TOXICOLOGICAL PROFILE FOR 

ARSENIC 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Public Health Service 

Agency for Toxic Substances and Disease Registry

August 2007 
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DISCLAIMER 

The use of company or product name(s) is for identification only and does not imply endorsement by the 

Agency for Toxic Substances and Disease Registry. 
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UPDATE STATEMENT 

A Toxicological Profile for Arsenic, Draft for Public Comment was released in September 2005. 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-32 

Atlanta, Georgia 30333 
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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 hazardous substance described therein. Each peer-reviewed profile identifies 

and reviews the key literature that describes a hazardous 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 focus of the profiles is 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. The adequacy of information 

to determine a substance's health effects is described in a health effects summary. Data needs that are of 

significance to protection of public health are identified by ATSDR and EPA. 

Each profile includes the following: 

(A) The examination, summary, and interpretation of available toxicologic information and 

epidemiologic evaluations on a hazardous substance to ascertain the levels of significant 

human exposure for the substance and the associated acute, subacute, and chronic health 

effects; 

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

available or in the process of development to determine levels of exposure that present a 

significant risk to human health of acute, subacute, and chronic health effects; and 

(C) Where appropriate, identification of 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 health professionals at the Federal, State, 

and local levels; 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 have also reviewed the profile. In addition, this profile has been peer-reviewed by a 

nongovernmental panel and is being made available for public review. Final responsibility for the 

contents and views expressed in this toxicological profile resides with ATSDR. 
vi 

The toxicological profiles are developed in response to the Superfund Amendments and 

Reauthorization Act (SARA) of 1986 (Public Law 99-499) which amended the Comprehensive 

Environmental Response, Compensation, and Liability Act of 1980 (CERCLA or Superfund). This 

public law directed ATSDR to prepare 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. The availability of the revised priority 

list of 275 hazardous substances was announced in the Federal Register on December 7, 2005 (70 FR 

72840). For prior versions of the list of substances, see Federal Register notices dated April 17, 1987 

(52 FR 12866); October 20, 1988 (53 FR 41280); October 26, 1989 (54 FR 43619); October 17, 1990 (55 

FR 42067); October 17, 1991 (56 FR 52166); October 28, 1992 (57 FR 48801); February 28, 1994 (59 

FR 9486); April 29, 1996 (61 FR 18744); November 17, 1997 (62 FR 61332); October 21, 1999 (64 FR 

56792); October 25, 2001 (66 FR 54014); and November 7, 2003 (68 FR 63098). Section 104(i)(3) of 

CERCLA, as amended, directs the Administrator of ATSDR to prepare a toxicological profile for each 

substance on the list. 
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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 the following 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), by route of exposure, and by 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 necessarily 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 
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Hazards; Skin Lesions and Environmental Exposures; Cholinesterase-Inhibiting Pesticide 

Toxicity; and numerous chemical-specific case studies. 

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. 
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CONTRIBUTORS 

CHEMICAL MANAGER(S)/AUTHOR(S): 

Selene Chou, Ph.D. 

Carolyn Harper, Ph.D. 

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

Lisa Ingerman, Ph.D., DABT 

Fernando Llados, Ph.D. 

Joan Colman, Ph.D. 

Lara Chappell, Ph.D. 

Mark Osier, Ph.D., DABT 

Marc Odin, M.S. 

Gloria Sage, Ph.D. 

Syracuse Research Corporation, 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. 
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PEER REVIEW 

A peer review panel was assembled for arsenic. The panel consisted of the following members: 

1. Toby Rossman, Ph.D., Professor of Environmental Medicine, New York University School of 

Medicine, Nelson Institute of Environmental Medicine, Tuxedo, New York; 

2. Rosalind Schoof, Ph.D., DABT, Integral Consulting, Inc., Mercer Island, Washington; and 

3. Allan Smith, M.D., Ph.D., Professor of Epidemiology, School of Public Health, University of 

California, Berkeley, California. 

Draft for Public Comment: 

1. Alan Hall, M.D., Toxicology Consulting and Medical Translating Services, Inc. (TCMTS, Inc.), 

Elk Mountain, Wyoming; 

2. Gary Pascoe, Ph.D., Pascoe Environmental Consulting, Port Townsend, Washington; and 

3. Toby Rossman, Ph.D., Professor of Environmental Medicine, New York University School of 

Medicine, Nelson Institute of Environmental Medicine, Tuxedo, New York. 

These experts collectively have knowledge of arsenic'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. 
ARSENIC xii 

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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 ARSENIC?.................................................................................................................1 

1.2 WHAT HAPPENS TO ARSENIC WHEN IT ENTERS THE ENVIRONMENT?....................3 

1.3 HOW MIGHT I BE EXPOSED TO ARSENIC? ........................................................................4 

1.4 HOW CAN ARSENIC ENTER AND LEAVE MY BODY? .....................................................6 

1.5 HOW CAN ARSENIC AFFECT MY HEALTH? ......................................................................6 

1.6 HOW CAN ARSENIC AFFECT CHILDREN? .........................................................................8 

1.7 HOW CAN FAMILIES REDUCE THE RISK OF EXPOSURE TO ARSENIC? ...................10 

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

EXPOSED TO ARSENIC? .......................................................................................................12 

1.9 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH?...............................................................................................13 

1.10 WHERE CAN I GET MORE INFORMATION? .....................................................................14 

2. RELEVANCE TO PUBLIC HEALTH .................................................................................................15 

2.1 BACKGROUND AND ENVIRONMENTAL EXPOSURES TO ARSENIC IN THE 

 UNITED STATES.....................................................................................................................15 

2.2 SUMMARY OF HEALTH EFFECTS......................................................................................16 

2.3 MINIMAL RISK LEVELS (MRLs) .........................................................................................28 

3. HEALTH EFFECTS..............................................................................................................................41 

3.1 INTRODUCTION.....................................................................................................................41 

3.2 DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE ..................................41 

3.2.1 Inhalation Exposure ..............................................................................................................44 

3.2.1.1 Death ............................................................................................................................56 

3.2.1.2 Systemic Effects...........................................................................................................56 

3.2.1.3 Immunological and Lymphoreticular Effects...............................................................64 

3.2.1.4 Neurological Effects.....................................................................................................64 

3.2.1.5 Reproductive Effects....................................................................................................66 

3.2.1.6 Developmental Effects .................................................................................................67 

3.2.1.7 Cancer...........................................................................................................................68 

3.2.2 Oral Exposure........................................................................................................................73 

3.2.2.1 Death ............................................................................................................................74 

3.2.2.2 Systemic Effects.........................................................................................................162 

3.2.2.3 Immunological and Lymphoreticular Effects.............................................................179 

3.2.2.4 Neurological Effects...................................................................................................180 

3.2.2.5 Reproductive Effects..................................................................................................183 
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3.2.2.6 Developmental Effects ...............................................................................................185 

3.2.2.7 Cancer.........................................................................................................................188 

3.2.3 Dermal Exposure.................................................................................................................194 

3.2.3.1 Death ..........................................................................................................................194 

3.2.3.2 Systemic Effects.........................................................................................................196 

3.2.3.3 Immunological and Lymphoreticular Effects.............................................................198 

3.2.3.4 Neurological Effects...................................................................................................198 

3.2.3.5 Reproductive Effects..................................................................................................198 

3.2.3.6 Developmental Effects ...............................................................................................198 

3.2.3.7 Cancer.........................................................................................................................198 

3.3 GENOTOXICITY ...................................................................................................................199 

3.4 TOXICOKINETICS................................................................................................................211 

3.4.1 Absorption...........................................................................................................................211 

3.4.1.1 Inhalation Exposure....................................................................................................211 

3.4.1.2 Oral Exposure.............................................................................................................212 

3.4.1.3 Dermal Exposure ........................................................................................................215 

3.4.2 Distribution .........................................................................................................................216 

3.4.2.1 Inhalation Exposure....................................................................................................216 

3.4.2.2 Oral Exposure.............................................................................................................216 

3.4.2.3 Dermal Exposure ........................................................................................................218 

3.4.2.4 Other Routes of Exposure ..........................................................................................218 

3.4.3 Metabolism..........................................................................................................................219 

3.4.4 Elimination and Excretion...................................................................................................225 

3.4.4.1 Inhalation Exposure....................................................................................................225 

3.4.4.2 Oral Exposure.............................................................................................................226 

3.4.4.3 Dermal Exposure ........................................................................................................227 

3.4.4.4 Other Routes of Exposure ..........................................................................................228 

3.4.5 Physiologically Based Pharmacokinetic (PBPK)/Pharmacodynamic (PD) Models ...........228 

3.4.5.1 Summary of PBPK Models........................................................................................231 

3.4.5.2 Arsenic PBPK Model Comparison.............................................................................231 

3.4.5.3 Discussion of Models.................................................................................................231 

3.5 MECHANISMS OF ACTION ................................................................................................ 247 

3.5.1 Pharmacokinetic Mechanisms............................................................................................. 247 

3.5.2 Mechanisms of Toxicity......................................................................................................248 

3.5.3 Animal-to-Human Extrapolations.......................................................................................251 

3.6 TOXICITIES MEDIATED THROUGH THE NEUROENDOCRINE AXIS ........................252 

3.7 CHILDREN’S SUSCEPTIBILITY.........................................................................................253 

3.8 BIOMARKERS OF EXPOSURE AND EFFECT ..................................................................257 

3.8.1 Biomarkers Used to Identify or Quantify Exposure to Arsenic ..........................................258 

3.8.2 Biomarkers Used to Characterize Effects Caused by Arsenic ............................................261 

3.9 INTERACTIONS WITH OTHER CHEMICALS ..................................................................262 

3.10 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE............................................. 264 

3.11 METHODS FOR REDUCING TOXIC EFFECTS................................................................. 266 

3.11.1 Reducing Peak Absorption Following Exposure ............................................................267 

3.11.2 Reducing Body Burden...................................................................................................268 

3.11.3 Interfering with the Mechanism of Action for Toxic Effects .........................................269 

3.12 ADEQUACY OF THE DATABASE......................................................................................269 

3.12.1 Existing Information on Health Effects of Arsenic ........................................................270 

3.12.2 Identification of Data Needs ...........................................................................................273 

3.12.3 Ongoing Studies..............................................................................................................286 
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4. CHEMICAL AND PHYSICAL INFORMATION..............................................................................291 

4.1 CHEMICAL IDENTITY.........................................................................................................291 

4.2 PHYSICAL AND CHEMICAL PROPERTIES......................................................................291 

5. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL..........................................................303 

5.1 PRODUCTION .......................................................................................................................303 

5.2 IMPORT/EXPORT .................................................................................................................309 

5.3 USE..........................................................................................................................................309 

5.4 DISPOSAL..............................................................................................................................312 

6. POTENTIAL FOR HUMAN EXPOSURE .........................................................................................313 

6.1 OVERVIEW............................................................................................................................313 

6.2 RELEASES TO THE ENVIRONMENT................................................................................316 

6.2.1 Air .......................................................................................................................................316 

6.2.2 Water...................................................................................................................................322 

6.2.3 Soil ......................................................................................................................................323 

6.3 ENVIRONMENTAL FATE....................................................................................................324 

6.3.1 Transport and Partitioning...................................................................................................324 

6.3.2 Transformation and Degradation ........................................................................................331 

6.3.2.1 Air...............................................................................................................................331 

6.3.2.2 Water ..........................................................................................................................331 

6.3.2.3 Sediment and Soil.......................................................................................................333 

6.3.2.4 Other Media................................................................................................................335 

6.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT...............................336 

6.4.1 Air .......................................................................................................................................336 

6.4.2 Water...................................................................................................................................337 

6.4.3 Sediment and Soil ...............................................................................................................344 

6.4.4 Other Environmental Media................................................................................................348 

6.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE .....................................356 

6.6 EXPOSURES OF CHILDREN...............................................................................................367 

6.7 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES ...........................................374 

6.8 ADEQUACY OF THE DATABASE......................................................................................375 

6.8.1 Identification of Data Needs ...............................................................................................376 

6.8.2 Ongoing Studies ..................................................................................................................379 

7. ANALYTICAL METHODS ...............................................................................................................383 

7.1 BIOLOGICAL MATERIALS.................................................................................................383 

7.2 ENVIRONMENTAL SAMPLES............................................................................................ 387 

7.3 ADEQUACY OF THE DATABASE......................................................................................388 

7.3.1 Identification of Data Needs ...............................................................................................392 

7.3.2 Ongoing Studies ..................................................................................................................393 

8. REGULATIONS AND ADVISORIES ...............................................................................................395 

9. REFERENCES ....................................................................................................................................401 

10. GLOSSARY ......................................................................................................................................493 
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APPENDICES 

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

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

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

D. INDEX ................................................................................................................................................D-1 
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LIST OF FIGURES 

3-1. Levels of Significant Exposure to Inorganic Arsenic – Inhalation..................................................... 49 

3-2. Levels of Significant Exposure to Dimethylarsinic Acid – Inhalation............................................... 54 

3-3. Levels of Significant Exposure to Inorganic Arsenic – Oral............................................................ 117

3-4. Levels of Significant Exposure to Monomethylarsonic Acid – Oral................................................ 133 

3-5. Levels of Significant Exposure to Dimethylarsinic Acid – Oral ...................................................... 149 

3-6. Levels of Significant Exposure to Roxarsone – Oral ....................................................................... 159 

3-7. Inorganic Arsenic Biotransformation Pathway................................................................................. 220 

3-8. Alternative Inorganic Arsenic Biotransformation Pathway..............................................................223 

3-9. Conceptual Representation of a Physiologically Based Pharmacokinetic (PBPK) Model for a 

Hypothetical Chemical Substance .....................................................................................................230 

3-10. Parameters Used in the Mann PBPK Model for Animals ..............................................................233 

3-11. Parameters Used in the Mann PBPK Model for Humans............................................................... 238 

3-12. Parameters Used in the Yu PBPK Model for Animals...................................................................244 

3-13. Existing Information on Health Effects of Inorganic Arsenic ........................................................271 

3-14. Existing Information on Health Effects of Organic Arsenic ..........................................................272 

6-1. Frequency of NPL Sites with Arsenic Contamination......................................................................314 

6-2. Counties in Which at Least 25% of Wells Exceed Different Arsenic Levels...................................339 
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LIST OF TABLES 

3-1. Levels of Significant Exposure to Inorganic Arsenic – Inhalation..................................................... 45 

3-2. Levels of Significant Exposure to Dimethylarsinic Acid – Inhalation............................................... 52 

3-3. Levels of Significant Exposure to Inorganic Arsenic – Oral.............................................................. 75 

3-4. Levels of Significant Exposure to Monomethylarsonic Acid – Oral................................................ 125 

3-5. Levels of Significant Exposure to Dimethylarsinic Acid – Oral ...................................................... 137 

3-6. Levels of Significant Exposure to Roxarsone – Oral ....................................................................... 152 

3-7. Levels of Significant Exposure to Inorganic Arsenic – Dermal....................................................... 195 

3-8. Genotoxicity of Inorganic Arsenic In Vitro......................................................................................200 

3-9. Genotoxicity of Inorganic Arsenic In Vivo.......................................................................................206 

3-10. Genotoxicity of Organic Arsenic....................................................................................................209 

3-11. Parameters Used in the Mann PBPK Model for Animals ..............................................................234 

3-12. Tissue Affinity Constants (Kij) Obtained for the Mann PBPK Model for Animals by Fitting 

for Rabbits and Hamsters................................................................................................................235 

3-13. Metabolic Rate Constants for the Mann PBPK Model for Animals Obtained by Fitting for 

Rabbits and Hamsters......................................................................................................................236 

3-14. Fitted Gastrointestinal Tract and Lung Absorption Half-time for the Hamster for the Mann 

 PBPK Model ...................................................................................................................................237 

3-15. Physiological Data Used in the Mann PBPK Model for Humans..................................................239 

3-16. Tissue Affinity Constants (Kij) Obtained by Fitting the Mann PBPK Animal Model for Use 

 with Humans ...................................................................................................................................240 

3-17. Parameters Used in the Yu PBPK Model.......................................................................................245 

3-18. Ongoing Studies on Health Effects of Arsenic, Federally Funded.................................................287 

4-1. Chemical Identity of Arsenic and Selected Inorganic Arsenic Compounds.....................................292 

4-2. Chemical Identity of Selected Organic Arsenic Compounds ...........................................................294 

4-3. Physical and Chemical Properties of Arsenic and Selected Inorganic Arsenic Compounds............297 

4-4. Physical and Chemical Properties of Selected Organic Arsenic Compounds..................................299 
ARSENIC xx 

5-1. Facilities that Produce, Process, or Use Arsenic ..............................................................................304 

5-2. Facilities that Produce, Process, or Use Arsenic Compounds..........................................................306 

5-3. Current U.S. Manufacturers of Selected Arsenic Compounds.........................................................308 

6-1. Releases to the Environment from Facilities that Produce, Process, or Use Arsenic .......................317 

6-2. Releases to the Environment from Facilities that Produce, Process, or Use Arsenic 

 Compounds........................................................................................................................................319 

6-3. Regional Occurrence of Arsenic in U.S. Water Sources and Finished Drinking Water...................342 

6-4. Levels of Arsenic in Fish and Shellfish—Recent Studies................................................................349 

6-5. Mean Daily Dietary Intake of Arsenic for Selected U.S. Population Groups ..................................357 

6-6. Levels of Arsenic in Human Tissue and Urine—Recent Studies.....................................................361 

6-7. Ongoing Studies on the Environmental Fate and Exposure of Humans to Arsenic .........................380 

7-1. Analytical Methods for Determining Arsenic in Biological Samples..............................................385 

7-2. Analytical Methods for Determining Arsenic in Environmental Samples.......................................389 

7-3. Ongoing Studies on Analytical Methods for Arsenic in Environmental and Biological 

 Samples..............................................................................................................................................394 

8-1. Regulations and Guidelines Applicable to Arsenic and Arsenic Compounds..................................396 
ARSENIC 1 

1. PUBLIC HEALTH STATEMENT 

This public health statement tells you about arsenic 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. Arsenic has been found in at least 1,149 of the 

1,684 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 arsenic 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 harm you. 

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 arsenic, many factors will determine whether you will be harmed. These 

factors include the dose (how much), the duration (how long), 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 ARSENIC? 

Arsenic is a naturally occurring element that is widely distributed in the Earth’s crust. Arsenic is 

classified chemically as a metalloid, having both properties of a metal and a nonmetal; however, 

it is frequently referred to as a metal. Elemental arsenic (sometimes referred to as metallic 

arsenic) is a steel grey solid material. However, arsenic is usually found in the environment 

combined with other elements such as oxygen, chlorine, and sulfur. Arsenic combined with 
ARSENIC 2 

1. PUBLIC HEALTH STATEMENT 

these elements is called inorganic arsenic. Arsenic combined with carbon and hydrogen is 

referred to as organic arsenic. 

Most inorganic and organic arsenic compounds are white or colorless powders that do not 

evaporate. They have no smell, and most have no special taste. Thus, you usually cannot tell if 

arsenic is present in your food, water, or air. 

Inorganic arsenic occurs naturally in soil and in many kinds of rock, especially in minerals and 

ores that contain copper or lead. When these ores are heated in smelters, most of the arsenic 

goes up the stack and enters the air as a fine dust. Smelters may collect this dust and take out the 

arsenic as a compound called arsenic trioxide (As2O3). However, arsenic is no longer produced 

in the United States; all of the arsenic used in the United States is imported. 

Presently, about 90% of all arsenic produced is used as a preservative for wood to make it 

resistant to rotting and decay. The preservative is copper chromated arsenate (CCA) and the 

treated wood is referred to as “pressure-treated.” In 2003, U.S. manufacturers of wood 

preservatives containing arsenic began a voluntary transition from CCA to other wood 

preservatives that do not contain arsenic in wood products for certain residential uses, such as 

play structures, picnic tables, decks, fencing, and boardwalks. This phase out was completed on 

December 31, 2003; however, wood treated prior to this date could still be used and existing 

structures made with CCA-treated wood would not be affected. CCA-treated wood products 

continue to be used in industrial applications. It is not known whether, or to what extent, CCAtreated wood products may contribute to exposure of people to arsenic. 

In the past, inorganic arsenic compounds were predominantly used as pesticides, primarily on 

cotton fields and in orchards. Inorganic arsenic compounds can no longer be used in agriculture. 

However, organic arsenic compounds, namely cacodylic acid, disodium methylarsenate 

(DSMA), and monosodium methylarsenate (MSMA), are still used as pesticides, principally on 

cotton. Some organic arsenic compounds are used as additives in animal feed. Small quantities 

of elemental arsenic are added to other metals to form metal mixtures or alloys with improved 
ARSENIC 3 

1. PUBLIC HEALTH STATEMENT 

properties. The greatest use of arsenic in alloys is in lead-acid batteries for automobiles. 

Another important use of arsenic compounds is in semiconductors and light-emitting diodes. 

To learn more about the properties and uses of arsenic, see Chapters 4 and 5. 

1.2 WHAT HAPPENS TO ARSENIC WHEN IT ENTERS THE ENVIRONMENT? 

Arsenic occurs naturally in soil and minerals and it therefore may enter the air, water, and land 

from wind-blown dust and may get into water from runoff and leaching. Volcanic eruptions are 

another source of arsenic. Arsenic is associated with ores containing metals, such as copper and 

lead. Arsenic may enter the environment during the mining and smelting of these ores. Small 

amounts of arsenic also may be released into the atmosphere from coal-fired power plants and 

incinerators because coal and waste products often contain some arsenic. 

Arsenic cannot be destroyed in the environment. It can only change its form, or become attached 

to or separated from particles. It may change its form by reacting with oxygen or other 

molecules present in air, water, or soil, or by the action of bacteria that live in soil or sediment. 

Arsenic released from power plants and other combustion processes is usually attached to very 

small particles. Arsenic contained in wind-borne soil is generally found in larger particles. 

These particles settle to the ground or are washed out of the air by rain. Arsenic that is attached 

to very small particles may stay in the air for many days and travel long distances. Many 

common arsenic compounds can dissolve in water. Thus, arsenic can get into lakes, rivers, or 

underground water by dissolving in rain or snow or through the discharge of industrial wastes. 

Some of the arsenic will stick to particles in the water or sediment on the bottom of lakes or 

rivers, and some will be carried along by the water. Ultimately, most arsenic ends up in the soil 

or sediment. Although some fish and shellfish take in arsenic, which may build up in tissues, 

most of this arsenic is in an organic form called arsenobetaine (commonly called "fish arsenic") 

that is much less harmful. 

For more information on how arsenic behaves in the environment, see Chapter 6. 
ARSENIC 4 

1. PUBLIC HEALTH STATEMENT 

1.3 HOW MIGHT I BE EXPOSED TO ARSENIC? 

Since arsenic is found naturally in the environment, you will be exposed to some arsenic by 

eating food, drinking water, or breathing air. Children may also be exposed to arsenic by eating 

soil. Analytical methods used by scientists to determine the levels of arsenic in the environment 

generally do not determine the specific form of arsenic present. Therefore, we do not always 

know the form of arsenic a person may be exposed to. Similarly, we often do not know what 

forms of arsenic are present at hazardous waste sites. Some forms of arsenic may be so tightly 

attached to particles or embedded in minerals that they are not taken up by plants and animals. 

The concentration of arsenic in soil varies widely, generally ranging from about 1 to 40 parts of 

arsenic to a million parts of soil (ppm) with an average level of 3–4 ppm. However, soils in the 

vicinity of arsenic-rich geological deposits, some mining and smelting sites, or agricultural areas 

where arsenic pesticides had been applied in the past may contain much higher levels of arsenic. 

The concentration of arsenic in natural surface and groundwater is generally about 1 part in a 

billion parts of water (1 ppb), but may exceed 1,000 ppb in contaminated areas or where arsenic 

levels in soil are high. Groundwater is far more likely to contain high levels of arsenic than 

surface water. Surveys of U.S. drinking water indicate that about 80% of water supplies have 

less than 2 ppb of arsenic, but 2% of supplies exceed 20 ppb of arsenic. Levels of arsenic in food 

range from about 20 to 140 ppb. However, levels of inorganic arsenic, the form of most concern, 

are far lower. Levels of arsenic in the air generally range from less than 1 to about 

2,000 nanograms (1 nanogram equals a billionth of a gram) of arsenic per cubic meter of air (less 

than 1–2,000 ng/m3

), depending on location, weather conditions, and the level of industrial 

activity in the area. However, urban areas generally have mean arsenic levels in air ranging from 

20 to 30 ng/m3. 

You normally take in small amounts of arsenic in the air you breathe, the water you drink, and 

the food you eat. Of these, food is usually the largest source of arsenic. The predominant 

dietary source of arsenic is seafood, followed by rice/rice cereal, mushrooms, and poultry. While 

seafood contains the greatest amounts of arsenic, for fish and shellfish, this is mostly in an 

organic form of arsenic called arsenobetaine that is much less harmful. Some seaweeds may 
ARSENIC 5 

1. PUBLIC HEALTH STATEMENT 

contain arsenic in inorganic forms that may be more harmful. Children are likely to eat small 

amounts of dust or soil each day, so this is another way they may be exposed to arsenic. The 

total amount of arsenic you take in from these sources is generally about 50 micrograms 

(1 microgram equals one-millionth of a gram) each day. The level of inorganic arsenic (the form 

of most concern) you take in from these sources is generally about 3.5 microgram/day. Children 

may be exposed to small amounts of arsenic from hand-to-mouth activities from playing on play 

structures or decks constructed out of CCA-treated wood. The potential exposure that children 

may receive from playing in play structures constructed from CCA-treated wood is generally 

smaller than that they would receive from food and water. Hand washing can reduce the 

potential exposure of children to arsenic after playing on play structures constructed with CCAtreated wood, since most of the arsenic on the children’s hands was removed with water. 

In addition to the normal levels of arsenic in air, water, soil, and food, you could be exposed to 

higher levels in several ways, such as the following: 

•	 Some areas of the United States contain unusually high natural levels of arsenic in rock, 

and this can lead to unusually high levels of arsenic in soil or water. If you live in an area 

like this, you could take in elevated amounts of arsenic in drinking water. Children may 

be taking in higher amounts of arsenic because of hand-to-mouth contact or eating soil in 

areas with higher than usual arsenic concentrations. 

•	 Some hazardous waste sites contain large quantities of arsenic. If the material is not 

properly disposed of, it can get into surrounding water, air, or soil. If you live near such a 

site, you could be exposed to elevated levels of arsenic from these media. 

•	 If you work in an occupation that involves arsenic production or use (for example, copper 

or lead smelting, wood treating, or pesticide application), you could be exposed to 

elevated levels of arsenic during your work. 

•	 If you saw or sand arsenic-treated wood, you could inhale some of the sawdust into your 

nose or throat. Similarly, if you burn arsenic-treated wood, you could inhale arsenic in 

the smoke. 

•	 If you live in a former agricultural area where arsenic was used on crops, the soil could 

contain high levels of arsenic. 
ARSENIC 6 

1. PUBLIC HEALTH STATEMENT 

•	 In the past, several kinds of products used in the home (rat poison, ant poison, weed 

killer, some types of medicines) had arsenic in them. However, most of these uses of 

arsenic have ended, so you are not likely to be exposed from home products any longer. 

You can find more information on how you may be exposed to arsenic in Chapter 6. 

1.4 HOW CAN ARSENIC ENTER AND LEAVE MY BODY? 

If you swallow arsenic in water, soil, or food, most of the arsenic may quickly enter into your 

body. The amount that enters your body will depend on how much you swallow and the kind of 

arsenic that you swallow. This is the most likely way for you to be exposed near a waste site. If 

you breathe air that contains arsenic dusts, many of the dust particles settle onto the lining of the 

lungs. Most of the arsenic in these particles is then taken up from the lungs into the body. You 

might be exposed in this way near waste sites where arsenic-contaminated soils are allowed to 

blow into the air, or if you work with arsenic-containing soil or products. If you get arseniccontaminated soil or water on your skin, only a small amount will go through your skin into your 

body, so this is usually not of concern. 

Both inorganic and organic forms leave your body in your urine. Most of the inorganic arsenic 

will be gone within several days, although some will remain in your body for several months or 

even longer. If you are exposed to organic arsenic, most of it will leave your body within several 

days. 

You can find more information on how arsenic enters and leaves your body in Chapter 3. 

1.5 HOW CAN ARSENIC AFFECT MY HEALTH? 

Scientists use many tests to protect the public from harmful effects of toxic chemicals and to find 

ways for treating persons who have been harmed. 
ARSENIC 7 

1. PUBLIC HEALTH STATEMENT 

One way to learn whether a chemical will harm people is to determine how the body absorbs, 

uses, and releases the chemical. For some chemicals, animal testing may be necessary. Animal 

testing may also help identify health effects such as cancer or birth defects. Without laboratory 

animals, scientists would lose a basic method for getting information needed to make wise 

decisions that protect public health. Scientists have the responsibility to treat research animals 

with care and compassion. Scientists must comply with strict animal care guidelines because 

laws today protect the welfare of research animals. 

Inorganic arsenic has been recognized as a human poison since ancient times, and large oral 

doses (above 60,000 ppb in water which is 10,000 times higher than 80% of U.S. drinking water 

arsenic levels) can result in death. If you swallow lower levels of inorganic arsenic (ranging 

from about 300 to 30,000 ppb in water; 100–10,000 times higher than most U.S. drinking water 

levels), you may experience irritation of your stomach and intestines, with symptoms such as 

stomachache, nausea, vomiting, and diarrhea. Other effects you might experience from 

swallowing inorganic arsenic include decreased production of red and white blood cells, which 

may cause fatigue, abnormal heart rhythm, blood-vessel damage resulting in bruising, and 

impaired nerve function causing a "pins and needles" sensation in your hands and feet. 

Perhaps the single-most characteristic effect of long-term oral exposure to inorganic arsenic is a 

pattern of skin changes. These include patches of darkened skin and the appearance of small 

"corns" or "warts" on the palms, soles, and torso, and are often associated with changes in the 

blood vessels of the skin. Skin cancer may also develop. Swallowing arsenic has also been 

reported to increase the risk of cancer in the liver, bladder, and lungs. The Department of Health 

and Human Services (DHHS) has determined that inorganic arsenic is known to be a human 

carcinogen (a chemical that causes cancer). The International Agency for Research on Cancer 

(IARC) has determined that inorganic arsenic is carcinogenic to humans. EPA also has 

classified inorganic arsenic as a known human carcinogen. 

If you breathe high levels of inorganic arsenic, then you are likely to experience a sore throat and 

irritated lungs. You may also develop some of the skin effects mentioned above. The exposure 

level that produces these effects is uncertain, but it is probably above 100 micrograms of arsenic 
ARSENIC 8 

1. PUBLIC HEALTH STATEMENT 

per cubic meter (μg/m3) for a brief exposure. Longer exposure at lower concentrations can lead 

to skin effects, and also to circulatory and peripheral nervous disorders. There are some data 

suggesting that inhalation of inorganic arsenic may also interfere with normal fetal development, 

although this is not certain. An important concern is the ability of inhaled inorganic arsenic to 

increase the risk of lung cancer. This has been seen mostly in workers exposed to arsenic at 

smelters, mines, and chemical factories, but also in residents living near smelters and arsenical 

chemical factories. People who live near waste sites with arsenic may have an increased risk of 

lung cancer as well. 

If you have direct skin contact with high concentrations of inorganic arsenic compounds, your 

skin may become irritated, with some redness and swelling. However, it does not appear that 

skin contact is likely to lead to any serious internal effects. 

Almost no information is available on the effects of organic arsenic compounds in humans. 

Studies in animals show that most simple organic arsenic compounds (such as methyl and 

dimethyl compounds) are less toxic than the inorganic forms. In animals, ingestion of methyl 

compounds can result in diarrhea, and lifetime exposure can damage the kidneys. Lifetime 

exposure to dimethyl compounds can damage the urinary bladder and the kidneys. 

You can find more information on the health effects of inorganic and organic arsenic in 

Chapters 2 and 3. 

1.6 HOW CAN ARSENIC 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 exposed to arsenic in many of the same ways that adults are. Since arsenic is found 

in the soil, water, food, and air, children may take in arsenic in the air they breathe, the water 

they drink, and the food they eat. Since children tend to eat or drink less of a variety of foods 

and beverages than do adults, ingestion of contaminated food or juice or infant formula made 
ARSENIC 9 

1. PUBLIC HEALTH STATEMENT 

with arsenic-contaminated water may represent a significant source of exposure. In addition, 

since children often play in the soil and put their hands in their mouths and sometimes 

intentionally eat soil, ingestion of contaminated soil may be a more important source of arsenic 

exposure for children than for adults. In areas of the United States where natural levels of 

arsenic in the soil and water are high, or in areas in and around contaminated waste sites, 

exposure of children to arsenic through ingestion of soil and water may be significant. In 

addition, contact with adults who are wearing clothes contaminated with arsenic (e.g., with dust 

from copper- or lead-smelting factories, from wood-treating or pesticide application, or from 

arsenic-treated wood) could be a source of exposure. Because of the tendency of children to 

taste things that they find, accidental poisoning from ingestion of pesticides is also a possibility. 

Thus, although most of the exposure pathways for children are the same as those for adults, 

children may be at a higher risk of exposure because of normal hand-to-mouth activity. 

Children who are exposed to inorganic arsenic may have many of the same effects as adults, 

including irritation of the stomach and intestines, blood vessel damage, skin changes, and 

reduced nerve function. Thus, all health effects observed in adults are of potential concern in 

children. There is also some evidence that suggests that long-term exposure to inorganic arsenic 

in children may result in lower IQ scores. We do not know if absorption of inorganic arsenic 

from the gut in children differs from adults. There is some evidence that exposure to arsenic in 

early life (including gestation and early childhood) may increase mortality in young adults. 

There is some evidence that inhaled or ingested inorganic arsenic can injure pregnant women or 

their unborn babies, although the studies are not definitive. Studies in animals show that large 

doses of inorganic arsenic that cause illness in pregnant females can also cause low birth weight, 

fetal malformations, and even fetal death. Arsenic can cross the placenta and has been found in 

fetal tissues. Arsenic is found at low levels in breast milk. 

In animals, exposure to organic arsenic compounds can cause low birth weight, fetal 

malformations, and fetal deaths. The dose levels that cause these effects also result in effects in 

the mothers. 
ARSENIC 10 

1. PUBLIC HEALTH STATEMENT 

You can find more information about how arsenic can affect children in Sections 3.7 and 6.6. 

1.7 HOW CAN FAMILIES REDUCE THE RISK OF EXPOSURE TO ARSENIC? 

If your doctor finds that you have been exposed to substantial amounts of arsenic, ask whether 

your children might also have been exposed. Your doctor might need to ask your state health 

department to investigate. 

Many communities may have high levels of arsenic in their drinking water, particularly from 

private wells, because of contamination or as a result of the geology of the area. The north 

central region and the western region of the United States have the highest arsenic levels in 

surface water and groundwater sources, respectively. Wells used to provide water for drinking 

and cooking should be tested for arsenic. As of January 2006, EPA’s Maximum Contaminant 

Level (MCL) for arsenic in drinking water is 10 ppb. If you have arsenic in your drinking water 

at levels higher that the EPA’s MCL, an alternative source of water should be used for drinking 

and cooking should be considered. 

If you use arsenic-treated wood in home projects, personal protection from exposure to arseniccontaining sawdust may be helpful in limiting exposure of family members. These measures 

may include dust masks, gloves, and protective clothing. Arsenic-treated wood should never be 

burned in open fires, or in stoves, residential boilers, or fire places, and should not be composted 

or used as mulch. EPA’s Consumer Awareness Program (CAP) for CCA is a voluntary program 

established by the manufacturers of CCA products to inform consumers about the proper 

handling, use, and disposal of CCA-treated wood. You can find more information about this 

program in Section 6.5. Hand washing can reduce the potential exposure of children to arsenic 

after playing on play structures constructed with CCA-treated wood, since most of the arsenic on 

the children’s hands was removed with water. 

If you live in an area with a high level of arsenic in the water or soil, substituting cleaner sources 

of water and limiting contact with soil (for example, through use of a dense groundcover or thick 

lawn) would reduce family exposure to arsenic. By paying careful attention to dust and soil 
ARSENIC 11 

1. PUBLIC HEALTH STATEMENT 

control in the home (air filters, frequent cleaning), you can reduce family exposure to 

contaminated soil. Some children eat a lot of soil. You should prevent your children from eating 

soil. You should discourage your children from putting objects in their mouths. Make sure they 

wash their hands frequently and before eating. Discourage your children from putting their 

hands in their mouths or engaging in other hand-to-mouth activities. Since arsenic may be found 

in the home as a pesticide, household chemicals containing arsenic should be stored out of reach 

of young children to prevent accidental poisonings. Always store household chemicals in their 

original labeled containers; never store household chemicals in containers that children would 

find attractive to eat or drink from, such as old soda bottles. Keep your Poison Control Center’s 

number by the phone. 

It is sometimes possible to carry arsenic from work on your clothing, skin, hair, tools, or other 

objects removed from the workplace. This is particularly likely if you work in the fertilizer, 

pesticide, glass, or copper/lead smelting industries. You may contaminate your car, home, or 

other locations outside work where children might be exposed to arsenic. You should know 

about this possibility if you work with arsenic. 

Your occupational health and safety officer at work can and should tell you whether chemicals 

you work with are dangerous and likely to be carried home on your clothes, body, or tools and 

whether you should be showering and changing clothes before you leave work, storing your 

street clothes in a separate area of the workplace, or laundering your work clothes at home 

separately from other clothes. Material safety data sheets (MSDS) for many chemicals used 

should be found at your place of work, as required by the Occupational Safety and Health 

Administration (OSHA) in the U.S. Department of Labor. MSDS information should include 

chemical names and hazardous ingredients, and important properties, such as fire and explosion 

data, potential health effects, how you get the chemical(s) in your body, how to properly handle 

the materials, and what to do in the case of emergencies. Your employer is legally responsible 

for providing a safe workplace and should freely answer your questions about hazardous 

chemicals. Your state OSHA-approved occupational safety and health program or OSHA can 

answer any further questions and help your employer identify and correct problems with 

hazardous substances. Your state OSHA-approved occupational safety and health program or 
ARSENIC 12 

1. PUBLIC HEALTH STATEMENT 

OSHA will listen to your formal complaints about workplace health hazards and inspect your 

workplace when necessary. Employees have a right to seek safety and health on the job without 

fear of punishment. 

You can find more information about how arsenic can affect children in Sections 3.7 and 6.6. 

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

EXPOSED TO ARSENIC? 

Several sensitive and specific tests can measure arsenic in your blood, urine, hair, or fingernails, 

and these tests are often helpful in determining if you have been exposed to above-average levels 

of arsenic in the past. These tests are not usually performed in a doctor’s office. They require 

sending the sample to a testing laboratory. 

Measurement of arsenic in your urine is the most reliable means of detecting arsenic exposures 

that you experienced within the last several days. Most tests measure the total amount of arsenic 

present in your urine. This can sometimes be misleading, because the nonharmful forms of 

arsenic in fish and shellfish can give a high reading even if you have not been exposed to a toxic 

form of arsenic. For this reason, laboratories sometimes use a more complicated test to separate 

“fish arsenic” from other forms. Because most arsenic leaves your body within a few days, 

analysis of your urine cannot detect if you were exposed to arsenic in the past. Tests of your hair 

or fingernails can tell if you were exposed to high levels over the past 6–12 months, but these 

tests are not very useful in detecting low-level exposures. If high levels of arsenic are detected, 

this shows that you have been exposed, but unless more is known about when you were exposed 

and for how long, it is usually not possible to predict whether you will have any harmful health 

effects. 

You can find more information on how arsenic can be measured in your hair, urine, nails, and 

other tissues in Chapters 3 and 7. 
ARSENIC 13 

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-to-exceed 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 ARSENIC include the following: 

The federal government has taken several steps to protect humans from arsenic. First, EPA has 

set limits on the amount of arsenic that industrial sources can release into the environment. 

Second, EPA has restricted or canceled many of the uses of arsenic in pesticides and is 

considering further restrictions. Third, in January 2001, the EPA lowered the limit for arsenic in 

drinking water from 50 to 10 ppb. Finally, OSHA has established a permissible exposure limit 

(PEL), 8-hour time-weighted average, of 10 μg/m3 for airborne arsenic in various workplaces 

that use inorganic arsenic. 

You can find more information on regulations and guidelines that apply to arsenic in Chapter 8. 
ARSENIC 14 

1. PUBLIC HEALTH STATEMENT 

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-32 

 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/ 
ARSENIC 15 

2. RELEVANCE TO PUBLIC HEALTH 

2.1 BACKGROUND AND ENVIRONMENTAL EXPOSURES TO ARSENIC IN THE UNITED 

STATES 

Arsenic is widely distributed in the Earth's crust, which contains ~3.4 ppm arsenic. In nature, arsenic is 

mostly found in minerals and only to a small extent in its elemental form. Arsenic is mainly obtained as a 

byproduct of the smelting of copper, lead, cobalt, and gold ores. Arsenic trioxide is the primary form in 

which arsenic is marketed and consumed. There has been no domestic production of arsenic since 1985. 

In 2003, the world’s largest producer of arsenic compounds was China, followed by Chile and Peru. 

In 2003, the United States was the world's largest consumer of arsenic. Production of wood preservatives, 

primarily copper chromated arsenate (CCA), CrO3•CuO•As2O5, accounted for >90% of domestic 

consumption of arsenic trioxide. In response to consumer concerns, U.S. manufacturers of arsenical 

wood preservative began a voluntary transition from CCA to other wood preservatives for certain 

residential wood products. This phase-out was completed on December 31, 2003; wood treated prior to 

this date could still be used and CCA-treated wood products continue to be used in industrial applications. 

Other uses for arsenic compounds include the production of agricultural chemicals, as an alloying element 

in ammunition and solders, as an anti-friction additive to metals used for bearings, and to strengthen leadacid storage battery grids. High-purity arsenic (99.9999%) is used by the electronics industry for galliumarsenide semiconductors for telecommunications, solar cells, and space research. Various organic 

arsenicals are still used in the United States as herbicides and as antimicrobial additives for animal and 

poultry feed. However, the use of inorganic arsenic compounds in agriculture has virtually disappeared 

beginning around the 1960s. Arsenic trioxide and arsenic acid were used as a decolorizer and fining 

agent in the production of bottle glass and other glassware. Arsenic compounds also have a long history 

of use in medicine, and have shown a re-emergence of late with the recent introduction of arsenic trioxide 

treatment for acute promyelocytic leukemia. 

The principal route of exposure to arsenic for the general population is likely to be the oral route, 

primarily in the food and in the drinking water. Dietary exposures to total arsenic were highly variable, 

with a mean of 50.6 μg/day (range of 1.01–1,081 μg/day) for females and 58.5 μg/day (range of 0.21– 

1,276 μg/day) for males. U.S. dietary intake of inorganic arsenic has been estimated to range from 1 to 

20 μg/day, with grains and produce expected to be significant contributors to dietary inorganic arsenic 
ARSENIC 16 

2. RELEVANCE TO PUBLIC HEALTH 

intake. Drinking water generally contains an average of 2 μg/L of arsenic, although 12% of water 

supplies from surface water sources in the North Central region of the country and 12% of supplies from 

groundwater sources in the Western region have levels exceeding 20 μg/L. Arsenic is also widely 

distributed in surface water, groundwater, and finished drinking water in the United States. Surveys of 

arsenic concentrations in rivers and lakes indicate that most values are below 10 μg/L, although individual 

samples may range up to 3,400 μg/L. Arsenic released to the land at hazardous waste sites is likely to be 

relatively immobile due to a high capacity for soil binding, particularly to iron and manganese oxides. 

Exposure to arsenic from other pathways is generally small, but may be significant for areas with high 

levels of arsenic contamination or in occupational settings. For a more complete discussion of possible 

exposures to arsenic, see Chapter 6 of the profile. 

2.2 SUMMARY OF HEALTH EFFECTS 

Arsenic is a potent toxicant that may exist in several oxidation states and in a number of inorganic and 

organic forms. Most cases of arsenic-induced toxicity in humans are due to exposure to inorganic arsenic, 

and there is an extensive database on the human health effects of the common arsenic oxides and 

oxyacids. Although there may be some differences in the potency of different chemical forms (e.g., 

arsenites tend to be somewhat more toxic than arsenates), these differences are usually minor. An 

exception would be arsine, which is highly toxic. However, because arsine and its methyl derivatives are 

gases or volatile liquids and are unlikely to be present at levels of concern at hazardous waste sites, health 

effect data for these compounds are not discussed in this document. Humans may be exposed to organic 

arsenicals (mainly methyl and phenyl derivatives of arsenic acid) that are used in agriculture and to 

organic arsenicals found in fish and shellfish (arsenobetaine and arsenocholine). Although the toxicity of 

organic arsenicals has not been as extensively investigated as inorganic arsenicals, there are sufficient 

animal data to evaluate the toxicity of methyl arsenates (e.g., monomethylarsonic acid [MMA] and 

dimethylarsinic acid [DMA]) and roxarsone. The so-called “fish arsenic” compounds (e.g., 

arsenobetaine) are not thought to be toxic and health effects data are not discussed in this document. 

It is generally accepted that the arsenic-carbon bond is quite strong and most mammalian species do not 

have the capacity to break this bond; thus, inorganic arsenic is not formed during the metabolism of 

organic arsenicals. In most species, including humans, ingested (or exogenous) MMA(V) and DMA(V) 

undergo limited metabolism, do not readily enter the cell, and are primarily excreted unchanged in the 

urine. This is in contrast to inorganic arsenic, which undergoes sequential reduction and methylation 

reactions leading to the formation of MMA and DMA. Inorganic As(V) is readily reduced to inorganic 
ARSENIC 17 

2. RELEVANCE TO PUBLIC HEALTH 

As(III), which is taken up by the cell. Within the cell (primarily in the liver), As(III) is methylated to 

form MMA(V), which is reduced to MMA(III); MMA(III) subsequently undergoes oxidative 

methylations to form DMA(V). DMA(V) is the primary excretion product in humans. Because inorganic 

and organic arsenicals exhibit distinct toxicokinetic characteristics, the health effects and MRLs are 

considered separately. 

Inorganic Arsenicals. Exposures of humans near hazardous waste sites could involve inhalation of 

arsenic dusts in air, ingestion of arsenic in water, food, or soil, or dermal contact with contaminated soil 

or water. Increased risk of lung cancer, respiratory irritation, nausea, skin effects, and neurological 

effects have been reported following inhalation exposure. There are only a few quantitative data on 

noncancer effects in humans exposed to inorganic arsenic by the inhalation route. Animal data similarly 

identify effects on the respiratory system as the primary noncancer effect of inhaled inorganic arsenic 

compounds, although only a few studies are available. Only limited data on the effects of inhaled organic 

arsenic compounds in humans or animals are available; these studies are generally limited to high-dose, 

short-term exposures, which result in frank effects. 

Relatively little information is available on effects due to direct dermal contact with inorganic arsenicals, 

but several studies indicate that the chief effect is local irritation and dermatitis, with little risk of other 

adverse effects. 

The database for the oral toxicity of inorganic arsenic is extensive, containing a large number of studies of 

orally-exposed human populations. These studies have identified effects on virtually every organ or 

tissue evaluated, although some end points appear to be more sensitive than others. The available data 

from humans identify the skin as the most sensitive noncancer target following long-term oral arsenic 

exposure. Typical dermal effects include hyperkeratinization of the skin (especially on the palms and 

soles), formation of multiple hyperkeratinized corns or warts, and hyperpigmentation of the skin with 

interspersed spots of hypopigmentation. Oral exposure data from studies in humans indicate that these 

lesions typically begin to manifest at exposure levels of about 0.002–0.02 mg As/kg/day, but one study 

suggests that lesions may appear at even lower levels. At these exposure levels, peripheral vascular 

effects are also commonly noted, including cyanosis, gangrene, and, in Taiwanese populations, the 

condition known as “Blackfoot Disease.” Other reported cardiovascular effects of oral exposure to 

inorganic arsenic include increased incidences of high blood pressure and circulatory problems. The use 

of intravenous arsenic trioxide as therapy for acute promyelocytic leukemia has raised further concerns 

about the cardiovascular effects of arsenic, including alterations in cardiac QT interval and the 
ARSENIC 18 

2. RELEVANCE TO PUBLIC HEALTH 

development of torsades de pointes. Decrements in lung function, assessed by spirometry, have been 

reported in subjects exposed to approximately 0.008–0.04 mg As/kg/day in the drinking water who 

exhibited skin lesions. 

In addition to dermal, cardiovascular, and respiratory effects, oral exposure to inorganic arsenic may 

result in effects on other organ systems. Nausea, vomiting, and diarrhea are very common symptoms in 

humans following oral exposure to inorganic arsenicals, both after acute high-dose exposure and after 

repeated exposure to lower doses; these effects are likely due to a direct irritation of the gastrointestinal 

mucosa. Acute, high-dose exposure can lead to encephalopathy, with clinical signs such as confusion, 

hallucinations, impaired memory, and emotional lability, while long-term exposure to lower levels can 

lead to the development of peripheral neuropathy characterized by a numbness in the hands and feet that 

may progress to a painful "pins and needles" sensation. Recent studies also have reported 

neurobehavioral alterations in arsenic-exposed children. 

Chronic exposure of humans to inorganic arsenic in the drinking water has been associated with excess 

incidence of miscarriages, stillbirths, preterm births, and infants with low birth weights. Animal data 

suggest that arsenic may cause changes to reproductive organs of both sexes, including decreased organ 

weight and increased inflammation of reproductive tissues, although these changes may be secondary 

effects. However, these changes do not result in a significant impact on reproductive ability. Animal 

studies of oral inorganic arsenic exposure have reported developmental effects, but generally only at 

concentrations that also resulted in maternal toxicity. 

Arsenic is a known human carcinogen by both the inhalation and oral exposure routes. By the inhalation 

route, the primary tumor types are respiratory system cancers, although a few reports have noted 

increased incidence of tumors at other sites, including the liver, skin, and digestive tract. In humans 

exposed chronically by the oral route, skin tumors are the most common type of cancer. In addition to 

skin cancer, there are a number of case reports and epidemiological studies that indicate that ingestion of 

arsenic also increases the risk of internal tumors (mainly of bladder and lung, and to a lesser extent, liver, 

kidney, and prostate). 

The Department of Health and Human Services (DHHS) has concluded that inorganic arsenic is known to 

be a human carcinogen. The International Agency for Research on Cancer (IARC) cites sufficient 

evidence of a relationship between exposure to arsenic and human cancer. The IARC classification of 

arsenic is Group 1. The EPA has determined that inorganic arsenic is a human carcinogen by the 
ARSENIC 19 

2. RELEVANCE TO PUBLIC HEALTH 

inhalation and oral routes, and has assigned it the cancer classification, Group A. EPA has calculated an 

oral cancer slope factor of 1.5 (mg/kg/day)

-1 and a drinking water unit risk of 5x10-5 (μg/L)-1 for inorganic 

arsenic based on human dose-response data. The inhalation unit risk for cancer is calculated to be 

0.0043 (μg/m3

)

-1. The unit risk is the upper-bound excess lifetime cancer risk estimated to result from 

continuous exposure to an agent at a concentration of 1 μg/L in water or 1 μg/m3

 in air. EPA is currently 

revising the assessment for inorganic arsenic; a more detailed discussion of the uncertainties associated 

with human cancer risk levels for arsenic is presented in Section 3.2.2.7. 

The following sections discuss significant effects resulting from exposure to inorganic arsenic in greater 

detail: dermal, cardiovascular, respiratory, gastrointestinal, neurological, and cancer. Additional 

information on these effects and on other effects is discussed in Section 3.2. 

Dermal Effects. The most characteristic effect of long-term oral exposure to inorganic arsenic 

compounds is the development of skin lesions; these lesions are often used as diagnostic criteria for 

arsenicosis. The three lesions most often associated with chronic arsenicosis are hyperkeratinization of 

the skin (especially on the palms and soles), formation of multiple hyperkeratinized corns or warts, and 

hyperpigmentation of the skin with interspersed spots of hypopigmentation. Numerous studies of longterm, low-level exposure to inorganic arsenic in humans have reported the presence of these lesions. In 

general, they begin to manifest at chronic exposure levels >0.02 mg As/kg/day. Chronic oral studies of 

lower exposure levels, ranging from 0.0004 to 0.01 mg As/kg/day, have generally not reported dermal 

effects. However, in a study with detailed exposure assessment, all confirmed cases of skin lesions 

ingested water containing >100 μg/L arsenic (approximately 0.0037 mg As/kg/day) and the lowest known 

peak arsenic concentration ingested by a case was 0.115 μg/L (approximately 0.0043 mg As/kg/day). 

Another large study reported increased incidence of skin lesions associated with estimated doses of 

0.0012 mg As/kg/day (0.023 mg As/L drinking water). The mechanism(s) by which inorganic arsenic 

causes dermal effects is not well-understood. Elucidating the mechanism of dermal effects has been 

particularly difficult because the dermal effects common in humans have not been seen in studies in 

animals. 

Dermal effects have also been reported following inhalation exposures to inorganic arsenic, although they 

are not as diagnostic as for oral exposure. Several studies of arsenic-exposed workers have reported the 

development of dermatitis; exposure levels required to produce this condition are not well-established. 

Altered dermal pigmentation and hyperkeratosis have also been reported in studies of humans exposed to 

inorganic arsenic by inhalation, although exposure levels have varied considerably. Direct dermal contact 
ARSENIC 20 

2. RELEVANCE TO PUBLIC HEALTH 

with inorganic arsenicals may cause irritation and contact dermatitis. Usually, the effects are mild 

(erythema and swelling), but may progress to papules, vesicles, or necrotic lesions in extreme cases; these 

conditions tend to heal without treatment if exposure ceases. 

Cardiovascular Effects. A large number of studies in humans have reported cardiovascular effects 

following oral exposure to inorganic arsenic compounds. The cardiac effects of arsenic exposure are 

numerous, and include altered myocardial depolarization (prolonged QT interval, nonspecific ST segment 

changes), cardiac arrhythmias, and ischemic heart disease. These effects have been seen after acute and 

long-term exposure to inorganic arsenic in the environment, as well as side effects from intravenous 

therapy with arsenic trioxide for acute promyelocytic leukemia. Exposure levels for environmental 

exposures have not been well characterized, but intravenous doses for arsenic trioxide therapy are 

generally on the order of 0.15 mg As/kg/day. 

Chronic exposure to inorganic arsenic has also been shown to lead to effects on the vascular system. The 

most dramatic of these effects is “Blackfoot Disease,” a disease characterized by a progressive loss of 

circulation in the hands and feet, leading ultimately to necrosis and gangrene. Blackfoot Disease is 

endemic in an area of Taiwan where average drinking water levels of arsenic range from 0.17 to 

0.80 ppm, corresponding to doses of about 0.014–0.065 mg As/kg/day. The results of a another study 

suggested that individuals with a lower capacity to methylate inorganic arsenic to DMA have a higher risk 

of developing peripheral vascular disease in the Blackfoot Disease-hyperendemic area in Taiwan. 

Arsenic exposure in Taiwan has also been associated with an increased incidence of cerebrovascular and 

microvascular diseases and ischemic heart disease. While Blackfoot Disease itself has not been reported 

outside of Taiwan, other vascular effects are common in areas with high arsenic exposures, and include 

such severe effects as increases in the incidences of Raynaud's disease and of cyanosis of fingers and toes 

as well as hypertension, thickening and vascular occlusion of blood vessels, and other unspecified 

cardiovascular conditions. However, while the majority of human studies have reported cardiovascular 

effects following exposure to inorganic arsenic, some have found no such effects. 

Changes in cardiac rhythm and in some vascular end points have also been reported in animal studies of 

inorganic arsenicals, but generally only at higher exposure levels and not to the degree of severity seen in 

humans. 

Respiratory Effects. While case reports and small cohort studies have routinely reported an increase 

in respiratory symptoms of humans exposed occupationally to inorganic arsenic, dose-response data for 
ARSENIC 21 

2. RELEVANCE TO PUBLIC HEALTH 

these symptoms are generally lacking. The only study that evaluated respiratory effects (changes in chest 

x-ray or respiratory performance) and reported an exposure estimate did not report significant changes at 

an exposure level of 0.613 mg As/m3

. Exposed workers often report irritation of the mucous membranes 

of the nose and throat, which may lead to laryngitis, bronchitis, or rhinitis. Increased mortality due to 

respiratory disease has been reported in some cohort mortality studies of arsenic-exposed workers, but no 

conclusive evidence of an association of these diseases with arsenic exposure has been presented. It is not 

known whether respiratory effects following inhaled inorganic arsenic compounds are due to a direct 

effect of arsenic on respiratory tissues, general effects of foreign material in the lungs, or an effect of 

arsenic on the pulmonary vasculature. Similar responses, including rales, labored breathing, and 

respiratory hyperplasia, have been noted in animal studies of inhaled or instilled inorganic arsenic 

compounds. 

Respiratory effects have also been reported following oral exposure of humans to inorganic arsenic. 

Acute oral exposure to ≥8 mg As/kg may result in serious respiratory effects, including respiratory 

distress, hemorrhagic bronchitis, and pulmonary edema; however, it is not clear whether these are primary 

effects or are the result of damage to the pulmonary vascular system. In general, respiratory effects have 

not been widely associated with long-term oral exposure to low arsenic doses. However, some studies 

have reported minor respiratory symptoms, such as cough, sputum, rhinorrhea, and sore throat, in people 

with repeated oral exposure to 0.03–0.05 mg As/kg/day. More serious respiratory effects, such as 

bronchitis and sequelae (bronchiectasis, bronchopneumonia) have been observed in patients chronically 

exposed to arsenic and at autopsy in some chronic poisoning cases. There are few animal data reporting 

respiratory effects of oral exposure to inorganic arsenic, and those studies generally found effects only at 

very high dose levels. 

Gastrointestinal Effects. Both short-term and chronic oral exposures to inorganic arsenicals have 

been reported to result in irritant effects on gastrointestinal tissues. Numerous studies of acute, high-dose 

exposure to inorganic arsenicals have reported nausea, vomiting, diarrhea, and abdominal pain, although 

specific dose levels associated with the onset of these symptoms have not been identified. Chronic oral 

exposure to 0.01 mg As/kg/day generally results in similar reported symptoms. For both acute and 

chronic exposures, the gastrointestinal effects generally diminish or resolve with cessation of exposure. 

Similar gastrointestinal effects have been reported after occupational exposures to inorganic arsenicals, 

although it is not known if these effects were due to absorption of arsenic from the respiratory tract or 

from mucociliary clearance resulting in eventual oral exposure. 
ARSENIC 22 

2. RELEVANCE TO PUBLIC HEALTH 

Neurological Effects. A common effect following both oral and inhalation exposure to inorganic is 

the development of peripheral neuropathy. Following occupational exposure to inorganic arsenic in 

pesticide plants or smelters, exposed workers have shown increased incidence of neurological changes, 

including altered nerve conduction velocities. One study reported that these effects were seen after 

28 years of exposure to 0.31 mg As/m3

. In another study, signs and symptoms of sensory and motor 

polyneuropathy on both upper and lower extremities were reported in workers at a power station in 

Slovakia. The average length of exposure was 22.3 years (standard deviation [SD] ±8.4 years) and the 

average arsenic exposure in inhaled air ranged from 4.6 to 142.7 μg/m3

. 

Following high-dose (>2 mg As/kg/day) acute oral exposures to inorganic arsenicals in humans, reported 

effects include headache, lethargy, mental confusion, hallucination, seizures, and coma. Following 

longer-term exposure to 0.03–0.1 mg As/kg/day, peripheral neuropathy, characterized initially by 

numbness of the hands and feet and a “pins and needles” sensation and progressing to muscle weakness, 

wrist-drop and/or ankle-drop, diminished sensitivity, and altered reflex action. Histological features of 

the neuropathy include a dying-back axonopathy and demyelination. Following removal from exposure, 

the neuropathy is only partially reversible and what recovery does occur is generally slow. Reports of 

neurological effects at lower arsenic levels (0.004–0.006 mg As/kg/day) have been inconsistent, with 

some human studies reporting fatigue, headache, depression, dizziness, insomnia, nightmare, and 

numbness while others reported no neurological effects. Some studies also have reported that exposure to 

arsenic may be associated with intellectual deficits in children. Neurological effects have also been 

reported in oral studies of arsenic toxicity in animals, although these were generally performed at higher 

doses (0.4–26.6 mg As/kg/day) than has been reported in exposed human populations. The mechanism(s) 

of arsenic-induced neurological changes has not been determined. 

Cancer. There is clear evidence from studies in humans that exposure to inorganic arsenic by either the 

inhalation or oral routes increases the risk of cancer. Numerous studies of copper smelters or miners 

exposed to arsenic trioxide have reported an increased risk of lung cancer. Increased incidence of lung 

cancer has also been observed at chemical plants where exposure was primarily to arsenate. Other studies 

suggest that residents living near smelters or arsenical chemical plants may have increased risk of lung 

cancer, although the reported increases are small and are not clearly detectable in all cases. In general, 

studies reporting long-term exposure to 0.07 mg As/m3

 or greater have shown an increased incidence of 

lung cancer, while at lower exposure levels, the association has been less clear or not present. 
ARSENIC 23 

2. RELEVANCE TO PUBLIC HEALTH 

There is convincing evidence from a large number of epidemiological studies and case reports that 

ingestion of inorganic arsenic increases the risk of developing skin cancer. The most common tumors 

seen are squamous cell carcinomas, which may develop from the hyperkeratotic warts or corns commonly 

seen as a dermal effect of oral inorganic arsenic exposure. Early studies of populations within the United 

States did not suggest an increased risk of cancer from oral inorganic arsenic exposure. Later studies 

have found suggestive evidence that the possibility of arsenic-induced skin cancers cannot be discounted 

based on an association between toenail arsenic levels and incidence of skin cancer. 

There is increasing evidence that long-term exposure to arsenic can result in the development of bladder 

cancer, with transitional cell cancers being the most prevalent. While studies have noted statistical doseresponse trends in arsenic-induced bladder cancers, reliable quantitative assessments of dose-response 

relationships have not been presented. Several studies have also shown that chronic oral exposure to 

arsenic results in the development of respiratory tumors, making lung cancer an established cause of death 

from exposure to arsenic in drinking water. Exposure levels in studies evaluating respiratory and bladder 

cancers have been comparable to those in studies evaluating skin tumors. Studies of U.S. populations 

have not identified an increased risk of bladder or respiratory tumors following oral exposure to inorganic 

arsenic. 

Animal studies of both inhalation and oral exposure to inorganic arsenicals have not resulted in increased 

incidence of cancer formation in adult animals. However, a series of studies have shown that inorganic 

arsenic can induce cancer in the offspring from mice exposed to arsenic during gestation (transplacental 

carcinogen) and acts as a co-carcinogen with UV light and polycyclic aromatic hydrocarbons (PAHs). 

Organic Arsenicals. Humans may be exposed to organic arsenicals via inhalation of dusts, ingestion of 

organic arsenic in water, food, soil, or dermal contact with contaminated soil, water or plants following 

pesticide application. There are limited data on the toxicity of organic arsenicals following inhalation 

exposure in humans and animals and these data do not allow for identification of critical effects. 

Keratosis was observed in workers exposed to 0.065 mg/m3 arsanilic acid (i.e., 4-aminophenyl arsenic 

acid); no alterations in gastrointestinal symptoms or hematological alterations were observed. In animals, 

very high concentrations (>3,000 mg/m3

) of DMA results in respiratory distress, diarrhea, and 

erythematous lesions on the feet and ears. No adverse effects were observed in rats exposed to DMA 

concentrations as high as 100 mg DMA/m3

 for 95 days. 
ARSENIC 24 

2. RELEVANCE TO PUBLIC HEALTH 

Similarly, the available dermal toxicity data do not allow for identification of critical effects. Contact 

dermatitis was observed in workers applying DMA (and its sodium salt) and mild dermal irritation was 

observed in a Draize test in rabbits (adverse effect level not reported). Intermediate duration (21 days) 

exposure studies in rabbits did not result in systemic toxicity or skin irritation following 5 day/week 

exposure to 1,000 mg/kg/day MMA or DMA. 

The preponderance of toxicity data for organic arsenicals involves oral exposure. Human data are limited 

to three case reports of individuals intentionally ingesting pesticides containing organic arsenicals. 

Gastrointestinal irritation (vomiting, nausea, and diarrhea) were consistently reported in these cases. 

Animal data has primarily focused on the toxicity of MMA, DMA, and roxarsone; these data suggest that 

the targets of toxicity may differ between the compounds. 

MMA. The gastrointestinal tract appears to be the most sensitive target of toxicity for MMA. Diarrhea 

and tissue damage in the large intestine have been reported in several animal species following dietary, 

gavage, and capsule exposure. For diarrhea, both the time of onset and incidence appear to be doserelated. In rats, diarrhea was observed in 100% of females exposed to 98.5 mg MMA/kg/day, 55% of 

females exposed to 33.9 mg MMA/kg/day, and 5.1% of females exposed to 3.9 mg MMA/kg/day. The 

increased incidence of diarrhea was observed after 3 weeks of exposure to 98.5 mg MMA/kg/day, 

4 weeks at 33.9 mg MMA/kg/day, and 18 months at 3.9 mg MMA/kg/day. Histological damage 

consisting of squamous metaplasia of the epithelial columnar absorptive cells in the cecum, colon, and 

rectum was observed in rats and mice chronically exposed to 72.4 or 67.1 mg MMA/kg/day, respectively. 

Hemorrhagic, necrotic, ulcerated, or perforated mucosa were also observed in the large intestine of rats 

exposed to 67.1 mg MMA/kg/day for 2 years. In rats, the damage to the large intestine resulted in 

intestinal contents leaking into the abdominal cavity and the development of peritonitis. The available 

data provide suggestive evidence that there may be some species differences in the sensitivity to 

gastrointestinal damage; however, some of these differences may be due to the route of administration. 

The lowest adverse effect levels, regardless of duration of exposure, for gastrointestinal effects in rats, 

mice, rabbits, and dogs are 25.7, 67.1, 12, and 2 mg MMA/kg/day, respectively; the no adverse effect 

levels in rats and mice (NOAELs were not identified in rabbits and dogs) were 3.0 and 24.9 mg 

MMA/kg/day. However, the rabbit and dog studies involved bolus administration (gavage and capsule 

administration), which may have increased sensitivity; the rat and mouse studies involved dietary 

exposure. 
ARSENIC 25 

2. RELEVANCE TO PUBLIC HEALTH 

The kidney also appears to be a sensitive target in rats and mice chronically exposed to MMA. An 

increase in the severity of progressive glomerulonephropathy was observed in female rats exposed to 

33.9 mg MMA/kg/day for 2 years and an increase in the incidence of progressive glomerulonephropathy 

was observed in male mice exposed to 6.0 mg MMA/kg/day for 2 years. Other adverse effects that have 

been observed in animals exposed to MMA include hypertrophy of the thyroid follicular cells in rats 

exposed to 33.9 mg MMA/kg/day in the diet for 2 years, reproductive toxicity, and developmental 

toxicity. Decreases in pregnancy rate and male fertility index were observed in F0 and F1 rats exposed to 

76 mg MMA/kg/day for 14 weeks prior to mating and during the mating period; the findings were not 

significantly different than control values but were considered treatment-related because they were 

outside the range found in historical controls. This study also reported a decrease in pup survival in the F1 

and F2 offspring of rats exposed to 76 mg MMA/kg/day; as with the reproductive effects, the incidence 

was not statistically different from controls but was considered biologically significant because survival 

in the MMA pups was outside the range found in historical controls. Another study reported impaired 

fetal growth (decreases in fetal weights and incomplete ossification) and minor skeletal defects (an 

increase in the number of fetuses with supernumerary thoracic ribs and eight lumbar vertebrae) in rat and 

rabbit fetuses exposed to 500 or 12mg MMA/kg/day, respectively; maternal toxicity was also observed at 

these dose levels and the effects may be secondary to maternal stress rather than a direct effect on the 

developing organisms. A 2-year bioassay did not result in significant increases in the incidence of 

neoplastic lesions in rats and mice exposed to doses as high as 72.4 and 67.1 mg MMA/kg/day, 

respectively. 

DMA. The most sensitive targets of DMA toxicity in rats are the urinary bladder and kidneys. In the 

bladder, the effects progress from cytotoxicity to cellular necrosis to regenerative proliferation and 

hyperplasia. At dietary doses of 11 mg DMA/kg/day, cytotoxicity is observed as early as 6 hours after 

exposure initiation and cellular proliferation (as evident by increased BrdU labeling) was observed after 

2 weeks of exposure. After 10 weeks of exposure, necrosis and hyperplasia were also observed. The 

lowest adverse effect levels for urinary bladder effects following intermediate or chronic duration 

exposure were 5 mg DMA/kg/day for evidence of regenerative proliferation and 3.1 mg DMA/kg/day for 

vacuolar degeneration of urothelium and hyperplasia. Vacuolization of the superficial cells of the 

urothelium was observed in mice exposed to 7.8 mg DMA/kg/day and higher for 2 years. However, 

unlike the vacuolar degeneration observed in rats, the vacuolization observed in mice was not associated 

with cytotoxicity, necrosis, inflammation, or hyperplasia. 
ARSENIC 26 

2. RELEVANCE TO PUBLIC HEALTH 

Kidney damage characterized by increased urinary calcium levels, calcification, nephrocalcinosis, and 

necrosis of the renal papillae have been observed in rats following intermediate- or chronic-duration 

exposure. Increases in urine calcium levels and corticomedullary junction calcification were observed in 

rats exposed to 5 or 10 mg DMA/kg/day for 10 weeks and cortical degeneration and necrosis were 

observed in rats exposed to 57 mg DMA/kg/day for 4 weeks. Chronic-duration exposure to 3.1 mg 

DMA/kg/day resulted in an increased incidence of nephrocalcinosis and necrosis of the renal papillae in 

rats; these lesions are typical in aged rats, although DMA exposure appeared to exacerbate them. An 

exacerbation of age-related kidney lesion (progressive glomerulonephropathy and nephrocalcinosis) has 

also been observed in male mice exposed to 37 or 94 mg DMA/kg/day, respectively, for 2 years. A 

consistent finding in intermediate and chronic rat studies is an increase in urine volume, which 

corresponds to an increase in water consumption; the toxicological significance of this finding is not 

known. The observed decreases in electrolyte levels and specific gravity are likely due to the higher urine 

volume. 

Although gastrointestinal effects have been observed in animals exposed to DMA, it does not appear to be 

as sensitive a target compared to MMA. Diarrhea has been observed in rats exposed to a lethal dose of 

190 mg DMA/kg/day for 4 weeks and in dogs administered via 16 mg DMA/kg/day. No gastrointestinal 

effects were observed in rats or mice chronically exposed to 7.8 or 94 mg DMA/kg/day. 

Other adverse effects that have been observed in animals exposed to organic arsenicals include 

hypertrophy of thyroid follicular cells in rats exposed to 4.0 mg DMA/kg/day in the diet for 13 weeks and 

7.8 mg DMA/kg/day in the diet for 2 years and developmental effects in rats and mice. Decreases in fetal 

growth and delays in ossification have been observed in rat fetuses exposed to ≥36 mg DMA/kg/day; 

these alterations typically occur at doses associated with decreases in maternal weight gain. Other 

developmental effects that have been reported include an increase in the incidences of irregular palatine 

rugae in rats exposed to 30 mg DMA/kg/day, diaphragmatic hernia in rats exposed to 36 mg 

DMA/kg/day, and cleft palate in mice exposed to 400 mg DMA/kg/day. No developmental effects were 

observed in rabbits exposed to 12 mg DMA/kg/day. 

The available data provide strong evidence that DMA is carcinogenic in rats. A 2-year exposure to DMA 

resulted in significant increases in the incidence of neoplastic urinary bladder tumors in rats exposed to 

7.8 mg DMA/kg/day in the diet or 3.4 mg DMA/kg/day in drinking water. No increases in neoplastic 

tumors were observed in mice exposed to doses as high as 94 mg DMA/kg/day for 2 years; however, a 
ARSENIC 27 

2. RELEVANCE TO PUBLIC HEALTH 

50-week exposure to 10.4 mg DMA/kg/day did result in an increased incidence of lung tumors in 

A/J mice. 

The available data for DMA suggest that there are species differences in terms of the critical effects and 

sensitivity. In rats, the urinary bladder and kidneys are the most sensitive targets with effects occurring at 

5 mg DMA/kg/day following intermediate-duration exposure and 3.1 mg DMA/kg/day following 

chronic-duration exposure. Although the urinary bladder and kidneys are also sensitive targets in mice 

with LOAELs of 7.8 and 37 mg DMA/kg/day, respectively, following chronic exposure, the effects are 

not associated with cytotoxicity or elevated urine calcium levels. In dogs, the most sensitive effect is 

gastrointestinal tract irritation (diarrhea), which occurs at 16 mg DMA/kg/day. 

There is concern that the rat may not be a good model to predict the human risk associated with organic 

arsenic exposure due to the unique toxicokinetic properties of DMA in rats. In humans and most animal 

species, DMA is rapidly eliminated from the body; >90% of the dose is excreted 2–3 days after dosing. 

In contrast, DMA is slowly eliminated in rats. One study estimated that 45% of an initial oral DMA dose 

was eliminated with a half-time of 13 hours; the remaining 55% of the dose DMA dose had an 

elimination half-time of 50 days. In rats, DMA has a strong affinity for hemoglobin resulting in an 

accumulation of DMA in erythrocytes. Species differences in DMA metabolism have also been found. 

In particular, DMA undergoes further methylation to trimethylarsine oxide (TMAO) in rats. In most 

animal species, almost the entire oral DMA dose is excreted in the urine unchanged; however, in rats, 

about half of the dose is excreted in the urine as DMA and the other half as TMAO. During the 

metabolism of DMA to TMAO, DMA(III) is formed as a metabolic intermediate. The formation of this 

highly reactive intermediate and the excretion of small amounts of DMA(III) in urine may damage the 

urinary bladder. 

There are limited data on the mode of action of DMA for most end points. Recently, there has been 

considerable research on the mode of action for the development of neoplastic urinary bladder tumors in 

rats. Although the mechanisms have not been fully elucidated, it has been proposed that the mode of 

action involves cytotoxicity leading to necrosis and subsequent regeneration of the urinary bladder 

urothelium. There is strong evidence to suggest that DMA(III) is the causative agent for the urothelial 

cytotoxicity. The strongest evidence comes from the finding that urinary concentrations of DMA(III) 

measured in rats exhibiting urothelial cytotoxicity are equivalent to DMA(III) concentrations that are 

cytotoxic to urothelial cells in vitro. Urothelial cytotoxicity, regenerative urothelial proliferation, and 

urothelial tumors have not been detected in other animal species. Other animal species, including 
ARSENIC 28 

2. RELEVANCE TO PUBLIC HEALTH 

humans, only metabolize a small percentage of ingested DMA to TMAO; thus, much lower levels of 

DMA(III) are produced, suggesting that rats may be very sensitive to toxicity of DMA and therefore are 

not an appropriate model for human risk assessment. 

Roxarsone. The available data on the toxicity of roxarsone suggest that following bolus administration, 

the gastrointestinal tract, kidney, and nervous system are sensitive end points of roxarsone toxicity. 

Vomiting and gastrointestinal hemorrhage were observed in dogs receiving a single capsulized dose of 

50 mg/kg roxarone; no gastrointestinal effects were observed in rats or mice administered 4 or 

42 mg/kg/day roxarsone for 2 years. Kidney effects included increases in kidney weight, minimal tubular 

epithelial cell degeneration, and focal mineralization in rats exposed to 32 mg roxarsone/kg/day for 

13 weeks; no kidney effects were observed at 16 mg/kg/day or in mice exposed to doses as high as 

136 mg/kg/day for 13 weeks or 43 mg/kg/day for 2 years. Hyperexcitability, ataxia, and/or trembling 

were observed in rats exposed to 20 mg/kg/day for 13 weeks or 64 mg/kg/day for 13 weeks. A 14-day 

study in rats reported slight inactivity in rats exposed to 32 mg/kg/day, but this was not observed in 

longer-term studies. Neurological effects were observed in mice exposed to doses as high as 

136 mg/kg/day for 13 weeks or 43 mg/kg/day for 2 years, although a slight decrease in activity at 

42 mg/kg/day was reported in a 14 day study. Pigs appear to be especially sensitive to the neurotoxicity 

of roxarsone. Muscle tremors have been observed at doses of ≥6.3 mg roxarsone/kg/day and myelin 

degeneration in the spinal cord was noted at 6.3 mg/kg/day. Both the clinical signs of neuropathy and the 

myelin degeneration followed a time-related pattern. Mild lethargy and ataxia were observed 7 days after 

exposure initiation, exercise-induced muscle tremors and clonic seizures were observed at day 11, 

paraparesis was observed at day 22, and paraplegia was observed at day 33. At day 11, equivocal lesions 

were observed in the cervical spinal cord, and the severity of these lesions increased with time; myelin 

degeneration was observed in the peripheral nerves and optic nerve starting at day 32 (2 days after 

exposure termination). Equivocal evidence of carcinogenicity (a slight increase in the incidence of 

pancreatic tumors) was found in male rats chronically exposed to roxarsone; no increases in neoplastic 

tumors were observed in female rats or male and female mice. 

2.3 MINIMAL RISK LEVELS (MRLs) 

Estimates of exposure levels posing minimal risk to humans (MRLs) have been made for arsenic. 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 
ARSENIC 29 

2. RELEVANCE TO PUBLIC HEALTH 

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 1990i), 

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. 

Inorganic Arsenicals 

Inhalation MRLs. No inhalation MRLs were derived for inorganic arsenic. Human data suggest that 

dermal or respiratory effects may be the most prevalent (Lagerkvist et al. 1986; Mohamed 1998; Perry et 

al. 1948); respiratory or immunological effects appeared to be the most common following inhalation 

exposure to inorganic arsenic in animals (Aranyi et al. 1985; Holson et al. 1999). Adequate human 

studies evaluating dose-response relationships for noncancer end points were not located for inorganic 

arsenic, and animal data on the health effects of inorganic arsenic following inhalation exposure are 

limited to studies that did not evaluate a suitable range of health effects. Lacking suitable studies upon 

which to base the MRLs, no inhalation MRLs were derived for inorganic arsenic. 

Oral MRLs 

•	 An MRL of 0.005 mg As/kg/day has been derived for acute-duration (14 days or less) oral 

exposure to inorganic arsenic. 

Mizuta et al. (1956) summarized findings from 220 poisoning cases associated with an episode of arsenic 

contamination of soy sauce in Japan. The soy sauce was contaminated with approximately 0.1 mg 

As/mL, probably as calcium arsenate. Arsenic intake in the cases was estimated by the researchers to be 

3 mg/day (0.05 mg/kg/day, assuming 55 kg average body weight for this Asian population). The duration 

of exposure was 2–3 weeks in most cases. The primary symptoms were edema of the face, and 

gastrointestinal and upper respiratory symptoms initially, followed by skin lesions and neuropathy in 
ARSENIC 30 

2. RELEVANCE TO PUBLIC HEALTH 

some patients. Other effects included mild anemia and leukopenia, mild degenerative liver lesions and 

hepatic dysfunction, abnormal electrocardiogram, and ocular lesions. For derivation of the acute oral 

MRL, facial edema and gastrointestinal symptoms (nausea, vomiting, diarrhea), which were characteristic 

of the initial poisoning and then subsided, were considered to be the critical effects. The MRL of 

0.005 mg As/kg/day was calculated by applying an uncertainty factor of 10 (10 for use of a lowestobserved-adverse-effect level (LOAEL) and 1 for human variability) to the LOAEL of 0.05 mg As/kg/day 

(see Appendix A for MRL worksheets). 

An intermediate-duration oral MRL for inorganic arsenic was not derived due to inadequacy of the 

database. The lowest LOAEL identified in a limited number of intermediate-duration human studies 

available was 0.05 mg As/kg/day in a study by Mizuta et al. (1956) (summarized above). While this 

study was considered appropriate to derive an acute-duration oral MRL for inorganic arsenic, there is 

considerable uncertainty regarding what the effects and severity might be beyond the relatively short 2– 

3 weeks of exposure that most subjects experienced. There are numerous studies in animals dosed for 

intermediate durations, but as indicated in Section 3.5.3, animals are not appropriate models for effects of 

inorganic arsenic in humans. 

•	 An MRL of 0.0003 mg As/kg/day has been derived for chronic-duration (365 days or more) oral 

exposure to inorganic arsenic. 

Tseng et al. (1968) and Tseng (1977) investigated the incidence of Blackfoot Disease and dermal lesions 

(hyperkeratosis and hyperpigmentation) in a large number of poor farmers (both male and female) 

exposed to high levels of arsenic in well water in Taiwan. A control group consisting of 17,000 people, 

including one group in which arsenic exposure was “undetermined” and which included those villages 

where arsenic-contaminated wells were no longer used or the level could not be classified, and a control 

population of 7,500 people who consumed water from wells almost free of arsenic (0.001–0.017 ppm) 

was also examined. The authors stated that the incidence of dermal lesions increased with dose, but 

individual doses were not provided. However, incidence data were provided based on stratification of the 

exposed population into low (<300 μg/L), medium (300–600 μg/L), or high (>600 μg/L) exposure levels. 

Doses were calculated from group mean arsenic concentrations in well water, assuming the intake 

parameters described by IRIS (IRIS 2007). Accordingly, the control, low-, medium-, and high-exposure 

levels correspond to doses of 0.0008, 0.014, 0.038, and 0.065 mg As/kg/day, respectively. The noobserved-adverse-effect level (NOAEL) identified by Tseng (1977) (0.0008 mg As/kg/day) was limited 

by the fact that the majority of the population was <20 years of age and the incidence of skin lesions 

increased as a function of age, and because the estimates of water intake and dietary arsenic intake are 
ARSENIC 31 

2. RELEVANCE TO PUBLIC HEALTH 

highly uncertain. Schoof et al. (1998) estimated that dietary intakes of arsenic from rice and yams may 

have been 15–211 μg/day (mean=61 μg/day), based on arsenic analyses of foods collected in Taiwan in 

1993–1995. Use of the 50 μg/day estimate would result in an approximate doubling of the NOAEL 

(0.0016 mg/kg/day) (see Appendix A for MRL worksheets). The MRL was derived by applying an 

uncertainty factor of 3 (for human variability) to the NOAEL of 0.0008 mg/kg/day. 

The MRL is supported by a large number of well-conducted epidemiological studies that identify reliable 

NOAELs and LOAELs for dermal effects. EPA (1981b) identified a NOAEL of 0.006–0.007 mg 

As/kg/day for dermal lesions in several small populations in Utah. Harrington et al. (1978) identified a 

NOAEL of 0.003 mg As/kg/day for dermal effects in a small population in Alaska. Guha Mazumder et 

al. (1988) identified a NOAEL of 0.009 mg As/kg/day and a LOAEL of 0.006 mg As/kg/day for 

pigmentation changes and hyperkeratosis in a small population in India. Haque et al. (2003) identified a 

LOAEL of 0.002 mg As/kg/day for hyperpigmentation and hyperkeratosis in a case-control study in 

India. Cebrián et al. (1983) identified a NOAEL of 0.0004 mg As/kg/day and a LOAEL of 0.022 mg 

As/kg/day in two regions in Mexico. Borgoño and Greiber (1972) and Zaldívar (1974) identified a 

LOAEL of 0.02 mg As/kg/day for abnormal skin pigmentation in patients in Chile, and Borgoño et al. 

(1980) identified a LOAEL of 0.01 mg As/kg/day for the same effect in school children in Chile. 

Valentine et al. (1985) reported a NOAEL of 0.02 mg As/kg/day for dermal effects in several small 

populations in California. Collectively, these studies indicate that the threshold dose for hyperpigmentation and hyperkeratosis is approximately 0.002 mg As/kg/day. While many of these studies also 

identified effects on other end points at these exposure levels, including effects on gastrointestinal 

(Borgoño and Greiber 1972; Cebrián et al. 1983; Guha Mazumder et al. 1988; Zaldívar 1974), 

cardiovascular (Tseng et al. 1995, 1996), hepatic (Hernández-Zavala et al. 1998), and neurological end 

points (Guha Mazumder et al. 1988; Lianfang and Jianzhong 1994; Tsai et al. 2003), the overall database 

for dermal effects is considerably stronger than for effects on other end points. 

Organic Arsenicals 

Inhalation MRLs. No inhalation MRLs were derived for organic arsenic. Human data are limited to an 

occupational exposure study of workers exposed to 0.065 mg/m3

 ansanilic acid (Watrous and McCaughey 

1945). The exposed workers more frequently complained of keratosis than nonexposed workers. A 

limited number of animal studies have examined the toxicity of organic arsenicals following inhalation 

exposure. Respiratory distress and diarrhea were observed in rats and mice exposed to high 

concentrations of MMA and DMA (Stevens et al. 1979); at lower concentrations (1,540–3,150 mg 

DMA/m3

), respiratory irritation, as evidenced by a decrease in respiration rate, was observed in animals 
ARSENIC 32 

2. RELEVANCE TO PUBLIC HEALTH 

exposed to MMA or DMA (Stevens et al. 1979). The acute-duration studies do not clearly identify the 

most sensitive targets of inorganic arsenical toxicity; the available studies are of limited scope and none 

included a comprehensive histological examination. 

One study examined the toxicity of DMA in rats following intermediate-duration exposure. This study 

(Whitman 1994) found an increase in intracytoplasmic eosinophilic globules in the nasal turbinates of rats 

exposed to 34 or 100 mg/m3

 DMA 6 hours/day, 5 days/week for 67–68 exposures; no other adverse 

effects were observed in this comprehensive study. As discussed in greater detail in the oral MRL 

section, the toxicokinetic properties of DMA in rats differ from other species and rats do not appear to be 

a good model for human exposure. The half-time of DMA in the body is much longer in rats compared to 

other species, including humans, and DMA is more extensively methylated in rats. In the absence of data 

to determine whether the observed effect is due to a direct interaction of DMA, derivation of an 

intermediate-duration MRL using rat data is not recommended at this time. 

No studies examined the chronic toxicity of organic arsenicals precluding the derivation of a chronicduration inhalation MRL. 

Oral MRLs 

MMA. A limited number of animal studies have examined the acute oral toxicity of MMA. These 

studies consisted of LD50 studies in rats (Gur and Nyska 1990), mice (Kaise et al. 1989), and rabbits 

(Jaghabir et al. 1988) and developmental toxicity studies in rats (Irvine et al. 2006) and rabbits (Irvine et 

al. 2006); all studies administered MMA via gavage. Adverse effects reported in the LD50 studies 

included diarrhea in rats at 2,030 mg monosodium methane arsonate (MSMA)/kg (Gur and Nyska 1990), 

mice at 2,200 mg MMA/kg (Kaise et al. 1989) and rabbits at 60 mg MSMA/kg (Jaghabir et al. 1988) and 

respiratory arrest in mice at 1,800 mg MMA/kg/day (Kaise et al. 1989). These doses were at or near the 

LD50 levels of 2,449 mg MSMA/kg, 1,800 mg MMA/kg, 100 mg MSMA/kg for the rats, mice, and 

rabbits, respectively. In the developmental toxicity studies (Irvine et al. 2006), maternal effects included 

decreases in maternal body weight gain in rats (17% less than controls) and rabbits (70% less than 

controls) receiving gavage doses of 100 and 12 mg MMA/kg/day, respectively, and loose feces/diarrhea 

in rabbit does administered 12 mg MMA/kg/day. The NOAELs for maternal effects were 10 and 7 mg 

MMA/kg/day in the rats and rabbits, respectively. Minor developmental effects (decreased fetal weight, 

incomplete ossification, and supernumerary ribs) were also observed at the maternally toxic doses in the 

rats and rabbits (Irvine et al. 2006); these effects were probably secondary to the maternal stress. These 
ARSENIC 33 

2. RELEVANCE TO PUBLIC HEALTH 

data, coupled with the results of longer-term studies (Arnold et al. 2003; Waner and Nyska 1988), suggest 

that the gastrointestinal tract is a sensitive target of MMA toxicity. The rabbit developmental toxicity 

study (Irvine et al. 2006) identified the lowest LOAEL (12 mg MMA/kg/day) for gastrointestinal 

irritation. However, this study is not suitable for the derivation of an acute-duration oral MRL for MMA 

because the MMA was administered via bolus doses. It is likely that the observed gastrointestinal effect 

is a concentration-dependent effect; thus, at a given dose level, effects are more likely to occur following 

bolus administration. A marked decrease in body weight gain was also observed at this dose level. 

•	 An MRL of 0.1 mg MMA/kg/day has been derived for intermediate-duration (15–364 days) oral 

exposure to MMA. 

Three studies have examined the intermediate-duration toxicity of MMA; two of these are chronicduration studies reporting diarrhea and decreases in body weight gain after MMA exposure for <1 year. 

Diarrhea was observed in rats exposed to 30.2 mg MMA/kg/day in the diet (Arnold et al. 2003) and in 

dogs exposed via a capsule to 2 mg MMA/kg/day (Waner and Nyska 1988). Decreases in body weight 

were observed at the next highest doses, 106.9 mg MMA/kg/day in rats and 8 mg MMA/kg/day in dogs. 

In the rat study (Arnold et al. 2003), diarrhea was observed in 16.7 and 40% of the males and females, 

respectively, exposed to 30.2/35.9 mg MMA/kg/day during the first 52 weeks of the study; diarrhea first 

occurred after 4 weeks of exposure. At the highest dose level (106.9 mg MMA/kg/day), diarrhea was 

observed in all exposed male and female rats. In dogs, the increased incidence of diarrhea first occurred 

during weeks 25–28; at the highest dose tested in the study (35 mg MMA/kg/day), vomiting was also 

observed. A NOAEL of 3.5 mg MMA/kg/day was identified in the rat study; a NOAEL was not 

identified in the dog study. The remaining study in the intermediate-duration database is a 2-generation 

study that reported reproductive (decreased pregnancy rate and male fertility index in F0 and F1 

generations) and developmental (decreased pup survival in F1 and F2 generation) effects in rats exposed to 

76 mg MMA/kg/day in the diet (Schroeder 1994). The lowest LOAEL identified in the intermediateduration database is 2 mg MMA/kg/day for diarrhea in dogs (Waner and Nyska 1988). Although dogs 

appear to be more sensitive to the gastrointestinal effects of MMA, a direct comparison of the two studies 

is not possible due to the difference in the routes of exposure. It is possible that the bolus administration 

of MMA, in the form of a capsule, resulted in increased sensitivity of the dogs. Because the most likely 

route of exposure for humans would be ingestion and the critical effect appears to be irritation of the 

gastrointestinal tract, studies involving bolus administration (gavage or capsule) were not considered for 

derivation of oral MRLs. The Arnold et al. (2003) and Schroeder (1994) studies were considered as the 

basis for an intermediate-duration MRL. Of these two studies, Arnold et al. (2003) identified the lowest 
ARSENIC 34 

2. RELEVANCE TO PUBLIC HEALTH 

LOAEL, 30.2 mg MMA/kg/day, for gastrointestinal effects and was selected as the principal study for the 

intermediate-duration oral MRL. 

Arnold et al. (2003) exposed groups of 60 male and 60 female Fischer 344 rats to 0, 50, 400, or 

1,300 ppm MMA in the diet for 104 weeks. Using the average doses for weeks 1–50 reported in an 

unpublished version of this study (Crown et al. 1990), doses of 0, 3.5, 30.2, and 106.9 mg MMA/kg/day 

and 0, 4.2, 35.9, and 123.3 mg MMA/kg/day were calculated for males and females, respectively. Body 

weights, food consumption, and water intake were monitored regularly. Blood was taken at 3, 6, and 

12 months for clinical chemistry measurements, and urine samples were collected at the same interval. 

Mortality was increased in high-dose males and females during the first 52 weeks of the study. Body 

weights were decreased in the mid- and high-dose groups of both sexes; however, at 51 weeks, only the 

body weight for the high-dose males was <10% of the control weight (14.5%). Food and water 

consumption was increased in the mid- and high-dose groups. Diarrhea was observed in 100% of the 

high-dose males and females and in 16.7 and 40% of the mid-dose males and females during the first 

52 weeks of exposure. Diarrhea first occurred after 3 weeks of exposure to the high dose and 4 weeks of 

exposure to the mid-dose group; the severity of the diarrhea was dose-related. The gastrointestinal system 

was the primary target in animals dying early; numerous macroscopic and histological alterations were 

observed. 

A benchmark dose (BMD) analysis of the incidence data for diarrhea was conducted; details of this 

analysis are presented in Appendix A. Using the female incidence data, a BMD (BMD10) of 16.17 mg 

MMA/kg/day, which corresponds to a 10% increase in the incidence of diarrhea, was calculated; the 95% 

lower confidence limit on the BMD (BMDL10) was 12.38 mg MMA/kg/day. The female incidence data 

were selected over the male data because the females may be more sensitive than the males. Thus, the 

intermediate-duration oral MRL of 0.1 mg MMA/kg/day is based on the BMDL10 of 12.38 mg 

MMA/kg/day in female rats and an uncertainty factor of 100 (10 to account for animal to human 

extrapolation and 10 for human variability). 

•	 An MRL of 0.01 mg MMA/kg/day has been derived for chronic-duration (365 days or longer) 

oral exposure to MMA. 

The available data on the chronic toxicity of MMA in animals (no human data are available) suggest that 

the gastrointestinal tract and the kidney are the most sensitive targets. Diarrhea has been observed in rats 

and mice exposed to MMA in the diet for 2 years (Arnold et al. 2003). The NOAEL and LOAEL values 

for diarrhea are 3.0 and 25.7 mg MMA/kg/day in rats, respectively, and 24.9 and 67.1 mg MMA/kg/day 
ARSENIC 35 

2. RELEVANCE TO PUBLIC HEALTH 

in mice, respectively. At 72.4 mg MMA/kg/day, necrotic, ulcerated, or perforated mucosa and metaplasia 

were observed in the cecum, colon, and rectum of rats. Squamous metaplasia was also observed in the 

cecum, colon, and rectum of mice exposed to 67.1 mg MMA/kg/day. Diarrhea was observed in dogs 

exposed via capsule to 2 mg MMA/kg/day for 52 weeks (Waner and Nyska 1988). The bolus 

administration used in the dog study probably increased the dog’s sensitivity to MMA. In both the rats 

and mice, chronic administration of MMA resulted in an exacerbation of chronic progressive 

nephropathy. In female rats, significant increases in the severity of chronic progressive nephropathy were 

observed at 33.9 and 98.5 mg MMA/kg/day; the NOAEL was 3.9 mg MMA/kg/day (Arnold et al. 2003). 

In male mice, there was an increased incidence of slight progressive nephropathy at doses ≥6.0 mg 

MMA/kg/day; the NOAEL was 1.2 mg MMA/kg/day (Arnold et al. 2003; incidence data reported in Gur 

et al. 1991). Nephrocalcinosis was also observed in male mice exposed to ≥24.9 mg MMA/kg/day 

(Arnold et al. 2003). Other effects that have been observed following chronic exposure MMA include 

decreased weight gain in male and female rats exposed to 25.7/33.9 mg MMA/kg/day and higher (Arnold 

et al. 2003) and hypertrophy of the thyroid follicular epithelium in female rats exposed to ≥33.9 mg 

MMA/kg/day (Arnold et al. 2003). A variety of other lesions including peritonitis, pancreatitis, 

inflammation of the ureter, uterus, prostate, testes, epididymis, and seminal vesicles, hydronephrosis, 

pyelonephritis, and cortical tubular cystic dilation were also observed in rats; however, these alterations 

were probably secondary to the ulceration and perforation of the large intestine, which resulted in leaking 

of gastrointestinal contents into the abdominal cavity. Hyperplasia of the urinary bladder was also 

observed in rats exposed to 2.1 mg MMA/kg/day as MMA in drinking water for 2 years (Shen et al. 

2003). Although hyperplasia of the urinary bladder is commonly observed in rats exposed to DMA, it 

was not observed in the Arnold et al. (2003) study at doses as high as 72.4 mg MMA/kg/day; thus, the 

significance of the results of the Shen et al. (2003) study is not known. 

The lowest reliable LOAEL identified in the chronic oral MMA database was 6.0 mg MMA/kg/day for an 

increased incidence of progressive glomerulonephropathy in mice (Arnold et al. 2003). Although the 

investigators noted that the kidney lesions were consistent with the normal spectrum of spontaneous renal 

lesions and that there was no difference in character or severity of lesions between groups, ATSDR 

considers the dose-related increase in glomerulonephropathy to be treatment-related. 

In the Arnold et al. (2003) study (incidence data reported in Gur et al. 1991), groups of 52 male and 

52 female B6C3F1 mice were exposed to 0, 10, 50, 200, or 400 ppm of MMA in the diet for 104 weeks. 

The average doses reported in Gur et al. (1991) were 0, 1.2, 6.0, 24.9, and 67.1 mg MMA/kg/day for 

males and 0, 1.4, 7.0, 31.2, and 101 mg MMA/kg/day for females. Body weights, food consumption, and 
ARSENIC 36 

2. RELEVANCE TO PUBLIC HEALTH 

water intake were monitored regularly. Blood was taken at 3, 6, 12, 18, and 24 months for white cell 

counts. At sacrifice, complete necropsies were performed, including histological examination of at least 

13 organs. No treatment-related increases in mortality were observed. Significant decreases in body 

weights were observed in males and females exposed to 67.1 or 101 mg MMA/kg/day, respectively; at 

week 104, the males and females weighed 17 and 23%, respectively, less than controls. Food 

consumption was increased in females exposed to 101 mg MMA/kg/day, and water consumption was 

increased in 67.1 mg MMA/kg/day males and 31.2 and 101 mg MMA/kg/day females. Loose and 

mucoid feces were noted in mice exposed to 67.1/101 mg MMA/kg/day. No changes were seen in white 

cell counts of either sex. Small decreases in the weights of heart, spleen, kidney, and liver weights were 

observed in some animals, but the decreases were not statistically significant. Squamous metaplasia of 

the cecum, colon, and rectum was observed at 67.1/101 mg MMA/kg/day. The incidence of metaplasia in 

the cecum, colon, and rectum were 29/49, 14/49, and 39/49 in males and 38/52, 17/52, and 42/52 in 

females; metaplasia was not observed in other groups of male or female mice. An increased incidence of 

progressive glomerulonephropathy (incidence of 25/52, 27/52, 38/52, 39/52, and 46/52 in the 0, 1.2, 6.0, 

24.9, and 67.1 mg MMA/kg/day males, respectively) was observed in males; the incidence was 

significantly higher (Fisher Exact Test) than controls at ≥6.0 mg MMA/kg/day. Significant increases in 

the incidence of nephrocalcinosis was observed in the males at 24.9 and 67.1 mg MMA/kg/day (Fisher 

Exact Test) (incidences of 25/52, 30/52, 30/52, 45/52, and 45/51 in males and 0/52, 1/52, 1/52, 2/52, and 

5/52 in females). A reduction in the incidence of cortical focal hyperplasia in the adrenal gland of male 

mice exposed to 67.1 mg MMA/kg/day was possibly related to MMA exposure; the toxicological 

significance of this effect is not known. Thus, this study identifies a NOAEL of 1.2 mg MMA/kg/day and 

a LOAEL of 6.0 mg MMA/kg/day for progressive glomerulonephropathy in male mice. 

As described in greater detail in Appendix A, BMD was applied to the incidence data for progressive 

glomerulonephropathy in male mice using all available dichotomous models in EPA’s Benchmark Dose 

Software (version 1.4.1) to calculate predicted doses associated with a 10% extra risk. As assessed by the 

Akaike’s Information Criteria (AIC), the log-logistic model provided the best fit to the data. The 

predicted BMD10 and BMDL10 are 2.09 and 1.09 mg MMA/kg/day. The BMDL10 was selected as the 

point of departure and divided by an uncertainty factor of 100 (10 for extrapolation from animals to 

humans and 10 for human variability) to derive a chronic-duration oral MRL of 0.01 mg MMA/kg/day. 

DMA. As discussed in greater detail in Section 2.2, urinary bladder effects characterized by cytotoxicity 

and regenerative proliferation and hyperplase have been observed in rats, but not in other species. The 

LOAELs for these effects are lower than the LOAELs for sensitive effects in other species. Additionally, 
ARSENIC 37 

2. RELEVANCE TO PUBLIC HEALTH 

rats have a much greater capacity than other species to metabolize ingested DMA to form DMA(III) (a 

reactive intermediate) and TMAO (Cohen et al. 2006; Marafante et al. 1987b; Yoshida et al. 1998). It is 

likely that DMA(III) is the causative agent for the urothelial cytoxicity observed in rats (Cohen et al. 

2006). Thus, rats were not considered a suitable model for humans and these data were not considered for 

derivation of MRLs for DMA. 

There are limited data to assess the acute toxicity of DMA in species other than rats. Diarrhea, increased 

startle reflex, and ataxia were observed in mice exposed to a lethal gavage dose of 1,757 mg DMA/kg 

(Kaise et al. 1989); vomiting and diarrhea were also observed during the second week of a 52-week study 

in dogs exposed via capsule to 16 mg DMA/kg/day (Zomber et al. 1989). The remaining studies in the 

acute database are developmental toxicity studies in mice and rabbits. Rabbits appear to be more 

sensitive than mice to maternal and developmental effects. Gavage exposure to 48 mg DMA/kg/day on 

gestational days 7–19 resulted in maternal weight loss and abortion in approximately 75% of the does; no 

adverse effects were observed at 12 mg DMA/kg/day (Irvine et al. 2006). In mice, decreases in maternal 

body weight gain were observed at gavage doses of 200 mg DMA/kg/day on gestational days 7– 

16 (Rogers et al. 1981), decreases in fetal body weight, delays in ossification, and increased incidence of 

cleft palate were observed at 400 mg DMA/kg/day on gestational days 7–16 (Rogers et al. 1981) and fetal 

deaths, decreases in growth, and increased incidence of malformations were observed in mice 

administered 1,600 mg DMA/kg on gestational day 8 (Kavlock et al. 1985). The acute-duration database 

for DMA was not considered adequate for derivation of an oral MRL. The database is lacking a 

comprehensive toxicity study, which would be useful in establishing the critical target of toxicity. In a 

chronic-duration study in mice (Arnold et al. 2006), vacuolization was observed in the urinary bladder at 

≥7.8 mg DMA/kg/day; it is not known if these effects would also be observed after acute-duration 

exposure. Thus, it is not known if systemic effects would occur at lower doses than the maternal 

developmental effects observed in rabbits exposed to 48 mg DMA/kg/day (Irvine et al. 2006); an acuteduration oral MRL for DMA is not recommended at this time. 

Excluding rat studies, the database on the toxicity of DMA following intermediate-duration oral exposure 

is limited to a chronic study of dogs exposed to DMA via capsule 6 days/week for 52 weeks (Zomber et 

al. 1989). Diarrhea and vomiting were observed at 16 and 40 mg DMA/kg/day starting after the first 

week of exposure. A slight decrease in erythrocyte levels and increase in total leukocyte levels were 

observed in males exposed to 40 mg DMA/kg/day for 51 weeks. This dog study was not selected as the 

basis of an MRL because it is likely that bolus administration of DMA would increase sensitivity to the 

gastrointestinal effects. 
ARSENIC 38 

2. RELEVANCE TO PUBLIC HEALTH 

•	 An MRL of 0.02 mg DMA/kg/day has been derived for chronic-duration (365 days or longer) 

oral exposure to DMA. 

Two studies investigated the chronic-duration toxicity of DMA in a species other than rats. In dogs, 

diarrhea and vomiting were observed after 52 weeks of exposure to 16 or 40 mg As/kg/day (Zomber et al. 

1989); no histological alterations were observed. In mice exposed to DMA in the diet for 2 years, 

vacuolization of the urothelium in the urinary bladder was observed at ≥7.8 mg DMA/kg/day and 

progressive glomerulonephropathy was observed at ≥37 mg DMA/kg/day (Arnold et al. 2006). As noted 

in Section 2.2, the vacuolization was not associated with cytotoxicity or proliferation. Because the 

bladder effects in mice occurred at the lowest adverse effect level for the database, it was selected as the 

critical effect and Arnold et al. (2006) was selected as the principal study. 

In the Arnold et al. (2006) study, groups of 56 male and 56 female B6C3F1 mice were exposed to 0, 8, 40, 

200, or 500 ppm DMA in the diet for 2 years; the results of this study were also reported in an 

unpublished paper (Gur et al. 1989b) submitted to EPA under Federal Insecticide, Fungicide, and 

Rodenticide Act (FIFRA). The investigators reported dietary doses of approximately 0, 1.3, 7.8, 37, and 

94 mg DMA/kg/day. The following parameters were used to assess toxicity: clinical observations, body 

weight, food consumption, water consumption, differential leukocyte levels measured at 12, 18, and 

24 months in mice in the control and 94 mg DMA/kg/day groups, organ weights (brain, kidneys, liver, 

and testes), and histopathological examination of major tissues and organs. No deaths or treatmentrelated clinical signs were observed. Decreases in body weight gain were observed in the male mice 

exposed to 94 mg DMA/kg/day; the difference was <10% and not considered adverse. An increase in 

water consumption was observed in males exposed to 94 mg DMA/kg/day during weeks 60–96. In the 

female mice exposed to 51 mg As/kg/day, a statistically significant decrease in lymphocytes and an 

increase in monocytes were observed at 24 months. Treatment related nonneoplastic alterations were 

observed in the urinary bladder and kidneys. In the urinary bladder, increases in the vacuolization of the 

superficial cells of the urothelium were observed in males exposed to 37 or 94 mg DMA/kg/day (0/44, 

1/50, 0/50, 36/45, 48/48) and in females exposed to 7.8, 37, and 94 mg DMA/kg/day (1/45, 1/48, 26/43, 

47/47, 43/43); incidence data reported in Gur et al. (1989b). An increased incidence of progressive 

glomerulonephropathy was observed in males at 37 mg DMA/kg/day (16/44, 22/50, 17/50, 34/45, 30/50) 

and an increased incidence of nephrocalcinosis was also observed in male mice at 94 mg DMA/kg/day 

(30/44, 25/50, 27/50, 29/50, 45/50). Neoplastic alterations were limited to an increased incidence of 

fibrosarcoma of the skin in females exposed to 94 mg DMA/kg/day (the incidence of 3/56, 0/55, 1/56, 
ARSENIC 39 

2. RELEVANCE TO PUBLIC HEALTH 

1/56, and 6/56 in the 0, 1.3, 7.8, 37, and 94 mg DMA/kg/day groups, respectively); however, it was 

concluded that this lesion was not related to DMA exposure. 

As described in detail in Appendix A, BMD analysis was applied to the incidence data for vacuolization 

of the urothelium in the urinary bladder of female mice using all available dichotomous models in EPA’s 

Benchmark Dose Software (version 1.4.1) to calculate predicted doses associated with a 10% extra risk. 

As assessed by the AIC, the multi-stage model provided the best fit to the data. The predicted BMD10 and 

BMDL10 are 2.68 and 1.80 mg DMA/kg/day. The BMDL10 was selected as the point of departure and 

divided by an uncertainty factor of 100 (10 for extrapolation from animals to humans and 10 for human 

variability) to derive a chronic-duration oral MRL of 0.02 mg DMA/kg/day. 

Roxarsone. A series of three National Toxicology Program (NTP) studies in rats and mice (NTP 1989b) 

and a study in dogs (Kerr et al. 1963) have examined the acute toxicity of roxarsone; adverse effects have 

also been reported within the first 2 weeks of a longer-term study in pigs (Rice et al. 1985; Kennedy et al. 

1986). A single exposure study reported diarrhea and ataxia in rats and mice exposed to doses that 

exceeded the LD50 (NTP 1989b). In another study, no alterations in hematological parameters (only end 

point assessed) were found after 10 or 9 days of dietary exposure in rats and mice, respectively (NTP 

1989b). In a 14-day study (NTP 1989b), a decrease in body weight gain and slight inactivity were 

observed in rats exposed to 32 mg roxarsone/kg/day and slight inactivity was observed in mice exposed to 

42 mg roxarsone/kg/day; a decrease in body weight gain was also observed in mice exposed to 168 mg 

roxarsone/kg/day. The dog study was considered inadequate because a small number (n=3) of animals 

were tested and no control group was used. In a 30-day dietary exposure study in pigs (Rice et al. 1985; 

Kennedy et al. 1986), mild lethargy and ataxia were observed from day 7 forward and exercise-induced 

muscle tremors and clonic seizures were observed from day 11 forward in pigs exposed to 6.3 mg 

roxarsone/kg/day; equivocal evidence of myelin degeneration was also observed in pigs sacrificed after 

11 days of exposure. These data clearly identify pigs as the most sensitive species following acuteduration oral exposure; in the absence of data to the contrary, it is assumed that pigs are a good model to 

predict the toxic potential of roxarsone in humans. Because the lowest dose tested in pigs was a serious 

LOAEL for neurotoxicity and a NOAEL for this effect was not identified, an acute-duration oral MRL 

cannot be derived for roxarsone. 

As with the acute-duration database, pigs appear to be the most sensitive species; neurotoxicity has been 

observed at ≥6.3 mg roxarsone/kg/day. In a study reported by Rice et al. (1985) and Kennedy et al. 

(1986), exercise-induced muscle tremors and clonic convulsions were observed in pigs during the early 
ARSENIC 40 

2. RELEVANCE TO PUBLIC HEALTH 

part of the study; when the pigs returned to a recumbent position, the seizures and tremors stopped. 

Paraparesis, evidenced by reluctance to rise and the pigs dragging their hindquarters on the ground, was 

observed at day 22; paraplegia was observed 2 days after exposure termination. In addition to these 

clinical signs of neuropathy, histological alterations consisting of myelin degeneration was observed in 

the spinal cord, peripheral nerves, and optic nerve. The lesions were first detected in the spinal cord on 

day 15 and in the peripheral nerves and optic nerve 2 days after exposure termination. The Rice et al. 

(1985) and Kennedy et al. (1986) studies did not identify a NOAEL. Muscle tremors were also observed 

in pigs exposed to 10 mg roxarsone/kg/day for 28 days (Edmonds and Baker 1986). This study was not 

designed to assess neurotoxicity and did not include histological examination of the spinal cord or nerves. 

Trembling, ataxia, and hyperexcitability were also observed in rats exposed to 64 mg roxarsone/kg/day 

for 13 weeks (NTP 1989b). Other effects that have been observed include tubular degeneration and focal 

regenerative hyperplasia in the kidney and decreased body weight in rats exposed to 32 mg roxarsone/ 

kg/day for 13 weeks (NTP 1989b) and decreased body weight in mice at 136 mg roxarsone/kg/day for 

13 weeks (NTP 1989b). The lowest identified adverse effect level is 6.3 mg roxarsone/kg/day for serious 

neurological effects in pigs (Kennedy et al. 1986; Rice et al. 1985) and is not suitable for the derivation of 

an intermediate-duration oral MRL. 

The chronic toxicity of roxarsone has been examined in rats (NTP 1989b; Prier et al. 1963), mice (NTP 

1989b; Prier et al. 1963), and dogs (Prier et al. 1963) in 2-year dietary exposure studies. None of these 

studies reported adverse effects at the highest doses tested; the highest NOAELs for each species are 10, 

43, and 5 mg roxarsone/kg/day for rats, mice, and dogs, respectively. The results from shorter duration 

studies suggest that pigs are more sensitive to the neurotoxic effects of roxarsone than rats, mice, or dogs. 

Because no chronic duration pig studies were identified and deriving an MRL using a potentially less 

sensitive species may not be protective of human health, a chronic-duration oral MRL is not 

recommended at this time. 
ARSENIC 41 

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 arsenic. 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 
ARSENIC 42 

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 arsenic are 

indicated in Tables 3-1 and 3-3 and Figures 3-1 and 3-3. Because cancer effects could occur at lower 

exposure levels, Figures 3-1 and 3-3 also show 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. 

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. 

Chemical Forms of Concern. Analysis of the toxic effects of arsenic is complicated by the fact that 

arsenic can exist in several different oxidation states and many different inorganic and organic 

compounds. Most cases of human toxicity from arsenic have been associated with exposure to inorganic 

arsenic, so these compounds are the main focus of this profile. 

The most common inorganic arsenical in air is arsenic trioxide (As2O3), while a variety of inorganic 

arsenates (AsO4

-3) or arsenites (AsO2-

) occur in water, soil, or food. A number of studies have noted 

differences in the relative toxicity of these compounds, with trivalent arsenites tending to be somewhat 

more toxic than pentavalent arsenates (Byron et al. 1967; Gaines 1960; Maitani et al. 1987a; Sardana et 

al. 1981; Willhite 1981). However, these distinctions have not been emphasized in this profile, for 

several reasons: (1) in most cases, the differences in the relative potency are reasonably small (about 2– 

3-fold), often within the bounds of uncertainty regarding NOAEL or LOAEL levels; (2) different forms of 

arsenic may be interconverted, both in the environment (see Section 6.3) and the body (see Section 3.4); 

and (3) in many cases of human exposure (especially those involving intake from water or soil, which are 

of greatest concern to residents near wastes sites), the precise chemical speciation is not known. 
ARSENIC 43 

3. HEALTH EFFECTS 

Gallium arsenide (GaAs) is another inorganic arsenic compound of potential human health concern, due 

to its widespread use in the microelectronics industry. Available toxicokinetic data suggest that although 

gallium arsenide is poorly soluble, it undergoes slow dissolution and oxidation to form gallium trioxide 

and arsenite (Webb et al. 1984, 1986). Therefore, the toxic effects of this compound are expected to be 

attributable to the arsenite that is liberated, plus the additional effects of the gallium species. 

It is beyond the scope of this profile to provide detailed toxicity data on other less common inorganic 

arsenic compounds (e.g., As2S3), but these are expected to be of approximately equal or lesser toxicity 

than the oxycompounds, depending mainly on solubility (see Section 3.4). 

Although organic arsenicals are usually viewed as being less toxic than the inorganics, several methyl and 

phenyl derivatives of arsenic that are widely used in agriculture are of possible human health concerns 

based on their toxicity in animal species (Arnold et al. 2003, 2006; NTP 1989b). Chief among these are 

monomethylarsonic acid (MMA) and its salts (monosodium methane arsonate [MSMA] and disodium 

methane arsonate [DSMA]), dimethylarsinic acid (DMA, also known as cacodylic acid) and its sodium 

salt (sodium dimethyl arsinite, or sodium cacodylate), and roxarsone (3-nitro-4-hydroxyphenylarsonic 

acid). However, it should be noted that food is the largest contributor to background intakes of organic 

arsenicals. Estimates on the concentration of organic arsenicals in the diet were not located; Cohen et al. 

(2006) estimated that the intake of DMA from food and water is <1 ng/kg/day. As with the inorganic 

compounds, there are toxicological differences between these various organic derivatives; because of 

these differences, the discussion of the health effects of MMA, DMA, and roxarsone are discussed 

separately. As discussed below, animals do not appear to be good quantitative models for inorganic 

arsenic toxicity in humans, but it is not known if this also applies to toxicity of organic arsenicals. 

Several organic arsenicals are found to accumulate in fish and shellfish. These derivatives (mainly 

arsenobetaine and arsenocholine, also referred to as "fish arsenic") have been studied by several 

researchers and have been found to be essentially nontoxic (Brown et al. 1990; Cannon et al. 1983; 

Charbonneau et al. 1978; Kaise et al. 1985; Luten et al. 1982; Siewicki 1981; Tam et al. 1982; Yamauchi 

et al. 1986). Thus, these compounds are not considered further here. 

Arsine (AsH3) and its methyl derivatives, although highly toxic, are also not considered in this profile, 

since these compounds are either gases or volatile liquids that are unlikely to be present at levels of 

concern at hazardous waste sites. 
ARSENIC 44 

3. HEALTH EFFECTS 

Use of Animal Data. An additional complexity to the analysis of arsenic toxicity is that most laboratory 

animals appear to be substantially less susceptible to inorganic arsenic than humans. For example, 

chronic oral exposure of humans to inorganic arsenic at doses of 0.05–0.1 mg/kg/day is frequently 

associated with neurological (Barton et al. 1992; Goddard et al. 1992; Guha Mazumder et al. 1988; 

Haupert et al. 1996; Hindmarsh et al. 1977; Huang et al. 1985; Sass et al. 1993; Silver and Wainman 

1952; Szuler et al. 1979; Tay and Seah 1975; Valentine et al. 1981) or hematological signs of arsenic 

toxicity (Glazener et al. 1968; Guha Mazumder et al. 1988; Prasad and Rossi 1995; Sass et al. 1993; Tay 

and Seah 1975), but no characteristic neurological or hematological signs of arsenism were detected in 

monkeys, dogs, or rats chronically exposed to arsenate or arsenite at doses of 0.7–2.8 mg As/kg/day 

(Byron et al. 1967; EPA 1980f; Heywood and Sortwell 1979). This may be because the studies were not 

conducted for a sufficient length of time, or because too few animals were used. Moreover, while there is 

good evidence that inorganic arsenic is carcinogenic in humans by both oral and inhalation routes, 

evidence of inorganic arsenic-induced carcinogenicity in animals is mostly negative, with the exception of 

studies in mice demonstrating transplacental carcinogenesis. For these reasons, quantitative doseresponse data from animals are not judged to be reliable for determining levels of significant human 

exposure, and will be considered only briefly except when human data are lacking. 

3.2.1 Inhalation Exposure 

Most information on human inhalation exposure to arsenic derives from occupational settings such as 

smelters and chemical plants, where the predominant form of airborne arsenic is arsenic trioxide dust. 

One limitation to this type of study is that exposure data are usually difficult to obtain, especially from 

earlier time periods when exposure levels were higher than in recent years. This is further complicated by 

the fact that significant oral and dermal exposures are also likely to occur under these conditions and 

co exposure to other metals and chemicals is also common. Thus, studies of this type are, like virtually 

all epidemiological studies, subject to some limitations and uncertainties. Table 3-1 and Figure 3-1 

summarize studies that provide the most reliable quantitative data on health effects in humans, along with 

several studies in animals exposed to arsenic trioxide and other inorganic arsenic compounds by the 

inhalation route. Data for DMA are shown in Table 3-2 and Figure 3-2. All exposure data are expressed 

as milligrams of arsenic (as the element) per cubic meter of air (mg As/m3

). These studies and others that 

provide useful qualitative information on health effects of inorganic and organic arsenicals are discussed 

below. 
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Inorganic Arsenic - Inhalation

Species

(Strain)

LOAEL

System 

NOAEL

(mg/m3)

Less Serious

(mg/m3)

Serious

(mg/m3)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

ACUTE EXPOSUREImmuno/ Lymphoret

1

266

Aranyi et al. 1985As(+3)

0.123 F

0.123

0.271 F (decreased pulmonary

bactericidal activity andincreased susceptibilityto streptococcal infection)

0.271

Mouse(CD-1)

3 hr

2

266a

Aranyi et al. 1985As(+3)

0.259 F

0.259

0.519 F (decreased pulmonary

bactericidal activity andincreased susceptibilityto streptococcal infection)

0.519

Mouse(CD-1)

5 d3 hr/d

Developmental

3

107

Nagymajtenyi et al. 198As(+3)

0.2

0.2

2.2 (10% decreased average

fetal body weight)

2.2

21.6 (increased fetal deaths,

skeletal malformations,and retarded growth)

21.6

Mouse(CFLP)

Gd 9-124 hr/d

INTERMEDIATE EXPOSUREDeath

4

3003

Holson et al. 1999As(+3)

20 F (5/10 dams died)

20

Rat(CD)

14 pmd- Gd 197 d/wk6 hr/d

Systemic

5

3001a

Holson et al. 1999As(+3)

Resp 2 F

2

8 F (rales, dried red material

around nose)

8

Rat(CD)

14 pmd- Gd 197 d/wk6 hr/d

Bd Wt 2 F

2

8 F (decreased body weight

gain during gestation)

8
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Inorganic Arsenic - Inhalation (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/m3)

Less Serious

(mg/m3)

Serious

(mg/m3)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

6

3003a

Holson et al. 1999As(+3)

Resp 0.9 F

0.9

8 F (rales)

8

20 F (labored breathing,

gasping)

20

Rat(CD)

14 pmd- Gd 197 d/wk6 hr/d

Gastro 8 F

8

20 F (gross gastrointestinal

lesions)

20

Bd Wt 8 F

8

20 F (drastic decrease body

weight)

20

Immuno/ Lymphoret

7

106

Aranyi et al. 1985As(+3)

0.126 F

0.126

0.245 F (decreased pulmonary

bactericidal activity)

0.245

Mouse(CD-1)

4 wk5 d/wk3 hr/d

Reproductive

8

3001b

Holson et al. 1999As(+3)

8 F

8

Rat(CD)

14 pmd- Gd 197 d/wk6 hr/d

9

3003c

Holson et al. 1999As(+3)

20 F

20

Rat(CD)

14 pmd- Gd 197 d/wk6 hr/d

Developmental

10

3001

Holson et al. 1999As(+3)

8

8

Rat(CD)

14 pmd- Gd 197 d/wk6 hr/d
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Inorganic Arsenic - Inhalation (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/m3)

Less Serious

(mg/m3)

Serious

(mg/m3)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

11

3003b

Holson et al. 1999As(+3)

8

8

20 (marked increase in postimplantation loss and

marked decrease inviable fetuses)

20

Rat(CD)

14 pmd- Gd 197 d/wk6 hr/d

CHRONIC EXPOSURESystemic

12

14

Lagerkvist et al. 1986As(+3)

Cardio 0.36 M (increased incidence of

vasospasticity andclinical Raynaud'sphenomenon)

0.36

Human 23 yr (avg)

(occup)

13

183

Perry et al. 1948As(+3)

Resp 0.613

0.613

Human 0.5-50 yr

(occup)

Dermal 0.078 (mild pigmentation

keratosis of skin)

0.078

0.613 (gross pigmentation with

hyperkeratinization ofexposed areas, wartformation)

0.613

Neurological

14

2027

Lagerkvist and ZetterlunAs(+3)

0.31 M (decreased nerve

conduction velocity)

0.31

Human 28 yr (avg)

(occup)

Cancer

15

5

Enterline et al. 1987aAs(+3)

0.213 M (CEL: lung cancer)

0.213

Human 1- >30 yr

(occup)

16

90

Enterline et al. 1987bAs(+3)

0.069 M (CEL: lung cancer)

0.069

Human 19.5 yr

(avg)(occup)
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Inorganic Arsenic - Inhalation (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/m3)

Less Serious

(mg/m3)

Serious

(mg/m3)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

17

313

Jarup and Pershagen 1As(+3)

0.2 M (CEL: lung cancer)

0.2

Human 3 mo- >30 yr

(occup)

18

6

Jarup et al. 1989As(+3)

0.05 M (CEL: lung cancer)

0.05

Human 3 mo- >30 yr

(occup)

19

91

Lee-Feldstein 1986As(+3)

0.38 M (CEL: lung cancer)

0.38

Human 1- >30 yr

(occup)

20

5005

Lubin et al. 2000As(+3)

0.29 M (CEL: lung cancer)

0.29

Human >25 yr

(occup)

21a The number corresponds to entries in Figure 3-1.avg = average; Bd Wt = body weight; Cardio = cardiovascular; CEL = cancer effect level; d = day(s); F = female; Gastro = gastrointestinal; Gd = gestation day; hr = Immuno/Lymphoret = immunological/lymphoreticular; LOAEL = lowest-observable-adverse-effect level; M = male; mo = month(s); NOAEL = no-observable-adversenot specified; occup = occupational; pmd = pre-mating day; Resp = respiratory; wk = week(s); yr = year(s)

9

Welch et al. 1982As(+3)

0.3 M (CEL: lung cancer)

0.3

Human 14.8 yr (avg)

(occup)
0.1

1

10

100

Immuno/Lymphor

1m

1m

2m

2m

Developmental

3m

3m

3m

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

 for effects

 other than

 Cancer

mg/m3

Figure 3-1 Levels of Significant Exposure to Inorganic Arsenic - Inhalation

Acute (≤14 days)

 Minimal Risk Level

ARSENIC

3. HEALTH EFFECTS

49
0.1

1

10

100

Death

4r

Respiratory

5r

5r

6r

6r

6r

Gastrointestinal

6r

6r

Body Weight

5r

5r

6r

6r

Immuno/Lymphor

7m

7m

Reproductive

8r

9r

Developmental

10r

11r

11r

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

 for effects

 other than

 Cancer

Figure 3-1 Levels of Significant Exposure to Inorganic Arsenic - Inhalation (Continued)

Intermediate (15-364 days)

mg/m3

Systemic

 Minimal Risk Level

ARSENIC

3. HEALTH EFFECTS

50
1E-8

1E-7

1E-6

1E-5

0.0001

0.001

0.01

0.1

1

Respiratory

13

Cardiovascular

12

Dermal

13

13

Neurological

14

Cancer *

15

16

17

18

1920 21

Estimated

Upper-Bound

Human Cancer

Risk Levels

10

10

10

10

-7

-6

-5

-4

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

 for effects

 other than

 Cancer

Chronic (≥365 days)

Figure 3-1 Levels of Significant Exposure to Inorganic Arsenic - Inhalation (Continued)

 Minimal Risk Level

mg/m3

*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.

Systemic

ARSENIC

3. HEALTH EFFECTS

51
a

Key to

Figure

Table 3-2 Levels of Significant Exposure to Dimethylarsinic Acid - Inhalation

Species

(Strain)

LOAEL

System 

NOAEL

(mg/m3)

Less Serious

(mg/m3)

Serious

(mg/m3)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

ACUTE EXPOSUREDeath

1

52

Stevens et al. 1979DMA

3900 F (LC50)

3900

Rat(Sherman)

2 hr

Systemic

2

53

Stevens et al. 1979DMA

Resp 4000 (respiratory distress)

4000

Rat(Sherman)

2 hr

Gastro 4000 (diarrhea)

4000

Dermal 4100

4100

6900 F (erythematous lesions of

ears and feet)

6900

Ocular 4000 (eye encrustation)

4000

Bd Wt 4000 (unspecified decrease in

body weight)

4000

3

56

Stevens et al. 1979DMA

Resp 3150 M (RD50)

3150

Mouse(SwissWebster)

5 min

INTERMEDIATE EXPOSURESystemic

4

5159

Whitman 1994DMA

Resp 10

10

34 (intracytoplasmic

eosinophilic globules innasal turbinates)

34

Rat(SpragueDawley)

6 hr/d5 d/wk67-68exposures

Cardio 100

100

Gastro 100

100

Hemato 100

100

Hepatic 100

100

Renal 100

100

Endocr 100

100

Dermal 100

100
a

Key to

Figure

Table 3-2 Levels of Significant Exposure to Dimethylarsinic Acid - Inhalation (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/m3)

Less Serious

(mg/m3)

Serious

(mg/m3)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

a The number corresponds to entries in Figure 3-2.Bd Wt = body weight; Cardio = cardiovascular; d = day(s); DMA = dimethylarsinic acid; F = female; Gastro = gastrointestinal; Hemato = hematological; hr = hour(s); concentration, 50% kill; LOAEL = lowest-observable-adverse-effect level; M = male; min = minute(s); NOAEL = no-observable-adverse-effect level; RD50 = 50% derespiration rate; Resp = respiratory; wk = week(s); yr = year(s)

Bd Wt 100

100
1000

10000

Death

1r

Respiratory

3m

2r

Gastrointestinal

2r

Dermal

2r

2r

Ocular

2r

Body Weight

2r

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

 for effects

 other than

 Cancer

Figure 3-2 Levels of Significant Exposure to Dimethylarsinic Acid - Inhalation

Acute (≤14 days)

 Minimal Risk Level

Systemic

mg/m3

ARSENIC

3. HEALTH EFFECTS

54
10

100

1000

Respiratory

4r

4r

Cardiovascular

4r

Gastrointestinal

4r

Hematological

4r

Hepatic

4r

Renal

4r

Endocrine

4r

Dermal

4r

Body Weight

4r

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

 for effects

 other than

 Cancer

Figure 3-2 Levels of Significant Exposure to Dimethylarsinic Acid - Inhalation (Continued)

Intermediate (15-364 days)

 Minimal Risk Level

Systemic

mg/m3

ARSENIC

3. HEALTH EFFECTS

55
ARSENIC 56 

3. HEALTH EFFECTS 

3.2.1.1 Death 

Inorganic Arsenicals. Although there are many studies of humans exposed to arsenic in air, no cases of 

lethality from short-term exposure were located. This suggests that death is not likely to be of concern 

following acute exposure, even at the very high exposure levels (1–100 mg As/m3

) found previously in 

the workplace (e.g., Enterline and Marsh 1982; Järup et al. 1989; Lee-Feldstein 1986). Delayed lethality 

from chronic exposure attributable to increased risk of cardiovascular disease or lung cancer is discussed 

below in Sections 3.2.1.2 and 3.2.1.7, respectively. The only report of a lethal effect of inhaled inorganic 

arsenic in animals was a developmental toxicology study in which four of nine pregnant rats died, and one 

rat was euthanized in extremis, between days 12 and 19 of gestation after 30–35 days of exposure to an 

aerosol of arsenic trioxide at an exposure concentration of 20 mg As/m3

 (Holson et al. 1999). These 

animals exhibited severe hyperemia and plasma discharge into the intestinal lumen at autopsy. In this 

same study, there was 100% mortality in groups of 10 pregnant rats after 1 day of exposure to 

concentrations ≥100 mg/m3

 (76 mg As/m3). 

Organic Arsenicals. No studies were located regarding death in humans after inhalation exposure to 

organic arsenicals. A 2-hour LC50 of 3,900 mg DMA/m3

 was calculated for DMA in female rats (Stevens 

et al. 1979). This LC50 is shown in Table 3-2 and Figure 3-2. Male rats and mice of both sexes were less 

susceptible, with only a few deaths after 2-hour exposures as high as 6,900 mg DMA/m3

 in rats and 

6,400 mg DMA/m3

 in mice (Stevens et al. 1979). The cause of death was not specified, but was probably 

due to lung injury (see Section 3.2.1.2). No deaths were observed among rats and mice exposed to 

DSMA (the disodium salt of MMA) at concentrations up to 6,100 mg DSMA/m3

 in rats and 6,900 mg 

DSMA/m3

 in mice (Stevens et al. 1979). Chamber atmospheres at these high concentrations were so 

dense that it was difficult to see the animals clearly. These data indicate that there is no significant risk of 

acute lethality from concentrations of DMA or MMA that might be encountered in the environment or the 

workplace. 

3.2.1.2 Systemic Effects 

The highest NOAEL values and all reliable LOAEL values for systemic effects from inhalation exposure 

to inorganic arsenicals in each species and duration category are recorded in Table 3-1 and plotted in 

Figure 3-1, while the corresponding data for DMA are shown in Table 3-2 and Figure 3-2. 
ARSENIC 57 

3. HEALTH EFFECTS 

Respiratory Effects. 

Inorganic Arsenicals. Workers exposed to arsenic dusts in air often experience irritation to the mucous 

membranes of the nose and throat. This may lead to laryngitis, bronchitis, or rhinitis (Dunlap 1921; 

Morton and Caron 1989; Pinto and McGill 1953), and very high exposures (characteristic of workplace 

exposures in the past) can cause perforation of the nasal septum (Dunlap 1921; Pinto and McGill 1953; 

Sandstrom et al. 1989). Despite the known respiratory irritant effects of arsenic, there have been few 

systematic investigations of respiratory effects in humans exposed to arsenic. Perry et al. (1948) found no 

difference in chest x-rays or respiratory performance (vital capacity and exercise-tolerance tests) between 

unexposed and exposed workers in a cross-sectional study at a factory where sodium arsenite was 

prepared. The NOAEL of 0.613 mg As/m3

 for respiratory effects in this study is shown in Table 3-1 and 

plotted in Figure 3-1. 

Increased mortality due to respiratory disease has been reported in some cohort mortality studies of 

arsenic-exposed workers, but no conclusive evidence of an association with arsenic has been produced. 

In studies of workers exposed to arsenic trioxide at the Anaconda copper smelter in Montana, mortality 

due to noncancer respiratory disease (e.g., emphysema) was significantly increased compared to the 

general population (Lee-Feldstein 1983; Lubin et al. 2000; Welch et al. 1982). However, the data were 

not adjusted for smoking (a well-known confounder for respiratory disease), and analysis of the data with 

respect to arsenic exposure level did not show a clear dose-response. Similarly, Enterline et al. (1995) 

found a significant excess of nonmalignant respiratory disease mortality in workers at the ASARCO 

copper smelter in Tacoma, Washington, but only a slight negative relation to cumulative arsenic 

exposure. Xuan et al. (1993) found an increase in the relative risk of mortality from pneumoconiosis 

associated with arsenic exposure in a cohort of tin miners in China. However, this finding was based on a 

small number of observations (n=32), a clear exposure-response relationship with arsenic was not 

established, and the miners experienced confounding exposures to dust (a known risk factor for 

pneumoconiosis) and to radon. These studies were all considered to be inconclusive as to the relationship 

between inhaled inorganic arsenic and respiratory disease. 

Respiratory symptoms were observed in a study of developmental effects in rats. Pregnant female rats 

exposed to arsenic trioxide dust starting 14 days prior to mating and continuing through mating and 

gestation exhibited rales at 8 mg As/m3

 and labored breathing and gasping at 20 mg As/m3, with no 

symptoms at 2 mg As/m3

 (Holson et al. 1999). The lungs were examined by gross necropsy and no 

lesions were found. Intratracheal instillation of arsenic trioxide (13 mg As/kg) or gallium arsenide (1.5– 
ARSENIC 58 

3. HEALTH EFFECTS 

52 mg As/kg) can cause marked irritation and hyperplasia in the lungs of rats and hamsters (Goering et al. 

1988; Ohyama et al. 1988; Webb et al. 1986, 1987). Since this sort of response is produced by a number 

of respirable particulate materials, it is likely that the inflammatory response is not specifically due to the 

arsenic. 

Organic Arsenicals. No studies were located regarding respiratory effects in humans exposed to organic 

arsenicals. Short-term exposure of rats and mice to high concentrations (≥4,000 mg/m3

) of DMA caused 

respiratory distress, and necropsy of animals that died revealed bright red lungs with dark spots (Stevens 

et al. 1979). Respiratory distress was also observed in rats and mice exposed to high levels 

(≥6,100 mg/m3

) of the disodium salt of MMA (Stevens et al. 1979), although none of the MMA-exposed 

animals died. Respiratory distress appears to be associated with inhalation of very high concentrations of 

organic arsenicals. In 5-minute whole-body plethysmography trials, DMA and the disodium salt of 

MMA had RD50 (concentration calculated to produce a 50% decrease in respiration rate) values of 

3,150 and 1,540 mg/m3

, respectively (Stevens et al. 1979). Based on these RD50 values, neither DMA nor 

MMA is considered to be a potent respiratory irritant. At low concentrations of DMA (34 or 100 mg 

DMA/m3

), an increase in intracytoplasmic eosinophilic globules were found in the nasal turbinates of rats 

exposed to DMA 6 hours/day, 5 days/week for 67–68 exposures (Whitman 1994). 

Cardiovascular Effects. 

Inorganic Arsenicals. There is some evidence from epidemiological studies that inhaled inorganic 

arsenic can produce effects on the cardiovascular system. Cardiovascular effects following oral exposure 

to arsenic are well known (see Section 3.2.2.2). A cross-sectional study of workers exposed to an 

estimated time-weighted average of 0.36 mg As/m3

 (as arsenic trioxide) at the Ronnskar copper smelter in 

Sweden for an average of 23 years showed that smelter workers had significantly increased incidences of 

Raynaud’s phenomenon (a peripheral vascular disease characterized by spasm of the digital arteries and 

numbness of the fingers) and showed increased vasospasticity (constriction of blood vessels) in response 

to cold when tested in the fingers (Lagerkvist et al. 1986). A follow-up study conducted 2–3 years later 

found that vasospasticity measurements in exposed workers had improved concurrent with a reduction in 

arsenic exposure levels, although symptoms of peripheral vascular effects (cold hands or feet, white 

fingers, numbness in fingers or feet) were still common (Lagerkvist et al. 1988). A cross-sectional study 

including 46 workers in Denmark with varying, unquantified occupational exposure to arsenic in different 

occupations found that systolic blood pressure was significantly increased in the arsenic workers 

(median=125 mmHg) compared with controls (median=117 mmHg) (Jensen and Hansen 1998). Diastolic 
ARSENIC 59 

3. HEALTH EFFECTS 

pressure was also increased in this study (77.9 vs. 74.7 mmHg), although the difference from controls was 

not statistically significant. 

Cohort mortality studies of arsenic-exposed workers at the ASARCO copper smelter in Tacoma, 

Washington (Enterline et al. 1995), Anaconda copper smelter in Montana (Lee-Feldstein 1983; Welch et 

al. 1982), Ronnskar copper smelter in Sweden (Wall 1980), orchard workers in Washington state 

(Tollestrup et al. 1995), and tin miners in China (Qiao et al. 1997; Xuan et al. 1993) have all reported 

increased risk of mortality from cardiovascular disease, specifically ischemic heart disease and 

cerebrovascular disease, in the cohorts studied. However, none of these studies provided conclusive 

evidence that the observed increase in risk was due to arsenic exposure. The studies in the ASARCO and 

Anaconda copper smelter workers failed to find a clear dose-response relationship with arsenic (Enterline 

et al. 1995; Welch et al. 1982), while a follow-up study of the Ronnskar smelter workers not only found 

lack of a dose-response, but also that the risk of cardiovascular disease was no longer elevated in the 

cohort (Järup et al. 1989). The studies in orchard workers and tin miners were limited by confounding 

exposures to copper, lead, and radon, respectively (Qiao et al. 1997; Tollestrup et al. 1995). The risk of 

cardiovascular disease mortality in the tin miners not only showed no dose-response relationship with 

arsenic exposure, but was positively associated with radon exposure, suggesting that radon may have been 

responsible for the increased cardiovascular risk in this cohort (Xuan et al. 1993). 

The LOAEL for Raynaud’s phenomenon and vasospasticity identified by Lagerkvist et al. (1986) is 

shown in Table 3-1 and Figure 3-1. No studies were located regarding cardiovascular effects in animals 

after inhalation exposure to inorganic arsenic. 

Organic Arsenicals. No studies were located regarding cardiovascular effects in humans after inhalation 

exposure to organic arsenicals. No histological alterations were observed in the hearts of rats exposed to 

100 mg DMA/m3

 for 67–68 exposures (Whitman 1994). 

Gastrointestinal Effects. 

Inorganic Arsenicals. Several case studies have reported nausea, vomiting, and diarrhea in workers with 

acute arsenic poisoning following occupational inhalation exposure (Beckett et al. 1986; Bolla-Wilson 

and Bleecker 1987; Ide and Bullough 1988; Morton and Caron 1989; Pinto and McGill 1953). Although 

gastrointestinal effects are not typically associated with arsenic poisoning by inhalation (Pinto and McGill 

1953), such effects are a common feature of oral ingestion of high doses of arsenic (see Section 3.2.2.2), 
ARSENIC 60 

3. HEALTH EFFECTS 

and it is possible that mucociliary transport of arsenic dust from the lungs to the gut could be responsible 

for the effects in these cases. Exposure levels were not reliably estimated for any of these cases. 

The only report of gastrointestinal effects of inhaled inorganic arsenic in animals was a developmental 

toxicology study in which four of nine pregnant rats died, and one rat was euthanized in extremis, 

between days 12 and 19 of gestation after 30–35 days of exposure to an aerosol of arsenic trioxide at an 

exposure concentration of 20 mg As/m3 (Holson et al. 1999). These animals exhibited severe hyperemia 

and plasma discharge into the intestinal lumen at autopsy. Exposure to 8 mg As/m3

 did not produce gross 

gastrointestinal lesions. 

Organic Arsenicals. Data regarding gastrointestinal effects in people exposed to organic arsenic in the 

air are limited. The frequency of gastrointestinal complaints was no higher than controls in workers 

exposed to arsanilic acid (i.e., 4-aminophenyl arsonic acid) at mean concentrations up to 0.17 mg/m3

 in a 

chemical factory (Watrous and McCaughey 1945). However, this sort of data might easily be biased by 

workers who chose not to complain about minor symptoms, so no conclusion can be reached. Rats and 

mice exposed to very high levels (above 3,000 mg/m3

) of MMA (disodium salt) or DMA experienced 

diarrhea (Stevens et al. 1979). The diarrhea could be due to transport of inhaled particulate material from 

the lungs to the gastrointestinal system or to direct ingestion of the compound (e.g., from grooming of the 

fur). No gastrointestinal effects were observed in rats repeatedly exposed to 100 mg DMA/m3 

6 hours/day, 5 days/week for 67–68 exposures (Whitman 1994). 

Hematological Effects. 

Inorganic Arsenicals. Although anemia is a common feature of arsenic poisoning following oral 

exposure in humans (see Section 3.2.2.2), case studies of workers with arsenic poisoning from 

occupational inhalation exposure reported no effects on red blood cell count (Beckett et al. 1986; BollaWilson and Bleecker 1987; Ide and Bullough 1988; Morton and Caron 1989). The reason for this 

apparent route specificity is not clear, but might simply be related to dose. No studies were located 

regarding hematological effects in animals after inhalation exposure to inorganic arsenicals. 

Organic Arsenicals. No effect on levels of hemoglobin, red cells, or white cells was detected in the 

blood of manufacturing workers (323 counts in 35 workers) exposed to airborne arsanilic acid dusts at a 

mean concentration of 0.17 mg/m3

 in the workplace (Watrous and McCaughey 1945). Controls were an 

unspecified number of unexposed manufacturing workers with 221 complete blood counts. No 
ARSENIC 61 

3. HEALTH EFFECTS 

hematological alterations were observed in rats exposed to 100 mg DMA/m3 for an intermediate duration 

(Whitman 1994). 

Musculoskeletal Effects. 

Inorganic Arsenicals. Few data were located regarding musculoskeletal effects associated with 

inhalation exposure to inorganic arsenic, and none to suggest the existence of any such effects. 

Electromyographic examination of the calves and feet showed no differences between control and 

arsenic-exposed workers in a cross-sectional study of workers at the Ronnskar copper smelter in Sweden 

(Blom et al. 1985). No studies were located regarding musculoskeletal effects in animals after inhalation 

exposure to inorganic arsenicals. 

Organic Arsenicals. No studies were located regarding musculoskeletal effects in humans or animals 

after inhalation exposure to organic arsenicals. 

Hepatic Effects. 

Inorganic Arsenicals. There is no evidence that inhaled inorganic arsenic produces effects on the liver, 

although few data are available. Case studies of workers with inhalation arsenic poisoning that included 

liver function tests did not find any evidence of hepatic dysfunction (Bolla-Wilson and Bleecker 1987; 

Ide and Bullough 1988). No studies were located regarding hepatic effects in animals after inhalation 

exposure to inorganic arsenicals. 

Organic Arsenicals. No studies were located regarding hepatic effects in humans after inhalation 

exposure to organic arsenicals. No histological alterations were observed in the livers of rats exposed to 

100 mg DMA/m3

 for 67–68 exposures (Whitman 1994). 

Renal Effects. 

Inorganic Arsenicals. The limited data available do not suggest any relationship between inhalation of 

inorganic arsenic and kidney effects. A cross-sectional study of renal function parameters in glass factory 

workers exposed to arsenic (concentrations unknown) found no meaningful differences from controls in 

urinary levels of several proteins (albumin, retinol binding protein, β2-microglobulin, brush-border 

antigen) used as markers of glomerular damage or tubular cell exfoliation (Foà et al. 1987). Routine 
ARSENIC 62 

3. HEALTH EFFECTS 

clinical urinalysis was normal when included in case studies of workers with inhalation arsenic poisoning 

(Ide and Bullough 1988; Morton and Caron 1989). No studies were located regarding renal effects in 

animals after inhalation exposure to inorganic arsenicals. 

Organic Arsenicals. No studies were located regarding renal effects in humans after inhalation exposure 

to organic arsenicals. No renal effects were reported in rats exposed to 100 mg DMA/m3

 6 hours/day, 

5 days/week for 67–68 exposures (Whitman 1994). 

Dermal Effects. 

Inorganic Arsenicals. Dermatitis has frequently been observed in industrial workers exposed to 

inorganic arsenic in the air, with the highest rates occurring in the workers with the greatest arsenic 

exposure (Cöl et al. 1999; Dunlap 1921; Holmqvist 1951; Lagerkvist et al. 1986; Pinto and McGill 1953). 

Limited quantitative information is available regarding the exposure levels that produce dermatitis, and 

the high likelihood of co-exposure by the dermal route makes dose-response analysis difficult. A crosssectional study of workers at a factory where sodium arsenite was prepared found that workers with the 

highest arsenic exposure (mean air levels ranging from 0.384 to 1.034 mg As/m3

 and estimated to average 

0.613 mg As/m3

) tended to be grossly pigmented with hyperkeratinization of exposed skin and to have 

multiple warts (Perry et al. 1948). In the same study, workers with lower arsenic exposure (estimated to 

average 0.078 mg As/m3

) were much less affected, but still had a higher incidence of pigmentation 

keratosis than controls. LOAEL values identified by Perry et al. (1948) and Mohamed (1998) are shown 

in Table 3-1 and Figure 3-1. NOAEL values for dermal irritation have not been identified. Dermal 

effects (hyperkeratoses, hyperpigmentation) are also very common in people exposed to inorganic arsenic 

by the oral route (see Section 3.2.2.2). No studies were located on dermal effects in animals after 

inhalation exposure to inorganic arsenicals. 

Organic Arsenicals. Data regarding dermal effects in people exposed to organic arsenic in the air are 

limited. Complaints of keratosis were roughly 2-fold higher than unexposed controls in female packaging 

workers exposed to arsanilic acid at an average concentration of 0.065 mg/m3

 and in male manufacturing 

workers exposed to an average concentration of 0.17 mg/m3

 in a chemical factory (Watrous and 

McCaughey 1945). Limitations in study methodology (e.g., alternate sources of effects were not 

investigated, workers might choose not to report minor complaints to company officials) make the 

reliability of this observation uncertain. Female rats exposed to DMA at 6,900 mg/m3

 developed 

erythematous lesions on the feet and ears (Stevens et al. 1979); these lesions did not develop in females 
ARSENIC 63 

3. HEALTH EFFECTS 

exposed at lower concentrations (4,100 mg/m3) or males. It seems likely that these effects were due to 

direct irritation from dermal contact with the dust. No dermal effects were observed in rats repeatedly 

exposed to lower levels of DMA (100 mg/m3

) (Whitman 1994). 

Ocular Effects. 

Inorganic Arsenicals. Chemical conjunctivitis, characterized by redness, swelling, and pain, has been 

observed in workers exposed to arsenic dusts in air, usually accompanied by facial dermatitis (Dunlap 

1921; Pinto and McGill 1953). No information was located regarding air levels of arsenic that produce 

this effect. No studies were located on ocular effects in animals after inhalation exposure to inorganic 

arsenicals. 

Organic Arsenicals. No studies were located on ocular effects in humans after inhalation exposure to 

organic arsenicals. Rats and mice exposed to high concentrations of DMA (≥4,000 mg/m3

) developed an 

encrustation around the eyes (Stevens et al. 1979). It seems likely that these effects were due to direct 

irritation from ocular contact with the dust. 

Body Weight Effects. 

Inorganic Arsenicals. No studies were located on body weight effects in humans after inhalation 

exposure to inorganic arsenicals. Female rats exposed to arsenic trioxide dust starting 14 days before 

mating and continuing through mating and gestation showed a marked decrease in body weight and food 

consumption at 20 mg As/m3

 (preliminary study) and a smaller decrease at 8 mg As/m3 (definitive study), 

with no effect at 2 mg As/m3

 (Holson et al. 1999). 

Organic Arsenicals. No studies were located on body weight effects in humans after inhalation exposure 

to organic arsenicals. Rats and mice exposed to high concentrations of DMA (≥4,000 mg/m3

) for 2 hours 

had an unspecified decrease in body weight gain during the subsequent 14 days (Stevens et al. 1979). No 

alterations in body weight gain were observed in rats exposed to 100 mg DMA/m3

 for 67–68 exposures 

(Whitman 1994). 
ARSENIC 64 

3. HEALTH EFFECTS 

3.2.1.3 Immunological and Lymphoreticular Effects 

Inorganic Arsenicals. A single study was located regarding the immunological and lymphoreticular 

effects of inhaled inorganic arsenic in humans. Bencko et al. (1988) detected no abnormalities in serum 

levels of immunoglobins in 47 workers exposed to arsenic (exposure levels not measured) in a coalburning power plant. However, serum levels of other proteins such as transferrin, orosomucoid, and 

ceruloplasmin were significantly elevated compared to levels in a group of 27 workers from a different 

plant in which the arsenic content in the coal was 10 times lower. The investigators suggested that the 

increased levels of ceruloplasmin might be related to higher cancer mortality rates found among these 

workers. 

The immune effects of inhaled arsenic in animals were studied by Aranyi et al. (1985). Female mice 

exposed to arsenic trioxide aerosol for 3 hours showed a concentration-related decrease in pulmonary 

bactericidal activity (presumably as a result of injury to alveolar macrophages) and a corresponding 

concentration-related increase in susceptibility to introduced respiratory bacterial pathogens. Similar 

results were found when the exposure was repeated over 1- and 4-week periods. The NOAEL and 

LOAEL values for this study are shown in Table 3-1 and Figure 3-1. 

Intratracheal studies in animals offer some support for an immune effect of inhaled inorganic arsenic. 

Decreases in humoral response to antigens and in several complement proteins were noted in mice given 

an intratracheal dose of 5.7 mg As/kg as sodium arsenite (Sikorski et al. 1989), although these changes 

were not accompanied by any decrease in resistance to bacterial or tumor cell challenges. Animals given 

an intratracheal dose of GaAs (25 mg As/kg or higher) also displayed a variety of changes in numerous 

immunological end points (some increased, some decreased) (Burns and Munson 1993; Sikorski et al. 

1989). Whether these effects were due to a direct effect on the immune system or were secondary to the 

inflammatory effect of GaAs on the lung (see Section 3.2.1.2, above) is uncertain. 

Organic Arsenicals. No studies were located regarding immunological and lymphoreticular effects in 

humans or animals after inhalation exposure to organic arsenicals. 

3.2.1.4 Neurological Effects 

Inorganic Arsenicals. There is evidence from epidemiological studies that inhaled inorganic arsenic can 

produce neurological effects. A study by Gerr et al. (2000) reported an elevated incidence of peripheral 

neuropathy in subjects who lived near an arsenic-using pesticide plant (13/85=15.3%; odds ratio 
ARSENIC 65 

3. HEALTH EFFECTS 

[OR]=5.1, p=0.004), relative to subjects who lived farther from the plant (4/118=3.4%). Concentrations 

of arsenic in soil and house dust were elevated (~30–300 μg As/g) for residences near the plant, according 

to 1993–1995 monitoring data. Studies of copper smelter workers at the ASARCO smelter in Tacoma, 

Washington (Feldman et al. 1979), a power station in Slovakia (Buchancová et al. 1998), and the 

Ronnskar smelter in Sweden (Blom et al. 1985; Lagerkvist and Zetterlund 1994) have demonstrated 

peripheral neurological effects in workers associated with arsenic trioxide exposure. At the ASARCO 

smelter, the prevalence of clinically diagnosed peripheral neuropathy was markedly higher in arsenicexposed workers (26/61=43%) than controls (4/33=12%), and although the difference in mean nerve 

conduction velocities (NCV) was not statistically significant, mean peroneal motor NCV was lower in 

arsenic-exposed workers than controls and all 12 cases of abnormally low NCV occurred in the arsenic 

group (Feldman et al. 1979). In the study of 70 workers in Slovakia, the investigators described 16 cases 

of arsenic intoxication. Among these, 13 had signs and symptoms of sensory and motor polyneuropathy 

on both upper and lower extremities, 10 were diagnosed with pseudoneurasthenic syndrome, and 

6 suffered from toxic encephalopathy (Buchancová et al. 1998). The average length of exposure was 

22.3 years (SD ±8.4 years) and the average arsenic exposure in inhaled air ranged from 4.6 to 

142.7 μg/m3

. Similar results were observed at the Ronnskar smelter, where Blom et al. (1985) reported 

significantly increased prevalence of workers with abnormally low NCV in the exposed group, and lower, 

but not statistically significant, mean NCV in five peripheral nerves. A follow-up study on the Ronnskar 

workers 5 years later found that the prevalence of abnormally low NCV remained significantly increased 

in the exposed workers, but that the decrease in mean NCV was now also statistically significant in the 

tibial (motor) and sural (sensory) nerves (Lagerkvist and Zetterlund 1994). Blood lead was monitored in 

this study as a potential confounder, but levels were low and not considered likely by the researchers to 

have had any influence on the results. The follow-up Ronnskar study provided enough information to 

estimate that mean arsenic exposure was 0.31 mg As/m3

 and lasted an average of 28 years in the exposed 

group, and this LOAEL is shown in Table 3-1 and Figure 3-1. 

The literature also contains several case studies of workers with inhalation arsenic poisoning who 

developed neurological symptoms. Although these studies do not provide reliable information on 

exposure levels or conclusive evidence that the observed effects were related to arsenic, the findings are 

suggestive. Symptoms in these cases included not only indicators of peripheral neuropathy (numbness, 

loss of reflexes, muscle weakness, tremors) (Ide and Bullough 1988; Morton and Caron 1989), but also 

frank encephalopathy (hallucinations, agitation, emotional lability, memory loss) (Beckett et al. 1986; 

Bolla-Wilson and Bleecker 1987; Morton and Caron 1989). Both peripheral neuropathy and 

encephalopathy are associated with oral exposure to inorganic arsenic (see Section 3.2.2.4). 
ARSENIC 66 

3. HEALTH EFFECTS 

The possible association between arsenic in air and neurological effects in children has also been 

examined. A study by Bencko et al. (1977) reported that children of approximately 10 years of age 

(n=56) living near a power plant burning coal of high arsenic content showed significant hearing losses 

(increased threshold) compared to a control group of children (n=51) living outside the polluted area 

(Bencko et al. 1977). The effect was most marked at low frequencies. The precise site affected within 

the auditory pathway was not determined and could have been in the periphery, centrally-located, or both. 

A small study of children in Mexico reported a significant negative correlation between tests of verbal IQ 

and urinary arsenic in children (n=41) living in an urban area near a smelter complex (Calderón et al. 

2001). Exposure concentrations were not available in either study. 

No studies were located regarding neurological effects in animals after inhalation exposure to inorganic 

arsenicals. Mice given a single intratracheal dose of 200 mg/kg of GaAs displayed a decrease in overall 

activity 6–8 hours later, but no additional neurological evaluations were conducted on these animals 

(Burns and Munson 1993). 

Organic Arsenicals. Data regarding neurological effects in people exposed to organic arsenic in the air 

are limited to a single study. The frequency of central nervous system complaints was no higher than 

controls in workers at a chemical factory exposed to arsanilic acid at mean concentrations up to 

0.17 mg/m3

 (Watrous and McCaughey 1945). Although peripheral nerve complaints were higher in 

arsenic packaging workers (mean exposure=0.065 mg/m3

) than in unexposed controls, this was not the 

case in manufacturing workers with higher arsenic exposure (mean=0.17 mg/m3

). This suggests that the 

effects on the peripheral nerves in the exposed packaging workers were not due to arsenic. The reliability 

of these data is limited by shortcomings in the study methodology (e.g., the data might easily be biased by 

workers who chose not to complain about minor symptoms). No studies were located regarding 

neurological effects in animals after inhalation exposure to organic arsenicals. 

3.2.1.5 Reproductive Effects 

Inorganic Arsenicals. No studies were located regarding reproductive effects in humans after inhalation 

exposure to inorganic arsenicals. Reproductive performance was evaluated in female rats exposed to 

0.08–20 mg As/m3

 (preliminary study) or 0.2–8 mg As/m3 (definitive study) as As2O3 6 hours daily from 

14 days prior to mating through gestation day 19 (Holson et al. 1999). No changes occurred in the 

precoital interval (time to mating), mating index (percentage of rats mated), or fertility index (percentage 
ARSENIC 67 

3. HEALTH EFFECTS 

of matings resulting in pregnancy). The NOAEL values for this study are shown in Table 3-1 and 

Figure 3-1. 

Organic Arsenicals. No studies were located regarding reproductive effects in humans or animals after 

inhalation exposure to organic arsenicals. 

3.2.1.6 Developmental Effects 

Inorganic Arsenicals. Developmental effects associated with occupational and environmental exposure 

to airborne arsenic have been investigated in a series of studies at the Ronnskar copper smelter in northern 

Sweden (Nordström et al. 1978a, 1978b, 1979a, 1979b). In comparison to a northern Swedish reference 

population, female employees of the smelter had a significantly increased incidence of spontaneous 

abortion (Nordström et al. 1979a), and their children had a significantly increased incidence of congenital 

malformations (Nordström et al. 1979b) and significantly decreased average birth weight (Nordström et 

al. 1978a). Increased incidence of spontaneous abortion and decreased average birth weight of children 

were also found in populations living in close proximity to the smelter (Nordström et al. 1978a, 1978b, 

1979b). While these data are suggestive of developmental effects associated with occupational and 

environmental exposure from the smelter, the reported effects are not large, the analyses include only 

limited consideration of potential confounders (e.g., smoking), and there are no data relating the apparent 

effects specifically to arsenic exposure. 

Ihrig et al. (1998) conducted a case-control study of stillbirths in the vicinity of a Texas arsenic pesticide 

factory that included estimation of environmental arsenic exposures using atmospheric dispersion 

modeling and multiple regression analysis considering arsenic exposure, race/ethnicity, maternal age, 

median income, and parity as explanatory variables. There was a statistically significant increase in the 

risk of stillbirth in the highest exposure category (>100 ng As/m3

, midpoint=682 ng/m3). Further analysis 

showed that this increase in risk was limited to people of Hispanic descent, who the researchers 

speculated may be an especially sensitive population due to a genetic impairment in folate metabolism. 

Interpretation of this study is limited by small numbers of cases and controls in the high exposure group, 

lack of data on smoking, potential confounding exposures to other chemicals from the factory, and failure 

to take into account previous years of deposition in the exposure estimates. 

Arsenic has been shown to produce developmental effects by inhalation exposure in laboratory animals, 

although it is unclear whether or not the effects occur only at maternally toxic doses. Mice exposed to 
ARSENIC 68 

3. HEALTH EFFECTS 

22 mg As/m3 (as As2O3) for 4 hours on days 9–12 of gestation had serious developmental effects 

(significant increases in the percentage of dead fetuses, skeletal malformations, and the number of fetuses 

with retarded growth), while those exposed to 2.2 mg As/m3

 had only a 10% decrease in average fetal 

body weight, and those exposed to 0.20 mg As/m3

 had no effects (Nagymajtényi et al. 1985). The study 

was limited by failure to quantify malformations on a litter basis, discuss the nature and severity of the 

observed malformations, or report on the occurrence of maternal effects. No increases in fetal 

resorptions, fetal mortality, or malformations, and no decreases in fetal body weight occurred when rats 

were exposed to 0.2–8 mg As/m3

 (as As2O3), 6 hours daily from 14 days prior to mating through gestation 

day 19 (Holson et al. 1999). At the 8 mg/m3

 exposure level, toxicity was observed in the dams, including 

rales, a dried red exudate at the nose, and lower gains in net body weight than controls. In a preliminary 

dose-range study, there was a marked significant increase in postimplantation loss (primarily early 

resorptions) and consequent marked significant decrease in viable fetuses per litter at 20 mg As/m3

, a 

concentration that also produced severe maternal effects including mortality (Holson et al. 1999). 

The NOAEL and LOAEL values for increased risk of stillbirth in humans identified by Ihrig et al. (1998) 

and those for developmental effects in rodents found by Nagymajtényi et al. (1985) and Holson et al. 

(1999) are shown in Table 3-1 and Figure 3-1. 

Organic Arsenicals. No studies were located regarding developmental effects in humans or animals after 

inhalation exposure to organic arsenicals. 

3.2.1.7 Cancer 

Inorganic Arsenicals. There is convincing evidence from a large number of epidemiological studies that 

inhalation exposure to inorganic arsenic increases the risk of lung cancer. Most studies involved workers 

exposed primarily to arsenic trioxide dust in air at copper smelters (Axelson et al. 1978; Brown and Chu 

1982, 1983a, 1983b; Enterline and Marsh 1982; Enterline et al. 1987a, 1987b, 1995; Ferreccio et al. 1996; 

Järup and Pershagen 1991; Järup et al. 1989; Lee and Fraumeni 1969; Lee-Feldstein 1983, 1986; Lubin et 

al. 2000; Mazumdar et al. 1989; Pinto et al. 1977, 1978; Sandstrom et al. 1989; Viren and Silvers 1999; 

Wall 1980; Welch et al. 1982) and mines (Liu and Chen 1996; Qiao et al. 1997; Taylor et al. 1989; Xuan 

et al. 1993), but increased incidence of lung cancer has also been observed at chemical plants where 

exposure was primarily to arsenate (Bulbulyan et al. 1996; Mabuchi et al. 1979; Ott et al. 1974; Sobel et 

al. 1988). In addition, several studies suggest that residents living near smelters or arsenical chemical 

plants may also have increased risk of lung cancer (Brown et al. 1984; Cordier et al. 1983; Matanoski et 
ARSENIC 69 

3. HEALTH EFFECTS 

al. 1981; Pershagen 1985), although the increases are small and are not clearly detectable in all cases 

(e.g., Frost et al. 1987). The strongest evidence that arsenic is responsible for the observed lung cancer 

comes from quantitative dose-response data relating specific arsenic exposure levels to lung cancer risk. 

These data are available for arsenic-exposed workers at the ASARCO copper smelter in Tacoma, 

Washington (Enterline and Marsh 1982; Enterline et al. 1987a, 1995; Mazumdar et al. 1989), the 

Anaconda copper smelter in Montana (Lee-Feldstein 1986; Welch et al. 1982), eight other U.S. copper 

smelters (Enterline et al. 1987b), and the Ronnskar copper smelter in Sweden (Järup and Pershagen 1991; 

Järup et al. 1989). A common limitation of these studies is confounding exposure to other chemicals, 

such as sulfur dioxide, and cigarette smoking. 

Enterline and Marsh (1982) reported a significant increase in respiratory cancer mortality (standard 

mortality ratio [SMR]=189.4) based on 104 observed respiratory cancer deaths and only 54.9 expected 

over the years 1941–1976 in a cohort of 2,802 male workers employed for ≥1 year between 1940 and 

1964 at the ASARCO smelter. When the cohort was separated into low and high arsenic exposure 

groups, with mean estimated time-weighted average arsenic exposures of 0.054 and 0.157 mg As/m3

, 

respectively (based on work history, historical urinary arsenic measurements, and an experimentally 

derived relationship between urinary and inhaled arsenic), respiratory cancer mortality was significantly 

increased in both groups in a concentration-related fashion (SMR=227.7 and 291.4 in the low and high 

groups, respectively). Enterline et al. (1987a) re-analyzed these data using improved exposure estimates 

that incorporated historical measurements of arsenic in the ambient air and personal breathing zone of 

workers. Respiratory cancer mortality was significantly increased in a concentration-related fashion in 

the low (SMR=213.0), medium (SMR=312.1), and high (SMR=340.9) arsenic exposure groups, which 

had mean estimated time-weighted average arsenic exposures of 0.213, 0.564, and 1.487 mg As/m3

, 

respectively. An alternative analysis of these data by Mazumdar et al. (1989) produced similar results. 

Enterline et al. (1995) extended the mortality follow-up from 1976 to 1986, but reported findings similar 

to the earlier study in a less thorough analysis. The CEL from Enterline et al. (1987a), the most complete 

analysis of the ASARCO cohort with the best exposure estimates, is presented in Table 3-1 and 

Figure 3-1. 

Respiratory cancer mortality was significantly increased (SMR=285) based on 302 observed respiratory 

deaths between 1938 and 1977 in a cohort of 8,045 white male workers employed for at least 1 year 

between 1938 and 1956 at the Anaconda smelter (Lee-Feldstein 1986). When workers were categorized 

according to cumulative arsenic exposure and date of hire, lung cancer mortality was significantly 

increased in all groups hired between 1925 and 1947. Workers in the lowest cumulative exposure group 
ARSENIC 70 

3. HEALTH EFFECTS 

(<10 mg-mo/m3) were reported to have had <2 years of exposure at an average arsenic concentration of 

0.38 mg/m3

. An alternative analysis of a subset of the Anaconda cohort (n=1,800, including all 

277 employees with heavy arsenic exposure and 20% of the others) that included information on smoking 

and other occupational exposures was performed by Welch et al. (1982). This analysis showed that lung 

cancer mortality increased with increasing time-weighted average arsenic exposure, with a small 

nonsignificant increase in the low group (SMR=138) exposed to 0.05 mg/m3

 and significant increases in 

the medium (SMR=303), high (SMR=375), and very high (SMR=704) groups exposed to 0.3, 2.75, and 

5.0 mg/m3

, respectively. Cohort members were more likely to be smokers than U.S. white males, but 

smoking did not differ among the arsenic exposure groups. Exposure-response analysis of smokers was 

similar to the analysis based on the full subcohort, while analysis of nonsmokers (limited by small group 

sizes) also showed a similar pattern, but with lower SMRs. In a followup analysis of the same cohort, 

Lubin et al. (2000) re-weighted the exposure concentrations based on duration and time of exposure and 

re-evaluated the effects of exposure. Relative risks for respiratory cancer increased with increasing 

duration in each arsenic exposure area (light, medium, and heavy) after adjustment for duration in the 

other two exposure areas. SMRs were significantly elevated following exposure to 0.58 mg/m3

 (medium; 

SMR=3.01, 95% CI=2.0–4.6) or 11.3 mg/m3

 (high; SMR=3.68, 95% CI=2.1–6.4) for 10 or more years, 

and following exposure to 0.29 mg/m3

 (low; SMR=1.86, 95% CI=1.2–2.9) for 25 or more years. The 

CELs from the analyses of the Anaconda cohort are presented in Table 3-1 and Figure 3-1. 

Enterline et al. (1987b) studied the mortality experience from 1949 to 1980 of a cohort of 6,078 white 

males who had worked for 3 years or more between 1946 and 1976 at one of eight U.S. copper smelters in 

Arizona, Utah, Tennessee, and Nevada. Lung cancer mortality was significantly increased only in the 

Utah smelter (SMR=226.7), which had the highest average arsenic exposure concentration (0.069 mg/m3 

vs. 0.007–0.013 mg/m3

 in the other smelters) and also contributed the largest number of cohort members 

(n=2,288 vs. 189–965 from the other smelters). A nested case-control study showed that arsenic exposure 

and cigarette smoking were significant risk factors for lung cancer in the smelter workers. Smoking was 

lower in the Utah smelter workers than in the other smelter workers, but still higher than in the referent 

Utah population, suggesting that the risk attributable to arsenic in this study population is somewhat 

lower than indicated by the SMR reported above. The CEL from this study is presented in Table 3-1 and 

Figure 3-1. 

Järup et al. (1989) reported significantly increased lung cancer mortality (SMR=372, 95% confidence 

interval [CI]=304–450) based on 106 lung cancer deaths in a cohort of 3,916 male workers employed for 

≥3 months between 1928 and 1967 at the Ronnskar smelter and followed for mortality through 1981. 
ARSENIC 71 

3. HEALTH EFFECTS 

Workers were separated into low, medium, and high arsenic exposure groups with mean time-weighted 

average exposure estimates of 0.05, 0.2, and 0.4 mg/m3

, respectively. Lung cancer mortality was 

significantly increased in all three exposure groups in a concentration-related fashion (SMR=201, 353, 

and 480, respectively). A nested case-control analysis of 102 lung cancer cases and 190 controls from the 

cohort showed that lung cancer risk increased with increasing arsenic exposure in nonsmokers, light 

smokers, and heavy smokers (Järup and Pershagen 1991). The results demonstrated that arsenic is a risk 

factor for lung cancer in the smelter workers, but also suggested a greater-than-additive interaction 

between smoking and arsenic exposure. In this analysis, in contrast to the cohort study, lung cancer risk 

due to arsenic was increased only in the higher arsenic-exposure groups. Potential explanations for this 

difference between the cohort and case-control analyses include a higher proportion of smokers in the 

smelter workers than in the regional referent population in the cohort study, and limited power to detect 

increased risk in the case-control study due to small group sizes in the dose-response analysis. The CELs 

from both the cohort and case-control studies are presented in Table 3-1 and Figure 3-1. 

Several researchers have examined the histological cell types of lung cancer (epidermoid carcinoma, 

small cell carcinoma, adenocarcinoma) in arsenic-exposed workers (e.g., Axelson et al. 1978; Newman et 

al. 1976; Pershagen et al. 1987; Qiao et al. 1997; Wicks et al. 1981). Although the incidence of the 

various cell types varied from population to population, all studies found an increase in several tumor 

types. This indicates that arsenic does not specifically increase the incidence of one particular type of 

lung cancer. 

The studies of the ASARCO cohort (Enterline and Marsh 1982; Enterline et al. 1987a, 1995) noted a 

supralinear exposure-response relationship (i.e., steeper at lower doses) between arsenic exposure and 

lung cancer mortality. Hertz-Picciotto and Smith (1993) extended this observation to several other 

occupationally exposed cohorts with quantitative exposure information. The authors suggest that neither 

toxicokinetic mechanisms nor confounding from age, smoking, or other workplace carcinogens that differ 

by exposure level are likely explanations for the curvilinearity. Plausible explanations offered include: 

(1) synergism (with smoking), which varies in magnitude according to the level of arsenic exposure, 

(2) long-term survivorship at higher exposures among the healthier, less susceptible individuals, and 

(3) exposure estimate errors that were more prominent at higher-exposure levels as a result of past 

industrial hygiene sampling or worker protection practices. 

Quantitative risk estimates for inhaled inorganic arsenic have been derived using the exposure-response 

data. EPA derived a unit risk estimate (the excess risk of lung cancer associated with lifetime exposure to 
ARSENIC 72 

3. HEALTH EFFECTS 

1 μg/m3) of 4.3x10-3 per (μg/m3) based on the dose-response relationships between arsenic exposure and 

excess lung cancer mortality in workers at the Anaconda smelter in Montana (Brown and Chu 1982, 

1983a, 1983b; Lee-Feldstein 1983; and an unpublished paper by Higgins and associates) and the 

ASARCO smelter in Tacoma, Washington (Enterline and Marsh 1982; EPA 1984a; IRIS 2007). In some 

cases, calculations of exposure, as well as the procedures for generating quantitative risk estimates, are 

quite complex and the interested reader is referred to the EPA documents (EPA 1981c, 1984a, 1987e, 

1996b; IRIS 2007) for a detailed description. Viren and Silvers (1994) re-evaluated the unit risk estimate 

using the same methods as EPA, but incorporating updated results from the ASARCO smelter (Enterline 

et al. 1987a; Mazumdar et al. 1989) and the findings from the Swedish smelter (Järup et al. 1989). Their 

analysis yielded a revised unit risk of 1.28x10-3 per (μg/m3

) that, when pooled with the earlier estimate 

from the Montana smelter cohort, yielded a composite unit risk of 1.43x10-3 per (μg/m3

). This unit risk 

estimate is a factor of 3 smaller than the EPA’s current estimate of 4.3x10-3 per (μg/m3

). Figure 3-1 

shows the air concentrations that correspond to excess lifetime cancer risks of 10-4–10-7 based on the EPA 

unit risk estimate. 

There have been occasional reports of other types of cancer (i.e., nonrespiratory cancer) potentially 

associated with inhalation exposure to inorganic arsenic, but there is no strong evidence for any of them. 

For example, Enterline et al. (1995) found significantly increased mortality due to cancer of the large 

intestine and bone cancer in the ASARCO cohort. However, neither cancer showed any relation to 

cumulative arsenic exposure, and the purported increase in bone cancer risk was based on a very small 

number of observations. Pesch et al. (2002) reported an increase in nonmelanoma skin cancers resulting 

from exposure from a Slovakian coal-burning power plant, but exposure levels associated with the lesions 

were not presented. Bencko et al. (2005) also reported an increase in the incidence of nonmelanoma skin 

cancer among workers of a power plant burning coal of a high arsenic content and in the population living 

in the vicinity of the power plant. Bulbulyan et al. (1996) reported an increase in risk of stomach cancer 

among workers exposed to the highest average arsenic concentrations at a Russian fertilizer plant, but this 

finding, which was based on a small number of observations and was only marginally statistically 

significant, was confounded by exposure to nitrogen oxides, which were more convincingly associated 

with stomach cancer in this study. Wingren and Axelson (1993) reported an association between arsenic 

exposure and stomach and colon cancer in Swedish glass workers, but this result was confounded by 

concomitant exposure to other metals. Lee-Feldstein (1983) observed a small, marginally significant 

increase in digestive tract cancer (SMR=125) in one study of the Anaconda cohort, but this was not found 

in other studies of this cohort (Lee and Fraumeni 1969; Lee-Feldstein 1986; Welch et al. 1982). Wulff et 

al. (1996) observed an apparent increase in the risk of childhood cancer (all types combined) in the 
ARSENIC 73 

3. HEALTH EFFECTS 

population living within 20 km of the Ronnskar smelter, but the apparent increase was based on a small 

number of cases (13 observed vs. 6.7 expected) and was not statistically significant, and exposure to 

arsenic was confounded by exposure to lead, copper, cadmium, sulfur dioxide, and possibly other 

emissions such as nickel and selenium. A retrospective study of deaths due to unspecified types of 

malignancies among workers of power plants found no significant differences in death rate between two 

groups whose exposure levels to arsenic had a difference of one order of magnitude (Bencko et al. 1980). 

However, the mean age of those deceased due to cancer in the high-exposure group was 55.9 years 

compared to 61.2 years in the low-exposure group, and this difference was statistically significant 

(p<0.05). Also, when the workers were stratified by exposure-duration, there was a significantly higher 

frequency of tumors in the high-exposure group after shorter employment periods (<5 or 6–10 years) than 

after a longer employment period (≥11 years). No information was provided regarding specific types of 

cancer. Various case reports have implicated occupational arsenic exposure as a potential contributing 

factor in workers who developed sinonasal cancer (Battista et al. 1996), hepatic angiosarcoma (Tsai et al. 

1998a), and skin cancer (Cöl et al. 1999; Tsuruta et al. 1998), but provide no proof that inhaled arsenic 

was involved in the etiology of the observed tumors. Wong et al. (1992) found no evidence that 

environmental exposure to airborne arsenic produced skin cancer in residents living near the Anaconda 

smelter or an open pit copper mine. 

No studies were located regarding cancer in animals after inhalation exposure to inorganic arsenicals, 

although several intratracheal instillation studies in hamsters have provided evidence that both arsenite 

and arsenate can increase the incidence of lung adenomas and/or carcinomas (Ishinishi et al. 1983; 

Pershagen and Björklund 1985; Pershagen et al. 1984; Yamamoto et al. 1987). These data support the 

conclusion that inhalation of arsenic may lead to lung cancer in humans. 

Organic Arsenicals. No studies were located regarding cancer effects in humans or animals after 

inhalation exposure to organic arsenicals. 

3.2.2 Oral Exposure 

There are a large number of studies in humans and animals on the toxic effects of ingested arsenic. In 

humans, most cases of toxicity have resulted from accidental, suicidal, homicidal, or medicinal ingestion 

of arsenic-containing powders or solutions or by consumption of contaminated food or drinking water. In 

some cases, the chemical form is known (e.g., the most common arsenic medicinal was Fowler's solution, 

which contained 1% potassium arsenite or arsenic trioxide), but in many cases (e.g., exposures through 
ARSENIC 74 

3. HEALTH EFFECTS 

drinking water), the chemical form is not known. In these cases, it is presumed that the most likely forms 

are either inorganic arsenate [As(+5)], inorganic arsenite [As(+3)], or a mixture. Table 3-3 and 

Figure 3-3 summarize a number of studies that provide reliable quantitative data on health effects in 

humans and animals exposed to inorganic arsenicals by the oral route. Similar data for MMA, DMA, and 

roxarsone are listed in Tables 3-4, 3-5, and 3-6, and shown in Figures 3-4, 3-5, and 3-6, respectively. All 

exposure data are expressed as milligrams of arsenic (as the element) per kilogram body weight per day 

(mg As/kg/day). These studies and others that provide useful qualitative information are summarized 

below. 

3.2.2.1 Death 

Inorganic Arsenicals. There are many case reports of death in humans due to ingestion of high doses of 

arsenic. In nearly all cases, the most immediate effects are vomiting, diarrhea, and gastrointestinal 

hemorrhage, and death may ensue from fluid loss and circulatory collapse (Levin-Scherz et al. 1987; 

Saady et al. 1989; Uede and Furukawa 2003). In other cases, death may be delayed and result from the 

multiple tissue injuries produced by arsenic (Campbell and Alvarez 1989). Some accounts of fatal arsenic 

poisoning describe both gastrointestinal effects soon after ingestion and extensive damage to multiple 

organ systems prior to death (Quatrehomme et al. 1992). A precise estimate of the ingested dose is 

usually not available in acute poisonings, so quantitative information on lethal dose in humans is sparse. 

The lethal doses ranged from 22 to 121 mg As/kg in four cases where known amounts were ingested as a 

single bolus (Civantos et al. 1995; Hantson et al. 1996; Levin-Scherz et al. 1987; Quatrehomme et al. 

1992). Two people in a family of eight died from ingestion of water containing about 110 ppm of arsenic 

for a week (Armstrong et al. 1984). This corresponded to a dose of about 2 mg As/kg/day. Based on a 

review of clinical reports in the older literature, Holland (1904) estimated the minimum lethal dose to be 

about 130 mg (also about 2 mg/kg). A similar estimate of 70–180 mg (about 1–3 mg/kg) was provided 

by Vallee et al. (1960). Death due to chronic arsenic exposure has been reported at lower concentrations. 

Five children between the ages of 2 and 7 years died from late sequelae of chronic arsenic poisoning after 

drinking contaminated water throughout their lives at estimated average doses of 0.05–0.1 mg As/kg/day 

(Zaldívar and Guillier 1977). A 22-year-old man with chronic arsenical dermatosis died from arsenicrelated effects after lifetime exposure to an estimated average dose of 0.014 mg As/kg/day in the drinking 

water (Zaldívar et al. 1981). Systematic studies of lethality from chronic exposure attributable to 

increased risk of cardiovascular disease or cancer are discussed below in Sections 3.2.2.2 and 3.2.2.7, 

respectively. 
193

2

320

121

361

108

40

22

868

93

97

104

271

112

84

44

84a

175

118

15

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral 

Exposure/ LOAEL 

Duration/ 

a 

Key to 

Figure 

Species 

(Strain) 

Frequency 

(Route) 

ACUTE EXPOSURE Death 

1 Human 1 wk 

(W) 

System 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

2 (death) 

2 Human once 

(IN) 

121 M (death) 

3 Human once 

(IN) 108 M (death) 

4 Human once 

(IN) 

22 M (death) 

5 Human once 

(IN) 93 M (death) 

6 Rat 

(wild Norway) 

once (G) 104 (LD50) 

7 Rat 

(Sherman) 

once (G) 

112 F (LD50) 

8 Rat 

(Sherman) 

once (G) 

44 F (LD50) 

9 Rat 

(Sherman) 

once (G) 175 F (LD50) 

10 Rat 

(SpragueDawley) 

once (GW) 15 M (LD50) 

Reference Chemical Form 

Armstrong et al. 1984 

NS 

Civantos et al. 1995 As(+5) Hantson et al. 1996 As(+3) Levin-Scherz et al. 1987 As(+3) Quatrehomme et al. 199As(+3) Dieke and Richter 1946 As(+3) Gaines 1960 As(+5) calcium arsenatGaines 1960 As(+3) Gaines 1960 As(+5) lead arsenate Harrisson et al. 1958 As(+3) 
919

145

3012b

23

119

39

915

26

916

32

917

26

221

26

3020

1.49

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to 

Figure 

11 12 13 14 15 16 17 18 

Species 

(Strain) 

Rat (SpragueDawley) Rat (CD) Mouse (SwissWebster) Mouse (C57H46) Mouse (Dba2) Mouse (C3H) Mouse (ddY) Rabbit (New Zealand) 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) Serious (mg/kg/day) 

once (F) 145 M (LD50) once Gd 9 (GW) 

23 F (7/25 dams died) 

once (GW) 39 M (LD50) once (GW) 26 M (LD50) once (GW) 32 M (LD50) once (GW) 26 M (LD50) once (GW) Gd 6-18 1 x/d (GW) 

26 M (LD50) 

1.49 F (7/20 dams died) 

Reference Chemical Form 

Harrisson et al. 1958 As(+3) Stump et al. 1999 As(+3) Harrisson et al. 1958 As(+3) Harrisson et al. 1958 As(+3) Harrisson et al. 1958 As(+3) Harrisson et al. 1958 As(+3) Kaise et al. 1985 As(+3) Nemec et al. 1998 As(+5) 
194

0.2 2

0.20.40.2

0.2

321

121121121

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

Systemic 

19 Human 1 wk 

(W) Gastro 0.2 (vomiting, diarrhea, abdominal pain) 2 M (diffuse inflammation of the GI tract) Armstrong et al. 1984 NS 

Hemato 0.2 (pancytopenia, 

leukopenia) 

Hepatic Renal Ocular 0.2 (periorbital swelling) 

0.4 (hepatitis) 0.2 (nephropathy) 

20 Human once 

(IN) Resp 121 M (respiratory distress, lung hemmorhage and 

edema) 

Civantos et al. 1995 As(+5) 

Cardio 121 M (hypotension, ventricular 

fibrillation, cardiac arrest) 

Gastro 121 M (ulceration of upper 

gastrointestinal tract) 
821

1919

191919

94

888888

8

28a

0.05

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ 

Duration/ 

a 

Key to Species Frequency 

Figure (Strain) (Route) 

21 Human once 

(IN) 

22 Human once 

(NS) 

Human 1 or 2 x 

(W) 

LOAEL 

System 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Reference Chemical Form 

Cardio 19 F (tachycardia) Cullen et al. 1995 

As (+5) 

Gastro 19 F (profuse vomiting and 

diarrhea) 

Hemato 19 F Hepatic 19 F Renal 19 F 

Resp 8 M (hemorrhagic bronchitis, Fincher and Koerker 19

pulmonary edema) As(+3) 

Cardio 8 M (hypotension, 

tachycardia, massive cardiomegaly) 

Gastro 8 M (gastrointestinal 

bleeding) 

Hemato 8 M (hemolysis) Musc/skel 8 M (marked atrophy of distal 

muscle groups) 

Renal 8 M (acute renal failure) Dermal 8 M (truncal macular rash) 

Gastro 0.05 (occasional nausea, Franzblau and Lilis 198

diarrhea, and abdominal As(+3) As(+5) cramps) 

23 
20

120120

120

358

222

4014

1313

1313

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ 

Duration/ 

a 

Key to Species Frequency 

Figure (Strain) (Route) 

24 Human once 

(W) 

25 Human once 

(IN) 

26 Human once 

(IN) 

LOAEL 

System 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Reference Chemical Form 

Gastro 120 M (vomiting and diarrhea) Goebel et al. 1990 

NS 

Renal 120 M (anuria) 

Dermal 120 M (hyperkeratosis) 

Gastro 2 F (vomiting) Hantson et al. 1996 

As(+3) 

Hepatic 2 F (slight increase in serum 

bilirubin) 

Renal 2 F (altered renal function 

tests) 

Gastro 13 M (frequent vomiting, Kamijo et al. 1998 

diarrhea) As(+3) 

Hepatic 13 M (large increase in serum 

bilirubin, ALT, AST, LDH) 

Dermal 13 M (erythematous eruption) Ocular 13 M (constricted vision) 
96

2222222222

1035

66

6

6

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

27 Human once 

(IN) Resp 22 M (tachypnea, respiratory failure) Levin-Scherz et al. 1987 As(+3) 

Cardio 22 M (cyanosis, hypotension, 

tachycardia, ventricular fibrillation) 

Gastro 22 M (abdominal pain, nausea, 

diarrhea, massive vomiting, dysphagia, hemorrhage) 

Hepatic 22 M (large increase in serum 

AST and LDH) 

Renal 22 M (large increase in serum 

creatinine and BUN indicating acute renal failure) 

28 Human once 

pregnancy wk 30 (IN) 

Cardio 6 F (hypotension, rapid 

pulse) 

Lugo et al. 1969 As(+3) 

Gastro 6 F (abdominal pain, 

vomiting) 

Hemato 6 F (high leukocyte count, 

low hematocrit) 

Renal 6 F (acute renal failure) 
188

0.05

0.050.05

0.050.050.05

0.05

0.050.05

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

29 Human 2-3 wk 

(F) Resp 0.05 (sore throat, rhinorrhea, cough, sputum) Mizuta et al. 1956 As(+5) 

Cardio 0.05 (abnormal 

electrocardiogram) 

Gastro 

b

0.05 (nausea, vomiting, 

diarrhea, occult blood in feces and gastric and duodenal juice) 

Hemato 0.05 (mild anemia, 

leukopenia) 

Musc/skel 0.05 (tender calf muscle) Hepatic 0.05 (mild hepatomegaly, 

impaired liver function, degenerative lesions) 

Renal 0.05 Dermal 0.05 (pigmentation, itching, 

desquamation, exanthema) 

Ocular 0.05 (edema of eyelids, 

conjunctivitis, central scotoma, neuro-retinitis) 
810

11

43

11

4311

43

11

43

869

9393939393

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - 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 

30 Human once 

(IN) Resp 11 M 43 M (shortness of breath, decreased oxygen 

saturation) 

Moore et al. 1994a As(+3) 

Cardio 11 M 43 M (hypotension, asystolic 

cardiac arrest) 

Gastro 11 M (profuse diarrhea and 

vomiting, severe abdominal pain) 

Hemato 43 M Renal 11 M (increased serum 

creatinine) 

43 M (acute renal failure) 

31 Human once 

(IN) Resp 93 M (pulmonary edema) Quatrehomme et al. 199

As(+3) 

Gastro 93 M (ulcero-necrotic 

hemorrhagic gastritis) 

Hepatic 93 M (hepatomegaly, diffuse 

fatty degeneration) 

Renal 93 M (glomerular congestion) Dermal 93 M (dermoepidermic 

separation) 
117

3

6

3

6

3

6

904

2

11

2 11

333

14

0.9

14

352

8

24

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to Species 

Figure (Strain) 

32 Monkey 

(Rhesus) 

33 Rat 

(WistarBarby) 

34 Rat 

(SpragueDawley) 

35 Rat 

(SpragueDawley) 

Exposure/ 

Duration/ 

Frequency 

(Route) 

13 d 1 x/d (IN) 4-14 d 5 d/wk 1 x/d (G) 2 x (GW) 2 x (GW) 

LOAEL 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Reference Chemical Form 

3 6 (vomiting, unformed 

stool, "loss of condition") 

Heywood and Sortwell 1As(+5) 

3 6 (decreased liver 

glycogen, vacuolation of hepatocytes) 

3 6 (dilation of proximal 

tubules) 

2 F 11 F (decreased 

vasoreactivity) 

Bekemeier and Hirsche1989 As(+3) 

2 F 11 F (diarrhea, bloody stools) 

14 F Brown and Kitchin 1996 

As(+3) 

0.9 F (slight increased 

ornithine decarboxylase and heme oxygenase activity in liver) 

14 F 

8 F 24 F (increased heme 

oxygenase activity in liver) 

Brown et al. 1997c As(+5) 

System 

Gastro 

Hepatic 

Renal 

Cardio 

Gastro 

Resp 

Hepatic 

Dermal 

Hepatic 
5031

10

20

3012a

15

23

3025

12

24

716

3

6

5012

3.8

5002

0.37

1.49

195

2

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

1 x/d 15 d (G) 

Bd Wt 10 M 20 M (20-25% decreased body 

weight) 

Rodriguez et al. 2001 As(+3) 

once Gd 9 (GW) 

Bd Wt 15 F 23 F (decreased body weight 

gain) 

Stump et al. 1999 As(+3) 

Gd 6-15 1 x/d (GW) 

Bd Wt 12 F 24 F (decreased body weight 

gain during gestation) 

Nemec et al. 1998 As(+5) 

1 or 4 d 1 x/d (GW) 

Hemato 3 M 6 M (decreased 

polychromatic erythrocytes in bone marrow) 

Tice et al. 1997 As(+3) 

1 x/d 8 d (G) 

Cardio 3.8 M (prolongation of QT 

interval) 

Chiang et al. 2002 As2O3 

Gd 6-18 1 x/d (GW) 

Bd Wt 0.37 F 1.49 F (loss of body weight 

during treatment during gestation) 

Nemec et al. 1998 As(+5) 

1 wk (W) 

2 (encephalopathy, 

peripheral neuropathy) 

Armstrong et al. 1984 

NS 

a 

Key to Species 

Figure (Strain) 

36 Rat 

(SpragueDawley) 

37 Rat 

(CD) 

38 Mouse 

(CD-1) 

39 Mouse 

(B6C3F1) 

40 Gn Pig 41 Rabbit 

(New Zealand) 

Neurological 

42 Human 
322

121

821

19

93

8

21

120

362

216

4014a

13

938

22

187

0.05

811

43

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to 

Figure 

43 44 45 46 47 48 49 50 51 

Species 

(Strain) 

Human Human Human Human Human Human Human Human Human 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) Serious (mg/kg/day) 

once (IN) 

121 M (confusion, brain edema) 

once (IN) 19 F (lethargy) once (NS) 8 M (severe, persistent encephalopathy and 

peripheral neuropathy) 

once (W) 120 M (severe polyneuropathy) once (IN) 216 M (peripheral neuropathy) once (IN) 13 M (peripheral neuropathy) once (IN) 

22 M (agitation, disorientation, 

paranoia, violent reactions) 

2-3 wk (F) 0.05 (hypesthesia in legs, abnormal patellar reflex) once (IN) 43 M 

Reference Chemical Form 

Civantos et al. 1995 As(+5) Cullen et al. 1995 As (+5) Fincher and Koerker 19As(+3) Goebel et al. 1990 NS Hantson et al. 1996 As(+3) Kamijo et al. 1998 As(+3) Levin-Scherz et al. 1987 As(+3) Mizuta et al. 1956 As(+5) Moore et al. 1994a As(+3) 
871

93

920

3

6

5030

10

20

5002

0.37 1.49

1038

6

3012

15

23

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species 

Figure (Strain) 

52 Human 53 Monkey 

(Rhesus) 

54 Rat 

(SpragueDawley) 

55 Rabbit 

(New Zealand) 

Developmental 

56 Human 57 Rat 

(CD) 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) Serious (mg/kg/day) 

once (IN) 13 d 1 x/d (IN) 

3 

93 M (encephalopathy) 

6 (marked salivation, 

uncontrolled head shaking) 

1 x/d 15 d (G) 

10 M 20 M (altered spontaneous 

locomotor activity) 

Gd 6-18 1 x/d (GW) 

0.37 F 1.49 F (prostration, ataxia) 

once pregnancy wk 30 (IN) 

6 (severe pulmonary 

hemorrhage that may have contributed to death in premature neonate) 

once Gd 9 (GW) 

15 23 (increased 

post-implantation loss and decreased viable fetuses) 

Reference Chemical Form 

Quatrehomme et al. 199As(+3) Heywood and Sortwell 1As(+5) Rodriguez et al. 2001 As(+3) Nemec et al. 1998 As(+5) Lugo et al. 1969 As(+3) Stump et al. 1999 As(+3) 
68

11

23

67

48

3019

12

24

69

11

14

5000

0.37

1.49

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species 

Figure (Strain) 

58 Mouse 

(CD-1) 

59 Mouse 

(CD-1) 

60 Mouse 

(CD-1) 

61 Hamster 

(Lak:LVG [SYR]) 

62 Rabbit 

(New Zealand) 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) Serious (mg/kg/day) 

once Gd 8-15 (GW) 

11 23 (increased fetal mortality, 

exencephaly) 

once Gd 7-15 (GW) 

48 (increased fetal death, 

decreased fetal weight, gross and skeletal malformations) 

Gd 6-15 1 x/d (GW) 

12 24 (increased resorptions 

per litter, decreased live fetuses per litter, decreased mean fetal weight) 

once Gd 8-12 (GW) 

11 14 (increased fetal mortality, 

decreased fetal weight) 

Gd 6-18 1 x/d (GW) 

0.37 1.49 (increased resorptions 

per litter, decreased live fetuses per litter) 

Reference Chemical Form 

Baxley et al. 1981 As(+3) Hood et al. 1978 As(+5) Nemec et al. 1998 As(+5) Hood and Harrison 198As(+3) Nemec et al. 1998 As(+5) 
5069

9.5519.13

28

0.10.10.1

0.10.1

1030

0.05

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

Cancer 

63 Mouse 

C3H 

10 d (W) 9.55 M (CEL: liver and adrenal tumors) Waalkes et al. 2003 As(+3) 

19.13 F (CEL: ovarian and lung 

tumors) 

INTERMEDIATE EXPOSURE Systemic 

64 Human 3 mo 

(W) Gastro 0.1 (severe nausea, diarrhea, pain, cramps, 

vomiting, traces of blood in stool) 

Franzblau and Lilis 198As(+3) As(+5) 

Hemato 0.1 (anemia, leukopenia) 

Hepatic 0.1 (large increased AST and 

ALT) 

Dermal 0.1 (diffuse erythematous 

and scaly rash) 

Ocular 0.1 (swelling and irritation of 

the eyes, impaired peripheral vision) 

65 Human 0.5-14 yr 

(W) Dermal 0.05 (hyperpigmentation with keratosis, possibly 

pre-cancerous) 

Huang et al. 1985 NS 
57

0.060.060.060.06

47

11

285

4.7

9.4

10.9

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to Species 

Figure (Strain) 

66 Human 67 Rat 

(WistarBarby) 

68 Rat 

(SpragueDawley) 

Exposure/ 

Duration/ 

Frequency 

(Route) 

4 mo (W) 4 wk 5 d/wk 1 x/d (GW) 6 wk (W) 

LOAEL 

Reference Chemical Form 

Wagner et al. 1979 NS Bekemeier and Hirsche1989 As(+3) Brown et al. 1976 As(+5) 

System 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Gastro 0.06 F (nausea, vomiting, 

diarrhea) 

Hemato 0.06 F (anemia, leukopenia, 

erythroid hyperplasia of bone marrow) 

Dermal 0.06 F (persistent extensive 

hyperkeratosis of palms and soles) 

Bd Wt 0.06 F (40 lb weight loss) 

Cardio 11 F (decreased 

vasoreactivity) 

Renal 4.7 M (increased relative kidney 

weight, impaired renal mitochondrial respiration, ultrastructural changes in proximal tubule) 

Bd Wt 9.4 M 10.9 M (decreased body weight 

gain) 
5056

0.14

108

3

6

6

12

3011b

4

8

2 44 84

8

5045

0.92

2.3

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

69 Rat 

(Wistar) 

1 x/d 28 d (G) 

Bd Wt 0.14 F Chattopadhyay et al. 20

As(+3) 

70 Rat 

(CD) 

6 wk (W) Hepatic 3 M 6 M (ultrastructural changes in hepatocytes, impaired 

liver mitochondrial respiration) 

Fowler et al. 1977 As(+5) 

Bd Wt 6 M 12 M (final body weight 28% 

lower than controls) 

71 Rat 

(CD) 

14 pmd- Gd 19 7 d/wk 6 hr/d (GW) 

Gastro 4 F 8 F (stomach adhesions, 

eroded luminal epithelium in the stomach) 

Holson et al. 2000 As(+3) 

Hepatic 

Renal Bd Wt 

2 F 

4 F 4 F 

4 F (increased liver weight) 8 F (increased kidney weight) 8 F (decreased body weight 

gain) 

72 Rat 

(NS) 

16 wk (W) Hemato 0.92 M (decreased erythrocyte and leukocyte numbers) Kannan et al. 2001 As(+3) 

Hepatic 2.3 M 
5014

0.12

0.3

5024

2.3

5061

19199.5

19

108

5

10

5

10

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

4 wk (W) Hemato 0.12 0.3 (increased platelet aggregation) Lee et al. 2002 As(+3) 1 x/d 30 d (G) 

Endocr 2.3 M (decreased islet cells in 

pancreas, increased pancreatic SOD and catalase) 

Mukherjee et al. 2003 As2O3 

1 x/d 5 d/wk 12 wk (G) 

Resp 

Renal 

Bd Wt 

19 M 

19 M 

9.5 M 19 M (~17% decreased body 

weight gain) 

Schulz et al. 2002 As(+3) 

6 wk (W) Hepatic 5 M 10 M (ultrastructural changes in hepatocytes, impaired 

liver mitochondrial respiration) 

Fowler and Woods 1979 As(+5) 

Bd Wt 5 M 10 M (decreased body weight 

gain) 

a 

Key to Species 

Figure (Strain) 

73 Rat 

(SpragueDawley) 

74 Rat 

(NS) 

75 Rat 

(Wistar) 

76 Mouse 

(C57BL) 
277a

2525

5046

0.690.69

49

1.9

0.8

1.90.8

1.5 1.9

277

25

27

0.1

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ 

Duration/ 

a 

Key to Species Frequency 

Figure (Strain) (Route) 

77 Mouse 14 wk 

(C57BL/6 B6) (W) 

78 Gn Pig 16 wk 

(NS) (W) 

79 Dog 26 wk 

(Beagle) ad lib 

(F) 

Immuno/ Lymphoret 

80 Mouse 14 wk 

(C57BL/6 B6) (W) 

Neurological 

81 Human 3 mo 

(W) 

LOAEL 

System 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Reference Chemical Form 

Hepatic 

Renal 

25 M 

25 M 

Kerkvliet et al. 1980 As(+5) 

Hemato 0.69 M (decreased erythrocyte 

number and leukocyte number, decreased 

ALAD levels) 

Kannan et al. 2001 As(+3) 

Hepatic 0.69 M (increased ALAS activity) 

Hemato 1.9 F Neiger and Osweiler 19

As(+3) 

Hepatic 0.8 F (mild increased serum 

ALT/AST) 

Renal 1.9 F Bd Wt 0.8 F 1.5 F (decreased body weight 

gain) 

1.9 F (25% decrease in body 

weight) 

25 M Kerkvliet et al. 1980 

As(+5) 

0.1 (paresthesia of hands 

and feet; confusion, disorientation and mental sluggishness) 

Franzblau and Lilis 198As(+3) As(+5) 
55

0.06

5044

0.92

2.3

5060

19

5047

0.69

1.7

5055

0.14

3011a

8

72

1

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

4 mo (W) 16 wk (W) 0.92 M 2.3 M (decreased brain neurotransmitter levels) 

0.06 F (weakness, paresthesia) Wagner et al. 1979 

NS Kannan et al. 2001 As(+3) 

1 x/d 5 d/wk 12 wk (G) 

19 M Schulz et al. 2002 

As(+3) 

16 wk (W) 0.69 M 1.7 M (changes in brain neurotransmitter levels) Kannan et al. 2001 As(+3) 1 x/d 28 d (G) 

0.14 F (changes in uterine and 

ovarian weights, decreased estradiol) 

Chattopadhyay et al. 20As(+3) 

14 pmd- Gd 19 7 d/wk 6 hr/d (GW) 

8 F Holson et al. 2000 

As(+3) 

3 gen (W) 

1 (decreased litter size) Schroeder and Mitchen

As(+3) 

a 

Key to Species 

Figure (Strain) 

82 Human 83 Rat 

(NS) 

84 Rat 

(Wistar) 

85 Gn Pig 

(NS) 

Reproductive 

86 Rat 

(Wistar) 

87 Rat 

(CD) 

88 Mouse 

(CD) 
3011

4

8

5048

2.93

72a

1

191

0.05

1125

0.014

115

3

134a

30

111

1

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - 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) 

Developmental 

89 Rat 

(CD) 

14 pmd- Gd 19 7 d/wk 6 hr/d (GW) 

4 8 (decreased fetal body 

weight, increased skeletal variations) 

Reference Chemical Form 

Holson et al. 2000 As(+3) Rodriguez et al. 2002 As(+3) Schroeder and MitchenAs(+3) Zaldivar and Guillier 197NS 

Zaldivar et al. 1981 NS 

Heywood and Sortwell 1As(+5) Kroes et al. 1974 As(+5) lead arsenate Schroeder and Balassa As(+3) 

90 Rat Gd 15 or pnd 1-

(Sprague- 4 mo 2.93 M Dawley) (W) 

91 Mouse 3 gen 

(CD) (W) 

CHRONIC EXPOSURE Death 

92 Human 2-7 yr 

children (W) 

93 Human 22 yr 

(W) 

94 Monkey 1 yr 

(Rhesus) (IN) 

95 Rat 27 mo 

(Wistar) (F) 

96 Mouse 2 yr 

(CD) (W) 

(impaired performance in 

postnatal neurobehavioral tests) 

1 (decreased litter size) 

0.05 (death) 

0.014 M (death) 

3 (2/7 died) 

30 (increased mortality) 

1 (increased mortality, 

decreased life span) 
102

2.4

102a

2.4

4000

0.032

0.0320.032

5126

0.0012

74

0.1

4001

0.0140.014

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

97 Dog 

(Beagle) 

2 yr (F) Byron et al. 1967 As(+3) 2.4 (6/6 died) 

98 Dog 

(Beagle) 

2 yr (F) 

Systemic 

99 Human NS 

(W) Resp 

Dermal 

0.032 (cough) 

Byron et al. 1967 As(+5) 

2.4 (1/6 died) 

Ahmad et al. 1997 

NS 

0.032 (melanosis, keratosis, 

hyperkeratosis, and depigmentation) 

Ocular 0.032 (chronic conjunctivitis) 

100 Human >8 yr 

(W) Dermal 0.0012 (increased risk of premalignant skin 

lesions) 

Ahsan et al. 2006 

(NS) 

101 Human 4 yr 

(IN) Dermal Bickley and Papa 1989 As(+3) 0.1 F (de-pigmentation with hyperkeratosis, possibly pre-cancerous) 

102 Human NS 

(W) Cardio 

Dermal 

Biswas et al. 1998 NS 

0.014 (gangrene of feet) 

0.014 (melanosis and keratosis 

of hand palms and foot soles) 
178

0.02

0.02

0.02

179

0.01

11

0.0004

0.022

0.0004

0.022

23

0.046

0.046

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ 

Duration/ 

a 

Key to Species Frequency 

Figure (Strain) (Route) 

103 Human 12 yr 

(W) 

104 Human 11-15 yr 

(W) 

105 Human NS 

(W) 

106 Human 1-11 yr 

(W) 

LOAEL 

Reference Chemical Form 

Borgono and Greiber 19NS Borgono et al. 1980 NS Cebrian et al. 1983 As(+5) Chakraborty and Saha NS 

NOAEL Less Serious Serious 

System (mg/kg/day) (mg/kg/day) (mg/kg/day) 

Cardio 0.02 (Raynaud's disease, 

gangrene of toes) 

Gastro 0.02 (diarrhea, abdominal 

pain) 

Dermal 0.02 (abnormal pigmentation 

with hyperkaratosis, possibly pre-cancerous) 

Dermal 0.01 (hypo- and 

hyperpigmentation) 

Gastro 0.0004 0.022 (gastrointestinal irritation, 

diarrhea, nausea) 

Dermal 0.0004 0.022 (pigmentation changes 

with hyperkeratosis, possibly pre-cancerous) 

Hepatic 0.046 (hepatomegaly) 

Dermal 0.046 (pigmentation changes 

with keratosis, possibly pre-cancerous) 
44

0.064

311

0.0008

0.022

4005

0.002

169

0.0060.0070.00090.001

853

0.050.05

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - 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) 

107 Human NS 

(W) Cardio 0.064 (Blackfoot disease) 

108 Human >10 yr 

(W) Cardio 0.0008 0.022 (increased risk of ischemic heart disease 

mortality) 

109 Human NS 

(W) Cardio 0.002 (increased prevalence of cerebrovascular disease 

and cerebral infarction) 

110 Human >5 yr 

(W) Hemato 

c

0.006 M 0.007 F 

Dermal 

c

0.0009 M 

0.001 F 

111 Human 3-7 yr 

(W) Cardio 

Dermal 

0.05 

0.05 

(Blackfoot disease) 

(melanosis with 

hyperkeratosis, possibly pre-cancerous) 

Reference Chemical Form 

Chen et al. 1988b NS Chen et al. 1996 NS Chiou et al. 1997 NS EPA 1981b NS Foy et al. 1992 NS 
15

0.080.08

5122

0.16

39

0.004 0.0140.004

0.014

939

0.060.06

0.060.06

4009

0.0016

0.009

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

112 Human 2-6 yr 

(IN) Hepatic 

Dermal 

0.08 M (cirrhosis, ascites) 

0.08 M (pigmentation with 

hyperkeratosis, possibly pre-cancerous) 

Franklin et al. 1950 As(+3) 

113 Human 1-15 yr 

(W) Hepatic 0.16 (portal fibrosis of the liver) Guha Mazumder 2005 (NS) 

114 Human NS 

(W) Hepatic 

Dermal 

0.004 

0.004 

0.014 0.014 

(hepatomegaly) (pigmentation changes with hyperkaratosis, possibly pre-cancerous) 

Guha Mazumder et al. 1NS 

115 Human 1-20 yr 

(W) Gastro 

Hemato 

Hepatic Dermal 

0.06 

0.06 

(abdominal pain) 

(anemia) 

0.06 0.06 

(hepatomegaly, fibrosis) (hyperpigmentation with 

hyperkeratosis, possibly pre-cancerous) 

Guha Mazumder et al. 1NS 

116 Human NS 

(W) Dermal 0.0016 0.009 (hyperpigmentation with keratosis, possibly 

pre-cancerous) 

Guha Mazumder et al. 1NS 
5028

0.0014

5026

0.0043

175

0.00460.00460.0046

4010

0.0008

0.006

5125

0.002

4012

0.067

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

117 Human (W) Dermal 0.0014 (arsenical dermatosis) Guo et al. 2001a 

(NS) 

118 Human NS 

(W) 

Dermal 0.0043 (hyperkeratosis, 

hyperpigmentation) 

Haque et al. 2003 (NS) 

119 Human 10 yr 

(W) Gastro 

Hemato 

Dermal 

0.0046 

0.0046 

0.0046 

Harrington et al. 1978 NS 

120 Human NS 

(W) Hepatic 0.0008 0.006 (increased serum alkaline phosphatase and 

bilirubin) 

Hernandez-Zavala et alNS 

121 Human lifetime 

(W) Hemato 0.002 F (anemia during pregnancy) Hopenhayn et al. 2006 (NS) 

122 Human NS 

(W) Cardio 0.067 (ischemic heart disease) Hsueh et al. 1998b NS 
186

0.05

937

0.030.03

4016

0.004

0.005

0.004

0.005

60

0.050.050.05

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - 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) 

123 Human 0.5-14 yr 

(W) Dermal 0.05 (hyperpigmentation with keratosis, possibly 

pre-cancerous) 

124 Human 15 yr 

(IN) Gastro 0.03 M (hematemesis, hemoperitoneum, 

melena) 

Dermal 0.03 M (hyperkeratosis - possibly 

pre-cancerous) 

125 Human NS 

(W) Cardio 0.004 0.005 (cyanosis of extremities, palpitations/chest 

discomfort) 

Dermal 0.004 0.005 (keratosis, 

hyperpigmentation, depigmentation) 

126 Human 3-22 yr 

(IN) Gastro 0.05 M (gastrointestinal hemorrhages) 

Hepatic 0.05 M (vascular fibrosis, portal 

hypertension) 

Dermal 0.05 M (hyperpigmentation with 

keratoses, possibly pre-cancerous) 

Reference Chemical Form 

Huang et al. 1985 NS Lander et al. 1975 As(+3) Lianfang and Jianzhong NS Morris et al. 1974 As(+3) 
34

0.050.05

4019

0.11

4020

0.018 0.055

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

127 Human 15 yr 

(IN) Hepatic 

Dermal 

0.05 F 

0.05 F 

(central fibrosis) 

(hyperkeratosis, possibly 

pre-cancerous) 

Piontek et al. 1989 As(+3) 

128 Human NS 

(W) Endocr 0.11 (diabetes mellitus) Rahman et al. 1998 NS 

129 Human NS 

(W) Cardio 0.018 0.055 (hypertension) Rahman et al. 1999 NS 
209

0.06

0.06

0.06

0.06

0.06

0.06

0.06

146

0.030.03

140

0.014

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ 

Duration/ 

a 

Key to Species Frequency 

Figure (Strain) (Route) 

130 Human 28 mo 

(IN) 

131 Human 55 yr 

(IN) 

132 Human 45 yr 

(W) 

LOAEL 

Reference Chemical Form 

Silver and Wainman 19As(+3) Szuler et al. 1979 As(+3) Tseng 1977 NS 

System 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Cardio 0.06 F 

Gastro 0.06 F (intermittent, 

progressively severe nausea, cramps, and diarrhea) 

Hemato 0.06 F Hepatic 0.06 F (hepatomegaly, fatty 

liver) 

Renal 0.06 F Dermal 0.06 F (melanosis with 

hyperkeratosis, possibly pre-cancerous) 

Ocular 0.06 F (conjunctival injection, 

periocular edema) 

Hepatic 0.03 M (portal fibrosis and 

hypertension, bleeding from esophageal varices) 

Dermal 0.03 M (hyperpigmentation with 

hyperkeratosis, possibly pre-cancerous) 

Cardio 0.014 (Blackfoot disease) 
42

0.014

142

0.0008

0.014

1062

0.064

4027

0.016

0.031

99

0.10.10.1

0.1

0.1

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ 

Duration/ 

a 

Key to Species Frequency 

Figure (Strain) (Route) 

133 Human NS 

(W) 

134 Human >45 yr 

(W) 

135 Human >30 yr 

(W) 

136 Human 52.6 yr 

(avg) (W) 

137 Human 16 mo 

(IN) 

LOAEL 

Reference Chemical Form 

Tseng 1989 NS Tseng et al. 1968 NS Tseng et al. 1995 As(+3) Tseng et al. 1996 NS Wade and Frazer 1953 As(+3) 

NOAEL Less Serious Serious 

System (mg/kg/day) (mg/kg/day) (mg/kg/day) 

Cardio 0.014 (Blackfoot disease) Dermal 

d

0.0008 M 0.014 M (hyperkeratosis and 

hyperpigmentation) 

Cardio 0.064 M (deficits in cutaneous 

microcirculation of the toes) 

Cardio 0.016 0.031 (peripheral vascular 

disease) 

Resp 0.1 M 

Cardio 0.1 M 

Hemato 0.1 M Hepatic 0.1 M (liver enlargment) Dermal 0.1 M (hyperkeratosis, 

hyperpigmentation with hyperkeratosis, possibly pre-cancerous) 
1011

0.015

177

0.0150.018

0.0150.018

0.0150.0180.0150.0180.0150.018

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

138 Human 30-33 yr 

(W) Dermal 0.015 M (hyperkeratosis of foot, possibly pre-cancerous) Zaldivar 1974 NS 

139 Human 12 yr 

(W) Resp 

c

0.015 M (bronchitis, 

bronchiectasis) 

Zaldivar 1974 NS 

0.018 F (bronchitis, 

bronchiectasis) 

Cardio 

c

0.015 M (Raynaud's disease, 

thrombosis) 

Gastro 

c

0.015 M (diarrhea) 

0.018 F 

Dermal 

0.018 F (diarrhea) 

c

0.015 M (scaling of skin, 

hyperkeratosis, leukoderma, melanoderma) 

Bd Wt 

0.018 F 

c

0.015 M (unspecified decreased 

body weight) 

0.018 F (unspecified decreased 

body weight) 
190

0.063

1014

0.080.050.050.050.08

0.08

0.05

192

0.06

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

140 Human NS 

(W) Dermal 0.063 (hyperpigmentation with keratoses, possibly 

pre-cancerous) 

Zaldivar 1977 NS 

141 Human 2-7 yr 

children (W) 

Resp 0.08 (inflammation of bronchi 

and larynx, bronchopneumonia) 

Zaldivar and Guillier 197NS 

Cardio 0.05 (vascular spasms, 

thrombosis, ischemia, hypotension, cardiac failure) 

Gastro 0.05 (nause, vomiting, 

diarrhea, intestinal hemorrhage) 

Hemato Hepatic Renal 0.08 (cloudy swelling in 

kidneys) 

0.05 0.08 

(anemia) (cirrhosis) 

Dermal 0.05 (hyperkeratosis of palms 

and soles, melanoderma, leukoderma) 

142 Human 1-39 yr 

(W) Cardio 0.06 (arterial thickening, Raynaud's disease) Zaldivar and Guillier 197

NS 
105

2020209

20

4

9

9 202

4

105a

303030309 209 20

2

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System 

143 Rat 

(OsborneMendel) 

2 yr (F) Resp 

Cardio 

Gastro Hemato Hepatic Renal Bd Wt 

144 Rat 

(OsborneMendel) 

2 yr (F) Resp 

Cardio 

Gastro Hemato Hepatic Renal Bd Wt 

LOAEL 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Reference Chemical Form 

20 Byron et al. 1967 

As(+3) 

20 

20 

9 20 (slight transient decrease 

in Hb and Hct values) 

4 9 (enlarged bile duct, bile 

duct proliferation) 

9 20 (pigmentation) 

2 4 (decreased body weight 

gain) 

30 Byron et al. 1967 

As(+5) 

30 

30 

30 

9 20 (enlarged bile duct) 9 20 (pigmentation, cysts) 

2 (decreased body weight 

gain in females) 
229

77777777

7

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

145 Rat 

(Wistar) 

27 mo (F) Resp 7 Kroes et al. 1974 As(+5) 

Cardio 7 

Gastro 7 Hemato 7 Musc/skel 7 Hepatic 7 Renal 7 Endocr 7 Bd Wt 7 (decreased body weight 

gain) 
229a

3030307 30307

30

30307

30

114

0.60.60.60.60.60.6

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

146 Rat 

(Wistar) 

27 mo (F) Resp 

Cardio 

30 

30 

Kroes et al. 1974 As(+5) lead arsenate 

Gastro 30 Hemato Musc/skel Hepatic 

7 

30 

7 

30 (slight anemia) 

30 (enlarged bile duct with 

extensive dilation and inflammation) 

Renal 30 Endocr 30 Bd Wt 7 30 (decreased body weight 

gain) 

147 Rat 

(LongEvans) 

3 yr (W) Resp 0.6 Schroeder et al. 1968 As(+3) 

Cardio 0.6 

Hepatic Renal 

0.6 0.6 

Dermal 0.6 Bd Wt 0.6 
5018

11.1

5.6

11.1

5019

18.5

18.5

18.5

5015

0.70.7

112

1

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to Species 

Figure (Strain) 

148 Mouse 

(NS) 

48 wk (W) 

149 Mouse 

(NS) 

48 wk (W) 

150 Mouse 

(BALB/c) 

15 mo (W) 

151 Mouse 

(CD) 

2 yr (W) 

Exposure/ 

Duration/ 

Frequency 

(Route) 

LOAEL 

System 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Reference Chemical Form 

Hepatic 11.1 Liu et al. 2000 

As(+3) 

Renal 5.6 (histological alterations of 

the kidney) 

Bd Wt 11.1 

Hepatic 18.5 Liu et al. 2000 

As (+5) 

Renal 18.5 (increased relative kidney 

weight) 

Bd Wt 18.5 

Hepatic 0.7 M (increased liver weight, Santra et al. 2000 

altered liver (NS) histopathology, decreased hepatic enzymes in serum) 

Bd Wt 0.7 M (13-17% decreased body 

weight) 

Bd Wt 1 (decreased body weight Schroeder and Balassa 

gain after the first 6 As(+3) months of the study) 
103

2.42.41 2.41

2.4

1

2.4

2.41 2.4

103a

2.42.42.41 2.41

2.4

2.41

2.4

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System 

152 Dog 

(Beagle) 

2 yr (F) Resp 

Cardio 

Gastro Hemato Hepatic Renal Bd Wt 

153 Dog 

(Beagle) 

2 yr (F) Resp 

Cardio 

Gastro Hemato Hepatic Renal Bd Wt 

LOAEL 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Reference Chemical Form 

2.4 Byron et al. 1967 

As(+3) 

2.4 

1 2.4 (bleeding in the gut) 

1 2.4 (slight to moderate 

anemia) 

1 2.4 (hemosiderin deposits in 

hepatic macrophages) 

2.4 

1 2.4 (44-61% weight loss) 

2.4 Byron et al. 1967 

As(+5) 

2.4 

2.4 

1 2.4 (mild anemia) 1 2.4 (pigmentation in hepatic 

macrophages) 

2.4 

1 2.4 (marked decreased 

weight gain) 
168

0.0060.007

854

0.11

941

0.06

174

0.0046

288

0.0014 0.04

4030

0.004

0.005

208

0.06

1001

0.03

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to Species 

Figure (Strain) 

Neurological 

154 155 156 157 158 159 160 161 

Human Human Human Human Human Human Human Human 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

>5 yr (W) 

c

0.006 M 0.007 F 

EPA 1981b NS 

3-7 yr (W) 1-20 yr (W) 0.06 (tingling of hands and feet) 

0.11 F (wrist weakness) Foy et al. 1992 

NS Guha Mazumder et al. 1NS 

10 yr (W) NS (W) NS (W) 

0.0046 0.0014 

0.004 0.005 (fatigue, headache, 

dizziness, insomnia, nighmare, numbness) 

0.04 (functional denervation) 

Harrington et al. 1978 NS Hindmarsh et al. 1977 NS Lianfang and Jianzhong NS 

28 mo (IN) 55 yr (IN) 0.03 M (absent ankle jerk reflex and vibration sense in 

legs) 

0.06 F (paresthesia) Silver and Wainman 19

As(+3) Szuler et al. 1979 As(+3) 
5081

0.0017

5032

0.005

5137

0.0008

0.003

5049

0.008

5118

0.006

5119

0.02

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

Exposure/ LOAEL 

Duration/ 

a 

Key to Species 

Figure (Strain) 

162 Human 163 Human 164 Human 

Reproductive 

165 Human 166 Human 167 Human 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) Serious (mg/kg/day) 

NS (W) 0.0017 (decreased performance in neurobehavioral tests) lifetime continuous (W) 

0.005 (decreased performance 

in neurobehavioral tests) 

lifetime 0.0008 0.003 (decreased score in 

Performance domain of an intelligence scale) 

NS (W) 0.008 F (increased frequencies for spontaneous abortion, 

stillbirth, and preterm birth rates) 

lifetime (W) 0.006 F (increased incidence of spontaneous abortion) lifetime (W) 0.02 F (increased risk of stilbirth) 

Reference Chemical Form 

Tsai et al. 2003 (NS) Wasserman et al. 2004 (NS) Wasserman et al. 2007 (NS) Ahmad et al. 2001 

(NS) 

Milton et al. 2005 (NS) von Ehrenstein et al. 20(NS) 
5050

0.002

5138

0.03

5120

0.008

11

0.022

79

0.064

43

0.064

5090

0.003

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System 

LOAEL 

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) 

Reference Chemical Form 

Developmental 

168 Human continuous 

(W) Hopenhayn et al. 2003a (NS) 0.002 (reduced birth weight) 

169 Human >1 yr 

1 x/d (W) 

Smith et al. 2006 (NS) 

0.03 (increased SMR for 

malignant and non-malignant lung disease) 

170 Human lifetime 

(W) 

von Ehrenstein et al. 20(NS) 

0.008 

Cancer 

171 Human NS 

(W) 

Cebrian et al. 1983 As(+5) 

0.022 (CEL: skin cancer) 

172 Human NS 

(W) 

Chen et al. 1986 NS 

0.064 (CEL: bladder, lung and 

liver cancers) 

173 Human 174 Human 

NS (W) NS (W) 

Chen et al. 1988b NS 

0.064 (CEL: malignant 

neoplasms of the bladder, skin, lung and liver) 

Chiou et al. 2001 (NS) 

0.003 (CEL: bladder cancer) 
2033

3.67

4008

0.0011

5088

0.0017

5089

0.018

5092

0.018

338

0.052

5103

0.00490.0094

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - 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 

175 Human 2 wk- 12 yr 

(IN) 

176 Human NS 

(W) 

177 Human NS 

(W) 

178 Human NS 

(W) 

179 Human NS 

(W) 

180 Human NS 

(W) 

181 Human NS 

(W) 

3.67 

0.0011 0.0017 

0.018 0.018 0.052 

c

0.0049 M 0.0094 F 

(CEL: bladder cancer 

risk) 

(CEL: lung cancer) (CEL: lung cancers) (CEL: lung cancer mortality) (CEL: bladder cancer) (CEL: increased incidence of transitional cell carcinomas of the bladder, kidney, ureters, and all urethral cancer) 

(CEL: squamous cell carcinoma of the skin) 

Cuzick et al.1992 As(+3) Ferreccio et al. 1998 NS Ferreccio et al. 2000 (NS) Guo 2004 (NS) Guo and Tseng 2000 (NS) Guo et al. 1997 NS Guo et al. 2001b (NS) 
314

0.0075

283

0.04

52

0.038

141

0.014

315

0.033

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - 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) 

182 Human >1 yr 

(W) 0.0075 (CEL: basal or squamous skin carcinoma) 

183 Human 16 yr (avg) 

(IN) 0.04 M (CEL: basal cell and squamous cell 

carcinomas of the skin, small cell and squamous cell carcinoma of the lung) 

184 Human 60 yr 

(W) 

185 Human >45 yr 

(W) 

186 Human ~5 yr 

(W) 

0.038 (CEL: intraepidermal 

carcinoma) 

0.014 (CEL: squamous cell 

carcinoma of the skin) 

0.033 (CEL: lung, urinary tract 

cancer) 

Reference Chemical Form 

Haupert et al. 1996 NS Luchtrath 1983 As(+5) Tseng 1977 NS Tseng et al. 1968 NS Tsuda et al. 1995a As(+3) 
176

0.0150.018

160

0.014

Table 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (continued) 

a 

Key to 

Figure 

Species 

(Strain) 

Exposure/ 

Duration/ 

Frequency 

(Route) System NOAEL (mg/kg/day) Less Serious (mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) 

Reference Chemical Form 

187 Human 12 yr 

(W) 

c

0.015 M (CEL: squamous cell 

carcinoma of the skin) 

Zaldivar 1974 NS 

0.018 F (CEL: squamous cell 

carcinoma of the skin) 

188 Human 22-34 yr 

(W) 0.014 M (CEL: basal cell and squamous cell 

carcinomas of the skin, hemangioendothelioma of the liver) 

Zaldivar et al. 1981 NS 

a The number corresponds to entries in Figure 3-3. b Used to derive provisional acute oral minimal risk level (MRL) of 0.005 mg/kg/day; dose divided by an uncertainty factor of 10 (for extrapolation from a LOAEL to c Differences in levels of health effects and cancer effects between male and females are not indicated in Figure 3-3. Where such differences exist, only the levels most sensitive gender are presented. d Used to derive chronic oral minimal risk level (MRL) of 0.0003 mg/kg/day; dose divided by an uncertainty factor of 3 (for human variability). avg = average; ALAD = delta-aminolevulinic acid dehydratase; ALAS = delta-aminolevulinic acid synthetase; ALT = alanine aminotransferase; AST = aspartate amWt = body weight; BUN = blood urea nitrogen; Cardio = cardiovascular; CEL = cancer effect level; d = day(s); Endocr = endocrine; (F) = feed; F = female; (G) = gavgastrointestinal; Gd = gestational day; GI = gastrointestinal; (GW) = gavage in water; gen = generation; Gd = gestation day; Gn pig = guinea pig; Hemato = hematohemoglobin; Hct = hematocrit; Hemato = hematological; hr = hour(s); (IN) = ingestion; LD50 = lethal dose, 50% kill; LDH = lactate dehydrogenase; LOAEL = lowest-observable-adverse-effect level; M = male; Metab = metabolic; mo = month(s); Musc/skel = musculoskeletal; NOAEL = no-observable-adverse-effect level; Npmd = pre-mating day; pnd = post-natal day; Resp = respiratory; SMR =standardized mortality ratio; (W) = drinking water; wk = week(s); x = time(s); yr = year(s) 
Death 

Respiratory Cardiovascular Gastrointestinal Hematological Musculoskeletal Hepatic 

Figure 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral 

Acute (≤14 days) 

Systemic 

ARSENIC

mg/kg/day 

1000

9r 11r 2 7r 20 20 20 24 100 3 6r 5 31 31 31

8r 30 30 30 13m 15m 14m 16m 17m 4 12r 27 27 27 27 21 21 21 21

10r 34r 26 26 30 30 33r 30 33r 10 22 22 22 22 22

28 28 32k 28 39m 32k 

40g 32k 39m 32k 

1 33r 19 25 33r 25

18h 

1 34r 

19

19 19

0.1 

29 29 23 29 29 29 29

0.01 

0.001 

3. HEALTH EFFECTS

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 

117
Hepatic 

Renal Dermal Ocular Body Weight Neurological Developmental Cancer * 

ARSENIC

Figure 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (Continued)

Acute (≤14 days) 

Systemic 

mg/kg/day 

1000

47

24 24 43 46 100 31 31 52

30 51 59m

35r 27 38m 37r 49 58m 60m 57r 21 36r 44 54r 63m

34r 37r 61s 57r

30 26 26 38m 48 61s 58m 60m 10 36r 54r 63m 35r 22 22 45

28 32k 53k 56

32k 53k 

25 42

41h 55h 62h

1

41h 55h 62h 

19 19

0.1 

29 29 29 50

0.01 

*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. 0.001 

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

 LOAEL, Less Serious-Animals

NOAEL - Animals

 LOAEL, Less Serious-Humans for effects

 Cancer Effect Level-Animals

 LOAEL, More Serious-Animals LOAEL, More Serious-Humans Minimal Risk Level

 Cancer Effect Level-Humans

 NOAEL - Humans

 LD50/LC50

 other than

 Cancer 

3. HEALTH EFFECTS

118
Respiratory 

Cardiovascular Gastrointestinal Hematological Hepatic Renal Endocrine Dermal Ocular Body Weight Immuno/Lymphor Neurological Reproductive Developmental 

Figure 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (Continued)

Intermediate (15-364 days)

Systemic 

ARSENIC

mg/kg/day 

100 

77m 77m 80m 

75r 75r 75r 84r 

70r 67r 68r 10 76m 76m 68r 75r

71r 71r 71r 87r 89r 

70r 70r 

76m 68r 76m

71r 71r 71r 71r 89r 

70r 90r 

72r 74r 83r

79d 71r 79d 79d 85g 79d 

1 72r 83r 88m 91m

79d 79d 78g 78g 85g 

73r 

69r 86r 73r 

0.1 64 64 64 64 64 81 

66 66 66 66 82 

65 

0.01 

3. HEALTH EFFECTS

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

 for effects

 other than

 Cancer 

Minimal Risk Level 

119
Death 

Respiratory Cardiovascular Gastrointestinal 

Figure 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (Continued)

Chronic (≥365 days)

Systemic 

ARSENIC

mg/kg/day 

100

95r 144r 146r 144r 146r

143r 143r

10 145r 145r 

94k 97d 98d 152d 153d 152d 153d 152d 153d 

1 96m 152d 

147r 147r 

0.1 137 137 141 107 122 129 130 135 142 92 111 141

99 136

103 108 129 103 93 139 102 132 133 136 139

0.01 

125 125

109

0.001 108

0.0001 

1E-5 

1E-6 

1E-7 

1E-8 

3. HEALTH EFFECTS

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

 for effects

 other than

 Cancer 

Minimal Risk Level 

120
Gastrointestinal 

Hematological Musculoskeletal Hepatic 

Figure 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (Continued)

Chronic (≥365 days) 

Systemic 

ARSENIC

mg/kg/day 

100

144r 146r 144r 146r 146r

143r 143r 149m 

10 143r 148m 143r 145r 145r 146r 145r 

143r 

152d 153d 152d 153d 

1 152d 153d 152d 153d 150m 

113

0.1 137 137 112 141 115 130 115 130 115 130 126 141 141 106 126 127

124 131 105 139 114 0.01 

110 120 119 119 114

121

0.001 120

105

0.0001 

1E-5 

1E-6 

1E-7 

1E-8 

3. HEALTH EFFECTS

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

 for effects

 other than

 Cancer 

Minimal Risk Level 

121
Hepatic 

Renal Endocrine Dermal 

ARSENIC

Figure 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (Continued)

Chronic (≥365 days) 

Systemic mg/kg/day 

100

146r 146r 146r

144r 149m 143r 144r

10 144r 143r 144r 145r 146r 145r 145r 148m 

152d 153d

1

147r 147r 

0.1 128 101 137 141 112 130 115 130 106 111 123 126 127

99 124 131

103 105

102 114 134 138

0.01 104 116

119 125 114 118 125

116 117 100 0.001 110 134

105

0.0001 

1E-5 

1E-6 

1E-7 

1E-8 

3. HEALTH EFFECTS

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

 for effects

 other than

 Cancer 

Minimal Risk Level 

122
Dermal 

Ocular Body Weight Neurological Reproductive Developmental Cancer * 

ARSENIC

Figure 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (Continued)

Chronic (≥365 days) 

Systemic 

mg/kg/day 

100

146r 

149m

10 148m 

145r 146r 

143r 175

152d 153d 143r 144r

1 152d 153d 151m

147r 150m 147r 

155

140

0.1 

130 156 160 172 173 141 180 158 183 99 161 169

167 171 178 179 139 139

0.01 165 170 182 154 166 157 159 163 181 159 164 174

168 162 177 158 0.001 176 164

0.0001 

1E-5 

1E-6 

1E-7 

*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. 1E-8 

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

 LOAEL, Less Serious-Animals

NOAEL - Animals

 LOAEL, Less Serious-Humans for effects

 Cancer Effect Level-Animals

 LOAEL, More Serious-Animals LOAEL, More Serious-Humans Minimal Risk Level 

Cancer Effect Level-Humans

 NOAEL - Humans

 LD50/LC50

 other than

 Cancer 

3. HEALTH EFFECTS

123
Cancer * 

ARSENIC

Figure 3-3 Levels of Significant Exposure to Inorganic Arsenic - Oral (Continued)

Chronic (≥365 days)

mg/kg/day 

100

10

1

0.1 

184 186

185 187 188 0.01 

0.001 

0.0001

10-4

Estimated

Upper-Bound 1E-5

10-5 Human Cancer

Risk Levels

1E-6

10-6

1E-7

10-7

*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. 1E-8 

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

 LOAEL, Less Serious-Animals

NOAEL - Animals

 LOAEL, Less Serious-Humans for effects

 Cancer Effect Level-Animals

 LOAEL, More Serious-Animals LOAEL, More Serious-Humans Minimal Risk Level 

Cancer Effect Level-Humans

 NOAEL - Humans

 LD50/LC50

 other than

 Cancer 

3. HEALTH EFFECTS

124
a

Key to

Figure

Table 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

ACUTE EXPOSUREDeath

1

5163

Gur and Nyska 1990MSMA

3184 M (LD50)

3184

b

2449 F (LD50)

2449

Rat(SpragueDawley)

once(GW)

2

6

Kaise et al. 1989MMA

1800 M (LD50)

1800

Mouse(ddY)

once(GW)

3

3

Jaghabir et al. 1988MSMA

102 M (LD50)

102

Rabbit(NewZealand)

once(GW)

Systemic

4

5164

Gur and Nyska 1990MSMA

Gastro 2030 (mucoid feces and

diarrhea)

2030

Rat(SpragueDawley)

once(GW)

Bd Wt 2030

2030

5

5129

Irvine et al. 2006MMA

Bd Wt 10 F

10

100 F (17% decrease in

maternal body weightgain)

100

500 F (40% decrease in

maternal body weightgain)

500

Rat(SpragueDawley)

Gd 6-15(GW)

6

932

Kaise et al. 1989MMA

Resp 1800 M (respiratory arrest)

1800

Mouse(ddY)

once(GW)

Gastro 2200 M (diarrhea, slight

congestion of the smallintestine)

2200
a

Key to

Figure

Table 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

7

5131

Irvine et al. 2006MMA

Gastro 7 F

7

12 F (loose feces/diarrhea in

7/14 pregnant rabbits)

12

Rabbit(NewZealand)

Gd 7-19(GW)

Bd Wt 7 F

7

12 F (67% decrease in

maternal body weightgain)

12

8

928

Jaghabir et al. 1988MSMA

Gastro 60 M (diarrhea)

60

Rabbit(NewZealand)

once(GW)

Developmental

9

5128

Irvine et al. 2006MMA

100

100

500 (decreased fetal weight

and increased fetalincidence of imcompleteossification of thoracicvertebrae)

500

Rat(SpragueDawley)

Gd 6-15(GW)

10

5130

Irvine et al. 2006MMA

7

7

12 (supernumerary thoracic

ribs and eight lumbarvertebrae)

12

Rabbit(NewZealand)

Gd 7-19(GW)

INTERMEDIATE EXPOSUREDeath

11

5140

Arnold et al. 2003

MMA

106.9 M (increased mortality)

106.9

Rat(Fischer- 344)

52 wk(F)
a

Key to

Figure

Table 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

Systemic

12

5139

Arnold et al. 2003

MMA

Gastro

c

3.5 M

3.5

30.2 M (diarrhea)

30.2

Rat(Fischer- 344)

52 wk(F)

Bd Wt 30.2 M

30.2

106.9 M (14% decrease in body

weight)

106.9

13

5160

Schroeder 1994MMA

Bd Wt 76

76

Rat(SpragueDawley)

146-171 dpre-mating,mating,gestation, andlactation(F)

14

5169

Waner and Nyska 1988MMA

Gastro 2 M (diarrhea)

2

Dog(Beagle)

52 wk(C)

Bd Wt 2 F

2

8 F (decrease in body

weight)

8

Reproductive

15

5161

Schroeder 1994MMA

22

22

76 (decreased pregnancy

rate and male fertilityindex in F0 and F1)

76

Rat(SpragueDawley)

146-171 dpre-mating,mating,gestation, andlactation(F)

16

13

Prukop and Savage 198MSMA

119 M (reduced fertility)

119

Mouse(Swiss)

19 d3 d/wk(GW)
a

Key to

Figure

Table 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

Developmental

17

5162

Schroeder 1994MMA

22

22

76 (decreased pup survival

F1 and F2)

76

Rat(SpragueDawley)

146-171 dpre-mating,mating,gestation, andlactation(F)

CHRONIC EXPOSUREDeath

18

5065

Arnold et al. 2003

MMA

72.4 M (increased mortality)

72.4

Rat(Fischer- 344)

104 wk(F)
a

Key to

Figure

Table 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

Systemic

19

5063

Arnold et al. 2003

MMA

Gastro 3 M

3

25.7 M (diarrhea)

25.7

72.4 M (necrosis, ulceration,

perforation in largeintestine)

72.4

Rat(Fischer- 344)

104 wk(F)

Hemato 72.4 M

72.4

Musc/skel 72.4 M

72.4

Hepatic 72.4 M

72.4

Renal 3.9 F

3.9

33.9 F (increased absolute

kidney weight andprogressiveglomerulonephropathy)

33.9

Endocr 3.9 F

3.9

33.9 F (hypertrophy of thyroid

follicular epithelium,decreased absolutethyroid weight)

33.9

Dermal 72.4 M

72.4

Ocular 72.4 M

72.4

Bd Wt 3 M

3

25.7 M (15% decrease in body

weight)

25.7

33.9 F (30% decrease in body

weight)

33.9
a

Key to

Figure

Table 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

20

5085

Shen et al. 2003MMA

Hemato 8.4 M

8.4

Rat(Fischer- 344)

104 wk(W)

Hepatic 2.1 M

2.1

8.4 M (increased

GST-P-positive foci)

8.4

Renal 2.1 M (hyperplasia of the

bladder)

2.1

Bd Wt 8.4 M

8.4

21

5067

Arnold et al. 2003

MMA

Cardio 67.1 M

67.1

Mouse(B6C3F1)

104 wk(F)

Gastro 24.9 M

24.9

67.1 M (loose and mucoid feces,

metaplasia of the cecumand colon)

67.1

Musc/skel 67.1 M

67.1

Hepatic 67.1 M

67.1

Renal

d

1.2 M

1.2

6 M (increased incidence of

progressiveglomeruloephropathy)

6

Dermal 67.1 M

67.1

Ocular 67.1 M

67.1

Bd Wt 24.9 M

24.9

67.1 M (17% decrease in body

weight)

67.1
a

Key to

Figure

Table 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

22

5149

Waner and Nyska 1988MMA

Resp 35

35

Dog(Beagle)

52 wk(C)

Gastro 2 M (diarrhea)

2

Hemato 35

35

Hepatic 35

35

Renal 8 (increased urine specific

gravity; increased kidneyweight)

8

Ocular 35

35

Bd Wt 2 F

2

8 F (42% decrease in body

weight)

8

Neurological

23

5150

Waner and Nyska 1988MMA

35

35

Dog(Beagle)

52 wk(C)

Reproductive

24

5151

Waner and Nyska 1988MMA

35 M

35

8 F

8

35 F (decrease in estrus)

35

Dog(Beagle)

52 wk(C)
a

Key to

Figure

Table 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

Cancer

25a The number corresponds to entries in Figure 3-4.b Differences in levels of health effects and cancer effects between male and females are not indicated in Figure 3-4. Where such differences exist, only the levels most sensitive gender are presented.c The intermediate-duration oral MRL of 0.1 mg MMA/kg/day was calculated using a benchmark dose analysis. The BMDL10 of 12.38 mg MMA/kg/day was divided factor of 100 (10 to account for extrapolation from animals to humans and 10 for human variability)d The chronic-duration oral MRL of 0.01 mg MMA/kg/day was calculated using a benchmark dose analysis. The BMDL10 of 1.09 mg MMA/kg/day was divided by afactor of 100 (10 to account for extrapolation from animals to humans and 10 for human variability)Bd Wt = body weight; (C) = capsule; Cardio = cardiovascular; d = day(s); Endocr = endocrine; (F) = feed; F = female; Gastro = gastrointestinal; (GO) = gavage in oin water; Gd = gestation day; GST-P = glutathione S-transferase placental form; Hemato = hematological; IN = ingestion; LD50 = lethal dose, 50% kill; LOAEL =lowest-observable-adverse-effect level; M = male; MMA = monomethylarsonic acid; MSMA = monosodium methane arsonate; Musc/skel = musculoskeletal; NOAEno-observable-adverse-effect level; Resp = respiratory; (W) = drinking water; wk = week(s); x = time(s)

5084

Shen et al. 2003MMA

8.4 M

8.4

Rat(Fischer- 344)

104 wk(W)
1

10

100

1000

10000

Death

2m

1r

3h

Respiratory

6m

Gastrointestinal

6m 4r

7h

7h

8h

Body Weight

4r

5r

5r

5r

7h

7h

Developmental

9r

9r

10h

10h

mg/kg/day

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

 for effects

 other than

 Cancer

mg/kg/day

Figure 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral

Acute (≤14 days)

 Minimal Risk Level

Systemic

ARSENIC

3. HEALTH EFFECTS

133
0.1

1

10

100

1000

Death

11r

Gastrointestinal

14d

12r

12r

Body Weight

14d

14d

12r

12r

13r

Reproductive

16m

15r

15r

Developmental

17r

17r

mg/kg/day

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

 for effects

 other than

 Cancer

Figure 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral (Continued)

Intermediate (15-364 days)

 Minimal Risk Level

Systemic

ARSENIC

3. HEALTH EFFECTS

134
0.01

0.1

1

10

100

Death

18r

Respiratory

22d

Cardiovascular

21m

Gastrointestinal

22d

21m

21m

19r

19r

19r

Hematological

22d

19r

20r

Musculoskeletal

21m 19r

Hepatic

22d

21m 19r

20r

20r

Renal

22d

21m

21m

19r

19r

20r

Endocrine

19r

19r

Dermal

21m 19r

Ocular

22d

21m 19r

Body Weight

22d

22d

21m

21m 19r

19r

19r

20r

Neurological

23d

Reproductive

24d

mg/kg/day

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

 for effects

 other than

 Cancer

Chronic (≥365 days)

Figure 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral (Continued)

 Minimal Risk Level

Systemic

ARSENIC

3. HEALTH EFFECTS

135
0.01

0.1

1

10

100

Reproductive

24d

24d

mg/kg/day

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

 for effects

 other than

 Cancer

Chronic (≥365 days)

Figure 3-4 Levels of Significant Exposure to Monomethylarsonic Acid - Oral (Continued)

 Minimal Risk Level

ARSENIC

3. HEALTH EFFECTS

136
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

ACUTE EXPOSUREDeath

1

5167

Crown et al. 1987DMA

475 M (100% mortality during

first 2 weeks of study)

475

Rat(Fischer- 344)

13 wk(F)

2

29

Rogers et al. 1981DMA

60 F (67% mortality)

60

Rat(CD)

10 dGd 7-161 x/d(GW)

3

5

Kaise et al. 1989DMA

1200 M (LD50)

1200

Mouse(ddY)

once(GW)

4

27

Rogers et al. 1981DMA

600 F (59% mortality)

600

Mouse(CD-1)

10 dGd 7-161 x/d(GW)

Systemic

5

5017

Cohen et al. 2001DMA

Renal 11 F (altered bladder cell

surface characteristics)

11

Rat(Fischer- 344)

2 wk(F)

Bd Wt 11 F

11

6

5168

Crown et al. 1987DMA

Gastro 475 M (diarrhea and congestion

and hemorrhagiccontents ingastrointestinal tract inrats dying during first 2weeks)

475

Rat(Fischer- 344)

13 wk(F)
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

7

5136

Irvine et al. 2006DMA

Bd Wt 12 F

12

36 F (decreased maternal

body weight gain)

36

Rat(SpragueDawley)

Gd 6-15(GW)

8

980

Rogers et al. 1981DMA

Bd Wt 40 F (27% decreased

maternal weight gain)

40

Rat(CD)

10 dGd 7-161 x/d(GW)

9

3013

Ahmad et al. 1999a

DMA

Resp 720 F (decreased lung ODC)

720

Mouse(B6C3F1)

24 hr1 or 2 x(GW)

Hepatic 720 F (decreased liver GSH,

GSSG, CYP-450 andODC; increased serum

ALT)

720

10

930

Kaise et al. 1989DMA

Resp 900 M (respiratory arrest)

900

Mouse(ddY)

once(GW)

Gastro 1757 M (diarrhea, slight

congestion of theintestion)

1757

11

979

Rogers et al. 1981DMA

Bd Wt 200 F (26% decreased

maternal weight gain)

200

Mouse(CD-1)

10 dGd 7-161 x/d(GW)

12

5155

Zomber et al. 1989DMA

Gastro 6.5

6.5

16 (vomiting and diarrhea)

16

Dog(Beagle)

52 wk(C)
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

13

5133

Irvine et al. 2006DMA

Gastro 12 F

12

48 F (fluid gastrointestinal

tract contents)

48

Rabbit(NewZealand)

Gd 7-19(GW)

Bd Wt 12 F

12

48 F (maternal weight loss)

48

Neurological

14

931

Kaise et al. 1989DMA

1757 M (increased startle reflex;

ataxia)

1757

Mouse(ddY)

once(GW)

Developmental

15

5147

Chernoff et al. 1990DMA

40 F (decreased fetal body

weight)

40

Rat(SpragueDawley)

GD6-15(GW)

16

5135

Irvine et al. 2006DMA

12

12

36 (decreases in number of

live fetuses and fetalweight; increases infetuses withdiaphragmatic hernia;delayed ossification)

36

Rat(SpragueDawley)

Gd 6-15(GW)

17

30

Rogers et al. 1981DMA

15

15

30 (malformed palates in

15%)

30

Rat(CD)

10 dGd 7-161 x/d(GW)
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

18

5148

Kavlock et al. 1985DMA

1600 F (fetal deaths, decreased

fetal weight, delayedossification, skeletalmalformations)

1600

Mouse(CD-1)

Gd 8(GW)

19

28

Rogers et al. 1981DMA

200

200

400 (18% decrease in fetal

weight, delayedossification, cleft palatein 12/28; irregularpalatine rugae in 4.8%)

400

Mouse(CD-1)

10 dGd 7-161 x/d(GW)

20

5132

Irvine et al. 2006DMA

12

12

Rabbit(NewZealand)

Gd 7-19(GW)

INTERMEDIATE EXPOSUREDeath

21

5166

Crown et al. 1987DMA

190 M (100% mortality during

first 4 weeks of study)

190

Rat(Fischer- 344)

13 wk(F)

22

340

Murai et al. 1993DMA

57 (50% survival in males;

20% survival in females)

57

Rat(Fischer- 344)

4 wk5 d/wk1 x/d(G)
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

23

329

Wanibuchi et al. 1996DMA

17 M (10/10 died)

17

Rat(Fischer- 344)

8 wk(W)

Systemic

24

5021

Arnold et al. 1999

DMA

Renal 1 F

1

10 M (necrosis in bladder

epithelium)

10

b

5 F (increased kidney weight,

calcification atcorticomedullary junction;increased bladder weightand increased BrdUlabelling in bladderepithelium)

5

Rat(Fischer- 344)

10 or 20 wk(F)

Bd Wt 10

10

25

5016

Cohen et al. 2001DMA

Renal 11 F (increased bladder and

kidney weights,hyperplasia and necrosisof bladder epithelium)

11

Rat(Fischer- 344)

10 wk(F)
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

26

5165

Crown et al. 1987DMA

Resp 43.2 M

43.2

Rat(Fischer- 344)

13 wk(F)

Cardio 43.2 M

43.2

Gastro 43.2 M

43.2

190 M (diarrhea and congestion

and hemorrhagiccontents ingastrointestinal tissues)

190

Hemato 0.44 F

0.44

4.5 F (decreased hemoglobin

and erythrocyte levels)

4.5

Hepatic 23.5 M

23.5

Renal 0.4 M

0.4

4 M (increased urine volume

and decreased specificgravity)

4

Endocr 0.4 M

0.4

4 M (hypertrophy of thyroid

follicle epithelium)

4

Bd Wt 43.2 M

43.2

27

341

Murai et al. 1993DMA

Renal 57 (papillary necrosis and

hyperplasia; corticaldegeneration andnecrosis)

57

Rat(Fischer- 344)

4 wk5 d/wk1 x/d(G)

Bd Wt 57 (decreased body weight)

57
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

28

5153

Rubin et al. 1989DMA

Resp 16.5

16.5

Rat(SpragueDawley)

10 wkpre-mating,gestation andlactationperiods(F)

Cardio 16.5

16.5

Hemato 0.34 M

0.34

2.3 M (decreased mean

corpscular hemoglobinconcentration)

2.3

Hepatic 16.5

16.5

Renal 16.5

16.5

Endocr 2.3 F

2.3

16.5 F (hypertrophy of thyroid

follicle epithelium)

16.5

Bd Wt 16.5

16.5

29

26

Siewicki 1981DMA

Hemato 3.7 M

3.7

Rat(SpragueDawley)

42 d(F)

Hepatic 3.7 M

3.7

Renal 3.7 M

3.7

Bd Wt 3.7 M

3.7
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

30

5179

Zomber et al. 1989DMA

Gastro 6.5

6.5

16 (vomiting and diarrhea)

16

Dog(Beagle)

6 d/wk52 wk(C)

Hemato 16 M

16

40 M (decreased erythrocyte

and increased leukocytelevels)

40

Reproductive

31

5152

Rubin et al. 1989DMA

16.5

16.5

Rat(SpragueDawley)

10 wkpre-mating,gestation andlactationperiods(F)

Cancer

32

3011

Hayashi et al. 1998DMA

10.4 M (CEL: lung tumors)

10.4

MouseA/J

50 wkad lib(W)
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

CHRONIC EXPOSURESystemic

33

5141

Arnold et al. 2006

DMA

Resp 7.8

7.8

Rat(Fischer- 344)

daily2 yr(F)

Cardio 7.8

7.8

Gastro 7.8

7.8

Hemato 7.8

7.8

Musc/skel 7.8

7.8

Hepatic 7.8

7.8

Renal 0.77 M

0.77

0.77 F

0.77

3.1 M (nephrocalcinosis)

3.1

3.1 F (urothelial vacular

degeneration andhyperplasia of urothelialcells in urinary bladder)

3.1

Endocr 3.1

3.1

7.8 (hypertrophy of thyroid

follicle epithelium)

7.8

Dermal 7.8

7.8

Ocular 7.8

7.8

Bd Wt 7.8

7.8

34

5173

Wei et al. 1999, 2002DMA

Renal 0.75 M

0.75

3.4 M (nodular or papillary

hyperplasia in urinarybladder)

3.4

Rat(Fischer- 344)

104 wk(W)
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

35

5144

Arnold et al. 2006

DMA

Resp 94

94

Mouse(B6C3F1)

daily2 yr(F)

Cardio 94

94

Gastro 94

94

Hemato 94 F

94

94 F (decreased lymphocytes

and increasedmonocytes)

94

Musc/skel 94

94

Hepatic 94

94

Renal

c

1.3 F

1.3

37 M (progressive

glomerulonephropathy)

37

b

7.8 F (vacuolization of

superficial cells ofurotheliumin urinarybladder)

7.8

Dermal 94

94

Ocular 94

94

Bd Wt 94

94
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

36

5154

Zomber et al. 1989DMA

Resp 40

40

Dog(Beagle)

6 d/wk52 wk(C)

Cardio 40

40

Gastro 6.5

6.5

16 (vomiting and diarrhea)

16

Hepatic 40

40

Renal 40

40

Reproductive

37

5143

Arnold et al. 2006

DMA

7.8

7.8

Rat(Fischer- 344)

daily2 yr(F)

38

5145

Arnold et al. 2006

DMA

94

94

Mouse(B6C3F1)

daily2 yr(F)

Cancer

39

5142

Arnold et al. 2006

DMA

7.8 (CEL: urothelial cell

papillomas andcarcinomas in urinarybladder)

7.8

Rat(Fischer- 344)

daily2 yr(F)

40

5068

Wei et al. 1999, 2002DMA

3.4 M (CEL: urinary bladder

tumors)

3.4

Rat(Fischer- 344)

104 wk(W)
a

Key to

Figure

Table 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

41a The number corresponds to entries in Figure 3-5.b Differences in levels of health effects and cancer effects between male and females are not indicated in Figure 3-5. Where such differences exist, only the levels most sensitive gender are presented.c The chronic-duration oral MRL of 0.02 mg DMA/kg/day was calculated using a benchmark dose analysis. The BMDL10 of 1.80 mg DMA/kg/day was divided by afactor of 100 (10 to account for extrapolation from animals to humans and 10 for human variability)ad lib = ad libitum; ALT = alanine aminotransferase; Bd Wt = body weight; BrdU = bromodeoxyuridine; (C) = capsule; Cardio = cardiovascular; CEL = cancer effect cytochrome p; d= day(s); DMA = dimethylarsinic acid; Endocr = endocrine; (F) = feed; F = female; (G) = gavage; Gastro = gastrointestinal; Gd = gestation day; GSH glutathione; GSSG = oxidized glutathione; (GW) = gavage in water; Hemato = hematological; hr = hour(s); LD50 = lethal dose, 50% kill; ODC = ornithine decarboxylowest-observable-adverse-effect level; M = male; mo = month; Musc/skel = musculoskeletal; NOAEL = no-observable-adverse-effect level; Resp = respiratory; (Wwk = week(s); x = time(s); yr = year(s)

5082

Salim et al. 2003DMA

11.8 M (CEL)

11.8

Mouseknockout

continuous18 mo(W)
Death 

Respiratory Gastrointestinal Hepatic Renal Body Weight Neurological Developmental 

ARSENIC

Figure 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral 

Acute (≤14 days) 

Systemic 

mg/kg/day 

10000 

10m 14m 18m 

3m
 1000
 10m
 

9m
 9m 

4m
 

1r
 6r 

19m 

11m 19m 

100 

2r 

13h 13h 

8r 15r 7r 16r 

17r 

12d 17r 

13h 7r 13h 16r 20h 5r 5r 10 

12d 

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

LOAEL, Less Serious-Animals

NOAEL - Animals

LOAEL, Less Serious-Humans for effects

 Cancer Effect Level-Animals

 LOAEL, More Serious-Animals LOAEL, More Serious-Humans Minimal Risk Level 

Cancer Effect Level-Humans

NOAEL - Humans

 LD50/LC50

 other than

 Cancer 

3. HEALTH EFFECTS

149
Death 

Respiratory Cardiovascular Gastrointestinal Hematological Hepatic Renal Endocrine Body Weight Reproductive Cancer * 

ARSENIC

Figure 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (Continued)

Intermediate (15-364 days) 

Systemic 

mg/kg/day 

1000 

21r 

100 

22r 

23r 

10 

1 

0.1 

3. HEALTH EFFECTS

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

 for effects

 other than

 Cancer 

Minimal Risk Level 

150

26r 

26r 26r 26r 30d 

26r 

28r 28r 30d 30d 28r 

30d 

26r 

29r 29r 

28r 

26r 

28r 

27r 

26r 

27r 

24r 

24r 

25r 

26r 

26r 

28r 

29r 

26r 

26r 

28r 

28r 

24r 

28r 

29r 

31r 

32m 

*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. 
Respiratory 

Cardiovascular Gastrointestinal Hematological Musculoskeletal Hepatic Renal Endocrine Dermal Ocular Body Weight Reproductive Cancer * 

Figure 3-5 Levels of Significant Exposure to Dimethylarsinic Acid - Oral (Continued)
 

Chronic (≥365 days)
 

Systemic 

ARSENIC

mg/kg/day 

100 35m 35m 35m 35m 35m 35m 35m 35m 35m 35m 38m 

36d 36d 36d 36d 

36d 

41m 

10 

33r 33r 33r 33r 33r 33r 35m 33r 33r 33r 33r 37r 39r 

36d 

33r 33r 34r 33r 40r 

35m
 

1 

33r
 33r 34r 

0.1 

3. HEALTH EFFECTS

*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. 

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 

n-Mink 

o-Other 

g-Guinea Pig 

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

 for effects

 Minimal Risk Level 

other than

 Cancer 

151

0.01 
a

Key to

Figure

Table 3-6 Levels of Significant Exposure to Roxarsone - Oral

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

ACUTE EXPOSUREDeath

1

78

Kerr et al. 1963ROX

155 (LD50)

155

Rat(Holtzman)

once(GW)

2

37

NTP 1989bROX

150 M (5/5 died)

150

b

81 F (LD50)

81

Rat(Fischer- 344)

once(GO)

3

39

NTP 1989bROX

b

128 M (3/5 died)

128

144 F (5/5 died)

144

Rat(Fischer- 344)

14 d(F)

4

36

NTP 1989bROX

300 M (5/5 died)

300

b

244 F (LD50)

244

Mouse(B6C3F1)

once(GO)

5

41

NTP 1989bROX

168 F (5/5 died)

168

Mouse(B6C3F1)

14 d(F)

Systemic

6

40

NTP 1989bROX

Bd Wt 16 M

16

32 M (22% reduced body

weight)

32

Rat(Fischer- 344)

14 d(F)

7

42

NTP 1989bROX

Bd Wt 84

84

168 (34% decrease in body

weight)

168

Mouse(B6C3F1)

14 d(F)

Neurological

8

950

NTP 1989bROX

16 M

16

32 M (slight inactivity)

32

Rat(Fischer- 344)

14 d(F)
a

Key to

Figure

Table 3-6 Levels of Significant Exposure to Roxarsone - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

9

951

NTP 1989bROX

20

20

42 (slight inactivity; ruffled

fur)

42

Mouse(B6C3F1)

14 d(F)

10

5180

Rice et al. 1985; Kenne1986ROX

6.3 (muscle tremors and

clonic convulsions)

6.3

Pig(Landrace)

30 dad lib(F)

INTERMEDIATE EXPOSUREDeath

11

75

Kerr et al. 1963ROX

20 (10/12 died)

20

Rat(Holtzman)

13 wk(F)

12

43

NTP 1989bROX

64 M (3/10 died)

64

Rat(Fischer- 344)

13 wkad lib(F)

13

952

NTP 1989bROX

136 (6/10 males and 8/10

females died)

136

Mouse(B6C3F1)

13 wkad lib(F)
a

Key to

Figure

Table 3-6 Levels of Significant Exposure to Roxarsone - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

Systemic

14

38

NTP 1989bROX

Hemato 32 M

32

Rat(Fischer- 344)

31 or 90 dad lib(F)

Hepatic 9 F

9

36 F (decreased absolute and

relative liver weight)

36

Renal 8 M

8

32 M (increased kidney weight;

minimal tubulardegeneration)

32

Bd Wt 8 M

8

32 M (27% decrease in body

weight)

32
a

Key to

Figure

Table 3-6 Levels of Significant Exposure to Roxarsone - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

15

44

NTP 1989bROX

Resp 64 M

64

Rat(Fischer- 344)

13 wkad lib(F)

Cardio 64 M

64

Gastro 64 M

64

Musc/skel 64 M

64

Hepatic 4 M

4

8 M (increased relative liver

weight)

8

Renal 16 M

16

32 M (interstitial inflammation,

focal regenerativehyperplasia of tubular cellepithelium andmineralization)

32

Endocr 64 M

64

Dermal 64 M

64

Bd Wt 8 M

8

16 M (14% decreased body

weight)

16

32 M (26% decreased body

weight)

32
a

Key to

Figure

Table 3-6 Levels of Significant Exposure to Roxarsone - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

16

46

NTP 1989bROX

Cardio 136

136

Mouse(B6C3F1)

13 wkad lib(F)

Gastro 136

136

Musc/skel 136

136

Hepatic 136

136

Renal 136

136

Endocr 136

136

Dermal 136

136

Bd Wt 136 (18% decreased body

weight in males; 11%decreased body weight infemales)

136

17

47

NTP 1989bROX

Hemato 68

68

Mouse(B6C3F1)

29 or 91 dad lib(F)

Hepatic 68

68

Renal 68

68

Neurological

18

31

NTP 1989bROX

32 M

32

64 M (trembling, ataxia,

hyperexcitability, slightinactivity, ruffled fur)

64

Rat(Fischer- 344)

13 wkad lib(F)
a

Key to

Figure

Table 3-6 Levels of Significant Exposure to Roxarsone - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

19

64

Edmonds and Baker 19ROX

10 (muscle tremors)

10

Pig 28 d

(F)

20

20

Rice et al. 1985; Kenne1986ROX

6.3 (paraplegia, myelin

degeneration in spinalcord, peripheral nerves,optic nerve)

6.3

Pig(Landrace)

30 dad lib(F)

CHRONIC EXPOSURESystemic

21

966

NTP 1989bROX

Resp 4

4

Rat(Fischer- 344)

103 wkad lib(F)

Cardio 4

4

Gastro 4

4

Musc/skel 4

4

Hepatic 4

4

Renal 4

4

Endocr 4

4

Dermal 4

4

Ocular 4

4

Bd Wt 4

4

22

971

NTP 1989bROX

Resp 43 M

43

Mouse(Fischer- 344)

103 wkad lib(F)

Cardio 43 M

43

Gastro 43 M

43

Musc/skel 43 M

43

Hepatic 43 M

43
a

Key to

Figure

Table 3-6 Levels of Significant Exposure to Roxarsone - Oral (continued)

Species

(Strain)

LOAEL

System 

NOAEL

(mg/kg/day)

Less Serious

(mg/kg/day)

Serious

(mg/kg/day)

ReferenceChemical Form

Exposure/

Duration/

Frequency

(Route)

Renal 43 M

43

Endocr 43 M

43

Dermal 43 M

43

Ocular 43 M

43

a The number corresponds to entries in Figure 3-6.b Differences in levels of health effects and cancer effects between male and females are not indicated in Figure 3-6. Where such differences exist, only the levels most sensitive gender are presented.ad lib = ad libitum; Bd Wt = body weight; Cardio = cardiovascular; d = day(s); Endocr = endocrine; (F) = feed; F = Female; Gastro = gastrointestinal; (GO) = gavage gavage in water; Hemato = hematological; LC50 = lethal concentration, 50% kill, LD50 = lethal dose, 50% kill; LOAEL = lowest-observed-adverse-effect level; M = musculoskeletal; NOAEL = no-observed-adverse-effect level; occup = occupational; Resp = respiratory; wk = week(s)

Bd Wt 43 F

43
1

10

100

1000

Death

4m

5m 1r

2r

3r

Body Weight

7m

7m

6r

6r

Neurological

9m

9m

8r

8r

10p

mg/kg/day

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

 for effects

 other than

 Cancer

Figure 3-6 Levels of Significant Exposure to Roxarsone - Oral

Acute (≤14 days)

 Minimal Risk Level

Systemic

ARSENIC

3. HEALTH EFFECTS

159
1

10

100

1000

Death

13m

11r

12r

Respiratory

15r

Cardiovascular

16m

15r

Gastrointestinal

16m

15r

Hematological

17m

14r

Musculoskeletal

16m

15r

Hepatic

16m

17m

14r

14r

15r

15r

Renal

16m

17m

14r

14r 15r

15r

Endocrine

16m

15r

Dermal

16m

15r

Body Weight

16m

14r

14r

15r

15r

15r

Neurological

18r

18r

19p

20p

mg/kg/day

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

 for effects

 other than

 Cancer

Figure 3-6 Levels of Significant Exposure to Roxarsone - Oral (Continued)

Intermediate (15-364 days)

 Minimal Risk Level

Systemic

ARSENIC

3. HEALTH EFFECTS

160
1

10

100

Respiratory

22m

21r

Cardiovascular

22m

21r

Gastrointestinal

22m

21r

Musculoskeletal

22m

21r

Hepatic

22m

21r

Renal

22m

21r

Endocrine

22m

21r

Dermal

22m

21r

Ocular

22m

21r

Body Weight

22m

21r

mg/kg/day

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

 for effects

 other than

 Cancer

Chronic (≥365 days)

Figure 3-6 Levels of Significant Exposure to Roxarsone - Oral (Continued)

 Minimal Risk Level

Systemic

ARSENIC

3. HEALTH EFFECTS

161
ARSENIC 162 

3. HEALTH EFFECTS 

Available LD50 values for arsenate and arsenite in rats and mice range from 15 to 175 mg As/kg (Dieke 

and Richter 1946; Gaines 1960; Harrisson et al. 1958; Kaise et al. 1985). The variability can be attributed 

to differences based on species, strain, specific route of exposure (feed vs. gavage), specific compound 

tested, and testing laboratory. Most deaths occurred within 1 day of exposure, but details regarding cause 

of death were not generally reported. Seven of 25 pregnant rats given a single gavage dose of 23 mg 

As/kg as arsenic trioxide on day 9 of gestation died soon after dosing, while no deaths occurred at doses 

of 4–15 mg As/kg (Stump et al. 1999). Data on lethality from repeated exposure studies in animals are 

relatively sparse. Seven of 20 pregnant rabbits died from repeated gavage doses of 1.5 mg As/kg/day as 

arsenic acid during gestation, while none died at 0.1–0.4 mg As/kg/day (Nemec et al. 1998). Chronic 

studies observed treatment-related mortality in monkeys exposed to 3 mg As/kg/day as arsenate 

(Heywood and Sortwell 1979), dogs exposed to 2.4 mg As/kg/day as arsenite or arsenate (Byron et al. 

1967), mice exposed to 1 mg As/kg/day as arsenite (Schroeder and Balassa 1967), and rats exposed to 

30 mg As/kg/day as lead arsenate (Kroes et al. 1974). 

Reliable LOAEL and LD50 values for lethality from oral exposure to inorganic arsenicals in each species 

and duration category are recorded in Table 3-3 and plotted in Figure 3-3. 

Organic Arsenicals. No studies were located regarding death in humans after oral exposure to organic 

arsenicals, but the acute lethality of MMA, DMA, and roxarsone have been investigated in several animal 

studies. The LD50 values for MMA (including MSMA), DMA, and roxarsone are 102–3,184 mg/kg 

MMA or MSMA (Gur and Nyska 1990; Jaghabir et al. 1988; Kaise et al. 1989), 1,200 mg DMA/kg/day 

(Kaise et al. 1989), and 14.2–69.5 mg DMA/kg/day (Kerr et al. 1963; NTP 1989b), respectively. The 

cause of death was not investigated in any of these studies. Intermediate-duration exposure to MMA, 

DMA, or roxarsone resulted in increased mortality in laboratory animals exposed to 106.9 mg 

MMA/kg/day (Arnold et al. 2003), 17–190 mg DMA/kg/day (Crown et al. 1987; Murai et al. 1993; 

Wanibuchi et al. 1996) or 20–64 mg/kg/day roxarsone (Edmonds and Baker 1986; Kerr et al. 1963; NTP 

1989b), respectively. Increased mortality was also observed in rats chronically exposed to 72.4 mg 

MMA/kg/day (Arnold et al. 2003). 

3.2.2.2 Systemic Effects 

The highest NOAEL values and all reliable LOAEL values for systemic effects from oral exposure in 

each species and duration category are recorded in Table 3-3 and plotted in Figure 3-3. Similar data for 
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3. HEALTH EFFECTS 

oral exposure to MMA, DMA, and roxarsone are shown in Tables 3-4, 3-5, and 3-6, and shown in 

Figures 3-4, 3-5, and 3-6, respectively. 

Respiratory Effects. 

Inorganic Arsenicals. Serious respiratory effects, including respiratory distress, hemorrhagic bronchitis, 

and pulmonary edema, have been reported in some cases of acute oral arsenic poisoning at doses of 8 mg 

As/kg and above (e.g., Civantos et al. 1995; Fincher and Koerker 1987; Levin-Scherz et al. 1987; Moore 

et al. 1994b; Quatrehomme et al. 1992). These effects may be secondary to injury to the pulmonary 

vasculature (see Cardiovascular Effects, below). In addition, bronchitis and sequelae (bronchiectasis, 

bronchopneumonia) have been observed in patients and at autopsy in some chronic poisoning cases (Guha 

Mazumder et al. 2005; Milton and Rahman 2002; Rosenberg 1974; Tsai et al. 1999; Zaldívar 1974; 

Zaldívar and Guillier 1977). Bronchopneumonia secondary to arsenic-induced bronchitis was considered 

to be the cause of death in one young child who died after several years of exposure to an average dose of 

0.08 mg As/kg/day (Zaldívar and Guillier 1977). Decrements in lung function, measured as decreased 

FEV1, FVC, and FEF25–75 have also been reported in subjects exposed to 0.1–0.5 mg As/L in the drinking 

water and exhibiting skin lesions (von Ehrenstein et al. 2005). In general, however, respiratory effects 

have not been widely associated with repeated oral ingestion of low arsenic doses. Nevertheless, a few 

studies have reported minor respiratory symptoms, such as cough, sputum, rhinorrhea, and sore throat, in 

people with repeated oral exposure to 0.03–0.05 mg As/kg/day (Ahmad et al. 1997; Mizuta et al. 1956). 

There are few data regarding respiratory effects in animals following acute oral exposure to inorganic 

arsenic. An infant Rhesus monkey that died after 7 days of oral exposure to a complex arsenate salt at a 

dose of 3 mg As/kg/day exhibited bronchopneumonia with extensive pulmonary hemorrhage, edema, and 

necrosis (Heywood and Sortwell 1979). Two other monkeys in this treatment group survived a 1-year 

exposure period and had no gross or microscopic pulmonary lesions at sacrifice. Increased relative lung 

weights were seen in rats exposed to 6.66 mg As/kg/day as sodium arsenite 5 days/week for 12 weeks 

(Schulz et al. 2002). Chronic oral studies in dogs and rats treated with arsenate or arsenite failed to find 

respiratory lesions (Byron et al. 1967; Kroes et al. 1974; Schroeder et al. 1968). 

One study utilizing gallium arsenide included limited investigation of respiratory function. Respiration 

rate was significantly decreased in rats following ingestion of a single dose of gallium arsenide at 

1,040 mg As/kg, but was unaffected at a dose of 520 mg As/kg (Flora et al. 1997a). Respiration rate was 

measured 1, 7, and 15 days after dosing, but the decrease was most noticeable after 15 days. 
ARSENIC 164 

3. HEALTH EFFECTS 

Organic Arsenicals. No respiratory effects were noted after acute human ingestion of 1,714 mg 

MSMA/kg (Shum et al. 1995). Mice exhibited respiratory arrest after a single oral dose of 1,800 mg 

MMA/kg (Kaise et al. 1989) or 900 mg DMA/kg (Kaise et al. 1989) and lung ornithine decarboxylase 

activity was reduced after ingestion of one or two doses of 720 mg DMA/kg (Ahmad et al. 1999a). 

Localized lung hemorrhage was observed in dogs after a single oral dose of 14.2 mg/kg roxarsone in a 

capsule (Kerr et al. 1963). No respiratory effects were seen after intermediate or chronic exposure of rats, 

mice, or dogs exposed to 35 mg MMA/kg/day (Waner and Nyska 1988), 7.8–94 mg DMA/kg/day 

(Arnold et al. 2006; Crown et al. 1987; Rubin et al. 1989; Zomber et al. 1989), or 4–136 mg/kg/day 

roxarsone (NTP 1989b). 

Cardiovascular Effects. 

Inorganic Arsenicals. A number of studies in humans indicate that arsenic ingestion may lead to serious 

effects on the cardiovascular system. Characteristic effects on the heart from both acute and long-term 

exposure include altered myocardial depolarization (prolonged QT interval, nonspecific ST segment 

changes) and cardiac arrhythmias (Cullen et al. 1995; Glazener et al. 1968; Goldsmith and From 1986; 

Heyman et al. 1956; Little et al. 1990; Mizuta et al. 1956; Moore et al. 1994b; Mumford et al. 2007). A 

significant dose-related increase in the prevalence of cardiac electrophysiologic abnormalites was 

observed in residents of Inner Mongolia, China; the incidences of QT prolongation were observed in 3.9, 

11.1, and 20.6% of the residents with drinking water levels of <21, 110–300, and 430–690 μg/L, 

respectively (Mumford et al. 2007). Hypertrophy of the ventricular wall was observed at autopsy after 

acute exposure to 93 mg of arsenic (Quatrehomme et al. 1992). Long-term, low-level exposures may also 

lead to damage to the vascular system. The most dramatic example of this is "Blackfoot Disease," a 

condition that is endemic in an area of Taiwan where average drinking water levels of arsenic range from 

0.17 to 0.80 ppm (Tseng 1977), corresponding to doses of about 0.014–0.065 mg As/kg/day (IRIS 2007). 

The disease is characterized by a progressive loss of circulation in the hands and feet, leading ultimately 

to necrosis and gangrene (Chen et al. 1988b; Ch’i and Blackwell 1968; Tseng 1977, 1989; Tseng et al. 

1968, 1995, 1996). Several researchers have presented evidence that other factors besides arsenic (e.g., 

other water contaminants, dietary deficits) may play a role in the etiology of this disease (Ko 1986; Lu et 

al. 1990; Yu et al. 1984). While this may be true, the clear association between the occurrence of 

Blackfoot Disease and the intake of elevated arsenic levels indicates that arsenic is at least a contributing 

factor. The results of a recent study suggested that individuals with a lower capacity to methylate 
ARSENIC 165 

3. HEALTH EFFECTS 

inorganic arsenic to DMA have a higher risk of developing peripheral vascular disease in the Blackfoot 

Disease-hyperendemic area in Taiwan (Tseng et al. 2005). 

Arsenic exposure in Taiwan has also been associated with an increased incidence of cerebrovascular and 

microvascular diseases (Chiou et al. 1997; Wang et al. 2002, 2003) and ischemic heart disease (Chang et 

al. 2004; Chen et al. 1996; Hsueh et al. 1998b; Tsai et al. 1999; Tseng et al. 2003). Moreover, effects of 

arsenic on the vascular system have also been reported in a number of other populations. For example, 

hypertension, defined as a systolic blood pressure of ≥140 mm Hg in combination with a diastolic blood 

pressure of ≥90 mm Hg, was associated with estimated lifetime doses of approximately 0.055 mg 

As/kg/day (0.25 mg/L in water) in a study of people in Bangladesh (Rahman et al. 1999); no significant 

association was found with estimated doses of 0.018 mg As/kg/day (0.75 mg/L in water). Wang et al. 

(2003) found an increased incidence of microvascular and macrovascular disease among subjects in 

Taiwan living in an arseniasis-endemic area in which the water of artesian wells had arsenic 

concentrations >0.35 mg/L (estimated doses of >0.03 mg As/kg/day). An additional study of Taiwanese 

subjects reported a significant increase in incidence of hypertension associated with concentrations of 

arsenic in the water >0.7 mg/L (estimated doses of >0.06 mg As/kg/day) (Chen et al. 1995). Studies in 

Chile indicate that ingestion of 0.6–0.8 ppm arsenic in drinking water (corresponding to doses of 0.02– 

0.06 mg As/kg/day, depending on age) increases the incidence of Raynaud's disease and of cyanosis of 

fingers and toes (Borgoño and Greiber 1972; Zaldívar 1974, 1977; Zaldívar and Guillier 1977). Autopsy 

of five children from this region who died of apparent arsenic toxicity showed a marked thickening of 

small and medium sized arteries in tissues throughout the body, especially the heart (Rosenberg 1974). In 

addition, cardiac failure, arterial hypotension, myocardial necrosis, and thrombosis have been observed in 

children who died from chronic arsenic ingestion (Zaldívar 1974), as well as adults chronically exposed to 

arsenic (Dueñas et al. 1998). Likewise, thickening and vascular occlusion of blood vessels were noted in 

German vintners exposed to arsenical pesticides in wine and in adults who drank arsenic-contaminated 

drinking water (Roth 1957; Zaldívar and Guillier 1977). A survey of Wisconsin residents using private 

wells for their drinking water found that residents exposed for at least 20 years to water concentrations of 

>10 μg As/L had increased incidences of cardiac bypass surgery, high blood pressure, and circulatory 

problems as compared with residents exposed to lower arsenic concentrations (Zierold et al. 2004). 

Similarly, Lewis et al. (1999) reported increased mortality from hypertensive heart disease in both men 

and women among a cohort exposed to arsenic in their drinking water in Utah, as compared with the 

general population of Utah. Limitations in the study included lack of evaluation of smoking as a 

confounder and of other dietary sources of arsenic, and the lack of a dose-response for hypertensive heart 

disease. Another ecological study (Engel and Smith 1994) found significant increases in deaths from 
ARSENIC 166 

3. HEALTH EFFECTS 

arteriosclerosis, aortic aneurysm, and all other diseases of the arteries, arterioles, and capillaries among 

U.S. residents with arsenic drinking waters of >20 μg/L; the increase in deaths from congenital anomalies 

of the heart and other anomalies of the circulatory system also observed in this subpopulation limits the 

interpretation of the findings. 

Similar alterations in vascular reactivity have been noted in rats given repeated oral doses of arsenic 

trioxide (11 mg As/kg/day) for several weeks (Bekemeier and Hirschelmann 1989), although no 

histological effects could be detected in the hearts of rats or dogs exposed to up to 30 mg As/kg/day as 

arsenate or arsenite for 2 years (Byron et al. 1967; Kroes et al. 1974; Schroeder et al. 1968). Acute 

exposure of rats to gallium arsenide at a dose of 1,040 mg As/kg resulted in an increase in blood pressure 

and heart rate, while 520 mg As/kg had no effect (Flora et al. 1997a). Guinea pigs exposed to arsenic 

trioxide for 1 day (0, 7.6, 22.7, or 37.9 mg As/kg) or 8 days (0 or 3.8 mg As/kg/day) showed prolongation 

of the cardiac QT interval and action potential duration (Chiang et al. 2002). 

Organic Arsenicals. No adverse cardiovascular effects were noted after acute human ingestion of 

1,714 mg MSMA/kg (Shum et al. 1995). However, sinus tachycardia was noted after acute ingestion of 

73 mg DMA/kg (as dimethyl arsenic acid and dimethyl arsenate) (Lee et al. 1995). No cardiovascular 

effects were seen after intermediate or chronic exposure of laboratory animals to 35–67.1 mg 

MMA/kg/day (Arnold et al. 2003; Waner and Nyska 1988), 7.8–94 mg DMA/kg/day (Arnold et al. 2006; 

Crown et al. 1987; Rubin et al. 1989; Zomber et al. 1989), or 4–136 mg/kg/day roxarsone (NTP 1989b). 

Gastrointestinal Effects. 

Inorganic Arsenicals. Clinical signs of gastrointestinal irritation, including nausea, vomiting, diarrhea, 

and abdominal pain, are observed in essentially all cases of short-term high-dose exposures to inorganic 

arsenic (e.g., Armstrong et al. 1984; Bartolome et al. 1999; Campbell and Alvarez 1989; Chakraborti et 

al. 2003a; Cullen et al. 1995; Fincher and Koerker 1987; Goebel et al. 1990; Kingston et al. 1993; LevinScherz et al. 1987; Lugo et al. 1969; Moore et al. 1994b; Muzi et al. 2001; Uede and Furukawa 2003; 

Vantroyen et al. 2004). Similar signs are also frequently observed in groups or individuals with longerterm, lower-dose exposures (e.g., Borgoño and Greiber 1972; Cebrián et al. 1983; Franzblau and Lilis 

1989; Guha Mazumder et al. 1988, 1998a; Haupert et al. 1996; Holland 1904; Huang et al. 1985; Mizuta 

et al. 1956; Nagai et al. 1956; Silver and Wainman 1952; Wagner et al. 1979; Zaldívar 1974), but effects 

are usually not detectable at exposure levels below about 0.01 mg As/kg/day (Harrington et al. 1978; 

Valentine et al. 1985). These symptoms generally decline within a short time after exposure ceases. 
ARSENIC 167 

3. HEALTH EFFECTS 

Gastrointestinal irritation symptoms form the basis (in part) for the acute oral MRL of 0.005 mg/kg/day 

for inorganic arsenic, as described in footnote b in Table 3-3. More severe symptoms (hematemesis, 

hemoperitoneum, gastrointestinal hemorrhage, and necrosis) have been reported in some cases with acute 

exposure to 8 mg As/kg or more (Civantos et al. 1995; Fincher and Koerker 1987; Levin-Scherz et al. 

1987; Quatrehomme et al. 1992), and also in some people with long-term ingestion of 0.03–0.05 mg 

As/kg/day as a medicinal preparation (Lander et al. 1975; Morris et al. 1974). 

Clinical signs of gastrointestinal irritation were observed in monkeys and rats given repeated oral doses of 

arsenic (6 and 11 mg As/kg/day, respectively) for 2 weeks (Bekemeier and Hirschelmann 1989; Heywood 

and Sortwell 1979). Hemorrhagic gastrointestinal lesions have also been reported in animal studies. A 

monkey that died after repeated oral treatment with 6 mg As/kg/day for approximately 1 month was found 

to have acute inflammation and hemorrhage of the small intestine upon necropsy (Heywood and Sortwell 

1979). This lesion was not found in other monkeys that died in this study, or in the survivors. Two 

pregnant mice that died after repeated gavage treatment with 24 mg As/kg/day as arsenic acid had 

hemorrhagic lesions in the stomach (Nemec et al. 1998). Gross gastrointestinal lesions (stomach 

adhesions, eroded luminal epithelium in the stomach) were seen frequently in rats treated by gavage with 

8 mg As/kg/day as arsenic trioxide starting before mating and continuing through the end of gestation 

(Holson et al. 2000). The lesions were not found in rats treated with 4 mg As/kg/day in this study. No 

histological evidence of gastrointestinal injury was detected in rats exposed to arsenate or arsenite in the 

feed for 2 years at doses up to 30 mg As/kg/day, but dogs fed a diet containing 2.4 mg As/kg/day as 

arsenite for 2 years had some bleeding in the gut (Byron et al. 1967; Kroes et al. 1974). 

Organic Arsenicals. Vomiting was noted after ingestion of 793 mg/kg arsenic (as monosodium 

methanearsenate) in a suicide attempt (Shum et al. 1995). Ingestion of 78 mg DMA/kg (as dimethyl 

arsenic acid and dimethyl arsenate) induced vomiting, abdominal pain, hyperactive bowel, and diarrhea 

(Lee et al. 1995). 

The gastrointestinal tract appears to be the critical target of toxicity following oral exposure to MMA. 

Diarrhea/loose feces has been reported in mice and rabbits following a single gavage dose of 2,200 mg 

MMA/kg or 60 mg MSMA/kg, respectively (Jaghabir et al. 1988; Kaise et al. 1989), pregnant rabbits 

administered 12 mg MMA/kg/day via gavage (Irvine et al. 2006), rats exposed to 30.2 mg MMA/kg/day 

in the diet during the first year of a 2-year study (Arnold et al. 2003), dogs administered 2 mg 

MMA/kg/day via capsule for 52 weeks (Waner and Nyska 1988), rats fed diets containing 25.7 mg 

MMA/kg/day for 2 years (Arnold et al. 2003), and mice exposed to 67.1 mg MMA/kg/day in the diet for 
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3. HEALTH EFFECTS 

2 years (Arnold et al. 2003). However, the increased incidence of diarrhea is not always accompanied by 

macroscopic or histological alterations in the gastrointestinal tissues. For example, in the 2-year rat study 

(Arnold et al. 2003; incidence data reported in Crown et al. 1990), an increased incidence of diarrhea was 

observed at 25.7 mg MMA/kg/day; macroscopic or histological alterations were observed in some 

animals, but the incidence was similar to controls. At the next highest dose level (72.4 mg 

MMA/kg/day), thickened wall and edema and hemorrhagic, necrotic, ulcerated, or perforated mucosa 

were observed in the large intestine and significant increases in the incidence of squamous metaplasia of 

the epithelial columnar absorptive cells were found in the cecum, colon, and rectum. Squamous 

metaplasia was also observed in the cecum and colon of mice chronically exposed to 67.1 mg 

MMA/kg/day (Arnold et al. 2003; incidence data reported in Gur et al. 1991). 

There are some reports of gastrointestinal effects in rats and dogs exposed to DMA; however, the 

LOAELs for these effects are higher than the LOAELs for MMA and most rodent studies do not report 

effects at nonlethal doses. Diarrhea with congestion and hemorrhagic gastrointestinal contents were 

observed in rats exposed to a lethal dose of 190 mg DMA/kg/day in the diet for 4 weeks (Crown et al. 

1987) and diarrhea and vomiting were reported in dogs administered 16 mg DMA/kg/day via capsule 

6 days/week (Zomber et al. 1989). No gastrointestinal effects were observed in rats or mice chronically 

exposed to 7.8 or 94 mg DMA/kg/day, respectively (Arnold et al. 2006). 

Vomiting and gastrointestinal hemorrhage were observed in dogs after a single capsulized dose of 

50 mg/kg roxarsone (Kerr et al. 1963), although slightly higher doses administered for 13 weeks to rats 

and mice had no effect (NTP 1989b). No gastrointestinal effects were seen after chronic exposure of rats 

(4 mg/kg/day) or mice (43 mg/kg/day) to roxarsone (NTP 1989b). 

Hematological Effects. 

Inorganic Arsenicals. Anemia and leukopenia are common effects of arsenic poisoning in humans, and 

have been reported following acute (Armstrong et al. 1984; Goldsmith and From 1986; Mizuta et al. 

1956; Muzi et al. 2001; Westhoff et al. 1975), intermediate (Franzblau and Lilis 1989; Heyman et al. 

1956; Nagai et al. 1956; Wagner et al. 1979), and chronic oral exposures (Chakraborti et al. 2003a; 

Glazener et al. 1968; Guha Mazumder et al. 1988; Hopenhayn et al. 2006; Kyle and Pease 1965; Tay and 

Seah 1975) at doses of 0.002 mg As/kg/day or more. These effects may be due to both a direct cytotoxic 

or hemolytic effect on the blood cells (Armstrong et al. 1984; Fincher and Koerker 1987; Goldsmith and 

From 1986; Kyle and Pease 1965; Lerman et al. 1980) and a suppression of erythropoiesis (Kyle and 
ARSENIC 169 

3. HEALTH EFFECTS 

Pease 1965; Lerman et al. 1980). However, hematological effects are not observed in all cases of arsenic 

exposure (EPA 1981b; Harrington et al. 1978; Huang et al. 1985; Silver and Wainman 1952) or even all 

acute poisoning cases (Cullen et al. 1995; Moore et al. 1994b). 

In an acute animal study, Tice et al. (1997) found that there was a decrease in polychromatic erythrocytes 

in the bone marrow of mice treated with 6 mg As/kg/day for 1 or 4 days. There was no effect at 3 mg 

As/kg/day. Long-term studies found mild anemia in dogs fed arsenite or arsenate for 2 years at 2.4 mg 

As/kg/day, but no hematological effect in dogs fed 1 mg As/kg/day for 2 years or 1.9 mg As/kg/day for 

26 weeks (Byron et al. 1967; Neiger and Osweiler 1989). Chronic rat studies found little or no evidence 

of anemia at doses up to 30 mg As/kg/day, even with co-exposure to lead (Byron et al. 1967; Kroes et al. 

1974). No hematological effects were found in monkeys exposed to arsenic doses of 3–6 mg As/kg/day 

for 1 year (Heywood and Sortwell 1979). 

Rats exposed to arsenate for 6 weeks had decreased activities of several enzymes involved in heme 

synthesis, but data were not provided on whether this resulted in anemia (Woods and Fowler 1977, 1978). 

Exposure of rats to ≥5 ppm of arsenic (0.30 mg As/kg/day as sodium arsenite) in the drinking water for 

4 weeks resulted in increased platelet aggregation, while 10 or 25 ppm (0.60 or 1.5 mg As/kg/day) was 

associated with increased P-selectin-positive cells and decreased occlusion time (Lee et al. 2002), 

representing a change in platelet function. Similarly, exposure of rats or guinea pigs to 10 or 25 ppm of 

arsenic as arsenite (approximate doses of 0, 0.92, or 2.3 mg As/kg/day for rats and 0, 0.69, or 1.7 mg 

As/kg/day for guinea pigs) in the drinking water for 16 weeks (Kannan et al. 2001) resulted in decreases 

in erythrocyte and leukocyte numbers (rats and guinea pigs), increased blood mean corpuscular volume 

and corpuscular hemoglobin mass (guinea pigs only), and decreased mean corpuscular hemoglobin 

concentration (rats only). Gallium arsenide also disrupts heme synthesis in rats, although the evidence 

suggests that this effect is due primarily to the gallium moiety (Flora et al. 1997a). 

Organic Arsenicals. No adverse hematological effects were noted in a man who ingested 78 mg/kg as 

dimethyl arsenic acid and dimethyl arsenate (Lee et al. 1995). No hematological effects were observed in 

rats exposed to 8.4 or 72.4 mg MMA/kg/day for 2 years (Arnold et al. 2003; Shen et al. 2003) or dogs 

administered 35 mg MMA/kg/day for 52 weeks (Waner and Nyska 1988); additionally, no alterations in 

total or differential leukocyte levels were observed in mice exposed to 67.1 mg MMA/kg/day for 2 years 

(Arnold et al. 2003). Although some studies have reported hematological alterations following oral 

exposure to DMA, this is not a consistent finding. Observed alterations include decreased mean 

corpuscular hemoglobin concentration in rats exposed to 2.3 mg DMA/kg/day for 10 weeks (Rubin et al. 
ARSENIC 170 

3. HEALTH EFFECTS 

1989), decreased hemoglobin and erythrocyte levels in rats exposed to 4.5 mg DMA/kg/day for 13 weeks 

(Crown et al. 1987), decreased erythrocyte levels and increased leukocyte levels in dogs administered 

capsules containing 40 mg DMA/kg/day for 52 weeks (Zomber et al. 1989), and decreased lymphocyte 

and increased monocyte levels were observed in mice chronically exposed to 94 mg DMA/kg/day 

(Arnold et al. 2006). No hematological alterations have been observed in rats exposed to 7.8 mg 

DMA/kg/day for 2 years (Arnold et al. 2006). Similarly, no hematological effects were observed in rats 

(Kerr et al. 1963; NTP 1989b), mice (NTP 1989b), or dogs (Prier et al. 1963) exposed to 20–32, 68, or 

5 mg/kg/day roxarsone, respectively, for intermediate or chronic durations 

Musculoskeletal Effects. 

Inorganic Arsenicals. No studies were located regarding musculoskeletal effects in humans or animals 

after oral exposure to inorganic arsenicals. 

Organic Arsenicals. No studies were located regarding musculoskeletal effects in humans after oral 

exposure to organic arsenicals. No musculoskeletal effects were seen after intermediate or chronic 

exposure of rats and mice to MMA (Arnold et al. 2003), DMA (Arnold et al. 2006), or roxarsone (NTP 

1989b). 

Hepatic Effects. 

Inorganic Arsenicals. A number of studies in humans exposed to inorganic arsenic by the oral route 

have noted signs or symptoms of hepatic injury. Clinical examination often reveals that the liver is 

swollen and tender (Chakraborty and Saha 1987; Franklin et al. 1950; Guha Mazumder et al. 1988, 

1998a; Liu et al. 2002; Mizuta et al. 1956; Silver and Wainman 1952; Wade and Frazer 1953; Zaldívar 

1974), and analysis of blood sometimes shows elevated levels of hepatic enzymes (Armstrong et al. 1984; 

Franzblau and Lilis 1989; Guha Mazumder 2005; Hernández-Zavala et al. 1998). These effects are most 

often observed after repeated exposure to doses of 0.01–0.1 mg As/kg/day (Chakraborty and Saha 1987; 

Franklin et al. 1950; Franzblau and Lilis 1989; Guha Mazumder et al. 1988; Mizuta et al. 1956; Silver and 

Wainman 1952; Wade and Frazer 1953), although doses as low as 0.006 mg As/kg/day have been 

reported to have an effect following chronic exposure (Hernández-Zavala et al. 1998). Hepatic effects 

have also been reported in acute bolus poisoning cases at doses of 2 mg As/kg/day or more (Hantson et al. 

1996; Kamijo et al. 1998; Levin-Scherz et al. 1987; Quatrehomme et al. 1992; Vantroyen et al. 2004), 

although acute exposure to 19 mg As/kg did not cause hepatic effects in an infant (Cullen et al. 1995). 
ARSENIC 171 

3. HEALTH EFFECTS 

Histological examination of the livers of persons chronically exposed to similar doses has revealed a 

consistent finding of portal tract fibrosis (Guha Mazumder 2005; Guha Mazumder et al. 1988; Morris et 

al. 1974; Piontek et al. 1989; Szuler et al. 1979), leading in some cases to portal hypertension and 

bleeding from esophageal varices (Szuler et al. 1979); cirrhosis has also been reported at an increased 

frequency in arsenic-exposed individuals (Tsai et al. 1999). Several researchers consider that these 

hepatic effects are secondary to damage to the hepatic blood vessels (Morris et al. 1974; Rosenberg 

1974), but this is not directly established. 

Acute exposure of monkeys to 6 mg As/kg/day resulted in vacuolization of the hepatocytes (Heywood 

and Sortwell 1979). Studies in dogs or mice have not detected clinically significant hepatic injury 

following exposure to either arsenite or arsenate (Byron et al. 1967; Fowler and Woods 1979; Kerkvliet et 

al. 1980; Neiger and Osweiler 1989; Schroeder and Balassa 1967), although enlargement of the common 

bile duct was noted in rats fed either arsenate or arsenite in the diet for 2 years (Byron et al. 1967; Kroes 

et al. 1974) and lipid vacuolation and fibrosis were seen in the livers of rats exposed to 12 mg As/kg/day 

as arsenate in the drinking water for 6 weeks (Fowler et al. 1977). Similarly, fatty changes and 

inflammatory cell infiltration were seen in the livers of both normal and metallothionein-null mice 

exposed to 5.6 mg arsenic/kg/day in the drinking water for 48 weeks (Liu et al. 2000). Increases in liver 

zinc and copper concentrations were noted in rats receiving a single oral dose of 10 mg As/kg as sodium 

arsenite (Flora and Tripathi 1998) and hepatic levels of malondialdehyde were increased and glutathione 

levels were decreased in livers of rats receiving 200 mg As/kg as GaAs (Flora et al. 1998). An increase in 

indices of peroxidation was reported in rats dosed with approximately 0.02 mg As/kg/day for 60 days 

from drinking water containing 2.5 mg sodium arsenite/L (Bashir et al. 2006); absolute liver weight was 

also increased at this dose level. Elevated levels of serum aspartate aminotransferase (AST) were 

observed in rats administered a single oral dose of 100 mg As/kg as GaAs (Flora et al. 1998). Exposure 

of guinea pigs to 0.69 or 1.7 mg As/kg/day in the drinking water for 16 weeks, but not in rats exposed to 

0.92 or 2.3 mg As/kg/day, resulted in increases in delta-aminolevulinic acid synthetase (ALAS) levels 

(Kannan et al. 2001). Exposure of BALB/C mice to 0.7 mg arsenic/kg/day in the drinking water for 

15 months resulted in increased liver weights, changes in liver enzymes (glutathione S-transferase, 

glutathione reductase, catalase, glucose-6-phosphate dehydrogenase, glutathione peroxidase), fatty liver, 

and fibrosis (Santra et al. 2000). 

Organic Arsenicals. No adverse hepatic effects were noted after ingestion of 1,714 mg/kg MSMA or 

78 mg DMA/kg (as dimethyl arsenic acid and dimethyl arsenate) in a suicide attempt (Lee et al. 1995; 

Shum et al. 1995). No other studies of the hepatic effects of organic arsenicals in humans were located. 
ARSENIC 172 

3. HEALTH EFFECTS 

Histological examination of livers from rabbits given repeated oral doses of MMA showed diffuse 

inflammation and hepatocellular degeneration (Jaghabir et al. 1989), but the lesions were not severe. 

Male rats exposed to a time-weighted average (TWA) dose of 72.4 mg MMA/kg/day for 104 weeks 

showed a decrease in absolute liver weight, while females exposed to 98.5 mg MMA/kg/day showed 

histiocytic proliferation of the liver (Arnold et al. 2003); however, these effects were probably due to a 

decrease in body weight and secondary complications of perforation and ulceration of the gastrointestinal 

effect, respectively. Shen et al. (2003) reported increases in and the number of GST-P-positive foci in the 

livers of rats exposed to average concentrations of 8.4 mg MMA/kg/day in the diet for 104 weeks. No 

effects were observed in rats exposed to DMA (Siewicki 1981), but mice exposed to one or two oral 

doses of 720 mg DMA/kg had decreased liver glutathione and cytochrome P-450 content and serum 

ornithine decarboxylase activity (Ahmad et al. 1999a). Generalized icterus was reported in dogs after 

acute exposure to roxarsone (Kerr et al. 1963). Some small fluctuations in liver weight have been noted 

in rats and mice after intermediate oral exposure to roxarsone, but the toxicological significance of this is 

not clear and is not observed after chronic exposure of rats and mice to lower doses (NTP 1989b). 

Renal Effects. 

Inorganic Arsenicals. Most case studies of acute and chronic arsenic toxicity do not report clinical signs 

of significant renal injury, even when other systems are severely impaired (e.g., Cullen et al. 1995; 

Franzblau and Lilis 1989; Jenkins 1966; Kersjes et al. 1987; Mizuta et al. 1956; Silver and Wainman 

1952). In some cases, elevated serum levels of creatinine or bilirubin have been noted (Armstrong et al. 

1984; Levin-Scherz et al. 1987; Moore et al. 1994b), and mild proteinuria may occur (Armstrong et al. 

1984; Glazener et al. 1968; Tay and Seah 1975). Acute renal failure in some bolus poisoning episodes 

(e.g., Fincher and Koerker 1987; Goebel et al. 1990; Levin-Scherz et al. 1987; Lugo et al. 1969; Moore et 

al. 1994b) is probably a result of fluid imbalances or vascular injury (Rosenberg 1974; Zaldívar 1974). 

Glomerular congestion has been observed after an acute exposure to high doses (Quatrehomme et al. 

1992). 

Studies in animals also indicate that the kidney is not a major target organ for inorganic arsenic (Byron et 

al. 1967; Schroeder and Balassa 1967; Woods and Southern 1989), although some effects have been 

reported at high exposure levels. Mild histological changes in the renal tubules of monkeys exposed to 

arsenate for 2 weeks were noted by Heywood and Sortwell (1979), and some mild alterations in renal 

mitochondria in rats exposed to arsenate for 6 weeks were noted by Brown et al. (1976). Mild proteinuria 
ARSENIC 173 

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(Flora et al. 1998) and an increase in kidney zinc concentration (Flora and Tripathi 1998) have also been 

noted in rats exposed orally to a single dose of 100 mg As/kg as GaAs or 10 mg As/kg as sodium arsenite, 

respectively. These data suggest that the kidney is relatively less sensitive to arsenic than most other 

organ systems, and renal effects are unlikely to be of concern except secondary to fluid imbalances or 

cardiovascular injury. 

Organic Arsenicals. No adverse renal effects were noted after ingestion of 1,714 mg MSMA/kg in a 

suicide attempt (Shum et al. 1995). Animal studies have reported renal and urinary bladder effects 

following oral exposure to organic arsenicals; the available data suggest that the urinary system is a more 

sensitive target for DMA, than for MMA or roxarsone. A decrease in urine volume was observed in 

rabbits following a single gavage dose of 30 mg MSMA/kg/day (Jaghabir et al. 1988) and a decrease in 

urine volume (35 mg MMA/kg/day) and an increase in urine specific gravity (8 mg MMA/kg/day) were 

observed in dogs administered MMA via capsule for 52 weeks (Waner and Nyska 1988). However, these 

effects may be indicative of dehydration due to diarrhea rather than a direct effect on the kidney. In a 

2-year study in rats (Arnold et al. 2003), an increase in the severity of progressive glomerulonephropathy 

was observed in females at 33.9 mg MMA/kg/day. Hydronephrosis, pyelonephritis, cystitis, and 

decreases in urine volume and pH were also observed 72.4 mg MMA/kg/day; however, the investigators 

noted that these lesions probably resulted from urinary tract obstruction, which was secondary to 

peritonitis caused by gastrointestinal tract ulcerations. An increased incidence of progressive 

glomerulonephropathy was also observed in male mice exposed to ≥6.0 mg MMA/kg/day in the diet for 

2 years (Arnold et al. 2003; incidence data reported in Gur et al. 1991); the investigators (Gur et al. 1991) 

noted that the kidney lesions were consistent with the normal spectrum of spontaneous lesions and that 

there were no differences in character or severity of the lesions between the different groups. 

Exposure to DMA has resulted in kidney effects in rats and mice exposed to at least 3.1 or 37 mg 

DMA/kg/day, respectively; no renal effects were observed in dogs exposed to doses as high as 40 mg 

As/kg/day for 52 weeks (Zomber et al. 1989). In rats, the renal damage is characterized by increased 

urine volume and pH, decreased urine osmolarity and electrolyte (sodium, potassium, chlorine) levels, 

increased urinary calcium levels, and increased organ weight, nephrocalcinosis, and necrosis in the renal 

papillae and/or cortex; an increase in water consumption is also typically observed. The LOAELs for 

these effects are 5–57 mg DMA/kg/day in intermediate-duration studies (Arnold et al. 1999; Crown et al. 

1987; Murai et al. 1993) and 3.1 mg DMA/kg/day in a chronic-duration study (Arnold et al. 2006). 

Another study did not find renal effects in rats exposed to 16.5 mg DMA/kg/day (Rubin et al. 1989). This 

study involved exposure to Sprague-Dawley rats compared to Fischer 344 rats used in the studies with 
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positive results; it is not known if this reflects a difference in strain sensitivity. In mice, progressive 

glomerulonephropathy was observed at 37 mg DMA/kg/day and nephrocalcinosis was observed at 94 mg 

DMA/kg/day (Arnold et al. 2006). 

Increased kidney weights and minimal tubular epithelial cell degeneration, tubular casts, and focal 

mineralization were observed in rats exposed to 32 mg/kg/day roxarsone for 13 weeks (NTP 1989b). No 

adverse effects were observed in rats at doses as high as 20 mg/kg/day (Kerr et al. 1963; NTP 1989b) for 

13 weeks or 10 mg/kg/day for 2 years (NTP 1989b; Prier et al. 1963). No adverse renal effects have been 

observed in mice exposed to roxarsone doses as high as 136 mg/kg/day (NTP 1989b) or 43 mg/kg/day 

(NTP 1989b; Prier et al. 1963) for intermediate or chronic durations, respectively, or in dogs exposed to 

5 mg/kg/day for a chronic duration (Prier et al. 1963). 

Damage to the urinary bladder has been observed in several studies in which rats were exposed to DMA. 

The observed effects include altered bladder cell surface characteristics in rats exposed to 11 mg 

DMA/kg/day in the diet for 2 weeks (Cohen et al. 2001), increased bladder weight and regenerative 

proliferation (measured as an increase in BrdU labeling) in bladder epithelium at 5 mg DMA/kg/day for 

10 weeks (Arnold et al. 1999), necrosis of bladder epithelium at 10 mg DMA/kg/day for 10 weeks 

(Arnold et al. 1999), nodular or papillar hyperplasia at 3.4 mg DMA/kg/day for 2 years (Wei et al. 2002), 

and urothelial vacuolar degeneration and hyperplasia of urothelial cells at 3.1 mg DMA/kg/day for 2 years 

(Arnold et al. 2006). Vacuolization of the urothelium in the urinary bladder have also been observed in 

mice exposed to 7.8 mg DMA/kg/day in the diet for 2 years (Arnold et al. 2006). Inconsistent results 

were found for MMA. Hyperplasia was observed in the bladders of rats exposed to 1 mg As/kg/day as 

MMA in drinking water for 2 years (Shen et al. 2003), but bladder effects were not observed in another 

2-year study (Arnold et al. 2003) in which rats were exposed to doses as high as 34.8 mg As/kg/day as 

MMA in the diet. No urinary bladder effects were found in rats and mice exposed to 64 or 

136 mg/kg/day roxarsone for 13 weeks (NTP 1989b) or 4 or 43 mg/kg/day roxarsone for 2 years (NTP 

1989b). 

Endocrine Effects. 

Inorganic Arsenicals. Very little has been written about the effects of oral exposure to arsenic on 

endocrine glands. In a report of the autopsies of five children who died in Chile after chronic exposure to 

arsenic in the drinking water, arterial thickening in the pancreas was noted (Rosenberg 1974). An 

association has been demonstrated between exposure to arsenic in drinking water and an increased 
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incidence of diabetes mellitus (Lai et al. 1994; Rahman et al. 1998; Tsai et al. 1999; Tseng et al. 2000; 

Wang et al. 2003), although dose-response relationships are not available. 

Exposure of rats to 2.3 mg As/kg/day as arsenic trioxide for 30 days resulted in reductions in the number 

of islet cells in the pancreas, as well as significant reductions in pancreatic superoxide dismutase (SOD) 

and catalase enzyme levels and increases in the production of nitric oxide and malondialdehyde 

(Mukherjee et al. 2004). 

Organic Arsenicals. No studies of effects of organic arsenic compounds on endocrine glands in humans 

were found. Hypertrophy of thyroid epithelium was observed in rats exposed to 33.9 mg MMA/kg/day in 

the diet for 2 years (Arnold et al. 2003), 4.0 mg DMA/kg/day in the diet for 13 weeks (Crown et al. 

1987), 16.5 mg DMA/kg/day in the diet for at least 10 weeks (Rubin et al. 1989), and 7.8 mg 

DMA/kg/day in the diet for 2 years (Arnold et al. 2006). No other biologically significant effects were 

observed in other endocrine tissues following exposure to MMA or DMA. No adverse effects were seen 

in the adrenal or pituitary glands, thyroid, or pancreas after intermediate or chronic exposure of rats (20– 

64 or 4 mg/kg/day, respectively) and mice (136 or 43 mg/kg/day, respectively) to roxarsone (NTP 1989b). 

Dermal Effects. 

Inorganic Arsenicals. One of the most common and characteristic effects of arsenic ingestion is a pattern 

of skin changes that include generalized hyperkeratosis and formation of hyperkeratotic warts or corns on 

the palms and soles, along with areas of hyperpigmentation interspersed with small areas of 

hypopigmentation on the face, neck, and back. These and other dermal effects have been noted in a large 

majority of human studies involving repeated oral exposure (e.g., Ahmad et al. 1997, 1999b; Ahsan et al. 

2000; Bickley and Papa 1989; Borgoño and Greiber 1972; Borgoño et al. 1980; Cebrián et al. 1983; 

Chakraborti et al. 2003a, 2003b; Chakraborty and Saha 1987; Foy et al. 1992; Franklin et al. 1950; 

Franzblau and Lilis 1989; Guha Mazumder et al. 1988, 1998a, 1998b, 1998c; Guo et al. 2001a; Haupert et 

al. 1996; Huang et al. 1985; Lander et al. 1975; Liu et al. 2002; Lüchtrath 1983; Milton et al. 2004; 

Mizuta et al. 1956; Morris et al. 1974; Nagai et al. 1956; Piontek et al. 1989; Rosenberg 1974; Saha and 

Poddar 1986; Silver and Wainman 1952; Szuler et al. 1979; Tay and Seah 1975; Tseng et al. 1968; Wade 

and Frazer 1953; Wagner et al. 1979; Wong et al. 1998a, 1998b; Zaldívar 1974, 1977). In cases of lowlevel chronic exposure (usually from water), these skin lesions appear to be the most sensitive indication 

of effect, so this end point is considered to be the most appropriate basis for establishing a chronic oral 

MRL. This is supported by the finding that other effects (hepatic injury, vascular disease, neurological 
ARSENIC 176 

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effects) also appear to have similar thresholds. As shown in Table 3-3 and Figure 3-3, numerous studies 

in humans have reported dermal effects at chronic dose levels generally ranging from about 0.01 to 

0.1 mg As/kg/day (Ahmad et al. 1997; Bickley and Papa 1989; Borgoño and Greiber 1972; Borgoño et al. 

1980; Cebrián et al. 1983; Chakraborty and Saha 1987; Foy et al. 1992; Franklin et al. 1950; Guha 

Mazumder et al. 1988; Huang et al. 1985; Lüchtrath 1983; Piontek et al. 1989; Silver and Wainman 1952; 

Tseng et al. 1968; Zaldívar 1974, 1977). However, in a study with detailed exposure assessment, all 

confirmed cases of skin lesions ingested water containing >100 μg/L arsenic (approximately 0.0037 mg 

As/kg/day) and the lowest known peak arsenic concentration ingested by a case was 0.115 μg/L 

(approximately 0.0043 mg As/kg/day) (Haque et al. 2003). Another large study reported increased 

incidence of skin lesions associated with estimated doses of 0.0012 mg As/kg/day (0.023 mg As/L 

drinking water) (Ahsan et al. 2006). Several epidemiological studies of moderately sized populations 

(20–200 people) exposed to arsenic through drinking water have detected no dermal or other effects at 

average chronic doses of 0.0004–0.01 mg As/kg/day (Cebrián et al. 1983; EPA 1981b; Guha Mazumder 

et al. 1988; Harrington et al. 1978; Valentine et al. 1985), and one very large study detected no effects in 

any person at an average total daily intake (from water plus food) of 0.0008 mg As/kg/day (Tseng et al. 

1968). This value has been used to calculate a chronic oral MRL for inorganic arsenic of 

0.0003 mg/kg/day, as described in footnote c in Table 3-3. 

Another prominent dermal effect associated with chronic ingestion of inorganic arsenic is skin cancer. As 

discussed in greater detail in Section 3.2.2.7 (below), some of these skin cancers may evolve from the 

hyperkeratotic corns or warts, while the areas of altered pigmentation are not considered to be 

precancerous (EPA 1988d). 

Dermal lesions similar to those observed in humans have not been noted in oral exposure studies in 

monkeys (Heywood and Sortwell 1979), dogs (Byron et al. 1967), or rodents (Schroeder et al. 1968). 

However, a hyperplastic response to oral arsenic exposure was reported in arsenic-exposed mice 

(Rossman et al. 2004). 

Organic Arsenicals. No studies were located regarding dermal effects in humans after oral exposure to 

organic arsenicals. No gross or histological skin alterations were observed in rats or mice following 

intermediate- or chronic-duration exposure to MMA (Arnold et al. 2003; as reported in Crown et al. 1990; 

Gur et al. 1991), DMA (Arnold et al. 2006; as reported in Gur et al. 1989a, 1989b), or roxarsone (NTP 

1989b) 
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Ocular Effects. 

Inorganic Arsenicals. Periorbital swelling was reported in people drinking contaminated well water at an 

approximate dose of 0.2 mg As/kg for 1 week (Armstrong et al. 1984). Facial edema, generally involving 

the eyelids, was a prominent feature of arsenic poisoning among 220 cases associated with an episode of 

arsenic contamination of soy sauce in Japan (Mizuta et al. 1956). Exposure was to an estimated dose of 

0.05 mg/kg/day and lasted for up to 2–3 weeks. The edema developed soon after the initial exposure and 

then subsided. This effect forms the basis (in part) for the acute oral MRL of 0.005 mg/kg/day for 

inorganic arsenic, as described in footnote b in Table 3-3. Nemec et al. (1998) noted the appearance of 

dried red material around the eyes of mice receiving daily oral doses of 24 mg As/kg as arsenic acid for 

10 days during gestation. 

Organic Arsenicals. No studies were located regarding ocular effects in humans or animals after oral 

exposure to organic arsenicals. No gross or histological alterations in the eye were observed in rats or 

mice following intermediate- or chronic-duration exposure to MMA (Arnold et al. 2003; as reported in 

Crown et al. 1990; Gur et al. 1991), DMA (Arnold et al. 2006; as reported in Gur et al. 1989a, 1989b), or 

roxarsone (NTP 1989b). 

Body Weight Effects. 

Inorganic Arsenicals. A 41-year old woman exposed to arsenic in the drinking water for 4 months at an 

approximate dose of 0.06 mg As/kg/day reported losing 40 pounds (18 kg) of body weight before seeking 

treatment (Wagner et al. 1979). Weight loss was also among the effects observed in a series of 

475 chronic arsenism patients hospitalized in Antofagasto, Chile after receiving approximate doses of 

0.02 mg As/kg/day in the drinking water for an unspecified number of years (Zaldívar 1974). 

Reductions in body weight gain are commonly seen in animal studies of ingested arsenic. In pregnant 

rats, body weight gain was reduced by gavage treatment with 23 mg As/kg/day as arsenic trioxide on 

day 9 of gestation (NOAEL=15 mg As/kg/day, Stump et al. 1999), and by repeated gavage treatment with 

8 mg As/kg/day as arsenic trioxide from 2 weeks prior to mating through gestation (NOAEL=4 mg 

As/kg/day, Holson et al. 2000). Exposure of rats by gavage to 26.6 mg As/kg/day as sodium arsenite, but 

not 13.3 mg As/kg/day or lower, 5 days/week for 4 weeks resulted in a significant decrease in body 

weight (Schulz et al. 2002). In 6-week rat studies, body weight gain was decreased at 11–12 mg 

As/kg/day, but not at 6–9 mg As/kg/day (Brown et al. 1976; Fowler et al. 1977). In a 12-week oral 
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3. HEALTH EFFECTS 

gavage study, rats dosed with 1.5 mg/kg/day sodium arsenite had a median final body weight 18% lower 

than controls Dhar et al. (2005). A 60-day rat study with sodium arsenite in the drinking water reported a 

13% reduction in final body weight in rats dosed with approximately 0.02 mg As/kg/day (Bashir et al. 

2006). In chronic rat studies of arsenate and arsenite, body growth decreases were found at doses as low 

as 2 mg As/kg/day in feeding studies (Byron et al. 1967; Kroes et al. 1974), while rats exposed to lower 

levels of sodium arsenite in the drinking water (0.6 mg As/kg/day) throughout their lifetimes grew 

normally (Schroeder et al. 1968). Rats given a single oral dose of 100 mg As/kg as GaAs exhibited a 

15% reduction in body weight compared to controls 7 days after exposure (Flora et al. 1998). Body 

weight gain was decreased in mice at 24 mg As/kg/day in a gestation exposure study (Nemec et al. 1998), 

10 mg As/kg/day in a 6-week study (Fowler and Woods 1979), and 1 mg As/kg/day in a 2-year study 

(Schroeder and Balassa 1967). Growth was unaffected in mice that received 12 mg As/kg/day in the 

gestation exposure study (Nemec et al. 1998), 5 mg As/kg/day in the 6-week study (Fowler and Woods 

1979), or 0.7–0.8 mg As/kg/day in 1–3 month arsenate drinking water studies (Healy et al. 1998). Dogs 

chronically treated with 2.4 mg As/kg/day as sodium arsenite lost 44–61% of their starting body weight 

and died, while lower doses had no effect on growth (Byron et al. 1967). Weight depression was also 

reported in dogs chronically treated with 2.4 mg As/kg/day as sodium arsenate (Byron et al. 1967). Feed 

consumption and body weight gain were significantly reduced in a dose-related manner in dogs fed 1.5 or 

1.9 mg As/kg/day as sodium arsenite in the diet (Neiger and Osweiler 1989). Dogs in the high-dose 

group lost 25% of their body weight over the 17-week study period. Pair-fed controls lost weight at the 

same rate as high-dose dogs, showing that the effect on body weight was due to reduced feed 

consumption, rather than a direct effect of arsenic. 

Organic Arsenicals. No studies were located regarding body weight effects in humans after oral 

exposure to organic arsenicals. In animal studies of organic arsenicals, decreases in body weight gain 

were observed in rats and mice after acute, intermediate, and chronic duration exposure to MMA (Arnold 

et al. 2003; Waner and Nyska 1988), DMA (Murai et al. 1993), and roxarsone (NTP 1989b); decreases in 

body weight gain have also been reported in pregnant rats and rabbits exposed to MMA (Irvine et al. 

2006) or DMA (Irvine et al. 2006; Rogers et al. 1981). For MMA, the decreases in body weight gain 

were observed following intermediate-duration exposure of rats and dogs to 106.9 or 8 mg MMA/kg/day 

(Arnold et al. 2003; Waner and Nyska 1988), respectively, and following chronic-duration exposure of 

rats, mice, and dogs to 25.7, 67.1, or 8 mg MMA/kg/day, respectively (Arnold et al. 2003; Waner and 

Nyska 1988). The decreases in body weight gain occurred at doses that were associated with diarrhea and 

histological alterations in the gastrointestinal tract (Arnold et al. 2003; Waner and Nyska 1988). One 

DMA study in nonpregnant animals reported decreases in body weight gain in rats administered 57 mg 
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3. HEALTH EFFECTS 

DMA/kg/day via gavage 5 days/week for 4 weeks (Murai et al. 1993); other DMA studies have not 

reported decreases in body weight gain in rats following exposure to 11 mg DMA/kg/day for acute 

durations (Cohen et al. 2001), 3.7–60 mg DMA/kg/day for intermediate durations (Arnold et al. 1999; 

Crown et al. 1987; Rubin et al. 1989; Siewicki 1981; Wanibuchi et al. 1996; Yamamoto et al. 1995), or 

0.77 mg DMA/kg/day for chronic durations (Arnold et al. 2006). No alterations in body weight gain were 

observed in mice exposed to 94 mg DMA/kg/day for 2 years (Arnold et al. 2006). The lowest doses of 

roxarsone to produce a decrease in growth were 32 and 16 mg/kg/day in rats following acute- or 

intermediate-duration exposure, respectively, and 168 and 136 mg/kg/day in mice following acute or 

intermediate exposure (NTP 1989b); at the highest dose tested in chronic studies, no significant 

alterations in body weight gain were observed in rats at 4 mg/kg/day or in mice at 43 mg/kg/day (NTP 

1989b). 

3.2.2.3 Immunological and Lymphoreticular Effects 

Inorganic Arsenicals. No studies were located regarding immunological and lymphoreticular effects in 

humans after oral exposure to inorganic arsenicals. No evidence of immunosuppression was detected in 

mice exposed to arsenate at levels up to 100 ppm (20 mg As/kg/day) in drinking water (Kerkvliet et al. 

1980). This NOAEL is shown in Table 3-3 and Figure 3-3. Gallium arsenide at doses of 52–260 mg 

As/kg/day produced significant, dose-related decreases in relative spleen weight, spleen cellularity, 

humoral immune response (antibody forming cell response to sheep RBC), and delayed type 

hypersensitivity in rats (Flora et al. 1998). However, it is not clear to what extent these effects are due to 

the arsenic moiety. 

Organic Arsenicals. No studies were located regarding immunological and lymphoreticular effects in 

humans or animals after oral exposure to organic arsenicals. No histological alterations were observed in 

immunological or lymphoreticular tissues following intermediate-duration exposure of rats to 43.2 mg 

DMA/kg/day in the diet (Crown et al. 1987) or rats and mice to 18.23 or 38.7 mg As/kg/day as roxarsone, 

respectively (NTP 1989b) or following chronic-duration exposure of rats and mice to 72.4 or 67.1 mg 

MMA/kg/day (Arnold et al. 2003), 7.8 or 94 mg DMA/kg/day (Arnold et al. 2006), or 4 or 43 mg/kg/day 

roxarsone (NTP 1989b). No studies examined immune function following oral exposure to organic 

arsenicals. 
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3. HEALTH EFFECTS 

3.2.2.4 Neurological Effects 

Inorganic Arsenicals. A large number of epidemiological studies and case reports indicate that ingestion 

of inorganic arsenic can cause injury to the nervous system. Acute, high-dose exposures (2 mg As/kg/day 

or above) often lead to encephalopathy, with signs and symptoms such as headache, lethargy, mental 

confusion, hallucination, seizures, and coma (Armstrong et al. 1984; Bartolome et al. 1999; Civantos et 

al. 1995; Cullen et al. 1995; Danan et al. 1984; Fincher and Koerker 1987; Levin-Scherz et al. 1987; 

Quatrehomme et al. 1992; Uede and Furukawa 2003; Vantroyen et al. 2004). Repeated exposures to 

lower levels (0.03–0.1 mg As/kg/day) are typically characterized by a symmetrical peripheral neuropathy 

(Chakraborti et al. 2003a, 2003b; Foy et al. 1992; Franzblau and Lilis 1989; Guha Mazumder et al. 1988; 

Hindmarsh et al. 1977; Huang et al. 1985; Lewis et al. 1999; Mizuta et al. 1956; Muzi et al. 2001; Silver 

and Wainman 1952; Szuler et al. 1979; Wagner et al. 1979). This neuropathy usually begins as numbness 

in the hands and feet, but later may develop into a painful "pins and needles" sensation. Both sensory and 

motor nerves are affected, and muscle weakness often develops, sometimes leading to wrist-drop or 

ankle-drop (Chhuttani et al. 1967; Heyman et al. 1956). Diminished sensitivity to stimulation and 

abnormal patellar reflexes have also been reported (Mizuta et al. 1956). Histological examination of 

nerves from affected individuals reveals a dying-back axonopathy with demyelination (Goebel et al. 

1990; Hindmarsh and McCurdy 1986). Some recovery may occur following cessation of exposure, but 

this is a slow process and recovery is usually incomplete (Fincher and Koerker 1987; Le Quesne and 

McLeod 1977; Murphy et al. 1981). Peripheral neuropathy is also sometimes seen following acute highdose exposures, with or without the previously described encephalopathy (Armstrong et al. 1984; Baker et 

al. 2005; Fincher and Koerker 1987; Goebel et al. 1990; Hantson et al. 1996; Kamijo et al. 1998). 

Neurological effects were not generally found in populations chronically exposed to doses of 0.006 mg 

As/kg/day or less (EPA 1981b; Harrington et al. 1978; Hindmarsh et al. 1977), although fatigue, 

headache, dizziness, insomnia, nightmare, and numbness of the extremities were among the symptoms 

reported at 0.005, but not 0.004 mg As/kg/day in a study of 31,141 inhabitants of 77 villages in Xinjiang, 

China (Lianfang and Jianzhong 1994), and depression was reported in some Wisconsin residents exposed 

to 2–10 μg As/L in the drinking water for 20 years or longer (Zierold et al. 2004). 

There is emerging evidence suggesting that exposure to arsenic may be associated with intellectual 

deficits in children. For example, Wasserman et al. (2004) conducted a cross-sectional evaluation of 

intellectual function in 201 children 10 years of age whose parents were part of a larger cohort in 

Bangladesh. Intellectual function was measured using tests drawn from the Wechsler Intelligence Scale 

for Children; results were assessed by summing related items into Verbal, Performance, and Full-Scale 
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3. HEALTH EFFECTS 

raw scores. The mean arsenic concentration in the water was 0.118 mg/L. The children were divided into 

four exposure groups, representing <5.5, 5.6–50, 50–176, or 177–790 μg As/L drinking water. After 

adjustment for confounding factors, a dose-related inverse effect of arsenic exposure was seen on both 

Performance and Full-Scale subset scores; for both end points, exposure to ≥50 μg/L resulted in 

statistically significant differences (p<0.05) relative to the lowest exposure group (<5.5 μg/L). In a later 

report, the same group of investigators examined 301 6-year-old children from the same area (Wasserman 

et al. 2007). In this case, the children were categorized into the following quartiles based on water arsenic 

concentration: 0.1–20.9, 21–77.9, 78–184.9, and 185–864 μg/L. After adjustment for water Mn, blood 

lead, and sociodemographic features known to contribute to intellectual function, water arsenic was 

significantly negatively associated with both Performance and Processing speed raw scores. Analyses of 

the dose-response showed that compared to the first quartile, those in the second and third categories had 

significantly lower Performance raw scores (p<0.03 and p=0.05, respectively). Those in the fourth 

category had marginally significantly lower Full-Scale and Processing Speed raw scores. It should be 

mentioned, however, that in general, arsenic in the water explained <1% of the variance in test scores. 

Water arsenic made no contribution to IQ outcomes. A study of 351 children age 5–15 years from West 

Bengal, India, found significant associations between urinary arsenic concentrations and reductions in 

scores of tests of vocabulary, object assembly, and picture completion; the magnitude of the reductions 

varied between 12 and 21% (von Ehrenstein et al. 2007). In this cohort, the average lifetime peak arsenic 

concentration in well water was 0.147 mg/L. However, no clear pattern was found for increasing 

categories of peak arsenic water concentrations since birth and children’s scores in the various 

neurobehavioral tests conducted. Furthermore, using peak arsenic as a continuous variable in the 

regression models also did not support an adverse effect on the tests results. Exposure to arsenic in utero 

also did not suggest an association with the tests scores. Von Ehrestein et al. (2007) concluded that the 

study provided little evidence for an effect of long-term arsenic concentrations in drinking water and that 

the lack of findings with past exposures via drinking water may be due to incomplete assessment of past 

exposure, particularly exposure originating from food. Wasserman’s results are consistent with those of 

ecological studies in children in Taiwan (Tsai et al. 2003) and in China (Wang et al. 2007). In the former, 

adolescents exposed to low (0.0017–0.0018 mg As/kg/day; n=20) levels of inorganic arsenic in the 

drinking water showed decreased performance in the switching attention task, while children in the high 

exposure group (0.0034–0.0042 mg As/kg/day; n=29) showed decreased performance in both the 

switching attention task and in tests of pattern memory, relative to unexposed controls (n=60). In the 

study in China (age 8– 12 years), 87 children whose mean arsenic concentration in the drinking water was 

0.190 mg/L had a mean IQ score of 95 compared with 101 for children (n=253) with 0.142 mg/L arsenic 

in the water and 105 for control children (n=196) with 0.002 mg/L arsenic in the drinking water (Wang et 
ARSENIC 182 

3. HEALTH EFFECTS 

al. 2007). The differences in IQ scores between the two exposure groups and the control group were 

statistically significant. 

Neurological effects have also been observed in animal studies. Rodriguez et al. (2001) evaluated 

neurobehavioral changes in male Sprague-Dawley rats exposed to 0, 5, 10, or 20 mg As/kg/day as sodium 

arsenite by gavage for 2 or 4 weeks; significant effects were seen in spontaneous locomotor activity and 

the food pellet manipulation test in the high-dose animals, while no effects were seen in the low- or middose rats. Decreased performance in open field tests were also seen in rats exposed to 26.6 mg 

As/kg/day, but not to 13.3 mg/kg/day or less, as sodium arsenite for 4 weeks (Schulz et al. 2002); 

curiously, the behavioral changes were no longer present at 8 and 12 weeks of exposure, which may 

suggest an adaptive response. Heywood and Sortwell (1979) reported salivation and uncontrolled head 

shaking in two monkeys given several doses of 6 mg As/kg/day as arsenate, while no such effects were 

noted in monkeys given 3 mg As/kg/day for 2 weeks. Nemec et al. (1998) observed ataxia and 

prostration in pregnant female rabbits treated with 1.5 mg As/kg/day repeatedly during gestation, but not 

in rabbits treated with 0.4 mg As/kg/day. Some changes in levels of neurotransmitters (dopamine, 

norepinephrine, and 5-hydroxytryptamine) were seen in rats exposed to 2.3 mg As/kg/day as sodium 

arsenite and guinea pigs exposed to 1.7 mg As/kg/day as sodium arsenite in the drinking water for 

16 weeks (Kannan et al. 2001) or in rats exposed to 0.14 mg As/kg/day as sodium arsenite by gavage for 

28 days (Chattopadhyay et al. 2001), but the functional significance of these changes is not clear. 

The highest NOAEL values and all reliable LOAEL values for neurological effects from inorganic arsenic 

in each species and duration category are recorded in Table 3-3 and plotted in Figure 3-3. 

Organic Arsenicals. Numbness and tingling of the fingertips, toes, and circumoral region were reported 

by a women exposed to an unspecified amount of organic arsenic in bird’s nest soup. Discontinuation of 

exposure resulted in the disappearance of symptoms (Luong and Nguyen 1999). Decreased absolute 

brain weights were seen in male rats exposed to 25.7 mg MMA/kg/day and female rats exposed to 

≥33.9 mg MMA/kg/day, but decreased body weight also occurred at these exposure levels, and relative 

brain weights were increased in the males at 25.7 mg MMA/kg/day and the females at ≥33.9 mg 

MMA/kg/day in this study (Arnold et al. 2003). No neurological clinical signs or brain lesions were 

observed following chronic exposure of rats to 72.4 mg MMA/kg/day or mice to 67.1 mg MMA/kg/day 

(Arnold et al. 2003). Decreased spontaneous motility, increased startle response, and ataxia were 

observed in mice receiving a single gavage dose of 1,757 mg DMA/kg/day (Kaise et al. 1989); no other 

evidence (clinical signs or histological alterations) were observed in chronic studies of DMA in which 
ARSENIC 183 

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rats and mice were exposed to 7.8 or 94 mg DMA/kg/day, respectively (Arnold et al. 2006). Two studies 

in pigs indicate that repeated oral doses of roxarsone (6.3–20 mg/kg/day for 1 month) can cause 

significant neurotoxicity (Edmonds and Baker 1986; Kennedy et al. 1986; Rice et al. 1985). The main 

signs were time-dependent degenerations of myelin and axons (Kennedy et al. 1986; Rice et al. 1985). 

Evidence of neurological effects (hyperexcitability, ataxia, trembling) was noted in some rat and mouse 

studies (Kerr et al. 1963; NTP 1989b). Reliable NOAELs and LOAELs are presented in Tables 3-4, 3-5, 

and 3-6, and Figures 3-4, 3-5, and 3-6. 

3.2.2.5 Reproductive Effects 

Inorganic Arsenicals. Exposure to arsenic in drinking water has been associated with adverse 

reproductive outcomes in some studies. For example, a study of 96 women in Bangladesh who had been 

drinking water containing ≥0.10 mg As/L (approximately 0.008 mg As/kg/day) for 5–10 years reported a 

significant increase in spontaneous abortions (p=0.008), stillbirth (p=0.046), and preterm birth (p=0.018) 

compared to a nonexposed group (Ahmad et al. 2001). Similar results were reported by Milton et al. 

(2005) who found a significant association between concentrations of arsenic in the water >0.05 mg/L 

(approximately 0.006 mg As/kg/day) and spontaneous abortion (odds ratio [OR]=2.5; 95% CI=1.5–4.3) in 

a study of 533 women, also from Bangladesh. A study of 202 women from West Bengal, India, reported 

that exposure to arsenic concentrations of arsenic ≥0.2 mg/L in drinking water (approximately 0.02 mg 

As/kg/day) during pregnancy were associated with a 6-fold increased risk of stillbirth (OR=6.1; 95% 

CI=1.54–24.0) after adjustment for confounders (von Ehrenstein et al. 2006). No association was found 

between arsenic exposure and risk of spontaneous abortion (OR=1.01; 95% CI=0.73–10.8). An earlier 

study of 286 women in the United States also found no significant association between arsenic in the 

drinking water (0.0016 mg/L; approximately 0.00005 mg As/kg/day) and spontaneous abortion (OR=1.7; 

95% CI=0.7–4.2) (Aschengrau et al. 1989). 

Lugo et al. (1969) reported a case of a 17-year-old mother who ingested inorganic arsenic (Cowley's Rat 

and Mouse Poison) at week 30 of pregnancy. Twenty-four hours after ingestion of approximately 30 mL 

of arsenic trioxide (0.39 mg As/kg), she was admitted for treatment of acute renal failure. She went into 

labor and delivered a live female infant weighing 2 pounds, 7 ounces with a 1-minute Apgar score of 4. 

The infant's clinical condition deteriorated and she died at 11 hours of age. 

Reproductive performance was not affected in female rats that received gavage doses of 8 mg As/kg/day 

(as As2O3) from 14 days prior to mating through gestation day 19 (Holson et al. 2000). Reproductive 
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indices that were evaluated included the precoital interval (time to mating), mating index (percentage of 

rats mated), and fertility index (percentage of matings resulting in pregnancy). In a 3-generation study in 

mice given sodium arsenite in drinking water at an average dose of 1 mg As/kg/day, there was a 

significant increase in the incidence of small litters and a trend toward a decreased number of pups per 

litter in all three generations of the treated group (Schroeder and Mitchener 1971). This finding is 

consistent with the results of developmental toxicity studies reported in Section 3.2.2.6. Female rats 

exposed to 0.24 mg As/kg/day (as arsenite) for 28 days showed changes in several reproductive system 

end points, including decreases in wet weights of the ovary and uterus, inhibition of steroidogenic 

enzymes, decreased ovarian and uterine peroxidase activities, and decreased estradiol levels relative to 

controls (Chattopadhyay et al. 2001). NOAEL and LOAEL values from these studies are shown in 

Table 3-3 and Figure 3-3. 

Organic Arsenicals. No studies were located regarding reproductive effects in humans after oral 

exposure to organic arsenicals. No histological alterations in male or female reproductive tissues were 

observed in laboratory animals following exposure to MMA (Arnold et al. 2003), DMA (Arnold et al. 

2006), or roxarsone (NTP 1989b) and no alterations in sperm parameters were observed in male rats 

exposed to 76 mg MMA/kg/day for at least 14 weeks (Schroeder 1994). However, some functional 

alterations have been reported in animals exposed to MMA or DMA. A decrease in estrus was observed 

in dogs exposed to 35 mg MMA/kg/day for 52 weeks (Waner and Nyska 1988); decreases in body weight 

gain (terminal body weight was 59% lower than controls) were also observed at this dose level and the 

effect may have been secondary to systemic toxicity. Decreases in pregnancy rate and male fertility index 

were observed in F0 and F1 rats exposed to 76 mg MMA/kg/day for 14 weeks prior to mating and during 

the mating, gestation, and lactation periods (Schroeder 1994). In the F0 animals, the pregnancy rate and 

male fertility index were not statistically different from controls; however, the values were below 

historical controls and the investigators considered the effect to be treatment-related. In the F1 animals, 

the male fertility index was statistically different from controls but the pregnancy rate was not; both 

parameters were within the range found in historical controls, but the investigators considered the effect 

to be treatment-related due to the consistency of the findings in the F0 and F1 animals. Impaired fertility, 

as evidenced by a decreased number of litters, was observed in male mice dosed with MSMA 

(119 mg/kg/day) during a 19-day mating period with unexposed females (Prukop and Savage 1986); the 

poor reporting of the study protocol and results precludes drawing conclusions from this study. An 

increase in the number of does with aborted fetuses was observed in rabbits exposed to 48 mg 

DMA/kg/day as DMA (Irvine et al. 2006); severe maternal toxicity (weight loss, reduced food intake, and 
ARSENIC 185 

3. HEALTH EFFECTS 

diarrhea) was also observed at this dose level. No reproductive effects were observed in a 2-generation 

rat study in which rats were exposed to 16.5 mg DMA/kg/day (Rubin et al. 1989). 

3.2.2.6 Developmental Effects 

Inorganic Arsenicals. Whether ingestion of inorganic arsenic may cause developmental effects in 

humans has not been extensively investigated. Lugo et al. (1969) reported a case of a mother who 

ingested inorganic arsenic (Cowley's Rat and Mouse Poison) at 30 weeks of gestation. Twenty-four hours 

after ingestion, she went into labor and delivered a live female infant weighing 2 pounds, 7 ounces with a 

1-minute Apgar score of 4. The infant's clinical condition deteriorated with frequent episodes of apnea 

and bradycardia; subsequent venous blood gas determinations documented hypoxia, hypercapnea, and 

acidosis. The infant died at 11 hours of age. Autopsy performed 8 hours after death showed organ 

immaturity, generalized petechial hemorrhages, and hyaline membrane disease. Severe intra-alveolar 

pulmonary hemorrhage was remarkable. High arsenic levels were found in the infant’s liver, kidney, and 

brain, demonstrating easy passage of inorganic arsenic across the placenta. The authors considered most 

of the findings in the neonate to be attributable to immaturity, but suggested that arsenic may have played 

a role in the severe intra-alveolar hemorrhaging that contributed to death. 

Chronic exposure of women to arsenic in the drinking water has been associated with infants with low 

birth weights in Taiwan (Yang et al. 2003) and Chile (Hopenhayn et al. 2003a). Similar associations have 

been made between late fetal mortality, neonatal mortality, and postneonatal mortality and exposure to 

high levels of arsenic in the drinking water (up to 0.86 mg/L during over a decade), based on comparisons 

between subjects in low- and high-arsenic areas of Chile (Hopenhayn-Rich et al. 2000). More recently, 

von Ehrenstein et al. (2006) reported no significant association between exposure to concentrations of 

≥0.1 mg/L arsenic in drinking water (approximately 0.008 mg As/kg/day) (n=117; 29 women were 

exposed to ≥0.5 mg/L) and increased risk for neonatal death or infant mortality during the first year of life 

in a study of a population in West Bengal, India. The same group of investigators reported significantly 

increased SMRs for lung cancer and bronchiectasis among subjects in a city in Chile who had probable 

exposure in utero (maternal exposure) or during childhood to high levels of arsenic (near 0.9 mg/L) in the 

drinking water (Smith et al. 2006). For those exposed in early childhood, the SMR for lung cancer was 

7.0 (95% CI=5.4–8.9, p<0.001) and for bronchiecstasis 12.4 (95% CI=3.3–31.7, p<0.001). For those 

born during the high-exposure period, the corresponding SMRs were 6.1 (95% CI=3.5–9.9, p<0.001) and 

46.2 (95% CI=21.1–87.7, p<0.001). The mortality data analyzed were for the age range 30–49 years. 
ARSENIC 186 

3. HEALTH EFFECTS 

No overall association between arsenic in drinking water and congenital heart defects was detected in a 

case-control study in Boston (Zierler et al. 1988), although an association with one specific lesion 

(coarctation of the aorta) was noted (OR=3.4, 95% CI=1.3–8.9). A study of 184 women with neural tube 

defects in the offspring living in a Texas county bordering Mexico found that exposure to levels of 

arsenic in the drinking water >0.010 mg/L (range or upper limit not specified) did not significantly 

increase the risk for neural tube defects (OR=2.0, 95% CI=0.1–3.1) (Brender et al. 2006). 

Studies in animals, however, suggest that ingested inorganic arsenic may produce developmental effects 

at high doses that also produce overt maternal toxicity. Rats treated with a single gavage dose of 23 mg 

As/kg as arsenic trioxide on day 9 of gestation had a significant increase in postimplantation loss and a 

decrease in viable fetuses per litter, while those treated with 15 mg As/kg showed no effects (Stump et al. 

1999). Rats treated by daily gavage with 8 mg As/kg/day starting 14 days before mating and continuing 

through gestation had significantly reduced fetal body weights and significantly increased incidences of 

several skeletal variations (unossified sternebrae #5 or #6, slight or moderate sternebrae malalignment, 

7th cervical ribs) that the researchers considered to be consequences of developmental growth retardation 

(Holson et al. 2000). No developmental effects were found at 4 mg As/kg/day in this study. Exposure of 

rats to 2.93–4.20 mg As/kg/day throughout gestation and for 4 months postnatally resulted in alterations 

in neurobehavioral parameters in the offspring, including increased spontaneous locomotor activity and 

number of errors in a delayed alternation task; maternal behavior was not affected (Rodriguez et al. 2002). 

Studies in mice found increased fetal mortality, decreased fetal body weight, a low incidence of gross 

malformations (primarily exencephaly), and an increase in skeletal malformations in mice given single 

gavage doses of 23–48 mg As/kg during gestation (Baxley et al. 1981; Hood et al. 1978), with no effects 

at 11 mg As/kg. Similarly, in mice treated with 24 mg As/kg/day as arsenic acid on days 6–15 of 

gestation, there was a significant increase in the number of resorptions per litter (42% vs. 4% in controls) 

and significant decreases in the number of live pups per litter (6.6 vs. 12.3 in controls) and mean fetal 

weight (1.0 g vs. 1.3 g in controls), while no developmental effects were found at 12 mg As/kg/day 

(Nemec et al. 1998). Hamsters treated with a single gavage dose of 14 mg As/kg during gestation also 

had increased fetal mortality and decreased fetal body weight (Hood and Harrison 1982), with no effect at 

11 mg As/kg. However, the most sensitive species was the rabbit, which had increased resorptions and 

decreased viable fetuses per litter at 1.5 mg As/kg/day and a developmental NOAEL of 0.4 mg 

As/kg/day, following repeated gavage dosing with arsenic acid during gestation (Nemec et al. 1998). In 

each of these studies (except Hood et al. 1978, which failed to report maternal effects), overt maternal 

toxicity, including death in some cases, was found at the same or lower doses as the developmental 
ARSENIC 187 

3. HEALTH EFFECTS 

effects (Baxley et al. 1981; Holson et al. 2000; Hood and Harrison 1982; Nemec et al. 1998; Stump et al. 

1999). 

It is noteworthy that the effect in the 3-generation reproduction study in mice by Schroeder and Mitchener 

(1971), decreased pups per litter (all generations), is consistent with the findings of many of these shorterterm studies (Baxley et al. 1981; Hood and Harrison 1982; Hood et al. 1978; Nemec et al. 1998; Stump et 

al. 1999). The dose in this long-term study was 1 mg As/kg/day; in a 2-year study by these researchers, 

this dose produced effects such as decreased body weight gain and increased mortality (Schroeder and 

Balassa 1967). 

A series of studies presented evidence that inorganic arsenic may be a transplacental carcinogen in 

animals. Waalkes et al. (2003, 2004a, 2004b, 2004c) exposed timed-pregnant AJ mice to 0, 42.5, or 

85 ppm of sodium arsenite in the drinking water from gestation day 8 through 18 and observed the 

offspring for 90 weeks following birth; the study authors estimated daily doses at 9.55 and 19.3 mg 

As/kg/day. A dose-related increase was reported in the incidence of hepatocellular carcinomas and 

adrenal tumors in the male offspring from both treatment levels, while male offspring from high-dose 

animals showed an increase in total number of tumors. In female offspring, an increase in uterine 

hyperplasia was seen in the offspring of both treated groups while the offspring of high-dose animals 

showed increased incidence of lung carcinomas. For both exposed groups, regardless of gender, the 

offspring showed a significant increase in the number of malignant tumors (Waalkes et al. 2003). More 

recent studies from the same group of investigators have suggested that aberrant estrogen signaling, 

potentially through inappropriate estrogen receptor-α (ER-α), may play a role in arsenic-induced liver 

tumors in male offspring (Waalkes et al. 2006a) and in arsenic-induced uterine and bladder carcinoma in 

female offspring (Waalkes et al. 2006b). The latter was based on the observation of over-expression of 

ER-α and pS2, an estrogen-regulated gene, in the respective tissues. 

These studies (shown in Table 3-3 and Figure 3-3) indicate that the fetus may be affected by ingested 

arsenic. 

Organic Arsenicals. No studies were located regarding developmental effects in humans after oral 

exposure to organic arsenicals. The developmental toxicity of organic arsenicals has been investigated in 

rats and rabbits for MMA and in rats, mice, and rabbits for DMA. Decreased fetal weights and an 

increased incidence of fetuses with incomplete ossification of thoracic vertebrae were observed in the 

offspring of rats administered via gavage 500 mg MMA/kg/day on gestational days 6–15; no 
ARSENIC 188 

3. HEALTH EFFECTS 

developmental effects were observed at 100 mg MMA/kg/day (Irvine et al. 2006). Decreases in maternal 

body weight gain were observed at 100 and 500 mg MMA/kg/day. A decrease in pup survival was 

observed in F1 and F2 offspring of rats exposed to 76 mg MMA/kg/day (Schroeder 1994); although pup 

survival was not statistically different from controls, the investigators considered the effect to be 

biologically significant because survival in the MMA pups was outside the lower range of survival in 

historical controls. Increases in the number of fetuses with supernumerary thoracic ribs and eight lumbar 

vertebrae were observed in the offspring of rabbits administered to 12 mg MMA/kg/day on gestational 

days 7–19 (Irvine et al. 2006); the investigators noted that these effects were probably secondary to 

maternal stress. 

No developmental effects were observed in the offspring of rats administered via gavage 15 mg 

DMA/kg/day on gestational days 7–16 (Rogers et al. 1981). At 30 mg DMA/kg/day, there was an 

increase in the percentage of fetuses with irregular palatine rugae; no maternal effects were observed at 

this dose level (Rogers et al. 1981). The investigators noted that the functional significance of aberrant 

rugae in rats is not known. Doses of ≥36 mg DMA/kg/day resulted in decreases in fetal weights and 

delays in ossification (Chernoff et al. 1990; Irvine et al. 2006; Rogers et al. 1981); decreases in maternal 

body weight gain were often observed at the same dose levels. Irvine et al. (2006) also reported an 

increase in the occurrence of diaphragmatic hernia in the offspring of rats exposed to 36 mg DMA/kg/day 

as DMA on gestational days 6–15. Mice appear to be less sensitive than rats to the developmental 

toxicity of DMA. No developmental effects were observed in the offspring of mice administered 200 mg 

DMA/kg/day on gestational days 7–16 (Rogers et al. 1981); at higher doses, decreases in fetal body 

weight, delays in ossification, and cleft palate were observed (Kavlock et al. 1985; Rogers et al. 1981). In 

rabbits, a NOAEL of 12 mg DMA/kg/day was identified (Irvine et al. 2006); at 48 mg DMA/kg/day, there 

were increased maternal deaths and abortions. 

3.2.2.7 Cancer 

Inorganic Arsenicals. There is convincing evidence from a large number of epidemiological studies and 

case reports that ingestion of inorganic arsenic increases the risk of developing skin cancer (Alain et al. 

1993; Beane Freeman et al. 2004; Bickley and Papa 1989; Cebrián et al. 1983; Chen et al. 2003; Guo et 

al. 2001a; Haupert et al. 1996; Hsueh et al. 1995; Lewis et al. 1999; Lüchtrath 1983; Mitra et al. 2004; 

Morris et al. 1974; Piontek et al. 1989; Sommers and McManus 1953; Tay and Seah 1975; Tsai et al. 

1998a, 1999; Tseng 1977; Tseng et al. 1968; Zaldívar 1974; Zaldívar et al. 1981). Lesions commonly 

observed are multiple squamous cell carcinomas, some of which appear to develop from the 
ARSENIC 189 

3. HEALTH EFFECTS 

hyperkeratotic warts or corns described in Section 3.2.2.2. In addition, multiple basal cell carcinomas 

may occur, typically arising from cells not associated with hyperkeratinization. In most cases, skin cancer 

develops only after prolonged exposure, but one study has reported skin cancer in people exposed for 

<1 year (Reymann et al. 1978). Although both types of skin cancer can be removed surgically, they may 

develop into painful lesions that may be fatal if left untreated (Shannon and Strayer 1989). 

A number of studies that identify CELs in exposed humans are summarized in Table 3-3 and shown in 

Figure 3-3. The EPA reviewed the studies that provided dose-response data on the risk of skin cancer 

(EPA 1988d) and concluded that the most useful study for the purposes of quantitative risk assessment 

was the ecologic epidemiology study by Tseng et al. (1968). In this study, the incidence of skin cancer 

was measured as a function of exposure level in over 40,000 people residing in 37 villages in Taiwan, and 

compared to a control group of over 7,500 people. Beyond the very large sample size, other strengths of 

this study include excellent case ascertainment (physical examination), inclusion of both males and 

females, and lifetime exposure duration. Weaknesses and uncertainties include poor nutritional status of 

the exposed populations, their genetic susceptibility, their exposure to inorganic arsenic from nonwater 

sources, and the applicability of extrapolating data from Taiwanese to the U.S. population because of 

different background rates of cancer, possibly genetically determined, and differences in diet other than 

arsenic (e.g., low protein and fat and high carbohydrate) (EPA 1988d). Because of a lack of information 

on the amount of individual exposure, subjects were classified into three exposure groups (i.e., high, 

medium, and low). Based upon pooled data for skin cancer incidence and average well concentrations for 

each village in the Tseng et al. (1968) study, the EPA calculated a unit risk (the upper-bound excess 

cancer risk from lifetime exposure to water containing 1 μg As/L) of 5x10-5 (IRIS 2007). The average 

daily doses (expressed as mg As/kg/day) that correspond to excess cancer risks of 1x10-4–1x10-7 are 

shown in Figure 3-3. 

The use of a cancer risk estimate derived from the Tseng et al. (1968) study for a U.S. population has 

been the source of intense debate. Some have argued and have provided data in support of the view that 

there is persuasive evidence that inorganic arsenic is a cause of human cancer at several sites (i.e., Smith 

et al. 1992, 1995, 2002). On the other hand, a number of concerns have been raised regarding the 

strength, or lack of strength, of the database, including: the adequacy of the model used by EPA and the 

accuracy and reliability of the exposure data (Brown et al. 1997a, 1997b); a number of host and 

environmental factors among the Taiwanese not applicable elsewhere (Carlson-Lynch et al. 1994); a 

possible threshold for arsenic carcinogenicity and nonlinearities in the dose-response curve (Abernathy et 

al. 1996; Slayton et al. 1996); differences in health and nutrition between Taiwan and the United States 
ARSENIC 190 

3. HEALTH EFFECTS 

that might increase cancer risk in Taiwan (Beck et al. 1995); the possibility that lower doses of arsenic 

may be beneficial role in some physiological processes (EPA 1988d; FNB/IOM 2001; NRC 1999, 2001); 

and the possibility of significant exposure to arsenic from sources other than the well water (Chappell et 

al. 1997). Many of these factors were recognized by EPA (1988d). A report by NRC (2001) suggested 

that the risks calculated based on increases in incidence of lung and bladder cancers may be greater than 

those calculated by the EPA based on incidences of skin cancer. 

Several early epidemiological studies performed in the United States did not report an increased 

frequency of skin cancer in small populations consuming water containing arsenic at levels of around 0.1–

0.2 ppm (EPA 1981b; Goldsmith et al. 1972; Harrington et al. 1978; Morton et al. 1976). These early 

data suggested that arsenic-associated skin cancer is not a common problem in this country, but these 

studies lacked sufficient statistical power to detect small increases in skin cancer incidence that might 

have occurred at these low doses (EPA 1983g). Later studies in exposed U.S. populations from Utah 

(Lewis et al. 1999) and Iowa (Beane Freeman et al. 2004) have suggested that arsenic-exposed 

individuals within the United States may have increased incidence or risk of mortality from some skin 

cancers, melanoma in particular; however, exposure data from these studies are generally insufficient for 

dose-response analysis. Another study found a suggestion of an arsenic-induced effect on the 

development of skin cancer, but the association did not achieve statistical significance (Karagas et al. 

2001). Therefore, the risk of arsenic-induced skin cancers in U.S. populations, while it may appear to be 

less than in some other evaluated populations, may be the reflection that, in most studies, exposures were 

lower. 

In addition to the risk of skin cancer, there is mounting evidence that ingestion of arsenic may increase 

the risks of internal cancers as well. Many case studies have noted the occurrence of internal tumors of 

the liver and other tissues in patients with arsenic-induced skin cancer (Falk et al. 1981b; Kasper et al. 

1984; Koh et al. 1989; Lander et al. 1975; Regelson et al. 1968; Sommers and McManus 1953; Tay and 

Seah 1975; Zaldívar et al. 1981). These studies are supported by large-scale epidemiological studies, 

where associations and/or dose response trends have been detected for tumors of the bladder, kidney, 

liver, lung, and prostate (Chen and Wang 1990; Chen et al. 1985, 1986, 1988a, 1988b, 1992; Chiou et al. 

1995; Cuzick et al. 1992; Ferreccio et al. 1998; Guo et al. 1997; Hopenhayn-Rich et al. 1998; Kurttio et 

al. 1999; Lewis et al. 1999; Moore et al. 2002; Rivara et al. 1997; Smith et al. 1998; Tsuda et al. 1995a; 

Wu et al. 1989). The EPA has not yet calculated a unit risk value or slope factor for arsenic-induced 

internal tumors. 
ARSENIC 191 

3. HEALTH EFFECTS 

There is increasingly convincing evidence that long-term exposure to arsenic can result in the 

development of bladder cancer (Bates et al. 2004; Chen et al. 1992, 2003; Chiou et al. 1995, 2001; Cuzick 

et al. 1992; Guo et al. 2001b; Karagas et al. 2004; Lamm et al. 2004; Michaud et al. 2004; Steinmaus et 

al. 2003), with transitional cell cancers being the most prevalent. Chiou et al. (1995) reported a doseresponse relationship between long-term arsenic exposure from drinking artesian well water and the 

incidence of lung cancer, bladder cancer, and cancers of all sites combined (after adjustment for age, sex, 

and cigarette smoking) in four townships in Taiwan exposed to inorganic arsenic in drinking water (0– 

1.14 mg/L). In a later followup study of the same cohort, the increase in bladder cancer was found to be 

statistically significant only in subjects exposed for 40 years or longer (Chiou et al. 2001). Cuzick et al. 

(1992) evaluated a cohort treated with Fowler's solution (potassium arsenite) in Lancashire, England, 

during the period 1945–1969 and followed through 1991; the cohort of 478 patients showed a significant 

excess of bladder cancer, but no excess for other causes of death. Of a subcohort of 142 patients 

examined for signs of arsenicism around 1970 (Cuzick et al. 1992), all 11 subsequent cancer deaths 

occurred in those with signs of arsenicism (p=0.0009). Hopenhayn-Rich et al. (1996a) investigated 

bladder cancer mortality for the years 1986–1991 in the 26 counties of Cordoba, Argentina, and reported 

that bladder cancer SMRs were consistently higher in counties with documented arsenic exposure; a later 

case-control study by the same authors (Bates et al. 2004) did not report statistically significant increases 

in bladder cancers resulting from arsenic exposure, except in individuals exposed for 50 years or longer. 

Guo et al. (2001a) reported significantly increased rate differences for bladder cancer in men and women 

in Taiwan exposed to 0.64 mg arsenic/L in the drinking water, but not at lower exposure levels. The 

arsenic-induced bladder tumors do not appear to be histologically different than similar bladder tumor 

types of nonarsenic origin (Chow et al. 1997), although they tended to be more pronounced. In contrast, 

Michaud et al. (2004) reported no correlation between arsenic levels in toenails and the incidence of 

bladder cancers in Finnish workers. Among evaluated U.S. cohorts, there has generally been no 

association between arsenic exposure (~60–100 μg As/L) and the incidence of mortality from bladder 

cancers (Lamm et al. 2004; Steinmaus et al. 2003), although it is possible that smoking may render 

individuals more susceptible to arsenic-induced bladder tumors (Karagas et al. 2004; Steinmaus et al. 

2003). 

Studies have also suggested that chronic oral exposure to arsenic may result in the development of 

respiratory tumors and increased incidence of lung cancer (Ferreccio et al. 2000; Guo 2004; Nakadaira et 

al. 2002; Smith et al. 1998; Viren and Silvers 1999). A study of arsenic-exposed individuals in northern 

Chile reported significantly increased odds ratios for lung cancer among subjects with ≥30 μg As/L of 

drinking water (Ferreccio et al. 2000), although when adjusted for socioeconomic status, smoking, and 
ARSENIC 192 

3. HEALTH EFFECTS 

other factors, the increase was only significant at 60 μg As/L or greater. Guo (2004) reported 

significantly increased rates differences (RD) for lung cancer for Taiwanese men and women exposed to 

0.64 mg As/L or greater, with those subjects >50 years of age being particularly at risk. Nakadaira et al. 

(2002) suggested that even comparatively short exposure durations (≤5 years) may be sufficient for the 

development of arsenic-induced lung cancer. 

Studies in U.S. populations exposed to arsenic in drinking water (EPA 1981b; Lamm et al. 2004; Lewis et 

al. 1999; Morton et al. 1976; Steinmaus et al. 2003; Valentine et al. 1992) have not yielded the cancer 

incidences and health effects noted in Taiwan, Mexico, and Chile. Whether this difference is due to a 

smaller population of subjects compared to Taiwan, to overall lower doses in exposed U.S. populations, 

or to differences in nutritional or socioeconomic conditions has not been resolved. It should be noted that 

exposed populations in Mexico and Chile are also smaller than those in Taiwan. 

Most studies of animals exposed to arsenate or arsenite by the oral route have not detected any clear 

evidence for an increased incidence of skin cancer or other cancers (Byron et al. 1967; Kroes et al. 1974; 

Schroeder et al. 1968). Arsenic has sometimes been called a “paradoxical” human carcinogen because of 

this lack of animal data (Jager and Ostrosky-Wegman 1997). The basis for the lack of tumorigenicity in 

animals is not known, but could be related to species-specific differences in arsenic distribution, and 

induction of cell proliferation (Byrd et al. 1996) (see Section 3.5). As discussed in Section 3.5 below, the 

carcinogenic effects of arsenic may partially result from its function as a cocarcinogen, which would not 

manifest in most animal carcinogenicity studies. 

One mouse study using transgenic mice (which carry the v-Ha-ras oncogene) administered 48 mg 

As/kg/day as sodium arsenite in drinking water for 4 weeks followed by dermal application of 

12-O-tetradecanoylphorbol-13-acetage (TPA) to shaved back skin twice a day for 2 weeks showed an 

increase in the incidence of skin papillomas when compared to transgenic mice receiving only TPA 

treatment, only arsenic, or to wild-type mice receiving both TPA and arsenic (Germolec et al. 1998); 

arsenic treatment alone did not result in increased papilloma incidence. Increases in mRNA transcripts 

for the growth factors transforming growth factor-α (TGF-α) and granulocyte/ macrophage-colony 

stimulating factor (GM-CSF) were detected in the epidermis of the arsenic-treated mice. 

A few studies in mice have noted that arsenic ingestion may actually decrease the incidence of some 

tumor types. For example, arsenic exposure caused decreased incidence of urethane-induced pulmonary 

tumors (Blakley 1987), spontaneous mammary tumors (Schrauzer and Ishmael 1974; Schrauzer et al. 
ARSENIC 193 

3. HEALTH EFFECTS 

1976), and tumors resulting from injection of mouse sarcoma cells (Kerkvliet et al. 1980). However, 

arsenic also increased the growth rate of the tumors that did occur, resulting in a net decrease in survival 

time in tumor-bearing animals (Kerkvliet et al. 1980; Schrauzer and Ishmael 1974). These observations 

suggest that arsenic may affect different types of neoplastic cells differently, perhaps acting mainly as a 

tumor promoter (Schrauzer and Ishmael 1974; Shirachi et al. 1983), although some studies have 

suggested that arsenic’s actions are not consistent with tumor promotion (Baroni et al. 1963; Boutwell 

1963). 

There is evidence suggesting that inorganic arsenic can induce cancer in the offspring from mice exposed 

to arsenic during gestation (transplacental carcinogen) (Waalkes et al. 2003, 2004a, 2004b, 2004c, 2006a, 

2006b). These studies are summarized in Section 3.2.2.6, Developmental Effects. 

Organic Arsenicals. No studies were located regarding cancer in humans after oral exposure to organic 

arsenicals. Two lifetime carcinogenicity studies with MMA did not find significant increases in tumors in 

rats exposed to 72.4 mg MMA/kg/day in the diet for 2 years (Arnold et al. 2003) or 8.4 mg MMA/kg/day 

in drinking water for 2 years (Shen et al. 2003). No significant increases in neoplastic lesions were 

observed in mice exposed to 67.1 mg MMA/kg/day in the diet for 2 years (Arnold et al. 2003). 

In contrast, significant increases in the incidence of urinary bladder tumors have been observed in rats 

exposed for 2 years to 7.8 mg DMA/kg/day in the diet (Arnold et al. 2006) or 3.4 mg DMA/kg/day in 

drinking water (Wei et al. 1999, 2002). The incidence of bladder tumors was similar to controls in the 

rats exposed to 0.77 mg DMA/kg/day (Arnold et al. 2006) or 0.75 mg DMA/kg/day (Wei et al. 1999, 

2002). Neither study reported significant increases in the incidence of neoplastic lesions in other tissues. 

Arnold et al. (2006) did not find increases in the incidence of neoplastic lesions in mice exposed to doses 

as high as 94 mg DMA/kg/day in the diet for 2 years. Hayashi et al. (1998) reported that exposure of 

A/J mice (a strain susceptible to lung tumorigenesis) to 10.4 mg DMA/kg/day (but not 1.3 or 5.2 mg 

DMA/kg/day) in drinking water for 50 weeks resulted in an increased incidence of papillary adenomas 

and/or adenocarcinomas and an increased number of lung tumors per mouse. 

The incidence of basophilic foci (believed to be a precancerous lesion) in the liver of rats initiated with 

diethylnitrosamine was increased by subsequent 6-month drinking water exposure to 11 mg DMA/kg/day, 

suggesting that this compound could act as a cancer promoter (Johansen et al. 1984). Additional evidence 

for the possible role of DMA as a promoter comes from Yamamoto et al. (1995), who reported that 15 or 

60 mg DMA/kg/day in the drinking water for 24 weeks significantly enhanced the tumor induction in the 
ARSENIC 194 

3. HEALTH EFFECTS 

urinary bladder, kidney, liver, and thyroid gland in male F344 rats treated with a series of initiators. 

Wanibuchi et al. (1996) reported that treatment of F344 rats for 32 weeks with up to 14.3 mg 

DMA/kg/day DMA in the drinking water did not result in increased incidences of urinary bladder 

papillomas or carcinomas, but that incidence of these tumors was elevated if the animals were first 

pretreated with an initiating compound (BBN). A later study by Li et al. (1998) reported that NBR rats 

(which do not synthesize α2μ-globulin) exposed to an initiator for 4 weeks followed by DMA for 

32 weeks, similar to the Wanibuchi et al. (1996) study, showed a statistically significant increase in 

simple hyperplasia and papillary or nodular hyperplasia of the bladder. A study by Salim et al. (2003) 

suggested that DMA primarily exerts its carcinogenic effects on spontaneous tumor development. 

No increases in tumor incidence were observed in rats, mice, or dogs exposed to 10, 13, or 5 mg/kg/day 

roxarsone, respectively, in the diet for 2 years (Prier et al. 1963). Similarly, no evidence of carcinogenicity was observed in female rats or male or female mice exposed to 4 or 43 mg/kg/day as roxarsone 

in the diet for 2 years (NTP 1989b). However, a slight increase in pancreatic tumors was noted in male 

rats exposed to 4 mg/kg/day (NTP 1989b); this was considered to constitute equivocal evidence of 

carcinogenicity. 

3.2.3 Dermal Exposure 

Adverse effects from dermal exposure to inorganic or organic arsenicals have not been extensively 

investigated. Table 3-7 summarizes studies in animals and humans that provide quantitative data on 

dermal exposure-effect relationships for inorganic arsenicals. No quantitative data on dermal exposure to 

organic arsenicals were located. Available quantitative and qualitative data are discussed in greater detail 

below. 

3.2.3.1 Death 

Inorganic Arsenicals. No studies were located regarding death in humans after dermal exposure to 

inorganic arsenicals. In rats, no deaths resulted from dermal exposure to arsenate or arsenite at doses up 

to 1,000 mg As/kg (Gaines 1960). These data indicate that dermal exposure to inorganic arsenic 

compounds is very unlikely to result in death. 

Organic Arsenicals. No studies were located regarding death in humans after dermal exposure to organic 

arsenicals. No deaths were observed in rabbits receiving daily dermal applications of 540 mg As/kg as 
Table 3-7 Levels of Significant Exposure to Inorganic Arsenic - Dermal

Species

(Strain)

Exposure/

Duration/

Frequency

(Route) System NOAEL Less Serious 

LOAEL

Serious

ReferenceChemical Form

ACUTE EXPOSURE

Immuno/ Lymphoret

(Hartley)Gn Pig once 580

mg/L

mg/L

Wahlberg and Boman 1

As(+3)

(Hartley)Gn Pig once 4000

mg/L

mg/L

Wahlberg and Boman 1

As(+5)

INTERMEDIATE EXPOSURE

Systemic

(Rockland)Mouse

F = female; Gn pig = guinea pig; Immuno/Lymphoret = immunological/lymphoreticular; wk = week(s); x = time(s)

30 wk11 x/wk Dermal 6 F (gross hyperplasia,

ulceration)

mg/kg/day

mg/kg/day

Boutwell 1963

As(+3)
ARSENIC 196 

3. HEALTH EFFECTS 

MMA 5 days/week for 21 days (Margitich and Ackerman 1991b) or 1,000 mg DMA/kg/day 5 days/week 

for 21 days (Margitich and Ackerman 1991a). 

3.2.3.2 Systemic Effects 

No studies were located that have associated respiratory, cardiovascular, gastrointestinal, hematological, 

musculoskeletal, hepatic, renal, endocrine, ocular, or body weight effects in humans or animals with 

dermal exposure to inorganic arsenicals. 

Respiratory Effects. No studies were located regarding respiratory effects in humans after dermal 

exposure to organic arsenicals. No histological effects were observed in the respiratory tracts of rabbits 

following dermal application of 1,000 mg/kg/day MMA or DMA 5 days/week for 21 days (Margitich and 

Ackerman 1991a, 1991b). 

Cardiovascular Effects. No studies were located regarding cardiovascular effects in humans after 

dermal exposure to organic arsenicals. No histological effects were observed in the hearts of rabbits 

following dermal application of 1,000 mg/kg/day MMA or DMA 5 days/week for 21 days (Margitich and 

Ackerman 1991a, 1991b). 

Hematological Effects. No studies were located regarding hematological effects in humans after 

dermal exposure to organic arsenicals. No treatment-related hematological alterations were observed in 

rabbits receiving dermal applications of 1,000 mg MMA/kg/day (Margitich and Ackerman 1991a) or 

1,000 mg DMA/kg/day 5 days/week for 21 days (Margitich and Ackerman 1991b). 

Hepatic Effects. No studies were located regarding hepatic effects in humans after dermal exposure 

to organic arsenicals. No significant alterations in blood clinical chemistry, liver weights, or 

histopathology were observed in rabbits dermally exposed to 1,000 mg/kg/day MMA or DMA 

5 days/week for 21 days (Margitich and Ackerman 1991a, 1991b). 

Renal Effects. No studies were located regarding renal effects in humans after dermal exposure to 

organic arsenicals. No significant alterations in urinalysis, kidney weights, or histopathology were 

observed in rabbits following dermal exposure to 1,000 mg MMA/kg/day (Margitich and Ackerman 

1991a) or 1,000 mg DMA/kg/day 5 days/week for 21 days (Margitich and Ackerman 1991b). 
ARSENIC 197 

3. HEALTH EFFECTS 

Endocrine Effects. No studies were located regarding endocrine effects in humans after dermal 

exposure to organic arsenicals. No alterations in adrenal gland weight or histopathology of the adrenal 

glands, pancreas, pituitary gland, thyroid gland, and parathyroid gland were observed in rabbits following 

dermal application of 1,000 mg/kg/day MMA or DMA 5 days/week for 21 days (Margitich and 

Ackerman 1991a, 1991b). 

Dermal Effects. 

Inorganic Arsenicals. Several studies of humans exposed to arsenic dusts in the workplace have reported 

that inorganic arsenic (usually arsenic trioxide) can cause contact dermatitis (Holmqvist 1951; Pinto and 

McGill 1953). Typical responses included erythema and swelling, with papules and vesicles in more 

severe cases (Holmqvist 1951). The dermal contact rates that cause these effects in humans have not been 

quantified, but a similar direct irritation of the skin has been noted in mice exposed to 4 mg As/kg/day as 

potassium arsenite for 30 weeks (Boutwell 1963). In contrast, no significant dermal irritation was noted 

in guinea pigs exposed to aqueous solutions containing 4,000 mg As/L as arsenate or 580 mg As/L as 

arsenite (Wahlberg and Boman 1986). These studies indicate that direct contact may be of concern at 

high exposure levels, but do not suggest that lower levels are likely to cause significant irritation. 

Studies on possible dermal sensitization by inorganic arsenicals are discussed in Section 3.2.3.3 below. 

Organic Arsenicals. Contact dermatitis was reported in workers involved in the application of an organic 

arsenical herbicide, which is a mixture of DMA and its sodium salt (Peoples et al. 1979). 

Application of an unspecified amount of MMA to the skin of rabbits was reported to result in mild dermal 

irritation in a Draize test (Jaghabir et al. 1988). No dermal irritation was reported in rabbits repeatedly 

exposed to 1,000 mg MMA/kg/day (Margitich and Ackerman 1991a) or 1,000 mg DMA/kg/day 

5 days/week for 21 days (Margitich and Ackerman 1991b). 

Ocular Effects. No studies were located regarding ocular effects in humans or animals after dermal 

exposure to organic arsenicals. 

Body Weight Effects. No studies were located regarding body weight effects in humans after dermal 

exposure to organic arsenicals. No significant alterations in body weight gain were observed in rabbits 
ARSENIC 198 

3. HEALTH EFFECTS 

following a 5 day/week exposure to 1,000 mg/kg/day MMA or DMA for 21 days (Margitich and 

Ackerman 1991a, 1991b). 

3.2.3.3 Immunological and Lymphoreticular Effects 

Inorganic Arsenicals. Examination of workers exposed to arsenic trioxide dusts in a copper smelter led 

Holmqvist (1951) to suspect that repeated dermal contact could lead to dermal sensitization. In support of 

this, Holmqvist (1951) found a positive patch test in 80% of the exposed workers compared to 30% in a 

control population. These data do suggest that workers may be sensitized to arsenic, but the high 

response rate in controls seems unusual. A much lower response rate (0.5%) was noted in another patch 

test study of dermal sensitization (Wahlberg and Boman 1986), and the few positive responses seemed to 

be due to a cross-reactivity with nickel. Mohamed (1998) evaluated 11 male workers at a tin smelting 

factory where arsenic trioxide levels ranged from 5.2 to 14.4 mg/m3

. The workers experienced symptoms 

of generalized itch, dry and hyperpigmented skin, folliculitis, and superficial ulcerations. The authors 

concluded that arsenic-containing dust collected on the sweat on the workers’ skin, causing contact 

dermatitis. Studies in guinea pigs did not yield evidence of a sensitization reaction to inorganic arsenic 

(Wahlberg and Boman 1986). 

Organic Arsenicals. Support for sensitization to DMA is provided in a case report of a 26-year-old 

woman who was occupationally exposed to DMA and experienced eczema on her face (Bourrain et al. 

1998). Patch testing confirmed an allergic reaction to DMA, and avoidance of DMA resulted in 

disappearance of the symptoms. No studies were located regarding immunological or lymphoreticular 

effects in animals after dermal exposure to organic arsenicals. 

No studies were located that have associated any of the following effects in humans or animals with 

dermal exposure to inorganic or organic arsenicals: 

3.2.3.4 Neurological Effects 

3.2.3.5 Reproductive Effects 

3.2.3.6 Developmental Effects 

3.2.3.7 Cancer 

Inorganic Arsenicals. No studies were found that have associated cancer in humans with dermal 

exposure to arsenic. Application of arsenic acid to the skin of mice pretreated with dimethylbenz­
ARSENIC 199 

3. HEALTH EFFECTS 

anthracene did not result in any skin tumors (Kurokawa et al. 1989), suggesting that arsenic does not act 

as a promoter in this test system. 

Organic Arsenicals. No studies were located regarding cancer in humans or animals after dermal 

exposure to organic arsenicals. 

3.3 GENOTOXICITY 

Inorganic Arsenicals. There have been a large number of studies of the genotoxic effects of arsenic. 

Tables 3-8 and 3-9 summarize a number of reports on the in vitro and in vivo genotoxicity of inorganic 

arsenicals, respectively. In general, in vitro studies in prokaryotic organisms have been negative for gene 

mutations (Lantzsch and Gebel 1997; Löfroth and Ames 1978; Nishioka 1975; Rossman et al. 1980; 

Ulitzur and Barak 1988). Studies in human fibroblasts, lymphocytes, and leukocytes, mouse lymphoma 

cells, Chinese hamster ovary cells, and Syrian hamster embryo cells demonstrate that in vitro arsenic 

exposure can induce chromosomal aberrations and sister chromatid exchange (see Table 3-8 for citations). 

I vitro studies in human, mouse, and hamster cells have also been positive for DNA damage and repair 

and enhancement or inhibition of DNA synthesis. 

Studies of humans have detected a higher-than-average incidence of chromosomal aberrations in 

peripheral lymphocytes, both after inhalation exposure (Beckman et al. 1977; Nordenson et al. 1978) and 

oral exposure (Burgdorf et al. 1977; Nordenson et al. 1979). These studies must be interpreted with 

caution, since in most cases, there were only a small number of subjects and a number of other chemical 

exposures were possible (EPA 1984a). Human and animal data are available indicating that inhaled 

inorganic arsenic is clastogenic. Workers exposed to unspecified concentrations of arsenic trioxide at the 

Ronnskar copper smelter in Sweden were found to have a significant increase in the frequency of 

chromosomal aberrations in peripheral lymphocytes (Beckman et al. 1977; Nordenson et al. 1978). This 

result is supported by an animal study that found increased chromosomal aberrations in the livers of 

fetuses from pregnant mice exposed to 22, but not 2.2 or 0.20, mg As/m3

 as arsenic trioxide on days 9– 

12 of gestation (Nagymajtényi et al. 1985). Workers in the arsenic-based glass making industry in 

southern India had a significantly increased frequency of micronuclei in buccal cells and increased DNA 

damage in leukocytes compared to a control group (Vuyyuri et al. 2006). Exposure levels were not 

available, but the concentration of arsenic in the blood from workers was approximately 5 times higher 

than in the reference group. 
ARSENIC 200 

3. HEALTH EFFECTS 

Table 3-8. Genotoxicity of Inorganic Arsenic In Vitro 

Results 

With Without 

Valence Species (test system) End point activation activation Reference 

Prokaryotic organisms: 

As+3 Escherichia coli Reverse mutation No data + Nishioka 1975 

As+3 E. coli PQ37 Gene mutation No data – Lantzsch and 

Gebel 1997 

As+3 E. coli (six strains) Reverse mutation No data – Rossman et al. 

1980 

As+3 Salmonella typhimurium Gene mutation No data – Löfroth and 

Ames 1978 

As+3 Photobacterium fischeri Gene mutation No data – Ulitzur and Barak 

1988 

As+5 S. typhimurium Gene mutation No data – Löfroth and 

Ames 1978 

As+5 P. fischeri Gene mutation No data + Ulitzur and Barak 

1988 

Eukaryotic organisms: 

Fungi: 

As+3; 

As+5 

Saccharomyces 

cerevisiae 

Gene mutation No data – Singh 1983 

 Mammalian cells: 

As+3 Human fibroblasts DNA repair inhibition No data + Okui and 

Fujiwara 1986 

As+3 Human fibroblasts DNA repair and mutant + + Wiencke et al. 

frequencies 1997 

As+3 Human fibroblasts DNA repair inhibition + + Hartwig et al. 

1997 

As+3 Human fibroblasts DNA migration No data + Hartmann and 

(MRC5CV1) Speit 1996 

As+3 Human fibroblasts (HFW Cytotoxicity No data + Lee and Ho 1994 

cells) 

As+3 Human skin fibroblasts Chromosome No data + Huang et al. 

(HFW) endoreduplication 1995 

As+3 Human skin fibroblasts Chromosomal No data + Yih et al. 1997 

aberrations 

As+3 Human fetal lung DNA strand breaks No data + Dong and Luo 

fibroblasts 1993 

As+3 Human fetal lung DNA damage and repair No data + Dong and Luo 

fibroblasts (2BS cells) 1994 

As+3; 

As+5 

Human umbilical cord 

fibroblasts 

Chromosomal 

aberrations 

No data + Oya-Ohta et al. 

1996 

As+3 Diploid human fibroblasts Morphological No data + Landolph 1994 

transformation 
ARSENIC 201 

3. HEALTH EFFECTS 

Table 3-8. Genotoxicity of Inorganic Arsenic In Vitro 

Results 

With Without 

Valence Species (test system) End point activation activation Reference 

As+3 Human leukocytes Chromosomal aberration No data + Nakamuro and 

Sayato 1981 

As+3 Human lymphocytes DNA protein cross-links – – Costa et al. 1997 

As+3; Human lymphocytes Enhancement or No data + Meng 1993a 

As+5 inhibition on DNA 

synthesis 

As+3; Human lymphocytes Enhancement or No data + Meng 1993b 

As+5 inhibition on DNA 

synthesis 

As+3; Human lymphocytes Enhancement or No data + Meng 1994 

As+5 inhibition on DNA 

synthesis 

As+3 Human lymphocytes Hyperdiploidy and No data (+) Rupa et al. 1997 

chromosomal breakage 

As+3 Human lymphocytes Hyperdiploid nuclei No data + Ramirez et al. 

1997 

As+3 Human lymphocytes Chromosomal aberration No data + Beckman and 

Nordenson 1986 

As+3 Human lymphocytes Chromosomal No data + Nordenson et al. 

aberrations and sister 1981 

chromatid exchange 

As+3 Human lymphocytes Chromosomal aberration No data + Sweins 1983 

As+3 Human lymphocytes Chromosomal No data + Yager and 

aberrations Wiencke 1993 

As+3 Human lymphocytes Chromosomal No data + Vega et al. 1995 

aberrations 

As+3 Human lymphocytes Chromosomal No data + Wan et al. 1982 

aberrations 

As+3 Human lymphocytes Chromosomal No data + Wiencke and 

aberrations and sister Yager 1992 

chromatic exchange 

As+3 Human lymphocytes Chromosome aberrations No data + Larramendy et al. 

and sister chromatid 1981 

exchanges 

As+3 Human lymphocytes Sister chromatid No data + Gebel et al. 1997 

exchange 

As+5 Human lymphocytes Sister chromatid No data – Gebel et al. 1997 

exchange 

As+3 Human lymphocytes Sister chromatid No data + Hartmann and 

exchange Speit 1994 

As+3 Human lymphocytes Sister chromatid No data + Jha et al. 1992 

exchange 

As+3 Human lymphocytes Sister chromatid No data + Rasmussen and 

exchange Menzel 1997 
ARSENIC 202 

3. HEALTH EFFECTS 

Table 3-8. Genotoxicity of Inorganic Arsenic In Vitro 

Results 

With Without 

Valence Species (test system) End point activation activation Reference 

As+3; Human T-cell lymphoma- PARP activity inhibition No data + Yager and 

As+5 derived cell line (Molt-3) Wiencke 1997 

As+3 Human cervix carcinoma DNA repair modification + + Chao 1996 

HeLa and cisplatinresistant HeLa/CPR 

variant cells 

As+3 Human cervix carcinoma DNA damage recognition No data - Hartwig et al. 

cells (HeLa) 1998 

As+3 Human osteosarcoma DNA repair No data + Hu et al. 1998 

cells (HOS) 

As+3 Human osteosarcoma Cell transformation No data + Mure et al. 2003 

cells (HOS) 

As+3 Human-hamster hybrid DNA adducts No data + Kessel et al. 

A1 cells 2002 

As+3 Mouse lymphoma cells Enhanced viral forward No data (+) Oberly et al. 

mutation 1982 

As+3; Mouse lymphoma cells Chromosomal mutations No data + Moore et al. 

As+5 [L5178Y/TK+

/

-

(-3.7.2C)] 1997a 

As+3 Mouse lymphoma cells Mutagenicity No data + Oberly et al. 

[L5178Y tk+

/

-

 (3.7.sc)] 1996 

As+3; Mouse lymphoma cells Chromosomal No data + Moore et al. 

As+5 aberrations 1994a 

As+3 Mouse lymphoma cells Chromosomal No data + Sofuni et al. 1996 

aberrations 

As+3 Mouse 3T6 cells Gene amplification No data + Lee et al. 1988 

As+3 Mouse embryo Morphological No data + Landolph 1994 

fibroblasts (C3H/10T/2 transformation 

Cl8) 

As+3 Chinese hamster V79 Gene mutation No data – Li and Rossman 

cells 1991 

As+3 Chinese hamster V79 Gene mutation No data – Rossman et al. 

cells 1980 

As+3 Chinese hamster V79 DNA damage, DNA- No data + Gebel et al. 

cells protein cross-linking, 1998a 

micronucleus induction 

As+3 Chinese hamster V79 DNA repair and mutant No data + Li and Rossman 

cells frequencies 1991 

As+3 Chinese hamster V79 Intrachromosomal No data + Helleday et al. 

cells homologous 2000 

recombination 

As+3 Chinese hamster ovary Gene mutation No data + Hei et al. 1998 

cells (CHO-AL) 

As+3 Chinese hamster ovary Mutagenicity No data + Meng and Hsie 

cells (CHO-AS52) 1996 
ARSENIC 203 

3. HEALTH EFFECTS 

Table 3-8. Genotoxicity of Inorganic Arsenic In Vitro 

Results 

With Without 

Valence Species (test system) End point activation activation Reference 

As+3 Chinese hamster ovary Gene mutation No data + Yang et al. 1992 

cells 

As+3 Chinese hamster ovary DNA repair inhibition No data + Lee-Chen et al. 

cells 1993 

As+3 Chinese hamster ovary DNA repair inhibition No data – Lee-Chen et al. 

cells 1992 

As+3 Chinese hamster ovary DNA strand breaks + + Lee-Chen et al. 

cells (CHO-K1) 1994 

As+3 Chinese hamster ovary DNA strand breaks No data + Lynn et al. 1997 

cells (CHO-K1) 

As+3 Chinese hamster ovary Aberrant metaphases No data + Jan et al. 1986 

cells 

As+3 Chinese hamster ovary Aberrant metaphases No data + Lee et al. 1986 

cells 

As+3 Chinese hamster ovary Chromosomal + + Huang et al. 

cells aberrations 1992 

As+3 Chinese hamster ovary Chromosomal No data + Huang et al. 

cells (CHO-K1) aberrations 1993 

As+3; Chinese hamster ovary Chromosomal No data + Kochhar et al. 

As+5 cells (CHO-K1) aberrations and sister 1996 

chromatid exchange 

As+3 Chinese hamster ovary Chromosomal + + Lin and Tseng 

cells aberrations and sister 1992 

chromatid exchange 

As+3 Chinese hamster ovary Chromosomal No data + Wan et al. 1982 

cells aberrations and sister 

chromatid exchange 

As+3 Chinese hamster ovary Sister chromatid No data + Fan et al. 1996 

cells exchange and 

micronucleus induction 

As+3 Chinese hamster ovary Cell-killing and No data + Wang and Huang 

cells micronucleus induction 1994 

As+3 Chinese hamster ovary Micronuclei No data + Liu and Huang 

cells 1997 

As+3 Chinese hamster ovary Micronuclei formation No data + Yee-Chien and 

cells Haimei 1996 

As+3 Chinese hamster ovary Micronuclei induction No data + Wang et al. 1997 

cells 

As+3 Chinese hamster ovary Cytotoxicity No data – Lee and Ho 1994 

cells 

As+3 Syrian hamster embryo Gene mutation No data – Lee et al. 1985 

cells 
ARSENIC 204 

3. HEALTH EFFECTS 

Table 3-8. Genotoxicity of Inorganic Arsenic In Vitro 

Results 

With Without 

Valence Species (test system) End point activation activation Reference 

As+3 Syrian hamster embryo Chromosome aberrations No data + Larramendy et al. 

cells and sister chromatid 1981 

exchanges 

As+3 Syrian hamster embryo Chromosomal aberration No data + Lee et al. 1985 

cells 

As+3 Syrian hamster embryo Sister chromatid No data + Lee et al. 1985 

cells exchange 

As+3 Syrian hamster embryo Micronuclei induction No data – Gibson et al. 

cells 1997 

As+3 Syrian hamster embryo Micronuclei induction No data – Gibson et al. 

cells 1997 

As+3 Syrian hamster embryo Morphological No data + Kerckaert et al. 

cells transformation 1996 

As+3 Syrian hamster embryo Morphological No data + Lee et al. 1985 

cells transformation 

As+3 Syrian hamster embryo Morphological No data + Casto et al. 1979 

cells transformation 

As+5 Human fibroblasts DNA repair inhibition No data – Okui and 

Fujiwara 1986 

As+5 Human leukocytes Chromosomal No data (+) Nakamuro and 

aberrations Sayato 1981 

As+5 Human lymphocytes Chromosomal No data – Nordenson et al. 

aberrations 1981 

As+5 Human lymphocytes Chromosome aberrations No data + Larramendy et al. 

and sister chromatid 1981 

exchanges 

As+5 Human lymphocytes Sister chromatid No data – Rasmussen and 

exchange Menzel 1997 

As+5 Human peripheral Sister chromatid No data + Zanzoni and 

lymphocytes exchange Jung 1980 

As+5 Human keratinocyte line Keratinocyte No data + Kachinskas et al. 

SCC-9 cells programming and 1997 

transcriptional activity 

As+5 Mouse lymphoma cells Gene mutation No data – Amacher and 

Paillet 1980 

As+5 Mouse lymphoma cells Gene mutation No data – Amacher and 

Paillet 1980 

As+5 Chinese hamster ovary Chromosomal No data + Wan et al. 1982 

cells aberrations 

As+5 Syrian hamster embryo Gene mutation No data – Lee et al. 1985 

cells 

As+5 Syrian hamster embryo Chromosome aberrations No data + Larramendy et al. 

cells and sister chromatid 1981 

exchanges 
ARSENIC 205 

3. HEALTH EFFECTS 

Table 3-8. Genotoxicity of Inorganic Arsenic In Vitro 

Results 

With Without 

Valence Species (test system) End point activation activation Reference 

As+5 Syrian hamster embryo Chromosomal No data + Lee et al. 1985 

cells 

As+5 Syrian hamster embryo Sister chromatid No data + Lee et al. 1985 

cells 

As+5 Syrian hamster embryo Morphological No data + Lee et al. 1985 

aberrations 

exchange 

transformation 

As+5 Syrian hamster embryo 

cells 

Morphological No data + DiPaolo and 

transformation Casto 1979 

cells 

(+) = weakly positive or marginal result; – = negative result; + = positive result; DNA = deoxyribonucleic acid 
ARSENIC 206 

3. HEALTH EFFECTS 

Table 3-9. Genotoxicity of Inorganic Arsenic In Vivo 

Exposure Species (test 

Valence route system) End point Results Reference 

Nonmammalian 

As+3 As+5 Injection Drosophila Somatic mutations and + Ramos-Morales and 

melanogaster mitotic recombination Rodriguez-Arnaiz 

1995 

As+3 As+5 Larval feeding D. melanogaster Somatic mutations and + Ramos-Morales and 

mitotic recombination Rodriguez-Arnaiz 

1995 

As+5 Larvae D. melanogaster Mitotic recombinations + de la Rosa et al. 1994 

Mammalian 

As+3 Inhalation Human (lymphocytes) Chromosomal – Beckman et al. 1977 

aberrations 

As+3 Inhalation Human (lymphocytes) Chromosomal + Nordenson et al. 1978 

aberrations 

As+3 Oral Human (lymphocytes) Chromosomal – Burgdorf et al. 1977 

aberrations 

No data Oral Human (lymphocytes) Chromosomal – Vig et al. 1984 

aberrations 

No data Oral Human (skin) DNA adducts + Matsui et al. 1999 

As+3 Oral Human (lymphocytes) Sister chromatid – Burgdorf et al. 1977 

exchange 

As+3 Oral Human (lymphocytes) Sister chromatid + Hsu et al. 1997 

exchange 

No data Oral Human (lymphocytes) Sister chromatid + Lerda 1994 

exchange 

No data Oral Human (lymphocytes) Sister chromatid + Liou et al. 1999 

exchange 

No data Oral Human (lymphocytes) Sister chromatid + Mahata et al. 2003 

exchange 

As+3 Oral Human (lymphocytes) Sister chromatid – Nordenson et al. 1978 

exchange 

No data Oral Human (lymphocytes) Sister chromatid – Vig et al. 1984 

exchange 

No data Oral Human skin Mutation and + Hsu et al. 1999 

carcinoma overexpression of p53 

As+3 Oral Exfoliated human Micronuclei + Moore et al. 1996 

epithelial cells 

As+3 Oral Exfoliated human Micronuclei + Tian et al. 2001 

epithelial cells 

No data Oral Human (bladder Micronuclei + Moore et al. 1995 

cells) 

No data Oral Human (lymphocytes) Micronuclei + Martínez et al. 2004 

No data Oral Human (lymphocytes) Micronuclei + Basu et al. 2004 

No data Oral Human (oral mucosa Micronuclei + Basu et al. 2004 

cells) 
ARSENIC 207 

3. HEALTH EFFECTS 

Table 3-9. Genotoxicity of Inorganic Arsenic In Vivo 

Exposure Species (test 

Valence route system) End point Results Reference 

No data Oral Human (urothelial Micronuclei + Basu et al. 2004 

cells) 

As+5 Oral Rat (bone marrow Chromosomal + Datta et al. 1986 

cells) aberrations 

As+3 Inhalation Mouse (fetal liver) Chromosomal (+) Nagymajtényi et al. 

aberrations 1985 

As+3 Oral Mouse (bone marrow Chromosomal + Das et al. 1993 

cells) aberrations 

As+3 Oral Mouse (bone marrow Chromosomal + Poddar et al. 2000 

cells) aberrations 

As+3 Oral Mouse (bone marrow Chromosomal breaks, – Poma et al. 1987 

cells) exchanges 

As+3 Oral Mouse Chromosomal – Poma et al. 1987 

(spermatogonia) aberrations 

As+3 Oral Mouse (leukocytes) Chromosomal breaks + McDorman et al. 2002 

As+3 Intraperitoneal Mouse (bone marrow Chromosomal breaks, – Poma et al. 1981 

cells) exchanges 

As+3 Intraperitoneal Mouse (bone marrow Micronuclei + DeKnudt et al. 1986 

cells) 

As+3 Intraperitoneal Mouse Spermatongonia – Poma et al. 1981 

(spermatogonia) 

As+3 Intraperitoneal Mouse Sperm morphology – DeKnudt et al. 1986 

(spermatogonia) 

As+3 Intraperitoneal Mouse Dominant lethal – DeKnudt et al. 1986 

(spermatogenesis) mutations 

(+) = weakly positive or marginal result; – = negative result; + = positive result; DNA = deoxyribonucleic acid 
ARSENIC 208 

3. HEALTH EFFECTS 

Investigations of genotoxic effects of ingested arsenic have yielded mixed results possibly due to the 

different types of cells examined and the different exposure levels experienced by the populations studied. 

A study of p53 mutations in arsenic-related skin cancers from patients in Taiwan exposed to arsenic from 

drinking water found a high rate of p53 mutations and different types of p53 mutations compared with 

those seen in UV-induced skin cancers (Hsu et al. 1999); similar results have been found in mice (Salim 

et al. 2003). In humans exposed to Fowler's solution (potassium arsenite, usually taken at a dose of about 

0.3 mg As/kg/day [Holland 1904]), increased sister chromatid exchanges, but no increase in chromosomal 

aberrations, was reported in one study (Burgdorf et al. 1977), while just the converse (increased 

aberrations but no increase in sister chromatid exchange) was reported in another (Nordenson et al. 1979). 

Moore et al. (1997a) reported an exposure-dependent increase in the occurrence of micronucleated cells 

in epithelial cells from the bladder in a male population in northern Chile chronically exposed to high and 

low arsenic levels in their drinking water (average concentrations, 600 and 15 μg As/L, respectively), and 

noted that chromosome breakage was the major cause of micronucleus (MN) formation. Similar results 

were reported by Martínez et al. (2004) who evaluated micronuclei formation in peripheral lymphocytes 

from people in northern Chile exposed to up to 0.75 mg As/L in their drinking water. In contrast, 

Martínez et al. (2005) did not find a significant increase in micronuclei in buccal cells from subjects from 

the same area relative to a low exposure group. Vig et al. (1984) found no significant differences in the 

frequency of chromosomal aberrations or sister chromatid exchanges between two populations in Nevada 

with differing levels of arsenic in their drinking water (mean concentrations of 5 and 109 μg/L). In 

animal studies, an increased incidence of chromosomal abnormalities was detected in rats given oral 

doses of sodium arsenate (4 mg As/kg/day) for 2–3 weeks (Datta et al. 1986), but no consistent increase 

in chromosomal aberrations was detected in bone marrow cells or spermatogonia from mice given sodium 

arsenite (about 50 mg As/kg/day) for up to 8 weeks (Poma et al. 1987). These studies suggest that 

ingested arsenic may cause chromosomal effects, but these data are too limited to draw a firm conclusion. 

Organic Arsenicals. The genotoxicity of the organic arsenicals has been investigated in a number of 

studies (see Table 3-10). Several tests indicate that DMA and roxarsone may be able to cause 

chromosome aberrations, mutations, and deoxyribonucleic acid (DNA) strand breaks; in vitro studies with 

MMA did not find significant increases in the occurrence of chromosome aberrations, forward or reverse 

mutations, unscheduled DNA synthesis (Chun and Killeen 1989a, 1989b, 1989c, 1989d). An increased 

number of DNA strand breaks were detected in lung and other tissues of mice and rats given oral doses of 

~1,500 mg/kg DMA (Okada and Yamanaka 1994; Yamanaka et al. 1989a); this effect appeared to be 

related to the formation of some active oxygen species. These breaks were largely repaired within 

24 hours, so the relevance with respect to health risk is uncertain. 
ARSENIC 209 

3. HEALTH EFFECTS 

Table 3-10. Genotoxicity of Organic Arsenic 

Results 

With Without 

Chemical form Species (test system) End point activation activation Reference 

Prokaryotic organisms (in vitro): 

MMA Salmonella typhimurium Gene mutation – – Chun and 

Killeen 1989c 

DMA Escherichia coli Gene mutation No data + Yamanaka et 

al. 1989b 

Roxarsone S. typhimurium Gene mutation – – NTP 1989b 

Eukaryotic organisms (in vitro): 

MMA Chinese hamster ovary Chromosome – – Chun and 

cells aberrations Killeen 1989a 

MMA Mouse lymphoma cells Forward mutation – – Chun and 

(L5178Y/TK+/-) Killeen 1989b 

MMA Rat heptocytes Unscheduled DNA No data – Chun and 

synthesis Killeen 1989d 

DMA Human peripheral Mitogenesis No data – Endo et al. 

lymphocytes inhibited 1992 

DMA Human lymphocytes Sister chromatid No data – Rasmussen 

exchange and Menzel 

1997 

DMA Human alveolar (L-132) Lung-specific DNA No data + Kato et al. 

cells damage 1994 

DMA Human alveolar type II DNA single-strand + + Kawaguchi et 

(L-132) cells breaks al. 1996 

DMA Human diploid L-132 DNA single-strand No data + Rin et al. 1995 

epithelial cells breaks 

DMA Human alveolar type II DNA strand breaks No data + Tezuka et al. 

(L-132) cells 1993 

DMA Human embryonic cell DNA single-strand No data + Yamanaka et 

line of type II alveolar breaks and DNA- al. 1993 

epithelial cells (L-132) protein crosslinks 

DMA Human alveolar DNA single-strand No data + Yamanaka et 

epithelial (L-132) cells breaks and DNA- al. 1995 

protein crosslinks 

DMA Human pulmonary DNA single-strand No data + Yamanaka et 

epithelial (L-132) cells breaks al. 1997 

DMA Human umbilical cord Chromosomal No data + Oya-Ohta et al. 

fibroblasts aberrations 1996 

DMA Mouse lymphoma cells Chromosomal No data + Moore et al. 

(L5178Y/TK+

/

-

-3.7.2C) mutations 1997a 

DMA Chinese hamster lung Mitotic arrest and No data + Endo et al. 

and diploid cells (V79) tetraploid 1992 

formation 
ARSENIC 210 

3. HEALTH EFFECTS 

Table 3-10. Genotoxicity of Organic Arsenic 

Results 

With Without 

Chemical form Species (test system) End point activation activation Reference 

DMA Chinese hamster V79 Chromosomal No data + Ueda et al. 

cells aberrations 1997 

DMA Chinese hamster lung Chromosomal No data + Kitamura et al. 

and diploid cells (V79) aberrations 2002 

DMA Chinese hamster lung Chromosomal + + Kuroda et al. 

and diploid cells (V79) aberrations 2004 

DMA Chinese hamster V79 Tetraploids and No data + Eguchi et al. 

cells mitotic arrest 1997 

MMA Human umbilical cord Chromosomal No data + Oya-Ohta et al. 

fibroblasts aberrations 1996 

MMA Chinese hamster V79 Tetraploids and No data + Eguchi et al. 

cells mitotic arrest 1997 

Roxarsone Drosophila Sex linked No data – NTP 1989b 

melanogaster recessive 

Roxarsone Rat hepatocyte DNA double- No data + Storer et al. 

strand breaks 1996 

Roxarsone A31-1-13 clone of Transformation No data – Matthews et al. 

BALB/c-3T3 cells response and 1993 

mutagenicity 

Roxarsone Mouse lymphoma Trifluorothymidine No data + NTP 1989b 

(L5178Y) cells resistance 

Eukaryotic organisms (in vivo): 

DMA Rat (oral exposure) DNA single-stand No data + Yamanaka and 

breaks in lung Okada 1994 

DMA Mouse (oral exposure) DNA strand breaks No data + Yamanaka et 

in tissues al. 1989b 

DMA Mouse (oral exposure) DNA single-stand No data + Yamanaka et 

breaks in lung al. 1993 

DMA Mouse (oral exposure) DNA single-strand No data – Yamanaka et 

breaks in lung al. 1989a 

DMA Mouse (oral exposure) DNA adduct No data + Yamanaka et 

formation al. 2001 

DMA Mouse (injection) Aneuploidy in No data + Kashiwada et 

bone marrow cells al. 1998 

– = negative result; + = positive result; DMA = dimethylarsinic acid; DNA = deoxyribonucleic acid; MMA = monomethylarsonic acid 
ARSENIC 211 

3. HEALTH EFFECTS 

3.4 TOXICOKINETICS 

There is an extensive database on the toxicokinetics of inorganic arsenic. Most studies have been 

performed in animals, but there are a number of studies in humans as well. These studies reveal the 

following main points: 

•	 Both arsenate and arsenite are well absorbed by both the oral and inhalation routes. Absorption by 

the dermal route has not been well characterized, but is low compared to the other routes. Inorganic 

arsenic in soil is absorbed to a lesser extent than solutions of arsenic salts. 

•	 The rate of absorption of arsenic in highly insoluble forms (e.g., arsenic sulfide, lead arsenate) is 

much lower than that of more soluble forms via both oral and inhalation routes. 

•	 Once absorbed, arsenites are oxidized to arsenates and methylated. This process may then be 

repeated to result in dimethylated arsenic metabolites. 

•	 Distribution of arsenic in the rat is quite different from other animal species, suggesting that the rat is 

probably not an appropriate toxicokinetic model for distribution, metabolism, or excretion of arsenic 

by humans. 

•	 The As(+3) form undergoes enzymic methylation primarily in the liver to form MMA and DMA. 

The rate and relative proportion of methylation production varies among species. The rate of 

methylation varies considerably among tissues. 

•	 Most arsenic is promptly excreted in the urine as a mixture of As(+3), As(+5), MMA, and DMA; 

DMA is usually the primary form in the urine. Smaller amounts are excreted in feces. Some arsenic 

may remain bound to tissues, depending inversely on the rate and extent of methylation. 

Less information is available for the organic arsenicals. It appears that both MMA and DMA are well 

absorbed, but are rapidly excreted in the urine and feces. MMA may be methylated to DMA, but neither 

MMA nor DMA are demethylated to yield inorganic arsenic. 

A review of the evidence that supports these conclusions is presented below. 

3.4.1 Absorption 

3.4.1.1 Inhalation Exposure 

Inorganic Arsenicals. Since arsenic exists in air as particulate matter, absorption across the lung 

involves two processes: deposition of the particles onto the lung surface, and absorption of arsenic from 

the deposited material. In lung cancer patients exposed to arsenic in cigarette smoke, deposition was 
ARSENIC 212 

3. HEALTH EFFECTS 

estimated to be about 40% and absorption was 75–85% (Holland et al. 1959). Thus, overall absorption 

(expressed as a percentage of inhaled arsenic) was about 30–34%. In workers exposed to arsenic trioxide 

dusts in smelters, the amount of arsenic excreted in the urine (the main route of excretion; see 

Section 3.4.4) was about 40–60% of the estimated inhaled dose (Pinto et al. 1976; Vahter et al. 1986). 

Absorption of arsenic trioxide dusts and fumes (assessed by measurement of urinary metabolites) 

correlated with time weighted average arsenic air concentrations from personal breathing zone air 

samplers (Offergelt et al. 1992). Correlations were best immediately after a shift and just before the start 

of the next shift. Although the percent deposition was not measured in these cases, it seems likely that 

nearly all of the deposited arsenic was absorbed. This conclusion is supported by intratracheal instillation 

studies in rats and hamsters, where clearance of oxy compounds of arsenic (sodium arsenite, sodium 

arsenate, arsenic trioxide) from the lung was rapid and nearly complete (60–90% within 1 day) 

(Marafante and Vahter 1987; Rhoads and Sanders 1985). In contrast, arsenic sulfide and lead arsenate 

were cleared more slowly (Marafante and Vahter 1987), indicating that the rate of absorption may be 

lower if the inhaled arsenic is in a highly insoluble form. There are no data to suggest that absorption of 

inhaled arsenic in children differs from that in adults. 

Organic Arsenicals. No studies were located regarding absorption of organic arsenicals in humans or 

animals after inhalation exposure. However, DMA instilled in the lungs of rats was absorbed very rapidly 

(half-time of 2.2 minutes) and nearly completely (at least 92%) (Stevens et al. 1977). This indicates that 

organic arsenicals are likely to be well absorbed by the inhalation route. 

3.4.1.2 Oral Exposure 

Inorganic Arsenicals. Several studies in humans indicate that arsenates and arsenites are well absorbed 

across the gastrointestinal tract. The most direct evidence is from a study that evaluated the 6-day 

elimination of arsenic in healthy humans who were given water from a high-arsenic sampling site (arsenic 

species not specified) and that reported approximately 95% absorption (Zheng et al. 2002). A similar 

absorption efficiency can be estimated from measurements of fecal excretion in humans given oral doses 

of arsenite, where <5% was recovered in the feces (Bettley and O'Shea 1975). This indicates absorption 

was at least 95%. These results are supported by studies in which urinary excretion in humans was found 

to account for 55–87% of daily oral intakes of arsenate or arsenite (Buchet et al. 1981b; Crecelius 1977; 

Kumana et al. 2002; Mappes 1977; Tam et al. 1979b). In contrast, ingestion of arsenic triselenide 

(As2Se3) did not lead to a measurable increase in urinary excretion (Mappes 1977), indicating that 
ARSENIC 213 

3. HEALTH EFFECTS 

gastrointestinal absorption may be much lower if highly insoluble forms of arsenic are ingested. There 

are no data to suggest that absorption of arsenic from the gut in children differs from that in adults. 

These observations in humans are supported by a number of studies in animals. Fecal excretion of 

arsenates and arsenites ranged from 2 to 10% in monkeys and mice, with 70% or more appearing in urine 

(Charbonneau et al. 1978; Roberts et al. 2002; Vahter 1981; Vahter and Norin 1980). Oral absorption of 

[

73As] labeled sodium arsenate in mice was unaffected by dose (0.0005–5 mg/kg) as reflected in 

percentage of dose excreted in feces over 48 hours (Hughes et al. 1994). Absorption ranged from 82 to 

89% at all doses. Gonzalez et al. (1995) found that the percentage of arsenate that was absorbed in rats 

decreased as the dose increased from 6 to 480 μg, suggesting saturable, zero-order absorption of arsenate 

in this species. Hamsters appear to absorb somewhat less than humans, monkeys, and mice, since fecal 

excretion usually ranges from 10 to 40% (Marafante and Vahter 1987; Marafante et al. 1987a; Yamauchi 

and Yamamura 1985). Rabbits also appear to absorb less arsenate than humans, monkeys, or mice after 

oral exposure (Freeman et al. 1993). After a gavage dose of 1.95 mg/kg sodium arsenate, 45% of the 

arsenate was recovered in feces in males and 52% in females. As in humans, when highly insoluble 

arsenic compounds are administered (arsenic trisulfide, lead arsenate), gastrointestinal absorption is 

reduced 20–30% (Marafante and Vahter 1987). 

Bioavailability of arsenic was measured in rabbits ingesting doses of smelting soils that contained arsenic 

primarily in the form of sulfides (Freeman et al. 1993). Bioavailability was assessed by comparing the 

amounts of arsenic that was excreted after ingestion of the soil to that excreted after an intravenous dose 

of sodium arsenate. The bioavailability of the arsenic in the ingested soil was 24±3.2% and that of 

sodium arsenate in the gavage dose was 50±5.7%. Approximately 80% of the arsenic from ingested soil 

was eliminated in the feces compared with 50% of the soluble oral dose and 10% of the injected dose. In 

another study, rabbits dosed with sodium arsenite (0.8 mg As/kg) had 5 times greater blood arsenic 

concentrations than rabbits dosed with arsenic-containing soil (2.8 mg As/kg), suggesting a lower 

bioavailability of the arsenic in soil (Davis et al. 1992). 

Studies of the bioavailability of arsenic suggest that absorption of arsenic in ingested dust or soil is likely 

to be considerably less than absorption of arsenic from ingested salts (Davis et al. 1992, 1996; EPA 

1997g; Freeman et al. 1993, 1995; Pascoe et al. 1994; Roberts et al. 2002, 2007; Rodriguez et al. 1999). 

Oral absorption of arsenic in a group of three female Cynomolgus monkeys from a soluble salt, soil, and 

household dust was compared with absorption of an intravenous dose of sodium arsenate (Freeman et al. 

1995). Mean absolute percentage bioavailability based on urine arsenic excretion was reported at 
ARSENIC 214 

3. HEALTH EFFECTS 

67.6±2.6% (gavage), 19.2±1.5% (oral dust), and 13.8±3.3% (oral soil). Mean absolute percentage 

bioavailability based on blood arsenic levels was reported at 91.3±12.4% (gavage), 9.8±4.3% (oral dust), 

and 10.9±5.2% (oral soil). The arsenic in the dust and soil was approximately 3.5–5-fold (based on levels 

in the urine) and 8–9-fold (based on levels in the blood) less bioavailable than arsenic in solution. Two 

other studies in monkeys reported relative bioavailability of arsenic in soil from a number of locations 

(electrical substation, wood preserving sites, pesticide sites, cattle-dip sites, volcanic soil, and mining 

sites) ranged from 5 to 31% (Roberts et al. 2002, 2007). A study in beagle dogs fed with soil containing 

As2O5 or treated with intravenous soluble arsenic found that compared to injection the bioavailability of 

arsenic from ingested soil was 8.3±2.0% (Groen et al. 1993). The bioavailability of arsenic in soil has 

been studied in juvenile swine that received daily oral doses of soil or sodium arsenate (in food or by 

gavage) for 15 days (EPA 1997g). The soils were obtained from various mining and smelting sites and 

contained, in addition to arsenic at concentrations of 100–300 μg/g, lead at concentrations of 3,000– 

14,000 μg/g. The arsenic doses ranged from 1 to 65.4 μg/kg/day. The fraction of the arsenic dose 

excreted in urine was measured on days 7 and 14 and the relative bioavailability of the soil-borne arsenic 

was estimated as the ratio of urinary excretion fractions, soil arsenic:sodium arsenate. The mean relative 

bioavailability of soil-borne arsenic ranged from 0 to 98% in soils from seven different sites (mean±SD, 

45%±32). Estimates for relative bioavailability of arsenic in samples of smelter slag and mine tailings 

ranged from 7 to 51% (mean±SD, 35%±27). Rodriguez et al. (1999) used a similar approach to estimate 

the relative bioavailability of arsenic in mine and smelter wastes (soils and solid materials) in juvenile 

swine. Samples included iron slag deposits and calcine deposits and had arsenic concentrations that 

ranged from 330 to 17,500 μg/g. Relative bioavailability (waste:sodium arsenate) ranged from 3 to 43% 

for 13 samples (mean, 21%) and was higher in iron slag wastes (mean, 25%) than in calcine wastes 

(mean, 13%). 

Bioavailability of arsenic from soil is reduced by low solubility and inaccessibility due to the presence of 

secondary reaction products or insoluble matrix components (Davis et al. 1992). This is supported by 

studies conducted with in vitro simulations of the gastric and/or intestinal fluids (Hamel et al. 1998; 

Pouschat and Zagury 2006; Rodriguez et al. 1999; Ruby et al. 1996, 1999; Williams et al. 1998). When 

soils containing arsenic are incubated in simulated gastrointestinal fluids, only a fraction of the arsenic 

becomes soluble. Estimates of the soluble, or bioaccessible, arsenic fraction have ranged from 3 to 50% 

for various soils and mining and smelter waste materials (Pouschat and Zagury 2006; Rodriguez et al. 

1999; Ruby et al. 1996); these estimates are similar to in vivo estimates of the relative bioavailability of 

arsenic in these same materials (Ruby et al. 1999). 
ARSENIC 215 

3. HEALTH EFFECTS 

Organic Arsenicals. Based on urinary excretion studies in volunteers, it appears that both MMA and 

DMA are well absorbed (at least 75–85%) across the gastrointestinal tract (Buchet et al. 1981a; Marafante 

et al. 1987b). This is supported by studies in animals, where at least 75% absorption has been observed 

for DMA (Marafante et al. 1987b; Stevens et al. 1977; Vahter et al. 1984; Yamauchi and Yamamura 

1984) and MMA (Hughes et al. 2005; Yamauchi et al. 1988). In mice, the relative bioavailability of 

MMA appears to be dose-dependent; 81% was absorbed following a single gavage dose of 0.4 mg 

MMA/kg/day compared to 60% following administration of 4 mg MMA/kg/day (Hughes et al. 2005). 

3.4.1.3 Dermal Exposure 

Inorganic Arsenicals. No quantitative studies were located on absorption of inorganic arsenicals in 

humans after dermal exposure. Percutaneous absorption of [73As] as arsenic acid (H3AsO4) alone and 

mixed with soil has been measured in skin from cadavers (Wester et al. 1993). Labeled arsenic was 

applied to skin in diffusion cells and transit through the skin into receptor fluid measured. After 24 hours, 

0.93% of the dose passed through the skin and 0.98% remained in the skin after washing. Absorption was 

lower with [73As] mixed with soil: 0.43% passed through the skin over 24 hours and 0.33% remained in 

the skin after washing. 

Dermal absorption of arsenic has been measured in Rhesus monkeys (Lowney et al. 2005; Wester et al. 

1993). After 24 hours, 6.4% of [73As] as arsenic acid was absorbed systemically, as was 4.5% of [73As] 

mixed with soil (Wester et al. 1993). Similarly, 2.8% of soluble arsenic in water was detected in the urine 

24 hours after exposure (Lowney et al. 2005). However, arsenic from soil was poorly absorbed; 0.12% 

was detected in the urine after 24 hours. Differences between the Wester et al. (1993) and Lowney et al. 

(2005) studies in terms of uptake from soil may be due to the differences in forms of arsenic in the soil. 

In the Wester et al. (1993) study, soil was mixed with radiolabelled arsenic acid in water; Lowney et al. 

(2005) used soil samples from a pesticide manufacturing facility that historically manufactured arsenical 

pesticides (the arsenic was primarily in the iron oxide and iron silicate mineral phases). Lowney et al. 

(2005) also measured urinary levels of arsenic following dermal application of CCA residues and found 

that the levels did not increase from background. Uptake of arsenic into blood or tissues was undetectable 

for up to 24 hours in rats whose tails were immersed in solutions of sodium arsenate for 1 hour. 

However, arsenic began to increase in blood, liver, and spleen over the next 5 days (Dutkiewicz 1977). 

The rate of uptake was estimated to be 1–33 μg/cm2

/hour. These findings suggest that dermal exposure 

leads initially to arsenic binding to skin, and that the bound arsenic may slowly be taken up into the 

blood, even after exposure ends. 
ARSENIC 216 

3. HEALTH EFFECTS 

Organic Arsenicals. No studies were located on absorption of organic arsenicals in humans or animals 

after dermal exposure. 

3.4.2 Distribution 

3.4.2.1 Inhalation Exposure 

Inorganic Arsenicals. No studies were located on the distribution of arsenic in humans or animals after 

inhalation exposure, but intratracheal administration of arsenic trioxide to rats resulted in distribution of 

arsenic to the liver, kidney, skeleton, gastrointestinal tract, and other tissues (Rhoads and Sanders 1985). 

This is consistent with data from oral and parenteral studies (below), which indicate that absorbed arsenic 

is distributed throughout the body. 

Organic Arsenicals. No studies were located regarding the distribution of organic arsenicals in humans 

or animals after inhalation exposure. However, DMA administered to rats by the intratracheal route was 

distributed throughout the body (Stevens et al. 1977), suggesting that inhalation of organic arsenicals 

would also lead to widespread distribution. 

3.4.2.2 Oral Exposure 

Inorganic Arsenicals. Analysis of tissues taken at autopsy from people who were exposed to background 

levels of arsenic in food and water revealed that arsenic is present in all tissues of the body (Liebscher and 

Smith 1968). Most tissues had about the same concentration level (0.05–0.15 ppm), while levels in hair 

(0.65 ppm) and nails (0.36 ppm) were somewhat higher. This indicates that there is little tendency for 

arsenic to accumulate preferentially in any internal organs. However, exposure levels may not have been 

high enough to cause elevated levels in tissues. Arsenic exposure may have been low enough that the 

methylation process in the body resulted in limited accumulation in internal organs. Tissue analysis of 

organs taken from an individual following death from ingestion of 8 g of arsenic trioxide (about 3 g of 

arsenic) showed a much higher concentration of arsenic in liver (147 μg/g) than in kidney (27 μg/g) or 

muscle, heart, spleen, pancreas, lungs, or cerebellum (11–12 μg/g) (Benramdane et al. 1999a). Small 

amounts were also found in other parts of the brain (8 μg/g), skin (3 μg/g), and hemolyzed blood 

(0.4 μg/g). Many studies have been performed where arsenic levels in hair and nails have been measured 

and correlations with exposure analyzed. Some of these studies are discussed in Section 3.8, Biomarkers 

of Exposure. 
ARSENIC 217 

3. HEALTH EFFECTS 

Inorganic arsenic passes easily through the placenta. High levels of arsenic were found in the liver, 

kidney, and brain during autopsy of an infant prematurely born to a young mother who had ingested 

inorganic arsenic at week 30 of gestation (Lugo et al. 1969). Arsenic was detected in human breast milk 

at concentrations of 0.00013–0.00082 ppm in a World Health Organization study (Somogyi and Beck 

1993). Arsenic concentrations were 0.0001–0.0044 ppm in human milk sampled from 88 mothers on the 

Faroe Islands whose diets were predominantly seafood (Grandjean et al. 1995). Exposures to arsenic 

from the seafood diet in this population was most likely to organic “fish arsenic.” In a population of 

Andean women exposed to high concentrations (about 200 ppb) of inorganic arsenic in drinking water, 

concentrations of arsenic in breast milk ranged from about 0.0008 to 0.008 ppm (Concha et al. 1998b). 

Studies in mice and hamsters given oral doses of arsenate or arsenite have found elevated levels of arsenic 

in all tissues examined (Hughes et al. 2003; Vahter and Norin 1980; Yamauchi and Yamamura 1985), 

including the placenta and fetus of pregnant females (Hood et al. 1987, 1988). Inorganic arsenic crosses 

the placental barrier and selectively accumulates in the neuroepithelium of the developing animal embryo 

(Hanlon and Ferm 1977; Lindgren et al. 1984). In mice, radiolabel from orally administered 74-As was 

widely distributed to all tissues, with the highest levels in skin, kidney, and liver (Hughes et al. 2003). No 

obvious differences between As(+3) and As(+5) were found, although residual levels after 24 hours 

tended to be higher for As(+3) than As(+5) (Vahter and Norin 1980). However, in vitro studies have 

found that the cellular uptake of As(+3) was higher than that of As(+5) (Bertolero et al. 1987; Dopp et al. 

2004); in mouse cells, the difference was 4-fold (Bertolero et al. 1987). In hamsters, increases in tissue 

levels were noted after oral treatment with As(+3) for most tissues (hair, kidney, liver, lung, skin, 

muscle), with the largest increases in liver and lung (Yamauchi and Yamamura 1985). Liver and kidney 

arsenic concentrations increased with dose in dogs fed arsenite in the diet for 6 months (Neiger and 

Osweiler 1992). A study examining the speciation of arsenic following a single dose exposure to sodium 

arsenate to mice (Kenyon et al. 2005) found that the levels of inorganic arsenic and DMA were similar in 

the blood, liver, and kidney; much lower levels of MMA were found in these tissues. The concentration 

of DMA in the lungs exceeded inorganic arsenic and the levels of inorganic arsenic and MMA were 

similar; the DMA concentration was about 6 times higher than that of inorganic arsenic. 

Inorganic arsenic crosses the placental barrier and selectively accumulates in the neuroepithelium of the 

developing animal embryo (Hanlon and Ferm 1977; Lindgren et al. 1984). Following maternal exposure 

to arsenite or arsenate throughout gestation and lactation, inorganic arsenic and DMA were detected in the 
ARSENIC 218 

3. HEALTH EFFECTS 

newborn mouse brains (Jin et al. 2006). The levels of inorganic arsenic in the brain were similar to those 

in the newborn livers; however, the levels of DMA in the brain were about twice as high as in the liver. 

Organic Arsenicals. No studies were located on the distribution of organic arsenicals in humans 

following oral exposure. Studies in animals found MMA and DMA distributed to all tissues after acute 

oral doses (Hughes et al. 2005; Stevens et al. 1977; Vahter et al. 1984; Yamauchi and Yamamura 1984; 

Yamauchi et al. 1988). In mice, MMA is rapidly distributed throughout the body with peak tissue 

concentrations occurring between 0.25 and 4 hours after administration of a single gavage dose of 0.4 or 

4 mg MMA/kg (Hughes et al. 2005). The peak levels of MMA in the bladder, kidneys, and lungs were 

higher than blood, with the highest levels occurring in the bladder. The terminal half-lives of MMA were 

4.2–4.9 hours in the liver, lung, and blood, 9.0 hours in the urinary bladder, and 15.9 hours in the kidney 

in mice dosed with 0.4 mg MMA/kg; similar half-lives were measured in the 4.0 mg MMA/kg mice. 

Two hours after dosing, most of the methylated arsenic in the tissues was in the form of MMA. In rats 

exposed to 100 mg/kg DMA in the diet for 72 days, high levels of arsenic was detected in the blood (Lu 

et al. 2004a). The arsenic was primarily found in the erythrocyte; the concentration in the erythrocyte 

was 150 times higher than the arsenic concentration in the plasma. 

3.4.2.3 Dermal Exposure 

No studies were located regarding distribution of inorganic or organic arsenicals in humans or animals 

after dermal exposure. 

3.4.2.4 Other Routes of Exposure 

Inorganic Arsenicals. Studies in mice, rabbits, and monkeys injected intravenously with solutions of 

arsenite or arsenate confirm that arsenic is widely distributed throughout the body (Lindgren et al. 1982; 

Marafante and Vahter 1986; Vahter and Marafante 1983; Vahter et al. 1982). Shortly after exposure, the 

concentration of arsenic tends to be somewhat higher in liver, kidney, lung, and gastrointestinal 

epithelium (Hughes et al. 2000; Lindgren et al. 1982; Vahter and Marafante 1983; Vahter et al. 1982), but 

levels tend to equilibrate over time. Arsenate shows a tendency to deposit in skeletal tissue that is not 

shared by arsenite (Lindgren et al. 1982, 1984), presumably because arsenate is an analog of phosphate. 

The distribution of arsenic in the rat is quite different from other animal species. Following intramuscular 

injection of carrier-free radio-arsenate in rats, most of the injected arsenic became bound to hemoglobin 

in red blood cells, and very little reached other tissues (Lanz et al. 1950). However, similar experiments 
ARSENIC 219 

3. HEALTH EFFECTS 

in dogs, mice, guinea pigs, rabbits, and chicks found very little uptake of arsenic into the blood in these 

species (cats gave intermediate results). 

Organic Arsenicals. Following intravenous administration of DMA in mice, DMA is rapidly distributed 

throughout the body (Hughes et al. 2000). In the blood, the DMA was initially detected in the plasma, but 

fairly rapidly equilibrated between the plasma and erythrocytes. Blood, plasma, erythrocyte, liver, and 

kidney distribution and elimination of DMA did not differ in groups of mice administered 1.11 or 111 mg 

DMA/kg. However, a significant difference in DMA elimination from the lungs was observed; the 

elimination half-time increased from 91 minutes in the 1.11 mg DMA/kg group to 6,930 minutes in the 

111 mg DMA/kg group. 

3.4.3 Metabolism 

Inorganic Arsenicals. The metabolism of inorganic arsenic has been extensively studied in humans and 

animals, and is diagrammed in Figure 3-7. Two basic processes are involved: (1) reduction/oxidation 

reactions that interconvert As(III) and As(V), and (2) methylation reactions, which convert arsenite to 

MMA and DMA. The resulting series of reactions results in the reduction of inorganic arsenate to 

arsenite (if necessary), methylation to MMA(V), reduction to MMA(III), and methylation to DMA(V). 

These processes appear to be similar whether exposure is by the inhalation, oral, or parenteral route. The 

human body has the ability to change inorganic arsenic to organic forms (i.e., by methylation) that are 

more readily excreted in urine. In addition, inorganic arsenic is also directly excreted in the urine. It is 

estimated that by means of these two processes, >75% of the absorbed arsenic dose is excreted in the 

urine (Marcus and Rispin 1988), although this may vary with the dose and exposure duration. This 

mechanism is thought to have an upper-dose limit which, when overwhelmed, results in a higher 

incidence of arsenic toxicity. This is supported by a case report of an individual who died 3 days after 

ingesting 8 g of arsenic trioxide (about 3 g of arsenic) (Benramdane et al. 1999a). Only 20% of the total 

arsenic in all tissues analyzed was methylated (14% MMA, 6% DMA), while 78% remained as arsenite 

and 2% as arsenate. 

The majority of the evidence characterizing the metabolic pathways of arsenic is derived from analysis of 

urinary excretion products. Exposure of humans to either arsenates or arsenites results in increased levels 

of inorganic As(+3), inorganic As(+5), MMA, and DMA in urine (Aposhian et al. 2000a, 2000b; Buchet 

et al. 1981a, 1981b; Concha et al. 1998a, 1998b; Crecelius 1977; Kurttio et al. 1998; Lovell and Farmer 
ARSENIC 220 

3. HEALTH EFFECTS 

Figure 3-7. Inorganic Arsenic Biotransformation Pathway 

Arsenate (AsV) Arsenite (AsIII) 

OH 

AsIII

OH 

GSH 

O OH HO OH

Arsenate 

AsV

O Reductase 

SAM 

Arsenite 

Methyltransferase 

SAHC 

O 

OH 

OH 

As CH3

V 

Methylarsonic acid (MMAV) 

MMAV GSH 

Reductase 

OH MMA 

AsIII 

OH

Methyltransferase

As O V CH CH3 3 

CH OH

3 

Dimethylarsinic acid SAHC SAM Methylarsonous acid 

(DMAV) (MMAIII) 

SAHC = S-adenosylhomocysteine; SAM = S-adenosylmethionine 

Source: adapted from Aposhian et al. 2000b 
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3. HEALTH EFFECTS 

1985; Smith et al. 1977; Tam et al. 1979b; Vahter 1986). Similar results are obtained from studies in 

mice (Vahter 1981; Vahter and Envall 1983), hamsters (Hirata et al. 1988; Marafante and Vahter 1987; 

Takahashi et al. 1988), and rabbits (Maiorino and Aposhian 1985; Marafante et al. 1985; Vahter and 

Marafante 1983). Historically, little distinction was made between MMA(V) and MMA(III) in the urine 

in most studies, and the assumption was that the majority of MMA in the urine was MMA(V); however, 

Aposhian et al. (2000a, 2000b) demonstrated that the methylated arsenic atom may be in either valance 

state. 

The relative proportions of As(+3), As(+5), MMA, and DMA in urine can vary depending upon the 

chemical administered, time after exposure, route of exposure, dose level, and exposed species. In 

general, however, DMA is the principal metabolite following long-term exposure, with lower levels of 

inorganic arsenic [As(+3) and As(+5)] and MMA. In humans, the relative proportions are usually about 

40–75% DMA, 20–25% inorganic arsenic, and 15–25% MMA (Buchet et al. 1981a; Hopenhayn et al. 

2003b; Loffredo et al. 2003; Mandal et al. 2001; Smith et al. 1977; Tam et al. 1979b; Tokunaga et al. 

2002; Vahter 1986). With relatively constant exposure levels, these metabolic proportions remain similar 

over time (Concha et al. 2002), and appear to be similar among family members (Chung et al. 2002). One 

study of groups of women and children in two villages in Argentina showed that children ingesting large 

amounts of arsenic in their drinking water (200 μg/L) excreted about 49% inorganic arsenic and 47% 

DMA (Concha et al. 1998b). This compared to 32% inorganic arsenic and 66% DMA for the women in 

the study. This may indicate that metabolism of arsenic in children is less efficient than in adults. The 

rabbit has a ratio of metabolites similar to human adults (Maiorino and Aposhian 1985), suggesting that 

this may be a good animal model for toxicokinetics in humans. Mice may also be a good human 

toxicokinetic model based on the similarity of arsenic metabolism and deposition (Vahter et al. 2002). In 

contrast, the guinea pig, marmoset, and tamarin monkey do not methylate inorganic arsenic (Healy et al. 

1998; Vahter and Marafante 1985; Vahter et al. 1982; Zakharyan et al. 1996); thus, they may be poor 

models for humans. 

Reduction of arsenate to arsenite can be mediated by glutathione (Menzel et al. 1994). Scott et al. (1993) 

showed that glutathione forms complexes with both arsenate and arsenite in vitro, and that glutathione is 

oxidized (and arsenate reduced) in the glutathione-arsenate reaction. Studies in vitro indicate that the 

substrate for methylation is As(+3), and that As(+5) is not methylated unless it is first reduced to As(+3) 

(Buchet and Lauwerys 1985, 1988; Lerman et al. 1983). The main site of methylation appears to be the 

liver, where the methylation process is mediated by enzymes that utilize S-adenosylmethionine as 

cosubstrate (Buchet and Lauwerys 1985, 1988). Under normal conditions, the availability of methyl 
ARSENIC 222 

3. HEALTH EFFECTS 

donors (e.g., methionine, choline, cysteine) does not appear to be rate limiting in methylating capacity, 

either in humans (Buchet et al. 1982) or in animals (Buchet and Lauwerys 1987; Buchet et al. 1981a). 

However, severe dietary restriction of methyl donor intake can result in significant decreases in 

methylating capacity (Buchet and Lauwerys 1987; Vahter and Marafante 1987). 

Arsenic methyltransferase and MMA methyltransferase activities have been purified to homogeneity from 

cytosol of rabbit liver (Zakharyan et al. 1995), Rhesus monkey liver (Zakharyan et al. 1996), and rat liver 

(Thomas et al. 2004). It appears that a single protein catalyzes both activities. This activity transfers a 

methyl group from S-adenosylmethionine to As(+3) yielding MMA, which is then further methylated to 

DMA. Reduced glutathione is probably a co-factor in vivo, but other thiols can substitute in vitro 

(L-cysteine, dithiothreitol). The substrate saturation concentration for rabbit arsenite methyltransferase is 

50 μM, for MMA methyltransferase it is 1,000 μM. The purified activity is specific for arsenite and 

MMA; selenite, selenate, selenide, and catechols do not serve as substrates. Thomas et al. (2004) 

reported cloning the gene for an S-adenosylmethionine-dependent methyltransferase from rat liver cytosol 

that catalyzes the conversion of arsenic to methylated and dimethylated species. It bears a high similarity 

to translations of cyt19 genes in both the mouse and the human; both this gene and protein are now 

termed arsenic (+3 oxidation state) methyltransferase (AS3MT). 

Studies in mice indicate that exposure to arsenic does not induce arsenic methylation activity (Healy et al. 

1998). Mice receiving up to 0.87 mg As/kg/day as sodium arsenate in drinking water for 91 days had the 

same arsenic methylating activity as unexposed controls. Specific activities were highest in testis 

(1.45 U/mg) followed by kidney (0.70 U/mg), liver (0.40 U/mg), and lung (0.20 U/mg). None were 

affected by arsenic exposure. 

An alternative biotransformation pathway (Figure 3-8) has recently been proposed for arsenic (Hayakawa 

et al. 2005) based on the nonenzymatic formation of glutathione complexes with arsenite resulting in the 

formation of arsenic triglutathione. The arsenic triglutathione is subsequently methylated by AS3MT to 

form monomethyl arsenic glutathione. At low glutathione levels (1 mM), the monomethyl arsenic 

glutathione is hydrolyzed to form MMA(III). At high glutathione levels (5 mM), the monomethyl arsenic 

glutathione is methylated to dimethylarsinic glutathione by AS3MT. Dimethylarsinic glutathione is 

quickly hydrolyzed to form DMA(III) (Hayakawa et al. 2005; Thomas et al. 2007). In the classical 

inorganic arsenic biotransformation pathway (Figure 3-7), MMA(V) is converted to the more toxic 

MMA(III); in contrast, in the alternative pathway, MMA(III) is converted to the less toxic MMA(V). 
ARSENIC 223 

3. HEALTH EFFECTS 

Figure 3-8. Alternative Inorganic Arsenic Biotransformation Pathway 

Arsenate (AsV) Arsenite (AsIII

) ATG 

OH OH GSH SG

III 

O As HO As OH GS As SG V OH 

OH SAM 

SAHC 

OH OH SG 

HO As CH3 GS As CH3 

O MMAIII 

HO As CH3 

MADG 

MMAV GSH SAM 

SAHC 

CH3 CH3 CH3 

HO As CH3 HO As CH3 GS As CH3 

O DMAIII DMAG 

DMAV GSH 

ATG = arsenic triglutathione; DMAG = dimethylarsinic glutathione; GSH = glutathione; MADG = monomethyl arsenic 

glutathione; SAHC = S-adenosylhomocysteine; SAM = S-adenosylmethionine 

Source: Hayakawa et al. 2005; Thomas et al. 2007 
ARSENIC 224 

3. HEALTH EFFECTS 

Since methylation tends to result in lower tissue retention of inorganic arsenic (Marafante and Vahter 

1984, 1986; Marafante et al. 1985; Vahter and Marafante 1987), the methylation process is usually 

viewed as a detoxification mechanism. However, several studies showing an elevated toxicity of 

MMA(III) relative even to As(III) in cultured human liver cells (Petrick et al. 2000, 2001) have called this 

assumption into question. Because methylation is an enzymic process, an important issue is the dose of 

arsenic that saturates the methylation capacity of an organism, resulting in a possible increased level of 

the more toxic As(III) in tissues, or whether or not such a dose exists. Limited data from studies in 

humans suggest that methylation may begin to become limiting at doses of about 0.2–1 mg/day (0.003– 

0.015 mg/kg/day) (Buchet et al. 1981b; Marcus and Rispin 1988). However, these observations are 

relatively uncertain since they are based on data from only a few subjects, and the pattern of urinary 

excretion products in humans who ingested high (near lethal) oral doses or were exposed to elevated 

levels in the workplace is not much different from that in the general population (Lovell and Farmer 

1985; Vahter 1986). Furthermore, the nutrient intakes reported by Engel and Receveur (1993) were 

sufficient to accommodate the body stores of methyl groups needed for arsenic biomethylation. At the 

highest arsenic level reported in the endemic area, the biomethylation process required only a few percent 

of the total daily methyl intake (Mushak and Crocetti 1995). Thus, the dose rate at which methylation 

capacity becomes saturated cannot be precisely defined with current data. 

Organic Arsenicals. With the exception of arsenosugars, which may undergo extensive metabolism, 

organic arsenicals appear to undergo little metabolism. Humans who ingested a dose of MMA converted 

a small amount (about 13%) to DMA (Buchet et al. 1981a). Similarly, in mice and hamsters, DMA and 

MMA are primarily excreted unchanged in the urine (Hughes et al. 2005; Marafante et al. 1987b; Vahter 

et al. 1984). In mice, a small percentage of MMA is methylated to DMA and some is further methylated 

to trimethylarsine oxide (TMAO) (Hughes et al. 2005). In contrast, administration of MMA(III) to mice 

resulted in the excretion of mostly DMA(V) and smaller amounts of MMA(V), MMA(III), and DMA(III) 

(Hughes et al. 2005). As with MMA, only a small percentage (<10%) of the DMA is methylated to 

TMAO (Hughes et al. 2005; Marafante et al. 1987b; Yamauchi and Yamamura 1984; Yamauchi et al. 

1988). 

MMA and DMA are more extensively methylated in rats compared to other animal species. After 1 week 

of exposure to 100 mg As/kg/day as MMA in drinking water, rats excreted 50.6% of the total arsenic in 

urine as MMA, 19.0% as DMA, 6.9% as TMAO, and 0.4% as tetramethylarsonium (Yoshida et al. 1998). 

In contrast, mice exposed to a single dose of 40 mg As/kg as MMA excreted 89.6% of the dose as MMA, 

6.2% as DMA, and 1.9% as TMAO (Hughes et al. 2005). Similarly, 24 hours after administration of a 
ARSENIC 225 

3. HEALTH EFFECTS 

single oral dose of 50 mg As/kg as MMA in hamsters, 26.9% was excreted in urine as MMA, 1.43% as 

DMA, and 0.07% as trimethylarsenic compound (Yamauchi et al. 1988). As with MMA, oral exposure of 

mice and hamsters to DMA results in most of the dose being excreted in the urine in the form of DMA (or 

DMA complex) (Marafante et al. 1987b); in rats, the levels of DMA and TMAO are about equal (Yoshida 

et al. 1998). 

The available data suggest that the methylarsenates are not demethylated to inorganic arsenic either in 

humans (Buchet et al. 1981a; Marafante et al. 1987b) or in animals (rats and hamsters) (Stevens et al. 

1977; Yamauchi and Yamamura 1984; Yoshida et al. 2001). 

3.4.4 Elimination and Excretion 

3.4.4.1 Inhalation Exposure 

Inorganic Arsenicals. As noted previously (see Section 3.4.1.1), urinary excretion of arsenic appears to 

account for 30–60% of the inhaled dose (Holland et al. 1959; Pinto et al. 1976; Vahter et al. 1986). Since 

the deposition fraction usually ranges from about 30 to 60% for most respirable particles (EPA 1989b), 

this suggests that nearly all arsenic that is deposited in the lung is excreted in the urine. The time course 

of excretion in humans exposed by inhalation has not been thoroughly investigated, but urinary arsenic 

levels in workers in a smelter rose within hours after they came to work on Monday and then fell over the 

weekend (Vahter et al. 1986). This implies that excretion is fairly rapid, and this is supported by 

intratracheal studies in rats (Rhoads and Sanders 1985) and hamsters (Marafante and Vahter 1987), where 

whole-body clearance of administered arsenate or arsenite occurred with a half-time of 1 day or less. 

However, the study in rats (Rhoads and Sanders 1985) found that the clearance of arsenic trioxide was 

biphasic, with 95% cleared with a half-time of 29 minutes and the remaining arsenic cleared with a halftime of 75 days. For sodium arsenate and sodium arsenite, <0.1% of the dose was retained in the lung 

3 days after exposure of hamsters; 1.3% of the arsenic trisulfide dose was retained after 3 days (Marafante 

and Vahter 1987). The Marafante and Vahter (1987) study suggested that lung clearance was influenced 

by compound solubility. The primary forms of arsenic found in the urine of inhalation-exposed humans 

are DMA and MMA, with inorganic arsenic comprising <25% of the total urinary arsenic (Apostoli et al. 

1999). 

Organic Arsenicals. No studies were located regarding the excretion of organic arsenicals by humans or 

animals after inhalation exposure. However, rats that were given a single intratracheal dose of DMA 
ARSENIC 226 

3. HEALTH EFFECTS 

excreted about 60% in the urine and about 8% in the feces within 24 hours (Stevens et al. 1977). This 

indicates that organic arsenicals are likely to be promptly excreted after inhalation exposure. 

3.4.4.2 Oral Exposure 

Inorganic Arsenicals. Direct measurements of arsenic excretion in humans who ingested known 

amounts of arsenite or arsenate indicate that very little is excreted in the feces (Bettley and O'Shea 1975), 

and that 45–85% is excreted in urine within 1–3 days (Apostoli et al. 1999; Buchet et al. 1981a; Crecelius 

1977; Mappes 1977; Tam et al. 1979b). At low exposure levels, urinary arsenic levels generally increase 

linearly with increasing arsenic intake (Calderon et al. 1999). During lactation, a very small percent of 

ingested arsenic may also be excreted in the breast milk (Concha et al. 1998a). A similar pattern of 

urinary and fecal excretion is observed in hamsters (Marafante and Vahter 1987; Yamauchi and 

Yamamura 1985) and mice (Vahter and Norin 1980); this pattern is typically modeled as a biphasic 

process (e.g., Hughes et al. 2003). Generally, whole body clearance is fairly rapid, with half-times of 40– 

60 hours in humans (Buchet et al. 1981b; Mappes 1977). Clearance is even more rapid in mice and 

hamsters, with 90% removed in 2 days (Hughes et al. 2003; Marafante and Vahter 1987; Vahter 1981; 

Vahter and Norin 1980). 

A study in pregnant women exposed to elevated levels of inorganic arsenic in drinking water found that 

most of the ingested arsenic was excreted in the urine as DMA (79–85%), with smaller amounts excreted 

as inorganic arsenic (8–16%) or MMA (5–6%) (Christian et al. 2006). Similarly, in mice, arsenate is 

primarily excreted in the urine as DMA, with lesser amounts of inorganic arsenic and MMA (Kenyon et 

al. 2005). Following a single oral dose of 10 μmol/kg sodium arsenate, 78.4% was excreted as DMA, 

20.2% as inorganic arsenic, and 1.45% as MMA; at a 10-fold higher dose, the ratio of DMA to inorganic 

arsenic decreased (57.7% DMA, 39.8% inorganic arsenic, and 2.59% MMA). 

Arsenic is also excreted in the bile via the formation of two arsenic-glutathione complexes (arsenic 

triglutathione and methylarsenic diglutathione) (Kala et al. 2000). In rats administered 5.0 mg/kg sodium 

arsenite, equal amounts of arsenic triglutathione and methylarsenic diglutathione were found in the bile 

18–20 minutes after exposure. At a lower arsenic dose (0.5 mg/kg), only methylarsenic diglutathione was 

found. As discussed in Section 3.4.4.4, biliary excretion of arsenic has also been detected in mice, 

hamsters, guinea pigs, and rabbits following parenteral exposure (Csanaky and Gregus 2002). 
ARSENIC 227 

3. HEALTH EFFECTS 

Organic Arsenicals. Studies in humans indicate that ingested MMA and DMA are excreted mainly in the 

urine (75–85%), and this occurs mostly within 1 day (Buchet et al. 1981a; Marafante et al. 1987b). This 

is supported by studies in rats, mice, and hamsters, although in animals, excretion is more evenly 

distributed between urine and feces (Hughes et al. 2005; Marafante et al. 1987b; Stevens et al. 1977; 

Yamauchi and Yamamura 1984; Yamauchi et al. 1988). In mice administered 40 mg As/kg as DMA, 

56.4% was excreted in the urine as DMA, 7.7% as a DMA complex, and 3.5% as TMAO during a 

48-hour period after dosing; in the feces, 24.3% was DMA and 4.9% as DMA complex (Marafante et al. 

1987b). In hamsters, 38.7% was DMA, 11.2% as DMA complex, and 6.4% as TMAO in the urine; in the 

feces, 37.3% as DMA and 4.9% as DMA complex. As with DMA, most MMA is excreted in the urine 

and feces as parent compound. In the urine of mice administered 0.4 mg As/kg as MMA, 98.2% of the 

urinary arsenicals was in the form of MMA(V) and 1.8% as MMA(III) (Hughes et al. 2005); at a 10-fold 

higher dose, 89.6% was excreted as MMA(V), 1.2% as MMA(III), 6.2% as DMA(V), 1.1% as DMA(III), 

and 1.9% as TMAO. As discussed previously, exposure of rats to MMA or DMA results in the excretion 

of a higher percentage of metabolites. After 1 week exposure to MMA, 50.6% of the dose was excreted 

as MMA, 19.0% as DMA, and 6.9% of TMAO (Yoshida et al. 1998). A 1-week exposure to DMA, 

44.9% was excreted as DMA in the urine and 40.0% as TMAO (Yoshida et al. 1998). A longer-term 

exposure to DMA (>7 months) resulted in a higher percentage of the amount of parent compound 

excreted; 56–65% as DMA and 23–35% as TMAO (Li et al. 1998; Wanibuchi et al. 1996; Yoshida et al. 

1998). 

In mice and hamsters, DMA and MMA are rapidly cleared from the body (Hughes et al. 2005; Marafante 

et al. 1987b; Vahter et al. 1984). In mice, 85% of the initial oral dose of DMA was eliminated from the 

body with a half-life of 2.5 hours (Vahter et al. 1984). In contrast to the mouse data, 45% on the initial 

DMA dose to rats was eliminated with a half-time of 13 hours and the remaining 55% had an elimination 

half-time of 50 days (Vahter et al. 1984). 

3.4.4.3 Dermal Exposure 

Inorganic Arsenicals. No studies were located regarding excretion of inorganic arsenicals in humans or 

animals following dermal exposure. In rats, arsenic absorbed through the tail was excreted approximately 

equally in urine and feces, similar to the excretion pattern following oral exposure (Dutkiewicz 1977). 

Organic Arsenicals. No studies were located regarding excretion of organic arsenicals in humans or 

animals following dermal exposure. 
ARSENIC 228 

3. HEALTH EFFECTS 

3.4.4.4 Other Routes of Exposure 

Inorganic Arsenicals. Excretion of arsenate and arsenite following parenteral exposure of animals is 

similar to that seen following oral exposure. In rabbits and mice, urinary excretion within 8 hours usually 

accounts for about 50–80% of the dose (Maehashi and Murata 1986; Maiorino and Aposhian 1985; 

Vahter and Marafante 1983). Somewhat lower levels (30–40%) are excreted in the urine of marmoset 

monkeys (Vahter and Marafante 1985; Vahter et al. 1982), probably because of the absence of 

methylation in this species. Whole-body clearance studies in mice indicate that arsenate is over 65% 

removed within 24 hours, while arsenite is about 86% removed at 24 hours (Lindgren et al. 1982). A 

relatively small proportion of an injected dose of arsenic V (10% for rats, 4% for mice, and <2% for 

hamsters, guinea pigs, and rabbits) was found to be excreted into the bile within the first 2 hours 

postinjection (Csanaky and Gregus 2002). Following arsenic III injection, a much greater percentage 

(92% for guinea pigs and 75% for rats) of the arsenic was found in the bile in the first 2 hours after 

administration (Csanaky and Gregus 2002). Similarly, approximately 40% of an intravenous dose of 

sodium arsenite was excreted into the bile of rats, most of it occurring during the first hour after exposure 

(Kala et al. 2000). Kala et al. (2000) determined that the biliary transport of arsenic was dependent on the 

formation of arsenic-glutathione complexes, which were transported out of hepatocytes by multidrug 

resistance associated protein 2 (MRP2/cMOAT); most of the arsenic in bile was in the form of arsenic 

triglutathione or methylarsenic diglutathione. 

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. 

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 
ARSENIC 229 

3. HEALTH EFFECTS 

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, and 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 3-9 shows a conceptualized representation of a PBPK model. 

If PBPK models for arsenic 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. 
ARSENIC 230 

3. HEALTH EFFECTS 

Figure 3-9. Conceptual Representation of a Physiologically Based 

Pharmacokinetic (PBPK) Model for a 

Hypothetical Chemical Substance 

Lu n g s 

Live r 

Fa t 

S low ly 

pe rfu s e d 

tis s u e s 

R ic h ly 

pe rfu s e d 

tis s u e s 

K idn ey 

Sk in 

V 

E 

N 

O 

U 

S 

B 

L 

O 

O 

D 

A 

R 

T 

E 

R 

I 

A 

L 

B 

L 

O 

O 

D 

V ma x 

K m 

In g e s tio n 

In h ale d c h em ic a l E x h ale d c h em ic a l 

GI 

T ra c t 

Fe c e s 

U rin e

 Ch e m ic a ls 

contac ting skin 

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 
ARSENIC 231 

3. HEALTH EFFECTS 

Several PBPK models have been developed for inorganic arsenic; the Mann, Yu, and Menzel models are 

discussed below. A joint research effort between the Chemical Industry Institute of Toxicology (CIIT) 

Centers for Health Research, EPA, ENVIRON International, and the Electric Power Research Institute 

(EPRI) is underway to develop a biologically based dose response model of carcinogenicity. Part of this 

effort involves refining the existing PBPK models (Clewell et al. 2007). 

3.4.5.1 Summary of PBPK Models 

The Mann model (Gentry et al. 2004; Mann et al. 1996a, 1996b), Yu model (Yu 1998a, 1998b; Yu 1999a, 

1999b), and Menzel model (Menzel et al. 1994) are the PBPK models for arsenic currently available. The 

Mann model simulates the absorption, distribution, metabolism, elimination, and excretion of As(+3), 

As(+5), MMA, and DMA after oral and inhalation exposure in mice, hamsters, rabbits, and humans. The 

Yu model simulates the absorption, distribution, metabolism, elimination, and excretion of As(+3), 

As(+5), MMA, and DMA after oral exposure to inorganic arsenic in mice, rats, or humans. The Menzel 

model is a preliminary model that predicts internal organ burden of arsenic during specific oral exposures, 

simulating the metabolism, distribution to organs and binding to organs in mice, rats, and humans. 

3.4.5.2 Arsenic PBPK Model Comparison 

The Mann model is a well-derived model, consisting of multiple compartments and metabolic processes, 

and modeling four chemical forms of arsenic (two organic and two inorganic), which has been validated 

using experimental data. The Yu model has more compartments than the Mann model, also models 

metabolism and fate of four forms of arsenic, and has likewise been validated using experimental data. 

The Menzel model is still preliminary and has not been validated. 

3.4.5.3 Discussion of Models 

The Mann Model 

Risk assessment. The Mann model was not used for risk assessment. 

Description of the model. The Mann model was initially developed to simulate oral, intratracheal, 

and intravenous exposure to arsenic in rabbits and hamsters (Mann et al. 1996a). In a companion paper, 

the model was expanded to include inhalation exposure and extrapolated and applied to humans (Mann et 

al. 1996b). A subsequent paper further expanded the model to include mice (Gentry et al. 2004). 
ARSENIC 232 

3. HEALTH EFFECTS 

The model consists of six tissue compartments: blood, liver, kidneys, lungs, skin, and other tissues. The 

blood compartment is divided into plasma and red blood cell subcompartments, considered to be at 

equilibrium. Three routes of exposure are considered in the model. Oral exposure is considered to enter 

the liver from the gastrointestinal tract via first-order kinetics. Intratracheal exposure results in deposition 

into the pulmonary and tracheo-bronchial regions of the respiratory tract. Uptake into blood from the 

pulmonary region is considered to be via first order kinetics into plasma, uptake from the tracheobronchial region is by both transfer into plasma and transport into the gastrointestinal tract. Intravenous 

injection results in a single bolus dose into the plasma compartment. 

Metabolism in the model consists of oxidation/reduction and two methylation reactions. The 

oxidation/reduction of inorganic arsenic was modeled as a first order process in the plasma, with 

reduction also included in the kidneys. Methylation of As(+3) was modeled as a two-step process 

occurring in the liver according to Michaelis-Menton kinetics. 

Most physiological parameters were derived by scaling to body weight. In cases where parameters were 

not available (absorption rates, tissue affinity, biotransformation), estimates were obtained by fitting. 

This was done by duplicating the initial conditions of published experiments in the model, varying the 

unknown parameters and comparing the results of the simulation to the reported results. Tissue affinity 

constants were estimated using reported arsenic levels in tissues at various times after exposure. 

Metabolic rate constants and absorption rate constants were estimated using data for excretion of arsenic 

metabolites in urine and feces. Figure 3-10 shows the animal model and Tables 3-11, 3-12, 3-13, and 

3-14 provide the parameters used in the animal model. The human model is similar to the animal models 

with adjustments for body weight and absorption and metabolic rates. A naso-pharynx compartment is 

included in the human model, which was not present in the animal models. Penetration and deposition in 

the respiratory tract are based on the log-normal particle size distribution of the aerosol. Metabolic and 

absorption rate constants were fitted using experimental data on urinary excretion of arsenic following a 

single oral dose of As(+3) (Buchet et al. 1981a) or As(+5) (Tam et al. 1979b) in volunteers. The lung 

absorption rate constant was obtained by fitting the total urinary excretion of arsenic as predicted with the 

model to experimental data obtained from occupational exposure to arsenic trioxide (Offergelt et al. 

1992). Figure 3-11 shows the human model, and Tables 3-15 and 3-16 provide the data and constants 

used in the human model. 
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3. HEALTH EFFECTS 

Figure 3-10. Parameters Used in the Mann PBPK Model for Animals 

Intratracheal Intravenous instillation injection Oral dose (μg As/kg BW) (μg As/kg BW) (μg As/kg BW) 

Urine Feces 

Kidneys 

Others 

Lungs 

Skin 

Liver 

Plasma 

RBCs 

GI tract 

Nasopharynx (NP) 

Tracheao-bronchiol (TB) 

Pulmonary (P) 

Keratin 

Source: Mann et al. 1996b 
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3. HEALTH EFFECTS 

Table 3-11. Parameters Used in the Mann PBPK Model for Animals 

Physiological parameter Rabbit (body weight=3.5 kg) Hamster (body weight=0.100 kg) 

Blood volume (mL) 253 7.0 

Organ weight (g) 

Liver 121 4.8 

Kidneys 25 1.2 

 Lungs 31 1.0 

Skin 420 17.1 

Organ volume (mL) 

Others 2,386 62.0 

Lumen volume (mL) 

Stomach 15 0.5 

 Small intestine 20 0.6 

Blood flow (mL/minute) 

 Cardiac output 556 38.3 

 Liver, hepatic 25 1.2 

 Liver, splanchic 98 6.0 

Kidneys 100 7.0 

 Lungs 13 0.7 

Skin 38 2.6 

Others 282 20.8 

Clearance (mL/minute) 

Glomerular Filtration Rate 10 0.6 

Small intestine length (cm) 180 56.0 

Total capillary surface area (cm2

) 93,835 2,681.0 

PBPK = physiologically based pharmacokinetic 

Source: Mann et al. 1996a 
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3. HEALTH EFFECTS 

Table 3-12. Tissue Affinity Constants (Kij) Obtained for the Mann PBPK Model for

Animals by Fitting for Rabbits and Hamsters 

Kij (unitless) 

Tissue (i) As(V) As(III) MMA DMA 

Liver 1 200 10 1 

Kidneys 40 20 100 5 

Lungs 1 1 1 20 

Skin 1 60 50 1 

Others 10 40 1 1 

DMA = dimethylarsinic acid; MMA = monomethylarsonic acid; PBPK = physiologically based pharmacokinetic 

Source: Mann et al. 1996a 
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3. HEALTH EFFECTS 

Table 3-13. Metabolic Rate Constants for the Mann PBPK Model for Animals 

Obtained by Fitting for Rabbits and Hamsters 

Oxidation/reduction First order Rabbit Hamster 

Reduction (1/hour) 3,000.00 100.00 

Oxidation (1/hour) 6,000.00 400.00 

Kidney reduction (1/hour) 30.00 1.00 

Methylation Michaelis–Menten 

1st step KMMMA (μmol/mL) 0.05 0.12 

VMAXMMA (μmol/mL-hour) 4.00 0.12 

2nd step KMDMA (μmol/mL) 0.90 0.08 

VMAXDMA (μmol/mL-hour) 1.50 0.12 

DMA = dimethylarsinic acid; MMA = monomethylarsonic acid; PBPK = physiologically based pharmacokinetic 

Source: Mann et al. 1996a 
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3. HEALTH EFFECTS 

Table 3-14. Fitted Gastrointestinal Tract and Lung Absorption Half-time for the

Hamster for the Mann PBPK Model 

 Absorption, half-time (hour) 

Arsenic compound Gastrointestinal tract Lung 

As(V) 

Na3(AsO4) 0.08 12 

Pb3(AsO4) 0.39 690 

As2O5 0.28 — 

As(III) 

 NaAsO2 0.08 12 

As2S3 0.48 12 

As2O3 0.02 — 

DMA 0.09 — 

DMA = dimethylarsinic acid; PBPK = physiologically based pharmacokinetic 

Source: Mann et al. 1996a 
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3. HEALTH EFFECTS 

Figure 3-11. Parameters Used in the Mann PBPK Model for Humans 

Inhalation 

(μg As/h) 

Oral dose 

(μg As/kg BW) 

Keratin Urine Feces 

Kidneys 

Others 

Lungs 

Skin 

Liver 

Plasma 

RBCs 

GI tract 

Pulmonary (P) 

Tracheao-bronchiol (TB) 

Nasopharynx (NP) 

Source: Mann et al. 1996b 
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3. HEALTH EFFECTS 

Table 3-15. Physiological Data Used in the Mann PBPK Model for Humans 

Physiological parameter 

Blood volume 

Organ Units 

mL 

Human 

(body weight=70 kg) 

5,222 

Organ weight 

Lumen volume 

Liver 

Kidneys 

 Lungs 

Skin 

Others 

Stomach 

g 

g 

g 

g 

g 

mL 

1,856 

314 

584 

6,225 

55,277 

274 

 Small intestine mL 393 

Blood flow 

Creatinine 

Cardiac output 

 Liver, hepatic 

 Liver, splanchic 

Kidneys 

 Lungs 

Skin 

Others 

L/minute 

L/minute 

L/minute 

L/minute 

L/minute 

L/minute 

L/minute 

5.29 

0.32 

1.02 

0.95 

0.16 

0.35 

2.49 

Male g/day 1.7 

Female g/day 1.0 

Clearance 

Glomerular filtration rate mL/minute 156 

Small intestine length 

Nasopharynx area 

Tracheobronchial area 

Pulmonary area 

Total capillary surface area 

cm 

cm2

cm2

cm2

cm2

481 

177 

5,036 

 712,471 

1,877x106 

DMA = dimethylarsinic acid; MMA = monomethylarsonic acid; PBPK = physiologically based pharmacokinetic 

Source: Mann et al. 1996b 
ARSENIC 240 

3. HEALTH EFFECTS 

Table 3-16. Tissue Affinity Constants (Kij) Obtained by Fitting the Mann PBPK 

Animal Model for Use with Humans 

Kij (unitless) 

Tissue (i) As(V) As(III) MMA DMA 

Liver 1 200 10 1 

Kidneys 40 20 100 5 

Lungs 1 1 1 20 

Skin 1 60 50 1 

Red blood cells 0.2 1.5 0.2 0.2 

Others 10 40 1 1 

DMA = dimethylarsinic acid; MMA = monomethylarsonic acid; PBPK = physiologically based pharmacokinetic 

Source: Mann et al. 1996b 
ARSENIC 241 

3. HEALTH EFFECTS 

Validation of the model. The model was generally successful in describing the disposition of an 

intravenous dose of sodium arsenate in rabbits over a 24-hour period (Marafante et al. 1985). 

Discrepancies included a 6–7-fold overestimation of levels in skin at 24 hours and underestimation of 

As(+5) in plasma in the hour following injection. A statistical assessment of how well the model fit the 

empirical data was not presented. In hamsters, the model was also generally predictive of oral and 

intratracheal exposures (Marafante and Vahter 1987). Generally, predictions were better for the 

exposures to As(+5) than for those to As(+3). 

The human model was validated using data from studies of repeated oral intake of sodium arsenite in 

volunteers (Buchet et al. 1981b), occupational exposure to arsenic trioxide and elemental arsenic (Vahter 

et al. 1986), and community exposure to As(+5) via drinking water (Harrington et al. 1978; Valentine et 

al. 1979). Simulations were generally in good agreement with the experimental data. 

The predictions of tissue distribution, metabolism, and elimination of arsenic compounds from the mouse 

model were compared with experimental data, and showed generally good agreement. The model tended 

to overpredict the concentration of organic arsenicals in the lungs, and to a lesser extent in the kidneys 

and liver, while for inorganic arsenic, the model overpredicted the levels of arsenic (V) present in the 

urine of acutely-exposed mice. 

Target tissues. Levels in skin were not well predicted by this model in animals. Results for the lung 

were not presented, except for the mouse model, which tended to overpredict lung levels. The human 

model was only used to predict urinary metabolites. 

Species extrapolation. Species extrapolation was not attempted in this model. However, tissue 

affinities derived for the rabbit and hamster models were used in the human model. 

Interroute extrapolation. Interroute extrapolation was not attempted in this model. 

The Menzel Model 

Risk assessment. The Menzel model was not used for risk assessment. 
ARSENIC 242 

3. HEALTH EFFECTS 

Description of the model. The Menzel model was developed to simulate oral exposure to arsenic 

from drinking water and food. Inhalation of arsenic in the particulate phase or as arsine gas is not 

considered. The chemical species in drinking water is assumed to be As(+5). 

The model consists of two sets of compartments: those in which the pools of arsenic are not influenced by 

blood perfusion, and those in which blood perfusion does determine arsenic burden. The former set of 

compartments includes the gut, feces, hair, bladder, and urine. The latter set of compartments included 

lung, liver, fat, skin, kidney, and other tissues. Oral exposure is considered to enter the liver from the 

gastrointestinal tract. 

The model followed that of Andersen and coworkers (Andersen et al. 1987; Ramsey and Andersen 1984). 

Data from mice were used to test predictions of absorption. Excretion is considered to be rapid and 

complete into the urine, with no reabsorption from the kidney. Fecal arsenic content accounts for 

unabsorbed arsenic excreted in the bile, and complex arsenic species from food. Metabolism includes 

reduction by glutathione and methylation. Arsenic accumulation in the skin, hair and nails was included 

by assuming that arsenic binds irreversibly to protein sulfide groups in hair and nails. 

Validation of the model. The model was preliminary and has not been validated. 

Target tissues. Target tissues have not yet been modeled. 

Species extrapolation. Species extrapolation was not attempted in this model. 

Interroute extrapolation. Interroute extrapolation was not attempted in this model. 

The Yu Model 

Risk assessment. The Yu model was not used for risk assessment. 

Description of the model. The Yu model was developed to simulate oral exposure to arsenic in 

mice and rats (Yu 1998a, 1998b), and was later adapted for oral exposures in humans (Yu 1999a, 1999b). 

Inhalation of arsenic in the particulate phase or as arsine gas is not considered. As(+3), As(+5), MMA, 

and DMA were all considered in the model, though the movements of MMA and DMA were not 

considered. 
ARSENIC 243 

3. HEALTH EFFECTS 

The model consists of eight tissue compartments: intestine, skin, muscle, fat, kidney, liver, lung, and 

vessel-rich group (VRG, e.g., brain); in the human model, the VRG and kidney compartments were 

combined. Only oral exposure was considered. Absorption is based on absorption to the stomach, which 

then passes the arsenic to the gastrointestinal tract. From the gastrointestinal tract, arsenic is either 

transferred to the blood or excreted in the feces. 

The physiological parameters for the model were obtained from published values in the literature. 

Tissue/blood partition coefficients were based on the postmortem blood and tissue concentrations from a 

fatal human poisoning case study (Saady et al. 1989). Tissue volumes and blood flow rates were based on 

published values from a number of sources (EPA 1988e; Reitz et al. 1990). Absorption and excretion rate 

constants were based on experimental observations of blood concentrations and urinary and fecal 

excretion following oral administration of inorganic arsenic (Odanaka et al. 1980; Pomroy et al. 1980). 

Metabolic rate constants for the methylation and dimethylation of inorganic arsenic were also based on 

experimental observations (Buchet et al. 1981a; Crecelius 1977). Figure 3-12 shows the model and 

Table 3-17 provides the parameters used for each species. 

Validation of the model. The model was generally successful at predicting the urinary excretion 

48 hours after administration of 5 mg/kg inorganic arsenic in both rats and mice. After 48 hours, the 

observed/predicted ratios associated with excreted doses ranged from 0.78 to 1.11 for the mouse and from 

0.85 to 0.93 for the rat. However, the model overpredicted the amount of inorganic arsenic found in the 

feces of mice at 24 and 48 hours, and overpredicted the amount of DMA formed by exposed mice at 

48 hours. In rats, the model overestimated the urinary and fecal excretion of inorganic arsenic at 24 hours 

postexposure, though at 48 hours, measured values all fell within the predicted ranges. The human model 

was also generally successful at predicting the urinary excretion of arsenic compounds following oral 

exposure, based on results of controlled human exposure studies (Buchet et al. 1981a; Vahter 1983). In 

general, however, the model underpredicts excretion at early time points and overpredicts at later time 

points, with 24 hours being the time at which its predictive capabilities agreed most strongly with 

available data. 

The ability of the model to predict tissue burdens was not compared to actual data for any species. 
ARSENIC 244 

3. HEALTH EFFECTS 

Figure 3-12. Parameters Used in the Yu PBPK Model for Animals 

LUNG 

Qca Qcard rd 

Cv,ave Ca

FAT 

Cv Qfat ,fat 

Cv,vrg 

VRG 

Qvrg 

Cv,kid 

KIDNEY 

Qkid 

Cv,mus 

MUSCLE 

Qmus 

Cv,skin 

SKIN 

Qskin 

Cv,liv 

LIVER 

Qliv 

Bile excretion MMA 

INTESTINE 

Cv,int 

Methylation 

Urine 

DMA 

Qint 

Perfused tissue group 

Non-perfused tissue group 

Feces G.I. TRACT STOMACH Oral Intake 
ARSENIC 245 

3. HEALTH EFFECTS 

Table 3-17. Parameters Used in the Yu PBPK Model 

Mouse Rat Human 

Partition coefficients (AsIII/AsV/MMA/DMA) 

Intestine 6.0 6.0 2.8/2.8/1.2/1.4 

Skin 5.0 5.0 2.5/2.5/1.25/1.25 

VRG 6.0 6.0 Combined with kidney 

Muscle 5.0 10.0 2.6/2.6/1.8/2.8 

Fat — 0.5 0.3/0.3/0.3/0.3 

Kidney 8.5 7.5 4.15/4.15/1.8/2.075 

Liver 10.0 10.0 5.5/5.3/2.35/2.65 

Lung 4.0 4.0 4.15/4.15/1.8/2.075 

Blood flow rate (mL/hour) 

Intestine 100 528 1,810 

Skin 7.68 37.8 130 

VRG 157 960 N/A 

Muscle 153 1,260 25,850 

Fat — 253.2 6,467 

Kidney 255 255 45,240 

Liver 255 1,260 32,320 

Lung N/R N/R 129,000 

Tissue volume (mL) 

Intestine 1.94 6.9 558 

Skin 1.83 15.4 606 

VRG 0.81 23.0 N/A 

Muscle 19.9 162 6,989 

Fat — 14.5 2,328 

Kidney 0.484 1.63 248 

Liver 1.67 5.82 422 

Lung 0.124 1.0 400 

Metabolism constants 

Vmax(MMA) (μmol/hour) 0.45 0.15 11.25 

Vmax(DMA) (μmol/hour) 0.375 0.06 22.25 

Km(MMA) (μmol/hour) 1.0 0.2 0.01 

Km(DMA) (μmol/hour) 0.2 0.2 0.01 
ARSENIC 246 

3. HEALTH EFFECTS 

Table 3-17. Parameters Used in the Yu PBPK Model 

Mouse Rat Human 

First-order rate constants (AsIII/AsV/MMA/DMA) 

KSI (hour-1) 0.3 0.3 -/1.2/-/-

KAI (hour-1) 1.5 3.6 -/1.2/-/-

Kfecal (hour-1) 0.33 0.048 -/0.0012/0.0/0.0 

Kurinary (hour-1) 1.32 0.9 0.05/0.075/0.07/0.04 

Kbiliary (hour-1) 0.33 0.3 -/0.018/-/- 

DMA = dimethylarsinic acid; MMA = monomethylarsonic acid; N/A = not applicable; N/R = not reported 

Source: Yu 1998a, 1998b, 1999a, 1999b 
ARSENIC 247 

3. HEALTH EFFECTS 

Target tissues. Model predictions of tissue burdens were not compared to actual data. The model 

accurately predicted, with a few exceptions, the urinary and fecal excretion of inorganic arsenic and its 

metabolites in rats, mice, and humans. 

Species extrapolation. Species extrapolation beyond rats and mice was not attempted using this 

model. The human model has not been compared to, or linked with, either of the rodent models. 

Interroute extrapolation. Interroute extrapolation was not attempted using this model. 

3.5 MECHANISMS OF ACTION 

3.5.1 Pharmacokinetic Mechanisms 

Arsenic absorption depends on its chemical form. In humans, As(+3), As(+5), MMA, and DMA are 

orally absorbed ≥75%. Arsenic is also easily absorbed via inhalation. Absorption appears to be by 

passive diffusion in humans and mice, although there is evidence (Gonzalez et al. 1995) for a saturable 

carrier-mediated cellular transport process for arsenate in rats (for review, see Rosen 2002). Dermal 

absorption appears to be much less than by the oral or inhalation routes. Bioavailability of arsenic from 

soil appears to be lower via the oral route than it is for sodium salts of arsenic. Arsenic in soil may form 

water insoluble compounds (e.g., sulfides), which are poorly absorbed. 

Arsenic and its metabolites distribute to all organs in the body; preferential distribution has not been 

observed in human tissues at autopsy or in experiments with animal species other than rat (in which 

arsenic is concentrated in red blood cells). Since the liver is a major site for the methylation of inorganic 

arsenic, a “first-pass” effect is possible after gastrointestinal absorption; however, this has not been 

investigated in animal models. 

Arsenic and its metabolites are largely excreted via the renal route. This excretion mechanism is not 

likely to be saturated within the dose range expected from human exposure. Excretion can also occur via 

feces after oral exposure; a minor excretion pathway is nails and hair. The methylation of inorganic 

arsenic is the major metabolism pathway. The proportion of metabolites recovered in urine (As(+3), 

As(+5), MMA, DMA) are roughly consistent in humans regardless of the exposure scenario. However, 

interindividual variation is great enough that it cannot be determined if capacity limitation may occur in 

some individuals. 
ARSENIC 248 

3. HEALTH EFFECTS 

The manifestation of arsenic toxicity depends on dose and duration of exposure. Single oral doses in the 

range of 2 mg As/kg and higher have caused death in humans. Doses as low as 0.05 mg As/kg/day over 

longer periods (weeks to months) have caused gastrointestinal, hematological, hepatic, dermal, and 

neurological effects. These effects appear to be a result of direct cytotoxicity. Long-term exposure 

(years) to drinking water at levels as low as 0.001 mg As/kg/day have been associated with skin diseases 

and skin, bladder, kidney, and liver cancer. Long-term inhalation exposure to arsenic has also been 

associated with lung cancer at air levels as low as 0.05–0.07 mg/m3

. It is not clear at this time why longterm toxicity is different between the oral and inhalation routes, given that arsenic is easily absorbed into 

the systemic circulation by both routes. 

Studies in mice and rats have shown that arsenic compounds induce metallothionein, a metal-binding 

protein thought to detoxify cadmium and other heavy metals, in vivo (Albores et al. 1992; Hochadel and 

Waalkes 1997; Kreppel et al. 1993; Maitani et al. 1987a). The potency of arsenic compounds in inducing 

metallothionein parallels their toxicity (i.e., As(+3) > As(+5) > MMA > DMA). For cadmium, it is 

thought that metallothionein binds the metal, making it biologically inactive. For arsenic, however, only 

a small percentage of the administered arsenic is actually bound to metallothionein (Albores et al. 1992; 

Kreppel et al. 1994; Maitani et al. 1987a). In vitro studies have shown that affinity of arsenic for 

metallothionein is much lower than that of cadmium or zinc (Waalkes et al. 1984). It has been proposed 

that metallothionein might protect against arsenic toxicity by acting as an antioxidant against oxidative 

injury produced by arsenic (NRC 1999). 

3.5.2 Mechanisms of Toxicity 

Mechanisms of arsenic-induced toxicity and carcinogenicity have not been clearly identified. However, 

recent efforts to elucidate mechanisms of arsenic toxicity and carcinogenicity have resulted in numerous 

in vitro and in vivo reports. Whereas these mechanistic studies typically employed relatively high arsenic 

exposure levels, some of the most recent studies were performed using more environmentally-relevant 

exposure levels. Due to the extremely large amount of mechanistic data for arsenic, it is not feasible to 

include all pertinent primary studies that address issues concerning proposed mechanisms of arsenic 

toxicity and carcinogenicity. Therefore, the following discussion of mechanisms of arsenic toxicity 

represents a summary of information from several recent review articles (Chen et al. 2004, 2005; Florea et 

al. 2005; Hughes 2002; Kitchin 2001; Lantz and Hays 2006; Navas-Acien et al. 2005; Rossman 2003; 

Roy and Saha 2002; Thomas et al. 2007; Vahter 2002). 
ARSENIC 249 

3. HEALTH EFFECTS 

It is becoming increasingly evident that the toxicity and carcinogenicity of arsenic is likely to be closely 

associated with metabolic processes. Absorbed pentavalent arsenic (AsV) is rapidly reduced to trivalent 

arsenic (AsIII) at least partially in the blood. Much of the formed AsIII is distributed to tissues and taken 

up by cells (particularly hepatocytes). Many cell types appear to accumulate AsIII more rapidly than 

AsV. Because AsIII (as arsenite) is known to be more highly toxic than AsV (as arsenate), the reduction 

step may be considered bioactivation rather than detoxification. Glutathione appears to play a role in the 

reduction of AsV to AsIII, which is required prior to methylation. Methylation of arsenic ultimately 

forms relatively less toxic MMA and DMA; this process is accomplished by alternating between the 

reduction of AsV to AsIII and the addition of a methyl group; S-adenosylmethionine is considered to be 

the source of the methyl group. Both MMA and DMA are less reactive with tissue constituents than 

inorganic arsenic and both are readily excreted in the urine. The methylation process appears to include 

multiple intermediates, some of which are more reactive than inorganic arsenic. For example, reactive 

trivalent metabolites, MMAIII and DMAIII, have been detected in the urine of human subjects 

chronically exposed to arsenic in drinking water, and in vitro studies have demonstrated MMAIII to be 

more toxic than arsenite or arsenate to human hepatocytes, epidermal keratinocytes, and bronchial 

epithelial cells. Additional in vitro studies have demonstrated genotoxic and DNA damaging properties 

of both MMAIII and DMAIII. 

AsV (as arsenate) has been demonstrated to: (1) replace phosphate in glucose-6-phosphate and 

6-phosphogluconate in vitro, (2) replace phosphate in the sodium pump and the anion exchange transport 

system of human red blood cells, (3) diminish the in vitro formation of adenosine-t′-triphosphate (ATP) 

by replacing phosphate in enzymatic reactions, and (4) deplete ATP in some cellular systems, but not in 

human erythrocytes. However, it is becoming more apparent that the major source of arsenic toxicity and 

carcinogenicity is related to its reduction to arsenite. 

AsIII (as arsenite) is known to react with thiol-containing molecules such as glutathione and cysteine 

in vitro. Methylated trivalent arsenics such as MMAIII are potent inhibitors of glutathione reductase and 

thioredoxin reductase. It has been suggested that binding of arsenite and methylated trivalent arsenicals 

to critical thiol groups could lead to the inhibition of essential biochemical reactions, alteration of cellular 

redox status, and eventual cytotoxicity. Binding of MMAIII and DMAIII to protein has also been 

demonstrated in vitro. Arsenite inhibits pyruvate dehydrogenase (PDH), a complex that oxidizes 

pyruvate to acetyl-CoA, a precursor to intermediates of the citric acid cycle that provides reducing 

equivalents to the electron transport system for ATP production. This property may explain the depletion 

of carbohydrates in arsenite-treated rats. 
ARSENIC 250 

3. HEALTH EFFECTS 

Evidence that arsenic may induce alterations in nitric oxide metabolism and endothelial function includes 

findings that persons exposed to high levels of arsenic in drinking water had decreased serum and urine 

concentrations of nitric oxide metabolites, which was reversed upon intervention with drinking water 

containing lower levels of arsenic. Urinary arsenic levels have been inversely associated with nitric oxide 

production in activated monocytes. Arsenite concentrations of 1–25 μM inhibited endothelial nitric oxide 

synthase activity and resulting decreased cell growth in human endothelial cells, although lower 

concentrations up-regulated the expression of constitutive nitric oxide synthase 3, which might serve as 

an explanation for observed arsenic-induced cell growth and angiogenesis. 

Although epidemiological studies demonstrate the carcinogenicity of arsenic in humans, early animal 

cancer bioassays failed to demonstrate a carcinogenic effect following lifetime exposure to inorganic 

arsenic. However, more recent focus has resulted in the development of animal models that exhibit 

carcinogenic activity in skin, urinary bladder, liver, and lung, tissues implicated in arsenic-induced cancer 

in humans. This concordance in target sites among animal models and humans indicates that common 

mechanisms of action may be applicable to humans and laboratory animals. 

Several modes of action have been proposed to explain, at least in part, the carcinogenicity of arsenic. It 

is likely that multiple mechanisms are involved, some of which may relate to noncancer effects as well. 

Oxidative Stress. Mechanistic studies of arsenic toxicity have suggested a role of the generation of 

reactive oxygen species in the toxicity of inorganic arsenic. Results of both in vivo and in vitro studies of 

arsenic-exposed humans and animals suggest the possible involvement of increased lipid peroxidation, 

superoxide production, hydroxyl radical formation, blood nonprotein sulfhydrals, and/or oxidant-induced 

DNA damage. Reduction of cellular oxidant defense by treatment with glutathione-depleting agents 

results in an increased sensitivity of cells to arsenic toxicity. Support for mechanisms of toxicity that 

involves arsenic-induced oxidative stress includes findings that inhaled arsenic can predispose the lung to 

oxidative damage, chronic low-dose arsenic alters genes and proteins that are associated with oxidative 

stress and inflammation, and major transcriptional regulators of altered genes are redox sensitive. 

Genotoxicity. Collectively, in vitro and in vivo genotoxicity assays have demonstrated that arsenics cause 

single strand breaks, formation of apurinic/apyrimidinic sites, DNA base and oxidative base damage, 

DNA-protein crosslinks, chromosomal aberrations, aneuploidy, sister chromatid exchanges, and 

micronuclei. Chromosomal aberrations, characterized by chromatid gaps, breaks and fragmentation, 
ARSENIC 251 

3. HEALTH EFFECTS 

endoreduplication, and chromosomal breaks, are dose-dependent and arsenite is more potent than 

arsenate. Both MMAIII and DMAIII are directly genotoxic and are many times more potent than arsenite 

at inducing DNA damage. Inorganic arsenic can potentiate the mutagenicity observed with other 

chemicals, although arsenic itself does not appear to induce point mutations. Arsenic-induced 

genotoxicity may involve oxidants or free radical species. 

Altered Growth Factors→Cell Proliferation→Promotion of Carcinogenesis. Increased concentrations 

of growth factors can lead to cell proliferation and eventual promotion of carcinogenesis. Arsenicinduced cell death can also lead to compensatory cell regeneration and carcinogenesis. Altered growth 

factors, cell proliferation, and promotion of carcinogenesis have all been demonstrated in one or more 

systems exposed to arsenics. Altered growth factors and mitogenesis were noted in human keratinocytes. 

Cell death was observed in human hepatocytes and rat bladder epithelium. Cell proliferation was 

demonstrated in human keratinocytes and intact human skin and rodent bladder cells. Promotion of 

carcinogenesis was noted in rat bladder, kidney, liver, and thyroid, and mouse skin and lung. 

Additional Mechanisms of Toxicity Data. Inorganic arsenic exposure has been shown to modify the 

expression of a variety of genes related to cell growth and defense, including the tumor suppressor gene 

p53, as well as to alter the binding of nuclear transcription factors. Carcinogenic effects of arsenic may 

result from a cocarcinogenic effect. Whereas arsenic exposure alone did not elicit skin tumors in mice, 

co-exposure to arsenic and ultraviolet light resulted in skin tumors that were greater in number and larger 

in size than those produced by ultraviolet light alone. Arsenate and arsenite enhanced the amplification of 

a gene that codes for the enzyme dihydrofolate reductase, arsenate being more potent than arsenite. 

Furthermore, inhibition of DNA repair has been demonstrated in arsenic-treated cells. 

3.5.3 Animal-to-Human Extrapolations 

The usefulness of animal models for toxicity studies with arsenic is significantly limited by two major 

factors. First and most importantly, no animal model exists for the health effect of greatest concern for 

human exposure: carcinogenicity in skin and other organs after oral exposure. Second, the pattern of 

metabolism in humans (significant excretion of the methylated forms of arsenic) is unlike that of most 

other mammalian species (the mouse and rabbit may be exceptions). The ratios of inorganic to organic 

arsenic excreted also vary between species. The rat sequesters arsenic in its erythrocytes and is not a 

suitable model for human toxicity. 
ARSENIC 252 

3. HEALTH EFFECTS 

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 the EPA to 

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, 

scientists agree that these chemicals may affect the synthesis, secretion, transport, binding, action, or 

elimination of natural hormones in the body responsible for maintaining homeostasis, reproduction, 

development, and/or behavior (EPA 1997h). 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). 

There is little evidence to suggest that arsenic functions as an endocrine disruptor. An association has 

been demonstrated between exposure to arsenic in drinking water and increased incidence of diabetes 

mellitus (Rahman et al. 1998; Tsai et al. 1999; Tseng et al. 2000; Wang et al. 2003), although doseresponse relationships are not available and the mechanism of action for this response has not been 

characterized. Studies by Waalkes and coworkers (Waalkes et al. 2006a, 2006b) have suggested that in 
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mice, arsenic may interact with estrogens to enhance production of female urogenital cancers and male 

hepatocellular cancer following exposure to arsenic in utero. The mechanism by which this might happen 

has not been elucidated. No other relevant data were located in humans or animals. Data on general 

effects of arsenic compounds on the endocrine system are presented in Sections 3.2.1.2 and 3.2.2.2 above. 

In vitro studies provide suggestive evidence that arsenic may act as an endocrine disruptor. Studies by 

Bodwell et al. (2004, 2006) and Davey et al. (2007) demonstrate that arsenic can alter gene regulation of 

steroid hormone receptors for glucocorticoids, mineralocorticoids, progesterone, and estrogen. 

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. 

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 
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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 

alveoli being less developed, which results in a disproportionately smaller surface area for alveolar 

absorption (NRC 1993). 

Arsenic has been recognized as a human toxicant for many centuries, and the symptoms of acute 

poisoning are well known. Children who are exposed to high levels of arsenic exhibit symptoms similar 

to those seen in adults, including respiratory, cardiovascular, dermal, and neurological effects, and 

vomiting if the arsenic is ingested (Borgoño et al. 1980; Foy et al. 1992; Kersjes et al. 1987; Muzi et al. 

2001; Rosenberg 1974; Zaldívar 1974; Zaldívar and Guillier 1977). Arterial thickening of the pancreas 

was observed in five children who died in Chile after chronic exposure to arsenic (Rosenberg 1974). Foy 

et al. (1992) described systemic effects of chronic arsenic exposure in children in a village near a tin and 

tungsten mining operation in Thailand. The arsenic concentration in water samples from 35 shallow wells 

averaged 0.82 mg As/L (range, 0.02–2.7 mg As/L). Piped water (available in some homes) had a 

concentration of 0.07 mg As/L. A survey of skin manifestations of arsenic poisonings was conducted in 

the autumn of 1987. The case reports of four children were presented. All of the children had 

hyperkeratosis and hyperpigmentation of the extremities, including tibia, palms, and soles. In addition, 

one child had developed weakness 3 years previously and had anorexia and a chronic cough for 1 year. 

She had been held back twice in school as a slow learner. On examination, she had a runny nose and 
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weakness of her wrist joints. The liver was about 4 finger-breadths below the right costal margin with a 

sharp but tender edge. Blood arsenic levels ranged from 0.087 to 0.46 μg/mL and the arsenic level in hair 

ranged from 14.4 to 20 μg/g. The authors concluded that the finding of typical skin manifestations of 

chronic arsenic poisoning suggests that it may take a considerably shorter period of time to develop these 

manifestations than previously thought. However, it is not known what effect co-exposure to tin and 

tungsten might have had on skin manifestations in these children. Exposure to high arsenic levels during 

gestation and/or during early childhood also was associated with significant increases in SMRs for lung 

cancer and bronchiectasis during adulthood in a study of residents in a city in Chile with high arsenic 

levels in the drinking water (near 0.9 mg/L) during several years (Smith et al. 2006). 

As previously mentioned in Sections 3.2.1.4 and 3.2.2.4, exposure of children to arsenic also has been 

associated with neurological deficits in children. Studies by Wasserman et al. (2004, 2007) of 6- and 

10-year-old children from Bangladesh reported small but significant decreases in some tests of cognitive 

function associated with levels of arsenic in the water ≥0.05 mg/L. A study of pre-school age children in 

West Bengal, India, reported an association between current urinary arsenic concentrations, but not longterm water arsenic, and small decrements in intellectual tests (von Ehrenstein et al. 2007). Similar results 

were reported in a study of children in Taiwan (Tsai et al. 2003) and in China (Wang et al. 2007). 

Neurological effects have also been associated with elevated levels of arsenic in the air. For example, 

Bencko et al. (1977) reported that children of approximately 10 years of age living near a power plant 

burning coal of high arsenic content showed significant hearing losses (increased threshold) compared to 

a control group of children living outside the polluted area (Bencko et al. 1977). Also, in a study of 

Mexican children, Calderón et al. (2001) reported that children living near a smelter complex had poor 

performance on tests evaluating verbal IQ than children who lived farther from the smelter. Thus, the 

limited data available suggest that exposure of children to inorganic arsenic may result in detrimental 

effects on neurobehavioral parameters. 

Wulff et al. (1996) conducted a retrospective study of a cohort of children born between 1961 and 1990 in 

the municipality of Skelleftea, Sweden, where a smelter released arsenic and other pollutants including 

lead, copper, cadmium, and sulfur dioxide. Childhood cancer incidences among children born in the 

vicinity of the smelter (i.e., within 20 km) and distant from the smelter (>20 km) were compared with 

expected incidences based on Swedish national statistics. There appeared to be an increased risk of 

childhood cancer (all types combined) among children born in the vicinity of the smelter (SIR=195, 95% 

CI=88–300, based on 13 cases observed and 6.7 expected), but the increase was not statistically 

significant, and in any event, the role of arsenic in any finding from this study is confounded by the 
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presence of other metals. The number of cases (n=42) was very close to the expected number (n=41.8) 

among children born distant from the smelter. Similar results were reported in a study by Moore et al. 

(2002), which did not find increased incidence ratios for all childhood cancers or for childhood leukemias 

in children from an area of Nevada with high arsenic exposures. 

Inorganic arsenic has been characterized as a developmental toxicant. It is known to cross the placental 

barrier and selectively accumulate in the neuroepithelium of the developing animal embryo (Hanlon and 

Ferm 1977; Lindgren et al. 1984). Studies in animals have also revealed that various fetal malformations 

occur after embryonic exposure to arsenic in vitro; neural tube defects are the predominant and consistent 

malformation in these studies (Chaineau et al. 1990; Mirkes and Cornel 1992; Morrissey and Mottet 

1983; Mottet and Ferm 1983; Tabacova et al. 1996; Willhite and Ferm 1984; Wlodarczyk et al. 1996). 

In vivo studies have shown that high doses of ingested arsenic can produce developmental effects (fetal 

mortality, skeletal defects), but generally only at maternally toxic doses (Baxley et al. 1981; Holson et al. 

1999, 2000; Hood and Harrison 1982; Hood et al. 1978; Nemec et al. 1998; Stump et al. 1999). A series 

of studies showed an increased incidence of tumors in the offspring of mice exposed to arsenic from 

gestational day 8 through day 18(Waalkes et al. 2003, 2004a, 2004b, 2004c, 2006a, 2006b) (see 

Section 3.2.2.6 for further details). In humans, acute prenatal exposure to high doses of inorganic arsenic 

can result in miscarriage and early neonatal death (Bolliger et al. 1992; Lugo et al. 1969). Although 

several studies have reported marginal associations between prolonged low-dose human arsenic exposure 

and adverse reproductive outcomes, including spontaneous abortion, stillbirth, developmental 

impairment, and congenital malformation (Ahmad et al. 2001; Aschengrau et al. 1989; Chakraborti et al. 

2003c; Hopenhayn-Rich et al. 2000; Nordström et al. 1978a, 1979b; Yang et al. 2003; Zierler et al. 1988), 

none of these studies have provided convincing evidence for such effects or information concerning 

possible dose-response relationships. 

There is no evidence for differences in absorption of arsenic in children and adults. Ingestion of arsenic 

in dirt may be an important route of exposure for young children. A study that used a synthetic gastric 

juice designed to mimic gastric conditions in a 2-year-old child found that absorption of arsenic from 

contaminated soil was likely to be up to 5 times lower than the total concentration of arsenic in the soil 

(Williams et al. 1998). As previously mentioned, arsenic crosses the placenta and preferentially 

accumulates in the embryonic neuroepithelium. In addition, arsenic is known to be present in breast milk 

at low concentrations. Arsenic concentrations were low in human milk sampled from 88 mothers in the 

Faroe Islands (0.0001–0.0044 ppm), where the diet is predominantly seafood (exposures were primarily 

to “fish arsenic” [Grandjean et al. 1995]), in a population of Andean women (0.0008–0.008 ppm) exposed 
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to high concentrations of inorganic arsenic in drinking water (Concha et al. 1998b), and in a World Health 

Organization survey (0.00013–0.00082 ppm) (Somogyi and Beck 1993). There is no information in the 

literature describing storage of arsenic in maternal tissues. There is some evidence that metabolism of 

arsenic in children is less efficient than in adults. Children in two villages in Argentina ingesting large 

amounts of arsenic in their drinking water (200 μg/L) excreted about 49% inorganic arsenic and 47% 

DMA, compared to 32% inorganic arsenic and 66% DMA for the women in the study (Concha et al. 

1998b). No PBPK models specifically targeted at fetuses, infants, or children, or pregnant or lactating 

women were found in the literature. There are no biomarkers that have been specifically identified for 

children exposed to arsenic. In addition, no unique interactions of arsenic with other chemicals have been 

identified in children. 

The mechanism of toxic action of arsenic in the mammalian cell may involve inhibition of proliferation of 

cells (Dong and Luo 1993; Jha et al. 1992; Petres et al. 1977). In addition, high-dose arsenic impairs 

assembly and disassembly of microtubules, thus interfering with mitotic spindle formation and embryonal 

cell division (Léonard and Lauwerys 1980; Li and Chou 1992; Mottet and Ferm 1983). Arsenic 

compounds also cause chromosomal aberrations (Jha et al. 1992; Léonard and Lauwerys 1980), which 

may disrupt cell cycling. The direct toxic effects of high levels of arsenic in the developing embryo result 

not from a difference in the mechanism of toxicity during development, but rather from the existence of a 

unique target tissue, the neuroepithelium. The process of neurulation involves cell shape changes, 

cytokinesis, and cell adhesion, which are dependent upon cytoskeletal elements that are functionally 

affected by arsenic (Dallaire and Béliveau 1992; Edelman 1992; Gunn et al. 1992; Li and Chou 1992; 

Moriss-Kay et al. 1994; Schoenwolf and Smith 1990; Taubeneck et al. 1994). However, since arsenic is 

known to affect vasculature, and since altered placental and/or embryonal vasculature has been suggested 

as a mechanism leading to neural tube defects, the embryo may be sensitive to this manifestation of 

arsenic toxicity. 

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). 

Due to a nascent understanding of the use and interpretation of biomarkers, implementation of biomarkers 

as tools of exposure in the general population is very limited. A biomarker of exposure is a xenobiotic 
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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, 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 arsenic 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 not often substance specific. They also may not be directly 

adverse, but can indicate potential health impairment (e.g., DNA adducts). Biomarkers of effects caused 

by arsenic are discussed in Section 3.8.2. 

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 Arsenic 

Arsenic levels in blood, urine, hair, and nails have all been investigated and used as biological indicators 

of exposure to arsenic. Since arsenic is cleared from blood within a few hours (Tam et al. 1979b; Vahter 

1983), measurements of blood arsenic reflect exposures only within the very recent past. Typical values 

in nonexposed individuals are <1 μg/L (Heydorn 1970; Hindmarsh and McCurdy 1986; Valentine et al. 
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1979). Consumption of medicines containing arsenic is associated with blood values of 100–250 μg/L, 

while blood levels in acutely toxic and fatal cases may be 1,000 μg/L or higher (Driesback 1980). 

However, blood levels do not appear to be reliable indicators of chronic exposure to low levels of arsenic. 

For example, there was no correlation between the level of arsenic in blood of residents and the level of 

arsenic in drinking water in several U.S. communities where water levels ranged from about 6 to 

125 μg/L (Valentine et al. 1979, 1981). Consequently, measurement of blood arsenic is not generally 

considered to be a reliable means of monitoring human populations for arsenic exposure. 

As discussed in Section 3.4.4, most arsenic that is absorbed from the lungs or the gastrointestinal tract is 

excreted in the urine, mainly within 1–2 days. For this reason, measurement of urinary arsenic levels is 

generally accepted as the most reliable indicator of recent arsenic exposure, and this approach has proved 

useful in identifying above-average exposures in populations living near industrial point sources of 

arsenic (e.g., Milham and Strong 1974; Polissar et al. 1990). By the inhalation route, several researchers 

have found that there is a good quantitative correlation between the concentration of arsenic in workplace 

air (Cair, μg/m3

) and the concentration in the urine (Curine, μg/L) of exposed workers. For example, Pinto 

et al. (1976) found a linear relationship for exposures ranging up to 150 μg/m3

, given by the following 

equation: 

Cair=0.3 Curine 

Enterline et al. (1987a) reinvestigated this relationship over a wider range of exposures (up to 

3,500 μg/m3

), and found that the curve tended to be concave upward, as given by the following equation: 

Cair=0.0064 (Curine)

1.94 

This indicates that at higher exposure levels, a higher fraction of the dose is excreted in urine, although 

the toxicokinetic basis for this is not certain. Numerous studies have used above-average urinary levels 

(i.e., higher than about 100 μg/L) as evidence of recent arsenic ingestion (e.g., Borgoño et al. 1980; 

Fincher and Koerker 1987; Franzblau and Lilis 1989; Goldsmith and From 1986; Kyle and Pease 1965; 

Valentine et al. 1981). Calderon et al. (1999) found a quantitative correlation between the log of the 

mean total urinary arsenic concentration/creatinine (TAs/c, μg/mg) of people living in areas with arseniccontaminated drinking water sources and the log of the inorganic arsenic concentration in the drinking 

water (InAs, μg/L). The equation for the regression line is: 
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3. HEALTH EFFECTS 

TAs/c=10-2.57 x (InAs)0.63 

where -2.57 and 0.63 are the intercept and slope, respectively, for the regression of the log10-transformed 

data. Mixed model regression analysis showed that the log of estimated arsenic intake from drinking 

water (μg/day) is also a good predictor of TAs/c excretion (Calderon et al. 1999). 

There is some indication that speciation of urinary arsenic may indicate the extent of past cumulative 

exposure to arsenic. Hsueh et al. (1998a) reported higher levels of DMA and MMA in the urine of 

individuals with higher cumulative past exposure to inorganic arsenic. Speciated urinary arsenic is also a 

recommended biomarker for recent inorganic arsenic exposure. Walker and Griffin (1998) used the EPA 

Exposure Assessment Model and a number of site-specific data covering environmental and biological 

factors to predict total and speciated urinary arsenic concentrations for children living near high levels of 

arsenic-contaminated soil. There was reasonable agreement between the measured and predicted 

speciated urinary arsenic concentrations. 

An important limitation to the use of total urinary arsenic as a biomarker of exposure is that arsenobetaine 

is excreted (unmetabolized) in urine after ingestion of certain seafoods (Brown et al. 1990; Kalman 1987; 

Tam et al. 1982). Since "fish arsenic" is essentially nontoxic, analytical methods based on total urinary 

arsenic content may overestimate exposures to arsenic species that are of health concern. As discussed in 

Section 7.1, there are adequate methods for distinguishing arsenobetaine from other forms of arsenic in 

urine (inorganic, MMA, DMA), although these are not convenient to use as a routine screening method. 

Arsenic tends to accumulate in hair and nails, and measurement of arsenic levels in these tissues may be a 

useful indicator of past exposures. Normal levels in hair and nails are 1 ppm or less (Choucair and Ajax 

1988; Franzblau and Lilis 1989). These values may increase from several-fold to over 100-fold following 

arsenic exposure (Agahian et al. 1990; Bencko 2005; Bencko et al. 1986; de Peyster and Silvers 1995; 

EPA 1977a, 1981b; Karagas et al. 1996; Milham and Strong 1974; Valentine et al. 1979; Yamauchi et al. 

1989) and remain elevated for 6–12 months (Choucair and Ajax 1988). Minimum exposure levels that 

produce measurable increases in arsenic levels in hair and nails have not been precisely defined. For hair, 

ingestion of 50–120 ppb of arsenic in drinking water produced only a marginal effect, but a clear increase 

was noted at 393 ppb (Valentine et al. 1979). A study of children living in a region polluted with arsenic 

derived from a power plant burning coal with a high arsenic content found a significant correlation 

between arsenic levels in hair and distance from the source of emission (Bencko and Symon 1977). 
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3. HEALTH EFFECTS 

Inhalation exposure of workers to about 0.6 μg/m3 of arsenic in air significantly increased average levels 

in nails (Agahian et al. 1990), although there was wide variation between individuals. 

Analysis of hair may yield misleading results due to the presence of arsenic adsorbed to the external 

surface, but this can be minimized by collecting samples from close to the scalp or from unexposed areas 

and by washing the hair before analysis (e.g., Paschal et al. 1989). Similarly, extensive washing of nails 

is required to remove exogenous contamination (Agahian et al. 1990). The relationship between 

consumption of food items and levels of arsenic in toenails has been evaluated by MacIntosh et al. (1997) 

using standard multivariate regression models. This approach does not appear to be highly reliable, but 

may be sufficient for exploring associations between diet and disease. Kurttio et al. (1998) used linear 

regression models to show that there is a good association between arsenic concentration in hair (mg/kg) 

and total arsenic concentration in urine (μg/L), arsenic concentration in drinking water (μg/L) or daily 

intake of arsenic (μg/day). A 10 μg/L increase in the drinking water concentration or a 10–20 μg/day 

increase in daily arsenic intake corresponded to a 0.1 mg/kg increase in the arsenic concentration in hair. 

It is also important to note that the measurement of arsenic in hair and fingernails is a process not readily 

accessible to many clinical offices. 

3.8.2 Biomarkers Used to Characterize Effects Caused by Arsenic 

As discussed in Section 3.2, the characteristic pattern of skin changes caused by arsenic (hyperkeratinization, hyperpigmentation) is probably the most sensitive and diagnostic clinical indicator of chronic 

exposure to arsenic. However, no means has been developed for detecting these effects except by routine 

dermatological examination. 

Peripheral neuropathy is another characteristic effect of arsenic exposure, and several researchers have 

investigated decreased nerve conduction velocity or amplitude as a biomarker for peripheral neuropathy. 

While effects can usually be detected in individuals with clinical signs of neuropathy (e.g., Goebel et al. 

1990; Jenkins 1966; Le Quesne and McLeod 1977; Morton and Caron 1989; Murphy et al. 1981), effects 

are only marginal (EPA 1977a; Hindmarsh et al. 1977; Valentine et al. 1981) or undetectable (EPA 

1981b; Kreiss et al. 1983) in exposed populations without obvious clinical signs of toxicity. This 

indicates that this approach is probably not sufficiently sensitive to detect neurological effects earlier than 

by standard neurological examination (Hindmarsh and McCurdy 1986). Also, decreases in nerve 

conduction velocity or amplitude are not specific for arsenic-induced neuropathy. 
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3. HEALTH EFFECTS 

Arsenic is known to affect the activity of a number of enzymes, and some of these may have potential as 

biomarkers of effect. Most promising is the spectrum of effects caused by arsenic on the group of 

enzymes responsible for heme synthesis and degradation, including inhibition of coproporphyrinogen 

oxidase and heme synthetase (Woods and Fowler 1978; Woods and Southern 1989) and activation of 

heme oxygenase (Sardana et al. 1981). Menzel et al. (1998) has examined the in vitro induction of human 

lymphocyte heme oxygenase 1(HO1) as a biomarker of arsenite exposure. Arsenite did induce de novo 

synthesis of HO1 in human lymphoblastoid cells, but it has not been determined if the same response is 

induced in vivo. It has been shown in animals that these arsenic-induced enzymic changes result in 

increased urinary levels of uroporphyrin, coproporphyrin, and bilirubin (Albores et al. 1989; Woods and 

Fowler 1978), and it has been shown that these effects can be detected in the urine of arsenic-exposed 

humans (García-Vargas and Hernández-Zavala 1996). Therefore, altered urinary levels of these hemerelated compounds could serve as a biomarker of effect. However, it is known that numerous other toxic 

metals also have similar effects on heme metabolism (Albores et al. 1989; Sardana et al. 1981; Woods 

and Southern 1989), so it is likely that these effects would not be specific for arsenic. 

For more information on biomarkers for renal and hepatic effects of chemicals, see ATSDR/CDC 

Subcommittee Report on Biological Indicators of Organ Damage (Agency for Toxic Substances and 

Disease Registry 1990b) and for information on biomarkers for neurological effects, see OTA (1990). 

3.9 INTERACTIONS WITH OTHER CHEMICALS 

A number of researchers have found that arsenic compounds tend to reduce the effects of selenium (Hill 

1975; Howell and Hill 1978; Kraus and Ganther 1989; Levander 1977; Miyazaki et al. 2003; Moxon et al. 

1945; Schrauzer 1987; Schrauzer et al. 1978). Likewise, selenium can decrease the effects of arsenic, 

including clastogenicity (Beckman and Nordenson 1986; Biswas et al. 1999; Sweins 1983), delayed 

mutagenesis (Rossman and Uddin 2004), cocarcinogenesis (Uddin et al. 2005), cytotoxicity (Babich et al. 

1989; Rössner et al. 1977; Styblo and Thomas 2001), and teratogenicity (Holmberg and Ferm 1969). The 

mechanism of this mutual inhibition of effects is not known, but may be related to the formation of a 

selenium-arsenic complex (seleno-bis [S-gluthionyl] arsinium ion; Gailer et al. 2002) that is excreted 

more rapidly than either arsenic or selenium alone (Cikrt et al. 1988; Hill 1975; Levander 1977; Levander 

and Baumann 1966) or due to selenium-induced changes in arsenic methylation (Styblo and Thomas 

2001; Walton et al. 2003). There is little direct evidence that variations in selenium exposure in humans 

lead to significant increases or decreases in arsenic toxicity, although copper smelter workers who 

developed lung cancer had lower tissue levels of selenium than workers who did not develop lung tumors 
ARSENIC 263 

3. HEALTH EFFECTS 

(Gerhardsson et al. 1985, 1988). This suggests that selenium deficiency could significantly increase the 

risk of lung cancer following inhalation exposure to arsenic, but it is difficult to distinguish cause from 

effect in such a study. However, there is evidence that administration of selene can facilitate recovery 

from arsenic poisoning. In residents living in an area of Inner Mongolia with high levels of arsenic in 

drinking water, administration of 100–200 μg selenium/day in the form of selenium yeast and exposure to 

arsenic-free water for 14 months resulted in a greater improvement in clinical signs and symptoms, liver 

function, and EKG readings as compared to residents administered arsenic-free water only (Wuyi et al. 

2001; Yang et al. 2002). An improvement in skin lesions was observed in 67 and 21% of the subjects in 

the selenium-supplemented and control groups (Yang et al. 2002). Additionally, the levels of arsenic in 

blood, hair, and urine were significantly lower after the 14-month period only in the selenium 

supplemented group. 

The interaction between cigarette smoking, inhalation of arsenic, and the risk of lung cancer has not been 

extensively investigated. Smoking appeared to increase lung cancer risk synergistically (multiplicatively) 

in one study of smelter workers (Pershagen et al. 1981), although the data are not adequate to exclude a 

simple additive interaction (Thomas and Whittemore 1988). Cigarette smoking has been shown to 

increase the occurrence of lung cancer in people with high levels of arsenic in the drinking water (Chiou 

et al. 1995; Tsuda et al. 1995a). Suggestive evidence of a positive interaction between arsenic and 

benzo(a)pyrene has also been noted for induction of lung adenocarcinomas in hamsters (Pershagen et al. 

1984). 

Co-exposure to ethanol and arsenic may exacerbate the toxic effects of arsenic. Simultaneous exposure of 

rats to ethanol (10% in drinking water) and arsenic (dose not stated) for 6 weeks produced a significant 

increase in the concentration of arsenic in the kidney, a nonsignificant increase of arsenic in the liver and 

a significant increase in the concentration of glutathione in the liver, compared to rats treated with either 

ethanol or arsenic alone (Flora et al. 1997a, 1997b). Histological damage to the liver, but not the kidneys, 

was increased in rats treated with both ethanol and arsenic compared to those receiving only arsenic. 

Studies of rats exposed to arsenic, lead, and cadmium, alone or in combination, have revealed mainly 

additive or subadditive effects on body weight, hematological parameters, and enzymes of heme synthesis 

(Mahaffey and Fowler 1977; Mahaffey et al. 1981). Similarly, studies of the tissue levels of arsenic in 

rats fed arsenic with or without lead or cadmium revealed only limited evidence of any toxicokinetic 

interactions (Mahaffey et al. 1981). Pretreatment of rats with a nontoxic dose of cadmium had no effect 

on the lethality of a high dose of arsenic and did not reduce arsenic-induced hepatotoxicity (Hochadel and 
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3. HEALTH EFFECTS 

Waalkes 1997). These data do not suggest that arsenic toxicity is likely to be significantly influenced by 

concomitant exposure to these metals. However, supplementation with zinc or chromium may be useful 

in reducing chronic arsenism. Arsenic has been shown to cause an increase in total plasma cholesterol; 

co-administration of chromium(III) counteracts this effect (Aguilar et al. 1997). Pretreatment of mice 

with zinc, at least 24 hours before injection with arsenic-73, reduced arsenic retention compared to 

controls that did not receive the zinc pretreatment or received it only a short time before the 

administration of arsenic (Kreppel et al. 1994). Zinc is an inducer of metallothionein, but this induction 

does not appear to be the mechanism that reduces arsenic toxicity because other inducers of 

metallothionein did not reduce arsenic toxicity and arsenic elimination was increased by the zinc 

pretreatment. 

Since methylation of arsenic is a detoxification mechanism, it is possible that chemicals that interfere with 

the methylation process could increase toxicity. This is supported by studies in animals in which reagents 

that inhibit methylation enzymes (e.g., periodate-oxidized adenosine) caused an increase in tissue levels 

of inorganic arsenic (Marafante and Vahter 1986; Marafante et al. 1985). Similarly, cellular glutathione 

levels appear to play a role in the methylation process, and treatment with reagents (e.g., phorone) that 

decrease glutathione levels increases arsenic toxicity (Buchet and Lauwerys 1987). Inadequate dietary 

intake of methionine, choline, or protein may also exacerbate arsenic toxicity. Rabbits pretreated with 

diets low in choline, methionine, or protein showed a significant increase in tissue retention of arsenic and 

a significant decrease in the excretion of dimethylarsinic acid (Vahter and Marafante 1987). The 

increased retention of arsenic in rabbits fed these deficient diets is likely to be due to a reduction in 

arsenic methylation. Thus, the toxic effects of chronic arsenic ingestion may be increased in populations 

that are also subject to malnutrition. 

3.10 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE 

A susceptible population will exhibit a different or enhanced response to arsenic than will most persons 

exposed to the same level of arsenic 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 arsenic, or compromised function of organs 

affected by arsenic. Populations who are at greater risk due to their unusually high exposure to arsenic 

are discussed in Section 6.7, Populations with Potentially High Exposures. 
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No studies were located that identified an unusual susceptibility of any human subpopulation to arsenic. 

Several studies have evaluated possible sex-related differences in arsenic toxicity and carcinogenesis 

(Aposhian et al. 2000a, 2000b; Calderon et al. 1999; Loffredo et al. 2003; Mandal et al. 2001; Watanabe 

et al. 2001), but have not consistently identified differences. However, since the degree of arsenic 

toxicity may be influenced by the rate and extent of its methylation in the liver (see Section 3.4.3), it 

seems likely that some members of the population might be especially susceptible because of lower than 

normal methylating capacity. Studies of exposed humans in Taiwan suggested that subjects with lower 

secondary methylation indices have an increased risk of bladder cancer (Chen et al. 2003) and peripheral 

vascular disease (Tseng et al. 2005), particularly in subjects with high exposure levels. Reduced hepatic 

methylation could result from dietary deficiency of methyl donors such as choline or methionine (Buchet 

and Lauwerys 1987; Vahter and Marafante 1987), although this is unlikely to be a concern for most 

people in the United States. There is evidence that methylation capacity can vary greatly among 

individuals (e.g., Buchet et al. 1981a; Foà et al. 1984; Hopenhayn-Rich et al. 1996b; Tam et al. 1979b), 

but the basis of this variation and its impact on human susceptibility have not been fully established. 

There is some evidence that low dietary protein intake and possibly other nutritional deficiencies can 

decrease arsenic methylation (Steinmaus et al. 2005a). Recently, Heck et al. (2007) examined whether 

the capacity to methylate arsenic differs by nutrient intake in a cohort of 1,016 Bangladeshi adults 

exposed to arsenic in drinking water. The results showed that higher intakes of cysteine, methionine, 

calcium, protein, and vitamin B-12 were associated with lower percentages of inorganic arsenic and 

higher ratios of MMA to inorganic arsenic in urine. In addition, higher intakes of niacin and choline were 

associated with higher DMA/MMA ratios, after adjustment for sex, age, smoking, total urinary arsenic, 

and total energy intake. The issue of increased susceptibility to arsenic due to poor nutrition was 

discussed by NRC (2001), it was concluded that, with regard to skin effects, studies of cohorts from India, 

Bangladesh, and Taiwan suggest that nutrition plays an important role in arsenic toxicity. On the other 

hand, studies in other regions of the world (i.e., Chile) involving populations with much better nutrition 

argue against poor nutrition having a major impact on arsenic toxicity. 

Various genetic polymorphisms also seem to play a role in arsenic-induced toxicity. For example, a study 

of 85 lung cancer patients and 108 healthy controls in northern Chile reported that there was a 

nonstatistically significant difference for the frequency of the GSTM1 null genotype between the healthy 

and lung cancer patients stratified by gender and smoking status. The same results were observed for the 

MspI CYP450 1A1 polymorphism (Adonis et al. 2005). Hsueh et al. (2005) examined the association of 

four polymorphisms: NAD(P)H oxidase, manganese superoxide dismutase (MnSOD), catalase, and 

endothelial nitric oxide synthase (eNOS) with arsenic related hypertension risk among 79 hypertensive 
ARSENIC 266 

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cases and 213 controls in an arseniasis-hyperendemic area in Taiwan. The results showed that MnSOD 

polymorphism significantly increased the risk of hypertension regardless of exposure to arsenic. 

NAD(P)H oxidase and eNOS polymorphisms were significantly associated with increased risk of 

hypertension in subjects with higher cumulative arsenic exposure (≥10.5 mg/L x year), whereas catalase 

polymorphism was not associated with hypertension. The results also showed that the association 

between MnSOD, NAD(P)H oxidase, and eNOS polymorphisms and risk of hypertension were more 

pronounced in subjects with high triglyceride level. A study of a population of West Bengal, India, 

exposed to arsenic via drinking water reported that the frequencies of null genotype in GSTT1 were 

13.52 and 12.92% in skin-symptomatic and skin-asymptomatic individuals, and GSTM1 null genotype 

were 13.90 and 22.47% in skin-symptomatic and skin-asymptomatic individuals, respectively (Ghosh et 

al. 2006). Compared to those with GSTM1 null genotype, subjects with GST1-positive (at least one 

allele) had significantly higher risk of arsenic-induced skin lesions. Recently, Steinmaus et al. (2007) 

investigated urinary arsenic methylation patterns and genetic polymorphisms in methylenetetrahydrofolate reductase (MTHFR) and GST in 170 subjects (139 males) from an arsenic-exposed region in 

Argentina. MTHFR is a key enzyme in the metabolism of folate and has been linked to arsenic 

metabolism and toxicity (NRC 1999). Steinmaus et al. (2007) found that subjects with the TT/AA variant 

of MTHFR 677/1298 (associated with lower MTHFR activity) excreted a significantly higher proportion 

on ingested arsenic as inorganic arsenic and a smaller proportion as DMA(V). The study also reported 

that women with null genotype of GSTM1 excreted a significantly higher proportion of arsenic as 

monomethylarsenate than women with the active genotype. The study also found no association between 

polymorphisms in GSTT1 and arsenic methylation. 

There is a report that described severe arsenic-induced neuropathy that developed only in a 

5,10-methylenetetrahydrofolate-reductase (MTHFR) deficient member of a family that had been exposed 

to arsenic (Brouwer et al. 1992). The authors suggest that the MTHFR deficiency in this girl might 

explain the fact that of all the family members exposed to arsenic, only she developed severe clinical 

signs of arsenic poisoning. Liver disease does not appear to decrease methylation capacity in humans, at 

least at low levels of arsenic exposure (Buchet et al. 1982; Geubel et al. 1988). 

3.11 METHODS FOR REDUCING TOXIC EFFECTS 

This section will describe clinical practice and research concerning methods for reducing toxic effects of 

exposure to arsenic. 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 arsenic. When specific 
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exposures have occurred, poison control centers and medical toxicologists should be consulted for 

medical advice. The following texts provide specific information about treatment following exposures to 

arsenic: 

Tintinalli JE, Ruiz E, Krone RL, eds. 1996. Emergency medicine. A comprehensive study. American 

College of Emergency Physicians. 4th ed. New York, NY: The McGraw-Hill Companies, Inc. 

Goldfrank RL, Flomenbaum NE, Lewin NA, et al., eds. 1998. Goldfrank's toxicologic emergencies. 6th 

ed. Stamford, CT: Appleton and Lange. 

Ellenhorn MJ. 1997. Ellenhorn's medical toxicology. Diagnosis and treatment of human poisoning. 

Baltimore, MD: Williams & Wilkins. 

3.11.1 Reducing Peak Absorption Following Exposure 

No data were located regarding the reduction of absorption after inhalation exposure to arsenic. 

There are a number of methods for reducing absorption of arsenic following oral exposure. In cases of 

acute high-dose exposure, the removal of arsenic from the gastrointestinal tract may be facilitated by 

gastric lavage, stomach intubation, induced emesis, or use of cathartics (saline, sorbitol) within a few 

hours after ingestion (Agency for Toxic Substances and Disease Registry 1990a; Aposhian and Aposhian 

1989; Campbell and Alvarez 1989; Driesback 1980; Ellenhorn and Barceloux 1988; EPA 1989e; Haddad 

and Winchester 1990; Kamijo et al. 1998; Stutz and Janusz 1988). However, the efficacy of several of 

these methods has been questioned by some authors, and in some cases, the treatments may be 

contraindicated. For example, vomiting and diarrhea often occur soon after ingesting arsenic, and 

therefore, use of an emetic or cathartic may not be necessary. Also, emesis should not be induced in 

obtunded, comatose, or convulsing patients (Campbell and Alvarez 1989; Ellenhorn and Barceloux 1988; 

EPA 1989e), and saline cathartics should be used with caution in patients with impaired renal function 

(Campbell and Alvarez 1989). Vantroyen et al. (2004) described a case of a massive arsenic trioxide 

overdose that was successfully treated by continuous gastric irrigation with sodium bicarbonate, forced 

diuresis, and administration of BAL and DMSA. Treatments of this sort are unlikely to be required 

following low-level exposures. 

Another possible approach for reducing absorption following oral exposure is to administer substances 

that bind the arsenic in the gastrointestinal tract. For example, activated charcoal is sometimes used for 

this purpose (Campbell and Alvarez 1989; EPA 1989e; Stutz and Janusz 1988), although the effectiveness 

of this treatment is not well established. Because pentavalent arsenic is a phosphate analogue, 
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administration of phosphate-binding substance such as aluminum hydroxide might possibly be useful, but 

this has not been investigated. Sulfhydryl compounds might be given to bind trivalent arsenic, but it 

seems unlikely that these would be effective under the acid conditions in the stomach, and it is not clear 

that such complexes would have reduced gastrointestinal absorption. 

Following dermal or ocular exposure to arsenic, several measures can be taken to minimize absorption. 

All contaminated clothing should be removed, and contacted skin should be immediately washed with 

soap and water. Eyes that have come in contact with arsenic should be flushed with copious amounts of 

clean water (EPA 1989e; Stutz and Janusz 1988). 

3.11.2 Reducing Body Burden 

Acute arsenic intoxication may require treatment with chelating agents such as dimercaprol (BAL) and 

D-penicillamine. Although body burden is not necessarily reduced, these chelators bind free arsenic and 

serve to reduce the body's pool of biologically active arsenic. Chelation therapy is most effective when 

instituted within a few hours after exposure, and efficacy decreases as time after exposure increases 

(Agency for Toxic Substances and Disease Registry 1990a; Kamijo et al. 1998; McFall et al. 1998; 

Peterson and Rumack 1977). 

In general, chelating agents should be used with caution, since they may have serious side effects such as 

pain, fever, hypotension, and nephrotoxicity (Ellenhorn and Barceloux 1988). Some water-soluble and 

less toxic analogues of BAL such as dimercaptosuccinic acid (DMSA), dimercaptopropyl phthalamadic 

acid (DMPA), and dimercaptopropane sulfonic acid (DMPS) are currently under investigation and may 

prove to be promising treatments for arsenic poisoning (Agency for Toxic Substances and Disease 

Registry 1990a; Aposhian and Aposhian 1989; Aposhian et al. 1997; Guha Mazumder 1996; Kreppel et 

al. 1995). However, a randomized placebo trial of 2,3-dimercaptosuccinic acid as a therapy for chronic 

arsenosis due to drinking contaminated water found no significant difference between patients treated 

with 2,3-dimercaptosuccinic acid and those treated with a placebo (Guha Mazumder et al. 1998a). 

N-acetylcysteine has been used in animals to chelate arsenic (Haddad and Winchester 1990), and a human 

case study reported N-acetylcysteine to be successful in treating a case of arsenic poisoning that was not 

responding well to BAL treatment (Martin et al. 1990). Vantroyen et al. (2004) described a case of a 

massive arsenic trioxide overdose that was successfully treated by continuous gastric irrigation with 

sodium bicarbonate, forced diuresis, and administration of BAL and DMSA. 
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As discussed in Section 3.4.3, once arsenic has been absorbed into the blood stream, it undergoes 

methylation to yield MMA and DMA. These forms of arsenic are less toxic than inorganic arsenic and 

are cleared from the body by excretion in the urine. Therefore, if it were possible to enhance arsenic 

methylation, both body burden and toxicity of arsenic might be reduced. However, experimental 

evidence in animals and humans suggests that arsenic methylation is not enhanced to any significant 

degree by supplementation with methylation cofactors (Buchet and Lauwerys 1987; Buchet et al. 1982), 

presumably because it is enzyme level and not cofactor availability that is rate limiting in arsenic 

methylation. 

3.11.3 Interfering with the Mechanism of Action for Toxic Effects 

It is generally thought that trivalent arsenic exerts its toxic effects mainly by complexing with sulfhydryl 

groups in key enzymes within the body, thereby inhibiting critical functions such as gluconeogenesis and 

DNA repair (Aposhian and Aposhian 1989; Li and Rossman 1989). Therefore, administration of 

sulfhydryl-containing compounds soon after exposure could provide alternative target molecules for 

arsenic, and prevent inhibition of enzyme functions. In fact, many of the chelating agents discussed 

above (BAL, DMSA, DMPA, DMPS, N-acetylcysteine) contain sulfhydryl groups, and this may account 

for their efficacy. 

The mechanism by which pentavalent arsenic acts is less certain. Since pentavalent arsenic is reduced in 

the body to the trivalent state, pentavalent arsenic may act in a similar manner as described above for 

trivalent arsenic. If this is the case, efforts to inhibit the reduction of pentavalent arsenic would decrease 

its toxicity. However, no methods are currently recognized for blocking this reduction. Pentavalent 

arsenic may also exert effects by acting as a phosphate analogue. As a phosphate analogue, pentavalent 

arsenic could potentially affect a number of biological processes, including ATP production, bone 

formation, and DNA synthesis. However, any effort to interfere in normal phosphate metabolism could 

produce serious side effects, and no method is known for selectively interfering with arsenate metabolism. 

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 arsenic is available. Where adequate information is not 

available, ATSDR, in conjunction with the National Toxicology Program (NTP), is required to assure the 
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initiation of a program of research designed to determine the health effects (and techniques for developing 

methods to determine such health effects) of arsenic. 

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 Arsenic 

The existing data on health effects of inhalation, oral, and dermal exposure of humans and animals to 

inorganic and organic arsenic are summarized in Figures 3-13 and 3-14, respectively. The purpose of this 

figure is to illustrate the existing information concerning the health effects of arsenic. 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 3-13, there is a substantial database on the toxicity of inorganic arsenicals, both in 

humans and in animals. The oral route has been most thoroughly investigated, and reports are available 

on most end points of concern following acute, intermediate, and chronic exposure. The inhalation route 

has also been studied extensively, mainly in humans, with special emphasis on lung cancer. A number of 

noncancer end points have also been studied following inhalation exposure, but information on these 

effects is less extensive. Limited information on the effects of dermal exposure is also available in both 

humans and animals, focusing mainly on direct irritancy and dermal sensitization reactions. The absence 

of studies on other effects of inorganic arsenic following dermal exposure is probably not a critical data 

need, since dermal uptake of inorganic arsenic appears to be sufficiently limited that other routes of 

exposure (oral or inhalation) would almost always be expected to be of greater concern. 
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3. HEALTH EFFECTS 

Figure 3-13. Existing Information on Health Effects of Inorganic Arsenic 

Death

Acute 

Intermediate 

Chronic 

Immunologic/Lymphoretic 

Neurologic 

Reproductive 

Developmental 

Genotoxic 

Cancer 

Systemic 

Human 

Inhalation 

Oral 

Dermal 

Death

Acute 

Intermediate 

Chronic 

Immunologic/Lymphoretic 

Neurologic 

Reproductive 

Developmental 

Genotoxic 

Cancer 

Systemic 

Animal 

Inhalation 

Oral 

Dermal 

Existing Studies 
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3. HEALTH EFFECTS 

Figure 3-14. Existing Information on Health Effects of Organic Arsenic 

Death

Acute 

Intermediate 

Chronic 

Immunologic/Lymphoretic 

Neurologic 

Reproductive 

Developmental 

Genotoxic 

Cancer 

Systemic 

Human 

Inhalation 

Oral 

Dermal 

Death

Acute 

Intermediate 

Chronic 

Immunologic/Lymphoretic 

Neurologic 

Reproductive 

Developmental 

Genotoxic 

Cancer 

Systemic 

Animal 

Inhalation 

Oral 

Dermal 

Existing Studies 
ARSENIC 273 

3. HEALTH EFFECTS 

As shown in Figure 3-14, very little information is available on the effects of organic arsenic compounds 

in humans, although there are a number of studies in animals. These studies mainly involve the oral 

route, since all of these compounds are nonvolatile solids, although a few acute inhalation studies have 

been performed. Limited information is available on acute dermal lethality and dermal irritancy of some 

organic arsenicals, but data are lacking on other effects of organic arsenicals following dermal exposure. 

As discussed previously, in evaluating the adequacy of the database on arsenic, it is important to keep in 

mind that most studies in animals indicate that they are quantitatively less sensitive to arsenic than 

humans. For this reason, data from animal studies should be used to draw inferences about effects in 

humans only with caution. 

3.12.2 Identification of Data Needs 

Acute-Duration Exposure. 

Inorganic Arsenicals. There is only limited information on the effects of acute inhalation exposure to 

arsenic in humans, but the chief symptoms appear to be irritation of the respiratory and gastrointestinal 

tracts (Beckett et al. 1986; Bolla-Wilson and Bleecker 1987; Dunlap 1921; Ide and Bullough 1988; 

Morton and Caron 1989; Pinto and McGill 1953). Quantitative data are lacking, but effects generally 

appear to be mild even at high-exposure levels. On this basis, it seems that risks of acute effects are 

probably low for inhalation exposures in the environment or near waste sites. Research to obtain a 

quantitative acute inhalation NOAEL value that could be used to derive an acute inhalation MRL would, 

therefore, be useful but not critical. There are numerous case studies in humans on the acute oral toxicity 

of arsenic, and the main end points (gastrointestinal irritation, pancytopenia, hepatic injury, neuropathy) 

are well characterized (Armstrong et al. 1984; Fincher and Koerker 1987). An acute oral MRL of 

0.005 mg As/kg/day was derived for inorganic arsenic based on a LOAEL for gastrointestinal symptoms 

and facial edema reported by Mizuta et al. (1956). Additional studies to define an acute oral NOAEL 

would be useful to reduce uncertainty in the MRL derivation. Acute dermal exposure is unlikely to cause 

serious systemic injury, but it can lead to contact dermatitis and skin sensitization (Holmqvist 1951; Pinto 

and McGill 1953). However, available data do not permit a quantitative estimate of the concentration of 

arsenic on the skin or in air, dust, soil, or water that causes these effects. Further research would be 

valuable to obtain a quantitative NOAEL for direct dermal effects, since humans may have dermal contact 

with contaminated soil or water near hazardous waste sites. 
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Organic Arsenicals. Information on the acute toxicity of organic arsenicals in humans is limited to 

reports of gastrointestinal irritation in individuals ingesting pesticides containing organic arsenicals (Lee 

et al. 1995; Shum et al. 1995); these case reports provide limited dosing information. Acute lethality and 

systemic toxicity data exist for several compounds by inhalation, oral, and dermal exposure of animals. 

Inhalation data are limited to a lethality study of rats and mice exposed to MMA or DMA that reported 

respiratory and ocular irritation (Stevens et al. 1979). The oral acute studies consist of lethality studies 

for MMA (Gur and Nyska 1990; Jaghabir et al. 1988; Kaise et al. 1989), DMA (Kaise et al. 1989), and 

roxarsone (Kerr et al. 1963; NTP 1989b), systemic toxicity studies (or longer-term studies reporting 

effects within the first 2 weeks of exposure) for MMA (Irvine et al. 2006), DMA (Ahmad et al. 1999a; 

Chernoff et al. 1990; Cohen et al. 2001; Crown et al. 1987; Irvine et al. 2006; Kavlock et al. 1985; Rogers 

et al. 1981; Zomber et al. 1989), or roxarsone (NTP 1989b). For MMA, the available data suggest that 

the gastrointestinal tract may be the most sensitive target of toxicity; however, the study identifying the 

lowest LOAEL (Irvine et al. 2006) involved bolus administration and this is not an appropriate exposure 

route to estimate human risk for gastrointestinal effects following environmental exposure to MMA. The 

available animal studies for DMA have examined urinary bladder (Cohen et al. 2001) and developmental 

toxicity (Chernoff et al. 1990, Irvine et al. 2006; Kavlock et al. 1985; Rogers et al. 1981). For DMA, 

acute-duration studies in rats suggest that the urinary bladder is the most sensitive target of toxicity in rats 

(Cohen et al. 2001); however, there is evidence from longer-term studies that rats may be more sensitive 

than humans and other species for bladder effects. Thus, rat data were not considered as the basis of an 

acute-duration oral MRL for DMA. Other effects observed following acute exposure to DMA include 

developmental and maternal effects in mice (Kavlock et al. 1985; Rogers et al. 1981) and rabbits (Irvine 

et al. 2006) and diarrhea and vomiting in dogs receiving a bolus dose of DMA (Zomber et al. 1989). An 

acute-duration oral MRL was not derived for DMA because it is not known if systemic effects would 

occur at lower doses than the developmental effects. For roxarsone, the available data suggest that the 

most sensitive effect following acute oral exposure is neuropathy observed in pigs (Kennedy et al. 1986; 

Rice et al. 1985). At the only dose tested in this study, tremors, clonic convulsions, and equivocal 

evidence of myelin degeneration were observed; these were considered serious effects and not suitable for 

the derivation of an acute-duration oral MRL for roxarsone. Additional studies are needed for MMA, 

DMA, and roxarsone that examine a variety of end points in several species; studies for roxarsone should 

also include examination of neurological end points, which would be useful for identifying the critical 

targets of toxicity and establishing dose-response relationships. 
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Intermediate-Duration Exposure. 

Inorganic Arsenicals. Intermediate-duration inhalation exposure of humans to arsenic appears to result 

in respiratory tract irritation (occasionally including perforation of the nasal septum) and mild 

gastrointestinal tract irritation (Ide and Bullough 1988). Quantitative data are too limited (only one study, 

of one individual) to derive an intermediate-duration inhalation MRL. Further studies to define the 

NOAEL for intermediate-duration inhalation exposure of humans would be valuable, since humans could 

be exposed to arsenic-containing airborne dusts near smelters, chemical plants, or waste sites. Effects of 

intermediate-duration oral exposure are similar to those of acute oral exposure, but may also include 

development of vascular injury and a characteristic group of skin changes (Franzblau and Lilis 1989; 

Holland 1904; Wagner et al. 1979). Most studies indicate that these effects occur at doses of about 

0.05 mg As/kg/day or higher, but the data do not provide a firm basis for identifying the intermediateduration NOAEL. For this reason, no intermediate-duration oral MRL has been derived. Further studies 

to establish the NOAEL would be valuable, since humans could have intermediate-duration oral 

exposures to arsenic through ingestion of contaminated soil or water near smelters, chemical factories, or 

waste sites. Since dermal effects appear to be restricted to acute irritancy, intermediate-duration dermal 

studies are probably not essential. 

Organic Arsenicals. No information was located on the intermediate-duration toxicity of organic 

arsenicals in humans. Several studies have examined the intermediate-duration oral toxicity of MMA; 

dietary exposure studies in rats and mice (Arnold et al. 2003) identify the gastrointestinal tract as the most 

sensitive target. Diarrhea and lesions in the cecum, colon, and rectum have been observed. The rat 

13-week study (Arnold et al. 2003) was used as the basis of the MRL. Because rats appear to be more 

sensitive to the toxicity of DMA, rat studies were not considered for MRL derivation. The only non-rat 

study was a chronic-duration dog study reporting effects during the first 51 weeks of exposure (Zomber et 

al. 1989); these effects included diarrhea and vomiting. However, because DMA was administered via 

capsule, this study was not considered adequate for derivation of an MRL. Additional studies are needed 

for DMA to identify critical targets of toxicity and establish dose-response relationships in non-rat 

species. The available data for roxarsone suggest that neurotoxicity in pigs is the most sensitive end 

point. One of the two available neurotoxicity studies in pigs (Edmonds and Baker 1986) did not include 

sensitive tests of toxicity and was not considered for MRL derivation; the other study identified a serious 

LOAEL at the only dose tested and thus, was not suitable for MRL derivation. Several comprehensive 

studies examined the toxicity of roxarsone in rats and mice (NTP 1989b). Renal tubular damage in rats 

was the most sensitive end point (NTP 1989b); however, the LOAEL for this effect was 9 times higher 
ARSENIC 276 

3. HEALTH EFFECTS 

than the dose associated with neurotoxicity in pigs. Additional studies are needed to establish a no effect 

level for neurotoxicity in pigs, which could be used to derive an intermediate duration MRL for 

roxarsone. Further studies on the intermediate-duration inhalation and dermal toxicity of these 

compounds would be valuable, especially in humans, since people may be exposed to organic arsenicals 

during their manufacture or use, or from materials deposited in waste sites. 

Chronic-Duration Exposure and Cancer. 

Inorganic Arsenicals. The target tissues of chronic-duration exposure of humans to inorganic arsenic are 

the same as for intermediate-duration exposure for both the oral and inhalation routes. Effects of dermal 

exposure appear to be restricted to direct irritation of exposed surfaces. Therefore, chronic-duration 

studies are probably not essential for the dermal route. Quantitative data from one study identify an 

inhalation exposure level of about 0.1 mg As/m3

 as the LOAEL for skin changes (Perry et al. 1948), but 

because there are no additional supporting studies and a NOAEL is not clearly established, a chronicduration inhalation MRL has not been derived. Additional studies in humans to define the chronic 

inhalation NOAEL for dermal or other effects would be valuable, since humans may be chronically 

exposed to arsenic dusts in air near smelters, chemical factories, or waste sites. Chronic oral exposure 

data from studies in humans indicate that the LOAEL for skin lesions and other effects is probably about 

0.01–0.02 mg As/kg/day (10–20 μg As/kg/day), and that the NOAEL is probably between 0.0004 and 

0.0009 mg As/kg/day (0.4–0.9 μg As/kg/day) (Cebrián et al. 1983; EPA 1981b; Hindmarsh et al. 1977; 

Tseng 1977; Tseng et al. 1968). The NOAEL of 0.0008 mg As/kg/day from the study by Tseng et al. 

(1968) is appropriate for derivation of a chronic-duration oral MRL, but an uncertainty factor of 3 was 

required to account for the fact that the population that constituted the no-effect group were relatively 

young (possibly decreasing the ability to detect dermal or other effects that increase in prevalence with 

age). Another issue that needs to be acknowledged, which is common to ecological studies and 

contributes to uncertainty, is the fact that individual doses were not available and were calculated from 

group mean arsenic concentrations in well water using estimated water intake parameters. For this 

reason, further epidemiological studies that do not rely on an ecological-based exposure assessment that 

would provide additional support for the threshold dose for arsenic in humans would be valuable. 

There are numerous studies in humans that support the carcinogenic effects of inorganic arsenic from 

inhalation exposure (Enterline et al. 1987a, 1987b, 1995; Järup and Pershagen 1991; Järup et al. 1989; 

Lee-Feldstein 1986; Welch et al. 1982) and oral exposure (Chen et al. 1986, 1988b, 1992; Chiou et al. 

1995; Ferreccio et al. 1996; Hsueh et al. 1995; Lander et al. 1975; Liu and Chen 1996; Lüchtrath 1983; 
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3. HEALTH EFFECTS 

Smith et al. 1992; Tseng 1977; Tseng et al. 1968; Yu et al. 1992; Zaldívar 1974; Zaldívar et al. 1981). 

Quantitative slope factors have been derived for both routes. There is a noticeable absence, however, of 

2-year animal carcinogenicity studies for either the inhalation or oral route of exposure (Chan and Huff 

1997). In light of the ongoing controversy over the reasons for the absence of a carcinogenic effect in 

animals, it seems prudent to firmly establish a negative effect in a 2-year study. The carcinogenic effects 

of chronic dermal exposure to inorganic arsenicals have not been studied, but dermal exposure is a 

relatively minor route of exposure, and these studies would not be a top priority. 

The mechanism of arsenic carcinogenicity is not known, although the current view is that it functions 

mainly as a promoter or cocarcinogen. Further studies on the mechanism of arsenic toxicity would be 

particularly valuable to improve our ability to evaluate human cancer risks from inhalation or oral 

exposures that might occur near waste sites. Also, mechanistic studies could help in the evaluation of 

cancer risks from organic derivatives (see below). 

Organic Arsenicals. There is very little information on the chronic toxicity of organic arsenicals in 

humans. One study of workers exposed to arsanilic acid did not identify any adverse effects, but no 

systematic, clinical, or toxicological examinations of exposed people were performed (Watrous and 

McCaughey 1945). Chronic toxicity studies are available for rats, mice, and dogs exposed to MMA 

(Arnold et al. 2003; Waner and Nyska 1988), DMA (Arnold et al. 2006; Zomber et al. 1989), and 

roxarsone (NTP 1989b; Prier et al. 1963). Chronic exposure to MMA results in diarrhea in rats, mice, 

and dogs (Arnold et al. 2003; Waner and Nyska 1988) and an increase in progressive nephropathy in rats 

and mice (Arnold et al. 2003). The increased incidence of progressive nephropathy was used as the basis 

of the chronic-duration oral MRL for MMA. For DMA, chronic exposure also resulted in an increased 

incidence of diarrhea and vomiting in dogs (Zomber et al. 1989) and an increased incidence of 

vacuolization in the urinary bladder and progressive nephropathy in mice (Arnold et al. 2006). The 

vacuolization in the urinary bladder was used as the basis of a chronic-duration oral MRL for DMA. The 

available data for chronic-exposure to roxarsone were considered inadequate for derivation of an MRL. 

The highest doses tested in the rat, mouse, and dog studies (NTP 1989b; Prier et al. 1963) were NOAELs. 

Intermediate-duration studies identify neurotoxicity in pigs as the most sensitive end point; this has not 

been adequately examined following chronic exposure and studies are needed. 

No information was located on carcinogenic effects of organic arsenicals in humans. The carcinogenic 

potential of MMA (Arnold et al. 2003), DMA (Arnold et al. 2006), and roxarsone (NTP 1989b) following 

oral exposure has been investigated in rats and mice. No evidence of carcinogenicity was observed 
ARSENIC 278 

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following oral exposure to MMA (Arnold et al. 2003) and equivocal evidence of carcinogenicity was 

found in male rats, with no evidence of carcinogenicity in female rats or in male or female mice orally 

exposed to roxarsone (NTP 1989b). Oral exposure to DMA resulted in an increased incidence of urinary 

bladder tumors in rats and no evidence of carcinogenicity in mice (Arnold et al. 2006). However, there is 

concern that the rat is not a good model to assess the carcinogenic potential of DMA in humans due to 

species differences in the toxicokinetic properties of DMA. No information was located on the 

carcinogenicity of organic arsenicals following inhalation or dermal exposure. Studies of humans 

exposed in the workplace would provide valuable information on the carcinogenic potential of organic 

arsenicals, particularly DMA. Studies on cancer risk following inhalation and dermal exposure to organic 

arsenicals are would be useful since these are possible routes of exposure for humans. 

Genotoxicity. 

Inorganic Arsenicals. There are several studies that suggest that inorganic arsenic may cause 

genotoxicity (mainly chromosomal effects) in exposed humans (Burgdorf et al. 1977; Nordenson et al. 

1978), and this is supported by numerous studies in animals (Datta et al. 1986; DeKnudt et al. 1986; 

Nagymajtényi et al. 1985) and cultured cells (Beckman and Nordenson 1986; Casto et al. 1979; DiPaolo 

and Casto 1979; Lee et al. 1985; Nakamuro and Sayato 1981; Nishioka 1975; Oberly et al. 1982; Okui 

and Fujiwara 1986; Sweins 1983; Ulitzur and Barak 1988; Zanzoni and Jung 1980). The mechanism of 

genotoxicity is not known, but may be due to the ability of arsenite to interfere with DNA repair (Li and 

Rossman 1989) or to alter apoptosis (Pi et al. 2005) or the ability of arsenate to act as a phosphate analog. 

Further studies to improve our understanding of the mechanism of genotoxicity would be valuable, since 

this could aid in the understanding of arsenic-induced cancer risk. 

Organic Arsenicals. For organic arsenicals, in vitro genotoxicity studies are available for arsenobetaine 

(Eguchi et al. 1997; Oya-Ohta et al. 1996), MMA (Chun and Killeen 1989a, 1989b, 1989c, 1989d; Eguchi 

et al. 1997; Oya-Ohta et al. 1996), DMA (Eguchi et al. 1997; Endo et al. 1992; Kato et al. 1994; 

Kawaguchi et al. 1996; Kitamura et al. 2002; Kuroda et al. 2004; Moore et al. 1997a; Oya-Ohta et al. 

1996; Rasmussen and Menzel 1997; Rin et al. 1995; Tezuka et al. 1993; Ueda et al. 1997; Yamanaka et 

al. 1989b, 1993, 1995, 1997), and roxarsone (Matthews et al. 1993; NTP 1989b; Storer et al. 1996) and 

in vivo studies are available for DMA (Kashiwada et al. 1998; Yamanaka and Okada 1994; Yamanaka et 

al. 1989a, 1989b, 1993, 2001). The results of these studies suggest that DMA and roxarsone are 

clastogenic and can cause DNA strand breaks. Additional in vivo studies are needed to evaluate the 

genotoxic potential of MMA and roxarsone. 
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Reproductive Toxicity. 

Inorganic Arsenicals. Several studies have examined reproductive function in populations living in 

Bangladesh or India exposed to high levels of arsenic in drinking water and found increases in 

spontaneous abortions/stillbirths or preterm births (Ahmad et al. 2001; von Ehrenstein et al. 2006); 

another study in U.S. women did not find an increase in adverse reproductive outcomes (Aschengrau et 

al. 1989). Available animal studies did not find evidence for reproductive effects following inhalation or 

oral exposure (Holson et al. 1999, 2000), except for a trend toward decreased pups per litter in mice in a 

3-generation study (Schroeder and Mitchener 1971) that is consistent with embryolethality observed in 

developmental studies of inorganic arsenic. Studies on spermatogenesis and reproductive success in 

arsenic-exposed workers would be valuable in evaluating whether there are significant reproductive risks 

of arsenic in humans, and this could be further strengthened by studies including histopathological 

examination of reproductive tissues (which was not done in the existing studies) in animals. 

Organic Arsenicals. No information was located on reproductive effects of organic arsenicals in humans 

and no inhalation or dermal exposure animal studies were located. Intermediate- and chronic-duration 

oral studies for MMA (Arnold et al. 2003), DMA (Arnold et al. 2006), and roxarsone (NTP 1989b) have 

not reported histological damage to reproductive tissues. Decreases in pregnancy rate and male fertility 

index were observed in a two-generation study in rats (Schroeder 1994) and a single generation study in 

mice (Prukop and Savage 1986) exposed to MMA; the poor reporting in the Prukop and Savage (1986) 

study limits its usefulness in assessing reproductive toxicity. However, in the two-generation study, the 

differences between control and exposed rats were not statistically different; the effect was considered 

biologically significant because effects observed in the exposed rats were outside the range found in 

historical controls. Another reproductive performance study to confirm these results would be useful. No 

reproductive effects were observed in a two generation study in rats exposed to DMA (Rubin et al. 1989). 

Developmental Toxicity. 

Inorganic Arsenicals. There are several epidemiological studies that suggest that inhalation (Ihrig et al. 

1998; Nordström et al. 1978a, 1978b, 1979a, 1979b) or oral (Hopenhayn et al. 2003a; Yang et al. 2003) 

exposure to inorganic arsenic might increase the risk of low birth weight, congenital defects, or abortion 

in exposed women. These studies do not establish that arsenic was responsible, since all involved 

exposures to other chemicals or risk factors, but do suggest that additional studies on developmental 
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parameters in humans exposed to arsenic would be valuable in determining whether this is an effect of 

concern. Other human studies have not found significant associations between arsenic levels in drinking 

water and increased neonatal deaths or infant mortality (von Ehrenstein et al. 2006) or the increase in 

congenital heart defects (Zierler et al. 1988) or neural tube defects (Brender et al. 2006). Studies in 

animals support the view that oral, inhalation, and parenteral exposure to inorganic arsenic can all 

increase the incidence of fetotoxicity and teratogenicity, although this appears to occur only at doses that 

are toxic or even lethal to the dams (Baxley et al. 1981; Beaudoin 1974; Carpenter 1987; Ferm and 

Carpenter 1968; Ferm et al. 1971; Hanlon and Ferm 1986; Holson et al. 1999, 2000; Hood and Bishop 

1972; Hood and Harrison 1982; Hood et al. 1978; Mason et al. 1989; Nagymajtényi et al. 1985; Nemec et 

al. 1998; Stump et al. 1999; Willhite 1981). There are also some data to suggest that it may increase the 

risk of transplacental cancer in humans (Smith et al. 2006) and animals (Waalkes et al. 2003). Thus, 

additional studies in animals may be useful in defining the mechanisms of these developmental effects 

and in identifying the time of maximum susceptibility of the fetus, but such studies probably will not help 

identify a safe exposure level for humans. 

Organic Arsenicals. No information was located regarding developmental effects in humans after oral or 

inhalation exposure to organic arsenicals. Animal studies conducted in rats (Chernoff et al. 1990; Irvine 

et al. 2006; Rogers et al. 1981), mice (Kavlock et al. 1985; Rogers et al. 1981), and rabbits (Irvine et al. 

2006) have examined the developmental toxicity of organic arsenicals. Decreases in fetal body weights 

and delays in ossification were commonly reported at maternally toxic (decreases in body weight gain) 

doses of DMA (Irvine et al. 2006; Kavlock et al. 1985; Rogers et al. 1981). However, one study found 

increases in the percentage of fetuses with irregular palatine rugae at DMA doses not associated with 

maternal toxicity (Rogers et al. 1981). This effect has not been reported in other studies and additional 

developmental studies are needed to confirm the finding. In view of the apparent differences in 

susceptibility between animals and humans, it would be valuable to investigate whether there are any 

measurable effects on development in humans exposed to organic arsenicals in the workplace or the 

environment. 

Immunotoxicity. 

Inorganic Arsenicals. No studies were located on immunotoxic effects in humans after oral exposure to 

inorganic arsenic. One inhalation study in humans (Bencko et al. 1988), an inhalation study in animals 

(Aranyi et al. 1985), one oral study in animals (Kerkvliet et al. 1980), and one intratracheal instillation 

study in animals (Sikorski et al. 1989) suggest that arsenic causes little or no functional impairment of the 
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immune system, but one inhalation study in animals found decreased pulmonary bactericidal activity and 

increased susceptibility to streptococcal infection in exposed mice (Aranyi et al. 1985). Additional 

studies (both in humans and animals) would be valuable to investigate this end point further. Dermal 

exposure of humans to high levels of arsenic dusts may cause dermal sensitization (Holmqvist 1951), but 

the dose and time dependence of this phenomenon are not known. Studies to determine whether dermal 

sensitization occurs in people with low level dermal exposures to arsenic in dust or soil, such as might 

occur for residents near an arsenic-containing waste site, would be valuable in assessing the significance 

of this effect to nonoccupationally exposed populations. 

Organic Arsenicals. No information was located on the effect of organic arsenicals exposure in humans 

or animals on immune function. Since there are suggestions that inorganic arsenic may cause some 

changes in the immune system, studies on possible immune effects of the common organic arsenicals 

might be helpful. 

Neurotoxicity. 

Inorganic Arsenicals. There is convincing evidence from studies in humans that inorganic arsenic can 

cause serious neurological effects, both after inhalation (Beckett et al. 1986; Bencko et al. 1977; Blom et 

al. 1985; Buchancová et al. 1998; Calderón et al. 2001; Danan et al. 1984; Feldman et al. 1979; Gerr et al. 

2000; Lagerkvist and Zetterlund 1994; Morton and Caron 1989) and oral exposure (Armstrong et al. 

1984; Bartolome et al. 1999; Chakraborti et al. 2003a, 2003b; Civantos et al. 1995; Cullen et al. 1995; 

Danan et al. 1984; EPA 1977a; Feldman et al. 1979; Fincher and Foy et al. 1992; Franzblau and Lilis 

1989; Guha Mazumder et al. 1988; Hindmarsh et al. 1977; Huang et al. 1985; Fincher and Koerker 1987; 

Levin-Scherz et al. 1987; Lewis et al. 1999; Mizuta et al. 1956; Muzi et al. 2001; Quatrehomme et al. 

1992; Silver and Wainman 1952; Szuler et al. 1979; Tsai et al. 2003; Uede and Furukawa 2003; 

Vantroyen et al. 2004; Wagner et al. 1979). This is based mainly on clinical observations and 

neurological examinations of exposed persons. Available studies provide a reasonable estimate of 

LOAEL and NOAEL values by the oral route, but similar data are lacking for the inhalation route. 

Further studies designed to identify the threshold for neurological effects in humans exposed by the 

inhalation route would be valuable, since humans may be exposed to arsenic dusts in air from smelters, 

chemical factories, or waste sites. Adult animals appear to be much less susceptible than humans to the 

neurological effects of inorganic arsenic, so studies in adult animals would probably not help in 

estimation of a safe exposure limit. However, in light of recent findings of possible associations between 

arsenic in drinking water and neurobehavioral alterations in children (Tsai et al. 2003; von Ehrenstein et 
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al. 2007; Wang et al. 2007; Wasserman et al. 2004, 2007), studies in animals, in which confounding can 

be eliminated, may be warranted. 

Organic Arsenicals. Information on neurological effects of organic arsenicals in humans is limited to an 

occupational study that did not find increases in the frequency of central or peripheral nervous system 

complaints (Watrous and McCaughey 1945) and a case report of a women of a women reporting 

numbness and tingling of the fingertips, toes, and circomoral region who was exposed to organic arsenic 

in soup (Luong and Nguyen 1999). Neurological effects have also been observed in some animal studies. 

Decreases spontaneous motility, ataxia, and increased startle response were observed in mice exposed to a 

single high dose of DMA (Kaise et al. 1989). Degeneration of myelin and axons were observed in several 

studies involving oral exposure of pigs to roxarsone (Edmonds and Baker 1986; Kennedy et al. 1986; 

Rice et al. 1985). Hyperexcitability, ataxia, and trembling have also been observed in rats and mice orally 

exposed to roxarsone (Kerr et al. 1963; NTP 1989b). These findings suggest that more extensive 

investigations of the neurotoxic potential of roxarsone and other organic arsenicals would be valuable to 

determine the potential human health risk from these compounds, since humans could be exposed during 

the manufacture or use of these compounds, or near waste sites where they have been deposited. 

Epidemiological and Human Dosimetry Studies. Numerous epidemiologic studies of humans 

exposed to inorganic arsenic by the oral and inhalation routes constitute the database on arsenic-related 

cancer and noncancer human health effects. As with virtually all epidemiologic investigations, these 

studies are limited by possible confounding from factors such as smoking, exposure to other chemicals, 

and differences in population characteristics (e.g., nutritional state, metabolism, and toxicokinetics) that 

inhibit extrapolation of study results to a wider population. Moreover, many of these studies lack good 

dose estimates for study participants. Some studies lack quantitative data altogether. For this reason, 

improved data on confounding factors and improved methods of human dosimetry would be valuable in 

any further human epidemiologic studies of arsenic, either in the workplace or in the general 

environment. Recent work has broadened the qualitative dose-response information beyond the highly 

exposed Taiwanese population, but additional studies of persons with lower exposure levels would be 

especially valuable for risk assessments for the U.S. population. From a public health standpoint, well 

designed studies of common noncancer health outcomes (e.g., cardiovascular disease and diabetes) could 

be more important than additional studies of cancer. Availability of methods for biomonitoring of 

exposure are discussed below. 
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3. HEALTH EFFECTS 

Biomarkers of Exposure and Effect. 

Exposure. There are sensitive and specific methods for measuring arsenic in blood, urine, hair, nails, and 

other tissues, and this is the approach normally employed for measuring arsenic exposure in humans. 

Usually total arsenic is measured, but methods are available for measuring inorganic arsenic and each of 

the organic derivatives separately. Urinary levels are generally considered to be the most reliable 

indication of recent exposures (Enterline et al. 1987a; Milham and Strong 1974; Pinto et al. 1976; Polissar 

et al. 1990), but if a high urinary level is present, care must be taken to account for the presence of 

nontoxic forms of arsenic from the diet. Blood levels are sometimes used to evaluate the status of acutely 

poisoned individuals (Driesback 1980; Heydorn 1970; Hindmarsh and McCurdy 1986; Valentine et al. 

1979, 1981), but this approach is not generally useful for biomonitoring of long-term exposure to low 

levels. Hair and nails provide a valuable indication of exposures that occurred 1–10 months earlier 

(Agahian et al. 1990; Bencko et al. 1986; Choucair and Ajax 1988; EPA 1977a, 1981b; Milham and 

Strong 1974; Valentine et al. 1979; Yamauchi et al. 1989), although care must be taken to exclude 

external contamination of these samples. Cumulative urinary arsenic levels may be used to derive a 

quantitative estimate of exposure (Enterline et al. 1987a; Pinto et al. 1976), but data on the quantitative 

relation between exposure and arsenic levels in nails and hair were not located. Efforts to establish an 

algorithm for estimating past exposure levels from hair or nail levels would be valuable in quantifying 

average long-term exposure levels in people where repeated urinary monitoring is not feasible. 

Effect. The effects of arsenic are mainly nonspecific, but the combined presence of several of the most 

characteristic clinical signs (e.g., nausea, diarrhea, peripheral neuropathy, anemia, vascular lesions, 

hyperkeratinization, hyperpigmentation) is usually adequate to suggest arsenic intoxication. Although 

there are standard clinical methods for detecting and evaluating each of these effects, there are no 

recognized methods for identifying early (preclinical) effects in exposed persons. Neurophysiological 

measurements of nerve conduction velocity or amplitude have been investigated (Goebel et al. 1990; 

Jenkins 1966; Le Quesne and McLeod 1977; Morton and Caron 1989; Murphy et al. 1981), but at present, 

this approach does not seem to offer much advantage over a standard neurological examination. Changes 

in urinary excretion levels of several heme-related metabolites appear to be a good indication of 

preclinical effects of arsenic toxicity in animals (Albores et al. 1989; Sardana et al. 1981; Woods and 

Fowler 1978; Woods and Southern 1989), but this has not been established in humans and is not specific 

for arsenic-induced effects. Further efforts to develop these approaches and to identify other more 

specific biochemical or physiological indicators of arsenic-induced effects would be very valuable in 

monitoring the health of persons exposed to low levels of arsenic in the environment or near waste sites. 
ARSENIC 284 

3. HEALTH EFFECTS 

Absorption, Distribution, Metabolism, and Excretion. Available data from toxicokinetic 

studies in humans reveal that arsenates and arsenites are well absorbed following both oral and inhalation 

exposure. Data on distribution are limited, but it appears that arsenic is transported to nearly all tissues. 

Metabolism involves mainly reduction-oxidation reactions that interconvert As(+5) and As(+3) and 

methylation of As(+3) to yield MMA and DMA. Most arsenic is rapidly excreted in the urine as a 

mixture of inorganic arsenics, MMA, and DMA, although some may remain bound in tissues (especially 

skin, hair, and fingernails). These findings are strongly supported by numerous studies in animals. 

Because methylation represents a detoxification pathway, an area of special interest is the capacity of the 

human body to methylate inorganic arsenic. Limited data suggest that the methylation system might 

begin to become saturated at intakes of about 0.2–1 mg As/day (Buchet et al. 1981b; Marcus and Rispin 

1988), but this is uncertain. Further studies to define the rate and saturation kinetics of whole-body 

methylation in humans would be especially helpful in evaluating human health risk from the low levels of 

arsenic intake that are usually encountered in the environment. Along the same line, further studies to 

determine the nature and magnitude of individual variations in methylation capacity and how this depends 

on diet, age, and other factors would be very useful in understanding and predicting which members of a 

population are likely to be most susceptible. 

The toxicokinetics of dermal exposure have not been studied. It is usually considered that dermal uptake 

of arsenates and arsenites is sufficiently slow that this route is unlikely to be of health concern (except 

that due to direct irritation), but studies to test the validity of this assumption would be valuable. Also, 

dermal uptake of organic arsenicals could be of concern, and quantitative data on the rate and extent of 

this would be helpful in evaluating risks from application of arsenical pesticides or exposures to organic 

arsenicals in waste sites. 

Comparative Toxicokinetics. Available toxicity data indicate that arsenic causes many of the same 

effects in animals that are observed in humans, but that animals are significantly less sensitive. The basis 

for this difference in susceptibility is not certain but is probably mainly a result of differences in 

absorption, distribution, metabolism, or excretion. For example, rats strongly retain arsenic in red blood 

cells (Lanz et al. 1950), while humans (and most other species) do not. Similarly, marmoset monkeys do 

not methylate inorganic arsenic (Vahter and Marafante 1985; Vahter et al. 1982), while humans and other 

animal species do. Because of these clear differences in toxicity and toxicokinetics between species, 

further comparative toxicokinetic studies that focus on the mechanistic basis for these differences would 

be very valuable. At a minimum, this would help clarify which laboratory species are the most useful 
ARSENIC 285 

3. HEALTH EFFECTS 

models for humans and could ultimately lead to development of a PBPK model that would permit reliable 

extrapolation of observations across species. 

Methods for Reducing Toxic Effects. There are a number of general methods for reducing the 

absorption of arsenic in the gastrointestinal tract and skin, but there are currently no methods for reducing 

the absorption of arsenic from the lungs. The removal of arsenic from the gastrointestinal tract is usually 

facilitated by the use of emetics, cathartics, lavages, or activated charcoal (Agency for Toxic Substances 

and Disease Registry 1990a; Aposhian and Aposhian 1989; Campbell and Alvarez 1989; Driesback 1980; 

Ellenhorn and Barceloux 1988; EPA 1989e; Haddad and Winchester 1990; Mitra et al. 2004; Stutz and 

Janusz 1988). Studies that investigate the effects of phosphate-binding chemicals (aluminum hydroxide) 

and nonabsorbable sulfhydryl compounds on the absorption of pentavalent and trivalent arsenic, 

respectively, may be useful in developing treatments that are more specific to arsenic intoxication. Once 

arsenic is in the body, treatment usually involves the use of one or more chelators, such as BAL or 

penicillamine. However, these agents often exhibit adverse side effects (Agency for Toxic Substances 

and Disease Registry 1990a; Ellenhorn and Barceloux 1988), and are generally only applied following 

high-dose acute exposure. Further studies investigating the efficacy of less toxic arsenic chelators, such 

as DMSA, DMPA, DMPS, and N-acetyl cysteine, may lead to the development of safer treatment 

methods. Studies on the efficacy of chelators and agents to enhance methylation and elimination in 

treatment of chronic arsenic exposure would also be helpful, as available treatment methods for chronic 

arsenic exposure are limited. Trivalent arsenic is generally believed to exert toxic effects by binding to 

the vicinal sulfhydryl group of key enzymes, thereby interfering with a number of biological processes, 

such as gluconeogenesis and DNA repair (Li and Rossman 1989; Szinicz and Forth 1988). Since 

pentavalent arsenic may need to be reduced in the body to the trivalent state before it can exert toxic 

effects, studies that investigate methods for blocking this conversion may lead to a method for interfering 

with the mechanism of action for pentavalent arsenic. The insufficient intake of calcium, animal protein, 

folate, selenium, and fiber may enhance the toxic effects of inorganic arsenic (Mitra et al. 2004), but it is 

not known if dietary supplementation will prove effective in patients who already show arsenic-induced 

symptoms. 

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. 
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3. HEALTH EFFECTS 

A majority of the data on the effects of exposure of humans to arsenic has focused on adults. Although a 

few studies of acute poisoning and chronic exposure specifically describe children (Borgoño et al. 1980; 

Concha et al. 1998a, 1998b, 1999; Foy et al. 1992; Kersjes et al. 1987; Rosenberg 1974; Zaldívar 1974; 

Zaldívar and Guillier 1977), in general, data are lacking. Specifically, although there is a substantial 

database on the effect of arsenic on animal development, there are few data describing developmental 

effects in humans. Additional research in this area, using populations in areas of endemic arsenic 

exposure, would be useful. 

Although there is no reason to suspect that the pharmacokinetics of arsenic differs in children and adults, 

there are few data available on this topic. Research on absorption, distribution, metabolism, and excretion 

in children would aid in determining if children are at an increased risk, especially in areas where chronic 

exposure to an environmental source occurs. With regard to exposure during development, additional 

research on maternal kinetics, and transfer via breast milk would be useful in obtaining a more complete 

picture of prenatal and neonatal development, especially with regard to neural development and the 

possible development of childhood cancer. 

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 

A number of researchers are continuing to investigate the toxicity and toxicokinetics of arsenic. 

Table 3-18 summarizes studies being sponsored by agencies of the U.S. federal government (FEDRIP 

2007). Additional research is being sponsored by industry groups and other agencies, and research is also 

ongoing in a number of foreign countries. 
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3. HEALTH EFFECTS 

Table 3-18. Ongoing Studies on Health Effects of Arsenic, Federally Funded 

Investigator Affiliation Title Sponsor 

Ahsan, H Columbia University, New Chemoprevention of arsenic-induced skin NCI 

York, New York cancer 

Ahsan, H Columbia University, New Genetic susceptibility to arsenic-induced NCI 

York, New York skin cancer 

Andrew, A Darmouth College, Bladder cancer prognostic indicators NCI 

Hanover, New Hampshire 

Beckman, K Children’s Hospital and Fetal arsenic-nutrient interaction in adult- NIEHS 

Research Center, Oakland, onset cancer 

California 

Bodwell, J Darmouth College, Arsenic effects on glucocorticoid receptor NIEHS 

Hanover, New Hampshire action 

Calderon, R EPA, Research Triangle Arsenic-induced skin conditions identified in HEERL 

Park, North Carolina Southwest United States 

Christiani, D Harvard University, Boston, Arsenic and health in Bangladesh NIEHS 

Massachusetts 

Dong, Z University of Minnesota, Molecular basis of arsenic-induced cell NCI 

Minneapolis, Minnesota transformation 

Finnell, R Texas A & M University Sensitive genotypes to arsenic as a model NIEHS 

College Station, Texas environmental toxicant 

Frenkel, K New York University, New Metal induced inflammatory factors, NIEHS 

York, New York oxidative stress, and suppression 

Futscher, B University of Arizona, Epigenetic remodeling by environmental NCI 

Tucson, Arizona arsenicals 

Gamble, M Columbia University, New Nutritional influences on arsenic toxicity NIEHS 

York, New York 

Germolec, D NIH, Research Triangle The role of growth factors and inflammatory NIEHS 

Park, North Carolina mediators in arsenic-induced 

dermatotoxicity 

Guallar, E Johns Hopkins University, Mercury, arsenic, and carotid NIEHS 

Baltimore, Maryland atherosclerosis 

He, K Northwestern University, Trace elements and CVD risks factors NHLBI 

Chicago, Illinois among young adults 

Hei, T Columbia University, New Mechanisms of arsenic carcinogenesis NIEHS 

York, New York 

Huang, C New York University, New Effects of arsenic on PI-3K signaling NCI 

York, New York pathway 

Hudgens, E EPA, Research Triangle Study of individuals chronically exposed to HEERL 

Park, North Carolina arsenic in drinking water 

Hughes, M EPA, Research Triangle Biomarkers of exposure: a case study with HEERL 

Park, North Carolina inorganic arsenic 

Hughes, M EPA, Research Triangle Tissue dosimetry, metabolism, and HEERL 

Park, North Carolina excretion of pentavalent arsenic 

Jing, Y New York University, New Arsenic trioxide and acute myeloid leukemia NCI 

York, New York 
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3. HEALTH EFFECTS 

Table 3-18. Ongoing Studies on Health Effects of Arsenic, Federally Funded 

Investigator Affiliation Title Sponsor 

Jung, M Georgetown University, Epigenetic regulation by poly(ADP-ribose) NIEHS 

Washington, DC in response to arsenite 

Karin, M University of California San Interaction of heavy metal ions with the NIEHS 

Diego, La Jolla, California human genome 

Kelsey, K Harvard University, Boston, Arsenic mode of action in cancer—models NIEHS 

Massachusetts of epigenetic mechanism 

Liu, K University of New Mexico, Oxidative mechanisms of arsenic-induced NIEHS 

Albuquerque, New Mexico carcinogenesis 

Markowski, V University of Southern Developmental arsenic exposure produces NIEHS 

Maine, Portland, Maine cognitive impairment 

Martin, M Georgetown University, Arsenic and epigenetic regulation of gene NIEHS 

Washington, DC expression 

Muscarella, D Cornell University Ithaca, Arsenite effects on CD40 signaling and B­ NIEHS 

Ithaca, New York cell apoptosis 

Nichols, R Dartmouth College, Effect of arsenic on cytochrome P450 NIEHS 

Hanover, New Hampshire 

Nriagu, J University of Michigan, Ann Arsenic exposure and bladder cancer in NCI 

Harbor, Michigan Michigan 

Rosen, B Wayne State University, Mechanisms of arsenical transport NIGMS 

Detroit, Michigan 

Rosen, B Wayne State University, Metal binding domains in metallo-regulatory NIAID 

Detroit, Michigan proteins 

Rosenblatt, A University of Miami, Coral Environmental arsenic and androgen NIEHS 

Gables, Florida receptor regulation 

Rossman, T New York University, New Investigation and genetic analysis of the NIEHS 

York, New York human arsenite efflux pump 

Schwartz, J Harvard University, Boston Epigenetic effects of particles and metals NIEHS 

Massachusetts on cardiac health of an aging cohort 

Self, W University of Central Impact of arsenicals on selenoprotein NIEHS 

Florida, Orlando, Florida synthesis 

Sens, D University of North Dakota, Metallothionein isoform-3 urinary marker NIEHS 

Grand Forks, North Dakota bladder cancer 

Sheldon, L Dartmouth College, Arsenic, histone modification, and NIEHS 

Hanover, New Hampshire transcription 

Shi, X University of Kentucky, Mechanism of arsenic-induced NCI 

Lexington, Kentucky carcinogenesis 

Smith, A University of California, Arsenic biomarker epidemiology NIEHS 

Berkeley, California 

Spallholz, J Texas Tech University, Selenium against arsenic toxicity and skin NCI 

Lubbock, Texas lesions 

States, C University of Louisville, Arsenic induced miotic arrest associated NIEHS 

Louisville, Kentucky apoptosis 

Styblo, M University of North Metabolism and toxicity of arsenic in human NIEHS 

Carolina, Chapel Hill, North liver 

Carolina 
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3. HEALTH EFFECTS 

Table 3-18. Ongoing Studies on Health Effects of Arsenic, Federally Funded 

Investigator Affiliation Title Sponsor 

Taylor, P Division of Cancer 

Epidemiology and 

Genetics, NCI, Bethesda, 

Biologic specimen bank for early lung 

cancer markers in Chinese tin miners 

NCI 

Maryland 

Taylor, B University of Louisville, 

Louisville, Kentucky 

Arsenite inhibition of mitotic progression NIEHS 

Vaillancourt, R University of Arizona, 

Tucson, Arizona 

Modulation of Prostaglandins by Arsenic NIEHS 

Willett, W Harvard University, Boston, 

Massachusetts 

Prospective studies of diet and cancer in 

men and women 

NCI 

Wright, R Brigham and Women’s 

Hospital, Boston, 

Massachusetts 

Metal mixtures and neurondevelopment NIEHS 

Zhang, D University of Arizona, 

Tucson, Arizona 

The protective role of Nrf2 in arsenicinduced toxicity and carcinogenicity NIEHS 

EPA = Environmental Protection Agency; NHEERL = National Health and Environmental Effects Research 

Laboratory; NCI = National Cancer Institute; NHLBI = National Heart, Lung, and Blood Institute; NIEHS = National 

Institute of Environmental Health Sciences; NIAID= National Institute of Allergy and Infectious Diseases; 

NIGMS = National Institute of General Medical Sciences; NIH = National Institute of Health 

Source: FEDRIP 2007 
ARSENIC 290 

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ARSENIC 291 

4. CHEMICAL AND PHYSICAL INFORMATION 

4.1 CHEMICAL IDENTITY 

Information regarding the chemical identity of arsenic and some common inorganic and organic arsenic 

compounds are located in Tables 4-1 and 4-2, respectively. 

4.2 PHYSICAL AND CHEMICAL PROPERTIES 

Information regarding the physical and chemical properties of arsenic and some common inorganic and 

organic arsenic compounds is located in Tables 4-3 and 4-4, respectively. 

Arsenic appears in Group 15 (V) of the periodic table, below nitrogen and phosphorus. Arsenic is 

classified chemically as a metalloid, having both properties of a metal and a nonmetal; however, it is 

frequently referred to as a metal. Elemental arsenic, which is also referred to as metallic arsenic, (As(0)) 

normally occurs as the α-crystalline metallic form, which is a steel gray and brittle solid. The β-form is a 

dark gray amorphous solid. Other allotropic forms of arsenic may also exist. In compounds, arsenic 

typically exists in one of three oxidation states, -3, +3, and +5 (Carapella 1992). Arsenic compounds can 

be categorized as inorganic, compounds without an arsenic-carbon bond, and organic, compounds with an 

arsenic-carbon bond. 
ARSENIC 292 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-1. Chemical Identity of Arsenic and Selected Inorganic Arsenic 

Compoundsa

Characteristic Arsenic Arsenic acid Arsenic pentoxide Arsenic trioxide 

Synonym(s) Arsenic black; Orthoarsenic acid Arsenic(V) oxide; Arsenic(III) oxide; 

colloidal arsenic; arsenic acid arsenious acid; 

gray arsenic, metallic anhydride; diarsenic arsenious oxide; 

arsenic pentoxide white arsenic 

Registered trade 

name(s) 

No data Zotox; Hi-Yield 

Desiccant H-10; 

Desiccant L-10; 

Crab Grass Killer 

No data White Arsenic; 

Arsenicum Album 

Chemical formula As H3AsO4 As2O5 As2O3 

Chemical structure O 

As HO As OH [As5+]2 [O2-]5 [As3+]2 [O2-]3 

OH 

Identification numbers: 

CAS registry 

NIOSH RTECSb

7440-38-2 

 CG0525000 

7778-39-4 

CG0700000 

1303-28-2 

CG2275000 

1327-53-3 

CG3325000 

EPA hazardous waste D004 D004, P010 D004, P011 D004, P012 

OHM/TADS 

DOT/UN/NA/IMDG 

shipping 

HSDB 

No data 

UN1558/IMDG 6.1 

509 

No data 

UN1553 (liquid)/ 

UN1554 (solid)/ 

IMDG 6.1 (liquid 

and solid) 

431 

No data 

UN1559/IMDG 6.1 

429 

No data 

UN1561/ 

IMDG 6.1 

419 

EINECS 231-148-6 231-901-9 215-116-9 215-481-4 

NCI No data No data No data No data 
ARSENIC 293 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-1. Chemical Identity of Arsenic and Selected Inorganic Arsenic 

Compoundsa

Gallium 

Characteristic Calcium arsenate arsenide Sodium arsenate Sodium arsenite 

Synonym(s) Calcium ortho- Gallium mono- Disodium arsenate, Arsenenous acid, 

arsenate; arsenic arsenide dibasic; disodium sodium salt; 

acid, calcium salt hydrogen arsenate; sodium metaarsenic acid, arsenite 

disodium salt 

Registered trade Pencal; Security; No data No data Atlas "A"; Penite; 

name(s) Turf-Cal; Chip-Cal; Kill-All; ChemSPRA-Cal Sen 56; Chem 

Pels C; 

Progalumnol 

Double 

Chemical formula Ca3(AsO4)2 GaAs Na2HAsO4 NaAsO2 

Chemical structure O 

O 

Ca O As O 2+ 

O 3 

2 

Ga:As Na HO As O + 

O 2 

O 

As O Na+ 

Identification numbers: 

CAS registry 7778-44-1 1303-00-0 7778-43-0 7784-46-5 

NIOSH RTECSb

 CG0830000 LW8800000 CG0875000 CG3675000 

EPA hazardous waste D004 D004 D004 D004 

OHM/TADS No data No data No data 7800057 

DOT/UN/NA/IMDG UN1573/IMDG 6.1 UN 2803; UN 1685/IMDG 6.1 UN1686 

shipping Gallium/ (aqueous 

IMDG 8.0; solution)/UN2027 

Gallium (solid)/IMDG 6.1 

HSDB 1433 4376 1675 693 

EINECS 233-287-8 215-114-8 231-902-4 232-070-5 

NCI No data No data No data No data 

a

All information obtained from HSDB 2007 and CHEMIDplus 2007, except where noted. b

RTECS 2007 

CAS = Chemical Abstracts Service; DOT/UN/NA/IMDG = Department of Transportation/United Nations/North 

America/Intergovernmental Maritime Dangerous Goods Code; EINECS = European Inventory of Existing Chemical 

Substances; EPA = Environmental Protection Agency; HSDB = Hazardous Substances 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 
ARSENIC 294 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-2. Chemical Identity of Selected Organic Arsenic Compoundsa 

Characteristic Arsanilic acid Arsenobetaine Dimethylarsinic acid 

Synonym(s) (4-Aminophenyl)arsonic Arsonium, Cacodylic acid; hydroxydiacid; antoxylic acid; (carboxymethyl)­ methyl-arsine oxide; DMA; 

atoxylic acid, Pro-Gen trimethyl-, hydroxide, DMAA 

inner salt 

Registered trade No data No data 510; Arsan; Phytar 560; 

name(s) Rad-E-Cate 35 

Chemical formula C6H8AsNO3 C5H11AsO2 C2H7AsO2 

Chemical structure O O CH3 O

HO As NH2 + H3C As OH H3C As OH 

CH

O CH3

3 

Identification numbers: 

CAS registry 98-50-0 64436-13-1 75-60-5 

NIOSH RTECSb

 CF7875000 CH9750000 CH7525000 

EPA hazardous waste D004 No data U136/D004 

OHM/TADS No data No data No data 

DOT/UN/NA/IMDG No data No data UN1572/IMDG 6.1 

shipping 

HSDB 432 No data 360 

EINECS 202-674-3 No data 200-883-4 

NCI No data No data No data 
ARSENIC 295 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-2. Chemical Identity of Selected Organic Arsenic Compoundsa 

Disodium methane- 3-Nitro-4-hydroxy-phenylCharacteristic arsonate Methanearsonic acid arsonic acid 

Synonym(s) DSMA; disodium Arsonic acid, methyl-; Roxarsone; 3-nitromonomethane arsonate monomethylarsonic acid 4-hydroxyphenylarsonic acid; 

3-Nitro-10 

Registered trade Ansar 8100; Arrhenal; No data No data 

name(s) Ansar DSMA Liquid; 

Dinate; Crab-E-Rad; 

Chipco Crab Kleen; 

Arsinyl; Sodar; Methar; 

Drexel DSMA Liquid; DiTac; Ansar 184; Weed-ERad; Versar DSMA-LQ; 

Calar-E-Rad; Dal-E-Rad; 

Jon-Trol; Namate 

Chemical formula CH3AsO3Na2 CH5AsO3 C6H6AsNO6 

Chemical structure O O O 

NO2 

H3C As O Na+ H3C As HO As OH + 

O Na OH OH 

OH 

Identification 

numbers: 

CAS registry 144-21-8 124-58-3 121-19-7 

NIOSH RTECSb

 PA2275000 PA1575000 CY5250000 

EPA hazardous D004 D004 D004 

waste 

OHM/TADS No data No data No data 

DOT/UN/NA/IMDG No data No data No data 

shipping 

HSDB 1701 845 4296 

EINECS 205-620-7 204-705-6 204-453-7 

NCI No data No data C5608 
ARSENIC 296 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-2. Chemical Identity of Selected Organic Arsenic Compoundsa 

Sodium 

Characteristic Sodium arsanilate Sodium dimethylarsinate methanearsonate 

Synonym(s) (4-Aminophenyl)arsonic acid Sodium cacodylate; cacodylic Arsonic acid, methyl-, 

sodium salt; arsanilic acid acid, sodium salt; sodium monosodium salt; 

sodium salt; arsamin; atoxyl; dimethylarsonate monosodium acid 

soamin; trypoxyl metharsonate; MSMA 

Registered trade No data Ansar 160; Ansar 560; Bolls- Ansar 529; Ansar 170; 

name(s) Eye; Chemaid; Phytar 560, Target MSMA; Phyban 

component of (with 012501); H.C.; Deconate; 

Rad-E-Cate 25. Mesamate; Bueno; 

Monate Merge 823; 

Dal-E-Rad; Weed-SRad; Arsanote liquid; 

Silvisar 550. 

Chemical formula C6H7AsNO3Na C2H6AsO2Na CH4AsO3Na 

Chemical structure O O O + + 

NH2 

H3C As O Na H O Na 3C As + 

Na O As 

OH CH3 OH 

Identification 

numbers: 

CAS registry 127-85-5 124-65-2 2163-80-6 

NIOSH RTECSb

 CF9625000 CH7700000 PA2625000 

EPA hazardous D004 D004 D004 

waste 

OHM/TADS No data No data No data 

DOT/UN/NA/IMDG UN2473/IMDG 6.1 UN1688/IMDG 6.1 No data 

shipping 

HSDB 5189 731 754 

EINECS 204-869-9 204-708-2 218-495-9 

NCI C61176 No data C60071 

a

All information obtained from HSDB 2007 and CHEMIDplus 2007, except where noted. b

RTECS 2007 

CAS = Chemical Abstracts Service; DOT/UN/NA/IMDG = Dept. of Transportation/United Nations/North 

America/Intergovernmental Maritime Dangerous Goods Code; EINECS = European Inventory of Existing Chemical 

Substances; EPA = Environmental Protection Agency; HSDB = Hazardous Substances 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 
ARSENIC 297 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-3. Physical and Chemical Properties of Arsenic and Selected Inorganic 

Arsenic Compoundsa

Arsenic 

Property Arsenic Arsenic acid pentoxide Arsenic trioxide 

Molecular weight 

Color 

74.9216 

Silver-gray or tinwhite 

141.944 

Whiteb

229.840 

White 

197.841 

White 

Physical state Solid Solidb

 Solid Solid 

Melting point 817 °C (triple point) 35 °C Decomposes at 

~300 °C 

313 °C (claudetite) 

274 °C (arsenolite) 

Boiling point 614 °C sublimes Loses H2O at 

160 °C b 

No data 460 °C 

Density 5.778 g/cm3

 at 

25 °C 

~2.2 g/cm3 4.32 g/cm3 3.865 g/cm3 (cubes) 

4.15 g/cm3

 (rhombic 

crystals) 

Odor Odorless No data No data Odorless 

Odor threshold: 

Water No data No data No data No data 

Air No data No data No data No data 

Solubility: 

Water Insoluble 302 g/L at 12.5 °Cb 2,300 g/L at 20 °C 17 g/L at 16 °C 

 Organic 

solvent(s) 

No data Soluble in alcohol, 

glycerolb 

Soluble in alcohol Practically insoluble in 

alcohol, chloroform, 

ether; soluble in 

glycerol 

Other Insoluble in caustic 

and nonoxidizing 

acids 

No data Soluble in acid, 

alkali 

Soluble in dilute 

hydrochloric acid, 

alkali hydroxide, 

carbonate solution 

Partition 

coefficients: 

 Log Kow No data No data No data No data 

 Log Koc No data No data No data No data 

pKa

Vapor pressure 

 No data 

7.5x10-3 mmHg at 

280 °C 

pKa1=2.22; pKa2=6.98 

pKa3=11.53c No data 

No data No data 

No data 

2.47x10-4 mmHg at 

25 °C 

Autoignition 

temperature 

No data No data No data Not flammable 

Flashpoint No data No data No data No data 

Flammability 

limits in air 

No data No data No data No data 

Conversion No data No data No data No data 

factors 

Explosive limits No data No data No data No data 
ARSENIC 298 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-3. Physical and Chemical Properties of Arsenic and Selected Inorganic 

Arsenic Compoundsa

Disodium 

Property Calcium arsenate Gallium arsenide arsenate Sodium arsenite 

Molecular weight 

Color 

Physical state 

Melting point 

Boiling point 

Density 

398.072 

Colorless 

Solid 

Decomposes on 

heating 

No data 

3.620 g/cm3

144.64 

Dark gray 

Solid 

1,238 °C 

No data 

 5.3176 g/cm3 at 

25 °C 

185.91 

Colorlessd 

Solidd

57 °Cd

No data 

1.87 g/cmd

130.92 

White to gray-white 

Solid 

 No data 

No data 

 1.87 g/cm3 

Odor Odorless Garlic odor Odorlessd

 No data 

Odor threshold: 

Water No data No data No data No data 

Air No data No data No data No data 

Solubility: 

Water 0.13 g/L at 25 °C <1 mg/mL at 20 °C Soluble 1:3 parts 

in waterd 

Freely soluble in water

 Organic 

solvents 

Other 

Partition 

Insoluble 

Soluble in dilute 

acids 

<1 mg/mg dimethyl 

sulfoxide, ethanol, 

methanol, acetone 

Soluble in 

hydrochloric acid 

Slightly soluble in 

alcohol; soluble in 

glycerold 

Slightly soluble in 

alkaline solutiond 

Slightly soluble in 

alcohol 

No data 

coefficients: 

 Log Kow 

 Log Koc 

pKa 

Vapor pressure 

Autoignition 

temperature 

Flashpoint 

Flammability 

limits in air 

No data 

No data 

No data 

~0 mmHg at 20 °C 

Not combustible 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

No data 

Not combustible 

No data 

No data 

Conversion No data No data No data No data 

factors 

Explosive limits No data No data No data No data 

a

All information from HSDB 2007, except where noted. b

Value for arsenic acid hemihydrate c

NRC 1999 d

Value for disodium arsenate heptahydrate 
ARSENIC 299 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-4. Physical and Chemical Properties of Selected Organic Arsenic 

Compoundsa 

Property 

Molecular weight 

Arsenilic acid 

217.06 

Arsenobetaine 

196.1b

Dimethylarsinic acid 

138.00 

Color White No data Colorless 

Physical state Solid Solidb

 Solid 

Melting point 232 °C 203–210 °C 

(decomposes)b 

195 °C 

Boiling point 

Density 1.9571 g/cm3

 at 10 °C 

No data 

No data 

>200 °C 

No data 

Odor Practically odorless No data Odorless 

Odor threshold: 

Water No data No data No data 

Air No data No data No data 

Solubility: 

Water Slightly soluble in cold 

water; soluble in hot water 

No data 2,000 g/L at 25 °C 

Organic solvent(s) Slightly soluble in alcohol; 

soluble in amyl alcohol; 

insoluble in ether, acetone, 

benzene, chloroform 

No data Soluble in alcohol; 

insoluble in diethyl 

ether 

Acids Slightly soluble in acetic 

acid; soluble in alkaki 

carbonates; moderately 

soluble in concentrated 

No data Soluble in acetic acid 

mineral acids; insoluble in 

dilute mineral acids 

Partition coefficients: 

 Log Kow No data No data No data 

 Log Koc 

pKa

No data 

 No data 

No data 

2.2c

No data 

1.57 

Vapor pressure No data No data No data 

Henry's law constant No data No data No data 

Autoignition temperature No data No data No data 

Flashpoint No data No data No data 

Flammability No data No data Nonflammable 

Conversion factors No data No data No data 

Explosive limits No data No data No data 
ARSENIC 300 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-4. Physical and Chemical Properties of Selected Organic Arsenic 

Compoundsa 

3-Nitro-4-hydroxyProperty Methanearsonic acid phenylarsonic acid Sodium arsanilate 

Molecular weight 139.97 263.03 239.04 

Color White Pale yellow White or creamy white 

Physical state Solid Solid Solid 

Melting point 160.5 °C No data No data 

Boiling point No data No data No data 

Density No data No data No data 

Odor No data No data Odorless 

Odor threshold: 

Water No data No data No data 

Air No data No data No data 

Solubility: 

Water 256 g/L at 20 °C Slightly soluble in cold Soluble 1 part in 3 parts 

water; soluble in about water 

30 parts boiling water 

Organic solvents Soluble in ethanol Soluble in methanol, Soluble 1 part in 

ethanol, acetone; 150 parts alcohol; 

insoluble in ether, ethyl practically insoluble in 

acetate chloroform, ether 

Acids No data Soluble in acetic acid, No data 

alkalies; sparingly 

soluble in dilute mineral 

acids 

Partition coefficients: 

 Log Kow No data No data No data 

 Log Koc No data No data No data 

pKa pKa1=4.1; pKa2=9.02 No data No data 

Vapor pressure at 25 °C <7.5x10-8 mmHg No data No data 

Henry's law constant No data No data No data 

Autoignition temperature No data No data No data 

Flashpoint No data No data No data 

Flammability No data No data No data 

Conversion factors No data No data No data 

Explosive limits No data No data No data 
ARSENIC 301 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-4. Physical and Chemical Properties of Selected Organic Arsenic 

Compoundsa 

Disodium Sodium Sodium 

Property methanearsonate dimethylarsinate methanearsonate 

Molecular weight 183.93 159.98 161.95 

Color White Colorless to light yellow White 

Physical state Solid Solid Solid 

Melting point >355 °C 200 °C 130–140 °C 

Boiling point No data No data No data 

Density 1.04 g/cm3

 >1 g/cm3 at 20 °C 1.55 g/mLd 

Odor No data Odorless Odorless 

Odor threshold: 

Water No data No data No data 

Air No data No data No data 

Solubility: 

Water 432 g/L at 25 °C 200 g/L at 25 °C 580 g/L at 20 °C 

Organic solvents Soluble in methanol; No data Insoluble in most 

practically insoluble in most organic solvents 

organic solvents 

Acids No data No data No data 

Partition coefficients: 

 Log Kow <1 No data -3.10 

 Log Koc No data No data No data 

pKa pKa1=4.1; pKa2=8.94 6.29 pKa1=4.1; pKa2=9.02 

Vapor pressure at 25 °C 10-7 mmHg No data 7.8x10-8 mmHg 

Henry's law constant No data No data No data 

Autoignition temperature No data No data No data 

Flashpoint No data No data No data 

Flammability Nonflammable No data Nonflammable 

Conversion factors No data No data No data 

Explosive limits No data No data No data 

a

All information from HSDB 2007, except where noted. b

Cannon et al. 1981 (arsenobetaine as monohydrate) c

Teräsahde et al. 1996 d

Value for Ansar 6.6 
ARSENIC 302 

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ARSENIC 303 

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

5.1 PRODUCTION 

Arsenic is presently obtained as a byproduct of the smelting of copper, lead, cobalt, and gold ores. 

Arsenic trioxide is volatilized during smelting and accumulates in the flue dust, which may contain up to 

30% arsenic trioxide. The crude flue dust is further refined by mixing with small amounts of galena or 

pyrite to prevent the formation of arsensites and roasting to yield arsenic trioxide of 90–95% purity. By 

successive sublimations, a purity of 99% can be obtained. Elemental arsenic can be prepared by the 

reduction of arsenic oxide with charcoal. Demand for elemental arsenic is limited and thus, about 95% of 

arsenic is marketed and consumed in combined form, principally as arsenic trioxide, which is 

subsequently converted to arsenic acid (Carapella 1992; Hanusch et al. 1985; USGS 2006a). 

Since 1985, when the ASARCO smelter in Tacoma, Washington ceased operation, there has been no 

domestic production of arsenic trioxide or elemental arsenic and consequently, the United States remains 

entirely dependent on imports (U.S. Bureau of Mines 1988, 1990; USGS 2006a). Prior to its cessation, 

U.S. production of arsenic trioxide had been 7,300 metric tons in 1983, 6,800 metric tons in 1984, and 

2,200 metric tons in 1985 (U.S. Bureau of Mines 1988). In 2005, arsenic trioxide was obtained from the 

treatment of nonferrous ores or concentrates in 14 countries. In 2005, the world’s largest producer of 

arsenic trioxide was China, followed by Chile and Peru. China is the world leader in the production of 

commercial-grade arsenic followed by Japan. The United States, with an apparent demand of 

8,800 metric tons in 2005, is the world's leading consumer of arsenic, mainly for CCA. This is an 

increase over 2004 with an apparent demand of 6,800 metric tons, but far less than that of 2003, 

21,600 metric tons (USGS 2006a). 

Tables 5-1 and 5-2 list facilities in each state that manufacture or process arsenic and arsenic compounds, 

respectively, as well as the intended use and the range of maximum amounts of arsenic or arsenic 

compounds that are stored on site. In 2004, there were 58 and 361 reporting facilities that produced, 

processed, or used arsenic and arsenic compounds, respectively, in the United States. The data listed in 

Tables 5-1 and 5-2 are derived from the Toxics Release Inventory (TRI04 2006). Only certain types of 

facilities were required to report. Therefore, this is not an exhaustive list. Current U.S. manufacturers of 

selected arsenic compounds are given in Table 5-3. 
ARSENIC 304 

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

Table 5-1. Facilities that Produce, Process, or Use Arsenic 

Minimum Maximum 

Number of amount on site amount on site 

Statea facilities in poundsb in poundsb Activities and usesc 

AK 1 1,000,000 9,999,999 1, 13 

AL 18 0 9,999,999 1, 2, 3, 5, 7, 8, 11, 12, 13, 14 

AR 4 1,000 999,999 7, 8 

AZ 9 0 99,999 1, 3, 4, 5, 8, 12, 13 

CA 31 0 9,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13 

CO 8 0 999,999 2, 7, 8, 11, 12 

FL 10 1,000 999,999 1, 3, 5, 7, 8, 11, 12 

GA 16 100 49,999,999 2, 3, 4, 6, 7, 8, 11, 12, 13, 14 

HI 1 10,000 99,999 8 

IA 4 100 99,999 6, 7, 8 

ID 7 0 49,999,999 1, 2, 3, 5, 6, 7, 9, 12, 13 

IL 16 0 999,999 1, 3, 4, 5, 6, 7, 8, 12, 14 

IN 17 0 999,999 1, 3, 5, 6, 7, 8, 9, 12, 13 

KY 9 0 999,999 1, 2, 3, 5, 6, 7, 8, 11 

LA 8 0 999,999 1, 2, 3, 7, 8, 12, 13 

MA 5 1,000 999,999 3, 7, 8 

MD 9 0 999,999 1, 2, 4, 5, 6, 7, 8 

MI 10 0 999,999 3, 7, 8, 12, 13 

MN 5 100 99,999 1, 7, 8, 13 

MO 6 100 999,999 1, 2, 3, 4, 5, 6, 7, 8 

MS 9 1,000 49,999,999 2, 3, 4, 7, 8, 9 

NC 21 0 49,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 13, 14 

ND 2 0 99,999 8 

NE 1 0 99 8 

NJ 9 0 99,999 1, 2, 3, 5, 7, 8, 9 

NM 2 10,000 999,999 7, 12 

NV 6 1,000 99,999,999 1, 2, 4, 5, 6, 7, 8, 11, 12, 13 

NY 4 0 99,999 7, 8, 12 

OH 15 0 999,999 1, 2, 3, 4, 5, 8, 9, 12, 13 

OK 9 0 99,999 1, 2, 5, 6, 7, 9, 11, 12, 13 

OR 6 10,000 999,999 1, 5, 7, 8, 12 

PA 24 0 999,999 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13 

PR 3 1,000 99,999 8, 11 

SC 9 0 9,999,999 1, 2, 3, 5, 6, 8, 12 

SD 1 10,000,000 49,999,999 1, 7, 11, 13 

TN 11 0 999,999 1, 2, 3, 6, 7, 8, 11, 12, 14 

TX 29 0 49,999,999 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14 

VA 8 0 999,999 2, 3, 7, 8, 10 
ARSENIC 305 

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

Table 5-1. Facilities that Produce, Process, or Use Arsenic 

Minimum Maximum 

Number of amount on site amount on site 

Statea facilities in poundsb in poundsb Activities and usesc 

WA 3 0 99,999 5, 7, 8 

WI 9 0 99,999 1, 2, 3, 4, 5, 6, 7, 8, 12 

WV 19 100 999,999 1, 2, 3, 5, 7, 8, 10, 11, 12 

WY 1 100 999 1, 13 

a

Post office state abbreviations used b

Amounts on site reported by facilities in each state c

Activities/Uses: 

1. Produce 

2. Import 

3. Onsite use/processing 

4. Sale/Distribution 

5. Byproduct 

6. Impurity 

7. Reactant 

8. Formulation Component 

9. Article Component 

10. Repackaging 

11. Chemical Processing Aid 

12. Manufacturing Aid 

13. Ancillary/Other Uses 

14. Process Impurity 

Source: TRI04 2006 (Data are from 2004) 
ARSENIC 306 

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

Table 5-2. Facilities that Produce, Process, or Use Arsenic Compounds 

Minimum Maximum 

Number of amount on site amount on site 

Statea facilities in poundsb in poundsb Activities and usesc 

AK 6 1,000 49,999,999 1, 5, 7, 12, 13, 14 

AL 37 0 499,999,999 1, 2, 3, 4, 5, 7, 8, 9, 11, 12, 13 

AR 20 1,000 99,999,999 1, 2, 3, 7, 8, 9, 11, 12, 13, 14 

AZ 29 100 499,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 

CA 40 100 99,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14 

CO 9 1,000 49,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12 

DE 1 10,000 99,999 1, 5, 9 

FL 30 0 999,999 1, 3, 4, 5, 7, 8, 9, 11, 12, 13, 14 

GA 50 0 49,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14 

HI 6 1,000 99,999 7, 8, 11 

IA 22 0 9,999,999 1, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13 

ID 6 10,000 9,999,999 1, 3, 5, 6, 7, 8, 9, 12, 13 

IL 44 0 999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 

IN 54 0 9,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14 

KS 14 0 999,999 1, 3, 4, 5, 6, 7, 8, 12, 13, 14 

KY 29 0 999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 

LA 32 0 499,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13 

MA 9 0 999,999 1, 4, 5, 6, 7, 8 

MD 19 0 999,999 1, 4, 5, 7, 8, 9, 11, 12, 13 

ME 2 1,000 99,999 7 

MI 32 0 999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14 

MN 13 0 999,999 1, 3, 4, 5, 7, 8, 9, 11, 12, 13 

MO 32 0 499,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14 

MS 28 1,000 49,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13 

MT 8 1,000 10,000,000,000 1, 2, 3, 4, 5, 6, 7, 12, 13, 14 

NC 65 0 9,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 

ND 11 1,000 99,999 1, 5, 8, 9, 11, 12, 13, 14 

NE 6 1,000 999,999 1, 2, 3, 4, 5, 6, 8, 9, 12, 13 

NH 2 1,000 99,999 8, 11 

NJ 35 0 999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 13 

NM 11 1,000 499,999,999 1, 5, 7, 12, 13 

NV 31 1,000 10,000,000,000 1, 2, 3, 5, 6, 7, 9, 11, 12, 13, 14 

NY 27 0 9,999,999 1, 2, 3, 4, 5, 7, 8, 9, 12, 13 

OH 50 0 999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14 

OK 14 100 9,999,999 1, 2, 3, 4, 5, 6, 8, 12, 13, 14 

OR 12 100 99,999 1, 2, 3, 7, 8, 12 

PA 53 0 999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14 

PR 8 1,000 99,999 1, 2, 3, 5, 8, 11 

RI 7 100 99,999 7, 8 
ARSENIC 307 

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

Table 5-2. Facilities that Produce, Process, or Use Arsenic Compounds 

Minimum Maximum 

Number of amount on site amount on site 

Statea facilities in poundsb in poundsb Activities and usesc 

SC 34 0 49,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14 

SD 6 1,000 99,999,999 1, 5, 6, 7, 8, 11, 12, 13 

TN 29 0 99,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 

TX 54 0 499,999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14 

UT 23 0 499,999,999 1, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13 

VA 24 0 499,999,999 1, 2, 3, 4, 5, 7, 8, 9, 11, 12, 13, 14 

WA 14 0 999,999 1, 2, 3, 4, 5, 7, 8, 9, 11, 12, 13 

WI 13 100 99,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 11 

WV 26 0 999,999 1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 13, 14 

WY 9 1,000 99,999 1, 3, 4, 5, 7, 8, 9, 12, 13 

a

Post office state abbreviations used b

Amounts on site reported by facilities in each state c

Activities/Uses: 

1. Produce 

2. Import 

3. Onsite use/processing 

4. Sale/Distribution 

5. Byproduct 

6. Impurity 

7. Reactant 

8. Formulation Component 

9. Article Component 

10. Repackaging 

11. Chemical Processing Aid 

12. Manufacturing Aid 

13. Ancillary/Other Uses 

14. Process Impurity 

Source: TRI04 2006 (Data are from 2004) 
ARSENIC 308 

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

Table 5-3. Current U.S. Manufacturers of Selected Arsenic Compoundsa 

Company Location(s) 

Arsenic acid 

Arch Wood Protection, Inc. Conley, Georgia 

Osmose Wood Preserving, Inc. Millington, Tennessee 

Arsanilic acid 

Fleming Laboratories, Inc. Charlotte, North Carolina 

Copper Chromated Arsenic (CCA) 

Arch Wood Protection, Inc. Conley, Georgia; Kalama, Washington; Smyrna, Georgiab

; 

Valparaiso, Indiana 

Chemical Specialties, Inc.b Charlotte, North Carolina 

Osmose Wood Preserving, Inc.b

 Buffalo, New York 

Calcium acid methanearsonate (CAMA) 

Drexel Chemical Company (formulator)c No information provided 

Disodium methanearsonate (DSMA) 

Drexel Chemical Company Tunica, Mississippi 

Monosodium methyl arsonate (MSMA) 

Drexel Chemical Company Tunica, Mississippi 

Gallium arsenide 

Atomergic Chemetals Corporation Farmingdale, New York 

a

Derived from Stanford Research Institute (SRI 2006), except where otherwise noted. SRI reports production of 

chemicals produced in commercial quantities (defined as exceeding 5,000 pounds or $10,000 in value annually) by 

the companies listed. b

USGS 2006a 

c

Meister et al. 2006 
ARSENIC 309 

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

5.2 IMPORT/EXPORT 

Since U.S. production ceased in 1985, all arsenic consumed in the United States is imported. Imports of 

arsenic (metal and compounds combined) have increased substantially since the mid-1980s, reaching 

8,810 metric tons (as arsenic content) in 2005, of which 812 metric tons was as elemental arsenic. In 

2005, 11,000 metric tons of arsenic trioxide was imported into the United States. China is the major 

import source for elemental arsenic from 2001 to 2004, supplying 81%, followed by Japan (15%) and 

Hong Kong (2%). China is also the major import source in 2001–2004 for arsenic trioxide, supplying 

59% to the United States, followed by Morocco (22%), Chile (7%), and Mexico (5%) (USGS 2006a, 

2006b). 

U.S. exports of elemental arsenic were 220 metric tons in 2004 and are estimated to be 200 metric tons in 

2005 (USGS 2006b). In 2005, U.S. import of arsenic was approximately 8.1x105

 kilograms (810 metric 

tons) (ITA 2007a, 2007b). 

5.3 USE 

In 2003, the United States was the world's largest consumer of arsenic, with an apparent demand of 

21,600 metric tons. In 2005, the Unites States was still the world’s largest consumer of arsenic, mainly 

for CCA. Production of wood preservatives, primarily CCA, CrO3•CuO•As2O5, accounted for >90% of 

domestic consumption of arsenic trioxide prior to 2004. In 2005, about 65% of domestic consumption of 

arsenic trioxide was used for the production of CCA. The remainder was used for the production of 

agricultural chemicals, including herbicides, and insecticides. The major U.S. producers of CCA in 

2005 included Arch Wood Protection, Inc., Smyrna Georgia; Chemical Specialties Inc., Charlotte, North 

Carolina; and Osmose Wood Preserving, Inc., Buffalo, New York (USGS 2006a). CCA is the most 

widely used wood preservative in the world. Wood treated with CCA is referred to as ‘pressure treated’ 

wood (American Wood Preservers Association 2007; Page and Loar 1993). In 1997, approximately 

727.8 million cubic feet (20.6 million cubic meters) of wood products were pressure treated in the United 

States. CCA is a water-based product that protects several commercially available species of western 

lumber from decay and insect attack. It is widely used in treating utility poles, building lumber, and wood 

foundations. CCA comes in three types, A, B, and C, which contain different proportions of chromium, 

copper, and arsenic oxides. Type C, the most popular type, contains CrO3, CuO, and As2O5 in the 

proportions 47.5, 18.5, and 34.0%, respectively. The retention levels are 0.25 pounds per cubic feet (pcf) 

for above ground use such as fencing and decking, 0.40 pcf for lumber used in ground contact such as 
ARSENIC 310 

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

fence posts and deck posts, and 0.60 pcf for all weather wood foundations (Chicago Flameproof 2000; 

Permapost 2000). Piling used for fresh and saltwater contact should contain 0.80 and 2.5 pcf of CCA, 

respectively. Ammoniacal copper zinc arsenate (ACZA) is another arsenic containing preservative used 

to treat wood; however, it is not as widely used as CCA–C (Lebow et al. 2000). 

In 2003, U.S. manufacturers of arsenical wood preservatives began a voluntary transition from CCA to 

other wood preservatives in wood products for certain residential uses, such as play structures, picnic 

tables, decks, fencing, and boardwalks. This phase out was completed on December 31, 2003; wood 

treated prior to this date could still be used and structures made with CCA-treated wood would not be 

affected. CCA-treated wood products continue to be used in industrial applications (EPA 2003a). 

Elemental arsenic is used as an alloying element in ammunition and solders, as an anti-friction additive to 

metals used for bearings, and to strengthen lead-acid storage battery grids. In the past, the predominant 

use of arsenic was in agriculture. The uses of lead arsenate as a growth regulator on citrus, calcium 

arsenate as an herbicide on turf, sodium arsenite as a fungicide on grapes, and arsenic acid as a desiccant 

on okra for seed and cotton were voluntarily cancelled in the late 1980s and the early 1990s (EPA 2006). 

The herbicides, MSMA and DSMA, are registered for weed control on cotton, for turf grass and lawns, 

and under trees, vines, and shrubs; calcium acid methanearsonate (CAMA) is registered for postemergent 

weed control on lawns. Cacodylic acid, a defoliant and herbicide, is registered for weed control under 

nonbearing citrus trees, around buildings and sidewalks, and for lawn renovation (EPA 2006). 

Approximately 3 million pounds of MSMA or DSMA, and 100,000 pounds of cacodylic acid are applied 

in the U.S. annually based on EPA’s Screening Level Use Analysis data. Data were not available for 

CAMA. Application to cotton and turf (residential and golf courses) are the major uses of organic 

arsenical herbicides. Currently, there are approximately 90, 25, 4, and 35 end-use products containing 

MSMA, DSMA, CAMA, and cacodylic acid, respectively (EPA 2006). 

Other organic arsenicals used in agriculture include arsanilic acid, sodium arsanilate, and 3-nitro4-hydroxyphenylarsonic acid (roxarsone), which are antimicrobials used in animal and poultry feeds 

(Beerman 1994). While the U.S. Food and Drug Administration (FDA) has authorized the used of these 

compounds as medicinal feed additives, only one of the arsenical compounds may be used at a time as the 

sole source of organic arsenic in the feed (EPA 1998k). In 1999–2000, about 70% of the broiler industry 

added roxarsone to broiler poultry feed; concentrations of roxarsone in feed range from 22.7 to 45.4 g/ton 

(Garbarino et al. 2003). 
ARSENIC 311 

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

From the mid-nineteenth century to the introduction of organic pesticides in the 1940s, inorganic arsenic 

compounds were the dominant pesticides available to farmers and fruit growers. Calcium arsenate was 

formerly used to control the boll weevil and cotton worm and was used as an herbicide. Lead arsenate 

was used on apple and other fruit orchards as well as on potato fields. Sodium arsenite was used to 

control weeds on railroad right-of-ways, potato fields, and in industrial areas, as well as in baits and to 

debark trees. Sodium arsenate had some application in ant traps. The use of inorganic arsenic 

compounds in agriculture has virtually disappeared beginning around the 1960s (Azcue and Nriagu 1994; 

Meister 1987; Merwin et al. 1994; Sanok et al. 1995). Food uses were voluntarily cancelled in 1993 as 

was the use of arsenic acid as a defoliant on cotton plants; inorganic arsenic’s remaining allowable uses 

are in ant baits and wood preservatives (EPA 1999h). In 1987, EPA issued a preliminary decision to 

cancel the registration of most inorganic arsenicals used as nonwood pesticides (Loebenstein 1994) (see 

Chapter 8). According to the California Department of Pesticide Regulation, arsenic acid, arsenic 

pentoxide, and arsenic trioxide are registered currently as pesticides in the United States; there are no 

active registrants listed for calcium arsenate, lead arsenate, or sodium arsenite (NPIRS 2007). 

High-purity arsenic (99.9999%) is used by the electronics industry for gallium-arsenide semiconductors 

for telecommunications, solar cells, and space research (USGS 2006b). Arsenic trioxide and arsenic acid 

were used as a decolorizer and fining agent in the production of bottle glass and other glassware 

(Carapella 1992). 

Arsenic compounds have a long history of use in medicine. Inorganic arsenic was used as a therapeutic 

agent through the mid-twentieth century, primarily for the treatment of leukemia, psoriasis, and chronic 

bronchial asthma; organic arsenic antibiotics were extensively used in the treatment of spirochetal and 

protozoal disease (NRC 1999). The availability of inorganic arsenicals in Western medicines ended in the 

1970s, although they may still be encountered in non-Western traditional medicines. By the 1980s, the 

only remaining medicinal organic arsenical was melarsoprol for treatment of the meningoencephalitic 

stage of African trypanosomiasis. There has been renewed interest in arsenic as a therapeutic agent, 

namely the use of arsenic trioxide in the treatment of acute promyelocytic leukemia (APL) (Gallagher 

1998; Kroemer and de Thé 1999; Miller 1998; Wang 2001). In 2000, the FDA approved arsenic trioxide 

for this use (FDA 2000). 
ARSENIC 312 

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

5.4 DISPOSAL 

Wastes containing arsenic are considered hazardous wastes, and as such, their treatment, storage, and 

disposal are regulated by law (see Chapter 8). The main route of disposal of solid wastes containing 

arsenic is landfilling. EPA has promulgated rules and treatment standards for landfilling liquid arsenical 

wastes (EPA 1990e). Arsenic-containing electronic components such as relays, switches, and circuit 

boards are disposed of at hazardous waste sites, and the elemental arsenic is not reclaimed. Process water 

at wood treatment plants that contained arsenic contained was reused. Gallium-arsenide scrap from the 

manufacture of semiconductor devices was reprocessed for arsenic recovery. Arsenic was not recovered 

from arsenical residues and dusts at domestic nonferrous smelters (USGS 2006b). 

CCA-treated wood is classified as nonhazardous waste under the Federal Resource Conservation and 

Recovery Act (RCRA). CCA-treated wood is disposed of with regular municipal trash (i.e., municipal 

solid waste, not yard waste). It should not be burned in open fires, stoves, residential boilers, or fire 

places and should not be composted or used as mulch. Treated wood from commercial or industrial 

applications may only be burned in commercial or industrial incinerators in accordance with state and 

federal regulations (Adobe Lumber 2002; EPA 2005a). 

Arsenic is listed as a toxic substance under Section 313 of the Emergency Planning and Community Right 

to Know Act (EPCRA) under Title III of the Superfund Amendments and Reauthorization Act (SARA) 

(EPA 1995c). Disposal of wastes containing arsenic is controlled by a number of federal regulations (see 

Chapter 8). 
ARSENIC 313 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.1 OVERVIEW 

Arsenic has been identified in at least 1,149 of the 1,684 hazardous waste sites that have been proposed 

for inclusion on the EPA National Priorities List (NPL) (HazDat 2006). However, the number of sites 

evaluated for arsenic is not known. The frequency of these sites can be seen in Figure 6-1. Of these sites, 

1,134 are located within the United States and 11, 2, and 2 are located in the Commonwealth of Puerto 

Rico, the Virgin Islands, and Guam (not shown). 

Arsenic is widely distributed in the Earth's crust, which contains about 3.4 ppm arsenic (Wedepohl 1991). 

It is mostly found in nature in minerals, such as realgar (As4S4), orpiment (As2S3), and arsenolite (As2O3), 

and only found in its elemental form to a small extent. There are over 150 arsenic-bearing minerals 

(Budavari et al. 2001; Carapella 1992). While arsenic is released to the environment from natural sources 

such as wind-blown soil and volcanoes, releases from anthropogenic sources far exceed those from 

natural sources. Anthropogenic sources of arsenic include nonferrous metal mining and smelting, 

pesticide application, coal combustion, wood combustion, and waste incineration. Most anthropogenic 

releases of arsenic are to land or soil, primarily in the form of pesticides or solid wastes. However, 

substantial amounts are also released to air and water. 

Arsenic found in soil either naturally occurring or from anthropogenic releases forms insoluble complexes 

with iron, aluminum, and magnesium oxides found in soil surfaces, and in this form, arsenic is relatively 

immobile. However, under reducing conditions, arsenic can be released from the solid phase, resulting in 

soluble mobile forms of arsenic, which may potentially leach into groundwater or result in runoff of 

arsenic into surface waters. In aquatic systems, inorganic arsenic occurs primarily in two oxidation states, 

As(V) and As(III). Both forms generally co-exist, although As(V) predominates under oxidizing 

conditions and As(III) predominates under reducing conditions. Arsenic may undergo a variety of 

reactions in the environment, including oxidation-reduction reactions, ligand exchange, precipitation, and 

biotransformation (EPA 1979, 1984a; Pongratz 1998; Welch et al. 1988). These reactions are influenced 

by Eh (the oxidation-reduction potential), pH, metal sulfide and sulfide ion concentrations, iron 

concentration, temperature, salinity, and distribution and composition of the biota (EPA 1979; Wakao et 

al. 1988). Much of the arsenic will adsorb to particulate matter and sediment. Arsenic released to air 

exists mainly in the form of particulate matter. Arsenic released from combustion processes will 

ARSENIC 315 

6. POTENTIAL FOR HUMAN EXPOSURE 

generally occur as highly soluble oxides. These particles are dispersed by the wind and returned to the 

earth in wet or dry deposition. Arsines that are released to the atmosphere as a result of microbial action 

are oxidized to nonvolatile species that settle back to the ground. 

Because arsenic is a natural component of the Earth's crust, low levels of the element are found in all 

environmental media. Atmospheric levels of arsenic in remote locations (away from human releases) 

range from 1 to 3 ng/m3

, while concentrations in urban areas may range from 20 to 100 ng/m3. 

Concentrations in water are usually <10 μg/L, although higher levels may occur near natural mineral 

deposits or anthropogenic sources. Natural levels of arsenic in soil usually range from 1 to 40 mg/kg, 

with a mean of 5 mg/kg, although much higher levels may occur in mining areas, at waste sites, near high 

geological deposits of arsenic-rich minerals, or from pesticide application. Arsenic is also found in many 

foods, at concentrations that usually range from 20 to 140 μg/kg. Total arsenic concentrations may be 

substantially higher in certain seafoods. However, the general consensus in the literature is that about 85– 

>90% of the arsenic in the edible parts of marine fish and shellfish is organic arsenic (e.g., arsenobetaine, 

arsenochloline, dimethylarsinic acid) and that approximately 10% is inorganic arsenic (EPA 2003b). 

Drinking water in the United States generally contains an average of 2 μg/L of arsenic (EPA 1982c), 

although 12% of water supplies from surface water sources in the north Central region of the United 

States and 12% of supplies from groundwater sources in the western region have levels exceeding 

20 μg/L (Karagas et al. 1998). In January 2001, EPA adopted a new standard that arsenic levels in 

drinking water were not to exceed 10 μg/L, replacing the previous standard of 50 μg/L. The date for 

compliance with the new MCL was January 23, 2006 (EPA 2001). 

For most people, diet is the largest source of exposure to arsenic. Mean dietary intakes of total arsenic of 

50.6 μg/day (range of 1.01–1,081 μg/day) and 58.5 μg/day (range of 0.21–1,276 μg/day) has been 

reported for females and males (MacIntosh et al. 1997). U.S. dietary intake of inorganic arsenic has been 

estimated to range from 1 to 20 μg/day, with grains and produce expected to be significant contributors to 

dietary inorganic arsenic intake (Schoof et al. 1999a, 1999b). The predominant dietary source of arsenic 

is generally seafood. Inorganic arsenic in seafood sampled in a market basket survey of inorganic arsenic 

in food ranged from <0.001 to 0.002 μg/g (Schoof et al. 1999a, 1999b). Intake of arsenic from air and 

soil are usually much smaller than that from food and water (Meacher et al. 2002). 

People who produce or use arsenic compounds in occupations such as nonferrous metal smelting, 

pesticide manufacturing or application, wood preservation, semiconductor manufacturing, or glass 

production may be exposed to substantially higher levels of arsenic, mainly from dusts or aerosols in air. 
ARSENIC 316 

6. POTENTIAL FOR HUMAN EXPOSURE 

Exposure at waste sites may occur by a variety of pathways, including inhalation of dusts in air, ingestion 

of contaminated soil or water, or through the food chain. The magnitude of the exposures can only be 

evaluated on a site-by-site basis; however, exposures generally do not exceed background intakes from 

food and drinking water. 

Tables 4-1, 4-2, 4-3, and 4-4 summarize all of the names, abbreviations, and structures of the various 

arsenic compounds that are discussed in Chapter 6. 

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 2005k). 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 2005k). 

6.2.1 Air 

Estimated releases of 4,800 pounds (~2.2 metric tons) of arsenic to the atmosphere from 58 domestic 

manufacturing and processing facilities in 2004, accounted for about 0.52% of the estimated total 

environmental releases from facilities required to report to the TRI (TRI04 2006). Estimated releases of 

0.13 million pounds (~59 metric tons) of arsenic compounds to the atmosphere from 361 domestic 

manufacturing and processing facilities in 2004, accounted for about 0.11% of the estimated total 

environmental releases from facilities required to report to the TRI (TRI04 2006). These releases for 

arsenic and arsenic compounds are summarized in Table 6-1 and 6-2, respectively. 
ARSENIC 317 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-1. Releases to the Environment from Facilities that Produce, Process, or 

Use Arsenica

Reported amounts released in pounds per yearb 

Total release 

Statec RFd Aire Water

f

 UIg Landh Otheri On-sitej

 Off-sitek 

On- and 

off-site 

AL 1 51 162 0 110,264 0 110,425 52 110,477 

AR 2 0 0 No data 0 0 No data 0 0 

AZ 2 10 0 0 20,717 0 20,727 0 20,727 

CA 3 13 14 0 5,482 0 13 5,497 5,510 

FL 2 4 0 0 0 4,950 4 4,950 4,954 

GA 4 8 10 0 1,603 5 13 1,613 1,626 

IA 1 0 1 0 0 0 0 1 1 

ID 1 39 0 0 361,252 0 361,291 0 361,291 

IL 2 250 129 0 14,087 0 379 14,087 14,466 

IN 1 5 5 0 13,250 250 5 13,505 13,510 

KS 1 0 0 No data 0 0 No data 0 0 

KY 1 0 1 0 0 6 1 6 7 

MI 2 0 5 0 0 750 5 750 755 

MN 1 15 47 0 14,504 0 15 14,551 14,566 

MO 1 5 0 0 0 4,040 5 4,040 4,045 

MS 2 0 0 0 0 0 0 0 0 

NC 4 35 8 0 1 1 43 2 45 

NV 1 0 0 0 0 0 0 0 0 

NY 4 0 1 0 26,525 1 26,401 126 26,527 

OH 2 13 0 0 0 0 13 0 13 

OR 1 0 0 0 92,606 0 92,606 0 92,606 

PA 5 166 8 0 14,362 26,140 199 40,477 40,676 

SC 3 10 10 0 0 1,002 15 1,007 1,022 

TN 3 3,988 0 0 0 0 3,988 0 3,988 

TX 5 139 376 168,563 12,600 0 181,636 42 181,678 
ARSENIC 318 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-1. Releases to the Environment from Facilities that Produce, Process, or 

Use Arsenica

Reported amounts released in pounds per yearb 

Total release 

Statec RFd Aire Water

f

 UIg Landh Otheri On-sitej

 Off-sitek 

On- and 

off-site 

WI 2 15 0 0 760 0 15 760 776 

WV 1 0 0 0 10,135 0 10,135 0 10,135 

Total 58 4,766 778 168,563 698,149 37,145 807,935 101,466 909,401 

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: TRI04 2006 (Data are from 2004) 
ARSENIC 319 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-2. Releases to the Environment from Facilities that Produce, Process, or 

Use Arsenic Compoundsa

Reported amounts released in pounds per yearb 

Total release 

Statec RFd Aire Water

f

 UIg Landh Otheri On-sitej

 Off-sitek 

On- and offsite 

AK 1 511 0 1,400,000 1,200,000 0 2,600,511 0 2,600,511 

AL 19 4,299 18,127 0 853,469 7,555 875,876 7,574 883,450 

AR 12 0 0 0 133 26,435 0 26,568 26,568 

AZ 5 5,421 0 0 402,335 422 394,749 13,429 408,178 

CA 5 65 14 0 355,660 86,396 160,673 281,461 442,134 

CO 1 11 0 0 4,094 0 4,105 0 4,105 

CT 1 0 0 0 0 0 No data 0 0 

FL 15 3,208 503 0 343,508 4,057 346,310 4,966 351,276 

GA 23 8,643 7,823 0 422,124 5,127 437,496 6,221 443,717 

HI 1 0 0 0 0 0 No data 0 0 

IA 4 1,291 482 0 0 35,324 1,773 35,324 37,097 

ID 3 332 20 0 1,056,904 0 1,057,256 0 1,057,256 

IL 11 3,960 3,110 0 96,093 21,038 71,819 52,382 124,202 

IN 21 13,786 8,282 0 768,297 42,808 632,704 200,470 833,174 

KS 4 924 0 0 12,082 1 13,006 1 13,007 

KY 18 14,406 8,427 0 616,074 95,285 578,080 156,112 734,192 

LA 7 265 23 0 25,426 0 25,563 151 25,714 

MA 1 0 0 0 0 500 0 500 500 

MD 8 1,870 291 0 34,130 114,115 2,661 147,745 150,406 

MI 10 1,123 2,310 68,924 101,857 1,059 77,505 97,769 175,274 

MN 2 10 130 0 19,270 0 19,410 0 19,410 

MO 6 462 116 0 27,855 936 10,026 19,343 29,369 

MS 6 61 121 0 11,676 46 11,228 676 11,904 

MT 3 630 0 0 2,138,190 37 2,138,820 37 2,138,857 

NC 15 5,626 4,732 0 168,030 2,429 178,388 2,429 180,818 

ND 6 6,326 5 0 318,175 0 137,961 186,545 324,506 

NE 2 180 0 0 11,000 0 11,180 0 11,180 

NJ 2 0 1 0 0 8 0 9 9 

NM 2 130 0 0 18,326 0 18,456 0 18,456 

NV 10 3,041 30,017 0 98,894,564 0 98,927,328 294 98,927,622 

NY 3 67 36 0 27,059 802 27,141 823 27,964 

OH 17 8,595 8,352 81,024 741,730 274 668,157 171,818 839,975 

OK 4 115 13 0 25,000 4,202 115 29,215 29,330 

OR 4 0 5 0 0 4,012 5 4,012 4,017 

PA 23 18,963 2,166 0 666,753 69,053 403,582 353,353 756,935 

PR 3 0 0 0 0 0 No data 0 0 

RI 1 0 8 0 0 1,006 8 1,006 1,014 
ARSENIC 320 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-2. Releases to the Environment from Facilities that Produce, Process, or 

Use Arsenic Compoundsa

Reported amounts released in pounds per yearb 

Total release 

Statec RFd Aire Water

f

 UIg Landh Otheri On-sitej

 Off-sitek 

On- and offsite 

SC 13 2,178 1,443 0 25,817 22,705 29,438 22,705 52,143 

SD 1 0 0 0 0 0 No data 0 0 

TN 13 3,379 25,878 0 292,914 17,219 258,643 80,746 339,389 

TX 17 4,616 199 33,148 196,385 31,557 226,751 39,155 265,906 

UT 5 6,715 4,500 0 6,368,500 3,500 6,379,715 3,500 6,383,215 

VA 11 1,911 2,773 0 160,154 8,463 164,789 8,512 173,301 

WA 4 0 0 0 0 0 No data 0 0 

WI 4 94 21 0 1,313 9,216 223 10,421 10,644 

WV 12 2,693 2,417 0 536,628 10,000 441,237 110,501 551,738 

WY 2 3,300 0 0 10,800 0 14,100 0 14,100 

Total 361 129,205 132,347 1,583,096 116,952,326 625,588 117,346,787 2,075,775 119,422,562 

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: TRI04 2006 (Data are from 2004) 
ARSENIC 321 

6. POTENTIAL FOR HUMAN EXPOSURE 

Arsenic naturally occurs in soil and will be present in the atmosphere as airborne dust. It is also emitted 

from volcanoes and in areas of dormant volcanism (e.g., fumaroles). Gaseous alkyl arsenic compounds 

may be released from soil that has been treated with inorganic arsenic compounds as a result of biogenic 

processes (Schroeder et al. 1987; Tamaki and Frankenberger 1992). Arsenic naturally occurs in sea water 

and vegetation and is released into the atmosphere in sea salt spray and forest fires. Anthropogenic 

sources of arsenic include nonferrous metal smelting, coal, oil and wood combustion, and municipal 

waste incineration. Arsenic naturally occurs in coal and oil and therefore, coal- and oil-fired power plants 

release arsenic to the atmosphere in their emissions (Pacyna 1987). Arsenic’s use in agriculture and 

industrial processes also contributes to its emissions. One important source of arsenic emissions is cotton 

ginning in which the cotton seeds are removed from the raw cotton. 

The National Air Toxics Assessment reported that total anthropogenic emissions for arsenic compounds 

in the United States in 1996 were 355 tons/year (EPA 2005b). EPA conducted a modeling study with the 

Assessment System for Population Exposure Nationwide (ASPEN) in which estimates of emissions of 

hazardous air pollutants were used to estimate air quality (Rosenbaum et al. 1999). Using 1990 data, the 

total emissions of arsenic in the conterminous 48 states, excluding road dust or windblown dust from 

construction or agricultural tilling was estimated to be 3.0 tons/day with 90% of emissions coming from 

point sources and 5% each from area and mobile sources. U.S. emissions of arsenic to the atmosphere 

were estimated as 3,300 metric tons per year between 1979 and 1986 (Pacyna et al. 1995). There is 

evidence that anthropogenic emissions, at least from smelters, are lower than they had been in the early 

1980s. It is likely that air releases of arsenic decreased during the 1980s due to regulations on industrial 

emissions (EPA 1986f), improved control technology for coal-burning facilities, and decreased use of 

arsenical pesticides. 

Nriagu and Pacyna (1988) and Pacyna et al. (1995) estimated worldwide emissions of arsenic to the 

atmosphere for 1983. Estimates of yearly emissions from anthropogenic sources ranged from 12,000 to 

25,600 metric tons with a median value of 18,800 metric tons. Natural sources contributed 1,100– 

23,500 metric tons annually. Chilvers and Peterson (1987) estimated global natural and anthropogenic 

arsenic emissions to the atmosphere as 73,500 and 28,100 metric tons per year, respectively. Copper 

smelting and coal combustion accounted for 65% of anthropogenic emissions. A U.S. Bureau of Mines 

study on the flow of mineral commodities estimated that global emissions of arsenic from metal smelting, 

coal burning, and other industrial uses ranged from 24,000 to 124,000 metric tons per year compared to 

natural releases, mostly from volcanoes, ranging from 2,800 to 8,000 metric tons per year (Loebenstein 

1994). 
ARSENIC 322 

6. POTENTIAL FOR HUMAN EXPOSURE 

Pirrone and Keeler (1996) compared trends of trace element emissions from major anthropogenic sources 

in the Great Lakes region with ambient concentrations observed in urban areas of the region. They found 

that arsenic emissions increased about 2.8% per year from 1982 to 1988 and then decreased steadily by 

about 1.4% per year to 1993. Coal combustion in electric utilities and in residential, commercial, and 

industrial facilities was an important source of arsenic in the region, accounting for about 69% of the total 

emissions. Iron-steel manufacturing accounted for about 13% of the region wide arsenic emissions and 

nonferrous metals production for 17%. 

Arsenic in the particulate phase is the predominant (89–98.6%) form of arsenic in the troposphere 

(Matschullat 2000). Inorganic species, most commonly trivalent arsenic, is the dominant form of arsenic 

in the air over emission areas; methylated forms of arsenic are probably of minor significance. Arseniccontaining air samples of smelter or coal-fired power plant origin consist largely of trivalent arsenic in 

both vapor and particulate form (Pacyna 1987). Oxides are the primary species evolved from fossil fuel 

and industrial processes. Additionally, arsenic trisulfide has also been reported from coal combustion, 

organic arsines from oil combustion, and arsenic trichloride from refuse incineration. 

Arsenic has been identified in 59 air samples collected from 1,684 current or former NPL hazardous 

waste sites where it was detected in some environmental media (HazDat 2006). 

6.2.2 Water 

Estimated releases of 780 pounds (~0.35 metric tons) of arsenic to surface water from 58 domestic 

manufacturing and processing facilities in 2004, accounted for about 0.09% of the estimated total 

environmental releases from facilities required to report to the TRI (TRI04 2006). Estimated releases of 

1.3x105 pounds (~59 metric tons) of arsenic compounds to surface water from 361 domestic 

manufacturing and processing facilities in 2004, accounted for about 0.11% of the estimated total 

environmental releases from facilities required to report to the TRI (TRI04 2006). These releases for 

arsenic and arsenic compounds are summarized in Tables 6-1 and 6-2, respectively. 

Arsenic may be released to water from the natural weathering of soil and rocks, and in areas of vulcanism. 

Arsenic may also leach from soil and minerals into groundwater. Anthropogenic sources of arsenic 

releases to water include mining, nonferrous metals, especially copper, smelting, waste water, dumping of 

sewage sludge, coal burning power plants, manufacturing processes, urban runoff, atmospheric deposition 

and poultry farms (Garbarino et al. 2003; Nriagu and Pacyna 1988; Pacyna et al. 1995). A contributory 
ARSENIC 323 

6. POTENTIAL FOR HUMAN EXPOSURE 

part of mining and coal burning power plants is leaching from abandoned mine tailing and fly ash waste 

piles. Significant amounts of arsenic are released in liquid effluents from gold-milling operations using 

cyanide (Environment Canada 1993). Nriagu and Pacyna (1988) and Pacyna et al. (1995) estimated 

global anthropogenic inputs of arsenic into rivers, lakes, and oceans for 1983; annual estimated inputs 

ranged from 11,600 to 70,300 metric tons with a median value of 41,800 metric tons. Arsenic was 

detected in 58% of samples of urban storm water runoff from 8 of 15 cities surveyed in the National 

Urban Runoff Program at concentrations ranging from 1 to 50.5 μg/L (Cole et al. 1984). 

Leaching of arsenic from soil, landfills, or slag deposits is a source of arsenic in groundwater (Francis and 

White 1987; Wadge and Hutton 1987). The arsenic in soil may be naturally-occurring or a result of the 

application of arsenic-containing pesticides or sludge. Wood treated with CCA is used in piers, piling 

and bulkheads and arsenic can leach from the treated wood (Breslin and Adler-Ivanbrook 1998; Brooks 

1996; Cooper 1991; Sanders et al. 1994; Weis et al. 1998). Ammoniacal copper zinc arsenate (ACZA) is 

another arsenic-containing waterborne preservative; however, it is not as widely used as CCA (Lebow et 

al. 2000). 

Arsenic has been identified in 846 groundwater and 414 surface water samples collected from 1,684 NPL 

hazardous waste sites, where it was detected in some environmental media (HazDat 2006). 

6.2.3 Soil 

Estimated releases of 0.70 million pounds (~320 metric tons) of arsenic to soils from 58 domestic 

manufacturing and processing facilities in 2004, accounted for about 77% of the estimated total 

environmental releases from facilities required to report to the TRI (TRI04 2006). An additional 

0.17 million pounds (~77 metric tons), constituting about 19% of the total environmental emissions, were 

released via underground injection (TRI04 2006). Estimated releases of 117 million pounds 

(~5.3x104 metric tons) of arsenic compounds to soils from 361 domestic manufacturing and processing 

facilities in 2004, accounted for about 98% of the estimated total environmental releases from facilities 

required to report to the TRI (TRI04 2006). An additional 1.6 million pounds (~720 metric tons), 

constituting about 1.3% of the total environmental emissions, were released via underground injection 

(TRI04 2006). These releases for arsenic and arsenic compounds are summarized in Tables 6-1 and 6-2, 

respectively. 

The soil receives arsenic from a variety of anthropogenic sources, including ash residue from power 

plants, smelting operations, mining wastes, and municipal, commercial, and industrial waste. Ash from 
ARSENIC 324 

6. POTENTIAL FOR HUMAN EXPOSURE 

power plants is often incorporated into cement and other materials that are used for roads and 

construction. Arsenic may be released from such material into soil. Nriagu and Pacyna (1988) and 

Pacyna et al. (1995) estimated global anthropogenic inputs of arsenic into soil for 1983. Excluding mine 

tailings and smelter slag, annual estimated inputs ranged from 52,000 to 112,000 metric tons with a 

median value of 82,000 metric tons. Mine tailings and smelter slag were estimated to add an additional 

7,200–11,000 and 4,500–9,000 metric tons, respectively. Old abandoned mine tailings undoubtedly 

contribute still more. Wood treated with CCA used in foundations or posts could potentially release 

arsenic into the surrounding soil. CCA preservatives have been shown to leach to varying degrees from 

wood, as well as through soils in both field and laboratory studies (Chirenje et al. 2003a; Hingston et al. 

2001; Lebow et al. 2000; Rahman et al. 2004; Stilwell and Graetz 2001; USDA/USDT 2000). Arsenic 

may also be released on land through the application of pesticides and fertilizer. Senesi et al. (1999) 

reported the range of arsenic in 32 fertilizers as 2.2–322 ng/g. Roxarsone (3-nitro-4-hydroxyphenylarsonic acid), which was used to treat poultry feed in approximately 70% of the broiler poultry operations 

in 1999–2000, is excreted unchanged in the manure. Poultry litter (manure and bedding) is routinely used 

as fertilizer to cropland and pasture. In 2000, assuming 70% of the 8.3 billion broiler poultry produced in 

the United States were fed roxarsone-treated feed, the resulting manure would contain approximately 

2.5x105

 kg of arsenic (Garbarino et al. 2003). Land application of sewage sludge is another source of 

arsenic in soil. Arsenic was detected in sewage sludge samples from 23 cities at concentrations of 0.3– 

53 μg/g (Mumma et al. 1984). 

Arsenic has been identified in 758 soil and 515 sediment samples collected from 1,684 NPL hazardous 

waste sites, where it was detected in some environmental media (HazDat 2006). 

6.3 ENVIRONMENTAL FATE 

6.3.1 Transport and Partitioning 

Arsenic in soil may be transported by wind or in runoff or may leach into the subsurface soil. However, 

because many arsenic compounds tend to partition to soil or sediment under oxidizing conditions, 

leaching usually does not transport arsenic to any great depth (EPA 1982c; Moore et al. 1988; PantsarKallio and Manninen 1997; Welch et al. 1988). Arsenic is largely immobile in agricultural soils; 

therefore, it tends to concentrate and remain in upper soil layers indefinitely. Downward migration has 

been shown to be greater in a sandy soil than in a clay loam (Sanok et al. 1995). Arsenic from lead 

arsenate that was used for pest control did not migrate downward below 20 cm in one fruit orchard; in 

another orchard, 15 years after sludge amendments and deep plowing, essentially all arsenic residues 
ARSENIC 325 

6. POTENTIAL FOR HUMAN EXPOSURE 

remained in the upper 40 cm of soil (Merwin et al. 1994). Leaching of arsenic in polluted wetland soil 

was low; leaching was correlated with the amount of dissolved organic matter in the soil (Kalbitz and 

Wennrich 1998). The effect of soil characteristics, namely pH, organic matter content, clay content, iron 

oxide content, aluminum oxide content, and cation exchange capacity (CEC), on the adsorption of various 

metals, including the metalloid arsenic, to 20 Dutch surface soils was assessed by regression analysis 

(Janssen et al. 1997). The most influential parameter affecting arsenic adsorption was the iron content of 

the soil. 

Arsenic that is adsorbed to iron and manganese oxides may be released under reducing conditions, which 

may occur in sediment or flooding conditions (LaForce et al. 1998; McGeehan 1996; Mok and Wai 

1994). In addition to reductive dissolution, when nutrient levels are adequate, microbial action can also 

result in dissolution (LaForce et al. 1998). Interestingly, drying of the previously flooded soil increases 

arsenic adsorption, possibly due to alterations in iron mineralogy (McGeehan et al. 1998). 

Darland and Inskeep (1997) conducted a study to determine the effects of pH and phosphate competition 

on the transport of arsenate (HxAsO4 

x-3) through saturated columns filled with sand containing free iron 

oxides. At pH 4.5 and 6.5, arsenate transport was strongly retarded, while at pH 8.5, it was rapid. The 

enhanced transport of arsenate at pH 8 is consistent with the pH dependence of surface complexation 

reactions describing arsenate sorption by metal oxide minerals that can be categorized as a ligand 

exchange mechanism. Phosphate was shown to compete effectively with arsenate for adsorption sites on 

the sand, but the competition was not sufficient to desorb all of the arsenate in batch column experiments, 

even when the applied phosphate exceeded the column adsorption capacity by a factor of two. The 

researchers concluded that arsenate desorption kinetics may play an important role in the transport of 

arsenate through porous media. In a study looking at the effect of competing anions on the adsorption of 

arsenite and arsenate on ferrihydrite, the effect of phosphate on arsenate adsorption was greater at higher 

pH than at low pH and the opposite trend was observed for arsenite. While sulfate did not change the 

affinity of arsenate for ferrihydrite, sulfate reduced the adsorption of arsenite at pHs below 7.0 (Jain and 

Loeppert 2000). 

Smith et al. (1999) investigated the sorption properties of both As(V) and As(III) in 10 Australian soils of 

widely different chemistry and mineralogy at commonly found arsenic levels. Adsorption of both 

arsenate and arsenite was rapid (1 hour). The amount of As(V) sorbed varied widely (1.7–62.0 L/kg); 

soils with lower amounts of oxidic material adsorbed much less arsenic than those with higher amounts of 

these minerals. Arsenate sorption was highly correlated with the iron oxide content of the soil and this 
ARSENIC 326 

6. POTENTIAL FOR HUMAN EXPOSURE 

factor probably accounts for much of the variation in soil adsorptivity. Considerable leaching of arsenic 

occurred at a separate site where cattle were treated with a dip containing arsenic (cattle dip site) and that 

contained similar soil properties to that studied by Smith et al. (1999). Arsenite adsorption, which was 

investigated in four of the Australian soils, was sorbed to a lesser extent than was arsenate. This was 

attributed to soil minerology and the species of As(V) (arsenate) and As(III) (arsenite) present in solution; 

- at pH 5–7, the dominant As(V) species are H2AsO4 and HAsO42- and neutral H3AsO3 is the dominant 

As(III) species. For soils containing low amounts of oxidic minerals, pH had little effect on As(V) 

sorption, while for oxidic soils, a decrease in sorption was evident as the pH increased. In contrast, 

As(III) sorption increased with increasing pH (Smith et al. 1999). Jain et al. (1999) reported similar 

results where arsenite were both found to bind strongly to iron oxides; however, the adsorption of 

arsenate decreases with increasing pH, while the adsorption of arsenite increases with increasing pH (Jain 

et al. 1999). As(III), which exists in a neutral form as arsenous acid, H3AsO3 (pKa=9.23, 12.13, 13.4), is 

less strongly adsorbed on mineral surfaces than the oxyanions of arsenic acid, H3AsO4, (pKa=2.22, 6.98, 

11.53) (NRC 1999). Based on its pKa values, arsenic acid would exist as a mixture of arsenate anions, 

H2AsO4

-

 and HAsO4

2-, under most environmental conditions (pH 5–9). 

The practice of liming to remediate contaminated soils and mine tailings has the potential to mobilize 

arsenic. Experiments performed by Jones et al. (1997) indicate that the increased mobility appears to be 

consistent with the pH dependence of sorption reactions of arsenic on iron oxide minerals rather than 

dissolution-precipitation reactions involving arsenic. They recommend that remediation of acidic mine 

tailings or other arsenic-contaminated soils be carefully evaluated with respect to potential arsenic 

mobilization, especially at contaminated sites hydraulically connected to surface or groundwaters. 

Transport and partitioning of arsenic in water depends upon the chemical form (oxidation state and 

counter ion) of the arsenic and on interactions with other materials present. Soluble forms move with the 

water, and may be carried long distances through rivers (EPA 1979). However, arsenic may be adsorbed 

from water onto sediments or soils, especially clays, iron oxides, aluminum hydroxides, manganese 

compounds, and organic material (EPA 1979, 1982c; Welch et al. 1988). Under oxidizing and mildly 

reducing conditions, groundwater arsenic concentrations are usually controlled by adsorption rather than 

by mineral precipitation. The extent of arsenic adsorption under equilibrium conditions is characterized 

by the distribution coefficient, Kd, which measures the equilibrium partitioning ratio of adsorbed to 

dissolved contaminant. The value of Kd depends strongly upon the pH of the water, the arsenic oxidation 

state, and the temperature. In acidic and neutral waters, As(V) is extensively adsorbed, while As(III) is 

relatively weakly adsorbed. Trivalent inorganic arsenic exists predominantly as arsenous acid (H3AsO3) 
ARSENIC 327 

6. POTENTIAL FOR HUMAN EXPOSURE 

at environmental pH and is not strongly adsorbed to suspended solids and sediments in the water column. 

- Pentavalent inorganic arsenic exists predominantly as H2AsO4 and HAsO42- in most environmental 

waters, which has considerably greater adsorption characteristics than arsenous acid. While in acidic and 

neutral waters, As(V) is more strongly adsorbed relative to As(III), in high-pH waters (pH >9) aquifer Kd 

values are considerably lower for both oxidation states (Mariner et al. 1996). Sediment-bound arsenic 

may be released back into the water by chemical or biological interconversions of arsenic species (see 

Section 6.3.2). 

Arsenic enters rivers from where mining operations occurred and is transported downstream, moving 

from water and sediment into biofilm (attached algae, bacterial, and associated fine detrital material), and 

then into invertebrates and fish. The source of arsenic in the water column may be resuspended sediment. 

While arsenic bioaccumulates in animals, it does not appear to biomagnify between tropic levels (Eisler 

1994; Farag et al. 1998; Williams et al. 2006). 

Most anthropogenic arsenic emitted to the atmosphere arises from high temperature processes (e.g., coal 

and oil combustion, smelting operations, and refuse incineration) and occurs as fine particles with a mass 

median diameter of about 1 μm (Coles et al. 1979; Pacyna 1987). These particles are transported by wind 

and air currents until they are returned to earth by wet or dry deposition. Their residence time in the 

atmosphere is about 7–9 days, in which time the particles may be transported thousands of kilometers 

(EPA 1982b; Pacyna 1987). Long-range transport was evident in analyzing deposition of arsenic in 

countries like Norway; there was no indication that the marine environment contributed significantly to 

the deposition (Steinnes et al. 1992). Atmospheric fallout can be a significant source of arsenic in coastal 

and inland waters near industrial areas. Scudlark et al. (1994) determined the average wet depositional 

flux of arsenic as 49 μg As/m2

/year for two sites in Chesapeake Bay, Maryland from June 1990 to 

July 1991. They found a high degree of spatial and temporal variability. The elemental fluxes derived 

predominantly from anthropogenic sources. Golomb et al. (1997) report average total (wet + dry) 

deposition rates to Massachusetts Bay of 132 μg/m2

/year, of which 21 μg/m2/year was wet deposition 

during the period September 15, 1992–September 16, 1993. Hoff et al. (1996) estimated the following 

arsenic loadings into the Great Lakes for 1994 (lake, wet deposition, dry deposition): Superior, 

11,000 kg/year, 3,600 kg/year; Michigan, 5,000 kg/year, 1,800 kg/year; Erie, 5,500 kg/year, 

1,800 kg/year; and Ontario, 3,000 kg/year, 580 kg/year. The measured dry deposition fluxes of arsenic at 

four sampling sites around Lake Michigan ranged approximately from 0.01 to 1.5 μg As/m2

/day; 

estimated inputs of arsenic into Lake Michigan were reported to be 1.4x103

 kg/year (Shahin et al. 2000). 
ARSENIC 328 

6. POTENTIAL FOR HUMAN EXPOSURE 

Terrestrial plants may accumulate arsenic by root uptake from the soil or by absorption of airborne 

arsenic deposited on the leaves, and certain species may accumulate substantial levels (EPA 1982b). Yet, 

even when grown on highly polluted soil or soil naturally high in arsenic, the arsenic level taken up by the 

plants is comparatively low (Gebel et al. 1998b; Pitten et al. 1999). Kale, lettuce, carrots, and potatoes 

were grown in experimental plots surrounding a wood preservation factory in Denmark where waste 

wood was incinerated to investigate the amount and pathways for arsenic uptake by plants (Larsen et al. 

1992). On incineration, the arsenate in the wood preservative was partially converted to arsenite; the 

arsenic emitted from the stack was primarily particle bound. Elevated levels of inorganic arsenic were 

found in the test plants and in the soil around the factory. Statistical analyses revealed that the 

dominating pathway for transport of arsenic from the factory to the leafy vegetables (kale) was by direct 

atmospheric deposition, while arsenic in the root crops (potatoes and carrots) was a result of both soil 

uptake and atmospheric deposition. Arsenic accumulation by plants is affected by arsenic speciation. 

Uptake of four arsenic species (arsenite, arsenate, methylarsonic acid, and dimethylarsinic acid) by 

turnips grown under soilless culture conditions showed that while uptake increased with increasing 

arsenic concentration in the nutrient, the organic arsenicals showed higher upward translocation than the 

inorganic arsenical (Carbonell-Barrachina et al. 1999). The total amount of arsenic taken up by the turnip 

plants (roots and shoots) followed the trend methylarsenate (MMA)<dimethylarsinic acid (DMA) 

<arsenite<arsenate. In a similar experiment, conducted with tomato plants, the total amount of arsenic 

taken up by the tomato plants followed the trend DMA<MMA<arsenate≈arsenite, with arsenic 

concentrations in the plants increasing with increasing arsenic concentration in the nutrient solution. 

Arsenic was mainly accumulated in the root system (85%) with smaller amounts translocating to the fruit 

(1%). However, plants treated with MMA and DMA had higher arsenic concentrations in the shoots and 

fruit than those treated with arsenite or arsenate (Burlo et al. 1999). Terrestrial plants growing on land 

bordering arsenic-contaminated waters show relatively little arsenic content, even though the sediments 

have arsenic concentrations as high as 200 μg/g (Tamaki and Frankenberger 1992). Arsenic 

concentrations in vegetables grown in uncontaminated soils and contaminated soils containing arsenic, as 

well as other metals and organic contaminants, were generally <12 μg/kg wet weight. A maximum 

arsenic concentration of 18 μg/kg wet weight was found in unpeeled carrots grown in soil, which 

contained a mean arsenic concentration of 27 mg/kg dry weight (Samsøe-Petersen et al. 2002). 

In a study by Rahman et al. (2004), CCA-treated lumber was used to construct raised garden beds to 

determine how far the components of CCA migrated in the soil and the uptake of these components by 

crops grown in the soil. Arsenic was found to diffuse laterally into the soil from the CCA-treated wood, 

with the highest concentrations found at 0–2 cm from the treated wood and a steady decline in 
ARSENIC 329 

6. POTENTIAL FOR HUMAN EXPOSURE 

concentration with increased distance. The highest average arsenic concentrations found in soil closest 

(0–2 cm) to the CCA-treated wood were 56 and 46 μg/g in loamy sand and sandy loam soils, respectively. 

At a distance of 30–35 cm from the CCA-treated wood, arsenic concentrations were approximately 7 μg/g 

in both soils. All samples were of the top 0–15 cm of soil. Crops grown in both soil types within 0–2 cm 

of the CCA-treated wood contained higher concentrations of arsenic, 0.186 and 10.894 μg/g for carrots 

without peal and bean leaves and stems, respectively, than those grown at 1.5 m from the CCA-treated 

wood, 0.006 and 0.682 μg/g for bean pods and bean leaves and stems, respectively. However, based on 

FDA guidelines on tolerance limits, these crops would be considered approved for human consumption. 

Studies by Chirenje et al. (2003a) also showed that elevated arsenic concentrations were found in surface 

(0–5 cm) soils immediately surrounding, within the first 0.3 m, of utility poles, fences, and decks made 

with CCA-treated wood. Factors such as the preservative formula, fixation temperature, post treatment 

handling, and timber dimensions of CCA-treated wood, as well as the pH, salinity, and temperature of the 

leaching media can affect the leach rates from CCA-treated wood (Hingston et al. 2001). Studies of 

leaching of the components of CCA- and ACZA-treated wood used to construct a boardwalk in wetland 

environments reported elevated arsenic levels in soil and sediment below and adjacent to these structures. 

Generally, these levels decreased with increasing distance from the structure (Lebow et al. 2000). 

Increased concentrations of arsenic were also observed under CCA-treated bridges. Arsenic levels 

declined with distance from the bridge and were near background levels at 1.8–3 m from the bridge’s 

perimeter (USDA/USDT 2000). 

In a study by Lebow et al. (2003), the use of a water repellent finish on CCA-treated wood significantly 

reduces the amount of arsenic, as well as copper and chromium, in the run-off water. It was also observed 

the exposure to UV radiation caused a significant increase in leaching from both finished and unfinished 

samples of CCA-treated wood. Small amounts of arsenic can be transferred from CCA-treated wood to 

skin from touching CCA-treated wood surfaces (Hemond and Solo-Gabriele 2004; Kwon et al. 2004; 

Shalat et al. 2006; Ursitti et al. 2004; Wang et al. 2005). 

Breslin and Adler-Ivanbrook (1998) examined the leaching of the copper, chromium, and arsenic from 

CCA-treated wood in laboratory studies using samples of treated southern yellow pine in solutions 

simulating estuarine waters. The tank leaching solutions were frequently sampled and replaced to 

approximate field conditions. Initial 12-hour fluxes ranging from 0.2x10-10 to 5.2x10-10

 mol/mm2 d was 

reported for arsenic. After 90 days, arsenic fluxes decreased to 0.5x10-11–3.1x10-11

 mol/mm2 d. A study 

by Cooper (1991) demonstrated that the buffer system used in leaching studies of components from CCAtreated wood can significantly change the amount arsenic released from treated wood. Samples of four 
ARSENIC 330 

6. POTENTIAL FOR HUMAN EXPOSURE 

species of CCA-treated wood were exposed to four acidic leaching solutions. In the samples exposed to 

water adjusted to pHs of 3.5, 4.5, and 5.5, losses of arsenic after 13 days were generally <7%. However, 

when a leaching solution of sodium hydroxide and citric acid buffer (pH 5.5) was used, the percent of 

arsenic leached ranged from 27.4 to 46.7% (Cooper 1991). 

Arsenic bioaccumulation depends on various factors, such as environmental setting (marine, estuarine, 

freshwater), organism type (fish, invertebrate), trophic status within the aquatic food chain, exposure 

concentrations, and route of uptake (Williams et al. 2006). Bioaccumulation refers to the net 

accumulation of a chemical by aquatic organisms as a result of uptake from all environmental sources, 

such as water, food, and sediment, whereas bioconcentration refers to the uptake of a chemical by an 

aquatic organism through water (EPA 2003b). Biomagnification in aquatic food chains does not appear 

to be significant (EPA 1979, 1982b, 1983e, 2003b; Mason et al. 2000; Williams et al. 2006). 

Bioconcentration of arsenic occurs in aquatic organisms, primarily in algae and lower invertebrates. Both 

bottom-feeding and predatory fish can accumulate contaminants found in water. Bottom-feeders are 

readily exposed to the greater quantities of metals, including the metalloid arsenic, which accumulate in 

sediments. Predators may bioaccumulate metals from the surrounding water or from feeding on other 

fish, including bottom-feeders, which can result in the biomagnification of the metals in their tissues. An 

extensive study of the factors affecting bioaccumulation of arsenic in two streams in western Maryland in 

1997–1998 found no evidence of biomagnification since arsenic concentrations in organisms tend to 

decrease with increasing tropic level (Mason et al. 2000). Arsenic is mainly accumulated in the 

exoskeleton of invertebrates and in the livers of fish. No differences were found in the arsenic levels in 

different species of fish, which included herbivorous, insectivorous, and carnivorous species. The major 

bioaccumulation transfer is between water and algae, at the base of the food chain and this has a strong 

impact on the concentration in fish. National Contaminant Biomonitoring data produced by the Fish and 

Wildlife Service were used to test whether differences exist between bottom-feeders and predators in 

tissue levels of metals and other contaminants. No differences were found for arsenic (Kidwell et al. 

1995). The bioconcentration factors (BCFs) of bryophytes, invertebrates, and fish (livers) in Swedish 

lakes and brooks impacted by smelter emissions were 8,700, 1,900–2,200, and 200–800, respectively 

(Lithner et al. 1995). EPA (2003b) assessed a large dataset of bioaccumulation data for various fish and 

invertebrate species. BCF values in this dataset ranged from 0.048 to 1,390. 

Williams et al. (2006) reviewed 12 studies of arsenic bioaccumulation in freshwater fish, and proposed 

that BCF and bioaccumulation factor (BAF) values are not constant across arsenic concentrations in 
ARSENIC 331 

6. POTENTIAL FOR HUMAN EXPOSURE 

water. BCF or BAF values from these 12 studies ranged from 0.1 to 3,091. Williams et al. (2006) found 

that BCF and BAF values appear to be the highest within the range of ambient arsenic concentrations, and 

decline steeply to relatively low levels as the arsenic concentrations in water increase. Based on this 

analysis, arsenic concentrations in tissue and BAF values may be a power function of arsenic 

concentrations in water. EPA (2007b) also reported that for many nonessential metals, including arsenic, 

accumulation is nonlinear with respect to exposure concentration. 

6.3.2 Transformation and Degradation 

6.3.2.1 Air 

Arsenic is released into the atmosphere primarily as arsenic trioxide or, less frequently, in one of several 

volatile organic compounds, mainly arsines (EPA 1982b). Trivalent arsenic and methyl arsines in the 

atmosphere undergo oxidation to the pentavalent state (EPA 1984a), and arsenic in the atmosphere is 

usually a mixture of the trivalent and pentavalent forms (EPA 1984a; Scudlark and Church 1988). 

Photolysis is not considered an important fate process for arsenic compounds (EPA 1979). 

6.3.2.2 Water 

Arsenic in water can undergo a complex series of transformations, including oxidation-reduction 

reactions, ligand exchange, precipitation, and biotransformation (EPA 1979, 1984a; Sanders et al. 1994; 

Welch et al. 1988). Rate constants for these various reactions are not readily available, but the factors 

most strongly influencing fate processes in water include Eh, pH, metal sulfide and sulfide ion 

concentrations, iron concentrations, temperature, salinity, distribution and composition of the biota, 

season, and the nature and concentration of natural organic matter (EPA 1979; Farago 1997; Redman et 

al. 2002; Wakao et al. 1988). Organic arsenical pesticides, such as MSMA, DSMA, and DMA do not 

degrade by hydrolysis or by aquatic photolysis (EPA 2006). No formation of arsine gas from marine 

environments has been reported (Tamaki and Frankenberger 1992). 

Inorganic species of arsenic are predominant in the aquatic environment. In the pH range of natural 

- waters, the predominant aqueous inorganic As(V) species are the arsenate ions, H2AsO4 and HAsO42-; the 

predominant inorganic As(III) species is As(OH)3 (Aurillo et al. 1994; EPA 1982c). As(V) generally 

dominates in oxidizing environments such as surface water and As(III) dominates under reducing 

conditions such as may occur in groundwater containing high levels of arsenic. However, the reduction 

of arsenate to arsenite is slow, so arsenate can be found in reducing environments. Conversely, the 

oxidation of arsenite in oxidizing environments is moderately slow (half-life, 0.4–7 days in coastal 
ARSENIC 332 

6. POTENTIAL FOR HUMAN EXPOSURE 

systems) and therefore, arsenite can be found in oxidizing environments (Mariner et al. 1996; Sanders et 

al. 1994). The main organic species in fresh water are MMA and DMA; however, these species are 

usually present at lower concentrations than inorganic arsenic species (Eisler 1994). (The toxicities of 

MMA and DMA are discussed in Chapter 3.) Aquatic microorganisms may reduce the arsenate to 

arsenite, as well as methylate arsenate to its mono- or dimethylated forms (Aurillo et al. 1994; Benson 

1989; Braman and Foreback 1973; Edmonds and Francesconi 1987; Sanders et al. 1994). Methylated 

species are also produced by the biogenic reduction of more complex organoarsenic compounds like 

arsenocholine or arsenobetaine. Water samples from a number of lakes and estuaries, mostly in 

California, show measurable concentrations of methylated arsenic (equivalent to 1–59% of total arsenic) 

(Anderson and Bruland 1991). Within the oxic photic zone, arsenate and DMA were the dominant 

species. A seasonal study of one lake demonstrated that DMA was the dominant form of arsenic in 

surface waters during late summer and fall. Methylated species declined and arsenate species increased 

when the lake turned over in late fall. Mono Lake, a highly alkaline body of water, and four rivers did not 

have measurable concentrations of methylated arsenic. It was hypothesized that the reason why 

methylated forms were not detected in Mono Lake was that the extremely high inorganic arsenic 

concentrations in the lake, 230 μM (17 mg/L), could overwhelm the analysis of small amounts of organic 

forms. Other possibilities are that the high alkalinity or very high phosphate levels in the water, 260 μM 

(25 mg/L), are not conducive to biogenic methylation (Anderson and Bruland 1991). Both reduction and 

methylation of As(V) may lead to increased mobilization of arsenic, since As(III), dimethylarsinates, and 

monomethylarsonates are much less particle-reactive than As(V) (Aurillo et al. 1994). In the estuarial 

Patuxet River, Maryland, arsenate concentrations peaked during the summer, at 1.0 μg/L in 1988– 

1989 (Sanders et al. 1994). In contrast, winter to spring levels were around 0.1 μg/L. Arsenite 

concentrations were irregularly present at low levels during the year. Peaks of DMA occurred at various 

times, particularly in the winter and late spring and appeared to be linked with algal blooms. The DMA 

peak declined over several months that was followed by a rise in MMA. The MMA was thought to be 

occurring as a degradation product of DMA. A similar seasonal pattern of arsenic speciation was 

observed in Chesapeake Bay. Arsenite methylation took place during the warmer months leading to 

changes down the main stem of the bay; arsensite production dominated the upper reaches of the bay and 

methylated species dominated the more saline lower reaches. In coastal waters, reduced and methylated 

species are present in lower concentrations, around 10–20% of total arsenic (Sanders et al. 1994). In 

groundwater, arsenic generally exists as the oxyanion of arsenate (HxAsO4

3-x) or arsenite (HxAsO33-x), or 

both; however, the distribution between arsenite and arsenate is not always predictable based on 

oxidation-reduction potential (Robertson 1989; Welch et al. 1988). 
ARSENIC 333 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.3.2.3 Sediment and Soil 

In soil, arsenic is found as a complex mixture of mineral phases, such as co-precipitated and sorbed 

species, as well as dissolved species (Roberts et al. 2007). The degree of arsenic solubility in soil will 

depend on the amount of arsenic distributed between these different mineral phases. The dissolution of 

arsenic is also affected by particle size. The distribution between these phases may reflect the arsenic 

source (e.g., pesticide application, wood treatment, tanning, or mining operations), and may change with 

weathering and associations with iron and manganese oxides and phosphate minerals in the soil (Roberts 

et al. 2007; Ruby et al. 1999). Davis et al. (1996) reported that in soil in Anaconda, Montana, a smelting 

site from 1860 to 1980, contained arsenic that is only in a sparingly soluble form, consisting of primarily 

arsenic oxides and phosphates. 

The arsenic cycle in soils is complex, with many biotic and abiotic processes controlling its overall fate 

and environmental impact. Arsenic in soil exists in various oxidation states and chemical species, 

depending upon soil pH and oxidation-reduction potential. Under most environmental conditions, 

- inorganic As(V) will exist as a mixture of arsenate anions, H2AsO4 and HAsO42-, and inorganic As(III) 

will exist as H3AsO3. The arsenate and arsenite oxyanions have various degrees of protonation depending 

upon pH (EPA 1982b; McGeehan 1996). As(V) predominates in aerobic soils, and As(III) predominates 

in slightly reduced soils (e.g., temporarily flooded) or sediments (EPA 1982b; Sanders et al. 1994). 

As(III) commonly partitions to the aqueous phase in anoxic environments, and would be more mobile. 

As(V) usually remains bound to minerals, such as ferrihydrite and alumina, limiting its mobility and 

bioavailability (Rhine et al. 2006). 

Arsenite is moderately unstable in the presence of oxygen; however, it can be found under aerobic 

conditions as well (Sanders et al. 1994). While arsenate is strongly sorbed by soils under aerobic 

conditions, it is rapidly desorbed as the system becomes anaerobic. Once it is desorbed, arsenate can be 

reduced to arsenite, which exhibits greater mobility in soils (McGeehan 1996). Transformations between 

the various oxidation states and species of arsenic occur as a result of biotic or abiotic processes 

(Bhumbla and Keefer 1994). While degradation of an organic compound is typically considered 

complete mineralization, in the case of organic arsenic compounds, the element arsenic itself cannot be 

degraded. However, the organic portion of the molecule can be metabolized (Woolson 1976). 

Arsenicals applied to soils may be methylated by microorganisms to arsines, which are lost through 

volatilization, and organic forms may be mineralized to inorganic forms. Gao and Burau (1997) reported 
ARSENIC 334 

6. POTENTIAL FOR HUMAN EXPOSURE 

that the overall percentage of DMA and MMA minerialized after 70 days ranged from 3 to 87% in air-dry 

soil and a soil near saturation, respectively. The rate of demethylation of DMA increased with soil 

moisture. Over the same 70-day period, arsenic losses as volatile arsines were much lower than 

minerialization, ranging from 0.001 to 0.4%. Arsine evolution rates followed the order: 

DMA>MMA>arsenite=arsenate (Gao and Burau 1997). Woolson and Kearney (1973) reported that 

14C-labeled DMA degraded differently in soils under aerobic and anaerobic conditions. Under anaerobic 

conditions, 61% of the applied DMA was converted to a volatile alkyl arsine after 24 weeks, and lost 

from the soil system. Under aerobic conditions, 35% was converted to a volatile organo-arsenic 

compound, possibly dimethyl arsine, and 41% was converted to 14CO2 and arsenate after 24 weeks. 

Similar to microorganisms in soils, Reimer (1989) reported that microorganisms found in natural marine 

sediments and sediments contaminated with mine-tailings are also capable of methylating arsenic under 

aerobic and anaerobic conditions. Von Endt et al. (1968) reported that the degradation of 14C-labelled 

monosodium methanearsonate (MSMA) was found to range from 1.7 to 10% in Dundee silty clay loam 

soil and Sharkey clay soil after 60 days, respectively. MSMA decomposition to CO2 was a slow process 

without a lag period. Sterilized soils were found to produce essentially no 14CO2 (0.7%) after 60 days, 

indicating that soil bacteria contributed to the decomposition of MSMA (Von Endt et al. 1968). Akkari et 

al. (1986) studied the degradation of MSMA in various soils. At 20% water content, half-lives of 144, 88, 

and 178 days were reported in Sharkey clay, Taloka silt loam, and Steele-Crevasse sand loam, 

respectively. The Sharkey soil with the highest clay content was expected to have the greatest adsorptive 

capacity for both water and MSMA, reducing the amount of MSMA available in the soil solution to 

microorganisms that degrade the MSMA. The half-lives were 25, 41, and 178 days under anaerobic 

(flooded) conditions in Sharkey clay, Taloka silt loam, and Steele-Crevasse sand loam, respectively. 

Under flooded conditions, MSMA degradation occurs by reductive methylation to form arsinite and 

alkylarsine gas. The authors attributed the longer half-lives for MSMA degradation in the SteeleCrevasse sand loam soil to its low organic matter content, which may have supported fewer microbial 

populations needed for oxidation demethylation under aerobic conditions. Under flooded conditions, 

anaerobiosis is expected to be slowest in low organic matter sandy loam soils (Akkari et al. 1986). 

Organic arsenical pesticides, such as MSMA, DSMA, and DMA, do not degrade by hydrolysis or by soil 

photolysis (EPA 2006). 

Roxarsone (3-nitro-4-hydroxyphenylarsonic acid) used in poultry feed is found excreted unchanged in 

poultry litter (bedding and manure). Roxarsone found in poultry litter, which is used to amend 

agricultural soil, was found to degrade to arsenate in approximately 3–4 weeks upon composting 
ARSENIC 335 

6. POTENTIAL FOR HUMAN EXPOSURE 

(Garbarino et al. 2003). In addition, the arsenic in poultry litter was found to be easily mobilized by 

water; however, its leach rate from amended soils was slow enough that it accumulated in soils 

(Rutherford et al. 2003). 

A sequential fractionation scheme was used to assess the chemical nature, and thus the potential 

bioavailability, of arsenic at cattle dip sites in Australia where sodium arsenite was used extensively in 

cattle dips from the turn of the century until the early 1950s (McLaren et al. 1998). Most sites contained 

substantial amounts, 13% on the average, of arsenic in the two most labile fractions indicating a high 

potential for bioaccessibility and leaching. The bulk of the arsenic appeared to be associated with 

amorphous iron and aluminum minerals in soil. Similarly, arsenic in soil and mine waste in the Tamar 

Valley in England was found to be concentrated in a fraction associated with iron and organic-iron 

(Kavanagh et al. 1997). Laboratory studies were performed to assess the phase partitioning of trace 

metals, including the metalloid arsenic, to sediment from the Coeur d’Alene River, a mining area of 

Idaho, and the release of metals under simulated minor and major flooding events (LaForce et al. 1998). 

Arsenic was primarily associated with the iron and manganese oxides as seen by its large release when 

these oxides were reduced. Arsenic levels were comparatively low in the organic fraction and remaining 

residual fraction and negligible in the extractible fractions. 

6.3.2.4 Other Media 

Carbonell-Barrachina et al. (2000) found the speciation and solubility of arsenic in sewage sludge 

suspensions to be affected by pH and Eh. Under oxidizing conditions, the solubility of arsenic was low, 

with a major portion of the soluble arsenic present as organic arsenic compounds, mainly dimethylarsinic 

acid (approximately 74% of the total arsenic in solution). Under moderately reducing conditions (0– 

100 mV), inorganic arsenic accounted for the majority (90%) of the total arsenic in solution, and the 

solubility of arsenic was increased due to dissolution of iron oxyhydroxides. Under strongly reducing 

conditions (-250 mV), arsenic solubility was decreased by the formation of insoluble sulfides. The pH of 

the solution was also found to influence the speciation and solubility of arsenic. At neutral pH, the 

solubility of arsenic was at its maximum, and decreased under acidic or alkaline conditions. Inorganic 

arsenic species were the dominant species at pH 5.0; at pH 6.5, the major soluble forms were organic 

arsenic species. The biomethylation of arsenic was limited at acidic pH, and was at its maximum at near 

neutral pH (Carbonell-Barrachina et al. 2000). 
ARSENIC 336 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT 

Reliable evaluation of the potential for human exposure to arsenic depends in part on the reliability of 

supporting analytical data from environmental samples and biological specimens. Concentrations of 

arsenic 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 arsenic 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 arsenic in 

a variety of environmental media are detailed in Chapter 7. 

6.4.1 Air 

Arsenic in ambient air is usually a mixture of particulate arsenite and arsenate; organic species are of 

negligible importance except in areas of substantial methylated arsenic pesticide application or biotic 

activity (EPA 1984a). Mean levels in ambient air in the United States have been reported to range from 

<1 to 3 ng/m3

 in remote areas and from 20 to 30 ng/m3 in urban areas (Davidson et al. 1985; EPA 1982c; 

IARC 1980; NAS 1977a). EPA conducted a modeling study with the Assessment System for Population 

Exposure Nationwide (ASPEN) in which estimates of emissions of hazardous air pollutants were used to 

estimate ambient concentrations (Rosenbaum et al. 1999). Using 1990 data to estimate total emissions of 

arsenic in the conterminous 48 states, excluding road dust or windblown dust from construction or 

agricultural tilling, the 25th percentile, median, and 75th percentile arsenic concentration were estimated 

to be 9, 20, and 30 ng/m3

, respectively. Maps illustrating the amount of toxic air pollutant emissions, 

including arsenic compounds, by county in 1996 for the 48 coterminous states of the United States as well 

as Puerto Rico and the Virgin Islands are available on the internet at http://www.epa.gov/ttn/atw/­

nata/mapemis.html, as of March 2005. Schroeder et al. (1987) listed ranges of arsenic concentrations in 

air of 0.007–1.9, 1.0–28, and 2–2,320 ng/m3

 in remote, rural, and urban areas, respectively. The average 

annual arsenic concentration in air at Nahant, Massachusetts, just north of Boston, between September 

1992 and September 1993, was 1.2 ng/m3

; 75% of the arsenic was associated with fine (<2.5 μm) 

particles. The long-term means of the ambient concentrations of arsenic measured in urban areas of the 

Great Lakes region from 1982 to 1993 ranged from 4.2 to 9.6 ng/m3

 (Pirrone and Keeler 1996). Large 

cities generally have higher arsenic air concentrations than smaller ones due to emissions from coal-fired 

power plants (IARC 1980), but maximum 24-hour concentrations generally are <100 ng/m3

 (EPA 1984a). 

In the spring of 1990, aerosols and cloud water that were sampled by aircraft at an altitude of 1.2–3 km 

above the Midwestern United States had a mean mixed layer arsenic concentration of 

1.6±0.9 ng/m3

 (Burkhard et al. 1994). A mean arsenic concentration of 1.0±0.5 ng/m3 was reported at 
ARSENIC 337 

6. POTENTIAL FOR HUMAN EXPOSURE 

Mayville, New York, a site 400 km to the northwest of the sampling area and directly downwind on most 

days. 

Arsenic was monitored at an application site in the San Joaquin Valley, California and at four sites in 

nearby communities in 1987 where sodium arsenite was used as a fungicide on tokay grapes (Baker et al. 

1996). The maximum arsenic concentration measured 15–20 meters from the edge of the field was 

260 ng/m3

. The maximum arsenic concentration at four community sites in the area was 76 ng/m3. The 

concentration at an urban background site was 3 ng/m3

 (Baker et al. 1996). Sodium arsenite is no longer 

registered in California (Baker et al. 1996). The highest historic arsenic levels detected in the atmosphere 

were near nonferrous metal smelters, with reported concentrations up to 2,500 ng/m3

 (IARC 1980; NAS 

1977a; Schroeder et al. 1987). 

Arsenic air concentrations measured in several indoor public places (e.g., cafeteria, coffee house, music 

club, Amtrak train, and several restaurants) with environmental tobacco smoke (ETS) ranged from <0.1 to 

1 ng/m3

, with a mean of 0.4±0.3 ng/m3. Sites that were ETS-free (university office and library) had 

arsenic concentrations <0.13 ng/m3

 (Landsberger and Wu 1995). The Toxic Exposure Assessment at 

Columbia/Harvard (TEACH) study measured levels of various toxics in New York City air in 1999. 

Exposures were assessed in a group of 46 high school students in West Central Harlem. Mean arsenic 

concentrations in summer home outdoor, home indoor, and personal air of the participants were 0.37, 

0.40, and 0.45 ng/m3

, respectively (Kinney et al. 2002). Detected arsenic concentrations in indoor and 

outdoor air collected as part of the National Human Exposure Assessment Survey (NHEXAS) in Arizona 

ranged from 3.4 to 22.3 and from 3.5 to 25.7 ng/m3

, respectively, with 71 and 68% below the detection 

limit (1.8–14.3 ng/m3

) (O'Rourke et al. 1999). 

6.4.2 Water 

Arsenic is widely distributed in surface water, groundwater, and finished drinking water in the United 

States. A survey of 293 stations in two nationwide sampling networks on major U.S. rivers found median 

arsenic levels to be 1 μg/L; the 75th percentile level was 3 μg/L (Smith et al. 1987). Arsenic was detected 

in 1,298 of 3,452 surface water samples recorded in the STORET database for 2004 at concentrations 

ranging from 0.138 to 1,700 μg/L in samples where arsenic was detected (EPA 2005c). Two streams in 

western Maryland that were the focus of a major bioaccumulation study in 1997–1998 had arsenic 

concentrations of 0.370±0.200 and 0.670±0.460 μg/L (Mason et al. 2000). Surface water will be 

impacted by runoff from polluted sites. An average arsenic concentration of 5.12 μg/L was reported in 
ARSENIC 338 

6. POTENTIAL FOR HUMAN EXPOSURE 

water from Moon Lake, a Mississippi River alluvial floodplain in northwest Mississippi. Intensive 

cultivation has occurred in this area, including cotton, soybeans, and rice (Cooper and Gillespie 2001). 

Hard-rock mining activities occurred in the southern part of Colorado and New Mexico north of Taos 

since the latter part of the 19th century until recently, which have impacted the Rio Grande and its 

tributaries. A mean arsenic concentration of approximately 0.8 μg/L was reported for the main stem of 

the Rio Grande sampled in June and September 1994. Arsenic concentrations in the Alamosa River, 

Colorado were 0.11 and 0.14 μg/L in June and September 1994, respectively, and 1.4 μg/L in Big Arsenic 

Spring, New Mexico in September 1994 (Taylor et al. 2001). Arsenic concentrations in water from 

watersheds in Black Hills, South Dakota, an area impacted by gold mining activities ranged from 2.5 to 

55 μg/L and from 1.7 to 51 μg/L in unfiltered and filtered samples, respectively; concentrations from 

reference areas ranged from 1.1 to 3.4 μg/L and from 0.9 to1.9 μg/L in unfiltered and filtered samples, 

respectively (May et al. 2001). Arsenic concentrations ranged from 0.29 to 34.0 μg/L in water samples 

from Wakulla River and St. Joseph Bay North, along the Florida Panhandle; arsenic contamination in this 

area is likely to result from nonpoint source pollution (Philp et al. 2003). 

Data on total arsenic in surface water from a number of seas and oceans show levels of <1 μg/L, except in 

the Antarctic Ocean and Southwest Pacific Oceans where the levels are 1.1 and 1.2 μg/L, respectively. 

Levels in coastal waters and estuaries are generally somewhat higher, in the range of 1–3 μg/L. However, 

estuarine water in Salinas, California had arsenic levels of 7.42 μg/L (Francesconi et al. 1994). The 

dissolved arsenic concentration in water at 40 sites in the Indian River Lagoon System in Florida ranged 

from 0.35 to 1.6 μg/L with a mean of 0.89±0.34 μg/L (Trocine and Trefry 1996). Thermal waters 

generally have arsenic levels of 20–3,800 μg/L, although levels as high as 276,000 μg/L have been 

recorded (Eisler 1994). 

Arsenic levels in groundwater average about 1–2 μg/L, except in some western states with volcanic rock 

and sulfidic mineral deposits high in arsenic, where arsenic levels up to 3,400 μg/L have been observed 

(IARC 1980; Page 1981; Robertson 1989; Welch et al. 1988). In western mining areas, groundwater 

arsenic concentrations up to 48,000 μg/L have been reported (Welch et al. 1988). Arsenic concentrations 

in groundwater samples collected form 73 wells in 10 counties in southeast Michigan in 1997 ranged 

from 0.5 to 278 μg/L, with an average of 29 μg/L. Most (53–98%) of the arsenic was detected as arsenite 

(Kim et al. 2002). The U.S. Geological Survey mapped concentrations of arsenic in approximately 

31,350 groundwater samples collected between 1973 and 2001; the counties in which at least 25% of 

wells exceed various levels are shown in Figure 6-2 (USGS 2007a). Most arsenic in natural waters is a 
ARSENIC 339 

6. POTENTIAL FOR HUMAN EXPOSURE 

Figure 6-2. Counties in Which at Least 25% of Wells Exceed Different Arsenic 

Levels 

Source: USGS 2007a 
ARSENIC 340 

6. POTENTIAL FOR HUMAN EXPOSURE 

mixture of arsenate and arsenite, with arsenate usually predominating (Braman and Foreback 1973; EPA 

1982c, 1984a). Methylated forms have also been detected in both surface water and groundwater, at 

levels ranging from 0.01 to 7.4 μg/L (Braman and Foreback 1973; Hood 1985), with most values below 

0.3 μg/L (Hood 1985). In a survey of shallow groundwater quality in the alluvial aquifer beneath a major 

urban center, Denver, Colorado, arsenic levels in the 30 randomly-chosen wells sampled had median 

levels of <1 μg/L; the maximum level was 33 μg/L (Bruce and McMahon 1996). Arsenic levels in 

groundwater sometimes exceeded the EPA maximum contaminant level (MCL), which was 50 μg/L at 

the time, in the Willamette Valley, Oregon and a nine-county region of southeastern Michigan (USGS 

1999b, 1999c). 

Arsenic has also been detected in rainwater at average concentrations of 0.2–0.5 μg/L (Welch et al. 1988). 

This range is consistent with that found in a 1997–1998 study in western Maryland, which was the focus 

of a major bioaccumulation study (Mason et al. 2000). Arsenic levels in wet deposition in the watershed 

as well as throughfall into the two streams were 0.345±0.392, 0.400±0.400, and 0.330±0.250 μg/L, 

respectively. Median arsenic concentrations in 30-day rainwater composite samples collected 

May-September 1994 from eight arctic catchments in northern Europe at varying distances and wind 

directions from the emissions of a Russian nickel ore mining, roasting, and smelting industry on the Kola 

Peninsula ranged from 0.07 to 12.3 μg/L (Reimann et al. 1997). Rain and snow samples were collected 

during the fall of 1996 and winter of 1997 at eight locations in a semi-circular pattern radiating out (2– 

15 km) in the direction of the prevailing wind from the Claremont incinerator located in New Hampshire. 

This incinerator processes 200 tons of solid waste per day. Arsenic concentrations in rainwater and snow 

ranged from 0.020 to 0.079 μg/L and from 0.80 to 1.28 μg/L, respectively (Feng et al. 2000). 

Drinking water is one of the most important sources of arsenic exposure. Surveys of drinking water in the 

United States have found that >99% of public water supplies have arsenic concentrations below the EPA 

MCL, which was 50 μg/L at the time (EPA 1984a). In an EPA study of tap water from 3,834 U.S. 

residences, the average value was 2.4 μg/L (EPA 1982c). 

Before the MCL for arsenic in drinking water was lowered from 50 to 10 μg/L, studies were undertaken 

to ascertain how different standards would affect compliance. One such survey sponsored by the Water 

Industry Technical Action Fund was the National Arsenic Occurrence Survey (NAOS). NAOS was based 

on a representational survey of public water systems defined by source type, system size, and 

geographical location. Additionally, it included a natural occurrence factor, a stratifying variable that 

could qualitatively describe the likelihood of arsenic occurrence in the supply. To predict finished water 
ARSENIC 341 

6. POTENTIAL FOR HUMAN EXPOSURE 

arsenic concentrations, data on the water treatment options, efficiency, and frequency of use were 

factored in. The results of the NAOS are presented in Table 6-3. The NAOS results are in general 

agreement with two older and more limited national surveys, EPA’s National Inorganics and 

Radionuclides Survey (NIRS) and the Metropolitan Water District of Southern California Survey 

(MWDSC). The percentages of water systems that would be out of compliance are estimated to be 1.7, 

3.6, 9.3, and 20.7% for arsenic MCLs of 20, 10, 5, and 2 μg/L, respectively. Arsenic concentrations were 

determined in drinking in EPA Region V (Indiana, Illinois, Michigan, Minnesota, Ohio, and Wisconsin) 

as part of the NHEXAS; mean arsenic concentration in flushed and standing tap water were both 1.1 μg/L 

(Thomas et al. 1999). A review by Frost et al. (2003) of existing data from the EPA Arsenic Occurrence 

and Exposure Database, as well as additional data from state health and environmental departments and 

water utilities found that 33 counties in 11 states had estimated mean drinking water arsenic 

concentrations of 10 μg/L or greater. Eleven counties had mean arsenic concentrations of ≥20 μg/L, and 

two counties had mean arsenic concentrations of ≥50 μg/L (Frost et al. 2003). 

The north central region and the western region of the United States have the highest arsenic levels in 

surface water and groundwater sources, respectively. In a study of drinking water from New Hampshire, 

arsenic concentrations ranged from <0.01 to 180 μg/L in the 793 households tested. More than 10% of 

the private wells had arsenic concentrations >10 μg/L, and 2.5% had levels >50 μg/L (Karagas et al. 

1998). In New Hampshire, 992 randomly selected household water samples were analyzed for arsenic 

levels and the results for domestic well users were compared with those for users of municipal water 

supplies (Peters et al. 1999). The concentrations ranged from <0.0003 to 180 μg/L, with water from 

domestic wells containing significantly more arsenic than water from municipal supplies; the median 

concentration of the former was about 0.5 μg/L and the latter was 0.2 μg/L. None of the municipal 

supplies exceeded an arsenic concentration of 50 μg/L, and 2% of the domestic wells were found to have 

arsenic concentrations that exceeded 50 μg/L. Approximately 2% of the municipal water users have 

water with arsenic levels exceeding 10 μg/L compared with 13% of domestic wells. Twenty-five percent 

of domestic wells and 5% of municipal supplies were found to have arsenic concentrations exceeding 

2 μg/L. The highest arsenic levels in New Hampshire are associated with bedrock wells in the south 

eastern and south central part of the state (Peters et al. 1999). In a study of arsenic in well water supplies 

in Saskatchewan, Canada, 13% of samples were >20 μg/L and one sample exceeded 100 μg/L (Thompson 

et al. 1999). It was noted that the samples with high arsenic levels were derived from sites that were in 

near proximity to each other, indicating the presence of ‘hot spots’ with similar geological characteristics. 

As part of an epidemiological study, Engel and Smith (1994) investigated the levels of arsenic in drinking 
ARSENIC 342 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-3. Regional Occurrence of Arsenic in U.S. Water Sources and Finished 

Drinking Water 

Arsenic concentration in μg/L 

Geographical region <1 1–5 5–20 >20 

Occurrence in U.S. surface water sources 

Region 1. New England 50 50 0 0 

Region 2. Mid-Atlantic 84 12 4 0 

Region 3. South East 93 7 0 0 

Region 4. Midwest 24 76 0 0 

Region 5. South Central 32 55 13 0 

Region 6. North Central 33 22 33 0 

Region 7. Western 42 58 0 0 

Occurrence in U.S. groundwater sources 

Region 1. New England 71 21 7 0 

Region 2. Mid-Atlantic 81 4 11 4 

Region 3. South East 82 14 2 0 

Region 4. Midwest 40 40 15 5 

Region 5. South Central 68 27 15 0 

Region 6. North Central 30 40 30 0 

Region 7. Western 24 34 28 14 

Occurrence in U.S. finished surface water supplies 

Region 1. New England 88 12 0 0 

Region 2. Mid-Atlantic 92 8 0 0 

Region 3. South East 100 0 0 0 

Region 4. Midwest 73 27 0 0 

Region 5. South Central 74 19 7 0 

Region 6. North Central 44 44 0 12 

Region 7. Western 42 58 0 0 

Occurrence in U.S. finished groundwater supplies 

Region 1. New England 79 21 0 0 

Region 2. Mid-Atlantic 81 4 11 4 

Region 3. South East 94 4 2 0 

Region 4. Midwest 58 27 12 3 

Region 5. South Central 61 27 12 0 

Region 6. North Central 40 50 10 0 

Region 7. Western 20 40 22 12 

Source: National Arsenic Occurrence Survey (Frey and Edwards 1997) 
ARSENIC 343 

6. POTENTIAL FOR HUMAN EXPOSURE 

water throughout the United States between 1968 and 1984. They found that 30 counties in 11 states had 

mean arsenic levels of >5 μg/L, with a range of 5.4–91.5 μg/L; 15 counties had mean levels from 5 to 

10 μg/L; 10 counties had mean levels from 10 to 20 μg/L; and 5 counties had levels >20 μg/L. The 

highest levels were found in Churchill County, Nevada, where 89% of the population was exposed to a 

mean arsenic concentration of 100 μg/L and 11% to a mean of 27 μg/L. A study by Frost et al. (2003) 

identified 33 counties from 11 states in which the average arsenic concentration of at least 75% of public 

wells was >10 μg/L. Arsenic concentrations in drinking water from these counties ranged from 10.3 to 

90.0 μg/L in Pinal, Arizona and Churchill, Nevada, respectively (Frost et al. 2003). 

Many communities have high levels of arsenic in their drinking water because of contamination or as a 

result of the geology of the area. In Millard County, Utah, seven towns had median and maximum 

arsenic levels of 18.1–190.7 and 125–620 μg/L, respectively, in their drinking water (Lewis et al. 1999). 

The mean arsenic concentration in tap water from homes in Ajo, Arizona, about 2 miles from an open pit 

copper mine and smelter was 90 μg/L (Morse et al. 1979). The town’s water was supplied from five deep 

wells. 

Countries such as Mexico, Bangladesh, India, Chile, Argentina, and Vietnam have highly elevated levels 

of arsenic in drinking water in some regions (Bagla and Kaiser 1996; Berg et al. 2001; Tondel et al. 1999; 

WHO 2001; Wyatt et al. 1998a, 1998b). In Bangladesh and West Bengal, the soil naturally contains high 

levels of arsenic, which leaches into the shallow groundwater that is tapped for drinking water. In West 

Bengal, India, it is estimated that more than one million Indians are drinking arsenic-laced water and tens 

of millions more could be at risk in areas that have not been tested for contamination. Analysis of 

20,000 tube-well waters revealed that 62% have arsenic at levels above the World Health Organization 

(WHO) permissible exposure limit (PEL) in drinking water of 10 μg/L, with some as high as 3,700 μg/L 

(Bagla and Kaiser 1996). Analysis of 10,991 and 58,166 groundwater samples from 42 and 9 arsenicaffected districts in Bangladesh and West Bengal were found to have arsenic levels that were 59 and 34%, 

respectively, above 50 μg/L (Chowdhury et al. 2000). Berg et al. (2001), studied the arsenic 

contamination of the Red River alluvial tract in Hanoi, Vietnam and the surrounding rural areas. Arsenic 

concentrations in groundwater from private small-scale tube-wells averaged 159 μg/L, ranging from 1 to 

3,050 μg/L. Arsenic concentrations ranged from 37 to 320 μg/L in raw groundwater pumped from the 

lower aquifer for the Hanoi water supply (Berg et al. 2001). Several investigators have noticed a 

correlation between high levels of arsenic and fluoride in drinking water (Wyatt et al. 1998a, 1998b). 

Arsenic concentrations in drinking water from four villages in Bangladesh ranged from 10 to 2,040 μg/L 

(Tondel et al. 1999). 
ARSENIC 344 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.4.3 Sediment and Soil 

Arsenic is widely distributed in the Earth's crust, which contains about 3.4 ppm arsenic (Wedepohl 1991). 

It is mostly found in nature minerals, such as realgar (As4S4), orpiment (As2S3), and arsenolite (As2O3), 

and only found in its elemental form to a small extent. There are over 150 arsenic-bearing minerals 

(Budavari et al. 2001; Carapella 1992). Arsenic concentrations in soils from various countries can range 

from 0.1 to 50 μg/g and can vary widely among geographic regions. Typical arsenic concentrations for 

uncontaminated soils range from 1 to 40 μg/g, with the lowest concentrations in sandy soils and soils 

derived from granites. Higher arsenic concentrations are found in alluvial soils and soils with high 

organic content (Mandal and Suzuki 2002). Arsenic in soil may originate from the parent materials that 

form the soil, industrial wastes, or use of arsenical pesticides. Geological processes that may lead to high 

arsenic concentrations in rock and subsequently the surrounding soil include hydrothermic activity and 

pegmatite formation (Peters et al. 1999). In the first case, thermal activity results in the dissolution and 

transport of metals, including the metalloid arsenic, which are precipitated in fractures in rocks. In the 

second process, cooling magmas may concentrate metals that are injected into rocks, crystallizing as 

pegmatites. Areas of volcanic activity include large areas of California, Hawaii, Alaska, Iceland, and 

New Zealand. 

The U.S. Geological Survey reports the mean and range of arsenic in soil and other surficial materials as 

7.2 and <0.1–97 μg/g, respectively (USGS 1984). The concentrations of arsenic in 445 Florida surface 

soils ranged from 0.01 to 50.6 μg/g (Chen et al. 1999). The median, arithmetic mean, and geometric 

mean were 0.35, 1.34±3.77, and 0.42±4.10 μg/g, respectively. Chirenje et al. (2003b) reported a 

geometric mean arsenic concentrations of 0.40 (0.21–660) and 2.81 (0.32–110) μg/g in surface soil 

samples (0–20 cm) collected in May–June 2000 from Gainesville and Miami, Florida, respectively. The 

geometric mean arsenic concentration in 50 California soils was 2.8 μg/g (Chen et al. 1999). In the 

Florida surface soils, arsenic was highly correlated (α=0.0001) with the soil content of clay, organic 

carbon, CEC, total iron, and total aluminum. Arsenic tends to be associated with clay fractions and iron 

and manganese oxyhydroxides. Soils of granitic origin are generally low in arsenic, about 4 μg/g, 

whereas arsenic in soils derived from sedimentary rocks may be as high as 20–30 μg/g (Yan-Chu 1994). 

Soils overlying arsenic-rich geologic deposits, such as sulfide ores, may have soil concentrations two 

orders of magnitude higher (NAS 1977a). 
ARSENIC 345 

6. POTENTIAL FOR HUMAN EXPOSURE 

Soils in mining areas or near smelters may contain high levels of arsenic. Arsenic concentrations up to 

27,000 μg/g were reported in soils contaminated with mine or smelter wastes (EPA 1982b). Soils at an 

abandoned mining site in the Tamar Valley in southwest England have arsenic concentrations that may 

exceed 50,000 μg/g (Erry et al. 1999). The average arsenic levels in the top 2 cm of different soil types in 

the vicinity of a former copper smelter in Anaconda, Montana, ranged from 121 to 236 μg/g; levels were 

significantly related to proximity and wind direction to the smelter site (Hwang et al. 1997a). Smelter 

fallout can contaminate land miles from the source. Soils in mainland southern King County were studied 

for the presence of arsenic and lead (WSDOE 2005). Soil samples were collected in the fall of 1999 and 

the spring of 2001 from locations around the ASARCO smelter, which operated in Ruston from the 1890s 

to 1986. The study area ran roughly from the I-90 corridor south to the King-Pierce county line, from the 

Puget Sound shore to the Cascade foothills. Almost all of the contamination was found was in the 0– 

6-inch depths of the cores samples; 62 of the 75 samples were found to have arsenic levels above 20 ppm 

(WSDOE 2005). 

Soil on agricultural lands treated with arsenical pesticides may retain substantial amounts of arsenic. One 

study reported an arsenic concentration of 22 μg/g in treated soil compared to 2 μg/g for nearby untreated 

soil (EPA 1982b). Arsenic was measured in soil samples taken from 10 potato fields in Suffolk County 

on Long Island, New York, where sodium arsenite had been used for vine control and fall weed control 

for many years. Lead arsenate also may have been used as an insecticide in certain areas. The mean 

arsenic levels taken at a depth of 0–18 cm from each of the 10 fields ranged from 27.8±5.44 μg/g dry 

weight (n=10) to 51.0±7.40 μg/g dry weight (n=10). These levels were markedly higher than the level of 

2.26±0.33 μg/g (n=10) for untreated control soils (Sanok et al. 1995). A survey was conducted in 1993 to 

determine the concentrations of arsenic and lead in soil samples from 13 old orchards in New York State. 

Lead arsenate was used for pest control in fruit orchards for many years, mainly from the 1930s to 1960s, 

and residues remain in the soil. Concentrations of arsenic ranged from 1.60 to 141 μg/g dry weight 

(Merwin et al. 1994). Arsenic and lead concentrations were also measured in former orchard soils 

contaminated by lead arsenate from the Hanford site in Washington State. The mean arsenic 

concentration in surface (5–10 cm) and subsurface (10–50 cm) soils were 30 (2.9–270) and 74 (32– 

180) μg/g dry weight, respectively (Yokel and Delistraty 2003). Average arsenic concentration of 5.728, 

5.614, and 6.746 μg/g were reported in soils, lake sediments, and wetland sediments, respectively, from 

Moon Lake, a Mississippi River alluvial floodplain in northwest Mississippi. Intensive cultivation has 

occurred in this area, including cotton, soybeans, and rice (Cooper and Gillespie 2001). A geometric 

mean arsenic concentration of 20.6 mg/kg (range 4.6–340 mg/kg) was reported soil collected during the 
ARSENIC 346 

6. POTENTIAL FOR HUMAN EXPOSURE 

summer and fall of 2003 from 85 homes in Middleport, New York, where historical pesticide 

manufacturing was associated with arsenic in the soil (Tsuji et al. 2005). 

The Washington State Area-wide Soil Contamination Project provides various data on arsenic 

contamination in soils across Washington State (Washington State 2006). Arsenic concentrations within 

areas affected by area-wide soil contamination are highly variable, ranging from natural background 

levels to >3,000 ppm in smelter areas. Generally, average arsenic concentrations in soil at developed 

properties are <100 ppm. Areas affected by smelter emissions in King, Pierce, Snohomish, and Stevens 

Counties have a higher likelihood of arsenic soil contamination than other areas of the State due to 

historical emissions from metal smelters located in Tacoma, Harbor Island, Everett, Northport, and Trail, 

British Columbia. Areas where apples and pears were historically grown, such as Chelan, Spokane, 

Yakima, and Okanogan Counties, also have a higher likelihood of arsenic soil contamination than other 

areas due to the past use of lead arsenate pesticides. Generally, arsenic contamination in soils from 

historical smelter emissions and historical use of lead-arsenate pesticides is found in the upper 6– 

18 inches of soil (Washington State 2006). 

The New Jersey Department of Environmental Protection (Historic Pesticide Contamination Task Force 

1999) reported on the analysis of soil samples collected from 18 sites for various pesticide residues, 

including arsenic, from current and former agricultural sites in New Jersey in order to assess 

contamination from historic pesticide use. Arsenic was detected in all 463 samples, with concentrations 

ranging from 1.4 to 310 ppm. 

Natural concentrations of arsenic in sediments are usually <10 μg/g dry weight, but can vary widely 

around the world (Mandal and Suzuki 2002). Sediment arsenic concentrations reported for U.S. rivers, 

lakes, and streams range from about 0.1 to 4,000 μg/g (Eisler 1994; Heit et al. 1984; NAS 1977a; Welch 

et al. 1988). During August through November 1992 and August 1993, bed sediment in the South Platte 

River Basin (Colorado, Nebraska, and Wyoming) was sampled and analyzed for 45 elements, including 

arsenic. The range of arsenic found was 2.8–31 μg/g dry weight and the geometric mean (n=23) was 

5.7 μg/g (Heiny and Tate 1997). The arsenic concentration in surface sediment (0–2 cm) at 43 sites in the 

Indian River Lagoon System in Florida ranged from 0.6 to 15 μg/g dry weight with a mean of 

5.0±3.9 μg/g (Trocine and Trefry 1996). Arsenic levels were well correlated with those of aluminum. 

Correlation with aluminum levels is used to normalize sediment level concentrations to natural levels in 

Florida estuaries. Surficial sediments collected from 18 locations in 3 major tributaries to Newark Bay, 

New Jersey, were analyzed for 7 toxic metals, including arsenic (Bonnevie et al. 1994). The highest 
ARSENIC 347 

6. POTENTIAL FOR HUMAN EXPOSURE 

concentrations of arsenic were found in the Rahway River adjacent to a chemical plant, 58 μg/g dry 

weight, and in the Hackensack River adjacent to a coal-fired power plant, 49 μg/g. The average arsenic 

concentration for all sediments was 17±16 μg/g. Sediments collected from seven sites in Baltimore 

Harbor, Maryland, at five seasonal periods between June 1987 and June 1988 had a geometric mean 

maximum of 7.29 μg/g dry weight and a geometric mean minimum of 1.25 μg/g (Miles and Tome 1997). 

This harbor is one of two sub-tributaries of the Chesapeake Bay where contaminants have been 

discharged on a large scale. 

The upper Clark Fork River basin in western Montana is widely contaminated by metals from past 

mining, milling, and smelting activities. In a 1991 study, arsenic levels were determined in sediment 

along the river and in a reservoir 205 km downstream. Total arsenic in sediments from Clark Fork River 

decreased from 404 μg/g dry weight at the farthest upstream sampling station to 11 μg/g, 201 km 

downstream. Sediment samples from the Milltown Reservoir had arsenic concentrations ranging from 

6 to 56 μg/g (Brumbaugh et al. 1994). Total recoverable arsenic in nonfiltered pore water from the Clark 

Fork River decreased from 1,740 μg/L at the farthest upstream sampling station to 31 μg/L at the 201 km 

station (Brumbaugh et al. 1994). The Coeur d’Alene river basin in northern Idaho has been contaminated 

with heavy metals from mining and smelting operations since 1885 (Farag et al. 1998). A 1994 study 

determined the metal content of sediment, biofilm, and invertebrates at 13 sites in the basin, 10 with 

historic mining activity and 3 reference sites. The mean arsenic levels in sediment at the mining sites 

ranged from 8.3 to 179.0 μg/g dry weight, compared to 2.4–13.1 μg/g dry weight at the reference sites. 

The mean arsenic levels in biofilm adhering to rock in the water at the mining sites ranged from 7.5 to 

155.8 μg/g dry weight, compared to 7.2–27.3 μg/g dry weight at the reference sites. In Whitewood Creek, 

South Dakota, where as much as 100 million tons of mining and milling waste derived from gold mining 

activities were discharged between 1876 and 1977, mean and maximum sediment arsenic concentrations 

were 1,920 and 11,000 μg/g, respectively (USGS 1987). Uncontaminated sediment had mean arsenic 

levels of 9.2 μg/g. Arsenic concentrations in surface (0–5 cm) sediments from watersheds in Black Hills, 

South Dakota, an area impacted by gold mining activities, ranged from 23 to 1,951 μg/g dry weight; 

concentrations from reference areas ranged from 10 to 58 μg/g dry weight (May et al. 2001). Swan Lake, 

a sub-bay of Galveston Bay in Texas is a highly industrial area that received runoff from a tin smelter in 

the 1940s and 1950s. Surface sediments at 17 sites where oysters and mussels were collected ranged 

from 4.53 to 103 μg/g (Park and Presley 1997). A site in the channel leading from the old smelter had 

arsenic levels of 568 μg/g. Surface sediment was less contaminated than deeper sediment, indicating less 

arsenic input recently than in the past as a result of the smelter closing. 
ARSENIC 348 

6. POTENTIAL FOR HUMAN EXPOSURE 

It has been suggested that the wood preservative most commonly used in dock pilings and bulkheads, 

CCA, can be toxic to estuarine organisms. Wendt et al. (1996) measured arsenic in surface sediments and 

oysters from creeks with high densities of docks and from nearby reference creeks with no docks. The 

average concentrations in the sediments ranged from 14 to 17 μg/g throughout the study area, which is 

within the range of natural background levels. Weis et al. (1998) sampled sediments along a 10-m 

transect from CCA-treated wood bulkheads from four Atlantic coast estuaries. Arsenic concentrations 

were highest in the fine-grained portion of the sediments near the CCA-treated bulkhead (0–1 m); arsenic 

concentrations were generally at reference levels at distances >1 m from the bulkheads (Weis et al. 1998). 

Soils below and around play structures constructed from CCA-treated wood in the City of Toronto, 

Canada were sampled and analyzed for inorganic arsenic (Ursitti et al. 2004). A mean arsenic 

concentration of 2.1 μg/g (range 0.5–10 μg/g) was reported in soil samples taken within 1 m of the CCAtreated wood for all play structures. Soil samples that were collected 10 m from the play structures served 

as a background had arsenic concentration of 2.4 μg/g (range 0.5–13 μg/g). A mean arsenic concentration 

of 6.2 μg/g (range 0.5–47.5 μg/g) was reported in soil samples taken below CCA-treated wood for all play 

structures. Of the 217 play structures in the study, 32 had arsenic concentrations under the play structures 

that exceeded the Canadian federal soil guidelines with arsenic concentrations ranging from 12.4 to 

47.5 μg/g. From this study, the authors concluded that arsenic does not migrate laterally, but does 

accumulate in soil under elevated platforms constructed from CCA-treated wood (Ursitti et al. 2004). 

6.4.4 Other Environmental Media 

Low levels of arsenic are commonly found in food; the highest levels are found in seafood, meats, and 

grains. Typical U.S. dietary levels of arsenic in these foods range from 0.02 mg/kg in grains and cereals 

to 0.14 mg/kg in meat, fish, and poultry (Gartrell et al. 1986). Shellfish and other marine foods contain 

the highest arsenic concentrations and are the largest dietary source of arsenic (Gunderson 1995a; Jelinek 

and Corneliussen 1977; Tao and Bolger 1999). Arsenic levels in various fish and shellfish are presented 

in Table 6-4. In the U.S. Food and Drug Administration (FDA) Total Diet Study, 1991–1997, seafood 

contained the highest levels of arsenic, followed by rice/rice cereal, mushrooms, and poultry. 

Concentrations in canned tuna (in oil), fish sticks, haddock (pan-cooked), and boiled shrimp were 0.609– 

1.470, 0.380–2.792, 0.510–10.430, and 0.290–2.681 mg/kg, respectively (Tao and Bolger 1999). 

Typically, arsenic levels in foods in the Total Diet Study, 1991–1996 were low, <0.03 mg/kg; only 63 of 

the 264 foods contained arsenic above this level. Similar results were reported in the Total Diet Study, 
ARSENIC 349 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-4. Levels of Arsenic in Fish and Shellfish—Recent Studies 

Arsenic concentrationa 

Sample type (μg/g) Comments Reference 

Yellowtail flounder 

 Muscle (n=8) 

 Liver (n=6) 

 Gonad (n=6) 

Marine organisms 

Ray (n=8) 

Cod (n=8) 

Plaice (n=8) 

Sole (n=8) 

Sea-bream (n=8) 

Mussell (n=8) 

Bluefin tuna (Thunnus thynus) 

(n=14) 

Fish 

Bottom feeding (n=2,020) 

Predatory (n=12) 

Oysters 

<1 m from docks (n=10) 

>10 m from docks (n=10) 

Reference (no docks) 

(n=10 

Clams (n=22) 

Marine organisms 

Snails 

 Blue crab 

Fish 

Shrimp 

 Whole crab 

Oysters (n=10, pooled) 

Mussels (n=7, pooled) 

Marine organisms 

 Blue crab 

Fish 

Oysters, two areas 

n=78, pooled

n=874, pooled

Samples collected from Hellou et al. 1998 

8–37 Northwest Atlantic 1993 

7–60 

1.2–9.4 

Belgian fish markets in Buchet and Lison 

16.4 1991; inorganic arsenic 1998 

4.7 ranged from 0.003 to 

0.2 μg/g 19.8 

5.1 

2.4 

3.5 

3.2 Virgin Rocks, Grand Banks Hellou et al. 1992 

of Newfoundland, Canada, 

1990 

National Contaminant Kidwell et al. 1995 

0.16±0.23 wet weight Biomonitoring Program, 

0.16±0.140 wet weight 1984–1985, 112 stations 

South Carolina, private Wendt et al. 1996 

8.3±1.1 residential docks on tidal 

7.6±0.9 creeks, 1994 

8.4±1.3 

12±1.1 Indian River Lagoon, Trocine and Trefry 

Florida, 22 sites, 1990 1996 

Swan Lake, Galveston Bay, Park and Presley 

13.3±17.0 Texas, 1993 1997 

6.61 

0.82 

1.37±0.64 

5.35±2.51 

7.28±1.32 

7.75±2.15 

GPNEP, 1992, Galveston Park and Presley 

2.31±2.15 Bay, Texas 1997 

2.46 

NOAA NS&T Program, Park and Presley 

1986–1990 1997 

4.50±1.08 Galveston Bay 

9.67±7.00 Gulf of Mexico 
ARSENIC 350 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-4. Levels of Arsenic in Fish and Shellfish—Recent Studies 

Arsenic concentrationa 

Sample type (μg/g) Comments Reference 

Marine crustaceans 

Parapenaeus longirostris 

(pink shrimp) (n=826, 

10 pools 

Aristeus antennatus (red 

shrimp) (n=387, 8 pool) 

Plesionika martia (shrimp) 

(n=456, 7 pools) 

Nephrops norvegicus 

(Norway lobster) (n=270, 

5 pools) 

Freshwater fish

 Sabalo (Brycon 

melanopterus) (n=3) 

 Huazaco (Hoplias 

malabaracus) (n=4) 

 Bagre (Pimelodus ornatus) 

(n=8) 

 Boquichio (Prochilodus 

nigricans) (n=1) 

 Doncello (Pseudoplatystoma sp.) (n=1) 

Freshwater fish 

Bowfin (n=59) 

Bass (n=47) 

Channel catfish (n=50) 

Chain pickerel (n=19) 

Yellow perch (n=51) 

Black crappie (n=52) 

American eel (n=24) 

Shellcracker n=52) 

Bluegill (n=52) 

 Redbreast (n=43) 

Spotted sucker (n=35) 

34.84±19.21 

(12.01–62.60) 

17.09±3.49 

(10.45–20.82) 

40.82±2.50 

(36.37–44.06) 

43.48±14.21 

(35.63–69.15) 

0.015–0.101 

nd–0.005 

nd–0.201 

0.063 

0.055 

0.32±0.04 wet weight 

0.03±0 wet weight 

0.09±00.02 wet weight 

0.05±0.01 wet weight 

0.05±0.01 wet weight 

0.04±0.01 wet weight 

0.04±0.01 wet weight 

0.06±0 wet weight 

0.05±0.02 wet weight 

0.07±0.01 wet weight 

0.03±0 wet weight 

Commercial crustaceans Storelli and 

from the Mediterranean Marcotrigiano 2001 

Sea (Italy) 

Fish samples (muscle) Gutleb et al. 2002 

were collected in August 

1997 from the Candamo 

River, Peru; a pristine 

rainforest valley prior to the 

start of oil-drilling activities 

Savannah River, along and Burger et al. 2002 

below the Department of 

Energy’s Savannah River 

Site (SRS); samples 

analyzed were edible fillets 
ARSENIC 351 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-4. Levels of Arsenic in Fish and Shellfish—Recent Studies 

Arsenic concentrationa 

Sample type (μg/g) Comments Reference 

Horseshoe crabs 

Apodeme (n=74) 7.034±0.65 wet weight Overall mean in tissues of Burger et al. 2003 

Egg (n=63) 

Leg (n=74) 

5.924±0.345 wet weight 

14.482±0.685 wet 

crabs collected from New 

Jersey in 2000 

weight 

Apodeme (n=40) 7.513±0.835 wet weight Overall mean in tissues of 

Egg (n=35) 

Leg (n=40) 

6.766±0.478 wet weight 

18.102±1.489 wet 

crabs collected from 

Delaware in 2000 

weight 

a

Concentrations are means±standard deviation, unless otherwise stated. Concentrations are in a dry weight basis, 

unless otherwise stated. 

GM = geometric mean; GPNEP = Galveston Bay National Estuary Program; nd = not detected; 

NOAA NS&T = National Oceanic and Atmospheric Administration National Status and Trends 
ARSENIC 352 

6. POTENTIAL FOR HUMAN EXPOSURE 

1991–1997, where the mean arsenic concentration in all foods was 0.036 mg/kg dry weight and arsenic 

was not detectable in about 88% of the foods and was detected at trace levels in another 7.8% of foods. 

The foods with the highest mean arsenic levels were haddock, canned tuna, fish sticks, shrimp, and fish 

sandwiches, with arsenic concentrations ranging from 5.33 to 0.568 mg/kg dry weight (Capar and 

Cunningham 2000). Nriagu and Lin (1995) analyzed 26 brands of wild rice sold in the United States and 

found arsenic levels ranging from 0.006 to 0.142 μg/g dry weight. Arsenic concentrations ranging from 

0.05 to 0.4 μg/g are typically reported for rice from North America, Europe, and Taiwan (Meharg and 

Rahman 2003). 

During a comprehensive total diet study extending from 1985 to 1988, foods were collected in six 

Canadian cities and processed into 112 composite food samples (Dabeka et al. 1993). The mean, median, 

and range of total arsenic in all samples were 0.0732, 0.0051, and <0.0001–4.840 μg/g, respectively. 

Food groups containing the highest mean arsenic levels were fish (1.662 μg/g), meat and poultry 

(0.0243 μg/g), bakery goods and cereals (0.0245 μg/g), and fats and oils (0.0190 μg/g). Of the individual 

samples, marine fish had the highest arsenic levels, with a mean of 3.048 μg/g for the cooked composites 

and 2.466 μg/g for the raw samples. Canned fish (1.201 μg/g) and shellfish (2.041 μg/g) also contained 

high means. Cooked poultry, raw mushrooms, and chocolate bars contained 0.100, 0.084, and 

0.105 μg/g, respectively. 

National monitoring data from the Food Safety and Inspection Service National Residue Program (NRP) 

(1994–2000) found that the mean total arsenic concentration in livers of young chickens ranged from 

0.33 to 0.43 μg/g, with an overall mean of 0.39 μg/g (Lasky et al. 2004). The mean arsenic 

concentrations in liver for mature chickens, turkeys, hogs, and all other species over the same time period 

ranged from 0.10 to 0.16 μg/g. Lasky et al. (2004) used the NRP arsenic data in livers of young chickens 

to estimate the concentrations of arsenic in muscle tissue, the most commonly consumed part of the 

chicken. Assuming that 65% of the arsenic in poultry and meat is inorganic, at a mean level of chicken 

consumption of 60 g/person/day, people may ingest an estimated 1.38–5.24 μg/day of inorganic arsenic 

from chicken. 

A Danish study (Pedersen et al. 1994) reports the arsenic levels in beverages as the mean (range) in μg/L 

as follows: red wine, 9 (<2–25); white wine, 11 (<2–33); fortified wine, 5 (<2–11); beer, 7 (4–11); soft 

drinks, 3 (<2–8); miscellaneous juices, 8 (3–13); instant coffee, 4 (0.7–7); and instant cocoa, 5.6 (1.6– 

12.8). 
ARSENIC 353 

6. POTENTIAL FOR HUMAN EXPOSURE 

In a study of dietary arsenic exposure in the Indigenous Peoples of the western Northwest Territories, 

Canada, fish contained the highest arsenic concentrations in foods consumed by the Dene and Métis 

populations with the highest concentration, 1.960 μg/g, found in smoked/dried cisco (fish). Other foods 

derived from land mammals, birds, and plants contained lower arsenic concentrations. A mean arsenic 

intake of <1.0 μg/kg/day was reported for this population (Berti et al. 1998). 

The general consensus in the literature is that about 85–>90% of the arsenic in the edible parts of marine 

fish and shellfish is organic arsenic (e.g., arsenobetaine, arsenochloline, dimethylarsinic acid) and that 

approximately 10% is inorganic arsenic (EPA 2003b). However, the inorganic arsenic content in seafood 

may be highly variable. For example, a study in the Netherlands reported that inorganic arsenic 

comprised 0.1–41% of the total arsenic in seafood (Vaessen and van Ooik 1989). Buchet et al. (1994) 

found that, on the average, 3% of the total arsenic in mussels was inorganic in form. Some commercially 

available seaweeds, especially brown algae varieties, may have high percentages of the total arsenic 

present as inorganic arsenic (>50%) (Almela et al. 2002; Laparra et al. 2003). Arsenic concentrations 

ranging from 17 to 88 mg/kg dry weight were found in commercially available seaweeds (van Netten et 

al. 2000). Other arsenic compounds that may be found in seafood are arsenic-containing ribose 

derivatives called arsenosugars. Arsenosugars are the common organoarsenicals found in marine algae; 

they are also found in mussels, oysters, and clams (Le et al. 2004). Less information about the forms of 

arsenic in freshwater fish is known at this time (EPA 2003b). 

Schoof et al. (1999a) reported on the analysis of 40 commodities anticipated to account for 90% of dietary 

inorganic arsenic intake. In this study, the amount of inorganic arsenic was measured in these foods. 

Consistent with earlier studies, total arsenic concentrations were highest in the seafood sampled (ranging 

from 160 ng/g in freshwater fish to 2,360 ng/g in marine fish). In contrast, average inorganic arsenic in 

seafood ranged from <1 to 2 ng/g. The highest inorganic arsenic concentrations were found in raw rice 

(74 ng/g), followed by flour (11 ng/g), grape juice (9 ng/g), and cooked spinach (6 ng/g). 

Tobacco contains an average arsenic concentration of 1.5 ppm, or about 1.5 μg per cigarette (EPA 1998j). 

Before arsenical pesticides were banned, tobacco contained up to 52 mg As/kg, whereas after the ban, 

maximum arsenic levels were reduced to 3 μg/g (Kraus et al. 2000). An international literature survey 

reports arsenic yields of 0–1.4 μg/cigarette for mainstream (inhaled) cigarette smoke (Smith et al. 1997). 

The wide range of arsenic yields for flue-cured cigarettes suggests that the field history, soil, and fertilizer 

conditions under which the tobacco is grown will affect the arsenic concentration (Smith et al. 1997). 
ARSENIC 354 

6. POTENTIAL FOR HUMAN EXPOSURE 

Arsenic emission factors of 0.015–0.023 μg/cigarette (mean 0.018±0.003 μg/cigarette) have been 

measured for sidestream smoke from a burning cigarette (Landsberger and Wu 1995). 

A median arsenic concentration of 2.1 μg/g and a deposition rate of 0.008 μg/m2

/day was reported in 

house dust in homes evaluated as part of the German Environmental Survey in 1990–1992. A mean 

arsenic concentration of 7.3 μg/g was reported in house dust from 48 residences in Ottawa, Canada (Butte 

and Heinzow 2002). These arsenic concentrations are expected to be representative of background levels. 

In general high arsenic concentrations were found in household dust collected from homes in areas with 

known arsenic contamination. Mean arsenic concentrations of 12.6 (2.6–57) and 10.8 (1.0–49) μg/g were 

reported in house dust collected from the entryway and child play areas, respectively, from homes in a 

community in Washington State with a history of lead arsenate use (Wolz et al. 2003). Arsenic was 

detected in all 135 indoor floor dust samples collected as part of the NHEXAS from Arizona mining 

communities, ranging from 0.3–50.6 μg/g, (O'Rourke et al. 1999). A geometric mean arsenic 

concentration of 10.8 μg/g (range 1.0–172 μg/g) was reported in house dust from 96 homes in Middleport, 

New York, with historical pesticide manufacture, collected during the summer and fall of 2003 (Tsuji et 

al. 2005). 

Arsenic has also been detected in several homeopathic medicines at concentrations up to 650 μg/g (Kerr 

and Saryan 1986). Some Asian proprietary medicines that are manufactured in China, Hong Kong, and 

other Asian countries have been reported to contain levels of inorganic arsenic ranging from 25 to 

107,000 μg/g (Chan 1994). Fifty medicinally important leafy samples that were analyzed for elemental 

concentrations contained arsenic at levels ranging from 0.12 to 7.36 μg/g, with a mean of 2.38±1.2 μg/g 

(Reddy and Reddy 1997). Arsenic concentrations ranged from 0.005 to 3.77 μg/g in 95 dietary 

supplements purchased from retail stores in the Washington, DC area in 1999 (Dolan et al. 2003). 

Commercially available samples of Valarian, St. John's Wort, Passion Flower, and Echinacea were 

purchased in the United States and analyzed for various contaminants; arsenic concentrations were 

0.0016–0.0085, 0.0065–0.017.8, 0.0024–0.0124, and 0.0021–0.0102 μg/g, respectively, in these samples 

(Huggett et al. 2001). Concentrations of heavy metals including the metalloid arsenic were evaluated in 

54 samples of Asian remedies that were purchased in stores in Vietnam and Hong Kong that would be 

easily accessible to travelers, as well as in health food and Asian groceries in Florida, New York, and 

New Jersey. Four remedies were found to contain daily doses exceeding 0.1 mg. Two of these contained 

what would have been a potentially significant arsenic dose, with daily doses of 16 and 7.4 mg of arsenic 

(Garvey et al. 2001). 
ARSENIC 355 

6. POTENTIAL FOR HUMAN EXPOSURE 

The possible presence of toxic compounds in waste materials has raised concerns about the fate of these 

compounds either during the composting process or when the composted product is applied to soils. 

Three waste compost products generated at the Connecticut Agricultural Experiment Station had arsenic 

levels of 12.8, 9.8, and 13 μg/g dry weight, respectively (Eitzer et al. 1997). The arsenic levels in 

municipal solid waste composts from 10 facilities across the United States ranged from 0.9 to 15.6 μg/g 

dry weight with a mean of 6.7 μg/g (He et al. 1995). These are lower than the EPA 503 regulatory limit 

for arsenic of 41 μg/g for agricultural use of sewage sludge (EPA 1993b). Concentrations of arsenic in 

U.S. sewage sludges, which are sometimes spread on soil, were <1 μg/g. Arsenic is a common impurity 

in minerals used in fertilizers. A comprehensive Italian study found that the arsenic content in a number 

of mineral and synthetic fertilizers ranged from 2.2 to 322 mg/kg with a sample of triple superphosphate 

having the highest level (Senesi et al. 1999). Arsenic naturally occurs in coal and crude oil at levels of 

0.34–130 and 0.0024–1.63 ppm, respectively, which would account for its presence in flue gas, fly ash, 

and bottom ash from power plants (Pacyna 1987). 

Background arsenic levels in living organisms are usually <1 μg/g wet weight (Eisler 1994). Levels are 

higher in areas with mining and smelting activity or where arsenical pesticides were used. Eisler (1994) 

has an extensive listing of arsenic levels in terrestrial and aquatic flora and fauna from literature sources 

to about 1990. The U.S. Fish and Wildlife Service’s National Contaminant Biomonitoring Program have 

analyzed contaminants in fish at 116 stations (rivers and the Great Lakes) across the United States. The 

geometric mean concentration of arsenic for the five collection periods starting in 1976 were (period, 

concentration wet weight basis): 1976–1977, 0.199 μg/g; 1978–1979, 0.129 μg/g; 1980–1981, 

0.119 μg/g; 1984, 0.106 μg/g; and 1986, 0.083 μg/g (Schmitt et al. 1999). In 1986, the maximum and 

85th percentile arsenic levels were 1.53 and 0.24 μg/g, respectively. The highest concentrations of 

arsenic for all five collection periods were in bloaters from Lake Michigan at Sheboygan, Wisconsin. 

Arsenic levels declined by 50% at this site between 1976–1997 and 1984. The major source of arsenic 

into Lake Michigan was a facility at Marinette, Wisconsin, which manufactured arsenic herbicides. 

Table 6-4 contains arsenic levels in aquatic organisms from more recent studies. The Coeur d’Alene river 

basin in northern Idaho has been contaminated with heavy metals from mining and smelting operations 

since 1885 (Farag et al. 1998). A 1994 study determined the metal content of sediment, biofilm, and 

invertebrates at 13 sites in the basin, 10 with historic mining activity, and 3 reference sites. The mean 

arsenic levels in benthic macroinvertebrates at the mining sites ranged from 2.2 to 97.0 μg/g dry weight, 

compared to 2.1–2.4 μg/g dry weight at the reference sites. A study of aquatic organism in Swan Lake, a 

highly polluted sub-bay of Galveston Bay, Texas showed that arsenic concentrations were in the order 

snail>oyster>crab>shrimp>fish (Park and Presley 1997). In contrast to metals like silver, cadmium, 
ARSENIC 356 

6. POTENTIAL FOR HUMAN EXPOSURE 

copper, and zinc, arsenic concentrations in oysters and mussels were less than in the sediment from which 

they were collected. No significant correlation was found between levels of arsenic in clams in the Indian 

River Lagoon in Florida with those found in sediment or water samples (Trocine and Trefry 1996). Small 

animals living at mining sites ingest more arsenic in their diet and have higher arsenic levels in their 

bodies than those living on uncontaminated sites (Erry et al. 1999). Seasonal variations in both arsenic 

intake and dietary composition may affect the amount of arsenic taken up by the body and transferred to 

predator animals. Tissue arsenic content of wood mice and bank voles living on both arseniccontaminated mining sites and uncontaminated sites were greater in autumn than spring. The lower tissue 

arsenic levels in spring of rodents living on contaminated sites suggest that there is no progressive 

accumulation of arsenic in overwintering animals. 

6.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE 

Exposure to arsenic may include exposure to the more toxic inorganic forms of arsenic, organic forms of 

arsenic, or both. While many studies do not indicate the forms of arsenic to which people are exposed, 

this information may often be inferred from the source of exposure (e.g., fish generally contain arsenic as 

arsenobetaine). Yost et al. (1998) reported that the estimated daily dietary intake of inorganic arsenic for 

various age groups ranged from 8.3 to 14 μg/day and from 4.8 to 12.7 μg/day in the United States and 

Canada, respectively, with 21–40% of the total dietary arsenic occurring in inorganic forms. 

Drinking water may also be a significant source of arsenic exposure in areas where arsenic is naturally 

present in groundwater. While estimates of arsenic intake for typical adults drinking 2 L of water per day 

average about 5 μg/day (EPA 1982c), intake can be much higher (10–100 μg/day) in geographical areas 

with high levels of arsenic in soil or groundwater (see Figure 6-2). It is assumed that nearly all arsenic in 

drinking water is inorganic (EPA 2001). 

In the United States, food intake of arsenic has been estimated to range from 2 μg/day in infants to 

92 μg/day in 60–65-year-old men (see Table 6-5) (Tao and Bolger 1999). The average intake of 

inorganic arsenic are estimated to range from 1.34 μg/day in infants to 12.54 μg/day in 60–65-year-old 

men. Tao and Bolger (1999) assumed that 10% of the total arsenic in seafood was inorganic and that 

100% of the arsenic in all other foods was inorganic. The greatest dietary contribution to total arsenic 

was seafood (76–96%) for all age groups, except infants. For infants, seafood and rice products 

contributed 42 and 31%, respectively. Adult dietary arsenic intakes reported for other countries range 
ARSENIC 357 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-5. Mean Daily Dietary Intake of Arsenic for Selected U.S. Population 

Groups 

Date of study 

Mean daily intake (μg/kg body weight/day) 1984–1986a

 1986–1991b 1991–1997c 

Provisional tolerable daily intake (PTDI)d 2.1 2.1 2.1 

6–11 months 0.82 0.5 0.31 

2 years 1.22 0.81 1.80 

14–16 years, female 0.54 0.36 0.41 

14–16 years, male 0.60 0.39 0.24 

25–30 years, female 0.66 0.44 0.44 

25–30 years, male 0.76 0.51 0.72 

60–65 years, female 0.71 0.46 1.08 

60–65 years, male 0.74 0.48 1.14 

a

Gunderson 1995a b

Gunderson 1995b c

Tao and Bolger 1999 d

No agreement has been reached on a maximum acceptable intake for total arsenic; the FAO/WHO has assigned a 

PTDI for inorganic arsenic of 2.1 μg/kg body weight for adults. Data from FDA studies. FDA does not recommend 

daily intake levels for Arsenic. 
ARSENIC 358 

6. POTENTIAL FOR HUMAN EXPOSURE 

from 11.7 to 280 μg/day (Tao and Bolger 1999). Schoof et al. (1999b) estimated that intake of inorganic 

arsenic in the U.S. diet ranges from 1 to 20 μg/day, with a mean of 3.2 μg/day. In contrast, these 

estimates of inorganic arsenic intakes are based on measured inorganic arsenic concentrations from a 

market basket survey. 

The FDA conducted earlier Total Diet Studies in 1984–1986 and 1986–1991. For the sampling period of 

June 1984 to April 1986, the total daily intake of arsenic from foods was 58.1 μg for a 25–30-year-old 

male with seafood contributing 87% of the total (Gunderson 1995a). For the sampling period from July 

1986 to April 1991, the total daily intake of arsenic from foods was lower, 38.6 μg for a 25–30-year-old 

male. Seafood again was the major source of arsenic, contributing 88% of the total (Gunderson 1995b). 

Results of the two Total Diet Studies for selected population groups are shown in Table 6-5. The Total 

Diet Study for the sampling period from September 1991 to December 1996, shows that arsenic, at 

≥0.03 μg/g, was found in 55 (21%) of the 261–264 foods/mixed dishes analyzed. The highest 

concentrations again were found in seafood, followed by rice/rice cereal, mushrooms, and poultry. The 

estimated total daily intake of arsenic from foods was 56.6 μg for a 25–30-year-old male. Seafood was 

the major contributor, accounting for 88–96% of the estimated total arsenic intake of adults. 

Average daily dietary exposures to arsenic were estimated for approximately 120,000 U.S. adults by 

combining data on annual diet, as measured by a food frequency questionnaire, with residue data for 

table-ready foods that were collected for the annual FDA Total Diet Study. Dietary exposures to arsenic 

were highly variable, with a mean of 50.6 μg/day (range, 1.01–1,081 μg/day) for females and 58.5 μg/day 

(range, 0.21–1,276 μg/day) for males (MacIntosh et al. 1997). Inorganic arsenic intake in 969 men and 

women was assessed by a semi-quantitative food frequency questionnaire in combination with a database 

for total arsenic content in foods and by toenail concentrations of arsenic. The mean estimated average 

daily consumption of inorganic arsenic was 10.22 μg/day with a range of 0.93–104.89 μg/day. An 

assumption of 1.5% of the total arsenic in fish and 20% of the total arsenic in shellfish was inorganic 

arsenic was used in this assessment (MacIntosh et al. 1997). 

During a comprehensive total diet study extending from 1985 to 1988, the estimated daily dietary 

ingestion of total arsenic by the average Canadian was 38.1 μg and varied from 14.9 μg for the 1–4 yearold-age group to 59.2 μg for 20–39-year-old males (Dabeka et al. 1993). Daily intakes of arsenic from 

food by women in the Shiga Prefecture, Japan, were investigated by the duplicate portion method and by 

the market basket method. In 1991 and 1992, the daily intakes determined by the duplicate portion 
ARSENIC 359 

6. POTENTIAL FOR HUMAN EXPOSURE 

method were 206 and 210 μg, respectively. Those determined by the market basket method were 160 and 

280 μg, respectively (Tsuda et al. 1995b). 

Arsenic concentrations in human breast milk have been reported to range from 4 to <10 μg/L in pooled 

human milk samples from Scotland and Finland to 200 μg/L in samples from Antofagasta, Chile, where 

there is a high natural environmental concentration of arsenic (Broomhall and Kovar 1986). The arsenic 

concentration in the breast milk of 35 women in Ismir, Turkey, a volcanic area with high thermal activity 

ranged from 3.24 to 5.41 μg/L, with a median of 4.22 μg/L (Ulman et al. 1998). Sternowsky et al. (2002) 

analyzed breast milk from 36 women from three different regions in Germany. These regions included 

the city of Hamburg, a rural area, Soltau, Lower Saxony, and Munster, the potentially contaminated area. 

Arsenic was not detected (<0.3 μg/L) in 154 of 187 samples, with the highest concentration, 2.8 μg/L, 

found in a sample from the rural area. The geometric means from the three areas were comparable. 

The mean arsenic levels in three groups of cows in the region that grazed on land impacted by lava and 

thermal activity were 4.71, 4.46, and 4.93 μg/L, compared to 5.25 μg/L for cows kept in sheds and fed 

commercial pellet feed and municipal water (Ulman et al. 1998). Mean arsenic concentrations in cow's 

milk ranging from 18.6 to 17.1 μg/L and from 16.7 to 18.0 μg/L were reported for cow's grazing in 

nonindustrial and an industrial regions, respectively, in Turkey (Erdogan et al. 2004). 

A Danish study found that carrots grown in soil containing 30 μg/g of arsenic, which is somewhat above 

the 20 μg/g limit for total arsenic set by Denmark for growing produce, contained 0.014 μg/g fresh weight 

of arsenic, all in the form of inorganic As(III) and As(V) (Helgesen and Larsen 1998). An adult 

consuming 376 grams of vegetables a day (90th percentile) represented solely by carrots would consume 

5.3 μg of arsenic a day. The study concluded that the estimated intake of arsenic from produce grown in 

soil meeting regulatory limits was low compared with other food sources and water. 

If vegetables are grown in planters made of wood treated with CCA, arsenic may leach out of the wood 

and be taken up by the vegetables. In a study by Rahman et al. (2004), arsenic was found to diffuse into 

the soil from the CCA-treated wood, with the highest concentrations found at 0–2 cm from the CCAtreated wood and a steady decline in concentration with increased distance from the wood. Crops grown 

within 0–2 cm of the CCA-treated wood contained higher concentrations of arsenic than those grown at 

1.5 m from the treated wood. However, the concentrations are below U.S. FDA tolerance limits that have 

been set for arsenic in select food items. In addition, food grown in this manner is unlikely to constitute a 

significant part of a person’s diet. 
ARSENIC 360 

6. POTENTIAL FOR HUMAN EXPOSURE 

In 2003, U.S. manufacturers of arsenical wood preservatives began a voluntary transition from CCA to 

other wood preservatives in wood products for certain residential uses, such as play structures, picnic 

tables, decks, fencing, and boardwalks. This phase out was completed on December 31, 2003; wood 

treated prior to this date could still be used and structures made with CCA-treated wood would not be 

affected. CCA-treated wood products continue to be used in industrial applications (EPA 2003a). EPA’s 

Consumer Awareness Program (CAP) for CCA is a voluntary program established by the manufacturers 

of CCA products to inform consumers about the proper handling, use, and disposal of CCA-treated wood. 

Additional information about this program can be found from EPA (2007a). 

The arsenic content in the human body is 3–4 mg and tends to increase with age. Arsenic concentrations 

in most tissues of the human body are <0.3 to 147 μg/g dry weight, excluding hair, nails, and teeth. 

Mammals tend to accumulate arsenic in keratin-rich tissues such as hair and nails. The normal 

concentrations of arsenic range from about 0.08 to 0.25 μg/g in hair, and 0.34 μg/g in nails. The normal 

concentration of arsenic in urine can range from 5 to 40 μg per day (total) (Mandal and Suzuki 2002). 

Table 6-6 contains arsenic levels in various human tissues. 

A German study investigated the transfer of arsenic from the environment to humans in the northern 

Palatine region, a former mining area characterized by high soil levels of arsenic (<2–605 μg/g) in 

residential areas compared to a region in southern lower Saxony with nonelevated levels of arsenic in soil 

(Gebel et al. 1998a). None of the residents were occupationally exposed to arsenic and the arsenic levels 

in drinking water were generally below 0.015 mg/L. The mean levels of arsenic in urine and hair were 

lower in the reference area than in the former mining area (see Table 6-6), although within the mining 

area, there was a slight increase in arsenic levels in hair and arsenic excreted in urine with increasing 

arsenic content in soil. Children in the Palatine region did not have higher contents of arsenic in their hair 

or urine. The most significant factor contributing to elevated levels of arsenic in hair and urine was 

seafood consumption. In the combined population of people living in mining areas containing high levels 

of arsenic in soil and other areas, the level of arsenic in urine was positively associated with the extent of 

seafood consumption. However, the study also showed that seafood consumption does not lead to an 

extreme increase in excretion of arsenic in the urine. There are apparently other, unidentified factors 

affecting the urine levels. Only arsenic in urine, not in hair, was significantly correlated with age. The 

level of arsenic in urine was very slightly, but significantly correlated with the consumption of homegrown produce. Tobacco smoking had no correlation with the arsenic content of either hair or urine 

(Gebel et al. 1998a). 
ARSENIC 361 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-6. Levels of Arsenic in Human Tissue and Urine—Recent Studies 

Concentration 

Site population Sample Meana Range Units Reference 

Fort Valley, Georgia, Pesticide manufacturing facility (Superfund site) 

40 workers (samples collected Urine, random 11.6 <1–57 μg/L Hewitt et al. 

at end of work week) Urine, 24-hour 11.0 <1–54 μg/L 1995 

Hair 0.78 <0.01–6.3 μg/g 

Fingernails 0.79 <0.01–6.1 μg/g 

Hermosa, Sonora, Mexico 

Children, ages 7–11, exposed Urine, 24-hour Wyatt et al. 

to arsenic in water (mean 1998a, 

concentration [mean dose]): 1998b 

9 μg/L [0.481 μg/kg/day] 10.26 4.05–19.68 μg/day 

15 μg/L [0.867 μg/kg/day] 10.54 2.82–20.44 μg/day 

30 μg/L [1.92 μg/kg/day] 25.18 5.44–93.28 μg/day 

Glasgow, Scotland 

Adults, normal (n=1,250) Hair 0.650 0.20–8.17 μg/g Raie 1996 

Adults, postmortem (n=9) Liver 0.048 [0.024] 0.011–0.152 μg/g 

Infants, postmortem (n=9) Liver 0.0099 [0.007] 0.0034–0.019 μg/g 

Adults, postmortem (n=8) Lung 0.044 [0.022] 0.0121–0.125 μg/g 

Infants, postmortem (n=9) Lung 0.007 [0.0055] 0.0011–0.015 μg/g 

Adults, postmortem (n=9) Spleen 0.015 [0.008] 0.001–0.063 μg/g 

Infants, postmortem (n=8) Spleen 0.0049 0.0011– μg/g 

[0.0045] 0.0088 

Palatinate Region, Germany (high As)b 

Residents (n=199) Urine, 24-hour 3.96 [3.21] <0.1–18.32 μg/g Gebel et al. 

Residents (n=211) Hair 0.028 [0.016] <0.005–0.154 μg/g 1998a 

Saxony, Germany (low As—reference)b 

Residents (n=75) Urine, 24-hour 7.58 [6.20] 0.29–23.78 μg/g Gebel et al. 

Residents (n=74) Hair 0.069 [0.053] 0.013–0.682 μg/g 1998a 

Ismir, Turkey, (volcanic area with high thermal activity) 

 Nonoccupationally exposed Breast milk 4.23 [4.26] 3.24–5.41 μg/L Ulman et al. 

women (n=35) 1998 

Erlangen-Nurenberg Germany 1/92–12/93 

 Nonoccupationally exposed Lung 5.5 <1–13.0 ng/g Kraus et al. 

people (n=50) ww 2000 

28.4 <1–73.6 ng/g 

dw 
ARSENIC 362 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-6. Levels of Arsenic in Human Tissue and Urine—Recent Studies 

Concentration 

Site population Sample Meana Range Units Reference 

Tarragona (Catalonia, Spain) 1997–1999 

 Nonoccupationally exposed Lung <0.05 μg/g Garcia et al. 

people (n=78) ww 2001 

Bone <0.05 

Kidney <0.05 

Liver <0.05 

Lung <0.05 

West Bengal, India 

Residents consuming arsenic- Fingernail 7.32 2.14–40.25 μg/g Mandal et 

contaminated water (n=47) al. 2003 

Hair 4.46 0.70–16.17 

 Residents consuming Fingernail 0.19 0.11–0.30 

nonarsenic-contaminated water 

(n=15) 

Hair 0.07 0.03–0.12 

Middleport, NY, USA 

Children <7 years (n=77) Urine 15.1c

 2.1–59.6 μg/L Tsuji et al. 

Children <13 years (n=142) Urine 15.7c

 2.1–59.9 2005 

Children ≥7 years and adults Urine 15.8c

 3.9–773 

(n=362) 

 All participants Urine 15.7c 2.1–773 

a

Medians, if reported, are in brackets. b

The reference group (Saxony) had significantly higher levels of arsenic in urine and hair. However, data from both 

groups correspond to normal range reference data. c

Geometric mean, total arsenic 

dw = dry weight; ww = wet weight 
ARSENIC 363 

6. POTENTIAL FOR HUMAN EXPOSURE 

A study was performed to look at the arsenic levels, as well as the arsenic species present, in hair and nail 

samples from individuals in an arsenic-affected area in West Bengal, India. Mean arsenic concentrations 

in hair and fingernails of the chronically arsenic exposed population were 4.46 and 7.32 μg/g, respectively 

and were 0.07 and 0.19 μg/g in a control population. Fingernail samples were found to contain mostly 

inorganic arsenic (>80%) as a mixture of As(III) and As(V), as well as DMA(III) and DMA(V). Hair 

samples also mostly contained inorganic arsenic (>90%), as well as MMA(V) and DMA(V) (Mandal et 

al. 2003). 

Arsenic in soil in communities surrounding former smelters is a public health concern, especially for 

infants and children who may consume significant quantities of soil. Since lead arsenate was used in 

apple and other fruit orchards, often at very high application rates, and this compound would be expected 

to accumulate and persist in surface soil, there are concerns to human health when these when old 

orchards are converted into subdivisions or when they are used to grow food crops or forage. However, 

arsenic in soil may be imbedded in minerals or occur as insoluble compounds such as sulfides and 

therefore, not be taken up by the body from the gastrointestinal tract. In addition, oxidation of mineral 

surfaces may result in armoring the primary mineral grain by a secondary reaction product. Arsenicbearing solids are often encapsulated in insoluble matrices such as silica, further diminishing arsenic 

availability (Davis et al. 1992). 

Sarkar and Datta (2004) examined the bioavailability of arsenic from two soils with different arsenic 

retention capacities. In this study, Immokalee (Florida) and Orelia (Texas) soils were incubated after 

spiking with sodium arsenate for 4 months. The Immokalee soil is a sandy spodosol with low Fe/Al, 

Ca/Mg, and P contents and is likely to have minimal arsenic retention capacity. The Orelia soil is a sandy 

clay that is expected to have strong arsenic retention capacity. Arsenic speciation and bioavailability 

were studied immediately after spiking and after 4 months of incubation. Approximately 85% of the total 

arsenic (soluble and exchangeable fractions) was considered bioavailable and phytoavailable immediately 

after pesticide application for the Immokalee soil; after 4 months of incubation, this decreased to 

approximately 46%. Immediately after pesticide application, the amounts of arsenic extracted in the 

soluble/exchangeable and Fe/Al-bound fractions were similar that of the Immokalee soil. After 4 months, 

the soluble arsenic decreased to approximately 45% and the Fe/Al-bound arsenic increased to about 40%. 

Experiments looking at the bioavailability of arsenic from these two soils indicated that the potentially 

irreversible adsorption of arsenic by the Orelia soil rendered a significant portion of the total arsenic 

unavailable for absorption by the human gastrointestinal system. Initially after pesticide application, 
ARSENIC 364 

6. POTENTIAL FOR HUMAN EXPOSURE 

100% of the arsenic was bioavailable; after 4 months, the bioavailable fraction was found to decrease to 

88 and 69% in the Immokalee and Orelia soils, respectively (Sarkar and Datta 2004). 

Hamel et al. (1998) used synthetic gastric juice to estimate the bioaccessible fraction of metals in the 

stomach with varying liquid to solid ratios. They found that the bioaccessibility may vary in different 

soils and with varying liquid to solid ratios. Bioaccessibility was defined as the amount of metal that is 

soluble in synthetic gastric juice and therefore, potentially available for uptake across the intestinal lumen, 

while bioavailability was defined as the amount that was actually taken across the cell membranes. 

Arsenic bioaccessibility for National Institute of Standards and Technology (NIST) Montana Soil SRM 

2710, with a certified arsenic concentration of 626 μg/g, was fairly consistent across the liquid-to-solid 

ratios and ranged from 41.8±18 to 56±21%. The extractability of a hazardous waste contaminated soil 

from Jersey City, New Jersey, was different than that observed for the Montana NIST soil. For the Jersey 

City soil, which had an arsenic concentration of 1,120 μg/g, there was an increase in the bioaccessible 

arsenic as the liquid-to-solid ratio increased. Bioaccessible arsenic ranged from 4.5±0.8 (at a liquid-tosolid ratio of 100:1) to 25±9% (at a ratio of 5,000:1). Similarly, smelter impacted soils from Anaconda, 

Montana contain metal-arsenic oxides and phosphates whose bioaccessibility is limited by solubility 

restraints for residence times typical of the gastrointestinal tract (Davis et al. 1992, 1996). 

Inhalation of arsenic from ambient air is usually a minor exposure route for the general population. For 

example, the dose to a person who breathes 20 m3

/day of air containing 20–30 ng/m3 (see Section 6.4.1) 

would be about 0.4–0.6 μg/day. However, smokers may be exposed to arsenic by inhalation of 

mainstream smoke. Assuming that 20% of the arsenic in cigarettes is present in smoke, an individual 

smoking two packs of cigarettes per day would inhale about 12 μg of arsenic (EPA 1984a). However, a 

German study of the arsenic levels in lung tissue of 50 unexposed deceased people (see Table 6-6) found 

no significant difference in lung arsenic concentrations of smokers versus nonsmokers, nor were there any 

significant age- or sex-related differences (Kraus et al. 2000). Before arsenical pesticides were banned, 

tobacco contained up to 52 μg As/g, whereas after the ban, maximum arsenic levels were reduced to 

3 μg/g. 

Occupational exposure to arsenic may be significant in several industries, mainly nonferrous smelting, 

arsenic production, wood preservation, glass manufacturing, and arsenical pesticide production and 

application. Since arsenic compounds are used as a desiccant for cotton, workers involved in harvesting 

and ginning cotton may be exposed to arsenic. Occupational exposure would be via inhalation and 

dermal contact. Should any arsenic be retained in the cotton, workers handling the fabric and the general 
ARSENIC 365 

6. POTENTIAL FOR HUMAN EXPOSURE 

public would be exposed. The electronics industry is expanding the use of gallium arsenide in the 

production of electro-optical devices and integrated circuits, and workers in the industry where gallium 

arsenide is used may be exposed to hazardous substances such as arsenic, arsine, and various acids 

(Sheehy and Jones 1993). Occupational exposure to arsenic is generally assessed by measuring urinary 

excretion of arsenic. Past exposure is commonly assessed by arsenic levels in hair. Different types of 

occupational exposures may result in different uptakes of arsenic because of the bioavailability of the 

form of arsenic to which workers are exposed. For example, maintenance workers at a Slovak coal-fired 

power plant exposed to 8-hour TWA arsenic air concentrations of 48.3 μg/m3

 (range, 0.17–375.2) had 

urinary total arsenic levels of 16.9 μg As/g creatinine (range, 2.6–50.8), suggesting that bioavailability of 

arsenic from airborne coal fly ash is about one-third that from in copper smelters and similar settings 

(Yager et al. 1997). Approximately 90% of the arsenic-containing particulates were ≥3.5 μm. Apostoli et 

al. (1999) monitored 51 glass workers exposed to arsenic trioxide by measuring dust in the breathing 

zone. The mean concentration of arsenic in air was 82.9 μg/m3

 (1.5–312 μg/m3); exposure was higher for 

workers involved in handling the particulate matter. The occupation exposures to principal contaminants, 

including arsenic, at five coal-fired power plants were evaluated during June–August 2002. Eight air 

samples were collected per similar exposure group at four of the five facilities; inorganic arsenic 

concentrations in all samples were below the limit of detection (0.37–0.72 μg/m3

), as well as being below 

the OSHA permissible exposure limit (PEL) of 10 μg/m3

 (Bird et al. 2004). 

NIOSH researchers conducted a study of arsenic exposures and control systems for gallium arsenide 

operations at three microelectronics facilities during 1986–1987 (Sheehy and Jones 1993). Results at one 

plant showed that in all processes evaluated but one, the average arsenic exposures were at or above the 

OSHA action level of 5 μg/m3

, with a maximum exposure of 8.2 μg/m3. While cleaning the Liquid 

Encapsulated Czochralski (LEC) pullers, the average potential arsenic exposure of the cleaning operators 

was 100 times the OSHA PEL of 10 μg/m3

. Area arsenic samples collected at the plant in break-rooms 

and offices, 20–60 feet from the process rooms, had average arsenic concentrations of 1.4 μg/m3

. At the 

other two plants, personal exposures to arsenic were well controlled for all processes evaluated. 

A study has been conducted to examine the relationship between total arsenic levels in hair of employees 

in a semiconductor fabrication facility and job responsibility, a surrogate variable for arsenic exposure 

(de Peyster and Silvers 1995). Airborne arsenic was found in areas where equipment was cleaned but not 

in administrative areas. The highest airborne arsenic level found in the study, 15 μg/m3

, was collected 

from the breathing zone of a maintenance employee who was cleaning a source housing over a period of 

2 hours in an area with local exhaust ventilation. A concentration of 2 μg/m3

 was found during the 
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6. POTENTIAL FOR HUMAN EXPOSURE 

remainder of the cleaning period (~53 minutes). Workers in maintenance who were regularly assigned to 

cleaning equipment, and therefore presumed to have the highest exposure potential, had a mean hair 

arsenic level of 0.042 μg/g. This was higher than the mean of 0.033 μg/g observed in administrative 

controls, but the difference was not significant. Maintenance workers who only occasionally cleaned and 

maintained arsenic-contaminated equipment had a mean hair arsenic level of 0.034 μg/g, which was 

comparable to the controls. The highest group mean hair arsenic level of 0.044 μg/g, surprisingly, was 

found in supervisors and engineers who were presumed to have the lowest exposure potential of all 

workers in the process areas. However, the highest concentrations of hair arsenic in engineers, 0.076 and 

0.106 μg/g, were observed in two heavy smokers who smoked 1–2 packs of cigarettes per day. A 2-way 

analysis of variance indicated that smoking appeared to be a significant contributing factor whereas 

occupational exposure was not. 

Hwang and Chen (2000) evaluated arsenic exposure in 21 maintenance engineers (exposed group) and 

10 computer programmers (control group) at 3 semiconductor manufacturing facilities. Samples of air, 

wipe, and urine, as well as used cleaning cloths and gloves were collected to determine arsenic exposure. 

Arsenic was undetectable in 46 of the 93 air samples, and most samples were generally below the 

recommended occupational exposure limit (10 μg/m3

) in work areas during ion implanter maintenance. 

Arsine was detectable in 22 of the 45 area air samples and in 15 of the 35 personal air samples; however, 

all concentrations were well below the occupational exposure limit of 50 ppb (160 μg/m3

). Mean arsine 

concentrations ranged from not detected to 4.0 ppb (15 μg/m3

) in area air samples, and the mean arsine 

concentration of personal air for maintenance engineers was 4.3 ppb (14 μg/m3

). Arsenic concentrations 

in wipe samples, used cleaning cloths, and gloves, varied from not detected to 146 μg/cm2

. During ion 

implanter maintenance, urinary arsenic levels were found to increase (1.0–7.8 μg/g creatinine) in the 

maintenance engineers, from a mean baseline concentration of 3.6 μg/g creatinine. The average urinary 

arsenic level for the computer programmers was 3.8 μg/g creatinine (Hwang and Chen 2000). Mean 

arsenic concentrations in blood of 103 workers in the optoelectronic industry and 67 controls were 

8.58 and 7.85 μg/L, respectively (Liao et al. 2004). 

Concentrations of various metals, including arsenic, were measured in autopsy tissues (liver, lung, kidney, 

brain, and bone) collected from 78 nonoccupationally exposed subjects from Tarragona County, Spain 

between 1997 and 1999. In general, arsenic concentrations were under the analytical detection limit 

(0.05 μg/g wet weight) in all tissues (Garcia et al. 2001). 
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6. POTENTIAL FOR HUMAN EXPOSURE 

CCA preservatives are commonly used for treating timber used in constructions in marine and other 

humid environments or in contact with the ground. Exposure to CCA compounds may occur through 

dermal contact and inhalation of dust while working with the treated timber. Nygren et al. (1992) 

investigated the occupational exposure to airborne dust, chromium, copper, and arsenic in six joinery 

shops in Sweden where impregnated wood was used for most of their production. The mean airborne 

concentration of arsenic around various types of joinery machines ranged from 0.54 to 3.1 μg/m3

. No 

increased concentrations of arsenic were found in the workers’ urine. A study was carried out in 

Denmark to evaluate arsenic exposure in taxidermists, workers impregnating wood with CCA solutions, 

fence builders, construction workers, and workers impregnating electric pylons with arsenic solution 

(Jensen and Olsen 1995). Airborne arsenic exposure was documented in 19 of 27 individuals working 

with products containing arsenic. The maximum exposure concentration was 17.3 μg/m3

, found for a 

single worker who was filling an impregnation container with CCA paste. Median exposures for indoor 

workers producing garden fences and weekend cottages were 3.7 and 0.9 μg/m3

, respectively. The 

maximum urine concentration reported in the study was 294.5 nanomoles arsenic per millimole creatinine 

(195 μg As/g creatinine) and was from the injector impregnating electric pylons. The median 

concentration in workers on electric pylons was 80 nanomoles arsenic per millimole creatinine (53 μg 

As/g creatinine), which was 6 times the concentration in reference individuals. Urine arsenic levels in 

workers producing garden fences and in taxidermists were 2.9 and 1.8 times the reference level, 

respectively. 

The NIOSH National Occupational Exposure Survey (NOES) conducted in 1981–1983 estimated that 

about 55,000 workers were potentially exposed to arsenic (NOES 1990). The NOES was based on field 

surveys of 4,490 facilities that included virtually all workplace environments, except mining and 

agriculture, where eight or more persons are employed. The principal exposure pathway is probably 

inhalation of arsenic adsorbed to particulates, but ingestion and possibly dermal exposure may also be 

common. Since arsenic is no longer produced in the United States (see Section 5.1) and many arsenical 

pesticide uses have been banned (see Chapter 8), it is likely that the number of workers occupationally 

exposed to arsenic has decreased markedly in more recent years. 

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. 
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6. POTENTIAL FOR HUMAN EXPOSURE 

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 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 use the judgment of adults to avoid hazards (NRC 1993). 

As with adults, most children are exposed to arsenic largely through their diet. Since the greatest dietary 

intake of arsenic is from fish and seafood, infants and young children for whom a substantial part of their 

food is milk, would not be exposed to arsenic from dietary sources as much as older children. Even when 

mothers consumer large amounts of seafood, there does not appear to be any major transfer of 

arsenobetaine, the major form of arsenic in seafood, from seafood to milk (Grandjean et al. 1995). 

Arsenic concentrations were very low in human milk sampled from 88 mothers in the Faroe Islands, 

where the seafood diet includes pilot whale meat and blubber. The total arsenic concentrations ranged 

from 0.1 to 4.4 μg/kg, with a median of 1.6 μg/kg (Grandjean et al. 1995). The arsenic concentration in 

the breast milk of 35 women in Ismir, Turkey, a volcanic area with high thermal activity ranged from 

3.24 to 5.41 μg/L, with a median of 4.22 μg/L (Ulman et al. 1998). The mean arsenic levels in three 

groups of cows in the region that grazed on land impacted by lava and thermal activity were 4.71, 4.46, 

and 4.93 μg/L, compared to 5.25 μg/L for cows kept in sheds and fed commercial pellet feed and 

municipal water. The arsenic levels in the urine of pregnant women and the cord blood of their infants 

were 0.625±0.027 and 0.825±0.079 μg/L, respectively. The authors concluded that there was no harmful 

exposure to arsenic in volcanic areas with high arsenic levels from suckling infants or feeding them local 

cow’s milk, nor was there harm to the newborns from their mother’s diet. Sternowsky et al. (2002) 

analyzed breast milk from 36 women from three different regions in Germany. These regions included 

the city of Hamburg, a rural area, Soltau, Lower Saxony, and Munster, the potentially contaminated area. 

Arsenic was not detected (<0.3 μg/L) in 154 of 187 samples, with the highest concentration, 2.8 μg/L, 

found in a sample from the rural area. The geometric mean arsenic concentrations from the three areas 

were comparable. Calculated oral intakes of arsenic were between 0.12 and 0.37 μg/day for an infant at 

3 months of age and weighing 6 kg. 

According to the FDA study of 1986–1991, the mean daily intakes of arsenic are 0.5 and 0.81 μg/kg body 

weight per day for a 6–11-month-old infant and 2-year-old child, respectively (Gunderson 1995b). This 
ARSENIC 369 

6. POTENTIAL FOR HUMAN EXPOSURE 

can be compared to a mean daily intake of 0.51 μg/kg-body weight per day for a 25–30-year-old male 

(see Table 6-5). A Total Diet Study, from September 1991 to December 1996, estimated that the average 

inorganic arsenic intake for children of various age/sex groups were (age-sex group, total arsenic intake in 

μg/day, inorganic arsenic intake in μg/day): 6–11 months, 2.15, 1.35; 2 years, 23.4, 4.41; 6 years, 30.3, 

4.64; 10 years, 13.3, 4.21; and 14–16 years (females), 21.8, 5.15; 14–16 years (males), 15.4, 4.51 (Tao 

and Bolger 1999). The greatest dietary contribution (76–96%) of total arsenic intake for all age groups 

other than infants was seafood. For infants, 41 and 34% of the estimated total arsenic intakes are from 

seafood and rice/rice cereals, respectively (Tao and Bolger 1999). Only for toddlers does the intake 

approach the World Health Organization’s (WHO) provisional tolerable daily intake (PTDI) for inorganic 

arsenic (see Table 6-5). A 1985–1988 Canadian total diet study estimated that 1–4-year-olds ingested 

14.9 μg of total arsenic per day compared with 38.1 μg by the average Canadian and 59.2 μg for 20– 

39-year-old males (Dabeka et al. 1993). Yost et al. (2004) estimated the mean dietary intake for inorganic 

arsenic for children (1–6 years of age) to be 3.2 μg/day, with a range of 1.6–6.2 μg/day for the 10th and 

95th percentiles, respectively. Inorganic arsenic intake was predominantly contributed by grain and grain 

products, fruits and fruit juices, rice and rice products, and milk (Yost et al. 2004). Total arsenic and 

arsenobentaine concentrations were measured in 16 baby food samples obtained from manufactures in 

Spain; total arsenic concentrations ranged from 2.042 to 0.270 μg/g in plaice with vegetables and sole 

with white sauce, respectively. Arsenobetaine, which is the arsenical commonly found in fish, accounted 

for essentially 100% of the arsenic present in the samples (Vinas et al. 2003). 

Arsenic exposure from drinking water may be elevated especially in groundwater from areas where 

arsenic occurs naturally in soil such as the western and north central sections of the United States (see 

Table 6-3 and Figure 6-2). 

Arsenic exposure in communities near mining and smelting facilities or where arsenic had formerly been 

applied to agricultural land are a public health concern, especially for infants and children. Since arsenic 

remains in the surface soil indefinitely and long past land uses may be forgotten, people may not realize 

that they are living in areas where high levels of arsenic may occur in soil. Contaminated soils pose a 

particular hazard to children because of both hand-to-mouth behavior and intentional ingestion of soil 

(pica) that contains metals and other contaminants (Hamel et al. 1998). In these communities, arsenic 

may contaminate carpeting or may have been tracked in from outside. Children may be exposed to this 

arsenic while crawling around or playing on contaminated carpeting. Exposure may also result from 

dermal contact with the soil, or by inhaling the dust and then swallowing it after mucociliary transport up 
ARSENIC 370 

6. POTENTIAL FOR HUMAN EXPOSURE 

out of the lungs. Because much of the arsenic in soil is embedded in or adsorbed to soil particles or 

insoluble, it may not be in a form accessible for uptake by the body. 

Hwang et al. (1997b) studied the arsenic exposure of children in Anaconda, Montana, in the vicinity of a 

former copper smelter from the summer of 1992 through the summer of 1993. Environmental samples 

and first morning voided urine samples from 414 children <72 months old were collected. Attention was 

focused on that fraction of the environmental source that was thought to be of the greatest risk to the child 

(i.e., arsenic in small particles [<250 μm]) that could most readily adhere to hands and toys and could be 

inadvertently ingested. Average arsenic levels in different types of soil ranged from 121 to 236 μg/g. 

Several studies have reported mean soil ingestion values for children ranging from 9 to 1,834 μg /day. 

Assuming that high arsenic exposure areas have average arsenic levels in soil from 60 to 150 μg/g, the 

resulting daily arsenic intake from soil could range from 1 to 275 μg/day per child. The geometric mean 

of speciated urinary arsenic (combined As(III), As(V), MMA and DMA) was 8.6±1.7 μg/L (n=289) in the 

Hwang study. A nationwide survey on arsenic exposure in the vicinity of smelter sites revealed that 

children without excess arsenic exposure had average total urinary arsenic levels ranging from 5 to 

10 μg/L (Hwang et al. 1997a). Compared to these values, the mean total urinary arsenic values found in 

the Hwang study were markedly higher, but they were still well below the WHO-recommended 

maximum excretion level for total arsenic of 100 μg/L as an action level for intervention. The 

investigators hypothesized that the relatively low urinary arsenic levels found in the study were probably 

a reflection of the low bioavailability of some forms of arsenic in contaminated soil. Hwang et al. 

(1997a) stated that arsenic intake through skin contact is insignificant and may be neglected in the 

assessment of childhood arsenic exposure. They recommend that parents or guardians pay more attention 

to their children’s activity, especially hand-to-mouth behavior, even though the environmental 

contaminants might be elevated only slightly. Children in the northern Palatine region of German study, 

a former mining area characterized by high levels of arsenic (<2–605 μg/g) in residential areas did not 

show higher arsenic levels in their hair or urine than children from a reference area of Germany (Gebel et 

al. 1998a). 

While CCA registrants voluntarily canceled the production of CCA-treated wood for residential use in 

2003, there is a potential for exposure to arsenic from existing structures (Zartarian et al. 2006). Based on 

a review of existing studies, Hemond and Solo-Gabriele (2004) estimated that children with contact with 

CCA-treated wood may be subjected to doses in the range of tens of micrograms of arsenic per day. The 

most important route of exposure appeared to be by hand-to-mouth activities after contact with the CCAtreated wood. Kwon et al. (2004) compared the amounts of water-soluble arsenic on hands of children in 
ARSENIC 371 

6. POTENTIAL FOR HUMAN EXPOSURE 

contact with CCA-treated wood structures or sand in playgrounds. The mean amount of water-soluble 

arsenic on children’s hands from playgrounds without CCA-treated wood was 0.095 μg (range 0.011– 

0.41 μg). A mean amount of water-soluble arsenic on children’s hands from playgrounds with CCAtreated wood was 0.5 μg (range 0.0078–3.5 μg) (Kwon et al. 2004). Additional data from the study by 

Kwon et al. (2004) showed that total arsenic collected in hand-washing water (insoluble arsenic on the 

filter combined with the water-soluble arsenic in the filtrate) was 0.934 and 0.265 μg for the CCA 

playgrounds and the non-CCA playgrounds, respectively (Wang et al. 2005). Two wood surface swab 

samples collected from 217 play structures constructed from CCA-treated wood in the City of Toronto, 

Canada were sampled and analyzed for inorganic arsenic (Ursitti et al. 2004). Dislodgeable arsenic 

concentrations were found to vary widely from nondetectable (0.08–0.25 μg/100 cm2

) to 

521 μg/100 cm2

 (mean = 41.6 μg/100 cm2), and were found to not be a useful predictor of soil arsenic 

levels (Ursitti et al. 2004). 

Shalat et al. (2006) evaluated postexposure hand rinses and urine for total arsenic for 11 children (13– 

71 months) in homes in Miami-Dade County, Florida, with and without CCA-treated playgrounds. Seven 

playgrounds were included in this study, and five of these contained either CCA-treated or partially CCAtreated wood. In addition, samples of wood, soil (5–8 cm from the base of the playground structure), 

mulch (when present), and synthetic wipes were analyzed for total arsenic. Wood and soil arsenic 

concentration were <2.0 and <3 mg/kg for the non-CCA-treated playgrounds, respectively. Mean arsenic 

concentrations of 2,380 mg/kg (range 1,440–3,270 mg/kg) and 19 mg/kg (4.0–42 mg/kg) were reported 

for wood and soil, respectively, in the playgrounds with CCA-treated wood. An arsenic concentration in 

mulch at one playground without CCA-treated wood was 0.4 mg/kg, and arsenic concentrations were 

0.6 and 69 mg/kg in mulch at two of the playgrounds with CCA-treated wood. The amount of arsenic 

removed by synthetic wipes from the non-CCA-treated wood was <0.5 μg, while the mean amount of 

arsenic removed from the CCA-treated wood was 117 μg (range 1.0–313 μg). The amount of arsenic in 

hand rinses from children who played at the playgrounds with non-CCA-treated wood and at the 

playgrounds with CCA-treated wood were <0.2 and 0.6 μg (range <0.2–1.9 μg), respectively. The mean 

urinary total arsenic concentration was 0.0136 μg/L (range 0.0072–0.0231 μg/L) for all children. No 

association between assess to CCA-treated playgrounds and urinary arsenic levels was found (Shalat et al. 

2006). 

The potential exposure children may receive from playing in play structures constructed from CCAtreated wood is generally smaller than that they would receive from food and water. For comparison, 

Yost et al. (2004) estimated the mean dietary intake for inorganic arsenic for children (1–6 years of age) 
ARSENIC 372 

6. POTENTIAL FOR HUMAN EXPOSURE 

to be 3.2 μg/day, with a range of 1.6–6.2 μg/day for the 10th and 95th percentiles, respectively. In a Total 

Diet Study, from September 1991 to December 1996, estimated average total intakes for children aged 6– 

11 months, 2 years, 6 years, and 10 years were 2.15, 23.4, 30.3, and 13.3 μg/day, respectively. Average 

inorganic arsenic intakes for the same age groups were estimated as 1.35, 4.41, 4.64, and 4.21 μg/day, 

respectively, based on data for total arsenic in foods and the assumption that 10% of the total arsenic in 

seafood was inorganic and that 100% of the arsenic in all other foods was inorganic (Tao and Bolger 

1999). Hand washing after play would reduce the potential exposure to children to arsenic after playing 

on play structures constructed with CCA-treated wood, since most of the arsenic on the children’s hands 

was removed with water (Kwon et al. 2004). 

Concentrations of several toxic metals, including the metalloid arsenic, were measured in the placentas of 

200 women in two urban cities in Ukraine, Kyiv and Dniprodzerzhinsk. Arsenic was detected in only 5% 

of the samples with concentrations ranging from <0.156 to 0.378 μg/g. In a study in Bulgaria, placental 

arsenic concentrations of 7 and 23 μg/g were reported in a control and smelter area, respectively. A 

placental arsenic concentration of 34 μg/g was reported in a region of Argentina with high concentrations 

of arsenic in drinking water (Zadorozhnaja et al. 2000). 

Parents can inadvertently carry hazardous materials home from work on their clothes, skin, hair, and 

tools, and in their vehicles (DHHS 1995). Falk et al. (1981b) reported a case of hepatic angiosarcoma in a 

child that could be associated with arsenic contamination of a parent’s clothing, the water supply, and the 

environment. The father worked in a copper mine and smelter area where his clothing was contaminated 

with dust containing arsenic. His daughter, who exhibited a high degree of pica, ate soil from the yard, 

and licked soil off her father’s shoes. In a study of arsenic levels in homes in Hawaii, Klemmer et al. 

(1975) found higher levels in homes of employees of firms that used arsenic for pesticides or wood 

preservation, compared to homes where residents’ work did not involve arsenic. The concentration of 

arsenic in dust from the homes of workers exposed to arsenic ranged from 5.2 to 1,080 μg/g, compared to 

concentrations of 1.1–31 μg/g in dust from control homes. 

While the harmful effects of many components of tobacco smoke are well known, those due to heavy 

metals in the smoke have not been sufficiently emphasized. The adverse health effects of these toxic 

metals on the fetus through maternal smoking are of special concern (Chiba and Masironi 1992). The 

concentration of arsenic in tobacco is relatively low, usually below detectable limits (<1 μg/g). Although 

the concentrations of inorganic and organic arsenic in the urine of adults do not appear to be influenced 

by smoking, a positive association was found between urinary arsenic levels in children and parental 
ARSENIC 373 

6. POTENTIAL FOR HUMAN EXPOSURE 

smoking habits. As detailed in a WHO report, the mean arsenic level in the urine of children of 

nonsmoking parents was 4.2 μg/g creatinine, in children with one smoking parent, it was 5.5 μg/g, and in 

children with both parents smoking, it was 13 μg/g (Chiba and Masironi 1992). Tsuji et al. (2005) 

reported geometric mean concentrations of total arsenic of 15.1 and 15.7 μg/L in children <7 and 

<13 years old, respectively, from households in Middleport, New York, where historical pesticide 

manufacture was associated with arsenic in soil. Geometric mean concentrations of inorganic arsenic, 

MMA, and DMA were 0.81, 0.54, and 2.5 μg/L, respectively, in children <7 years old and 0.83, 0.55, and 

3.0 μg/L, respectively, in children <13 years old (Tsuji et al. 2005). 

The use of Chinese herbal medicines (CHM) appears to be common among Chinese women. Both CHM 

and Chinese proprietary medicines (CPM) are used for treatment of minor ailments in babies and 

children. Herbal medicines are available in capsule or tablet form in drug stores, supermarkets, and by 

mail. The CPM “Sin Lak Pill,” “Lu Shen Wan,” and other anti-asthma preparations have been found to 

contain inorganic arsenic levels ranging from 25 to 107,000 μg/g, and cases of acute arsenic poisoning 

have been found in children and adults using these CPM (Chan 1994). Babies and children are 

particularly at risk because they may be given higher doses of these preparations per kg of body weight 

than adults would normally consume. They may also lack the hepatic enzymes responsible for drug 

biotransformation and detoxification (Chan 1994). Concentrations of heavy metals, including arsenic, 

were evaluated in 54 samples of Asian remedies that were purchased in stores in Vietnam and Hong Kong 

that would be easily accessible to travelers, as well as in health food and Asian groceries in Florida, New 

York, and New Jersey. One remedy that was recommended to treat children’s fever would expose a 

15 kg child to approximately 5.0 mg of arsenic per day (Garvey et al. 2001). A folk remedy, purchased in 

California, for the treatment of chicken pox, flu-like symptoms, and nasal congestion, which had been 

given to two children in Wisconsin, was found to contain 36% arsenic acid. One-half teaspoon of this 

powder (about 500 mg of arsenic) was dissolved in hot water and taken 2–3 times per day (Werner et al. 

2001). 

Various metallic pigments and colors in the form of salts or lakes are used in toy production. Therefore, 

children may be exposed to toxic metals while playing with toys, especially when they lick, suck, or 

swallow a toy or a piece of a toy. Toys produced in European Union Markets must conform to 

restrictions concerning the bioavailability of toxic metals, including arsenic. The maximum limit for 

bioavailability of arsenic from the accessible parts of a toy is set to 0.1 μg/day. This corresponds to an 

arsenic migration limit of 25 μg/g for all toy material, including modeling clay and paints (Rastogi and 

Pritzl 1996). A study was carried out to determine whether crayons, water colors, and water-based paints 
ARSENIC 374 

6. POTENTIAL FOR HUMAN EXPOSURE 

conform with the migration limits for toxic metals (Rastogi and Pritzl 1996). For the analysis, 94 samples 

representing 48 products were obtained from China, Taiwan, Japan, the United States, and European 

countries. Fifty-two samples showed migration of arsenic, ranging from 0.01 to 3.75 μg/g. 

6.7 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES 

In addition to individuals who are occupationally exposed to arsenic (see Section 6.5), there are several 

groups within the general population that have potentially high exposures (higher than background levels) 

to arsenic. These populations include individuals living in proximity to sites where arsenic was produced, 

used (e.g., as a pesticide), or disposed, and individuals living near one of the 1,684 NPL hazardous waste 

sites where arsenic has been found at elevated levels in some environmental media (HazDat 2006). It also 

includes point sources such as smelters, coal-fired power plants, and municipal incinerators. People 

living in areas of volcanic activity may be exposed to higher levels of arsenic since high levels are more 

likely to be present in the environment. Other populations at risk of potentially high levels of exposure 

include those whose water supply contains high levels of arsenic and those consuming large amounts of 

seafood or seaweed. However, as pointed out previously (see Section 6.4.4), arsenic in fish and shellfish, 

is largely in the form of the less harmful organic arsenical, arsenobetaine; however, some commercially 

available seaweeds, especially brown algae varieties, may have high percentages of the total arsenic 

present as inorganic arsenic (>50%) (Almela et al. 2002; Laparra et al. 2003). While elevated urinary 

arsenic excretion levels have been associated with the consumption of fish and seafood, in a study of 

32 sport fish consumers from Lakes Erie, Huron, and Michigan, only 6 (19%) had detectable urine arsenic 

concentrations, >4 μg/L, and 5 of these consumed fish from Lake Huron (Anderson et al. 1998). 

Exposure of high levels of arsenic in drinking water is more apt to be absorbed by the body and be 

harmful than exposure to arsenic in seafood. For example, a group of 36 people in Zimapán, Mexico who 

consumed water from an aquifer with 1.0 mg As/L had hair arsenic levels of 2.6–14.1 μg/g (10 μg/g 

average), compared with 2.4–13.9 μg/g (6.19 μg/g average) for a reference population that consumed 

bottled water with <0.014 mg/L arsenic (Armienta et al. 1997). 

A study was conducted to determine if significant arsenic exposure was occurring at a Superfund site in 

Fort Valley, Georgia (Hewitt et al. 1995). Random urine, 24-hour urine, hair, and fingernail samples 

were collected at the end of the workweek from 40 employees at an active pesticide manufacturing 

facility where arsenical pesticides had been produced for over 50 years prior to the mid-1970s. 

Measurement of arsenic in the urine is considered to be the best method for monitoring recent exposure in 

industrial populations. Hair and fingernail analyses may provide an indication of exposures that occurred 
ARSENIC 375 

6. POTENTIAL FOR HUMAN EXPOSURE 

up to several months prior to testing, but both can adsorb and strongly retain arsenic from external 

sources. Since arsenic is rapidly cleared from the blood (half-life of 3–4 hours), blood arsenic levels are 

not considered suitable for monitoring populations for chronic low-level arsenic exposure. Results of the 

Hewitt study are summarized in Table 6-6. Urinary arsenic levels for all workers were well within the 

commonly accepted normal range of <100 μg/L. 

As noted above, workers in a number of industries may have high exposures to arsenic, especially if 

proper safety procedures are not followed. For members of the general population, above-average 

exposure to arsenic from drinking water is possible in areas of high natural arsenic levels in groundwater 

or elevated arsenic levels in drinking water due to industrial discharges, pesticide applications, or leaching 

from hazardous waste facilities. Individuals living in the vicinity of large smelters and other industrial 

emitters of arsenic may be exposed to above-average arsenic levels both in the air, and as a result of 

atmospheric deposition, in water and soil and subsequent uptake into crops. 

People sawing or drilling arsenic-treated wood without protective masks or burning this wood may be 

exposed to elevated levels of arsenic in air. 

Recreational and subsistence fishers who consume appreciably higher amounts of locally caught fish from 

contaminated bodies of water may be exposed to higher levels of arsenic associated with dietary intake. 

Arsenic contamination has triggered the issuance of several human health advisories (EPA 1998g). As of 

December 1997, arsenic was identified as the causative pollutant in a restricted consumption advisory for 

the general population for all fish in a 7-mile area including Devil’s Swamp Lake and Bayou Baton 

Rouge in Louisiana. A public health advisory has been issued for consumption of fish and shellfish from 

the Duwamish River, Seattle, Washington due to arsenic and other chemicals (WSDOE 2005). 

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 arsenic 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 arsenic. 
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6. POTENTIAL FOR HUMAN EXPOSURE 

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. The chemical and physical properties of the arsenic species of 

chief toxicological and environmental concern are sufficiently well characterized to allow estimation of 

the environmental fates of these compounds. However, more information regarding the Kow and Koc 

values of the organic arsenicals would help predict the fate of these compounds in the environment. 

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 2004, became available in May of 2006. This database is updated yearly and should provide a list of 

industrial production facilities and emissions. 

While arsenic has not been produced in the United States since 1985, the United States is the largest 

consumer of arsenic and substantial quantities of arsenic are imported, primarily as arsenic trioxide 

(USGS 2006a). The agricultural use of inorganic arsenic pesticides have been discontinued in the United 

States. However, some organic arsenicals still may be used in agriculture. Current production and use 

data for individual arsenical pesticides and other arsenic compounds would help to estimate human 

exposure to the various arsenic species. Because arsenical pesticides are so persistent, a more complete 

picture of past use of these products would enable us to predict what areas may contain high levels of 

arsenic in soil. 

Comprehensive estimates on emissions of arsenic date to the early 1980s (Nriagu and Pacyna 1988). The 

industrial picture has changed considerably since then and emission controls are being mandated more 

and more. For example, emission factors for Canadian smelters calculated in 1993 were grossly lower 

than those estimated in 1983 (Skeaff and Dubreuil 1997). There is a need for accurate and up-to-date 

measurements of atmospheric arsenic releases from both natural and anthropogenic sources to better 

assess human exposure to arsenic and guide environmental protection measures. 
ARSENIC 377 

6. POTENTIAL FOR HUMAN EXPOSURE 

Environmental Fate. The interconversion of the various arsenic species and transport among the 

environmental media is complex and not all aspects are well-studied. Additional quantitative data on the 

rates of oxidation, reduction, and biotransformation reactions of arsenic compounds, and how these 

depend on environmental conditions would be useful in evaluating and predicting the fate and transport of 

arsenic at hazardous waste sites and other areas. 

Bioavailability from Environmental Media. Toxicokinetic and toxicity studies establish that 

bioaccessible (e.g., soluble, not strongly adsorbed to soil or embedded in minerals) arsenic is highly 

absorbed following inhalation and oral exposure (see Sections 3.4.1.2 and 3.4.1.1). Some work has been 

done on the effect of environmental matrix (soil, food) on accessibility and absorption of arsenic (Davis et 

al. 1992, 1996; Hamel et al. 1998; Roberts et al. 2002, 2007), but additional data would be valuable. 

Limited data suggests that dermal absorption of arsenic is very low (see Section 3.4.1.3) (Lowney et al. 

2005), further data would be useful to establish whether arsenic uptake occurs from contact with 

contaminated soil or water, since humans may be exposed by these routes near hazardous waste sites. 

Food Chain Bioaccumulation. Bioconcentration factors have been measured for several freshwater 

and marine species. While some species (mainly marine algae and shellfish) tend to bioconcentrate 

arsenic (EPA 1980a; Roper et al. 1996), it is not biomagnified through the food chain (Eisler 1994; EPA 

1979, 1982b, 1983e, 2003b; Williams et al. 2006). 

Carrots growing on land containing somewhat more than the permissible of arsenic in crop land did not 

contain levels of arsenic that were harmful (Helgesen and Larsen 1998). However, further research on the 

uptake of arsenic by a variety of plants in a wide range of arsenic polluted sites (e.g., mining area, 

orchards previously treated with lead arsenate) would be valuable in assessing human exposure near such 

sites through the consumption of vegetables from home gardens. 

Exposure Levels in Environmental Media. Additional reliable monitoring data for the levels of 

arsenic in contaminated media at hazardous waste sites are needed or need to be made available, so that 

the information obtained on levels of arsenic in the environment can be used in combination with the 

known body burden of arsenic to assess the potential risk of adverse health effects in populations living in 

the vicinity of hazardous waste sites. 
ARSENIC 378 

6. POTENTIAL FOR HUMAN EXPOSURE 

Extensive monitoring data are available for total arsenic in all environmental media. Additional 

monitoring studies, specifically those that include identification of arsenic species, would allow more 

precise estimation of current exposure levels and possible human health risks. 

Exposure Levels in Humans. Arsenic has been detected in human tissues, including blood, urine, 

hair, nails, and internal organs. Data are available for populations exposed in the workplace and for the 

general population (de Peyster and Silvers 1995; Jensen and Olsen 1995; Nygren et al. 1992), and some 

studies have been published on exposures near waste sites (Hwang et al. 1997a; Tsuji et al. 2005). 

Additional biomonitoring studies of residents near waste sites that contain arsenic would be helpful in 

evaluating the likely human health risks from these sites. 

While some data are available on the speciation of arsenic in food, additional data on the particular 

species of arsenic, rather than just the total arsenic concentration, present in foods, especially seafood, are 

needed to better estimate the potential hazards to human health by the consumption of these foods (Ryan 

et al. 2001). 

This information is necessary for assessing the need to conduct health studies on these populations. 

Exposures of Children. Contaminated soils pose a particular hazard to children because of pica and 

hand-to-mouth activities. Some studies have been performed on exposure and body burden (Hwang et al. 

1997a), but additional studies, including investigations of unique pathways for exposures of children and 

the amount of soil a child ingests, would provide valuable data. Small amounts of arsenic were found to 

be transferred to hands of children playing on play structures constructed from CCA-treated wood 

(Hemond and Solo-Gabriele 2004; Kwon et al. 2004; Shalat et al. 2006; Ursitti et al. 2004; Wang et al. 

2005). Based on a review of existing studies, Hemond and Solo-Gabriele (2004) estimated that children 

with contact with CCA-treated wood may be subjected to doses in the range of tens of micrograms of 

arsenic per day and suggested that exposure by this route warrants further study. The PTDI assigned by 

the Food and Agriculture Organization of the United Nations and the World Health Organization 

(FAO/WHO) applies to adults. Studies are needed to assess whether children are different in their weight 

adjusted intake of arsenic. No childhood-specific means for reducing exposure were identified. 

Child health data needs relating to susceptibility are discussed in Section 3.12.2, Identification of Data 

Needs: Children’s Susceptibility. 
ARSENIC 379 

6. POTENTIAL FOR HUMAN EXPOSURE 

Exposure Registries. No exposure registries for arsenic 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. 

6.8.2 Ongoing Studies 

The Federal Research in Progress (FEDRIP 2006) 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. These 

studies are summarized in Table 6-7. 

The U.S. Geological Survey, along with other federal and state agencies, industry, and academia, is 

conducting the National Geochemical Survey (NGS) in order to produce a body of geochemical data for 

the United States based primarily on stream sediments that have been analyzed using a consistent set of 

analytical methods. The goal of the NGS is to analyze at least one stream sediment sample in every 

289 km2

 area by a single analytical method across the entire United States (USGS 2007b). 

EPA is conducting a 4-year (2000–2003) national screening-level study of contaminants in freshwater 

fish, referred to as the National Fish Tissue Study (EPA 2004c). This study will allow the EPA to 

develop national estimates of the mean concentrations of 268 chemicals in tissues of fish from lakes and 

reservoirs of the coterminous United States. EPA analysis of the data from this study was scheduled to 

begin in January 2005, with the final report scheduled to be released in 2006. Interim raw data have been 

released each year, and are available from EPA. Fish samples have been analyzed for total inorganic 

arsenic (As(III) and As(V) combined), arsenic(III), arsenic(V), MMA(V), and DMA(V). Analysis for 

total arsenic was not performed as part of this study. 

The American Water Works Association Research Foundation (AWWARF) supports research on arsenic 

in drinking water. 
ARSENIC 380 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-7. Ongoing Studies on the Environmental Fate and Exposure of Humans 

to Arsenic 

Investigator Affiliation Research description Sponsor 

Basta, NT Ohio State University, 

School of Natural 

Resources, Columbus, Ohio 

Heavy metal and trace element 

biogeochemistry in soils; 

chemical speciation, 

bioavailability, and toxicity 

USDA 

Blum, CB Columbia University Health 

Sciences, New York, New 

Bioavailability lead and arsenic 

in soil to humans 

NIEHS 

York 

Hamilton, JW Dartmouth College, 

Hanover, New Hampshire 

Toxic metals—biological and 

environmental implications 

NIEHS 

Hoppin, J Not specified Monitoring of arsenic and other 

compounds in the blood and 

urine of a cohort of pregnant 

women in Norway 

NIEHS 

Kpomblekou, AK; 

Ankumah, RO 

Tuskegee University, 

Agriculture and Home 

Economics, Tuskegee, 

Alabama 

Biochemical processes in soils 

treated with trace-elementenriched broiler litter; to 

determine total arsenic and 

USDA 

other metal concentrations and 

the distribution of their chemical 

forms in soils under long-term 

broiler litter treatments 

Loeppert, RH Texas A&M University, Soil 

and Crop Sciences, College 

Station, Texas 

Inorganic chemical processes 

influencing soil and water 

quality 

USDA 

Peryea, FJ Wenatchee Tree Fruit 

Research & Extension 

Center Washington State 

University, Pullman, 

Washington 

Quantification of 

biogeochemical processes in 

lead arsenate-contaminated 

orchard soils and development 

of soil and plant management 

practices to minimize the 

toxicity risks that these soils 

impose on agricultural crops 

and to human and 

USDA 

environmental health 

Miller, DM; DeLaune, 

P; Miller, WP 

University of Arkansas, 

Crop, Soil and 

Environmental Sciences, 

Arsenic levels in soils of 

northwest Arkansas 

USDA 

Fayetteville, Arkansas 

van Geen, A Columbia University, 

Lamont-Doherty Earth 

Observatory, Palisades, 

New York 

Studies on arsenic in 

groundwater in Bangladesh 

NSF 
ARSENIC 381 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-7. Ongoing Studies on the Environmental Fate and Exposure of Humans 

to Arsenic 

Investigator Affiliation Research description Sponsor 

Walker, MJ et al. University of Nevada, 

Natural Resources and 

Arsenic in Churchill County, 

Nevada domestic water 

USDA 

Environmental Sciences, 

Reno, Nevada 

supplies 

Zheng, Y Columbia University Health 

Sciences, New York, New 

York 

Arsenic mobilization in 

Bangladesh groundwater 

NIEHS 

NIEHS = National Institute of Environmental Health Sciences; NSF = National Science Foundation; USDA = U.S. 

Department of Agriculture 

Source: FEDRIP 2006 
ARSENIC 382 

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ARSENIC 383 

7. ANALYTICAL METHODS 

The purpose of this chapter is to describe the analytical methods that are available for detecting, 

measuring, and/or monitoring arsenic, its metabolites, and other biomarkers of exposure and effect to 

arsenic. 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 are included that modify previously used methods to obtain lower 

detection limits and/or to improve accuracy and precision. 

7.1 BIOLOGICAL MATERIALS 

Atomic absorption spectrophotometry (AAS) is the most common analytical procedure for measuring 

arsenic in biological materials (Curatola et al. 1978; Foà et al. 1984; Johnson and Farmer 1989; Mushak 

et al. 1977; Norin and Vahter 1981; Sotera et al. 1988). In AAS analysis, the sample is heated in a flame 

or in a graphite furnace until the element atomizes. The ground-state atomic vapor absorbs monochromatic radiation from a source and a photoelectric detector measures the intensity of transmitted 

radiation (APHA 1989b). Inductively-coupled plasma atomic emission spectrometry (ICP-AES) and 

ICP-mass spectrometry (ICP-MS) are increasingly common techniques for the analysis of arsenic; both 

methods can generally provide lower detection limits than absorbance detection methods. 

Samples may be prepared for AAS in a variety of ways. Most often, the gaseous hydride procedure is 

employed (Curatola et al. 1978; Foà et al. 1984; Johnson and Farmer 1989; Norin and Vahter 1981). In 

this procedure, arsenic in the sample is reduced to arsine (AsH3), a gas that is then trapped and introduced 

into the flame. This approach measures total inorganic arsenic, but may not detect all organic forms 

unless preceded by a digestion step. Digestion or wet-ashing with nitric, sulfuric, and/or perchloric acids 

degrades the organic arsenic species to inorganic arsenic so that recovery of total arsenic from biological 

materials can be achieved (Maher 1989; Mushak et al. 1977; Versieck et al. 1983). In microwave assisted 

digestion, harsh oxidation conditions are used in conjunction with microwave heating (Benramdane et al. 

1999b). For accurate results, it is important to check the completeness of the oxidation; however, this is 

seldom done (WHO 1981). 
ARSENIC 384 

7. ANALYTICAL METHODS 

The arsenic concentration in biological fluids and tissues may also be determined by neutron activation 

analysis (NAA) (Landsberger and Simsons 1987; Versieck et al. 1983). In this approach, the sample is 

irradiated with a source of neutrons that converts a portion of the arsenic atoms to radioactive isotopes, 

which can be quantified after separation from radioisotopes of other chemicals. Neutron activation has 

limited use because of the limited number of nuclear reactors in the United States providing this service 

and the need to dispose of radioactive waste. X-ray fluorescence is also capable of measuring arsenic in 

biological materials (Bloch and Shapiro 1986; Clyne et al. 1989; Nielson and Sanders 1983) and 

environmental samples (see Section 7.2). This method has the advantage that no sample digestion or 

separation steps are required. Hydride generation combined with atomic fluorescence spectroscopy (HGAFS) is a relatively new technique that provides freedom from interference offered by hydride generation 

with sensitivity better than to 20 parts per trillion and linearity up to 10 ppm (PSA 2000). 

Speciation of arsenic (i.e., analysis of organic arsenic compounds or different inorganic species, rather 

than total arsenic) is usually accomplished by employing separation procedures prior to introduction of 

the sample material into a detection system. Various types of chromatography or chelation-extraction 

techniques are most commonly used in combination with AAS, ICP-AES, or ICP-MS detection methods 

(Dix et al. 1987; Foà et al. 1984; Johnson and Farmer 1989; Mushak et al. 1977; Norin et al. 1987; 

Thomas and Sniatecki 1995). In one method, high performance liquid chromatography (HPLC) is 

combined with HG-AFS to quantify As(III), dimethylarsinic acid (DMA), momomethyl arsonic acid 

(MMA), and As(V) (PSA 2000). Another approach involves selective reduction of arsenate and arsenite 

(permitting quantification of individual inorganic arsenic species), and selective distillation of methyl 

arsines to quantify MMA and DMA (Andreae 1977; Braman et al. 1977; Crecelius 1978). Most methods 

for measuring arsenic in biological samples are unable to measure arsenobetaine with any accuracy 

because it does not form a hydride and it gives a different response from inorganic arsenic in 

electrothermal AAS. Ebdon et al. (1999) successfully employed HPLC coupled with ICP-MS to 

determine arsenic speciation in blood plasma, which was entirely arsenobetaine. Øygard et al. (1999) 

developed a simple method to determine inorganic arsenic in biological samples. Their method, which 

involves initially distilling inorganic arsenic from the sample as AsCl3 using HCl, avoids separating and 

quantifying all of the different arsenic species, which is both costly and time-consuming. 

Table 7-1 summarizes a variety of methods for measuring total arsenic and individual arsenic species in 

biological materials. None of these methods have been standardized by EPA or other federal agencies. 
ARSENIC 385 

7. ANALYTICAL METHODS 

Table 7-1. Analytical Methods for Determining Arsenic in Biological Samples 

Sample Analytical Sample Percent 

matrix Preparation method method detection limit recovery Reference 

Methods for total arsenic: 

Blood Digestion with nitric acid and 

hydrogen peroxide; dry ash with 

magnesium oxide/magnesium 

nitrate; reduction with sodium 

borohydride 

Blood, hair Wet ash with nitric/perchloric 

acids; reduction with sodium 

borohydride 

Serum Irradiation; digestion with nitric/ 

perchloric/sulfuric acids; 

extraction with toluene 

Urine Irradiate epithermally 

Urine Digestion with nitric and 

perchloric acid; reduction with tin 

chloride; generation arsine by 

addition of zinc; reaction with 

SDDC 

Urine Pretreatment with L-cysteine; 

reduction with potassium iodide/ 

ascorbic acid 

Urine Drying sample; irradiation with 

x-rays 

Hair Wet ashing with nitric/sulfuric 

acids and hydrogen peroxide; 

reduction to arsine with sodium 

borohydride 

Soft tissue Digestion with nitric/sulfuric 

acids; complexation with DDDC 

in potassium iodide; extraction 

with chloroform 

Nails Wet ashing with nitric/sulfuric 

acids and hydrogen peroxide; 

reduction to arsine with sodium 

borohydride 

Methods for arsenic speciation: 

Urine Separation of As+3, As+5, MMA, 

and DMA on anion/cation 

exchange resin column; 

reduction to respective arsines 

with sodium borohydride 

Urine Reduction of As+3, As+5, MMA, 

and DMA to arsines with sodium 

borohydride 

HGAAS 0.5 μg/L 95–102 Foà et al. 1984 

HGAAS 0.1 μg/La 95–105 Valentine et al. 

1979 

NAA 0.088 ng/mLa 94–98 Versieck et al. 

1983 

NAA 

Colorimetric 

photometry 

40–100 ng/g 

0.5 μg/sample 

93–109 

90–110 

Landsberger and 

Simsons 1987 

Pinto et al. 1976 

Flow injection 

HGAAS 

0.1 μg/L 95–100 Guo et al. 1997 

XRF 0.2 μg/La 92–108 Clyne et al. 1989 

HGAAS 0.06 μg/g 93 Curatola et al. 

1978 

GFAAS 0.2 ppm 79.8 Mushak et al. 

1977 

HGAAS 1.5 μg/g No data Agahian et al. 

1990 

IEC/HGAAS 0.5 μg/L 93–106 Johnson and 

Farmer 1989 

HGAAS 0.08 μg/L 97–104 Norin and Vahter 

1981 
ARSENIC 386 

7. ANALYTICAL METHODS 

Table 7-1. Analytical Methods for Determining Arsenic in Biological Samples 

Sample Analytical Sample Percent 

matrix Preparation method method detection limit recovery Reference 

Urine Reduction of As+3, As+5, MMA, Atomic ≤1 ng for all No data Braman et al. 

and DMA to arsines; collection in emission four species 1977 

cold trap; selective distillation by (directslow warming current 

plasma) 

Urine Extraction with chloroform/ 

methanol; column separation 

HGAAS/TLC/ 

HRMS 

0.34 mg/ 

samplea 

No data Tam et al. 1982 

with chloroform/methanol; elution 

on cation exchange column with 

ammonium hydroxide 

Blood/ Acidification with hydrochloric GLC/ECD 0.1 mg/mL No data Dix et al. 1987 

tissue acid; complexation with TGM; 

extraction into cyclohexane; 

separation on capillary column 

Blood Separation by HPLC HPLC/ICP­ 2.5 ng As/mL ~100 Ebdon et al. 

plasma MS 1999 

Urine Separation by anion exchange IEC/ICP-MS <0.45 μg/L for No data Inoue et al. 1994 

chromatography; detection by all species 

direct coupling of column to ICPMS 

Marine Extraction with methanol-water; HPLC/ICP­ 6–25 ng/mL 94.6 (fish Sniatecki 1994 

biota removal of fats by liquid-liquid MS muscle 

extraction or solid-phase CRM) 

cartridge 

Marine Separation by anion exchange HPLC/ 0.3–0.9 ng 95–110 Lópezbiota coupled with HPLC; on-line HGAAS (recovery Gonzálvez et al. 

microwave oxidation of spike 1994 

in fish 

tissue) 

Biological Distill inorganic arsenic as AsCl3 Flow-injection 0.045 mg/kg No data Øygard et al. 

samples— using HCl after prereduction of HGAAS (dry matter) 1999 

Inorganic As(V) with KI/HCl 

arsenic 

a

Lowest reported concentration 

CRM = certified reference material; DDDC = diethylammonium diethyldithiocarbamate; DMA = dimethylarsinate; 

ECD = electron capture detector; GFAAS = graphite furnace atomic absorption spectrometry; GLC = gas-liquid 

chromatography; HGAAS = hydride generation atomic absorption spectrometry; HRMS = high resolution mass 

spectrometry; ICP-MS = inductively-coupled plasma mass spectrometry; IEC = ion exchange chromatography; 

HPLC = high-performance liquid chromatography; MMA = monomethylarsonate; NAA = neutron activation analysis; 

SDDC = silver diethyldithiocarbamate; TGM = thioglycolic acid methylester; TLC = thin layer chromatography; 

XRF = x-ray fluorescence 
ARSENIC 387 

7. ANALYTICAL METHODS 

Detection limits in blood and urine are about 0.1–1 ppb for most techniques; limits for hair and tissues are 

usually somewhat higher. 

7.2 ENVIRONMENTAL SAMPLES 

Arsenic in environmental samples is also measured most often by AAS techniques, with samples prepared 

by digestion with nitric, sulfuric, and/or perchloric acids (Dabeka and Lacroix 1987; EPA 1983b, 1994a, 

1994b; Hershey et al. 1988). Other methods employed include a spectrophotometric technique in which a 

soluble red complex of arsine and silver diethyldithiocarbamate (SDDC) is formed (APHA 1977; EPA 

1983c, 1983d), ICP-AES (EPA 2000c; NIOSH 2003), graphite furnace AAS (EPA 1983b, 1994b; NIOSH 

1994b), ICP-MS (EPA 1991, 1994a, 1998j), and x-ray fluorescence (Khan et al. 1989; Nielson and 

Sanders 1983). 

HPLC is currently the most common technique for separation of the species of arsenic found in seafood 

(Benramdane et al. 1999b; Guerin et al. 1999; Kumaresan and Riyazuddin 2001). An advantage of HPLC 

over other separation methods (e.g., gas chromatography [GC]) is that the arsenic species do not need to 

be derivatized prior to separation, avoiding concerns over complete conversion to the derivative for 

detection. 

Since arsenic in air is usually associated with particulate matter, standard methods involve collection of 

air samples on glass fiber or membrane filters, acid extraction of the filters, arsine generation, and 

analysis by SDDC spectrophotometry or AAS (APHA 1977; NIOSH 1984). 

Methods standardized by the EPA for measuring total arsenic in water and waste water, solid wastes, soil, 

and sediments include: ICP-MS (EPA 1998j, 1994a, 1991), ICP-AES (EPA 1996d), graphite furnace 

AAS (EPA 1994b), quartz furnace hydride generation AAS (EPA 1996h), and an electrochemical method 

using anodic stripping voltammetry (ASV) (EPA 1996e). A modification using cryogenic GC to EPA 

Method 1632 (HG/AAS) allows the technique to be adopted for the species As(III), As(V), MMA, and 

DMA to the 0.003 ppb level (EPA 1998l). Similar methods are recommended by APHA for water using 

AAS/hydride generation (APHA 1989c), AAS/graphite furnace technique (APHA 1989b), ICP (APHA 

1989d), or SDDC spectrophotometry (APHA 1989a). The AAS/hydride generation method is generally 

resistant to matrix and chemical interferences (APHA 1989a). Techniques to compensate for these 

interferences have been described by EPA (1982b). 
ARSENIC 388 

7. ANALYTICAL METHODS 

Analysis for arsenic in foods is also most frequently accomplished by AAS techniques (Arenas et al. 

1988; Dabeka and Lacroix 1987; Hershey et al. 1988; Tam and Lacroix 1982). Hydride generation is the 

sample preparation method most often employed (Arenas et al. 1988; Hershey et al. 1988), but 

interferences must be evaluated and minimized. 

Speciation of inorganic arsenic in environmental samples is usually accomplished by chromatographic 

separation, chelation-extraction or elution of As(III), and then reduction of As(V) with subsequent similar 

treatment (Butler 1988; López-Gonzálvez et al. 1994; Mok et al. 1988; Rabano et al. 1989). 

Methods are also available for quantifying organic arsenicals in environmental media, including 

arsenobetaine in fish (Beauchemin et al. 1988; Cannon et al. 1983) and other organic forms of arsenic in 

water, soil, and foods using hyphenated methods of separation and detection (HPLC/ICP-MS, 

HPLC/HGAAS, IC/ICP-MS) (Andreae 1977; Braman et al. 1977; Comber and Howard 1989; Crecelius 

1978; Heitkemper et al. 1994; López-Gonzálvez et al. 1994; Odanaka et al. 1983; Teräsahde et al. 1996). 

Methods have been developed for extraction of arsenic species from solid seafood samples that included 

treatment of the sample with mixtures of organic solvents (alcohols or chloroform) and water to extract 

the arsenic compounds that are soluble in water or polar organic solvents. These extracts can be 

subsequently analyzed by HPLC. Enzymatic digestion using trypsin has also been used to extract arsenic 

compounds from seafood samples (Benramdane et al. 1999b). These extraction techniques are used in 

place of digestion when speciated data are needed. 

A summary of selected methods for analysis of total arsenic and individual inorganic and organic arsenic 

species in environmental samples is presented in Table 7-2. 

7.3 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 arsenic 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 arsenic. 
ARSENIC 389 

7. ANALYTICAL METHODS 

Table 7-2. Analytical Methods for Determining Arsenic in Environmental Samples 

Sample Analytical Sample Percent 

matrix Preparation method method detection limit recovery Reference 

Methods for total arsenic: 

Air Collection on cellulose ester 

(particulates) membrane filter; digestion 

with nitric acid, sulfuric acid, 

and perchloric acid 

Air Collection on 

(particulate Na2CO3-impregnated 

arsenic and cellulose ester membrane 

arsenic filter and H2O2 

trioxide 

vapor) 

Air Collection on cellulose ester 

membrane filter; digestion 

with nitric acid, sulfuric acid, 

and perchloric acid 

Water/waste Acid digestion 

water/solid 

wastes 

Water/waste Digestion with nitric and 

water/solid hydrochloric acids 

wastes 

Water/soil/ Digestion with nitric acid and 

solid waste hydrogen peroxide 

Water/waste Digestion with nitric acid 

water/solid 

waste 

Water/soil/ 

solid waste 

Digestion with nitric/sulfuric 

acid; reduction to As+3 with 

tin chloride; reduction to 

arsine with zinc in acid 

solution 

Water Reduction to arsine in acid 

solution; reaction with SDDC 

Water Digestion with 6M HCl; 

reduction to arsine with 

sodium borohydride; cold 

trap and desorption into 

quartz furnace 

NIOSH Method 0.02 μg/sample No data NIOSH 

7900; HGAAS 1994a 

NIOSH Method 0.06 μg/sample No data NIOSH 

7901; GFAAS 1994b 

NIOSH Method 0.140 μg/filter No data NIOSH 

7300; ICP-AES 2003 

EPA Method 35 μg/L 86 EPA 2000c 

6010C; ICPAES 

EPA Method 8 μg/L 106 EPA 1994c 

200.7; ICPAES 

EPA Methods 1 μg/L 85–106 EPA 1983b, 

206.2 and 1994b 

7060A; GFAAS 

with Ni(NO3)2 

modifier 

EPA Methods 0.4 μg/L 97–114 EPA 1991, 

200.8, 6020 1994a, 

and 6020A 1998j 

ICP-MS 

EPA Method 2 μg/L 85–94 EPA 1983c 

206.3 

EPA Method 10 μg/L 100 EPA 1983d 

206.4; SDDC 

colorimetric 

spectrophotometry at 

510 nm 

EPA Method 2 ng/L No data EPA 1998l 

1632; HGAAS 
ARSENIC 390 

7. ANALYTICAL METHODS 

Table 7-2. Analytical Methods for Determining Arsenic in Environmental Samples 

Sample Analytical Sample Percent 

matrix Preparation method method detection limit recovery Reference 

Food Digestion with nitric acid; dry 

ashing with magnesium 

oxide; reduction with 

ascorbic acid; precipitation 

with APDC in presence of 

nickel carrier 

Food Digestion with nitric/sulfuric/ 

perchloric acids; reduction to 

trivalent arsenic with potassium iodide; reduction to 

arsine with sodium borohydride 

Soil, rock, Preparation of pellet 

coal 

Methods for species of arsenic: 

Air Collection on PTFE filter 

(particulate 

organoarsenals) 

Air (arsine) Collection on coconut shell 

charcoal; digestion with nitric 

acid 

Air Collection on PFTE filter in 

particulates high volume dichotomous 

(As+3 and virtual impactor; desorption 

As+5 only) with ethanolic hydrochloric 

acid; selective reduction of 

As+3 to arsine with zinc in 

acid and reduction of As+5 to 

arsine with sodium tetrahydrodiborate 

Water Selective elution of As+3 with 

orthophosphoric acid; elution 

and conversion of As+5 to 

As+3 with sulfur dioxide 

Water/soil Selective complexation of 

As+5 with ammonium 

molybdate; extraction with 

isoamyl alcohol to separate 

from As+3 

GFAAS 10 ng 86–107 Dabeka and 

Lacroix 

1987 

HGAAS 0.1 μg/g 98–110 Hershey et 

al. 1988 

XRF 4 mg/kg SRM Nielson and 

(backscatter) recoveries: Sanders 

110±4 in 1983 

soil; 

100±1in 

rock; 97±18 

in coal 

NIOSH Method 0.2 μg No data NIOSH 

5022; ion As/sample 1994c 

chromatography/HGAAS 

NIOSH Method 0.004 μg/sample No data NIOSH 

6001; GFAAS 1994d 

HGAAS 1 ng/m3

 95±7 (As+3); Rabano et 

100±8 al. 1989 

(As+5) on 

spiked 

materials 

IEC/ampero- 0.9 μg/L 95% of Butler 1988 

metric detector converted 

(detects As+3 As+5 

only) recovered 

Colorimetric No data No data Brown and 

spectrometry at Button 1979 

712 nm 
ARSENIC 391 

7. ANALYTICAL METHODS 

Table 7-2. Analytical Methods for Determining Arsenic in Environmental Samples 

Sample Analytical Sample Percent 

matrix Preparation method method detection limit recovery Reference 

Water Selective extraction of As+3 NAA 0.01 ppb No data Braman et 

with APDC into chloroform; al. 1977 

back extraction with nitric 

acid; reduction of As+5 to 

As+3 with thiosulfate and 

extract 

Food (arseno- Extraction of arsenobetaine HPLC/ICP-MS 0.3 ng as 101±4 Beauchemin 

betaine in with methanol/chloroform; arsenobetaine recovery of et al. 1988 

fish) digestion with nitric acid/ arsenomagnesium nitrate for betaine 

remainder of As species 

Water/waste Acidification or digestion with EPA Method 0.1 μg/L 96–102 EPA 1996e 

water/soil hydrochloric acid 7063; ASV 

(inorganic 

species) 

Water (As(III), Cryogenic GC, Digestion EPA Method 3 ng/L No data EPA 1998l 

As(V), MMA, with 6M HCl; reduction to 1632 appendix; 

and DMA) arsine with sodium boro- HGAAS 

hydride; cold trap and 

desorption into quartz 

furnace 

Water Reduction to arsines; cold AAS 2 ng/L 91–109 Andreae 

trap and selectively warm to 1977 

separate arsine species 

Water Reduction of MMA, DMA HGAAS 0.019–0.061 ng No data Comber and 

and inorganic As (control pH 

to select As+3 or As+5) to 

Howard 

1989 

arsines with sodium tetrahydroborate; cold trap and 

selectively warm to separate 

arsine species 

Water/soil Extraction with sodium HG-HCT/GC­ 0.2–0.4 μg/L 97–102 Odanaka et 

bicarbonate; reduction of MID al. 1983 

inorganic arsenic, MMA and 

DMA to hydrides with 

sodium borohydride; cold 

trap arsines in n-heptane 

AAS = atomic absorption spectrophotometry; APDC = ammonium pyrrolidine dithiocarbamate; ASV = anodic 

stripping voltammetry; DMA = dimethylarsinate; EPA = Environmental Protection Agency; GC-MID = gas 

chromatography-multiple ion detection; GFAAS = graphite furnace atomic absorption spectrometry; HGAAS=hydride 

generation-atomic absorption spectroscopy; HG-HCT = hydride generation-heptane cold trap; HPLC = high 

performance liquid chromatography; ICP-AES = inductively coupled plasma-atomic emission spectrometry; 

ICP-MS = inductively coupled plasma-mass spectrometry; IEC = ion exchange chromatography; 

MMA = monomethylarsonate; NAA = neutron activation analysis; NIOSH = National Institute of Occupational Safety 

and Health; PTFE = polytetrafluoroethylene; SDDC = silver diethyldithiocarbamate; SRM = standard reference 

material; XRF = x-ray fluorescence 
ARSENIC 392 

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. 

7.3.1 Identification of Data Needs 

Methods for Determining Biomarkers of Exposure and Effect. The most common biomarker 

for arsenic exposure is analysis of total arsenic in urine (Hughes 2006). Existing methods are sufficiently 

sensitive to measure background levels of arsenic in various tissues and biological fluids for average 

persons, and to detect increases as a result of above-average exposure (Agahian et al. 1990; Clyne et al. 

1989; Curatola et al. 1978; Foà et al. 1984; Gebel et al. 1998b; Landsberger and Simsons 1987; Mushak 

et al. 1977; Pinto et al. 1976; Valentine et al. 1979; Versieck et al. 1983). The precision and accuracy of 

these methods are documented. Methods are also available that can distinguish nontoxic forms of arsenic 

(arsenobetaine) from inorganic and organic derivatives that are of health concern (Braman et al. 1977; 

Dix et al. 1987; Johnson and Farmer 1989; Norin and Vahter 1981; Tam et al. 1982). Further efforts to 

improve accuracy, reduce interferences, and detect multiple species using a single analysis would be 

valuable. Arsenic is believed to act by inhibition of numerous cellular and molecular processes. 

However, these effects are not specific to arsenic, and most can only be measured in tissue extracts. 

Methods for Determining Parent Compounds and Degradation Products in Environmental 

Media. Arsenic is ubiquitous in the environment. It is found in air, water, soil, sediments, and food in 

several inorganic and organic forms. Analytical methods exist for the analysis of arsenic species in all of 

these environmental media, and these methods have the sensitivity to measure background levels and to 

detect elevated concentrations due to emissions from sources such as smelters, chemical plants, or 

hazardous waste sites (APHA 1977, 1989c; EPA 1982b, 1983b, 1983c, 1983d, 1991, 1994b, 1994c, 

1996f, 1996h, 1998j, 2000c; NIOSH 1994a, 1994b, 2003). However, further research to reduce chemical 

and matrix interferences may improve the speed and accuracy of the analyses. 

Le et al. (2004) pointed out that there is a need for the development of certified reference materials 

(CRMs) for speciation analysis. A shortcoming of many CRMs is that they are only certified for the total 

concentration of arsenic, and only limited information is available on the identity and concentrations of 

specific arsenic species in some CRMs. 
ARSENIC 393 

7. ANALYTICAL METHODS 

Continued improvement of the methods for determination of the particular species of arsenic, rather than 

just the total arsenic concentration, present in foods, especially seafood, is needed since different arsenic 

species poses different hazards to individuals consuming these foods. 

7.3.2 Ongoing Studies 

The information in Table 7-3 was found as a result of a search of the Federal Research in Progress 

database (FEDRIP 2006). 
ARSENIC 394 

7. ANALYTICAL METHODS 

Table 7-3. Ongoing Studies on Analytical Methods for Arsenic in Environmental 

and Biological Samples 

Investigator Affiliation Research description Sponsor 

Styblo, M University of North 

Carolina Chapel Hill, 

Chapel Hill, North 

Carolina 

Optimized hydride 

generation system for 

arsenic analysis 

Fogarty International 

Center 

Dietze, WT Tracedetect, Inc., Seattle, A continuous monitor for NIEHS 

Washington arsenic in drinking water 

Dasgupta, PK Texas Tech University, 

Department of Chemistry, 

Lubbock, Texas 

A green fieldable 

analyzer for arsenic 

NSF 

NIEHS = National Institute of Environmental Health Sciences; NSF = National Science Foundation 

Source: FEDRIP 2006 
ARSENIC 395 

8. REGULATIONS AND ADVISORIES 

The international and national regulations and guidelines pertaining to arsenic and its metabolites in air, 

water, and other media are summarized in Table 8-1. 

ATSDR has not derived inhalation MRLs or an intermediate-duration oral MRL for inorganic arsenic, or 

any MRLs for organic arsenic, due to lack of suitable data. 

ATSDR has derived an acute-duration oral MRL for inorganic arsenic of 0.005 mg As/kg/day based on a 

LOAEL of 0.05 mg As/kg/day for gastrointestinal effects and facial edema in Japanese people who 

ingested arsenic-contaminated soy sauce for 2–3 weeks (Mizuta et al. 1956). An uncertainty factor of 

10 (10 for use of a LOAEL and 1 for human variability) was applied. 

ATSDR has derived a chronic-duration oral MRL of 0.0003 mg/kg/day for inorganic arsenic based on a 

NOAEL of 0.0008 mg As/kg/day for dermal effects in a Taiwanese farming population exposed to arsenic 

in well water (Tseng 1977; Tseng et al. 1968). An uncertainty factor of 3 (for human variability) was 

applied. 

EPA (IRIS 2007) has derived a chronic oral reference dose (RfD) of 0.0003 mg As/kg/day for inorganic 

arsenic, based on a NOAEL of 0.0008 mg As/kg/day for dermal effects and possible vascular 

complications in a Taiwanese farming population exposed to arsenic in well water (Tseng 1977; Tseng et 

al. 1968). An uncertainty factor of 3 (to account for the lack of reproductive data and uncertainty in 

whether the NOAEL accounts for all sensitive individuals) was applied. No reference concentration 

(RfC) for chronic inhalation exposures to arsenic was reported. EPA is currently revising the assessment 

for inorganic arsenic. 

The Department of Health and Human Services (DHHS) has determined that inorganic arsenic is known 

to be a human carcinogen (NTP 2005). The EPA has determined that inorganic arsenic is a human 

carcinogen and has assigned it the cancer classification, Group A (IRIS 2007). EPA’s quantitative 

estimates of carcinogenic risk from oral exposures include a cancer slope factor of 1.5 mg/kg/day and a 

drinking water unit risk of 5x10-5 μg/L. The inhalation unit risk for cancer is 0.0043 μg/m3

 (IRIS 2007). 
ARSENIC 396 

8. REGULATIONS AND ADVISORIES 

Table 8-1. Regulations and Guidelines Applicable to Arsenic and 

Arsenic Compounds 

Agency Description Information Reference 

INTERNATIONAL 

Guidelines: 

IARC Carcinogenicity classification for arsenic and Group 1a

 IARC 2004 

arsenic compounds 

WHO Air quality guidelines 1.5x10-3 unit riskb

 WHO 2000 

Drinking water quality guidelines for arsenic 0.01 mg/Lc

 WHO 2004 

NATIONAL 

Regulations and Guidelines: 

a. Air 

ACGIH TLV (TWA) for arsenic and inorganic compounds 0.01 mg/m3

 ACGIH 2004 

EPA Hazardous air pollutant (arsenic and inorganic Yes EPA 2004b 

compounds, including arsine) 42 USC 7412 

NIOSH REL (15-minute ceiling limit) for arsenic and 0.002 mg/m3 NIOSH 2005a 

inorganic compoundsd 

IDLH for arsenic and inorganic compoundsd 5 mg/m3 

OSHA PEL (8-hour TWA) for general industry for 0.5 mg/m3

 OSHA 2005d 

arsenic organic compounds 29 CFR 1910.1000 

PEL (8-hour TWA) for general industry for 10 μg/m3

 OSHA 2005c 

arsenic inorganic compounds 29 CFR 1910.1018 

PEL (8-hour TWA) for construction industry for 0.5 mg/m3

 OSHA 2005b 

arsenic organic compounds 29 CFR 1926.55 

PEL (8-hour TWA) for shipyard industry for 0.5 mg/m3

 OSHA 2005a 

arsenic organic compounds 29 CFR 1915.1000 

b. Water 

EPA Designated as hazardous substances in Yes EPA 2005d 

accordance with Section 311(b)(2)(A) of the 40 CFR 116.4 

Clean Water Act 

Arsenic pentoxide, arsenic trioxide, calcium 

arsenate, and sodium arsenite 

Drinking water standards and health advisories EPA 2004a 

for arsenic 

DWEL 0.01 mg/L 

National primary drinking water standards for EPA 2002a 

arsenic 

MCLG Zero 

MCL 0.01 mg/Le 

Reportable quantities of hazardous substances EPA 2005e 

designated pursuant to Section 311 of the Clean 40 CFR 117.3 

Water Act 

Arsenic pentoxide, arsenic trioxide, calcium 1 pound 

arsenate, sodium arsenite 
ARSENIC 

8. REGULATIONS AND ADVISORIES 

397 

Agency 

Table 8-1. Regulations and Guidelines Applicable to Arsenic and 

Arsenic Compounds 

Description Information Reference 

NATIONAL (cont.) 

EPA 

c. Food 

Water quality criteria for human health 

consumption of arsenic: 

Water + Organism 

Organism only 

EPA Tolerances for residues 

Dimethylarsinic acid 

Cotton (undelinted seed) 

Methanearsonic acid 

Cotton (undelinted seed) 

Cotton, hulls 

Fruit, citrus 

FDA Bottled drinking water 

USDA 

d. Other 

Nonsynthetic substances prohibited for use in 

organic crop production 

ACGIH Carcinogenicity classification for arsenic and 

arsenic compounds 

Biological exposure indices for inorganic arsenic 

plus methylated metabolites in urine at the end of 

the workweek 

EPA Carcinogenicity classification 

Oral slope factor 

Inhalation unit risk 

RfC 

RfD 

Superfund, emergency planning, and community 

right-to-know 

Designated CERCLA hazardous substance 

Reportable quantity 

 Arsenic 

Arsenic acid, arsenic pentoxide, arsenic 

trioxide, calcium arsenate, dimethylarsinic 

acid, and sodium arsenite 

Effective date of toxic chemical release 

reporting for arsenic 

0.018 μg/Lf 

0.14 μg/Lf 

2.8 ppm 

0.7 ppm 

0.9 ppm 

0.35 ppm 

0.01 mg/L 

Arsenic 

A1g 

35 μg As/L 

Group Ai 

1.5 per mg/kg/day 

4.3x10-3 per μg/m3

No data 

3x10-4 mg/kg/day 

Not applicablej 

1 pound 

01/01/87 

EPA 2002b 

EPA 2005i 

40 CFR 180.311 

EPA 2005j 

40 CFR 180.289 

FDA 2005 

21 CFR 165.110 

USDA 2004 

7 CFR 205.602 

ACGIH 2004

IRIS 2007 

EPA 2005f 

40 CFR 302.4 

EPA 2005h 

40 CFR 372.65 
ARSENIC 

8. REGULATIONS AND ADVISORIES 

398 

Agency 

Table 8-1. Regulations and Guidelines Applicable to Arsenic and 

Arsenic Compounds 

Description Information Reference 

NATIONAL (cont.)

 EPA Superfund, emergency planning, and community 

right-to-know 

Extremely hazardous substances EPA 2005g 

Reportable quantity 

Arsenic pentoxide, calcium arsenate, and 1 pound 

40 CFR 355, 

Appendix A 

sodium arsenite 

Threshold planning quantities 

 Arsenic pentoxide 100/10,000 pounds 

Calcium arsenate and sodium arsenite 500/10,000 pounds 

NTP Carcinogenicity classification Known human NTP 2005 

carcinogen 

a

Group 1: carcinogenic to humans b

Cancer risk estimates for lifetime exposure to a concentration of 1 μg/m3. c

Provisional guideline value: as there is evidence of a hazard, but the available information on health effects is limited. d

NIOSH potential occupational carcinogen e

MCL will become effective on 01/23/06. f

This criterion is based on carcinogenicity of 10-6 risk. g

A1: confirmed human carcinogen h

A3: confirmed animal carcinogen with unknown relevance to humans i

Group A: known human carcinogen j

Indicates that no reportable quantity is being assigned to the generic or broad class. 

ACGIH = American Conference of Governmental Industrial Hygienists; CERCLA = Comprehensive Environmetnal 

Response, Compensation, and Liability Act; CFR = Code of Federal Regulations; DWEL = drinking water equivalent 

level; EPA = Environmental Protection Agency; FDA = Food and Drug Administration; IARC = International Agency

for Research on Cancer; IDLH = immediately dangerous to life or health; IRIS = Integrated Risk Information System; 

MCL = maximum contaminant level; MCLG = maximum contaminant level goal; NAS/NRC = National Academy of 

Sciences/National Research Council; NIOSH = National Institute for Occupational Safety and Health; NTP = National 

Toxicology Program; OSHA = Occupational Safety and Health Administration; PEL = permissible exposure limit; 

REL = recommended exposure limit; RfC = inhalation reference concentration; RfD = oral reference dose; 

TLV = threshold limit values; TWA = time-weighted average; USC = United States Code; USDA = United States 

Department of Agriculture; WHO = World Health Organization
ARSENIC 399 

8. REGULATIONS AND ADVISORIES 

EPA is currently revising the assessment for inorganic arsenic. The International Agency for Research on 

Cancer (IARC) cites sufficient evidence of a relationship between exposure to arsenic and human cancer. 

IARC classification of arsenic is Group 1 (IARC 2004). The American Conference of Governmental 

Industrial Hygienists (ACGIH) classifies arsenic (elemental and inorganic compound) as a confirmed 

human carcinogen, cancer category A1 (ACGIH 2004). 

ATSDR has derived an intermediate-duration oral MRL of 0.1 mg MMA/kg/day for MMA based on a 

BMDL10 of 12.38 mg MMA/kg/day for diarrhea observed in rats exposed to MMA in the diet for 

13 weeks (Arnold et al. 2003) and an uncertainty factor of 100 (10 for animal to human extrapolation and 

10 for human variability). 

ATSDR has derived a chronic-duration oral MRL of 0.01 mg MMA/kg/day for MMA based on a 

BMDL10 of 1.09 mg MMA/kg/day for increased incidence of progressive nephropathy in male mice 

exposed to MMA in the diet for 2 years (Arnold et al. 2003) and an uncertainty factor of 100 (10 for 

animal to human extrapolation and 10 for human variability). 

ATSDR has derived a chronic-duration oral MRL of 0.02 mg DMA/kg/day for DMA based on a 

BMDL10 of 1.80 mg DMA/kg/day for increased vacuolization of the urothelium in the urinary bladder of 

female mice exposed to DMA in the diet for 2 years (Arnold et al. 2006) and an uncertainty factor of 

100 (10 for animal to human extrapolation and 10 for human variability). 

EPA has not derived RfD values for organic arsenicals (IRIS 2007). 
ARSENIC 400 

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____________________ 

ARSENIC 401 

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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. 
ARSENIC 494 

10. GLOSSARY 

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. 

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. 
ARSENIC 495 

10. GLOSSARY 

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. 

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. 
ARSENIC 496 

10. GLOSSARY 

Mortality—Death; mortality rate is a measure of the number of deaths in a population during a specified 

interval of time. 

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. 
ARSENIC 497 

10. GLOSSARY 

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 

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. 
ARSENIC 498 

10. GLOSSARY 

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. 

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. 
ARSENIC 499 

10. GLOSSARY 

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. 
ARSENIC 500 

This page is intentionally blank. 
ARSENIC 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 mean that adverse health effects will occur. 
ARSENIC A-2 

APPENDIX A 

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 

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-32, Atlanta, Georgia 30333. 
ARSENIC A-3 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: Inorganic Arsenic 

CAS Number: 7440-38-2 

Date: August 2007 

Profile Status: Post-Public Comment, Final Draft 

Route: [ ] Inhalation [X] Oral 

Duration: [X] Acute [ ] Intermediate [ ] Chronic 

Graph Key: 29 

Species: Human 

Minimal Risk Level: 0.005 [X] mg/kg/day [ ] ppm 

Reference: Mizuta N, Mizuta M, Ito F, et al. 1956. An outbreak of acute arsenic poisoning caused by 

arsenic-contaminated soy-sauce (shōyu): A clinical report of 220 cases. Bull Yamaguchi Med Sch 

4(2-3):131-149. 

Experimental design: Mizuta et al. (1956) summarized findings from 220 poisoning cases associated with 

an episode of arsenic contamination of soy sauce in Japan. The soy sauce was contaminated with 

approximately 0.1 mg As/mL, probably as calcium arsenate. Arsenic intake in the cases was estimated by 

the researchers to be 3 mg/day (0.05 mg/kg/day, assuming 55 kg average body weight for this Asian 

population). Duration of exposure was 2–3 weeks in most cases. Clinical symptoms were recorded. 

Seventy patients were examined opthalmologically. Laboratory tests were performed on some patients 

and included hematology, urinalysis, fecal exam, occult blood in gastric and duodenal juice, biochemical 

examination of blood, liver function tests, electrocardiograph, and liver biopsy. 

Effects noted in study and corresponding doses: The primary symptoms were edema of the face, and 

gastrointestinal and upper respiratory symptoms initially, followed in some patients by skin lesions and 

neuropathy. Other effects included mild anemia and leukopenia, mild degenerative liver lesions and 

hepatic dysfunction, abnormal electrocardiogram, and ocular lesions. For derivation of the acute oral 

MRL, facial edema and gastrointestinal symptoms (nausea, vomiting, diarrhea), which were characteristic 

of the initial poisoning and then subsided, were considered to be the critical effects. 

Dose and end point used for MRL derivation: 0.05 mg As/kg/day 

[ ] NOAEL [X] LOAEL 

Uncertainty factors used in MRL derivation: 

[ ] 1 [ ] 3 [X] 10 (for use of a LOAEL) 

[ ] 1 [ ] 3 [ ] 10 (for extrapolation from animals to humans) 

[X] 1 [ ] 3 [ ] 10 (for human variability) 

Was a conversion factor used from ppm in food or water to a mg/body weight dose? Not applicable. 

If an inhalation study in animals, list conversion factors used in determining human equivalent dose: Not 

applicable. 

Was a conversion used from intermittent to continuous exposure? Not applicable. 
ARSENIC A-4 

APPENDIX A 

Other additional studies or pertinent information that lend support to this MRL: The MRL is supported 

by the case of a man and wife in upstate New York who experienced gastrointestinal symptoms (nausea, 

diarrhea, abdominal cramps) starting almost immediately after beginning intermittent consumption of 

arsenic-tainted drinking water at an estimated dose of 0.05 mg As/kg/day (Franzblau and Lilis 1989). 

Gastrointestinal symptoms have been widely reported in other acute arsenic poisoning reports as well, 

although in some cases, the doses were higher and effects were severe, and in other cases, dose 

information was not available. The UF of 1 for intrahuman variability reflects the fact that the database 

includes persons of various ethnicities and age groups, including infants. 

Agency Contact (Chemical Manager): Selene Chou, Ph.D and Carolyn Harper, Ph.D. 
ARSENIC A-5 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: Inorganic Arsenic 

CAS Number: 7440-38-2 

Date: August 2007 

Profile Status: Post-Public Comment, Final Draft 

Route: [ ] Inhalation [X] Oral 

Duration: [ ] Acute [ ] Intermediate [X] Chronic 

Graph Key: 134 

Species: Human 

Minimal Risk Level: 0.0003 [X] mg/kg/day [ ] ppm 

References: Tseng, WP, Chu HM, How SW, et al. 1968. Prevalence of skin cancer in an endemic area of 

chronic arsenicism in Taiwan. J Natl Cancer Inst 40:453-463. 

Tseng, WP. 1977. Effects and dose-response relationships of cancer and Blackfoot disease with arsenic. 

Environ Health Perspect 19:109-119. 

Experimental design: Tseng et al. (1968) and Tseng (1977) investigated the incidence of Blackfoot 

disease and dermal lesions (hyperkeratosis and hyperpigmentation) in a large number of poor farmers 

(both male and female) exposed to high levels of arsenic in well water in Taiwan. A control group 

consisting of 17,000 people was identified. The authors stated that the incidence of dermal lesions 

increased with dose, but individual doses were not provided. However, incidence data were provided 

based on stratification of the exposed population into low (<300 μg/L), medium (300–600 μg/L), or high 

(>600 μg/L) exposure levels. Doses were calculated from group mean arsenic concentrations in well 

water, assuming the intake parameters described by Abernathy et al. (1989). Accordingly, the control, 

low-, medium-, and high-exposure levels correspond to doses of 0.0008, 0.014, 0.038, and 0.065 mg 

As/kg/day, respectively. The NOAEL identified by Tseng (1977) (0.0008 mg As/kg/day) was limited by 

the fact that the majority of the population was <20 years of age and the incidence of skin lesions 

increased as a function of age, and because the estimates of water intake and dietary arsenic intake are 

highly uncertain. Schoof et al. (1998) estimated that dietary intakes of arsenic from rice and yams may 

have been 15–211 μg/day (mean 61 μg/day), based on arsenic analyses of foods collected in Taiwan in 

1993–1995. Use of the 50 μg/day estimate would result in an approximate doubling of the NOAEL 

(0.0016 mg/kg/day). 

Effects noted in study and corresponding doses: A clear dose-response relationship was observed for 

characteristic skin lesions: 

0.0008 mg As/kg/day = control group (NOAEL) 

0.014 mg As/kg/day = hyperpigmentation and keratosis of the skin (less serious LOAEL) 

0.038–0.065 mg As/kg/day = increased incidence of dermal lesions 

Dose and end point used for MRL derivation: 0.0008 mg As/kg/day 

[X] NOAEL [ ] LOAEL 

Uncertainty factors used in MRL derivation: 

[ ] 1 [ ] 3 [ ] 10 (for use of a LOAEL)

[ ] 1 [ ] 3 [ ] 10 (for extrapolation from animals to humans) 
ARSENIC A-6 

APPENDIX A 

[ ] 1 [x] 3 [ ] 10 (for human variability) 

Was a conversion factor used from ppm in food or water to a mg/body weight dose? The arithmetic mean 

concentration of arsenic in well water for the control group (0.009 mg/L) was converted to a NOAEL of 

0.0008 mg As/kg/day as described below: 

⎡⎛ 0.009mg ⎞
 0.002 ⎤


This NOAEL conversion assumed a water intake of 4.5 L/day and a body weight of 55 kg, and includes 

an estimation of arsenic intake of 0.002 mg As/kg/day from food. These assumptions are detailed in 

Abernathy et al. (1989). This approach to deriving a chronic oral MRL is identical to EPA’s approach to 

deriving a chronic oral RfD. 

If an inhalation study in animals, list conversion factors used in determining human equivalent dose: Not 

applicable. 

Was a conversion used from intermittent to continuous exposure? Not applicable. 

Other additional studies or pertinent information that lend support to this MRL: The MRL is supported 

by a number of well conducted epidemiological studies that identify reliable NOAELs and LOAELs for 

dermal effects. EPA (1981b) identified a NOAEL of 0.006–0.007 mg As/kg/day for dermal lesions in 

several small populations in Utah. Harrington et al. (1978) identified a NOAEL of 0.003 mg As/kg/day 

for dermal effects in a small population in Alaska. Guha Mazumder et al. (1988) identified a NOAEL of 

0.009 mg As/kg/day and a LOAEL of 0.006 mg As/kg/day for pigmentation changes and hyperkeratosis 

in a small population in India. Haque et al. (2003) identified a LOAEL of 0.0043 mg As/kg/day for 

hyperpigmentation and hyperkeratosis in a case-control study in India. Cebrían et al. (1983) identified a 

NOAEL of 0.0004 mg As/kg/day and a LOAEL of 0.022 mg As/kg/day in two regions in Mexico. 

Borgoño and Greiber (1972) and Zaldívar (1974) identified a LOAEL of 0.02 mg As/kg/day for abnormal 

skin pigmentation in patients in Chile, and Borgoño et al. (1980) identified a LOAEL of 0.01 mg 

As/kg/day for the same effect in school children in Chile. Valentine et al. (1985) reported a NOAEL of 

0.02 mg As/kg/day for dermal effects in several small populations in California. Collectively, these 

studies indicate that the threshold dose for hyperpigmentation and hyperkeratosis is approximately 

0.002 mg As/kg/day. 

Agency Contacts (Chemical Managers): Selene Chou, Ph.D and Carolyn Harper, Ph.D. 

4.5L 

day 

mg 

day 

×
 +
 ÷
55kg 0.0008mgAs / kg / day ⎜

⎜

⎝

⎢

⎣ ⎥

⎦


=
 ⎟

⎟

L ⎠

ARSENIC A-7 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: Monomethylarsonic acid (MMA) 

CAS Number: 124-58-3 

Date: August 2007 

Profile Status: Post-Public Comment, Final Draft 

Route: [ ] Inhalation [X] Oral 

Duration: [ ] Acute [X] Intermediate [ ] Chronic 

Graph Key: 12 

Species: Rat 

Minimal Risk Level: 0.1 [X] mg MMA/kg/day [ ] ppm 

References: Arnold LL, Eldan M, van Gemert M, et al. 2003. Chronic studies evaluating the 

carcinogenicity of monomethylarsonic acid in rats and mice. Toxicology 190:197-219. 

Crown S, Nyska A, Waner T. 1990. Methanearsonic acid: Combined chronic feeding and oncogenicity 

study in the rat. Conducted by Life Science Research Israel Ltd., Ness Ziona Israel. Submitted to EPA 

Office of Pesticide Programs (MRID 41669001). 

Experimental design: Groups of 60 male and 60 female Fischer 344 rats were exposed to 0, 50, 400, or 

1,300 ppm MMA in the diet for 104 weeks. Using the average doses for weeks 1–50 reported in an 

unpublished version of this study (Crown et al. 1990), doses of 0, 3.5, 30.2, and 106.9 mg MMA/kg/day 

and 0, 4.2, 35.9, and 123.3 mg MMA/kg/day were calculated for males and females, respectively. Body 

weights, food consumption, and water intake were monitored regularly. Blood was taken at 3, 6, and 

12 months for clinical chemistry measurements, and urine samples were collected at the same interval. 

Effects noted in study and corresponding doses: Mortality was increased in high-dose males and females 

during the first 52 weeks of the study. Body weights were decreased in the mid- and high-dose groups of 

both sexes; however, at 51 weeks, only the body weight for the high-dose males was <10% of the control 

weight (14.5%). Food and water consumption was increased in the mid- and high-dose groups. Diarrhea 

was observed in 100% of the high-dose males and females and in 16.7 and 40% of the mid-dose males 

and females during the first 52 weeks of exposure. Diarrhea first occurred after 3 weeks of exposure to 

the high dose and 4 weeks of exposure to the mid-dose group; the severity of the diarrhea was doserelated. The gastrointestinal system was the primary target in animals dying early; numerous 

macroscopic and histological alterations were observed. 

Dose and end point used for MRL derivation: Benchmark dose analysis of the dose-response data 

(Table A-1) for diarrhea in male and female rats exposed to MMA in the diet for 1–52 weeks (incidence 

data reported in Crown et al. 1990) was conducted. All available dichotomous models in EPA’s 

Benchmark Dose Software (version 1.4.1) were fit to the data. Predicted doses associated with a 10% 

extra risk were calculated. As assessed by the chi-square goodness-of-fit statistic, all models, with the 

exception of the quantal linear model for male incidence data and the quantal linear model for female 

incidence data, provided an adequate fit (X2 

p>0.1) (Table A-2). Comparing across models, a better fit is 

generally indicated by a lower Akaike’s Information Criteria (AIC). As assessed by AIC, the gamma 

model for the males (Figure A-1) and the 2-degree polynomial multi-stage model for the females 

(Figure A-2) provide the best fit to the data. The predicted BMD10 and BMDL10 are 28.25 mg 

MMA/kg/day and 22.99 mg MMA/kg/day for the male rat incidence data and 16.17 mg MMA/kg/day, 

and 12.38 mg MMA/kg/day for the female rat incidence data. 
ARSENIC A-8 

APPENDIX A 

Table A-1. Incidences of Diarrhea in Rats Exposed to 

MMA in the Diet for 1–52 Weeks 

Dietary concentration (ppm) Dose (mg MMA/kg/day) Incidence 

Male rats 

0 0 2/60 

50 3.5 0/60 

400 30.2 10/60 

1,300 106.9 60/60 

Female rats 

0 0 0/60 

50 4.2 0/60 

400 35.9 24/60 

1,300 123.3 60/60 

Sources: Arnold et al. 2003; Crown et al. 1990 

Table A-2. Modeling Predictions for the Incidence of Diarrhea in Rats 

Exposed to MMA in the Diet for 1–52 Weeks 

Model 

BMD10 

(mg MMA/kg/day) 

BMDL10 

(mg MMA/kg/day) x2 p-value AIC 

Male rats 

Gammaa 28.25 22.99 0.36 78.41

 Logistic 

Log-logisticb 

 Multi-stagec

 Probit 

24.60 

29.32 

25.74 

23.11 

20.19 

24.73 

19.90 

18.67 

0.16 

0.15 

0.35 

0.11 

79.59 

80.41

78.51 

80.02 

Log-probitb

 Quantal linear 

 Weibulla

 28.79 

6.317 

27.99 

24.47 

5.079 

20.66 

0.15 

0.00 

0.15 

80.41 

123.06 

80.41 

Female rats 

Gammaa

 26.81 15.18 1.00 84.76 

 Logistic 

Log-logisticb 

Multi-stagec 

Probit 

32.85 

31.97 

16.17 

29.89 

21.49 

20.16 

12.38 

19.11 

1.00 

1.00 

0.90 

1.00 

84.76 

84.76 

83.88

84.76 

Log-probitb

 Quantal linear 

 Weibulla

 28.95 

5.33 

27.83 

18.87 

4.33 

13.58 

1.00 

0.00 

1.00 

84.76 

106.52 

84.76 

Sources: Arnold et al. 2003; Crown et al. 1990 

a

Restrict power ≥1. b

Slope restricted to >1. c

Restrict betas ≥0; lowest degree polynomial with an adequate fit is reported; degree of polynomial=3. d

Restrict betas ≥0; lowest degree polynomial with an adequate fit is reported; degree of polynomial=2. 
ARSENIC A-9 

APPENDIX A 

Figure A-1. Predicted and Observed Incidence of Diarrhea in Male Rats Exposed 

to MMA in the Diet for 1–52 Weeks* 

Gamma Multi-Hit Model with 0.95 Confidence Level 

0 

0.2 

0.4 

0.6 

0.8 

1 

Fraction Affected 

BMDL BMD 

Gamma Multi-Hit 

0 20 40 60 80 100 

dose 

09:50 08/03 2007 

*BMDs and BMDLs indicated are associated with a 10% extra risk change from the control, and are in units of mg MMA/kg/day. 
ARSENIC A-10 

APPENDIX A 

Figure A-2. Predicted and Observed Incidence of Diarrhea in Female Rats 

Exposed to MMA in the Diet for 52 Weeks* 

Multistage Model with 0.95 Confidence Level 

Fraction Affected 

1 

0.8 

0.6 

0.4 

0.2 

0 

0 20 40 60 80 100 120 

BMDL BMD 

Multistage 

dose 

10:42 08/03 2007 

*BMDs and BMDLs indicated are associated with a 10% extra risk change from the control, and are in units of mg MMA/kg/day. 

The BMDL10 of 12.38 mg MMA/kg/day for female rats was selected as the point of departure for deriving 

the intermediate-duration oral MRL because it was lower than the BMDL10 (22.99 mg MMA/kg/day) 

calculated using the male incidence data. 

[ ] NOAEL [ ] LOAEL [X] BMDL 

Uncertainty factors used in MRL derivation: 100 

[ ] 10 for use of a LOAEL 

[X] 10 for extrapolation from animals to humans 

[X] 10 for human variability 

Was a conversion factor used from ppm in food or water to a mg/body weight dose? Doses calculated 

using the average of the achieved doses for weeks 1–50 reported in Crown et al. (1990): 0, 3.5, 30.2, and 

106.9 mg MMA/kg/day for males and 0, 4.2, 35.9, and 123.3 mg MMA/kg/day for females. 

If an inhalation study in animals, list conversion factors used in determining human equivalent dose: Not 

applicable. 

Was a conversion used from intermittent to continuous exposure? Not applicable. 
ARSENIC A-11 

APPENDIX A 

Other additional studies or pertinent information that lend support to this MRL: Increases in the 

incidence of diarrhea has also been observed in dogs administered via capsule 2 mg MMA/kg/day for 

52 weeks (Waner and Nyska 1988); the increased incidence of diarrhea started during weeks 25–28. At 

35 mg MMA/kg/day, vomiting was also observed in the dogs. Diarrhea has also been observed in rats 

and mice exposed to MMA for 2 years (Arnold et al. 2003); the LOAELs are 25.7 and 67.1 mg 

MMA/kg/day, respectively. 

Agency Contacts (Chemical Managers): Selene Chou, Ph.D and Carolyn Harper, Ph.D. 
ARSENIC A-12 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: Monomethylarsonic acid (MMA) 

CAS Number: 124-58-3 

Date: August 2007 

Profile Status: Post-Public Comment, Final Draft 

Route: [ ] Inhalation [X] Oral 

Duration: [ ] Acute [ ] Intermediate [X] Chronic 

Graph Key: 21 

Species: Mouse 

Minimal Risk Level: 0.01 [X] mg MMA/kg/day [ ] ppm 

References: Arnold LL, Eldan M, van Gemert M, et al. 2003. Chronic studies evaluating the 

carcinogenicity of monomethylarsonic acid in rats and mice. Toxicology 190:197-219. 

Gur E, Piraic H, Waner T. 1991. Methanearsonic acid: Combined oncogenicity study in the mouse. 

Conducted by Life Science Research Israel Ltd., Ness Ziona Israel. Submitted to EPA Office of Pesticide 

Programs (MRID 42173201). 

Experimental design: Groups of 52 male and 52 female B6C3F1 mice were exposed to 0, 10, 50, 200, or 

400 ppm of MMA in the diet for 104 weeks. The reported MMA doses were 0, 1.2, 6.0, 24.9, and 

67.1 mg MMA/kg/day (males) and 0, 1.4, 7.0, 31.2, and 101 mg MMA/kg/day (females). Body weights, 

food consumption, and water intake were monitored regularly. Blood was taken at 3, 6, 12, 18, and 

24 months for white cell counts. At sacrifice, complete necropsies were performed, including histological 

examination of at least 13 organs. 

Effects noted in study and corresponding doses: No treatment-related increases in mortality were 

observed. Significant decreases in body weights were observed in males and females exposed to 32.2 or 

48.5 mg As/kg/day, respectively; at week 104, the males weighed 17% less than controls and females 

weighed 23% less. Food consumption was increased in females exposed to 101 mg MMA/kg/day, and 

water consumption was increased in 67.1 mg MMA/kg/day males and 31.2 and 101 mg MMA/kg/day 

females. Loose and mucoid feces were noted in mice exposed to 67.1/101 mg MMA/kg/day. No changes 

were seen in white cell counts of either sex. Small decreases in the weights of heart, spleen, kidney, and 

liver were seen in some animals, but the decreases were not statistically significant. Squamous 

metaplasia of the cecum, colon, and rectum was observed at 67.1/101 mg MMA/kg/day. The incidences 

of metaplasia in the cecum, colon, and rectum were 29/49, 14/49, and 39/49 in males and 38/52, 17/52, 

and 42/52 in females; metaplasia was not observed in other groups of male or female mice. An increased 

incidence of progressive glomerulonephropathy (incidence of 25/52, 27/52, 38/52, 39/52, and 46/52 in the 

0, 1.2, 6.0, 24.9, and 67.1 mg MMA/kg/day) was observed in males; the incidence was significantly 

higher (Fisher Exact Test) than controls at ≥6.0 mg MMA/kg/day. Significant increases in the incidence 

of nephrocalcinosis was observed in the males at 24.9 and 67.1 mg MMA/kg/day (Fisher Exact Test) 

(incidence of 25/52, 30/52, 30/52, 45/522 45/51 and 0/52, 1/52, 1/52, 2/52, and 5/52 in males and 

females, respectively). The investigators noted that the kidney lesions were consistent with the normal 

spectrum of spontaneous renal lesions and there was no difference in character or severity of the lesions 

between groups. A reduction in the incidence of cortical focal hyperplasia in the adrenal gland of male 

mice exposed to 67.1 mg MMA/kg/day was possibly related to MMA exposure; the toxicological 

significance of this effect is not known. 

Dose and end point used for MRL derivation: Benchmark dose analysis of the dose-response data 

(Table A-3) for progressive glomerulonephropathy in male mice exposed to MMA in the diet for 2 years 
ARSENIC A-13 

APPENDIX A 

(incidence data reported in Gur et al. 1991) was conducted. All available dichotomous models in EPA’s 

Benchmark Dose Software (version 1.4.1) were fit to the data. Predicted doses associated with a 10% 

extra risk were calculated. As assessed by the chi-square goodness-of-fit statistic, all models, with the 

exception of the log-probit model, provided an adequate fit (X2 

p>0.1) (Table A-4). Comparing across 

models, a better fit is generally indicated by a lower Akaike’s Information Criteria (AIC). As assessed by 

AIC, the log-logistic model (Figure A-3) provided the best fit to the data. The predicted BMD10 and 

BMDL10 for the incidence data are 2.09 and 1.09 mg MMA/kg/day. 

Table A-3. Incidence of Progressive Glomerulonephropathy in Male Mice

Exposed to MMA in the Diet for 2 Years 

Dietary Concentration (ppm) Dose (mg MMA/kg/day) Incidence 

0 0 25/52 

10 1.2 27/52 

50 6.0 38/52 

200 24.9 39/52 

400 67.1 46/52 

Sources: Arnold et al. 2003; Gur et al. 1991 

Table A-4. Modeling Predictions for the Incidence of Progressive 

Glomerulonephropathy in Male Mice Exposed to 

MMA in the Diet for 2 Years 

BMD10 BMDL10 

Model (mg MMA/kg/day) (mg MMA/kg/day) x2 p-value AIC 

Gammaa 4.60 3.15 0.18 309.33 

Logistic 6.09 4.45 0.13 310.15 

Log-logisticb 2.09 1.09 0.38 307.47 

Multi-stagec

 4.60 3.15 0.18 309.33 

Probit 6.62 5.00 0.11 310.43 

Log-probitb

 8.54 5.50 0.08 311.11 

Quantal linear 4.60 3.15 0.18 309.33 

Weibulla

 4.60 3.15 0.18 309.33 

Sources: Arnold et al. 2003; Gur et al. 1991 

a

Restrict power ≥1. b

Slope restricted to >1. c

Restrict betas ≥0; lowest degree polynomial with an adequate fit is reported; degree of polynomial=1. 
ARSENIC A-14 

APPENDIX A 

Figure A-3. Predicted and Observed Incidence of Progressive

Glomerulonephropathy in Male Mice Exposed to MMA* 

Log-Logistic Model with 0.95 Confidence Level 

0.3 

0.4 

0.5 

0.6 

0.7 

0.8 

0.9 

1 

Fraction Affected 

BMDL BMD 

Log-Logistic 

0 10 20 30 40 50 60 70 

dose 

10:57 08/03 2007 

*BMDs and BMDLs indicated are associated with a 10% extra risk change from the control, and are in units of mg MMA/kg/day. 

The BMDL10 of 1.09 mg MMA/kg/day for male mice was selected as the point of departure for deriving 

the chronic-duration oral MRL. 

[ ] NOAEL [ ] LOAEL [X] BMDL 

Uncertainty factors used in MRL derivation: 100 

[ ] 10 for use of a LOAEL 

[X] 10 for extrapolation from animals to humans 

[X] 10 for human variability 

Was a conversion factor used from ppm in food or water to a mg/body weight dose? Doses calculated 

using the average of the achieved doses reported in Gur et al. (1991): 0, 1.2, 6.0, 24.9, and 67.1 mg 

MMA/kg/day for males and 0, 1.4, 7.0, 31.2, and 101 mg MMA/kg/day for females. 

If an inhalation study in animals, list conversion factors used in determining human equivalent dose: Not 

applicable. 

Was a conversion used from intermittent to continuous exposure? Not applicable. 
ARSENIC A-15 

APPENDIX A 

Other additional studies or pertinent information that lend support to this MRL: An exacerbation of 

chronic progressive nephropathy (an increase in the severity of the nephropathy) has also been observed 

in rats exposed to ≥33.9 mg MMA/kg/day for 2 years (Arnold et al. 2003). 

Agency Contacts (Chemical Managers): Selene Chou, Ph.D and Carolyn Harper, Ph.D. 
ARSENIC A-16 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: Dimethylarsinic acid (DMA) 

CAS Number: 75-60-5 

Date: August 2007 

Profile Status: Post-Public Comment, Final Draft 

Route: [ ] Inhalation [X] Oral 

Duration: [ ] Acute [ ] Intermediate [X] Chronic 

Graph Key: 35 

Species: Mouse 

Minimal Risk Level: 0.02 [X] mg DMA/kg/day [ ] ppm 

References: Arnold LL, Eldan M, Nyska A, et al. 2006. Dimethylarsinic acid: Results of chronic 

toxicity/oncogenicity studies in F344 rats and B6C3F1 mice. Toxicology 223:82-100. 

Gur E, Nyska A, Pirak M, et al. 1989b. Cacodylic acid: Oncogenicity study in the mouse. Conducted 

by Life Science Research Israel Ltd., Ness Ziona Israel. Submitted to EPA Office of Pesticide Programs 

(MRID 41914601). 

Experimental design: Groups of 56 male and 56 female B6C3F1 mice were exposed to 0, 8, 40, 200, or 

500 ppm DMA in the diet for 2 years. The investigators reported the dietary doses were equivalent to 

approximately 0, 1.3, 7.8, 37, and 94 mg DMA/kg/day. The following parameters were used to assess 

toxicity: clinical observations, body weight, food consumption, water consumption, differential leukocyte 

levels measured at 12, 18, and 24 months in mice in the control and 94 mg DMA/kg/day groups, organ 

weights (brain, kidneys, liver, and testes), and histopathological examination of major tissues and organs. 

Effects noted in study and corresponding doses: No deaths were observed. Decreases in body weight 

gain were observed in the male mice exposed to 94 mg DMA/kg/day; the difference was <10% and was 

not considered adverse. An increase in water consumption was observed in males exposed to 94 mg 

DMA/kg/day during weeks 60–96. No treatment-related clinical signs were observed. In the female mice 

exposed to 94 mg DMA/kg/day, a statistically significant decrease in lymphocytes and increase in 

monocytes were observed at 24 months. Treatment related nonneoplastic alterations were observed in the 

urinary bladder and kidneys. In the urinary bladder, increases in the vacuolization of the superficial cells 

of the urothelium were observed in males exposed to 37 or 94 mg DMA/kg/day (0/44, 1/50, 0/50, 36/45, 

48/48) and in females exposed to 7.8, 37, or 94 mg DMA/kg/day (1/45, 1/48, 26/43, 47/47, 43/43); 

incidence data reported in Gur et al. (1989b). An increased incidence of progressive 

glomerulonephropathy was observed in males at 37 mg DMA/kg/day (16/44, 22/50, 17/50, 34/45, 30/50) 

and an increased incidence of nephrocalcinosis was also observed in male mice at 94 mg DMA/kg/day 

(30/44, 25/50, 27/50, 29/50, 45/50). Neoplastic alterations were limited to an increased incidence of 

fibrosarcoma of the skin in females exposed to 94 mg DMA/kg/day; the incidence was 3/56, 0/55, 1/56, 

1/56, and 6/56 in the 0, 1.3, 7.8, 37, and 94 mg DMA/kg/day groups, respectively; however it was 

concluded that this lesion was not related to DMA exposure. 

Dose and end point used for MRL derivation: Benchmark dose analysis of the dose-response data 

(Table A-5) for vacuolization of the urothelium in the urinary bladder in female mice exposed to DMA in 

the diet for 2 years (incidence data reported in Gur et al. 1989b) was conducted. All available 

dichotomous models in EPA’s Benchmark Dose Software (version 1.4.1) were fit to the data. Predicted 

doses associated with a 10% extra risk were calculated. As assessed by the chi-square goodness-of-fit 

statistic, all models, with the exception of the quantal linear model, provided an adequate fit (X2 

p>0.1) 

(Table A-6). Comparing across models, a better fit is generally indicated by a lower AIC. The AIC 
ARSENIC A-17 

APPENDIX A 

values were similar for the logistic, multi-stage, and probit models; of these three models, the multi-stage 

had the lowest BMD10 and was selected for the analysis (see Figure A-4). The predicted BMD10 and 

BMDL10 for the incidence data are 2.68 and 1.80 mg DMA/kg/day. 

Table A-5. Incidence of Vacuolization of Urotheium in Urinary Bladder of 

Female Mice Exposed to DMA in the Diet for 2 Years 

Dietary concentration (ppm) Dose (mg DMA/kg/day) Incidence 

0 0 1/45 

8 1.3 1/48 

40 7.8 26/43 

200 37 47/47 

500 94 43/43 

Sources: Arnold et al. 2006; Gur et al. 1989b 

Table A-6. Modeling Predictions for the Incidence of Vacuolization 

in of Urothelium in Urinary Bladder of Female Mice 

Exposed to DMA in the Diet for 2 Years 

BMD10 BMDL10 

Model (mg DMA/kg/day) (mg DMA/kg/day) x2 p-value AIC 

Gammaa 5.01 1.85 1.00 83.03 

Logistic 3.66 2.78 0.95 81.37 

Log-logisticb

 6.23 2.34 1.00 83.03 

Multi-stagec 2.68 1.80 0.90 81.69 

Probit 3.20 2.46 0.89 81.60 

Log-probitb

 5.03 2.00 1.00 83.03 

Quantal linear 0.98 0.76 0.07 91.75 

Weibulla

 4.77 1.88 1.00 83.03 

Sources: Arnold et al. 2006; Gur et al. 1989b 

a

Restrict power ≥1. b

Slope restricted to >1. c

Restrict betas ≥0; lowest degree polynomial with an adequate fit is reported; degree of polynomial=2. 
ARSENIC A-18 

APPENDIX A 

Figure A-4. Predicted and Observed Incidence of Vacuolization of 

Urothelium in Urinary Bladder of Female Mice* 

Multistage Model with 0.95 Confidence Level 

0 

0.2 

0.4 

0.6 

0.8 

1 

Fraction Affected 

BMDL BMD 

Multistage 

0 20 40 60 80 

dose 

13:25 08/03 2007 

Source: Arnold et al. 2006 

*BMDs and BMDLs indicated are associated with a 10% extra risk change from the control, and are in units of mg 

DMA/kg/day. 

The BMDL10 of 1.80 mg DMA/kg/day for female mice was selected as the point of departure for deriving 

the chronic-duration oral MRL. 

[ ] NOAEL [ ] LOAEL [X] BMDL 

Uncertainty factors used in MRL derivation: 100 

[ ] 10 for use of a LOAEL 

[X] 10 for extrapolation from animals to humans 

[X] 10 for human variability 

Was a conversion factor used from ppm in food or water to a mg/body weight dose? Doses reported in 

Gur et al. (1989b): 0, 1.3, 7.8, 37, and 94 mg DMA/kg/day. 

If an inhalation study in animals, list conversion factors used in determining human equivalent dose: Not 

applicable. 

Was a conversion used from intermittent to continuous exposure? Not applicable. 
ARSENIC A-19 

APPENDIX A 

Other additional studies or pertinent information that lend support to this MRL: One other study has 

investigated the chronic toxicity of DMA in species other than rats. In this study, administration of 16 mg 

DMA/kg/day via a capsule for 52 weeks resulted in increases in the incidence of diarrhea; no histological 

alterations were observed (Zomber et al. 1989). 

Agency Contacts (Chemical Managers): Selene Chou, Ph.D and Carolyn Harper, Ph.D. 
ARSENIC A-20 

This page is intentionally blank. 
ARSENIC B-1 

APPENDIX B. USER'S GUIDE 

Chapter 1 

Public Health Statement 

This chapter of the profile is a health effects summary written in nontechnical 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 
ARSENIC B-2 

APPENDIX B 

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. 

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. 
ARSENIC 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, 
ARSENIC B-4 

APPENDIX B 

which was used to derive an intermediate exposure, inhalation MRL of 0.005 ppm (see 

footnote "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. 
ARSENIC 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. 
SAMPLE 

1 →	 Table 3-1. Levels of Significant Exposure to [Chemical x] – Inhalation 

Key to figurea 

Exposure frequency/ 

Species duration System 

NOAEL (ppm) 

LOAEL (effect) 

Less serious (ppm) 

Serious (ppm) 

Re

2 → INTERMEDIATE EXPOSURE 3 4 

5 6 7 8 9 10

→ Systemic ↓ ↓ ↓ ↓ ↓ ↓ → 

13 wk 5 d/wk 6 hr/d 

18 RatCHRONIC EXPOSURE 

Resp 3b 10 (hyperplasia) 

Nit

Cancer 

↓ 

38 39 40 

Rat Rat Mouse 

18 mo 5 d/wk 7 hr/d 89–104 wk 5 d/wk 6 hr/d 79–103 wk 5 d/wk 6 hr/d 

20 10 10 

(CEL, multiple organs) (CEL, lung tumors, nasal tumors) (CEL, lung tumors, hemangiosarcomas) 

WNTNT

11 

12 →	 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). 

ARSENIC B-8 

APPENDIX B 

This page is intentionally blank. 
ARSENIC 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 
ARSENIC C-2 

APPENDIX C 

DOT/UN/ Department of Transportation/United Nations/ 

NA/IMCO North America/Intergovernmental Maritime Dangerous Goods Code 

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 
ARSENIC C-3 

APPENDIX C 

MCLG maximum contaminant level goal 

MF modifying factor 

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 
ARSENIC C-4 

APPENDIX C 

OWRS Office of Water Regulations and Standards, EPA 

PAH polycyclic aromatic hydrocarbon 

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 
ARSENIC 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 
ARSENIC C-6 

APPENDIX C 

This page is intentionally blank. 
APPENDIX D. INDEX 

absorbed dose............................................................................................................................................258 

adenocarcinoma ..........................................................................................................................................71 

adenocarcinomas............................................................................................................................... 193, 263 

adrenal gland....................................................................................................................................... 36, 197 

adrenal glands ...........................................................................................................................................197 

adsorbed ............................................................................................................ 261, 325, 326, 367, 370, 377

adsorption.................................................................................................................................. 325, 326, 363 

aerobic............................................................................................................................................... 333, 334 

ambient air .................................................................................................................................. 69, 336, 364 

anaerobic........................................................................................................................................... 333, 334 

androgen receptor......................................................................................................................................288 

anemia................................................................................................................................... 30, 60, 169, 283 

aspartate aminotransferase (see AST).......................................................................................................171 

AST (see aspartate aminotransferase).......................................................................................................171 

bioaccumulation........................................................................................................................ 330, 337, 340 

bioavailability ........................................................... 213, 214, 215, 333, 335, 363, 364, 365, 370, 373, 380

bioconcentration factor .............................................................................................................................330 

biomarker .................................................................................................. 257, 258, 260, 261, 262, 288, 392 

biomarkers ........................................................................................................................ 257, 258, 262, 383 

blood cell count...........................................................................................................................................60 

body weight effects ..................................................................................................... 63, 177, 178, 196, 197 

breast milk..................................................................................................... 9, 217, 226, 256, 286, 359, 368 

cancer ............................................................. 7, 8, 17, 18, 19, 22, 23, 42, 56, 64, 68, 69, 70, 71, 72, 73, 74, 

.............................................................. 176, 185, 188, 189, 190, 191, 192, 193, 198, 199, 211, 248, 250,

................................253, 254, 255, 262, 263, 265, 270, 277, 278, 280, 282, 286, 287, 288, 289, 395, 399 

carcinogen......................................................................................... 7, 18, 23, 187, 192, 193, 395, 398, 399 

carcinogenic ............................................................ 7, 26, 29, 41, 42, 44, 192, 194, 250, 276, 277, 395, 398 

carcinogenicity...................................... 28, 44, 189, 192, 193, 194, 231, 248, 249, 250, 251, 277, 289, 398 

carcinoma............................................................................................................................ 71, 187, 202, 206 

carcinomas .................................................................................................................... 23, 73, 187, 188, 194 

cardiac arrhythmia .............................................................................................................................. 20, 164 

cardiovascular ............................................. 17, 18, 19, 20, 31, 56, 58, 59, 74, 164, 166, 173, 196, 254, 282 

cardiovascular effects................................................................................ 17, 20, 58, 59, 163, 164, 166, 196 

chromosomal aberrations.................................................................................................. 199, 208, 250, 257 

clearance ..................................................................................................................... 21, 212, 225, 226, 228 

cognitive function .....................................................................................................................................255 

crustaceans................................................................................................................................................350 

death............................................ 7, 9, 23, 41, 56, 73, 74, 162, 163, 185, 186, 191, 194, 216, 248, 251, 256 

deoxyribonucleic acid (see DNA)..................................................................................... 205, 207, 208, 210 

dermal effects............................................................................ 17, 19, 31, 62, 175, 176, 197, 273, 275, 395 

DNA (see deoxyribonucleic acid).................................................... 199, 200, 201, 202, 203, 204, 205, 206, 

............................................................................... 207, 208, 209, 210, 249, 250, 251, 258, 269, 278, 285 

dopamine...................................................................................................................................................182 

elimination half-time................................................................................................................... 27, 219, 227 

endocrine........................................................................................................... 174, 175, 196, 197, 252, 253

Endocrine Effects.............................................................................................................................. 174, 197 

erythema.............................................................................................................................................. 20, 197 
ARSENIC C-8 

APPENDIX C 

estrogen receptor.......................................................................................................................................187 

fetal tissue .....................................................................................................................................................9 

fetus........................................................................................................................... 187, 217, 253, 280, 372 

gastrointestinal effects ................................................ 21, 24, 26, 28, 33, 37, 59, 60, 74, 166, 168, 274, 395 

general population......................................................................... 15, 57, 165, 224, 257, 364, 374, 375, 378 

genotoxic............................................................................................................. 41, 199, 208, 249, 251, 278

genotoxicity....................................................................................................................... 199, 208, 250, 278 

groundwater ..................................................................... 4, 10, 16, 313, 315, 322, 323, 326, 331, 337, 338, 

............................................................................................... 340, 341, 342, 343, 356, 369, 375, 380, 381 

growth retardation.....................................................................................................................................186 

half-life.............................................................................................................................. 227, 258, 331, 375 

hematological effects .................................................................................................................. 60, 169, 196 

hepatic effects ............................................................................................................. 61, 170, 171, 196, 262 

homeopathic..............................................................................................................................................354 

hydrolysis.......................................................................................................................................... 331, 334 

hydroxyl radical ........................................................................................................................................250 

immune system ................................................................................................................................... 64, 281 

immunological ................................................................................................................ 29, 41, 64, 179, 198 

immunological effects.................................................................................................................................29 

Kow .................................................................................................................... 297, 298, 299, 300, 301, 376

LD50............................................................................................................................................... 32, 39, 162 

leukemia.......................................................................................................................... 15, 17, 20, 287, 311 

leukopenia........................................................................................................................................... 30, 168 

lymphoreticular........................................................................................................................... 64, 179, 198 

melanoma..................................................................................................................................................190 

micronuclei ............................................................................................................................... 199, 208, 250 

milk ................................................................................................................... 217, 256, 359, 361, 368, 369

mucociliary ................................................................................................................................... 21, 60, 369 

musculoskeletal effects ....................................................................................................................... 61, 170 

neonatal............................................................................................................................. 185, 256, 280, 286 

neoplastic .......................................................................................................................... 25, 26, 27, 28, 193 

neurobehavioral........................................................................................... 18, 181, 182, 186, 252, 255, 281 

norepinephrine ..........................................................................................................................................182 

nuclear............................................................................................................................................... 251, 384 

ocular effects............................................................................................................................... 63, 177, 197 

odds ratio..................................................................................................................................... 64, 183, 191 

pancytopenia .............................................................................................................................................273 

partition coefficients .................................................................................................................................243 

pharmacodynamic .....................................................................................................................................228 

pharmacokinetic........................................................................ 228, 229, 230, 234, 235, 236, 237, 239, 240 

pharmacokinetics .............................................................................................................................. 253, 286 

photolysis .......................................................................................................................................... 331, 334 

placenta ................................................................................................................................. 9, 185, 217, 256 

placental barrier ................................................................................................................................ 217, 256 

rate constant .............................................................................................................................. 232, 243, 246 

renal effects........................................................................................................... 61, 62, 172, 173, 174, 196 

retention ............................................................................................................................ 224, 264, 309, 363 

salivation...................................................................................................................................................182 

sarcoma .....................................................................................................................................................193 

sodium pump.............................................................................................................................................249 

solubility ............................................................................................................. 43, 214, 225, 333, 335, 364
ARSENIC C-9 

APPENDIX C 

spermatogonia ................................................................................................................................... 207, 208 

T3............................45, 46, 47, 48, 52, 53, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 

.......................92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 

...............................112, 113, 114, 115, 116, 125, 126, 127, 128, 129, 130, 131, 132, 137, 138, 139, 140, 

....................................... 141, 142, 143, 144, 145, 146, 147, 148, 152, 153, 154, 155, 156, 157, 158, 195 

thyroid............................................................................................................. 25, 26, 35, 175, 194, 197, 251 

toxicokinetic.................................................. 17, 27, 32, 41, 43, 71, 211, 221, 259, 263, 278, 282, 284, 286 

tremors .................................................................................................................................... 28, 39, 65, 274 

tumors ................................... 18, 23, 26, 27, 28, 73, 187, 190, 191, 192, 193, 194, 199, 251, 256, 262, 278 

volatilization .............................................................................................................................................333 
ARSENIC D-1