United States
Environmental Protection
Agency
Office of Health and
Environmental Assessment
Washington DC 20460
EPA-600/8-84-006A
April 1984
External Review Draft
Research and Development
r/EPA
Health Assessment Review
Document for Draft
1 ,2-Dichloroethane
ir-j.l_ I l-k- I- 1 -.1 »
(Ethylene Dichlonde)
Part 1 of 2
Cite or Quote)
NOTICE
This document is a preliminary draft. It has not been formally
released by EPA and should not at this stage be construed to
represent Agency policy. It is being circulated for comment on its
technical accuracy and policy implications.
-------
/n M + EPA-600/8-84-006A
(Do Not A .. -00/l
Cite or Quote) April 1984
External Review Draft
Health Assessment Document
for 1,2,- Dichloroethane
(Ethylene Dichloride)
Part 1 of 2
NOTICE
This document is a preliminary draft. It has not been formally released by the U.S. Environmental
Protection Agency and should not at this stage be construed to represent Agency policy. It
is being circulated for comment on its technical accuracy and policy implications.
U.S. Environmental Protection Agency
Region V, Library
230 South Dearborn Street
Chicago, Illinois 60604
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Research Triangle Park, North Carolina 27711
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DISCLAIMER
This report is an external draft for review purposes only and does not
constitute Agency Policy. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
U,S. Environmental Protection Agency
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PREFACE
The Office of Health and Environmental Assessment has prepared this
health assessment to serve as a "source document" for EPA use. The health
assessment document was originally developed for use by the Office of Air
Quality Planning and Standards to support decision-making regarding possible
regulation of ethylene dichloride as a hazardous air pollutant. However, the
scope of this document has since been expanded to address multimedia aspects.
In the development of the assessment document, the scientific literature
has been inventoried, key studies have been evaluated and summary/conclusions
have been prepared so that the chemical's toxicity and related characteristics
are qualitatively identified. Observed effect levels and other measures of
dose-response relationships are discussed, where appropriate, so that the
nature of the adverse health responses are placed in perspective with observed
environmental levels.
111
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The EPA's Office of Health and Environmental Assessment (OHEA) is
responsible for the preparation of this health assessment document. The OHEA
Environmental Criteria and Assessment Office (ECAO-RTP) had overall
responsibility for coordination and direction of the document (Dr. Robert M.
Bruce, Project Manager). The chapters addressing physical and chemical
properties, sampling and analysis and toxic effects were either rewritten or
revised by Syracuse Research Corporation. The pharmacokinetics chapter was
written by Dr. I.W.F. Davidson of the Bowman Gray School of Medicine, Wake Forest
University. The air quality chapters addressing sources, emissions and ambient
concentrations were originally written by Syracuse Research Corporation and
revised by Radian Corporation under a contract with the Office of Air Quality
Planning and Standards.
The principal authors of the chapters prepared by Syracuse Research
Corporation are:
Stephen Bosch
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, New York 13210-4080
D. Anthony Gray, Ph.D.
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, New York 13210-4080
Joseph Santodonato, Ph.D., C.I.H.
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, New York 13210-4080
The OHEA Carcinogen Assessment Group (CAG) was responsible for preparation
of the sections on carcinogenicity. Participating members of the CAG are listed
below (principal authors of present carcinogenicity materials are designated by
an asterisk (*).
IV
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Roy Albert, M.D. (Chairman)
Elizabeth L. Anderson, Ph.D.
Larry D. Anderson, Ph.D.
Steven Bayard, Ph.D.
David L. Bayliss, M.S.
Chao W. Chen, Ph.D.*
Margaret M.L. Chu, Ph.D.
Herman J. Gibb, M.S., M.P.H.
Bernard H. Haberman, D.V.M., M.S.
Charalingayya B. Hiremath, Ph.D.*
Robert McGaughy, Ph.D.
Dharm V. Singh, D.V.M., Ph.D.
Todd W. Thorslund, Sc.D.
The OHEA Reproductive Effects Assessment Group (REAG) was responsible for
the preparation of sections on mutagenicity, teratogenicity and reproductive
effects. Participating members of REAG are listed below (principal authors of
present sections are indicated by an asterisk (*). The Environmental Mutagen
Information Center (EMIC), in Oak Ridge, TN, identified literature bearing on the
mutagenicity of EDC.
John R. Fowle III, Ph.D.*
Ernest R. Jackson, M.S.
Casey Jason, M.D., Medical Officer
David Jacobson-Kram, Ph.D.
K.S. Lavappa, Ph.D.
Sheila L. Rosenthal, Ph.D.
Carol N. Sakai, Ph.D.*
Carmella Tellone, B.S.
Vicki L. Vaughan-Dellarco, Ph.D.
Peter E. Voytek, Ph.D. (Director)
The following individuals provided peer review of this draft and/or earlier
drafts of this document:
U.S. Environmental Protection Agency
Karen Blanchard
Office of Air, Noise and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, NC
Robert M. Bruce, Ph.D.
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Research Triangle Park, NC
-------
Larry T. Cuppitt, Ph.D.
Office of Research and Development
Environmental Sciences Research Laboratory
Research Triangle Park, NC
James W. Falco, Ph.D.
Office of Health and Environmental Assessment
Exposure Assessment Group
Washington, DC
Lester D. Grant, Ph.D.
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Research Triangle Park, NC
Thomas G. McLaughlin, Ph.D.
Office of Health and Environmental Assessment
Exposure Assessment Group
Washington, DC
David Batriek » • ././;, ^ t-> >. .-.:•-•' ••• '
Office of Air, Noise and Radiation
Off ice,.of Air^Quajli&yj P.ljanni^ana-Statfdairds1-
Research Triangle Park, NC
David J. Reisman
Office of Health and Environmental Assessment
Environmental Criteria and A%sesrsinentT Office
Cincinnati, OH
Jerry F. Stara, D.V.M. ; ' " "<
Office of Health and Environmental Assessment
Environmental Criteria and A@se^sment:' Off i'ce
Cincinnati, OH
Consultants, reviewers and contribating .authors:
Joseph-F..Borzellecai Ph»-Du -
Virginia Commonwealth University
Richmond, VA
Mildred Christian, Ph.D.
Argus Research Laboratories, Inc.
Perkasia, PA
Herbert H. Cornish, Ph.D,. ' ::--'-
The University of Michigan •
Ypsilanti,""MI IV. .•"-'
I.W.F. Davidson, Ph.D.
Bowman Gray S@ho01*of, Medicine
Wake Forest University
Winston Salem, NC -" . "
vi
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Larry Fishbein, Ph.D.
National Center for lexicological Research
Jefferson, AR
Mark M. Greenberg
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Research Triangle Park, NC
Derek Hodgson, Ph.D.
University of North Carolina
Chapel Hill, NC
George R. Hoffman, Ph.D.
Holy Cross College
Worcester, MA
Rudolph J. Jaeger, Ph.D.
Consultant Toxicologist
7 Bolgert Place
Westwood, NJ
Marshall Johnson, Ph.D.
Thomas Jefferson Medical College
Philadelphia., PA
Bruce Kleinstein, Ph.D.
1500 Locust Street, Suite 3504
Philadelphia, PA
John L. Laseter, Ph.D.
Environmental Affairs, Inc.
New Orleans, LA
Edmond J. LaVoie, Ph.D.
American Health Foundation
Valhalla, NY
Marvin S. Legator, Ph.D.
University of Texas Medical Branch
Galveston, TX
P.O. Lotilaker, Ph.D.
Fels Research Institute
Temple University Medical Center
Philadelphia, PA
Jean C. Parker, Ph.D.
Office of Waste Programs Enforcement
U.S. Environmental Protection Agency
Washington, DC
vn
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Bernard Schwetz, Ph.D.
National Institute of Environmental Health Sciences
Research Triangle Park, NC
Sara Shibko, Ph.D.
Health and Human Services
Division of Toxicology
Washington, DC
Charles M. Sparacino, Ph.D.
Research Triangle Institute
Research Triangle Park, NC
Danial S. Straus, Ph.D.
University of California
Riverside, CA
Darrell D. Suraner, Ph.D.
CIBA GEIGY Corporation
High Point, NC
Robert Tardiff, Ph.D.
1423 Trapline Court
Vienna, VA
Norman M. Trieff, Ph.D.
University of Texas Medical Branch
Department of Pathology, UTMB
Galveston, TX
Benjamin Van Duuren, Ph.D.
New York University Medical Center
550 First Avenue
New York, NY
Jim Withey, Ph.D.
Department of National Health and Welfare
Tunney's Pasture
Ottawa, Ontario
CANADA K1A 01Z
Vlll
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TABLE OF CONTENTS
Page
LIST OF TABLES [[[ xi
LIST OF FIGURES [[[ xvi
1 . SUMMARY AND CONCLUSIONS ............................................ 1-1
2 . INTRODUCTION [[[ 2-1
3. PHYSICAL AND CHEMICAL PROPERTIES ................................... 3-1
3.1 NAME [[[ 3-1
3.2 CAS REGISTRY, RTECS, AND STORET NUMBERS ....................... 3-1
3 . 3 DESCRIPTION [[[ 3-1
3.4 STRUCTURE [[[ 3-1
3.5 PHYSICAL PROPERTIES OF PURE ETHYLENE DICHLORIDE ............... 3-1
4 . SAMPLING AND ANALYSIS OF ETHYLENE DICHLORIDE
4 . 1 SAMPLING [[[ 4-1
4 . 2 ANALYSIS [[[ 4-1
4.2.1 Ethylene Dichloride in Air ............................ 4-1
4.2.2 Ethylene Dichloride in Water .......................... 4-2
4.2.3 Ethylene Dichloride in Solid Samples .................. 4-3
4.2.4 Ethylene Dichloride in Blood .......................... 4-3
4.2.5 Ethylene Dichloride in Urine .......................... 4-3
4.2.6 Ethylene Dichloride in Tissue ......................... 4-4
5. SOURCES IN THE ENVIRONMENT ......................................... 5-1
5.1 PRODUCTION PROCESSES .......................................... 5-1
5.2 ETHYLENE DICHLORIDE PRODUCERS ................................. 5-2
5.3 ETHYLENE DICHLORIDE PRODUCTION AND TRENDS ..................... 5-2
5.4 ETHYLENE DICHLORIDE USES ...................................... 5-5
5.5 SOURCES OF EMISSIONS .......................................... 5-9
5.5.1 Production and Related Facilities ..................... 5-12
5.5.2 Dispersive Uses ....................................... 5-13
5.5.3 Conclusions ........................................... 5-14
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TABLE OF CONTENTS (cont.)
Page
7 . ENVIRONMENTAL LEVELS AND EXPOSURE 7-1
7.1 ENVIRONMENTAL LEVELS 7-1
7.1.1 Atmospheric Levels 7-1
7.1.2 Ground and Surface Water Levels 7-9
7.1.3 Soil and Sediment Levels 7-14
7.2 ENVIRONMENTAL EXPOSURE 7-14
7.2.1 Exposure from Air 7-18
7.2.2 Exposure from Water 7-20
7.2.3 Exposure from Food 7-20
7.3 CONCLUSIONS 7-20
8. ECOLOGICAL EFFECTS 8-1
9. BIOLOGICAL EFFECTS IN MAN AND EXPERIMENTAL ANIMALS 9-1
9 .1 PHARMACOKINETICS 9-1
9.1.1 Absorption and Distribution 9-1
9.1.2 Excretion 9-18
9.1.3 Metabolism 9-32
9.1.4 Summary and Conclusions 9-55
9.2 ACUTE, SUBCHRONIC AND CHRONIC TOXICITY 9-57
9.2.1 Effects in Humans 9-57
9.2.2 Effects in Animals 9-86
9.2.3 Summary of Acute, Subchronic and Chronic Toxicity 9-115
9.3 REPRODUCTIVE AND TERATOGENIC EFFECTS 9-122
9.3.1 Summary 9-129
9 .4 MUTAGENICITY 9-131
9.5 CARCINOGENICITY 9-166
9.5.1 Animal Studies 9-166
9.5.2 Epidemiologic Studies 9-205
9.5.3 Quantitative Estimates 9-206
9.5.4 Summary 9-233
9.5.5 Conclusions 9-234
10. REFERENCES 10~1
Appendix A
Appendix B
Appendix C
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LIST OF TABLES
Table Page
5-1 Major Manufacturers of Ethylene Bichloride 5-3
5-2 U.S. Production and Sales of Ethylene Dichloride 5-4
5-3 Ethylene Dichloride Uses 5-6
5-4 Comsumption of Ethylene Dichloride in 1979 and 1974 5-7
5-5 Uses of Ethylene Dichloride for Intermediate Purposes 5-8
5-6 Estimated Environmental Releases of Ethylene
Dichloride in 1979 5-11
6-1 Rate Constants for a Few Chlorinated Ethanes at
Room Temperature 6-3
7-1 Ambient Atmospheric Levels of Ethylene Dichloride 7-2
7-2 Ambient Concentrations of Ethylene Dichloride in
Urban Areas 7-8
7-3 Reported Occurrence of Ethylene Dichloride in Groundwater
System 7-15
7-4 Reported Occurrence of Ethylene Dichloride in Surface
Water Systems 7-16
7-5 State Data on Ethylene Dichloride in Groundwater 7-17
7-6 Estimated Respiratory Intake of Ethylene Dichloride by
Adults and Infants 7-19
7-7 Maximum Concentration Level in the Vicinity of Various
Emission Sources 7-21
7-8 Total Estimated Population (in Thousands) Exposed to
Ethylene Dichloride in Drinking Water at the Indicated
Concentration Ranges 7-22
7-9 Estimated Drinking Water Intake of Ethylene Dichloride
by Adults and Infants 7-23
9-1 Physical Properties of Ethylene Dichloride and
Other Chloroethanes 9-3
9-2 Partition Coefficients for Ethylene Dichloride 9-4
XI
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LIST OF TABLES (cont.)
Table Page
9-3 Fate of 14C-EDC in Rats 48 Hours After Oral (150 mg/kg)
or Inhalation (150 ppra, 6-hr) Exposure 9-6
9-4 Peak Blood and Tissue Levels After Single Oral Dosage
of EDC in Male Rats 9-8
9-5 The Absorption Rate Constants (k ) and Area Under Curve
(AUC) for Rats After Single Orll with Doses of EDC in Oil
and in Water as Vehicle and After Intravenous
Administration 9-9
9-6 EDC Tissue Levels After 50 ppra Inhalatory Exposure 9-14
9-7 EDC Tissue Levels After 250 ppm Inhalatory Exposure 9-15
9-8 Blood Tissue Levels of EDC in Male Rats 2 Hours After
Single Oral Doses in Corn Oil 9-17
9-9 Percent Distribution of Radioactivity Excreted (48-hr) by
Mice Receiving 1,2-Dichloroethane- C 9-20
9-10 Pharmacokinetic Parameters of EDC Administered as Single
Bolus Intravenous Injections in Saline to Sprague-Dawley
Male Rats. Parameters Calculated from a 2-Compartment
Open Model 9-24
9-11 Pharmacokinetic Parameters of EDC Administered as Single
Oral Doses in Corn Oil and Water to Sprague-Dawley Male
Rats. Parameters Calculated from a 2-Compartment Open
Model 9-26
9-12 Pharmacokinetic Parameters of EDC Following Termination of
Steady State Inhalation (5-hr Exposure) of 50 and 250 ppm
to Male Sprague-Dawley Rats 9-29
9-13 Pharmacokinetic Parameters of EDC Following Termination of
Steady State Inhalation Conditions; 6-Hr Exposure, 150 ppm
to Male Osborne-Mendel Rats. Parameters Calculated from a
2-Compartment Model 9-30
9-14 Identified Metabolites of Ethylene Dichloride and
Ethylene Bromide 9-34
9-15 Percent Distribution of Radioactivity Excreted (48-hr) as
Urinary Metabolites by Mice Receiving 1,2-Dichloroethane- C
or 2-Chloroacetic Acid- C 9-37
xii
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LIST OF TABLES (cont.)
Table
9-16 Total Macromolecular Binding and DNA Binding in Selected
Tissue of Rats After Exposure to C-EDC by Oral or
9-17
9-18
9-19
9-20
9-21
9-22
9-23
9-24
9-25
9-26
9-27
9-28
9-29
9-30
9-31
9-32
9-33
Effect of Dietary Disulfiram Upon the C Content of
Liver Nuclei Isolated 24 or 48 Hours After Administration
of a Single Oral Dose of 15 mg/rag [U- C]EDB
Effects Associated with Acute Lethal Oral Doses of
Ethylene Dichloride in Humans ,
Effects of Acute Oral Ingestion of 1 ,2-Dichloroethane
(Survey Results ) ,
Effect of Ethylene Dichloride Exposure on Eye
Sensitivity to Light ,
Morbidity and Lost Workdays of Aircraft Industry Gluers
Exposed to Ethylene Dichloride ,
Concentrations of Ethylene Dichloride in Oil Refinery
Mineral Oil Purification Process Air ,
Effects Observed in Polish Oil Refinery Workers
Effects of Acute Exposure to Ethylene Dichloride
Effect of Ethylene Dichloride on the Cornea
Effect of Subchronic Exposure to Ethylene Dichloride
Summary of Mutagenicity Testing of EDC: Gene Mutations
in Bacteria
Summary of Mutagenicity Testing of EDC: Higher Plants
Summary of Mutagenicity Testing of EDC: Gene Mutation
Tests in Insects
Summary of Mutagenicity Testing of EDC: Mammalian Cells
in Culture
Summary of Mutagenicity Testing of EDC: Chromosomal
Aberrations Tests
Summary of Mutagenicity Testing of EDC: PolA Assay
Summary of Mutagenicity Testing of EDC: DNA Binding
y-D
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LIST OF TABLES
Table
9-34 Design Summary for 1,2-Dichloroethane (EDC) Gavage
Experiment in Osborne-Mendel Rats 9-168
9-35 Terminal Survival of Osborne-Mendel Rats Treated With
1,2-Dichloroethane (EDC) 9-172
9-36 Squamous Cell Carcinomas of the Forestomach in Osborne-
Mendel Rats Treated With 1,2-Dichloroethane (EDC) 9-173
9-37 Hemangiosarcomas in Osborne-Mendel Rats Treated With
1,2-Dichloroethane (EDC) 9-174
9-38 Adenocarcinomas of the Mammary Gland in Female Osborne-
Mendel Rats Treated With 1,2-Dichloroethane (EDC) 9-175
9-39 Design Summary for 1,2-Dichloroethane (EDC) Gavage
Experiment in B6C3F1 Mice 9-177
9-40 Terminal Survival of B6C3F1 Mice Treated With
1,2-Dichloroethane (EDC) 9-178
9-41 Hepatocellular Carcinomas in B6C3F1 Mice Treated With
1,2-Dichloroethane (EDC) 9-181
9-42 Alveolar/Bronchiolar Adenomas in B6C3F1 Mice Treated
With 1,2-Dichloroethane (EDC) 9-182
9-43 Squamous Cell Carcinomas of the Forestomach in B6C3F1 Mice
Treated With 1,2-Dichloroethane (EDC) 9-183
9-44 Adenocarcinomas of the Mammary Gland in Female B6C3F1 Mice
Treated With 1,2-Dichloroethane (EDC) 9-184
9-45 Endometrial Polyp or Endometrial Stromal Sarcomas in Female
B6C3F1 Mice Treated With 1,2-Dichloroethane (EDC) 9-184
9-46 Characterization of 1,2-Dichloroethane (EDC) Inhalation
Experiment in Sprague-Dawley Rats 9-185
9-47 Design Summary for 1,2-Dichloroethane (EDC) Experiment
in Sprague-Dawley Rats 9-186
9-48 Survival of Sprague-Dawley Rats Exposed to EDC at 52 and
104 Weeks 9-188
9-49 Tumor Incidence in Sprague-Dawley Rats Exposed to EDC 9-189
9-50 Mammary Tumors in Sprague-Dawley Rats Exposed to EDC 9-193
xiv
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LIST OF TABLES
Table Page
9-51 Design Summary for 1,2-Dichloroethane (EDC) Experiment
9-52
9-53
9-51
9-55
9-56
9-57
9-58
9-59
in Swiss Mice
Survival of Swiss Mice Exposed to EDC at 52 and 78 Weeks
Tumor Incidence in Swiss Mice Exposed to EDC
Pulmonary Tumor Response in Strain A/st Mice
Injected with EDC
Mouse Skin Bioassay of 1 ,2-Dichloroethane and
Chloroacetaldehyde
Incidence Rates of Hemangiosarcomas in the Circulatory
Systems of Male Osborne-Mendel Rats
Incidence Rates of Hepatocellular Carcinomas in Male
B6C3F1 Mice
Upper-Bound Estimate of Risk At 1 Mg/kg/day
Relative Carcinogenic Potencies Among 53 Chemicals
9-196
9-197
9-198
9-202
9-204
9-220
9-220
9-223
Evaluated by the Carcinogen Assessment Group as Suspect
Human Carcinogens ' '3 9-230
xv
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LIST OF FIGURES
Figure Page
9-1 EDC levels after single oral administration in rats 9-7
9-2 Top: Blood levels of EDC observed during and following a
6-hour inhalation exposure to 150 ppm EDC. Bottom: Semi-
logarithmic plot of EDC blood levels vs. time after
exposure termination 9-12
9-3 Blood levels of EDC in rats after i.v. administration 9-23
9-4 Levels of EDC in rats after inhalatory exposure to 50 ppm
(top) and 250 ppm (bottom). Levels were measured at
termination of 5-hour exposure period 9-27
9-5 Microsomal oxidative metabolism of 1,2-dihaloethanes 9-39
9-6 Further metabolism of 2-chloroacetaldehyde and 1-chloroso-
2-chloroethane from microsomal oxidation 9-41
9-7 Cytosolic metabolism of ethylene dichloride 9-44
9-8 Growth curves for male and female Osborne-Mendel rats
administered 1,2-dichloroethane (EDC) by gavage 9-170
9-9 Survival comparisons for male and female Osborne-Mendel rats
administered 1,2-dichloroethane (EDC) by gavage 9-171
9-10 Growth curves for male and female B6C3F1 mice administered
1,2-dichloroethane (EDC) by gavage 9-179
9-11 Survival comparisons for male and female B6C3F1 mice
administered 1,2-Dichloroethane (EDC) by gavage 9-180
9-12 Point and upper-bound estimates of four dose-response models
over low-dose region on basis of hemangiosarcomas in rats;
dose with surface correction 9-224
9-13 Point and upper-bound estimates of four dose-response models
over low-dose region on the basis of liver carcinomas in
mice; dose with surface correction 9-225
9-14 Histogram representing the frequency distribution of the
potency indices of 53 suspect carcinogens evaluated by
the Carcinogen Assessment Group 9-229
xvi
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1. SUMMARY AND CONCLUSIONS
Ethylene dichoride (EDC) is a clear, colorless, volatile liquid with a
pleasant odor. EDC has a molecular weight of 98.96 amu, a boiling point of
83.7°C and a vapor pressure of 64 torr at 20°C. Unlike more highly chlorinated
hydrocarbons, EDC has a flashpoint (17°C closed cup), an autoignition tempera-
ture (413°C) and explosive limits (6.2-15.6% by volume in air). It has a water
solubility of 8820 mg/Jl and a log octanol/water partition coefficient of 1.48.
EDC is analyzed best by gas chroraatography using either an electron capture
or halogen specific (raicrocoulometric or electrolytic conductivity) detector.
Alternatively, a gas chroraatograph/mass spectrometer may be used. EPA methods
502.1, 601, 624 and 8010 detail the analysis of EDC from water, wastewater and
solid samples. Variations in these methods provide for analysis of EDC in
biological media (e.g., blood, urine and tissue). EDC in air is analyzed by
condensing the volatiles in a previously collected air sample in a GC column,
followed by temperature programming the column.
EDC is produced commercially by the direct chlorination or oxychlorination
of ethylene. Most of the production capacity, which exceeds nine million metric
tons annually, is located in Texas and Louisiana. Roughly 90? of the production
is captively consumed by the producers. Production during 1980, 1981 and 1982
totalled 5.037, 4.523 and 3.455 million metric tons, respectively. A major
portion (84$) of the United States EDC production is consumed to make vinyl
chloride monomer. It is also used to make chlorinated solvents, vinylidene
chloride and ethyleneamines.
The major source of EDC emissions to the environment are from vent gas
streams during the manufacture of EDC and its derivatives. Significant amounts
are also emitted to the environment from dispersive uses in gasoline, paints and
1-1
-------
cleaning agents. In 1979, an estimated 6696 metric tons of EDC were released to
the atmosphere from EDC and derivative production, while 49^4 metric tons were
released from dispersive uses (Seufert et al., 1980).
Based on available kinetic data and average tropospheric hydroxyl free
radical concentration, the half-life of EDC, the most likely removal mechanism
for EDC from the atmosphere, has been estimated to range from 36-127 days. Due
to different factors that may cause variations in «OH concentrations in the
troposphere, the persistence of EDC could vary somewhat from the estimated value.
Chloroacetyl chloride is probably the principal product resulting from the reac-
tion of EDC with -OH radicals.
EDC is not expected to play a significant role in stratospheric ozone
destruction reactions due to its relatively short tropospheric half-life.
However, chloroacetyl chloride may have sufficient stability to diffuse to the
stratosphere and may participate in UV reactions, producing chlorine atoms.
In the aquatic environment, volatilization appears to be the most
significant removal mechanism. The half-life for this process has been estimated
to be -4 hours.
From the little information that is available regarding the fate of EDC in
soil, it can be surmised that both volatilization from and leaching through soil
may be two significant removal mechanisms for EDC.
The highest atmospheric concentrations that have been monitored for EDC
have been detected near production and use facilities. Mean levels as high as
27.5 ppb have been monitored near production-use facilities in Lake Charles, LA
(Elfers, 1979). However, atmospheric exposure appears to vary greatly from one
location to another. The available monitoring data, which includes levels
detected in general ambient urban areas, indicate that most locations have
concentrations of <0.5 ppb. The data are not sufficient to determine regional
1-2
-------
variations in exposure levels. Using Federal Reporting Data System data,
Letkiewicz et al. (1982) have projected that EDC levels in all groundwater and
surface water systems in the United States fall below 10 pg/&, and that most are
<1.0 pg/2,. No data are available indicating the presence of EDC in finished
foods.
Pharmacokinetic studies with animals indicate that EDC is rapidly absorbed
following oral and inhalation exposure. Dermal absorption is negligible in most
vapor exposure situations, although absorption by this route may be significant
with direct liquid contact. Tissue distribution of EDC is consistent with its
lipophilic nature, and the chemical crosses the blood/brain and placental
barriers and distributes into breast milk. Up to 90$ of low oral or inhalation
doses are metabolized by rats and mice, with biotransformation occurring by
multiple pathways; EDC is metabolized to 2-chloroacetaldehyde, S-(2-chloroethyl)
glutathione and other putative reactive metabolites capable of covalent binding
to cellular macromolecules, as well as nonreactive glutathione conjugates.
Elimination of unmetabolized EDC occurs almost exclusively via the lungs, is
rapid and is consistent with a two-compartment system and Michaelis-Menten
kinetics. Significant bioaccumulation is not expected to occur.
The effects of acute inhalation exposure to EDC are similar in humans and
animals. Immediate symptoms of toxicity are CNS depression and irritation of the
respiratory tract and eyes. Death was usually ascribed to respiratory and
circulatory failure, and pathologic examinations typically revealed congestion,
degeneration, necrosis and hemorrhagic lesions of most internal organs (e.g.,
liver, kidneys, spleen, lungs, respiratory tract, gastrointestinal tract).
Limited data, primarily from the foreign literature, suggest that typical
symptoms and signs of acute toxicity may develop in humans with repeated
occupational exposure to higher concentrations (>60 ppm) of EDC vapor. Subtle
1-3
-------
neurological effects (e.g., fatigue, irritability, sleeplessness) may be more
prevalent than overt symptoms of CNS toxicity at lower concentrations. Studies
with multiple species of animals have shown that subchronic or chronic exposure
to EDC at vapor concentrations of < 100 ppm did not produce treatment-related
adverse effects on survival, growth, hematology, clinical chemistry, organ
weight or histology, toxic effects were apparent at higher concentrations and
were exposure-related; exposure to HOO-500 ppm produced high mortality and
histopathological alterations in rodents within a few exposures.
Limited data indicate that the toxic response to acute oral exposure is
similar to that of inhalation exposure in humans and animals. Subchronic/chronic
oral administration of EDC at daily dosages of =200 mg/kg and higher caused
decreased growth rate and mortality in mice, which may have been tumor-related.
Chronic oral administration of lower dosages of EDC (-34 mg/kg/day) to rats
produced mortality that appeared to be due to non-neoplastic lesions including
bronchiopneumonia and endocardial thrombosis.
The available evidence suggests that EDC does not adversely affect the
reproductive or development process in laboratory animals except at maternally
toxic levels. Additional studies are needed, however, particularly with humans,
to conclusively establish that EDC is not a teratogen and does not cause adverse
reproductive effects.
Positive responses in different test systems representing a wide range of
organisms indicate that EDC is a weak direct-acting mutagen capable of causing
gene mutations. Several of its putative metabolites, thought to be formed in
rats and mice, are judged to be more potent mutagens than EDC. EDC has not been
adequately tested for its ability to cause chromosomal aberrations or heritable
effects. Further testing is needed to assess its ability to cause these effects.
EDC was shown to be carcinogenic in a lifetime gavage bioassay that was
conducted by the National Cancer Institute, producing tumors in both rats
-------
(forestomach carcinomas, cirulatory system hemangiosarcomas, subcutaneous
fibromas, mammary gland adenocarcinomas) and mice (hepatocellular carcinomas,
alveolar/bronchiolar adenomas, mammary carcinomas, endometrial tumors). EDC did
not produce a statistically significant increase in the incidence of lung
adenomas in strain A mice when administered intraperitoneally. However, benign
lung tumors (but not skin tumors) were induced in mice when applied to the skin.
No statistically significant increases in tumors occurred in rats or mice
following lifetime inhalation exposure. No case reports or epidemiologic
studies concerning EDC were avilable in the published literature for analysis.
From a weight-of-evidence approach, the direct and supporting evidence for
carcinogenicity includes: 1) positive findings in one oral rat study and one oral
mouse study, and supportive evidence in two other mouse studies; and 2) findings
that EDC is weakly mutagenic, and that certain metabolites show evidence of even
greater mutagenic potency. By using the International Agency for Research on
Cancer (IARC) classification scheme, the level of animal evidence, combined with
the nonexistence of human data, would constitute sufficient animal evidence that
EDC is a probable human carcinogen, the overall IARC ranking being Group 2B.
Using the animal data and a linear multistage extrapolation model, the upper-
bound
estimate of potency for EDC is q = 7 x 10 mg/kg/day calculated on the
basis of hemangiosarcomas in rats. The upper-bound estimate of the cancer risk
from ingesting water contaminated with 1 pg/il of EDC is 2 x 10" . The potency
index for EDC lies in the fourth quartile among 53 suspect carcinogens evaluated
by the Carcinogen Assessment Group. These potency and risk values are upper-
bound estimates; that is to say that the true values, while not identifiable,
would not likely exceed the upper-bound, and may be lower.
1-5
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2. INTRODUCTION
EPA's Office of Research and Development has prepared this health assess-
ment to serve as a "source document" for Agency use. This health assessment was
originally developed for use by the Office of Air Quality Planning and Standards
to support decision-making regarding possible regulations of ethylene dichloride
under Section 112 of the Clean Air Act. However, based on the expressed interest
of other agency offices, the scope of this document was expanded to address
ethylene dichloride in relation to sectors of the environment outside of air. It
is fully expected that this document will serve the information needs of many
government agencies and private groups that may be involved in decision-making
activities related to ethylene dichloride.
In the development of the assessment document, existing scientific litera-
ture has been surveyed in detail. Key studies have been evaluated and summary
and conclusions have been prepared so that the chemical's toxicity and related
characteristics are qualitatively identified.
The document considers all sources of ethylene dichloride in the envi-
ronment, the likelihood for its exposure to humans, and the possible effect on
man and lower organisms from absorption. The information found in the document
is integrated into a format designed as the basis for performing risk assess-
ments. When appropriate, the authors of the document have attempted to identify
gaps in current knowledge that limit risk evaluation capabilities.
2-1
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3. PHYSICAL AND CHEMICAL PROPERTIES
3.1 - NAME
Ethylene dichloride (EDC) is the common name for 1,2-dichloroethane. It is
also commonly referred to as ethylene chloride and S-dichloroethane (Archer,
1979).
3.2. CAS REGISTRY, RTECS, AND STORET NUMBERS
CAS Registry: 107-06-2
RTECS: KI05250000
STORET: 3^531
3.3- DESCRIPTION
Ethylene dichloride is a clear, colorless, volatile liquid with a pleasant
odor, and is stable at ordinary temperatures (Archer, 1979).
3.4. STRUCTURE
C1CH2CH2C1
3-5. PHYSICAL PROPERTIES OF PURE ETHYLENE DICHLORIDE
The physical properties of pure ethylene dichloride were taken from Archer
(1979) and Weast (1980), unless otherwise stated.
Molecular weight: 98.96
Melting point: -35.3°C
Boiling point: 83-7°C
Density at 20°C: 1.2529 g/m£
Viscosity: 1 .4451 m Pa S (cP)
Flashpoint:
Closed cup 1 7°C
Open cup 21°C
Explosive limits in
air at 25°C: 6.2-1 5.6$ by volume
3-1
-------
Autoignition tempera-
ture in air: H
Vapor pressure: ^C kPa Torr
10 5.3 40
20 8.5 64
30 13.3 100
Solubility in water: 0.0891 M (Valvani et al., 1981)
8,820 mg/£
Log Octanol/Water
Partition Coefficient: 1.48 (Valvani et al., 1981)
Henry's Law Constant
O _•( _ll
atm nr rool : 9.14 x 10 (Mabey et al., 1981)
Blood/Air Partition
Coefficient (37°C): 19.5 + 0.5 (Sato and Nakajima, 1979)
3-2
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4. SAMPLING AND ANALYSIS OF ETHYLENE DICHLORIDE
4.1 . SAMPLING
Taking environmental samples representative of the area in question is a
complex task beyond the scope of this document. A number of documents either
devoted exclusively to sampling or containing considerable information relating
to the subject are listed below and should be consulted prior to initiating
environmental sampling. For air, Singh et al. (1979, 1983), Pellizzari (1978),
and Pellizzari et al. (1979) have detailed sampling methodologies that describe
and/or show equipment and strategies. Water and wastewater sampling is described
by U.S. EPA (!982a) and solids sampling by U.S. EPA (I982b).
4.2. ANALYSIS
4.2.1. Ethylene Dichloride in Air. Ethylene dichloride in air can be analyzed
by a number of methods; however, the method of Singh et al. (1980) appears to be
substantially free of artifact problems and completely quantitative. In this
method, an air sample in a stainless steel canister at 32 psig is connected to a
preconcentration trap consisting of a 4" x 1/16" ID stainless steel tube
containing glass beads, glass wool, or 3% SE-30 on acid washed 100/120 mesh
Chromosorb W. The sampling line and trap, maintained at 90°C, are flushed with
air from the canister; then the trap is immersed in liquid 0? and air is passed
through the trap, the initial and final pressure being noted (usually between 30
and 20 psig) on a high-precision pressure gauge. The ideal gas law can be used to
estimate the volume of air passed through the trap. The contents of the trap are
desorbed onto a chromatography column by backflushing it with an inert gas while
holding the trap at boiling water temperature. An Ascarite trap may be inserted
before the chromatography column to remove water. Suitable columns include 10%
SP-1000 on Supelcoport (100/120 mesh, 15' x 1/8" stainless steel) and 0.2% CW-
4-1
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1500 on Carbopack C (80/100 mesh, 10' x 1/8" Ni). Both columns can be operated at
45°C with a carrier gas flow of 25 rnB,/minute on the former column and 40 m£/min-
ute on the latter. An electron capture detector operating at 330°C was found to
be optimum. It should be noted that the above authors found Tenax to be unsuit-
able for air analyses because of the presence of artifacts in the spectrum from
oxidation of the Tenax monomer. In addition, when Tenax is used as a sorbent,
safe sampling volumes (i.e., that volume of air which, if sampled over a variety
of circumstances, will not cause significant breakthrough) should be adhered to.
Brown and Purnell (1979) determined the safe volume for ethylene dichloride per
gram Tenax to be 27 & (flow rate 5-600 mil/minute; ethylene dichloride cone. <250
mg/m ; temp, up to 20°C) with a safe desorption temperature of 90°C.
The detection limits of this method were not specified and are dependent on
the volume of air sampled. Analyses as low as 33 ppt have been reported using
this method (Singh et al., 1980).
4.2.2. Ethylene Dichloride in Water. Ethylene dichloride in water can be
analyzed by the purge-and-trap method (Method 502.1) as recommended by the
Environmental Monitoring and Support Laboratory of the U.S. EPA (1981). In this
method, an inert gas is bubbled through 5 ml of water at a rate of 4C mil/minute
for 11 minutes, allowing the purgable organic compounds to partition into the
gas. The gas is passed through a column containing 3% OV-1 on Chromosorb W,
Tenax GC silica gel, and coconut charcoal at 22°C, which traps most of the
organics removed from the water. The adsorption column is then heated rapidly to
180°C and backflushed with helium (20-60 mS,/minute, 4 minutes) to desorb the
trapped organics. The effluent of the column is passed into an analytical gas
chromatography column packed with "\% SP-1000 on Carbopack-B (60/80 mesh,
8' x 0.1" ID) maintained at 40°C. The column is then temperature programmed
starting at 45°C for 3 minutes and increasing at 8°C/minute until 220°C is
4-2
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reached; it is then held there for 15 minutes or until all compounds have eluted.
A halogen-specific detector (or GC-MS) having a sensitivity of 0.10 ug/£ with a
relative standard deviation of <1 0$ must be used. This method is similar to EPA
method 601,624 for use with wastewater (U.S. EPA, 19820).
4.2.3. Ethylene Bichloride in Solid Samples. Ethylene dichloride in solid
samples may be analyzed by EPA method 8010 "Halogenated Volatile Organics" (U.S.
EPA, 1982b). With this method, a portion of the sample is dispersed in poly-
ethylene glycol or methanol. The dispersion is then mixed with water and purged
in a manner identical to the analysis of EDC in water. The trap contains 3% OV-1
on Chromosorb W (60/80 mesh), Tenax GC (60/80 mesh), Grade 15 silica gel (35/60
mesh), and activated coconut charcoal (6/10 mesh); desorption is performed at
180°C for 4 minutes with a gas flow of 20 to 60 mil/minute. Gas chromotographic
conditions are identical to the analysis of ethylene dichloride in water.
4.2.4. Ethylene Dichloride in Blood. Ethylene dichloride in blood can be
analyzed by using a modified purge-and-trap method (Pellizzari et al., 1979).
This method involves diluting an aliquot of whole blood (with anticoagulant) to
=50 mi with prepurged, distilled water. The mixture is placed in a 1 00 ml 3-neck
round bottom flask along with a teflon-lined magnetic stirring bar. The necks of
the flask are equipped with a helium inlet, a Tenax trap, and a thermometer. The
Tenax trap is a 10 cm x 1 .5 cm ID glass tube containing pre-extracted (soxhlet,
methanol, 24 hrs) and conditioned (270°C, 30 raft/minute helium flow, 20 minutes)
35/60 mesh Tenax (=1.6 g, 6 cm). The sample is then heated to 50°C and purged
with a helium flow rate of 25 mi/min for 90 minutes. Analysis can be performed as
indicated in Section 4.2.2.
4.2.5. Ethylene Dichloride in Urine. Ethylene dichloride in urine can be
analyzed by using an apparatus identical to the one described in Section 4.2.4,
using 25 mi of urine, diluted to 50 mi, instead of blood.
4-3
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J4.2.6. Ethylene Bichloride in Tissue. Ethylene dichloride in tissue can be
analyzed by using an apparatus identical to the one described in Section 4.2.4,
using 5 g of tissue, diluted to 50 m.?,, instead of blood and macerated in an ice
bath. The purge time is reduced to 30 minutes.
4-4
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5. SOURCES IN THE ENVIRONMENT
5.1. PRODUCTION PROCESSES
Two commercial processes account for virtually all of the EDC produced
currently. One is the direct chlorination of ethylene with chlorine. The other
is an oxychlorination process in which ethylene, hydrogen chloride and oxygen are
reacted to form EDC. Currently, most production centers around large manufac-
turing plants employing a balanced combination of both of these two processes.
Over 80$ of the EDC produced is used to make vinyl chloride monomer via dehydro-
halogenation of EDC. Most EDC producers have nearby vinyl chloride production
facilities. The balanced plants use the hydrogen chloride recovered when the EDC
is dehydrohalogenated to vinyl chloride as feed to the oxychlorination reactor.
This requires roughly a 50-50 split between direct chlorination and oxychlorina-
tion for a completely balanced operation assuming all EDC is cycled to the vinyl
chloride facilities. In this manner, there will be no net production of hydrogen
chloride. As of 1974, =58$ of the total EDC production capacity was based upon
direct chlorination and -^2% was based upon oxychlorination (Pervier et al,
197^). Current capacities are judged to be roughly the same.
In the direct clorination process, EDC is produced by the catalytic vapor-or
liquid-phase chlorination of ethylene as follows (Archer, 1979):
FeCl
CH9 = CH,, + C19 (5% air) - ^ - > C1CH5CH5C1
* d
Most liquid-phase processes use ferric chloride as the catalyst. The chlori-
nation is carried out at J40-50°C with 5% air added to prevent substitution
chlorination of the product.
The oxychlorination process is usually incorporated into an integrated
vinyl chloride plant in which hydrogen chloride (which is recovered from cracking
5-1
-------
the EDC to vinyl chloride) is recycled to an oxychlorination unit (Archer, 1979).
The hydrogen chloride by-product is used as the chlorine source in the chlorina-
tion of ethylene in the presence of oxygen and copper chloride catalyst as
follows:
CuCl
2CH = CH? + 4HC1 + Op —> 2C1CH_CH,,C1 + HO
270°C d d d
5.2. ETHYLENE BICHLORIDE PRODUCERS
The producers of EDC in the U.S. are listed in Table 5-1 along with their
respective production capacities. As can be noted from Table 5-1 , most of the
production capacity is located in Texas and Louisiana. These production facili-
ties also captively consume the major portion of the EDC produced, as in the
manufacture of vinyl chloride and, to a much lesser extent, in the manufacture of
vinylidene chloride and various chlorinated solvents. From Table 5-2, it can be
noted that only -10% of the EDC production has been sold on the open market in
most recent years.
5.3. ETHYLENE DICHLORIDE PRODUCTION AND TRENDS
U.S. production volumes and sales of EDC are listed in Table 5-2. Blackford
(197-4) and the U.S. International Trade Commission 0974) have stated that the
production volumes as listed may be somewhat smaller than the actual production
because some EDC may be produced, but not separated or accurately measured (and
therefore not reported) by some producers. Blackford (1974) has estimated actual
productions on the order of 10? higher than the reported productions.
The demand for EDC for the years 1982 and 1983 has been estimated to be
4.127 and 4.716 million metric tons, respectively, while the demand for the year
1987 is expected to be 5.487 million metric tons (CMR, 1983). Production of EDC
in 1982 was sharply lower than in preceding years (see Table 5-2). This was
largely due to a recession in the vinyl chloride market and a decision of
5-2
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TABLE 5-1
Major Manufacturers of Ethylene Dichloridec
Manufacture
Plant Sites
Annual Capacity
(Millions of Metric Tons)
Atlantic Richfield (ARCO)
Borden, Inc.
Dow Chemical USA
E.I. duPont (Conoco)
Ethyl Corp.
Formosa Plastics Corp.
Georgia-Pacific Corp.
B.F. Goodrich Co.
PPG Industries
Shell Chem. Co.
Union Carbide Corp.
Vulcan Materials Co.
Port Arthur, TX
Geisrnar, LA
Freeport, TX
Oyster Creek, TX
Plaquemine, LA
Lake Charles, LA
Baton Rouge, LA
Pasadena, TX
Baton Rouge, LA
Point Comfort, TX
Plaquemine, LA
Deer Park, Tx
La Porte, TX
Calvert City, KY
Convent , LA
Lake Charles, LA
Deer Park, TX
Norco, LA
Taft, LAd
Texas City, TX
Geismar, LA
0.200
0.230
0.725
0.500
0.840
0.525
0.320
0.110
0.240
0.385
0.735
0.110
0.720
0.450
0.360
1 .230
0.620
0.540
0.070
0.070
0.160
Total 9.140
Note: Capacities are flexible depending on finishing capacities for
vinyl chloride and chlorinated solvents.
SRI, 1983; CMR, 1983
Operated under a toll agreement with Diamond Shamrock Corp.
'Closed for an indefinite time period because of the temporary closing
of Shell's vinyl chloride monomer plant located there.
Captive use only.
5-3
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TABLE 5-2
O
U.S. Production and Sales of Ethylene Dichloride
Year
1982
1981
1980
1979
1978
1977
1976
1975
1974
1973
1972
1971
1970
1965
1960
1950
Millions
Production
3.^55
4.523
5.037
5.349
4.989
4.987
3.647
3-617
4.156
4.214
3.541
3.428
3-383
1 .113
0.575
0.138
of Metric Tons
Sales
0.640
0.401
0.510
0.633
0.469
0.692
0.61 7
0.345
0.596
0.613
0.656
0.595
0.596
0.140
0.198
0.021
aUSITC, USTC, 1952-1982
Production totals may be understated in some years because some
ethylene dichloride is produced but not separated or accurately
measured (and therefore not reported) by some producers.
5-4
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producers to use their EDC inventories during the winter of 1982 (Chemical and
Engineering News, 1982, 1983). Production of EDC is expected to rebound during
1983. Historically, the demand for EDC grew at a rate of -1% per year during the
period from 1973-1982. Demand is anticipated to grow at a rate of 4? per year
through 198? (CMR, 1983).
5.4. ETHYLENE DICHLORIDE USES
A major portion (84$) of U.S. EDC production is converted to vinyl chloride
monomer. The major uses of EDC for the years 1983, 1980, 1977 and 1974 are given
in Table 5-3. Consumption of EDC for specific end-uses is given in Table 5-4.
In addition to vinyl chloride, EDC is used as a starting material in the
production of chlorinated solvents such as 1,1,1-trichloroethane, trichloro-
ethylene and perchloroethylene and as intermediate in the production of
ethylenearnines and vinylidene chloride (Archer, 1979; Blackford, 1974). Table
5-5 lists the users of EDC for these purposes. In general, these users are also
producers of EDC.
EDC is used as an additive (lead scavenger) in tetraethyllead antiknock
mixtures for gasolines. Scavenging agents are used in gasolines to transform the
combustion products of lead alkyls to forms that are more likely to be vaporized
from the engine surfaces. The most important lead scavengers used for this
purpose are EDC and ethylene dibromide (McCormack et al., 1981 ; Blackford, 1974).
The sale of tetraalkyllead compounds is always in admixture with EDC and/or
ethylene dibromide. Conventional motor-mix formulations contain 1 mol of EDC and
1/2 mol of ethylene dibromide per mol of tetraethyllead (McCormack et al., 1981).
This use of EDC is expected to decline in future years due to EPA regulations
concerning the use of leaded gasolines. CMR (1982) projects that the demand for
lead in gasoline will decrease at a rate of 11 % per year (average) through 1986.
5-5
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TABLE 5-3
Ethylene Bichloride Uses'
Use
Vinyl chloride monomer
Chlorinated solvents
Vinylidene chloride
Exports
Lead scavenger
Amines
Miscellaneous
1983
81
H
2
9
—
—
lb
Percent of Total
1980 1977
81 80
7 10
2
5
3
—
2b ?c
1974
78
8
—
—
3
2
9C
CMR, 197M, 1977, 1980, 1983
b.
includes lead scavenger
c.
includes exports
5-6
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TABLE 5-4
Consumption of Ethylene Bichloride in 1979 and 19743
Consumption (Thousands of Metric Tons)
Vinyl chloride monomer
1 ,1 , 1 -Trichloroethane
Trichloroethylene
Perchloroethylene
Vinylidene chloride
Ethyleneamines
Lead scavenger
Exports
Preparation of polysulfides
Paints, coatings and adhesives
Extraction solvents
Cleaning of fabric and polvinyl
chloride equipment
Grain fumigation
Other uses
Total
1979 %
4420 85.0
—
89.4 1.7
—
118.7 2.3
168.1 3.2
81.7 1.6
179.0 3.4
0.5
1.36
1.05
0.91
0.46
0.46
5199.44 99.8
1974
3894.2
153-3
132.8
124.7
97.0
131 .5
97.0
167.3
—
—
—
—
—
6.8
4804.4
%
81 .0
3.2
2.8
2.6
2.0
2.7
2.0
3.5
—
—
—
—
—
0.1
99.9
aSeufert et al., 1980; Blackford, 1974
5-7
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TABLE 5-5
Users of Ethylene Bichloride for Intermediate Purposes
Vinylidene
1 ,1 ,1-Trichloroethane Trichloroethylene Perchloroethylene Ethyleneamines Chloride
ui
do
Dow Chem. USA
Freeport, TX
Plaquemine, LA
PPG Industries
Lake Charles, LA
Union Carbide Co.
Taft, LA
Texas City, TX
Diamond Shamrock Corp.
Deer Park, TX
E.I. duPont
Corpus Christi, TX
X
X
X
X
X
X
X
X
SRI, 1983; Blackford, 1974
X = produces this chemical from ethylene dichloride
-------
Exports of EDC have been increasing in recent years (see Table 5-6).
Exports may grow by as much as 8% per year through the mid-8Os (CMR, 1983). The
Japanese are expected to become major importers as they close down significant
amounts of mercury cell chlor-alkali capacity because of environmental regula-
tions. However, part of that demand will be filled by Shell's one billion
pounds/year EDC plant in Jubail, Saudi Arabia, which is due on stream in 1985.
EDC has a variety of relatively small miscellaneous uses. It is used as a
solvent in applications that include textile and PVC cleaning, metal degreasing,
extractions, and use in paints, coatings and adhesives. As an intermediate, EDC
is used to produce polysulfide elastomers and ethylenimine (aziridine). Dow
chemical captively consumes several million pounds per year of EDC at their
Freeport, TX, facility to produce ethylenimine. EDC is used as a grain fumigant;
Auerbach Associates (1978) estimated grain fumigant uses in grain; Metcalf
(1981 ) lists EDC as a fumigant for use in household and soil applications. Other
uses mentioned for EDC include varnish and finish removers, soaps and scouring
compounds, wetting and penetrating agents and ore flotation (Hawley, 1981).
5.5. SOURCES OF EMISSIONS
EDC can enter the environment through atmospheric emissions, waste
effluents to waterways, and land disposals of liquid and solid wastes. EDC in
liquid and solid waters evaporates rapidly because of its high volatility;
consequently, releases to land and water can be expected to predominantly enter
the atmosphere. The sources of EDC emissions are during EDC manufacture, inter-
mediate use of EDC in production of other chemicals, and dispersive uses of EDC
in end-point product applications.
A number of estimates have been generated which predict the amount of EDC
that is released to the environment. These estimates are based, in large part,
on a sampling of monitoring data and a variety of engineering estimates. In many
5-9
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instances, the impact of current control technology may not have been adequately
assessed. Therefore, the estimates that have been generated for EDC releases
should not be interpreted as exact measurements, but are best regarded as order
of magnitude estimates. Estimates of releases are in Table 5-6.
Table 5-6 lists sources of EDC emissions in 1979 and estimates of the
amounts released in air, water, and solid waste. Total 1979 emissions to the
atmosphere, water, and solid waste amounted to 12,238 metric tons. The data in
Table 5-6 indicate that gaseous emissions from EDC production amounted to 52.3%
of total atmospheric releases, while feedstock uses, dispersive applications,
and exports accounted for 12.6, 33.6, and 1.5/6, respectively (Seufert et al.,
1980).
Utilizing data from EDC producers, state and local emissions control
agencies, and the open literature, Hobbs and Key (1978) estimated 1978 emissions
of EDC at -11,000 metric tons. The degree of current emissions control on
domestic processes involved in the primary production of EDC was assessed by
Hobbs and Key (1978).
Estimates by SRI International (U.S. EPA, I979a) indicated that total
domestic emissions of EDC from primary production, fugitive sources, and tank
storage are 44,000 metric tons or -O.Q% of the amount produced. The impact of
current control technology was not addressed in the report.
Eimutis and Quill (1977) estimated process emissions of EDC for 1977 at
50,000 metric tons. Presumably, this estimate did not take into account current
control technology.
For 1974, Patterson et al. (1975) estimated total domestic emissions at
74,000 metric tons. Total domestic emissions for 1973 were reported at 54,000
metric tons by Shamel et al. (1975). The sources of EDC releases are discussed
below.
5-10
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TABLE 5-6
Estimated Environmental Releases of Ethylene Bichloride in 1979
Application
Production of 1 ,2-dichloroethane
Indirect production
Feedstock uses
Trichloroethylene
Tetrachloroethylene
1 ,1 -Dichloroethylene
Ethyleneamines
Preparation of polysulfides
Vinyl chloride
Exports
Dispersive uses
Lead scavenging
Fabric and PVC equipment cleaning
Paints, coatings, adhesives
Extraction solvents
Grain fumigation
Miscellaneous uses
Total
Releases (metric
Air Water
6 , 1 54 61
65 191
73
138
86
1 04
5
136
180
956
864
1,364
1,000
460
300
11,885 252
tons)
Solid waste
5
46
50
101
aSeufert et al., 1980
5-11
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5.5.1. Production and Related Facilities. In general, EDC is produced commer-
cially at an integrated manufacturing facility which uses some or all of the
produced EDC to make vinyl chloride and, in some cases, other derivatives. In a
typical vinyl chloride manufacturing facility, waste streams are generated by
the three distinct processes: direct chlorination of ethylene, oxy-chlorination
of ethylene, and dehydrochlorination to vinyl chloride, these are typically
combined at a given facility for recovery, treatment and disposal. The specific
number of point sources of releases at a manufacturing site is a function of
plant design. Point sources of EDC loss from an integrated vinyl chloride plant
include direct and oxy-chlorination reactor vent streams, light-ends distilla-
tion column vent, heavy-ends from the EDC recovery tower, wastewater from drying
columns and scrubbers, and fugitive emissions from storage, pumps, seals, etc.
(Catalytic, 1979; U.S. EPA, I979b). Releases from these manufacturing sites are
mostly to the atmosphere and arise largely from vent gas streams (U.S. EPA,
I979b). Control devices used to limit EDC escape to the atmosphere include
thermal oxidizers, catalytic oxidizers, vent condensers, scrubbers, and vent gas
post-reactors (Hobbs and Key, 1978).
Combined wastewaters which are generated from EDC manufacture (vent gas
scrubbers, water produced during oxy-chlorination, and washwater) are treated in
several ways depending upon the plant (Catalytic, 1979). Treatments include pre-
treatment and steam stripping prior to biological treatment, incineration of a
portion of the waste stream, neutralization and chemical treatment, secondary
treatments and final discharges to surface waters, to public owned treatment
works, or to deep-well injection. Estimates of the amounts of EDC released to
the surface waters are dependent upon engineering estimates of the overall
success of treatments and the volume of wastewater flow.
5-12
-------
Solid wastes generated at an integrated vinyl chloride plant are usually
treated to recover organic compounds present, Wastes are subsequently disposed
of in a landfill or incinerated, recovering chlorine as hydrogen chloride
(McPherson et al., 1979). Some solid wastes, possibly tars and heavy-ends, may
be a suitable feedstock for tetrachloroethylene/carbon tetrachloride via a
chlorination process.
5.5.2. Dispersive Uses.
5-5.2.1 . LEAD SCAVENGING — Seufert et al. (1980) estimated that, 956 metric-
tons of EDO were released to the environment in 1979 from lead scavenging
applications. Releases occur during blending of the gasolines, refueling of
automobiles, filling and evaporation from gasoline storage tanks, and combustion
of the gasoline. Approximately '% of the EDC used for lead scavenging is
estimated to be released into the environment; the remainder is converted to
hydrogen chloride and then to lead chloride during combustion.
5.5.2.2. PAINTS, COATINGS, ADHESIVES — In this application, EDC is used as
a solvent that is allowed to evaporate. Therefore, all of the EDC is emitted to
the environment.
5.5.2.3. GRAIN FUMIGATION -- Fumigants are defined as gaseous pesticides.
They must remain in the gas or vapor state and in sufficient concentration to be
lethal to the target pest species. Therefore, all of the EDC used for this
purpose will be vented to the atmosphere, as there are no control methods used.
5.5.2.4. FABRIC AND PVC CLEANING — It is presumed that most EDC used for
cleaning purposes will eventually be emitted to the atmosphere. Some cleaning
wastes from PVC reactors may be drummed for landfill disposal.
5.5.2.5. OTHER DISPERSIVE USES — In ether dispersive uses, it has been
assumed that most EDC will eventually be emitted to the atmosphere. Some may be
landfill, as with extraction solvents, and some may be incinerated.
-------
5.5.3. Conclusions. The major sources of EDC emissions are from vent gas
streams released during the manufacture of EDC and subsequent integrated produc-
tion of vinyl chloride monomer, and other EDC derivatives. Significant amounts
of EDC are also released to the environment from dispersive uses. In 1979, an
estimated 6,696 metric tons of EDC were released to the atmosphere from EDC
production and feedstock uses, while an estimated 4,944 metric tons were released
to the atmosphere from dispersive uses (see Table 5-6).
5-14
-------
6. FATE AND TRANSPORT IN THE ENVIRONMENT
The fate and transport of EDC in the environment depend on the medium in
which it is present. The fate and transport of EDC in three environmental media
(atmosphere, water and soil) are discussed below. Since a large percent of EDC
emitted into the environment is in the atmospheric medium (see Chapter 4), the
fate and transport of the chemical in this medium deserve special attention.
6.1. ATMOSPHERE
The fate of EDC in the atmosphere is dictated by its ability to undergo
chemical and physical removal processes in this medium. Reaction with *OH
radicals is the principal chemical process by which many organic compounds
including EDC are removed from the atmosphere (Crutzen and Fishman, 1977; Singh,
1977; Altshuller, 1979; Cupitt, 1980). Photolysis of 0_ in the troposphere
produces singlet atomic oxygen [01 n] that then reacts with water vapor to produce
•OH radicals. The tropospheric half-life (t. .„) of a compound is related to the
•OH radical concentration according to the expression:
t 0-693
1/2 ~ Kt'OH]
where K is the rate constant of the reaction and [»OH] is the concentration of
•OH radicals.
It is obvious from the above equation that an estimation of the tropospheric
half-life for EDC due to »OH radical reaction requires that the values of both K
and [*OH] be known. There are only two measurements of EDC reaction rate
constant with *OH radicals. The absolute rate constant for EDC reaction with 'OH
radicals was determined by Howard and Evenson (1976) in a conventional discharge
flow system. The value of the rate constant obtained in the system at pressures
6-1
-------
ranging from 0.7 to 7 mm Hg and at a temperature of 23°C was 22+5 (standard
deviation of average) cm molecule" sec" .
The rate constant for the reaction of «OH radicals with EDC in the presence
of Op and N? was determined by Butler et al. (1978). At 29.5°C and a total
pressure of 400 mm Hg, the reaction rate constant was determined to have a
probable value of 6.5 x 10~^ cm molecule" sec" with an upper limit value of
29 x 10~ cm molecule" sec" . Although Butler et al. (1978) argued that the
presence of oxygen and nitrogen at a pressure of 400 mm Hg was more represen-
tative of actual tropospheric conditions, the presence of 0? and N? actually
complicated the reaction scheme through side reactions and made the extraction of
kinetic data more difficult. It is for this reason that Butler et al. (1978)
failed to determine the precision of the determined rate constant value.
Therefore, the measured rate constant value of 22.0 + 5 cm molecule" sec" for
EDC reaction with »OH radicals as reported by Howard and Evenson (1976) appears
to be more accurate than the value of 6.5 x 10" cm molecule" sec" as given by
Butler et al. (1978).
In Table 6-1, the rate constants for a number of chlorinated ethanes,
including EDC, at room temperature have been shown. It seems clear from this
_1 ii o _i _i
table that a value of 22.0 x 10 cnr molecule sec is more consistent with
-1 4
the measured K values for other chlorinated ethanes than a value of 6.5 x 10
3 -, -, -1 -1
cm molecule sec
On the basis of the above discussion, it is reasonable to accept a value of
22 x 10" cm molecule" sec" as the rate constant value for EDC reaction with
•OH radicals at 296°K (room temperature).
It should be recognized that the value of K is dependent on temperature.
The temperature in the troposphere is dependent on latitude, altitude and
seasonal variations. The average annual tropospheric temperature weighted over
6-2
-------
TABLE 6-1
Rate Constants for a Few Chlorinated Ethanes
at Room Temperature
Compound
. Rate Constant
10 cm molecule" sec~
Reference
CH_CHC12
CH2C1CH2C1
CH2C1CHC12
39, 44
26
22, 6.5
33
Howard and Evenson,
1976; Butler et al.,
1978
Howard and Evenson,
1976
Howard and Evenson,
1976; Butler et al.,
1978
Singh et al., 1981
6-3
-------
those variables is close to 265°K, or -8°C (Altshuller, 1979). Therefore, the
evaluation of reaction rate at this temperature representing an average
tropospheric reaction rate must incorporate the rate constant value at 265°K.
When the rate constant is not known, Altshuller (1979) estimated it by dividing
the K value at 298°K by 1.75. This is an empirical relationship and is
applicable only to saturated organic compounds. Therefore, the rate constant for
? x U
1 .75
-1 4
EDC reaction with *OH at 265°K can be estimated as cm molecule" sec"
or 12.6 cm molecule" sec
The second factor required for the evaluation of tropospheric half-life for
EDC reaction with «OH radicals is the average 'OH concentration. Besides
hemispheric difference, the concentration of *OH radicals in the troposphere is
dependent on latitude, altitude and seasonal variations. The concentration of
tropospheric *OH radicals in the Northern Hemisphere across the latitudes of the
continental United States has been estimated by different investigators to range
f T
from 0.2 to 0.9 x 10 molecules cm"3 annually (Logan et al., 1981; Crutzen and
Fishman, 1977; Neely and Plonka, 1978). Singh et al. (1983) have recently
estimated a mean hydroxyl radical concentration of 0.4-0.6 x 10 molecules cm
over the troposphere of continental United States. Therefore, a value of 0.5 x
1 0 molecules cm is a good estimate for the average tropospheric hydroxyl
radical concentration over the continental United States. It should be
emphasized that the *OH concentration can vary substantially from the average
value of 0.5 x 10 molecules cm . Calvert (1976) estimated the average ambient
level of *OH radicals in the morning hours in Los Angeles to be -2.6+2x10
molecules cm. Assuming equal periods of daylight and darkness, the average
concentration for a 24-hour day should be -1 x 10 molecules cm" .
The calculations of tropospheric half-life for EDC reaction with *OH
radical can be made under two scenarios. In the first case, a rate constant
_11| o _•) _i
value at ambient temperature (22 x 10 cnr molecule sec ) and an
6-4
-------
•OH concentration of 1 x 1 0 molecule cm~^ can be used to derive the half-life
value of 36 days. In the second case, a rate constant value of 265°K
corresponding to annual average tropospheric temperature over continental United
States (12.6 x 10" cm3 molecule" sec" ) and a value of *OH concentration of
0.5 x 10 molecules cm~-^ corresponding to the annual average tropospheric
concentration of *OH radical over continental United States can be used to derive
a half-life value of 127 days. Therefore, the tropospheric half-life for EDC
reaction with 'OH may vary from 36 to 127 days.
The reactivity of EDC with chlorine atoms was studied by Spence and Harst
(1978). These investigators found that the chlorine-sensitized photooxidation
of 10 ppm EDC with H ppm Cl at 22.5°C and irradiated by UV lamp (365 nm
wavelength max.) and sun lamp (310 nm wavelength max.) produced a number of
reaction products. Although hydrochloric acid (6.5 ppm), carbon monoxide (1
ppm), formyl chloride (3.5 ppm), CO (2 ppm) and chloroacetyl chloride (0.5 ppm)
were formed, no phosgene could be detected as a reaction product. EDC was found
to have a relatively low reactivity towards Cl atoms compared to other
chlorinated ethanes.
That a chlorine-sensitized photooxidation is representative of actual
tropospheric conditions has been contested by Singh (1978), This investigator
estimated that chlorine atom concentrations in simulation chambers can be 1 0 to
10 times larger than in the troposphere. Thus, the role of chlorine atoms would
be minimal under actual tropospheric conditions where »OH radicals are
predominant.
The role of halocarbons in the catalytic destruction of ozone (0_) is well
documented (Altshuller, 1979; Altshuller and Hanst, 1975). Any halogenated
compound with a sufficiently long lifetime may be transported to the stratosphere
where photolytic mechanisms may release halogen atoms to participate in the
6-5
-------
destruction of 0_. The rate of reaction of *OH with halocarbons is one mechanism
which competes with stratospheric photolysis as a halocarbon sink.
Since transport to the stratosphere is a relatively slow process, the
reported half-life for EDC suggests that only a small fraction released in the
troposphere will reach the stratosphere. Thus, emissions of EDC would not be
expected to play a significant role in the catalytic destruction of ozone.
However, in the view of Altshuller and Hanst (1975), EDC should be considered a
threat in this regard since the production volume of EDC is so large. These
investigators cite chloroacetyl chloride as the sole product of EDC reaction with
•OH. The possibility that this reaction product may have sufficient stability to
travel to the stratosphere was raised. If formed in the troposphere, most of the
chloroacetyl chloride probably will be washed out by rain. If it travels to the
stratosphere, however, it may undergo photodissociation to form atomic chlorine.
The three most likely physical processes that may participate in the removal
of EDC from the atmosphere were studied by Cupitt (1980). The half-life for EDC
removal by rain droplets was estimated to be 390 years. EDC in the vapor phase
may be adsorbed on aerosol particles and removed from the atmosphere with the
aerosol. However, the half-life of this removal process was estimated to be =13
years (Cupitt, 1980). It has been estimated by Cupitt (1980) that compounds with
_7
saturation vapor pressures of <10 mm Hg are likely to be adsorbed on
atmospheric aerosols. Since the vapor pressure of EDC is much higher, it is not
expected to be adsorbed by aerosol and the probability of its removal by this
process seems to be remote.
The third physical removal mechanism, dry deposition of EDC, was also
studied by Cupitt (1980). He estimated a half-life value of 25 years for this
process. Therefore, it is not expected to be a significant EDC removal mechanism
from the atmosphere.
6-6
-------
It is apparent from the above discussion that physical processes are not
significant for the removal of EDC from the atmosphere. Of the chemical
processes, the most significant reaction that may account for the partial removal
of EDC from the atmosphere is its reaction with *OH radicals. The half-life for
the process has been estimated to be =36 to 127 days. Therefore, it is
anticipated that EDC will persist for a relatively long time in the atmosphere
and may participate in intramedia transport from its source of emissions.
6.2. AQUATIC MEDIA
The fate of EDC in aquatic media is expected to be determined by its
chemical, physical and microbiological removal mechanisms. The fate of EDC with
respect to its possible chemical reactions has been reported by Callahan et al.
(1979). Both photolysis and hydrolysis of EDC in aquatic media are expected to
be insignificant fate processes (Callahan et al., 1979). Based on the oxidation
rate constant data given by Mabey et al. (1981) and the concentration of free
radicals in aquatic media given by Mill et al. (1982), the oxidation of EDC by
singlet oxygen (K«360 M~ hr~ ) and peroxy radicals (1 M hr ) can be
predicted to be environmentally insignificant processes.
The degradation possibilities of EDC by microorganisms in aquatic media
have been studied by several authors. From the results of the laboratory tests
conducted by several investigators with activated sludge or sewage seed as
raicrobial inoculum in aquatic media, it can be concluded that EDC may biodegrade
slowly under these conditions (Price et al., 197**; Tabak et al., 1981; Ludzack
and Etlinger, 1960; Henckelikian and Rand, 1955; Stover and Kincannon, 1983).
Under anoxic conditions, Bouwer and McCarty (1983) observed very little
degradation of EDC with anaerobic inoculum. In a river die-away test, Mudder et
al. (1982) reported no degradation of EDC at concentrations of -1 ppm and above.
It can be concluded from these discussions that biodegradation will be an
insignificant fate process for EDC in ambient aquatic media.
6-7
-------
The two likely physical processes that may remove EDC from aquatic media are
sorption and volatilization. The removal of EDC by sorption on sediments and the
subsequent sedimentation is probably not a significant process (Callahan et al.,
1979; Mabey et al., 1981). A calculation based on EXAMS modeling by the method
of Burns et al. (1982) with the input parameters given in Section 3 also shows
that EDC is not likely to be significantly sorbed onto particulate matter in
water.
The evaporation half-life for EDC from water at a depth of 1.6 cm, a
concentration of 2 ppm, and a temperature of 24°C was estimated to be 8 minutes
under stirring (Chiou et al., 1980). Under more realistic conditions of a wind
speed of 3 m/sec, water current of 1 m/sec, and a water depth of 1 m, Lyman et al.
(1982) calculated the evaporation half-life of EDC as 4 hours.
The bioconcentration factor (BCF) for EDC in aquatic organisms was
estimated as 6.03 by Kenaga (1980) from the water solubility and a linear
regression equation. In a 14-day exposure experiment with bluegill sunfish
(Lepomis macrochirus), Barrows et al. (1980) determined a BCF of 2.0 for this
compound. Therefore, EDC is not likely to bioconcentrate in aquatic organisms.
It can be concluded from the discussion above that the primary removal
mechanism of EDC from aquatic media is probably volatilization. The half-life
for volatilization is such that the compound may persist in aquatic media for a
reasonable period and may participate in transport in aquatic bodies.
6.3. SOIL
Data pertaining to the fate of EDC in soil are very limited. If one
considers the chemical reactivity of EDC in aquatic media (see Section 6.2), it
is possible to speculate that chemical reactions of EDC may be faster in soil
than in water, particularly with soil acclimatized with EDC. However, Wilson et
6-8
-------
al. (1981 ) found virtually no biodegradation of EDC with soils collected near
Ada, OK, that contained an average sand of 92% and organic carbon of 0.09?.
The sorption constant (K ) of EDC on soils was predicted by Kenaga (1980)
OC
to be 43 (standardized with respect to soil organic content) from regression
equation and solubility of this chemical in water. Chiou et al. (1979) estimated
a value of 19 for K with Williamette silt loam containing 1 .6$ organic matter,
oc
26% clay, 3.3% sand and 69$ silt. Therefore, the compound is not expected to be
sorbed strongly onto soils, particularly onto soils containing low organic
matter, and may percolate through the soil column. This has been confirmed by
Wilson et al. (1980), who found -50% percolation of EDC through a column of 140
cm depth containing the previously described Oklahoma soil. The fact that Page
(1981) reported the detection of EDC in 10% groundwater samples in NJ also
indicates that the compound may transport downwards through some soils.
The volatilization of EDC from soil may be an important removal mechanism.
However, very few investigative data are available on this subject. Again, if
one considers the investigation of Wilson et al. (1981 ) that reported the loss of
50% EDC from the soil column through volatilization, one can conclude that
volatilization may be one of the most significant physical removal processes for
EDC from soil
6.4. SUMMARY
Based on available kinetic data and average tropospheric hydroxyl free
radical concentration, the half-life of EDC, the most likely removal mechanism
for EDC from the atmosphere, has been estimated to range from 36 to 127 days. Due
to different factors that may cause variations in *OH concentrations in the
troposphere, the persistence of EDC could vary somewhat from the estimated value.
Chloroacetyl chloride is probably the principal product resulting from the
reaction of EDC with *OH radicals.
6-9
-------
EDC is not expected to play a significant role in stratospheric ozone
destruction reactions due to its relatively short tropospheric half-life.
However, chloroacetyl chloride may have suffficient stability to diffuse to the
stratosphere and may participate in UV reactions producing chlorine atoms.
In the aquatic environment, the most significant removal mechanism appears
to be its volatilization. The half-life for this process has been estimated to
be -4 hours. Therefore, EDC may persist in the aquatic media for a reasonable
period and may participate in its transport in water bodies.
From the little information that is available regarding the fate of EDC in
soil, it has been concluded that both volatilization from and leaching through
soil are the two significant removal mechanisms for EDC.
6-10
-------
7. ENVIRONMENTAL LEVELS AND EXPOSURE
7.1 . ENVIRONMENTAL LEVELS
EDC contamination of the environment can result from the manufacture, use
and disposal of the chemical. Sources of environmental release and quantitative
estimates of releases are discussed in Section 5 of this report. This section is
concerned with the levels of EDC that have been detected in various areas and
monitoring sites. Sizeable quantities of EDC are judged to be released to the
air during manufacture and conversion to vinyl chloride at an integrated manufac-
turing site. This judgement is borne out by the high ambient concentrations of
EDC found near several of these sites.
7.1 .1 . Atmospheric Levels. In addition to atmospheric releases of EDC from
manufacture and feedstock uses, EDC can be released to the air from dispersive
uses such as grain fumigation, solvent uses in paints, coating and adhesives,
cleaning applications, and gasoline uses related to lead scavenging.
Recent air monitoring data for EDC are listed in Table 7-1 . These data
indicate that EDC is often present in ambient air in urban and industrial areas,
especially near plants manufacturing or using the chemical. Recent measurements
made at sites in three geographical areas central to EDC production and user
facilities indicated EDC concentrations as high as 18H ppb (Elfers, 1979). These
levels were associated with industrial sources and occurred during atmospheric
conditions of calm or low wind speeds. Measurements were made during 10 to 13
day periods at Lake Charles and New Orleans, LA, and at Calvert City, KY. The
highest concentrations were reported for the Lake Charles area, with the highest
single concentration being 184 ppb and the average detectable concentration
being 27.5 ppb. In Calvert City, ambient concentrations ranged from <0.12 to
7-1
-------
TABLE 7-1
Ambient Atmospheric Levels of Ethylene Diehloride
Location
ALABAMA
Birmingham
Birmingham
ARIZONA
Phoenix
Grand Canyon
CALIFORNIA
Dominguez
Los Angeles
Oakland
Riverside
Upland
Upland
COLORADO
Denver
ILLINOIS
Chicago
KENTUCKY
Calvert City
Calvert City
LOUISIANA
Baton Rouge
Baton Rouge
Geismar
Iberville Parish
Lake Charles
Type of Site Date
April, 1977
April, 1977
urban
rural Nov-Dec 1977
May, 1976
urban
urban Aug-Sept 1977
August, 1980
Aug-Sept 1977
June, 1980
April, 1981
12 cites near Aug-Sept 1978
chem. plant
Aug-Sept 1978
March, 1977
March, 1977
Industrial Feb, Mar 1977
Jan, Feb 1977
June-Oct 1978
Analytical Number of
Method Samples
2
7 (1 ND)
GC/ECD
7 (7 ND)
1
GC/ECD
GC/ECD
GC/ECD 1 02
8
16 (11 ND)
GC/ECD 9 5
GC/ECD NR
156
GC/MS 88
25 (9 ND)
GC/MS 18 (2 ND)
10 (1 ND)
11
98
Concentration (ppt, v/v)a
Max.
98.6
99
1151 .1
—
—
1351.8
813.0
580
212.9
210
180
2820
17819.2
17800
630
2556.5
2551.5
1161.2
61000
Min.
50.7
0
38.8
173.0
38.3
89
61.8
0
100
22
0
<120
0
19.3
21.7
2.2
150
Avg.
71.7
35
216.3
3662.3
519.2
82.5
360
110.3
27
210
195
1631.6
5000
270
129.1
760.1
320.9
27000
Reference
Pellizzari and
Bunch, 1979
Pellizzari, I979a
Singh et al., 1980
Pellizzari, I979a
Pellizzari and
Bunch, 1979
Singh et al., 1980
Singh et al,, 1980
Singh et al., 1980
Pellizzari and
Bunch , 1 9 79
Pellizzari, I979a
Singh et al., 1980
Singh et al., 1982
Suta, 1979
Elfers, 1979
Pellizzari et al., 1979
Pellizzari, 1978a
Pellizzari, I978a
Pellizzari, I978a
Pellizzari, !979b
-------
TABLE 7-1 (cont.)
Location
LOUISIANA (cont.)
Lake Charles
Lake Charles
Lake Charles
New Orleans
New Orleans
Plaquemlne
MISSOURI
St. Louis
NEW JERSEY
Batsto
Bound Brook
Bridgeport
Brldgewater
Burlington
Camden
Carlstadt
Clifton
Deepwater
East Brunswick
Edison
Edison
Type of Site Date
June, 1978
Sept-Oct 1978
12 sites near Sept, Oct 1978
chem. plant
October, 1978
near chem. October, 1978
plant
Jan, Feb 1977
May-June 1980
rural Feb-Dec 1979
off highway March, 1976
September, 1977
July-Aug 1978
September, 1977
urban Apr-Oct 1979
September, 1979
March, 1976
near chem. June, 1977
plant
marina July, 1976
Mar-July 1976
near waste Mar-July 1976
disposal area
Analytical Number of
Method Samples
6
GC/MS 1 1 0
144
GC/MS 91
120
11
GC/ECD 90
GC/FID-ECD-MS 42 (40 ND)
1
2
22 (18 ND)
1
GC/FID-EDC-MS 23 (21 ND)
GC/MS 16 (7 ND)
1
6 (3 traces)
2
33 (20 ND)
16 (1 trace)
Concentration (ppt, v/v)a
Max.
307.3
184000
191 545.6
41 700
40222.6
921.4
260
___
380
—
998.0
13.1
85.8
3400
14091 .5
Min.
5.2
<120
0
<120
0
2.2
65
— _ _
__-
0
33.4
5.9
37.1
8.6
53.6
Avg.
86.5
27500
18121.2
2900
1780.0
337.2
120
Trace
(2 samples)
Trace
Trace
170
Trace
Trace
(2 samples)
537.2
15950
7.4
61.6
1600
2712
Reference
Pellizzari and
Bunch , 1 9 79
Elfers, 1979
Suta, 1979
Elfers, 1979
Suta, 1979
Pellizzari and
Bunch, 1979
Singh et al. ,
Bozzelli et al
Pellizzari and
Bunch , 1 9 79
Pellizzari and
Bunch , 1 9 79
Bozzelli et al
Pellizzari and
Bunch , 1 9 79
Bozzelli et al
1980
., 1980
., 1979
., 1980
Pellizzari, I978b
Pellizzari and
Bunch, 1979
Pellizzari and
Bunch , 1 9 79
Pellizzari and
Bunch, 1979
Pellizzari and
Bunch, 1979
Pellizzari and
Bunch, 1979
-------
TABLE 7-1 (oont.)
Location
NEW JERSEY (cont.)
Elizabeth
Elizabeth
Fords
Hoboken
Linden
Linden
Middlesex
-~3 Newark
_J_ Newark
Newark
Passalo
Paterson
Rahway
Rutherford
Rutherford
Sayreville
Somerset
South Amboy
NEW YORK
Niagara Falls
Staten Island
Staten Island
Type of Site Date
Sept 1978-Dec 1979
near Indus- Jan-Dec 1979
trial plant
March, 1976
March, 1976
industrial June, Nov 1977
June, 1977
July, 1978
, urban Jan-Dec 1979
urban March, 1976
urban Mar 1976-Dec 1979
March, 1976
March, 1976
September, 1978
May 1978-Dec 1979
suburban May, 1979
July, 1976
July, 1978
industrial Jan-Dec 1979
residential February, 1978
(Love Canal)
urban November , 1 9 76
Mar-Apr 1981
Analytical Number of
Method Samples
GC/FID-ECD-MS 71 (53 ND)
GC/FID-ECD-MS 54
.
16
GC/MS 1 1
18
GC/FID-ECD-MS 37
160
GC/FID-ECD-MS 196
46
29
48
9
GC/ECD
(7 trace, 46 ND)
1
2 (2 ND)
(1 trace)
(1 ND)
(13 ND)
(9 trace, 28 ND)
1
(112 ND)
1
1
16
(141 ND)
(3 trace, 42 ND)
1
(17 ND)
(4 trace, 44 ND)
(2 trace, 7 ND)
3
NR
Concentration (ppt, v/v)a
Max.
2200
0
48.2
4.9
290
5800
775.5
3200
1800
50.7
4312
Min.
0
0
2.0
4.9
28
0
165.4
0
0
46.0
55
Avg.
220
2202.7
Trace
0
14.3
4.9
110
Trace
Trace
450
Trace
Trace
525.8
370
593.3
9372.8
490
Trace
Trace
48.2
256
Reference
Bozzelli et al., 1980;
Pellizzari, 1979a
Bozzelli et al., 1980
Pellizzari and
Bunch, 1979
Pellizzari, I977a;
Pellizzari et al., 1979
Pellizzari and
Bunch, 1979
Pellizzari, 1978c
Bozzelli et al., 1979
Bozzelli et al., 1980
Pellizzari and
Bunch, 1979
Bozzelli and
Kebbekus, 1979;
Bozzelli et al., 1980;
Pellizzari, 1977
Pellizzari and
Bunch , 1 9 79
Pellizzari and
Bunch , 1 9 79
Pellizzari, I978b,d
Bozzelli et al. ,
1979, 1980
Bozzelli et al., 1980
Pellizzari and
Bunch, 1979
Bozzelli et al., 1979
Bozzelli et al., 1980
Pellizzari, I978c,d
Pellizzari and
Bunch, 1979
Singh et al., 1982
-------
TABLE 7-1 (cont.)
Location
NORTH CAROLINA
Chapel Hill
OKLAHOMA
Liberty Mound
Tulsa
Vera
PENNSYLVANIA
Bristol
Marcus Hook
N. Philadelphia
Pittsburgh
TEXAS
Aldine
Beaumont
Deer Park
El Paso
Free port
Houston
Houston
Houston
La Porte
Pasadena
UTAH
Magna
Analytical
Type of Site Date Method
June, 1980
July-Sept 1977
July-Sept 1977
July, 1977
August, 1977
August, 1977
August, 1977
urban April, 1981 GC/ECD
June-Oct 1977
March, 1980
industrial August, 1977
Apr-May 1978
industrial August, 1977
July 1976-May 1980 GC/ECD
urban NR
streets, July 1976, June,
parks, rural July 1978
highway August, 1976
July, 1976
Oct-Nov 1977
Number of
Samples
6
2 (2 ND)
2 (2 ND)
1 (1 ND)
2
2
H
NR
3 (3 ND)
11
6 (3 trace)
22 (19 ND)
2
99 (5 ND)
30
10 (1 trace)
1
1
9 (9 ND)
Concentration (ppt, v/v)a
Max.
110
0
0
0
238.6
237
0
670
16390.6
29
1112.5
3000
16390.6
109.8
39
0
Min.
110
0
0
0
H.3
66
0
670
1002.5
0
815.8
50
73.1
30.1
39
0
Avg.
110
0
0
0
63.8
18.2
139.2
121
0
670
6353.5
1.3
961.2
1300
893.0
63.0
192.3
39
0
Reference
Wallace, 1981
Pellizzari, I978e
Pellizzari, I978e
Pellizzari, I978e
Pellizzari and
Bunch, 1979
Pellizzari and
Bunch, 1979
Pellizzari and
Bunch, 1979
Singh et al., 1982
Pellizzari et all, 1979
Wallace, 1981
Pellizzari and
Bunch, 1979
Pellizzari, I979a
Pellizzari and
Bunch , 1 9 79
Pellizzari et al., 1979
Singh et al., 1980
Pellizzari, 1978b
Pellizzari and
Bunch, 1979
Pellizzari and
Bunch, 1979
Pellizzari et al., 1979
Pellizzari, 1979a
-------
TABLE 7-1 (cont.)
Location
VIRGINIA
Front Royal
WEST VIRGINIA
Charleston
Charleston
Institute
Institute
Nitro
I
cr> Nitro
St. Albans
St. Albans
S. Charleston
S. Charleston
W. Belle
W. Belle
WASHINGTON
Pullman
Pullman
Analytical
Type of Site Date Method
Oct, Nov 1977
Sept, Nov 1977
Sept-Nov 1977 GC/MS
November, 1977 GC/MS
November, 1977
Oct, Nov 1977
Sept-Oct 1977 GC/MS
October, 1977
Sept-Nov 1977 GC/MS
Mar, Sept-Nov 1977
Mar-Nov 1977 GC/MS
Sept-Nov 1977 GC/MS
Sept-Nov 1977
rural Dec 1971-Feb 1975 GC/MS
rural November, 1975 GC/ECD
Number of
Samples
16
3
1) (1) ND)
2 (2 ND)
3
1)
6 (6 ND)
1
1) (D ND)
6
16 (1 5 ND)
6 (6 ND)
1)
NR
1
Concentration (ppt, v/v)a
Max.
86.0
0
0
63.8
0
—
0
63.8
37
0
61.8
—
— —
Min.
37.3
—
0
0
37.3
0
0
37.3
0
0
37.3
<5
10
Avg.
1)8.2
57.1
0
0
37.3
46.7
0
1)8.2
0
52.4
2.3
0
1)7.0
Reference
Pellizzari and
Bunch, 1979
Pellizzari and
Bunch, 1979
Pellizzari, I978e
Pellizzari, I978e
Pellizzari and
Bunch, 1979
Pellizzari and
Bunch, 1979
Pellizzari, I978e
Pellizzari and
Bunch, 1979
Pellizzari, I978e
Pellizzari and
Bunch , 1 9 79
Pellizzari, I979a;
Pellizzari, I978e
Pellizzari, I978e
Pellizzari and
Bunch, 1979
Grimsrud and
Rassmussen, 1975
Harsoh et al. , 1979
Assume ambient temperature of 258C and atmospheric pressure of 760 mmHg.
ND = Not detected
NR = Not reported
BCD = Electron capture detection
FID = Flame ionization detection
GC = Gas chromatography
MS = Mass spectrometry
-------
17.8 ppb. Levels recorded in the New Orleans study area ranged from <0.12 to
41 .7 ppb.
Analyses done by Elfers (1979) were performed by collecting ambient air on
charcoal tubes followed by desorption by carbon disulfide. Detection and quanti-
tation was made by gas-chromatograph-mass spectrometry. Quality control check
sample analysis indicated that recovery of standard concentrations was highly
variable. The detection limit of the gas chromatographic method was reported as
1 ^ig. The relative standard deviation of replicate standard solutions was found
to be 3%. The precision of the analytical and sampling methods together was 6%.
The accuracy of the analytical method varied between 72 and 97/&.
The highest reported reading for a single sample listed in Table 7-1 is
191 .5 ppb, which was recorded in Lake Charles, LA, the site for several EDC-vinyl
chloride manufacturing facilities. Concentrations in excess of 15 ppb for a
single sample were also reported near manufacturing facilities in Calvert City,
KY; New Orleans, LA; Deer Park and Houston, TX.
Recent studies have measured general urban ambient concentrations of EDC in
ten cities (Singh et al., 1980, 1981, 1982). The results of these studies are
summarized in Table 7-2. The averaging time for the mean concentrations in these
studies was 2 weeks. Electron capture detector-gas chromatography was the
primary means of analysis.
Low levels of EDC were recorded in a year-long monitoring program of five
cities in industrial northern New Jersey (Bozzelli et al., 1980). Samples were
collected at the five sites regularly throughout 1979. Only two of the 208
samples analyzed had EDC concentrations higher than trace (41 ng/nr or 10 ppt).
In a survey of air contaminants in the rural northwest, Grimsrud and
Rasmussen (1975) found EDC concentration of <5 ppt.
7-7
-------
TABLE 7-2
Ambient Concentrations of Ethylene Bichloride in Urban Areas
City
Los Angeles, CA
Phoenix, AZ
Oakland , CA
Houston, TX
St. Louis, MO
Denver, CO
Riverside, CA
Staten Island, NY
Pittsburgh, PA
Chicago, IL
Ethylene
Mean
519
216
83
1512
124
241
357
256
121
195
Bichloride Concentrations (ppt)
Maximum
1353
1450
842
7300
607
2089
2505
4312
237
2820
Minimum
173
39
38
50
45
56
63
55
66
22
aSingh et al., 1980, 1981, 1982
7-8
-------
7.1.2. Ground and Surface Water Levels. EDC can be released to the water
environment via wastewaters generated during production of ethylene dichloride
and its derivatives. It is also possible that EDC may be inadvertently produced
in the water environment due to chlorination processes of public water supplies
or chlorination of sewage or wastewaters (Versar, 1975; Seufert et al., 1980).
One chemical reaction which could lead to EDC production during water treatment
is the reaction of alkenes with hypochlorite. However, it is expected that
industrial discharges to surface water and leaching from solid waste are the
primary causes of EDC contamination in drinking water (Letkiewicz et al., 1982).
Most discharges of EDC are judged to ultimately reach the atmosphere because of
its high volatility (Letkiewicz et al., 1982). The identification and levels of
EDC which have been found in the ground and surface water of the U.S. are
discussed below.
EDC was reported to be a principal contaminant in finished water in 1975 by
Dowty et al. (1975). Because the gas chromatographic peak could not be resolved,
it was not possible to quantitate EDC. It was indicated that EDC levels could be
increased as a result of the water treatment processes and could pass the treat-
ment plant without removal. The water analyzed in this study was obtained from
the Mississippi River.
Deinzer et al. (1978), citing the results of a 1975 national drinking water
survey, reported EDC concentrations ranging from 0 to 6 ppb.
While sampling for pollutants in 14 heavily-industrialized river basins in
the United States, Ewing et al. (1977) found that EDC was present in 53 of the 204
samples purged for volatile organic analysis. The majority of the 81 purgeable
organic compounds detected were C^ to C, halogenated hydrocarbons. Only chloro-
form, trichloroethylene and tetrachloroethylene were found with greater
7-9
-------
frequencies. Identification was made by a GC-MS procedure. The limit of sensi-
tivity was <1 ppb.
In a compilation of pollutants found in water, Shackleford and Keith (1976)
identified EDC as having been found in industrial effluents, in finished drinking
water, and in river waters.
Letkiewicz et al. (1982), in a recent study for the U.S. EPA, discuss the
results of six federal surveys in which a number of public water supplies were
selected for analysis of chemical contaminants, including EDC. The six Federal
drinking water surveys providing data on EDC include the National Organics
Reconnaissance Survey (NORS), the National Organics Monitoring Survey (NOMS),
the National Screening Program for Organics in Drinking Water (NSP), the 1978
Community Water Supply Survey (CWSS), the Groundwater Supply Survey (GWSS), and
the Rural Water Survey (RWS). All surveys sampled both ground and surface waters
except for the GWSS. The scope and methodology of each survey is outlined below,
along with the identification of EDC presence.
The National Organics Reconnaissance Survey (NORS) was conducted in 1975 to
determine the extent of the presence of EDC, carbon tetrachloride, and four
trihalomethanes in drinking water supplies from 80 cities across the country
(Syraons et al., 1975). Another stated objective of the study was to determine
the effect of raw water source and treatment practices on the formation of these
compounds. The water samples were collected in 50 m& sealed vials, with vola-
tilization prevented by the absence of head space. Samples were subsequently
shipped on ice to the EPA Water Supply Research Lab in Cincinnati for analysis.
Analyses were performed by purge-and-trap gas chromatography with an
electrolytic conductivity detector. A population base of 36 million from 80
cities across the country was covered during the study.
7-10
-------
In the NORS study, 16 groundwater systems were analyzed for EDC contamina-
tion. None of the 16 systems contain detectable levels. Of the 64 surface water
samples analyzed for EDC, six were found to contain quantifiable levels of EDC at
0.2-6.0 mg/Q,.
The National Organics Monitoring Survey (NOMS) was instituted to identify
contaminant sources, to determine the frequency of occurrence of specific
drinking water contaminants, and to provide data for the establishment of maximum
contaminant levels (MCL's) for various organic compounds in drinking water (U.S.
EPA, 1977). The NOMS was conducted in three phases, March-April 1976, May-July
1976, and November 1976-January 1977. Drinking water samples from 113 communi-
ties were analyzed for 21 different compounds by purge-and-trap gas chromato-
graphy with electrolytic conductivity detectors. During Phase I the samples were
collected in 25- or 40-m2. open-top screw cap septum vials with no head space, a
feature that prevented volatilization of the compounds of interest. These
samples were then stored at 2-8°C for 1-2 weeks prior to analysis. Samples were
collected in a similar fashion for Phases II and III, but were held at 20°C for
periods up to 6 weeks. Sodium thiosulfate was added to a number of samples from
Phases II and III to reduce any residual chlorine present.
Of 18 groundwater systems analyzed for EDC during Phase I of the NOMS study
(March to April 1976), none contained quantifiable levels. When these systems
were sampled again during Phase II (May to July 1976), one system was found to
contain EDC, at 0.02 ug/1. No detectable levels of EDC were found during Phase
III of the study (November 1976 to January 1977).
In Phase I of the NOMS (March to April 1976), water samples from 87 surface
water systems were analyzed for EDC. Of these 87 systems, only one was found to
contain EDC, at 2.0 ug/1. When these systems were sampled again during the
second phase of the survey, one was found to be contaminated, at 1.8 ug/1.
7-n
-------
During the third phase of the NOMS (November 1976 to January 1977), analyses
revealed EDC contamination in one system, at 1 .25 (ig/1.
In the National Screening Program for Organics in Drinking Water (NSP),
conducted from June 1977 to March 1981, both raw and finished drinking water
samples from 1 69 water systems in 33 states were analyzed for 51 organic chemical
contaminants (SRI, 1981). Analyses were carried out by gas chromatography with
various detection methods, including the mass spectrometer, halogen-specific
detector, and flame ionization detector.
Thirteen groundwater supplies were tested for EDC contamination during the
NSP study. Of these systems, one was found to be contaminated with EDC at 0.2
ug/5,. Surface water samples for 107 drinking water systems were analyzed for
EDC. Of these, only one system was found to be contaminated with EDC, at 3.8
ug/2,.
In the Community Water Supply Survey (CWSS), carried out in 1978, 110
surface water and 330 groundwater supplies were examined for contamination by
volatile organic chemicals (U.S. EPA, 1981 a). Fourteen purgeable organic
compounds were analyzed, and total organic carbon levels were determined. At the
time of analysis, the samples were 1 to 2 years old. Long storage periods may
have resulted in the loss of some aromatics and unsaturated halocarbons due to
biological action. The analytical method of choice for the CWSS was purge-and-
trap gas chromatography with an electrolytic conductivity detector for halo-
carbons and a flame ionization detector for aromatic analysis.
The CWSS survey provided information on EDC levels in finished groundwater
supplies from 312 systems. Of the samples taken from these systems, three
contained detectable quantities of EDC with levels of 0.57, 1.06 and 1 .1 ug/
-------
The Groundwater Supply Survey of 1980 (GWSS) was initiated to provide a
clearer picture of the extent of contamination of groundwater supplies with
volatile organic compounds (U.S. EPA, 1982). A total of 9^5 systems were
sampled, of which 466 were chosen at random and 1*79 were picked from locations
near potential sources of contamination. Samples were collected at points close
to the actual distribution source, with mercuric chloride added as a preservative
to prevent biodegradation of aromatics. Sodium thiosulfate was also added to the
vials to reduce any residual chlorine, thus preventing its reaction with organic
matter. Analyses were made for 37 volatile organic compounds by purge-and-trap
gas chromatography with electrolytic conductivity detectors. Of the 466
randomly chosen water systems, seven were contaminated with EDC, at concentra-
tions ranging from 0.29-0.57 [ig/S,. Of the seven positive samples, six were from
systems serving populations in excess of 10,000 people. The average for all
randomly chosen systems was 0.5 ng/.l. Of the 479 nonrandom locations sampled,
nine were contaminated with EDC, at concentrations between 0.33-9.8 ng/£. Of the
nine positive samples, four were from systems serving populations in excess of
10,000 people. The average EDC level for the nonrandom systems was 2.7 \ig/H.
The Rural Water Survey (RWS), conducted in 1978 (Brass, 1981), was carried
out in response to Section 3 of the Safe Drinking Water Act, which mandated that
EPA "conduct a survey of the quantity, quality and availability of rural drinking
water supplies." A total of 800 of the 2655 samples collected in the RWS were
analyzed for volatile organic chemicals. Three hundred of the samples were
selected by a random generation procedure and 500 were picked randomly by state
(10 per state). There were 633 samples from groundwater, U7 samples from surface
water, and 81 samples from other water source categories.
Of 633 groundwater samples, five were found to have EDC present (minimum
quantification limit generally 0.5-1.0 ug/£). The range of concentrations was
7-13
-------
0.5-18 |ig/H; the mean and median concentrations of the positive values were 5.6
and 1 .7 |ig/5-, respectively. Both the mean and median values of all samples were
<0.5 |ig/£. Of the 47 surface water samples, only one (2.1$) was found to have EDC
present (minimum quantification limit generally 0.5-1.0 ng/?,). The concentra-
tion of the one positive sample was 19 ug/&. The mean and median values of all
samples were both <0.5 \ig/l>
The combined EDC groundwater data and surface water data from the above
Federal studies are summarized in Tables 7-3 and 7-4, respectively. The RWS
study was deleted from these summarizations because the RWS data were recorded by
number of service connections rather than population served. From the data
presented in Tables 7-3 and 7-4, Letkiewicz et al. (1982) have projected that EDC
levels in all groundwater and surface water systems in the United States fall
below 10 |ig/&, and that most are below 1.0 ng/fi,.
In addition to the six Federal surveys discussed by Letkiewicz et al.
(1982), six states (California, Connecticut, Deleware, Indiana, Massachussetts
and New Jersey) provided the U.S. EPA with information concerning EDC contamina-
tion in groundwater supplies. These data are listed in Table 7-5. The only
state-supplied surface water information on EDC was from New York; one sample
from Poughkeepsie assayed positive at 5.9 n.g/& (Letkiewicz et al., 1932).
7.1.3. Soil and Sediment Levels
No data were available on monitoring of EDC concentrations in soils, sedi-
ments or solid wastes in the sources consulted for this report.
7.2. ENVIRONMENTAL EXPOSURE
The general population can be exposed to EDC from three sources, air
emissions, drinking water and consumed foods. Some individuals may be exposed to
EDC from sources other than the three considered here, such as in occupational
settings and in the use of consumer products containing EDC. However, this
7-14
-------
TABLE 7-3
Reported Occurrence of Ethylene Dichloride in Groundwater Systems —
Combined Federal Data (NORS, NOMS, NSP, CWSS, GWSS)a
System size
(population
served)
<100
101-500
501-1 ,000
1 ,001-2,500
2,501-3,300
3,301-5,000
5,001-10,000
10,001-50,000
50,001-75,000
75,001-100,000
>100,000
Number of
systems
in U.S.
19,632
15,631
1,909
1,331
881
1 ,065
1 ,159
1 ,101
68
16
58
Number of
positive
systems
Number of
systems
sampled
1/175
0/220
0/111
3/151
0/10
2/79
1/111
11/296
1/37
0/12
1/13
Positive
systems
(*)
0.6
0.0
0.0
2.0
0.0
2.5
0.9
3.7
2.7
0.0
2.3
Number
undetected
<1 .0 ug/2,
171
220
111
118
10
77
113
285
36
12
12
Number of systems with
measured concentration
(iig/J,) of:
<1 .0
1
0
0
1
0
1
0
6
1
0
1
1 .0-5
0
0
0
2
0
1
1
1
0
0
0
>5-10
0
0
0
0
0
0
0
1
0
0
0
>10
0
0
0
0
0
0
0
0
0
0
0
Letkiewicz et al., 1982
bPositive systems are those with quantified levels of ethylene dichloride.
-------
TABLE 7-4
Reported Occurrence of Ethylene Bichloride in Surface Water Systems —
Combined Federal Data (NORS, NOMS, NSP, CWSS)a
System size
(population
served)
<100
101-500
501-1 ,000
1 ,001-2,500
2,501-3,300
3,301-5,000
5,001-10,000
10,001-50,000
50,001-75,000
75,001-100,000
>100,000
Number of
systems
in U.S.
1 ,412
2,383
1,341
1,911
514
720
912
1,306
156
85
218
Number of
positive
systems
Number of
systems
sampled
0/4
0/19
0/13
1/22
0/6
1/15
0/10
1/38
2/22
0/14
5/102
Positive
systems
(*)
0.0
0.0
0.0
4.5
0.0
6.7
0.0
2.6
9.0
0.0
4.9
Number
undetected
<1 . 0 ng/P,
4
19
13
21
6
14
10
37
20
14
97
Number of systems with
measured concentration
(UK/JO of:
<1 .0
0
0
0
1
0
0
0
1
1
0
3
1 .0-5
0
0
0
0
0
1
0
0
1
0
1
>5-10
0
0
0
0
0
0
0
0
0
0
1
,,0
0
0
0
0
0
0
0
0
0
0
0
aFour systems reported as undetected with the unusually high detection limit of 2.0 pg/?, were deleted.
bPositive systems are those with quantified levels of ethylene dichloride.
Source: Letkiewicz et al., 1932
-------
TABLE 7-5
State Data on Ethylene Dichloride in Groundwatere
Location
CALIFORNIA
Baldwin Park
Morada
Unspecified
Unspecified
CONNECTICUT
Colchester
Danbury
DELAWARE
Collins Park
Midvale
Newark
(North and South)
INDIANA
Elkhart
Granger
MASSACHUSETTS
Acton
Belchertown
Dartmouth
Rowley
NEW JERSEY
Bergen County
Essex County
Fair Lawn
Morris County
Passaic County
9 counties
1 2 counties
Water
type
N/S
N/S
N/S
N/S
D
D
F
F
F
F, N/S
N/S
F
F
F
F
N/S
N/S
F, N/S
N/S
N/S
N/S
N/S
N/S
N/S
N/S
Mean Range
(ug/£) (fig/A)
21
12
1 .2
1.2, 5.3
ND
7.8
ND
ND
ND
777 30-2,100
19, 160
ND
14.5 10.1-19.1
11 .6, 18.2
ND
ND
ND
1.3 1.1-1.9
2.0-2.1
ND
ND
ND
0.1-0.9
1-10
1 0-1 00
Number
of
samples
1
1
2 (1
2
1
1
1
1
2
11 (4
15 (13
H
10 (7
2
1
U
7
15
13 (11
1
154
228
4
4
1
ND)
ND)
ND)
ND)
ND)
Letkiewicz et al., 1982
ND = Not detected, N/S = Not specified, F
= Finished, D = Distribution
7-17
-------
section is limited to air, drinking water and food since these are considered to
be general sources common to most individuals. It must be noted that individual
exposure will vary widely depending upon factors such as where the individual
lives, works or travels, or what the individual may eat or drink. Individuals
living in the same neighborhood ' can experience vastly different exposure
patterns.
Unfortunately, methods for estimating the exposure of identifiable popula-
tion subgroups from all sources simultaneously have not yet been developed
(Letkiewicz et al., 1982). Exposure from the three sources considered here are
discussed below.
7.2.1 . Exposure from Air. Atmospheric exposure to EDC appears to vary greatly
from one location to another. Mean levels as high as 27.5 ppb have been
monitored near production and use facilities in Lake Charles, LA (Elfers, 1979).
However, the available monitoring data (see Section 7.1) indicate that most
locations have EDC concentrations of 0.5 ppb or less. The monitoring data
presented are not sufficient to determine regional variations in exposure levels
for EDC. The majority of high values reported were for samples taken near
production and use facilities.
Letkiewicz et al. (1982) have estimated respiratory intake of ethylene
dichloride by adults and infants; these estimates are summarized in Table 7-6.
From available monitoring data, Letkiewicz et al. (1982) estimated that low,
?
intermediate and high exposure levels for EDC in air were 0.25, 2.5 and 25 ug/m ,
respectively. Daily intake of EDC for adults in intermediate exposure levels was
estimated at 0.82 ug/kg.
Dispersion models have also been used to estimate ambient concentrations.
Based on modeled results for individual plants, maximum concentration levels in
the vicinity of various emission sources have been calculated (SRI Interna-
7-18
-------
TABLE 7-6
Estimated Respiratory Intake of Ethylene Bichloride
by Adults and Infants
Low:
Intermediate:
High:
Exposure
Ug/nr
0.25
2.5
25
Level
(ppb)
(0.062)
(0.62)
(6.20)
Intake
Adult
0.08
0.82
8.21
(ng/kg/day)
Infant
0.06
0.57
5.71
Assumptions: 70 kg=man, 3.5 kg-infant, 20 m^ of air inhaled/day (man),
0.8 nP of air inhaled/day (infant).
aLetkiewicz et al., 1982
7-19
-------
tional, 1979). Table 7-7 shows a summary of estimated maximum concentrations
that people may be exposed to in the vicinity of specific emission sources.
7.2.2. Exposure from Water. Letkiewicz et al. (1982) have projected that EDC
levels in all groundwater and surface water systems in the U.S. fall below 10
\ig/i, and that most are below 1.0 ug/& (see Section 7.1.2). The total estimated
population exposed to EDC from both ground and surface water sources is shown in
Table 7-8. The values in the table were obtained by use of the Federal Reporting
Data System data on populations served by primary water supply systems and data
on the estimated number of these water systems which contain a given level of EDC
(see Section 7.1.2).
Letkiewicz et al. (1982) have also estimated daily intakes of EDC from
drinking water. These estimates are given in Table 7-9.
7.2.3- Exposure from Food. EDC is used as a fumigant for grain, so contamina-
tion of flour and bread is possible. Several studies on this question have
indicated that EDC dissipates when the bagged flour is exposed to air, and that
no detectable EDC remains after baking (U.S. EPA, I98lb). No further information
on the presence of EDC in food was uncovered in the literature search.
7.3- CONCLUSIONS
Most EDC exposures result from the production and use of the chemical. The
highest atmospheric concentrations monitored for EDC have been detected near
production and use facilities. Therefore, it appears that the risk for popula-
tion exposure to EDC is greatest in the vicinity of these sources.
7-20
-------
TABLE 7-7
Maximum Concentration Level in the Vicinity of
Various Emission Sources3
Source
Maximum Annual Average EDC
Concentration Level (ppb)
EDC Production Facilities
End Use Production Facilities
Gasoline Service Stations
Automobile Emissions
Automobile Refueling
0.60 - 0.99
0.01 - 0.029
0.01 - 0.029
<0.01
SRI International, 1979
An accurate estimate cannot be determined from this reference, but it is
thought to be in the range of 10-15 ppb.
7-21
-------
TABLE 7-8
Total Estimated Population (in Thousands) Exposed to Ethylene
Dichloride in Drinking Water at the Indicated Concentration Ranges
System type
Groundwater
Surface water
TOTAL
(* of total)
Total
served
in U.S.
(thousands)
69,239
126,356
195,595
(100*)
Population (thousands)
to concentrations (ug
<1.0 1.0-5 >S-1
69,239
126,356
195,595
(100*)
exposed
/£) of:
0 >1 0
0.0
0.0
0.0
(0.0*)
Letkiewicz et al., 1982
7-22
-------
TABLE 7-9
Estimated Drinking Water Intake of Ethylene
Dichloride by Adults and Infants
Intake(ug/kg/day)
Exposure Level
1 .0
5
10
100
Adult
0.029
0.14
0.29
2.9
Infant
0.24
1 .2
2.4
24.0
Assumptions: 70 kg-man, 3.5 kg-infant, 2 I of water/day (man),
0.85 i of water/day (infant).
aLetkiewicz et al., 1982
7-23
-------
8. ECOLOGICAL EFFECTS
A variety of studies have demonstrated that EDC, in the role of a fumigant,
is toxic to insects infesting stored grains (Wadhi and Soares, 1964; Ellis and
Morrison, 1967; Vincent and Lindgren, 1965; Snapp, 1958; Krohne and Lingren,
1958; Finnegan and Stewart, 1962; Lindgren et al., 1954; and Bang and Telford,
1966). Little is known, however, of the effects of EDC to soil micoflora.
1,2-Dichloroethane has been reported to be non-toxic to many economically
important plant species when directly applied to growing plants (Cast and Early,
1956).
Toxicity of EDC to barnacles (Barnacle nauplii) and unicellular algae has
been reported (Pearson and McConnell, 1975). The LC5Q for Barnacle nauplii was
reported to be 186 mg/S,. The effective concentration needed to reduce the
photosynthetic ability of unicellular algae by 50% was 340 ppm (340 mg/5,).
A 21-hour median tolerance limit of 320 ppm (320 mg/S,) was reported for
brine shrimp under static test conditions (Price and Conway, 1974).
Static 24-hour and 96-hour LC™ concentrations of >600 and 430 mg/Jl,
respectively, have been determined for the freshwater bluegill (Lepomis
macrochirus) (Buccafusco et al., 1981). Garrett (1957) reported that the
concentration of EDC needed to produce >50% mortality in the marine pinperch
(Lagodon rhomeboides) under static conditions was 175 mg/S-.
An acute LC(-0 of 115 mg/J, was reported for the marine flatfish (Limanda
limanda) (Pearson and McConnell, 1975). In acute tests with another marine
species, static 24-, 48-, 72- and 96-hour LC5Qs in the range of 130-230 mg/5,
were determined for sheepshead minnows (Cyprinodon variegatus) (Heitmuller et
al., 1981); the observed no-effect concentration was reported to be 130 mg/l.
The estimated acceptable concentration of EDC in a 32-day early life stage
8-1
-------
toxicity test with freshwater fathead minnows (Pimephales promelas) lies in the
range of 29-99 mg/J, (Benoit et al., 1982).
8-2
-------
9. BIOLOGICAL EFFECTS IN MAN AND EXPERIMENTAL ANIMALS
9.1. PHARMACOKINETICS
9.1.1. Absorption and Distribution. Ethylene dichloride [EDC; 1,2-dichloro-
ethane] is a colorless, oily liquid with a sweet taste and with a chloroform-like
odor detectable over a range of 6-40 ppm. It is appreciably soluble in water
(0.869 g/1 00 mH) (Von Oettingen, 1964), with a vapor pressure of 64 torr at room
temperature (20°C). Consequently, EDC is rapidly and extensively absorbed
through the lungs in its vapor form and from the gastrointestinal tract in
solution. Inhalation is considered the primary route of entrance into man from
occupational exposure and air pollution. Absorption after oral ingestion is of
particular interest for EDC as a contaminating component of drinking water and
foodstuffs. Skin absorption is negligible in most industrial vapor exposure
situations, although absorption may be significant by this route with direct
liquid contact, as evidenced by toxic symptomatology in man (Section 9.2), and
also quantitative animal measurements.
9.1.1.1 DERMAL ABSORPTION -- Tsuruta (1975, 1977) studied the percuta-
neous absorption of a series of chlorinated organic solvents (including EDC)
applied to a standard area of shaved abdominal mouse skin for 15 minute periods.
Absorption was quantitated by the presence of the compound in total mouse body
plus expired air, as determined by gas chromatography (GC). For all solvents,
percutaneous absorption linearly increased with time and the rate was directly
related to water solubility. For EDC, the absorption rate was 479 nmoles/min/cra2
skin, second highest of 8 solvents measured. Tsuruta concluded that skin absorp-
tion from liquid contact could be a significant route for EDC entry into the
body.
9-1
-------
Jakobson et al. (1983) also carried out dermal absorption studies with
guinea pigs for 10 chlorinated organic solvents including EDC. Liquid contact
p
(skin area, 3.1 cm ) was maintained for up to 12 hours and solvent concentration
monitored in blood during and following dermal application. Dermal absorption,
as reflected by blood concentration profile, was again observed to be related to
the water solubility of the solvent. For solvents like EDC, which are relatively
hydrophilic [300-900 mg/dl], the blood concentration increased steadily during
the entire exposure. EDC reached 20 ug/mJ, blood in 12 hours. With extended
dermal exposure, the blood concentration eventually became fatal. This pattern
of steady blood accumulation indicates that dermal absorption occurs faster than
body elimination by metabolism or pulmonary excretion. Following dermal expo-
sure, the EDC concentration in blood declined in a manner consistent with a two-
compartment kinetic model, i.e., the sum of two exponential terms.
9.1 .1 .2 ORAL ABSORPTION — In man, gastrointestinal absorption of EDC has
not been specifically studied, although the absorption rate after oral ingestion
has been determined in animal studies. As expected from the neutral and lipo-
philic properties of EDC (Tables 9-1 and 9-2), transmucosal diffusive passage
occurs readily. There are numerous reports of poisoning in humans as a result of
accidental or suicidal ingestion of EDC and the peroral LD,.Q approximates 0.2-1
g/kg (NIOSH, 1976).
In animals, extensive gastrointestinal absorption of EDC has also been
clearly demonstrated by the biological effects produced by peroral administra-
tion of a wide range of dosages and dosing schedules in toxicity studies in rats,
mice, guinea pigs and dogs (Section 9.2) and in metabolism studies in rats (Reitz
et al., 1980, 1982; Spreafico et al., 1978, 1979, 1980). Reitz et al. (1980,
1982) found that C-EDC in corn oil given perorally to rats (150 mg/kg) was
completely absorbed by virtue of a complete recovery of radioactivity in exhaled
9-2
-------
Table 9-1 Physical Properties of Ethylene Bichloride
and Other Chloroethanes
1 ,2-Dichloroethane
1 ,1 -Dichloroethane
1 ,1 ,1 -Trichloroethane
Vapor Press.
at 25°C, torr.
80
250
125
Ostwald
Water/
Air
11.3
2.7
0.93
Solubility
Blood/
Air
19.5
4.7
3.3
Coeff., 37°C
Olive Oil/
Air
W7
187
356
Adapted from Sato and Nakajima, 1979.
9-3
-------
Table 9-2 Partition Coefficients for Ethylene Dichloride
MAN
Blood/air, 37°C
Adipose tissue/blood, 25°C
19.5
56.7
Sato and Nakajima, 1979
Bonitenko et al., 1977
RAT, 250 ppra inhalation exposure*
Blood/air, 37°C, 250 ppm 30.3
37°C, 150 ppm 14.9
Adipose tissue/blood 8.7**
Lung tissue/blood 0.45**
Liver tissue/blood 0.72**
Spreafico et al., 1980
Reitz et al., 1980
Reitz et al., 1980
Reitz et al., 1980
Reitz et al., 1980
•Conversion factors:
••Dose-dependent
At 25°C/760 torr, 1 ppm in air =4.05 mg/m3
1 mg/liter air = 247 ppm
9-4
-------
air, urine and carcass (Table 9-3). Spreafico et al. (1978, 1979, 1980) found
that 25, 50 and 1 50 mg/kg administered orally to rats in corn oil was rapidly
absorbed with peak blood levels occurring within 20 minutes. Their data, given
in Figure 9-1, show the time-course of blood, liver, lung and adipose tissue
following oral administration of the three dose levels. The peak blood levels,
which, according to linear kinetics, should be proportional to the amount of EDC
absorbed into the rat body, are summarized in Table 9-^. Although the peak blood
levels in this study do not deviate drastically from linearity, the peak tissue
levels are not linearly proportional to the three oral doses. These results
strongly suggest a passive transport across the gastrointestinal tract of EDC and
the occurrence of nonlinear elimination kinetics for EDC, i.e., a nonlinear dose-
dependency related to saturation of liver metabolism of EDC. An influence of the
dose on kinetic parameters has also been found for halogenated ethylene compounds
(e.g., vinyl chloride, vinylidene chloride) by other investigators (Gehring et
al., 1976, 1977, 1978; Bolt, 1978; McKenna et al., 1978; Reichert and Henschler,
1978; Filser and Bolt, 1979).
Table 9-5 gives the absorption rate constants (k ) and areas under the blood
Si
concentration curves (AUC) found by Spreafico et al. (1978, 1979, 1980) for rats
given a single oral dose of EDC. The rate constant for absorption was dose-
dependent and was probably influenced by liver metabolism. A markedly lower
value was observed for the highest dose (1 50 mg/kg) at which saturation of liver
metabolism probably occurs. Nonetheless, these data show that EDC is absorbed
from the gastrointestinal tract rapidly, with one-half the dose absorbed within
3-3 minutes for the lowest dose given in corn oil (25 mg/kg) and 6.U minutes for
the highest dose in corn oil (150 mg/kg). As expected, absorption of EDC
occurred significantly faster with an oral dose in water than in oil [k , 0.299
9-5
-------
Table 9-3 Fate of C-EDC in Rats 48 Hours After Oral (150 mg/kg) or
Inhalation (1 50 ppm, 6-hr) Exposure
Charcoal trap
(B)
Oral
Inhalation
iunole/kg
metabolites
nmole/kg
447 + 60
9.4 + 0.4
metabolites
Body burden 1 539 + 391
(total radio-
activity)
512
9.4
+ 135
+ 0.4
Total metabolites
(A-B)
Urine
CO trap
Total carcass
(48 hr after
exposure)
Feces
Cage wash
(1092)
926 + 348
83.1 + 11 .9
46.9 + 14.7
26.3 + 1*».7
12.5 + 6.37
(100)
85.7
7.7
4.3
2.1
1 .1
(503)
432 + 121
36.1 + 6.89
22.7 + 3-38
8.90 + 2.84
3.3^ ± 1.34
(100)
84.4
7.0
4.4
1 .7
0.7
Values are mean + S.D., with n = 4 for each route.of exposure and are umole equiva-
lents of EDC, based on the specific activity of C-EDC (3.2 mCi/mM).
From Reitz et al., 1980.
9-6
-------
0.1
1h 2h 3h Sh 8h
Figure 9-1 EDC levels after single oral administration in rats:
Top panel. 25 mg/kg; middle. 50 mg/kg; bottom. 150 mg/kg
dose. Adipose tissue ( • ). blood ( o ). liver ( •). lung ( * ).
Source: Spreafico et at. (1978. 1979. 1980).
9-7
-------
Table 9-4 Peak Blood and Tissue Levels After Single Oral Dosage
of EDC in Male Rats
Dose
mg/kg
25
50
150
Blood
13.29
31 .94
66.78
Adipose tissue
Hg/ml or \ig/g
110.67
148.92
259.88
Lung
2.92
7.20
8.31
Liver
30.02
55.00
92.10
Adapted from Spreafico et al., 1980
9-8
-------
Table 9-5 The Absorption Rate Constants (k ) and Area Under Curve
(AUC) for Rats After Single Oral ^ith Doses of EDC in Oil
and in Water as Vehicle and After Intravenous Administration
Dose
(mg/kg)
Oral 25
50
ka
. -1
mm
0.299
0.209
0.185
0.181
(water)
(oil)
(oil, male)
(oil, female)
AUC (blood)
ug x min x ml"
466
466
1700
1685
150
0.109 (oil)
7297
Intravenous (water) 1
5
25
9
54
595
From Spreafico, 1978, 1979, 1980
9-9
-------
(water) vs. k , 0.209 (oil); 25 mg/kg]. There appears to be no gender difference
a,
for absorption.
Comparison of the area under the blood concentration curve (AUC) after
intravenous administration with AUC after the same oral dose provides a measure
of the extent or completeness of oral absorption. Table 9-5 shows that the AUC
was 595 ug x rain x m£~ after a 25 mg/kg intravenous dose and was 466 ug x rain x
mil" after 25 mg/kg oral dose. These results indicate that absorption of the
oral dose was very extensive, averaging TQ% of complete absorption, or 100?
absorption if it is assumed that the first-pass effects in liver (metabolism) and
lung (elimination) after oral absorption decreased EDC appearance in systemic
blood (Reitz, 1980, 1982). It is notable that the AUCs for differing intravenous
doses, where intestinal absorption is not a factor (Table 9-5), are not linearly
proportional, providing further evidence of the occurence of Michaelis-Menten
elimination kinetics for EDC.
Withey et al. (1982) investigated the effect of the dosing vehicle on
intestinal absorption of EDC in fasting rats (400 g) following intragastric
intubation of equivalent doses (100 mg/kg) in -4 m£ of water or of corn oil. The
post-absorptive peak blood concentration averaged 5 times higher for water
vehicle than corn oil (84.6 vs 15.9 ug/m&); moreover, the peak blood
concentration was reached 3 times faster for water solution than for oil solution
(3.2 vs. 10.6 minutes). The ratio of the areas under the blood concentration
curves for 5 hours after dosing (AUC, 5 hr) was 3.0; water:corn oil. These
results are in general agreement with those of Spreafico et al. (1978, 1979,
1980) (Tables 9-4 and 9-5), who found that intestinal absorption was faster with
an oral dose in water than in oil. The observations of these investigators
stress again the dependence of oral absorptive rate in rats not only on the dose,
but also on the vehicle. While these factors are unlikely to affect the
9-10
-------
pharmacokinetics of EDC in man in any practical way, they are of importance to
interpretation of data from long-term carcinogenicity tests of EDC in rodents
where the modes of intragastric dosing employed may differ by both dose and
vehicle.
9.1.1.3 PULMONARY ABSORPTION — EDC has a moderately high vapor pressure
(80 torr at 25°C; Table 9-1) and, in man, a high blood/air partition coefficient
compared to chloroethanes (19.5 at 27°C; Table 9-2). Hence, its vapor in ambient
air is a primary mode of exposure, and the lungs are a principal route of entry
into the body. The total amount absorbed via the lungs (as for all vapors) can be
expected theoretically to be directly proportional to: (1 ) the concentration of
the inspired air; (2) the duration of exposure; (3) the blood/air Ostwald solu-
bility coefficient; (U) the solubility in the various body tissues; and (5)
physical activity which increases pulmonary ventilation rate and cardiac output.
Hence, the basic kinetic parameters of pulmonary absorption of EDC and its
equilibrium in the body are as valid for the very low concentrations expected in
urban ambient air as for the higher vapor concentrations found in the industrial
environment and the workplace. However, these parameters of pulmonary absorp-
tion have not been studied in any detail in man, although some information is
available from pharmacokinetic studies in rats.
Urosova (1953) reported that women exposed during a normal day in the work-
place to =15.5 ppm EDC in air accumulated the chemical in breast milk and that
initial concentrations in exhaled air following daily exposure were 14.5 ppm.
These observations indicate that the women absorbed EDC through their lungs and
reached blood and total body equilibrium with inspired air concentration within
the daily work period.
Spreafico et al. (1978, 1979, 1980) and Reitz et al. (1980, 1982) have
studied the kinetics of pulmonary absorption of EDC in rats. Figure 9-2 shows
the time-course pf blood concentration of EDC, observed by Reitz et al. (1980,
9-11
-------
12
200 300 400
TIME (minutes)
600
10.0
O
O
O
O
O
IU
CO
S
c
o
O
cc
O
40 80
TIME (minutes)
Figure 9-2 Top; Blood |evell of EDC observed during and follow-
ing a 6-hour inhalation exposure to 150 ppm EDC. Data from
four male Osborne-Mendel rats were fitted to a two-compart-
ment open model as described by Gehring et al.35 The compu-
ter plot is shown. The arrow indicates exposure termination.
Bottom: Semi-logarithmic plot of EDC blood levels vs. time
after exposure termination. Source: Reitzetal. (19RO. 1932).
9-12
-------
1982) during a 6-hour inhalation exposure to 150 ppm EDC. Blood and body
equilibrium with the blood concentration maintained a plateau level of 9 ng/m?,
(blood/air partition coefficient, 14.9). Spreafico et al. (1980) exposed their
rats to 50 and 250 ppm EDC for 6 hours. Their data are given in Tables 9-6 and
9-7. Blood and body equilibrium (liver, lung and adipose tissue) was established
at =2 hours for 50 ppm exposure, and at 3 hours for 250 ppm exposure. During
inhalation of EDC, when equilibrium is achieved, the arterial blood concentra-
tion of EDC should theoretically always be directly proportional to inspired air
concentration. This fixed relationship is defined by the blood/air Ostwald
solubility coefficient for EDC. As calculated from the data for 50 and 250 ppm
exposures of Spreafico and co-workers, the blood/air partition coefficients for
EDC are 6.3 and 30.3, respectively. Including the data of Reitz et al. (1980)
for 150 ppm exposure in rats (Figure 9-2), these results do not demonstrate a
direct proportional relationship between inspired air concentration and blood
concentration of EDC, i.e., a constant blood/air partition coefficient value.
Furthermore, linear kinetics for EDC during inhalation exposure cannot be
presumed, and indeed these data suggest otherwise, and are in accord with the
evidence of nonlinear kinetics after oral and intravenous dosing as noted above
(Table 9-5).
9.1.1.M TISSUE DISTRIBUTION ~ After pulmonary or peroral absorption, EDC
is distributed into all body tissues. As expected from its general anesthetic
properties in man and in animals, EDC readily passes the blood-brain barrier.
The compound crosses the placental barrier and has been found in the fetus
(Vozovaya, 1975, 1976, 1977). EDC also distributes into human colostrum and
mature breast milk. Urusova (1953) found EDC concentrated in breast milk
(5.M-6.1J mg/2,) in the workplace. The compound remained in breast milk for 18
hours following workday exposure, even though its concentration in exhaled air
9-13
-------
Table 9-6 EDC Tissue Levels After 50 ppm Inhalatory Exposure
Time of
Exposure
30 minutes
1 hour
2 hours
4 hours
6 hours
EDC ug/g or ug/ral + S.E.
Blood Liver Lung Adipose Tissue
0.48 + 0.05 0.32 + 0.02 0.14 + 0.02 2.91 + 0.22
0.92 + 0.09 0.67 ± 0.04 0.27 ± 0.03 7.49 + 0.60
1.34 ± 0.09 0.84 + 0.09 0.34 + 0.03 10.31 ± 0.94
1.34 + 0.11 1.14 + 0.17 0.42 + 0.05 11.08+0.77
1.37+0.11 1.02 + 0.10 0.38+0.02 10. 19 +1.00
From Spreafico et al., 1980
9-14
-------
Table 9-7 EDC Tissue Levels After 250 ppm Inhalatory Exposure
Time of
Exposure
30 minutes
1 hour
2 hours
3 hours
6 hours
EDC ug/g or ug/ml + S.E.
Blood Liver Lung
6.33 ± 1.04 3-82 + 0.78 2.19 + 0.21
11.65 + 1.12 7.34+0.74 6.40+0.20
23.64 + 0.91 16. 39 ±1.18 14.07+0.47
29.36 + 1.01 20.83 ± 2.21 14.47 + 1.12
31.29 + 1.19 22.49 + L12 14.14 + 0.90
Adipose Tissue
26.75 + 3.12
82.64 + 2.19
151 .53 + 12.17
252.18 + 14.62
273-32 + 12.46
From Spreafico et al., 1980
9-15
-------
fell to 4 ppm. Sykes and Klein (1957) have demonstrated the presence of EDC in
cows' milk after oral administration.
There is little information on EDC distribution and concentration in the
various body tissues of man after exposure, and few controlled exposure studies
in animals investigating the distribution of EDC in body tissues and defining
dose-dependent tissue concentrations. Spreafico et al. (1978, 1979, 1980)
determined EDC levels in rat blood, liver, lung and epididymal adipose tissue
after single oral administration of 25, 50 and 1 50 mg/kg. The time-course of EDC
concentrations are shown in Figure 9-1. This figure shows that tissue accumula-
tion occurs most rapidly in the liver where peak concentrations were reached
within 10 minutes of administration. Following- complete absorption and body
equilibration after 2 hours, the decay in tissue concentrations of liver, lung
and adipose tissue parallel the first-order decline in blood concentration.
Table 9-8 summarizes blood and tissue concentrations determined at 2 hours
following administration. Blood levels and tissue levels in liver and adipose
tissues were not found to be linearly proportional to dose, but increased
exponentially, providing evidence of liver metabolism saturation and nonlinear
kinetics after oral administration. At oral dose levels of 25, 50 and 1 50 mg/kg,
adipose tissue displayed the greatest concentration of EDC with adipose
tissue/blood partition coefficients of 17, 9 and 7, respectively. No other
tissue, including liver, demonstrated a partition coefficient >1.0. The very low
concentration levels of EDC in lung tissue may occur as a result of EDC elimina-
tion by this route.
Table 9-8 also gives blood concentrations after chronic oral administration
to rats (11 daily doses) of 50 mg EDC/kg. Comparison of these tissue levels with
those following a single oral administration of 50 mg/kg EDC provides no evidence
of blood or tissue accumulation with chronic administration.
9-16
-------
Table 9-8 Blood and Tissue Levels of EDC in Male Rats 2 Hours
After Single Oral Doses in Corn Oil
Tissue
(|ig/ml, or
lig/g ± SE) 25
Blood 0.46 + 0.04
Liver 0.32 + 0.01
Kidney
Brain
Spleen
Lung <0.05
Adipose 7.80 + 0.72
Dose, mg/kg
50
5.89 + 0.41
3.81 + 0.45
3.43 + 0.26
2.96 + 0.36
1 .79 + 0.35
1 .44 + 0.10
55.78 + 6.88
150
26.60 + 1 .23
21 .62 + 3.99
1 .62 + 0.25
178.50 + 24.66
Blood and Tissue Levels of EDC in Male Rats 2 Hours After the
Last of 11 Daily Oral Doses in Oil (50 mg/kg)
Blood 8.11 + 0.23
Liver 3.95 ± 0.48
Lung 2.24 ± 0.47
Adipose 53-71 ± 10.07
From Spreafico et al., 1978, 1979, 1980.
9-17
-------
Spreafico and his colleagues (1978, 1979, 1980) also investigated blood and
tissue concentrations in rats during inhalation exposure to 50 and 250 ppm EDC.
The results of these experiments are given in Tables 9-6 and 9-7. Blood and
tissue equilibrium (liver, lung and adipose tissue) occurred at 2 hours and 3
hours, respectively, for the two inspired air concentrations. In general, the
blood and tissue distribution of EDC at body equilibrium is similar to the
results obtained with oral administration given in Table 9-8. A very clear dose
dependence in tissue levels of EDC was again found with the two inhalation
concentrations, with differences in EDC concentrations on the order of 20-30
times when blood, liver, lung and adipose tissue are considered. The highest
absolute levels of EDC were measured again in adipose tissue with concentrations
that were between 8 and 9 times greater than those measured in the blood. As
previously noted for oral administration (Table 9-8), liver and lung concentra-
tions were less than blood concentrations.
A comparison of the absolute blood and tissue concentrations at body equili-
brium for oral and inhalatory modes of administration (Tables 9-6, 9-7 and 9-8)
indicates that 50 ppm inhalation roughly equates to 25 mg/kg oral, while 250 pprn
inhalation provides blood, liver and adipose tissue levels slightly greater than
a 150 rag/kg oral dose.
9.1.2 Excretion. Elimination of EDC from the body is perforce the sum of
metabolism and excretion of unchanged EDC via pulmonary and other routes.
Unmetabolized EDC is excreted almost exclusively through the lungs; however,
metabolism of EDC is extensive, with the proportion excreted unchanged dependent
on body doses. While no controlled experimental studies have been made on the
kinetics of excretion of EDC in man, recent studies have been performed on
experimental animals.
9-18
-------
9.1.2.1 PULMONARY EXCRETION — Urusova (1953) reported that women exposed
to -15.5 ppm EDC in ambient air of industrial environs demonstrated initial EDC
concentrations in exhaled air of 14.5 ppm. The breath concentration declined to
=3 ppro after 18 hours. These values lead to an approximation of 9 hours for the
half-time of pulmonary elimination of EDC in man. Similar observations have been
made for animals (monkey, dog, cat, rabbit, rat and guinea pig) in early investi-
gations of the anesthetic properties and toxicities of EDC (Heppel et al., 19^5;
Kistler and Luckhardt, 1929; Lehman and Schmidt-Kehl, 1936). In controlled
studies in mice, Yllner (1971 a) found that up to ^5% of an intraperitoneal
injected dose of EDC (1 70 mg/kg) was recoverable unchanged in exhaled air (Table
9-9). The percentage of EDC recovered unchanged in exhaled air increased expo-
nentially with the dose, indicating a limited capacity of biotransformation,
i.e., non-linear kinetics. Thus, in mice, pulmonary excretion of EDC is a major
route of elimination, increasing in importance with higher body doses.
Similar observations have been made for the rat by Reitz et al. (1980,
1 4
1982). In a balance study utilizing C-EDC given orally (150 mg/kg) and by
inhalation (150 ppm, 6 hours), these investigators found that for the oral dose,
29? was recovered unchanged in exhaled air, and that only 1 .8/6 of the lower
inhalation dose was excreted by the pulmonary route (see Table 9-3). Sopikov and
Gorshunova (1979) observed that after an intraperitoneal 250 mg/kg dose to rats,
30$ of the EDC dose was eliminated in the exhaled air within 5 hours.
9.1.2.2 OTHER ROUTES OF EXCRETION — EDC is not ordinarily eliminated in
significant amounts from the body by any route other than pulmonary. However,
Shchepotin and Bondarenko (1978) identified EDC by gas chromatography (GC)
methods in the urine of persons with severe symptoms of EDC poisoning. Studies
of chlorinated compounds in the urine after EDC inhalation exposure or peroral
dosage to experimental animals have failed to detect unchanged EDC (Spreafico et
9-19
-------
Table 9-9 Percent Distribution of Radioactivity Excreted (48-hr) by Mice
Receiving 1,2-Dichloroethane- C
0.05
Dose g/kg
0.10 O.U
0.1?
C02 (exhaled air) 13
Dichloroethane (exhaled air) 11
Urinary metabolites 73
8 4 5
21 46 45
70 48 50
Adapted from Yllner (1971 a)
9-20
-------
al.f 1980; Yllner, 19 71 a). Mutagenic metabolites of EDC have been reported in
rat and mouse bile (Rannug and Beije, 1979; Rannug, 1980), but EDC itself has not
been found. Diffusion of volatile haloalkane anesthetic agents into bowel space
and through skin is known to occur (Stoelting and Eger, 1969), and these routes
of excretion may also be significant for EDC because of similarity of structure
and comparable high lipid/blood partition coefficients.
9.1.2.3 KINETICS OF EXCRETION -- While the kinetic parameters of elimina-
tion of EDC for each of the various routes of excretion, i.e., pulmonary, metabo-
lism, etc., are not well defined for either man or experimental animals, several
investigative groups have determined the kinetic parameters for whole-body and
tissue compartment excretion of EDC in the rat (Retiz et al., 1980; Spreafico et
al., 1978, 1979, 1980; Withey and Collins, 1980).
Withey and Collins (1980) determined the kinetics of distribution and
elimination of EDC from blood of Wistar rats after intravenous administration of
3, 6, 9, 12 or 15 mg/kg of EDC given in 1 mS, water intrajugularly. For the two
lower doses (3 and 6 mg/kg), the blood decay curves exhibited two components of
exponential disappearance and best fitted a first-order two compartment model
with kinetic parameters of: k , 0.24 min" ; V., 43 ml; k.. ? and k?1 , 0.02 and 0.04
rain" , respectively. For higher doses (9,10 and 15 mg/kg), these investigators
found their data best fitted a first-order three compartment model; they suggest
that the shift from two to three compartment kinetics may have occurred either
because of a dose-related alteration in the kinetic mechanisms of uptake, distri-
bution, metabolism and elimination, or that three compartment kinetics were
followed at all dose levels but with lower doses; the third exponential compo-
nent, representing the third compartment, was obscured by the limit of analytical
sensitivity. Average kinetic values for the three compartment model were: k ,
6
0.094 min" ; V 67.9 m£; k12, k21 , k^, k^ ; 0.06, 0.08, 0.01 and 0.01 min" ,
9-21
-------
respectively. Withey and Collins state that they found no evidence in their
kinetic analysis of the disposition of intravenous bolus injections of EDC into
the rat of nonlinear or dose-dependent Michaelis-Menten kinetics. These workers
suggested that a dose of 1 5 mg/kg EDC in the rat is below hepatic metabolism
saturation.
Spreafico et al. (1978, 1979, 1980) intravenously administered EDC in water
to Sprague-Dawley rats as bolus injections of 1 , 5 and 25 mg/kg and determined
the whole blood concentration of EDC as it decayed with time. Figure 9-3 shows
the semilog plot of the results of these experiments. A biphasic decline of EDC
blood concentration was evident for all doses, indicative of a two-compartment
system, with a distributive phase (a) and an excretion phase ($). The data for
intravenous treatment were analyzed by computer fitting to a two-compartment
open model with the results shown in Table 9-10. Of immediate note is the fact
that the kinetic parameters are not independent of the dose as required by linear
kinetics. Thus the half-time (T1 . ) of body elimination from central or blood
compartment increases with the dose, while whole-body clearance (Cl) and the
volume of distribution (V ) decrease with an increase of the dose. These results
indicate that the rate of whole-body excretion of EDC is largely determined by
the metabolism of EDC, a saturable process and a major route of elimination.
Spreafico and his co-workers (1978, 1979, 1980) have also investigated the
whole-body kinetics of oral administration of EDC in rats. Figure 9-1 shows
semilog plots of blood and tissue concentrations during and after absorption
(excretory phase) following single oral doses of 25, 50 and 1 50 mg/kg given in
corn oil. In general, the slopes of the disappearance curves (excretion compo-
nent) for adipose, liver and lung tissues roughly parallel and reflect the blood
decay curve. The data for blood were computer-fitted to the kinetic equations
9-22
-------
1 1
0.01
0.5 h
V« h
Figure 9-3 Blood levels of EDC in rats after i.v. administration. ( •) 25 mg/kg i.v.;
(O) 5 mg/kg i.v.; (A) 1 mg/kg i.v. Source: Spreaficoet al.(1976. 1979. 1980).
9-23
-------
Table 9-10 Pharmacokinetic Parameters of EDC Administered as Single Bolus
Intravenous Injections in Saline to Sprague-Dawley Male Rats.
Parameters Calculated from a 2-Compartment Open Model.
Parameter
GO, ug x ml"
K , min
V • ~1
K.. _ , mm
v • -1
K21 , mm
AUC, ug x min x
ml
T 1 /2 3 min
Dose , mg/kg
1 5 25
1 . 50 8 . 00 38 . 1 2
0.277 0.142 0.078
0.121 0.063 0.040
0.158 0.140 0.118
9 54 595
7.30 9.49 14.07
Clearance 21.98 17.46 7.98
ml x m~
Vol. distr., ml 231 239 1 62
K12
^
21
el (inhalation)
or
V (Km + C) (oral)
From Spreafico et al., 1979, 1980.
9-24
-------
for a two-compartment open model for oral absorption; the results are given in
Table 9-11. Like the kinetics observed for intravenous dosing, the values for
the parameters, T1 ,p, Cl and V., are dose-dependent. Furthermore, the oral
dosing vehicle also affects the parameters. Comparison of the absorption rate
constants, K , half-times of elimination, T1 <2 and volumes of distribution, V,,
for 1 5 mg/kg EDC in oil and 25 mg/kg EDC in water indicates a faster absorption of
EDC in water, a shorter half-time of body elimination and a small volume of
distribution. Nonetheless, the AUCs indicative of the total absorbed dose were
similar for oil and water vehicles, as were the body clearance rates of EDC. On
the other hand, no significant differences in the kinetic parameters were seen
for male and female rats given the same dose, nor were significant differences
observed between a single dose and 11 daily administrations of the same dose (50
mg/kg) of EDC.
Spreafico et al. included in their comprehensive studies on the pharmaco-
kinetics of EDC in the rat, experiments to determine the kinetics of EDC after
inhalation dosing. Rats were exposed to 50 and 250 ppm EDC for 5 hours, a period
sufficiently long to estabish and maintain whole body steady-state conditions
with these inspired air concentrations (Tables 9-6 and 9-7). The exposure was
terminated and blood and other tissues were sampled to determine the decay of EDC
concentrations in these tissues with time. The results of these experiments are
presented as semilog plots of tissue concentrations versus time in Figure 9-^.
As for oral dosing, the slopes of the tissue decay curves parallel and reflect
generally the blood concentration curves. In contrast to intravenous and oral
dosing, which have several components to their curves representing absorption
and/or distribution, the curves after steady-state inhalation are monophasic,
representing only excretion. Thus, the pharmacokinetic parameters calculated
from the blood decay curves following the steady-state inhalation conditions are
9-25
-------
Table 9-11 Pharmacokinetic Parameters of EDC Administered as Single Oral
Doses in Corn Oil and Water to Sprague-Dawley Male Rats.
Parameters Calculated from a 2-Compartment Open Model.
Parameter
Oil Vehicle
Ka, min"
Kel' min"
AUC, ug x min x ml"
T 1 /2 3 min
Clearance, ml x min"
Vol. Distr., ml.
Aqueous Vehicle
_1
K min
. -1
K , , mm
AUC, ug x min x ml
T 1/2 3 min
Clearance, ml x min"
Vol. Distr. , ml.
Dose, mg/kg
25 50 1 50
0.209 0.185 0.109
0.029 0.017 0.010
446 1 700 729 7
24.62 44.07 56.70
10.64 5.58 3-90
367 328 390
0.299
0.046
446
14.12
10.20
221
From Spreafico et al., 1979, 1980.
9-26
-------
1000 er
100 9-
1 1 1 1 1 1
li
0.5h
1.5h
2h
1000
0.1
Ij—•
E
0.5h
1h
1.5h
2h
2.5h
3h
Figure 9-4 Levels of EDC in rats after inhalatory exposure to 50 ppm
(top) and 250 ppm (bottom). Levels were measured at termination of
5-hour exposure period. Adipose tissue ( • ). blood ( o), liver ( •).
lung (A). Source: Spreaf ico et al. (1978, 1979, 1980).
9-27
-------
essentially those applicable to a single compartment open model. The kinetic
parameters are given in Table 9-12. The body burden or "dose" of EDC in the
animals at termination of inhalation exposure is not known; however, a comparison
of the areas under the blood decay curves, a reflection of body burden, suggests
that the body burden after 250 pprn exposure was 40 times, not the 5 times
expected of the 50 ppm exposure. Similarly, the half-life of EDC and the zero-
time blood concentrations are dose-dependent. These results from inhalation
exposure are in accord with the dose-dependent pharmacokinetics exhibited after
intravenous and oral dosing of EDC. They strongly indicate that the kinetics of
absorption, distribution and elimination of EDC are appropriately described by
nonlinear kinetics that take into account saturable processes, presumably in
this case the metabolism of EDC by the organism.
The pharmacokinetics of EDC after inhalation have also been explored by
Reitz et al. (1980, 1982) in male Osborne-Mendel rats. These investigators
determined the whole-blood levels of EDC during and following a 6-hour inhalation
exposure to 150 ppm EDC. Figure 9-2 shows the data obtained from 4 rats,
computer-fitted to the equations of a two-compartment model and the idealized
computer-fit plotted. Within 2 hours of exposure, the animals approached a
steady-state blood concentration (9 (ig/mi) with the inspired air concentration;
but, following termination of exposure at 6 hours, the blood concentration of EDC
rapidly decayed to near zero within 10 hours. Figure 9-2 shows also the semilog
plot of computer-fitted data of EDC blood concentration levels vs. time after
exposure termination. In contrast to the observation of Spreafico et al. (Figure
9-4) that only a monophasic plot was obtained following inhalation exposure,
Reitz et al. found a biphasic elimination with an initial rapid alpha phase and a
slower beta phase. Table 9-13 gives the pharmacokinetic parameters calculated
9-28
-------
Table 9-12 Pharmacokinetic Parameters of EDC Following Termination
of Steady State Inhalation Conditions (5-hr Exposure) of 50 and 250 ppm
to Male Sprague-Dawley Rats.
Parameter Exposure Concentration, ppm
50 350
CQ, jig x ml"1 1 .42 30.92
Kel, rain" 0.0561 0.0313
T 1/2, min 12.69 22.13
AUC, ug x min x ml" 26 1023
From Spreafico et al., 1979, 1980
9-29
-------
Table 9-13 Pharmacokinetic Parameters of EDC Following Termination
of Steady State Inhalation Conditions; 6-Hr Exposure, 150 ppm to Male
Osborne-Mendel Rats. Parameters Calculated from a 2-Compartment Model.
Parameter
CQ, ,ig x ml~1 9.0
Kel, min~1 0.092
v . -1 0.019
K-p, rain
K21 , min~1 0.025
AUC, ug x min x ml" 3018
35
Vol. Distr, ml. 51 3
From Reitz et al., 1980
9-30
-------
from a two-compartment open model. These results may be compared with data
obtained by Spreafico et al. for inhalation exposure (Table 9-12).
Reitz et al. (1982) determined also in the rat the pharmacokinetics after
single oral dosing (150 mg/kg in corn oil). In this case, a semilog plot of blood
EDC levels after absorption produced an elimination curve typical of nonlinear
kinetics. These workers therefore computer-fitted the data to a two-compartment
nonlinear model and calculated the rate of elimination from the central compart-
ment (blood) according to Michaelis-Menten kinetics. Table 9-13 gives the
pharmacokinetic parameters calculated from the model.
Several differences exist between the observed data and calculated para-
meters of Reitz et al. for inhalation vs. oral exposure (Table 9-13) as well as
those of Spreafico et al. (Table 9-12). The EDC inhalation concentration used by
Reitz et al. (150 ppm) was intermediate to those of Spreafico et al. (50 and 250
ppm). Plateau blood concentrations in the three inhalation studies (1.4 at 50;
8.3 at 150; and 30.9 ug/mSl at 250 ppm), clearly demonstrate saturation of an
elimination process, presumably metabolism. Reitz et al. found peak blood levels
following oral dosing (30-^4 ug/mP. at 150 mg/kg) to be similar to those found by
Spreafico et al. after a 250 ppm inhalation exposure. Reitz et al. found also a
biphasic elimination after both oral and inhalation exposure with the second or
8 phase essentially equal (T1/2 = 28 rain), and similar to the monophasic
elimination calculated by Spreafico et al. for the 250 ppm exposure (T.. /? = 22
min). The relatively slow alpha elimination phase (T1/2, 90 min) following oral
dosing of 150 mg/kg suggested to Reitz et al. a saturable elimination process.
The data of Spreafico and co-workers are generally in agreement with this
treatment; however, several kinetic parameters are not in good agreement between
the studies. Of particular note are the biphasic and monophasic elimination
curves and the large discrepancy of AUG. The explanation for these differences
9-31
-------
may lie in the different kinetic models, species differences and inability of
linear kinetics to accurately describe the kinetics of EDC body elimination.
9.1.2.4 BIOACCUMULATION — There is no definitive experimental evidence
in the literature concerning bioaccumulation in man after chronic or repeated
daily exposure to EDC. While EDC has a moderately high fat tissue/blood parti-
tion coefficient (Table 9-2), its half-time of elimination in man appears to be
=6-8 hours (Urusova, 1953). In the rat, Spreafico et al. (1978, 1979, 1980) and
Retiz et al. (1980, 1982) have provided estimates of half-time of whole-body
elimination of 25-57 minutes for acute oral dosing, and 13-35 minutes after 5-6
hour inhalation exposures. The half-time of elimination of EDC from the
epididymal adipose tissue was essentially the same as whole-body elimination.
These relatively short half-times of elimination indicate that the risk of
significant bioaccumulation of EDC is small. These investigators observed also
that their pharmacokinetic data in rats predict essentially complete elimination
of EDC from the body in 24 hours following acute oral or 5-6 hour inhalation
exposure. Furthermore, Spreafico et al. (1979, 1980) found no significant
differences in the kinetic parameters of EDC elimination between a single dose
and multiple daily oral administration of EDC.
9.1 .3. Metabolism
9.1.3.1 KNOWN METABOLITES — Metabolism of EDC in man during or after
exposure has not been studied. However, one of the earliest suggestive reports
of an active mammalian biotransformation of EDC is related to human exposure. In
1945, Bryzkin reported that EDC underwent rapid transformation to an "organic
chloride" in patients who died after ingesting 1 50-200 m?; EDC itself was not
detectable in tissues at autopsy. Although Heppel and Porterfield demonstrated
as early as 1948 that both ethylene dichloride and dibromide were dehalogenated
by rat liver enzyme preparations, current knowledge of mammalian metabolism of
9-32
-------
EDC derives primarily from studies performed within the last 10 years. Metabo-
lites which have been identified either in vivo in mice and rats or in liver and
kidney tissue crude enzyme systems are listed in Table 9-14. In addition to the
very active metabolite, 2-haloacetaldehyde, other possible reactive interme-
diates formed during the metabolism of 1 ,2-dihaloethylenes by glutathione-depen-
dent reactions, such as an episulfonium ion, may be involved in the covalent
binding to tissue macromolecules leading to tissue damage (Rannug and Beije,
1979; Hill et al., 1978; McCann et al., 1975; Guengerich et al., 1980; Anders and
Livesey, 1980).
9.1.3.2 MAGNITUDE OF EDC METABOLISM — The capacity of mammalian
organisms to metabolize EDC has been studied only in the mouse and rat. In these
two species, the extent of biotransformation of single doses of EDC has been
1 U
estimated by balance studies utilizing C-EDC.
Yllner (1971 a) administered intraperitoneally doses of 50-170 mg/kg of
1 4
C-EDC to mice in metabolism units with CO- and solvent traps. Yllner recovered
97-100$ of radioactivity in exhaled air and urine within 2*) hours. The results
of his balance studies are summarized in Table 9-9- For the low dose of 50 mg/kg,
Yllner found that 86$ was metabolized to CO,, (13$) and water and to other
metabolites appearing in the urine (73$). Unchanged EDC did not appear in the
urine, but 11 $ of the dose was eliminated unchanged in exhaled air. An increase
of the intraperitoneal dose resulted in a smaller percentage of the dose being
metabolized. For the largest dose, 170 mg/kg, 55$ was metabolized to C0? (5$)
and urine metabolites (50$). These results indicate that extensive biotransfor-
mation (55-86$) occurs in the mouse. Furthermore, the extent of metabolism is
dose-dependent, suggesting a limited capacity for biotransformation with satura-
tion of the metabolizing system(s). Saturation of metabolism to CO- and urinary
9-33
-------
Table 9-1 4 Identified Metabolites of Ethylene Dichloride and Ethylene Bromide.
System
Reference
Inorganic halide
co2
2-Chloroethanol
2-Chloroacetic acid
Bromoacetaldehyde
Thiodiglycolic acid
Ethylene
S-(2-hydroxyethyl)-cysteine
N-acetyl-S-(2-hydroxyethyl)-
cysteine
N-acetyl-S-(2-hydroxyethyl)-
oxide
S-carboxymethyl cysteine
S-(2-hydroxyethyl)-glutathione
S-(2-hydroxyethyl)-S-oxide
rat liver
cytosol
mouse, rat
exhaled air
mouse, rat
urine, blood
mouse urine
rat liver
microsoraes
mouse, rat
urine
rat liver
cytosol
rat liver
cytosol,
rat urine
rat urine
blood
mouse urine
rat liver
cytosol,
tissue
Heppel and Porterfield, 1948
Nachtomi, 1970
Yllner, 19 Tib
Reitz et al., 1980
Yllner, 19Tlb
Kokarovtseva and
Kiseleva, 1978
Yllner, l9Tlb
Hill et al., 1978
Yllner, l9Tib
Spreafico et al., 1979
Livesey and Anders, 1979
Nachtomi et al., 1966
Edwards et al., 1970
Edwards et al. , 1970
Yllner, l9Tlb
Nachtomi, 1970
S,S'-ethylene-bis-glutathione rat liver
Nachtomi, 1970
-------
metabolites occurred at a dose level of between 100-140 mg/kg and 50-100 mg/kg,
respectively.
Reitz et al. (1980, 1982) have found that EDC is also extensively metabo-
lized in the rat. These investigators conducted balance studies with C-EDC in
Osborne-Mendel rats after oral (150 mg/kg) and inhalation (150 ppm for 6 hours)
exposure. Their results are summarized in Table 9-3. In the oral balance study,
1 4
150 mg/kg of C-EDC (or, 1520 itmoles/kg) were administered. The sum of radio-
activity recovered in exhaled air, urine and feces, and that remaining in the
carcass was 101$ or complete recovery. Some 29$ of the dose was excreted
1 4
unchanged in exhaled air; 5% was metabolized completely to C0_ and 60$ of the
1 4
dose was metabolized to C-metabolites appearing in the urine. Less than 3%
radioactivity remained in the body 48 hours after dosing (probably as covalently
bound metabolites). These results indicate that the extent of total metabolism
of the oral dose was =70$ in these rats. For the inhalation exposure study, the
absolute dose administered by a 150 ppm, 6-hr exposure was unknown. From the
1 4
recovery after termination of exposure of C-radioactivity in exhaled air,
urine and feces, and radioactivity remaining in the carcass 48 hours after
exposure, it was estimated that the inhalation dose was 50.5 mg/kg (512
limoles/kg) or one-third of the oral dose. Of this dose, 2$ was excreted
unchanged in exhaled air, 7$ was metabolized completely to C02, and 84$ was
1 4
metabolized to C-metabolites appearing in the urine. Less than 5$ of the
radioactivity was left in the body 48 hours 'after inhalation exposure. Ignoring
the pharmacokinetic differences between acute oral and inhalation dosing, the
results of Reitz et al. demonstrate extensive biotransformation in the rat
(70-91$) and also suggest a dose dependency with greater metabolism for lower
doses, as Yllner (1971 a) observed in the mouse.
9-35
-------
The balance studies of both Yllner (oral dosing) and Reitz et al. (oral and
inhalation dosing) demonstrate that the primary route of elimination of EDC is by
metabolism. Renal excretion of nonvolatile metabolites predominates; however,
5-10$ is metabolized completely to CO- and water. It is of interest to note that
a small amount of EDC or its metabolites appear in the feces (<2%) , even from
inhalation exposure. Yllner (19 71 a) identified the metabolites appearing in the
urine of mice after dosing with C-EDC (1 70 mg/kg) and found six C-metabo-
lites; the three principal metabolites were: S-carboxymethylcysteine
thiodiacetic acid (33%) and chloroacetic acid (1 5%) (Table 9-15). However,
1 4
Spreafico et al. (1979) dosed rats with 50 and 150 mg/kg C-EDC and found the
principal metabolite to be thiodiacetic acid; chloroacetic acid was not detected
and S-carboxymethylcysteine was found only in trace amounts.
9.1.3.3 PATHWAYS OF METABOLISM — A number of studies have been carried
out describing the metabolism of 1 , 2-dihaloalkanes. Two principal pathways,
involving microsomal and cystosolic enzymes, respectively, have been proposed.
These pathways account for the formation of the metabolites identified in both in
vivo and in vitro studies listed in Table 9-1 ^ and also suggest the nature of the
reactive intermediates involved in the covalent binding to cellular macromole-
cules (protein and DNA) which has been demonstrated in both in vivo and in vitro
studies (Section 9.1.3-5).
A. Microsomal Reactions; Yllner (1971 a) originally proposed that the
degradation of 1 ,2-dichloroethane to 2-chloroacetic acid involved a primary
reaction in which chlorine was removed from one of the carbon atoms (hydrolytic
dehalogenation) to yield 2-chloroethanol. As evidence for this reaction, he
found chloroethanol to be a minor metabolite in the urine of mice injected with
EDC (Table 9-15). Following 2-chloroethanol formation, Yllner proposed that
alcohol was enzymatically converted to 2-chloroacetic acid (a major urinary
9-36
-------
Table 9-1 5 Percent Distribution of Radioactivity Excreted (M-hr) as Urinary
Metabolites by Mice Receiving 1,2-Dichloroethane- C or
2-Chloroacetic Acid- C.
Metabolite
Chloroacetic acid
2-chloroethanol
S-carboxymethylcysteine
Conjugated S-carboxymethyl-
cysteine
Thiodiacetic acid
S , S-ethylene-bis-cysteine
Glycolic acid
Oxalic acid
After
dichloroethane
(0.17 g/kg)
16
0.3
45
3
33
0.9
—
—
After
chloroacetate
(0.10 g/kg)
13
—
39
3
37
—
4
0.2
Adapted from Yllner (1971a,b)
9-37
-------
metabolite) via 2-chloroacetaldehyde. Kokarovtseva and Kiseleva (1978) have
also identified chloroethanol in the blood of rats (T /_ ca. 9 hours), and in rat
liver tissue within 1 hour and for 24-48 hours after oral administration of EDC
(750 mg/kg). Van Dyke and Wineman (1971) and subsequently Salmon et al. (1978,
1981) found that rat microsomal fractions, in the presence of 0- and NADPH,
dechlorinated a series of haloalkanes including EDC. The reaction for EDC had a
Vm of 0.24 nmol/min/mg protein with a K of 0.14 mM (Salmon et al., 1981).
ID 3.X ID
Thus, EDC and other haloalkanes interact with cytochrome P-450 to give a Type I
difference spectra associated with the metabolism of these substrates by direct
C-hydroxylation (Ivanetick et al., 1978). Besides EDC, Ivanetick et al. (1978)
observed that chloroacetaldehyde and chloroethanol also interacted with cyto-
chrome P450 with K values of 10.3, 30 and =15, respectively. Hill et al. (1978)
3
reported that 1,2-dibromoethane was activated to an irreversibly-bound species
by microsomal mixed-function oxidases, and also provided evidence that 2-bromo-
acetyaldehyde was formed in such reactions. More recently, Guengerich et al.
(1980) showed that 2-chloroethanol was a product of rat microsomal mixed-
function oxidation of EDC, requiring 0- and NADPH. The reaction was blocked by
classic P450 inhibitors and increased by pre-treatment with phenobarbital.
Guengerich et al. (1980) proposed that part of the microsomal mixed-function
oxidative metabolism of EDC proceeded from oxygen insertion into a C-H bond to
form an unstable chlorohydrin which spontaneously dehydrohalogenates to form 2-
chloroacetaldehyde. Figure 9-5 illustrates the proposed reaction and pathway.
Chloroacetaldehyde is then reduced to chloroethanol by alcohol dehydrogenase in
the presence of NADH, or oxidized to 2-chloroacetic acid by aldehyde dehydro-
genase. Johnson (1967) previously had observed that chloroethanol was readily
dehydrogenated to chloroacetaldehyde by alcohol dehydrogenases from yeast or
horse liver. The reaction, therefore, proceeds in either direction depending on
9-38
-------
NADPH
H
-HX
Hi 0 Alco. D
,x.c __
BINDING
PROTEIN. DNA 2.ha,oacat.
aldehyde fr Aid. D
H.
I
H,
2-hatoethanol
2-hatoacetic acid
5'i' P450.0, . F V'"1 * "1
-C-C-CI NADPH X-C-C-CI-O
BINDING
PROTEIN. DNA
•1 -haloso 2-chloroethane
BINDING
PROTEIN. DNA'
/OH
2-haloethanol
2-haloacetaldehyde
f Ald.D.
H» o
CI-C—C*-OH
2 haloacetic acid
Figure 9-5 Microsomal oxidative metabolism of 1.2-dihaloethanes.
Source: Adapted from Guengerich et al. (1980), Anders and
Livesey(1980).
9-39
-------
enzyme, substrate and cofactor concentrations. Williams (1959) also had
suggested that chloracetic acid appeared iri vivo via chloroacetaldehyde.
Further evidence for this reaction sequence has been provided by Guengerich
et al. (1980). These workers observed that covalent binding to microsomal
protein and DNA was inhibited 30-40? by inclusion of alcohol or aldehyde dehydro-
genases in the reaction mixture, strongly indicating that chloroacetaldehyde was
the reactive intermediate responsible for this portion of the total irreversible
binding of EDC. Chloroethanol itself, when added to the microsomal system, gave
only a low level of irreversible binding. In order to account for the remainder
of the microsomal mixed-function oxidative irreversible binding of EDC,
Guengerich et al. (1980) proposed the oxidative formation of the reactive meta-
bolite 1-chloroso-2-chloroethane, which spontaneously rearranges to 1-chloro-
acetaldehyde via a hypochlorite. The reaction is illustrated in Figure 9-5.
These workers noted that a reactive chloroso compound could react directly with
macromolecules, or hydrolyze (with release of hypochlorite ion) to form 2-
chloroethanol.
As a consequence of microsomal P-lJSO-mediated oxidation of EDC as
illustrated in Figure 9-5, further metabolism of the oxidative metabolites, 2-
chloroacetaldehyde and 1-chloroso-2-chloroethane, leads either to a "detoxifica-
tion" or to a further formation of reactive intermediates, respectively, as
illustrated in Figure 9-6.
Regarding detoxification reactions of chloroacetaldehyde with glutathione,
Johnson (1955, 1966a,b, 196?) found that Chloroethanol, administered orally to
the rat, caused rapid depletion of liver glutathione (GSH) with a concomitant
formation of S-carboxymethylglutathione. In vitro, the reaction with a rat liver
cytosol fraction required stoichiometric amounts of GSH (1 mole) and NAD (2
moles). Since pyruvate was also required for reaction, Johnson (1967) postulated
9-40
-------
2-cMoroacetaldehyde 2-chloroacetate
-Cl'
GSH
-CI"
-t?-H
GS
S-formylmethylglutathlone
S-carboxymethyl glutathione
glutathionase
< r (liver, kidney)
HOOC-CH-CH,-S-CH,-COOH
S-carboxymethyl cyt teine
t^CH,-
-COOH
'CH.-COOH
Thiodlglycolic ecid
f V't * "1
[ci-c-c-ci-oj
1 -chloroso-2-chloroethane
iSH I -H
H, H, f
GSH
Hi . •« T
CI-C-C-SG
S-(2 chloroethyl) gtutathlone
HOH
-cr
GS^JBINDING PROTEIN.
N DNA
episutfonium ion
GSH
GS-CH,-CH,-SG
S.S'-ethylene-bis-
HOH
glutathione
GS-CH.-CH.-OH
S42 hydroxyethyl)
glutathione
GSH. glutathione; Aid. D. aldehyde dehydrogenase; GT. GSH tranferase;
DH. dehydrogenase
Figure 9-6 . Further metabolism of 2-chloroacetaldehyde and l-chloroso-2-chloro-
ethane from microsomal oxidation. Source: Adapted from Guengerich et at. (1980)
and Anders and Livesey < 1980).
9-lM
-------
that chloroethanol was converted by alcohol dehydrogenase to chloroacetaldehyde,
which then conjugated with GSH to give S-formylmethylglutathione, and thence by
an NAD requiring dehydrogenation to S-carboxymethylglutathione. Johnson (I966b)
reported that chloroacetaldehyde also rapidly conjugates with GSH in vitro by a
non-enzymatic reaction at pH 7.0. He also has shown that S-carboxymethylgluta-
thione is rapidly degraded by rat kidney homogenate to yield glycine, glutamic
acid and S-carboxymethylcysteine, part of which is further metabolized to
thiodiglycolic acid. Yllner (1971 a) found that these latter two metabolites were
the two major urinary compounds after administering EDC to mice (Table 9-15).
Since these two compounds were also the major urinary metabolites after adminis-
tering 2-chloroacetate to mice (Table 9-15), Yllner 0971b) proposed that 2-
chloroacetic acid could also conjugate with GSH with chloride excision forming S-
carboxyraethylcysteine and thereby enter the pathway (Figure 9-6). Spreafico et
al. (1979) found that after rats were given oral doses of 50 and 1 50 mg/kg EDC, 2-
chloroacetic acid did not appear in the urine, but thiodiglycolic acid did appear
as the major urinary product. The difference between the urinary metabolites
found in mice by Yllner and those observed in rats by Spreafico et al. may be
explained by the availability of GSH in the livers of the animals in the two
studies.
Reactions of putative 1-chloroso-2-chloroethane: Guengerich et al. (1980)
noted that the chloroso compound which they proposed was formed by microsomal
P450 oxidative emtabolism of EDC, would be extremely reactive and could be
expected to either rearrange to 2-chloroacetaldehyde, hydrolyze to 2-chloro-
ethanol, or react directly with microsoraal protein (Fig. 9-5). In addition,
these workers postulated that the chloroso compound may react with GSH to form S-
(2-chloroethyl)glutathione, a half sulfur mustard, which could react via an
episulfonium ion intermediate with macromolecules (Fig. 9-6). However, in an
9-42
-------
Ames test with S. typhimurium TA1 535, EDC activated with rat liver microsomes,
NADPH, 0 and added GSH, did not enhance mutagenic activity. In contrast, the
use of 100,000 g liver supernatant containing GSH and GSH transferases markedly
increased the number of revertants per 1,2-dichloroethane plate. These results
suggested that either the putative chloroso compound is not formed in the micro-
somal system, or that differences in the subcellular systems contribute to
differences in covalent binding and mutagenicity.
B. Cytosolic reactions; Heppel and Porterfield (19^8) obtained an enzyme
preparation from rat liver capable of hydrolyzing the carbon-halogen bonds of
chloro derivatives of methane and ethane, including EDC. Bray et al. (1952) also
studied the dehalogenation of dichloroethane and other halogenated hydrocarbons
by rabbit liver extracts and nonenzymatic dechlorination by direct interaction
with sulfhydryl groups of GSH and cysteine. Nachtomi et al. (1966, 1970), found
that an enzyme system from the soluble supernatant fraction of rat liver
catalyzed a reaction between EDC and GSH. The formation of inorganic halide in
these studies could occur as a consequence of attack by GSH resulting in the
excision of halide, and the formation of S-(2-haloethyl)-GSH (Fig. 9-7). This
metabolite is a reactive intermediate, a half sulfur mustard, which, via its
episulfonium ion and further reaction with a second GSH or with water, may be
expected to form S,S-ethylene-bis-GSH or S-(2-hydroxyethyl)-GSH. The S,S'-
ethylene-bis-GSH may be presumed to be subject to degradation to S,S-ethylene-
bis-cysteine by glutathione in liver and kidney. Yllner (I97la,b) found small
amounts of S,Sf-ethylene-bis-cysteine in the urine of mice injected with EDC
(Table 9-15). Nachtomi et al. (1970) found that the products of the soluble
fraction of rat liver reaction with EDC were S,S'-ethylene-bis-glutathione and
S-(1-hydroxyethyl)glutathione. Nachtomi et al. (1970) identified the same two
compounds plus the sulfoxides of the former in urine of EDC- and dibromoethane-
-------
V-Y-
CI-C-C-CI
GT
GSH
-Cl
S-t2-chloro«thyl)-GSH
HOH
-cr
Ethylene
GS\J
Episulfonium ion
HOH
*»GS-CH,-CH,OH
I
GSH
S42 hydroxyethyDGSH
glutathionasa
GS-CH,-CH,OH
Oxide
GS-CH.-CH.-SG
S.S'-ethylene bit-GSH
NH,
HOOC-CH-CH.-S-CH.-C^OH
S-<2 hydroxyethyl) cystalna
Acetyl CoA Transferase
N-acetyl S-(2-hydroxyethyl) cysteine and oxide
Figure 9-7 . Cytosolic metabolism of ethylene dichtoride. Source:
Adapted from Anders and Livesey (1930).
-------
treated rats. Nachtomi et al. (1966) have also identified N-acetyl-S-(2-
hydroxyethyDcysteine in the urine of EDC- and 1 ,2-dibromoethane-treated rats.
Jones and Edwards (1968) and Edwards et al. (1970) confirmed the work of Nachtomi
with dibromoethane, and moreover, isolated the sulfoxides of both S-(2-hydroxy-
ethyDcysteine and its mercapturic acid from the urine of dibromoethane-treated
rats.
The half sulfur mustard, S-(2-chloroethyl)-GSH, and its episulfonium ion
formed by cytosolic GSH-dependent transferase metabolism (Fig. 9-7) has been
suggested by Rannug et al. (1978, 1979, 1980) to be responsible for the mutagenic
action of EDC in S. typhimurium TA1 535. These workers found that activation of
EDC occurred only with the soluble fraction of rat liver homogenates or with
purified GSH transferase enzyme in the presence of GSH. Their findings have been
confirmed by Guengerich et al. (1980). In addition, Rannug and co-workers
demonstrated that S-(1-chloroethyDcysteine and N-acetyl-S-(2-chloroethyl)-
cysteine produced direct mutagenic effects when tested on Salmonella, whereas S-
(2-hydroxethyl)cysteine showed no mutagenic effect. These results showed that
the enzymatic degradation of the GSH moiety does not abolish the mutagenic
properties of the conjugate, whereas a substitution of the chlorine with a
hydroxyl group does.
C. Formation of ethylene: Livesey and Anders (1979) have identified
ethylene in rat liver and kidney cytosol incubated with EDC. Ethylene was
produced in only small amounts which were, however, linearly independent on the
cytosolic protein concentration. The enzymatic conversion was glutathione
dependent and specific for this thiol. Studies of substrate specificity with
1 ,2-dihaloethanes showed that reactivity following the halide order with C-Br
bond cleavage and elimination occurring at a faster rate than C-C1 bond breakage.
Whereas EDC conversion was primarily an enzymatic reaction, ethylene formation
-------
occurred equally well from 1 ,2-dibroraoethane by a nonenzymatic reaction with
GSH. The microsomal P-H50 inhibitor, SKF 525-A, had no effect on EDC metabolism,
but the reaction was inhibited by p-chloromercuribenzoic acid, methyl iodide and
diethylmaleate. Livesey and Anders proposed that the intermediate in the conver-
sion of EDC to ethylene was S-(2-chloroethyl)glutathione (Fig. 9-7). An analog
of this intermediate, S-(2-chloroethyl) cysteine, was nonenzymatically converted
to ethylene in the presence of glutathione and other thiols.
1 U
D. Oxidation of EDC to CO ; After oral dosing of C-EDC, Yllner (1971 a)
in the mouse and Reitz et al. (1982) in the rat found that 5-10? of the dose was
metabolized completely to CO and water. Yllner 0971 b) also observed that after
2-chloroacetate administration, small amounts of glycolic and oxalic acids
appeared in urine (Table 9-15). Since these acids are known to be metabolized to
COp, Yllner proposed that 2-chloroacetate, arising from EDC metabolism (Fig.
9-5) is enzymatically hydrolyzed to glycolate by dehydrohalogenation, a portion
of which is further oxidized to oxalic acid.
E. Comparison of the metabolism of EDC to vinyl chloride; Rannug and
Beije (1979) have drawn attention to the similarities in the biotransformation
pathways of EDC and vinyl chloride. For both metabolisms, S-(2-chloroethyl)-
cysteine, thiodiglycolic acid, S-(2-hydroxyethyl)cysteine and its mercapturic
are involved as end products. Guengerich et al. (1980) considered the possibi-
lity that reductive dechlorination of EDC would yield chloride ion plus a chloro-
ethyl radical, which could either react with macromolecular targets, or lose a
hydrogen atom to form vinyl chloride. Alternatively, some other dehydrohalo-
genation mechanism (-HC1) could give rise to vinyl chloride. Vinyl chloride
could then be microsomally oxidized to 1-chloroethylene oxide, which can either
react with macromolecules, or be rearranged to 2-chloroacetaldehyde and proceed
through the pathway of Figure 9-6. However, Guengerich et al. found that reduc-
9-16
-------
tive dechlorination of EDC to a chloroethyl radical was an unlikely reaction
because metabolism and binding of EDC was dependent upon the presence of 0? in
microsomal incubations containing NADPH. Guengerich et al. calculated that the
rate of EDC conversion to either a total nonvolatile or to an irreversibly bound
metabolite was =25-50 times too high to support an obligatory role for vinyl
chloride as an intermediate. Moreover, they found that irreversible binding of
label from vinyl chloride to microsomal protein was inhibited 95% by either
alcohol or aldehyde dehydrogenase in microsomal incubations while these condi-
tions produced only 30-U05t inhibition of binding for EDC. These investigators
concluded that the metabolism of EDC probably does not involve vinyl chloride as
an intermediate.
9.1.3.4 METABOLISM, TOXICITY AND MODIFIERS — Dichloroethane metabolites,
chloroacetaldehyde, chloroethanol (oral LD,_0 for rats, 96 mg/kg), and chloro-
acetic acid (oral LD Q for rats, 76 mg/kg) are several times more toxic than EDC
itself (oral LD^ for rats, 770 mg/kg) (Heppel et al., 19^5, 19^6; Woodward et
al., 19^1; Ambrose, 1950; Hayes et al., 1973). Since the symptoms of poisoning
from both accidental and occupational exposures of humans and experimental
exposures of animals to these metabolites are very similar to those resulting
from EDC, it can be assumed that the toxicity of EDC for both man and animals is
in large part the result of biotransformation to these metabolites. Johnson
(1967) was the first to suggest that chloroacetaldehyde may be the premier toxic
metabolite, since this very reactive compound is capable of both enzymatic and
non-enzymatic interaction with cellular sulfhydryl groups (Fig. 9-6). However,
Yllner (I97la,b) found that chloroacetic acid also reacted extensively with
sulfhydryl compounds in vivo.
Heppel et al. (19^5, 19**6, 19^7) found a high mortality (35%) in rats given
1.3 g/kg EDC orally. Mortality was reduced by pre- or post-administration of
methionine, cysteine and other sulfhydryl compounds. Sulfur-containing amino
9-47
-------
acids, cysteine and methionine, also protected young rats from inhalation expo-
sure. This protective effect of sulfhydryl compounds is clearly related to the
marked depletion of glutathione levels which occurs in the livers of rats given
EDC, chloroethanol or chloroacetaldehyde (Johnson, 1965, 1966, 196?) and to the
enzyme pathways of metabolism of EDC (Figs. 9-5 to 9-7). Johnson (1965, 196?)
has noted that the morbidity and mortality of young rats given chloroethanol
orally was reduced by concomitant administration of ethanol. He postulated that
the protective effect of ethanol was due to simple substrate competition for
alcohol dehydrogenase which catalyzes the conversion of chloroethanol to chloro-
acetaldehyde (Fig. 9-5). Ethanol also inhibited early effects of chloroethanol
on liver glutathione depletion in these animals. This author also suggested that
the minimal toxicity observed with chronic low inhalation doses of EDC in
different animal species may be simply explained by the rapid replenishment of
tissue glutathione.
Similar observations on the relation of the level of glutathione in liver
and other tissues, and toxicity of the chlorocarbons, have been made by Jaeger
and his co-workers 097*1, 1979). Like EDC, vinylidene chloride is detoxified by
glutathione-dependent pathways. Jaeger et al. 097*0 found in rats that an 18-
hour overnight fast decreased the LC from a 4-hour inhalation concentration of
vinylidene chloride from 15,000 ppm (fed) to 600 ppm (fasted) and decreased the
concentration of vinylidene chloride that produced a significant plasma eleva-
tion of ct-ketoglutarate transaminase, evidence of liver cytoxicity (2000 ppm,
fed; 150 ppm, fasted). Increased susceptibility to hepatotoxicity was shown to
be related to a decreased hepatic glutathione concentration associated with the
fasting. Jaeger (1979) also demonstrated in rats a circadian rhythm for tissue
glutathione concentration of liver, blood, lung and kidney. For rats maintained
on a 12-hour light-dark cycle (6 pm to 6 am, dark), hepatic glutathione content
9-48
-------
was lowest at 6-10 pm and highest at 4-12 am; these periods correspond to the
greater and lesser hepatotoxicity respectively associated with vinylidene
chloride exposure during these two periods.
Nakajima and Sato (1979) studied the metabolism of the chlorocarbons in
vitro with microsomes from livers of fed and fasted male rats and found that the
metabolism of EDC increased 1 .5-fold as the result of a 24-hour fast, although
fasting produced no significant increase in the microsomal protein and cyto-
chrome P-450 liver contents. Microsomes from livers of fasted female rats
displayed even more active metabolism of EDC (3.6-fold over fed rats). These
observations suggest that the increased toxicity of EDC that occurs with food
deprivation may be due not only to decreased liver glutathione content, but also
to a greater production of toxic metabolites: chloroacetaldehyde, chloroethanol
and chloroacetic acid.
Sato et al. (1980) have studied the effect of chronic ethanol consumption on
hepatic metabolism of chlorinated hydrocarbons in rats to provide information on
the effect of ethanol consumption on the toxic effects of chlorinated hydro-
carbons in the work environment. Male rats were maintained on a daily intake of
ethanol amounting to 30$ of their total energy intake for 3 weeks. The hepatic
microsomal metabolism of EDC was increased 5.5-fold over microsomes from livers
of ethanol-free rats, although ethanol feeding produced only a slight increase in
the microsomal P-450 content. The increase in enzyme metabolism of EDC occurred
only with microsomal fractions and not with cytosolic fractions, and one day
withdrawal of ethanol feeding almost completely abolished the effect of chronic
alcohol consumption.
Sato et al. (1981 ) studied also the effects of an acute single dose of
ethanol (given as an aqueous solution by gastric intubation) on the metabolism of
chlorinated hydrocarbons in rats. Hepatic metabolism of EDC (by a 10,000 g liver
9.49
-------
fraction) added in vitro was accelerated (up to 2.5-fold) by doses of ethanol up
to 4 mg/kg without causing any increase in P-450 content. The stimulation was
not seen and even suppression occurred with higher doses of ethanol. Increased
metabolism was most marked 16-18 hours after ethanol administration. Ethanol
added directly to the incubation mixture, however, depressed EDC metabolism.
These investigators suggest that ethanol is capable of exerting a dual effect on
EDC-metabolizing enzymes, i.e., inhibition and stimulation, depending on ethanol
concentration.
9.1.3.5 METABOLISM AND COVALENT BINDING — The metabolism of EDC results
in the production of reactive metabolites of an electrophilic nature such as
those proposed to be formed in the metabolic schemes of Figures 9-5 to 9-7. The
occurrence of these metabolites, chloroacetaldehyde, the putative 1-chloroso-2-
chloroethane, the half-mustard S-(2-chloroethyl)glutathione and its episulfonium
ion, provides a theoretical basis for the covalent binding observed with EDC to
cellular macromolecules such as protein and DNA with consequent possibility of
damage to cellular integrity and genetic apparatus. Such covalent binding reac-
tions are known to be related to teratogenesis, rautagenesis and carcinogenesis,
although chemical reactivity alone is not evidence of genetic damage (Lutz,
1979). The amount of covalent binding, and hence damage potential, is related to
the pharmacokinetics of EDC exposure. At least in the rat, there is ample
evidence from pharraacokinetic studies of EDC that the metabolic capacity for EDC
metabolism is saturable (Sections 9.1.2 and 9-1.3). It may therefore be specu-
lated that the organism when confronted with low quantities of EDC utilizes
glutathione conjugation detoxification reactions (Fig. 9-6) and nonelectrophilic
metabolites are primarily produced, but when confronted with higher EDC doses,
increasing amounts of electrophilic metabolites are produced to a saturating and
limiting rate for their enzymatic pathways (Figs. 9-6 and 9-7). Reitz et al.
9-50
-------
(1980, 1982) determined total covalent binding and binding to DNA in rats exposed
1 4
to C-EDC by the oral (150 mg/kg) and inhalation (150 ppm, 6 hour) routes. The
results of their study with these presumably saturating doses are given in Table
9-16. These results show no striking difference between the two routes of
exposure in the distribution of covalent binding and DNA binding among the
various organ tissues, although the tissue levels of covalent binding are
generally higher after inhalation exposure for total binding and after gavage
exposure for DNA binding. The exposure doses used in these studies of Reitz et
al. are comparable to the oral doses of EDC use in the lifetime NCI carcino-
genicity study (NCI, 1978) and to the inhalation doses of the carcinogenicity
studies in rats of Maltoni et al. (1980). No excess tumors were reported by
Maltoni et al., while liver and forestomach were sites of malignant tumors in the
NCI study. Recently, Storer et al. (1982) determined DNA damage produced in vivo
in the livers of male B6C3F1 mice following single oral doses of EDC (100 mg/kg).
DNA damage was evaluated by sedimentation of liver nuclei in alkaline sucrose
density centrifugation, and by DNA recovery. Nuclei from EDC-treated mice
isolated 4 hours after dosing sedimented more slowly and the total DNA recovery
was decreased 16$ from untreated mice. However, dimethyl nitrosamine, used as a
positive control, decreased recovery of DNA 61$.
In contrast to the low covalent binding potential of EDC in vivo, inhalation
exposure of rats to only 20 ppm, 1,2-dibromoethane (EDB; 7 hours/day, 5 days/week
for 18 months) produced tumors in the liver and kidney, sites of covalent binding
(Hill et al., 1978). Furthermore, Plotnick et al. (1980) found that the carcino-
genicity of EDB was enhanced by the dietary addition of disulfiram (0.05% by
weight; an inhibitor of aldehyde dehydrogenase) which blocks the further oxida-
tion of bromoacetaldehyde formed in the metabolism of EDB (Fig. 9-5) and which
presumably results in increased tissue levels of bromoacetaldehyde with an
9-51
-------
TABLE 9-16
Total Macromolecular Binding and DNA Binding in Selected Tissues
of Rats After Exposure to C-EDC by Oral or Inhalation Routes .
Nanomole equivalents EDC/g tissue
oral inhalation
(1 50 mg/kg) (150 ppm 6 hr)
Total Binding (n=4)
Liver
Kidney
Spleen3
Lung
Forestomacha
Stomach
DNA Binding (nr3)
Experiment 1
Livera
Spleen
Kidney
Stomach
Experiment 2
175
183
65
106
160
90
24
25
21
34
19
2
268
263
130
14?
71
156
45
48
22
16
19
29
21.3 ± 7.4
5.8 + 0.7
17.4 + 2.3
14.9
8.2 ± 3.3
1 .8 + 0.3
5.2 ± 3.7
2.8
Liver
Spleen3
Kidney
Stomach
13.9 + 2.1
2.5 + 0.3
14.5 + 6.2
6.7
3.3 ± 1 .2
1 .8 + 0.5
2.0 + 0.3
1 .9
Results are reported as nanomole equivalents of EDC/g tissue + S.D.
Animals were sacrificed 4 hr after oral dosing or immediately following a 6-hr
inhalation exposure.
Site where malignant tumors were observed in the NCI study (1978) after EDC was
given by gavage, also forestomach. No excess tumors were reported in the inhala-
tion carcinogenicity bioassay (Maltoni et al., 1980).
bReitz et al., 1982.
9-52
-------
increase of covalent binding. Plotnick et al. (1980) showed that dietary disul-
firam markedly increased covalent binding of C-EDB in the nuclei of liver cells
in rats dosed with EDB (Table 9-17).
Covalent binding of metabolites from both oxidative microsomal and cyto-
solic metabolism of EDC has been demonstrated in vitro by several investigative
groups. Van Duuren and his colleagues (Banerjee et al., 1978, I979a,b, 1980)
observed microsomal-activated covalent binding of both EDC and EDB to native DNA
from salmon sperm, and to liver and lung microsomal protein from rats and mice.
Binding to DNA did not occur in the absence of microsoraes or in the presence of
denatured microsoraes. Cytosolic metabolism produced insignificant metabolic
activation and binding. The microsomal-activated binding was enhanced by pheno-
barbital and 3-methylcholanthrene pretreatment, whereas the addition of gluta-
thione to the microsomal reaction reduced the binding. Similar results were
obtained by Sipes and Gandolfi (1980). Van Duuren and his co-workers suggested
that EDC and EDB were biotransformed by microsomal oxidative reactions to the
reactive transient metabolites, 2-haloacetaldehyde, 2-haloethanol or halo-
ethylene oxide, all of which are electrophilic in nature. Banerjee, Van Duuren
and Kline 0979b) demonstrated that both 2-bromoacetaldehyde and 2-bromoethanol
bind covalently to protein and DNA without metabolic activation. Guengerich et
al. (1980) have found that C-EDC is metabolized by both microsomes and cyto-
solic systems to metabolites that covalently bind to protein and calf thymus DNA.
Cytosolic metabolism depended upon the presence of glutathione and involved
glutathione transferases (Fig. 9-7), although glutathione inhibited raicrosomal-
activated binding to protein but stimulated binding to DNA. These investigators
also produced evidence that 2-chloroacetaldehyde, S-(2-chloroethyl)glutathione,
and their putative 1-chloroso-2-chloroethane are the metabolites involved in the
covalent binding.
9-53
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Table 9-1 7 Effect of Dietary Disulfiram Upon the V Content of Liver
Nuclei Isolated 24 or 48 Hours After Administration of a Single Oral Dose of
1 5 mg/mg [U- • C]EDB
Time Interval Control Disulfiram
24 hours 68 7 + 82* 1 773 + 31 4
48 hours 460 + 42 1534 + 197
•Results are expressed as dpm/pellet (mean + S.E.M.) of duplicate determinations
on 6 animals per group at 24-hr and 5 animals per group at 48 hr.
From Plotnick et al., 1980.
9-54
-------
9.1.4. Summary and Conclusions. At ambient temperatures, EDC is a volatile
liquid with appreciable solubility in water, and hence the principal routes of
entry to the body are by pulmonary and oral absorption. The pharmacokinetics of
absorption and excretion of EDC have been studied extensively in the mouse and
rat. Absorption from the gastrointestinal tract is rapid and complete, occurring
by first order passive processes with a half-time of <6 min. A dose-dependent
first-pass effect with pulmonary elimination of unchanged EDC occurs with oral
ingestion, thus decreasing the amount reaching the systemic circulation. At the
low concentration of EDC existent in food and water, nearly complete extraction
by the liver is expected. With inhalation exposure, a blood/air partition
coefficient of =20 at 37°C has been observed. Tissue distribution of EDC is
consistent with its lipophilic nature. The chemical crosses the blood brain and
placental barriers and distributes into breast milk. The adipose tissue/blood
partition coefficient varies from 7-57 depending on dose.
Excretion of unmetabolized EDC is almost exclusively via the lungs;
however, metabolism and excretion of the metabolites by other routes is extensive
and dose-related. In the mouse and rat, after both oral and inhalation exposure,
the half-life of EDC in blood increases with dose, although it is <60 min at high
doses. The parameters of total body elimination are compatible with a 2-compart-
ment system and Michaelis-Menten kinetics. The short half-life of EDC suggests
that the risk of bioaccumulation from intermittent multiple oral and inhalation
exposures is small. Daily oral dosing of rats does not result in significant
bioaccumulation in blood or other tissues.
Biotransformation of EDC has been shown to occur by multiple pathways, in
both liver microsomal and cytosol fractions. In the mouse and rat up to 90$ of
low oral or inhalation doses (<50 mg/kg) are metabolized, with a decreasing
percentage of the dose metabolized as the dose approaches and exceeds saturation
9-55
-------
of metabolic capacity. Metabolism produced 2-chloroacetaldehyde, S-(2-chloro-
ethyDglutathione (a half sulfur mustard) and other putative reactive metabo-
lites capable of covalent binding to cellular macromolecules, as well as nonreac-
tive glutathione conjugates from "detoxification reactions." The intensity of
covalent binding of reaction metabolites to proteins, lipids and DNA, however, is
considerably less than that observed with the carcinogenic bromine analog and
other known carcinogens.
Exposure to EDC decreases liver levels of reduced glutathione in a dose-
dependent manner. Glutathione plays an important role through glutathione
conjugation detoxification mechanisms in protecting against binding and cellular
toxicity. Covalent binding, hepatotoxicity and mortality of experimental
animals are all reduced by administration of sulfhydryl amino acids or gluta-
thione. Conversely, toxicity is enhanced by low liver and tissue concentrations
of glutathione. Phenobarbital and other inducers of P-450 metabolism increase
the metabolism of EDC, the toxicity and covalent binding. Fasting reduces gluta-
thione tissue content and increases both the metabolism and toxicity of EDC.
Ethanol, acutely or chronically administered, may either enhance or inhibit EDC
metabolism and toxicity depending on the tissue alcohol concentration.
9-56
-------
9.2. ACUTE, SUBCHRONIC AND CHRONIC TOXICITY
9.2.1. Effects in Humans. The preponderance of reports on the toxicity of EDC
to humans was published in the foreign literature (primarily German, Russian, and
Polish). Many of these reports involved exposure to high levels of compound,
involved single cases or small numbers of individuals, were anecdotal in nature
and discussed observations that related to the overall toxicity of this chemical
in man, and/or provided little detailed correlation between toxic effects and the
amount or duration of exposure. Since detailed reviews of the foreign studies
were available from NIOSH (1976) and the U.S. EPA (1979), these sources were used
in part as a basis for the following discussion of human health effects. Trans-
lations were obtained and evaluated independently for all foreign studies that
provided dose-response data of relevance to human risk assessment. Reports in
which exposures were not primarily to EDC (i.e., most reports of mixed solvent
exposures) were not discussed.
9.2.1.1. ACUTE EXPOSURES
9.2.1.1.1. Case Reports and Surveys.
9.2.1.1.1.1. Oral Exposure. Information on the effects of ingested EDC
is available solely from clinical case reports and surveys involving accidental
and intentional exposures. Many of the cases involved fatalities and described
symptoms and signs of poisoning that preceded death. The progression of
signs/symptoms and the outcome/findings of cases in which the quantity of EDC
ingested leading to death was reported are summarized in Table 9-18. Ingestion
of quantities of EDC estimated to range from 8 to 200 mS, (=1 U3-3571 mg/kg,
assuming 70 kg body weight) were reported as lethal to adult males. Following
ingestion there was often a latent period, generally 30 minutes to 3 hours, prior
to the onset of symptoms. Symptoms were indicative of CNS effects and gastro-
9-57
-------
TABLE 9-18
Effects Associated with Acute Lethal Oral Doses of Ethylene Bichloride in Humans
Patient8
Sex/Age
Amount
Ingested
Symptoms and Signs
Outcome and Findings
Reference
males/20 to 29 years
3 males/19 to 27 years
a
Male/NS
Hale/63 years
1 50 to 200 mi
(=188 to 250.6 g)
70, 80 and 100 mil
(=«7.7, 100.2 and
125.3 g)
=62 mi (=102.7 g)
mixed with coffee
and beer
2 oz. (=75.2 g)
mixed with orange
Juice and ginger ale
Symptoms were not specified,
but appeared after 3 to U hours.
Onset of symptoms within a
few minutes: vomiting;
weakness; dizziness; lost
consciousness
Intoxication; vomiting;
diarrhea; unconsciousness;
dypsnea
Onset of symptoms after 2 hours:
nausea; faintness; vomiting.
Subsequently, cyanosis; dilated
pupils; coarse rales; weak
and rapid pulse; diarrhea;
increased cyanosis; absence
of pulse and heart sounds;
dypsnea
Deaths after 10, 15, 33 and Bryzhin, 19«5
35 hours. Punctuate
heraorrhaging in the epi-
cardium, pleura, and mucous
membranes of the stomach and
duodenum; varying degrees of
liver damage with focal
hemorrhaging in one case; yellow-
white fibrinous bundles of blood
in the heart cavities and lesser
circulatory vessels; hemolytlc
Jaundice of the endocardium,
aortal intima, and dura mater;
evidence of decomposition of
circulating erythrocytes
Deaths after 5 to 8 hours
Hyperemia and hemorrhagic
lesions (see text);
evidence of overt bleeding
into the visceral organs
Death after 6 hours
Hyperemia and hemorrhagic
lesions (see text)
Death after 22 hours
attributed to circulatory
failure. Extensive
hemorrhagic colitis; nephrosis
with calcifications of the
tubular epithelium and tubular
and vascular elastic membranes;
fatty degeneration of the liver;
spleen and lungs; multiple
perivascular hemorrhages of
the brain.
Kaira, 1966C
Noetzel,
Hueper and Smith,
1935
-------
TABLE 9-18
Patient3
Sex/Age
Male/1 6 years
Amount
Ingested
50 ml
(=62.7 g)
Symptoms and Signs Outcome and Findings
Vomiting; epigastric pain; Death after 91 hours
muscle spasms, hiccups, rapid
Reference
Roubal, I947b
Male/80 years
Male/18 years
50 mfc
(=<62.7 g)
50 ml
(=62.7 g)
Male/57 years
DO mJ,
(~ 50.1 g)
pulse and lack of eyelid
response to light on the 4th
day
Elevated serum enzymes: LDH;
SCOT; SGPT; alkaline phosphatase
glutamic dehydrogenase; RNAase.
Onset of symptoms after 1 hour:
somnolence and cyanosis.
Diarrhea after 4 hours.
Impaired blood coagulation
after 5.5 hours: increased
prothrombin time; decrease in
clotting factors II and V;
thrombocytopenia; no increase
in fibrinolysis
Somnolence; vomiting; sinus
tachycardia; ventricular
extrasystoles; regained
consciousness after 14 hours;
dypsnea; loss of blood
pressure; cardiac arrest.
Impaired blood coagulation
observed after 21 hours;
prolonged bleeding from
venipunctures; reduction In
activity of clotting factors
II, V, VII and VIII; complete
defibrination; thrombo-
cytopenia; increased thrombin
time
Death within a few hours
Death after 17 hours
attributed to circulatory
shock. Intravascular
thrombosis were not found.
Secchl et al., 1968'
Schonborn et al.,
I970b
Death after 24 hours.
Thrombi In the pulmonary
arterloles and capillaries;
hemorrhages into the mucosa
of the esophagus, stump of the
stomach, rectum and in the
subepicardial, subendocardial
and myocardial tissues. The
coagulation disorder with
thrombocytopenia attributed
to disseminated intravascular
coagulopathy and hyper-
fibrinolysis
Martin et al., 1969
-------
TABLE 9-18 (cont.)
Patient3
Sex/Age
Male/30 years
Amount
Ingested
1)0 mi
( = 50.1 g)
Symptoms and Signs
Slight cough; reddened
conjunct! vae; shock; weak,
Outcome and Findings
Death after 28 hours
Hyperemia and hemorrhagio
Reference
Garrison and
Leadingham, I954b
Male/50 years
Male/55 years
(asthmatic)
Male/NS
Male/NS
=<30 ml
(=37.6 g)
20 mi
(=25.1 g)
=20 mi
(=25.1 g)
=20 ml
(=25.1 g)
rapid pulse. Regained
consciousness after
3 hours; hyperactlvity
alternated with
semicomatose condition
Onset of symptoms after
30 minutes: unconsciousness;
vomiting; cyanosis;
dilated and fixed pupils;
pulmonary edema; extreme
dypsnea
Epigastric pain; extreme
dizziness; sleeplessness;
vomiting; slow pulse
Onset of symptoms after 1 hour:
repeated vomiting. Cyanosis
and dypsnea after 12 hours
Symptoms not reported
lesions (see text); evidence
of overt bleeding into the
visceral organs
Death after 1 0 hours
Diffuse hemorrhaglc
gastritis; bilateral
pulmonary congestion;
acute necrotizlng
bronohiolltis and
bronchitis; acute toxic
nephrosis; diffuse hepatic
necrosis; hyperemia of the
brain with scattered peri-
vascular hemorrhages in
the pons
Death after 21 hours
Death after 1 3 hours
Death within 12 hours
Lochhead and Close,
1951
Roubal, 1947°
Flowtow, 1952L
Flowtow, 1952
-------
TABLE 9-18 (cont.)
Patient*
Sex/Age
Male/1 U years
Amount
Ingested
15 mJi,
(= 18.8 g)
Symptoms and Signs
Onset of symptoms after 2 hours:
Progressive appearance of
Outcome and Findings
Death after 6 days
Extensive mid-zonal liver
Reference
Yodaiken and
Babcock, 1973
Male/32 years
8 mi
(=10 g)
Male/32 years
glass
severe headache; staggering;
lethargy; periodic vomiting;
decreased blood pressure;
oliguria; dypsnea; somnolence;
increased dypsnea; and oliguria,
hemorrhaglc nasogastric aspirate;
ecchymoses; sinus tachycardia;
cardiac arrest, pulmonary
edema; refractory hypotension.
Hypoglycemia on day 2 and
hypercalcemia on day 4.
Progressive decrease in blood
coagulation ability: increased
prothrombin time; all clotting
factors except VIII were
markedly decreased on day U.
Burning sensation in mouth,
throat and stomach; drank milk
and vomited; weakness; speech
retardation; lethargy; asthenia;
cold sweat; muffled heart sound;
weak and rapid pulse. 22 hours
after ingestion: excitation;
restlessness; delirium; flushed
face; systolic murmur; respiratory
depression; circulatory weakness;
anuria
Vomiting, weakness, stomach
pains. On 3rd day: rest-
lessness, coated and dry
tongue; bloody diarrhea;
abdomen painful on palpitation;
enlarged liver; dry, moist rales;
rapid, weak pulse; anuria;
increasing cyanosis; un-
consciousness
necrosis; renal tubular
necrosis; focal adrenal
degeneration and necrosis
Death after 56 hours
Bogoyavlenski et al.,
19686
Death on the 3rd day
Hyperemia and hemorrhagie
lesions (see text)
Agranovich,
-------
TABLE 9-18 (cont.)
Patient"
Sex/Age
Amount
Ingested
Symptoms and Signs
Outcome and Findings
Reference
Male/27 years
half glass
Male/13 years
(alcoholic)
4 drinks diluted
with orange Juice0
I
cr>
no
Male/43 years
(alcoholic)
Male/NS
4 drinks diluted
with orange juice0
several mouthfuls
Onset of symptoms after
2.5 hours: Unconsciousness
that was regained after
12 hours; vomiting
(dark vomitus); burning
sensation in the digestive
tract; dypsnea; nausea;
cyanosis; depressed
respiratory rate; moist
rales; muffled heart sounds;
rapid pulse; extrasystoles;
anuria
Unconsciousness
Confusion; deep sleepiness;
unconsciousness; vomiting
with blood
Death after 19 hours
Hyperemia and hemorrhagic
lesions (see text); evidence
of overt bleeding into the
visceral organs
Bogoyavlenski et al.,
1968
Onset of symptoms after
30 min: vertigo; nausea;
vomiting; slightly muffled
heart sound; tachycardia.
After 17.5 hours: headache;
substernal pain; cyanosis;
rapid, weak pulse; dry rales;
decreased blood pressure;
vomiting with bile; diarrhea;
subconjunctival hemorrhage;
oliguria; paranephric hemorrhage.
5th day pulmonary edema and
unconsciousness
Death after 8 hours
Hyperemia and hemorrhagic
lesions (see text);
evidence of overt bleeding
into the visceral organs
and lungs. Death after
24 hours. Hyperemia and
hemorrhagic lesions (see
text); evidence of overt
bleeding into the visceral
organs and lungs
Death after 24 hours
Hyperemia and hemorrhagic
lesions (see text); evidence
of overt bleeding into the
visceral organs and lungs
Death on the 5th day
Hulst et al., 1946
Hulst et al., 1946
Morozov, 1958
-------
TABLE 9-18 (cont.)
Patient"
Sex/Age
Amount
Ingested
Symptoms and Signs
Outcome and Findings
Reference
Male/63 years
1 or 2 sips
I
o>
OJ
Male/1 1/2 years
Male/79 years
Male/2 years
Male/23 years
1 sip
1 sip
1 sip
1 sip
Unconsciousness shortly after
ingestion, but soon
regained; strong vomiting;
period of improvement;
unconsciousness again
after 10.5 hours; falling
blood pressure
Extreme weakness; comatose;
vomiting
Vomiting; weakness; pale;
cyanosis; scarcely conscious;
vagueness; rapid, regular
pulse; blood pressure not
measurable
Vomiting; diarrhea; tonic
spasms; increasing loss of
consciousness; dypsnea;
impaired circulation
Onset of symptoms after 1 hour:
dizziness; nausea; unconscious-
ness; vomiting; cyanosis; no
pupil reaction; no corneal
reflex; dypsnea; strong motor
unrest.
Death after 14 hours
attributed to circulatory
failure. Hyperemia and
hemorrhagic lesions (see text)
Death the next day
Hyperemia and hemorrhagic
lesions (see text)
Death after 10 hours
attributed to heart and
circulatory failure.
Hyperemic and hemorrhagic
lesions (see text)
Death after 20 hours
Hyperemia and hemorrhagic
lesions (see text)
Death after 8 hours
attributed to respiratory
and circulatory failure
Hyperemia and hemorrhagio
lesions (see text); evidence
of overt bleeding into the
visceral organs
Freundt et al., 1963°
Keyzer,
Weiss, 1957
Heinfried, 1953
Reinfried, 1953
NS = Not stated
bData compiled from NIOSH, 1976
cPresumably EDC was mixed instead of alcohol
-------
intestinal disturbances, and frequently included dizziness, nausea, headache,
periodic vomiting, diarrhea, epigastric pain or tenderness, dilated pupils and
lack of corneal reflex, rapid and weak pulse rates, progressive cyanosis, dyspnea
and unconsciousness. These symptoms of toxicity are characteristic of those
produced by many of the chlorinated aliphatic hydrocarbons. Somnolence,
oliguria and anuria, muffled heart sounds and motor unrest have also been
described in a number of cases.
The results of several health surveys of large numbers of orally exposed
individuals have recently been reported by Russian investigators, and summarized
by U.S. EPA (1979) (Akimov et al., 1976, 1978; Shchepotin and Bondarenko, 1978;
Bonitenko et al., 1974, 1977; Luzhnikov et al., 1974; Luzhnikov and Savina, 1976)
and Chemical Abstracts (Andriukin, 1979). Information regarding the design of
these surveys is not available, and dosage information is either not available or
not adequately reported (i.e., not correlated with effects) (Table 9-19). The
clinical symptoms and signs of exposure recorded in the surveys are consistent
with those described in single case reports (see Table 9-18) (i.e., neurological
effects and evidence of liver and kidney dysfunction), but there appears to be a
more frequent indication of cardiovascular insufficiency. The range of doses
that elicited effects in the surveys (-12.5 to 250.6 g) also appear to be consis-
tent with the single case reports (see Table 9-18), but incidences of fatalities
were not presented in the available summaries. Although none of the effects
reported in the surveys were correlated with specific doses, several of the
studies indicated that the severity of poisoning was related to blood levels of
EDC (Bonitenko, 1974, 1977; Luzhnikov et al., 1974, 1976).
The clinical syndrome of oral EDC poisoning in children is similar to that
seen in adults, but the lethal dose range is somewhat lower (0.3 to 0.9 g/kg)
(Hinkel, 1965). This range of doses did not always cause death, and is derived
9-64
-------
TABLE 9-19
Effects of Acute Oral Ingestlon of 1 ,2-Dichloroethane (Survey Results)
Route
No. of Subjects
Dose
Principal Findings
Reference
Oral
121
20 to 200 ml
(=25 to 250.6 g)
U1
Oral
Inhalation
211
37
NR
NR x 20 to 30 minutes
110
Mild to severe poisoning characterized by
pronounced DCE odor on breath (91$), dry skin
(75$), hypotension (7W, extreme pupil dilation
(72$), mucosal cyanosis (67$), tachycardia (62%),
respiratory difficulty (59$). muscular
hypotonia (46$), decrease in tendon reflexes (46$),
loss of consciousness (12$). Neurological syn-
dromes noted in 118 subjects: comatose C*2$),
atactlc (12$), asthenic with autonomic vascular
Insufficiency (27$), extrapyramidal (23$),
convulsive (7.W, psychotic (5$). Lethality
not reported.
Aggregate findings for 218 total patients reported.
Neurological disorders (incl. unconsciousness,
respiratory depression) (100$), cardiovascular
insufficiency (incl., arrhythmias, hypotension,
reduced cardiac output, decreased peripheral
resistance) (60$), liver dysfunction (incl.,
enlargement, hyperbilirubinemia, increased
serum albumin and asparagine transaminase (35$).
Nephropathology (ollguria, proteinuria, azotemia,
acute renal failure with disturbed acid/base
balance) particularly associated with inhalation
exposures. Gastroenteritis milder in subjects
exposed via inhalation. No correlation between
severity of poisoning and the blood or urine
concentration or the amount inhaled.
Acute gastritis with vomiting (77$), neurological
disorders including coma (81$), acute cardio-
vascular insufficiency (57$), hepatitis (56$)
with liver enlargement and dysfunction
(abnormal bromosulfalein, plasma bilirubin,
plasma glutamine - aparagine transaminase).
Clinical symptoms of poisoning were observed
at blood concentrations of 0.5 mg $, and coma
developed at 5 to 7 mg $.
Akimov et al.,
1976, 1978
Schepotln and
Bondarenko, 1978
Luzhnlkov et al.,
1976, 1978
-------
TABLE 9-19 (cont.)
Route
No. of Subjects
Dose
Principal Findings
Reference
NSa
160C
NA
Oral
Inhalation
21
3
10 to 100 mi (=12.5 to 125 g)
NR
Oral
32
Hemodynamic shock due to myocardial dysfunction.
Characterized by compensatory (increased
peripheral resistance, normal or slightly
increased arterial blood pressure, decreased
cardiac output and blood volume, decreased
cardiac isometric contraction, increased
ventricular expulsion time, asynchronous
contractions) and decompensatory (pronounced
and progressive hypotension, decreased cardiac
output, normal or slightly decreased peripheral
resistance, decreased myocardial contractile
force during ventricular systole, prolonged
periods of asynchronous contractions) phases.
EKG changes including arrhythmias observed in
both compensated and decompensated shock.
Pathologic changes in the myocardium charac-
terized by capillary endothelial cell edema,
capillary lumen stenosis, edema of the
myocardial interstices with leukocyte
accumulation and microfocal hemorrhages,
decreased glycogen, degenerative changes, and
decreased mitochondrial enzyme activities.
1 7 patients exhibited manifestations of
light/mild poisoning: headache, vertigo,
abdominal pain, nausea, vomiting, and signs of
cardiac insufficiency (increased contraction
rate, decreased minute volume, decreased
circulating blood volume, decreased cardiac index);
5 of 1 7 had hepatomegaly, icteric skin, solera,
and increased billrubin levels. The other 10
patients were comatose and had more pronounced
symptoms of cardiac insufficiency.
Gastroenteritis and proteinuria. Elevated
leukocyte count and elevated alanine/aspartate
aminotransferase activities correlated with
severity of poisoning. Coma was associated with
blood concentrations of 15 to 30 mg J, and
consciousness returned at levels below 8 to
10 mg %. Adipose tissue and blood levels of
68 and 1.2 mg >, respectively, at autopsy.
Luzhnikov et al.,
1976, 1978
Andriukin, 1979
Bonitenko et al.,
1971, 1977
-------
TABLE 9-19 (cont.)
Route
Oralc
No. of Subjects Dose
7 children HR
(1 to 6 years)
Principal Findings
Clinical syndrome similar to that in adults:
severe and persistent vomiting (within 1 hour),
Reference
Hinkel, 1965
and subsequent (immediate to 10 to 12 hours)
narcotic effects (e.g., somnolence, motor unrest,
reflex increases, convulsions or coma). Less
frequent Indications of circulatory failure,
kidney and liver functional disturbances, and
tachycardia. No remarkable hematologlc changes.
Typical pathological anatomical findings.
LD2Q reportedly ranged from 0.3 to 0.9 g/kg.
Route is probably oral, but not specifically stated in the EPA O979) summary of this study.
The EPA summary of this study stated that "at least" 160 patients were studied.
cExposure to a. "nerve balsam" medicine that was 75t 1,2-dichlorethane (other components not stated in EPA summary).
-------
from a review of seven cases of accidental poisoning in children that ranged in
age from 1 to 6 years.
Foreign reports of individual non-fatal cases of EDC ingestion (lenistea
and Mezincesco, 19^3; Bloch, 1946; Stuhlert, 1949; Flowtow, 1952; Kaira, 1966;
Rohmann et al., 1969; Gikalov et al., 1969; Pavlova et al., 1965; Agranovich,
1948) were in most instances not detailed in the NIOSH (1976) or U.S. EPA (1979)
reviews, presumably because the effects were similar to those that preceded death
with lethal exposures, and because the quantities ingested were not known. Bloch
(1946) did note bloody diarrhea and evidence of adverse liver (enlargement,
slightly increased serum bilirubin, urobilinogen, abnormal galactose and alcohol
load test results) and kidney (oliguria, albumin and casts in the urine,
temporary retention of nitrogenous substances) effects in one man who claimed to
have swallowed "only a small amount" of EDC.
Death was usually ascribed to circulatory and respiratory failure, and
autopsies revealed tissue congestion, cellular degeneration, necrosis and
hemorrhagic lesions of most organs, including the stomach, intestines, liver,
kidneys, spleen, heart, lungs, respiratory tract and brain (see Table 9-18).
There was occasionally evidence of gross bleeding into the visceral organs or
lungs. Several of the more recent reports (Martin et al., 1969; Schonborn
et al., 1970; Yodaiken and Babcock, 1973) indicated that the hemorrhagic effects
may have been exacerbated by a condition known as disseminated intravascular
coagulation (DIG). DIG is characterized by a depletion (consumption) of clotting
factors, hypofibrinogenemia and thrombocytopenia, and the resultant effect is a
severe bleeding tendency.
The results of the studies by Luzhnikov and coworkers (1976, 1978) suggest
that EDC can exert a direct toxic effect on the myocardium (see Table 9-19).
Pathologic examinations of EDC exposed individuals (amount ingested and number
9-68
-------
examined not available) revealed significant edema in the capillary endothelial
cells and stenosis of the capillary lumens, pronounced edema of the myocardial
interstices with accumulation of polymorphonuclear leukocytes, microfocal hemor-
rhages, diminished glycogen content, and degenerative changes. Mitochondrial
damage was indicated by a decrease in enzyme activities. Myocardial functional
changes (e.g., decreased contractile force, asynchronous contractions) were also
observed prior to death. The cardiotoxic effect of EDC apparently precipitated a
clinical state of shock; hemodynamic disorders commonly observed in at least
160 patients included increased peripheral resistance, decreased cardiac output,
hypotension and EKG changes including arrhythmias.
9.2.1.1.1.2. Inhalation Exposure. Reports of numerous cases of acute
occupational exposure to EDC vapor have been published (NIOSH, 1976). These
acute exposures have involved both fatal (27 cases) (Wendel, 1948; Brass, 1949;
Hadengue and Martin, 1953; Ollivier et al., 1954; Domenici, 1955; Salvini and
Mazzuchelli, 1958; Guarino and Lioia, 1958; Troisi and Cavallazzi, 1961 ) and non-
fatal (57 cases) outcomes (Wirtschafter and Schwartz, 1939; Jordi, 1944;
Agronovich, 1948; Baader, 1950; Paparopoli and Cali, 1956; Menschick, 1957;
Smirnova and Granik, 1970), but none of the reports provided exposure concentra-
tions. Furthermore,, although EDC was usually reported to be the primary vapor to
which the workers were exposed, the preponderance of exposures were to poorly
characterized mixtures of EDC and other solvents, or to EDC of unknown purity.
The occupational exposures were generally associated with maintenance and
cleaning operations or the use of EDC as a paint thinner, but many (39 cases)
involved exposure to Granosan, a fumigant composed of 30% carbon tetrachloride
and 70* EDC (Doraenici, 1955; Salvini and Mazzucchelli, 1958; Guarino and Lioia,
1958; Paparopoli and Cali, 1956).
9-69
-------
The effects associated with the above cited fatal and non-fatal acute
inhalation exposures were very similar to those found after ingestion (NIOSH,
1976). In general, the initial symptoms appeared to be consistent with both CNS
effects (headache, dizziness, lethargy, feelings of drunkenness, unconscious-
ness) and gastrointestional disturbances (nausea, vomiting, diarrhea), which are
characteristic of chlorinated aliphatic hydrocarbon toxicity. In some cases
workers were asymptomatic and were not overcome during exposure, but later became
unconscious. Other signs and symptoms of inhalation exposure commonly included
cyanosis, epigastric tenderness and/or pain, hepatomegaly, and jaundice.
Laboratory studies were consistent with these observations and indicative of
hepatic dysfunction (increased serum bilirubin and urobilinogen, hypoglycemia,
abnormal function tests) and renal disturbances (oliguria, anuria, abnormal
function tests). In addition, conjunctivitis, respiratory tract irritation and
inflammation, rales and leukocytosis were occasionally associated with the acute
vapor exposures.
Death from acute inhalation exposure was generally attributed to respira-
tory and circulatory failure (NIOSH, 1976), although it is not certain if EDO
exerted a direct toxic effect on the cardiopulmonary system or precipitated a
shock-like state which could have elicited many of the changes observed at
autopsy. Autopsies frequently revealed pulmonary edema, congestion of internal
organs (liver, kidneys, spleen, lungs, brain) and cellular degeneration and
necrosis (liver and kidneys). Hyperemia and hemorrhagic lesions were also
observed in the kidneys, brain, respiratory tract, lungs, and heart.
9.2.1.1.1.3. Dermal Exposure. Several reports described instances (a
total of 6 cases) in which skin contact with EDC occurred concurrently with
inhalation exposures (Wirtschafter and Schwartz, 1939; Anonymous, 19^6;
Rosenbaum, 19^7; Hadengue and Martin, 1953). Severe dermatitis was a commonly
9-70
-------
reported result of the dermal exposures, as is the case with many chlorinated
hydrocarbons which produce defatting of the skin. Several of these reports also
suggest that dermal absorption may significantly contribute to total exposure
(characteristic symptoms of intoxication were noted in workers who were wearing
EDC-soaked clothing).
9.2.1.1.2. Experimental Investigations.
9.2.1.1.2.1. Physiologic Effects. Borisova (1957) examined eye sensi-
i
tivity to light and plethysmographic and spirographic responses in a small number
of subjects (3 to 4) who were experimentally exposed to concentrations of EDC
that ranged from -1 to 12.4 ppm (4 to 50 mg/m ). This range of concentrations
represented subthreshold, threshold and above threshold odor perception concen-
trations (Section 7.1.2.2). The concentration of EDC in air was determined
nephelometrically; the method is sensitive enough (0.001 mg/sample reported) to
monitor EDC at levels lower than the lowest concentration tested (4 mg/m ).
In the light sensitivity experiment baseline perception thresholds were
determined prior to the exposures for each of 3 subjects (17 to 24 years old),
and the subjects inhaled EDC vapor for 15 minutes prior to testing (Borisova,
1957). When tested after 40 minutes of dark adaptation, the threshold (inten-
sity) at which light was perceived was found to be higher during exposure to EDC,
and the threshold appeared to increase with increasing concentrations of EDC
(Table 9-20). No change in the light sensitivity of eyes was observed in any of
the subjects at 1 ppm, and the lowering of eye sensitivity to light was most
marked at 12.4 ppm.
The effect of low concentrations of EDC on blood volume (vascular con-
striction) and pulse fluctuations was studied with a finger plethysmograph
(Borisova, 1957). Four subjects were exposed to vapor concentrations of 1, 1.5,
3, 5.7 and 12.4 ppm for 30 seconds or 15 minutes. A 30 second exposure at
9-71
-------
TABLE 9-20
Effect of Ethylene Dichloride Exposure on Eye Sensitivity to Light*
Concentration
ppm (mg/nr)
1 (4)
1.5 (6)
2.2 (9)
3 (12)
4.3 (17.5)
5.7 (23.2)
6.2 (25)
7.4 (30)
12.4 (50)
Subject 1
no effect
-0.2
-0.25
-0.25
-0.3
-0.45
-0.45
-0.5
-1 .2
Perception Threshold3
(Units of Optical Density)
Subject 2
no effect
<0.05
-0.3
-0.25
-0.35
-0.4
-0.5
-0.5
-1 .2
Subject 3
no effect
no effect
+0.1 5
no effect
-0.45
-0.25
-0.7
-0.75
-0.6
Source: Borisova, 1957
aEye sensitivity to light was determined after 40 minutes of adaptation in the
dark at different EDC concentrations.
9-72
-------
1.5 ppm resulted in a temporary vasoconstriction in all 4 subjects. Complete
data was not reported, but vasoconstriction appeared to be more pronounced at
3 ppm and higher concentrations. Results of tests in which EDC exposure was
extended to 15 minutes reportedly showed that the above concentrations caused
"characteristic changes" in the plethysmograms of all subjects that included
increased pulse beat, pulse waves, and pulse amplitude. The observations at the
higher concentrations in both the 30-second and 15-minute exposure experiments
also suggested that the degree of response was proportional to the exposure
concentration. Exposure to concentrations of 1.5, 3, 5.7, and 12.4 ppm for
1 minute produced changes in depth of breathing in 4 subjects (as indicated by
increased amplitude of respiratory waves on spirograms), but concentrations of
1 ppm reportedly had no effect on respiration (Borisova, 1957).
9.2.1.1.2.2. Odor Detection and Recognition Thresholds. Hellman and
Small (1973, 197*0 determined an absolute odor threshold of 6.0 ppm and an odor
recognition threshold of 40 ppm for EDC. A trained odor panel was used to
characterize the odor properties of this compound and 101 other petrochemicals,
but the number of panelists was not stated. The absolute odor threshold is the
concentration at which 50? of the odor panel observed an odor, and the recogni-
tion threshold is the concentration at which 100$ of the panel defined the odor
as representative of EDC. Borisova (1957) determined the odor threshold of EDC
with 20 subjects and a total of 1256 tests. Thirteen subjects perceived EDC
vapor at a concentration of approximately 6 ppm (23.2 to 24.9 mg/nr), 6 subjects
•3
perceived EDC at 4.5 ppm (17.5 mg/m ), and 1 subject detected the compound at
3 ppm (12.2 mg/nr).
When diluted in water,the odor recognition threshold of EDC was determined
to be 29 ppm (v/v water) (Araoore and Venstrom, 1966). An odor panel of 13 men
and 16 women was used for the determination, and the threshold defined by the
9-73
-------
panelists was the concentration of EDC that yielded 70? correct response (signi-
ficant at the 1$ level) in a paired comparison against pure water as a control.
9.2.1.2. REPEATED AND CHRONIC EXPOSURES.
9.2.1.2.1. Case Reports — Repeated exposure to EDC vapor in the work-
place has resulted in effects which are consistent with those resulting from
acute exposures. Symptoms and signs including anorexia, nausea, vomiting,
weakness and fatigue, nervousness, epigastric pain/discomfort and irritation of
the respiratory tract and eyes were described in numerous case reports of indus-
trial exposures (McNally and Fostvedt, 19^1; Siegel, 19^7; Rosenbaum, 1939;
Watrous, 19^7; Rejsek and Rejskova, 19^7; Delplace et al., 1962; Suveev and
Babichenko, 1969). In one study (Suveev and Babichenko, 1969), examination of 12
symptomatic workers that were brought to a clinic revealed paleness and cold
sweat (12 of 12), bradycardia (9 of 12), systolic murmur (5 of 12), diarrhea (5
of 12; 3 of 12 with blood) and enlarged livers that were soft and tender to
palpitation (9 of 12); muffled heart sounds, increased rate of respiration,
rales, coated and dry tongues were also observed but incidences of occurrence
were not stated. Signs indicative of nervous system dysfunction have also been
reported in cases of chronically exposed workers; these include nystagmus, fine
tongue tremors and sluggish patellar reflex (McNally and Fostvedt, 19JH),
encephalic disorders (Delplace et al., 1962), and decreased muscle tone, loss of
reflexes, a positive Romberg's sign, and deafness (Suveev and Babichenko, 1969).
Complaints of hand and arm eczema that appeared within the first year of exposure
were recorded in 11 of 16 cases by Delplace et al. (1962). It should be noted
that exposure concentrations and information on the types of exposures were not
provided in any of the above cited reports.
Rosenbaum 0947) discussed experiences with cases of EDC intoxication in
Russian industries from 193^ to 19^5. He observed over a period of 10 years that
9-71
-------
characteristic symptoms of acute poisoning could develop with repeated exposure
to concentrations of 75 to 125 ppm in air. Fatalities have resulted when workers
experienced these symptoms 2 or more times in a period of 2 to 3 weeks. There was
no mention, however, of the number of people affected or durations of exposure.
Byers 09^3) noted that a "number of persons" exposed to EDC complained of
delayed toxic effects. The workers stated that the worst effects, which varied
from lassitude and malaise to nausea, vomiting and abdominal pain, occurred after
the evening meal. These symptoms were associated with exposure to concentrations
"only slightly in excess of 100 ppm for 7.5 hours daily", and were not completely
alleviated when ventilation procedures reduced the EDC concentration to 70 ppm.
Exposure conditions were described in partial detail for 2 workers who we^e
chronically exposed to EDC for 7 and 9 months during the manufacture of hexa-
chlorophene (Guerdjikoff, 1955). EDC was used as a catalyst in this process.
During one of the operations, which was repeated for 2 to 3 minutes several times
a day for a total of about 30 minutes, exposures were associated with adding EDC,
trichlorophenol and sulfuric acid to the reaction vat. EDC exposure concentra-
tions were not measured during the filling operations, but the workers wore an
air-supplied respirator and were probably only exposed to EDC occasionally due to
improper fit. During another operation which lasted 10 minutes and was repeated
3 to *J times a day, the exposure concentration of EDC was about 120 ppm. During a
final operation, the workers were exposed once a day for =10 to 15 minutes when
an EDC pipe was cleaned; these exposure concentrations were not measured but were
considered by Guerdjikoff (1955) to be more than 120 ppm. Both workers exhibited
similar symptoms, typical of EDC exposures, of anorexia, epigastric pain,
fatigue, irritability, and nervousness after about 3 weeks of exposure. Neuro-
logical effects such as hand tremors, hyperhidrosis, and difficulty in walking
were eventually experienced.
9-75
-------
9.2.1.2.2. Health Surveys — Kozik (1957) reported the results of a
health and morbidity survey of Russian aircraft industry workers. All of the
workers in the study group (size not stated) were employed in a shop where glue
that contained EDC as a solvent was used to bond rubber sheets to metal forms in a
soft tank fabrication process. Most of these workers were gluers, but a small
number worked inside the completed tanks to disassemble the forms. EDC was
emitted to the air during application and glue drying.
About 500 atmospheric measurements of EDC were reported to have been taken
(Kozik, 1957). Although the sampling and analytical methods were not mentioned,
NIOSH (1976) felt that the data were presented in sufficient detail to permit
estimations of TWA exposures. NIOSH estimated that 44 to H6% of the total
exposure occurred during the gluing operations, when the TWA concentrations were
=28 ppm during application and =16 ppm when the glue was drying. When other
operations were performed in the same shop (during the second half of the work-
shift), the EDC TWA concentrations were =11 ppm. The TWA for the total shift was
estimated to be 15 ppm. Concentrations ranged from approximately 4 to 50 ppm;
concentrations in excess of 20 ppm were associated only with the gluing and
drying operations and occurred about 15^ of the time. NIOSH (1976) has noted,
however, that the aforementioned TWA concentrations may be an overestimate of
most of the workers' exposures for several reasons. First, the tabulation of
measurements in the glue application category also contained high values (45 to
52 ppm) that were experienced only by an insignificant number of workers who
disassembled the molds within the finished tanks. Second, the measurements were
apparently not breathing zone measurements and third, the ventilation system was
designed with the exhaust ducts on the floor. In light of these considerations,
NIOSH concluded that a more realistic appraisal of the TWA exposure of the
majority of the workers is 10 to 15 ppra.
9-76
-------
Workers (total number not stated) who were engaged in the production of soft
tanks during the years 1951 to 1955 experienced increased morbidity and lost
workdays when compared with workers in the entire factory (Table 9-21). Disease
categories examined included acute gastrointestinal disorders, neuritis and
radiculitis, and other diseases. An in-depth analysis of the morbidity rate with
temporary disability for 195^ to 1955 reportedly showed high rates for gastro-
intestinal diseases, liver and gall bladder diseases, and diseases of the muscle,
tendons and ganglion (Table 9-21). The liver and gall bladder diseases were
considered by Kozik (1957) to be related to a specific toxic effect of EDC (the
dyspeptic symptoms it causes reportedly are often diagnosed as gastritis), but
the diseases of the muscle, tendon and ganglia were associated with the numerous
repetitive motions the workers had to make when applying the glue. Further
examination of 83 of the gluers revealed diseases of the liver and bile ducts (19
of 83), neurotic conditions (13 of 83), autonomic dystonia (11 of 83), asthenic
conditions (5 of 83), and goiter and hyperthyroidism (10 of 83).
Visual-motor reactions were studied at the beginning and end of 1 4 workdays
in 1 7 of the gluers and 10 control machinists (Kozik, 1957). It was stated that a
device was used to determine simple and complex reaction (color differentiation)
times, as well as reaction times in a modification of the complex reaction task;
a total of 3700 reaction tests were conducted, but details of the tests were not
given. A comparison of the mean rates for all three reactions show no signifi-
cant differences in the two groups either before'or after work. Nervous system
dysfunction was suggested, however, by the inadequately reported results of the
complicated reaction tests. "Most" of the gluers made errors in the complex
reaction task, while the machinists did not make any errors (additional data are
not available). In the modified complex reaction test, errors were committed
9-77
-------
TABLE 9-21
Morbidity and Lost Workdays of Aircraft Industry Gluers Exposed to Ethylene Dichloride3
(Rates/100 Workers)
Tear
1 9 51 Cases
"•o Days
1
oi
1952 Cases
Days
1953 Cases
Days
1951 Cases
Days
1 9 55 Cases
Days
Total
Morbidity
Plant
120.2
995.8
121.0
960.9
135.6
1010.8
150.7
1175.9
127.6
978.1
Shop
159.8
1115.5
137.6
996.0
163.9
1236.5
19L8
1563.2
176.6
1162.1
Acute Gastro-
intestinal
Disorders
Plant
5.1
19.3
1.2
15.1
11.1
15.6
5.3
19.3
3.6
12.1
Shop
11.6
13.5
5.7
23-1
6.2
19.1
9.6
31.8
5.0
15.3
Neuritis
and
Radioulitis
Plant
5.2
99.9
5.0
HI. 8
7.5
67.3
7.9
73.8
5.9
51.1
Shop
13
127
9
91
16
116
16
182
10
90
.0
.0
.7
.5
.5
.0
.7
.8
.3
.2
Other
Diseases
Plant
31.1
351.2
31.0
335.2
35.3
338.3
10.8
386.1
37.9
315.7
Diseases of
the Muscles,
Liver and Gall Acute Chronic Tendons,
Bladder Diseases Gastritis" Gastritis" and Ganglia"
Shop
13
511
10
378
53
521
63
596
63
610
.2
.8
.8
.7
.5
.0
.8 21
.2 251.5
.3 21
.5 290
_ «• •
_
_
— _ -
.
— — -
13 6 18
61.5 15 170
838
27 11 50
"Source: Kozik, 1957
The incidences are reportedly elevated, but reference values were not given.
-------
both before and after work by 1 5 of 1 7 gluers; U of 1 0 machinists made errors, but
only at the end of the workday.
Cetnarowicz (1959) investigated the possibility of EDC poisoning in Polish
oil refinery workers. The workers were employed in a mineral oil purification
(dewaxing) process that involved mixing oils with a solvent that contained 80?
EDC and 20$ benzene at 40°C; the mixture was subsequently cooled to -24°C, and
precipitated paraffin was separated by centrifugation. Durations of exposure
were not stated, but concentrations of EDC ranged from =10 to 200 ppm (0.04 to
0.8 mg/£), with the highest excursions in the centrifuge room (Table 9-22).
Benzene concentrations ranged from -3.1 to 7.8 ppm (0.01 to 0.025 mg/£), but were
not specifically reported for the different work areas detailed in Table 9-22.
Nineteen workers (18 to 48 years old; 18 men, 1 woman) that had been employed for
2 to 8 months were included in the initial study group; 2 men and the woman were
not examined due to medical history complications. The results of these examina-
tions are summarized in Table 9-23 and in the text below.
Ten of the 16 workers were employed in the centrifuge room, where EDC
concentrations ranged from 62 to 200 ppm. All 1 0 of these workers complained of
a burning sensation in the eyes and lacrimation, and 6 of the 10 workers stated
that they had experienced dryness of the mouth, an unpleasant sweet aftertaste,
dizziness, fatigue, drowsiness, nausea, occasional vomiting, constipation, and
loss of appetite. Three of these workers also complained of pain in the epigas-
trum. All of the above-mentioned subjective complaints disappeared when the
workers changed workplaces, but reappeared upon reexposure. Of the 6 workers
employed in the pump and recrystallization rooms (10 to 37 ppm), only 1
complained of similar symptoms. As detailed in Table 9-23, clinical evaluation
of the 16 workers indicated the likelihood of liver effects (tenderness to
palpitation with minimal enlargement, epigastric pain, elevated urobilinogen
9-79
-------
TABLE 9-22
Concentrations of Ethylene Dichloride in Oil Refinery
Mineral Oil Purification Process Air*
Location
Centrifuge room
Pump room 1
Pump room 2
Pump room 2
Crystallization room
(repeated
64
16
25
30
30
ppm
measurements)
62
10
13
37
37
200
17
-
-
-
Source: Derived from Cetnarowicz, 1959 by NIOSH, 1976.
9-80
-------
TABLE 9-23
Effects Observed in Polish Oil Refinery Workers*
Concentration of 1,2-DCEa Effect Incidence
62, 64 and 200 ppm Dryness of the mouth; unpleasant sweet aftertaste; 6/10
dizziness; lassitude; sleepiness; nausea;
vomiting; poor appetite .
Burning sensation of the eyes that disappeared with 10/10
adaptation to the atmosphere .
Epigastrium pain 3/10
Insignificant tenderness of the epigastrium 7/1 0
\o Livers tender to palpitation with minimal enlargement 4/10
AD Normal arterial blood pressure 1 0/1 Q
Relaxed pulse (60 to 65/minutes) 6/10
Intensified reflexes and autoraic neuroses 3/10
10 to 37 ppm Complaints similar to those associated with 1/6
exposure to 62, 64 and 200 ppm
10 to 200 ppm Sweet aftertaste; dizziness; nausea; vomiting; lack 6/42
of appetite .
Livers tender to palpitation with insignificant 3/42
enlargement .
Epigastrium pain 2/42
Emaciation (2 to 10 kg below expected weight) 16/16
Unremarkable opthalmologic examination 1 6/1 6
Unremarkable examination of upper respiratory tract, 16/1 6
lungs, and heart
Augmented reflexes and vegetative neurosis 3/1 6
-------
TABLE 9-23 (cont.)
Concentration of 1,2-DCEs
Effect
Incidence
10 to 200 ppra (cont.)
\)
Icteric skin coloration
Elevated urobilinogen levels
X-ray observable chronic catarrh of the stomach with
atrophy of the mucous membrane
Periodic spasm of the pylorus
Moderate hyperchromic anemia
(3,430,000 erythrocytes/cu ram and 60% hemoglogin)
Slight reticulocytosis (0.1 to 0.3%)
Diminished osmotic fragility of erythrocytes in NaCl
Slight leukocytes (11,200/cu mm)
Low platelet count (40,000 to 55,000 cu mm)
Decreased number of neutrophils (40 to 50%)
Slightly increased number of neutrophils (70 to T&%)
with decreased number of lymphocytes (1 5 to 25%)
"Abnormal" distribution of white blood cells
Increased number of erythrocytes, increased percentage
of polyraorphonuclear neutrophils, mild stimulation
of erythropoiesis with a less significant increase
of leukopoiesis in the bone marrow
Elevated serum bilirubin (2.3 mg %)
1/16
"majority"
of 16
6/16
3/16
1/1 3e
4/1 3e
6/1 3e
1/1 3e
2/1 3e
2/1 3e
6/1 3e
U/136
5/1 3e
1/16
-------
TABLE 9-23 (cont.)
Concentration of 1,2-DCEc
Effect
Incidence
CO
10 to 200 ppm (cont.)
Elevated blood nonprotein nitrogen (55 mg /&)
Normal overall quantity of serum protein
Diminished serum albumin
Elevated serum globulin levels
Diminished blood fibrin content
Positive Takata-Ara liver function test
Borderline Takata-Ara liver function test
Positive Cadmium turbidity test
Borderline Cadmium turbidity test
Negative glucose tolerance test
Decreased secretion of gastric hydrochloric acid
X-ray observable catarrhal changes of gastric mucosa
Periodic pyloric spasms
1/16
16/16
6/16
8/16
3/16
4/16
5/16
6/16
5/16
8/16
12/16
6/16
3/6F
Source: Cetnarowicz, 1959 (derived from NIOSH, 1976)
Concurrent exposure to =3 to 8$ benzene (see text)
Workers employed in the centrifuge room (see Table 9-22)
°Workers employed in the pump and crystallization rooms (see Table 9-22)
42 workers initially examined; effects on these workers prompted further examinations of 16 workers from
one shift (see below).
Q
Heraatological examinations were performed on 13 workers.
f3 of the 6 with catarrh
-------
levels, positive Takata-Ara liver function teats, negative glucose tolerance
tests), and changes in the gastrointestinal tract (X-ray observable chronic
gastritis with mucosal inflammation, pyloric spasms, impaired hydrochloric acid
secretion). The distribution of these findings by room (i.e., high or low
exposure) was not, however, given. Other abnormal findings included blood and
bone marrow changes that may be attributable to the concurrent exposure to
benzene (Table 9-23).
Rozenbaum 09^7) reported the results of studies of approximately 100
Russian workers from different industries (not specified) who had experienced
exposure to EDC at levels below 25 ppm (<0.1 mg/S,) in air for 6 months to
5 years. "Many" of these workers exhibited non-specific functional nervous
system disorders (e.g., red dermographism, muscular torus, bradycardia,
increased perspiration), and "some" of the subjects complained of fatigue,
irritability, headaches and insomnia. Hematologic or functional organ changes
(not elaborated) were not, however, noted. The incidence of the observed
effects, average exposure concentrations, the range of exposure concentrations
to which the workers were exposed and information on experimental design were not
reported.
Brzozowski et al. 095*0 considered that absorption of EDC through the skin
was largely responsible for adverse health effects among certain agricultural
workers in Poland. EDC was used as a fumigant and work practices involved
transport of the liquid to fields in barrels, pouring the EDC by hand into
buckets, carrying the open buckets to the site of application, and pouring the
EDC into a series of holes in the ground. The workers were exposed to particu-
larly high concentrations of EDC vapor during pouring. Significant dermal
exposure is indicted by the frequent spilling of quantities of EDC on clothes and
sleeves during the transport of the open buckets to the places of application
9-84
-------
(resulting in soaked clothing that was not changed), and by the fact that the
workers used EDO to wash their skin. A single atmospheric sample, comprising 10
subsamples collected from locations representative of the working zone (the
collection apparatus was moved from place to place with the workers), showed a
concentration of 4 ppm of EDC. Because of the practical difficulties of sample
collection (the workers did not stay at one location sufficiently long to collect
an entire sample), conditions were simulated in a laboratory to better estimate
potential exposure concentrations. Analysis of laboratory samples showed
concentration of =14.5 to 15 ppra; a sample taken during the pouring of EDC into
buckets, considered to be the maximum exposure of a worker, contained 60 ppm.
Medical examinations were performed on 118 of the agricultural workers
(Brzozowski et al., 1954). Ninety had positive findings that included conjunc-
tival congestion (82/118), weakness (54/118), reddening of the pharynx (50/118),
bronchial symptoms (43/118), metallic taste in the mouth (40/118), headache
(39/118), dermatographism (37/118), nausea (31/118), cough (30/118), liver pain
(29/118), conjunctival burning sensation (24/118), tachycardia (21/118), and
dyspnea after effort (21/118). The Quick Test for hippuric acid was used to
evaluate liver function and was reported to be positive in 40 of 56 investiga-
tions. Skin sensitization tests with pieces of gauze soaked with 0.1$ EDC in
alcohol or 50% EDC in soybean oil were reportedly negative when scored after
40 hours of contact, but the number of workers tested was not stated.
9-85
-------
9.2.2. Effects in Animals
9.2.2.1. ACUTE EXPOSURE
9.2.2.1.1. Exposure — The observed toxic effects of ingested EDC in
laboratory animals summarized in Table 9-24 tend to confirm the findings from
cases involving human oral exposures. The LD for a single oral exposure was
reported to be 680 mg/kg in a study that employed 80 rats and 4 dosage levels
(McCollister et al., 1956) and 770 mg/kg in a range-finding study of rats (Smyth
et al., 1969). These data suggest that EDC is moderately hazardous by the oral
route, and indicate that the compound is more acutely toxic than 1 ,1 -dichloro-
ethane, 1 ,1 ,1-trichloroethane, pentachloroethane, and hexachloroethane (Patty,
1981). According to a World Health Organization report (1970; cited by Torkelson
and Rowe, 1981 ) rabbits and mice are as susceptible as rats to EDC. Heppel et al.
(1945) observed 60% mortality (6 of 10 treated) in mice 10 days after an acute
oral dose of 700 mg EDC/kg body weight, which was administered as a 5% solution
in olive oil. Similar treatment with 900 mg/kg EDC in 5% olive oil produced
mortality in 10/10 mice, but 6/6 survived a dose of 500 mg/kg given as a
10 percent solution in olive oil. Munson et al. (1982) recently determined that
the single oral dose LD 's of EDC for male and female CD-1 mice were 489 and 413
rag/kg, respectively. In these studies, EDC was apparently administered in water
solution, and all mice died over a 48-hour period. Gross pathologic examination
indicated that the lungs and liver appeared to be the target organs. Dogs and
humans may tolerate larger doses. Since EDC causes vomiting, the higher
tolerance in dogs and humans is likely attributed to the ability to vomit in
these two species. Ristler and Luckhardt (1929) found that oral doses >5QO mg/kg
tended to be vomited by dogs.
In 2 unanesthetized dogs (weighing 9 and 12.5 kg) administration of 0.63
g/kg EDC by gavage produced initial excitement (8 minutes after treatment)
9-86
-------
TABLE 9-21
Effect of Acute Exposure to Ethylene Dichloride
Route
Oral
Oral
Oral
Oral
Oral
Inhalation
Inhalation
Species
rats
rats
mice
mice
(CD-1 , male)
mice
(CD-1 .female)
rats
rats
(female)
Number
80
6 /group
10
10
6
NS
NS
6 male or female
Sherman Strain
(100-150 weight)
1-6/group
Dose
0.68 g/kg
0.77 g/kg
0.90 g/kg (in olive oil)
0.70 g/kg (in olive oil)
0.50 g/kg
0.189 g/kg (in water)
0.113 g/kg
1 000 ppm for 1 h
12,000 ppm for 0.1 h
0.2 h
Effect
LD50
LD50
10/10 dead
6/1 0 dead
no deaths
LD50
LD50
2/6, 3/6 or 1/6 dead in
11 day observation period.
No adverse effects
Adverse effect
Reference
McCollister et al.,
Smyth et al., 1969
Heppel et al., 1915
Munson et al., 1982
Munaon et al . , 1 98 2
Carpenter et al., 19
Spencer et al., 1951
1956
19
3000 ppm for 0.3 h
0.5 h
1000 ppm for 1 .5 h
3.0 h
300 ppm for 3.0 h
5.5 h
200 ppm for 7.0 h
No adverse effect
Adverse effect
No adverse effect
Adverse effect
No adverse effect
Adverse effect
No adverse effect
-------
-TABLE 9-24 (cont.)
i
CO
CO
Route Species Number
Inhalation rats 20
22
HO
HO
51
1)4
32
414
22
10
30
10
11
21
10
32
31
32
30
20
33
20
20
Inhalation rats 20
15
15
12
13
mice 22
20
23
guinea pigs 1 1
12
rabbits 16
cats 3
hogs 2
raccoons 2
Dose
3000 ppm for 6 h
3000 ppm for 5 h
3000 ppm for 1 h
3000 ppm for 3 h
3000 ppm for 2 h
3000 ppm for 1 .6 h
3000 ppm for 1 .0 h
3000 ppm for 0.7 h
3000 ppm for 0.5 h
1 500 ppm for 8 h
1 500 ppm for 7 h
1 500 ppm for 6 h
1 500 ppm for 1 h
1 500 ppm for 3 h
1 500 ppm for 2 h
1 000 ppm for 8 h
1 000 ppm for 7 h
1 000 ppm for 6 h
800 ppm for 7 h
600 ppm for 8 h
600 ppm for 7 h
600 ppm for 5 h
300 ppm for 7 h
3000 ppm for 7 h
3000 ppm for 3.5 h
3000 ppra for 1 . 5 h
1 500 ppra for 7 h
1 500 ppm for 1 h
3000 ppm for 7 h
1 500 ppm for 7 h
1 500 ppm for 2 h
3000 ppm for 7 h
1 500 ppra for 7 h
3000 ppm for 7 h
3000 ppm for 7 h
3000 ppm for 7 h
3000 ppra for 7 h
Effect Reference
20/20 dead Spencer et al., 1951
22/22 dead
38 /UO dead
214/1)0 dead
6/51 dead
1/11 dead
1 /32 dead
1/414 dead
0/22 dead
7/10 dead
214/30 dead
7/10 dead
2/141 dead
1/2U dead
0/10 dead
20/32 dead
1 7/31 dead
5/32 dead
10/30 dead
4/20 dead
3/33 dead
0/20 dead
0/20 dead
20/20 dead Heppel et al., 1945
1 5/1 5 dead
0/1 5 dead
14/20 dead
0/13 dead
22/22 dead
20/20 dead
1/23 dead
114/11 dead
6/12 dead
12/16 dead
0/3 dead
2/2 dead
0/2 dead
-------
TABLE 9-21 (Cont.)
Houte
Species
vo
A,
Subcutaneous
dogs
oats
rabbits
Subcutaneous
Subcutaneous
rats
mice
Number
Intraperitioneal guinea pig I/group
(male)
6
NS
NS
albino rats NS
10/group
1/group at
the lowest dose
10/group
Dose
1 50, 300 and 600 mg/kg
1 dose
0.94 or 1.26 g/kg body weight
0.91 or 1.26 g/kg body weight
0.91 or 1 .26 g/kg body weight
0.91 or 1.26 g/kg body weight
0.3% 0.5, 0.75, 1.0,
1.25 g/kg (in olive oil)
0.25, 0.38, 0.75 g/kg
(in olive oil)
Effect
Reference
No effect on liver histology
21 hours after injection.
No effect on serum ornithine
carbamyl transferase (OCT)
activity 21 hours later at
1 50 or- 300 mg/kg.
Increased OCT activity at
GOO mg/kg; death of 1 animal.
Death within 21 hours at
higher dose; histology: mild
perilobular fatty degeneration
in liver, swelling of tubular
cells and mild hemorrhage In
the kidney, lung edema his-
tological changes more marked
in dogs.
In dogs only: corneal opacity
evident by 10 hours; necrosis
of corneal endothellum; corneas
became clear by fifth day.
0.75/kg: 50$ mortality;
0.38 g/kkg: no deaths
Divincenzo and Krasavage,
1971
Kuewabara et al., 1968
0.38 g/kg:
0.25 g/kg:
8 Of mortality
no deaths
Heppel et al., 1915
Heppel et al., 1915
h = hours
-------
followed by decreased excitement. Progressive incoordination and salivation was
evident. In 2*4 minutes, sleep (from which the dogs could be aroused) supervened
for another 20 minutes, at which time depression was relieved. Vomiting occurred
subsequently, after which signs of recovery were evident (Kistler and Luckhardt,
1929). Larger doses of 1.26 g/kg in 2 dogs, 1.89 g/kg in one dog, and 2.51 g/kg
in two dogs produced similar symptoms of greater severity. Vomiting occurred
earlier after administration of the compound; little food or water was ingested
and vomiting persisted in one dog that received 1.26 g/kg EDC. The corneas of
the eyes in all five animals were opaque within 2*1 hours.
9.2.2.1.2. Dermal Exposure — Skin absorption LD values of 4.9 g/kg
(Torkelson and Rowe, 1981) and 2.8 g/kg (Torkelson and Rowe, 1981 ) have been
determined with rabbits. Strong erythema, edema, or slight necrosis was produced
upon application of 0.01 mil of undiluted EDC to the uncovered rabbit belly (Smyth
et al., 1969).
9.2.2.1.3. Inhalation Exposure — Sayers et al. (1930, cited in
Browning, 1965 and NIOSH, 1976) reported that death occurred in guinea pigs
within a few minutes of exposure to 100,000 ppm EDC, and on the day following
exposure to 10,000 ppm EDC for 25 minutes. Progressive signs of intoxication
were observed in groups of 3 or 6 guinea pigs that were exposed to EDC at
concentrations ranging from 600 to 60,000 ppm for durations up to 8 hours. One
third of each group was sacrificed immediately after exposure, another one-third
sacrificed after 4 days of exposure and the final one-third was sacrificed at the
end of the eighth post-exposure day unless death supervened. The signs of
intoxication (squinting and lacrimation of the eyes and rubbing of the nose,
vertigo, static and motor ataxia, retching movements, unconsciousness, incoordi-
nation of extremities, and marked changes in respiration) appeared in less than
10 minutes, and death occurred in 30 minutes, after exposure to 60,000 ppm EDC.
9-90
-------
Exposure to a lower concentration (10,000 ppm) for 15 to 20 minutes produced
these symptoms in 25 minutes and delayed death a day or more after exposure. No
mortality or signs of intoxication occurred in guinea pigs exposed to 1200 ppra
for 8 hours.
Congestion and edema of the lungs and generalized passive congestion of the
visceral organs were observed in animals that died during exposure (Sayers et
al., 1930, cited in NIOSH, 1976). In animals sacrificed immediately after
exposure, congestion of the liver, spleen, lungs, and kidneys was observed.
Pulmonary congestion, pulmonary edema and renal hyperemia were seen in those
animals that died 1 to 8 days after exposure, and the renal and lung effects were
more pronounced in the animals sacrificed 3 to 4 days post-exposure than in those
sacrificed immediately after exposure. Partial resolution of visceral effects
were observed by 8 days after exposure. In these studies, the severity of
pathological changes was dependent on duration and concentation of exposure.
Heppel et al. 0945) reported that a single exposure to 3000 ppm EDC (12.4
mg/2,) for 7 hours produced death in all of 14 treated guinea pigs within 3 days of
exposure. The guinea pigs were inactive and breathing was labored after expo-
sure. Microscopic examination of 11 guinea pigs revealed congestion in the
liver, lung and adrenal glands. Focal necrosis of the adrenal cortex in 5 of the
guinea pigs, and slight to moderate fatty degeneration of renal tubular epithe-
lium was noted in 8 of the animals. In another group of 8 guinea pigs similarly
exposed to 3000 ppm EDC, fatty infiltration of the myocardium was observed in all
of 7 animals that were examined histologically. Changes in the lung, kidney and
adrenal cortex, similar to those observed in the first group of animals were also
found.
Heppel et al. (1945) also found that inhalation exposure to 3000 ppm EDC
(12.4 mg/&) for 7 hours was fatal to rats, mice and rabbits within 3 days of
9-91
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exposure. Varying degrees of narcosis were observed in the animals during
exposure, and dyspnea and increasing weakness preceded death. Pulmonary conges-
tion, mild to moderate degeneration of renal tubular epithelium and liver, and
occasional necrosis of the adrenal cortex were observed at autopsy; congestion of
the spleen was additionally found in rats. Inhalation of 3000 ppm EDC for 7
hours was fatal for 2 hogs but was not fatal for 2 raccoons or 3 cats. Reduction
of dose by exposure to one-half the concentration of EDC (1 500 ppm) for a similar
duration (7 hours) was lethal to 6 of 1 2 guinea pigs and to less than one-fifth of
the rats (U of 20). This lower dose was fatal, however, to all of a group of 20
mice. Reduction of the duration of exposure in rats to 4 hours and mice to
2 hours decreased mortality (Heppel et al., 19^).
Spencer et al. (1951) subjected groups of 4 to 6 female rats to varying
concentrations of EDC (200, 300, 1000, 3000 or 12,000 ppra) for varying durations
to determine the doses and durations of single exposures that produced and did
not produce adverse effects. No-adverse effect exposures ranged from 200 ppm
(0.8 mg/3.) for 7 hours to 12,000 ppm (48.6 mg/fc) for 0.1 hours. Doubling the
duration of exposure at 12,000 ppm produced adverse effects. Exposure to 3000
ppm EDC for 0.3 hours was without effect, but increasing the duration of exposure
to 0.5 hours caused adverse effects.
Spencer et al. (1951) also sacrificed groups of 10-5^ rats after inhalation
exposure to EDC at concentrations ranging from 300 to 20,000 ppm for durations of
8.0 to 0.1 hours. A decrease in body weight, increase in liver and kidney
weight, increase of blood urine nitrogen, increase of plasma prothrombin
clotting time, decrease in serum phosphatase, increase in liver lipids and histo-
logical changes in the kidneys, liver and adrenal glands were observed. The
kidney changes consisted of tubular damage that ranged from slight parenchyraa-
tous degeneration of the epithelium to complete necrosis accompanied by inter-
9-92
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stitial edema, congestion and hemorrhage. Changes ranging from slight conges-
tion and slight parenchymatous degeneration to marked hemorrhagic necrosis were
observed in the liver. Some parenchymatous degeneration of the adrenal cortex
was found in the most severely affected animals. Pulmonary congestion and edema
was observed at concentrations above 3000 ppra. Carpenter et al. 0949) reported
an inhalation LC,_0 in rats to be 1000 ppm in air for a 4-hour exposure.
9.2.2.1.3-1 Central Nervous System and Cardiovascular System. Inhala-
tion of 3000 ppm EDC (12.4 mg/P.) for 7 hours in five species (rabbits, guinea
pigs, hogs, rats and mice) produced varying degrees of narcosis (Heppel et al.,
1945). Spencer et al. (1951) partially attributed the inactivity or stupor and a
slower response to handling in rats, at vapor concentrations of 3000 ppm and
lower, to toxic injury to organs other than depression of the central nervous
system. At concentrations of 12,000 ppra and lower varying degrees of "drunken-
ness" were attributed to depression of the central nervous system. Considerable
depression of the central nervous system was produced at 22,000 ppm causing death
in rats within 0.4 hours. Animals that died from exposure to 20,000 ppm EDC were
in a state of deep anesthesia during the period of exposure. At all vapor
concentrations a large proportion of the rats died suddenly after leaving the
exposure chamber. Marked cyanosis, reduced body temperature, stupor or coma, and
failing respiration were observed. Spencer et al. (1951) hypothesized that this
response is suggestive of cardiovascular collapse. Other deaths, which occurred
over a period of two to seven days, were accompanied by loss in body weight and
other signs of toxicity; the authors attribute these deaths to renal injury.
Inhalation of EDC (0.1 to 5 cc, introduced by volatilization into a Jackson
Carbon Dioxide Absorption Apparatus) produced a drop in blood pressure, depres-
sion of the knee jerk reflex and stimulation followed by a short cessation of
respiration in sodium barbital anesthetized dogs (number unspecified) (Kistler
9-93
-------
and Luckhardt, 1929). These dogs had been subjected to spinal cord transection
prior to EDC treatment. Similar effects on blood pressure and the knee jerk were
observed in sodium barbital anesthetized dogs (11-20 kg) after intravenous
injection of amounts as small as 0.1 cc, while 0.3 cc caused a cessation of
respiration for a duration of up to 40 seconds.
9.2.2.1.3.2. Eyes. Inhalation of EDC was observed to produce a clouding
of the cornea in dogs and foxes, but not in rabbits, guinea pigs, mice, rats,
hogs, raccoons, chickens or cats (Heppel et al., 1944). A single exposure to a
vapor concentration of 1000 ppm for 7 hours produced turbidity in the eyes of
dogs (Table 9-25). A higher concentration of 3000 ppm caused turbidity in the
cornea of the red fox after a single exposure of 7 hours duration. Repeated
exposure interspersed with two days of no exposure at a lower concentration of
400 ppm produced clouding in the cornea of six dogs, which cleared during the
days free of exposure. Development of resistance to toxic effects in the cornea
after repeated exposure was observed.
Corneal opacity was also observed within 1 0 hours in 6 dogs that received a
subcutaneous injection of 0.94 g/kg EDC (Kuwabara et al., 1968) (Table 9-25).
Marked swelling of most of the endothelial cells of the cornea was seen at 12
hours, and the reparative process was found to occur by 24 hours. Similar
corneal changes were produced in dogs, rabbits and cats when EDC (a 1$ suspension
dissolved in mineral oil and homogenized in 0.5% gelatin solution) was instilled
directly into the anterior chamber of the eye. The authors suggested that the
apparent vulnerability of the dog eye to EDC by routes other than direct local
application was due to "a greater amount of dichloroethane coming in contact with
the dog endothelium rather than an unusual susceptibility of the eye itself."
9-94
-------
TABLE 9-25
Effect of Ethylene Bichloride on the Cornea
Route Species
Inhalation rabbits
guinea pigs
mice
rats
hogs
raccoons
vO
vo cats
VJl
Number of
Animals Dose
1 6 3000 ppn for 7 h
1 exposure
14
19
20
2
2
2
Effect Reference
No effect on eyes Heppel et al., 1944
Inhalation red fox 1 3000 ppm for 7 h
1 exposure
Inhalation red fox 1 (same animal 1500 and 1000 ppm for 7 h
as tested above) 1 exposure at each
concentration
raccoon 2
Inhalation dog 6 1500 ppm for 7 h,
1 exposure
Loss of appetite; barely
detectable turbidity in eyes
within 6 h; eyes were opaque
2 d later; death 6 d after
exposure.
No adverse effect on eyes
No effect on cornea of 1;
faint turbidity in eye of 1;
Intense clouding of both
corneas In 4; histology;
corneal edema, degeneration
of corneal epithelium,
infiltration of polymorpho-
nuclear leucocytes into sub-
stantia propria.
Heppel et al., 1944
Heppel et al., 1944
Heppel et al., 1944
-------
TABLE 9-25 (Cont.)
Route
Inhalation
Species
dog
Number of
Animals
10
Dose
1 000 ppm for 7 h ,
Effect
Symmetric turbidity In the
Reference
Heppel et al., 19 14
Inhalation
Inhalation
guinea pigs
rats
rabbits
dog
NS
NS
NS
3
1 exposure
1 500 ppm for 7 h,
repeated exposure
1 500 pptn for 7 h, repeated
exposure
corneas of 8 j up to 3 weeks
required for partial
regression.
Death in most animals
after 4 exposures;
no adverse effect on eyes.
Intense bilateral corneal
opacity In both eyes 48 h
after first exposure; death
after 5, 6 or 30 exposures.
Turbidity in eyes retained
throughout.
Heppel et al., 1944
Heppel et al. 1944
Inhalation
dog
10
Inhalation
oats NS
monkeys
chickens
rodents (species, NS)
1000 ppm for 7 h, 5 d/wk,
repeated exposure,
length NS
1000 ppm for 7 h, 5 d/wk,
repeated exposure, length NS
Increasing turbidity of
cornea during 5 exposure days,
clearing during 2 non-exposure
days; increased tolerance with
successive bouts of exposure;
complete resistance of cornea
finally.
No adverse effects in eyes
Heppel et al., 1944
Heppel et al., 1944
-------
TABLE 9-25 (Cont.)
Route
Subcutaneous
Inhalation
Speples
dogs
(puppies and
adults)
cats
rabbits
albino rats
dogs
Number of
Animals
6
NS
NS
NS
6
Dose
0.91 g/kg
0.91* g/kg
0.91 g/kg
0.91 g/kg
UOO ppm for 7 h, 5 d/wk,
Effect
Corneal opacity evidence within
10 hours; necrosis of corneal
endothelium; clearing by
fifth day.
No effect on cornea
No effect on cornea
No effect on cornea
Mild clouding during first
Reference
Kuwabara et al . ,
Kuwabara et al . ,
Kuwabara et al . ,
Kuwabara et al . ,
Heppel et al., 1?
1968
1968
1968
1968
W
for 10 weeks
week, cleared during 2 non-
exposure days; 5th week of
exposure; faint opacity of
cornea 10th week of exposure:
no trace of turbidity.
h = hour; d = day; wk = week
-------
9.2.2.2. SUBCHRONIC AND CHRONIC EXPOSURE
9.2.2.2.1. Oral Exposure — EDC has been tested for carcinogenicity in
an NCI bioassay with Osborne-Mendel rats and B6C3F1 mice (NCI, 1978). The
compound was administered at time-weighted average doses of 95 and 47 mg/kg (rats
of both sexes), 195 and 97 mg/kg (male mice) and 299 and 149 mg/kg (female mice)
for a period of 78 weeks, according to the regimen described in Section 9.5.
Fifty animals of each sex were treated/dose level, and the animals were observed
for an additional 28 weeks (rats) or 12-13 weeks (mice) after pretreatment.
As detailed in Section 9.5, no distinct dose-related mean body weight
depression was apparent in either male or female rats relative to vehicle
controls. Mortality was, however, early and severe in many of the dosed rats,
particularly those given the highest dose. Mean survival was -55 weeks for the
high-dose males and females. Toxic rather than carcinogenic effects of EDC
appeared to be responsible for the deaths. No distinct, dose-related mean body
weight depression was observed in male mice or in low-dose female mice, but mean
body weight depression for high-dose female mice was apparent as early as the
1 5th week of treatment. A significant positive association between increased
dosage and elevated mortality was found for female mice; 12% (36/50) of the
females died between weeks 60 and 80. The presence of one or more tumors in these
mice suggests that these deaths may have been tumor related. There was no
statistically significant association between dosage and mortality for male
mice.
Munson et al. (1982) evaluated the effect of subchronic 1 M-day and 90-day
oral EDC exposures on the immune response of male CD-1 mice. EDC was adminis-
tered daily by gavage in the 14-day study at levels of 4.9 and 49 mg/kg, which
represent 0.01 and 0.1 times the single dose LD5Q determined in a preliminary
9-98
-------
study (Section 9.2.2.1.1). For the 90-day study, EDC was administered in the
drinking water at levels intended to be equivalent to those administered by
gavage; in addition, a 10-fold higher dose was added because the results of the
14-day exposure indicated that doses >49 mg/kg could be tolerated. The calcu-
lated time-weighted average doses of EDC delivered in the 90-day study based on
actual fluid consumed were reported to be 3, 21 and 189 mg/kg. Results of
standard toxicological analyses showed that body weight was unaltered during the
11-day study, but that EDC did elicit a dose-dependent decrease in growth rate
and fluid consumption when administered over 90 days. Thirty-two mice per dose
were weighed in the 90-day study but the numbers weighed in the 1 4-day study were
not stated. EDC did not alter the weights of selected organs (liver, spleen,
lungs, thymus, kidneys, brain) in either of the studies. It was further found
that exposure to 49 mg/kg/day EDC caused a 30$ decrease in leukocyte number in
the 14-day study, although the number of leukocytes was normal after 90 days of
exposure. Other hematologic parameters (hematocrit and hemoglobin evaluated
after 14 or 90 days, erythrocytes and platelets evaluated after 90 days), coagu-
lation values (fibrinogen and prothrombin time evaluated after 14 days), and
clinical chemistry parameters (lactic dehydrogenase, serum glutamic-pyruvate
transaminase and blood urea nitrogen evaluated after 14 days) were unaltered by
EDC exposure. The hematological/coagulation/clinical chemistry parameters were
assessed in 10-12 and 16 mice/dose in the 14-day and 90-day studies, respec-
tively.
The status of the humoral immune system was determined by measuring the
number of IgM spleen antibody-forming cells (AFC) to sheep erythrocytes (sRBC)
after 14 and 90 days, the serum antibody level to sRBC after 90 days, and the
lymphocyte response to the B-cell mitogen LPS (lipopolysaccharide from
Salmonella typhosa 0901 ) after 90 days (Munson et al., 1982). Results of assays
9-99
-------
with 10-12 mice (14 days) and 16 mice/dose showed that EDC produced a significant
(P<0.05) reduction in AFCs at 4.9 and 49 mg/kg in the 14-day study (25 and 40*
suppression, respectively), but that EDC exposure for 90 days caused no signifi-
cant (P<0.05) change in the number of AFC spleen cells (although there was an
indication of suppression at 189 mg/kg/day). There also appeared to be an EDC
dose-dependent reduction in hemagglutination titer after 90 days, although this
response was not significant at the p<0.05 level. EDC did not alter the spleen
cell response to three concentrations of LPS. Cell-mediated immunity was
assessed by measuring the delayed hypersensitivity response (DTH) to sRBC and the
response to the T-lymphocyte mitogen, concanavalin A. EDC produced a slight but
significant (P<0.05) non-dose-dependent inhibition at both 4.9 and 49 mg/kg in
the 14-day study, but 90-day exposure did not alter DTH response or spleen
lymphocyte response to concanavalin A. EDC did not alter the functional activity
of the reticuloendothelial system, as measured by the vascular clearance rate and
tissue (i.e., liver, spleen, lungs, thymus or kidneys) uptake of Cr after 90
days. Dexamethasone was used as a positive control in the above studies.
Results of similar tests with female mice were not presented, but reportedly were
not remarkably different from the males.
The results of the above experiments (Munson et al., 1982) indicate that EDC
produced a suppression of both humoral and cell-mediated immunity when adminis-
tered daily for 14 days by stomach tube, but not when consumed in the drinking
water for 90 days (although there were trends toward suppression at the high
exposure level). Two explanations were offered for these results. First, the
effective dose at the immunocompetent cell may be higher with the bolus presenta-
tion than with the semi-continuous self-administration in the drinking water.
Second, EDC may induce its own metabolism over the longer exposure period,
thereby effectively reducing the amount of chemical reaching the immune cells.
9-100
-------
9.2.2.2.2. Inhalation Exposure — Four animal species (15 rats of both
sexes, 8 guinea pigs of both sexes, 2 male and 1 female rabbits, and 2 male
monkeys) were exposed to EDC vapor at levels of 400 ppm (1.62 mg/S,) and 100 ppm
(0.105 mg/£) for 7 hours daily, 5 days/week for 6 months (Spencer et al., 1951).
In addition, 15 rats of both sexes and 8 guinea pigs of both sexes were similarly
exposed to 200 ppm EDC (0.81 mg/fc) for 151 and 180 7-hour periods, respectively.
Repeated exposure at 100 ppm did not produce adverse effects in any of the four
species as determined by general appearance and behavior, mortality, growth,
body and organ weights, and gross and microscopic examination of tissues (Table
9-26). No adverse effects were indicated by periodic hematological examination
of the treated rats, guinea pigs, or rabbits. Exposure to 200 ppm EDC did not
produce any adverse effects in the rats, but did elicit slight parenchymatous
degeneration of the liver with a few diffusely distributed fat vacuoles in half
of the guinea pigs. A slight increase of total lipid, phospholipid, neutral fat
and free and esterified chloresterol was also found in the guinea pigs exposed to
200 ppm EDC, and the final body weights of the treated male guinea pigs were
significantly different from control animals. Severe toxic effects were found in
the rats, guinea pigs, and monkeys that were exposed to 400 ppm EDC (1.62 mg/Jl)
(see Table 9-26). The three rabbits that were exposed to MOO ppm EDC were not
adversely affected, although Heppel et al. (1946) reported a high mortality in
rabbits exposed to this concentration of EDC.
Heppel et al. O945) exposed rats, mice, rabbits, guinea pigs, hogs and dogs
to 1500 ppm EDC (6.4 mg/S,). Almost all of these animals died before 6 daily
exposures of 7 hours each were completed. Hemorrhaging in the lungs, gastro-
intestinal tract and adrenals; fatty degeneration of the myocardium; degenera-
tion within the renal tubules; and congestion of the liver and intestines were
found at autopsy.
9-101
-------
TABLE 9-26
Effect of Subchronlc Exposure to Ethylene Dichloride
Route
Species
Number
Dose
Effect
Reference
Inhalation
rats
26 1000 ppm (3.0 mg/fc) 7 h/d x 5 d/wk 20 dead within 15 exposures; Heppel et al., 1916
(average weight: progressive weakness culmin-
198 g) ating in inability to stand.
Histology of 4 rats:
degeneration and proliferation
changes in renal tubular
epithelium; chronic splenitis
in 20 rats; pulmonary congestion
in 2 rats.
o
ro
Inhalation rabbits 6 1000 ppm (3.9 mg/Jl) 7 h/d x 5 d/wk 5 dead within 43 exposures
(average weight: survivor exposed 64 days
2480 g)
Heppel et al., 1946
Inhalation
Inhalation
guinea pig
guinea pig
guinea pig
dogs
15 1000 ppm (3.9 mg/Jl) 7 h/d x 5 d/wk 10 dead within 2 exposures Heppel et al., 1946
(average weight:
161 g)
10 1000 ppm (3.9 mg/Jl) 7 h/d x 5 d/wk 10 dead within 2 exposures Heppel et al., 1946
(average weight:
558 g)
16 1000 ppm (3.9 mg/Jl) 7 h/d x 5 d/wk 16 dead within 4 exposures Heppel et al., 1946
(average weight: lacrimation and marked
900 g) inactivity during exposure;
congestion of lung, liver,
heart, kidney, adrenal gland
and spleens.
6 (7000-8300 g) 1000 ppm (3.9 mg/Jl 7 h/d x 5 d/wk 1 dead after 30 exposures
1 dead after 43 exposures
Heppel et al., 1946
-------
TABLE 9-26 (Cont.)
o
U)
Route
Inhalation
Inhalation
Species
cats
monkeys
Number
6 (2660 g
average weight)
2 (4880 g
average weight)
Dose
1000 ppm (3.9 mg/fc) 7 h/d x 5 d/wk
1000 ppm (3.9 mg/Jl) 7 h/d x 5 d/wk
Effect
2 dead after 43 exposures
congestion and fatty meta-
morphosis in liver of all.
1 dead after 2 exposures
1 dead after 43 exposures;
Reference
Heppel et al., 1946
Heppel et al., 1946
Inhalation
cats
500 ppm 6 h/d x 5 d/wk for 6 wka
fatty degeneration of liver
and slight fatty changes in
kidney; focal myocarditis in
1 monkey.
No deaths; dilated hearts; Hoffmann et al., 1971
blood urea nitrogen increased
to 114 mg/100 mfc.
Inhalation
rabbits
500 ppm 6 h/d x 5 d/wk for 6 wks
3/4 dead after 10-17 exposures; Hoffman et al., 19TI
dilated hearts.
Inhalation
guinea pigs 10
500 ppm 6 h/d x 5 d/wk for 6 wks
9/10 dead after 4-14 exposures; Hoffman et al., 1971
apathy and weight loss, fatty
degeneration and necrosis of
myocardium, liver, kidney and
adrenals.
Inhalation
rats
10
500 ppm 6 h/d x 5 d/wk for 6 wks
All dead after 1-5 exposures;
hyperemia of lungs; fatty
degeneration and necrosis of
myocardium, liver, kidney,
and adrenals.
Hoffman et al., 19 71
-------
TABLE 9-26 (Cont.)
Route
Species
Number
Dose
Effect
Reference
Inhalation
rats
Inhalation
guinea pigs
I
o
Inhalation
Inhalation
rabbits
dogs
15 male
1 female
(average weight:
167 g)
23 controls
18 male
2 female
(average weight:
303-737)
30 controls
2 male
3 female
(average weight:
3110 g)
4 controls
3 male puppies
(average weight:
1330 g)
6 female adult
(average weight:
9100 g)
4 controls
100 ppm (1.54 rng/d) for
7 h/d x 5 d/wk for
60 exposures
400 ppm (1.54 mg/Jl) for
7 h/d x 5 d/wk
400 ppm (1.54 mg/Jl) for
7 h/d x 5 d/wk
400 ppm (1 .54 mg/Jl) for
7 h/d x 5 d/wk for
167-1 77 exposures
Total dead: 9
(6 dead after 4 exposures)
Histology in 6 survivors:
no changes in 5; diffuse
myocarditis and fatty
degeneration of liver,
kidney and heart In 1.
1 dead.
Histology: no change.
13 dead after 45 exposures
1 dead after 65 exposures
Histology in 10: fatty
degeneration of liver and
kidney in 4 dead; fatty
degeneration of heart In
2 dead; no hlstologlcal
change In 6 survivors of
exposure.
3 deaths.
All dead after 97 exposures.
No hematologlcal changes.
No deaths.
No deaths; 6 adults: no
effect on mean arterial
pressure, bromsulfaleln
excretion rate, prothrombin
time, plasma total protein,
albumin, globulin, non-
protein nitrogen, icterus
Index, urine; slight fatty
change in livers of 5 and
kidney of 1.
No deaths.
Heppel et al., 1946
Heppel et al., 1946
Heppel et al., 1946
Heppel et al., 1946
-------
TABLE 9-26 (Cont.)
Route
Species
Number
Dose
Effect
Reference
Inhalation
Inhalation
rats
rats
15 male,
1 5 female
20 male,
20 female
100 ppm (1.62 mg/i) 7 h/d,
5 d/wk
400 ppm (1.62 mg/J,) 7 h/d,
5 d/wk
I
o
Inhalation
guinea pigs 8 male,
8 female
Inhalation guinea pigs 2 male
100 ppm (1.62 mg/S.) 7 h/d,
5 d/ wk
400 ppm (1.62 mg/d) 7 h/d,
5 d/wk
Females died within 1 0
exposures.
Males died within HO
exposures.
60% mortality after 2 or 3
exposures; rapid loss of
body weight; slight increase
of liver and kidney weight;
slight cloudy swelling of
liver with a few large fat
vacuoles.
No significant differences in
blood urea nitrogen, non-
protein nitrogen, serum
phosphatase and plasma
prothrombin clotting time.
Males died within 10
exposures.
Females died within 24
exposures.
Sacrificed after 1, 3, 4, and
10 exposures; rapid loss of
body weight; increased liver
and kidney weight; slight to
moderate central fatty
degeneration of liver; slight
to moderate cloudy swelling of
renal tubular epithelium; no
alteration in lungs, heart,
spleen and testes; increased
BUN and increased blood non-
protein nitrogen levels; no
change in serum phosphatase
or plasma prothrombin clotting
time.
Spencer et al., 1951
Spencer et al., 19 51
Spencer et al., 19 51
-------
TABLE 9-26 (Cont.)
Route
Species
Number
Dose
Effect
Reference
Inhalation rabbits
2 male,
1 female
100 ppm (1 .62 mg/Jl) 7 h/d,
5 d/wk for 165 exposures
No effect on general
appearance, behavior;
mortality, body weight,
histology of liver, kidney,
lungs, heart, spleen or testes;
organ weights, blood non-
protein nitrogen. BUN,
serum phosphatase, plasma
prothrombin clotting time.
Spencer et al., 1951
_^ Inhalation monkeys
o
2 males
400 ppm (1.62 mg/Jl) 7 h/d,
5 d/wk
One sacrificed in moribund
condition after 8 exposures:
enlarged liver with in-
creased neutral fat and
esterified cholesterol
content, marked degeneration
and vacuolation of hepatic
cells; moderate degeneration
of renal tubular epithelium
with cast formation; in-
creased plasma prothrombin
clotting time.
Second sacrificed after 12
exposures: similar, but
milder, changes.
No significant hematological
change.
Spencer et al., 1951
Inhalation rats
12 male
Osborne-Mendel
(average weight:
72 g)
12 controls
200 ppm (0.73 mg/Jl) 7 h/d x 5 d/wk 8 dead after 6 exposures
No deaths.
Heppel et al., 1946
-------
TABLE 9-26 (Cont.)
Route
Species
Number
Dose
Effect
Reference
Inhalation
rats
I
o
1 male Wlatar
11 female Wistar
(average weight:
219 g)
200 ppm (0.73 mg/O 7 h/d x 5 d/wk
11 controls
7 dead; 1 after 73 exposures,
6 after 11 exposures.
Symptoms: weight loss;
listless; crusting of eyes.
Histology of 5 rats killed
after 86 exposures: fatty
degeneration of kidney in
1 rat; no other changes
noted in liver, heart, lungs,
kidney, adrenals and spleen;
no effect on red and white
blood cell count, hemoglobin
and differential counts
(7 treated compared with 6
control rats).
1 dead.
Heppel et al., 1916
Inhalation
Inhalation
mice
guinea pigs
20
12 male,
2 female
(average weight:
376 g)
18 controls
200 ppm (0.73 mg/Jl) 7 h/d x 5 d/wk 18 dead after 7 exposures. Heppel et al., 1916
200 ppm (0.73 mg/Jl) 7 h/d x 5 d/wk
14 dead after 88 exposures;
1 dead after 115 exposures.
Histology of 9 guinea pigs
killed after 121 exposures:
pulmonary congestion in 1,
liver necrosis in 1,
necrosis of adrenal cortex
in 1.
1 dead.
Histology of 5 guinea pigs:
fatty liver and myocardium
of 2; no other changes noted
in liver, heart, lung,
kidneys, adrenals and spleen.
Heppel et al., 1916
-------
TABLE 9-26 (Cont.)
Route
Species
Number
Dose
Effect
Reference
Inhalation
rabbits
(average weight:
2720)
controls
200 ppm (0.73 mg/J,) 7 h/d x 5 d/wk
No deaths.
No histological changes
found; no effect on red
and white blood cell
count, hemoglobin, and
differential counts
compared with controls.
No deaths.
Heppel et al., 1946
Inhalation
monkeys
'-X)
i
2 males
(average weight:
8710 g)
no controls
200 ppm (0.73 mg/fc) 7 h/d x 5 d/wk
for 125 exposures
No deaths
Histology of both: focal
calcification in adrenal
medulla of 1; fatty
droplets in liver and
myocardium of both.
Heppel et al., 1946
Inhalation
rats
15 male,
1 5 female
Inhalation
guinea pigs 8 male,
8 female
200 ppm (0.81 mg/JO 7h/d,
5 d/wk for 1 51 exposures
200 ppm (0.81 mg/fc) 7 h/d,
5 d/ wk for 180 exposures
No adverse effects on
general appearance, behavior,
growth, mortality, final
body and organ weights,
hematology, gross and
microscopic histology.
Spencer et al., 19 51
Final body weight
significantly different
from controls In males, and
growth less than controls,
but not sigifleant in females.
Significant increase in male
liver weights only; slight
parenchymatous hepatic
degeneration in half of
guinea pigs of both sexes;
no effect on hematology; slight
increase in trial lipid,
phospholipid, neutral fat,
free and esterifled cholesterol.
Spencer et al., 1951
-------
TABLE 9-26 (Cont.)
Route
Species
Number
Dose
Effect
Reference
Inhalation
rats
15 male, 100 ppm (0.405 mg/Jl) 7 h/d,
1 5 female 5 d/wk
males: 151 exposures
females: 142 exposures
No adverse effect on general
appearance, behavior,
mortality, growth, final body
and organ weights, hematology,
gross and microscopic histology,
BUN, blood non-protein nitrogen,
serum phosphatase, plasma
prothrombin clotting time,
total levels llpid, phospho-
llpids, neutral fat in liver,
free and esterified
cholesterol in liver.
Spencer et al., 19 51
Inhalation
guinea pigs
8 male,
8 female
Inhalation
rabbits
Inhalation
monkeys
2 male,
1 female
2 male
100 ppm (0.405 mg/1) 7 h/d,
5 d/wk
males: 121 exposures
females: 162 exposures
100 ppm (0.405 mg/fc) 7 h/d,
5 d/wk for 178 exposures
100 ppm (0.405 mg/J,) 7 h/d,
5 d/wk for 148 exposures
No adverse effect on
mortality, growth, final
body and organ weights,
BUN, blood non-protein
nitrogen, serum phosphatase,
plasma prothrombin clotting
time, gross and microscopic
histology, total liver lipid
phospholiplds, neutral fat
in liver, free and esterified
cholesterol in liver.
No adverse effect on
appearance, behavior,
growth, final body and
organ weights, gross and
microscopic histology,
hematology.
No adverse effect on
appearance, behavior,
growth, final body and
organ weights, gross and
microscopic histology,
hematology.
Spencer et al., 1951
Spencer et al., 19 51
Spencer et al., 1951
-------
TAPLE 9-26 (Cont.)
Route
Species
Number
Dose
Effect
Reference
Inhalation
rats
^ Inhalation
guinea pigs
Inhalation
mice
16 female
23 male
100 ppm (0.42 mg/i) 7 h/d x 5 d/wk
for 4 months
10 male
6 female
30 control
19 Juveniles
100 ppm (0.12 mg/J,) 7 h/d x 5 d/wk
for 4 months
100 ppm (0.42 mg/Jt) 7 h/d x 5 d/wk
for 19 exposures
No deaths, no effect on rate
of growth in 1 5 males
compared with 1 5 male
controls.
15 of 1 6 females became
pregnant; rat pups were
unaffected by exposure.
No histological effects in
liver, heart, lungs, kidney,
adrenal glands and spleen of
10 rats examined.
2 dead (disease of neck with
enlarged caseous glands)
No histological effects in
liver, heart, lungs, kidney,
adrenal glands and spleen of
10 animals examined.
3 dead (disease of neck with
enlarged caseous glands).
No deaths; no effect on weight
gain.
Heppel et al., 1946
Heppel et al., 1946
Heppel et al., 1946
Inhalation
cats 4
rabbits 4
guinea pigs 10
rats 10
100 ppm 6 h/d x 5 d/wk for 17 wks
No clinical symptoms
No effect on serum levels of
creatinlne, urea, SCOT,
SGPT, on body weight.
No changes In liver, kidney,
and other organs (not specified).
Hoffman et al., 1971
h = hour; d = day; wk = week
BUN = Blood urea nitrogen
-------
In another study, Heppel et al. 0946) found that repeated exposure (7
hours/day, 5 days/week) to 1000 ppm EDC elicited death in most of the exposed
rats, rabbits, guinea pigs, dogs, cats and monkeys (see Table 9-26). Rats,
rabbits and guinea pigs appeared to be more susceptible than the other species
tested. Pathological changes, which were varied, included congestion of lung,
liver, heart, kidney, adrenal gland and spleen in guinea pigs; congestion and
fatty metamorphosis in the liver of all exposed cats; renal changes in exposed
monkeys and rats; and pulmonary congestion in a few rats. Chronic splenitis
occurred in all rats exposed to repeated inhalation of 1000 ppm EDC. Focal
myocarditis was found in one monkey. Similar repeated exposures to 400 ppm EDC
produced high mortality in rabbits, rats, and guinea pigs (see Table 9-26), but
mortality was not observed in 9 dogs subjected to from 167 to 177 exposures at
this concentration. No changes were observed in a variety of clinical parameters
that were assessed in 6 adult dogs, although slight fatty changes were noted in
the livers of five and the kidney of one of the dogs. Rat and guinea pig
survivors of 400 ppm EDC exposure did not exhibit histological changes with the
exception of 1 of 6 rats that exhibited diffuse myocarditis and fatty degenera-
tion of the liver, kidney and heart. Repeated inhalation exposure to 200 ppm EDC
produced mortality in mice, rats and guinea pigs, but not in rabbits or monkeys
(see Table 9-26). Pathologic effects of exposure to 200 ppm EDC included a few
cases of pulmonary congestion, fatty degeneration in the kidney of one rat,
necrosis of the liver and adrenal cortex in one guinea pig, and fatty droplets in
the liver and myocardium of both monkeys. No clinical or histopathological
effects were observed in 39 rats or 1 6 guinea pigs exposed to 100 ppm EDC for 4
months or in 19 juvenile mice exposed to this level of EDC for 19 exposures.
Hoffman et al. (1971) exposed groups of 4 cats, 4 rabbits, 10 guinea pigs
and 10 rats to 500 or 100 ppm EDC for 6 hours/day, 5 days/week for 6 weeks.
9-111
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Mortality from exposure to 500 ppm EDC was high (see Table 9-26). Variable
changes in the heart, lungs, liver, kidney, and adrenals were found at autopsy.
No toxic effects were observed in the exposed animals at 100 ppm. An elevation
of BUN and creatinine was noted in 1/H rabbits, but the significance of these
changes is uncertain. The exposed cats did not grow as well as the control cats.
The effect of EDC on blood elements and on renal and liver function was
investigated using groups of 10 rabbits that were exposed to 3000 ppm for 1
hours, or to 3000 ppm for 2 hours/day, 5 days/week for 90 days (Lioia,
I959a,b,c,d). The only significant changes observed after the acute 4-hour
exposure were granulations in about 20? of the granulocytes. Varying degrees of
anemia accompanied by leukopenia and thrombocytopenia and frequent hyperplasia
of granuloblastic and erythroblastic parenchyma in the bone marrow were observed
after subchronic exposure. There was also a reduction in leukolipids, but no
change in polysaccharides, peroxidase, or ribonucleic acid. In tests for liver
function, a decrease in albumin-globulin ratio, a slightly elevated BSP
retention, slightly elevated values in colloidal tests (cadmium and
cholesterol), and normal Van den Berg (indicating an absence of elevated serum
bilirubin) and blood amino acid levels were observed. Measurement of creatinine
clearance, portal blood flow, and glomerular filtration rate indicated altered
renal function. Congestion, vascular degeneration and small necrotic areas were
found in livers and kidneys.
Dimitrieva and Kuleshov (1971) examined the effect of EDC on brain activity
in 18 albino rats exposed to 1235 ppm EDC (5 mg/£) for 3.5 months. The duration,
frequency and number of exposures were not reported. Electroencephalograms were
recorded before exposure and at monthly intervals thereafter from silver and
platinum electrodes implanted in the brains of the test animals. The stimulus
was composed of an arhythmic photic stimulus of constant intensity and pulse
9-112
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duration. A maintained frequency of activity was observed in the EEC of the
treated rats. A progressive diminution of amplitude of vacillations occurred,
with the amplitude of delta rhythms reaching 50-70 MV (amplitude of delta rhythm
before exposures was not specified) while the amplitude of beta rhythm decreased
to 1 0 to 1 5 MV (amplitudes of pre-exposure beta rhythms were 30 to 80 MV). A loss
of ability to assimilate an imposed rhythm was observed by the authors.
The results of an inhalation bioassay for carcinogenesis with
Sprague-Dawley rats and Swiss mice have been published (Maltoni et al., 1981).
The experimental design and results of these assays are detailed in Section 9.5,
but it should be noted that exposure to 250 to 150 ppm, 50, 10 or 5 ppm EDC for 7
hours/day, 5 days/week for 78 weeks elicited no treatment-related changes in body
weight or survival ability in rats of either sex or male mice. There was,
however, decreased survival ability in female mice exposed to the high level, of
EDC. The animals exposed to 250 ppm at the onset of the study exhibited signs of
toxicity (i.e., ruffling of hair, hypomotility and loss of muscle tone),
prompting dose decrease to 150 ppm after several weeks. Systemic pathological
examinations were performed on all the major organs of all animals with or
without pathological changes, but the only non-neoplastic histologic effects
reported were some "regressive" changes in the liver and adrenal glands that were
not dose-related (Cox, 1982).
In a related study with Sprague-Dawley rats, Spreafico et al. (1981 ) inves-
tigated the effect of inhalation exposure to identical levels of EDC (250 to 150,
50, 10 and 5 ppm) on blood clinical chemistry parameters. Histological examina-
tions were not performed on the rats exposed to EDC in this study. Eight to 1 0
animals per dose level were sacrificed after 3, 6, 12, or 18 months of 7
hours/day, 5 days/week exposure. Rats used for the 3, 6 and 18 month measure-
9-113
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ments were started at 3 months of age, and the 12 month determination was made
with animals that were exposed from 14 months of age.
The results suggest that long-term inhalation exposure of one year or longer
to EDC at levels of 1 50 ppm do not produce marked toxicity in rats exposed from 3
months of age (Spreafico et al., 1981). There were no statistically significant
*
changes between treated and control animals with respect to circulating levels of
red blood cells, total white blood cell numbers, platelet numbers, relative
percentages of lymphocytes, granulocytes and monocytes, and circulating protein
levels. Percent albumin values were significantly increased in both sexes at 3
and 18 months but not at 6 months, but no clear dose-response relationship was
apparent. Gamma globulin percentages were significantly lower at 3 months in the
1 50 ppm EDC group. Although changes were not apparent at 6 months, at 18 months
there was a significant decrease observed only at 5 and 1 0 ppra.
No treatment related effects were found on levels of y-glutamyl trans-
peptidase (y-GT), serum glutamic-oxalacetic transaminase (SCOT), serum
glumatic-pyruvic transaminase (SGPT), serum alkaline phosphatase, bilirubin or
cholesterol (Spreafico et al., 1931). A slight, but not significant, increase in
creatine phosphokinase (CPK) level was seen at 18 months in males exposed to 50
and 1 50 ppm EDC. Lactic acid dehydrogenase (LDH) levels were significantly
elevated after 3 months of exposure in both treated male and female groups, but a
dose-response relationship was apparent only in males. At 6 months, there was an
insignificant increase in LDH levels. At 18 months, significantly higher LDH
levels were observed only in males exposed to 5, 50 and 150 ppm EDC without an
apparent dose-response relationship. No clear changes were observed for BUN
levels, serum glucose levels or uric acid levels (Spreafico et al., 1981).
No consistent and significant differences in a battery of urinary tests (pH,
proteins, bilirubin, glucose, hemoglobin, erythrocytes, leukocytes, epithelial
9-114
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cells, casts, cystals, mucus and microorganisms) were observed after 18 months
of inhalation exposure (Spreafico et al., 1981).
Changes in liver and kidney function were indicated, however, in rats
exposed to EDC at 14 months of age. SGPT levels were significantly increased in
rats of both sexes exposed to 50 and 150 ppm. y-GT levels were significantly
elevated in females treated with 50 and 1 50 ppm. SGOT levels were significantly
elevated at the two lower doses (5 and 10 ppm), and significant decreases were
observed at the 2 higher doses (50 and 150 ppm). Cholesterol levels were signi-
ficantly lower at 50 and 150 ppm in both sexes, but there were no significant
changes in bilirubin, CPK, alkaline phosphatase, LDH or glucose levels. Signifi-
cantly higher levels of uric acid were found at 50 and 1 50 ppm and higher blood
glucose levels were observed at 1 50 ppra. No significant changes were found in
blood elements or in the battery of tests conducted on urine in the rats that
were initially exposed at 1 U months of age (Spreafico et al., 1981).
9.2.3. Summary of Acute, Subchronic and Chronic Toxicity.
9.2.3.1. INHALATION EXPOSURE ~ Information regarding the acute effects of
inhaled EDC in humans is available primarily from cases of occupational exposure
(see Section 9.2.1.1). Although the reported^jjases had both fatal and non-fatal
outcomes, many of the reports were foreign and none of the reports provided
quantitative exposure data. Further, although EDC was usually reported to be the
primary vapor to which the workers were exposed, the preponderance of exposures
were to poorly characterized mixtures of EDC and other solvents, or to EDC of
unknown purity. Symptoms and signs of acute inhalation exposure were often
indicative of CNS and gastrointestinal disturbances, and clinical evidence of
liver and kidney dysfunction, as well as irritation of the respiratory tract and
eyes, have also been observed. Death was usually ascribed to respiratory and
circulatory failure, and autopsies frequently revealed pulmonary edema and
9-115
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congestion, cellular degeneration, necrosis and hemorrhagic lesions of most
internal organs (e.g., liver, kidneys, spleen, lungs and respiratory tract,
brain, stomach and intestines).
The results of acute experimental studies with three or four subjects
suggest that the threshold of light perception (duration of exposure not stated),
depth of breathing (1-minute exposure) and vasoconstriction (30-second and 15-
minute exposures) increased with exposure to EDC (Borisova, 1957). Spirographic
and plethysmographic responses reportedly first differed from baseline values at
1.5 ppm and appeared to be dose-related to 12.4 ppm, the highest level tested;
exposure to 1 ppm (the lowest level tested) reportedly had no effect on the
physiologic endpoints. Although these Russian experiments appear to indicate a
threshold of toxic action, the reliability of the data is uncertain due to the
small number of subjects tested and an absence of reported baseline measurements
for each subject. Some assurance of data credibility can be gleaned from the
fact that the range of concentrations tested (i.e., =1-12.4 ppm) represented
corroborated subthreshold, threshold and above threshold odor perception concen-
trates. Borisova (1957) determined the odor perception threshold of EDC to be -6
ppm, and this value is consistent with an absolute odor threshold of 6 ppm that
was determined by Hellman and Small (1973, 1974) in a Union Carbide study.
Further, the sensitivity of the analytic method used by Borisova (nephelometry)
appears to be more than adequate to determine EDC at the reported experimental
levels. Hellman and Small (1973, 1974) also determined an odor recognition
threshold of 40 ppm for EDC.
Acute inhalation studies with a variety of animal species indicate that the
effects of single EDC exposures are similar to those in humans. Immediate
symptoms of toxicity are related to CNS depression (e.g., narcosis) and delayed
histopathologic changes (e.g., congestion and degenerative effects) have been
9-116
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observed primarily in the liver, spleen, kidneys, lungs and adrenals. As
detailed in Section 9.2.2.1.3 and Table 9-24, the severity of effects are depen-
dent upon duration and concentration of exposure. For rats exposed for 5-8
hours, it appears that adverse effects are not elicited by exposure at 200 ppm
(Spencer et al., 1951); signs of intoxication first appear at 300 ppm (Spencer et
al., 1951) and mortality at >600 ppm (Heppel et al., 1974; Carpenter, 1949).
Concentrations as high as 12,000 ppm were inhaled by rats for 0.1 hours without
adverse effects (Spencer et al., 1951).
The dose-response relationships for acute inhalation exposure are not as
thoroughly characterized for other species. Corneal opacity was observed in dogs
exposed via inhalation to 1000 ppm for 7 hours (Heppel et al., 1944). Signs of
intoxication were not present in guinea pigs that were exposed to 1200 ppm EDC
for 8 hours (Sayers et al., 1930), but exposure to 1500 ppm for 7 hours produced
mortality in mice, guinea pigs and rabbits (Heppel et al., 1945). Histopatho-
logical effects (e.g., pulmonary congestion/edema, alterations to kidneys,
liver, spleen and adrenals) were generally apparent in rats, mice, guinea pigs
and rabbits at concentrations of >3000 ppm (Spencer et al., 1951 ; Heppel et al.,
1945; Sayers et al., 1930). Spencer et al. (1930) felt that narcosis that was
elicited by concentrations <3000 ppm was attributable to organ injury rather than
depression of the CNS.
Limited quantitative data are available, primarily from the foreign litera-
ture, regarding the effects of repeated EDC exposure on humans. The studies that
are available are deficient because control data are lacking and because dura-
tions of exposure and numbers of subjects were poorly characterized. The avail-
able data suggest that chronic intermittent exposure in the range of 10-37 ppm
may represent a lowest-observed-adverse-effect level (LOAEL) but, as summarized
9-117
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subsequently, the data do not provide a basis for identifying a no-observed-
adverse-effect level (NOAEL) or a no-observed-effect-level (NOEL) for humans.
Case reports (Byers, 19^3; Rosenbaum, 19^7; Guerdjikoff, 1955) and a
foreign health survey (Cetnarowicz, 1959) of workers who were exposed repeatedly
to 1 ,2-EDC vapor indicate that typical symptoms and signs of acute poisoning
developed with exposure to concentrations in the range of =60-200 ppm. In the
Cetnarowicz (1959) survey, 16 workers who were exposed to =10-200 ppm for 2-8
months were examined; 10 of 10 who were exposed to 60-200 ppro complained of
adaptable eye irritation and 6 of the 10 experienced typical symptoms of expo-
sure, but only 1 of 6 exposed to 10-37 ppm were symptomatic. Positive symptoms
and signs of exposure, particularly those indicative of mucous membrane irrita-
tion, were also observed in 90 of 118 agricultural workers who were concurrently
exposed to EDC vapor (=15-60 ppm) and liquid (prolonged dermal contact)
(Brzozowski et al., 1954).
The results of two other foreign health surveys of workers exposed to EDC in
the range of the Cetnarowicz (1959) low exposure group (10-37 ppm) support
Cetnarowicz's apparent finding that overt symptoms may not be the predominant
effect of lower exposures; there appears, instead, to be a prevalence of neuro-
logic and clinical effects. Rosenbaum (1947) examined 100 workers who were
exposed to <25 ppm for 6 months to 5 years and found disturbances that included
"heightened lability" of the autonoraic nervous system, increased hidrosis and
frequent complaints of fatigue, irritability and sleeplessness, but no hemato-
logic or functional changes of the internal organs. In the study by Kozik
(1957), which is particularly notable for its reliable exposure data, workers
exposed to time-weighted average concentrations of 10-15 ppm experienced
increased morbidity, particularly from gastrointestinal, liver and bile duct
disorders. The number of workers surveyed in this study was not clearly stated
9-118
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in the available translation, but it was >83- The occurrence of overt symptoms
in these workers was not discussed, but impaired performance on control reaction
time tests suggested a possible effect on the nervous system.
Case reports of workers who were repeatedly exposed to unknown concentra-
tions of EDC also suggest that neurologic effects such as nervousness, irrita-
bility, tremors and loss of reflexes (McNally and Fostvedt, 19^1 ; Delplace et
al., 1962; Suveev and Babichenko, 1969) and complaints of skin and mucous
membrane irritation (Suveev and Babichenko, 1969; Rosenbaum, 19^7; Guerdjikoff,
1955) are more prevalent in chronically exposed workers than in workers who were
acutely exposed.
Studies with several species of animals provide information regarding the
threshold region of effects for subchronic and chronic inhalation exposure to
EDC. Three studies in which rats, guinea pigs, rabbits, cats and monkeys were
exposed to 100 ppm EDC for 7 hours/day, 5 days/week for U-6 months have shown no
treatment-related adverse effects on survival, growth, hematology, clinical
chemistry, organ weights or histology (Heppel et al., 19^6; Spencer et al., 1951 ;
Hoffman et al., 1971 ). Adverse effects were also not noted in juvenile mice that
were exposed to 100 ppm EDC for 19 exposures (Heppel et al., 19^6). The apparent
NOAEL of 100 ppm is supported by the results of comprehensive chronic studies
with rats in which similar weekly exposures to EDC (7 hours/day, 5 days/week) at
concentrations of 5, 10 or 50 ppm for 18-19 months had no significant treatment-
related adverse effects on histology (Maltoni et al., 1981) or blood or urine
clinical chemistry indices (Spreafico et al., 1981) in rats of either sex;
exposure to 150 ppm elicited decreased survival in female rats, but no clear
effects on clinical chemistry parameters in either sex. There was an indication
of renal and liver damage (increased SGPT, increased serum Y~GT> decreased
cholesterol, increased uric acid, increased blood glucose) in mature (i.e., 1U-
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months-old) rats that were similarly exposed to 50 or 150 ppm EDC for 12 months,
but hematologic effects were not found and histological examinations were not
conducted.
Subchronic exposure to 200 ppm EDC (7 hours/day, 5 days/week) produced toxic
effects in several species, but the severity of effects appeared to vary with
investigation. Heppel et al. (19*16) observed mortality among rats, mice and
guinea pigs exposed to 200 ppm EDC, but not among rabbits or monkeys, and histo-
logical lesions were not found in any of these species. Spencer et al. (1951 )
did not observe mortality in rats or guinea pigs similarly exposed to 200 ppm
EDC, but other effects were noted in the guinea pigs (decreased body weight gain
and increased liver weight in males, slight hepatic degeneration in males and
females). Rabbits and monkeys were not tested by Spencer et al. (1951). An
unequivocal frank-effect level (PEL) of 400 ppm is representative for EDC as
indicated by production of high mortality and histopathological alterations in
the liver and kidney in rats and guinea pigs after a few exposures (Heppel et
al., 1946; Spencer et al., 1951). Spencer et al. (1951) reported that exposure
to 400 ppm EDC had no effect on rabbits (as reported at 200 ppm), but Heppel et
al. (1946) observed some mortality at this level. Exposure to 500 ppra EDC
produced high mortality in rats, guinea pigs and rabbits within a few exposures
(Hoffman et al., 1971 ).
9.2.3.2. ORAL EXPOSURE — Limited data are available on the effects of
oral exposure to EDC. Human case reports of accidental or intentional ingestion
of EDC indicate that the toxic response to oral exposure is similar to that of
inhalation exposure (Section 9.2.1.1.1.1). Ingestion of quantities of EDC esti-
mated to have ranged from 8-200 m£ have been reported to be lethal (see Table
9-18). This is equivalent to =140-3570 rag/kg if it is assumed that an average
human weighs 70 kg. Median lethal doses in rats (McCollister et al., 1956; Smyth
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et al.f 1969) and mice (Heppel et al., 19*15) have been reported in the range of
700 mg/kg. Higher oral doses (up to 2.5 g/kg) were tolerated by dogs without
mortality (Kistler and Luckhardt, 1929). The apparent higher tolerance in dogs
and some humans may be related to the ability of these species to vomit. Dose
information was not reported in human case reports of non-lethal ingestion of
EDC.
Administration of 189 mg/kg/day EDC in the drinking water for 90 days caused
a decrease in growth rate in mice, but no significant effects on organ weights,
hematology indices, clinical chemistry indices, blood coagulation or immune
system function, although a trend towards immunosuppression was noted (Munson et
al., 1982). Similar administration of 24 or 3 mg/kg/day EDC in the drinking
water for 90 days had no effect on mice.
The only dose-response data that are available for chronic oral exposure to
EDC are the results of a 78-week NCI carcinogenesis bioassay with rats and mice
(NCI, 1978). Administration of 95 mg/kg/day EDC via gavage (5 days/week) caused
early and severe mortality in rats of both sexes, and ^7 mg/kg/day caused
decreased survival in male rats (after 90 days) and female rats (throughout the
experiment). Non-carcinogenic toxic effects appeared to be the cause of the
deaths, as indicated by the presence of a variety of lesions including broncho-
pneumonia and endocardial thrombosis. Body weight depression was not found in
any of the treated male or female rats. Treatment-related weight depression and
mortality was found in female mice that were similarly exposed to 299 mg/kg/day,
but not in females exposed to 1U9 mg/kg/day or in males exposed to 195 or 97
mg/kg/day. The presence of tumors in the high dose female mice suggested,
however, that the deaths may have been tumor-related.
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9.3. REPRODUCTIVE AND TERATOGENIC EFFECTS
Murray et al. (1980, unpublished) performed a subchronic inhalation study
to determine the effects of ethylene dichloride (1,2-dichloroethane, EDC) on
the reproductive ability of rats and effects on their offspring (Murray et
al., 1980). The results of this study were reported at the fifth annual
Banbury Conference (Rao et al., 1980). Twenty to thirty male and female
Sprague-Dawley rats were initally exposed to 25, 75 and 150 ppm EDC (lot no.
TAC06228, analyzed as 99.98$ pure by Dow Chemical Laboratories) for 60 days (6
hrs/day, 5 days/week for 12 weeks), and then were successively bred to produce
two litters, the F. and F.._. The breeding protocol consisted of caging one
male and one female rat for 4 consecutive days, and remating any females that
had not mated (no sperm in vaginal smear) with a different male after a 3 day
rest period. The results from remated animals were combined with those of the
first breeding. The females were exposed to EDC throughout breeding,
gestation and lactation (6 hrs/day, 7 day/week) except for day 21 of gestation
to day 4 postpartum to allow for delivery and rearing of the young. A second
mating, for the production of the F generation took place after the FIA
litter was sacrificed (day 21 of birth).
During the seventh week of this study, both control and treated animals
suffered from symptoms of sialoacryoadenitis (red crusty material around the
eyes and nose and conjunctivitis), which was thought to have resulted from a
viral infection. The authors noted that more males than females contracted
the disease but suggested that this greater incidence was related to the
housing accomodations (males were caged away from females) and not to any
greater suceptibility of the males for developing infection after EDC
9-122
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exposure. All animals (both control and experimental) recovered one to two
weeks after the onset of the disease with no recurrence for the duration of
the study.
Murray et al. (1980) reported that the physical well being of the
parental generation was not significantly affected by EDC exposure. However,
during the first and second weeks of exposure, the females consumed
significantly less food than the controls, although for the rest of the study,
there was no alterations in food consumptions. In the males, food consumption
was both sporadically increased and decreased throughout the study with a
general trend for increased food consumption in males exposed to the highest
concentration of EDC (150 ppm) for longer durations of exposure (weeks 15 to
29).
There was a statistical increase in the absolute liver weight at the 150
ppm level, and a statistical linear trend for increased liver weights in adult
male rats exposed to EDC (Murray et al., 1980). However, this trend was not
observed for liver weights in relation to body weight. All adult males
displayed some degree of chronic renal disease, however, the severity of the
disease did not appear to be related to treatment. Both control and
experimental females displayed signs of renal disease. There was a greater
incidence of inflammation and edema of the salivary glands in males exposed to
150 ppm. Three deaths occurred during the course of the study, but these
deaths did not appear to be related to EDC exposure.
The fertility and survival index on days 1, 7, I1* or 21, were not
statistically different at any dose level. However the greatest pup mortality
was observed in groups exposed to 150 ppm between days 14 and 21. The sex
ratio, average number of live pups per litter and neonatal body weight were
9-123
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not affected. There were sporadic, statistically significant differences in
reproductive indices of treated versus control groups, however, these did not
appear to be attributable to EDC exposure. A few neonates exhibited external
and internal malformations, however, the incidence of these effects were
sporadic and statistically insignificant, reflecting natural variability and
not the result of EDC exposure (Murray et al., 1980). Therefore, it was
concluded that EDC exposure, under these conditions, did not adversely affect
reproduction in rats or the development of their offspring.
Lane, Riddle and Borzelleca (1981) evaluated the effects of EDC on the
reproductive capability of mice using a multigenerational reproductive
protocol modified for screening teratogenic and dominant lethal effects.
Animals were exposed to EDC for 35 days, then 10 males and 30 female mice
(parental genration F/0) were mated to produce the first set offspring (F/1A).
After the F/1A were weaned, the F/0 adults were remated to produce the second
set of offspring (F/1B). A parental stock was chosen from the F/1B litter (30
females, 10 males) to produce a second generation of offspring (F/2A). After
weaning the F/1B adults were remated to produce offspring (F/2B) for use in
teratology and dominant lethal screening tests.
In this study, the EDC (Aldrich Chemical Co. 99% pure) was dissolved in a
1/t solution of Emulphor EL-620 (GAP Corp., Linden, NJ) and then further
diluted with deionized water to concentrations of 0.03, 0.09, and 0.29 mg/ml
or a nominal dose of approximately 5, 15, and 50 mg/kg/day. The test animals
were continuously maintained on EDC solutions or control solution (deionized
water, or water containing 0.17 mg/ml p-dioxane dissolved in 1.0J Emulphor
solution). Fresh drinking solutions were prepared twice weekly and placed in
amber glass bottles with cork stoppers and stainless steel drinking tubes.
9-124
-------
The authors reported no decreases in fluid consumptions in either the EDC or
the solvent control groups.
Lane (1981) reported that EDC produced no treatment-related signs of
toxicity such as lowered body weights or gross pathological changes in major
organs. There were no significant differences in the fertility index or
gestation index observed in the P/1A, F/1B or F/2A generations. There were
sporadic incidences of increased mortality throughout the generations but
these were not dose-related; the reason for the deaths was not apparent at
necropsy. There was no difference in the litter sizes at birth, pup body
weights, survival of pups at days 4 and 21 of birth. There was a decrease in
the survival indices for the F/2A generation as compared to values for the
F/1A and F/1B generation but these decreases were not dose related. In the
dominant lethal screening tests there were no statistically significant dose-
related effects, however both increases as well as decreased were observed in
the ratios of dead to live. fetuses. In the teratology screening, continous
administration of EDC produced no apparent adverse reproductive effects or
observable abnormalities. It should be noted that continuous exposure used in
this study is not a recommended protocol for evaluating teratogenic effects.
In teratology testing, the duration of exposures is usually limited to the
period of organogenesis. Also, in the study the F/1C skeletal specimens were
lost and, therefore, these effects could not be evaluated.
From this study, (Lane et al., 1981) it is not possible to conclusively
determine whether EDC has the potential to cause adverse reproductive or
teratogenic effects because the doses were not high enough to produce any
adverse effects, including maternally toxic effects. However, under the
conditions of the experiment, it appears that EDC given in drinking water
9-125
-------
(nominal doses of 5, 15, 50 mg/kg/day) produced no observable adverse
reproductive effects in Swiss ICR mice.
Schlachter et al. (1979) conducted teratology testing in 16 to 30
Sprague-Dawley rats and 19 to 21 New Zealand white rabbits. The animals were
exposed by inhalation to either 100 or 300 ppm EDC (Lot Nos. TA0201851L and
TA022851L, analyzed as >99.95& pure by the Dow Chemical Laboratories). The
rats were exposed 7 hrs/day on days 6 through 15 of gestation. The rabbits
were exposed 7 hrs/day on days 6 through 18 of gestation. Two thirds of the
maternal rats died when exposed to 300 ppm EDC in contrast to no deaths
occurring in the control and 100 ppm groups. In the 300 ppm group, only one
rat in six survivors had implantation sites; all of these sites were resorbed.
Two additional rats at the 300 ppm level showed early implantation sites when
the uterus was stained with sodium sulfide. In the 100 ppm group, threee rats
delivered early on day 21; however there were no indication of embryo or
fetotoxicity in the offspring. In addition, the rest of the rats at the 100
ppm level delivered normally with no alterations in litter size, number or
resorptions of fetal body measurements (crown to rump length).
At the 300 ppm level, one of the six surviving rats had a decrease in
mean body weight gain, while in the 100 ppm level, there was an increase in
body weights on days 6, 8, 10, 16 and 21 of gestation. At the 300 ppm level,
the absolute liver weight was decreased, while the relative liver weight was
increased; at the 100 ppm level there was no difference. In the 100 ppm
group, there was an increase in water consumption on days 15-17 and 18-20 of
gestation, but food consumption was not altered. There was no increase in the
occurrence of malformations with only isolated sporadic incidents observed
within the range of normal variability.
9-1 26
-------
In this teratology study (Schlachter et al., 1979), four out of twenty-
one rabbits in the 100 ppm group, and three out of nineteen rabbits in the 300
ppm group died. Three control rabbits delivered early (days 15, 28, 29 of
gestation) as did one animal at the 300 ppm level (day 28 of gestation). Two
animals that died at the 100 ppm level, also aborted on days 26 and 28 of
gestation. There was no effect on mean litter size, incidence of resorptions
or fetal body measurements (crown to rump length) in animals delivering
normally. Staining of the uterus revealed only one additional implantation
site in control animals. The mean body weights of pregnant animals were
generally comparable to that of controls, but there was an increase in mean
body weight gains in the 300 ppm group on days 19 through 28 of gestation. A
slight but statistically insignificant increase in both absolute and relative
liver weights were observed in both the 100 and 300 ppm groups. There was no
increase in the incidence of malformations, although sporadic occurances
within the range of normal variability were reported. It was concluded from
this study that EDC exposure does not produce adverse effects on the
developing conceptus.
Several Russian studies by Vozovaya (1971, 1975, 1976, 1977) have
reported that EDC produces a number of adverse reproductive outcomes which
include: lengthening the total estrus cycle, changes in the duration of
various stages of the estrus cycle, increases the number of perinatal
embryonic deaths, decreases in the weight of newborn animals, and decreases in
the weight gain of offspring after birth. In addition, EDC was reported to
concentration in the placenta, amniotic fluid and fetal tissue. However, it
is difficult to evaluate or seriously consider these reports since they are
presented with insufficient detail for critical scientific review.
9-127
-------
Inadequacies in these reports include: lack of original data, various
techniques and tests mentioned but results not presented, no information on
the source of purity of the chemical, statistical analysis mentioned, but the
type of statistical tests not stated.
The above comments apply similarily to the study by another Russian
scientist, Urusova (1980), who reported that the EDC accumulated in the milk
of nursing mothers. This is obviously an important observation, however, it
cannot be accepted as scientific evidence. This report was presented in a
subjective, anecdotal manner with many inadequencies in reporting. These
inadequencies include: lack of details concerning the numbers of women
involved in the study, no data on women's age or physical status, no reporting
on the concentrations and duration of EDC exposure after dermal exposure, no
information on the repeatability of this finding and no information on number
of samples analyzed.
Because of the concern for EDC contamination in mother's milk, Sykes and
Klein (1957) conducted a study to determine whether oral administrations of
EDC might pass into the milk of cows. Only five cows were used in this study;
two cows were exposed to 100 ppm EDC for 22 days; two cows were administered
500 ppm EDC for 10 days followed by 1000 ppm for 12 days; one cow was used as
the control. Two different breeds of cows, Holstein and Jersey cows were used
but it was not stated which cows received which dose. Seven milk samples
collected over a three week period containing no more than 0.4 ppm EDC,
however, the authors stated that this amount was too low for accurate
detection by the Volhard titration method used in this study. The samples
collected from cows ingesting EDC had consistently higher concentration of EDC
than the controls, but because of the small sample size, and the lack of
9-128
-------
sophisticated analytical procedures, it is not possible to make firm
conclusions as to the amount of EDC entering the milk supply. More
importantly, this study was not designed to evaluate the possible health
consequences of EDC injested in the milk of nursing offspring. However,
recent pharmacokinetic studies do indicate that EDC has a tendency to
accumulate in fatty tissues (Spreafico et al., 1980) although the reproductive
health effects of EDC in breast milk have not been evaluated.
9.3.1. Summary. The available scientific information on the potential of
ethylene dichloride (EDC) to adversely affect reproductive or developmental
processes includes a teratoglogy test conducted in rats and rabbits
(Schlachter et al., 1980), a single-generation reproductive test conducted in
rats (Murray et al., 1980), a multigenerational reproductive test conducted in
mice (Lane et al., 1981), several reports by Russian scientists describing a
number of adverse reproductive effects observed in laboratory animals and man
(Vozovaya 1971, 1975, 1976, and Urusova 1953), and an investigation measuring
the amount of EDC found in the milk of cows after ingesting EDC (Sykes and
Klein, 1953).
The results of reproductive and teratogenicity testing (Murray et al.,
1980, Schlachter et al., 1979, and Lane et al., 1981) indicate that EDC has
little potential for producing adverse reproductive affects or adversely
affecting the developing conceptus, except when the mother is exposed to doses
high enough to produce maternal toxicity. The Russian studies describing a
variety of adverse reproductive effects associated with EDC exposure do not
provide conclusive scientific evidence because the studies were inadequately
performed or reported. The study of EDC in the milk of cows is inadequate
9~129
-------
since only a few animals were used and the biological effects of EDC-
contaminated milk were not investigated.
In conclusion the available studies indicate that the EDC has little
ability to adversely affect the reproductive or developmental processes in
laboratory animals except at maternally toxic levels. However, it should be
noted that these studies have inadequacies which weaken the strength of this
conclusion. The multigenerational study by Lane et al., 1981, does not
include a range of doses which include maternally toxic doses. The study by
Murray et al. (1980) does not evaluate reproductive effects for more than a
single generation. The studies by Sykes and Klein, 1953 on the effects on
lactation are inadequate. In addition, no properly conducted epidemiological
study has been done to evaluate the effects of EDC on human reproduction.
Therefore, although the studies to date indicate that EDC does not pose a
specific hazard to reproductive or developmental system, this cannot be
conclusively established, especially for humans, without additional studies.
The chemical similarity of EDC to ethylene dibromide (EDB) and 1,2-dibromo-
chloropropane (DBCP) might suggest that additional testing related to
testicular toxicity would be appropriate.
9-130
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9.1. MUTAGENICITY
Ethylene dichloride (EDC) has been tested for mutagenic activity in bac-
teria, plants, Drosophila, mammalian cells in vitro, and rodents. These studies
are discussed below and are summarized in Tables 9-27 to 9-32. The reader may
also refer to published reviews of the mutagenic potential of EDC (e.g., Fishbein
1976 and 1979, Fabricant and Chalmers 1980, Rannug 1980, or Simmon 1980).
GENE MUTATION STUDIES
Bacterial Test Systems
Many investigators have studied the ability of EDC to cause gene mutations
in bacteria (Table 9-27). Most reported marginal positive responses without
metabolic activation and stronger positive responses with exogenous hepatic
metabolic activation, indicating that EDC is weakly mutagenic by itself but that
metabolites, such as S-(2-chloroethyl)-L-cysteine, are more potent mutagens.
Ethylene dichloride has been reported positive in four Salmonella/microsome
plate incorporation assays (McCann et al. 1975, Rannug 1976, Rannug and Ramel
1977, and Rannug et al. 1978), in assays testing the mutagenicity of bile
obtained from EDC-perfused rat livers or livers from EDC-treated mice (Rannug and
Beije 1979) and in two Salmonella spot tests. In one of the Salmonella spot
tests, (Brem et al. 197M) an analysis of duplicate experiments carried out on at
least three different occasions revealed a twofold increase in revertant counts
for strains TA1 530 and TA1 535 (mean values of 50 and 5^ revertants on treated
plates versus 23 and 26 in control plates for TA1 530 and TA1 535, respectively).
No difference in revertant counts was noted for strain TA1 538. This response is
consistent with that expected for an alkylating agent. The authors stated that
plate incorporation tests could not be performed because of the volatility of the
test agent. Positive and negative control tests were conducted for these experi-
9-131
-------
TABLE 9-27
Summary of Mutagenioity Testing of EDC: Gene Mutations in Bacteria
Test Activation Chemical
Reference System Strains System Information
Brem et al. Salmonella TA1 535 None 10 nmoles on filter
1971 (spot test) TA1535 disk
TA1538
^ Source: Not given
^ Purity: Not given
Results
Weak positive
Comments
1 . Could not perform
plate incorporation
tests because of
volatility.
Salmonella revertants
TA1 530
EDC 50
Water 23
Chloramphenicol 20
TA1 535 TA1 538
5U 19
26 19
31 m
-------
TABLE 9-27 (cont.)
vo
I
CO
CO
Test
Reference System
Principe et Salmonella/
at . 1981 mammalian
mlcrosome
assay (spot
test)
S. coelicolor
forward mutation
assay to Strr
Strains Dose uSVPlate
-S9
0 100
TA1 535 39 46
TA1 537 17 8
TA1 538 19 12
TA98 82 83
TA100 188 188
•P<0.01
Dose lilt/plate
0
2
10
20
100
0
33
10
21
77
171
Survival
100
100
100
100
100
+S9
100
103»
8
27
84
169
Comments
1 . Positive controls indicated system
working properly.
2. Positive results In Salmonella in
test with TA1 535.
spot
3. No precautions taken to prevent excessive
evaporation of EDC and insure adequate
exposure.
4. Toxicity results indicate exposure
minimal.
was
J Strr/plate
2.5
0.2
0.7
0.7
1 .0
+ 0.6
+ 0.2
+ 0.4
+ 0.4
+ 0.8
8-AG/Plate
A. nldulans
forward mutation
to 8-AGr
0
250
500
100
100
42
2.5
2.0
1.0
-f 0.9
+ 1 .1
+ 0.7
-------
TABLE 9-27 (oont.)
Reference
McCann et al.
1975
Test
System
Salmonella/
microsome assay
(plate test)
Activation Chemical
Strains System Information
TA100 PCB-induced Concentration Tested:
rat liver S9 1 .3 x 10 (ig/plate
mix (13 junoles)
Source: Aldrieh
Chemical Co.
Purity: Not given,
but stated
to be highest
purity.
Results
Negative or at
best only marginal
positive response.
Induced 25
colonies
plate above
background .
(0.19 rever-
tants/nmol)
in TA100
Comments
1 . Non-mutagenic or
extremely weak
mutagen in this study
Reproducible dose-
response curves not
obtained .
2. Metabolic activation
did not Increase
positive response.
3. Chloroethanol and
CO
-tr
Rannug 1976
Salmonella/
microsome assay
(plate test)
TA1535 Liver fractions
from Sprague-
Dawley or R
strain Histar
rats Induced
with phenobar-
bital with and
without NADPH-
generating system
and with and
without gluta-
thione S-trans-
ferases A, B
and C.
Concentration tested:
Up to 60 iimol/plate
Source: BDH Chemicals, Ltd.
Purity: Not given but
reported to be
checked by glass
capillary column
chromatography
using a flame
ionization detector
Marginally
positive
without activation
(twofold increases);
positive response
with activation
(tenfold increases).
Spontaneous back-
ground 8-11
revertants/plate.
chloroacetaldehyde
(two putative
Intermediates in the
metabolism of EDC in
mammals) tested
positive (I.e., 0.06
and 746 revertants/
(imol, respectively).
EDC activated by the
liver cytosol
fraction, Mixed-
function oxygenases
not involved.
NADPH-independent GSH
S-transferase dependent
activation.
Strain differences noted
in ability to metabolize
EDC.
Thought that mugateniclty
of EDC after activation
caused by formation of
highly reactive half
aulfur mustard,
S-(2-chloroethyl)-L-
cysteine.
-------
TABLE 9-27 (cont.)
Reference
Test
System
Activation
Strains System
Chemical
Information
Results Comments
Rannug and Ramel
1977
Salmonella/
microsome assay
(plate test)
TA1 535
Rannug et al.
1978
Salmonella/
mlcrosome assay
(plate test)
TA1 535
S9 mix from
livers of un-
induced male
R strain
Wistar rats
plus NADPH
generating
system
Rat liver
microsome
system with
and without
NADP
Concentration tested:
Up to M5 vimol /plate
Source: BDH Chemicals, Ltd.
Purity: Not given
Concentration tested:
i»5 ninol/plate
Source: EDC given BDH
Chemicals, Ltd.
Purity: Not given for
EDC, but checked
using glass
capillary chroma-
tography using
a flame ioniza-
zation detector.
Positive response
(two fold increase
without activation;
nearly tenfold
increase with
activation. )
Negative controls
yielded roughly
1 5 revertants/
plates.
Marginal positive
response without
activation (twofold
increase 21.8 +
3.06 at 15 nmol
v. 13.0 + 1.76
control);
positive response
with activation
(10-fold increase)
Independent of
presence of NADP.
Compared mutagenicity
of EDC tar with EDC.
The level of EDC
present at the highest
dose tested for EDC
tar would only exert
a weak mutagenlc
effect, yet a strong
response was
observed.
Activation of EDC
tar dependent on
NADPH. EDC activa-
tion independent
of NADPH.
EDC major component
of EDC tar.
Mutagenlcicity of
tar increased with
metabolic activation
only with addition
of NADP.
Mutagenicity of EDC
tar not solely due
to EDC.
-------
TABLE 9-27 (cont.)
Test
Reference System
Rannug and Beije Salmonella/
1979 isolated
perfused
rat liver
Salmonella/
(plate test)
Activation Chemical
Strains System Information
TA1 530 Isolated Concentration tested:
TA1535 perfused liver 0.1 mH (1.3 mMoles)
from male R for up to !* hours.
strain Wistar
rats.
TA1 535 Bile from male 80 mg/kg EDC i.p.;
CBA nice. removal of liver and
Results Comments
Positive. Highest 1 . Positive
response 1 5-60 responses consis-
minutes after tent with conju-
addition of EDC gation of EDC
CJ5-60 revertants with glutathlone.
compared to 7-1 0
in controls).
Positive. Greater
than twofold
-------
TABLE 9-27 (oont.)
vo
I
Reference
Nestman et al.
1980
Test
System
Salmonella/
mlcrosome assay
(plate test and
and desiccator
exposure) .
Strains
TA1 535
TA100
TA1 537
TA1538
TA98
Activation
System
PCB-induced
rat liver S9
mix.
Chemical
Information
Concentration tested:
Up to 9 mg/plate (91
(imoles) In desiccators.
10 mg/plate in plate tests.
Source: Chem Service
Purity: Not given
Solvent: DMSO
Results
Negative in
standard test.
Positive in
desiccator testing
in strain TA1 535.
Comments
1 . Stated that
maximum yield with
TA100 is 20
revertants above
background (i.e.,
negative). For
TA1 535 a doubling
of mutant colonies
observed. No
other data pre-
sented.
Stolzenberg and
Mine, 1980
Salmonella/
microsome
assay (plate test)
TA100 PCB-induced
rat liver 39
mix (2 mg
protein/0.5 mfc).
Concentration tested:
Up to 10 (imoles/plate
Negative
Source:
Aldrioh
Chemical Co.
Purity: 99< pure
2. Cannot adequately
evaluate results.
1 . All compounds
tested in trip-
licate with and
without S9 mix.
2. Experimental
values minus
background
revertants.
Revertants
umoles/plate -S9 +S9
10-1
1
10
0
0
15
Toxic
0
0
No growth
-------
TABLE 9-27 (cent.)
Reference
Barber et al.
1981
Test
System
Salmonella/
microsome assay
(vapor exposure)
Strains
TA1 535
TA100
TA1538
TA98
Activation
System
PCB-induced
rat liver S9
mix.
Chemical
Information
Concentration tested:
Up to 231 .8 (imole/plate
as determined by GLC
analysis of distilled
water samples.
Results
Negative in
standard plate
test. Positive
in desiccator
testing in strains
TA1535 and TA100.
Comments
1 . Bacteria exposed in
gas tight exposure
chambers .
2. Plastic plates
found to absorb
VO
I
Source: Eastman Kodak Co.
Purity: 99.98J
dibromomethane
in parallel
experiment. Thus,
glass plates used
for all other
testing.
Weak positive
result. 0.002
revertants/nmole
TA1 535 with or
without activation.
0.001 revertants/
naiol TA1 00 with or
without activation.
Revertants selected
from each experiment
and tested to ensure
that they were
actually his .
-------
merits and indicated the systems were working properly. Principe et al. 0981)
conducted a spot test using strains TA1 535, TA1 537, TA1 538, TA98, and TA100. A
positive response was observed for TA1 535 when a triangular shaped paper disc
soaked with 1 00 \il EDC was placed on the agar in the presence of 39 from Aroclor
1254-induced rat liver (i.e., 103 revertants on the treated plate vs. 33 rever-
tants for the negative control). " Negative responses were obtained with the other
strains. A negative response was also obtained in plate incorporation tests
conducted with TA1 00 and TA1 535 at doses up to 100 iiSVplate. A standard assay
was conducted; no precautions were taken to prevent excessive evaporation of the
EDC. Similarly in forward mutation tests conducted with Streptomyces coelicolor
and Aspergillus nidulans negative responses were obtained at doses up to 1 00 and
500 ufc/plate in plate incorporation and spot tests. There was a 100? survival in
the test conducted with S. coelicolor and a 60% reduction in cell survival at the
highest dose with A. nidulans. Thus, these tests are judged to provide less than
adequate conditions for assessing the mutagenicity of EDC because insufficient
exposure to the test organisms may have occurred.
McCann et al. (1975) exposed Salmonella strains TA1 525, TA100, and TA98 to
EDC (Aldrich, stated to be highest purity available) concentrations as high as 13
mg/plate (131 umoles/plate). A weak positive response was observed in TA100
(0.19 revertants/umol). However, reproducible dose-related response curves were
not obtained. The presence of an exogenous S9 mix metabolic activation system
(from rat livers induced with either phenobarbital or Aroclor 125*0 did not
increase the weak positive response. Chloroacetic acid, which is a known mamma-
lian metabolite of EDC, and the putative intermediates (i.e., chloroethanol and
chloroacetaldehyde see sections 9.1.3.3A), were also tested for their mutagenic
potential. Chloroacetic acid was negative, but chloroethanol yielded a weak
positive and chloroacetaldehyde a strong positive result (0.06 and 7^6 rever
9-139
-------
tants/nmol, respectively, in TA100). The authors speculated that the weak rauta-
genic response of EDC may be due to relatively inefficient conversion of chloro-
ethanol to chloroacetaldehyde in the in vitro system.
Two reports (Rannug 1976; and Rannug and Ramel 1977) compared the muta-
genicity of EDC with that of EDC tar, a complex mixture formed during the
manufacture of vinyl chloride from either acetylene, ethylene, or a mixture of
the two. The mixture is called EDC tar because ethylene dichloride is a major
component comprising about 30% of the mass. The sample of EDC tested in these
studies was from British Drug House (BDH) Chemicals, Ltd. (purity not given).
Salmonella tester strain TA1 535 was dosed up to 45 ^moles/plate in the presence
or absence of an exogenous metabolic activation system (from livers of male
strain R Wistar rats) with and without NADP. Weak positive (twofold) increases
in revertant frequencies over background (13.0 + 1.76) were observed in the
plates receiving the highest dose (24.8 + 3-06) in tests conducted without
metabolic activation. However, with activation, a strong positive response was
observed. The revertant count was elevated tenfold over the spontaneous level
(132.8 + 8.35 v. 15.5 + 1.21). The response to EDC was independent of the
presence of NADP; in constrast, the mutagenicity of EDC tars was increased with
metabolic activation only in the presence of NADP. It was concluded that the
mutagenicity of EDC tar cannot be ascribed primarily to EDC, because EDC and EDC
tar have different requirements for metabolic activation. In addition, the
concentration of EDC present in EDC tar at the highest dose tested would yield
only a weak positive response if tested alone, while in fact a strong response
was observed for the EDC tar.
Following these observations, Rannug et al. (1978) tested Salmonella strain
TA1 535 with EDC (BDH Chemicals Ltd.; although the purity was not reported, the
material was checked by glass capillary chromatography using a flame ionization
9-1 MO
-------
detector) at doses up to 60 (imoles/plate. Tests were conducted with and without
an exogenous rat liver metabolic activation system. The components of the
activation system were varied in order to study the mechanism of activation of
EDC. Phenobarbital-induced liver fractions from Sprague-Dawley or R strain
Wistar rats were prepared with and without an NADPH-generating system and with
and without glutathione transferases A, B, and C. It was observed that EDC is
activated by the cytosol fraction of liver homogenates; thus, mixed-function
oxygenases are not involved. The activation was NADPH-independent but required
glutathione (GSH) A or C S-transferase enzyme activity. The extent of activation
was found to be dependent on the rat strain used (liver fractions from R strain
rats were more effective than those from Sprague-Dawley rats) and the handling of
the extract (e.g., storage on ice or freezing reduced the effectiveness of the
activation system). The report by McCann et al. (1975) (described earlier in
this section) that EDC was not metabolized to a mutagenic intermediate may be due
to differences in the exogenous activation system used (S9 mix rather than
cytosol fraction) in the two studies. Rannug et al. (1978) hypothesize that the
mutagenicity of EDC after metabolic activation is caused by the formation of a
highly reactive half sulfur mustard, S-(2-chloroethyl)-L-cysteine (see section
9.1.3-3-B). This compound (>99$ purity) was found to be more strongly mutagenic
in TA1535 than is EDC. AT 0.2 ^moles/plate, 12.8 ±1.5 and 176.8 +11.1
revertants were observed per plate after treatment with EDC and S(2-chloro-
ethyl )-L-cysteine, respectively. At 5.0 umoles/plate the observed numbers of
revertants per plate were 13.0 + 1.1 and 195*1 (only one plate tested), respec-
tively. Thus, S-(2-chloroethyl)-L-cysteine gives a strong direct mutagenic
effect at low doses where no effect can be seen for EDC.
In intact mammals most GSH conjugates are normally excreted in bile. Rannug
and Bieje (1979) reasoned that if EDC were metabolically activated by conjugation
9-141
-------
with glutathione to form a half sulfur mustard, mutagenic products in the bile
would be produced in EDC-treated mammals or perfused livers. To test this
hypothesis, an EDC concentration of 0.1 m£ (1.3 mmoles) were perfused through R
strain Wistar rat livers for up to 4 hours. Bile was collected right after
addition of EDC and at 15 and 30 minutes, as well as 1, 1.5, 1.75, 2, 3, and U
hours later. The bile was then added directly to top agar or diluted about 5 to
10 times in sterile water and added to top agar containing Salmonella strain
TA1 535 for plate incorporation tests. Positive responses were obtained. The
greatest response (45-60 revertants per plate, compared to 7-10 in negative
controls) was reached about 15 minutes to 1 hour after addition of EDC. In a
second experiment, 80 mg/kg EDC was given to male CBA mice intraperitoneally.
The animals were sacrificed, their livers removed, and bile collected 30 and 60
minutes later for mutagenicity testing with TA1 535 in plate incorporation tests.
An increase in revertants (greater than twofold) was observed for bile collected
30 minutes after treatment compared to bile from negative control animals (28.8 +
27 revertants and 11.3 + 1-1 revertants, respectively). The positive responses
obtained with bile from the perfused rat livers and intact mouse livers are
consistent with the hypothesis that EDC is activated by conjugation with gluta-
thione.
Four studies have been reported in which EDC was found to be negative in the
standard Salmonella/microsome assay plate incorporation tests (King et al. 1979,
Nestmann et al. 1980, Stolzenberg and Hine 1980, and Barber et al. 1981). The
maximum doses employed in the first three studies were 36 iimoles/plate, 91
limoles/plate, and 10 umoles/plate, respectively; the fourth study did not report
the doses used. The doses reported in these studies therefore encompass a range
at which positive responses have been reported in other studies. Except for the
report by Stolzenberg and Hine (1980), the negative Salmonella plate incorpora-
9-142
-------
tion studies were conducted with appropriate positive controls. Each test was
conducted with and without PCB-induced rat liver S9 mix. It should be pointed
out, however, that the positive controls, which require activation, were not
structually similar to EDC. Therefore, these positive controls may not be able
to determine the effectiveness of the components in the S9 mix necessary for EDC
activation. King et al. (1979) also reported negative responses when E. coli
K1 2/343/113 was tested in either a liquid suspension test or an intrasanguineous
host-mediated assay.
Two of the negative studies (i.e., Nestmann et al. 1980 and Barber et al.
1981 ) reported that although EDC did not induce mutations in standard plate
incorporation tests, positive responses were obtained when the studies were
conducted in air tight exposure chambers. Nestmann et al. (1980) exposed
Salmonella strains TA1 535 and TA100 to doses from 3 to 9 mg/plate (30 to 91
umoles/plate) in desiccators. It was reported that this treatment yielded posi-
tive results, at least for TA1 535 in which there was a doubling in the number of
mutant colonies over the control. It was stated that concentrations were tested
up to levels where cell-killing was observed, but no data are given and insuffi-
cient detail is provided to allow the results be adequately evaluated.
Barber et al. (1981) exposed Salmonella tester strains TA1 535, TA98, and
TA100 to four levels of EDC vapors (Eastman Kodak Co., 99.98$ pure) in a 3.4
liter airtight exposure chamber. These exposures resulted in estimated plate
concentrations ranging from 31 .8 to 231 .8 umoles/plate as determined by gas
liquid chromatography analysis of distilled water samples placed in the exposure
chamber. Linear, dose-related increases in revertant counts were observed for
TA1 535 and TA100. The mutagenicity of EDC in these two strains was 0.002 and
0.001 revertants/nmole, respectively. No difference in revertant counts or
potency of EDC was noted in comparisons of tests done with and without metabolic
9-143
-------
activation. The positive results were obtained by Nestmann et al. (1980) and
Barber et al. 0981 ) only when tests were conducted in airtight exposure
chambers. This suggests that standard mutagenicity testing of EDC (bp 83-34°)
may not provide an adequate assessment of its mutagenic potential due to
excessive evaporation.
In summary, the positive responses obtained without metabolic activation
indicate that EDC is a weak direct-acting mutagen in bacteria. The positive
responses obtained with metabolic activation indicate that one or more of its
metabolites are more potent mutagens. The negative findings reported in
bacterial tests are not considered to contradict the reported positive results,
because the negative results may have been due to excessive evaporation of EDC or
to inadequacy of the S9 activation system.
Eucaryotic Test Systems
In addition to causing gene mutations in bacteria, EDC also has been shown
to cause gene mutations in eukaryotes.
Higher Plants —
Two reports were evaluated concerning the ability of EDC to induce mutations
in higher plants (Table 9-28). Ehrenberg et al. (197*0 treated b?rley seeds
(variety Bonus) with 30.3 mmoles EDC (Merck, purity not given) for 24 hours and
scored for sterile spikelets at maturity or chlorophyll mutations in about 600
spike progenies in the subsequent generation. The dose level tested corresponds
to the LD _. EDC treated kernels had an increased incidence of chlorophyll
mutations (6.8$) compared to untreated controls (0.06%}.
Kirichek (1974) exposed eight varieties of pea seeds (100 each) to gaseous
EDC (purity and concentration not given) for 4 hours. The germination of treated
seeds differed with the variety tested but was reduced (15-50$ germination)
compared to negative control seeds exposed to water vapor for 4 hours (100$
9-144
-------
TABLE 9-26
Summary of Mutagenicity Testing of EDC: Higher Plants
Reference
Ehrenberg et al.
197H
Test
System
Segregating
chlorophyll
(gene) mutations
in barley.
Chemical
Information
Concentration tested:
200 seeds treated
with 30.3 mnoles/24
hours (LD Q) in a
closed vessel.
Results Comments
Positive response. 1. About 600 spike progeny were tested.
(6-8$ mutants from
treated progeny vs.
0.06$ mutants from
control progeny).
FCiricheck, 197"»
Visible mutations
in peas, 8 varieties
Concentration tested:
EDC (concentration not
reported) or water
(negative controls)
vapors for 1 hours.
Source: Not reported
Purity: Not reported
Source: Merck Co.
Purity: Not given
Reported postive.
5.12-28.13< of
seeds reported
to be mutated.
1. English translation of Russian article.
2. Germination of the treated seed varied
with the variety tested from 1 5% to 5B<
compared to 100$ germination of the
control seeds.
3. Control mutation frequency not given.
4. Putative mutations not characterized.
5. Not possible to adequately evaluate
results.
-------
germination). From 5.4$ to 28.13? of the seeds were reported to be mutated. It
is reported that two times as many morphological mutants were induced as chloro-
phyll mutations. The author considered this a positive response, but the muta-
tion frequency for negative controls was not given. This limitation of the
report plus a lack of information concerning the characterization of the putative
mutations precludes an adequate evaluation of the results.
Insects —
Four studies were evaluated concerning the ability of EDC to cause mutations
in Drosophila melanogaster (Table 9-29). These studies demonstrated the ability
of EDC to cause sex-linked recessive lethal mutations (Shakarnis 1969, Shakarnis
1970, and King et al. 1979). The fourth study demonstrated the induction of
somatic cell mutations by EDC (Nylander et al. 1979).
Shakarnis (1969, 1970) performed two experiments to assess the ability of
EDC (purity not given) to cause sex-linked recessive lethal mutations in
Drosophila. In the first study (Shakarnis 1969), adult females from a radio-
sensitive strain (Canton S) were exposed to 0.07$ EDC gas for 4 or 8 hours at 24°-
25°C. Immediately after treatment the females were mated to Muller-5 or In w B
males. In fertility of treated females was reduced 47$ by the 4 h treatment and
91$ by the 8 h treatment. The F- progeny were scored for lethality (measured as
the absence of M5 or In wa B males). A statistically significant (P<0.05) time-
related increase in the incidence of sex-linked recessive lethals was observed.
The frequencies of lethals were 0.3$ (negative controls), 3.2$ (4 h treatment)
and 5.9$ (8 h treatment). In his second study, Shakarnis (1970) exposed females
from a radiostable strain (D-32) of Drosophila melanogaster to 0.07$ EDC vapors
(source and purity not reported) for 4 or 6 hours. Immediately after treatment
they were mated to Muller 5 males and the F2 progeny scored for sex-linked
recessive lethals. The 4 h treatment did not significantly reduce fertility but
9-146
-------
TABLE 9-29
Summary of Mutagenicity Testing of EDC: Gene Mutation Teats in Insects
Test Chemical
Reference System Information Results
Shakarnis, 1969 Drosophila Concentration tested: Postive response 1.
aelanogaster virgin 3-day-old
sex-linked Canton S females 2.
recessive lethal exposed to 0.07<
test. EDC gas for 1 or 8
hours at 2U-25°C.
Source: Not given 3.
Purity: Not given
Duration of
Treatment
(h) with Number of
0.071 EDC Chromosomes Scored
Control 191 0
M 2061
8 U750
Comments
Muller-5 or In wa B males.
Fertility of treated females
reduced significantly (U7< after
1 hour treatment and 91 1 after
8 hour treatment).
Canton S strain reported to be
sensitive.
Lethal Mutations
No. %
15 0.30
67 3.22
261 5.91
p<0.05
-------
TABLE 9-29 (oont.)
Reference
Test
System
Chemical
Information
Results
Comments
Shakarnis, 1970
Drosophilia
melanogaster
sex-linked
recessive lethal
test.
Concentration tested:
virgin 3-day-old
radiostable D-32
strain females
exposed to 0.07< EDC
gas for 4 or 6 hours
at 24-25°C.
Source: Not given
Purity: Not given
Positive response 1.
2.
Muller-5 males.
Experiment conducted twice for
4 hour exposure and three times
for 6 hour exposure.
4 hour treatment did not
significantly reduce fertility
but 6 hour treatment reduced it
by 50%.
Duration of
Treatment
(h) with
0.07* EDC
Control
4
6
Number of
Chromosomes Scored
1904
2205
2362
Lethal
No.
1
46
78
Mutations
*
0.05
2.00
3.30
(P<0.05)
-------
TABLE 9-29 (cont.)
Reference
Test
System
Chemical
Information
Results
Comments
King et al.
1979
Drosophila
melanogaster
sex-linked
recessive lethal
test.
vO
I
Concentration tested:
50 mM solution of EDC
in 5% sucrose fed to
1- to 2-day-old Berlin K
males for 3 days (Near
Source: Merck Co.
Darmstadt, FRG
Purity: Not given but
stated to have
correct melting
point and
elemental
analysis.
Positive response
Base females.
Lethal frequency increased for all
broods. Greatest effect in brood
II, which corresponds to the
spermatid stage of spermatogenesis.
Cone.
(mM)
0
50
Brood
I-III
I
II
III
I-III
Days after
Treatment
0-9
0-3
1-6
7-9
0-9
Number of
Lethal Mutations
Chromosomes Scored No. %
22,018
1,185
1,179
156
2,520
17
6
11
2
19
0.21
0.51
3.18
1.28
1.91
P
<0.01
<0.01
-------
TABLE 9-29 (cont.)
Reference
Nylander et al.
1978
Test
System
Droaophila
melanogaster
somatic cell
mutations so
- - !§Tel9
stocks.
Chemical
Information Results
Concentration tested: Positive response
0.1* and 0.5* EDC in
food at 25°C and 75*
humidity during larval
development.
Source: Fisher
Comments
1 . Mutations at z locus scored in
flies of stable and unstable
genotype. Both have same phenotype
Instability thought to be caused
by transposable genetic element.
2. Survival of treated flies reduced
Scientific Co.
Purity: Not given
01
o
significantly in both genetically
stable (34* reduction for 0.1* and
77* reduction for 0.5* dose) and
genetically unstable stocks (86$
reduction for 0.5% dose).
Treatment
Control
Stable
Unstable
0.01*
Stable
Unstable
0.05*
Stable
Unstable
Number
Males
Scored
I»»»H1
5363
6260
2689
610
201
Number
with
Sectors
2
U
263
271
K4
50
0
0
H
9
7
2H
*
.Ot5
.075
.20
.28
.21
.88
t Value
Within
-
18
214
11
13
Differences
Genotypes
--
.7*:
.31
X
.12
t Value
Between
0.
9.
5.
Differences
Genotypes
60
16§
66'
-------
the 6 h treatment reduced it by 50%. As in the first study, a statistically
significant (P<0.05) time-related increase in sex-linked recessive lethals was
observed. A frequency of 0.05$ lethals was observed in the negative controls,
and frequencies of 2.00* and 3.30* lethals were observed in offspring from the 4
h and 6 h treatments, respectively.
King et al. (1979) also studied the ability of EDC to cause sex-linked
recessive lethals in Drosophila. One to two day old Berlin K males were fed a 50
mM solution of EDC (Merck and Co., purity not given but correct melting point
(sic) and elemental analysis reported) in 5% sucrose for 3 days. This dose
approximated the LE> The males were immediately mated to virgin Base females
every 3 days for a total of 9 days to determine if EDC preferentially damaged
particular stages in spermatogenesis. Progeny of the F2 generation were scored
for lethality. The lethal frequency was found to be elevated for all three
broods (0.51$, 3.W!>%, and 1.28*, respectively, for broods I, II, and III)
compared to the negative controls (0.21*). The highest lethal frequency (3.^*)
was found in brood II (P<0.01), which corresponds primarily to the spermatid
stage of spermatogenesis.
Nylander et al. (1979) raised flies on food containing 0.1* and 0.5* EDC
(Fisher Scientific Co., purity not given) during larval development and scored F1
progeny for the induction of somatic cell sex-linked mutations in the eye. A
genetically unstable stock (sc z w+) and a genetically stable stock
(z Dp w+ e ) both having the same phenotype were used in these studies and
mated to attached X females. Mutations result in the expression of normal (dark
red) eye pigment in adult treated males. The genetic instability of sc z w is
caused by the insertion of a transposable genetic element. The survival of flies
raised on the EDC-treated food was significantly reduced compared to the negative
control values (e.g., 77* reduction for the stable stock and 86* reduction of the
9-151
-------
unstable stock at 0.5% EDC). Statistically significant increases in somatic cell
mutations occurring in both stocks were observed at both the low and high doses
(P<0.001 ).
The positive responses in Drosophila indicate that EDC is capable of causing
both somatic cell and heritable germinal mutations in a multicellular eukaryote.
Mammalian Cells In Culture —
Tan and Hsie (1981) found that EDC (Matheson, Coleman and Bell, purity not
given) caused a dose-related increase in HGPRT mutations in cultured Chinese
hamster ovary (CHO) cells (Table 9-30). CHO-F^ -BH^ cells were exposed in suspen-
sion culture for a period of 5 hours to EDC concentrations ranging up to 3mM (30%
survival) in tests with exogenous rat liver S9 mix for metabolic activation and
concentrations ranging up to 50mM (50% survival) in tests conducted without
metabolic activation. Weak positive responses were observed both in tests with
(5 mutants/10 cells/mM) and without (1 mutant/10 cells/mM) metabolic activa-
tion (P<0.01). EDC was detected as a direct-acting mutagen only at high doses,
but the induced mutation frequency was increased about tenfold over control
values. Only about a fourfold additional increase in mutagenicity was noted with
metabolic activation but excessive toxicity precluded testing at concentrations
greater than 3mM (i.e., S9 mix increased mutagenic activity by approximately
fourfold and cytotoxic activity from 5 to 25-fold). The metabolic activation
system was only effective in the presence of NADP. This contrasts with Rannug
(1976) who found metabolic activation of EDC to be NADP-independent.
The consistency of positive results obtained in higher plants, Drosophila,
and cultured mammalian cells demonstrates that EDC causes gene mutations in
higher eukaryotes.
9-1 52
-------
TABLE 9-30
Summary of Mutageniclty Testing of EDC: Mammalian Cells in Culture
Reference
Tan and Hsie,
1981
Test
System
Chinese hamster
ovary cell HGPRT
gene mutation
assay.
Chemical
Information
Concentration tested:
Up to 3 nM in tests
with rat liver S9 mix
and up to 50 mM in
tests without
metabolic activation.
LD is 1 mM with
activation and 6 mM
without activation.
Results
Positive response ,
60 v. 3 mutants/106
olonable cells for
50 and 0 mM EDC
without activation.
26 v. 3 mutants/106
clonable cells for
1 . 5 and 0 raM EDC
with activation.
Comments
1 . Mutagenic activity of EDC without and
with metabolic activation calculated
to be 1 and 5 mutants/1 0 cells/
milHraole, respectively.
2. S9 mix increases mutagenicity by
about fourfold and cytotoxicity
5- to 25-fold.
3.
NADP required in S9 mix for
metabolic activation.
-------
CHROMOSOME ABERRATION STUDIES
Five studies were evaluated regarding the ability of EDC to cause chromosome
aberrations (Table 9-31). One was an abstract of testing EDC for its ability to
cause chromosome breakage in Allium root tips and cultured human lymphocytes
(Kristoffersson 197*0. Two were Drosophila melanogaster X chromosome nondis-
junction tests (Shakarnis 1969 and 1970), and two were micronucleus tests (King
et al. 1979 and Jenssen and Ramel 1980).
In the report by Kristoffersson (1974) EDC (source, purity, and concentra-
tion not given) was reported to cause C-mitoses in Allium root tip cells but not
to cause chromosome breaks in Allium root tip cells, human lymphocytes or to
induce prophage from E. coli K 39 (X). Because the report was an abstract,
insufficient information was available to substantiate the reported results.
However, the induction of C-mitoses in Allium root tip cells suggests that EDC
can interfere with the mitotic spindle apparatus.
Data consistent with this possibility are found in studies by Shakarnis
(1969 and 1970) using Drosophila melanogaster. Females were exposed to 0.07? EDC
vapors (source and purity not given). In the first study (1969) a statistically
significant (P<0.05) increase in exceptional F1 progeny, indicative of meiotic
nondisjunction, was seen after a 4 h treatment (0.03? exceptional females) and 8
h treatment (0.18? exceptional females and 0.09? exceptional males) compared to
the negative control value (0?; 0/11575 progeny). In the second study, the
incidence of exceptional progeny was elevated in the treated groups but not
significantly so. However, in this study 38,437 fewer progeny of the 4 h
treatment group were scored for exceptional progeny than in the first study.
Furthermore, the longest treatment time was 6 h (i.e., 2 h shorter than in the
first study), and 8,086 fewer progeny were scored at this time point than for the
longest time point in the first study. It may be that the sample sizes were too
9-154
-------
TABLE 9-31
Summary of Mutageniclty Testing of EDC: Chromosomal Aberrations Teats
Ul
Reference
Shakarnis, 1969
Test
System
Drosophila
aelanogaater
X chromosome
nondisjunctlon
Chemical
Information
Concentration tested:
virgin Canton S females
exposed to 0.7$ EDC
in 1 . 5 I. desiccator
for 4 and 8 hours at
2l»-25°C.
Source: Not given
Results Comments
Statistically
significantly
(P<0.05) increases
in exceptional
female progeny
for 4 hour exposure
and male and female
progeny for 8 hour
exposure .
Purity: Not given
0.07* EDC
Duration of
Treatment
(h)
Control
4
8
Normal Progeny
No. Females
5,848
24,125
8,437
No. Males
5,727
21,297
7,773
Exceptional
Females
No.
0
8
15
*
0
0.03*
0.18*
Progeny
Males
No. *
0 0
3 0.01
7 0.09*
•P<0.05
-------
TABLE 9-31 (cont.)
Reference
Test
System
Chemical
Information Results
Comments
Shakarnis, 1970
Drosophila
melanogaster
X chromosome
nondisjunction
vo
I
Concentration tested:
3-day-old females
from radiostable D-32
strain exposed to 0.07H
EDC in a 1.5 H
desiccator for M or 6
hours at 24-25'C.
Source: Not given
Purity: Not given
Incidence of nondis- 1
junction greater in
treated group than
in control. Increase
not statistically
significant. 2,
Not as many individuals scored
as in 1969 study. Sample size
may not have been sufficiently
large.
Longest exposure time 2 hours
shorter than in previous
experiment; may have been too
short.
0.07< EDC
Duration of
Treatment
(h)
Normal Progeny
No. Females No. Males
Exceptional Progeny
Females Males
No. % No. )
Control
1)
6
2172
35B4
2205
3H01
U090
0
0.03
0.10
1 0.03
1 0.03
3 0.07
-------
TABLE 9-31 (cont.)
Reference
King et al.
1979
Test
System
Micronucleua test:
NMRI mice
Chemical
Information
Concentration tested:
2 i.p. injections of
Results
Negative
Comments
1 . 1 ,000 polychromatic erythrocytes
analyzed/animal .
i» mmoles/kg (UOO mg/lcg)
given 24 hours apart.
1 animals/dose
sacrificed after
second injection.
Source: Merck Co.
Darmstadt, FRG
Purity: Not specified,
but melting
point and ele-
mental analysis
were correct.
2. Frequency of micronuclei not
given.
Jenssen and Ranel,
1980
Mioronucleua test:
CBA mice
Concentration tested:
single i.p. injection
100 mg/kg.
Source:
BDH Chemicals,
Ltd.
Purity: Not given
Negative.
(0.15 ± 0.1U) poly-
eromatlc erythocytes
with micronuclei in
controls v. 0.1 7 +
0.10 in treated
animals).
-------
small or the duration of exposure too short in the second study to be able to
detect a statistically significant effect.
Micronucleus tests were performed by King et al. (1979) and Jenssen and
Ramel (1980). Both studies reported negative results. King et al. (1979)
injected NMRI mice with two intraperitoneal injections of 4 mmoles/kg (400 mg/kg)
EDC (Merck Co., purity not specified but melting point (sic) and chemical
analysis reported to be correct). The authors state this corresponds to an
"approximate lethal dose" (the LD1 Q for intraperitoneal injections of EDC in mice
is 250 mg/kg). The injections were given 2H h apart; the animals were killed 6 h
after the second injection and bone marrow smears made. One thousand poly-
chromatic erythrocytes (PCEs) were analyzed per animal. Frequencies of micro-
nuclei were not given, but the results were evaluated to be negative by the
authors.
Jenssen and Ramel (1980) also reported negative results in a micronucleus
test. CBA mice were given a single intraperitoneal injection of EDC (DBH
Chemicals Ltds., England, purity not given) at a dosage of 100 mg/kg. The
animals were sacrificed the next day and PCEs (number not given) were scored for
micronuclei. The frequencies of PCEs with micronuclei were 0.15 + C.11 in the
controls and 0.17 + 0.10 in treated animals.
The positive response in the X-chromosome test in Drosophila (Shakarnis
1969) suggests EDC is capable of causing meiotic non-disjunction resulting in
numerical chromosomal abnormalities. The negative responses obtained in the
micronucleus tests may indicate that EDC does not cause chromosomal damage in
mice. However, because EDC has not been adequately tested for its ability to
cause structural chomosomal aberrations, it would be appropriate to perform
mammalian in vitro and in vivo cytogenetic tests. Such testing is required
9-158
-------
before a judgment can be made on the ability of EDC to cause chromosomal aberra-
tions.
OTHER EVIDENCE OF DNA DAMAGE
Three other tests have been conducted on the genotoxicity of EDC. These
tests do not measure mutagenic events per s_e in that they do not demonstrate the
induction of heritable (i.e., somatic or germinal) genetic alterations, but
positive results in these test systems show that DNA has been damaged. Such test
systems provide supporting evidence useful for assessing genetic risk.
Bacterial Test Systems
PolA Assay —
Ethylene dichloride has been reported positive in the polA assay which
measures toxicity associated with unrepaired damage in DNA (Table 9-32). Brem et
al. 097*0 soaked sterile filter disks with 10 uS, (80 umoles) EDC. These were
centered on the agar surface of petri dishes covered with bacteria (one set with
polA* strain, the other with polA" strain). After incubation the plates were
scored for differential inhibition of growth. An 8 mm zone of growth inhibition
was observed in the polA+ strain compared to a 9 mm zone of inhibition for the
polA" strain. These repsonses were said to be reproducible. The ratio between
the zones of inhibition (polA+/polA~) was 1.26 which is interpreted by the
authors to be a positive response. However, it should be noted that 1 mm is not a
big difference, and the ratio may be misleading.
Eukaryotic Test Systems
Unscheduled DNA Synthesis —
One test has been performed to assess the ability of EDC to cause
unscheduled DNA synthesis (Perocco and Prodi 1981). Although demonstration that
a chemical causes unscheduled DNA synthesis does not provide a measurement of its
mutagenicity per se, it does indicate that the material damages DNA. Perocco and
9-159
-------
TABLE 9-32
Summary of Mutagenioity Testing of EDC: PolA ASSAY
Reference
Test
System
Strains
Activation
System
Chemical
Information
Results
Comments
Brem et al. polA differential E. coll
1971 cell killing polA~~
assay polA*
None
Concentration tested:
10 »l on filter disk
I
o
Questionable 1. All assays carried out in
positive duplicate on at least
three different occasions.
2. Only a small difference
in diameter (I.e. 1 mm)
was noted between the
zones of killing In the
two strains. Thus, the
A*/A~ ratio may be
misleading.
Pol A Zone of Inhib.
EDC
(MS
Chloramphenlcol
A+
mm
8
15
26
A"
mm
9
51
28
A*/A"
1.26
1.11
1.00
-------
Prodi (1981 ) collected blood samples from healthy humans, separated the lympho-
cytes, and cultured 5 x 10 of them in 0.2 mfc medium for 4 h at 37°C in the
presence or absence of EDC (Carlo Erban, Milan, Italy or Merch-Schuchardt,
Darmstadt, FRG, 97-99$ pure). The tests were conducted both in the presence and
in the absence of PCB-induced rat liver S9 mix. A comparison was made between
treated and untreated cells for scheduled DNA synthesis (i.e., DNA replication)
and unscheduled DNA synthesis. No difference was noted between the groups with
respect to scheduled DNA synthesis measured as dpm of [ H] deoxythymidylic acid
(TdR) after 1 h of culture (2661 + 57 dpm in untreated cells compared to 228 7 + 60
dpm in cells treated with 5 \iH/mH [0.06 umole/mfc] EDC). Subsequently 2.5, 5, and
10 uH/mS, (0.03, 0.06 and 0.1 umole/m&) EDC was added to cells which were cultured
in 10 mM hydroxyurea to suppress scheduled DNA synthesis. The amount of
unscheduled DNA synthesis was estimated by measuring dpm from incorporated
[3H]TdR 4 h later. At 10 nfc/mJ, EDC 483 ± 37 and 532 + 21 dpm were counted without
and with exogenous metabolic activation, respectively. Both values were lower
than corresponding negative controls of 71 5 + 24 and 61 2 + 26 dpm, respectively.
No positive controls were run to ensure that the system was working properly
although testing of chloromethyl methyl ether (CMME) with activation resulted in
a doubling of dpms over the corresponding negative control values (1320 + 57 at 5
nl/mS, CMME versus 612+26 untreated). The authors calculated an effective DNA
repair value (r) for each chemical based on the control and experimental values
with and without metabolic activation. Ethylene dichloride was evaluated by the
authors as positive in the test, but they did not state their criteria for
classifying a chemical as positive. It is important to note that none of the
experimental values from cells treated with EDC without metabolic activation had
higher dpm values than the controls. Furthermore, although two out of three
experimental values were greater than the controls with metabolic activation
9-161
-------
(673 + 45 at 5 ui/ml and 630 + 34 at 2.5 \iH/m!L compared to control value of *vi 2 ±
26) the increases were not statistically significant. The positive finding
reported in this work is therefore judged to be inconclusive.
Detection of DNA Adducts —
Reitz et al. (1982) compared the pharmacokinetics of EDC administered to
Osborne-Mendel rats after inhalation and after exposure by gavage. (See section
9.1.3, especially 9.1.3.5.) As part of their study, DNA alkylation was measured
in bacteria at EDC cytosol concentrations corresponding to those used in the DNA
binding study (Table 9-33). Two gram aliquots of TA1 535 were incubated with 7.06
Hinol [ C] EDC/mH (sp. act. =3.2 mCi/mmol) and varying amounts of cytosol. DNA
alyklation values at cytosol concentrations of 2.2, 7.8, 27, and 71$ were 8.65,
27, 107, and 137 dpm/mg purified DNA, respectively. This corresponds to 4, 12.5,
49, and 64 alkylations x 10~ DNA nucleotides. The corresponding reversion
frequencies were 4.6 + 0.82, 23-5 + 3.0, 80.2 + 9.6, and m + 2.6, respectively
(n = 3 in each case). A direct correlation between the degree of alkylation and
an increase in mutation frequency was indicated by linear regression analysis
(r = 0.9976). In the DNA alkylation studies with rats [14C] EDC (sp. act. = 0.32
mCi/mmol) was administered to groups of three animals by gavage (150 mg/kg) or
inhalation (150 ppm, 6 h). The animals were subsequently sacrificed and DNA was
extracted from the liver, spleen, kidney, and stomach for measurement of DNA
alkylation. Overall, there was three to five times more DNA alkylation after
gavage than after inhalation. The values ranged from 5.8 + 0.7 to 23.1 + 7.4
alkylation/10 nucleotides for gavage versus 1.8 + 0.3 to 8.2 + 3.3 alkyla-
tion/10 nucleotides for inhalation. Under the conditions of test used in the
experiments by Reitz et al. (1982) EDC exposure resulted in a similar degree of
adduct formation in both rats and bacteria. Because DNA is the genetic material
in both bacteria and rats, these data predict that mutations were induced in the
9-162
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TABLE 9-33
Summary of Mutagenioity Testing of EDC: DNA Binding Studies
Activation
Reference Teat System Strains System
Reitz et al. DNA alkylation TA1 535 Phenobarbital
1982 and mutageneala induced rat % Cytoaol
in Salmonella liver cytosol 2.2
vo 7.8
L 27
CT> 71
t-o
DNA alkylation Osborne- NA
in rats Mendel rat Route of
Exposure
Gavage
1 50 mg/kg
Inhalation
1 50 ppm , 6 h
Chemical Information
Revertants
4.6 + 0.82
23.5 + 3.0
80.2 + 9.6
111 + 2.6
Tissue
Liver
Spleen
Kidney
Stomach
Liver
Spleen
Kidney
Stomach
Alkylation x 1 0~6
Hue leot ides
4
12.5
49
64
Alkylation x 1 0
Nucleotldes (means
from 2 experiments
21.3
5.8
17.4
14.9
8.2
1.8
5.2
2.8
13.9
2.5
14.5
6.7
3-3
1.8
2.0
1.9
Comments
1 . Bacteria incubated with
7.06 (imol EDC/ml.
2. Significant correlation
between degree of alkylation
and Increased reversion
frequency (r = 0.9976).
3. Rats sacrificed 4 h post
gavage or immediately after
inhalation.
4. Sp. act. 3.2 mCi/nmol for
bacteria; 0.32 mCi/mmol
for rats.
-------
rat at the exposures used. This is in keeping with the positive responses in
other eukaryotes including Drosophila and cultured CHO cells. DNA alkylation was
not measured in rat gonads so it is not possible to estimate what the heritable
genetic risk might be.
SUMMARY AND CONCLUSIONS
Ethylene dichloride (EDC) has been shown to cause gene mutations in
bacteria, plants, Drosophila and cultured Chinese hamster ovary (CHO) cells.
Weak positive responses were observed in the bacterial and CHO tests in the
absence of an exogenous metabolic activation system. Stronger positive
responses were found when hepatic metabolic activation systems were
incorporated. Based on these positive findings in different test systems
representing a wide range of organisms, EDC is judged to be capable of causing
gene mutations.
EDC has been reported to cause meiotic chromosomal nondisjunction in
Drosophila. The induction of meiotic nondisjunction is a significant genotoxic
effect; however, a positive response in another test system is needed to permit a
judgment on the generality of this effect. With respect to its ability to cause
structural chromosomal aberrations, sufficient testing has not been performed.
There is only one study on the ability of EDC to cause structural chromosomal
aberrations (i.e. in Allium root tip cells and human lymphocytes). Because this
study was reported in an abstract, the author's conclusions are unsubstantiated.
Even though negative results are reported from micronucleus tests, additional
information is needed to draw conclusions on the ability of EDC to cause
chromosomal aberrations. For example, it would be appropriate to test EDC in in
vitro and in vivo mammalian cytogenetic assays. A sister chromatid exchange
assay would also be useful in assessing the ability of EDC to cause chromosome
damage.
9-16U
-------
There are no available data on the ability of EDC to damage DNA in mammalian
germ cells. Thus, studies on the ability of EDC to reach germinal tissue would
be appropriate to determine whether EDC has the potential to cause heritable
mutations which may contribute to the genetic disease burden. The finding that
EDC causes heritable mutations in Drosophila and alkylates DNA in several somatic
tissues in the rat reinforces the need for further germ cell studies in mammals.
Based on the weight-of-evidence, EDC is judged to be a weak direct-acting
mutagen. Several of its putative metabolites, thought to be formed in mice and
rats, are Judged to be more potent mutagens (e.g., S-[2-chloroethyl]-L-cysteine
or chloroacetaldehyde) than EDC with the potential to cause adverse effects in
humans.
9-165
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9.5 CARCINOGENICITY
The purpose of this section is to provide an evaluation of the likelihood
that ethylene dichloride (EDC) (1,2-dichloroethane) is a human carcinogen and,
on the assumption that it is a human carcinogen, to provide a basis for estimating
its public health impact, including a potency evaluation in relation to other
carcinogens. The evaluation of carcinogenicity depends heavily on animal
bioassays and epidemiologic evidence. However, other factors, including
mutagenicity, metabolism (particularly in relation to interaction with DNA),
and pharmacokinetic behavior, have an important bearing on both the qualitative
and quantitative assessment of carcinogenicity. The available information on
these subjects is reviewed in other sections of this document. This section
presents an evaluation of the animal bioassays, the human epidemiologic evidence,
the quantitative aspects of assessment, and finally, a summary and conclusions
dealing with all of the relevant aspects of the carcinogenicity of EDC.
9.5.1 Animal Studies
The carcinogenic potential of EDC has been investigated in a number of
studies in which EDC was administered to rats and mice via various routes of
administration. Five studies will be discussed: one gavage study performed
by the National Cancer Institute (1978) in which EDC was administered to rats
and mice; two inhalation studies, including one by Spencer et al. (1951) using
rats, and one bioassay by Maltoni et al. (1980) in which EDC was administered
to rats and mice; one intraperitoneal study by Theiss et al. (1977) in which
EDC was administered to mice; and one skin-painting study by Van Duuren et al.
(1979) in which EDC was administered to mice.
9-166
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9.5.1.1 National Cancer Institute (1978) Rat Study—Hazleton Laboratories
America Inc., Vienna, Virginia, under the sponsorship of the NCI, conducted a
bioassay of 1,2-dichloroethane (EDC) using Osborne-Mendel rats. The NCI pub-
lished a final report of the bioassay in 1978. Their results were also reported
by Weisburger (1977), the International Agency for Research on Cancer (IARC
1979), and Ward (1980).
Technical-grade EDC, obtained for this study from the Dow Chemical Company,
Midland, Michigan, was tested for its purity. Gas-liquid chromatography revealed
a purity of 98% to 99% EDC with 4 to 10 minor peaks (Ward 1980). However, in
the NCI bioassay a purity of greater than 90% was reported, with only two
unidentified minor contaminants. Recently this discrepancy was resolved when
the original sample of EDC was reanalyzed, at which time the EDC was found to
be greater than 99% pure, with several unidentified contaminants. This analysis
was also performed by the National Institute for Occupational Safety and Health
(NIOSH) after completion of the bioassay; the sample contained about 99% 1,2-
dichloroethane, with chloroform as the major contaminant (Hooper et al. 1980).
Solutions of EDC were prepared in corn oil and administered by oral
intubation to 200 Osborne-Mendel rats starting at 8 weeks of age. The design
summary of this experiment is given in Table 9-34. On the basis of a sub-
chronic EDC study, 50 rats of each sex were used for each of two dose levels
in the chronic study. The maximum tolerated dose (MTD) was determined to be 95
mg/kg/day for both males and females; the second dose was one-half the MTD
(47 mg/kg/day).
Twenty animals of each sex served as untreated controls; an equal number
were given the vehicle (corn oil) by gavage. Because of the inadequacies of the
subchronic studies, the initial doses administered to the test animals were
9-167
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TABLE 9-34 . DESIGN SUMMARY FOR 1,2-DlCHLOROETHANE (EDC) GAVAGE
EXPERIMENT IN OSBORNE-MENDEL RATS
(NCI 1978)
Group
Initial
numbe r of
animals
1,2-dichloro-
ethane
dosage3
Observation period
Treated Untreated
(weeks) (weeks)
Time-weighted
average dosage
over a 78-week
period*5
Males
Untreated control
20
106
Vehicle-control 20
Low-dose 50
High-dosed 50
0
50
75
50
50C
0
100
150
100
100C
0
78
7
10
18
34
— — —
7
10
18
34
— ~~~~
32
- —
9
32
9
23
0
47
95
— — —
Females
Untreated control 20
Vehicle-control 20
0
78
106
32
Low-dose
50
50
75
50
50C
0
7
10
18
34
47
9
32
High-dosed
50
100
150
100
100C
0
7
10
18
34
95
9
15
aDosage, given in rag/kg body weight, was administered by gavage five consecutive
days per week.
^Time-weighted average dosage = (dosage x weeks received)
78 weeks
cThese dosages were cyclically administered with a pattern of one dosage-free
week followed by 4 weeks (5 days per week) of dosage at the level indicated.
dAll animals in this group died before the bioassay was terminated.
9-168
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found to be inappropriate. Early signs of toxicity necessitated several changes
in the dosages (Table 9-34). Animal weight and food consumption per cage were
obtained weekly for the first 10 weeks and monthly thereafter. Animals were
checked daily for mortality. Weight depression was observed in both groups
exposed to EDC. By 50 weeks, the weight depression averaged 12% in high-dose
rats (Figure 9-8 )• Mortality was early and severe in dosed animals, especially
those given the highest doses. The mean survival was approximately 55 weeks on
test for high-dose males and females (Figure 9-9 and Table 9-35). The early
deaths were usually not due to cancer; rather, the toxic effects of EDC appeared
to be responsible for these deaths. Rats dying early had a variety of lesions,
including bronchopneumonia and endocardial thrombosis, which may have contributed
to early death. The pneumonia may have been the result of a viral, bacterial,
or mycoplasmal infection, and the exposure to the chemical may have increased
the tendency to develop severe pulmonary lesions, which would lead to death.
For the high-dose male rats, 50% (25/50) were alive at week 55 and 16% (8/50)
were alive at week 75. Survival was higher in the other groups; 52% (26/50) of
the rats in the low-dose group lived at least 82 weeks, and 50% (10/20) in the
vehicle-control group lived at least 72 weeks. In the high-dose female rats,
50% (25/50) were alive at week 57; 20% (10/50) of the rats in the low-dose
group were alive at week 85. Despite the sacrifice of five females at week 57,
65% (13/22) of the untreated control group survived until the end of the study.
A gross necropsy was performed on each animal that died during the experi-
ment or was killed at the end. A total of 28 organs, plus any tissues contain-
ing visible lesions, were fixed in 10% buffered formalin, embedded in paraplast,
and sectioned at 5 u for slides. Hematoxylin and eosin stain were used rou-
tinely, and other stains were employed when necessary. Diagnoses of tumors
9-169
-------
750
600-
CD
h_
o
E 450-
O
ULJ
£ 300 H
o
CO
z
^ 150^
MALE RATS
Untreated Control
Vehicle-Control
Low-Dose
High-Dose
•750
-600
-450
-300
-150
i '—i—i—i—i—i—i—i—i—r
0 15 30 45 60 75
TIME ONTEST(Weeks)
1
90
105
0
120
750
600-
co
k.
CD
I 450 -^
LJJ
O
m
300 -|
150H
FEMALE RATS
T
15
750
T
I
T
T"
45 60 75
TIME ON TEST (Weeks)
Untreated Control
Vehicle-Control
Low-Dose
High-Dose
1 1 1 r—
-600
-450
-300
-150
90
105
120
Figure 9-8 . Growth curves for male and female Osborne-Mendel rats
administered 1,2-dichloroethane (EDC) by gavage.
(NCI 1978)
9-170
-------
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-------
and other lesions were coded according to the Systematized Nomenclature of
Pathology (SNOP) of the College of American Pathologists (1965).
TABLE 9-35 . TERMINAL SURVIVAL OF OSBORNE-MENDEL RATS
TREATED WITH 1,2-DICHLOROETHANE (EDC)
(adapted from NCI 1978)
Group
Untreated control
Vehicle-control
Low-dose
High-dose
Weeks in
study
106
110
110
101
Males
Females
Animals alive
at end of study
4/203
4/20
1/50
0/50b
(20%)
(20%)
(2%)
(0%)
Weeks in
study
106
110
101
93
Animals
at end of
13/203
8/20
1/50
0/50*>
alive
study
(65%)
(40%)
(2%)
(0%)
aFive rats were sacrificed at 75 weeks.
t>All animals in this group died before the bioassay was terminated.
Squamous cell carcinomas of the forestomach occurred in 3/50 (6%) low-dose
males, 9/50 (18%) high-dose males, 0/50 (0%) high-dose females, and 1/49 (2%)
low-dose females (Table 9-36). None of these tumors occurred in the controls.
For male rats, the Cochran-Armitage Trend Test indicated a significant
(P = 0.01) positive association between dosage and the incidence of squamous
cell carcinoma of the stomach. The Fisher Exact Test confirmed the significance
of these results with P values of 0.039 and 0.001 when comparisons were made
with the matched vehicle-control group and the pooled vehicle-control* group,
respectively.
Squamous cell carcinomas of the forestomach were first observed in high-
dose male rats at 51 weeks after oral intubation of EDC. These lesions were
*The pooled vehicle-control group combined the vehicle-controls from the
studies of 1,2-dichloroethane, 1,1,2-trichloroethane, and trichloroethane.
9-172
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characterized microscopically by acanthosis and hyperkeratosis in the super-
ficial area. The basal epithelial layer contained papillary cords and nests of
anaplastic squamous epithelium supported by a dense band of fibrous connective
tissue. These carcinomas extended through the muscularis mucosa, submucosa,
muscular layers, and serosa, and in one high-dose male, metastasized to adjacent
tissues.
TABLE 9-36 . SQUAMOUS CELL CARCINOMAS OF THE FORESTOMACH IN OSBORNE-MENDEL
RATS TREATED WITH 1,2-DICHLOROETHANE (EDC)
(adapted from NCI 1978)
Group
Untreated control
Matched vehicle-
control
Pooled vehicle-
control
Low-dose
High-dose
Males P value3
0/20 (0%)
0/20 (0%)
0/60 (0%)
3/50 (6%) NS
9/50 (18%)b 0.001
Females P value3
0/20 (0%)
0/20 (0%)
0/59 (0%)
1/49 (2%) NS
0/50 (0%) NS
3P values calculated using the Fisher Exact Test. Treated versus pooled vehicle-
control.
^A squamous cell carcinoma of the forestomach metastasized in one male in this
group.
NS = not significant when P values are greater than 0.05.
Hemangiosarcomas were noted in some treated rats, as described in Table
9-37, but not in any of the controls. Low-dose males and females showed
higher incidences of hemangiosarcoma than high-dose animals. Tumors were
observed in several sites, including spleen, liver, adrenal glands, pancreas,
large intestine, subcutaneous tissue, and abdominal cavity. The Cochran-Armitage
Trend Test indicated a significant (P = 0.021) positive association between
dosage and the incidence of hemangiosarcomas in male rats as compared to the
9-173
-------
pooled vehicle-control rats; the trend was also positive in female rats (P =
0.042). The Fisher Exact Test confirmed these findings, with statistically
significant P values for high-dose males versus pooled vehicle-controls (P =
0.016), for low-dose males versus pooled vehicle-controls (P = 0.003), and
for both low- and high-dose females versus pooled vehicle-controls (P = 0.0*41).
Table 9-37. HEMANGIOSARCOMAS IN OSBORNE-MENDEL RATS TREATED WITH
1 ,2-DICHLOROETHANE (EDO)
(adapted from NCI 1978)
Group
Untreated control
Matched vehicle-
Males
0/20 (0%)
0/20 (0%)
P value3 Females
0/20 (0*)
0/20 (0$)
P value3
control
Pooled vehicle-
control
Low-dose
High-dose0
1/60 (2%)
9/50 (18?)
7/50 (14*)'
0/59 (0%)
0.003
0.016
4/50 (8$) 0.041
4/50 (8$) 0.041
P values calculated using the Fisher Exact Test (one-tailed). Treated
versus pooled vehicle-control.
Only 48 animals were examined for hemangiosarcomas of the large intestine.
°0nly 49 animals were examined for hemangiosarcomas of the spleen and
adrenals and 48 for hemangiosarcomas of the pancreas.
NS = Not significant.
In addition to stomach carcinomas and hemangiosarcomas, EDC-treated
female rats showed significant increases in the incidence of mammary adenocarcinoraas
(Table 9-38). Tumors were observed in the high-dose group as early as 20
weeks after treatment. The Cochran-Armitage Trend Test detected a significant
(P<0.001 ) positive association between the dosage and the incidence of mammary
adenocarcinomas when compared with either control group. This tumor incidence
was significant when the high-dose group was compared with either the matched
vehicle-control group (P<0.001) or the pooled vehicle-control group (P=0.002)
9-174
-------
using the Fisher Exact Test. Historically, this tumor was observed in 4/200
(2%) of the vehicle-control females.
TABLE 9-38. ADENOCARCINOMAS OF THE MAMMARY GLAND IN FEMALE OSBORNE-
MENDEL RATS TREATED WITH 1,2-DICHLOROETHANE (EDC)
(adapted from NCI 1978)
Adenocarcinoma of
Group the mammary gland P value3
Untreated control 2/20 (10?)
Matched vehicle-control 0/20 (O/O
Pooled vehicle-control 1/59 (2$)
Low-dose 1/50 (2?) NS
High-dose 18/50 (36$) 0.0008
P values calculated using the Fisher Exact Test (one-tailed). Treated
versus pooled vehicle-control.
NS = Not significant.
An increased incidence of fibromas of the subcutaneous tissue was reported in
both high-dose (P = 0.007) and low-dose (P = 0.017) male rats when compared to the
pooled vehicle-control group.
In summary, a statistically significant increase in the incidence of squamous cell
carcinomas of the forestomach, hemangiosarcomas of the circulatory system, and fibromas
of the subcutaneous tissue occurred in male rats. There was also a statistically signifies
increase in the incidence of adenocarcinomas of mammary gland and hemangiosarcomas
of the circulatory system in female rats.
9.5.1.2. National Cancer Institute (1978) Mouse Study — Hazleton Laboratories America
Inc., under the sponsorship of the NCI, conducted a bioassay of 1,2-dichloroethane (EDC)
using B6C3F1 mice. The results of this study were published
9-175
-------
by the NCI (1978) and were also reported by Weisburger (1977), the International
Agency for Research on Cancer (IARC, 1979), and Ward (1980).
Technical-grade EDC (with the same purity as that described in the NCI
rat study) was administered to 200 B6C3F1 mice starting at 5 weeks of age.
The design summary for this experiment is given in Table 9-39- On the basis
of results of the subchronic studies, 50 mice of each sex were used at each
of the two dose levels for the chronic study. The MTD was determined to be
195 mg/kg/day for male mice and 299 mg/kg/day for female mice. The second
dose, which was one-half the MTD, was determined to be 97 mg/kg/day for male
mice and 149 mg/kg/day for female mice.
Twenty mice of each sex served as untreated controls, and an equal number
were given the vehicle (corn oil) by gavage. Because of inadequacies in the
subchronic studies, the initial doses administered to the test animals were
found to be inappropriate. Signs of toxicity in these animals early in the
study led to changes of the dosages several times (Table 9-40). Animal weights
and food consumption were recorded for the first 10 weeks and monthly thereafter.
Animals were checked daily for mortality and signs of toxic effects. No dose-
related mean body weight depression was observed in male mice or low-dose female
mice (Figure 9-10). A depression in the mean body weight of the high-dose
female mice was apparent as early as week 1 5. The estimated probabilities of
survival for male and female mice in the control and EDC-dosed groups are shown
in Figure 9-31- Terminal survival of treated and control mice is shown in
Table 9-40. For male mice, no statistically significant association between
dosage and mortality was observed. In the high-dose group, 50$ (25/50) of
the mice were alive at 84 weeks and 42$ (21/50) survived until the end of the
study. In a low-dose group, however, survival was low. By 24 weeks, 52%
(26/50) of the low-dose group and 55$ (11/20) of the untreated control group
9-176
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TABLE 9-39 • DESIGN SUMMARY FOR 1,2-DICHLOROETHANE (EDC) GAVAGE
EXPERIMENT IN B6C3F1 MICE
(adapted from NCI 1978)
Group
Initial 1,2-dichloro- Observation period
number of ethane Treated Untreated
animals dosage3 (weeks) (weeks)
Time-weighted
average dosage'3
Males
Untreated control
Vehicle- control
Low-dose
High-dose
Females
Untreated control
Vehicle -control
Low-dose
High-dose
20
20
50
50
20
20
50
50
aDosage, given in tng/kg body
days per week.
''Time-weighted average dosage
0
75
100
0
150
200
0
0
125
200
150
0
250
400
300
0
78
8
70
____
8
70
___
78
8
3
67
— • — — •
8
3
67
weight, was administered by
= (dosage x weeks received)
weeks
receiving chemical
90
12
12
— __
13
91
32
13
___
13
gavage
0
97
— __
195
~" — *~
0
149
_^ —
299
— —
five consecutive
9-177
-------
had died. In the high-dose group, 72% (36/50) of the animals died between weeks
60 and 80. These deaths may have been tumor-related, since 69% (25/36) had one
or more tumors. Survival was high in the other groups; 68% (35/50) of the low-
dose and 80% (16/20) of the untreated control groups survived until the end of
the study.
TABLE 9-40 . TERMINAL SURVIVAL OF B6C3F1 MICE TREATED WITH
1,2-DICHLOROETHANE (EDC)
(adapted from NCI 1978)
Group
Untreated control
Vehicle -control
Low-dose
High-dose
Weeks in
study
90
90
90
91
Males
Animals alive
at end of study
7/20 (35%)
11/20 (55%)
11/50 (22%)
21/50 (42%)
Females
Weeks in
study
90
90
91
91
Animals alive
at end of study
16/20 (80%)
16/20 (80%)
34/50 (68%)
1/50 (2%)
A gross necropsy was performed on each animal that died during the experi-
ment or was killed at the end. Twenty-eight organs in all, plus any tissues
containing visible lesions, were fixed in 10% buffered formalin, embedded in
paraplast, and sectioned at 5 u for slides. Hematoxylin and eosin stain were
used routinely, with other stains employed as necessary. Diagnoses of tumors
and other lesions were coded according to the Systematized Nomenclature of
Pathology (SNOP) of the College of American Pathologists.
The histopathologic findings of the study concerning hepatocellular
carcinomas in mice are tabulated in Table 9-41. Hepatocellular carcinomas
occurred in 2/17 (12%) untreated control males, 1/19 (5%) low-dose males, and
9-178
-------
50
Untreated Control
Vehicle-Control
Low-Dose
High-Dose
MALE MICE
T
T
15
T~
30
45 60 75
TIME ON TEST (Weeks)
50
-40
-30
-20
-10
90 105 120
50
I 40-
(0
O
»-
O 30^
UJ
0 20 H
o
CD
10-
Untreated Control
Vehicle-Control
Low-Dose
High-Dose
FEMALE MICE
I
15
50
-40
-30
-20
-10
30 45 60 75
TIM EON TEST (Weeks)
90
105 120
Figure 9-1O Growth curves for male and female B6C3F1 mice administered
1,2-dichloroethane (EDC) by gavage. (NCI 1978)
9-179
-------
00
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PROBABILITY OF SURVIVAL
PROBABILITY OF SURVIVAL
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-------
12/48 (25%) high-dose males. A significant number of hepatocellular carcinomas
were observed in high-dose males. The Cochran-Armitage Trend Test indicated
a positive dose-response association when the high-dose group was compared with
either the matched vehicle-controls (P = 0.025) or the pooled vehicle-controls
(P = 0.006). The Fisher Exact Test supported this finding with a significant
(P = 0.009) comparison of the high-dose to the pooled control group.
TABLE 9~H HEPATOCELLULAR CARCINOMAS IN B6C3F1 MICE TREATED
WITH 1,2-DICHLOROETHANE (EDC)
(adapted from NCI 1978)
Group
Untreated controls
Matched vehicle-
controls
Pooled vehicle-
controls
Low-dose
High-dose
Males P value3
2/17 (12%)
1/19 (5%)
4/59 (7%)
6/47 (13%) NS
12/48 (25%) 0.009
Females
0/19 (0%)
1/20 (5%)
0/50 (0%)
1/47 (2%)
P value3
NS
NS
3P values calculated using the Fisher Exact Test (one-tailed). Treated versus
pooled vehicle-control.
NS = not significant.
A large number of alveolar/bronchiolar adenomas were found in mice
treated with EDC (Table 9-42); 31% in both male (15/48) and female (15/48)
high-dose mice. These adenomas were not observed in untreated or vehicle-
control males. For both sexes the Cochran-Armitage Trend Test showed a sig-
nificant (P = 0.005) positive dose-response association when the dosed groups
were compared to either control group. The Fisher Exact Test also indicated
that the high-dose group for both sexes had significantly higher (P = 0.016)
9-181
-------
incidence rates than either of the two control groups. For female mice, the
Fisher Exact Test comparing the low-dose group to the pooled vehicle-control
group was also statistically significant (P = 0.046).
TABLE 9-42. ALVEOIAR/BRONCHIOLAR ADENOMAS IN B6C3F1 MICE TREATED
WITH 1,2-DICHLOROETHANE (EDC)
(adapted from NCI 1978)
Group
Untreated controls
Matched vehicle-
controls
Pooled vehicle-
controls
Low-dose
High-dose^
Males P value3
0/20
0/19
0/59
1/47
15/48
(0%)
(0%)
(3%)
(2%) NS
(31%) 0.0025
Females
1/19
1/20
2/60
7/50
15/48
(5%)
(5%)
(3%)
(14%)
(31%)
P value3
0.046
0.0201
aP values calculated using the Fisher Exact Test (one-tailed). Treated versus
pooled vehicle-control.
^In addition, one high-dose female mouse had an alveolar/bronchiolar carcinoma.
NS = not significant.
Squamous cell carcinomas of the forestomach occurred in 1/19 (5%) vehicle-
control males, 1/46 (2%) low-dose females, and 5/48 (10%) high-dose females
(Table 9-43 ). For female mice, the Cochran-Armitage Trend Test indicated a
significant (P = 0.035) positive association between dosage and the incidence
of squamous cell carcinomas of the forestomach when comparing the dosed groups
to the pooled vehicle-controls. The Fisher Exact Test, however, was not
significant. The microscopic appearance of the stomach of mice was comparable
to that described for rats.
9-182
-------
TABLE 9-43 . SQUAMOUS CELL CARCINOMAS OF THE FORESTOMACH
IN B6C3F1 MICE TREATED WITH 1,2-DICHLOROETHANE (EDC)
(adapted from NCI 1978)
Group
Untreated control
Matche i vehicle-
contr )l
Pooled vehicle-
contr )1
Low-do ;e
High-d >se
Males P value3
0/20 (0%)
1/19 (5%)
1/59 (2%)
1/46 (2%) NS
2/50 (4%) NS
Females P value3
0/20 (0%)
1/20 (5%)
1/60 (2%)
2/50 (4%) NS
5/48 (10%) NS
aP values calculated using the Fisher Exact Test (one-tailed). Treated versus
vehic Le-control.
NS = not significant.
The incidence of adenocarcinomas of the mammary gland in female mice
treate< with EDC is presented in Table 9-44 . The Cochran-Armitage Trend
Test indicated a significant (P = 0.007) positive association between dosage
and th< incidence of adenocarcinomas of the mammary gland when compared to the
pooled controls. The Fisher Exact Test confirmed these results with a
significant (P _<_ 0.003) comparison of both high-dose (7/48) and low-dose
(9/50) groups to the pooled vehicle-control groups (0/60).
Er.dometrial tumors observed in female mice are described in Table 9-45 .
The Cochran-Armitage Trend Test indicated a significant (P = 0.017) positive
association between dosage and combined incidence. The Fisher Exact Test
showed a statistically significant (P = 0.014) incidence in the high-dose
(5/47) group.
9-183
-------
TABLE 9-44. ADENOCARC1NOMAS OF THE MAMMARY GLAND IN FEMALE B6CJF1
MICE TREATED WITH ],2-DICHLOROETHANE (EDC)
(adapted from NCI 1978)
Group
Adenocarcinoma of
the mammary gland
P value3
Pooled vehicle-control
Matched vehicle-control
Low-dose
High-dose
0/60 (0%)
0/20 (0%)
9/50 (18%)
7/48 (15%)
0.0005
0.0026
aP values calculated using the Fisher Exact Test (one-tailed). Treated versus
pooled vehicle-control.
TABLE 9-45 . ENDOMETRIAL POLYP OR ENDOMETRIAL STROMAL SARCOMAS IN
FEMALE B6C3F1 MICE TREATED WITH 1,2-DICHLOROETHANE (EDC)
(adapted from NCI 1978)
Group
Endometrial polyp or
endometrial stromal sarcomas
P value3
Pooled vehicle-control
Matched vehicle—control
Low-dose
High-dose
0/60 (0.0%)
0/20 (0.0%)
5/49 (10.0%)
5/47 (11.0%)
0.016
0.014
aP values calculated using the Fisher Exact Test (one-tailed). Treated versus
pooled vehicle-control.
In summary, the NCI study in B6C3F1 mice demonstrated a statistically
significant increase in incidences of hepatocellular carcinomas and alveolar/
bronchiolar adenomas in male mice and a statistically significant increase in
incidences of alveolar/bronchiolar adenomas, mammary carcinomas, and endometrial
tumors in female mice.
9-184
-------
9.5.1.3 Spencer et al. (1951) Rat Study—An early inhalation study conducted
by Spencer et al. (1951) found no evidence of carcinogenic activity when 15
male and 15 female Wistar rats were exposed 151 times during a 212-day period
to EDC at 200 ppm for 7 hours per exposure.
9.5.1.A Maltoni et al. (1980) Rat Study—A more recent inhalation study con-
ducted by Maltoni et al. (1980) in Sprague-Dawley rats provided no evidence of
carcinogenicity after lifetime exposure to EDC. The EDC used in this study was
supplied by Montedison, and had a purity of 99.82%, with five contaminants
(Table 9-46 ). The design of the experiment is given in Table 9-47 .
TABLE 9-46 . CHARACTERIZATION OF 1,2-DICHLOROETHANE (EDC) INHALATION
EXPERIMENT IN SPRAGUE-DAWLEY RATS
(Maltoni et al. 1980)
Component
Purity
1,2-Dichloroethane
1,1-Dichloroethane
Carbon tetrachloride
Trichloroethylene
Perchloroethylene
Benzene
99.82%
0.02%
0.02%
0.02%
0.03%
0.09%
9-185
-------
TABLE 9-47 . DESIGN SUMMARY FOR 1,2-DICHLORUETHANE (EDC)
EXPERIMENT IN SPRAGUE-DAWLEY RATS3
(Maltoni et al. 1980)
Group
I
II
III
IV
V
VI
Concentration Sex
250-150 ppmc M
F
50 ppm M
F
10 ppm M
F
5 ppm M
F
Controls in chambers M
F
Controls M
F
Animals**
Number
90
90
90
90
90
90
90
90
90
90
90
90
aExposed 7 hours/day, 5 days/week, for 78 weeks.
bSprague-Dawley rats, 12 weeks old at start.
cAfter a few weeks the dose was reduced to 150 ppm, because of high toxicity
at the 250 ppm level.
Maltoni et al. exposed four groups of 12-week-old Sprague-Dawley rats
(each group consisting of 180 rats of both sexes) to EDC concentrations of 250-
150 ppm, 50 ppm, 10 ppm, and 5 ppm, respectively, 7 hours per day, 5 days per
week, for 78 weeks. After several days of 250 ppm exposure, the rats began to
exhibit severe toxic effects, and the concentration was reduced to 150 ppm. Two
groups, composed of 180 rats per group, served as controls. One of the two
control groups was kept in an exposure chamber under the same conditions and for
the same length of time as the exposed rats. At the end of the treatment
period, the animals were allowed to live until spontaneous death. Animals
were weighed every 2 weeks during the treatment period and every 8 weeks there-
9-186
-------
after. All detectable gross pathologic changes were recorded. A complete
autopsy was performed on each animal, with histopathologic examinations conducted
on the following: brain, Zymbal glands, retrobulbar glands, interscapular
brown fat, salivary gland, tongue, lungs, thymus, diaphragm, liver, pancreas,
kidneys, spleen, stomach, various segments of the intestine, bladder, gonads,
lymph nodes (axillary, inguinal, and mesenteric), and any other organ with
pathologic lesions.
The extent of mentality varied with the different groups, but there
appears to be no direct relationship between mortality and exosure to EDC
(Table 9-48 ). The highest survival rate was observed in both males and
females of the group exposed to EDC at 5 ppm. In females the highest mortality
rate was observed in the control group in the chamber and in the group ex-
posed to EDC at 250-150 ppm. The survival rates at 52 and 104 weeks of age
are reported in Table 9-48 . At these ages the overall survival rates were
93.9% and 27.3%, respectively. The survival rates after 52 weeks from the
start of the experiment are also given in Table 9-48 • The overall sur-
vival rate was 83.7%.
The results of histopathologic analysis are shown in Table 9-49 • No
statistically significant increase in the incidence of any specific type of
tumor was found in the treated rats when compared with controls. There was,
however, an increased incidence of mammary tumors in some rats in Group IV,
particularly when compared with the control group in the chamber (Table 9-50 )•
It appears that the increase in mammary tumors in some of the treated
groups, particularly when compared to controls in the chamber, was not due to
malignant tumors, but to fibromas and fibroadenomas. The increased incidence of
mammary fibromas and fibroadenomas is statistically significant in groups ex-
posed to EDC at 250-150 ppm, 50 ppm, and 5 ppm, when compared to controls in the
9-187
-------
TABLE 9-48 . SURVIVAL OF SPRAGUE-DAWLEY RATS EXPOSED TO EDC AT 52 AND 104 WEEKS3
(Maltoni et al. 1980)
Dose
Group (ppm)
I 250-15Qb
£ II 50
00
III 10
IV 5
V Controls
in chambers
VI Controls
Sex
M
F
M
F
M
F
M
F
M
F
M
F
Initial
numbe rs
90
90
90
90
90
90
90
90
90
90
90
90
Survivors at
52 weeks of age
Number
79
84
87
87
81
87
89
90
80
79
83
88
Percent
87.8
93.3
96.7
96.7
90.0
96.7
98.9
100.0
88.9
87.8
92.2
97.8
Survivors at
104 weeks of age
Number
10
21
17
29
13
26
45
48
12
22
16
36
Percent
11.1
23.3
18.9
32.2
14.4
28.9
50.0
53.3
13.3
24.4
17.8
40.0
Survivors
52 weeks
start of
Numbe r
67
79
70
84
70
81
75
85
64
73
72
84
after
from
study
Percent
74.4
87.8
77.8
93.3
77.8
90.0
83.3
94.4
71.1
81.1
80.0
93.3
aRats were 12 weeks old at the start of the experiment.
''After a few weeks the dose was reduced to 150 ppm because of high toxicity at the 250 ppm level.
-------
TAHLK 9-49 TUMOR INClliKNCK HI M'RACUF-IIAWI KY RATS KKPOSKI) TO K.DC
(M.iltnnl ct al. IIHII)
An lm,i Is wi tli
M.imtn.ir v Lumoi s
Animals3
Croup <>incp"t rnt i on Sex
I -J50- 1 "7(1 ppjnr M
F
M ,-inrl F
I t 50 ppm M
P
1 M and F
5§ '11 10 ppm M
F
M and F
IV 5 ppm H
F
M and F
V Controls In M
chambers F
M and F
VI Controls M
F
M and F
Total
Number
at start
90
90
180
90
90
180
90
90
180
90
90
180
90
90
180
90
90
180
1080
Correct ed
numbe r
89
90
179
90
90
180
89
90
179
90
90
180
90
90
180
90
90
180
1070
Total
numbe r
1 1
52
63
10
58
68
5
43
48
11
65
76
8
38
46
5
52
57
Percent1'
12. 1
57.7
35.2
1 I.I
64.4
37.8
5.6
47.8
26.8
12.2
72.2
42.2
8.9
Iti.l
25.5
5.5
57.8
31.7
Average
1 at encv
lime
(wkK
92.9
78.6
81 .1
HH.S
78.5
80. o
60.8
79.4
77.5
110.2
83.2
87.1
85.5
83. 1
83.6
92.0
85.5
86.1
Total
number
0
2
2
0
1
1
0
0
0
0
2
2
1
0
1
1
0
1
/.vmbal
Pe rcent b
„_
2.2
I.I
1 .1
0.6
—
—
-__
2.2
1.1
1.1
0.6
I.I
0.6
gland carcinoms
A ve r a Re
latency
t i me
(uk)d
_-_
78.0
78.0
86.0
86.0
—
.__
47.D
47.0
78.0
78.0
74.0
74.0
Tot a 1
numbe r
0
0
0
1
2
1
4
0
4
2
6
8
1
3
4
0
3
3
r urior s
LCI
Percent"
...
—
1. 1
2.2
1.7
4.6
2.2
2.2
6.7
4.4
1.1
1. )
2.2
3.3
1.7
ikemi as
A ve r a p,c
la tency
t Ime
(wk)''
...
— -
HI! .0
7-1.5
76.3
74. o
74.0
133.5
83.5
90.0
17.0
64.3
59.5
79.1
79.1
Nephroblns tomap
Average
la t encv
Total time
number Percent" (wV)^
D
II
„
I,
O
II
II
(1
II
1 I.I 8'..n
(1
1 0.7 84.0
I,
D
0
0
(1 — —
,1
1
(coitt t miptt on the f o I I nwt IK;
-------
TABLE
9-49.
(Continued)
Animals with tumors
Angiosar comas
Group Concentration Sex
I 250-150 ppmf M
F
M and
v£> I I 50 ppm M
1 F
H1 ,
vo M a nd
O
HI 10 ppm M
F
M and
IV 5 ppm M
F
M and
V Controls In M
chambers F
M and
VI Controls M
F
M and
Liver
Average
1 a tency
Total time
number Percent*1 (wk)d
0 —
0
F 0
l\
0 — -
F 0
0 '
0
F 0
i\ __
0
F 0
0
0
F 0
„
0
F 0
Other Sites
Average
latency
Total time
number Percent*1 (wk)d
0
0
0
0
0 —
0
0
0
0 — — — — — —
0
0
0
0
0
0
0
0
0
Angiomas and f ibroangl omas
Liver
Ave rage
latency
Total time
number Percent*1 (wk)^
0
0
0
o — —
0
0
0
o — —
0
0
0
o — —
o — —
o — —
0
o — —
0
o — —
Total
numbe r
0
0
0
0
0
0
0
0
0
1
1
i
0
0
0
1
0
1
Other sites
Average
latency
t imp
Percent*1 (wk )d
—
1.1 125. f»
1.1 1)1. 0
l.l J2K.O
_-_
1.1 130.0
0.7 1)0.0
-------
UHl.h 9-49. (cout Inucd)
Animals with tumors
Group Con < f*n t rat ion Sex
I 25H-I50 ppm1" M
F
M and F
I I 5li ppm M
F
M and F
111 10 ppm M
F
M and F
IV 5 ppm M
F
H and F
V Controls in M
chambers F
M and F
VI Controls M
F
M and F
Hc'patomas
Average
latency
Total t line
number Percent*" (wk)<*
0
n — —
0
(i — —
0
0
0 — —
0
0
rj — —
0 —
0
„
0
0 -—
0
0
n — —
Korestomach epithelial
Total
number
II
II
II
1
0
1
0
1
1
1
0
1
2
1
3
2
1
3
Percent0
1 . 1
0.6
1.1
0.6
1.1
0.6
1. 1
1.1
1.7
2.2
1.1
1.7
Average
latency
t Imc
60.0
60.0
78.0
78.0
101.0
101.0
78.5
6).o
73.3
110.0
102. U
107.3
Skin carcinomas
Aver.-iRe
la tencv
Tot a 1 1 1 me
number Percent0 (wk)^
0
O
0
1 1.1 56.0
()
1 0.6 56.0
I 1.1 94.0
(1
1 0.6 94.0
0
0
I) — —
0
0
II
II
0
I) — —
Total
number Percent0
0
(1
0
(i
0
II
0
0
o —
1 1.1
0
1 (1.6
0
1 1.1
1 II. n
0
0
0
A ver.i^e
litpnrv
1 Imc
—
—
io.o
30.0
—
78. 0
7H.O
i
-------
TAB1F. 9-49- Out Inued)
Animals with tumors
tiroup
I
I 1
II 1
IV
V
VI
Exposure
Results
Concent rat Ion
250-150 ppme
M
50 ppm
H
10 ppm
H
5 ppm
M
Controls in
chninbe rs
H
Controls
M
by inhalation to F.DC
after 148 wk (end of
^The percentages refer to the
^ ra'!e
""Af t PT a
Sex
M
F
and F
M
F
and F
M
F
and F
M
F
and F
M
F
and F
M
F
and F
Nen rob las to
Total
number Percent0
0
0
II
0
0
0
0
0
0
II —
0
0
[1
II
II —
0
0
u —
in air at 250-150, 50 ppm,
expert me n t ).
correct ed
few werks the dose was reduced
numbe rs .
airy p
to 1 5O ppn, be c i u
I nccpha I 1 c tumors
mas Other
Average
la t encv
time Total
(wk )(' number
0
0
0
1
1
2
0
2
T
0
0
0
— 1
1
2
0
3
i
10 ppn, and 5 ppm, / hr/
se of the high toxicltv
sites
Peri en t ^
I.I
I.I
I.I
l.l
2.2
. . i
1 .1
1 . 1
3.3
1.7
day, 5 day
others
Total
numbe r
9
1 1
20
14
b
20
4
4
8
Ib
9
25
8
4
12
7
8
n
s wk, for 78 wk.
Ben l^n
numbe r
7
5
12
14
3
17
2
3
5
15
5
20
7
2
9
7
5
12
Ma 1 1 pnant
uumbe r
2
ft
8
0
3
3
2
1
3
1
4
5
1
2
5
0
)
3
Number
15
54
f.9
20
5b
76
1 )
43
5b
30
h5
95
17
38
55
14
5b
70
Total -f
Number nf
dl f f'.rent
t urn-i r=: •' t iimr. r-
IVrrent ho.irinq l"ln,il'
1 h . 9 1 . _>
h 1 1 . O 2 . ' '
)8.5 1.?
22.2 1 . »-
b2.2 1.7
42.2 1 . '
14. b 1 .1
47.R 1...
H . 3 1.5
33.3 1.4
72.2 I.1-
52.8 1 . "
18.9 1 . 1
'i>.: i . u
30. h 1."
1 5 . b I.I
b2.: i .
<«.9 1.1,
at the 250 ppm level.
-------
TABLE
9-50
MAMMARY TUMORS IN SPRAGUE-DAWLEY RATS
EXPOSED TO EDC
(Maltoni et al. 1980)
vO
OJ
Animals
Group Concentration Sex
I 250-150 ppmd M
F
M and F
II 50 ppm M
F
M and F
III 10 ppm M
F
M and F
IV 5 ppm M
F
M and F
V Controls in M
chambe rs F
M and F
VI Controls M
F
M and F
Total
Number
at start
90
90
180
90
90
180
90
90
180
90
90
180
90
90
180
90
90
180
1080
Corrected
number3
89
90
179
90
90
180
89
90
179
90
90
180
90
90
180
90
90
180
1078
Total
numbe r
11
52
63
10
58
68
5
43
48
11
65
76
8
38
46'
5
52
57
Mammary
Percent15
12.3
57.7
35.2
11.1
64.4
37.8
5.6
47.8
26.8
12.2
72.2
42.2
8.9
42.2
25.5
5.5
57.8
31.7
tumors
Average
latency
time
92.9
78.6
81.1
88.8
78.5
80.0
60.8
79.4
77.5
110.2
83.2
87.1
85.5
83.3
83.6
92.0
85.5
86.1
Number of
tumors/tumor-
bearing animals
1
1.1
1.9
1.7
1.4
1.5
1.5
1.0
1.4
1.4
1.4
1.6
1.5
1.0
1.8
1.6
1.0
1.5
1.5
. — i
(continued on the following page)
-------
TABLE 9-50 (l-onttnuod)
Mammary tumorse
HlsLolotjlcal evaluation
Mammary tumors
Group Concentration Sex
I 250-150 ppm 4.1 7 i . 0
2 3.7 M.I)
^Fhc percent n^cs ref e r to the corrected mmbe rs.
cAverage age at the onset of first mamma ry tumor per aninwl, dctpctfd at the periodic control or at autopsv.
^After a Few weeks the dose was reduced to 150 ppm, because of the hiRh toxirlty at the tunv> r <; nf MIP same or different tvpes (flbro.ldr nnrn;i ^ , r a rri nnm \ ^ , >>a rr oms , c.i rri nos ;i rcoTiai ) nnv
be present in the same animal.
* The pe rcentaj^e^ rt'f •=> r t n tor al numbe r of
-------
chamber, but not significant when compared to controls outside of the chamber.
Although the author stated that the onset of fibromas and fibroadenomas was
age-correlated, the incidences of these tumors observed in the various groups
were probably due instead to the differences in survival rates within the
groups. The highest difference in incidence was found between the control
groups in the chamber, which had low survival rates, and the groups treated
with EDC at 5 ppm, which had high survival rates. The difference in survival
rates is thus seen to be related to the differences in incidence in the two
control groups.
9.5.1.5 Maltoni et al. (1980) Mouse Study—Four groups of Swiss mice (180 mice
of both sexes per group) were exposed to EDC, at the level of purity previously
described for the rat inhalation study, in concentrations of 250-150 ppm, 50
ppm, 10 ppm, and 5 ppm, respectively, 7 hours per day, 5 days per week, for 78
weeks. After several days of 250 ppm exposure, the mice began to exhibit
severe toxic effects, and the concentration was reduced to 150 ppm. One group
of 249 mice served as controls. The design of the experiment is given in
Table 9-51.
At the end of the treatment period, the animals were allowed to live until
spontaneous death. The remainder of the procedure was the same as that described
previously for the Maltoni et al. (1980) rat study.
The survival rates for female mice were slightly lower in the group treated
with EDC at 250-150 ppm. The survival rates for mice at 52 and 78 weeks of age
are shown in Table 9-52 . At 52 and 78 weeks, the overall survival rates were
82.4% and 45.9%, respectively. The survival rates after 52 weeks from the start
of the experiment are also given in Table 9-52 . The overall survival rate was
67.8%.
9-195
-------
TABLE 9-51. DESIGN SUMMARY FOR 1,2-DICHLOROETHANE (EDC)
EXPERIMENT IN SWISS MICEa
(Maltoni et al. 1980)
Animals"
Group Concentration Sex
I 250-150 ppmc M
F
II 50 ppm M
F
III 10 ppm M
F
IV 5 ppm M
F
V Control M
F
Numbe r
90
90
90
90
90
90
90
90
115
134
aExposed 7 hours/day, 5 days/week, for 78 weeks.
bSwiss mice, 11 weeks old at start.
cAfter a few weeks the dose was reduced to 150 ppm, because of high
toxicity at the 250 ppm level.
The results of histopathologic analysis of various tumors are shown in
Table 9-53 . These results do not indicate a statiscally significant increase
in the incidence of any specific type of tumor in the treated mice as compared
with controls.
In conclusion, although Maltoni et al. conducted extensive carcinogenicity
studies in rats and mice, no significant incidences of tumors were seen in any
of the target organs. Several factors may have contributed to these findings,
such as differences in the strains of rats used, and dose levels that appear
to have been less than maximally tolerated doses.
9-196
-------
TABLE 9-52 . SURVIVAL OF SWISS MICE EXPOSED TO EDC AT 52 and 78 WEEKS3
(Maltoni et al. 1980)
Survivors at
Dose
Group (ppm) Sex
I 250-150 ppmb M
F
II 50 M
F
III 10 M
F
IV 5 M
F
V Control M
F
Initial
numbers
90
90
90
90
90
90
90
90
115
134
52
of
Number
56
75
68
83
74
86
54
84
91
127
weeks
age
Percent
62.2
83.3
75.6
92.2
82.2
95.6
60.0
93.3
79.1
94.8
Survivors at
78
of
Number
26
44
30
49
34
50
26
68
42
76
weeks
age
Percent
28.9
48.9
33.3
54.4
37.8
55.6
28.9
75.6
36.6
56.8
Survivors
52 weeks
start of
after
from
study
Number Percent
39
58
46
73
59
72
42
84
72
112
43.3
64.4
51.1
81.1
65.6
80.0
46.7
93.3
62.6
83.6
were 11 weeks old at the start of the experiment.
^After a few weeks the dose was reduced to 150 ppm, because of high toxicity at the 250 ppm level.
-------
| |UUJ )
646
4V4 4'x 17 b'Vt (M X
t ' 14 (Ml 51 7/15 O'l 1
W54 ','5 4 5'Bi 4'1 •?
iv< re n x'4z 7't i
X ' (> 4 / ' 4 4 0 ' i B 5 ' V '/
ll'hl 6V 7 U'V1? V'l 1
r'\t 7'4 1 1 0'iZ I'l t
4'64 ^'5 5 5'1 5 1 V Z
5''/5 ft 4 r^B 4'» i?
•J-S4 /•«, 1)1 U'',/ 6V <,
7'6(, 4-t; i; ^'t// fV 7
h'64 6'4 4 f'W Vf {
0'64 i"t ? Z'iH H'l I
li'O ri 1 ^'tW 9'C (
ll'i/ Z' 1 1 0
Ijl1)") 31U->TJ"H 4rf>|UIIU p(1") j3U.I.O-lu,| JjqUJPIU
r»ui|) lt3"J. .MU |i-'l"l
A-'U J 1 1' [ A JU<1 j I/ |
dJt'JHA\' t)HtJ.)AV
•.t )uja^l)R'| bt?UUUK1|>l' A 1 L'UIHU | l)t|
SJOUI1) LHlrt <'IU(UV
3 dnoj;)
QO
i
(OHM 'I1' )•' l»"l|iw)
O.L (HM)dX.H H:)1H S.SlttS Nl IIN'*II.JW1
t"C— A
-------
fABLF. 9-53 (continued)
Animals with tumors
Anglosarcomas
Croup Concentration Sex
1 2r)0-lSU ppm1" H
F
M and F
v-° II 50 ppm H
.1 F
VO M and F
III 10 ppm M
F
M and F
IV 5 ppm M
F
M and F
V Controls In M
rhnmbers F
H and F
VI Controls M
F
H and F
Nephroblastomas
Ave rage
latency
Total time
number Percent0 (wk)"1
II
0
0
0
0
0
0 —
o
(I — —
(1 — —
0 —
1) — —
0 —
0
0
0
0
0
Kidney adenocarclnomas
Average
latency
Total time
number Percent0 (wk)^
0
0
0
(1 — —
(1 — —
,)
o
0
0 —
0
1 1.1 «.2.U
1 0.6 62.0
0
n — -_.
0
I)
(1 — —
I)
Liver
Ave r.ige
latency
Total time
number Percent0 (uk)1'
0
0
0
(1 — —
1) —
0
0
u — —
„
0
0
0
0
U
(1 — —
0
{1
1) — —
Total
number
1
- 0
1
0
CP
0
0
I)
(1
o
0
0
0
u
0
1
0
1
Other sites
Aver, --Re
latencv
t imp
Pert/put c (wk )
1.2 -io.ii
O.h 4(1. u
—
125. o
131.0
UH.ll
(1.9 '^.0
0.4 M.O
(continued on the fnllnuliiK
-------
TABI.K 9-53 (r/HitlniM-il)
vO
to
0
O
Group Concentration Sex
1 2V.-I5" ppm" M
F
M and F
1 1 VI ppm H
F
M and F
lit HI ppm M
F
M and F
IV 5 ppm M
F
M and K
V Omtrolq In M
chamber* F
M a fid F
Angfoma'
Liver
Average
latent y
Tot a 1 1 1 me
mimher Percent c (wk )^
II
n
n — —
ti — —
1 1.1 81.0
1 <>.ft fll.ll
n — —
n — —
o — —
i) — —
0 — —
it — —
II 11.9 Ii9.ll
II
I) O.'i h4.ll
; and f Ihronngiomas
Other iltei
Aver.tge
1 a I enc v
Tot a I 1 1 me
number Percent1" (wk)<*
1,
II
II
1 I.I 7h.ll
1 I.I 83.11
2 I.I 79. "i
II --- 9t.(l
1 I.I 91.11
1 II. h
H
(1
11
1 n.9 76.11
11
1 11.4 7h.H
Hepiit omai
Ave rage
latency
Total time
number Percentr (wk)1*
11
O
(I
()
M
o
0
(1 — —
0
M.
1) — —
0
4 !.•> R2.ll
O
4 l.h H2.ll
Knre* t ornach epithelial
tumors
Avenue
1 .1 lenc v
Total ( Ine
number Pnrrentr (wV I'1
(I
II
()
II
II
(1
II
|l
(1
II
1)
II
II
II
II
(r.mt i.i.u-.l on t lie rnllowlnr p
-------
TMMK 9-53
Anlmils wtth Lunvirs
Uronp (>>ncent rat Ion Sex
I J5H-I5II ppm* H
F
'1 an.l
M ''ii ppm M
vO f
1 M and
rJ
3 HI 1" Prra M
F
M ami
l
IV 'i ppn M
F
M and
V Controls In M
rlnmbprs F
H and
Exposure by Inhalation to KUC In
Results niter 119 weeks (end of
"Animals alive after 24 wkf when
"Average time from the start of
eAfter a few weeks the dose was
Skin
Total
number
1)
(1
F ('
I)
1
F 1
(1
0
F (I
II
1
F 1
1
1
F 2
air at 2511-
experlment )
t lie first t
the t'xperlme
reduced to 1
epithelial tumors Subcutaneous saicotnas
Averapp Average
lat en< v latent v
t l"ip Total t Imp
Percent0 (wk )"* number I'erci-iii'" (wk)"1
l,
— o —
o
1,
I.I IIK.II o — —
o.n lui.n (i — —
1 I.I 77. II
1 I.I 25.11
2 I.I SI. il
— 0
1.1 7'>.tl I)
O.b 79.11 II
'1.9 lOt.tl 1 !).<> IDh.ll
11.7 77.O II
I'.K 91.11 U (1.4 IDh.d
1511 ppm, 5(1 ppm, 10 ppm, ami ^ ppm, 7 hr/tl.iv, 5 davs/wk,
nmor (a lenkemli) was observed.
nt to netettlon .it the period)' (ontrol or at .nitopsy.
V pfm, he'-.iiisr of hlRh toxi> Itv .'t the .|r»o ppm level.
Total
nninbe r
II
2
2
1
It
s
1
2
1
1
6
5
1
4
lor 7H
Others
Be 11 it'll
number
H
2
2
II
(
1
1
1
2
;l
)
1
1
2
t-k.
Malignant
nnmhe r
II
(1
(1
1
1
2
(1
1
1
1
1
2
y
2
2
Nnmbe r
2
U
1 1
9
15
2
-------
9.5.1.6 Theiss et al. (1977) Mouse Study—Theiss et al. (1977) conducted a
pulmonary tumor bioassay with EDC and other organic contaminants of drinking
water in the United States. The compounds were injected intraperitoneally into
6- to 8-week-old mice of the A/st strain. Each dose of reagent-grade EDC, with
tricaprylin as the vehicle, was injected into mice in groups of 20, three times
a week, for a total of 24 injections per mouse. Dose levels of 20, 40, and 100
mg/kg (the maximum tolerated dose) were used.
The mice were sacrificed 24 weeks after the first injection, and their
lungs were placed in Tellyesniczky's fluid. After 48 hours, the lungs were
examined microscopically for surface adenomas, and the frequency of lung tumors
in each group was compared with that in a vehicle-treated control group by
means of the Student's t Test. The incidence of lung tumors increased with
dose, but none of the groups had pulmonary adenoma responses that were
significantly greater (P > 0.05) than that of the vehicle-treated control mice
(Table 9-54 ). Because they found a non-significant elevation in pulmonary
tumor response, the authors suggested further investigation of the carcinogenic
potential of EDC.
TABLE 9-54. PULMONARY TUMOR RESPONSE IN STRAIN A/st MICE INJECTED WITH EDC
(Theiss et al. 1977)
Dose/injection Number of
(mg/kg) injections
Oa 24
20 24
40 24
100 24
Fraction
surviving
46/50
14/20
16/20
20/20
(92%)
(70%)
(80%)
(100%)
Number of
tumors/mouse
0.39 _+ 0.06
0.21 +_ 0.06
0.44 +_ 0.11
0.75 + 0.17
aTricaprylin vehicle
9-202
-------
9.5.1.7 Van Duuren et al. (1979) Mouse Study—Van Duuren et al. (1979) con-
ducted a bioassay of EDC and of a suspected metabolite, chloracetaldehyde, as
initiators, promoters, and complete carcinogens using two-stage skin tests.
Female non-inbred ICR/Ha Swiss mice were used, with treatment beginning at 6-8
weeks of age. The experimental group consisted of 30 animals, exclusive of the
no-treatment groups or those receiving repeated application of phorbol myristate
acetate (PMA). The results of this study are given in Table 9-55 . The com-
pounds, in 0.1 ml and 0.2 ml acetone, were applied three times a week to the
dorsal skin. Skin lesions were diagnosed as papillomas when they reached
approximately 1 mm and persisted for 30 days or more.
All animals were examined daily and weighed monthly; findings were recorded
monthly. Animals in poor health or with large tumor masses were killed. Ani-
mals were completely autopsied at the termination of the experiment or at death.
Tissue sections were fixed in 10% formalin, processed, blocked in paraffin, and
stained with hematoxylin and eosin for pathologic diagnosis. The results indi-
cate that neither EDC nor chloroacetaldehyde induced a statistically significant
increase in the incidence of carcinomas of the skin. This result was probably
due to the low dose levels used in the study. EDC was found to induce a statis-
tically significant increase in the incidence of benign lung papillomas.
In summary, the NCI study (1978), as well as the studies by Theiss et al.
(1977) and Van Duuren et al. (1979), show that, under appropriate conditions,
EDC can increase the incidence of tumors. The data obtained in mutagenicity
studies have also shown that, under appropriate experimental conditions, EDC
can cause DMA damage (Storer et al. 1982) and mutations (Guengerich et al.
1980). In contrast, the lifetime inhalation study conducted by Maltoni et al.
(1980) showed no increased incidence of tumors.
9-203
-------
TABLE 9-55, MOUSE SKIN BIOASSAY OF 1 ,2-OICIILOROKTHANE ANU CHLOROACETAI.DEHYDE
(adapted from Van Duuren el al. 1979)
Initial ton-promot iona
Dose Days lo
mg/appllcat Ion/ first
Compound mouse tumor
1,2-IHchloroethane 12b.O 337
Chloroac.'taldehvde 1.0 152
1
O PMA controls
*• (120 mice) 0.0025 141
(90 mice ) 0.0050 449
Acetone (0.1 ml)
No treatment
(100 mice)
Repeated application15
Mice with Dose Days to Mice with No. of mice
paplllomas0/ mg/appll ca t ion/ first papillomasC/ with distant
total paplllomas mouse tumor total paplllomas tumors"
J/3 12h.O 0 2(i lung
P<0.0005
3 stomach
42.0 0 17 lung
1 stomach
3/J (1 ) 1.0 0 14 luii);
1 stomach
9/10 (1)
6/7 (2)
0.1 ml 0 1 1 lung
2 s tomach
0 30 lung
5 stomach
aAll applications were to the dorsal skin by mlcroplpette. 1 ,2-dl chlorocthane was administered once only in 0.2
ml acetone, followed 14 days later by 5 ug of PMA In O.2 ml acetone three times weekly. Chloroaceta1dehyde
was administered once only in O.I ml acetone, followed 14 days later by 2.5 up, of PMA in 0.1 ml acetone three
times weekly.
" I , 2-d 1 rh 1 o roe t hane was administered In 0.2 ml arrlone. Ch loroace t al dehyde was administered lliroe t imns weekly
in O.I ml acetone. (
cNnmbe r of mice with srjnamous cell carcinomas arc given in a parentheses.
dA! I lung tumors are benign paplllomas; stomach tumors are paplllomas of the forestomach and squamou--- cell ca I—
clnomas of the forestomach. P values are given only where significant, i.e., P < (1.05.
-------
The apparent discrepancies between inhalation and other routes of exposure
in the oncogenicity studies have led to considerable discussion of the conduct
and results of these studies (Maltoni et al. 1980, Hooper et al. 1980, Reitz
et al. 1982). The NCI Clearing House Committee review of the NCI bioassay
report (1978) acknowledged several design features which may have adversely
affected the outcome of the experiment. For example, the studies were con-
ducted in rooms housing animals dosed with other volatile carcinogens. It was
concluded, however, that these shortcomings were not significant enough to
invalidate the findings. Other investigators (Hooper et al. 1980) have con-
cluded that unless unusual and unexpected synergisms occurred, the presence of
other animals in the test rooms would not have affected the results.
Reitz et al. (1982) proposed that basic metabolism rate differences,
specifically the saturation of the detoxification/excretion mechanism, occurred
between the single gavage dose (and presumably other routes) and the longer-
term inhalation dose. Their calculations suggest that EDC is metabolized by
non-linear kinetics, and that the inhalation study did not produce peak blood
levels sufficiently high to overcome the detoxification mechanism and produce
a detectable incidence of tumors.
Regardless of the explanations for the observed differences (Hooper et
al. 1980, Reitz et al. 1982), the data show both an ability of EDC to produce
neoplasms and an inhalation level at which no tumors are formed. Thus, the
results indicate the EDC is carcinogenic in rats and mice, and is a weak
mutagen.
9.5.2 Epidemiologic Studies
No epidemiologic studies have been published regarding the carcino-
genicity of EDC.
9-205
-------
9.5.3 Quantitative Estimates
This quantitative section deals with estimation of the unit risk for EUC
as a potential carcinogen in air and water, and with the potency of EDC rela-
tive to other carcinogens that have been evaluated by the CAG. The unit risk
for an air or water pollutant is defined as the lifetime risk of cancer to
humans from daily exposure to a concentration of 1 ug/nH of the pollutant in
air by inhalation, or to a concentration of 1 ug/L in water by ingestion.
The unit risk estimate for EDC represents an extrapolation below the dose
range of experimental data. There is currently no solid scientific basis for
any mathematical extrapolation model that relates exposure to cancer risk at
the extremely low concentrations, including the unit concentration given
above, that must be dealt with in evaluating environmental hazards. For practi-
cal reasons the correspondingly low levels of risk cannot be measured directly
either by animal experiments or by epidemiologic studies. Low-dose extrapola-
tion must, therefore, be based on current understanding of the mechanisms of
carcinogenesis. At the present time the dominant view of the carcinogenic
process involves the concept that most cancer-causing agents also cause irre-
versible damage to DNA. This position is based in part on the fact that a
very large proportion of agents that cause cancer are also mutagenic. There
is reason to expect that the quantal response that is characteristic of muta-
enesis is associated with a linear (at low doses) non-threshold dose-response
relationship. Indeed, there is substantial evidence from mutagenicity studies
with both ionizing radiation and a wide variety of chemicals that this type of
dose-response model is the appropriate one to use. This is particularly true at
the lower end of the dose-response curve; at higher doses, there can be an
upward curvature, probably reflecting the effects of multistage processes on
the mutagenic response. The linear non-threshold dose-response relationship
9-206
-------
is also consistent with the relatively few epidemiologic studies of cancer
responses to specific agents that contain enough information to make the eval-
uation possible (e.g., radiation-induced leukemia, breast and thyroid cancer,
skin cancer induced by arsenic in drinking water, liver cancer induced by
aflatoxins in the diet). Some supporting evidence also exists from animal
experiments (e.g., the initiation stage of the two-stage carcinogenesis model
in rat liver and mouse skin). Linearity is also supported when the mode of
action of the carcinogen in question is similar to that of the background can-
cer production in the exposed population.
Because its scientific basis, although limited, is the best of any of the
current mathematical extrapolation models, the non-threshold model, which is
linear at low doses, has been adopted as the primary basis for risk extrapo-
lation to low levels of the dose-response relationship. Any risk estimates
made with such a model should be regarded as conservative, representing the
plausible upper limit for the risk; i.e., the true risk is not likely to be
higher than the estimate, but it could be lower.
The unit risk estimate based on animal bioassays is only an approximate
indication of the absolute risk in populations exposed to known carcinogen
concentrations. This is true for several reasons. First, there are important
species differences in uptake, metabolism, and organ distribution of carcino-
gens, as well as species differences in target site susceptibility, immuno-
logical responses, hormone function, dietary factors, and disease. Second,
the concept of equivalent doses for humans as compared to animals, based on
a ratio of weight to surface area, is virtually without experimental verifi-
cation as regards carcinogenic response. Finally, human populations are
variable with respect to genetic constitution and diet, living environment,
activity patterns, and other cultural factors.
9-207
-------
The unit risk estimate can give a rough indication of the relative
carcinogenic potency of a given agent, as compared with that of other
carcinogens. Such estimates are, of course, more reliable when the
comparisons are based on studies in which the test species, strain, sex,
and routes of exposure are similar.
The quantitative aspect of carcinogen risk assessment is addressed here
because of its possible value in the regulatory decision-making process, e.g.,
in setting regulatory priorities, evaluating the adequacy of technology-based
controls, etc. However, the imprecision of presently available technology
for estimating cancer risks to humans at low levels of exposure should be
recognized. At best, the linear extrapolation model used here provides a
rough but plausible estimate of the upper limit of risk—that is, with this
model it is not likely that the true risk would be much more than the estimated
risk, but it could be considerably lower. The risk estimates presented in
subsequent sections should not be regarded, therefore, as accurate representa-
tions of the true cancer risks even when the exposures involved are accurately
defined. The estimates presented may, however, be factored into regulatory
decisions to the extent that the concept of upper-risk limits is found to
be useful.
9.5.3.1 Procedures for the Determination of Unit Risk—
9.5.3.1.1 Low-dose extrapolation model. The mathematical formulation chosen to
describe the linear non-threshold dose-response relationship at low doses is the
linearized multistage model. This model employs enough arbitrary constants to
be able to fit almost any monotonically increasing dose-response data, and it
incorporates a procedure for estimating the largest possible linear slope (in
9-208
-------
the 95% confidence limit sense) at low extrapolated doses that is consistent
with the data at all dose levels of the experiment.
Let P(d) represent the lifetime risk (probability) of cancer at dose d.
The multistage model has the form
P(d) = 1 - exp [-(q0 H
where
qi >_ 0, i = 0, 1, 2, .... k
Equivalently,
Pt(d) = 1 - exp [-(qj^d + q2d2 + ... + q^d1*-)]
where
P (d) = P(d) - P(0)
t 1 - P(0)
is the extra risk over background rate at dose d.
The point estimate of the coefficients q^, i = 0, 1, 2, ..., k, and
consequently, the extra risk function, Pt(d), at any given dose d, is
calculated by maximizing the likelihood function of the data.
The point estimate and the 95% upper confidence limit of the extra risk,
Pt(d), are calculated by using the computer program, GLOBAL79, developed by
Crump and Watson (1979). At low doses, upper 95% confidence limits on the
extra risk and lower 95% confidence limits on the dose producing a given risk
are determined from a 95% upper confidence limit, q*, on parameter qj. When-
ever qj > 0, at low doses the extra risk Pt(d) has approximately the form
Pt(d) = q* x d. Therefore, q* x d is a 95% upper confidence limit on the
extra risk and R/q* is a 95% lower confidence limit on the dose, producing an
extra risk of R. Let LQ be the maximum value of the log-likelihood function.
9-209
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The upper-limit q* is calculated by increasing q\ to a value q* such that when
the log- likelihood is remaximized subject to this fixed value q* for the linear
coefficient, the resulting maximum value of the log-likelihood Lj satisfies the
equation
2 (L0 - LX) = 2.70554
where 2.70554 is the cumulative 90% point of the chi-square distribution with
one degree of freedom, which corresponds to a 95% upper-limit (one-sided). This
approach of computing the upper confidence limit for the extra risk Pt(d) is an
improvement on the Crump et al. (1977) model. The upper confidence limit for
the extra risk calculated at low doses is alway linear. This is conceptually
consistent with the linear nonthreshold concept discussed earlier. The slope,
q*, is taken as an upper bound of the potency of the chemical in inducing
cancer at low doses. (In the section calculating the risk estimates, Pt(d)
will be abbreviated as P.)
In fitting the dose-response model, the number of terms in the polynomial
is chosen equal to (h-1), where h is the number of dose groups in the experiment,
including the control group.
Whenever the multistage model does not fit the data sufficiently well, data
at the highest dose is deleted and the model is refit to the rest of the data.
This is continued until an acceptable fit to the data is obtained. To
determine whether or not a fit is acceptable, the chi-square statistic
NiPi
9-210
-------
is calculated where N is the number of animals in the i dose group, X.^ is
the number of animals in the i dose group with a tumor response, P^ is the
probability of a response in the i dose group estimated by fitting the multistage
model to the data, and h is the number of remaining groups. The fit is determined
P
to be unaccepatable whenever X is larger than the cumulative 99% point of
the chi-square distribution with f degrees of freedom, where f equals the number
of dose groups minus the number of non-zero multistage coefficents.
9.5.3.1.2 Selection of data. For some chemicals, several studies in different
animal species, strains, and sexes, each run at several doses and different
routes of exposure, are available. A choice must be made as to which of the
data sets from several studies to use in the model. It may also be appropriate
to correct for metabolism differences between species and for absorption factors
via different routes of administration. The procedures used in evaluating
these data are consistent with the approach of making a maximum-likely risk
estimate. They are as follows:
1. The tumor incidence data are separated according to organ sites or
tumor types. The set of data (i.e., dose and tumor incidence) used in the
model is the set where the incidence is statistically significantly higher
than the control for at least one test dose level and/or where the tumor incidence
rate shows a statistically significant trend with respect to dose level. The
data set that gives the highest estimate of the lifetime carcinogenic risk,
q.j*, is selected in most cases. However, efforts are*made to exclude data
sets that produce spuriously high risk estimates because of a small number
of animals. That is, if two sets of data show a similar dose-response relationship,
and one has a very small sample size, the set of data having the larger sample
size is selected for calculating the carcinogenic potency.
9-211
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2. If there are two or more data sets of comparable size that are
identical with respect to species, strain, sex, and tumor sites, the geometric
mean of q*, estimated from each of these data sets, is used for risk assessment,
The geometric mean of numbers A^, A£, •••, Am is defined as
\" i X Ao X ••* X A )
3. If two or more significant tumor sites are observed in the same study,
and if the data are available, the number of animals with at least one of the
specific tumor sites under consideration is used as incidence data in the model.
9.5.3.1.3 Calculation of human equivalent dosages. Following the suggestion of
Mantel and Schneiderman (1975), it is assumed that mg/surface area/day is an
equivalent dose between species. Since, to a close approximation, the surface
area is proportional to the two-thirds power of the weight, as would be the case
for a perfect sphere, the exposure in mg/day per two-thirds power of the weight
is also considered to be equivalent exposure. In an animal experiment, this
equivalent dose is computed in the following manner.
Let
Le = duration of experiment
le = duration of exposure
m = average dose per day in mg during administration of the agent (i.e.,
during le), and
W = average weight of the experimental animal
The lifetime exposure is then
d -
L x W2/3
e
9-212
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9.5.3.1.3.1 Oral. Often exposures are not given in units of mg/day, and
it becomes necessary to convert the given exposures into mg/day. Similarly, in
drinking water studies, exposure is expressed as ppm in the water. For example,
in most feeding studies exposure is given in terms of ppm in the diet. In
these cases, the exposure in mg/day is
m = ppm x F x r
where ppm is parts per million of the carcinogenic agent in the diet or water,
F is the weight of the food or water consumed per day in kg, and r is the
absorption fraction. In the absence of any data to the contrary, r is assumed
to be equal to one. For a uniform diet, the weight of the food consumed is
proportional to the calories required, which in turn is proportional to the
surface area, or two-thirds power of the weight. Water demands are also
assumed to be proportional to the surface area, so that
m a ppm x
or
W2/3
ppm
As a result, ppm in the diet or water is often assumed to be an equivalent
exposure between species. However, this is not justified for the present
study, since the ratio of calories to food weight is very different in the
diet of man as compared to laboratory animals, primarily due to differences
in the moisture content of the foods eaten. For the same reason, the amount
of drinking water required by each species also differs. It is therefore
necessary to use an empirically derived factor, f = F/W, which is the
fraction of an organism's body weight that is consumed per day as food,
expressed as follows:
9-213
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Fraction of body
weight consumed as
Species W ffood ^water
Man
Rats
Mice
70
0.35
0.03
0.028
0.05
0.13
0.029
0.078
0.17
Thus, when the exposure is given as a certain dietary or water concentration in
ppm, the exposure in mg/W^/3 ±s
* F = ppm x f x W = p x f x w1/3
rW2/3 w2/3 w2/3
When exposure is given in terms of mg/kg/day = m/Wr = s, the conversion is
simply
m = s x W1/3
rW2/3
9.5.3.1.3.2 Inhalation. When exposure is via inhalation, the calcula-
tion of dose can be considered for two cases where 1) the carcinogenic agent is
either a completely water-soluble gas or an aerosol and is absorbed propor-
tionally to the amount of air breathed in, and 2) where the carcinogen is a
poorly water— soluble gas which reaches an equilibrium between the air breathed
and the body compartments. After equilibrium is reached, the rate of absorption
of these agents is expected to be proportional to the metabolic rate, which in
turn is proportional to the rate of oxygen consumption, which in turn is a
function of surface area.
9.5.3.1.3.2.1 Case 1 — Agents that are in the form of particulate matter or
virtually completely absorbed gases, such as sulfur dioxide, can reasonably be
9-214
-------
expected to be absorbed proportionally to the breathing rate. In this case the
exposure in mg/day may be expressed as
m = I x v x r
where 1 = inhalation rate per day in m3, v = mg/m3 of the agent in air, and
r = the absorption fraction.
The inhalation rates, I, for various species can be calculated from the
observations of the Federation of American Societies for Experimental Biology
(FASEB 1974) that 25 g mice breathe 34.5 liters/day and 113 g rats breathe 105
liters/day. For mice and rats of other weights, W (in kilograms), the surface
area proportionality can be used to find breathing rates in m3/day as follows:
For mice, I = 0.0345 (W/0.025)2/3 m3/day
For rats, 1 = 0.105 (W/0.113)2/3 m3/day
For humans, the value of 30 m3/day* is adopted as a standard breathing rate
(International Commission on Radiological Protection 1977). The equivalent
exposure in mg/W2/3 for these agents can be derived from the air intake data
in a way analogous to the food intake data. The empirical factors for the air
intake per kg per day, i = I/W, based upon the previously stated relationships,
are tabulated as follows:
Species W i = I/W
Man
Rats
Mice
70
0.35
0.03
0.29
0.64
1.3
*From "Recommendation of the International Commission on Radiological Protection,
page 9. The average breathing rate is 10' cm3 per 8-hour workday and 2 x 10' cm
in 24 hours.
9-215
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Therefore, for particulates or completely absorbed gases, the equivalent
exposure in mg/W^/-' is
d = m = Ivr = iWvr =
w2/3 w2/3 w2/3
In the absence of experimental information or a sound theoretical argument
to the contrary, the fraction absorbed, r, is assumed to be the same for all
species.
9.5.3.1.3.2.2 Case 2 — The dose in rag/day of partially soluble vapors is
2 / 3
proportional to the 02 consumption, which in turn is proportional to W ' and
is also proportional to the solubility of the gas in body fluids, which can be
expressed as an absorption coefficient, r, for the gas. Therefore, expressing
2/3
the 0? consumption as Oo = k W ' , where k is a constant independent of species,
it follows that
m = k W^/3 x v x r
or
d - m - kvr
w2/3
As with Case 1, in the absence of experimental information or a sound theoretical
argument to the contrary, the absorption fraction, r, is assumed to be the same
for all species. Therefore, for these substances a certain concentration in
ppm or ug/m3 in experimental animals is equivalent to the same concentration
in humans. This is supported by the observation that the minimum alveolar
concentration necessary to produce a given "stage" of anesthesia is similar
in man and animals (Dripps et al. 1977). When the animals are exposed via
the oral route and human exposure is via inhalation or vice versa, the
9-216
-------
assumption is made, unless there is pharmacokinetic evidence to the contrary,
that absorption is equal by either exposure route.
9.5.3.1.4 Calculation of the unit risk from animal studies. The risk associated
with d mg/kg2/3/day ±s obtained from GLOBAL79 and, for most cases of interest to
risk assessment, can be adequately approximated by P(d) = 1 - exp (-q*d). A
"unit risk" in units X is simply the risk corresponding to an exposure of X = 1.
This value is estimated simply by finding the number of mg/kg2/3/day that cor-
responds to one unit of X, and substituting this value into the above relation-
ship. Thus, for example, if X is in units of ug/m3 in the air, then for case
1, d = 0.29 x 701/3 x 10~3 mg/kg2/3/day, and for case 2, d = 1, when ug/m3 is
the unit used to compute parameters in animal experiments.
If exposures are given in terms of ppm in air, the following calculation
may be used:
1 ppm = 1.2 x molecular weight (gas) mg/m3
molecular weight (air)
Note that an equivalent method of calculating unit risk would be to use mg/kg
for the animal exposures, and then to increase the jt*1 polynomial coefficient
by an amount
(Wh/Wa)J/3 j = 1, 2, .... k
and to use mg/kg equivalents for the unit risk values.
9.5.3.1.4.1 Adjustment for less than the natural lifetime of an experiment.
If the duration of experiment Le is less than the natural lifespan of the test
animal L, the slope q*, or more generally the exponent g(d), is increased by
o
multiplying a factor (L/L£) . We assume that if the average dose d is continued,
the age-specific rate of cancer will continue to increase as a constant function
9-217
-------
of the background rate. The age-specific rates for humans increase at least by
the third power of the age, and often by a considerably higher power, as demon-
strated by Doll (1971). Thus, it is expected that the cumulative tumor rate
would increase by at least the third power of age. Using this fact, it is
assumed that the slope q*, or more generally the exponent g(d), would also
increase by at least the third power of age. As a result, if the slope q* [or
g(d)] is calculated at age Le, it is expected that if the experiment had been
continued for the full lifespan L at the given average exposure, the slope q*
o
[or g(d)] would have been increased by at least (L/Lg) .
This adjustment is conceptually consistent with the proportional hazard
model proposed by Cox (1972) and the time-to-tumor model considered by Daffer et
al. (1980), where the probability of cancer by age t and at dose d is given by
P(d,t) = 1 - exp [-f(t) x g(d)]
9.5.3.2 Unit Risk Estimates—
9.5.3.2.1 Data available for potency calculation. The carcinogenic potency of
EDC can only be estimated from animal data, since no human epidemiologic studies
are available at the present time. EDC was shown to be carcinogenic in both
rats and mice in a gavage study by the National Cancer Institute (NCI 1978). The
only available inhalation study (Maltoni et al. 1980) did not indicate any signi-
ficant carcinogenic effects in either rats or mice. The reason for this non-
responsiveness by inhalation is not known. In their evaluation of inhalation
and gavage studies on EDC, Hooper et al. (1980) concluded that the discrepant
results between the two exposure routes might be ascribed to one or more of the
following causes:
(1) The strains of test animals differ in responsiveness;
9-218
-------
(2) The route of exposure does make a difference concerning the carcino-
genic action of EDC; or
(3) An artifact has been introduced by the intercurrent mortality.
Two approaches have been used herein to estimate the cancer risk from
inhalation of EDC: direct estimation based on the results of the EDC gavage
study, and indirect estimation based on the results of ethylene dibromide (EDB)
inhalation and gavage studies.
The multistage model is used in connection with the most sensitive tumor
sites, and for purposes of comparison, other extrapolation models and data sets
are also used to estimate the carcinogenic potency of EDC.
Data from both rats and mice (NCI 1978) are used to estimate the carcino-
genic potency of EDC. For rats, hemangiosarcomas in the circulatory system of
male rats were selected, because these tumors are the most sensitive and were
not located at the site of direct contact with the agent. Because of the high
mortality rate in the high-dose group, the cancer risk is calculated by using
two types of data:
1. Dichotomous data. The number of animals that survived at least
50 weeks was used as the denominator of the incidence rate (see
Table 9_56.
2. Time-to-death data (see Table B-l, Appendix B).
For mice, hepatocellular carcinomas in male mice (Table 9-57 ) were used.
Again, this tumor site was selected because it is the most sensitive in mice.
9.5.3.2.2 Choice of low-dose extrapolation models. In addition to the multi-
stage model currently used by the CAG for low-dose extrapolation, three more
models, the probit, the Weibull, and the one-hit, are also employed for pur-
poses of comparison. These models cover almost the entire spectrum of risk
estimates that could be generated from existing mathematical extrapolation
9-219
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TABLE 9-5$ INCIDENCE RATES OF HEMANGIOSARCOMAS IN THE CIRCULATORY
SYSTEMS OF MALE OSBORNE-MENDEL RATS
(NCI 1978)
Human (animal)
dose (mg/kg/day)a Incidence rates
0
4.85 (47)
9.80 (95)
0/40
9/48
7/27
aHuman equivalent dose is calculated by d x (5/7) x (78/104) x (D.5/70)1/^
= 0.103 x d, where d is the experimental dose in mg/kg/day, administered
5 days per week for 78 weeks. The lifespan for rats is assumed to be 104
weeks. The body weights are assumed to be 0.5 kg for rats and 70 kg for
humans. This dose conversion assumes that the doses in mg per surface area
are equivalent between species. For comparison, the risk is also calculated
under the assumption that doses in mg/kg/day (i.e., without surface cor-
rection) are equivalent between species.
TABLE 9.57. INCIDENCE RATES OF HEPATOCELLULAR CARCINOMAS
IN MALE B6C3F1 MICE
(NCI 1978)
Human (animal)
dose (mg/kg/day)a Incidence rates
0 1/19
4.76 (97) 6/47
9.57 (195) 12/48
aHuman equivalent dose is calculated by d x (5/7) x (78/90) x (0.035/70)WJ
= 4.91 x 10~2 x d, where d is the animal dose in mg/kg/day, administered
5 days per week for 78 weeks. The lifespan for mice is assumed to be 90
weeks. The body weights are 0.035 kg for male mice and 70 kg for humans.
For comparison, the risk is also calculated under the assumption that doses
in mg/kg/day (i.e., without surface correction) are equivalent between
species.
9-220
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models. Generally statistical in character, these models are not derived
from biological arguments, except for the multistage model, which has been
used to support the somatic mutation hypothesis of carcinogenesis (Armitage
and Doll 1954, Wittemore 1978, Whittemore and Keller 1978). The main
difference among these models is the rate at which the response function
P(d) approaches zero or P(0) as dose d decreases. For instance, the probit
model would usually predict a smaller risk at low doses that the multistage
model because of the difference of the decreasing rate in the low-dose region.
However, it should be noted that one could always artificially give the multi-
stage model the same (or even greater) rate of decrease as the probit model
by making some dose transformation and/or by assuming that some of the para-
meters in the multistage model are zero. This, of course, is not reasonable
without knowing, a priori, what the carcinogenic process for the agent is.
Although the multistage model appears to be the most reasonable or at least
the most general model to use, the point estimate generated from this model
is of limited value because it does not help to determine the shape of the
dose-response curve beyond experimental exposure levels. Furthermore, point
estimates at low doses extrapolated beyond the experimental doses could be
extremely unstable and could differ drastically, depending on the amount of
the lowest experimental dose. Since upper-bound estimates from the multi-
stage model at low doses are relatively more stable than point estimates,
it is suggested that the upper-bound estimate for the risk (or the lower-
bound estimates for the dose) be used in evaluating the carcinogenic potency
of a suspect carcinogen. The upper-bound estimate can be taken as a
plausible estimate if the true dose-response curve is actually linear at
low doses. The upper-bound estimate means that the risks are not likely to
be higher, but could be lower if the compound has a concave upward dose-
9-221
-------
response curve or a threshold at low doses. Another reason one can, at
best, obtain an upper-bound estimate of the risk when animal data are used
is that the estimated risk is a probability conditional to the assumption
that an animal carcinogen is also a human carcinogen. Therefore, in
reality, the actual risk could range from a value near zero to an upper-
bound estimate.
9.5.3.2.3 Calculation of the carcinogenic potency of EDC. Using the incidence
data in Tables 9-56 and 9-57 and tne corresponding human equivalent doses, with
and without body surface correction, the maximum likelihood estimates of the
parameters in each of four extrapolation models are calculated and presented in
Table A-l of Appendix A. These models can be used to calculate point estimates
of risk at given doses or at doses for given levels of risk. The upper-bound
estimates of the risk at 1 mg/kg/day, calculated by various models using
different data sets, are presented in Table 9-58' From this table, it is
observed that the multistage model predicts a comparable risk on the basis
of either hemangiosarcomas in male rats or liver carcinomas in male mice,
while the probit and Weibull models are extremely unstable and predict a wide
range of risk, depending on the data base used. Figures 9~12and 9-13compare
the maximum likelihood estimates of the four models over the relatively low
dose range.
For the reasons discussed previously, the CAG recommends that the
estimate q* = 6.9 x 10~2 mg/kg/day be used to represent the carcinogenic
potency of EDC by oral exposure. This value is calculated on the basis of
hemangiosarcomas in male rats using the multistage model with the time
factor. This value will also be used to estimate the risk of EDC by
inhalation.
9-222
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TABLE 9-58. UPPER-BOUND ESTIMATE OF RISK AT 1 MG/KG/DAY
*£>
NJ
NJ
OJ
Data base
Hemangiosarcomas ,
dose with surface
correction
Hemangiosarcomas ,
dose without
surface correction
Hepatocellular carcinomas,
dose with surface
correction
(with
5.4
(6.
7.0
(1.
3.8
Multistage
time factor) Probit Weibull One-hit
x 10~2 0.29 0.28 5.4 x 10~2
9 x 10~2)
\
x 10~3 0.17 0.19 7.0 x ID'3
3 x ID"2)
x ID'2 2.4 x 10-2 4.3 x 10-2 3>8 x 10-2
Hepatocellular carcinomas,
dose without surface
correction
3.0 x 10~3
1.1 x 10~5 1.9 x 10~3 3.0 x 10~3
-------
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O
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Carcinogenic Response
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-------
0.0529
0.0
0.6
Dose in mg/kg/day
1.2
Multistage
Probit
Weibull
One-hit
— — ^—• — •— — — M.L.E. (maximum likelihood estimate)
A A A Upper-bound estimate
M.L.E.
•+ Upper-bound estimate
• - M.L.E.
•O
D Upper-bound estimate
M LE.
O Upper-bound estimate
FIGURE 9_ig Point and upper-bound estimates of four dose-response models
over low-dose region on the basis of liver carcinomas in mice;
dose with surface correction. (NCI 1978)
9-225
-------
9.5.3.2.4 Risk associated with 1 ug/L of EDC in drinking water. It is
assumed that 100% of EDC in drinking water can be absorbed, and that the
water intake is 2 L/day. Under these assumptions, the daily dose from con-
sumption of water containing 1 ug/L (1 ppb) of EDC is
d = 1 ug/L x 2 L/day x 10~3 mg/ug x 1/70 kg = 2.9 x 10~5 mg/kg/day
Therefore, the risk associated with 1 ug/L of EDC in drinking water is
P = 6.9 x 10~2 x 2.9 x 10~5 = 2 x I0~b
9.5.3.2.5 Risk associated with 1 ug/m3 of EDC in air. Two approaches are
used herein to estimate the carcinogenic potency of EDC by inhalation:
(1) direct estimation based on the EDC gavage study, and (2) an indirect
estimation based on EDB studies.
9.5.3.2.5.1 Direct estimate based on EDC gavage study. It was estimated in
the previous section that the carcinogenic potency of EDC by gavage is q* = 6.9 x
10~2 mg/kg/day. If the relative absorption rate of EDC by inhalation and gavage
in animals is known, it is possible to estimate carcinogenic potency by inhalation
if the potency calculated from the gavage study is adjusted proportionately.
As an approximation, it can be assumed that the effective dose by inhalation is
only one-third of that by gavage. This assumption is motivated by the observation
(Reitz et al. 1982) that DNA alkylation after gavage was 2 to 5 times higher
than after inhalation. To calculate potency in terms of ug/m3, it is assumed
that the daily intake of air for a 70-kg person is 20 m3. Thus, for 1 ug/m3 of
EDC in air, the corresponding dose in mg/kg/day is
(1/3) x (1 ug/m3) x (20 rag/day) x (1/70 kg) x (10~3 mg/ug)
= 9.52 x 10~5 mg/kg/day
9-226
-------
On the basis of the above calculations, the carcinogenic potency of EDC by
inhalation is estimated as follows:
q* = (6.90 x ID"2) x (9.52 x 1CT5) = 6.6 x 1CT6 ug/m3.
9.5.3.2.5.2 Indirect estimate based on EDB studies. The carcinogenic poten-
cy of EDC by inhalation can be estimated by utilizing the following assumption:
P(EDC, I) = P(EDC, G)
P(EDB, I) P(EDB, G)
where P(EDC, I) and P(EDC, G) indicate the potencies of EDC by inhalation
and by gavage, respectively, and P(EDB, I) and P(EDB, G) indicate the potency
of EDC by inhalation and by gavage, respectively.
The potencies for EDC and EDB by gavage are estimated from the hemangio-
sarcomas in male rats in the NCI studies on EDC (NCI 1978) and EDB (NCI 1979).
On the basis of gavage studies, it is estimated that EDB is approximately 10
times more potent than EDC. The estimation and the data used for calculating
the EDB potency by gavage are presented in Appendix C.
The potency of EDB by inhalation is calculated as P(EDB, I) = 6.77 x 10~5
ug/m3, on the basis of nasal cavity tumors in male rats (NCI 1979). The cal-
culation and data are presented in Appendix C. On this basis, the potency of
EDC by inhalation is calculated as follows:
P(EDC.I) = P(EDC, G> x P(EDB, I)
P(EDB, G)
= _1 x 6.77 x 10~5
10
= 6.8 x 10-6 Ug/m3
9-227
-------
Practically no difference exists between this estimate and that calculated
directly from the EDC gavage study data.
9.5.3.3 Comparison of Potency with Other Compounds—One of the uses of
quantitative potency estimates is to compare the relative potencies of carcino-
gens. Figure 9-14is a histogram representing the frequency distribution of
potency indices of 53 suspect carcinogens evaluated by the CAG. The data
summarized by the histogram are presented in Table 9-59 • The potency index is
derived from q*, the 95% upper bound of the linear component in the multistage
model, and is expressed in term of (mMol/kg/day)~~ . Where human data were
available for an agent, they have been used to calculate the index. Where no
human data were available, animal oral studies have been used in preference to
animal inhalation studies, since oral studies constitute the majority of animal
studies.
Based on available data concerning hemangiosarcomas in male rats (NCI
1978), the potency index for EDC has been calculated as 7 x 10™. This figure
is derived by multiplying the slope q* = 6.9 x 10~2 mg/kg/day and the
molecular weight of EDC, 98.9. This places the potency index for EDC in the
fourth quartile of the 53 suspect carcinogens evaluated by the CAG.
The ranking of relative potency indices is subject to the uncertainties
involved in comparing a number of potency estimates for different chemicals
based on varying routes of exposure in different species, by means of data
from studies whose quality varies widely. All of the indices presented
are based on estimates of low-dose risk, using linear extrapolation from
the observational range. These indices may not be appropriate for the compari-
son of potencies if linearity does not exist at the low-dose range, or if
9-228
-------
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468
LOG OF POTENCY INDEX
Figure 9-16 Histogram representing the frequency distribution of the
potency indices of 53 suspect carcinogens evaluated by the
Carcinogen Assessment Group.
9-229
-------
TABLE 9-59. RELATIVE CARCINOGENIC POTENCIES AMONG 53 CHEMICALS EVALUATED BY
THE CARCINOGEN ASSESSMENT GROUP AS SUSPECT HUMAN CARCINOGENS1'2'3
Slope Molecular
Compound (mg/kg/day)"1 weight
Acrylonitr ile
Af la toxin B,
Aldrin
Allyl chloride
Arsenic
B[a]P
Benzene
Benzidene
Beryllium
Cadmium
Carbon tetrachloride
Chlordane
Chlorinated ethanes
1 , 2-dichloroethane
hexachloroe thane
1,1,2, 2-tetrachloroethane
1,1, 1-trichloroethane
1,1, 2-trichloroethane
Chloroform
Chromium
DDT
Dichlorobenzidine
1 , 1-dichloroethylene
Dieldrin
0.24(W)
2924
11.4
1.19xlO-2
15(H)
11.5
5.2xlCT2(W)
234 (W)
1.40
6.65(W)
1. SOxlO'1
1.61
6.9xlO-2
1.42x10-2
0.20
1.6xlO-3
5.73x10-2
7x10-2
41(W)
8.42
1.69
1.47xlQ-1(I)
30.4
53.1
312.3
369.4
76.5
149.8
252.3
78
184.2
9
112.4
153.8
409.8
98.9
236.7
167.9
133.4
133.4
119.4
100
354.5
253.1
97
380.9
Potency
index
1x10+1
9xlO+5
4xlO+3
9x10-1
2xlO+3
3xlO+3
4x10°
4xlO+A
1x10+1
7x10+2
2x10+1
7x10+2
7x1 00
3x10°
3x10+1
2x10-1
8x10°
8x1 00
4xlO+3
3xlO+3
4xlO+2
1x10+1
lxlO+4
Order of
magnitude
(logio
index)
+ 1
+6
+4
0
+3
-t-3
+1
+5
+1
+3
+1
+3
+1
0
+ 1
-1
+1
+ 1
+4
+3
+3
+1
+4
(continued on the following page)
9-230
-------
TABLE 9-59 (cont.)
Compound
Dinitrotoluene
Diphenylhydrazine
Epichlorohydrin
Bis(2-chloroethyl)ether
Bis (chloromethyl) ether
Ethylene dibromide (EDB)
Ethylene Oxide
Heptachlor
Hexachlorobenzene
Hexachlorobutadiene
Hexachlorocyclohexane
technical grade
alpha isomer
beta isomer
gamma isomer
Methylene chloride
Nickel
Nitrosamines
Dimethylnitrosamine
Diethylnitrosamine
Dibutylnitrosamine
N-nitrosopyrrolidine
N-nitroso-N-ethylurea
N-nitroso-N-methylurea
N-nitroso-diphenylamine
PCBs
Slope
(mg/kg/day)"
0.31
0.77
9.9xlO"3
1.14
9300(1)
8.51
0.63(1)
3.37
1 .67
7.75xiO~2
4.75
11 .12
1.84
1.33
6.3X10"11
1 J5(W)
25. 9 (not by q.,«)
43.5(not by q^)
5.43
2.13
32.9
302.6
4.92x10~3
..3*
Molecular
weight
182
180
92.5
143
115
187.9
44.0
373.3
284.4
261
290.9
290.9
290.9
290.9
84.9
58.7
74.1
102.1
158.2
100.2
117.1
103.1
198
324
Potency
index
6x1 0+1
1 xi 0+2
9x1 O"1
2x1 0+2
1 x1 0+6
2x1 0+3
3x1 O"1"1
1x1 0+3
5x1 O*2
2x1 0+
3x1 o*3
5x1 0+J;
4x1 O"1"2
5x1 0~2
7x1 0+
2x1 0+3
4x1 O"1"3
9x1 O^2
2x1 0*^
4x1 0+^
3x1 0*
1x10
1 x1 O"1"3
Order of
magnitude
(log
index;
+2
+2
0
+2
+6
+3
+1
+3
+3
+1
+3
+3
+3
+3
-1
+2
+3
+4
+3
+2
+4
+4
0
+3
9-231
-------
TABLE 9-59 . (continued)
Order of
Compound
Phenols
2,4 ,6-trichlorophenol
Tetrachlorodioxin
Te trachloroethylene
Toxaphene
Trichloroethylene
Vinyl chloride
Remarks:
1 . Animal slopes are
Slope
(mg/kg/day) L
1.99xlO-2
4.25xl05
3.5xlO-2
1.13
1.9xlO"2
1.75x10-2(1)
95% upper-limit sl<
magnitude
Molecular Potency (logio
weight index index)
197.4 4x10°
322 lxlO+8
165.8 6x10°
414 5x10+2
131.4 2.5x10°
62.5 1x10°
Dpes based on the linearized
+ 1
+8
+ 1
+3
0
0
mult istage
model. They are calculated based on animal oral studies, except for those
indicated by 1 (animal inhalation), W (human occupational exposure), and H
(human drinking water exposure). Human slopes are point estimates based on
the linear non-threshold model.
2. The potency index is a rounded-off slope in (mMol/kg/day)~^ and is calcu-
lated by multiplying the slopes in (mg/kg/day)-1 by the molecular weight
of the compound.
3. Not all of the carcinogenic potencies presented in this table represent
the same degree of certainty. All are subject to change as new evidence
becomes available.
9-232
-------
comparison is to be made at the high-dose range. If the latter is the case,
then an index other than the one calculated above may be more appropriate.
9.5.^ Summary
9-5.U.1 Qualitative—Although several cancer bioassay studies of EDC have
been reported, only the NCI bioassay in which EDC was administered to rats
and mice by gavage produced a clear positive tumorigenic response.
In the NCI (1978) rat study, EDC produced a statistically significant
increase in the incidence of squamous cell carcinomas of the forestomach,
hemangiosarcomas of the circulatory system, and fibromas of subcutaneous
tissue in male rats. There was also a statistically significant increased
incidence of adenocarcinomas of the mammary gland and hemangiosarcomas of the
circulatory system in female rats.
In the NCI (1978) studies in mice, EDC produced a statistically significant
increased incidence of hepatocellular carcinomas and alveolar/bronchiolar
adenomas in male mice and a statistically significant increased incidence
of alveolar/bronchiolar adenomas, mammary carcinomas, and endometrial tumors
in female mice.
Two inhalation studies of EDC were conducted. The study by Spencer
et al. (1951) in Wistar rats showed no evidence of a postive response. However,
this study was inadequate to assess the carcinogenicity of EDC because the
experiment was conducted in a small number of animals for 212 days with 1 51
exposure days at 200 ppm. A second study by Maltoni et al. (1980), conducted
in both rats and mice, did not produce a statistically significant increase
in tumor incidences in any organ sites as compared to control animals.
The study by Theiss et al. (1977), a pulmonary bioassay in which EDC was
administered intraperitoneally to strain A mice, produced a statistically
insignificant increase in the incidence of lung tumors in treated animals.
9-233
-------
In a study by Van Duuren et al. (1979), EDC was applied to the skin of
ICR/Ha mice to assess its carcinogenic potential as a skin tumorigen. This
study did not show a statistically significant increase in skin carcinomas;
a significantly increased incidence of benign lung tumors in mice treated with
the high dose (126/mg/mouse) was reported.
No case reports or epidemiologic studies concerning EDC were available
in the published literature.
9.5.4.2 Quantitative—Data from studies using both rats and mice were used
to estimate the carcinogenic potency of EDC. For rats, data on hemangiosar-
comas in the circulatory system were used. For mice, data on hepatocellular
carcinomas were used. The carcinogenic potencies estimated on the basis of
these two data sets are comparable when the linearized multistage model is
used. The upper-bound estimate of EDC potency is q* = 7 x 10~2 mg/kg/day,
calculated on the basis of hemangiosarcomas using the time-to-death data.
The upper-bound estimate of the cancer risk from 1 ug/nH of EDC in air is
7 x 10~6. The upper-bound estimate of the risk from 1 ug/L of EDC in
drinking water is 2 x 10~6. The cancer risk of EDC by inhalation is calcu-
lated by two methods: 1) a direct estimation based on the EDC gavage study,
assuming that the absorption rate by inhalation is one-third of that by the
oral route; and 2) an indirect estimation from the EDB inhalation study. The
potencies calculated from both approaches are practically identical.
The potency index for EDC, defined as q* x molecular weight, lies in the
fourth quartile among the 53 suspect carcinogens evaluated by the Carcinogen
Assessment Group.
9.5.5 Conclusions
There is evidence that EDC is a potential human carcinogen. This conclusion
9-234
-------
is based on: 1) positive findings in one oral rat study and one oral mouse
study and supportive evidence in two other mouse studies; 2) a positive mutage-
nicity response in multiple tests; and 3) demonstrated evidence of the presence
of reactive metabolites and covalent binding to DNA.
The estimated carcinogenic potency of EDC places it in the 4th quartile of
the 53 suspect carcinogens evaluated by the CAG.
Applying the International Agency for Research on Cancer (1ARC) classifica-
tion scheme, this level of evidence in animals would be considered sufficient
for concluding that EDC is a potential human carcinogen with a rank of 2B.
9-235
-------
United States
Environmental Protection
Agency
Office of Health and
Environmental Assessment
Washington DC 20460
EPA-600/8-84-006A
April 1984
External Review Draft
Research and Development
x>EPA
Health Assessment Review
Document for Draft
1 ,2-Dichloroethane
._ . . I-N- i i -i»
(Ethylene Dichloride)
Part 2 of 2
Cite or Quote)
NOTICE
This document is a preliminary draft. It has not been formally
released by EPA and should not at this stage be construed to
represent Agency policy. It is being circulated for comment on its
technical accuracy and policy implications.
-------
(DO Not EPA-600/8-?4:°°6*
Cite or Quote) c , D APnl ^98*
External Review Draft
Health Assessment Document
for 1,2,- Dichloroethane
(Ethylene Dichloride)
Part 2 of 2
NOTICE
This document is a preliminary draft. It has not been formally released by the U.S. Environmental
Protection Agency and should not at this stage be construed to represent Agency policy. It
is being circulated for comment on its technical accuracy and policy implications.
U.S. Environmental Protection Agency
Region V, Library
230 South DearL'C-Ti C'.rest
Chicago, Illinois 60604
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Research Triangle Park, North Carolina 27711
-------
DISCLAIMER
This report is an external draft for review purposes only and does not
constitute Agency Policy. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
U.S. Environmental Protection Agency
ii
-------
PREFACE
The Office of Health and Environmental Assessment has prepared this
health assessment to serve as a "source document" for EPA use. The health
assessment document was originally developed for use by the Office of Air
Quality Planning and Standards to support decision-making regarding possible
regulation of ethylene dichloride as a hazardous air pollutant. However, the
scope of this document has since been expanded to address multimedia aspects.
In the development of the assessment document, the scientific literature
has been inventoried, key studies have been evaluated and summary/conclusions
have been prepared so that the chemical's toxicity and related characteristics
are qualitatively identified. Observed effect levels and other measures of
dose-response relationships are discussed, where appropriate, so that the
nature of the adverse health responses are placed in perspective with observed
environmental levels.
111
-------
The EPA's Office of Health and Environmental Assessment (OHEA) is
responsible for the preparation of this health assessment document. The OHEA
Environmental Criteria and Assessment Office (ECAO-RTP) had overall
responsibility for coordination and direction of the document (Dr. Robert M.
Bruce, Project Manager). The chapters addressing physical and chemical
properties, sampling and analysis and toxic effects were either rewritten or
revised by Syracuse Research Corporation. The pharmacokinetics chapter was
written by Dr. I.W.F. Davidson of the Bowman Gray School of Medicine, Wake Forest
University. The air quality chapters addressing sources, emissions and ambient
concentrations were originally written by Syracuse Research Corporation and
revised by Radian Corporation under a contract with the Office of Air Quality
Planning and Standards.
The principal authors of the chapters prepared by Syracuse Research
Corporation are:
Stephen Bosch
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, New York 13210-U080
D. Anthony Gray, Ph.D.
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, New York 13210-H080
Joseph Santodonato, Ph.D., C.I.H.
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, New York 13210-4080
The OHEA Carcinogen Assessment Group (CAG) was responsible for preparation
of the sections on carcinogenicity. Participating members of the CAG are listed
below (principal authors of present carcinogenicity materials are designated by
an asterisk (»).
iv
-------
Roy Albert, M.D. (Chairman)
Elizabeth L. Anderson, Ph.D.
Larry D. Anderson, Ph.D.
Steven Bayard, Ph.D.
David L. Bayliss, M.S.
Chao W. Chen, Ph.D.*
Margaret M.L. Chu, Ph.D.
Herman J. Gibb, M.S., M.P.H.
Bernard H. Haberman, D.V.M., M.S.
Charalingayya B. Hiremath, Ph.D.*
Robert McGaughy, Ph.D.
Dharm V. Singh, D.V.M., Ph.D.
Todd W. Thorslund, Sc.D.
The OHEA Reproductive Effects Assessment Group (REAG) was responsible for
the preparation of sections on mutagenicity, teratogenicity and reproductive
effects. Participating members of REAG are listed below (principal authors of
present sections are indicated by an asterisk (*). The Environmental Mutagen
Information Center (EMIC), in Oak Ridge, TN, identified literature bearing on the
mutagenicity of EDC.
John R. Fowle III, Ph.D.*
Ernest R. Jackson, M.S.
Casey Jason, M.D., Medical Officer
David Jacobson-Kram, Ph.D.
K.S. Lavappa, Ph.D.
Sheila L. Rosenthal, Ph.D.
Carol N. Sakai, Ph.D.*
Carmella Tellone, B.S.
Vicki L. Vaughan-Dellarco, Ph.D.
Peter E. Voytek, Ph.D. (Director)
The following individuals provided peer review of this draft and/or earlier
drafts of this document:
U.S. Environmental Protection Agency
Karen Blanchard
Office of Air, Noise and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, NC
Robert M. Bruce, Ph.D.
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Research Triangle Park, NC
-------
Larry T. Cuppitt, Ph.D.
Office of Research and Development
Environmental Sciences Research Laboratory
Research Triangle Park, NC
James W. Falco, Ph.D.
Office of Health and Environmental Assessment
Exposure Assessment Group
Washington, DC
Lester D. Grant, Ph.D.
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Research Triangle Park, NC
Thomas G. McLaughlin, Ph.D.
Office of Health and Environmental Assessment
Exposure Assessment Group
Washington, DC
David Patrick
Office of Air, Noise and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, NC
David J. Reisman
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Cincinnati, OH
Jerry F. Stara, D.V.M.
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Cincinnati, OH
Consultants, reviewers and contributing authors:
Joseph F. Borzelleca, Ph.D.
Virginia Commonwealth University
Richmond, VA
Mildred Christian, Ph.D.
Argus Research Laboratories, Inc.
Perkasia, PA
Herbert H. Cornish, Ph.D.
The University of Michigan
Ypsilanti, MI
I.W.F. Davidson, Ph.D.
Bowman Gray School of Medicine
Wake Forest University
Winston Salem, NC
VI
-------
Larry Fishbein, Ph.D.
National Center for lexicological Research
Jefferson, AR
Mark M. Greenberg
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Research Triangle Park, NC
Derek Hodgson, Ph.D.
University of North Carolina
Chapel Hill, NC
George R. Hoffman, Ph.D.
Holy Cross College
Worcester, MA
Rudolph J. Jaeger, Ph.D.
Consultant Toxicologist
7 Bolgert Place
Westwood, NJ
Marshall Johnson, Ph.D.
Thomas Jefferson Medical College
Philadelphia, PA
Bruce Kleinstein, Ph.D.
1500 Locust Street, Suite 3504
Philadelphia, PA
John L. Laseter, Ph.D.
Environmental Affairs, Inc.
New Orleans, LA
Edmond J. LaVoie, Ph.D.
American Health Foundation
Valhalla, NY
Marvin S. Legator, Ph.D.
University of Texas Medical Branch
Galveston, TX
P.O. Lotilaker, Ph.D.
Pels Research Institute
Temple University Medical Center
Philadelphia, PA
Jean C. Parker, Ph.D.
Office of Waste Programs Enforcement
U.S. Environmental Protection Agency
Washington, DC
vn
-------
Bernard Schwetz, Ph.D.
National Institute of Environmental Health Sciences
Research Triangle Park, NC
Sam Shibko, Ph.D.
Health and Human Services
Division of Toxicology
Washington, DC
Charles M. Sparacino, Ph.D.
Research Triangle Institute
Research Triangle Park, NC
Danial S. Straus, Ph.D.
University of California
Riverside, CA
Darrell D. Suraner, Ph.D.
CIBA GEIGY Corporation
High Point, NC
Robert Tardiff, Ph.D.
1423 Trapline Court
Vienna, VA
Norman M. Trieff, Ph.D.
University of Texas Medical Branch
Department of Pathology, UTMB
Galveston, TX
Benjamin Van Duuren, Ph.D.
New York University Medical Center
550 First Avenue
New York, NY
Jim Withey, Ph.D.
Department of National Health and Welfare
Tunney's Pasture
Ottawa, Ontario
CANADA K1A 01Z
viii
-------
TABLE OF CONTENTS
Page
. LIST OF TABLES xi
LIST OF FIGURES xvi
1. SUMMARY AND CONCLUSIONS 1-1
2. INTRODUCTION 2-1
3. PHYSICAL AND CHEMICAL PROPERTIES 3-1
3.1 NAME 3-1
3.2 CAS REGISTRY, RTECS, AND STORET NUMBERS 3-1
3.3 DESCRIPTION 3-1
3.1 STRUCTURE 3-1
3.5 PHYSICAL PROPERTIES OF PURE ETHYLENE DICHLORIDE 3-1
1 . SAMPLING AND ANALYSIS OF ETHYLENE DICHLORIDE 1-1
1 . 1 SAMPLING 1-1
4.2 ANALYSIS 1-1
1.2.1 Ethylene Dichloride in Air 1-1
1.2.2 Ethylene Dichloride in Water 1-2
1.2.3 Ethylene Dichloride in Solid Samples 1-3
1.2.1 Ethylene Dichloride in Blood 1-3
1.2.5 Ethylene Dichloride in Urine 1-3
1.2.6 Ethylene Dichloride in Tissue 1-1
5. SOURCES IN THE ENVIRONMENT 5-1
5.1 PRODUCTION PROCESSES 5-1
5.2 ETHYLENE DICHLORIDE PRODUCERS 5-2
5.3 ETHYLENE DICHLORIDE PRODUCTION AND TRENDS 5-2
5.1 ETHYLENE DICHLORIDE USES 5-5
5.5 SOURCES OF EMISSIONS 5-9
5.5.1 Production and Related Facilities 5-12
5.5.2 Dispersive Uses 5-13
5.5.3 Conclusions 5-11
6. FATE AND TRANSPORT IN THE ENVIRONMENT 6-1
6.1 ATMOSPHERE 6-1
6.2 AQUATIC MEDIA 6-7
6.3 SOIL 6-8
6.1 SUMMARY 6-9
IX
-------
TABLE OF CONTENTS (cont.)
Page
7. ENVIRONMENTAL LEVELS AND EXPOSURE 7-1
7.1 ENVIRONMENTAL LEVELS 7-1
7.1.1 Atmospheric Levels 7-1
7.1.2 Ground and Surface Water Levels 7-9
7.1.3 Soil and Sediment Levels 7-14
7.2 ENVIRONMENTAL EXPOSURE 7-14
7.2.1 Exposure from Air 7-18
7.2.2 Exposure from Water 7-20
7.2.3 Exposure from Food 7-20
7.3 CONCLUSIONS 7-20
8. ECOLOGICAL EFFECTS 8-1
9. BIOLOGICAL EFFECTS IN MAN AND EXPERIMENTAL ANIMALS 9-1
9.1 PHARMACOKINETICS 9-1
9.1.1 Absorption and Distribution 9-1
9.1.2 Excretion 9-18
9.1.3 Metabolism 9-32
9.1.4 Summary and Conclusions 9-55
9.2 ACUTE, SUBCHRONIC AND CHRONIC TOXICITY 9-57
9.2.1 Effects in Humans 9-57
9.2.2 Effects in Animals 9-85
9.2.3 Summary of Acute, Subchronic and Chronic Toxicity 9-115
9.3 REPRODUCTIVE AND TERATOGENIC EFFECTS 9-122
9.3.1 Summary 9-129
9.4 MUTAGENICITY 9-131
9.5 CARCINOGENICITY 9-166
9.5.1 Animal Studies 9-166
9.5.2 Epidemiologic Studies 9-205
9.5.3 Quantitative Estimates 9-206
9.5.4 Summary 9-233
9.5.5 Conclusions 9-234
10. REFERENCES 10-1
Appendix A
Appendix B
Appendix C
-------
LIST OF TABLES
Table Page
5-1 Major Manufacturers of Ethylene Dichloride 5-3
5-2 U.S. Production and Sales of Ethylene Dichloride 5-4
5-3 Ethylene Dichloride Uses 5-6
5-4 Comsumption of Ethylene Dichloride in 1979 and 1974 5-7
5-5 Uses of Ethylene Dichloride for Intermediate Purposes 5-8
5-6 Estimated Environmental Releases of Ethylene
Dichloride in 1979 5-11
6-1 Rate Constants for a Few Chlorinated Ethanes at
Room Temperature 6-3
7-1 Ambient Atmospheric Levels of Ethylene Dichloride 7-2
7-2 Ambient Concentrations of Ethylene Dichloride in
Urban Areas 7-8
7-3 Reported Occurrence of Ethylene Dichloride in Groundwater
System 7-15
7-4 Reported Occurrence of Ethylene Dichloride in Surface
Water Systems 7-16
7-5 State Data on Ethylene Dichloride in Groundwater 7-17
7-6 Estimated Respiratory Intake of Ethylene Dichloride by
Adults and Infants 7-19
7-7 Maximum Concentration Level in the Vicinity of Various
Emission Sources 7-21
7-8 Total Estimated Population (in Thousands) Exposed to
Ethylene Dichloride in Drinking Water at the Indicated
Concentration Ranges 7-22
7-9 Estimated Drinking Water Intake of Ethylene Dichloride
by Adults and Infants 7-23
9-1 Physical Properties of Ethylene Dichloride and
Other Chloroethanes 9-3
9-2 Partition Coefficients for Ethylene Dichloride 9-4
xi
-------
LIST OF TABLES (cont.)
Table Page
9-3 Fate of li4C-EDC in Rats 18 Hours After Oral (150 mg/kg)
or Inhalation (150 ppm, 6~hr) Exposure ........................ 9-6
9-1 Peak Blood and Tissue Levels After Single Oral Dosage
of EDC in Male Rats ........................................... 9-8
9-5 The Absorption Rate Constants (k ) and Area Under Curve
(AUC) for Rats After Single Orll with Doses of EDC in Oil
and in Water as Vehicle and After Intravenous
Administration ............................. . .................. 9-9
9-6 EDC Tissue Levels After 50 ppm Inhalatory Exposure ........... ... 9-11
9-7 EDC Tissue Levels After 250 ppm Inhalatory Exposure ............. 9-15
9-8 Blood Tissue Levels of EDC in Male Rats 2 Hours After
Single Oral Doses in Corn Oil ................................. 9-17
9-9 Percent Distribution of Radioactivity Excreted (18-hr) by
Mice Receiving 1 ,2-Dichloroethane- C ...................... 9-29
9-10 Pharmacokinetic Parameters of EDC Administered as Single
Bolus Intravenous Injections in Saline to Sprague-Dawley
Male Rats. Parameters Calculated from a 2-Compartment
Open Model [[[ 9-24
9-11 Pharmacokinetic Parameters of EDC Administered as Single
Oral Doses in Corn Oil and Water to Sprague-Dawley Male
Rats. Parameters Calculated from a 2-Compartment Open
Model [[[ 9-26
9-12 Pharmacokinetic Parameters of EDC Following Termination of
Steady State Inhalation (5-hr Exposure) of 50 and 250 ppm
to Male Sprague-Dawley Rats ................................... 9-29
9-13 Pharmacokinetic Parameters of EDC Following Termination of
Steady State Inhalation Conditions; 6-Hr Exposure, 150 ppm
to Male Osborne-Mendel Rats. Parameters Calculated from a
2-Compartment Model ......................................... . . 9-30
9-H Identified Metabolites of Ethylene Dichloride and
Ethylene Bromide .............................................. 9-31
9-15 Percent Distribution of Radioactivity Excreted (18-hr) as
Urinary Metabolites by Mice Receiving 1 ,2-Dichloroethane- C
-------
LIST OF TABLES (oont.)
Table Page
9-16 Total Macromolecular Binding and DMA Binding in Selected
Tissue of Rats After Exposure to C-EDC by Oral or
9-17
9-18
9-19
9-20
9-21
9-22
9-23
9-24
9-25
9-26
9-27
9-28
9-29
9-30
9-31
9-32
9-33
iii
Effect of Dietary Disulfiram Upon the C Content of
Liver Nuclei Isolated 24 or 48 Hours After Administration
of a Single Oral Dose of 15 mg/mg [U- C]EDB
Effects Associated with Acute Lethal Oral Doses of
Ethylene Dichloride in Humans
Effects of Acute Oral Ingestion of 1 ,2-Dichloroethane
(Survey Results)
Effect of Ethylene Dichloride Exposure on Eye
Sensitivity to Light
Morbidity and Lost Workdays of Aircraft Industry Gluers
Exposed to Ethylene Dichloride
Concentrations of Ethylene Dichloride in Oil Refinery
Mineral Oil Purification Process Air
Effects Observed in Polish Oil Refinery Workers
Effects of Acute Exposure to Ethylene Dichloride
Effect of Ethylene Dichloride on the Cornea
Effect of Subchronic Exposure to Ethylene Dichloride ,
Summary of Mutagenicity Testing of EDC: Gene Mutations
in Bacteria
Summary of Mutagenicity Testing of EDC: Higher Plants ,
Summary of Mutagenicity Testing of EDC: Gene Mutation
Summary of Mutagenicity Testing of EDC: Mammalian Cells
in Culture
Summary of Mutagenicity Testing of EDC: Chromosomal
Aberrations Tests ,
Summary of Mutagenicity Testing of EDC: PolA Assay ,
Summary of Mutagenicity Testing of EDC: DNA Binding
9-54
9-58
9-65
9-72
9-78
9-80
9-81
9-87
9-95
9-102
9-132
9-145
9-147
9-153
9-155
9-160
Studies. 9-163
xiii
-------
LIST OF TABLES
Table
9-3*4 Design Summary for 1,2-Dichloroethane (EDC) Gavage
Experiment in Osborne-Mendel Rats 9-168
9-35 Terminal Survival of Osborne-Mendel Rats Treated With
1,2-Dichloroethane (EDC) 9-172
9-36 Squamous Cell Carcinomas of the Forestomach in Osborne-
Mendel Rats Treated With 1,2-Dichloroethane (EDC) 9-173
9-37 Hemangiosarcomas in Osborne-Mendel Rats Treated With
1,2-Dichloroethane (EDC) 9-171
9-38 Adenocarcinomas of the Mammary Gland in Female Osborne-
Mendel Rats Treated With 1,2-Dichloroethane (EDC) 9-175
9-39 Design Summary for 1,2-Dichloroethane (EDC) Gavage
Experiment in B6C3F1 Mice 9-177
9-10 Terminal Survival of B6C3F1 Mice Treated With
1,2-Dichloroethane (EDC) 9-178
9-11 Hepatocellular Carcinomas in B6C3F1 Mice Treated With
1,2-Dichloroethane (EDC) 9-181
9-12 Alveolar/Bronchiolar Adenomas in B6C3F1 Mice Treated
With 1,2-Dichloroethane (EDC) 9-182
9-13 Squamous Cell Carcinomas of the Forestomach in B6C3F1 Mice
Treated With 1 ,2-Dichloroethane (EDC) 9-183
9-11 Adenocarcinomas of the Mammary Gland in Female B6C3F1 Mice
Treated With 1 ,2-Dichloroethane (EDC) 9-181
9-15 Endometrial Polyp or Endometrial Stromal Sarcomas in Female
B6C3F1 Mice Treated With 1,2-Dichloroethane (EDC) 9-181
9-16 Characterization of 1,2-Dichloroethane (EDC) Inhalation
Experiment in Sprague-Dawley Rats. 9-185
9-17 Design Summary for 1,2-Dichloroethane (EDC) Experiment
in Sprague-Dawley Rats 9-186
9-18 Survival of Sprague-Dawley Rats Exposed to EDC at 52 and
101 Weeks 9-188
9-19 Tumor Incidence in Sprague-Dawley Rats Exposed to EDC 9-189
9-50 Mammary Tumors in Sprague-Dawley Rats Exposed to EDC 9-193
xiv
-------
LIST OF TABLES
Table
9-51 Design Summary for 1,2-Dichloroethane (EDC) Experiment
in Swiss Mice 9-196
9-52 Survival of Swiss Mice Exposed to EDC at 52 and 78 Weeks 9-197
9-53 Tumor Incidence in Swiss Mice Exposed to EDC 9-198
9-54 Pulmonary Tumor Response in Strain A/st Mice
Injected with EDC 9-202
9-55 Mouse Skin Bioassay of 1,2-Dichloroethane and
Chloroacetaldehyde 9-204
9-56 Incidence Rates of Hemangiosarcomas in the Circulatory
Systems of Male Osborne-Mendel Rats 9-220
9-57 Incidence Rates of Hepatocellular Carcinomas in Male
B6C3F1 Mice 9-220
9-58 Upper-Bound Estimate of Risk At 1 Mg/kg/day 9-223
9-59 Relative Carcinogenic Potencies Among 53 Chemicals
Evaluated by the Carcinogen Assessment Group as Suspect
Human Carcinogens ' '3 9-230
xv
-------
LIST OF FIGURES
Figure Page
9-1 EDC levels after single oral administration in rats ............. 9-7
9-2 Top: Blood levels of EDC observed during and following a
6-hour inhalation exposure to 150 ppm EDC. Bottom: Semi-
logarithmic plot of EDC blood levels vs. time after
exposure termination .......................................... 9-12
9-3 Blood levels of EDC in rats after i.v. administration ........... 9-23
9-4 Levels of EDC in rats after inhalatory exposure to 50 ppm
(top) and 250 ppm (bottom). Levels were measured at
termination of 5-hour exposure period ......................... 9-27
9-5 Microsomal oxidative metabolism of 1 ,2-dihaloethanes ............ 9-39
9-6 Further metabolism of 2-chloroacetaldehyde and 1-chloroso-
2-chloroethane from microsomal oxidation ...................... 9-4 1
9-7 Cytosolic metabolism of ethylene dichloride ..................... 9-44
9-8 Growth curves for male and female Osborne-Mendel rats
administered 1 ,2-dichloroethane (EDC) by gavage ............... 9-170
9-9 Survival comparisons for male and female Osborne-Mendel rats
administered 1 ,2-dichloroethane (EDC) by gavage ............... 9-171
9-10 Growth curves for male and female B6C3F1 mice administered
1,2-dichloroethane (EDC) by gavage ............................ 9-179
9-11 Survival comparisons for male and female B6C3F1 mice
administered 1 ,2-Dichloroethane (EDC) by gavage ............... 9-180
9-12 Point and upper-bound estimates of four dose-response models
over low-dose region on basis of hemangiosarcomas in rats;
dose with surface correction .................................. 9-224
9-13 Point and upper-bound estimates of four dose-response models
over low-dose region on the basis of liver carcinomas in
mice; dose with surface correction ............................ 9-225
9-T4 Histogram representing the frequency distribution of the
potency indices of 53 suspect carcinogens evaluated by
the Carcinogen Assessment Group ............................... 9-229
xvi
-------
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APPENDIX A
COMPARISON AMONG DIFFERENT EXTRAPOLATION MODELS
Four models used for low-dose extrapolation, assuming the independent
background, are:
Multistage: P(d) = 1 - exp [~(q±d + ... + qkdk)]
where q^ are non-negative parameters;
Probit: A + Bln(d)
P(d) = / F(x) dx
where f(.) is the standard normal probability density function;
Weibull: P(d) = 1 - exp [-bdk]
where b and k are non-negative parameters; and
One-hit: P(d) = 1 - exp [~bd]
where b is a non-negative parameter.
The maximum likelihood estimates (MLE) of the parameters in the multi-
stage and one-hit models are calculated by means of the program GLOBAL82,
which was developed by Howe and Crump (1982). The MLE estimates of the
parameters in the probit and Weibull models are calculated by means of the
program RISK81, which was developed by Kovar and Krewski (1981).
Table A-l presents the MLE of parameters in each of the four models
that are applicable to a data set.
A-l
-------
TABLE A-l. MAXIMUM LIKELIHOOD ESTIMATES OF THE PARAMETERS FOR EACH OF THE FOUR
EXTRAPOLATION MODELS BASED ON DIFFERENT DATA BASES
Data base
Hemangiosarcomas in male
rats, dose with surface
correction
N) Hemangiosarcomas in male
rats, dose without
surface correction
He pa to cellular carcinomas
in male mice, dose with
surface correction
Heptocellular carcinomas in
male mice, dose without
Multistage
ql = 3.65 x
q2 = 0
qi = 7.03 x
q2 = 0
q^ = 1.03 x
(\2 ~ 1 «^7 x
q: = 8.18 x
q? = 9.25 x
Pro bit
io-2
10~"3
io-2
10~3
io-4
10~6
A =
B =
A =
B =
A =
B =
A =
B =
-1.43
0.34
-1.99
0.34
-2.75
0.86
-4.92
0.86
Weibull
b
k
b
k
b
k
b
k
= 9.08 x 10 2
= 0.52
= 3.84 x 10~2
= 0.52
= 8.07 x 10~~3
= 1.49
= 1.84 x 10~4
= 1.49
One-hit
b = 3.65 x 10~2
b = 7.03 x 10~3
b = 2.32 x 10"2
b = 3.04 x 10~3
surface corrections
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APPENDIX B
RISK CALCULATION BASED ON TIME-TO-EVENT DATA
Because of the high mortality rate of rats in the high-dose group of
the NCI (1978) gavage study, it is more appropriate to use time-to-event
data (Table B-l) to calculate the potency of EDC. The probability of
cancer by time t at dose d is given by:
P(d,t) = 1 - exp l-f(t) x g(d)]
where g(d) is a polynomial in dose d, and f(t) is a function of time t. The
maximum likelihood estimate of the parameters and the asymptotic properties
of the incremental risk estimate were investigated by Daffer et al. (1980).
Their approach to estimating the parameters resembles Cox's regression-life-
table approach (Cox 1972), in which the time function f(t) need not be
specified.
Using the data in Table B-l, the lifetime cancer risk is estimated to be
q* = 6.9 x ID"2 mg/kg/day
This value is the 95% upper bound of the risk calculated at t = 90 weeks.
Since the model fits the data very well up to 90 weeks but poorly beyond
90 weeks (overestimates), P(d, 90) is used to approximate the lifetime risk.
This seems reasonable because the median lifespan for control animals is also
less than 90 weeks (approximately 70% of the control animals died before 90
weeks).
B-l
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TABLE B-l. TIME-TO-DEATH IN WEEKS FROM HEMANGIOSARCOMAS
IN MALE OSBORNE-MENDEL RATS FED EDC BY GAVAGE
Control (vehicle and untreated):
28, 37, 50, 50, 53, 53, 53, 54, 57, 57, 57, 57, 57, 61, 61,
69, 71, 76, 78, 80, 80, 83, 85, 86, 87, 89, 90, 101, 101,
104, 10.6, 106, 106, 106, 106, 108, 110, 110, 110, 110.
Low-dose group:
30, 34, 36, 51, 52, 52, 55, 55, 59, 61, 63, 65, 69, 73(H)a,
74(H), 75, 75, 76, 77, 77, 77(H), 77, 80, 81, 82, 82, 82, 84,
87(H), 89(H), 89, 89, 89, 90, 92, 92, 93(H), 95(H), 96, 97,
98, 99, 99, 102(H), 103, 103, 104, 104, 109(H), 110.
High-dose group:
3, 8, 9, 9, 10, 10, 10, 10, 10, 11, 15, 15, 16, 20, 22, 33,
33, 33, 34, 37, 41, 48, 51, 52, 54, 57, 58, 59, 60, 61(H),
62, 63, 63, 68(H), 68(H), 71, 72, 73, 74, 7A(H), 74, 74, 76(H),
76, 78(H), 83(H), 84, 89, 101.
aH indicates death from hemangiosarcoma.
B-2
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APPENDIX C
CALCULATION OF EDB CARCINOGENIC POTENCIES BY GAVAGE AND INHALATION ROUTES
The data used for calculating the potency of EDB by gavage are presented in
Table C-l. The data from the high-dose group are not used because the dose
pattern from the high-dose group was drastically modified during the experi-
ment, resulting in a time-weighted dose almost identical to that of the low-
dose group. Using the life-table approach (Kaplan and Meier 1958), the
probability of cancer at week 49 (the end of the study) is 0.37 with the 95%
one-sided upper-confidence limit at 0.46. Thus, the upper-bound estimate of
the slope in the one-hit model, P = 1 - exp (-bd), is:
b = t-ln (l-P)]/d
= [-In (1-0.46J/5.01
= 0.12 mg/kg/day.
The lifetime cancer potency, adjusting for the less-than-lifetime study, is
B - 0.12 x (90/49)3 = 0.74 mg/kg/day
where 90 weeks is the lifespan that is also used in the EDC calculation when
time-to-event data are used.
Therefore, EDB is approximately 10 times more potent than EDC (i.e.,
0.74/0.069).
C-l
-------
The data used for calculating the potency of EDB by inhalation are
presented in Table C-2. The carcinogenic potency of EDB by inhalation is
calculated on the basis of nasal cavity tumors in male rats from the NCI
inhalation study on EDB (NCI 1979), using the linearized multistage model.
The potency of EDB by inhalation is
6.77 x 10-5/(ug/m3).
C-2
-------
TABLE C-l. TIME-TO-DEATH IN WEEKS FROM HEMANGIOSARCOMAS
IN MALE OSBORNE-MENDEL RATS FED EDB BY GAVAGE
(NCI 1978)
Low-dose group (38 mg/kg/day)a
31(H)b, 32, 34(H), 34(H), 35, 36, 37, 38(H), 39, 39, 40, 41,
42, 43, 43, 43, 43, 43, 43, 44, 44, 44, 46, 46, 47, 47, 48(H),
48, 48, 48, 48, 49(H), 49(H), 49(H), 49(H), 49(H), 49(H), 49,
49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49.
aThe animals were fed EDB 5 days per week for 47 weeks (out of 49 weeks observa-
tion period). The human equivalent dose is (38 mg/kg/day) x (5/7) x (47/49) x
(0.5/70)1/3 = 5.01 mg/kg/day.
bH indicates that the animals died from hemangiosarcomas. It is assumed that
all animals observed with tumors at week 49 died from the tumors. This
assumption seems reasonable, since the time from exposure to tumor death was
very short.
TABLE C-2. INCIDENCE OF NASAL CAVITY TUMORS IN MALE
FISCHER 344 RATS ADMINISTERED EDB BY INHALATION
(NCI 1979)
Human equivalent
dose (ug/m^)a
Animal dose
(ppm)
Response
0
1.39 x
5.57 x
0
10
40
0/50 (0%)
39/50 (78%)
41/50 (82%)
aHuman equivalent dose = d x (5/7) x (6/24) = 0.178 x d.
to the unit of ug/m3 by using 1 ppm = 7.83 x 10^ ug/nH.
The dose is converted
C-3
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