2.2.6 Developmental Effects................................................................................................... 86
	

3.2.2.7 Cancer............................................................................................................................ 87
	
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE xiv 

3.2.3 Dermal Exposure................................................................................................................... 91
	

3.2.3.1 Death.............................................................................................................................. 91
	

3.2.3.2 Systemic Effects............................................................................................................. 94
	

3.2.3.3 Immunological and Lymphoreticular Effects................................................................ 95
	

3.2.3.4 Neurological Effects ...................................................................................................... 95
	

3.2.3.5 Reproductive Effects...................................................................................................... 95
	

3.2.3.6 Developmental Effects................................................................................................... 95
	

3.2.3.7 Cancer............................................................................................................................ 95
	

3.3 GENOTOXICITY........................................................................................................................ 95
	

3.4 TOXICOKINETICS..................................................................................................................... 99
	

3.4.1 Absorption........................................................................................................................... 100
	

3.4.1.1 Inhalation Exposure ..................................................................................................... 100
	

3.4.1.2 Oral Exposure .............................................................................................................. 100
	

3.4.1.3 Dermal Exposure ......................................................................................................... 101
	

3.4.2 Distribution ......................................................................................................................... 102
	

3.4.2.1 Inhalation Exposure ..................................................................................................... 102
	

3.4.2.2 Oral Exposure .............................................................................................................. 102
	

3.4.2.3 Dermal Exposure ......................................................................................................... 102
	

3.4.2.4 Other Routes of Exposure............................................................................................ 102
	

3.4.3 Metabolism.......................................................................................................................... 103
	

3.4.4 Elimination and Excretion................................................................................................... 108
	

3.4.4.1 Inhalation Exposure ..................................................................................................... 108
	

3.4.4.2 Oral Exposure .............................................................................................................. 108
	

3.4.4.3 Dermal Exposure ......................................................................................................... 109
	

3.4.4.4 Other Routes of Exposure............................................................................................ 109
	

3.4.5 Physiologically Based Pharmacokinetic (PBPK)/Pharmacodynamic (PD) Models........... 109
	

3.5 MECHANISMS OF ACTION ................................................................................................... 123
	

3.5.1 Pharmacokinetic Mechanisms............................................................................................. 123
	

3.5.2 Mechanisms of Toxicity...................................................................................................... 124
	

3.5.3 Animal-to-Human Extrapolations....................................................................................... 128
	

3.6 TOXICITIES MEDIATED THROUGH THE NEUROENDOCRINE AXIS........................... 129
	

3.7 CHILDREN’S SUSCEPTIBILITY............................................................................................ 130
	

3.8 BIOMARKERS OF EXPOSURE AND EFFECT ..................................................................... 133
	

3.8.1 Biomarkers Used to Identify or Quantify Exposure to 1,4-Dioxane................................... 134
	

3.8.2 Biomarkers Used to Characterize Effects Caused by 1,4-Dioxane..................................... 135
	

3.9 INTERACTIONS WITH OTHER CHEMICALS ..................................................................... 135
	

3.10 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE................................................ 136
	

3.11 METHODS FOR REDUCING TOXIC EFFECTS.................................................................... 136
	

3.11.1 Reducing Peak Absorption Following Exposure............................................................. 136
	

3.11.2 Reducing Body Burden ................................................................................................... 137
	

3.11.3 Interfering with the Mechanism of Action for Toxic Effects.......................................... 137
	

3.12 ADEQUACY OF THE DATABASE ........................................................................................ 137
	

3.12.1 Existing Information on Health Effects of 1,4-Dioxane.................................................. 137
	

3.12.2 Identification of Data Needs............................................................................................ 138
	

3.12.3 Ongoing Studies .............................................................................................................. 147
	

4. CHEMICAL AND PHYSICAL INFORMATION.............................................................................. 149
	

4.1 CHEMICAL IDENTITY............................................................................................................ 149
	

4.2 PHYSICAL AND CHEMICAL PROPERTIES......................................................................... 149
	
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE xv 

5. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL.......................................................... 153
	

5.1 PRODUCTION .......................................................................................................................... 153
	

5.2 IMPORT/EXPORT .................................................................................................................... 154
	

5.3 USE ............................................................................................................................................ 154
	

5.4 DISPOSAL................................................................................................................................. 157
	

6. POTENTIAL FOR HUMAN EXPOSURE ......................................................................................... 159
	

6.1 OVERVIEW...............................................................................................................................159
	

6.2 RELEASES TO THE ENVIRONMENT................................................................................... 161
	

6.2.1 Air ....................................................................................................................................... 162
	

6.2.2 Water................................................................................................................................... 162
	

6.2.3 Soil ...................................................................................................................................... 165
	

6.3 ENVIRONMENTAL FATE ...................................................................................................... 166
	

6.3.1 Transport and Partitioning................................................................................................... 166
	

6.3.2 Transformation and Degradation ........................................................................................ 167
	

6.3.2.1 Air................................................................................................................................ 167
	

6.3.2.2 Water............................................................................................................................ 168
	

6.3.2.3 Sediment and Soil ........................................................................................................ 169
	

6.3.2.4 Other Media ................................................................................................................. 169
	

6.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT.................................. 170
	

6.4.1 Air ....................................................................................................................................... 170
	

6.4.2 Water................................................................................................................................... 172
	

6.4.3 Sediment and Soil ............................................................................................................... 174
	

6.4.4 Other Environmental Media................................................................................................ 174
	

6.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE........................................ 177
	

6.6 EXPOSURES OF CHILDREN.................................................................................................. 180
	

6.7 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES .............................................. 180
	

6.8 ADEQUACY OF THE DATABASE ........................................................................................ 181
	

6.8.1 Identification of Data Needs ............................................................................................... 181
	

6.8.2 Ongoing Studies.................................................................................................................. 184
	

7. ANALYTICAL METHODS................................................................................................................ 185
	

7.1 BIOLOGICAL MATERIALS.................................................................................................... 185
	

7.2 ENVIRONMENTAL SAMPLES .............................................................................................. 186
	

7.3 OTHER SAMPLES.................................................................................................................... 189
	

7.4 ADEQUACY OF THE DATABASE ........................................................................................ 192
	

7.4.1 Identification of Data Needs ............................................................................................... 194
	

7.4.2 Ongoing Studies.................................................................................................................. 194
	

8. REGULATIONS, ADVISORIES, AND GUIDELINES..................................................................... 197
	

9. REFERENCES .................................................................................................................................... 201
	

10. GLOSSARY ...................................................................................................................................... 221
	

APPENDICES 

A. ATSDR MINIMAL RISK LEVELS AND WORKSHEETS .............................................................A-1
	

B. USER’S GUIDE.................................................................................................................................. B-1
	

C. ACRONYMS, ABBREVIATIONS, AND SYMBOLS...................................................................... C-1
	

D. HEALTH ADVISORY .......................................................................................................................D-1
	

E. INDEX................................................................................................................................................. E-1 
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1,4-DIOXANE xvii 

LIST OF FIGURES 
	

3-1. Levels of Significant Exposure to 1,4-Dioxane-Inhalation ................................................................ 44 

3-2. Levels of Significant Exposure to 1,4-Dioxane-Oral ......................................................................... 74 

3-3. Suggested Metabolic Pathways of 1,4-Dioxane in the Rat............................................................... 104
	

3-4. Conceptual Representation of a Physiologically Based Pharmacokinetic (PBPK) Model for a
	

Hypothetical Chemical Substance.................................................................................................... 111
	

3-5. Existing Information on Health Effects of 1,4-Dioxane................................................................... 139
	

6-1. Frequency of NPL Sites with 1,4-Dioxane Contamination .............................................................. 160
	
1,4-DIOXANE xviii 
 

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1,4-DIOXANE xix 

LIST OF TABLES
	 

3-1. Levels of Significant Exposure to 1,4-Dioxane-Inhalation ................................................................ 33 

3-2. Levels of Significant Exposure to 1,4-Dioxane-Oral ......................................................................... 56 

3-3. Levels of Significant Exposure to 1,4-Dioxane-Dermal .................................................................... 92 

3-4. Genotoxicity of 1,4-Dioxane In Vitro................................................................................................. 96
	

3-5. Genotoxicity of 1,4-Dioxane In Vivo.................................................................................................. 97
	

3-6. Parameters Used in the PBPK Model for 1,4-Dioxane .................................................................... 113
	

3-7. Parameters Used in the Reitz et al. (1990) PBPK Model for 1,4-Dioxane....................................... 116
	

3-8. Parameters Used in the Sweeney et al. (2008) PBPK Model for 1,4-Dioxane................................. 118
	

3-9. Parameters Used in the Takano et al. (2010) PBPK Model for 1,4-Dioxane ................................... 122
	

4-1. Chemical Identity of 1,4-Dioxane .................................................................................................... 150
	

4-2. Physical and Chemical Properties of 1,4-Dioxane ........................................................................... 151
	

5-1. Facilities that Produce, Process, or Use 1,4-Dioxane....................................................................... 155
	

6-1. Releases to the Environment from Facilities that Produce, Process, or Use 1,4-Dioxane................ 163
	

7-1. Analytical Methods for Determining 1,4-Dioxane in Biological Samples....................................... 187
	

7-2. Analytical Methods for Determining 1,4-Dioxane in Environmental Samples................................ 190
	

7-3. Analytical Methods for Determining 1,4-Dioxane in Food and Food Additives, Cosmetics, 

and Ethoxylated Surfactant Samples................................................................................................ 193
	

8-1. Regulations, Advisories, and Guidelines Applicable to 1,4-Dioxane .............................................. 199
	
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1,4-DIOXANE 1 

1. PUBLIC HEALTH STATEMENT 

This public health statement tells you about 1,4-dioxane and the effects of exposure to it. 

The Environmental Protection Agency (EPA) identifies the most serious hazardous waste sites in the 

nation. These sites are then placed on the National Priorities List (NPL) and are targeted for long-term 

federal clean-up activities. 1,4-Dioxane has been found in at least 31 of the 1,689 current or former NPL 

sites. Although the total number of NPL sites evaluated for this substance is not known, the possibility 

exists that the number of sites at which 1,4-dioxane is found may increase in the future as more sites are 

evaluated. This information is important because these sites may be sources of exposure, and exposure to 

this substance may be harmful. 

When a substance is released either from a large area, such as an industrial plant, or from a container, 

such as a drum or bottle, it enters the environment. Such a release does not always lead to exposure. You 

can be exposed to a substance only when you come in contact with it. You may be exposed by breathing, 

eating, or drinking the substance, or by skin contact. 

If you are exposed to 1,4-dioxane, many factors will determine whether you will be harmed. These 

factors include how much (the dose), how long (the duration), and how you come in contact with it. You 

must also consider any other chemicals you are exposed to and your age, sex, diet, family traits, lifestyle, 

and state of health. 

1.1 WHAT IS 1,4-DIOXANE? 

Clear liquid with 

faint odor 

1,4-Dioxane is a clear liquid with a faint pleasant odor. It mixes easily with 

water. 

A solvent and 

laboratory 

reagent 

It is used as a solvent in the manufacture of other chemicals and as a 

laboratory reagent. 

A contaminant 1,4-Dioxane is a trace contaminant of some chemicals used in cosmetics, 

detergents, and shampoos. 

Manufacturers now reduce 1,4-dioxane from these chemicals to low levels 

before these chemicals are made into products used in the home. 
 

 

 

 

 

 

 

 

 

1,4-DIOXANE 2 

1. PUBLIC HEALTH STATEMENT 

1.2 WHAT HAPPENS TO 1,4-DIOXANE WHEN IT ENTERS THE ENVIRONMENT? 

Found in air and 

water 

1,4-Dioxane can be released into the air, water, and soil at places where it is 

produced or used as a solvent. 

In soil, 1,4-dioxane does not stick to soil particles, so it can move from soil 

into groundwater. 

Break down Compounds in the air can break down 1,4-dioxane into different compounds 

rapidly. 

In water, 1,4-Dioxane is stable and does not break down. 

For more information on 1,4-dioxane in the environment, see Chapter 6. 

1.3 HOW MIGHT I BE EXPOSED TO 1,4-DIOXANE? 

Air You can be exposed to 1,4-dioxane by breathing contaminated air. 

Current levels of 1,4-dioxane in air are not known. In the mid-1980s, 

average levels of 1,4-dioxane in air samples from the United States were 

about: 

• 0.4 micrograms per cubic meter (μg/m3

) for outdoor air 

• 4 μg/m3 for indoor air 

Water You can be exposed to 1,4-dioxane in tap water. 

Current levels of 1,4-dioxane in water are not known. In the 1970s, the level 

of 1,4-dioxane in drinking water was 1 microgram per liter of water (1 μg/L). 

Consumer Your skin may come into contact with 1,4-dioxane when you use cosmetics, 

products detergents, and shampoos containing 1,4-dioxane. 

During 1992–1997, the average concentration of 1,4-dioxane in some 

cosmetic products reportedly ranged from 14 to 79 mg/kg. In a more recent 

survey reported by the Campaign for Safe Cosmetics, the levels of 

1,4-dioxane in cosmetic products were found to be lower (1.5–12 ppm in 

baby and children’s products and 2–23 ppm in adult products) than in the 

survey done by the FDA in the 1990s. 

For more information on human exposure to 1,4-dioxane, see Chapter 6. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 3 

1. PUBLIC HEALTH STATEMENT 

1.4 HOW CAN 1,4-DIOXANE ENTER AND LEAVE MY BODY? 

Rapidly enters 

your body 

Skin 

When you breathe air containing 1,4-dioxane, almost all of it will rapidly 

enter your body through your lungs. Almost all of the 1,4-dioxane in your 

drinking water will rapidly enter your body through the digestive tract. 

Studies have found that some 1,4-dioxane can pass through skin when 

applied with certain preparations such as lotions, but much of it will 

evaporate before it can be absorbed. . 

Rapidly leaves 

your body 

Once in your body, 1,4-dioxane is broken down into other chemicals. 

These other chemicals rapidly leave your body in the urine. 

1.5 HOW CAN 1,4-DIOXANE AFFECT MY HEALTH? 

This section looks at studies concerning potential health effects in animal and human studies. 

The effects of 1,4-dioxane on human health depends on how much 1,4-dioxane you are exposed to and 

the length of exposure. The limited environmental monitoring data available suggest that the levels of 

1,4-dioxane to which the general public might be exposed through contact or use of consumer products 

(including food), or that are normally found in environmental media, are generally significantly lower 

than those used in studies with experimental animals. 

Short-term 

exposure effects 

Eye and nose irritation was reported by people exposed to low levels of 

1,4-dioxane for short periods of time. Exposure to very high levels may 

cause severe kidney and liver effects and possibly death. 

Long-term 

exposure effects 

Studies in animals have shown that breathing vapors of 1,4-dioxane affects 

mainly the nasal cavity and the liver and kidneys. Swallowing liquid 

1,4-dioxane or contaminated drinking water, or having skin contact with 

liquid 1,4-dioxane also affects the liver and kidneys. 
 

 

 

 

 

 

 

1,4-DIOXANE 4 

1. PUBLIC HEALTH STATEMENT 

May cause cancer Studies in workers did not indicate whether 1,4-dioxane causes cancer. 

Laboratory rats that breathed vapors of 1,4-dioxane during most of their 

lives developed cancer inside the nose and in the abdominal cavity; they 

also developed benign tumors in the liver. Laboratory rats and mice that 

drank water containing 1,4-dioxane during most of their lives developed liver 

cancer; the rats also developed cancer inside the nose. Some scientists 

believe that 1,4-dioxane may cause cancer by a nongenotoxic mechanism. 

Scientists are debating the degree to which the findings in rats and mice 

apply to exposure situations commonly encountered by people. 

The International Agency for Research on Cancer (IARC) has determined 

that 1,4-dioxane is possibly carcinogenic to humans. 

The U.S. Department of Health and Human Services (HHS) considers 

1,4-dioxane as reasonably anticipated to be a human carcinogen. 

The EPA has established that 1,4-dioxane is likely to be carcinogenic to 

humans. 

Further information on the health effects of 1,4-dioxane in humans and animals can be found in 

Chapters 2 and 3. 

1.6 HOW CAN 1,4-DIOXANE AFFECT CHILDREN? 

This section discusses potential health effects in humans from exposures during the period from 

conception to maturity at 18 years of age. 

Children are likely 

to have similar 

effects as adults 

No data describe the effects of exposure to 1,4-dioxane on children or 

immature animals. It is likely that children would show the same health 

effects as adults. We do not know whether children differ from adults in 

their susceptibility to the effects of 1,4-dioxane. 

Birth defects We do not know whether 1,4-dioxane can harm an unborn child. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 5 

1. PUBLIC HEALTH STATEMENT 

1.7 HOW CAN FAMILIES REDUCE THEIR EXPOSURE TO 1,4-DIOXANE? 

Limit children’s 

exposure to 

consumer 

products which 

may contain 

1,4-dioxane 

1,4-Dioxane may be a contaminant in certain ingredients used in cosmetics, 

detergents, shampoos, and some pharmaceuticals. 1,4-Dioxane is not 

intentionally added, but may occur as an unintentional byproduct in some 

ingredients, that may be listed on the product label, including: 

• PEG 

• polyethylene 

• polyethylene glycol 

• polyoxyethylene 

• -eth 

• -oxynol 

Many products on the market today (foods, pharmaceuticals, cosmetic 

products, detergents, etc.) contain 1,4-dioxane in very small amounts. 

However, some cosmetics, detergents, and shampoos may contain 

1,4-dioxane at levels higher than recommended by the FDA for other 

products. Families wishing to avoid cosmetics containing the ingredients 

listed above may do so by reviewing the ingredient statement that is 

required to appear on the outer container label of cosmetics offered for retail 

sale. 

Limit exposure to 1,4-Dioxane has been detected in some drinking water supplies. Bottled 

contaminated water may be less likely to be contaminated with 1,4-dioxane, and 

drinking water consumers should contact the bottler with specific questions on potential 

contaminants. 

1.8 IS THERE A MEDICAL TEST TO DETERMINE WHETHER I HAVE BEEN EXPOSED TO 

1,4-DIOXANE? 

Can be measured 

in blood and urine 

1,4-Dioxane and its breakdown products (metabolites) can be measured in 

blood and urine. 

The detection of 1,4-dioxane or these metabolites cannot be used to predict 

the kind of health effects that might develop from that exposure. 

The tests need to be conducted within days after exposure because 

1,4-dioxane and its metabolites leave the body fairly rapidly. 

For more information on the different substances formed by 1,4-dioxane breakdown and on tests to detect 

these substances in the body, see Chapters 3 and 7. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 6 

1. PUBLIC HEALTH STATEMENT 

1.9 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

The federal government develops regulations and recommendations to protect public health. Regulations 

can be enforced by law. The EPA, the Occupational Safety and Health Administration (OSHA), and the 

Food and Drug Administration (FDA) are some federal agencies that develop regulations for toxic 

substances. Recommendations provide valuable guidelines to protect public health, but cannot be 

enforced by law. The Agency for Toxic Substances and Disease Registry (ATSDR) and the National 

Institute for Occupational Safety and Health (NIOSH) are two federal organizations that develop 

recommendations for toxic substances. 

Regulations and recommendations can be expressed as “not-to-exceed” levels, that is, levels of a toxic 

substance in air, water, soil, or food that do not exceed a critical value that is usually based on levels that 

affect animals; they are then adjusted to levels that will help protect humans. Sometimes these not-toexceed levels differ among federal organizations because they used different exposure times (an 8-hour 

workday or a 24-hour day), different animal studies, or other factors. 

Recommendations and regulations are also updated periodically as more information becomes available. 

For the most current information, check with the federal agency or organization that provides it. 

Some regulations and recommendations for 1,4-dioxane include the following: 

Levels in drinking 

water set by EPA 

The EPA has determined that exposure to 1,4-dioxane in drinking water at 

concentrations of 4 mg/L for one day or 0.4 mg/L for 10 days is not 

expected to cause any adverse effects in a child. 

Levels in 

workplace air set 

by OSHA 

OSHA set a legal limit of 100 ppm 1,4-dioxane in air averaged over an 

8-hour work day. 

Levels set by NAS The National Academy of Sciences (NAS) established a maximum 

specification of 10 ppm for 1,4-dioxane in the ingredient polysorbate, a food 

additive. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 7 

1. PUBLIC HEALTH STATEMENT 

Levels set by FDA FDA considered 10 ppm to be an acceptable limit for 1,4-dioxane during its 

evaluation of a spermicide, N-9, in a contraceptive sponge product. 

FDA also set a limit on 1,4-dioxane at 10 ppm in approving glycerides and 

polyglycerides for use as excipients in products such as dietary 

supplements. 

FDA keeps a record of raw materials and products contaminated with 

1,4-dioxane. 

1.10 WHERE CAN I GET MORE INFORMATION? 

If you have any more questions or concerns, please contact your community or state health or 

environmental quality department, or contact ATSDR at the address and phone number below. 

ATSDR can also tell you the location of occupational and environmental health clinics. These clinics 

specialize in recognizing, evaluating, and treating illnesses that result from exposure to hazardous 

substances. 

Toxicological profiles are also available on-line at www.atsdr.cdc.gov and on CD-ROM. You may 

request a copy of the ATSDR ToxProfilesTM CD-ROM by calling the toll-free information and technical 

assistance number at 1-800-CDCINFO (1-800-232-4636), by e-mail at cdcinfo@cdc.gov, or by writing 

to: 

Agency for Toxic Substances and Disease Registry
	

Division of Toxicology and Environmental Medicine
	

1600 Clifton Road NE
	

Mailstop F-62 

Atlanta, GA 30333
	

Fax: 1-770-488-4178
	

Organizations for-profit may request copies of final Toxicological Profiles from the following: 

National Technical Information Service (NTIS)
	

5285 Port Royal Road
	

Springfield, VA 22161
	

Phone: 1-800-553-6847 or 1-703-605-6000
	

Web site: http://www.ntis.gov/
	
 

1,4-DIOXANE 8 

1. PUBLIC HEALTH STATEMENT 

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1,4-DIOXANE 9 

2. RELEVANCE TO PUBLIC HEALTH
	

2.1 BACKGROUND AND ENVIRONMENTAL EXPOSURES TO 1,4-DIOXANE IN THE 

UNITED STATES 

1,4-Dioxane is a stable, clear liquid at ambient temperatures and is miscible with water. It is used 

primarily as a solvent for chemical processing. It has also been used as a laboratory reagent; in plastic, 

rubber, insecticides, and herbicides; as a chemical intermediate; as part of a polymerization catalyst; and 

as an extraction medium of animal and vegetable oils. 1,4-Dioxane may also be found as a contaminant 

in ethoxylated surfactants, which are used in consumer cosmetics, detergents, and shampoos. Currently, 

manufacturers remove 1,4-dioxane from ethoxylated surfactants to low levels by vacuum stripping. 

Current levels of 1,4-dioxane in ambient air, drinking water, and food samples are not available. In the 

mid 1980s, levels of 1,4-dioxane in ambient outdoor air ranged from 0.1 to 0.4 μg/m3

 (0.028–0.11 ppb). 

Mean concentrations of 1,4-dioxane in indoor air were a factor of 10 higher at 3.704 μg/m3

 (1.029 ppb). 

In the 1970s, municipal water supplies in the United States were reported to contain 1 μg/L (ppb) of 

1,4-dioxane. 1,4-Dioxane has been detected in food volatiles which may indicate that 1,4-dioxane may be 

a natural constituent in some foods. Volatiles from chicken, meat, tomatoes, and small shrimp have been 

reported to contain 1,4-dioxane at unquantified levels. Dermal exposure to 1,4-dioxane may occur with 

the use of consumer cosmetics, detergents, and shampoos containing ethoxylated surfactants. Between 

the years 1992 and 1997, the average concentration of 1,4-dioxane in cosmetic finished products was 

reported to fluctuate from 14 to 79 ppm (mg/kg). In a more recent survey reported by the Campaign for 

Safe Cosmetics, the levels of 1,4-dioxane in cosmetic products that were tested were found to be lower 

(1.5–12 ppm in baby and children’s products and 2–23 ppm in adult products) than in the survey done by 

the FDA in the 1990s. 

2.2 SUMMARY OF HEALTH EFFECTS 

Limited information exists regarding the health effects of 1,4-dioxane in humans. Yet, the available data 

are sufficient to clearly identify the liver and kidneys as the target organs for 1,4-dioxane toxicity 

following short-term exposure to relatively high amounts of 1,4-dioxane, regardless of the route of 

exposure. This has been corroborated in studies in animals. Workplace exposures to undetermined, but 

presumably high concentrations of 1,4-dioxane have resulted in death. Inhalation was the most likely 

route of exposure, although considerable dermal contact may also have taken place in one of these cases. 

Evaluation of the subjects prior to death did not provide a picture that could be considered unique to 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 10 

2. RELEVANCE TO PUBLIC HEALTH 

1,4-dioxane. Subjects often complained of gastrointestinal pain, had high blood pressure, anuria, and 

leukocytosis, and exhibited signs of nervous system involvement. The deaths occurred 5–8 days after the 

initial symptoms of illness. Postmortem evaluation revealed extensive liver and kidney damage and in 

three out of five cases described in one study, kidney disease was considered to be the direct cause of 

death. Controlled exposures of volunteers to airborne 1,4-dioxane for periods ranging from a few minutes 

to 6 hours produced eye, nose, and throat irritation. The lowest exposure concentration that produced eye 

irritation was 50 ppm during a 6-hour exposure, but exposure in a much older study to 2,000 ppm for 

3 minutes produced no complaints of eye or nasal discomfort. In a more recent study, exposure of 

volunteers to 20 ppm for 2 hours did not induce eye or respiratory irritation. Little is known about longterm exposure to lower concentrations of 1,4-dioxane. A study of workers exposed to 0.006–14.3 ppm 

1,4-dioxane for an average of 25 years found no evidence of liver or kidney disease or any other clinical 

effects. An additional study that examined mortality rates among workers employed at a manufacturing 

and processing facility found no differences between observed and expected incidences of cancer. 

However, this study was limited in size and exposure duration. Although no information was available 

regarding reproductive, developmental, or immunological effects specific to 1,4-dioxane in humans, some 

occupational studies of workers exposed to 1,4-dioxane in combination with other solvents have reported 

elevated rates of spontaneous abortion, stillbirths, premature births, and low birth weights. These effects 

cannot be attributed either solely or in part to 1,4-dioxane. 

Results from a recent 13-week study in rats and a 2-year study in rats indicate that the tissues in the nasal 

cavity are the most sensitive target for 1,4-dioxane following inhalation exposure. Adverse nasal effects 

were seen in rats exposed to ≥100 ppm in the 13-week study and in rats exposed to ≥50 ppm in the 2-year 

study. These exposure concentrations were the lowest tested. The liver and kidneys are also targets of 

1,4-dioxane toxicity in animals following inhalation, oral and dermal exposure. There are no studies of 

the effects of 1,4-dioxane on reproductive function or immunocompetence in animals, and only one study 

in rats evaluated developmental end points following oral exposure during gestation. Slight fetotoxicity 

occurred at 1,033 mg/kg/day, a dose level that also affected the mothers. Chronic inhalation exposure of 

male rats to 1,4-dioxane induced benign tumors in the liver (1,250 ppm but not 250 ppm), squamous cell 

carcinoma in the nasal cavity (1,250 ppm but not 250 ppm), and mesothelioma in the peritoneum 

(≥250 ppm but not 50 ppm). Chronic administration of 1,4-dioxane in the drinking water produced liver 

cancer in rats (range, 398–1,015 mg/kg/day), mice (range, 77–380 mg/kg/day), and guinea pigs 

(1,014 mg/kg/day), and cancer of the nasal cavity in rats (range, 429–833 mg/kg/day). However, a 2-year 

inhalation study in rats exposed to 111 ppm 1,4-dioxane (equivalent to oral doses of approximately 

105 mg/kg/day), provided no evidence of carcinogenicity or any other health effect. The mechanism of 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 11 

2. RELEVANCE TO PUBLIC HEALTH 

carcinogenicity of 1,4-dioxane has not been elucidated, but the lack of or weak genotoxicity of 

1,4-dioxane, its strong promotion properties, and the extensive cytotoxicity observed in some studies at 

dose levels that induce tumors suggest that 1,4-dioxane may be acting through a non-genetic mode of 

action. 

Liver and Cancer Effects. Liver effects have occurred in humans and animals exposed to 

1,4-dioxane, and the data in animals suggest that they occur regardless of the route of exposure. An 

occupational study and a case report provided a detailed description of the liver pathology in subjects 

following exposure to 1,4-dioxane that resulted in deaths within 1–2 weeks after the exposure. Upon 

postmortem examination, enlarged and pale liver and centrilobular necrosis were commonly observed. 

None of the subjects showed jaundice before death. Neither workers exposed to lower concentrations of 

1,4-dioxane for many years nor volunteers exposed for a single 6-hour period to 50 ppm 1,4-dioxane 

showed indications of liver alterations. 

One study provided detailed descriptions of liver pathology in several animal species exposed 

intermittently to 1,4-dioxane by inhalation for a period of up to 13 weeks and also exposed orally and by 

dermal contact. Both lethal and non-lethal concentrations (1,000–10,000 ppm) caused degrees of 

degeneration that varied from cloudy swelling to large areas of complete necrosis. Similar effects were 

seen following oral (1,428 mg/kg/day in rats) and dermal (143 mg/kg/day in guinea pigs; 57 mg/kg/day in 

rabbits) exposure. Hepatocyte vacuolation and swelling were reported in rats and mice dosed with 

1,4-dioxane in the drinking water for 2 weeks (>2,500 mg/kg/day) or 13 weeks (≥126 mg/kg/day in rats; 

>550 mg/kg/day in mice). Evidence of hepatic degenerative changes was seen in Sherman rats that died 

after 2–4 months of receiving doses of 1,015 mg/kg/day 1,4-dioxane via the drinking water in a 2-year 

bioassay. Chronic inhalation exposure of male F344 rats to 1,250 ppm induced hepatic centrilobular 

necrosis and nuclear enlargement. Long-term oral studies in animals described hepatocellular 

degeneration and necrosis in Sherman rats at about 94 mg 1,4-dioxane/kg/day and increased cell foci in 

F344 rats at ≥55 mg/kg/day; hepatocytomegaly was observed in female Osborne-Mendel rats treated with 

approximately 350 mg/kg/day. The apparent different lesions and thresholds for the effects in the liver 

may reflect strain differences. 

The mechanism by which 1,4-dioxane induces liver damage in unknown. Results from some studies 

suggest that toxicity occurs at high doses when the metabolism of 1,4-dioxane is saturated, which would 

suggest that the parent compound is the toxic form. This also is consistent with more recent observations 

that induction of hepatic CYP2B1/2 and CYP2E1 did not play a role in the toxicity of 1,4-dioxane, which 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 12 

2. RELEVANCE TO PUBLIC HEALTH 

suggested that highly reactive and toxic intermediates do not play a major role in the liver toxicity of 

1,4-dioxane, even under conditions of enhanced metabolism. Conversely, it has also been reported that 

the metabolite, 1,4-dioxane-2-one, was several-fold more toxic than 1,4-dioxane based on intraperitoneal 

LD50 determinations in rats. 

All long-term studies in rats dosed with 1,4-dioxane via the drinking water reported an increased 

incidence of liver tumors, generally in the high-dose groups. In the better reported studies, tumor 

development occurred at doses that produced extensive liver toxicity, including hepatocellular hyperplasia 

and degeneration and evidence of hepatic regeneration, which has led some to suggest that cell damage 

and degeneration may be a necessary occurrence for the formation of liver tumors in rats. Oral exposure 

to 1,4-dioxane also induced tumors in the nasal cavity in rats and liver tumors in mice and guinea pigs. 

The relevance of the nasal tumors to humans following oral exposure to 1,4-dioxane has been questioned 

and some scientists suggested that the tumors resulted from inspiration of water containing 1,4-dioxane 

into the nasal cavity. A study reported that the addition of a fluorescent dye mixture to water containing 

0.5% 1,4-dioxane and offered to rats as drinking water resulted in the fluorescent dye readily observed in 

numerous areas in the nasal cavity where bioassays have identified tumors. Little or no fluorescence 

associated with the dye mixture was found in a single rat that received the dye mixture by gavage. One 

study concluded that these results indicate that the rat nasal tissues are exposed by direct contact with 

drinking water under conditions of the bioassay. However, there is also evidence in support of the nasal 

alterations being caused, at least in part, by systemic delivery of either 1,4-dioxane or a metabolite (see 

Section 3.5.2). The lack of nasal cytotoxicity and nasal tumors in Wistar rats exposed intermittently to 

111 ppm 1,4-dioxane in the air for 2 years suggests that the minimal effective dose may not have been 

reached, whether by direct contact alone or a combination of direct contact and internal exposure. 

The mechanism of carcinogenicity of 1,4-dioxane has not been elucidated, but the results from several 

lines of investigation have led some to conclude that 1,4-dioxane has a non-genotoxic, yet unknown, 

mode of action. The EPA has developed cancer risk values for oral exposure to 1,4-dioxane, last revised 

in 2010, based on the increased incidence of hepatocellular adenoma and carcinomas in female Crj:BDF1 

mice in a 2-year drinking-water bioassay. 

Liver toxicity has been proposed to be necessary for liver tumor formation in rats. Since this suggests to 

some scientists the existence of a threshold, they have suggested using approaches other than the 

Linearized Multistage Model for estimating human cancer risk due to exposure to 1,4-dioxane. Based on 

inadequate evidence in humans and sufficient evidence in experimental animals, the International Agency 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 13 

2. RELEVANCE TO PUBLIC HEALTH 

for Research on Cancer (IARC) has determined that 1,4-dioxane is possibly carcinogenic to humans. The 

Department of Health and Human Services (DHHS) has stated that 1,4-dioxane is reasonably anticipated 

to be a human carcinogen based on sufficient evidence of carcinogenicity in experimental animals. The 

EPA has established that 1,4-dioxane is likely to be carcinogenic to humans based on inadequate evidence 

of carcinogenicity in humans and sufficient evidence in animals. 

Renal Effects. Kidney lesions appeared to be the cause of death of five workers who were exposed to 

unknown concentrations of 1,4-dioxane primarily by the inhalation route. Death occurred 1–2 weeks 

after episodes of elevated exposure started at work. All five cases experienced oliguria or anuria. Post 

mortem examination revealed swollen kidneys with hemorrhages and necrosis of the cortex. Similar 

findings were reported in a fatal case report. No renal alterations, as judged by urinalyses, were described 

in other reports of long-term occupational exposure to low levels of 1,4-dioxane or in a group of 

volunteers following a single 6-hour exposure to 50 ppm 1,4-dioxane. Very similar kidney lesions were 

observed in animals exposed to 1,4-dioxane by several routes of exposure. Rodents exposed to acutely 

lethal concentrations of 1,4-dioxane (≥5,000 ppm) showed severe kidney damage consisting of marked 

patchy cell degeneration of the cortical tubules and intense vascular congestion and hemorrhages both 

inter- and intra-tubular. Well-marked kidney lesions were present in animals that survived intermittent 

inhalation exposure to 1,000 ppm 1,4-dioxane for up to 12 weeks. Similar observations were made in 

intermediate-duration studies in rats and mice exposed orally (1,400–2,900 mg 1,4-dioxane/kg/day) and 

in guinea pigs (143 mg/kg) and rabbits (57 mg/kg) following dermal application of 1,4-dioxane. 

Evidence of renal degenerative changes was seen in Sherman rats that died after 2–4 months of treatment 

with 1,015 mg 1,4-dioxane/kg/day in a 2-year drinking water bioassay. Nuclear enlargement of the 

proximal tubule was reported in rats exposed to 657 mg 1,4-dioxane/kg/day in a 13-week study. 

Increased incidence of degeneration and necrosis of the tubular epithelium was seen in rats that received 

94 mg/kg/day and survived until termination of the study, and similar findings were reported in OsborneMendel rats that received 240 mg/kg/day. Nuclear enlargement in the proximal convoluted tubule was 

reported in male F344 rats exposed to ≥250 ppm 1,4-dioxane vapors for 2 years. No compound-related 

neoplastic lesions were observed in the kidneys in other long-term studies conducted with 1,4-dioxane in 

rodents. The mechanism(s) by which 1,4-dioxane induces kidneys lesions is not known, and virtually no 

discussion about this topic was found in the reviews available. The findings in the case studies are 

consistent with an acute nephritic syndrome, which is characterized by oliguria and acute renal failure. It 

is not expected that exposure to concentrations commonly in the environment would cause adverse kidney 

effects in humans. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

	 

 

 

 

1,4-DIOXANE 14 

2. RELEVANCE TO PUBLIC HEALTH 

2.3 MINIMAL RISK LEVELS (MRLs) 

Estimates of exposure levels posing minimal risk to humans (MRLs) have been made for 1,4-dioxane. 

An MRL is defined as an estimate of daily human exposure to a substance that is likely to be without an 

appreciable risk of adverse effects (noncarcinogenic) over a specified duration of exposure. MRLs are 

derived when reliable and sufficient data exist to identify the target organ(s) of effect or the most sensitive 

health effect(s) for a specific duration within a given route of exposure. MRLs are based on 

noncancerous health effects only and do not consider carcinogenic effects. MRLs can be derived for 

acute, intermediate, and chronic duration exposures for inhalation and oral routes. Appropriate 

methodology does not exist to develop MRLs for dermal exposure. 

Although methods have been established to derive these levels (Barnes and Dourson 1988; EPA 1990), 

uncertainties are associated with these techniques. Furthermore, ATSDR acknowledges additional 

uncertainties inherent in the application of the procedures to derive less than lifetime MRLs. As an 

example, acute inhalation MRLs may not be protective for health effects that are delayed in development 

or are acquired following repeated acute insults, such as hypersensitivity reactions, asthma, or chronic 

bronchitis. As these kinds of health effects data become available and methods to assess levels of 

significant human exposure improve, these MRLs will be revised. 

Inhalation MRLs 

•	 An MRL of 2 ppm has been derived for acute-duration inhalation exposure (14 days or less) to 

1,4-dioxane. 

The acute-duration inhalation MRL is based on a no-observed-adverse-effect level (NOAEL) of 20 ppm 

for eye and respiratory irritation and pulmonary function effects in humans (Ernstgård et al. 2006). In 

that study, six male and six female volunteers were exposed to 0 or 20 ppm 1,4-dioxane vapor for 2 hours 

under dynamic conditions. Each subject was exposed on two separate occasions to 0 or 20 ppm. End 

points monitored included self-rated symptoms on a visual analogue scale that measured discomfort of the 

eyes, nose and throat, breathing difficulty, solvent smell, headache, fatigue, nausea, dizziness and ‘feeling 

of intoxication’. Rating was performed before, during (3, 60, and 118 minutes), and after exposure 

(20 and 180 minutes). Respiratory function was assessed by spirometry before exposure, immediately 

after and 3 hours after exposure ceased. The specific parameters measured included vital capacity, forced 

vital capacity, forced expiratory volume in 1 second, peak expiratory flow, and forced expiratory flow at 

25, 50, and 75% of the forced vital capacity. Also assessed was nasal swelling before, immediately after, 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 15 

2. RELEVANCE TO PUBLIC HEALTH 

and 3 hours after exposure. Eye blinking was monitored throughout the exposure period by 

electromyography. Also, two inflammatory markers, high sensitivity C-reactive protein and interleukin 6, 

were measured in blood before and 3 hours after exposure. Exposure to 1,4-dioxane under the conditions 

of the study did not significantly affect any of the end points monitored except the perception of smell of 

the chemical, which increased significantly after 3, 60, and 118 minutes of exposure. The NOAEL of 

20 ppm was divided by an uncertainty factor of 10 (for human variability) to yield the MRL of 2 ppm. 

Support for the acute-duration inhalation MRL of 2 ppm is provided by a study by Young et al. (1977) in 

which four healthy male volunteers were exposed to 50 ppm 1,4-dioxane for 6 hours under dynamic 

airflow conditions. Prior to the study, the subjects provided a complete history and underwent tests 

including chest x-ray, EKG, respiratory function tests, a conventional battery of 12 blood chemistry tests 

plus triglyceride and creatinine determinations, and complete hematological and urine analyses. Except 

for the chest x-ray, the tests were repeated 24 hours and 2 weeks after the exposure. The tests conducted 

24 hours and 2 weeks after exposure did not reveal any exposure-related abnormalities, although no data 

were provided in the study. Eye irritation was a frequent and only complaint throughout the exposure. 

Perception of the odor of 1,4-dioxane diminished with time. Two of the subjects could not perceive the 

odor after 4 and 5 hours in the chamber. The 50 ppm exposure level constitutes a minimal LOAEL for 

eye irritation, although there was no control experiment, and possible low humidity in the exposure 

chamber (not addressed in the report) might have contributed to the eye irritation. 

Other studies with volunteers also support the findings of Ernstgård et al. (2006) and Young et al. (1977). 

For example, Silverman et al. (1946) exposed 12 subjects to various concentrations of 1,4-dioxane for 

only 15 minutes and determined a no-observed-adverse-effect level (NOAEL) of 200 ppm for eye and 

nose irritation; the LOAEL was 300 ppm. Wirth and Klimmer (1936) reported that slight mucous 

membrane irritation started to take place in volunteers exposed to concentrations about 278 ppm for a few 

minutes (unspecified) and that at 1,390 ppm for several minutes, the subjects described prickling in the 

nose and scratchiness and dryness in the throat. Fairley et al. (1934) reported a NOAEL of 2,000 ppm 

(only level tested) for respiratory and ocular effects in six subjects exposed to 1,4-dioxane for only 

3 minutes. Finally, Yant et al. (1930) described slight eye, nose, and throat irritation in a group of five 

subjects exposed to 1,600 ppm (only level tested) 1,4-dioxane for only 10 minutes. The available studies 

in animals used exposure concentrations that often caused death among the animals and were much 

higher than the concentrations tested by Ernstgård et al. (2006) and Young et al. (1977). 
 

 

 

 

 

 

 

 

 

 

 

 

	 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 16 

2. RELEVANCE TO PUBLIC HEALTH 

•	 An MRL of 0.2 ppm has been derived for intermediate-duration inhalation exposure (15–
	

364 days) to 1,4-dioxane.
	

The intermediate-duration database for 1,4-dioxane consists of only two studies: an early study that 

exposed several animal species to high concentrations of 1,4-dioxane and monitored limited end points 

(Fairley et al. 1934); and a recent study that evaluated a comprehensive number of end points in rats 

exposed to several concentrations of 1,4-dioxane (Kasai et al. 2008). Fairley et al. (1934) exposed rats, 

mice, guinea pigs, and rabbits to airborne 1,4-dioxane 3 hours/day, 5 days/week for periods of up to 

12 weeks. At termination, examination of the animals revealed moderate to severe liver and kidney 

toxicity occurring at all exposure levels in all of the species tested. The lowest exposure level was 

1,000 ppm. In the recent study, groups of F344/DuCrj rats (10/sex/group) were exposed to target 

concentrations of 0 (clean air), 100, 200, 400, 800, 1,600, 3,200, or 6,400 ppm 1,4-dioxane vapors 

6 hours/day, 5 days/week for 13 weeks (Kasai et al. 2008). End points evaluated included mortality, 

clinical signs (daily), body weight and food consumption (once per week), hematology, clinical chemistry 

and urinalysis at termination, and gross and microscopic pathology of all major organs and tissues. All 

rats in the 6,400 ppm group died during the first week of the study. Examination of these rats showed 

that death was primarily caused by renal failure, as judged by marked necrosis observed in the renal 

tubules. Lung congestion was also observed in males and females from this exposure group. At the 

remaining exposure concentrations, no abnormal clinical signs were observed during the study. Terminal 

body weight was reduced in all treated groups except the 100 ppm group; the final weight was reduced 

more than 10% relative to controls only in females exposed to 3,200 ppm. Data on food consumption 

were not provided. Significant changes in organ weight (>10% difference with controls) were limited to 

the liver, kidneys, and lungs and consisted of increases in relative organ weight, generally in the high dose 

groups of up to 15% relative to controls; data on absolute organ weights were not provided. Significant 

changes (although within normal values) in hematology and clinical chemistry parameters were limited to 

the 3,200 ppm groups and consisted of increases in mean corpuscular volume and serum alanine 

aminotransferase (ALT) in males, decrease in glucose and triglycerides in males, and increases in red 

blood cell count, hemoglobin, hematocrit, and aspartate aminotransferase (AST) and ALT serum 

activities in females. Histologically, exposure to 1,4-dioxane affected principally the respiratory tract, in 

particular the nasal cavity of males and females. Significant nuclear enlargement of the respiratory 

epithelium was seen in all exposed groups. The incidences in males were 0/10 in the control group and 

7/10, 9/10, 7/10, 10/10, 10/10, and 10/10 in the exposed groups up to 3,200 ppm, respectively. The 

corresponding incidences in females were 0/10, 5/10, 9/10, 10/10, 10/10, 10/10, and 10/10. The severity 

of the lesion was concentration-related. Significant nuclear enlargement of the olfactory epithelium 

started at 200 ppm (5/10 in males and 6/10 in females). Similar lesions in the trachea and bronchus 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 17 

2. RELEVANCE TO PUBLIC HEALTH 

appeared only in the high-exposure groups. The nuclear enlargement was characterized by the epithelial 

cells having a round to oval or elongated nucleus at least 4 times larger in diameter than normal. 

Significantly increased incidence of vacuolic change in the olfactory epithelium started in males at 

400 ppm (0/10, 1/10, 3/10, 6/10, 10/10, 9/10) and in females at 800 ppm (0/10, 1/10, 2/10, 3/10, 7/10, 

9/10, 10/10), while atrophy of the olfactory epithelium started in females at 800 ppm (0/10, 0/10, 2/10, 

3/30, 5/10, 5/10, 4/10) and none was seen in males. Significant single cell necrosis and centrilobular 

swelling occurred in the liver of males exposed to 3,200 ppm 1,4-dioxane; females in this exposure group 

showed only centrilobular swelling. Significant kidney changes were seen only in females from the 

3,200 ppm exposure group and consisted of hydropic changes in the proximal tubule. No treatmentrelated lesions were reported in any other tissue or organ examined. 

Although nuclear enlargement of the respiratory and olfactory epithelium occurred at lower exposure 

levels than other nasal lesions, it was not selected as the critical effect for MRL derivation on the grounds 

that the toxicological significance of the lesion is uncertain. There is some evidence, although not 

conclusive at this time, suggesting that this alteration may represent a preneoplastic lesion. Indeed, 

preneoplastic and neoplastic lesions were observed in rats exposed chronically in the Kasai et al. (2009) 

study. Furthermore, as discussed by Kasai et al. (2008), nuclear enlargement occurred as an early 

histopathological change in the respiratory tract of rats simultaneously exposed to sulfur dioxide and 

treated intraperitoneally with several N-nitrosamines known to induce nasal tumors in rats (Fowlie et al. 

1990). In addition, studies have shown a good correlation between in vivo carcinogenicity and the extent 

of nuclear enlargement in HeLa cells in vitro (Grant and Grasso 1978). Since MRLs are not based on a 

consideration of cancer effects, nuclear enlargement is not considered an appropriate basis for MRL 

derivation. 

Incidence data for vacuolic change in the olfactory epithelium in male and female rats and for atrophy of 

the olfactory epithelium in female rats exposed to 1,4-dioxane vapors (Kasai et al. 2008) were analyzed 

using the benchmark dose/concentration (BMD/BMC) approach for MRL derivation (further details of 

the modeling are presented in Appendix A). A multistage (1-degree) model provided the best fit to the 

vacuolic change in both the male and female data, whereas a log-logistic model provided the best fit for 

the atrophy of the olfactory epithelium in female rats. From these models, the lowest predicted exposure 

concentrations associated with a 10% extra risk (BMC10) was 40.39 ppm and corresponded to vacuolic 

changes in the respiratory epithelium of male rats; the corresponding lower 95% confidence limits on this 

concentration (BMCL10) was 27.99 ppm. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 18 

2. RELEVANCE TO PUBLIC HEALTH 

The BMCL10 of 27.99 ppm was converted to a human equivalent exposure concentration (HEC) 

(BMCL10[HEC]) in consideration of EPA (1994) cross-species dosimetric methodology for inhaled gases. 

Although 1,4-dioxane produces portal-of-entry effects typical of a category 1 gas, it deviates from the 

strict definition of a category 1 gas in that: (1) it is not potently reactive, (2) it enters the systemic 

circulation via portal-of entry tissues, and (3) it induces systemic effects following inhalation exposure 

(i.e., liver and kidney effects). Both (1) and (3) are consistent with category 3 gases; however, atypical of 

a category 3 gas, 1,4-dioxane’s critical effect from repeated inhalation exposure is a portal-of-entry effect 

(nasal lesions). 1,4-Dioxane may be more appropriately classified as a category 2 gas (moderately watersoluble and moderately to slowly reactive in respiratory tissue; EPA 1994); however, the EPA (1994) 

default dosimetric equations for respiratory effects from category 2 gases have not been widely used 

because they lead to human equivalent concentrations that are orders of magnitude lower than 

concentrations administered to rodents. Dosimetric equations for a category 1 gas (based on a ratio of the 

ratios of ventilation rate to extrathoracic surface area in rats to humans) indicate that effects observed in 

rodents at a specific air concentration will occur in humans at lower air concentrations (i.e., a LOAELhuman 

will be about 0.25 x a LOAELrat, or the nasal dose experienced by humans at a specific air concentration 

will be higher than nasal doses experienced by rodents). In contrast, dosimetric equations for category 3 

gases indicate that steady-state blood concentrations (and nasal doses) are determined principally by 

blood:air coefficients, and that, for chemicals like 1,4-dioxane with higher blood:air coefficients in rats 

(1,861; Sweeney et al. 2008) than in humans (1,666; Sweeney et al. 2008), effects observed in rats at a 

specific air concentration will occur in humans at equivalent or higher air concentrations (EPA 1994). 

This means that at a specific air concentration, nasal doses in humans would be equivalent to or less than 

nasal doses in rats. More sophisticated dosimetric cross-species extrapolation approaches have been 

developed for several other nasal toxicants linking computerized fluid dynamic (CFD) nasal airflow 

patterns and species-specific anatomical features with physiologically based pharmacokinetic (PBPK) 

models incorporating species-specific information about diffusion, metabolism, and kinetic distribution of 

the agents among tissues. Predictions from these models indicate that, at a specific air concentration, 

nasal doses would be nearly equivalent between humans and rats (e.g., vinyl acetate [Andersen et al. 

2002]) or would be lower in humans than in rats (methyl acrylate [Andersen et al. 2002]; ethyl acrylate 

[Sweeney et al. 2004]; and formaldehyde [Conolly et al. 2004; Kimbell et al. 2001]). Because of these 

predictions, it is expected that the category 3 gas dosimetric equation is more appropriate for 1,4-dioxane 

than the category 1 gas dosimetric equation. Thus, the EPA (1994) category 3 gas dosimetric equation 

was used in deriving the MRL, in addition to a duration adjustment (6/24 hours x 5/7 days), which was 

considered appropriate in the absence of information regarding whether Haber’s Law is applicable under 

the experimental conditions of the study. 
 

 

 

 

 

 

 

 

 

 

 

 

	 

 

 

 

 

1,4-DIOXANE 19 

2. RELEVANCE TO PUBLIC HEALTH 

The MRL is derived as follows: 

BMCL10[HEC] = BMCL10[ADJ] x (Hb/gA / Hb/gH) 

where:
	

BMCL10[ADJ] = 27.99 ppm x 6/24 hours x 5/7 days = 4.998 ppm and 

Hb/gA = animal blood:air partition coefficient = 1,861 (Sweeney et al. 2008)
	

Hb/gH = human blood:air partition coefficient = 1,666 (Sweeney et al. 2008)
	

(Hb/gA / Hb/gH) = 1,861/1,666 = 1.117 

Because the ratio of the partition coefficients is higher than 1, a default value of 1 is used in accordance 

with EPA’s RfC methodology (EPA 1994). 

BMCL[HEC] = 4.998 ppm x 1 = 4.998 ppm 

Applying an uncertainty factor of 30 (3 for extrapolation from animals to humans with dosimetric 

adjustment and 10 for human variability) to the BMCL[HEC] , rounded to the nearest single digit, yields an 

intermediate-duration inhalation MRL of 0.2 ppm for 1,4-dioxane. 

•	 An MRL of 0.03 ppm has been derived for chronic-duration inhalation exposure (365 days or 

more) to 1,4-dioxane. 

The chronic inhalation database for 1,4-dioxane in humans and animals is limited. An occupational study 

by Thiess et al. (1976) provided no evidence of ill effects in a group of 74 German workers exposed to 

concentrations ranging from 0.006 to 14.3 ppm for an average of 25 years. In another epidemiological 

study, mortality rates were evaluated among workers exposed to 0.1–17 ppm 1,4-dioxane for up to 

21 years (Buffler et al. 1978). No differences were found between observed and expected incidences of 

cancer. These studies were not considered for MRL derivation because they do not provide enough 

information to verify the conclusions of the authors. 

Two chronic-duration inhalation studies in animals are available for 1,4-dioxane (Kasai et al. 2009; 

Torkelson et al. 1974). In a study conducted by Torkelson et al. (1974), groups of Wistar rats (288/sex) 

were exposed to 1,4-dioxane vapors at a concentration of 0.4 mg/L (111 ppm) 7 hours/day, 5 days/week 

for 2 years. Controls were exposed to filtered room air. End points examined included clinical signs, eye 

and nasal irritation, skin condition, respiratory distress, and tumor formation. Hematological parameters 

(hemoglobin, red blood cell count, total and differential leukocyte counts, corpuscular volume) were 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 20 

2. RELEVANCE TO PUBLIC HEALTH 

determined after 16 and 23 months of exposure. Blood collected at termination was used also for 

determination of clinical chemistry parameters (serum ALT and AP activity, BUN, total protein). Liver, 

kidneys, and spleen were weighed and the major tissues and organs were processed for microscopic 

examination. Exposure to 1,4-dioxane vapors had no significant effect on mortality or body weight gain 

and induced no signs of eye or nasal irritation or respiratory distress. Slight but statistically significant 

changes in hematological and clinical chemistry parameters were within the normal physiological limits 

and were considered of no toxicological importance. Organ weights were not significantly affected. 

Microscopic examination of organs and tissues did not reveal treatment-related effects. It should be 

noted, however, that the tissues from the nasal cavity were not listed among the tissues that were 

subjected to microscopic examination by Torkelson et al. (1974), although in the discussion of the results, 

the investigators state that no nasal tumors were observed in any rats. Although there were no clinical 

signs, early mortality, nasal tumors, or any other indication that the health of the rats was compromised in 

the 2-year study, there is uncertainty regarding the possibility that the nuclear enlargement observed in the 

13-week study might progress to cancer. 

Kasai et al. (2009) whole-body exposed groups of male F344/DuCrj rats (50/group) to target 

concentrations of 0, 50, 250, or 1,250 ppm 1,4-dioxane vapors 6 hours/day, 5 days/week for 104 weeks; 

controls were exposed to clean air. End points evaluated included clinical signs and mortality (daily) and 

body weight and food consumption (once/week for the first 14 weeks, every 4 weeks thereafter). All rats 

were subjected to complete necropsy. Blood was collected at termination for clinical chemistry and 

hematology tests; urinary pH was measured in the last week of the study. All major organs were 

removed, weighed, and examined for macroscopic lesions. All major tissues and organs, including the 

entire respiratory tract, were examined microscopically. Survival rates in rats exposed to 250 ppm tended 

to decrease relative to controls, but the difference with controls was not statistically significant. Exposure 

to 1,250 ppm 1,4-dioxane significantly reduced (p<0.05) survival rate beginning on week 91. Terminal 

survival rate was 37/50, 37/50, 29/50, and 25/50 in the control, low-, mid-, and high-exposure groups, 

respectively. The decrease in survival rates was attributed to increased number of deaths due primarily to 

peritoneal mesotheliomas, although nasal tumors contributed to the causes of death. Terminal body 

weight was reduced 6.3% in the high-exposure group. Food consumption was not affected by exposure to 

1,4-dioxane. Statistically significant increases in relative liver (27%) and lung (2%) weights were 

reported in the high-exposure group, but there was no clear dose-response relationship. Significant 

changes in hematology and clinical chemistry tests included reduced hemoglobin (13%), mean 

corpuscular volume (MCV, 6%), mean corpuscular hemoglobin (MCH, 8%), increased serum AST 

(46%), ALT (95%), AP (15%), and gamma-glutamyl transpeptidase (γ-GTP, 6–7-fold); urinary pH was 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 21 

2. RELEVANCE TO PUBLIC HEALTH 

reduced 7%. All of these changes were restricted to the high-exposure group. Treatment-related pre- and 

nonneoplastic lesions occurred in the nasal cavity, liver, and kidney. All exposed groups had significant 

increases in nuclear enlargement of the respiratory epithelium (0/50, 50/50, 48/50, 38/50), nuclear 

enlargement of the olfactory epithelium (0/50, 48/50, 48/50, 45/50), atrophy of the olfactory epithelium 

(0/50, 40/50, 47/50, 48/50), and respiratory metaplasia of the olfactory epithelium (11/50, 34/50, 49/50, 

48/50). Incidences of hydropic change and sclerosis of the lamina propia were significantly increased 

only in the mid- and high-exposure groups. Significant increases in liver lesions (centrilobular nuclear 

enlargement, acidophilic cell foci, basophilic cell foci, spongiosis hepatis, and centrilobular necrosis) 

occurred in the high-exposure group. Significant increases in nuclear enlargement of the proximal kidney 

tubule occurred in the mid- and high-exposure groups; significantly increased incidence of hydropic 

changes in the proximal tubule occurred in the high-exposure group. No significant changes occurred in 

other organs or tissues. The lowest exposure concentration tested, 50 ppm 1,4-dioxane, is a LOAEL for 

nasal lesions (atrophy of the olfactory epithelium); a NOAEL was not defined in this study. 

Of the two available studies, the study by Kasai et al. (2009) was selected for MRL derivation because it 

conducted a complete examination of the respiratory tract, including nasal passages, plus Torkelson et al. 

(1974) established a free-standing NOAEL. The results of Kasai et al. (2009) clearly show that the nasal 

cavity was the most sensitive tissue following 2 years of exposure to 1,4-dioxane vapors. As discussed in 

the derivation of the intermediate-duration inhalation MRL for 1,4-dioxane, nuclear enlargement was not 

considered as the basis of an MRL because of evidence suggesting that the alteration may represent a preneoplastic lesion. Incidences of atrophy (0/50, 40/50, 47/50, and 48/50) and respiratory metaplasia 

(11/50, 34/50, 49/50, and 48/50) of the olfactory epithelium were also significantly elevated at all 

exposure levels tested. Of these two lesions, the atrophy of the olfactory epithelium was selected as the 

critical effect for MRL derivation because it showed a higher incidence rate at the LOAEL than 

respiratory metaplasia. Because the incidence of this lesion at the lowest exposure level (50 ppm) was 

close to the maximal response level (80% of 50-ppm animals showed this lesion), BMD analysis of the 

data was not conducted. This decision is in accordance with guidelines stating that studies in which 

responses are at or near the maximal response level are not considered adequate for BMD analysis (EPA 

2000a). 

The LOAEL of 50 ppm was converted to a HEC using the EPA cross-species dosimetric methodology 

(EPA 1994) for a category 3 gas as explained in the derivation of the intermediate-duration inhalation 

MRL. A duration adjustment (6/24 hours x 5/7 days) seemed appropriate in the absence of information 
 

 

 

 

 

 

 

 

 

 

	 

 

 

 

 

1,4-DIOXANE 22 

2. RELEVANCE TO PUBLIC HEALTH 

regarding whether Haber’s Law is applicable under the experimental conditions of the study. The MRL is 

derived as follows: 

LOAEL[HEC] = LOAEL[ADJ] x (Hb/gA / Hb/gH) 

where:
	

LOAEL[ADJ] = 50 ppm x 6/24 hours x 5/7 days = 8.9286 ppm and 

Hb/gA = animal blood:air partition coefficient = 1,861 (Sweeney et al. 2008)
	

Hb/gH = human blood:air partition coefficient = 1,666 (Sweeney et al. 2008)
	

(Hb/gA / Hb/gH) = 1,861/1,666 = 1.117 

Because the ratio of the partition coefficients is higher than 1, a default value of 1 is used in accordance 

with EPA’s RfC methodology (EPA 1994). 

LOAEL[HEC] = 8.9286 ppm x 1 = 8.9286 ppm 

Applying an uncertainty factor of 300 (10 for use of a LOAEL, 3 for extrapolation from animals to 

humans with dosimetric adjustment, and 10 for human variability) to the LOAEL[HEC] yields a chronicduration inhalation MRL of 0.03 ppm for 1,4-dioxane. 

Oral MRLs 

•	 An MRL of 5 mg/kg/day has been derived for acute-duration oral exposure (14 days or less) to 

1,4-dioxane. 

Only two acute-duration oral studies potentially useful for MRL derivation are available for 1,4-dioxane. 

JRBC (1998) conducted a 2-week drinking water study in F344 rats and B6C3F1 mice and reported that 

the most sensitive effect was an increased incidence of nuclear enlargement of the olfactory epithelium in 

male and female rats receiving doses of approximately 1,010 and 1,040 mg 1,4-dioxane/kg/day, 

respectively; the corresponding NOAELs were 370 and 400 mg/kg/day. Liver and kidney alterations 

were observed at higher doses. Giavini et al. (1985) administered 1,4-dioxane by gavage in water to 

pregnant Sprague-Dawley rats on gestation days (Gd) 6 through 15 and reported slight but significant 

reductions in fetal weight and in the percent of ossified sternebrae in the group treated with the highest 

dose of 1,4-dioxane, 1,033 mg/kg/day; the NOAEL was 516 mg/kg/day. Most of the rest of the acute 

database consists of high-dose early studies aimed mainly at determining LD50 values and inadequate for 

risk assessment (de Navasquez 1935; Kesten et al. 1939; Laug et al. 1939; Pozzani et al. 1959; Smyth et 

al. 1941). The lowest dose that caused lethality was 327 mg 1,4-dioxane/kg/day in a study that tested 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 23 

2. RELEVANCE TO PUBLIC HEALTH 

only three dogs (Schrenk and Yant 1936). This dose was provided in the drinking water and resulted in 

the death of one dog after 10 days of treatment. Doses of 375 mg/kg/day resulted in the death of another 

dog in 9 days. However, because the dogs were allowed to drink the 1,4-dioxane solution only twice 

daily and no other source of water was available, dehydration may have played a role in the death of the 

animals. 

Of the two potentially useful studies for MRL derivation mentioned above, the developmental study 

conducted by Giavini et al. (1985) is preferred as basis for the acute-duration oral MRL for 1,4-dioxane 

mainly due to overall deficiencies in the JRBC (1998) study, namely, lack of statistical analysis of the 

results due to the fact that only 2 or 3 animals (out of 10/group) were examined, and the fact that end 

points such as hematology, clinical chemistry, clinical signs, and gross examinations were not conducted 

or reported. These limitations severely compromise the interpretation of the results. 

In the study selected as basis for the acute oral MRL, groups of 17–20 pregnant Sprague-Dawley rats 

were treated with 0, 0.25, 0.5, or 1 mL 1,4-dioxane/kg/day (0, 258, 516, or 1,033 mg 1,4-dioxane/kg/day 

based on a specific gravity of 1.034) by gavage in water on Gd 6–15 (Giavini et al. 1985). Food 

consumption was determined daily and body weight was monitored every three days. Sacrifices were 

conducted on Gd 21 and the number of corpora lutea, implantations, resorptions and live fetuses was 

recorded. The fetuses were weighed and inspected for external malformations and half were examined 

for visceral abnormalities and the other half for skeletal malformations. Rats treated with 1,033 mg 

1,4-dioxane/kg/day gained 18% less weight than controls during treatment days, although the difference 

was not statistically significant. Food consumption was slightly (5%) but significantly (p<0.05) reduced 

in these rats during treatment. The average fetal weight in the high-dose group was slightly but 

significantly (p<0.01) lower than in controls. Also, a slight but significant (p<0.05) reduction in sternum 

ossification was seen in high-dose fetuses. There were no significant effects on the number of 

implantations and live fetuses, post-implantation loss, or incidence of malformations. Based on the 

reduced maternal and fetal body weight and reduced sternum ossification, a maternal and developmental 

LOAEL of 1,033 mg 1,4-dioxane/kg/day can be defined; the maternal and developmental NOAEL is 

516 mg/kg/day. Attempts made to apply dose-response models to the data were unsuccessful, as no 

adequate fits of EPA BMDS models to the data were obtained; therefore, the NOAEL/LOAEL approach 

was used for MRL derivation. An acute-duration oral MRL of 5 mg/kg/day was derived for 1,4-dioxane 

by dividing the NOAEL of 516 mg/kg/day by an uncertainty factor of 100 (10 for animal to human 

extrapolation and 10 for human variability). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

	 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 24 

2. RELEVANCE TO PUBLIC HEALTH 

•	 An MRL of 0.5 mg/kg/day has been derived for intermediate-duration oral exposure (15–
	

364 days) to 1,4-dioxane.
	

The intermediate-duration oral MRL is based on a NOAEL of 52 mg 1,4-dioxane/kg/day for liver effects 

in rats (Kano et al. 2008). In that study, groups of F344/DuCrj rats (10/sex/group) were administered 

1,4-dioxane in the drinking water in concentrations of 0, 640, 1,600, 4,000, 10,000, or 25,000 ppm for 

13 weeks (0, 52, 126, 274, 657, or 1,554 mg/kg/day in males; 0, 83, 185, 427, 756, or 1,614 mg/kg/day in 

females, estimated by the investigators). End points evaluated included clinical signs, food and water 

consumption, body weight, complete hematology and clinical chemistry tests, urinalysis, organ weights, 

gross necropsy, and histopathology. One female in the 1,614 mg/kg/day group died. Body weight gain 

was reduced at 756 mg/kg/day (12%) and 1,614 mg/kg/day (21%) in females and at 1,554 mg/kg/day 

(21%) in males. Food consumption was reduced 13% in females at 1,614 mg/kg/day. Water 

consumption was reduced in a dose-related manner in all male groups and in females at ≥126 mg/kg/day. 

Hematology tests showed significant increases in erythrocyte counts, hemoglobin, hematocrit, and 

neutrophils, and a decrease in lymphocytes in males at 1,554 mg/kg/day, and decreases in mean 

corpuscular volume and platelets in females at 1,614 mg/kg/day. Total protein and albumin were 

decreased in males at ≥274 mg/kg/day and in females at ≥427 mg/kg/day. Serum AST, ALT, alkaline 

phosphatase (AP), and leucine aminopeptidase (LAP) activities, and levels of cholesterol, triglycerides, 

sodium, and glucose were significantly elevated in high dose males and females. Urinary pH was 

decreased in males at ≥274 mg/kg/day and in females at ≥756 mg/kg/day. Absolute and relative kidney 

weights were increased in females at ≥231 mg/kg/day. Nuclear enlargement of the respiratory epithelium 

occurred in males at ≥126 mg/kg/day and in females at ≥185 mg/kg/day; nuclear enlargement of the 

olfactory and tracheal epithelium occurred in males at ≥274 mg/kg/day and in females at ≥427 mg/kg/day. 

Swelling of the central area of the liver was observed in males at ≥126 mg/kg/day and in females at 

≥756 mg/kg/day, and vacuolar changes in the liver occurred in males at ≥657 mg/kg/day and in females at 

1,614 mg/kg/day. The incidences of swelling of the central area of the liver in males were 0/10, 0/10, 

9/10, 10/10, 10/10, and 10/10 in the control, 52, 126, 274, 657, and 1,554 mg/kg/day dose groups, 

respectively. Nuclear enlargement of the proximal tubule of the kidneys was seen in males at 

≥657 mg/kg/day and in females at ≥756 mg/kg/day. Hydropic changes in the proximal tubule of the 

kidneys and vacuolar changes in the brain occurred in high-dose males and females (1,554 and 

1,614 mg/kg/day, respectively). The study LOAEL was 126 mg/kg/day for liver effects in male rats. 

Limitations of the study include the lack of reporting on clinical signs and gross necropsy. To derive the 

MRL, the NOAEL of 52 mg/kg/day for liver effects in males was divided by an uncertainty factor of 

100 (10 for animal to human extrapolation and 10 for human variability), yielding an intermediate-
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

	 

 

 

1,4-DIOXANE 25 

2. RELEVANCE TO PUBLIC HEALTH 

duration oral MRL of 0.5 mg/kg/day. The steepness of the dose-response relationship for liver lesions 

rendered the data set inadequate for BMD analysis. 

A promotion study by Lundberg et al. (1987) supports the liver findings of Kano et al. (2008). The study 

used male Sprague-Dawley rats (8–11/group) that were treated with 100 or 1,000 mg 1,4-dioxane/kg by 

gavage in saline 5 days/week for 7 weeks. One week after the last treatment, the rats were sacrificed, and 

the livers were processed for microscopic examination. The livers of high-dose rats showed enlarged 

foamy hepatocytes mainly in midzonal regions. The foamy appearance was due to vacuoles shown to 

contain fat. No treatment-related histopathological alterations were observed in the liver at the 

100 mg/kg/day dose level. Because of the limited scope of the study by Lundberg et al. (1987) (only the 

liver was examined) and because the NOAEL of 100 mg/kg/day is practically the same as the LOAEL of 

126 mg/kg/day identified by Kano et al. (2008), the latter study was preferred for MRL derivation. Also 

supporting the findings from Kano et al. (2008) is a report by Stott et al. (1981) who found that repeated 

dosing of rats with 1,000 mg 1,4-dioxane/kg/day for 7 or 11 weeks produced hepatocyte swelling and 

histopathology. Similar findings were reported in an earlier study in which rats were treated with doses of 

approximately 1,428 mg 1,4-dioxane/kg/day in the drinking water for 34 days (Fairley et al. 1934). 

Although available rat and mouse PBPK models (Leung and Paustenbach 1990; Reitz et al. 1990; 

Sweeney et al. 2008) provide adequate fits of high-dose observations, they do not perform well against 

low-dose data; thus, they were not used for MRL derivation. The human model could not replicate the 

limited human experimental inhalation data available (Sweeney et al. 2008). Further, it assumes 

equivalency with mice in eliminating β-hydroxyethoxyacetic acid (HEAA), and has no value derived for 

oral absorption. Based on these significant limitations, the Sweeney et al. (2008) model for 1,4-dioxane 

in rats, mice, and humans, which is a more refined version of the earlier models, is not adequate for MRL 

derivation. This applies also to the use of PBPK models for derivation of the chronic-duration oral MRL 

for 1,4-dioxane described below. 

•	 An MRL of 0.1 mg/kg/day has been derived for chronic-duration oral exposure (365 days or 

more) to 1,4-dioxane. 

The chronic-duration oral MRL is based on a NOAEL of 9.6 mg 1,4-dioxane/kg/day for liver effects in 

male rats in a study by Kociba et al. (1974). In that study, groups of Sherman rats (60/sex/dose level) 

were treated with 1,4-dioxane in the drinking water at levels of 0 (controls), 0.01, 0.1, or 1% for 716 days. 

Based on body weight and water consumption data, the investigators estimated that the water provided 

doses of 1,4-dioxane of 0, 9.6, 94, and 1,015 mg/kg/day for males and 0, 19, 148, and 1,599 mg/kg/day 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 26 

2. RELEVANCE TO PUBLIC HEALTH 

for females. Blood samples were collected from controls and high-dose rats during the 4th, 6th, 12th, and 

18th months of the study and at termination. Additional end points evaluated included clinical signs, 

body weight, organ weights, and gross and microscopic examination of major tissues and organs. 

Treatment with 1,4-dioxane significantly increased mortality in males dosed with 1,015 mg/kg/day and in 

females dosed with 1,599 mg/kg/day beginning at about 2–4 months of treatment. These rats showed 

degenerative changes in both the liver and kidneys. Rats in these groups also showed significantly 

reduced water consumption during the first year of the study and body weight gain was significantly 

reduced from the beginning of the study. Microscopic lesions in other groups were restricted to the liver 

and kidneys in males treated with ≥94 mg/kg/day and females dosed with ≥148 mg/kg/day. The liver 

lesions consisted of various degrees of hepatocellular degeneration and necrosis and evidence of hepatic 

regeneration as indicated by hepatocellular hyperplastic nodule formation. The NOAEL for liver effects 

was 9.6 mg/kg/day in males and 19 mg/kg/day in females. The LOAELs were 94 mg/kg/day in males 

and 148 mg/kg/day in females. The kidneys showed tubular epithelial degeneration and necrosis, and 

there was evidence of renal tubular regeneration as indicated by increased tubular epithelial regenerative 

activity (≥94 mg/kg/day in males and ≥148 mg/kg/day in females). There were no compound-related 

alterations in hematological parameters at any time point. The MRL of 0.1 mg/kg/day was calculated by 

dividing the male rat NOAEL of 9.6 mg/kg/day by an uncertainty factor of 100 (10 for animal to human 

extrapolation and 10 for human variability). The lack of quantitative information regarding incidences of 

non-neoplastic lesions precludes the use of BMD methodology for MRL derivation. 

The NOAEL and LOAEL for liver effects from Kociba et al. (1974) are supported by the results of Kano 

et al. (2009). In that study, groups of F344/DuCrj rats (50/sex/dose level) received 1,4-dioxane in the 

drinking water for 104 weeks. 1,4-Dioxane was administered at levels of 0, 200, 1,000, and 5,000 ppm 

for 2 years (0, 11, 55, and 274 mg/kg/day for males; 0, 18, 83, and 429 mg/kg/day for females). End 

points evaluated included clinical signs, food and water consumption, body and organ weights, and gross 

and microscopic examination of major organs and tissues. Terminal body weight was reduced 9% in 

high-dose males (274 mg/kg/day) and 20% in high-dose females (429 mg/kg/day). In males, relative liver 

weight was significantly increased at 55 mg/kg/day (14%) and 274 mg/kg/day (72%). A significant 

increase incidence of mixed cell foci was observed in the liver from male rats dosed with ≥55 mg 

1,4-dioxane/kg/day. Increased incidence of acidophilic and mixed cell foci were reported in the liver 

from high-dose females (429 mg/kg/day). In addition, both high-dose male (274 mg/kg/day) and female 

(429 mg/kg/day) rats had significantly increased incidence of nuclear enlargement and squamous cell 

metaplasia of the respiratory epithelium; females dosed with ≥83 mg 1,4-dioxane/kg/day also showed a 

significantly increased incidence of nuclear enlargement of the nasal olfactory epithelium. 
 

 

 

 

 

 

1,4-DIOXANE 27 

2. RELEVANCE TO PUBLIC HEALTH 

The NCI (1978) bioassay in Osborne-Mendel rats used somewhat higher dose levels than Kociba et al. 

(1974) and Kano et al. (2009), but did not observe liver lesions in male rats dosed with 240 mg 

1,4-dioxane/kg/day. However, a dose level of 55 mg/kg/day induced cell foci in the liver from male 

F344 rats, and 94 mg/kg/day caused hepatocyte degeneration in Sherman rats. Since the dosing method 

was the same in all three studies (via the drinking water) the different results may reflect differences in 

strain sensitivity. 
 

1,4-DIOXANE 28 

2. RELEVANCE TO PUBLIC HEALTH 

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1,4-DIOXANE 29 

3. HEALTH EFFECTS 

3.1 INTRODUCTION 

The primary purpose of this chapter is to provide public health officials, physicians, toxicologists, and 

other interested individuals and groups with an overall perspective on the toxicology of 1,4-dioxane. It 

contains descriptions and evaluations of toxicological studies and epidemiological investigations and 

provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health. 

A glossary and list of acronyms, abbreviations, and symbols can be found at the end of this profile. 

3.2 DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE 

To help public health professionals and others address the needs of persons living or working near 

hazardous waste sites, the information in this section is organized first by route of exposure (inhalation, 

oral, and dermal) and then by health effect (death, systemic, immunological, neurological, reproductive, 

developmental, genotoxic, and carcinogenic effects). These data are discussed in terms of three exposure 

periods: acute (14 days or less), intermediate (15–364 days), and chronic (365 days or more). 

Levels of significant exposure for each route and duration are presented in tables and illustrated in 

figures. The points in the figures showing no-observed-adverse-effect levels (NOAELs) or lowestobserved-adverse-effect levels (LOAELs) reflect the actual doses (levels of exposure) used in the studies. 

LOAELs have been classified into "less serious" or "serious" effects. "Serious" effects are those that 

evoke failure in a biological system and can lead to morbidity or mortality (e.g., acute respiratory distress 

or death). "Less serious" effects are those that are not expected to cause significant dysfunction or death, 

or those whose significance to the organism is not entirely clear. ATSDR acknowledges that a 

considerable amount of judgment may be required in establishing whether an end point should be 

classified as a NOAEL, "less serious" LOAEL, or "serious" LOAEL, and that in some cases, there will be 

insufficient data to decide whether the effect is indicative of significant dysfunction. However, the 

Agency has established guidelines and policies that are used to classify these end points. ATSDR 

believes that there is sufficient merit in this approach to warrant an attempt at distinguishing between 

"less serious" and "serious" effects. The distinction between "less serious" effects and "serious" effects is 

considered to be important because it helps the users of the profiles to identify levels of exposure at which 

major health effects start to appear. LOAELs or NOAELs should also help in determining whether or not 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 30 

3. HEALTH EFFECTS 

the effects vary with dose and/or duration, and place into perspective the possible significance of these 

effects to human health. 

The significance of the exposure levels shown in the Levels of Significant Exposure (LSE) tables and 

figures may differ depending on the user's perspective. Public health officials and others concerned with 

appropriate actions to take at hazardous waste sites may want information on levels of exposure 

associated with more subtle effects in humans or animals (LOAELs) or exposure levels below which no 

adverse effects (NOAELs) have been observed. Estimates of levels posing minimal risk to humans 

(Minimal Risk Levels or MRLs) may be of interest to health professionals and citizens alike. 

Levels of exposure associated with carcinogenic effects (Cancer Effect Levels, CELs) of 1,4-dioxane are 

indicated in Table 3-2 and Figure 3-2. Because cancer effects could occur at lower exposure levels, 

Figure 3-2 also shows a range for the upper bound of estimated excess risks, ranging from a risk of 1 in 

10,000 to 1 in 10,000,000 (10-4 to 10-7), as developed by EPA. 

Estimates of exposure levels posing minimal risk to humans (MRLs) have been made for 1,4-dioxane. 

An MRL is defined as an estimate of daily human exposure to a substance that is likely to be without an 

appreciable risk of adverse effects (noncarcinogenic) over a specified duration of exposure. MRLs are 

derived when reliable and sufficient data exist to identify the target organ(s) of effect or the most sensitive 

health effect(s) for a specific duration within a given route of exposure. MRLs are based on 

noncancerous health effects only and do not consider carcinogenic effects. MRLs can be derived for 

acute, intermediate, and chronic duration exposures for inhalation and oral routes when suitable data are 

available. Appropriate methodology does not exist to develop MRLs for dermal exposure. 

Although methods have been established to derive these levels (Barnes and Dourson 1988; EPA 1990), 

uncertainties are associated with these techniques. Furthermore, ATSDR acknowledges additional 

uncertainties inherent in the application of the procedures to derive less than lifetime MRLs. As an 

example, acute inhalation MRLs may not be protective for health effects that are delayed in development 

or are acquired following repeated acute insults, such as hypersensitivity reactions, asthma, or chronic 

bronchitis. As these kinds of health effects data become available and methods to assess levels of 

significant human exposure improve, these MRLs will be revised. 

A User's Guide has been provided at the end of this profile (see Appendix B). This guide should aid in 

the interpretation of the tables and figures for Levels of Significant Exposure and the MRLs. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 31 

3. HEALTH EFFECTS 

3.2.1 Inhalation Exposure 

3.2.1.1 Death 

Several cases of death in humans have been documented after exposure to high concentrations of 

1,4-dioxane. Barber (1934) described five deaths that occurred within a period of 2 weeks among factory 

workers engaged in a process that involved primarily exposure to 1,4-dioxane vapors, although minimal 

dermal exposure could not have been avoided. Three of the subjects suffered from abdominal pain and 

vomiting before death occurred. Post-mortem examination of the subjects showed extensive gross and 

microscopic lesions to the liver and kidneys. Based on his observations, Barber (1934) suggested that the 

effects on the kidneys may have been responsible for the fatal outcome and that liver necrosis, although 

widespread, was compatible with recovery. No exposure levels were available in these case reports. 

Johnstone (1959) described an additional fatal case of a worker exposed to 1,4-dioxane for only 1 week 

and whose post-mortem examination showed kidney and liver alterations similar to those described by 

Barber (1934). In the Johnstone case, the room in which the patient had worked had no exhaust 

ventilation and the worker was not provided a respirator. The minimum concentration of 1,4-dioxane in 

the room was 208 ppm and the maximum was in excess of 650 ppm; the average concentration was 

470 ppm. In addition, dermal exposure may have been considerable in this case. 

Studies in animals, mostly early studies, provide information on lethality of relatively high concentrations 

of 1,4-dioxane in several species and also indicate that the kidneys and liver, and in some cases, the lungs, 

are the main targets of high airborne concentrations of 1,4-dioxane. Short-term exposure to 5,000 ppm 

1,4-dioxane was lethal to rats, mice, and rabbits, whereas 10,000 ppm was lethal to guinea pigs (Fairley et 

al. 1934). A 4-hour LC50 of 14,261 ppm was calculated for rats (Pozzani et al. 1959). An additional 

study in guinea pigs reported that the minimum period of exposure that caused the death of the majority 

of a group of six animals was 180 minutes to 30,000 ppm; no deaths occurred in groups exposed to up to 

10,000 ppm for up to 480 minutes (Yant et al. 1930). One out of four rabbits exposed to 2,000 ppm 

1,4-dioxane 3 hours/day, 5 days/week died on week 4 of exposure, and the cause of death was attributed 

to renal and hepatic lesions (Fairley et al. 1934). In a more recent 13-week intermittent exposure study, 

all rats (10/sex) exposed to 6,400 ppm 1,4-dioxane vapors 6 hours/day, 5 days/week died during the first 

week of the study (Kasai et al. 2008). The primary cause of death was reported to be renal failure, as 

judged by marked necrosis of the renal tubules. Similar exposure of male rats to 1,250 ppm 1,4-dioxane 

for 2 years significantly decreased survival rate relative to controls beginning on week 91 of the study 

(Kasai et al. 2009). This was attributed to increased number of deaths due primarily to peritoneal 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 32 

3. HEALTH EFFECTS 

mesotheliomas, although nasal tumors also contributed. Exposure to 250 ppm 1,4-dioxane did not 

significantly decrease survival rates. 

The LOAEL values for death in each species and duration category are recorded in Table 3-1 and plotted 

in Figure 3-1. 

3.2.1.2 Systemic Effects 

No studies were located regarding musculoskeletal, endocrine, dermal, or body weight effects in humans 

after inhalation exposure to 1,4-dioxane. 

The highest NOAEL and all reliable LOAEL values from each study for systemic effects in each species 

and duration category are recorded in Table 3-1 and plotted in Figure 3-1. 

Respiratory Effects. In a group of six individuals exposed to 2,000 ppm 1,4-dioxane vapors for 

3 minutes in a 10 m3 chamber, there were no complaints of nasal discomfort, but one out of four subjects 

exposed to 1,000 ppm for 5 minutes complained of constriction of the throat (Fairley et al. 1934); 

however, the exposure concentrations were not verified. Exposure of five subjects to about 278 ppm for a 

few minutes (unspecified) produced slight mucous membrane irritation, and 1,390 ppm caused a slight 

prickling in the nose and scratchiness and dryness in the throat (Wirth and Klimmer 1936). Exposure to 

300 ppm 1,4-dioxane for 15 minutes produced nose and throat irritation among a group of 12 volunteers 

(Silverman et al. 1946). At 200 ppm, the report does not indicate the presence or absence of symptoms, 

but considers the exposure acceptable. A 10-minute exposure to 1,600 ppm 1,4-dioxane produced slight 

nose and throat irritation that persisted throughout the test in a group of five individuals (Yant et al. 

1930). In another experiment by the same investigators, exposure of the same five persons to 5,500 ppm 

1,4-dioxane for 1 minute resulted in a burning sensation to the nose and throat (Yant et al. 1930). 

Exposure of four men to 50 ppm for 6 hours reportedly caused no adverse respiratory signs or alterations 

in respiratory function, assessed 24 hours and 2 weeks after exposure (Young et al. 1977); however, no 

data were provided in the study. Exposure of 12 volunteers (6 males and 6 females) to 20 ppm 

1,4-dioxane for 2 hours caused no significant respiratory effects during exposure or up to 3 hours after 

exposure (Ernstgård et al. 2006). Subjective symptoms were assessed with a questionnaire and 

respiratory function was assessed by spirometry. Also assessed was nasal swelling. The study by 

Ernstgård et al. (2006) was used to derive an acute-duration inhalation MRL for 1,4-dioxane. 
44

5000

139

6400

59

14261

45

5000

42

10000

38

30000

43

5000

Table 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) 

ACUTE EXPOSURE Death 

1 Rat 

(NS) 

1 wk 5 d/wk 3 hr/d 

System 

NOAEL 

(ppm) 

Less Serious 

(ppm) 

LOAEL 

Serious 

(ppm) 

Reference Chemical Form 

5000 (3/3 deaths before a total Fairley et al. 1934

of 16 hours of exposure) 

2 Rat 

(Fischer- 344) 

13 wk 5 d/wk 6 hr/d 

6400 (all rats died during first 

week of exposure) 

Kasai et al. 2008 

3 Rat 

(Wistar) 

4 hr 14261 F (4-hour LC50) Pozzani et al. 1959 

4 Mouse 

(NS) 

1 wk 5 d/wk 3 hr/d 

5000 (1/3 deaths after 3 hours 

of exposure) 

Fairley et al. 1934 

5 Gn Pig 

(NS) 

1 wk 5 d/wk 3 hr/d 

10000 (6/6 deaths before 7.5 

hours of exposure) 

Fairley et al. 1934 

6 Gn Pig 

(NS) 

10-540 min 30000 (death of majority of 

animals in 180 minutes) 

Yant et al. 1930 

7 Rabbit 

(NS) 

1 wk 5 d/wk 3 hr/d 

5000 (1/4 death after 16.5 

hours of exposure) 

Fairley et al. 1934 
136

2020

135

1000

46

20002000

72

200

300

200 300

40

16001600

Table 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference (Route) Figure (Strain) System (ppm) (ppm) (ppm) Chemical Form 

Systemic 

8 Human 2 hr Resp b 20 Ernstgard et al. 2006 

Ocular 20 

9 Human 5 min Resp 1000 (1/4 throat constriction) Fairley et al. 1934 

10 Human 3 min Resp 2000 Fairley et al. 1934 

Ocular 2000 

11 Human 15 min Resp 200 300 (nose and throat 

irritation) 

Silverman et al. 1946 

Ocular 200 300 (eye irritation) 

12 Human 10 min Resp 1600 (slight nose and throat 

irritation) 

Yant et al. 1930 

Ocular 1600 (slight eye irritation and 

lacrimation) 
67

5050505050

50

62

1000

39

1000

30000

1000 2000

61

1500

3000

Table 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference (Route) Figure (Strain) System (ppm) (ppm) (ppm) Chemical Form 

13 Human 6 hr Resp 50 M Young et al. 1977 

Cardio 50 M 

Hemato 50 M Hepatic 50 M Renal 50 M Ocular 50 M (eye irritation) 

14 Rat 

(CD) 

4 hr Hepatic 1000 M (increased serum 

transaminases indicative of liver injury) 

Drew et al. 1978 

15 Gn Pig 

(NS) 

10-540 min Resp 1000 (immediate nasal 

irritation) 

30000 (dyspnea, gasping, 

shallow breathing, hyperemia, congestion) 

Yant et al. 1930 

Ocular 1000 2000 (eye irritation) 

Neurological 

16 Rat 

(Wistar) 

2 wk 5 d/wk 4 hr/d 

1500 F 3000 F (depressed avoidance 

response) 

Goldberg et al. 1964 
74

2000

76

1000

10001000

Table 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System 

NOAEL 

(ppm) 

Less Serious 

(ppm) 

LOAEL 

Serious 

(ppm) 

Reference Chemical Form 

INTERMEDIATE EXPOSURE Death 

17 Rabbit 

(NS) 

3-12 wk 5 d/wk 3 hr/d 

2000 (1/4 death on week 4 of 

exposure) 

Fairley et al. 1934 

Systemic 

18 Rat 

(NS) 

3-12 wk 5 d/wk 3 hr/d 

Resp 1000 Fairley et al. 1934 

Hepatic 1000 (hepatocyte 

degeneration) 

Renal 1000 (renal cortex 

degeneration) 
140

200

400

32003200320032001600

3200

1600

3200

3200320032001600

3200

Table 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (continued) 

Exposure/

Duration/

a Frequency Key to Species (Route) Figure (Strain) System 

19 Rat 13 wk Resp (Fischer- 344) 5 d/wk 6 hr/d 

Cardio Gastro Hemato Musc/skel Hepatic Renal Endocr Dermal Ocular Bd Wt 

NOAEL 

(ppm) 

200 M 

3200 

3200 

3200 3200 

1600 M 1600 F 

3200 3200 3200 

1600 F 

LOAEL 

Less Serious 

(ppm) 

Serious 

(ppm) 

Reference Chemical Form 

c

400 M (vacuolic change in 

olfactory epithelium) 

Kasai et al. 2008 

3200 M (cell necrosis, 

centrilobular swelling) 

3200 F (hydropic change in 

proximal tubule) 

3200 F (final body weight 

reduced 10.2%) 
77

1000

10001000

73

5000

10001000

75

1000

10001000

20 21 22 

Table 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (continued) 

Exposure/ 

Duration/ 

a Frequency Key to Species (Route) Figure (Strain) 

Mouse 3-12 wk 

5 d/wk (NS) 3 hr/d 

Gn Pig 3-12 wk 

5 d/wk (NS) 3 hr/d 

Rabbit 3-12 wk 

5 d/wk (NS) 3 hr/d 

LOAEL 

NOAEL Less Serious Serious Reference 

System (ppm) (ppm) (ppm) Chemical Form 

Resp 1000 Fairley et al. 1934 

Hepatic 1000 (hepatocyte 

degeneration) 

Renal 1000 (renal cortex 

degeneration) 

Resp 5000 Fairley et al. 1934 

Hepatic 1000 (hepatocyte 

degeneration) 

Renal 1000 (cortical cell 

degeneration) 

Resp 1000 Fairley et al. 1934 

Hepatic 1000 (hepatocyte 

degeneration) 

Renal 1000 (cortical cell 

degeneration) 
141

3200

142

3200

143

3200

149

1250

Table 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference (Route) Figure (Strain) System (ppm) (ppm) (ppm) Chemical Form 

Immuno/ Lymphoret 

23 Rat 

(Fischer- 344) 

13 wk 5 d/wk 6 hr/d 

3200 Kasai et al. 2008 

Neurological 

24 Rat 

(Fischer- 344) 

13 wk 5 d/wk 6 hr/d 

3200 Kasai et al. 2008 

Reproductive 

25 Rat 

F344/DuCrj 

13 wk 5 d/wk 6 hr/d 

3200 Kasai et al. 2008 

CHRONIC EXPOSURE Death 

26 Rat 

F344/DuCrj 

104 wk 5 d/wk 6 hr/day 

1250 M (decreased survival rate) Kasai et al. 2009 
144

50

12501250250

1250

1250250

1250

50

250

1250125012501250

Table 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (continued) 

Exposure/

Duration/

a Frequency Key to Species (Route) Figure (Strain) System 

Systemic 

27 Rat 104 wk Resp F344/DuCrj 5 d/wk 6 hr/day 

Cardio Gastro Hemato Musc/skel Hepatic Renal Endocr Dermal Ocular Bd Wt 

LOAEL 

NOAEL Less Serious Serious Reference 

(ppm) (ppm) (ppm) Chemical Form 

50 

d

M (atrophy of olfactory 

epithelium) 

Kasai et al. 2009 

1250 M 1250 M 

250 M 1250 M (decreased hemoglobin, 

MCV and MCH) 

1250 M 

250 M 1250 M (centrilobular nuclear 

enlargement and necrosis; increased serum transaminases) 

50 M 250 M (nuclear enlargement in 

proximal tubule) 

1250 M 1250 M 1250 M 1250 M 
20

111111111111111111111111111111

145

1250

22

111

Table 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (continued) 

Exposure/ 

Duration/ 

a Frequency Key to Species (Route) Figure (Strain) 

28 Rat 2 yr 

5 d/wk (Wistar) 7 hr/d 

Immuno/ Lymphoret 

29 Rat 104 wk 

F344/DuCrj 5 d/wk 6 hr/day 

30 Rat 2 yr 

5 d/wk (Wistar) 7 hr/d 

System 

Resp 

Cardio Gastro Hemato Hepatic Renal Endocr Dermal Ocular Bd Wt 

LOAEL 

NOAEL Less Serious Serious Reference

(ppm) (ppm) (ppm) Chemical Form 

111 Torkelson et al. 1974 

111 

111 111 

111 111 

111 

111 

111 111 

1250 M Kasai et al. 2009 

111 Torkelson et al. 1974 
146

1250

23

111

147

1250

24

111

Table 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (continued) 

a 

Key to Species 

Figure (Strain) 

Neurological 

31 Rat 

F344/DuCrj 

32 Rat 

(Wistar) 

Reproductive 

33 Rat 

F344/DuCrj 

34 Rat 

(Wistar) 

Exposure/ LOAEL 

Duration/ 

Frequency NOAEL Less Serious Serious Reference 

(Route) System (ppm) (ppm) (ppm) Chemical Form 

104 wk 5 d/wk 6 hr/day 2 yr 5 d/wk 7 hr/d 104 wk 5 d/wk 6 hr/day 2 yr 5 d/wk 7 hr/d 

1250 M 

111 

1250 M 

111 

Kasai et al. 2009 Torkelson et al. 1974 Kasai et al. 2009 Torkelson et al. 1974 
148

250

Table 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference (Route) Figure (Strain) System (ppm) (ppm) (ppm) Chemical Form 

Cancer 

35 Rat 

F344/DuCrj 

104 wk 5 d/wk 6 hr/day 

250 M (CEL:peritoneum 

mesothelioma) 

Kasai et al. 2009 

a The number corresponds to entries in Figure 3-1. b Used to derive an acute-duration inhalation minimal risk level (MRL) of 2 ppm for 1,4-dioxane; the MRL was derived by dividing the NOAEL by an uncertainty factvariability. c Used to derive an intermediate-duration inhalation MRL of 0.2 ppm for 1,4-dioxane; the MRL was derived by dividing the BMCL10HEC by an uncertainty factor of dosimetric adjustments and 10 for human variability). d Used to derive a chronic-duration inhalation MRL of 0.03 ppm for 1,4-dioxane; the MRL was derived by dividing the LOAELHEC by an uncertainty factor of 300 (3 

dosimetric adjustments, 10 for using a LOAEL, and 10 for human variability). Bd Wt = body weight; Cardio = cardiovascular; d = day(s); EKG = electrocardiogram; F = Female; Gastro = gastrointestinal; Gn pig = guinea pig; Hemato = hematohour(s); LC50 = lethal concentration, 50% kill; LOAEL = lowest-observed-adverse-effect level; M = male; min = minute(s); NOAEL = no-observed-adverse-effect levspecified; ppm = parts per million; Resp = respiratory; wk = week(s); yr = year(s) 
Death 

Respira CardiovHematoHepaticRenal Ocular Neurolo 


	


	

tory 

ascular 

logical 

gical 

Figure 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation
	

Acute (≤14 days)
	

Systemic 

ppm 

100000 

6g 15g 

3r 

10000 5g 

2r 

4m 1r 7h 

10 15g 10 

12 12 

1000 15g 9 14r 15g 

11 11 

11 11 

100 

13 13 13 13 13 13 

8 8 

10 

1 

c-Cat 

d-Dog

r-Rat 

p-Pig

q-Cow

 -Humans 

k-Monkey

m-Mouse 

h-Rabbit 

a-Sheep 

f-Ferret 

j-Pigeon

e-Gerbil 

s-Hamster 

g-Guinea Pig 

n-Mink 

o-Other

 Cancer Effect Level-Animals

 LOAEL, More Serious-Animals

LOAEL, Less Serious-Animals

NOAEL - Animals

 Cancer Effect Level-Humans

 LOAEL, More Serious-Humans

LOAEL, Less Serious-Humans

NOAEL - Humans

 LD50/LC50

Minimal Risk Level

 for effects

 other than

 Cancer 

16r 

16r 

1,4-DIOXANE 44 3. HEALTH EFFECTS
Death 

Cardiovascular GastrointestinalHematological Musculoskeletal Hepatic Renal Endocrine Dermal Ocular Body Weight Immuno/LymphNeurological Re


	


	


	


	

 


	

Respiratory 

or 

Figure 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (Continued)
 

Intermediate (15-364 days)
	

Systemic 

ppm 

10000 

21g 

19r 19r 19r 19r 19r 19r 19r 19r 19r 19r 23r 24r 25r 

17h 

19r 19r 19r
	

1000
	 20m 18r 22h 21g 20m 18r 22h 21g 20m 18r 22h 

19r 

19r
	

100
	

10 

1 

0.1 

c-Cat -Humans f-Ferret n-Mink Cancer Effect Level-Animals Cancer Effect Level-Humans LD50/LC50

d-Dog k-Monkey j-Pigeon o-Other LOAEL, More Serious-Animals LOAEL, More Serious-Humans Minimal Risk Level 

r-Rat m-Mouse e-Gerbil LOAEL, Less Serious-Animals LOAEL, Less Serious-Humans for effects 

p-Pig h-Rabbit s-Hamster NOAEL - Animals NOAEL - Humans other than 

q-Cow a-Sheep g-Guinea Pig Cancer 

pr oductive 

1,4-DIOXANE 3. HEALTH EFFECTS 45
Death 

Respiratory Cardiovascular Gastrointestinal Hematological Musculoskeletal Hepatic Renal Endocrine Dermal Ocular Body Weight Immuno/Lymphor Neurological Reproductive Cancer * 

 

 


	


	


	


	

 


	

Figure 3-1 Levels of Significant Exposure to 1,4-Dioxane - Inhalation (Continued)
 

Chronic (≥365 days)

Systemic 

ppm
	

10000
	

26r 27r 27r 27r 27r 27r 27r 27r 27r 27r 29r 31r 33r 1000 

27r 27r 27r 35r
	

100
	 28r 28r 28r 28r 28r 28r 28r 28r 28r 28r 30r 32r 34r 

27r 27r 

10 

1 

0.1 

0.01 

0.001 

-4 0.0001 10 

Estimated 

Upper-Bound -5 1E-5 10 Human Cancer 

Risk Levels 

-6 1E-6 10 

*Doses represent the lowest dose tested per study that produced a tumorigenic 

response and do not imply the existence of a threshold for the cancer endpoint. 10-7 1E-7 

c-Cat -Humans f-Ferret n-Mink Cancer Effect Level-Animals Cancer Effect Level-Humans LD50/LC50

d-Dog k-Monkey j-Pigeon o-Other LOAEL, More Serious-Animals LOAEL, More Serious-Humans Minimal Risk Level 

r-Rat m-Mouse e-Gerbil LOAEL, Less Serious-Animals LOAEL, Less Serious-Humans for effects 

p-Pig h-Rabbit s-Hamster NOAEL - Animals NOAEL - Humans other than 

q-Cow a-Sheep g-Guinea Pig Cancer 

1,4-DIOXANE 3. HEALTH EFFECTS 46
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 47 

3. HEALTH EFFECTS 

In a study in guinea pigs exposed to 1,000–30,000 ppm 1,4-dioxane for periods ranging from 10 to 

540 minutes, nasal irritation was evident almost immediately at all exposure levels (Yant et al. 1930). No 

functional respiratory changes were noticed with concentrations of up to 10,000 ppm for 480 minutes, but 

dyspnea and gasping occurred at 30,000 ppm in 45–116 minutes. The 30,000 ppm level caused death in 

the animals in about 180 minutes. Gross necropsy revealed exposure-duration-related hyperemia in the 

lungs. Surviving guinea pigs autopsied 8–10 days after exposure showed no gross pathological changes 

except for a few cases of hyperemic areas of congestion in the lungs. Exposure of rats and guinea pigs to 

acute lethal concentrations of 1,4-dioxane produced vascular congestion of the lungs (Fairley et al. 1934). 

No lung lesions were seen in rats, mice, or rabbits exposed to 1,000 ppm 1,4-dioxane for 3–12 weeks or 

in guinea pigs exposed to 5,000 ppm for the same duration (Fairley et al. 1934). However, male and 

female F344 rats exposed intermittently to ≥100 ppm 1,4-dioxane vapors for 13 weeks showed an 

increased incidence of nuclear enlargement of the respiratory epithelium of the nasal cavity (Kasai et al. 

2008). Nuclear enlargement of the olfactory epithelium was reported at ≥200 ppm and vacuolar changes 

and atrophy in the olfactory epithelium were noted at ≥400 ppm. Similar changes were reported in the 

tracheal and bronchial epithelium, but only in rats exposed to ≥1,600 ppm 1,4-dioxane. The study by 

Kasai et al. (2008) was used to derive an intermediate-duration inhalation MRL for 1,4-dioxane. In the 

2-year inhalation study in rats by Torkelson et al. (1974), intermittent exposure to 111 ppm 1,4-dioxane 

caused no signs of nasal irritation, respiratory distress, or histopathologic alterations in the lungs and 

trachea of the animals. However, it appears that the rats’ nasal cavity may have not been examined. 

More recently, a 2-year study in male F344 rats reported that intermittent exposure to ≥50 ppm 

1,4-dioxane vapors (the lowest exposure concentration tested) significantly increased the incidence of 

nuclear enlargement in the respiratory and olfactory epithelia and also induced atrophy and respiratory 

metaplasia in the olfactory epithelium (Kasai et al. 2009). This study was used to derive a chronicduration inhalation MRL for 1,4-dioxane. 

Cardiovascular Effects. A study of four men exposed to 50 ppm 1,4-dioxane for 6 hours reported no 

abnormalities in the electrocardiograms (EKG) taken 24 hours and 2 weeks after exposure compared to 

EKGs taken prior to the study (Young et al. 1977); however, no data were provided in the study. High 

blood pressure was reported in subjects who eventually died following exposure to high amounts of 

1,4-dioxane (Barber 1934; Johnstone 1959), but this may have been a non-specific response to a stressful 

condition or due to acute renal failure. 

The only available information in animals is that no gross or histopathological alterations were observed 

in the heart from rats exposed to up to 3,200 ppm 1,4-dioxane 6 hours/day, 5 days/week for 13 weeks 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 48 

3. HEALTH EFFECTS 

(Kasai et al. 2008), to 111 ppm 1,4-dioxane for 7 hours/day, 5 days/week for 2 years (Torkelson et al. 

1974), or to up to 1,250 ppm 1,4-dioxane 6 hours/day, 5 days/week for 2 years (Kasai et al. 2009). 

Gastrointestinal Effects. Abdominal pain and vomiting were common features among subjects who 

eventually died after exposure to high concentrations of 1,4-dioxane (Barber 1934; Johnstone 1959). 

Barber (1934) suggested that the abdominal pain may have been due to stretching of the capsule of the 

liver and kidneys. No gross or histologic alterations were observed in the gastrointestinal tract from rats 

exposed to up to 3,200 ppm 1,4-dioxane 6 hours/day, 5 days/week for 13 weeks (Kasai et al. 2008), to 

111 ppm 1,4-dioxane 7 hours/day, 5 days/week for 2 years (Torkelson et al. 1974), or to up to 1,250 ppm 

1,4-dioxane 6 hours/day, 5 days/week for 2 years (Kasai et al. 2009). 

Hematological Effects. A study of four male volunteers exposed to 50 ppm 1,4-dioxane for 6 hours 

reportedly did not show any significant effect of exposure on hematology parameters (Young et al. 1977); 

however, no data were provided in the study. Blood was collected prior to exposure and 24 hours and 

2 weeks after exposure and subjected to a complete hematological analysis. Leukocytosis and 

eosinophilia were described in subjects who survived exposure to high concentrations of 1,4-dioxane 

described by Barber (1934). A cross-sectional study of 74 workers exposed to concentrations of 

1,4-dioxane between 0.006 and 14.3 ppm for an average length of exposure of almost 25 years found no 

significant alterations in hemoglobin concentration, erythrocyte counts, and total and differential 

leukocyte counts among the subjects (Thiess et al. 1976). 

Female rats exposed intermittently to 3,200 ppm 1,4-dioxane for 13 weeks showed statistically significant 

elevations in red blood cell counts, hemoglobin, and hematocrit, whereas males showed only an increase 

in mean corpuscular volume (Kasai et al. 2008). The values were elevated <5% relative to controls and 

were within normal limits. No statistically significant changes were reported at ≤1,600 ppm 1,4-dioxane. 

In the 2-year inhalation study in rats by Torkelson et al. (1974), hematological parameters were measured 

in blood collected after 16 and 23 months of exposure. In this study, the rats were exposed to 111 ppm 

1,4-dioxane 7 hours/day, 5 days/week. The specific hematological parameters measured were packed 

corpuscular volume, erythrocyte counts, hemoglobin concentration, and total and differential leukocyte 

counts. No toxicologically significant deviations from normal limits were found. Intermittent exposure 

to 1,250 ppm 1,4-dioxane for 2 years induced significant decreases in hemoglobin (13%), MCV (6%), 

and MCH (8%) (Kasai et al. 2009). No significant effects were seen in rats exposed to ≤250 ppm 

1,4-dioxane. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 49 

3. HEALTH EFFECTS 

Musculoskeletal Effects. Intermittent exposure of rats to up to 3,200 ppm 1,4-dioxane for 13 weeks 

did not result in gross or microscopic alterations in bone (sternum, femur, and joint) or skeletal muscle 

(thigh) (Kasai et al. 2008). No gross or microscopic alterations were reported in skeletal muscle or bone 

from male rats exposed intermittently to up to 1,250 ppm 1,4-dioxane for 2 years (Kasai et al. 2009). No 

further information was located. 

Hepatic Effects. Short-term exposure of humans to concentrations that eventually caused death 

produced serious liver damage. Barber (1934) described five lethal cases in which postmortem 

examination of the patients revealed an enlarged liver and centrilobular necrosis of the liver cells. Similar 

lesions were observed in a lethal case described by Johnstone (1959). A group of four men were exposed 

to 50 ppm 1,4-dioxane for 6 hours and were given 12 “standard clinical chemistry tests” at 24 hours and 

2 weeks after exposure (Young et al. 1977). Although the nature of clinical chemistry tests was not 

specified, there were no effects related to exposure. A cross sectional study of 74 workers exposed to 

concentrations of 1,4-dioxane between 0.006 and 14.3 ppm for an average length of exposure of almost 

25 years found no conclusive evidence of serious liver damage (Thiess et al. 1976). Although 6 out of 

24 current workers had elevated serum transaminase levels, all 6 were known as habitual alcohol drinkers. 

Guinea pigs exposed to acute lethal concentrations of 1,4-dioxane had liver lesions ranging from cloudy 

swelling to areas of complete necrosis (Fairley et al. 1934). The effect of 1,4-dioxane on the levels of 

serum ALT, AST, ornithine carbamyl transferase (OCT), and glucose-6-phosphatase was studied in 

groups of male rats exposed to 0, 1,000, or 2,000 ppm 1,4-dioxane for 4 hours (Drew et al. 1978). The 

enzyme levels were used as indication of liver damage. Exposure to 1,4-dioxane markedly increased the 

activities (concentration-related) of AST, ALT, and OCT, particularly 48 hours after exposure. The 

activity of glucose-6-phosphatase was slightly increased 48 hours after exposure. 

A study in which rats, mice, guinea pigs, and rabbits were exposed to 1,000 ppm (the lowest 

concentration tested) 3 hours/day, 5 days/week for 3–12 weeks reported hepatocyte degeneration of 

varying severity in all of the species tested (Fairley et al. 1934). Increased incidence of single cell 

necrosis and centrilobular swelling was described in the liver of male rats exposed intermittently to 

3,200 ppm 1,4-dioxane for 13 weeks; no such effects were observed at ≤1,600 ppm (Kasai et al. 2008). 

Females exposed to 3,200 ppm only showed centrilobular swelling. In the 2-year inhalation bioassay in 

rats exposed intermittently to 111 ppm 1,4-dioxane, there was no evidence of any exposure-related gross 

or microscopic liver alterations or alterations in serum AST and AP activities (Torkelson et al. 1974). 

Another study reported significant increases in the incidences of centrilobular nuclear enlargement, 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 50 

3. HEALTH EFFECTS 

acidophilic and basophilic cell foci, spongiosis hepatis, and centrilobular necrosis in male rats following 

exposure to 1,250 ppm 1,4-dioxane for 2 years (Kasai et al. 2009). No such alterations were observed in 

the liver of rats exposed to ≤250 ppm 1,4-dioxane, which is consistent with the findings of Torkelson et 

al. (1974). Serum transaminases were also significantly elevated following exposure to 1,250 ppm 

1,4-dioxane. 

Renal Effects. Swollen kidneys with hemorrhage was seen in subjects who died following exposure 

to unknown amounts of 1,4-dioxane in the air described by Barber (1934). These subjects showed 

oliguria and/or anuria, and in one case there was bloody urine. Microscopic examination showed 

hemorrhage around the glomeruli with some necrosis. Barber (1934) stated that in at least three of the 

five cases he described, kidney disease was the direct cause of death. In a fatal case of a patient described 

by Johnstone (1959), postmortem examination revealed necrosis in the kidney cortex, with extensive 

interstitial hemorrhage and oliguria. A group of four men were exposed to 50 ppm 1,4-dioxane for 

6 hours and were given urinalysis tests at 24 hours and 2 weeks after exposure (Young et al. 1977). There 

were no effects related to exposure. No evidence of kidney damage was found in a cross-sectional study 

of 74 workers exposed to concentrations of 1,4-dioxane between 0.006 and 14.3 ppm for an average 

length of exposure of almost 25 years (Thiess et al. 1976). 

Kidney lesions were commonly observed in rodents exposed to acute lethal concentrations of 1,4-dioxane 

(Fairley et al. 1934). Examination of rats, mice, guinea pigs, and rabbits exposed to 1,000 ppm 

1,4-dioxane (the lowest concentration tested) 3 hours/day, 5 days/week for 3–12 weeks, showed varying 

degrees of kidney damage ranging from vascular congestion to renal cortex degeneration (Fairley et al. 

1934). In general, exposure to higher concentrations increased the severity of the effects. In a 13-week 

intermittent exposure study, female rats exposed to 3,200 ppm 1,4-dioxane showed a significant increased 

incidence of hydropic change in the proximal tubule; however, no renal alterations were seen in males 

exposed to that concentration or in females exposed to ≤1,600 ppm 1,4-dioxane (Kasai et al. 2008). In a 

2-year inhalation study in rats exposed intermittently to 111 ppm 1,4-dioxane, there were no treatmentrelated gross or microscopic alterations in the kidneys or significant alterations in blood-urea nitrogen and 

total protein concentration (Torkelson et al. 1974). In other 2-year study, intermittent exposure of male 

rats to ≥250 ppm 1,4-dioxane significantly increased the incidence of nuclear enlargement in the proximal 

tubule and (Kasai et al. 2009); exposure to 1,250 ppm also increased the incidence of hydropic change in 

the proximal tubule. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 51 

3. HEALTH EFFECTS 

Endocrine Effects. No gross or microscopic alterations were observed in the pituitary, adrenal, 

thyroid, or parathyroid glands from rats exposed intermittently to up to 3,200 ppm 1,4-dioxane for 

13 weeks (Kasai et al. 2008), in the thyroid and pituitary glands from rats exposed intermittently to 

111 ppm for 2 years (Torkelson et al. 1974), or in the thyroid, parathyroid, adrenal, and pituitary glands 

from male rats exposed intermittently to up to 1,250 ppm 1,4-dioxane for 2 years (Kasai et al. 2009). 

Dermal Effects. No gross or microscopic alterations were reported in the skin from rats exposed 

intermittently to up to 3,200 ppm 1,4-dioxane for 13 weeks (Kasai et al. 2008). In the 2-year study in rats 

by Torkelson et al. (1974), the investigators indicated that intermittent exposure to a concentration of 

111 ppm 1,4-dioxane in the air had no significant effect on skin condition; no microscopic examination of 

the skin was conducted. However, Kasai et al. (2009) conducted microscopic examinations of the skin of 

male rats exposed to up to 1,250 ppm 1,4-dioxane for years and did not report significant alterations. Had 

skin condition been affected in these studies, it would have been most likely due to direct contact with the 

chemical rather than due to inhaled 1,4-dioxane. 

Ocular Effects. In a group of six individuals exposed to 2,000 ppm 1,4-dioxane vapors for 3 minutes 

in a 10-m3

 chamber, there were no complaints of ocular discomfort (Fairley et al. 1934). Exposure to 

300 ppm 1,4-dioxane for 15 minutes produced eye irritation among a group of 12 volunteers (Silverman 

et al. 1946). A 10-minute exposure to 1,600 ppm 1,4-dioxane produced slight eye irritation and 

lacrimation that persisted throughout the test in a group of five individuals (Yant et al. 1930). In another 

experiment by the same investigators, exposure of the same five persons to 5,500 ppm 1,4-dioxane for 

1 minute resulted in irritation of the eyes (Yant et al. 1930). Eye irritation throughout exposure was a 

frequent and the only complaint among four men exposed to 50 ppm for 6 hours in a study by Young et 

al. (1977). It is assumed that, in these cases, the irritation was caused by direct contact of the vapor with 

the eyes. In addition, there was no control experiment, and possible low humidity in the exposure 

chamber might contribute to the eye irritation. A study of six men and six women exposed to 20 ppm 

1,4-dioxane for 2 hours reported no discomfort in the eyes (burning, irritation, or running eyes) among the 

subjects during or after exposure (Ernstgård et al. 2006). Also unaffected was the eye blinking frequency, 

monitored by electromyography. 

In a study in guinea pigs exposed to 1,000–30,000 ppm 1,4-dioxane for 10–540 minutes, eye irritation 

was observed at 2,000 ppm in a 5-minutes exposure and 3,000 ppm for 8 minutes of exposure, but not at 

1,000 ppm for 480 minutes (Yant et al. 1930). No exposure-related gross or microscopic alterations were 

reported in the eyes (retina, optic nerve, and eyelids) of rats exposed to up to 3,200 ppm 1,4-dioxane for 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 52 

3. HEALTH EFFECTS 

13 weeks (Kasai et al. 2008). No evidence of eye irritation was observed in rats exposed intermittently to 

111 ppm 1,4-dioxane for 2 years, but no histological examination of the eyes was performed (Torkelson 

et al. 1974). Microscopic examination of the eyes of male rats exposed to up to 1,250 ppm 1,4-dioxane 

for 2 years did not reveal exposure related alterations (Kasai et al. 2009). 

Body Weight Effects. Intermittent exposure of rats to 200–3,200 ppm 1,4-dioxane for 13 weeks 

resulted in <10% reduction in final body weight relative to controls, except in females exposed to 

3,200 ppm, whose final body weight was reduced by 10.2% (Kasai et al. 2008). Food consumption data 

were not provided in that study. No significant effect on body weight gain was observed in rats exposed 

to 111 ppm 1,4-dioxane 7 hours/day, 5 days/week for 2 years (Torkelson et al. 1974). Intermittent 

exposure of male rats to up to 1,250 ppm 1,4-dioxane for 2 years resulted in a terminal body weight 6.3% 

lower than control rats (Kasai et al. 2009); food consumption was not affected. 

3.2.1.3 Immunological and Lymphoreticular Effects 

Exposure of 12 volunteers to 20 ppm 1,4-dioxane for 2 hours did not result in inflammatory changes, as 

measured by the levels of high sensitivity C-reactive protein and interleukin 6 in blood collected before 

and 3 hours after exposure (Ernstgård et al. 2006). No further information was located regarding 

immunological and lymphoreticular effects in humans following inhalation exposure to 1,4-dioxane. 

No gross or microscopic alterations were observed in the spleen, thymus, or lymph nodes of rats exposed 

intermittently to up to 3,200 ppm 1,4-dioxane for 13 weeks (Kasai et al. 2008), in the lymph nodes or the 

spleen from rats exposed to intermittently to 111 ppm 1,4-dioxane for 2 years (Torkelson et al. 1974), or 

in the spleen, thymus, and lymph nodes from male rats exposed to up to 1,250 ppm 1,4-dioxane for 

2 years (Kasai et al. 2009). These values are presented as NOAELs for lymphoreticular effects in 

Table 3-1 and plotted in Figure 3-1. 

3.2.1.4 Neurological Effects 

In a study of volunteers (six males and six females) exposed to 20 ppm 1,4-dioxane for 2 hours, selfreported ratings of headache, fatigue, nausea, and ‘feeling of intoxication’ during and after exposure were 

no different than before exposure (Ernstgård et al. 2006). Edema of the brain was observed in three of the 

five fatal cases described by Barber (1934). However, as suggested by NIOSH (1977), these changes 

were probably terminal, rather than specific toxic effects of 1,4-dioxane. Also, brain damage, possibly 

secondary to anoxia and cerebral edema, was observed in a worker who died following combined 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 53 

3. HEALTH EFFECTS 

inhalation and dermal exposure to a high amount of 1,4-dioxane (Johnstone 1959). Postmortem 

examination showed moderate perivascular widening of the brain and demyelination and partial loss of 

nerve fibers in small areas of the basal nuclei. 

Exposure of rats to ≥3,000 ppm 1,4-dioxane 4 hours/day 5 days/week for 2 weeks resulted in depression 

of an avoidance response (Goldberg et al. 1964). The maximal effect was obtained after the second day 

of exposure. All of the effects on behavior were reversible. Intermittent exposure of rats to up to 

3,200 ppm 1,4-dioxane for 13 weeks did not affect the gross or microscopic appearance of the brain, 

spinal cord, or peripheral nerves (Kasai et al. 2008). Exposure of rats to 111 ppm 1,4-dioxane for 2 years 

caused no significant gross or microscopic alterations in the brain (Torkelson et al. 1974). Similar 

exposure of male rats to up to 1,250 ppm 1,4-dioxane for 2 years also did not cause gross or microscopic 

alterations in the brain, spinal cord, or peripheral nerves (Kasai et al. 2009). Although no neurological 

testing was conducted in these studies, the rats were observed throughout the studies for signs of toxicity, 

including activity and demeanor; therefore, the values of 3,200 ppm, 111 ppm, and 1,250 ppm are 

presented as NOAELs for neurological effects in Table 3-1 and are plotted in Figure 3-1. 

3.2.1.5 Reproductive Effects 

Elevated rates of spontaneous abortion and stillbirths were associated with occupational exposure to a 

combination of chemicals (1,4-dioxane among them) used in a silk screening process (NIOSH 1988). 

Increased incidences of miscarriages, premature births, and low birth weights were also reported in 

women occupationally exposed to a combination of chemicals that included 1,4-dioxane in the electronics 

industry in Russia, as noted by the Australia National Industrial Chemicals Notification and Assessment 

Scheme (NICNAS 1998). These effects cannot be attributed solely to 1,4-dioxane. 

No alterations were observed in the primary and secondary reproductive organs from male and female 

rats exposed intermittently to up to 3,200 ppm 1,4-dioxane for 13 weeks (Kasai et al. 2008) or similarly to 

111 ppm 1,4-dioxane for 2 years (Torkelson et al. 1974). Exposure of male rats to up to 1,250 ppm 

1,4-dioxane for 2 years also did not induce gross or microscopic alterations in the reproductive organs 

(Kasai et al. 2009). These NOAELs are presented in Table 3-1 and plotted in Figure 3-1. 

3.2.1.6 Developmental Effects 

No studies were located regarding developmental effects in humans or in animals following inhalation 

exposure to 1,4-dioxane. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 54 

3. HEALTH EFFECTS 

3.2.1.7 Cancer 

Limited information exists regarding exposure to 1,4-dioxane and cancer in humans. Thiess et al. (1976) 

conducted a cross-sectional study of 74 workers exposed to concentrations of 1,4-dioxane between 

0.006 and 14.3 ppm for an average length of exposure of almost 25 years. Twelve deaths had been 

reported and two were attributed to cancer, but the overall death rate and the cancer death rate were not 

significantly different than expected rates. Buffler et al. (1978) also found no evidence 1,4-dioxaneinduced cancer in an occupational study of 165 workers exposed intermittently to mean concentrations of 

1,4-dioxane between 0.1 and 17 ppm (the maximums ranged between 1.5 and 3.2 ppm) at least 1 month 

during a 21-year period. However, the study was limited in power to detect an effect due to the small size 

of the cohort, low levels of exposure, and the relatively short exposures. 

No evidence of carcinogenicity due to 1,4-dioxane was found in a study in Wistar rats (288/sex) in which 

the animals were exposed to 111 ppm 1,4-dioxane 7 hours/day, 5 days/week for 2 years (Torkelson et al. 

1974). A group of 192 rats of each sex served as controls, and the evaluation included all major tissues 

and organs, but there was no direct indication that the nasal cavity was examined. In the 2-year study 

conducted by Kasai et al. (2009), male F344/DuCrj rats were exposed intermittently to 0, 50, 250, or 

1,250 ppm 1,4-dioxane. Significantly increased incidences of peritoneum mesothelioma occurred in the 

250 and 1,250 ppm groups compared to controls (2/50, 4/50, 14/50, and 41/50 in control, low-, mid-, and 

high-exposure groups, respectively) (p<0.01 in both the mid- and high-exposure groups). Exposure to 

1,250 ppm 1,4-dioxane also significantly increased the incidence of squamous cell carcinoma in the nasal 

cavity (0/50, 0/50, 1/50, 6/50) (p<0.05). High-exposure rats also showed a significant increase in the 

incidence of hepatocellular adenoma (1/50, 2/50, 3/50, 21/50) (p<0.01). 

The EPA is in the process of deriving a cancer risk assessment for inhalation exposure to 1,4-dioxane. 

3.2.2 Oral Exposure 

3.2.2.1 Death 

No reports of death in humans following oral exposure to 1,4-dioxane were found in the literature 

reviewed. Studies in animals have reported lethal doses in various species. Reported single dose LD50 

values in rats include 5,346 mg/kg (Laug et al. 1939), 6,369 mg/kg (Pozzani et al. 1959), and 7,120 mg/kg 

(Smyth et al. 1941). Laug et al. (1939) also reported an LD50 of 5,852 mg/kg in mice and 4,033 mg/kg in 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 55 

3. HEALTH EFFECTS 

guinea pigs. Two of 10 female rats dosed with 2,750 mg 1,4-dioxane/kg/day for 2 weeks in the drinking 

water died before the end of the study (JBRC 1998). Smyth et al. (1941) calculated an LD50 of 

3,150 mg/kg in guinea pigs, whereas de Navasquez (1935) reported 100% lethality in a group of five 

rabbits within 6 days of administration of a single dose of 2,068 mg of 1,4-dioxane/kg by gavage in 

water; a lower dose of 1,034 mg/kg was not lethal, but produced narcolepsy, and doses of 207 mg/kg 

repeated at weekly intervals did not appear to affect the animals. All 10 female mice dosed with 

3,230 mg 1,4-dioxane/kg/day in the drinking water died, and 9 of 10 males dosed with 3,630 mg/kg/day 

also died (JBRC 1998). In a study using three dogs, consumption of approximately 327 mg 

1,4-dioxane/kg/day via the drinking water killed one dog in 10 days, and consumption of approximately 

375 mg/kg/day was lethal to an additional dog in 9 days (Schrenk and Yant 1936). Upon necropsy, 

common features in these animals were severe kidney and liver lesions consisting of cellular degeneration 

of the renal cortex, hemorrhages and vascular congestion in the kidneys, and cellular degeneration in the 

liver. Because the dogs were allowed to drink the 1,4-dioxane solution only twice daily and no other 

source of water was available, dehydration may have played a role in their death. 

In an intermediate-duration study, five of six rats dosed through drinking water that provided 

approximately 1,000 mg 1,4-dioxane/kg/day died between the 14th and 35th day of the study (Fairley et al. 

1934). Necropsy of these animals revealed kidney and liver lesions. In a 2-year cancer bioassay in 

Sherman rats, significant early mortality beginning at about 2–4 months in the study was observed in 

males and females treated with 1,015 and 1,599 mg 1,4-dioxane/kg/day, respectively, in the drinking 

water (Kociba et al. 1974). Although the specific cause of death was not discussed, the investigators 

indicated that rats dying early showed degenerative changes in the liver and kidneys. Early mortality also 

was reported in other long-term studies in rats given ≥240 mg 1,4-dioxane/kg/day in the drinking water 

for 104–110 weeks (NCI 1978), or ≥274 mg/kg/day for 2 years (Kano et al. 2009) and in mice treated 

similarly with ≥380 mg/kg/day for 90–104 weeks (NCI 1978) or ≥278 mg/kg/day for 2 years (Kano et al. 

2009). In the Kano et al. (2009) study, early death in male rats was attributed to nasal cavity tumors and 

peritoneal mesothelioma; deaths in female rats were attributed to nasal and hepatic tumors. Death in mice 

was attributed to liver tumors. 

The LOAEL values for death in each species and duration category are recorded in Table 3-2 and plotted 

in Figure 3-2. 
105

2750

54

1034

37

5346

60

6369

56

7120

106

3230

36

5852

35

4033

57

3150

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) 

ACUTE EXPOSURE Death 

1 Rat 

(Fischer- 344) 

2 wk ad lib (W) 

System 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

2750 F (2/10 deaths) 

Reference Chemical Form 

JBRC 1998a 

2 Rat 

(NS) 

12 d (W) 1034 (8/10 deaths within 12 days) Kesten et al. 1939 

3 Rat 

(NS) 

once (G) 5346 (LD50) Laug et al. 1939 

4 Rat 

(Wistar) 

once (G) 6369 F (LD50) Pozzani et al. 1959 

5 Rat 

(Wistar) 

once (GW) 7120 (LD50) Smyth et al. 1941 

6 Mouse 

(B6C3F1) 

2 wk ad lib (W) 

3230 F (10/10 deaths) JBRC 1998a 

7 Mouse 

(NS) 

once (G) 5852 (LD50) Laug et al. 1939 

8 Gn Pig 

(NS) 

once (G) 4033 (LD50) Laug et al. 1939 

9 Gn Pig 

(NS) 

once (GW) 3150 (LD50) Smyth et al. 1941 
52

2068

102

370

1010

1040

2750

1040

2750

1040

2750

55

1034

1034

25

1000

99

1380 25501380 2550

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference 

Figure (Strain) (Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Chemical Form 

10 Rabbit 

(NS) 

once (GW) 2068 (5/5 deaths in 2-6 days) De Navasquez 1935 

Systemic 

11 Rat 

(Fischer- 344) 

2 wk ad lib (W) 

Resp 370 M 1010 M (nuclear enlargement of 

olfactory epithelium) 

JBRC 1998a 

Hepatic 1040 F 2750 F (hepatocyte swelling and 

vacuolation) 

Renal 1040 F 2750 F (hydropic change in 

proximal tubule) 

Bd Wt 1040 F 2750 F (24% reduced body 

weight gain) 

12 Rat 

(NS) 

12 d (W) Hepatic 1034 (unspecified liver abnormalities) Kesten et al. 1939 

Renal 1034 (kidney degeneration) 

13 Rat 

(SpragueDawley) 

once (GW) Hepatic 1000 M Stott et al. 1981 

14 Mouse 

(B6C3F1) 

2 wk ad lib (W) 

Hepatic 1380 M 2550 M (swelling of central area) JBRC 1998a 

Bd Wt 1380 M 2550 M (swelling of central area) 
104

1040

2750

112

207

1034

53

1760 4400

78

516

1033

47

1000

15

1015

16 20 

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference 

Figure (Strain) (Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Chemical Form 

Neurological 

15 Rat 2 wk 1040 F 2750 F (vacuolar changes in the JBRC 1998a ad lib (Fischer- 344) brain) (W) 

Rabbit once 207 1034 (narcolepsy, slow gate, De Navasquez 1935 (NS) (GW) ataxia) 

17 Rabbit 

(NS) 

once (G) 1760 4400 (staggering) Knoefel 1935 

Developmental 

18 Rat 

(SpragueDawley) 

9 d Gd 6-15 (GW) 

b

516 1033 (decreased fetal weight; 

reduced sternum ossification) 

Giavini et al. 1985 

INTERMEDIATE EXPOSURE Death 

19 Rat 

(NS) 

34 d ad lib (W) 

1000 (5/6 deaths before the 

35th day) 

Fairley et al. 1934 

Rat 2-4 mo 1015 M (significant early mortality Kociba et al. 1974 ad lib (Sherman) beginning at 2 months in (W) the study) 
48

1428

14281428

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference (Route) Figure (Strain) System (mg/kg) (mg/kg) (mg/kg) Chemical Form 

Systemic 

21 Rat 

(NS) 

34 d ad lib (W) 

Gastro 1428 (gastroenteritis) Fairley et al. 1934 

Hepatic 1428 (hepatocyte 

degeneration) 

Renal 1428 (renal cortex 

degeneration) 
103

52

126

16141614657

1554

161452 12627483

657185

161416141614657

756 1614

28

100

1000

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ 

Duration/ 

a 

Key to Species Frequency 

Figure (Strain) (Route) 

22 Rat 13 wk 

ad lib (Fischer- 344) (W) 

23 Rat 7 wk 

5 d/wk (SpragueDawley) (GW) 

System 

Resp 

Cardio Gastro Hemato Musc/skel Hepatic Renal Endocr Dermal Ocular Bd Wt 

Hepatic 

NOAEL 

(mg/kg/day) 

52 M 

1614 F 1614 F 

657 M 

1614 F 

c

52 M 

274 M 

d

83 F 

1614 F 1614 F 1614 F 

657 M 

100 M 

LOAEL 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Reference Chemical Form 

126 M (nuclear enlargement of 

respiratory epithelium) 

Kano et al. 2008 

1554 M (increased red blood cell, 

hemoglobin, hematocrit, neutrophils) 

126 M (swelling in central area) 657 M (nuclear enlargement of 

proximal tubule) 

d

185 F (increased kidney weight) 756 F (12% reduction in weight 

gain) 

1614 F (21% reduction in body 

weight gain) 

1000 M (fatty vacuoles in 

cytoplasm of hepatocytes) 

Lundberg et al. 1987 
26

10

1000

1000

49

29162916

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference 

Figure (Strain) (Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Chemical Form 

24 Rat 

(SpragueDawley) 

11 wk ad lib (W) 

Hepatic 10 M 1000 M (minimal hepatocellular 

swelling) 

Stott et al. 1981 

Bd Wt 1000 M 

25 Mouse 

(NS) 

67 d ad lib (W) 

Hepatic 2916 (hepatocyte 

degeneration) 

Fairley et al. 1934 

Renal 2916 (cell degeneration in 

renal cortex) 
101

170

387

26692669882

1570

2669231

585

1620

2669

2669266926698822669

1570

120

1614

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ 

Duration/ 

a Frequency Key to Species (Route) Figure (Strain) 

26 Mouse 13 wk 

ad lib (B6C3F1) (W) 

Immuno/ Lymphoret 

27 Rat 13 wk 

(Fischer- 344) ad lib 

(W) 

System 

Resp 

Cardio Gastro Hemato Musc/skel Hepatic Renal Endocr Dermal Ocular Bd Wt 

NOAEL 

(mg/kg/day) 

170 F 

2669 F 2669 F 

882 M 

2669 F 

231 M 

1620 F 2669 F 2669 F 2669 F 

d

882 M 

2669 F 

1614 F 

LOAEL 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Reference Chemical Form 

387 F (nuclear enlargement of 

bronchial epithelium) 

Kano et al. 2008 

1570 M (increase red blood cell, 

hemoglobin, hematocrit, corpuscular volume) 

585 M (single cell necrosis and 

swelling of central area) 

2669 F (increased relative kidney 

weight) 

1570 M (29% reduced body 

weight gain) 

Kano et al. 2008 
121

2669

108

657

1554

122

2669

107

15541614

109

15702669

129

274

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference 

Figure (Strain) (Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Chemical Form 

28 Mouse 

(B6C3F1) 

13 wk ad lib (W) 

2669 F Kano et al. 2008 

Neurological 

29 Rat 

(Fischer- 344) 

13 wk ad lib (W) 

657 M 1554 M (vacuolar changes in the 

brain) 

Kano et al. 2008 

30 Mouse 

(B6C3F1) 

13 wk ad libi (W) 

2669 F Kano et al. 2008 

Reproductive 

31 Rat 

(Fischer- 344) 

13 wk ad lib (W) 

d

1554 M 1614 F 

Kano et al. 2008 

32 Mouse 

(B6C3F1) 

13 wk ad lib (W) 

d

1570 M 2669 F 

Kano et al. 2008 

CHRONIC EXPOSURE Death 

33 Rat 

F344/DuCrj 

2 yr ad lib (W) 

274 M (increased early 

mortality) 

Kano et al. 2009 
114

240

133

278

116

380

118

584

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to 

Figure 

Species 

(Strain) 

Frequency 

(Route) System 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

34 Rat 

(OsborneMendel) 

110 wk ad lib (W) 

240 M (early mortality) 

35 Mouse 

Crj:BDF1 

2 yr ad lib (W) 

278 F (increased early 

mortality) 

36 Mouse 

(B6C3F1) 

Systemic 

37 Rat 

(Wistar) 

90 wk ad lib (W) 452 d ad lib (W) 

Renal 

380 F (early mortality) 584 M (glomerulonephritis) 

Reference Chemical Form 

NCI 1978 Kano et al. 2009 

NCI 1978 Argus et al. 1965 
123

18

83

42942942911 5542942942942983

429

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

LOAEL 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System 

NOAEL 

(mg/kg/day) 

38 Rat 

F344/DuCrj 

2 yr ad lib (W) 

Resp 18 F 

Cardio Gastro Musc/skel Hepatic Renal Endocr Dermal Ocular Bd Wt 

429 F 429 F 429 F 

11 M 

429 F 429 F 429 F 429 F 

83 F 

Less Serious Serious 

(mg/kg/day) (mg/kg/day) 

83 F (nuclear enlargement of 

olfactory epithelium) 

55 M (mixed cell foci) 

429 F (20% reduced body 

weight gain) 

Reference Chemical Form 

Kano et al. 2009 
14

15991599159915999.6

94

9.6

94

159994

1015

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference 

Figure (Strain) (Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Chemical Form 

39 Rat 

(Sherman) 

716 d ad lib (W) 

Resp 1599 F Kociba et al. 1974 

Cardio 1599 F Gastro 1599 F Hemato 1599 F Hepatic 

e

9.6 M 94 M (hepatocellular 

degeneration and necrosis) 

Renal 9.6 M 94 M (degeneration and 

necrosis of tubular epithelium) 

Endocr 1599 F Bd Wt 94 M 1015 M (>10% reduced weight 

gain) 
2

240

640

240

640240 350

240

640640240

530

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference 

Figure (Strain) (Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Chemical Form 

40 Rat 

(OsborneMendel) 

110 wk ad lib (W) 

Resp 240 M (increased incidence of 

pneumonia) 

NCI 1978 

Cardio 640 F Gastro Musc/skel Hepatic Renal 

640 F 240 M 

240 M (stomach ulcers) 350 F (hepatocytomegaly) 

240 M (cortical tubular 

degeneration) 

Endocr 640 F Dermal 640 F Bd Wt 240 M 530 M (reduced body weight 

gain, unquantified) 
128

49

191

96496496449

191

96496496496419166

278 677

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

ey to Species Frequency NOAEL Less Serious Serious Reference 

igure (Strain) (Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Chemical Form 

1 Mouse 2 yr Resp 49 M Crj:BDF1 ad lib

(W) 

Cardio 964 F Gastro 964 F Musc/skel 964 F Hepatic 49 M Renal 964 F Endocr 964 F Dermal 964 F Ocular 964 F Bd Wt 191 M 

d

66 F 

191 M (nuclear enlargement of 

olfactory epithelium in nasal cavity) 

191 M (increased relative liver 

weight) 

278 F (16% reduced terminal 

body weight) 

Kano et al. 2009 

677 M (45% reduced terminal 

body weight) 

K

F

4
7

380

860860860860860860860830380

860

126

429

16

1599

4

640

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference 

Figure (Strain) (Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Chemical Form 

42 Mouse 

(B6C3F1) 

90 wk ad lib (W) 

Resp 380 F (increased incidence of 

pneumonia) 

NCI 1978 

Cardio 860 F Gastro 860 F Musc/skel 860 F Hepatic 860 F Renal 860 F Endocr 860 F Dermal 860 F 

Immuno/ Lymphoret 

43 Rat 

F344/Du/DuCr 

2 yr ad lib (W) 

Bd Wt 830 M 

d

380 F 429 F 

860 F (decreased body weight 

gain, unquantified) 

Kano et al. 2009 

44 Rat 

(Sherman) 

716 d ad lib (W) 

1599 F Kociba et al. 1974 

45 Rat 

(OsborneMendel) 

110 wk ad lib (W) 

640 F NCI 1978 
132

964

9

860

125

429

17

1599

5

640

130

964

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

a 

Key to Species 

Figure (Strain) 

46 Mouse 

Crj:BDF1 

47 Mouse 

(B6C3F1) 

Neurological 

48 Rat 

F344/DuCrj 

49 Rat 

(Sherman) 

50 Rat 

(OsborneMendel) 

51 Mouse 

Crj:BDF1 

Exposure/ LOAEL 

Duration/ 

Frequency NOAEL Less Serious Serious Reference 

(Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Chemical Form 

2 yr ad lib (W) 90 wk ad lib (W) 2 yr ad lib (W) 716 d ad lib (W) 110 wk ad lib (W) 2 yr ad lib (W) 

964 F 860 F 429 F 

1599 F 

640 F 964 F 

Kano et al. 2009 NCI 1978 Kano et al. 2009 Kociba et al. 1974 NCI 1978 Kano et al. 2009 
10

860

124

429

18

1599

6

640

131

964

11

860

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

a 

Key to Species 

Figure (Strain) 

52 Mouse 

(B6C3F1) 

Reproductive 

53 Rat 

F344/DuCrj 

54 Rat 

(Sherman) 

55 Rat 

(OsborneMendel) 

56 Mouse 

Crj:BDF1 

57 Mouse 

(B6C3F1) 

Exposure/ LOAEL 

Duration/ 

Frequency NOAEL Less Serious Serious Reference 

(Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Chemical Form 

90 wk ad lib (W) 2 yr ad lib (W) 716 d ad lib (W) 110 wk ad lib (W) 2 yr ad lib (W) 90 wk ad lib (W) 

860 F 429 F 

1599 F 

640 F 964 F 860 F 

NCI 1978 Kano et al. 2009 Kociba et al. 1974 NCI 1978 Kano et al. 2009 NCI 1978 
13

584

127

274

19

1015

3

350240

134

66

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

a 

Key to 

Figure 

Cancer 

58 59 60 61 62 

Species 

(Strain) 

Rat (Wistar) Rat F344/DuCrj Rat (Sherman) Rat (OsborneMendel) Mouse Crj:BDF1 

Exposure/ 

Duration/ 

Frequency 

(Route) 

452 d ad lib (W) 

2 yr ad lib (W) 716 d ad lib (W) 110 wk ad lib (W) 2 yr ad lib (W) 

NOAEL Less Serious 

System (mg/kg/day) (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

584 M (CEL: liver tumors) 274 M (CEL: hepatocellular 

adenoma or carcinoma; mesothelioma of the peritoneum) 

1015 M (CEL: hepatocellular 

carcinomas) 

350 F (CEL: hepatocellular 

carcinomas) 

240 (CEL: nasal carcinomas 

in both sexes) 

66 F (CEL: hepatocellular 

adenomas or carcinomas) 

Reference Chemical Form 

Argus et al. 1965 

Kano et al. 2009 Kociba et al. 1974 NCI 1978 Kano et al. 2009 
8

380

66

1014

Table 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species Frequency NOAEL Less Serious Serious Reference 

Figure (Strain) (Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Chemical Form 

63 Mouse 

(B6C3F1) 

90 wk ad lib (W) 

64 Gn Pig 

(NS) 

23 mo ad lib (W) 

380 F (CEL: increased 

incidence of hepatocellular carcinomas and adenomas) 

1014 M (CEL: increased 

incidence of hepatomas) 

NCI 1978 Hoch-Ligeti and Argus 1

a The number corresponds to entries in Figure 3-2. b Used to derive an acute-duration oral minimal risk level (MRL) of 5.0 mg/kg/day for 1,4-dioxane; the MRL was derived by dividing the NOAEL by an uncertainty faanimal to human extrapolation and 10 to protect sensitive populations). c Used to derive an intermediate-duration oral minimal risk level (MRL) of 0.5 mg/kg/day for 1,4-dioxane; the MRL was derived by dividing the NOAEL by an uncert(10 animal to human extrapolation and 10 to protect sensitive populations). d Differences in levels of health effects and cancer effects between male and females are not indicated in Figure 3-2. Where such differences exist, only the levels most sensitive gender are presented. e Used to derive a chronic-duration oral minimal risk level (MRL) of 0.1 mg/kg/day for 1,4-dioxane; the MRL was derived by dividing the NOAEL by an uncertainty faanimal to human extrapolation and 10 to protect sensitive populations). ad lib = ad libitum; ALT = alanine aminotransferase; AST = aspartate aminotransferase; Bd Wt = body weight; Cardio = cardiovascular; CEL = cancer effect level; d = endocrine; F = Female; (G) = gavage; Gastro = gastrointestinal; Gd = gestational day; Gn pig = guinea pig; (GW) = gavage in water; Hemato = hematological; LD50% kill; LOAEL = lowest-observed-adverse-effect level; M = male; NOAEL = no-observed-adverse-effect level; NS = not specified; Resp = respiratory; (W) = drinkweek(s) 
Death 

Respiratory Hepatic Renal Body Weig Neurologic Developme 


	


	


	


	


	


	


	

10000 

ht 

al 

ntal 

Figure 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral
	

Acute (≤14 days)
	

Systemic 

mg/kg/day 

5r 4r 7m 3r 

17h 8g
	

9g
	 6m

1r 11r 11r 11r 15r 14m 14m 

10h 

17h 

14m 14m 

1000 2r 11r 12r 11r 12r 11r 15r 16h 18r 

18r 

11r 

16h
	

100
	

11r 13r 

10 

1 

c-Cat 

d-Dog

r-Rat 

p-Pig

q-Cow

 -Humans 

k-Monkey

m-Mouse 

h-Rabbit 

a-Sheep 

f-Ferret 

j-Pigeon

e-Gerbil 

s-Hamster 

g-Guinea Pig 

n-Mink 

o-Other

 Cancer Effect Level-Animals

 LOAEL, More Serious-Animals

LOAEL, Less Serious-Animals

NOAEL - Animals

 Cancer Effect Level-Humans

 LOAEL, More Serious-Humans

LOAEL, Less Serious-Humans

NOAEL - Humans

 LD50/LC50

Minimal Risk Level

 for effects

 other than

 Cancer 

1,4-DIOXANE 3. HEALTH EFFECTS 74
Death 

Respiratory Cardiovascular Gastrointestinal Hematological Musculoskeletal Hepatic Renal Endocrine Dermal Ocular Body Weight 


	


	

 


	

Figure 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (Continued)
 

Intermediate (15-364 days)
	

Systemic 

mg/kg/day 

10000 

26m 26m 26m 25m 25m 26m 26m 26m 26m 26m 

22r 22r 26m 22r 22r 26m 22r 22r 22r 26m 22r 21r 21r 21r
	

1000
	 19r 20r 23r 24r 24r 26m 26m 22r 22r 22r 22r 26m 

26m 

22r 26m 

22r 26m 

22r 22r 

100 23r 22r 

22r 22r 

10 24r 

1 

0.1 

c-Cat 

d-Dog

r-Rat 

p-Pig

q-Cow

 -Humans 

k-Monkey

m-Mouse 

h-Rabbit 

a-Sheep 

f-Ferret 

j-Pigeon

e-Gerbil 

s-Hamster 

g-Guinea Pig 

n-Mink 

o-Other

 Cancer Effect Level-Animals

 LOAEL, More Serious-Animals

LOAEL, Less Serious-Animals

NOAEL - Animals

 Cancer Effect Level-Humans

 LOAEL, More Serious-Humans

LOAEL, Less Serious-Humans

NOAEL - Humans

 LD50/LC50

Minimal Risk Level

 for effects

 other than

 Cancer 

1,4-DIOXANE 3. HEALTH EFFECTS 75
Immuno/Lymphor 

Neurological Reproductive 

 


	

Figure 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (Continued)
 

Intermediate (15-364 days)
	

mg/kg/day 

10000 

28m 30m 32m 

27r 31r 

1000 

29r 

29r 32m 31r 

100 

10 

1 

0.1 

c-Cat 

d-Dog

r-Rat 

p-Pig

q-Cow

 -Humans 

k-Monkey

m-Mouse 

h-Rabbit 

a-Sheep 

f-Ferret 

j-Pigeon

e-Gerbil 

s-Hamster 

g-Guinea Pig 

n-Mink 

o-Other

 Cancer Effect Level-Animals

 LOAEL, More Serious-Animals

LOAEL, Less Serious-Animals

NOAEL - Animals

 Cancer Effect Level-Humans

 LOAEL, More Serious-Humans

LOAEL, Less Serious-Humans

NOAEL - Humans

 LD50/LC50

Minimal Risk Level

 for effects

 other than

 Cancer 

1,4-DIOXANE 76 3. HEALTH EFFECTS
Death 

Respiratory Cardiovascular Gastrointestinal Hematological Musculoskeletal Hepatic Renal 

 


	

Figure 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (Continued)
 

Chronic (≥365 days)

Systemic 

mg/kg/day 

10000 

39r 39r 39r 39r 

1000 41m 42m 41m 42m 41m 42m 42m 42m

38r 40r 38r 38r 40r 37r

35m 36m 42m 33r 41m 40r 41m 34r 41m 40r 40r 41m 40r 40r 

100 38r 38r 38r 39r 38r 39r 41m 41m 41m 41m

38r 38r 38r 38r 

10 39r 39r 

1 

0.1 

0.01 

0.001 

0.0001 

1E-5 

1E-6 

c-Cat 

d-Dog

r-Rat 

p-Pig

q-Cow

 -Humans 

k-Monkey

m-Mouse 

h-Rabbit 

a-Sheep 

f-Ferret 

j-Pigeon

e-Gerbil 

s-Hamster 

g-Guinea Pig 

n-Mink 

o-Other

 Cancer Effect Level-Animals

 LOAEL, More Serious-Animals

LOAEL, Less Serious-Animals

NOAEL - Animals

 Cancer Effect Level-Humans

 LOAEL, More Serious-Humans

LOAEL, Less Serious-Humans

NOAEL - Humans

 LD50/LC50

Minimal Risk Level

 for effects

 other than

 Cancer 

1,4-DIOXANE 3. HEALTH EFFECTS 77
Endocrine 

Dermal Ocular Body Weight Immuno/Lymphor Neurological Reproductive Cancer * 

 

 


	


	

 

10000 

Figure 3-2 Levels of Significant Exposure to 1,4-Dioxane - Oral (Continued)
 

Chronic (≥365 days)
	

Systemic
	

mg/kg/day 

39r 44r 49r 54r 

1000 41m 41m 41m 39r 46m 51m 56m 64g 60r 42m 42m 41m 42m 42m 47m 52m 57m

38r 40r 38r 40r 38r 40r 43r 45r 48r 50r 53r 55r 58r

41m 42m 38r 63m 59r 61 41m 40r 61r 

100 38r 39r 41m 62m 

10 

1 

0.1 

0.01 -4 10 

Estimated 

Upper-Bound

0.001 -5 10 Human Cancer 

Risk Levels 

0.0001 -6 10 

1E-5 -7 10 

*Doses represent the lowest dose tested per study that produced a tumorigenic 

1E-6 response and do not imply the existence of a threshold for the cancer endpoint. 

c-Cat 

d-Dog

r-Rat 

p-Pig

q-Cow

 -Humans 

k-Monkey

m-Mouse 

h-Rabbit 

a-Sheep 

f-Ferret 

j-Pigeon

e-Gerbil 

s-Hamster 

g-Guinea Pig 

n-Mink 

o-Other

 Cancer Effect Level-Animals

 LOAEL, More Serious-Animals

LOAEL, Less Serious-Animals

NOAEL - Animals

 Cancer Effect Level-Humans

 LOAEL, More Serious-Humans

LOAEL, Less Serious-Humans

NOAEL - Humans

 LD50/LC50

Minimal Risk Level

 for effects

 other than

 Cancer 

1,4-DIOXANE

r

3. HEALTH EFFECTS 78
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 79 

3. HEALTH EFFECTS 

3.2.2.2 Systemic Effects 

No studies were located regarding respiratory, cardiovascular, gastrointestinal, hematological, 

musculoskeletal, hepatic, renal, endocrine, dermal, ocular, and body weight effects in humans after oral 

exposure to 1,4-dioxane. 

The highest NOAEL and all reliable LOAEL values from each study for systemic effects in each species 

and duration category are recorded in Table 3-2 and plotted in Figure 3-2. 

Respiratory Effects. Information exists regarding nasal and respiratory effects in animals after oral 

exposure to 1,4-dioxane. Nuclear enlargement of the olfactory epithelium was observed in male and 

female F344/DuCrj rats dosed with 1,010 and 1,040 mg 1,4-dioxane/kg/day, respectively, in the drinking 

water for 2 weeks (JBRC 1998); the respective NOAELs were 370 and 400 mg/kg/day. The same type of 

lesions were observed in male and female rats treated with 126 and 185 mg 1,4-dioxane/kg/day, 

respectively, for 13 weeks; the respective NOAELs were 52 and 83 mg/kg/day (Kano et al. 2008). It 

should be noted, however, that a recent study suggested that the nasal lesions in rats exposed to 

1,4-dioxane in drinking water may be caused by direct contact of the chemical with the nasal tissue as the 

rats drink the water (Sweeney et al. 2008). Male and female Crj:BDF1 mice dosed with 585 and 387 mg 

1,4-dioxane/kg/day, respectively, in the drinking water for 13 weeks showed nuclear enlargement of the 

bronchial epithelium; higher doses also involved the nasal cavity, trachea, and lungs (Kano et al. 2008); 

the respective NOAELs were 231 and 170 mg/kg/day. No histopathologic changes were observed in the 

lungs and nasal turbinates from Sherman rats dosed with up to 1,599 mg 1,4-dioxane/kg/day in the 

drinking water for 716 days (Kociba et al. 1974). No significant non-neoplastic lesions were seen in the 

lungs and trachea from Osborne-Mendel rats dosed with up to 640 mg 1,4-dioxane/kg/day via drinking 

water for 110 weeks (NCI 1978). However, an increased incidence of pneumonia was seen in treated 

males and females, although the incidence was not dose-related. The investigators speculated that the 

development of nasal carcinomas might have been a contributing factor (NCI 1978). Female F344 rats 

dosed with ≥83 mg 1,4-dioxane/kg/day, also in the drinking water, for 104 weeks showed increased 

incidence of nuclear enlargement of the olfactory epithelium in the nasal cavity; the NOAEL was 

18 mg/kg/day (Kano et al. 2009). In males, nasal cavity lesions were observed at 274 mg/kg/day, and the 

NOAEL in males was 55 mg/kg/day. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 80 

3. HEALTH EFFECTS 

In B6C3F1 mice treated with 1,4-dioxane in the drinking water for 90 weeks, there was a dose-related 

increase in the incidence of pneumonia in males and females and of rhinitis in females (NCI 1978); males 

were dosed with 720 or 830 mg/kg/day and females were dosed with 380 or 860 mg/kg/day. Examination 

of the lungs and trachea did not reveal any other treatment-related non-neoplastic alterations. Male 

Crj:BDF1 mice dosed with ≥191 mg 1,4-dioxane/kg/day in the drinking water for 2 years showed nuclear 

enlargement of olfactory epithelium in the nasal cavity; the NOAEL was 49 mg/kg/day (Kano et al. 

2009). This lesion was significantly increased in females dosed with ≥278 mg/kg/day, but not 66 

mg/kg/day. Doses of 677 mg/kg/day in males and 964 mg/kg/day in females significantly increased the 

incidence of nuclear enlargement of the respiratory epithelium in the nasal cavity. 

Cardiovascular Effects. No gross or histological alterations were observed in the heart from rats and 

mice dosed with up to 1,614 and 2,669 mg 1,4-dioxane/kg/day, respectively, in the drinking water for 

13 weeks (Kano et al. 2008). Also, no gross or histological alterations were reported in the heart from 

rats dosed with up to 1,599 mg 1,4-dioxane/kg/day in the drinking water for 2 years (Kano et al. 2009; 

Kociba et al. 1974; NCI 1978) or in mice dosed with up to 860 mg/kg/day for 90 weeks (NCI 1978) or 

964 mg/kg/day for 2 years (JBRC 1998b). 

Gastrointestinal Effects. Hemorrhage of the stomach was reported in rats, mice, guinea pigs, and 

dogs administered acute lethal doses of 1,4-dioxane by gavage (Laug et al. 1939; Schrenk and Yant 1936; 

Smyth et al. 1941). Gastroenteritis was also reported in rats that died after drinking water that provided 

approximately 1,428 mg 1,4-dioxane/kg/day for up to 34 days (Fairley et al. 1934). No gross or 

histological alterations were observed in the gastrointestinal tract from rats and mice dosed with up to 

1,614 and 2,669 mg 1,4-dioxane/kg/day, respectively, in the drinking water for 13 weeks (Kano et al. 

2008). In chronic-duration studies, no gastrointestinal alterations were reported in Sherman rats dosed 

with up to 1,599 mg 1,4-dioxane/kg/day (Kociba et al. 1974), in F344/DuCrj rats dosed with up to 

429 mg/kg/day (Kano et al. 2009), in B6C3F1 mice treated with up to 860 mg/kg/day (NCI 1978), or in 

Crj:BDF1 mice dosed with up to 964 mg/kg/day (Kano et al. 2009). However, male Osborne-Mendel rats 

treated with ≥240 mg/kg/day for 110 weeks developed stomach ulcers; no such lesions were seen in 

control males or in female rats (NCI 1978). 

Hematological Effects. Hematological changes consisting of increased red blood cell counts, 

hemoglobin, and hematocrit were reported in F344/DuCrj male rats dosed with 1,554 mg 1,4-dioxane 

/kg/day in the drinking water for 13 weeks; no significant changes occurred at 657 mg/kg/day (Kano et al. 

2008). In females, there was a decrease in mean corpuscular volume and platelet concentration at 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 81 

3. HEALTH EFFECTS 

1,614 mg/kg/day. Sherman rats showed no significant deviations from normality in hematological 

parameters in a 2-year study (Kociba et al. 1974). In that study, the rats received doses of up to 1,599 mg 

1,4-dioxane/kg/day in the drinking water; blood samples were collected during the 4th, 6th, 12th, and 

18th month and at termination, and analyzed for packed cell volume, total erythrocyte counts, hemoglobin 

concentration, and total and differential white blood cell counts. 

Musculoskeletal Effects. No gross or histological alterations were observed in bone and skeletal 

muscle (neither bone or muscle were specified) from rats and mice dosed with up to 1,614 and 2,669 mg 

1,4-dioxane/kg/day, respectively, in the drinking water for 13 weeks (Kano et al. 2008), or in rats and 

mice dosed with up to 429 and 964 mg 1,4-dioxane/kg/day, respectively, for 2 years (Kano et al. 2009). 

Similarly, no histopathologic alterations were observed in skeletal muscle from rats dosed with up to 

640 mg 1,4-dioxane/kg/day for 110 weeks or in mice treated with up to 860 mg/kg/day for 90 weeks (NCI 

1978). 

Hepatic Effects. Acute oral doses of 1,4-dioxane that caused lethality in rats, mice, rabbits, guinea 

pigs, and dogs (see Section 3.2.2.1) induced varying degrees of liver damage, including liver congestion 

and degeneration (de Navasquez 1935; Kesten et al. 1939; Laug et al. 1939; Schrenk and Yant 1936; 

Smyth et al. 1941). In general, single doses that caused death were higher than 2,000 mg/kg. A single 

dose of 1,000 mg/kg administered to rats, and that did not cause death, produced no histopathologic 

alterations in the liver (Stott et al. 1981). Hepatocyte swelling and vacuolation of the central area were 

reported in the liver from F344/DuCrj rats dosed with 2,750–2,960 mg 1,4-dioxane/kg/day for 2 weeks in 

the drinking water (JBRC 1998), but no significant liver alterations were seen at 1,010–1,040 mg/kg/day. 

Crj:BDF1 mice treated in the same manner with 2,550–3,230 mg 1,4-dioxane/kg/day showed single cell 

necrosis and swelling of the central area; no significant alterations were reported at 1,380– 

1,780 mg/kg/day (JBRC 1998). 

Repeated administration of doses of approximately 1,428 mg 1,4-dioxane/kg/day in the drinking water for 

34 days was lethal to rats, and examination of the animals showed liver congestion and hepatocyte 

degeneration (Fairley et al. 1934). The same types of liver lesions were seen in mice treated in the same 

manner with approximately 2,916 mg 1,4-dioxane/kg/day; in this experiment, the mice survived up to 

day 67, at which time they were sacrificed (Fairley et al. 1934). Repeated dosing of rats with 1,000 mg 

1,4-dioxane/kg/day for 7 or 11 weeks produced hepatocyte swelling and histopathology (Stott et al. 1981) 

and fatty vacuoles in the hepatocytes (Lundberg et al. 1987). Male F344/DuCrj rats dosed with ≥126 mg 

1,4-dioxane/kg/day for 13 weeks in the drinking water showed swelling of the central area (Kano et al. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 82 

3. HEALTH EFFECTS 

2008); the NOAEL was 52 mg/kg/day. Higher doses also produced vacuolar changes and granulation, 

and changes in clinical chemistry parameters indicative of liver toxicity. In female rats, granulation was 

evident at 427 mg/kg/day and hepatocyte swelling at 756 mg/kg/day. The findings from the Kano et al. 

(2008) study in rats were used to derive an intermediate-duration oral MRL of 0.5 mg/kg/day for 

1,4-dioxane based on a NOAEL of 52 mg/kg/day for male rats. In Crj:BDF1 mice treated in the same 

manner, doses of 585–898 mg 1,4-dioxane/kg/day caused single cell necrosis and swelling in the central 

area, but doses ≤410 mg/kg/day were without significant effect (Kano et al. 2008). Changes in clinical 

chemistry parameters suggestive of liver damage were reported also in mice dosed with ≥585 mg 

1,4-dioxane/kg/day (Kano et al. 2008). 

In the 2-year bioassay by Kociba et al. (1974) in Sherman rats, significant early deaths occurred with 

doses between 1,015 and 1,599 mg/kg/day beginning at about 2–4 months in the study, and the authors 

indicated that these rats exhibited degenerative changes in the liver, although it was not made clear 

whether these changes along with renal lesions were the cause of death. Rats treated chronically with 

1,4-dioxane in the drinking water (≥94 mg/kg/day for males, ≥148 mg/kg/day for females) had liver 

lesions consisting of various degrees of hepatocellular degeneration and necrosis and evidence of hepatic 

regeneration, as indicated by hepatocellular hyperplastic nodule formation (Kociba et al. 1974). No 

significant effects were seen in males at 9.6 mg/kg/day and in females at 19 mg/kg/day. The findings 

from Kociba et al. (1974) were used to derive a chronic-duration oral MRL of 0.1 mg/kg/day for 

1,4-dioxane. An elevated incidence of hepatocytomegaly was observed in female rats treated with 

≥350 mg 1,4-dioxane/kg/day (the lowest dose tested in females) and in males dosed with 530 mg/kg/day 

of the chemical in the drinking water for 2-years (NCI 1978); the NOAEL in males was 240 mg/kg/day. 

In another 2-year drinking water study in F344/DuCrj rats, males dosed with ≥55 mg/kg/day showed 

increased mixed cell foci; the NOAEL was 11 mg/kg/day (Kano et al. 2009). Females treated with 

429 mg/kg/day showed increased mixed cell foci, but no such lesions were observed at 83 mg/kg/day. 

Mice dosed with up to 860 mg 1,4-dioxane/kg/day via the drinking water for 90 weeks showed no 

treatment-related non-neoplastic liver lesions (NCI 1978). Although the investigators stated that 

hepatocytomegaly was commonly found in treated mice, the incidences were not significantly different 

than in controls, and no trend was apparent. Male Crj:BDF1 mice dosed with ≥191 mg 1,4-dioxane for 

2 years had significantly increased relative liver weight (Kano et al. 2009); no significant increase was 

reported at 49 mg/kg/day. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 83 

3. HEALTH EFFECTS 

Renal Effects. Acute lethal doses of 1,4-dioxane in rodents caused kidney lesions ranging from 

kidney enlargement to extensive kidney degeneration (de Navasquez 1935; Kesten et al. 1939; Laug et al. 

1939; Smyth et al. 1941). Severe kidney damage was seen also in an acute study in dogs (Schrenk and 

Yant 1936). Hydropic changes of the proximal renal tubule were reported in male and female 

F344/DuCrj rats dosed with 2,960 and 2,750 mg 1,4-dioxane/kg/day, respectively, in the drinking water 

for 2 weeks (JBRC 1998); the corresponding NOAELs were 1,010 and 1,040 mg/kg/day. Treatment for 

13 weeks resulted in nuclear enlargement of the proximal renal tubules at 657 and 756 mg 

1,4-dioxane/kg/day in male and female rats, respectively (Kano et al. 2008); higher doses also induced 

hydropic changes in the proximal tubules. The NOAELs for morphological alterations in the kidneys 

were 274 and 427 mg/kg/day in males and females, respectively. Other significant findings in this study 

were a decrease in urinary pH in males at ≥274 mg/kg/day and an increase in absolute and relative kidney 

weight in females at ≥185 mg/kg/day. In another study, rats dosed for up to 34 days with 1,428 mg 

1,4-dioxane/kg/day, a dose that caused deaths, had vascular congestion in the kidneys and cell 

degeneration in the cortical epithelium (Fairley et al. 1934). Similar lesions were observed in mice 

treated in the same fashion with approximately 2,916 mg/kg for up to 67 days (Fairley et al. 1934). 

Changes resembling glomerulonephritis were reported in male Wistar rats exposed to approximately 

584 mg 1,4-dioxane/kg/day in the drinking water for about 452 days (Argus et al. 1965). Treatment of 

female Crj:BDF1 mice with 1,620 mg 1,4-dioxane/kg/day in the drinking water for 13 weeks increased 

absolute kidney weight and decreased urinary pH; urinary pH was decreased in males at 882 mg/kg/day. 

Doses of 585 and 898 mg/kg/day in males and females, respectively, did not cause any significant renal 

effects (Kano et al. 2008). 

Kociba et al. (1974) observed degenerative changes in the kidneys from Sherman rats that died after 2– 

4 months of drinking water that provided approximately 1,015 mg 1,4-dioxane to males and 

1,599 mg/kg/day to females. At termination of this 2-year study, the kidneys of both males 

(≥94 mg/kg/day) and females (≥148 mg/kg/day) showed tubular epithelial degeneration and necrosis, and 

there was evidence of renal tubular regeneration as indicated by increased tubular epithelial regenerative 

activity. The NOAELs in males and females were 9.6 and 19 mg/kg/day, respectively, which were also 

the NOAELs for liver effects in the study (Kociba et al. 1974). In the NCI (1978) bioassay in OsborneMendel rats, kidney lesions consisting of vacuolar degeneration and/or focal tubular epithelial 

regeneration in the proximal cortical tubules and occasionally hyaline casts were seen with significantly 

higher incidence in treated males (≥240 mg/kg/day, dose-related) and in high-dose females 

(640 mg/kg/day). No significant histological alterations were reported in the kidneys from F344/DuCrj 

rats or Crj:BDF1 mice dosed with up to 429 or 964 mg 1,4-dioxane/kg/day, respectively, in the drinking 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 84 

3. HEALTH EFFECTS 

water for 2 years (Kano et al. 2009). No treatment-related kidney lesions were observed in B6C3F1 mice 

treated via the drinking water with up to 860 mg 1,4-dioxane/kg/day for 90 weeks (NCI 1978). 

Endocrine Effects. No gross or histological alterations were observed in the thyroid, parathyroid, 

adrenal, pituitary, pancreas, and salivary glands from rats and mice dosed with up to 1,614 and 2,669 mg 

1,4-dioxane/kg/day, respectively, in the drinking water for 13 weeks (Kano et al. 2008), or in rats and 

mice dosed with up to 429 and 964 mg 1,4-dioxane/kg/day, respectively, for 2 years (Kano et al. 2009). 

No gross or microscopic alterations were seen in the pituitary, adrenal, thyroid, and parathyroid glands 

from rats dosed with up to 1,599 mg 1,4-dioxane/kg/day in the drinking water for 2 years (Kociba et al. 

1974; NCI 1978) or in the same organs from mice dosed in the same manner with up to 860 mg 

1,4-dioxane/kg/day (NCI 1978). No further information was located on effects of 1,4-dioxane on 

endocrine parameters. 

Dermal Effects. No gross or histological alterations were observed in the skin from rats and mice 

dosed with up to 1,614 and 2,669 mg 1,4-dioxane/kg/day, respectively, in the drinking water for 13 weeks 

(Kano et al. 2008), or in rats and mice dosed with up to 429 and 964 mg 1,4-dioxane/kg/day, respectively, 

for 2 years (Kano et al. 2009). Treatment of rats with up to 640 mg 1,4-dioxane/kg/day in the drinking 

water for 2 years or mice with up to 860 mg 1,4-dioxane/kg/day had no significant effect on the gross or 

microscopic appearance of the skin (NCI 1978). 

Ocular Effects. No gross or histological alterations were observed in the eyes from rats and mice 

dosed with up to 1,614 and 2,669 mg 1,4-dioxane/kg/day, respectively, in the drinking water for 13 weeks 

(Kano et al. 2008), or in rats and mice dosed with up to 429 and 964 mg 1,4-dioxane/kg/day, respectively, 

for 2 years (Kano et al. 2009). No other relevant information was located. 

Body Weight Effects. Administration of a single dose of 10 mg 1,4-dioxane/kg by gavage in water 

to rats reduced body weight gain by approximately 32% relative to controls in a 7-day period (Stott et al. 

1981). According to the investigators, this was likely due to a reduction in food consumption, consistent 

with the histological observation that hepatocytes were depleted of glycogen. However, treatment with 

10 mg/kg/day by gavage in water for 11 weeks had no significant effect on weight gain, and doses of 

1,000 mg/kg/day for 11 weeks decreased body weight only about 9% relative to controls (Stott et al. 

1981). In 2-week drinking water studies, doses of approximately 2,750–2,960 mg 1,4-dioxane/kg/day 

reduced body weight gain in F344/DuCrj rats (JBRC 1998). In Crj:BDF1 mice, a significant reduction in 

body weight gain occurred in males at 2,550 mg/kg/day, but not at 1,380 mg/kg/day (JBRC 1998). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 85 

3. HEALTH EFFECTS 

Reduced body weight gain was also reported in female F344/DuCrj rats treated for 13 weeks with 

≥756 mg 1,4-dioxane/kg/day and in male and female Crj:BDF1 mice treated for the same duration with 

≥1,570 mg/kg/day (Kano et al. 2008). In the JBRC (1998) and Kano et al. (2008) studies, reduction in 

weight gain was usually associated with reduced food consumption and/or reduced water consumption. 

Sherman rats treated with 1,015–1,599 mg 1,4-dioxane/kg/day for 2 years gained approximately 10% less 

weight throughout the study (estimated from graphic data in the paper) than controls or rats dosed with 

94–148 mg/kg/day (Kociba et al. 1974). In the NCI (1978) bioassay, body weight of male rats in the 

high-dose group (530 mg/kg/day) and female mice (860 mg/kg/day) were lower than controls during the 

second year of the study. No data on food consumption were provided in these two chronic-duration 

studies. In another chronic study, treatment of male F344/DuCrj rats with up to 274 mg 1,4-dioxane/kg/ 

day did not significantly affect body weight, but females dosed with 429 mg/kg/day had a terminal weight 

20% lower than controls; the NOAEL in females was 83 mg/kg/day (Kano et al. 2009). Neither food nor 

water consumption was significantly altered in this case. Male Crj:BDF1 mice dosed with 677 mg 

1,4-dioxane/kg/day for 2 years had a terminal weight 45% lower than controls, and females dosed with 

278 and 964 mg/kg/day had a final weight 16% and 45% lower than controls, respectively (Kano et al. 

2009). The NOAELs for males and females were 191 and 66 mg/kg/day, respectively. In mice, the 

reductions in weight gain were accompanied by significant reductions in water and food consumption. 

3.2.2.3 Immunological and Lymphoreticular Effects 

No studies were located regarding immunological and lymphoreticular effects in humans after oral 

exposure to 1,4-dioxane. No gross or histological alterations were observed in the lymph nodes, spleen, 

and thymus from rats and mice dosed with up to 1,614 and 2,669 mg 1,4-dioxane/kg/day, respectively, in 

the drinking water for 13 weeks (Kano et al. 2008), or in rats and mice dosed with up to 429 and 964 mg 

1,4-dioxane/kg/day, respectively, for 2 years (Kano et al. 2009). No histopathologic alterations were 

observed in the spleen, thymus, and lymph nodes from rats dosed via drinking water with up to 1,599 mg 

1,4-dioxane/kg/day for 2 years or from mice dosed similarly with up to 860 mg/kg/day (Kociba et al. 

1974; NCI 1978). These NOAEL values for lymphoreticular effects are listed in Table 3-2 and plotted in 

Figure 3-2. 

3.2.2.4 Neurological Effects 

No studies were located regarding neurological effects in humans after oral exposure to 1,4-dioxane. In 

an acute study in rabbits, a single gavage dose of 4,400 mg 1,4-dioxane/kg induced staggering in one of 

three rabbits, and 6,600 mg/kg produced narcosis in one of three rabbits and was lethal to two other 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 86 

3. HEALTH EFFECTS 

rabbits (Knoefel 1935). No further details were provided in this early study. Male and female 

F344/DuCrj rats dosed with 2,960 and 2,750 mg 1,4-dioxane/kg/day, respectively, for 2 weeks showed 

vacuolar changes in the brain (JBRC 1998); the respective NOAELs were 1,010 and 1,040 mg/kg/day. 

Similar effects were reported in male and female F344/DuCrj rats dosed with 1,554 and 1,614 mg 

1,4-dioxane/kg/day, respectively, for 13 weeks in the drinking water (Kano et al. 2008); the respective 

NOAELs were 657 and 756 mg/kg/day. However, no significant alterations were seen in the spinal cord 

or sciatic nerve. In the same study, no histopathological alterations were observed in the brain, spinal 

cord, and sciatic nerve from Crj:BDF1 mice dosed with up to 2,669 mg 1,4-dioxane/kg/day. No 

histopathologic alterations were observed in the brain, spinal cord, and sciatic nerve from rats dosed via 

the drinking water with up to 1,599 mg 1,4-dioxane/kg/day for 2 years or from mice dosed similarly with 

up to 964 mg/kg/day (Kano et al. 2009; Kociba et al. 1974; NCI 1978). The NOAEL and LOAEL values 

for neurological effects are listed in Table 3-2 and plotted in Figure 3-2. 

3.2.2.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans after oral exposure to 1,4-dioxane. 

Standard reproductive toxicity studies on 1,4-dioxane in animals were not located. Only ancillary 

information is available. No gross or histological alterations were observed in the reproductive organs 

(testes, prostate, seminal vesicles, epididymis, uterus, ovaries, vagina) from rats and mice dosed with up 

to 1,614 and 2,669 mg 1,4-dioxane/kg/day, respectively, in the drinking water for 13 weeks (Kano et al. 

2008), or in rats and mice dosed with up to 429 and 964 mg 1,4-dioxane/kg/day, respectively, for 2 years 

(Kano et al. 2009). No evidence of gross or microscopic alterations was found in the reproductive organs 

from rats exposed through the drinking water to up to 1,599 mg 1,4-dioxane/kg/day for up to 2 years 

(Kociba et al. 1974; NCI 1978) or from mice exposed to up to 860 mg 1,4-dioxane/kg/day for up to 

90 weeks (NCI 1978). These values are presented in Table 3-2 and plotted in Figure 3-2. 

3.2.2.6 Developmental Effects 

No studies were located regarding developmental effects in humans after oral exposure to 1,4-dioxane. 

Only one relevant animal study was located. In that study, groups of pregnant Sprague-Dawley rats were 

administered 0, 258, 516, or 1,033 mg 1,4-dioxane by gavage on gestation days 6–15 and sacrifices were 

conducted on gestation day 21 (Giavini et al.1985). Dams in the high-dose group gained less weight than 

controls, and fetal weight in this group was reduced by 5.3% relative to controls. In addition, a slightly 

but significantly higher incidence of reduced sternum ossification was noticed in the high-dose group. No 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 87 

3. HEALTH EFFECTS 

other significant differences between treated and control groups were observed, including number of 

implantations and of live fetuses, post-implantation loss, and incidence of malformations. This study was 

used to derive an acute-duration oral MRL for 1,4-dioxane. The NOAEL and LOAEL values are 

presented in Table 3-2 and plotted in Figure 3-2. 

3.2.2.7 Cancer 

No studies were located regarding oral exposure of humans to 1,4-dioxane and cancer, but numerous 

studies have examined the carcinogenicity of 1,4-dioxane in animals exposed orally; in all of them the test 

material has been administered in the drinking water. In general, the studies in animals can be divided 

into a group in which numerous limitations are apparent, including small number of animals, low tumor 

incidences, lack of statistical analyses, and only one dose level tested, and another small group of 

standard bioassays. To the former category belong Argus et al. (1965, 1973), Hoch-Ligeti and Argus 

(1970), and Hoch-Ligeti et al. (1970), whereas the standard bioassays include JBRC (1998b), Kociba et 

al. (1974), and NCI (1978). 

Argus et al. (1965) exposed a group of 26 male Wistar rats to 1,4-dioxane in the drinking water at a 

concentration of 1% for 452 days. Nine rats served as controls. The maximal dose per rat was 132 g, 

which divided by an average exposure time of 452 days yields a daily dose of 584 mg/kg/day, assuming a 

reference body weight of 0.5 kg for mature male Wistar rats. End points examined included gross 

necropsy and histopathologic examination of tissues, but the range of tissues examined was not specified. 

Six of the 26 rats treated with 584 mg 1,4-dioxane/kg/day developed liver tumors that ranged in 

appearance from small neoplastic nodules to multifocal hepatocellular carcinomas. One treated rat had a 

transitional cell carcinoma of the kidney and one rat that received a total dose of 116 g for 387 days 

(599 mg/kg/day) developed leukemia. One control rat developed a lymphosarcoma. 

In a subsequent study by the same group of investigators, groups of male Sprague-Dawley rats (28– 

32/group) were treated with 1,4-dioxane in the drinking water for 13 months at levels of 0 (controls), 

0.75, 1.0, 1.4, or 1.8% (Hoch-Ligeti et al. 1970). At termination, complete necropsy and histopathological examinations were conducted. Doses were estimated by ATSDR to be approximately 444, 607, 

833, and 1,004 mg/kg/day assuming 13 months equals 390 days, a body weight of 0.6 kg for the rats, and 

the total dose provided in the study was 104–256 g. Six treated rats developed tumors of the nasal cavity. 

All of the tumors consisted of squamous cell carcinomas with marked keratinization. The incidences 

were as follows: one at 0.75%, one at 1%, two at 1.4%, and two at 1.8%. Hepatocellular carcinomas 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 88 

3. HEALTH EFFECTS 

were also observed in the rats that had nasal carcinomas in the 1.4 and 1.8% groups (Argus et al. 1973). 

In the latter study, in addition to incidences of hepatomas and hepatocellular carcinomas, the authors 

reported the incidences of “incipient” hepatomas. Two types of incipient hepatomas were observed, one 

consisting of large cells, apparently filled and distended with fat, and the other of finger-like strands of 

rather smaller hepatocytes with large hyperchromic nuclei and dense cytoplasm. According to Argus et 

al. (1973), these nodules appeared as histologically characteristic of fully developed hepatomas. The 

following tumor incidences were reported: 4 incipient tumors at 0.75%, 9 incipient tumors at 1%, 

13 incipient tumors and 3 hepatomas at 1.4%, and 11 incipient tumors and 12 hepatomas at 1.8% 

1,4-dioxane. No tumors were found in the lungs. The authors stated that the effective tumor dose (TD5), 

the 50% tumor dose (TD50), and the maximum effective dose (TD95) were 72, 149, and 260 g, 

respectively, evaluated from the probit plot of the dose-response (Argus et al. 1973). 

In the Kociba et al. (1974) study, groups of Sherman rats (60/sex/dose level) were treated with 

1,4-dioxane in the drinking water at levels of 0 (controls), 0.01, 0.1, or 1% for 716 days. This 

corresponded to doses of 0, 9.6, 94, and 1,015 mg/kg/day in males and 0, 19, 148, and 1,599 mg/kg/day in 

females based on body weight and water consumption data. Treatment with 1,4-dioxane significantly 

increased mortality in high-dose males and females beginning at about 2–4 months of treatment. These 

rats showed degenerative changes in both the liver and kidneys. Body weight gain was significantly 

reduced in high-dose animals from the beginning of the study. Carcinogenic effects were limited to the 

liver and nasal turbinates. The investigators combined the incidence of tumors in males and females and 

expressed them as the effective incidences in the number of rats that survived for 12 months. The 

incidence of all hepatic tumors was 2/106 (1.9%), 0/110 (0%), 1/106 (0.9%), and 12/66 (18.2%, 

p=0.0022) in controls, low-, mid-, and high-dose rats, respectively. The corresponding incidences of 

hepatocellular carcinomas were 1/106 (0.9%), 0/110 (0%), 1/106 (0.9%), and 10/66 (15.2%, p=0.00033). 

Only three high-dose rats (one male and two females) had nasal carcinomas (p=0.05491) that were 

considered treatment-related by the investigators. 

In the NCI (1978) bioassay, groups of Osborne-Mendel rats (35/sex/dose level) were administered 

1,4-dioxane in the drinking water for 110 weeks. The estimated doses were 0 (controls), 240, and 

530 mg/kg/day in males and 0, 350, and 640 mg/kg/day in females. Neoplasms associated with the 

administration of 1,4-dioxane occurred in the nasal cavity from males and females, liver from females, 

and testis/epididymis in males. The incidences of squamous cell carcinomas in the nasal turbinates were 

0/33, 12/33 (36%), and 16/34 (47%) in control, low-, and high-dose males, respectively; the 

corresponding incidences in females were 0/34, 10/35 (29%), and 8/35 (23%). The first tumors were seen 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 89 

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at week 52 in males and week 66 in females. Statistical analyses of these incidences revealed a 

significant dose-related trend and significant differences between treated groups and controls. The 

incidences of hepatocellular carcinomas in females were 0/31, 10/33 (30%), and 11/32 (34%) in controls, 

low-, and high-dose groups, respectively. A higher incidence of mesotheliomas of the vaginal tunics of 

the testis/epididymis was seen in treated males than in controls (2/33, 4/33, and 5/34 in controls, low-, and 

high-dose, respectively). The incidences of other neoplasms were not related to treatment with the test 

material by type, site, test group, or sex. Under the conditions of the study, NCI (1978) concluded that 

1,4-dioxane induced hepatocellular carcinomas in female rats and squamous cell carcinoma of the nasal 

turbinates in male and female rats. 

In the Kano et al. (2009) study, groups of F344/DuCrj rats (50/sex/dose level) received 1,4-dioxane in the 

drinking water at levels of 200, 1,000, and 5,000 ppm for 2 years (0, 11, 55, and 274 mg/kg/day for 

males; 0, 18, 83, and 964 mg/kg/day for females). Survival was significantly decreased in the high-dose 

groups due to nasal and peritoneal mesothelioma in males and nasal and hepatic tumors in females. 

Twenty-two of 50 high-dose male rats survived compared to 40/50 in controls; 24/50 of high-dose 

females survived compared to 38/50 in controls. In high-dose males (278 mg/kg/day), the incidence of 

combined nasal cavity tumors was 7/50 (p<0.01) compared to none in the other groups; in high-dose 

females (429 mg/kg/day), the combined incidence was 8/50 (p<0.01) compared to none in the other 

groups. The nasal tumors included squamous cell carcinomas and esthesioneuroepithelioma, and the 

incidence of squamous cell carcinoma was significant by itself (7/50 p<0.05). The incidence of combined 

hepatocellular adenoma or carcinoma in males was 3/50, 4/50, 7/50, and 39/50 (p<0.01) in the control, 

low-, mid-, and high-dose male rats, respectively; the corresponding incidences in females were 3/50, 

1/50, 6/50, and 48/50 (p<0.01). High-dose males also had an increased incidence of mesothelioma of the 

peritoneum (28/50 compared to 2/50 in controls, p<0.01). High-dose females had an increased incidence 

of mammary gland adenomas (16/50 compared to 6/50 in controls, p<0.05). 

Two studies have been conducted in mice. Groups of B6C3F1 mice (50/sex/dose level) were 

administered 1,4-dioxane in the drinking water for 90 weeks (NCI 1978). Based on body weight and 

water consumption data, the investigators estimated that the water provided doses of 0 (controls), 720, 

and 830 mg/kg/day in males, and 0, 380, and 860 mg/kg/day in females. Mortality was significantly 

increased (dose-related) in female mice. In female mice, 28/50, (56%) in the high-dose group, 

39/50 (78%) in the mid-dose group, and 45/50 (90%) in the control group were still alive on week 91 of 

the study. In males, at least 90% of the mice in each group were still alive at week 91. Treatment with 

1,4-dioxane significantly increased the incidence of liver tumors. The incidences of hepatocellular 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 90 

3. HEALTH EFFECTS 

carcinoma were 2/49 (4%), 18/50 (36%), and 24/47 (51%), in controls, low-, and high-dose males, 

respectively; the corresponding incidences in females were 0/50, 12/48 (25%), and 29/37 (78%). The 

incidences of hepatocellular carcinomas or adenomas in males were 8/49 (16%), 19/50 (38%), and 

28/47 (60%); the incidences in females were 0/50, 21/48 (44%), and 35/37 (95%) for the respective 

control, low-, and high-dose groups. Statistical analysis showed significance for dose-related trend and 

for direct comparisons with controls. No other neoplasm, benign or malignant, was found to be 

associated to treatment with 1,4-dioxane. 

In another study (Kano et al. (2009), groups of Crj:BDF1 mice (50/sex/dose level) received 1,4-dioxane in 

the drinking water at levels of 500, 2,000, and 8,000 ppm for 2 years (0, 49, 191, 677 mg/kg/day for 

males; 0, 66, 278, and 964 mg/kg/day for females). Early mortality occurred in female mice, and this was 

attributed to liver tumors. Survival rates at 104 weeks in females were 29/50, 29/50, 17/50, and 5/50 in 

control, low-, mid-, and high-dose groups, respectively. A significant and dose-related increase in the 

incidence of liver adenomas or carcinomas was found in female mice. The incidences of combined 

adenomas or carcinomas in control, low-, mid-, and high-dose females were 5/50, 35/50, 41/50, and 46/50 

(p<0.01 for all treated groups). High-dose males (677 mg/kg/day) also showed a significant increased 

incidence of hepatocellular carcinomas; the combined incidences of adenomas or carcinomas, as the dose 

increased, were 23/50 (controls), 31/50, 37/50 (p<0.05), and 40/50 (p<0.01). There were no nasal cavity 

tumors in male or female mice. 

In the single study in guinea pigs, a group of 22 male guinea pigs was administered 1,4-dioxane in the 

drinking water at concentrations of 0.5–2% for 23 months (Hoch-Ligeti and Argus 1970). Ten guinea 

pigs served as controls. The investigators stated that the total intake of 1,4-dioxane during the 23 months 

of the experiment was 588–625 g. Assuming a reference body weight of 0.84 kg and converting 

23 months into 690 days (30 days/month), the intake of 1,4-dioxane was approximately 1,014– 

1,075 mg/kg/day. All of the animals were sacrificed within 28 months. Very little additional data were 

presented in this brief note. Examination of the lungs revealed peri- or intrabronchial epithelial 

hyperplasia and nodular mononuclear infiltration in nine of the treated guinea pigs. In addition, two 

guinea pigs had carcinoma of the gall bladder, three had early hepatomas, and one had adenoma of the 

kidney. No tumors were found in the controls. 

1,4-Dioxane was tested also as a cancer initiator in mice (Bull et al. 1986) and promoter in rats (Lundberg 

et al. 1987). Female Sencar mice received doses of 1,000 mg 1,4-dioxane/kg by gavage before receiving 

topical applications of 1 μg of 12-O-tetradecanoylphorbol-13-acetate (TPA) 3 times/week for 20 weeks. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 91 

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A control group was initiated with acetone before the TPA application. Administration of 1,4-dioxane 

did not increase the formation of papillomas compared to mice initiated with the solvent (unspecified 

whether emulphor, saline, or water) and promoted with TPA, indicating a lack of initiating activity under 

the conditions of the study. The tumor promotion activity of 1,4-dioxane was also studied in groups of 

male Sprague-Dawley rats (8–11/group) (Lundberg et al. 1987). All rats underwent a 2/3 hepatectomy 

before receiving a single intraperitoneal injection of 30 mg/kg of diethylnitrosamine (DENA). Five days 

later, treatment by gavage with 100 or 1,000 mg/kg of 1,4-dioxane in saline started once daily, 

5 days/week for 7 weeks. One week after the last treatment, the rats were killed, the liver was removed 

and stained for gamma-glutamyl-transpeptidase (GGT), and the number and total volume of 

GGT-positive foci was studied. 1,4-Dioxane alone had no significant effect on the end points evaluated. 

In DENA initiated rats, the high-dose of 1,4-dioxane induced a significant increase in the number of foci 

and total volume of foci relative to rats treated with DENA alone. The livers of high-dose rats showed 

enlarged foamy hepatocytes mainly in midzonal regions. The foamy appearance was due to vacuoles 

shown to contain fat. Thus, 1,4-dioxane promoted the carcinogenic potential of DENA. 

The data available indicate that 1,4-dioxane produced liver and nasal cancer in rats and liver tumors in 

mice. The EPA has derived an oral cancer potency factor of 0.1 (mg/kg/day)-1 for 1,4-dioxane using the 

Log-Logistic Model (IRIS 2011). This factor was calculated from oral exposure data reported by Kano et 

al. (2009) regarding incidence of hepatocellular adenoma or carcinoma in female BDF1 mice exposed to 

1,4-dioxane in the drinking water for 2 years. The lifetime average doses that would result in risk of 

1x10-4, 1x10-5, 1x10-6, and 1x10-7 are 1x10-3, 1x10-4, 1x10-5, and 1x10-6 mg/kg/day, respectively, as 

indicated in Figure 3-2. 

3.2.3 Dermal Exposure 

3.2.3.1 Death 

As mentioned in Section 3.2.1.1, Johnstone (1959) described a fatal case of a worker exposed to 

1,4-dioxane for only 1 week and whose post-mortem examination showed kidney and liver alterations. 

The room in which the patient had worked had no exhaust ventilation, and the worker was not provided a 

respirator. Dermal exposure in this case may have been considerable, since the worker used liquid 

1,4-dioxane to keep his hands free of glue. A dermal LD50 of 7,600 mL/kg was reported for rabbits 

(RTECS 2004); this value is presented in Table 3-3. 
84

ml/kg

80

ppm

81

ppm ppm

82

ppm

83

ppm

58

mg/kg

Table 3-3 Levels of Significant Exposure to 1,4-Dioxane - Dermal 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) 

ACUTE EXPOSURE 

Death 

(NS) Rabbit once 

System NOAEL Less Serious 

LOAEL 

7600 

ml/kg 

Serious 

(LD50) 

Reference Chemical Form 

RTECS 2004 

Systemic 

Human 3 min Ocular 2000 

ppm 

Fairley et al. 1934 

Human 15 min Ocular 200 B 

ppm 

300 B 

ppm 

(eye irritation) Silverman et al. 1946 

Human 10 min Ocular 1600 

ppm 

(slight eye irritation) Yant et al. 1930 

Human 6 hr Ocular 50 M 

ppm 

(eye irritation) Young et al. 1977 

(Wistar) Rat once Dermal 8300 M 

mg/kg 

Clark et al. 1984 
51

mg/kg

mg/kg

mg/kg

50

mg/kg

mg/kg

mg/kg

Table 3-3 Levels of Significant Exposure to 1,4-Dioxane - Dermal (continued) 

Exposure/ 

Duration/ 

LOAEL 

Species 

(Strain) 

Frequency 

(Route) System NOAEL Less Serious Serious 

Reference Chemical Form 

INTERMEDIATE EXPOSURE 

Systemic 

(NS) Gn Pig 49-101 d 

5 d/wk 2 x/d 

Hepatic 143 

mg/kg 

(cloudy swelling and patchy cell degeneration) 

Fairley et al. 1934 

Renal 143 (degeneration and 

mg/kg necrosis of cortical tubules) 

Dermal 143 

mg/kg 

(NS) Rabbit 49-101 d 

5 d/wk 2 x/d 

Hepatic 57 

mg/kg 

(patchy cell 

degeneration) 

Fairley et al. 1934 

Renal 57 (tubular cell 

mg/kg degeneration) 

Dermal 57 

mg/kg 

B = both male and female; d = day(s); Gn pig = guinea pig; hr = hour(s); LD50 = lethal dose, 50% kill; LOAEL = lowest-observed-adverse-effect level; M = male; miNOAEL = no-observed-adverse-effect level; NS = not specified; ppm = parts per million; wk = week(s); x = time(s) 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 94 

3. HEALTH EFFECTS 

3.2.3.2 Systemic Effects 

No studies were located regarding respiratory, cardiovascular, gastrointestinal, hematological, 

musculoskeletal, endocrine, or body weight effects in humans or in animals after dermal exposure to 

1,4-dioxane. No studies were located regarding hepatic and renal effects in humans following dermal 

exposure to 1,4-dioxane. 

The highest NOAEL and all reliable LOAEL values from each study for systemic effects in each species 

and duration category are recorded in Table 3-3. 

Hepatic Effects. In a study with four guinea pigs, approximately 143 mg 1,4-dioxane/kg was applied 

to a clipped area of the nape 5 days/week for 49–101 days (Fairley et al. 1934). Upon sacrifice on 

days 49, 66, 77, and 101, no gross alterations of the liver were observed, but there were indications of 

patchy cell degeneration. The same protocol conducted in four rabbits applied doses of approximately 

57 mg/kg showed vascular congestion of the liver and patchy cell degeneration in two of the rabbits 

(Fairley et al. 1934). 

Renal Effects. Application of approximately 143 mg 1,4-dioxane/kg to a clipped area of the nape of 

guinea pigs 5 days/week for 49–101 days resulted in renal cortical cell degeneration and hemorrhages. 

The same experiment conducted in rabbits applied approximately 57 mg 1,4-dioxane/kg resulted in the 

same type of kidney lesions (Fairley et al. 1934). 

Dermal Effects. Application of a single dose of up to 8,300 mg 1,4-dioxane/kg to an uncovered area 

of the skin of rats produced no signs of skin irritation within the period of observation of 14 days (Clark 

et al. 1984). Application of approximately 143 mg 1,4-dioxane/kg 5 days/week for 40–101 days to a 

clipped area of the nape from guinea pigs did not produce skin irritation (Fairley et al. 1934). Similar 

results were obtained in rabbits applied approximately 57 mg 1,4-dioxane/kg using the same protocol 

(Fairley et al. 1934). 

Ocular Effects. The ocular effects observed in humans and in animals described in Section 3.2.1.2 

and listed in Table 3-1 are assumed to have occurred by direct contact of vapors of 1,4-dioxane with eyes 

and are also listed in Table 3-3. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 95 

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No studies were located regarding the following health effects in humans or animals after dermal 

exposure to 1,4-dioxane: 

3.2.3.3 Immunological and Lymphoreticular Effects 

3.2.3.4 Neurological Effects 

3.2.3.5 Reproductive Effects 

3.2.3.6 Developmental Effects 

3.2.3.7 Cancer 

The carcinogenicity and initiator and promoter properties of 1,4-dioxane have been evaluated. To test 

whether 1,4-dioxane is a complete carcinogen, 0.2 mL of a solution of 1,4-dioxane in acetone 

(unspecified concentration) were applied 3 times/week to the shaved back from Swiss-Webster mice for 

60 weeks (King et al. 1973). Examination of the skin at week 60 revealed only one skin sarcoma and one 

lymphoma, suggesting that under the conditions of the study, 1,4-dioxane was not a complete carcinogen. 

King et al. (1973) also tested whether 1,4-dioxane is a promoter by applying 50 μg of dimethylbenzanthracene (DMBA) to groups of Swiss-Webster followed 1 week later by the application of 0.2 mL 

of a solution of 1,4-dioxane (unspecified concentration) to the shaved back for 60 weeks. At week 60, 

only 4 males and 5 females were still alive (out of 30/sex). Treatment with 1,4-dioxane in mice initiated 

with DMBA resulted in an increased number of tumors in the skin, lungs, and kidneys. The activity of 

1,4-dioxane in promoting skin tumors was similar to that observed with croton oil as a promoter. 

However, croton oil led to a much higher multiplicity of skin tumors per mouse than 1,4-dioxane. Bull et 

al. (1986) tested 1,4-dioxane as an initiator. In that study, female Sencar mice were applied topical doses 

of 1,000 mg 1,4-dioxane/kg before receiving topical applications of 1 μg 12-O-tetradecanoylphorbol13-acetate (TPA) 3 times/week for 20 weeks. A control group received an application of acetone before 

the TPA application. 1,4-Dioxane did not increase the formation of papillomas compared to mice 

initiated with acetone and promoted with TPA. 

3.3 GENOTOXICITY 

Studies of the in vitro and in vivo genotoxicity of 1,4-dioxane are summarized in Tables 3-4 and 3-5, 

respectively. 1,4-Dioxane was not genotoxic in standard in vitro tests of gene mutation in bacteria in the 

presence or absence of metabolic activation (Haworth et al. 1983; Khudoley et al. 1987; Morita and 

Hayashi 1998; Nestmann et al. 1984; Stott et al. 1981). Kwan et al. (1990) tested 1,4-dioxane in a strain 

of Photobacterium phosphoreum, which is sensitive to chemicals that are DNA-damaging agents, 
 

1,4-DIOXANE 96 

3. HEALTH EFFECTS 

Table 3-4. Genotoxicity of 1,4-Dioxane In Vitro 

Results 

With Without 

Species (test system) End point activation activation Reference 

Salmonella typhimurium (TA100, Gene mutation – – Haworth et al. 1983 

TA98, TA1535, TA1537) 

S. typhimurium (TA98, TA100, Gene mutation – – Stott et al. 1981 

TA1535, TA1537, TA1538) 

S. typhimurium (TA100, Gene mutation – – Nestmann et al. 1984 

TA1535) 

S. typhimurium (TA98, TA100, Gene mutation – – Khudoley et al. 1987 

TA1530, TA1535, TA1537) 

Photobacterium phosphoreum DNA damage NT – Kwan et al. 1990 

Escherichia coli K-12 uvrB/recA DNA damage – – Hellmer and Bolcsfoldi 

1992 

S. typhimurium (TA98, TA100, Gene mutation – – Morita and Hayashi 1998 

TA1535, TA1537) 

E. coli (WP2, WP2 uvrA) Gene mutation – – Morita and Hayashi 1998 

Saccharomyces cerevisiae (D61M) Chromosomal NT – Zimmermann et al. 1985 

malsegregation 

Mouse lymphoma cells Gene mutation – – Morita and Hayashi 1998 

CHO cells Chromosomal – – McElroy et al. 2003 

aberrations 

CHO-K1 cells Chromosomal – – Morita and Hayashi 1998 

aberrations 

CHO-K1 cells Sister chromatid – – Morita and Hayashi 1998 

exchange 

CHO-K1 cells Micronuclei – – Morita and Hayashi 1998 

Rat hepatocytes DNA repair – – Goldsworthy et al. 1991 

CHO-W-B1 cells Chromosomal – – Galloway et al. 1987 

aberrations 

CHO-W-B1 cells Sister chromatid – ± Galloway et al. 1987 

exchange 

Mouse lymphoma cells Gene mutation – – McGregor et al. 1991 

BALB/3T3 cells Cell NT + Sheu et al. 1988 

transformation 

– = negative result; + = positive result; ± = weak positive result; CHO = Chinese hamster ovary; NT = not tested 
 

1,4-DIOXANE 97 

3. HEALTH EFFECTS 

Table 3-5. Genotoxicity of 1,4-Dioxane In Vivo 

Species (test system) End point Results Reference 

Human peripheral Chromosomal aberrations – Thiess et al. 1976 

lymphocytes 

Rat hepatocytes DNA repair – Goldsworthy et al. 1991 

Rat nasal epithelial cells DNA repair – Goldsworthy et al. 1991 

Mouse hepatocytes Micronuclei + Morita and Hayashi 1998 

Mouse hepatocytes Micronuclei + Roy et al. 2005 

Mouse peripheral blood Micronuclei – Morita and Hayashi 1998 

Rat hepatocytes DNA alkylation or repair – Stott et al. 1981 

Rat hepatocytes DNA damage + Kitchin and Brown 1990, 

1994 

Mouse bone marrow Micronuclei – Tinwell and Ashby 1994 

Mouse bone marrow Micronuclei + Roy et al. 2005 

Mouse bone marrow Micronuclei + Mirkova 1994 

(C57BL6) 

Mouse bone marrow Micronuclei – Mirkova 1994 

(BALB/c) 

Mouse bone marrow Micronuclei inc McFee et al. 1994 

Drosophila (food) Dominant lethal – Yoon et al. 1985 

Drosophila (food) Meiotic non-disjunction + Muñoz and Barnett 2002 

– = negative result; + = positive result; ± = weak positive result; inc = inconclusive 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 98 

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DNA-intercalating agents, DNA-synthesis inhibitors, and direct mutagens. 1,4-Dioxane showed no 

activity in the absence of metabolic activation, but was not tested with metabolic activation. No evidence 

of DNA damage was seen in Escherichia coli K-12 uvrB/recA incubated with 1,4-dioxane with or without 

metabolic activation (Helmér and Bolcsfoldi 1992). A study in the yeast Saccharomyces cerevisiae strain 

D61M also gave negative results for chromosomal aneuploidy without activation (Zimmermann et al. 

1985), but was not tested in the presence of metabolic activation. Studies with isolated mammalian cells 

exposed to 1,4-dioxane have also yielded negative results. For example, assays for induction of 

micronuclei, sister chromatid exchanges, and chromosomal aberrations in Chinese hamster ovary cells 

(CHO) were negative with and without metabolic activation (McElroy et al. 2003; Morita and Hayashi 

1998). A similar study by Galloway et al. (1987) also found no increase in chromosomal aberrations in 

CHO cells, but did observe a slight increase in the incidence of sister chromatid exchanges in the absence 

of activation. Morita and Hayashi (1998) and McGregor et al. (1991) found no increase in gene 

mutations in mouse lymphoma cells incubated with 1,4-dioxane. 1,4-Dioxane did not induce DNA 

damage in rat hepatocytes (Goldsworthy et al. 1991), but increased cell transformations in BALB/3t3 

cells at cytotoxic concentrations (Sheu et al. 1988). A test for DNA single strand breaks in rat 

hepatocytes incubated with 1,4-dioxane yielded positive results only at cytotoxic concentrations of 

1,4-dioxane (Sina et al. 1983). 

Studies of in vivo exposure of organisms to 1,4-dioxane also have been mostly negative, although some 

positive results have been reported. The only information in humans is that no increases in chromosomal 

aberrations were observed in peripheral lymphocytes from a groups of six workers employed in 

1,4-dioxane production, relative to observations made in six control subjects (Thiess et al. 1976). 

Several studies have reported results regarding micronuclei formation. An assay in bone marrow cells 

from C57BL6 mice after single gavage doses of up to 3,600 mg 1,4-dioxane/kg found a dose-related 

increase in the incidence of micronuclei, but the results in BALB/c mice were negative (Mirkova 1994). 

A similar study by Tinwell and Ashby (1994) found that 1,4-dioxane did not induce micronuclei in bone 

marrow cells from CBA mice treated with a single oral dose of 1,800 mg/kg or from C57BL6 mice dosed 

with 3,600 mg/kg. Studies reported by McFee et al. (1994) of several trials conducted by two different 

laboratories yielded equivocal results for micronuclei formation in mouse bone marrow. More recent data 

by Morita and Hayashi (1998) in CD-1 mice treated with a single gavage dose of up to 3,000 mg 

1,4-dioxane/kg showed an increase in micronuclei in hepatocytes, but not in peripheral blood 

reticulocytes. Roy et al. (2005) also reported an increased incidence of micronuclei in hepatocytes and 

bone marrow from male CD-1 mice treated for 5 days with ≥2,500 and ≥1,500 mg 1,4-dioxane/kg, 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 99 

3. HEALTH EFFECTS 

respectively. Their results indicate that at high doses, 1,4-dioxane can induce chromosome breakage 

resulting in micronuclei. 

Hepatocytes from Sprague-Dawley rats dosed with a single dose of 1,000 mg 1,4-dioxane/kg by gavage 

showed no evidence of DNA alkylation or DNA repair activity (Stott et al. 1981). This dose level 

administered via the drinking water to the rats for 11 weeks induced minimal hepatocellular swelling, 

which was accompanied by increased DNA synthesis (Stott et al. 1981). In male F344 rats administered 

single doses of up to 2,000 mg 1,4-dioxane/kg by gavage, 1,4-dioxane did not induce replicative DNA 

synthesis in hepatocytes (Uno et al. 1994), but it did in a subsequent study by the same group of 

investigators (Miyagawa et al. 1999). In liver tissue from Sprague-Dawley rats given two doses of 

2,550 or 4,200 mg 1,4-dioxane/kg, there was a dose-related increase in DNA damage (assessed by 

alkaline elution) and cytochrome P-450 content; no significant effect was seen at ≤840 mg/kg (Kitchin 

and Brown 1990). Administration of a single oral dose of 1,000 mg 1,4-dioxane/kg to F344 rats produced 

no evidence of hepatocyte DNA repair, and the same negative response was obtained in rats dosed for a 

week via drinking water containing up to 2% 1,4-dioxane (Goldsworthy et al. 1991). No DNA repair 

activity was also observed in nasal epithelial cells from rats given 1% 1,4-dioxane in the drinking water 

for 8 days followed by a single gavage dose of 1,000 mg/kg (Goldsworthy et al. 1991). 1,4-Dioxane did 

not induce sex-linked recessive lethal mutations in Drosophila melanogaster in one study (Yoon et al. 

1985), but was positive for meiotic non-disjunction in another study in D. melanogaster (Muñoz and 

Barnett 2002). 

The information available indicates that 1,4-dioxane is not genotoxic in in vitro tests in eukaryotic and 

prokaryotic cells. Tests in vivo have been mostly negative, but a few tests yielded positive results in 

animals treated with 1,4-dioxane in high doses, many times higher than environmental exposures. 

3.4 TOXICOKINETICS 

Data in volunteers acutely exposed to vapors of 1,4-dioxane suggest that the chemical is readily and 

almost completely absorbed through the lungs. Studies in animals also show that 1,4-dioxane is readily 

absorbed after inhalation and oral exposure, but much less through the skin. No information is available 

regarding distribution of 1,4-dioxane or metabolites in humans. In animals injected with radiolabelled 

1,4-dioxane, 1,4-dioxane-derived radioactivity distributed widely throughout the body, and no organ 

seemed to preferentially accumulate radiolabel. In humans and animals, 1,4-dioxane is metabolized to 

HEAA by mixed-function oxidase enzymes; HEAA can be converted to 1,4-dioxane-2-one under acidic 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 100 

3. HEALTH EFFECTS 

conditions. Both of these products are rapidly and extensively eliminated in the urine. Unchanged 

1,4-dioxane can also be excreted in the urine and in exhaled air, but mainly after high-dose exposure. 

Studies have shown that the metabolism of 1,4-dioxane in rats is saturable at high doses. There is 

virtually no information regarding the toxicokinetics of 1,4-dioxane in humans following oral or dermal 

exposure. There is no indication that 1,4-dioxane or HEAA accumulates in the body. 

3.4.1 Absorption 

3.4.1.1 Inhalation Exposure 

Young et al. (1977) exposed a group of four healthy male volunteers to 50 ppm of 1,4-dioxane vapor for 

6 hours. Plasma concentrations of 1,4-dioxane climbed rapidly during the first 2 hours of exposure, 

indicating an initial rapid absorption. This was followed by a gradual slow down in the rate of absorption 

until a plateau was reached at approximately 3 hours. Thus, steady state was reached during exposure. In 

contrast, the concentration of HEAA in plasma peaked approximately one hour after exposure ceased. 

Based on the presence of 1,4-dioxane and its main metabolite (HEAA) in the urine, the investigators 

calculated that the subjects absorbed a total mean dose of 5.4 mg 1,4-dioxane/kg at a mean rate of 

76.1 mg/hour. 

Experiments conducted in four male Sprague-Dawley rats exposed head-only to 50 ppm 1,4-dioxane 

vapors revealed that during a 6-hour exposure period, the rats absorbed a mean total dose of 71.9 mg 

1,4-dioxane/kg; this figure is based on the amounts of parent compound and HEAA measured in the urine 

over a 48-hour period (Young et al. 1978a, 1978b). At the end of the exposure period, the concentration 

of 1,4-dioxane in the plasma was 7.3 μg/mL. It is worth noting that the value for total absorbed dose in 

this study, on a per body weight basis, is considerably greater than that calculated from volunteers 

exposed to the same airborne concentration of 1,4-dioxane for the same length of time (Young et al. 

1977). 

3.4.1.2 Oral Exposure 

Data on the absorption of 1,4-dioxane following oral exposure in humans are not available. 

Young et al. (1978a, 1978b) administered single doses of 10, 100, or 1,000 mg/kg of uniformly labeled 

14C-1,4-dioxane exposed to groups of male Sprague-Dawley rats by gavage for 17 days, and reported that 

<2% of the label was found in the feces in the first 24 hours (10 mg/kg dose) or 72 hours (100 or 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 101 

3. HEALTH EFFECTS 

1,000 mg/kg doses), indicating rapid and nearly-complete absorption of the compound from the 

gastrointestinal tract. In another experimental series reported in the same manuscripts (Young et al. 

1978a, 1978b), groups of male Sprague-Dawley rats were given 10, 100, or 1,000 mg/kg of uniformly 

labeled 14C-1,4-dioxane by gavage daily for 17 days. Less than 2% of the total administered label was 

recovered in the feces in 480 hours post-exposure, indicating that at least 98% absorption had occurred. 

3.4.1.3 Dermal Exposure 

Data on the absorption of 1,4-dioxane in humans following dermal exposure are not available, but a study 

with excised human skin reported that 10 times more 1,4-dioxane penetrates the skin under occluded 

conditions than under unoccluded conditions (3.2% of the applied dose vs. 0.30%, values obtained 

205 minutes after application) (Bronaugh 1982). In the experiments, 14C-1,4-dioxane was dissolved in a 

popular lotion and applied to the skin in occluded and unoccluded diffusion cells. The author explained 

that rapid evaporation was easily observed in the experiment. The rate of penetration of 1,4-dioxane in 

water (0.36±0.03 μg cm-2hr-1) was similar to that in a popular lotion (0.23±0.03 μg cm-2hour-1) and about 

3 times slower than in a lipoidal vehicle, isopropyl myristate (0.94±0.10 μg cm-2hour-1) (Bronaugh 1982). 

A lethal case of intoxication with 1,4-dioxane in which the patient had extensive dermal contact with 

1,4-dioxane in addition to inhalation of vapors suggests that dermal absorption is possible (Johnstone 

1959). 

Data in animals are limited to a study by Marzulli et al. (1981) in which uniformly labeled 

14C-1,4-dioxane, dissolved in either methanol or skin lotion, was applied to the unoccluded, clipped skin 

of Rhesus monkeys (4 μg/cm2 over 3–12 cm2

) for 24 hours. Assuming a body weight of approximately 

10 kg for an adult Rhesus monkey, the applied dose of 1,4-dioxane ranged from 1.2 to 4.8 mg/kg. The 

ability of the compound to penetrate the skin was assessed by analysis of radiolabel in the urine. The skin 

penetration of 1,4-dioxane was <4% in all cases; however, because the skin was unoccluded, evaporation 

may have influenced the study results. The differences between the results in the Bronaugh (1982) 

absorption data and those of Marzulli et al. (1981) could be due to differences in experimental conditions, 

that is, excised human skin in diffusion cells versus in vivo exposure of monkey skin. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 102 

3. HEALTH EFFECTS 

3.4.2 Distribution 

3.4.2.1 Inhalation Exposure 

Data on the distribution of 1,4-dioxane following inhalation exposure in humans or animals are not 

available. 

3.4.2.2 Oral Exposure 

Data on the distribution of 1,4-dioxane following oral exposure in humans or animals are not available. 

3.4.2.3 Dermal Exposure 

Data on the distribution of 1,4-dioxane following dermal exposure in humans or animals are not available. 

3.4.2.4 Other Routes of Exposure 

The only relevant information regarding distribution of 1,4-dioxane is that reported in studies involving 

intraperitoneal exposure of animals. In a study by Woo et al. (1977b), the distribution of 3

H-1,4-dioxanederived radioactivity was followed in tissues from male Sprague-Dawley rats administered a single dose 

of 6.97 mg/kg intraperitoneally. Levels of radioactivity were measured in whole blood, liver, kidney, 

spleen, lung, colon, and skeletal muscle at 1, 2, 6, and 16 hours after dosing. The radioactivity was found 

to be widely distributed among the tissues examined and, for the most part, tissues had comparable levels 

of specific activity (nmol/g wet tissue). For example, the concentrations of dioxane-derived radioactivity 

at 1 and 16 hours decreased from 93.4 to 41.4 nmol/mL in the blood, from 59.1 to 24.2 nmol/g in the 

liver, from 116.1 to 31.9 nmol/g in the kidney, from 49.6 to 30 nmol/g in the spleen, from 52.2 to 

23.2 nmol/g in the lung, from 56.1 to 27.7 nmol/g in the colon, and from 45.3 to 28.1 nmol/g in skeletal 

muscle. It should be noted that the tissue samples were not perfused or corrected for levels of blood in 

the tissue, so there might have been some influence of the blood-borne activity on the reported tissue 

values. Within the tissues, the percent covalent binding at 16 hours was universally <20%, with the 

highest levels in the colon (17.3% bound), spleen (16.4% bound), and liver (13.7% bound), followed by 

the lung (11.2% bound), kidney (9.5% bound), whole blood (3.1% bound), and skeletal muscle (2.7% 

bound). Within the cells, the highest activity levels were found in the cytosol (~68% at 6 hours postexposure), with lesser amounts in the microsomal (~15% at 6 hours post-exposure), mitochondrial (~14% 

at 6 hours post-exposure), and nuclear (<3% at 6 hours post-exposure) fractions. Interestingly, percent 

covalent binding was entirely opposite in proportion to total activity levels, with the greatest percent 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 103 

3. HEALTH EFFECTS 

binding found in the nuclear fraction (~65%), followed by the mitochondrial (~46%), microsomal 

(~34%), and cytosolic (~5%) fractions. 

Mikheev et al. (1990) exposed rats to 14C-1,4-dioxane by intraperitoneal injection and evaluated the levels 

of radioactivity in the blood, brain, testes, liver, and kidney at 5, 15, and 30 minutes and at 1, 3, and 

6 hours post-injection in order to determine the tissue:blood concentration ratios. For all evaluated tissues 

at all time points, the tissue:blood ratio was between 0.5 and 1.5, indicating that 1,4-dioxane is distributed 

evenly and does not appreciably accumulate in any of the evaluated tissues. The maximum accumulation 

time (Tmax) was 5 minutes for liver and kidney, and 15 minutes for the blood, brain, and testes. 

3.4.3 Metabolism 

A proposed metabolism scheme for 1,4-dioxane is diagrammed in Figure 3-3. 

The exact metabolic pathways of 1,4-dioxane are not known. However, numerous studies have reported 

that 1,4-dioxane is metabolized to a single urinary metabolite, believed to be HEAA. There is some 

question as to whether HEAA or 1,4-dioxane-2-one is the ultimate metabolite (Braun and Young 1977; 

Woo et al. 1977a, 1977b, 1977c; Young et al. 1977). This arises from the fact that under acid conditions, 

such as are often used in analytical assays, HEAA can be converted to 1,4-dioxane-2-one, and under 

alkaline conditions, the reverse reaction occurs. It is of note that HEAA is not volatile, and as a result, is 

often catalyzed to 1,4-dioxane-2-one in order to facilitate analysis, which may explain why Woo et al. 

(1977a, 1977d) reported 1,4-dioxane-2-one, rather than HEAA. As mentioned above, acid conditions, 

such as were employed by the assays of Woo et al. (1977a, 1977d) result in the formation of 

1,4-dioxane-2-one from HEAA. Additional evidence for HEAA as the primary metabolite, rather than 

1,4-dioxane-2-one, comes from structure-activity relationship analyses of the genotoxicity of the two 

putative 1,4-dioxane metabolites (Blake 1995; Gombar 1995). 1,4-Dioxane-2-one is predicted to be 

strongly mutagenic, based on its structure, while HEAA would be only weakly genotoxic; the observed 

results of tests of genotoxicity for 1,4-dioxane correlate much closer with the predicted results from 

HEAA than from those of 1,4-dioxane-2-one. Further support for HEAA as the main metabolite of 

1,4-dioxane was provided by the results of U.S. Army (2010), which showed no 1,4-dioxane-2-one in the 

urine of rats during an 8-hour period following a single gavage dose of 10 or 1,000 mg 1,4-dioxane/kg. 

Furthermore, incubating a urine sample from untreated rats with 1,4-dioxane-2-one showed rapid break 

down of the compound, presumably to HEAA, with a half-life of approximately 0.4 hours. Similar 

incubation with HEAA showed no conversion to 1,4-dioxane-2-one. An experiment conducted in 
 

 

 

(b) 

Figure 3-3. Suggested Metabolic Pathways of 1,4-Dioxane in the Rat 

O 

O 

O OH OH O

O O

HOH2C HOH2C 

(c) 

[V] [VI] 

(a) CH2OH COOH 

O O 

[II] [III] [I] 

+H -H2O 2O 

O O 

O 

[IV] 

I = 1,4-dioxane; II = diethylene glycol; III = β-hydroxyethoxy acetic acid (HEAA); IV = 1,4-dioxane-2-one; 

V = 1,4-dioxane-2-ol; VI = β-hydroxyethoxy acetaldehyde 

Source: adapted from Woo et al. (1977c) 

1,4-DIOXANE 104 

3. HEALTH EFFECTS 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 105 

3. HEALTH EFFECTS 

nonbiological media that did not involve extraction, separation, or derivatization of the two metabolites 

showed a primary equilibrium constant of 0.016 ± 0.001 between the two compounds, indicating that 

thermodynamically HEAA is very strongly favored in the equilibrium. Mixed-function oxidase enzymes, 

and cytochrome P-450 in particular, are critical to the metabolism of 1,4-dioxane, as induction of these 

enzymes increases the rate of HEAA formation, and inhibition decreases HEAA formation (Woo et al. 

1977c, 1978). The initial step in metabolism is likely a P-450-catalyzed oxidative step; however, the 

specific oxidation that occurs has not yet been determined. One possibility is diagrammed in pathway (a) 

of Figure 3-3. Cytochrome P-450 could act on one of the oxane oxygens, resulting in decyclization and 

the formation of diethylene glycol. Evidence supporting this pathway comes from the fact that in animals 

injected with diethylene glycol, HEAA was found as the major metabolite (Woo et al. 1977a). Diethylene 

glycol could then be further metabolized to HEAA through an additional oxidative metabolic step. 

Alternately, cytochrome P-450 enzymes could act on one of the carbons in 1,4-dioxane to add a single 

oxygen atom, resulting in the direct formation of 1,4-dioxane-2-one as diagrammed in pathway (b) of 

Figure 3-3; however, no evidence is presently available to support this possible pathway. Another 

possibility is that rather than a single oxygen, a hydroxyl group could be added to a carbon atom, 

resulting in 1,4-dioxane-2-ol, as shown in pathway (c) of Figure 3-3. Additional oxidation to HEAA, 

resulting in a breaking of the ring structure and further hydrolysis to HEAA could follow. As with 

pathway (b), there is no direct evidence supporting pathway (c) as the pathway for 1,4-dioxane 

metabolism. 

1,4-Dioxane is extensively metabolized to HEAA in humans. Young et al. (1977) reported that over 99% 

of the urinary elimination of 1,4-dioxane after a 4-hour exposure of volunteers to 50 ppm occurred as 

HEAA rather than the parent compound. In an earlier study, the ratio of HEAA to dioxane in the urine of 

humans following a 7.5-hour exposure to 1.6 ppm dioxane was 118:1, indicating nearly complete 

metabolism at this exposure concentration (Young et al. 1976). 

Recently, Sweeney et al. (2008) reported that rate constants and the metabolic profile from isolated 

human hepatocytes were very similar to those from isolated hepatocytes from rats and mice. The Vmax for 

the production of HEAA from 1,4-dioxane in human hepatocytes ranged from 2.4 to 8.7 μg/h/106 cells, 

and the Km ranged from 3.8 to 17.6 mg/mL. The respective mean values in rats and mice were 1.92 and 

3.74 μg/h/106

 cells and 2.51 and 2.63 mg/mL. Additional studies with the metabolism marker substrates 

coumarin and dextromethorphan suggested the involvement of the combined activities of P-450s 2A and 

2D in the metabolism of 1,4-dioxane. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 106 

3. HEALTH EFFECTS 

The metabolism of 1,4-dioxane to HEAA in animals is nearly complete, as evidenced by studies 

examining the urine of exposed animals. Following inhalation exposure of rats to 50 ppm of 1,4-dioxane 

for 6 hours, the ratio of HEAA to dioxane in the urine over the 48-hour observation period was >3,000, 

indicating that for urinary elimination, nearly all of the compound was eliminated as the metabolite, rather 

than as the parent compound (Young et al. 1978a, 1978b). 

The available animal data indicate that the metabolism of 1,4-dioxane is saturable. Young et al. (1978a, 

1978b) reported that with an increasing oral dose level, a greater percentage of the total dose was 

eliminated as expired 1,4-dioxane, suggesting that the normally-rapid metabolism of 1,4-dioxane had 

reached a maximum, allowing the free compound to circulate in the blood and be eliminated by 

expiration; no dose-related differences were seen in elimination as CO2 or in the feces that could 

otherwise account for this difference. A similar pattern was seen following 17 repeated doses of 10 or 

1,000 mg/kg of 14C-1,4-dioxane by gavage, with a greater elimination of label, primarily as the 

metabolite, in the urine at the lower dose, with the higher dose resulting in a greater elimination, as both 

14C-1,4-dioxane and 14CO2, in the expired air (Young et al. 1978a, 1978b). In an intravenous study 

reported in the same manuscript, the metabolic clearance of 1,4-dioxane decreased from 2.82 mL/minute 

following a single injection of 10 mg/kg to 0.17 mL/minute following an injection of 1,000 mg/kg, 

indicating that the metabolic capacity to metabolize 1,4-dioxane to HEAA had been saturated. 

Woo et al. (1977a) reported that in the urine of rats orally exposed to 1–4 g/kg, only one metabolite was 

detected by gas chromatography. This metabolite was identified as 1,4-dioxane-2-one using nuclear 

magnetic resonance (NMR), infrared, and gas chromatograph-mass spectroscopy. Administration of 

diethylene glycol to rats resulted in the formation of the same metabolite, leading the study authors to 

hypothesize that diethylene glycol may represent an intermediate metabolite in the formation of 

1,4-dioxane-2-one. In a later study by the same authors (Woo et al. 1977b), urine samples were collected, 

with glacial acetic acid as a preservative, from rats for 2 days following intraperitoneal injection of 50– 

400 mg/kg 1,4-dioxane. Gas chromatography identified a single metabolite, which was confirmed to be 

1,4-dioxane-2-one by NMR, infrared, and mass spectroscopy. 

Braun and Young et al. (1977) exposed groups of rats to radiolabeled 1,4-dioxane and characterized the 

major radiolabeled metabolite in the urine. The metabolite behaved identically to standards of both 

HEAA and 1,4-dioxane-2-one when evaluated using gas chromatography coupled with mass 

spectroscopy, preventing determination of the identity of the metabolite by this method. Using thin-layer 

chromatography, the metabolite’s Rf value (the ratio of spot distance traveled to distance of the solvent 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 107 

3. HEALTH EFFECTS 

front) of 0.60 correlated with that of HEAA (0.61) rather than that of 1,4-dioxane-2-one (1.00). The study 

authors therefore concluded that the identity of the urinary metabolite in rats was HEAA, rather than 

1,4-dioxane-2-one, but noted the tendency for HEAA to cyclize under acidic conditions, forming 

1,4-dioxane-2-one. 

Woo et al. (1977c, 1978) pretreated groups of rats with phenobarbital (PB), Arochlor 1254 (PCB), or 

3-methylcholanthrene (MC) and examined the effects on the metabolism of an intraperitoneal dose of 

1,4-dioxane. Pretreatment with PB resulted in a much more rapid metabolism of 1,4-dioxane, with the 

majority of the dose eliminated in the urine as HEAA within 32 hours, compared to 40 hours for the 

controls. The addition of 2,4-dichloro-6-phenylphenoxy ethylamine (DPEA), an inhibitor of cytochrome 

P-450, resulted in a reversal of this effect. Pretreatment with PCB resulted in similar effects as PB, while 

pretreatment with MC had no effect. Pretreatment with cobaltous chloride, to suppress P-450 synthesis, 

resulted in decreased metabolite elimination, further implicating cytochrome P-450 enzymes in the 

metabolism of 1,4-dioxane. 

A study in male Sprague-Dawley rats showed that 1,4-dioxane induces several isomers of cytochrome 

P-450 in various tissues from male Sprague-Dawley rats and that the induction is tissue-specific (Nannelli 

et al. 2005). For example, administration of 2,000 mg 1,4-dioxane/kg/day by gavage for 2 days or 

ingestion of 1.5% 1,4-dioxane in the drinking water (approximately 2,200 mg 1,4-dioxane/kg/day) 

resulted in significant increases in the activities of CYP2B1/2, CYP2C11, and CYP2E1 in hepatic 

microsomes, but only CYP2E1 activity was increased in the kidney and nasal mucosa, and no alterations 

of P-450 activities were recorded in the lungs. Administration of the chemical by gavage also resulted in 

a significant increase in CYP3A activity in the liver. In addition, CYP4A1 activity was not enhanced by 

any treatment with 1,4-dioxane. According to Nannelli et al. (2005), the increase in liver CYP2C11 

activity (2α-testosterone hydroxylase), which is normally under hormonal control and is suppressed in the 

presence of CYP2B1/2 and CYP2E1, may have been due to 1,4-dioxane altering plasma growth hormone 

levels. It was also noted that the increases in CYP2E1 activities in the kidney and renal mucosa were 

accompanied by increases in 2E1 mRNA, which suggested that 2E1 induction in these tissues is 

controlled by transcriptional activation. In contrast, the lack of an increase in 2E1 mRNA in the liver 

suggested that induction of CYP2E1 in hepatocytes is regulated via a post-transcriptional mechanism. In 

a different experiment, Nannelli et al. (2005) showed that induction of CYPB1/2 and CYP2E1 with 

phenobarbital or fasting did not increase the toxicity of 1,4-dioxane as measured by hepatic glutathione 

content or serum activity of ALT. This led the authors to suggest that reactive intermediates do not play a 

major role in the liver toxicity of 1,4-dioxane. The authors also suggested that a sustained induction of 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 108 

3. HEALTH EFFECTS 

CYP2E1 may lead to production of reactive oxygen species that contribute to target organ toxicity and 

regenerative cell proliferation, but no data were provided to support this hypothesis. 

3.4.4 Elimination and Excretion 

3.4.4.1 Inhalation Exposure 

1,4-Dioxane and its metabolite, HEAA, were found in the urine of workers exposed to a time-weighted 

average concentration of 1.6 ppm of 1,4-dioxane for 7.5 hours (Young et al. 1976). The concentration of 

HEAA was 414 μmol/L, and that of unchanged 1,4-dioxane was only 3.5 μmol/L, suggesting rapid and 

extensive metabolism. In four volunteers exposed to 50 ppm of 1,4-dioxane for 6 hours, over 99% of the 

urinary elimination of the compound occurred as its metabolite HEAA (Young et al. 1977) during the 

exposure period or within 18 hours post-exposure; the remainder of the urinary elimination occurred as 

the parent compound. The half-life of elimination of 1,4-dioxane from plasma was 59 minutes, of 

dioxane in urine was 48 minutes, and of HEAA in the urine was 2.7 hours. The urinary elimination data 

suggested that elimination kinetics of 1,4-dioxane and HEAA are best described with first-order, onecompartment kinetic models. Elimination by other pathways (e.g., feces, expired air) was not evaluated 

in this study. 

Following inhalation exposure in animals, the primary route of elimination is believed to be the urine. 

Young et al. (1978a, 1978b) reported that following inhalation exposure in rats, urinary elimination of 

1,4-dioxane was primarily as HEAA, rather than as the parent compound. 

3.4.4.2 Oral Exposure 

Data on the elimination of 1,4-dioxane in humans following oral exposure are not available. 

The administered dose of 1,4-dioxane has an effect on elimination of the compound. While urinary 

elimination is the predominant pathway regardless of dose, at large doses, elimination in the expired air 

plays a greater role, possibly due to the saturable pathways of 1,4-dioxane metabolism. After single oral 

doses of 14C-1,4-dioxane in rats, 99% of the label was recovered in the urine and <1% was recovered in 

the expired air at 10 mg/kg; 86% of the label was recovered in the urine and 4.7% in the expired air at 

100 mg/kg; and 76% of the label was found in the urine and 25% in the expired air at 1,000 mg/kg 

(Young et al. 1978a, 1978b). Similar results were seen following 17 daily gavage doses of 

14C-1,4-dioxane in rats, with 99 and 83% of the label found in the expired air, 1.3 and 8.9% of the label 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 109 

3. HEALTH EFFECTS 

found as expired dioxane, and 4.1 and 7% found as expired CO2 in animals receiving 10 and 1,000 mg/kg, 

respectively. Elimination of 1,4-dioxane in both the expired air and in the urine appear to be first-order 

kinetic processes (Young et al. 1978a, 1978b). 

3.4.4.3 Dermal Exposure 

Data on the elimination of 1,4-dioxane following dermal exposure in humans and animals are not 

available. 

3.4.4.4 Other Routes of Exposure 

After a single intravenous dose of 10 mg/kg of 1,4-dioxane in rats, 4% of the dioxane was eliminated in 

the urine as dioxane, 92% as HEAA, and 1% was eliminated in the expired air (Young et al. 1978a, 

1978b). Following a 1000 mg/kg dose, 11% was eliminated in the urine as dioxane, 60% as HEAA, and 

27% in the expired air, indicating a dose-related shift in the elimination of the compound, possibly due to 

metabolic saturation. At low intravenous doses, 1,4-dioxane is eliminated from the plasma with 

apparently linear kinetics, while higher doses are eliminated progressively more slowly, achieving linear 

kinetics only after a non-linear phase. This indicates the involvement of a saturable process, very likely 

metabolic saturation, in elimination of the compound. Elimination of 1,4-dioxane in both the expired air 

and in the urine following intravenous exposure appear to be first-order kinetic processes (Young et al. 

1978a, 1978b). Pretreatment of rats with phenobarbital resulted in a 2.7-fold greater elimination of 

HEAA in the urine than in rats that were not pretreated (Woo et al. 1977c, 1978). The addition of DPEA 

partly reduced this effect, with the PB + DPEA animals eliminating 1.8-fold the HEAA of controls. 

3.4.5 Physiologically Based Pharmacokinetic (PBPK)/Pharmacodynamic (PD) Models 

Physiologically based pharmacokinetic (PBPK) models use mathematical descriptions of the uptake and 

disposition of chemical substances to quantitatively describe the relationships among critical biological 

processes (Krishnan et al. 1994). PBPK models are also called biologically based tissue dosimetry 

models. PBPK models are increasingly used in risk assessments, primarily to predict the concentration of 

potentially toxic moieties of a chemical that will be delivered to any given target tissue following various 

combinations of route, dose level, and test species (Clewell and Andersen 1985). Physiologically based 

pharmacodynamic (PBPD) models use mathematical descriptions of the dose-response function to 

quantitatively describe the relationship between target tissue dose and toxic end points. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 110 

3. HEALTH EFFECTS 

PBPK/PD models refine our understanding of complex quantitative dose behaviors by helping to 

delineate and characterize the relationships between: (1) the external/exposure concentration and target 

tissue dose of the toxic moiety, and (2) the target tissue dose and observed responses (Andersen and 

Krishnan 1994; Andersen et al. 1987). These models are biologically and mechanistically based and can 

be used to extrapolate the pharmacokinetic behavior of chemical substances from high to low dose, from 

route to route, between species, and between subpopulations within a species. The biological basis of 

PBPK models results in more meaningful extrapolations than those generated with the more conventional 

use of uncertainty factors. 

The PBPK model for a chemical substance is developed in four interconnected steps: (1) model 

representation, (2) model parameterization, (3) model simulation, and (4) model validation (Krishnan and 

Andersen 1994). In the early 1990s, validated PBPK models were developed for a number of 

toxicologically important chemical substances, both volatile and nonvolatile (Krishnan and Andersen 

1994; Leung 1993). PBPK models for a particular substance require estimates of the chemical substancespecific physicochemical parameters, as well as species-specific physiological and biological parameters. 

The numerical estimates of these model parameters are incorporated within a set of differential and 

algebraic equations that describe the pharmacokinetic processes. Solving these differential and algebraic 

equations provides the predictions of tissue dose. Computers then provide process simulations based on 

these solutions. 

The structure and mathematical expressions used in PBPK models significantly simplify the true 

complexities of biological systems. If the uptake and disposition of the chemical substance(s) are 

adequately described, however, this simplification is desirable because data are often unavailable for 

many biological processes. A simplified scheme reduces the magnitude of cumulative uncertainty. The 

adequacy of the model is, therefore, of great importance, and model validation is essential to the use of 

PBPK models in risk assessment. 

PBPK models improve the pharmacokinetic extrapolations used in risk assessments that identify the 

maximal (i.e., the safe) levels for human exposure to chemical substances (Andersen and Krishnan 1994). 

PBPK models provide a scientifically sound means to predict the target tissue dose of chemicals in 

humans who are exposed to environmental levels (for example, levels that might occur at hazardous waste 

sites), based on the results of studies where doses were higher or were administered in different species. 

Figure 3-4 shows a conceptualized representation of a PBPK model. 
 

 

 

 

Figure 3-4. Conceptual Representation of a Physiologically Based
	

Pharmacokinetic (PBPK) Model for a 

Hypothetical Chemical Substance
	

V 

E 

N 

O 

U 

S 

B 

L 

O F ec es O 

D 

Lungs 

Liv er 

F at 

S lo w ly 

perfus ed 

tis s ues 

R ic h ly 

perfus ed 

tis s ues 

A 

R 

T 

E 

R 

I 

A 

L 

B 

L 

O 

O 

D 

V m a x 

K m 

Inges tion 

Inhaled c hem ic al E x haled c hem ic al 

GI 

T ra c t 

K idney 

U rin e

 C h e m ic a ls 

contacting skin 

S k in 

Note: This is a conceptual representation of a physiologically based pharmacokinetic (PBPK) model for a 

hypothetical chemical substance. The chemical substance is shown to be absorbed via the skin, by inhalation, or by 

ingestion, metabolized in the liver, and excreted in the urine or by exhalation. 

Source: adapted from Krishnan and Andersen 1994 

1,4-DIOXANE 111 

3. HEALTH EFFECTS 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 112 

3. HEALTH EFFECTS 

If PBPK models for 1,4-dioxane exist, the overall results and individual models are discussed in this 

section in terms of their use in risk assessment, tissue dosimetry, and dose, route, and species 

extrapolations. 

Leung and Paustenbach (1990) Model. 

Leung and Paustenbach (1990) developed a PBPK model for 1,4-dioxane for rats and humans, based on 

the styrene model of Ramsey and Andersen (1984). The model simulates concentrations of 1,4-dioxane 

in the four modeled tissue compartments, as well as in arterial and venous blood, and the amount of 

metabolites formed. 

Description of the Model. The model consists of compartments for liver, fat, slowly perfused 

tissues, and richly perfused tissues. Model parameters are presented in Table 3-6. Model inputs included 

inhalation, where 1,4-dioxane input was assumed to occur at a rate equal to the cardiac output, and 

drinking water, where 1,4-dioxane absorption was considered to be a zero-order process depositing 

1,4-dioxane directly into the liver compartment. Tissue/air partition coefficients for rat blood, liver, fat, 

and muscle were determined by vial equilibration, and tissue/blood values were calculated by dividing the 

tissue/air coefficient by the blood/air coefficient. The richly perfused coefficient was set equal to that of 

the liver. Human coefficients were assumed to be identical to the rat. For the human model, alveolar 

ventilation rate and cardiac output were estimated using a (body weight)0.74 scalar. The metabolic 

constants were obtained by optimization of the model with experimental data from Young et al. (1977, 

1978a, 1978b); these studies were also used to calibrate the model, using data on blood 1,4-dioxane 

levels, 1,4-dioxane in expired air, and urinary excretion of 1,4-dioxane and HEAA to compare with model 

predictions. 

Validation of the Model. The model parameters were optimized against the rat and human data of 

Young et al. (1977, 1978a, 1978b). Comparisons of model simulations against data from studies other 

than those used in model development were not presented. 

Risk Assessment. The model attempts to estimate concentrations of 1,4-dioxane in the blood and in 

the tissue compartments, as well as the levels of metabolites formed, following an inhalation or oral 

exposure to 1,4-dioxane. These internal dose surrogates could be used in the assessment of health risks 

from exposure to 1,4-dioxane. The study authors used liver tumor data from a rat study (Kociba et al. 

1974) to estimate risk-specific doses for tumor formation following oral exposure, fitting the rat data to a 
 

 

1,4-DIOXANE 113 

3. HEALTH EFFECTS 

Table 3-6. Parameters Used in the PBPK Model for 1,4-Dioxane 

Rat Human 

Weights 

Body (kg) 0.25 84.1 

Liver (percent) 4 4 

Fat (percent) 7 20 

Richly perfused (percent) 5 5 

Slowly perfused (percent) 75 62 

Blood Flow 

Cardiac output (L/hour) 5.4 399 

Liver (percent) 25 25 

Fat (percent) 5 5 

Richly perfused (percent) 51 51 

Slowly perfused (percent) 19 19 

Air flow 

Alveolar ventilation (L/hour) 5.4 399 

Partition coefficients 

Liver/blood 0.85 0.85 

Fat/blood 0.4 0.4 

Richly perfused/blood 0.85 0.85 

Slowly perfused/blood 0.54 0.2a 

Metabolic constants 

Vmax 1.9a 300a 

Km 7.5a 15a 

a

Values obtained by model optimization. 

Source: Adapted from Leung and Paustenbach (1990) 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 114 

3. HEALTH EFFECTS 

multistage model and using liver dioxane concentrations as the dose metric for conversion from rat to 

human values. Human risk levels calculated by dividing the rat value by 5.5 (a body surface area scaling 

factor) were compared with values calculated using the model to calculate a human equivalent 

concentration; the model values resulted in a 7–8-fold greater value for maximum likelihood exposure 

(MLE) risk values than did division of the rat values by 5.5. It is important to note that the application of 

a PBPK model only addresses differences in pharmacokinetic behavior between species, and that 

differences in pharmacodynamic behavior must be discussed separately. 

Target Tissues. The model simulates concentrations of 1,4-dioxane in the four modeled tissue 

compartments, as well as in arterial and venous blood, and the amount of metabolites formed. While two 

of the compartments represent actual body tissues (liver, fat), it is not known whether the model’s 

estimates of tissue concentrations of 1,4-dioxane in these tissues is representative of the actual 

concentration in the tissues. However, the model’s predictions of metabolite formation have been 

calibrated with actual data, providing evidence that the estimate of internal dose to the liver (where all 

metabolism is assumed to occur) is accurate. 

Species Extrapolation. The Leung and Paustenbach (1990) PBPK model for 1,4-dioxane was 

developed in rats and humans, and human data on the pharmacokinetics of 1,4-dioxane was used in the 

optimization of model parameters. As such, interspecies extrapolation using the two models should be 

possible, although it has not yet been presented. 

Interroute Extrapolation. The model includes inputs for both inhalation and oral exposures, and as 

such, should provide a means to estimate an internal dose to a target tissue compartment or other dose 

metric regardless of which of these two exposure routes is used. The use of the model for interroute 

extrapolation is therefore feasible, although it has not yet been performed. 

Reitz et al. (1990) Model 

Reitz et al. (1990) have also published a PBPK model for 1,4-dioxane in rats, mice, and humans, again 

building on the basic structure of the Ramsey and Andersen (1984) model for styrene. The model 

estimates concentrations of 1,4-dioxane in the modeled tissue compartments, as well as in arterial and 

venous blood, and the amount of metabolites formed. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 115 

3. HEALTH EFFECTS 

Description of the Model. The model consisted of six compartments: lung, fat, liver, venous blood, 

slowly perfused tissues, and richly perfused tissues. The model was designed to simulate inhalation, 

intravenous, and oral exposures. Oral exposures could be by gavage or in the drinking water, and were 

assumed to pass through the liver before entering the systemic circulation. Intravenous injection was 

simulated by direct addition to the venous blood compartment, while inhalation deposited directly into 

arterial blood at a rate dependent on ventilation, cardiac output, and the blood/air partition coefficient for 

1,4-dioxane. Tissue/air partition coefficients for 1,4-dioxane in human blood, rat blood, rat fat, rat 

muscle, and rat liver were determined by vial equilibration. Organ volumes, blood flows, and air flows 

were similar to those employed by Andersen et al. (1987), except that ventilation and cardiac output rates 

in humans were increased to provide a better simulation of the human blood level data. Metabolic rate 

constants were determined from data presented by Young et al. (1977, 1978a, 1978b) during optimization 

of the model. Metabolism was assumed to occur only in the liver, and metabolites were assumed to be 

removed from the system. Elimination of parent compound was modeled in the expired air and in the 

urine. The model parameters are presented in Table 3-7. After optimization using data from Young et al. 

(1977, 1978a, 1978b) the results of model runs and the corresponding experimental data were presented 

for venous blood concentrations in rats and humans following inhalation exposure, and venous blood 

concentrations in rats following intravenous exposure. 

Validation of the Model. The model parameters were optimized against the rat and human data of 

Young et al. (1977, 1978a, 1978b). Comparisons of model simulations against data from studies other 

than those used in model development were not presented. 

Risk Assessment. The model attempts to estimate concentrations of 1,4-dioxane in the blood and in 

the tissue compartments, as well as the levels of metabolites formed, following an inhalation, oral, or 

intravenous exposure to 1,4-dioxane. These internal dose surrogates could be used in the assessment of 

health risks from exposure to 1,4-dioxane. The study authors used the model to estimate “Human 

Virtually Safe Doses” (VSDs) based on tumor data from oral and inhalation studies in rats and mice 

(Kociba et al. 1974; NCI 1978; Torkelson et al. 1974). The VSDs were calculated by converting the rat 

no observable effect level (NOEL) for tumor formation to a human equivalent dose, and then dividing by 

a safety factor 100. The authors calculated a risk-specific water concentration of 20,000 μg/L for upper 

bound lifetime cancer risk of 1 in 100,000, calculated to represent the lower 95% confidence limit on 

administered dose producing a lifetime increase in risk of developing liver cancer, using the weighted 

average of area under the liver concentration/time curve and area under the metabolite concentration/time 

curve as the dose surrogate for conversion between species. Assuming a daily water intake of 2 L and a 
 

Table 3-7. Parameters Used in the Reitz et al. (1990) PBPK Model for 1,4 -Dioxane 

Mice Rats Humans 

Body weight (kg) 

Percentage of body weight 

Liver 

Fat 

Rapidly perfused 

Slowly perfused 

Blood 

Flows (L/hour) 

Alveolar ventilation 

Cardiac output 

Percent of cardiac output 

Liver 

Fat 

Rapidly perfused 

Slowly perfused 

Partition coefficients 

Blood/air 

Liver/air 

Fat/air 

Rapidly perfused/air 

Slowly perfused/air 

Saline/air 

Metabolic constants (allometric) 

Vmaxc (mg/hour) 

Km (mg/L) 

Miscellaneous constants 

Ka (hour-1) 

Kme (hour-1) 

Water consumption (mL/day) 

0.035 

4.0 

4.0 

5.0 

73.0 

5.0 

2.34 

2.34 

25.0 

5.0 

52.0 

18.0 

2,750 

1,557 

851 

1,557 

1,557 

2,066 

10.0 

16.2 

5.0 

0.42 

9.8 

0.400 

4.0 

7.0 

5.0 

70.0 

5.0 

7.61 

7.61 

25.0 

5.0 

52.0 

18.0 

1,850 

1,557 

851 

1,557 

1,557 

2,066 

13.7 

29.4 

5.0 

0.28 

54 

70.0 

3.1 

23.1 

3.7 

56.1 

5.0 

696 

696 

25.0 

5.0 

52.0 

18.0 

3,650 

1,557 

851 

1,557 

1,557 

2,066 

6.35 

3.00 

5.0 

0.56 

2,000 

1,4-DIOXANE 116 

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1,4-DIOXANE 117 

3. HEALTH EFFECTS 

reference body weight of 70 kg, 20,000 μg/L of 1,4-dioxane in drinking water corresponds to a dose of 

approximately 0.6 mg/kg/day. For the purpose of comparison, the intake estimated by EPA for the same 

upper bound lifetime cancer risk shown in Figure 3-2 is 0.0001 mg/kg/day. It is important to note, 

however, that the application of a PBPK model only addresses differences in pharmacokinetic behavior 

between species, and that differences in pharmacodynamic behavior must be discussed separately. 

Target Tissues. The model simulates concentrations of 1,4-dioxane in the four modeled tissue 

compartments, as well as in arterial and venous blood, and the amount of metabolites formed. While 

three of the compartments represent actual body tissues (liver, fat, venous blood), experimental data been 

compared to model simulations for only venous blood levels. It is not known whether the model’s 

estimates of tissue concentrations of 1,4-dioxane in the other tissues is representative of the actual 

concentration in the tissues. However, the model’s predictions of metabolite formation have been 

calibrated with actual data, providing evidence that the estimate of internal dose to the liver (where all 

metabolism is assumed to occur) is accurate. 

Species Extrapolation. The Reitz et al. (1990) PBPK model for 1,4-dioxane was developed for rats, 

mice, and humans. Human and rat data on the pharmacokinetics of 1,4-dioxane were used in the 

optimization of model parameters; mouse parameters were generally assumed to be equivalent to those in 

the rat. As such, interspecies extrapolation using the models for the different species should be possible. 

Interroute Extrapolation. The model includes inputs for both inhalation, oral, and intravenous 

exposures, and as such, should be able to estimate an internal dose to a target tissue compartment or other 

dose metric regardless of which of these exposure routes is used. The use of the model for interroute 

extrapolation is therefore feasible, although it has not yet been performed. 

Sweeney et al. (2008) Model 

Sweeney et al. (2008) developed a PBPK model for 1,4-dioxane for mice, rats, and humans. The model 

simulates concentrations of 1,4-dioxane in the four tissue compartments and venous blood. The amount 

and total body concentration of unspecified metabolite (presumed to be HEAA) is also simulated. 

Description of the Model. The model consists of compartments for liver, fat, slowly perfused 

tissues (i.e., muscle and skin), well perfused tissues (excluding the liver), and venous blood. The model 

parameter values are presented in Table 3-8. Values for tissue volumes and fractional blood flow rates 
 

 

 

 

 

 

 

 

 

 

 

Rats Mice Humans 

Body weight (kg) 0.25 0.025 70.0 

Percentage of body weight 

Liver 3.4 5.5 3.3 

Fat 7.0 7.0 21.4 

Rapidly perfused 1 – (sum of other tissue volumes) 

Slowly perfused 59.4 54.9 43.7 

Blood 7.4 4.9 7.9 

Unperfused tissue 5.0 5.4 7.1 

Flows (L/hour/kg0.74) 

Alveolar ventilation 13 20 13 

Cardiac output 13 20 13 

Percent of cardiac output 

Liver 18.3 16.1 22.7 

Fat 7.0 7.0 5.2 

Rapidly perfused 1 – (flow to liver, fat, and slowly perfused) 

Slowly perfused 33.6 21.7 24.9 

Partition coefficients 

Blood/air 1,861 2,002 1,666 

Liver/air 1,862 1,143 1,500 

Fat/air 851 879 865 

Rapidly perfused/air 560 560 560 

Slowly perfused/air 1,341 1,705 1,503 

Saline/air 2,446 2,446 2,446 

Metabolic constants (allometric) 

Vmaxc (mg/hour/kg0.74)

a 7.5 or 12.7 39 or 46 54, 75, or 192 

Km (mg/L) a 21 21 29, 32, or 147 

Miscellaneous constants 

Ka (hour-1)

a 0.8 0.8 Not derived 

Kme (hour-1)

a 0.48 0.35 0.35 

Metabolite volume of distribution (L/kg) 1.0 0.83 0.83 

a

Values obtained by model optimization. 

Source: Adapted from Sweeney et al. (2008) 

 

 

Table 3-8. Parameters Used in the Sweeney et al. (2008)
	

PBPK Model for 1,4-Dioxane
	

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1,4-DIOXANE 119 

3. HEALTH EFFECTS 

were taken from the compendium of physiological parameters by Brown et al. (1997). Gastrointestinal 

absorption is described as first-order transport of the oral dose from the stomach to the liver. The firstorder oral absorption rate constant (Ka) of 0.8 h-1 was optimized in mice using 2,000 mg/kg gavage data 

generated by the model authors. This value was assumed for rats. No value for Ka was derived for 

humans. Inhalation assumes rapid equilibration of the 1,4-dioxane concentration between inhaled air and 

blood described by an experimentally measured blood:air partition coefficient. 

1,4-Dioxane is distributed throughout the body via venous blood flow to the tissue compartments with 

transfer from blood to tissues governed by tissue:blood partition coefficients, which were derived by 

dividing the measured tissue:air by blood:air partition coefficients. Blood:air partition coefficients were 

measured by the model authors for all three species. The authors also measured tissue:air partition 

coefficients for liver, fat, kidney, and muscle in mice, and liver and muscle in rats. Mouse values for 

kidney:air and muscle:air were used as surrogates for rapidly and slowly perfused tissue:air. These 

values, as well as mouse fat:air and kidney:air, were used for rats. The average values for rat and mouse 

tissue:air partition coefficients were used for humans. Elimination of 1,4-dioxane occurs by exhalation or 

following hepatic metabolism. 

Metabolism of 1,4-dioxane is described as a saturable Michaelis-Menten process. Two parameter values 

for maximum metabolic velocity (Vmaxc in mg/hour/kg body weight0.7) and metabolic affinity (Km in 

mg/L) were fitted for rats. Because the intravenous data of Young et al. (1978a, 1978b) suggest that 

higher doses result in rapid induction of metabolic activity, the 1,000 mg/kg intravenous data were used to 

optimize Vmaxc values in the “induced “ state, while data for intravenous doses of 3, 10, 30, or 100 mg/kg 

were used to optimize Vmaxc in the “uninduced” state. The Km for rats was fitted to all of the Young et al. 

(1978a, 1978b) intravenous data. The Km for mice was chosen to be equivalent to rats because the in 

vitro values for rat and mouse Km were very similar. Mouse Vmaxc was optimized against the gavage data 

from 200 and 2,000 mg/kg doses generated by the model authors. The human Vmaxc and Km values were 

derived by multiplying the in vitro value from human hepatocytes, measured by the study authors, by the 

ratio of rat optimized Vmaxc and scaled Vmaxc (from rat hepatocytes) (known as the parallelogram 

approach). 

The metabolite is eliminated via a first-order elimination rate constant (Kme). For the rat, Kme was 

optimized against the urinary HEAA data following intravenous doses of 100 or 1,000 mg/kg 1,4-dioxane 

and gavage doses of 10, 100, or 1,000 mg/kg (Young et al. 1978a, 1978b). For mice, Kme and the volume 

of distribution (VDMC) for total 1,4-dioxane metabolite was derived by optimization of data for HEAA 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 120 

3. HEALTH EFFECTS 

in blood following gavage doses of 200 or 2,000 mg/kg 1,4-dioxane. The value for human Kme was 

assumed to be equivalent to that of mice. 

Validation of the Model. Following optimization of parameter values for Vmaxc, Km, Ka, Kme, and 

VDMC (for mice), additional data from intravenous, gavage, and inhalation exposures were used to 

evaluate model performance. For the rat model, simulated exhaled 1,4-dioxane levels were very similar 

to observations from intravenous or gavage doses of 1,000 mg/kg, but were ~3–5-fold higher than 

observations for 10 mg/kg doses. For 6-hour 50 ppm exposures to 1,4-dioxane, rat simulations of blood 

levels were similar to observations, but HEAA urinary excretion was 3-fold lower than observations. For 

mice, simulations of 20 mg/kg gavage doses predicted no rise of blood 1,4-dioxane levels above the 

observed background concentration of 1.6 mg/L, but predicted levels of HEAA were not in agreement 

with observations. Human predictions of blood 1,4-dioxane levels and urinary HEAA excretion during 

and following a 6-hour 50 ppm inhalation exposure were not in good agreement with observations. The 

model authors attempted to model the 1,4-dioxane body burden in workers based on cumulative 

1,4-dioxane and HEAA in urine samples following a single 7.5-hour inhalation exposure to an average of 

1.6 ppm 1,4-dioxane (Young et al. 1976). Although the predicted and observed body burdens were 

similar, the results are uncertain because the scheme used to calculate body burden was unclear. The 

human urinary production rate was assumed to be 1 mL/hour, and human urinary HEAA elimination was 

determined using elimination parameter values for mice. 

Risk Assessment. The mouse, rat, and human models have not been used previously in risk 

assessment. Although the rat and mouse models provide adequate fits of high-dose observations, they do 

not perform well against low-dose data. The human model could not replicate the limited human 

experimental inhalation data available. Further, it assumes equivalency with mice in eliminating HEAA, 

and has no value derived for oral absorption. Based on these significant limitations, the Sweeney et al. 

(2008) model for 1,4-dioxane in rats, mice, and humans is not adequate for MRL derivation. 

Target Tissues. The model simulates concentrations of 1,4-dioxane in liver, fat, and lumped rapidly 

and slowly perfused tissues. However, performance of the model to predict tissue levels of 1,4-dioxane 

or metabolites cannot be evaluated, as experimental data for tissues are not available for rodents or 

humans. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 121 

3. HEALTH EFFECTS 

Species Extrapolation. The Sweeney et al. (2008) model for 1,4-dioxane was developed for mice, 

rats, and humans. However, the inability of the model to replicate low-dose 1,4-dioxane levels in rats or 

humans precludes its use for species extrapolation. 

Interroute Extrapolation. The model includes inputs for intravenous, oral, and inhalation exposures, 

providing a direct means for interroute extrapolation. 

Takano et al. (2010) Model 

Takano et al. (2010) developed a simplified two-compartment PBPK model for 1,4-dioxane for rats and 

humans. 

Description of the Model. The Takano et al. (2010) model simulates 1,4-dioxane in two 

compartments: the liver compartment and the central compartment. The model used data from (1) in vivo 

studies in rats (repeated oral exposure to 500 mg/kg/day for 14 days and using intraperitoneal 

administration of 500 mg/kg) to establish absorption elimination kinetics and cytochrome P450 

parameters, (2) in vitro studies using rat and human liver microsomes, and (3) in silico estimation of the 

fraction of unbound plasma 1,4-dioxane and octanol-water partition coefficient. Other parameters, such 

as hepatic volumes and blood flow rates, were taken from the literature. The model parameter values are 

presented in Table 3-9. The rat model simulated 1,4-dioxane levels in the blood were similar to measured 

blood levels. The PBPK model showed little accumulation of 1,4-dioxane in the rat 24 hours after daily 

treatment with 1,4-dioxane. Comparisons of simulated blood 1,4-dioxane levels after single or multiple 

exposures to 500 mg/kg in humans showed an accumulation of 1,4-dioxane. 

Validation of the Model. Comparisons of model simulations against data from studies other than 

those used in model development were not presented. 

Risk Assessment. The model attempts to estimate concentrations of 1,4-dioxane in the blood 

following oral exposure to 1,4-dioxane. Although the model provided adequate fit of rat blood 

1,4-dioxane data, the model has not been validated using different dose levels or using data from other 

studies. Based on these significant limitations, this model is not adequate for MRL derivation. 
 

 

1,4-DIOXANE 122 

3. HEALTH EFFECTS 

Table 3-9. Parameters Used in the Takano et al. (2010) PBPK Model for 

1,4-Dioxane 

Rat Human 

Octanol-water partition coefficient -0.31 -0.31 

Hepatic intrinsic clearance (L/hour) 0.0244 1.76 

Liver-plasma concentration ratio 0.692 0.692 

Renal clearance (L/hour) 0.000290 0.0873 

Plasma unbound fraction 0.806 0.806 

Ratio of blood to plasma concentration 1.00 1.00 

Volume of systemic circulation (L) 0.0810 23.7 

Hepatic volume (L) 0.00850 1.50 

Hepatic blood flow rate of systemic circulation to tissue 0.853 96.6 

compartment (L/hour) 

Absorption rate constant (hour-1) 0.280 0.208 

Fraction absorbed x intestinal availability 1.00 1.00 

Dose (mg) 125 3,500 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 123 

3. HEALTH EFFECTS 

Target Tissues. The model simulates concentrations of 1,4-dioxane in blood. However, performance 

of the model to predict tissue levels of 1,4-dioxane or metabolites cannot be evaluated, as experimental 

data for tissues, as experimental data for tissues are not available for rats or humans. 

Species Extrapolation. The Takano et al. (2010) PBPK model for 1,4-dioxane was developed for rats 

and humans. Human and rat data on the pharmacokinetics of 1,4-dioxane were used in the optimization 

of model parameters. As such, interspecies extrapolation using the models for the different species 

should be possible. 

Interroute Extrapolation. The model is limited to oral exposure and does not provide a means for 

interroute extrapolation. 

Fisher et al. (1997) Model 

Fisher et al. (1997) have published a general PBPK model for volatile organic chemicals, which 

incorporates a compartment for elimination of the chemical in the breast milk. Model simulations 

predicted a high degree (18%) of lactational transfer of 1,4-dioxane. While the study authors note that the 

model is applicable to 1,4-dioxane, simulations using the model have not been compared to data from 

humans or animals exposed to 1,4-dioxane. 

3.5 MECHANISMS OF ACTION 

3.5.1 Pharmacokinetic Mechanisms 

Absorption. The absorption of 1,4-dioxane following inhalation or oral exposure is rapid and 

essentially complete; absorption following dermal exposure is very low (Marzulli et al. 1981; Young et al. 

1977, 1978a, 1978b). The mechanisms involved in the absorption of 1,4-dioxane have not been 

evaluated, but given the speed of the absorption and the chemical similarity of 1,4-dioxane to other lowmolecular-weight compounds, absorption is generally assumed to occur through passive diffusion. 

Distribution. The mechanisms of distribution of 1,4-dioxane have not been evaluated. Data on the 

distribution of 1,4-dioxane are limited to studies following injection of the compound (Mikheev et al. 

1990; Woo et al. 1977b). In those studies, distribution of 1,4-dioxane was rapid (5–15 minutes to Tmax). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 124 

3. HEALTH EFFECTS 

1,4-Dioxane has been detected in all tissues that have been evaluated, but has not been shown to 

appreciably accumulate in tissues, possibly due to its high water solubility. 

Metabolism. Studies on the metabolism of 1,4-dioxane have clearly identified the primary metabolite 

as HEAA/1,4-dioxane-2-one, but have not confirmed a clear pathway for the formation of metabolites 

from 1,4-dioxane. Cytochrome P-450 enzymes are clearly involved, as evidenced by the studies of Woo 

et al. (1977c, 1978) and Nannelli et al. (2005). It has been suggested that P-450-mediated metabolism 

may result in the formation of diethylene glycol, since injection of diethylene glycol in rats also results in 

the formation of HEAA (Woo et al. 1977a); however, additional data supporting this pathway have not 

been presented. 

The issue of whether metabolism of 1,4-dioxane represents a detoxifying event or a process that generates 

toxic intermediates has not been resolved. Data from Kociba et al. (1974, 1975) and Young et al. (1978a, 

1978b) indicate that toxicity occurs at high doses when the metabolism of 1,4-dioxane is saturated, which 

would suggest that the parent compound is the toxic form. This also is consistent with more recent data 

from Nannelli et al. (2005) who observed that induction of hepatic CYP2B1/2 and CYP2E1 did not play a 

role in the toxicity of 1,4-dioxane, which suggested that highly reactive and toxic intermediates do not 

play a major role in the liver toxicity of 1,4-dioxane, even under conditions of enhanced metabolism. On 

the other hand, Woo et al. (1978) reported that the metabolite, 1,4-dioxane-2-one, was several-fold more 

toxic than 1,4-dioxane based on intraperitoneal LD50 determinations in rats. 

Excretion. The elimination of 1,4-dioxane occurs primarily (>95%) in the urine, as the primary 

metabolite, at low doses. At higher doses, metabolism becomes saturated, and a greater fraction is 

eliminated in the expired air; however, urinary elimination remains the primary method of elimination. 

Elimination of 1,4-dioxane in both the expired air and the urine following intravenous exposure appear to 

be first-order kinetic processes (Young et al. 1978a, 1978b). Evidence for active secretion or uptake of 

1,4-dioxane from the kidney has not been reported. 

3.5.2 Mechanisms of Toxicity 

The mechanism of carcinogenicity of 1,4-dioxane has not been elucidated, but the results from several 

lines of investigation suggest that 1,4-dioxane has a non-genotoxic mode of action (Goldsworthy et al. 

1991; Leung and Paustenbach 1990; Stott et al. 1981). Briefly, the collective evidence from evaluations 

of genetic toxicity suggests that 1,4-dioxane is unlikely to be genotoxic (see Section 3.3, Genotoxicity). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 125 

3. HEALTH EFFECTS 

1,4-Dioxane was not mutagenic in bacterial assays with or without metabolic activation (Haworth et al. 

1983; Khudoley et al. 1987; Morita and Hayashi 1998; Nestmann et al. 1984; Stott et al. 1981), did not 

induce chromosomal aneuploidy in yeast (Zimmermann et al. 1985), mutations in mouse lymphoma cells 

(Morita and Hayashi 1998; McGregor et al. 1991), or sex-linked recessive lethal mutations in 

D. melanogaster (Yoon et al. 1995). Moreover, in an occupational study there was no evidence of an 

increased incidence of chromosomal aberrations among workers chronically exposed to relatively low 

levels of 1,4-dioxane compared to controls (Thiess et al. 1976). No significant increase in chromosomal 

aberrations was observed in Chinese hamster ovary cells incubated with 1,4-dioxane with or without 

metabolic activation, but there was a weak increase in sister chromatid exchanges when the cells were 

incubated without metabolic activation (Galloway et al. 1987). Also, incubation of BALB/3t3 cells with 

1,4-dioxane increased the incidence of transformations leading to the formation of foci, but at 

concentrations of 1,4-dioxane that were cytotoxic to over 50% of the cells (Sheu et al. 1998). 

Several structure-activity analyses have been conducted to study the mechanism of carcinogenicity of 

1,4-dioxane. For example, a computerized structure relationship analysis using TOPKAT (version 3.0) in 

male rat and female mouse models showed that the -O-CH2- fragment of the molecule increased the 

carcinogenic potential in both models; however, the male rat model indicated that the symmetry of the 

1,4-dioxane molecule is more important in the carcinogenicity of 1,4-dioxane than the -O-CH2- fragment 

(Blake 1995). Additional modeling efforts of the potential role of 1,4-dioxane’s metabolites, HEAA and 

1,4-dioxane-2-one, in the carcinogenicity and genotoxicity of 1,4-dioxane predicted that HEAA would be 

noncarcinogenic and nonmutagenic, whereas 1,4-dioxane-2-one was predicted to have a strong positive 

influence in the female mouse carcinogenicity model and the Ames mutagenicity model (Gombar 1995). 

It should be noted, as mentioned in Section 2.4.3, Metabolism, experiments conducted by U.S. Army 

(2010) showed that the chemical instability of 1,4-dioxane-2-one suggested that it is unlikely to be 

involved in the mode of action for carcinogenesis of 1,4-dioxane. A structure-activity relationship 

analysis using the Computer-Automated Structure Evaluation (CASE) methodology found the fragment 

-O-CH2- to be associated with a high probability of induction of micronuclei in mice bone marrow cells 

(Rosenkranz and Klopman 1992). According to unpublished results cited by Rosenkranz and Klopman 

(1992), the concordance between experimental results and CASE predictions of the induction of 

micronuclei is in excess of 83%. However, Rosenkranz and Klopman (1992) indicated that because the 

-O-CH2- fragment does not seem to have intrinsic electrophilicity, they could not envision a possible 

DNA-reactive metabolite; however, the -O-CH2- fragment might contribute to a non-genotoxic effect of 

1,4-dioxane resulting in the induction of micronuclei. Since the experimental results of micronucleiinduction studies in mice have been mixed (McFee et al. 1994; Mirkova 1994; Morita and Hayashi 1998; 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Tinwell and Ashby 1994), Ashby (1994) suggested that it is not always possible to categorize a chemical 

as either unequivocally positive or negative in genotoxic activity. 

Numerous studies have examined the possible role of DNA damage, DNA synthesis, cell proliferation, or 

peroxisome proliferation in the carcinogenic effects of 1,4-dioxane. For instance, a test for DNA single 

strand breaks in rat hepatocytes incubated with 1,4-dioxane gave positive results, although only at 

cytotoxic concentrations (Sina et al. 1983). Stott et al. (1981) reported that hepatocytes from SpragueDawley rats dosed with 1,4-dioxane for 11 weeks showed no evidence of DNA alkylation or DNA repair 

activity, but showed increased levels of DNA synthesis. Based on these results, Stott et al. (1981) 

suggested that 1,4-dioxane induces tumors by a non-genetic mechanism. 

The role of cell proliferation in the carcinogenicity of 1,4-dioxane was further evaluated in two studies 

that yielded inconclusive results. Administration of single doses of up to 2,000 mg 1,4-dioxane/kg by 

gavage to male F344 failed to induce replicative DNA synthesis in hepatocytes (Uno et al. 1994), which 

led the authors to suggest that 1,4-dioxane may induce liver cancer only in initiated cells. However, in a 

subsequent study by the same group of investigators, and using the same experimental protocol, 

1,4-dioxane did increase hepatocyte cell proliferation (Miyagawa et al. 1999); the reason for the 

discrepancy in the results between the two studies is not apparent. 

In liver tissue from Sprague-Dawley rats given single doses of 1,4-dioxane, there was a small but 

statistically significant amount of DNA damage (assessed by alkaline elution) at dose levels that did not 

induce cytotoxicity (Kitchin and Brown 1990, 1994). Liver toxicity was assessed by light microscopy 

and measurements of serum levels of ALT (no significant increase was observed). The DNA damage was 

accompanied by an increase in cytochrome P-450 content and by large increases in the activity of hepatic 

ornithine decarboxylase, suggesting strong promoter activity for 1,4-dioxane. 

Another study of the potential mechanisms of carcinogenicity of 1,4-dioxane showed that neither 

1,4-dioxane nor the metabolite 1,4-dioxane-2-one induced DNA repair activity in primary rat hepatocytes 

following incubation in vitro with the chemicals (Goldsworthy et al. 1991). Administration of a single 

oral dose of 1,4-dioxane to F344 rats produced no evidence of hepatocyte DNA repair, and did not 

increase DNA synthesis, relative liver weight, or the activity of palmitoyl CoA oxidase (an indicator of 

peroxisome proliferation) (Goldsworthy et al. 1991). Furthermore, administration of a single dose of 

1,000 mg/kg of 1,4-dioxane did not increase the hepatocyte labeling index 24 or 48 hours after dosing, but 

exposure to 1% 1,4-dioxane in the drinking water for 2 weeks resulted in a 2-fold increase in hepatic 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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labeling index (Goldsworthy et al. 1991); the latter suggested that cell proliferation may play a role in the 

induction of liver carcinoma. In addition, no DNA repair activity or evidence of cells proliferation was 

observed in nasal epithelial cells from rats administered 1% 1,4-dioxane in the drinking water for 2 weeks 

(Goldsworthy et al. 1991). However, it must be mentioned that Goldsworthy et al. (1991) acknowledged 

that a 2-week period of exposure might have been too short for detecting a proliferative response. 

Goldsworthy et al. (1991) concluded that the mechanism of carcinogenicity of 1,4-dioxane remains 

obscure and may involve a novel mechanism. In support of some of Goldsworthy’s findings, Nannelli et 

al. (2005) also provided evidence that excluded peroxisome proliferation as a way to explain the toxicity 

of 1,4-dioxane. These investigators found that administration of approximately 2,200 mg 1,4-dioxane/kg/ 

day in the drinking water for 10 days to rats also failed to induce palmitoyl CoA oxidase activity. 

Gold et al. (1993) analyzed 351 chemicals in the Carcinogenic Potency Database (CPDB) and pointed out 

that, relative to non-mutagenic chemicals, mutagens are more likely to be carcinogenic, more likely to 

induce tumors at multiple target sites and, more likely to be carcinogenic in two species. Since 

1,4-dioxane was carcinogenic in more than one species and induced tumors at multiple sites, one would 

expect that 1,4-dioxane would behave like a mutagen, but the empirical data suggest otherwise. Gold 

(1993) pointed out that among the CPDB chemicals tested for mutagenicity, 75% are mutagens, compared 

to 45% for non-mutagens. This suggested that administration of large doses in cancer bioassays result in 

mitogenesis, which in turn increases the rate of mutagenesis and thus carcinogenesis. 

The lack of significant genotoxicity along with the cytotoxicity observed at dose levels that induce tumors 

supports the view that 1,4-dioxane acts via an unknown non-genotoxic mechanism. 

The mechanism(s) by which 1,4-dioxane induces kidneys lesions is not known, and virtually no 

discussion about this topic was found in the available reviews. The findings in the cases described by 

Barber (1934) and Johnstone (1959) are consistent with an acute nephritic syndrome, which is 

characterized by acute renal failure and oliguria. The impaired glomerular filtration rate causes 

extracellular fluid volume expansion, edema, and hypertension. A study of controlled exposures in 

volunteers showed that 1,4-dioxane has poor renal clearance, 0.34 mL/minute (Young et al. 1977), which 

probably contributes to accumulation of the chemical in the kidneys as biotransformation to the 

metabolite HEAA becomes saturated under conditions of high exposure. 

The issue of the nasal effects observed in rats exposed to 1,4-dioxane via the drinking water studies is 

controversial. As indicated in Section 2.2, Sweeney et al. (2008) presented evidence suggesting that nasal 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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effects may result from the splashing of drinking water into the nasal cavity. However, in the 13-week 

drinking water study by Kano et al. (2008), the enlarged nuclei of the respiratory and olfactory epithelial 

cells were distributed over the entire respiratory and olfactory region, respectively. Similarly, Kano et al. 

(2009) also found nasal tumors distributed over the entire region of the nasal cavity from rats exposed to 

1,4-dioxane in the drinking water for 2 years. These findings support a systemic delivery of a chemical. 

The mechanism by which oral exposure to 1,4-dioxane can lead to effects on the respiratory epithelium 

has not been elucidated. However, Kasai et al. (2009) suggested that induction of P-450 isozymes in the 

olfactory epithelium, as shown by Nannelli et al. (2005), may lead to the formation of toxic metabolites 

not only from the inhaled and circulating 1,4-dioxane, but also from the 1,4-dioxane exhaled from the 

alveoli. A role for unchanged 1,4-dioxane cannot be ruled out. Further research on this issue is 

necessary. 

3.5.3 Animal-to-Human Extrapolations 

Exposure to high concentrations of 1,4-dioxane induces liver and kidneys effects in humans and in 

animals, regardless of the route of exposure. Based solely on the similarity of target organs, it would 

appear that results from animal studies could be used as valid models to predict health effects in humans 

resulting from high-dose exposure to 1,4-dioxane. 

Long-term oral exposure of rodents to 1,4-dioxane has induced liver tumors in rats and mice as well as 

tumors in the nasal cavity of rats (JBRC 1998b; Kociba et al. 1974; NCI 1978). Therefore, the issue is 

whether these long-term, relatively high-exposure studies in animals are relevant to the low 

environmental exposures to 1,4-dioxane experienced by the general population. Studies of humans 

exposed chronically to relatively low concentrations of 1,4-dioxane in the air in occupational settings 

have provided no evidence of ill effects, including cancer, associated with 1,4-dioxane among the workers 

(Buffler et al. 1978; Thiess et al. 1976). However, it is unclear if the effects reported in humans are 

consistent with the potency estimated in rodents. 

Some studies have shown that the liver tumors in rats are accompanied by extensive toxicity, as 

evidenced by hepatocyte hyperplasia, accumulation of fat in the cytoplasm, and degenerative changes 

(JBRC 1998b; Kociba et al. 1974; NCI 1978), which has led some to suggest that cell damage and 

degeneration may be a necessary occurrence for the formation of liver tumors in rats. Since liver toxicity 

in rats seems to occur only at dose levels at which plasma clearance and excretion of HEAA are reduced 

and plasma concentrations of unchanged 1,4-dioxane are increased, it may be appropriate to consider the 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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differences in metabolic disposition when extrapolating from effects that occur only with high doses to 

low-dose events (Kociba et al. 1975). 

The relevance to humans of the nasal lesions and nasal tumors consistently seen in rats following 

exposure to 1,4-dioxane through the drinking water in many studies has been questioned (Stickney et al. 

2003). Some have suggested that the tumors resulted from inspiration of water containing 1,4-dioxane 

into the nasal cavity (Goldsworthy et al. 199; Reitz et al. 1990; Sweeney et al. 2008). However, as 

mentioned above, there are studies that support a systemic delivery of 1,4-dioxane or a metabolite (Kano 

et al. 2008, 2009). The lack of nasal tumors in mice in chronic drinking water studies could be due to 

differences in tissue sensitivity and/or repair mechanisms, or to differences in anatomical features. 

However, species differences are difficult to establish, since 1,4-dioxane acts via an unknown mechanism 

to produce tumors in liver, nasal cavity, and other sites. 

3.6 TOXICITIES MEDIATED THROUGH THE NEUROENDOCRINE AXIS 

Recently, attention has focused on the potential hazardous effects of certain chemicals on the endocrine 

system, because of the ability of these chemicals to mimic or block endogenous hormones. Chemicals 

with this type of activity are most commonly referred to as endocrine disruptors. However, appropriate 

terminology to describe such effects remains controversial. The terminology endocrine disruptors, 

initially used by Thomas and Colborn (1992), was also used in 1996 when Congress mandated that EPA 

develop a screening program for “...certain substances [which] may have an effect produced by a 

naturally occurring estrogen, or other such endocrine effect[s]...”. To meet this mandate, EPA convened a 

panel called the Endocrine Disruptors Screening and Testing Advisory Committee (EDSTAC), and in 

1998, the EDSTAC completed its deliberations and made recommendations to EPA concerning endocrine 

disruptors. In 1999, the National Academy of Sciences released a report that referred to these same types 

of chemicals as hormonally active agents. The terminology endocrine modulators has also been used to 

convey the fact that effects caused by such chemicals may not necessarily be adverse. Many scientists 

agree that chemicals with the ability to disrupt or modulate the endocrine system are a potential threat to 

the health of humans, aquatic animals, and wildlife. However, others think that endocrine-active 

chemicals do not pose a significant health risk, particularly in view of the fact that hormone mimics exist 

in the natural environment. Examples of natural hormone mimics are the isoflavinoid phytoestrogens 

(Adlercreutz 1995; Livingston 1978; Mayr et al. 1992). These chemicals are derived from plants and are 

similar in structure and action to endogenous estrogen. Although the public health significance and 

descriptive terminology of substances capable of affecting the endocrine system remains controversial, 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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scientists agree that these chemicals may affect the synthesis, secretion, transport, binding, action, or 

elimination of natural hormones responsible for maintaining homeostasis, reproduction, development, 

and/or behavior in humans (EPA 1997b). Stated differently, such compounds may cause toxicities that 

are mediated through the neuroendocrine axis. As a result, these chemicals may play a role in altering, 

for example, metabolic, sexual, immune, and neurobehavioral function. Such chemicals are also thought 

to be involved in inducing breast, testicular, and prostate cancers, as well as endometriosis (Berger 1994; 

Giwercman et al. 1993; Hoel et al. 1992). 

Based on the available information, there is no evidence that 1,4-dioxane is an endocrine disruptor in 

humans or in animals, but appropriate tests have not been conducted. The only relevant information that 

was located is that 1,4-dioxane tested negative for estrogenic activity in a reporter gene expression assay 

using yeast cells (Nishihara et al. 2000). A substance was considered positive when its activity was more 

than 10% of the activity of 10-7 M 17β-estradiol. 

Long-term oral studies have found no histopathologic (non-neoplastic) alterations in endocrine glands and 

reproductive organs from rats and mice (Kociba et al. 1974; NCI 1978), and the same was found in a 

chronic-duration inhalation study in rats (Torkelson et al. 1974). However, neoplasms associated with the 

administration of 1,4-dioxane occurred in the testis/epididymis in male rats administered ≥240 mg 

1,4-dioxane/kg/day in the drinking water for 2 years (NCI 1978). Another 2-year bioassay reported an 

increased incidence of mammary gland adenomas in rats treated with 514 mg 1,4-dioxane/kg/day in the 

drinking water (JBRC 1998b). 

Standard reproductive toxicity studies on 1,4-dioxane were not located, and only one study that examined 

the developmental effects of 1,4-dioxane was available (Giavini et al. 1985). The latter study reported 

slight fetotoxicity occurring at a dose level that also affected the mothers. 

3.7 CHILDREN’S SUSCEPTIBILITY 

This section discusses potential health effects from exposures during the period from conception to 

maturity at 18 years of age in humans, when all biological systems will have fully developed. Potential 

effects on offspring resulting from exposures of parental germ cells are considered, as well as any indirect 

effects on the fetus and neonate resulting from maternal exposure during gestation and lactation. 

Relevant animal and in vitro models are also discussed. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Children are not small adults. They differ from adults in their exposures and may differ in their 

susceptibility to hazardous chemicals. Children’s unique physiology and behavior can influence the 

extent of their exposure. Exposures of children are discussed in Section 6.6, Exposures of Children. 

Children sometimes differ from adults in their susceptibility to hazardous chemicals, but whether there is 

a difference depends on the chemical (Guzelian et al. 1992; NRC 1993). Children may be more or less 

susceptible than adults to health effects, and the relationship may change with developmental age 

(Guzelian et al. 1992; NRC 1993). Vulnerability often depends on developmental stage. There are 

critical periods of structural and functional development during both prenatal and postnatal life, and a 

particular structure or function will be most sensitive to disruption during its critical period(s). Damage 

may not be evident until a later stage of development. There are often differences in pharmacokinetics 

and metabolism between children and adults. For example, absorption may be different in neonates 

because of the immaturity of their gastrointestinal tract and their larger skin surface area in proportion to 

body weight (Morselli et al. 1980; NRC 1993); the gastrointestinal absorption of lead is greatest in infants 

and young children (Ziegler et al. 1978). Distribution of xenobiotics may be different; for example, 

infants have a larger proportion of their bodies as extracellular water, and their brains and livers are 

proportionately larger (Altman and Dittmer 1974; Fomon 1966; Fomon et al. 1982; Owen and Brozek 

1966; Widdowson and Dickerson 1964). The infant also has an immature blood-brain barrier (Adinolfi 

1985; Johanson 1980) and probably an immature blood-testis barrier (Setchell and Waites 1975). Many 

xenobiotic metabolizing enzymes have distinctive developmental patterns. At various stages of growth 

and development, levels of particular enzymes may be higher or lower than those of adults, and 

sometimes unique enzymes may exist at particular developmental stages (Komori et al. 1990; Leeder and 

Kearns 1997; NRC 1993; Vieira et al. 1996). Whether differences in xenobiotic metabolism make the 

child more or less susceptible also depends on whether the relevant enzymes are involved in activation of 

the parent compound to its toxic form or in detoxification. There may also be differences in excretion, 

particularly in newborns who all have a low glomerular filtration rate and have not developed efficient 

tubular secretion and resorption capacities (Altman and Dittmer 1974; NRC 1993; West et al. 1948). 

Children and adults may differ in their capacity to repair damage from chemical insults. Children also 

have a longer remaining lifetime in which to express damage from chemicals; this potential is particularly 

relevant to cancer. 

Certain characteristics of the developing human may increase exposure or susceptibility, whereas others 

may decrease susceptibility to the same chemical. For example, although infants breathe more air per 

kilogram of body weight than adults breathe, this difference might be somewhat counterbalanced by their 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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alveoli being less developed, which results in a disproportionately smaller surface area for alveolar 

absorption (NRC 1993). 

There are no studies that specifically address the health effects of exposure to 1,4-dioxane in children or 

in immature animals; therefore, it is unknown whether children differ from adults in their susceptibility to 

health effects from 1,4-dioxane. Data in adults were derived from occupational studies (Barber 1934; 

Buffler et al. 1978; Thiess et al. 1976) and studies in volunteers (Fairley et al. 1934; Silverman et al. 

1946; Yant et al. 1930; Young et al. 1977). The former showed that exposure to high concentrations of 

1,4-dioxane in the air (and also dermally) can severely damage the liver and kidneys and can be lethal. 

The studies of controlled exposure with volunteers showed that exposure to 1,4-dioxane in the air can 

produce eye, nose, and throat irritation. It is reasonable to assume that the same types of effects would be 

seen in children accidentally exposed to high amounts of 1,4-dioxane. 

There is no information regarding possible adverse developmental effects in humans exposed to 

1,4-dioxane. A study in rats exposed orally to 1,4-dioxane during gestation found slight fetotoxicity, but 

at a dose level that also affected the mothers (Giavini et al. 1985). There is evidence that 1,4-dioxane is at 

most a weak genotoxic compound. Therefore, it is unlikely that parental exposure would result in adverse 

childhood development or cancer development as a result of 1,4-dioxane metabolite exposures to parental 

germ cells. 

There is no information regarding pharmacokinetics of 1,4-dioxane in children. Analysis of urine 

samples from humans exposed to 1,4-dioxane suggests the involvement mainly of phase I metabolic 

enzymes in the biotransformation and elimination of 1,4-dioxane. A recent study showed that 

1,4-dioxane can induce several P-450 isozymes in the liver of rats (Nannelli et al. 2005), and one of them 

was CYP2E1, which has been shown to be developmentally-regulated (Vieira et al. 1996). However, the 

question of whether metabolism of 1,4-dioxane represents a detoxifying mechanism or a process 

generating toxic intermediates is still unclear. It is not known whether 1,4-dioxane can cross the placenta, 

and there are no reports on levels of 1,4-dioxane in maternal milk. 

There are no biomarkers of exposure or effect for 1,4-dioxane that have been validated in children or in 

adults exposed as children. No relevant studies were located regarding interactions of 1,4-dioxane with 

other chemicals in children or adults. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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No information was located regarding pediatric-specific methods for reducing peak absorption following 

exposure to 1,4-dioxane, reducing body burden, or interfering with the mechanisms of action for toxic 

effects. 

3.8 BIOMARKERS OF EXPOSURE AND EFFECT 

Biomarkers are broadly defined as indicators signaling events in biologic systems or samples. They have 

been classified as markers of exposure, markers of effect, and markers of susceptibility (NAS/NRC 

1989). 

A biomarker of exposure is a xenobiotic substance or its metabolite(s) or the product of an interaction 

between a xenobiotic agent and some target molecule(s) or cell(s) that is measured within a compartment 

of an organism (NAS/NRC 1989). The preferred biomarkers of exposure are generally the substance 

itself or substance-specific metabolites in readily obtainable body fluid(s) or excreta. However, several 

factors can confound the use and interpretation of biomarkers of exposure. The body burden of a 

substance may be the result of exposures from more than one source. The substance being measured may 

be a metabolite of another xenobiotic substance (e.g., high urinary levels of phenol can result from 

exposure to several different aromatic compounds). Depending on the properties of the substance (e.g., 

biologic half-life) and environmental conditions (e.g., duration and route of exposure), the substance and 

all of its metabolites may have left the body by the time samples can be taken. It may be difficult to 

identify individuals exposed to hazardous substances that are commonly found in body tissues and fluids 

(e.g., essential mineral nutrients such as copper, zinc, and selenium). Biomarkers of exposure to 

1,4-dioxane are discussed in Section 3.8.1. 

Biomarkers of effect are defined as any measurable biochemical, physiologic, or other alteration within an 

organism that, depending on magnitude, can be recognized as an established or potential health 

impairment or disease (NAS/NRC 1989). This definition encompasses biochemical or cellular signals of 

tissue dysfunction (e.g., increased liver enzyme activity or pathologic changes in female genital epithelial 

cells), as well as physiologic signs of dysfunction, such as increased blood pressure or decreased lung 

capacity. Note that these markers are often not substance specific. They also may not be directly 

adverse, but can indicate potential health impairment (e.g., DNA adducts). Biomarkers of effects caused 

by 1,4-dioxane are discussed in Section 3.8.2. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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A biomarker of susceptibility is an indicator of an inherent or acquired limitation of an organism's ability 

to respond to the challenge of exposure to a specific xenobiotic substance. It can be an intrinsic genetic or 

other characteristic or a preexisting disease that results in an increase in absorbed dose, a decrease in the 

biologically effective dose, or a target tissue response. If biomarkers of susceptibility exist, they are 

discussed in Section 3.10, “Populations That Are Unusually Susceptible.” 

3.8.1 Biomarkers Used to Identify or Quantify Exposure to 1,4-Dioxane 

1,4-Dioxane and its metabolite, HEAA, were found in the urine of workers exposed to a time-weighted 

average air concentration of 1.6 ppm of 1,4-dioxane for 7.5 hours (Young et al. 1976). The concentration 

of HEAA was 414 μmol/L and that of unchanged 1,4-dioxane was only 3.5 μmol/L, suggesting rapid and 

extensive metabolism. 1,4-Dioxane in the urine is a specific biomarker for exposure to 1,4-dioxane, but 

HEAA can also be produced by exposure to 1,4-dioxane-2-one and diethylene glycol. In a controlledexposure study with volunteers exposed to 50 ppm 1,4-dioxane vapors for 6 hours, the half-life for 

elimination of 1,4-dioxane from plasma was 59 minutes (Young et al. 1977). The plasma concentration 

of HEAA reached a peak at about 1 hour after exposure ceased and decreased linearly thereafter. Of all 

the 1,4-dioxane detected in the urine within a 48-hour period, 90% was excreted during the exposure 

period and none could be detected 6 hours after termination of the exposure. The half-life for elimination 

of 1,4-dioxane in the urine was 48 minutes, and that of HEAA was 2.7 hours. Almost all the 1,4-dioxane 

was excreted in the urine as HEAA. About half of the total HEAA excreted was excreted during the 

exposure period, and the excretion was complete 18 hours after the exposure ceased. A simulation of 

repeated exposures to 50 ppm 1,4-dioxane for 8 hours/day showed that 1,4-dioxane will reach a peak in 

plasma at the end of each exposure day and will not accumulate; neither will HEAA. Collectively, these 

results imply that 1,4-dioxane and HEAA in plasma and urine can be used as biomarkers of recent 

isolated exposure or multiple daily exposures, but that could not differentiate between the two types of 

exposure (providing the exposure concentrations are below about 50 ppm). In addition, because these 

substances are rapidly eliminated, they cannot be used as biomarkers of past exposure to 1,4-dioxane. 

Given the low levels of 1,4-dioxane reported in the environment, it is not unlikely that the levels of 

1,4-dioxane and HEAA in members from the general population fall under the detection levels of the 

available analytical methods. 

Some chemicals bind to macromolecules (i.e., DNA, hemoglobin, etc.) to form compounds that can be 

used as specific biomarkers of exposure. That is not the case for 1,4-dioxane. In liver preparations from 

rats administered a single intraperitoneal dose of radioactive 1,4-dioxane, most of the radioactivity was 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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bound non-covalently in the cytosol (Woo et al. 1977b). Covalent binding to macromolecules was 

highest in nuclear fraction followed by mitochondrial, microsomal, whole homogenate, and cytosol 

fractions. The binding was nonspecific and not associated with DNA. Pretreatment of rats with 

microsomal enzyme inducers had no significant effect on the covalent binding to macromolecules. There 

was no microsomally-mediated binding of radioactivity to DNA. 

3.8.2 Biomarkers Used to Characterize Effects Caused by 1,4-Dioxane 

The liver and kidneys are targets for 1,4-dioxane toxicity, but lesions to these organs cannot be considered 

specific biomarkers for 1,4-dioxane because, exposure to many different chemicals or health conditions 

unrelated to chemical exposures can produce similar effects. 

3.9 INTERACTIONS WITH OTHER CHEMICALS 

The only information located that is relevant to environmental or occupational exposures is from a study 

by Buffler et al. (1978) in workers, even though it provides only suggestive evidence that interactions 

may have played a role in the outcome. In a cohort of 165 workers exposed intermittently to 

concentrations of 1,4-dioxane between 0.1 and 17 ppm, seven deaths were identified among those 

working in the manufacturing area and five among those involved in the processing area (Buffler et al. 

1978). The exposure histories of the seven subjects indicated that all were exposed to other chemicals of 

possible significance at earlier times and for longer intervals than their exposure to 1,4-dioxane. In 

addition, the five deaths that occurred among the processing area were exposed to vinyl chloride 

simultaneously with their exposure to 1,4-dioxane. No firm conclusions can be drawn from this study 

regarding interactions of 1,4-dioxane with other chemicals. 

If cytochrome CYP2E1 is involved in the metabolism of 1,4-dioxane (the cytochrome P-450 system is 

known to be involved in 1,4-dioxane metabolism), then ethanol could alter the hepatic effects of 

1,4-dioxane if one assumes that the toxic entity is a metabolite of 1,4-dioxane. In the Thiess et al. (1976) 

study, some workers exposed to 1,4-dioxane who consumed alcohol frequently had elevated serum levels 

of transaminases; however, the values became normal after the workers reduced their alcohol 

consumption, suggesting that the elevated transaminase values were purely or largely primarily due to 

exposure to ethanol and not to the combination of 1,4-dioxane and ethanol, at least at the relative low 

level of exposure experienced by the workers in this occupational study (maximum 14.3 ppm). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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3.10 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE 

A susceptible population will exhibit a different or enhanced response to 1,4-dioxane than will most 

persons exposed to the same level of 1,4-dioxane in the environment. Reasons may include genetic 

makeup, age, health and nutritional status, and exposure to other toxic substances (e.g., cigarette smoke). 

These parameters result in reduced detoxification or excretion of 1,4-dioxane, or compromised function 

of organs affected by 1,4-dioxane. Populations who are at greater risk due to their unusually high 

exposure to 1,4-dioxane are discussed in Section 6.7, Populations with Potentially High Exposures. 

Because 1,4-dioxane is a liver and kidney toxicant at high concentrations, people with compromised liver 

or kidney function may be more susceptible to the effects of exposure to 1,4-dioxane than healthy 

individuals. Among those unusually susceptible would be, for example, individuals who drink excessive 

amounts of alcohol, those on medications known to affect the liver or the kidneys, or those with genetic or 

other diseases of the kidney. 

3.11 METHODS FOR REDUCING TOXIC EFFECTS 

This section will describe clinical practice and research concerning methods for reducing toxic effects of 

exposure to 1,4-dioxane. However, because some of the treatments discussed may be experimental and 

unproven, this section should not be used as a guide for treatment of exposures to 1,4-dioxane. When 

specific exposures have occurred, poison control centers and medical toxicologists should be consulted 

for medical advice. 

No information was found that provided specific information about treatment following exposure to 

1,4-dioxane. 

3.11.1 Reducing Peak Absorption Following Exposure 

The only relevant information that was located is that the skin and eyes should be immediately flushed 

with water for at least 15 minutes following skin and eye contact (NIOSH 1977). If 1,4-dioxane is 

swallowed, vomiting should be induced immediately if the patient is conscious (NIOSH 1977). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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3.11.2 Reducing Body Burden 

No information was located regarding reducing body burden following exposure to 1,4-dioxane. As 

mentioned in Section 3.4, Toxicokinetics, 1,4-dioxane and its main metabolites do not accumulate and are 

rapidly eliminated from the body in the urine. 

3.11.3 Interfering with the Mechanism of Action for Toxic Effects 

The liver and kidneys are targets for 1,4-dioxane toxicity in humans and animals. Lesions have been 

found in humans acutely exposed to relatively high concentrations of 1,4-dioxane and in animals 

following inhalation, oral, and dermal exposure (see Section 3.2). Also, 1,4-dioxane has induced liver 

cancer in rats and mice and nasal cancer in rats. The mechanism(s) of toxic action of 1,4-dioxane has not 

been elucidated, but there is increasing evidence that the liver lesions seen in animals evolve into 

neoplasms induced by 1,4-dioxane through a non-genotoxic mechanism of action. Any attempt to discuss 

possible mechanisms to interfere with this action would be pure speculation at this time. 

3.12 ADEQUACY OF THE DATABASE 

Section 104(I)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with the 

Administrator of EPA and agencies and programs of the Public Health Service) to assess whether 

adequate information on the health effects of 1,4-dioxane is available. Where adequate information is not 

available, ATSDR, in conjunction with the National Toxicology Program (NTP), is required to assure the 

initiation of a program of research designed to determine the health effects (and techniques for developing 

methods to determine such health effects) of 1,4-dioxane. 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean 

that all data needs discussed in this section must be filled. In the future, the identified data needs will be 

evaluated and prioritized, and a substance-specific research agenda will be proposed. 

3.12.1 Existing Information on Health Effects of 1,4-Dioxane 

The existing data on health effects of inhalation, oral, and dermal exposure of humans and animals to 

1,4-dioxane are summarized in Figure 3-5. The purpose of this figure is to illustrate the existing 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 138 

3. HEALTH EFFECTS 

information concerning the health effects of 1,4-dioxane. Each dot in the figure indicates that one or 

more studies provide information associated with that particular effect. The dot does not necessarily 

imply anything about the quality of the study or studies, nor should missing information in this figure be 

interpreted as a “data need”. A data need, as defined in ATSDR’s Decision Guide for Identifying 

Substance-Specific Data Needs Related to Toxicological Profiles (Agency for Toxic Substances and 

Disease Registry 1989), is substance-specific information necessary to conduct comprehensive public 

health assessments. Generally, ATSDR defines a data gap more broadly as any substance-specific 

information missing from the scientific literature. 

As shown in Figure 3-5, there is limited information on the effects of 1,4-dioxane in humans. The 

available information is derived from occupational studies in which exposure was assumed to have been 

primarily by inhalation of vapors, but that may have also involved dermal exposure. These studies 

provided information on acute systemic effects and lethality and also effects due to long-term exposure. 

A few studies of controlled inhalation exposures with volunteers are also available and these studies 

provided data on acute systemic effects. No information was located regarding oral exposure of humans 

to 1,4-dioxane. 

In animals, the studies available for review provided information on lethality and on systemic, 

neurological, and cancer effects following inhalation exposure to 1,4-dioxane. For oral exposure, there 

are studies that evaluated systemic, neurological, developmental, genotoxic, and cancer effects. No 

studies were available regarding chronic systemic effects, or immunological, neurological, reproductive, 

developmental, or genotoxic effects after dermal exposure to 1,4-dioxane. 

The information available from human and animals studies suggests that the effects of 1,4-dioxane are not 

route-dependent. In addition, the limited environmental monitoring data available suggests that the levels 

of 1,4-dioxane to which the general population might be exposed through contact or use of consumer 

products (including food), or that are normally found in environmental media, are generally orders of 

magnitude lower than those used in studies with experimental animals. 

3.12.2 Identification of Data Needs 

Acute-Duration Exposure. Two occupational studies provided acute inhalation data for 

1,4-dioxane, Barber (1934) and Johnstone (1959). Barber (1934) described five lethal cases among 

factory workers exposed to 1,4-dioxane, whereas Johnstone (1959) described one additional lethal, 
 

Figure 3 -5. Existing Information on Health Effects of 1,4 -Dioxane 

Death

Acute

Intermediate 

Chronic 

Immunologic/Lymphoretic 

Neurologic 

Reproductive 

Developmental 

Genotoxic 

Cancer 

Systemic 

Inhalation 

Oral 

Dermal 

Human 

Death

Acute 

Intermediate 

Chronic 

Immunologic/Lymphoretic 

Neurologic 

Reproductive 

Developmental 

Genotoxic 

Cancer 

Systemic 

Inhalation 

Oral 

Dermal 

Animal 

Existing Studies 

1,4-DIOXANE 139 

3. HEALTH EFFECTS 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 140 

3. HEALTH EFFECTS 

occupational case in which dermal exposure also occurred. Exposure to unknown, but lethal 

concentrations of 1,4-dioxane produced serious liver and kidney effects. A few additional studies in 

volunteers evaluated mostly clinical signs, such as eye and nose irritation, during exposures varying from 

3 minutes to 6 hours (Ernstgård et al. 2006; Fairley et al. 1934; Silverman et al. 1946; Yant et al. 1930; 

Young et al. 1977). Ernstgård et al. (2006) also evaluated pulmonary function by spirometry immediately 

after and 3 hours after exposure of volunteers to 20 ppm 1,4-dioxane for 2 hours and reported no 

alterations relative to measurements before exposure. The lowest concentration that produced an effect in 

the studies mentioned above was 50 ppm during a 6-hour exposure, which caused eye irritation (Young et 

al. 1977). Data from the studies by Young et al. (1977) and Ernstgård et al. (2006) were used to derive an 

acute-duration inhalation MRL for 1,4-dioxane. 

The animal database consists mainly of early studies in rodents exposed to lethal or near lethal 

concentration of 1,4-dioxane that indicated that the liver and kidneys are the main targets of 1,4-dioxane 

toxicity in animals (Fairley et al. 1934; Yant et al. 1930). Additional acute inhalation studies conducted 

according to current guidelines would be helpful to establish dose-response relationships for liver and 

kidney effects at low levels of exposure. No data were located regarding acute oral exposure of humans 

to 1,4-dioxane. Most studies in animals provided lethal dose levels and also showed that the liver and 

kidneys are the organs most severely affected by high oral doses of 1,4-dioxane (de Navasquez 1935; 

Kesten et al. 1939; Laug et al. 1939; Schrenk and Yant 1936; Smyth et al. 1941). A more recent 2-week 

drinking water study in rats, although with limitations, provided information on systemic end points but 

had limitations that precluded its use for derivation of an acute-duration oral MRL for 1,4-dioxane (JBRC 

1998). Instead, a developmental study in rats was used as the basis for deriving an acute-duration oral 

MRL for 1,4-dioxane (Giavini et al. 1985). 

Additional acute oral studies conducted according to current guidelines could provide information on 

thresholds for liver and kidney effects. Also, exposures to low or moderate single oral doses followed by 

long observation periods would provide information on reversibility of the effects. Limited acute dermal 

data were found. In the lethal occupational case described by Johnstone (1959), considerable dermal 

exposure occurred, since the subject used to wipe his hands with 1,4-dioxane to clean them; this probably 

contributed to the liver and kidney toxicity observed. In the studies with volunteers mentioned above, eye 

irritation was most likely due to direct contact of the eye with the vapors of 1,4-dioxane and not due to 

inhaled 1,4-dioxane. A study in rats applied a dose of 8,300 mg/kg of 1,4-dioxane to a shaved area of the 

skin found no signs of skin irritation during a 14-day observation period (Clark et al. 1984). Additional 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 141 

3. HEALTH EFFECTS 

acute dermal studies may be tied to studies of the pharmacokinetics of 1,4-dioxane by this route of 

exposure, which has not been well characterized. 

Intermediate-Duration Exposure. No intermediate-duration studies in humans were available. An 

early study by Fairley et al. (1934) in several animal species provided enough information to determine 

that the liver and kidneys are targets for 1,4-dioxane toxicity. The lowest concentration of 1,4-dioxane to 

which rats, mice, and guinea pigs were exposed intermittently for 3–12 weeks was 1,000 ppm, which 

caused moderate to severe kidney toxicity. A 13-week inhalation study in rats (Kasai et al. 2008) 

reported nasal lesions in males and females exposed to ≥100 ppm and served as the basis for derivation of 

an intermediate-duration inhalation MRL for 1,4-dioxane. Several oral studies in animals provided 

information on lethal doses (Fairley et al. 1934; Kociba et al.1974) and on systemic effects, mostly 

hepatic and renal (Fairley et al. 1934; Lundberg et al. 1987; Stott et al. 1981). A more recent 90-day 

drinking water study in rats provided sufficient information on multiple end points and was used as the 

basis (liver effects) for an intermediate-duration oral MRL for 1,4-dioxane (Kano et al. 2008). Kano et al. 

(2008) also reported nasal lesions in rats. Further research to elucidate the mechanism by which oral 

exposure to 1,4-dioxane can cause nasal lesions is warranted. Information by the dermal route of 

exposure was limited to a study of intermittent application of 1,4-dioxane to the skin of rabbits and guinea 

pigs for up to 101 days (Fairley et al. 1934). There were no dermal effects in either species at dose levels 

that induced liver and kidney lesions, which appeared to be more severe in rabbits than in guinea pigs. 

Although the study by Kasai et al. (2008) showed that the most sensitive target for 1,4-dioxane in rats 

following inhalation exposure is the nasal cavity, additional inhalation studies with lower concentrations 

of 1,4-dioxane and following current testing standards are needed to better define the threshold region. 

Information on effects on other organs is limited in intermediate-duration oral studies. 

Chronic-Duration Exposure and Cancer. An occupational study of workers exposed to 

1,4-dioxane provides information regarding long-term exposure to this chemical. Thiess et al. (1976) 

found no adverse effects in workers exposed to 0.006–14.3 ppm 1,4-dioxane for an average of 25 years. 

Two chronic-duration studies by the inhalation route are available (Kasai et al. 2009; Torkelson et al. 

1974). The study by Torkelson et al. (1974) provided information on multiple organs and tissues and 

hematology parameters in rats exposed to 111 ppm 1,4-dioxane; no adverse effects were found. Since 

only one exposure concentration was tested, the NOAEL may be higher. In addition, the study did not 

explicitly indicate whether the nasal cavity was examined. The nasal cavity was a target for 1,4-dioxane 

in a 13-week inhalation study in rats (Kasai et al. 2008). The chronic-duration study by Kasai et al. 

(2009) also provided information on multiple organs and tissues, including the nasal cavity. The latter 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 142 

3. HEALTH EFFECTS 

was the most sensitive target and the increased incidence of vacuolic changes in the olfactory epithelium 

of the nasal cavity in male rats was used to derive a chronic-duration inhalation MRL for 1,4-dioxane. 

Additional studies in animals do not seem necessary at this time. Several chronic-duration oral studies in 

rats and mice are available (Kano et al. 2009; Kociba et al. 1974; NCI 1978). These studies provided 

information on clinical signs, changes in body weight, hematology, blood chemistry, urinalysis, and gross 

and microscopic appearance of major organs and tissues. The liver and kidneys were the main targets for 

1,4-dioxane toxicity. A NOAEL of 9.6 mg/kg/day for liver effects in male Sherman rats was used to 

derive a chronic-duration oral MRL for 1,4-dioxane (Kociba et al. 1974). Additional chronic oral studies 

do not seem necessary at this point. No chronic dermal studies were located, but it is not apparent what 

new key information such studies could provide. 

Very limited information was found regarding human exposure to 1,4-dioxane and cancer. A study of 

165 workers exposed intermittently to 0.1–17 ppm 1,4-dioxane for up to 21 years found no significant 

increases in the incidences of deaths due to cancer (Buffler et al. 1978). 1,4-Dioxane was not 

carcinogenic in rats in the only single inhalation bioassay (Torkelson et al. 1974). However, only one 

exposure level was used; therefore, a dose-response relationship for cancer could not be estimated. In 

addition, the maximum tolerated dose (MTD) may have not been achieved. Increased incidences of 

squamous cell carcinoma in the nasal cavity and hepatocellular adenomas were reported in male rats 

exposed intermittently to 1,250 ppm 1,4-dioxane for 2 years (Kasai et al. 2009); exposure concentrations 

≥250 ppm significantly increased the incidence of peritoneum mesothelioma. Long-term oral 

administration of 1,4-dioxane induced liver cancer in rats and mice, peritoneum mesothelioma in male 

rats, and also nasal tumors in rats (Argus et al. 1965, 1973; Hoch-Ligeti et al. 1970; Kano et al. 2009; 

Kociba et al. 1974; NCI 1978). 1,4-Dioxane was not a complete carcinogen in a 60-week dermal 

exposure study in mice (King et al. 1973), but showed promoter activity in oral (Lundberg et al. 1987) 

and dermal studies (King et al. 1973). 1,4-Dioxane was not an initiator in a dermal assay in mice (Bull et 

al. 1986). Since the mechanism of carcinogenicity of 1,4-dioxane is yet unknown, continued research on 

this topic and on the role of metabolism in carcinogenicity is necessary, particularly regarding a 

mechanism by which oral exposure to 1,4-dioxane can induce nasal tumors. Some have suggested that 

liver toxicity and subsequent tumor development in rats only occurs when metabolism of 1,4-dioxane is 

saturated. Under current EPA guidelines for assessing cancer risk (EPA 2005a), it might be more 

appropriate to apply a nonlinear model to cancer risk assessment. The EPA (IRIS 2011) derived an oral 

slope factor of 1x10-1 per mg/kg/day for 1,4-dioxane based on increased incidences of hepatocellular 

adenoma and carcinoma in female BDF1 mice in a drinking water study (Kano et al. 2009). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 143 

3. HEALTH EFFECTS 

Genotoxicity. The genotoxic effects of 1,4-dioxane have been well characterized in studies in 

microorganisms in vitro (Haworth et al. 1983; Hellmer and Bolcsfoldi 1992; Khudoley et al. 1987; Kwan 

et al. 1990; Morita and Hayashi 1998; Nestmann et al. 1984; Stott et al. 1981; Zimmermann et al. 1985) 

and in mammalian cells (Galloway et al. 1987; Goldsworthy et al. 1991; McGregor et al. 1991; Morita 

and Hayashi 1998; Sheu et al. 1988). Most of these studies were conducted both in the presence and 

absence of metabolic activation systems, which would suggest that metabolites of 1,4-dioxane are also not 

mutagenic. The results from in vivo studies also provided mostly negative evidence of genotoxicity 

(Goldsworthy et al. 1991; Kitchin and Brown 1990, 1994; McFee et al. 1994; Mirkova 1994; Morita and 

Hayashi 1998; Muñoz and Barnett 2002; Stott et al. 1981; Tinwell and Ashby 1994; Yoon et al. 1985). 

The total weight of evidence suggests that 1,4-dioxane is either weakly genotoxic or not genotoxic, and it 

is unlikely that further studies will provide new information. 

Reproductive Toxicity. No reliable information was located regarding reproductive effects of 

1,4-dioxane in humans. There are studies that examined the gross and microscopic appearance of the 

reproductive organs from rats following intermediate (Kasai et al. 2008) chronic inhalation exposure 

(Torkelson et al. 1974) and from rats and mice following intermediate oral exposure (Kano et al. 2008) 

and chronic oral exposure to 1,4-dioxane (JBRC 1998b; Kociba et al. 1974; NCI 1978), but no 

assessments of reproductive function or examinations of sperm characteristics have been made. The lack 

of effects on reproductive organs observed in these studies diminishes the need to conduct a 2-generation 

reproductive study. In addition, only one study was located that tested the estrogenic properties of 

1,4-dioxane in an assay in vitro (Nishihara et al. 2000), with negative results. Additional standard in vivo 

and in vitro studies to assess whether 1,4-dioxane has endocrine disruptor properties would be useful. 

Developmental Toxicity. There is no information on developmental effects in humans exposed to 

1,4-dioxane. If populations were identified that are exposed to high levels of 1,4-dioxane, it would be 

useful to determine whether 1,4-dioxane or metabolites are found in breast milk. This can also be done in 

surveys monitoring chemicals in the general population at the national level. Only one study was located 

that evaluated developmental parameters in rats exposed orally by gavage during gestation (Giavini et al. 

1985). Slight fetotoxicity was seen at a dose level that affected the mothers. The study by Giavini et al. 

(1985) was used as the basis for derivation of an acute-duration oral MRL for 1,4-dioxane. Additional 

studies are necessary to determine whether adverse developmental effects can occur without maternal 

toxicity. In addition, a developmental neurotoxicity study in rats in which pups are tested at various ages 

after being exposed in utero and/or via maternal milk would fill a data gap. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 144 

3. HEALTH EFFECTS 

Immunotoxicity. Virtually no information was located regarding immunotoxic effects in humans 

following exposure to 1,4-dioxane. Ernstgård et al. (2006) reported that exposure of volunteers to 20 ppm 

1,4-dioxane did not cause inflammatory changes as monitored by measurements of high sensitivity 

C reactive protein and interleukin 6 in blood. This information is clearly insufficient to determine 

whether exposure to 1,4-dioxane affects the immune system in humans. The information from animal 

studies is restricted to gross and microscopic examination of the spleen, thymus, and lymph nodes from 

rats exposed intermittently to up to 3,200 ppm 1,4-dioxane for 13 weeks (Kasai et al. 2008), of the lymph 

nodes and spleen from rats similarly exposed to 111 ppm 1,4-dioxane vapors for 2 years (Torkelson et al. 

1974), and of the lymph nodes, spleen, and thymus from rats and mice dosed with up to 2,669 mg 

1,4-dioxane/kg/day in the drinking water for 13 weeks (Kano et al. 2008), or in rats and mice dosed with 

up to 1,599 mg 1,4-dioxane/kg/day in the drinking water for up to 2 years (JBRC 1998b; Kociba et al. 

1974; NCI 1978). No treatment-related effects were observed. Although there was no indication that 

immunocompetence was compromised in these studies, a study performing a complete Tier I battery of 

tests may be warranted to evaluate the possibility that exposure to 1,4-dioxane might cause subtle 

alterations in immune parameters. 

Neurotoxicity. Edema of the brain was observed in lethal cases of intoxication with 1,4-dioxane 

vapors (Barber 1934; Johnstone 1959). Occupational studies of long-term exposure to lower 

concentrations of 1,4-dioxane did not report signs or symptoms that would indicate neurological damage, 

but sensitive tests were not conducted (Buffler et al. 1978; Thiess et al. 1976). Exposure of mice and rats 

for 4 hours to 1,800–2,400 ppm 1,4-dioxane had a narcotic effect (Frantik et al. 1994), and exposure to 

3,000 ppm intermittently for 2 weeks affected an avoidance response in rats (Goldberg et al. 1964), which 

also could have been due to narcosis. High oral doses also induced narcosis in rabbits (Knoefel 1935). 

Vacuolar changes were observed in the brain from rats exposed to 2,750–2,960 mg 1,4-dioxane/kg/day 

for 2 weeks (JBRC 1998) and from rats exposed to 1,554–1,614 mg/kg/day for 13 weeks (Kano et al. 

2008). Long-term inhalation (Kasai et al. 2008; Torkelson et al. 1974) and oral studies (JBRC 1998b; 

Kano et al. 2008; Kociba et al. 1974; NCI 1978) in rats and mice have provided no indication of adverse 

clinical signs in the animals, and examination of the brain, spinal cord, and sciatic nerve was 

unremarkable. The overall information suggests that 1,4-dioxane may have narcotic properties at high 

concentrations, but it would be useful to determine whether possible subtle behavioral effects can be 

detected with more sensitive tests at exposure concentrations that do not induce narcosis. 

Epidemiological and Human Dosimetry Studies. Information on the health effects of 

1,4-dioxane in humans is derived from cases of accidental exposure at work to relatively high 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 145 

3. HEALTH EFFECTS 

concentrations of 1,4-dioxane, which caused death (Barber 1934; Johnstone 1959), and studies of longterm exposure, also at work, to lower concentrations of 1,4-dioxane (Buffler et al. 1978; Thiess et al. 

1976). Follow-up evaluations of individuals who may have been occupationally exposed would provide 

valuable information. No specific group from the general population that may have been subjected to 

unusually high amounts of 1,4-dioxane was identified. If such a situation arises, for example due to an 

accidental spill or leak from a waste site resulting in contaminated water or soil, individuals potentially 

exposed to 1,4-dioxane should be monitored for liver and kidney effects with standard function tests, 

since the liver and the kidneys have been identified as targets for 1,4-dioxane toxicity. 

Biomarkers of Exposure and Effect. 

Exposure. 1,4-Dioxane and its main metabolite, HEAA, have been identified in the blood and urine from 

workers exposed to 1,4-dioxane vapors (Young et al. 1976) and from volunteers exposed to controlled 

amounts 1,4-dioxane vapors (Young et al. 1977). Under condition of low to moderate exposure, the 

transformation of 1,4-dioxane to HEAA is rapid and extensive, and HEAA is rapidly eliminated in the 

urine (Young et al. 1977). The development of models that would support quantitative estimates of 

exposure to 1,4-dioxane based on urine levels of HEAA may be valuable in cases of high exposure, but 

given the very low levels of 1,4-dioxane to which the general population is exposed, the development of 

analytical methods capable to detect and quantify HEAA in the general population may be more useful. 

Effect. There are no biomarkers of effect specific for 1,4-dioxane. Exposure to high amounts of 

1,4-dioxane affects the liver and kidneys, but no 1,4-dioxane-induced health effects have been reported in 

populations exposed to low amounts of 1,4-dioxane (Buffler et al. 1978; Thiess et al. 1976). Research to 

identify reliable biomarkers for exposure to 1,4-dioxane in humans would be useful in order to evaluate 

the prevalence and magnitude of exposure in an at-risk population. 

Absorption, Distribution, Metabolism, and Excretion. Among the areas of absorption, 

distribution, metabolism, and excretion, the greatest data need lies in metabolism, specifically, the 

determination of the metabolic pathways involved in the metabolism of 1,4-dioxane to its primary 

metabolite, HEAA or 1,4-dioxane-one (Braun and Young 1977; Woo et al. 1977a, 1977b, 1977c; Young 

et al. 1977). While the identity of the metabolite has been determined and the involvement of cytochrome 

P-450 enzymes has been demonstrated (Nannelli et al. 2005; Woo et al. 1977c, 1978), the formation of 

intermediate metabolites, and their identities, has not been demonstrated. Additional information 

regarding this pathway may be useful in the refinement of PBPK models and in the development of 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 146 

3. HEALTH EFFECTS 

biomarkers of exposure and/or effect. Data are lacking on the absorption of 1,4-dioxane in humans 

following oral exposure and dermal exposure in vivo, but this information would likely do little to further 

our understanding of the pharmacokinetic processes of 1,4-dioxane. 

Comparative Toxicokinetics. Studies directly comparing the toxicokinetics of 1,4-dioxane across 

species are not available. Some limited data on 1,4-dioxane absorption following inhalation exposure 

suggest large differences in the absorbed dose, expressed on a per body weight basis, between rats and 

humans (Young et al. 1977, 1978a, 1978b). However, these studies did not measure absorption 

efficiencies. Studies examining absorption efficiency in humans and rats following inhalation and oral 

exposures would provide valuable data for evaluating possible species differences. The available data on 

metabolism and elimination of 1,4-dioxane in humans and rats indicate that the compound behaves 

similarly in the two species (Woo et al. 1977a, 1977b, 1977c, 1978; Young et al. 1976, 1977, 1978a, 

1978b). Studies of the toxicokinetic behavior of 1,4-dioxane in animal species other than the rat would 

provide additional insight into potential interspecies differences, while studies directly comparing the 

toxicokinetic behavior of 1,4-dioxane in multiple species would add to our understanding of the 

comparative toxicokinetic behavior of 1,4-dioxane. Limitations of the available PBPK models (Leung 

and Pastenbauch 1990; Reitz et al. 1990; Sweeney et al. 2008) precluded their use for MRL derivation; 

further refinement of these models is necessary. 

Methods for Reducing Toxic Effects. No specific methods for the mitigation of effects of acute 

exposure to 1,4-dioxane were located other than measures to support vital functions. No information was 

located concerning mitigation of effects of lower-level or longer-term exposure to 1,4-dioxane. This, in 

part, may reflect the fact that no population has been identified as having been subjected or currently 

undergoing exposure to excessive amounts of 1,4-dioxane. Attempts to propose studies of specific 

methods to reduce possible adverse effects do not appear warranted at this time. 

Children’s Susceptibility. Data needs relating to both prenatal and childhood exposures and 

developmental effects expressed either prenatally or during childhood are discussed in detail in the 

Developmental Toxicity subsection above. 

There are no studies that specifically addressed exposure to 1,4-dioxane in children. Workers exposed to 

high amounts of 1,4-dioxane vapors experienced liver and kidney effects and some died (Barber 1934; 

Johnstone 1959). Volunteers exposed to low concentrations of 1,4-dioxane in the air experienced eye and 

nose irritation (Silverman et al. 1946; Yant et al. 1930; Young et al. 1977). It is reasonable to assume that 
 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 147 

3. HEALTH EFFECTS 

children exposed in similar manners will experience similar effects. There is no information on whether 

the developmental process is altered in humans exposed to 1,4-dioxane. Very limited evidence with 

1,4-dioxane in rats suggests that fetotoxicity may occur only at maternally toxic levels (Giavini et al. 

1985), but further studies are necessary on this issue. The possibility that 1,4-dioxane may have 

endocrine-disrupting ability in mammals has not been systematically studied. 

There are no data to evaluate whether pharmacokinetics of 1,4-dioxane in children are different from 

adults. There is no information on whether 1,4-dioxane can cross the placenta and there are no studies on 

whether 1,4-dioxane can be transferred from mother to offspring through maternal milk. Cross-fostering 

studies can provide important information regarding the role of in utero vs. lactation exposure to 

1,4-dioxane in normal development. There are no data to permit an evaluation of whether metabolism of 

1,4-dioxane is different in children from adults. 

Research into the development of sensitive and specific biomarkers of exposures and effects for 

1,4-dioxane would be valuable for both adults and children. There are no data on the interactions of 

1,4-dioxane with other chemicals in children. There are no pediatric-specific methods to reduce peak 

absorption 1,4-dioxane, to reduce body burdens, or to interfere with the mechanisms of action. Based on 

the information available, it is reasonable to assume that the supportive methods recommended for 

maintaining vital functions in adults will also be applicable to children. 

Child health data needs relating to exposure are discussed in Section 6.8.1, Identification of Data Needs: 

Exposures of Children. 

3.12.3 Ongoing Studies 

No ongoing studies pertaining to 1,4-dioxane were identified in the Federal Research in Progress 

(FEDRIP 2009) database. 
 

 

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1,4-DIOXANE 149 

4. CHEMICAL AND PHYSICAL INFORMATION
	

4.1 CHEMICAL IDENTITY 

1,4-Dioxane or para-dioxane is also commonly referred to as simply ‘dioxane’. However, 1,4-dioxane 

should not be confused with dioxin (or dioxins), which are a different class of chemical compounds. 

Information regarding the chemical identity of 1,4-dioxane is located in Table 4-1. 

4.2 PHYSICAL AND CHEMICAL PROPERTIES 

1,4-Dioxane is a colorless liquid. 1,4-Dioxane is also completely miscible in water and organic solvents. 

The technical-grade product is >99.9% pure, but may contain bis(2-chloroethyl) ether as an impurity 

(DeRosa et al. 1996). Information regarding the physical and chemical properties of 1,4-dioxane is 

located in Table 4-2. 
 

 

	 

 

	 

	 

	 

1,4-DIOXANE	 150 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-1. Chemical Identity of 1,4-Dioxane 

Characteristic Information 

Chemical name	 1,4-Dioxane 

Synonym(s)	 1,4-diethylenedioxide; 1,4-dioxacyclohexane; 1,4-dioxanne (French); di(ethylene 

oxide); diethylene dioxide; diethylene ether; dioksan (Polish); diossano-1,4 

(Italian); dioxaan-1,4 (Dutch); dioxan; dioxan-1,4 (German); dioxane; dioxane-1,4; 

dioxanne (French); dioxyethylene ether; glycol ethylene ether; para-dioxane; 

p-dioxan (Czech); p-dioxane; p-dioxin, tetrahydro-; tetrahydro-1,4-dioxin; 

tetrahydro-para-dioxin; tetrahydro-p-dioxin 

Registered trade No data 

name(s) 

Chemical formula	 C4H8O2 

Chemical structure 

Identification numbers: 

CAS Registry 123-91-1 

NIOSH RTECS JG8225000 

EPA Hazardous U108; A toxic waste when a discarded commercial chemical product or 

Waste manufacturing chemical intermediate or an off-specification commercial chemical 

product or a manufacturing chemical intermediate 

OHM/TADS No data 

DOT/UN/NA/IMDG UN 1165; IMDG 3.2 

HSDB 81 

NCI No data 

O 

O 

CAS = Chemical Abstracts Services; CIS = Chemical Information System; DOT/UN/NA/IMDG = Department of 

Transportation/United Nations/North America/International Maritime Dangerous Goods Code; EPA = Environmental 

Protection Agency; HSDB = Hazardous Substance Data Bank; NCI = National Cancer Institute; NIOSH = National 

Institute for Occupational Safety and Health; OHM/TADS = Oil and Hazardous Materials/Technical Assistance Data 

System; RTECS = Registry of Toxic Effects of Chemical Substances 
 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 151 

4. CHEMICAL AND PHYSICAL INFORMATION 

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

Property 

Molecular weight (g/mol) 88.11a 

Color Clearb 

Physical state Liquida 

Melting point 11.8 °Ca 

Boiling point 101.1 °Ca 

Density 1.0329a 

Odor Faint pleasant odora 

Odor threshold: 

Water 230 ppm w/vb 

Air 24 ppm v/vb 

Taste No data 

Solubility: 

Water Misciblec 

Other solvents Soluble in organic solventsa 

Partition coefficients: 

Log Kow -0.27d 

Log Koc 1.23b 

Vapor pressure at 25 °C 38.1 mm Hge 

OH radical rate constant 1.09x10-11 cm3/molecule-secf 

Henry's law constant at 25 °C 4.80x10-6 atm-cm3/moleg 

Autoignition temperature 356 °F (180 °C)h 

Flashpoint 5–18 °Ca 

Flammability limits at 25 °C Lower: 2.0%; Upper: 22%b 

Incompatibilities Strong oxidizers, decaborane, triethynyl aluminumh 

Conversion factors (25 °C and 1 atm) 1 ppm = 3.6 mg/m3; 1 mg/m3 = 0.278 ppmb 

Explosive limits Vapor forms explosive mixtures with air over wide rangei 

a

O’Neil et al. 2001.
 b

EC 2002.
 c

Riddick et al. 1986.
 d

Hansch et al. 1995.
 e

Daubert and Danner 1985.
 f

Atkinson 1989.
 g

Park et al. 1987.
 h

NIOSH 2001.
 i

ScienceLab 2005.
 
 

 

1,4-DIOXANE 152
 

4. CHEMICAL AND PHYSICAL INFORMATION 

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1,4-DIOXANE 153 

5. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

5.1 PRODUCTION 

1,4-Dioxane is manufactured in a closed system by acid catalyzed conversion of diethylene glycol via 

dehydration and ring closure. The use of mono-, tri-, and polyethylene glycol and their ethers as raw 

materials has also been reported. Concentrated sulfuric acid (ca. 5%) is used as the acid catalyst, although 

phosphoric acid, p-toluenesulfonic acid, strongly acidic ion-exchange resins, and zeolites are alternatives. 

Operating conditions vary; temperatures range from 130 to 200 °C, and pressures range from a partial 

vacuum to slight pressure (i.e., 188–825 mm Hg). The ideal temperature is reported to be 160 °C. The 

reaction process is continuous and carried out in a heat vessel. The raw 1,4-dioxane product forms an 

azeotrope with water, which is then vaporized from the reaction vessel by distillation. 1,4-Dioxane 

vapors are passed through an acid trap and two distillation columns to remove water and purify the 

product. Yields of ca. 90% are achievable. 2-Methyl-1,3-dioxolane, 2-ethyl-1,3-dioxolane, and 

acetaldehyde are the main by-products. To a lesser extent, crotonaldehyde and polyglycol are also 

formed during the production. The crude 1,4-dioxane is further cleaned by heating with acids, distillation 

(to remove glycol and acetaldehyde), salting out with NaCl, CaCl2, or NaOH, and fine subsequent 

distillation (EC 2002; Surprenant 2002). 

While the latter production process is the most important industrially, two other processes are especially 

useful for the production of substituted dioxanes. 1,4-Dioxane can be prepared by ring closure of 

2-chloro-2’-hydroxydiethyl ether (formed from ethylene glycol reacting with 1,2-dibromoethane) through 

heating with 20% sodium hydroxide, and by catalysed cyclo-dimerisation of ethylene oxide either over 

NaHSO4, SiF4, or BF3, or at an elevated temperature with an acidic cation-exchange resin (EC 2002; 

Surprenant 2002). 

Commercial production of 1,4-dioxane in the United States was first reported in 1951, but semicommercial quantities were available in 1929 (NCI 1985). Currently, 1,4-dioxane is produced in the 

United States by two manufacturers: Dow Chemical (production site, Freeport, Texas) and Ferro 

Corporation (production site, Baton Rouge, Louisiana) (SRI 2003). Outside of the United States, 

1,4-dioxane is produced by BASF AG in Lugwigshafen, Germany, Osaka Yuki and Toho Chem, Japan; 

and also in other countries around the world (EC 2002). 

Recent information was not available on the production volumes of 1,4-dioxane in the United States. The 

total production of 1,4-dioxane for 1982 was estimated at 15 million pounds (6,800 metric tons), up from 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 154 

5. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

12 million pounds (5,400 metric tons) reported in 1977 (HSDB 2010). Between 1 and 10 million pounds 

of 1,4-dioxane were produced in the United States in 2002 (HSDB 2010). The worldwide production 

capacity in 1985 was estimated to be 11,000–14,000 metric tons/year. In 1995, the production capacity of 

known producers and the worldwide production volume were estimated at 8,000 and 10,000 metric 

tons/year, respectively. In Europe, the production volume in 1997 was estimated to be 2,000– 

2,500 metric tons (EC 2002). However, current production levels of 1,4-dioxane are expected to be 

significantly less due to changing use patterns. 

Table 5-1 lists the facilities in each state that manufacture or process 1,4-dioxane, the intended use, and 

the range of maximum amounts of 1,4-dioxane that are stored on-site. There are 381 facilities that 

produce or process 1,4-dioxane in the United States. The data from the Toxics Release Inventory (TRI) 

listed in Table 5-1 should be used with caution, however, since only certain types of facilities were 

required to report (EPA 1995). This is not an exhaustive list (TRI07 2009). 

5.2 IMPORT/EXPORT 

No information was located on the current import/export levels of 1,4-dioxane for the United States. In 

1977, at least 9.1x104 kg of 1,4-dioxane were imported into the United States (HSDB 2010). However, 

current import levels of 1,4-dioxane are expected to be significantly less due to changing use patterns. 

5.3 USE 

Because of its broad range of solvent properties, 1,4-dioxane has found a variety of applications. 

1,4-Dioxane is used as a solvent for chemical processing. 1,4-Dioxane has also been used as a laboratory 

reagent (e.g., mobile phase in chromatography); in plastic, rubber, insecticide, and herbicides; as a 

chemical intermediate; as part of a polymerization catalyst; and as an extraction medium of animal and 

vegetable oils. Other minor uses are in the manufacture of membrane filters, for measuring optical 

activity, and for cryoscopic determination. 1,4-Dioxane has been reported to be used in the production 

processes of the following product categories: pharmaceuticals/pesticides, magnetic tape, and adhesives. 

In the past, 1,4-dioxane was used primarily as a stabilizer in chlorinated solvents, particularly 

1,1,1-trichloroethane. Approximately 90% of former production of 1,4-dioxane was used in this 

application. 1,4-Dioxane was typically used at a concentration of about 3.5% in chlorinated solvents. 

However, at the end of 1995, the use of 1,1,1-trichloroethane was limited under the Montreal Protocol due 

to the ozone depletion potential of 1,1,1-trichloroethane. Thus, current use of 1,4-dioxane as a stabilizer 

of 1,1,1-trichloroethane will not be significant (EC 2002; Hartung 1989; HSDB 2010; NICNAS 1998). 
 

Table 5-1. Facilities that Produce, Process, or Use 1,4 -Dioxane 

Statea 

Number of 

facilities 

Minimum 

amount on site 

in poundsb 

Maximum 

amount on site 

in poundsb c Activities and uses

AL 

AR 

AZ 

CA 

CO 

CT 

GA 

IA 

IL 

IN 

KS 

KY 

LA 

MA 

MD 

ME 

MI 

MN 

MO 

MS 

NC 

NE 

NH 

NJ 

NY 

OH 

OK 

OR 

PA 

PR 

SC 

TN 

TX 

UT 

VA 

WA 

WI 

6 

6 

1 

34 

1 

5 

3 

4 

14 

12 

2 

2 

23 

5 

1 

2 

10 

9 

15 

12 

21 

2 

2 

6 

17 

21 

2 

2 

9 

4 

23 

16 

41 

10 

7 

1 

9 

1,000 

1,000 

1,000 

0 

1,000 

100 

0 

0 

100 

0 

0 

100 

0 

1,000 

1,000 

100 

0 

0 

0 

0 

0 

10,000 

100 

0 

100 

0 

100 

1,000 

100 

0 

0 

0 

0 

0 

0 

1,000 

0 

999,999 

999,999 

9,999 

99,999 

9,999 

99,999 

9,999 

99,999 

9,999,999 

99,999 

999 

999 

49,999,999 

99,999 

9,999 

9,999 

99,999 

99,999 

999,999 

999,999 

9,999,999 

99,999 

99,999 

99,999 

99,999 

999,999 

9,999 

99,999 

99,999 

999,999 

9,999,999 

99,999 

9,999,999 

999,999 

99,999 

9,999 

999,999 

1, 5, 6, 7, 10, 11 

1, 5, 7, 10, 12 

12 

2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13 

10 

1, 2, 3, 5, 6, 8, 10 

1, 5, 7 

8, 12 

1, 2, 4, 5, 7, 9, 10, 11, 12 

2, 7, 10, 11, 12 

1, 2, 3, 7, 11 

7, 12 

1, 4, 5, 7, 9, 11, 12, 13 

7, 10, 11, 12 

7 

11, 12 

7, 9, 11, 12 

1, 2, 3, 4, 5, 7, 10, 11, 12, 13 

1, 3, 5, 6, 7, 8, 9, 10, 12, 13 

1, 2, 5, 6, 7, 9, 11, 12 

1, 2, 5, 6, 7, 9, 12, 13, 14 

12 

11 

1, 2, 4, 5, 7, 9, 10, 12, 14 

1, 5, 7, 9, 10, 11, 12, 13 

1, 5, 7, 9, 10, 11, 12 

7, 8 

10 

7, 9, 10, 11, 12 

10, 12 

1, 5, 6, 7, 9, 11, 12, 13, 14 

1, 5, 10, 12, 13, 14 

1, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14 

7, 10, 11, 12 

1, 2, 5, 10, 12 

11 

1, 5, 7, 9, 10, 11, 12, 13 

1,4-DIOXANE 155 

5. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 
 

 

 

1,4-DIOXANE 156 

5. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

Table 5-1. Facilities that Produce, Process, or Use 1,4-Dioxane 

Minimum Maximum 

Number of amount on site amount on site 

Statea facilities in poundsb in poundsb Activities and usesc 

WV 20 0 999,999 1, 3, 5, 6, 7, 8, 12, 13, 14 

WY 1 0 99 12 

a

Post office state abbreviations used. b

Amounts on site reported by facilities in each state. c

Activities/Uses: 

1. Produce 6. Impurity 11. Chemical Processing Aid 

2. Import 7. Reactant 12. Manufacturing Aid 

3. Onsite use/processing 8. Formulation Component 13. Ancillary/Other Uses 

4. Sale/Distribution 9. Article Component 14. Process Impurity 

5. Byproduct 10. Repackaging 

Source: TRI07 2009 (Data are from 2007) 
 

 

 

 

 

1,4-DIOXANE 157 

5. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

1,4-Dioxane has been found as an impurity in cosmetics, household and industrial detergents, and 

pharmaceuticals due to its occurrence as a by-product in ethoxylated emulsifiers (Hartung 1989). 

Currently, most manufacturers utilize vacuum stripping to remove 1,4-dioxane before formulation of 

ethoxylated surfactants in consumer cosmetics and household products (EC 2002). 

5.4 DISPOSAL 

The primary method of disposal of 1,4-dioxane is by incineration. Small amounts of 1,4-dioxane can be 

diluted with large amounts of water and subsequently discharged to waste water treatment plants (United 

Nations 1985). However, since 1,4-dioxane does not undergo significant biodegradation in waste water 

treatment plants, much of the 1,4-dioxane disposed by this method will end up in the environment. 

In contrast to biological or physical methods, chemical treatment has been found to be highly effective for 

the removal of 1,4-dioxane from water. 1,4-Dioxane is rapidly degraded by hydrogen peroxide in 

combination with a ferrous salt. Chlorination has also been found to be highly effective for the removal 

of 1,4-dioxane from water. For example, chlorine and hypochlorous acid are capable of oxidizing 

1,4-dioxane (Dow Chemical Co. 1989). However, the extent to which 1,4-dioxane is removed from waste 

streams by these methods is unknown. 
 

 

1,4-DIOXANE 158
 

5. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

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1,4-DIOXANE 159 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.1 OVERVIEW 

1,4-Dioxane has been identified in at least 31 of the 1,689 hazardous waste sites that have been proposed 

for inclusion on the EPA National Priorities List (NPL) (HazDat 2007). However, the number of sites 

evaluated for 1,4-dioxane is not known. The frequency of these sites can be seen in Figure 6-1. Of these 

sites, all are located within the United States. 

1,4-Dioxane is released into the environment during its production, the processing of other chemicals, its 

use, and with its unintentional formation during the manufacture of ethoxylated surfactants (EC 2002). In 

the past, 1,4-dioxane was released into the environment with its use as a stabilizer for 1,1,1-trichloroethane (TCA). Since the use of TCA has been discontinued, current releases from this source are 

expected to be very low. 

Given its vapor pressure and Henry’s Law constant, the rate of volatilization of 1,4-dioxane from water 

and soil surfaces is expected to be moderate. In air, it is subject to photooxidation with an estimated halflife of 1–3 days. 1,4-Dioxane biodegrades very slowly in water and soils and is considered recalcitrant. 

It adsorbs weakly to soil and will move quickly into groundwater. Bioconcentration, bioaccumulation, 

and biomagnification are not considered important environmental fate processes for 1,4-dioxane. 

Current levels of 1,4-dioxane in the environment are unavailable. Historical data (i.e., 1980s or earlier) 

suggest that ambient levels were 0.1–0.4 μg/m3

 in air and 1 μg/L in water. Higher concentrations of 

1,4-dioxane have been observed primarily in groundwaters. 

The general population is exposed to negligible levels of 1,4-dioxane. The primary routes of human 

exposure to 1,4-dioxane are inhalation of 1,4-dioxane in air, ingestion of contaminated food and drinking 

water containing 1,4-dioxane, and dermal contact with contaminated consumer products (e.g., products 

containing ethoxylated surfactants). Because 1,4-dioxane may be found in tap water, human exposure to 

1,4-dioxane may also occur during activities such as showering, bathing, and laundering. Occupational 

exposure occurs during the production, processing, and use of 1,4-dioxane, which results in inhalation or 

dermal exposure. 
1,4-DIOXANE 160 

6. POTENTIAL FOR HUMAN EXPOSURE 

Figure 6-1. Frequency of NPL Sites with 1,4-Dioxane Contamination 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 161 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.2 RELEASES TO THE ENVIRONMENT 

The Toxics Release Inventory (TRI) data should be used with caution because only certain types of 

facilities are required to report (EPA 2005b). This is not an exhaustive list. Manufacturing and 

processing facilities are required to report information to the TRI only if they employ 10 or more full-time 

employees; if their facility is included in Standard Industrial Classification (SIC) Codes 10 (except 1011, 

1081, and 1094), 12 (except 1241), 20–39, 4911 (limited to facilities that combust coal and/or oil for the 

purpose of generating electricity for distribution in commerce), 4931 (limited to facilities that combust 

coal and/or oil for the purpose of generating electricity for distribution in commerce), 4939 (limited to 

facilities that combust coal and/or oil for the purpose of generating electricity for distribution in 

commerce), 4953 (limited to facilities regulated under RCRA Subtitle C, 42 U.S.C. section 6921 et seq.), 

5169, 5171, and 7389 (limited S.C. section 6921 et seq.), 5169, 5171, and 7389 (limited to facilities 

primarily engaged in solvents recovery services on a contract or fee basis); and if their facility produces, 

imports, or processes ≥25,000 pounds of any TRI chemical or otherwise uses >10,000 pounds of a 

TRI chemical in a calendar year (EPA 2005b). 

1,4-Dioxane is released into the environment during its production, processing, use, and with its 

unintentional formation during the manufacture of ethoxylated surfactants (EC 2002). In the past, 

1,4-dioxane was released into the environment with its use as a stabilizer for TCA. Since the use of TCA 

has been discontinued, current releases from this source are expected to be very low. 

1,4-Dioxane is unintentionally formed as an impurity during the manufacture of alkyl ether sulphates 

(AES) and other ethoxylated substances. However, much of the 1,4-dioxane impurity in these chemicals 

is removed through a stripping process during their manufacture. The stripper condensates from the 

manufacturing processes are discharged through normal plant effluents, where they are diluted by other 

waste streams and discharged as industrial wastes (NICNAS 1998). 1,4-Dioxane remaining as a 

by-product in end-use products (a large percentage of which may be used in domestic detergents and 

personal care products) will be released to publicly owned treatment works (POTWs) along with the 

surfactants, although this release will be far more diffuse. 

According to the TRI, a total of 182,338 pounds (82,693 kg) of 1,4-dioxane were released to the 

environment in 2007 from facilities required to report to the TRI (TRI07 2009). In addition, an estimated 

2,794 pounds (361 kg) were transferred off-site, including to POTWs (TRI07 2009). The TRI data should 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 162 

6. POTENTIAL FOR HUMAN EXPOSURE 

be used with caution, because only certain types of facilities are required to report. This is not an 

exhaustive list. Since 1988, total on-site releases of 1,4-dioxane appear to be decreasing from a high of 

1,234,968 pounds (560,172 kg) in 1993 to a low of 182,338 (82, 707) pounds in 2007. 

6.2.1 Air 

Estimated releases of 125,341 pounds (~57 metric tons) of 1,4-dioxane to the atmosphere from 

45 domestic manufacturing and processing facilities in 2007 accounted for about 69% of the estimated 

total on-site environmental releases from facilities required to report to the TRI (TRI07 2009). These 

releases are summarized in Table 6-1. 

1,4-Dioxane may be released to air during its production, the processing of other chemicals (e.g., 

pharmaceuticals/pesticides), and its use (EC 2002). The total emissions of 1,4-dioxane from stationary 

sources in California are estimated to be at least 210,000 pounds per year, based on data reported under 

the Air Toxics “Hot Spots” Program (California ARB 1997). 

No further information was located on the emissions of 1,4-dioxane to air. 

1,4-Dioxane has been identified in air samples collected at 6 of the 1,689 NPL hazardous waste sites, 

where it was detected in some environmental media (air, groundwater, surface water, soil, and sediment) 

(HazDat 2007). 

6.2.2 Water 

Estimated releases of 56,996 pounds (~26 metric tons) of 1,4-dioxane to surface water from 45 domestic 

manufacturing and processing facilities in 2006 accounted for about 31% of the estimated total on-site 

environmental releases from facilities required to report to the TRI (TRI07 2009). An additional 

2,794 pounds (~1 metric ton) were transferred off-site, which included releases to POTWs (TRI07 2009). 

These releases are summarized in Table 6-1. 

1,4-Dioxane may be released to surface water and groundwater during its production, the processing of 

other chemicals, its use, and with its unintentional formation during the manufacture of ethoxylated 

surfactants (EC 2002). 
 

1,4-DIOXANE 163 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-1. Releases to the Environment from Facilities that Produce, Process, or
	

Use 1,4-Dioxanea
	

Reported amounts released in pounds per yearb 

Total release 

Statec RFd Aire Waterf UIg Landh Otheri On-sitej Off-sitek On- and off-site 

AL 1 1,038 0 0 0 0 1,038 0 1,038 

AR 2 7,383 49 0 0 490 7,432 490 7,922 

CA 2 2,554 0 0 0 0 2,554 0 2,554 

CO 1 1,000 0 0 0 0 1,000 0 1,000 

CT 1 0 No data 0 0 0 0 0 0 

IL 1 6,209 0 0 2 0 6,211 0 6,211 

LA 4 3,702 13,711 0 3 840 17,413 843 18,256 

MI 1 0 No data 0 0 0 0 0 0 

MN 1 1,950 No data 0 0 870 1,950 870 2,820 

MO 2 20 1 0 0 0 21 0 21 

MS 1 1,508 0 0 2 0 1,508 2 1,511 

NC 4 20,230 4,926 0 12 0 25,156 12 25,168 

OH 1 250 0 0 500 0 250 500 750 

OR 1 908 0 0 24 0 908 24 932 

PA 1 1,660 No data 0 0 0 1,660 0 1,660 

PR 1 156 0 0 34 0 156 34 190 

SC 8 38,818 13,876 0 18 0 52,694 18 52,713 

TN 2 7,840 23,167 0 0 0 31,007 0 31,007 

TX 5 30,088 1,266 0 0 0 31,354 0 31,354 

WI 2 10 0 0 0 0 10 0 10 
 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 164 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-1. Releases to the Environment from Facilities that Produce, Process, or
	

Use 1,4-Dioxanea
	

Reported amounts released in pounds per yearb 

Total release 

Statec RFd Aire Waterf UIg Landh Otheri On-sitej Off-sitek On- and off-site 

WV 2 16 0 0 0 0 16 0 16 

Total 44 125,341 56,996 0 596 2,200 182,338 2,794 185,132 

a

The TRI data should be used with caution since only certain types of facilities are required to report. This is not an 

exhaustive list. Data are rounded to nearest whole number.
 b

Data in TRI are maximum amounts released by each facility.
 c

Post office state abbreviations are used.
 d

Number of reporting facilities.
 e

The sum of fugitive and point source releases are included in releases to air by a given facility.
 f

Surface water discharges, waste water treatment-(metals only), and publicly owned treatment works (POTWs) (metal
 

and metal compounds).
 g

Class I wells, Class II-V wells, and underground injection. h

Resource Conservation and Recovery Act (RCRA) subtitle C landfills; other on-site landfills, land treatment, surface 

impoundments, other land disposal, other landfills.

i

Storage only, solidification/stabilization (metals only), other off-site management, transfers to waste broker for
 

disposal, unknown

j

The sum of all releases of the chemical to air, land, water, and underground injection wells.

k

Total amount of chemical transferred off-site, including to POTWs.
 

RF = reporting facilities; UI = underground injection 

Source: TRI07 2009 (Data are from 2007) 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 165 

6. POTENTIAL FOR HUMAN EXPOSURE 

1,4-Dioxane was detected at 1 μg/L in effluents from the North Side and Calumet sewage treatment plants 

on the Lake Michigan Basin (Konasewich et al. 1978). 1,4-Dioxane has been detected in discharges into 

Lake Michigan near Chicago in 1977 (Konasewich et al. 1978) and in the Haw River in North Carolina 

(Dietrich et al. 1988). However, no information about the concentration of 1,4-dioxane or detection limit 

was provided in these sources. 

The U.S. Geological Survey (USGS) sampled groundwater and surface water in the vicinity of a former 

waste-oil refinery near Westville, Indiana from 1997 to 2000 (USGS 2002). The site was operational 

from the mid 1930s until 1987, and included numerous storage tanks, a filter press, several cracking 

towers, a cannery, and waste oil storage lagoons. 1,4-Dioxane concentrations in the groundwater plume 

ranged from 3 to 31,000 μg/L and eventually discharged to a ditch approximately half a mile away from 

the refinery. 1,4-Dioxane levels ranged from 8 to 140 μg/L in the surface water collected from the 

network of ditches surrounding the site. 

Effluent of a sewage treatment plant discharging into the River Lee (United Kingdom) contained <1 ng/L 

in 8-hour mixed samples (EC 2002). Effluent of a sewage treatment plant from a polyethylene 

terephthalate (PET) manufacturing process contained 100 mg/L of 1,4-dioxane in 1995 (EC 2002). 

In Kanagawa prefecture, Japan, Abe (1999) reported that 1,4-dioxane concentrations in effluents from 

chemical plants that used the compound as a solvent ranged from 0.4 to 4,020 μg/L the combined 

collection treatments of apartment houses and river basin sewage systems were 0.8–46 and 1.0–97 μg/L, 

respectively. No further data were located for emissions of 1,4-dioxane to water. 

1,4-Dioxane has been identified in surface water and groundwater samples, collected at 5 and 18 sites, 

respectively, of the 1,689 NPL hazardous waste sites, where it was detected in some environmental media 

(HazDat 2007). 

6.2.3 Soil 

Estimated releases of 596 pounds (<1 metric ton) of 1,4-dioxane to soils from 45 domestic manufacturing 

and processing facilities in 2007 accounted for <1% of the estimated total on-site environmental releases 

from facilities required to report to the TRI (TRI07 2009). These releases are summarized in Table 6-1. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 166 

6. POTENTIAL FOR HUMAN EXPOSURE 

1,4-Dioxane may be released to soil during its production, the processing of other chemicals, its use, and 

with its unintentional formation during the manufacture of ethoxylated surfactants (EC 2002). 

Between 1976 and 1985, Pall Life Sciences’ (PLS) predecessor, Gelman Sciences in Ann Arbor, 

Michigan disposed of large quantities of waste water containing 1,4-dioxane on soil in a holding pond and 

through a waste injection well. 1,4-Dioxane was used as a solvent for cellulose acetate, a component of 

micro-porous filters. This chemical contaminated soil and rock layers and seeped into the groundwater. 

Disposal of this chemical in this way was stopped in 1986 (City of Ann Arbor 2003; MSU 2001). No 

further data were located for emissions of 1,4-dioxane to soil. 

1,4-Dioxane has been identified in soil samples collected at 6 of the 1,689 NPL hazardous waste sites, 

where it was detected in some environmental media (HazDat 2007). 

6.3 ENVIRONMENTAL FATE 

1,4-Dioxane is expected to volatilize at a moderate rate from water and soil surfaces. In air, it is subject 

to photooxidation with an estimated half-life of 1–3 days. 1,4-Dioxane is relatively resistant to 

biodegradation in water and soils. It binds weakly to soils and will therefore move readily into 

groundwater. Bioconcentration, bioaccumulation, and biomagnification are not significant for 

1,4-dioxane. 

6.3.1 Transport and Partitioning 

The Henry's law constant for 1,4-dioxane is 4.8x10-6 atm m3

/mole, which indicates that 1,4-dioxane is 

expected to volatilize from water surfaces (Park et al. 1987; Thomas 1990). Based on this Henry's law 

constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/second, wind velocity of 

3 m/second) is estimated as 7 days. The volatilization half-life from a model lake (1 m deep, flowing 

0.05 m/second, wind velocity of 0.5 m/sec) is estimated as 56 days (EPA 2000b). The Henry's law 

constant for 1,4-dioxane also indicates that volatilization from moist soil surfaces may occur. The 

potential for volatilization of 1,4-dioxane from dry soil surfaces may exist based upon a vapor pressure of 

38.1 mm Hg (Daubert and Danner 1985). Even though volatilization of 1,4-dioxane may occur, risks to 

human health from inhalation exposures are expected to be low under environmental conditions. 

According to a classification scheme, an estimated Koc value of 17 suggests that 1,4-dioxane is expected 

to have very high mobility in soil (Swann et al. 1983). This estimated Koc value was calculated using a 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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6. POTENTIAL FOR HUMAN EXPOSURE 

log Kow of -0.27 and a regression-derived equation (Hansch et al. 1995; Thomas 1990). In the absence of 

significant degradation processes (see Section 6.3.2), 1,4-dioxane is susceptible to leaching from soil into 

groundwater. In clay soils, 1,4-dioxane will not be adsorbed as a result of any specific interaction with 

the surface of clay minerals. However, 1,4-dioxane can get trapped in the interfacial region of clay soils 

due to its strong interaction with water molecules. This may result in a lower than expected mobility for 

1,4-dioxane in clay soils (Zhang et al. 1990). Groundwater retardation factors (Rt) for 1,4-dioxane range 

from 1.0 to 1.6. These values indicate that 1,4-dioxane is expected to be a mobile compound (e.g., Rf for 

chloride=1.0, which is indicative of no retardation) in groundwater (Priddle and Jackson 1991). 

According to a classification scheme, a bioconcentration factor (BCF) value of 3 for 1,4-dioxane suggests 

that the potential for bioconcentration in aquatic organisms is low (Franke et al. 1994). This estimated 

BCF (the BCF is the concentration of the chemical in fish tissues over concentration of chemical in water) 

was calculated using a log Kow of -0.27 and a regression-derived equation (Hansch et al. 1995; Meylan et 

al. 1999). The results of an experimental bioconcentration study also reported very low BCF values (e.g., 

0.2–0.7) for 1,4-dioxane (EC 2002). Therefore, bioconcentration, bioaccumulation, and biomagnification 

are unlikely to be significant for 1,4-dioxane. 

6.3.2 Transformation and Degradation 

6.3.2.1 Air 

The primary loss mechanism for 1,4-dioxane in the atmosphere is photooxidation with OH radicals, while 

photolysis, reaction with ozone molecules, and reaction with nitrate radicals are insignificant in 

comparison (Grosjean 1990). The second-order rate constant for OH radical photooxidation of 

1,4-dioxane is 1.09x10-11 cm3

/molecule-sec (Atkinson 1989). Using OH radical concentrations between 

0.5x106 and 1.5x106 OH radicals/cm3 and a 12-hour day, the atmospheric half-lives for 1,4-dioxane are 

2.9 and 1.0 days, respectively. A reaction product from OH radical photooxidation is 2-oxodioxane (or 

c-C4H7O2). The lifetime of this alkyl radical, 2-oxodioxane in air at 1 atm is 0.02 microseconds with 

respect to the addition of O2 to give the corresponding peroxy radical (c-C4H7O2)O2. These radicals react 

rapidly (t1⁄2=6 minutes based on NO concentration of 2.5x108 molecules/cm3

) with NO to produce NO2 and 

by inference (c-C4H7O2)O alkoxy radicals. The sole atmospheric fate of this alkoxy radical is 

decomposition via C-C bond scission, leading to the formation of ethylene glycol diformate (Platz et al. 

1997). There are no known reactions for the in situ formation of 1,4-dioxane in the atmosphere (Grosjean 

1990). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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6. POTENTIAL FOR HUMAN EXPOSURE 

6.3.2.2 Water 

Since 1,4-dioxane does not have functional groups that are susceptible to hydrolysis (Wolfe and Jeffers 

2000), hydrolysis of 1,4-dioxane is not expected to occur in the environment. Since 1,4-dioxane does not 

adsorb light in the environmental spectrum (i.e., >290 nm), 1,4-dioxane is not expected to undergo direct 

photolysis in aqueous media. 1,4-Dioxane may undergo indirect photolysis by aqueous hydroxyl radicals 

near the water surface. The half-life for this reaction is 336 days at pH 7 (Anbar and Neta 1967). 

However, the extent of this reaction of OH radicals with 1,4-dioxane in the environment is unknown. 

1,4-Dioxane has been found to be resistant to biodegradation (Alexander 1973; Dow Chemical Co. 1989; 

Fincher and Payne 1962; Heukelekian and Rand 1955; Mills and Stack 1954). Results of a biological 

oxygen demand (BOD) test for 1,4-dioxane indicate that negligible oxygen was consumed over a 20-day 

test period (Swope and Kenna 1950). Mills and Stack (1954) noted that degradation of 1,4-dioxane was 

not observed in cultures of sewage microorganisms exposed for 1 year to waste water treatment plant 

effluents adjusted to contain 1,4-dioxane at concentrations ranging from 100 to 900 mg/L. In a different 

study, microorganisms present in either municipal or industrial activated sludge were unable to degrade 

1,4-dioxane during 2 days of continuous exposure to concentrations ranging from 10 to 100 mg/L (Dow 

Chemical Co. 1989). Accordingly, it appears that 1,4-dioxane will not undergo significant degradation in 

conventional biological treatment systems. Thus, 1,4-dioxane has been classified as not readily 

biodegradable, and it is not expected to rapidly biodegrade in the environment (Kawasaki 1980; Lyman et 

al. 1982). 

Acclimated microbial cultures may be capable of degrading 1,4-dioxane under certain conditions. Roy et 

al. (1994) investigated the biodegradability of 1,4-dioxane in industrial wastes using microorganisms 

obtained from acclimated industrial waste. These authors found that pure 1,4-dioxane and industrial 

wastes containing 1,4-dioxane are biodegradable. Following a 10-day lag period, complete degradation 

of 150 mg/L of 1,4-dioxane was observed after 32 days of treatment using a electrolytic respirometer cell. 

However, partial degradation of 1,4-dioxane was observed at higher concentrations, which may have 

resulted from the build up of intermediates inhibitory to the biodegradation process (Roy et al. 1994, 

1995). Zenker et al. (2000) reported that a mixed microbial culture enriched from a 1,4-dioxane 

contaminated aquifer was capable of aerobically degrading 1,4-dioxane in the presence of tetrahydrofuran 

(THF). No biodegradation of 1,4-dioxane was observed in the absence of THF, and the measured cell 

yield was similar during degradation of 1,4-dioxane with THF or with THF alone. This suggests that 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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1,4-dioxane was biodegraded via a co-metabolic process (i.e., transformation of a non-growth substance 

[1,4-dioxane] in the presence of a growth substrate [THF] or another transformable compound). 

Zenker et al. (1999) reported that a mixed microbial culture enriched from a 1,4-dioxane contaminated 

soil was capable of aerobically degrading 1,4-dioxane in the presence of THF. 1,4-Dioxane and THF 

were added to the soil microcosm at a concentration of 200 mg/L under enhanced conditions, which 

included incubation at 35 °C and the addition of nitrogen, phosphorus, and trace minerals. Both 

1,4-dioxane and THF were completely degraded within 100 days, while 1,4-dioxane alone degraded 

completely after 300 days of incubation. Microcosms incubated under ambient conditions exhibited no 

biodegradation of 1,4-dioxane or THF (Zenker et al. 1999). 

6.3.2.3 Sediment and Soil 

Limited information was located on the transformation and degradation of 1,4-dioxane in soils and 

sediment. Kelley et al. (2001) investigated the potential to enhance 1,4-dioxane biodegradation in both 

planted and unplanted soil, by adding the 1,4-dioxane-degrading actinomycete, Amycolata sp. CB1190. 

1,4-Dioxane was not removed within 120 days in sterile controls or in viable microcosms not amended 

with CB1190. Popular root extract (40 mg/L as chemical oxygen demand [COD]) stimulated 1,4-dioxane 

degradation in bioaugmented soil, and 100 mg/L of 1,4-dioxane was removed within 45 days. Other 

co-substrates that enhanced 1,4-dioxane degradation by CB1190 included THF and 1-butanol, while 

glucose and soil extract did not affect 1,4-dioxane degradation (Kelley et al. 2001). While long-term 

enrichments eventually yield cultures of CB1190 that are capable of growth on 1,4-dioxane alone, THF 

appears to be the preferred growth substrate for CB1190 (Parales et al. 1994). 

6.3.2.4 Other Media 

Pure 1,4-dioxane is known to react with molecular oxygen at ambient temperatures to form peroxides and 

hydroperoxides in the course of long-term storage and handling (Howard and Ingold 1969). Peroxides are 

formed primarily with exposure to air and UV light. Formate esters are formed from subsequent 

transformations of peroxides and hydroperoxides by way of free-radical mechanisms (Jewett and Lawless 

1980). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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6. POTENTIAL FOR HUMAN EXPOSURE 

6.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT 

Reliable evaluation of the potential for human exposure to 1,4-dioxane depends in part on the reliability 

of supporting analytical data from environmental samples and biological specimens. Concentrations of 

1,4-dioxane in unpolluted atmospheres and in pristine surface waters are often so low as to be near the 

limits of current analytical methods. In reviewing data on 1,4-dioxane levels monitored or estimated in 

the environment, it should also be noted that the amount of chemical identified analytically is not 

necessarily equivalent to the amount that is bioavailable. The analytical methods available for monitoring 

1,4-dioxane in a variety of environmental media are detailed in Chapter 7. 

Recent information on the levels of 1,4-dioxane in the ambient environment are unavailable. Historical 

data (i.e., 1980s or earlier) suggest that ambient levels were 0.1–0.4 μg/m3

 in air and 1 μg/L in water. 

Higher concentrations of 1,4-dioxane in groundwaters have been observed in aquifers contaminated with 

TCA. 

6.4.1 Air 

Recent information on the ambient levels of 1,4-dioxane in air is unavailable. Because the use of 

1,4-dioxane has declined in recent years, current levels of 1,4-dioxane in the ambient air are likely to be 

less than levels reported in the 1980s or in earlier periods. In 1984, the concentration of 1,4-dioxane 

ranged from 0.1–0.4 μg/m3 in ambient air sampled from the United States. No information was provided 

in this source on the locations where the air sampling occurred (EC 2002). In the early to mid 1980s, the 

mean ambient levels of 1,4-dioxane in outdoor air was measured as part of the VOC National Ambient 

Database in the United States (Shah and Singh 1988). The mean concentration of 1,4-dioxane was 

0.107 ppbv or 0.385 μg/m3 (n=617; median, 0.000 ppbv). 1,4-Dioxane was detected in outdoor air 

samples from the United States between 1981 and 1984 (detection limit unspecified). In the winter of 

1984, 1,4-dioxane was detected in 67% of outdoor air samples from Los Angeles communities (n=25) at a 

median concentration of 0.27 μg/m3

. In the summer of 1984, 1,4-dioxane was detected in 22% of outdoor 

air samples from Los Angeles communities (n=23) at a median concentration of 0.02 μg/m3

. In the 

summer of 1984, 1,4-dioxane was detected in 20% of outdoor air samples from Antioch/West Pittsburg, 

California (n=10) at a median concentration of 0.03 μg/m3 (Pellizzari et al. 1986). Between 1979 and 

1984, the mean concentration of 1,4-dioxane in ambient air was 0.44 μg/m3 (range, 0–30 μg/m3

; detected 

in 187 of 533 samples) in samples collected from 12 unspecified urban/suburban locations in the United 

States (EPA 1993). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 171 

6. POTENTIAL FOR HUMAN EXPOSURE 

In the summer of 1981 (July 6–August 16), the geometric mean concentrations of 1,4-dioxane in air near 

three industrialized urban areas (i.e., Newark, Elizabeth, and Camden, New Jersey) of the United States 

were 0.01 (21 of 38 samples positive), 0.02 (15 of 38 samples positive), and 0.005 μg/m3

 (21 of 

35 samples positive), respectively (Harkov et al. 1983). The three same sites were also sampled from 

January 18–February 26, 1982. The geometric means of these samples ranged from 0 to 0.01 μg/m3

; 20% 

of samples were positive, with a maximum value of 5.31 μg/m3

 (Harkov et al. 1984; EC 2002). Two 

ambient air samples taken in New Jersey were reported to contain 1,4-dioxane (Harkov et al. 1985). In 

1983, near the Kramer Landfill in New Jersey, sampled ambient air contained 1,4-dioxane at a geometric 

mean concentration of 0.01 ppbv or 0.4 μg/m3

 (maximum, 0.09 ppbv or 0.3 μg/m3). In 1982, at an 

urban/industrial site in Newark, New Jersey, ambient air contained 1,4-dioxane at a geometric mean 

concentration of 0.01 ppbv, or 0.4 μg/m3

 (n=26; maximum, 1.45 ppbv or 5.22 μg/m3). At various landfills 

in the United States, the concentration of 1,4-dioxane in landfill gas was reported to be 0.62 μg/m3

 and 

0.33 g/m3

 (EC 2002). 

In the early to mid 1980s, the mean ambient levels of 1,4-dioxane in indoor air was measured as part of 

the VOC National Ambient Database in the United States (Shah and Singh 1988). The mean 

concentration of 1,4-dioxane in indoor air was 1.029 ppbv, or 3.704 μg/m3

 (n=585; median, 0.000 ppbv). 

1,4-Dioxane was detected in indoor air samples from the United States between 1981 and 1984 (detection 

limit unspecified). In the winter of 1984, 1,4-dioxane was detected in 64% of indoor air samples from 

Los Angeles communities (n=25) at a median concentration of 0.26 μg/m3

. In the summer of 1984, 

1,4-dioxane was detected in 17% of indoor air samples from Los Angeles communities (n=23) at a 

median concentration of 0.02 μg/m3

. In the summer of 1984, 1,4-dioxane was detected in 10% of indoor 

air samples from Antioch/West Pittsburg, California (n=10) at a median concentration of 0.07 μg/m3 

(Pellizzari et al. 1986). In a multi-national survey taken between 1978 and 1990, mean 1,4-dioxane levels 

were 11 μg/m3 in indoor air samples taken from buildings (i.e., schools and offices) with reported 

unspecified complaints among the occupants (Brown et al. 1994). In June of 1990, 125 households in 

Woodland, California were monitored for a variety of toxic air contaminants. Approximately 21% of the 

indoor samples collected contained measurable amounts of 1,4-dioxane. The average concentration of 

1,4-dioxane was below the quantifiable limit of 0.11 μg/m3

, and the measurements ranged from below the 

quantifiable limit to 140 μg/m3 (California ARB 1997). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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6.4.2 Water 

Recent information on the concentration levels of 1,4-dioxane in groundwater, surface water, and 

drinking water is limited. However, because the use of 1,4-dioxane has declined in recent years, current 

levels of 1,4-dioxane in aqueous media are likely to be less than levels reported in the 1980s or in earlier 

periods. 

In the 1970s, municipal water supplies in the United States were reported to contain 1 μg/L of 

1,4-dioxane (Kraybill 1978); however, the frequency of this level was not provided. In a drinking water 

well in Massachusetts, a concentration of 2,100 μg/L was reported (Burmaster 1982). However, this well 

appeared to be contaminated. In six drinking water wells (37% of samples) near a solid waste landfill 

located 60 miles southwest of Wilmington, Delaware, two wells were found to contain 0.1 and 0.5 μg/L 

1,4-dioxane, but no 1,4-dioxane was detectable in the finished drinking water in the municipality using 

that well field (DeWalle and Chian 1981). Concentrations in private wells ranged from 0.001–1 to 

200 mg/L (from 1–1,000 to 200,000 μg/L). The concentration of 1,4-dioxane in five wells near 

Circleville, Ohio ranged from <1 to 360 μg/L after contamination of groundwater following treatment of 

industrial waste water (Hartung 1989). Drinking water from the Netherlands contained 1,4-dioxane at a 

concentration of 0.5 μg/L (EC 2002). Drinking water samples from homes near the Durham Meadows 

Superfund site in Durham, Connecticut had maximum 1,4-dioxane concentrations of 26 μg/L in untreated 

water in one residential well and 12 μg/L in treated water from another residential well (EPA 2004g). 

1,4-Dioxane was determined at 1.1–109 μg/L in contaminated groundwater in California (Draper et al. 

2000). Extensive groundwater contamination (<0.01–220 mg/L or <10–220,000 μg/L) with more limited 

surface water contamination (<0.01–0.29 mg/L or <10–290 μg/L) resulted from treatment of industrial 

waste water in an unlined oxidation lagoon in Ann Arbor, Michigan (DeRosa et al. 1996). Current levels 

of 1,4-dioxane were about 1 μg/L in eight groundwater wells located in the vicinity of this site. However, 

the number of non-detects was not provided in this source (Michigan DEQ 2004). 1,4-Dioxane was 

discovered in groundwater at more than 250 ppm (mg/L) at a San Jose, California solvent recycling 

facility in 1998. In a survey of TCA release sites in California, it was found that 1,4-dioxane was present 

in a majority of these sites (concentrations unspecified) (Mohr 2004). At the Stanford Linear Accelerator 

Center (SLAC) in Menlo Park, California, the occurrence of 1,4-dioxane in groundwater is closely 

associated with TCA and its abiotic degradation product, 1,1-dichloroethane. It was found at this location 

at a maximum concentration of 7,300 ppb (Mohr 2004). Leachates from wells located near low level 

radioactive waste disposal sites contained 1,4-dioxane, but no quantitative data were presented (Francis et 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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6. POTENTIAL FOR HUMAN EXPOSURE 

al. 1980). Between 1983 and 1986, 1,4-dioxane was detected in groundwater near three landfills in 

Canada at concentrations <1 μg/L (EC 2002). In groundwater beneath a landfill, the concentration of 

1,4-dioxane was 500 μg/L at a site in Canada sampled in 1982 (EC 2002). Groundwater samples 

obtained from an abandoned waste-oil refinery near Westville, Indiana contained 1,4-dioxane at levels 

ranging from approximately 3 to 31,000 μg/L (USGS 2002). 

In 1982, 1,4-dioxane was detected in samples of river water from the Haw River in North Carolina, which 

flows through an industrialized section of the North Carolina Piedmont (Dietrich et al. 1988). However, 

no information on the levels of 1,4-dioxane in these samples were reported by the authors. 1,4-Dioxane at 

1 μg/L was detected in the Chicago Sanitary and Ship Channel in the Lake Michigan basin (Konasewich 

et al. 1978). Surface water from the provincial area of Drenthe in the Netherlands contained 1,4-dioxane 

at concentrations ranging from 1 to 10 μg/L (EC 2002). At five different locations near the banks of the 

Rhine River in Germany, surface water contained <10 μg/L 1,4-dioxane in 1996 (EC 2002). River water 

collected from an unspecified river in the United Kingdom contained 1,4-dioxane, but no quantitative data 

were presented (Gelman Sciences 1989c). Dioxane concentrations in river water ranged from <0.024 to 

0.69 μg/L in Kitakyushu, Japan (Kawata et al. 2003) and from 0.1 to 16 μg/L in Kanagawa, Japan (Abe 

1999). The Japanese Ministry of the Environment reported that 1,4-dioxane in river and coastal waters 

ranged from <0.08 to 46 μg/L at 34–35 sites in Japan during fiscal years 1997–1999 (Kawata et al. 2003). 

1,4-Dioxane was detected in surface water samples from 11 of 19 sites from Niigata, Japan at 

concentrations ranging from <0.03 to 0.39 μg/L (Kawata et al. 2003). 

During the period of 1988–1991, the maximum concentration of 1,4-dioxane detected at Superfund sites 

in 21 states was 10 μg/L (Canter and Sabatinti 1994). 1,4-Dioxane ranged in concentration from 1.1 to 

109 μg/L in leachate from hazardous waste disposal sites in Japan (Yasuhara et al. 1997). In 2000–2001, 

the concentration of 1,4-dioxane in leachate from a closed hazardous waste landfill in Japan ranged from 

0.16 to 0.50 μg/L. At an open hazardous waste landfill, the concentration of 1,4-dioxane in leachate 

ranged from 0.91 to 10.6 μg/L (Yasuhara et al. 2003). At these landfills, waste plastics were disposed 

after either incineration or crushing and pressing under heat. The heating process appears to have resulted 

in the formation of 1,4-dioxane, although a mechanism for this process was not provided (Yasuhara et al. 

2003). The concentration of 1,4-dioxane in landfill leachates from eight hazardous disposal sites in Japan 

ranged from 1.100 to 109 μg/L (median, 3.900 μg/L) (Yasuhara et al. 1997). In May 1988, the 

concentration of 1,4-dioxane in an outwash aquifer near the Gloucester Hazardous Waste Landfill 

(Ottawa, Canada) ranged from ~300 to 2,000 μg/L, with a 13% frequency of detection (detection 
 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 174 

6. POTENTIAL FOR HUMAN EXPOSURE 

limit=150 μg/L) (Lesage et al. 1990). The concentrations of 1,4-dioxane were reported to be 11, 8, and 

36 μg/L in landfill leachates sampled from three municipal landfills in Göteburg, Sweden (Paxéus 2000). 

In an industrial/urban area of Japan (i.e., Kanagawa prefecture), the concentration of 1,4-dioxane in river 

water ranged from 0.3 to 0.9 μg/L during the period of 1996–1998; the concentration in groundwater 

ranged from 0.2 to 0.4 μg/L during the period of 1995–1997 in the same area (Abe 1999). High 

concentrations of 1,4-dioxane in polluted groundwater from this area ranged from <0.1 (not detected) to 

52 μg/L and were correlated with TCA contamination of groundwater (Abe 1999). Romero et al. (1998) 

measured the concentration of 1,4-dioxane in industrial waste waters from producers of polyester resins in 

Barcelona, Spain. The polymer resins were polymerized using different glycols in acid catalyzed 

condensation reactions. In these waste water samples, 1,4-dioxane was detected at a mean concentration 

of 6,400 μg/L (range, <100–31,400 μg/L) and a frequency of 48.6% (Romero et al. 1998). 

6.4.3 Sediment and Soil 

No quantitative data were located on the concentrations of 1,4-dioxane in sediments or soil. 

6.4.4 Other Environmental Media 

There have been no systematic studies designed to determine the levels of 1,4-dioxane in foods. 

However, 1,4-dioxane has been detected in some foods, which may indicate that 1,4-dioxane may be a 

natural constituent. 1,4-Dioxane was identified, but not quantified, in chicken flavor and meat volatiles 

(Shahidi et al. 1986). 1,4-Dioxane was also identified in volatile flavor compounds from fried chicken 

(Tang et al. 1983); however, no concentration levels were reported. Chung et al. (1983) identified 

1,4-dioxane in the volatile components of tomato juices and tomato juice products by mass spectrometry, 

although levels of 1,4-dioxane were not quantified. 1,4-Dioxane was formed in trilinolein (a component 

of fat oil used in deep-frying foods) after deep-fry heating (Chang et al. 1978). However, the 

concentration of 1,4-dioxane was not specified. Odor from cooked small shrimp was reported to contain 

1,4-dioxane at unquantified levels (Choi et al. 1983). Sanceda et al. (1984) detected 1,4-dioxane in patis, 

a Philippine fermented fish sauce, which is a commonly used food condiment in the diet of Southeast 

Asian people. Patis also may be readily available in some gourmet food stores in the United States. The 

concentration of 1,4-dioxane in patis was not specified. A study of the Japanese diet found that samples 

of a representative basket of foods contained 1,4-dioxane in levels from undetected to 13 ppm (mg/kg) 

(Nishimura et al. 2004). 1,4-Dioxane was identified, but not quantified, in adipose tissue of pasture-
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 175 

6. POTENTIAL FOR HUMAN EXPOSURE 

raised or concentrate-fed lambs (Sivadier et al. 2008). No further information on the detection of 

1,4-dioxane in foods was located. 

Food additives have been reported to contain 1,4-dioxane, although current levels were unavailable. For 

example, polysorbate 60 and polysorbate 80, which are used as food additives, have historically been 

found to contain 1,4-dioxane (Birkel et al. 1979). Polysorbate 60 and polysorbate 80 are produced from 

the polymerization of polyoxyethylene. Levels of 1,4-dioxane in these compounds have been reported to 

range from 4.8 to 6.0 ppm (mg/L) and from 5.3 to 5.8 ppm (mg/L), respectively. No further information 

on the levels of 1,4-dioxane in food additives was located. 

In the FDA Cosmetic Handbook, it was reported that “cosmetics containing as ingredients ethoxylated 

surface active agents, i.e., detergents, foaming agents, emulsifiers, and certain solvents identifiable by the 

prefix, word or ‘PEG,’ ‘Polyethylene,’ ‘Polyethylene glycol,’ ‘Polyoxyethylene,’ ‘-eth-,’ or ‘-oxynol-,’ 

may be contaminated with 1,4-dioxane.” It is also reported that “it (1,4-dioxane) may be removed from 

ethoxylated compounds by means of vacuum stripping at the end of the polymerizations process without 

unreasonable increase in raw material cost” (FDA 1992). 

Although manufacturers are able to remove 1,4-dioxane from ethoxylated raw materials by vacuum 

stripping, studies by FDA indicate that some ethoxylated raw materials may still contain 1,4-dioxane at 

significant levels. Since 1979, FDA has conducted periodic surveys of levels of 1,4-dioxane in 

ethoxylated raw materials used in cosmetic products and finished cosmetic products (Black et al. 2001). 

In 1997, the average concentration of 1,4-dioxane in ethoxylated raw materials used in cosmetic products 

was 348 ppm (range, 45–1,102 ppm). In previous years, the average concentrations of 1,4-dioxane were 

49 ppm (1979), 207 ppm (1980), 71 ppm (1993), and 180 ppm (1996). The average concentration of 

1,4-dioxane in ethoxylated alkyl sulfate surfactants was reported to be 229 ppm (range, 71–580 ppm), 

226 ppm (range, 6–1,410 ppm), 80 ppm (range, 16–243 ppm), 188 ppm (range, 20–653 ppm), and 

348 ppm (range, 45–1,102 ppm) in the years 1979, 1980, 1983, 1993, 1996, and 1997, respectively (Black 

et al. 2001). 

Although industry has taken steps to reduce 1,4-dioxane in ethoxylated surfactants, some cosmetic and 

household products may contain 1,4-dioxane at levels >10 ppm. For example, EPA (1992) examined 

1,159 household products for chemical contaminants such as 1,4-dioxane. In one of six samples of 

laundry presoak spray analyzed, 1,4-dioxane was reported at a concentration of 15.0 w/w% In an FDA 

survey of cosmetic finished products in the United States, the average concentrations of 1,4-dioxane were 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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reported to be 50 ppm (range, 2–279 ppm), 19 ppm (range, 2–36 ppm), and 2 ppm (range, 1–8 ppm) for 

the years 1981, 1982, and 1983, respectively (Black et al. 2001). After a 10-year break, FDA resumed its 

surveys of cosmetic finished products in 1992. The number of products analyzed for 1,4-dioxane 

between 1992 and 1997 totaled 99. Since 1994, the focus was on children’s shampoos and bubble baths, 

which are typically formulated with ethoxylated raw materials. FDA observed that the previous 

downward trend in the levels of 1,4-dioxane in products in the late 1980s was no longer evident in the 

1990s. The average concentrations of 1,4-dioxane in cosmetic finished products were reported to be 

41 ppm (range, 5–141 ppm), 79 ppm (range, 50–112 ppm), 45 ppm (range, 20–107 ppm), 74 ppm (range, 

42–90 ppm), 14 ppm (range, 6–34 ppm), and 19 ppm (range, 6–34 ppm) in the years 1992, 1993, 1994, 

1995, 1996, and 1997, respectively (Black et al. 2001). Although these levels are considered low and not 

expected to pose a hazard for consumers, the authors of the study commented that some raw material 

producers were not effectively controlling the levels of 1,4-dioxane in certain products. A more recent 

survey reported by the Campaign for Safe Cosmetics (2007) found that the levels of 1,4-dioxane in 

cosmetic products that were tested were slightly lower than in the survey conducted by the FDA in the 

1990s. The levels of 1,4-dioxane in these products ranged from 1.5 to 12 ppm in baby and children’s 

products and from 2 to 23 ppm in adult products. A second survey released in March of 2009 had similar 

results. Thirty-two out of 48 consumer products had detectable levels of 1,4-dioxane, with levels ranging 

from 0.27 to 35 ppm (Campaign for Safe Cosmetics 2009). Other studies reported that household 

laundry detergents, shampoos, soaps, and skin cleansers were found to contain 1,4-dioxane at levels 

ranging from 6 to 160 ppm (Gelman Sciences 1989a, 1989b). In Denmark, cosmetic products and 

dishwashing detergent, which used polyethoxylated surfactants, contained 1,4-dioxane at levels ranging 

from 0.3 to 96 ppm and from 1.8 to 65 ppm, respectively (Rastogi 1990). The FDA has indicated that the 

levels of 1,4-dioxane found in their monitoring of cosmetics do not present a hazard to consumers (FDA 

2009). 

1,4-Dioxane has been reported to be a contaminant in other consumer products. For example, 

1,4-dioxane was found to be an impurity at concentrations of 0.5 and 1–3% in two household adhesive 

products from the United States (NIH 2004). 1,4-Dioxane was detected in 2 of 62 samples of household 

adhesives at concentrations of 1.0 w/w% for boot cement and 2.8 w/w% for universal cement (EPA 

1992). 1,4-Dioxane was identified, but not quantified, in the headspace gas phase of a sample of 

dishwashing detergent, but was not identified in 58 other consumer products tested (Kwon et al. 2007). 

1,4-Dioxane is formed from the breakdown of diethylene glycol. In 1988, consumer anti-freeze products 

contained 1,4-dioxane at concentrations ranging from 100 to 3,400 ppb (Gelman Sciences 1989c). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 177 

6. POTENTIAL FOR HUMAN EXPOSURE 

Radiator fluids have been found to contain slightly higher levels of 1,4-dioxane at concentrations ranging 

from 10 to 22,000 ppb (Gelman Sciences 1989c). 

1,4-Dioxane was detected in 39 household aerosol products from Japan. In each of these samples, TCA 

was detected. The range of 1,4-dioxane concentration was 0.17–2.25% (Mori et al. 1992). A good 

correlation between the contents of 1,4-dioxane and TCA suggest that TCA containing 3% of 1,4-dioxane 

was used historically in the manufacture of aerosol products. However, because the use of TCA has been 

phased out in the United States since 1996, current levels of 1,4-dioxane in aerosol products should be 

limited. 

1,4-Dioxane was identified but not quantified in human feces obtained from a healthy male individual 

from the former Soviet Union (Dmitriev et al. 1985). However, no information was provided in this 

study on the possible source of 1,4-dioxane in this feces sample or whether or not the individual was 

occupationally exposed to 1,4-dioxane. 

Krotosznski et al. (1979) found 1,4-dioxane in the expired air of 24.8% of the samples taken from 

54 healthy humans. The geometric mean concentration was 0.253 μg/m3

. This concentration is 

significantly higher than those reported in the ambient air studies in New Jersey (see Section 6.4.1). 

However, no attempt was made to correlate the concentrations in the expired air with those found in the 

ambient air, nor was there an attempt to correlate these concentrations with life style or occupational 

exposures. Conkle et al. (1975) also found 1,4-dioxane (0.41 μg/hour) in the expired air of one out of 

eight volunteers. These authors speculated that 1,4-dioxane was a normal metabolic product, although 

neither this study nor the former monitoring study cited above had undertaken rigorous steps to prevent 

contamination with 1,4-dioxane during the analysis. 

In 1989, 1,4-dioxane was detected in highway rest-stop radiator boil-over pools at concentrations ranging 

from <10 to 2,300 ppb (Gelman Sciences 1989a, 1989b). 

6.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE 

The primary routes of human exposure to 1,4-dioxane for the general population are inhalation of 

1,4-dioxane in air, ingestion of contaminated food and drinking water containing 1,4-dioxane, and dermal 

contact with consumer products. Because 1,4-dioxane may be found in tap water, human exposure to 

1,4-dioxane may also occur during activities such showering, bathing, and laundering. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 178 

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A study conducted by the Centers for Disease Control and Prevention (CDC) collected human blood 

specimens in 2007–2008 from a geographically-diverse population of U.S. residents ≥12 years old. No 

detectable concentrations of 1,4-dioxane were found in 2,053 human blood specimens analyzed (Wang et 

al. 2009). The authors concluded that despite the potential for human exposure to 1,4-dioxane from 

consumer products, the low dermal penetrability is likely to result in a negligible internal dose. 

Recent levels of 1,4-dioxane in air are not available. In 1984, the concentration of 1,4-dioxane ranged 

from 0.1 to 0.4 μg/m3

 in ambient air sampled from the United States. Assuming that an adult breathes 

approximately 20 m3

 of air per day, the inhalation exposure would be 2–8 μg of 1,4-dioxane per day. 

Current exposure from air is likely to be less than this value. Exposure may be somewhat higher for 

persons living near sources of 1,4-dioxane emission. Individuals employed at industrial facilities that 

produce, process, and use 1,4-dioxane will also have higher exposures. Similarly, 1,4-dioxane is taken 

into the body by ingestion of drinking water. Current levels of 1,4-dioxane in drinking water are not 

available. In the 1970s, drinking waters in the United States were reported to contain 1 μg/L of 

1,4-dioxane (Kraybill 1978). Using this concentration and the consumption rate as 2 L/day, the 

1,4-dioxane intake from drinking water would be 2 μg/day. Current exposure from drinking water may 

likely be less than this value. Recently, a Total Diet Study in Japan determined the intake of 1,4-dioxane 

in food based on the average intake of food in the Kanto area of Japan (Nishimura et al. 2004). The 

1,4-dioxane content of 12 food groups ranged between 2 and 15 μg/kg inclusive. From these results, the 

total daily intake of 1,4-dioxane was calculated to be 0.440 μg. This study indicates that the amount of 

1,4-dioxane intake contributed from food is very low. FDA has estimated the exposure to 1,4-dioxane 

from the use of polyethylene glycol mono-isotridecyl ether sulfate sodium salt as a surfactant in adhesives 

intended for use in contact with food. Based on a daily diet of 3 kg, exposure to 1,4-dioxane has been 

estimated to be 0.2 ppb of daily diet or 0.6 μg/person/day (FDA 1998). Since most consumer products 

(e.g., detergents, shampoos, and cosmetic products) containing 1,4-dioxane may be diluted with water 

prior to application, dermal exposure is expected to be small in comparison to other exposures such as air, 

drinking water, and food. 

The National Industrial Chemicals Notification and Assessment Scheme (NICNAS) administered by the 

National Occupational Health and Safety Commission of Australia developed a ‘worst-case scenario’ for 

daily intake (inhalation and dermal exposure) for 1,4-dioxane from consumer products (not including 

pharmaceuticals or food products). The average daily intake from these exposures was calculated at 

around 7 μg/kg, based on an assumed level of 30 ppm 1,4-dioxane in end-use products (NICNAS 1998). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 179 

6. POTENTIAL FOR HUMAN EXPOSURE 

Occupational exposure of individuals involved in the production, processing, or use of 1,4-dioxane may 

result from inhalation or dermal exposure (De Rosa et al. 1996). The National Occupational Exposure 

Survey (1981–1983) indicated that 86,489 individuals, including 30,542 women, potentially were 

exposed to 1,4-dioxane (NIOSH 1977). This estimate was derived from observations of the actual use of 

the compound (25% of total observations) and the use of trade name products known to contain the 

compound (75%). The National Occupation Hazard Survey conducted by NIOSH from 1972 to 1974 

estimated that 334,000 individuals were occupationally exposed to 1,4-dioxane, including 

100,000 individuals occupationally exposed as a result of 1,4-dioxane used as a stabilizer in TCA 

(NIOSH 1976). In 1977, NIOSH estimated that 2,500 individuals were occupationally exposed to 

1,4-dioxane, in addition to the 100,000 individuals occupationally exposed to both TCA and 1,4-dioxane 

(NIOSH 1977). OSHA reported that as many as 466,000 individuals may be occupationally exposed to 

1,4-dioxane. 

Individuals employed at chemical plants may be exposed to 1,4-dioxane as solvent vapors (Buffler et al. 

1978). Between the period of 1994–1996, a survey in Hiroshima Prefecture, Japan was conducted to 

determine the levels of solvent vapors in 196 workplace areas. The survey was repeated every 6 months 

during this 3-year period. 1,4-Dioxane was reported in 6 of 1,176 cases at median and maximum 

concentrations of 0.5 and 0.8 ppm, respectively. 1,4-Dioxane was only detected in work areas where 

degreasing, cleaning, and wiping operations had occurred (Yasugi et al. 1998). During 1979, industrial 

hygiene monitoring was conducted at several plants which produced alcohol ethoxysulfate salts (Shell Oil 

Co. 1988). Time-weighted-average concentrations of 1,4-dioxane in air samples collected for five 

different jobs and locations within these plants were at or below the detection limit of <0.1 ppm. A 

maximum TWA concentration of 0.4 ppm reported in this monitoring study. In another 

study,1,4-Dioxane and HEAA were detected in the urine of individuals occupationally exposed to 

1,4-dioxane. Individuals were exposed to a time-weighted average concentration of 1.6 ppm 1,4-dioxane 

for 7.5 hours. The mean concentration of 1,4-dioxane and HEAA in urine samples from exposed 

individuals at the end of each workday were 3.5 and 414 μmol/L (0.31 and 36.5 mg/L), respectively 

(Young et al. 1976). 

Individuals involved in the manufacture of ethoxylated chemicals may be exposed to 1,4-dioxane from its 

occurrence as a by-product, and in particular during the stripping process, which is carried out to remove 

1,4-dioxane from certain ethoxylated chemicals (mainly surfactants and emulsifiers) (EC 2002). Because 

of large quantities of TCA were previously used, past occupational exposure to 1,4-dioxane (used as a 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 180 

6. POTENTIAL FOR HUMAN EXPOSURE 

stabilizer) may have been significant, particularly in metal degreasing operations. As the manufacture of 

TCA is currently restricted, only limited exposure from this exposure source is expected to occur. 

6.6 EXPOSURES OF CHILDREN 

This section focuses on exposures from conception to maturity at 18 years in humans. Differences from 

adults in susceptibility to hazardous substances are discussed in Section 3.7, Children’s Susceptibility. 

Children are not small adults. A child’s exposure may differ from an adult’s exposure in many ways. 

Children drink more fluids, eat more food, breathe more air per kilogram of body weight, and have a 

larger skin surface in proportion to their body volume. A child’s diet often differs from that of adults. 

The developing human’s source of nutrition changes with age: from placental nourishment to breast milk 

or formula, then to the diet of older children who eat more of certain types of foods than adults. A child’s 

behavior and lifestyle also influence exposure. Children crawl on the floor, put things in their mouths, 

sometimes eat inappropriate things (such as dirt or paint chips), and spend more time outdoors. Children 

also are closer to the ground, and they do not have the judgment of adults to avoid hazards (NRC 1993). 

Specific information on the exposure of children to 1,4-dioxane does not exist. As for adults in the 

general population, small exposures occur from the normal ingestion of food and drinking water, inhaling 

air, and dermal contact with contaminated consumer products (e.g., containing ethoxylated surfactants). 

Home exposures may result from the unintentional consumption of consumer products (e.g., baby 

shampoo, household detergents) containing 1,4-dioxane. However, the extent of this possible exposure 

route in the general population is unknown. 

6.7 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES 

Individuals who consume drinking water from contaminated wells may be exposed to higher levels of 

1,4-dioxane. For example, groundwater has been reported to be contaminated with 1,4-dioxane in the 

following locations: Ann Arbor, Michigan; San Jose, California; and Menlo Park, California (DeRosa et 

al. 1996; Mohr 2004). The extent of 1,4-dioxane exposure for these populations is not known. 

Individuals employed in occupations involved in the manufacture, processing and handling, and use of 

1,4-dioxane will have potentially higher exposures to this chemicals. In addition, individuals involved in 

analytical science and research and development activities, which may utilize 1,4-dioxane as a solvent, 

may be exposed to higher levels of 1,4-dioxane. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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6. POTENTIAL FOR HUMAN EXPOSURE 

6.8 ADEQUACY OF THE DATABASE 

Section 104(i)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with the 

Administrator of EPA and agencies and programs of the Public Health Service) to assess whether 

adequate information on the health effects of 1,4-dioxane is available. Where adequate information is not 

available, ATSDR, in conjunction with NTP, is required to assure the initiation of a program of research 

designed to determine the health effects (and techniques for developing methods to determine such health 

effects) of 1,4-dioxane. 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that, if met, would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean 

that all data needs discussed in this section must be filled. In the future, the identified data needs will be 

evaluated and prioritized, and a substance-specific research agenda will be proposed. 

6.8.1 Identification of Data Needs 

Physical and Chemical Properties. Sufficient information regarding the chemical and physical 

properties (i.e., log Kow, log Koc, Henry’s law constant, vapor pressure, etc.) of 1,4-dioxane is available to 

evaluate its environmental fate (see Table 4-2). There are no data needs at this time. 

Production, Import/Export, Use, Release, and Disposal. According to the Emergency 

Planning and Community Right-to-Know Act of 1986, 42 U.S.C. Section 11023, industries are required 

to submit substance release and off-site transfer information to the EPA. The TRI, which contains this 

information for 2007, became available in February of 2009. This database is updated yearly and should 

provide a list of industrial production facilities and emissions. 

1,4-Dioxane is currently produced in the United States, although current production volumes are not 

available. Information on current and future production and importation levels of 1,4-dioxane are needed 

to determine whether the risk for human exposure to 1,4-dioxane is significant. Although 1,4-dioxane is 

not widely used in the home, environment, or most workplaces, it can be present as a contaminant in 

materials that are found or used in these environments and, therefore, human exposures to 1,4-dioxane 

can occur. 1,4-Dioxane is used primarily as a solvent. 1,4-Dioxane has been found as an impurity in 

cosmetics, household and industrial detergents, and pharmaceuticals due to its occurrence as a by-product 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 182 

6. POTENTIAL FOR HUMAN EXPOSURE 

in ethoxylated emulsifiers. 1,4-Dioxane may be present as a contaminant of food. However, no 

information is available that quantifies actual levels of 1,4-dioxane in food. Water is the most likely 

media to be contaminated with significant quantities of 1,4-dioxane (EC 2003; Hartung 1989). 

Pure or nearly pure 1,4-dioxane is disposed of by incineration. It is expected that 1,4-dioxane is 

completely destroyed by this method. Aqueous solutions of 1,4-dioxane are disposed in waste water 

treatment facilities. Because 1,4-dioxane is resistant to biodegradation, complete mineralization of this 

chemical is not efficient. Thus, there may be need to develop effective methods of disposal for aqueous 

solutions of 1,4-dioxane. Additional information is needed on the amounts of 1,4-dioxane disposed of by 

each method. 

Environmental Fate. There are no data needs regarding the environmental fate of 1,4-dioxane. 

1,4-Dioxane is miscible in water and partitions primarily to the aqueous media in the environment. 

1,4-Dioxane has high mobility in soil and has the potential to migrate into groundwater. In air, 

1,4-dioxane will degrade by reaction with OH radicals with a half-life of <1 day (EPA 2000b). 

1,4-Dioxane has been found to be resistant to biodegradation in the environment (Alexander 1973; Dow 

Chemical Co. 1989; Fincher and Payne 1962; Heukelekian and Rand 1955; Mills and Stack 1954). 

1,4-Dioxane is expected to persist in both water and soil. 

Bioavailability from Environmental Media. 1,4-Dioxane is absorbed following inhalation, oral, 

and dermal contact (see Chapter 3). However, 1,4-dioxane is not bioconcentrated. Based on dermal 

penetration studies, dermal absorption of 1,4-dioxane is limited. No data needs have been identified at 

this time. 

Food Chain Bioaccumulation. Because 1,4-dioxane is miscible in water, it is not bioconcentrated 

in plants, aquatic organisms, or animals. 1,4-Dioxane is not biomagnified to any extent in prey 

organisms. No data needs have been identified at this time. 

Exposure Levels in Environmental Media. Reliable monitoring data for the levels of 1,4-dioxane 

in contaminated media at hazardous waste sites are needed so that the information obtained on levels of 

1,4-dioxane in the environment can be used in combination with the known body burden of 1,4-dioxane 

to assess the potential risk of adverse health effects in populations living in the vicinity of hazardous 

waste sites. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 183 

6. POTENTIAL FOR HUMAN EXPOSURE 

1,4-Dioxane has been detected in air, water, and foodstuff. Although historical data are available (e.g., 

1980s and earlier), recent information on the levels of 1,4-dioxane in these media are not available. 

Reliable monitoring data for the levels of 1,4-dioxane in contaminated media at hazardous waste sites are 

needed so that the information obtained on levels of 1,4-dioxane in the environment can be used in 

combination with the known body burden of 1,4-dioxane to access the potential risk of adverse health 

effects in populations living in the vicinity of hazardous waste sites. Estimates have been made for 

human intakes of 1,4-dioxane from air and drinking water. However, these estimates are based on 

historical monitoring data which may not be representative of current levels of 1,4-dioxane in 

environmental media. It is unclear how extensive the human exposure to 1,4-dioxane is indoors and from 

consumer products. Additional data that determines current levels of 1,4-dioxane in air, drinking water, 

food, and consumer products are necessary to assess human exposure to 1,4-dioxane. 

Exposure Levels in Humans. 1,4-Dioxane has been detected in the urine of individuals who are 

occupationally exposed to 1,4-dioxane (Young et al. 1976). Two studies conducted by Conkle et al. 

(1975) and Krotosznski et al. (1979) involving 54 and 8 volunteers, respectively, detected 1,4-dioxane in 

a small number of expired air samples collected from these volunteers, but the source of the measured 

1,4-dioxane could not be determined because the studies did not adequately document lifestyle or 

occupation. No other biological monitoring studies have been done in populations surrounding hazardous 

waste sites or in the general population. This information is necessary for assessing the need to conduct 

health studies on these populations. No estimates have been made for human intake of 1,4-dioxane from 

various environmental media. This information is necessary for determining the routes of exposure to 

1,4-dioxane from these various media. 

This information is necessary for assessing the need to conduct health studies on these populations. 

Exposures of Children. Children are exposed to 1,4-dioxane in the same manner as adults. 

Exposure and body burden studies on children would be useful. Children who take frequent bubble baths 

may be exposed to higher levels of 1,4-dioxane than adults due to possible contamination of ethoxylated 

surfactants found in some of these commercial products. Additional studies are needed to determine 

whether this is a significant exposure route for children. It is not known whether children are different in 

their weight-adjusted intake of 1,4-dioxane. Additional studies would help to determine if children are 

more or less exposed to 1,4-dioxane compared to adults. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 184 

6. POTENTIAL FOR HUMAN EXPOSURE 

Child health data needs relating to susceptibility are discussed in Section 3.12.2, Identification of Data 

Needs: Children’s Susceptibility. 

Exposure Registries. No exposure registries for 1,4-dioxane were located. This substance is not 

currently one of the compounds for which a sub-registry has been established in the National Exposure 

Registry. The substance will be considered in the future when chemical selection is made for subregistries to be established. The information that is amassed in the National Exposure Registry facilitates 

the epidemiological research needed to assess adverse health outcomes that may be related to exposure to 

this substance. 

Historically, 1,4-dioxane has been used as a stabilizer in TCA at concentrations up to 4%. Often 

1,4-dioxane is present at sites where TCA has been found as a contaminant. TCA is currently one of the 

compounds for which a Subregistry has been established in the Volatile Organic Compounds (VOCs) 

Registry. The VOCs Registry is part of the National Exposure Registry (NER), which was created and is 

being maintained by the Agency for Toxic Substances and Disease Registry. 

6.8.2 Ongoing Studies 

The FEDRIP (2009) database provides additional information obtainable from a few ongoing studies that 

may fill in some of the data needs identified in Section 6.8.1. 

Researchers at North Carolina State University are investigating the intermediates and pathways of the 

microbial degradation of several important ether pollutants including 1,4-dioxane. In addition, the key 

enzymes responsible involved in the biodegradation of these important pollutants are to be characterized 

and subsequently identify and characterize the genes encoding these enzymes. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 185 

7. ANALYTICAL METHODS 

The purpose of this chapter is to describe the analytical methods that are available for detecting, 

measuring, and/or monitoring 1,4-dioxane, its metabolites, and other biomarkers of exposure and effect to 

1,4-dioxane. The intent is not to provide an exhaustive list of analytical methods. Rather, the intention is 

to identify well-established methods that are used as the standard methods of analysis. Many of the 

analytical methods used for environmental samples are the methods approved by federal agencies and 

organizations, such as EPA and the National Institute for Occupational Safety and Health (NIOSH). 

Other methods presented in this chapter are those that are approved by groups such as the Association of 

Official Analytical Chemists (AOAC) and the American Public Health Association (APHA). 

Additionally, analytical methods that modify previously used methods to obtain lower detection limits 

and/or to improve accuracy and precision are included. 

Levels of 1,4-dioxane in environmental and biological samples are determined analytically by gas 

chromatography-mass spectrometry (GC-MS) or gas chromatography-flame ionization detection 

(GC-FID). The determination of 1,4-dioxane at parts-per-billion (ppb or μg/L) concentrations in samples 

where water is present (e.g., water, soil, sediment, and tissues) is difficult. The miscibility of 1,4-dioxane 

in water causes poor purging efficiency, resulting in the relatively high reporting limits. 

The purge-and-trap technique also suffers from interferences by some substances. 1,4-Dioxane gives 

poor response with headspace sample introduction due to its low volatility from water. The partition 

coefficients for 1,4-dioxane lead to low recoveries in single contact liquid-liquid extraction (LLE), and 

very large solvent-to-water ratios are needed to achieve acceptable recoveries (Draper et al. 2000). 

Because of these limitations, alternative techniques have been developed to improve the determination of 

1,4-dioxane. Methods have been developed to extract 1,4-dioxane from the aqueous phase using solid 

phase extraction (SPE) followed by desorption with an organic solvent, heated purge-and-trap with salting 

out, azeotropic distillation, and continuous LLE. Isotopic dilution has also been used to correct for 

variability in MS instrument response. 

7.1 BIOLOGICAL MATERIALS 

Methods for the specific analysis of 1,4-dioxane and its metabolites in biological tissues and fluids are 

limited. Since the human body rapidly metabolizes 1,4-dioxane to 1,4-dioxane-2-one and HEAA, the 

metabolites of 1,4-dioxane may be used as biomarkers of exposure to 1,4-dioxane (Young et al. 1976, 

1977). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 186 

7. ANALYTICAL METHODS 

Using heated headspace technique, 1,4-dioxane was determined in blood or urine (e.g., 4–5 mg) by 

heating a sample in a sealed tube to 120 °C. Volatiles from this sample were then analyzed by gas 

chromatography with the limit of detection being 0.01–0.02 μg (Royal Society of Chemistry 1988). 

Groves et al. (1997) described the analysis of organic vapors in exhaled breath, which could provide 

information about occupational exposures to 1,4-dioxane. Analysis was conducted using an array of four 

polymer-coated surface-acoustic-wave (SAW) sensors and an adsorbent preconcentrator for rapid breath 

analysis. The adsorbent used in the preconcentrator was a porous styrene-divinylbenzene resin. Limits of 

detection range from 3.7 to 10.2 μg/L for 1,4-dioxane. 

Biomarkers of exposure to 1,4-dioxane are the urinary metabolites 1,4-dioxane-2-one and HEAA (Royal 

Society of Chemistry 1988). Young et al. (1976) described a method for detection of 1,4-dioxane and 

HEAA in urine. Urine samples were treated with hydrochloric acid/methanol to convert HEAA to its 

methyl ester. Samples were then directly injected into a GC-MS for simultaneous analysis of 1,4-dioxane 

and HEAA. The detection limits were 0.07 and 0.1 μg/mL, respectively. 

Analytical methods for the determination of 1,4-dioxane and its metabolites in biological samples are 

given in Table 7-1. 

7.2 ENVIRONMENTAL SAMPLES 

NIOSH 1602 is used to determine the concentration of 1,4-dioxane in a 10-L air sample by GC-FID. 

Samples are collected by drawing air through a solid sorbent tube containing coconut shell charcoal. The 

flow rate is between 0.01 and 0.2 L/minute for a total sample size of 0.5–15 L. 1,4-Dioxane is eluted 

from the solid sorbent with agitation using carbon disulfide. The carbon disulfide eluent sample is then 

injected directly into the GC-FID. The detection limit is 0.01 mg per sample (NIOSH 1994). This 

method is similar to a GC-FID method described by Bozzelli et al. (1980), in which the air samples were 

pumped through two sorbent filters and 1,4-dioxane was extracted at elevated temperatures with either a 

solvent or steam. The detection limit reported in this study was 0.01 ppb. A portable selected ion flow 

tube-mass spectrometer (SIFT-MS) described by Francis et al. (2009), can provide real-time 

environmental monitoring of several air pollutants, including 1,4-dioxane. The limits of detection and 

quantification were reported as 530 and 740 parts per trillion by volume, respectively. 
 

 

 

 

 

 

 

1,4-DIOXANE 187 

7. ANALYTICAL METHODS 

Table 7-1. Analytical Methods for Determining 1,4-Dioxane in Biological Samples 

Sample 

matrix Preparation method 

Analytical 

method 

Sample 

detection limit 

Percent 

recovery Reference 

Blood or 

urine 

Heat sample in a sealed 

tube to 120 °C; inject 

headspace into GC 

GC 0.01–0.02 μg No data Royal Society 

of Chemistry 

1988 

Blood or 

urine 

Blood plasma or urine 

samples were analyzed by 

direct injection into the GC 

GC/MS 0.1 μg/mL (blood)

0.2 μg/mL (urine)

No data Young et al. 

(1977) 

Exhaled 

breath 

Pre-concentrate on breath 

sample on porous styrenedivinylbenzene resin 

Four polymercoated surfaceacoustic-wave 

(SAW) sensors 

3.7–10.2 μg/L No data Groves et al. 

1997 

Urine Samples treated with 

HCl/methanol to convert 

HEAA to its methyl ester; 

samples then directly 

injected into GC-MS 

GC-MS 0.07 μg/mL 

(1,4-dioxane); and 

0.1 μg/mL (HEAA)

No data Young et al. 

1976 

GC = gas chromatography; HCl = hydrochloric acid; HEAA = β-hydroxyethoxyacetic acid; MS = mass spectrometry 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 188 

7. ANALYTICAL METHODS 

EPA Method 8015B is used to determine the concentration of 1,4-dioxane in environmental samples by 

GC. Samples may be introduced into the GC by direct injection (e g., aqueous samples) including the 

concentration of analytes by azeotropic distillation (EPA Method 5031). Purge-and-trap and solvent 

extraction are not appropriate for this method. Detection of the analyte is achieved by using a FID. 

Method detection limits for 1,4-dioxane in water, groundwater, and leachate are 12, 15, and 16 μg/L, 

respectively. Method detection limits for 1,4-dioxane in solids (e.g., incinerator ash and kaolin) are 

0.31 and 0.16 mg/kg, respectively. Using azeotropic microdistillation, recoveries for 1,4-dioxane in 

groundwater, leachate, incinerator ash, and kaolin were 96–124, 102–103, 48–106, and 48–105%, 

respectively (EPA 1996a). 

EPA Method 8260B is used to determine 1,4-dioxane in a variety of solid waste matrices by GC. This 

method is applicable to nearly all types of samples, regardless of water content, including various air 

sampling trapping media, groundwater and surface water, aqueous sludges, caustic liquors, acid liquors, 

waste solvents, oily wastes, mousses, tars, fibrous wastes, polymeric emulsions, filter cakes, spent 

carbons, spent catalysts, soils, and sediments. Samples may be introduced to the capillary GC column by 

direct injection following dilution, sample concentration by azeotropic distillation (EPA Method 5031), 

and closed system vacuum distillation (EPA Method 5032) for aqueous, soil, oil, and tissue samples. 

Detection of the analyte eluted from the capillary column is achieved by using MS. The estimated 

quantitation limit for 1,4-dioxane is somewhat instrument dependent and also dependant on the choice of 

sample preparation/introduction method. No information on the recoveries for 1,4-dioxane were provided 

for this method (EPA 1996b). 

EPA Method 1624 is used to determine 1,4-dioxane in water and in municipal and industrial discharges 

by isotopic dilution GC-MS. In this method, isotopically labeled 1,4-dioxane-d8 is added to the sample as 

an isotope dilution standard. The samples are then introduced into the GC using a purge-and-trap 

methodology. 1,4-Dioxane is separated by GC and detected by MS. The labeled compounds serve to 

correct for the variability of the analytical technique. The detection limit for this method is 10 μg/L (EPA 

2001). 

Draper et al. (2000) described a sensitive method for detection of 1,4-dioxane in drinking water. This 

method was based on continuous LLE of 1,4-dioxane from aqueous samples by dichloromethane. 

Extraction of 1,4-dioxane in dichloromethane was followed by analysis using GC-MS. Detection limits 

as low as 0.2 μg/L were achieved in this method. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 189 

7. ANALYTICAL METHODS 

Epstein et al. (1987) described two methods for the determination of 1,4-dioxane in water and in solids 

and sediments. In the first method, 1,4-dioxane is extracted from water and soil samples using a heated 

purge-and-trap system following salting out with sodium sulfate at 1.6 M. GC-MS is then used as the 

method of analysis. The detection limit reported for this method was 2 ppb, with recoveries averaging 

85%. In the second method, 1,4-dioxane is adsorbed on coconut shell charcoal followed by desorption 

with carbon disulfide/methanol. Analysis of the desorbate is conducted by GC with flame ionization 

detection. The limit of quantitation is around 2 ppb with recoveries ranging from 63 to 129%. 

Kadokami et al. (1990) described a method for analysis of 1,4-dioxane in water by GC-MS. 

Preconcentration of 1,4-dioxane is achieved by passing the aqueous sample through an activated carbon 

column, followed by elution with acetone-dichloromethane. The organic extract is then concentrated with 

a Kuderna-Danish concentrator, followed by direct injection into the GC-MS with a selective ion monitor. 

The method detection limit was reported to be 0.024 μg/L. Recoveries of 1,4-dioxane from organic-free 

water, seawater, and river water were 98–101, 102, and 101%, respectively. Kawata et al. (2001) 

described a similar method of analysis for 1,4-dioxane in water. However, in this method, the solid-phase 

extraction media was activated carbon fiber felt with acetone as the elution media. Analytical 

determination of 1,4-dioxane was accomplished by GC-MS detection. The method detection limit was 

reported to be 0.03 μg/L. Recoveries of 1,4-dioxane in groundwater and river water were 97 and 92%, 

respectively. 

Analytical methods for the determination of 1,4-dioxane in environmental samples are given in Table 7-2. 

7.3 OTHER SAMPLES 

Several methods that may be used to determine 1,4-dioxane in food, consumer cosmetic products, and 

surfactant raw materials are available. 

The concentration of 1,4-dioxane in food additives may be determined using the 1,4-dioxane limit test 

(Committee on Food Chemicals Codex 1996). 1,4-Dioxane is extracted from a sample placed in a closedsystem vacuum distillation apparatus. The distillate is then analyzed using GC-FID. The detection limit 

was not specified for this method. Daniels et al. (1981) utilized a similar methodology in the analysis of 

1,4-dioxane in the food additive, polysorbate 65. The detection limit was not specified. Recoveries for 

1,4-dioxane concentrations ranging from 0.5 to 600 ppm were from 85 to 101%, respectively. 
 

 

 

 

 

1,4-DIOXANE 190 

7. ANALYTICAL METHODS 

Table 7-2. Analytical Methods for Determining 1,4-Dioxane in Environmental
	

Samples
	

Sample matrix Preparation method 

Sample 

Analytical detection 

method limit 

Percent 

recovery Reference 

Air Samples were collected by 

drawing air through a solid 

sorbent tube containing 

coconut shell charcoal; 

1,4-dioxane eluted with 

agitation using carbon 

disulfide. 

GC-FID 0.01 mg per 

sample 

No data NIOSH 1994 

(NIOSH 

Method 

1602) 

Air Samples were collected by GC-FID 

pumping air through two 

filters: Tenax, a porous 

polymer and Spherocarb, a 

carbon molecular sieve. 

0.01 ppb No data Bozzelli et 

al. (1980) 

Solvent or steam extraction 

at elevated temperature 

was used to remove 

1,4-dioxane from the filters. 

Air Ions from samples are SIFT-MS 

created using an ion source 

external to the flow tube; 

ions are then extracted 

530 ppt No data Francis et 

al. 2009 

from the ion source using a 

quadrupole mass filter and 

injected into a flowing 

carrier gas and analyzed 

via an ion detector. 

Drinking water Continuous liquid-liquid 

extraction using 

dichloromethane 

GC-MS 0.2 μg/L No data Draper et al. 

2000 

Water, seawater, and 

river water 

Pre-concentration by 

passing aqueous sample 

through an activated 

carbon column followed by 

elution with acetoneGC-MS 0.024 μg/L

with a 

selective 

ion monitor 

98–102% Kadokami et 

al. 1990 

dichloromethane; organic 

extract concentrated with a 

Kuderna-Danish 

concentrator 

Groundwater and river 

water 

Solid-phase extraction GC-MS 

using activated carbon fiber 

felt with acetone as eluent 

0.03 μg/L 97%, 92% Kawata et 

al. 2001 
 

 

 

 

 

 

 

 

	 

	 

 

	 

 

	 

	 

	 

	 

	 

Sample 

Analytical detection Percent 

Sample matrix Preparation method method limit recovery Reference 

Water, groundwater, 

leachate 

Water, and municipal 

and industrial discharges 

Water, and solids and 

sediments 

Water, and solids and 

sediments 

Groundwater and 

surface water, aqueous 

sludges, caustic liquors, 

acid liquors, waste 

solvents, oily wastes, 

mousses, tars, fibrous 

wastes, polymeric 

emulsions, filter cakes, 

spent carbons, spent 

catalysts, soils, and 

sediments 

Direct injection or 

azeotropic distillation (i.e., 

EPA Method 5031) 

Isotopically labeled 

1,4-dioxane-d8 is added to 

the sample as an isotope 

dilution standard 

Adsorbed on coconut shell 

charcoal followed by 

desorption with carbon 

disulfide/methanol 

Extracted from water and 

soil samples using a 

heated purge-and-trap 

system following salting out 

with sodium sulfate at 

1.6 M 

Azeotropic distillation (i.e., 

EPA Method 5031) or 

closed system vacuum 

distillation (i.e., EPA 

Method 5032) 

GC-FID	 12–16 μg/L 

Purge-and- 10 μg/L

trap GCMS 

GC-FID	 2 ppb (μg/L 

or μg/kg)

GC-MS	 2 ppb (μg/L 

or μg/kg)

GC-MS	 No data 

96–124% EPA 1996a 

(ground- (EPA 

water), Method 

102–103% 8015B) 

(leachate) 

No data	 EPA 2001 

(EPA 

Method 

1624) 

63–129%	 Epstein et 

al. 1987 

85%	 Epstein et 

al. 1987 

No data	 EPA 1996b 

(EPA 

Method 

8260B) 

 

 

 

1,4-dioxane-d8 = deuterium labeled 1,4-dioxane (or C4D8O2); EPA = Environmental Protection Agency; FID = flame 

ionization detector; GC = gas chromatography; kg = 103 grams; mg = 10-3 grams; μg = 10-6 grams; MS = mass 

spectrometry; NIOSH = National Institute for Occupational Safety and Health; ppb = parts per billion; ppt = parts per 

trillion; SIFT = selected ion flow tube 

 

 

Table 7-2. Analytical Methods for Determining 1,4-Dioxane in Environmental
	

Samples
	

1,4-DIOXANE	 	 191 

7. ANALYTICAL METHODS 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 192 

7. ANALYTICAL METHODS 

Stafford et al. (1980) described the determination of 1,4-dioxane in ethoxylated surfactants using a direct 

injection GC method. 1,4-Dioxane is extracted from the ethoxylated surfactants using chlorobenzene, 

which is then diluted and injected directly into the GC-FID. The detection limit was reported to be 

0.5 mg/kg, with a recovery of approximately 100%. Rastogi (1990) reported a method for the 

identification and quantification of 1,4-dioxane in polyethoxylated surfactants using headspace GC-MS. 

Dichloromethane and 1,4-dioxane-d8 are added to the surfactant sample in a closed vial, which is then 

heated at 80 °C for 16–18 hours. The headspace gases are sampled with a gas-tight syringe and injected 

into the GC-MS for quantitative analysis. The detection limit for this method was approximately 0.3 ppm 

with recoveries of 92–94%. 

1,4-Dioxane may be quantified in commercial cosmetic products by reversed-phase high-performance 

liquid chromatography (Scalia et al. 1990). Cosmetic samples are extracted using solid-phase extraction 

cartridges. Samples are then analyzed directly on a reverse-phase column with spectrophotometric 

detection at 200 nm and acetonitrile-water as eluent. The limit of detection was reported to be 6.5 μg/g. 

The recovery of 1,4-dioxane was between 81.5 and 90.1% in the 30–90 μg/g range. Ghassempour et al. 

(1998) described a modified GC-MS method for determination of 1,4-dioxane in cosmetic products (i.e., 

polyoxyethylene compound). Cosmetic product samples are prepared by dissolution of the material in 

dichloromethane. Samples are then analyzed directly by injection into a programmable temperature 

vaporizer attached to GC-MS. The minimum detection limit was reported to be 1 ng/L for this method. 

However, as this value is very low, the detection limit is likely much higher than reported by the authors. 

Analytical methods for the determination of 1,4-dioxane in food and food additives, cosmetics, and 

ethoxylated surfactant samples are given in Table 7-3. 

7.4 ADEQUACY OF THE DATABASE 

Section 104(i)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with the 

Administrator of EPA and agencies and programs of the Public Health Service) to assess whether 

adequate information on the health effects of 1,4-dioxane is available. Where adequate information is not 

available, ATSDR, in conjunction with NTP, is required to assure the initiation of a program of research 

designed to determine the health effects (and techniques for developing methods to determine such health 

effects) of 1,4-dioxane. 
 

 

 

 

 

 

 

1,4-DIOXANE 193 

7. ANALYTICAL METHODS 

Table 7-3. Analytical Methods for Determining 1,4-Dioxane in Food and Food 

Additives, Cosmetics, and Ethoxylated Surfactant Samples
	

Sample 

detection Percent 

Sample matrix Preparation method Analytical method limit recovery Reference 

Food, food 

chemicals 

Extraction followed by 

closed-system vacuum 

distillation 

GC-FID No data No data Committee on 

Food Chemicals 

CODEX 1996 

Food additives (e.g., Extraction followed by 

polysorbate 65) closed-system vacuum 

distillation 

GC-FID No data 85–101% Daniels et al. 

1981 

Ethoxylated 

surfactants 

Extraction using 

chlorobenzene 

GC-FID 0.5 mg/kg ~100% Stafford et al. 

1980 

Polyethoxylated 

surfactants 

Dichloromethane and 

1,4-dioxane-d8 added to 

sample in a closed vial 

which is then heated at 

Headspace GCMS 

0.3 ppm 92–94% Rastogi 1990 

80°C for 16–18 hours 

Commercial 

cosmetic products 

None Reversed-phase 

high-performance 

liquid 

chromatography 

6.5 μg/g 81.5– 

90.1% 

Scalia et al. 

1990 

Cosmetic products 

(i.e., 

polyoxyethylene 

compound) 

Dissolution in 

dichloromethane 

Programmable 

temperature 

vaporizer-GC-MS 

1 ng/L No data Ghassempour 

et al. 1998 

1,4-dioxane-d8 = deuterium labeled 1,4-dioxane (or C4D8O2); CODEX = Codex Alimentarius Commission; 

FID = flame ionization detector; g = grams; GC = gas chromatography; kg = 103 grams; MS = mass spectrometry; 

ng = 10-9 grams; ppm = parts per million; μg = 10-6 grams 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 194 

7. ANALYTICAL METHODS 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that, if met, would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean 

that all data needs discussed in this section must be filled. In the future, the identified data needs will be 

evaluated and prioritized, and a substance-specific research agenda will be proposed. 

7.4.1 Identification of Data Needs 

Methods for Determining Biomarkers of Exposure and Effect. 

Exposure. Existing methods do not appear to be sensitive enough to measure background levels of 

1,4-dioxane and its metabolite, HEAA, in the population (Young et al. 1976). Standard methods for the 

determination of 1,4-dioxane and its metabolite, HEAA, are needed to determine whether the general 

population is exposed to 1,4-dioxane. 

Effect. Existing methods appear to be sensitive enough to measure levels of 1,4-dioxane and its 

metabolite, HEAA, at levels at which biological effects may occur in humans (Young et al. 1976). 

Methods for Determining Parent Compounds and Degradation Products in Environmental 

Media. The purpose of analytical methods is to identify contaminated areas and to determine if 

contaminant levels constitute a concern for human health. The media that are of most concern for human 

exposure to 1,4-dioxane are drinking water, food, and cosmetic products. In water, there are methods 

sensitive enough to measure background levels in the environment down to the sub-ppb level (<1 μg/L) 

(Draper et al. 2000; Kadokami et al. 1990; Kawata et al. 2001). Standard methods are also available for 

measurement of 1,4-dioxane in air and water samples (EPA 1996a, 1996b; NIOSH 1994). Methods have 

also been reported for the determination of 1,4-dioxane in food and food additives (Committee on Food 

Chemicals Codex 1996; Daniels et al. 1981), cosmetics (Ghassempour et al. 1998; Scalia et al. 1990), and 

ethoxylated surfactant materials (Rastogi 1990; Stafford et al. 1980). 

7.4.2 Ongoing Studies 

The Environmental Health Laboratory Science Division of the National Center for Environmental Health, 

Centers for Disease Control and Prevention, is developing methods for the analysis of 1,4-dioxane and 

other volatile organic compounds in blood. These methods use purge-and-trap methodology, high 
 

 

 

1,4-DIOXANE 195 

7. ANALYTICAL METHODS 

resolution gas chromatography, and magnetic sector mass spectrometry, which give detection limits in the 

low parts per trillion (ppt) range. 

No ongoing studies on 1,4-dioxane were found as a result of a search of the Federal Research in Progress 

database (FEDRIP 2009). 
 

 

1,4-DIOXANE 196
 

7. ANALYTICAL METHODS 

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1,4-DIOXANE 197 

8. REGULATIONS, ADVISORIES, AND GUIDELINES 
	

MRLs are substance specific estimates, which are intended to serve as screening levels used by ATSDR 

health assessors and other responders to identify contaminants and potential health effects that may be of 

concern at hazardous waste sites. 

ATSDR has derived an acute-duration inhalation MRL of 2 ppm for 1,4-dioxane based on a NOAEL of 

20 ppm for sensory irritation and pulmonary function in humans (Ernstgård et al. 2006). An uncertainty 

factor of 10 was used for human variability. 

ATSDR has derived an intermediate-duration inhalation MRL of 0.2 ppm for 1,4-dioxane based on an 

increased incidence of nasal lesions in rats exposed to 1,4-dioxane 6 hours/day, 5 days/week for 13 weeks 

(Kasai et al. 2008). The MRL was derived using BMD modeling of incidence data for nasal lesions in 

rats. The predicted exposure concentration associated with a 10% extra risk for nasal lesions (BMC10) for 

nasal lesions in female rats was 40.39 ppm; the lower 95% confidence limit on this concentration 

(BMCL10) was 27.99 ppm. An uncertainty factor of 30 was used (3 for using dosimetric adjustments and 

10 for human variability). 

ATSDR has derived a chronic-duration inhalation MRL of 0.03 ppm for 1,4-dioxane based on a LOAEL 

of 50 ppm for increased incidence of nasal lesions in male rats exposed to 1,4-dioxane 6 hours/day, 

5 days/week for 2 years (Kasai et al. 2009). An uncertainty factor of 300 was used (3 for using dosimetric 

adjustments, 10 for using a LOAEL, and 10 for human variability). 

ATSDR has derived an acute-duration oral MRL of 5 mg/kg/day for 1,4-dioxane based on a NOAEL of 

516 mg/kg/day for developmental and maternal effects in rats (Giavini et al. 1985). The LOAEL was 

1,033 mg/kg/day. An uncertainty factor of 100 was used (10 for animal to human extrapolation and 

10 for human variability). 

ATSDR has derived an intermediate-duration oral MRL of 0.5 mg/kg/day for 1,4-dioxane based on a 

NOAEL of 52 mg 1,4-dioxane/kg/day for liver effects in male rats (Kano et al. 2008). The LOAEL was 

126 mg/kg/day in males and 185 mg/kg/day in females. An uncertainty factor of 100 was used (10 for 

animal to human extrapolation and 10 for human variability). 
 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 198 

8. REGULATIONS, ADVISORIES, AND GUIDELINES 

ATSDR has derived a chronic-duration oral MRL of 0.1 mg/kg/day for 1,4-dioxane based on a NOAEL 

of 9.6 mg 1,4-dioxane/kg/day for liver effects in male rats (Kociba et al. 1974). The LOAEL was 

94 mg/kg/day in males and 148 mg/kg/day in females. An uncertainty factor of 100 was used (10 for 

animal to human extrapolation and 10 for human variability). 

The EPA (IRIS 2011) has derived a reference dose (RfD) of 0.03 mg/kg/day for 1,4-dioxane based on a 

NOAEL of 9.6 mg/kg/day for liver and kidney toxicity in male Sherman rats in a 2-year drinking water 

study (Kociba et al. 1974). The EPA (IRIS 2011) also derived an oral slope factor of 

1x10-1 (mg/kg/day)

-1 based on increased incidence of hepatocellular adenoma and carcinoma in female 

BDF1 mice in a 2-year drinking water study (Kano et al. 2009). 

The National Academy of Sciences (NAS) established a maximum specification of 10 ppm for 

1,4-dioxane in the ingredient polysorbate, a food additive (NAS 2003). It is also listed as an indirect food 

additive [21 CFR 175.105] (FDA 2003). FDA considered the same level, 10 ppm, to be an acceptable 

limit for 1,4-dioxane, during its consideration of a spermicide, N-9, in a contraceptive sponge product 

(prior to at least 1997) (FDA 1997). FDA also set a limit on 1,4-dioxane at 10 ppm in approving 

glycerides and polyglycerides for use as excipients in products such as dietary supplements (FDA 2006). 

(This regulation is located at 21 CFR 172.736.) 

The international and national regulations, advisories, and guidelines regarding 1,4-dioxane in air, water, 

and other media are summarized in Table 8-1. 
 

 

1,4-DIOXANE 199 

8. REGULATIONS, ADVISORIES, AND GUIDELINES 

Table 8-1. Regulations, Advisories, and Guidelines Applicable to 1,4-Dioxane 

Agency Description Information Reference 

INTERNATIONAL 

Guidelines: 

IARC Carcinogenicity classification Group 2Ba IARC 1999 

WHO Air quality guidelines No data WHO 2000 

Water quality guidelines No data WHO 2004 

NATIONAL 

Regulations and Guidelines: 

a. Air 

ACGIH TLV (8-hour TWA) 20 ppmb ACGIH 2011 

NIOSH REL (30-minute ceiling TWA) 1 ppmc NIOSH 2004 

IDLH 500 ppm 

EPA Hazardous air pollutant EPA 2004d 

42 USC 7412 

OSHA PEL (8-hour TWA) for general industry 100 ppmb OSHA 2004c 

29 CFR 1910.1000, 

Table Z-1 

PEL (8-hour TWA) for construction 100 ppmb OSHA 2004b 

industry 29 CFR 1926.55, 

Appendix A 

PEL (8-hour TWA) for shipyard 100 ppmb OSHA 2004a 

industry 29 CFR 1915.1000, 

Table Z 

b. Water 

EPA Drinking water standards and health EPA 2004b 

advisories 

1-Day HA for a 10-kg child 4.0 mg/L 

10-Day HA for a 10-kg child 

10-4 cancer risk 

0.4 mg/L 

0.3 mg/L 

c. Food 

FDA Indirect food additive for use only as a FDA 2003 

component of adhesives 21 CFR 175.105 

d. Other 

ACGIH Carcinogenicity classification Group A3d ACGIH 2011 

EPA Carcinogenicity classification Likely to be IRIS 2011 

carcinogenic to humans 

No data 

RfC 0.03 mg/kg/day 

RfD 

Oral slope factor 1x10-1 (mg/kg/day)-1 

Drinking water unit risk 2.9x10-6 (μg/L)-1 
 

 

 

 

 

 

 

 

 

 

 

 

Table 8 -1. Regulations, Advisories, and Guidelines Applicable to 1,4-Dioxane 

Agency Description Information Reference 

NATIONAL (cont.) 

Community right-to-know; toxic 01/01/1987 EPA 2004e 

chemical release reporting; effective 40 CFR 372.65 

date 

EPA Superfund, Emergency Planning, and EPA 2004a 

Community Right-To-Know Programs; 40 CFR 302.4 

designated as a hazardous substance 

pursuant to Section 112 of the Clean 

Air Act and Section 3001 of RCRA 

Reportable quantity 100 pounds 

Hazardous waste identification U108 EPA 2004c 

40 CFR 261, 

Appendix VIII 

NTP Carcinogenicity classification Reasonably anticipated NTP 2011 

to be a human 

carcinogen 

STATE 

a. Air 

No data 

b. Water 

California Drinking water guidelines 3 μg/L HSDB 2010 

Florida Drinking water guidelines 5 μg/L

Maine Drinking water guidelines 32 μg/L

Massachusetts Drinking water guidelines 50 μg/L

c. Food 

No data 

d. Other 

No data 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 200 

8. REGULATIONS, ADVISORIES, AND GUIDELINES 

a

Group 2B: Possibly carcinogenic to humans.

b

Skin designation: Potential significant contribution to the overall exposure by the cutaneous route, including 

mucous membranes and the eyes, either by contact with vapors, or of probable greater significance, by direct skin 

contact with the substance.
 c

Potential occupational carcinogen. d

Group A3: Confirmed animal carcinogen with unknown relevance to humans.
 

ACGIH = American Conference of Governmental Industrial Hygienists; CFR = Code of Federal Regulations;
 

EPA = Environmental Protection Agency; FDA = Food and Drug Administration; HA = Health Advisory;
 

HSDB = Hazardous Substances Data Bank; IARC = International Agency for Research on Cancer;
 

IDLH = immediately dangerous to life or health; IRIS = Integrated Risk Information System; NIOSH = National
 

Institute for Occupational Safety and Health; NTP = National Toxicology Program; OSHA = Occupational Safety and 

Health Administration; PEL = permissible exposure limit; RCRA = Resource Conservation and Recovery Act;
 

RfC = reference concentration; RfD = reference dose; TLV = threshold limit values; TWA = time-weighted average;
 

USC = United States Codes; WHO = World Health Organization
 
 

 

 

 

 

 

 

_______________________ 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 201 

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1,4-DIOXANE 221 

10. GLOSSARY 

Absorption—The taking up of liquids by solids, or of gases by solids or liquids. 

Acute Exposure—Exposure to a chemical for a duration of 14 days or less, as specified in the 

Toxicological Profiles. 

Adsorption—The adhesion in an extremely thin layer of molecules (as of gases, solutes, or liquids) to the 

surfaces of solid bodies or liquids with which they are in contact. 

Adsorption Coefficient (Koc)—The ratio of the amount of a chemical adsorbed per unit weight of 

organic carbon in the soil or sediment to the concentration of the chemical in solution at equilibrium. 

Adsorption Ratio (Kd)—The amount of a chemical adsorbed by sediment or soil (i.e., the solid phase) 

divided by the amount of chemical in the solution phase, which is in equilibrium with the solid phase, at a 

fixed solid/solution ratio. It is generally expressed in micrograms of chemical sorbed per gram of soil or 

sediment. 

Benchmark Dose (BMD)—Usually defined as the lower confidence limit on the dose that produces a 

specified magnitude of changes in a specified adverse response. For example, a BMD10 would be the 

dose at the 95% lower confidence limit on a 10% response, and the benchmark response (BMR) would be 

10%. The BMD is determined by modeling the dose response curve in the region of the dose response 

relationship where biologically observable data are feasible. 

Benchmark Dose Model—A statistical dose-response model applied to either experimental toxicological 

or epidemiological data to calculate a BMD. 

Bioconcentration Factor (BCF)—The quotient of the concentration of a chemical in aquatic organisms 

at a specific time or during a discrete time period of exposure divided by the concentration in the 

surrounding water at the same time or during the same period. 

Biomarkers—Broadly defined as indicators signaling events in biologic systems or samples. They have 

been classified as markers of exposure, markers of effect, and markers of susceptibility. 

Cancer Effect Level (CEL)—The lowest dose of chemical in a study, or group of studies, that produces 

significant increases in the incidence of cancer (or tumors) between the exposed population and its 

appropriate control. 

Carcinogen—A chemical capable of inducing cancer. 

Case-Control Study—A type of epidemiological study that examines the relationship between a 

particular outcome (disease or condition) and a variety of potential causative agents (such as toxic 

chemicals). In a case-controlled study, a group of people with a specified and well-defined outcome is 

identified and compared to a similar group of people without outcome. 

Case Report—Describes a single individual with a particular disease or exposure. These may suggest 

some potential topics for scientific research, but are not actual research studies. 

Case Series—Describes the experience of a small number of individuals with the same disease or 

exposure. These may suggest potential topics for scientific research, but are not actual research studies. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 222 

10. GLOSSARY 

Ceiling Value—A concentration of a substance that should not be exceeded, even instantaneously. 

Chronic Exposure—Exposure to a chemical for 365 days or more, as specified in the Toxicological 

Profiles. 

Cohort Study—A type of epidemiological study of a specific group or groups of people who have had a 

common insult (e.g., exposure to an agent suspected of causing disease or a common disease) and are 

followed forward from exposure to outcome. At least one exposed group is compared to one unexposed 

group. 

Cross-sectional Study—A type of epidemiological study of a group or groups of people that examines 

the relationship between exposure and outcome to a chemical or to chemicals at one point in time. 

Data Needs—Substance-specific informational needs that if met would reduce the uncertainties of human 

health assessment. 

Developmental Toxicity—The occurrence of adverse effects on the developing organism that may result 

from exposure to a chemical prior to conception (either parent), during prenatal development, or 

postnatally to the time of sexual maturation. Adverse developmental effects may be detected at any point 

in the life span of the organism. 

Dose-Response Relationship—The quantitative relationship between the amount of exposure to a 

toxicant and the incidence of the adverse effects. 

Embryotoxicity and Fetotoxicity—Any toxic effect on the conceptus as a result of prenatal exposure to 

a chemical; the distinguishing feature between the two terms is the stage of development during which the 

insult occurs. The terms, as used here, include malformations and variations, altered growth, and in utero 

death. 

Environmental Protection Agency (EPA) Health Advisory—An estimate of acceptable drinking water 

levels for a chemical substance based on health effects information. A health advisory is not a legally 

enforceable federal standard, but serves as technical guidance to assist federal, state, and local officials. 

Epidemiology—Refers to the investigation of factors that determine the frequency and distribution of 

disease or other health-related conditions within a defined human population during a specified period. 

Genotoxicity—A specific adverse effect on the genome of living cells that, upon the duplication of 

affected cells, can be expressed as a mutagenic, clastogenic, or carcinogenic event because of specific 

alteration of the molecular structure of the genome. 

Half-life—A measure of rate for the time required to eliminate one half of a quantity of a chemical from 

the body or environmental media. 

Immediately Dangerous to Life or Health (IDLH)—The maximum environmental concentration of a 

contaminant from which one could escape within 30 minutes without any escape-impairing symptoms or 

irreversible health effects. 

Immunologic Toxicity—The occurrence of adverse effects on the immune system that may result from 

exposure to environmental agents such as chemicals. 

Immunological Effects—Functional changes in the immune response. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 223 

10. GLOSSARY 

Incidence—The ratio of individuals in a population who develop a specified condition to the total 

number of individuals in that population who could have developed that condition in a specified time 

period. 

Intermediate Exposure—Exposure to a chemical for a duration of 15–364 days, as specified in the 

Toxicological Profiles. 

In Vitro—Isolated from the living organism and artificially maintained, as in a test tube. 

In Vivo—Occurring within the living organism. 

Lethal Concentration(LO) (LCLO)—The lowest concentration of a chemical in air that has been reported 

to have caused death in humans or animals. 

Lethal Concentration(50) (LC50)—A calculated concentration of a chemical in air to which exposure for 

a specific length of time is expected to cause death in 50% of a defined experimental animal population. 

Lethal Dose(LO) (LDLo)—The lowest dose of a chemical introduced by a route other than inhalation that 

has been reported to have caused death in humans or animals. 

Lethal Dose(50) (LD50)—The dose of a chemical that has been calculated to cause death in 50% of a 

defined experimental animal population. 

Lethal Time(50) (LT50)—A calculated period of time within which a specific concentration of a chemical 

is expected to cause death in 50% of a defined experimental animal population. 

Lowest-Observed-Adverse-Effect Level (LOAEL)—The lowest exposure level of chemical in a study, 

or group of studies, that produces statistically or biologically significant increases in frequency or severity 

of adverse effects between the exposed population and its appropriate control. 

Lymphoreticular Effects—Represent morphological effects involving lymphatic tissues such as the 

lymph nodes, spleen, and thymus. 

Malformations—Permanent structural changes that may adversely affect survival, development, or 

function. 

Minimal Risk Level (MRL)—An estimate of daily human exposure to a hazardous substance that is 

likely to be without an appreciable risk of adverse noncancer health effects over a specified route and 

duration of exposure. 

Modifying Factor (MF)—A value (greater than zero) that is applied to the derivation of a Minimal Risk 

Level (MRL) to reflect additional concerns about the database that are not covered by the uncertainty 

factors. The default value for a MF is 1. 

Morbidity—State of being diseased; morbidity rate is the incidence or prevalence of disease in a specific 

population. 

Mortality—Death; mortality rate is a measure of the number of deaths in a population during a specified 

interval of time. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 224 

10. GLOSSARY 

Mutagen—A substance that causes mutations. A mutation is a change in the DNA sequence of a cell’s 

DNA. Mutations can lead to birth defects, miscarriages, or cancer. 

Necropsy—The gross examination of the organs and tissues of a dead body to determine the cause of 

death or pathological conditions. 

Neurotoxicity—The occurrence of adverse effects on the nervous system following exposure to a 

chemical. 

No-Observed-Adverse-Effect Level (NOAEL)—The dose of a chemical at which there were no 

statistically or biologically significant increases in frequency or severity of adverse effects seen between 

the exposed population and its appropriate control. Effects may be produced at this dose, but they are not 

considered to be adverse. 

Octanol-Water Partition Coefficient (Kow)—The equilibrium ratio of the concentrations of a chemical 

in n-octanol and water, in dilute solution. 

Odds Ratio (OR)—A means of measuring the association between an exposure (such as toxic substances 

and a disease or condition) that represents the best estimate of relative risk (risk as a ratio of the incidence 

among subjects exposed to a particular risk factor divided by the incidence among subjects who were not 

exposed to the risk factor). An OR of greater than 1 is considered to indicate greater risk of disease in the 

exposed group compared to the unexposed group. 

Organophosphate or Organophosphorus Compound—A phosphorus-containing organic compound 

and especially a pesticide that acts by inhibiting cholinesterase. 

Permissible Exposure Limit (PEL)—An Occupational Safety and Health Administration (OSHA) 

allowable exposure level in workplace air averaged over an 8-hour shift of a 40-hour workweek. 

Pesticide—General classification of chemicals specifically developed and produced for use in the control 

of agricultural and public health pests. 

Pharmacokinetics—The dynamic behavior of a material in the body, used to predict the fate 

(disposition) of an exogenous substance in an organism. Utilizing computational techniques, it provides 

the means of studying the absorption, distribution, metabolism, and excretion of chemicals by the body. 

Pharmacokinetic Model—A set of equations that can be used to describe the time course of a parent 

chemical or metabolite in an animal system. There are two types of pharmacokinetic models: data-based 

and physiologically-based. A data-based model divides the animal system into a series of compartments, 

which, in general, do not represent real, identifiable anatomic regions of the body, whereas the 

physiologically-based model compartments represent real anatomic regions of the body. 

Physiologically Based Pharmacodynamic (PBPD) Model—A type of physiologically based doseresponse model that quantitatively describes the relationship between target tissue dose and toxic end 

points. These models advance the importance of physiologically based models in that they clearly 

describe the biological effect (response) produced by the system following exposure to an exogenous 

substance. 

Physiologically Based Pharmacokinetic (PBPK) Model—Comprised of a series of compartments 

representing organs or tissue groups with realistic weights and blood flows. These models require a 

variety of physiological information: tissue volumes, blood flow rates to tissues, cardiac output, alveolar 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 225 

10. GLOSSARY 

ventilation rates, and possibly membrane permeabilities. The models also utilize biochemical 

information, such as air/blood partition coefficients, and metabolic parameters. PBPK models are also 

called biologically based tissue dosimetry models. 

Prevalence—The number of cases of a disease or condition in a population at one point in time. 

Prospective Study—A type of cohort study in which the pertinent observations are made on events 

occurring after the start of the study. A group is followed over time. 

q1*—The upper-bound estimate of the low-dose slope of the dose-response curve as determined by the 

multistage procedure. The q1* can be used to calculate an estimate of carcinogenic potency, the 

incremental excess cancer risk per unit of exposure (usually μg/L for water, mg/kg/day for food, and 

μg/m3 for air). 

Recommended Exposure Limit (REL)—A National Institute for Occupational Safety and Health 

(NIOSH) time-weighted average (TWA) concentration for up to a 10-hour workday during a 40-hour 

workweek. 

Reference Concentration (RfC)—An estimate (with uncertainty spanning perhaps an order of 

magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups) 

that is likely to be without an appreciable risk of deleterious noncancer health effects during a lifetime. 

The inhalation reference concentration is for continuous inhalation exposures and is appropriately 

expressed in units of mg/m3 or ppm. 

Reference Dose (RfD)—An estimate (with uncertainty spanning perhaps an order of magnitude) of the 

daily exposure of the human population to a potential hazard that is likely to be without risk of deleterious 

effects during a lifetime. The RfD is operationally derived from the no-observed-adverse-effect level 

(NOAEL, from animal and human studies) by a consistent application of uncertainty factors that reflect 

various types of data used to estimate RfDs and an additional modifying factor, which is based on a 

professional judgment of the entire database on the chemical. The RfDs are not applicable to 

nonthreshold effects such as cancer. 

Reportable Quantity (RQ)—The quantity of a hazardous substance that is considered reportable under 

the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Reportable 

quantities are (1) 1 pound or greater or (2) for selected substances, an amount established by regulation 

either under CERCLA or under Section 311 of the Clean Water Act. Quantities are measured over a 

24-hour period. 

Reproductive Toxicity—The occurrence of adverse effects on the reproductive system that may result 

from exposure to a chemical. The toxicity may be directed to the reproductive organs and/or the related 

endocrine system. The manifestation of such toxicity may be noted as alterations in sexual behavior, 

fertility, pregnancy outcomes, or modifications in other functions that are dependent on the integrity of 

this system. 

Retrospective Study—A type of cohort study based on a group of persons known to have been exposed 

at some time in the past. Data are collected from routinely recorded events, up to the time the study is 

undertaken. Retrospective studies are limited to causal factors that can be ascertained from existing 

records and/or examining survivors of the cohort. 

Risk—The possibility or chance that some adverse effect will result from a given exposure to a chemical. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE 226 

10. GLOSSARY 

Risk Factor—An aspect of personal behavior or lifestyle, an environmental exposure, or an inborn or 

inherited characteristic that is associated with an increased occurrence of disease or other health-related 

event or condition. 

Risk Ratio—The ratio of the risk among persons with specific risk factors compared to the risk among 

persons without risk factors. A risk ratio greater than 1 indicates greater risk of disease in the exposed 

group compared to the unexposed group. 

Short-Term Exposure Limit (STEL)—The American Conference of Governmental Industrial 

Hygienists (ACGIH) maximum concentration to which workers can be exposed for up to 15 minutes 

continually. No more than four excursions are allowed per day, and there must be at least 60 minutes 

between exposure periods. The daily Threshold Limit Value-Time Weighted Average (TLV-TWA) may 

not be exceeded. 

Standardized Mortality Ratio (SMR)—A ratio of the observed number of deaths and the expected 

number of deaths in a specific standard population. 

Target Organ Toxicity—This term covers a broad range of adverse effects on target organs or 

physiological systems (e.g., renal, cardiovascular) extending from those arising through a single limited 

exposure to those assumed over a lifetime of exposure to a chemical. 

Teratogen—A chemical that causes structural defects that affect the development of an organism. 

Threshold Limit Value (TLV)—An American Conference of Governmental Industrial Hygienists 

(ACGIH) concentration of a substance to which most workers can be exposed without adverse effect. 

The TLV may be expressed as a Time Weighted Average (TWA), as a Short-Term Exposure Limit 

(STEL), or as a ceiling limit (CL). 

Time-Weighted Average (TWA)—An allowable exposure concentration averaged over a normal 8-hour 

workday or 40-hour workweek. 

Toxic Dose(50) (TD50)—A calculated dose of a chemical, introduced by a route other than inhalation, 

which is expected to cause a specific toxic effect in 50% of a defined experimental animal population. 

Toxicokinetic—The absorption, distribution, and elimination of toxic compounds in the living organism. 

Uncertainty Factor (UF)—A factor used in operationally deriving the Minimal Risk Level (MRL) or 

Reference Dose (RfD) or Reference Concentration (RfC) from experimental data. UFs are intended to 

account for (1) the variation in sensitivity among the members of the human population, (2) the 

uncertainty in extrapolating animal data to the case of human, (3) the uncertainty in extrapolating from 

data obtained in a study that is of less than lifetime exposure, and (4) the uncertainty in using lowestobserved-adverse-effect level (LOAEL) data rather than no-observed-adverse-effect level (NOAEL) data. 

A default for each individual UF is 10; if complete certainty in data exists, a value of 1 can be used; 

however, a reduced UF of 3 may be used on a case-by-case basis, 3 being the approximate logarithmic 

average of 10 and 1. 

Xenobiotic—Any chemical that is foreign to the biological system. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-1 

APPENDIX A. ATSDR MINIMAL RISK LEVELS AND WORKSHEETS 

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) [42 U.S.C. 

9601 et seq.], as amended by the Superfund Amendments and Reauthorization Act (SARA) [Pub. L. 99– 

499], requires that the Agency for Toxic Substances and Disease Registry (ATSDR) develop jointly with 

the U.S. Environmental Protection Agency (EPA), in order of priority, a list of hazardous substances most 

commonly found at facilities on the CERCLA National Priorities List (NPL); prepare toxicological 

profiles for each substance included on the priority list of hazardous substances; and assure the initiation 

of a research program to fill identified data needs associated with the substances. 

The toxicological profiles include an examination, summary, and interpretation of available toxicological 

information and epidemiologic evaluations of a hazardous substance. During the development of 

toxicological profiles, Minimal Risk Levels (MRLs) are derived when reliable and sufficient data exist to 

identify the target organ(s) of effect or the most sensitive health effect(s) for a specific duration for a 

given route of exposure. An MRL is an estimate of the daily human exposure to a hazardous substance 

that is likely to be without appreciable risk of adverse noncancer health effects over a specified duration 

of exposure. MRLs are based on noncancer health effects only and are not based on a consideration of 

cancer effects. These substance-specific estimates, which are intended to serve as screening levels, are 

used by ATSDR health assessors to identify contaminants and potential health effects that may be of 

concern at hazardous waste sites. It is important to note that MRLs are not intended to define clean-up or 

action levels. 

MRLs are derived for hazardous substances using the no-observed-adverse-effect level/uncertainty factor 

approach. They are below levels that might cause adverse health effects in the people most sensitive to 

such chemical-induced effects. MRLs are derived for acute (1–14 days), intermediate (15–364 days), and 

chronic (365 days and longer) durations and for the oral and inhalation routes of exposure. Currently, 

MRLs for the dermal route of exposure are not derived because ATSDR has not yet identified a method 

suitable for this route of exposure. MRLs are generally based on the most sensitive chemical-induced end 

point considered to be of relevance to humans. Serious health effects (such as irreparable damage to the 

liver or kidneys, or birth defects) are not used as a basis for establishing MRLs. Exposure to a level 

above the MRL does not necessarily mean that adverse health effects will occur. 

MRLs are intended only to serve as a screening tool to help public health professionals decide where to 

look more closely. They may also be viewed as a mechanism to identify those hazardous waste sites that 
 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-2 

APPENDIX A 

are not expected to cause adverse health effects. Most MRLs contain a degree of uncertainty because of 

the lack of precise toxicological information on the people who might be most sensitive (e.g., infants, 

elderly, nutritionally or immunologically compromised) to the effects of hazardous substances. ATSDR 

uses a conservative (i.e., protective) approach to address this uncertainty consistent with the public health 

principle of prevention. Although human data are preferred, MRLs often must be based on animal studies 

because relevant human studies are lacking. In the absence of evidence to the contrary, ATSDR assumes 

that humans are more sensitive to the effects of hazardous substance than animals and that certain persons 

may be particularly sensitive. Thus, the resulting MRL may be as much as 100-fold below levels that 

have been shown to be nontoxic in laboratory animals. 

Proposed MRLs undergo a rigorous review process: Health Effects/MRL Workgroup reviews within the 

Division of Toxicology and Environmental Medicine, expert panel peer reviews, and agency-wide MRL 

Workgroup reviews, with participation from other federal agencies and comments from the public. They 

are subject to change as new information becomes available concomitant with updating the toxicological 

profiles. Thus, MRLs in the most recent toxicological profiles supersede previously published levels. 

For additional information regarding MRLs, please contact the Division of Toxicology and 

Environmental Medicine, Agency for Toxic Substances and Disease Registry, 1600 Clifton Road NE, 

Mailstop F-62, Atlanta, Georgia 30333. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-3 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: 1,4-Dioxane 

CAS Number: 123-91-1 

Date: August 2011 

Profile Status: Final 

Route: [X] Inhalation [ ] Oral 

Duration: [X] Acute [ ] Intermediate [ ] Chronic 

Graph Key: 8 

Species: Human 

Minimal Risk Level: 2 [ ] mg/kg/day [X] ppm 

Reference: Ernstgård L, Iregren A, Sjögren B, et al. 2006. Acute effects of exposure to vapours of 

dioxane in humans. Human Exp Toxicol 25:723-729. 

Experimental design: The acute-duration inhalation MRL is based on a NOAEL of 20 ppm for eye and 

respiratory effects in volunteers. In that study, six male and six female volunteers were exposed to 0 or 

20 ppm 1,4-dioxane vapor for 2 hours under dynamic conditions. Each subject was exposed on two 

separate occasions to 0 or 20 ppm. End points monitored included self-rated symptoms on a visual 

analogue scale that measured discomfort of the eyes, nose and throat, breathing difficulty, solvent smell, 

headache, fatigue, nausea, dizziness and 'feeling of intoxication'. Rating was performed before, during (3, 

60, and 118 minutes), and after exposure (20 and 180 minutes). Respiratory function was assessed by 

spirometry before exposure, immediately after, and 3 hours after exposure ceased. The specific 

parameters measured included vital capacity, forced vital capacity, forced expiratory volume in 1 second, 

peak expiratory flow, and forced expiratory flow at 25, 50, and 75% of the force vital capacity. Also 

assessed was nasal swelling before, immediately after, and 3 hours after exposure. Eye blinking was 

monitored throughout the exposure period by electromyography. Also, two inflammatory markers, high 

sensitivity C reactive protein and interleukin 6, were measured in blood before and 3 hours after exposure. 

Effects noted in study and corresponding doses: Exposure to 1,4-dioxane under the conditions of the 

study did not significantly affect any of the end points monitored except the perception of smell of the 

chemical, which increased significantly after 3, 60, and 118 minutes if exposure. The NOAEL of 20 ppm 

was divided by an uncertainty factor of 10 (for human variability) to yield the MRL of 2 ppm. An 

adjustment to 24-hour exposure was not necessary because the first effects observed, as shown by Young 

et al. (1977), are local irritation effects that are not time-dependent. 

Dose and end point used for MRL derivation: 20 ppm; NOAEL for eye and respiratory effects in 

humans. 

[X ] NOAEL [ ] LOAEL 

Uncertainty Factors used in MRL derivation: 

[ ] 10 for use of a LOAEL 

[ ] 10 for extrapolation from animals to humans 

[X] 10 for human variability 

Was a conversion used from ppm in food or water to a mg/body weight dose? Not applicable. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-4 

APPENDIX A 

If an inhalation study in animals, list the conversion factors used in determining human equivalent dose: 

Not applicable. 

Other additional studies or pertinent information which lend support to this MRL: Support for the acuteduration inhalation MRL of 2 ppm is provided by a study by Young et al. (1977) in which four healthy 

male volunteers were exposed to 50 ppm 1,4-dioxane for 6 hours under dynamic airflow conditions. Prior 

to the study, the subjects provided a complete history and underwent tests including chest x-ray, EKG, 

respiratory function tests, a conventional battery of 12 blood chemistry tests plus triglyceride and 

creatinine determinations, and complete hematological and urine analyses. Except for the chest x-ray, the 

tests were repeated 24 hours and 2 weeks after the exposure. The tests conducted 24 hours and 2 weeks 

after exposure did not reveal any exposure-related abnormalities, although no data were provided in the 

study. Eye irritation was a frequent and the only complaint throughout the exposure. Tolerance to the 

odor of 1,4-dioxane occurred during exposure. Two of the subjects could not perceive the odor after 

4 and 5 hours in the chamber. The 50 ppm exposure level constitutes a minimal LOAEL for eye 

irritation, although there was no control experiment, and possible low humidity in the exposure chamber 

(not addressed in the report) might have contributed to the eye irritation. 

Other studies with volunteers also support the findings of Ernstgård et al. (2006) and Young et al. (1977). 

For example, Silverman et al. (1946) exposed 12 subject to various concentrations of 1,4-dioxane for only 

15 minutes and determined a NOAEL of 200 ppm for eye and nose irritation; the LOAEL was 300 ppm. 

Wirth and Klimmer (1936) reported that slight mucous membrane irritation started to take place in 

volunteers at exposure concentrations about 278 ppm for a few minutes (unspecified) and that at 

1,390 ppm for several minutes, the subjects described prickling in the nose and scratchiness and dryness 

in the throat. Fairley et al. (1934) reported a NOAEL of 2,000 ppm (only level tested) for respiratory and 

ocular effects in six subjects exposed to 1,4-dioxane for only 3 minutes. Finally, Yant et al. (1930) 

described slight eye, nose, and throat irritation in a group of five subjects exposed to 1,600 ppm (only 

level tested) 1,4-dioxane for only 10 minutes. The available studies in animals used exposure 

concentrations that often caused death among the animals and were much higher than the concentrations 

tested by Young et al. (1977). 

Agency Contact (Chemical Manager): Sharon Wilbur 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-5 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: 1,4-Dioxane 

CAS Number: 123-91-1 

Date: August 2011 

Profile Status: Final 

Route: [X] Inhalation [ ] Oral 

Duration: [ ] Acute [X] Intermediate [ ] Chronic 

Graph Key: 19 

Species: Rat 

Minimal Risk Level: 0.2 [ ] mg/kg/day [X] ppm 

Reference: Kasai T, Saito M, Senoh H, et al. (2008). Thirteen-week inhalation toxicity of 1,4-dioxane in 

rats. Inhalation Toxicol 20: 961-971. 

Experimental design: Groups of F344 DuCrj rats (10/sex/group) were exposed to target concentrations of 

0 (clean air), 100, 200, 400, 800, 1,600, 3,200, or 6,400 ppm 1,4-dioxane vapors 6 hours/day, 

5 days/week, for 13 weeks (Kasai et al. 2008). End points evaluated included mortality, clinical signs 

(daily), body weight and food consumption (once per week), hematology, clinical chemistry and 

urinalysis at termination, and gross and microscopic pathology of all major organs and tissues. 

Effects noted in study and corresponding doses: All rats in the 6,400 ppm group died during the first 

week of the study. Examination of these rats showed that death was primarily caused by renal failure, as 

judged by marked necrosis observed in the renal tubules. Lung congestion was also observed in males 

and females from this exposure group. No abnormal clinical signs were observed during the study. 

Terminal body weight was reduced in all treated groups except the 100 ppm group, but not in a doserelated manner; the final weight reduced more than 10% relative to controls only in females exposed to 

3,200 ppm. Data on food consumption were not provided. Changes in organ weight were limited to the 

liver, kidneys, and lungs and consisted in increases in relative organ weight generally in the high-dose 

groups of up to 15% relative to controls; data on absolute organ weights were not provided. Significant 

changes (although within normal values) in hematology and clinical chemistry parameters were limited to 

the 3,200 ppm groups and consisted of increases in mean corpuscular volume and serum ALT in males, 

decreases in glucose and triglycerides in males, and increases in red blood cell count, hemoglobin, 

hematocrit, and AST and ALT serum activities in females. Histologically, exposure to 1,4-dioxane 

affected principally the respiratory tract, in particular the nasal cavity of males and females. Significant 

nuclear enlargement of the respiratory epithelium was seen in all exposed groups. The incidences in 

males were 0/10 in the control group and 7/10, 9/10, 7/10, 10/10, 10/10, and 10/10 in exposed groups up 

to 3,200 ppm, respectively. The corresponding incidences in females were 0/10, 5/10, 9/10, 10/10, 10/10, 

10/10, and 10/10. Severity of the lesion was dose-related. Significant nuclear enlargement of the 

olfactory epithelium started at 200 ppm (5/10 in males and 6/10 in females). Similar lesions in the 

trachea and bronchus appeared only in the high-exposure groups. The nuclear enlargement was 

characterized by the epithelial cells having a round to oval or elongated nucleus at least 4 times larger in 

diameter than normal. Significantly increased incidence of vacuolic change started in males at 400 ppm 

(0/10, 1/10, 3/10, 6/10, 10/10, 9/10) and in females at 800 ppm (0/10, 1/10, 2/10, 3/10, 7/10, 9/10, 10/10), 

while atrophy of the olfactory epithelium started in females at 800 ppm (0/10, 0/10, 2/10, 3/10, 5/10, 5/10, 

4/10); incidence of atrophy of the olfactory epithelium in males was not presented. Significant single cell 

necrosis and centrilobular swelling occurred in the liver of males exposed to 3,200 ppm 1,4-dioxane; 

females in this exposure group showed only centrilobular swelling. Significant kidney changes were seen 

only in females from the 3,200 ppm exposure group and consisted of hydropic changes in the proximal 

tubule. No treatment-related lesions were reported in any other tissue or organ examined. Although 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-6 

APPENDIX A 

nuclear enlargement of the respiratory and olfactory epithelium occurred at lower exposure levels than 

other nasal lesions, it was not selected as the critical effect for MRL derivation on the grounds that the 

toxicological significance of the lesion is uncertain. There is some evidence suggesting that this alteration 

may represent a preneoplastic lesion. As discussed by Kasai et al. (2008), nuclear enlargement occurred 

as an early histopathological change in the respiratory tract of rats simultaneously exposed to sulfur 

dioxide and treated intraperitoneally with several N-nitrosamines known to induce nasal tumors in rats 

(Fowlie et al. 1990). In addition, studies have shown a good correlation between in vivo carcinogenicity 

and the extent of nuclear enlargement in HeLa cells in vitro (Grant and Grasso 1978). Since MRLs are 

not based on a consideration of cancer effects, nuclear enlargement is not considered a suitable basis of an 

MRL. 

Dose and end point used for MRL derivation: BMCL10 of 27.99 ppm for lesions in the olfactory 

epithelium of the nasal cavity in male rats. 

[ ] NOAEL [ ] LOAEL [X] BMCL10 

Uncertainty Factors used in MRL derivation: 

[ ] 10 for use of a LOAEL 

[X] 3 for extrapolation from animals to humans with dosimetric adjustment 

[X] 10 for human variability 

Was a conversion used from ppm in food or water to a mg/body weight dose? Not applicable. 

If an inhalation study in animals, list the conversion factors used in determining human equivalent dose: 

The intermediate-duration inhalation MRL was calculated using EPA’s methodology (EPA 1994) for a 

category 3 gas, as explained in detail in Section 2.3 (derivation of the intermediate-duration inhalation 

MRL). A duration adjustment (6/24 hours x 5/7 days) seemed appropriate in the absence of information 

regarding whether Haber’s Law is applicable under the experimental conditions of the study. 

The MRL is derived as follows: 

BMCL10[HEC] = BMCL10[ADJ] x (Hb/gA / Hb/gH) 

where:
	

BMCL10[ADJ] = 27.99 ppm x 6/24 hours x 5/7 days = 4.998 ppm and 

Hb/gA = animal blood:air partition coefficient = 1,861 (Sweeney et al. 2008)
	

Hb/gH = human blood:air partition coefficient = 1,666 (Sweeney et al. 2008)
	

(Hb/gA / Hb/gH) = 1,861/1,666 = 1.117 

Because the ratio of the partition coefficients is higher than 1, a default value of 1 is used in accordance 

with EPA’s RfC methodology (EPA 1994). 

BMCL[HEC] = 4.998 ppm x 1 = 4.998 ppm 

Other additional studies or pertinent information which lend support to this MRL: Only one additional 

intermediate-duration inhalation study that exposed several animal species to high concentrations of 

1,4-dioxane and monitored limited end points is available (Fairley et al. 1934). In that study, rats, mice, 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-7 

APPENDIX A 

guinea pigs, and rabbits were exposed to airborne 1,4-dioxane 3 hours/day, 5 days/week for periods of up 

to 12 weeks. At termination, examination of the animals revealed moderate to severe liver and kidney 

toxicity occurring at all exposure levels in all of the species tested. The lowest exposure level was 

1,000 ppm. In a 2-year inhalation study, nasal alterations in both the respiratory and olfactory epithelium 

were reported in male rats (females were not tested) exposed to ≥50 ppm 1,4-dioxane vapors 6 hours/day, 

5 days/week (Kasai et al. 2009). In the chronic-duration inhalation study in rats conducted by Torkelson 

et al. (1974), no interim histopathological evaluations were performed. In that study, rats were exposed 

111 ppm 1,4-dioxane 7 hours/day (1 hour longer than Kasai et al. [2008]), 5 days/week for 2 years. 

Although Torkelson et al. (1974) reported that there were no treatment-related gross or microscopic 

lesions in the tissues examined and explicitly mention that there were no nasal tumors, the nasal cavity 

was not listed among the tissues and organs that were subjected to microscopic examination. 

Agency Contact (Chemical Manager): Sharon Wilbur 

BENCHMARK MODELING FOR CHANGES IN THE OLFACTORY EPITHELIUM IN RATS 

Incidence data (Table A-1) for vacuolic change in the olfactory epithelium in male and female rats and of 

atrophy of the olfactory epithelium in female rats exposed to 1,4-dioxane vapors (Kasai et al. 2008) were 

analyzed using the BMD/BMC approach for MRL derivation. Models in the EPA Benchmark Dose 

Software (BMDS version 2.1.1) (Gamma, Logistic, Log-logistic, Multi-stage, Probit, Log-probit, Weibull 

models) were fit to the nasal lesions data to determine potential points of departure for the MRL. 

Adequate model fit is judged by three criteria: goodness-of-fit (p>0.1), visual inspection of the doseresponse curve, and scaled residual at the data point (except the control) closest to the predefined BMR. 

Among all of the models providing adequate fit to the data, the lowest benchmark concentration (BMCL, 

the lower limit of a one-sided 95% confidence interval on the BMC) is selected as the point of departure 

when differences between the BMCLs estimated from these models are more than 3-fold; otherwise, the 

BMCL from the model with the lowest Akaike's information criterion (AIC) is chosen. In accordance 

with EPA (2000a) guidance, BMCs and BMCLs associated with an extra risk of 10% are calculated for 

all models. Attempts to model the incidence of vacuolic change in the olfactory epithelium from male 

rats were unsuccessful in that none of the models could fit the data and/or had overall largest scaled 

residuals that exceeded the maximum value criteria of 2 (Table A-2). However, all models provided 

adequate fits after the highest dose was dropped. The best fit was provided by a Multistage (1-degree) 

model with a lowest predicted exposure concentrations associated with a 10% extra risk (BMC10) of 

40.39 ppm and a corresponding lower 95% confidence limit on this concentration (BMCL10) of 

27.99 ppm. Graphic representation of the fit is presented in Figure A-1. The best fit for the incidence 

data for vacuolic change in the olfactory epithelium from female rats was provided also by a Multistage 

(1-degree) model; the BMC10 and BMCL10 values were 80.30 and 56.78 ppm, respectively (Table A-3); 

the dose-response curve is shown in Figure A-2. The best fit for the incidence data for atrophy of the 

olfactory epithelium in female rats was provided by a LogLogistic model; the BMC10 and BMCL10 values 

were 172.57 and 103.81 ppm, respectively (Table A-4); the graphic representation of the fit is shown in 

Figure A-3. In order to be protective of human health, the lowest BMCL10 of 27.99 ppm from the 

incidence of vacuolic change in the olfactory epithelium of male rats is selected as point of departure for 

MRL derivation. The BMCL10 of 27.99 ppm was converted to a HEC (BMCL10[HEC]) using the EPA 

cross-species dosimetric methodology (EPA 1994) for a category 3 gas, as explained in detail in Section 

2.3. 
 

 

1,4-DIOXANE A-8 

APPENDIX A 

Table A-1. Incidence Data for Vacuolic Change and Atrophy in the Nasal Cavity
	

Olfactory Epithelium in F344 Rats Exposed to 1,4-Dioxane
	

Exposure concentration (ppm) 

0 100 200 400 800 1,600 3,200 

Male rats (vacuolic change) 

0/10 1/10 3/10 6/10 10/10 10/10 9/10 

Female rats (vacuolic change) 

0/10 1/10 2/10 3/10 7/10 9/10 10/10 

Female rats (atrophy) 

0/10 0/10 2/10 3/10 5/10 5/10 4/10 

Source: Kasai et al. 2008 
χ2 

Goodness 

b Scaled residuals

Dose Dose 

of fit below above Overall BMC10 BMCL10 

Model DF χ2 a p-value BMC BMC largest AIC (ppm) (ppm) 

All doses c Gamma 6 43.56 0 0.00 -0.60 -6.30 52.92 ND ND 

Logistic 5 316.7 0 -1.10 -0.07 -17.55 66.26 ND ND 

d LogLogistic 5 9.35 0.10 0.00 -0.15 -2.70 49.16 ND (LS) ND (LS) 

LogProbitd 6 11.88 0.06 0.00 -0.33 -3.04 48.51 ND ND 

Multistage (1-degree)e 6 43.56 0 0.00 -0.60 -6.30 52.92 ND ND 

Multistage (2-degree)e 6 43.56 0 0.00 -0.60 -6.30 52.92 ND ND 

Multistage (3-degree)e 6 43.56 0 0.00 -0.60 -6.30 52.92 ND ND 

Multistage (4-degree)e 6 43.56 0 0.00 -0.60 -6.30 52.92 ND ND 

Multistage (5-degree)e 6 43.56 0 0.00 -0.60 -6.30 52.92 ND ND 

Multistage (6-degree)e 6 43.56 0 0.00 -0.60 -6.30 52.92 ND ND 

Probit 5 56.22 0 -1.42 -0.30 -6.40 71.55 ND ND 

Weibullc 6 43.56 0 0.00 -0.60 -6.30 52.92 ND ND 

Highest dose dropped c Gamma 4 0.79 0.94 0.25 0.09 -0.61 37.29 112.53 47.46 

Logistic 4 1.09 0.90 0.07 0.65 0.65 37.70 140.81 91.82 

d LogLogistic 4 1.65 0.80 0.48 0.06 -0.82 38.47 121.09 64.79 

LogProbitd 4 1.48 0.83 0.50 -0.09 -0.78 38.16 118.46 66.52 

Multistage (1-degree)e,f 5 3.09 0.69 0.00 -0.98 1.19 38.86 40.39 27.99 

Multistage (2-degree)e 4 0.42 0.98 0.05 0.20 -0.45 36.76 103.17 42.53 

Multistage (3-degree)e 4 0.22 0.99 0.00 -0.16 0.30 36.45 86.98 39.84 

Multistage (4-degree)e 3 0.16 0.98 0.00 -0.22 0.28 38.35 82.28 37.99 

Multistage (5-degree)e 3 0.12 0.99 0.00 -0.19 0.25 38.30 84.93 37.02 

Probit 4 0.79 0.94 0.09 0.57 0.57 37.26 131.72 86.59 

Weibullc 4 0.52 0.97 0.19 0.23 -0.51 36.87 111.01 49.07 

 

 

 

 

 

 

 

1,4-DIOXANE A-9 

APPENDIX A 

Table A-2. Model Predictions for the Incidence of Vacuolic Change in the
	

Olfactory Epithelium In Male Rats Exposed to 1,4-Dioxane
	

a

Values <0.1 fail to meet conventional goodness-of-fit criteria. b

Scaled residuals at doses immediately below and above the BMD; also the largest residual at any dose.
 c

Power restricted to ≥1.
 d

Slope restricted to ≥1.
 e

Betas restricted to ≥0.
 f

Selected model. 

AIC = Akaike Information Criterion; BMD = maximum likelihood estimate of the exposure concentration associated 

with the selected benchmark response; BMDL = 95% lower confidence limit on the BMD (subscripts denote 

benchmark response: i.e., 10 = exposure concentration associated with 10% extra risk); DF = degrees of freedom; 

ND = not determined, goodness-of-fit criteria, p<0.10; ND (LS) = not determined; largest scaled residual >2 
 

 

 

 

 

 

 

Figure A-1. Fit of Multistage 1 Degree Polynomial Model to Data on 1,4-Dioxane,
	

Incidence of Vacuolic Change in the Olfactory Epithelium of Male Rats 

Exposed via Inhalation for 13 Weeks
	

Multistage Model with 0.95 Confidence Level 

1

 0.8

 0.6

 0.4

 0.2

 0 

dose 

BMDL BMD

Multistage 

0 200 400 600 800 1000 1200 1400 1600 

09:30 08/24 2011 

Source: Kasai et al. 2008 Fraction Affected 

1,4-DIOXANE A-10 

APPENDIX A 
Table A-3. Model Predictions for the Incidence of Vacuolic Change in the 

Olfactory Epithelium in Female Rats Exposed by Inhalation to 

1,4-Dioxane Vapor for 13 Weeks 

Model DF χ2

χ2 

Goodness 

of fit a p-value

b Scaled residuals

AIC 

BMC10 

(ppm) 

BMCL10 

(ppm) 

Dose Dose 

below above Overall 

BMC BMC largest c Gamma 5 0.46 0.99 0.22 0.14 -0.51 51.97 119.11 58.89 

Logistic 

d LogLogistic

LogProbitd 

Multistage (1-degree)e,f 

Multistage (2-degree)e 

Multistage (3-degree)e 

Multistage (4-degree)e 

Multistage (5-degree)e 

Multistage (6-degree)e 

Probit 

5 2.48 

5 1.30 

5 1.35 

6 0.90 

5 0.39 

5 0.39 

4 0.40 

4 0.39 

4 0.39 

5 2.59 

0.78 

0.93 

0.93 

0.99 

1.00 

1.00 

0.98 

0.98 

0.98 

0.76 

0.35 

0.59 

0.64 

0.00 

0.04 

0.04 

0.04 

0.03 

0.03 

0.33 

0.18 

0.25 

0.12 

-0.22 

0.09 

0.09 

0.09 

0.08 

0.08 

0.19 

-0.97 

-0.75 

-0.81 

0.39 

-0.41 

-0.41 

0.42 

0.43 

0.43 

-0.96 

54.53 

53.05 

53.00 

50.52 

51.86 

51.86 

53.86 

53.85 

53.85 

54.71 

238.59 

141.58 

136.97 

80.30 

104.27 

104.27 

103.74 

103.04 

102.80 

230.67 

165.80 

64.86 

95.47 

56.78 

59.36 

59.36 

59.36 

59.32 

59.27 

165.00 

Weibullc 5 0.42 0.99 0.19 0.14 -0.47 51.90 116.72 59.17 

a

Values <0.1 fail to meet conventional goodness-of-fit criteria.

 bScaled residuals at doses immediately below and above the BMD; also the largest residual at any dose.
 

 c

Power restricted to ≥1.
 d

Slope restricted to ≥1. 
 e

Betas restricted to ≥0. 
 f

Selected model. 

AIC = Akaike Information Criterion; BMC = maximum likelihood estimate of the exposure concentration associated 

with the selected benchmark response; BMCL = 95% lower confidence limit on the BMC (subscripts denote 

benchmark response: i.e., 10 = exposure concentration associated with 10% extra risk); DF = degrees of freedom 

1,4-DIOXANE A-11 

APPENDIX A 
 

 

 

 

 

 

Figure A-2. Fit of Multistage 1 Degree Polynomial Model to Data on 1,4-Dioxane,
	

Incidence of Vacuolic Change in the Olfactory Epithelium of Female Rats 

Exposed via Inhalation for 13 Weeks
	

Multistage Model with 0.95 Confidence Level 

1

 0.8

 0.6

 0.4

 0.2

 0 

dose 

BMDL BMD

Multistage 

0 500 1000 1500 2000 2500 3000 

10:16 08/24 2011 

Source: Kasai et al. 2008 Fraction Affected 

1,4-DIOXANE A-12 

APPENDIX A 
 

 

 

 

 

 

1,4-DIOXANE A-13 

APPENDIX A 

Table A-4. Model Predictions for the Incidence of Atrophy of the Olfactory
	

Epithelium in Female Rats Exposed by Inhalation to 1,4-Dioxane Vapor
	

for 13 Weeks
	

χ2 Scaled residualsb 

Goodness Dose Dose 

of fit below above Overall BMC10 BMCL10 

Model DF χ2 p-valuea BMC BMC largest AIC (ppm) (ppm) 

Gammac 5 9.15 0.10 0.77 1.05 -1.71 77.39 336.54 193.55 

Logistic 5 10.35 0.07 1.84 1.08 1.84 80.74 898.33 580.22 

LogLogisticd,e 6 6.47 0.37 -0.80 0.86 -1.84 71.99 172.57 103.81 

LogProbitd 5 11.48 0.04 1.17 1.78 -1.87 80.50 ND ND 

Multistage (1-degree)f 5 9.15 0.10 0.77 1.05 -1.71 77.39 336.54 193.55 

Multistage (2-degree)f 5 9.15 0.10 0.77 1.05 -1.71 77.39 336.54 193.55 

Multistage (3-degree)f 5 9.15 0.10 0.77 1.05 -1.71 77.39 336.54 193.55 

Multistage (4-degree)f 5 9.15 0.10 0.77 1.05 -1.71 77.39 336.54 193.55 

Multistage (5-degree)f 5 9.15 0.10 0.77 1.05 -1.71 77.39 336.54 193.55 

Multistage (6-degree)f 5 9.15 0.10 0.77 1.05 -1.71 77.39 336.54 193.55 

Probit 5 10.26 0.07 1.85 1.06 -1.48 80.52 846.81 557.27 

Weibullc 5 9.15 0.10 0.77 1.05 -1.71 77.39 336.54 193.55 

a

Values <0.1 fail to meet conventional goodness-of-fit criteria. b

Scaled residuals at doses immediately below and above the BMD; also the largest residual at any dose.
 c

Power restricted to ≥1. d

Slope restricted to ≥1. e

Selected model. 

f

Betas restricted to ≥0.

AIC = Akaike Information Criterion; BMC = maximum likelihood estimate of the exposure concentration associated 

with the selected benchmark response; BMDL = 95% lower confidence limit on the BMC (subscripts denote 

benchmark response: i.e., 10 = exposure concentration associated with 10% extra risk); DF = degrees of freedom; 

ND = not determined, goodness-of-fit criteria, p<0.10 
 

 

Figure A -3. Fit of Log Logistic Model to Data on 1,4 -Dioxane, Incidence of 
	

Atrophy of the Olfactory Epithelium in Female Rats Exposed via 

Inhalation for 13 Weeks
	

Log-Logistic Model with 0.95 Confidence Level 

0

 0.1

 0.2

 0.3

 0.4

 0.5

 0.6

 0.7

 0.8 

Fraction Affected 

BMDL BMD 

Log-Logistic 

0 500 1000 1500 2000 2500 3000 

dose 

10:52 08/24 2011 

Source: Kasai et al. 2008 

1,4-DIOXANE A-14 

APPENDIX A 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-15 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: 1,4-Dioxane 

CAS Number: 123-91-1 

Date: August 2011 

Profile Status: Final 

Route: [X] Inhalation [ ] Oral 

Duration: [ ] Acute [ ] Intermediate [X] Chronic 

Graph Key: 27 

Species: Rat 

Minimal Risk Level: 0.03 [ ] mg/kg/day [X] ppm 

Reference: Kasai T, Kano H, Umeda Y, et al. 2009. Two-year inhalation study of carcinogenicity and 

chronic toxicity of 1,4-dioxane in male. Inhal Toxicol 21:889-897. 

Experimental design: Groups of male F344/DuCrj rats (50/group) were exposed whole-body to target 

concentrations of 0, 50, 250, or 1,250 ppm 1,4-dioxane vapors 6 hours/day, 5 days/week for 104 weeks; 

controls were exposed to clean air. End points evaluated included clinical signs and mortality (daily) and 

body weight and food consumption (once /week for the first 14 weeks, every 4 weeks thereafter). All rats 

were subjected to complete necropsy. Blood was collected at termination for clinical chemistry and 

hematology tests; urinary pH was measured in the last week of the study. All major organs were 

removed, weighed, and examined for macroscopic lesions. All major tissues and organs, including the 

entire respiratory tract, were examined microscopically. 

Effects noted in study and corresponding doses: Survival rates in rats exposed to 250 ppm tended to 

decrease relative to controls, but the difference with controls was not statistically significant. Exposure to 

1,250 ppm 1,4-dioxane significantly reduced (p<0.05) survival rate beginning on week 91. Terminal 

survival rate was 37/50, 37/50, 29/50, and 25/50 in the control, low-, mid-, and high-exposure groups, 

respectively. The decreased survival rates were attributed to increased number of deaths due primarily to 

peritoneal mesotheliomas, although nasal tumors contributed to the causes of death. Terminal body 

weight was reduced 6.3% in the high-exposure group. Food consumption was not affected by exposure to 

1,4-dioxane. Significant increases in relative liver (27%) and lung (2%) weights were reported in the 

high-exposure group but there was no clear dose-response relationship. Significant changes in 

hematology and clinical chemistry tests included reduced hemoglobin (13%), MCV (6%), MCH (8%), 

increased serum AST (46%), ALT (95%), AP (15%), and γ-GTP (6–7-fold); urinary pH was reduced 7%. 

All of these changes were restricted to the high-exposure group. Treatment-related pre- and 

nonneoplastic lesions occurred in the nasal cavity, liver, and kidney. All exposed groups had significant 

increases in nuclear enlargement of the respiratory epithelium (0/50, 50/50, 48/50, 38/50), nuclear 

enlargement of the olfactory epithelium (0/50, 48/50, 48/50, 45/50), atrophy of olfactory epithelium (0/50, 

40/50, 47/50, 48/50), and respiratory metaplasia of the olfactory epithelium (11/50, 34/50, 49/50, 48/50). 

Significant increases in liver lesions (centrilobular nuclear enlargement, acidophilic cell foci, basophilic 

cell foci, spongiosis hepatis, and centrilobular necrosis) occurred in the high-exposure group. Significant 

increases in nuclear enlargement of the proximal kidney tubule occurred in the mid- and high-exposure 

groups; significantly increased incidence of hydropic changes in the proximal tubule occurred in the highexposure group. No significant changes occurred in other organs or tissues. The lowest exposure 

concentration tested, 50 ppm 1,4-dioxane, is a LOAEL for nasal lesions (atrophy of the olfactory 

epithelium), a NOAEL was not defined in this study. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-16 

APPENDIX A 

The results of Kasai et al. (2009) clearly show that the nasal cavity was the most sensitive tissue 

following 2 years of exposure to 1,4-dioxane vapors. As discussed in the derivation of the intermediateduration inhalation MRL for 1,4-dioxane, nuclear enlargement will not be considered a suitable basis for 

derivation of an MRL because it may represent a pre-neoplastic lesion. Incidences of atrophy (0/50, 

40/50, 47/50, and 48/50) and respiratory metaplasia (11/50, 34/50, 49/50, and 48/50) of the olfactory 

epithelium were also significantly elevated at all exposure levels tested. Of these two lesions, the atrophy 

of the olfactory epithelium was selected as the critical effect for MRL derivation because it showed a 

higher incidence rate at the LOAEL than respiratory metaplasia. Because the incidence of this lesion at 

the lowest exposure level (50 ppm) was close to the maximal response level (80% of 50-ppm animals 

showed this lesion), BMD analysis of the data was not conducted. This decision is in accordance with 

guidelines stating that studies in which responses are at or near the maximal response level are not 

considered adequate for BMD analysis (EPA 2000a). 

Dose and end point used for MRL derivation: 50 ppm; LOAEL for atrophy of the olfactory epithelium of 

the nasal cavity in male rats. 

[ ] NOAEL [ X] LOAEL 

Uncertainty Factors used in MRL derivation: 

[X] 10 for use of a LOAEL 

[X] 3 for extrapolation from animals to humans with dosimetric adjustment 

[X] 10 for human variability 

Was a conversion used from ppm in food or water to a mg/body weight dose? Not applicable. 

If an inhalation study in animals, list the conversion factors used in determining human equivalent dose: 

The chronic-duration inhalation MRL was calculated using EPA’s methodology (EPA 1994) for a 

category 3 gas, as explained in detail in Section 2.3 (derivation of the intermediate-duration inhalation 

MRL). A duration adjustment (6/24 hours x 5/7 days) seemed appropriate in the absence of information 

regarding whether Haber’s Law is applicable under the experimental conditions of the study. 

The MRL is derived as follows: 

LOAEL[HEC] = LOAEL[ADJ] x (Hb/gA / Hb/gH) 

where:
	

LOAEL[ADJ] = 50 ppm x 6/24 hours x 5/7 days = 8.9286 ppm and 

Hb/gA = animal blood:air partition coefficient = 1,861 (Sweeney et al. 2008)
	

Hb/gH = human blood:air partition coefficient = 1,666 (Sweeney et al. 2008)
	

(Hb/gA / Hb/gH) = 1,861/1,666 = 1.117 

Because the ratio of the partition coefficients is higher than 1, a default value of 1 is used in accordance 

with EPA’s RfC methodology (EPA 1994). 

LOAEL[HEC] = 8.9286 ppm x 1 = 8.9286 ppm 

Other additional studies or pertinent information which lend support to this MRL: In a study conducted 

by Torkelson et al. (1974), groups of Wistar rats (288/sex) were exposed to 1,4-dioxane vapors at a 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-17 

APPENDIX A 

concentration of 0.4 mg/L (111 ppm) 7 hours/day, 5 days/week for 2 years. Controls were exposed to 

filtered room air. End points examined included clinical signs, eye and nasal irritation, skin condition, 

respiratory distress, and tumor formation. Hematological parameters (hemoglobin, red blood cell count, 

total and differential leukocyte counts, corpuscular volume) were determined after 16 and 23 months of 

exposure. Blood collected at termination was used also for determination of clinical chemistry 

parameters (serum ALT and alkaline phosphatase activity, BUN, total protein). Liver, kidneys, and 

spleen were weighed and the major tissues and organs were processed for microscopic examination. 

Exposure to 1,4-dioxane vapors had no significant effect on mortality or body weight gain and induced no 

signs of eye or nasal irritation or respiratory distress. Slight but statistically significant changes in 

hematological and clinical chemistry parameters were within the normal physiological limits and were 

considered of no toxicological importance. Organ weights were not significantly affected. Microscopic 

examination of organs and tissues did not reveal treatment-related effects. It should be noted, however, 

that the tissues from the nasal cavity were not listed among the tissues that were subjected to microscopic 

examination by Torkelson et al. (1974); therefore, the possibility exists that nasal lesions were present but 

were not detected. This possibility is strengthened by the results of Kasai et al. (2008) that reported a 

significant incidence of nasal lesions in rats following inhalation exposure to 100 ppm 1,4-dioxane for 

13 weeks. 

Agency Contact (Chemical Manager): Sharon Wilbur 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-18 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: 1,4-Dioxane 

CAS Number: 123-91-1 

Date: August 2011 

Profile Status: Final 

Route: [ ] Inhalation [X] Oral 

Duration: [X] Acute [ ] Intermediate [ ] Chronic 

Graph Key: 18 

Species: Rat 

Minimal Risk Level: 5 [X] mg/kg/day [ ] ppm 

Reference: Giavini E, Vismara C, Broccia MA. 1985. Teratogenesis study of dioxane in rats. Toxicol 

Letters 26:85-88. 

Experimental design: Groups of 17–20 pregnant Sprague-Dawley rats were treated with 0, 0.25, 0.5, or 

1 mL 1,4-dioxane/kg/day (0, 258, 516, or 1,033 mg 1,4-dioxane/kg/day based on a specific gravity of 

1.034) by gavage in water on Gds 6–15. Food consumption was determined daily and body weight was 

monitored every 3 days. Sacrifices were conducted on Gd 21 and the number of corpora lutea, 

implantations, resorptions, and liver fetuses was recorded. The fetuses were weighed and inspected for 

external malformations and half were examined for visceral abnormalities; the other half were examined 

for skeletal malformations. 

Effects noted in study and corresponding doses: Rats treated with 1,033 mg 1,4-dioxane/kg/day gained 

18% less weight than controls during treatment days, although the difference was not statistically 

significant. Food consumption was slightly (5%) but significantly (p<0.05) reduced in these rats during 

treatment. The average fetal weight in the high-dose group was slightly but significantly (p<0.01) lower 

than in controls. Also, a slight but significant (p<0.05) reduction in sternum ossification was seen in 

high-dose fetuses. There were no significant effects on the number of implantations and live fetuses, 

post-implantation loss, or incidence of malformations. Based on the reduced maternal and fetal body 

weight and reduced sternum ossification, a maternal and developmental LOAEL of 1,013 mg 

1,4-dioxane/kg/day can be defined; the maternal and developmental NOAEL is 516 mg/kg/day. Attempts 

made to apply dose-response models to the data were unsuccessful, as no adequate fits of EPA BMDS 

models to the data were obtained; therefore, the NOAEL/LOAEL approach was used for MRL derivation. 

Dose and end point used for MRL derivation: 516 mg/kg/day; NOAEL for developmental and maternal 

effects in rats. 

[X] NOAEL [ ] LOAEL 

Uncertainty Factors used in MRL derivation: 

[ ] for use of a LOAEL 

[X] 10 for extrapolation from animals to humans 

[X] 10 for human variability 

Was a conversion used from ppm in food or water to a mg/body weight dose? A conversion was done 

from mL of 1,4-dioxane to mg of 1,4-dioxane using the specific gravity of 1,4-dioxane. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-19 

APPENDIX A 

If an inhalation study in animals, list the conversion factors used in determining human equivalent dose: 

Not applicable. 

Other additional studies or pertinent information which lend support to this MRL: JRBC (1998) 

conducted a 2-week drinking water study in F344 rats and B6C3F1 mice and reported that the most 

sensitive effect was an increased incidence of nuclear enlargement of the olfactory epithelium in male and 

female rats receiving doses of approximately 1,010 and 1,040 mg 1,4-dioxane/kg/day, respectively; the 

corresponding NOAELs were 370 and 400 mg/kg/day. The use of the nasal lesions as the point of 

departure for MRL derivation was precluded by recent data strongly suggesting that these lesions in rats 

are due to direct contact of the drinking water containing 1,4-dioxane with nasal epithelium while the rats 

drink the water(Sweeney et al. 2008). Increased incidence of hepatocyte swelling and vacuolation and 

hydropic changes in the renal proximal tubule were also reported in male and female rats dosed with 

2,960 and 2,750 mg 1,4-dioxane/kg/day, respectively; the corresponding NOAELs were 1,010 and 

1,040 mg/kg/day. Although the NOAELs for liver and kidney changes could have been considered as 

points of departure for MRL derivation, several study limitations, including the lack of statistical analysis 

of the results due to the fact that only 2 or 3 animals (out of 10/group) were examined, and the fact that 

end points such as hematology, clinical chemistry, clinical signs, and gross examinations were not 

conducted or reported, severely compromise the interpretation of the results. 

Agency Contact (Chemical Manager): Sharon Wilbur 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-20 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: 1,4-Dioxane 

CAS Number: 123-91-1 

Date: August 2011 

Profile Status: Final 

Route: [ ] Inhalation [X] Oral 

Duration: [ ] Acute [X] Intermediate [ ] Chronic 

Graph Key: 22 

Species: Rat 

Minimal Risk Level: 0.5 [X] mg/kg/day [ ] ppm 

Reference: Kano et al. 2008. Thirteen-week oral toxicity of 1,4-dioxane in rats and mice. J Toxicol Sci 

33:141-153. 

Experimental design: The intermediate-duration oral MRL is based on a NOAEL of 52 mg 1,4-dioxane/ 

kg/day for liver effects in rats. Groups of F344/DuCrj rats (10/sex/group) were administered 1,4-dioxane 

in the drinking water in concentrations of 0, 640, 1,600, 4,000, 10,000, or 25,000 ppm for 13 weeks (0, 

52, 126, 274, 657, or 1,554 mg/kg/day in males; 0, 83, 185, 427, 756, or 1,614 mg/kg/day in females, 

estimated by the investigators). End points evaluated included clinical signs (daily), food (once a week) 

and water consumption (daily), body weight (once a week), complete hematology and clinical chemistry 

tests (at termination), urinalysis (at termination), organ weights, gross necropsy and histopathology. 

Effects noted in study and corresponding doses: One female in the 1,614 mg/kg/day group died. Body 

weight gain was reduced at 756 mg/kg/day (12%) and 1,614 mg/kg/day (21%) in females and at 

1,554 mg/kg/day (21%) in males. Food consumption was reduced 13% in females at 1,614 mg/kg/day. 

Water consumption was reduced in a dose-related manner in all male groups and in females at 

≥126 mg/kg/day. Hematology tests showed significant increases in erythrocyte counts, hemoglobin, 

hematocrit, and neutrophils, and a decrease in lymphocytes in males at 1,554 mg/kg/day, and decreases in 

mean corpuscular volume and platelets in females at 1,614 mg/kg/day. Total protein and albumin were 

decreased in males at ≥274 mg/kg/day and in females at ≥427 mg/kg/day. Serum AST, ALT, AP, and 

LAP activities, and levels of cholesterol, triglycerides, sodium, and glucose were significantly elevated in 

high dose males and females. Urinary pH was decreased in males at ≥274 mg/kg/day and in females at 

≥756 mg/kg/day. Absolute and relative kidney weights were increased in females at ≥231 mg/kg/day. 

Nuclear enlargement of the respiratory epithelium occurred in males at ≥126 mg/kg/day and in females at 

≥185 mg/kg/day; nuclear enlargement of the olfactory and tracheal epithelium occurred in males at 

≥274 mg/kg/day and in females at ≥427 mg/kg/day. Swelling of the central area of the liver was observed 

in males at ≥126 mg/kg/day and in females at ≥756 mg/kg/day, and vacuolar changes in the liver occurred 

in males at ≥657 mg/kg/day and in females at 1,614 mg/kg/day. The incidences of swelling of the central 

area of the liver in males were 0/10, 0/10, 9/10, 10/10, 10/10, and 10/10 in the control, 52, 126, 274, 657, 

and 1,554 mg/kg/day dose groups, respectively. Nuclear enlargement of the proximal tubule of the 

kidneys was seen in males at ≥657 mg/kg/day and in females at ≥756 mg/kg/day. Hydropic changes in 

the proximal tubule of the kidneys and vacuolar changes in the brain occurred in high-dose males and 

females (1,554 and 1,614 mg/kg/day, respectively). The study LOAEL was 126 mg/kg/day for liver 

effects in male rats. Limitations of the study include the lack of reporting on clinical signs and gross 

necropsy. To derive the MRL, the NOAEL of 52 mg/kg/day for liver effects in males was divided by an 

uncertainty factor of 100 (10 for animal to human extrapolation and 10 for human variability), yielding an 

intermediate-duration oral MRL of 0.5 mg/kg/day. The steepness of the dose-response relationship for 

liver lesions rendered the data set inadequate for BMD analysis. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-21 

APPENDIX A 

Dose and end point used for MRL derivation: 52 mg/kg/day; NOAEL for liver effects in rats. 

[X] NOAEL [ ] LOAEL 

Uncertainty Factors used in MRL derivation: 

[ ] for use of a LOAEL 

[X] 10 for extrapolation from animals to humans 

[X] 10 for human variability 

Was a conversion used from ppm in food or water to a mg/body weight dose? The conversion was done 

by the investigators, and the doses listed are means of ranges provided by the investigators. 

If an inhalation study in animals, list the conversion factors used in determining human equivalent dose: 

Not applicable. 

Other additional studies or pertinent information which lend support to this MRL: A study by Lundberg 

et al. 1987) supports the liver findings of Kano et al. (2008). The study used male Sprague-Dawley rats 

(8–11/group) that were treated with 100 or 1,000 mg 1,4-dioxane/kg by gavage in saline 5 days/week for 

7 weeks. One week after the last treatment, the rats were killed and the livers were processed for 

microscopic examination. The livers of high-dose rats showed enlarged foamy hepatocytes mainly in 

midzonal regions. The foamy appearance was due to vacuoles shown to contain fat. No treatment-related 

histopathological alterations were observed in the liver at the 100 mg/kg/day dose level. Also supporting 

the findings from Kano et al. (2008) is a report by Stott et al. (1981) who found that repeated dosing of 

rats with 1,000 mg 1,4-dioxane/kg/day for 7 or 11 weeks produced hepatocyte swelling and 

histopathology. Similar findings were reported in an earlier study in which rats were treated with doses of 

approximately 1,428 mg 1,4-dioxane/kg/day in the drinking water for 34 days (Fairley et al. 1934). 

Agency Contact (Chemical Manager): Sharon Wilbur 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-22 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: 1,4-Dioxane 

CAS Number: 123-91-1 

Date: August 2011 

Profile Status: Final 

Route: [ ] Inhalation [X] Oral 

Duration: [ ] Acute [ ] Intermediate [X] Chronic 

Graph Key: 39 

Species: Rat 

Minimal Risk Level: 0.1 [X] mg/kg/day [ ] ppm 

Reference: Kociba RJ, McCollister SB, Park C, et al. 1974. 1,4-Dioxane. I. Results of a 2-year 

ingestion study in rats. Toxicol Appl Pharmacol 30:275-286. 

Experimental design: Groups of Sherman rats (60/sex/dose level) were treated with 1,4-dioxane in the 

drinking water at levels of 0 (controls), 0.01, 0.1, or 1% for 716 days. Based on body weight and water 

consumption data, the investigators estimated that the water provided doses of 1,4-dioxane of 0, 9.6, 94, 

and 1,015 mg/kg/day for males and 0, 19, 148, and 1,599 mg/kg/day for females. Blood samples were 

collected from controls and high-dose rats during the 4th, 6th, 12th, and 18th months of the study and at 

termination. Additional end points evaluated included clinical signs, body weight, organ weights, and 

gross and microscopic examination of major tissues and organs. 

Effects noted in study and corresponding doses: Treatment with 1,4-dioxane significantly increased 

mortality in high-dose males and females beginning at about 2–4 months of treatment. These rats showed 

degenerative changes in both the liver and kidneys. Body weight gain was significantly reduced in highdose animals from the beginning of the study. Microscopic lesions were restricted to the liver and 

kidneys from the mid- and high-dose groups. The liver lesions consisted of various degrees of 

hepatocellular degeneration and necrosis and evidence of hepatic regeneration as indicated by 

hepatocellular hyperplastic nodule formation. The NOAEL for liver effects was 9.6 mg/kg/day in males 

and 19 mg/kg/day in females. The LOAELs were 94 mg/kg/day in males and 148 mg/kg/day in females. 

The kidneys showed tubular epithelial degeneration and necrosis, and there was evidence of renal tubular 

regeneration as indicated by increased tubular epithelial regenerative activity (≥94 mg/kg/day in males 

and ≥148 mg/kg/day in females). There were no compound-related alterations in hematological 

parameters at any time point. The MRL of 0.1 mg/kg/day was calculated by dividing the male rat 

NOAEL of 9.6 mg/kg/day by an uncertainty factor of 100 (10 for animal to human extrapolation and 

10 for human variability). The lack of quantitative information regarding incidences of non-neoplastic 

lesions precludes the use of BMD methodology for MRL derivation. 

Dose and end point used for MRL derivation: 9.6 mg/kg/day; NOAEL for liver effects in rats. 

[X] NOAEL [ ] LOAEL 

Uncertainty Factors used in MRL derivation: 

[ ] for use of a LOAEL 

[X] 10 for extrapolation from animals to humans 

[X] 10 for human variability 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE A-23 

APPENDIX A 

Was a conversion used from ppm in food or water to a mg/body weight dose? A conversion was done by 

the investigators. 

If an inhalation study in animals, list the conversion factors used in determining human equivalent dose: 

Not applicable. 

Other additional studies or pertinent information which lend support to this MRL: The NOAEL and 

LOAEL for liver effects from Kociba et al. (1974) are supported by the results of Kano et al. (2009). In 

that study, groups of F344/DuCrj rats (50/sex/dose level) received 1,4-dioxane in the drinking water for 

104 weeks. 1,4-Dioxane was administered at levels of 0, 200, 1,000, and 5,000 ppm for 2 years (0, 11, 

55, and 274 mg/kg/day for males; 0, 18, 83, and 429 mg/kg/day for females). End points evaluated 

included clinical signs, food and water consumption, body and organ weights, and gross and microscopic 

examination of major organs and tissues. Terminal body weight was reduced 9% in high-dose males 

(274 mg/kg/day) and 20% in high-dose females (429 mg/kg/day). In males, relative liver weight was 

significantly increased at 55 mg/kg/day (14%) and 274 mg/kg/day (72%). A significant increased 

incidence of mixed cell foci was observed in the liver from male rats dosed with ≥55 mg 

1,4-dioxane/kg/day. Increased incidence of acidophilic and mixed cell foci were reported in the liver 

from high-dose females (429 mg/kg/day). In addition, both high-dose male (274 mg/kg/day) and female 

(429 mg/kg/day) rats had significantly increased incidence of nuclear enlargement and squamous cell 

metaplasia of the respiratory epithelium; females dosed with ≥83 mg 1,4-dioxane/kg/day also showed 

significantly increased incidence of nuclear enlargement of the nasal olfactory epithelium. 

The NCI (1978) bioassay in Osborne-Mendel rats used somewhat higher dose levels than Kociba et al. 

(1974) and Kano et al. (2009), but did not observe liver lesions in male rats dosed with 240 mg 

1,4-dioxane/kg/day, a dose level that caused liver hyperplasia in male F344 rats dosed with 81 mg/kg/day 

or that caused hepatocyte degeneration in Sherman rats dosed with 94 mg/kg/day. Since the dosing 

method was the same in the three studies, the drinking water, the different results may reflect differences 

in strain sensitivity. 

Agency Contact (Chemical Manager): Sharon Wilbur 
1,4-DIOXANE A-24 
 

APPENDIX A 

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1,4-DIOXANE	 B-1 

APPENDIX B. USER'S GUIDE 

Chapter 1 

Public Health Statement 

This chapter of the profile is a health effects summary written in non-technical language. Its intended 

audience is the general public, especially people living in the vicinity of a hazardous waste site or 

chemical release. If the Public Health Statement were removed from the rest of the document, it would 

still communicate to the lay public essential information about the chemical. 

The major headings in the Public Health Statement are useful to find specific topics of concern. The 

topics are written in a question and answer format. The answer to each question includes a sentence that 

will direct the reader to chapters in the profile that will provide more information on the given topic. 

Chapter 2 

Relevance to Public Health 

This chapter provides a health effects summary based on evaluations of existing toxicologic, 

epidemiologic, and toxicokinetic information. This summary is designed to present interpretive, weightof-evidence discussions for human health end points by addressing the following questions: 

1. What effects are known to occur in humans? 

2. What effects observed in animals are likely to be of concern to humans? 

3. What exposure conditions are likely to be of concern to humans, especially around hazardous 

waste sites? 

The chapter covers end points in the same order that they appear within the Discussion of Health Effects 

by Route of Exposure section, by route (inhalation, oral, and dermal) and within route by effect. Human 

data are presented first, then animal data. Both are organized by duration (acute, intermediate, chronic). 

In vitro data and data from parenteral routes (intramuscular, intravenous, subcutaneous, etc.) are also 

considered in this chapter. 

The carcinogenic potential of the profiled substance is qualitatively evaluated, when appropriate, using 

existing toxicokinetic, genotoxic, and carcinogenic data. ATSDR does not currently assess cancer 

potency or perform cancer risk assessments. Minimal Risk Levels (MRLs) for noncancer end points (if 

derived) and the end points from which they were derived are indicated and discussed. 

Limitations to existing scientific literature that prevent a satisfactory evaluation of the relevance to public 

health are identified in the Chapter 3 Data Needs section. 

Interpretation of Minimal Risk Levels 

Where sufficient toxicologic information is available, ATSDR has derived MRLs for inhalation and oral 

routes of entry at each duration of exposure (acute, intermediate, and chronic). These MRLs are not 

meant to support regulatory action, but to acquaint health professionals with exposure levels at which 

adverse health effects are not expected to occur in humans. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE B-2 

APPENDIX B 

MRLs should help physicians and public health officials determine the safety of a community living near 

a chemical emission, given the concentration of a contaminant in air or the estimated daily dose in water. 

MRLs are based largely on toxicological studies in animals and on reports of human occupational 

exposure. 

MRL users should be familiar with the toxicologic information on which the number is based. Chapter 2, 

"Relevance to Public Health," contains basic information known about the substance. Other sections such 

as Chapter 3 Section 3.9, "Interactions with Other Substances,” and Section 3.10, "Populations that are 

Unusually Susceptible" provide important supplemental information. 

MRL users should also understand the MRL derivation methodology. MRLs are derived using a 

modified version of the risk assessment methodology that the Environmental Protection Agency (EPA) 

provides (Barnes and Dourson 1988) to determine reference doses (RfDs) for lifetime exposure. 

To derive an MRL, ATSDR generally selects the most sensitive end point which, in its best judgement, 

represents the most sensitive human health effect for a given exposure route and duration. ATSDR 

cannot make this judgement or derive an MRL unless information (quantitative or qualitative) is available 

for all potential systemic, neurological, and developmental effects. If this information and reliable 

quantitative data on the chosen end point are available, ATSDR derives an MRL using the most sensitive 

species (when information from multiple species is available) with the highest no-observed-adverse-effect 

level (NOAEL) that does not exceed any adverse effect levels. When a NOAEL is not available, a 

lowest-observed-adverse-effect level (LOAEL) can be used to derive an MRL, and an uncertainty factor 

(UF) of 10 must be employed. Additional uncertainty factors of 10 must be used both for human 

variability to protect sensitive subpopulations (people who are most susceptible to the health effects 

caused by the substance) and for interspecies variability (extrapolation from animals to humans). In 

deriving an MRL, these individual uncertainty factors are multiplied together. The product is then 

divided into the inhalation concentration or oral dosage selected from the study. Uncertainty factors used 

in developing a substance-specific MRL are provided in the footnotes of the levels of significant exposure 

(LSE) tables. 

Chapter 3 

Health Effects 

Tables and Figures for Levels of Significant Exposure (LSE) 

Tables and figures are used to summarize health effects and illustrate graphically levels of exposure 

associated with those effects. These levels cover health effects observed at increasing dose 

concentrations and durations, differences in response by species, MRLs to humans for noncancer end 

points, and EPA's estimated range associated with an upper- bound individual lifetime cancer risk of 1 in 

10,000 to 1 in 10,000,000. Use the LSE tables and figures for a quick review of the health effects and to 

locate data for a specific exposure scenario. The LSE tables and figures should always be used in 

conjunction with the text. All entries in these tables and figures represent studies that provide reliable, 

quantitative estimates of NOAELs, LOAELs, or Cancer Effect Levels (CELs). 

The legends presented below demonstrate the application of these tables and figures. Representative 

examples of LSE Table 3-1 and Figure 3-1 are shown. The numbers in the left column of the legends 

correspond to the numbers in the example table and figure. 
 

 

 

 

 

 

 

 

 

 

 

 

 

	 

	 

 

 

 

	 

 

 

	 

 

 

	 

 

	 

 

	 

 

 

 

	 

 

 

 

	 

 

1,4-DIOXANE	 B-3 

APPENDIX B 

LEGEND 

See Sample LSE Table 3-1 (page B-6) 

(1)		 Route of Exposure. One of the first considerations when reviewing the toxicity of a substance 

using these tables and figures should be the relevant and appropriate route of exposure. Typically 

when sufficient data exist, three LSE tables and two LSE figures are presented in the document. 

The three LSE tables present data on the three principal routes of exposure, i.e., inhalation, oral, 

and dermal (LSE Tables 3-1, 3-2, and 3-3, respectively). LSE figures are limited to the inhalation 

(LSE Figure 3-1) and oral (LSE Figure 3-2) routes. Not all substances will have data on each 

route of exposure and will not, therefore, have all five of the tables and figures. 

(2)		 Exposure Period. Three exposure periods—acute (less than 15 days), intermediate (15– 

364 days), and chronic (365 days or more)—are presented within each relevant route of exposure. 

In this example, an inhalation study of intermediate exposure duration is reported. For quick 

reference to health effects occurring from a known length of exposure, locate the applicable 

exposure period within the LSE table and figure. 

(3)		 Health Effect. The major categories of health effects included in LSE tables and figures are 

death, systemic, immunological, neurological, developmental, reproductive, and cancer. 

NOAELs and LOAELs can be reported in the tables and figures for all effects but cancer. 

Systemic effects are further defined in the "System" column of the LSE table (see key number 

18). 

(4)		 Key to Figure. Each key number in the LSE table links study information to one or more data 

points using the same key number in the corresponding LSE figure. In this example, the study 

represented by key number 18 has been used to derive a NOAEL and a Less Serious LOAEL 

(also see the two "18r" data points in sample Figure 3-1). 

(5)		 Species. The test species, whether animal or human, are identified in this column. Chapter 2, 

"Relevance to Public Health," covers the relevance of animal data to human toxicity and 

Section 3.4, "Toxicokinetics," contains any available information on comparative toxicokinetics. 

Although NOAELs and LOAELs are species specific, the levels are extrapolated to equivalent 

human doses to derive an MRL. 

(6)		 Exposure Frequency/Duration. The duration of the study and the weekly and daily exposure 

regimens are provided in this column. This permits comparison of NOAELs and LOAELs from 

different studies. In this case (key number 18), rats were exposed to “Chemical x” via inhalation 

for 6 hours/day, 5 days/week, for 13 weeks. For a more complete review of the dosing regimen, 

refer to the appropriate sections of the text or the original reference paper (i.e., Nitschke et al. 

1981). 

(7)		 System. This column further defines the systemic effects. These systems include respiratory, 

cardiovascular, gastrointestinal, hematological, musculoskeletal, hepatic, renal, and 

dermal/ocular. "Other" refers to any systemic effect (e.g., a decrease in body weight) not covered 

in these systems. In the example of key number 18, one systemic effect (respiratory) was 

investigated. 

(8)		 NOAEL. A NOAEL is the highest exposure level at which no harmful effects were seen in the 

organ system studied. Key number 18 reports a NOAEL of 3 ppm for the respiratory system, 

which was used to derive an intermediate exposure, inhalation MRL of 0.005 ppm (see 

footnote "b"). 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

	 

	 

 

 

 

 

	 

	 

 

	 

 

 

	 

 

	 

 

	 

	 

 

 

	 

1,4-DIOXANE	 B-4 

APPENDIX B 

(9)		 LOAEL. A LOAEL is the lowest dose used in the study that caused a harmful health effect. 

LOAELs have been classified into "Less Serious" and "Serious" effects. These distinctions help 

readers identify the levels of exposure at which adverse health effects first appear and the 

gradation of effects with increasing dose. A brief description of the specific end point used to 

quantify the adverse effect accompanies the LOAEL. The respiratory effect reported in key 

number 18 (hyperplasia) is a Less Serious LOAEL of 10 ppm. MRLs are not derived from 

Serious LOAELs. 

(10)		 Reference. The complete reference citation is given in Chapter 9 of the profile. 

(11)		 CEL. A CEL is the lowest exposure level associated with the onset of carcinogenesis in 

experimental or epidemiologic studies. CELs are always considered serious effects. The LSE 

tables and figures do not contain NOAELs for cancer, but the text may report doses not causing 

measurable cancer increases. 

(12)		 Footnotes. Explanations of abbreviations or reference notes for data in the LSE tables are found 

in the footnotes. Footnote "b" indicates that the NOAEL of 3 ppm in key number 18 was used to 

derive an MRL of 0.005 ppm. 

LEGEND 

See Sample Figure 3-1 (page B-7) 

LSE figures graphically illustrate the data presented in the corresponding LSE tables. Figures help the 

reader quickly compare health effects according to exposure concentrations for particular exposure 

periods. 

(13)		 Exposure Period. The same exposure periods appear as in the LSE table. In this example, health 

effects observed within the acute and intermediate exposure periods are illustrated. 

(14)		 Health Effect. These are the categories of health effects for which reliable quantitative data 

exists. The same health effects appear in the LSE table. 

(15)		 Levels of Exposure. Concentrations or doses for each health effect in the LSE tables are 

graphically displayed in the LSE figures. Exposure concentration or dose is measured on the log 

scale "y" axis. Inhalation exposure is reported in mg/m3

 or ppm and oral exposure is reported in 

mg/kg/day. 

(16)		 NOAEL. In this example, the open circle designated 18r identifies a NOAEL critical end point in 

the rat upon which an intermediate inhalation exposure MRL is based. The key number 18 

corresponds to the entry in the LSE table. The dashed descending arrow indicates the 

extrapolation from the exposure level of 3 ppm (see entry 18 in the table) to the MRL of 

0.005 ppm (see footnote "b" in the LSE table). 

(17)		 CEL. Key number 38m is one of three studies for which CELs were derived. The diamond 

symbol refers to a CEL for the test species-mouse. The number 38 corresponds to the entry in the 

LSE table. 
 

 

 

	 

	 

 

 

	 

1,4-DIOXANE	 B-5 

APPENDIX B 

(18)		 Estimated Upper-Bound Human Cancer Risk Levels. This is the range associated with the upperbound for lifetime cancer risk of 1 in 10,000 to 1 in 10,000,000. These risk levels are derived 

from the EPA's Human Health Assessment Group's upper-bound estimates of the slope of the 

cancer dose response curve at low dose levels (q1*). 

(19)		 Key to LSE Figure. The Key explains the abbreviations and symbols used in the figure. 
1 

2 3 4 12 

→

SAMPLE 

Table 3-1. Levels of Significant Exposure to [Chemical x] – Inhalatio

→→

Exposure 

Key to frequency/ figurea Species duration 

INTERMEDIATE EXPOSURE 

5 6 

Systemic ↓ ↓

NOAEL 

System (ppm) 

7 8 ↓ ↓

LOAEL (effect) Less serious (ppm) 9 

↓

Serious (ppm) 

Re

10 

↓

→→

18 Rat 13 wk Resp 3b 10 (hyperplasia) 

5 d/wk Nit6 hr/d 

CHRONIC EXPOSURE Cancer 11 

↓

38 Rat 18 mo 20 (CEL, multiple Wo

5 d/wk organs) 7 hr/d 

39 Rat 89–104 wk 10 (CEL, lung tumors, NT

5 d/wk nasal tumors) 6 hr/d 

40 Mouse 79–103 wk 10 (CEL, lung tumors, NT

5 d/wk hemangiosarcomas) 6 hr/d 

a The number corresponds to entries in Figure 3-1. b Used to derive an intermediate inhalation Minimal Risk Level (MRL) of 5x10-3 ppm; dose adjusted for intermittent ex

by an uncertainty factor of 100 (10 for extrapolation from animal to humans, 10 for human variability). 

1,4-DIOXANE B-8 
 

APPENDIX B 

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1,4-DIOXANE C-1 

APPENDIX C. ACRONYMS, ABBREVIATIONS, AND SYMBOLS
	

ACGIH American Conference of Governmental Industrial Hygienists 

ACOEM American College of Occupational and Environmental Medicine 

ADI acceptable daily intake 

ADME absorption, distribution, metabolism, and excretion 

AED atomic emission detection 

AFID alkali flame ionization detector 

AFOSH Air Force Office of Safety and Health 

ALT alanine aminotransferase 

AML acute myeloid leukemia 

AOAC Association of Official Analytical Chemists 

AOEC Association of Occupational and Environmental Clinics 

AP alkaline phosphatase 

APHA American Public Health Association 

AST aspartate aminotransferase 

atm atmosphere 

ATSDR Agency for Toxic Substances and Disease Registry 

AWQC Ambient Water Quality Criteria 

BAT best available technology 

BCF bioconcentration factor 

BEI Biological Exposure Index 

BMD benchmark dose 

BMR benchmark response 

BSC Board of Scientific Counselors 

C centigrade 

CAA Clean Air Act 

CAG Cancer Assessment Group of the U.S. Environmental Protection Agency 

CAS Chemical Abstract Services 

CDC Centers for Disease Control and Prevention 

CEL cancer effect level 

CELDS Computer-Environmental Legislative Data System 

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

CFR Code of Federal Regulations 

Ci curie 

CI confidence interval 

CL ceiling limit value 

CLP Contract Laboratory Program 

cm centimeter 

CML chronic myeloid leukemia 

CPSC Consumer Products Safety Commission 

CWA Clean Water Act 

DHEW Department of Health, Education, and Welfare 

DHHS Department of Health and Human Services 

DNA deoxyribonucleic acid 

DOD Department of Defense 

DOE Department of Energy 

DOL Department of Labor 

DOT Department of Transportation 

DOT/UN/ Department of Transportation/United Nations/ 

NA/IMCO North America/Intergovernmental Maritime Dangerous Goods Code 
 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE C-2 

APPENDIX C 

DWEL drinking water exposure level 

ECD electron capture detection 

ECG/EKG electrocardiogram 

EEG electroencephalogram 

EEGL Emergency Exposure Guidance Level 

EPA Environmental Protection Agency 

F Fahrenheit F1 first-filial generation 

FAO Food and Agricultural Organization of the United Nations 

FDA Food and Drug Administration 

FEMA Federal Emergency Management Agency 

FIFRA Federal Insecticide, Fungicide, and Rodenticide Act 

FPD flame photometric detection 

fpm feet per minute 

FR Federal Register 

FSH follicle stimulating hormone 

g gram 

GC gas chromatography 

gd gestational day 

GLC gas liquid chromatography 

GPC gel permeation chromatography 

HPLC high-performance liquid chromatography 

HRGC high resolution gas chromatography 

HSDB Hazardous Substance Data Bank 

IARC International Agency for Research on Cancer 

IDLH immediately dangerous to life and health 

ILO International Labor Organization 

IRIS Integrated Risk Information System 

Kd adsorption ratio 

kg kilogram 

kkg metric ton Koc organic carbon partition coefficient Kow octanol-water partition coefficient 

L liter 

LC liquid chromatography 

LC50 lethal concentration, 50% kill 

LCLo lethal concentration, low 

LD50 lethal dose, 50% kill 

LDLo lethal dose, low 

LDH lactic dehydrogenase 

LH luteinizing hormone 

LOAEL lowest-observed-adverse-effect level 

LSE Levels of Significant Exposure 

LT50 lethal time, 50% kill 

m meter 

MA trans,trans-muconic acid 

MAL maximum allowable level 

mCi millicurie 

MCL maximum contaminant level 

MCLG maximum contaminant level goal 

MF modifying factor 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE C-3 

APPENDIX C 

MFO mixed function oxidase 

mg milligram 

mL milliliter 

mm millimeter 

mmHg millimeters of mercury 

mmol millimole 

mppcf millions of particles per cubic foot 

MRL Minimal Risk Level 

MS mass spectrometry 

NAAQS National Ambient Air Quality Standard 

NAS National Academy of Science 

NATICH National Air Toxics Information Clearinghouse 

NATO North Atlantic Treaty Organization 

NCE normochromatic erythrocytes 

NCEH National Center for Environmental Health 

NCI National Cancer Institute 

ND not detected 

NFPA National Fire Protection Association 

ng nanogram 

NHANES National Health and Nutrition Examination Survey 

NIEHS National Institute of Environmental Health Sciences 

NIOSH National Institute for Occupational Safety and Health 

NIOSHTIC NIOSH's Computerized Information Retrieval System 

NLM National Library of Medicine 

nm nanometer 

nmol nanomole 

NOAEL no-observed-adverse-effect level 

NOES National Occupational Exposure Survey 

NOHS National Occupational Hazard Survey 

NPD nitrogen phosphorus detection 

NPDES National Pollutant Discharge Elimination System 

NPL National Priorities List 

NR not reported 

NRC National Research Council 

NS not specified 

NSPS New Source Performance Standards 

NTIS National Technical Information Service 

NTP National Toxicology Program 

ODW Office of Drinking Water, EPA 

OERR Office of Emergency and Remedial Response, EPA 

OHM/TADS Oil and Hazardous Materials/Technical Assistance Data System 

OPP Office of Pesticide Programs, EPA 

OPPT Office of Pollution Prevention and Toxics, EPA 

OPPTS Office of Prevention, Pesticides and Toxic Substances, EPA 

OR odds ratio 

OSHA Occupational Safety and Health Administration 

OSW Office of Solid Waste, EPA 

OTS Office of Toxic Substances 

OW Office of Water 

OWRS Office of Water Regulations and Standards, EPA 

PAH polycyclic aromatic hydrocarbon 
 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE C-4 

APPENDIX C 

PBPD physiologically based pharmacodynamic 

PBPK physiologically based pharmacokinetic 

PCE polychromatic erythrocytes 

PEL permissible exposure limit 

pg picogram 

PHS Public Health Service 

PID photo ionization detector 

pmol picomole 

PMR proportionate mortality ratio 

ppb parts per billion 

ppm parts per million 

ppt parts per trillion 

PSNS pretreatment standards for new sources 

RBC red blood cell 

REL recommended exposure level/limit 

RfC reference concentration 

RfD reference dose 

RNA ribonucleic acid 

RQ reportable quantity 

RTECS Registry of Toxic Effects of Chemical Substances 

SARA Superfund Amendments and Reauthorization Act 

SCE sister chromatid exchange 

SGOT serum glutamic oxaloacetic transaminase 

SGPT serum glutamic pyruvic transaminase 

SIC standard industrial classification 

SIM selected ion monitoring 

SMCL secondary maximum contaminant level 

SMR standardized mortality ratio 

SNARL suggested no adverse response level 

SPEGL Short-Term Public Emergency Guidance Level 

STEL short term exposure limit 

STORET Storage and Retrieval 

TD50 toxic dose, 50% specific toxic effect 

TLV threshold limit value 

TOC total organic carbon 

TPQ threshold planning quantity 

TRI Toxics Release Inventory 

TSCA Toxic Substances Control Act 

TWA time-weighted average 

UF uncertainty factor 

U.S. United States 

USDA United States Department of Agriculture 

USGS United States Geological Survey 

VOC volatile organic compound 

WBC white blood cell 

WHO World Health Organization 
 

 

1,4-DIOXANE C-5 

APPENDIX C 

> greater than 

≥ greater than or equal to 

= equal to 

< less than 

≤ less than or equal to 

% percent 

α alpha 

β beta 

γ gamma 

δ delta 

μm micrometer 

μg microgram q1

* cancer slope factor 

– negative 

+ positive 

(+) weakly positive result 

(–) weakly negative result 
1,4-DIOXANE C-6 
 

APPENDIX C 

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1,4-DIOXANE D-1 

APPENDIX D. HEALTH ADVISORY 

Health Advisory - An Overview for the Public 

1,4-Dioxane 

August 2007 

Why is 1,4-dioxane currently a potential health concern? 

Conflicting reports 

regarding 

1,4-dioxane 

exposure from use 

of some bath and 

cosmetic products 

Recent reports in the media about 1,4-dioxane contamination of 

children’s bath products prompted ATSDR to reexamine its 

recommendations to families on reducing risks of exposure to 

1,4-dioxane. Note: The acute effects described in this document 

are not likely to occur at concentrations of 1,4-dioxane that are 

normally found in the U.S. environment. 

Why has the Agency for Toxic Substances and Disease Registry (ATSDR) provided this 

health advisory for 1,4-dioxane? 

ATSDR provides 

trusted health 

information to the 

public 

What is 1,4-dioxane? 

1,4-Dioxane is used 

in manufacturing 

and in household 

products 

ATSDR’s mission is to serve the public by using the best science, 

taking responsive public health actions, and providing trusted health 

information to prevent harmful exposures and disease related 

exposures to toxic substances. 

1,4-Dioxane (also called dioxane) is produced in large amounts 

(between 10 million and 18 million pounds in 1990) by three 

companies in the United States. Companies use dioxane: 

• for a solvent for paper, cotton, and textile processing 

• for chemical manufacturing, and 

• in automotive coolant liquid. 
 

 

 

 

 

1,4-DIOXANE D-2 

APPENDIX D 

How are people exposed to 1,4-dioxane? 

Transmission 

through inhalation, 

ingestion, or skin 

contact 

Where is 1,4-dioxane found ? 

1,4-Dioxane enters the body when people breathe air or consume 

water or food contaminated with 1,4-dioxane. People can also be 

exposed following contact with cosmetics, shampoo, or bubble bath 

that contain certain ingredients in which 1,4-dioxane may be a 

contaminant. 1,4-Dioxane does not remain in the body because it 

breaks down into chemicals that are removed quickly. 

Food Traces of 1,4-dioxane can be ingested from: 

• some food supplements 

• food containing residues from packaging adhesives 

• food sprayed with pesticides containing 1,4-dioxane as a 

solvent or inert ingredient 

Ground Water A few communities’ water supplies are contaminated with 

1,4-dioxane. Information on the concentrations of 1,4-dioxane in 

groundwater, surface waters and drinking water are limited. 

Household 

products 

1,4-Dioxane may be present as a trace contaminant in household 

products such as: 

• shampoo 

• liquid dishwashing soap 

• baby lotion 

• hair lotions 

• bath foam 

• and other cosmetic products 

Industrial 

solvents 

1,4-Dioxane is primarily used as an industrial solvent in several 

manufacturing processes. 

Spermicidal 

agents 

1,4-Dioxane is found in some over-the-counter spermicidal sponges. 
 

 

 

 

 

 

 

 

 

 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

1,4-DIOXANE	 D-3 

APPENDIX D 

What are the health effects of 1,4-dioxane exposure? 

Effects of 1,4-dioxane on human health and the environment depend on how much 1,4-dioxane is present 

and the length and frequency of exposures. Note: The acute effects described below are not likely to 

occur at concentrations of 1,4-dioxane that are normally found in the U.S. environment. 

Short-term 

exposure to 

1,4-dioxane 

Long-term exposure 

to 1,4-dioxane 

Reproductive 

health/infants and 

1,4-dioxane 

•	 Breathing: 1,4-Dioxane for short periods of time causes 

irritation of the eyes, nose and throat in humans. Exposure to 

large amounts of 1,4-dioxane can cause kidney and liver 

damage. 

•	 Accidental worker exposure to large amounts of 1,4-dioxane 

has resulted in several deaths. Symptoms associated with 

these industrial deaths suggest 1,4-dioxane causes adverse 

nervous system effects. 

•	 Animal studies: Laboratory studies show that repeated 

exposure to large amounts of 1,4-dioxane in drinking water, in 

air, or on the skin causes liver and kidney damage in animals 

Laboratory studies also show that oral exposure to 1,4-dioxane 

over a lifetime causes cancer in animals. Skin exposure of 

animals to 1,4-dioxane has shown that it can increase the 

cancer-causing properties of other chemicals. 

•	 Human studies: There is little specific information regarding the 

non-cancer outcomes in workers following repeatedly breathing 

small amounts of 1,4-dioxane over long periods of time. 

•	 Cancer classifications: (based on inadequate evidence in 

humans and sufficient evidence in animals): 

o	 Department of Health and Human Services (HHS) 

considers 1,4-dioxane as reasonably anticipated to be 

a human carcinogen. 

o	 Environmental Protection Agency (EPA) established 

that 1,4-dioxane is a probable human carcinogen. 

o	 International Agency for Research on Cancer (IARC) 

has determined that 1,4-dioxane is possibly 

carcinogenic to humans. 

•	 Miscarriage and stillbirths: There are studies that show elevated 

rates of spontaneous abortion and stillbirths associated with 

occupational exposure to a combination of chemicals that 

included 1,4-dioxane, but the role of 1,4-dioxane, if any, is 

unknown. 

•	 Breast milk transfer: A nursing mother exposed to a high 

amount of 1,4-dioxane might pass it to the infant through her 

breast milk. This concern is based on scientific models, not on 

actual data from the breast milk of women exposed to 

1,4-dioxane. 
 

 

 

 

 

	 

	 

	 

	 

	 

	 

1,4-DIOXANE	 D-4 

APPENDIX D 

Is there a medical test to show whether I've been exposed to 1,4-dioxane? 

1,4-Dioxane and its 

breakdown 

products can be 

measured in your 

blood and urine 

1,4-Dioxane and its breakdown products can be measured in your 

blood and urine, and positive results indicate you have been 

exposed to 1,4-dioxane. The tests are not routinely available at 

your doctor’s office because they require special equipment, but the 

doctor can collect the samples and send them to a special 

laboratory. The tests need to be conducted within days after the 

exposure because 1,4-dioxane and its breakdown products leave 

the body fairly rapidly. These tests do not predict whether exposure 

to 1,4-dioxane will produce harmful health effects. 

What levels of 1,4-dioxane are considered acceptable by regulatory agencies? 

1,4-Dioxane levels 

in food set by the 

Food and Drug 

Administration 

(FDA) 

1,4-Dioxane levels 

in cosmeticsvoluntary 

cooperation 

1,4-Dioxane levels 

in ground water 

•	 The National Academy of Sciences (NAS) specified a maximum 

limit of 10 ppm (parts per million) for 1,4-dioxane in the 

ingredient polysorbate, a food additive (NAS 2003). 

•	 FDA also set a limit on 1,4-dioxane at 10 ppm in approving 

glycerides and polyglycerides in products such as dietary 

supplements. This regulation is located at 21 CFR 172.736. 

The FDA regulation for 1,4-dioxane as an indirect food additive 

is also 10 ppm and refers to its use as an adhesive component 

in packaging material. 

•	 FDA’s regulatory legal authority over the cosmetics is different 

from other products regulated by the agency such as drugs, 

biologics, and medical devices. Consequently, FDA must rely, 

in part, on voluntary industry cooperation. 

•	 Whereas the press has recently reported that FDA 

recommends 10 ppm for 1,4-dioxane in cosmetic products, the 

FDA does not have a recommendation for 1,4-dioxane in 

cosmetic products. 

•	 The Environmental Protection Agency (EPA) recommends that 

the levels of 1,4-dioxane in drinking water that children drink for 

1 day not exceed 4 milligrams per liter (mg/L) or 0.4 mg/L, if 

they drink water for 10 days. However, EPA has not 

established a federal drinking water standard (maximum 

contaminant level or MCL). 
 

 

 

 

 

 

	 

 

	 

 

	 

1,4-DIOXANE	 D-5 

APPENDIX D 

What do studies show about the levels of 1,4-dioxane in shampoos and bubble baths? 

Note: Much of the information in this section is from: Black RE, Hurley FJ, Havery DC. 2001. 

Occurrence of 1,4-dioxane in cosmetic raw materials and finished cosmetic products. J AOAC Int 

84(3):666-670. 

1979: 1,4-Dioxane 

identified in raw 

materials used in 

the manufacture of 

cosmetic products 

1980s- Downward 

trend in levels of 

1,4-dioxane. 

1990s- Levels 

increase 

In 1979-1980, the FDA urged the cosmetic industry to monitor their 

raw materials for 1,4-dioxane. 

The results of surveys suggested a downward trend in the levels of 

1,4-dioxane in cosmetic finished products analyzed between 1981 

and 1984. Changes in the manufacturing process may be 

responsible for the apparent trend. FDA surveys were then 

suspended in 1984 but were resumed in 1992. 

Ninety-nine products were analyzed between 1992 and 1997. The 

products analyzed since 1994 focused on children’s shampoos 

because the process used in their manufacturing was linked to 

1,4-dioxane. The downward trend in the levels of 1,4-dioxane 

previously observed in products analyzed in the 1980s was no 

longer evident in the products analyzed in the 1990s. Of particular 

concern were levels of 1,4-dioxane observed in children’s 

shampoos analyzed in 1994/95 manufactured by two companies. 

1,4-Dioxane was frequently present at levels in excess of 85 ppm. 

Can high levels of 1-4-dioxane be avoided in cosmetics, bath products and shampoos? 

High levels can be The low levels of 1,4-dioxane observed in some raw materials and 

avoided	 finished products demonstrate that with current technology, 

excessive levels of 1,4-dioxane are avoidable. Continued periodic 

monitoring of cosmetic ingredients and cosmetic finished products 

for the presence of 1,4-dioxane is necessary. 
 

 

 

 

 

 

 

1,4-DIOXANE D-6 

APPENDIX D 

What can I do to ensure that my family is not exposed to 1,4-dioxane? 

Check ingredients 

listed on product 

packaging 

Given the expanding range of consumer products that may contain 

1,4-dioxane as a contaminant, families should exercise caution in 

selecting products that do not clearly specify the ingredients that 

contain 1,4-dioxane. 

The ingredients that may be listed on cosmetics, detergents, and 

shampoos include: 

• polyethylene glycol (PEG), 

• polyethylene, 

• polyoxyethylene,
 

• or oxynolThese ingredients are most likely to contain 1,4-dioxane. 

Where can I find more information regarding 1,4-dioxane? 

Document Source 

ATSDR ToxFAQs http://www.atsdr.cdc.gov/toxfaqs/TF.asp?id=954&tid=199 

EPA dioxane fact 

sheets 

http://www.epa.gov/opptintr/chemfact/dioxa-sd.txt 

http://www.epa.gov/chemfact/dioxa-fs.pdf 

FDA: Cosmetics Cosmetic Handbook. 1992. U.S. Food and Drug Administration. 

Center for Food Safety and Applied Nutrition. FDA/IAS Booklet: 1992. 

FDA: Food 

Additives 

FDA's website at 

http://www.fda.gov/Food/FoodIngredientsPackaging/ucm115333.htm. 

National Industrial 

Chemicals 

Notification and 

Assessments 

System 

http://www.nicnas.gov.au/publications/car/pec/pec7/pec7_full_report_pd 

f.pdf 

This is a full public report on 1,4-dioxane from the National Industrial 

Chemicals Notification and Assessments Scheme. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE D-7 

APPENDIX D 

Atlanta Journal and Constitution. 2007. Chemical in bath product for children raises alarms. By Carlene 

Olsen colsen@coxnews.com. Atlanta Journal and Constitution, February 12, 2007. 

ATSDR. 1986. Health Consultation on Gelman Sciences, Ann Arbor, Michigan. Written communication 

(May 22) to Louise A. Fabinski, Public Health Advisor, EPA Region V, Chicago, IL from Jeffrey A. 

Lybarger, M.D., Acting Director, Office of Health Assessment. Atlanta, GA: U.S. Department of Health 

and Human Services. Public Health Service. Agency for Toxic Substances and Disease Registry,. 

ATSDR. 1989. Written communication (September 14) to Raj M. Wiener, Director, Michigan Department 

of Public Health, Lansing, MI from Barry L. Johnson, Ph.D., Assistant Administrator. Atlanta, GA: U.S. 

Department of Health and Human Services. Public Health Service Agency for Toxic Substances and 

Disease Registry. 

ATSDR. 1994. Chemical specific health consultation for 1,4-Dioxane. Atlanta, GA: U.S. Department of 

Health and Human Services. Public Health Service. Agency for Toxic Substances and Disease Registry. 

ATSDR. 2007. Toxicological Profile for 1,4-Dioxane. U.S. Department of Health and Human Services. 

Public Health Service. Atlanta, GA: Agency for Toxic Substances and Disease Registry. 

Australia NICNAS. 1998. 1,4-Dioxane priority existing chemical No. 7. Full public report. National 

Industrial Chemicals Notification and Assessment Scheme. Commonwealth of Australia. 

http://www.nicnas.gov.au/publications/car/pec/pec7/pec7_full_report_pdf.pdf. 

Black RE, Hurley FJ, Havery DC. 2001. Occurrence of 1,4-dioxane in cosmetic raw materials and 

finished cosmetic products. J AOAC International 84(3):666-670. 

Campaign for Safe Cosmetics. 2007. Cancer-causing chemical found in children's bath products. 

http://www.safecosmetics.org/newsroom/press.cfm?pressReleaseID=21. August 22, 2007. 

Cosmetic Handbook. 1992. U.S. Food and Drug Administration. Center for Food Safety and Applied 

Nutrition. FDA/IAS Booklet: 1992. 

De Rosa CT, Wilbur S, Holler J, et al. 1996. Health evaluation of 1,4-dioxane. Toxicol Ind Health 

12(1):1-43. 

Environment News Service. 2007. Cosmetics industry approves controversial chemicals. By Cat 

Lazaroff. Environment News Service, February 14, 2007. 

FDA. 1998. 21CFR Part 175 (Docket No 98F-0433). Indirect food additives: adhesives and components 

of coatings. Final Rule. U.S. Food and Drug Administration. Federal Register 63(205):56786-56789. 

NAS. 2003. Polysorbate 20. In: Food chemicals codex. 5th ed. Washington, DC: National Academy of 

Sciences, 346-347. 

NIOSH. 1988. HHE Report No. HETA-86-051-1911, National Cover of Atlanta, Inc., Lawrenceville, 

Georgia. National Institute for Occupational Safety and Health. 

http://www.cdc.gov/niosh/hhe/reports/pdfs/1986-0051-1911.pdf. June 05, 2007. 
1,4-DIOXANE D-8 
 

APPENDIX D 

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1,4-DIOXANE E-1 

APPENDIX E. INDEX 

absorbed dose............................................................................................................................ 100, 134, 146
	

adipose tissue ............................................................................................................................................ 174 

adsorbed............................................................................................................................................ 167, 189
	

alanine aminotransferase (see ALT)........................................................................................................... 16 

ALT (see alanine aminotransferase) ................................................................... 16, 20, 21, 24, 49, 107, 126
	

ambient air .................................................................................................................... 9, 170, 171, 177, 178
	

aspartate aminotransferase (see AST)......................................................................................................... 16 

AST (see aspartate aminotransferase)....................................................................................... 16, 21, 24, 49
	

bioaccumulation........................................................................................................................ 159, 166, 167
	

bioconcentration factor ............................................................................................................................. 167 

biodegradation................................................................................................... 157, 166, 168, 169, 182, 184 

biomarker .......................................................................................... 132, 133, 134, 135, 145, 146, 147, 185
	

blood cell count......................................................................................................................... 16, 20, 48, 80
	

body weight effects............................................................................................................. 32, 52, 79, 84, 94
	

breast milk................................................................................................................................. 123, 143, 180
	

cancer ................................................................................. 4, 10, 12, 17, 19, 20, 30, 54, 55, 87, 90, 91, 115, 

117, 126, 127, 128, 131, 132, 137, 138, 142, 199
	

carcinogen......................................................................................................................... 4, 13, 95, 142, 200
	

carcinogenic .................................................................... 4, 13, 14, 29, 30, 91, 125, 126, 127, 142, 199, 200
	

carcinogenicity........................................................................ 10, 12, 13, 17, 54, 87, 95, 124, 125, 126, 142
	

carcinoma ............................................................................ 10, 12, 54, 79, 87, 88, 89, 90, 91, 127, 142, 198
	

cardiovascular ....................................................................................................................................... 79, 94
	

cardiovascular effects............................................................................................................................ 47, 80
	

chromosomal aberrations.................................................................................................................... 98, 125
	

clearance ........................................................................................................................... 106, 122, 127, 128
	

cosmetics........................................................................................... 1, 2, 5, 9, 157, 175, 176, 181, 192, 194
	

death.................................................. 3, 9, 11, 13, 15, 16, 20, 23, 29, 31, 32, 47, 49, 50, 54, 55, 81, 82, 145
	

dermal effects.......................................................................................................................... 51, 84, 94, 141
	

detergents.................................................................................. 1, 2, 5, 9, 157, 161, 175, 176, 178, 180, 181
	

DNA.................................................................................................... 95, 96, 97, 98, 99, 125, 126, 133, 134
	

elimination rate ......................................................................................................................................... 119 

endocrine................................................................................................... 32, 79, 84, 94, 129, 130, 143, 147
	

endocrine effects ................................................................................................................................... 51, 84
	

estrogenic .......................................................................................................................................... 130, 143
	

fetus........................................................................................................................................................... 130 

gastrointestinal effects .......................................................................................................................... 48, 80
	

general population............................................................. 128, 134, 138, 143, 145, 159, 177, 180, 183, 194
	

genotoxic................................................................... 12, 29, 95, 99, 103, 124, 125, 127, 132, 137, 138, 143
	

genotoxicity........................................................................................................... 11, 95, 103, 125, 127, 143
	

groundwater .................................................. 2, 159, 162, 165, 166, 167, 172, 174, 180, 182, 188, 189, 191
	

half-life.............................................................................................. 103, 108, 133, 134, 159, 166, 168, 182
	

HEAA .......................................................... 25, 99, 100, 103, 104, 105, 106, 107, 108, 109, 112, 117, 119, 

120, 124, 125, 127, 128, 134, 145, 179, 185, 186, 187, 194 

hematological effects ............................................................................................................................ 48, 80
	

hepatic effects ......................................................................................................................... 49, 81, 94, 135
	

hydrolysis.......................................................................................................................................... 105, 168
	

hydroxyl radical ........................................................................................................................................ 168 

immune system ......................................................................................................................................... 144 

immunological .................................................................................................................. 10, 29, 52, 85, 138
	
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1,4-DIOXANE E-2 

APPENDIX E 

immunological effects................................................................................................................................. 10 

Kow ............................................................................................................................................ 151, 167, 181
	

LC50............................................................................................................................................................. 31 

LD50................................................................................................................................... 12, 22, 54, 91, 124
	

leukemia...................................................................................................................................................... 87 

lymphoreticular..................................................................................................................................... 52, 85
	

mass spectroscopy..................................................................................................................................... 106 

micronuclei ......................................................................................................................................... 98, 125
	

milk ........................................................................................................................................... 132, 143, 147
	

musculoskeletal effects ......................................................................................................................... 49, 81
	

nasal cavity................................ 3, 10, 12, 16, 20, 21, 47, 54, 55, 79, 80, 87, 88, 89, 90, 128, 129, 141, 142
	

neoplasm ..................................................................................................................................................... 90 

neoplastic .................................................................................................. 13, 17, 21, 26, 79, 80, 82, 87, 130
	

neurobehavioral......................................................................................................................................... 130 

nuclear................................................... 11, 16, 17, 20, 21, 22, 24, 26, 47, 49, 50, 79, 80, 83, 102, 106, 135
	

octanol-water partition coefficient............................................................................................................ 121 

ocular effects......................................................................................................................................... 15, 94
	

partition coefficients ............................................................................................. 19, 22, 112, 115, 119, 185
	

pharmacodynamic ..................................................................................................................... 109, 114, 117
	

pharmacokinetic.................................................. 18, 109, 110, 111, 114, 117, 123, 131, 132, 141, 146, 147
	

photolysis.......................................................................................................................................... 167, 168
	

placenta ............................................................................................................................................. 132, 147
	

rate constant ...................................................................................................... 105, 115, 119, 122, 151, 167 

renal effects............................................................................................................................... 13, 50, 83, 94
	

sarcoma ....................................................................................................................................................... 95 

sister chromatid exchange........................................................................................................................... 96 

solubility ................................................................................................................................................... 124 

thyroid................................................................................................................................................... 51, 84
	

toxicokinetic................................................................................................................................ 29, 100, 146
	

tumors ........................................... 4, 10, 12, 17, 20, 32, 55, 87, 88, 89, 90, 91, 95, 126, 127, 128, 129, 142
	

vapor pressure ........................................................................................................................... 159, 166, 181
	

volatility.................................................................................................................................................... 185 

volatilization ..................................................................................................................................... 159, 166