National Cancer Institute 

CARCINOGENESIS 

Technical Report Series 

No. 66 

1978 

BIOASSAY OF 

1,1-DICHLOROETHANE 

FOR POSSIBLE CARCINOGENICITY 

CAS No. 75-34-3 

NCI-CG-TR-66 

U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE 

Public Health Service 

National Institutes of Health 

BIOASSAY OF
 

1,1-DICHLOROETHANE
 

FOR POSSIBLE CARCINOGENICITY
 

Carcinogenesis Testing Program
 

Division of Cancer Cause and Prevention
 

National Cancer Institute
 

National Institutes of Health
 

Bethesda, Maryland
 

U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
 

Public Health Service
 

National Institutes of Health
 

DHEW Publication No. (NIH) 78-1316
 

REPORT ON THE BIOASSAY OF 1,1-DICHLOROETHANE
 

FOR POSSIBLE CARCINOGENICITY
 

CARCINOGENESIS TESTING PROGRAM
 

DIVISION OF CANCER CAUSE AND PREVENTION
 

NATIONAL CANCER INSTITUTE, NATIONAL INSTITUTES OF HEALTH
 

CONTRIBUTORS: This report presents the results of the bioassay of
 

1,1-dichloroethane conducted for the Carcinogenesis Testing Program,
 

Division of Cancer Cause and Prevention, National Cancer Institute
 

(NCI), National Institutes of Health, Bethesda, Maryland. This bioassay was conducted by Hazleton Laboratories America, Inc·, Vienna,
 

Virginia, initially under direct contract to the NCI and currently
 

under a subcontract to Tracor Jitco, Inc., prime contractor for the
 

NCI Carcinogenesis Bioassay Program.
 

The experimental design was determined by the NCI Project Officers, Dr. J. Η. Weisburger (1,2) and Dr. E. K. Weisburger (1). The
 

principal investigators for the contract were Dr. Μ. Β· Powers (3),
 

Dr. R. W. Voelker (3), Dr. W. A. Olson (3,4) and Dr. W. M. Weatherholtz (3). Chemical analysis was performed by Dr. C. L. Guyton (3,
 

5) and the analytical results were reviewed by Dr. N. Zimmerman (6);
 

the technical supervisor of animal treatment and observation was Ms.
 

K. J. Petrovics (3).
 

Histopathologic examinations were performed by Dr. R. H. Habermann (3) and reviewed by Dr. R. W. Voelker (3) at the Hazleton Laboratories America, Inc., and the diagnoses included in this report
 

represent the interpretation of these pathologists. Histopathology
 

findings and reports were reviewed by Dr. R. L. Schueler (7).
 

Compilation of individual animal survival, pathology, and
 

summary tables was performed by EG&G Mason Research Institute (8);
 

the statistical analysis was performed by Mr. W. W. Belew (6) and
 

Dr. J. R. Joiner (7), using methods selected for the Bioassay Program
 

by Dr. J. J. Gart (9).
 

This report was prepared at METREK, a Division of The MITRE Corporation (6) under the direction of the NCI. Those responsible for
 

this report at METREK are the project coordinator, Dr. L. W. Thomas
 

(6), the task leader, Dr. M. R. Kornreich (6), the senior biologist,
 

Ms. P. Walker (6), and the technical editor, Ms. P. A. Miller (6).
 

The final report was reviewed by members of the participating organizations.
 

iii
 
The statistical analysis was reviewed by members of the Mathematical Statistics and Applied Mathematics Section of the NCI: Dr·
 

J. J. Gart (9), Mr. J. Nam (9), Dr. H. M. Pettigrew (9), and Dr. R.
 

E. Tarone (9).
 

The following other scientists at the National Cancer Institute
 

were responsible for evaluating the bioassay experiment, interpreting
 

the results, and reporting the findings: Dr. K. C. Chu (1), Dr. C.
 

Cueto, Jr. (1), Dr. J. F. Douglas (1), Dr. D. G. Goodman (1), Dr. R.
 

A. Griesemer (1), Dr. H. A. Milman (1), Dr. T. W. Orme (1), Dr. R. A.
 

Squire (1,10), and Dr. J. Μ. Ward (1).
 

1.	 Carcinogenesis Testing Program, Division of Cancer Cause and
 

Prevention, National Cancer Institute, National Institutes of
 

Health, Bethesda, Maryland.
 

2.	 Now with the Naylor Dana Institute for Disease Prevention,
 

American Health Foundation, Hammon House Road, Valhalla,
 

New York.
 

3.	 Hazleton Laboratories America, Inc., 9200 Leesburg Turnpike,
 

Vienna, Virginia.
 

4.	 Now with the Center for Regulatory Services, 2347 Paddock Lane,
 

Reston, Virginia.
 

5.	 Now with Rhodia, Inc., 23 Belmont Drive, Somerset, New Jersey.
 

6.	 The MITRE Corporation, METREK Division, 1820 Dolley Madison
 

Boulevard, McLean, Virginia.
 

7.	 Tracor Jitco, Inc., 1776 East Jefferson Street, Rockville,
 

Maryland.
 

8.	 EG&G Mason Research Institute, 1530 East Jefferson Street,
 

Rockville, Maryland.
 

9.	 Mathematical Statistics and Applied Mathematics Section, Biometry
 

Branch, Field Studies and Statistics Program, Division of Cancer
 

Cause and Prevention, National Cancer Institute, National Institutes of Health, Bethesda, Maryland.
 

10.	 Now with the Division of Comparative Medicine, Johns Hopkins
 

University, School of Medicine, Traylor Building, Baltimore,
 

Maryland.
 

iv 
SUMMARY
 

A bioassay of technical-grade 1,1-dichloroethane for possible
 

carcinogenicity was conducted using Osborne-Mendel rats and B6C3F1
 

mice· 1,1-Dichloroethane in corn oil was administered by gavage, at
 

either of two dosages, to groups of 50 male and 50 female animals of
 

each species, 5 days a week for a period of 78 weeks, followed by an
 

observation period of 33 weeks for rats and 13 weeks for mice.
 

A preliminary subchronic toxicity test, consisting of 6 weeks
 

of 1,1-dichloroethane administration at five dosage levels followed
 

by 2 weeks of observation, was performed for the purpose of selecting
 

initial dosages. Subsequent dosage adjustments were made during the
 

course of the study. The high and low time-weighted average dosages
 

of 1,1-dichloroethane were, respectively, 764 and 382 mg/kg/day for
 

male rats; 950 and 475 mg/kg/day for female rats; 2885 and 1442 mg/
 

kg/day for male mice; and 3331 and 1665 mg/kg/day for female mice.
 

For each species, 20 animals of each sex were placed on test as
 

vehicle controls. These animals were gavaged with corn oil at the
 

same times that dosed animals were gavaged with 1,1-dichloroethane
 

mixtures. Twenty animals of each sex were placed on test as untreated controls for each species. These animals were not intubated.
 

Survival was poor in all rat groups and several mouse groups.
 

Survival at the end of the study in the untreated control, vehicle
 

control, low dose, and high dose groups was, respectively, 30, 5, 4,
 

and 8 percent in male rats; 40, 20, 16 and 18 percent in female rats;
 

35, 55, 62 and 32 percent in male mice; and 80, 80, 80 and 50 percent
 

in female mice. Pneumonia was observed in 80 percent of the rats in
 

this bioassay.
 

There were dose-related marginal increases in mammary adenocarcinomas and in hemangiosarcomas among female rats and there was a
 

statistically significant increase in the incidence of endometrial
 

stromal polyps among dosed female mice as compared to controls.
 

These findings are indicative of the possible carcinogenic potential
 

of the test compound. However, it must be recognized that under the
 

conditions of this bioassay there was no conclusive evidence for the
 

carcinogenicity of 1,1-dichloroethane in Osborne-Mendel rats or
 

B6C3F1 mice.
 

ν
 

TABLE OF CONTENTS
 

Page
 

I. INTRODUCTION 1
 

II. MATERIALS AND METHODS 2
 

A. Chemicals 2
 

B. Dosage Preparation 2
 

C. Animals 2
 

D. Animal Maintenance 3
 

E· Gastric Intubation 4
 

F· Selection of Initial Dose Levels 5
 

G. Experimental Design 6
 

H. Clinical and Histopathologic Examinations 10
 

I. Data Recording and Statistical Analyses 11
 

III. CHRONIC TESTING RESULTS: RATS 17
 

A· Body Weights and Clinical Observations 17
 

B. Survival 19
 

C. Pathology 21
 

D. Statistical Analyses of Results 22
 

IV. CHRONIC TESTING RESULTS: MICE 32
 

A. Body Weights and Clinical Observations 32
 

B. Survival 32
 

C. Pathology 35
 

D. Statistical Analyses of Results 36
 

V. DISCUSSION 46
 

VI. BIBLIOGRAPHY 48
 

APPENDIX A SUMMARY OF THE INCIDENCE OF NEOPLASMS
 

IN RATS TREATED WITH 1,1-DICHLOROETHANE A-l
 

APPENDIX Β SUMMARY OF THE INCIDENCE OF NEOPLASMS
 

IN MICE TREATED WITH 1,1-DICHLOROETHANE B-l
 

APPENDIX C SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC
 

LESIONS IN RATS TREATED WITH 1,1-DICHLOROETHANE C-l
 

APPENDIX D SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC
 

LESIONS IN MICE TREATED WITH 1,1-DICHLOROETHANE D-l
 

vii
 
LIST OF ILLUSTRATIONS
 

Figure Number Page
 

1 GROWTH CURVES FOR 1,1-DICHLOROETHANE

STUDY RATS

 CHRONIC 

 18 

2 SURVIVAL COMPARISONS OF

CHRONIC STUDY RATS

 1,1-DICHLOROETHANE 

 20 

3 GROWTH CURVES FOR 1,1-DICHLOROETHANE

STUDY MICE

 CHRONIC 

 33 

4 SURVIVAL COMPARISONS OF

CHRONIC STUDY MICE

 1,1-DICHLOROETHANE 

 34 

LIST OF TABLES 

Table Number Page 

1 DESIGN SUMMARY FOR OSBORNE-MENDEL RATS — 

1,1-DICHLOROETHANE GAVAGE EXPERIMENT 7 

2 DESIGN SUMMARY FOR B6C3F1 MICE—1,1-DICHLOROETHANE GAVAGE EXPERIMENT 8 

3 ANALYSES OF THE INCIDENCE OF PRIMARY TUMORS 

AT SPECIFIC SITES IN MALE RATS TREATED WITH 

1,1-DICHLOROETHANE 23 

4 ANALYSES OF THE INCIDENCE OF PRIMARY TUMORS 

AT SPECIFIC SITES IN FEMALE RATS TREATED WITH 

1,1-DICHLOROE THANE 2 5 

5 ANALYSES OF THE INCIDENCE OF PRIMARY MAMMARY 

TUMORS IN FEMALE RATS LIVING OVER 52 WEEKS 

TREATED WITH 1,1-DICHLOROETHANE 28 

6 ANALYSES OF THE INCIDENCE OF PRIMARY TUMORS 

AT SPECIFIC SITES IN MALE MICE TREATED WITH 

1,1-DICHLOROETHANE 37 

7 ANALYSES OF THE INCIDENCE OF PRIMARY TUMORS 

AT SPECIFIC SITES IN FEMALE MICE TREATED WITH 

1,1-DICHLOROETHANE 40 

viii
 
LIST OF TABLES (Concluded) 

Table Number Page 

8 ANALYSES OF THE INCIDENCE OF HEPATOCELULLAR 

CARCINOMA IN MALE MICE LIVING OVER 52 WEEKS 

TREATED WITH 1,1-DICHLOROETHANE 45 

Al SUMMARY OF THE INCIDENCE OF NEOPLASMS IN 

MALE RATS TREATED WITH 1,1-DICHLOROETHANE A-3 

A2 SUMMARY OF THE INCIDENCE OF NEOPLASMS IN 

FEMALE RATS TREATED WITH 1,1-DICHLOROETHANE A-7 

Bl SUMMARY OF THE INCIDENCE OF NEOPLASMS IN MALE 

MICE TREATED WITH 1,1-DICHLOROETHANE B-3 

B2 SUMMARY OF THE INCIDENCE OF NEOPLASMS IN 

FEMALE MICE TREATED WITH 1,1-DICHLOROETHANE B-6 

CI SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC 

LESIONS IN MALE RATS TREATED WITH 

1,1-DICHLOROETHANE C-3 

C2 SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC 

LESIONS IN FEMALE RATS TREATED WITH 

1,1-DICHLOROETHANE C-7 

Dl SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC 

LESIONS IN MALE MICE TREATED WITH 

1,1-DICHLOROETHANE D-3 

D2 SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC 

LESIONS IN FEMALE MICE TREATED WITH 

1,1-DICHLOROETHANE D-6 

ix
 

I. INTRODUCTION
 

1,1-Dichloroethane (NCI No· CO4535) is one of a group of halogenated solvents selected for bioassay by the National Cancer Institute·
 

The Chemical Abstracts Service (CAS) Ninth Collective Index (1977)
 

name for this compound is 1,1-dichloroethane· It is also called
 

ethylidene chloride·
 

The major industrial uses of 1,1-dichloroethane are as a chemical
 

intermediate and as a solvent for extraction and degreasing (international Technical Information Institute, 1975; Hardie, 1964; Mullin,
 

1964)· Human exposure to 1,1-dichloroethane occurs principally by
 

inhalation in those industries using or manufacturing the chemical.
 

The CAS registry number is 75-34-3
 

1 
II. MATERIALS AND METHODS
 

A. Chemicals
 

One batch of technical-grade 1,1-dichloroethane was purchased by
 

Hazleton Laboratories America, Inc., Vienna, Virginia, from Aldrich
 

Chemical Company, Inc., Milwaukee, Wisconsin. The purity of the compound was determined using gas-liquid chromatography (GLC) total area
 

analysis and infrared spectroscopy. The GLC analysis revealed six
 

peaks; the major peak accounted for over 99 percent of the total area.
 

The infrared spectrum of the chemical tested was consistent with that
 

expected from the structure of 1,1-dichloroethane, and no bands that
 

might indicate impurities were observed.
 

Throughout this report the term 1,1-dichloroethane refers to this
 

technical-grade material.
 

B· Dosage Preparation
 

Fresh solutions of 1,1-dichloroethane in Dukefs®corn oil (S. F.
 

Sauer Company, Richmond, Virginia) were prepared weekly, sealed, and
 

stored at 1°C. Concentrations of 1,1-dichloroethane in corn oil of
 

15 to 36 percent and 30 to 90 percent were utilized for mice and rats,
 

respectively. These 1,1-dichloroethane solutions were considered
 

generally stable for 10 days under the indicated storage conditions.
 

C. Animals
 

Two animal species, rats and mice, were used in the carcinogenicity bioassay. The Osborne-Mendel rat was selected on the basis of a
 

2
 
comparative study of the tumorigenic responsiveness to carbon tetrachloride of five different strains of rats (Reuber and Glover, 1970)·
 

The B6C3F1 mouse was selected because it has been used by the NCI for
 

carcinogenesis bioassays and has proved satisfactory in this capacity.
 

Rats and mice of both sexes were obtained through contracts of
 

the Division of Cancer Treatment at the National Cancer Institute.
 

The Osborne-Mendel rats were procured from the Battelle Memorial
 

Institute, Columbus, Ohio, and the B6C3F1 mice were obtained from the
 

Charles River Breeding Laboratories, Inc., Wilmington, Massachusetts.
 

Upon receipt, animals were quarantined for at least 10 days, observed
 

for visible signs of disease or parasites, and assigned to the various
 

dosed and control groups.
 

D· Animal Maintenance
 

All animals were housed by species in temperature- and humidity-


controlled rooms. The temperature range was 20° to 25°C and the
 

relative humidity was maintained between 45 and 55 percent. The air
 

conditioning system in the laboratory provided filtered air at a rate
 

of 12 complete changes of room air per hour. Fluorescent lighting
 

was provided on a 12-hour-daily cycle.
 

The rats were individually housed-in suspended galvanized-steel
 

wire-mesh cages with perforated floors, while mice were housed by sex
 

in groups of 10 in solid-bottom polypropylene cages equipped with
 

filter tops. Sanitized cages with fresh bedding (Sanichips , Pinewood
 

Sawdust Company, Moonachie, New Jersey) were provided once each week
 

for mice. Rats received sanitized cages with no bedding with the
 

3
 
same frequency· Food hoppers were changed and heat-sterilized once a
 

week for the first 10 weeks and once a month thereafter, while fresh
 

heat-sterilized glass water bottles were provided three times a week.
 

Food (Wayne Lab~Blox®meal, Allied Mills, Inc., Chicago, Illinois)
 

and tap water were available ad libitum.
 

The 1,1-dichloroethane-treated and vehicle control rats were
 

housed with other rats intubated with 1,2-dichloroethane (107-06-2),
 

carbon disulfide (75-15-0), trichloroethylene (79-01-6), and dibromochloropropane (96-12-8). The untreated control rats were housed with
 

other rats intubated with 1,1,2-trichloroethane (79-00-5) and tetrachloroethylene (127-18-4). 1,1-Dichloroethane-treated and control
 

mice were maintained in the same room as other mice intubated with
 

1,1,2,2-tetrachloroethane (79-34-5), allyl chloride (107-05-1),
 

1,1, 2-trichloroethane (79-00-5), dibromochloropropane (96-12-8),
 

chloropicrin (76-06-2), chloroform (67-66-3), 1,2-dibromoethane
 

(106-93-4), tetrachloroethylene (127-18-4), iodoform (75-47-8),
 

1,2-dichloroethane (75-34-3), methylchloroform (71-55-6), trichloroethylene (79-01-6), trichlorofluoromethane (75-69-4), carbon disulfide (75-15-0), hexachloroethane (67-72-1), carbon tetrachloride
 

(56-23-5), and 3-sulfolene (77-79-2).
 

E. Gastric Intubation
 

Intubation was performed for five consecutive days per week on
 

a mg/kg body weight basis utilizing the most recently observed group
 

CAS registry numbers are given in parentheses.
 

4
 
mean body weight as a guide for determining the dosage· Mean body
 

weights for each group were recorded at weekly intervals for the
 

first 10 weeks and at monthly intervals thereafter· All animals of
 

one sex within a treated group received the same dose· Gavage of
 

treated animals was performed under a hood to minimize extraneous
 

exposure of other animals and laboratory personnel to the chemical.
 

F. Selection of Initial Dose Levels
 

In order to establish the maximum tolerated dosages of 1,1­

dichloroethane for administration to treated animals in the chronic
 

studies, subchronic toxicity tests were conducted with both rats and
 

mice· Animals of each species were distributed among six groups,
 

each consisting of five males and five females· 1,1-Dichloroethane
 

dissolved in corn oil was introduced by gavage to five of the six rat
 

groups at dosages of 562, 1000, 1780, 3160, and 5620 mg/kg/day and
 

five of the six mouse groups at dosages of 1000, 1780, 3160, 5620,
 

and 10,000 mg/kg/day. The sixth group of each species received only
 

corn oil. Intubation was performed 5 days per week for 6 weeks, followed by a 2-week observation period to detect any delayed toxicity.
 

The mean body weight depression in the male rats at 562 and 1000
 

mg/kg/day was 16 and 29 percent, respectively. In the female rats a
 

20 percent mean body weight depression was observed at 1780 and 3160
 

mg/kg/day; however, two animals died at the latter level· The
 

initial high dosages estimated for the chronic study were 700 and
 

1500 mg/kg/day for male and female rats, respectively.
 

5
 
No mean body weight depression was observed in mice; however,
 

two male and three female mice died at 5620 mg/kg/day. The initial
 

high dose estimated for the chronic study was 1800 mg/kg/day for mice
 

of both sexes·
 

G· Experimental Design
 

The experimental design parameters for the chronic study (species, sex, group size, dosages administered, duration of treated and
 

untreated observation periods, and the time-weighted average dosages)
 

are summarized in Tables 1 and 2·
 

Intubation was performed five consecutive days per week· The
 

initial doses utilized for male rats were 700 and 350 mg/kg/day,
 

respectively, while for female rats they were 1500 and 750 mg/kg/day,
 

respectively· Throughout this report those rats receiving the higher
 

of the two dosages administered to their sex are referred to as the
 

high dose group and those receiving the lower of the two dosages are
 

referred to as the low dose group. During week 9 of the experiment,
 

due to apparent tolerance to the chemical, the high and low doses for
 

male rats were increased to 900 and 450 mg/kg/day, and the high and
 

low doses for the female rats were increased to 1800 and 900 mg/kg/
 

day· In week 18, the dosages administered to the female groups were
 

halved, to 900 and 450 mg/kg/day, respectively· Fourteen weeks after
 

this dose decrease (week 32 of the experiment), intubation of all
 

animals ceased for 1 week, followed by 4 weeks of 1,1-dichloroethane
 

administration at the previous levels. This cyclic pattern of
 

6
 
TABLE 1
 

DESIGN SUMMARY FOR OSBORNE-MENDEL RATS
 

1,1-DICHLOROETHANE GAVAGE EXPERIMENT
 

TIME-WEIGHTED 

INITIAL 1,1-DICHLORO­ OBSERVATION PERIOD AVERAGE DOSAGE 

GROUP ETHANE TREATED UNTREATED OVER A 78-WEEK 

SIZE DOSAGE3 (WEEKS) (WEEKS) PERIODb 

MALE
 

UNTREATED CONTROL 20 0	 109 0
 

VEHICLE CONTROL 20 0 78 33	 0
 

LOW DOSE 50	 350 8 382
 

450 23
 

450C 37 10
 

0	 33
 

HIGH DOSE 50	 700 8 764
 

900 23
 

900C 37 10
 

0	 33
 

FEMALE
 

UNTREATED CONTROL 20 0	 105 0
 

VEHICLE CONTROL 20 0 78 33	 0
 

LOW DOSE 50	 750 8 475
 

900 9
 

450 14
 

450c 37 10
 

0	 33
 

HIGH DOSE 50 1500 8	 950
 

1800 9
 

900 14
 

900C 37 10
 

0	 33
 

a 

Dosage, given in mg/kg body weight, was administered by gavage five 

consecutive days per week. 

b Σ(dosage X number of weeks received) Time-weighted average dosage =
 78 weeks
 

These dosages were cyclically administered with a pattern of 1 dosage-


free week followed by 4 weeks (5 days per week) of dosage at the level
 

indicated.
 

7
 

C 
TABLE 2
 

DESIGN SUMMARY FOR B6C3F1 MICE
 

1,1-DICHLOROETHANE GAVAGE EXPERIMENT
 

INITIAL 1,1-DICHLORO­ OBSERVATION PERIOD TIME-WEIGHTED 

GROUP ETHANE TREATED UNTREATED AVERAGE 

SIZE DOSAGEa (WEEKS) (WEEKS) DOSAGE 

MALE
 

UNTREATED CONTROL 20 0	 90 0
 

VEHICLE CONTROL 20 0 78 12	 0
 

LOW DOSE 50 900 6 1442
 

1200 3
 

1500 69
 

0	 13
 

HIGH DOSE 50	 1800 6 2885
 

2400 3
 

3000 69
 

0	 13
 

FEMALE
 

UNTREATED CONTROL 20 0	 91 0
 

VEHICLE CONTROL 20 0 78 12	 0
 

LOW DOSE 50 900 6 1665
 

1200 3
 

1500 11
 

1800 58
 

0	 13
 

HIGH DOSE 50	 1800 6 3331
 

2400 3
 

3000 11
 

3600 58
 

0	 13
 

a. Dosage, given in mg/kg body weight, was administered by gavage five 

consecutive days per week· 

b	 Σ(dosage X number of weeks received) Time-weighted average dosage =
 Σ(weeks receiving chemical)
 

8
 
chemical administration continued until dosage termination in week
 

78. These total dosage decreases were in response to the observed
 

toxicity of the compound·
 

The vehicle control rats received corn oil in volumes equal to
 

those administered to the high dose groups· The low dose, high
 

dose, and vehicle control rats were all approximately 8 weeks old at
 

the time the experiment began. The untreated controls, which were
 

approximately 6 weeks younger than the other three rat groups, were
 

included in the test approximately 4 weeks after intubation of the
 

other rats had begun·
 

The untreated control, low dose, and high dose mice were all
 

approximately 5 weeks old on the day the first dose was administered,
 

while the vehicle control mice were approximately 2 weeks older.
 

Therefore, administration of corn oil to the vehicle controls began
 

correspondingly earlier than did 1,1-dichloroethane administration to
 

the dosed mice. The male and female mice received initial dosages of
 

1800 and 900 mg/kg/day, respectively. Throughout this report those
 

mice receiving the former dosage are referred to as the high dose
 

groups, while those receiving the latter dosage are referred to as
 

the low dose groups. The doses were increased in week 7 for both
 

levels in both sexes, the high dose to 2400 mg/kg/day, and the low
 

dose to 1200 mg/kg/day. In week 10, high and low doses were increased
 

to 3000 and 1500 mg/kg/day for both males and females. In week 21 the
 

high and low doses administered to the female mice were increased to
 

9
 
3600 and 1800 mg/kg/day, respectively, while the male groups continued
 

to receive 3000 and 1500 mg/kg/day, respectively· The dosages were
 

increased because the treated animals were exhibiting no apparent
 

toxic effects. The vehicle control mice were the same used for the
 

1,2-dichloroethane carcinogenesis bioassay and received corn oil by
 

gavage in amounts and frequencies corresponding to the high dose
 

1,2-dichlorethane-treated mice.
 

The untreated controls received no 1,1-dichloroethane or corn
 

oil, while the vehicle controls were administered pure corn oil by
 

gavage.
 

H #

 Clinical and Histopathologic Examinations
 

Animals were weighed immediately prior to initiation of the
 

experiment. From the first day, all animals were inspected daily
 

for mortality. Body weights, food consumption, and data concerning
 

appearance, behavior, signs of toxic effects, and incidence, size,
 

and location of tissue masses were recorded at weekly intervals for
 

the first 10 weeks and at monthly intervals thereafter. The presence
 

of tissue masses was determined by observation and palpation of each
 

animal.
 

A necropsy was performed on each animal regardless of whether it
 

died, was killed when moribund, or was sacrificed at the end of the
 

bioassay. The animals were euthanized by exsanguination under sodium
 

pentobarbital anesthesia, and were immediately necropsied. The histopathologic examination consisted of gross and microscopic examination
 

10
 
of major tissues, organs, or gross lesions taken from sacrificed animals and, whenever possible, from animals found dead.
 

Slides were prepared from the following tissues: skin, subcutaneous tissue, lungs and bronchi, trachea, bone marrow, spleen, lymph
 

nodes, thymus, heart, salivary gland, liver, gallbladder and bile
 

duct (mice), pancreas, esophagus, stomach, small intestine, large
 

intestine, kidney, urinary bladder, pituitary, adrenal, thyroid,
 

parathyroid, testis, prostate, brain, uterus, mammary gland, and
 

ovary.
 

Tissues for which slides were prepared were preserved in 10 percent buffered formalin, embedded in paraffin, sectioned, and stained
 

with hematoxylin and eosin prior to microscopic examination. An
 

occasional section was subjected to special staining techniques for
 

more definitive diagnosis.
 

A few tissues were not examined for some animals, particularly
 

for those that died early. Also, some animals were missing, cannibalized, or judged to be in such an advanced state of autolysis as to
 

preclude histopathologic interpretation. Thus, the number of animals
 

for which particular organs, tissues, or lesions were examined microscopically varies and does not necessarily represent the number of
 

animals that were placed on experiment in each group.
 

I. Data Recording and Statistical Analyses
 

Pertinent data on this experiment have been recorded in an automatic data processing system, the Carcinogenesis Bioassay Data System
 

11
 
(Linhart et al., 1974)· The data elements include descriptive information on the chemicals, animals, experimental design, clinical observations, survival, body weight, and individual pathologic results, as
 

recommended by the International Union Against Cancer (Berenblum,
 

1969)· Data tables were generated for verification of data transcription and for statistical review.
 

These data were analyzed using the statistical techniques
 

described in this section. Those analyses of the experimental results
 

that bear on the possibility of carcinogenicity are discussed in the
 

statistical narrative sections.
 

Probabilities of survival were estimated by the product-limit
 

procedure of Kaplan and Meier (1958) and are presented in this report
 

in the form of graphs. Animals were statistically censored as of the
 

time that they died of other than natural causes or were found to be
 

missing; animals dying from natural causes were not statistically
 

censored. Statistical analyses for a possible dose-related effect on
 

survival used the method of Cox (1972) for testing two groups for
 

equality and used Taronef

s (1975) extensions of Cox's methods for
 

testing a dose-related trend. One-tailed P-values have been reported
 

for all tests except the departure from linearity test, which is only
 

reported when its two-tailed P-value is less than 0.05.
 

The incidence of neoplastic or nonneoplastic lesions has been
 

given as the ratio of the number of animals bearing such lesions at a
 

specific anatomic site (numerator) to the number of animals in which
 

12
 
that site was examined (denominator)· In most instances, the denominators included only those animals for which that site was examined
 

histologically· However, when macroscopic examination was required
 

to detect lesions prior to histologic sampling (e.g., skin or mammary
 

tumors), or when lesions could have appeared at multiple sites (e.g.,
 

lymphomas), the denominators consist of the numbers of animals necropsied.
 

The purpose of the statistical analyses of tumor incidence is to
 

determine whether animals receiving the test chemical developed a significantly higher proportion of tumors than did the control animals.
 

As a part of these analyses, the one-tailed Fisher exact test (Cox,
 

1970, pp. 48-52) was used to compare the tumor incidence of a control
 

group to that of a group of treated animals at each dose level. When
 

results for a number of treated groups, k, are compared simultaneously
 

with those for a control group, a correction to ensure an overall
 

significance level of 0.05 may be made. The Bonferroni inequality
 

(Miller, 1966, pp. 6-10) requires that the P-value for any comparison
 

be less than or equal to 0.05/k. In cases where this correction was
 

used, it is discussed in the narrative section. It is not, however,
 

presented in the tables, where the Fisher exact P-values are shown.
 

The Cochran-Armitage test for linear trend in proportions, with
 

continuity correction (Armitage, 1971, pp. 362-365), was also used.
 

Under the assumption of a linear trend, this test determined if the
 

slope of the dose-response curve is different from zero at the
 

13
 
one-tailed 0.05 level of significance· Unless otherwise noted, the
 

direction of the significant trend was a positive dose relationship·
 

This method also provides a two-tailed test of departure from linear
 

trend.
 

A time-adjusted analysis was applied when numerous early deaths
 

resulted from causes that were not associated with the formation of
 

tumors. In this analysis, deaths that occurred before the first
 

tumor was observed were excluded by basing the statistical tests on
 

animals that survived at least 52 weeks, unless a tumor was found at
 

the anatomic site of interest before week 52. When such an early
 

tumor was found, comparisons were based exclusively on animals that
 

survived at least as long as the animal in which the first tumor was
 

found. Once this reduced set of.data was obtained, the standard procedures for analyses of the incidence of tumors (Fisher exact tests,
 

Cochran-Armitage tests, etc.) were followed.
 

When appropriate, life-table methods were used to analyze the
 

incidence of tumors. Curves of the proportions surviving without an
 

observed tumor were computed as in Saffiotti et al. (1972)· The week
 

during which animals died naturally or were sacrificed was entered as
 

the time point of tumor observation. Cox's methods of comparing
 

these curves were used for two groups; Tarone's extension to testing
 

for linear trend was used for three groups. The statistical tests for
 

the incidence of tumors which used life-table methods were one-tailed
 

and, unless otherwise noted, in the direction of a positive dose
 

14
 
relationship· Significant departures from linearity (P < 0·05, two-


tailed test) were also noted·
 

The approximate 95 percent confidence interval for the relative
 

risk of each dosed group compared to its control was calculated from
 

the exact interval on the odds ratio (Gart, 1971). The relative risk
 

is defined as ρ / where ρ is the true binomial probability of the
 

incidence of a specific type of tumor in a treated group of animals
 

and ρ is the true probability of the spontaneous incidence of the
 

same type of tumor in a control group· The hypothesis of equality
 

between the true proportion of a specific tumor in a treated group
 

and the proportion in a control group corresponds to a relative risk
 

of unity. Values in excess of unity represent the condition of a
 

larger proportion in the tr-eated group than in the control.
 

The lower and upper limits of the confidence interval of the
 

relative risk have been included in the tables of statistical analyses. The interpretation of the limits is that in approximately 95
 

percent of a large number of identical experiments, the true ratio
 

of the risk in a treated group of animals to that in a control group
 

would be within the interval calculated from the experiment. When
 

the lower limit of the confidence interval is greater than one, it
 

can be inferred that a statistically significant result (a P < 0.025
 

one-tailed test when the control incidence is not zero, Ρ < 0·050
 

when the control incidence is zero) has occurred. When the lower
 

limit is less than unity but the upper limit is greater than unity,
 

15
 
the lower limit indicates the absence of a significant result while
 

the upper limit indicates that there is a theoretical possibility
 

of the induction of tumors by the test chemical which could not be
 

detected under the conditions of this test·
 

16
 
III. CHRONIC TESTING RESULTS: RATS
 

A. Body Weights and Clinical Observations
 

As indicated in Figure 1, comparison of the mean body weight
 

patterns for vehicle control and treated rats revealed no apparent
 

differences· The untreated controls did maintain a body weight consistently higher than the other groups. Fluctuations in the growth
 

curve may be due to mortality; as the size of the group diminishes,
 

the mean body weight may be subject to wide variations.
 

During the first 20 weeks of the study the appearance and behavior of the treated rats were generally comparable to that of controls. From week 20 to cessation of intubation in week 78, a hunched
 

appearance and abdominal urine stains were observed with a slightly
 

greater frequency in the treated rats of both sexes than in their
 

corresponding controls. These observations were, however, noted with
 

comparable frequency in treated and control rats after cessation of
 

treatment. Respiratory signs characterized by labored respiration,
 

wheezing, nasal discharge, and/or a hunched appearance were observed
 

at a low to moderate incidence in all groups during the latter part
 

of the first year, increasing gradually for treated and control rats
 

during the last 10 months of the study. In week 110, all surviving
 

rats had a hunched appearance and showed labored respiration. Clinical signs commonly associated with aging in laboratory rats were
 

noted for all rats during the second year of the study· These signs
 

included sores on the tail, discolored or rough fur, soft feces, and
 

17
 
750 

UNTREATED CONTROL 

^^~^~' VEHICLE CONTROL 

LOW DOSE 

-.__ — HIGH DOSE 

TIME ON TEST (WEEKS) 

TIME ON TEST (WEEKS) 

FIGURE 1 

GROWTH CURVES FOR 1/1-DICHLOROETHANE CHRONIC STUDY RATS 

18 
eye discharge or reddish crust around the eyes. The incidence of
 

palpable nodules and/or tissue masses in the treated rats was observed at a frequency similar to that in the control animals.
 

B. Survival
 

The estimated probabilities of survival for male and female rats
 

in the control and 1,1-dichloroethane-dosed groups are shown in
 

Figure 2.
 

For male rats there was generally poor survival in all groups by
 

the end of the study. The survival curve for the high dose male rats
 

did not differ appreciably from the curve of the low dose male rats.
 

Survival of both high and low dose male rats was, however, significantly (P = 0.006) lower than survival of either the vehicle control
 

or the untreated control group. The median male survival was 62 weeks
 

for both dosed groups. Although the early deaths among the dosed
 

male rats were related to administration of 1,1-dichloroethane, the
 

deaths were not caused by tumors; only one dosed rat died with a
 

tumor during the first 62 weeks.
 

For female rats, survival was also poor. Although the survival
 

curves for the dosed female rats indicated lower survival rates than
 

those for the vehicle and untreated control animals from about week
 

15 to week 90, the Tarone test did not indicate a statistically significant association between dosage and mortality. No tumors were
 

observed in any of the low dose females that died by 65 weeks on
 

test, by which point 50 percent (25/50) of the group had died. Only
 

19
 
TIME ON TEST (WEEKS) 

FIGURE 2 

SURVIVAL COMPARISONS OF 1,1-DICHLOROETHANE CHRONIC STUDY RATS 

20 
one tumor was observed in the high dose group before the median survival for that group (week 70), and that tumor was detected during
 

week 54. Thus tumors do not appear to have caused these deaths.
 

Due to the high early mortality observed in dosed rats of both
 

sexes, the number of rats surviving long enough to be at risk from
 

late-developing tumors was low.
 

C. Pathology
 

Histopathologic findings on neoplasms in rats are tabulated in
 

Appendix A (Tables Al and A2); findings on nonneoplastic lesions are
 

tabulated in Appendix C (Tables CI and C2).
 

Histopathologic examination of the tissues and organs did not
 

indicate a carcinogenic effect for 1,1-dichloroethane in Osborne-


Mendel rats. An unusual tumor, an adenocarcinoma of the prostate,
 

that metastasized to the lung, liver, cecum, and tissue around the
 

prostate occurred in 1/33 low dose male rats. An adenocarcinoma of
 

the small intestine that metastasized to the pancreas was present in
 

1/47 high dose females. Adenocarcinomas of the mammary gland occurred in 1/20 vehicle control males, 1/20 untreated control females,
 

1/50 low dose females, and 5/50 high dose females.
 

A variety of other neoplasms, which have been encountered previously as spontaneous lesions in Osborne-Mendel rats, were present in
 

both treated and control rats. No appreciable difference in the incidence of neoplasia was noted in the control or the treated rats in
 

this study.
 

21
 
Inflammatory, degenerative, and proliferative lesions as seen in
 

the control and treated animals were similar in number and kind to
 

those naturally occurring lesions found in aged Osborne-Mendel rats·
 

The nonneoplastic lesions that were seen most frequently were chronic
 

murine pneumonia and chronic inflammation of the kidney·
 

D. Statistical Analyses of Results
 

The results of the statistical analyses of tumor incidence in
 

rats are summarized in Tables 3 and 4. The analysis for every type
 

of tumor that was observed in more than 5 percent of any of the
 

1,1-dichloroethane-dosed groups of either sex is included·
 

The untreated control groups were not used for these statistical
 

analyses because they were maintained in a different room from the
 

dosed animals and because the comparison of vehicle control to
 

treated groups was the comparison of choice· To gain more information on spontaneous rates of tumor incidence and to obtain a control
 

group of increased sample size, a pooled vehicle control group was
 

used in addition to the matched vehicle controls. This pooled vehicle control group was a combination of the vehicle controls used for
 

chronic bioassays of 1,1-dichloroethane and trichloroethylene· The
 

pooled control rats were of the saflie strain, were tested concurrently
 

for at least one year, and were examined by the same pathologist·
 

In the female rats the Cochran-Armitage test indicated a significant positive association between dosage and the incidence of
 

hemangiosarcoma when comparing both to the matched vehicle control
 

22
 
23
 

TABLE 3 

ANALYSES OF THE INCIDENCE OF PRIMARY TUMORS AT 

SPECIFIC SITES IN MALE RATS TREATED WITH 1,1-DICHLOROETHANE* 

POOLED MATCHED 

VEHICLE VEHICLE LOW HIGH 

TOPOGRAPHY: MORPHOLOGY CONTROL CONTROL DOSE DOSE 

Pituitary: Chromophobe Adenoma 1/40(0.03) 1/20(0.05) 0/44(0.00) 2/46(0.04) 

 Values0 N.S. N.S. N.S. N.S. 

Relative Risk (Pooled Vehicle 

Control)d 0.000 1.739 

Lower Limit 0.000 0.094 

Upper Limit 16.921 100.348 

Relative Risk (Matched Vehicle 

Control)d 0.000 0.870 

Lower Limit 0.000 0.049 

Upper Limit 8.471 50.196 

Weeks to First Observed Tumor 84 84 67 

Mammary Gland: Adenocarcinoma 1/40(0.03) 1/20(0.05) 0/50(0.00) 0/50(0.00) 

 Values0 N.S. N.S. N.S. N.S. 

Relative Risk (Pooled Vehicle 

Control)d 0.000 0.000 

Lower Limit 0.000 0.000 

Upper Limit 14.930 14.930 

Relative Risk (Matched Vehicle 

Control)d 0.000 0.000 

Lower Limit 0.000 0.000 

Upper Limit 7.475 7.475 

Weeks to First Observed Tumor 98 98 
TABLE 3
 

(CONCLUDED)
 

Treated groups received time-weighted average doses of 382 or 764 mg/kg by gavage.
 

Number of tumor-bearing animals/number of animals examined at site (proportion).
 

The probability level for the Cochran-Armitage test is given beneath the incidence of tumors
 

in the corresponding control group when Ρ <0,05; otherwise, not significant (N.S.) is indicated. The probability level for the Fisher exact test for the comparison of a treated
 

group with the pooled vehicle control group (*) or the matched vehicle control group (**)
 

is given beneath the incidence of tumors in that treated group when Ρ <0.05; otherwise, not
 

significant (N.S.) is indicated. For both Cochran-Armitage and Fisher exact tests a negative
 

designation (N) indicates a lower incidence in the treated group(s) than in the control group.
 

The 95% confidence interval on the relative risk of the treated group to the control group.
 
TABLE 4 

ANALYSES OF THE INCIDENCE OF PRIMARY TUMORS AT 

SPECIFIC SITES IN FEMALE RATS TREATED WITH 1,1-DICHLOROETHANE* 

POOLED MATCHED 

VEHICLE VEHICLE LOW HIGH 

TOPOGRAPHY: MORPHOLOGY CONTROL CONTROL DOSE DOSE 

Pituitary: Chromophobe Adenoma 6/39(0.15) 2/19(0.11) 6/48(0.13) 4/48(0.08) 

 Values0 N.S. N.S. N.S. N.S. 

Relative Risk (Pooled Vehicle 

Control)d 0.813 0.542 

Lower Limit 0.237 0.121 

Upper Limit 2.811 2.123 

Relative Risk (Matched Vehicle 

Control)d 1.188 0.792 

Lower Limit 0.243 0.127 

Upper Limit 11.426 8.329 

Weeks to First Observed Tumor 68 103 108 104 

Mammary Gland: Adenocarcinoma 1/39(0.03) 0/19(0.00) 1/50(0.02) 5/50(0.10) 

 Values0 N.S. = 0.043 N.S. N.S. 

Relative Risk (Pooled Vehicle 

Control)d 0.780 3.900 

Lower Limit 0.010 0.466 

Upper Limit 60.033 180.520 

Relative Risk (Matched Vehicle 

Control)d Infinite Infinite 

Lower Limit 0.021 0.503 

Upper Limit Infinite Infinite 

Weeks to First Observed Tumor 102 111 54 
26 

TOPOGRAPHY :MORPHOLOGY
 

Mammary Gland: Fibroadenoma
 

 Values
 

Relative Risk (Pooled Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Relative Risk (Matched Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Weeks to First Observed Tumor
 

Mammary Gland:, Adenocarcinoma or
 

Fibroadenoma
 

 Values0
 

Relative Risk (Pooled Vehicle
 

Control)^
 

Lower Limit
 

Upper Limit
 

Relative Risk (Matched Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

TABLE 4
 

(CONTINUED)
 

POOLED
 

VEHICLE
 

CONTROL
 

5/39(0.13)
 

N.S.
 

97
 

6/39(0.15)
 

N.S.
 

MATCHED
 

VEHICLE
 

CONTROL
 

2/19(0.11)
 

N.S.
 

97
 

2/19(0.11)
 

N.S.
 

LOW
 

DOSE
 

6/50(0.12)
 

N.S.
 

0.936
 

0.258
 

3.615
 

1.140
 

0.231
 

10.985
 

97
 

6/50(0.12)
 

N.S.
 

0.780
 

0.227
 

2.704
 

1.140
 

0.232
 

10.985
 

HIGH
 

DOSE
 

6/50(0.12)
 

N.S.
 

0.936
 

0.258
 

3.615
 

1.140
 

0.231
 

10.985
 

84
 

11/50(0.22)
 

N.S.
 

1.430
 

0.537
 

4.322
 

2.090
 

0.526
 

18.369
 

Weeks to First Observed Tumor 97 97 97
 54
 
TABLE 4
 

(CONCLUDED)
 

POOLED MATCHED 

VEHICLE VEHICLE LOW HIGH 

TOPOGRAPHY.: MORPHOLOGY CONTROL CONTROL DOSE DOSE 

Circulatory Systern:Hemangiasarcoma 0/39(0.00) 0/19(0.00) 0/50(0.00) 4/50(0.08) 

 Values0 = 0.021 - 0.041 N.S. N.S. 

Relative Risk (Pooled Vehicle 

Control)d Infinite 

Lower Limit 0.726 

Upper Limit Infinite 

Relative Risk (Matched Vehicle 

Control)d Infinite 

Lower Limit 0.726 

Upper Limit Infinite 

Weeks to First Observed Tumor ——— __— 86 

Treated groups received time-weighted average doses of 475 or 950,mg/kg by gavage.
 

Number of tumor-bearing animals/number of animals examined at site (proportion).
 

C

The probability level for the Cochran-Armitage test is given beneath the incidence of tumors
 

in the corresponding control group when P<0.05; otherwise, not significant (N.S.) is indicated. The probability level for the Fisher exact test for the comparison of a treated
 

group with the pooled vehicle control group (*) or the matched vehicle control group (**)
 

is given beneath the incidence of tumors in that treated group when p<0.05; otherwise, not
 

significant (N.S.) is indicated. For both Cochran-Armitage and Fisher exact tests a negative
 

designation (N) indicates a lower incidence in the treated group(s) than in the control group.
 

The 95% confidence interval on the relative risk of the treated group to the control group.
 
TABLE 5 

ANALYSES OF THE INCIDENCE OF PRIMARY MAMMARY TUMORS IN FEMALE

LIVING OVER 5 2 WEEKS TREATED WITH l,l-DICHLOROETHANEa 

MATCHED 

VEHICLE LOW 

TOPOGRAPHY: MORPHOLOGY CONTROL DOSE 

Mammary Gland : Adenocarcinoma 0/16(0.00) 1/28(0.04) 

 Values0 

 « 0.034 N.S. 

Relative Risk (Matched Vehicle Control) Infinite 

Lower Limit 0.032 

Upper Limit Infinite 

Weeks to First Observed Tumor -— 111 

oo 

Mammary Gland: Fibroadenoma 2/16(0.13) 6/28(0.21) 

 Values0 N.S. N.S. 

Relative Risk (Matched Vehicle Control) 1.714 

Lower Limit 0.362 

Upper Limit 15.948 

Weeks to First Observed Tumor 97 97 

Mammary Gland: Adenocarcinoma or Fibroadenoma 2/16(0.13) 6/28(0.21) 

 Values0 N.S. N.S. 

Relative Risk (Matched Vehicle Control) ___ 1.714 

Lower Limit — 0.362 

Upper Limit — 15.948 

Weeks to First Observed Tumor 97 97 

 RATS 

HIGH 

DOSE 

5/31(0.16) 

N.S. 

Infinite 

0.692 

Infinite 

54 

6/31(0.19) 

N.S. 

1.548 

0.326 

14.514 

84 

11/31(0.35) 

N.S. 

2.839 

0.743 

24.020 

54 
TABLE 5 (CONCLUDED) 

Treated groups received time-weighted average doses of 475 or 950 mg/kg by gavage. 

Number of tumor-bearing animals/number of animals examined at site (proportion)· 

Beneath the incidence of the control group is the probability level for the Cochran-Armitage 

test for dose-related trend in proportions when it is below 0.05; otherwise, not significant 

(N.S.) is indicated. 

Relative risk of the treated group versus the control group is shown along with the lower and 

upper limit of the 95% confidence interval for that relative risk. 

29 
( = 0.041) and to the pooled vehicle control ( = 0·021)· The Fisher
 

exact tests, however, did not detect any significant differences·
 

For females the Cochran-Armitage test also indicated a significant (P = 0.043) positive association between the incidence of mammary adenocarcinoma and dosage. Comparison with the pooled vehicle
 

controls, however, was not significant and none of the Fisher exact
 

tests indicated a significantly increased incidence of adenocarcinoma
 

in dosed rats. All tests of either the incidence of fibroadenoma of
 

the mammary gland or the combined incidence of fibroadenoma and
 

adenocarcinoma failed to indicate significant differences.
 

Due to the high early mortality noted in the dosed rats, an additional analysis was performed based only upon those rats that survived
 

at least 52 weeks. For this analysis, the only tumor for which a test
 

was statistically significant was the adenocarcinoma of the mammary
 

gland of female rats (Table 5): The Cochran-Armitage test showed a
 

significant (P = 0.034) positive association between dosage and tumor
 

incidence. The Fisher exact tests, however, were not significant.
 

All other statistical tests in male and female rats failed to
 

establish significant differences.
 

Based upon these results the statistical conclusion is that
 

there was insufficient evidence to indicate the carcinogenic effect
 

of 1,1-dichloroethane.
 

To provide additional insight into the possible carcinogenicity
 

of this compound, 95 percent confidence intervals on the relative
 

30
 
risk have been estimated and entered in the tables based upon the
 

observed tumor incidence rates. In all of the intervals shown in
 

Tables 3 and 4, the value one is included; this indicates the absence
 

of statistically significant results· It should also be noted that
 

all of the confidence intervals have an upper limit greater than one,
 

indicating the theoretical possibility of tumor induction in rats by
 

1,1-dichloroethane that could not be established under the conditions
 

of this test.
 

31
 
IV. CHRONIC TESTING RESULTS: MICE
 

A· Body Weights and Clinical Observations
 

As indicated in Figure 3, comparison of the mean body weight patterns for control and treated mice indicates no significant difference.
 

Therefore, it appears that 1,1-dichloroethane did not affect the growth
 

of mice at the dosage levels used in this bioassay·
 

Throughout the study no definitive evidence of the effect of chemcal administration with regard to physical appearance and behavior was
 

observed. During the first year, signs often observed in group-housed
 

laboratory mice were noted among both control and treated animals.
 

These included a hunched appearance, sores on the back and other parts
 

of the body (more prevalent in male than female mice), localized alopecia, and rough or stained fur. The incidence of these abnormalities
 

increased at a comparable rate in treated and control animals during
 

the remainder of the study. Other signs observed sporadically among
 

all the groups were penile or vulvar irritation (sometimes with red
 

discharge), anal prolapse, reddened or squinted eyes, head tilt or
 

circling, and bloating. Palpable subcutaneous nodules, masses, or
 

seemingly swollen areas were observed with comparable frequency among
 

the control and treated mice during the second year of the study.
 

B. Survival
 

The estimated probabilities of survival for male and female
 

mice in the control and 1,1-dichloroethane-dosed groups are shown in
 

Figure 4.
 

32
 
TIME ON TEST (WEEKS) 

FIGURE 3 

GROWTH CURVES FOR 1/l-DICHLOROETHANE CHRONIC STUDY MICE 

33 
TIME ON TEST (WEEKS)

 

FIGURE 4 

SURVIVAL COMPARISONS OF 1,1-DICHLOROETHANE CHRONIC STUDY MICE 

34 
For males the Tarone test indicated a significant positive association between dosage and mortality· The median survival in the
 

high dose male mouse group was 67 weeks; only 32 percent of these
 

animals survived until the end of the experiment· Since only two tumors were observed in the high dose males prior to week 89, the early
 

deaths do not appear to be tumor-related.
 

In the female mice, the Tarone test for a positive dose-related
 

trend in mortality was highly significant (P < 0.001)· This was due
 

mainly to mortality in the high dose group since the low dose and the
 

control group survival curves were quite similar· There was no evidence that the early deaths were tumor-related· Despite the elevated
 

mortality, 50 percent of the high dose female mice survived to the
 

end of the experiment, providing adequate numbers of animals to make
 

statistical analysis of late-appearing tumors possible.
 

C.	 Pathology
 

Histopathologic findings on neoplasms in mice are tabulated in
 

Appendix Β (Tables Bl and B2); findings on nonneoplastic lesions are
 

tabulated in Appendix D (Tables Dl and D2).
 

Hepatocellular carcinoma was the most commonly observed neoplasm
 

and was diagnosed in 2/17 untreated control males, 1/19 vehicle control males, 8/49 low dose males, 8/47 high dose males, 1/20 vehicle
 

control females, and 1/47 low dose females. The hepatic neoplasms
 

occurring in the control mice were not different in appearance from
 

those noted in the 1,1-dichloroethane-treated mice· No liver tumors
 

35
 
were seen in the 19 untreated control female or 46 high dose female
 

mice·
 

Endometrial stromal polyps (benign endometrial neoplasms) were
 

observed in 4/46 high dose females but were not found in any of the
 

other groups·
 

The nonneoplastic lesions such as degeneration, inflammation,
 

and proliferation occurring in the treated and control animals were
 

similar and in relatively low incidences·
 

D. Statistical Analyses of Results
 

The results of the statistical analyses of tumor incidence in
 

mice are summarized in Tables 6 and 7· The analysis for every type
 

of tumor that was observed in more than 5 percent of any of the
 

1,1-dichloroethane-dosed groups of either sex is included.
 

Since the comparison of vehicle control to treated groups was
 

the comparison of choice, the untreated control groups were not used
 

in these analyses. To gain more information on spontaneous rates of
 

tumor incidence and to obtain a control group of increased sample
 

size, pooled vehicle control groups were used in addition to the
 

groups designated in the experimental design as the vehicle control
 

groups for 1,1-dichloroethane (referred to in this section as the
 

"matched" vehicle controls). The pooled vehicle control groups were
 

a combination of the vehicle controls used for the chronic bioassays
 

of 1,1-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, and
 

allyl chloride. These control mice were of the same strain, were
 

36
 
TABLE 6
 

ANALYSES OF THE INCIDENCE OF PRIMARY TUMORS AT
 

SPECIFIC SITES IN MALE MICE TREATED WITH 1,1-DICHLOROETHANES
 

TOPOGRAPHY: MORPHOLOGY 

Liver: Hepatocellular Carcinoma 

 Values 

Relative Risk (Pooled Vehicle 

Control)d 

Lower Limit 

Upper Limit 

Relative Risk (Matched Vehicle 

Control) d 

Lower Limit 

Upper Limit 

Weeks to First Observed Tumor 

Control) d 

Hematopoietic System:

Lymphoma*5 

 Malignant 

 Values 0 

Relative Risk (Pooled Vehicle 

Lower Limit 

Upper Limit 

Relative Risk (Matched Vehicle 

Control) d 

Lower Limit 

Upper Limit 

POOLED 

VEHICLE 

CONTROL 

6/79(0.08) 

N.S. 

56 

5/79(0.06) 

N.S. 

MATCHED 

VEHICLE 

CONTROL 

1/19(0.05) 

N.S. 

90 

2/19(0.11) 

N.S. 

LOW
 

DOSE
 

8/49(0.16) 

N.S. 

2.150 

0.697 

7.032 

3.102 

0.469 

134.437 

91 

4/49(0.08) 

N.S. 

1.290 

0.267 

5.674 

0.776 

0.125 

8.165 

HIGH
 

DOSE
 

8/47(0.17) 

N.S. 

2.241 

0.726 

7.312 

3.234 

0.491 

140.000 

2/48(0.04) 

N.S . 

0.658 

0.064 

3.824 

0.396 

0.031 

5.212 

Weeks to First Observed Tumor 66 90 77 89 

70 
TOPOGRAPHY :MORPHOLOGY
 

Lung: Alveolar/Bronchiolar
 

Adenoma^
 

 Values0
 

Relative Risk (Pooled Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Relative Risk (Matched Vehicle
 

Control)d
 

oo Lower Limit
 

Upper Limit
 

Weeks to First Observed Tumor
 

Kidney: Tubular-Cell Adenoma
 

 Values0
 

Departure from Linear Trend
 

Relative Risk (Pooled Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Relative Risk (Matched Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Weeks to First Observed Tumor
 

TABLE 6
 

(CONTINUED)
 

POOLED MATCHED
 

VEHICLE VEHICLE
 

CONTROL CONTROL
 

3/79(0.04) 0/19(0.00)
 

N.S. N.S.
 

56
 

0/78(0.00) 0/18(0.00)
 

N.S. N.S.
 

 = 0.006
 

.
 

LOW
 

DOSE
 

1/49(0.02)
 

N.S.
 

0.537
 

0.010
 

6,4A2
 

Infinite
 

0.022
 

Infinite
 

77
 

3/49(0.06)
 

N.S.
 

Infinite
 

0.950
 

Infinite
 

Infinite
 

0.232
 

Infinite
 

87
 

HIGH
 

DOSE
 

4/47(0.09)
 

N.S.
 

2.241
 

0.397
 

14.623
 

Infinite
 

0.390
 

Infinite
 

0/47(0.00)
 

N.S.
 

20 
TABLE 6
 

(CONCLUDED)
 

aTreated groups received time-weighted average doses of 1442 or 2885 mg/kg by gavage.
 

Number of tumor-bearing animals/number of animals examined at site (proportion).
 

The probability level for the Cochran-Armitage test is given beneath the incidence of tumors
 

in the corresponding control group when P<0.05 ; otherwise, not significant (N.S.) is indicated. The probability level for the Fisher exact test for the comparison of a treated
 

group with the pooled vehicle control group (*) or the matched vehicle control group (**)
 

is given beneath the incidence of tumors in that treated group when P<0.05; otherwise, not
 

significant (N.S.) is indicated. For both Cochran-Armitage and Fisher exact tests a negative
 

designation (N) indicates a lower incidence in the treated group(s) than in the control group.
 

The 95% confidence interval on the relative risk of the treated group to the control group.
 

The probability level of the test for departure from linear trend is given beneath the control
 

group when P<0.05.
 
TABLE 7
 

ANALYSES OF THE INCIDENCE OF PRIMARY TUMORS AT
 

SPECIFIC SITES IN FEMALE MICE TREATED WITH 1,1-DICHLOROETHANE*
 

TOPOGRAPHY: MORPHOLOGY
 

Liver: Hepatocellular Carcinoma
 

 Values0
 

Relative Risk (Pooled Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Relative Risk (Matched Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Weeks to First Observed Tumor
 

Hematopoietic System: Malignant
 

Lymphoma*5
 

 Values0
 

Relative Risk (Pooled Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Relative Risk (Matched Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Weeks to First Observed Tumor
 

POOLED
 

VEHICLE
 

CONTROL
 

1/79(0.01)
 

N.S.
 

90
 

9/79(0.11)
 

N.S.
 

56
 

MATCHED
 

VEHICLE
 

CONTROL
 

1/20(0.05)
 

N.S.
 

90
 

4/20(0.20)
 

N.S.
 

56
 

LOW
 

DOSE
 

1/47(0.02)
 

N.S.
 

1.681
 

0.022
 

129.159
 

0.426
 

0.006
 

32.720
 

91
 

3/47(0.06)
 

N.S.
 

0.560
 

0.101
 

2.105
 

0.319
 

0.052
 

1.743
 

91
 

HIGH
 

DOSE
 

0/46(0.00)
 

N.S.
 

0.000
 

0.000
 

31.981
 

0.000
 

0.000
 

8.111
 

7/47(0.15)
 

N.S.
 

1.307
 

0.439
 

3.653
 

0.745
 

0.220
 

3.175
 

65 
TOPOGRAPHY -.MORPHOLOGY
 

Lung: Alveolar/Bronchiolar
 

Adenoma^
 

 Values0
 

Relative Risk (Pooled Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Relative Risk (Matched Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Weeks to First Observed Tumor
 

Uterus: Endometrial Stromal
 

Polypb
 

 Values0
 

Relative Risk (Pooled Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Relative Risk (Matched Vehicle
 

Control)d
 

Lower Limit
 

Upper Limit
 

Weeks to First Observed Tumor
 

TABLE 7
 

(CONTINUED)
 

POOLED
 

VEHICLE
 

CONTROL
 

3/79(0.04)
 

N.S.
 

90
 

0/79(0.00)
 

 - 0.005
 

MATCHED
 

VEHICLE
 

CONTROL
 

1/20(0.05)
 

N.S.
 

90
 

0/20(0.00)
 

 = 0.036
 

LOW
 

DOSE
 

2/47(0.04)
 

N.S.
 

1.121
 

0.095
 

9.380
 

0.851
 

0.048
 

49.165
 

91
 

0/47(0.00)
 

N.S.
 

HIGH
 

DOSE
 

0/47(0.00)
 

N.S.
 

0.000
 

0.000
 

2.796
 

0.000
 

0.000
 

7.942
 

4/46(0.09)
 

 = 0.017*
 

Infinite
 

1.578
 

Infinite
 

Infinite
 

0.420
 

Infinite
 

91
 
TABLE 7
 

(CONCLUDED)
 

a

Treated groups received time-weighted average doses of 1665 or 3331 mg/kg by gavage.
 

Number of tumor-bearing animals/number of animals examined at site (proportion).
 

C

The probability level for the Cochran-Armitage test is given beneath the incidence of tumors
 

in the corresponding control group when Ρ< ο.05· otherwise, not significant (N.S.) is indicated. The probability level for the Fisher exact test for the comparison of a treated
 

group with the pooled vehicle control group (*) or the matched vehicle control group (**)
 

is given beneath the incidence of tumors in that treated group when P<0.05 ; otherwise, not
 

significant (N.S.) is indicated. For both Cochran-Armitage and Fisher exact tests a negative
 

designation (N) indicates a lower incidence in the treated group(s) than in the control group.
 

The 95% confidence interval on the relative risk of the treated group to the control group.
 

The probability level of the test for departure from linear trend is given beneath the control
 

group when P< 0.05.
 
tested by the same laboratory no more than 6 months apart, and were
 

diagnosed by the same pathologist·
 

In female mice, the Cochran-Armitage tests indicated a positive
 

association between dosage and the incidence of endometrial stromal
 

polyps of the uterus for both the matched vehicle controls (P =
 

0.036), and the pooled vehicle controls (P = 0.005). The Fisher
 

exact test showed a significantly higher incidence of these tumors in
 

the high dose mice (P = 0.017) than in the pooled vehicle controls.
 

In historical data collected by Hazleton Laboratories for the NCI
 

Bioassay Program, none of the 180 female vehicle control B6C3F1 mice
 

had an endometrial stromal polyp. Assuming a probability of spontaneous incidence of 1/200, the probability of observing 4 or more such
 

tumors out of 46 females (as' in the high dose group) was Ρ = 0.005, a
 

significant result. These statistical results indicated an association between 1,1-dichloroethane treatment and endometrial stromal
 

polyps of the uterus. No other sites exhibited a significant incidence of tumors in female mice.
 

In male mice, neither the Cochran-Armitage tests for positive
 

dose-related trend nor any of the Fisher exact tests for tumors of
 

any site were significant.
 

Because the unusually high early death rate in the high dose
 

males resulted in many of the mice dying before being at risk from
 

late-developing tumors, the standard statistical analysis was repeated
 

using only the data for male mice that survived at least 52 weeks.
 

43
 
As shown in Table 8, the incidence of hepatocellular carcinoma in
 

male mice that survived at least 52 weeks was 1/19 (5 percent), 6/72
 

(8 percent), 8/48 (17 percent) and 8/32 (25 percent) for the matched
 

vehicle control, pooled vehicle control, low dose, and high dose
 

groups, respectively· Based upon these data, the Cochran-Armitage
 

test indicated a significant (P = 0.016) positive association between
 

dosage and tumor incidence when comparing to the pooled vehicle control. The Fisher exact test comparing the high dose to the pooled
 

vehicle control had a probability level of Ρ = 0.027, a marginal
 

result which was not significant under the Bonferroni criterion.
 

To provide additional insight into the possible carcinogenicity
 

of this compound, 95 percent confidence intervals on the relative risk
 

have been estimated and entered in the tables based upon the observed
 

tumor incidence rates. In many of the intervals shown in Tables 6,
 

7, and 8, the value one is included; this indicates the absence of
 

statistically significant results. It should also be noted that many
 

of the confidence intervals have an upper limit greater than one,
 

indicating the theoretical possibility of tumor induction in mice by
 

1,1-dichloroethane that could not be established under the conditions
 

of this test.
 

44
 
TABLE 8 

ANALYSES OF THE INCIDENCE OF HEPATOCELLULAR CARCINOMA IN MALE MICE 

LIVING OVER 52 WEEKS TREATED WITH l,l-DICHLOROETHANEa 

TOPOGRAPHY: MORPHOLOGY 

POOLED 

VEHICLE 

CONTROL 

MATCHED 

VEHICLE 

CONTROL 

LOW 

DOSE 

HIGH 

DOSE 

Liver: Hepatocellular Carcinoma 

 Values0 

6/72(0.08) 

 = 0.016 

1/19(0.05) 

N.S. 

8/48(0.17) 

N.S . 

8/32(0.25) 

 = 0.027* 

Relative Risk (Pooled , 

Vehicle Control) 

Lower Limit 

Upper Limit 

2.000 

0.648 

6.526 

3.000 

0.987 

9.453 

Ln Relative Risk (Matched 

Vehicle Control) 

Lower Limit 

Upper Limit 

3.167 

0.480 

137.162 

4.750 

0.727 

202.296 

Weeks to First Observed Tumor 56 90 91 70 

Treated groups received time-weighted average doses of 1442 or 2885 mg/kg by gavage. 

Number of tumor-bearing animals/number of animals examined at sit e (proportion). 

The probability level for the Cochran-Armitage test is given beneath the incidence of tumors in 

the corresponding control group when Ρ < 0.05; otherwise, not significant (N.S.) is indicated. 

The probability level for the Fisher exact test for the comparison of a treated group with the 

pooled vehicle control group (*) or the matched vehicle control group (**) is given beneath the 

incidence of tumors in that treated group when Ρ < 0.05; otherwise, not significant (N.S.) is 

indicated. For both Cochran-Armitage and Fisher exact tests a negative designation (N) indicates 

a lower incidence in the treated group(s) than in the control group. 

j?he 95% confidence interval on the relative risk of the treated group to the control group. 
V. DISCUSSION
 

High mortality rates of rats and mice during the course of this
 

study complicate interpretation of the results of this bioassay. The
 

final survivorship in the untreated control, vehicle control, low
 

dose, and high dose groups was, respectively, 30, 5, 4, and 8 percent
 

in the male rats; 40, 20, 16, and 18 percent in the female rats; 35,
 

55, 62, and 32 percent in the male mice; and 80, 80, 80, and 50 percent in the female mice· The high early mortality in rats appeared
 

to be related to a high incidence of pneumonia· Lesions of pneumonia
 

were observed during the histopathologic examination in approximately
 

80 percent of the rats used for this bioassay· Incidence of pneumonia
 

was similar in vehicle controls, untreated controls, high dose, and
 

low dose rats of both sexes· Animals dying early may not have been
 

at risk from types of tumors that characteristically appear late·
 

When statistical analyses based exclusively on animals surviving at
 

least 52 weeks were performed, the reduction in sample size increased
 

the probability that a statistical test would fail to detect a real
 

difference in tumor incidence·
 

Despite the fact that large numbers of rats of both sexes did
 

not survive long enough to be at risk from late-developing tumors,
 

there were suggestions of carcinogenicity to rats indicated by the
 

results of this bioassay· There was a significant positive relationship between dosage and the incidence of mammary adenocarcinomas in
 

female rats when compared to matched vehicle controls but not when
 

46
 
compared to pooled vehicle controls. Fisher exact tests did not,
 

however, indicate that the incidence in either dosed group was significantly greater than in the matched or pooled vehicle control
 

groups· Among female rats, a significant positive relationship
 

between dosage and the incidence of hemangiosarcomas resulted when
 

either the matched or pooled vehicle control groups was used, but
 

none of the Fisher exact tests indicated statistical significance.
 

A statistically significant incidence of endometrial stromal
 

polyps (a benign neoplasm) occurred in female mice, the only sex and
 

species in which at least half of the high dose group survived for
 

the duration of the chronic bioassay. A statistical analysis based
 

on data for mice surviving at least 52 weeks indicated a significant
 

positive relationship between dosage and the incidence of hepatocellular carcinoma in male mice compared to pooled vehicle controls;
 

this result was not, however, supported by Fisher exact tests using
 

the Bonferroni criterion.
 

There were dose-related increases in mammary adenocarcinomas and
 

in hemangiosarcomas among female rats, and there was a statistically
 

significant increase in the incidence of endometrial stromal polyps
 

among dosed female mice as compared to.controls. These findings are
 

indicative of the possible carcinogenic potential of the test compound·
 

However, it must be recognized that under the conditions of this
 

bioassay there was no conclusive evidence for the carcinogenicity of
 

1,1-dichloroethane in Osborne-Mendel rats or B6C3F1 mice.
 

47
 
VI. BIBLIOGRAPHY
 

Armitage, P., Statistical Methods in Medical Research, Chapter 14.
 

J. Wiley & Sons, New York, 1971.
 

Berenblum, I., editor, Carcinogenicity Testing. International Union
 

Against Cancer, Technical Report Series, Vol. 2. International
 

Union Against Cancer, Geneva, 1969.
 

Chemical Abstracts Service, The Chemical Abstracts Service (CAS)
 

Ninth Collective Index, Volumes 76-85, 1972-1976.

Chemical Society, Washington, D.C., 1977. 

 American 

Cox, D. R., Analysis of Binary Data, Chapters 4 and 5.

Co., Ltd., London, 1970. 

 Methuen and 

Cox, D. R., "Regression Models and Life-Tables·" Journal of the Royal
 

Statistical Society, Series "B" 34: 187-220, 1972.
 

Gart, J. J·, "The Comparison of Proportions: A Review of Significance
 

Tests, Confidence Limits, and Adjustments for Stratification·11
 

International Statistical Institute Review 39:148-169, 1971.
 

Hardie, D. W. F. , "Chlorocarbons and Chlorohydrocarbons·11 Kirk-Othmer
 

Encyclopedia of Chemical Technology, 2nd edition, Volume 5.
 

Interscience, New York, 1964.
 

International Technical Information Institute, Toxic and Hazardous
 

Industrial Chemicals Safety Manual. ITII, Tokyo, Japan, 1975.
 

Kaplan, E. L., and P. Meier, "Nonparametric Estimation from Incomplete
 

Observations·" Journal of the American Statistical Association
 

52:457-481, 1958.
 

Linhart, M. S., J. A. Cooper, R. L. Martin, N. P. Page, and J. A.
 

Peters, "Carcinogenesis Bioassay Data System." Computers
 

and Biomedical Research 7:230-248, 1974.
 

Miller, R. G., Simultaneous Statistical Inference. McGraw-Hill Book
 

Co., New York, 1966.
 

Mullin, C. R., "Photochemical Technology." Kirk-Othmer Encyclopedia
 

of Chemical Technology, 2nd edition, Vol. 15. Interscience, New
 

York, 1964.
 

48
 
Reuber, Μ. D. , and Ε· L· Glover, "Cirrhosis and Carcinoma of the Liver
 

in Male Rats Given Subcutaneous Carbon Tetrachloride·11 Journal
 

of the National Cancer Institute 44:419-423, 1970.
 

Saffiotti, U., R. Montesano, A. R· Sellakumar, F. Cefis, and D· G.
 

Kaufman, "Respiratory Tract Carcinogenesis in Hamsters Induced
 

by Different Numbers of Administration of Benzo (a) Pyrene and
 

Ferric Oxide." Cancer Research 32:1073-1079, 1972.
 

Tarone, R. E., "Tests for Trend in Life-Table Analysis." Biometrika
 

62:679-682, 1975.
 

49
 

APPENDIX A
 

SUMMARY OF THE INCIDENCE OF NEOPLASMS
 

IN RATS TREATED WITH 1,1-DICHLOROETHANE
 

TABLE Al
 

SUMMARY OF THE INCIDENCE OF NEOPLASMS IN MALE RATS TREATED WITH 1,1-DICHLOROETHANE
 

CONTROL (UNTR) CONTROL (VEH) LOW DOSE HIGH DOSE 

01-131 Μ 01 -08 1 Μ 01-082M 01-083M 

ANIMALS INITIALLY IN STUDY 20 20 50 50 

ANIMALS NFCROPSIED 20 20 50 50 

ANIMALS EXAMINED HISTOPATHOLOGICALLY** 20 20 50 50 

INTEGUMENTARY SYSTEM 

•SUBCUT TISSUE (20) (20) (50) (50) 

FIBRCMA 1 (2%) 

LIPOMA 1 (2%) 

RESPIRATOPY SYSTEM 

#LUNG (20) (2 0) (50) (50) 

ADENOCARCINOMA, NOS, METASTATIC 1 (2%) 

FIBROSARCOMA, METASTATIC 1 (2%) 

HEMATOPOIETIC SYSTEM 

•MULTIPLE ORGANS (20) (2 0) (50) (50) 

MALIG. LYMPHOMA, HISTIOCYTIC TYPE 1 (5%) 

iSPLEEN (20) (20) (49) (49) HEMANGIOSARCOMA 1 (2%) 

•CERVICAL LYMPH NODE (20) (20) (49) (50) 

MALIG.LYMPHOMA, HISTIOCYTIC TYPE 1 (5%) 

CIRCULATORY SYSTEM 

NONE 

DIGESTIVE SYSTEM 

#LIVER (20) (2 0) (50) (50) ADENOCARCINOMA, NOS, METASTATIC 1 (2%) 

HEPATOCELLULAR CARCINOMA 1 15%) 

# NUMBER OF ANIMALS WITH TISSUE EXAMINED MICROSCOPICALLY 

* NUMBER OF ANIMALS NECROPSIED 

**EXCLUDES PARTIALLY AUTOLYZED ANIMALS 

A-3
 
TABLE A l (CONTINUED) 

CONTROL (UNTR) CONTROL (VEH) LOW DOSE HIGH DOSE 

01-131M 01-081M 01-082M 01-083M 

•CECUM (20) (20) (50) (48)

 

ADENOCARCINOMA, NOS, METASTATIC 1 (2%)

 

URINARY SYSTEM 

•KIDNEY (20) (2 0) (50) (50)

 

LIPCSARCOMA 1 (5X)

 MIXED TUMOR, MALIGNANT 1 (2%)

 HAMARTOMA + 1 (5%) 1 (5X)

 

•FIGHT KIDNEY (20) (20) (50) (50)

 

MIXED TUMOR, MALIGNANT 1 (5%)

 

ENDCCSINE SYSTEM 

•PITUITARY (19 ) (20) (44) (46) 

CHROMOPHOBE ADENOMA 1 (5*) 2 (4%) 

•ADRENAL (20) (20) (50) (50) 

PHECCHROMOCYTOMA 2 (4%) MIXED TUMOR, METASTATIC 1 (5%) 

•THYROID (20) (19 ) (48) (48)

 

FOLLICULAR-CELL ADENOMA 1 (2X)

 

FOLLICULAR-CELL CARCINOMA 1 (5%) 1 (5%)

 C-CELL ADENOMA 1 (2X)

 

REPRODUCTIVE SYSTEM 

•MAMMARY GLAND (20) (2 0) (50) (50)

 

ADENOCARCINOMA, NOS 1 (5X)

 

•PROSTATE (17) (17) (33) (32)

 

ADENOCARCINOMA, NOS 1 (3X)

 

•TESTI S (20) (19) (50) (50)

 

INTERSTITIAL-CELL TUMOR 1 (5X)

 

NEFVOUS SYSTEM 

•BRAIN (20) (2 0) (50) (50) 

ASTPCCYTOMA 1 J5X) 112%) 

• NUMBER OF ANIMALS WITH TISSUE EXAMINED MICROSCOPICALLY 

* NUMBEP OF ANIMALS NECROPSIED 

+ THIS IS CONSIDERED TO BE A BENIGN FORM OF THE MALIGNANT MIXED TUMOR OF THE KIDNEY AND CONSISTS OF PROLIFERATIVE
 

LIPOCYTES, TUBULAR STRUCTURES, FIBROBLASTS, AND VASCULAR SPACES IN VARYING PROPORTIONS.
 

A-4
 
TABLE Al (CONTINUED) 

CONTROL (UNTR) CONTROL (VSH) 

01-131M 01-081M 

SPECIAL SENSE ORGANS 

NONE 

MUSCULOSKELETAL SYSTEM 

NONE 

BODY CAVITIES 

•ABDOMINAL	 CAVITY (20) (20)
 ADENOCARCINOMA, NO S, METASTATIC
 

FIBROSARCOMA
 

ALL OTHER SYSTEMS 

NO ΝE 

ANIMAI DISPOSITIO N SUMMARY 

ANIMALS INITIALLY I N STUDY 20 20
 

NATURAL DEATHS 14 19
 

MORIBUND SACRIFIC E
 

SCHEDULED SACRIFIC E
 

ACCIDENTALLY KILLED
 

TERMINAL SACRIFIC E 6 1
 ANIMAL MISSING
 

@ INCLUDES AUTOLYZED ANIMALS 

# NUMBER OF ANIMALS WITH TISSUE EXAMINED MICPOSCOPICALLY 

* NUMBER OF ANIMALS NECROPSISD 

LOW DOSE HIGH DOSE 

01-0Θ2Μ 01-Π83Μ 

(50) (50) 

1 (2%)
 

1 (2%)
 

50 50
 

4 7 4 5
 

1 1
 

2 4 

A-5
 
TABLE) Al (CONCLUDED) 

CONTROL (UNTR) CONTROL (VEH) LOW DOSE HIGH DOSE 

01-131 M 01-081M 01-082M 01-083M 

TUMOR SUMMARY 

TOTAL ANIMALS WITH PRIMARY TUMORS* 4 6 6

 

TOTAL PRIMARY TUMORS 4 9 6 7

 

TOTAL ANIMALS WITH BENIGN TUMORS 1 3 3 4

 

TOTAL BENIGN TUMORS 1 3 3 5

 

TOTAL ANIMALS WITH MALIGNANT TUMORS 3 5 3 2

 

TOTAL MALIGNANT TUMOPS 3 6 3 2

 

TOTAL ANIMALS WITH SECONDARY TUMORS# 1 2

 

TOTAL SECONDARY TUMORS 1 5

 

TOTAL ANIMALS WITH TUMORS UNCERTAINBENIGN OR MALIGNANT

 

TOTAL UNCERTAIN TUMORS 

TOTAL ANIMALS WITH TUMORS UNCEPTAINPRIMARY OR METASTATIC

 

TOTAL UNCERTAIN TUMORS 

* PRIMARY TUMORS: ALL TUMORS EXCEPT SECONDARY TUMORS 

# SECONDARY TUMORS: METASTATIC TUMORS OR TUMORS INVASIVE INTO AN ADJACENT ORGAN 

A-6 
TABLE A2
 

SUMMARY OF THE INCIDENCE OF NEOPLASMS IN FEMALE RATS TREATED WITH 1,1-DICHLOROETHANE
 

CONTROL (UNTR) CONTROL (VEH) 

01-131F 01-081F 

ANIMALS INITIALLY IN STUDY 20 20 

ANIMALS NECROPSIED 20 19 

ANIMALS EXAMINED HISTOPATHOLOGICALLY ** 20 19 

INTEGUMENTARY SYSTEM 

•SKIN	 (20) (19 ) 

SQUAMOUS CELL PAPILLOMA 

•SUBCUT	 TISSUE (20) (19 ) 

FIBROMA 2 (10%) 

HEMANGIOSARCOMA 

RESPIRATORY SYSTEM 

#LUNG (20) (19 ) 

ADENOCARCINOMA, NOS, METASTATIC 

HEM ANGIOSARCOMA 

HEMATOPOIETIC SYSTEM 

•MULTIPLE	 ORGANS (20) (19 ) 

MALIG. LYMPHOMA, HISTIOCYTIC TYPE 1 (5%) 

#SPLEEN (20) (19) 

HEMANGIOSARCOMA 

CIRCULATORY SYSTEM 

#ENDCCARDIUM (20) (19) 

SARCOMA, NOS 1 (5%) 

DIGESTIVE SYSTEM 

#LIVER (20) (19) 

NEOPLASTIC NODULE 1 (5%) 

# NUMBER OF ANIMALS WITH TISSUE EXAMINED MICROSCOPICALLY 

* NUMBER OF ANIMALS NECROPSIED 

**EXCLUDES PARTIALLY AUTOLYZED ANIMALS 

LOW DOSE 

01-084F 

50
 

50
 

50
 

(50) 

(50) 

1 (2%) 

(50) 

(50) 

(50) 

(49) 

(50) 

HIGH DOSE 

01-085F 

50
 

5Π
 

50
 

(50) 

1 (2%) 

(50) 

2 (4%) 

(50) 

1 (2%) 

1 (2%) 

(50) 

(49) 

1 (2%) 

(50) 

(50) 

1 12X1 

A-7
 
TABLE A2 (CONTINUED) 

CONTROL (UNTR) 

01-131F 

CONTROL (VEH) 

01-081F 

LOW DOSE 

01-084F 

HIGH DOSE 

01-085F 

• PANCREAS 

ADENOCARCINOMA,

•SMALL INTESTINE 

ADENOCARCINOMA,

 NOS,

 NOS 

 METASTATIC 

(20) 

(20) 

(19) 

(19) 

(50) 

(49) 

(50) 

1 (2%) 

(47) 

1 (2%) 

URINARY SYSTEM 

•KIDNEY 

NIXfD TUMOR, MALIGNANT 

(20) (19) (50) 

1 (2%) 

(50) 

ENDOCRINE SYSTEM 

•PITUITARY 

CHROMOPHOBE ADENOMA 

(20) 

2 (10%) 

(19) 

2 (11%) 

(48) 

6 (13%) 

(48) 

4 (8%) 

•ADRENAL 

LIPOSARCOMA 

MIXED TUMOR, METASTATIC 

•THYROID 

C-CELL CARCINOMA 

(20) 

1

(20) 

 (5%) 

(10 ) 

(18 ) 

(50) 

1

(46) 

1

 (2%) 

 (2%) 

(49) 

(43) 

• PANCREATIC ISLET S 

ISLET-CELL ADENOMA 

(20) (19 ) (50) (50) 

2 (4%) 

REPRODUCTIVE SYSTEM 

* Μ Μ MARY GLAND 

ADENCMA, NOS 

ADENOCARCINOMA,

FIBROADENOMA 

 NOS 

(20) 

1

6

 (5%) 

 (30%) 

(19 ) 

2 (11%) 

(50) 

1

6

 (2%) 

 (12%) 

(50) 

1

5

6

 (2%) 

 (10%) 

 (12%) 

•OVARY 

CYSTADENCMA,

LIPOMA 

 NOS 

(20) (19 ) (50) 

1 (2%) 

(49) 

1 (2%) 

NERVOUS SYSTEM 

NONE 

SPECIAL SENSE ORGANS 

NONE 

• NUMBER

* NUMBER

 OF

 OF

 ANIMALS

 ANIMALS

 WITH TISSUE

 NECROPSIED 

 EXAMINED MICROSCOPICALLY 
TABLE A2 (CONCLUDED) 

CONTROL (UNTR) 

01-131 F 

CONTROL (VE Η) 

01-081F 

LOW DOSE 

01-084F 

HIGH DOSE 

01-085F 

MUSCULOSKELETAL SYSTEM 

NONE 

BODY CAVITIES 

NONE 

ALL OTHER SYSTEMS 

NONE 

ANIMAL DISPOSITIO N SUMMARY 

ANIMALS INITIALLY I N STUDY 

NATURAL DEATHS 

MORIBUND SACRIFICE 

SCHEDULED SACRIFICE 

ACCIDENTALLY KILLED 

TERMINAL SACRIFICE 

ANIMAL MISSING 

20 

12 

β 

20 

15 

1 

4 

50 

40 

2 

β 

50 

39 

2 

9 

9 INCLUDES AUTOLYZED ANIMALS 

TUMOR SUMMARY 

TOTAL ANIMALS WITH PRIMARY

TOTAL PRIMARY TUMORS 

 TUMORS* 11 

15 

4 

4 

12 

1 7 

1 8 

2 6 

TOTAL ANIMALS WITH BENIGN TUMORS 

TOTAL BENIGN TUMORS 

9 

10 

4 

4 

11 

1 4 

10 

15 

TOTAL ANIMALS WITH MALIGNANT TUMORS 

TCTAL MALIGNANT TUMORS 

3 

4 

3 

3 

10 

10 

TOTAL ANIMALS WITH SECONDARY TUMORS* 

TOTAL SECONDARY TUMORS 

1 

1 

2 

2 

TOTAL ANIMALS WITH TUMORS UNCERTAINBENIGN OP MALIGNANT 

TOTAL UNCERTAIN TUMORS 

1 

1 

1 

1 

TOTAL ANIMALS WITH TUMORS UNCEPTAINPRIMAEY CR METASTATIC 

TOTAL UNCERTAIN TUMORS 

* PRIMARY TUMORS: ALL TUMORS EXCEPT SECONDARY TUMORS 

# SECONDARY TUMORS: METASTATIC TUMORS OR TUMORS INVASIVE INTO AN ADJACENT ORGAN 

A-9
 

APPENDIX B
 

SUMMARY OF THE INCIDENCE OF NEOPLASMS
 

IN MICE TREATED WITH 1,1-DICHLOROETHANE
 

TABLE B1
 

SUMMARY OF THE INCIDENCE OF NEOPLASMS IN MALE MICE TREATED WITH 1,1-DICHLOROETHANE
 

CONTROL (UNTR) 

02-Η0Θ1 

CONTROL (VEH) 

02-M071 

LOW DOSE 

02-M082 

HIGH DOSE 

02-H08 3 

ANIMALS INITIALLY IN STODY 

ANIMAIS NECROFSIED 

ANIMALS EXAMINED HISTOPATHOLOGICALLY** 

20 

18 

17 

20 

19 

19 

50 

49 

49 

50 

48 

47 

INTEGUMENTARY SYSTEM 

•SKIN 

SQUAMOUS CELL

FIBROSARCOMA 

 CARCINOMA (18) 

1 (6%) 

(19 ) (49) 0*8) 

1 (2X) 

•SUBCUT TISSU E 

FIBROSARCOMA 

(18) (19 ) (49) 

3 (6%) 

(48) 

RESPIRATORY SYSTEM 

#LUNG 

ALVEOLAP/BRCNCHIOLAR ADENOMA 

(17) (19 ) (49) 

1 (2%) 

(47) 

4 (9%) 

HEMATOPOIETIC SYSTEM 

•MULTIPLE ORGANS 

HALIG. LYMPHOMA,

ΜALIG.LYMPHOMA,

 LYMPHOCYTIC

 HISTIOCYTIC

 TYPE 

 TYPE 

(18 ) (19 ) 

1 (5%) 

(49) 

2 (4%) 

(48) 

1 (2%) 

•SUBCUT TISSUE/BACK 

MALIG. LYMPHOMA, HISTIOCYTIC TYPE 

(18 ) (19) (49) 

1 (2%) 

(48) 

•SUBCUT TISSUE/GROIN 

HALIG.LYMPHOMA, LYMPHOCYTIC TYPE 

(18 ) (19) (49) 

1 (2%) 

(48) 

«SPLEEN 

HEMANGIOSARCOMA 

MALIG.LYMPHOMA, HISTIOCYTIC TYPE 

(17 ) (18) (49) 

1 (2%) 

(47) 

1 (2%) 

«RENAL LYMPH NODE 

SQUAMOUS CELL CARCINOMA, METASTA 

(17 ) (19) 

1 (5%) 

(49 ) (47) 

«KIDNEY 

MALIG.LYMPHOMA­ LYMPHOCYTIC TYPE 

(17 ) (18) 

1 (6%) 

(49) (47) 

« NUMBER OF ANIMALS WITH TISSUE EXAMINED

• NUMBER OF ANIMALS NECROPSIED 

••EXCLUDES PARTIALLY AUTOLYZED ANIMALS 

 MICROSCOPICALLY 

B-3
 
TABLE B1 (CONTINUED) 

CIRCULATCPY SYSTEM 

NONE 

DIGESTIVE SYSTEM 

•SALIVARY GLAND 

SQUAMOUS CELL CARCINOMA 

•LIVER 

HEPATOCELLULAR CARCINOMA 

•STOMACH 

SQUAMOUS CELL CARCINOMA 

URINARY SYSTEM 

•KIDNEY 

TUBULAR-CELL ADENOMA 

ENDOCRINE SYSTEM 

•THYROID 

FCLIICULAR-CELL ADENOMA 

REPRODUCTIVE SYSTEM 

•TESTIS 

INTERSTITIAL-CELL TUMOR 

NERVOUS SYSTEM 

NONE 

SPECIAL SENSE ORGANS 

NONE 

MUSCULOSKELETAL SYSTEM 

NONE 

• NUMBER OF ANIMALS WITH TISSUE 

* NUMBER OF ANIMALS NECROPSIED 

LOW DOSE 

02-M08 2 

(49) 

(49) 

8 (16%) 

(49) 

1 (2%) 

(49) 

3 (6%) 

(49) 

(49) 

1 (2%) 

HIGH DOSE 

02-H083 

(47) 

1 (2%) 

(47) 

8 (17%) 

(47) 

(47) 

1 (2%) 

(47) 

CONTROL (UNTR) 

02-M08 1 

(17) 

(17) 

2 (12%) 

(17) 

(17) 

(17) 

(17) 

EXAMINED MICROSCOPICALLY 

CONTROL (VEH) 

02-M07 1 

(19) 

(19) 

1 <5X) 

(19) 

1 (5%) 

(18 ) 

(17) 

(19) 

B-4 
TABLE Bl (CONCLUDED) 

CONTROL (UNTR) 

02-M081 

CONTROL (VEH) 

02-M071 

LOW DOSE 

02-M08 2 

HIGH DOSE 

02-M083 

BODY CAVITIES 

NONE 

ALL CTHER SYSTEMS 

NONE 

ANIMAL DISPOSITION SUMMARY 

ANIMALS INITIALLY I N STUDY 

NATURAL DEATHS 

MORIBUND SACRIFICE 

SCHEDULED SACRIFICE 

ACCIDENTALLY KILLED 

TERMINAL SACRIFICE 

ANIMAL MISSING 

20 

12 

1 

7 

2 0 

9 

11 

50 

19 

31 

50 

3 2 

1 

1 

16 

 INCLUDES AUTOLYZED ANIMALS 

TUMCR SUGARY 

TOTAL ANIMALS WITH PRIMARY

TOTAL PRIMARY TUMORS 

 TUMORS* 2 

3 

α 

α 

19 

2 2 

1 5 

1 7 

TOTAL ANIMALS WITH BENIGN TUMORS 

TOTAL BENIGN TUMORS 

5 

5 

5 

S 

TOTAL ANIMALS WITH MALIGNANT TUMORS 

TCTAL MALIGNANT TUMORS 

2 

3 

α 

α 

16 

17 

11 

1 2 

TOTAL ANIMALS WITH SECONDARY

TOTAL SECONDARY TUMORS 

 TUMORS* 1 

1 

TOTAL ANIMALS WITH TUMORS

BENIGN OR MALIGNANT 

TOTAL UNCERTAIN TUMORS 

 UNCERTAINTOTAL ANIMALS WITH TUMORS

PRIMARY CR METASTATIC 

TOTAL UNCERTAIN TUMORS 

 UNCERTAIN­

* PRIMARY TUMORS: ALL TUMORS EXCEPT SECONDARY TUMORS 

# SECONDARY TUMORS: METASTATIC TUMORS OR TUMORS INVASIVE INTO AN ADJACENT ORGAN 

B-5
 
TABLE B2

 

SUMMARY OF THE INCIDENCE OF NEOPLASMS IN FEMALE MICE TREATED WITH 1,1-DICHLOROETHANE 

CONTROL (UNTR) CONTROL (VEH) LOW DOSE HIGH DOSE 

02-F081 02-F071 02-F084 02-F085 

ANIMALS INITIALLY IN STUDY 20 20 50 50 

ANIMALS NECROPSISD 19 20 47 4 7 

ANIMALS EXAMINED HISTOPATHOLOGIC LLY ** 19 20 47 47 

INTEGUMENTARY SYSTEM 

NONE 

RESPIRATORY SYSTEM 

• LUNG (19) (20) (47) (47) ALVECLAR/BRCNCHIOLAR ADENOMA 1 (5%) 1 (5%) 2 (4%) 

HEMATOPOIETIC SYSTEM 

•MULTIPLE ORGANS (19) (20) (47) (47) MALIG. LYMPHOMA, LYMPHOCYTIC TYPE 2 (11%) 2 (10%) 1 (2X) MALIG.LYMPHOMA, HISTIOCYTIC TYPE 1 (5%) 2 (10%) 4 (9%) 

tSPLEEN (19) (20) (47) (46) 

MALIG. LYMPHOMA, HISTIOCYTIC TYPE 1 (2%) 

#CERVICAL LYMPH NODE (19) (20) (47) (47) 

MALIG .LYMPHOMA, HISTIOCYTIC TYPE 2 (4%) 

#LIVER (19) (20) (47) (46) 

MALIG· LYMPHOMA, HISTIOCYTIC TYPE 1 (2%) 1 (2%) 

CIRCULATORY SYSTEM 

NONE 

DIGESTIVE SYSTEM 

#LIVER (19) (20) (47) (46) 

HEPATOCELLULAR CARCINOMA 1 (5%) 1 (2%) 

# NUMBER OF ANIMALS WITH TISSUE EXAMINED MICROSCOPICALLY 

• NUMBER OF ANIMALS NECROPSIED 

**EXCLUDES PARTIALLY AUTOLYZED ANIMALS 

B-6 
TABLE B2 (CONTINUED) 

CONTROL (UNTR) CONTROLS EH) LOW DOSE HIGH DOSE 

02-F081 02-F071 02-F084 02-F085 

•STOMACH (19) (20) (47) (46) 

SQUAMOUS CELL CARCINOMA 1 (5X) 

URINARY SYSTEM 

NONE 

ENDOCRINE SYSTEM 

NONE 

REPRODUCTIVE SYSTEM 

•VAGINA (19) (20) (47) (47) 

PAPILLOMA, NOS 1 (2%) 

#UTERUS (19) (20) (47) (46) 

ENDOMETRIAL STROMAL POLYP 4 (9%) 

#OVARY (19) (20) (47) (47) 

CYSTADENCMA, NOS 1 (2%) 

NERVOUS SYSTEM 

NONE 

SPECIAL SENSE ORGANS 

NONE 

MUSCULOSKELETAL SYSTEM 

NONE 

BODY CAVITIES 

NONE 

ALL OTHE* SYSTEMS 

NONE 

# NUMBER OF ANIMALS WITH TISSUE EXAMINED MICROSCOPICALLY 

* NUMBER OF ANIMALS NECSOPSIED 

B-7 
TABLE B2 (CONCLUDED) 

(

:ONTFOL (UNTR) 

0 2-F081 

CONTROL (VEH) 

02-F071 

LOW DOSE 

02-F084 

HIGH DOSE 

02-F08 5 

ANIMAL DISPOSITION SUMMARY 

ANIFALS INITIALLY IN STUDY 

NATURAL DEATHd 

MORIBUND SACRIFICE 

SCHEDULED SACRIFICE 

ACCIDENTALLY KILLED 

TERMINAL SACRIFICE 

ANIPAL MISSING 

2 0 

3 

1 

16 

2 0 

4 

16 

50 

10 

40 

50 

25 

25 

d INCLUDES AUTOLYZED ANIMALS 

TUMOR SUMMARY 

TOTAL ANIMALS WITH PRIMARY TUMORS* 

TOTAL PRIMARY TUMORS 

TOTAL ANIMALS WITH BENIGN TUMORS 

TOTAL BENIGN TUMORS 

4 

n 

1 

1 

6 

7 

1 

1 

6 

7 

3 

3 

12 

12 

5 

5 

TOTAL ANIMALS WITH MALIGNANT TUMORS 

TOTAL MALIGNANT TUMORS 

3 

3 

5 

6 

4 

4 

7 

7 

TOTAL ANIMALS WITH SECONDARY

TOTAL SECONDARY TUMORS 

 TUMORSt 

TOTAL ANIMALS WITH TUMORS

BENIGN OR MALIGNANT 

TOTAL UNCERTAIN TUMORS 

 UNCERTAINTOTAL ANIMALS WITH TUMORS

PHIMAEY CR METASTATIC 

TOTAL UNCERTAIN TUMORS 

 UNCERTAIN­

* PRIMARY TUMORS: ALL TUMORS EXCEPT SECONDARY TUMORS 

# SECONDARY TUMORS: METASTATIC TUMORS OR TUMORS INVASIVE INTO AN ADJACENT ORGAN 

B-8 
APPENDIX C
 

SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC
 

LESIONS IN RATS TREATED WITH 1,1-DICHLOROETHANE
 

TABLE CI 

SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC LESIONS IN MALE RATS 

TREATED WITH 1,1-DICHLOROETHANE 

CONTROL (UNTR) CONTROL (VEH) LOW DOSE HIGH DOSE 

01-131 H 01-081M 01-082M 0T-083H 

ANIMALS INITIALLY IN STUDY 20 20 50 50 

ANIMALS SECROPSIED 20 20 50 50 ANIMALS EXAMINED HISTOPATHOLOGICALLY** 20 20 50 50 

INTEGUMENTARY SYSTEM 

*SKIN (20) (20) (50) (50) 

EPIDERMAL INCLUSION CYST 1 (5%) INFLAMMATION, NOS 1 (2%) 

*SUBCUT TISSUE (20) (20) (50) (50)

 ABSCESS, NOS 1 (5%) 1 (2X)

 

RESPIRATORY SYSTEM 

tTPACHEA (20) (20) (50) (50) INFLAMMATION, NOS 1 (5%) 1 (2%) 

«LUNG (20) (20) (50) (50) PNEUMONIA, CHRONIC MURINE 14 (70%) 19 (95*) 40 (80%) 42 (84%) CALCIUM DEPOSIT 1 (2%) 

HEMATOPOIETIC SYSTEM 

tSPLEEN (20) (20) (49) (49) 

HEMATOPOIESIS 1 (5*) 1 (5%) 3 (6%) 2 (4%) 

«CERVICAL LYMPH NODE (20) (20) (49) (50) 

INFLAMMATION, NOS 1 (2%) 

«TRACHEAL LYMPH NODE (20) (20) (49) (50) 

ANGIECTASIS 1 (5%)

 

«MESENTERIC L. NODE (20) (20) (49) (50) 

PERIARTERITIS 1 (2%) 

CIRCULATORY SYSTEM 

«MYOCARDIUM (20) (20) (50) (50)

 FIBROSIS 3 (15%)

 

# NUMBER OF ANIMALS WITH TISSUE EXAMINED MICROSCOPICALLY 

* NUMBER OF ANIMALS NECROPSIED 

**EXCLUDES PARTIALLY AUTOLYZED ANIMALS 
TABLE CI (CONTINUED)
 

CONTROL(UNTR) 

01-131 B 

CONTROL (VEH) 

01-081M 

LOW DOSE 

01-082M 

HIGH DO SB 

01-083M 

DEGENERATION, NOS 1 (2%) 

IENDOCARDIUM 

HYPERPLASIA, NOS 

(20) (20) 

1 (5%) 

(50) (50) 

• AORTA 

THROMBUS, ORGANIZED 

INFLAMMATION, NOS 

MEDIAL CALCIFICATION 

(20) 

2 (1O%) 

2 (10%) 

(20) (50) 

1 (2X) 

1 (2%) 

(50) 

1 (2X) 

•MESENTERIC ARTERY 

MEDIAL CALCIFICATION 

(20) (20) (50) 

1 (2%) 

(50) 

1 (2X) 

DIGESTIVE SYSTEM 

•LIVER 

INFLAMMATION, NOS 

GRANULOMA, NOS 

PELIOSIS HEPATIS 

METAMORPHOSIS FATTY 

ANGIECTASIS 

(20) 

2 (10%) 

1 (5%) 

1 (5%) 

1 (5%) 

(2 0) (50) 

3 (6X) 

(50) 

2 (U%) 

1 (2%) 

#LIVER/CENTRILOBULAR 

CEGENERATION, NOS 

(20) 

1 (5%) 

(20) (50) (50) 

•BILE DUCT 

HYPERPLASIA, NOS 

(20)

2 (10%) (20)1 (5%) 

(50) 

1 (2%) 

(50) 

1 (2%) 

«PANCREAS 

PERIARTERITIS 

(20) 

1 (5%) 

(20) 

1 (5%) 

(50) 

2 (4%) 

(50) 

5 (10%) 

•STCMACH 

CALCIUM DEPOSIT 

(20) 

2 (10%) 

(20) (50) 

1 (2%) 

(50) 

1 (2%) 

URINARY SYSTEM 

#KIDHEY 

PYELONEPHRITIS, NOS 

INFLAMMATION, CHRONIC 

CALCIUM DEPOSIT 

(20) 

13 (65%) 

1 (5%) 

(20) 

4 (20%) 

12 (60%) 

(50) 

14 (28%) 

(50) 

16 (32%) 

1 (2%) 

#LEFT KIDNEY 

INFLAMMATION, CHRONIC 

(20) 

1 (5%) 

(20) (50) (50) 

• URINARY BLADDER 

INFL.AHMATION^_]JOS _ 

(17) (20) (50) (<*7) 

1_12%L 

• NUMBER OF ANIMALS WITH TISSUE EXAMINED MICROSCOPICALLY 

* NUMBER OF ANIMALS NECROPSIED 

C-4 
TABLE CI (CONTINUED) 

CONTROL (UNTR) CONTROL (VEH)

01-131M 01-081M 

ENDOCRINE SYSTEM 

•PITUITARY	 ( 1 Q ) (20)
 

ANGIECTASIS 1 (5%)
 

#ADRENAL CORTEX (20) (20)
 

ANGIECTASIS 1 (5%)
 

«ADRENAL MEDULLA (20) (20)
 

CALCIUM DEPOSIT
 

•THYROID	 (2 0) (19)
 

FOLLICULAR CYST, NOS 1 (5%)
 

•PARATHYROID	 (20) (20)
 

HYPERPLASIA, NOS 4 (20%)
 

REPPODUCTIVE SYSTEM 

•PROSTATE	 (17) (17) 

INFLAMMATION, NOS 2 (12%) 

•TESTIS	 (20) (19) 

ATROPHY, NOS 5 (25*) 7 (37%) 

NERVOUS SYSTEM 

NONE 

SPECIAL SENSE OPGANS 

•EYE	 (20) (2 0)
 

SYNECHIA, ANTERIOR 1 (5%)
 

*EYE/CORNEA (20) (20)
 

VASCULARIZATION 1 (5%)
 

MUSCULOSKELETAL SYSTEM 

ΝONE 

• NUMBER OF ANIMALS WITH TISSUE EXAMINED MICROSCOPICALLY 

* NUMBER OF ANIMALS NECPOPSIED 

LOW DOSE 

01-082M 

(44) 

(50) 

2 (4%) 

(50) 

(48) 

(50) 

1 (2%) 

(33) 

4 (12%) 

(50) 

11 (22%) 

(50) 

(50) 

HIGH DOSE 01-083M 

(46) 

(50) 

1 (2%) 

(50) 

1 (2%) 

(48) 

(50) 

2 (4%) 

(32) 

1 (3%) 

(50) 

16 (32%) 

(50) 

(50) 

C-5
 
TABLE CI (CONCLUDED) 

CONTROL (UNT8) CONTROL (VE Η) LOW DOSE HIGH DOSE 

01-131M 01-081 M 01-082M 01-083H 

BODY CAVITIES 

• MESENTERY (20) (20) (50) (50) 

PERIARTERITIS 1 (5%) 1 (5%) 3 (6%) 

NECROSIS, FAT 1 (5%) 

ALL OTHER SYSTEMS 

NONE 

SPECIAL MORPHOLOGY SUMMARY 

NO LESION REPORTED 1 1 7 6 

# NUMBER OF ANIMALS WITH TISSUE EXAMINED MICROSCOPICALLY 

* NUMBER OF ANIMALS NECROPSIED 

C-6
 
TABLE C2

 

SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC LESIONS IN FEMALE RATS 

TREATED WITH 1,1-DICHLOROETHANE

 

CONTROL (UNTR) 

ANIMALS INITIALLY IN STUDY 

ANIMALS NECROPSIED 

ANIMALS EXAMINED HISTOPATHOLOGICALLY **

INTEGUMENTARY SYSTEM 

*SUBCUT TISSUE 

ABSCESS, NOS

 

RESPIRATOFY SYSTEM 

#TRACHEA 

INFLAMMATION, NOS 

#LUNG 

PNEUMONIA, CHRONIC

HEMATOPOIETIC SYSTEM 

tSPLEEN 

HEMATOPOIESIS 

#SPLENIC CAPSULE 

INFLAMNATION, NOS 

#CERVICAL LYMPH NODE 

INFLAMMATION, NOS 

#TR\CHEAL LYMPH NODE 

INFLAMMATION, NOS 

•MESENTERIC L. NODE 

INFLAMMATION, NOS 

CIRCULATORY SYSTEM 

#HEAPT 

 MURINE 

THROMBUS, ORGANIZED 

# NUMBER OF ANIMALS WITH TISSUE

* NUMBER OF ANIMALS NECROPSIED 

**EXCLUDES PARTIALLY AUTOLYZED ANIMALS 

01-131F 

20 

20 

 20 

(20) 

(20) 

(20) 

17 (85%) 

(20) 

1 (5%) 

(20) 

1 (5%) 

(20) 

(20) 

(2 0) 

1 (5%) 

(20) 

1 15%) 

 EXAMINED MICROSCOPICALLY 

CONTROL (VEH) LOW DOSE HIGH DOSE 

01-081F 01-084F 01-085F 

20 50 50 

19 50 50 19 50 

(19 ) 

1 (5%) 

(50) (50)

1 (2%) 

(19) (**9) (50) 

1 (2%) 

(19) (50) (50) 

17 (89%) 34 (6 8%) 32 (64%) 

(19) (50) (49) 

1 (5%) 2 (4%) 4 (8%) 

(19 ) (50) (49) 

(19 ) (50) (50) 

1 (2%) 

(19 ) (50) (50) 

1 (2%) 

(19 ) (50) (50) 

(19) (49) (50) 

C-7 
•MYOCARDIUM

 

INFLAMMATION, NOS 

•AORTA 

MEDIAL CALCIFICATION 

DIGESTIVE SYSTEM 

•SALIVARY GLAND 

INFLAMMATION, NOS 

•LIVER 

HSTAMCRPHOSIS FATTY 

ANGIECTASIS 

*BILE DUCT 

HYPERPLASIA, NOS 

•PANCREAS 

INFLAMMATION, NOS 

FIBROSIS 

PERIARTERITIS 

ATROPHY, NOS

 

•STCMACH 

ULCER, FOCAL 

CALCIUM DEPOSIT 

URINARY SYSTEM 

•KIDNEY 

MINERALIZATION 

INFLAMMATION, CHRONIC 

CALCIUM DEPOSIT 

HYPERPLASIA, EPITHELIAL 

•KICNEY/CAPSULE 

INFLAMMATION, NOS

 

ENDOCRINE SYSTEM 

•PITUITARY 

ANGIECTASIS 

• NUMBER OF ANIMALS WITH TISSUE

* NUMBER OF ANIMALS NECROPSIED 

TABLE C2 (CONTINUED) 

CONTROL (UNTR) CONTROL (VEH) 

01-13 IF 01-081P 

(20) (19 ) 

(20) (19 ) 

1 (5%) 

(18) (15 ) 

(20) (19 ) 

1 (5%) 

(20) (19 ) 

(20) (19 ) 

1 (5%) 

1 (5%) 

(20) (19 ) 

1 (5%) 

1 (5%) 

(20) (19 ) 

1 (5%) 

8 (40%) 2 (11%) 

1 (5%) 

(20) (19 ) 

1 (5%) 

(20) (19 ) 

1 f5%> 

 EXAMINED MICROSCOPICALLY 

LOW DOSE 

01-084F 

(49) 

1 (2%) 

(50) 

(19) 

(50) 

1 (2%) 

1 (2%) 

(50) 

3 (6%) 

(50) 

(50) 

(50) 

2 (4%) 

(50) 

(48) 

HIGH DOSE 

01-085F 

(50) 

(50) 

(25) 

1 (4%) 

(50) 

(50) 

(50) 

1 (2%) 

1 (2%) 

1 (2%) 

(50) 

2 (4%) 

(50) 

7 (14%) 

1 (2%) 

(50) 

(48) 

C-8 
TABLE C2 (CONTINUED) 

• ADRENAL CORTEX 

DEGENERATION, NOS 

ANGIECTASIS 

•THYROID 

HYPERPLASIA, FOLLICULAR-CELL 

REPRODUCTIVE SYSTEM 

•VAGINA 

INFLAMMATION, NOS 

#UTERUS 

HYDRCMETRA 

#UTERUS/ENDOMETRIUM 

INFLAMMATION, NOS 

#OVAPY 

CYST, NOS 

INFLAMMATION, NOS 

NERVOUS SYSTEM 

NONE 

SPECIAL SENSE ORGANS 

•HARDERIAN GLAND 

HYPERPLASIA, NOS 

MUSCULOSKELETAL SYSTEM 

NONE 

BODY CAVITIES 

• ABDOMINAL CAVITY 

NECROSIS, FAT 

•PERITONEUM 

INFLAMMATION, NOS 

# NUMBER CF ANIMALS WITH TISSUE

• NUMBER OF ANIMALS NEC^OPSTED 

CONTROL (UNTR) CONTROL (VEH) 

01-1M F 01-081 F 

(20) (19 ) 

4 (20%) 3 (16%) 

(20) (18 ) 

(20) (19 ) 

(20) (19 ) 

(20) (19 ) 

1 (5%) 

(20) (19 ) 

1 (5%) 

1 (5%) 

(20) (19 ) 

(20) (19 ) 

1 (5%) 

(20) (19 ) 

1 (5%) 

 EXAMINED MICROSCOPICALLY 

LOW DOSE 

01-084F 

(50) 

2 (4%) 

(46) 

(50) 

1 (2%) 

(48) 

2 (4%) 

(48) 

2 (4%) 

(50) 

1 (2%) 

1 (2%) 

(50) 

(50) 

1 (2%) 

(50) 

HIGH DOSE 

01-085F 

(19) 

1 (2%) 

3 (6%) 

(43) 

1 (2%) 

(50) 

(48) 

2 (4%) 

(48) 

(49) 

(50) 

1 (2%) 

(50) 

(50) 

C-9 
TABLE C2 (CONCLUDED) 

CONTROL (ONTR) CONTROL (VEH) LOW DOSE HIGH DOSE 

01-131F 01-081F 01-084F 01-085F 

•PERICARDIUM (20) (19) (50) (50) 

INFLAMMATION, NOS 1 (2X) 1 (2%) 

• MESENTERY (20) (19) (50) (50) PERIARTERITIS 2 (10%) 1 (2%) 

ALL OTHER SYSTEMS 

NONE 

SPECIAL MORPHOLOGY SUMMARY 

NO LESION REPORTED 2 14 13 AUTOLYSIS/NO NECROPSY 1 

* NUMBER CF ANIMALS WITH TISSUE EXAMINED MICROSCOPICALLY 

• NUMBER OF ANIMALS NECROPSIZD 

C-IO 
APPENDIX D
 

SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC
 

LESIONS IN MICE TREATED WITH 1,1-DICHLOROETHANE
 

TABLE Dl

 

SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC LESIONS IN MALE MICI 

TREATED WITH 1,1-DICHLOROETHANE 

CONTROL (UNTR) 

02-M081 

CONTROL (VEH) 

02-M071 

LOW DOSE 

02-M082 

HIGH DOSE 

02-M083 

ANIMALS INITIALLY IN STUDY 

ANIMALS NECROPSIED 

ANIMALS EXAMINED HISTOPATHOLOGICALLY** 

20 

18 

17 

20 

19 

19 

50 

4 9 

4 9 

50 

4 8 

47 

INTEGUMENTARY SYSTEM 

*SKIN 

EPIDERMAL INCLUSION CYST 

INFLAMMATION, NOS 

(18) 

1 (6%) 

(19) 

1 (5*) 

(49) 

3 (6%) 

(48) 

1 (2%) 

1 (2%) 

•SUBCUT TISSUE 

ABSCESS, NOS 

(18) 

1 (6%) 

(19) 

1 (5%) 

(U9) 

3 (6%) 

(48) 

2 (4%) 

RESPIRATORY SYSTEM 

•TRACHEA 

INFLAMMATION, NOS 

(17) (19 ) (49) 

1 (2%) 

(47) 

• LUNG 

PNEUMONIA, CHRONIC MURINE 

(17) (19) (49) 

3 (6%) 

(47) 

2 (4%) 

HEMATOPOIETIC SYSTEM 

•SPLEEN 

AMYLOIDOSIS 

HEMATOPOIESIS 

(17) 

4 (24%) 

(18) 

7

1

 (39%) 

 (6%) 

(49) 

3

3

 (6%) 

 (6%) 

(47) 

3 (6%) 

• LYfPH NODE 

INFLAMMATION, NOS 

(17 ) (19) (49) 

1 (2%) 

(47) 

•MESENTERIC L. NODE 

INFLAMMATION, NOS 

ANGIECTASIS 

(17 ) (19) 

2

2

 (11%) 

 (11%) 

(49) 

3

1

 (6%) 

 (2%) 

(47) 

2 (4%) 

CIRCULATORY SYSTEM 

•HEART (17 ) (19) (49) (47) 

• NUMBER OF ANIMALS WITH TISSUE EXAMINED

* NUMBER OF ANIMALS NECROPSIED 

**EXCLUDES PARTIALLY AUTOLYZED ANIMALS 

 MICROSCOPICALLY 

D-3 
TABLE Dl (CONTINUED) 

#MYOCARDIUM 

INFLAMMATION, NOS 

•ENDOCARDIUM 

INFLAMMATION, NOS 

DIGESTIVE SYSTEM 

tSALIVARY GLAND 

CYST, NOS 

•LIVER 

INFLAMMATION, NOS 

AMYLOIDOSIS 

ANGIECTASIS 

#PANCREAS 

INFLAMMATION, NOS 

NECROSIS, FAT 

#STCMACH 

CALCIUM DEPOSIT 

HYPERKERATOSIS 

ACANTHOSIS 

#COLCN 

NEMATODIASIS 

URINARY SYSTEM 

•KIDNEY 

PYELONEPHRITIS, NOS 

INFLAMMATION, CHRONIC 

AMYLOIDOSIS 

CALCIUM DEPOSIT 

ENDOCRINE SYSTEM 

•THYROID 

FOLLICULAR CYST, NOS 

REPRODUCTIVE SYSTEM 

•PENIS 

fPI DERMAL INCLUSION CYST 

# NUMBER OF ANIMALS WITH TISSUE

• NUMBER OF ANIMALS NECROPSIED 

CONTROL (UNTR) CONTROL (VEH) 

O2-M0 81 0 2-MO71 

(17) (19 ) 

1 (5%) 

(17) (19) 

1 (5%) 

(17) (19) 

(17) (19) 

3 (16%) 

(17) (18) 

1 (6%) 

(17 ) (19) 

1 (5%) 

1 (5«) 

(17) (19) 

3 (16%) 

(17) (18) 3 (18%) 1 (6%) 5 (29%) 12 (67%) 4 (24%) 6 (33%) 

(17) (17) 

(18) (19 ) 

1 i5%) 

 EXAMINED MICROSCOPICALLY 

LOW DOSE 

02-M082 

(49) 

(49) 

(49) 

2 (4%) 

(49) 

2 (4%) 

1 (2%) 

(49) 

1 (2%) 

1 (2%) 

(49) 

1 f2%) 

1 (2%) 

1 (2%) 

(49) 

1 (2%) 

(49) 

1 (2%) 

8 (16%) 

2 (4%) 

(49) 

(49) 

HIGH DOSE 

02-H083 

(47) 

(47) 

(47) 

1 (2%) 

(*7) 

(47) 

(47) 

1 (2%) 

(47) 

1 (2%) 

(47) 

4 (9%) 

2 (4%) 

1 (2%) 

(47) 

1 (2%) 

(48) 

D~(4 
#PPCSTATE

 

INFLAMMATION, NOS

 

#TESTIS 

ATRCPHY, NOS

 

•EPIDIDYMIS 

GRANULOMA, SPERMATIC 

HERVCUS SYSTEM 

#BRAIN/MENINGES 

INFLAMMATION, NOS

 

SPECIAL SENSE ORGANS 

NONE 

MUSCULOSKELETAL SYSTEM 

NONE 

BODY CAVITIES 

NONE 

ALL OTHER SYSTEMS 

NONE 

SPECIAL MORPHOLOGY SUMMARY 

NO LESION REPORTED 

AUTO/NECPOPSY/NO HISTO 

AUTOLYSIS/NO NECROPSY 

# NUMBER OF ANIMALS WITH TISSUE

* NUMBER OF ANIMALS NECROPSIED 

TABLE Dl (CONCLUDED)
 

CONTROL (UMTR) CONTROL (VEH) 

0 2-B0 81 02-M071 

(17) (19) 

1 (5X) 

(17) (19) 

(18) (19) 

(17) (19) 

1 (5%) 

6 1 

1 

2 1 

 EXAMINED MICROSCOPICALLY 

LOW DOSE 

02-M082 

(^9) 

(49) 

2 (4%) 

(49) 

1 (2%) 

(49) 

16 

1 

HIGH DOSE 

02-M083 

(47) 

(47) 

2 (4%) 

(48) 

(47) 

23 

1 

2 

D-5 
TABLE D2

 

SUMMARY OF THE INCIDENCE OF NONNEOPLASTIC LESIONS IN FEMALE MICE 

TREATED WITH 1,1-DICHLOROETHANE 

CONTROL (ONTR) 

02-F081 

CONTROL (VEH) 

02-F071 

LOW DOSE 

02-F084 

ANIMALS

ANIMALS

ANIMALS

 INITIALLY IN STUDY 

 NECfiOFSIED 

 EXAMINED HISTOPATHOLOGICALLY** 

20 

1 9 

19 

20 

2 0 

2 0 

50 

. 47 

4 7 

INTEGUMENTARY SYSIEM 

NONE 

RESFIPATCRY SYSTEM 

#LONG 

PNEUMONIA, CHRONIC MURINE 

(19 ) (20) (47) 

3 (6%) 

HEMATOPOIETIC SYSTEM 

#SPLEEN 

HEMATOPOIESIS 

(19 ) (2 0) 

1 (5%) 

(47) 

•CERVICAL LYMPH NODE 

INFLAMMATION, NOS 

(19 ) (20) (47) 

CIRCULATORY SYSTEM 

N3NE 

DIGESTIVE SYSTEM 

•SALIVARY GLAND 

CYST, NOS 

ANGIECTASIS 

(19 ) (19 ) (46) 

•BIL E DUCT 

HYPERPLASIA, NOS 

(19 ) (20) (47) 

1 (2X) 

•PANCREAS 

CYST. NOS 

(19 ) (2 0) (47) 

# NUMBEP OF ANIMALS WITH TISSUE EXAMINED

* NUMBER OF ANIMALS NECROPSIED 

**EXCLUDES PARTIALLY AUTOLYZED ANIMALS 

 MICROSCOPICALLY 

HIGH DOSE 

02-F085 

50 

47 

4 7 

(47) 

1 (2%) 

(46) 

(47) 

1 (2%) 

(47) 

2 (4%) 

1 (2%) 

(47) 

(46) 

1 (2%) 

D-6 
INFLAMMATION, NOS
 

ATROPHY, NOS
 

tSTCMACH
 

HYPERKERATOSIS
 

ACANTHOSIS
 

#COLCN
 

NEMATOEIASIS
 

URINARY SYSTEM 

• URINARY BLADDER
 

INFLAMMATION, NOS
 

ENDOCRINE SYSTEM 

NONE 

REPRODUCTIVE SYSTEM 

#UTERUS
 

HYDROMETPA
 

•UTERUS/ENDOMSTRIUM
 

INFLAMMATION, NOS
 

HYPERPLASIA, CYSTIC
 

• OVARY
 

CYST, NOS
 

INFLAMMATION, NOS
 

NERVOUS SYSTEM 

NONE 

SPECIAL SEN$E ORGANS 

NONE 

MUSCULOSKELETAL SYSTEM 

NONE h 

#	 NUMBER OF ANIMALS WITH TISSUE

* NUMBER OF ANIMALS NECPOPSIED 

TABLE D2 (CONTINUED) 

CONTROL (UNTR) CONTROL (VE H) 

02-F081 02-F071 

1 (5%) 

(19)	 (20) 

1 (5%) 

1 (5%) 

(19)	 (19) 

1 (5%) 

(19)	 (19) 

1 (5%) 

(19)	 (2 0) 

3 (16%) 4 (20%) 

(19) (20) 

2 (11%) 2 (10%) 

7 (37%) 11 (55%) 

(19) (20) 

10	 (53%) 10 (50%) 

2 (11%) 3 (15%) 

 EXAMINED MICROSCOPICALLY 

LOW DOSE 

02-F084 

(47) 

(47) 

(47) 

(47) 

β (17%) 

(47) 

1 (2%) 

21 (45%) 

(47) 

5 (11%) 

HIGH DOSE 

02-F085 

1 (2%) 

(46) 

1 (2%) 

1 (2%) 

(47) 

(47) 

(46) 

5 (11%) 

(46) 

5 (11%) 

(47) 

10	 (21%) 

3 (6%) 

D-7
 
TABLE D2 (CONCLUDED) 

CONTROL (UNTR) CONTROL (VEH) LOW DOSE HIGH DOSE 

02-P08 1 02-F071 02-F084 02-PO85 

BODY CAVITIES 

NOME 

ALL CTHER SYSTEMS 

NOVE 

SPECIAL MORPHOLOGY SUMMARY 

NC LESION REPORTED 3 1 11 18 

ACCIDENTAL DEATH 1 

AOTO/NECROPSY/HISTO PERF 1 

AUTOLYSIS/NO NECROPSY 3 3 

* NUMBER CF ANIMALS WITH TISSUE EXAMINED MICROSCOPICALLY 

* NUMBER OF ANIMALS NECROPSIED 

D-8 
Review of the Bioassay of 1,1-Dichloroethane* for Carcinogenicity
 

by the Data Evaluation/Risk Assessment Subgroup of the
 

Clearinghouse on Environmental Carcinogens
 

January 18, 1978
 

The Clearinghouse on Environmental Carcinogens was
 

established in May, 1976, in compliance with DHEW Committee
 

Regulations and the Provisions of the Federal Advisory
 

Committee Act. The purpose of the Clearinghouse is to
 

advise the Director of the National Cancer Institute (NCI)
 

on its bioassay program to identify and to evaluate chemical
 

carcinogens in the environment to which humans may be
 

exposed. The members of the Clearinghouse have been drawn
 

from adademia, industry, organized labor, public interest
 

groups J State health officials, and quasi-public health
 

and research organizations. Members have been selected on
 

the basis of their experience in carcinogenesis or related
 

fields and, collectively, provide expertise in laboratory
 

animal sciences, chemistry, biochemistry, biostatistics,
 

toxicology, pathology, and epidemiology. Representatives
 

of various Governmental agencies participate as ad hoc
 

members. The Data Evaluation/Risk Assessment Subgroup of
 

the Clearinghouse is charged with the responsibility of
 

providing a peer review of reports prepared on NCI-sponsored
 

bioassajys of chemicals studied for carcinogenicity. It is
 

in thisi context that the below critique is given on the
 

bioassay of 1,1-Dichloroethane for carcinogenicity.
 

The primary reviewer said that 1,1-Dichloroethane was
 

not carcinogenic in the treated mice, under the conditions
 

of test. In the rats, he said that survival was too in­ adequate among the animals to reach any conclusion. He
 

noted that the study was conducted in the same room in
 

which 17 other compounds were studied. He added that at
 

the dose level administered, it is likely that a portion
 

of the dose was expelled through the lungs back into the
 

animal room. In conclusion, the primary reviewer said that
 

he agreed with the staff!

s conclusion in regard to the
 

negative mouse study but thought that the rat study was
 

too inadequate to draw any conclusion.
 

The secondary reviewer concurred with the primary
 

reviewer's critique. He was particularly critical of the
 

rat study in which there were too few controls, survival
 

was poor, the MTD was not adequately determined, and the
 

chronic treatment period was not continuous. Despite the
 

slight increases in mammary adenocarcinomas and hemangiosarcomas In the treated female rats, the secondary reviewer
 

concluded that the study was too inadequate to draw any
 

conclusion.
 

51
 
A discussion ensued as to whether the mouse bioassay
 

was adequate enough to reach a conclusion. It was agreed
 

that survival was sufficient and the dose level high enough
 

as to be able to make a judgment on the carcinogenicity of
 

1,1-Dichloroethane.
 

It was moved that there was no conclusive evidence as
 

to the carcinogenicity of 1,1-Dichloroethane in the treated
 

mice and that the rat study was inadequate to drawn any
 

conclusion. The motion was seconded and, subsequently an
 

amendment proposed that 1,1-Dichloroethane be referred to
 

the Chemical Selection Working Group to be considered for
 

retest in rats. Votes on the amendment and motion were
 

approved by all the Subgroup members except Dr. Rowe, who
 

abstained.
 

Members Present Were:
 

Arnold Brown (Acting Chairman), Mayo Clinic
 

Lawrence Garfinkel, American Cancer Society
 

Joseph Highland, Environmental Defense Fund
 

Charles Kensler, Arthur D. Little Company
 

Verald K. Rowe, Dow Chemical, U.S.A.
 

Sheldon Samuels, Industrial Union Department, APL-CIO
 

Louise Strong, University of Texas Health Sciences Center
 

Sidney Wolfe, Health Research Group
 

*	 Subsequent to this review^ changes may have been made
 

in the bioassay report either as a result of the review
 

or other reasons. Thus, certain comments and criticisms
 

reflected in the review may no longer be appropriate.
 

DHEW Publication No. (NIH) 78-1316