TOXICOLOGICAL PROFILE FOR
 

CHLORDANE
 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
 

Public Health Service
 

Agency for Toxic Substances and Disease Registry
 

May 1994 
CHLORDANE 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. 
CHLORDANE iii 

UPDATE STATEMENT
 

A Toxicological Profile for Chlordane was released on December 1989. This edition supersedes any 

previously released draft or final profile. 

Toxicological profiles are revised and republished as necessary, but no less than once every three 

years. For information regarding the update status of previously released profiles contact ATSDR at: 

Agency for Toxic Substances and Disease Registry
 

Division of Toxicology/Toxicology Information Branch
 

1600 Clifton Road NE, E-29
 

Atlanta, Georgia 30333
 



CHLORDANE vii 

CONTRIBUTORS 

CHEMICAL MANAGERS(S)/AUTHOR(S): 

Henry G. Abadin, M.S.P.H.
 

ATSDR, Division of Toxicology, Atlanta, GA
 

Ronald Baynes, D.V.M., M.S.
 

Paul F. Goetchius, D.V.M.
 

Syracuse Research Corporation, Syracuse, NY
 

THE PROFILE HAS UNDERGONE THE FOLLOWING ATSDR INTERNAL REVIEWS:
 

1 . Green Border Review. Green Border review assures the consistency with ATSDR policy. 

2 . 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 endpoints. 

3 . 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. 

4 . Quality Assurance Review. The Quality Assurance Branch assures that consistency across 

profiles is maintained, identifies any significant problems in format or content, and establishes 

that Guidance has been followed. 

CHLORDANE ix 

PEER REVIEW
 

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

1.	 Dr. Rajender Abraham, President, Abraham Associates, Limited, Albany, New York 

2.	 Dr. Syed M. GhiasUddin, Toxicologist, Indiana Department of Environmental Management, 

Indianapolis. Indiana 

3.	 Dr. Morris Cranmer, Private Consultant, Cranmer and Associates, Inc., Little Rock, AR. 

These experts collectively have knowledge of chlordane’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. A list of databases 

reviewed and a list of unpublished documents cited are also included in the administrative record. 

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. 









CHLORDANE 1 

1. PUBLIC HEALTH STATEMENT
 

This Statement was prepared to give you information about chlordane and to emphasize the human 

health effects that may result from exposure to it. The Environmental Protection Agency (EPA) has 

identified 1,350 hazardous waste sites as the most serious in the nation. These sites comprise the 

“National Priorities List” (NPL): Those sites which are targeted for long-term federal cleanup 

activities. Chlordane has been found in at least 176 of the sites on the NPL. However, the number of 

NPL sites evaluated for chlordane is not known. As EPA evaluates more sites, the number of sites at 

which chlordane is found may increase. This information is important because exposure to chlordane 

may cause harmful health effects and because these sites are potential or actual sources of human 

exposure to chlordane. 

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

a drum or bottle, it enters the environment. This 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 substances containing the substance or by skin contact with it. 

If you are exposed to a substance such as chlordane, many factors will determine whether harmful 

health effects will occur and what the type and severity of those health effects will be. These factors 

include the dose (how much), the duration (how long), the route or pathway by which you are exposed 

(breathing, eating, drinking, or skin contact), the other chemicals to which you are exposed, and your 

individual characteristics such as age, gender, nutritional status, family traits, life-style, and state of 

health. 

1.1 WHAT IS CHLORDANE? 

Chlordane is a man-made chemical that was used as a pesticide in the United States from 1948 to 

1988. It is sometimes referred to by the trade names Octachlor and Velsicol 1068. It is a thick liquid 

whose color ranges from colorless to amber, depending on its purity. It may 
CHLORDANE 2 

1. PUBLIC HEALTH STATEMENT 

have no smell or a mild, irritating smell. We do not know what it tastes like. Chlordane is
 

not a single chemical, but is a mixture of many related chemicals, of which about 10 are
 

major components. Some of the major components are trans-chlordane, cis-chlordane,
 

ß-chlordene, heptachlor, and trans-nonachlor. Chlordane does not dissolve in water.
 

Therefore, before it can be used as a spray, it must be placed in water with emulsifiers (soaplike
 

substances), which results in a milky-looking mixture.
 

From 1983 until 1988, chlordane’s only approved use was to control termites in homes. The
 

pesticide was applied underground around the foundation of homes. When chlordane is used
 

in the soil around a house, it kills termites that come into contact with it.
 

Before 1978, chlordane was also used as a pesticide on agricultural crops, lawns, and gardens
 

and as a fumigating agent. Because of concerns over cancer risk, evidence of human
 

exposure and build up in body fat, persistence in the environment, and danger to wildlife, the
 

EPA canceled the use of chlordane on food crops and phased out other above-ground uses
 

over the next 5 years. In 1988, when the EPA canceled chlordane’s use for controlling
 

termites, all approved use of chlordane in the United States stopped. Manufacture for export
 

continues. For more information see Chapters 3 and 4.
 

1.2 WHAT HAPPENS TO CHLORDANE WHEN IT ENTERS THE ENVIRONMENT? 

When used as a pesticide on crops, on lawns and gardens, and to control termites in houses, 

chlordane enters the environment. Although it is no longer used in the United States, it may 

be used in other countries. In soil, it attaches strongly to particles in the upper layers of soil 

and is unlikely to enter into groundwater. It is not known whether chlordane breaks down in 

most soils. If breakdown occurs, it is very slow. Chlordane is known to remain in some 

soils for over 20 years. Persistence is greater in heavy, clayey or organic soil than in sandy 

soil. Most chlordane is lost from soil by evaporation. Evaporation is more rapid from light, 

sandy soils than from heavy soils. Half of the chlordane applied to the soil surface may 

evaporate in 2 to 3 days. Evaporation is much slower after chlordane penetrates into the soil. 

In water, some chlordane attaches strongly to sediment and particles in the water column and 
CHLORDANE 3 

1. PUBLIC HEALTH STATEMENT 

some is lost by evaporation. It is not known whether much breakdown of chlordane occurs in 

water or in sediment. Chlordane breaks down in the atmosphere by reacting with light and 

with some chemicals in the atmosphere. However, it is sufficiently long lived that it may 

travel long distances and be deposited on land or in water far from its source. Chlordane or 

the chemicals that chlordane changes into accumulate in fish, birds, and mammals. Chlordane 

stays in the environment for many years and is still found in food, air, water, and soil. 

Chlordane is still commonly found in some form in the fat of fish, birds, mammals, and 

almost all humans. For more information see Chapter 5. 

1.3 HOW MIGHT I BE EXPOSED TO CHLORDANE? 

Everyone in the United States has been exposed to low levels of chlordane. A more relevant 

question is whether or not you may have been exposed to high levels of chlordane. Before its 

ban in 1988, you might have been exposed to high levels of chlordane if you worked in the 

manufacture, formulation, or application of chlordane. Therefore, farmers and lawn-care 

workers may have been exposed to chlordane before 1978, and pest control workers may have 

been exposed to chlordane before 1988 by skin contact and breathing dust and vapor. A 

national survey conducted from 1980 to 1983 estimated that 3,732 workers were potentially 

exposed to chlordane in the United States. This number of potentially exposed workers 

should have decreased after chlordane’s use was banned in the United States. However, the 

ban on chlordane did not eliminate it from your environment, and some of your opportunities 

for exposure to chlordane continue. 

Today, people receive the highest exposure to chlordane from living in homes that were 

treated with chlordane for termites. Chlordane may be found in the air in these homes for 

many years after treatment. Houses in the deep south and southwest were most commonly 

treated. However, chlordane use extended from the lower New England States south and 

west to California. Houses built since 1988 have not been treated with chlordane for termite 

control. You can determine if your home was treated with chlordane by examining your 

records or contacting your termite treatment service. 
CHLORDANE 4 

1. PUBLIC HEALTH STATEMENT 

Over 50 million persons have lived in chlordane-treated homes. Indoor air in the living 

spaces of treated homes have been found to contain average levels of between 0.00003 and 

0.002 milligram (mg) of chlordane in a cubic meter of air (mg/m3). However, levels as high 

as 0.06 mg/m3 have been measured in the living areas of these homes. Even higher levels are 

found in basements and crawl spaces. 

The most common source of chlordane exposure is from ingesting chlordane-contaminated 

food. Chlordane remains in the food supply because much of the farmland was treated with 

chlordane in the 1960s and 1970s and it remains in some soil for over 20 years. However, 

since chlordane has been banned, the levels in soils would be expected to decrease with the 

passage of time. Chlordane may also be found in fish and shellfish caught in chlordane contaminated 

waters. If you are in doubt about whether a lake or river is contaminated, call your local Game and 

Fish or Health departments. Chlordane is almost never detected in 

drinking water. A survey conducted by the Food and Drug Administration (FDA) determined 

daily intake of chlordane from food to be 0.0013 microgram per kilogram of body weight 

μg/kg) for infants and 0.0005-0.0015 μg/kg for teenagers and adults (a microgram is one 

thousandth of a milligram). The average adult would, therefore, consume about 0.11 μg of 

chlordane. 

You may come into contact with chlordane while digging in soil around the foundation of 

homes where it was applied to protect the homes against termites. Soil may also be 

contaminated with chlordane around certain NPL hazardous waste sites. Chlordane has been 

found at 176 of 1,350 hazardous waste sites on the NPL in the United States. The highest 

level of chlordane found in soil near an NPL site was 344 ppm. People may be exposed to 

chlordane at these sites by breathing low levels of chlordane volatilizing from the soil or from 

touching the soil. Levels of chlordane found in groundwater near NPL sites containing 

chlordane ranged from 0.02 to 830 parts of chlordane per billion parts of water (ppb). 

Finally, some chlordane may be left over from pre-ban days. Old containers of material 

thought to contain chlordane should be disposed of carefully and contact with the skin and 

breathing vapors should be avoided. For more information see Chapter 5. 
CHLORDANE 5 

1. PUBLIC HEALTH STATEMENT 

1.4 HOW CAN CHLORDANE ENTER AND LEAVE MY BODY? 

Chlordane can enter the body through the skin if skin contact occurs with contaminated soils, 

through the lungs if breathed in with contaminated air, and through the digestive tract if 

swallowed. Uptake through the skin and digestive tract increases if chlordane is in an oily 

mixture, which might occur at hazardous waste sites. The importance of each of these ways 

for chlordane to enter the body depends on the kind of exposure. For example, people living 

in houses that have been treated with chlordane will be exposed mostly by breathing the 

vapor in the air. Workers who sprayed chlordane as a pesticide were exposed mostly by 

breathing the compound in the air and by contact with the skin. Other people may be 

exposed to small quantities by eating food or drinking water that contains chlordane. People 

at or near waste sites may be exposed by touching chlordane in the soil, by breathing 

chlordane that evaporates into the air, by drinking water that contains chlordane or by eating 

contaminated fish or crops. The amount of chlordane that enters the body depends on the 

amount in air, food, or water, and the length of time a person is exposed to it. Most 

chlordane that enters the body leaves in a few days, mostly in the feces, and a much smaller 

amount leaves in the urine. Chlordane and its breakdown products may be stored in body fat, 

where they cause no bad effects, unless released from body fat in large amounts. It may take 

months or years before the chlordane and the breakdown products that are stored in fat are 

able to leave the body. More information on how chlordane moves in the body can be found 

in Chapter 2. 

1.5 HOW CAN CHLORDANE AFFECT MY HEALTH? 

Most health effects in humans that may be linked to chlordane exposure are on the nervous 

system, the digestive system, and the liver. These effects were seen mostly in people who 

swallowed chlordane mixtures. Large amounts of chlordane taken by mouth can cause 

convulsions and death. Convulsions occurred in a man who had long-term skin contact with 

soil containing large amounts of chlordane. Swallowing small amounts or breathing air 

containing high concentrations of chlordane vapors can cause a variety of nervous system 
 

CHLORDANE 6 

1. PUBLIC HEALTH STATEMENT 

effects, including headaches, irritation, confusion, weakness, and vision problems, as well as 

upset stomach, vomiting, stomach cramps, diarrhea, and jaundice. 

No harmful effects on health have been confirmed in studies of workers who made chlordane. 

One study found minor changes in liver function in workers in Japan who used chlordane as a 

pesticide. There are indications that chlordane may cause anemia and other changes in the 

blood cells, but the evidence is not very strong. 

Animals given high levels of chlordane by mouth for short periods of time died or had 

convulsions. Long-term exposure of animals to chlordane in their food caused harmful 

effects in the liver. It is not known whether chlordane will cause cancer in humans after 

long-term exposure. Studies of workers who made or used chlordane do not link exposure 

with cancer, but the information is not sufficient to know for sure. Mice fed low levels of 

chlordane in their food for most of their lifetimes developed liver cancer. The International 

Agency for Research on Cancer (IARC) has determined that chlordane is not classifiable as to 

its carcinogenicity to humans. It is not known whether chlordane will cause reproductive or 

birth defects in humans. Studies of workers who made or used chlordane do not link 

exposure to the chemical with birth defects, but there are not enough studies in humans to 

know for sure. There is some evidence that animals exposed before birth or while nursing 

develop behavioral effects while growing up. More information on the effects of chlordane 

on health can be found in Chapter 2. 

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

 EXPOSED TO CHLORDANE? 

Chlordane and its breakdown products (metabolites) can be measured in human blood, urine, 

feces, and breast milk. Tests have shown that most Americans have low levels of chlordane 

metabolites in their body fat. The breakdown products can stay in body fat for very long 

periods, so finding them in body fat or breast milk does not tell how much or how long ago 

exposure to chlordane occurred. Not all of the breakdown products are specific for chlordane. 

Finding chlordane and/or breakdown products in your body also cannot predict what health 
CHLORDANE 7 

1. PUBLIC HEALTH STATEMENT 

effects will occur, if any. Levels in blood and fat can be tested, although the tests are not 

routinely available. More information on medical tests can be found in Chapters 2 and 6. 

1.7 	 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO

 PROTECT HUMAN HEALTH? 

The EPA guidelines for drinking water suggest that no more than 60 ppb chlordane should be 

present in drinking water that children consume for longer than 10 days. Drinking water 

should contain no more than 0.5 ppb for children or 2 ppb for adults if they drink the water 

for longer periods. 

EPA stopped all use of chlordane on food crops, effective March 1978. Until 1988, EPA 

permitted chlordane use for termite control or dipping the roots or tops of nonfood plants. 

On April 14, 1988, however, EPA stopped all sales and commercial use of chlordane. 

The Food and Drug Administration has established that the levels of chlordane and its 

breakdown products in most fruits and vegetables should not be greater than 300 ppb and in 

animal fat and fish should not be greater than 100 ppb. 

Federal regulations limit the amount of chlordane that factories can release into waste water. 

The EPA requires industry to report releases or spills of 1 pound or more. A temporary 

guideline of the National Research Council indicated that 0.005 mg/m3 should be the 

maximum amount allowed in the air of military housing. 

The Occupational Safety and Health Administration (OSHA) regulates chlordane levels in the 

workplace. The maximum allowable level in workplace air is 0.5 mg/m3

 for a person who is 

exposed for 8 hours per workday and 40 hours per workweek. The National Institute for 

Occupational Health and Safety (NIOSH) also recommends an exposure limit of 0.5 mg/m3 

for a person exposed to chlordane in the workplace for 8 hours per workday and 40 hours per 

workweek. Chapter 7 provides more information on chlordane regulations. 
CHLORDANE 8 

1. PUBLIC HEALTH STATEMENT 

1.8 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: 

Agency for Toxic Substances and Disease Registry 

1600 Clifton Road NE, E-29 

Atlanta, Georgia 30333 

(404) 639-6000 

This agency can also provide you with information on the location of occupational and 

environmental health clinics. These clinics specialize in the recognition, evaluation, and 

treatment of illness resulting from exposure to hazardous substances. 
CHLORDANE 9 

2. HEALTH EFFECTS 

2.1 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 of the toxicology of chlordane. 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. 

In the studies discussed in this chapter, exposure of animals may have been to analytical grade 

chlordane, technical grade chlordane, or to individual cis- or trans-chlordane. Exposure of humans was 

mainly to technical chlordane. As discussed in Section 3.1, technical chlordane is a mixture of >140 

related chemicals, of which the major other constituents include heptachlor, nonachlor, chlordene, 

among others. In addition to being constituents or contaminants of technical chlordane, these and other 

chemicals are also formed during the metabolism of chlordane (see Section 2.3.3), and may influence 

the toxicity of chlordane. 

2.2 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 lowest­
CHLORDANE 10 

2. HEALTH EFFECTS 

observed-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 

hose 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 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 chlordane are 

indicated in Table 2-2 and Figure 2-2. Because cancer effects could occur at lower exposure levels, 

the figures also show a range for the upper bound of estimated excess risks, ranging from a risk of 1 

in 10,000 to 1 in 10,000,000 (10-4 to 10-7), as developed by EPA. 

A User’s Guide has been provided at the end of this profile (see Appendix A). This guide should aid 

in the interpretation of the tables and figures for Levels of Significant Exposure and the MRLs. 
CHLORDANE 11 

2. HEALTH EFFECTS 

2.2.1 Inhalation Exposure 

2.2.1.1 Death 

Retrospective cohort mortality studies of workers in chlordane and other organochlorine 

manufacturing plants reported no increase in mortality rate and no increase in any specific cause of 

death attributed to chlordane exposure (MacMahon et al. 1988; Shindell and Ulrich 1986). Wang and 

MacMahon (1979b) reported no increase in mortality rate in a prospective study of pesticide 

applicators. However, in a retrospective mortality study of 1,403 men employed for 23 months at two 

plants, a significantly increased risk of death from cerebrovascular disease was found, but the authors 

could not definitively attribute this excess to chlordane exposure (Wang and MacMahon 1979a). In 

another retrospective mortality study of four cohorts (305-1,155 workers/plant exposed for ≥6 months) 

from four manufacturing plants, there was a significantly increased risk of death from noncancer 

respiratory disease, and a slight excess risk of cancer of the esophagus, rectum, liver, and 

hematopoietic system at plant 3, and a slightly greater risk of stomach cancer at plant 1 (Ditraglia et al. 

1981). Chlordane was the only pesticide manufactured at plant 1, while aldrin, dieldrin, endrin, and 

dichlorodiphenyltrichloroethane were manufactured at plant 3. The statistical power did not allow for a 

conclusion that no association existed between cause-specific mortality and employment at the plants. 

However, in a follow-up study of these cohorts, which added 11 years of follow-up, no statistically 

significant excess risk of death from any cause was found (Brown 1992). All of these studies had 

serious limitations, including unquantified exposure concentrations and exposure to several pesticides. 

An early study by Frings and O’Tousa (1950) reported mortality in mice exposed to chlordane. This 

study will not be discussed further because it has been established that the mortality and other toxic 

effects observed were due to the use of “early” production chlordane (Ingle 1953, 1965). Early 

production chlordane was frequently contaminated with hexachlorocyclopentadiene, a highly volatile 

and toxic reaction intermediate that Ingle (1953, 1965) concluded was largely responsible for the 

observed effects. In another inhalation study (Ingle 1953), none of the mice died after 14-25 days of 

continuous exposure to “later” production (more highly purified) chlordane at estimated concentrations 

of 25-50% saturation (estimated levels in air not reported). In rats exposed to an unspecified 

concentration of “refined technical grade” of chlordane for l-8 hours for up to 10 days, three of five 

died between days 4 and 10 of exposure (Ambrose et al. 1953a). 
CHLORDANE 12 

2. HEALTH EFFECTS 

More recently, rats exposed for 2 days (8 hours/day) to 413 mg technical chlordane/m3 or similarly for 

5 days to 154 mg/m3

 died; rats similarly exposed to 28.2 mg/m3 for 28 days survived (Khasawinah et 

al. 1989). The female rats were more sensitive than the males. There was no mortality in rats or 

monkeys exposed intermittently to technical chlordane at 10 mg/m3 8 hours/day, 5 days/week for 

90 days (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). The LOAELs for death in rats after 

acute duration exposure are recorded in Table 2-1 and plotted in Figure 2-l. 

2.2.1.2 Systemic Effects 

The systemic effects in humans and animals after inhalation exposure to chlordane are discussed 

below. The highest NOAEL values and the LOAEL values for each systemic effect from all reliable 

studies for each species and duration category are recorded in Table 2-1 and plotted in Figure 2-1. 

Respiratory Effects. Physical examination of library workers acutely exposed to high but 

unquantified concentrations of chlordane from a spill revealed no indication of respiratory effects 

(NIOSH 1984a). Chest pains, dyspnea, and shortness of breath were reported in a compilation of 

cases and personal reports of humans accidentally exposed to chlordane by inhalation (EPA 1980a); 

exposures frequently involved a mixture of chemicals (such as other related and nonrelated pesticides) 

and vehicles (including petroleum distillates). Therefore, these effects cannot be attributed to 

chlordane alone. Results of a questionnaire indicated increases (compared with the National Center for 

Health Statistics 1979 National Health Interview Survey) in sore throat and respiratory infections in 

humans shortly after their homes were treated for termites (Menconi et al. 1988). Chronic exposure in 

pesticide treated homes was associated with bronchitis and sinusitis, which increased in incidence with 

higher concentrations of pesticides in the air. Because aldrin and heptachlor were included with 

chlordane in the analysis for pesticides in the indoor air, these effects cannot be attributed 

unequivocally to chlordane exposure. Other limitations of the Menconi et al. (1988) study include 

self-selection of respondents. Respiratory effects generally were not found in occupational exposure 

studies (Alvarez and Hyman 1953; Fishbein et al. 1964; Princi and Spurbeck 1951). However, in a 

retrospective mortality study of four cohorts (305-1,155 workers/plant exposed for ≥6 months) from 

four manufacturing plants, there was a significantly increased risk of death from noncancer respiratory 

disease at plant 3 where only aldrin, dieldrin, endrin, and dichlorodiphenyltrichloroethane were 

manufactured (Ditraglia et al. 1981). However, increased mortality risk from noncancer respiratory 

disease was not observed in workers at plant 1 where only chlordane was manufactured. The 







CHLORDANE 20 

2. HEALTH EFFECTS 

statistical power did not allow for a conclusion that no association existed between cause-specific 

mortality and employment at the plants. However, in a follow-up study of these cohorts, which added 

11 years of follow-up, no statistically significant excess risk of death from any cause was found 

(Brown 1992). 

Mice exposed continuously to an unspecified concentration of chlordane for 14-25 days had slight 

lung congestion and proliferation of bronchiole lining cells (Ingle 1953). In a series of experiments, 

rats exposed to 413 mg technical chlordane/m3 for 3 days had epithelial degeneration and cellular 

debris in the bronchii and alveoli (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). Respiratory 

tract lesions were not observed in rats intermittently exposed to technical chlordane at ≤128.2 mg/m3 

8 hours/day, 5 days/week for 28 days or similarly to 10 mg/m3 for 90 days. Abnormal respiratory 

movements seen in rats in the 28-day study exposed to ≥154 mg/m3 were considered signs of 

neurologic involvement. There were no adverse histopathological changes in the respiratory tract or 

changes in pulmonary function in monkeys exposed to technical chlordane at 10 mg/m3 8 hours/day, 5 

days/week for 90 days. 

Cardiovascular Effects. Tachycardia was among the symptoms attributed to chlordane exposure in 

a compilation of cases and personal reports of accidental human inhalation exposure to high 

concentrations of chlordane (EPA 1980b). Cardiovascular effects were not reported in library workers 

acutely exposed to high but unquantified concentrations of chlordane from a spill (NIOSH 1984a). 

Cardiovascular effects were not found in occupational exposure studies (Alvarez and Hyman 1953; 

Fishbein et al. 1964; Princi and Spurbeck 1951). Equivocal evidence of increased risk of 

cerebrovascular disease was reported in workers involved in the manufacture of chlordane (Wang and 

MacMahon 1 979a ) . 

Histopathological changes in the heart were not observed in rats exposed to technical chlordane at 

≤28.2 mg/m3 8 hours/day, 5 days/week for 28 days or similarly to 10 mg/m3

 for 90 days (Khasawinah 

et al. 1989; Velsicol Chemical Co. 1984). No adverse histopathological lesions were observed in the 

hearts of monkeys exposed to technical chlordane at 10 mg/m3

 8 hours/day, 5 days/week for 90 days 

(Khasawinah et al. 1989; Velsicol Chemical Co. 1984). 

Gastrointestinal Effects. Gastrointestinal effects (cramps, diarrhea, nausea) were a consistent 

observation in a compilation of cases and personal reports of accidental human inhalation exposure to 
CHLORDANE 21 

2. HEALTH EFFECTS 

high concentrations of chlordane (EPA 1980a). NIOSH (1984a) also reported gastrointestinal 

symptoms (nausea, diarrhea) in 4 of 13 humans within 4 days of inhalation and/or dermal exposure as 

a result of 1% chlordane being spilled in a subterranean library room. The greatest prevalence of 

symptoms occurred in those directly involved in the cleanup, where potential for exposure to higher 

concentrations was greatest. Concentrations in air, taken ≈4.5 months after the spill, ranged from 

0.0001 to 0.0003 mg/m3

. Because air concentration data are not available for the first 4 days of 

exposure, concentrations associated with the observed effects cannot be estimated. Occupational 

exposure, however, has not been associated with gastrointestinal effects. Alvarez and Hyman (1953) 

reported no gastrointestinal effects in a group of 24 workers involved in chlordane manufacture. Both 

inhalation and dermal exposure occurred. Princi and Spurbeck (1951) reported no effects in workers 

involved in the manufacture of insecticides (chlordane, aldrin, and dieldrin) when air concentrations of 

total chlorinated hydrocarbons were ≤10 mg/m3; exposure was by inhalation and skin contact for 

11-36 months. Fishbein et al. (1964) reported no gastrointestinal effects in production workers 

exposed to chlordane concentrations of 0.0012-0.0017 mg/m3 over a period of 1-15 years. 

No histopathological lesions in the gastrointestinal tract were observed in rats exposed to technical 

chlordane at ≤28.2 mg/m3 8 hours/day, 5 days/week for 28 days, or in rats and monkeys exposed to 

technical chlordane at 0, 0.1, 1.0, or 10 mg/m3 for 90 days (Khasawinah et al. 1989; Velsicol 

Chemical Co. 1984). 

Hematological Effects. A questionnaire survey revealed that 4% of persons living in homes treated 

with chlordane to control termites reported anemia as a chronic effect (Menconi et al. 1988). The 

effect cannot be attributed to chlordane alone, because the quantitative amounts of aldrin and 

heptachlor were combined with the chlordane measurement in the analysis of indoor air. A number of 

anecdotal reports of blood dyscrasia associated with organochlorine pesticides (chlordane, lindane, 

DDT), suggest that there may be an unusually susceptible subpopulation (Ellenhom and Barceloux 

1988). Several cases of blood dyscrasia (aplastic anemia, hemolytic anemia, thrombocytopenic 

purpura, acute disseminated hemorrhages, pernicious anemia, megaloblastic anemia) were observed in 

persons exposed to chlordane or heptachlor in their home or garden or as a result of their profession as 

pest control operators (Epstein and Ozonoff 1987; Infante et al. 1978). The usefulness of these reports 

is limited because exposure to chlordane was unquantified, the individuals were exposed to other 

chemicals, and there were other confounding factors. Although the existing case reports are not 

sufficient to indict chlordane as the etiologic agent, they indicate the need for further epidemiologic 
CHLORDANE 22 

2. HEALTH EFFECTS 

study (see also Section 2.2.1.8). No effects on hemoglobin concentrations or sedimentation rates were 

found in a group of 24 men employed in chiordane manufacture, where exposure was both via 

inhalation and dermal contact (Alvarez and Hyman 1953). Furthermore, no effects on typical 

hematological parameters were found in 34 workers exposed to chlordane at unspecified 

concentrations (Princi and Spurbeck 1951) or in 15 workers exposed to 0.0012-0.0017 mg/m3 

(Fishbein et al. 1964). 

No hematological effects were observed in rats exposed to technical chlordane at ≤28.2 mg/m3 

8 hours/day, 5 days/week for 28 days or similarly to 154 mg/m3 for 11 days, or in monkeys similarly 

exposed to ≤10 mg/m3 for 90 days (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). Male and 

female rats were similarly exposed to 0.1 and 1.0 mg/m3 for 90 days. Female, but not male rats 

exposed to 1.0 mg/m3

 had increased leukocyte counts and decreased platelet counts, which suggests 

that chlordane may have an effect on hematopoiesis and that females may be more sensitive than 

males. 

Musculoskeletal Effects. The only study regarding musculoskeletal effects in humans after 

exposure to chlordane was a report of increased serum levels of creatine phosphokinase, particularly 

the isoenzyme associated with skeletal muscle damage, in three of nine pesticide applicators (Ogata 

and Izushi 1991). This study does not provide convincing evidence of muscular damage, as no other 

indices were examined. 

No histological evidence of musculoskeletal effects were observed in rats exposed to technical 

chlordane at ≤28.2 mg/m3

 8 hours/day, 5 days/week for 28 days or in rats or monkeys similarly 

exposed to ≤10 mg/m3 for 90 days (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). 

Hepatic Effects. Hepatic effects were not reported in library workers acutely exposed to high but 

unquantified concentrations of chlordane from a spill (NIOSH 1984a). Jaundice, reflecting liver 

effects, was sometimes reported in cases of inhalation exposure to chlordane in a compilation of cases 

and personal reports of accidental exposure (EPA 1980a). When reported, jaundice was frequently 

associated with continued exposure such as living in a house in which chlordane had been used to 

control termites (EPA 1980a). Occupational exposures to chlordane, until recently, have not been 

associated with liver effects (Alvarez and Hyman 1953; Fishbein et al. 1964; Princi and Spurbeck 

1951). More recently, however, elevated serum levels of triglycerides, lactic acid dehydrogenase, and 

gamma-glutamyl transferase were measured in pesticide applicators (Ogata and Izushi 1991). 
CHLORDANE 23 

2. HEALTH EFFECTS 

Biochemical evidence of liver damage (increased blood glutamic oxaloacetic transaminase [GOT], 

glutamic pyruvic transaminase [GPT], glutamate dehydrogenase [GDH], bile acids, and cholesterol), 

as well as hepatocellular enlargement and vacuolation, were observed in rats exposed to 154 mg 

technical chlordane/m3 8 hours/day, 5 days/week for 11 exposures or to 413 mg/m3 8 hours/day for 3 

exposures (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). Increased liver weight was found in 

female rats exposed to technical chlordane at 5.8 mg/m3 8 hours/day, 5 days/week for 28 days. Serum 

chemistry changes indicative of liver damage occurred in females, and increased liver weight occurred 

in males exposed to 28.2 mg/m3

 8 hours/day, 5 days/week for 28 days. Both sexes exposed to 

28.2 mg/m3 had centrilobular hepatocyte enlargement. Lesions in the rats exposed to 154 mg/m3 for 

11 exposures included hepatocellular enlargement and vacuolation; frank necrosis occurred in rats 

exposed to 413 mg/m3

 for 3 exposures. The female rats appeared to be more sensitive than the males. 

A 90-day inhalation study in male and female rats exposed intermittently to technical chlordane at 0, 

0.1, 1.0, or 10 mg/m3 reported mild liver lesions (hepatocellular enlargement or vacuolization) and 

slight changes in serum chemistry at ≤1.0 mg/m3 and increased liver weight in both sexes at 10 mg/m3 

(Khasawinah et al. 1989; Velsicol Chemical Co. 1984). The lowest concentration, 0.1 mg/m3, was 

judged a NOAEL. In monkeys exposed by the same protocol, no effects occurred at 1.0 mg/m3 but 

10 mg/m3 was associated with increased mean liver weight. The NOAEL of 0.1 mg/m3 in rats was 

used to derive an intermediate-duration inhalation MRL of 0.0002 mg/m3

 and a chronic-duration 

inhalation MRL of 0.00002 mg/m3 as described in the footnote to Table 2-l and Section 2.4. 

Renal Effects. Evidence of altered renal function was not reported in library workers acutely 

exposed to high but unquantified concentrations of chlordane from a spill (NIOSH 1984a), or in a 

compilation of cases and personal reports of accidental exposure (EPA 1980a). No kidney effects 

were found in occupational studies of chlordane manufacture (Alvarez and Hyman 1953; Fishbein et 

al. 1964; Princi and Spurbeck 1951). 

Increased kidney weight was noted in male rats exposed 8 hours/day, 5 days/week to 28.2, but not to 

5.8 mg/m3

, for 28 days (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). No histopathological 

lesions of the kidney were observed in either sex. The 28.2 mg/m3

 level is considered a NOAEL. 

Elevated kidney weights were found in both sexes of rats similarly exposed to technical chlordane at 

10 mg/m3, but not at 1.0 mg/m3, for 90 days. No histopathological lesions were observed at 
CHLORDANE 24 

2. HEALTH EFFECTS 

1 or 10 mg/m3. No kidney effects were observed in monkeys in the same study at 10 mg/m3, which is 

also considered a NOAEL. 

Dermal/Ocular Effects. Dermatitis was found by a questionnaire survey to occur in persons living 

in homes treated with chlordane, with greater frequency than in a reference population (Menconi et al. 

1988). The effects, however, cannot be attributed to chlordane alone, because aldrin and heptachlor 

were included in the analysis for chlordane in the residents indoor air. 

No dermal/ocular effects were found in rats exposed to technical chlordane at ≤28.2 mg/m3 

8 hours/day, 5 days/week for 28 days. No ophthalmoscopic or histopathological changes were 

observed in the eyes or skin of rats or monkeys similarly exposed to ≤10 mg/m3

 for 90 days 

(Khasawinah et al. 1989; Velsicol Chemical Co. 1984). 

Other Systemic Effects. Body weight loss and increased height of the thyroid follicular cells were 

observed in rats exposed to 154 mg technical chlordane/m3

, 8 hours/day, 5 days/week for 11 exposures 

(Khasawinah et al. 1989; Velsicol Chemical Co. 1984). The 28-day inhalation study in rats reported 

decreased body weight gain in females exposed to 28.2 mg chlordane/m3 8 hours/day, 5 days/week. 

Food consumption also decreased, confounding interpretation of this finding. Thyroid weight 

increased in males exposed to 5.8 or 28.2 mg/m3

 and increased height of thyroid follicular epithelial 

cells occurred in males exposed to 28.2 mg/m3

 for 28 days. In the 90-day inhalation experiments in 

rats and monkeys, a slightly increased height in the follicular cells of the thyroid was found in rats 

intermittently exposed to 10 mg/m3

. No statistically significant histopathological effects on the thyroid 

were observed at 1.0 mg/m3

. There were no effects on food intake (rats only), body weight, or on the 

histopathological appearance of other organs or tissues not discussed previously or below. 

2.2.1.3 Immunological Effects 

Chlordane caused statistically significant immune alterations in humans who had been exposed to 

chlordane aerosols in the home or in the workplace for periods ranging from 3 days to 15 months 

(average exposure period, 5.84 months) (McConnachie and Zahalsky 1992). The length of time from 

exposure to testing ranged from 4 months to 10 years, and the mean interval was 2.4 years. Impaired 

proliferative responses to all three plant mitogens tested suggested that chlordane exposure was 

associated with immune deficiency. Eleven of 12 subjects tested for autoimmunity demonstrated an 
CHLORDANE 25 

2. HEALTH EFFECTS 

increased titer of a form of autoantibody. The authors proposed that deposition of chlordane in the 

bone marrow could account for the long-term persistence of phenotypic and functional differences in 

the immune system of individuals exposed to chlordane. 

Reduced thymus weight was observed in female, but not male rats exposed 8 hours/day, 5 days/week 

to 28.2 mg chlordane/m3 for 28 days (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). Altered 

thymus weight was not observed in females exposed to 5.8 mg/m3

 or in male or female rats exposed 8 

hours/day, 5 days/week to 10 mg chlordane/m3 for 90 days. Female rats exposed 8 hours/day, 5 

days/week to 1.0 or 10 mg chlordane/m3 for 90 days had increased leukocyte counts. No histological 

lesions in thymus or lymph nodes were observed in monkeys exposed to 10 mg/m3 8 hours/day, 5 

days/week for 90 days, but immune function was not assessed. The NOAEL and LOAEL values for 

immunological effects in rats exposed for an intermediate duration are recorded in Table 2-l and 

plotted in Figure 2-l. 

2.2.1.4 Neurological Effects 

Neurological signs and symptoms including headache, dizziness, vision problems, incoordination, 

irritability, excitability, weakness, muscle twitching, and convulsions were reported consistently in a 

compilation of cases and personal reports of humans accidentally exposed by inhalation to 

unquantified concentrations of chlordane (EPA 1980a). EPA (1986d) reported three cases of optic 

neuritis that may have been due to chlordane exposure in homes treated for termites. Humans have 

experienced neurological symptoms (headache, fatigue, sleeping disturbance, blurred vision, weakness, 

fainting, confusion) shortly after their homes were treated for termites (Menconi et al. 1988). Chronic 

exposure in the treated homes was associated with migraines and neuritis/neuralgia, which increased in 

incidence with higher concentrations of pesticide in the air. Because aldrin and heptachlor were 

included in the analysis for chlordane in indoor air, these effects cannot be attributed unequivocally to 

chlordane. NIOSH (1984a) reported neurological symptoms (headache, dizziness, blurred vision, 

irritability, paresthesia, muscle dysfunction) in 4 of 13 humans within 4 days of inhalation and/or 

dermal exposure as a result of 1% chlordane being spilled in a subterranean library room. The greatest 

prevalence of symptoms occurred in those directly involved in the cleanup, where rhe potential for 

exposure to the highest concentrations was greatest. Concentrations in air, taken ≈4.5 months after the 

spill, ranged from 0.1 to 0.3 μg/m3

. Because air concentration data were not available for the first 4 

days of exposure, concentrations associated with the observed effects cannot be estimated. No 
CHLORDANE 26 

2. HEALTH EFFECTS 

neurological effects, however, were found in epidemiological studies of workers in chlordane 

manufacture (Alvarez and Hyman 1953; Fishbein et al. 1964; Princi and Spurbeck 1951). However, in 

a retrospective mortality study of 1,403 men employed for ≥3 months at two plants, a significantly 

increased risk of death from cerebrovascular disease was found, but the authors could not definitively 

attribute this excess to chlordane exposure (Wang and MacMahon 1979a). 

Abnormal respiratory movements, excess salivation, and convulsions occurred in rats exposed 

8 hours/day, 5 days/week to 154 mg technical chlordane/m3 for 11 exposures or similarly to 

413 mg/m3 for 3 exposures (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). 

Female rats exposed 8 hours/day, 5 days/week to 28.2 mg chlordane/m3

 for 28 days showed 

hypersensitivity to touch from day 16 of the study (Khasawinah et al. 1989; Velsicol Chemical Co. 

1984). This effect did not occur in rats similarly exposed to 5.8 mg/m3

. Intermediate duration 

inhalation studies in rats and monkeys 8 hours/day, 5 days/week at 10 mg/m3

 for 90 days resulted in 

no histopathological lesions in the brain, and no overt signs of neurotoxicity were reported. However, 

tests for more subtle neurological effects were not conducted. The NOAEL and LOAEL values for 

neurological effects in rats for intermediate-duration exposure are recorded in Table 2-l and plotted in 

Figure 2-1. 

2.2.1.5 Reproductive Effects 

Chronic exposure in homes treated with chlordane for termites was associated with an increased 

incidence of unspecified ovarian and uterine disease, compared with a reference population (Menconi 

et al. 1988). Because aldrin and heptachlor were included in the analysis for chlordane in indoor air, 

these effects cannot be unequivocally attributed to chlordane. 

Histopathological effects on the reproductive organs were not observed in rats exposed to chlordane in 

air at 28.2 mg/m3

 8 hours/day, 5 days/week for 28 days, or in rats or monkeys similarly exposed to 

10 mg/m3

 for 90 days (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). However, reproductive 

function was not assessed. 
CHLORDANE 27 

2. HEALTH EFFECTS 

2.2.1.6 Developmental Effects 

No studies were located regarding developmental effects in humans or animals after inhalation 

exposure to chlordane. 

2.2.1.7 Genotoxic Effects 

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

chlordane. Genotoxicity studies are discussed in Section 2.4. 

2.2.1.8 Cancer 

Chronic exposure of humans in homes treated with chlordane for termites was associated with an 

increased incidence of unspecified skin neoplasms, compared with a reference population (Menconi et 

al. 1988). Because aldrin and heptachlor were included in the analysis for chlordane in indoor air, 

these effects cannot be unequivocally attributed to chlordane. 

Retrospective mortality studies of workers involved in the manufacture of chlordane (Shindell and 

Ulrich 1986; Wang and MacMahon 1979a) reported no increased incidence of total deaths due to 

cancer or to a specific type of cancer. In a prospective study of pesticide applicators, Wang and 

MacMahon (1979b) reported an increased standardized mortality ratio (SMR) for death due to bladder 

cancer that was “on the borderline of statistical significance,” but did not attribute this observation to 

exposure to chlordane because a similar effect was not observed in the manufacturing study (Wang 

and MacMahon 1979a). A follow-up study on a larger cohort of pesticide applicators found no 

association of exposure to chlordane with total deaths due to cancer or to a specific type of cancer 

(MacMahon et al. 1988). In another retrospective mortality study of four cohorts (305-1,155 

workers/plant exposed for ≥6 months) from four manufacturing plants, there was a significantly 

increased risk of death from noncancer respiratory disease, and a slight excess risk of cancer of the 

esophagus, rectum, liver, and hematopoietic system at plant 3, and a slightly greater risk of stomach 

cancer at plant 1 (Ditraglia et al. 1981). However, chlordane was the only pesticide manufactured at 

plant 1, while aldrin, dieldrin, endrin, and dichlorodiphenyltrichloroethane were manufactured at 

plant 3. The statistical power did not allow for a conclusion that no association existed between 

cause-specific mortality and employment at the plants. However, in a follow-up to the study by 
CHLORDANE 28 

2. HEALTH EFFECTS 

Ditraglia et al. (1981), the carcinogenic risk among workers exposed to organochlorines was assessed 

(Brown 1992). This study added 11 years to the previous follow-up study, thus providing 40 years of 

observation for the cohort. As 23 years was the minimum time elapsed since each cohort member was 

first employed at the study plants, this allowed more time for diseases with long latency periods to 

develop. The investigator concluded that the mortality for all causes and all malignant neoplasms was 

lower than expected. In addition, the study was limited by a lack of exposure data and the potential 

for exposure to other chemicals. A small but insignificant increase in non-Hodgkin’s lymphoma was 

observed in farmers exposed to chlordane in a case control study (Woods and Polissar 1989). These 

studies were limited because of unquantified exposure frequency, duration, and concentration, 

exposure to other compounds, and other confounding factors. Several cases of leukemia and 

neuroblastoma were reported in persons exposed to chlordane or heptachlor in their home or garden, or 

as a result of their profession as pest control operators (Epstein and Ozonoff 1987; Infante et al. 1978). 

Although case reports are not sufficient to indict chlordane as the etiologic agent, they indicate the 

need for further epidemiological study. A small case-control study found that levels of chlordane 

residues (heptachlor epoxide, oxychlordane, trans-nonachlor) in the breast fat from 20 women with 

malignant breast disease were not significantly different from 20 women with benign breast disease 

(largely nonproliferative fibrocystic changes) (Falck et al. 1992). 

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

chlordane. EPA used the oral q1* of 1.3 (mg/kg/day)-1 (see Section 2.2.2.8) for oral exposure to 

calculate a unit risk in air of 3.7x10-4 (μg/m3)

-1 (IRIS 1992). This corresponds to upper bound 

individual lifetime cancer risks at 10-4 to 10-7 of 3x10-4 to 3x10-7 mg/m3

. The unit risk should not be 

used if the concentration in air exceeds 3x10-2 mg/m3

, above this concentration the slope factor may 

differ from the slope factor from which the unit risk was derived. 

2.2.2 Oral Exposure 

2.2.2.1 Death 

Most cases of acute human oral exposure to chlordane involved accidental ingestion by children 

(Aldrich and Holmes 1969; Curley and Garrettson 1969; EPA 1980a). The estimated doses of 

chlordane ingested are 11.0 mg/kg; complete recovery generally followed medical intervention. In 

humans, an estimated acute oral lethal dose of chlordane (WHO 1984) was between 25 and 50 mg/kg, 
CHLORDANE 29 

2. HEALTH EFFECTS 

but documentation was not provided and the method of estimation was not discussed. A man who 

accidentally ingested an unknown quantity of chlordane developed convulsions shortly after the 

ingestion and subsequently died (Kutz et al. 1983). No studies were located regarding lethality in 

humans following longer term oral exposure to chlordane. 

The dose of chlordane associated with death following acute oral exposure in animals depends on the 

species and the composition of the chlordane sample administered. Studies published in or prior to 

1950 are not included herein because the chlordane produced during this period contained 

hexachlorocyclopentadiene, which has been shown to be very toxic (WHO 1984; Ingle 1965). In rats, 

the reported oral LD50 value is between 83 and 590 mg/kg (Ambrose et al. 1953a; Ben-Dyke et al. 

1970; Boyd and Taylor 1969; Deichmann and Keplinger 1970; Gaines 1960; Lehman 1951; Podowski 

et al. 1979; Truhaut et al. 1974, 1975). The low value of 83 mg/kg (Podowski et al. 1979) is for the 

99.9% pure cis isomer, which is less likely than the technical product to be encountered in the 

environment near waste sites. Oral LD50 values for technical grade chlordane in the rat range from 

137 to 590 mg/kg. The Gaines (1960) study provided the most information and reported separate LD50 

values for males (335 mg/kg) and females (430 mg/kg). Oral LD50 values for the mouse have been 

reported at 390 (Gak et al. 1976; Truhaut et al. 1974, 1975) or 145 mg/kg/day (NIOSH 1988). 

Documentation for the NIOSH (1988) value, however, was unavailable. The hamster appears to be 

relatively resistent to death following acute oral dosing with chlordane; the reported LD50 value in this 

species was 1,720 mg/kg (Gak et al. 1976; Truhaut et al. 1974, 1975). Truhaut et al. (1975) 

speculated, on the basis of different activities of liver microsomal enzymes in rats, mice, and hamsters, 

that species differences in LD50 values may reflect differences in the rate of metabolism of the 

constituents of chlordane. Daily gavage treatment with 50 mg/kg/day caused the death of two of five 

rats on day 9 and 12 (Ambrose et al. 1953a). No deaths occurred in rats similarly treated with 

25 mg/kg/day for 15 days. Technical chlordane at 300 mg/kg/day given by gavage resulted in death 

of 4 of 10 mice within 7 days, but no mice died at a dose of 100 mg/kg/day for 30 days (Balash et al. 

1987). In a developmental study in rats, four of eight rats died after exposure to 80 mg/kg/day 

technical chlordane in olive oil by gavage on days 7-17 of gestation (Usami et al. 1986). No deaths 

occurred in 21 rats similarly treated at 40 mg/kg/day. In a developmental study in mice, 3 of 25 mice 

died after treatment with 50 mg/kg/day technical chlordane in corn oil on days 8-12 of gestation 

(Chernoff and Kavlock 1982). No other dose levels were included. 
CHLORDANE 30 

2. HEALTH EFFECTS 

In a 6-week dose-range finding study conducted by NCI (1977), mortality was significantly increased 

in male and female rats fed diets containing analytical grade chlordane (71.7% cis- and 23.1% 

trans-chlordane) at doses of 40 mg/kg/day (females) or 80 mg/kg/day (females and males). The deaths 

occurred within the first 14 days. Mortality did not increase at 20 mg/kg/day. In a 6-week dietary 

study in mice (NCI 1977), mortality increased significantly at 20.8 mg/kg/day but not at 

10.4 mg/kg/day. Doses for rats and mice in the 6-week NCI (1977) study were estimated by applying 

reference food factors to the average dietary concentrations reported by the investigators. Dietary 

exposure of rats to technical chlordane at 32 mg/kg/day for 15-163 days resulted in 100% mortality 

(Ambrose et al. 1953a). 

In the chronic (80-week) dietary study by NCI (1977), a dose-related increase in mortality was 

observed in female rats at doses of 6.0 and 12.1 mg/kg/day. No significant increase in mortality was 

observed in male rats at doses of 10.2 or 20.4 mg/kg/day in this study. There appears to be a sexrelated 

difference in mortality in this study. No effect on survival was reported by Velsicol Chemical 

Co. (1983a) in rats at the highest dose (1.175 mg/kg/day in males, 1.409 mg/kg/day in females) in a 

30-month dietary study. In the NCI (1977) study, mortality increased significantly in male mice at 

doses of 3.9 and 7.3 mg/kg/day for 80 weeks; mortality did not increase in female mice at doses of 3.9 

and 8.3 mg/kg/day. Doses in the chronic NCI (1977) study were estimated by applying reference food 

factors to the time-weighted average dietary concentrations reported by the authors. The relatively 

high resistance to death among the female mice in this study is not readily explained. Although one 

may suspect gender-related differences in metabolism, supporting data were not located. Increased 

mortality occurred in mice exposed to 6.5 mg/kg/day in an l8 month dietary study (IRDC, 1973). In 

a 24-month dietary study in mice, there was no effect on survival of either sex at 1.21 mg/kg/day, the 

highest dose tested (Velsicol Chemical Co. 1983b). All reliable LD50 and LOAEL values for lethality 

in each species and duration category are recorded in Table 2-2 and plotted in Figure 2-2. 

2.2.2.2 Systemic Effects 

The systemic effects in humans and animals after oral exposure to chlordane are discussed below. The 

highest NOAEL values and the LOAEL values for each systemic effect from all reliable studies for 

each species and duration category are recorded in Table 2-2 and plotted in Figure 2-2. 














CHLORDANE 45 

2. HEALTH EFFECTS 

Respiratory Effects. No respiratory effects were reported in a compilation of cases and personal 

reports of acute human exposure (EPA (1980a). Reports of other acute oral exposure cases (Curley 

and Garrettson 1969; Olanoff et al. 1983) did not list pneumonia as a part of the syndrome. Aldrich 

and Holmes (1969) diagnosed “probable bilateral bronchopneumonia” by radiograph in a 4-year-oId 

girl with neurological symptoms who had ingested chlordane, but whether this was thought to be due 

to chlordane exposure was not stated. Approximately 3 hours after a 15-month-old girl ingested 

11.1 mg/kg chlordane, respiration rate was irregular and breathing was shallow (Lensky and Evans 

1952). The investigators were unable to determine whether respiratory depression was due to 

chlordane ingestion or to the large amount of barbiturate given to control chlordane-induced seizures. 

In animals, acute oral exposure to chlordane does not appear to have adverse respiratory effects. In 

single-dose experiments, no histopathological lesions of the lungs were found in rats or mice treated 

by gavage with 200 mg/kg or hamsters treated by gavage with 1,200 mg chlordane/kg (Truhaut et al. 

1974, 1975). Comprehensive histopathological examinations performed on rats following dietary 

exposure for 80 weeks of ≤20.4 mg chlordane/kg/day in males and 12.1 mg chlordane/kg/day in 

females (NCI 1977) or 30 months of ≤1.175 mg chlordane/kg/day in males and 1.409 mg 

chlordane/kg/day in females (Khasawinah and Grutsch 1989a; Velsicol Chemical Co. 1983a) revealed 

no evidence of effects in the respiratory tract. Histological examination of the lungs of rats exposed to 

technical chlordane in the diet at doses ≤16 mg/kg/day for 407 days revealed no lesions; however, 

only five males and five females per group were used (Ambrose et al. 1953a). Comprehensive 

histopathological examinations performed on mice following dietary exposure for 80 weeks of ≤7.3 

mg chlordane/kg/day in males and 8.3 mg chlordane/kg/day in females (NCI 1977) or 24 months of 

≤1.21 mg chlordane/kg/day (Khasawinah and Grutsch 1989b; Velsicol Chemical Co. 1983b) revealed 

no evidence of effects in the respiratory tract. 

Cardiovascular Effects. No cardiovascular effects were reported in a compilation of cases and 

personal reports of acute human exposure (EPA (1980a) or in the case of a 15 month-old girl who 

ingested about 11.1 mg/kg chlordane (Lensky and Evans 1952). Elevated pulse rates were also found 

in other cases of human ingestion of chlordane (Curley and Garrettson 1969; Olanoff et al. 1983). 

Acute oral exposure of animals to chlordane does not appear to have adverse effects on the 

cardiovascular system. In single-dose experiments, no histopathological lesions of the cardiovascular 

system were found in rats or mice treated with 200 mg chlordane/kg or hamsters treated with 
CHLORDANE 46 

2. HEALTH EFFECTS 

1,200 mg chlordane/kg (Truhaut et al. 1974, 1975). Comprehensive histopathological examinations 

performed on rats following dietary exposure for 80 weeks of ≤20.4 mg chlordane/kg/day in males and 

12.1 mg chlordane/kg/day in females (NCI 1977) or 30 months of ≤l.175 mg chlordane/kg/day in 

males and 1.409 mg chlordane/kg/day in females (Khasawinah and Grutsch 1989a; Velsicol Chemical 

Co. 1983a) revealed no evidence of effects in the cardiovascular system. Histological examination of 

the hearts of rats exposed to technical chlordane in the diet at doses≤16 mg/kg/day for 407 days 

revealed no lesions; however, only five males and five females per group were used (Ambrose et al, 

1953a). Comprehensive histopathological examinations performed on mice following dietary exposure 

for 80 weeks of ≤7.3 mg chlordane/kg/day in males and 8.3 mg chlordane/kg/day in females (NCI 

1977) or 24 months of ≤1.21 mg chlordane/kg/day (Khasawinah and Grutsch 1989b; Velsicol 

Chemical Co. 1983b) revealed no evidence of effects in the cardiovascular system. 

Gastrointestinal Effects. Data from a compilation of cases and personal reports reveal that 

gastrointestinal effects such as upset stomach, nausea, abdominal cramps, and diarrhea are among the 

earliest signs and symptoms observed in humans who have ingested chlordane (EPA 1980a). A 

number of other cases of human ingestion of chlordane have reported such effects as gastritis, nausea, 

vomiting, and diarrhea (Curley and Garrettson 1969; Dadey and Kammer 1953; Olanoff et al. 1983). 

Gastrointestinal symptoms were reported by 18% of the residents of 42 homes in Chattanooga, 

Tennessee, in which accidental contamination of part of the public water system with chlordane 

resulted in concentrations ranging from 0.1 to 92,500 ppb (Harrington et al. 1978). Serum levels of 

trans-nonachlor and oxychlordane, however, were approximately twice as high in asymptomatic as in 

symptomatic individuals, raising serious questions about the validity of the association between 

exposure to chlordane and the reported effects. These data are insufficient to estimate an effect level 

for gastrointestinal effects in humans. 

Acute oral exposure of animals to chlordane does not appear to produce adverse effects on the 

gastrointestinal system. No histopathological lesions were observed in the gastrointestinal tracts of rats 

or mice treated with 200 mg chlordane/kg or in hamsters treated with 1,200 mg chlordane/kg (Truhaut 

et al. 1974, 1975). In chronic studies, dietary exposure to chlordane did not produce lesions of the 

gastrointestinal tracts of rats at doses of 12.1 mg/kg/day (females) or 20.4 mg/kg/day (males) (NCI 

1977) or 1.175 mg/kg/day (males) or 1.409 mg/kg/day (females) (Khasawinah and Grutsch 1989a; 

Velsicol Chemical Co. 1983a). Gastrointestinal lesions were not reported in chronic dietary 

experiments in mice at 7.3 mg/kg/day (males) or 8.3 mg/kg/day (females) (NCI 1977) or at 
CHLORDANE 47 

2. HEALTH EFFECTS 

1.21 mg/kg/day (Khasawinah and Grutsch 1989b; Velsicol Chemical Co. 1983b). Histological 

examination of the small intestine and stomach of rats exposed to technical chlordane in the diet at 

doses ≤16 mg/kg/day for 407 days revealed no lesions; however, only five males and five females per 

group were used (Ambrose et al. 1953a). 

Hematological Effects. Limited data were located regarding hematological effects in humans after 

oral exposure to chlordane. In one study, ingestion of approximately 32 mg/kg chlordane did not 

adversely affect red blood cell and white blood cell counts up to 5 days after exposure (Dadey and 

Kammer 1953). However, because the patient vomited after ingestion, the dose of 32 mg/kg does not 

reflect the dose available for absorption. In another study, a mild hypochromic anemia was diagnosed 

in a 15-month-old girl following ingestion of 11.1 mg/kg chlordane (Lensky and Evans 1952). 

Because this hematological effect was observed within a short time period after exposure and no 

hematological tests were performed prior to exposure, it possible that this hematological effect may 

have been a preexisting condition in the infant and not due to chlordane exposure. In another case 

report, white blood cell count decreased from 13,650/mm to 8350/mm 24 hours after a 20-month-old 

infant had ingested an unknown amount of chlordane (Curley and Garrettson 1969). As with the 

previous case report, a hypochromic microcytic anemia compatible with a poor iron nutrition was also 

observed. 

Mice treated by gavage with 8 mg trans-chlordanelkglday for 14 days developed leukocytosis 

associated with lymphocytosis (Johnson et al. 1986). A dose of 4 mg/kg/day was without effect. The 

toxicological significance of this effect to humans is unknown. Chronic dietary exposure of rats 

(Khasawinah and Grutsch 1989a; Velsicol Chemical Co. 1983a) and mice (Khasawinah and Grutsch 

1989b; Velsicol Chemical Co. 1983b) produced no hematological effects at doses of 

1.175-l .409 mg/kg/day (rats) or 1.21 mg/kg/day (mice). Hematological parameters (erythrocyte 

counts, leucocyte counts, and hemoglobin concentration), which were monitored frequently in rats 

exposed to technical chlordane in the diet at doses ≤16 mg/kg/day for 407 days, were not affected; 

however, only five males and five females per group were used (Ambrose et al. 1953a). 

Musculoskeletal Effects. No musculoskeletal effects were reported in a compilation of cases and 

personal reports of acute human exposure (EPA 1980a). 
CHLORDANE 48 

2. HEALTH EFFECTS 

Single oral doses of 260 mg chlordane/kg caused hypertonicity of skeletal muscle in rats, but this may 

represent a neurological effect (Santolucito and Whitcomb 1971). There was no effect on the 

mechanical response of the muscle measured with a strain-gauge transducer In situ; therefore, these 

results are not interpreted as indicating that oral exposure to chlordane was associated with 

musculoskeletal effects. Furthermore, no significant increase in the serum level of creating 

phosphokinase was found in rats treated orally with 100 mg/kg/day technical chlordane for 4 days 

(Ogata and Izushi 1991). Comprehensive histopathological examination performed on rats following 

dietary exposure for 80 weeks of ≤20.4 mg chlordane/kg/day in males and 12.1 mg chlordane/kg/day 

in females (NCI 1977) or 30 months of ≤1.175 mg chlordane/kg/day in males and 1.409 mg 

chlordane/kg/day in females (Khasawinah and Grutsch 1989a; Velsicol Chemical Co. 1983a) revealed 

no evidence of effects in the musculoskeletal system. Comprehensive histopathological examinations 

performed on mice following dietary exposure for 80 weeks of ≤7.3 mg chlordane/kg/day in males and 

8.3 mg chlordane/kg/day in females (NCI 1977) or 24 months of ≤1.21 mg chlordane/kg/day 

(Khasawinah and Grutsch 1989b; Velsicol Chemical Co. 1983b) revealed no evidence of effects in the 

musculoskeletal system. 

Hepatic Effects. There is little information in the available literature concerning hepatic effects in 

humans following oral exposure to chlordane. A compilation of cases and personal reports of human 

exposure (EPA 1980a) did not suggest that liver effects are a predominant part of the clinical picture 

for acute exposure. Results of various liver function and damage tests were within normal limits in a 

20-month-old male who ingested an unknown amount of technical grade (74%) chlordane (Curley and 

Garrettson 1969). Evaluations were made at 20 hours to 3 days after exposure. 

In animals, liver effects from acute oral exposure of animals to chlordane include liver microsomal 

enzyme induction, alterations in the activities of mitochondrial enzymes, histochemical and 

histomorphological alterations, and increased liver weight. In a 14-day feeding study in rats, Den 

Tonkelaar and Van Esch (1974) reported significant liver drug metabolizing enzyme induction (aniline 

hydroxylase, aminopyrine demethylase, and hexobarbital oxidase) at dietary concentrations equivalent 

to 0.50-2.5 mg/kg/day, but not at 0.25 mg/kg/day. Liver microsomal enzyme induction is considered 

an adaptative rather than an adverse effect. It should be noted, however, that in the case of exposure 

to chlordane, which induces enzymes associated with its own metabolism (see Section 2.3.3), some of 

the metabolites of chlordane are potentially more toxic than the parent compound. A single oral dose 

of 200 mg/kg cis-chlordane in rats significantly decreased liver glycogen and significantly increased 
CHLORDANE 49 

2. HEALTH EFFECTS 

the activities of hepatic enzymes associated with gluconeogenesis (i.e., pyruvate carboxylase, fructose1,6-diphosphatase and glucose-6-phosphatase) when measured 1 hour after treatment (Kacew and 

Singhal 1973; Singhal and Kacew 1976). These investigators also found that the activity of adenyl 

cyclase increased in the livers of these rats and that levels of hepatic cyclic adenosine monophosphate 

(AMP) correspondingly increased. Rats treated by gavage with 100 mg/kg/day technical chlordane for 

4 days had increased liver weight and liver lipid content, hypertrophy, and increased serum 

triglyceride, cholesterol, and gamma-glutamyl transferase (Ogata and Izushi 1991). There were no 

effects on activities of serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic 

transaminase (SGPT), creatinine phosphokinase or lactate dehydrogenase (LDH). Liver toxicity 

characterized by hypertrophy, dilatation of centrilobular sinuses, and congestion by increased SGPT 

and serum LDH and decreased serum cholinesterase, and by decreased liver GOT, LDH, 

cholinesterase, and glucose-6-phosphate dehydrogenase occurred in rats given a single oral dose of 

200 mg/kg (Truhaut et al. 1974, 1975). In mice given 200 mg/kg, hepatic hypertrophy, congestion, 

and dilatation of centrilobular sinuses were also seen (Truhaut et al. 1975). In addition, SGPT and 

serum LDH were increased, as were hepatic GPT and GOT. In hamsters given 1,200 mg/kg, serum 

cholinesterase was depressed, while hepatic LDH was decreased and hepatic glucose-6-phosphate 

dehydrogenase was increased (Truhaut et al. 1974, 1975). Hamsters also had congestion, dilatation of 

centrilobular sinuses, and hypertrophy. In mice treated by gavage for 2 weeks, liver weight increased 

at 8 mg/kg/day but not at 4 mg/kg/day (Johnson et al. 1986), but histological examination was not 

performed. 

In a 28-day feeding study, a dose-related increase in liver microsomal enzyme activity and relative 

liver weights was reported in rats at doses of 6.25-25 mg chlordane/kg/day (Casterhne and Williams 

1971). Intracytoplasmic bodies were found in the liver cells of rats treated by gavage with 

≥6.25 mg/kg/day technical chlordane for 15 days (Ambrose et al. 1953a). In addition, centrilobular 

hypertrophy and cytoplasmic inclusions were found in rats exposed to technical chlordane in the diet 

at doses ≥0.125 mg/kg/day for 2-9 months (Ortega et al. 1957). No histopathological liver lesions or 

increased levels of SGPT or serum alkaline phosphatase were found in rats exposed to chlordane in the 

diet at 0.1 mg/kg/day for 10-20 weeks (Mahon et al. 1978). However, cytochrome P-450 content was 

significantly increased at 10 weeks, and microsomal protein content was significantly decreased at 

20 weeks, when compared with controls. The 0.125 mg/kg/day dose in the study by Ortega et al. 

(1957) study is used as a supporting study for an intermediate-duration oral MRL which is based on 
CHLORDANE 50 

2. HEALTH EFFECTS 

the Khasawinah and Grutsch (1989a; Velsicol Chemical Co. 1983a) chronic-duration study (see 

below). 

NCI (1977) reported no compound-related liver lesions in rats of either sex in an 80-week study with 

pure analytical grade chlordane (72% cis and 23% tram isomers) at doses of 6.0-20.4 mg/kg/day. In 

a 30-month study in rats, no liver effects occurred in males at 1.175 mg/kg/day, the highest dose 

tested, but regional liver hypertrophy occurred in females at 0.273 mg/kg/day (Khasawinah and 

Grutsch 1989a; Velsicol Chemical Co. 1983a). No effects on the liver were found at 

0.055 mg/kg/day. The NOAEL of 0.055 mg/kg/day in the study by Khasawinah and Grutsch (1989a) 

was used to derive an intermediate-duration oral MRL of 0.0006 mg/kg/day and a chronic-duration 

oral MRL of 0.0006 mg/kg/day as described in the footnote in Table 2-2. Significantly increased liver 

weight, liver cell inclusion bodies, and hepatocellular hypertrophy were found in rats given technical 

chlordane in the diet at doses ≥4 mg/kg/day for 407 days (Ambrose et al. 1953a). These lesions were 

not observed at 2 mg/kg/day. 

NCI (1977) reported no compound-related liver lesions in mice of either sex in an SO-week study with 

pure analytical grade chlordane at doses of 3.9-8.3 mg/kg/day. The 24-month study in mice identified 

the lowest dose tested, 0.10 mg/kg/day, as a NOAEL for liver effects in both sexes (Khasawinah and 

Grutsch 1989b; Velsicol Chemical Co. 1983b). The next higher dose, 0.47 mg/kg/day was a LOAEL 

in both sexes associated with histopathological alterations. Lesions in the females were limited to 

hepatocellular swelling and degeneration. In males, these lesions had progressed to hepatocellular 

necrosis. In an unpublished 18-month dietary study in mice (IRDC 1973), which was reviewed by 

Epstein (1976), significantly increased liver weights and hepatocytomegaly were observed at all dose 

levels tested (0.65-6.5 mg/kg/day), but this may be related to enzyme induction, which is not 

considered adverse. 

Renal Effects. Few data were located regarding renal effects in humans after oral exposure to 

chlordane. A compilation of cases and personal reports (EPA 1980a) did not mention kidney effects 

as a part of the clinical picture of acute human exposure. In one case report, no apparent renal effects 

were observed in an 18-year-old girl 24-48 hours after an acute exposure to 32 mg/kg of chlordane 

(Dadey and Kammer 1953). Because the patient vomited after ingestion, the dose of 32 mg/kg does 

not reflect the dose available for absorption. 
CHLORDANE 51 

2. HEALTH EFFECTS 

In acute gavage studies, Truhaut et al. (1974, 1975) reported congestion of the kidneys in rats and 

mice treated with 200 mg/kg and hamsters treated with 1,200 mg chlordane/kg, respectively, but 

kidney weight was unaffected. A single oral dose of 200 mg/kg cis-chlordane significantly increased 

kidney gluconeogenic enzymes, kidney basal and fluoride-stimulated adenyl cyclase, and cyclic AMP 

(Kacew and Singhal 1973; Singhal and Kacew 1976). No histopathological renal lesions were found 

in rats exposed to 1.25 mg/kg/day technical chlordane in the diet for 2-9 months (Ortega et al. 1957). 

No histopathological lesions of the kidney were observed in rats consuming doses of ≤20.4 mg 

chlordane/kg/day in the males and 12.1 mg chlordane/kg/day in the females, or in mice consuming 

doses of ≤7.3 mg chlordane/kg/day in the males and 8.3 mg chlordane/kg/day in the females in an 

80-week dietary study (NCI 1977). No histopathological lesions of the kidney, no blood chemistry 

alterations suggesting kidney effects, and no effects on urinalysis were reported in rats consuming 

≤1.175 mg chlordane/kg/day in the males and 1.409 mg chlordane/kg/day in the females for 30 months 

(Khasawinah and Grutsch 1989a; Velsicol Chemical Co. 1983a) and in mice consuming ≤1.21 mg 

chlordane/kg/day for 24 months (Khasawinah and Grutsch 1989b; Velsicol Chemical Co. 1983b). 

Histological examination of the kidneys of rats exposed to technical chlordane in the diet at doses 

≤16 mg/kg/day for 407 days revealed no lesions; however, only five males and five females per group 

were used (Ambrose et al. 1953a). 

Dermal/ocular Effects. Few data were located regarding dermal/ocular effects in humans after oral 

exposure to chlordane. A compilation of cases and personal reports (EPA 1980a) did not mention 

dermal/ocular effects as a part of the clinical picture of acute human exposure. 

Comprehensive histopathological examination performed on rats following dietary exposure for 

80 weeks of ≤20.4 mg chlordane/kg/day in males and ≤12.1 mg chlordane/kg/day in females (NCI 

1977) or 30 months of ≤1.175 mg chlordane/kg/day in males and ≤1.409 mg chlordane/kg/day in 

females (Khasawinah and Grutsch 1989a; Velsicol Chemical Co. 1983a) revealed no evidence of 

derma.l/ocular effects. Comprehensive histopathological examination performed on mice following 

dietary exposure for 80 weeks to doses ≤7.3 mg chlordane/kg/day in males and 8.3 mg 

chlordane/kg/day in females (NCI 1977) or 24 months to doses ≤1.21 mg chlordane/kg/day 

(Khasawinah and Grutsch 1989b; Velsicol Chemical Co. 1983b) revealed no evidence of 

dermal/ocular effects. 
CHLORDANE 52 

2. HEALTH EFFECTS 

Other Systemic Effects. In single-dose experiments, no histopathological lesions of the adrenal 

were found in rats or mice treated with 200 mg chlordane/kg or hamsters treated with 1,200 mg 

chlordane/kg (Truhaut et al. 1974, 1975). Treatment of mice on gestation days 8-12 with 50 

mg/kg/day by gavage had no effect on maternal body weight (Chemoff and Kavlock 1982). Gavage 

treatment of rats with 50 mg/kg/day for 15 days resulted in weight loss (Ambrose et al. 1953a). No 

effect was observed in rats similarly treated with 25 mg/kg/day. In addition, rapid weight loss 

occurred prior to death in rats given 32 mg/kg/day technical chlordane for 15-163 days (Ambrose et 

al. 1953a). Comprehensive histopathological examination performed on rats following dietary 

exposure for 80 weeks to doses ≤20.4 mg chlordane/kg/day in the males and 12.1 mg 

chlordane/kg/day in the females (NCI 1977) or 30 months to doses ≤1.2 mg chlordane/kg/day in the 

males and 1.4 mg chlordane/kg/day in the females (Khasawinah and Grutsch 1989a; Velsicol Chemical 

Co. 1983a) revealed no evidence of other organ effects. Decreased rate of body weight gain and 

reduced terminal body weights were observed in the NCI (1977) study in rats. Female rats had 

reduced body weight at 12.1 mg/kg/day, but not at 6 mg/kg/day. Decreased body weight gain 

occurred in the male rats at 20.4 mg/kg/day, but not at 10.2 mg/kg/day. No effects on body weight 

were identified in male rats exposed to ≤1.175 mg/kg/day or in female rats exposed to ≤1.409 

mg/kg/day for 30 days (Khasawinah and Grutsch 1989a; Velsicol Chemical Co. 1983a). 

Comprehensive histopathological examination performed on mice following dietary exposure for 

80 weeks to doses ≤7.3 mg chlordane/kg/day in males and 8.3 mg chlordane/kg/day in females (NCI 

1977) or 24 months to doses ≤1.21 mg chlordane/kg/day (Khasawinah and Grutsch 1989b; Velsicol 

Chemical Co. 1983b) revealed no evidence of other organ effects. Neither study identified effects on 

body weight. Body weights were decreased by 1l-l8% in rats exposed to technical chlordane in the 

diet at 16 mg/kg/day, but not at 18 mg/kg/day, for 407 days (Ambrose et al. 1953a). 

2.2.2.3 Immunological Effects 

No studies were located regarding immunological effects in humans after oral exposure to chlordane. 

In single-dose experiments, no histopathological lesions of the spleen were found in rats or mice 

treated with 200 mg chlordane/kg or in hamsters treated with 1,200 mg chlordane/kg, but tests of 

immune function were not performed (Truhaut et al. 1974, 1975). In a 14-day gavage study, no 

definitive evidence of immune dysfunction was observed in mice treated with 8 mg/kg/day, but 
CHLORDANE 53 

2. HEALTH EFFECTS 

leukocytosis associated with lymphocytosis were observed at this dose (Johnson et al. 1986). Oral 

treatment of adult mice for 18 days with 8 mg/kg/day had no effect on granulocyte-macrophage and 

spleen colony forming stem cell populations in the bone marrow (Bamett et al. 1990a). No effects on 

spleen weight or spleen histology were found in rats exposed to technical chlordane at 

≥1.25 mg/kg/day chlordane in the diet for 2-9 months (Ortega et al. 1957) or in rats exposed to 

technical chlordane in diet at ≤16 mg/kg/day for 407 days (Ambrose et al. 1953a). However, only five 

of six males and five of six females per group were used, and immune function was not assessed in 

these studies. The NOAEL values for immunological effects in mice for acute and intermediate 

durations in studies that assessed immune function are recorded in Table 2-2 and plotted in Figure 2-2. 

Information on immune effects in prenatally exposed mice is presented in Section 2.2.2.6, 

Developmental Effects. 

2.2.2.4 Neurological Effects 

Central nervous system effects including ataxia, headache, dizziness, irritability, excitability, 

confusion, incoordination, muscle tremors, seizures, convulsions, and coma have been described in 

a compilation of cases and personal reports as a consistent and predictable part of the clinical 

picture of acute human oral exposure to insecticidal formulations of chlordane (EPA 1980a). By 

accident, part of the public water system of Chattanooga, Tennessee, became contaminated, and the 

tap water of 42 houses had chlordane concentrations ranging from 0.1 to 92,500 ppb (Harrington et 

al. 1978). When the affected residents were surveyed, 18% reported neurological symptoms 

consistent with acute chlordane toxicity. Serum levels of trans-nonachlor and oxychlordane, 

however, were approximately twice as high in asymptomatic as in symptomatic individuals, raising 

serious questions about the validity of the association between exposure to chlordane and the 

reported effects. Most of the information on acute human oral exposure comes from cases of 

accidental or suicidal ingestion; therefore, doses of ingested chlordane are not readily quantifiable. 

Determination of a dose-effect response is further complicated because vomiting or lavage reduced 

the amount of ingested chlordane actually available for systemic absorption. In one such case, 

ingestion of 32 mg/kg of chlordane by a girl resulted initially in diplopia, blurred vision, and 

twitching of the extremities followed by vomiting and eventually muscle tremors and generalized 

convulsions (Dadey and Kammer 1953). The investigators also estimated that after vomiting, only 

about 10 mg/kg was available for absorption. In another case, a man who ingested 3,041 mg/kg 

chlordane developed seizures and became comatose (Olanoff et al. 1983), but he also vomited, 

invalidating this dose. Clonic convulsions also developed in a 4-year-old girl who 
CHLORDANE 54 

2. HEALTH EFFECTS 

ingested chlordane (Aldrich and Holmes 1969). A dose of 0.15 mg/kg was estimated after gastric 

lavage. In a 15 month-old child who ingested 11.1 mg/kg chlordane, tremors and convulsions began 

about 3 hours after ingestion, which was prior to gastric lavage (Lensky and Evans 1952). These 

subsided by the second day, followed by moderate ataxia and irritability. Convulsions were also 

observed in patients who ingested unknown quantities of chlordane (Curley and Garrettson 1969; Kutz 

et al. 1983). 

Central nervous system effects consisting of tremors, convulsions, and paralysis of the hindlimbs 

occurred in rats following single gavage doses of chlordane ≥200 mg chlordane/kg (Hrdina et al. 

1974). Hypothermia occurred at 100 mg/kg. Histological examination of the brains of rats and mice 

given a single oral dose of 200 mg/kg and hamsters given a single dose of 1,200 mg/kg revealed 

congestion in the brain (Truhaut et al. 1975). In rats exposed to ≥200 mg/kg/day by gavage once or to 

50 mg/kg/day by gavage for 9-12 days, convulsions preceded death (Ambrose et al. 1953a). Neither 

death nor convulsions occurred in those similarly treated with 25 mg/kg/day for 15 days. No ataxia or 

change in the level of cerebral amino acids was observed in mice treated by gavage with 25 mg/kg/day 

for 45 consecutive days (Matin et al. 1977). In a 12-week dietary study, a dose of 5 mg/kg/day 

caused convulsions in rats (LOAEL for serious effects), and 1.25 mg/kg/day significantly inhibited 

brain ATPase (LOAEL for less serious effects), which may be involved in the mechanism of chlordane 

induced neurotoxicity (Drummond et al. 1983). In chronic feeding studies, chlordane induced tremors 

in female rats at 12.1 mg/kg/day, but not at 6 mg/kg/day and only during week 44 of the 80-week 

study (NCI 1977). Similar signs were not observed in male rats, which were tested at 10.2 and 

20.4 mg/kg/day. No brain lesions were found in rats of either sex. Neither central nervous system 

signs nor histopathological lesions of the nervous system were found in a 30-month dietary study in 

which male rats received doses ≤1.175 mg/kg/day and female rats received doses ≤1.409 mg/kg/day 

(Khasawinah and Grutsch 1989a; Velsicol Chemical Co. 1983a). Both sexes of mice in the 80-week 

chronic study (NCI 1977) had tremors at the high dose (8.3 mg/kg/day in females and 7.3 mg/kg/day 

in males) but not at the lower dose (3.9 mg/kg/day in both sexes). NCI (1977) reported no 

histopathological lesions in the brains of treated mice of either sex. Neither central nervous system 

signs nor histopathological lesions of the nervous system were found in a 24-month dietary study in 

which mice received doses ≤1.21 mg/kg/day (Khasawinah and Grutsch 1989b; Velsicol Chemical Co. 

1983b). No evidence of neurological effects, such as tremors of sensitization to auditory stimuli, were 

found in rats exposed to technical chlordane in the diet at ≤16 mg/kg/day for 407 days (Ambrose et al. 

1953a). However, only five males and five females were used. The highest NOAEL values and all 
CHLORDANE 55 

2. HEALTH EFFECTS 

reliable LOAEL values for neurological effects in each species and duration category are recorded in 

Table 2-2 and plotted in Figure 2-2. 

2.2.2.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans after oral exposure to chlordane. 

Histological examination of the testes of rats and mice given a single oral dose of 200 mg/kg or 

hamsters given a single oral dose of 1,200 mg/kg revealed no lesions (Truhaut et al. 1975), but 

reproductive function was not assessed. In the only evaluation of fertility with oral exposure, Ambrose 

et al. (1953a) reported reduced fertility, reflected as a reduction in the number of mated females that 

delivered litters, when male and female rats were fed a diet that provided chlordane at 16 mg/kg/day. 

Treatment began at weaning of the parental generation and continued through lactation. None of the 

litters survived to weaning. Treatment of male mice by gavage with 100 or 300 mg/kg/day for 

30 days resulted in reduced size of seminiferous tubules and degeneration of spermatogenic epithelium 

(Balash et al. 1987). Administration of 19.5 mg chlordane/kg/day to male rats for 90 days increased 

androgen receptor sites in the ventral prostate (Shain et al. 1977). There were no effects on ventral 

prostate or testicular weight, or on plasma testosterone level, and the toxicological significance of this 

observation to humans is unclear. No histopathological lesions were reported in the reproductive tracts 

of rats consuming doses ≤20.4 mg chlordane/kg/day in the males and 12.1 mg chlordane/kg/day in the 

females in an 80-week dietary study (NCI 1977) or in rats consuming doses ≤1.175 mg 

chlordane/kg/day in the males and ≥1.409 mg chlordane/kg/day in the females in a 30-month dietary 

study (Khasawinah and Grutsch 1989a; Velsicol Chemical Co. 1983a). NCI (1977) found no 

treatment-related histopathological lesions in the reproductive tracts of male (<7.3 mg/kg/day) or 

female (≤8.3 mg/kg/day) mice in an 80-week dietary study with analytical grade cis and trcllzs 

isomers. No histopathological lesions in mice were reported in a 24-month dietary study with ≤1.21 

mg technical chlordane/kg/day (Khasawinah and Grutsch 1989b; Velsicol Chemical Co. 1983b). In 

male and female rats given diets providing ≤16 mg/kg/day chlordane for 407 days, no 

histopathological lesions were found in reproductive organs (Ambrose et al. 1953a). However, only 

five male and five female rats per groups were used. 

The LOAEL values for reproductive effects in rats and mice are recorded in Table 2-2 and plotted in 

Figure 2-2. However, NOAEL values are not identified in Table 2-2 and Figure 2-2 for studies that 
CHLORDANE 56 

2. HEALTH EFFECTS 

found no histopathological lesions in reproductive organs because these studies did not assess 

reproductive function. 

2.2.2.6 Developmental Effects 

No studies were located regarding developmental effects in humans after oral exposure to chlordane. 

There was no effect on the incidence of malformations and no evidence of fetal toxicity, including 

retarded skeletal development, in the fetuses of rats treated by gavage with 0, 20, 40, or 80 mg 

chlordane/kg/day during gestation, although four of the eight rats treated with 80 mg/kg/day died 

(Usami et al. 1986). No effects on viability and postnatal growth were observed in the offspring in a 

developmental toxicity screening test in which mice were treated with an undescribed sample of 

chlordane at 50 mg/kg/day during gestation days 8-12 (Chemoff and Kavlock 1982). The offspring of 

mice treated at 1 and 2.5 mg chlordane/kg/day during the third trimester exhibited depressed 

acquisition of avoidance response, increased seizure threshold, and increased exploratory activity in a 

study that assessed neurobehavioral effects after in utero exposure (Al-Hachim and Al-Baker 1973). 

The authors concluded that chlordane affected the fetal brain. Exposure could also have occurred via 

nursing, because the pups were allowed to nurse the treated dams. The LOAEL of 1 mg/kg/day in the 

study by Al-Hachim and Al-Baker (1973) was used to derive an acute-duration oral MRL of 

0.001 mg/kg/day as described in the footnote in Table 2-2. 

Cranmer et al. (1984) administered analytical grade chlordane in peanut homogenate at 0, 0.16, or 

8.00 mg/kg/day to groups of mice throughout gestation to measure endocrinological performance of 

adult offspring. Although mice in both treated groups gave birth to approximately equal numbers of 

viable offspring of “average” body weight that were grossly normal in appearance, 55% of the 

offspring of the high-dose dams died within the first week of the nursing period. The authors stated 

only that the cause of death was not apparent from gross necropsy; however, it is possible that 

exposure to high levels of chlordane and/or metabolites in the dam’s milk may have been responsible 

for these deaths, based on data reported in Sections 2.3.3 and 2.3.4 on metabolism and excretion of 

chlordane. Postweaning survival was not affected by treatment. Plasma corticosterone in the offspring 

measured at 400 days of age was elevated in females at 0.16. but not at 8.0 mg/kg/day, and in males 

at both dose levels. These effects were not apparent at 800 days of age in either sex, although not 

enough high-dose males survived for evaluation. The investigators hypothesized that elevated plasma 
CHLORDANE 57 

2. HEALTH EFFECTS 

levels of corticosterone may reflect the diminished ability of the liver to metabolically reduce 

corticosterone. The effects on plasma corticosterone levels in females did not occur in a dose-related 

fashion and the toxicological significance of this effect is unclear. Therefore, this effect is not 

considered in estimating levels of significant exposure. 

Studies have been conducted in which pregnant mice were treated with chlordane, and the effects on 

the immune system of the offspring were assessed (Bamett et al. 1985a, 1985b; Menna et al. 1985; 

Spyker-Cranmer et al. 1982). These studies suggested to the investigators that in utero and/or neonatal 

exposure to chlordane suppressed cell-mediated immunity, as manifested by depressed delayed-type 

hypersensitivity reactions in the offspring of treated mice. There was no effect on humoral-mediated 

immunity. It is likely that the nursing pups continued to be exposed to chlordane because chlordane is 

excreted in milk (see Section 2.3). 

More recent studies by these investigators indicate that prenatal treatment of mice depressed 

granulocyte-macrophage and spleen-forming stem cells in the bone marrow (Bamett et al. 1990a) and 

the liver (Bamett et al. 1990b), but had no effect on cytotoxic T-lymphocyte activity (Blaylock et al. 

1990a). Further mechanistic studies demonstrated that prenatal exposure of mice to chlordane (dams 

treated with 8 mg/kg/day during gestation days 1-18) alters the macrophage in such a manner that it 

now has phenotypic characteristics of a cell that has achieved inflammatory status (Theus et al. 1992). 

The significance of this effect is not well understood. The reliable NOAEL and LOAEL values for 

developmental effects in each species and duration category for all reliable studies are recorded in 

Table 2-2 and plotted in Figure 2-2. 

2.2.2.7 Genotoxic Effects 

No studies were located regarding genetic effects in humans or animals after oral exposure to 

chlordane. Genotoxicity studies are discussed in Section 2.4. 

2.2.2.8 Cancer 

No studies were located regarding cancer in humans after oral exposure to chlordane. 
CHLORDANE 58 

2. HEALTH EFFECTS 

Studies using three different strains of mice (one strain had an historically low incidence of 

spontaneous liver tumors) have demonstrated that dietary administration of chlordane is associated 

with the development of hepatocellular carcinomas in this species. An unpublished study by IRDC 

(1973), which was available only in reviews by EPA (1986c, 1987e), Epstein (1976), IRIS (1992), and 

Reuber (1978), found significant increases in the incidence of hepatocellular carcinomas in male and 

female CD-l mice fed analytical grade technical chlordane in the diet at doses of 3.25 and 6.5 

mg/kg/day for 18 months. In an NCI (1977) chronic dietary study with a mixture of analytical cis 

(72%) and trans (23%) isomers of chlordane, there was a dose-related increase in the incidence of 

hepatocellular carcinomas in male and female B6C3Fl mice that was statistically significant in both 

treated groups of males and in the high-dose females. Becker and Sell (1979) used male C57BL/6N 

strain mice that are historically resistant to spontaneous liver tumors. Those treated with chlordane in 

the diet at 3.25 mg/kg/day had a 27% incidence of hepatocellular carcinoma. The incidence of 

hepatocellular carcinoma in 200 control mice observed over a period of 18 months was zero. This 

study demonstrated that chlordane was capable of inducing hepatocellular carcinomas in a strain of 

mouse that does not develop spontaneous liver lesions. An increased incidence of hepatocellular 

adenomas and hemangiomas developed in male mice, but not female mice, maintained on a diet 

providing ≈1.21 mg chlordane/kg/day for 2 years (Khasawinah and Grutsch 1989b; Velsicol Chemical 

Co. 1983b). This report stands in contrast to the NCI (1977) study in which a significantly increased 

incidence of hepatocellular carcinomas was observed in both sexes of mice. Nonetheless, dose levels 

in the Khasawinah and Grutsch (1989b) and Velsicol Chemical Co. (1983b) reports were lower than 

those in the NCI (1977) bioassay, and a different strain of mice was used. 

The 80-week NCI (1977) dietary study provided no evidence for the carcinogenicity of chlordane in 

rats. The IRIS (1992) review of the 30-month dietary study (Khasawinah and Grutsch 1989a; Velsicol 

Chemical Co. 1983a) in rats concluded that an increased incidence of hepatocellular adenomas 

occurred in male rats at 1.175 mg/kg/day. Subsequent EPA reviews and reevaluations of the original 

slides (EPA 1985a, 1985b, 1988b) concluded that the increased incidence of hepatocellular adenomas 

in rats in this study was not statistically significant. Classification of the evidence for carcinogenicity 

in animals as sufficient is suitable without positive results in this study, and the assignment of 

chlordane to EPA group B2 is appropriate (IRIS 1992). Using the tumor data from male and female 

mice in the NCI (1977) and IRDC (1973), studies, EPA (1986c) derived a q1* for oral exposure of 1.3 

(mg/kg/day)-1 and a unit risk in drinking water of 3.7x10-8 mg/L (3.7x10-8 ppm) that have been verified 

(IRIS 1992). This q1* corresponds to upper bound individual lifetime cancer risks at 10-4 to l0-7 risk 
CHLORDANE 59 

2. HEALTH EFFECTS 

levels of 8x10-5 to 8x10-8 mg/kg/day, which are plotted in Figure 2-2. The unit risk should not be 

used if the water concentration exceeds 3x10-1 mg/L (3x10-1 ppm), because above this concentration 

the slope factor may differ from that stated. The Cancer Effect Levels (CELs) are recorded in 

Table 2-2 and plotted in Figure 2-2. 

Chlordane potentiated the development of liver neoplasms in mice fed a diet providing 3.25 mg/kg/day 

for 25 weeks, following exposure to diethylnitrosamine in the drinking water for 14 weeks (Williams 

and Numoto 1984). The investigators observed that chlordane enhanced the development of 

neoplasms in liver cells in which diethylnitrosamine had previously induced subtle biochemical 

changes. Because chlordane is not strongly genotoxic, the investigators concluded that chlordane acted 

as a tumor promotor rather than a cocarcinogen. 

2.2.3 Dermal Exposure 

2.2.3.1 Death 

Only one report was found regarding mortality in humans following dermal exposure to chlordane. 

The usefulness of this report is limited, however, because the individual was exposed to chlordane, 

DDT, Velsicol AR50, and triton X-100 mixed together in the form of a suspension. After a woman 

spilled the suspension on the front of her clothes, she became confused, developed convulsions, and 

died within minutes after exposure (Derbes et al. 1955). At autopsy, the brain, lungs, and kidneys 

were found to have nonspecific pathological changes. Deaths were not reported in a compilation of 

cases and personal reports of acute human dermal exposure to chlordane (EPA 1980a). 

Dermal toxicity data in animals is largely limited to LD50 data. Gaines (1960) reported dermal LD50 

values of 840 mg/kg in male rats and 690 mg/kg in female rats for technical grade chlordane in 

xylene. The dermal LD50 value of undiluted technical chlordane in female rats (not determined for 

male rats) was 530 mg/kg. However, Ben-Dyke et al. (1970) reported that the dermal LD50 in rats was 

>1,600 mg/kg (highest dose tested). The vehicle in which chlordane is administered may influence the 

toxicity. No deaths occurred when 273 mg/kg/day chlordane in alcohol was applied to the depilated 

skin of rats for 4 days (Ambrose et al. 1953a). However, a single dose of 222 mg/kg in cottonseed oil 

was fatal to one of five rats, and daily doses of 217 mg/kg/day in cottonseed oil for 2 days was fatal 

to one of five rats, and for 3-4 days was fatal to all rats. Death occurred from 1 to 12 days after the 
CHLORDANE 60 

2. HEALTH EFFECTS 

ast application. Frings and O’Tousa (1950) reported decreased survival in female mice treated 

dermally with 7.4 mg chlordane/kg/day for 100 days. This study involved the use of “early” 

production chlordane containing significant amounts of the reaction intermediate 

hexachlorocyclopentadiene. Ingle (1965) reported a difference between “early” production and “later” 

production (i.e., more highly purified) chlordane with respect to dermal toxicity in rabbits; the LD50 for 

“early” production chlordane was <780 mg/kg, and the LD50 for “later” production chlordane was 

1,100-1,200 mg/kg. The reliable dermal LD50 values are presented in Table 2-3. 

2.2.3.2 Systemic Effects 

No studies were located regarding cardiovascular, hematological, or musculoskeletal effects in humans 

or animals after dermal exposure to chlordane. 

Respiratory Effects. Respiratory effects in humans were not reported in a compilation of cases and 

personal reports of acute dermal exposure to chlordane (EPA 1980a). Edema and congestion of the 

lungs were observed in a woman who died within minutes after dermal exposure to a suspension 

containing chlordane, DDT, and other chemicals (Derbes et al. 1955). 

The only information regarding respiratory effects in animals after dermal exposure to chlordane is that 

hemorrhage of lungs was found in mice treated with 7.4 mg/kg/day 5 days/week for 20 weeks (Frings 

and O’Tousa 1950). The chlordane used in this study was probably “early production chlordane,” 

which contains hexachlorocyclopentadiene. 

Gastrointestinal Effects. Gastrointestinal effects in humans were not reported in a compilation of 

cases and personal reports of acute human dermal exposure to chlordane (EPA 1980a). Vomiting 

occurred in an infant who was reported to have “prolonged” derrnal exposure to liquid chlordane 

(Balistreri et al. 1973). Congestion of the stomach was observed in a woman who died within minutes 

after dermal exposure to a suspension containing chlordane, DDT, and other chemicals (Derbes et al. 

1955). 

No studies were located regarding gastrointestinal effects in animals after dermal exposure to 

chlordane. 

CHLORDANE 62 

2. HEALTH EFFECTS 

Hepatic Effects. Liver effects in humans were not reported in a compilation of cases and personal 

reports of acute dermal exposure to chlordane (EPA 1980a). Balistreri et al. (1973) reported clinical 

hepatic effects consisting of jaundice, hepatomegaly and elevated serum transaminases in an infant 

following “prolonged” dermal exposure to liquid chlordane. Liver biopsy revealed centrilobular 

necrosis, fatty infiltration, and minimal inflammation. Liver function tests were normal in a 47-yearold nurseryman who handled soil sprayed with chlordane and other chemicals for ≈2 years (Barnes 

1967); there was no estimate of exposure concentration or dose. 

Frings and O’Tousa (1950) reported hepatic centrilobular necrosis in mice treated dermally with 

“early” production chlordane (7.4 or 29.6 mg/kg/day) 5 days/week for 20 weeks. “Early” production 

chlordane was frequently contaminated with hexachlorocyclopentadiene, which is very toxic and 

highly irritating (Ingle 1965). Liver cell inclusion bodies were observed in some rats that received 

dermal applications of 217-273 mg/kg/day chlordane in alcohol or cottonseed oil for l-4 days 

(Ambrose et al. 1953a). Additional details were not reported. These data are not considered for 

estimation of levels of significant exposure. 

Renal Effects. Renal effects in humans were not reported in a compilation of cases and personal 

reports of acute human dermal exposure to chlordane (EPA 1980a). Nonspecific pathological changes 

were observed in the kidneys of a woman who died within minutes after dermal exposure to a 

suspension of chlordane, DDT, and other chemicals (Derbes et al. 1955). 

White blotches were observed on the kidneys of mice dermally exposed to 7.4 mg chlordane/kg/day, 

5 days/week for 20 weeks (Frings and O’Tousa 1950), but the test sample was probably contaminated 

with hexachlorocyclopentadiene. A large number of yellow droplets in the renal cortex tubular 

epithelium and many faintly yellow or colorless, rod-shaped, apparently crystalline structures in the 

cytoplasm of the cortical tubules were found in all rats that received dermal applications of 

217-273 mg/kg/day chlordane in alcohol or cottonseed oil for l-4 days (Ambrose et al. 1953a). The 

toxicological significance of these findings is not clear as other studies by any route did not describe 

similar effects and no control rats were used. 

Dermal/Ocular Effects. In a compilation of many cases and personal reports of accidental dermal 

exposure to chlordane, frequently reported signs and symptoms included burning sensations, rashes, 

and pruritus (EPA 1980a). Accidental spraying of chlordane mixtures in the eyes consistently causes 
CHLORDANE 63 

2. HEALTH EFFECTS 

conjunctivitis (EPA 1980a). These reports of dermal and ocular effects are complicated by exposure 

to mixtures of chemicals including other pesticides and vehicles such as petroleum distillates, known 

to be irritants. Dermal lesions were not reported in a woman who exhibited generalized convulsions 

and died within minutes of dermal exposure to a suspension of chlordane, DDT, and other chemicals. 

The woman’s thighs and abdomen were washed after the spill (Derbes et al. 1955). 

No local reactions were observed in rats treated dermally with 273 mg/kg/day chlordane in alcohol for 

4 days (Ambrose et al. 1953a). Whether skin reactions were observed in the rats treated with 

chlordane in cottonseed oil was not reported. Datta et al. (1977) reported hyperkeratinization, cellular 

degeneration such as vacuolization, and a multinucleated condition in cells of the malpighian layer in 

the skin of dermally treated guinea pigs. No changes were observed in the dermis. Chlordane in 

acetone was applied to the open, shaved skin at 168 mg/kg once daily for 90 days. This LOAEL for 

skin effects in guinea pigs is presented in Table 2-3. 

2.2.3.3 Immunological Effects 

No studies were located regarding immunological effects in humans after dermal exposure to 

chlordane. 

Datta et al. (1977) did not report evidence of sensitization in guinea pigs dermally treated once daily 

for 90 days with chlordane in acetone (see Dermal/ocular effects). It is not clear, however, that 

evidence of sensitization would have been detected by the experimental protocol. 

2.2.3.4 Neurological Effects 

There are several reports regarding central nervous system effects in humans after dermal exposure to 

chlordane. None of the reports quantified exposure, and in several of the reports, exposure involved 

chlordane and one or more other pesticides. Derbes et al. (1955) reported the death of a woman 

dermally exposed to a suspension containing chlordane, DDT, Velsicol AR50, and triton X-100. 

Mental confusion and convulsions preceded death. Nonspecific pathological changes were found in 

the brain at autopsy. Balistreri et al. (1973) reported seizures in an infant following “prolonged” 

dermal exposure to liquid chlordane. Barnes (1967) reported a case involving a 47-year-old 

nurseryman who handled soil that had been sprayed with chlordane. Exposure took place over a 
CHLORDANE 64 

2. HEALTH EFFECTS 

period of 2 years during which time the nurseryman was also exposed to DDT, plant hormone sprays, 

and arsenic pesticides. During the exposure period, the nurseryman experienced Jacksonian and grand 

ma1 convulsions and electroencephalographic evidence of generalized dysrhythmia. Chlordane was 

considered to be the cause because the patient’s condition improved when he ceased using chlordane. 

Application of chlordane in alcohol at 273 mg/kg/day or in cottonseed oil at 217 or 222 mg/kg/day for 

l-4 days to depilated skin of rats did not result in tremors (Ambrose et al. 1953a). “Early production 

chlordane” induced tremors, convulsions, and seizures in rabbits to which 780 mg/kg was applied to 

the skin (Ingle 1965). Frings and O’Tousa (1950) also noted tremors, convulsions, and seizures in 

mice treated topically with “early” production chlordane. These effects were observed at 7.4 and 

29.6 mg chlordane/kg/day in mice treated 5 days/week for 20 weeks. Data generated with “early” 

production chlordane are not used to estimate levels of significant exposure. 

2.2.3.5 Reproductive Effects 

Only one case report was available that described reproductive effects in humans after dermal exposure 

to chlordane. In this study, a woman accidentally spilled an unknown quantity of suspension 

containing chlordane down the front of her clothes and died shortly afterwards (Derbes et al. 1955). 

An autopsy of the woman revealed endometrial hemorrhage and superficial ulceration of the vaginal 

mucosa. Because of an inadequate medical history, these lesions may not be treatment-related. 

No studies were located regarding reproductive effects in animals after dermal exposure to chlordane. 

2.2.3.6 Developmental Effects 

No studies were located regarding developmental effects in humans or animals after dermal exposure 

to chlordane. 

2.2.3.7 Genotoxic Effects 

No studies were located regarding genotoxicity in humans after dermal exposure to chlordane. 
CHLORDANE 65 

2. HEALTH EFFECTS 

Chlordane was applied to the plucked skin of male CD-l mice at doses of 0, l/32, l/16, or l/8 of the 

published dermal LD50 (about 0, 51, 102, or 205 mg/kg body weight). The high dose induced a 

significant incidence of micronuclei formation in the bone marrow cells (Schop et al. 1990). All of 

the doses induced a significant and dose-related increase in the incidence of nuclei aberrations in the 

hair follicles. Other genotoxicity studies are discussed in Section 2.4. 

2.2.3.8 Cancer 

Only one epidemiological study was identified in the literature that investigated cancer in humans after 

dermal exposure to chlordane. In this population based case-control study, the risk of non-Hodgkins 

lymphoma (NHL) among farmers was significantly elevated (odds ratio, 1.7) for personal handling, 

mixing, or application of chlordane as an animal insecticide or as a crop insecticide (Cantor et al. 

1992). The odds ratio for NHL was also greater among farmers who first used chlordane before 1965 

(15-18 years before diagnosis) or those farmers who did not use protective equipment. The study 

was, however, limited by incomplete reporting of duration of exposure to chlordane and the amount of 

chlordane or other pesticides farmers were simultaneously exposed to. 

No studies were located regarding cancer in animals after dermal exposure to chlordane. 

2 . 3 TOXICOKINETICS 

The fate of chlordane in the body reflects the lipophilicity and metabolism of the chemical. Chlordane 

appears to be readily absorbed, regardless of the route of exposure, as expected for highly lipophilic 

substances. Initially, tissue levels are highest in the liver and kidneys, reflecting the high degree of 

vascularity of these tissues. Subsequently, chlordane and its metabolites are relocated in fat, where 

they persist for long periods of time. Metabolism results in a number of oxidation products, including 

oxychlordane, which persist in body fat as the predominant chlordane residues. Free radicals formed 

by reductive dehalogenation may play an important role in the toxicity of chlordane. Except for the 

rabbit, chlordane and its metabolites are excreted more readily in the bile than in the urine, due to the 

general lack of polarity and high lipophilicity of the terminal metabolites. Substantial amounts are 

also excreted via lactation, even after exposure has ceased, rendering the nursing young particularly 

susceptible to toxicity. 
CHLORDANE 66 

2. HEALTH EFFECTS 

Effects attributed to chlordane exposure include blood dyscrasia, hepatotoxicity, neurotoxicity, 

immunotoxicity and cancer. Possible mechanisms of toxicity relevant to all target organs include the 

ability of chlordane and its metabolites to bind irreversibly to cellular macromolecules, inducing cell 

death or disrupting normal cell function. In addition, chlordane may increase tissue production of 

superoxide, which can accelerate lipid peroxidation, disrupting the function of cellular and subcellular 

membranes. Chlordane induces its own metabolism to toxic intermediates, which may exacerbate its 

hepatotoxicity. This may involve suppression of hepatic mitochondrial energy metabolism. 

The neurotoxicity of chlordane may be related to effects on the levels of endogenous neurotransmitters 

in various regions of the brain. Immune effects following prenatal exposure may arise from a 

reduction in the population in the bone marrow of stem cells responsible for differentiation into 

various types of immunoactive cells. Chlordane is considered an epigenetic carcinogen, causing liver 

cancer in mice, probably by suppressing gap junction intercellular communication. 

2.3.1 Absorption 

2.3.1.1 Inhalation Exposure 

Data obtained from humans exposed via inhalation to chlordane in the air of termite-treated homes in 

Japan (Taguchi and Yakushiji 1988) or as the result of pesticide spraying (Kawano and Tatsukawa 

1982; Saito et al. 1986; Takamiya 1987) indicate that blood or tissue levels of chlordane and/or its 

metabolites increase with exposure duration. Although these data are not sufficient to quantify 

absorption from the respiratory tract, they confirm qualitatively that absorption occurs. 

An intratracheal study suggests that absorption of chlordane by the respiratory system of rats is rapid. 

A peak blood concentration of radioactivity equivalent to ≈4% of an intratracheal dose of radiolabeled 

chlordane was reached in <5 minutes (Nye and Dorough 1976). The value of this study was limited 

by the mode in which the chlordane was delivered, the use of ethanol as a vehicle, and the unknown 

impact of anesthesia and surgical preparation on uptake from the respiratory tract. In reviewing the 

data from this study, Nomeir and Hajjar (1987) noted that ≈24% of the dose of radioactivity was 

present in the lungs 1 hour after treatment and concluded that ≈76% of the dose had been absorbed 

from the respiratory tract. 
CHLORDANE 67 

2. HEALTH EFFECTS 

2.3.1.2 Oral Exposure 

Information on the absorption of chlordane following oral exposure in humans comes largely from 

case reports involving accidental ingestion. A chlordane level of 2.71 mg/L was measured in the 

blood of a 20-month-old boy 2.75 hours after he had ingested an unknown amount of technical grade 

(74%) chlordane (Curley and Garrettson 1969). A chlordane concentration of 3.4 mg/L was measured 

in a serum sample taken from a 4-year-old girl at an unspecified time following the ingestion of an 

unknown amount of a 45% chlordane formulation (Aldrich and Holmes 1969). Chlordane was found 

in the blood plasma (concentration of 4.87 μg/g) and in several tissues (adipose, 22.00 μg; spleen, 

19.15 μg/g; brain, 23.27 μg/kg; liver, 59.93 μg/g) of a 59-year-old male ≈2 hours after he ingested an 

unknown amount of chlordane (Kutz et al. 1983). A whole blood chlordane concentration of 5 mg/L 

was measured in a 62-year-old male 3.5 hours after he had ingested 300 mL of a 75% chlordane 

solution (215 g) (Olanoff et al. 1983). While these case reports do not provide information on the rate 

and extent of absorption in humans after oral exposure to chlordane, they indicate that the compound 

is absorbed from the gastrointestinal tract. 

Excretion of radioactivity in the urine of rats given a single oral dose of radiolabeled chlordane 

accounted for ≈2-8.5% of the administered dose (Bamett and Dorough 1974). The chlordane doses 

used in this study were 0.05-1.0 mg/kg of a 3:l mixture of cis- and trans-chlordane, or 0.2 mg/kg of 

each isomer separately. Based on these urinary excretion data, EPA (1987e) stated that chlordane 

absorption from the gastrointestinal tract of rats was at least 28.5% of the administered dose. More 

recent information (Ewing et al. 1985; Ohno et al. 1986), however, indicates that absorption from the 

gastrointestinal tract of rats and mice may be substantially higher than previously estimated. Biliary 

excretion of chlordane (and/or its metabolites) played a significant role in the elimination of this 

compound in both species, suggesting that a large amount of the radioactivity found in the feces 

following oral administration of radiolabeled chlordane represents absorbed material. A first-order 

absorption model suitably described the experimental data in rats (Ohno et al. 1986). The extent of 

chlordane absorption after oral exposure was estimated by comparing areas under the plasma 

concentration versus time curves (AUC) of radioactive equivalents of chlordane after oral or 

intravenous dosing at 0.1-1.0 mg/kg. Absorption was estimated to be ≈80% of the administered dose 

in rats, and this percentage did not vary significantly over the dose range tested (Ohno et al. 1986). 
CHLORDANE 68 

2. HEALTH EFFECTS 

Chlordane appears to be rapidly absorbed from the gastrointestinal tract of rats; peak blood levels of 

radioactivity occurred ≈2-4 hours following administration of oral doses ranging from 0.1 to 

1.0 mg/kg (Ewing et al. 1985; Ohno et al. 1986). Peak blood levels of radioactivity following a 

1.0 mg/kg dose of 14C-chlordane were between ≈81 ng chlordane equivalents/ml for the cis isomer 

(Ewing et al. 1985) and 175 ng chlordane equivalents/ml for the trans isomer (Ohno et al. 1986). 

Absorption in the mouse was slower than in the rat after oral exposure to chlordane; a peak blood 

level of 113 ng equivalents/ml of blood was observed in the mouse 8 hours after administration of a 

1 mg/kg dose of 14C-cis-chlordane (Ewing et al. 1985). Absorption was not quantified following oral 

dosing in the mouse, but intraperitoneal studies indicated that a significant degree of biliary excretion 

also occurs in this species (Ewing et al. 1985). Administration of a mixture (1:1) of cis and trans 

isomers of chlordane (20 mg/kg for each of the isomers) to male mice resulted in peak absorption of 

cis- and trans-chlordane within 24 hours (Satoh and Kikawa 1992). The authors did not specify the 

time of peak absorption for either isomer. Although the distribution data suggest that more 

cis-chlordane was absorbed than trans-chlordane, data were insufficient to compare the rate of 

absorption of cis- and trans-chlordane. The mouse may be similar to the rat in that a large percentage 

of an oral dose of chlordane is absorbed in the gastrointestinal tract of both species. 

In rabbits, the estimated absorption of chlordane following various repeated oral dosing regimens with 

radiolabeled compound has been between 30% and 50% of the cumulative 14C dose, based on 

radioactivity eliminated in the urine (Balba and Saha 1978; Barnett and Dorough 1974; Poonawalla 

and Korte 1971). The various dosing regimens used in these studies included: radiolabeled 

trans-chlordane given to male rabbits at ≈3.8 mg/kg/day for 10 weeks (Poonawalla and Korte 1971), 

25 ppm of a mixture of cis- and trans-chlordane fed to a male rabbit for 2 days (≈1.22 mg/kg/day) 

(Barnett and Dorough 1974), and cis- or trans-chlordane (30 and 67 mg/kg/day, respectively) given in 

gelatin capsules to male rabbits for 4 days (Balba and Saha 1978). Biliary excretion was not studied 

in the rabbit, and the estimation of 30-50% absorption (based on urinary excretion) must be 

considered a minimum estimate. 

2.3.1.3 Dermal Exposure 

No quantitative data regarding absorption in humans after dermal exposure to chlordane were located. 

Kazen et al. (1974) reported that chlordane tends to persist on the hands of pest control operators 
CHLORDANE 69 

2. HEALTH EFFECTS 

(exposure duration not reported) for at least 2 years after exposure to the pesticide has been I 

terminated. This claim is questionable, however, because the subject in the study was not followed 

closely enough to determine the absence of chlordane exposure during the 2-year period. It is 

possible, for example, that chlordane may have been present on the subject’s clothing or shoes, 

resulting in continued exposure. Derbes et al. (1955) reported a case of accidental death preceded by 

neurological signs typical of chlordane toxicity in a woman who was dermally exposed to a mixture of 

chlordane and other chemicals. These data suggest that chlordane is absorbed through human skin. In 

a more recent study involving 248 male and 227 female outpatients, the investigators were unable to 

find a strong correlation between skin chlordane levels and blood chlordane levels in men, although a 

significant correlation (r=0.47; p<0.01) was observed in women (Hirai and Tomokuni 1993). In 

addition, a small correlation (r=0.37; p<0.05) was observed between skin chlordane levels and blood 

oxychlordane levels in both sexes. 

The dermal route of exposure is relatively significant for chlordane. Ambrose et al. (1953a) indicated 

that a topical dose of chlordane in rats (50 mg/kg) is more readily absorbed when the compound is 

administered in an oil vehicle instead of ethyl alcohol. In an in vitro study using diffusing cells in 

which 14C-chlordane (0.0027-0.003 mg/cm3

/day) was applied to human skin from cadavers for 24 

hours, the amount of the applied dose of radioactivity recovered from the receptor fluid (human 

plasma) was 0.04% when the application medium was soil and 0.07% when the application medium 

was acetone (Wester et al. 1992). Much larger proportions (0.34% from soil and 10.9% from acetone) 

were retained within the layers of the skin. In an in vivo study, 14C-chlordane in soil or acetone was 

applied to the skin of monkeys for 24 hours (Wester et al. 1992). Absorption accounted for 4.2% of 

the dose in soil and 6% of the dose in acetone, based on recovery of 14C in the urine following dermal, 

compared with intravenous, dosing. 

2.3.2 Distribution 

Several studies report chlordane residues in the blood or fat of pest control operators (spray men), 

residents in homes treated for termites, or residents with no known mode of exposure other than 

background. Background exposures include inhalation of the material in ambient air and ingestion 

through food (Dearth and Hites 1991a; Sasaki et al. 1991a; Wariishi and Nishiyama 1989); dermal 

exposure also may be possible, although data regarding dermal exposure were not located. In pesticide 

spray applicators properly attired in protective clothing, the inhalation route is probably most important 
CHLORDANE 70 

2. HEALTH EFFECTS 

(Takamiya 1987). Nevertheless, most humans with any body burden of chlordane residues were 

probably exposed by multiple routes; therefore, except for those few cases reports in which oral 

exposure was known, human data are presented here. 

Generally, levels of total chlordane residues in blood and milk fat increase as duration of exposure 

increases (Ogata and Izushi 1991; Saito et al. 1986; Taguchi and Yakushiji 1988; Takamiya 1987). 

Human milk fat contained total mean chlordane residues of ≤188 ppm, and blood levels were 

≤0.015 ppm in exposed individuals (Ogato and Izushi 1991; Taguchi and Yakushiji 1988). Levels in 

fat and liver exceeded levels in the blood (Mussalo-Rauhamaa 1991). 

2.3.2.1 Inhalation Exposure 

Data regarding tissue levels of chlordane residues in humans after purely inhalation exposure were not 

located. 

Intratracheal administration of radiolabeled chlordane in rats resulted in the following tissue 

distributions of radioactivity (expressed as percent of administered dose) 1 hour after administration: 

23.9% in lungs, 19.6% in liver, 0.3% in kidney, and 0.1% in the bladder and its contents (Nye and 

Dorough 1976). Limitations of this study are discussed in Section 2.3.1.1. 

Total chlordane residue levels following continual 13-week exposure of rats and monkeys are highest 

in the fat (69-200 ppm), followed by the liver (3.5-11 ppm) and blood (0.2-0.3 ppm) (Khasawinah 

1989). Tissue residues in rats are predominantly oxidation products; residues in monkeys are 

predominantly unchanged components of technical chlordane, suggesting that monkeys are less 

efficient metabolizers than rats of chlordane components. 

2.3.2.2 Oral Exposure 

Information on the distribution of chlordane and/or its metabolites in humans after oral exposure is 

from case reports involving ingestion of the compound. Approximately 2 hours after a 59-year-old 

male ingested a fatal dose of chlordane, autopsy revealed concentrations of chlordane in several tissues 

(Kutz et al. 1983). The tissues analyzed and their respective chlordane concentrations were: adipose 

tissue 22 μg, spleen 19.15 μg/g, brain 23.27 μglg, kidney 14.10 μg, and liver 59.93 μg/g. The 
CHLORDANE 71 

2. HEALTH EFFECTS 

level of chlordane in the adipose tissue of a 20-month-old boy who drank an unknown amount of
 

technical grade (74%) chlordane was 3.12 μg/g 30 minutes after ingestion (Curley and Garrettson
 

1969). The concentration in adipose tissue peaked at 30-35 ug/g of fat ≈8 days following the
 

incident. Fifty-eight days after a 62-year-old male ingested 215 g of chlordane, the reported levels of
 

chlordane components and metabolites (oxychlordane, trans-nonachlor, and heptachlor epoxide) in the
 

adipose tissue were 5 μg/g of fat (Olanoff et al. 1983). Although this level is considerably below that
 

reported in the 20-month-old boy (30-35 μg/g of fat) on day 8 by Curley and Garrettson (1969), it is
 

still significantly higher than the average concentration of oxychlordane (a metabolite of chlordane)
 

detected in the adipose tissue of members of the general population of the United States. Levels of
 

oxychlordane in human adipose tissue range from 0.03 to 0.49 μg/g of fat, with average concentrations
 

of ≈0.11-0.19 μg/g of fat (Barquet et al. 1981; Biros and Enos 1973; Kutz et al. 1976, 1979).
 

The pattern of tissue distribution of chlordane and/or its metabolites in animals after oral exposure
 

does not appear to depend on the size of the dose or whether exposure is to single or to multiple
 

doses. The tissue distribution patterns of radioactivity in rats, 1 day after exposure to a single oral
 

dose of a 3:l mixture of radiolabeled cis- and trans-chlordane, were similar over a dose range of
 

0.05-1.0 mg/kg (Bamett and Dorough 1974). Levels of tissue radioactivity increased with increasing
 

dose; at all dose levels, the highest concentrations of radioactivity were found in the fat followed, in
 

order, by the liver and kidney. Lower concentrations were found in the brain and muscle. In this
 

same study, oral administration of chlordane over a longer period of time did not change the
 

distribution pattern of radioactivity from that observed following a single oral exposure. Rats fed the
 

same mixture of chlordane (i.e., 3 cis-:1 trans-) for 56 days at dietary concentrations of 1, 5, or
 

25 ppm were observed to have high levels of radioactivity in the fat and much lower levels of
 

radioactivity (in decreasing order) in the liver, kidney, brain, and muscle. The concentrations of
 

radioactivity measured in these tissues were dose-dependent.
 

The accumulation of chlordane and its metabolites in fat appears to depend on exposure duration.
 

Takeda et al. (1984) treated rats by gavage with technical chlordane at 10 μg/kg/day for 7 or 14 days,
 

Chlordane and metabolites measured in the fat reached 30.4 μg/g wet tissue at the end of 7 days of
 

treatment and 77.4 μg/g at the end of 14 days of treatment.
 

Distribution to the liver and kidneys of rats after a single oral dose of chlordane is more rapid than
 

distribution to adipose tissue. Levels of radioactivity peaked in the liver and kidneys of rats 2-4 hours
 
CHLORDANE 72 

2. HEALTH EFFECTS 

after the administration of a single oral dose of radiolabeled γ-chlordane (0.05 or 10 mg/kg) (Ohno et 

al. 1986). In this same study, the level of radioactivity in the adipose tissue peaked at 16 hours (dose 

of 10 mg/kg) and 4 days (dose of 0.05 mg/kg) after administration of the compound. The 

concentrations of γ-chlordane equivalents in adipose tissue 10 days after the administration of either 

dose (0.05 or 10.0 mg/kg) were ≈10 times higher than levels in the liver and kidney. 

More recently, Dearth and Hites (1991b) measured the half-lives of depuration of 14 different 

chlordane components (e.g., cis- and trans-chlordane and cis- and trans-nonachlor) and metabolites 

(e.g., heptachlor epoxide, oxychlordane) from the fat of rats fed chlordane in the diet for 28 days. 

Half-lives ranged from 5.92 days (cis-chlordane) to 54.1 days (nonachlor III) and were apparently 

related to the metabolism rate of the various compounds. Structural characteristics associated with 

slowed depuration included an increasing number of chlorines on ring 1, the chlorine on Cl existing in 

an endo- (compared with an exo-) configuration, and the presence of two chlorines on C2. In mice 

treated once or every other day for 29 days, the whole body content of cis- and trans-chlordane 

remained at very low levels; the content of cis- and trans-nonachlor and oxychlordane continued to 

increase with continued treatment (Hirasawa and Takizawa 1989). The investigators concluded that 

the chlordane isomers were readily metabolized, but that the nonachlor isomers were not. 

Oxychlordane, a metabolic intermediate of both chlordane isomers, is very slowly metabolized and 

tends to persist. 

Elimination of radioactivity from the liver and kidney of rats treated with radiolabeled chlordane 

differs from elimination of radioactivity from peritesticular adipose tissue. Elimination of radioactivity 

from the kidneys and livers of rats treated with either high (10 mg/kg) or low (0.05 mg/kg) doses of 

γ-chlordane was biphasic - the initial rapid phase had half-lives in both organs ranging from ≈5.9 to 

9.6 hours (Ohno et al. 1986). Half-lives for the slower, terminal phase of elimination in these organs 

ranged from ≈4.4 to 5.0 days. In contrast, elimination of radioactivity from peritesticular adipose 

tissue was monophasic and relatively slow (elimination half-lives of 9.1 days in the low-dose group 

and 8.4 days in the high-dose group). Skin retained radioactivity longer than any other tissue 

(elimination half-lives of 15.2 and 10.4 days for the low- and high-dose groups, respectively). Ewing 

et al. (1985) confirmed that peak concentrations of radioactivity were found in the livers of rats and 

mice 2-4 hours after administration of a single oral dose of radiolabeled cis-chlordane (1.0 mg/kg). 

The investigators observed that radioactivity was eliminated much more slowly from the livers of mice 

than from the livers of rats. They speculated that this may explain the susceptibility of mice to the 
CHLORDANE 73 

2. HEALTH EFFECTS 

development of hepatocellular carcinomas; whereas, rats appear to be relatively insensitive to the 

formation of this tumor following chlordane administration (NCI 1977). 

Several of these oral studies with radiolabeled chlordane (Ambrose et al. 1953b; Barnett and Dorough 

1974; Street and Blau 1972) reported that female rats had higher levels of radioactivity in the fat than 

did the males. Levels of radioactivity in perirenal adipose tissue from female rats were as much as 

twice the levels observed in males (Ambrose et al. 1953b), and females tended to store a much larger 

proportion of this radioactivity in abdominal fat in the form of oxychlordane (Street and Blau 1972). 

Another recurrent observation in these distribution studies is an isomer effect on the amount of 

radioactivity that is distributed to the various tissues. Studies by Barnett and Dorough (1974) and 

Street and Blau (1972) indicated that significantly higher concentrations of radioactivity are stored in 

the tissues of rats following oral administration of the trans isomer, compared to the concentrations 

observed following administration of the cis isomer. This observation also holds true for rabbits. 

Balba and Saha (1978) administered four doses of either cis-chlordane (67 mg/kg body weight/dose) or 

trans-chlordane (30 mg/kg body weight/dose) to rabbits for 4 days. Although the administered dose of 

the cis isomer was more than twice the dose of the trans isomer, tissue levels of radioactivity were 

higher in animals given the trans isomer. When a 1:l mixture of cis- and trans-chlordane (total dose: 

40 mg/kg) was administeredeto mice, higher concentrations of cis-chlordane were found in muscle 

tissues than of trans-chlordane (Satoh and Kikawa 1992). At day one, cis-chlordane concentrations in 

muscle, liver, kidney, brain, and spleen were 1,260, 377, 136, 56, and 34 ppb, respectively, while 

tram-chlordane concentrations in these tissues were 766, 103, 82, 37, and 22 ppb, respectively. The 

concentrations of cis- and trans-chlordane were similar in blood (29 and 22 ppb, respectively). 

Oxychlordane concentrations peaked in the liver (1,918 ppb) at day 2, and peaked at day 1 in the 

following tissues: muscle (569 ppb), kidney (326 ppb), brain (226 ppb), spleen (126 ppb), and blood 

(103 ppb). The level of oxychlordane in adipose tissue was 2,890 ppb on week 8, but by week 52, it 

had decreased to 648 ppb. In addition, oxychlordane levels were higher in adipose tissue than any 

other tissue at 52 weeks. 

2.3.2.3 Dermal Exposure 

No studies were located regarding tissue distribution in humans or animals after dermal exposure to 

chlordane. 
CHLORDANE 74 

2. HEALTH EFFECTS 

2.3.3 Metabolism 

Information on the metabolism of chlordane in humans is limited. Tashiro and Matsumura (1978) 

identified the metabolites of cis- and trans-chlordane following incubation of these compounds with 

human liver microsomal preparations. The following rnetabolites (in order of decreasing 

concentration) were identified: chlordene chlorohydrin, monohydroxylated dihydrochlordene, 

oxychlordane, and relatively smaller but similar amounts of 1,2-dichlorochlordene, l-hydroxy2-chlorochlordene, 1-hydroxy-2-chloro-2,3-epoxychlordene, 1,2-hydroxychlordene, 

trihydroxydihydrochlordene, and β-glucuronide-l-hydroxydihydrochlordene. Patterns of metabolites 

were similar whether the starting material was the cis or trans isomer. Kutz et al. (1976, 1979) 

reported the presence of oxychlordane in most adipose tissue samples taken at surgery or necropsy 

from humans. Data were not located regarding the levels of chlordane metabolites in the urine of 

exposed humans. 

Tashiro and Matsumura (1978) reported that experiments with liver microsomal preparations from rats 

yielded results nearly identical to those for human preparations. These investigators noted, however, 

that rat microsomal preparations efficiently metabolized trans-nonachlor (a predominant component of 

technical chlordane) to trans-chlordane, but that human microsomal preparations did not. These data 

suggest that the metabolism of pure isomers of chlordane by humans and rats is similar, but that 

metabolism of components other than the pure isomers present in the technical product may differ. 

Data regarding the nature of tissue residues in rats and monkeys following continual inhalation 

exposure for 90 days (see Section 2.3.2.1) indicate that monkeys are less efficient metabolizers of 

chlordane than are rats (Kbasawinah 1989). Oxychlordane is the predominant metabolite of 

trans-chlordane in rats and monkeys (Khasawinah 1989; Sasaki et al. 1992). 

Chlordane has been known to undergo biotransformation in animals since the mid 196Os, when it was 

demonstrated by Poonawalla and Korte (1964) that 10-80s of the radioactivity found in the tissues 

and excreta of rats given an intravenous dose of radiolabeled cis-chlordane was in the form of water 

soluble metabolites. Subsequently, several metabolic schemes have been proposed based on 

information obtained from in vivo and in vitro studies in rats (Bamett and Dorough 1974; Brimfield et 

al. 1978; Tashiro and Matsumura 1978) and rabbits (Balba and Saha 1978; Poonawalla and Korte 

1971). These proposed schemes lack consistency, and controversial issues include: differences in the 
CHLORDANE 75 

2. HEALTH EFFECTS 

identity of metabolites observed in in vivo versus in vitro experiments, possible isomer differences 

(i.e., cis versus trans) in the routes of metabolism followed, and whether metabolites thought to be 

terminal by some investigators (e.g., oxychlordane) are capable of undergoing further 

biotransformation by mammals. The metabolic scheme for chlordane in animals presented in 

Figure 2-3 was proposed recently as a synthesis of the available information by Nomeir and Hajjar 

(1987). This scheme involves four routes of metabolism for the chlordane molecule. No distinction is 

made between cis- and [runs-chlordane in the qualitative nature of the metabolites formed. The first 

proposed metabolic route starts with hydroxylation at position three of the molecule to form 

3-hydroxychlordane. This reaction is thought to be mediated by the microsomal mixed-function 

oxidase (MFO) system. Dehydration of 3-hydroxychlordane leads to 1,2-dichlorochlordene and 

eventually to other metabolites such as oxychlordane and l-hydroxy-2-chlorochlordene. Alternatively, 

3-hydroxychlordane may undergo replacement of chlorines by hydroxyl groups to form 

monochlorodihydroxylated and -trihydroxylated derivatives. The second pathway starts with 

dehydrochlorination to form heptachlor. The mechanism of this reaction is not completely understood 

but is thought to be mediated by the cytochrome P-450 system and/or by glutathione-S-transferase type 

enzymes. Further metabolism of heptachlor leads to 1-hydroxychlordene, heptachlor epoxide, or 

eventually to 1-chloro-2,3-dihydroxydihydrochlordene. The third pathway starts with dehalogenation 

of chlordane to form l-chlorodihydrochlordene, probably mediated by microsomal MFO systems. 

Further reactions probably involve hydrolysis and conjugation with glucuronic acid. The fourth 

metabolic pathway, and probably the least understood, involves hydrolytic removal of a chlorine atom 

and its replacement by a hydroxyl group to form l-chloro-2-hydroxychlordene chlorohydrin. This 

product may undergo further metabolism to form monochlorodihydroxy- and trihydroxy- derivatives 

of dihydrochlordene. Studies with rat hepatic microsomes suggest that cytochrome P-450 may be the 

most important enzyme to catalyze degradation of trans-chlordane (Kawano et al. 1989). Epoxide 

hydrolase is probably the predominant enzyme to catalyze degradation of oxychlordane. Reductive 

dehalogenation, with the production of free radicals, may also be important in the toxicity of chlordane 

(Brimfield and Street 1981; Kawano et al. 1989). 

The metabolic rate of various chlordane components appears to depend on three structural features 

(Dearth and Hites 1991b). First, compounds with two chlorines on ring 1 are metabolized 3 times as 

rapidly as those with three chlorines. Second, compounds with the chlorine on C2 in an exoconfiguration are metabolized 20-25% more quickly than compounds with an endo-configuration. 

Third, compounds with one chlorine on C2 are metabolized 3 times as rapidly as those with two 

CHLORDANE 77 

2. HEALTH EFFECTS 

chlorines. Dechlorination of compounds with three chlorines on ring one appears to be the first and 

rate-limiting step of metabolism of these compounds. 

In mice treated orally every other day for 28 days with technical chlordane, cis- and trans-chlordane 

reached peak levels in the whole body on the first day and declined to lower levels in spite of repeated 

dosing; cis- and trans-nonachlor and oxychlordane increased during the entire study period (Hirasawa 

and Takizawa 1989). The ratio of cis- to trans-chlordane and cis- to trans-nonachlor in the test 

sample (6:7 and 1:4, respectively) and in the mouse body at termination of the experiment (5:3 and 

1:7, respectively) suggests that trans-chlordane is metabolized more readily than cis-chlordane and that 

cis-nonachlor is metabolized more readily than trans-nonachlor. The decreasing content of the 

chlordane isomers and the increasing content of oxychlordane with repeated dosing suggests that 

chlordane induces its own metabolism. 

2.3.4 Excretion 

Lactation is probably the route of excretion of most interest, because of concern that nursing mothers 

may pass chlordane residues to their infants in this manner. Documentation of toxicity in infants 

induced in this manner, however, was not located in the available literature. While cis- and 

trans-chlordane have not been identified in human milk, chlordane metabolites and related chemicals 

present in commercial products (e.g., oxychlordane, trans-nonachlor and heptachlor epoxide) have 

been identified in human milk. Oxychlordane residues were detected in 46% of 57 human milk 

samples in Arkansas/Mississippi (Strassman and Kutz 1977), in 68% of 6 samples in low pesticide 

usage areas of Mississippi (Bamett et al. 1979), and in 100% of 50 samples in Hawaii (Jensen 1983). 

On a whole milk basis, mean concentrations of oxychlordane ranged from 0.002 to 0.005 mg/L 

(Bamett et al. 1979; Strassman and Kutz 1977). All three routes of exposure (inhalation, oral, dermal) 

may have been involved in the accumulation of chlordane residues in the mothers. 

2.3.4.1 Inhalation Exposure 

No studies were located regarding excretion in humans after inhalation exposure to chlordane. 
CHLORDANE 78 

2. HEALTH EFFECTS 

Six days after the endotracheal administration of radiolabeled chlordane to rats, 52% of the 

administered dose of radioactivity was recovered from the feces and 12% was recovered from the 

urine (Nye and Dorough 1976). The limitations of this study are discussed in Section 2.3.1.1. 

2.3.4.2 Oral Exposure 

Information regarding the excretion of chlordane and/or its metabolites from the human body after oral 

exposure is from case reports of accidental ingestion. These reports conclude that elimination from the 

plasma was biphasic in nature (Aldrich and Holmes 1969; Curley and Garrettson 1969; Olanoff et al. 

1983). Marked differences existed, however, in the reported half-life of the terminal (slow) phase. 

Values reported for the terminal phase were 88 days (Aldrich and Holmes 1969), 21 days (Curley and 

Garrettson 1969), and 34 days (Olanoff et al. 1983). Small amounts of chlordane have been excreted 

in the urine of humans after oral ingestion of the compound. Aldrich and Holmes (1969) reported that 

the urinary concentration of chlordane decreased from 1.93 to 0.05 mg/L over the first 3 days 

following the ingestion of an unknown amount of chlordane by a 4-year-old girl. Curley and 

Garrettson (1969) reported a chlordane concentration in the urine of 0.309 mg/L 24 hours after the 

ingestion of an unknown amount of chlordane by a 20-month-old boy. Fecal chlordane concentrations 

of 719 and 105 ppm have been reported on days 2 and 3, respectively, following chlordane ingestion 

by a 4-year-old girl (Aldrich and Holmes 1969). 

The excretion of chlordane and/or its metabolites has been studied in animals following oral 

administration. In rats, ≈70-90% of the radioactivity administered (depending on the isomer) was 

eliminated within 7 days following a single oral dose of the radiolabeled pesticide (Bamett and 

Dorough 1974; Ewing et al. 1985; Tashiro and Matsumura 1977). In these studies, the cis isomer was 

eliminated more quickly than the trans isomer. From 70% to 90% of the radioactivity orally 

administered to rats was excreted in the feces; excretion of radioactivity in the urine ranged from 2% 

to 8% of the administered dose (Bamett and Dorough 1974). In another study, cis- and 

trans-chlordane were cleared from the blood within 7 days after male mice received a total dose of 

40 mg/kg chlordane mixture (1:1) of both isomers (Satoh and Kikawa 1992). Although the cis isomer 

tended to accumulate more than the trans isomer, no difference in the half-lives in tissues (0.6-2 days) 

was observed between the two isomers. Both isomers were rapidly metabolized to oxychlordane. 

Oxychlordane was eliminated very slowly compared to the isomers and its half-life in blood was 

determined to be 25 days. 
CHLORDANE 79 

2. HEALTH EFFECTS 

Recent studies by Ohno et al. (1986) and Ewing et al. (1985) indicate that biliary excretion of 

chlordane and/or its metabolites is significant in both rats and mice and is the source of fecal excretion 

by these species. Ewing et al. (1985) administered a 1.0 mg/kg dose of radiolabeled cis-chlordane to 

rats and mice by intraperitoneal injection and recovered 47% (rats) and 67% (mice) of the dose in the 

feces within 7 days. By using bile duct-cannulated rats, Ohno et al. (1986) showed that bilk-y 

excretion occurred more rapidly after oral administration than after intravenous administration, 

probably as a result of the first pass of blood from the digestive tract through the liver via the hepatic 

portal circulation. The relative proportions of fecal and urinary excretion of radioactivity after oral 

administration of radiolabeled chlordane in rats do not appear to change significantly with dose over 

ranges of 0.05-10.0 mg/kg (Bamett and Dorough 1974; Ohno et al. 1986). In addition, longer-term 

administration of chlordane in the diet (1, 5, or 25 ppm for 56 days) did not change the excretion 

pattern significantly in rats from that observed following single oral doses (Bamett and Dorough 

1974). 

In contrast to the excretion pattern of radioactivity observed in rats following oral exposure to 

radiolabeled chlordane, rabbits tend to excrete larger percentages of the administered dose in the urine. 

The percentage of the administered radioactivity excreted in the urine of rabbits following multiple 

oral doses ranged from ≈28% to 47% (Balba and Saha 1978; Poonawalla and Korte 1971). In these 

same studies, fecal excretion in the rabbit ranged from ≈22% to 48% of the administered dose. The 

greater urinary excretion of radioactivity in rabbits compared with rats may be due to the greater 

ability of rabbits to form water soluble conjugates of chlordane metabolites. Biliary excretion was not 

studied in these experiments. 

2.3.4.3 Dermal Exposure 

No studies were located regarding excretion in humans or animals after dermal exposure to chlordane. 

2.3.5 Mechanisms of Action 

Although the data suggest that chlordane is readily absorbed from the respiratory (Nye and Dorough 

1976) and gastrointestinal tracts (Ohno et al. 1986), and that dermal absorption is sufficient to cause 

toxicity in humans and animals (Derbes et al. 1955; Gaines 1960), data regarding the mechanisms of 

absorption were not located. Generally, highly lipophilic organic compounds cross membranes largely 
CHLORDANE 80 

2. HEALTH EFFECTS 

by passive diffusion. Since chlordane is highly lipophilic (see Chapter 3), it is expected that 

absorption of chlordane by all routes of exposure would involve primarily passive diffusion. This is 

consistent with the observation by Ohno et al. (1986) that little difference in the extent of 

gastrointestinal absorption occurred over a 10-fold difference in dose. 

The metabolism of the components of chlordane and the lipophilicity of the components and 

metabolites influence their distribution. Initial distribution to the liver and kidneys is more rapid than 

to fat (Ohno et al. 1986), probably reflecting differences in vascularity of these sites. Subsequently, 

redistribution results in higher levels in the fat than other tissues. Low levels of cis- and 

trans-chlordane in fat and relatively higher levels of oxychlordane (a metabolite) and trans-nonachlor 

(a component) reflect the relative lability of the chlordane isomers and stability of the latter two 

compounds (Hirasawa and Takizawa 1989; Sasaki et al. 1991a, 1992). 

Metabolism of the cis and trans isomers of chlordane by humans and laboratory animals appears to be 

qualitatively similar (Kutz et al. 1976, 1979), although monkeys may be less efficient than rats 

(Khasawinah 1989), and rats may metabolize trans-nonachlor more efficiently than humans do 

(Tashiro and Matsumura 1978). Metabolism appears to be largely oxidative, involving hepatic 

microsomal cytochrome P-450 (Kawano et al. 1989). Epoxide hydrolase is probably the predominant 

enzyme involved in further degradation of oxychlordane, but the process appears to be slow in animals 

and humans. In addition, reductive dehalogenation, probably resulting in the formation of reactive free 

radical intermediates, may be important in the toxicity of chlordane (Brimfield and Street 1981; 

Kawano et al. 1989). 

The strong lipophilicity and relatively weak hydrophilicity of chlordane and its metabolites suggest 

that excretion would be largely by passive diffusion. This is supported by the observation that fecal 

(biliary) excretion exceeds urinary excretion in humans and rats (Aldrich and Holmes 1969; Ohno et 

al. 1986), indicating that renal tubular excretion is probably not a major factor in excretion. Passive 

tubular resorption probably accounts for the lesser role that renal excretion plays in the fate of 

chlordane, compared with most organic chemicals, for which biotransformation results in the 

formation of more polar (hydrophilic) products. 

The principal effects of exposure to chlordane include liver effects, neurological effects, 

immunological effects, and liver cancer. Although mechanisms of toxicity specific for each of these is 
CHLORDANE 81 

2. HEALTH EFFECTS 

discussed below, general mechanisms that may apply to many organ systems are discussed here. The 

first is the ability of cis- and trans-chlordane and their metabolites to bind irreversibly with cellular 

macromolecules such as protein, ribonucleic acid (RNA), and deoxyribonucleic acid (DNA) (Brimfield 

and Street 1981). Binding to these macromolecules may lead to cell death or altered cellular function. 

In addition, cis- and trans-chlordane, heptachlor, and heptachlor epoxide increase the generation of 

superoxide in cultures of guinea pig polymorphonuclear leukocytes (Suzaki et al. 1988). This was 

probably an indirect effect of activation of phospholipase C, or of increasing the intracellular 

concentration of free ionized calcium, rather than a direct effect on protein kinase C. 

Many animal studies identify the liver as an important target organ for chlordane. Rats appear to be 

more sensitive than mice (Khasawinah and Grutsch 1989a, 1989b; Khasawinah et al. 1989; Velsicol 

Chemical Co. 1983a, 1983b, 1984). The primary effect, induction of hepatic cytochrome P-450 and 

other microsomal protein, is accompanied by a large increase in the volume of the smooth 

endoplasmic reticulum, which results in hepatocellular enlargement and hypertrophy (Khasawinah et 

al. 1989). These effects appear to be reversible. Reversible enzyme induction accompanied by 

hyperplasia is considered to be an adaptive response. In mice treated repeatedly over several weeks, 

the body burden of the chlordane isomers decreased, and the body burden of oxychlordane increased 

with time (Hirasawa and Takizawa 1989). This suggests that chlordane induces its own metabolism, 

probably to intermediates that bind to and disrupt the function of vital cellular macromolecules 

(Brimfield and Street 1981). A possible mechanism may be that the components and metabolites of 

chlordane exert their effects by altering the permeability of the mitochondrial membrane, inhibiting 

mitochondrial oxidative phosphorylation (Ogata et al. 1989). Also, chlordane may induce production 

of superoxide (Suzaki et al. 1988), which may result in lipoperoxidation, a known mechanism of 

toxicity to the liver. 

Neurotoxicity is a consistent effect of acute exposure to chlordane in humans and animals. Little is 

known, however, regarding the mechanisms of neurotoxicity. In rats, a single oral 200-300 mg/kg 

dose induced tremor, paralysis, and tonic-clonic convulsions, and a 100 mg/kg dose induced 

hypothermia (Hrdina et al. 1974). The convulsive signs were accompanied by a decrease in cortical 

and striatal acetylcholine and an increase in acetylcholinesterase activity. Although the decrease in 

availability of the neurotransmitter acetylcholine may alter neuronal calcium ion levels at the synaptic 

plate, there is no evidence that this accounts for the convulsions induced by chlordane (Grutsch and 

Khasawinah 1991). In mice, a single 1,000 mg/kg intraperitoneal injection of chlordane induced 
CHLORDANE 82 

2. HEALTH EFFECTS 

convulsions accompanied by reduced ν-aminobutyric acid (GABA) levels in five regions of the brain 

(Fishman and Gianutsos 1985). Grutsch and Khasawinah (1991) speculate that chlordane may 

competitively inhibit GABA, reducing the ability of GABA to inhibit post-synaptic neuronal 

excitability. The hypothermia was accompanied by a decrease in brain stem levels of norepinephrine. 

The investigators speculated that the reduced levels of norepinephrine arose from release and use of 

this transmitter amine to activate heat-loss mechanisms, resulting in hypothermia. In more recent 

investigations, Inoue et al. (1989) reported that chlordane inhibits nicotine-induced neurocellular 

uptake of Ca++, which is required for release of norepinephrine. Therefore, chlordane may inhibit 

neural transmission by altering membrane permeability to Ca++ restricting the release of 

norepinephrine. 

Reduced fertility, observed in mice and rats treated with high doses of chlordane (Ambrose et al. 

1953a; Welch et al. 1971), may arise from altered metabolism and circulating levels of steroid 

hormones (Cranmer et al. 1984; Welch et al. 1971) or from reduced binding of progesterone to its 

cytosolic receptor site in the endometrium (Lundholm 1988). 

There is little evidence that altered immunological function in adults is a prominent effect of chlordane 

exposure, since exposure induced no clear effects on cellular or humoral immune response or on 

granulocyte-, macrophage-, or splenocyte-forming stem cell populations in the bone marrow of adult 

mice. (Bamett et al. 1990a; Johnson et al. 1986). In vitro experiments, however, showed that 

trans-chlordane and its metabolites, including oxychlordane, suppressed both cell-mediated and 

humoral immune responses, possibly by depressing immune cell proliferation early in the chain of 

events involved in an immune response (Johnson et al. 1987). The addition of small amounts of 

mouse or human serum blocked chlordane-induced immunosuppression in the in vitro studies, 

suggesting that factors in the serum may have blocked immunosuppression in the in vivo studies. 

Studies in mice suggest that prenatal and early postnatal exposure may have lasting effects on the 

immune system, including a reduction in the population of primitive granulocyte-, macrophage-, and 

splenocyte-forming stem cells in the bone marrow (Barnett et al. 1990a) and liver (Barnett et al. 

1990b), without reducing the total cellularity of these tissues. Reasons for the apparent greater 

sensitivity of the developing immune system are not clear. A weak association of chlordane exposure 

with human blood dyscrasia, including leukemia, has been suggested (Epstein and Ozonoff 1987; 
CHLORDANE 83 

2. HEALTH EFFECTS 

Infante et al. 1978). Although no mechanism has been suggested, it is not unreasonable to suspect that 

disruption of hematopoietic stem cell populations could be involved. 

Although chlordane clearly induces liver cancer in mice (IRDC 1973; NCI 1977; Khasawinah and 

Grutsch 1989b; Velsicol Chemical Co. 1983b), epidemiological data provide no convincing evidence 

that it induces cancer in humans (Ditraglia et al. 1981; MacMahon et al. 1988; Shindell and Ulrich 

1986; Wang and MacMahon 1979a, 1979b). Most genotoxicity tests with chlordane yielded negative 

results (see Section 2.4), suggesting an epigenetic mechanism of carcinogenicity. Chlordane inhibited 

gap junction intercellular communication in the rat hepatocyte/liver epithelial system metabolic 

cooperation assay (Tong and Williams 1988) and in the Lucifer yellow CH dye-coupling test in rat 

and mouse hepatocytes (Ruth et al. 1990). These results suggest that chlordane acts as a tumor 

promoter, depressing intercellular communication that checks uncontrolled proliferation of 

transformed or neoplastic cells (Tong and Williams 1988). Ruth et al. (1990) suggested that inhibition 

of intercellular communication may involve alteration of CAMP-dependent protein kinase 

phosphorylation of hepatocellular gap junction proteins, which would increase permeability at the gap 

junctions. Moser and Smart (1989), who noted that chlordane stimulated protein kinase C activity in 

several tissues of mice in vitro, provide support for this theory. Nonetheless, Suzaki et al. (1988) did 

not observe a chlordane-induced increase in protein kinase C activity in vitro in the rat .brain. 

2.4 RELEVANCE TO PUBLIC HEALTH 

Chlordane, an insecticide formerly used to treat field crops and as a soil treatment to kill termites, is of 

considerable concern to human health. Reasons for this concern include its potential for inducing 

adverse health effects, its presence in breast milk, its persistence in adipose tissue in the human body, 

and its persistence in all environmental media. 

Chlordane’s persistence in soil may lead to dermal exposure and also to oral exposure from eating 

field or garden crops grown on the treated soil. Soil ingestion by children is another possible exposure 

pathway. It is not expected to leach readily into groundwater, except at hazardous waste sites where 

the presence of organic solvents may dissolve it and facilitate its movement through soil. However, 

erosion of treated soil has contaminated the sediment found in many bodies of surface water. Human 

exposure has occurred from ingestion of contaminated drinking water or fish taken from contaminated 
CHLORDANE 84 

2. HEALTH EFFECTS 

waters, or from bathing with contaminated water. Levels that induce subchronic or chronic disease in 

humans are not known. 

Inhalation exposure for the general population arises chiefly from living in homes treated with 

chlordane, because chlordane volatilizes from the treated soil and accumulates in indoor air. Although 

levels at which adverse effects occur are not definitely known, neurological symptoms and jaundice 

have been associated with chlordane in treated homes. Levels in treated homes have been measured at 

0.61 mg/m3. Adverse effects have not been reported for industrial exposure; levels at which adverse 

effects would occur in occupationally exposed workers are not known. Presumably, exposure to 

≤0.5 mg/m3, the current OSHA standard, would not lead to adverse health effects in most healthy 

persons. No data are available regarding levels of chlordane in the air near hazardous waste sites, so it 

is not known if adverse effects would be expected to occur in humans in these areas. 

Chlordane residues stored in fat in the human body are probably innocuous. It is possible that toxicity 

may occur when stores of body fat are mobilized in response to stress or dieting, or in the case of 

nursing mothers, who mobilize substantial amounts of body fat to maintain lactation, although 

examples were not located in the available literature. 

The effects observed in humans or animals exposed to chlordane do not appear to be route-dependent, 

probably because absorption occurs readily by any route of exposure. It seems reasonable, therefore, 

that the effects of human exposure would be similar in people exposed at hazardous waste sites or in 

their homes. 

Acute exposure of humans to high levels is characterized by gastrointestinal upset and neurological 

signs, including tremors and convulsions. Death may ensue, often preceded by convulsions. 

Neurological signs have been consistently observed in animal poisoning as well, firmly establishing 

chlordane as a neurotoxicant. Longer term exposure of humans to lower levels also caused 

neurological signs, including grand-mal seizures and altered EEG, but levels of exposure were not 

quantified. The occurrence of jaundice in persons living in chlordane treated homes and the alteration 

of serum enzyme levels in persons working as pesticide applicators suggest that the liver is an 

important target organ in humans. 
CHLORDANE 85 

2. HEALTH EFFECTS 

Data were not located regarding reproductive or developmental effects in humans. In animals, 

however, increased mortality was observed in the offspring of treated dams, probably due to 

transmission of substantial amounts of chlordane residues from the body fat of the dams to the 

suckling offspring through the milk. Prenatally exposed mice appear to be more sensitive than adults 

to the immunological and neurological effects of chlordane. Given the generally greater sensitivity to 

toxins of incompletely developed tissues, it seems possible that prenatal exposure of humans to 

chlordane could result in compromised immunocompetence and subtle neurological effects. 

Only one genotoxicity study in humans was located. Human HeLa cells were negative for evidence of 

DNA damage. Most genotoxicity studies in microorganisms or other mammalian systems were also 

negative. 

Minimal Risk Levels for Chlordane 

Inhalation MRLs 

•	 An MRL of 0.0002 mg/m3 has been derived for intermediate-duration (15-364 days) 

inhalation exposure to chlordane. 

This derivation was based on the NOAEL of 0.1 mg/m3 for liver effects in rats exposed intermittently 

for 90 days (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). Similar exposure to 1.0 mg/m3 

was associated with hepatocellular hypertrophy, and exposure to 10 mg/m3 was associated with 

increased liver weight. Hepatocellular hypertrophy was the most sensitive end point in animals 

exposed by inhalation. 

•	 An MRL of 0.00002 mg/m3 has been derived for chronic-duration (≥365 days) inhalation 

exposure to chlordane. 

This derivation was based on the study and end point used to derive the intermediate-duration MRL 

(Khasawinah et al. 1989; Velsicol Chemical Co. 1984), as described above. An additional uncertainty 

factor of 10 was applied to account for extrapolation from an intermediate-duration to chronic-duration 

exposure. 
CHLORDANE 86 

2. HEALTH EFFECTS 

An MRL has not been derived for acute-duration inhalation exposure to chlordane. Only one acute 

inhalation study (Khasawinah et al. 1989; Velsicol Chemical Co. 1984) was located, and this study did 

not sufficiently identify target organs, and serious effects (death, convulsions) occurred at the lowest 

concentration tested. 

Oral MRLS 

•	 An MRL of 0.001 mg/kg/day has been derived for acute-duration (≤14 days) oral exposure 

to chlordane. 

This derivation is based on a LOAEL of 1 mg/kg/day for developmental (depressed conditioned 

avoidance response acquisition, increased exploratory activity in open field test, and increased seizure 

threshold) effects in the offspring of mice exposed to chlordane during the third trimester (Al-Hachim 

and Al-Baker 1973). Developmental effects, as well as neurological effects, have been observed in a 

number of other acute-duration oral studies. 

•	 An MRL of 0.0006 mg/kg/day has been derived for intermediate-duration (15-364 days) 

oral exposure to chlordane. 

This derivation was based on a NOAEL of 0.055 mg/kg/day for hepatic effects in female rats given 

chlordane in the diet for 30 months (Khasawinah and Grutsch 1989a; Velsicol Chemical Co. 1983a). 

The hepatic effects (hepatocellular hypertrophy) were observed at 0.273 mg/kg/day. The Ortega et al. 

(1957) study which found centrilobular hepatocellular hypertrophy and cytoplasmic inclusions in rats 

exposed to 0.125 mg/kg/day chlordane in the diet for 2-9 months supports the selection of the 

Khasawinah and Grutsch (1989a; Velsicol Chemical Co. 1983a) as the critical study. The selection of 

Khasawinah and Grutsch (1989a; Velsicol Chemical Co. 1983a) as the critical study [as opposed to 

Ortega et al. (1957)] was based on a higher degree of confidence in the quality of the study. A 

LOAEL of 0.1 mg/kg/day for increased hepatic cytochrome P-450 content at 10 weeks and decreased 

microsomal protein at 20 weeks in rats given chlordane in the diet (Mahon et al. 1979) supports the 

NOAEL of 0.055 mg/kg/day in the Khasawinah and Grutsch (1989a; Velsicol Chemical 1983a) study 

and the LOAEL of 0.125 mg/kg/day in the study by Ortega et al. (1957). 
CHLORDANE 87 

2. HEALTH EFFECTS 

•	 An MRL of 0.0006 mg/kg/day has been derived for chronic-duration (≥365 days) oral 

exposure to chlordane. 

This derivation is based on a NOAEL of 0.055 mg/kg/day for hepatic effects in rats given chlordane in 

the diet for 30 months (Khasawinah and Grutsch 1989a; Velsicol Chemical Co. 1983a). The LOAEL 

was 0.273 mg/kg/day, at which an increased incidence of hepatocellular hypertrophy was observed in 

female rats. 

Death. Absorption following ingestion of or skin contact with chlordane can be fatal to humans. 

WHO (1984) reported that an acute oral dose ≤25 mg/kg can result in death, although documentation 

was not available for this estimation. This estimated dose is ≈10 times lower than oral LD50 values 

reported for animals. Mortality increased among mice chronically ingesting 3.9 mg/kg/day through 

feed (NCI 1977), suggesting that mortality could occur in humans chronically exposed to doses much 

lower than 25 mg/kg/day. The dermal dose that causes death of humans is not known, but dermal 

LD50 values in animals are relatively low. A dose of 690 mg/kg of technical chlordane was a dermal 

LD50 in rats (Gaines 1960) and 1,100-1,200 mg/kg of “later” production chlordane (not contaminated 

with hexachlorocyclopentadiene) was a dermal LD50 in rabbits (Ingle 1965). Therefore, caution should 

be exercised when handling chlordane because of the possibility of dermal absorption. 

Epidemiological studies (Brown 1992; Ditraglia et al. 1981; MacMahon et al. 1988; Shindell and 

Ulrich 1986; Wang and MacMahon 1979a, 1979b) and case reports of acute exposure (EPA 1980a) do 

not suggest that inhalation exposure is likely to result in human deaths. Also, animal studies do not 

suggest that mortality would be expected in humans exposed by inhalation to low levels of chlordane, 

although exposure to high levels may cause death. Velsicol Chemical Co. (1984) and Khasawinah et 

al. (1989) reported no mortality in rats intermittently exposed to 10 mg/m3

 for 90 days, but mortality 

occurred in rats exposed to 154 or 413 mg/m3 for 3 days. Although accidental or intentional 

ingestion of high doses of chlordane can lead to death, levels of chlordane found in drinking water, 

air, or soil near waste sites are not likely to result in noncancer human fatality. 

Systemic Effects 

Respiratory Effects. Most of the data from human or animal studies do not indicate that respiratory 

effects are likely in humans exposed to chlordane. Several cases and personal reports involving acute 

inhalation, oral, or dermal exposure (Curley and Garrettson 1969; EPA 1980a; Harrington et al. 1978; 
CHLORDANE 88 

2. HEALTH EFFECTS 

NIOSH 1984a; Olanoff et al. 1983) and epidemiological studies of chlordane manufacture (Alvarez 

and Hyman 1953; Brown 1992; Fishbein et al. 1964; Princi and Spurbeck 1951) do not report 

respiratory effects in exposed humans. One study, however, reported sore throat and respiratory 

infections were in humans shortly after their homes were treated for termites (Menconi et al. 1988). In 

addition, a case report of acute ingestion of chlordane by a human described bronchopneumonia as a 

possible effect (Aldrich and Holmes 1969). Slight lung congestion and proliferation of bronchiole 

lining cells were also observed in mice exposed continuously to an unspecified concentration of 

chlordane in air for 14-25 days (Ingle 1953). Repeated exposure to chlordane vapor or aerosols does 

not appear to cause respiratory effects in rats (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). 

It is unlikely that respiratory effects would be important in humans exposed to chlordane in food, 

drinking water, air, or soil near waste sites. 

Cardiovascular Effects. Although equivocal evidence of increased risk of cerebrovascular disease was 

reported in workers involved in the manufacture of chlordane (Wang and MacMahon 1979a), 

cardiovascular effects associated with exposure to chlordane were not reported in other studies of 

occupational exposure during manufacture (Alvarez and Hyman 1953; Brown 1992; Fishbein et al. 

1964; Princi and Spurbeck 195l), following inhalation and dermal exposure resulting from a chemical 

spill in a library room (NIOSH 1984a), or in the majority of cases and personal reports of acute oral, 

inhalation, or dermal exposure compiled by EPA (1980a). A few of the cases compiled by EPA 

(1980a) reported tachycardia, chest pains, and shortness of breath, but exposure often involved a 

mixture of pesticides and vehicles such as petroleum distillates that may have caused these effects. 

Several case reports of accidental or intentional ingestion of chlordane by humans reported tachycardia 

or elevated pulse rates (Curley and Garrettson 1969; Olanoff et al. 1983). No histopathological heart 

lesions were found in rats, mice, or hamsters treated acutely with oral doses of chlordane (Truhaut et 

al. 1974, 1975) or in rats or mice in chronic dietary (Khasawinah and Grutsch 1989a, 1989b; NCI 

1977; Velsicol Chemical Co. 1983a, 1983b) or inhalation (Ingle 1953; Khasawinah et al. 1989; 

Velsicol Chemical Co. 1984) studies. Thus, it is unlikely that exposure to chlordane per se would 

cause cardiovascular effects in humans exposed to chlordane in food, drinking water, or soil near 

hazardous waste sites. 

Gastrointestinal Effects. Gastrointestinal symptoms are an early and consistent observation in a 

number of cases and personal reports of acute human oral and inhalation exposure (Curley and 

Garrettson 1969; Dadey and Kammer 1953; EPA 1980a; Olanoff et al. 1983). These symptoms 
CHLORDANE 89 

2. HEALTH EFFECTS 

include gastritis, nausea, vomiting, intestinal cramps, abdominal pain, and diarrhea. NIOSH (1984a) 

reported gastrointestinal symptoms in library workers following inhalation and dermal exposure to 

high (unquantified) levels of chlordane resulting from a spill. Humans accidently exposed to chlordane 

in their drinking water at levels ranging from 0.1 to 92,500 ppb reported gastrointestinal symptoms 

(Harrington et al. 1978). Gastrointestinal symptoms were not reported in a number of epidemiology 

studies of chlordane manufacture (Alvarez and Hyman 1953; Fishbein et al. 1964; Princi and Spurbeck 

1951), nor in a compilation of cases of acute dermal exposure (EPA 1980a). However, vomiting 

(Balistreri et al. 1973) has been reported in case reports of humans exposed dermally to chlordane. 

No histopathological lesions in the gastrointestinal tract were found in rats, mice, or hamsters treated 

acutely with oral doses of chlordane (Truhaut et al. 1974), or in rats or mice in chronic feeding studies 

(Ambrose et al. 1953a; Khasawinah and Grutsch 1989a, 1989b; NCI 1977; Velsicol Chemical Co. 

1983a, 1983b), or in rats exposed by inhalation (Ingle 1953; Khasawinah et al. 1989; Velsicol 

Chemical Co. 1984). 

Case reports (EPA 1980a) mention oral irritation after acute accidental ingestion. These observations 

suggest that chlordane, especially in large doses, is irritating to the gastrointestinal tract when ingested. 

The gastrointestinal symptoms (vomiting, abdominal pain, and diarrhea) reported in humans following 

inhalation exposure and ingestion of relatively smaller doses may reflect a primary effect on other 

organs or systems, such as the central nervous system. These data suggest that gastrointestinal 

symptoms would be among the earliest complaints of those exposed to chlordane at low levels in the 

air or drinking water. The threshold concentrations for these effects in environmental media are 

unknown, and the likelihood of their occurrence near waste sites cannot be predicted. 

Hematological Effects. Hematological effects specifically related to exposure to chlordane were not 

reported in a compilation of cases and personal reports of acute oral, inhalation, or dermal exposures 

(EPA 1980a). Limited hematological examinations revealed no effects on workers involved in 

chlordane manufacture (Alvarez and Hyman 1953; Fishbein et al. 1964; Princi and Spurbeck 1951). 

There were several reports of cases of blood dyscrasia in humans exposed to chlordane (Epstein and 

Ozonoff 1987; Infante et al. 1978), but most were exposed to other chemicals as well, and the 

association of blood dyscrasia with chlordane is very weak. However, the existence of a number of 

anecdotal reports of blood dyscrasia associated with several organochlorine pesticides (chlordane, 

lindane, DDT), suggests that there may be a an unusually susceptible subpopulation (Curley and 
CHLORDANE 90 

2. HEALTH EFFECTS 

Garrettson 1969; Ellenhorn and Barceloux 1988; Lensky and Evans 1952). Leukocytosis associated 

with lymphocytosis was reported in mice treated by gavage with 8 mg/kg/day for 14 days (Johnson et 

al. 1986), but the toxicological significance of an elevated leukocyte count is unclear. Hematological 

examination revealed no effects in rats exposed for 90 days by inhalation (Khasawinah et al. 1989; 

Velsicol Chemical Co. 1984) or in rats or mice chronically exposed to chlordane in the diet (Ambrose 

et al. 1953a; Khasawinah and Grutsch 1989a, 1989b; Velsicol Chemical Co. 1983a, 1983b). The 

available data suggest that hematological effects might occur in unusually sensitive humans exposed to 

low levels of chlordane in environmental media near waste sites. 

Musculoskeletal Effects. Musculoskeletal effects in humans were not reported in a compilation of 

cases and personal reports of acute oral, inhalation, or dermal exposure to chlordane (EPA 1980a), in 

library workers exposed to high levels resulting from a spill (NIOSH 1984a), or in workers involved in 

chlordane manufacture (Alvarez and Hyman 1953; Fishbein et al. 1964; Princi and Spurbeck 1951). 

Three of nine pesticide applicators were reported to have elevated serum levels of creatine 

phosphokinase (Ogata and Izushi 1991), but this does not constitute convincing evidence of muscle 

damage. 

Musculoskeletal lesions were not found in rats or mice exposed to chlordane chronically in the diet 

(Khasawinah and Grutsch 1989a, 1989b; NCI 1977; Velsicol Chemical Co. 1983a, 1983b) or in rats or 

monkeys exposed intermittently by inhalation for 90 days (Khasawinah et al. 1989; Velsicol Chemical 

Co. 1984). Rats treated orally with chlordane did not have increased levels of creatine phosphokinase 

in serum, but rats injected intraperitoneally did (Ogata and Igushi 1991). It is not likely that humans 

would develop musculoskeletal lesions after prolonged exposure to low doses of chlordane. 

Hepatic Effects. Hepatic effects were reported in a small proportion of a compilation of cases and 

personal reports of acute oral, inhalation, or dermal exposure to chlordane (EPA 1980a), but not in 

library workers acutely exposed to high (unquantified) levels resulting from a spill (NIOSH 1984a). 

Liver function tests were normal in a 20-month-old male child between 20 hours to 3 days after 

ingesting chlordane (Curley and Garrettson 1969), in a nurseryman who developed neurological effects 

after handling soil that contained chlordane and other chemicals (Barnes 1967), and in workers 

involved in the manufacture of chlordane (Alvarez and Hyman 1953; Fishbein et al. 1964; Princi and 

Spurbeck 1951). Subtle serum chemistry changes indicative of altered liver function (increased 

triglycerides and lactate dehydrogenase activity), however, were observed in pesticide applicators in 
CHLORDANE 91 

2. HEALTH EFFECTS 

Japan exposed to chlordane (Ogata and Izushi 1991). Jaundice has been reported in humans living in 

homes treated with chlordane for termite control (EPA 1980a). Acute, prolonged dermal exposure of 

an infant to liquid chlordane was associated with jaundice, liver necrosis, fatty infiltration, and 

inflammation diagnosed from a biopsy sample (Balistreri et al. 1973). 

Reliable acute oral and parenteral studies in animals exposed to chlordane indicate that enzyme 

induction, minor histochemical and histomorphological changes, and liver hypertrophy occur 

within hours of treatment and at very low doses (Casterline and Williams 1971; Cram et al. 1956; Den 

Tonkelaar and Van Esch 1974: Hart et al. 1963; Johnson et al. 1986; Truhaut et al. 1974, 1975). 

Enzyme induction in the absence of evidence of liver damage or impaired liver function is considered 

an adaptative rather than an adverse effect. In the case of chlordane, however, it should be noted that 

metabolites of chlordane, such as oxychlordane, heptachlor, and heptachlor epoxide, are more toxic 

than the parent compound. Moreover, enzyme induction can accelerate metabolism of therapeutic 

drugs and hormones (Welch and Harrison 1966; Welch et al. 1971). Liver cell inclusion bodies were 

found in some rats,exposed dermally to chlordane for a few days (Ambrose et al. 1953a). In 

prolonged inhalation (Ambrose et al. 1953a; Khasawinah et al. 1989; Velsicol Chemical Co. 1984) and 

oral exposure studies (Ambrose et al. 1953a; IRDC 1973; Khasawinah and Grutsch 1989a, 1989b; 

Ortega et al. 1957; Velsicol Chemical Co. 1983a, 1983b), mild histopathological changes in the liver 

occurred in mice and rats. 

Although reports of serious liver disease in humans exposed to chlordane are uncommon, animal 

studies suggest that more subtle effects, including altered enzyme activities and mild morphological 

changes, may be expected from any route of exposure to low doses. The more subtle effects are 

expected to occur at lower doses and shorter durations of exposure than jaundice or other indications 

of severe liver dysfunction or histopathological effects. Histopathological effects are not likely to be 

diagnosed routinely, however, because invasive procedures such as liver biopsy would be required. 

Physicians prescribing therapeutic drugs or hormones should be aware that doses may require 

adjustment in patients exposed to chlordane. 

Renal Effects. Renal effects were not reported in a compilation of cases and personal reports of acute 

human oral, inhalation, or dermal exposure to chlordane (Dadey and Kammer 1953; EPA 1980a), in 

library workers exposed to high levels resulting from a spill (NIOSH 1984a), or in workers involved in 

chlordane manufacture (Alvarez and Hyman 1953; Fishbein et al. 1964; Princi and Spurbeck 1951). 
CHLORDANE 92 

2. HEALTH EFFECTS 

Derbes et al. (1955) reported pathological changes in the kidneys of a woman who died within minutes 

after an accidental spill resulted in dermal exposure to chlordane and other pesticides. 

Kidney congestion was observed in rats, mice, and hamsters given large acute oral doses of 200, 200, 

and 1,200 mg/kg, respectively (Truhaut et al. 1974, 1975). Kidney lesions were not found in rats 

exposed to chlordane in the diet at ≤20.4 mg/kg/day or in mice similarly exposed to ≤8.3 mg/kg/day 

(Ambrose et al. 1953a; Khasawinah and Grutsch 1989a, 1989b; NCI 1977; Ortega et al. 1957; Velsicol 

Chemical Co. 1983a, 1983b) or in rats or monkeys exposed intermittently by inhalation for 90 days to 

10 mg chlordane/m3

 (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). Rats in the inhalation 

study, however, exhibited elevated kidney weights. It is not known whether humans could develop 

kidney lesions after prolonged exposure to low doses of chlordane. 

Dermal/OcularEffects. Dermal effects were not reported in a compilation of cases and personal 

reports of acute oral and inhalation exposure to chlordane (EPA 1980a), in a group of library workers 

following inhalation and dermal exposure resulting from a spill (NIOSH 1984a), in workers involved 

in chlordane manufacture (Alvarez and Hyman 1953; Fishbein et al. 1964; Princi and Spurbeck 1951), 

or in a woman who died within minutes of spilling a mixture of chemicals including chlordane on the 

front of her clothing (Derbes et al. 1955). EPA (1980a), however, reported burning sensations of the 

skin, rashes and pruritus in cases of accidental acute dermal exposure to chlordane. Accidental 

spraying of chlordane in the eyes consistently resulted in conjunctivitis (EPA 1980a). These reports of 

dermal and ocular effects are complicated by exposure to mixtures of chemicals including other 

pesticides and vehicles, such as petroleum distillates, that are known to be irritants. 

Oral exposure of rats and mice (NCI 1977; Khasawinah and Grutsch 1989a, 1989b; Velsicol Chemical 

Co. 1983a, 1983b) and inhalation exposure of rats and monkeys (Khasawinah and Grutsch 1989a, 

1989b; Velsicol Chemical Co. 1984) produced no skin or ocular lesions. Datta et al. (1975) reported 

changes in the malpighian cells of guinea pigs dermally exposed once daily for 90 days to a high dose 

of chlordane (168 mg/kg). No changes were observed in the dermis. However, no local dermal 

reactions were found in rats treated dermally with 273 mg/kg/day for 4 days (Ambrose et al. 1953a). 

These data suggest that both ocular and dermal exposure to liquid chlordane may cause adverse 

effects, but these effects are unlikely at concentrations expected in environmental media near waste 

sites. 
CHLORDANE 93 

2. HEALTH EFFECTS 

Other Systemic Effects. Other effects observed in animals exposed to chlordane include effects on 

body weight and the thyroid. In intermediate-duration inhalation studies, increased height of the 

thyroid follicular cells were observed in rats and monkeys (Khasawinah et al. 1989; Velsicol Chemical 

Co. 1984). Rats also lost body weight. Body weight loss was also observed in rats treated orally with 

chlordane for intermediate and chronic durations (Ambrose et al. 1953a; NCI 1977). Whether 

exposure of humans to chlordane at hazardous waste sites would result in body weight or thyroid 

effects is not known. 

Immunological Effects. Chlordane appears to have caused impaired proliferative responses to plant 

mitogens in humans following inhalation exposure for periods ranging from 3 days to 15 months 

(McConnachie and Zahalsky 1992). Further testing of similarly exposed individuals demonstrated an 

increased autoantibody titer; suggesting chlordane-induced autoimmunity. 

In intermediate-duration inhalation studies, female rats, but not male rats, exposed to 28.2 mg/m3 

chlordane for 28 days had reduced thymus weight (Khasawinah et al. 1989; Velsicol Chemical Co. 

1984). However, thymus weight was not altered in either sex of rats exposed to 10 mglm3

 for 

90 days, but female rats had increased leukocyte counts at 1 or 10 mg/m’. No histopathological 

lesions were found in the thymus or lymph nodes of monkeys similarly exposed to chlordane. 

Sensitization was not reported in guinea pigs treated once daily for 90 days with dermal applications 

of chlordane in acetone (Datta et al. 1975). It is not clear, however, that the protocol would have 

reliably identified dermal sensitization. Oral studies conducted in mice suggest that chlordane causes 

leukocytosis associated with lymphocytosis (Johnson et al. 1986), depresses cell-mediated immunity, 

as manifested by a depression in delayed-type hypersensitivity reactions and depressed mixed 

lymphocyte reactivity (Barnett et al. 1985a, 1985b; Menna et al. 1985; Spyker-Cranmer et al. 1982). 

There were no effects on humoral-mediated immunity. In some of these studies, the mice tested were 

the offspring of dams treated during gestation and allowed to nurse their young. Therefore, the mice 

had been exposed to chlordane and its metabolites during gestation and lactation. The effect on 

delayedtype hypersensitivity occurred at very low levels in mice. Data from an in vitro study suggested 

that chlordane may interfere with cell-mediated immune proliferative response in rhesus monkeys 

(Chuang et al. 1992). In this study, cultures of rhesus monkey peripheral blood mononuclear cells 

(PBMC) were prepared and 10 or 80 μM of chlordane along with conventional mitogens were added at 

the onset of the culture. At 10 μM concentration, chlordane modulated T cell mitogenic response or 

acted as a mitogen for T lymphocytes in the absence of conventional mitogens. The study also 
CHLORDANE 94 

2. HEALTH EFFECTS 

demonstrated that at 80 μM concentration, chlordane completely impaired the functions of monkey 

lymphocytes. It is possible that effects on immune function could occur in humans exposed to 

chlordane at hazardous waste sites. 

Neurological Effects. Chlordane clearly causes neurological effects in humans following acute or 

prolonged oral, inhalation, or dermal exposure (Aldrich and Holmes 1969; Balistreri et al. 1973; 

Barnes 1967; Curley and Garrettson 1969; Dadey and Kammer 1953; Derbes et al. 1955; EPA 1980a; 

Harrington et al. 1978; Kutz et al. 1983; Lensky and Evans 1952; Menconi et al. 1988; NIOSH 1984a; 

Olanoff et al. 1983). Neurological effects, including headache, dizziness, irritability, muscle tremors, 

confusion, convulsions, and coma are frequently the earliest reported in cases of human intoxication 

with chlordane. It is possible that gastrointestinal symptoms such as nausea, abdominal pain, and 

diarrhea may result from effects on the nervous system. Oral exposure has been associated with 

central nervous system effects in children (Aldrich and Holmes 1969). The threshold concentration in 

air for neurological effects in humans has not been identified, but cases and personal reports (EPA 

1980a; NIOSH 1984a) suggest that these effects may occur at concentrations encountered in recently 

treated homes. Neurological symptoms, however, have not been reported in studies of occupational 

exposure (Alvarez and Hyman 1953; Fishbein et al. 1964; Princi and Spurbeck 1951), although 

equivocal evidence of increased risk of cerebrovascular disease was reported in workers involved in 

the manufacture of chlordane (Wang and MacMahon 1979a). Abnormal respiratory movement, 

excessive salivation, and convulsions occurred in rats exposed by inhalation to chlordane for acute 

durations, and hypersensitivity to touch was observed in female rats exposed by inhalation for 

intermediate durations (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). Acute (Ambrose et al. 

1953a; Hrdina et al. 1974) and prolonged (Drummond et al. 1983; NCI 1977) oral exposure in animals 

has been associated with frank neurological signs such as tremor and convulsions. Neither human nor 

animal studies, however, have investigated subtle neurological or behavioral effects, which may occur 

at doses lower than the frank effects that have been associated with chlordane exposure. Therefore, it 

is not possible to predict the likelihood of subtle neurological effects in humans exposed to the low 

levels of chlordane expected in environmental media located near waste sites. 

Reproductive Effects. Compared with the control population from the National Center for Health 

Statistics 1979 National Health Interview Survey (NHIS), the incidence rates of unspecified ovarian 

and uterine disease were significantly (p<0.05) elevated in women who were exposed to chlordane 
CHLORDANE 95 

2. HEALTH EFFECTS 

vapors in their homes (Menconi et al. 1988). Because the case report and the epidemiological study 

have several limitations, it is doubtful that the reported lesions and diseases are treatment-related. 

Male mice treated by gavage with 100 or 300 mg/kg/day for 30 days had reduced size of seminiferous 

tubules and degeneration of spermatogenic epithelium (Balash et al. 1987). Oral administration of 

chlordane to male rats (19.5 mg/kg/day for 90 days) increased androgen receptor sites in the ventral 

prostate (Shain et al. 1977). However, histological examination of testes of rats and mice given a 

single oral dose of 200 mg/kg or hamsters given a single oral dose of 1,200 mg/kg revealed no 

treatment-related lesions (Truhaut et al. 1975). Lesions in male or female reproductive organs were 

not reported in rats or mice in chronic dietary studies (Ambrose et al. 1953a; Khasawinah and Grutsch 

1989a, 1989b; NCI 1977; Velsicol Chemical Co. 1983a, 1983b) or in rats or monkeys in a 90-day 

inhalation study (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). Datta et al. (1975) reported 

mild degenerative changes in the testes of guinea pigs treated with dermal applications of chlordane in 

acetone at 168 mg/kg once daily for 90 days. Ambrose et al. (1953a) reported reduced fertiiity, 

reflected as a reduction in the number of mated females that delivered litters, when male and female 

rats were fed a diet that provided chlordane at 16 mg/kg/day. Treatment began at weaning and 

continued through lactation. None of the delivered litters survived to weaning. Reduced fertility, 

reflected as a reduction in the number of females that became pregnant, was observed in mice given 

intraperitoneal injections of chlordane (25 mg/kg) once weekly for 3 weeks before being mated to 

untreated males of proven fertility (Welch et al. 1971). Data indicate that exposure to chlordane can 

affect metabolism and circulating levels of steroid hormones (Cranmer et aI. 1984; Welch et al. 1971) 

and can reduce the binding of progesterone to its cytosolic receptor in the endometrium (Lundholm 

1988). 

Data regarding effects on the fertility of rats and mice are limited by study design. Dose levels were 

not chosen to detect thresholds for effects on fertility, and the studies were not designed to investigate 

the mechanisms by which chlordane may interfere with fertility. The data in animals are not sufficient 

to indicate whether chlordane can cause reproductive effects in humans, or whether such effects would 

be expected in humans exposed to chlordane near waste sites. 

Developmental Effects. No data were located regarding developmental effects in humans after 

exposure to chlordane. 
CHLORDANE 96 

2. HEALTH EFFECTS 

No developmental effects were observed in rats treated orally during gestation with doses sufficient to 

cause death of 50% of the dams (Usami et al. 1986). In a screening study, no effects on viability or 

postnatal growth were observed in the offspring of mice treated orally during gestation (Chemoff and 

Kavlock 1982). Pregnant mice were treated with chlordane in order to study the immunological, 

behavioral, and endocrine effects on the offspring. The offspring were allowed to nurse their dams; 

therefore, they were exposed to chlordane and metabolites during gestation and nursing. The results of 

immunological tests suggest that chlordane suppressed cell-mediated immunity (Barnett et al. 1985a, 

1985b, 1990a, 1990b; Menna et al. 1985; Spyker-Cranmer et al. 1982; Theus et al. 1992). Results of 

behavioral tests indicate that chlordane depressed the acquisition of avoidance behavior, raised seizure 

thresholds, and increased exploratory activity (Al-Hachim and Al-Baker 1973). Increased plasma 

levels of corticosterone were observed in the offspring of mice treated during gestation; the change 

implies an effect on neuroendocrinological feedback, possibly resulting from the liver’s reduced ability 

to metabolize corticosterone (Cranmer et al. 1984). The relevance of these findings to humans is not 

known, and the likelihood of effects on human development resulting from exposure to chlordane near 

waste sites is unpredictable. 

Genotoxic Effects. Chlordane has been tested for mutagenicity in several systems. As seen from 

Table 2-4, mostly negative results have been obtained for reverse mutations, DNA repair, and 

dominant and recessive lethal assays. Chlordane induced mitotic gene conversion in Saccharomyces 

cerevisiae in the presence, but not the absence, of metabolic activation; and in prophage in Escherichia 

coli, regardless of metabolic activation. Chlordane induced forward mutation in mouse lymphoma 

L5178Y cells without metabolic activation, and also induced sister chromatid exchange in human 

lymphoid cells. Dermal application of chlordane to mice induced micronuclei formation in the bone 

marrow cells and nuclei aberrations in the hair follicles (Schop et al. 1990). The generally negative 

results for mutagenicity of chlordane are consistent with an epigenetic mechanism of carcinogenicity 

(see below). 

Cancer. Retrospective mortality studies provide no convincing evidence of a link between exposure 

to chlordane, during its manufacture or during its application as a pesticide, and increased risk of death 

due to cancer (Brown 1992; Cantor et al. 1992; Ditraglia et al. 1981; MacMahon et al. 1988; Shindell 

and Ulrich 1986; Wang and MacMahon 1979a, 1979b). Weak evidence suggests a link between 

chronic residence in chlordane-treated homes or gardens and increased risk of unspecified skin 

neoplasms (Menconi et al. 1988) or leukemia (Epstein and Ozonoff 1987; Infante et al. 1978) and 

result 


CHLORDANE 99 

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between the use of chlordane in farming operations and increased risk of non-Hodgkins lymphoma 

(Woods and Pollissar 1989). Chronic oral treatment with chlordane at ≥1.21 mg/kg/day significantly 

increased hepatocellular carcinomas in mice (EPA 1985a, 1986c, 1987e; Epstein 1976; IRDC 1973; 

IRIS 1992; Khasawinah and Grutsch 1989b; NCI 1977; Reuber 1978; Velsicol Chemical Co. 1983b). 

Becker and Sell (1979) demonstrated that chlordane could induce hepatocellular carcinomas in a strain 

of mice that historically is not predisposed to liver tumors. No statistically significant increase in 

tumor incidence was observed in dietary studies in rats in the NCI (1977) study or in EPA (1988b) 

reevaluations of the Khasawinah and Grutsch (1989a) and Velsicol Chemical Co. (1983a) study. 

Negative responses in a number of mutagenicity tests suggest an epigenetic mechanism of 

carcinogenicity, perhaps involving a promoting effect on predisposed cells (Ashby and Tennant 1988; 

Maslansky and Williams 1981). Ashby and Tennant (1988) also noted that a positive carcinogenic 

response in the mouse liver in NCI/NTP studies may reflect an epigenetic as well as a genotoxic 

mechanism. Williams and Numoto (1984) presented evidence that chlordane acts as a promoter of 

liver tumor formation in cells initiated by diethylnitrosamine. Telang et al. (1982) observed a marked 

inhibition of intercellular communication in cultured rat liver cells treated with chlordane. The 

investigators reported that this effect is common to other organochlorine pesticides that appear to act 

as tumor promoting agents. EPA (IRIS 1992) considered the data in laboratory animals sufficient to 

classify chlordane in Group B2, that is, as a probable human carcinogen. 

2.5 BIOMARKERS OF EXPOSURE AND EFFECT 

Biomarkers are broadly defined as indicators signaling events in biologic systems or samples. They 

have been classified as markers of exposure, markers of effect, and markers of susceptibility 

(NAS/NRC 1989). 

A biomarker of exposure is a xenobiotic substance or its metabolite(s), or the product of an interaction 

between a xenobiotic agent and some target molecule(s) or cell(s) that is measured within a 

compartment of an organism (NAS/NRC 1989). The preferred biomarkers of exposure are generally 

the substance itself or substance-specific metabolites in readily obtainable body fluid(s) or excreta. 

However, several factors can confound the use and interpretation of biomarkers of exposure. The 

body burden of a substance may be the result of exposures from more than one source. The substance 

being measured may be a metabolite of another xenobiotic substance (e.g., high urinary levels of 

phenol can result from exposure to several different aromatic compounds). Depending on the 
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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 chlordane are discussed in Section 2.5.1. 

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 chlordane are discussed in Section 2.5.2. 

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 2.7, “Populations That Are Unusually Susceptible.” 

2.5.1 Biomarkers Used to Identify or Quantify Exposure to Chlordane 

It is possible to measure chlordane and/or a number of its metabolites in a variety of human tissues 

and fluids (i.e., blood, adipose tissue, brain, liver, kidney, milk, sebum (or skin lipids), urine, and 

feces). Generally, total chlordane residue levels are higher in fat and liver than in the blood (MussaloRauhamaa 1991). There is no information in the literature, however, correlating the levels found in 

these tissues and fluids with the environmental chlordane concentrations to which the individual was 

exposed. Furthermore, the data do not reveal how long after exposure residues may be detected in the 

various body tissues and fluids. 

Kawano and Tatsukawa (1982) measured “total” chlordane (cis- and trans-chlordane, heptachlor 

epoxide, oxychlordane and trans-nonachlor) residues in the blood of pest control operators and 
CHLORDANE 101 

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nonexposed workers in Japan. Not all of these residues (e.g., heptachlor epoxide) are specific for 

exposure to chlordane. Levels in the blood of four of five unexposed workers were below 0.10 ng/g, 

the limit of detection. A level of 0.13 ng/g was reported for the fifth unexposed worker, who had 

lived for 2 years in a termite-treated home. Levels in the blood of 21 pest control operators ranged 

from 0.57 to 83 ng/g, with an average of 12 ng/g, approximately two orders of magnitude greater than 

levels in unexposed workers. There was no mention or indication of signs of chlordane toxicity in 

either the unexposed workers or pest control operators. Katz (1983) reported mean levels in human 

serum for each of four components or metabolites of chlordane at <l ppb. It was not possible, 

however, to estimate the mean level of “total” chlordane from these data. Kutz et al. (1976, 1979) 

reported mean levels of heptachlor epoxide of ≈0.1 ppm in adipose tissue samples collected from the 

U.S. population. Levels of oxychlordane in these samples also averaged ≈0.1 ppm. There appeared to 

be no significant change in the concentration of either chlordane metabolite over a 5-year period from 

1970 to 1975. The individuals sampled by Kutz (1983) and Kutz et al. (1976, 1979) are assumed to 

be asymptomatic, so the reported levels were not associated with effects of chlordane toxicity. 

Oxychlordane has been measured at concentrations ranging from 0.002 to 0.005 mg/L in human breast 

milk (whole milk basis) in samples taken at random from subjects with infants assumed to be 

asymptomatic (Bamett et al. 1979; Strassman and Kutz 1977). In Finnish human milk samples, total 

chlordane residues in positive samples averaged 0.41 mg/kg of milk fat (Mussalo-Rauhamaa et al. 

1988). 

Several components of chlordane (trans- and cis-chlordane, trans- and cis-nonachlor, heptachlor, 

gamma-chlordene) were detected in the skin lipids of humans (Sasaki et al. 1991b). The samples were 

taken by swabbing the face with cotton soaked with 70% ethanol 3-4 hours after the face was washed 

with soap. Because all samples from inhabitants of an area known to be contaminated with chlordane 

contained chlordane residues, and because the profile of chlordane components in skin lipids closely 

resembled those in technical chlordane, the authors suggested that skin lipid analysis is a satisfactory 

indicator of dermal exposure to airborne chlordane, such as occurs in homes treated for termites. 

Oxychlordane in the skin lipids was positively correlated (correlation coefficient = 0.68, p<0.01) with 

concentrations in internal adipose tissue. The authors concluded that the concentration of 

oxychlordane in skin lipids was a satisfactory indicator of body accumulation of chlordane. 

A later study in monkeys confirmed that chlordane residues in skin lipids correlate closely with 

residues in blood (Sasaki et al. 1992). In this study, monkeys were given 5 consecutive, weekly, 
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subcutaneous doses of 1 or 10 mg trans-chlordane/kg, and blood, adipose tissue and skin lipids were 

sampled up to 28 weeks after the last treatment for analysis for trans-chlordane and oxychlordane. 

Trans-chlordane concentrations in adipose tissue declined rapidly after the last dose; oxychlordane 

concentrations increased for about 5 weeks and leveled off. The correlation coefficients for 

trans-chlordane in the adipose tissue and blood, and in the adipose tissue and skin lipids were 0.93 

and 0.72, respectively. The correlation coefficients for oxychlordane in the adipose tissue and blood, 

and in the adipose tissue and skin lipids were 0.94 and 0.83, respectively. These data suggest that 

trans-chlordane concentrations in skin lipids are a satisfactory biomarker of recent exposure, and that 

oxychlordane concentrations in skin lipids are a satisfactory marker of previous exposure and of the 

body burden (in adipose tissue) of oxychlordane. 

Data are available that correlate exposure to chlordane with levels of the pesticide and/or its 

metabolites in biological samples taken from humans. Total chlordane residues in the blood were 

≈3-16 times higher in pesticide applicators, and ≈1.5-10 times higher in residents of a heavily 

contaminated area, where many of the houses were treated for termites with chlordane, than in 

residents of a relatively noncontaminated area (Wariishi and Nishiyama 1989). Recent information 

indicates a relatively strong correlation between the length of exposure to atmospheric chlordane in a 

termite-treated home and the concentration of chlordane in human milk fat (Taguchi and Yakushiji 

1988); however, actual atmospheric chlordane concentrations were not reported. A relatively strong 

correlation between blood chlordane concentration and the number of days that a pest control operator 

has sprayed has been reported by Saito et al. (1986). Takamiya (1987) demonstrated a strong 

correlation between total chlordane residues (i.e., trans-nonachlor plus oxychlordane) in the blood of 

pest control operators and their duration of exposure. The atmospheric concentrations of chlordane to 

which these pest control operators had been exposed were not reported (Saito et al. 1986; Takamiya 

1987). Kawano and Tatsukawa (1982) showed that the levels of heptachlor epoxide, oxychlordane, 

and trans-nonachlor in the blood of pest control operators in Japan increased with increased duration 

of exposure (years of employment). 

More recently, elevated serum levels of creatinine phosphokinase (CPK) were measured in Japanese 

pest control operators exposed to chlordane (Ogata and Izushi 1991). Levels of SGOT and SGPT 

were not elevated, and the investigators concluded that elevated CPK was somewhat specific for 

exposure to chlordane, compared with other organochlorine compounds. 
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2.5.2 Biomarkers Used to Characterize Effects Caused by Chlordane 

The most sensitive indicators of acute chlordane toxicity in humans are central nervous system effects 

including headache, confusion, behavioral aberrations, and tremors (EPA 1980a; Harrington et al. 

1978). At high levels of exposure, central nervous system effects include convulsions, coma, 

respiratory failure, and eventually death. Effects on the liver appear to be the only manifestations in 

humans of chronic exposure to chlordane (EPA 1980a; Ogata and Izushi 1991). 

The most sensitive target organ in animals appears to be the liver, and the most sensitive effect 

appears to be induction of hepatic microsomal xenobiotic-metabolizing enzymes at ≥0.50 mg/kg/day 

(Casterline and Williams 1971; Den Tonkelaar and Van Esch 1974). Determination of enzyme 

induction would be an inappropriate assay for most cases of suspected human intoxication, because 

enzyme induction is not specific for exposure to chlordane and because invasive techniques would be 

required to obtain liver tissue. More recently, Ogata and Izushi (1991) observed subtle evidence of 

liver effects, elevated serum triglycerides, CPK, and LDH in pesticide workers, compared with normal 

values. The elevated CPK was considered to be somewhat specific for chlordane exposure. 

Discussions of other biomarkers for liver damage and neurological effects in humans are found in 

CDC/ATSDR (1990) and OTA (1990). A more detailed discussion of the health effects caused by 

chlordane can be found in Section 2.2 of Chapter 2. 

2.6 INTERACTIONS WITH OTHER SUBSTANCES 

Chlordane, like other organochlorine insecticides, functions as a potent inducer of hepatic microsomal 

enzymes. Induction of these enzymes following chlordane administration is associated with an 

increased rate of metabolism of many endogenous and xenobiotic compounds, including therapeutic 

drugs and hormones (Welch and Harrison 1966; Welch et al. 1971). The literature regarding enzyme 

induction by chlordane is voluminous. It is beyond the intended scope of this document to review all 

this literature. Instead the reader is referred to several review articles (Albrecht and Manchon 1974; 

Azamoff 1977; Campbell et al. 1983; Fabacher et al. 1980; Hodgson et al. 1980; Smith 1991). Health 

practitioners should be aware that doses of therapeutic drugs and hormones may require adjustment in 

patients exposed to chlordane, although data regardin, 0 enzyme induction in humans exposed to 

chlordane were not located. 
CHLORDANE 104 

2. HEALTH EFFECTS 

Health practitioners should also be aware that exposure to other pesticides or chemicals that induce 

hepatic microsomal enzymes may increase the toxicity of chlordane, probably by enhancing the 

transformation of chlordane to more highly toxic metabolites. For example, previous exposure to 

aldrin, dieldrin, or DDT increased the acute toxicity of chlordane to rats by ≈2.3-4.6 times 

(Deichmann and Keplinger 1970). When given simultaneously to rats or mice, the acute lethal effects 

of chlordane in combination with most pesticides appeared to be roughly additive, except that aldrin or 

endrin and chlordane, and methoxychlor and chlordane were more than additive in mice (Keplinger 

and Deichmann 1967). 

The acute toxicity of chlordane in rats increased when rats were fed protein deficient diets (Boyd and 

Taylor 1969). Chlordane treatment has also been demonstrated to enhance the hepatotoxic effects 

produced by carbon tetrachloride in rats, as indicated by its effect on SGPT levels, presumably by 

inducing the metabolism of carbon tetrachloride to its toxic metabolite (Mahon et al. 1978; Stenger et 

al. 1975). On the other hand, chlordane provided some protection against carbon tetrachloride-induced 

liver necrosis in rats, possibly by inducing a type of cytochrome P-450 with diminished ability to 

metabolize carbon tetrachloride to its toxic metabolite (Mahon et al. 1978). Pretreatment of rats with 

chlordane accelerated the metabolism of lindane, presumably by the same mechanism (Chadwick et al. 

1977). 

2.7 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE 

A susceptible population will exhibit a different or enhanced response to chlordane than will most 

persons exposed to the same level of chlordane in the environment. Reasons include genetic make-up, 

developmental stage, age, health and nutritional status (including dietary habits that may increase 

susceptibility, such as inconsistent diets or nutritional deficiencies), and substance exposure history 

(including smoking). These parameters result in decreased function of the detoxification and excretory 

processes (mainly hepatic, renal, and respiratory) or the pre-existing compromised function of target 

organs (including effects or clearance rates and any resulting end-product metabolites). For these 

reasons we expect the elderly with declining organ function and the youngest of the population with 

immature and developing organs will generally be more vulnerable to toxic substances than healthy 

adults. Populations who are at greater risk due to their unusually high exposure are discussed in 

Section 5.6, “Populations With Potentially High Exposure.” 
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2. HEALTH EFFECTS 

Humans with chronic liver disease or impaired liver function may be unusually susceptible to 

chlordane toxicity. Infante et al. (1978) speculated on the existence of an unusually susceptible 

population prone to the development of blood dyscrasia (i.e., aplastic anemia and leukemias) following 

exposure to chlordane. Such a population was thought to have some sort of idiosyncratic response to 

chlordane exposure, but identification of this population was not thought to be possible. Although 

data are not available, humans exposed to other chemicals that induce hepatic microsomal enzymes 

may be unusually susceptible to chlordane, because the induced enzymes may enhance the 

transformation of chlordane to more highly toxic metabolites. Studies with rats show that males 

generally respond more than females to xenobiotic-induced enzyme induction (Kinoshita et al. 1966), 

but information regarding sex differences in enzyme induction in humans was not located. 

Evidence in mice indicates that the fetus may be particularly susceptible to compromised 

immunocompetence due to altered stem cell populations of key immunoactive cells (Bamett et al. 

1990a, 1990b). Infants may be unusually susceptible to a chronic seizure disorder following exposure 

to chlordane, particularly if they have a hereditary predisposition, such as a positive familial history of 

febrile convulsions (Bernad 1989). 

2.8 METHODS FOR REDUCING TOXIC EFFECTS 

This section will describe clinical practice and research concerning methods for reducing toxic effects 

of exposure to chlordane. 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 chlordane. 

When specific exposures have occurred, poison control centers and medical toxicologists should be 

consulted for medical advice. 

2.8.1 Reducing Peak Absorption Following Exposure 

Methods for reducing absorption of chlordane include those general route-specific measures that would 

be considered for any poisoning (Ellenhorn and Barceloux 1988; Haddad and Winchester 1990; 

Rumack and Lovejoy 1991). Generally, little can be done to reduce absorption following inhalation 

exposure. Recommendations include keeping the victim quiet and removing them to fresh air as 

quickly as possible. In the case of dermal/ocular exposure, medical reference texts recommend 

removal of contaminated clothing as quickly as possible and washing contaminated skin with soap and 
CHLORDANE 106 

2. HEALTH EFFECTS 

water. The use of oils could facilitate dermal absorption and their use has not been recommended. If 

the material enters the eyes, thorough rinsing with sterile physiological saline has been suggested. 

If chlordane has been ingested , gastric lavage is not usually considered beneficial unless performed 

very soon after ingestion of an extremely large dose (Ellenhorn and Barceloux 1988; Haddad and 

Winchester 1990; Rumack and Lovejoy 1991). Emesis may or may not be induced, depending on the 

situation. Emesis may be contraindicated if the victim is comatose, convulsing, has lost the gag reflex, 

or if the chlordane was suspended in petroleum distillates, so that there is danger that emesis would 

result in aspiration. Emesis may be followed by giving activated charcoal and saline cathartics. 

Oilbased cathartics are considered to be contraindicated because they may hasten the absorption of the 

ingested chlordane. Cholestyramine or other agents that may bind to chlordane may be useful in 

limiting absorption. 

2.8.2 Reducing Body Burden 

Following absorption, chlordane rapidly leaves the blood for initial distribution to the liver and 

kidneys, followed by redistribution to adipose tissue (Ewing et al. 1985; Ohno et al. 1986). Once 

chlordane has been absorbed, little can be done to reduce the body burden (Ellenhorn and Barceloux 

1988; Haddad and Winchester 1990; Rumack and Lovejoy 1991). Diuresis is not likely to be effective 

because of the high lipophilicity of chlordane. Dialysis and hemoperfusion are not expected to be 

practical because of the rapidity with which chlordane leaves the blood and locates in peripheral 

compartments, suggesting that chlordane has a large apparent volume of distribution. However, 

continued dosing with charcoal and cholestyramine may be useful to prevent reabsorption following 

biliary excretion. The barbiturates, which have been used to control poison-induced convulsions, may 

hasten metabolism and elimination of chlordane (Smith 1991). The barbiturates may also induce 

epoxide hydrolase (Sipes and Gandolfi 1991), hastening the elimination of oxychlordane, a toxic 

metabolite of chlordane. 

2.8.3 Interfering with the Mechanism of Action for Toxic Effects 

The initial effects of acute toxicity of chlordane are gastrointestinal, which probably result from 

neurological involvement, and other definite neurological symptoms of central nervous system 

stimulation, such as tremor, paralysis, and convulsions (Ellenhom and Barceloux 1988). The rapid 
CHLORDANE 107 

2. HEALTH EFFECTS 

onset of these effects suggests that they are due to the parent compound(s) rather than to metabolite(s). 

The mechanism(s) of action of the neurological effects is (are) not certain, but may involve changes in 

the levels of neurotransmitters (norepinephrine, acetylcholine) and GABA at synapses (Fishman and 

Gianutsos 1985; Grutsch and Khasawinah 1991; Hrdina et al. 1974; Inoue et al. 1989). The 

benzodiazepine sedatives (e.g., diazepam) have been used to control convulsions (Ellenhorn and 

Barceloux 1988; Rumack and Lovejoy 1991). Epinephrine is usually avoided, unless needed to 

reverse cardiopulmonary arrest, because of the possibility that chlordane (as an organochlorine 

compound) may sensitize the heart to epinephrine-induced arrhythmias (Haddad and Winchester 

1990). After the mechanisms of toxicity are better understood, it may be possible to develop more 

specific methods to interfere with the toxic effects of chlordane (i.e., more specific ways of countering 

GABA inhibition) (Grutsch and Khasawinah 1991). There is no known antidote for chlordane toxicity 

(Ellenhorn and Barceloux 1988). 

Intermediate and chronic duration exposure of humans to chlordane has been associated with blood 

dyscrasia (Ellenhorn and Barceloux 1988; Epstein and Ozonoff 1987; Infante et al. 1978), liver effects 

(EPA 1980a; Ogata and Izushi 1991) and neurological symptoms (EPA 1980a; Menconi et al. 1988). 

Although human data are lacking, animal data suggest that intermediate or chronic duration exposure 

may induce immunological effects, particularly if exposure is prenatal. It seems likely that the effects 

of intermediate or chronic duration exposure may result from metabolites of chlordane, rather than 

from chlordane itself, because the metabolites have been shown to be more toxic than the parent 

compound (Brimfield and Street 1981). The reductive formation of free radicals may be important in 

inducing toxicity. Increased dietary vitamins C or E, or increased dietary selenium may be protective 

by reducing the superoxide formation induced by highly reactive free radicals. 

2.9 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 chlordane 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 chlordane. 
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2. HEALTH EFFECTS 

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. 

2.9.1 Existing Information on Health Effects of Chlordane 

The existing data on health effects of inhalation, oral, and dermal exposure of humans and animals to 

chlordane are summarized in Figure 2-4. The purpose of this figure is to illustrate the existing 

information concerning the health effects of chlordane. Each dot in the figure indicates that one or 

more studies provide information associated with that particular effect. The dot does not imply 

anything about the quality of the study or studies. Gaps in this figure should not be interpreted as 

“data needs.” A data need, as defined in ATSDR’s Decision Guide for Identifying Substance-Specific 

Data Needs Related to Toxicological Profiles (ATSDR 1989a), is substance-specific information 

necessary to conduct comprehensive public health assessments. Generally, ATSDR defines a data gap 

more broadly as any substance-specific information missing from the scientific literature. 

As seen from Figure 2-4, data regarding systemic and neurological effects in humans are available for 

acute inhalation, oral, and dermal exposure. These data come from case reports of accidental or 

intentional exposure. Oral and dermal exposure may lead to death, but data were not located regarding 

death from inhalation exposure. Human data for chronic systemic effects and carcinogenicity come 

from epidemiological studies involving chlordane manufacture or application of chlordane as a 

pesticide, or studies of humans living in homes treated with chlordane as a termiticide. One case 

report of chronic dermal exposure was also located. Notably missing are data regarding 

developmental, reproductive, and genotoxic effects in humans. 

Inhalation data in animals consist of a comprehensive study of intermediate duration in rats and 

monkeys. The oral toxicity of chlordane in animals has been studied extensively, and data are 

available for all important effects except genotoxicity. Dermal data in animals consist of acute 

lethality data, a go-day study in guinea pigs, and a genotoxicity study in mice. 

Dermal data in animals are restricted to investigations of lethality and one 90-day study in guinea pigs. 

CHLORDANE 110 

2. HEALTH EFFECTS 

2.9.2 Identification of Data Needs 

Acute-Duration Exposure. Acute inhalation, oral, and dermal exposure data in humans have 

identified neurological, gastrointestinal, hematological, and respiratory effects, and jaundice as the 

presenting symptoms in persons exposed to high doses (Balistreri et al. 1973; Curley and Garrettson 

1969; Dadey and Kammer 1953; EPA 1980a; Harrington et al. 1978; Lensky and Evans 1952; 

Menconi et al. 1988; NIOSH 1984a; Olanoff et al. 1983). Oral exposure to high levels may be lethal 

(Aldrich and Holmes 1969; Curley and Garrettson 1969; EPA 1980a; Lensky and Evans 1952). The 

data suggested that the central nervous system and liver are the target organs for acute exposure in 

humans. Specific levels associated with effects in these organs in acutely exposed humans are not 

known. 

Acute inhalation data in rats have identified a level associated with mortality (Khasawinah et al. 1989). 

Acute oral and dermal exposure data in animals have identified LD50 values and levels associated with 

mortality in rats, hamsters, and mice (Ben-Dyke et al. 1970; Deichmann and Keplinger 1970; Gaines 

1960; Gak et al. 1976; Ingle 1965; Podowski et al. 1979; Truhaut et al. 1975; Usami et al. 1986). 

Acute oral data also have identified the liver and the central nervous system as target organs in rats 

(Den Tonkelaar and Van Esch 1974; Hrdina et al. 1974; Kacew and Singhal 1973; Ogata and Izushi 

1991; Singhal and Kacew 1976; Truhaut et al. 1974, 1975). Generally, the animal data confirmed the 

target organs in humans, and, based on similar target organs and metabolic pathways (Tashiro and 

Matsumara 1978), the rat appears to be an appropriate model for toxicity in humans. The data were 

insufficient to derive an acute inhalation MRL for chlordane because neurological effects have not 

been sufficiently studied to aid in the identification of the most sensitive end point. An acute-duration 

oral MRL of 0.001 mg/kg/day was derived from a LOAEL of 1 mg/kg/day for developmental effects 

in the offspring of mice exposed to chlordane in the diet during the third timester of pregnancy 

(Al-Hachim and Al-Baker 1973). The pharmacokinetic data in animals, which indicate that absorption 

occurs following exposure by any route (Ambrose et al. 1953a; Ewing et al. 1985; Nye and Dorough 

1976), and the human effects data indicate that the central nervous system and liver would be the 

target organs of dermal exposure. More animal studies by all three routes of exposure may be helpful 

to identify thresholds for the more subtle and less studied manifestations of hepatic and neurological 

toxicity. These data are important because humans may be exposed by all routes to low or moderate 

levels of chlordane near hazardous waste sites or in homes and gardens previously treated with 

chlordane. 
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Intermediate-Duration Exposure. Intermediate-duration oral or dermal human exposure data were 

not located. 

Intermediate-duration inhalation exposure data in rats, mice, and monkeys have identified the lungs, 

hematological system, liver, central nervous system, thyroid, and possibly the thymus in female rats, as 

the target organs (Ingle 1953; Khasawinah et al. 1989; Velsicol Chemical Co. 1984). Intermediateduration oral studies have identified levels in rats, mice, and rabbits associated with death, and 

identified the liver, central nervous system, and developing immune system as target organs (Bamett et 

al. 1985a, 1985b, 1990a, 1990b; Blaylock et al. 1990a; Casterline and Williams 1971; Cranmer et al. 

1984; Drummond et al. 1983; Mahon et al. 1978; Matin et al. 1977; Menna et al. 1985; NCI 1977; 

Ortega et al. 1957; Spyker-Cranmer et al. 1982; Stohlman et al. 1950). Intermediate-duration dermal 

exposure induces convulsions and liver necrosis in mice and hyperkeratosis of the skin of guinea 

pigs(Datta et al. 1975; Frings and O’Tousa 1950). An intermediate-duration inhalation MRL of 0.0002 

mg/m3

 was derived based on a NOAEL for hepatic effects in rats exposed to chlordane 

intermittently for 90 days (Khasawinah et al. 1989; Velsicol Chemical Co. 1984). An 

intermediateduration oral MRL of 0.0006 mg/kg/day was derived based on a NOAEL of 0.055 

mg/kg/day for hepatic effects in rats given chlordane in the diet for 30 months (Khasawinah and 

Grutch 1989a; Velsicol Chemical Co. 1983a). The 2- to 9-month rat dietary study conducted by Ortega 

et al. (1975) which identified a minimal LOAEL of 0.125 mg/kg/day for hepatic effects supports the 

Khasawinah and Grutsch (1989a; Velsicol Chemical Co. 1983a) study. The pharmacokinetic data in 

animals, which indicate that absorption occurs following exposure by any route (Ambrose et al. 1953a; 

Ewing et al. 1985; Nye and Dorough 1976), and effects data in animals indicate that the liver and 

central nervous system are the principal target organs by all routes of exposure. Additional animal 

studies by all three routes of exposure may be helpful for identifying thresholds for the more subtle and 

less studied manifestations of hepatic, immunological, and neurological toxicity. These data might be 

important because humans may be exposed by all routes to low or moderate levels of chlordane near 

hazardous waste sites or in homes and gardens previously treated with chlordane. 

Chronic-Duration Exposure and Cancer. Chronic-duration inhalation data include two case 

report studies of blood dyscrasia, and several studies of humans living in chlordane-treated homes or 

exposed to chlordane during its manufacture or during its use as a pesticide (Brown 1992; Ditraglia et 

al. 1981; Epstein and Ozonoff 1987; Fishbein et al. 1964; Infante et al. 1978; Kawano and Tatsukawa 

1982; Menconi et al. 1988; Ogata and Izushi 1991; Wang and MacMahon 1979a, 1979b). Dermatitis, 
CHLORDANE 112 

2. HEALTH EFFECTS 

migraine headaches, unspecified skin neoplasms, and unspecified ovarian and uterine disease have 

been reported by these authors to be associated with chronic inhalation exposure to chlordane. A 

chronic-duration inhalation MRL of 0.00002 mg/m3

 was derived from the NOAEL for hepatic effects 

in rats exposed to chlordane intermittently for 90 days (Khasawinah et al. 1989; Velsicol Chemical Co. 

1984). Elevated serum levels of hepatic enzymes associated with liver damage were found in pesticide 

applicators (Ogata and Izushi 1991). No studies of chronic oral exposure to chlordane were located 

for humans. Chronic-duration dermal data in humans are limited to a report of seizures in a nursery 

owner who handled soil containing chlordane. 

Chronic-duration animal exposure data, located only for oral exposure, have identified levels in rats 

and mice associated with reduced survival, and identify the liver and central nervous system as target 

organs (Epstein 1976; IRDC 1973; Khasawinah and Grutsch 1989a, 1989b; NCI 1977; Velsicol 

Chemical Co. 1983a, 1983b). A chronic-duration oral MRL of 0.0006 mg/kg/day was derived based 

on the NOAEL for hepatic effects in rats given chlordane in the diet for 30 months (Khasawinah and 

Grutsch 1989a; Velsicol Chemical Co. 1983a). Chlordane induced liver tumors in mice, and chlordane 

has not been sufficiently studied for reproductive effects. The pharmacokinetic data in animals, which 

indicate that absorption occurs following exposure by any route (Ambrose et al. 1953a; Ewing et al. 

1985; Nye and Dorough 1976), and the effects data in animals, particularly for acute- and 

intermediate-duration exposure, indicate that the liver and central nervous system would be principal 

target organs by all routes of chronic exposure. No chronic inhalation studies of chlordane in animals 

were located. Additional animal studies by all three routes of exposure may be helpful for identifying 

thresholds for the more subtle and less studied manifestations of hepatic, immunological, and 

neurological toxicity. These data are important because humans may be exposed by all routes to low 

or moderate levels of chlordane near hazardous waste sites or in homes and gardens previously treated 

with chlordane. 

The epidemiology studies and case reports discussed above revealed no convincing evidence of 

carcinogenicity in humans, except for a weak association with leukemia and neuroblastoma (Epstein 

and Ozonoff 1987; Infante et al. 1978). One epidemiological study also investigated the risk of 

non-Hodgkins lymphoma in farmers who were dermally exposed to chlordane for prolonged periods 

(Cantor et al. 1992). Although odds ratio data were derived, the study was limited by the lack of 

exposure data. Oral studies in animals have confirmed that chlordane induces liver tumors in mice, 

but not rats, exposed to high levels (Becker and Sell 1979; Epstein 1976; IRDC 1973; Khasawinah and 
CHLORDANE 113 

2. HEALTH EFFECTS 

Grutsch 1989a, 1989b; NCI 1977; Velsicol Chemical Co. 1983a, 1983b; Williams and Numoto 1984). 

Chronic-duration inhalation and dermal studies were not located, but it seems likely that the 

carcinogenicity of chlordane in mice is not route-dependent, because the pharmacokinetic data in 

animals indicate that absorption occurs following any route of exposure, and because the liver is a 

target organ for non-cancer effects regardless of route of exposure. Most genotoxicity tests with 

chlordane yielded negative results (Arnold et al. 1977; Ashley and Tenant 1988; Blevins and Sholes 

1978; Brandt et al. 1972; Maslansky and Williams 1981) (see Section 2.4), suggesting an epigenetic 

mechanism of carcinogenicity. In support of this theory, chlordane inhibited gap junction intercellular 

communication (Ruth et al. 1990; Tong and Williams 1988). These results suggest that chlordane acts 

as a tumor promoter, depressing intercellular communication that checks uncontrolled proliferation of 

transformed or neoplastic cells. Further mechanistic studies may provide useful information regarding 

the potential carcinogenicity to humans chronically exposed to low levels. These studies are important 

because humans may be chronically exposed by living in previously treated homes or near hazardous 

waste sites. 

Genotoxicity. Studies of genotoxic effects in humans are limited to an in vitro study of 

chlordaneinduced sister chromatid exchange in lymphoid cells and a positive response was obtained 

(Sobti et al. 1983). In vivo mouse studies provided mixed results; chlordane did not induce dominant 

lethal mutations in mice (Arnold et al. 1977; Epstein et al. 1972), but did induce micronucleus 

formation in the bone marrow cells and nuclei aberrations in the hair follicles (Schop et al. 1990). The 

most prevalent metabolite of the chlordane isomers, oxychlordane, although an epoxide, appears to be 

relatively inert (Khasawinah 1989; Sasaki et al. 1992), and probably does not bind strongly to tissue 

macromolecules. Free radicals formed as a result of reductive dehalogenation, however, may bind to 

DNA and other macromolecules (Brimfield and Street 1981; Kawano et al. 1989), inducing genetic 

defects or interfering with DNA repair. Additional in vivo mutation and chromosomal aberration tests 

in animals may clarify the ability of chlordane to induce genotoxicity in humans. 

Reproductive Toxicity. Data from one human case report involving a woman who was exposed to 

a lethal dermal dose of chlordane (Derbes et al. 1955) and a cross-sectional epidemiological 

investigation involving women exposed to chlordane vapors (Menconi et al. 1988) did not provide 

conclusive evidence that the reproductive system is a potential target organ in humans exposed to 

chlordane. Inhalation and oral acute-, intermediate-, or chronic-duration exposure studies in animals, 

in which the reproductive organs were examined histopathologically, did not identify lesions in the 
CHLORDANE 114 

2. HEALTH EFFECTS 

reproductive organs (Khasawinah and Grutsch 1989a, 1989b; Khasawinah et al. 1989; NCI 1977; 

Truhaut et al. 1975; Velsicol Chemical Co. 1983a, 1983b, 1984). However, treatment of male mice by 

gavage with chlordane for 30 days resulted in reduced size of seminiferous tubules and degeneration of 

spermatogenic epithelium (Balash et al. 1987). No studies were located regarding reproductive effects 

in animals after dermal exposure to chlordane. Of more concern is the observation that oral exposure 

to a large dose decreased fertility in rats and resulted in the death of all offspring before weaning 

(Ambrose et al. 1953a). The death of the offspring may have resulted from chlordane residues in milk 

transferred from the dam. The pharmacokinetic data in animals indicated that absorption occurs 

following any route of exposure, and that chlordane residues tend to accumulate in body fat; therefore, 

impaired reproductive performance in humans may occur following any route of exposure. Because of 

the tendency for chlordane residues to accumulate in body fat, multi-generation reproduction studies in 

animals by the inhalation and oral routes are recommended. Epidemiological investigations of 

reproductive effects in humans living in homes previously treated with chlordane, or those exposed 

during its manufacture or use as a pesticide, would also be useful, if an adequate cohort can be 

identified. 

Developmental Toxicity. Data were not located regarding the developmental effects of chlordane 

in humans. Effects data from animals, available only for oral exposure, suggest that subtle behavioral 

and immunological effects occur in developing mice (Al-Hachim and Al-Baker 1973; Bamett et al. 

1985a, 1985b, 1990a, 1990b; Chemoff and Kavlock 1982; Cranmer et al. 1984; Menna et al. 1985; 

Spyker-Cranmer et al. 1982; Theus et al. 1992; Usami et al. 1986). Pharmacokinetic data in animals 

indicate that absorption occurs following any route of exposure; therefore, developmental effects may 

occur following any route of exposure. Additional developmental studies in other animal species may 

clarify the developmental effects that could be anticipated in humans via inhalation, oral, and dermal 

routes of exposure. Particularly useful would be studies designed to locate thresholds for subtle 

immunological and neurological effects following both pre- and postnatal exposure. Epidemiological 

investigation of developmental effects in humans living in homes treated with chlordane, or those 

exposed during its manufacture or use as a pesticide, would also be useful. 

Immunotoxicity. Data from one human study suggest that chlordane may cause autoimmunity as 

well as impaired proliferative responses to plant mitogens following inhalation exposure to chlordane 

(McConnachie and Zahalsky 1992). In vitro studies with rhesus monkey peripheral blood 

mononuclear cells suggest that chlordane may impair cell-mediated immunity in rhesus monkeys 
CHLORDANE 115 

2. HEALTH EFFECTS 

(Chuang et al. 1992). Mice exposed to chlordane developed leukocytosis and decreased thymus 

weight (Johnson et al. 1986; Khasawinah et al. 1989). Decreased myeloid cell colony forming 

capacity and depressed delayed type hypersensitivity occurred in the offspring of mice exposed orally 

to chlordane during gestation (Bamett et al. 1985a, 1985b, 1990a, 1990b; Menna et al. 1985; SpykerCranmer et al. 1982). Because chlordane is absorbed following any route of exposure, immunological 

effects may be expected in humans exposed by any route. Further testing of immune function in mice 

and other animals may provide useful information regarding the immunotoxicity in humans. In 

addition, epidemiology studies, perhaps comparing persons with high and low levels of chlordane 

residues in the blood, fat or breast milk, may provide useful information. Parameters evaluated may 

include the frequency of allergic and autoimmune disorders, susceptibility to opportunistic infections 

(e.g., colds or flu), and alterations in absolute and differential leukocyte counts. 

Neurotoxicity. Neurotoxicity is a consistent and predictable finding in humans (Aldrich and Holmes 

1969; Balistreri et al. 1973; Barnes 1967; Curley and Garrettson 1969; Dadey and Kammer 1953; EPA 

1980a, 1986d; Harrington et al. 1978; Lensky and Evans 1952; Menconi et al. 1988; NIOSH 1984a; 

Olanoff et al. 1983) and animals (Drummond et al. 1983; Frings and O’Tousa 1950; Hrdina et al. 

1974; Ingle 1952; Khasawinah et al. 1989; NCI 1977; Stohlman et al. 1950) exposed to chlordane by 

any route. In the human studies, clinical signs and symptoms included migraines, convulsion, and 

seizures following inhalation, oral, or dermal routes of exposure. In the animal studies, convulsions 

and seizures were consistent findings after inhalation, oral, and dermal routes of exposure to chlordane 

(Ambrose et al. 1953a; Hrdina et al. 1974; Ingle 1953; Khasawinah et al. 1989; NCI 1977; Velsicol 

Chemical Co. 1984). Further testing should be designed to investigate subtle effects on neurobehavior 

and central nervous system function. Epidemiological investigation of subtle neurological and 

behavioral effects in humans living in homes treated with chlordane, or those exposed during its 

manufacture or use as a pesticide, would also be useful. 

Epidemiological and Human Dosimetry Studies. Several epidemiological studies have 

investigated the cancer and noncancer effects of chlordane in humans exposed in their homes or 

occupationally in the manufacture of chlordane or in its application as a pesticide (Alvarez and Hyman 

1953; Brown 1992; Cantor et al. 1992; Ditraglia et al. 1981; Kawano and Tatsukawa 1982; MacMahon 

et al. 1988; Menconi et al. 1988; Ogata and Izushi 1991; Wang and MacMahon 1979a, 1979b; Woods 

and Polissar 1989). Limitations of these studies include unquantified exposure levels of chlordane, 

exposure to a mixture of chemicals, and failure to investigate subtle neurological, behavioral, and 
CHLORDANE 116 

2. HEALTH EFFECTS 

hepatic effects in the exposed persons. Additional multi-end point epidemiological studies should be 

designed to study these subtle effects, as well as hematological effects such as blood dyscrasia and 

leukemia, in the exposed populations mentioned above. Further, case-control designed epidemiological 

studies would help to establish a cause/effect relationship among a better defined population. 

Biomarkers of Exposure and Effect 

Exposure. Biomarkers of exposure include various components of commercial chlordane (principally 

cis- and trans-chlordane, cis- and trans-nonachlor) and its metabolites (principally oxychlordane). 

These substances are specific for exposure to chlordane. Detection of heptachlor and its metabolite, 

heptachlor epoxide, could reflect exposure to chlordane, because heptachlor is a component of 

commercial chlordane, or exposure to heptachlor, which is an insecticide in its own right. Data were 

not located that permit differentiation of the route, magnitude, or duration of exposure based on 

biomarkers of exposure. 

Detectable levels in urine would probably reflect recent or ongoing exposure, because urinary 

excretion is not prominent for chlordane (Aldrich and Holmes 1969; Bamett and Dorough 1974; 

Ewing et al. 1985; Ohno et al. 1986; Tashiro and Matsumura 1977). Higher levels of chlordane 

residues occur in the feces of acutely poisoned humans (Aldrich and Holmes 1969). Generally, levels 

of chlordane residues in blood are below those in liver and fat (Mussalo-Rauhamaa 1991); blood 

(serum) levels may be reasonable indicators of recent or ongoing exposure (Ogam and Izushi 1991). 

Recent studies evaluated the use of levels of chlordane residues in skin surface lipids as a biomarker 

of exposure, to avoid the invasive techniques necessary to obtain blood or body fat (Sasaki et al. 

1991b; Wariishi and Nishiyama 1989). In monkeys, levels of trans-chlordane and oxychlordane in 

surface skin lipids correlated fairly well with levels in subcutaneous fat. Further refinement of this 

technique could increase the utility of chlordane residues in skin surface lipids as biomarkers of 

exposure. 

Effect. Known biomarkers of effect are limited to slight alterations in serum chemistry. Elevated 

serum triglycerides, CPK and LDH, evidence of subtle liver effects, were observed in pesticide 

workers (Ogata and Izushi 1991). The elevated CPK was considered somewhat specific for chlordane 

exposure. Carefully performed epidemiological studies might provide data that clarify the relation 
CHLORDANE 117 

2. HEALTH EFFECTS 

between exposure to chlordane and optic neuritis or other disease states. Such studies may also 

identify alterations in blood chemistry indices or other clinicopathological end points that are useful 

for identifying the presence or pathogenesis of disease states associated with chlordane exposure. 

Absorption, Distribution, Metabolism, and Excretion. There are no quantitative absorption 

data regarding human exposure by any route. However, that chlordane is absorbed by humans is 

indicated from measurement of blood and tissue levels of chlordane in persons exposed via inhalation 

from homes treated for termite control (Kawano and Tatsukawa 1982; Saito et al. 1986; Taguchi and 

Yakushiji 1988; Takamiya 1987), in case reports of accidental ingestion (Aldrich and Holmes 1969; 

Curley and Garrettson 1969; Kutz et al. 1983; Olanoff et al. 1983), and from systemic toxicity after 

dermal exposure (Barnes 1967). One human study also attempted to correlate skin chlordane levels 

with blood chlordane levels in 248 male and 227 female outpatients (Hirai and Tomokuni 1993). 

Although chlordane was potentially absorbed by the dermal route, the data from this study did not 

demonstrate any strong correlations between skin chlordane levels and blood chlordane levels. The rat 

data for inhalation absorption are limited to an intratracheal study, which is inadequate for estimating 

absorption via the respiratory tract (Nye and Dorough 1976). Oral data in rats and mice indicate that 

gastrointestinal absorption occurs readily (Ewing et al. 1985; Ohno et al. 1986). Quantitative dermal 

absorption data are lacking, but absorption is indicated by lethality in rats and rabbits exposed 

dermally (Gaines 1960; Ingle 1965). Quantitative inhalation and dermal absorption data would be 

useful, because these routes are toxicologically significant to humans. 

Distribution data available for humans are limited to levels of chlordane metabolites in several tissues 

after acute poisoning, and in blood, liver, fat, and breast milk after chronic-duration exposure 

following the oral route (Aldrich and Holmes 1969; Curley and Garrettson 1969; Dearth and Hites 

1991a; Hirai and Tomokuni 1991a, 1991b; Kutz 1983; Kutz et al. 1976, 1983; Mussalo-Rauhamaa 

1991; Ogata and Izushi 1991; Olanoff et al. 1983; Sasaki et al. 1991a; Wariishi and Nishiyama 1989). 

Rat studies regarding inhalation, oral, and parenteral exposure demonstrate that initial distribution is to 

the liver and kidney, followed by redistribution to body fat (Ambrose et al. 1953b; Balba and Saha 

1978; Bamett and Dorough 1974; Dearth and Hites 1991b; Ewing et al. 1985; Khasawinah 1989; Nye 

and Dorough 1976; Ohno et al. 1986; Poonawalla and Korte 1971; Sasaki et al. 1992; Street and Blau 

1972; Takeda et al. 1984). One oral study in mice demonstrated that chlordane is initially distributed 

to the muscles and that higher levels of the cis isomer accumulate in tissues than the trans isomer 

(Satoh and Kikawa 1992). Additional dermal exposure studies would be useful for elucidating patterns 
CHLORDANE 118 

2. HEALTH EFFECTS 

of distribution by this route. Of particular interest would be studies of distribution to the central 

nervous system, since neurological effects are a consistent part of the clinical picture in humans 

exposed by any route. The ability of chlordane to cross the placenta and its presence in milk should 

also be investigated, because data show that prenatally exposed mice are more sensitive than adults to 

the immunological effects of chlordane (Barnett et al. 1985a, 1985b; Menna et al. 1985; SpykerCranmer et al. 1982). Determination of apparent volume of distribution and the extent of binding to 

tissue proteins may provide data that would be useful in the management of clinical cases of 

poisoning. 

Human metabolism data are limited to in vitro studies (Kutz et al. 1976, 1979; Tashiro and Matsumura 

1978). In vivo and in vitro animal studies, however, are sufficient to propose probable metabolic 

pathways (Balba and Saha 1978; Bamett and Dorough 1974; Brimfield et al. 1978; Nomeir and Hajjar 

1987; Poonawalla and Korte 1964; Sasaki et al. 1992; Tashiro and Matsumura 1978). Further studies 

could be designed to estimate metabolic rate constants and to determine the levels at which saturation 

of specific pathways occurs with different routes of exposure. 

Data from environmentally exposed humans suggest that substantial excretion occurs via lactation 

(Barnett et al. 1979; Strassman and Kutz 1977; Taguchi and Yakushiji 1988; WHO 1984). Data 

regarding acute poisoning in humans after acute oral exposure to chlordane indicate that most 

chlordane-derived material is excreted in the feces (Aldrich and Holmes 1969; Curley and Garrettson 

1969; Olanoff et al. 1983). Studies involving intratracheal dosing of rats and acute, oral dosing of 

rats, mice, and rabbits confirm that fecal, probably biliary, excretion is more important than renal 

excretion (Barnett and Dorough 1974; Ewing et al. 1985; Tashiro and Matsumura 1977; Nye and 

Dorough 1976; Ohno et al. 1986). Additional animal studies might elucidate the relative importance 

of various routes of excretion following inhalation and dermal exposure, and might provide useful 

information regarding the rate and extent of excretion via lactation. 

Comparative Toxicokinetics. Data in rats, mice, and rabbits following oral exposure to chlordane 

indicate that there are some species differences in absorption, distribution, and excretion (Balba and 

Saha 1978; Barnett and Dorough 1974; Ewing et al. 1985; Ohno et al. 1986; Poonawalla and Korte 

1971; Satoh and Kikawa 1992). The available data on metabolites in human tissues and in vitro 

studies both indicate qualitatively that metabolism of chlordane in rats and humans is similar (Tashiro 

and Matsumura 1978), and that rats and mice are satisfactory animal models for the toxicity of 
CHLORDANE 119 

2. HEALTH EFFECTS 

chlordane. Data regarding urinary metabolites of chlordane in humans were not available. Analysis of 

the urine of humans with known exposure to chlordane (e.g., those living in previously treated houses) 

could provide a means of further studying the differences and similarities between animal species and 

humans and of monitoring humans for exposure. 

Methods for Reducing Toxic Effects. Although it is suspected that absorption occurs by passive 

diffusion, this has not been established, and data on the mechanism of chlordane absorption is not 

known. Distribution appears to reflect the lipophilicity of chlordane, but additional studies could 

determine the extent of binding to serum proteins and the apparent volume of distribution. This 

information may be useful in the clinical management of cases of poisoning, although such cases 

would be rare because the use of chlordane in the United States has been canceled. Methods for 

reducing the toxic effects of chlordane are limited to general methods for reducing absorption and 

body burden in cases of acute poisoning, and to the use of sedatives to control convulsions. There are 

no methods to reduce body burden from long-term exposure. Additional information on the 

mechanisms of toxicity, specifically on methods to counter chlordane-induced reduction of GABA 

activity, may be helpful in managing clinical cases of poisoning. Further studies in animals may be 

helpful for determining the usefulness of cholestyramine or other binding agents to sequester chlordane 

in the gut, thereby reducing body burden, and to locate other agents that would control convulsions 

without danger of respiratory depression. 

2.9.3 On-going Studies 

Several on-going investigations of the toxicity of chlordane were located. Kocoshis, sponsored by the 

National Institutes of Health, is studying liver and psychomotor function in children exposed to 

chlordane (CRISP 1992); and Zahm et al. (1988) is performing a case-control study of the risk of nonHodgkin’s lymphoma among farmers exposed to herbicides and insecticides. An odds ratio of 2.1 was 

estimated for farmers exposed to chlordane. Adeshina (1989) developed a method for estimating daily 

dose in humans based on levels of oxychlordane in adipose tissue. Omiecinski of the University of 

Washington, sponsored by NIEHS, is testing the hypothesis that animal and human exposure to a 

various class of chemicals can be monitored through composite measure of expression patterns for key 

P-450 gene products in peripheral cells (FEDRIP 1993). P-450 gene expression patterns in cultured 

cells will be evaluated subsequent to exposure to chlordane. 
CHLORDANE 120 

2. HEALTH EFFECTS 

Spyker et al. (1989) observed an increase in neurological effects, associated with increased body 

burden of chlordane, in persons living in homes treated with chlordane. These patients also had a high 

incidence of abnormal electromyogram, electronystagmogram, and findings on neuropsychiatric 

testing. With further information and validation, abnormal electromyogram and electronystagmogram 

may become reliable biomarkers of effects in humans. Sponsored by the National Institutes of Health, 

Spyker et al. (1989) is studying the decontamination of humans poisoned by chlordane (CRISP 1992). 

Neurotoxicity is a consistent effect in humans intoxicated with chlordane, and several on-going studies 

in animals are designed to clarify the effects of exposure and elucidate the mechanisms of these 

effects. Woolley, sponsored by the U.S. Department of Agriculture, is studying the neurochemical and 

neurobehavioral effects of acute and chronic exposure in rats (FEDRIP 1992). Woolley has further 

proposed to determine if adrenal steroids and cholecystokinin antagonists can ameliorate or exacerbate 

toxicity induced by heavy metals and insecticides in rats or mice (CRISUSDA 1993; FEDRIP 1993). 

Abstracts of studies yet to be published indicate that myoclonic seizures in rats induced with chlordane 

appeared to be related to increased limbic excitability (Dai et al. 1989; Hasan et al. 1989). That 

chlordane inhibits nicotine-stimulated neuronal release of norepinephrine, probably by interfering with 

opening of voltage-dependent calcium channels is suggested in an abstract of a study yet to be 

published (Inoue et al. 1989). In studies sponsored by the National Institute of Environmental Health 

Sciences (NIEHS), Matsumura is investigating the effects of chlorinated pesticides on sodium and 

calcium regulation in the nervous system (CRISP 1992). Uphouse is studying the neuroreproductive 

effects in rats of chlorinated pesticides (CRISP 1992). These studies are sponsored by the National 

Institute of General Health Sciences. In an abstract of a yet to be published report, the effects of preand 

postnatal chlordane exposure on neurobehavioral indices in the rat are being investigated (Cassidy 

et al. 1992). In this study, time pregnant dams were exposed daily from day 4 of pregnancy and 

through lactation. The resulting offspring received three levels of technical chlordane from day 22 of 

age through day 80. At low dose exposure, heptachlor epoxide plasma levels in the dam and in the 

offspring (day 80) was representative of those found in the United States populace at the 99th percentile 

(3 μg/L). The rats were tested in the Cincinnati maze between days 74 and 78 of age for 

alteration of behavior on days 76 and 77. Changes in open field activity, auditory startle, and shuttle 

box escape were evaluated on day 81 of age. 

Researchers at the University of Arkansas (Barnett et al. 1990a, 1990b; Blaylock et al. 1990a; Menna 

et al. 1985) reported that, in mice, the fetal immune system appears to be markedly more susceptible 
CHLORDANE 121 

2. HEALTH EFFECTS 

to chlordane than the immune system of the adult. Additional studies planned by Barnett, sponsored 

by NIEHS, will investigate further the effect of prenatal treatment of mice on immune function 

(CRISP 1992; FEDRIP 1993). 

Chlordane is clearly carcinogenic in mice, inducing increased incidence of hepatocellular carcinomas 

(NCI 1977). Chlordane probably acts as a tumor promoter, rather than a genotoxic agent (Tong and 

Williams 1988). Smart is conducting further studies on the mechanism of tumor promotion, sponsored 

by NIEHS (CRISP 1992) and the Department of Agriculture (FEDRIP 1992). Reynolds, in studies 

sponsored by NIEHS, is investigating the role of oncogene activation in liver tumor induction in mice 

(CRISP 1992). Goodman is planning similar studies, also sponsored by NIEHS (CRISP 1992; 

FEDRIP 1993). Goodman and Robens of the University of Michigan, sponsored by the U.S. 

Department of Agriculture, further propose to determine whether alterations in the methylation status 

of proto-oncogenes is the mechanism for the promotion stage of carcinogenesis (CRISUSDA 1993; 

FEDRIP 1993). 

The use of the hepatocyte DNA repair assay in combination with the replicative DNA synthesis (RDS) 

assay in the detection of mouse carcinogens has been reported in an abstract of a study yet to be 

published (Millner et al. 1988). Mice treated orally with chlordane had increased RDS, but no 

increase in DNA repair. The investigators suggest that the combination test may be useful in 

elucidating the mechanism of hepatocarcinogenesis. 

 

CHLORDANE 123 

3. CHEMICAL AND PHYSICAL INFORMATION 

3.1 CHEMICAL IDENTITY 

Data pertaining to the chemical identity of chlordane are listed in Table 3-l. Technical chlordane is a 

mixture of >140 related compounds, 120 of which have been recently identified by high resolution gas 

spectroscopy with electron capture, negative ionization mass spectroscopy (Dearth and Hites 1991c). 

Most of these compounds are minor or trace components. Sixty to 85% of technical chlordane 

consists of the stereoisomers cis- and trans-chlordane (Buchert et al. 1989; Worthing and Walker 

1987). The ratio of the cis and trans isomers depends on the manufacturing process (Buchert et al. 

1989). Cis-chlordane (lα,2α,3aα,4ß,7ß,7aα) is also known as α-chlordane. trans-chlordane 

(1α,2ß,3aα,4ß,7ß,7aα) is commonly known as γ-chlordane, although it is occasionally referred to as 

ß-chlordane (EPA 1984; CAS 1992; Worthing and Walker 1987). This is particularly confusing 

because γ-chlordane is also the common name of the 2,2,4,5,6,7,8,8 octachloro isomer. We will use 

the names cis- and trans-chlordane in this document to avoid confusion. 

Other major constituents of technical chlordane are chlordene; heptachlor; cis-, and trans-nonachlor; 

α-, ß-, and γ-chlordene; 3a,4,5,5a,6-exo-hexachloro-la,2,3,3a5a,5b-hexahydro-1,4-methano-1Hcyclobuta[cd]pentalene; and 2,4,4,5,6,6,7,8-octachloro-2,3,3a,4,5,7a-hexahydro-1,4-methano-1Hindene (Miyazaki et al. 1985; Parlar et al. 1979). 

3.2 PHYSICAL AND CHEMICAL PROPERTIES 

The physical and chemical properties of chlordane are presented in Table 3-2. The physical and 

chemical properties of technical chlordane are difficult to specify since there are many components in 

the technical mixture. For example, technical chlordane is a viscous liquid made of a mixture of many 

compounds that are solids when pure (a eutectic mixture). The state of the technical product alone 

will effect the properties of the product. For example, the vapor pressure of the pure components of 

chlordane will be lower than the technical product because they are solids and have crystal lattice 

energies that reduce their vapor pressures relative to a liquid (Bidleman and Foreman 1987). The 

vapor pressure of the mixture will also change over time since the more volatile components will be 

removed faster, changing the composition of the mixture. Compositional changes with time may also 


CHLORDANE 126 

3. CHEMICAL AND PHYSICAL INFORMATION 

result from different rates of degradation and transport among the constituents of the mixture. 

Additionally, physical properties are not always available for the technical product, which makes 

comparing properties difficult and increases the uncertainty of any calculated properties. Finally, the 

overall effect of these differences cannot be evaluated since a complete set of physical properties for 

the components and technical product is not available. 
CHLORDANE 127 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

4.1 PRODUCTION 

Chlordane is produced by chlorinating cyclopentadiene to form hexachlorocyclopentadiene and 

condensing the latter with cyclopentadiene to form chlordene. The chlordene is further chlorinated at 

high temperature and pressure to chlordane (Dearth and Hites 1991c; Whetstone 1964). EPA (1987g) 

estimated that ≈3.5-4.0 million pounds of chlordane were distributed in 1986. Table 4-1 lists the 

facilities that manufacture or process chlordane according to the 1990 Toxic Chemical Release 

Inventory. Velsicol Chemical Company in Memphis, Tennessee, is presently the only U.S. 

manufacturer of chlordane; between 100,000 and 1 million pounds of chlordane is produced (SRI 

1990; TRI90 1992). It was the only domestic manufacturer of chlordane at the time that the EPA 

canceled its registration for commercial production, delivery, sale, and use in the United States (EPA 

1988c; SRI 1988). This cancellation became effective April 14, 1988 (EPA 1988c). Technical 

heptachlor contains 20-22% trans-chlordane (Kutz et al. 1991). The registration of heptachlor was 

also canceled by EPA. 

4.2 IMPORT/EXPORT 

Chlordane is not imported into the United States (EPA 1988c). Chlordane is still produced for export, 

but is no longer used in the United States. No data on export volumes are available. 

4.3 USE 

As of April 14, 1988, all commercial use of chlordane in the United States was canceled (EPA 1988c). 

Between July 1, 1983 and April 14, 1988 the sole use for chlordane was to control subterranean 

termites (EPA 19878). For this purpose, chlordane was applied primarily as a liquid that was poured 

or injected around the foundation of a building (Wallace 1991). Chlordane, in conjunction with 

heptachlor, was at one time widely used as a pesticide for the control of insects on various types of 

agricultural crops and vegetation. The use pattern for chlordane in the mid 1970s was as follows: 35% 

used by pest control operators, mostly on termites; 28% on agricultural crops, including corn and 

citrus; 30% for home lawn and garden use; and 7% on turf and omamentals (HSDB 1988). On 

CHLORDANE 129 

4. PRODUCTION, IMPORT, USE, AND DISPOSAL 

March 6, 1978 a final cancellation notice was issued which called for the suspension of the use of 

chlordane except for subsurface injection to control termites and for dipping roots and tops of nonfood 

plants. Minor use of chlordane for treating nonfood plants was canceled by 1983 (EPA 1987g). The 

use of chlordane decreased drastically in the 1970s when EPA moved to cancel all uses other than 

subterranean termite control (Kutz et al. 1991). 

4.4 DISPOSAL 

According to TRI90 (1992), 99 pounds of chlordane was disposed of in publicly operated treatment 

plants (POTWs) and 523 pounds were transferred to off-site facilities. Chlordane may be disposed of 

by dissolving it in a flammable solvent and incinerating it under controlled conditions. The incinerator 

should be equipped with an afterburner and an acid scrubber to remove halo acids from the effluent 

gas, and adequate ash disposal procedures should be followed (EPA 1991; HSDB 1988; OHM-TADS 

1988). Before disposing waste residue containing chlordane (including waste sludge) on land, 

environmental regulatory agencies should be consulted for guidance on acceptable disposal practices 

(HSDB 1988). EPA has promulgated standards for the disposal of waste chlordane in sewage sludge 

(EPA 1993). 

In situ vitrification is a thermal treatment technology in which substantial quantities of energy are 

introduced into contaminated soil, thereby destroying organic compounds and immobilizing inorganic 

compounds (Dragun 1991). This technology has been applied to chlordane-contaminated soils. 

CHLORDANE 131 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.1 OVERVIEW 

Chlordane is an insecticide formerly used to treat field crops (especially corn) and other types of 

vegetation and to control termites. As such, it was intentionally applied to soils both in agricultural 

and urban settings. Table 5-l lists releases from facilities in the United States that produced, 

processed, or used chlordane in 1990, according to TRI (TRI90 1992). All but 1 pound of these 

releases, which totaled 4,423 pounds, were released to air. These releases were almost exclusively 

from the sole producer of chlordane in the United States, Velsicol Chemical Corporation. Chlordane 

has been identified in at least 176 of the 1,350 hazardous waste sites that have been proposed for 

inclusion on the EPA’s NPL (HAZDAT 1992). However, the number of sites evaluated for chlordane 

is not known. The frequency of these sites can be seen in Figure 5-1. Of these sites, 175 are located 

in the United States and 1 is located in the Commonwealth of Puerto Rico (not shown). Chlordane is 

extremely persistent in the environment. In some soils it may persist for >20 years. Volatilization 

appears to be the only major removal mechanism from soil. However, at waste sites that contain high 

levels of organic solvents, leaching to groundwater may occur. Adsorption to sediments and 

volatilization are important removal mechanisms in water. In air, chlordane exists predominantly in 

the vapor phase. However, the relatively small fraction of particle-bound chlordane appears to be of 

major importance in atmospheric deposition (Atlas and Giam 1988). Vapor-phase chlordane degrades 

by photolysis and hydroxyl radical reaction. Chlordane may be transported long distances and 

deposited by wet or dry deposition. As a result of this long range transport and its high 

bioconcentration factor, chlordane is now prevalent in the Arctic food web (Hargrave et al. 1992). 

Chlordane’s persistence in the environment from its use as a termiticide is the major factor for 

exposure in the general population. Chlordane has been detected in the indoor air of homes 15 years 

after treatment. EPA (19878) estimated that over 80 million people in the United States have lived in 

homes treated with cyclodiene termiticides, and ≈65% of these people have lived in homes treated 

with chlordane. Thus, ≈52 million people have been exposed to chlordane in their homes. The total 

number of exposed people is much greater since some foods, especially fish, are contaminated with 

chlordane; additional intake may result from this ingestion of contaminated foods. 


CHLORDANE 134 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.2 RELEASES TO THE ENVIRONMENT 

5.2.1 Air 

According to TRI90 (1992), 4,422 pounds of chlordane were discharged to air from facilities that 

produced, processed, or used chlordane in the United States in 1990. These releases were almost 

exclusively from the sole producer of chlordane in the United States, Velsicol Chemical Corporation. 

At least in recent years in the United States, chlordane’s use has been restricted and then banned; 

however, chlordane is still present in soil from it’s past use as a crop pesticide and termiticide. 

Chlordane, nonetheless, is present in the atmosphere, which is probably due to volatilization from soils 

and water as well as wind erosion. These processes are believed to account for the loss of chlordane 

into air at NPL sites. Several investigators have reported that chlordane volatilizes after termiticide 

application to soils at rates that vary depending on soil characteristics and application methods (Atallah 

et al. 1979; Glotfelty et al. 1984; Nash 1983a, 1983b). Volatilization also occurs following runoff into 

water bodies (Atlas et al. 1982; Mackay et al. 1986). In addition, chlordane has been detected in the 

indoor air of homes 15 years after treatment with chlordane for termites (Livingston and Jones 1981). 

These data suggest that chlordane is present in air as a result of its former use as a pesticide. No data 

are available regarding emissions of chlordane from NPL sites. 

5.2.2 Water 

Chlordane is not directly applied to water but is present in runoff from urban uses as a termiticide 

(EPA 19878; Nightingale 1987) and its former agricultural use on field crops. A field study in 12 

urban areas in the Canadian Great Lakes Basin measured the concentrations of cis- and 

trans-chlordane in urban runoff and street sediment (Marsalek and Schroeter 1988). These mean 

concentrations combined with runoff volumes and sediment yields were then used to estimate pollutant 

loadings into the Great Lakes Basin. Total chlordane loadings into Lakes Erie, Huron, Ontario, St. 

Chair, and Superior were 0.59, 0.47, 2.48, 0.34, and 0.07 kg/year for a annual basin loading of 3.9 kg. 

According to sediment concentrations in EPA’s STORET database, releases to water have been highest 

in the west north central region of the United States and lowest in New England (Phillips and Birchard 

1991). 
CHLORDANE 135 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.2.3 Soil 

Chlordane was used for ≈40 years, mainly as a field crop insecticide and termiticide (EPA 19878). 

Both of these uses involve the intentional application of the chemical to the soil. The total 

environmental burden of chlordane for the past 40 years can be roughly estimated using several 

assumptions. Before 1978, chlordane was used for many applications and probably had a much higher 

production. An estimated 4.0 million pounds were used in 1986 when its use was limited to 

subterranean applications as a termiticide (EPA 1987g). On the basis of historic production figures, an 

estimated 70,000 tons of chlordane were produced since 1946, of which 25-50% still exists unaltered 

in the environment (Dearth and Hites 1991c). This material was exclusively released to soil. 

Chlordane was applied in a geographically disperse manner on both rural and urban soils. In recent 

years, the majority of use probably was from Pennsylvania and the lower New England states south 

and west to the lower portion of Colorado and up to northern California, since termite infestations are 

most common in these areas (EPA 1987g). The northern plains and mountain states and northern New 

England states have much lower incidence of termites although chlordane was used on field crops 

before 1978 in these states. EPA (1987g) estimated that ≈19.5 million structures have been treated 

with chlordane, which means that the soils around the treated houses may contain chlordane. 

5.3 ENVIRONMENTAL FATE 

5.3.1 Transport and Partitioning 

Chlordane may be transported long distances in the atmosphere. The United States appears to be the 

main source of chlordane in the air over the North Atlantic (Bidelman et al. 1987). Concentrations of 

cis-chlordane ≤0.0054 ng/m3

 in the Norwegian Arctic are believed to originate in the Soviet Union, 

thousands of miles away (Pacyna and Oehme 1988). Similarly, the source of chlordane-related 

compounds in brown snow in the central Canadian Arctic, based on back-trajectories of air masses, 

was probably western China (Welch et al. 1991). It is estimated that ≈3,300 kg of chlordane are 

deposited annually in the Arctic regions (from 60° N. latitude to the pole) (Cotham and Bidleman 

1991). 

There is a large body of information concerning the transport and partitioning of chlordane in the 

environment. In outdoor air, chlordane exists predominately in the vapor phase (Atlas and Giam 1988; 
CHLORDANE 136 

5. POTENTIAL FOR HUMAN EXPOSURE 

Bidleman et al. 1986; Bidleman and Foreman 1987; Foreman and Bidleman 1987), whereas 

particleadsorbed chlordane will contribute relatively minor amounts to the environmental burden (Starr 

et al. 1974; Tucker and Preston 1984). Air monitoring data are derived by the following method: 

chlordane is first pulled through a fiber filter and then trapped on a solid adsorbent; the amounts of 

chlordane retained on the filter and on the adsorbent is used to estimate the proportion of particulatebound and vapor phase chemical. Air monitoring data derived by this method indicate that 0.7% and 

11% of chlordane is bound to particulate matter at 20° and 0°C respectively (Bidelman et al. 1986). At 

28°C the average temperature at which one of the arctic air monitoring studies was performed, about 

45% of chlordane is bound to particulate matter (Patton et al. 1991). However, the small amount of 

adsorbed chlordane at ordinary temperatures appears to play an important role in atmospheric 

deposition. In samples collected in a rural area of Texas, 98% of the chlordane scavenged rain was 

particle-bound chlordane, rather than vapor-phase chlordane that partitioned into rain drops (Atlas and 

Giam 1988). The chlordane concentration in rain was 1,900 times the concentration in air. The 

contribution of dry deposition to total (wet and dry) deposition in a 24-hour period was 8.9%. 

Chlordane applied to the foundation of homes for termite treatment can enter the home through cracks 

in the foundation or in heating ducts in the slabs. Chlordane disperses through the house by diffusion 

and convection (Livingston and Jones 1981). 

Chlordane in water will both adsorb to bed and suspended sediments and volatilize. The partitioning 

of chlordane to sediment correlates with the organic carbon content of the sediment. The mean log 

Koc for trans-chlordane to samples of suspended particulate matter from the St. Clair and Detroit 

Rivers was 6.3 (Lau et al. 1989). Where, concentrations of suspended sediment are high, such as in 

rivers near sources of industrial discharge, substantial amounts of pollutants like chlordane would be 

transported with suspended sediment. The rate of volatilization of chlordane from water depends to a 

large extent on the amount, size, and composition (i.e., percent organic matter) of the suspended 

material in the water body since adsorption to suspended solids and sediments attenuates the rate of 

volatilization (Oloffs et al. 1972, 1973). The rate of volatilization is also affected by temperature, 

wind, and water turbulence. Chlordane adsorbed almost completely to sediments in laboratory 

experiments over a period of ≈6 days (Oloffs et al. 1972, 1973). It also volatilizes reasonably rapidly 

from water (Huang 1970), and it appears that volatilization kinetics may be faster than adsorption 

kinetics. The majority of chlordane, however, probably enters water as runoff from urban and 

agricultural soils, and is adsorbed to particulates before entering a body of water. The chlordane 

repartitions in the water and volatilizes rapidly near the water surface. Using the EPA EXAMS model 
CHLORDANE 137 

5. POTENTIAL FOR HUMAN EXPOSURE 

(EPA 1985c), the estimated volatilization half-lives of chlordane from a typical pond and lake are 

<10 days. Nonetheless, monitoring data indicate that sediment concentrations of chlordane are much 

higher than the overlying water, suggesting that volatilization from water may not be as fast as 

predicted. A field experiment was performed to study the persistence and mobility of technical 

chlordane applied to an intertidal sandflat (Smith et al. 1992). The chlordane was applied at mid-tide 

level to a depth of 10 cm and sediment cores to a depth of 10 cm were sampled before treatment and 

1, 3, 5, 13, 19, 44, 71, 112, and 199 tides after treatment. The overall change of mass was about 62% 

over a period of 106 days with more than half occurring during the first tide cycle. The main decrease 

in concentration was in the top 2 cm where mass transport and bioaccumulation are most effective. 

Concentrations for the 2-5 and 5-10 cm depth intervals showed little change between tides 3 and 71. 

Thus, after some initial displacement, possibly into more organically enriched sediment, there was 

little vertical movement of chlordane. The composition of the technical chlordane was essentially 

constant during the experiment which. suggested that processes such as hydrolysis, dechlorination, and 

volatilization were much less important pathways for chlordane removal from this environment than 

sediment transport. 

Chlordane will bioconcentrate in both marine (bioconcentration factor 3,000-12,000 [Zaroogian et al. 

19851) and fresh water (bioconcentration factor 18,500 in rainbow trout [Oliver and Niimi 19851) 

species, as well as bacteria [bioconcentration factor of 200-55,900 (Grimes and Morrison 1975)]. See 

Gobas et al. (1988) and Isnard and Lambert (1988) for further information on bioaccumulation in fish. 

Biomagnification of chlordane-related compounds, including heptachlor epoxide, was studied in three 

trophic levels in the Arctic marine food chain, namely, Arctic cod, ringed seals, and polar bears (Muir 

et al. 1988). The biomagnification from fish to seal (male/female) was 7.3/4.7 and that between seal 

(male/female) and bear was 6.6/9.5 resulting in an overall fish to bear biomagnification factor of 44.2. 

Both chlordane isomers decrease in higher trophic levels with only the metabolite oxychlordane 

present in polar bears (Hargrave et al. 1992). It should be noted that biomagnification of chlordane is 

a tricky concept because the compositional pattern of chlordane compounds and metabolites varies 

among different trophic levels and species (Kawano et al. 1988). Chlordane is taken up by rooted 

aquatic vascular plants both from the water and from the sediment. The bioconcentration factor of 

chlordane in the submerged vascular plant, Hydrillu verticillatu, was 1.060 (Hinman and Klaine 1992). 

Chlordane also bioconcentrates in the roots from contaminated sediment and translocates into the 

shoots. However, acropetal translocation is not extensive. 
CHLORDANE 138 

5. POTENTIAL FOR HUMAN EXPOSURE 

In soil, chlordane adsorbs to the organic matter and volatilizes slowly over time. Chlordane does not 

leach significantly. In general, chlordane remains in the top 20 cm of most soils and for some soils, it 

stays at this level for over 20 years (Beeman and Matsumura 1981; Bennett et al. 1974). Its behavior 

is somewhat dependant on the composition of the soil (Bennett et al. 1974; Carter and Stringer 1971; 

Haque and Freed 1974; Jury et al. 1987a; Sears and Chapman 1979; Stewart and Chisholm 1971; 

Stewart and Fox 1971; Tafuri et al. 1977). A study by the California Department of Food and 

Agriculture classified chlordane as a “nonleacher” based on records of groundwater contamination 

following normal agricultural use (Gustafson 1989). The distribution coefficient between chlordane 

and geologic material collected near a hazardous waste site in Memphis, Tennessee ranged from 18 to 

220 mL/g or Koc of 20,000 to 76,000 (Johnson-Logan et al. 1992). Chlordane will bind tenaciously 

to dissolved organic carbon (DOC) in water which will result in increased apparent solubility and 

mobility in the presence of DOC. For example, the solubility of chlordane in groundwater 

downstream of a hazardous waste site in Memphis, Tennessee, was 150 μg/L compared to 30 μg/L in 

purified water due to the presence of DOC (Johnson-Logan et al. 1992). Therefore, it is expected that 

chlordane mobility will be enhanced at this site. Volatilization from soil is a major loss mechanism 

for chlordane; the rate depends on such parameters as the soil organic content, water content, 

temperature, and relative humidity as well as its vapor pressure and adsorption to soil (Atallah et al. 

1979; Glotfelty et al. 1984; Glotfelty and Schomburg 1989; Jury et al. 1987b; Nash 1983a, 1983b; 

Wilson and Oloffs 1973). In general, sandy soils and soils with small amounts of organic matter 

retain chlordane less than soils with high clay and/or organic content (Wiese and Basson 1966). Soil 

moisture, however, is the most important factor. Within an hour of being sprayed on the surface of 

moist bare soil in a pesticidal mixture, the vapor pressure of chlordane near the soil surface was 

5.8x10-7 mmHg (Glotfelty and Schomburg 1989). The time for 50% of the chlordane to volatilize is 

2-3 days. In time, the spray penetrates the soil and longer term volatilization is controlled by back 

diffusion out of the soil layer. Losses are also highest near noon and lowest at night. It has been 

shown that the loss rate of chlordane applied to the surface of moist soil is proportional to the amount 

of remaining residue and inversely proportional to the square root of the daylight hours since 

application. In dry soil, the organic vapors are much more strongly adsorbed with a resulting decrease 

in volatilization (Glotfelty and Schomburg 1989; Nash 1983a). Incorporation of chlordane into the 

soil reduces volatilization because of dilution and because volatilization depends on slow diffusion and 

convective flow processes. It is estimated that 4.0 cm of sandy soil or 3.9 cm of clayey soil is 

sufficient to restrict chlordane volatilization losses to <0.7% of the mass incorporated in the soil (Jury 

et al. 1990). Volatilization in some cases will continue for many years, as evidenced by the detection 
CHLORDANE 139 

5. POTENTIAL FOR HUMAN EXPOSURE 

of indoor air concentrations of chlordane 15 years after application (Livingston and Jones 1981): Crop 

cover does not markedly alter the rate of volatilization. In a 3-year field experiment in which 

chlordane was incorporated into the top 10 cm of sandy loam soil, the half-lives of chlordane in 

cropped and fallow plots were 93.2 and 154 days, respectively (Singh et al. 1991). Initially, the 

dissipation rate of cis-chlordane was slightly higher in the fallow plots. trans-Chlordane disappeared 

from the soil column after 210 days but then reappeared, suggesting that cis-chlordane was isomerizing 

from trans-chlordane. At the end of the experiment, the highest residues were in the top 10 cm of soil 

for both the cropped and fallow plots. However, the proportion of trans-chlordane was markedly 

lower in the cropped plots. Small amounts of chlordane can translocate from contaminated soil into 

plants, and there is some evidence that cis-chlordane can isomerize to trans-chlordane in plants (Singh 

et al. 1990; Singh et al. 1991). The amount taken up varies with species and stage of plant 

development. 

5.3.2 Transformation and Degradation 

5.3.2.1 Air 

Chlordane degrades in air by both photolysis and oxidation. trans-Chlordane photochemically 

degrades more readily than the cis isomer. This is indicated from the fact that the translcis ratio of 

chlordane transported long distances to the Norwegian Arctic changes from around 1 in the winter to 

0.5 in the summer (Oehme 1991). Many papers have been published that detail the photoproducts of 

chlordane (principally cis-chlordane) and mechanisms of photoproduct formation (Feroz et al. 1981; 

Ivie et al. 1972; Onuska and Comba 1975; Parlar and Korte 1973, 1977, 1979, 1980; Podowski et al. 

1979; Vollner et al. 1971). The most common photoproduct for cis-chlordane is the cage 

configuration that results from proton migration to the dichloroethylene moiety and carbon-carbon 

bond formation from one of the cyclopentane carbons. These photoreactions may also occur on leaf 

surfaces (Parlar 1978; Podowski et al. 1979); although the significance of this reaction to the overall 

removal of chlordane is not clear. Hydroxyl radical reactions of chlordane may be a significant 

removal mechanism in addition to photolysis. Atkinson (1987) developed a method to estimate the 

rate of reaction for hydroxyl radicais with organic vapors in the atmosphere. This method is based on 

the molecular structure of the organic compound, Using this method, an overall reaction rate of 

12.4x10-12

 cm3/molecule-sec was calculated. Assuming an average ambient hydroxyl radical 
CHLORDANE 140 

5. POTENTIAL FOR HUMAN EXPOSURE 

concentration of 5x105 molecules/cm3, averaged over a 24-hour time period (Atkinson 1985), this 

reaction rate yields an atmospheric half-life of 1.3 days for chlordane vapor. 

5.3.2.2 Water 

The degradation of chlordane in water has not been extensively studied. Eichelberger and Lichtenberg 

(1971) reported results of a river die-away test in which 85% of the original concentration of 

chlordane added to river water remained at the end of 2 weeks and persisted at that level for 8 weeks. 

Oloffs et al. (1972) found that 2.3-50.7% of the chlordane added to three river water samples 

remained in the aqueous phase after 12 weeks. It was concluded that at least some of the loss was 

from volatilization. Speidel et al. (1972) reported that chlordane adsorbed to microbially generated 

floe, and Tabak et al. (198la, 1981b) reported no degradation in 7 days using domestic waste water as 

a seed. These studies indicate that chlordane will not degrade rapidly in water and that transport is 

probably a faster removal mechanism than degradation. No information is available on whether 

chlordane undergoes photochemical reactions in the aquatic environment. 

5.3.2.3 Sediment and Soil 

Numerous papers have detailed the degradation of chlordane in soils. In general, chlordane appears to 

persist for potentially long periods of time (>20 years) in some soils, but much less in others. Beeman 

and Matsumura (1981), Bennett et al. (1974), Lichtenstein and Schulz (1959), Nash and Woolson 

(1967), Stewart and Chisholm (1971), and Stewart and Fox (1971) all reported finding chlordane 

residues in excess of 10% of the initially applied amount, 10 years or more after application. Other 

authors, (Harris and Sans 1976; Mullins et al. 1971; Tafuri et al. 1977; Wiese and Basson 1966) have 

reported faster removal from soils, but detectable concentrations appear to remain for at least 10 years 

for most application rates. At chlordane-treated subterranean sites on the University of MissouriColumbia campus, >70% of the originally applied chlordane could be accounted for 7 years after 

application (Puri et al. 1990). The fact that the chromatographic profiles of the technical chlordane 

components were almost identical to the original formulation indicates that little chemical or 

biochemical transformations had occurred. Sethunathan (1973) reported that chlordane does not 

degrade under anaerobic conditions in flooded soils. A 1989 study of organochlorine pesticide 

residues in 12 vegetable farms (four of each of three soil types), in the Fraser Valley of British 

Columbia, found a marked difference in residue levels with soil type. Farms with loamy sand soil had 
CHLORDANE 141 

5. POTENTIAL FOR HUMAN EXPOSURE 

no detectable chlordane, while one of those with silt loam soil contained mean concentrations of total 

chlordane of 170 ppb (dry wt), and three muck farms contained mean chlordane levels of 830 ppb 

(Szeto and Price 1991). Chlordane was used extensively on farms in this region as a soil insecticide 

on potatoes prior to the mid 1970s. These findings support the theory that organochlorine pesticides 

persist much longer in heavy soils with high organic content. The dissipation of chlordane from the 

loamy sand soil may be due to high initial volatilization. 

Only a few microorganisms have been isolated that are capable of degrading chlordane. Iyengar and 

Prabhakara Rao (1973) reported that a pure culture of Aspergillus niger degraded chlordane after 

adaptation, but Beeman and Matsumura (1981) found it to be inactive and speculated that the former 

authors had not considered other factors such as adsorption to glass and volatilization. Beeman and 

Matsumura (198l), however, reported that a Nocardiopsis sp. isolated from chlordane treated soil was 

capable of degrading chlordane to dichlorochlordene, oxychlordane, heptachlor, heptachlor 

endoepoxide, chlordane chlorohydrin, and 3-hydroxy-trans-chlordane. More recently, the lignindegrading white rot fungi, Phanerochaete chrysosporium, was found to extensively degrade chlordane 

(Kennedy et al. 1990). In inoculated soil cultures, 28% of the chlordane degraded and 14.9% 

mineralized to carbon dioxide in 60 days. In liquid cultures, 36.8% of the chlordane degraded and 

9.4% mineralized in 30 days. More mineralization occurs under low nutrient nitrogen concentrations 

(Aust 1990). The bulk of the literature indicates that chlordane does not degrade rapidly in soils and 

persists for over 20 years in some cases. 

5.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT 

5.4.1 Air 

Chlordane has been detected in outside urban and rural air, in indoor air, and in the breathing zone 

during personal monitoring (Table 5-2). In urban air, mean concentrations have ranged from below 

the detection limits (generally <0.1 ng/m3

) to 58 ng/m3, whereas rural and background concentrations 

are much lower (0.01-l ng/m3

). 

Chlordane concentrations in indoor air are much higher than in either urban or rural air. Indoor air 

levels in the living areas of treated homes often exceed 1 μg/m3 in the vapor phase. These data, 

however, may be skewed since most of the indoor monitoring was performed on homes that had been 



CHLORDANE 145 

5. POTENTIAL FOR HUMAN EXPOSURE 

sprayed with chlordane to control termites. Thus, the frequency of detection indicated in Table 5-2 

may not be representative of the general population. Dust vacuumed from homes of controls, farmers, 

and formulators had mean chlordane levels of 7.6, 5.8, and 23.1 ppm, respectively (Starr et al. 1974). 

Since chlordane is poured or injected into soil around the foundation of houses, the appearance of 

chlordane vapor in the living quarters of treated houses may indicate the intrusion of soil gas into the 

home through cracks, drains, or ducting in the basement or ground floor (Anderson and Hites 1989; 

Wallace 1991). Several studies indicate that concentrations of chlordane are much higher in the 

basement than in living areas of homes (Anderson and Hites 1989; Fenske and Sternbach 1987). 

Anderson and Hites (1989) found that the basement concentrations of chlordane are often a factor of 

3-10 higher than in living areas and 2-3 orders of magnitude higher than outdoors. Fenske and 

Stembach (1987) additionally reported that homes with crawl spaces and forced air heating systems 

had significantly higher levels of chlordane (11.2 ug/m3

 median) than homes with basements and 

forced air heat (0.33 ug/m3

), radiant heat (0.93 ug/m3), in-slab ducts and forced air heat (3.42 ug/m3). 

However, misapplication of chlordane by the pest control company (as determined by the New Jersey 

Department of Environmental Protection) had occurred in all of the homes with the 11.2 ug/m3

 median 

level and in 67% of the home with the 3.42 pg/m3 median level. When misapplication occurred, 

living area samples had median levels of 3.28 μg/m3 with 40% of samples exceeding 5 μg/m3, 

compared with <0.1 ug/m3

 and no samples exceeding 5 g/m3 in homes with no misapplication 

(Fenske and Stembach 1987). 

5.4.2 Water 

Chlordane has been detected in surface water, groundwater, suspended solids, sediments, bottom 

detritus, drinking water, sewage sludge, urban runoff, and in rain (Table 5-3). Recent concentrations 

of chlordane in ocean and lake water are <0.000l ng/L. Recent studies in the Great Lakes indicate 

that the levels of the cis isomer in water is roughly 2-3 times that of trans-chlordane (Biberhofer and 

Stevens 1987; Stevens and Neilson 1989). The presence of chlordane in drinking water appears to 

almost always result from an accidental event, such as back siphoning during dilution of a pesticide 

spray (CDC 1976), but concentrations can persist for months. 

Chlordane has been reported in groundwater at NPL sites and in New Jersey (HAZDAT 1992; Page 

1981), but it does not generally appear as a contaminant of groundwater. Groundwater monitoring 

data from 479 disposal site investigations detected chlordane in 23 samples at 10 sites, ranking it 80th 



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5. POTENTIAL FOR HUMAN EXPOSURE 

among the 208 RCRA Appendix IX organic chemicals investigated (Plumb 1991). According to the 

EPA database Pesticides in Groundwater, chlordane has been confirmed in groundwater only in 

Massachusetts as a result of normal agricultural use and only in Idaho from a point source (Ritter 

1990; Williams et al. 1988b). Based on average chlordane concentrations in EPA’s STORET database 

for 1978-1987, the west south central section of the United States had the highest concentrations of 

chlordane in groundwater and New England had the lowest (Phillips and Birchard 1991). The 

presence of chlordane in groundwater at Cape Cod golf courses is thought to be due to macropore 

flow of particle-bound pesticide or contamination during well construction (Cohen et al. 1990). 

Chlordane was used at these golf courses from the 1950s to 1970s. 

5.4.3 Sediment and Soil 

Chlordane has been detected in both rural and urban soils (Table 5-4) in concentrations from <1 ppb 

to 141 ppm. In general monitoring programs of rural and urban soils, chlordane was consistently 

found; however, detections generally mirrored use patterns and are, for the most part, from studies 

performed in the late 1960s to middle 1970s. Very few recent general soil monitoring data are 

available; these data show that chlordane is still present in soils, but insufficient detections are 

available to estimate any trends (see Table 5-4). A sampling of soil around New Orleans’ houses 

treated with chlordane showed that chlordane levels were variable. Mean residue levels sampled at 30 

houses varied from 22 to 2,540 ppm (Delaplane and La Fage 1990). 

Recent sediment concentrations of chlordane in Great Lakes harbors and a tributary of the Missouri 

River in Missouri range from 1.4 to 14 ppb and 1.5 to 310 ppb, respectively (Puri et al. 1990; 

Verbrugge et al. 1991). A Missouri study performed in the 1980s demonstrated that chlordane in 

sediment of Missouri streams were of recent origin and correlated with urban development (Puri et al. 

1990). Chlordane levels in sediment from predominately agricultural areas were approximately two 

orders of magnitude lower than in urban areas. Based on average chlordane concentrations in EPA’s 

STORET database for 1978-1987, the west north central section of the United States had the highest 

concentrations of chlordane in sediment, and New England had the lowest (Phillips and Birchard 1991) 


CHLORDANE 152 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.4.4 Other Environmental Media 

Chlordane has been detected in many other media. Table 5-5 summarizes the data available for food 

monitoring, Table 5-6 summarizes data for aquatic organisms, Table 5-7 summarizes data for 

terrestrial organisms, and Table 5-8 summarizes data for monitoring human samples. The data in these 

tables clearly show the widespread occurrence of chlordane throughout the United States. Based on 

average chlordane concentrations in EPA’s STORET database for 1978-1987, the west south central 

section of the United States had the highest concentrations of chlordane in fish tissue, and New 

England had the lowest (Phillips and Birchard 1991). 

Total chlordane concentrations in bluefish fillet are reduced an average 29% by trimming those 

portions of fillet with the highest concentrations of lipid, such as the skin, dorsal fat, and bellyflap 

(Sanders and Haynes 1988). Cooking did not significantly change the chlordane concentration in 

bluefish (Trotter et al. 1989). 

5.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE 

A major route of exposure to chlordane in the United States is from living in chlordane treated houses. 

Many of these houses are in the deep south and far southwest where termites are a significant 

problem, but moderate to heavy use of chlordane extended from Pennsylvania and the lower New 

England states south and west to the lower portion of Colorado and up to northern California. 

Chlordane vaporizes gradually in treated homes for over 10 years. It accumulates in residents’ bodies 

by inhalation of the vapor, by eating food that has adsorbed the vapor, or dermal contact with the 

chemical. Indoor air concentrations often exceed 1 μg/m3 (see Table 5-2) and persist for many years 

(Livingston and Jones 1981). A recent study of chlordane concentrations in 19 houses treated for 

subterranean termite control indicated that the chlordane concentration in the air of treated homes 

occurred during treatment and declined significantly after 24 hours (Kamble et al. 1992). While there 

was a slight reduction in chlordane concentration from the 24-hour levels 7 days posttreatment, these 

changes were not significant. Concentrations of chlordane remained essentially the same from 30 to 

180 days after treatment, and these concentrations were similar to pretreatment levels. The EPA 

(1987g) estimated that, up until 1988, 1.3-1.8 million people per year were exposed to cyclodiene 

termiticides, as occupants of newly treated structures. They further estimated that ≈30 million 

structures had been treated for termites with these chemicals resulting in the exposure of over 












CHLORDANE 165 

5. POTENTIAL FOR HUMAN EXPOSURE 

80 million people. Of these structures, ≈65% were treated with chlordane, or 19.5 million structures, 

resulting in the exposure of 52 million people. The exact concentrations they were exposed to are 

difficult to estimate from the available data. A Japanese study showed that the concentration of 

chlordane and oxychlordane in the milk fat of lactating women living in chlordane-treated houses was 

13.8 and 33.6 ppb, respectively, versus 3.6 and 19.3 ppb for unexposed controls (Taguchi and 

Yakushiji 1988). Chlordane and oxychlordane levels in milk increased with years since treatment. 

A major study of general population exposure to pesticides, including chlordane, was included in the 

Nonoccupational Pesticide Exposure Study (NOPES) (EPA 1990b). This study applied probabilistic 

population sampling techniques, indoor, outdoor, and personal breathing zone air monitoring, and 

human activity pattern data for multiple routes of exposure to assess total human exposure. These 

techniques were applied to the communities of Jacksonville, Florida, and Springfield/Chicopee, 

Massachusetts, over three and two seasons, respectively. For Jacksonville, the personal breathing zone 

air concentration was relatively stable, and the yearly means for 1986-1988 ranged from 191 to 

212 ng/m3

 over all three seasons, with 50-93% of samples containing detectable levels of chlordane. 

The corresponding results for SpringfieWChicopee was 36 ng/m3 in winter and 253 ng/m3

 in the 

spring; 50-87% of the samples had detectable levels of chlordane. Several observations were made 

from the study. Indoor levels of chlordane are highest in summer and lowest in winter. They were 

higher in older housing units and households with reported termiticide use. For chlordane, mean air 

exposure in homes with detectable levels of chlordane was always much higher (~25 times) than 

exposure from food. Routine sampling of the public water supplies prior to NOPES and tap water in 

Jacksonville, Florida, and Springfield/Chicopee, Massachusetts, revealed no detectable levels of 

chlordane in drinking water. 

In addition to living in chlordane-treated structures, ingestion of contaminated food is another major 

route of exposure. Duggan et al. (1983) and Gartrell et al. (1985a, 1985b, 1985c, 1985d, 1986a, 

1986b) have estimated yearly dietary intake of chlordane since 1965 for 16- to 19-year-old males. In 

more recent years, toddlers and infants have been included in these estimates (Gunderson 1988). FDA 

(1989a, 1990, 1991) has estimated dietary chlordane intake for various age/sex groups for 1982-1984, 

1989, 1990, and 1991. Their results are listed in Table 5-9. The data show a relatively steady intake 

over the years from 1977 to 1982, indicating that chlordane residues had not decreased significantly in 

agricultural soils (if that is where the chlordane originates). In addition, infants and toddlers will 

generally have higher intakes of chlordane than adults because of the high fat content of the foods they 

CHLORDANE 167 

5. POTENTIAL FOR HUMAN EXPOSURE 

eat (Table 5-9). The results for the 1991 FDA Total Diet Study are 0.0013 μg/kg/day for infants and 

0.0005-0.0015 μg/kg/day for teenagers and adults (FDA 1991). The total daily dietary intake of 

chlordane per unit body weight, according to results of the 1982-1984 FDA’s Total Diet Study is 

0.0051 μg/kg/day for infants, 0.0065 μg/kg/day for toddlers, and 0.002-0.0027 μg/kg/day for teenagers 

and adults (Gunderson 1988). The Total Diet Study analyzes foods prepared for consumption. After 

1982, 234 foods were selected to represent 5,000 different food items identified in dietary surveys. 

Dermal exposures may result from children or adults coming into contact with contaminated soils or 

house dust near treated houses, lawns, or gardens. Dermal exposures cannot be quantified with the 

available information. 

Previous exposure to chlordane is often gauged by the concentration of chlordane compounds (usually 

oxychlordane) in human adipose tissue. According to EPA’s National Human Monitoring Program 

and other broad based U.S. surveys, the geometric mean concentration of oxychlordane in human 

adipose tissue has ranged from 90 to 120 ppb between 1971 and 1983 with no clear temporal trend 

(Adeshina and Todd 1990; Kutz et al. 1991). North Texas and Canadian studies show increasing 

oxychlordane levels with age in selected age groups, but no difference in levels according to sex 

(Adeshina and Todd 1990; Mes et al. 1990). It is not clear whether higher oxychlordane levels in 

older age groups are due primarily to longer exposure or decreased use of chlordane. 

Workers may be exposed to chlordane during its manufacture, formulation, shipping, storage, 

application, and disposal. The National Occupational Exposure Survey (NOES) conducted by NIOSH 

from 1981 to 1983 estimated that 3,732 workers were potentially exposed to chlordane in the 

workplace in the United States (NIOSH 1989a). The NOES was based on field surveys of 4,490 

businesses employing nearly 1.8 million workers and was designed as a nationwide survey based on a 

statistical sample of virtually all workplace environments in the United States in which eight or more 

persons are employed in all standard industrial codes except mining or agriculture. 

Workplace monitoring data are available from two studies conducted simultaneously by Velsicol 

(Cahill et al. 1979) and the State of California (Maddy et al. 1979). In these studies, patches were 

attached to the inside and outside of the applicators’ coveralls, and breathing zone air was monitored 

while chlordane was applied to six houses (three with a crawl space and three on a concrete slab). 

Cahill et al. (1979) reported that 0.015-7.96 mg/cm2

 (median 0.175 mg/cm2, 24 samples) was found on 
CHLORDANE 168 

5. POTENTIAL FOR HUMAN EXPOSURE 

the 100 cm2 denim patches attached just above the knees and elbows of the applicators coveralls, 

whereas Maddy et al. (1979) found 0.005-2.9 mg/cm2

 (median 0.12 mg/cm2, 23 samples) for 100 cm2 

duck cotton cloth (similar to denim) patches attached below the knees and elbows. Concentrations 

inside the coveralls were determined by Cahill et al. (1979) by attaching a denim patch to the work 

pants (worn under the coveralls) at the knee and to the inside of the coveralls at the elbow (but not 

overlapping the outside elbow patch). Maddy et al. (1979) determined inside concentrations by 

attaching eight layers of cotton cheese cloth backed by aluminum foil to the inner surface of the duck 

cloth patches attached below the knees and elbows of the applicators. Cahill et al. (1979) found 

0.0053-0.127 mg/cm2 (median 0.024 mg/cm2, 24 samples) on the inside patches, whereas Maddy et al. 

(1979) found 0.009-l .9 mg/cm2 (median 0.082 mg/cm2, 23 samples) on the cheese cloth backing. 

Air impingers were worn by the applicators both on the lapel and on the chin inside the respirator. 

Air concentrations were reported for both inside and outside the respirator by Maddy et al. (1979), but 

only one value was reported by Cahill et al. (1979). Cahill et al. (1979) reported finding chlordane in 

all four samples analyzed (0.16-14.2 mg/m3

), whereas Maddy et al. (1979) found 0.007, 0.008, and 

0.110 mg/m3

 in three of five samples taken outside the respirator and 0.011 and 0.27 mg/m3 in two of 

six samples taken inside the respirator. No detection limit was reported by Maddy et al. (1979); 

therefore, no information is available concerning the samples with concentrations too low to detect. 

Kamble et al. (1992) studied the exposure of 29 commercial applicators exposed to Termide EC 

(technical chlordane 39.22% plus heptachlor 19.6%), diluted to 0.75% (active ingredient) during 

subterranean termite treatment of homes. Dermal exposure was monitored using 14 gauze pads for 

each applicator attached to exterior and interior parts of clothing for an average duration of 

138 minutes. Exposure to hands was monitored by hand rinses immediately after application. 

Respiratory exposure was assessed with personnel-type air samplers (see Table 5-2). Total dermal 

exposure to applicators to chlordane was 2.5 μg/kg/hour. The most exposed body regions in 

descending order were: hands, forearms, head, lower legs, thighs, back trunk, front trunk, upper arms, 

and back neck. Approximately 25% of the chlordane on the exterior surface of clothing was likely to 

penetrate through the fabric. Respiratory exposure was 0.04 μg/kg/hour. 

Elia et al. (1983) reported that chlordane was detected in the water and air of a sewage treatment plant 

near Memphis, Tennessee, and suggested that occupational exposures to semi-volatile compounds such 

as chlordane could occur at these plants. No chlordane data, however, were presented. Former 
CHLORDANE 169 

5. POTENTIAL FOR HUMAN EXPOSURE 

occupational exposures, in addition to termite control, include chlordane manufacturing, formulation, 

distribution, and agricultural and lawn care pesticide application. Since chlordane is no longer used 

commercially in the United States (EPA 1988c), many of these occupational exposures no longer exist. 

No data are available that would allow the estimation of workplace levels during manufacture and use. 

5.6 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES 

A segment of the general population with potentially high exposure to chlordane includes those people 

living in structures that have been treated with chlordane for termite control or people digging in soil 

around these houses. The majority of these structures are located in the deep south and far southwest 

where termites are a significant problem, but moderate to heavy use of chlordane extended from 

Pennsylvania and the lower New England states south and west to the lower portion of Colorado and 

up to northern California. The available data indicate that these exposures will be much greater than 

exposures from other sources of chlordane. Persons involved in the manufacture of chlordane and 

persons involved in the application of chlordane before its use was banned on April 14, 1988 may 

have been exposed to relatively high levels. Similarly, lawn care workers and farmers that handled 

chlordane before above-ground uses were banned may have been exposed to high levels of the 

chemical. Populations living near waste disposal sites containing chlordane may have been exposed to 

elevated levels of chlordane. 

5.7 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 chlordane is available. Where adequate information is 

not available, ATSDR, in conjunction with the 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 chlordane. 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NVP, 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 
CHLORDANE 170 

5. POTENTIAL FOR HUMAN EXPOSURE 

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. 

5.7.1 Identification of Data Needs 

Physical and Chemical Properties. The physical and chemical properties of chlordane listed in 

Table 3-2 are not complete. These properties are difficult to specify since the technical product is a 

mixture of over 140 compounds. The composition of technical chlordane varies according to 

conditions during its manufacture. In addition, properties of a mixture differ from the properties of the 

components. Even minor components can affect physical and chemical properties. Some of the 

properties reported in Table 3-2 are those of particular components such as cis- and trans-chlordane, 

The value for log Kow listed in Table 3-2 is a particularly crude estimate for technical chlordane since 

this value was estimated for the chlordane structure. In addition the values for water solubility of 

chlordane vary widely. This is probably due to differences in composition of the chlordane studied. 

Suntio et al. (1988) and Weil et al. (1974) did not indicate whether the chlordane used in their studies 

was technical grade or a mixture of chlordane isomers. Despite the limitations discussed above, the 

physical chemical properties available for chlordane are adequate to estimate its partitioning in the 

environment. More significantly, there are numerous monitoring studies that have been performed 

over several decades that give us this information concerning chlordane’s fate in the environment. 

Production, Import/Export, Use, Release, and Disposal. Although the use of chlordane in the 

United States has been banned since April 1988, chlordane is still manufactured for export. Since 

chlordane is extremely persistent in the environment, knowledge of the former use pattern for this 

compound is useful in making estimations concerning potential for human exposure and sources of 

release. Environmental burdens of chlordane can be roughly estimated by relying on production and 

use data and by using a few basic assumptions. Production methods for chlordane are documented in 

the literature, however recent production volumes are not available. A breakdown of the former uses 

of chlordane and its use pattern is available, which indicates that chlordane was widely used in the 

home, on food and nonfood crops, and on lawns and gardens. Disposal information is useful in 

determining environmental burden and potential concentrations where environmental exposures may 

be high. This type of information may be obtained by polling the manufacturer or other commercial 

organizations to determine methods of chlordane disposal. For example, asking exterminators how 

they disposed of contaminated materials or unused product may provide disposal information for much 
CHLORDANE 171 

5. POTENTIAL FOR HUMAN EXPOSURE 

of the chlordane not directly applied to soils or dwellings. Current disposal practices are not known. 

Chlordane has been designated as a hazardous waste, and regulations guide the disposal of such waste. 

Chlordane is also regulated in effluent by provisions of the Clean Water Act. 

According to the Emergency Planning and Community Right-to-Know Act of 1986, 42 U.S.C. Section 

11023, industries are required to submit chemical release and off-site transfer information to the EPA. 

The Toxics Release Inventory (TRI), which contains this information for 1988, became available in 

May of 1990. This database will be updated yearly and should provide a list of industrial production 

facilities and emissions. 

Environmental Fate. Data are available (Atallah et al. 1979; Atlas and Giam 1988; Beeman and 

Matsumura 1981; Bennett et al. 1974; Bidelman et al. 1987; Bidleman and Foreman 1987; Bidleman 

et al. 1986; Cotham and Bidleman 1991; Foreman and Bidleman 1987; Glotfelty and Schomburg 

1989; Glotfelty et al. 1984; Gustafson 1989; Jury et al. 1987a; Lau et al. 1989; Oliver and Niimi 1985; 

Oloffs et al. 1972, 1973; Pacynba and Oehme 1988; Singh et al. 1991; Zaroogian et al. 1985) to 

characterize the partitioning and transport of chlordane. We also know from monitoring studies that 

chlordane is very persistent in soil, lasting over 20 years in some soils (Beeman and Matsumura 1981; 

Bennett et al. 1974; Harris and Sans 1976; Lichtenstein and Schulz 1959; Mullins et al. 1971; Nash 

and Woolson 1967; Stewart and Chisholm 1971; Stewart and Fox 1971; Szeto and Price 1991; Tafuri 

et al. 1977; Wiese and Basson 1966). However, chlordane’s degradation products in soil have not 

been reported. However, more information would be useful on the transformation of chlordane in the 

environment. There are data needs regarding biodegradation and photolysis of chlordane in water 

systems and oxidation of this compound in air. Natural water grab sample biodegradation studies 

carried out under both aerobic and anaerobic conditions would be useful in establishing the 

biodegradation half-life of chlordane. A number of studies have been carried out that show chlordane 

is photolyzed in air; however, there is a lack of data pertaining to photolysis of chlordane that is 

adsorbed to particulate matter in air or in water and its significance for the removal of chlordane from 

these media. A photolysis study carried out under conditions simulating those found in the 

environment would be useful in establishing the significance of this reaction in air and natural waters. 

One of the dominant removal mechanisms for vapor phase chlordane in air is expected to be reaction 

with photochemically generated hydroxyl radicals; however, no experimental data are available 

concerning the kinetics of this reaction, the reaction pathway, or the products of these types of 
CHLORDANE 172 

5. POTENTIAL FOR HUMAN EXPOSURE 

reactions. Photolysis, photooxidation, and biodegradation of particulate-bound chlordane is unknown. 

These types of data would be useful in understanding the fate of this compound in the environment. 

Bioavailability. Data are available that correlate length of exposure to atmospheric chlordane and 

levels of chlordane and/or metabolites in human blood and milk (Kawano and Tatsukawa 1982; Saito 

et al. 1986; Taguchi and Yakushiji 1988; Takamiya 1987). Similar data are not available for human 

exposure to chlordane in water or soil. A deficiency in the inhalation studies is that exposure 

concentrations have not been quantified. Therefore it is not possible, based on current knowledge, to 

correlate levels of chlordane and/or metabolites in human biosamples with specific concentrations in 

air, soil, or water. Studies in animals may provide valuable information regarding bioavailability and 

bioaccumulation of chlordane residues from air, water, and soil. 

Food Chain Bioaccumulation. Chlordane has been found to bioconcentrate in marine and 

freshwater fish and shellfish, and biomagnify in animals that prey upon these fish. Available data 

indicate that organisms that have bioaccumulated chlordane are geographically distributed across the 

United States. This type of information is useful in determining how levels in the environment affect 

the food chain and potentially impact on human exposure levels. 

Exposure Levels in Environmental Media. In general, the monitoring database for chlordane is 

not very broadly based or recent. Data for soils are especially out of date. Chlordane levels in soil 

and sediment are particularly important, as these are the repositories for chlordane, and broadly-based 

monitoring data in these media are the best way of assessing environmental trends. 

Reliable monitoring data for the levels of chlordane in contaminated media at hazardous waste sites 

are needed so that the information obtained on levels of chlordane in the environment can be used in 

combination with the known body burden of chlordane to assess the potential risk of adverse health 

effects in populations living in the vicinity of hazardous waste sites. 

Exposure Levels in Humans. Estimates have been made for the human intake of chlordane from 

food, air, and water. Chlordane has been measured in adipose tissue, blood, serum, sebum, and 

seminal fluid. Only data in adipose tissue is of recent origin. 

This information is necessary for assessing the need to conduct health studies on these populations. 
CHLORDANE 173 

5. POTENTIAL FOR HUMAN EXPOSURE 

Exposure Registries. No exposure registries for chlordane were located. This substance is not 

currently one of the compounds for which a subregistry 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. 

5.7.2 On-going Studies 

ATSDR has funded a grant to the Missouri Department of Health to determine exposure levels from 

consuming fish from selected Missouri rivers and to better quantify the risk of eating contaminated 

fish (ATSDR 1992). This study will compare the serum levels of chlordane and other organochlorine 

compounds in different groups of people. Results are expected in FY 1992. A study on the transport 

and degradation of organic substances in streams is investigating whether differences in the 

concentrations of chlordane and nonachlor can be used to distinguish whether these compounds 

resulted Born resuspension of bottom sediments or from surface runoff (Rathbun 1992). Work is 

continuing on the degradation of chlordane by white rot fungi and its enzymes (Aust 1992). Work is 

starting on a project that is designed to build a database of chlordane and other contaminant 

concentrations in the most contaminated tributaries emptying into Lake Michigan in northeast Indiana 

and using this information will be used to assess contaminant mobility and loading into Lake Michigan 

(FEDRIP 1993). 

CHLORDANE 175 

6. ANALYTICAL METHODS
 

The purpose of this chapter is to describe the analytical methods that are available for detecting, and/or 

measuring, and/or monitoring chlordane, its metabolites, and other biomarkers of exposure and effect 

to chlordane. 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 may be 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 may be included that modify previously used methods to 

obtain lower detection limits, and/or to improve accuracy and precision. 

6.1 BIOLOGICAL MATERIALS 

Since technical chlordane is a mixture of organochlorine compounds and since many of these 

chemicals are metabolized in the body, analytical methods for chlordane are designed to quantitate 

major components of technical chlordane and their metabolites. The methods commonly used for the 

quantification of chlordane compounds in human blood, adipose tissue, and milk are given in 

Table 6- 1. Generally, these methods employ procedures such as digestion, extractions with solvents, 

or column chromatography to reduce interferences from lipids and other pollutants that may be present 

in the sample. Recently, supercritical carbon dioxide as the extraction medium has received some 

attention (Lopez-Avila et al. 1990a; Nam et al. 1989, 1990). Methods using supercritical fluid 

extraction (SCF) have good recoveries and avoid the use of potentially polluting solvents. Gas 

chromatography with electron capture detection (GC/ECD) is the method of choice for quantification, 

because of its high sensitivity for chlordane compounds and its lack of sensitivity for the large 

excesses of lipids in the sample matrix (Young et al. 1984). The use of capillary columns is likely to 

show better resolution of the components, although high resolution gas chromatography columns 

(HRGC) have rarely been used for biological samples for chlordane. Recently, techniques have been 

developed in which enantomers (optical isomers) of technical chordane components can be determined. 

This has been accomplished by using chiral high-resolution GC columns containing ß-cyclodextrin 

derivatives (Buser et al. 1992). Using such techniques, enantiospecific biological processes affecting 



CHLORDANE 179 

6. ANALYTICAL METHODS 

biological behavior and biodegradation may be better understood and readily differentiated from 

nonenantiospecific abiotic processes. 

6.2 ENVIRONMENTAL SAMPLES 

The analytical methods used for the quantification of chlordane in environmental samples are given in 

Table 6-2. The collection efficiencies for chlordane from air by five solid sorbents (C-18, Carbowax 

GC, Chromosorb 102, polyurethane foam, and Tenax GC) have been compared, and both Chromosorb 

102 and polyurethane foam are preferable. Though Chromosorb 102 is more efficient than 

polyurethane foam at low sampling rates, it has the disadvantage of giving more interference during 

gas chromatography analysis than polyurethane foam (Roper and Wright 1984). A more recent study 

compared the trapping efficiencies of chlordane on four absorbents used by government and 

laboratories to collect airborne pesticides, chromosorb 102, ORB0 44, polyurethane foam (PUF), and 

Tenax GC (Leidy and Weight 1991). The efficiencies of all absorbents were comparable and ranged 

from 87-92%. Environmental samples are prepared and interferences removed by a variety of 

methods such as solvent extraction, column chromatography, gel permeation chromatography (GPC), 

sulfuric acid treatment, and activated copper treatment (Alford-Stevens et al. 1988; EPA 1986a, 

Hopper 1982; Young et al. 1984). The different methods for extraction and cleanup of chlordane in 

soil and sediment samples have been compared; it was concluded that mechanical shaking with Florisil 

clean up provided the best precision, but sonication with gel permeation chromatography (GPC) was 

less time consuming and may be applicable to a wide variety of pollutants (Alford-Stevens et al. 

1988). Treatment with sulfuric acid was found to reduce interferences from polychlorinated biphenyls 

and p,p-DDT in waste water samples without altering the concentration of chlordane; sample treatment 

with ethanolic potassium hydroxide may partially destroy chlordane (Hemandez et al. 1987). 

The preferred method for the quantification of chlordane in environmental samples is gas 

chromatography (GC) with electron capture detector (ECD) and the subsequent confirmation by mass 

spectrometry (MS). The ECD discriminates large excesses of lipids from the matrix, that otherwise 

interfere with MS (Sperling et al. 1985). Interferences by phthalate esters can pose a serious problem 

in chlordane determinations using ECD. These can be avoided by using a microcoulometric or 

electrolytic conductivity detector (EPA 1982a). Otherwise, this interference is minimized by avoiding 

contact with plastics and by scrupulous cleanup of glassware and reagents. The use of capillary 

columns will provide better separation of components (Sperling et al. 1985). 




CHLORDANE 184 

6. ANALYTICAL METHODS 

An enzyme immunoassay has been developed for screening soil samples for chlordane (U.S. EPA 

1988d). While the method is potentially inaccurate, due to cross reactivity of the enzyme with other 

cyclodiene pesticides, it is rapid, simple, sensitive, and inexpensive and is therefore useful for 

screening purposes and field applications. 

6.3 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 chlordane is available. Where adequate information is 

not available, ATSDR, in conjunction with the 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 chlordane. 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean 

that all data needs discussed in this section must be filled. In the future, the identified data needs will 

be evaluated and prioritized, and a substance-specific research agenda will be proposed. 

6.3.1 Identification of Data Needs 

Methods for Determining Biomarkers of Exposure and Effect. Levels of various components 

of technical chlordane (principally cis- and trans-chlordane, cis- and trans-nonachlor) and its 

metabolites (principally oxychlordane) in body tissue and fluids are elevated in individuals exposed to 

chlordane. While analytical methods are available (Aldrich and Holmes 1969; Barquet et al. 1981; 

EPA 1977; Griffith and Blanke 1974; LeBel and Williams 1986; Mussalo-Rauhamaa 1991; Saito et al. 

1985; Tojo et al. 1986; Wariishi et al. 1986) for the quantification of chlordane compounds and their 

metabolites in biological matrices, and these methods have good sensitivity and specificity, there are 

no data correlating these levels with environmental chlordane concentrations to which a person was 

exposed. 

There are no biomarkers of effect for chlordane. 
CHLORDANE 185 

6. ANALYTICAL METHODS 

Methods for Determining Parent Compounds and Degradation Products in 

Environmental Media. The levels of chlordane in different environmental media can be used to 

indicate exposure of humans to mixture compounds through the inhalation of air, ingestion of drinking 

water and foods, and exposure to soils containing chlordane. If a correlation with human tissue or 

body fluid levels is available, the intake levels from different environmental sources can be used to 

estimate the body burden of the chemical in humans. Although the products of biotic and abiotic 

processes of chlordane in the environment are known, few systematic studies are available in which 

the concentrations of its reaction products were measured in the environment. In instances where the 

product(s) of an environmental reaction is (are) more toxic than the parent compound, it is important 

that the level of the degradation products in the environment be known. Analytical methods for the 

determination of chlordane compounds and their degradation products in air, water, soil, sediment, and 

food are available, and these methods have good sensitivity and specificity. The methods for 

determining degradation products of chlordane compounds are similar to those for the parent 

compounds. 

6.3.2 On-going Studies 

No significant on-going studies are in progress for the development of new analytical methodologies 

for analysis of this compound in environmental or biological samples. 

CHLORDANE 187 

7. REGULATIONS AND ADVISORIES
 

IARC (1987) determined that the available epidemiological data on chlordane were inadequate to 

evaluate human cancer risk, and that there was limited evidence from experimental animals of its 

carcinogenicity. 

WHO (1984) classified technical chlordane as moderately hazardous, 

The WHO/FAO (1978) has issued practical advice in a Data Sheet on Pesticides, No. 36 (Chlordane), 

dealing with labeling, safe-handling, transport, storage, disposal, decontamination, training and 

medical supervision of workers, first aid, and medical treatment. 

On March 6, 1978, registrations for all uses of chlordane on food crops were canceled (EPA 1978). 

Exempt were (1) certain registrations for uses on nonfood plants, which were instead phased out over 

the next 5 years, and (2) the continued use through subsurface ground insertion for termite control. In 

1987, a negotiated agreement covering the termiticide products of the primary chlordane manufacturer 

voluntarily canceled all but certain unaffected uses and imposed limitations on the continued sale, 

distribution, and use of the canceled products (EPA 1987b). On April 14, 1988, the EPA moved to 

cancel the registrations of other producers’ termiticide products containing chlordane and to forbid the 

sale or commercial use of those products (EPA 1988c). These actions did not address the use of any 

remaining containers of products that had been canceled earlier, such as those that were involved in 

the March 6, 1978, decision. 

Chlordane is regulated by the Clean Water Act Effluent Guidelines for the following industrial point 

sources: electroplating, steam electric production, asbestos production, timber products processing, 

metal finishing, paving and roofing, paint formulating, ink formulating, gum and wood processing, 

pesticide production, and carbon black production (EPA 1988a). For many of these industrial sources 

(asbestos production, timber products processing, paving and roofing, paint formulating, ink 

formulating, gum and wood processing, and carbon black production) the discharge limits have been 

set at zero. 
CHLORDANE 188 

7. REGULATIONS AND ADVISORIES 

An MRL for intermediate-duration inhalation exposure of 0.0002 mg/m3 was derived based on the 

NOAEL of 0.1 mg/m3 for hepatic effects in rats in the 90-day intermittent exposure study by 

Khasawinah et al. (1989) and Velsicol Chemical Co. (1984). The LOAEL was 1.0 mg/m3, at which 

rats had hepatocellular hypertrophy and increased cytochrome P-450 content. 

An MRL for chronic-duration inhalation exposure of 0.00002 mg/m3

 was also derived from the 90-day 

study by Khasawinah et al. (1989). An additional uncertainty factor of 10 was used to extrapolate 

from intermediate- to chronic-duration. 

An MRL for acute-duration oral exposure of 0.001 mg/kg/day was derived based on a LOAEL of 

1 mg/kg/day for developmental effects (depressed conditioned avoidance response acquisition, 

increased exploratory activity in open field test, and increased seizure threshold) in the offspring of 

mice exposed to chlordane during the last trimester (Al-Hachim and Al-Baker 1973). 

An MRL for intermediate-duration oral exposure of 0.0006 mg/kg/day was derived based on a 

NOAEL of 0.055 mg/kg/day for hepatic effects in female rats exposed to chlordane in the diet for 

30 months. Hepatocellular hypertrophy was observed in the rats exposed to 0.273 mg/kg/day 

(Khasawinah and Grutsch 1989a; Velsicol Chemical Co. 1983a). 

An MRL for chronic-duration oral exposure of 0.0006 mg/kg/day was derived based on a NOAEL of 

0.055 mg/kg/day for hepatic effects in rats in a 30-month dietary study by Khasawinah and Grutsch 

(1989a) and Velsicol Chemical Co. (1983a). The LOAEL was 0.273 mg/kg/day at which 

hepatocellular hypertrophy was found in female rats. 

The EPA (IRIS 1992) derived an oral RfD of 0.00006 mg/kg/day from the rat NOAEL for regional 

liver hypertrophy of 0.06 mg/kg/day in the 30-month feeding study by Khasawinah and Grutsch 

(1989a) and Velsicol Chemical Co. (1983a). 

National and state regulations and guidelines applicable to chlordane are summarized in Table 7-l. 




___________________ 

CHLORDANE 193 

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CHLORDANE 194 

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CHLORDANE 197 

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CHLORDANE 224 

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CHLORDANE 226 

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CHLORDANE 227 

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CHLORDANE 230 

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CHLORDANE 231 

9. GLOSSARY
 

Acute Exposure -Exposure to a chemical for a duration of 14 days or less, as specified in the
 

Toxicological Profiles.
 

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 a 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.
 

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.
 

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.
 

Ceiling Value (CL) - 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.
 

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.
 

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 occurred. The terms, as used here, include malformations and variations,
 

altered growth, and in utero death.
 

EPA Health Advisory - An estimate of acceptable drinkiig 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.
 

Immediately Dangerous to Life or Health (IDLH) - The maximum environmental concentration of
 

a contaminant from which one could escape within 30 min without any escape-impairing symptoms or
 

irreversible health effects.
 
CHLORDANE 232 

9. GLOSSARY 

Intermediate Exposure - Exposure to a chemical for a duration of 15-364 days, as specified in the 

Toxicological Profiles. 

Immunologic Toxicity - The occurrence of adverse effects on the immune system that may result 

from exposure to environmental agents such as chemicals. 

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 which 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 is expected to have caused death in humans or animals. 

Lethal Dose(50) (LD50) - The dose of a chemical which 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 dose 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. 

Malformations - Permanent structural changes that may adversely affect survival, development, or 

function. 

Minimal Risk Level - An estimate of daily human exposure to a dose of a chemical that is likely to 

be without an appreciable risk of adverse noncancerous effects over a specified duration of exposure. 

Mutagen -A substance that causes mutations. A mutation is a change in the genetic material in a 

body cell. Mutations can lead to birth defects, miscarriages, or cancer. 

Neurotoxicity -The occurrence of adverse effects on the nervous system following exposure to 

chemical. 

No-Observed-Adverse-Effect Level (NOAEL) -The dose of 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. 
CHLORDANE 233 

9. GLOSSARY 

Permissible Exposure Limit (PEL) - An allowable exposure level in workplace air averaged over 

an 8-hour shift. 

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). 

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 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 CERCLA. Reportable quantities are (1) 1 pound or greater or (2) for selected substances, an 

amount established by regulation either under CERCLA or under Sect. 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. 

Short-Term Exposure Limit (STEL) -The maximum concentration to which workers can be 

exposed for up to 15 min continually. No more than four excursions are allowed per day, and there 

must be at least 60 min between exposure periods. The daily TLV-TWA may not be exceeded. 

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) - A concentration of a substance to which most workers can be 

exposed without adverse effect. The TLV may be expressed as a TWA, as a STEL, or as a CL. 

Time-Weighted Average (TWA) - An allowable exposure concentration averaged over a normal 8­

hour workday or 40-hour workweek. 

Toxic Dose (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. 
CHLORDANE 234 

9. GLOSSARY 

Uncertainty Factor (UF) - A factor used in operationally deriving the RfD 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 LOAEL data rather than NOAEL data. Usually each of these factors is set equal 

to 10. 
CHLORDANE A-1 

APPENDIX A 

USER’S GUIDE 

Chapter 1 

Public Health Statement 

This chapter of the profile is a health effects summary written in nontechnical language. Its intended 

audience is the general public especially people living in the vicinity of a hazardous waste site or 

substance 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 substance. 

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 

Tables and Figures for Levels of Significant Exposure (LSE) 

Tables (2-1, 2-2, and 2-3) and figures (2-l and 2-2) are used to summarize health effects by duration 

of exposure and end point and to illustrate graphically levels of exposure associated with those effects. 

All entries in these tables and figures represent studies that provide reliable, quantitative estimates of 

No-Observed-Adverse-Effect Levels (NOAELs), Lowest-Observed-Adverse-Effect Levels (LOAELs) 

for Less Serious and Serious health effects, or Cancer Effect Levels (CELs). In addition, these tables 

and figures illustrate differences in response by species, Minimal Risk Levels (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. The LSE tables and figures can be used 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. 

The legends presented below demonstrate the application of these tables and figures. A representative 

example of LSE Table 2-l and Figure 2-1 are shown The numbers in the left colwnn of the legends 

correspond to the numbers in the example table and figure. 

LEGEND 

See LSE Table 2-1 

(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. 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 

dennal (LSE Table 2-1, 2-2, and 2-3, respectively). LSE figures are limited to the inhalation 

(LSE Figure 2-l) and oral (LSE Figure 2-2) routes. 

(2). Exposure Duration Three exposure periods: acute (14 days or less); intermediate (15 to 

364 days); and chronic (365 days or more) are presented within each route of exposure. In this 

example, an inhalation study of intermediate duration exposure is reported. 
 

CHLORDANE A-2 

APPENDIX A 

(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. 

(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 define a NOAEL and a Less Serious LOAEL 

(also see the two “I 8r” data points in Figure 2-l). 

(5). Species The test species, whether animal or human, are identified in this column. Species 

(6). Exposure Frequency/Duration The duration of the study and the weekly and daily exposure 

regimen 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 [substance x] via 

inhalation for 13 weeks, 5 days per week, for 6 hours per day. 

(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 in this study. 

(8). NOAEL A No-Observed-Adverse-Effect Level (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”). 

(9). LOAEL A Lowest-Observed-Adverse-Effect Level (LOAEL) is the lowest exposure level 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 “Less Serious” respiratory effect reported in key number 18 (hyperplasia) 

occurred at a LOAEL of 10 ppm. 

(10). Reference The complete reference citation is given in Chapter 8 of the profile. 

(11). CEL A Cancer Effect Level (CEL) is the lowest exposure level associated with the onset of 

carcinogenesis in experimental or epidemiological studies. CELs are always considered serious 

effects. The LSE tables and figures do not contain NOAELs for cancer, but the text may report 

doses which did not cause a measurable increase in cancer. 

(12) Footnotes Explanations of abbreviations or reference notes for data in the LSE tables are found 

in the footnotes. Footnote “b” indicates the NOAEL of 3 ppm in key number 18 was used to 

derive an MRL of 0.005 ppm. 

LEGEND See LSE Figure 2-1 

LSE figures graphically illustrate the data presented in the corresponding LSE tables. Figures help the 

reader quickly compare health effects according to exposure levels for particular exposure duration. 


CHLORDANE	 A-5 

APPENDIX A 

(13).	 Exposure Duration The same exposure periods appear as in the LSE table. In this example, 

health effects observed within the intermediate and chronic exposure periods are illustrated. 

(14).	 Health Effect These are the categories of health effects for which reliable quantitative data 

exist. The same health effects appear in the LSE table. 

(15).	 Levels of Exposure Exposure levels for each health effect in the LSE tables are graphically 

displayed in the LSE figures. Exposure levels are reported 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, 18r NOAEL is the critical end point for which an intermediate 

inhalation exposure MRL is based. As you can see from the LSE figure key, the 

open-circle symbol indicates a NOAEL for the test species (rat). 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 38r is one of three studies for which Cancer Effect Levels (CELs) were 

derived. The diamond symbol refers to a CEL for the test species (rat). The number 38 

corresponds to the entry in the LSE table. 

(18).	 Estimated Upper-Bound Human Cancer Risk Levels This is the range associated with the 

upper-bound for lifetime cancer risk of 1 in 10,000 to 1 in 10,000,000. These risk levels are 

derived from 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. 

Chapter 2 (Section 2.4) 

Relevance to Public Health 

The Relevance to Public Health section provides a health effects summary based on evaluations of 

existing toxicological, epidemiological, and toxicokinetic information. This summary is designed to 

present interpretive, weight-of-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 section discusses health effects by end point. Human data are presented first, then animal data. 

Both are organized by route of exposure (inhalation, oral, and dermal) and by duration (acute, 

intermediate, and chronic). In vitro data and data from pamnteral routes (intramuscular, intravenous, 

subcutaneous, etc.) are also considered in this section. If data are located in the scientific literature, a 

table of genotoxicity information is included. 
CHLORDANE A-6 

APPENDIX A 

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. MRLs for noncancer end points if derived, and the end 

points from which they were derived are indicated and discussed in the appropriate section(s). 

Limitations to existing scientific literature that prevent a satisfactory evaluation of the relevance to 

public health are identified in the Identification of Data Needs section. 

Interpretation of Minimal Risk Levels 

Where sufficient toxicologic information was available, MRLs were derived. MRLs are specific for 

route (inhalation or oral) and duration (acute, intermediate, or chronic) of exposure. Ideally; MRLs can 

be derived from all six exposure scenarios (e.g., Inhalation - acute, -intermediate, -chronic; Oral ­

acute, -intermediate, - 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. They should help physicians and public health officials determine the safety of a 

community living near a substance emission, given the concentration of a contaminant in air or the 

estimated daily dose received via food or water. MRLs are based largely on toxicological studies in 

animals and on reports of human occupational exposure. 

MRL users should be familiar with the toxicological information on which the number is based. 

Section 2.4, “Relevance to Public Health,” contains basic information known about the substance. 

Other sections such as 2.6, “Interactions with Other Chemicals” and 2.7, “Populations that am 

Unusually Susceptible” provide important supplemental information. 

MRL users should also understand the MRL derivation methodology. MRLs am derived using a 

modified version of the risk assessment methodology used by the Environmental Protection Agency 

(EPA) (Barnes and Dourson 1988; EPA 1989a) to derive reference doses (RfDs) for lifetime exposure. 

To derive an MRL, ATSDR generally selects the 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 effects (e.g., systemic, neurological, and developmental). In order to compare NOAEZLs and 

LOAELs for specific end points, all inhalation exposure levels are adjusted for 24 hr exposures and all 

intermittent exposures for inhalation and oral routes of intermediate and chronic duration are adjusted 

for continuous exposure (i.e., 7 days/week). If the 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 NOAEL that does not exceed any 

adverse effect levels. The NOAEL is the most suitable end point for deriving an MRL. When a 

NOAEL is not available, a Less Serious LOAEL can be used to derive an MRL, and an uncertainty 

factor of (1, . MRLs are not derived from Serious LOAELs. Additional uncertainty factors 

of (1, 3, or 10 ) are used for human variability to protect sensitive subpopulations (people who are 

most susceptible to the health effects caused by the substance) and (1, 3, or 10) are used for 

interspecies variability (extrapolation from animals to humans). In deriving an MRL, these individual 

uncertainty factors are multiplied together. Generally an uncertainty factor of 10 is used; however, the 

MRL Workgroup reserves the right to use uncertainty factors of (1, 3, or 10) based on scientific 

judgement. The product is then divided into the adjusted 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 LSE Tables.