TOXICOLOGICAL PROFILE FOR 

HEPTACHLOR and HEPTACHLOR EPOXIDE 

Prepared by: 

Syracuse Research Corporation 

Under Contract No. 200-2004-09793 

Prepared for: 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Public Health Service 

Agency for Toxic Substances and Disease Registry

November 2007 
HEPTACHLOR AND HEPTACHLOR EPOXIDE ii 

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. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE iii 

UPDATE STATEMENT 

A Toxicological Profile for Heptachlor/Heptachlor Epoxide, 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 
HEPTACHLOR AND HEPTACHLOR EPOXIDE iv 

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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. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE vii 

QUICK REFERENCE FOR HEALTH CARE PROVIDERS 

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

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

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

patients potentially exposed to hazardous substances will find 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 

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

Toxicity; and numerous chemical-specific case studies. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE viii 

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

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

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

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

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

professionals treating patients exposed to hazardous materials. 

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

Other Agencies and Organizations 

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

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

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

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

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

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

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

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

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

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

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

• Phone: 800-35-NIOSH. 

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

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

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

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

Referrals 

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

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

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

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

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

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

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

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

CONTRIBUTORS 

CHEMICAL MANAGER(S)/AUTHOR(S): 

Zemoria E. Rosemond, B.A. 

G. Daniel Todd, Ph.D. 

Malcolm Williams, D.V.M., Ph.D. 

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

Lisa Ingerman, Ph.D. 

Sari Paikoff, Ph.D. 

Jennifer Rhoades, B.A. 

Fernando Llados, Ph.D. 

Stephen Bosch, B.S. 

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. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE x 

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HEPTACHLOR AND HEPTACHLOR EPOXIDE xi 

PEER REVIEW 

A peer review panel was assembled for heptachlor and heptachlor epoxide. The panel consisted of the 

following members: 

1. Richard Dickerson, Ph.D., DABT, Department of Pharmacology and Neuroscience and 

Department of Environmental Toxicology, Texas Tech University Health Sciences Center, 

Lubbock, TX; 

2. Sam Kacew, Ph.D., Department of Cellular and Molecular Medicine, University of Ottawa, 

Ottawa, Ontario, Canada; and 

3. James Klaunig, Ph.D., Department of Pharmacology and Toxicology, Indiana University School 

of Medicine, Indianapolis, IN. 

These experts collectively have knowledge of heptachlor and heptachlor epoxide'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. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE xii 

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HEPTACHLOR AND HEPTACHLOR EPOXIDE xiii 

CONTENTS 

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

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

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

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

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

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

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

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

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

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

1.1 WHAT ARE HEPTACHLOR AND HEPTACHLOR EPOXIDE? ............................................ 1 

1.2 WHAT HAPPENS TO HEPTACHLOR AND HEPTACHLOR EPOXIDE WHEN THEY 

ENTER THE ENVIRONMENT? ...............................................................................................2 

1.3 HOW MIGHT I BE EXPOSED TO HEPTACHLOR AND HEPTACHLOR EPOXIDE?........ 3 

1.4 HOW CAN HEPTACHLOR AND HEPTACHLOR EPOXIDE ENTER AND LEAVE MY 

BODY? ........................................................................................................................................4 

1.5 HOW CAN HEPTACHLOR AND HEPTACHLOR EPOXIDE AFFECT MY HEALTH?......5 

1.6 HOW CAN HEPTACHLOR AND HEPTACHLOR EPOXIDE AFFECT CHILDREN? ......... 6 

1.7 HOW CAN FAMILIES REDUCE THE RISK OF EXPOSURE TO HEPTACHLOR AND 

 HEPTACHLOR EPOXIDE?.......................................................................................................7 

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

TO HEPTACHLOR AND HEPTACHLOR EPOXIDE?............................................................ 7 

1.9 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH?.................................................................................................8 

1.10 WHERE CAN I GET MORE INFORMATION? .......................................................................9 

2. RELEVANCE TO PUBLIC HEALTH .................................................................................................11 

2.1 BACKGROUND AND ENVIRONMENTAL EXPOSURES TO HEPTACHLOR AND 

HEPTACHLOR EPOXIDE IN THE UNITED STATES .........................................................11 

2.2 SUMMARY OF HEALTH EFFECTS......................................................................................11 

2.3 MINIMAL RISK LEVELS (MRLs) .........................................................................................13 

3. HEALTH EFFECTS..............................................................................................................................19 

3.1 INTRODUCTION.....................................................................................................................19 

3.2 DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE ..................................19 

3.2.1 Inhalation Exposure ..............................................................................................................20 

3.2.1.1 Death ............................................................................................................................20 

3.2.1.2 Systemic Effects...........................................................................................................21 

3.2.1.3 Immunological and Lymphoreticular Effects...............................................................22 

3.2.1.4 Neurological Effects.....................................................................................................22 

3.2.1.5 Reproductive Effects....................................................................................................22 

3.2.1.6 Developmental Effects .................................................................................................22 

3.2.1.7 Cancer...........................................................................................................................22 

3.2.2 Oral Exposure........................................................................................................................23 

3.2.2.1 Death ............................................................................................................................23 

3.2.2.2 Systemic Effects...........................................................................................................24 

3.2.2.3 Immunological and Lymphoreticular Effects...............................................................40 

3.2.2.4 Neurological Effects.....................................................................................................41 
HEPTACHLOR AND HEPTACHLOR EPOXIDE xiv 

3.2.2.5 Reproductive Effects....................................................................................................41 

3.2.2.6 Developmental Effects .................................................................................................43 

3.2.2.7 Cancer...........................................................................................................................45 

3.2.3 Dermal Exposure...................................................................................................................46 

3.2.3.1 Death ............................................................................................................................47 

3.2.3.2 Systemic Effects...........................................................................................................47 

3.2.3.3 Immunological and Lymphoreticular Effects...............................................................47 

3.2.3.4 Neurological Effects.....................................................................................................47 

3.2.3.5 Reproductive Effects....................................................................................................47 

3.2.3.6 Developmental Effects .................................................................................................47 

3.2.3.7 Cancer...........................................................................................................................47 

3.3 GENOTOXICITY .....................................................................................................................47 

3.4 TOXICOKINETICS..................................................................................................................51 

3.4.1 Absorption.............................................................................................................................51 

3.4.1.1 Inhalation Exposure......................................................................................................51 

3.4.1.2 Oral Exposure...............................................................................................................51 

3.4.1.3 Dermal Exposure ..........................................................................................................51 

3.4.2 Distribution ...........................................................................................................................52 

3.4.2.1 Inhalation Exposure......................................................................................................52 

3.4.2.2 Oral Exposure...............................................................................................................52 

3.4.2.3 Dermal Exposure ..........................................................................................................53 

3.4.3 Metabolism............................................................................................................................53 

3.4.4 Elimination and Excretion.....................................................................................................54 

3.4.4.1 Inhalation Exposure......................................................................................................54 

3.4.4.2 Oral Exposure...............................................................................................................56 

3.4.4.3 Dermal Exposure ..........................................................................................................56 

3.4.5 Physiologically Based Pharmacokinetic (PBPK)/Pharmacodynamic (PD) Models .............57 

3.5 MECHANISMS OF ACTION .................................................................................................. 58 

3.5.1 Pharmacokinetic Mechanisms...............................................................................................58 

3.5.2 Mechanisms of Toxicity........................................................................................................58 

3.5.3 Animal-to-Human Extrapolations.........................................................................................60 

3.6 TOXICITIES MEDIATED THROUGH THE NEUROENDOCRINE AXIS ..........................60 

3.7 CHILDREN’S SUSCEPTIBILITY...........................................................................................61 

3.8 BIOMARKERS OF EXPOSURE AND EFFECT ....................................................................63 

3.8.1 Biomarkers Used to Identify or Quantify Exposure to Heptachlor and Heptachlor 

Epoxide .................................................................................................................................64 

3.8.2 Biomarkers Used to Characterize Effects Caused by Heptachlor and Heptachlor 

Epoxide .................................................................................................................................65 

3.9 INTERACTIONS WITH OTHER CHEMICALS ....................................................................65 

3.10 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE............................................... 66 

3.11 METHODS FOR REDUCING TOXIC EFFECTS...................................................................67 

3.11.1 Reducing Peak Absorption Following Exposure ..............................................................67 

3.11.2 Reducing Body Burden.....................................................................................................68 

3.11.3 Interfering with the Mechanism of Action for Toxic Effects ...........................................68 

3.12 ADEQUACY OF THE DATABASE........................................................................................69 

3.12.1 Existing Information on Health Effects of Heptachlor and Heptachlor Epoxide .............70 

3.12.2 Identification of Data Needs .............................................................................................72 

3.12.3 Ongoing Studies................................................................................................................80 
HEPTACHLOR AND HEPTACHLOR EPOXIDE xv 

4. CHEMICAL AND PHYSICAL INFORMATION................................................................................81 

4.1 CHEMICAL IDENTITY...........................................................................................................81 

4.2 PHYSICAL AND CHEMICAL PROPERTIES........................................................................81 

5. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL............................................................85 

5.1 PRODUCTION .........................................................................................................................85 

5.2 IMPORT/EXPORT ...................................................................................................................87 

5.3 USE............................................................................................................................................87 

5.4 DISPOSAL................................................................................................................................88 

6. POTENTIAL FOR HUMAN EXPOSURE ...........................................................................................89 

6.1 OVERVIEW..............................................................................................................................89 

6.2 RELEASES TO THE ENVIRONMENT..................................................................................92 

6.2.1 Air .........................................................................................................................................93 

6.2.2 Water.....................................................................................................................................93 

6.2.3 Soil ........................................................................................................................................93 

6.3 ENVIRONMENTAL FATE......................................................................................................93 

6.3.1 Transport and Partitioning.....................................................................................................93 

6.3.2 Transformation and Degradation ..........................................................................................97 

6.3.2.1 Air.................................................................................................................................97 

6.3.2.2 Water ............................................................................................................................98 

6.3.2.3 Sediment and Soil.........................................................................................................99 

6.3.2.4 Other Media................................................................................................................100 

6.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT...............................100 

6.4.1 Air .......................................................................................................................................100 

6.4.2 Water...................................................................................................................................101 

6.4.3 Sediment and Soil ...............................................................................................................103 

6.4.4 Other Environmental Media................................................................................................104 

6.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE .....................................106 

6.6 EXPOSURES OF CHILDREN...............................................................................................109 

6.7 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES ...........................................110 

6.8 ADEQUACY OF THE DATABASE......................................................................................111 

6.8.1 Identification of Data Needs ...............................................................................................112 

6.8.2 Ongoing Studies ..................................................................................................................115 

7. ANALYTICAL METHODS ...............................................................................................................117 

7.1 BIOLOGICAL MATERIALS.................................................................................................117 

7.2 ENVIRONMENTAL SAMPLES............................................................................................ 120 

7.3 ADEQUACY OF THE DATABASE......................................................................................124 

7.3.1 Identification of Data Needs ...............................................................................................124 

7.3.2 Ongoing Studies ..................................................................................................................125 

8. REGULATIONS AND ADVISORIES ...............................................................................................127 

9. REFERENCES ....................................................................................................................................133 

10. GLOSSARY ......................................................................................................................................153 
HEPTACHLOR AND HEPTACHLOR EPOXIDE xvi 

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 
HEPTACHLOR AND HEPTACHLOR EPOXIDE xvii 

LIST OF FIGURES 

3-1. Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - Oral.................................. 34 

3-2. Metabolic Scheme for Heptachlor in Rats.......................................................................................... 55

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

Hypothetical Chemical Substance...................................................................................................... 59

3-4. Existing Information on Health Effects of Heptachlor and Heptachlor Epoxide ............................... 71

6-1. Frequency of NPL Sites with Heptachlor Contamination .................................................................. 90

6-2. Frequency of NPL Sites with Heptachlor Epoxide Contamination.................................................... 91
HEPTACHLOR AND HEPTACHLOR EPOXIDE xviii 

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HEPTACHLOR AND HEPTACHLOR EPOXIDE xix 

LIST OF TABLES 

3-1. Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - Oral.................................. 25 

3-2. Genotoxicity of Heptachlor and Heptachlor Epoxide In Vitro...........................................................48 

4-1. Chemical Identity of Heptachlor and Heptachlor Epoxide.................................................................82

4-2. Physical and Chemical Properties of Heptachlor and Heptachlor Epoxide........................................83 

5-1. Facilities that Produce, Process, or Use Heptachlor...........................................................................86 

6-1. Releases to the Environment from Facilities that Produce, Process, or Use Heptachlor....................94 

7-1. Analytical Methods for Determining Heptachlor and Heptachlor Epoxide in Biological 

Materials...........................................................................................................................................118 

7-2. Analytical Methods for Determining Heptachlor and Heptachlor Epoxide in Environmental 

Samples ............................................................................................................................................121 

8-1. Regulations and Guidelines Applicable to Heptachlor and Heptachlor Epoxide .............................128 
HEPTACHLOR AND HEPTACHLOR EPOXIDE xx 

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HEPTACHLOR AND HEPTACHLOR EPOXIDE 1 

1. PUBLIC HEALTH STATEMENT 

This public health statement tells you about heptachlor and heptachlor epoxide and the effects of 

exposure to them. 

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. Heptachlor has been found in at least 210 of the 

1,684 current or former NPL sites. Heptachlor epoxide has been found in at least 200 NPL sites. 

Although the total number of NPL sites evaluated for these substances is not known, the 

possibility exists that heptachlor and heptachlor epoxide may be found in the future as more sites 

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

exposure to these substances 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 heptachlor or heptachlor epoxide, 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 them. 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 ARE HEPTACHLOR AND HEPTACHLOR EPOXIDE? 

Heptachlor is a manufactured chemical that was used in the past for killing insects in homes, in 

buildings, and on food crops. It has not been used for these purposes since 1988. There are no 

natural sources of heptachlor or heptachlor epoxide. Trade names for heptachlor include 

Heptagran®, Heptamul®, Heptagranox®, Heptamak®, Basaklor®, Drinox®, Soleptax®, Gold Crest 

H-60®, Termide®, and Velsicol 104®. Heptachlor is both a breakdown product and a component 

of the pesticide chlordane (approximately 10% by weight). Pure heptachlor is a white powder. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 2 

1. PUBLIC HEALTH STATEMENT 

Technical-grade heptachlor is a tan powder and has a lower level of purity than pure heptachlor. 

Technical-grade heptachlor was the form of heptachlor used most often as a pesticide. 

Heptachlor smells somewhat like camphor. Heptachlor does not burn easily and does not 

explode. It does not dissolve easily in water. 

Like pure heptachlor, heptachlor epoxide is a white powder that does not explode easily. It was 

not manufactured and was not used as an insecticide like heptachlor. Bacteria and animals break 

down heptachlor to form heptachlor epoxide. This profile describes these two chemicals 

together because about 20% of heptachlor is changed within hours into heptachlor epoxide in the 

environment and in your body. 

You might find heptachlor or heptachlor epoxide in the soil or air of homes treated for termites, 

dissolved in surface water or groundwater, or in the air near hazardous waste sites. You might 

also find heptachlor or its byproduct, heptachlor epoxide, in plants and animals near hazardous 

waste sites. Heptachlor can no longer be used to kill insects on crops or in homes and buildings. 

However, heptachlor is still approved by EPA for killing fire ants in buried power transformers, 

although it is unclear whether or not it is still being used for this purpose in the United States. 

More information on the chemical and physical properties of heptachlor and heptachlor epoxide 

is found in Chapter 4 of this document. More information on the production and use of 

heptachlor is found in Chapter 5. 

1.2 WHAT HAPPENS TO HEPTACHLOR AND HEPTACHLOR EPOXIDE WHEN 

THEY ENTER THE ENVIRONMENT? 

From 1953 to 1974, heptachlor entered the soil and surface water when farmers used it to kill 

insects in seed grains and on crops. It also entered the air and soil when homeowners and 

professional insect exterminators used it to kill termites. Today, heptachlor is no longer used by 

homeowners to kill termites or other insects. However, exterminators can still use existing 

stocks of heptachlor to kill fire ants in underground power transformers. 

Heptachlor and heptachlor epoxide can enter the air, soil, groundwater, and surface water from 

leaks at hazardous waste sites or landfills. Heptachlor sticks to soil very strongly and evaporates 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 3 

1. PUBLIC HEALTH STATEMENT 

slowly into the air. Heptachlor does not dissolve easily in water. Heptachlor epoxide dissolves 

more easily in water than heptachlor does and evaporates slowly from water. Like heptachlor, 

heptachlor epoxide sticks to soil. 

Both heptachlor and heptachlor epoxide can travel long distances in the wind from places where 

they are released, such as treated fields or manufacturing sites. In soil and water, heptachlor is 

changed by bacteria into the more harmful substance, heptachlor epoxide, or into other less 

harmful substances. Plants can absorb heptachlor through their roots from the soil. Heptachlor 

in the air can be deposited on plant leaves and enter the plant from contaminated soil. 

Animals that eat plants containing heptachlor can also absorb it. Animals can also change 

heptachlor to heptachlor epoxide in their bodies. Heptachlor epoxide breaks down very slowly 

in the environment. It can stay in soil and water for many years. Both heptachlor and heptachlor 

epoxide build up in fish and in cattle. People store heptachlor epoxide in their fatty tissue. Some 

studies show that heptachlor epoxide can still be measured in fatty tissue 3 years after a person is 

exposed to it. 

Most of the breakdown products of heptachlor are thought to be less harmful than heptachlor 

itself. However, in laboratory animals, heptachlor epoxide is more harmful than heptachlor. For 

more information on heptachlor and heptachlor epoxide in the environment, see Chapters 5 

and 6. 

1.3 HOW MIGHT I BE EXPOSED TO HEPTACHLOR AND HEPTACHLOR 

EPOXIDE? 

Exposure to heptachlor and heptachlor epoxide most commonly occurs when you eat food 

contaminated with those chemicals. Contaminated foods might include fish, shellfish (such as 

clams), dairy products, meat, and poultry. Children and toddlers drink large amounts of milk and 

may have greater exposure if the milk is contaminated with heptachlor or heptachlor epoxide. 

Infants can be exposed to these compounds from drinking breastmilk or cow's milk. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 4 

1. PUBLIC HEALTH STATEMENT 

Exposure can also occur when you drink water, breathe air, or touch contaminated soil at 

hazardous waste sites that contain heptachlor or heptachlor epoxide. People whose homes have 

been treated with heptachlor to kill termites can be exposed by breathing heptachlor in the air. 

After heptachlor is changed to heptachlor epoxide in the soil, it can get into the air. People who 

breathe this air will be exposed to heptachlor epoxide. Workers who use heptachlor to kill fire 

ants are exposed if they breathe in the heptachlor or get it on their skin. 

Background levels of a substance are levels found in the environment that cannot be traced to a 

specific source. Information on background levels of heptachlor and heptachlor epoxide in the 

air was not found. In one survey, the background levels of heptachlor in drinking water and 

groundwater in the United States ranged from 20 to 800 parts of heptachlor in one trillion parts 

of water (ppt). Heptachlor was found in less than 2% of U.S. groundwater samples that are 

known to be contaminated from pesticide application. The average level of heptachlor in the 

contaminated groundwater samples was 800 ppt. No information was found for levels of 

heptachlor epoxide in groundwater or drinking water. Heptachlor epoxide has been found in 

surface water (river, lakes) at levels between 0.1 and 10 parts of heptachlor epoxide in one 

billion parts of water (ppb, 1 ppb is 1 thousand times more than 1 ppt). 

Heptachlor and heptachlor epoxide stick to sediment and soil. Sediment in stream beds is likely 

to contain a lot of the heptachlor that enters the water. Heptachlor and heptachlor epoxide were 

found in less than 0.7 and 1.8% of river bed sediments that were tested from 2003 to 2005. 

Contaminated fish and shellfish have been found to contain 2–750 ppb heptachlor and 0.1– 

480 ppb heptachlor epoxide. Heptachlor epoxide has been found in human milk samples at 

levels ranging from 0.13 to 128 ppb. See Chapter 6 for more information on how you might be 

exposed to heptachlor and heptachlor epoxide. 

1.4 HOW CAN HEPTACHLOR AND HEPTACHLOR EPOXIDE ENTER AND LEAVE 

MY BODY? 

When you breathe air containing heptachlor or heptachlor epoxide, both can enter your 

bloodstream through your lungs. It is not known how fast these compounds enter and remain in 

the bloodstream. Both heptachlor and heptachlor epoxide can also enter your body through your 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 5 

1. PUBLIC HEALTH STATEMENT 

stomach after you eat food or drink water or milk containing them. Most of the heptachlor that is 

swallowed passes through your stomach into your blood. It can also enter your body through 

your skin. Heptachlor and heptachlor epoxide can pass directly from a mother's blood to an 

unborn baby through the placenta. It can also pass from the mother to an infant through breast 

milk. 

Once inside your body, heptachlor is changed to heptachlor epoxide and other related chemicals. 

Most of the heptachlor, heptachlor epoxide, and other breakdown products leave your body in 

the feces within a few days after exposure. Some breakdown products can also leave in the 

urine. Some heptachlor and heptachlor epoxide are stored in your body fat for long periods after 

exposure has occurred. The heptachlor and heptachlor epoxide that have been stored in fat leave 

your body much more slowly. Chapter 3 contains more information on how heptachlor and 

heptachlor epoxide can enter and leave the body. 

1.5 HOW CAN HEPTACHLOR AND HEPTACHLOR EPOXIDE 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. 

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. 

People can begin to smell heptachlor or heptachlor epoxide at around 0.3 milligrams in a cubic 

meter of air (0.3 mg/m3

). No reliable studies in humans were found that show whether harmful 

health effects occur as a result of breathing heptachlor or heptachlor epoxide. No animal studies 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 6 

1. PUBLIC HEALTH STATEMENT 

examining the harmful effects resulting from breathing air that contains heptachlor or heptachlor 

epoxide were found. 

In addition, no reliable human studies were found that show whether harmful effects occur from 

eating contaminated foods or by drinking liquids contaminated with heptachlor or heptachlor 

epoxide. Studies have shown a number of harmful health effects when animals were fed 

heptachlor or heptachlor epoxide. These effects were more harmful when the exposure levels 

were high or when exposure lasted many weeks. The effects observed in animals include 

damage to the liver, excitability, and decreases in fertility. 

Animals fed heptachlor throughout their lifetime had more liver tumors than animals that ate 

food without heptachlor. EPA and the International Agency for Research on Cancer have 

classified heptachlor as a possible human carcinogen. EPA also considers heptachlor epoxide as 

a possible human carcinogen. 

Chapter 3 contains more information on the adverse health effects of heptachlor and heptachlor 

epoxide. 

1.6 HOW CAN HEPTACHLOR AND HEPTACHLOR EPOXIDE AFFECT 

CHILDREN? 

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

conception to maturity at 18 years of age. 

Some studies in animals suggest that young animals exposed during gestation and infancy may 

be very sensitive to heptachlor and heptachlor epoxide. Changes in nervous system and immune 

function were found in these animals. There is some evidence that similar effects may occur in 

humans, but a study that found some changes in performance on some tests that measure nervous 

system function is not conclusive and exposure to other chemicals cannot be ruled out. Exposure 

to higher doses of heptachlor in animals can also result in decreases in body weight and death in 

animal newborn babies. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 7 

1. PUBLIC HEALTH STATEMENT 

1.7 HOW CAN FAMILIES REDUCE THE RISK OF EXPOSURE TO HEPTACHLOR 

AND HEPTACHLOR EPOXIDE? 

If your doctor finds that you have been exposed to substantial amounts of heptachlor and 

heptachlor epoxide, ask whether your children might also have been exposed. Your doctor might 

need to ask your state health department to investigate. 

Heptachlor is no longer used in the United States except to control fire ants; therefore, exposure 

should be limited. Before the use of heptachlor was cancelled in 1988, it was used on various 

agricultural crops, in homes for the treatment of termites, and in power lines for fire ant control. 

However, because of the persistence of both heptachlor and heptachlor epoxide, exposure to the 

general population can occur from contaminated water, soil, and air. People who live in homes 

where heptachlor was used for termite control or on farms where heptachlor was used on crops 

may have a higher risk of exposure through contaminated crops, soil, water, and air. To avoid 

exposure from contaminated soil, you should discourage your children from eating or playing 

with dirt near home or barn foundations. Make sure they wash their hands frequently and before 

eating. Discourage children from putting their hands in their mouths or other hand-to-mouth 

activities. 

Heptachlor and heptachlor epoxide are also persistent in food and milk. Eating fish from 

contaminated water can increase exposure to heptachlor. Avoid eating fish from contaminated 

water. Local fishing advisories can tell you if the water is contaminated. 

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

EXPOSED TO HEPTACHLOR AND HEPTACHLOR EPOXIDE? 

Laboratory tests can detect heptachlor and heptachlor epoxide in blood, fat, breast milk, and 

body tissues after exposure to high levels of these chemicals. These tests are not commonly 

available at your doctor's office. Most often, the test for heptachlor epoxide is used because 

heptachlor is quickly changed into heptachlor epoxide in your body. Blood samples are used 

most often because they are easy to collect. These tests are specific for heptachlor and 

heptachlor epoxide. However, heptachlor is both a breakdown product and a component of 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 8 

1. PUBLIC HEALTH STATEMENT 

chlordane, another pesticide. So if heptachlor and heptachlor epoxide are measured in the blood, 

the actual exposure could have been to chlordane. Methods for measuring heptachlor and 

heptachlor epoxide in body fat are more precise and can detect lower levels than tests that 

measure levels in blood. If heptachlor or heptachlor epoxide is found in your blood or fat, it is 

not possible to tell when you were exposed to these chemicals or if harmful health effects will 

occur. See Chapters 3 and 7 for more information on detecting these chemicals in the 

environment or in human tissues. 

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 heptachlor and heptachlor epoxide 

include the following: 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 9 

1. PUBLIC HEALTH STATEMENT 

For exposures of up to 10 days, EPA recommends that a child weighing 22 pounds or less not 

drink water containing more than 0.01 mg heptachlor or heptachlor epoxide per liter of water 

(0.01 mg/L or 0.01 ppm). EPA requires that drinking water should not contain more than 

0.0004 mg/L (0.0004 ppm) heptachlor and 0.0002 mg/L (0.0002 ppm) of heptachlor epoxide. 

FDA controls the amount of heptachlor and heptachlor epoxide on raw food crops and on edible 

seafood. The limit for most food crops is 0.01 parts heptachlor per million parts food 

(0.01 ppm). The limit in milk is 0.1 parts heptachlor per million parts of milk fat. The limit on 

edible seafood is 0.3 ppm. 

OSHA has set a limit of 0.5 mg/m3 for heptachlor in workplace air over an 8-hour workday for a 

40-hour workweek. For more information on standards and guidelines for heptachlor and 

heptachlor epoxide, see Chapter 8. 

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: 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 10 

1. PUBLIC HEALTH STATEMENT 

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/ 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 11 

2. RELEVANCE TO PUBLIC HEALTH 

2.1 BACKGROUND AND ENVIRONMENTAL EXPOSURES TO HEPTACHLOR AND 

HEPTACHLOR EPOXIDE IN THE UNITED STATES 

Heptachlor is a polychlorinated cyclodiene insecticide that was extensively used prior to 1970 to kill 

termites, ants, and soil insects in seed grains and on crops. In 1983, the manufacturers voluntarily 

cancelled its registered uses, with the exception of termite and fire ant control. Currently, the only 

permitted use of heptachlor is for fire ant control in buried power transformers; however, there are no 

actively registered pesticides containing heptachlor as an active ingredient. Heptachlor epoxide is the 

primary degradation product of heptachlor. Heptachlor epoxide is more persistent in the environment 

than heptachlor and biomagnifies in the terrestrial food chain. Although the use of heptachlor is 

restricted, exposure to the general population can occur through the ingestion of contaminated food, 

inhalation of vapors from contaminated soil and water, and dermal contact with contaminated soil and 

water. The food classes most likely to contain residues are milk and other dairy products, vegetables, 

meat, fish, and poultry. 

2.2 SUMMARY OF HEALTH EFFECTS 

There are limited data on the toxicity of heptachlor or heptachlor epoxide following inhalation or dermal 

exposure. Most of the available information on the toxicity of heptachlor comes from oral exposure 

studies in laboratory animals, although some human data have been identified. Oral exposure of 

laboratory animals to heptachlor results in a variety of adverse effects including liver effects, neurological 

effects, reproductive system dysfunction, and developmental effects. Although there are very few studies 

involving exposure to heptachlor epoxide, it is likely that the effects resulting from heptachlor exposure 

are due to its metabolism to heptachlor epoxide. Several human studies have examined the possible 

relationship between increased serum levels of heptachlor or heptachlor epoxide and adverse health 

outcomes. Most of these studies involved exposure to a variety of organochlorine pesticides and the 

observed effects cannot be ascribed to heptachlor. Additionally, a small number of studies have 

examined populations consuming milk products from cows fed heptachlor-contaminated feed. In these 

types of studies, there is a greater degree of certainty in attributing the observed effects to heptachlor 

exposure. 

In mature animals, liver and neurological effects appear to have similar thresholds of toxicity. Acute- or 

intermediate-duration exposure of rats or mice to 5–10 mg/kg/day has resulted in a variety of liver effects 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 12 

2. RELEVANCE TO PUBLIC HEALTH 

including increases in serum alanine aminotransferase activity, necrosis, hepatocytomegaly, hepatitis, and 

increased liver weights. These studies suggest that the severity of the hepatic lesions is related to the 

duration of exposure. No alterations in serum liver enzyme activity levels or hepatocytomegaly incidence 

were observed in individuals exposed to heptachlor and heptachlor metabolites in contaminated milk 

products. Neurological alterations indicative of excitability and increased arousal were observed in rats 

exposed to 7 mg/kg/day for an acute duration and mink exposed to 1.7 or 6.2 mg/kg/day for an 

intermediate duration. At higher doses (17 mg/kg/day), mice exhibited difficult standing, walking, and 

righting. Seizures have also been observed in mink prior to death. 

The reproductive system may be a more sensitive target of heptachlor toxicity than the liver or nervous 

system. A decrease in fertility and an increase in resorptions were observed in female rats acutely 

exposed to 1.8 mg/kg/day. Exposure of males to 0.65 mg/kg/day for 70 days resulted in decreased 

epididymal sperm count and increased resorptions when the males were mated with untreated females. In 

contrast, two acute studies involving exposure to 10 mg/kg/day heptachlor, 8 mg/kg/day heptachlor 

epoxide, or 15 mg/kg heptachlor/ heptachlor epoxide mixture did not find dominant lethal effects. 

Reduced fertility has also been observed in mice exposed to 8.4 mg/kg/day. 

The available data provide suggestive evidence that the developing organism is the most sensitive target 

of heptachlor toxicity. Increases in pup mortality have been observed at doses of 5.0 mg/kg/day and 

higher in rats and at 1.7 mg/kg/day in mink; these doses were also associated with serious maternal 

toxicity. Decreases in pup body weight have also been observed at 4.5 mg/kg/day and higher. Heptachlor 

does not appear to increase the occurrence of anomalies or malformations. Perinatal and postnatal 

exposure adversely affected the development of the nervous and immune systems; the lowest-observedadverse-effect level (LOAEL) for these effects is 0.03 mg/kg/day. No adverse effects were observed in 

the developing reproductive system. Studies of a population exposed to heptachlor-contaminated milk 

products found similar effects to those reported in animals. The risk of fetal or neonatal deaths, low birth 

weight infants, or major congenital malformations was not significantly altered. However, alterations in 

neurobehavioral performance were found when the children of women exposed to contaminated milk 

products reached high school. In particular, abstract concept formation, visual perception, and motor 

planning were adversely affected. 

The carcinogenicity of heptachlor and heptachlor epoxide has been evaluated in a number of human 

studies. In general, these studies have examined possible associations between heptachlor and/or 

heptachlor epoxide tissue levels or a surrogate of heptachlor exposure and the prevalence of cancer. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 13 

2. RELEVANCE TO PUBLIC HEALTH 

Mixed results have been reported across tumor types and within tumor types. Interpretation of the studies 

is limited by the lack of information on heptachlor exposure, variables that may affect organochlorine 

levels (including diet and body mass index), and possible concomitant exposure to other chemicals. 

Increases in the incidence of hepatocellular carcinoma were observed in mice exposed to 2.4 mg/kg/day 

heptachlor and higher for 2 years, but not in rats exposed to 2.6 mg/kg/day and higher. The EPA has 

classified heptachlor and heptachlor epoxide in group B2 (probable human carcinogen) and the 

International Agency for Research on Cancer (IARC) considers heptachlor as possibly carcinogenic to 

humans (Group 2b). EPA has derived an oral slope factor of 4.5 per (mg/kg)/day for heptachlor and 

9.1 per (mg/kg)/day for heptachlor epoxide. These slope factors correspond to drinking water unit risk 

levels of 1.3x10-4 and 2.6x10-4 per (μg/L), respectively. 

2.3 MINIMAL RISK LEVELS (MRLs) 

Estimates of exposure levels posing minimal risk to humans (MRLs) have been made for heptachlor. An 

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

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

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

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

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

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

methodology does not exist to develop MRLs for dermal exposure. 

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

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

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

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

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

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

significant human exposure improve, these MRLs will be revised. 

Inhalation MRLs 

Data on the toxicity of heptachlor or heptachlor epoxide following inhalation exposure are limited to 

several mortality studies of pesticide applicators or manufacturers (Blair et al. 1983; MacMahon et al. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 14 

2. RELEVANCE TO PUBLIC HEALTH 

1988; Shindell and Associates 1981; Wang and MacMahon 1979a) and a case control study examining 

the possible association between organochlorine pesticide exposure and aplastic anemia (Wang and 

Grufferman 1981). No significant associations were found. Interpretation of the results are limited by coexposure to other organochlorine pesticides and lack of monitoring data. No inhalation exposure animal 

studies were identified. 

The available inhalation data are considered inadequate for the development of MRLs for heptachlor and 

heptachlor epoxide. 

Oral MRLs 

Heptachlor. 

• An MRL of 0.0006 mg/kg/day has been derived for acute-duration oral exposure (14 days or less) 

to heptachlor. 

A number of studies have examined the toxicity of heptachlor following acute-duration oral exposure; 

many of the toxicity studies are limited by the lack of statistical analysis and poor reporting of the 

observed effects, including incidence data. Despite the limitations in the studies, the acute database does 

identify several targets of toxicity including the liver, nervous system, reproductive capacity, and the 

developing offspring. Although some other adverse health effects have been reported, they have not been 

replicated in other studies or were observed at lethal doses. The most sensitive effect following acuteduration exposure appears to be a decrease in fertility and an increase in resorptions observed in female 

rats administered via gavage 1.8 mg/kg/day heptachlor in groundnut oil for 14 days prior to mating 

(Amita Rani and Krishnakumari 1995). Gestational exposure to 4.5 or 6.8 mg/kg/day resulted in 

decreases in pup body weight (Narotsky and Kavlock 1995; Narotsky et al. 1995); a decrease in pup 

righting reflex was also observed at 4.2 mg/kg/day (Purkerson-Parker et al. 2001b). At twice these dose 

levels, an increase in pup mortality was observed (Narotsky et al. 1995; Purkerson-Parker et al. 2001b). 

Liver effects were observed at doses similar to those resulting in developmental effects. Increases in 

serum alanine aminotransferase and aldolase activity levels, hepatocytomegaly, and minimal 

monocellular necrosis were observed in rats administered 7 mg/kg/day heptachlor in oil for 14 days 

(Berman et al. 1995; Krampl 1971). Exposure to 7 mg/kg/day also resulted in excitability and increased 

arousal in rats administered heptachlor in oil via gavage for 1 or 14 days (Moser et al. 1995). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 15 

2. RELEVANCE TO PUBLIC HEALTH 

The lowest LOAEL identified in the acute-duration oral database is 1.8 mg/kg/day for reduced fertility 

and an increase in resorptions in female rats (Amita Rani and Krishnakumari 1995). In this study, groups 

of 30 female CFT-Wistar rats received gavage doses of heptachlor in groundnut oil for 14 days 

(presumably 7 days/week). The total administered doses were 25 and 50 mg/kg body weight and the 

daily doses were 1.8 and 3.6 mg/kg/day. A vehicle control group was also used. After 14 days of 

exposure, the animals were mated with unexposed male rats. A significant decrease in the number of 

pregnant females (56.3 and 44.4%) and increase in the number of resorptions (18.90 and 11.40%) were 

observed in both groups of heptachlor-exposed rats. Significant decreases in estradiol-17beta and 

progesterone levels were also observed in the 1.8 mg/kg/day group. No alterations in the number of 

implantations were observed. The investigators noted that focal necrosis was observed in the liver; 

however, they did not note at which dose level and no incidence data were provided. This LOAEL of 

1.8 mg/kg/day was divided by an uncertainty factor of 1,000 (10 for use of a LOAEL, 10 for extrapolation 

from rats to humans, and 10 for human variability) and a modifying factor of 3 to account for the use of a 

serious end point, resulting in an acute-duration oral MRL of 0.0006 mg/kg/day. 

• An MRL of 0.0001 mg/kg/day has been derived for intermediate-duration oral exposure (15– 

364 days) to heptachlor. 

Intermediate-duration oral exposure studies have identified a number of targets of heptachlor toxicity 

including the liver, nervous system, reproductive system, and the developing offspring. Other less 

documented effects have also been observed. In the absence of maternal toxicity, heptachlor is not 

associated with alterations in pup mortality or body weight gain (Lawson and Luderer 2004; PurkersonParker et al. 2001b; Smialowicz et al. 2001). Additionally, gestational exposure does not appear to result 

in significant alterations in the occurrence of anomalies or abnormalities (Narotsky et al. 1995; 

Smialowicz et al. 2001) or the development of the reproductive system (Lawson and Luderer 2004; 

Smialowicz et al. 2001). In utero exposure followed by postnatal exposure (until postnatal day 42) did 

not alter reproductive function (Smialowicz et al. 2001), but did adversely affect neurobehavioral 

performance (Moser et al. 2001) and immune function (Smialowicz et al. 2001). The neurological effects 

included impaired spatial memory at 0.03 mg/kg/day and higher, impaired spatial learning at 0.3 or 

3 mg/kg/day, and decreased righting reflex (Moser et al. 2001; Purkerson-Parker et al. 2001b) and 

increased open field activity (Moser et al. 2001) at 3 mg/kg/day. When the exposure was terminated at 

postnatal day 21, rather than postnatal day 42, spatial memory and learning were not adversely affected 

(Moser et al. 2001). The difference in results may have been due to higher heptachlor epoxide body 

burden in rats exposed to postnatal day 42, testing at different ages, or exposure may have occurred 

during a critical window of vulnerability. The effects observed in rats are consistent with those observed 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 16 

2. RELEVANCE TO PUBLIC HEALTH 

in humans. Impaired performance on several neurobehavioral tests, including abstract concept formation, 

visual perception, and motor planning, was observed in high school students presumably prenatally 

exposed to heptachlor from contaminated milk products (Baker et al. 2004b). Alterations in immune 

function were also observed in the rats exposed until postnatal day 42. At 0.03 mg/kg/day and higher, 

suppression of the immune response to sheep red blood cells was observed (Smialowicz et al. 2001). A 

reduction in the percentage of B lymphocytes was also observed in the spleen of rats exposed to 

3 mg/kg/day. Other tests of immune function were not significantly altered. 

The liver effects observed in rats or mice exposed to heptachlor in the diet include increased liver weights 

(Izushi and Ogata 1990; Pelikan 1971), increased serum alanine aminotransferase activity levels (Izushi 

and Ogata 1990), steatosis (Pelikan 1971), and hepatitis and necrosis (Akay and Alp 1981). The lowest 

LOAEL values for these effects range from 5 to 8.4 mg/kg/day. Neurological signs such as 

hyperexcitability, seizures, and difficulty standing, walking, and righting were observed at similar dose 

levels; LOAELs ranged from 1.7 to 17 mg/kg/day (Akay and Alp 1981; Aulerich et al. 1990; Crum et al. 

1993). Decreases in epididymal sperm count were observed in rats administered 0.65 mg/kg/day 

heptachlor in groundnut oil for 70 days (Amita Rani and Krishnakumari 1995). This dose also resulted in 

increased resorptions when the exposed males were mated with unexposed females. Reduced fertility 

was observed in all mice exposed to 8.4 mg/kg/day heptachlor for 10 weeks (Akay and Alp 1981). 

The intermediate-duration oral MRL for heptachlor is based on the results of the study reported by Moser 

et al. (2001) and Smialowicz et al. (2001), which found alterations in development of the nervous and 

immune systems. In this study, groups of 15–20 pregnant Sprague Dawley rats were administered via 

gavage 0, 0.03, 0.3, or 3 mg/kg/day heptachlor in corn oil on gestational day 12 through postnatal day 7; 

pups were also exposed from postnatal day 7 to 21 or 42. The liver, kidneys, adrenals, thymus, spleen, 

ovaries, uterus/vagina, testes, epididymides, seminal vesicles/coagulating glands, and ventral and 

dorsolateral prostate were histologically examined in the offspring on postnatal day 46. Neurological 

(functional observational battery tests, motor activity, passive avoidance tests learning and memory, and 

Morris water maze test to assess spatial and working memory) and immunological (splenic 

lymphoproliferative responses to T cell mitogens, and to allogeneic cells in a mixed lymphocyte reaction, 

primary immunoglobulin M (IgM) antibody response to sheep red blood cells, examination of splenic 

lymphocytes subpopulations, and delayed-type and contact hypersensitivity) function tests were 

performed on the offspring exposed until postnatal day 42; neurological function tests were also 

performed on offspring exposed until postnatal day 21. Reproductive assessment included evaluation of 

vaginal opening (index of female puberty) and prepuce separation (index of male puberty) beginning at 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 17 

2. RELEVANCE TO PUBLIC HEALTH 

postnatal days 25 and 35, respectively. The offspring were mated with an untreated mate and the dams 

were allowed to rear the first litter to postnatal day 10. The results of the neurobehavioral assessment 

were reported by Moser et al. (2001); the remaining results were reported by Smialowicz et al. (2001). 

No significant alterations in maternal body weight, number of dams delivering litters, litter size, or pup 

survival were observed. Additionally, no alterations in pup growth rates, age at eye opening, anogenital 

distance, or age at vaginal opening or preputial separation were observed. A significant decrease in pup 

body weight at postnatal day 1 was observed at 3 mg/kg/day; this effect was not observed at postnatal 

days 7, 14, or 21. No consistent, statistically significant alterations in offspring body weights were 

observed at post natal days 21, 28, 35, or 42. Significant alterations in absolute and relative liver weights 

were observed in males and females exposed to 3 mg/kg/day; increases in absolute and relative ovary 

weights were also observed at 3 mg/kg/day. No histological alterations were observed in the examined 

tissues. No alterations in fertility were observed in the adult males and females mated to untreated 

partners, and no effects on soft tissue or gross body structure of the offspring (F2 generation) were 

observed. No alterations in sperm count or sperm motility were observed. 

A dose-related, statistically significant suppression of primary IgM antibody response to sheep red blood 

cells (sRBC) was found in male offspring, but not females. The primary IgM response to sRBCs was 

reduced in 21-week-old males exposed to 0.3 mg/kg/day. A second immunization with sRBCs 

administered 4 weeks later resulted in a significant reduction in IgG antibody response in males 

administered 0.03, 0.3, or 3 mg/kg/day heptachlor; no response was seen in females. A decrease in the 

OX12+

OX19- (i.e., B/plasma cells) population was also found in the spleen of males exposed to 

3 mg/kg/day. No alterations in the following immunological parameters assessed at 8 weeks of age were 

found: lymphoid organ weights, splenic NK cell activity, splenic cellularity or cell viability, and 

lymphoproliferative responses of splenic lymphocytes to T-cell mitogens ConA and phytohemagglutinin 

(PHA) or to allogenic cells in the mixed lymphocyte reaction. The results of this portion of the study 

suggest that exposure to heptachlor adversely affects the development of the immune system. 

Righting was significantly delayed in the female offspring of rats exposed to 3 mg/kg/day heptachlor; no 

significant alterations were observed in the male offspring. The investigators suggested that this was due 

to a delay in the ontogeny of righting rather than an inability to perform the task. The following 

significant alterations in the functional observation battery (FOB) and motor activity tests were found in 

the offspring dosed until postnatal day 21: increased open field activity in 3 mg/kg/day males, non-doserelated increased activity in figure-eight chambers in females (significant only in 0.03 mg/kg/day group), 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 18 

2. RELEVANCE TO PUBLIC HEALTH 

and faster decline in habituation of activity in 3 mg/kg/day males. Alterations in the offspring dosed until 

postnatal day 42 included: increased levels of urination in males in the 0.03 and 0.3 mg/kg/day groups, 

increased landing foot splay in males in the 0.03 mg/kg/day group, and removal reactivity in males and 

females in the 0.03 mg/kg/day group. No alterations in the passive avoidance test were observed in the 

offspring exposed until postnatal day 21; in those exposed until postnatal day 42, an increase in the 

number of nose pokes was observed in all groups of females. No significant alterations in performance 

on the water maze test were found in the offspring exposed until postnatal day 21. In those exposed until 

postnatal day 42, increases in latency to find the platform were observed in males and females exposed to 

3 mg/kg/day and increases in the time spent in the outer zone were found in males exposed to 0.3 or 

3 mg/kg/day. In the water maze memory trial, no differences in performance were found between 

controls and animals exposed until postnatal day 21. Alterations in significant quadrant bias were 

observed in 0.03, 0.3, and 3 mg/kg/day males during the first probe test and in 0.3 and 3 mg/kg/day males 

and 3 mg/kg/day females in the second probe test. The study investigators noted that the heptachlorexposed rats did not develop an efficient search strategy for locating the platform; they spent more time 

circling the outer zone of the tank. By the second week of the test, control rats had learned to venture into 

the zone where the platform was located. 

The Smialowicz et al. (2001) and Moser et al. (2001) study identified a LOAEL of 0.03 mg/kg/day for 

developmental immunological and neurological effects. These alterations were considered to be 

minimally adverse and suggestive of immunotoxicity and neurotoxicity. An intermediate-duration oral 

MRL was calculated by dividing the minimal LOAEL of 0.03 mg/kg/day by an uncertainty factor of 

300 (3 for use of a minimal LOAEL, 10 for extrapolation from animals to humans, and 10 for human 

variability). The resulting MRL is 0.0001 mg/kg/day. 

There is a limited publicly available database on the chronic oral toxicity of heptachlor. In a 

multigeneration study conducted by Mestitzova (1967), decreases in litter size, increased postnatal 

mortality, and increased occurrence of lens cataracts (observed in F0, F1, and F2 generations) were 

observed at a heptachlor dose of 6 mg/kg/day. Because the only reliable chronic-duration study identified 

a serious LOAEL at the lowest dose tested, a chronic-duration MRL was not derived for heptachlor. 

Heptachlor Epoxide. Publicly available data on the toxicity of heptachlor epoxide are limited to an LD50 

study (Podowski et al. 1979), and a dominant lethal study (Epstein et al. 1972). Neither of these studies is 

suitable for derivation of MRLs for heptachlor epoxide. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 19 

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 heptachlor and 

heptachlor epoxide. 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 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 20 

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 heptachlor and 

heptachlor epoxide are indicated in Table 3-1 and Figure 3-1. 

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. 

3.2.1 Inhalation Exposure 

3.2.1.1 Death 

Limited information exists regarding exposure to heptachlor or heptachlor epoxide and mortality. One of 

the four reports available studied pesticide manufacturers (Wang and MacMahon 1979b), whereas the 

other three examined pesticide applicators (Blair et al. 1983; MacMahon et al. 1988; Shindell and 

Associates 1981; Wang and MacMahon 1979a). Exposure data were not available in any of these studies 

and none of them provided specific information for heptachlor or heptachlor epoxide. An occupational 

mortality study on workers employed in the manufacture of heptachlor and other chlorinated hydrocarbon 

pesticides for at least 3 months between 1952 and 1979 revealed no pattern of disease or medical 

condition that indicated that persons were at greater risk of adverse outcome than the general population 

(Shindell and Associates 1981). The only significant finding observed in workers employed at two 

facilities manufacturing chlordane or heptachlor and endrin was an excess of deaths from cerebrovascular 

disease, which was unrelated to duration of exposure or latency, and occurred exclusively after 

termination of employment (Wang and MacMahon 1979b). In professional pesticide applicators at three 

U.S. companies who were employed for 3 months or longer between 1967 and 1976, only deaths due to 

bladder cancer were significantly elevated in the applicators as a whole (Wang and MacMahon 1979a). 

In a separate analysis conducted for persons ever holding jobs as “termite control operators,” a group 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 21 

3. HEALTH EFFECTS 

more likely to be exposed to chlordane and heptachlor, bladder cancer was elevated in both the termite 

control operators and the group comprising the rest of the applicators. However, since confidence 

intervals were not provided, it is unknown whether this increase was statistically significant. A follow-up 

analysis of the same cohort extending to the end of 1984 reported that deaths due to cancer of the lung 

was the only outcome significantly elevated in the group as a whole (MacMahon et al. 1988). Separate 

analyses, as done in the earlier study, revealed that deaths due to lung cancer were not significantly 

elevated in the group with the highest likelihood of exposure to chlordane and heptachlor. In the last 

study of licensed male pesticide applicators in Florida, the standardized mortality ratio (SMR) for all 

causes of death was 103, but increased SMRs, although not statistically significant, were seen for 

leukemia, cancers of the brain, and lung cancer (Blair et al. 1983). The increased SMRs for brain and 

leukemia were based on small numbers. Mortality from lung cancer was related to years licensed, but 

could not be attributed to any specific pesticide due to lack of information on frequency and intensity of 

exposures. Furthermore, information on smoking was not available. In conclusion, the information 

available is insufficient to determine whether there is an association between exposure of workers to 

heptachlor or heptachlor epoxide and mortality. 

No studies were located regarding death in animals after inhalation exposure to heptachlor or heptachlor 

epoxide. 

3.2.1.2 Systemic Effects 

No studies were located regarding respiratory, cardiovascular, gastrointestinal, musculoskeletal, hepatic, 

renal, dermal, or ocular effects in humans or animals after inhalation exposure to heptachlor or heptachlor 

epoxide. 

Hematological Effects. The available data on potential hematological effects following inhalation 

exposure to heptachlor or heptachlor epoxide are limited to a case-control study of exterminators, 

gardeners, and agricultural workers exposed to several organochlorine pesticides (heptachlor among 

them) (Wang and Grufferman 1981). No dose-dependent causal relationship between exposure to several 

organochlorine pesticides and deaths from aplastic anemia was found. 

No studies were located regarding hematological effects in animals after inhalation exposure to 

heptachlor or heptachlor epoxide. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 22 

3. HEALTH EFFECTS 

No studies were located regarding the following effects in humans or animals after inhalation exposure to 

heptachlor or heptachlor epoxide: 

3.2.1.3 Immunological and Lymphoreticular Effects 

3.2.1.4 Neurological Effects 

3.2.1.5 Reproductive Effects 

3.2.1.6 Developmental Effects 

3.2.1.7 Cancer 

Several studies have examined the possible association between cancer and environmental and/or 

occupational exposure to chlordane and heptachlor (Epstein and Ozonoff 1987; MacMahon et al. 1988; 

Shindell and Associates 1981; Wang and MacMahon 1979a, 1979b). Several occupational cohorts 

showed that workers who were involved in the manufacture of chlordane and heptachlor did not have a 

significant increase in death from any type of cancer (MacMahon et al. 1988; Shindell and Associates 

1981; Wang and MacMahon 1979a, 1979b). These occupational studies are presumed to reflect primarily 

inhalation exposure, with some concomitant dermal exposure. Among workers at pesticide 

manufacturing facilities, the SMR for bladder cancer was of borderline statistical significance (Wang and 

MacMahon 1979a). A follow-up study identified an increase in lung cancer, but the SMR for deaths from 

lung cancer in the group with the highest chance of exposure was not significant (MacMahon et al. 1988). 

No information on cigarette smoking was obtained from the participants. A retrospective mortality study 

conducted on male workers engaged in chlordane, heptachlor, and endrin manufacture for at least 

3 months also showed a slight excess of lung cancer compared to the general U.S. population, but the 

increase was not statistically significant (Wang and MacMahon 1979b). Leukemia was associated with 

exposure to chlordane and heptachlor following home termiticide use (Epstein and Ozonoff 1987). An 

increased risk of prostate cancer was found among Hispanic farm workers potentially exposed to 

heptachlor (Mills and Yang 2003). Among the workers employed in counties with the highest heptachlor 

use, the odds ratio (adjusted for age, surrogates for exposure initiation, and duration) was 2.01 (95% 

confidence interval of 1.12–3.60). 

It is difficult to determine from these studies whether or not exposure to heptachlor or heptachlor epoxide 

causes cancer. Although some studies suggest an association between exposure and cancer, other studies 

have not found significant associations, and there were many limitations among the studies. Limitations 

include the lack of quantitative exposure information, concomitant exposure to other chemicals, lack of 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 23 

3. HEALTH EFFECTS 

control measures for confounding factors, lack of information on diet, smoking habits, and liver function, 

and lack of complete occupational history, including other potential causal factors such as genetic 

disposition or immunologic disorders. 

No studies were located regarding cancer in animals after inhalation exposure to heptachlor or heptachlor 

epoxide. 

3.2.2 Oral Exposure 

3.2.2.1 Death 

No studies were located regarding death in humans after oral exposure to heptachlor or heptachlor 

epoxide. 

Acute oral LD50 values for heptachlor in rodents (rats, mice, hamsters, and guinea pigs) and rabbits range 

from 40 to 2,302 mg/kg (purity ranging from unspecified to 99.9%) (Ben-Dyke et al. 1970; Berman et al. 

1995; Eisler 1968; Gaines 1969; Gak et al. 1976; Lehman 1951; Podowski et al. 1979; Sperling et al. 

1972; Sun 1972). The differences in the purity of the administered heptachlor may have influenced 

lethality. Pure heptachlor appears to be more lethal than technical-grade heptachlor (Berman et al. 1995; 

Podowski et al. 1979). Acute oral LD50 values for heptachlor epoxide in rodents (rats and mice) and 

rabbits range from 39 to 144 mg/kg (Eisler 1968; Podowski et al. 1979; Sperling et al. 1972). 

Heptachlor can be converted to its photoisomer, photoheptachlor, in the presence of sunlight or ultraviolet 

light. This photolysis can take place on plant leaves. Photoheptachlor was found to be more toxic to rats 

than heptachlor or heptachlor epoxide; the LD50 for photoheptachlor was 3.8 mg/kg (Podowski et al. 

1979). 

The results of the non-LD50 studies indicate that the lethal dose decreases with duration of exposure. A 

single gavage dose of up to 129 mg/kg technical-grade heptachlor (73% heptachlor, 26% chlordane) did 

not result in mortality in rats (Berman et al. 1995). However, repeated doses of 23 or 69 mg/kg/day of 

technical-grade heptachlor resulted in 100% mortality after 6 or 3 doses, respectively (Berman et al. 1995; 

Moser et al. 1995). Increases in mortality were also observed in male rats exposed to 30 mg/kg/day and 

female rats exposed to 15 mg/kg/day technical-grade heptachlor (73% heptachlor, 22% chlordane, 5% 

nonachlor) in the diet for 6 weeks, followed by a 2-week period of observation (NCI 1977). No deaths 

were observed at 14 mg/kg/day in males and 7.6 mg/kg/day in females. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 24 

3. HEALTH EFFECTS 

Similar lethal doses were observed in mice and mink exposed to heptachlor in the diet for intermediate 

durations. The lethal doses were 14 mg/kg/day for mice fed diets containing technical-grade heptachlor 

(73% heptachlor, 22% chlordane, 5% nonachlor) for 6 weeks, followed by a 2-week period of observation 

(NCI 1977) and 6.19 mg/kg/day for mink fed technical-grade heptachlor (72% heptachlor) for 28 days 

(Aulerich et al. 1990) or 1.7 mg/kg/day for 181 days (Crum et al. 1993). No alterations in mortality were 

observed in mice exposed to doses of 5.2 mg/kg/day or in mink at doses of 5.67 mg/kg/day. In chronicduration studies, no statistically significant alterations in survival were observed in male or female mice 

exposed to 2.4 or 3.0 mg/kg/day, respectively, technical-grade heptachlor in the diet for 80 weeks (NCI 

1977). 

All reliable LD50 values and all reliable LOAEL values for death in each species and duration category 

are recorded in Table 3-1 and plotted in Figure 3-1. 

3.2.2.2 Systemic Effects 

No studies were located regarding respiratory, musculoskeletal, or dermal effects in humans or animals 

after oral exposure to heptachlor or heptachlor epoxide. 

The highest NOAEL values and all reliable LOAEL values for systemic effects in each species and 

duration category are recorded in Table 3-1 and plotted in Figure 3-1. 

Cardiovascular Effects. The information regarding cardiovascular effects in humans associated 

with heptachlor and heptachlor epoxide exposure is limited to a study that found statistically higher 

heptachlor epoxide serum levels among individuals with moderate to severe arterosclerosis (Pines et al. 

1986). This report cannot be construed as showing a causal relationship between heptachlor epoxide 

exposure and arteriosclerosis because no adjustments for other risk factors were made. 

Animal data are limited to a study that found increases in relative heart weight (statistical significance not 

reported) in female rats exposed to heptachlor in the diet 5 days/week for 4 weeks (Enan et al. 1982). The 

investigators noted that 10 mg/kg heptachlor was added to the diet; it is not known if this is a dietary 

concentration or dose. The biological significance of this effect is not known, particularly since no 

information on body weight changes or food intake were provided and a histological examination was not 

performed. 
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - 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

272

Berman et al. 1995heptachlor

230 F (LD50)

230

Rat(Fischer- 344)

once(GO)

2

12

Gaines 1969heptachlor

b

100 M (LD50)

100

162 F (LD50)

162

Rat(Sherman)

1 d1 x/d(GO)

3

6

Gak et al. 1976heptachlor

105 (LD50)

105

Rat(NS)

once(GO)

4

282

Narotsky et al. 1995heptachlor

12 F (38% mortality in

pregnant rats)

12

Rat(Fischer- 344)

Gd 6-15(GO)

5

210

Podowski et al. 1979heptachlor

71 M (LD50)

71

Rat(NS)

once

6

296

Podowski et al. 1979heptachlor epoxide

60 M (LD50)

60

Rat(NS)

once

7

7

Gak et al. 1976heptachlor

70 (LD50)

70

Mouse(NS)

once(GO)

8

8

Gak et al. 1976heptachlor

100 (LD50)

100

Hamster(NS)

once(GO)
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - 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

9

273

Berman et al. 1995heptachlor

Hepatic 2 F

2

7 F (hepatocytomegaly)

7

Rat(Fischer- 344)

14 d1 x/d(GO)

10

17

Krampl 1971heptachlor

Hepatic 60 F (increased serum ALT

and aldolase levels,decreased liver ALT andaldolase levels,vacuolated cells, pyknoticnuclei)

60

Rat(Wistar)

once(GO)

11

30

Krampl 1971heptachlor

Hepatic 7 F (decreased liver ALT and

aldolase levels,increased serum ALTand aldolase levels;monocellular necrosisand vacuolar dystrophy)

7

Rat(Wistar)

3, 7, or 14 d(GO)

12

292

Pelikan 1971heptachlor

Resp 5

5

Rat(Wistar)

14 d(F)

Cardio 5

5

Gastro 5 (slightly hyperemic

stomach and intestinalwall)

5

Hepatic 5

5

Renal 5

5

Bd Wt 5

5
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - 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

243

Akay et al. 1982

heptachlor

Endocr 87 F (atrophy in adrenal

cortex)

87

Mouse(albino)

11 d(W)

Immuno/ Lymphoret

14

270

Berman et al. 1995heptachlor

69 F

69

129 F (necrotic lymphocytes in

spleen and thymus)

129

Rat(Fischer- 344)

once(GO)

15

271

Berman et al. 1995heptachlor

69 F

69

Rat(Fischer- 344)

14 d1 x/d(GO)

16

219

Pelikan 1971heptachlor

5

5

Rat(Wistar)

14 d(F)

Neurological

17

267

Moser et al. 1995heptachlor

7 F (excitability)

7

Rat(Fischer- 344)

once(GO)

18

268

Moser et al. 1995heptachlor

2 F

2

7 F (increased arousal)

7

Rat(Fischer- 344)

14 d1 x/d(GO)

Reproductive

19

280

Amita Rani and Krishna

1995heptachlor

c

1.8 F (decreased fertility;

increased resorptions)

1.8

Rat(Wistar)

14 d(GO)

20

238

Arnold et al. 1977

heptachlor

15 M

15

Mouse(CD-1)

1 d1 x/d(G)
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - 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)

21

25

Epstein et al. 1972heptachlor epoxide

8 M

8

Mouse(ICR)

5 d(G)

22

26

Epstein et al. 1972heptachlor

10 M

10

Mouse(ICR)

5 d(G)

Developmental

23

283

Narotsky and Kavlock 1heptachlor

4.5 (decreased pup body

weight at pnd 6)

4.5

Rat(Fischer- 344)

Gd 6-19(GO)

24

281

Narotsky et al. 1995heptachlor

5.1 F

5.1

6.8 F (decreased pup body

weight)

6.8

9 F (pup mortality)

9

Rat(Fischer- 344)

Gd 6-15(GO)

25

285

Purkerson-Parker et al. heptachlor

4.2 F (decreased righting reflex

in pups)

4.2

8.4 F (decreased pup survival)

8.4

Rat(SpragueDawley)

Gd 10-21(GO)

INTERMEDIATE EXPOSUREDeath

26

216

NCI 1977heptachlor

30 M (2/5 male rats died)

30

b

15 F (4/5 female rats died)

15

Rat(OsborneMendel)

6 wk(F)

27

217

NCI 1977heptachlor

14 M (5/5 males died)

14

Mouse(B6C3F1)

6 wk(F)

28

239

Aulerich et al. 1990

heptachlor

6.2 M (3/8 died)

6.2

Mink(NS)

28 d(F)
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - 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)

29

276

Crum et al. 1993heptachlor

1.7 F (67% mortality)

1.7

Mink(NS)

181 d(F)

Systemic

30

266

Akhtar et al. 1996

heptachlor

Endocr 1 M

1

Rat(albino)

21 d(G)

Bd Wt 1 M

1

31

218

Pelikan 1971heptachlor

Resp 5

5

Rat(Wistar)

28 d(F)

Cardio 5

5

Gastro 5 (thin mucous secretion

covering the stomachand intestine mucosa)

5

Hepatic 5 (steatosis, 21-23%

increased relative liverweight)

5

Renal 5

5

Bd Wt 5

5
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - 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)

32

242

Akay and Alp 1981

heptachlor

Hepatic 9.3 (hepatitis, necrosis,

granuloma, congestion)

9.3

Mouse(NS)

10 wk(F)

Renal 37 (granuloma)

37

Bd Wt 9.3 (unspecified decrease in

body weight)

9.3

33

294

Akay et al. 1982

heptachlor

Endocr 87 F (lipid accumulation and

extensive degenerationand fibrosis in adrenalcortex)

87

Mouse(albino)

26 d(W)

34

241

Izushi and Ogata 1990heptachlor

Hepatic 6.9 M (increased serum ALT

activity levels and liverweight)

6.9

Mouse(DDY)

180 dad lib(W)

Bd Wt 6.9 M

6.9

Metab 6.9 M

6.9

35

244

Izushi and Ogata 1990heptachlor

Hepatic 10 M (increased serum ALT,

alkaline phosphatase,and triglyceride levels,liver triglyceride levels,and liver weight)

10

Mouse(DDY)

92 d2 x/wk(GO)

Bd Wt 10 M

10

Metab 10 M

10
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - 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

247

Aulerich et al. 1990

heptachlor

Bd Wt 3.1 M

3.1

5.7 M (22% decrease in body

weight)

5.7

Mink(NS)

28 d(F)

Immuno/ Lymphoret

37

293

Pelikan 1971heptachlor

5

5

Rat(Wistar)

28 d(F)

38

248

Akay and Alp 1981

heptachlor

19

19

37 (splenic fibrosis)

37

Mouse(NS)

10 wk(F)

39

249

Aulerich et al. 1990

heptachlor

5.7 M

5.7

6.2 M (49% decrease in

spleen/brain weight)

6.2

Mink(NS)

28 d(F)

Neurological

40

250

Akay and Alp 1981

heptachlor

9.3

9.3

19 F (difficulty standing,

walking, and righting)

19

Mouse(NS)

10 wk(F)

41

251

Aulerich et al. 1990

heptachlor

5.7 M

5.7

6.2 M (clinical signs of

hyperexcitability andincoordination)

6.2

Mink(NS)

28 d(F)

42

277

Crum et al. 1993heptachlor

1 F

1

1.7 F (hyperexcitability and

seizures)

1.7

Mink(NS)

181 d(F)
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - 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)

Reproductive

43

279

Amita Rani and Krishna

1995heptachlor

0.65 M (decreased epididymal

sperm count)

0.65

0.65 M (increased resorptions)

0.65

Rat(Wistar)

70 d(GO)

44

254

Akay and Alp 1981

heptachlor

9.3 (100% infertility)

9.3

Mouse(NS)

10 wk(F)

45

275

Crum et al. 1993heptachlor

1.7 F

1.7

Mink(NS)

181 d(F)

Developmental

46

331

Lawson and Luderer 20heptachlor

5 F (increased pup mortality

and decreased birthweights)

5

Rat(SpragueDawley)

dailyGd 8-21, Ld0-21(GO)

47

286

Moser et al. 2001heptachlor

0.03 (impaired spatial

memory)

0.03

Rat(SpragueDawley)

Gd 12- pnd 7;pups exposedfrom pnd 7-21or pnd 7-42(GO)

48

284

Purkerson-Parker et al. heptachlor

0.3

0.3

3 (decrease in righting

reflex)

3

8.4 (decreased pup survival)

8.4

Rat(SpragueDawley)

Gd 10- Ld 7;pups exposedon days 7-21 or42(GO)

49

287

Smialowicz et al. 2001heptachlor

d

0.03 (suppression of immune

response to sheep RBCin offspring)

0.03

Rat(SpragueDawley)

Gd 12- pnd 71;pups exposedto day 42(GO)
a

Key to

Figure

Table 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - 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)

50

278

Crum et al. 1993heptachlor

1

1

1.7 (increased stillbirths and

decreased kit survival)

1.7

Mink(NS)

181 d(F)

CHRONIC EXPOSURECancer

51a The number corresponds to entries in Figure 3-1.b Differences in levels of health effects and cancer effects between male and females are not indicated in Figure 3-1. Where such differences exist, only the levels most sensitive gender are presented.c Used to derive an acute oral minimal risk level (MRL) of 0.0006 mg/kg/day; dose divided by an uncertainty factor of 1000 (10 for use of a LOAEL, 10 for extrapolato humans, and 10 for human variability) and a modifying factor of 3 for the use of a serious endpoint.d Used to derive an intermediate oral minimal risk level (MRL) of 0.0001 mg/kg/day; dose divided by an uncertainty factor of 300 (3 for use of a minimal LOAEL, 10 from animals to humans, and 10 for human variability).ALT = alanine aminotransferase; Bd Wt = body weight; Cardio = cardiovascular; d = day(s); Endocr = endocrine; (F) = feed; F = Female; (G) = gavage; Gastro = ga

= gestational day; (GO) = gavage in oil; Ld = lactation day; LD50 = lethal dose, 50% kill; LOAEL = lowest-observed-adverse-effect level; M = male; Metab = metabono-observed-adverse-effect level; NS = not specified; pnd = post-natal day; RBC = red blood cell(s); Resp = respiratory; x = time(s); (W) = drinking water; wk = wee

235

NCI 1977heptachlor

2.4 M (hepatocellular

carcinoma)

2.4

Mouse(B6C3F1)

80 wk(F)
0.0001

0.001

0.01

0.1

1

10

100

1000

Death

8s

7m

1r

2r 3r

4r

5r 6r

Respiratory

12r

Cardiovascular

12r

Gastrointestinal

12r

Hepatic

9r

9r

10r

11r

12r

Renal

12r

Endocrine

13m

Body Weight

12r

Immuno/Lymphor

14r

14r 15r

16r

Neurological

17r

18r

18r

Reproductive

20m

21m 22m

19r

Developmental

23r

24r

24r

24r

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

25r

25r

Systemic

Figure 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - Oral

Acute (≤14 days)

 Minimal Risk Level

34
0.0001

0.001

0.01

0.1

1

10

100

Death

28n

29n

27m 26r

Respiratory

31r

Cardiovascular

31r

Gastrointestinal

31r

Hepatic

32m

34m

35m

31r

Renal

32m

31r

Endocrine

33m

30r

Body Weight

36n

36n

32m

34m

35m

30r

31r

Metabolic

34m

35m

Immuno/Lymphor

39n 39n

38m

38m

37r

Neurological

41n 41n

42n

42n

40m

40m

Reproductive

45n

44m

43r 43r

Developmental

50n

50n

46r

47r

48r

48r

48r

49r

mg/kg/day

Intermediate (15-364 days)

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

Systemic

Figure 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - Oral (Continued)

35
1E-8

1E-7

1E-6

1E-5

0.0001

0.001

0.01

0.1

1

10

Cancer *

51m

Estimated

Upper-Bound

Human Cancer

Risk Levels

For Heptachlor

10

10

10

10

-7

-6

-5

-4

mg/kg/day

Figure 3-1 Levels of Significant Exposure to Heptachlor and Heptachlor Epoxide - Oral (Continued)

Chronic (�365 days)

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

Estimated

Upper-Bound

Human Cancer

Risk Levels

For Heptachlor Epoxide

10

10

10

10

-7

-6

-5

-4

*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.
HEPTACHLOR AND HEPTACHLOR EPOXIDE 37 

3. HEALTH EFFECTS 

Gastrointestinal Effects. No studies were located regarding gastrointestinal effects in humans after 

oral exposure to heptachlor or heptachlor epoxide. Gross necropsy showed that the stomach and intestinal 

walls were slightly hyperemic in rats exposed to 5 mg/kg/day of heptachlor in the diet for 14 days 

(Pelikan 1971); after 28 days of exposure, the mucosa of the stomach and intestine was covered by a thin 

mucus secretion. No histological alterations were observed in gastrointestinal tissues at either duration. 

Ulceration and bloody mucus were observed in the stomachs of mink exposed to 1.7 or 3.1 mg/kg/day 

heptachlor in the diet for 181 days (Crum et al. 1993). These doses were also associated with mortality 

and pronounced neurological effects; the investigators also noted that the animals stopped eating 1– 

2 weeks prior to death. 

Hematological Effects. No studies were located regarding hematological effects in humans after oral 

exposure to heptachlor or heptachlor epoxide; one animal study examining hematological end points was 

identified. A statistically significant increase in total leukocyte levels was observed in rats exposed to 

heptachlor in the diet for 1, 7, or 28 days (Enan et al. 1982). No alterations in erythrocyte levels were 

found. As noted previously, it is not known if the reported concentration of 10 mg/kg is a dietary 

concentration or dose. 

Hepatic Effects. Very limited information is available regarding hepatic effects of heptachlor or 

heptachlor epoxide in humans. Evaluation of individuals exposed for an unspecified period of time to 

contaminated raw milk products from cattle fed heptachlor-contaminated feed revealed significantly 

elevated serum levels of heptachlor metabolites relative to national background levels from National 

Health and Nutrition Examination Survey (NHANES) II and to levels monitored in unexposed reference 

subjects (Stehr-Green et al. 1986, 1988). Compared to the reference subjects, no significant alterations in 

serum liver enzyme activity levels were found, and no hepatomegaly was detected by clinical 

examination. This information is insufficient to draw any meaningful conclusion regarding liver effects 

of heptachlor in humans. 

A number of animal studies have reported liver effects following oral exposure to heptachlor. Although 

collectively, the studies indicate that the liver is a target of toxicity, interpretation of many of the 

individual studies is limited by the lack of statistical analysis and the incomplete descriptions of the 

observed effects (including incidence data). No histological alterations and a small increase (15–17%) in 

relative liver weight were observed in rats exposed to 5 mg/kg/day in the diet for 14 days (Pelikan 1971). 

In another acute exposure study, hepatocytomegaly was observed at 7 mg/kg/day in rats administered 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 38 

3. HEALTH EFFECTS 

heptachlor in corn oil via gavage for 14 days (Berman et al. 1995). Monocellular necrosis and vacuolar 

dystrophy (statistical significance not reported) were observed in rats administered 7 mg/kg/day 

heptachlor in corn oil for 3, 7, or 14 days (Krampl 1971); decreases in liver alanine aminotransferase and 

aldolase activity levels and increases in serum alanine aminotransferase and aldolase activity levels were 

also observed at this dose level. A single dose of 60 mg/kg heptachlor resulted in similar enzyme activity 

changes (Krampl 1971); minimal evidence of single monocellular necrosis with inflammatory reaction, 

vacuolated cells, and pyknotic nuclei were observed 72 hours after dosing. The investigator noted that the 

histological alterations paralleled the time course for the enzyme changes. 

At longer durations, the severity of the liver effects appeared to increase. Steatosis was observed in rats 

exposed to 5 mg/kg/day in the diet for 28 days (Pelikan 1971) and hepatitis, necrosis, granuloma, and 

congestion were observed in mice fed diets containing 9.3 mg/kg/day heptachlor for 10 weeks (Akay and 

Alp 1981). As with acute exposure, intermediate exposure to heptachlor also resulted in alterations in 

serum enzyme levels; increases in serum aldolase, alanine aminotransferase, and alkaline phosphatase 

activity levels were observed at 6.9 mg/kg/day and higher (Izushi and Ogata 1990; Krampl 1971). 

Additionally, increases in serum and hepatic triglyceride levels were observed in mice administered 

10 mg/kg heptachlor in olive oil twice weekly (2.9 mg/kg/day) for 92 days (Izushi and Ogata 1990), but 

not in mice fed 6.9 mg/kg/day in the diet for 180 days (Izushi and Ogata 1990). Liver effects have also 

been observed in non-rodent experimental animals. Ultrastructural changes indicative of liver cell 

damage were observed in a small number of pigs administered 2 mg/kg/day “heptachlorine” in the diet for 

78 days (Dvorak and Halacka 1975; Halacka et al. 1974); no histological alterations were observed. Fatty 

liver was reported in mink exposed to 6.2 mg/kg/day heptachlor in the diet for 28 days (Aulerich et al. 

1990) or 1.7 mg/kg/day in the diet for 181 days (Crum et al. 1993). In both studies, these doses were 

associated with increased mortality. One chronic exposure study reported no clear effects on liver 

function (BSP clearance) in rats exposed to 6 mg/kg/day for 18 months (Mestitzova 1967). 

Renal Effects. No studies were located regarding renal effects in humans after oral exposure to 

heptachlor or heptachlor epoxide. Several studies have examined the potential of heptachlor to induce 

renal effects in animals. No histological alterations were observed in the kidneys from rats exposed to 

5 mg/kg/day heptachlor in the diet for 14 or 28 days (Pelikan 1971) or from rats exposed to 6 mg/kg/day 

for 18 months (Mestitzova 1967). Increased blood urea levels were observed after 7 or 28 days in rats 

exposed to 10 mg/kg heptachlor in the diet (Enan et al. 1982); an increase and decrease in relative kidney 

weight were observed after 7 or 28 days, respectively. As noted previously, interpretation of the results of 

this study is limited by the poor reporting of the dose. Granulomas were observed in the kidneys of mice 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 39 

3. HEALTH EFFECTS 

that received 37 mg heptachlor/day for 10 weeks (Akay and Alp 1981); however, no incidence data or 

statistical analysis was reported, limiting the interpretation of the results. A significant decrease in 

kidney-to-brain-weight ratio and granulation and discoloration of kidneys were reported in minks fed 

6.2 mg/kg/day of heptachlor daily for 28 days (Aulerich et al. 1990); the incidence of kidney damage was 

not reported. 

Endocrine Effects. There is limited information on the potential of heptachlor to induce endocrine 

effects. Cortical atrophy and slight hypertrophy in the zona glomerulosa of the adrenal gland was 

observed in mice exposed to 87 mg/kg/day for 11 days (Akay et al. 1982). When the exposure was 

continued for 26 days, heavy lipid accumulation, congestion, cell degeneration, and extensive fibrosis 

were observed in the adrenal cortex (Akay et al. 1982). The interpretation of these findings is limited by 

the poor reporting of the study and the lack of incidence data. One other study examined endocrine end 

points; no alterations in thyroxine, triiodothyronine, or thyroid stimulating hormone levels were observed 

in rats administered 1 mg/kg/day via gavage for 21 days (Akhtar et al. 1996). 

Ocular Effects. No studies were located regarding ocular effects in humans after oral exposure to 

heptachlor or heptachlor epoxide. Lens cataracts were observed in 22% of adult rats exposed to 

6 mg/kg/day heptachlor in the diet for 4.5–9.5 months; cataracts were not observed in the controls 

(Mestitzova 1967). As discussed in the developmental toxicity section, cataracts were also observed in 

the F1 and F2 offspring. Other studies have not reported this finding among adults, although no studies 

were specifically designed to assess this end point. Additionally, Narotsky and Kavlock (1995) did not 

find increases in cataracts in the offspring of rats administered up to 6 mg/kg/day heptachlor via gavage 

on gestational days 6–19. 

Body Weight Effects. No studies were located regarding body weight effects in humans after oral 

exposure to heptachlor or heptachlor epoxide. The available animal data do not suggest that oral 

exposure to heptachlor adversely affects body weight gain in the absence of decreases in food 

consumption. No alterations in body weight were observed in rats or mice exposed daily to doses as high 

as 1 and 6.9 mg/kg/day, respectively, for intermediate durations (Akhtar et al. 1996; Izushi and Ogata 

1990) or mice administered 10 mg/kg 2 times/week for 92 days (Izushi and Ogata 1990). Decreases in 

body weight gain were observed in mink exposed to heptachlor in the diet at doses of 5.7 mg/kg/day for 

28 days (Aulerich et al. 1990) or 1.7 mg/kg/day for 181 days, which included pregnancy and lactation 

periods (Crum et al. 1993); significant decreases in food consumption were observed in both studies. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 40 

3. HEALTH EFFECTS 

Metabolic Effects. No studies were located regarding metabolic effects in humans after oral exposure 

to heptachlor or heptachlor epoxide. Studies in animals suggest that exposure to heptachlor may disrupt 

carbohydrate metabolism. Significant decreases in liver glycogen levels, increases in liver and kidney 

gluconeogenic enzymes, and increases in blood glucose levels were observed in rats administered a single 

dose of 200 mg/kg heptachlor (Kacew and Singhal 1973). Decreases in liver glycogen levels and 

increases in blood glucose were also observed in rats exposed to 10 mg/kg for 1, 7, or 28 days (Enan et al. 

1982). The investigators noted that 10 mg/kg was added to the diet; it is not known if this is the dietary 

concentration (dose would be approximately 0.9 mg/kg/day) or dose. No alterations in blood glucose 

levels were observed in mice administered 6.9 mg/kg/day heptachlor in the diet for 180 days or 10 mg/kg 

via gavage 2 times/week (Izushi and Ogata 1990). 

3.2.2.3 Immunological and Lymphoreticular Effects 

No studies were located regarding immunological or lymphoreticular effects in humans after oral 

exposure to heptachlor or heptachlor epoxide. 

No studies were located that specifically investigated the effects on the immune system of oral exposure 

to heptachlor or heptachlor epoxide in adult animals. However, several studies have found alterations in 

the lymphoreticular system. Necrotic lymphocytes were observed in the spleen and thymus of rats 

administered a single dose of 129 mg/kg heptachlor via gavage (Berman et al. 1995); the investigators 

noted that the effect may have been secondary to generalized toxicity. Fibrosis was observed in the 

spleens of mice exposed to 37 mg/kg/day heptachlor in the diet for 10 weeks (Akay and Alp 1981). 

Enlarged and hyperemic spleens were observed in rats exposed to 5 mg/kg/day heptachlor in the diet for 

14 or 28 days (Pelikan 1971); however, no apparent alterations in relative spleen weight or histological 

alterations were observed and the gross changes were not considered to be biologically significant. A 

decrease in spleen-to-brain-weight ratio was reported in minks receiving 6.2 mg/kg/day heptachlor in the 

diet for 28 days (Aulerich et al. 1990); this dose was also associated with mortality, weight loss, and 

decreased food consumption. 

The highest LOAEL values for lymphoreticular effects in each species following intermediate exposure 

are recorded in Table 3-1 and plotted in Figure 3-1. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 41 

3. HEALTH EFFECTS 

3.2.2.4 Neurological Effects 

No studies were located regarding neurological effects in humans after oral exposure to heptachlor or 

heptachlor epoxide. 

Several studies in animals have reported adverse neurological effects shortly after exposure to heptachlor. 

At lethal doses, tremors and convulsions were observed in rats (Lehman 1951). Hyperexcitability, 

incoordination, and seizures were also observed in mink exposed to lethal doses (1.7 or 6.2 mg/kg/day) 

for intermediate durations (Aulerich et al. 1990; Crum et al. 1993). At nonlethal doses, alterations in a 

number of functional observational battery tests indicative of excitability were observed in rats following 

a single dose or 14 doses of 7 mg/kg (Moser et al. 1995); the excitability changes included increased 

arousal and reactivity to removal from the home cage and handling. The persistence of the effect was 

directly related to dose level. Decreases in motor activity and hunched posture in the home cage was 

observed 4 hours after a single dose of 129 mg/kg (Moser et al. 1995). Another study conducted by this 

group (Moser et al. 2003) found decreases in motor activity, increases in forelimb and hindlimb grip 

strength, handling reactivity and arousal, gait abnormalities, tremors, and piloerection in rats receiving 

gavage doses of 1–14 mg/kg/day for 10 days; a LOAEL cannot be identified from this study because the 

investigators did not provide data for individual end points or dose levels. Similar to the effects noted in 

the Moser studies, Akay and Alp (1981) reported difficulty in standing, walking, and righting in mice 

exposed to 19 mg/kg/day heptachlor in the diet for 10 weeks. In addition to these effects observed in 

mature animals, adverse neurological effects have been observed in the offspring of rats exposed to 

heptachlor during gestation, lactation, and postnatally; these studies are discussed in Section 3.2.2.6. 

Statistically significant changes in electroencephalogram (EEG) patterns were reported in mature female 

rats administered heptachlor in the diet at levels of 1 and 5 mg/kg/day for three generations (Formanek et 

al. 1976). Interpretation of these findings is difficult because details of the dosing, the procedures used, 

and conditions of the rats were not described. 

The highest NOAEL values and all reliable LOAEL values for neurological effects in each species 

following intermediate exposure are recorded in Table 3-1 and plotted in Figure 3-1. 

3.2.2.5 Reproductive Effects 

Significantly higher levels of heptachlor epoxide were detected in the sera of a group of women identified 

through hospital records with premature delivery than in the sera of a control group with normal delivery 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 42 

3. HEALTH EFFECTS 

(Wassermann et al. 1982). However, sera levels of 8 of the 10 organochlorine pesticides for which 

analytical data were obtained were all significantly higher in the premature delivery group. In addition, 

route, duration, and level of exposure information was not reported. Heptachlor epoxide has been 

detected in stillborn infant brain, adrenal, lung, heart, liver, kidneys, spleen, and adipose tissue, indicating 

transplacental transfer of heptachlor or heptachlor epoxide (Curley et al. 1969). These studies also 

reported the presence of polychlorinated biphenyls (PCBs), lindane, and dieldrin in the samples. It is 

difficult to assess the causal relationship between adverse reproductive outcome in humans and exposure 

to heptachlor and heptachlor epoxide due to lack of control for confounding factors such as smoking and 

concomitant exposure to other pesticides and lack of completeness of report data. No adverse effects on 

reproduction (no decrease in fertility, no increase in fetal or neonatal deaths) were reported by Le 

Marchand et al. (1986) among women of child-bearing age following ingestion of heptachlor-containing 

milk in excess of 0.1 ppm for 27–29 months. 

A number of animal studies have demonstrated that exposure to heptachlor can result in decreased 

fertility and increased pregnancy losses. Impaired fertility was reported in female rats administered via 

gavage 0.65 mg/kg/day heptachlor in groundnut oil for 14 days prior to mating (Amita Rani and 

Krishnakumari 1995) and male and female rats fed 0.25 mg/kg/day heptachlor for 60 days (Green 1970); 

100% infertility was observed in mice fed 9.3 mg/kg/day heptachlor for 10 weeks (Akay and Alp 1981). 

No effect on fertility was observed in male mice administered via gavage 10 mg/kg/day heptachlor or 

8 mg/kg/day heptachlor epoxide for 5 days (Epstein et al. 1972) or a single dose of 15 mg/kg 

heptachlor:heptachlor epoxide (25%:75%) (Arnold et al. 1977). 

Significant increases in resorptions were observed in male and female rats receiving gavage doses of 

0.65 or 1.8 mg/kg/day, respectively, heptachlor for 70 or 14 days, respectively, prior to mating to control 

animals (Amita Rani and Krishnakumari 1995) and male and female rats fed 0.25 mg/kg/day heptachlor 

for 60 days prior to mating and throughout gestation (Green 1970). An increase in the incidence of 

stillbirths was observed in mink fed a diet containing 1.7 mg/kg/day heptachlor for 42 days prior to 

mating and throughout gestation (Crum et al. 1993). Similarly, a decrease in litter size was observed in 

rats exposed to 6 mg/kg/day heptachlor in the diet for an unspecified portion of an 18-month study 

(Mestitzova 1967). No alterations in preimplantation losses or early fetal deaths were observed in control 

females mated to males administered via gavage 10 mg/kg/day heptachlor or 8 mg/kg/day heptachlor 

epoxide for 5 days (Epstein et al. 1972) or a single dose of 15 mg/kg/day heptachlor:heptachlor epoxide 

mixture (Arnold et al. 1977). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 43 

3. HEALTH EFFECTS 

Other reproductive alterations include a decrease in epididymal sperm count in rats administered gavage 

doses of 0.65 mg/kg/day heptachlor for 70 days (Amita Rani and Krishnakumari 1995) and decreases in 

estradiol-17β and progesterone levels in rats gavaged with 1.8 mg/kg/day for 14 days (Amita Rani and 

Krishnakumari 1995). Vaginal bleeding was reported in some rats exposed to 2.0 or 4.0 mg/kg/day 

technical-grade heptachlor for 80 weeks (NCI 1977); however, the incidence and statistical significance 

were not reported. 

All reliable LOAEL values for reproductive effects in each species and duration category are recorded in 

Table 3-1 and plotted in Figure 3-1. 

3.2.2.6 Developmental Effects 

Several studies have examined potential developmental effects in the children of women exposed to 

elevated levels of heptachlor or heptachlor epoxide. Between 1980 and 1982, the commercial supply of 

cow’s milk for the Hawaiian island of Oahu was contaminated with heptachlor epoxide; the source of 

exposure was treated pineapple plants that were used as cattle feed. Cow milk fat levels of heptachlor 

measured in Hawaii during this time ranged from 0.12 to 5.00 ppm (EPA’s action level is 0.1 ppm); in a 

prior analysis (1978–1980), the levels were comparable to the rest of the United States. Using hospital 

records, Le Marchand et al. (1986) examined a possible association between heptachlor epoxide exposure 

and birth defects. No increase in fetal or neonatal deaths or incidence of low birth weight infants were 

found in this study cohort. Of the 23 categories of major congenital malformations evaluated, 22 were 

found to be decreased in the study population when compared with cohorts from the other Hawaiian 

islands and from the U.S. general population for the same time period. One type of malformation 

(anomalies of the abdominal wall) was found to be slightly increased in the study cohort during the period 

of known exposure compared with the control cohorts. However, the baseline data for this type of 

malformation were not available prior to study initiation, and birth defects may be underreported. It was, 

therefore, not possible to document the temporal change in the incidence of this type of malformation. 

Since women who might not have consumed the contaminated milk were included in the study group, 

positive findings may have been diluted as a result of misclassification bias. A subsequent study of high 

school students born on Oahu and likely prenatally exposed to heptachlor epoxide was conducted by 

Baker et al. (2004b; available as an abstract). As compared to high school students living on Oahu since 

first grade (but not born on Oahu), an association between gestational exposure to heptachlor epoxide and 

lower neurobehavioral performance was found. In particular, impaired performance was found on tests of 

abstract concept formation, visual perception, and motor planning; this group also had more reported 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 44 

3. HEALTH EFFECTS 

behavioral problems. No significant associations between school-based performance measures, such as 

grade point average, and gestational heptachlor epoxide exposure were found. 

Two studies examined possible associations between maternal heptachlor epoxide levels and early 

childhood development (Hertz-Picciotto et al. 2004) or birth weight (Gladen et al. 2003). An association 

between maternal serum heptachlor epoxide levels and their children’s performance on a test of nonverbal 

perceptual reasoning was found in San Francisco residents. However, inclusion of PCBs in the model 

severely reduced the magnitude of the association (Hertz-Picciotto et al. 2004; only available as an 

abstract). The investigators concluded that the cognitive deficits were probably due to co-exposure to 

other compounds. Gladen et al. (2003) found no significant association between breast milk levels of 

heptachlor epoxide (taken 4–5 days after birth) and birth weight among residents of two cities in Ukraine. 

Several animal studies have examined the potential developmental toxicity of heptachlor. In utero 

exposure to heptachlor doses of 5.0 mg/kg and higher has resulted in pup mortality (Lawson and Luderer 

2004; Narotsky et al. 1995; Purkerson-Parker et al. 2001b). These doses are also associated with 

significant maternal toxicity such as mortality, convulsions, and/or weight loss; however, at 

5.0 mg/kg/day, increased pup mortality was also observed in dams without overt signs of toxicity 

(Lawson and Luderer 2004). 

Gestational exposure to lower doses results in decreases in pup body weight. The threshold for this effect 

appears to be around 4–5 mg/kg/day (Lawson and Luderer 2004; Narotsky and Kavlock 1995; Narotsky 

et al. 1995). No alterations in pup body weight were observed at 3 mg/kg/day (Moser et al. 2001; 

Purkerson-Parker et al. 2001b; Smialowicz et al. 2001). Exposure to heptachlor does not appear to result 

increased frequency of anomalies or abnormalities (Narotsky et al. 1995; Smialowicz et al. 2001). 

Additionally, heptachlor does not appear to impair the development of the reproductive system. No 

delays in vaginal opening or prepuce separation (indices of female and male puberty respectively) were 

observed in the offspring of rats administered via gavage to 3 mg/kg/day heptachlor on gestational day 12 

through postnatal day 21 (Smialowicz et al. 2001) or 5 mg/kg/day on gestational days 8–21 and 

lactational days 1–21 (Lawson and Luderer 2004). Additionally, continued exposure of the offspring 

until postnatal day 42 and subsequent mating with untreated animals did not result in adverse 

reproductive or developmental outcomes (Smialowicz et al. 2001). 

Developmental studies have found neurological and immunological effects in offspring. Gestational, 

lactational, and offspring exposure until postnatal day 21 or 42 to 3 mg/kg/day heptachlor resulted in 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 45 

3. HEALTH EFFECTS 

significant delays in righting reflex, likely due to a delay in the ontogeny of righting rather than an 

inability to perform the task (Moser et al. 2001; Purkerson-Parker et al. 2001b). No alterations in motor 

activity ontogeny were observed (Moser et al. 2001; Purkerson-Parker et al. 2001b). Some alterations in 

functional observation battery tests were observed in rats exposed to heptachlor during gestation, 

lactation, and postnatally until day 21 or 42 (Moser et al. 2001). Many of these alterations were only 

significant at the lowest dose tested (0.03 mg/kg/day). In water maze tests, exposure to 0.03 mg/kg/day 

heptachlor and higher resulted in slowed acquisition of a spatial task and impaired recall (Moser et al. 

2001). This was observed in rats exposed in utero, during lactation, and until postnatal day 42, but not in 

rats exposed until postnatal day 21. 

Smialowicz et al. (2001) found a significant suppression of the immune response to sheep red blood cells 

in rats exposed to 0.03 mg/kg/day in utero, during lactation, and postnatally until day 42 of age. No 

significant alterations in the response to T-cell mitogens or in delayed-type and contact hypersensitivity 

were observed. A decrease in OX12+

OX19- splenic populations was observed at 3.0 mg/kg/day. 

The reliable LOAEL values for developmental effects in rats following intermediate and chronic exposure 

are recorded in Table 3-1 and plotted in Figure 3-1. 

3.2.2.7 Cancer 

There is limited information on the carcinogenicity of heptachlor or heptachlor epoxide in humans 

following oral exposure; several studies have examined the possible association between heptachlor 

epoxide tissue levels and cancer risk. Interpretation of the studies is limited by the lack of information on 

heptachlor exposure (including the route of exposure), variables that may affect organochlorine levels 

(including diet and body mass index), and possible concomitant exposure to other chemicals. No 

significant associations were found for endometrial cancer in women in the United States (Sturgeon et al. 

1998) or breast cancer in Norwegian women (Ward et al. 2000). Another study found a significant 

association between heptachlor epoxide levels in breast tissue and the prevalence of breast cancer 

(Cassidy et al. 2005). Two case control studies examined the possible association between heptachlor 

epoxide levels and non-Hodgkin’s lymphoma. One study found a significant association among 

individuals with the highest heptachlor epoxide adipose levels (odds ratio of 3.41, 95% confidence 

interval of 1.89–6.16) (Quintana et al. 2004), whereas the other study did not found a significant 

association between serum heptachlor epoxide levels and non-Hodgkin’s lymphoma (Cantor et al. 2003). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 46 

3. HEALTH EFFECTS 

Animal studies provide some evidence for the carcinogenicity of heptachlor. Significant increases in the 

incidence of hepatocellular carcinoma were observed in male and female mice exposed to time-weighted 

average (TWA) doses of 2.4 or 3.0 mg/kg/day, respectively, technical-grade heptachlor (72% heptachlor, 

20% chlordane) in the diet for 80 weeks. Although increases in liver tumors were also observed at a 

lower dose (0.8 mg/kg/day for males and 1.2 mg/kg/day for females), the incidence was not significantly 

different than controls (NCI 1977). No significant increases in neoplastic tumor incidence were observed 

in male or female rats similarly exposed to technical-grade heptachlor TWA doses of 3.9 or 

2.6 mg/kg/day, respectively (NCI 1977). Although a statistically significant increase in the incidence of 

follicular cell neoplasms (adenomas and carcinomas) was observed in the thyroid of female rats fed a 

TWA dose of 2.0 mg/kg/day technical-grade heptachlor for 80 weeks, the study investigators did not 

judge the alterations to be sufficient to clearly indicate a carcinogenic effect in the thyroid gland (NCI 

1977). No other significant alterations were observed in the rats (NCI 1977). The Cancer Effect Level 

(CEL) in mice from chronic exposure to heptachlor is recorded in Table 3-1 and plotted in Figure 3-1. 

The positive carcinogenicity findings of the mouse NCI (1977) study is supported by evidence that 

heptachlor is a tumor promoter. Dietary administration of ≥0.65 mg/kg/day heptachlor (97.6% purity) for 

25 weeks promoted the development of hepatocellular foci and hepatocellular neoplasms in male mice 

previously initiated with 3.8 mg/kg/day diethylnitrosamine in drinking water for 14 weeks (Williams and 

Numoto 1984). 

EPA has classified heptachlor and heptachlor epoxide in Group B2 (probable human carcinogen) (IRIS 

2006). EPA has derived an oral slope factor of 4.5 per (mg/kg)/day for heptachlor and 9.1 per 

(mg/kg)/day for heptachlor epoxide. The doses corresponding to cancer risk levels ranging from 10-4 to 

10-7 are 2.0x10-5–2.0x10-8 mg/kg/day for heptachlor and 1.0x10-5–1.0x10-8 mg/kg/day for heptachlor 

epoxide as indicated in Figure 3-1. The oral cancer potency factor is a plausible upper-bound estimate of 

the lifetime probability of an individual developing cancer as a result of oral exposure per unit intake of 

the chemical. The International Agency for Research on Cancer (IARC) has classified heptachlor and 

heptachlor epoxide as Group 2b chemicals (possibly carcinogenic to humans) (IARC 2001). 

3.2.3 Dermal Exposure 

There is very little information on dermal exposures in either humans or animals. Most occupational 

exposures to heptachlor and heptachlor epoxide are assumed to be some combination of inhalation and 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 47 

3. HEALTH EFFECTS 

dermal exposure, but there are no data to quantify the relative contribution of each route. The 

occupational studies on pesticide workers are discussed in Section 3.2.1. 

3.2.3.1 Death 

No studies were located regarding death in humans after dermal exposure to heptachlor or heptachlor 

epoxide. 

For heptachlor dissolved in xylene and administered once, Gaines (1969) reported dermal LD50 values in 

Sherman rats of 195 mg/kg (males) and 250 mg/kg (females). 

3.2.3.2 Systemic Effects 

No studies were located regarding systemic effects in humans or animals after dermal exposure to 

heptachlor or heptachlor epoxide. 

No studies were located regarding the following health effects in humans or animals after dermal 

exposure to heptachlor or heptachlor epoxide: 

3.2.3.3 Immunological and Lymphoreticular Effects 

3.2.3.4 Neurological Effects 

3.2.3.5 Reproductive Effects 

3.2.3.6 Developmental Effects 

3.2.3.7 Cancer 

3.3 GENOTOXICITY 

There are limited mammalian in vivo data on the genotoxicity of heptachlor or heptachlor epoxide. 

Heptachlor, heptachlor epoxide, and a mixture of heptachlor and heptachlor epoxide (25:75) were found 

to be negative in in vivo dominant lethal studies in the germ-line cells of male Charles River or Swiss 

mice (Arnold et al. 1977; Epstein et al. 1972). 

Several in vitro studies have examined the genotoxicity of heptachlor or heptachlor epoxide (Table 3-2). 

The available weight of evidence suggests that neither compound alters the frequency of gene mutations 

in prokaryotic organisms (Glatt et al. 1983; Marshall et al. 1976; NTP 1987; Probst et al. 1981; Zeiger et 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 48 

3. HEALTH EFFECTS 

Table 3-2. Genotoxicity of Heptachlor and Heptachlor Epoxide In Vitro 

Results 

With Without Chemical 

Species (test system) End point activation activation form Reference 

Prokaryotic organisms: 

Salmonella typhimurium Gene mutation B B Heptachlor Zeiger et al. 

(histidine reversion) 1987 

S. typhimurium (Ames Gene mutation B B Heptachlor Marshall et al. 

assay) 1976; NTP 

1987 

S. typhimurium (Ames Gene mutation B B Heptachlor Marshall et al. 

assay) epoxide 1976; NTP 

1987 

S. typhimurium (Ames Gene mutation + B Heptachlor Gentile et al. 

assay) 1982 

S. typhimurium (modified Gene mutation B B Heptachlor Probst et al. 

Ames assay) 1981 

S. typhimurium (modified Gene mutation B B Heptachlor Glatt et al. 

Ames assay) epoxide 1983 

Escherichia coli (modified Gene mutation B B Heptachlor Probst et al. 

Ames assay) 1981 

S. typhimurium (disc DNA damage No data B Heptachlor Rashid and 

assay) Mumma 1986 

E. coli (DNA repair assay) DNA damage No data B Heptachlor Rashid and 

Mumma 1986 

Eukaryotic organisms: 

Fungi: 

Saccharomyces Gene conversion B B Heptachlor Gentile et al. 

cerevisiae (ade, trp loci 1982 

assay) 

Aspergillus nidulans Gene mutation No data B Heptachlor Crebelli et al. 

(strain 35/liquid medium) epoxide 1986 

A. nidulans (strain Chromosome No data B Heptachlor Crebelli et al. 

P1/liquid medium) malsegregation epoxide 1986 

Mammaliam cells: 

Mouse (L5178Y tk+

/tk- Gene mutation No data + Heptachlor McGregor et 

lymphoma cell forward al. 1988 

mutation assay) 

Rat (ARL-HGPRT assay) Gene mutation B NA Heptachlor Telang et al. 

1982 

Chinese hamster (ovary Chromosomal + B Heptachlor NTP 1987 

cells) aberrations 

Chinese hamster (ovary Sister chromatid + + Heptachlor NTP 1987 

cells) exchange 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 49 

3. HEALTH EFFECTS 

Table 3-2. Genotoxicity of Heptachlor and Heptachlor Epoxide In Vitro 

Results 

With Without Chemical 

Species (test system) End point activation activation form Reference 

Rat (primary hepatocytes) Unscheduled B NA Heptachlor Probst et al. 

DNA synthesis 1981; 

Maslansky 

and Williams 

1981 

Mouse (primary Unscheduled B NA Heptachlor Maslansky 

hepatocyte) DNA synthesis and Williams 

1981 

Syrian hamster (primary Unscheduled B NA Heptachlor Maslansky 

hepatocytes) DNA synthesis and Williams 

1981 

Human (SV-40 Unscheduled + B Heptachlor Ahmed et al. 

transformed fibroblasts) DNA synthesis 1977 

Human (SV-40 Unscheduled + B Heptachlor Ahmed et al. 

transformed fibroblasts) DNA synthesis epoxide 1977 

B = negative result; + = positive result; ade = adenine; ARL = adult rat liver epithelial cell line; 

DNA = deoxyribonucleic acid; HGPRT = hypoxanthine-guanine phosphoribosyl transferase; NA = not applicable; 

tk = thymidine kinase locus; trp = tryptophan
HEPTACHLOR AND HEPTACHLOR EPOXIDE 50 

3. HEALTH EFFECTS 

al. 1987). Heptachlor without metabolic activation caused gene mutations in mouse lymphoma cells but 

not in adult rat liver cells (McGregor et al. 1988; Telang et al. 1982). No alterations in gene conversion 

were observed in Saccharomyces cerevisiae following heptachlor exposure with and without activation 

(Gentile et al. 1982); heptachlor epoxide was also negative for gene mutation in Aspergillus nidulans 

(Crebelli et al. 1986). 

Heptachlor did not cause DNA damage in Salmonella typhimurium or Escherichia coli in the absence of 

metabolic activators (Rashid and Mumma 1986). Heptachlor was negative for unscheduled DNA 

synthesis (UDS) in rat, mouse, and hamster (Maslansky and Williams 1981; Probst et al. 1981). In 

contrast, an increase in UDS was observed in human SV-40 transformed fibroblasts after exposure to 

heptachlor and heptachlor epoxide in the presence of metabolic activators (Ahmed et al. 1977). 

Heptachlor epoxide did not alter the occurrence of chromosome malsegregration in A. nidulans (Crebelli 

et al. 1986). Chromosomal alterations were observed in mammalian cells. Chromosomal aberrations 

were observed in Chinese hamster ovary cells following exposure to heptachlor with metabolic activation 

and sister chromatid exchange was observed both with and without metabolic activation (NTP 1987). 

Refer to Table 3-2 for a summary of the results of these in vitro studies. 

Several studies were located involving heptachlor genotoxicity in plants. A positive response was noted 

for the waxy gene mutation in maize (Zea mays) following exposure to heptachlor in situ (Gentile et al. 

1982). A micronucleus test in Tradescantia produced a significant positive dose-related response at 

1.88 ppm heptachlor, suggesting that heptachlor has clastogenic potential in plants (Sandhu et al. 1989). 

Early separation during metaphase, condensation, stickiness, and chromatin bridges were observed after 

heptachlor treatment on mitotic chromosomes in Lens culinaris, Lens esculenta, Pisum sativum, and 

Pisum arvense (Jain and Sarbhoy 1987a). Chromosomal abnormalities such as stickiness, non-orientation 

during metaphase I, fragments, multivalents, and bridges were also observed in meiotic chromosomes 

after heptachlor treatment (Jain and Sarbhoy 1987b). These studies by Jain and Sarbhoy report no 

statistical comparisons with which to interpret the results; therefore, it is difficult to evaluate the 

significance of their research. Even though these plant studies suggest that heptachlor is potentially 

genotoxic, the applicability to mammalian genotoxicity remains questionable. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 51 

3. HEALTH EFFECTS 

3.4 TOXICOKINETICS 

3.4.1 Absorption 

3.4.1.1 Inhalation Exposure 

No studies were located regarding absorption in humans after inhalation exposure to heptachlor or 

heptachlor epoxide. One animal study provides suggestive evidence of absorption following inhalation 

exposure to heptachlor epoxide (Arthur et al. 1975). Elevated levels of heptachlor epoxide were found in 

the fat (0.039 versus 0.016 ppm in controls) of rabbits housed outdoors in an area of pesticide use; the air 

concentrations of DDT, dieldrin, and heptachlor epoxide were 649.6, 4.59, and 1.86 ng/m3

, respectively. 

3.4.1.2 Oral Exposure 

No information on the extent of oral absorption of heptachlor or heptachlor epoxide in humans was 

identified. Qualitative evidence of absorption was found in a study of families consuming dairy products 

contaminated with heptachlor epoxide (Stehr-Green et al. 1988). Higher serum heptachlor epoxide levels 

were detected in the family members compared to an unexposed population (0.84 versus 0.50 ppb). 

Heptachlor is absorbed from the gastrointestinal tract of rats (Radomski and Davidow 1953; Tashiro and 

Matsumura 1978) and cattle (Harradine and McDougall 1986) as indicated by the presence of heptachlor 

and/or its metabolites in serum, fat, liver, kidneys, and muscle (Radomski and Davidow 1953). Based on 

available toxicity data (Podowski et al. 1979), it is assumed that heptachlor epoxide is also absorbed via 

the gastrointestinal tract. One study provides suggestive evidence that at least 50% of an orally 

administered dose of heptachlor is absorbed by rats (Tashiro and Matsumura 1978). Ten days after 

administration of a single dose, 6% of the radioactivity from radiolabeled (14C) heptachlor was found in 

the urine and 60% was detected in the feces (primarily present as heptachlor metabolites). 

3.4.1.3 Dermal Exposure 

No studies were located regarding absorption in humans after dermal exposure to heptachlor or heptachlor 

epoxide. 

Heptachlor is absorbed through the skin following topical application as indicated by its dermal toxicity 

in rats (Gaines 1969), but quantitative data are not available. However, the data should be interpreted 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 52 

3. HEALTH EFFECTS 

cautiously because heptachlor epoxide ingestion was not prevented by restraining the animals or 

removing excess heptachlor from the skin. 

3.4.2 Distribution 

3.4.2.1 Inhalation Exposure 

No studies were located regarding distribution of heptachlor or heptachlor epoxide in humans or animals 

following inhalation exposure. 

3.4.2.2 Oral Exposure 

No human studies were located regarding the distribution of heptachlor and its metabolites after oral 

exposure. A number of monitoring studies found elevated levels of heptachlor epoxide in fat, serum, 

liver, and brain. It is not known if the elevated levels of heptachlor epoxide were the result of heptachlor 

or heptachlor epoxide exposure or chlordane exposure (heptachlor epoxide is a minor metabolite of 

chlordane) (Adeshina and Todd 1990; Barquet et al. 1981; Burns 1974; Greer et al. 1980; Klemmer et al. 

1977; Polishuk et al. 1977b; Radomski et al. 1968; Stehr-Green et al. 1988; Wassermann et al. 1974). 

Heptachlor epoxide was measured in a strip of skin, fat, and subcutaneous tissue from 68 children who 

died in the perinatal period and ranged from not detected (nondetectable) to 0.563 ppm (mean, 

0.173 ppm) (Zavon et al. 1969). In 10 other stillborn infants, heptachlor epoxide levels measured in 

various tissues were as follows: brain (nondetectable), lung (0.17"0.07 ppm), adipose (0.32"0.10 ppm), 

spleen (0.35"0.08 ppm), liver (0.68"0.50 ppm), kidneys (0.70"0.28 ppm), adrenals (0.73"0.27 ppm), and 

heart (0.80"0.30 ppm) (Curley et al. 1969). Selby et al. (1969) reported a placenta/maternal blood 

concentration ratio for heptachlor epoxide of 5.8. In another study, the following heptachlor epoxide 

levels were measured in extracted lipids from mothers and newborn infants: maternal adipose tissue 

(0.28"0.31 ppm), maternal blood (0.28"0.46 ppm), uterine muscle (0.49"0.51 ppm), newborn blood 

(1.00"0.95 ppm), placenta (0.50"0.40 ppm), and amniotic fluid (0.67"1.16 ppm) (Polishuk et al. 1977a). 

These data provide evidence of transplacental transfer to the fetus. 

Animal studies regarding heptachlor and heptachlor epoxide distribution in body tissues are limited. 

Analysis of body fat from 20 adult female rats fed heptachlor in their diet at a level of 35 ppm for 

3 months revealed a high concentration of heptachlor epoxide but not heptachlor (Radomski and Davidow 

1953). Further analysis showed that accumulation of heptachlor epoxide was directly related to the dose 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 53 

3. HEALTH EFFECTS 

of heptachlor given. Examination of other tissues in addition to adipose tissue showed that fat had the 

highest concentrations of heptachlor epoxide; markedly lower amounts were found in liver, kidneys, and 

muscle, and none was found in the brain. In a parallel study, three dogs were also examined. Doses of 

1 mg/kg/day for 12–18 months produced the same distribution pattern as in rats, but the livers of dogs 

contained more heptachlor epoxide than the kidneys and muscle tissue. Levels in all tissues were higher 

in female dogs than in males. 

The rate of heptachlor epoxide accumulation in, and elimination from, fat was determined in rats fed diets 

containing 30 ppm heptachlor for 12 weeks, then fed untreated diets for 12 more weeks (Radomski and 

Davidow 1953). Interim sacrifices at various times during treatment showed that the residue in the fat of 

males reached a plateau at approximately 2–8 weeks. Thereafter, the levels decreased and were below the 

detection limit by the end of week 6 post-dosing. In females, the heptachlor epoxide level in fat was 

much higher than males by the second week and throughout the remainder of the study. By the end of the 

8th week post-dosing, the heptachlor epoxide level was below the detection limit in females. No 

estimates of elimination half-lives from fat were provided. 

Heptachlor and heptachlor epoxide residues were found in the fat (≥0.16 and ≥18.25 ppm, respectively), 

liver (≥0.08 and ≥2.11 ppm, respectively), and muscle (0 and ≥0.03 ppm, respectively) of pigs fed 

2 mg/kg/day heptachlorine (purity unspecified) for 78 days (Halacka et al. 1974). When pigs were fed 

5 mg/kg/day, the levels of heptachlor and heptachlor epoxide were higher: 0.37 and 25.82 ppm, 

respectively, in the fat; 0.23 and 4.94 ppm, respectively, in liver; and 0 and 0.7 ppm, respectively, in 

muscle. 

3.4.2.3 Dermal Exposure 

No studies were located regarding distribution in humans or animals after dermal exposure to heptachlor 

or heptachlor epoxide. 

3.4.3 Metabolism 

No studies were located regarding metabolism of heptachlor or heptachlor epoxide in humans exposed to 

these pesticides. However, information is available regarding in vivo metabolism in rats and in vitro 

metabolism by human and rat liver microsomes. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 54 

3. HEALTH EFFECTS 

Ten days after male rats were administered a single oral dose of 14C-heptachlor by gavage in corn oil, 

about 72% of the radioactivity was eliminated in the feces in the form of metabolites and 26% as parent 

compound. The major fecal metabolites were heptachlor epoxide (13.1% of total 14C compounds), 1-exohydroxychlordene (19.5%), 1-exo-hydroxy-2,3-exo-epoxychlordene (17.5%), and 1,2-dihydroxydihydrochlordene (3.5%), as well as two unidentified products (Tashiro and Matsumura 1978). The proposed 

metabolic scheme for heptachlor is presented in Figure 3-2. 

Tashiro and Matsumura (1978) also conducted experiments to compare in vitro metabolism of 

14C-heptachlor in microsomal preparations from human livers and rat livers. The primary metabolites 

produced by in both preparations were heptachlor epoxide, 1-exo-hydroxychlordene, 1-exo-hydroxy-2,3­

exo-epoxychlordene, and 1,2-dihydroxydihydrochlordane. However, the levels of heptachlor epoxide 

were 4 times higher in the rat microsomal preparations than in the humans; 85.8% of the radiolabel was in 

the form of heptachlor epoxide in rat microsomes compared to 20.4% for human microsomes. These in 

vivo and in vitro data suggest that the ratio of heptachlor to heptachlor epoxide stored in adipose tissue 

would be higher in humans than rats (Tashiro and Matsumura 1978). 

Heptachlor also is a metabolic product of chlordane. Both heptachlor and heptachlor epoxide are active 

inducers of microsomal epoxidation (Gillett and Chan 1968). In male Wistar rats fed a diet containing 

5 ppm heptachlor or heptachlor epoxide for 10 days, the latter was much more effective in inducing 

epoxidation of aldrin than heptachlor (Gillett and Chan 1968). The minimally effective dietary 

concentration for inducing significant epoxidation was estimated to be between 1 and 5 ppm for both 

compounds (Gillett and Chan 1968). Heptachlor epoxide is considered more toxic than its parent 

compound and, like heptachlor, is primarily stored in adipose tissue (Barquet et al. 1981; Burns 1974; 

Greer et al. 1980; Harradine and McDougall 1986). 

3.4.4 Elimination and Excretion 

3.4.4.1 Inhalation Exposure 

No studies were located regarding excretion in humans or animals after inhalation exposure to heptachlor 

or heptachlor epoxide. Based on the data from oral studies, heptachlor is expected to be excreted 

primarily in the form of metabolites and also as unchanged parent compound. 
3. HEALTH EFFECTS 

Figure 3-2. Metabolic Scheme for Heptachlor in Rats 

Cl Cl 

Cl 

Cl 

Cl

Cl Cl 

heptachlor 

Cl Cl Cl Cl 

OH Cl Cl Cl 

Cl Cl 

O Cl Cl Cl Cl 

heptachlor epoxide 1-exo-hydroxychlordene 

Cl Cl Cl Cl 

OH OH Cl Cl 

Cl Cl O O Cl Cl Cl Cl 

dehydrogenated derivative 

of 1-exo-hydroxy-2,3-exo 1-exo-2,3-exo-epoxychlordene 

epoxychlordene 

Cl 

Cl Cl 

Cl 

Cl Cl 

OH 

OH 

HEPTACHLOR AND HEPTACHLOR EPOXIDE 55 

1,2-dihydroxydihydrochlordene 

Source: adapted from Tashiro and Matsumura (1978) 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 56 

3. HEALTH EFFECTS 

3.4.4.2 Oral Exposure 

No studies were located regarding excretion in humans after oral exposure to heptachlor or heptachlor 

epoxide. 

Due to their relatively high lipid solubility, heptachlor and heptachlor epoxide can accumulate in breast 

milk. For example, heptachlor and heptachlor epoxide were measured in 51 samples of human milk at 

average concentrations of 0.0027 and 0.019 ppm, respectively, from women with unknown exposure 

histories (Jonsson et al. 1977). Heptachlor epoxide was found in 24% of the samples, and heptachlor was 

found in 6%. Other investigators have reported the presence of heptachlor epoxide in human milk at 

concentrations ranging from not detected to 0.46 ppm (Kroger 1972; Larsen et al. 1971; MussaloRauhamaa et al. 1988; Polishuk et al. 1977b; Ritcey et al. 1972; Savage et al. 1981; Takei et al. 1983). 

These findings suggest a potential for transfer to the nursing infant (see also Sections 3.5.1 and 6.5). 

In a study in cows, the concentration of heptachlor epoxide in cow’s milk reached a maximum within 3– 

7 days after the cows began grazing 18 hours/day on pastures immediately following treatment of the 

grasses with heptachlor and declined steadily thereafter. The level of heptachlor epoxide in the milk 

reached a concentration of 0.22 ppm (Gannon and Decker 1960). 

The elimination of a single oral gavage dose of 14C-heptachlor in male rats showed that most of the 

radioactivity was eliminated in the feces (Tashiro and Matsumura 1978). One day after dosing, 36% of 

the dose had been eliminated, and by day 10, approximately 62% had been eliminated in the feces. 

Elimination of the radioactive label in urine accounted for only 6% of the total dose in 10 days. 

Approximately 26.2% of the total radioactivity recovered from the feces was the parent compound and 

the remainder was in the form of metabolites. 

3.4.4.3 Dermal Exposure 

No studies were located regarding excretion in humans or animals after dermal exposure to heptachlor or 

heptachlor epoxide. Based on the data from oral studies, heptachlor is expected to be excreted primarily 

in the form of metabolites and also as unchanged parent compound. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 57 

3. HEALTH EFFECTS 

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 

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 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 58 

3. HEALTH EFFECTS 

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 3-3 shows a conceptualized representation of a PBPK model. 

If PBPK models for heptachlor and heptachlor epoxide 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. 

No PBPK models were identified for heptachlor or heptachlor epoxide. 

3.5 MECHANISMS OF ACTION 

3.5.1 Pharmacokinetic Mechanisms 

There is limited information on the toxicokinetics of heptachlor. No dermal toxicokinetic data were 

located. Heptachlor is absorbed via the lungs and digestive tract, although the site and mechanism of 

absorption are not known. Heptachlor is metabolized to heptachlor epoxide and is stored in the body as 

the parent compound and as this metabolite. Heptachlor and heptachlor epoxide are highly lipid soluble 

and are stored in adipose tissue; both compounds can also accumulate in breast milk. Heptachlor is 

primarily excreted in the feces as heptachlor epoxide. 

3.5.2 Mechanisms of Toxicity 

The available data suggest that the developing nervous system is the most sensitive target of heptachlor 

toxicity. Impaired spatial memory was observed in rats exposed to 0.03 mg/kg/day heptachlor during 

gestation and from postnatal day 7–42 (Moser et al. 2001). The cause of these alterions is not known. 

Moser et al. (2001) noted that heptachlor and other cyclodiene insecticides have a high affinity for 

GABAA (gamma-amino butyric acid) receptors and can alter the expression of the GABAA receptor 
3. HEALTH EFFECTS 

Figure 3-3. Conceptual Representation of a Physiologically Based 

Pharmacokinetic (PBPK) Model for a 

Hypothetical Chemical Substance 

Lungs 

Liver 

F a t 

S lo w ly 

perfu sed 

tissues 

R ic h ly 

perfu sed 

tissues 

K idney 

S k 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 m a x 

K m 

Ingestion 

Inhaled chem ic al E x haled chem ic al 

GI 

T ra c t 

F e c e s 

U rin e

 C hem ic als 

contacting 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 

HEPTACHLOR AND HEPTACHLOR EPOXIDE 59 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 60 

3. HEALTH EFFECTS 

during development. In the Moser et al. (2001) study, alterations in GABAA binding sites were observed 

in the brainstem of female rats, but not in the cortex. However, no alterations in the functional response 

of the GABA receptor binding were observed. This study does not address whether the heptachlorinduced alterations in GABAA receptors and the observed neurobehavioral alterations are related. 

3.5.3 Animal-to-Human Extrapolations 

There are limited available data with which to compare humans and other animal species. The absorption 

and distribution properties of heptachlor and heptachlor epoxide appear to be the same in both humans 

and animals. For the most part, the human toxicity data do not allow for quantitative or qualitative 

comparisons with the available animal data; an exception is the neurodevelopmental toxicity data. 

Impaired performance on tests of abstract concept formation, visual perception, and motor planning was 

observed in adolescents exposed during gestation to heptachlor and/or heptachlor epoxide (Baker et al. 

2004b). In rats exposed during gestation and for the first 42 postnatal days, impaired spatial memory and 

learning were observed (Moser et al. 2001). These data provide some qualitative support for 

extrapolating the rat data for human risk assessment. 

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 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 61 

3. HEALTH EFFECTS 

(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 1997). 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). 

No studies were located regarding endocrine disruption in humans or animals after exposure to heptachlor 

or heptachlor epoxide. An animal study examining the impact of in utero and lactational exposure to 

heptachlor on the development of the reproductive system (Smialowicz et al. 2001) did not find 

alterations in vaginal opening, prepuce separation, or adverse reproductive or developmental outcomes 

when exposed offspring were mated with controls. Additionally, no in vitro studies were located 

regarding endocrine disruption of heptachlor or heptachlor epoxide. 

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 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 62 

3. HEALTH EFFECTS 

critical periods of structural and functional development during both prenatal and postnatal life, and a 

particular structure or function will be most sensitive to disruption during its critical period(s). Damage 

may not be evident until a later stage of development. There are often differences in pharmacokinetics 

and metabolism between children and adults. For example, absorption may be different in neonates 

because of the immaturity of their gastrointestinal tract and their larger skin surface area in proportion to 

body weight (Morselli et al. 1980; NRC 1993); the gastrointestinal absorption of lead is greatest in infants 

and young children (Ziegler et al. 1978). Distribution of xenobiotics may be different; for example, 

infants have a larger proportion of their bodies as extracellular water, and their brains and livers are 

proportionately larger (Altman and Dittmer 1974; Fomon 1966; Fomon et al. 1982; Owen and Brozek 

1966; Widdowson and Dickerson 1964). The infant also has an immature blood-brain barrier (Adinolfi 

1985; Johanson 1980) and probably an immature blood-testis barrier (Setchell and Waites 1975). Many 

xenobiotic metabolizing enzymes have distinctive developmental patterns. At various stages of growth 

and development, levels of particular enzymes may be higher or lower than those of adults, and 

sometimes unique enzymes may exist at particular developmental stages (Komori et al. 1990; Leeder and 

Kearns 1997; NRC 1993; Vieira et al. 1996). Whether differences in xenobiotic metabolism make the 

child more or less susceptible also depends on whether the relevant enzymes are involved in activation of 

the parent compound to its toxic form or in detoxification. There may also be differences in excretion, 

particularly in newborns who all have a low glomerular filtration rate and have not developed efficient 

tubular secretion and resorption capacities (Altman and Dittmer 1974; NRC 1993; West et al. 1948). 

Children and adults may differ in their capacity to repair damage from chemical insults. Children also 

have a longer remaining lifetime in which to express damage from chemicals; this potential is particularly 

relevant to cancer. 

Certain characteristics of the developing human may increase exposure or susceptibility, whereas others 

may decrease susceptibility to the same chemical. For example, although infants breathe more air per 

kilogram of body weight than adults breathe, this difference might be somewhat counterbalanced by their 

alveoli being less developed, which results in a disproportionately smaller surface area for alveolar 

absorption (NRC 1993). 

There are suggestive data indicating that children, particularly children exposed in utero and during 

infancy may be unusually susceptible to the toxicity of heptachlor. Although no studies comparing the 

toxicity of heptachlor in adults and children were identified, there is a possibility that very young children 

may exhibit particular susceptibility to hepatic effects because of the immaturity of the hepatic 

microsomal system. Heptachlor is bioactivated to produce heptachlor epoxide, which is more toxic than 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 63 

3. HEALTH EFFECTS 

heptachlor. Pre-adolescent children have a greater rate of glutathione turnover, and they are expected to 

be more susceptible to heptachlor epoxide-induced toxicity. Their susceptibility would probably depend 

upon their ability to detoxify heptachlor epoxide. However, Harbison (1975) observed that heptachlor 

was less toxic in newborn rats than in adult rats. Newborn rats pretreated with phenobarbital were more 

sensitive to the effects of heptachlor than those not pretreated. Thus, the ability to metabolize and 

bioactivate heptachlor correlates with its toxicity in the newborn. 

Several developmental toxicity studies have identified the developing organisms as a sensitive 

subpopulation. Heptachlor exposure does not appear to increase the risk of malformations in humans (Le 

Marchand et al. 1986) or animals (Narotsky et al. 1995; Smialowicz et al. 2001), although increases in 

pup mortality (Narotsky et al. 1995; Purkerson-Parker et al. 2001b) and decreases in pup body weight 

(Narotsky and Kavlock 1995; Narotsky et al. 1995) have been observed in animal studies. There is some 

indication that the developing nervous system may be unusually susceptible to the toxicity of heptachlor. 

A study of high school students exposed to heptachlor epoxide in utero and during early childhood found 

impaired performance on tests of abstract concept formation, visual perception, and motor planning 

(Baker et al. 2004b). Delays in the righting reflex, slowed acquisition of a spatial task, and impaired 

recall were observed in rat offspring exposed during gestation, lactation, and postnatally (Moser et al. 

2001; Purkerson-Parker et al. 2001b). The impaired learning and memory was the basis of the 

intermediate-duration oral MRL. In addition to the neurological effects, suppression of the immune 

response to sheep red blood cells was observed at the same dose level as the impaired learning and 

memory (Smialowicz et al. 2001). 

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 

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 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 64 

3. HEALTH EFFECTS 

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 heptachlor and heptachlor epoxide 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 heptachlor and heptachlor epoxide 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 Heptachlor and Heptachlor 

Epoxide 

Heptachlor and heptachlor epoxide can be measured in blood, adipose tissue, breast milk, and urine. The 

analytical methods available can be used to determine whether exposure has occurred, but the results 

cannot tell whether adverse health effects will occur. The presence of heptachlor epoxide may reflect an 

exposure to heptachlor or possibly chlordane since heptachlor epoxide is a metabolite of both these 

pesticides. However, in the absence of stable chlordane residues (e.g., nonachlor and oxychlordane), the 

heptachlor epoxide would most likely have been derived from heptachlor. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 65 

3. HEALTH EFFECTS 

Detection of heptachlor or heptachlor epoxide in the body may indicate either recent or past exposure. 

Heptachlor epoxide has a long half-life, particularly in adipose tissue because it is very lipophilic and can 

remain dissolved in adipose tissue for months to years. An example of this can be found in a report in 

which analysis of human adipose tissue samples obtained during autopsy between 1987 and 1988 from 

residents of North Texas showed that tissue levels of heptachlor epoxide in subjects from the above 

geographical region had not significantly decreased since 1970 (Adeshina and Todd 1990). However, 

heptachlor epoxide is eventually mobilized into the blood and subsequently to the liver for further 

breakdown. Blood levels of heptachlor epoxide are often taken to indicate a more recent exposure. 

As indicated in Section 3.4.4.2, due to their relatively high lipid solubility, heptachlor and heptachlor 

epoxide can accumulate in breast milk fat. Heptachlor and heptachlor epoxide were measured in 

51 samples of human milk at average concentrations of 0.0027 and 0.019 ppm, respectively, from women 

with unknown exposure histories (Jonsson et al. 1977). Heptachlor epoxide was found in 24% of the 

samples, and heptachlor was found in 6%. Other investigators have reported the presence of heptachlor 

epoxide in human milk at concentrations ranging from not detected to 0.46 ppm (Kroger 1972; Polishuk 

et al. 1977b; Savage et al. 1981; Takei et al. 1983). These findings suggest a potential for transfer to the 

nursing infant (see also Sections 3.5.1 and 6.5). Other studies that have reported levels of heptachlor or 

heptachlor epoxide in humans’ breast milk include Larsen et al. (1971), Ritcey et al. (1972), and MussaloRauhamaa et al. (1988). 

No studies were found correlating levels to which humans were exposed with actual body burdens. 

3.8.2 Biomarkers Used to Characterize Effects Caused by Heptachlor and Heptachlor 

Epoxide 

No clinical conditions due to specific exposure to heptachlor or heptachlor epoxide are known. The 

neurological and hepatic effects seen from exposure to heptachlor and heptachlor epoxide are typical of 

exposure to other chlorinated pesticides. 

3.9 INTERACTIONS WITH OTHER CHEMICALS 

Dietary administration of heptachlor (97.6% purity) at 0.65 or 1.3 mg/kg/day in diet for 25 weeks 

promoted the development of hepatocellular foci and hepatocellular neoplasms in male B6C3F1 mice 

previously initiated with 3.8 mg/kg/day diethylnitrosamine given in the drinking water for 14 weeks 

(Williams and Numoto 1984). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 66 

3. HEALTH EFFECTS 

Nutritional factors may influence the toxicity of pesticides. Research in this area has primarily focused 

on the role of dietary proteins, particularly sulfur-containing amino acids, trace minerals, and vitamins A, 

C, D, and E. Studies in rats show that inadequate dietary protein enhances the toxicity of most pesticides 

but decreases, or fails to affect, the toxicity of a few. The results of these studies have shown that at oneseventh or less normal dietary protein, the hepatic toxicity of heptachlor is diminished as evidenced by 

fewer enzyme changes (Boyd 1969; Shakman 1974). The lower-protein diets may decrease metabolism 

of heptachlor to heptachlor epoxide. 

Male weanling rats were fed a 5, 20, or 40% casein diet for 10 days and then given heptachlor 

intraperitoneally. The animals receiving the 5% casein diet showed a 3-fold tolerance to heptachlor 

toxicity, but the toxicity of heptachlor epoxide was not affected (Weatherholtz et al. 1969). This was 

probably due to inability of weanling rats to metabolically convert heptachlor to the more toxic heptachlor 

epoxide. This fact is further supported by the observation that changes in protein percentage in diet did 

not affect the toxicity of heptachlor epoxide itself. 

Walter Reed-Wistar and Charles River male adult rats were exposed to oral doses of turpentine or to 

turpentine vapors, which consisted of α- and β-pinene. These exposures were followed by oral 

administration of heptachlor epoxide or of one of three pesticides, paraoxon, heptachlor, or parathion, or 

by an intraperitoneal injection of hexobarbital. The studies revealed that pretreatment with turpentine 

reduced hexobarbital sleeping time, reduced the parathion LD50, and increased the heptachlor LD50. The 

paraoxon and heptachlor epoxide LD50 values were unchanged. α-Pinene and β-pinene vaporized from 

turpentine had no effect on either hexobarbital sleeping time or parathion, paraoxon, or heptachlor 

epoxide mortality but did increase the heptachlor LD50 (Sperling et al. 1972). The authors speculated that 

increases in hepatic microsomal enzyme activity are responsible for these differences. 

3.10 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE 

A susceptible population will exhibit a different or enhanced response to heptachlor and heptachlor 

epoxide than will most persons exposed to the same level of heptachlor and heptachlor epoxide 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 heptachlor and heptachlor epoxide, or compromised function of organs affected by 

heptachlor and heptachlor epoxide. Populations who are at greater risk due to their unusually high 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 67 

3. HEALTH EFFECTS 

exposure to heptachlor and heptachlor epoxide are discussed in Section 6.7, Populations with Potentially 

High Exposures. 

3.11 METHODS FOR REDUCING TOXIC EFFECTS 

This section will describe clinical practice and research concerning methods for reducing toxic effects of 

exposure to heptachlor and heptachlor epoxide. 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 

heptachlor and heptachlor epoxide. When specific 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 heptachlor and heptachlor epoxide: 

Ellenhorn MJ. 1997. Ellenhorn's medical toxicology. Diagnosis and treatment of human poisoning. 2nd 

ed. Baltimore, MD: Williams and Wilkins, 1614-1631. 

EPA. 1999. Recognition and management of pesticide poisonings. 5th. Washington, DC: U.S. 

Environmental Protection Agency. EPA735R98003. PB99149551. 

Goldfrank L, Flomenbaum N, Lewin N, et al. 2002. Goldfrank's toxicologic emergencies. 7th ed. New 

York, NY: McGraw-Hill, 1366-1378. 

3.11.1 Reducing Peak Absorption Following Exposure 

Human exposure to heptachlor or heptachlor epoxide can occur by inhalation, oral, or dermal contact. 

Treatment of exposure to these substances is primarily supportive. Following a significant inhalation 

exposure, the patient is removed from the source to fresh air. Treatment may include administering 

oxygen and, if needed, maintaining ventilation with artificial respiration (Bronstein and Currance 1988; 

HSDB 2007a). General recommendations for reducing absorption of heptachlor following acute dermal 

exposure have included removal of contaminated clothing followed by washing the skin and hair with 

soap and water, (HSDB 2007a; Morgan 1989). Since leather absorbs pesticides, it has been 

recommended that leather not be worn while using heptachlor or heptachlor epoxide, and that any leather 

contaminated with these substances be discarded (HSDB 2007a). Oils have not been recommended as 

dermal cleansing agents because they could increase absorption (Haddad and Winchester 1990). If the 

eyes have been exposed, they are flushed with water (Bronstein and Currance 1988; HSDB 2007a). 

Treatment for ingestion of this substance may require gastric emptying by gastric lavage (Haddad and 

Winchester 1990) and administration of activated charcoal and cathartic (Haddad and Winchester 1990; 

HSDB 2007a; Morgan 1989). Heptachlor may be present with a hydrocarbon vehicle, which could result 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 68 

3. HEALTH EFFECTS 

in aspiration pneumonitis following the induction of emesis. Therefore, emesis may not be indicated. 

Some sources do not recommend the use of emetics (Bronstein and Currance 1988), although others do 

under some circumstances (HSDB 2007a; Morgan 1989). Treatments such as emesis and lavage may be 

most appropriate following ingestion of large quantities; it is unlikely that the types of exposure likely to 

occur at hazardous waste sites would require such measures. Treatment with milk, cream, or other 

substances containing vegetable or animal fats, which enhance absorption of chlorinated hydrocarbons, 

has not been recommended (Haddad and Winchester 1990; Morgan 1989). If seizures occur, diazepam 

administration, followed if necessary by additional anticonvulsant medicines such as phenytoin, 

pentobarbital, thiopental, or succinylcholine, may be recommended (Bronstein and Currance 1988; HSDB 

2007a; Morgan 1989). As adrenergic amines, such as epinephrine, may further increase myocardial 

irritability and produce refractory ventricular arrhythmias, their use has not been recommended 

(Bronstein and Currance 1988; Haddad and Winchester 1990; HSDB 2007a; Morgan 1989). 

3.11.2 Reducing Body Burden 

Heptachlor is rapidly metabolized by the body, mostly to heptachlor epoxide. Most of the metabolites are 

rapidly excreted in the feces, with the adipose tissue serving as the major storage depot for the remainder. 

From the fat, heptachlor epoxide can be slowly released into the bloodstream for further metabolism and 

excretion. Cholestyramine resin may accelerate the biliary-gastrointestinal excretion of the more slowly 

eliminated organochlorine compounds, and its use has been suggested (Morgan 1989). Because of the 

lipophilicity of heptachlor and heptachlor epoxide, dialysis and exchange transfusion are thought to be 

ineffective (HSDB 2007a). 

Because heptachlor epoxide is lipophilic, it is likely that the loss of adipose tissue, as may occur during 

fasting, will mobilize the stored compound and increase the rate of its elimination. However, this 

mobilization is also likely to temporarily increase the blood levels of heptachlor epoxide. Hence, any 

possible benefits due to a reduced body burden accompanying fat reduction would need to be balanced 

against potential harmful results due to the expected temporary increase in blood levels. 

3.11.3 Interfering with the Mechanism of Action for Toxic Effects 

Since the metabolized form of heptachlor, heptachlor epoxide, is the most toxic, it may be possible to 

reduce the toxic effects of heptachlor by inhibiting the enzyme catalyzing this conversion. This is the 

same enzyme that catalyzes the epoxidation of aldrin to dieldrin (Gillett and Chan 1968). Further 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 69 

3. HEALTH EFFECTS 

research into the specificity of this enzyme, drugs that could inhibit the enzyme, and any side effects of 

these drugs could help to determine the feasibility of such a treatment strategy. 

In the central nervous system, symptoms observed in animals following exposure include tremors, 

convulsions, ataxia, and changes in EEG patterns (Formanek et al. 1976). These central nervous system 

symptoms could be due either to (1) inhibition of the Na+

/K+ ATPase or the Ca+/Mg+ ATPase activity, 

which can then interfere with nerve action or release of neurotransmitters (Yamaguchi et al. 1979) and/or 

(2) inhibition of the function of the receptor for GABA (Yamaguchi et al. 1980). In support of the latter 

possibility, another study showed that heptachlor epoxide inhibited the GABA-stimulated chloride uptake 

in the coxal muscle of the American cockroach and directly competed against [3

H]a-dihydropierotoxinin 

for binding in the rat brain synaptosomes. These results indicate that some of the nerve excitation 

symptoms that insecticides cause are probably due to their interaction with the picrotoxin binding site of 

the GABA receptor (Matsumura and Ghiasuddin 1983). A more detailed understanding of the 

mechanism of heptachlor/heptachlor epoxide action on the central nervous system may lead to new 

approaches for reducing the toxic effects. 

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 heptachlor and heptachlor epoxide is available. Where 

adequate information is not available, ATSDR, in conjunction with the National Toxicology Program 

(NTP), is required to assure the initiation of a program of research designed to determine the health 

effects (and techniques for developing methods to determine such health effects) of heptachlor and 

heptachlor epoxide. 

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. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 70 

3. HEALTH EFFECTS 

3.12.1 Existing Information on Health Effects of Heptachlor and Heptachlor Epoxide 

The existing data on health effects of inhalation, oral, and dermal exposure of humans and animals to 

heptachlor and heptachlor epoxide are summarized in Figure 3-4. The purpose of this figure is to 

illustrate the existing information concerning the health effects of heptachlor and heptachlor epoxide. 

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. 

Most of the data located concerning the health effects of heptachlor and heptachlor epoxide in 

humans come from case reports and occupational epidemiology studies of workers engaged either in the 

manufacture or application of pesticides. There is some information on people who have consumed 

heptachlor-contaminated food or dairy products, but no adverse health effects have been related to these 

exposures. The occupational studies involve exposures that are predominantly inhalation with 

contributions from dermal exposure, whereas all the animal studies were conducted using oral or 

intraperitoneal exposures. The occupational and case reports provide no quantitation of dose or duration 

of exposure, which makes it impossible to determine with any precision the effect levels for humans. 

There are no data that indicate that heptachlor or heptachlor epoxide are carcinogenic to humans. 

However, human studies are limited by the long latency period of carcinogenesis and by ascertainment 

and follow-up biases. 

The animal studies for oral exposure to heptachlor and heptachlor epoxide are almost all limited to some 

extent by the number of doses used, the lack of appropriate statistics, or the small number or lack of 

controls. No information was located regarding the health effects of inhalation or dermal exposure, with 

the exception of a dermal LD50 in rats. Exposure of the general population via the inhalation and dermal 

routes may result from contaminated soil or vapors from treated houses. Some exposures from 

contaminated soil or water may occur in populations located near hazardous waste sites in which these 

chemicals have been stored or from food grown in contaminated soil. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 71 

3. HEALTH EFFECTS 

Figure 3-4. Existing Information on Health Effects of Heptachlor and Heptachlor 

Epoxide 

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 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 72 

3. HEALTH EFFECTS 

3.12.2 Identification of Data Needs 

Acute-Duration Exposure. There are no studies that have evaluated the acute toxicity of heptachlor 

or heptachlor epoxide following inhalation exposure; thus, acute-duration inhalation MRLs were not 

derived. A number of studies have evaluated the toxicity of heptachlor following acute oral exposure. 

The results of these studies suggest several sensitive targets of toxicity including the liver, nervous 

system, reproductive system, and the developing organism (Amita Rani and Krishnakumari 1995; 

Berman et al. 1995; Krampl 1971; Narotsky and Kavlock 1995; Narotsky et al. 1995; Purkerson-Parker et 

al. 2001b). The available data suggest that the most sensitive effect is impaired fertility observed in 

female rats administered heptachlor for 14 days prior to mating (Amita Rani and Krishnakumari 1995); 

this end point was used to derive an acute-duration oral MRL. Additional studies that examined a variety 

of systemic, neurological, reproductive, and developmental end points are needed to support the 

identification of critical effect and to establish dose-response relationships. Although there are limited 

toxicokinetic and mechanistic data for heptachlor, it is likely that its toxicity is not route-specific. The 

identified target organs would likely be the same for oral, inhalation, and dermal exposure; however, it is 

not possible to predict threshold concentrations. Toxicokinetic studies, which would allow for route-toroute extrapolation, and inhalation and dermal toxicity studies would be useful for confirming whether the 

toxicity of heptachlor is independent of route of exposure. 

The available acute-duration studies for heptachlor epoxide are limited to oral lethality and dominant 

lethal studies (Epstein et al. 1972; Podowski et al. 1979). The toxicity of heptachlor is likely due to 

heptachlor epoxide; thus, the targets of toxicity are likely to be the same as those observed following 

heptachlor exposure. However, the toxic thresholds are likely to be different. Studies are needed to 

establish dose-response relationships and to confirm whether the targets of toxicity are the same as those 

identified for heptachlor. 

Intermediate-Duration Exposure. The targets of toxicity of heptachlor following intermediateduration oral exposure appear to be the same as those identified following acute-duration oral exposure 

and include the liver, nervous system, reproductive system, and the developing organism (Akay and Alp 

1981; Amita Rani and Krishnakumari 1995; Aulerich et al. 1990; Crum et al. 1993; Izushi and Ogata 

1990; Moser et al. 2001; NCI 1977; Pelikan 1971; Purkerson-Parker et al. 2001b; Smialowicz et al. 

2001). Of these targets, the developing organism appears to be the most sensitive (Moser et al. 2001; 

Smialowicz et al. 2001). Impaired development of the nervous and immune systems have been observed 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 73 

3. HEALTH EFFECTS 

in rats exposed to heptachlor in utero, during lactation, and from postnatal day 7 through 42; a NOAEL 

has not been identified for these end points. The intermediate-duration oral MRL for heptachlor was 

based on these developmental effects. The potential systemic toxicity of heptachlor has not been 

adequately assessed; although several studies have evaluated systemic end points (Akay and Alp 1981; 

Akay et al. 1982; Akhtar et al. 1996; Izushi and Ogata 1990; Pelikan 1971), many of these studies were 

poorly reported or examined a limited number of end points. Studies examining a variety of systemic end 

points would be useful for identifying target tissues and establishing dose-response relationships. No 

intermediate-duration inhalation or dermal studies were identified. As discussed in the Acute-Duration 

Exposure section, it is likely that the targets of toxicity would be the same for inhalation, oral, and dermal 

exposure; however, toxicokinetic data are not available to confirm this conjecture. Inhalation and dermal 

exposure studies are needed. 

No publicly available studies on the intermediate-duration toxicity of heptachlor epoxide were identified. 

A 60-day dog study, which was submitted to EPA under the Federal Insecticide, Fungicide, and 

Rodenticide Act (FIFRA) identifies the liver as a critical target of toxicity (IRIS 2006). It is likely that 

the targets of heptachlor epoxide toxicity are the same as those for heptachlor. Additional studies, 

particularly those examining the development of the nervous and immune systems are needed to identify 

targets of toxicity and establish dose-response relationships. 

Chronic-Duration Exposure and Cancer. There are no data on chronic oral exposures in humans. 

There are occupational studies of workers engaged in the manufacture of heptachlor in which the 

exposures are presumed to be predominantly inhalation with contributions from the dermal route. No 

adverse health effects have been identified in these cohorts that could be positively associated with 

heptachlor exposure (Infante et al. 1978; MacMahon et al. 1988; Stehr-Green et al. 1988). There is a 

limited publicly available database on the chronic oral toxicity of heptachlor. The database is limited to a 

multigeneration study (Mestitzova 1967), which reported increased postnatal mortality at the lowest dose 

tested, and a study examining a limited number of noncancer end points (NCI 1977); thus, the database 

was not considered adequate for derivation of a chronic duration oral MRL. A 2-year study submitted to 

EPA under FIFRA identified the liver as a critical target of toxicity (IRIS 2006). This finding is 

consistent with the available intermediate-duration studies. However, intermediate-duration studies have 

also identified the nervous system, reproductive system, and the developing organism as targets of 

toxicity. Additional studies are needed to identify the most sensitive target following chronic duration 

exposure and to establish dose-response relationships; these studies would be useful for deriving an oral 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 74 

3. HEALTH EFFECTS 

MRL. Inhalation and dermal studies are also needed; these studies in animals would be useful for 

determining whether the target organ is the same across routes of exposure. 

As with the other durations of exposure, limited publicly available data were located for heptachlor 

epoxide. A study submitted to EPA under FIFRA identified the liver as the most sensitive target of 

toxicity (IRIS 2006). Additional studies are needed that could be used to derive inhalation and oral 

MRLs for heptachlor epoxide and to establish the targets of toxicity for dermal exposure. 

There are occupational mortality studies that have collected data appropriate for determining whether 

those engaged in the manufacture or application of heptachlor are at increased risk for dying of cancer. 

These studies have not shown an increased risk of cancer mortality (Infante et al. 1978; MacMahon et al. 

1988). Occupational studies that collected cancer incidence data, rather than just mortality data, would be 

useful for further exploration of this issue. Carcinogenicity studies have been identified for rats and mice 

(NCI 1977). These data show increases in tumorigenesis following exposure to heptachlor. Chronic 

studies of inhalation exposure in relation to oncogenesis in animals might be useful for determining 

mechanism of action and the consistency of effect across routes of exposure. There are no toxicokinetic 

data that indicate that there will be route-specific differences. 

Genotoxicity. Information on the in vivo genotoxic effects of heptachlor or heptachlor epoxide is 

limited to dominant lethality assays with negative results (Arnold et al. 1977; Epstein et al. 1972). More 

case reports and epidemiology studies are needed to properly evaluate genotoxic effects in humans 

exposed to heptachlor or heptachlor epoxide. The results of in vitro studies suggest that neither 

compound alters the frequency of gene mutations (Crebelli et al. 1986; Gentile et al. 1982; Glatt et al. 

1983; Marshall et al. 1976; NTP 1987; Probst et al. 1981; Zeiger et al. 1987), and that heptachlor does not 

induce DNA damage in bacteria (Rashid and Mumma 1986) or rodents (Maslansky and Williams 1981; 

Probst et al. 1981). Alterations were observed in assays of unscheduled DNA synthesis in human 

fibroblasts (Ahmed et al. 1977) and chromosomal alterations in Chinese hamster ovary cells (NTP 1987). 

In vivo animal research into the effects of heptachlor and heptachlor epoxide on sister chromatid 

exchange, chromosomal aberrations and anomalies, DNA adduct formation, gene mutation, and other 

genotoxic parameters would be helpful in assessing the genotoxic potential of heptachlor and heptachlor 

epoxide. 

Reproductive Toxicity. Although a couple of studies have attempted to establish an association 

between heptachlor epoxide blood levels and premature delivery or stillbirth among women presumably 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 75 

3. HEALTH EFFECTS 

exposed via ingestion (Curley et al. 1969; Wassermann et al. 1982), elevated levels of other compounds 

(particularly PCBs, lindane, and dieldrin) limit the interpretation of the results. Animal studies have 

found impaired fertility and pregnancy losses following oral exposure to heptachlor (Akay and Alp 1981; 

Amita Rani and Krishnakumari 1995; Green 1970; Mestitzova 1967). The mechanism of the 

reproductive toxicity has not been elucidated; the available data suggest that both males and females may 

be affected. Additional studies are needed to identify NOAELs for reproductive effects, confirm the 

observed results, and identify the critical targets within the reproductive system. 

Developmental Toxicity. Several studies have examined the potential developmental toxicity of 

heptachlor or heptachlor epoxide. These studies examined potential effects in the children of women 

exposed to heptachlor and heptachlor epoxide in contaminated cow’s milk (Baker et al. 2004b; Le 

Marchand et al. 1986) or examined the possible association between maternal heptachlor epoxide levels 

and developmental effects (Gladen et al. 2003; Hertz-Picciotto et al. 2004). Several animal studies have 

also examined developmental toxicity (Lawson and Luderer 2004; Moser et al. 2001; Narotsky and 

Kavlock 1995; Narotsky et al. 1995; Purkerson-Parker et al. 2001b; Smialowicz et al. 2001). The finding 

of impaired development of the nervous and immune systems was used as the basis of the intermediateduration oral MRL for heptachlor. This study (Moser et al. 2001; Smialowicz et al. 2001) did not identify 

a NOAEL for these effects, additional studies would be useful for more clearly defining the threshold of 

toxicity. Impaired spatial memory was observed at the lowest dose tested among the offspring exposed 

until postnatal day 42, but not in rats exposed until postnatal day 21 (Moser et al. 2001); studies that 

would address the cause of the conflicting results would also be useful. 

Immunotoxicity. No studies were located that specifically addressed immune function parameters 

following heptachlor or heptachlor epoxide exposure, although several studies have reported alterations in 

the lymphoreticular system (e.g., fibrosis in spleen, and increased size of spleen; decreased relative spleen 

weight) (Akay and Alp 1981; Aulerich et al. 1990; Pelikan 1971). A developmental toxicity study found 

suppression of the immune response in rats orally exposed in utero, during lactation, and postnatally until 

day 42 (Smialowicz et al. 2001). It is not known if these effects would also occur in mature animals. A 

study involving a battery of immune function tests would be useful for establishing whether heptachlor or 

heptachlor epoxide is toxic to the immune system. 

Neurotoxicity. No human data on the neurotoxicity of heptachlor or heptachlor epoxide were 

identified. No data exist describing neurologic effects in animals following inhalation or dermal exposure 

of any duration. Several studies have demonstrated that exposure to heptachlor can result in neurological 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 76 

3. HEALTH EFFECTS 

effects, in particular, excitability and decreased motor activity (Akay and Alp 1981; Aulerich et al. 1990; 

Crum et al. 1993; Moser et al. 1995, 2003). As discussed in the Developmental Toxicity section, 

exposure to heptachlor (and presumably heptachlor epoxide) can result in impaired learning and memory; 

studies are needed to evaluate whether exposure of mature animals to heptachlor or heptachlor epoxide 

can also result in impaired learning and memory. 

Epidemiological and Human Dosimetry Studies. The existing epidemiological studies are 

primarily of occupational cohorts (Blair et al. 1983; MacMahon et al. 1988; Shindell and Associates 

1981; Wang and MacMahon 1979a), case reports of health effects seen in groups exposed to 

contaminated milk (Baker et al. 2004b; Chadduck et al. 1987; Le Marchand et al. 1986; Stehr-Green et al. 

1986, 1988), or studies examining the possible association between elevated heptachlor/heptachlor 

epoxide blood levels and adverse health effects (Cantor et al. 2003; Cassidy et al. 2005; Curley et al. 

1969; Gladen et al. 2003; Hertz-Picciotto et al. 2004; Pines et al. 1986; Quintana et al. 2004; Sturgeon et 

al. 1998; Wang and Grufferman 1981; Ward et al. 2000; Wassermann et al. 1982). These studies have 

generally not included good quantitation of the exposure to heptachlor or heptachlor epoxide. In many 

cases, it is not possible to determine the exact identity of the contaminants involved. Although use of this 

compound has been discontinued, exposure could nevertheless occur through food grown in contaminated 

soil, through contact with pesticides applied to homes and other structures, or from hazardous waste sites. 

Analytical methods are available to determine exposure to heptachlor or heptachlor epoxide (Curley et al. 

1969; Klemmer et al. 1977; Radomski et al. 1968). However, no information is available that correlates 

levels of heptachlor epoxide in tissue with either level or duration of exposure. Occupational exposure 

levels are likely to be high enough to enable distinction from background levels. However, many 

epidemiological studies examining outcomes of exposure are limited by the accuracy of determining the 

exposure status of those individuals who show adverse health effects and those who show none. The 

precision and reliability of categorizing exposed individuals and non-exposed individuals contribute 

significantly to the statistical power of a study and greatly assist in accurate estimation of an increased 

risk. If data on exposure parameters are sparse or show very wide variation, it is difficult to determine 

what constitutes an exposure. More data on the correlation of tissue levels to exposure parameters would 

be useful for increasing the power of epidemiological studies to measure statistically significant 

associations between heptachlor exposure and health effects in cohorts from both occupational and 

contaminated community environments. Additionally epidemiology studies should focus on critical end 

points identified in animal studies including developmental toxicity (including neurological and 

immunological end points), liver effects, and cancer. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 77 

3. HEALTH EFFECTS 

Biomarkers of Exposure and Effect. 

Exposure. Exposure to heptachlor and heptachlor epoxide is currently measured by determining the level 

of these chemicals in the blood or adipose tissue in living organisms (Curley et al. 1969; Klemmer et al. 

1977; Radomski et al. 1968). This measure is specific for both heptachlor and heptachlor epoxide. 

Heptachlor epoxide is also a metabolite of chlordane, and thus its presence is not specific for exposure to 

heptachlor alone. However, in the absence of stable chlordane residues (e.g., nonachlor and 

oxychlordane), the heptachlor epoxide would most likely have been derived from heptachlor. Because 

heptachlor is believed to be converted rapidly in the body to heptachlor epoxide, it is impossible to 

determine whether the exposure was to one or the other of these two compounds. Heptachlor and 

heptachlor epoxide accumulate in adipose tissue and are released slowly over long periods of time. 

Therefore, it is not possible to accurately identify whether the exposure was recent or what the duration of 

exposure was. However, the ratio of heptachlor epoxide to heptachlor increases over time and therefore 

may be used as a biomarker of possible exposure to heptachlor. The sensitivity of the methods for 

identifying these compounds in human tissue appears to be only sufficient to measure background levels 

of heptachlor epoxide in the population. Additional biomarkers of exposure to heptachlor would be 

helpful at this time. 

Effect. There is no clinical disease state unique to heptachlor. A major problem in developing a 

biomarker of effect for heptachlor or heptachlor epoxide is that human exposures to these compounds 

have occurred concomitantly with exposures to other chemicals, and it is difficult to attribute the health 

effects to heptachlor or heptachlor epoxide alone. More data that quantify the biological effects as well as 

data that distinguish heptachlor and heptachlor epoxide exposures from those of other chemicals would be 

useful for developing biomarkers of effect for population monitoring. Biomarkers that could indicate the 

length of time since exposure would also be useful. 

Absorption, Distribution, Metabolism, and Excretion. There are very few data available to 

assess the relative rates of pharmacokinetic parameters with respect to route of exposure for either 

heptachlor or heptachlor epoxide. There are no human or animal inhalation or dermal studies on 

absorption, distribution, metabolism, or excretion. The only human data on metabolism come from in 

vitro studies using liver microsomes that indicate that, qualitatively, human microsomes metabolize 

heptachlor to the same end products as do rat microsomes (Tashiro and Matsumura 1978). Oral exposure 

in members of farm families led to elevated serum levels of heptachlor metabolites (Stehr-Green et al. 

1986), indicating that the compound is absorbed through the gastrointestinal tract. Animal studies also 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 78 

3. HEALTH EFFECTS 

suggest that uptake occurs through the gastrointestinal tract following oral dosing; excretion of these 

doses occurs primarily through the bile duct into the feces (Tashiro and Matsumura 1978). Lethality data 

suggest that heptachlor can be absorbed through the skin (Gaines 1969), but there are no data on 

absorption, distribution, metabolism, or excretion of dermally absorbed doses. Heptachlor epoxide is 

more toxic than heptachlor and has a longer half-life. Additional absorption, distribution, metabolism, 

and excretion data would be useful in order to gain a thorough understanding of the pharmacokinetic 

parameters of heptachlor and heptachlor epoxide. 

Comparative Toxicokinetics. There are limited available data with which to compare humans and 

other animal species. Although human toxicity data are available (Baker et al. 2004b; Blair et al. 1983; 

Cantor et al. 2003; Cassidy et al. 2005; Chadduck et al. 1987; Curley et al. 1969; Gladen et al. 2003; 

Hertz-Picciotto et al. 2004; Le Marchand et al. 1986; MacMahon et al. 1988; Pines et al. 1986; Quintana 

et al. 2004; Shindell and Associates 1981; Stehr-Green et al. 1986, 1988; Sturgeon et al. 1998; Wang and 

Grufferman 1981; Wang and MacMahon 1979a; Ward et al. 2000; Wassermann et al. 1982), the results of 

these studies are difficult to compare with the animal studies (Akay and Alp 1981; Amita Rani and 

Krishnakumari 1995; Aulerich et al. 1990; Berman et al. 1995; Crum et al. 1993; Izushi and Ogata 1990; 

Krampl 1971; Moser et al. 2001; Narotsky and Kavlock 1995; Narotsky et al. 1995; NCI 1977; Pelikan 

1971; Purkerson-Parker et al. 2001b; Smialowicz et al. 2001) because the exposure was not well 

characterized in the human studies and often involved exposure to multiple chemicals. As discussed in 

the previous section, there are limited data on the toxicokinetics of heptachlor and heptachlor epoxide. 

With the exception of human monitoring studies examining the levels of heptachlor/heptachlor epoxide in 

various tissues (Adeshina and Todd 1990; Barquet et al. 1981; Burns 1974; Greer et al. 1980; Klemmer et 

al. 1977; Polishuk et al. 1977b; Radomski et al. 1968; Stehr-Green et al. 1988; Wassermann et al. 1974), 

the available toxicokinetic data are in animals. Thus, direct comparisons between humans and animals 

can not be made. An in vitro comparative study found that the metabolites produced in humans and rats 

are identical, but the amounts differ (Tashiro and Matsumura 1978). Moreover, the rate of metabolism is 

not similar in both species. Thus, the rat may not be an appropriate metabolic model for humans. 

Additional studies, particularly in vivo studies, are needed to support these findings and identify the most 

appropriate animal model. There is a lack of information regarding kinetic changes after prolonged 

exposure. This kind of information would be useful because most exposures in the general population 

(e.g., from contaminated food or improperly applied pesticides) are likely to be long-term and low-dose. 

Methods for Reducing Toxic Effects. The mechanism by which heptachlor and heptachlor 

epoxide are absorbed from the gastrointestinal tract is unknown. Current methods for reducing absorption 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 79 

3. HEALTH EFFECTS 

from the gastrointestinal tract involve removing these chemicals from the site of absorption (Haddad and 

Winchester 1990; HSDB 2007a; Morgan 1989). Additional studies examining the method of absorption 

would provide valuable information for developing methods that can interfere with gastrointestinal 

absorption. Numerous studies have examined the distribution of heptachlor and heptachlor epoxide 

(Barquet et al. 1981; Burns 1974; Curley et al. 1969; Greer et al. 1980; Jonsson et al. 1977; Polishuk et al. 

1977b; Radomski et al. 1968). Additional studies on distribution are not necessary at this time. No 

established methods exist for reducing body burden of heptachlor and heptachlor epoxide. However, 

available information suggests that removal of these compounds via biliary-gastrointestinal excretion can 

be accelerated (Morgan 1989). Reducing enterohepatic recirculation before these chemicals partition to 

tissues may be effective (Haddad and Winchester 1990; HSDB 2007a). Thus, studies examining the 

effectiveness of repeated doses of activated charcoal or cholestyramine in reducing body burden would be 

useful. Adipose tissue serves as a major storage repository for both heptachlor and heptachlor epoxide 

(Barquet et al. 1981; Burns 1974; Greer et al. 1980; Harradine and McDougall 1986). Losing fat can 

mobilize the stored compound and increase the rate of its elimination. However, it may temporarily 

increase the blood levels of heptachlor epoxide. Studies that would examine the benefits of reducing 

body burden with accompanying fat reduction while balancing against harmful effects from temporary 

increase in blood level would be useful. Since heptachlor undergoes epoxidation to produce heptachlor 

epoxide which is more toxic than the parent compound, studies examining drugs that would inhibit the 

enzyme catalyzing this conversion would be helpful. Neurotoxicity of heptachlor epoxide is believed to 

result, at least in part, from interference with GABA receptor function (Yamaguchi et al. 1980). The 

available data suggest that benzodiazepenes and barbiturates may be useful in mitigating some of the 

neurological symptoms of heptachlor epoxide (Bronstein and Currance 1988; HSDB 2007b; Morgan 

1989). However, additional studies examining the effectiveness of GABAergic function in mitigating 

heptachlor epoxide's neurologic effects would be useful. The liver also appears to be a major target organ 

for the toxic effects of heptachlor and heptachlor epoxide in animals (Akay and Alp 1981; Krampl 1971; 

Pelikan 1971). An understanding of the mechanism of action in the liver may identify new approaches 

for reducing the toxic effects. 

Children’s Susceptibility. Data needs relating to both prenatal and childhood exposures, and 

developmental effects expressed either prenatally or during childhood, are discussed in detail in the 

Developmental Toxicity subsection above. 

There are suggestive data indicating that children, particularly children exposed in utero and during 

infancy, may be unusually susceptible to the toxicity of heptachlor. A study in adolescents exposed to 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 80 

3. HEALTH EFFECTS 

heptachlor and heptachlor epoxide during gestation found significant alterations in neurobehavioral 

function (Baker et al. 2004b). Similarly, alterations in neurobehavioral function were observed in rats 

exposed during gestation through postnatal day 42 (Moser et al. 2001). Because neurobehavioral 

performance has not been investigated in adults, it is difficult to determine whether children are more 

susceptible to the neurotoxicity of heptachlor than adults. Additionally, no studies have investigated 

whether there are age-specific differences in the toxicokinetic properties of heptachlor or heptachlor 

epoxide. Additional studies are needed to evaluate potential age-related differences in the toxicity of 

heptachlor and heptachlor epoxide. 

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 

Patrick Wong at the University of California at Davis is investigating ligand-independent endocrine 

disruption by several pesticides include heptachlor epoxide. Ongoing research by D.E. Wooley, also at 

the University of California at Davis, is investigating the neurotoxic effects and mechanisms of action of 

environmental toxicants including heptachlor following acute and chronic exposure. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 81 

4. CHEMICAL AND PHYSICAL INFORMATION 

4.1 CHEMICAL IDENTITY 

Information regarding the chemical identity of heptachlor and heptachlor epoxide is located in Table 4-1. 

4.2 PHYSICAL AND CHEMICAL PROPERTIES 

Information regarding the physical and chemical properties of heptachlor and heptachlor epoxide is 

located in Table 4-2. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 82 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-1. Chemical Identity of Heptachlor and Heptachlor Epoxidea 

Characteristic Heptachlor Heptachlor epoxide 

Synonym(s) 3-Chlorochlordene; 

1,4,5,6,7,8,8a-heptachloro-3a,4,7,7a-tetrahydro4,7-methanoindene; 

1,4,5,6,7,8,8-heptachloro3A,4,5,5a tetrahydro; alphadicylcopentadiene, 3,4,5,6,8,8a 

heptachloro, and others 

Epoxyheptachlor; 

1,4,5,6,7,8,8a-heptachloro-2,3-epoxy-3a,4,7,7a-tetrahydro-4,7-methanoindene; 

4,7-methanoindan, 1,4,5,6,7,8, 

8-heptachloro-2,3-epoxy3a,4,7,7a-tetrahydro-; 

2,5-methano-2h-indeno 

(1,2-b)oxirene, 2,3,4,5,6,7, 

7-heptachloro-1a,1b, 

5,5a,6,6a-hexahydro-, 

(1aalpha,1bbeta,2alpha,5alpha, 

5abeta,6beta,6aalpha)- 

Registered trade name(s) Basaklor; Gold Crest H-60; 

Termide; Heptagran; 

Heptagranox; Heptamak; 

Heptamul; Soleptax; Velsicol 104 

Velsicol 53-CS-17 

Chemical formula C10H5Cl7 C10H5Cl7O 

Chemical structure 

Identification numbers: 

 CAS registry 76-44-8 1024-57-3 

 NIOSH RTECS PC0700000 

EPA hazardous waste P059 D031 

 OHM/TADS 7216526 833300216 

DOT/UN/NA/IMDG shipping UN 2761, UN2782, UN 2995, 

UN2996, IMO 3.0, IMO 6.1 

UN 2761, UN2782, UN 2995, 

UN2996, IMO 3.0, IMO 6.1 

HSDB 554 6182 

NCI C00180 

a

All information obtained from HSDB 2007a for heptachlor or HSDB 2007b for heptachlor epoxide unless otherwise 

noted. 

CAS = Chemical Abstracts Services; DOT/UN/NA/IMDG = Department of Transportation/United Nations/North 

America/International Maritime Dangerous Goods Code; 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 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 83 

4. CHEMICAL AND PHYSICAL INFORMATION 

Table 4-2. Physical and Chemical Properties of Heptachlor and Heptachlor 

Epoxidea

Property Heptachlor Heptachlor epoxide 

Molecular weight 373.32 389.40 

Color White (pure); tan (technical grade)

b

 Whiteb 

Physical state Crystalline solid Crystalline solidb 

Melting point 95B96 EC (pure); 46B74 EC (technical 

grade)c 

160B161.5 EC 

Boiling point 145 EC No data 

Specific Gravity: 

at 9 EC 1.57 No data 

Odor Camphor-like No data 

Odor threshold: 

Water No data No data 

Air 0.3 mg/m3

 0.3 mg/m3 

Solubility: 

Water at 25 EC 0.05 mg/Ld

 0.275 mg/Ld 

Organic solvent(s) Soluble in most organic solvents Soluble in most organic solventsb 

Partition coefficients: 

 Log Kow 6.10 5.40 

 Log Koc 4.34e 3.34B4.37f 

Vapor pressure 

3x10-4 mmHgg

 at 20 EC 1.95x10-5 mmHg at 30 EC h 

3x10-4 mmHg at 25 EC No data 

Henry's law constant: 

at 25 EC 2.94x10-4 atm-m3

/mol 3.2x10-5 atm-m3/mol 

Autoignition No data No data 

temperature 

Flashpoint No data No data 

Flammability limits Highly flammable Non-combustible 

Conversion factors 1 ppm=15.27 mg/m3

 at 25 EC, 1 atm 1 ppm=15.93 mg/m3 at 25 EC, 1 atm 

Explosive limits Non-combustible Containers may explode when 

heated 

a

All information obtained from HSDB 2007a for heptachlor or HSDB 2007b for heptachlor epoxide unless otherwise 

noted 

b

IARC 1974 

c

Worthing and Walker 1987 d

EPA 1987 

e

Chapman 1989 f

Estimated from Lyman et al. 1982 

g

ACGIH 1986 h

Nash 1983 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 84 

4. CHEMICAL AND PHYSICAL INFORMATION 

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HEPTACHLOR AND HEPTACHLOR EPOXIDE 85 

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

5.1 PRODUCTION 

Heptachlor was first registered for use in the United States as an insecticide in 1952 and commercial 

production began the following year (EPA 1986a). Nearly all registered uses of heptachlor were canceled 

in 1974 by EPA because of its potential cancer risk and its persistence and bioaccumulation throughout 

the food chain (EPA 1986a). The sale of heptachlor was voluntarily canceled in 1987 by its sole U.S. 

manufacturer, the Velsicol Chemical Corporation. The sale, distribution, and shipment of existing stocks 

of all canceled chlordane and heptachlor products were prohibited in the United States as of April 1988 

(EPA 1990a; SRI 1990). Heptachlor is a constituent of technical-grade chlordane, approximately 10% by 

weight (HSDB 2007a). Heptachlor epoxide is an oxidation product of heptachlor and of chlordane; it is 

not produced commercially in the United States (IARC 1979). 

Crown chemical company, the last company in the United States reported to have manufactured 

heptachlor, transferred its registry to Wood Protection Products, Inc. on October 8, 1985. Since 1985, 

heptachlor use in the United States has been limited to treatment of fire ants in power transformers. All 

other heptachlor uses have been banned in the United States. 

Table 5-1 summarizes the facilities in the United States that manufacture or process heptachlor. It also 

lists the maximum amounts of heptachlor that are allowed at these sites and the end uses of the 

heptachlor. This information is based on the release data reported to the Toxics Release Inventory (TRI) 

in 2004 (TRI04 2006). The majority of facilities that reported heptachlor release in 2004 were hazardous 

waste treatment plants that processed heptachlor for safe disposal. 

Heptachlor is produced commercially by the free-radical chlorination of chlordene in benzene containing 

0.5–5.0% of fuller's earth. The reaction is run for up to 8 hours. The chlordene starting material is 

prepared by the Diels-Alder condensation of hexachlorocyclopentadiene with cyclopentadiene (Sittig 

1980). Technical-grade heptachlor usually consists of 72% heptachlor and 28% impurities such as 

trans-chlordane, cis-chlordane, and nonachlor (HSDB 2007a). 

The U.S. International Trade Commission (USITC) did not report the domestic production volume of 

heptachlor separately for the years 1981–1985 (USITC 1982b, 1983b, 1984b, 1985, 1986). Only yearly 

totals were reported for all cyclic insecticides. The USITC reports production volume data only for 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 86 

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

Table 5-1. Facilities that Produce, Process, or Use Heptachlor 

Minimum Maximum 

Number of amount on site amount on site 

Statea facilities in poundsb in poundsb Activities and usesc 

AR 3 0 99,999 7, 12 

CA 1 0 99 12 

FL 1 10,000 99,999 7 

GA 1 1,000 9,999 7 

IL 3 0 9,999 12 

KY 2 100 9,999 12 

LA 2 0 9,999 12 

MI 1 0 99 12 

MS 1 0 99 12 

NE 2 100 9,999 12 

NJ 2 0 9,999 12 

NV 1 100 999 2, 3, 12 

OH 3 100 99,999 12 

OR 2 100 9,999 12 

PA 1 0 99 12 

SC 1 100,000 999,999 12 

TN 4 10,000 999,999 1, 4, 7 

TX 5 0 999,999 12 

UT 3 0 9,999 12 

a

Post office state abbreviations used b

Amounts on site reported by facilities in each state c

Activities/Uses: 

1. Produce 6. Impurity 11. Chemical Processing Aid 

2. Import 7. Reactant 12. Manufacturing Aid 

3. Onsite use/processing 8. Formulation Component 13. Ancillary/Other Uses 

4. Sale/Distribution 9. Article Component 14. Process Impurity 

5. Byproduct 10. Repackaging 

Source: TRI04 2006 (Data are from 2004) 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 87 

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

chemicals for which three or more manufacturers report volumes that exceed certain minimum output 

levels. 

5.2 IMPORT/EXPORT 

The USITC did not report separate import data for heptachlor for the years 1981, 1982, or 1983 (USITC 

1982a, 1983a, 1984a). The sale, distribution, and shipment of existing stocks of all canceled heptachlor 

products were prohibited by EPA in 1988 (EPA 1990a). According to the USITC, heptachlor has not 

been imported into the United States from 1986 to 2007 (USITC 2007). 

No information was located regarding the exportation of heptachlor or heptachlor epoxide. 

5.3 USE 

Heptachlor is a persistent insecticide that kills insects by both ingestion and dermal contact. It is 

nonphytotoxic at insecticidal concentrations (Worthing and Walker 1987). Heptachlor was used 

extensively from 1953 to 1974 as a soil and seed treatment to protect corn, small grains, and sorghum 

from pests. It was used to control ants, cutworms, maggots, termites, thrips, weevils, and wireworms in 

both cultivated and uncultivated soils. Heptachlor was also used nonagriculturally during this time period 

to control termites and household insects (EPA 1986a; Worthing and Walker 1987). 

EPA proposed cancellation of nearly all registered uses of heptachlor in 1974 because of its potential 

cancer risk and its persistence and bioaccumulation throughout the food chain. The few agricultural uses 

that were not canceled in 1974, treatment of field corn, seed (for corn, wheat, oats, barley, rye, and 

sorghum), citrus, pineapple, and narcissus bulbs, were phased out gradually over a 5-year period ending 

on July 1, 1983 (EPA 1986a). By April 1988, heptachlor could no longer be used for the underground 

control of termites. That same year, EPA prohibited the sale, distribution, and shipment of existing stocks 

of all canceled chlordane and heptachlor products. Subsequently, virtually all uses of heptachlor products 

were voluntarily canceled by the registrant, Velsicol Chemical Corporation (EPA 1990a). The only 

current use of heptachlor is in the treatment of fire ants in underground power transformers. This use was 

specifically exempted from EPA's suspension and cancellation actions because it was believed to result in 

insignificant exposure and, consequently, insignificant risk. It is unclear whether or not this exempted use 

is currently supported since Velsicol voluntarily chose not to renew their registration for technical-grade 

heptachlor in 1999 (EPA 1999a). A search of the National Pesticide Information Retrieval System, which 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 88 

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

lists all of the labels for currently registered pesticides, produced no active labels for heptachlor (NPIRS 

2007). 

5.4 DISPOSAL 

Heptachlor and heptachlor epoxide are Resource Conservation and Recovery Act (RCRA) hazardous 

wastes and hazardous constituents (EPA 1986b); as such, they must be disposed of in secure landfills in 

compliance with all federal, state, and local regulations. They may also be incinerated at 1,500 °F for 

0.5 seconds for primary combustion and at 3,200 °F for 1 second for secondary combustion, with 

adequate scrubbing of incinerator exhaust and disposal of ash (Sittig 1985). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 89 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.1 OVERVIEW 

Heptachlor and heptachlor epoxide have been identified in at least 210 and 200 of the 1,684 hazardous 

waste sites, respectively, that have been proposed for inclusion on the EPA National Priorities List (NPL) 

(HazDat 2006). However, the number of sites evaluated for heptachlor is not known. The frequency of 

these sites can be seen in Figure 6-1 and 6-2, respectively. Of these sites for heptachlor, 207 are located 

within the United States, 2 are located in the Commonwealth of Puerto Rico (not shown), and 1 is located 

in the Virgin Islands. For heptachlor epoxide, 195 of these sites are located within the United States, 

2 are located in Guam, 2 are located in the Commonwealth of Puerto Rico, and 1 is located in the Virgin 

Islands. 

Heptachlor was used extensively until the 1970s as a broad-spectrum insecticide on a wide variety of 

agricultural crops, with the major use on corn. It also had nonagricultural uses including seed treatment, 

home and garden uses, and termite control. In 1974, EPA proposed cancellation of nearly all registered 

uses of heptachlor except termite and fire ant control and dipping of roots or tops of nonfood plants, a use 

that was subsequently voluntarily canceled by the registrant in 1983 (EPA 1986a). In 1988, the sale, 

distribution, and shipment of existing stocks of all heptachlor products were prohibited in the United 

States with an exemption for the use of fire ant control. As of April 1988, heptachlor could no longer be 

used for the underground control of termites. Currently, the only commercial use of heptachlor still 

permitted in the United States is fire ant control in underground power transformers (EPA 1990a); 

however, in 1999, the sole manufacturer of heptachlor chose not to renew its registration with the EPA 

(EPA 1999a). As of April 2007, there were no active pesticide labels containing heptachlor (NPIRS 

2007). Therefore, it is unclear whether heptachlor is still available in the United States. 

Heptachlor is converted to heptachlor epoxide and other degradation products in the environment. 

Heptachlor epoxide degrades more slowly and, as a result, is more persistent than heptachlor. Heptachlor 

epoxide has been found in food crops grown in soils treated with heptachlor many years before. Both 

heptachlor and heptachlor epoxide adsorb strongly to sediments, and both are bioconcentrated in aquatic 

and terrestrial organisms. Biomagnification of heptachlor and heptachlor epoxide in aquatic food chains 

is significant. Because heptachlor is readily metabolized to heptachlor epoxide by higher trophic level 

organisms, biomagnification of heptachlor itself is not significant. Because of the more persistent nature 

of heptachlor epoxide and its lipophilicity, biomagnification of heptachlor epoxide in terrestrial food 

chains is significant. 


HEPTACHLOR AND HEPTACHLOR EPOXIDE 92 

6. POTENTIAL FOR HUMAN EXPOSURE 

In the past (prior to 1974), exposure of humans to heptachlor and heptachlor epoxide was directly related 

to the application of heptachlor as an insecticide. However, because of the persistence and 

bioaccumulation of heptachlor and heptachlor epoxide, exposure of the general population can occur 

through ingestion of contaminated food (especially cow or human milk), inhalation of vapors from 

contaminated soil and water, or direct contact with residual heptachlor from pesticide application. People 

whose homes have been treated may continue to be exposed to these chemicals in the air over long 

periods. Occupational exposure can occur in the manufacture of the chemical or from use of heptachlor 

to control fire ants. The most likely routes of exposure at hazardous waste sites are unknown. Heptachlor 

has been found infrequently in soil and groundwater at hazardous waste sites. Children who eat 

contaminated soil or people who obtain tap water from wells located near hazardous waste sites might be 

exposed to heptachlor. Further, since both compounds can volatilize from soil, people living near 

hazardous waste sites may be exposed to the compounds in the air. People whose homes have been 

professionally treated for termites, either by spraying or subsurface injection, may continue to be exposed 

to heptachlor and possibly to its transformation product, heptachlor epoxide, in the indoor air over long 

periods. Releases can also occur from the use of existing stocks in the possession of homeowners (EPA 

1990a). 

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 2005f). 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 2005f). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 93 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.2.1 Air 

Estimated releases of 2 pounds of heptachlor and heptachlor epoxide to the atmosphere from 14 domestic 

manufacturing and processing facilities in 2004, accounted for <0.1% of the estimated total 

environmental releases from facilities required to report to the TRI (TRI04 2006). These releases are 

summarized in Table 6-1. 

6.2.2 Water 

Estimated releases of 9 pounds of heptachlor and heptachlor epoxide to surface water from 14 domestic 

manufacturing and processing facilities in 2004, accounted for about 0.3% of the estimated total 

environmental releases from facilities required to report to the TRI (TRI04 2006). These releases are 

summarized in Table 6-1. These releases were predominantly from hazardous waste disposal agencies 

(TRI04 2006). 

Heptachlor and heptachlor epoxide may enter surface water and groundwater in runoff from contaminated 

soils or in discharges of waste water from production facilities. 

6.2.3 Soil 

Estimated releases of 3,140 pounds of heptachlor and heptachlor epoxide to soils from 14 domestic 

manufacturing and processing facilities in 2004, accounted for >99% of the estimated total environmental 

releases from facilities required to report to the TRI (TRI04 2006). These releases are summarized in 

Table 6-1. These releases were predominantly from hazardous waste disposal agencies (TRI04 2006). 

6.3 ENVIRONMENTAL FATE 

6.3.1 Transport and Partitioning 

Heptachlor has a low vapor pressure (3.0x10-4 mmHg at 25 °C) and low water solubility (0.056 mg/L) 

(EPA 1987; Jury et al. 1987). The experimental value for the Henry's law constant is 

1.48x10-3 suggesting that heptachlor partitions somewhat rapidly to the atmosphere from surface water 

and that volatilization is significant (EPA 1987; Lyman et al. 1982). Heptachlor is also subject to longrange transport and wet deposition. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 94 

6. POTENTIAL FOR HUMAN EXPOSURE 

Table 6-1. Releases to the Environment from Facilities that Produce, Process, or 

Use Heptachlora

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 

AR 2 0 No data No data 0 0 0 0 0 

LA 1 0 No data No data 7 0 7 0 7 

NE 1 0 No data No data 0 0 0 0 0 

NJ 1 0 9 No data 7 0 16 0 16 

NV 1 0 No data No data 162 0 162 0 162 

OH 2 1 0 No data 1 0 1 1 2 

OR 1 0 No data No data 2,962 0 2,962 0 2,962 

PA 1 0 No data No data 0 0 0 0 0 

TX 3 0 0 No data 0 0 0 0 0 

UT 1 0 No data No data 0 0 0 0 0 

Total 14 2 9 No data 3,140 0 3,149 1 3,150 

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) 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 95 

6. POTENTIAL FOR HUMAN EXPOSURE 

The log soil organic carbon adsorption coefficient (log Koc) for heptachlor was estimated to be 

4.34 (Chapman 1989). The log Koc value indicates a very high sorption tendency, suggesting that it will 

adsorb strongly to soil and is not likely to leach into groundwater in most cases (Chapman 1989). The 

leaching potential at 15 cm (concentration in soil water/concentration in soil) for heptachlor is 0.06, and 

the volatilization potential at 15 cm (concentration in soil air/concentration in soil) determined in 

laboratory studies is 5.5x10-3, again suggesting that heptachlor is unlikely to leach appreciably in soil but 

has some volatilization potential (McLean et al. 1988). These are important properties since heptachlor 

can remain deep in soil for years. The organic matter content of the soil is another factor affecting 

mobility. Heptachlor is less likely to leach from soil with a high organic matter content. When released 

into water, it adsorbs strongly to suspended and bottom sediment. 

Volatilization from soil particles to the atmosphere is possible (McLean et al. 1988). Volatilization is an 

important mechanism of transport of heptachlor from land surfaces (Jury et al. 1987). When heptachlor 

was applied to orchard grass, approximately 90% was lost in 7 days. When it was applied to moist soil 

surfaces, 50% was lost in 6 days. When it was applied to dry soil surface, 14–40% was lost in 

approximately 2 days (50 hours). Volatilization was much less—only 7% in 167 days—when 

incorporated to a shallow depth of 7.5 cm (Jury et al. 1987). Temperature and humidity affect the 

persistence of heptachlor and total heptachlor (heptachlor plus heptachlor epoxide) in soil (Shivankar and 

Kavadia 1989). An increase in temperature resulted in a decrease in the volatilization half-lives of 

heptachlor and total heptachlor. For example, at 18"1 °C (90"5% relative humidity [RH]) and 35"1 °C 

(90"5% RH), the half-lives of heptachlor (6 ppm) were 44.8 days and 38 days, respectively. Persistence 

of heptachlor and total heptachlor was found to be greater at higher humidity, irrespective of temperature. 

At the combination of higher temperature (25"1 °C) and low humidity (55"5% RH), faster dissipation of 

heptachlor occurred (half-life=24.67 days). At lower temperatures (18"1 °C) and low humidity 

(55"5% RH), greater persistence of heptachlor was found (40.67 days). Half-lives of total heptachlor 

(6 ppm) were longer because of the more persistent nature of heptachlor epoxide (Shivankar and Kavadia 

1989). 

The logarithm of the n-octanol/water partition coefficient (log Kow) is a useful preliminary indicator of 

bioconcentration potential of a compound. The log Kow for heptachlor is 5.44 (Chapman 1989; MacKay 

1982), suggesting a high potential for bioaccumulation and biomagnification in the aquatic food chain. 

The bioconcentration factors (BCFs) for heptachlor were 10,630 in Asiatic clam fat (Corbicula 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 96 

6. POTENTIAL FOR HUMAN EXPOSURE 

manilensis), 2,570 in soft clams (Mya arenaria), and 8,511 in oysters (Crassostrea virginica) (Hawker 

and Connell 1986). 

Heptachlor epoxide is soluble in water at a concentration of 0.275 mg/L (EPA 1987). The experimental 

value for Henry's law constant is 3.2x10-5 (EPA 1987), suggesting that heptachlor epoxide partitions 

slowly to the atmosphere from surface water (Lyman et al. 1982). Based on regression equations, the log 

Koc for heptachlor epoxide was estimated to range between 3.34 and 4.37 (Lyman et al. 1982). These log 

Koc values suggest a high sorption tendency, meaning that this compound is not mobile in soil and has a 

low potential to leach. The organic matter content of soil affects the mobility of heptachlor epoxide. 

Heptachlor epoxide is less likely to leach from soil with a high organic matter content. If released into 

water, it adsorbs strongly to suspended and bottom sediments. 

The log Kow for heptachlor epoxide is 5.40 (MacKay 1982), indicating a high potential for bioconcentration and biomagnification in the aquatic food chain. Estimated BCFs for heptachlor epoxide are 

1,698 in mussels (Mytilus edulis), 851 in oysters (C. virginica) (Hawker and Connell 1986; Geyer et al. 

1982), and 2,330 in Asiatic clam fat (C. manilensis) (Hartley and Johnston 1983). The bioconcentration 

potentials of heptachlor and heptachlor epoxide differ, with the more polar epoxide being concentrated to 

a lesser degree than the parent compound (Hartley and Johnston 1983). Biomagnification of heptachlor 

and heptachlor epoxide in aquatic food chains is significant. Because heptachlor is readily metabolized to 

heptachlor epoxide by higher trophic level organisms, biomagnification of heptachlor itself is not 

significant. Because of the more persistent nature of heptachlor epoxide and its lipophilicity, 

biomagnification of heptachlor epoxide in terrestrial food chains is significant. 

Heptachlor and heptachlor epoxide are subject to long-range transport and removal from the atmosphere 

by wet deposition. Snowpack samples were collected at 12 sites in the Northwest Territories, Canada, in 

the winter of 1985–1986. Heptachlor epoxide was present in 20 of 21 samples at a mean concentration of 

0.18 ng/L (1.8x10-4 ppb) with reported concentrations ranging from 0.02 to 0.41 ng/L (from 2x10-5 to 

4.1x10-4 ppb). Heptachlor epoxide was present in both the Bering and Chukchi Seas in 1993 at mean 

concentrations of 2.4 and 2.8 ng/m3

, respectively (Macdonald et al. 2000). 

Heptachlor and heptachlor epoxide are also taken up by plants (translocated into plants by absorption 

through the roots). Loamy soils were treated with heptachlor at a total of 25 pounds per 5-inch acre over 

a 5-year period (1958–1962) (Lichtenstein et al. 1970). The commercial formulation of heptachlor used 

also contained γ-chlordane and nonachlor. Insecticide residues were absorbed by crops grown in these 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 97 

6. POTENTIAL FOR HUMAN EXPOSURE 

soils, with carrots absorbing the largest amounts. Although residue levels in soils increased up to 1962, 

the residue concentrations in both carrots and potatoes peaked during the 1960 growing season. During 

that year, the concentration of total heptachlor in carrots was 1,900 ppb. Residue levels of total 

heptachlor on potatoes never exceeded 540–510 ppb (1960–1962). Apparently, a threshold had been 

reached beyond which the content of insecticidal residues remained constant in these two crops. When 

insecticide residue levels in soil started to decline (1963), both carrots and potatoes also contained 

proportionally smaller amounts of residue. In the fall of 1968, residues of total heptachlor were found in 

the following crops: carrots, 413 ppb (92% heptachlor epoxide); potatoes, 70 ppb (98% heptachlor 

epoxide); beets, 60 ppb (100% heptachlor epoxide); radishes, 140 ppb (100% heptachlor epoxide); and 

cucumbers, 90 ppb (95% heptachlor epoxide) (Lichtenstein et al. 1970). Despite being banned in 

Argentina, trace amounts of heptachlor and heptachlor epoxide (<10 ng/g dry weight) were found in 

organically grown tomato plants that had never been sprayed with any pesticide outside of Buenos Aires 

(Gonzalez et al. 2003). Heptachlor epoxide was detected in spruce and pine trees of western Canada and 

the concentration of heptachlor in these trees seemed to increase as the altitude increased (Davidson et al. 

2003). 

6.3.2 Transformation and Degradation 

6.3.2.1 Air 

Heptachlor may undergo direct photolysis in sunlight and is also susceptible to photosensitized reactions 

(Graham et al. 1973; Ivie et al. 1972). Heptachlor epoxide is converted to intermediate and final 

photoproducts when exposed to sunlight or ultraviolet light on the surface of plants (Podowski et al. 

1979). About 40–50% conversion occurred in 4 hours on bean leaves treated with rotenone, an 

insecticide, acting as a photosensitizer. No detectable photoproducts (photoheptachlor epoxide) were 

formed in the absence of rotenone. The photolysis products were ketones. The intermediate 

photoproduct possesses a reduced toxicity in mice as compared to heptachlor epoxide, and it is 

completely nontoxic to houseflies. The final photoproduct is more toxic to flies and mice than the parent 

heptachlor epoxide (Ivie et al. 1972). The photoisomers of heptachlor epoxide are not expected to form in 

appreciable amounts in the environment unless a potent photosensitizer is present (Ivie et al. 1972). The 

photolysis of heptachlor epoxide as a solid (pressed) disk, as a powder, and as 0.5% heptachlor epoxide in 

a potassium bromide (a photosensitizer) disk was studied. The physical nature of the sample and the 

intensity of illumination affected the rate of photolysis. After 121 hours of exposure to sunlight in July, 

93, 98, and 0% heptachlor epoxide remained in the solid disk, powder, and potassium bromide disk, 

respectively. When a powdered sample of heptachlor epoxide was irradiated on a rooftop of an 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 98 

6. POTENTIAL FOR HUMAN EXPOSURE 

unspecified location from January through mid-September, degradation was almost negligible until May, 

then increased through July, reaching a maximum decomposition rate of 1% per day at the end of July. 

By the end of the experiment (8.5 months), 39% of the original sample had decomposed (Graham et al. 

1973). 

6.3.2.2 Water 

Heptachlor is hydrolyzed in surface water and distilled water to 1-hydroxychlordene and heptachlor 

epoxide. When heptachlor was added to a sample of river water maintained at room temperature and 

exposed to sunlight, only 25% remained after 1 week, and no heptachlor remained after the second week. 

The 75% loss of heptachlor after 1 week corresponds to a half-life of 3.5 days. It was observed that an 

equilibrium exists at the end of 4 weeks between 1-hydroxychlordene and heptachlor epoxide, so that 

approximately 60% of the converted heptachlor remained as 1-hydroxychlordene and 40% was converted 

to the epoxide. When heptachlor epoxide was added to a sample of river water (pH 7.3–8) and to distilled 

water, it remained unchanged for 8 weeks. A half-life of at least 4 years was calculated for heptachlor 

epoxide (Eichelberger and Lichtenberg 1971). 

When a 14C-heptachlor-treated model aquatic ecosystem was examined for transformation of heptachlor 

in water, the relative amounts of various transformation products in water were determined as the 

percentage of the total 14C label in the water sample. Heptachlor was found to decrease from 100% to 

approximately 10% of total 14C material in 1 day (Lu et al. 1975). After 1 day, 1-hydroxychlordene 

epoxide was present as 50% of the total 14C, rose to 70% on day 3, and then remained constant until 

day 13 of the experiment. The heptachlor hydrolysis product, 1-hydroxychlordene, reached a maximum 

of 10% of the total 14C at day 1 and decreased thereafter. A relatively small proportion of heptachlor 

epoxide was formed. Heptachlor epoxide was never found to be >10% of the total 14C in the water 

sample. The authors concluded that the major pathway of heptachlor in aquatic systems is rapid abiotic 

hydrolysis of heptachlor to 1-hydroxychlordene followed by metabolism to 1-hydroxychlordene epoxide 

(Lu et al. 1975). 

Heptachlor is metabolized by the freshwater microcrustacean, Daphnia magna, to heptachlor epoxide or 

1-hydroxychlordene. 1-Hydroxychlordene is then converted to 1-ketochlordene, 1-hydroxy2,3-epoxychlordene, and their glucosides, sulfates, and other conjugates (Feroz et al. 1990). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 99 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.3.2.3 Sediment and Soil 

Incubations of heptachlor with a mixed culture of soil microorganisms for 12 weeks showed slow 

conversion of heptachlor to chlordene, 1-exohydroxychlordene, heptachlor epoxide, and chlordene 

epoxide. A mixed culture of soil microorganisms, obtained from a sandy loamy soil, degraded heptachlor 

epoxide to the less toxic 1-exohydroxychlordene at a rate of 1% per week during the 12-week test period 

(Miles et al. 1971). 

Soil samples that contained heptachlor were taken from five locations selected to represent typical soil 

types and rainfall patterns in portions of the United States. The samples were taken from places where 

subterranean termites were a major problem and where heptachlor was applied for treatment (Carter and 

Stringer 1970). Residues were found in the soil 1, 2, and 3 years after application of heptachlor. 

Relatively high values for 1-hydroxychlordene, representing approximately 60% of the insecticide in the 

soil, were obtained from extracts of a Quincy loamy fine sand from Oregon 2 years after application. 

Significant amounts of 1-hydroxychlordene were also found in extracts of Lakeland sand from Florida. 

Generally, heptachlor epoxide represented only a small fraction of the insecticide present in the soils 

(Carter and Stringer 1970). Because the distribution and penetration of heptachlor were uneven, there 

were large variations in concentration in the soils and therefore, no general trends were recognized (Carter 

and Stringer 1970). 

Loamy soils treated with heptachlor at 25 pounds per 5-inch acre, over a 5-year period from 1958 through 

1962, contained about 5% of the applied dosages in the fall of 1968, primarily in the form of heptachlor 

epoxide. In addition to γ-chlordane and nonachlor, which were present in the original heptachlor 

formulation, two toxic metabolites (heptachlor epoxide and α-chlordane) as well as three unidentified 

compounds were detected, thus indicating the breakdown in soils of heptachlor and related compounds 

(Lichtenstein et al.1970). 

Experiments with thick anaerobically digested waste water sludge at 35EC showed that heptachlor was 

converted to an extractable degradation product that was more persistent than the initial heptachlor. 

About a 50% loss of heptachlor epoxide was found in anaerobic thick sludge after approximately 60 days. 

No information was given as to the identity of the product. No heptachlor epoxide loss occurred in 

aerobic dilute sludge, and only slight heptachlor epoxide loss occurred in anaerobic dilute sludge (Hill 

and McCarty 1967). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 100 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.3.2.4 Other Media 

Heptachlor was reported to degrade up to 45% after 3 weeks of composting. Heptachlor and heptachlor 

epoxide were found in concentrations of 8.5–26 and <3.8 μg/kg of municipal solid waste, respectively. 

Concentrations of biosolid and municipal solid waste compost were recorded at levels <0.23 and 

<0.63 μg/kg for heptachlor and heptachlor epoxide, respectively (Buyuksonmez et al. 2000). 

6.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT 

Reliable evaluation of the potential for human exposure to heptachlor and heptachlor epoxide depends in 

part on the reliability of supporting analytical data from environmental samples and biological specimens. 

Concentrations of heptachlor and heptachlor epoxide 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 

heptachlor and heptachlor epoxide 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 heptachlor and heptachlor epoxide in a 

variety of environmental media are detailed in Chapter 7. 

6.4.1 Air 

Indoor air levels of heptachlor were measured in various homes in Bloomington, Indiana, that had been 

professionally treated with a termiticide either by spraying or subsurface injection. Heptachlor was 

detected at concentrations ranging from 1.1 to 110 ng/m3

 (0.0001–0.007 ppb) (Anderson and Hites 1989). 

Three houses in North Carolina were treated with a termiticide containing both chlordane (0.5%) and 

heptachlor (0.25%). Immediately after treatment, the average ambient air level of heptachlor was 

1.41"0.64 μg/m3 (0.092 ppb). At 12 months post-treatment, the heptachlor level in the air was 

1.00"0.70 μg/m3

 (0.065 ppb) (Wright and Leidy 1982). Heptachlor was detected at levels ranging from 

1.64 to 13.2 ppb in workplace air in 1977 at the Velsicol Chemical Corporation plant in Tennessee that 

manufactured heptachlor (Netzel 1981). No heptachlor epoxide levels in air were detected (Netzel 1981). 

A study of nine households selected on the basis of high pesticide usage in an urban-suburban area in the 

southeastern United States found outdoor air levels of heptachlor ranging from not detectable 

(0.0006 ppb) to 0.003 ppb, with a mean of 0.001 ppb (Lewis et al. 1986). Heptachlor was found in seven 

of nine households at levels in indoor air ranging from not detectable to 0.02 ppb, with a mean of 

0.006 ppb (Lewis et al. 1986). Air samples taken from Corpus Christi, Texas in 1998 had a mean 

heptachlor concentration of 0.04 ng/m3 (Park et al. 2002). Heptachlor was measured in Alabama air from 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 101 

6. POTENTIAL FOR HUMAN EXPOSURE 

January to October 1996. Heptachlor was found in concentrations ranging from 20 to 50 pg/m3 with the 

highest concentrations in the summer months and the lowest concentrations in April and May. No 

heptachlor was detected in October (Jantunen et al. 2000). Heptachlor and heptachlor epoxide were also 

detected in air in Galveston, Texas in concentrations ranging from 6.1 to 77.2 and from not detected to 

30.4 pg/m3

, respectively (Park et al. 2001). 

Since heptachlor was used for termite control, monitoring the levels of heptachlor when applied in a home 

is of interest. In a study of 19 homes where heptachlor was used in the treatment of subterranean termite 

control, a mean concentration of 5 μg/m3 was observed during treatment. After 24 hours, the concentration of heptachlor decreased to about 2 μg/m3

. However, even after 180 days, heptachlor levels remained 

around 2 μg/m3

, which was much higher than the 0.5 μg/m3 mean from before treatment. Concentrations 

of heptachlor were highest in the basement of these homes with mean concentrations of 9 and 2 μg/m3 

during treatment and after 180 days, respectively (Kamble et al. 1992). 

6.4.2 Water 

A statewide survey (December 1985BFebruary 1986) was conducted in Kansas to determine the degree 

and extent of pesticide contamination of drinking water from approximately 100 private farmstead wells. 

Heptachlor was detected in 1% of the wells tested at a concentration range of 0.023–0.026 ppb with an 

average concentration of 0.025 ppb (detection limit=0.02 ppb) (Steichen et al. 1988). 

Heptachlor was included in EPA's Pesticides in Groundwater Database for 17 states and was found in 

6 states: Illinois, Indiana, Missouri, New Jersey, South Carolina, and Virginia. Concentrations of 

heptachlor in groundwater from these six states ranged from 6.6x10-5 to 0.052 ppb (EPA 1992). 

Heptachlor epoxide was included in EPA’s Pesticides in Groundwater Database for 16 states and was 

found in 7 states: Alabama, Illinois, Indiana, Kansas, Massachusetts, South Carolina, and Virginia. 

Concentrations of heptachlor in groundwater from these seven states ranged from a trace to 0.014 ppb 

(EPA 1992). 

Heptachlor and heptachlor epoxide were detected in water column samples at different depths in Lake 

Pontchartrain in New Orleans, Louisiana. Heptachlor was detected in the 1.5-m ebb- and flood-tide 

samples and in the 10-m flood-tide samples at concentrations of 0.6, 9.1, and 9.3 ppt, respectively. 

Heptachlor epoxide was detected in the 1.5-m ebb- and flood-tide samples and in the 10-m flood-tide 

sample at concentrations of 2, 3.9, or 2.5 ppt, respectively (McFall et al. 1985). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 102 

6. POTENTIAL FOR HUMAN EXPOSURE 

Findings from the Nationwide Urban Runoff Program priority pollutant samples collected in 1982 

showed that heptachlor and heptachlor epoxide were detected at a concentration of 0.1 ppb for both 

compounds (Cole et al. 1984). Heptachlor and heptachlor epoxide were detected in 5 and 1%, 

respectively, of the 86 urban storm water runoff samples taken from 15 cities. 

Despite being banned in 1988, heptachlor and heptachlor epoxide are still found in the water. Heptachlor 

was found in concentrations ranging from 180 to 22 ng/sample of lower Missouri River water (Petty et al. 

1995). Heptachlor epoxide was found in samples taken from the Mississippi Delta in May and July of 

1997 at concentrations of about 10 ng/g (Zimmerman et al. 2000). Heptachlor was found in 7% of the 

influent and 10% of the effluent of 84 New York City municipal waste water samples. Concentrations 

were 0.021–0.35 and 0.02–0.447 ng/L, respectively, for the years 1989–1993. Heptachlor epoxide was 

found in 1% the influent and 2% of the effluent out of 84 New York City municipal waste water samples 

in concentrations of 0.012 and 0.018–0.03 μg/L, respectively, for the years 1989–1993 (Stubin et al. 

1996). Heptachlor epoxide was found in 11 out of 242 groundwater samples taken from areas near golf 

courses in concentrations lower than the maximum contaminant level (MCL), 0.16 μg/L (Cohen et al. 

1999). 

Analysis of rain samples demonstrates how heptachlor can be deposited at sites where it was not applied. 

Heptachlor epoxide was detected in rain samples at concentrations ranging from 0.03 to 1 ppt at four 

widely separated sites in Canada from May to October in 1984. The sites are representative of overlake 

and shoreline locations (Strachan 1988). Snowpack samples representing snow accumulation for the 

winter of 1985–1986 were collected at a total of 12 widely distributed sites throughout the Northwest 

Territories, Canada, during the spring of 1986. Heptachlor epoxide was detected at 11 of the 12 sites at 

concentrations ranging from 0.2 to 0.41 ng/L (2x10-4–4x10-4 ppb). The only reasonable source for these 

compounds is long-range atmospheric transport and deposition (Gregor and Gummer 1989). Heptachlor 

was detected in wet precipitation samples (rain/snow) from Lake Erie at a volume-weighted mean 

concentration (based on the total volume collected over the 12-month period) of 0.1 ng/L (1x10-5 ppb) 

(Chan and Perkins 1989). Heptachlor epoxide was detected at volume-weighted mean concentrations of 

0.05 ng/L (5x10-5 ppb), 0.24 ng/L (2.4x10-4 ppb), and 0.02 ng/L (2x10-5 ppb) in wet precipitation samples 

from Lake Superior, Lake Erie, and Lake Ontario, respectively (Chan and Perkins 1989). Heptachlor and 

Heptachlor epoxide were detected in rain water near Galveston Bay, Texas in concentrations ranging as 

high as 139.7 and 155.7 pg/L, respectively (Park et al. 2001). Heptachlor epoxide was found in two of 

eight samples of rain water from horticultural areas in Denmark and in two of eight background areas in 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 103 

6. POTENTIAL FOR HUMAN EXPOSURE 

Denmark at concentrations of above the detection limit (0.011), 0.002, 0.005, and 0.002 μg/L, 

respectively (Hamers et al. 2001). In January 1997, heptachlor was found in rain water in farm, urban, 

and Oakdale samples in Iowa at concentrations of 0.016, 0.011, and 0.0073 μg/L, respectively 

(Hochstedler et al. 2000). 

Data maintained in the STORET database for 2003–2005 included heptachlor and heptachlor epoxide 

concentrations in industrial. Heptachlor was reported in 53% of the 804 water samples taken around the 

country in concentrations ranging from 1 μg/L to below quantification limits. Heptachlor epoxide was 

reported in 49% of the 809 water samples taken around the country in concentrations ranging from 1 μg/L 

to below quantification limits (EPA 2007). 

6.4.3 Sediment and Soil 

Data from the 1971 National Soils Monitoring Program at 1,486 sampling sites in 37 states showed that 

heptachlor was detected in 4.9% of the samples from cropland soils at concentrations ranging from 10 to 

1,370 ppb. Heptachlor epoxide was detected in 6.9% of the samples at concentrations ranging from 

100 to 430 ppb (Carey et al. 1978). A survey of agricultural soils (pasture soils) in the New South Wales 

North Coast region in Australia (1983–1984) showed soils contaminated with organochlorine residues. 

Heptachlor levels in the pasture soils generally averaged <100 ppb. Heptachlor epoxide residues were 

quantitatively higher. Heptachlor and heptachlor epoxide were generally highest in the top 22.5 cm of 

soil (McDougall et al. 1987). Heptachlor epoxide was detected in 17 out of 822 soil samples at 10 out of 

49 agricultural sites in Illinois with a mean concentration of 17 μg/kg. In the same study, heptachlor was 

detected in 26 soil samples from 14 different sites with a mean concentration of 50 μg/kg (Krapac et al. 

1995). Heptachlor was found in 3 out of 39 samples of Alabama soil with a geometric mean 

concentration of 0.037 ng/g. In the same study, heptachlor epoxide was found in 12 of the 26 soil 

samples with a geometric mean concentration of 0.099 ng/g (Harner et al. 1999). 

Heptachlor epoxide was detected in grab and core samples of southern Lake Michigan sediments (period 

of sampling, 1969–1970) at trace levels up to 0.7 ppb (Leland et al. 1973). The U.S. Geological Survey 

investigated the sediment quality of the upper Rockaway River in New Jersey. Sediment samples were 

collected from seven stations along the upper Rockaway River. Stations 1 and 2 drain primarily forested 

areas of the upper Rockaway basin. Stations 3–7 drain an area consisting primarily of residential, 

commercial, and industrial land usage, including six NPL sites. Concentrations of heptachlor epoxide 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 104 

6. POTENTIAL FOR HUMAN EXPOSURE 

were <0.1 ppb for stations 1 and 2. Heptachlor epoxide concentrations ranged from <0.1 to 10 ppb for 

stations 3–7 (Smith et al. 1987). 

Heptachlor and heptachlor epoxide were monitored at six different sites in the sediment of San Pablo Bay, 

California. Heptachlor was not detected in four of the samples, while the other two samples contained 

2.14 and 1.63 μg/kg of heptachlor. Heptachlor epoxide concentrations were below detection levels for all 

six samples (Baum et al. 2001). Heptachlor was found in the sediment of Casco Bay, Washington in 

concentrations ranging from 0.04 to 0.13 ppb (Kennicutt et al. 1994). 

Heptachlor, which may have been applied to the World Trade Center for termite control, was detected in 

concentrations too low to quantify in the dust that settled across lower Manhattan after September 11, 

2001 (Offenberg et al. 2003). 

Heptachlor and heptachlor epoxide have been monitored in all 50 states and parts of Canada by the 

United States Geological Society (USGS). Heptachlor was detected in sediment at 9 out of 1,148 sites in 

49 major hydrological basins at a maximum concentration of 8.3 μg/kg (USGS 2003); these data were 

collected from 1992 to 2001. In the same monitoring study, heptachlor epoxide was detected at 20 of the 

1,148 sites, at a maximum concentration of 19.7 μg/kg. Data maintained in the STORET database for 

2003–2005 included heptachlor and heptachlor epoxide concentrations in industrial effluent and ambient 

water. Heptachlor epoxide was reported in 4 of the 176 sediment samples taken with a maximum 

concentration of 0.621 μg/kg. Heptachlor was not reported in any of the 186 sites reporting data from 

2003 to 2005 (EPA 2007). 

6.4.4 Other Environmental Media 

Heptachlor and heptachlor epoxide have been detected in several aquatic species. Heptachlor was 

measured in shrimp collected from the Calcasieu River/Lake Complex in Louisiana at concentrations 

ranging from 10 to 750 ppb (Murray and Beck 1990). A survey of organic compound concentrations in 

whole body tissues of the Asiatic clam, C. manilensis, was conducted on the Apalachicola River in 

northwest Florida in 1979–1980 as part of the Apalachicola River Quality Assessment. Heptachlor 

epoxide was detected in the whole body tissue of the clam at concentrations ranging from <0.1 to 0.6 ppb, 

with a median concentration of 0.3 ppb (Elder and Mattraw 1984). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 105 

6. POTENTIAL FOR HUMAN EXPOSURE 

Composite whole fish samples taken from tributary rivers around the Great Lakes in 1980–1981 had 

heptachlor levels of <0.002 mg/kg (<2 ppb) at all sites except the Ashtabula River where a maximum 

concentration of 0.30 mg/kg (300 ppb) occurred. Heptachlor epoxide was detected at concentrations 

ranging from 0.003 to 0.48 mg/kg (3–480 ppb) (DeVault 1985). Freshwater fish collected in 1984 for the 

National Contaminant Biomonitoring Program run by the U.S. Fish and Wildlife Service contained a 

geometric mean residue concentration of total heptachlor (heptachlor epoxide plus traces of heptachlor) of 

0.01 ppm (wet weight). Heptachlor residues in fish were present in 49.1% of the collection stations 

(n=112) located at major rivers throughout the United States, including Alaska and Hawaii. 

Concentrations of heptachlor epoxide in whole fish samples remained highest in Hawaii and in the 

Midwest, especially in Lake Michigan and in the Mississippi, Missouri, Ohio, and Illinois Rivers (Schmitt 

et al. 1990). 

Average residue levels of total heptachlor detected in Illinois soybeans in 1980 (6.6 ppb) showed an 

increase from 1974 levels (5.3 ppb), even though the usage of heptachlor declined during that period 

(MacMonegle et al. 1984). Heptachlor residues above maximum residue limits were reported in 

Australian beef in 1987. Upon removing the animals from contaminated pastures, the proportion of 

samples of beef with residue levels above the permitted limits decreased from 0.42% in 1986–1987 to 

0.22% in 1987–1988 (Corrigan and Seneviratna 1989). In an earlier study, heptachlor epoxide levels in 

cow's milk reached a maximum of 0.22 ppm within 3–7 days after the animals had grazed on pastures 

immediately following treatment of the grasses with heptachlor (Gannon and Decker 1960). 

Heptachlor concentrations in pork and beef have decreased from 1974 to 1996. In 1974–1984, heptachlor 

was detected in beef and pork in concentrations of 0.1–54 and 11.2–970 ppb, respectively. By 1988, 

heptachlor was not detected in beef and was detected in 33% of the pork samples studied in concentrations ranging from 1 to 8 ppb with no other detections in pork after 1988. Heptachlor epoxide was 

detected in concentrations of 1.9–2.9 and 0.5–5.9 ppb in pork and beef, respectively, during studies from 

1974 to 1984. During the years 1985–1988, heptachlor epoxide was not detected in pork, but was 

detected in 35% of beef samples at concentrations ranging from 19 to 27 ppb. Heptachlor epoxide was 

still found in 3% of pork samples and 12% of beef samples taken from 1993 to 1996 (Cantoni and Comi 

1997). 

Monitoring data collected by the USGS from 1992 to 2001 at 1,148 sites in 49 U.S. major hydrological 

basins indicated that heptachlor and heptachlor epoxide were infrequently detected in fish (USGS 2003). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 106 

6. POTENTIAL FOR HUMAN EXPOSURE 

Heptachlor was detected in fish at 3 sites at a maximum concentration of 12 μg/kg and heptachlor epoxide 

was detected in fish at 88 sites at a maximum concentration of 270 μg/kg (USGS 2003). 

6.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE 

The general population is primarily exposed to heptachlor and heptachlor epoxide through diet. The food 

classes most likely to contain residues are milk and other dairy products, vegetables, meat, fish, and 

poultry. In the FDA Total Diet Study conducted between 1981 and 1982, levels of chemicals in the diet 

were determined by analyzing samples from retail markets in 13 cities throughout the continental United 

States. These samples represent the typical 14-day diet. Approximately 120 individual food items, 

including drinking water, were collected for each market basket sample; the infant diet consisted of about 

50 of these foods, and the toddler diet included 110. The average daily intake of heptachlor epoxide for 

infants was estimated to be 0.01 μg/kg/day. The 1981–1982 average daily intake of heptachlor epoxide 

for toddlers was reported to be 0.009 μg/kg/day. Whole milk, with an average concentration of 0.1 ppb, 

contributed the highest daily intake of heptachlor epoxide for both toddlers and infants (Gartrell et 

al. 1986b). In the FDA Total Diet Study conducted between 1982 and 1984, analyses were performed of 

234 items depicting the diets of eight population groups with members ranging in age from infants to 

elderly adults. The data represent eight food collections in regional metropolitan areas during the 2-year 

period. Toddlers (2 years old) had the highest daily intake of heptachlor epoxide (6.1 ng/kg/day). Infants 

had a daily intake of heptachlor epoxide of 2.7 ng/kg/day. Daily intake from whole milk was not included 

in this study. Adults had heptachlor epoxide intakes that ranged from 1.5 ng/kg/day (60–65-year-old 

females) to 2.8 ng/kg/day (14–16-year-old males). Heptachlor epoxide was found in 8% of the food 

samples analyzed between 1982 and 1984. Heptachlor intake was <0.1 ng/kg/day for all age/gender 

groups. Between 1980 and 1982–1984, daily intakes of heptachlor epoxide decreased from 19 to 

3 ng/kg/day for infants, from 20 to 6 ng/kg/day for toddlers, and from 7 to 2–3 ng/kg/day for adults 

(Gunderson 1988). Heptachlor epoxide was found in 45 different food items from a total diet study. 

From this information and from questionnaires, it was estimated that heptachlor epoxide was found at a 

mean concentration of 0.3 μg/day in people surveyed in 1990 (MacIntosh et al. 1996). 

The 1988 Acceptable Daily Intake (ADI) established by the United Nation's Food and Agriculture 

Organization and the World Health Organization (FAO/WHO) for total heptachlor was 0.5 μg/kg/day 

(FDA 1989). Total heptachlor intakes found in the Total Diet Analysis (1988) were 0.004 μg/kg/day for 

6–11-month-old infants, 0.017 μg/kg/day for 14–16-year-old males, and 0.0007 μg/kg/day for 60– 

63-year-old females (FDA 1989). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 107 

6. POTENTIAL FOR HUMAN EXPOSURE 

Adipose tissue samples from various body parts of people living in northeast Louisiana, an area of heavy 

agriculture, were taken during pathological examination. Heptachlor epoxide levels in the individual 

tissue samples ranged from 20 to 790 ppb (average=239 ppb) for the 1980 study and from 60 to 220 ppb 

(average=159 ppb) from adipose tissue samples taken from other donors for the 1984 study (Holt et 

al. 1986). 

Heptachlor and heptachlor epoxide have been found in human milk samples (Al-Omar et al. 1986; 

Fytianos et al. 1985; Larsen et al. 1971; Mes et al. 1986; Ritcey et al. 1972; Savage et al. 1981). Breast 

milk samples (n=210) taken from Canadian women from five different regions who had resided in 

Canada for at least 5 years were analyzed for chlorinated hydrocarbon contaminants as part of a 

monitoring program. Trends from 1967 to 1982 showed heptachlor epoxide levels decreased from a 

mean of 3 ppb in 1967 to a mean of <1 ppb in 1982 (maximum, 7 ppb) (Mes et al. 1986). Heptachlor 

epoxide was found in 62% of all samples taken in 1982 (Mes et al. 1986). Human milk samples obtained 

from 1,436 women residing in the United States were analyzed for chlorinated hydrocarbon insecticides. 

While heptachlor was recovered in <2% of the samples, heptachlor epoxide was found in 63% of the 

samples. The proportion of breast milk samples containing heptachlor epoxide varied significantly 

among the five geographic regions (66.1–128 ppb) with the southeastern states having the highest mean 

residual level. The reasons for higher levels of these chemicals in samples from women in the 

southeastern United States are not clear, but there may be several contributing factors. For example, more 

people in the southeast use pesticides in the home, lawn, and garden, and a larger proportion of 

southeastern U.S. homes have been treated with heptachlor for termite control. The mean residual level 

of heptachlor epoxide in breast milk for the whole United States was 91.4 ppb (Savage et al. 1981). A 

5-month follow-up study of four pregnant Iraqi women without occupational exposure to organochlorine 

pesticides found total heptachlor levels in the placenta immediately after delivery ranging from not 

detectable to 28 ppb total tissue weight. Milk samples were then taken for 20 consecutive weeks. 

Average total heptachlor levels in the mothers' milk ranged from 15 to 68 parts per billion parts of whole 

milk (Al-Omar et al. 1986). There was considerable fluctuation in the residue concentrations over the 

20 weeks. The authors suggest that the fluctuations could be attributed to changes in daily diet intake of 

residues and daily variations in milk production and fat content of the milk. 

A pilot study for EPA's Non-Occupational Exposure Study was conducted in August 1985 in order to 

assess nonoccupational exposures to pesticides, including heptachlor, in indoor air and personal 

respiratory air. The study was conducted in nine households selected on the basis of high pesticide usage 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 108 

6. POTENTIAL FOR HUMAN EXPOSURE 

in an urban-suburban area in the southeastern United States. The residents of these households were 

generally retired or semi-retired persons, who spent the majority of their time indoors (average=18 hours) 

and, consequently, do not represent the general adult population. The results showed that heptachlor was 

found in seven of nine households at levels in indoor air ranging from not detectable (at 0.0001 ppb) to 

0.31 μg/m3

 (0.02 ppb), with a mean of 0.088 μg/m3 (0.006 ppb). When residents wore personal monitors, 

operated only during periods of activity, heptachlor was detected in six of nine households at personal 

exposure levels of not detectable to 0.18 μg/m3

 (0.01 ppb), with a mean of 0.06 μg/m3 (0.004 ppb). 

Outdoor air levels of heptachlor were lower, ranging from not detectable to 0.048 μg/m3

 (0.003 ppb), with 

a mean of 0.016 μg/m3

 (0.001 ppb), and were detected in five of nine households (Lewis et al. 1986). 

Heptachlor has been routinely found in human breast milk as well as in animal and commercial milk 

products and has been studied extensively. A 25-year study of contaminants in human breast milk found 

that heptachlor in breast milk of Canadian mothers decreased from 3 ng/g in 1965 to 0.11 ng/g in 1992 

(Craan and Haines 1998). Heptachlor has been detected in milk and umbilical cord fluid of 13.5% of the 

385 mothers tested in the Arctic region of Canada with a mean concentration of 0.6 μg/L (Butler Walker 

et al. 2003). Termite control was associated with high heptachlor body burden as analyzed through breast 

milk in Australia where heptachlor epoxide was found in the breast milk of 575 of the 797 women tested 

in Victoria, Australia with concentration median of 0.007 mg/kg in 1997 (Sim et al. 1998). Average 

heptachlor epoxide levels in whole blood samples from non-occupationally exposed mothers and their 

newborns in Argentina were 0.23"0.29 ppb in 13 mothers and 0.06"0.01 ppb in 13 newborn infants 

(Radomski et al. 1971a). Heptachlor and heptachlor epoxide were found in 50 samples (51.5%) of 

pasteurized milk samples tested in Spain. Of the samples with heptachlor and heptachlor epoxide, eight 

of them contained levels that exceeded the limits stated by the European Union (Martinez et al. 1997). 

Heptachlor and heptachlor epoxide were found in cows’ milk at concentrations of 6.5–28.5 and 8.5– 

34 ng/g, respectively (Armendariz et al. 2004). 

In a study of non-occupationally exposed people in Jacksonville, Florida and Springfield/Chicopee, 

Massachusetts from 1986 to 1988, heptachlor was found in personal, outdoor, and indoor air samples. 

While Springfield/Chicopee did not have any samples that contained heptachlor, the concentration of 

heptachlor in samples from Jacksonville ranged from 0.1 to 0.8 ng/m3

 (Whitmore et al. 1994). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 109 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.6 EXPOSURES OF CHILDREN 

This section focuses on exposures from conception to maturity at 18 years in humans. Differences from 

adults in susceptibility to hazardous substances are discussed in Section 3.7, Children’s Susceptibility. 

Children are not small adults. A child’s exposure may differ from an adult’s exposure in many ways. 

Children drink more fluids, eat more food, breathe more air per kilogram of body weight, and have a 

larger skin surface in proportion to their body volume. A child’s diet often differs from that of adults. 

The developing human’s source of nutrition changes with age: from placental nourishment to breast milk 

or formula 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). 

Infants and toddlers are exposed to higher levels (based on their greater dose to surface area [or body 

weight] ratio) of heptachlor epoxide in the diet (particularly from milk) than are adults. Higher exposure 

rates in indoor air may occur for at least 1 year in homes that have been treated for termites with 

heptachlor in the past. Although the most likely routes of exposure at hazardous waste sites are unknown, 

exposure may result from ingestion of contaminated soil near these sites particularly by children. Since 

both heptachlor and heptachlor epoxide volatilize from soil, inhalation exposure may also be important 

for persons living near hazardous waste sites. Exposure via ingestion of contaminated drinking water 

obtained from wells near hazardous waste sites is unlikely. Heptachlor and heptachlor epoxide are 

considered too lipophilic to leach to groundwater. While some samples have been found in well water, 

this trend is not universal. Workers involved in the manufacture of heptachlor and in the application of 

heptachlor for fire ant control are at risk of exposure to heptachlor. People living in the southeastern 

United States may be exposed to higher than background levels of heptachlor or heptachlor epoxide 

because of the larger proportion of southeastern U.S. homes that have been treated with heptachlor for 

termite control and the greater usage of pesticides in the home, lawn, and garden. Infants living in this 

region may be more likely to ingest heptachlor or heptachlor epoxide from maternal breast milk, although 

this exposure pathway is not restricted to the southeastern United States. 

The average daily intake of heptachlor epoxide for infants was estimated to be 0.01 μg/kg/day. The 

1981–1982 average daily intake of heptachlor epoxide for toddlers was reported to be 0.009 μg/kg/day. 

Whole milk, with an average concentration of 0.1 ppb, contributed the highest daily intake of heptachlor 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 110 

6. POTENTIAL FOR HUMAN EXPOSURE 

epoxide for both toddlers and infants (Gartrell et al. 1986b). In the FDA Total Diet Study conducted 

between 1982 and 1984, analyses were performed of 234 items depicting the diets of eight population 

groups with members ranging in age from infants to elderly adults. The data represent eight food 

collections in regional metropolitan areas during the 2-year period. Toddlers (2 years old) had the highest 

daily intake of heptachlor epoxide (6.1 ng/kg/day). Infants had a daily intake of heptachlor epoxide of 

2.7 ng/kg/day. The 1988 Acceptable Daily Intake (ADI) established by the United Nation's Food and 

Agriculture Organization and the World Health Organization (FAO/WHO) for total heptachlor was 

0.5 μg/kg/day (FDA 1989). Total heptachlor intakes found in the Total Diet Analysis (1988) were 

0.004 μg/kg/day for 6–11-month-old infants, 0.017 μg/kg/day for 14–16-year-old males, and 

0.0007 μg/kg/day for 60–63-year-old females (FDA 1989). 

Heptachlor epoxide was found in whole blood samples from nonoccupationally exposed mothers and 

their newborns in Argentina (Radomski et al. 1971a). The average level of heptachlor epoxide was 

0.23"0.29 ppb in 13 mothers and 0.06"0.01 ppb in 13 newborn infants, although no blood samples were 

taken from the mothers during pregnancy (Radomski et al. 1971a). 

In order to understand the exposure of children to pesticides, studies have been done to monitor pesticide 

levels in areas and food that are specific to children. Heptachlor was not detected in apple, pear, squash, 

or carrot baby food. Both organic and traditional manufacturers were studied (Moore et al. 2000). 

Studies of school areas along the Mexican-Texas border found heptachlor in 63% of all soil samples 

tested in concentrations ranging from a trace to 5 ppb (Miersma et al. 2003). Heptachlor was one of the 

most frequent chemicals found in a study of children’s exposure to pesticides and was found in 8/9 home 

dust samples, 3/8 play areas, and 3/4 children’s hand rinse samples (Lewis et al. 1994). In a study of 

pesticide exposure of children of farmworkers in Virginia and North Carolina, heptachlor was found in 

10% of the floors at a mean concentration of 2 μg/m2

. Heptachlor, however, was not detected on any of 

the toys or hands of the children (Quandt et al. 2004). 

6.7 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES 

Data concerning occupational exposure levels of heptachlor are very limited. An industrial hygiene 

survey conducted in 1977 at the Velsicol Chemical Corporation, Memphis, Tennessee, a plant that 

manufactured heptachlor, detected heptachlor in workplace air at levels ranging from 0.025 to 

0.202 mg/m3

 (1.64–13.2 ppb) (Netzel 1981). Data from the National Occupational Exposure Survey 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 111 

6. POTENTIAL FOR HUMAN EXPOSURE 

(NOES) conducted by NIOSH from 1981 to 1983 were not available for heptachlor or heptachlor 

epoxide. 

People who worked with pesticides from 1954 to 1988, such as farmers and pest control workers, were at 

potentially higher risk of being exposed to heptachlor and heptachlor epoxide. People who worked in 

termite control before 1988 may have higher exposures to heptachlor since it was commonly used as a 

pesticide in the treatment of termites. High concentrations of heptachlor were found on applicators’ 

hands and forearms with exposure rates calculated at 83 and 23 ng/cm2

/hour (Kamble et al. 1992). 

Heptachlor was not found in the blood of Japanese termite control workers in 1987, 1 year after 

chlordane, which contained heptachlor, was banned in Japan. Heptachlor epoxide, however, was found in 

all of the Japanese termite workers monitored from 1987 to 1990. The highest level of heptachlor 

epoxide was in the blood of a worker who had been working in pest control for 20 years and almost all of 

the workers still had heptachlor epoxide in their blood in 1990 (Jitunari et al. 1995). A study showed that 

farmers and their spouses in Iowa and North Carolina were exposed to heptachlor epoxide at 

concentration ranges of 0.21–0.55 ng/mL. With the exception of two of the spouses, everyone in the 

study had exposure limits of 0.21 ng/mL or greater as analyzed from serum concentrations (Brock et al. 

1998). 

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 heptachlor and heptachlor epoxide 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 heptachlor and heptachlor epoxide. 

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. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 112 

6. POTENTIAL FOR HUMAN EXPOSURE 

6.8.1 Identification of Data Needs 

Physical and Chemical Properties. The physical and chemical properties of heptachlor and 

heptachlor epoxide are sufficiently well defined to allow assessments of the environmental fate of the 

compounds to be made (ACGIH 1986; Chapman 1989; HSDB 2007a; MacKay 1982). Some physical 

and chemical properties of heptachlor epoxide that are not relevant to environmental fate are lacking. 

Knowledge of these properties, such as odor, flashpoint, and flammability limits, would be useful for 

workers involved in the manufacture, use, or clean-up of heptachlor and heptachlor epoxide. 

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. 

The United States International Trade Commission (USITC) did not report separate import data for 

heptachlor for the years 1981, 1982, or 1983 (USITC 1982a, 1983a, 1984a). The sale, distribution, and 

shipment of existing stocks of all canceled heptachlor products were prohibited by EPA in 1988 (EPA 

1990a). According to the USITC, no heptachlor has been imported into the United States from 1996 

through 2007 (USITC 2007). 

Currently, heptachlor use in the United States is limited to fire ant control in power transformers (EPA 

1990a). However, because of former widespread use of heptachlor and the persistence of heptachlor 

epoxide, these compounds and their degradation products can still be found at low levels in indoor air, 

water, soil, and food. Disposal methods are well documented in the literature (EPA 1986b; Sittig 1985); 

however, more current information would be useful. Information on historical disposal practices would 

be helpful in evaluating the potential for environmental contamination. More information on the volume 

of heptachlor used in fire ant control would be useful in estimating potential occupational exposure. 

Environmental Fate. Heptachlor and heptachlor epoxide are partitioned to the air, water, and soil 

(EPA 1987; Jury et al. 1987; Lichtenstein et al. 1970; Shivankar and Kavadia 1989). They are both 

transported in air and water and sorb to soils and sediment (Chapman 1989; MacKay 1982). They are 

biotransformed in soil and surface water, with biotransformation occurring faster for heptachlor than for 

heptachlor epoxide. Current data on the biotransformation (including half-life data) of both compounds 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 113 

6. POTENTIAL FOR HUMAN EXPOSURE 

in surface water, surface soil, and subsurface soil would be useful in assessing the environmental 

persistence of these substances. Data on the toxicity of the biotransformation products of both 

compounds would assist in better characterizing the potential public health threat. Both heptachlor and 

heptachlor epoxide undergo photolysis (Graham et al. 1973; Ivie et al. 1972; Podowski et al. 1979). Data 

regarding the half-lives for photolysis would be helpful in determining the persistence of both 

compounds. 

Bioavailability from Environmental Media. The limited pharmacokinetic data indicate that both 

compounds are absorbed following inhalation, oral, and dermal exposure (Arthur et al. 1975; Gaines 

1969; Harradine and McDougall 1986). Additional information on the absorption of these compounds 

following inhalation and following ingestion of contaminated drinking water and soil would be useful in 

evaluating the relative importance of various routes of exposure to populations living in the vicinity of 

hazardous waste sites and those whose homes have been treated for termites with heptachlor or chlordane. 

Food Chain Bioaccumulation. Heptachlor and heptachlor epoxide accumulate in aquatic and 

terrestrial organisms (Elder and Mattraw 1984; Murray and Beck 1990; Schmitt et al. 1990). 

Biomagnification of heptachlor and heptachlor epoxide in aquatic food chains is significant (Connell et al. 

2002; Cullen and Connell 1994; Geyer et al. 1982; Hawker and Connell 1986). Because heptachlor is 

readily metabolized to heptachlor epoxide by higher trophic level organisms, biomagnification of 

heptachlor itself is not significant (Feroz et al. 1990). Because of the more persistent nature of heptachlor 

epoxide and its lipophilicity, biomagnification of heptachlor epoxide in terrestrial food chains is 

significant (Connell et al. 2002; Cullen and Connell 1994; Hartley and Johnston 1983). More current 

information regarding biomagnification of heptachlor epoxide in terrestrial food chains would be helpful 

in evaluating the extent of environmental contamination. 

Exposure Levels in Environmental Media. Reliable monitoring data for the levels of heptachlor 

and heptachlor epoxide in contaminated media at hazardous waste sites are needed so that the information 

obtained on levels of heptachlor and heptachlor epoxide in the environment can be used in combination 

with the known body burden of heptachlor and heptachlor epoxide to assess the potential risk of adverse 

health effects in populations living in the vicinity of hazardous waste sites. 

Heptachlor and heptachlor epoxide have been detected in indoor and outdoor air, surface water, 

groundwater, soil, sediment, food (Larsen et al. 1971; Lewis et al. 1986; MacIntosh et al. 1996; Park et al. 

2002; USGS 2003), and fish (USGS 2003). Current monitoring data on levels of both compounds in 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 114 

6. POTENTIAL FOR HUMAN EXPOSURE 

outdoor and indoor air and soil would be useful. Dietary intake data for the general population were 

located (FDA 1989; Gartrell et al. 1986b; Gunderson 1988; MacIntosh et al. 1996). Intake data for other 

media (air and water) are needed to estimate the risk of exposure of the general population. 

Exposure Levels in Humans. Heptachlor epoxide has been detected in human blood, tissues 

(including adipose tissue), and breast milk (Al-Omar et al. 1986; Butler Walker et al. 2003; Craan and 

Haines 1998; Holt et al. 1986; Larsen et al. 1971; Savage et al. 1981). The presence of heptachlor 

epoxide is used as an indicator of exposure to heptachlor. Current monitoring studies of heptachlor 

epoxide in these tissues and fluids would be helpful in assessing the extent to which populations, 

particularly in the vicinity of hazardous waste sites, have been exposed to heptachlor. Reliable data 

regarding heptachlor levels in the elderly were not found. The elderly who may have been exposed to 

heptachlor have reduced capability to eliminate toxicants. 

This information is necessary for assessing the need to conduct health studies on these populations. 

Exposures of Children. Heptachlor levels have been monitored in human breast milk as well as 

baby food (Moore et al. 2000). Heptachlor exposure of children at the Mexican-American border was 

studied as well as the exposure of children of farm workers and children whose homes were treated for 

termites (Lewis et al. 1994; Miersma et al. 2003; Quandt et al. 2004). Current monitoring studies of 

heptachlor and heptachlor epoxide in blood, fluids and tissues of children would be helpful in assessing 

the extent to which populations, particularly in the vicinity of hazardous waste sites, have been exposed to 

heptachlor. 

Child health data needs relating to susceptibility are discussed in Section 3.12.2, Identification of Data 

Needs: Children’s Susceptibility. 

Exposure Registries. No exposure registries for heptachlor 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. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 115 

6. POTENTIAL FOR HUMAN EXPOSURE 

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. The only 

current study pertaining to heptachlor was of the direct and indirect photolytic fate of persistent organic 

pollutants in Arctic surface waters. The principal investigator of this study is Yu-Ping Chin of Ohio State 

University. This research is funded by the National Science Foundation (NSF). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 116 

6. POTENTIAL FOR HUMAN EXPOSURE 

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HEPTACHLOR AND HEPTACHLOR EPOXIDE 117 

7. ANALYTICAL METHODS 

The purpose of this chapter is to describe the analytical methods that are available for detecting, 

measuring, and/or monitoring heptachlor and heptachlor epoxide, their metabolites, and other biomarkers 

of exposure and effect to heptachlor and heptachlor epoxide. 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 

Analytical methods exist for measuring heptachlor, heptachlor epoxide, and/or their metabolites in 

various tissues (including adipose tissue), blood, human milk, urine, and feces. The common method 

used is gas chromatography (GC) coupled with electron capture detection (ECD) followed by 

identification using GC/mass spectrometry (MS). Since evidence indicates that heptachlor is metabolized 

to heptachlor epoxide in mammals, exposure to heptachlor is usually measured by determining levels of 

heptachlor epoxide in biological media. A summary of the detection methods used for various biological 

media is presented in Table 7-1. 

Heptachlor and heptachlor epoxide are measured in adipose tissue, blood, and serum using GC/ECD 

(Adeshina and Todd 1990; Burse et al. 1990; Polishuk et al. 1977a, 1977b; Radomski et al. 1971a, 1971b) 

and identified by GC/MS (LeBel and Williams 1986). Sample preparation steps for adipose tissue vary 

but, in general, involve a lipid extraction step followed by a clean-up procedure involving gel permeation 

chromatography (GPC) and/or Florisil column clean-up. Using GPC with methylene chloride and 

cyclohexane as solvents, individual organochlorine contaminants can be separated from adipose tissue to 

produce extracts clean enough for direct GC analysis. Clean-up efficiency using GPC is 99.9% (LeBel 

and Williams 1986). The sensitivity obtained using GC/ECD is in the low-ppb range. Recoveries for 

heptachlor are adequate (72–87%); recoveries for heptachlor epoxide are good (84–98%). Precision is 

good for both (Adeshina and Todd 1990; LeBel and Williams 1986). The preparation step used for 

measuring heptachlor epoxide in blood and serum involves lipid extraction, clean-up with column 

chromatography, and elution with acetonitrile, hexane, and methylene chloride (Burse et al. 1990; 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 118 

7. ANALYTICAL METHODS 

Table 7-1. Analytical Methods for Determining Heptachlor and Heptachlor 

Epoxide in Biological Materials 

Sample Analytical Sample detection Percent 

matrix Preparation method method limit recovery Reference 

Adipose Lipid extraction with GC/ECD; 1.4 ng/g (heptachlor); 72–87% LeBel and 

tissue acetone-hexane; GC/MS 1.1 ng/g (heptachlor (heptachlor); Williams 

fractionation from fat by epoxide) 86–98% 1986 

gel permeation chromato- (heptachlor 

graphy; Florisil column epoxide) 

clean-up. 

Adipose Lipid extraction with GC/ECD 0.001 ppm 84% Adeshina 

tissue petroleum ether; (heptachlor epoxide) and Todd 

concentration; clean-up 1990 

on Florisil column. 

Human liver Grind liver tissue and GC/ECD NR NR Radomski et 

and brain extract with petroleum al. 1968 

tissue ether. Dry brain tissue 

and grind with petroleum 

ether. Centrifuge and 

inject. 

Human Homogenize. Extract with GC/ECD NR NR Klemmer et 

tissues hexane containing al. 1977 

anhydrous sodium sulfate. 

Evaporate. Redissolve in 

hexane. Clean-up on 

Florisil. 

Blood Lipid extraction with GC/ECD NR NR Polishuk et 

chloroform/methanol; al. 1977a, 

clean-up with column 1977b 

chromatography; elution 

with acetonitrile, hexane 

and methylene chloride. 

Serum Add methanol and extract GC/ECD NR 80–96% Burse et al. 

with hexane/ethyl ether. 1990 

Clean-up on Florisil 

column. Acid treatment 

and clean-up on silica gel 

column. 

Human milk Homogenize with chloro- GC/ECD NR NR Polishuk et 

form/methanol; lipid al. 1977b 

extract with petroleum 

ether or hexane; clean-up 

by column chromatography; elution with 

acetonitrile, hexane, and 

methylene chloride. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 119 

7. ANALYTICAL METHODS 

Table 7-1. Analytical Methods for Determining Heptachlor and Heptachlor 

Epoxide in Biological Materials 

Sample Analytical Sample detection Percent 

matrix Preparation method method limit recovery Reference 

Human milk Lipid extraction with GC/ECD 0.001 ppm NR Ritcey et al. 

acetone-hexane. (heptachlor epoxide) 1972 

Dissolve in benzeneacetone. Clean-up on 

Florisil. Elute with 

dichloromethanepetroleum ether. 

Concentrate and add 

hexane. 

Urine and Extract with acetone and GC/ECD NR NR Tashiro and 

feces hexane. Combine Matsumura 

(heptachlor, solvents and concentrate. 1978 

heptachlor Mix with silicic acid and air 

epoxide, dry. Clean-up on Florisil 

and column and silicic acid 

metabolites) column. Metabolites 

extracted into hexane for 

GC analysis. 

ECD = electron capture detector; GC = gas chromatography; MS = mass spectrometry; NR = not reported 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 120 

7. ANALYTICAL METHODS 

Polishuk et al. 1977a, 1977b). Recovery is adequate (80–96%). Precision is good (9–15%). Sensitivity 

was not reported (Burse et al. 1990). 

GC/ECD and GC equipped with a microcoulometric detector have been used to determine heptachlor and 

heptachlor epoxide in a variety of human tissues, including the liver, brain, adrenals, lungs, heart, 

kidneys, spleen, and pancreas (Curley et al. 1969; Klemmer et al. 1977; Radomski et al. 1968). Details of 

a sample preparation method were not reported for GC equipped with a microcoulometric detector 

(Curley et al. 1969). Sample preparation steps for GC/ECD include homogenization, extraction with 

petroleum ether or hexane, usually followed by a clean-up procedure (Klemmer et al. 1977; Radomski et 

al. 1968). Recovery, sensitivity, and precision data were not reported (Curley et al. 1969; Klemmer et al. 

1977; Radomski et al. 1968). 

Heptachlor and heptachlor epoxide have been measured in samples of human milk using GC/ECD and 

GC/MS (Mussalo-Rauhamaa et al. 1988; Polishuk et al. 1977b; Ritcey et al. 1972). Sample preparation 

steps for milk involve homogenization with chloroform/methanol, lipid extraction with petroleum ether, 

hexane or acetone-hexane, clean-up by column chromatography, and elution with acetonitrile, hexane, 

methylene chloride, or dichloromethane-petroleum ether. Precision, accuracy, and sensitivity were not 

reported for most of the studies; however, one study reported a sensitivity in the low-ppb range (Ritcey et 

al. 1972). 

Heptachlor, heptachlor epoxide, and their metabolites have been measured in urine and feces using 

GC/ECD (Tashiro and Matsumura 1978). Sample preparation steps involve extraction with acetone and 

hexane, clean-up on Florisil and silicic acid columns, and extraction of the derivatized metabolites into 

hexane for GLC analysis. Precision, accuracy, and sensitivity were not reported (Tashiro and Matsumura 

1978). 

7.2 ENVIRONMENTAL SAMPLES 

Methods exist for measuring heptachlor and heptachlor epoxide in air, water, soil, and food. The most 

common methods are GC/ECD and GC/MS. A summary of methods for detecting heptachlor and 

heptachlor epoxide in various environmental samples is presented in Table 7-2. 

Heptachlor is measured in indoor and outdoor air samples using GC/ECD and GC/MS (Anderson and 

Hites 1989; Leone et al. 2000; Lewis et al. 1986; Savage 1989). Heptachlor has also been measured in 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 121 

7. ANALYTICAL METHODS 

Table 7-2. Analytical Methods for Determining Heptachlor and Heptachlor Epoxide 

in Environmental Samples 

Sample Analytical Sample Percent 

matrix Preparation method method detection limit recovery Reference 

Outdoor air Sample collected with low-volume 

sampler consisting of a constant 

flow pump and a cartridge 

containing polyurethane foam. 

Extract with diethylether in hexane. 

Indoor air Sample collected with a 

polyurethane foam plug sampler. 

Soxhlet extraction with petroleum 

ether. 

House dust Sample collected with high-volume 

surface sampler; extract with diethyl 

ether in hexane. 

Water Extract with methylene chloride. 

Waste water Extract with methylene chloride; 

exchange to hexane. 

Waste water Extract with methylene chloride 

Drinking Extract with methylene chloride; 

water solvent exchange to methyl tertbutyl ether. 

Soil/ Extract with methylene chloride; 

sediment clean-up extract. 

and solid 

waste

Foodstuff Lipid extraction with automated gel 

(butterfat) permeation chromatography; direct 

injection. 

Milk Extract on solid-matrix disposable 

columns by means of acetonitrilesaturated light petroleum; Florisil7

clean-up. 

Water and Extracted with ethyl acetate; dried 

soft drink with sodium sulfate and then 

evaporated before taken up in 

methanol water solvent mixture 

GC/ECD; 0.0006 ppb 99% Lewis et al. 

GC/MS (heptachlor) 1986 

GC/ECD <3 ppt NR Leone et al. 

2000 

GC/ECD; NR NR Roberts and 

GC/MS (heptachlor) Camann 1989 

GC/MS NR 52B68% Alford-Stevens 

(heptachlor) et al. 1988 

GC/ECD 0.003 μg/L 69% EPA 1994a 

(EPA (heptachlor); (heptachlor); 

Method 0.083 μg/L 89% 

8080) (heptachlor (heptachlor 

epoxide) epoxide) 

GC/MS 1.9 μg/L 87% EPA 1994b 

(EPA (heptachlor); (heptachlor); 

Method 2.2 μg/L 92% 

8250) (heptachlor (heptachlor 

epoxide) epoxide) 

GC/ECD 0.01 μg/L 99% Lopez-Avila et 

(EPA (heptachlor); (heptachlor); al. 1990 

Method 0.015 μg/L 95% 

508) (heptachlor (heptachlor 

epoxide) epoxide) 

GC/MS 1.9 μg/L 87% EPA 1994a 

(EPA (heptachlor); (heptachlor); 

Method 2.2 μg/L 92% 

8250) (heptachlor (heptachlor 

epoxide) epoxide) 

GC/ECD NR 100% Hopper and 

(heptachlor Griffitt 1987 

epoxide) 

GC/ECD NR 99% DiMuccio et al. 

(heptachlor 1988 

epoxide) 

LC/MS/MS NR NR Chandramouli 

et al. 2004 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 122 

7. ANALYTICAL METHODS 

Table 7-2. Analytical Methods for Determining Heptachlor and Heptachlor Epoxide 

in Environmental Samples 

Sample Analytical Sample Percent 

matrix Preparation method method detection limit recovery Reference 

Water Extract placed on extraction well SPE-GC- 0.01–2.5 μg/L 90–99% Li et al. 

plates loaded with sorbent; MS (heptachlor) 2000 

standard solutions were added 

before injecting onto column 

Water 800 mL extracted with hexane; GC/MS 0.5 μg/L NR Canadian 

extract concentrated and Ministry of the 

reconstituted in toluene Environment 

2003 

ECD = electron capture detector; EPA = Environmental Protection Agency; GC = gas chromatography; LC = liquid 

chromatograph; MS = mass spectrometry; NR = not reported; SPE = solid phase extraction 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 123 

7. ANALYTICAL METHODS 

house dust (Roberts and Camann 1989). Preparation methods involve the use of a variety of air trapping 

samplers. Examples of these include the Greenburg-Smith impinger, Chromosorb 102, low-volume 

samplers, and the Millipore miniature vacuum pump with a sampling tube. The next step includes 

extraction with diethyl ether, acetone-hexane, or toluene (Anderson and Hites 1989; Roberts and Camann 

1989). For indoor air, sensitivity is in the sub-ppt range (Leone et al. 2000). For outdoor air, precision is 

good (13%) and recovery is excellent (99%). Sensitivity is in the sub-ppb range (Lewis et al. 1986). 

Heptachlor and heptachlor epoxide are measured in water, drinking water, waste water, soil/sediment, and 

solid waste using GC/ECD, GC/MS, and liquid chromatography (LC)/MS/MS (Alford-Stevens et al. 

1988; Canadian Ministry of the Environment 2003; Chandramouli et al. 2004; EPA 1994a, 1994b; 

Lopez-Avila et al. 1990; McDougall et al. 1987; Smith et al. 1987). Preparation of water, waste water, 

and drinking water samples involves extraction with methylene chloride, concentration, and solvent 

exchange to hexane or methyl tert-butyl ether. Mean recovery in water for heptachlor was low (52–68%) 

and precision was poor (48–57%) (Alford-Stevens et al. 1988). Poor recovery and precision data were 

thought to be attributable to chromatographic problems in some of the participating laboratories. For 

drinking water (EPA Method 508), recovery was excellent for heptachlor (99%) and heptachlor epoxide 

(95%). Precision was excellent for both compounds (<10%). Sensitivity was in the sub-ppb range 

(Lopez-Avila et al. 1990). Preparation of soil/sediment or solid waste samples involves extraction with 

methylene chloride, methylene chloride-acetone, methylene chloride-methanol, or acetone-hexane 

followed by clean-up with Florisil or GPC (Alford-Stevens et al. 1988; EPA 1994a). Overall precision 

was adequate to poor, ranging from 19 to 47% for heptachlor. Recovery and sensitivity were not reported 

(Alford-Stevens et al. 1988). EPA Test Methods 8080 and 8250 for evaluating waste water, soil 

sediment, and solid waste report sensitivity in the low-ppb range for both heptachlor and heptachlor 

epoxide (EPA 1994a, 1994b). Recovery for heptachlor is adequate (69–87%) and recovery for heptachlor 

epoxide is good (89–92%). Precision is adequate for both methods (EPA 1994a, 1994b). 

GC/ECD is the method used to detect heptachlor and heptachlor epoxide in foods (butterfat, fruits, 

vegetables, milk, and animal feed) (Di Muccio et al. 1988; Hopper and Griffitt 1987; Korfmacher et al. 

1987; Ober et al. 1987; Santa Maria et al. 1986). Preparation methods vary for the different types of 

foods. The sample preparation method for butterfat involves GPC. GPC is a rapid clean-up technique for 

separating pesticide residues from a lipid extract. It was developed into an automated clean-up apparatus 

for use on a wide variety of fats and oils. The automated GPC system is reproducible and reliable. After 

being cleaned on GPC, most samples can be analyzed by GC without additional clean-up (Hopper and 

Griffitt 1987). Recovery is complete (100%), and precision is very good (<3%). Sensitivity is in the sub­
HEPTACHLOR AND HEPTACHLOR EPOXIDE 124 

7. ANALYTICAL METHODS 

ppm range. The sample preparation for milk samples involves selective extraction on solid-matrix 

disposable columns by means of acetonitrile-saturated light petroleum, followed by Florisil column cleanup. Recovery is excellent (99%); precision is very good (<7%) (Di Muccio et al. 1988). Sample 

preparation for fruits, vegetables, and animal feed involves cyclic steam distillation extraction in hexane 

or isooctane with direct injection into the gas chromatograph. Recoveries for this method are very low 

(15–50%). This is an indication that heptachlor is not extracted quantitatively by steam distillation and is 

not a recommended preparation method (Ober et al. 1987; Santa Maria et al. 1986). 

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 heptachlor and heptachlor epoxide 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 heptachlor and heptachlor epoxide. 

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. 

Exposure. Methods exist for determining levels of heptachlor, heptachlor epoxide, and/or their 

metabolites in various tissues (including adipose tissues) (Adeshina and Todd 1990; Curley et al. 1969; 

Klemmer et al. 1977; LeBel and Williams 1986; Radomski et al. 1968), milk (Mussalo-Rauhamaa et al. 

1988; Polishuk et al. 1977b; Ritcey et al. 1972), blood (Polishuk et al. 1977a, 1977b), serum (Burse et al. 

1990), urine, and feces (Tashiro and Matsumura 1978). Methods for determining levels in adipose tissue 

are sensitive for measuring levels at which health effects might occur as well as background levels in the 

population. Methods for determining heptachlor and heptachlor epoxide in adipose tissue are relatively 

precise. Recovery is better for heptachlor epoxide than for heptachlor. Data on the determination of 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 125 

7. ANALYTICAL METHODS 

heptachlor and heptachlor epoxide in tissues, blood, serum, milk, urine, and feces are limited as precision, 

recovery, and/or sensitivity data were not reported for the existing methods. More information on the 

precision, accuracy, and sensitivity of these methods is needed to evaluate the value of using levels of 

heptachlor and heptachlor epoxide as biomarkers of exposure. 

Effect. There is no known effect of heptachlor or heptachlor epoxide that can be quantitatively related to 

exposure. 

Methods for Determining Parent Compounds and Degradation Products in Environmental 

Media. Existing methods for determining levels of heptachlor in air are sensitive enough to measure 

background levels in the environment, as well as levels at which health effects might occur. Data on the 

determination of heptachlor and heptachlor epoxide in air (Anderson and Hites 1989; Leone et al. 2000; 

Lewis et al. 1986; Roberts and Camann 1989; Savage 1989), water (Alford-Stevens et al. 1988; EPA 

1994a, 1994b; Lopez-Avila et al. 1990), soil (EPA 1994b; McDougall et al. 1987; Smith et al. 1987), and 

food (Di Muccio et al. 1988; Hopper and Griffitt 1987; Korfmacher et al. 1987; Ober et al. 1987; Santa 

Maria et al. 1986) are limited. Information on the accuracy, precision, and sensitivity of these methods 

would permit better assessment of the risk of low-level environmental exposure for these media. A 

preparation method for fruit and vegetable analysis that provides increased recovery would allow better 

assessment of the risk of dietary exposure. Research investigating the relationship between levels 

measured in air, water, soil, and food and observed health effects could increase our confidence in 

existing methods and/or indicate where improvements are needed. 

7.3.2 Ongoing Studies 

No ongoing studies regarding analytical methods were located for heptachlor or heptachlor epoxide. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 126 

7. ANALYTICAL METHODS 

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HEPTACHLOR AND HEPTACHLOR EPOXIDE 127 

8. REGULATIONS AND ADVISORIES 

The international and national regulations and guidelines regarding heptachlor and heptachlor epoxide in 

air, water, and other media are summarized in Table 8-1. 

ATSDR derived an acute-duration oral MRL of 0.0006 mg/kg/day for heptachlor. This MRL was based 

on a LOAEL of 1.8 mg/kg/day for impaired reproductive performance in female rats mated with 

unexposed males (Amita Rani and Krishnakumari 1995), an uncertainty factor of 1,000 (10 for use of a 

LOAEL, 10 for extrapolation from animals to humans, and 10 for human variability), and a modifying 

factor of 3 for the use of a serious end point. 

ATSDR derived an intermediate-duration oral MRL of 0.0001 mg/kg/day for heptachlor. This MRL was 

based on a minimal LOAEL of 0.03 mg/kg/day for developmental immunological and neurological 

effects in rats (Moser et al. 2001; Smialowicz et al. 2001) and an uncertainty factor of 300 (3 for use of a 

minimal LOAEL, 10 for extrapolation from animals to humans, and 10 for human variability). 

EPA (IRIS 2005) has derived an oral reference dose (RfD) for heptachlor of 5x10-4 mg/kg/day based on 

NOAEL of 0.15 mg/kg/day and LOAEL of 0.25 mg/kg/day for increased liver weight in rats exposed to 

heptachlor for 2 years and an uncertainty factor of 300 (10 for extrapolation from animals to humans, 

10 for human variability, and 3 to account for limitations in the database particularly the lack of a chronic 

study in a second species). 

EPA (IRIS 2005) also derived an RfD of 1.3x10-5 mg/kg/day for heptachlor epoxide. This RfD is based 

on a LOAEL of 0.0125 mg/kg/day for increased relative liver weight identified in a dog study submitted 

to EPA by Dow Chemical Company and an uncertainty factor of 1,000 to account for inter and 

intraspecies extrapolation and because a NOAEL was not attained. The studies which serve as the basis 

of the RfDs for heptachlor and heptachlor epoxide were not discussed in the toxicological profile because 

they were submitted to EPA under FIFRA and are not publicly available. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 128 

8. REGULATIONS AND ADVISORIES 

Table 8-1. Regulations and Guidelines Applicable to Heptachlor and Heptachlor 

Epoxide 

Agency Description Information Reference 

INTERNATIONAL 

Guidelines: 

 IARC Carcinogenicity classification 

Heptachlor Group 2Ba 

WHO Air quality guidelines No data 

Drinking water quality guidelines Guideline values have 

not been establishedb 

NATIONAL 

Regulations and Guidelines: 

a. Air 

ACGIH TLV-TWA 

Heptachlorc

 0.05 mg/m3 

Heptachlor epoxidec

 0.05 mg/m3 

EPA Hazardous air pollutant 

Heptachlor Yes 

NIOSH REL (10-hour TWA) 

Heptachlord,e 0.5 mg/m3

 IDLH 

Heptachlor 35 mg/m3 

OSHA PEL (8-hour TWA) for general industry 

Heptachlorf

 0.5 mg/m3 

PEL (8-hour TWA) for construction industry 

Heptachlorf

 0.5 mg/m3 

PEL (8-hour TWA) for shipyard industry 

Heptachlorf

 0.5 mg/m3 

b. Water 

EPA Designated as hazardous substances in 

accordance with Section 311 of the Clean 

Water Act 

Heptachlor Yes 

Drinking-water health advisories 

Heptachlor 

1-day health advisory for a 10-kg childg

 0.01 mg/L 

10-day health advisory for a 10-kg childh 0.01 mg/L 

DWELi

 0.02 mg/L 

10-4 Cancer riskj

 0.0008 mg/L 

IARC 2004 

WHO 2000 

WHO 2004 

ACGIH 2004 

EPA 2004b 

42 USC 7412 

NIOSH 2005 

OSHA 2005c 

29 CFR 

1910.1000 

OSHA 2005b 

29 CFR 1926.55 

OSHA 2005a 

29 CFR 

1915.1000 

EPA 2005a 

40 CFR 116.4 

EPA 2004a 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 129 

8. REGULATIONS AND ADVISORIES 

Table 8-1. Regulations and Guidelines Applicable to Heptachlor and Heptachlor 

Epoxide 

Agency Description Information Reference 

NATIONAL (cont.) 

EPA Drinking-water health advisories 

Heptachlor epoxide 

1-day health advisory for a 10-kg childg

10-day health advisory for a 10-kg childh 

DWELi

10-4 Cancer riskj

National primary drinking water regulationsk 

Heptachlor 

MCL 

MCLG 

Heptachlor epoxide 

MCL 

MCLG 

Reportable quantities of hazardous 

substances designated pursuant to 

Section 311 of the Clean Water Act 

Heptachlor 

Water quality criteria for human health 

consumption of: 

Heptachlorl 

Water + organism 

Organism only 

Heptachlor epoxidel 

Water + organism 

Organism only 

c. Food 

FDA Action level 

Heptachlor 

Artichokes; asparagus; Brassica (cole) 

leafy vegetables; bulb vegetables; cereal 

grains; citrus fruits; eggs; figs; fruiting 

vegetables; leafy vegetables; legume 

vegetables; peanuts; pome fruits; root 

and tuber vegetables; salsify tops; small 

fruits and berries; stone fruits; and 

sugarcane 

Cottonseed, cucurbit vegetables, 

pineapple, and rabbit (fat basis) 

Fish (edible portion)

Milk (fat basis) 

0.01 mg/L 

No data 

 0.0004 mg/L 

 0.0004 mg/L 

0.0004 mg/L 

Zero 

0.0002 mg/L 

Zero 

1 pound 

7.9x10-5 

7.9x10-5 

3.9x10-5 

3.9x10-5 

0.01 ppm 

0.02 ppm 

0.3 ppm 

0.1 ppm 

EPA 2004a 

EPA 2002a 

EPA 2005b 

40 CFR 117.3 

EPA 2002b 

FDA 2000 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 130 

8. REGULATIONS AND ADVISORIES 

Table 8-1. Regulations and Guidelines Applicable to Heptachlor and Heptachlor 

Epoxide 

Agency Description Information Reference 

NATIONAL (cont.) 

FDA Bottled water 

Heptachlor 

Heptachlor epoxide 

d. Other 

 ACGIH Carcinogenicity classification 

Heptachlor 

Heptachlor epoxide 

EPA Carcinogenicity classification 

Heptachlor 

Heptachlor epoxide 

RfC 

Heptachlor 

Heptachlor epoxide 

RfD 

Heptachlor 

Heptachlor epoxide 

Inhalation unit risk 

Heptachlor 

Heptachlor epoxide 

 Oral slope factor 

Heptachlor 

Heptachlor epoxide 

Superfund, emergency planning, and 

community right-to-know 

Designated CERCLA hazardous substance 

Heptachloro 

Reportable quantity 

RCRA waste number 

Heptachlor epoxidep 

Reportable quantity 

RCRA waste number 

Effective date of toxic chemical release 

reporting 

Heptachlor 

FDA 2004 

0.0004 mg/L 21 CFR 165.110 

0.0002 mg/L 

ACGIH 2004

A3m 

A3m 

IRIS 2005 

B2n 

B2n

Not available at this time 

Not available at this time 

5.0x10-4 mg/kg/day 

1.3x10-5 mg/kg/day 

1.3x10-3 per ug/m3 

2.6x10-3 per ug/m3

4.5 per mg/kg-day 

9.1 per mg/kg-day 

EPA 2005c 

40 CFR 302.4 

1 pound 

P059 

1 pound 

No data 

EPA 2005e 

40 CFR 372.65 

01/01/87 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 131 

8. REGULATIONS AND ADVISORIES 

Table 8-1. Regulations and Guidelines Applicable to Heptachlor and Heptachlor 

Epoxide 

Agency Description Information Reference 

NATIONAL (cont.) 

Threshold amounts for manufacturing EPA 2005d 

(including importing), processing, and 40 CFR 372.28 

otherwise using such toxic chemicals 

Heptachlor 10 pounds 

NTP Carcinogenicity classification No data NTP 2005 

a

Group 2B: possibly carcinogenic to humans b

Guideline values have not been established: heptachlor and heptachlor epoxide occurs in drinking water at 

concentrations well below those at which heptachlor epoxide toxic effects may occur. c

Skin notation: refers to the potential significant contribution to the overall exposure by the cutaneous route, including 

mucous membranes and the eyes, either by contact with vapors or, of probable greater significance, by direct skin 

contact with the substance. d

Potential occupational carcinogen e

Skin designation: indicates the potential for dermal absorption; skin exposure should be prevented as necessary 

through the use of good work practices and gloves, coveralls, goggles, and other appropriate equipment. f

Skin designation 

g

1-Day health advisory: the concentration of a chemical in drinking water that is not expected to cause any adverse 

noncarcinogenic effects for up to 1 day of exposure. The 1-day health advisory is normally designed to protect a 

10-kg child consuming 1 liter of water per day. h

10-Day health advisory: the concentration of a chemical in drinking water that is not expected to cause any adverse 

noncarcinogenic effects for up to 10 days of exposure. The 10-day health advisory is also normally designed to 

protect a 10-kg child consuming 1 liter of water per day. i

DWEL: a lifetime exposure concentration protective of adverse, noncancer health effects that assumes all of the 

exposure to a contaminant is from drinking water. 

j

10-4 Cancer risk: the concentration of a chemical in drinking water corresponding to an excess estimated lifetime 

cancer risk of 1 in 10,000. k

Potential health effects from ingestion of water include liver damage and increased risk of cancer. The contaminant 

in drinking water is the residue of a banned termiticide (heptachlor) and the breakdown of heptachlor from epoxide 

heptachlor. l

This criterion is based on carcinogenicity of 10-6 risk. mA3: not classifiable as a human carcinogen n

B2: probable human carcinogen o

Heptachlor: designated CERCLA hazardous substance pursuant to Section 311(b)(2) and 307(a) of the Clean 

Water Act, Section 112 of the Clean Air Act, and Section 3001 of RCRA. p

Heptachlor epoxide: designated CERCLA hazardous substance pursuant to Section 307(a) of the Clean Water Act. 

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 contaminat level; MCLG = maximum contaminant level goal; NIOSH = National Institute for 

Occupational Safety and Health; NTP = National Toxicology Program; OSHA = Occupational Safety and Health 

Administration; PEL = permissible exposure limit; RCRA = Resource Conservation and Recovery Act; 

REL = recommended exposure limit; RfC = inhalation reference concentration; RfD = oral reference dose; 

TLV = threshold limit values; TWA = time-weighted average; USC = United States Code; WHO = World Health 

Organization 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 132 

8. REGULATIONS AND ADVISORIES 

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HEPTACHLOR AND HEPTACHLOR EPOXIDE 133 

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HEPTACHLOR AND HEPTACHLOR EPOXIDE 153 

10. GLOSSARY 

Absorption—The taking up of liquids by solids, or of gases by solids or liquids. 

Acute Exposure—Exposure to a chemical for a duration of 14 days or less, as specified in the 

Toxicological Profiles. 

Adsorption—The adhesion in an extremely thin layer of molecules (as of gases, solutes, or liquids) to the 

surfaces of solid bodies or liquids with which they are in contact. 

Adsorption Coefficient (Koc)—The ratio of the amount of a chemical adsorbed per unit weight of 

organic carbon in the soil or sediment to the concentration of the chemical in solution at equilibrium. 

Adsorption Ratio (Kd)—The amount of a chemical adsorbed by sediment or soil (i.e., the solid phase) 

divided by the amount of chemical in the solution phase, which is in equilibrium with the solid phase, at a 

fixed solid/solution ratio. It is generally expressed in micrograms of chemical sorbed per gram of soil or 

sediment. 

Benchmark Dose (BMD)—Usually defined as the lower confidence limit on the dose that produces a 

specified magnitude of changes in a specified adverse response. For example, a BMD10 would be the 

dose at the 95% lower confidence limit on a 10% response, and the benchmark response (BMR) would be 

10%. The BMD is determined by modeling the dose response curve in the region of the dose response 

relationship where biologically observable data are feasible. 

Benchmark Dose Model—A statistical dose-response model applied to either experimental toxicological 

or epidemiological data to calculate a BMD. 

Bioconcentration Factor (BCF)—The quotient of the concentration of a chemical in aquatic organisms 

at a specific time or during a discrete time period of exposure divided by the concentration in the 

surrounding water at the same time or during the same period. 

Biomarkers—Broadly defined as indicators signaling events in biologic systems or samples. They have 

been classified as markers of exposure, markers of effect, and markers of susceptibility. 

Cancer Effect Level (CEL)—The lowest dose of chemical in a study, or group of studies, that produces 

significant increases in the incidence of cancer (or tumors) between the exposed population and its 

appropriate control. 

Carcinogen—A chemical capable of inducing cancer. 

Case-Control Study—A type of epidemiological study that examines the relationship between a 

particular outcome (disease or condition) and a variety of potential causative agents (such as toxic 

chemicals). In a case-controlled study, a group of people with a specified and well-defined outcome is 

identified and compared to a similar group of people without outcome. 

Case Report—Describes a single individual with a particular disease or exposure. These may suggest 

some potential topics for scientific research, but are not actual research studies. 

Case Series—Describes the experience of a small number of individuals with the same disease or 

exposure. These may suggest potential topics for scientific research, but are not actual research studies. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 154 

10. GLOSSARY 

Ceiling Value—A concentration of a substance that should not be exceeded, even instantaneously. 

Chronic Exposure—Exposure to a chemical for 365 days or more, as specified in the Toxicological 

Profiles. 

Cohort Study—A type of epidemiological study of a specific group or groups of people who have had a 

common insult (e.g., exposure to an agent suspected of causing disease or a common disease) and are 

followed forward from exposure to outcome. At least one exposed group is compared to one unexposed 

group. 

Cross-sectional Study—A type of epidemiological study of a group or groups of people that examines 

the relationship between exposure and outcome to a chemical or to chemicals at one point in time. 

Data Needs—Substance-specific informational needs that if met would reduce the uncertainties of human 

health assessment. 

Developmental Toxicity—The occurrence of adverse effects on the developing organism that may result 

from exposure to a chemical prior to conception (either parent), during prenatal development, or 

postnatally to the time of sexual maturation. Adverse developmental effects may be detected at any point 

in the life span of the organism. 

Dose-Response Relationship—The quantitative relationship between the amount of exposure to a 

toxicant and the incidence of the adverse effects. 

Embryotoxicity and Fetotoxicity—Any toxic effect on the conceptus as a result of prenatal exposure to 

a chemical; the distinguishing feature between the two terms is the stage of development during which the 

insult occurs. The terms, as used here, include malformations and variations, altered growth, and in utero 

death. 

Environmental Protection Agency (EPA) Health Advisory—An estimate of acceptable drinking water 

levels for a chemical substance based on health effects information. A health advisory is not a legally 

enforceable federal standard, but serves as technical guidance to assist federal, state, and local officials. 

Epidemiology—Refers to the investigation of factors that determine the frequency and distribution of 

disease or other health-related conditions within a defined human population during a specified period. 

Genotoxicity—A specific adverse effect on the genome of living cells that, upon the duplication of 

affected cells, can be expressed as a mutagenic, clastogenic, or carcinogenic event because of specific 

alteration of the molecular structure of the genome. 

Half-life—A measure of rate for the time required to eliminate one half of a quantity of a chemical from 

the body or environmental media. 

Immediately Dangerous to Life or Health (IDLH)—The maximum environmental concentration of a 

contaminant from which one could escape within 30 minutes without any escape-impairing symptoms or 

irreversible health effects. 

Immunologic Toxicity—The occurrence of adverse effects on the immune system that may result from 

exposure to environmental agents such as chemicals. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 155 

10. GLOSSARY 

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. 

Mortality—Death; mortality rate is a measure of the number of deaths in a population during a specified 

interval of time. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 156 

10. GLOSSARY 

Mutagen—A substance that causes mutations. A mutation is a change in the DNA sequence of a cell’s 

DNA. Mutations can lead to birth defects, miscarriages, or cancer. 

Necropsy—The gross examination of the organs and tissues of a dead body to determine the cause of 

death or pathological conditions. 

Neurotoxicity—The occurrence of adverse effects on the nervous system following exposure to a 

chemical. 

No-Observed-Adverse-Effect Level (NOAEL)—The dose of a chemical at which there were no 

statistically or biologically significant increases in frequency or severity of adverse effects seen between 

the exposed population and its appropriate control. Effects may be produced at this dose, but they are not 

considered to be adverse. 

Octanol-Water Partition Coefficient (Kow)—The equilibrium ratio of the concentrations of a chemical 

in n-octanol and water, in dilute solution. 

Odds Ratio (OR)—A means of measuring the association between an exposure (such as toxic substances 

and a disease or condition) that represents the best estimate of relative risk (risk as a ratio of the incidence 

among subjects exposed to a particular risk factor divided by the incidence among subjects who were not 

exposed to the risk factor). An OR of greater than 1 is considered to indicate greater risk of disease in the 

exposed group compared to the unexposed group. 

Organophosphate or Organophosphorus Compound—A phosphorus-containing organic compound 

and especially a pesticide that acts by inhibiting cholinesterase. 

Permissible Exposure Limit (PEL)—An Occupational Safety and Health Administration (OSHA) 

allowable exposure level in workplace air averaged over an 8-hour shift of a 40-hour workweek. 

Pesticide—General classification of chemicals specifically developed and produced for use in the control 

of agricultural and public health pests. 

Pharmacokinetics—The dynamic behavior of a material in the body, used to predict the fate 

(disposition) of an exogenous substance in an organism. Utilizing computational techniques, it provides 

the means of studying the absorption, distribution, metabolism, and excretion of chemicals by the body. 

Pharmacokinetic Model—A set of equations that can be used to describe the time course of a parent 

chemical or metabolite in an animal system. There are two types of pharmacokinetic models: data-based 

and physiologically-based. A data-based model divides the animal system into a series of compartments, 

which, in general, do not represent real, identifiable anatomic regions of the body, whereas the 

physiologically-based model compartments represent real anatomic regions of the body. 

Physiologically Based Pharmacodynamic (PBPD) Model—A type of physiologically based doseresponse model that quantitatively describes the relationship between target tissue dose and toxic end 

points. These models advance the importance of physiologically based models in that they clearly 

describe the biological effect (response) produced by the system following exposure to an exogenous 

substance. 

Physiologically Based Pharmacokinetic (PBPK) Model—Comprised of a series of compartments 

representing organs or tissue groups with realistic weights and blood flows. These models require a 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 157 

10. GLOSSARY 

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. 

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. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 158 

10. GLOSSARY 

Risk Factor—An aspect of personal behavior or lifestyle, an environmental exposure, or an inborn or 

inherited characteristic that is associated with an increased occurrence of disease or other health-related 

event or condition. 

Risk Ratio—The ratio of the risk among persons with specific risk factors compared to the risk among 

persons without risk factors. A risk ratio greater than 1 indicates greater risk of disease in the exposed 

group compared to the unexposed group. 

Short-Term Exposure Limit (STEL)—The American Conference of Governmental Industrial 

Hygienists (ACGIH) maximum concentration to which workers can be exposed for up to 15 minutes 

continually. No more than four excursions are allowed per day, and there must be at least 60 minutes 

between exposure periods. The daily Threshold Limit Value-Time Weighted Average (TLV-TWA) may 

not be exceeded. 

Standardized Mortality Ratio (SMR)—A ratio of the observed number of deaths and the expected 

number of deaths in a specific standard population. 

Target Organ Toxicity—This term covers a broad range of adverse effects on target organs or 

physiological systems (e.g., renal, cardiovascular) extending from those arising through a single limited 

exposure to those assumed over a lifetime of exposure to a chemical. 

Teratogen—A chemical that causes structural defects that affect the development of an organism. 

Threshold Limit Value (TLV)—An American Conference of Governmental Industrial Hygienists 

(ACGIH) concentration of a substance to which most workers can be exposed without adverse effect. 

The TLV may be expressed as a Time Weighted Average (TWA), as a Short-Term Exposure Limit 

(STEL), or as a ceiling limit (CL). 

Time-Weighted Average (TWA)—An allowable exposure concentration averaged over a normal 8-hour 

workday or 40-hour workweek. 

Toxic Dose(50) (TD50)—A calculated dose of a chemical, introduced by a route other than inhalation, 

which is expected to cause a specific toxic effect in 50% of a defined experimental animal population. 

Toxicokinetic—The absorption, distribution, and elimination of toxic compounds in the living organism. 

Uncertainty Factor (UF)—A factor used in operationally deriving the Minimal Risk Level (MRL) or 

Reference Dose (RfD) or Reference Concentration (RfC) from experimental data. UFs are intended to 

account for (1) the variation in sensitivity among the members of the human population, (2) the 

uncertainty in extrapolating animal data to the case of human, (3) the uncertainty in extrapolating from 

data obtained in a study that is of less than lifetime exposure, and (4) the uncertainty in using lowestobserved-adverse-effect level (LOAEL) data rather than no-observed-adverse-effect level (NOAEL) data. 

A default for each individual UF is 10; if complete certainty in data exists, a value of 1 can be used; 

however, a reduced UF of 3 may be used on a case-by-case basis, 3 being the approximate logarithmic 

average of 10 and 1. 

Xenobiotic—Any chemical that is foreign to the biological system. 
HEPTACHLOR AND HEPATCHLOR EPOXIDE 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. 

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 
HEPTACHLOR AND HEPATCHLOR EPOXIDE A-2 

APPENDIX A 

are not expected to cause adverse health effects. Most MRLs contain a degree of uncertainty because of 

the lack of precise toxicological information on the people who might be most sensitive (e.g., infants, 

elderly, nutritionally or immunologically compromised) to the effects of hazardous substances. ATSDR 

uses a conservative (i.e., protective) approach to address this uncertainty consistent with the public health 

principle of prevention. Although human data are preferred, MRLs often must be based on animal studies 

because relevant human studies are lacking. In the absence of evidence to the contrary, ATSDR assumes 

that humans are more sensitive to the effects of hazardous substance than animals and that certain persons 

may be particularly sensitive. Thus, the resulting MRL may be as much as 100-fold below levels that 

have been shown to be nontoxic in laboratory animals. 

Proposed MRLs undergo a rigorous review process: Health Effects/MRL Workgroup reviews within the 

Division of Toxicology and Environmental Medicine, expert panel peer reviews, and agency-wide MRL 

Workgroup reviews, with participation from other federal agencies and comments from the public. They 

are subject to change as new information becomes available concomitant with updating the toxicological 

profiles. Thus, MRLs in the most recent toxicological profiles supersede previously published levels. 

For additional information regarding MRLs, please contact the Division of Toxicology and 

Environmental Medicine, Agency for Toxic Substances and Disease Registry, 1600 Clifton Road NE, 

Mailstop F-32, Atlanta, Georgia 30333. 
HEPTACHLOR AND HEPATCHLOR EPOXIDE A-3 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: Heptachlor 

CAS Numbers: 76-44-8 

Date: August 2007 

Profile Status: Final 

Route: [ ] Inhalation [X] Oral 

Duration: [X] Acute [ ] Intermediate [ ] Chronic 

Graph Key: 19 

Species: Rat 

Minimal Risk Level: 0.0006 [X] mg/kg/day [ ] ppm 

Reference: Amita Rani BE, Krishnakumari MK. 1995. Prenatal toxicity of heptachlor in albino rats. 

Pharmacol Toxicol 76(2):112-114. 

Experimental design: Groups of 30 female CFT-Wistar rats received gavage doses of heptachlor in 

groundnut oil for 14 days (presumably 7 days/week). The total administered doses were 25 and 50 mg/kg 

body weight; the daily doses were 1.8 and 3.6 mg/kg/day; a vehicle control group was also used. After 

14 days of exposure, the animals were mated with controls. 

Effect noted in study and corresponding doses: A significant decrease in the number of pregnant females 

(56.3 and 44.4%) and increase in the number of resorptions (18.90 and 11.40%) were observed in both 

groups of heptachlor-exposed rats. Significant decreases in estradiol-17beta and progesterone levels were 

also observed in the 1.8 mg/kg/day group. No alterations in the number of implantations were observed. 

The investigators noted that focal necrosis was observed in the liver; however, they did not note at which 

dose level and no incidence data were provided. 

Dose and end point used for MRL derivation: The MRL is based on a serious LOAEL of 1.8 mg/kg/day 

for reproductive effects. 

[ ] NOAEL [X] LOAEL 

Uncertainty Factors used in MRL derivation: 1,000 

[X] 10 for use of a LOAEL 

[X] 10 for extrapolation from animals to humans 

[X] 10 for human variability 

Modifying Factor used in MRL derivation: 3 

[X] 3 for use of a serious end point 

Was a conversion factor used from ppm in food or water to a mg/body weight dose? No. 

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? No. 
HEPTACHLOR AND HEPATCHLOR EPOXIDE A-4 

APPENDIX A 

Other additional studies or pertinent information that lend support to this MRL: Several targets of 

toxicity have been identified, in addition to the impaired reproductive performance observed in the Amita 

Rani and Krishnakumari (1995) study. These include the liver, nervous system, and developing 

offspring. Gestational exposure to 4.5 or 6.8 mg/kg/day resulted in decreases in pup body weight 

(Narotsky and Kavlock 1995; Narotsky et al. 1995) and a decrease in pup righting reflex was observed at 

4.2 mg/kg/day (Purkerson-Parker et al. 2001b). At twice these dose levels, an increase in pup mortality 

was observed (Narotsky et al. 1995; Purkerson-Parker et al. 2001b). Liver effects were observed at doses 

similar to those resulting in developmental effects. Increases in serum alanine aminotransferase and 

aldolase activity levels, hepatocytomegaly, and minimal monocellular necrosis were observed in rats 

administered 7 mg/kg/day heptachlor in oil for 14 days (Berman et al. 1995; Krampl 1971). Exposure to 

7 mg/kg/day also resulted in excitability and increased arousal in rats administered heptachlor in oil via 

gavage for 1 or 14 days (Moser et al. 1995). 

Agency Contacts (Chemical Managers): Zemoria Rosemond, B.A.; G. Daniel Todd, Ph.D.; Malcolm 

Williams, D.V.M., Ph.D. 
HEPTACHLOR AND HEPATCHLOR EPOXIDE A-5 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: Heptachlor 

CAS Numbers: 76-44-8 

Date: June 2007 

Profile Status: Final 

Route: [ ] Inhalation [X] Oral 

Duration: [ ] Acute [X] Intermediate [ ] Chronic 

Graph Key: 49 

Species: Rat 

Minimal Risk Level: 0.0001 [X] mg/kg/day [ ] ppm 

Reference: Smialowicz RJ, Williams WC, Copeland CB, et al. 2001. The effects of perinatal/juvenile 

heptachlor exposure on adult immune and reproductive system function in rats. Toxicol Sci 61(1):164­

175. 

Moser VC, Shafer TJ, Ward TR, et al. 2001. Neurotoxicological outcomes of perinatal heptachlor 

exposure in the rat. Toxicol Sci 60(2):315-326. 

Experimental design: Groups of 15–20 pregnant Sprague Dawley rats were administered via gavage 0, 

0.03, 0.3, or 3 mg/kg/day heptachlor in corn oil on gestational day 12 through postnatal day 7; pups were 

also exposed from postnatal day 7 to 21 or 42. Neurobehavorial assessment consisted of righting reflex 

on postnatal days 2–5, functional observational battery test, motor activity, passive avoidance test of 

learning and memory, and Morris water maze to assess spatial and working memory. The liver, kidneys, 

adrenals, thymus, spleen, ovaries, uterus/vagina, testes, epididymides, seminal vesicles/coagulating 

glands, and ventral and dorsolateral prostate were histologically examined in 15–17 offspring from each 

group on postnatal day 46. The following immunological tests were performed in the 8-week-old 

offspring: splenic lymphoproliferative (LP) responses to T cell mitogens (e.g., concanavalin A [ConA], 

phytohemagglutinin [PHA]) and to allogeneic cells in a mixed lymphocyte reaction, primary IgM 

antibody response to sheep red blood cells, examination of splenic lymphocytes subpopulations, and 

delayed-type and contact hypersensitivity. Reproductive assessment included evaluation of vaginal 

opening (index of female puberty) and prepuce separation (index of male puberty) beginning at postnatal 

days 25 and 35, respectively. The offspring were mated with an untreated mate and the dams were 

allowed to rear the first litter to postnatal day 10. The results of the neurobehavioral assessment were 

reported by Moser et al. (2001); the remaining results were reported by Smialowicz et al. (2001). 

Effect noted in study and corresponding doses: No significant alterations in maternal body weight, 

number of dams delivering litters, litter size, or pup survival were observed. Additionally, no alterations 

in pup growth rates, age at eye opening, anogenital distance, or age at vaginal opening or preputial 

separation were observed. A significant decrease in pup body weight at postnatal day 1 was observed at 

3 mg/kg/day; this effect was not observed at postnatal days 7, 14, or 21. No consistent, statistically 

significant alterations in offspring body weights were observed at postnatal days 21, 28, 35, or 42. 

Significant alterations in absolute and relative liver weights were observed in males and females exposed 

to 3 mg/kg/day; increases in absolute and relative ovary weights were also observed at 3 mg/kg/day. No 

histological alterations were observed in the examined tissues. No alterations in fertility were observed in 

the adult males and females mated to untreated partners, and no effects on soft tissue or gross body 

structure of the offspring (F2 generation) were observed. No alterations in sperm count or sperm motility 

were observed. 
HEPTACHLOR AND HEPATCHLOR EPOXIDE A-6 

APPENDIX A 

Righting was significantly delayed in the female offspring of rats exposed to 3 mg/kg/day heptachlor; no 

significant alterations were observed in the male offspring. The investigators suggested that this was due 

to a delay in the ontogeny of righting rather than an inability to perform the task. The following 

significant alterations in the FOB and motor activity tests were found in the offspring dosed until 

postnatal day 21: increased open field activity in 3 mg/kg/day males, non-dose-related increased activity 

in figure-eight chambers in females (significant only in 0.03 mg/kg/day group), and faster decline in 

habituation of activity in 3 mg/kg/day males. Alterations in the offspring dosed until postnatal day 42 

included: increased levels of urination in males in the 0.03 and 0.3 mg/kg/day groups, increased landing 

foot splay in males in the 0.03 mg/kg/day group, and removal reactivity in males and females in the 

0.03 mg/kg/day group. No alterations in the passive avoidance test were observed in the offspring 

exposed until postnatal day 21; in those exposed until postnatal day 42, an increase in the number of nose 

pokes was observed in all groups of females. No significant alterations in performance on the water maze 

test were found in the offspring exposed until postnatal day 21. In those exposed until postnatal day 42, 

increases in latency to find the platform were observed in males and females exposed to 3 mg/kg/day and 

increases in the time spent in the outer zone were found in males exposed to 0.3 or 3 mg/kg/day. In the 

water maze memory trial, no differences in performance were found between controls and animals 

exposed until postnatal day 21. Alterations in significant quadrant bias were observed in 0.03, 0.3, and 

3 mg/kg/day males during the first probe test and in 0.3 and 3 mg/kg/day males and 3 mg/kg/day females 

in the second probe test. The study investigators noted that the heptachlor-exposed rats did not develop 

an efficient search strategy for locating the platform; they spent more time circling the outer zone of the 

tank. By the second week of the test, control rats had learned to venture into the zone where the platform 

was located. 

A dose-related, statistically significant suppression of primary IgM antibody response to sRBC was found 

in males, but not females. The primary IgM response to sRBCs was reduced in 21-week-old males 

exposed to 0.3 mg/kg/day. A second immunization with sRBCs administered 4 weeks later resulted in a 

significant reduction in IgG antibody response in males administered 0.03, 0.3, or 3 mg/kg/day 

heptachlor; no response was seen in females. A decrease in the OX12+

OX19- (i.e., B/plasma cells) 

population was also found in the spleen of males exposed to 3 mg/kg/day. No alterations in the following 

immunological parameters assessed at 8 weeks of age were found: lymphoid organ weights, splenic NK 

cell activity, splenic cellularity or cell viability, and lymphoproliferative responses of splenic lymphocytes 

to T-cell mitogens ConA and PHA or to allogenic cells in the mixed lymphocyte reaction. The results of 

this portion of the study suggest that exposure to heptachlor adversely affects the development of the 

immune system. 

Dose and end point used for MRL derivation: The MRL is based on a minimal LOAEL of 

0.03 mg/kg/day for developmental immunological and neurological effects. The observed alterations 

were considered to be minimally adverse and suggestive of immunotoxicity and neurotoxicity. 

[ ] NOAEL [X] LOAEL 

Uncertainty Factors used in MRL derivation: 

[X] 3 for use of a minimal 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? No. 

If an inhalation study in animals, list conversion factors used in determining human equivalent dose: Not 

applicable. 
HEPTACHLOR AND HEPATCHLOR EPOXIDE A-7 

APPENDIX A 

Was a conversion used from intermittent to continuous exposure? No. 

Other additional studies or pertinent information that lend support to this MRL: The results of the 

Smialowicz et al. (2001) study suggest that exposure to heptachlor adversely affects the development of 

the immune system. A framework for testing a chemical’s potential to induce developmental 

immunotoxicological effects has not been established. Based on the results of studies in mature animals 

(Luster et al. 1992), two panels of government, industry, and academia immunotoxicology experts 

(Holsapple et al. 2005; Luster et al. 2003) reached a consensus that assays measuring the response to a 

T-cell dependent antigen (e.g., sheep red blood cells) should be included in included in a developmental 

immunotoxicology protocol. In mature animals, the sheep red blood cells antibody plague-forming cell 

test was the most reliable single test predictor of immunotoxicity (Luster et al. 1992). 

Intermediate-duration oral exposure studies have identified a number of targets of heptachlor toxicity 

including the liver, nervous system, reproductive system, and the developing offspring. Other less 

documented effects have also been observed. The developing organism appears to be the most sensitive 

target. In the absence of maternal toxicity, heptachlor is not associated with alterations in pup mortality 

or body weight gain (Lawson and Luderer 2004; Purkerson-Parker et al. 2001b; Smialowicz et al. 2001) 

or alterations in the development of the reproductive system (Lawson and Luderer 2004; Smialowicz et 

al. 2001). In contrast, heptachlor appears to adversely affect the development of the nervous and immune 

systems. The observed effects include impaired spatial memory at 0.03 mg/kg/day and higher (Moser et 

al. 2001), impaired spatial learning at 0.3 mg/kg/day and higher (Moser et al. 2001), and decreased in 

righting reflex (Moser et al. 2001; Purkerson-Parker et al. 2001b) and increased open field activity (Moser 

et al. 2001) at 3 mg/kg/day. These effects were observed in rats exposed in utero, during lactation, and 

postnatally until day 42; spatial memory and learning were not adversely affected when the exposure was 

terminated at postnatal day 21 (Moser et al. 2001). The conflicting results may have resulted in the higher 

heptachlor epoxide body burden in rats exposed to postnatal day 42, testing at different ages, or exposure 

may have occurred during a critical window of vulnerability. The effects observed in rats are consistent 

with those observed in humans. Impaired performance on several neurobehavioral tests, including 

abstract concept formation, visual perception, and motor planning, was observed in high school students 

presumably prenatally exposed to heptachlor from contaminated milk products (Baker et al. 2004b). 

Alterations in immune function were also observed in the rats exposed until postnatal day 42. At 

0.03 mg/kg/day and higher, suppression of the immune response to sheep red blood cells was observed 

(Smialowicz et al. 2001). A reduction in the percentage of B lymphocytes was also observed in the 

spleen of rats exposed to 3 mg/kg/day. Other tests of immune function were not significantly altered. 

The liver effects observed in rats or mice exposed to heptachlor in the diet include increased liver weights 

(Izushi and Ogata 1990; Pelikan 1971), increased serum alanine aminotransferase levels (Izushi and 

Ogata 1990), steatosis (Pelikan 1971), and hepatitis and necrosis (Akay and Alp 1981). The lowest 

LOAEL values for these effects range from 5 to 8.4 mg/kg/day. Neurological signs such as 

hyperexcitability, seizures, and difficulty standing, walking, and righting were observed at similar dose 

levels; LOAELs ranged from 1.7 to 17 mg/kg/day (Akay and Alp 1981; Aulerich et al. 1990; Crum et al. 

1993). The reproductive system appeared to be more sensitive to heptachlor toxicity. Decreases in 

epididymal sperm count were observed in rats administered 0.65 mg/kg/day heptachlor in groundnut oil 

for 70 days (Amita Rani and Krishnakumari 1995). This dose also resulted in increased resorptions when 

the exposed males were mated with unexposed females. Infertility was observed in all mice exposed to 

8.4 mg/kg/day heptachlor for 10 weeks (Akay and Alp 1981). 

Agency Contacts (Chemical Managers): Zemoria Rosemond, B.A.; G. Daniel Todd, Ph.D.; Malcolm 

Williams, D.V.M., Ph.D. 
HEPTACHLOR AND HEPATCHLOR EPOXIDE A-8 

APPENDIX A 

This page is intentionally blank. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE B-1 

APPENDIX B. USER'S GUIDE 

Chapter 1 

Public Health Statement 

This chapter of the profile is a health effects summary written in non-technical language. Its intended 

audience is the general public, especially people living in the vicinity of a hazardous waste site or 

chemical release. If the Public Health Statement were removed from the rest of the document, it would 

still communicate to the lay public essential information about the chemical. 

The major headings in the Public Health Statement are useful to find specific topics of concern. The 

topics are written in a question and answer format. The answer to each question includes a sentence that 

will direct the reader to chapters in the profile that will provide more information on the given topic. 

Chapter 2 

Relevance to Public Health 

This chapter provides a health effects summary based on evaluations of existing toxicologic, 

epidemiologic, and toxicokinetic information. This summary is designed to present interpretive, weightof-evidence discussions for human health end points by addressing the following questions: 

1. What effects are known to occur in humans? 

2. What effects observed in animals are likely to be of concern to humans? 

3. What exposure conditions are likely to be of concern to humans, especially around hazardous 

waste sites? 

The chapter covers end points in the same order that they appear within the Discussion of Health Effects 

by Route of Exposure section, by route (inhalation, oral, and dermal) and within route by effect. Human 

data are presented first, then animal data. Both are organized by duration (acute, intermediate, chronic). 

In vitro data and data from parenteral routes (intramuscular, intravenous, subcutaneous, etc.) are also 

considered in this chapter. 

The carcinogenic potential of the profiled substance is qualitatively evaluated, when appropriate, using 

existing toxicokinetic, genotoxic, and carcinogenic data. ATSDR does not currently assess cancer 

potency or perform cancer risk assessments. Minimal Risk Levels (MRLs) for noncancer end points (if 

derived) and the end points from which they were derived are indicated and discussed. 

Limitations to existing scientific literature that prevent a satisfactory evaluation of the relevance to public 

health are identified in the Chapter 3 Data Needs section. 

Interpretation of Minimal Risk Levels 

Where sufficient toxicologic information is available, ATSDR has derived MRLs for inhalation and oral 

routes of entry at each duration of exposure (acute, intermediate, and chronic). These MRLs are not 

meant to support regulatory action, but to acquaint health professionals with exposure levels at which 

adverse health effects are not expected to occur in humans. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE B-2 

APPENDIX B 

MRLs should help physicians and public health officials determine the safety of a community living near 

a chemical emission, given the concentration of a contaminant in air or the estimated daily dose in water. 

MRLs are based largely on toxicological studies in animals and on reports of human occupational 

exposure. 

MRL users should be familiar with the toxicologic information on which the number is based. Chapter 2, 

"Relevance to Public Health," contains basic information known about the substance. Other sections such 

as Chapter 3 Section 3.9, "Interactions with Other Substances,” and Section 3.10, "Populations that are 

Unusually Susceptible" provide important supplemental information. 

MRL users should also understand the MRL derivation methodology. MRLs are derived using a 

modified version of the risk assessment methodology that the Environmental Protection Agency (EPA) 

provides (Barnes and Dourson 1988) to determine reference doses (RfDs) for lifetime exposure. 

To derive an MRL, ATSDR generally selects the most sensitive end point which, in its best judgement, 

represents the most sensitive human health effect for a given exposure route and duration. ATSDR 

cannot make this judgement or derive an MRL unless information (quantitative or qualitative) is available 

for all potential systemic, neurological, and developmental effects. If this information and reliable 

quantitative data on the chosen end point are available, ATSDR derives an MRL using the most sensitive 

species (when information from multiple species is available) with the highest no-observed-adverse-effect 

level (NOAEL) that does not exceed any adverse effect levels. When a NOAEL is not available, a 

lowest-observed-adverse-effect level (LOAEL) can be used to derive an MRL, and an uncertainty factor 

(UF) of 10 must be employed. Additional uncertainty factors of 10 must be used both for human 

variability to protect sensitive subpopulations (people who are most susceptible to the health effects 

caused by the substance) and for interspecies variability (extrapolation from animals to humans). In 

deriving an MRL, these individual uncertainty factors are multiplied together. The product is then 

divided into the inhalation concentration or oral dosage selected from the study. Uncertainty factors used 

in developing a substance-specific MRL are provided in the footnotes of the levels of significant exposure 

(LSE) tables. 

Chapter 3 

Health Effects 

Tables and Figures for Levels of Significant Exposure (LSE) 

Tables and figures are used to summarize health effects and illustrate graphically levels of exposure 

associated with those effects. These levels cover health effects observed at increasing dose 

concentrations and durations, differences in response by species, MRLs to humans for noncancer end 

points, and EPA's estimated range associated with an upper- bound individual lifetime cancer risk of 1 in 

10,000 to 1 in 10,000,000. Use the LSE tables and figures for a quick review of the health effects and to 

locate data for a specific exposure scenario. The LSE tables and figures should always be used in 

conjunction with the text. All entries in these tables and figures represent studies that provide reliable, 

quantitative estimates of NOAELs, LOAELs, or Cancer Effect Levels (CELs). 

The legends presented below demonstrate the application of these tables and figures. Representative 

examples of LSE Table 3-1 and Figure 3-1 are shown. The numbers in the left column of the legends 

correspond to the numbers in the example table and figure. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE B-3 

APPENDIX B 

LEGEND 

See Sample LSE Table 3-1 (page B-6) 

(1) Route of Exposure. One of the first considerations when reviewing the toxicity of a substance 

using these tables and figures should be the relevant and appropriate route of exposure. Typically 

when sufficient data exist, three LSE tables and two LSE figures are presented in the document. 

The three LSE tables present data on the three principal routes of exposure, i.e., inhalation, oral, 

and dermal (LSE Tables 3-1, 3-2, and 3-3, respectively). LSE figures are limited to the inhalation 

(LSE Figure 3-1) and oral (LSE Figure 3-2) routes. Not all substances will have data on each 

route of exposure and will not, therefore, have all five of the tables and figures. 

(2) Exposure Period. Three exposure periods—acute (less than 15 days), intermediate (15– 

364 days), and chronic (365 days or more)—are presented within each relevant route of exposure. 

In this example, an inhalation study of intermediate exposure duration is reported. For quick 

reference to health effects occurring from a known length of exposure, locate the applicable 

exposure period within the LSE table and figure. 

(3) Health Effect. The major categories of health effects included in LSE tables and figures are 

death, systemic, immunological, neurological, developmental, reproductive, and cancer. 

NOAELs and LOAELs can be reported in the tables and figures for all effects but cancer. 

Systemic effects are further defined in the "System" column of the LSE table (see key number 

18). 

(4) Key to Figure. Each key number in the LSE table links study information to one or more data 

points using the same key number in the corresponding LSE figure. In this example, the study 

represented by key number 18 has been used to derive a NOAEL and a Less Serious LOAEL 

(also see the two "18r" data points in sample Figure 3-1). 

(5) Species. The test species, whether animal or human, are identified in this column. Chapter 2, 

"Relevance to Public Health," covers the relevance of animal data to human toxicity and 

Section 3.4, "Toxicokinetics," contains any available information on comparative toxicokinetics. 

Although NOAELs and LOAELs are species specific, the levels are extrapolated to equivalent 

human doses to derive an MRL. 

(6) Exposure Frequency/Duration. The duration of the study and the weekly and daily exposure 

regimens are provided in this column. This permits comparison of NOAELs and LOAELs from 

different studies. In this case (key number 18), rats were exposed to “Chemical x” via inhalation 

for 6 hours/day, 5 days/week, for 13 weeks. For a more complete review of the dosing regimen, 

refer to the appropriate sections of the text or the original reference paper (i.e., Nitschke et al. 

1981). 

(7) System. This column further defines the systemic effects. These systems include respiratory, 

cardiovascular, gastrointestinal, hematological, musculoskeletal, hepatic, renal, and 

dermal/ocular. "Other" refers to any systemic effect (e.g., a decrease in body weight) not covered 

in these systems. In the example of key number 18, one systemic effect (respiratory) was 

investigated. 

(8) NOAEL. A NOAEL is the highest exposure level at which no harmful effects were seen in the 

organ system studied. Key number 18 reports a NOAEL of 3 ppm for the respiratory system, 

which was used to derive an intermediate exposure, inhalation MRL of 0.005 ppm (see 

footnote "b"). 
HEPTACHLOR AND HEPTACHLOR EPOXIDE B-4 

APPENDIX B 

(9) LOAEL. A LOAEL is the lowest dose used in the study that caused a harmful health effect. 

LOAELs have been classified into "Less Serious" and "Serious" effects. These distinctions help 

readers identify the levels of exposure at which adverse health effects first appear and the 

gradation of effects with increasing dose. A brief description of the specific end point used to 

quantify the adverse effect accompanies the LOAEL. The respiratory effect reported in key 

number 18 (hyperplasia) is a Less Serious LOAEL of 10 ppm. MRLs are not derived from 

Serious LOAELs. 

(10) Reference. The complete reference citation is given in Chapter 9 of the profile. 

(11) CEL. A CEL is the lowest exposure level associated with the onset of carcinogenesis in 

experimental or epidemiologic studies. CELs are always considered serious effects. The LSE 

tables and figures do not contain NOAELs for cancer, but the text may report doses not causing 

measurable cancer increases. 

(12) Footnotes. Explanations of abbreviations or reference notes for data in the LSE tables are found 

in the footnotes. Footnote "b" indicates that the NOAEL of 3 ppm in key number 18 was used to 

derive an MRL of 0.005 ppm. 

LEGEND 

See Sample Figure 3-1 (page B-7) 

LSE figures graphically illustrate the data presented in the corresponding LSE tables. Figures help the 

reader quickly compare health effects according to exposure concentrations for particular exposure 

periods. 

(13) Exposure Period. The same exposure periods appear as in the LSE table. In this example, health 

effects observed within the acute and intermediate exposure periods are illustrated. 

(14) Health Effect. These are the categories of health effects for which reliable quantitative data 

exists. The same health effects appear in the LSE table. 

(15) Levels of Exposure. Concentrations or doses for each health effect in the LSE tables are 

graphically displayed in the LSE figures. Exposure concentration or dose is measured on the log 

scale "y" axis. Inhalation exposure is reported in mg/m3

 or ppm and oral exposure is reported in 

mg/kg/day. 

(16) NOAEL. In this example, the open circle designated 18r identifies a NOAEL critical end point in 

the rat upon which an intermediate inhalation exposure MRL is based. The key number 18 

corresponds to the entry in the LSE table. The dashed descending arrow indicates the 

extrapolation from the exposure level of 3 ppm (see entry 18 in the table) to the MRL of 

0.005 ppm (see footnote "b" in the LSE table). 

(17) CEL. Key number 38m is one of three studies for which CELs were derived. The diamond 

symbol refers to a CEL for the test species-mouse. The number 38 corresponds to the entry in the 

LSE table. 
HEPTACHLOR AND HEPTACHLOR EPOXIDE 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) 

WoNTNT

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). 

HEPTACHLOR AND HEPTACHLOR EPOXIDE B-8 

APPENDIX B 

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HEPTACHLOR AND HEPTACHLOR EPOXIDE C-1 

APPENDIX C. ACRONYMS, ABBREVIATIONS, AND SYMBOLS 

ACGIH American Conference of Governmental Industrial Hygienists 

ACOEM American College of Occupational and Environmental Medicine 

ADI acceptable daily intake 

ADME absorption, distribution, metabolism, and excretion 

AED atomic emission detection 

AFID alkali flame ionization detector 

AFOSH Air Force Office of Safety and Health 

ALT alanine aminotransferase 

AML acute myeloid leukemia 

AOAC Association of Official Analytical Chemists 

AOEC Association of Occupational and Environmental Clinics 

AP alkaline phosphatase 

APHA American Public Health Association 

AST aspartate aminotransferase 

atm atmosphere 

ATSDR Agency for Toxic Substances and Disease Registry 

AWQC Ambient Water Quality Criteria 

BAT best available technology 

BCF bioconcentration factor 

BEI Biological Exposure Index 

BMD benchmark dose 

BMR benchmark response 

BSC Board of Scientific Counselors 

C centigrade 

CAA Clean Air Act 

CAG Cancer Assessment Group of the U.S. Environmental Protection Agency 

CAS Chemical Abstract Services 

CDC Centers for Disease Control and Prevention 

CEL cancer effect level 

CELDS Computer-Environmental Legislative Data System 

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

CFR Code of Federal Regulations 

Ci curie 

CI confidence interval 

CL ceiling limit value 

CLP Contract Laboratory Program 

cm centimeter 

CML chronic myeloid leukemia 

CPSC Consumer Products Safety Commission 

CWA Clean Water Act 

DHEW Department of Health, Education, and Welfare 

DHHS Department of Health and Human Services 

DNA deoxyribonucleic acid 

DOD Department of Defense 

DOE Department of Energy 

DOL Department of Labor 

DOT Department of Transportation 

DOT/UN/ Department of Transportation/United Nations/ 

NA/IMCO North America/Intergovernmental Maritime Dangerous Goods Code 
HEPTACHLOR AND HEPTACHLOR EPOXIDE C-2 

APPENDIX C 

DWEL drinking water exposure level 

ECD electron capture detection 

ECG/EKG electrocardiogram 

EEG electroencephalogram 

EEGL Emergency Exposure Guidance Level 

EPA Environmental Protection Agency 

F Fahrenheit 

F1 first-filial generation 

FAO Food and Agricultural Organization of the United Nations 

FDA Food and Drug Administration 

FEMA Federal Emergency Management Agency 

FIFRA Federal Insecticide, Fungicide, and Rodenticide Act 

FPD flame photometric detection 

fpm feet per minute 

FR Federal Register 

FSH follicle stimulating hormone 

g gram 

GC gas chromatography 

gd gestational day 

GLC gas liquid chromatography 

GPC gel permeation chromatography 

HPLC high-performance liquid chromatography 

HRGC high resolution gas chromatography 

HSDB Hazardous Substance Data Bank 

IARC International Agency for Research on Cancer 

IDLH immediately dangerous to life and health 

ILO International Labor Organization 

IRIS Integrated Risk Information System 

Kd adsorption ratio 

kg kilogram 

kkg metric ton 

Koc organic carbon partition coefficient 

Kow octanol-water partition coefficient 

L liter 

LC liquid chromatography 

LC50 lethal concentration, 50% kill 

LCLo lethal concentration, low 

LD50 lethal dose, 50% kill 

LDLo lethal dose, low 

LDH lactic dehydrogenase 

LH luteinizing hormone 

LOAEL lowest-observed-adverse-effect level 

LSE Levels of Significant Exposure 

LT50 lethal time, 50% kill 

m meter 

MA trans,trans-muconic acid 

MAL maximum allowable level 

mCi millicurie 

MCL maximum contaminant level 

MCLG maximum contaminant level goal 

MF modifying factor 
HEPTACHLOR AND HEPTACHLOR EPOXIDE C-3 

APPENDIX C 

MFO mixed function oxidase 

mg milligram 

mL milliliter 

mm millimeter 

mmHg millimeters of mercury 

mmol millimole 

mppcf millions of particles per cubic foot 

MRL Minimal Risk Level 

MS mass spectrometry 

NAAQS National Ambient Air Quality Standard 

NAS National Academy of Science 

NATICH National Air Toxics Information Clearinghouse 

NATO North Atlantic Treaty Organization 

NCE normochromatic erythrocytes 

NCEH National Center for Environmental Health 

NCI National Cancer Institute 

ND not detected 

NFPA National Fire Protection Association 

ng nanogram 

NHANES National Health and Nutrition Examination Survey 

NIEHS National Institute of Environmental Health Sciences 

NIOSH National Institute for Occupational Safety and Health 

NIOSHTIC NIOSH's Computerized Information Retrieval System 

NLM National Library of Medicine 

nm nanometer 

nmol nanomole 

NOAEL no-observed-adverse-effect level 

NOES National Occupational Exposure Survey 

NOHS National Occupational Hazard Survey 

NPD nitrogen phosphorus detection 

NPDES National Pollutant Discharge Elimination System 

NPL National Priorities List 

NR not reported 

NRC National Research Council 

NS not specified 

NSPS New Source Performance Standards 

NTIS National Technical Information Service 

NTP National Toxicology Program 

ODW Office of Drinking Water, EPA 

OERR Office of Emergency and Remedial Response, EPA 

OHM/TADS Oil and Hazardous Materials/Technical Assistance Data System 

OPP Office of Pesticide Programs, EPA 

OPPT Office of Pollution Prevention and Toxics, EPA 

OPPTS Office of Prevention, Pesticides and Toxic Substances, EPA 

OR odds ratio 

OSHA Occupational Safety and Health Administration 

OSW Office of Solid Waste, EPA 

OTS Office of Toxic Substances 

OW Office of Water 

OWRS Office of Water Regulations and Standards, EPA 

PAH polycyclic aromatic hydrocarbon 
HEPTACHL

OR AND HEPTACHLOR EPOXIDE C-4 

APPENDIX C 

PBPD physiologically based pharmacodynamic 

PBPK physiologically based pharmacokinetic 

PCE polychromatic erythrocytes 

PEL permissible exposure limit 

pg picogram 

PHS Public Health Service 

PID photo ionization detector 

pmol picomole 

PMR proportionate mortality ratio 

ppb parts per billion 

ppm parts per million 

ppt parts per trillion 

PSNS pretreatment standards for new sources 

RBC red blood cell 

REL recommended exposure level/limit 

RfC reference concentration 

RfD reference dose 

RNA ribonucleic acid 

RQ reportable quantity 

RTECS Registry of Toxic Effects of Chemical Substances 

SARA Superfund Amendments and Reauthorization Act 

SCE sister chromatid exchange 

SGOT serum glutamic oxaloacetic transaminase 

SGPT serum glutamic pyruvic transaminase 

SIC standard industrial classification 

SIM selected ion monitoring 

SMCL secondary maximum contaminant level 

SMR standardized mortality ratio 

SNARL suggested no adverse response level 

SPEGL Short-Term Public Emergency Guidance Level 

STEL short term exposure limit 

STORET Storage and Retrieval 

TD50 toxic dose, 50% specific toxic effect 

TLV threshold limit value 

TOC total organic carbon 

TPQ threshold planning quantity 

TRI Toxics Release Inventory 

TSCA Toxic Substances Control Act 

TWA time-weighted average 

UF uncertainty factor 

U.S. United States 

USDA United States Department of Agriculture 

USGS United States Geological Survey 

VOC volatile organic compound 

WBC white blood cell 

WHO World Health Organization 
HEPTACHL

OR AND HEPTACHLOR EPOXIDE 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 
HEPTACHLOR AND HEPTACHLOR EPOXIDE C-6 

APPENDIX C 

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HEPTACHLOR AND HEPTACHLOR EPOXIDE D-1 

APPENDIX D. INDEX 

absorbed dose........................................................................................................................................ 67, 82 

adipose tissue .............................................................. 43, 54, 55, 56, 60, 67, 68, 71, 81, 112, 119, 122, 129 

adrenal gland...............................................................................................................................................40 

adrenals ......................................................................................................................................... 16, 54, 125 

adsorption..................................................................................................................................................100 

aerobic.......................................................................................................................................................105 

alanine aminotransferase........................................................................................................... 12, 14, 16, 39 

ambient air ................................................................................................................................................106 

anaerobic...................................................................................................................................................105 

anemia................................................................................................................................................... 14, 21 

bioaccumulation...................................................................................................................... 89, 92, 97, 101 

bioconcentration factor .............................................................................................................................101 

biomarker ........................................................................................................................ 66, 67, 81, 122, 130 

body weight effects.....................................................................................................................................40 

breast milk........................................................................... 5, 7, 45, 58, 60, 67, 68, 112, 113, 114, 115, 119 

cancer .................................................................................. 5, 13, 20, 22, 23, 47, 48, 65, 78, 81, 89, 92, 136 

carcinogen................................................................................................................................. 6, 13, 48, 136 

carcinogenic .......................................................................................................... 13, 19, 20, 47, 48, 73, 136 

carcinogenicity........................................................................................................................ 13, 47, 48, 136 

carcinoma.............................................................................................................................................. 13, 47 

cardiovascular ....................................................................................................................................... 21, 24 

cardiovascular effects..................................................................................................................................24 

chromosomal aberrations............................................................................................................................78 

clearance .....................................................................................................................................................39 

death.............................................................................................................. 7, 12, 19, 21, 22, 23, 24, 38, 48

deoxyribonucleic acid (see DNA)...............................................................................................................51 

dermal effects..............................................................................................................................................24 

developmental effects ................................................................................. 11, 14, 22, 44, 46, 49, 77, 79, 84 

DNA (see deoxyribonucleic acid) ...................................................................................... 50, 51, 52, 67, 78 

endocrine................................................................................................................................... 40, 63, 64, 84 

endocrine effects .........................................................................................................................................40 

fetus....................................................................................................................................................... 54, 64 

gastrointestinal effects ................................................................................................................................38 

general population............................................................................... 7, 11, 20, 44, 66, 74, 83, 97, 111, 119 

genotoxic......................................................................................................................................... 19, 52, 78 

genotoxicity........................................................................................................................................... 49, 52 

groundwater .................................................................................................. 2, 4, 97, 98, 100, 107, 115, 119 

half-life.................................................................................................................... 67, 68, 82, 101, 103, 118 

hematological effects ...................................................................................................................... 21, 22, 38 

hepatic effects ................................................................................................................................. 38, 66, 68 

hydrolysis..................................................................................................................................................104 

immune system ....................................................................................................... 12, 16, 17, 41, 77, 79, 80 

immunological ................................................................................................ 16, 17, 18, 19, 41, 46, 81, 132 

immunological effects.................................................................................................................................46 

Kow ...................................................................................................................................................... 87, 101 

LD50............................................................................................................................... 18, 23, 24, 48, 69, 74 

leukemia......................................................................................................................................................21 

lymphoreticular............................................................................................................................... 41, 42, 79 

metabolic effects .........................................................................................................................................41 
HEPTACHLOR AND HEPTACHLOR EPOXIDE D-2 

APPENDIX D 

milk ...............................................................3, 4, 5, 7, 9, 11, 12, 15, 38, 43, 44, 58, 68, 71, 79, 80, 97, 110, 

111, 112, 113, 114, 115, 122, 123, 124, 125, 128, 129 

neonatal........................................................................................................................................... 12, 43, 44 

neoplastic ....................................................................................................................................................47 

neurobehavioral....................................................................................................... 12, 15, 16, 45, 63, 64, 84 

neurodevelopmental....................................................................................................................................63 

neurological effects....................................................................... 11, 15, 18, 22, 38, 42, 43, 49, 66, 80, 132

non-Hodgkin’s lymphoma ..........................................................................................................................47 

ocular effects......................................................................................................................................... 21, 40 

odds ratio............................................................................................................................................... 22, 47 

pharmacodynamic .......................................................................................................................................59 

pharmacokinetic.......................................................................................................... 59, 60, 62, 65, 82, 118 

photolysis .................................................................................................................................... 23, 103, 118 

placenta ........................................................................................................................................... 5, 54, 113 

renal effects.................................................................................................................................................39 

reproductive effects................................................................................................................... 22, 43, 44, 79 

solubility ....................................................................................................................................... 58, 68, 100 

systemic effects............................................................................................................................... 21, 24, 48 

thyroid................................................................................................................................................... 40, 47 

thyroid stimulating hormone.......................................................................................................................40 

thyroxine .....................................................................................................................................................40 

toxicokinetic............................................................................................................ 19, 60, 76, 77, 78, 82, 84 

tremors .................................................................................................................................................. 42, 72 

triiodothyronine...........................................................................................................................................40 

tumors .....................................................................................................................................................6, 47 

vapor pressure ...........................................................................................................................................100 

volatilization ..................................................................................................................................... 100, 101 

weanling......................................................................................................................................................69