TOXICOLOGICAL PROFILE FOR 

ENDRIN
	

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
	

Public Health Service 

Agency for Toxic Substances and Disease Registry
	

August 1996
	


 
ENDRIN 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. 
ENDRIN iii 

UPDATE STATEMENT 

A Toxicological Profile for endrin was released in May 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
 


vi 

*Legislative Background 

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

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

Environmental Response, Compensation, and Liability Act of 1980 (CERCLA or Super-fund). 

This public law directed ATSDR to prepare toxicological profiles for hazardous substances most 

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

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

availability of the revised priority list of 275 hazardous substances was announced in the Federal 

Register on April 29,1996 (61 FR 18744). For prior versions of the list of substances, see Federal 

Register notices dated April 17,1987 (52 FR 12866); October 20,1988 (53 FR 41280); October 

26,1989 (54 FR 43619); October 17,199O (55 FR 42067); October 17,199l (56 FR 52166); 

October 28,1992 (57 FR 48801); and February 28,1994 (59 FR 9486). Section 104(I)(3) of 

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

for each substance on the list. 
 

ENDRIN vii 

CONTRIBUTORS
 

CHEMICAL MANAGER(S)/AUTHOR(S): 

Jessilyn Taylor, M.S.
 

ATSDR, Division of Toxicology, Atlanta, GA
 

Jerry W. Spoo, DVM
 

Research Triangle Institute, Research Triangle Park, NC
 

Lorrene Buckley Kedderis, Ph.D., DABT
 

Research Triangle Institute, Research Triangle Park, NC
 

THE PROFILE HAS UNDERGONE THE FOLLOWING ATSDR INTERNAL REVIEWS: 

1 . Green Border Review. Green Border review assures 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 end points. 

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. 

ENDRIN ix 

PEER REVIEW 

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

1 . Dr. Gary Booth, Brigham Young University, Provo, Utah; 

2 . Dr. Donald Morgan, Private Consultant, Iowa City, Iowa; and 

3 . Dr. Martha J. Radike, Department of Environmental Health, University of Cincinnati, Cincinnati, 

Ohio. 

These experts collectively have knowledge of endrin’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(1)(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. 








ENDRIN 1 

1. PUBLIC HEALTH STATEMENT 

This statement was prepared to give you information about endrin and to emphasize the 

human health effects that may result from exposure to it. The Environmental Protection 

Agency (EPA) identifies the most serious hazardous waste sites in the nation. These sites 

make up the National Priorities List (NPL) and are the sites targeted for long-term federal 

clean-up activities. Endrin has been found in at least 120 (8.4%) of the current or former 

NPL sites. Endrin ketone has been found in at least 37 sites of the current or former sites on 

the NPL. However, the number of NPL sites evaluated for endrin ketone is not known. As 

the EPA evaluates more sites, the number of sites at which endrin ketone is found may 

increase. This information is important because exposure to endrin may cause harmful health 

effects and because these sites are potential or actual sources of human exposure to endrin. 

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 endrin, 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, sex, 

nutritional status, family traits, lifestyle, and state of health. 
ENDRIN 2 

1. PUBLIC HEALTH STATEMENT 

1.1 WHAT IS ENDRIN? 

This toxicologic profile focuses on endrin, but because of its close association to both endrin 

aldehyde and endrin ketone, the profile includes studies with data relevant to human exposure 

to these compounds when available. 

Endrin is a solid, white, almost odorless substance that was used as a pesticide to control 

insects, rodents, and birds. Endrin has not been produced or sold for general use in the 

United States since 1986. Little is known about the properties of endrin aldehyde, an 

impurity and breakdown product of endrin, or endrin ketone, which is a product of endrin 

when it is exposed to light. 

Further information on the properties and uses of endrin, endrin aldehyde, and endrin ketone 

is in Chapters 3 and 4. 

1.2 WHAT HAPPENS TO ENDRIN WHEN IT ENTERS THE ENVIRONMENT? 

Endrin does not dissolve very well in water. It has been found in ground water and surface 

water, but only at very low levels. It is more likely to cling to the bottom sediments of 

rivers, lakes, and other bodies of water. Endrin is generally not found in the air except when 

it was applied to fields during agricultural applications. 

The persistence of endrin in the environment depends highly on local conditions. Some 

estimates indicate that endrin can stay in soil for over 10 years. Endrin may also be broken 

down by exposure to high temperatures (230 (C) or light to form primarily endrin ketone and 

endrin aldehyde. 

It is not known what happens to endrin aldehyde or endrin ketone once they are released to 

the environment; however, the amount of endrin broken down to endrin aldehyde or endrin 

ketone is very small (less than 5%). Chapter 5 has information on the presence of endrin, 

endrin aldehyde, or endrin ketone in the environment. 
ENDRIN 3 

1. PUBLIC HEALTH STATEMENT 

1.3 HOW MIGHT I BE EXPOSED TO ENDRIN? 

Since endrin is no longer produced or used in the United States, you can probably be exposed 

to it only in areas where it is concentrated, such as a hazardous waste site. You may be 

exposed to endrin in air, water, or soil if you live near a hazardous waste site. Endrin has 

been detected at 120 (8.4%) such sites. Children living near hazardous waste sites could be 

exposed to endrin in contaminated soils, if they eat dirt. Detection of endrin in ground water 

or drinking water is rare. In the U.S. EPA 1989 National Pesticide in Groundwater Study, in 

which ground water was collected from areas with significant agricultural land uses as well as 

urban areas, only two wells were found with detectable levels of endrin. In wells drilled to 

access ground water near hazardous waste sites, 1.3% of 156 Resource Conservation and 

Recovery Act (RCRA) sites and 0.9% of 178 Comprehensive Environmental Response, 

Compensation, and Liability Act of 1980 (CERCLA) or Superfund sites had detectable levels 

of endrin in the early 1980s. No information about the presence of endrin aldehyde or endrin 

ketone in the environment was found. 

You may also be exposed to endrin by eating foods that contain endrin. Before cancellation 

of endrin use, reported concentrations of endrin in domestic and imported food samples 

ranged from 0.05 to 0.50 parts per million (ppm; where 1 ppm = 1 microgram per gram 

(μg/g) of food). However, no endrin was detected in food samples from a Texas survey and 

only 0.084% of over 13,000 food samples were found to contain endrin in 1989 after 

cancellation of endrin use. Endrin was found in less than 1% of all food sampled by the U.S. 

Food and Drug Administration (FDA) in 1991. Because endrin is no longer used in the 

United States, residues on imported foods are the main source of potential human exposure in 

food. The levels of endrin aldehyde or endrin ketone in foods are not known. 

Endrin levels can build up (bioaccumulate) in the tissues of organisms that live in water. In 

the 1986 EPA National Study of Chemical Residues in Fish, concentrations of endrin were 

found in fish at 11% of 362 sites surveyed (average 1.69 parts per billion [ppb; where 1 ppb 

= 1 nanogram per gram (ng/g) of food]; maximum 162 ppb). Endrin was also detected in 21 of 

31 samples of 2 commercial shrimp species from a Gulf Coast estuary receiving both 
ENDRIN 4 

1. PUBLIC HEALTH STATEMENT 

industrial discharges, and urban and agricultural runoff. The average concentration was 1,070 

and the maximum concentration was 9,470 ppb. Levels of endrin have probably declined, 

even in such polluted areas, since using endrin was banned. 

Endrin has been detected in human breast milk (0.02-6.24 milligrams endrin in each kilogram 

milk fat [mg/kg]); this may be a route of exposure for nursing infants. However, no studies 

of endrin in breast milk in United States or Canadian populations have been conducted. 

Further information on the ways you may be exposed to endrin is in Chapter 5. 

1.4 HOW CAN ENDRIN ENTER AND LEAVE MY BODY? 

Endrin and endrin aldehyde can enter your body when you eat foods or drink beverages or 

breathe air that contain this substance, or when it comes in contact with your skin. When 

endrin enters your body in any of these ways, it is rapidly changed into other substances. 

Endrin and its metabolic breakdown products are rapidly removed from the body, usually 

within a few days, through the urine and feces. There is some evidence that small amounts 

of endrin may remain in the fatty tissue of your body when you are exposed to high levels. 

No information is known about how endrin aldehyde or endrin ketone leaves the body. 

Further information on endrin uptake and excretion is in Chapter 2. 

1.5 HOW CAN ENDRIN AFFECT MY HEALTH? 

Exposure to endrin can cause various harmful effects including death and severe central 

nervous system (brain and spinal cord) injury. Swallowing large amounts of endrin (more 

than 0.2 mg/kg of body weight) may cause convulsions and kill you in a few minutes or 

hours. 
ENDRIN 5 

1. PUBLIC HEALTH STATEMENT 

Symptoms that may result from endrin poisoning are headache, dizziness, nervousness, 

confusion, nausea, vomiting, and convulsions. Some of these symptoms may continue for 

weeks after exposure to high doses of endrin. 

No long-term health effects have been noted in workers, either in factories or during field 

applications, who have been exposed to endrin by breathing or touching it. 

Studies in animals confirm that endrin’s main target is the nervous system, probably because 

the brain and other parts of the nervous system contain much fatty tissue, and endrin tends to 

stay in those tissues. Birth defects, especially abnormal bone formation, have been seen in 

some animal studies. While there are no human data on birth defects, evidence in rodents 

suggests that exposure to high doses of endrin during pregnancy could be a health risk to 

developing fetuses. 

In studies using rats, mice, and dogs, endrin did not produce cancer. However, most of these 

studies did not accurately evaluate the ability of endrin to cause cancer. No significant excess 

of cancer has been found in exposed factory workers, although endrin metabolites have been 

detected in their urine. The EPA has determined that endrin is not classifiable as to its 

human carcinogenicity because there is not enough information to allow classification. 

Endrin has also not been classified for carcinogenic effects by the Department of Health and 

Human Services (DHHS) or the International Agency for Research on Cancer (IARC). 

One study in rodents suggests that exposure to endrin aldehyde or endrin ketone may cause 

liver disease. No other studies were found on how endrin aldehyde or endrin ketone can 

affect your health. 

Further information on the health effects of endrin is in Chapter 2. 
ENDRIN 6 

1. PUBLIC HEALTH STATEMENT 

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

 EXPOSED TO ENDRIN? 

If you are exposed to endrin, the chemical can be detected in your blood, breast milk, or fatty 

tissue. Tests can measure endrin in the blood or fat of people recently exposed. Endrin is 

cleared from the blood rapidly, so samples should be taken within l-2 weeks of exposure. 

Since special analytical equipment is needed (see Chapter 6), these tests are not routinely 

performed in doctors’ offices. Although these tests can be used to confirm that a person has 

been exposed to endrin, it is not yet possible to use those tests to predict the type or severity 

of any health effects that might occur. Endrin metabolites have been found in urine 

(0.001-0.14 micrograms per milliliter [(μ/mL]; where 1 (μ/mL = 1 ppm) and feces of 

workers exposed to endrin. 

Further information on how endrin levels can be measured in exposed persons is in Chapter 6. 

No information is available on tests for exposure to endrin aldehyde or endrin ketone. 

1.7 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO

 PROTECT HUMAN HEALTH? 

In order to protect people from potential health effects, the EPA banned the production and 

use of endrin in the United States in 1986. The EPA’s proposed maximum contaminant level 

(MCL) in drinking water is 0.0002 milligrams per liter (mg/L; I mg/L = 1 ppm). The EPA 

has also set health advisories which are levels of a chemical in water that are safe. The l-day 

and 10-day health advisories for endrin are 0.02 mg endrin per liter of water for both children 

and adults. The longer-term health advisories for children and adults are 0.003 mg/L and 

0.01 mg/L, respectively. The lifetime health advisory for children and adults is 0.002 mg/L. 

The EPA recommends an ambient water quality criteria level of 0.001 mg/L to protect human 

health. 

The National Institute of Occupational Safety and Health (NIOSH) and the Occupational 

Safety and Health Administration (OSHA) have established a limit of 0.1 mg endrin per cubic 
ENDRIN 7 

1. PUBLIC HEALTH STATEMENT 

meter of air (0.1 mg/m3) averaged over an 8-hour day in an occupational setting for a 

40-hour work week. In addition, NIOSH considers that a person could escape within 

30 minutes from a concentration of 2,000 mg/m3

 without respiratory protection and without 

experiencing any escape-impairing or irreversible health effects. 

More detailed information on federal and state regulations related to endrin is in Chapter 7. 

No information can be found on government regulations for endrin aldehyde or endrin ketone. 

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
 

Division of Toxicology
 

1600 Clifton Road NE, Mailstop 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. 

ENDRIN 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 endrin, endrin 

ketone and endrin aldehydex. 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 

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-observedadverse-effect levels (LOAELs) reflect the actual doses (levels of exposure) used in the 

studies. LOAELS have been classified into “less serious” or “serious” effects. “Serious” effects are 

those that evoke failure in a biological system and can lead to morbidity or mortality (e.g., acute 

respiratory distress or death). “Less serious” effects are those that are not expected to cause significant 

dysfunction or death, or those whose significance to the organism is not entirely clear. ATSDR 

acknowledges that a considerable amount of judgment may be required in establishing whether an end 

point should be classified as a NOAEL, “less serious” LOAEL, or “serious” LOAEL, and that in some 

cases, there will be insufficient data to decide whether the effect is indicative of significant 

dysfunction. However, the Agency has established guidelines and policies that are used to classify 

these end points. ATSDR believes that there is sufficient merit in this approach to warrant an attempt 
ENDRIN 1 0 

2. HEALTH EFFECTS 

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 (LOAEL) 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. 

Estimates of exposure levels posing minimal risk to humans (Minimal Risk Levels or MRLs) have 

been made for endrin. An MRL is defined as an estimate of daily human exposure to a substance that 

is likely to be without an appreciable risk of adverse effects (noncarcinogenic) over a specified 

duration of exposure. MRLs are derived when reliable and sufficient data exist to identify the target 

organ(s) of effect or the most sensitive health effect(s) for a specific duration within a given route of 

exposure. MRLs are based on noncancerous health effects only and do not consider carcinogenic 

effects. MRLs can be derived for acute, intermediate, and chronic duration exposures for inhalation 

and oral routes. Appropriate methodology does not exist to develop MRLs for dermal exposure. 

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

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

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

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

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

asthma, or chronic bronchitis. As these kinds of health effects data become available and methods to 

assess levels of significant human exposure improve, these MRLs will be revised. 

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

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

2. HEALTH EFFECTS 

2.2.1 Inhalation Exposure 

Limited data are available regarding inhalation exposure of humans and animals. Results of these 

studies are discussed below and presented in Table 2-1 and Figure 2-1. 

2.2.1.1 Death 

Deaths in humans after occupational exposure to endrin have not been reported, although exposure was 

high enough to cause tonic-clonic contractions and seizures. One epidemiological study (Ditraglia et 

al. 1981) showed a significantly increased number of deaths due to nonmalignant respiratory system 

disease (pneumonia and “other respiratory diseases”) in the aldrin/dieldrin/endrin cohort in one 

manufacturing site. However, the observed increase in deaths due to nonmalignant respiratory disease 

cannot be clearly attributed to endrin because simultaneous exposure to other chemicals occurred and 

nonmalignant respiratory disease was not observed at another plant that also manufactured endrin 

(Ditraglia et al. 1981). In another study, the total observed mortality was 25 in a cohort of 232 aldrin/ 

dieldrin/endrin/telodrin-manufacturing workers versus 38 expected in the general male population 

(Ribbens 1985). The worker mortality study is limited by small cohort size with resulting low 

statistical power to detect increased mortality and by the fact that simultaneous exposure also occurred. 

A cat exposed twice for one hour to 6,500 mg/m3 (417 ppm) endrin as a spray of 1.5% aqueous 

solution died within 24 hours (Ressang et al. 1959). In another inhalation study, 6 species of animals 

were exposed to endrin vapor at 15 mg/m3

 (0.36 ppm) for 7 hours a day, 5 days a week for up to 

130 exposures (Treon et al. 1955). Two of 4 rabbits died after 26 and 90 exposures, and 1 of 3 mice 

died after 22 exposures. The cat, 2 guinea pigs, 2 hamsters, and 3 rats survived 130 exposures. 

Diffuse degenerative changes were observed in kidneys, livers, and brains in all animals that died, 

except in the mouse where effects on the brain were not observed. 

The concentrations associated with death in each species are recorded in Table 2-l and plotted in 

Figure 2-1. No studies were located regarding lethal effects in humans or animals after inhalation 

exposure to endrin aldehyde or endrin ketone. 
Table 2-1. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Inhalation 

Key toa 

figure 

Species 

(strain) 

Exposure/ 

duration/ 

frequency System 

NOAEL 

(ppm) 

Less serious 

(ppm) 

LOAEL 

Serious 

(ppm) Reference 

ACUTE EXPOSURE 

1 

Death 

Cat 

(NS) 

2x 

1 hr 

417 (1/1 died) Ressang et al. 

1959 

Endrin 

2 

Neurological 

Cat 

(NS) 

2x 

1 hr 

41 7 (slight degenerative lesions 

of ganglion cells in the 

brain) 

Ressang et al. 

Endrin 

1959 

INTERMEDIATE EXPOSURE 

Death 

3 Mouse 

(NS) 

107 d 

5 d/wk 

7 hr/d 

0.36 (1/3 mice died) Treon et al. 1955 

Endrin 

4 Rabbit 

(NS) 

118 d 

5 d/wk 

7 hr/d 

0.36 (2/4 rabbits died) Treon et al. 1955 

Endrin 

Systemic 

5 Mouse 

(NS) 

107 d 

5 d/wk 

7 hr/d 

Hepatic 

Renal 

0.36 

0.36 

(diffuse degenerative 

changes) 

(diffuse degenerative 

changes) 

Treon et al. 1955 

Endrin 

6 Rabbit 

(NS) 

118 d 

5 d/wk 

7 hr/d 

Resp 

Hepatic 

Renal 

0.36 

0.36 

0.36 

(granulomatous 

pneurnonitis) 

(diffuse degenerative 

changes) 

(diffuse degenerative 

changes) 

Treon et al. 1955 

Endrin 

ENDRIN 12

 2. HEALTH EFFECTS 
Table 2-1. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Inhalation (continued) 

Key toa 

figure 

Species 

(strain) 

Exposure/ 

duration/ 

frequency System 

NOAEL 

(ppm) 

Less serious 

(ppm) 

LOAEL 

Serious 

(ppm) Reference 

Neurological 

7 Mouse 107 d 0.36 Treon et al. 1955 

(NS) 5 d/wk 

7 hr/d 

Endrin 

8 Rabbit 

(NS) 

118d 

5 d/wk 

7 hr/d 

0.36 (diffuse degenerative 

lesions in brain) 

Treon et al. 1955 

Endrin 

a

The number corresponds to entries in Figure 2-1. 

d = day(s); hr = hour(s); LOAEL = lowest -observable -adverse -effect level; NOAEL = no-observable -adverse -effect level; NS = not specified; Resp = respiratory; wk = week(s); x = times 

ENDRIN 13

 2. HEALTH EFFECTS 
1c 2c
3m 4h 6h 5m 6h 5m 6h 7m 8h 
ENDRIN 16 

2. HEALTH EFFECTS 

2.2.1.2 Systemic Effects 

Studies regarding the systemic effects that have been observed in humans and animals after inhalation 

exposure to endrin are discussed below. The highest NOAEL and all LOAEL values from each 

reliable study for each systemic effect in each species and duration category are recorded in Table 2-l 

and plotted in Figure 2-1. No LSE studies were located regarding cardiovascular, gastrointestinal, 

hematological, musculoskeletal, endocrine, dermal, ocular, or body weight effects in humans or 

animals after inhalation exposure to endrin, endrin aldehyde, or endrin ketone. 

Respiratory Effects. Respiratory effects were reported in workers involved in the manufacture of 

aldrin/dieldrin/endrin (Ditraglia et al. 1981). Increased deaths due to nonmalignant respiratory diseases 

such as pneumonia were observed in workers at one of two plants that manufactured endrin. 

However, simultaneous exposure to other chemicals occurred, and increased respiratory disease was 

not observed in the second endrin manufacturing facility. 

Two rabbits which survived 118 periods of exposure to 0.36 ppm (15 mg/m3

) of endrin vapors 

developed a granulomatous pneumonitis (Treon et al. 1955). The pneumonitis was not observed in 

cats, guinea pigs, hamsters, rats, or mice, but the small number of animals tested limits the usefulness 

of this study. 

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

endrin aldehyde or endrin ketone. 

Hepatic Effects. Seven of 592 workers manufacturing aldrin/dieldrin/endrin had abnormal liver 

function tests, as shown by 3 cases of increased thymol turbidity, increased serum glutamic oxaloacetic 

transaminase (SCOT) in one worker, and increased serum glutamic pyruvate transaminase (SGPT) in 

4 workers (Hoogendam et al. 1965). Exposure to other compounds was not controlled, and test values 

returned to normal during continued exposure. 

Diffuse degenerative changes were observed in the livers of rabbits and mice exposed over 6 months 

at endrin concentrations of 15 mg/m3

 (0.36 ppm) which caused death (Treon et al. 1955). Details of 

the liver pathology were not provided. 
ENDRIN 17 

2. HEALTH EFFECTS 

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

endrin aldehyde or endrin ketone. 

Renal Effects. Diffuse degenerative changes were observed in the kidneys of rabbits and mice that 

died following exposure to 0.36 ppm (15 mg/m3

) of endrin (Treon et al. 1955). No further details of 

the kidney pathology were provided. No studies were located regarding renal effects in humans after 

inhalation exposure to endrin, endrin aldehyde, or endrin ketone. 

2.2.1.3 lmmunological and Lymphoreticular Effects 

No studies were located regarding immunological or lymphoreticular effects in humans or animals 

after inhalation exposure to endrin, endrin aldehyde, or endrin ketone. 

2.2.1.4 Neurological Effects 

Studies in humans demonstrate that the nervous system is a primary target for endrin toxicity. 

Convulsions occurred within two hours following occupational exposure to aldrin, dieldrin and endrin 

(Hoogendam et al. 1962, 1965). After removal from exposure, seizures subsided and complete 

recovery was achieved in l-3 days. Abnormal electroencephalograms (EEGs) were usually observed 

in endrin-poisoned workers, and sometimes occurred without any clinical symptoms. Predominately 

bilateral synchronous theta waves, and synchronous spike and wave complexes were seen (Hoogendam 

et al. 1962). These are believed to be associated with brain stem injury. Abnormal EEGs generally 

returned to normal within a period of 0.5-l month after removal of the worker from exposure 

(Hoogendam et al. 1965). 

Inhalation experiments in rabbits and mice showed diffuse degenerative lesions of the brain in rabbits 

(but not the mouse) that died after exposure to 15 mg/m3

 (0.36 ppm) of endrin for 118 days over a 

185-day period (Treon et al. 1955). Seizures were not observed prior to death. Ressang et al. (1959) 

reported slight degenerative lesions of ganglion cells in the brains of cats exposed to a lethal 

concentration of endrin via inhalation. No studies were located regarding neurological effects in 

humans or animals after inhalation exposure to endrin aldehyde or endrin ketone. 
ENDRIN 18 

2. HEALTH EFFECTS 

No studies were located regarding the following health effects in humans and animals after inhalation 

exposure to endrin, endrin aldehyde, or endrin ketone: 

2.2.1.5 Reproductive Effects 

2.2.1.6 Developmental Effects 

2.2.1.7 Genotoxic Effects 

Genotoxicity studies are discussed in Section 2.5. 

2.2.1.8 Cancer 

Studies of workers in the endrin manufacturing industry have not shown an association between 

occupational exposure to endrin and any type of human cancer. No excess cancers could be attributed 

to exposure to endrin in 52 chemical workers in an endrin manufacturing facility after exposures 

lasting 4-13 years (Versteeg and Jager 1973). Fifteen years later, the same worker cohort showed no 

evidence of increased cancer rates. The small size of the cohort gives the study a low statistical power 

(Ribbens 1985). 

In a retrospective cohort mortality study of U.S. pesticide manufacturing facilities, standardized 

mortality ratios (SMR) were calculated for all malignant neoplasms in 2,100 workers in 2 aldrin/ 

dieldrin/endrin plants. The SMRs were lower than expected. For “all malignant neoplasms,” the SMR 

ranged from 68 to 91, which was well below the expected level (SMR=l00), indicating a possible 

healthy worker effect (Ditraglia et al. 1981). For one of the plants, there was a limited follow-up and 

inadequacies were imposed by the loss of 10% of the cohort (Ditraglia et al. 1981). While there was 

no specific cancer risk at certain manufacturing sites, several occurrences of cancer in the aldrin/ 

dieldrin/endrin plants may be worthy of further study. There were slight excesses of cancer of the 

esophagus (2 versus 0.85 expected), liver (2 versus 0.89 expected), rectum (3 versus 1.24 expected), 

and of the lymphatic and hematopoietic systems (6 versus 4.09 expected) in one plant. However, the 

excesses were not statistically significant, and the elevated SMRs were based on small numbers of 

observed deaths (l-3 deaths except for lymphatic/hematopoietic cancers which were based on 

6 deaths). 
ENDRIN 19 

2. HEALTH EFFECTS 

No studies were located regarding cancer in animals after inhalation exposure to endrin, endrin 

aldehyde, or endrin ketone. 

2.2.2 Oral Exposure 

Ingestion of endrin can cause central nervous system effects as expressed by muscle contractions, 

hyperexcitability, and in severe cases, convulsions and sometimes death (Curley et al. 1970; Runhaar 

et al. 1985; Weeks 1967). 

Exposure of animals to endrin causes central nervous system effects, particularly convulsions 

(Deichmann et al. 1970; Quick et al. 1989; Treon et al. 1955). Nonspecific degeneration of the liver, 

kidney, and brain was observed in animals exposed to lethal doses of endrin (Treon et al. 1955). 

Endrin can cause abnormal bone formation, hyperactivity, and death in fetuses of dams exposed during 

gestation (Chernoff et al. 1979a; Gray et al. 1981; Kavlock et al. 1985; Ottolenghi et al. 1974). Most 

of the carcinogenicity bioassays for endrin were negative (Deichmann et al. 1970). Positive 

carcinogenic effects of endrin were reported by Reuber (1978); however, Reuber’s criteria for 

classifying tissues as tumorigenic were not consistent with other investigators (EPA 1979f). 

No studies were located regarding the health effects of endrin aldehyde or endrin ketone in humans 

following oral exposure. Limited data from a feeding study in rats suggest that endrin aldehyde and 

endrin ketone can cause hepatic effects (elevated serum enzymes) (Young and Mehendale 1986). 

2.2.2.1 Death 

Deaths as the result of acute exposure by ingestion of endrin have been observed in humans in a 

variety of incidents. In 1967, in Doha, Qatar, and Hofuf in Saudi Arabia, 874 people were 

hospitalized after an acute exposure to endrin-contaminated flour which resulted in 26 known deaths 

(Weeks 1967). Deaths occurred within 12 hours of the onset of symptoms of toxicity (convulsions, 

loss of consciousness, headache, nausea, vomiting); however, recovery of survivors was rapid. 

Concentrations of endrin in bread eaten by victims ranged from 48 to 1,807 ppm (Curley et al. 1970). 

The contaminated flour used to make the bread contained 2,153-3,367 ppm endrin. 
ENDRIN 20 

2. HEALTH EFFECTS 

An outbreak of acute human endrin poisoning associated with central nervous system toxicity and 

19 deaths in 194 known cases occurred in Pakistan in 1984 (Rowley et al. 1987). The vector for 

exposure was not identified, but contamination of a food item was the likely cause of poisoning. 

Ingestion of 12 g of endrin (dissolved in aromatic hydrocarbons) by a 49-year-old man in a suicide 

attempt caused convulsions persisting for 4 days; death occurred after 11 days (Runhaar et al. 1985). 

Death occurred in 11 other cases following ingestion of endrin; the time from administration to death 

ranged from 1 to 6 hours. In cases where endrin ingestion occurred with milk or alcohol, death 

occurred more rapidly (within l-2 hours) presumably as the result of enhanced absorption that 

increased toxicity (Tewari and Sharma 1978). 

Endrin is lethal to animals when sufficiently high doses are administered by oral gavage or in the diet. 

An early study of acute toxicity in animals (Treon et al. 1955) reported that minimum lethal doses in 

monkeys (l-3 mg/kg) were lower than minimum lethal doses in cats (<5 mg/kg), rats (<5-36 mg/kg), 

rabbits (5-7 mg/kg), and guinea pigs (lo-36 mg/kg). A single oral dose of 6 mg endrin/kg body 

weight in a cod liver oil emulsion caused the death of a cat within 24 hours (Ressang et al. 1959). 

Six-month-old female rats were more sensitive than were 34-week-old rats to lethal effects of endrin; 

male rats were more sensitive to endrin at 3-4 weeks than 6-month-old rats. The oral LD50 (the dose 

which has been calculated to cause death in 50% of the experimental animal population) was 7.3 and 

16.8 mg/kg for 6-month-old and 29-31-day-old female rats, respectively; and 43.4 and 28.8 mg/kg for 

6-month-old and 29-31-day-old male rats, respectively (Treon et al. 1955). Female rats, therefore, 

died at lower doses than male rats, Likewise, the oral LD50 in male and female adult Sherman rats 

was 17.8 and 7.5 mg/kg (Gaines 1960), respectively; and the lowest doses to cause lethality were 

10 and 6 mg/kg, respectively (Gaines 1969). Female guinea pigs appeared slightly more susceptible to 

the lethal effects of orally administered endrin than males; minimum lethal doses were estimated as 

lo-16 and 24-36 mg/kg endrin (LD50 for males was 36 mg/kg and 16 mg/kg for females) (Treon et 

al. 1955). In subsequent studies, an oral dose of 8 mg/kg caused 100% lethality in female rats 

(Numan et al. 1990b), and an LD50 of 5.6 mg/kg was reported for male rats and 5.3 mg/kg for female 

rats (Bedford et al. 1975a). Speck and Maaske (1958) found the oral LD50 for 6-month-old male 

Sprague-Dawley rats for endrin to be 40 mg/kg body weight. The oral LD50 in female hamsters was 

18.6 mg/kg (Chemoff et al. 1979a). Single or repeated doses of endrin to pregnant mice or hamsters 

during gestation also resulted in maternal or fetal lethality (Chemoff et al. 1979a; Gray et al. 1981; 

Kavlock et al. 1985). 
ENDRIN 21 

2. HEALTH EFFECTS 

The acute oral LD50 for endrin aldehyde in male mice was reported to be >500 mg/kg, although no 

experimental details were provided (Phillips et al. 1962). The LD50 values and the doses associated 

with death are recorded in Table 2-2 plotted in Figure 2-2. No studies were located regarding lethal 

effects in humans or animals following oral exposure to endrin ketone. 

Male and female mice administered 0.65 mg/kg (5 ppm) of endrin in feed for 120 days had significant 

mortality (Good and Ware 1969). Dogs of both sexes administered endrin in feed from 18 days to 

approximately 19 months had increased mortality at doses of 0.20-0.27 mg/kg/day (5 ppm) or greater, 

but animals survived at doses of 0.15-0.21 mg/kg/day (4 ppm) (Treon et al. 1955). Pine mice are 

susceptible to endrin lethality when exposed in the environment (Webb et al. 1973). Two pregnant 

female rats administered 2 mg/kg/day were found dead on gestation days 13 and 14 (Goldenthal 

1978a). Increased mortality was reported for female rats administered 1.25 mg/kg/day (25 ppm) 

endrin in the diet (Treon et al. 1955). 

2.2.2.2 Systemic Effects 

Studies regarding the systemic effects that have been observed in humans and animals after oral 

exposure to endrin are discussed below. The highest NOAEL and all LOAEL values from each 

reliable study for each systemic effect in each species and duration category are recorded in Table 2-2 

and plotted in Figure 2-2. No studies were located regarding musculoskeletal or ocular effects in 

humans or animals after oral exposure to endrin, endrin aldehyde, or endrin ketone. No studies were 

located regarding hepatic, endocrine, ocular, or body weight effects in humans. 

Respiratory Effects. Pulmonary edema was observed in a patient after an attempted suicide with 

endrin and was thought to be due to chemical pneumonitis following aspiration of aromatic 

hydrocarbons contained in the ingested formulation. The authors state that the hydrocarbons may have 

been the cause of the pulmonary effects (Runhaar et al. 1985), since hydrocarbon-induced chemical 

pneumonitis is a well established clinical entity. 

Rats treated for 17.6-20.8 months with 0.1 mg/kg/day of endrin exhibited focal hemorrhage and 

congestion of the lungs (Deichmann et al. 1970). Shortness of breath was reported in rats, but not 

mice, exposed to endrin for 80 weeks (NCI 1978). Pulmonary hyperplasia and edema were reported in 

dogs fatally poisoned by diets containing 5 ppm or greater (0.20-0.27 mg/kg/day) of endrin (Treon et 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral 

Exposure/ LOAEL 

Duration/

Key toa Species Frequency NOAEL Less Serious Serious

figure (Strain) (Specific Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Reference 

ACUTE EXPOSURE 

Death 

1 Human once 

(O) 

171 M (death 11 days after 

exposure) 

2 Rat 

(Carworth 

Farm E) 

once 

(G)

vehicle 

DMSO 

5.6 M (LD50) 

5.3 F (LD50) 

3 Rat 

(Sherman) 

once 

(GO) 

17.8 M (LD50) 

 7.5 F (LD50) 

4 Rat 

(Sherman) 

once 

(GO) 

 10 M (LDmin) 

 6 F (LDmin) 

5 Rat 

(CD) 

Gd 6-15 

(G) vehicle 

Methocel 

2 F (2/25 dead on Gd 13 

and 14) 

6 Rat 

(Carworth) 

once 

(GO) 

7.3 F (LD50) 

43.4 M (LD50) 

7 Rat 

(Carworth) 

once 

(GO) 

16.8 F (LD50) 

28.8 M (LD50) 

Runhaar et al 

1985 

Endrin 

Bedford et al. 

1975a 

Endrin 

Gaines 1960 

Endrin 

Gaines 1969 

Endrin 

Goldenthal et al. 

1978a 

Endrin 

Treon et al. 1955 

Endrin 

Treon el al. 7 955 

Endrin 

ENDRIN 22

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/ LOAEL 

Duration/

Key toa Species Frequency NOAEL Less Serious Serious

figure (Strain) (Specific Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Reference 

8 Mouse 

(CD-1) 

9 Gn Pig 

(NS) 

10 Hamster 

(Golden 

Syrian) 

11 Hamster 

(Golden 

Syrian) 

12 Hamster 

(Golden 

Syrian) 

13 Rabbit 

(NS) 

14 Cat 

(NS) 

Gd 8 

(GO) 

once 

(GO) 

10 d 

Gd 5-14 

(GO) 

once 

(GO) 

10 d 

Gd 5-14 

(GO) 

once 

(GO) 

once 

(GO) 

7 F (3/21 mice died) 

16 F (LD50) 

36 M (LD50)
 

1.5 F (37% of the dams died) 

18.6 F (LD50) 

1.5 F (57% of the dams died) 

7-10 F (LD50) 

3 (death; 100%) 

Kavlock et al. 

1985 

Endrin 

Treon et al. 1955 

Endrin 

Chernoff et al. 

1979a 

Endrin 

Chernoff et al. 

1979a 

Endrin 

Gray et al. 1981 

Endrin 

Treon et al. 1955 

Endrin 

Ressang et al. 

1959 

Endrin 

ENDRIN 23

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/ LOAEL 

Duration/

Key toa Species Frequency NOAEL Less Serious Serious

figure (Strain) (Specific Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Reference 

Systemic 

15 

(SpragueDawley) 

Rat 

ad lib 

(F) 

1-2 d Hepatic 8.2 F (increases in alkaline 

phosphatase(48%), 

glutamate oxaloacetate 

transaminase (82%) 

glutamate pyruvate 

transaminase (55%), 

isocitrate dehydrogenase 

(65%), cholesterol 

(27%-35%), and soluble 

proteins (35%); 

decreases in free amino 

Ali and Shakoori 

1993 

Endrin 

Bd Wt 8.2 F 

acids (34-40%) and 

glucose (41 -51 %); 

vacuolization; fatty 

infiltration) 

16 Rat 

(SpragueDawley) 

once 

(GO) 

Hepatic 3 F (1 1 % increase in relative 

liver weight) 

Bagchi et al. 

1992b 

Endrin 

Other 1.5 F (increased excretion of 

metabolites indicative of 

lipid peroxidation) 

17 Rat 

(SpragueDawley) 

once 

(GO) 

Hepatic 3 F (9% increase in relative 

liver weight, increase in 

mitochondrial iron and 

calcium; decrease in 

microsomal and nuclear 

Bagchi et al. 

1992c 

Endrin 

iron; increased 

microsomal and nuclear 

calcium) 

ENDRIN 24

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/ LOAEL 

Duration/

Key toa Species Frequency NOAEL Less Serious Serious

figure (Strain) (Specific Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Reference 

18 Rat 

(CD) 

9d 

(G ) vehicle 

Methocel 

Gd 6-15 

Bd Wt 0.5 F 2 F (decreased maternal 

weight gain (12% of 

control) during exposure) 

19 Rat 

(SpragueDawley) 

once 

(GO) 

Hepatic 

Renal 

20 

21 

Rat 

(SpragueDawley) 

Rat 

(CD) 

once 

(GO) 

14 d 

Gd 7-20 

(GO) 

Hepatic 

Hepatic 

Bd Wt 

0.45 F 

0.15 F 

4.5 F (14.5% increase in 

mitochondria1 lipid 

peroxidation at 6 hr; 

28% increase in 

microsomal lipid 

peroxidation at 12 hr) 

22 Mouse 

(Swiss

Webster) 

once 

(GO) 

Hepatic 

Renal 

4 M (necrosis, fatty 

degeneration, inflammation, 

cell regeneration, 1.9-fold 

increase in lipid 

peroxidation) 

4 F (necrosis of the tubules, 

hyalin and red cell casts, 

3.3-fold increase in lipid 

peroxidation) 

0.3 F (maternal body weight gain 

decreased by 38%) 

4 F (necrosis, inflammation; 

1.8-fold increase in lipid 

peroxidation) 

4 F (tubular necrosis; 1.7 -fold 

increase in lipid 

peroxidation) 

Goldenthal et al. 

1978a 

Endrin 

Hassan et al. 

1991 

Endrin 

Hassoun et al. 

1993 

Endrin 

Kavlock et al. 

1981 

Endrin 

Hassan et al. 

1991 

Endrin 

ENDRIN 25

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/

Duration/

Key to Frequency a Species figure (Strain) Route) System (Specific

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) Reference 

23 Mouse 11 d Hepatic 

Gd 7-17 

(GO) 

(CD-1) 

Bd Wt 

24 Gn Pig once Hepatic 

(NS) (GO) 

Renal 

25 Hamster 10 d Hepatic 

(Golden Gd 5-14 

Syrian) (GO) 

Bd Wt 

26 Hamster once Hepatic 

(NS) (GO) 

Renal 

Immunological/Lymphoreticular 

27 Rat once 

(Sprague- (GO) 

Dawley) 

0.5 F 

3.5 F 

0.75 F 

0.5 F (relative liver weight 

increased 7%) 

4 F (cloudy swelling and 

narrowing of tubular 

lumen) 

3 F (increase in relative 

spleen weight, 31% 

decrease in relative 

thymus weight) 

Kavlock et al. 

1981 

Endrin 

1 F (maternal body weight 

4 F (necrosis, inflammation, 

gain decreased 24%) 

and 1.3 -fold increase in 1991 

lipid peroxidation) Endrin 

Hassan et al. 

1.5 F (1 9 times more weight 

loss than controls) 

4 F (necrosis, inflammation, 

and 1.3 -fold increase in lipid 

peroxidation) 

and calcium containing 

casts, 

lipid peroxidation) 

4 F (tubular necrosis, hyalin 

Chernoff et al. 

1979a 

Endrin 

Hassan et al. 

1991 

Endrin 

Bagchi et al. 

1992b 

Endrin 

ENDRIN 26

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/

Duration/

Key to Frequency a Species figure (Strain) Route) System (Specific

28 Rat once 

29 Rat <= 14 d 

(Sprague- (GO) 

Dawley) 

Neurological 

30 Mouse <11 d 

(CD-1) (GO) 

(CD) (GO) 

NOAEL 

(mg/kg/day) 

LOAEL 

Less Serious 

(mg/kg/day) 

3 F (1 1 % increase in relative 

spleen weight, 31 % 

decrease in relative 

thymus weight) 

0.5 F (locomotor activity 

depressed) 

1.5 F (38- 46% decrease in 

locomotor activity) 

Serious 

(mg/kg/day) 

4 F (convulsions) 

Reference 

Bagchi et al. 

1992c 

Endrin 

Kavlock et al. 

1981 

Endrin 

Kavlock et al. 

1981 

Endrin 

31 Hamster Gd 8 

(Golden (GO)

Syrian) 

Reproductive 

32 Rat 9d 

(CD) Gd 7-15 

(GO) 

33 Hamster Gd 8 

(Golden (GO)

Syrian) 

34 Hamster 10 d 

(Golden Gd 5-14 

Syrian) (GO) 

7.5 F 

0.3 F 

10 F 

1.5 F 

10 F (1/30 animals displayed 

convulsions) 

Chernoff et al. 

1979a 

Endrin 

Gray et al. 1981 

Endrin 

Chernoff et al. 

1979a 

Endrin 

Gray et al. 1981 

Endrin 

ENDRIN 27

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/ LOAEL 

Duration/

Key toa Species Frequency NOAEL Less Serious Serious

figure (Strain) (Specific Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Reference 

Developmental 

35 Rat 9d 

(CD) Gd 6-15 

(G) vehicle 

Methocel 

0.5 F 2 F (decreased fetal body 

weight and crown -rump 

length) 

Goldenthal et al. 

1978a 

Endrin 

36 Rat 14 d 

(GO) 

(CD) Gd 7-20 

0.45 Kavlock et al. 

1981 

Endrin 

37 Mouse 11 d 

(GO) 

(CD-1) Gd 7-17 

0.5 1 (delayed ossification: 

38% increase in 

supraoccipital score; 

84% decrease in number 

Kavlock et al. 

1981 

Endrin 

of caudal vertebrae; 

decreased fetal body 

weight) 

38 Mouse Gd 8 

(CD-1) (NS) 

7 F (increased incidence of 

supernumerary ribs) 

Kavlock et al. 

1985 

Endrin 

39 Mouse Gd 9 

(CD-1) (GO) 

2.5 (significant increase in open 

eye [2.7%] and cleft palate 

[2.2%]) 

Ottolenghi et al. 

Endrin 

1974 

40 Hamster 10 d 

(Golden Gd 5-1 4 

Syrian) (GO) 

1.5 (irregular supraoccipitals, 

visceral abnormalities; 

2-fold increase in fetal 

mortality; 30% decrease in 

fetal weight) 

Chernoff et al. 

1979a 

Endrin 

41 Hamster Gd 8 

(Golden (GO)

Syrian) 

1.5 5.0 (increased incidence [5/7] 

of mening Oencephaloceles) 

Chernoff et al. 

1979a 

Endrin 

ENDRIN 28

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/

Duration/

Key to Frequency a Species figure (Strain) Route) System (Specific

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) Reference 

42 Hamster 10 d 

(Golden Gd 4-1 3 

Syrian) (G) -vehicle 

Methocel 

43 Hamster Gd 9 

(Golden (GO)

Syrian) 

2.5 F 

5 (increased incidence 

of cleft palate and fused 

ribs; decreased 

fetal weight) 

Goldenthal et al. 

1978b 

Endrin 

Ottolenghi et al. 

1974 

Endrin 

ENDRIN 29

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/ LOAEL 

Duration/

Key toa Species Frequency NOAEL Less Serious Serious

figure (Strain) (Specific Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Reference 

INTERMEDIATE EXPOSURE 

Death 

44 Mouse 120 d 0.65 (deaths in 33 of 101 Good and Ware 

(CFW Swiss) (F) breeding pairs) 1969 

Endrin 

45 Dog 18d- 0.20 M (death in 1/1) Treon et al. 1955 

(Beagle) 9.9 mo Endrin 

6 d/wk 

(F) 

Systemic 

46 Dog 18d- Resp 0.15 0.20 (respiratory distress, Treon et al. 1955 

(Beagle) 9.9 mo pulmonary hyperplasia and Endrin 

6 d/wk edema) 

(F) Cardio 0.15 0.20 (diffuse degenerative 

lesions of the heart) 

Gastro 0.1 5 0.20 (regurgitation of food) 

Hepatic 0.15 0.20 (diffuse degeneration, fatty 

vacuolization) 

Renal 0.1 5 0.20 (tubular degeneration and 

necrosis of convoluted 

tubules) 

Bd Wt 0.1 2 0.1 5 ("did not grow normally " - 0.49 (emaciation) 

no data presented) 

Neurological 

47 Dog 18d- 0.15 b 0.20 (convulsions, tremors, Treon et al. 1955 

(Beagle) 9.9 mo diffuse degenerative brain Endrin 

6 d/wk lesions) 

(F) 

ENDRIN 30

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/ LOAEL 

Duration/

Key toa Species Frequency NOAEL Less Serious Serious

figure (Strain) (Specific Route) System (mg/kg/day) (mg/kg/day) (mg/kg/day) Reference 

Reproductive 

48 Rat 79 d 0.1 Eisenlord et al 

1968 (Long Evans) (F) 

Endrin 

49 Mouse 120 d 0.65 F (reduced litter size) Good and Ware 

1969 (CFW Swiss) (F) 

Endrin 

Developmental 

50 Rat 79 d 0.1 Eisenlord et al. 

1968 (Long Evans) (F) 

Endrin 

ENDRIN 31

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/

Duration/

Key to Frequency a Species figure (Strain) Route) System (Specific

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) Reference 

CHRONIC EXPOSURE 

Death 

51 Rat 

(Carworth) 

2 yr 

(F) 

1.25 F (increased mortality) 

2.5 M (increased mortality) 

Treon et al. 1955 

Endrin 

Systemic 

52 

(Osborne 

Rat 

Mendel) 

20.8 mo 

17.6 -

(F) 

Resp 

Hepatic 

Renal 

Bd Wt 0.56 

0.1 

0.1 

(cloudy swelling of 

centrilobular cells) 

(cloudy swelling of tubule 

epithelial cells) 

0.1 (congestion, focal 

hemorrhage) 

Deichmann et al. 

Endrin 

1970 

53 Rat 

(OsborneMendel) 

80 wk 

(F) 

Resp 

Cardio 

Gastro 

0.3 

0.13 

0.13 

(short breath, epistaxis) 

(diarrhea) 

NCI 1978 

Endrin 

Hepatic 

Renal 

0.3 F 

0.1 3 (discolored urine) 

Endocr 0.1 3 (thyroid hyperplasia and 

pituitary cysts) 

Dermal 0.1 3 (dermatitis alopecia) 

Bd Wt 0.3 

ENDRIN 32

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/

Duration/

Key to Frequency a Species figure (Strain) Route) System (Specific

54 Rat 2 yr Hepatic 

(Carworth) (F) 

NOAEL 

(mg/kg/day) 

0.05 

LOAEL 

Less Serious 

(mg/kg/day) 

0.25 M (1 8% increased relative 

liver weight) 

Serious 

(mg/kg/day) Reference 

Treon et al. 1955 

Endrin 

Renal 

Endocr 

Bd Wt 

55 Mouse 80 wk Resp 

(B6C3F1) (F) 

Cardio 

Gastro 

0.25 

0.25 

0.25 

0.05 M 

5F 

0.42 

0.42 

1.25 (diffuse degeneration of 

1.25 (diffuse degeneration of 

1.25 (diffuse degeneration of 

liver) 

kidneys) 

adrenals) 

1.25 M (1 4% reduction in weight 

gain) 

0.21 (abdominal distention) 

NCI 1978 

Endrin 

Hepatic 

Renal 

Endocr 

Dermal 

Bd Wt 

0.42 

0.42 

0.42 

0.42 

0.21 (hair loss) 

ENDRIN 33

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/

Duration/

Key to Frequency a Species figure (Strain) Route) System (Specific

NOAEL 

(mg/kg/day) 

LOAEL 

Less Serious 

(mg/kg/day) 

Serious 

(mg/kg/day) Reference 

56 Dog 2 yr Hemato 

(F) Hepatic 

(Beagle) 1 hr/d 

Bd Wt 

57 Dog 64 -156 wk Hemato 

(F) Hepatic 

(Beagle) 1 hr/d 

Renal 

58 Dog 16.4 - Cardio 

(Beagle) 18.7 mo 

Hemato 

Renal 

6 d/wk 

(F) 

Bd Wt 

Immunological/Lymphoreticular 

(Beagle) 18.7 mo 

59 Dog 16.4 -

6 d/wk 

(F) 

Neurological 

(Osborne- 20.8 mo 

Mendel) (mean) 

60 Rat 17.6 -

(F) 

0.1 

0.025 

0.1 

0.059 F 

0.059 F 

0.059 F 

0.075 

0.075 

0.075 

0.05 (hepatic cell vacuolation, 

slightly increased liver 

weights) 

0.25 (cardiomegaly) 

0.075 (24% increased relative 

kidney weight) 

0.1 (convulsions and tremors) 

Kettering 1969 

Endrin 

Kettering 1971 

Endrin 

Treon et al. 1955 

Endrin 

Treon et al. 1955 

Endrin 

Deichmann et al. 

1970 

Endrin 

ENDRIN 34

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/

Duration/

Key to Frequency a Species figure (Strain) Route) System (Specific

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) Reference 

61 Rat 80 wk 0.25 M NCI 1978 

(OsborneMendel) (F) 

0.30 F 

Endrin 

62 Rat 

(Carworth) 

2 yr 

(F) 

1.25 

0.25 

2.5 

1.25 

(convulsions, 

hypersensitivity) 

(diffuse degeneration 

brain) 

of 

Treon et al. 1955 

Endrin 

63 Mouse 

(B6C3F1) 

80 wk 

(F) 

0.21 M (hyperexcitability) 

0.33 F (hyperexcitability) 

NCI 1978 

Endrin 

64 Dog 

(Beagle) 

2 yr 

1 hr/d 

(F) 

0.025c F 

0.05 M 

0.05 F (convulsions) 

0.1 M (convulsions) 

Kettering 1969 

Endrin 

65 Dog 

(Beagle) 

15 -38 mo 

1 hr/d 

(F) 

0.059 F (seizures) Kettering 1971 

Endrin 

Reproductive 

66 

(Beagle) 

Dog 

1 hr/d 

64 -1 56 Wk 

(F) 

0.059 F Kettenng 1971 

Endrin 

ENDRIN 35

 2. HEALTH EFFECTS 
Table 2-2. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Oral (continue) 

Exposure/

Duration/

Key to Frequency a Species figure (Strain) Route) System (Specific

NOAEL 

(mg/kg/day) 

Less Serious 

(mg/kg/day) 

LOAEL 

Serious 

(mg/kg/day) Reference 

Developmental 

67 

(Beagle) 

Dog 

1 hr/d 

64-1 56 wk 

(F) 

0.059 F Kettering 1971 

Endrin 

a

The number corresponds to entries in Figure 2-2. 

b

Used to derive an intermediate oral minimal risk level (MRL) of 0.002 mg/kg/day; dose divided by an uncertainty factor of 100 (10 for extrapolation from animals to humans and 

10 for human variability). 

c

Used to derive an chronic oral MRL of 0.0003 mg/kg/day; dose divided by an uncertainty factor of 100 (10 for extrapolation from animals to humans and 10 for human variability). 

ad lib = ad libitum; Bd Wt = body weight; Cardio = cardiovascular; d = day(s); DMSO = dimethyl sulfoxide; Endocr = endocrine; F = female; (F) = food; (G) = gavage; Gastro = 

gastrointestinal; Gd = gestational day; Gn pig = Guinea pig; (GO) = gavage in oil; Hemato = hematological; hr = hour(s); LD50 = lethal dose, 50% kill; LDmin = minimum lethal dose; LOAEL = 

lowest -observable -adverse -effect level; M = male; mo = month(s); NOAEL = no-observable -adverse -effect level; NS = not specified; (0) = Oral; Resp = respiratory; wk = week(s); yr = year 

ENDRIN 36

 2. HEALTH EFFECTS 
25s 

8m 

1 

2r 

3r 4r 

5r 

6r 

7r 9g 11s 

10s 12s

26s 

13h 15r 

14c 16r 17r 

19r 20r 22m 24g 

21r 23m 

26s 

25s 

25s 

24g 

23m 

23m 

21r 

21r 

19r 22m

18r 

18r 

15r 

16r 
27r 28r 29r 

30m 

31s 

31s 33s 

34s 

35r 

38m 

39m 

40s 

41s 

41s 

42s 

43s 

37m 

29r 35r 36r 

32r 

37m 
44m 49m

46d 

46d 46d 46d 46d 46d 47d 45d 46d 

48r 50r 

46d 46d 46d 46d 46d 47d 46d 
51r 54r 54r 54r 62r 

55m 55m

53r 

52r 

53r 58d 55m 

53r 

58d 56d 

57d 

55m 

53r 

52r 

54r 

54r 

56d 57d 

55m 

52r 

54r 

53r 

57d 

58d 

53r 

54r 

55m 

53r 

55m 

53r 

54r 

52r 

58d 

56d 

55m 

59d 60r 

61r 

62r 

63m 

64d 65d 66d 67d 

56d 64d 
ENDRIN 41 

2. HEALTH EFFECTS 

al. 1955). The dogs were observed regurgitating their food and may have aspirated endrincontaminated 

material. Severe congestion and serofibrinous exudate were observed in the lungs of 

dogs that died apparently following ingestion of endrin-containing bait (Quick et al. 1989). 

No studies were located regarding respiratory effects in humans or animals following oral exposure to 

endrin aldehyde or endrin ketone. 

Cardiovascular Effects. No studies were located regarding cardiovascular effects in humans 

following oral exposure to endrin, or in humans or animals to endrin aldehyde or endrin ketone. 

Limited reports of cardiovascular toxicity of orally administered endrin in animals were located. Dogs 

exposed to 3 ppm endrin in feed (0.12-0.25 mg/kg/day) had significantly enlarged hearts 

(cardiomegaly), but similar effects were not found at 1 ppm (0.045-0.12 mg/kg/day). Dogs exposed to 

diets containing 5 ppm endrin (0.20-0.27 mg/kg/day) had diffuse degenerative lesions (Treon et al. 

1955). Conclusions cannot be drawn from this study due to the small number of animals used and the 

lack of details regarding the histopathology performed. No cardiovascular lesions were noted in rats 

and mice chronically exposed to endrin (NCI 1978). 

Gastrointestinal Effects. Nausea and vomiting were reported in people consuming endrincontaminated 

taquitos (Waller et al. 1992). Rats administered endrin exhibited diarrhea; however, no 

gastrointestinal lesions were reported for either rats or mice (NCI 1978). Dogs were observed to 

regurgitate food containing endrin at levels of 5 ppm (0.20-0.27 mg/kg/day) or greater, while endrin 

concentrations of 4 ppm (0.15-0.21 mg/kg/day) or less were not associated with this effect (Treon et 

al. 1955). 

No gastrointestinal effects from endrin ketone or endrin aldehyde in humans or laboratory animals 

were located. 

Hematological Effects. No hematological effects have been reported in humans exposed to 

endrin, endrin ketone, or endrin aldehyde. There were no changes in the relative numbers or in the 

types of formed elements in the peripheral blood of male and female Beagle dogs which were 

administered endrin in their diet for periods of 16.4-18.7 months (Treon et al. 1955). No 

hematological changes were observed in Beagles administered 0.0025-0.1 mg/kg/day for 2 years or in 

Beagles administered 0.003-0.059 mg/kg/day for 64-l 56 weeks (Kettering 1971).
 
ENDRIN 42 

2. HEALTH EFFECTS 

Hepatic Effects. No studies were located regarding hepatic effects in humans following oral 

exposure to endrin, endrin aldehyde, or endrin ketone. 

In a study by Ali and Shakoori (1993), female Sprague-Dawley rats were dosed with a diet containing 

a diluted 20% emulsifiable concentrate of endrin. The average endrin intake was calculated by the 

authors of the study to be 8.2 mg/kg/day. One group (4 animals) was sacrificed 24 hours after 

treatment began, and the other at 48 hours after treatment began. At sacrifice, the animals were 

weighed, and their livers removed and weighed, and a representative hepatic tissue sample collected 

for histopathological analysis. Endrin treatment did not significantly affect relative liver weights. At 

24 hours, endrin exposure caused significant increases of alkaline phosphatase (AP), glutamate 

oxaloacetate transaminase (GOT), and glutamate pyruvate transaminase (GPT) (48, 82, and 55%, 

respectively), relative to controls; at 48 hours, AP (p<0.0), GOT (p<0.00) and GPT (p<0.01) were 

increased 69, 97, and 71%, respectively, relative to controls. Endrin exposure also resulted in a 

significant increase (65%) in isocitrate dehydrogenase (ICDH; p<0.05) at 48 hours. Serum cholesterol 

increased by 27 and 35% at 24 and 48 hours, respectively (p<0.05); free amino acids decreased by 

34 and 40% at 24 and 48 hours, respectively (p<0.00l); and glucose decreased by 41 and 51% at 

24 and 48 hours, respectively (p<0.01 and p<0.001). Hepatic DNA and RNA content was not 

significantly affected by endrin exposure. Histologically, significant alterations were noted in the liver 

at 48 hours. The prominent alterations included hepatic cell hypertrophy, dilation of sinusoidal spaces, 

zonal disorganization/degeneration, vacuolization, and fatty infiltration. 

A time- and dose-related increase in relative liver weight was observed in rats administered 3-6 mg/kg 

endrin (Bagchi et al. 1992a, 1992b, 1992c); however, no significant changes in absolute or relative 

liver weight were noted for rats 24 hours after oral administration of 4 mg/kg endrin (Numan et al. 

1990a). Maternal liver enlargement (increased relative liver weight) occurred in pregnant mice 

administered 0.5 mg/kg/day of endrin during gestation (Kavlock et al. 1981). Liver weight was 

unaffected in pregnant hamsters and rats at doses up to 3.5 or 0.45 mg/kg/day, respectively (Chernoff 

et al. 1979a; Kavlock et al. 1981). Rats, mice, and guinea pigs administered 4 mg/kg endrin and 

sacrificed 24 hours later exhibited moderate hepatic necrosis, fatty degeneration (rats), and 

inflammation; lipofuscin deposits were also observed in hepatocytes and Kupffer cells (Hassan et al. 

1991). Similar changes were observed in control and endrin-treated hamsters; however, the severity 

was increased in the treated animals, and only livers from treated animals had lipofuscin pigment 

deposits associated with lipid peroxidation (Hassan et al. 1991). Congestion and serofibrinous exudate 
ENDRIN 43 

2. HEALTH EFFECTS 

were observed in the livers of dogs that died apparently following ingestion of endrin-containing bait 

(Quick et al. 1989). Minor histologic changes (cloudy swelling of centrilobular cells) were described 

in rats administered 2 ppm (0.1 mg/kg/day); the mean survival rate was 18.1-20.8 months (Deichman 

et al. 1970). 

Serum enzyme levels were not significantly increased in rats exposed to 5 ppm (0.5 mg/kg/day) of 

endrin in the diet for 15 days (Young and Mehendale 1986), although alterations in hepatobiliary 

function, as measured by phenolphthalein glucuronide or bile flow, were reported (males decreased, 

females increased). During the third month of exposure, livers of rats exposed to 3.5 mg/kg/day of 

endrin appeared spotty with zones of basophilic cells around the central and portal veins (Speck and 

Maaske 1958). Diffuse degeneration of the livers of rats fed 25 ppm or more endrin in the diet 

(t1.25 mg/kg/day) for intermediate- and chronic-duration was reported by Treon et al. (1955). This 

effect not only occurred in the rats killed by endrin, but also in survivors. The diffuse degeneration 

observed in other organs was only seen in animals killed by endrin. Dogs fed lethal concentrations of 

5 ppm or more (0.20-0.27 mg/kg/day) of endrin also had degenerative lesions of the liver, and in 

some cases, fatty vacuolization occurred (number not specified); hepatic changes were not reported at 

levels of 4 ppm (0.15-0.21 mg/kg/day) or less (Treon et al. 1955). Slight vacuolization of hepatic 

cells and slightly increased relative liver weights were observed in dogs fed 2 ppm (0.05 mg/kg/day) 

and 4 ppm (0.1 mg/kg/day) for 2 years (Kettering 1969). No significant increase of nonneoplastic 

hepatic lesions was observed in rats or mice chronically administered endrin in a bioassay (NCI 1978) 

and in female Beagles administered endrin doses as high as 0.059 mg/kg/day for 64-156 weeks 

(Kettering 1971). 

Dietary exposure of rats to 10 ppm (0.5 mg/kg/day) endrin aldehyde or 5 ppm (0.25 mg/kg/day) endrin 

ketone for 15 days resulted in slight elevations (p<0.05) in SGPT and SGOT (Young and Mehendale 

1986). However, no alterations in liver weight or in hepatobiliary function, as measured by 

phenolphthalein glucuronide or bile flow, were reported. 

Hassoun et al. (1993) examined the effects of various pesticides on lipid peroxidation and DNA single 

strand breakage in the hepatic cells of female Sprague-Dawley rats. Animals were dosed orally once 

with endrin at 4.5 mg/kg, lindane at 30 mg/kg, chlordane at 120 mg/kg, or DDT (dichlorodiphenyl 

trichloroethane) at 40 mg/kg, or vehicle only (corn oil, control). At 6, 12, and 24 hours post-dosing, 

4 animals from each group were sacrificed, their livers removed, and prepared for lipid peroxidation 
ENDRIN 44 

2. HEALTH EFFECTS 

assay. Lipid peroxidation was measured calorimetrically by determining the amount of thiobarbituric 

acid reactive substances (TBARS) formed. Exposure to endrin resulted in a 14.5% increase in hepatic 

mitochondrial lipid peroxidation, compared to controls, beginning at 6 hours (6.99 + 0.20 versus 

6.10 + 0.36; p<0.05). Statistically significant (28%) increases in hepatic microsomal lipid peroxidation 

were also noted in endrin-treated animals beginning at 12 hours (4.98 + 0.48 versus 3.89 + 0.48; 

p<0.05). Lipid peroxidation remained elevated in both subcellular fractions through 24 hours, when 

the greatest differences were seen. The authors concluded that single doses of endrin are associated 

with induction of hepatic lipid peroxidation and suggest that reactive oxygen species and free radicals 

are involved in the pathology of endrin. 

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

to endrin, or in humans or animals to endrin aldehyde or endrin ketone. Rats and mice administered 

4 mg endrin/kg body weight and killed 24 hours later exhibited moderate tubular necrosis and 

congestion, inflammation, and interstitial edema. Hamsters and guinea pigs (4 mg/kg body weight, 

killed 24 hours later) exhibited similar changes without inflammation; cloudy swelling of cells and 

narrowing of tubular lumina were the only changes observed in exposed guinea pigs (Hassan et al. 

1991). Severe congestion and serofibrinous exudate were observed in the kidneys of dogs that died 

following apparent ingestion of endrin-containing bait (Quick et al. 1989). In animal studies, there 

was diffuse degeneration of the kidneys of dogs and rats administered lethal concentrations of endrin 

in the diet (Treon et al. 1955). Dogs exposed to 3 ppm endrin in feed (0.12-0.25 mg/kg/day) had 

enlarged kidneys. No effects were observed at 1 ppm ( 0.15 mg/kg/day). The renal damage in dogs 

was severe at a higher dose (5 ppm or 0.20-0.27 mg/kg/day) and was characterized by necrosis of the 

convoluted tubules (Treon et al. 1955). Cloudy swelling of tubule epithelial cells was also observed in 

rats chronically exposed to 2 ppm in the diet (0.1 mg/kg/day) (Deichmann et al. 1970). Renal effects 

were not observed in the NCI (1978) bioassay of mice and rats; however, discolored urine was 

reported in rats administered >2.5 ppm (>0.13 mg/kg/day). 

Endocrine Effects. Thyroid hyperplasia and pituitary cysts were observed in rats, but not mice, in 

a chronic bioassay study with endrin administered in the feed (NCI 1978). Treon et al. (1955) found 

diffuse degeneration of the adrenal glands in rats dosed with >1.25 mg/kg/day in their feed for 2 years; 

however, the adrenal effects were absent at the 0.25 mg/kg/day dose. There has been no evidence of 

endocrine effects in occupationally exposed human populations. 
 

ENDRIN 45 

2. HEALTH EFFECTS 

No endocrine effects have been reported for endrin aldehyde or endrin ketone in humans or in 

laboratory animals. 

Dermal Effects. Chronic administration of endrin in feed resulted in dermatitis in rats and alopecia 

in both rats and mice (NCI 1978). There has been no evidence of dermal effects in occupationally 

exposed populations. 

No dermal effects have been reported for endrin aldehyde or endrin ketone in humans or in laboratory 

animals. 

Body Weight Effects. Decreased body weight or body weight gain has been observed in 

numerous species following endrin exposure and was usually associated with administration of high 

doses (Chemoff et al. 1979a; Goldenthal 1978a; Kavlock et al. 1981; Treon et al. 1955). Effects on 

body weight were not observed in one acute-duration study (Ali and Shakoori 1993), in chronicduration 

rodent toxicity studies (Deichmann et al. 1970; NCI 1978), or in chronic-duration studies in 

dogs at a dietary level of 0.12-0.25 mg/kg/day (3 ppm) (Treon et al. 1955). A significant reduction 

(14-17%) in weight gain was noted in male rats exposed to 1.25 mg/kg/day of endrin in feed for 

2 years, but not in female rats exposed to levels as great as 5 mg/kg/day by the same route and 

duration (Treon et al. 1955). 

No body weight effects have been reported for endrin aldehyde or endrin ketone in humans or in 

laboratory animals. 

2.2.2.3 Immunological and Lymphoreticular Effects 

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

exposure to endrin, or in humans and animals after oral exposure to endrin aldehyde or endrin ketone. 

Time- and dose-related increases in spleen-to-body weight ratios were observed in rats administered a 

single oral dose of 1.5-6 mg endrin/kg body weight, while relative thymus weights were decreased 

(Bagchi et al. 1992b, 1992c). Concurrent control groups, in which animals received the same 

experimental handling as treated animals, were not included for comparison of organ weights over 

time. There were no effects on spleen weight of male and female Beagle dogs who were administered 
ENDRIN 4 6 

2. HEALTH EFFECTS 

0.025-0.075 mg/kg/day (1-3 ppm) endrin in their diet for periods of 16.4-18.7 months (Treon et al. 

1955). 

2.2.2.4 Neurological Effects 

Poisoning episodes in humans show that the central nervous system is the primary target system of 

orally administered endrin. Acute human poisonings by endrin-contaminated food caused symptoms of 

central nervous system toxicity such as jerking of arms and legs, tonic-clonic contractions, 

convulsions, and sudden collapse and death (Carbajal-Rodriquez et al. 1990; Coble et al. 1967; Davies 

and Lewis 1956; Rowley et al. 1987; Waller et al. 1992; Weeks 1967). 

Neurological effects are commonly observed in animals exposed to endrin. Beagle dogs which had 

apparently ingested endrin-containing bait exhibited tetanic convulsions (Quick et al. 1989). Death 

occurred within 45 minutes of the onset of convulsions in 5 of 8 dogs (and later for an additional 2 of 

8 dogs). Tremors and convulsions were noted in rats administered endrin at 5 mg/kg for 3 days 

(Mehorta et al. 1989) or following single high doses (Gaines 1960). Decreased activity levels were 

observed in pregnant mice (1.5 mg/kg/day) and pregnant rats (0.5 mg/kg/day) acutely administered 

endrin during gestation. Rats administered 4 mg/kg/day suffered convulsions (Kavlock et al. 1981). 

Convulsions were also observed in one of 30 golden Syrian hamsters administered 10 mg/kg endrin on 

gestation day 8 (Chemoff et al. 1979a). Hyperirritability to stimuli, tremors, convulsions, and ataxia 

occurred in 3 species of animals (dog, rat, and rabbit) administered endrin for acute, intermediate, and 

chronic durations (Treon et al. 1955). 

Rats administered 3.5 mg/kg/day of endrin for one week exhibited excitability and convulsions, in 

addition to irregular EEG recordings. The EEG changes resolved after exposure for two weeks. At 

three months of exposure, convulsions could be triggered by noise, and after exposure for seven 

months, convulsions were readily started (Speck and Maaske 1958). Hyperexcitability was observed in 

male mice administered 3.2 ppm (0.21 mg/kg/day) of endrin in feed for 80 weeks; however, no 

histologic changes in the brain were found. No clinical signs of neurotoxicity or brain lesions were 

observed in a similar study with rats (NCI 1978). Deichmann et al. (1970) reported episodes of 

tremors and clonic convulsions in rats fed endrin in the diet for 17.6-20.8 months at concentrations 

of 2-12 ppm (0.1-0.6 mg/kg/day). A dog exposed to 5 ppm endrin in the diet (0.20-0.27 mg/kg/day) had 

convulsions, tremors, and diffuse degenerative lesions of the brain; the animal died after 47 days 
ENDRIN 4 7 

2. HEALTH EFFECTS 

of feeding. A dietary level of 4 ppm (0.15-0.21 mg/kg/day) was not associated with these effects 

(Treon et al. 1955). Based on these findings, an intermediate oral MRL value of 0.002 mg/kg/day was 

calculated for endrin as described in the footnote of Table 2-2. Beagle dogs administered 2 ppm 

(0.05 or 0.059 mg/kg/day) or 4 ppm (0.1 mg/kg/day) endrin in the diet showed evidence of, or were 

observed having, convulsions (Kettering 1969, 1971). Petechial hemorrhages and cerebral edema were 

observed in the brain of one dog having convulsions at the time of death. Based on these findings, a 

chronic oral MRL value of 0.0003 mg/kg/day was calculated for endrin as described in the footnote of 

Table 2-2. 

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

endrin aldehyde or endrin ketone. 

2.2.2.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans after oral exposure to endrin, or in 

humans and animals to endrin aldehyde or endrin ketone. 

In a 3-generation reproduction study, inbred weanling rats were administered endrin-containing diets at 

0, 0.1, 1, or 2 ppm (0.0, 0.005, 0.05, or 0.1 mg/kg/day, respectively) (Eisenlord et al. 1968). There 

were no effects on indices of fertility, gestation, viability, or lactation. Interpretation of the study 

results is confounded by the potential presence of infection in controls and, thus, possibly in all 

animals in the study. 

In a single generation reproduction study, groups of 3 female Beagle dogs were administered 0, 0.1, 

0.5, 1, or 2 ppm (0.0, 0.003, 0.014, 0.027, or 0.059 mg/kg/day, respectively) endrin in the feed and 

mated with endrin-treated males from a concurrent chronic toxicity study (Kettering 1971). Four 

treated females (1 each at 0.014 and 0.027 mg/kg/day and 2 at 0.059 mg/kg/day) never accepted a 

male and, despite artificial insemination, did not become pregnant. Exploratory laparotomies and 

necropsies, and microscopic examination of ovaries and uteri at termination of these dogs revealed no 

specific changes due to endrin. The failure to conceive in the high-dose groups could suggest an 

endrin-mediated effect on fertility. It was concluded that dietary levels of endrin up to 2 ppm 

(0.59 mg/kg/day) had no effect on reproduction. However, the low number of animals, presence of a 
ENDRIN 48 

2. HEALTH EFFECTS 

Brucella canis infection, and failure of 2 of 3 control dogs to bring any pups to weaning confounds 

interpretation of the study. 

Groups of male and female CFW Swiss mice were given diets containing 5 ppm endrin for 120 days 

beginning 30 days before mating (Good and Ware 1969). There were deaths among one-third of the 

treatment pairs. There was a significant reduction in the size of the first litter, as well as all litters 

combined, but no significant change in the days to produce a litter. Endrin treatment did not have any 

effect on fertility or fecundity, but was associated with fetal mortality. 

In mallard ducks, dietary administration of endrin (0.5 or 3 ppm) had no effects on egg production, 

fertility, and ability to hatch, or 14-day hatchling survival, although a 9.6% drop in embryo survival 

was observed at the high dose (Roylance et al. 1985). 

Results of developmental toxicity studies (see Section 2.2.2.6) in rodents suggest endrin can adversely 

affect pregnancy outcomes. There was reduced survival of pups in hamsters exposed to a single dose 

of 5 mg/kg (38% mortality, 3% in untreated controls) during the eighth gestation day (Ottolenghi et al. 

1974). 

2.2.2.6 Developmental Effects 

No studies were located regarding developmental effects after oral exposure to endrin in humans, or in 

humans and animals to endrin aldehyde or endrin ketone. 

Developmental effects of endrin have been observed in hamsters and in mice. A statistically 

significant increase in the incidence of fused ribs and cleft palate was observed in fetuses from golden 

Syrian hamsters treated on gestation day 7, 8, or 9 with 5 mg/kg of endrin (0.5 LD50 dose). A 

significant increase in open eye and webbed foot occurred only in fetuses from mothers treated on 

day 8 (Ottolenghi et al. 1974). A single dose of endrin administered to hamsters on gestation day 8 

produced meningo-encephaloceles at a dose of 5 mg endrin/kg body weight and fused ribs at doses 

above 5 mg/kg (Chemoff et al. 1979a). Hamsters intubated with 1.5 mg/kg/day of endrin on gestation 

days 5-14 had pups that remained more active than controls through 125 days of age (Gray et al. 

1981). However, the 1.5 mg/kg/day dose killed more than half of the dams. Endrin was not 

teratogenic in a study in which pregnant hamsters were administered up to 2.5 mg/kg/day on gestation 
ENDRIN 49 

2. HEALTH EFFECTS 

days 4-13; slightly reduced maternal body weight gain was noted during treatment at 2.5 mg/kg/day 

(Goldenthal 1978b). 

Exposure of mice to 2.5 mg/kg on gestation day 9 resulted in significantly increased incidence of 

open eyes and cleft palate (Ottolenghi et al. 1974). No dose-related evidence of open eyes and cleft 

palate was seen in mice intubated with 1.5 mg/kg/day on gestation days 7-17 (Kavlock et al. 1981). 

Exencephaly (2 fetuses from 1 litter affected) and fused ribs (3 fetuses from 1 litter) were seen in 

offspring of pregnant mice treated with 7 or 9 mg/kg of endrin on gestation day 8 (Kavlock et al. 

1985); controls had 2 fetuses affected (2 litters) with exencephaly. 

No developmental effects were observed in rats administered 0.45 mg/kg/day of endrin on gestation 

days 7-20 (Kavlock et al. 1981). In a similar study with mice, there was a dose-related decrease in 

fetal body weight. There were no dose-related indications of skeletal or visceral anomalies in the 

mice, but delays in development were reflected in changes in the number of caudal vertebrae, 

development of the renal pelvis, and ossification of the supraoccipital bones (Kavlock et al. 1981). 

Increased incidences of supernumerary ribs were noted in the offspring of CD-1 mice administered a 

single 7 mg/kg endrin dose during gestation day 8 (Kavlock et al. 1985). Irregularly shaped 

supraoccipital bones, visceral abnormalities, a 2-fold increase in fetal mortality and a 30% decrease in 

fetal weight were also noted in golden Syrian hamster pups whose mothers received 1.5 mg/kg/day 

endrin administered by gavage in corn oil on gestation days 5-14. Gray et al. (1981) reported 

increased locomotor activity in CD rats exposed perinatally to 0.15 mg/kg/day of endrin; the increased 

activity disappeared by 90 days of age. Administration of 2 mg/kg/day endrin to pregnant female rats 

on gestation days 6-15 resulted in maternal death, decreased maternal body weight gains during 

treatment, and an increase in delayed ossification of stemebrae and skull in fetuses (Goldenthal 1978a). 

In a 3-generation reproduction study, weanling rats were administered endrin-containing diets at 0, 0.1, 

1, or 2 ppm (0.0, 0.005, 0.05, and 0.1 mg/kg/day, respectively) (Eisenlord et al. 1968). There were no 

effects on indices of fertility, gestation, viability, or lactation. The number of pups in the F3a litter of 

the high dose group was significantly increased relative to controls (11.2 versus 9.2; p=0.05), while 

F3a pup body weight in the low dose group was significantly decreased (87% of control; p=0.05). The 

21-day survival of F3a (0.005 mg/kg/day) and F3b, litters (all dose groups) was elevated compared with 

controls due to unexpectedly high mortality in the control group which was attributed to a putative 
ENDRIN 50 

2. HEALTH EFFECTS 

viral pneumonitis. Interpretation of the study results is confounded by the potential presence of 

infection in controls and, thus, possibly in all animals in the study. 

In a single generation reproduction study, groups of 3 female Beagle dogs were administered 0, 0.1, 

0.5, 1, or 2 ppm (0, 0.003, 0.014, 0.027, and 0.059 mg/kg/day, respectively) endrin in the feed and 

mated with endrin-treated males from a concurrent chronic toxicity study (Kettering 1971). There 

were no organ weight or morphologic changes in pups from endrin-treated females. However, the low 

number of treated animals, presence of a Brucella canis infection, and failure of 2 of 3 control dogs to 

bring any pups to weaning confounds interpretation of the study. 

2.2.2.7 Genotoxic Effects 

No studies were located regarding genotoxic effects in humans after oral exposure to endrin, or in 

humans or animals after exposure to endrin aldehyde or endrin ketone. 

In single dose oral studies with rats, endrin treatment was associated with an increased incidence 

(2.4-3.5-fold) in the number of DNA single strand breaks in hepatocytes (Bagchi et al. 1992a, 1993a, 

1993c; Hassoun et al. 1993). DNA damage was attributed to oxidative injury caused by endrin. 

Genotoxicity studies are discussed in Section 2.5. 

2.2.2.8 Cancer 

Endrin was found not to be carcinogenic in Osborne-Mendel rats and B6C3F1 mice under the 

conditions of a National Cancer Institute bioassay (NCI 1978). This conclusion is consistent with 

previously reported studies concerning endrin carcinogenicity in rats and mice. All reported studies, 

however, have study design limitations that make them inadequate for assessing the potential 

carcinogenicity of endrin in humans. 

Osborne-Mendel rats administered 0, 1, 3, or 6 ppm endrin in feed for 10 weeks, and then 0, 2, 6, or 

12 ppm endrin for an additional 106 weeks, had incidences of malignancies that were similar to 

control animals (Deichmann et al. 1970). The authors concluded that endrin was not carcinogenic or 
ENDRIN 51 

2. HEALTH EFFECTS 

tumorigenic. Not all tissues were examined microscopically, however, limiting the conclusi,ons that 

can be drawn from this study. 

An NCI bioassay (NCI 1978) administered time-weighted average (TWA) doses of 1.6-5 ppm endrin 

in feed to B6C3F1 mice and 2.5-6 ppm in feed to Osborne-Mendel rats for 80 weeks. No 

significantly increased incidence of tumors in treated animals was reported, but the study is limited by 

the less-than-lifetime dosing regime. 

The only positive carcinogenic effects of endrin were reported by Reuber (1978). Osborne-Mendel 

male and female rats fed 0, 0.1, 1, 5, 10, or 25 ppm endrin in the diet for 104 weeks developed high 

incidences of sarcoma and carcinomas (male rats at 0.1 ppm and females at 0.1 or 1 ppm). Treated 

rats of both sexes developed tumors in other sites, including the lungs, lymph nodes, thyroid, and renal 

cortex. However, Reuber’s criteria for classifying tissues as tumorigenic are not consistent with those 

of other investigators (EPA 1979f). 

Using EPA guidelines for classification of carcinogens, EPA has classified endrin in Group D, 

indicating there is inadequate evidence to assess the potential carcinogenicity of endrin in humans 

(IRIS 1994). The International Agency for Research on Cancer (IARC) (1974) has not evaluated the 

carcinogenic potential of endrin. 

No studies were located regarding carcinogenic effects in humans or animals after oral exposure to 

endrin aldehyde or endrin ketone. 

2.2.3 Dermal Exposure 

Although no dermal studies per sewere found regarding human exposure to endrin, several 

occupational exposure studies exist (Ditraglia et al. 1981; Hoogendam et al. 1962, 1965; Ribbens 

1985; Versteeg and Jager 1973). Wolfe et al. (1963) has shown that dermal exposure in the 

agricultural setting is significant. Therefore, the results of the occupational exposure studies, which 

are summarized in the inhalation exposure section (2.2.1), may be relevant to dermal exposure 

scenarios and, where appropriate, are briefly noted below. 
ENDRIN 52 

2. HEALTH EFFECTS 

Limited data are available regarding dermal exposure of animal to. endrin. Results of these studies are 

discussed below and presented in Table 2-3. 

2.2.3.1 Death 

No studies were located regarding lethal effects in humans after dermal exposure to endrin or in 

humans or animals after dermal exposure to endrin aldehyde or endrin ketone. 

A minimum lethal dose of 94 mg/kg body weight was reported for rabbits (1 of 3 died) exposed 

dermally to crystalline 100-mesh endrin powder for 24 hours (Treon et al. 1955). Convulsions were 

also reported. Similarly, 1 of 3 or 1 of 4 female rabbits exposed to daily doses of endrin ranging from 

20 to 42 mg/kg/day died after repeated dermal exposures to abraded or intact skin, and 3 of 3 died 

following exposure of intact skin to 67-91 mg/kg (Treon et al. 1955). Convulsions, tremors, and 

facial twitching were the chief signs of intoxication. The dermal LD50 for endrin in xylene was 

similar in male (18 mg/kg; minimum lethal dose 10 mg/kg) and female (15 mg/kg) rats (Gaines 1960, 

1969). Topical application of 75 mg/kg to a cat resulted in death 22 days later (Ressang et al. 1959). 

Topical application of a concentrated solution of endrin to 4 bullocks for tick infestation caused death 

in one bullock within 6 hours after exposure (Pandey 1978). 

2.2.3.2 Systemic Effects 

Studies regarding the systemic effects that have been observed in humans and animals after dermal 

exposure to endrin are discussed below. With regard to potential dermal effects, no reports of 

irritative effects have appeared in the medical or industrial hygiene literature despite several decades of 

use by hundreds of workers. No reliable studies were located regarding respiratory, cardiovascular, 

gastrointestinal, hematological, musculoskeletal, endocrine, dermal, ocular, or body weight effects in 

humans or animals after dermal exposure to endrin, endrin aldehyde, or endrin ketone. 

Hepatic Effects. No studies were located regarding hepatic effects in humans after dermal 

exposure to endrin. Rabbits fatally poisoned by an acute dermal endrin dose of 94 mg/kg body weight 

and higher had centrilobular degeneration of the liver (Treon et al. 1955). Details regarding the 

histopathology of the lesions were not provided, and only a small number of animals were tested. 

Rabbits surviving multiple skin applications exhibited severe fatty degeneration of the liver. 
Table 2-3. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Dermal 

Species

(Strain) 

Exposure/

Duration/

Frequency 

(Specific Route) System 

NOAEL 

(mg/kg) 

Less Serious 

(mg/kg) 

LOAEL 

Serious 

(mg/kg) 

Reference 

Chemical Form 

ACUTE EXPOSURE 

Death 

Rat 

(Sherman) 

once 15 F (LD50) Gaines 1960 

Endrin 

Rat 

(Sherman) 

once 10 M (LDmin) Gaines 1969 

Endrin 

Rabbit 

(NS) 

Cat 

(NS) 

Systemic 

Rabbit 

(NS) 

24 hr 

once 

24 hr Hepatic 

Renal 

Dermal 3600 F 

94 F (1/3 rabbits died) 

75 (death; 50%) 

94 F (centrilobular liver necrosis) 

94 F (degenerative changes) 

Treon et al. 1955 

Ressang et al. 1959 

Endrin 

Endrin 

Treon et al. 1955 

Endrin 

Neurological 

Rabbit 24 hr 

(NS) 

94 F (convulsions, diffuse brain 

necrosis) 

Treon et al. 1955 

Endrin 

ENDRIN 22

 2. HEALTH EFFECTS 
 

Table 2-3. Levels of Significant Exposure to Endrin/Endrin Aldehyde - Dermal (continued) 

Exposure/ LOAEL

Duration/

Species Frequency NOAEL Less Serious Serious Reference 

(Strain) (Specific System Route) (mg/kg) (mg/kg) (mg/kg) Chemical Form 

INTERMEDIATE EXPOSURE 

Death 

Rabbit 25-45x total, 2744 F (1/4 rabbit died) Treon et al. 1955 

(NS) 5 d/wk Endrin 

2 hr/d 

Rabbit 19 -70 x 2042 F (1/3 rabbits died) Treon et al. 1955 

(NS) total, Endrin 

5 d/wk 

2 hr/d 

Systemic 

Rabbit 19-70 x Hepatic 20-42 F (fatty degeneration) Treon et al. 1955 

(NS) total, Endrin 

Renal 5 d/wk 20-42 F (degenerative changes) 2 hr/d 

Dermal 67-91 F 

Neurological 

Rabbit 19-70 x 20-42 F (convulsions, tremors, Treon et al. 1955 

(NS) total, twitching of facial muscles, Endrin 

5 d/wk brain necrosis) 

2 hr/d 

d = day(s); F = female; hr = hour(s); LOAEL = lowest -observable -aderse -effect level; M = male; LD50 = lethal dose, 50% kill; LDmin= minimum lethal dose; NOAEL = 

no-observable -adverse -effect level; NS = not specified; wk = week(s); x = times 

ENDRIN 22

 2. HEALTH EFFECTS 
ENDRIN 55 

2. HEALTH EFFECTS 

No studies were located regarding hepatic effects in humans or animals after dermal exposure to 

endrin aldehyde or endrin ketone. 

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

endrin. Diffuse degenerative changes of the kidney occurred in rabbits exposed dermally to lethal 

doses of endrin once or for an intermediate duration (Treon et al. 1955). No studies were located 

regarding renal effects in humans or animals after dermal exposure to endrin aldehyde or endrin 

ketone. 

Dermal Effects. No studies were located regarding the dermal effects in humans after dermal 

exposure to endrin. No damage to the skin at the site of application was observed in rabbits exposed 

to a single or repeated dermal application of dry endrin (Treon et al. 1955); however, the rabbits had 

convulsions. 

No studies were located regarding the dermal effects in humans or laboratory animals after dermal 

exposure to endrin aldehyde or endrin ketone. 

2.2.3.3 Immunological and Lymphoreticular Effects 

No studies were located regarding immunological or lymphoreticular effects in humans or animals 

after dermal exposure to endrin, endrin aldehyde, or endrin ketone. 

2.2.3.4 Neurological Effects 

No studies were located regarding neurological effects in humans after dermal exposure to endrin or in 

humans or animals to endrin aldehyde or endrin ketone. 

Uncontrolled exposure to endrin caused twitching and jerking of muscles, dizziness, mental confusion, 

and epileptiform seizures occurring within 2 hours following occupational exposure (Hoogendam et al. 

1962, 1965). Clinical recovery was apparent within l-3 days, and abnormal EEGs (predominantly 

bilateral synchronous theta waves and synchronous spike and wave complexes) generally returned to 

normal within 0.5-l month. Convulsions, tremors, and/or twitching of the facial muscles were the 

chief signs of intoxication of rabbits and rats exposed dermally to endrin (Gaines 1960; Treon et al. 
ENDRIN 56 

2. HEALTH EFFECTS 

1955). Diffuse degenerative lesions of the brain were observed in rabbits that died (Treon et al. 1955). 

Convulsions, salivation, lachrymation, staggering gait, hypothermia, and shallow breathing were also 

recorded in bullocks treated topically with a concentrated endrin solution (Pandey 1978). 

No studies were located regarding the following health effects in human or animals after dermal 

exposure to endrin, endrin aldehyde, or endrin ketone: 

2.3.5 Reproductive Effects 

2.2.3.6 Developmental Effects 

2.2.3.7 Genotoxic Effects 

Genotoxicity studies are discussed in Section 2.5. 

2.2.3.8 Cancer 

Studies of workers in the endrin manufacturing industry have not shown an association between 

occupational exposure to endrin and any type of human cancer (Ribbens 1985; Versteeg and Jager 

1973). In a study of four U.S. industries, two of which manufactured endrin, slight excesses of cancer 

of the esophagus, rectum, and liver, and cancer of the lymphatic and hematopoietic systems were 

reported (Ditraglia et al. 1981). Although the excesses were not statistically significant and were 

based on small numbers of deaths, it may prove useful to follow these workers and reexamine their 

mortality patterns. 

No studies were located regarding carcinogenic effects in animals after dermal exposure to endrin or in 

humans or animals after exposure to endrin aldehyde or endrin ketone. 

2.3 TOXICOKINETICS 

To date, very little quantitative data exist regarding the toxicokinetics of endrin and its metabolites. 

Limited data were found regarding the absorption, distribution, metabolism, and excretion of endrin in 

humans and animals after inhalation, oral, or dermal exposure, which is especially relevant to 
ENDRIN 57 

2. HEALTH EFFECTS 

occupational exposure scenarios. Endrin appears to be well absorbed orally, and distribution is 

primarily to fat and skin. Endrin is excreted in urine and feces, and the major biotransformation 

product is anti-l 2-hydroxyendrin and the corresponding sulfate, and glucuronide metabolites. No 

studies were found that described the toxicokinetics of endrin aldehyde or endrin ketone. 

2.3.1 Absorption 

2.3.1.1 Inhalation Exposure 

Quantitative data describing the rate of absorption of endrin following inhalation exposure were not 

available. Cases of occupational exposure reported by Hoogendam and coworkers (1965) and 

laboratory animal studies reported by Treon et al. (1955) indicate that when endrin is inhaled and 

absorbed it can produce serious adverse biological effects. 

2.3.1.2 Oral Exposure 

Case studies reported that ingested endrin is absorbed by humans (Coble et al. 1967; Curley et al. 

1970; Kintz et al. 1992; Rowley et al. 1987; Runhaar et al. 1985; Weeks 1967). No studies have been 

located which report the rate or extent of absorption that occurs in orally exposed humans or animals. 

2.3.1.3 Dermal Exposure 

No studies were located regarding absorption of endrin in humans after dermal exposure. Agricultural 

worker exposure studies demonstrated that dermal exposure (18.7 mg/hour without gloves) was 

significantly greater than respiratory exposure (0.41 mg/hour) and that workers exposed to endrin 

received about 0.2-1.5% of a toxic dose per hour of exposure. No adverse effects were reported in 

the worker cohort (Wolfe et al. 1963). 

Dermal exposure of rats and rabbits to endrin resulted in toxicity and death (Gaines 1960; Treon et al. 

1955), indicating that percutaneous absorption of endrin occurs. It is likely that occupational 

poisonings reported by Hoogendam et al. (1962, 1965) also involved dermal absorption, but the extent 

and relative contribution of dermal exposure cannot be determined. Data describing the rate or extent of dermal 

absorption were not located. 
 

ENDRIN 58 

2. HEALTH EFFECTS 

2.3.2 Distribution 

2.3.2.1 Inhalation Exposure 

No studies were located regarding distribution of endrin in humans or animals after inhalation 

exposure. 

2.3.2.2 Oral Exposure 

Measurable levels of endrin have not been found in adipose tissue of the general population (Stanley 

1986; Williams et al. 1984). Measurable tissue concentrations of endrin have been observed in cases 

of acute poisoning. The time of sample collection is critical as endrin residues in tissues decline 

rapidly after exposure has ceased. 

A patient who consumed endrin-contaminated bread had serum levels of endrin of 0.053 ppm 

(0.053 mg/L); no endrin was detected in cerebrospinal fluid. The sample was taken 30 minutes after a 

convulsion (Coble et al. 1967). In another bread poisoning incident, blood from patients hospitalized 

with acute symptoms contained 0.007-0.032 ppm of endrin. Tissues taken at autopsy (elapsed time 

not specified) contained endrin at the following concentrations: stomach wall, 0.16 ppm; liver, 

0.685 ppm; and kidney, 0.116 ppm (Curley et al. 1970). 

In a poisoning incident in Pakistan, patients with convulsions (sampling time not specified) had 

measurable blood levels of endrin ranging from 0.0003 to 0.254 ppm (Rowley et al. 1987). Tissues of 

a suicide victim contained the following concentrations of endrin 11 days after ingestion of 12 g of 

endrin in a formulation product: 0.07 mg/L in blood, 89.5 mg/kg in adipose tissue, 0.87 mg/kg in 

heart, 0.89 mg/kg in brain, 0.55 mg/kg in kidneys, and 1.32 mg/kg in liver (Runhaar et al. 1985). 

Autopsy tissues and other biologic specimens from people fatally poisoned with endrin (by the oral or 

an unspecified route) were analyzed (Tewari and Sharma 1978). The “fatal period” (presumed to be 

the time from onset of symptoms until death) for the subjects studied ranged from 1 to 6 hours. As is 

characteristic of oral administration, highest tissue concentrations were observed in the stomach 

(1.04-14.5 mg/l00 g), intestine (1.31-66 mg/l00 g), and liver (0.94-20 mg/l00 g), followed by 
ENDRIN 59 

2. HEALTH EFFECTS 

kidney, spleen, heart, and lung. Blood concentrations were low (0.43-0.85 mg/l00 g) compared to 

tissue concentrations. 

A 21-year-old woman was found dead after apparent ingestion of endrin dissolved in xylene; high 

concentrations of endrin were detected in the stomach contents (47,351 mg/L), blood (544.9 mg/L), 

and bile (780.5 mg/L) (Kintz et al. 1992). The large amount of endrin found in the blood was 

interpreted to reflect the short time between ingestion and death. 

Endrin tends to bioaccumulate in fat because of its high lipid solubility. Three days after an acute oral 

dose of 2.5 mg/kg body weight of radio-labeled endrin, the percentages of the administered dose in 

male rat organs were 1.2% in liver, 0.6% in kidney, 1.7% in fat, 2.3% in skin, and 12.2% in the 

carcass. Female rats retained higher concentrations in tissues: 2% of the dose in liver, 0.35% in 

kidney, 8% in fat, 4% in skin, and 28.2% in carcass (Hutson et al. 1975). Following administration of 

radio-labeled endrin to lactating cows, the highest tissue concentrations were in the fat (about 8% of 

the total dose). Residues in liver, muscle, kidneys, and fat primarily contained unchanged endrin 

(Baldwin et al. 1976). Endrin and 12-ketoendrin were detected in the maternal liver and fetal tissue of 

rats and hamsters administered endrin during gestation (Chernoff et al. 1979a; Kavlock et al. 1981). 

Concentrations of endrin in fetal tissue ranged from 2 to 8% of those measured in maternal livers, 

indicating that endrin can cross the placenta. In a dietary study with mallard ducks, treated females 

developed higher body fat content and greater accumulation of endrin in the fat than males (Roylance 

et al. 1985). Endrin was deposited in the eggs of treated females at about the dietary concentration of 

endrin in their feed (0.5 and 3 ppm). 

In Beagle dogs that had died after apparent ingestion of endrin-containing bait, the stomach contents 

contained 34-5,000 mg/kg endrin (Quick et al. 1989). The highest tissue concentrations were found in 

the fat (5.4-40 mg/kg), followed by liver (0.82-4.5 mg/kg), and brain (0.34-2.7 mg/kg). Lower 

concentrations were found in lung and muscle. Following administration of 0.1 mg/kg/day in the feed 

for 128 days, concentrations of endrin in the blood of Beagle dogs showed no accumulation over time 

(Richardson et al. 1967). At termination, there was no correlation between the concentration of endrin 

in blood with that in heart, pancreas, liver, kidney, spleen, and lung, although a trend of high 

concentrations in fat (250-760 ppb) and high concentrations in blood (1-8 ppb) were noted. Highest 

tissue concentrations of endrin were generally found in fat, followed by muscle (120-310 ppb), heart (125-170 

ppb), pancreas (87-280), liver (77-84 ppb), kidney (38-82 ppb), and lung (17-33 ppb). 
ENDRIN 60 

2. HEALTH EFFECTS 

Concentrations in the spleen were highly variable (7-2,620 ppb). Results from this study may be 

somewhat confounded by a potential feeding error, as dieldrin (being fed to a concurrent group) was 

detected in the blood and tissues of the three endrin-treated dogs. 

2.3.2.3 Dermal Exposure 

No studies were located regarding distribution of endrin in humans or animals after dermal exposure. 

2.3.3 Metabolism 

The metabolism of endrin varies among species, regardless of the route of exposure. In all species, 

oxidation of the methylene bridge in endrin (Compound I in Figure 2-3) to syn-, but mostly anti12-hydroxyendrin occurs (Compounds II and III), followed by dehydrogenation to 12-ketoendrin 

(Compound VI). Minor independent pathways involve the hydrolysis of the epoxide to a transdiol 

(Compound V in Figure 2-3), and hydroxylation of the C-3 position (Compound IV) (Bedford et al. 

1975b; Hutson 1981). Hydroxylation at C-3 and C-4 is inhibited by the presence of the bulky 

hexachlorinated fragment (Hutson 1981). 

Hydroxylated metabolites are conjugated as glucuronides and sulfates. The balance of products in this 

last step and their distribution between urine and feces distinguishes the metabolism between humans, 

rats, and rabbits (Baldwin and Hutson 1980; Bedford et al. 1975b; Hutson 1981; Hutson et al. 1975), 

as discussed in Section 2.3.4. Similarly, studies in lactating cows ingesting radio-labeled endrin in the 

diet for 21 days suggest metabolic pathways similar to those in rats and rabbits with apparent 

differences between the 3 species attributed more to differences in biliary versus renal excretion 

(Baldwin et al. 1976). 

In workers in pesticide manufacturing plants, anti-12-hydroxyendrin as the glucuronide and 

12-ketoendrin were found in both urine and feces (3 of 7 workers) (Baldwin and Hutson 1980). 

Anti- and syn-12-hydroxyendrin and 12-ketoendrin are more toxic in the rat than endrin itself. The 

hydroxyendrins are rapidly converted to the more toxic 12-ketoendrin, and this latter metabolite is most likely 

the toxic entity of endrin (Bedford et al. 1975a; Hutson et al. 1975). 

ENDRIN 62 

2. HEALTH EFFECTS 

2.3.4 Excretion 

2.3.4.1 Inhalation Exposure 

Anti-12-hydroxyendrin and 12-ketoendrin were detected in the feces of pesticide manufacturing 

workers and its glucuronide conjugate and 12-ketoendrin have been detected in the urine (Baldwin and 

Hutson 1980). In another study, the levels of anti-12-hydroxyendrin increased accompanied by a sharp 

rise in D-glucaric acid levels in 29 workers after 7 days of exposure (Ottevanger and Van Sittert 1979; 

Vrij-Standhardt et al. 1979). 

No studies were located regarding excretion of endrin in animals following inhalation exposure. 

2.3.4.2 Oral Exposure 

Measurements of human serum concentrations of endrin following incidents of acute poisoning 

indicate rapid decline in concentration after exposure (Coble et al. 1967; Rowley et al. 1987). 

The bulk of endrin metabolites excreted by rats are in the bile (Hutson et al. 1975) as glucuronides. 

Rabbits excrete l 4C-endrin in the urine as sulfates (Bedford et al. 1975b). Studies in lactating cows 

ingesting endrin in the diet for 21 days show that 14C-endrin is readily excreted as unchanged endrin 

in the milk, accounting for 2.5-4.3% of the total dose (Baldwin et al. 1976). Similarly, endrin has 

been detected in the milk of lactating women (Alawi et al. 1992; Bordet et al. 1993). Due to its 

lipophilic nature (partition coefficient [Logow]: 5.6), endrin was contained in the lipid portion of the 

milk. 

In rats, 55-57% of 14C-endrin was metabolized, mostly as the glucuronide of anti-12-hydroxyendrin, 

in the bile within 24 hours of dosing with 0.5-2.5 mg/kg (Hutson et al. 1975). Other minor 

components (<10%) were the glucuronides of 3-hydroxy- and 12-ketoendrin. Male rats eliminated 

69% of the radioactive label within 3 days and females eliminated 45%. The major metabolite in 

female rat urine was 12-hydroxyendrin-O-sulfate. Baldwin et al. (1970) also detected 9-ketoendrin in 

the urine of rats. 
ENDRIN 63 

2. HEALTH EFFECTS 

There is a sex difference in rats in production and excretion of 12-ketoendrin, which is observed as a 

major urinary metabolite in the male rat; the major urinary metabolite in the female rat is the 

antihydroxyendrin-O-sulfate (Hutson et al. 1975). In studies with isolated perfused livers, 14C-endrin was 

excreted in the bile of livers from male rats at a rate 2-12 times higher than that for females (Klevay 

1971). 

In rabbits administered radio-labeled endrin, 50% of the radioactivity was excreted in the urine over a 

50-day period (Bedford et al. 1975b). Excretion of the label was 87% complete within 13 days. The 

major compounds detected in urine were anti-12-hydroxyendrin sulfate and 3-hydroxyendrin sulfate 

(14%). 

A heritable resistance in pine mice to endrin raises the LD50 from 3 mg/kg in sensitive voles to 

40 mg/kg in resistant animals (Webb et al. 1973). This trait is correlated with the greater excretion of 

endrin as the anti-12-hydroxy metabolite in the resistant mice. Associations between lethality and 

concentration of 12-ketoendrin residues has been made for rats (Hutson et al. 1975) rat fetuses 

(Kavlock et al. 1981), and hamster fetuses (Chemoff et al. 1979a). Toxicity also occurs when endrin 

itself appears in the tissues. 

2.3.4.3 Dermal Exposure 

No studies were located concerning excretion of endrin in animals or humans after dermal exposure. 

2.4 MECHANISMS OF ACTION 

The mechanism by which endrin induces its toxic effects has been the subject of a considerable 

number of research investigations. Endrin appears to exert its neurotoxic effects at the level of the 

central nervous system as evidenced by convulsions and seizures in humans and animals, and altered 

electrophysiologic activity in animals (Speck and Maaske 1958). The 12.5-fold greater toxicity of 

endrin when administered intracerebrally versus intraperitoneally to male mice supports the brain being 

the primary target site for endrin (Bloomquist 1992). Endrin decreased the seizure threshold for 

pentylenetetrazol in mice, although there were no correlations with effects on brain serotonin levels 

(Miller and Fink 1973). In vitro exposure of male rat brain preparations to endrin has been shown to 

induce noncompetitive inhibition of J-aminobutyric acid (GABA)-regulated chloride transport (Wafford 
ENDRIN 64 

2. HEALTH EFFECTS 

et al. 1989) and chloride current in patch clamp studies (Narahashi 1991). Other studies support the 

correlation between inhibition of GABA-dependent chloride uptake and the acute intracerebral toxicity 

of endrin (Bloomquist 1992). The results of these studies support the hypothesis that endrin disrupts 

the GABAergic system, which is an inhibitory neurotransmitter system, thus causing hyperexcitability 

of the central nervous system. 

Mehorta and coworkers (1989) observed that isolated fractions of brain and heart cells from rats orally 

administered 0.5-10 mg endrin/kg showed significant inhibition of Ca+2 pump activity and decreased 

levels of calmodulin, indicating disruption of membrane Ca+2 transport mechanisms; exogenous 

addition of calmodulin restored Ca+2-ATPase activity. In vitro exposure of rat brain synaptosomes 

and heart sarcoplasmic reticuli decreased total and calmodulin-stimulated calcium ATPase activity with 

greater inhibition in brain preparations (Mehorta et al. 1989). However, endrin showed no inhibitory 

effects on the calmodulin-sensitive calcium ATPase activity when incubated with human erythrocyte 

membranes (Janik and Wolf 1992). In vitro exposure of rat brain synaptosomes to endrin had no 

effect on the activities of adenylate cyclase or 3’,5’-cyclic phosphodiesterase, two enzymes associated 

with synaptic cyclic AMP metabolism (Kodavanti et al. 1988). 

Administration of endrin to animals has been associated with hepatic histopathology which includes 

the presence of lipofuscin pigment (Hassan et al. 1991). One laboratory has studied the ability of 

endrin to elicit hepatic lipid peroxidation and associated cell injury. Administration of single doses of 

endrin to rats was associated with increased lipid peroxidation, decreased membrane fluidity, and DNA 

damage (single strand breaks) in hepatocytes (Bagchi et al. 1992a, 1993c; Hassoun et al. 1993). The 

authors suggest that membrane alterations and DNA damage may result from the enhanced formation 

of free radical or reactive oxygen species. Endrin caused dose-related increases in lipid peroxidation 

in rats resulting in breakdown of polyunsaturated fatty acids as evidenced by the urinary excretion of 

the lipid metabolites formaldehyde, acetaldehyde, malondialdehyde, and acetone (Bagchi et al. 1992b). 

Endrin exposure was associated with decreased glutathione concentrations in liver, kidney, heart, 

spleen, brain, and lungs, and altered glutathione-regulating enzymes in liver and kidney (Numan et al. 

1990a, 1990b). Alterations in hepatic calcium and iron homeostasis were associated with acute endrin 

administration to rats (Bagchi et al. 1992c). Pretreatment with various antioxidants (Vitamin E succinate, 

ellagic acid) ameliorated endrin-related lethality, histopathologic damage, lipid peroxidation, DNA damage, 

glutathione depletion, alterations in iron homeostasis, and excretion of lipid metabolites (Bagchi et al. 1992c, 

1993c; Hassan et al. 1991; Numan et al. 1990a, 1990b). In studies with dioxin­
ENDRIN 65 

2. HEALTH EFFECTS 

responsive and non-responsive strains of mice, there was no clear evidence for involvement of the Ah 

receptor in endrin-induced lipid peroxidative effects in liver (Bagchi et al. 1993d). 

Macrophages from endrin-exposed rats or mice showed an increase in the concentration of nitric oxide 

(Akubue and Stohs 1992; Bagchi et al. 1993d) and increased chemiluminescence and production of 

superoxide anion (Bagchi et al. 1993a). Based on these results and those described above for hepatic 

microsomal and mitochondrial alterations, it appears that multiple sources of reactive oxygen species 

may be involved in endrin-mediated cell damage. 

2.5 RELEVANCE TO PUBLIC HEALTH 

The fact that endrin is no longer produced or used in the United States greatly reduces the potential for 

human exposure. Future levels of endrin, endrin aldehyde, and endrin ketone in environmental media 

are expected to be low. The most significant route of exposure is most likely ingestion of imported 

foods contaminated with endrin; however, there may also be some localized risks from exposures near 

waste disposal sites or from groundwater contaminated with endrin. 

Case reports of endrin toxicity in humans suggest that endrin is well absorbed following ingestion or, 

as evidenced by accounts in the occupational setting, dermal exposure. Limited data in animals 

suggest that endrin is also readily absorbed following inhalation exposure as well. Endrin is rapidly 

metabolized and excreted in the urine and feces. However, low concentrations of endrin may remain 

in adipose tissue following high exposures. 

The central nervous system is the primary target site for endrin toxicity. Convulsions and death have 

occurred within a few hours of ingestion. Less severe symptoms include headache, convulsions, 

dizziness, nausea, vomiting, nervousness, and confusion. No long-term health effects have been noted 

in occupationally exposed workers. Birth defects, especially abnormal bone formation (i.e., fused 

ribs), have been seen in some laboratory animal studies. In studies using rats, mice, and dogs, endrin 

did not produce cancer. However, most of these studies were not suitable for accurately evaluating the 

ability of endrin to cause cancer. There is no evidence that endrin can cause cancer in exposed 

humans. The EPA has determined that endrin is not classifiable as to its human carcinogenicity 

(Group D), because the available information is inadequate. 
 

 

 

ENDRIN 66 

2. HEALTH EFFECTS 

Minimum Risk Levels for Endrin. 

Inhalation MRLs 

MRLs for inhalation exposure to endrin, endrin aldehyde, and endrin ketone were not derived for any 

duration category because data are insufficient. 

Oral MRLs 

x An oral MRL of 0.002 mg/kg/day has been derived for intermediate-duration oral exposure

 (15-364 days) to endrin. 

An intermediate oral MRL was based on a NOAEL of 0.15 mg/kg/day for neurologic effects including 

convulsions and tremors in dogs administered endrin in the diet for 18 days to 9.9 months (Treon et 

al. 1955). In that study, a dog exposed to 5 ppm endrin in the diet (0.20-0.27 mg/kg/day) had 

convulsions, tremors, and diffuse degenerative lesions in the brain; the animal died after 47 days of 

feeding. A dietary level of 4 ppm (0.15-0.21 mg/kg/day) was not associated with these effects. The 

central nervous system is the primary target system for endrin as evidenced by reports of neurologic 

effects including convulsions and tremors in humans and other animal species (Curley et al. 1970; 

Deichmann et al. 1970; Treon et al. 1955; Waller et al. 1992). 

x An oral MRL of 0.0003 mg/kg/day has been derived for chronic-duration oral exposure

 (365 days or more) to endrin. 

The chronic oral MRL was based on a NOAEL of 0.025 mg/kg/day for convulsions in dogs 

administered endrin in the diet for 2 years (Kettering 1969). Concentrations of 0.05 and 

0.1 mg/kg/day were associated with convulsive activity, slight to moderate vacuolization of hepatic 

cells, and occasional slight increases in liver weights. Other studies have reported hepatotoxicity in 

animals treated orally with endrin (Hassan et al. 1991; Treon et al. 1955). 

Adverse health effects of exposure to endrin are described below. Except for 15-day feeding studies 

in rats, no information was found regarding health effects associated with oral exposure to endrin 
 

ENDRIN 67 

2. HEALTH EFFECTS 

aldehyde or endrin ketone. No information was found regarding the health effects associated with 

inhalation or dermal exposure to endrin aldehyde or endrin ketone. 

Death. Clinical reports in humans and studies in animals demonstrate that death due to central 

nervous system toxicity is the primary acute lethal effect associated with endrin exposure. A lethal 

dose of endrin in humans has not been identified, but 0.2-0.25 mg endrin/kg body weight is sufficient 

to cause convulsions (Davies and Lewis 1956). Liver, kidney, heart, and brain damage were reported 

following oral and inhalation exposures. Since endrin is no longer used commercially, the general 

public is not likely to encounter levels sufficient to lead to toxic neurological effects or death. 

However, endrin may be encountered in hazardous waste sites. Endrin is an acutely toxic pesticide 

that has caused deaths from the inadvertent ingestion of contaminated foods (Rowley et al. 1987; 

Tewari and Sharma 1978; Weeks 1967) and from suicides (Runhaar et al. 1985). Excess mortality has 

not been associated with chronic exposure to endrin (Ditraglia et al. 1981; Ribbens 1985). 

Endrin can be lethal to animals following inhalation, oral, and dermal exposure for acute, intermediate, 

and chronic durations. Fifteen mg/m3

 of endrin in air (0.36 ppm) was lethal to rabbits and mice, but 

not to a cat, rats, hamsters, or guinea pigs (Treon et al. 1955). The oral LD50 of endrin for rats was 

7-43 mg/kg, depending on the gender and age of the animal (Treon et al. 1955). A minimum lethal 

dermal dose of 67-91 mg/kg was reported for rabbits exposed acutely (Treon et al. 1955). 

Systemic Effects. Very limited studies were found on the systemic effects of endrin in humans. 

Liver, kidney, heart, and brain damage occurred in animals, but at relatively high doses or doses 

causing death. These data suggest that systemic effects involving liver, kidney, and heart may not be 

a potential area of concern following endrin exposure. No studies were found regarding 

musculoskeletal or ocular effects of endrin in humans or animals. 

Respiratory Effects. Increased deaths due to pneumonia and other nonmalignant respiratory diseases 

were observed in workers at one of two plants that manufactured endrin (Ditraglia et al. 1981). 

However, simultaneous exposure to other chemicals occurred, and increased respiratory disease was 

not observed in the second endrin manufacturing facility. Pulmonary edema was observed in a patient 

poisoned with endrin, but was thought to be due to chemical pneumonitis from aspiration of aromatic 

hydrocarbons contained in the formulation (Runhaar et al. 1985). Rats treated for 17.6-20.8 months 
 

 

 

ENDRIN 68 

2. HEALTH EFFECTS 

with 0.1 mg/kg/day exhibited focal hemorrhage and congestion of the lungs (Deichmann et al. 1970). 

Other histopathologic effects observed in animals probably occurred secondary to death. 

Curdiovascular Effects. Only limited reports of cardiovascular toxicity of endrin were located. 

Diffuse degenerative lesions of the heart were observed in dogs administered lethal doses of endrin 

(Treon et al. 1955), and enlarged hearts were observed at sublethal doses. The health significance of 

these finding is unclear, as the effects were not observed in other animal species. 

Gastrointestinal Effects. Nausea, vomiting, diarrhea, and abdominal distention have been reported in 

people consuming endrin-contaminated foods (Waller et al. 1992); however, no gastrointestinal lesions 

have been observed in animals (NCI 1978). 

Hemutologicul Effects. Hematological effects have not been observed in occupationally exposed 

worker populations (Hoogendam et al. 1962; Versteeg and Jager 1973). There were no changes in the 

relative numbers of types of formed elements in the peripheral blood of male and female Beagle dogs 

administered endrin in their diet for periods of 16.4-18.7 months (Treon et al. 1955). 

Heputic Effects. Workers monitored for liver function had increased serum levels of liver enzymes 

(Hoogendam et al. 1965). Only limited conclusions should be drawn from these results as the levels 

returned to normal within 1 week to 3 months; concurrent exposure to other chemicals and alcohol 

was not controlled. Diffuse degenerative hepatic lesions were observed in rabbits and mice exposed to 

lethal doses of endrin and in surviving animals (Treon et al. 1955). Rats, mice, guinea pigs, and 

hamsters administered a relatively high dose of endrin exhibited moderate hepatic histopathology 

(Hassan et al. 1991). 

Endrin has been shown to affect microsomal enzyme activity in voles and mice with differing effects 

(i.e., differing degree and direction of change) depending on species and model substrates (Hartgrove 

et al. 1977). Maternal liver enlargement occurred in pregnant mice administered endrin (Kavlock et al. 

1981). Liver effects of endrin have been observed; however, lesions occurred only at relatively high 

or lethal doses. While the liver is not the primary target system of endrin toxicity, toxic effects on the 

liver may occur after large doses (e.g., 4 mg/kg/day in mice, rats, and guinea pigs). 
 

 

 

ENDRIN 69 

2. HEALTH EFFECTS 

Renal Effects. Lethal doses of endrin caused diffuse degenerative lesions in the kidneys of dogs, 

mice, rabbits, and rats administered endrin (Treon et al. 1955). Renal histopathologic effects were also 

observed in rats, mice, and hamsters (Hassan et al. 1991). 

Endocrine Effects. Thyroid hyperplasia and pituitary cysts were observed in rats, but not in mice, in 

a chronic bioassay study with endrin administered in the feed (NCI 1978). There has been no 

evidence of endocrine effects in occupationally exposed populations. 

Dermal Effects. Chronic administration of endrin in feed resulted in dermatitis in rats and alopecia in 

both rats and mice (NCI 1978). There has been no evidence of dermal effects in occupationally 

exposed populations. 

Body Weight Effects. No specific effects on body weight have been noted in humans. Effects on 

body weight (decreases) in animals were usually associated with administration of high doses and were 

not observed in chronic toxicity studies (Chemoff et al. 1979a; Deichmann et al. 1970; Goldenthal 

1978a; Kavlock et al. 1981; NCI 1978; Treon et al. 1955). 

Immunological and Lymphoreticular Effects. No reports of immunological effects of endrin 

in exposed humans were found. Very few reports of immunological or lymphoreticular effects due to 

endrin toxicity have been reported in laboratory animals, and have mainly been limited to either no 

observed changes in spleen weights in dogs dosed with up to 3 mg/kg/day orally (Treon et al. 1955) tc 

relative changes in spleen and thymus weight changes in rats dosed with 3 mg/kg/day orally for acute 

durations (Bagchi et al. 1992b, 1992c). An in vitro study of endrin effects on human lymphocyte 

mitogenic responses to phytohemagglutinin and neutrophil chemotaxis was negative (Lee et al. 1979). 

Neurological Effects. The central nervous system is the primary target system of endrin. Acute 

human poisonings by endrin were characterized by symptoms of central nervous system toxicity such 

as jerking of arms and legs, twitching facial muscles, tonic and clonic contractions, convulsions and 

sudden collapse, and death (Coble et al. 1967; Curley et al. 1970; Davies and Lewis 1956; Rowley et 

al. 1987; Runhaar et al. 1985; Weeks 1967). Changes in EEG patterns were usually observed in 

poisoned humans (Hoogendam et al. 1962). 
ENDRIN 70 

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Neurological effects occurred in animals exposed to endrin. Behavioral effects (Gray et al. 1981), 

hyperexcitability, tremors, and convulsions (Deichmann et al. 1970; NCI 1978; Treon et al. 1955) were 

reported. Irregular EEG recordings were observed in rats (Speck and Maaske 1958). There is some 

evidence to show that occurrence of convulsions is related to blood-brain barrier permeability changes 

(Speck and Maaske 1958). 

Human and animal evidence suggests there is a health risk for neurological effects only when 

exposures are high. There remains uncertainty in predicting dose levels for neurobehavioral effects, 

but 0.2 mg/kg body weight has been proposed as a threshold for convulsions in humans (Hayes 1963). 

Reproductive Effects. No reports of reproductive effects in endrin-exposed humans have been 

located. Early single and 3-generation reproductive studies in dogs and rats, respectively, were 

inadequate for assessing potential reproductive effects (Eisenlord et al. 1968; Kettering 1971). 

Developmental Effects. Developmental effects associated with exposure of humans to endrin 

have not been reported. Prenatal exposure of animals to concentrations of endrin sufficient to cause 

maternal toxicity has resulted in a statistically significant increase in the incidence of fused ribs, cleft 

palate, exencephaly, microencephaloceles, and open eyes in hamsters and mice. Effects were not 

necessarily reproducible between studies. Adverse developmental effects generally have not been 

observed in rats (Kavlock et al. 1981) except for temporary increase in locomotor activity of pups 

(Gray et al. 1981) and delayed ossification at doses which resulted in maternal toxicity (Goldenthal 

1978a). Developmental effects were found primarily in one species. It is unknown if these effects 

would occur in humans. 

Genotoxic Effects. No in vivo studies of genotoxic effects in humans were located. The results 

of in vitro genotoxicity studies with endrin are summarized in Table 2-4. Endrin was not mutagenic 

in vitro in microbial assays with or without metabolic activation (Ames et al. 1975; Glatt et al. 1983; 

Moriya et al. 1983; Probst et al. 1981; Zeiger et al. 1987) or in the mouse lymphoma cell assay 

(McGregor et al. 1991). Exposure of primary rat, mouse, or hamster hepatocytes to endrin did not 

cause unscheduled DNA synthesis or repair (Maslansky and Williams 1981; Probst et al. 1981; 

Williams 1980). Sister chromatid exchange frequencies were not significantly elevated in activated 

and nonactivated human lymphoid cells (Sobti et al. 1983). Chromosomal aberrations observed in 

ENDRIN 72 

2. HEALTH EFFECTS 

testicular cells of rats following injection of endrin are of questionable relevance to human risk 

assessment due to the route of exposure, which was direct, intratesticular injection (Dikshith and Datta 

1973). The ability of endrin to cause an increase in hepatic DNA damage (single strand breaks) is 

attributed to endrin-induced oxidative damage (Bagchi et al. 1992a, 1993a, 1993c; Hassoun et al. 

1993), and is not suggestive of a direct, genotoxic effect of endrin. Data suggest that genotoxicity is 

not an area of concern in humans. 

Cancer. Studies of endrin-exposed workers have not detected significant increases in mortality due 

to cancer (Ribbens 1985). In two industries manufacturing endrin, small excesses of certain cancers 

were reported (Ditraglia et al. 1981). However, these findings were not statistically significant, and 

the studies were limited by concurrent exposure to other chemicals. Endrin was reported to be 

noncarcinogenic in animal studies (Deichmann et al. 1970; NCI 1978; Treon et al. 1955). Reuber 

(1978) has reported that endrin is carcinogenic; however, Reuber’s criteria for classifying tissues as 

tumorigenic were not consistent with other investigators (EPA 1979f). 

Limitations in existing studies in humans and studies in animals do not allow for a conclusive decision 

about the potential carcinogenicity of endrin in humans. 

2.6 BIOMARKERS OF EXPOSURE AND EFFECT 

Biomarkers are broadly defined as indicators signaling events in biologic systems or samples. They 

have been classified as markers of exposure, markers of effect, and markers of susceptibility 

(NAS/NRC 1989). 

Due to a nascent understanding of the use and interpretation of biomarkers, implementation of 

biomarkers as tools of exposure in the general population is very limited. A biomarker of exposure is 

a xenobiotic substance or its metabolite(s), or the product of an interaction between a xenobiotic agent 

and some target molecule(s) or cell(s) that is measured within a compartment of an organism (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 
ENDRIN 73 

2. HEALTH EFFECTS 

different aromatic compounds). Depending on the properties of the substance (e.g., biologic half-life) 

and environmental conditions (e.g., duration and route of exposure), the substance and all of its 

metabolites may have left the body by the time samples can be taken. It may be difficult to identify 

individuals exposed to hazardous substances that are commonly found in body tissues and fluids 

(e.g., essential mineral nutrients such as copper, zinc, and selenium). Biomarkers of exposure to 

endrin are discussed in Section 2.6.1. 

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 endrin are discussed in Section 2.6.2. 

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 2.8, Populations That Are Unusually Susceptible. 

2.6.1 Biomarkers Used to Identify or Quantify Exposure to Endrin 

While levels of endrin or endrin metabolites can be measured in tissue and excreta, thereby serving as 

biomarkers of exposure, the analytical techniques required are somewhat sophisticated and non-routine. 

Further, measurements of endrin in blood are best suited for detecting recent exposures because endrin 

is cleared rapidly from blood. The lack of persistence of endrin in human tissues and blood seen in 

the study of Coble et al. (1967) indicates a brief half-life for endrin on the order of l-2 days. Sera 

levels of endrin (time to sample not specified) in Pakistani patients who were poisoned with endrin 

ranged from 0.3 to 254 ppb (0.3-254 (Pg/L); survivors had sera levels that ranged from 1.3 to 17.4 ppb (1.3­

17.4 (Pg /L) (Rowley et al. 1987). An endrin concentration of 0.3 ppb was detected in the cerebrospinal fluid. 
ENDRIN 74 

2. HEALTH EFFECTS 

Measurements of metabolites of endrin can also be useful in monitoring exposure to endrin. The 

glucuronide of anti-12-hydroxyendrin and I2-ketoendrin have been detected in feces and urine 

(Baldwin and Hutson 1980). The anti-12-hydroxyendrin glucuronide marker is the most sensitive and 

specific urinary marker; however, this is a difficult assay to perform, and its accuracy and precision 

are limited. D-glucaric acid is a nonspecific marker that may indicate prior exposure to endrin (Hunter 

et al. 1972; Ottevanger and Van Sittert 1979; Vrij-Standhardt et al. 1979). High levels of D-glucaric 

acid were detected in workers for up to six weeks, after which levels returned to normal ranges 

(Ottevanger and Van Sittert 1979). 

Organochlorine pesticides have been detected in samples of fat tissues. However, endrin was not 

found in adipose tissue samples of the general population (Stanley 1986; Williams et al. 1988). In 

pesticide manufacturing workers, endrin was found in the adipose tissue only after very high 

exposures. Endrin has been detected in the milk of lactating women (0.02-6.24 mg/kg milk fat) 

(Alawi et al. 1992; Bordet et al. 1993). In conclusion, the quantitation of endrin exposure, via parent 

compound or metabolite, remains difficult at best. Further studies characterizing the pharmacokinetics 

of endrin are needed. 

2.6.2 Biomarkers Used to Characterize Effects Caused by Endrin 

Changes in the nervous system are the most common effects associated with ingestion of endrin in 

humans or exposure to its vapors. Various signs and symptoms of exposure include twitching of 

muscles, dizziness, mental confusion, and epileptiform seizures. Since these effects also occur 

following exposure to other organochlorine pesticides and other drugs, more specific indicators of 

endrin exposure are needed to assess adverse health effects which may occur in people living near 

hazardous waste sites. 

For more information on biomarkers for renal and hepatic effects of chemicals, see ATSDR/CDC 

Subcommittee Report on Biological Indicators of Organ Damage (1990), and for information on 

biomarkers for neurological effects see OTA (1990). 
ENDRIN 75 

2. HEALTH EFFECTS 

2.7 INTERACTIONS WITH OTHER CHEMICALS 

Very little published information is available about the interaction of endrin with other chemicals. The 

toxicity of endrin may be influenced by interactions with other chemicals and physical agents. Quails 

treated with endrin and chlordane had significantly lower endrin residues in brain tissue (p<0.025) than 

birds treated with endrin alone (Ludke 1976). The authors attributed this difference to the presence 

and accumulative toxic action of one or more of the chlordane components in the nervous system. 

Dietary endrin pretreatment potentiated CCl 4 hepatotoxicity, producing slight elevation of the serum 

enzymes SGPT and isocitrate dehydrogenase activities in rats (Young and Mehendale 1986). Changes 

in various enzymes (e.g., SGOT, SGPT, ATPase, acid and alkaline phosphatase, and glucose6-phosphatase) appeared earlier in irradiated rats and were more pronounced than in normal rats given 

endrin alone, except in the case of adenosine triphosphatase (Meena et al. 1978). 

Changes in the urinary excretion of D-glucaric acid and decreased serum levels of p,p’DDE (dichlorodiphenyl 

dichloroethene; a metabolite of DDT) observed in endrin workers were interpreted to signify 

induction of hepatic enzymes responsible for the metabolism of endogenous and exogenous chemicals 

(Hunter et al. 1972). 

2.8 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE 

A susceptible population will exhibit a different or more enhanced response than most persons exposed 

to the same level of endrin 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 to be generally more vulnerable to toxic substances than healthy adults. 

Populations at greater risk due to their unusually high exposure are discussed in Section 5.6, 

Populations With Potentially High Exposure. 
ENDRIN 76 

2. HEALTH EFFECTS 

Persons with a history of convulsive disorders would be expected to be at increased risk from exposure 

to endrin. Children may be more sensitive than adults to the acute toxic effects of endrin. In an 

endrin poisoning episode in Pakistan, children l-9 years old represented about 70% of the cases of 

convulsions (Rowley et al. 1987). The causative factor responsible for the outbreak was not identified, 

however, and the age distribution of cases could be explained by age-specific exposure situations. In 

general, following oral administration, female animals appear to be more susceptible to endrin toxicity 

than males (Gaines 1960; Treon et al. 1955). The difference may be due to the more rapid excretion 

of endrin by male versus female rats (Hutson et al. 1975; Klevay 1971; Korte et al. 1970). A sex-related 

difference in toxicity was not apparent following dermal exposure (Gaines 1960, 1969). No 

sex-based differences in endtin-related human toxicity have been documented. For example, an equal 

number of male and female patients were affected in the endrin poisoning episode in Pakistan (Rowley 

et al. 1987). 

2.9 METHODS FOR REDUCING TOXIC EFFECTS 

This section will describe clinical practice and research concerning methods for reducing toxic effects 

of exposure to endrin. 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 it. When specific 

exposures have occurred, poison control centers and medical toxicologists should be consulted for 

medical advice. 

2.9.1 Reducing Peak Absorption Following Exposure 

Human exposure to endrin may occur by ingestion, inhalation, or by dermal contact. Dermal 

absorption can be significant. Gastrointestinal absorption is enhanced by dietary fats. While not 

highly volatile, endrin-laden aerosols or dust particles can be trapped in respiratory mucus and 

swallowed, leading to gastrointestinal absorption. 

As endrin is one of the most toxic cyclodiene organochlorine pesticides, rapid decontamination is 

suggested to reduce absorption (Clayton and Clayton 1981). Rapid decontamination includes removal of 

contaminated clothing, washing exposed skin with copious amounts of soap and water, and cleansing the hair 

and nails thoroughly. It is also suggested that leather clothing, which absorbs pesticides, be discarded (TOMES 

1994). 
ENDRIN 77 

2. HEALTH EFFECTS 

In the event of contamination of the eyes, common treatment includes irrigation with copious amounts 

of tepid water or physiological saline for at least 15 minutes and, in the event of persistent irritation, 

pain, swelling, or photophobia, expert ophthalmologic consultation. In the event of acute poisoning, 

transport to an emergency room is suggested. 

Common treatment for inhalation exposure includes removal of the patient to fresh air and observation 

for respiratory distress. Pulmonary injury may occur from solvents used as carriers for organochlorine 

pesticides. A hydrocarbon pneumonitis may be produced if aspiration of the liquid solvent occurs. 

Emergency airway support and 100% supplemental oxygen with assisted ventilation under medical 

supervision may be necessary. 

If ingestion has occurred, gastric lavage is indicated. Emesis (vomiting) should not be induced due to 

the risk of sudden onset of seizures (Woo 1990) and increased chance of aspiration of stomach 

contents, which may later lead to aspiration pneumonitis. Administration of activated charcoal and 

cholestyramine has been used to reduce absorption and enhance elimination by interrupting 

enterohepatic circulation. Exchange transfusions, peritoneal dialysis, hemodialysis, and hemoperfusion 

are not likely to be beneficial due to the initial large volume of distribution of organochlorines. 

Administration of cathartics is ill-advised due to the possibility of increased intestinal absorption of 

endrin (TOMES 1994). 

Following acute exposure to cyclodiene organochlorine pesticides, seizures and respiratory depression 

may occur (Ellenhorn 1988; Proctor et al. 1988). Benzodiazepines (e.g., diazepam or lorazepam) or 

other anticonvulsant medications (e.g., phenobarbital) have been commonly used to control seizures 

(Ford 1993). Organochlorines may sensitize the myocardium to the proarrhythmic effects of 

adrenergic amines, potentially resulting in initiation of ventricular fibrillation (TOMES 1994). 

2.9.2 Reducing Body Burden 

Although endrin is a stereoisomer of dieldrin, it does not persist in the body as dieldrin does. The 

half-life of endrin in humans and animals is 2-6 days (Ert and Sullivan 1992). Thus, endrin is 

unlikely to accumulate in adipose tissue. There are reports of ingestion of bread contaminated with 

endrin which caused sudden convulsions in three persons. In one person, the serum level was 
ENDRIN 78 

2. HEALTH EFFECTS 

0.053 ppm 30 minutes after convulsion and 0.038 ppm after 20 hours. In the other 2 cases, no endrin 

was detected in the blood at 8.5 or 19 hours after the convulsions occurred (Proctor et al. 1988). 

There is no specific antidote and no currently recognized way to enhance elimination. Conventional 

treatment is entirely supportive. Cholestyramine has been shown to enhance elimination of chlordane 

and kepone (HSDB 1994), and may enhance elimination after ingestion of endrin. However, its 

effectiveness in endrin poisoning has not been tested. 

2.9.3 Interfering with the Mechanism of Action for Toxic Effects 

The most serious toxicological effect of endrin is central neurotoxicity (Klaasen et al. 1986). Organochlorines 

interfere with the normal flux of cations across the axon, disrupting central nervous system 

homeostasis (Finkel 1983; Klaasen et al. 1986). Endrin is one of the most toxic cyclodienes, and 

seizure activity may develop rapidly after exposure (Proctor et al. 1988). In most cases, recovery is 

rapid. However, headaches, dizziness, weakness, and anorexia may persist for 2-4 weeks. 

Although the exact mechanism causing neurotoxicity is unknown, it is reasonable to suppose that 

effects on neurotransmitters may be mitigated by pharmacological intervention. Benzodiazepines, 

which often are used to treat seizures resulting from endrin intoxication, potentiate inhibitory GABA 

neuronal activity in the central nervous system (Singh and Renzi 1993). Phenytoin has neuronal 

membrane stabilizing properties and is also frequently used in seizure control. 

Strong evidence indicates that endrin increases the activity of hepatic microsomal enzymes (Klaasen et 

al. 1986). Drugs which are strong inducers of microsomal enzymes may increase the metabolic 

elimination of endrin. 

Ascorbic acid supplementation has been shown to reduce the renal and hepatic toxicity of experimental 

animals undergoing dieldrin treatment (Bandyopadhyay et al. 1982). The effectiveness of ascorbic 

acid in humans exposed to endrin is unknown; however, studies in animals suggest that antioxidants 

can reduce endrin-related oxidative damage (Bagchi et al. 1992c, 1993c; Hassan et al. 1991; Numan et 

al. 1990a, 1990b). 
ENDRIN 79 

2. HEALTH EFFECTS 

2.10 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 endrin 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 endrin. 

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. 

2.10.1 Existing Information on Health Effects of Endrin 

The existing data on health effects of inhalation, oral, and dermal exposure of humans and animals to 

endrin are summarized in Figure 2-4. The purpose of this figure is to illustrate the existing 

information concerning the health effects of endrin. Each dot in the figure indicates that one or more 

studies provide information associated with that particular effect. The dot does not necessarily imply 

anything about the quality of the study or studies, nor should missing information in this figure be 

interpreted as a “data need.” A data need, as defined in ATSDR’s Decision Guide for Identifying 

Substance-Specific Data Needs Related to Toxicological Profiles (ATSDR 1989), is substance-specific 

information necessary to conduct comprehensive public health assessments. Generally, ATSDR 

defines a data gap more broadly as any substance-specific information missing from the scientific 

literature. 

Only one study (Young and Mehendale 1986) was found on the health effects of endrin aldehyde or 

endrin ketone in animals following oral exposure. 

ENDRIN 81 

2. HEALTH EFFECTS 

2.10.2 Identification of Data Needs 

Acute-Duration Exposure. No studies are available on the effects of human exposure to endrin 

by the inhalation or dermal routes. Acute human poisoning from endrin-contaminated food results in 

jerking of legs, tonic-clonic contractions, convulsions and sudden collapse, and death (Curley et al. 

1970; Rowley et al. 1987; Runhaar et al. 1985; Weeks 1967). Data in animals exposed via inhalation, 

oral, and dermal routes confirm that endrin can affect the nervous system, causing clinical signs 

including tremors and convulsions (Chernoff et al. 1979a; Gaines 1960; Kavlock et al. 1981; Treon et 

al. 1955). Decreases in body weight gain and histopathologic damage to liver and kidneys have been 

reported in animals following acute oral exposure (Hassan et al. 1991; Treon et al. 1955). Additional 

studies using other species and a range of dose levels could help determine other potential targets 

following acute exposure by all three routes, as well as acute threshold levels for effects observed. 

Data was not found to be sufficient to derive oral or inhalation acute-duration MRLs. 

Since information on acute adverse effects of endrin aldehyde or endrin ketone in humans or animals 

by inhalation, oral, and dermal routes is extremely limited, similar studies are needed to identify 

potential target tissues. 

Intermediate-Duration Exposure. No studies are available on the adverse health effects from 

intermediate-duration exposure in humans by any route. Studies in animals indicate that exposure to 

endrin via inhalation can be lethal and causes effects on the nervous and respiratory systems, the liver, 

the brain, adrenals, and kidneys (Treon et al. 1955). Since systemic effects were observed at levels 

which caused death, data are not sufficient to derive an intermediate-duration inhalation MRL. Animal 

studies also demonstrate that oral intermediate-duration exposure can lead to death in several species 

(rat, mouse, hamster, rabbit, monkeys, cat) (Treon et al. 1955). Endrin was lethal in rabbits following 

dermal exposure (Treon et al. 1955). No other treatment-related disorders are known. Additional 

studies for oral and dermal routes using a range of exposure levels would be useful in identifying 

potential target tissues. 

Since no information is available on adverse health effects of endrin aldehyde or endrin ketone 

following intermediate-duration exposure by the inhalation, oral, and dermal routes in humans or 

animals, studies using various dose levels and several animal species are needed to identify potential target 

tissues. 
ENDRIN 82 

2. HEALTH EFFECTS 

Chronic-Duration Exposure and Cancer. Studies of humans chronically exposed to endrin in 

the occupational setting indicate target tissues similar to those for acute exposure (Ditraglia et al. 1981; 

Ribbens 1985; Versteeg and Jager 1973). Quantitative exposure data are lacking in humans, but data 

in animals are sufficient to derive NOAELs and LOAELs for neurologic, hepatic, renal, and 

cardiovascular effects in dogs (Kettering 1969; Treon et al. 1955). A chronic MRL was based on a 

NOAEL for convulsions in dogs administered endrin in the feed (Kettering 1969) and it is anticipated 

that the chronic MRL should be protective for any exposure of acute or intermediate duration. No 

studies are available in humans or animals chronically exposed via dermal exposure. Additional 

studies are needed to determine whether similar effects via oral exposure occur by this route. 

Chronic studies of workers exposed to endrin via inhalation have not suggested an association between 

exposure and the occurrence of any type of cancer (Ditraglia et al. 1981; Ribbens 1985). However, 

these studies are limited by inadequate exposure data (including concurrent exposure to other 

chemicals), short follow-up, and small size of study cohort. No studies were located regarding cancer 

risk in humans via oral or dermal exposure. While no specific cancer risk has been determined, 

several occurrences of cancer may be worthy of further study. There were slight excesses of cancer of 

the esophagus, rectum, liver, respiratory system, bladder and urinary system, and of the lymphatic and 

hematopoietic systems in manufacturing workers exposed to vapors of endrin/aldrin/dieldrin in two 

plants (Ditraglia et al. 1981). However, as already noted, these findings were not statistically 

significant, the elevated standard mortality ratios (SMRs) were based on small numbers of observed 

deaths, and workers were subject to concurrent exposure to chemicals other than endrin. 

Oral exposure studies in rats and mice did not show association between exposure to endrin and 

increased incidence of cancer (Deichmann et al. 1970; NCI 1978; Treon et al. 1955). No chronic 

studies are available in animals exposed to endrin via inhalation or dermal exposure. In the absence of 

evidence of a carcinogenic effect in two animal species, additional studies are not warranted at this 

time. 

No studies have been conducted to evaluate adverse health effects in humans or animals following 

exposure to endrin aldehyde or endrin ketone by the inhalation, oral, or dermal route. Additional 

human and animal studies via all three of these routes of potential exposure are needed to determine 

potential carcinogenic risk in people who may be exposed to endrin aldehyde or endrin ketone near hazardous 

waste sites. 
ENDRIN 83 

2. HEALTH EFFECTS 

Genotoxicity. No in vivo studies were found in humans or animals following inhalation, oral, or 

dermal exposure to endrin. Microbial assays and one mammalian cell assay have demonstrated that 

endrin does not have mutagenic potential with or without metabolic activation (Ames et al. 1975; Glatt 

et al. 1983; McGregor et al. 1991; Moriya et al. 1983; Probst et al. 1981; Zeiger et al. 1987). 

Similarly, in vitro mammalian assays evaluating unscheduled DNA synthesis and sister chromatid 

exchanges were negative (Maslansky and Williams 1981; Probst et al. 1981; Sobti et al. 1983). 

Chromosomal aberrations observed in testicular cells of rats following injection of endrin are of 

questionable relevance to human risk assessment due to the route of exposure, which was direct, 

intratesticular injection (Dikshith and Datta 1973). Studies demonstrating an increased incidence of 

DNA single strand breaks suggest that these effects are the consequence of production of reactive 

oxygen species (Bagchi et al. 1993a, 1993c; Hassoun et al. 1993). The overall weight of evidence 

based on the existing data suggests that endrin is not mutagenic. Additional studies are not warranted 

at this time. 

No studies have been conducted to evaluate the genotoxicity of endrin aldehyde or endrin ketone in 

humans or animals by inhalation, oral, or dermal routes of exposure. Studies are needed to determine 

potential mutagenic risk for people who may be exposed near hazardous waste sites. 

Reproductive Toxicity. No information is available on the reproductive effects of endrin in 

humans after inhalation, oral, or dermal exposure. No studies are available on the reproductive effects 

of endrin in animals after inhalation or dermal exposure. Acute oral studies in animals and 

experimentally flawed intermediate-duration studies in rats and dogs suggest endrin can affect 

reproductive outcomes (Eisenlord et al. 1968; Good and Ware 1969; Kettering 1971). Additional, 

more definitive intermediate-duration tests evaluating various species and several dose levels via the 

oral route (and other routes as well) would be useful in assessing the potential reproductive risk in 

people who may be exposed to low levels of endrin near hazardous waste sites. Further, the 

demonstrated presence of endrin in milk from lactating mothers emphasizes the need for 

comprehensive, multigeneration studies in animals. 

No studies have been conducted to evaluate the reproductive effects of endrin aldehyde or endrin 

ketone in humans or animals via the inhalation, oral, and dermal routes of exposure. Additional 

animal studies and further human case studies are needed to determine the potential reproductive 
ENDRIN 84 

2. HEALTH EFFECTS 

hazard and to determine threshold levels for effects that may exist via all three of these routes of 

exposure. 

Developmental Toxicity. No information is available regarding the developmental toxicity of 

endrin in humans by inhalation, oral, or dermal exposure. No inhalation or dermal exposure route 

studies are available for laboratory animals; however, developmental effects have been demonstrated in 

laboratory animals exposed via the oral route. Offspring of mice and hamsters exposed to endrin 

during gestation showed statistically significant increases in the incidence of fused ribs, cleft palate, 

exencephaly, and microencephaloceles (Chernoff et al. 1979a; Kavlock et al. 1985; Ottolenghi et al. 

1974). Additional studies are needed to determine if these effects also occur following inhalation or 

dermal exposure. 

No studies have been conducted on the developmental toxicity of endrin aldehyde or endrin ketone in 

humans or animals by the inhalation, oral, or dermal route of exposure. Additional studies via the 

inhalation and dermal routes of exposure evaluating various dosages and in several species would be 

useful in assessing the potential for endrin aldehyde or endrin ketone to cause developmental effects. 

Immunotoxicity. No in vivo studies are available in humans or animals regarding the immunotoxicity 

of endrin after inhalation, oral, or dermal exposure. Results of in vitro assays evaluating 

inhibition of lymphocyte responses and neutrophilic chemotaxis were negative (Lee et al. 1979). Also, 

immunopathologic changes via inhalation, oral, and dermal routes of exposure were not observed in 

intermediate-duration studies (Treon et al. 1955). Additional in vivo (inhalation, oral, and dermal 

exposure routes), as well as additional in vitro testing involving humoral mediated immunity and 

nonspecific immunity would certainly be useful in confirming the apparent lack of significant 

immunotoxic potential. 

No studies have been conducted to evaluate the immunotoxicity of endrin aldehyde or endrin ketone in 

humans or animals by the inhalation, oral, or dermal route of exposure. Additional studies using 

several dose levels and various animal species would be useful in assessing the immunotoxic potential 

of endrin aldehyde or endrin ketone in humans following inhalation, oral, or dermal exposure. 

Neurotoxicity. Studies in humans indicate that endrin causes changes in the nervous system after 

inhalation or oral exposure (Curley et al. 1970; Davies and Lewis 1956; Hoogendam et al. 1962, 1965; 
ENDRIN 85 

2. HEALTH EFFECTS 

Rowley et al. 1987; Runhaar et al. 1985; Waller et al. 1992; Weeks 1967). Clinical symptoms
 

including twitching and jerking of muscles, seizures, dizziness, and mental confusion occurred within
 

2 hours following occupational exposure. Studies in animals confirm the neurotoxic potential of
 

endrin (Chemoff et al. 1979a; Deichmann et al. 1970; Gaines 1960, 1969; Kavlock et al. 1981;
 

Kettering 1969, 1971; Speck and Maaske 1958; Treon et al. 1955). While existing neurological effects
 

are well characterized following inhalation and oral exposures and, to a lesser extent, dermal exposure,
 

additional exposure data are needed to establish dose-response relationships.
 

No studies have been conducted to evaluate the neurotoxicity of endrin aldehyde or endrin ketone in
 

humans or animals by an inhalation, oral, or dermal route of exposure. Additional studies using all
 

three of these potential exposure routes are needed to determine if endrin aldehyde and endrin ketone
 

are potential neurotoxicants and to determine threshold levels for effects that may exist.
 

Epidemiological and Human Dosimetry Studies. There are reports on the adverse effects of
 

endrin in humans (Section 2.2). These reports involve acute exposures in people who ingested endrincontaminated food (Curley et al. 1970; Davies and Lewis 1956; Waller et al. 1992; Weeks 1967).
 

There are also studies of workers with acute exposures to contaminated air (Hoogendam et al. 1962,
 

1965). Existing studies identify the nervous system as a major target associated with exposure to
 

endrin. However, reliable quantitative exposure levels that lead to these effects are lacking.
 

Additional quantitative exposure data obtained from individuals occupationally exposed to low levels
 

of endrin would be useful in evaluating potential risk to people living near hazardous waste sites.
 

Biomarkers of Exposure and Effect. 

Exposure. Measurement of endrin and its metabolites can be useful indicators of exposure. Since 

endrin is cleared from the blood rapidly, such measurements are suitable only for recent exposures. 

Additional studies are needed to determine the usefulness of metabolites in urine as biomarkers of 

exposure in humans. A quantitative relationship between the urinary concentration of anti-l2-hydroxyendrin 

and the dose of endrin should be clarified. 

Effect. Changes in the nervous system appear to be the main effect associated with human exposure 

to endrin. Effects on the nervous system can be monitored in exposed individuals by measuring the incidence 

of signs and symptoms such as myoclonic jerking, seizures, convulsions, dizziness, and 
ENDRIN 86 

2. HEALTH EFFECTS 

mental confusion (Carbajal-Rodriguez et al. 1990; Rowley et al. 1987; Runhaar et al. 1985; Waller et 

al. 1992). Because these effects also occur following exposure to other organochlorine pesticides and 

drugs, the development of more specific biomarkers of endrin exposure would be useful for studying 

potential endrin-related adverse health effects. 

Absorption, Distribution, Metabolism, and Excretion. There are limited data on the 

absorption, distribution, metabolism, and excretion of endrin in humans and animals. Limited studies 

provide qualitative evidence that endrin is absorbed following inhalation, oral, and dermal exposures 

(Chernoff et al. 1979a; Fleming et al. 1994; Kintz et al. 1992; Teschke et al. 1993; Wolfe et al. 1963), 

however, no information is available on the rate or extent of absorption that occurs by any of these 

routes. Additional studies are needed to determine absorption rates following exposure by all routes. 

Data are sparse on the distribution of endrin. Limited data in humans indicate that significant amounts 

of endrin residues are found in adipose tissue of people occupationally exposed, but not in the general 

population (Baldwin and Hutson 1980; Ottevanger and Van Sittert 1979; Stanley 1986; Teschke et al. 

1993; Williams 1986; Williams et al. 1984). Low levels of endrin are found in the liver, kidneys, and 

brain in people exposed to endrin or endrin-contaminated food (Curley et al. 1970; Runhaar et al. 

1985; Tewari and Sharma 1978). The time of sample collection is critical since endrin residues in 

tissues decline rapidly after exposure has ceased. 

No studies were found regarding the metabolism of endrin in humans. However, anti-12-hydroxyendrin 

and/or the corresponding glucuronide conjugate was found in feces and urine from workers at 

an endrin manufacturing plant (Baldwin and Hutson 1980). Studies in animals (Bedford et al. 1975a) 

acutely exposed via the oral route demonstrated that oxidation of the methylene bridge in endrin to 

syn- and, to a greater extent, anti-12-hydroxyendrin, occur, followed by dehydrogenation to 

12-ketoendrin. Minor pathways involving hydrolysis and hydroxylation reactions were also 

demonstrated (Bedford et al. 1975a). 

Data are sparse on the excretion of endrin in humans and animals. The presence of unchanged endrin 

in the milk fat of lactating cows and humans has been shown (Alawi et al. 1992; Baldwin et al. 1976; 

Bordet el al. 1993; Kanja et al. 1992; Spicer and Kereu 1993). Existing data indicate that endrin is 

rapidly transformed in the body after inhalation and oral exposures and is eliminated primarily as metabolites 

(12-hydroxy endrin, 12-ketoendrin, etc.). The urinary metabolite profile appears to be 
ENDRIN 87 

2. HEALTH EFFECTS 

species specific. Anti-12-hydroxyendrin and/or its glucuronide conjugate has been found in feces and 

urine from workers at an endrin manufacturing plant (Baldwin and Hutson 1980). In animals, 

12-hydroxyendrin-O-sulfate or 12-ketoendrin were detected in urine of rats after oral exposure 

(Baldwin et al. 1975; Hutson et al. 1975), while anti-12-hydroxyendrin sulfate and 3-hydroxyendrin 

sulfate were found in the urine of rabbits (Bedford et al. 1975b). No studies were found regarding 

excretion of endrin in humans or animals after dermal exposure. Additional studies on the excretion 

of endrin and its metabolites via the dermal route would be useful since differences in urinary 

metabolite profiles have been observed following exposure to endrin by other routes (Baldwin et al. 

1975; Bedford et al. 1975b; Hutson et al. 1975; Kanja et al. 1992; Spicer and Kereu 1993). 

Comparative Toxicokinetics. There are limited data on the kinetics of endrin in humans. 

Studies in animals suggest that metabolism and urinary metabolite profiles vary among species 

(Baldwin et al. 1975; Hutson et al. 1975; Kanja et al. 1992; Spicer and Kereu 1993). Additional 

studies using all three potential routes of human exposure would be useful in understanding differences 

in species and in determining which animal species is the most appropriate model for human exposure. 

Methods for Reducing Toxic Effects. Currently, recommended treatment for endrin toxicity is 

generally supportive in nature and includes general hygienic procedures for rapid decontamination. 

Treatment with benzodiazepines and phenytoin may be useful in the treatment of endrin-induced 

seizures. Further studies using animal models might be helpful in identification of other effective 

pharmacologic agents to counteract the convulsive effects of endrin. 

2.10.3 Ongoing Studies 

Two ongoing studies were identified that were related to endrin, endrin aldehyde, or endrin ketone, 

and are summarized in Table 2-5. 

ENDRIN 89 

3. CHEMICAL AND PHYSICAL INFORMATION
 

3.1 CHEMICAL IDENTITY 

Information regarding the chemical identity of endrin, endrin aldehyde, and endrin ketone is located in 

Table 3-l. 

3.2 PHYSICAL AND CHEMICAL PROPERTIES 

Information regarding the physical and chemical properties of endrin, endrin aldehyde, and endrin 

ketone is located in Table 3-2. 





ENDRIN 95 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

4.1 PRODUCTION 

Endrin is a stereoisomer of dieldrin produced by the reaction of vinyl chloride and hexachlorocyclopentadiene to yield a product which is then dehydrochlorinated and condensed with 

cyclopentadiene to produce isodrin. This intermediate is then epoxidized with peracetic or perbenzoic 

acid to yield endrin. An alternative production method involves condensation of hexachlorocyclopentadiene with acetylene to yield the intermediate for condensation with cyclopentadiene (EPA 1985e; 

IARC 1974). 

Endrin is no longer manufactured in the United States. Velsicol Chemical Company, Memphis, 

Tennessee, was the producer of endrin until the final voluntary cancellation of registration with the 

Office of Pesticide Programs in 1991 (Bishop 1984, 1985, 1986; EPA 1983e; USDA 1995). It is 

estimated that 2.345 million kg (5.1-9.9 million pounds) of endrin were sold in the United States in 

1962, while less than 450,000 kg (990,000 pounds) were produced in 1971 (IARC 1974). More recent 

estimates of domestic production of endrin could not be found (HSDB 1995). As with many toxic 

chemicals, information on production or use of pesticides is often proprietary, and quantitative 

estimates of production of endrin are virtually impossible to obtain (Bason and Colbom 1992). 

Chemical manufacturers in the United States however, can legally produce pesticides for export that 

are currently banned or not registered for use in the United States (FASE 1996). No information on 

the production of endrin was available from the Toxic Release Inventory (TRI) because endrin is not 

one of the chemicals that facilities are required to report (EPA 1995a). 

Endrin aldehyde and endrin ketone were never commercial products, but occurred as impurities of 

endrin or as degradation products (EPA 1985e; IARC 1974; SRI 1987). While commercial 

preparations of solid endrin were typically 95-98% pure, the following chemicals (in addition to 

endrin aldehyde and endrin ketone) have been found as trace impurities: aldrin, dieldrin, isodrin, 

heptachloronorbornadiene, and heptachloronorborene (HSDB 1995). The active ingredient would often 

be mixed with one or more organic solvents for application in a liquid form. Carriers included xylene, 

hexane, and cyclohexane (HSDB 1995; Zabik et al. 1971). 
ENDRIN 96 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

4.2 IMPORT/EXPORT 

Data on historic imports and exports of endrin are sparse. The most recent data that could be located 

indicate that about 21,000 kg (46,000 pounds) of endrin were imported into the United States in 1972 

(IARC 1974). No information on export volumes of endrin was located. Recently, however, the 

Foundation for Advancements in Science and Education reported that almost 75% of the 750,000 tons 

of pesticides the United States exported from 1992 to 1994 lacked chemical-specific information 

(FASE 1996). Many of the exported pesticides were organochlorine pesticides which had been banned 

for use in the United States. 

4.3 USE 

Endrin was first used as an insecticide, rodenticide, and avicide beginning in 1951 to control 

cutworms, voles, grasshoppers, borers, and other pests on cotton, sugarcane, tobacco, apple orchards, 

and grain (EPA 1979e; HSDB 1995). It was also used as an insecticide agent on bird perches (EPA 

1985f). Unlike aldrin/dieldrin, with which it has many chemical similarities, endrin apparently was 

never used extensively for termite-proofing or other applications in urban areas (Blus et al. 1989; 

HSDB 1995). Endrin’s toxicity to nontarget populations of raptors and migratory birds was a major 

reason for its cancellation as a pesticide agent (Blus et al. 1989). (EPA 1979f; USDA 1995). Except 

for use as a toxicant on bird perches, which was canceled in 1991, all other uses of endrin in the 

United States were voluntarily canceled by the manufacturer in 1986 (Bishop 1984, 1985, 1986; EPA 

1983e; USDA 1995). It has been estimated that 6,250 kg (13,780 pounds) of endrin were used 

annually in the United States prior to 1983 (Gianessi 1986). Since endrin may still be used as a 

pesticide agent in foreign countries, residues on imported food items are still of some concern (FDA 

1990, 1991, 1992; Hundley et al. 1988) (see Section 5.4.4). Both the EPA and FDA revoked all food 

tolerances for endrin in 1993 (USDA 1995). 

4.4 DISPOSAL 

Because endrin and endrin aldehyde are listed as hazardous substances, disposal of wastes containing 

these compounds is controlled by a number of federal regulations (see Chapter 7). Land disposal 

restrictions apply to wastes containing endrin or endrin aldehyde (EPA 1986d, 1987b). Chemical 

treatment (reductive dechlorination) or incineration are possible disposal methods (HSDB 1995; IRPTC 
ENDRIN 97 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

1985). Past disposal methods included land disposal (EPA 1987c; Sittig 1980). In general, disposal 

methods for endrin residues or endrin-containing wastes are similar to those for wastes containing 

aldrin/dieldrin (HSDB 1995). No information was found in the available literature on regulations or 

methods for the disposal of endrin ketone. 

No information was found in the available literature on the amounts of endrin, endrin aldehyde, or 

endrin ketone disposed of in the United States by any method. 

ENDRIN 99 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.1 OVERVIEW 

Endrin was introduced in the United States in 1951 as an avicide, rodenticide and insecticide. Its 

principal use to control the cotton bollworm and tobacco budworm peaked in the early 1970s. In 

1979, the EPA canceled some uses of endrin and indicated its intent to cancel all uses of endrin (EPA 

1979f; USDA 1995). By 1986, all uses were voluntarily canceled (Bishop 1984, 1985, 1986; EPA 

1993e; USDA 1995), except for its use as a toxicant on bird perches, which was canceled in 1991 

(USDA 1995). Endrin also was a contaminant in dieldrin (Verschueren 1983); however, all uses of 

this pesticide have been canceled since the mid-1980s (EPA 1992b). Consequently, there are no 

longer any significant releases of endrin to the environment in the United States. 

Endrin tends to persist in the environment mainly in forms sorbed to sediments and soil particles. A 

conservative estimate of its half-disappearance time in sandy loam soils is approximately 14 years 

(41% of endrin applied still remained in the soil after 14 years) (Nash and Woolson 1967). Therefore, 

the exposure risks from endrin to the general population of the United States are likely to steadily 

decrease over time. 

Migration of endrin into groundwater would not generally be expected from normal agricultural 

application. However, endrin has been detected in some groundwater, suggesting that leaching may be 

possible in some soils under certain conditions (Cohen 1986; EPA 1989; HazDat 1996). 

Biodegradation does not appear to be a significant fate process for endrin in soils (Nash and Woolson 

1967). Hydrolysis in moist soils is also not expected to be significant (EPA 19798). In combination, 

losses from volatilization, photodegradation (Burton and Pollard 1974; EPA 1985e; Knoevenagel and 

Himmelreich 1976; Zabik et al. 1971), and heat transformation (primarily to endrin ketone, with minor 

amounts of endrin aldehyde) (EPA 19798; Phillips et al. 1962) account for the rapid decrease in endrin 

residues on soil surfaces exposed to bright sunlight. 

In spite of its low vapor pressure, endrin has been found to volatilize significantly (20-30%) from 

soils within days after application (Nash 1983). In air, endrin will be primarily absorbed to 

particulates which may be re-entrained to soil or surface water via wet or dry deposition. Laboratory 

studies have indicated that a predominant mechanism for the transformation and degradation of endrin 
ENDRIN 100 

5. POTENTIAL FOR HUMAN EXPOSURE 

in air under field conditions is via photochemical reactions and rearrangements to yield primarily 

endrin ketone, with minor amounts of endrin aldehyde (Burton and Pollard 1974; EPA 1985e; Zabik et 

al. 1971). Endrin may also be transformed by heat in the atmosphere, yielding primarily the 

pentacylic ketone and endrin aldehyde (EPA 1979g; Phillips et al. 1962). Endrin may also react with 

photochemically generated hydroxyl radicals in air, with a predicted half-life ranging from 1.45 hours 

(Howard 1991) to 1.8 days (SRC 1995a). 

Endrin may be transported from soil to surface water via runoff from rain or irrigation. When released 

to water, endrin strongly adsorbs to sediment (Kenaga 1980) and bioconcentrates significantly in 

aquatic organisms (ASTER 1995; EPA 1980a; Metcalf et al. 1973). Endrin appears to be 

biomagnified only slightly through various levels of the food chain (Metcalf et al. 1973). It is likely 

that endrin released to surface water will undergo photoisomerization to endrin ketone, with minor 

amounts of endrin aldehyde also being formed (Burton and Pollard 1974; Zabik et al. 1971). Endrin 

may be biodegraded in water, but most laboratory studies indicate that this will not be a significant 

fate process (Eichelberger and Lichtenberg 1971; Sharom et al. 1980b; Tabak et al. 1981). In 

addition, neither hydrolysis nor volatilization is a significant fate process for endrin in water. The 

estimated half-life for endrin in water is more than 4 years (EPA 1979g; Howard 1991). Degradation 

of endrin in soils under field conditions is not a significant fate process with a half-disappearance time 

of the order of 14 years (Nash and Woolson 1967). 

No studies on the environmental fate of endrin aldehyde or endrin ketone could be found in the 

available literature. Limited information on the physical and/or chemical properties of endrin aldehyde 

indicates that it is highly insoluble in water (EPA 1981a), highly immobile in soil, and will not 

volatilize significantly from water or soil. Any endrin aldehyde in air should exist predominantly in 

the adsorbed phase (Eisenreich et al. 1981). Atmospheric endrin aldehyde will be transported to soil 

and surface water via wet and dry deposition of associated particles. Endrin aldehyde may react with 

photochemically generated hydroxyl radicals in the atmosphere, with an estimated half-life of 

3.6 hours (SRC 1995a). In water, adsorption to sediments and bioconcentration are likely to be 

significant transport processes. Neither hydrolysis nor oxidation (via peroxy radicals or singlet 

oxygen) of endrin aldehyde is expected to be significant in aquatic systems (EPA 1979g, 1981a). The 

estimated half-life for endrin aldehyde is more than four years (EPA 1979g). By analogy to aquatic 

systems, neither hydrolysis nor oxidation is expected to be a significant transformation process for 
ENDRIN 101 

5. POTENTIAL FOR HUMAN EXPOSURE 

endrin aldehyde in soil. No information could be found on the biodegradation of endrin aldehyde in 

aquatic systems, sediment, or soil. 

Endrin ketone may react with photochemically generated hydroxyl radicals in the atmosphere, with an 

estimated half-life of 1.5 days (SRC 1995a). Available estimated physical/chemical properties of 

endrin ketone indicate that this compound will not volatilize from water; however, significant 

bioconcentration in aquatic organisms may occur. In soils and sediments, endrin ketone is predicted to 

be virtually immobile; however, detection of endrin ketone in groundwater and leachate samples at 

some hazardous waste sites suggests limited mobility of endrin ketone in certain soils (HazDat 1996). 

No other information could be found in the available literature on the environmental fate of endrin 

ketone in water, sediment, or soil. 

Information on current levels of endrin in the environment is limited; however, the available data 

indicate that concentrations in all environmental media are generally negligible or below levels of 

concern. The FDA has concluded that endrin is no longer present in the environment to the extent 

that it may be contaminating food or feed at levels of regulatory concern (USDA 1995). No 

information could be found in the available literature on levels of endrin aldehyde or endrin ketone in 

the environment. 

The main sources for potential human exposure to endrin are residues on imported food items, unused 

stocks, unregistered use, inappropriate disposal, and hazardous waste sites; however, there is no current 

evidence of significant exposures from any of these sources. Furthermore, it should be noted that in 

environmental media, especially in contaminated soils and sediments, the amount of endrin chemically 

identified by analysis is not necessarily the amount that is toxicologically available. 

Endrin has been identified in at least 102 of the 1,430 current and former hazardous waste sites that 

have been proposed for inclusion in the NPL (HazDat 1996), although the total number of sites 

evaluated for endrin is not known. The frequency of these sites can be seen in Figure 5-1. Of these 

sites, 102 are located in the United States. Endrin ketone has been identified in at least 37 of the 

1,430 current and former hazardous waste sites that have been proposed for inclusion in the NPL 

(HazDat 1996). However, the number of sites evaluated for endrin ketone is not known. The 

frequency of these sites can be seen in Figure 5-2. Of these sites, 37 are located in the United States. 


ENDRIN 104 

5. POTENTIAL FOR HUMAN EXPOSURE 

Endrin aldehyde has not been identified in any of the 1,430 current and former hazardous waste sites 

that have been proposed for inclusion in the EPA National Priorities List (NPL) (HazDat 1996); 

however, the number of sites evaluated for endrin aldehyde is not known. 

5.2 RELEASES TO THE ENVIRONMENT 

No information is available in the Toxic Release Inventory (TRI) database on the amounts of endrin, 

endrin aldehyde, or endrin ketone released to the environment from facilities, that manufacture or 

process these compound because these chemicals are not included under SARA, Title III and, 

therefore, are not required to be reported (EPA 1995a). 

Because virtually all uses of endrin in the United States were voluntarily canceled by 1986 (Bishop 

1984, 1985, 1986; EPA 1993e; USDA 1995) (see Section 4.3), releases to the environment of endrin, 

or of endrin aldehyde and endrin ketone which occur as impurities or degradation products of endrin, 

have decreased dramatically over the last decade. 

5.2.1 Air 

In the past, emissions from endrin production and processing facilities and agricultural applications 

were primary sources of releases of endrin to the atmosphere. During the period when endrin was 

extensively used in agriculture, 33% of the applied endrin was found to volatilize within 11 days, after 

which time further evaporation ceased (Nash 1983). 

There is also a potential for atmospheric release of endrin, endrin aldehyde, and endrin ketone from 

hazardous waste sites. Endrin has been detected in air samples collected at 4 of the 102 NPL sites 

where endrin has been detected in some environmental medium (HazDat 1996). No information was 

found on detections of endrin aldehyde or endrin ketone in air at any NPL hazardous waste site 

(HazDat 1996) 

5.2.2 Water 

In the past, endrin could have been released to surface water from manufacturing and processing 

facilities. No information on direct discharges or loadings of endrin into surface water was found. 

Based on amounts measured in rainfall at various stations in Canada, loading estimates for endrin and 
ENDRIN 105 

5. POTENTIAL FOR HUMAN EXPOSURE 

a number of other organochlorine pesticides have been attempted for portions of the Great Lakes basin 

(Strachan 1988). The sources for such loadings to receiving waters are not clear, but would likely 

involve in-place contaminants related to endrin’s past uses as a pesticide agent. Current studies in 

Oklahoma indicate that in some areas of the United States endrin is still being released to surface 

water from farmland soils that have been treated with endrin in the past (Petty et al. 1995). 

There is also a potential for release of endrin, endrin aldehyde, and endrin ketone to water from 

hazardous waste sites. Endrin has been detected in surface water samples collected at 10 of the 

102 NPL sites, in groundwater samples collected at 37 of the 102 NPL sites, and in leachate samples 

collected at 2 of the 102 NPL sites where endrin has been detected in some environmental medium 

(HazDat 1996). Endrin ketone has been detected in surface water samples collected at 5 of the 

37 NPL sites, in groundwater samples collected at 16 of the 37 NPL sites, and in leachate samples 

collected at 2 of the 37 NPL sites where endrin ketone has been detected in some environmental 

medium (HazDat 1996). No information was found on detections of endrin aldehyde in surface water, 

groundwater, or leachates at any NPL hazardous waste site (HazDat 1996) 

5.2.3 Soil 

Past use of endrin as an agricultural pesticide has been the principal source of its release to soils or 

aquatic sediments. There is also a potential for release of endrin, endrin aldehyde, and endrin ketone 

to soils and sediments from hazardous waste sites. Endrin has been detected in soil samples collected 

at 44 of the 102 NPL sites, and in sediment samples collected at 19 of the 102 NPL sites where endrin 

has been detected in some environmental medium (HazDat 1996). Endrin ketone has been detected in 

soil samples collected at 23 of the 37 NPL sites, and in sediment samples collected at 5 of the 37 NPL 

sites where endrin ketone has been detected in some environmental medium (HazDat 1996). No 

information was found on detections of endrin aldehyde in soils or sediments at any NPL hazardous 

waste site (HazDat 1996). 

5.3 ENVIRONMENTAL FATE 

5.3.1 Transport and Partitioning 

Endrin is extremely persistent when released to the soil. It adsorbs strongly to soil particles and tends to be 

immobile, based on an estimated Koc of 34,000 (Kenaga 1980; Swann et al. 1983). Endrin on 
 

ENDRIN 106 

5. POTENTIAL FOR HUMAN EXPOSURE 

soil may be transported to surface water via runoff from rain or irrigation. Since endrin in solid form 

is hydrophobic and sorbs strongly to soil particles, migration into groundwater would not generally be 

expected from normal agricultural application. In laboratory studies, endrin was found to be almost 

completely adsorbed to samples of sandy loam and organic soil (Sharom et al. 1980a). In sandy soil 

only 13.6% of the endrin was leached from the soil after 10 successive 200 mL water rinses. In 

organic soil, only 1.5% of the endrin was leached from the soil after 10 successive 200 mL water 

rinses. The mobility factors calculated for the sandy soil and organic soil were 0.52 and 0.040, 

respectively. Only dieldrin, leptophos, and p,p’-DDT were less mobile in the 2 soil types than endrin. 

However, endrin has been detected in some leachates and groundwaters from NPL hazardous waste 

sites (see Section 5.2.2) and in various other groundwaters, suggesting that leaching may be possible in 

some soils under certain conditions (Cohen 1986; EPA 1989; HazDat 1996). Furthermore, because 

endrin formulations in solvent carriers such as xylene or hexane were also commonly used, endrin 

could move into groundwater from spills of such formulations. Similarly, migration to groundwater 

might also occur at waste sites where endrin residues become mixed with organic solvents (Jaquess et 

al. 1989). 

Despite endrin’s low vapor pressure of 2.0x10-7 mm Hg (EPA 1981a), initial volatilization of 20-30% 

after agricultural application to soil has been reported to be rapid (Nash 1983). Within 11 days, 

however, further volatilization was no longer detected (Nash 1983). Unlike some other chlorinated 

pesticides, endrin volatilization was not enhanced after a rainfall. Small amounts of endrin in soil may 

also be transported to the air by dust particles. 

The presence of significant concentrations of endrin transformation products (including endrin ketone, 

endrin aldehyde, and endrin alcohol) in a variety of plants grown in soil treated with endrin for periods 

as long as 16 years prior to planting (Beall et al. 1972; Nash and Harris 1973) indicates that there 

may be significant uptake of endrin and/or its transformation products by plants from endrin-treated 

soil. 

Because of its high log Koc and log Kow values (4.53 and 5.34-5.6, respectively; see Table 3-2), when 

released to water, endrin strongly adsorbs to sediment (Kenaga 1980; Swann et al. 1983) and 

bioconcentrates significantly in aquatic organisms (ASTER 1995; EPA 1980a; Metcalf et al. 1973). Typical 

bioconcentration factors (BCFs) for freshwater and marine organisms range from 80 to 49,000 
ENDRIN 107 

5. POTENTIAL FOR HUMAN EXPOSURE 

(Table 5-l). Biomagnification of endrin with increasing trophic level is not expected to be significant 

(Leblanc 1995). Metcalf et al. (1973) reported a ratio of biomagnification through the aquatic food 

7chain to bioconcentration by direct uptake from water to be 2 for endrin compared to 2.50 for DDT. 

These authors used a model laboratory aquatic ecosystem containing algae (Oedogonium cardiacurn), 

snails (Physa sp.), water fleas (Daphnia magna), mosquito larvae (Culex pipens 

quinquefasciatus), and mosquito fish (Gambusia afinis). 

-7 -7 3 Based on its very small calculated Henry’s law constant of 4.0x10 -5.4xl0 atm-m /mol (see 

Table 3-2) and its strong adsorption to sediment particles, endrin would be expected to partition very 

little from water into air (Thomas 1990). The half-life for volatilization of endrin from a model river 

1 meter deep, flowing 1 meter per second, with a wind speed of 3 meters per second, was estimated to 

be 9.6 days; whereas, a half-life of greater than 4 years has been estimated for volatilization of endrin 

from a model pond (Howard 1991). Adsorption of endrin to sediment may reduce the rate of 

volatilization from water. 

In air, endrin is expected to be associated primarily with particulate matter, based on its low vapor 

pressure and high Koc (Kenaga 1980). However, small amounts of endrin in the atmosphere may exist 

in the vapor phase (Eisenreich et al. 1981). Because of its low solubility (200 (Pg /L, see Table 3-2) 

endrin would not be expected to be removed significantly from the atmosphere by wet deposition. 

Particle-adsorbed endrin will be removed from the atmosphere by both wet and dry deposition. In 

recent studies in the Great Lakes area, endrin was found in 5% of 450 wet deposition (rain/snow) 

samples collected between 1986-1991, at volume weighted mean concentrations ranging from 0.02 to 

0.98 ng/L (ppt) (Chan et al. 1994). 

No studies on the environmental transport and partitioning of endrin aldehyde could be found in the 

available literature. Values of the estimated log Kow for endrin aldehyde vary widely, ranging from 

3.1 to 5.6 (see Table 3-2). Based on the lowest estimated log Kow, the Koc value for endrin aldehyde 

can be estimated to be approximately 1,000 (Lyman 1990), indicating a low mobility in soil (Swann et 

al. 1983). Using the higher estimated values of log Kow (4.7-5.6), the Koc value for endrin aldehyde 

can be estimated to range from 8,500 to 380,000 (Lyman 1990), indicating that this compound will be 

virtually immobile in most soils (Swann et al. 1983). Because of its low vapor pressure of 


ENDRIN 110 

5. POTENTIAL FOR HUMAN EXPOSURE 

-7 -9 -8 3 2.0x10 mm Hg and Henry’s Law constant ranging from 2x10 -3.7xl0 atm-m /mol (see 

Table 3-2), endrin aldehyde would not be expected to volatilize significantly from soil or water 

(Eisenreich et al. 1981; Thomas 1990). Any endrin aldehyde in air should exist predominantly in the 

adsorbed phase (Eisenreich et al. 1981). Atmospheric endrin aldehyde will be transported to soil and 

surface water via wet and dry deposition of associated particles. In water, adsorption to sediments and 

bioconcentration are likely to be significant partitioning processes. Based on the lowest estimated 

value of 3.1 for log Kow (see Table 3-2), the BCF value for endrin aldehyde can be estimated to be 

only 86 (Veith et al. 1979), indicating little tendency to bioconcentrate in aquatic organisms. Using 

the higher estimates of 4.7-5.6 for log Kow (see Table 3-2), BCF values for endrin aldehyde are 

estimated to range from to 2,000 to 11,000 (Veith et al. 1979), indicating a much higher tendency for 

bioconcentration. 

No studies on the environmental transport or partitioning of endrin ketone could be found in the 

available literature, and only limited information was found on estimated values of physical and 

chemical properties. The very low estimated value of 2.02x10-8 atm-m 3

/mole for Henry’s Law 

constant for endrin ketone (see Table 3-2) indicates that this compound will not volatilize from water. 

Based on the estimated log Kow of 4.99 (see Table 3-2), the BCF value for endrin ketone can be 

estimated to be 3,500 (Veith et al. 1979), indicating that endrin ketone may be removed from water 

via bioconcentration in aquatic organisms. Also based on an estimated log Kow of 4.99, the Koc value 

for endrin ketone can be estimated to range from 5,500 to 90,000 (Lyman 1990), indicating that this 

compound will be virtually immobile in soil and sediments (Swann et al. 1983). However, detection 

of endrin ketone in groundwater and leachate samples at some NPL sites suggests some limited 

mobility of endrin ketone in certain soils (HazDat 1996). 

5.3.2 Transformation and Degradation 

5.3.2.1 Air 

Field studies on the transformation of endrin in the atmosphere were not located in the available 

literature. Photochemical isomerization of endrin, primarily to the pentacyclic ketone commonly called 

delta ketoendrin or endrin ketone, was observed after exposure of thin layers of solid endrin on glass 

to sunlight (Burton and Pollard 1974). Minor amounts of endrin aldehyde were also formed in this reaction. 

Results of seasonal studies indicated that this isomerization would proceed with a half-life 
 

 

ENDRIN 111 

5. POTENTIAL FOR HUMAN EXPOSURE 

(first-order kinetics) of 5-9 days in intense summer sunlight, with complete conversion to the 

pentacyclic ketone in 15-19 days. Knoevenagel and Himmelreich (1976) reported that 

photodegradation of solid endrin in the laboratory proceeded with a half-life (first-order kinetics) of 

20-40 hours. In laboratory studies conducted by Zabik et al. (1971) on endrin formulations in hexane 

and cyclohexane (similar to those commonly used for pesticide applications), endrin was found to 

undergo photolytic dechlorination when exposed to ultraviolet radiation, yielding a pentachlorinated 

half-cage ketone as the major product. This degradation product was also detected in environmental 

samples. Endrin may also be transformed by heat in the atmosphere, yielding primarily the pentacylic 

ketone and endrin aldehyde (EPA 19798; Phillips et al. 1962). Endrin may also react with 

photochemically generated hydroxyl radicals in air, with a predicted half-life (first-order kinetics) 

ranging from 1.45 hours (Howard 1991) to 1.8 days (SRC 1995a). No information could be found on 

the products of this reaction. The reaction of endrin with ozone in air is not significant. The 

predicted first-order rate constant for this reaction is 3.6x10-20

 cm

3

/molecule-sec, corresponding to a 

half-life of 320 days (SRC 1995a). 

Endrin aldehyde may react with photochemically generated hydroxyl radicals in the atmosphere, with 

an estimated overall first-order rate constant of 106x10-12

 cm

3

/molecule-see, which corresponds to a 

half-life of 3.6 hours, assuming a 24-hour concentration of hydroxyl radicals of 0.5x106 

molecules/cm3 (SRC 1995a). Endrin ketone may react with photochemically generated hydroxyl 

radicals in the atmosphere, with an estimated overall first-order rate constant of 

10.8x10-12 cm

3

/molecule-set, which corresponds to a half-life of 1.5 days, assuming a 24-hour 

concentration of hydroxyl radicals of 0.5x106

 molecules/cm3 (SRC 1995a). No other information 

could be found in the available literature on the transformation and degradation of endrin aldehyde or 

endrin ketone in air. 

5.3.2.2 Water 

Laboratory studies of the fate of endrin in water samples suggest a significant degree of stability, 

although there is evidence of varying degrees of biodegradation in some systems. Endrin was among 

the more stable of 12 insecticides incubated in water collected from the drainage canal of a vegetablegrowing site near Toronto, with about 80% of endrin remaining in the natural water after incubation 

for 16 weeks (Sharom et al. 1980b). There was little indication of chemical degradation of endrin in 

these studies. Studies in which sealed water samples from the Little Miami River were exposed to 
ENDRIN 112 

5. POTENTIAL FOR HUMAN EXPOSURE 

sunlight and artificial fluorescent light showed no measurable degradation of endrin over an 8-week 

period (Eichelberger and Lichtenberg 1971). However, microorganisms in fish pond water and algae 

from a fish pond were able to metabolize endrin (Patil 1972). In the case of the algae, the metabolite 

was 12-ketoendrin. The rate of metabolism was 35% for the water sample and 24% for the algal 

culture in one month. Using the static culture procedure, Tabak et al. (1981) found no biodegradation 

of endrin in domestic waste water samples. 

Based on laboratory experiments on solid endrin (Burton and Pollard 1974) and on endrin in organic 

solvents (Zabik et al. 1971), it is likely that endrin released to surface water will undergo 

photoisomerization to endrin ketone, with minor amounts of endrin aldehyde also being formed. 

Under real world conditions, endrin released to surface waters would not be expected to biodegrade or 

hydrolyze to any significant extent (Eichelberger and Lichtenberg 1971; EPA 19798). Endrin is very 

resistant to hydrolysis, with an estimated half-life (first-order kinetics) of more than 4 years (EPA 

19798). The predominant removal of endrin from water by photodegradation and sorption to 

suspended particulates or sediments (see Section 5.3.1) is consistent with the observed low incidence 

of detected endrin in ambient surface waters based on analyses of EPA National Urban Runoff 

Program (Cole et al. 1984) and STORET (Staples et al. 1985) data as described in Section 5.4.2. 

Little information could be found in the available literature on the transformation and degradation of 

endrin aldehyde in water. Neither hydrolysis nor oxidation (via peroxy radicals or singlet oxygen) are 

expected to be significant in aquatic systems (EPA 1981a). By analogy to endrin, the hydrolysis halflife 

(first-order kinetics) of endrin aldehyde in water is probably greater than four years (EPA 1979g). 

No information could be found on the biodegradation of endrin aldehyde in aquatic systems. 

No information could be found in the available literature on the transformation and degradation of 

endrin ketone in water. 

5.3.2.3 Sediment and Soil 

Biodegradation does not appear to be a significant degradation process for endrin in soils. The actual 

measurement of biodegradation of endrin under field conditions on well drained agricultural soil 

indicate a biodegradation half-disappearance time of approximately 14 years (Nash and Woolson 
ENDRIN 113 

5. POTENTIAL FOR HUMAN EXPOSURE 

1967), suggesting that endrin is resistant to biodegradation in soils under natural conditions. In this 

study, 41% of the initial endrin applied to an agricultural field was present in the soil after 14 years, 

Laboratory studies indicate that endrin can be biodegraded in various soils under various conditions; 

however, caution should be exercised in extrapolating laboratory results to field conditions. Twenty 

different isolates of soil organisms belonging to several different species (5 identified, 4 unidentified) 

were found to biodegrade endrin in the laboratory under aerobic conditions (Patil et al. 1970). The 

study revealed endrin as one of the more easily biodegradable insecticides, while lindane, for example, 

was not degraded by any of the 20 isolates. In contrast, Bartha et al. (1967) found no biodegradation 

of endrin, but they used rather insensitive analytical techniques compensated for by high endrin 

concentrations (0.25 ppm) that would not occur in normal agricultural practice. Nitrification was 

enhanced by endrin in this experiment. Endrin was also biodegraded to four unidentified metabolites 

in laboratory microcosms using flooded rice soils (Gowda and Sethunathan 1976). The most rapid 

degradation was seen in the saline acid sulfate soil, pokkali, followed by alluvial and laterite soils, 

where endrin concentrations dropped l0-20-fold in 55 days. Sandy soils were least active and reduced 

endrin concentration only by about 40% in 55 days. The addition of organic matter, such as rice 

straw, approximately doubled the rate of biodegradation. Half-disappearance times of endrin in soils 

ranged from less than 20 days under optimal conditions to about 80 days under less favorable 

conditions. A degradation half-life (first-order kinetics) of 26-32 weeks was reported for endrin 

(initial concentration approximately 1.6-2.0 ppm) in a clay soil under controlled, aerobic 

environmental conditions (30 (C; soil water content 10-33%), with slower degradation observed in 

soils with the lowest moisture content (Ghadiri et al. 1995). First-order rate equations best described 

the degradation. Virtually complete anaerobic biodegradation of endrin in laboratory microcosms 

within 4 days has been reported; however, the researchers caution that under natural conditions redox 

environments in many soils will not be suitable for anaerobic degradation, and that endrin residues 

sorbed to soil particles would often be rendered unavailable to bacteria (Maule et al. 1987). 

In combination, losses from volatilization, photodegradation (Burton and Pollard 1974; EPA 1985e; 

Knoevenagel and Himmelreich 1976; Zabik et al. 1971), and heat transformation (primarily to endrin 

ketone, with minor amounts of endrin aldehyde) (EPA 1979g; Phillips et al. 1962) are likely to 

account for a rapid decrease in endrin residues on soil or plant surfaces exposed to bright sunlight. 

Studies have also been conducted indicating significant concentrations of endrin transformation 
ENDRIN 114 

5. POTENTIAL FOR HUMAN EXPOSURE 

products (including endrin ketone, endrin aldehyde, and endrin alcohol) in plants grown in endrintreated 

soil (Beall et al. 1972; Nash and Harris 1973). 

Little information could be found in the available literature on the transformation and degradation of 

endrin aldehyde in sediment and soil. By analogy to aquatic systems, neither hydrolysis nor oxidation 

(via peroxy radicals or singlet oxygen) would be expected to be significant transformation processes. 

No information could be found on the biodegradation of endrin aldehyde in sediment or soil. 

No information could be found in the available literature on the transformation and degradation of 

endrin ketone in sediment and soil. 

5.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT 

Reliable evaluation of the potential for human exposure to endrin depends in part on the reliability of 

supporting analytical data from environmental samples and biological specimens. Endrin’s sensitivity 

to thermal degradation, however, may sometimes make it difficult to interpret analytical work 

conducted in the 1960s and 1970s because temperatures used in many types of gas chromatography 

analytical procedures for organochlorine pesticides at that time have been shown to isomerize endrin 

into a variety of ketones, aldehydes, alcohols, and other unidentified products (Phillips et al. 1962). In 

reviewing data on levels monitored or estimated in the environment, it should also be noted that the 

amount of the chemical identified analytically is not necessarily equivalent to the amount that is 

bioavailable. 

5.4.1 Air 

Endrin is relatively nonvolatile with a vapor pressure of 2.0x10-7 mm Hg (EPA 1981a; Worthing and 

Walker 1983). Despite its low volatility, initial loss of agriculturally applied endrin through 

volatilization was found to be comparable to more volatile pesticides (Nash 1983). No recent data on 

atmospheric concentrations of endrin could be found in the available literature. Endrin was detected in 

air samples collected at 4 of the 102 NPL sites where endrin has been detected in some environmental 

medium; however, concentrations were not available (HazDat 1996). 
ENDRIN 115 

5. POTENTIAL FOR HUMAN EXPOSURE 

Limited information was found on atmospheric concentrations of endrin between 1970 and the 

mid-1980s, prior to cancellation of virtually all uses (Bishop 1984, 1985, 1986; EPA 1993e; USDA 

1995) (see Section 4.3). The data were insufficient to identify any trends. The mean and maximum 

airborne concentrations of endrin in the United States in 1970-71 were reported to be 0.2 ng/m3

 and 

19.2 ng/m3

, respectively (Lee 1977). For that same time period, mean airborne concentrations at 

suburban sites near Jackson, Mississippi, and Columbia, South Carolina, were reported to be 0.1 ng/m3 

and 0.2 ng/m3, respectively (Bidleman 1981; Kutz et al. 1976). Endrin was not detected at Boston, 

Massachusetts, suburban sites (Bidleman 1981). A survey of airborne contaminants in the Great Lakes 

area in 1981 did not detect endrin (Eisenreich et al. 1981). 

Atmospheric concentrations of endrin in the vicinity of manufacturing facilities were higher than those 

found in non-source areas of the United States. Eight hundred meters from 2 formulation plants in 

Arkansas and 275 meters from one formulation plant in Tennessee, mean airborne concentrations of 

endrin were reported to be 3.3 ng/m3

 and 3.5 ng/m3, respectively, during 1970-72 (Lewis and Lee 

1976). Endrin was also detected in air in industrial or source-dominated regions of the Mississippi 

Delta in 1972-74, and in Tennessee in 1971 (EPA 1985e). 

Endrin may also be found in atmospheric precipitation. In an analysis of pesticides in rainfall from 

four stations in Canada in 1984, detectable concentrations of endrin were found at each site (Strachan 

1988). There was a noticeable pattern of decline in detections within the summer season 

(May-August). In more recent studies in the Great Lakes area, endrin was found in 5% of 450 wet 

deposition (rain/snow) samples collected between 1986 and 1991, at volume weighted mean 

concentrations ranging from 0.02 to 0.98 ng/L (ppt) (Chan et al. 1994). 

No information was found in the available literature on concentrations of endrin aldehyde or endrin 

ketone in ambient outdoor air or in indoor air. In addition, no information was available on 

occupational exposures to these chemicals. 

5.4.2 Water 

Very little recent information on concentrations of endrin in water could be found in the available 

literature. Unlike DDT, chlordane, aldrinidieldrin, and a variety of other chlorinated pesticides, endrin 

was never used extensively in urban areas. This is reflected in the results from EPA’s Nationwide 
ENDRIN 116 

5. POTENTIAL FOR HUMAN EXPOSURE 

Urban Runoff Program, which showed no detections in 86 high-flow water samples from 51 urbanized 

watersheds from 19 cities (Cole et al. 1984). Analysis of EPA STORET monitoring information from 

ambient surface water showed a significant percentage of detections for endrin (32% of 

8,789 samples), but most were near the detection limits, with a national median concentration of 

0.001 ppb (Staples et al. 1985). A similar analysis of STORET data for endrin aldehyde showed that 

this compound was not found in 770 samples of ambient surface water. More recently, endrin was not 

detected (detection limit 49 ng/L [0.045 ppb]) in surface water from the Yakima River Basin, 

Washington (Foster et al. 1993). However, in 1991-92, endrin was detected in first flush (first 

20 minutes) stormwater runoff samples at 4 of 6 sites in Louisville, Kentucky, at levels that exceeded 

U.S. Federal criteria (0.003 (Pg /L, [ppb]) (Marsh 1993). Maximum, minimum, and mean concentrations 

at the 4 sites ranged from 0.03 to 0.05, 0.02 to 0.04, and 0.03 to 0.04 (ppb), respectively. Endrin was 

not detected (detection limit not specified) in 3-hour composite samples of stormwater runoff from any 

of the 6 sites. Endrin has been detected in surface water samples collected at 10 of the 102 NPL sites 

where it was detected in some environmental media (HazDat 1996). 

Recent studies using semipermeable membrane devices to determine bioavailable (dissolved) 

organochlorine pesticide residues in streams receiving irrigation rainwater from agricultural activity in 

the Luger Altus Watershed in southwestern Oklahoma indicate that endrin may still be present in this 

aquatic ecosystem several years after discontinuation of its use (Petty et al. 1995). Calculated 

concentrations of bioavailable endrin at 6 sampling sites ranged from not detected (detection limit not 

specified) to 110 (Pg /L (ppb). Concentrations were higher in spring than in summer. There is an 

uncertainty in these estimates because they were derived from the dialysate data using models and 

preliminary data on uptake kinetics. 

Endrin is rarely detected in drinking water and any trace amounts of endrin that might be encountered 

in raw drinking water supplies will likely be removed in the treatment systems used by most 

communities. In 1966 and 1967, when the use of endrin was not restricted, endrin was detected in 

5 of 67 raw water samples from the Mississippi and Missouri Rivers (Schafer et al. 1969). At a later 

time when endrin use was substantially restricted, an Iowa study of 33 community water supplies 

using surface water found no detectable concentrations of endrin in the distribution systems (Wnuk et 

al. 1987). In an extensive water quality monitoring program conducted by the California Department 

of Health Services, endrin was detected (detection limit not specified) in only 2 of 5,109 public 

drinking water sources sampled from 1984 to 1992, at mean and maximum concentrations of 0.06 and 
ENDRIN 117 

5. POTENTIAL FOR HUMAN EXPOSURE 

0.10 ppb, respectively (Storm 1994). Concentrations did not exceed the Maximum Concentration 

Level (MCL) of 0.2 ppb. In another recent study, endrin was not detected (detection limit not 

specified) in 32 samples each of raw water and highly treated reclaimed waste water undergoing 

evaluation as a possible supplement to raw water sources in San Diego, California (De Peyster et al. 

1993). 

Detections of endrin in groundwater are also rare except from wells near hazardous waste sites. The 

EPA Pesticides in Groundwater Data Base (EPA 1989) contains groundwater data collected with good 

quality assurance/quality control (QA/QC) provisions from areas with significant agricultural land uses 

as well as from urban areas. Analysis of these data indicated there were only two wells with 

detectable levels of endrin within the entire United States. A detection occurred in a well in California 

(concentration not reported) where point source problems or spills were deemed the likely sources. 

Endrin contamination found in an Illinois well at an average concentration of 0.02 ppb was considered 

likely to have resulted from ordinary agricultural uses. In a groundwater contamination study of 

California’s 58 counties, in which over 50 pesticides were evaluated from both point and nonpoint 

sources, endrin was detected in only one sample (Cohen 1986). In a more recent study, endrin was 

detected at 0.9% of 178 CERCLA sites and 1.3% of 156 RCRA sites sampled; however, endrin 

concentrations were not reported (Plumb 1987). Endrin was also found in groundwater samples 

collected at 37 of the 102 NPL and in leachate samples collected at 2 of the 102 NPL sites where 

endrin has been detected in some environmental media; however, concentrations were not reported 

(HazDat 1996). 

No information was found in the available literature on levels of endrin aldehyde or endrin ketone in 

surface or groundwater. Endrin ketone has been detected in surface water samples collected at 5 of 

the 37 NPL sites, in groundwater samples collected at 16 of the 37 NPL sites, and in leachate samples 

collected at 2 of the 37 NPL sites where endrin ketone has been detected in some environmental 

medium; however, concentrations were not reported (HazDat 1996). 

5.4.3 Sediment and Soil 

Very little recent information on levels of endrin in soils was found in the available literature. From 

the available data it appears that, in general, endrin was found infrequently and at relatively low levels 

in both urban and cropland soils in the United States. Endrin was detected in only 10 of 
ENDRIN 118 

5. POTENTIAL FOR HUMAN EXPOSURE 

1,483 cropland soil samples in 1972 at concentrations up to 2.13 ppm (detection limit of 0.01 ppm) 

(Carey et al. 1979). These studies were part of the National Soils Monitoring Program carried out by 

EPA and the USDA under the National Pesticide Monitoring Program, which covered a total of 

1,533 sampling sites in 37 states. Endrin detections were documented in the following states: 

Alabama, Arkansas, Georgia, Illinois, Louisiana, Nebraska, New York, North Carolina, and South 

Dakota, as well as at sites from one or more of the mid-Atlantic states of Delaware, Maryland, and 

New Jersey. Endrin was also detected at a level of 0.017 ppm at a single site in California in a study 

that targeted rice-growing cropland soils in Arkansas, California, Louisiana, Mississippi, and Texas 

(Carey et al. 1980). Endrin was not detected in urban soils from 13 of 14 U.S. cities included in a 

1970 study of pesticide residues in urban soils (25-30 soil sampling sites were used for each of the 

urban areas) (Carey et al. 1976). The only detection was at a single site near Memphis, Tennessee, 

where the Velsicol Chemical Company (which produced endrin at that time) is located. The reported 

concentration for this site was 0.07 ppm; the mean concentration for all 28 Memphis sites was 

<0.01 ppm. 

Relatively little literature was identified concerning the analysis of endrin in aquatic sediments. The 

available data indicate that, historically, sediment concentrations of endrin have been very low. In a 

recent study of sediment contaminants in Casco Bay, Maine, endrin was found at concentrations near 

or below the method detection limit (<0.25 ppb) (Kennicutt et al. 1994). In the National Surface 

Water Monitoring Program conducted from 1976 to 1980, endrin was detected in 1.3% of the sediment 

samples analyzed (detection limit not reported) with a maximum concentration of 2.9 ppb (Carey and 

Kutz 1985). An analysis of EPA STORET data indicated endrin was detected in 24% of the 

1,802 sediment records listing endrin as a parameter code. The median endrin concentration for all 

records was 0.001 ppb (Staples et al. 1985). A similar analysis of STORET data indicated that endrin 

aldehyde was not found in any of 251 samples of sediment (Staples et al. 1985). In a study by Ford 

and Hill (1991) to evaluate organochlorine pesticide residues in sediments and aquatic animals in the 

vicinity of the Yazoo National Wildlife Refuge in the Mississippi Delta, a region that has experienced 

very high usage of pesticide agents, detectable levels of endrin were not found in sediments (detection 

limit 0.01 ppm [l0 ppb]). Similarly, endrin was not detected in sediment or pore water samples 

(detection limits 0.49 and 0.01 ppm [490 and 10 ppb], respectively) from 18 mosquito control 

impoundments in St. Lucie County, Florida, where organochlorine pesticides had been heavily used 

through the early 1960s (Parkinson et al. 1993). 
 

ENDRIN 119 

5. POTENTIAL FOR HUMAN EXPOSURE 

There is a potential for endrin to be present in soils and sediments at hazardous waste sites. Endrin 

has been detected in soil samples collected at 44 of the 102 NPL sites and in sediment samples 

collected at 19 of the 102 NPL sites where endrin has been detected in some environmental medium; 

however, concentrations were not reported (HazDat 1996). Endrin was not detected (detection limit 

0.01 ppm [l0 ppb] wet weight), however, in soils derived from dredged materials at 9 confined 

disposal facilities bordering the Great Lakes (Beyer and Stafford 1993). 

No information was found in the available literature on levels of endrin aldehyde in soil or endrin 

ketone in sediment or soil. Endrin ketone has been detected in soil samples collected at 23 of the 

37 NPL sites and in sediment samples collected at 5 of the 37 NPL sites where endrin ketone has been 

detected in some environmental medium; however, concentrations were not reported (HazDat 1996). 

5.4.4 Other Environmental Media 

Endrin has been found in many foods, but current levels appear to be very low and not of concern for 

human health. The FDA has concluded that endrin is no longer present in the environment to the 

extent that it may be contaminating food or feed at levels of regulatory concern (USDA 1995). An 

FDA survey of pesticide residues in samples of domestic and imported food and feed commodities 

from Fiscal Year (FY) 1982 to 1986 lists endrin levels for specific food items up to 0.50 ppm 

(500 ppb) (Hundley et al. 1988). This study was conducted by surveillance sampling with follow-up 

compliance sampling for sources of foodstuffs where the concentrations in surveillance samples 

violated EPA tolerance levels. In surveillance sampling, endrin was detected in 0.05% (3 of 

6,391 samples) and 1.5% (183 of 12,044 samples) of domestic and imported foods, respectively. The 

incidence of violative surveillance samples (endrin residues >0.05 ppm [50 ppb]) was higher for 

imported foods (0.1%; 12 violations) than for food items from domestic sources (0.02%; 1 violation). 

In follow-up compliance monitoring of 1,239 samples of imported foods, endrin was found in 

11 samples (0.9%); 2 of these samples (0.2%) were violative. In imported foods, endrin was detected 

in mung beans, cucumbers, pickling cucumbers, cantaloupe, acorn squash, cabocha squash, Italian 

squash, summer squash, and yellow squash (Hundley et al. 1988). No follow-up compliance 

monitoring of domestic samples for endrin residues was performed. 

In a more recent study of pesticide residues in food conducted in 10 states between 1988 and 1989, 

endrin was not detected in any of the 13,980 samples analyzed in 1988. In 1989, the detection 
 

ENDRIN 120 

5. POTENTIAL FOR HUMAN EXPOSURE 

frequencies for endrin and endrin ketone were 0.084% and 0.007%, respectively, for the 

13,085 samples analyzed (Minyard and Roberts 1991). In a Canadian study, reported concentrations 

of endrin in composite samples of fresh root vegetables, fruit, leafy and other above-ground 

vegetables, and cows’ milk ranged from 0.27 to 0.37 ppb; endrin was not detected in composite 

samples of fresh meat and eggs (detection limit 0.01 ppb) (Davies 1988). Endrin was detected each 

year in regulatory monitoring of domestic and imported foods conducted by the FDA from 1989 to 

1994 as part of its Pesticide Residue Monitoring Program (FDA 1990, 1991, 1992, 1993, 1994, 1995). 

Concentrations were not reported; however, <1% of the surveillance samples had any pesticide residue 

levels that were above established tolerances. Endrin was also detected in the FDA Total Diet Studies 

in 1987, 1988, 1989, and 1991, but not in 1990 (FDA 1988, 1989, 1990, 1991, 1992). Reports of 

1992-94 FDA Total Diet Studies did not indicate whether endrin was detected in those years (FDA 

1993, 1994, 1995). In the years in which endrin was detected in the FDA Total Diet Studies, it was 

not among the most frequently detected pesticides. Concentrations of endrin found in the FDA Total 

Diet studies were not reported. However, in an overall summary for the 5-year period 1986-91, 

average dietary intakes of endrin for 8 age/sex groups (6-l l-month-old infants, 2-year-old children, 

14-16-year-old males and females, 25-30-year-old males and females, and 60-65-year-old males and 

females) were all estimated to be <0.000l (Pg /kg body weight per day, less than 0.03% of the EPA 

RfD of 0.3 (Pg /kg body weight per day (FDA 1993). A food basket survey patterned after the FDA 

approach that was conducted in San Antonio, Texas did not find detectable concentrations of endrin 

(detection limit 0.050 ppm [50 ppb]) in 6,970 produce items (Schattenberg and Hsu 1992). 

Overall, in 234 ready-to-eat foods tested 37 times each as part of the FDA Total Diet Studies from 

1982 to 1991, endrin was found only 26 times at an average concentration of 0.0027 (Pg /g (2.7 ppb) in 

9 different foods: broccoli, cantaloupe, collards, cucumbers, onion rings, dill pickles, pumpkin pie, 

summer squash, and winter squash (KAN-DO Office and Pesticides Team 1995). Concentrations 

ranged from 0.0011 (Pg /g (1 .l ppb) (broccoli) to 0.0041 Pg/g (4.1 ppb) (summer squash). In a 

summary of 1985-91 FDA pesticide residue findings, endrin was not reported in more than 

10,000 surveillance samples of domestic and imported foods that may be eaten by infants or children, 

or in more than 4,000 analyses of Total Diet Study foods eaten by infants and children (Yess et al. 

1993). 

Other studies further indicate that the occurrence of endrin in the US. food supply is very low. In a 

1990-91 FDA survey of pesticide residues in milk representing most of the U.S. supply consumed in 
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5. POTENTIAL FOR HUMAN EXPOSURE 

metropolitan areas, endrin was detected at trace levels (0.0005-0.001 ppm [0.5-l.0 ppb]) in only 2 of 

806 composite samples (one sample each from Atlanta, Georgia and Dover, Delaware) (Trotter and 

Dickerson 1993). In another statistically based FDA study in 1992-93, endrin was not found as a 

violative residue in any of 710 domestic or 949 imported pear samples (Roy et al. 1995). Endrin was 

not reported among the pesticides detected in a 1994 FDA survey of pesticide levels in 160 samples of 

catfish, crayfish, shrimp, trout, salmon, oysters, and various other species from important aquaculture 

areas of the United States (FDA 1995). Comparable results were found in similar studies conducted 

by the FDA in 1990-93 (FDA 1995). 

Because of the persistence of endrin in the environment and its potential to bioconcentrate significantly 

in aquatic organisms, there has been continued concern over the levels of endrin in fish and shellfish. 

This concern, however, appears to be limited primarily to specific sites where endrin was used heavily 

in agriculture or was discharged by industrial plants. In 1963, at the height of agricultural endrin use, 

endrin levels in catfish poisoned by endrin exceeded 4 ppm (4,000 ppb) during a fish kill (Mount and 

Putnicki 1966). Endrin was detected in 2 species of commercial Penaeus shrimp collected at 21 of 

31 stations in the Calcasieu River Estuary in Louisiana, a Gulf Coast estuary receiving both industrial 

discharges, and urban and agricultural runoff (Murray and Beck 1990). The maximum, mean, and 

median concentrations of endrin reported were 9.47, 1.07, and 0.25 ppm (9,470, 1,070, and 250 ppb), 

respectively. Several more recent national studies, however, indicate that contaminated fish or 

shellfish currently are not a likely source of potentially high human exposure to endrin. In the 

National Contaminant Biomonitoring Program, maximum endrin concentrations in whole fish from 

around the United States for the periods 1976-77, 1978-79, 1980-81, and 1984 were 0.40, 0.11, 0.30, 

and 0.22 ppm (400, 110, 300, and 220 ppb), respectively. Corresponding geometric mean 

concentrations were <0.01 ppm (10 ppb) (Schmitt et al. 1985, 1990). The percentage of stations 

where detectable endrin residues were present also showed a relatively steady decline from 47.2% in 

1976-77 to 28% in 1984. The maximum concentration of 0.22 ppm (220 ppb) in 1984 was recorded 

near Memphis in the vicinity of the Velsicol Chemical Company. In portions of the Mississippi Delta 

within or bordering the Yazoo National Wildlife Refuge, endrin was found at the 0.01 ppm (10 ppb) 

detection limit in whole-body tissue samples from such rough fish as carp, smallmouth buffalo, 

bowfin, and spotted gar collected in 1988 (Ford and Hill 1991). In the 1986 National Study of 

Chemical Residues in Fish conducted by the EPA, endrin was detected in fish tissue samples at 11% 

of the 362 sites surveyed. The maximum, mean, and median concentrations of endrin reported were 
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5. POTENTIAL FOR HUMAN EXPOSURE 

0.162 ppm, 0.002 ppm, and not detected (<0.0025 ppm) (162, 2, and <2.5 ppb), respectively (EPA 

1992b). 

Endrin concentrations also have been monitored in several studies in the Great Lakes region. Endrin 

was detected in 8 fish species from 3 Great Lakes-influenced rivers in Michigan at average 

concentrations ranging from not detected (detection limit not specified) to 8.03 ppb wet weight (Giesy 

et al. 1994). Average concentrations exceeded 1.5 ppb for samples from only 2 of 23 species/site 

combinations and were less than 0.5 ppb for samples from 17 of 23 species/site combinations. Endrin 

was detected (detection limit 0.02 ppm [20 ppb] wet weight) in 5 of 10 samples of lake trout (mean 

concentration 0.03+0.01 ppm [30+10 ppb]) collected in Lake Michigan in 1982 (Miller 1993). It was 

not detected in 10 samples of lake trout collected in Lake Superior or in 18 samples of chinook 

salmon collected in Lake Michigan. Endrin was not detected (detection limit 2 ng/g [ppb] wet weight) 

in 16 skinless fillets of both rainbow trout (Oncorhyncus mykiss) and black bullheads (Ameiurus 

melas) cultivated for 6 and 3.5 months, respectively, in Lake Ontario waters (Buttner et al. 1995). 

Endrin also was not detected (detection limit not specified) in samples of whole Zebra mussels 

(Dreissena polymorpha) from populations infesting two power generating stations in Lake Erie 

(Doherty et al. 1993). 

Endrin has been detected in several marine fish species in regional or state monitoring studies. From 

1990 to 1993, endrin was found in 40 of 47 whole or fillet samples of red drum (Sciaenops ocellutus) 

at 2 of 4 sites along the South Carolina coast, at mean concentrations of 5.61+8.94 and 0.65+3.67 ppb 

wet weight (Mathews 1994). In this same study, endrin was found in 33 of 74 flounder (Pamlichthys 

lethostigma) samples, and in 19 of 58 seatrout (Cynoscion nebulosus) samples at only one coastal site, 

at mean concentrations of 0.14+0.81 and 2.68+11.13 ppb, respectively. Endrin was detected in all of 

10 liver tissue samples from cod (Gadus morhua) in the Northwest Atlantic at a mean concentration of 

9 ppb (range, 5-19 ppb), but not in muscle or ovary samples (Hellou et al. 1993). 

There may be a potential for contamination of fish and wildlife in the vicinity of hazardous waste 

sites. Endrin was detected in fish samples collected at 4 of the 102 NPL sites and in game animal 

samples collected at one of the 102 NPL sites where endrin has been detected in some environmental 

medium; however, levels of contamination were not reported (HazDat 1996). 
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5. POTENTIAL FOR HUMAN EXPOSURE 

Endrin was not detected (detection limit 0.005 ppm, wet weight) in liver samples of 118 mink from 

declining populations in coastal plain regions of Georgia, North Carolina, and South Carolina 

(Osowski et al. 1995). These results were not significantly different from levels found in nondeclining 

control populations (n= 46, median concentration 0.012 ppm, maximum concentration 0.49 ppm) from 

the Piedmont areas of these states. Endrin also was not detected (detection limit 0.01 ppm wet weight) 

in earthworms from 9 confined disposal facilities bordering the Great Lakes (Beyer and Stafford 

1993). 

No information was found on concentrations of endrin aldehyde or endrin ketone in other 

environmental media. 

5.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE 

Endrin is no longer registered for use in the United States. Consequently, the current potential for 

exposure of the general population to endrin appears to be very limited and will likely continue to 

diminish even more over time. Members of the general population may be exposed to very low levels 

of endrin through ingestion of contaminated foodstuffs, particularly those that are imported from areas 

where endrin is still being used. However, the FDA has concluded that endrin is no longer present in 

the environment to the extent that it may be contaminating food or feed at levels of regulatory concern 

(USDA 1995). Several studies indicate that human exposures are far below the levels of concern for 

human health. Based on results of FDA Total Diet Studies conducted from 1978 to 1982, estimated 

average dietary intakes were <0.001 (Pg /kg (ppb) body weight/day for infants and toddlers for all 

5 years (Gartrell et al. 1986). However, actual intakes must have been lower than these estimates 

because the reported average dietary intakes were based on the mean concentration of the positive 

samples only. A report summarizing the FDA Total Diet Studies from April 1982 to April 1984, 

indicated an estimated daily intake for 6-l l-month-old infants of 0.0003 (Pg /kg (ppb)body weight/day 

for that period, with estimated daily intakes for 14-16-year-old males and 60-65-year-old females 

essentially zero (Gunderson 1988). Endrin intakes, in (Pg /kg (ppb) body weight/day, estimated from 

the Total Diet Study analyses, were <0.000l, <0.000l, and 0.0001 in FY 1989 for 6-l l-month-old 

infants, 14-16-year-old males, and 60-65-year-old females, respectively (FDA 1990), and <0.000l in 

FY 1991 for all age categories (FDA 1992). Estimated endrin intakes were not reported for FY 1990 

(FDA 1991). In an overall summary of FDA Total Diet Studies for the 5-year period 1986-91, 

average dietary intakes of endrin for 8 age/sex groups (6-l l-month-old infants, 2-year-old children, 
ENDRIN 124 

5. POTENTIAL FOR HUMAN EXPOSURE 

14-16-year-old males and females, 25-30-year-old males and females, and 60-65year-old males and 

females) were all estimated to be <0.0001 Pg/kg (ppb) body weight per day, less than 0.03% of the 

EPA oral RfD of 0.3 (Pg /kg (ppb) body weight per day (FDA 1993). In Canada, where endrin was 

registered for use from 1954 to 1990, a dietary intake study estimated the adult annual intake of endrin 

at approximately 32 (g (0.001 (Pg /kg [ppb] body weight/day) (Davies 1988). 

Although endrin bioaccumulates significantly in aquatic organisms (ASTER 1995; EPA 1980a; Metcalf 

et al. 1973), recent studies indicate that in the United States endrin levels in fish and shellfish are not 

of concern for human health (EPA 1992a; Ford and Hill 1991; Murray and Beck 1990; Schmitt et al. 

1985, 1990). Dietary exposures to endrin from domestic fish were estimated from 1984 to 1988 FDA 

surveillance data to be 1.7x10m-5 (Pg /kg (ppb) body weight/day (Ahmed et al. 1993). At present, there 

are no fish consumption advisories for endrin in effect in the United States (EPA 1995b). 

The most recent National Human Adipose Tissue Survey did not detect endrin in adipose tissues from 

the general U.S. population (Stanley 1986). Endrin also was not detected in adipose breast tissue from 

breast cancer patients (n=5) or controls (n=5) in the United States (Djordjevic et al. 1994). A 1984 

study based on autopsied adipose tissue from 141 cadavers from six Canadian Great Lakes 

municipalities showed no detectable concentrations of endrin (detection limit 2.4 ppb) (Williams et al. 

1988). In a 1990-91 survey, only very low levels of endrin (average concentration 3.27 ng/g (ppb); 

range 0.23-8.56 ng/g [ppb] lipid) were found in adipose tissue samples from 3 of 41 residents of 

British Columbia, Canada, where endrin was registered for use from 1954 to 1990 (Teshke et al. 

1993). 

Endrin has been detected in the milk of lactating women living outside the United States; however, no 

data from the United States could be located. Data from other countries indicate that there is some 

correlation between the levels of endrin used in or transported to an area and concentrations found in 

breast milk. Endrin was not detected in breast milk samples from a remote area of Papua, New 

Guinea (Spicer and Kereu 1993). In a recent investigation of Inuit exposure to organochlorine 

pesticides through the aquatic food chain in arctic Quebec, endrin was detected in only 1 of 107 breast 

milk samples from Inuit women, at a concentration of <8 ng/g (ppb) in milk fat, and in none of 

50 samples from southern Quebec Caucasian women (Dewailly et al. 1993). In France, where endrin 

has not been used for over 20 years, endrin was detected in 8 of 20 human milk samples collected 

20-90 days after parturition. Concentrations ranged from 0.02 to 0.84 ppm (20-840 ppb) in milk fat, 
ENDRIN 125 

5. POTENTIAL FOR HUMAN EXPOSURE 

with a mean concentration of 0.06 ppm (60 ppb) (Bordet et al. 1993). Higher levels of endrin were 

found in human milk in a study conducted in Jordan, where endrin has been widely used over the past 

40 years (Alawi et al. 1992). In this study, endrin was detected in samples from 3 of 15 donors at 

concentrations ranging from 0.26 to 6.24 ppm (260-6,240 ppb) in milk fat. The median and 

maximum daily intakes of endrin for breast-fed infants were estimated to be 1.55 and 12.70 mg/kg 

(ppm) (1,550 and 12,700 ppb) body weight, respectively. The relevance of these findings to the 

U.S. population is unclear. 

Although all uses of endrin in the United States were canceled by 1991 (Bishop 1984, 1985, 1986; 

EPA 1993e; USDA 1995), occupational exposures to endrin, endrin aldehyde, and endrin ketone may 

occur among workers involved in the handling and treatment of materials at hazardous waste sites, and 

among agricultural workers at sites formerly treated with endrin. No information was found in the 

available literature on current occupational exposures. In the past, exposures of agricultural workers 

were significant. Seasonal agricultural workers dusting potatoes with 1% endrin dust were calculated 

to be exposed to a dermal dose of 2.0 mg/kg (ppm) body weight/day and an inhalation dose of 

0.04 mg/kg (ppm) body weight/day at a time when agricultural use of endrin was near its peak (Wolfe 

et al. 1963). 

Occupational exposure to endrin was not evaluated during the National Occupational Exposure Survey 

(NOES) conducted from 1981 to 1983 or its predecessor, the National Occupational Hazard Survey 

(NOHS) conducted from 1972 to 1974. The surveys conducted by NIOSH were designed to provide 

data necessary to describe potential exposure agents and profile health and safety programs in United 

States workplaces. According to OSHA (1974), the g-hour TWA permissible exposure level (PEL) for 

endrin is 0.1 mg/m3

. NIOSH (1992) advises that the recommended exposure limit for occupational 

exposure to endrin not exceed 0.1 mg/m3

 for a 10-hour TWA workday. In addition, the American 

Conference of Government Industrial Hygienists (ACGIH) recommended threshold limit value (TLVTWA) for occupational exposure is 0.1 mg/m3 (ACGIH 1988). 

No information could be found in the available literature on general population or occupational 

exposures to endrin aldehyde or endrin ketone. 
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5. POTENTIAL FOR HUMAN EXPOSURE 

5.6 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES 

Endrin has not been registered for use in the United States since voluntary cancellation of its final use 

as a toxicant on bird perches in 1991 (USDA 1995). All other uses of endrin were voluntarily 

canceled by 1986 (Bishop 1984, 1985, 1986; EPA 1993e; USDA 1995). Therefore, there are currently 

no population groups exposed to high levels of endrin associated with its application as a pesticide 

agent. Populations exposed to higher than background concentrations of endrin, endrin aldehyde, or 

endrin ketone include those living near hazardous waste sites where these compounds are present. 

Skin contact with or ingestion of endrin-contaminated soil may be an important source of exposure for 

children living near such hazardous waste sites. In addition, groundwater may be a source of exposure 

to endrin for adults and children if they consume drinking water from contaminated wells. 

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 endrin 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 endrin. 

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. 

5.7.1 Identification of Data Needs 

Physical and Chemical Properties. The physical and chemical properties of endrin have been 

sufficiently documented to permit estimation of its environmental fate (ACGIH 1986; EPA 1981a, 

1984a; HSDB 1995; Verschueren 1983). More complete information on the physical and chemical 

properties of endrin aldehyde and endrin ketone would be useful. 
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Production, Import/Export, Use, Release, and Disposal. Endrin is no longer registered for 

use and is not likely to be imported into the United States (Bishop 1984, 1985, 1986; EPA 1993e; 

HSDB 1995; USDA 1995). Consequently, the risk of human exposure to endrin (and to endrin 

aldehyde and endrin ketone, which occur as impurities or transformation products of endrin) from 

these activities is expected to be minimal. However, recent information suggests that several 

organochlorine pesticides that have been banned from use or have been voluntarily cancelled in the 

United States are still being manufactured in large quantities for export abroad (FASE 1996). 

Unfortunately, only 25% of the pesticides exported from 1992 to 1994 could be definitively identified 

(FASE 1996). Information as to whether endrin is currently being produced and the export volumes 

for endrin are needed to evaluate existing routes of exposure for the general population and 

occupationally exposed individuals. 

Endrin and endrin aldehyde are listed as hazardous wastes and disposal of wastes is controlled by a 

number of federal regulations. Past disposal methods have included landfills (EPA 1987c). Chemical 

treatment (reductive dechlorination) and incineration are possible disposal methods (HSDB 1995; 

IRPTC 1985). Existing information on disposal appears adequate. No information was found on 

disposal of endrin ketone; however, because endrin is no longer used in the United States, current 

levels of endrin ketone in wastes should be minimal and additional information on disposal is not 

needed. 

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 Toxic Release Inventory (TRI), which contains this information for 1993, became available in 

1995. This database will be updated yearly and should provide a list of industrial production facilities 

and emissions. No information was available from the Toxic Release Inventory (TRI) on production 

because endrin, endrin aldehyde, and endrin ketone are not among the chemicals that facilities are 

required to report (EPA 1995a). 

Environmental Fate. Endrin released to the environment partitions to several environmental 

compartments; air (Chan et al. 1994; Eisenreich et al. 1981; Nash 1983), soil and sediment (Kenaga 

1980; Sharom et al. 1980a; Swann et al. 1983), groundwater (Cohen 1986; EPA 1989; HazDat 1996) 

and biological organisms (ASTER 1995; EPA 1980a; Metcalf et al., 1973; Leblanc 1995). If released 

to soils, some endrin partitions to the atmosphere via volatilization from soil surfaces. Once in the 
ENDRIN 128 

5. POTENTIAL FOR HUMAN EXPOSURE 

atmosphere, endrin is associated primarily with particulate matter based on its low vapor pressure and 

high Koc (Kenaga 1980). Small amounts of endrin in the atmosphere may also exist in the vapor 

phase (Eisenreich et al. 1981). In addition to volatilization, endrin may be lost via photodegradation 

and heat transformation from soil and plant surfaces exposed to bright sunlight (Burton and Pollard 

1974; EPA 1979g; Knoevenagel and Himmelreich 1976; Phillips et al. 1962; Zabik et al. 1971). The 

remainder is adsorbed strongly to soil where it may persist for extended periods (half-life of months to 

years), depending on soil conditions (Nash and Woolson 1967). Leaching of endrin into groundwater 

is not expected to occur very rapidly under most circumstances, due to the compound’s high sorption 

characteristics (Kenaga 1980; Swann et al. 1983). 

Endrin released to water will adsorb to sediments or bioaccumulate in fish and other aquatic 

organisms. Both bioaccumulation and biomagnification of endrin were reported to occur in an aquatic 

laboratory microcosm system (Metcalf et al. 1973). In terrestrial ecosystems, endrin transformation 

products (endrin ketone, endrin aldehyde, and endrin alcohol) have been measured in plants grown on 

endrin-treated soil (Beall et al. 1972; Nash and Harris 1973). 

Information on biodegradation of endrin in soil under aerobic conditions exists, but degradation 

products are not identified (Nash and Woolson 1967; Patil et al. 1970). Anaerobic biodegradation, 

which may occur in river bottoms and in Superfund sites, has been studied in the laboratory, but not 

under natural conditions (Gowda and Sethunathan 1976; Maule et al. 1987). Further information on 

these processes, including identification of degradation products, would be useful in determining 

potential mechanisms and the potential for contamination of groundwater by endrin released from 

soils. 

No experimental data could be found in the available literature on the environmental fate of endrin 

aldehyde or endrin ketone, which occur as impurities in or degradation products of endrin. Estimated 

physical and chemical constants (see Table 3-2) allow some prediction of fate and transport processes 

for these compounds. However, additional experimental data on the physical and chemical properties 

of endrin aldehyde and endrin ketone would be useful in providing a clearer picture of their 

environmental fate. 

Bioavailability from Environmental Media. Absorption of endrin following inhalation has been 

shown to occur in laboratory animals (Treon et al. 1955) and endrin can also be absorbed by humans 
 

ENDRIN 129 

5. POTENTIAL FOR HUMAN EXPOSURE 

following inhalation of contaminated air (Hoogendam et al. 1965). Since endrin has a low volatility, 

inhalation is probably not a major concern except for potential inhalation of contaminated dust at 

hazardous waste sites. 

Endrin has also been shown to be absorbed after ingestion by humans (Coble et al. 1967; Curley et al. 

1970; Kintz et al. 1992; Rowley et al. 1987; Runhaar et al. 1985; Waller et al. 1992; Weeks 1967); 

however, no studies were located on the rate or extent of absorption that occurs in orally exposed 

humans or animals. Exposure to endrin through ingestion of contaminated drinking water is not 

expected to be an important source of concern because the compound has only rarely been detected in 

drinking water (Schafer et al. 1969; Wnuk et al. 1987). Since endrin is tightly bound to soil particles, 

ingestion of endrin-contaminated soil, particularly by children, may be an important route of exposure 

near hazardous waste disposal sites that contain endrin. 

Little information was available regarding the absorption of endrin following dermal exposure. 

Agricultural worker exposure studies demonstrated that dermal exposure was significantly greater than 

inhalation exposure (Wolfe et al. 1963). Dermal exposure of rats and rabbits to endrin indicates that 

percutaneous absorption of endrin occurs (Gaines 1960; Treon et al. 1955). Information regarding the 

bioavailability of endrin from both ingestion of soil-bound endrin and dermal contact with endrincontaminated soils would be helpful, particularly for population living near hazardous waste sites. 

No information could be found in the available literature on the bioavailability of endrin aldehyde or 

endrin ketone. This information would be useful for assessing the potential for exposure to these 

compounds from various environmental media, particularly in the vicinity of hazardous waste sites 

where endrin ketone has been found in surface water, groundwater, leachate, soil, and sediment 

(HazDat 1996). 

Food Chain Bioaccumulation. Endrin has been shown to bioaccumulate significantly in a 

variety of aquatic organisms (Argyle et al. 1973; ASTER 1995; Hanson et al. 1977; Jarvinen and Tyo 

1978; Lowe 1966; Mason and Rowe 1976; Metcalf et al. 1973; Mount and Putnicki 1966; Schimmel 

et al. 1975; Tyler-Schroeder 1979; Vance and Drummond 1969). The results of an aquatic ecosystem 

study suggest that biomagnification of endrin is relatively low compared to other organochlorine 

pesticides (Metcalf et al. 1973). Data on bioaccumulation and bioconcentration of endrin generally 

appear to be adequate, particularly since endrin has not been used in the United States since the 
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5. POTENTIAL FOR HUMAN EXPOSURE 

mid-1980s. Information on its bioconcentration by additional snail species would be useful as the 

pouch snail exhibited the highest BCF value and may serve as an environmental indicator of endrin 

contamination. 

No experimental information could be found in the available literature on biocdncentration or 

bioaccumulation of endrin aldehyde or endrin ketone. Estimated BCFs indicate some potential for 

bioaccumulation for both compounds. No information was found on concentrations of either of these 

compounds in aquatic systems, but it would be expected that levels would be nondetectable or very 

low, and that they would continue to decline. Therefore, additional information is not needed at this 

time. 

Exposure Levels in Environmental Media. Endrin has been reported to occur at very low 

levels in food (Davies 1988; FDA 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995; KAN-DO Office 

and Pesticides Team 1995; Minyard and Roberts 1991; Roy et al. 1995; Schattenburg and Hsu 1992; 

Trotter and Dickerson 1993; Yess et al. 1993) and air (Bidleman 1981; Kutz et al. 1976; Nash 1983). 

It has only rarely been detected in a number of national and regional surveys of drinking water 

supplies (Schafer et al. 1969; Wnuk et al. 1987). Because endrin is no longer commercially used in 

the United States, future levels of endrin, endrin aldehyde, and endrin ketone in environmental media 

are expected to be low. There are possibilities of exposure from foodstuffs imported from countries 

that still use endrin (Hundley et al. 1988). There may also be some localized risks from exposures 

near waste disposal sites or from groundwater contaminated with endrin (Cohen 1986; EPA 1989; 

HazDat 1996; Plumb 1987). Additional data on environmental concentrations of endrin, endrin 

aldehyde, and endrin ketone from these possible sources of exposure would be useful. 

Reliable monitoring data for the levels of endrin, endrin aldehyde, and endrin ketone in contaminated 

media at hazardous waste sites are needed so that the information obtained on levels of these 

substances in the environment can be used in combination with their known body burdens to assess 

the potential risk of adverse health effects in populations living in the vicinity of hazardous waste 

sites. 

Exposure Levels in Humans. Metabolism of endrin in humans is relatively rapid compared with 

other organochlorine pesticides. Thus, levels in human blood and tissue may not be reliable estimates 

of exposure except after very high occupational exposures or acute poisonings (Runhaar et al. 1985). 
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5. POTENTIAL FOR HUMAN EXPOSURE 

Endrin was not found in adipose tissue samples of the general U.S. population (Stanley 1986), or in 

adipose breast tissue from breast cancer patients in the United States (Djordjevic et al. 1994). Endrin 

has been detected in the milk of lactating women (Alawi et al. 1992; Bordet et al. 1993; Dewailly et 

al. 1993), but no data from the United States could be located. Data on the concentrations of endrin in 

breast milk from U.S. women would be useful. No information was found on levels of endrin, endrin 

aldehyde, or endrin ketone in blood and other tissues of people near hazardous waste sites. This 

information is necessary for assessing the need to conduct health studies on these populations. 

Exposure Registries. No exposure registries for endrin, endrin aldehyde, or endrin ketone were 

located. These substances are not currently among the compounds for which a subregistry has been 

established in the National Exposure Registry. These substances 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 these substances. 

5.7.2 Ongoing Studies 

A search of the Federal Research in Progress database (FEDRIP 1995) indicates that no research 

studies are in progress to fill the data needs identified in Section 5.7.1. 

ENDRIN 133 

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 endrin, its metabolites, and other biomarkers of exposure and effect to 

endrin. The intent is not to provide an exhaustive list of analytical methods. Rather, the intention is 

to identify well established methods that are used as the standard methods of analysis. Many of the 

analytical methods used for environmental samples are the methods approved by federal agencies and 

organizations such as EPA and the National Institute for Occupational Safety and Health (NIOSH). 

Other methods presented in this chapter are those that are approved by groups such as the Association 

of Official Analytical Chemists (AOAC) and the American Public Health Association (APHA). 

Additionally, analytical methods are included that modify previously used methods to obtain lower 

detection limits, and/or to improve accuracy and precision. 

6.1 BIOLOGICAL SAMPLES 

Endrin is relatively nonvolatile with a vapor pressure (25 (C) of only 2x10-7 torr. Its water solubility 

(25 oC) is 0.20 mg/L, which is much less than the water solubilities of most environmentally and 

toxicologically significant halogenated alkanes and alkenes, though similar to values for some other 

common organochlorine pesticides of similar structure. It has a high octanol/water partition coefficient 

(log Kow = 5.6), implying a strong affinity for lipids. Endrin aldehyde also has a low vapor pressure 

(2x10-7 torr at 25 oC). Its water solubility (25 oC) is 50 mg/L and its octanol/water partition 

coefficient value is approximately the same as that of endrin. There are few corresponding data for 

endrin ketone; based on its chemical structure, log Kow was calculated to be 4.99 (SRC 1995b) and 

this is in line with those calculated or measured for endrin aldehyde. These properties affect the 

manner in which biological samples are analyzed for endrin, endrin aldehyde, and endrin ketone. 

Specifically, the low volatilities of these compounds preclude their removal from biological samples by 

purging, and their lipophilicity complicates their removal from lipid fractions of such samples. 

Several basic steps are involved in determining high-boiling lipophilic analytes such as endrin and its 

oxidized derivatives (aldehyde and ketone) in biological materials. The purpose of most of these steps 

is to remove the analyte(s) from the biological matrix into a concentrated, interference-free form 

suitable for analysis. Several major steps may be involved. 
ENDRIN 134 

6. ANALYTICAL METHODS 

Tissue may have to be prepared (dried and homogenized) by grinding with sodium sulfate or materials 

such as reverse phase column packing. Prepared tissue or biological fluids are extracted with an 

organic solvent to remove analyte, usually with significant amounts of biological matter. The extract 

may be solvent-exchanged to a solvent more suitable for analysis. 

A clean-up step may be employed using gel permeation chromatography, Florisil, silica gel or alumina 

column fractionation, or solid phase extraction (SPE). 

Solvent evaporation/analyte concentration steps may be necessary. Diethyl ether has been a widely 

used solvent for the extraction of lipophilic organic analytes such as endrin and endrin aldehyde from 

biological fluids (Zlatkis and Kim 1976). Homogenization of tissue with the extractant, and lysing of 

cells improves extraction efficiency. When, as is often the case, multiple analytes are determined 

using solvent extraction, selective extraction and loss of low-boiling compounds can cause errors. The 

loss of volatile internal standards often results in a recovery of >l00% (Tang et al. 1993). The 

commercial availability of highly purified solvents has largely eliminated problems with solvent 

impurities, although high costs, solvent toxicities, and restrictions on spent solvent disposal must be 

considered. Extraction, the first step in the overall clean-up process, places the analyte in a form and 

matrix suitable for introduction into the instrument used for analysis. Clean-up of biological samples 

may often be complex and involve a number of steps (Walters 1986). 

In favorable cases, clean-up of biological samples containing endrin and/or endrin aldehyde can be 

simplified and made faster by using SPE (Marble and Delfino 1988). With this technique, solvent and 

sample are passed over disposable, prepacked, bonded-phase columns which either retain analyte (for 

subsequent elution) or retain interfering substances, while allowing for the passage of analyte. Tissue 

samples ground with reverse phase packing material, placed in a column over activated Florisil, and 

eluted using acetonitrile resulted in high extraction efficiency and clean-up in one step for crayfish and 

catfish samples (Long et al. 1991b; Lott and Barker 1993). Long et al. (1991a) also applied this 

technique to screening of chlorinated pesticides (including endrin) in beef fat. Di Muccio et al. (1990) 

have shown that sulfuric acid-impregnated Kieselguhr (diatomaceous earth) in SPE columns can 

improve the chromatography of organochlorine pesticides when the matrix contains fatty materials. 

A recent study (Viana et al. 1994) was conducted to examine the impact on recoveries of endrin, 

endrin aldehyde, and endrin ketone as a result of treatment of extracts with sulfuric acid, potassium 
ENDRIN 135 

6. ANALYTICAL METHODS 

hydroxide, or chromium (VI) oxide. The treatments are sometimes used in clean-up procedures or 

have been impregnated into adsorbents. Their data showed that endrin is unstable to acid and 

oxidizing conditions, but is stable in alkali. Endrin aldehyde is stable under acidic conditions, shows 

some loss with alkali, and is completely decomposed by oxidative conditions. Endrin ketone is stable 

under acidic and oxidizing conditions, but not to alkaline conditions. It is extremely important that the 

performance of any preparation scheme be validated with standard compounds before use. An 

apparently poor recovery for endrin, for example, could be related to its transformation as a result of 

the procedure. 

Procedures for the measurement of endrin and endrin aldehyde in biological samples are the same as 

those used for other organochlorine pesticides in similar samples. Endrin, endrin aldehyde and endrin 

ketone are measured by gas chromatography (GC) with electron capture detection (ECD) (EPA 1982a) 

or GC/MS detection (EPA 1982b). All recently reported work (approximately the past 10 years) used 

one or both of these techniques. GC/MS should be used to confirm any positive GU/ECD results, 

since organochlorine pesticides other than endrin respond to the ECD. As already stated, any 

extraction or processing steps that involve alkaline or acidic conditions may result in the 

decomposition of endrin or its transformation products (EPA 1982b; Viana et al. 1994). Analytical 

methods for the determination of endrin, endrin aldehyde, or endrin ketone in human biological 

samples are given in Table 6-1. 

6.2 ENVIRONMENTAL SAMPLES 

Endrin and endrin aldehyde are determined in environmental samples by extraction with an organic 

solvent and GC analysis (e.g., EPA 1982a, 1982b). Various extractions procedures have been 

evaluated including separatory funnel shake-out and continuous extraction at different pH values 

(Valkenburg et al. 1989), use of a one-step extractor/concentrator (Harrington-Fowler 1991), and use 

of a device (“Soxtec”) that has advantages over traditional Soxhlet extraction (Lopez-Avila et al. 

1993). Interferences may be eliminated by using silica, Florisil, or alumina column clean-up 

procedures (e.g., Cruz et al. 1993; Harrington-Fowler 1991). The clean-up of fatty materials as 

developed by Di Muccio and co-workers (1990) has been applied to vegetable oils (Di Muccio et al. 

1991) for analysis of 18 organochlorine pesticides, including endrin. The relatively recent application 


 

ENDRIN 138 

6. ANALYTICAL METHODS 

of supercritical fluid extraction (SFE) (Hopper and King 1991; Lopez-Avila et al. 1990; Snyder et al. 

1992) to a large number of both organochlorine and organophosphorus pesticides (including endrin and 

its aldehyde and ketone) showed the efficacy of this method, although it was determined to be more 

expensive than traditional Soxhlet methodology. SFE involves the use of carbon dioxide at high 

pressure for extraction. The technique is potentially advantageous because of the mildness of the 

extraction, and because solvent removal is easy (reduced pressure simply allows CO2 to convert from 

a supercritical state to a gas). As the emphasis shifts towards reduced use of organic solvents in 

general, and chlorinated solvents in particular, because of environmental concerns and costs associated 

with disposal, SFE can provide a quick payback and continued savings. 

As noted above for biological sample analysis, detection of endrin and its derivatives may be 

accomplished using either ECD or mass spectrometry (MS). The same concerns about chemical 

transformation of endrin, endrin aldehyde, and endrin ketone during sample preparation as discussed 

for biological samples are valid for environmental samples. Bentabol and Jodral (1995) showed that 

the use of sulfuric acid completely destroyed endrin during its isolation from cheese. Many of the 

EPA methods, such as Method 508 for drinking water (EPA 1988e), include steps to measure the 

degradation of endrin into endrin aldehyde and endrin ketone that results from the procedure. Active 

sites within the GC injector or column can also impact conversions (Grob and Wagner 1993). An 

immunoassay method has been reported as a screening procedure for endrin in selected vegetables 

(Wigfield and Grant 1992). Table 6-2 gives the analytical methods for the determination of endrin and 

the aldehyde and ketone in environmental samples. 

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 endrin 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 endrin. 




 

ENDRIN 143 

6. ANALYTICAL METHODS 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean 

that all data needs discussed in this section must be filled. In the future, the identified data needs will 

be evaluated and prioritized, and a substance-specific research agenda will be proposed. 

6.3.1 Identification of Data Needs 

Methods for Determining Biomarkers of Exposure and Effect. Endrin has been measured 

in various human samples including tissues, blood, and breast milk (Alawi et al. 1992; Burse et al. 

1990; Djordjevic et al. 1994; Ganguly and Bhattacharyya 1973). Methods have been published for use 

with animal tissues and could serve as the basis for work with human samples (see Table 6-l). The 

determination of the glucuronide of anti-12-hydroxyendrin in urine (Baldwin and Hutson 1980) 

provides for a biomarker of exposure that might be specific to endrin; anti-12-hydroxyendrin can 

undergo dehydrogenation to form 12-ketoendrin. If a concurrent exposure to keto-endrin occurred, 

12-hydroxyendrin could be formed by an in vivo reduction of 12-ketoendrin. The extent to which this 

could occur is not known. Baldwin and Hutson (1980) claimed 92% recovery for the method and did 

not detect any interferences in its application to urine from workers in an endrin synthesis plant. 

Based on this information, the method appears to be reliable. Work has been conducted to show that, 

as a result of endrin-induced oxidative stress, certain lipid metabolites are excreted in the urine of rats. 

Thus the levels of formaldehyde, acetaldehyde, malondialdehyde, and acetone were excreted in 

significantly increased quantities following exposure to endrin. These data probably reflect the 

response of the organism to a general xenobiotic-induced oxidative stress, and are not endrin-specific. 

In addition, various neurological effects can result from exposure to endrin (see Section 2.6.2), but 

these are not specific to endrin, endrin aldehyde, or endrin ketone. 

Cyclodiene pesticides, of which endrin and its oxidized analogs are representative, can also be 

estimated by receptor-assay technique. Cyclodiene pesticides exert their mode of action by altering 

central nervous system membrane ion transport. In work reported by Saleh et al. (1993), a labeled 

amino acid, GABA, that binds to the chloride channel receptor is displaced by endrin (and other 

similar molecules), and thus serves as an assay for these pesticides. The GABA receptor was shown 

to be a potentially useful biomarker for organochlorine pesticides such as lindane, toxaphene, endrin, 

chlordane, and others. The assay involves small quantities of blood (0.1 mL), and requires only that 
ENDRIN 144 

6. ANALYTICAL METHODS 

the plasma be separated from the blood for direct analysis. Sensitivity for several cyclodiene 

pesticides was in the low-to-mid-picomole range. 

Methods for Determining Parent Compounds and Degradation Products in 

Environmental Media. The MRL for chronic oral exposure to endrin is 0.0003 mg/kg/day. 

Assuming a 70-kg individual and oral intakes of either 2 L/day of water or 2 kg/day of food, 

analytical methods would need to have sensitivities below 10.5 ppb (10.5 (Pg /L or 10.5 (Pg /kg) in either 

medium. The methods reported for drinking water have limits of detection (LODs) far below this 

value and are adequate (ASTM 1988; EPA 1982a, 1988e; Russo et aI. 1993; Tomkins et al. 1992). 

The needed sensitivities can be achieved for some foods (Alawi et al. 1992; Davies 1988; Nakamura et 

al. 1994; Prapamontol and Stevenson 1991; Schmitt et al. 1985). The LODs of FDA methods (1994a, 

1994b) are within a factor of 2-3 of those needed to measure chronic exposure but can be used to 

monitor intermediate acute exposure (MRL = 0.002 mg/kg/day) where LODs of 70 ppb are needed. 

Additional methods for foods are needed to measure concentrations relevant to the chronic oral MRL. 

Many of the reported methods have not been validated for the oxygenated derivatives of endrin (endrin 

aldehyde and endrin ketone). Although many of the methods should work for these derivatives, this 

needs to be shown. No MRLs have been established for inhalation exposures. 

6.3.2 Ongoing Studies 

The Environmental Health Laboratory Sciences Division of the National Center for Environmental 

Health, Centers for Disease Control and Prevention, is developing methods for the analysis of endrin 

and other volatile organic compounds in blood. These methods use purge and trap methodology, high 

resolution CG and magnetic sector MS which gives detection limits in the low parts per trillion (ppt) 

range. 

The Environmental Health Laboratory Sciences Division of the National Center for Environmental 

Health, Centers for Disease Control and Prevention, is developing methods for the analysis of endrin 

and phenolic compounds in urine. These methods use high resolution GC and magnetic sector MS 

which gives detection limits in the low parts per trillion (ppt) range. 

No ongoing studies concerning techniques for measuring and determining endrin, endrin aldehyde, or 

endrin ketone in biological and environmental samples were reported. 
ENDRIN 145 

7. REGULATIONS AND ADVISORIES 

The international, national, and state regulations and guidelines regarding endrin in air, water, and 

other media are summarized in Table 7-1. 

ATSDR has derived an intermediate oral MRL of 0.002 mg/kg/day based on a laboratory animal study 

showing neurotoxic effects in dogs (Treon et al. 1955). 

ATSDR has derived a chronic oral MRL of 0.0003 mg/kg/day based on a laboratory animal study 

showing neurotoxic effects in dogs (Kettering Lab 1969). The EPA reference dose for endrin is 

3x10-4 mg/kg/day, and the critical dose is 0.025 mg/kg/day (IRIS 1995). Critical effects were 

occasional convulsions and mild histological lesions in the liver (Kettering Lab 1969). No EPA 

reference concentration exists for the compound. 

The EPA has determined that endrin is not classified as to its human carcinogenicity (Group D) 

because the available information is inadequate to allow the classification (IRIS 1995). No cancer 

classifications exist for the IARC (no adequate data) (IARC 1987). The National Toxicology Program 

(NTP) has assigned endrin the carcinogen code N (negative) (NTP 1995). 

Endrin is on the list of chemicals regulated based on “The Emergency Planning and Community RighttoKnow Act of 1986” (EPCRA) (EPA 1988a). Section 313 of Title III of EPCRA requires owners 

and operators of certain facilities that manufacture, import, process, or otherwise use the chemicals on 

this list to report annually their release of those chemicals to any environmental media. 

OSHA requires employers of workers who are occupationally exposed to endrin to institute 

engineering controls and work practices to reduce and maintain employee exposure at or below PELs. 

The employer must use engineering and work practice controls, if feasible, to reduce exposure to or 

below an 8-hour TWA of 0.1 mg/m3

. Respirators must be provided and used during the time period 

necessary to install or implement feasible engineering and work practice controls (OSHA 1989). Also, 

to prevent or reduce skin absorption, an employee’s skin exposure to endrin must be prevented or 

reduced to the extent necessary in the circumstances through the use of gloves, coveralls, goggles, or 

other appropriate personal protective equipment, engineering controls, or work practices. 
ENDRIN 146 

7. REGULATIONS AND ADVISORIES 

Endrin is regulated by the Clean Water Effluent Guidelines as stated in Title 40, Section 400-475, of 

the Code of Federal Regulations. For each point source category, endrin may be regulated as a group 

of chemicals controlled as Total Toxic Organics or may have a Zero Discharge Limitation. The point 

source categories for which endrin is controlled as a Total Toxic Organic include electroplating (EPA 

1981), metal finishing (EPA 1983a), and aluminum forming (EPA 1983b). The point source category 

for which endrin has a specific Regulatory Limitation is endrin manufacturing (EPA 1977a). There 

are no point source categories for which endrin has a Zero Discharge Limitation. 

Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), a 0 ppm food tolerance 

restriction is in place for endrin (EPA 1977b). 

The Resource Conservation and Recovery Act (RCRA) identifies endrin as a hazardous waste in two 

ways: (1) when it exceeds a toxicity characteristic leaching procedure test concentration of 0.02 mg/L 

(EPA 1980a); and (2) when it is discarded as a commercial chemical product, off-specification species, 

container residue, or spill residue (EPA 1980a). 














______________________ 

ENDRIN 161 

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ENDRIN 168 

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*EPA. 1982c. Steam electric power generating point source category. U.S. Environmental Protection 

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*EPA. 1983a. EPA administered permit programs: The National Pollutant Discharge Elimination 

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*EPA. 1983e. Status of pesticides in reregistration and special review. U. S. Environmental 

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*EPA. 1984a. Analytical reference standards and supplemental data: The pesticides and industrial 

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*EPA. 1984b. Identification of specific chemical substance and mixture testing requirements. U.S. 

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ENDRIN 169 

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*EPA. 1985c. Environmental effects testing guidelines. U.S. Environmental Protection Agency. 

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ENDRIN 170 

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ENDRIN 171 

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ENDRIN 172 

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ENDRIN 183 

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ENDRIN 189 

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-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 drinking water levels for a chemical substance based 

on health effects information. A health advisory is not a legally enforceable federal standard, but 

serves as technical guidance to assist federal, state, and local officials. 

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. 

Intermediate Exposure-Exposure to a chemical for a duration of 15-364 days, as specified in the 

Toxicological Profiles. 
ENDRIN 190 

9. GLOSSARY 

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 cause 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. 

Permissible Exposure Limit (PEL)-An allowable exposure level in workplace air averaged over an 

8-hour shift. 
ENDRIN 191 

9. GLOSSARY 

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 (Pg /L for water, mg/kg/day for food, and 

(Pg /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. 

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. 


ENDRIN A-2 

APPENDIX A 

MRLs are intended only to serve as a screening tool to help public health professionals decide where to 

look more closely. They may also be viewed as a mechanism to identify those hazardous waste sites that 

are not expected to cause adverse health effects. Most MRLs contain a degree of uncertainty because of 

the lack of precise toxicological information on the people who might be most sensitive (e.g., infants, 

elderly, nutritionally or immunologically compromised) to the effects of hazardous substances. ATSDR 

uses a conservative (i.e., protective) approach to address this uncertainty consistent with the public health 

principle of prevention. Although human data are preferred, MRLs often must be based on animal studies 

because relevant human studies are lacking. In the absence of evidence to the contrary, ATSDR assumes 

that humans are more sensitive to the effects of hazardous substance than animals and that certain persons 

may be particularly sensitive. Thus, the resulting MRL may be as much as a hundredfold below levels that 

have been shown to be nontoxic in laboratory animals. 

Proposed MRLs undergo a rigorous review process: Health Effects/MRL Workgroup reviews within the 

Division of Toxicology, expert panel peer reviews, and agencywide MRL Workgroup reviews, with 

participation from other federal agencies and comments from the public. They are subject to change as 

new information becomes available concomitant with updating the toxicological profiles. Thus, MRLs in 

the most recent toxicological profiles supersede previously published levels. For additional information 

regarding MRLs, please contact the Division of Toxicology, Agency for Toxic Substances and Disease 

Registry, 1600 Clifton Road, Mailstop E-29, Atlanta, Georgia 30333. 
ENDRIN A - 3 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: Endrin/Endrin Aldehyde 

CAS Number: ID1575000/PC8580000 

Date: August 1996 

Profile Status: Final 

Route: [ ] Inhalation [X] Oral 

Duration: [ ] Acute [X] Intermediate [ ] Chronic 

Key To Figure: 47 

Species: Dog 

3 MRL: 0.002 [X] mg/kg/day [ ] ppm [ ] mg/m


Reference: Treon et al. 1955 

Experimental Design: (Human study details or strain, number of animals per exposure/control group, sex, 

dose administration details): Endrin was administered at doses of 0.15, 0.20, 0.25, 0.29, 0.49,0.53, 1.21, 

and 2.50 mg/kg/day in the diet of dogs for 18 days to 9.9 months, 6 days per week. 

Effects Noted in Study and Corresponding Doses: Doses of 0.20 mgikg/day and greater resulted in 

neurotoxicity evidenced by convulsions, tremors, and degenerative lesions in the brain and systemic 

toxicity which included renal tubular necrosis, respiratory distress and pulmonary edema, and diffuse 

degenerative lesions of the heart. One animal administered diet corresponding to 0.20-0.27 mg/kg/day 

died after 47 days of feeding. 

Dose End noint Used for MRL Derivation: Doses of 0.20 mg/kg/day and greater resulted in neurotoxicity, 

systemic toxicity, and death. 

[X] NOAEL [ ] LOAEL 0.15 mg/kg/day 

Uncertainty Factors Used in MRL Derivation: 

[ ] 1 [ ] 3 [ ] l0(For use of a LOAEL)
 

[ ] 1 [ ] 3 [X] 10 (For extrapolation from animals to humans)
 

[ ] 1 [ ] 3 [X] 10 (For human variability)
 

Was a Conversion Factor used from prim in food or water to a mg/body weight dose? 

If so, explain: The food concentrations were presented in terms of ppm (mg endrin/kg food) and as ranges 

for daily dosages in relationship to body weight (mg/kg). If the minimum of each mg/kg/day range is used 

as a conservative estimate of dose, then the respective dose levels are: 0.15, 0.20, O-25,0.29, 0.49,0.53, 

1.21, and 2.50 for the 4, 5,2/8, 8, 10,5/20, 25, and 50 ppm groups, respectively. The 0.25 mg/kg/day dose 

was calculated as the time-weighted average (TWA) of the 2 ppm diet (0.09 mg/kg/day) for 2.9 months 

and the 8 ppm diet (0.29 mg/kg/day) for the remaining 7 months. The 0.53 ppm dose was calculated as the 

TWA of the 5 ppm diet (0.25 mg/kg/day) for 2.9 months and the 20 ppm diet (0.97 mg/kg/day) for the 

remaining 1.8 months. 
ENDRIN A-4 

APPENDIX A 

If an inhalation study in animals, list Conversion Factors used in determining human eauivalent dose: 

None. 

Was a Conversion used from intermittent to continuous exnosure? 

If so, explain: No. 

Other additional studies or pertinent information that lend support to this MRL: The central nervous 

system is the primary target system for endrin as evidenced by reports of neurologic effects including 

convulsions and tremors in humans and other animal species (e.g., Curley et al. 1970; Waller et al. 1992; 

Deichmann et al. 1970; Treon et al. 1955). 

Anency Contract (Chemical Manager): Jessilyn Taylor 
ENDRIN A - 5 

APPENDIX A 

MINIMAL RISK LEVEL (MRL) WORKSHEET 

Chemical Name: Endrin/Endrin Aldehyde 

CAS Number: I D1575000/PC8580000 

Date: August 1996 

Profile Status: Final 

Route: [ ] Inhalation [X] Oral 

Duration: [ ] Acute [ ] Intermediate [X] Chronic 

Key To Figure: 64 

Species: Dog 

MRL: 0.0003 [Xl mg/kg/day [ ] ppm [ ] mg/m3 

Reference: Kettering 1969 

Experimental Design: (Human study details or strain, number of animals per exposure/control group, sex, 

dose administration details): Beagle dogs were fed diets containing 0, 0.0025, 0.0125, 0.025, 0.05, or 

0.1 mg/kg/day endrin for 2 years. 

Effects Noted in Study and Corresponding Doses: Concentrations less than 0.05 mg/kg/day endrin in the 

daily diet did not elicit changes in the rate of growth, food consumption, usual activities, or any of the 

hematologic, biochemical or pathologic criteria evaluated. One female and 2 male dogs at 0.1 mg/kg/day 

dietary level and one female dog at the 0.05 mg/kg/day dietary level showed evidence of, or were observed 

having, convulsions. Concentrations of 0.05 mg/kg/day and 0.1 mg/kg/day endrin were associated with 

slight to moderate vacuolation of hepatic cells. Petechial hemorrhages and cerebral edema were observed 

in the brain of one dog having convulsions at the time of necropsy. There were occasional slight increases 

in the weight of livers from dogs fed diets containing endrin at 0.05 and 0.1 mg/kg/day. 

Dose End point Used for MRL Derivation: 0.025 mg/kg/day 

[X] NOAEL [ ] LOAEL 

Uncertainty Factors Used in MRL Derivation:
 

[ ] 1 [ ] 3 [ ] 10 (For use of a LOAEL)
 

[ ] 1 [ ] 3 [X] 10 (For extrapolation from animals to humans)
 

[ ] 1 [ ] 3 [X] 10 (For human variability)
 

Was a Conversion Factor used from num in food or water to a mg/body weight dose? 

If so, explain. 

No. 

If an inhalation studv in animals. list Conversion Factors used in determining human eouivalent dose: 

None. 
ENDRIN A-6 

APPENDIX A 

Was a conversion used from intermittent to continuous exposure?:
 

If so, explain: No.
 

Other additional studies or Dertinent information that lend support to this MRL:
 

Agencv Contract (Chemical Manager): Jessilyn Taylor
 
ENDRIN	 B-l 

APPENDIX B 

USER’S GUIDE 

Chapter 1 

Public Health Statement 

This chapter of the profile is a health effects summary written in non-technical language. Its intended 

audience is the general public especially people living in the vicinity of a hazardous waste site or chemical 

release. If the Public Health Statement were removed from the rest of the document, it would still 

communicate to the lay public essential information about the chemical. 

The major headings in the Public Health Statement are useful to find specific topics of concern. The topics 

are written in a question and answer format. The answer to each question includes a sentence that will 

direct the reader to chapters in the profile that will provide more information on the given topic. 

Chapter 2 

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 and illustrate 

graphically levels of exposure associated with those effects. These levels cover health effects observed at 

increasing dose concentrations and durations, differences in response by species, 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. Use the LSE tables and figures for a 

quick review of the health effects and to locate data for a specific exposure scenario. The LSE tables and 

figures should always be used in conjunction with the text. All entries in these tables and figures represent 

studies that provide reliable, quantitative estimates of No-Observed-Adverse- Effect Levels (NOAELs), 

Lowest-Observed- Adverse-Effect Levels (LOAELs), or Cancer Effect Levels (CELs). 

The legends presented below demonstrate the application of these tables and figures. Representative 

examples of LSE Table 2-l and Figure 2-l are shown. The numbers in the left column 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 exists, three LSE tables and two LSE figures are presented in the document. The three LSE 

tables present data on the three principal routes of exposure, i.e., inhalation, oral, and dermal (LSE 

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. Not all substances will have data on each route of exposure and 

will not therefore have all five of the tables and figures. 
ENDRIN	 B - 2 

APPENDIX B 

(2)	 Exposure Period Three exposure periods - acute (less than 15 days), intermediate (15364 days), 

andchronic (365 days or more) are presented within each relevant route of exposure. In this example, 

an inhalation study of intermediate exposure duration is reported. For quick reference to health effects 

occurring from a known length of exposure, locate the applicable exposure period within the LSE 

table and figure. 

(3)	 Health Effect The major categories of health effects included in LSE tables and figures are death, 

systemic, immunological, neurological, developmental, reproductive, and cancer. NOAELs and 

LOAELs can be reported in the tables and figures for all effects but cancer. Systemic effects are 

further defined in the “System” column of the LSE table (see key number 18). 

(4)	 Key to Figure Each key number in the LSE table links study information to one or more data points 

using the same key number in the corresponding LSE figure. In this example, the study represented by 

key number 18 has been used to derive a NOAEL and a Less Serious LOAEL (also see the 2 “18r” 

data points in Figure 2-l). 

(5)	 Species The test species, whether animal or human, are identified in this column. Section 2.5, 

“Relevance to Public Health,” covers the relevance of animal data to human toxicity and Section 2.3, 

“Toxicokinetics,” contains any available information on comparative toxicokinetics. Although 

NOAELs and LOAELs are species specific, the levels are extrapolated to equivalent human doses to 

derive an MRL. 

(6)	 Exposure Frequency/Duration The duration of the study and the weekly and daily exposure 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 toxaphene via inhalation for 6 hours per 

day, 5 days per week, for 3 weeks. For a more complete review of the dosing regimen refer to the 

appropriate sections of the text or the original reference paper, i.e., Nitschke et al. 1981. 

(7)	 System This column further defines the systemic effects. These systems include: respiratory, 

cardiovascular, gastrointestinal, hematological, musculoskeletal, hepatic, renal, and dermal/ocular. 

“Other” refers to any systemic effect (e.g., a decrease in body weight) not covered in these systems. In 

the example of key number 18, 1 systemic effect (respiratory) was investigated. 

(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 dose used in the study that 

caused a harmful health effect. LOAELs have been classified into “Less Serious” and “Serious” 

effects. These distinctions’help readers identify the levels of exposure at which adverse health effects 

first appear and the gradation of effects with increasing dose. A brief description of the specific end 

point used to quantify the adverse effect accompanies the LOAEL. The respiratory effect reported in 

key number 18 (hyperplasia) is a Less serious LOAEL of 10 ppm. MRLs are not derived from Serious 

LOAELs. 

(10) 	 Reference The complete reference citation is given in chapter 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 epidemiologic studies. CELs are always considered serious 
 

ENDRIN	 B-3 

APPENDIX B 

effects The LSE tables and figures do not contain NOAELs for cancer, but the text may report doses 

not causing measurable cancer increases. 

(12)	 Footnotes Explanations of abbreviations or reference notes for data in the LSE tables are found in the 

footnotes. Footnote “b” indicates the NQAEL of 3 ppm in key number 18 was used to derive an MRL 

of 0.005 ppm. 

LEGEND 

See 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 concentrations for particular exposure periods. 

(13) 	 Exposure Period The same exposure periods appear as in the LSE table. In this example, health effects 

observed within the intermediate and chronic exposure periods are illustrated. 

(14) 	 Health These are the categories of health effects for which reliable quantitative data exists. The same 

health effects appear in the LSE table. 

(15) 	 Levels of Exposure Concentrations or doses for each health effect in the LSE tables are graphically 

displayed in the LSE figures. Exposure concentration or dose is measured on the log scale “y” axis. 

Inhalation exposure is reported in mg/m3

 or ppm and oral exposure is reported in mg/kg/day. 

(16) 	 NOAEL In this example, 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 to 

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 entry18 in 

the Table) to the MRL of 0.005 ppm (see footnote “b” in the LSE table). 

(17) 	 CEL Key number 38r is 1 of 3 studies for which Cancer Effect Levels were derived. The diamond 

symbol refers to a Cancer Effect Level for the test species-mouse. 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 the EPA’s Human Health Assessment Group’s upper-bound estimates of the slope of the cancer 

dose response curve at low dose levels (q1*). 

(19) 	 Key to LSE Figure The Key explains the abbreviations and symbols used in the figure, 


 

 

 

ENDRIN B-6 

APPENDIX B 

Chapter 2 (Section 2.5) 

Relevance to Public Health 

The Relevance to Public Health section provides a health effects summary based on evaluations of existing 

toxicologic, epidemiologic, 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 covers end points in the same order they appear within the Discussion of Health Effects by Route 

of Exposure section, by route (inhalation, oral, dermal) and within route by effect. Human data are presented 

first, then animal data. Both are organized by duration (acute, intermediate, chronic). In vitro data and data 

from parenteral routes (intramuscular, intravenous, subcutaneous, etc.) are also considered in this section, If 

data are located in the scientific literature, a table of genotoxicity information is included. 

The carcinogenic potential of the profiled substance is qualitatively evaluated, when appropriate, using existing 

toxicokinetic, genotoxic, and carcinogenic data. ATSDR does not currently assess cancer potency or perform 

cancer risk assessments. Minimal risk levels (MRLs) for noncancer end points (if derived) and the end points 

from which they were derived are indicated and discussed. 

Limitations to existing scientific literature that prevent a satisfactory evaluation of the relevance to public 

health are identified in the Data Needs section. 

Interpretation of Minimal Risk Levels 

Where sufficient toxicologic information is available, we have derived minimal risk Ievels (MRLs) for 

inhalation and oral routes of entry at each duration of exposure (acute, intermediate, and chronic). These MRLs 

are not meant to support regulatory action; but to acquaint health professionals with exposure levels at which 

adverse health effects are not expected to occur in humans. They should help physicians and public health 

officials determine the safety of a community living near a chemical emission, given the concentration of a 

contaminant in air or the estimated daily dose in water. MRLs are based largely on toxicological studies in 

animals and on reports of human occupational exposure. 

MRL users should be familiar with the toxicologic information on which the number is based. Chapter 2.5, 

“Relevance to Public Health,” contains basic information known about the substance. Other sections such as 

2.7, “Interactions with Other Substances,” and 2.8, “Populations that are Unusually Susceptible” provide 

important supplemental information. 

MRL users should also understand the MRL derivation methodology. MRLs are derived using a modified 

version of the risk assessment methodology the Environmental Protection Agency (EPA) provides (Barnes and 

Dourson 1988) to determine reference doses for lifetime exposure (RfDs). 
ENDRIN B-7 

APPENDIX B 

To derive an MRL, ATSDR generally selects the most sensitive end point which, in its best judgement, 

represents the most sensitive human health effect for a given exposure route and duration. ATSDR cannot 

make this judgement or derive an MRL unless information (quantitative or qualitative) is available for all 

potential systemic, neurological, and developmental effects. If this information and reliable quantitative 

data on the chosen end point are available, ATSDR derives an MRL using the most sensitive species (when 

information from multiple species is available) with the highest NOAEL that does not exceed any adverse 

effect levels When a NOAEL is not available, a lowest-observed-adverse-effect level (LOAEL) can be 

used to derive an MRL, and an uncertainty factor (UF) of 10 must be employed. Additional uncertainty 

factors of 10 must be used both for human variability to protect sensitive subpopulations (people who are 

most susceptible to the health effects caused by the substance) and for interspecies variability (extrapolation 

from animals to humans) In deriving an MRL, these individual uncertainty factors are multiplied 

together. The product is then divided into the inhalation concentration or oral dosage selected from the 

study. Uncertainty factors used in developing a substance-specific MRL are provided in the footnotes of 

the LSE Tables.