United States
Environmental Protection
Agency
Office of Health and
Environmental Assessment
Washington DC 20460
EPA-600/8-83-031A
October 1983
External Review Draft
Research and Development
Health Assessment
Document for
Vinylidene Chloride
Review
Draft
(Do Not
Cite or Quote)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.
-------
Review Draft
EPA-600/8-83-031A
October 1983
Health Assessment Document
for Vinyiidene Chloride
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.
^nrnontai Protection Agency
• <-'_'-"" fy
'f:' ^••*•'-i'vOi'n Stresi
Illinois £0504'" ;-x
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
The 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.
ii
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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
vinylidene chloride 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.
iii
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The EPA 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 and production effort (Dr. Robert M.
Bruce, Project Manager). The chapters addressing physical and chemical proper-
ties, sampling and analysis, air quality and biological effects in animals and
man were all originally written by Syracuse Research Corporation. The principal
authors of these chapters are listed below.
Dr. Dipak K. Basu
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, NY
Mr. John Becker
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, NY
Dr. Joan T. Colman
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, NY
Dr. Michael W. Neal
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, NY
Dr. Joseph Santodonato
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, NY
Dr. Richard Sugatt
Life and Environmental Sciences Division
Syracuse Research Corporation
Syracuse, NY
The OHEA Carcinogen Assessment Group (CAG) was responsible for reviewing
and updating the sections on carcinogenicity that were originally written by
iv
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Syracuse Research Corporation. Participating members of the GAG are listed below
(principal authors of the present carcinogenicity sections are designated by
asterisk).
Roy Albert, M.D. (Chairman)
Elizabeth L. Anderson, Ph.D.
Larry D. Anderson*
Steven Bayard, Ph.D.*
David L. Bayliss, M.S.*
Chao W. Chen, 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 following individuals within EPA provided peer-review of this draft or
earlier drafts of this document:
Larry Anderson, Ph.D.
Office of Health and Environmental Assessment
Carcinogen Assessment Group
H. Matthew Bills
Acting Director for Monitoring
Systems and Quality Assurance
Office of Research and Development
Robert M. Bruce, Ph.D.
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
John B. Clements, Ph.D.
Environmental Monitoring and Support Laboratory, RTF
Office of Research and Development
Larry Cupitt, Ph.D.
Environmental Res. Lab. (RTF)
Office of Research and Development
Paul E. des Rosiers
Industrial and Extractive Processes Division
Office of Environmental Engineering and Technologies
Linda Erdreich, Ph.D.
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
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James W. Falco, Ph.D.
Office of Health and Environmental Assessment
Exposure Assessment Group
Bruce Gay, Ph.D.
Environmental Sciences Res. Lab. (RTF)
Office of Research and Development
Lester D. Grant, Ph.D.
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Larry L. Hall, Ph.D.
Health Effects Res. Lab. (RTP)
Gary E. Hatch, Ph.D.
Health Effects Research Laboratory
Office of Research and Development
Donna Kuroda
Office of Health and Environmental Assessment
Reproductive Effects Assessment Group
James J. Lichtenberg
Environmental Monitoring and Support Lab. (Cin.)
Office of Research and Development
Steve Lutkenhoff
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Robert McGaughy, Ph.D.
Office of Health and Environmental Assessment
Carcinogen Assessment Group
Raymond Merrill, Ph.D.
Industrial Environmental Res. Lab. (RTP)
Office of Research and Development
Joseph Padgett
Office of Air Quality Planning and Standards
Strategies and Air Standards Division
Nancy Pate, D.V.M.
Office of Air Quality Planning and Standards
Strategies and Air Standards Division
Shabeg Sandhu, Ph.D.
Health Effects Research Lab.
Office of Research and Development
vi
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Robert D. Schonbroo, Ph.D.
Environmental Monitoring Systems Laboratory
Las Vegas, Nevada
Office of Research and Development
Jerry F. Stara, D.V.M.
Office of Health and Environmental Assessment
Environmental Criteria and Assessment Office
Bruce Tichenor, Ph.D.
Industrial Environmental Research Laboratory (RTP)
Office of Research and Development
Peter Voytek, Ph.D.
Office of Health and Environmental Assessment
Reproductive Effects Assessment Group
Herbert Wiser, Ph.D.
Senior Science Advisor
Office of Research and Development
Consultants and/or Reviewers
Julian B. Andelman, Ph.D.
Professor of Chemistry
Graduate School of Public Health
University of Pittsburgh
Pittsburgh, PA
I.W.F. Davidson, Ph.D.
Professor of Pharmacology
Bowman Gray School of Medicine
Wake Forest University
Rudolph J. Jaeger, Ph.D.
Consulting Toxicologist
7 Bogert Place
Westwood, NJ
Edmond J. LaVoie, Ph.D.
Head, Metabolic Biochemistry Section
Naylor Dana Institute for Disease Prevention
American Health Foundation
Valhalla, NY
Richard R. Monson, M.D., S.C.D.
Assoc. Prof, of Epidemiology
School of Public Health
Harvard University
vii
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TABLE OF CONTENTS
1. SUMMARY AND CONCLUSIONS ............................................. 1-1
2 . INTRODUCTION ......................... . .............................. 2-1
3. PHYSICAL AND CHEMICAL PROPERTIES .................................... 3-1
3.1 SYNONYMS AND TRADE NAMES ....................................... 3-1
3.2 STRUCTURAL AND MOLECULAR FORMULAE AND MOLECULAR WEIGHT ......... 3-1
3.3 PHYSICAL PROPERTIES ............................................ 3-1
3.3.1 Description ..................... . ...................... 3-1
3.3.2 Boiling Point ............................. . ............ 3-1
3.3-3 Freezing Point. ........................................ 3-1
3.3.4 Density .. ............................................. 3-2
3.3.5 Refractive Index ...................................... 3-2
3.3.6 Solubility ............................................ 3-2
3.3-7 Volatility ....... . .................................... 3-2
3.3.8 Volatility from Water ........ . ........................ 3-2
3.3.9 Hazard Parameters ..................................... 3-3
3.3.10 Dielectric Constant ................................... 3-3
3.3.11 Thermodynamie Data ................. . .................. 3-3
3.3.12 Viscosity ......................................... .... 3-3
3.3.13 Conversion Factors at 25°C and 760 run pressure ........
3.4 STORAGE AND TRANSPORATION OF THE MONOMER ................ . ..... 3-4
3.5 CHARACTERISTICS OF THE COMMERICAL PRODUCT ..................... 3-5
3.6 PURIFICATION OF THE MONOMER ................................... 3-5
3.7 CHEMICAL REACTIVITY ...... . .................................... 3-5
4. SAMPLING AND ANALYTICAL METHODS ..................................... 4-1
4.1 AIR ......... . .................................................. 4-1
4.1.1 Air Sampling ............ .. ............................. 4-1
4.1.2 Storage of Samples Collected in Solid Sorbent Tubes.... 4-7
4.1.3 Analytical Methods ..................................... 4-7
4.2 WATER [[[ 4-13
4.2.1 Water Sampling ......................... . ............... 4-13
4.2.2 Analytical Methods ..................................... 4-14
4.3 SOIL AND DISPOSAL SITE SAMPLES ................................. 4-17
4.3.1 Sampling. . . ............................................ 4-17
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TABLE OF CONTENTS (cont.)
Page
4.4 MONOMER CONTENT IN POLYMERS AND MONOMER MIGRATION INTO
FOOD-SIMULATING SOLVENTS 4-19
4.4.1 Sample Collection 4-19
4.4.2 Analysis 4-19
4.5 ANALYSIS OF FOODS AND OTHER BIOLOGICAL SAMPLES 4-21
5. SOURCES IN THE ENVIRONMENT 5-1
5.1 SOURCES OF AIR POLLUTION 5-1
5.1.1 Manufacture of Vinylidene Chloride Monomer 5-2
5.1.2 Manufacture of Polymers Containing
Polyvinylidene Chloride 5-3
5.1.3 Processing of Fabrication of Polymers 5-8
5.1.4 Storage, Handling and Transportation
of the Monomer 5-8
5.1.5 Chemical Intermediate Production 5-15
5.1.6 Incineration of Polymers Containing
Polyvinylidene Chloride 5-15
5.2 SOURCES IN WATER 5-16
5.3 SOURCES IN OIL 5-16
5.4 SOURCES IN FOOD 5-17
5.5 SUMMARY OF ENVIRONMENTAL LOSSES 5-17
6. ENVIRONMENTAL FATE, TRANSPORT, AND DISTRIBUTION 6-1
6.1 ATMOSPHERIC FATE, TRANSPORT, AND DISTRIBUTION 6-1
6.1.1 Reaction with Atmospheric Radicals and Ozone 6-1
6.1.2 Atmospheric Photochemical Reactions 6-3
6.1.3 Atmospheric Physical Processes 6-4
6.2 AQUATIC FATE, TRANSPORT, AND BIOACCUMULATION 6-4
6.2.1 Fate and Transport in Water 6-5
6.2.2 Bioaccumulation of Vinylidene Chloride
in Aquatic Organisms 6-8
6.3 FATE, PERSISTENCE, AND TRANSPORT IN SOIL 6-8
7. ENVIRONMENTAL LEVELS AND EXPOSURE 7-1
7.1 AIR 7-1
7.1.1 Environmental Levels 7-1
7.1.2 Exposure 7-9
ix
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TABLE OF CONTENTS (cont.)
7 .2 WATER 7_ 11
7.2.1 Environmental Levels 7-11
7.2.2 Exposure 7-17
7.3 SOIL 7-17
7.4 FOODS 7-18
8 . BIOLOGICAL EFFECTS ON PLANTS AND MICROORGANISMS 8-1
9 . BIOLOGICAL EFFECTS ON AQUATIC ORGANISMS 9-1
9 .1 ACUTE TOXICITY 9-1
9.1.1 Freshwater Fish 9-1
9.1.2 Freshwater Invertebrates 9-1
9.1.3 Marine Fish 9.3
9.1.4 Marine Invertebrates 9-3
9 .2 SUBACUTE TOXICITY 9-3
10 . BIOLOGICAL EFFECTS 10-1
10.1 PHARMACOKINETICS 10-1
10.1.1 Absorption and Distribution 10-1
10.1.2 Metabolism 10-5
10 .1.3 Excretion 10-27
10.1.4 Summary of Pharmacokinetics 10-29
10.2 ACUTE, SUBACUTE, AND CHRONIC TOXICITY 10-31
10.2.1 Acute Exposure 10-31
10.2.2 Subacute and Chronic Exposure 10-48
10.2.3 Summary of Toxicity 10-58
10.3 TERATOGENICITY AND REPRODUCTIVE TOXICITY 10-59
10 .4 MUTAGENICITY 10-69
10.4.1 Mutagenicity in Bacteria ; 10-69
10.4.2 Mutagenicity in Plants and Yeast 10-74
10.4.3 Mutagenicity in Cultured Mammalian Cells 10-75
10.4.4 Mutagenicity In Vivo 10-75
10.4.5 In Vivo DNA Repair 10-76
10 .5 CARCINOGENICITY 10-?8
10.5.1 Animal Studies 10-78
10.5.2 Epidemiologic Studies 10-118
10.5.3 Quantitative Estimation 10-120
11 . REFERENCES 11-1
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LIST OF TABLES
No. Title
4-1 Breakthrough Volume of Vinylidene Chloride as a
Function of Flow Rate, Concentration, and
Relative Humidity .......................................... 4-5
5-1 Monomer Production Facilities in the United States
and their Capacities ............. . ............ . ............ 5-3
5-2 Air Emissions of Vinylidene Chloride During Monomer
Manuf ac ture ...... ..... .......... . .......................... 5-4
5-3 Yearly Consumption of Vinylidene Chloride in Different
Industries. .......... ........ *..... ........................ 5-5
5-4 Polymerization Processes, Products, and Their
Applications. ....... ..... ....... ........................... 5-7
5-5 Polymerization Sites and Type of Polymer Produced ............ 5-9
5-6 Estimated Annual Emissions of Vinylidene Chloride
from Polymer Synthesis ..................................... 5-10
5-7 Major Poly Vinylidene Chloride Processors ..................... 5-11
5-8 Manufacturers of Poly Vinylidene Chloride-Coated
Cellophane ____ . .. ......... . . ..... . ......................... 5-12
5-9 Major Extruders of Polyvinylidene Chloride Film .............. 5-13
5-10 Estimated Emissions from Polyvinylidene Chloride
Processing. ........ ....... . ................................ 5-14
5-11 Summary of Estimated Environmental Losses of
Vinylidene Chloride ............ , ........................... 5-18
7-1 Vinylidene Chloride Concentrations in the Ambient
Air Throughout the Continental U.S ......................... 7-4
7-2 Mean and Median Vinylidene Chloride Concentrations in
U.S. Ambient Air of Different Site Types ................... 7-8
7-3 Estimated Population Residing Near Plant Producing
or Fabricating Monomers and Polymers of Vinylidene
Chloride ........... ... ---- . ................................ 7-10
XI
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LIST OF TABLES (oont.)
No. Title Page
7-4 Industrial Occurrence of Vinylidene Chloride in
Raw Wastewater. 7-13
7-5 Industrial Occurrence of Vinylidene Chloride in
Treated Wastewater 7-14
7-6 Vinylidene Chloride Concentration in a Few Waters
Near Industrial Sites 7-15
7-7 Analysis of Food-Packaging Films for Vinylidene
Chloride „ 7-19
7-8 Migration of Vinylidene Chloride from Saran Films
to Heptane, Corn Oil, and Water at 49 °C. 7-20
9-1 Acute Toxicity Values for Marine and Freshwater Fish
and Invertebrates Exposed to Vinylidene Chloride 9-2
ill
10-1 End-Exposure Body Burdens and Disposition of C
Activity in Rats 72 Hours Following Exposure
to 10 or 200 ppm of C-Vinylidene Chloride
for 6 hours. 10-4
14
10-2 End-Exposure Body Burdens and Disposition of C
Activity in Rats and Mice 72 Hours Following
Inhalation Exposure to 10 ppm C-Vinylidene
Chloride for 6 Hours 10-14
14
10-3 Covalently Bound C-Activity in Tissues 72i[Hours
Following Inhalation Exposure to 10 ppm C
Vinylidene Chloride for 6 Hours 10-15
14
10-4 Relative Proportions of C Urinary Metabolites
After Intragastric Administration of 350 mg/kg
1- C-Vinylidene Chloride or 50 rag/kg C
Monochloroacetic Acid to Male Rats 10-19
14
10-5 Relative Proportions of C Excretory Products
After Intragastric Administration of 50 mg/kg of
1- C-Vinylidene Chloride to Male Rats or Mice 10-20
14
10-6 Metabolism of C-Vinylidene Chloride and Covalent
Binding of C Activity to Rat Hepatic Tissue
After Intragastric Dose of C-Vinylidene
Chloride 10-23
xn
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LIST OF TABLES (cont.)
No. Title
10-7 Metabolism of ^C-Vinylidene Chloride and Covalent
Binding of C Activity to Rat Hepatic Tissue
After Inhalation Exposure to 10 or 200 ppm of
1 C-Vinylidene Chloride 10-24
10-8 Excretion of Radioactivity by Male Rats Given 0.5
rag/kg or 350 rag/kg C-Vinylidene Chloride
Intragastrically, Intravenously, or
Intraperitoneally 10-28
ill
10-9 Half-Lives of Excretion of C-Vinylidene Chloride,
I^COp, and Radiolabeled Urinary Metabolites of
C-Vinylidene Chloride 10-30
10-10 Influence of 24-Hour Fasting on the Effect of Oral
Administration of Vinylidene Chloride (400 mg/kg)
in Corn Oil on Plasma Urea Nitrogen Concentration
in Male Rats 10-37
10-11 Relationships of Plasma Indicators of Kidney Damage
to Dose 24 Hours After Oral Administration of
Vinylidene Chloride to Male Rats 10-38
10-12 Comparison of Prevalence of Histopathologic Effects of
Oral Administration of Vinylidene Chloride (400 mg/kg)
in Male and Female Rat Kidneys 10-40
10-13 Toxicity of 60 ppm Vinylidene Chloride in Male
Mice and Rats 10-49
10-14 Effect on Experimental Animals of Long Term
Inhalation of Vinylidene Chloride 10-51
10-15 Pathologic Effects of Long-Term Ingestion of Vinylidene
Chloride Incorporated in the Drinking Water of
Sprague-Dawley Rats 10-57
10-16 Exposure Levels and Duration of Exposure to Vinylidene
Chloride During Gestation in Mice 10-61
10-17 Number of Animals and Exposure Levels Used to Study
the Tera to genie ity of Vinylidene Chloride 10-63
10-18 Incidence of Fetal Alterations Among Rats Exposed to
Vinylidene Chloride By Inhalation or By Ingestion 10-65
xiii
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LIST OF TABLES (cont.)
No. Title Page
10-19 Incidence of Fetal Malformation Among Litters of
Rabbits Exposed to Vinylidene Chloride 10-66
10-20 Mouse Tissue Mediated Mutagenicity of Vinylidene
Choride in S. typhimurium 10-73
10-21 Results of Carcinogenicity Bioassays of Vinylidene
Chloride 10-79
10-22 Gas Chromatography Analysis of Vinylidene Chloride 10-81
10-23 Experiment DT401: Exposure by Inhalation to Vinylidene
Chloride (VDC) in Air at 150, 100, 50, 25, 10 ppm,
4 Hours Daily, 4-5 Days Weekly, For 52 Weeks 10-81
10-24 Exposure By Inhalation to Vinylidene Chloride (VDC) in
Air at 200, 100, 50, 25, 10 ppm, 4 Hours Daily, 4-5
Days Weekly, For 52 weeks 10-82
10-25 Experiment BT405: Exposure By Inhalation to Vinylidene
Chloride (VDC) in Air at 25 ppm, 4 Hours Daily, 4-5
Days Weekly, For 52 Weeks 10-83
10-26 Experiment BT403: Exposure By Ingestion (Stomach Tube)
to Vinylidene Chloride in Olive Oil at 20, 10, 5 mg/kg
Body Weight, Once Daily 4-5 Days Weekly,
For 52 Weeks 10-84
Experiment BT404: Exposure by Ingestion (Stomach Tube)
to Vinylidene Chloride in Olive Oil at 0.5 mg/kg Body
Weight, Once Daily, 4-5 Days Weekly, for 52 Weeks 10-84
10-27 Experiment BT401: Exposure By Inhalation to Vinylidene
Chloride (VDC) in Air at 150, 100, 50, 25, 10 ppm,
4 Hours Daily, 4-5 Days For 52 Weeks. Results After
137 Weeks (End of Experiment) 10-86
10-28 Experiment BT402: Exposure By Inhalation to Vinylidene
Chloride (VDC) in Air at 200, 100, 50, 25, 10 ppm,
4 Hours Daily, 4-5 Days For 52 Weeks. Results After
121 Weeks (End of Experiment) 10-88
10-29 Statistical Analyses of Survival, Mammary Carcinoma
Incidence and Pulmonary Adenoma Incidence For Male
And Female Swiss Mice in a Carcinogenicity Study
of Vinylidene Chloride 10-9 1
10-30 Tumor Incidence in Rats and Mice Exposed to Vinylidene
Chloride 10-95
xiv
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LIST OF TABLES (cont.)
No. Titles
10-31 Tumor Incidence in Rats and Mice Exposed to Vinylidene
Chloride 10-97
10-32 Vinylidene Chloride: A Chronic Inhalation Toxicity
and Oncogenicity Study in Rats. Cumulative Percent
Mortality for Male Rats 10-99
10-33 Vinylidene Chloride: A Chronic Inhalation Toxicity
and Oncogenicity Study in Rats. Cumulative Percent
Mortality for Female Rats 10-100
10-34 Vinylidene Chloride: A Chronic Inhalation Toxicity
and Oncogenicity Study in Rats. Mean Body Weight for
Male Rats 10-101
10-35 Vinylidene Chloride: A Chronic Inhalation Toxicity
and Oncogenicity Study in Rats. Mean Body Weight for
Female Rats 10-102
10-36 Vinylidene Chloride: A Chronic Inhalation Toxicity
and Oncogenicity Study in Rats. Histopathologic
Diagnosis and Number of Tumors in Female Rats 10-104
10-37 Representative Tissue Specimens Obtained at Necropsy
From All Animals 10-106
10-38 Tumor Incidence Following Ingestion of VDC 10-108
10-39 Tissues Examined For Histologic Changes in the NCI
Bioassay 10-109
10-40 Mean Body Weight Change (Relative to Controls) of Mice
Administered Vinylidene Chloride by Gavage 10-110
10-41 Tumors With Increased Incidence in Rats and Mice, as
Indicated by the Fisher Exact Test or the Cochran-
Armitage Test for Linear Trend 10-112
10-42 Tumor Incidence in Female BDIV Rats Treated with VDC on
Day 17 of Pregnancy, in Their Progeny Treated Weekly
for Life and Controls 10-114
10-43 Estimated Cumulative Dose, Duration of Exposure and Date
of First Exposure Among 138 Individuals Exposed
to Vinylidene Chloride 10-120
xv
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LIST OF TABLES (cont.)
No. Title Page
10-44 Data From Maltoni Inhalation Study on Male Swiss
Mice 10-132
10-45 Relative Carcinogenic Potencies Among 53 Chemicals
Evaluated by the Carcinogen Assessment Group
as Suspect Human Carcinogens 10-135
xvi
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LIST OF FIGURES
No. Title
4-1 Desorption Efficiency vs. Amount Found by GC
Analysis 4-12
10-1 Metabolic Pathways for Vinylidene Chloride 10-6
10-2 Comparisons of Observed LT50 Data for Vinylidene
Chloride with Theoretical Curves Predicted for Two
Different Mechanisms of Toxicity 10-10
10-3 Dose-Response Relationship for Hepatic Glutathione (GSH)
Levels, Total Metabolism of C-Vinylidene Chloride
(VDC), and Covalent Binding of Radioactivity to Hepatic
Macromolecules 10-26
10-4 Dose-Mortality Curves for Administration of Single, Oral
Doses of Vinylidene Chloride Dissolved in Corn Oil to
Fasted Male Rats of Various Sizes 10-44
10-5 Effect of Increasing Concentration of Vinylidene Chloride
on Mortality in Mature Male Rats 10-47
10-6 Histogram Representing the Frequency Distribution of the
Potency Indices of 53 Suspect Carcinogens Evaluated by
the Carcinogen Assessment Group 10-134
xvi i
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1 . SUMMARY AND CONCLUSIONS
Vinylidene chloride is a highly reactive, flammable, clear, colorless
liquid that can produce complex peroxides in the absence of chemical inhibitors
(Hushon and Kornriech, 1978; Wessling and Edwards, 1970). The peroxides are
violently explosive, and formaldehyde, phosgene, and hydrochloric acid are
produced as decomposition products. Vinylidene chloride has a boiling point of
31.6°C at 760 mm Hg and a vapor pressure of 600 mm Hg at 25°C. The solubility of
Vinylidene chloride in water is 2250 mg/1 at 25°C, and the density of the liquid
is 1.2132 g/cm^ (20°C). Vinylidene chloride vapor is 3.34 times as dense as air.
Synonyms for Vinylidene chloride are 1,1-dichloroethene, 1,1-DCE, and
1,1-dichloroethylene. Vinylidene chloride has a molecular weight of 96.95 and a
molecular formula of C2H2C12. The structural formula is given below.
H Cl
\-S
/ \
H Cl
Vinylidene chloride monomer production capacity in the United States is
approximately 178 million pounds per year (Neufeld et al., 1977; Anonymous,
1978). Virtually all of the Vinylidene chloride produced is used in the
production of copolymers with vinyl chloride or acrylonitrile (Hawley, 1977). A
small percentage (4$) of Vinylidene chloride production is used as chemical
intermediates (Neufeld et al., 1977).
The two primary methods that have been used in recent years for the sampling
and analysis of Vinylidene chloride in ambient air are the freeze-trap method and
the sorption onto Tenax-GC method with subsequent analysis of the desorbed
Vinylidene chloride by high resolution gas chromatography with either flame
ionization, electron capture, electrical conductivity or mass spectrometric
1-1
-------
detectors. Both the freeze-trap and Tenax-GC methods of sample collection have
some disadvantages. For example, the freeze-trap method using liquid oxygen
(Singh et al., 1979) is a cumbersome method both for sample collection and
transportation, and the Tenax-GC method (Pellizzari and Bunch, 1979) may suffer
from serious problems of artifact formation.
The two methods commonly used for the analysis of vinylidene chloride in
grab aqueous samples are the static head-space method and the dynamic purge-trap
method. However, for aqueous samples containing very low levels of vinylidene
chloride (e.g., potable water), the dynamic purge-trap is more suitable than the
static head-space method because of the higher sensitivity of the former.
Although gas chromatography with either flame ionization, electron capture,
electrical conductivity or mass spectrometric detectors has been used for the
final quantification of vinylidene chloride by both methods, the electrical
conductivity detector is preferable to other detectors because of its greater
sensitivity and selectivity. The mass spectrometric method is usually used as a
confirmatory technique.
Vinylidene chloride in soil samples has been analyzed by solvent extraction
in sealed vials with subsequent quantification by GC-FID, and using mass spectro-
metry as the confirmatory technique (DeLeon et al., 1980). The analysis of
vinylidene chloride in food wrapping materials, foods, and biological tissues
has been performed either by the static head-space method or by the dynamic
purge-trap method in a manner similar to that employed for aqueous samples.
Because of the high volatility of vinylidene chloride, it is lost to the
atmosphere during industrial manufacturing of the monomer and polymer,and during
storage and handling. The total emission of vinylidene chloride to all media
from these facilities has been estimated to be 1,300,400 pounds per year.
Moreover, vinylidene chloride originally in aqueous solution is likely to
1-2
-------
contribute to air contamination as a result of its high volatility from water
(Billing, 1977).
Under atmospheric smog conditions, the half-life of vinylidene chloride in
air has been determined to be 5 to 12 hours (Billing et al.f 1976). In the
absence of smog conditions, vinylidene chloride may persist in the atmosphere
with a half-life of approximately 2 days (Cupitt, 1980). Volatilization from
aquatic media is probably the most significant fate-determining process for
vinylidene chloride, although the role of biodegradation still remains
uncertain. The half-lives of volatilization of vinylidene chloride from pond,
river, and lake water have been estimated to be 6.1 days, 1.2 days, and 4.2 days,
respectively. The fate of vinylidene chloride in soils has not been evaluated
with certainty. However, it has been concluded from the limited data that both
volatilization and leaching may play significant roles in determining the fate of
this chemical in soils.
The median ambient air level of vinylidene chloride in urban/suburban areas
of the U.S. was estimated to be 20 ng/m^ (averaging time ranged from 1 hour to
1091 days). However, the median concentration value is substantially higher (14
Hg/m ^) for ambient air in the vicinity of point sources of emission. The
estimated daily vinylidene chloride intake from ambient air in urban/suburban
areas through inhalation is 0.4 fig. However, the daily inhalation exposure from
ambient air may be as high as 0.3 mg in the immediate vicinity of point sources.
Vinylidene chloride has been detected in approximately 3% of the total drinking
water supplies in the U.S. at an estimated mean concentration of 0.3 |ig/l and a
concentration range of 0.2 to 0.5 ng/1. For the majority of the U.S. population,
the daily exposure to vinylidene chloride from ingestion of drinking water has
been estimated to be less than 0.6 ng, although the maximum daily exposure in
1-3
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certain communities could exceed 1 ^g. Because of the paucity of data, no
estimate of the dietary intake of vinylidene chloride in the U.S. can be made at
the present time.
Vinylidene chloride is acutely toxic to aquatic animals at exposure
concentrations in the milligrams per liter range. The lowest concentration
reported to be acutely toxic to an aquatic organism is 2.4 mg/1 (U.S. EPA, 1978).
Reported acute and subchronic LCrn values ranged between 11.6 and 250 mg/1 for
aquatic animals. Vinylidene chloride was not acutely toxic to aquatic algae at a
concentration of 712 to 798 mg/1. Vinylidene chloride was, however, toxic to
yeast. No information was found concerning the toxicity of vinylidene chloride
to domestic animals and non-aquatic wildlife.
Vinylidene chloride is readily absorbed by mammals following oral or
inhalation exposure. Vinylidene chloride is metabolized in the liver with a
number of possible reactive intermediates, including an epoxide, being formed.
These reactive intermediate metabolites can react with macromolecules; this is a
characteristic of many chemical carcinogens. The metabolites of vinylidene
chloride produce toxic lesions in the liver and kidneys, with inhibitors of
metabolism providing protection from vinylidene chloride toxicity. The
hepatotoxic effect can be extensive and histological effects can be noted within
2 hours after the onset of exposure. The acute hepatotoxicity of vinylidene
chloride was shown tc be greater than that of any other chloroethylene. The
liver and kidneys remain the target organs for toxic effects regardless of the
route of administration (administration vehicle may influence vinylidene
chloride metabolism and therefore affect the extent of toxicity) or whether
acute, subacute, or chronic exposure occurs.
Vinylidene chloride is mutagenic in bacterial assay systems with positive
results being reported in the Ames assay using S, typhimurium and in a reverse
-------
mutation assay using E. coli. In both assays metabolic activation was employed.
In the Ames assay, the efficiency of activation depended on both the species and
the tissue from which the enzyme system was prepared. There is also some
evidence that vinylidene chloride reacts with the DNA of mouse kidney in vivo
resulting in low levels of unscheduled DNA synthesis. Other assays, such as the
mutation in vitro of cultured Chinese hamster V79 cells and the in_ vivo dominant
lethal assay, have not been able to demonstrate an interaction of vinylidene
chloride with genetic material. Vinylidene chloride has not been adequately
tested to determine whether the positive mutagenic response observed in bacteria
is relevant to nonbacterial systems as well.
Vinylidene chloride has been described as a possible weak teratogen in a
study using rats and mice (Short et al., 1977c). In this study, the levels of
vinylidene chloride used were toxic to the dams which confounded the interpreta-
tion of the results. It was clear, however, that exposure of pregnant rats and
mice to high levels of vinylidene chloride could cause fetotoxicity and adversely
affect the outcome of pregnancy. Preliminary results from another study (Murray
et al., 1978) indicated that vinylidene chloride was not a teratogen in rats or
rabbits. The effect of vinylidene chloride on reproduction and fetal and
neonatal development of rats was tested in a three generation study with six
litter groups being produced (Nitschke et al., 1980). Some toxic effects were
seen in adults, but reproductive capacities were not altered and embryological
and neonatal development were not adversely affected.
A single epidemiological investigation (Ott et al., 1976) has been
performed on a cohort of 138 workers exposed primarily to vinylidene chloride.
From the data presented, the length and extent of exposure could not be
determined for each individual in the study. Thus, it is possible that the
population examined in this study was not adequate. For this cohort there was no
1-5
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significant difference in the results of clinical tests when compared to matched
controls.
There have been eight cancer bioassay studies (Table 10-21) in which
•
vinylidene chloride was administered to rats, mice, or hamsters by either the
inhalation or the oral route. Among these studies, only the interim report of
Maltoni et al. (1977) indicated a possible positive carcinogenic response.
Maltoni et al. (1977) exposed rats by inhalation to 10, 25, 50, and 100 ppm,
mice to 10 and 25 ppm, and hamsters to 25 pp» vinylidene chloride for M
hours/day, 5 days/week for 12 months. After approximately 80 weeks, preliminary
findings of this study were reported on the animals that had died or had palpable
tumors. During this observation period, hamsters developed no tumors. Rats
showed a possible treatment-related incidence of mammary carcinomas, although
the significance of these results was uncertain due to the lack of appropriate
control data presented in the the interim report. In male mice, kidney
carcinomas were observed at the 25 ppm exposure level, while no similar tumors
were seen in the control or exposed female mice or in the male mice of the 10 ppm
exposure group. The authors assert that these tumors were directly related to
the vinylidene chloride treatment; however, it is also possible that these tumors
arose as a result of the non-specific facilitation of tumor development as a
result of the severe chronic toxicity of vinylidene chloride in male mice.
In a personal communication (Norris, 1982) following the completion of this
study, Maltoni stated that the number of mammary carcinomas was not significantly
increased in rats. The kidney tumor incidence was considered to be significantly
elevated; however, Maltoni said that he has not been able to reproduce these
results in other strains of mice. The other seven chronic toxicity studies,
including data from an NCI/NTP (1982) bioassay, have failed to demonstrate a
significant carcinogenic response with vinylidene chloride in rats or mice.
1-6
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Thus only limited data suggest that vinylidene chloride may be an animal
carcinogen. Vinylidene chloride has been shown to be a mutagen in the Ames assay
in the presence of a metabolic activation system, and vinylidene chloride has
produced kidney tumors in male Swiss mice, which appears to be a strain-specific
response (Norris, 1982; Maltoni, 1977). There is some suggestion that the kidney
tumors were produced by a non-specific mechanism as a result of severe kidney
toxicity and accompanying compensatory growth. Other bioassays, however, have
not been able to demonstrate that vinylidene chloride is a carcinogen in rats,
hamsters, or other strains of mice. Although the only available epidemiological
study also showed no difference between the exposed and control groups, the study
population was small and the extent of individual exposure unknown. Applying the
International Agency for Research on Cancer (IARC) criteria for animal studies,
the level of currently available evidence for vinylidene chloride
carcinogenicity would be regarded as limited and insufficient to provide a firm
conclusion regarding its carcinogenic potential in humans.
1-7
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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 vinylidene chloride
under the Clean Air Act. However, the scope of this document has been expanded
to address vinylidene chloride in relation to sectors of the environment outside
of air. It is expected that this document will be able to serve the information
needs of many government agencies and private groups that may be involved in
decision-making activities related to vinylidene chloride.
2-1
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3. PHYSICAL AND CHEMICAL PROPERTIES
The data and the discussion presented below have been obtained from Hushon
and Kornreich (1978) and Wessling and Edwards (1970), except in cases where the
reference is specifically cited.
3.1 SYNONYMS AND TRADE NAMES
Chemical Abstracts Name: 1,1-dichloroethene
CAS No.: 75-35-4
RTECS No.: KV92750
Synonyms: VDC, 1,1-dichloroethene (1,1-DCE), 1,1-dichloroethylene,
vinylidene chloride monomer, vinylidene dichloride
3.2 STRUCTURAL AND MOLECULAR FORMULAE AND MOLECULAR WEIGHT
H /C1
X
H Cl
C2H2C12 Molecular Weight: 96.95
3.3 PHYSICAL PROPERTIES
3.3-1 Description
Vinylidene chloride is a clear, colorless liquid with a characteristic
"sweet" odor.
3.3.2 Boiling Point
31.56°C (at 760 mm Hg)
3-3-3 Freezing Point
-122.5°C
3-1
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3.3.4 Density
Liquid density at 0°C: 1.2517 g/cvr
Liquid density at 20°C: 1.2132 g/cm
Vapor density: 3.34 (air = 1)
Density in saturated air: 2.8 (air =1)
Percent in saturated air: 78^
3.3.5 Refractive Index
n^°: 1.42468
3.3-6 Solubility
Solubility of vinylidene chloride in water: 2250 mg/1 (at 25°C) (Delassus
and Schmidt, 1981)
Solubility of water in vinylidene chloride: 0.35 g/1 (at 25°C)
Vinylidene chloride is soluble in acetone , ethanol , benzene , diethyl ether , and
chloroform.
3.3.7 Volatility
Vapor Pressure (P) in mm Hg: log P = 6.9820 -
. -
mm t + 237.7
(where t = temperature in °C)
Therefore, P = 600 mm Hg at 25°C
3.3.8 Volatility from water
Calculated Henry's law constant (unitless) at 25°C: 7.8 (Dilling, 1977).
Half-life (t, ,-) for evaporation from water at 25°C for a solution depth of 6.5
cm (Dilling, 1977):
Calculated: 20.1 min
Experimental: 27.2 min
The theoretical equation of Dilling (1977) was derived for a specific
hydrodynamic regime and may not be applicable for all waters.
3-2
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3.3-9 Hazard Parameters
Flash point (tag open-cup): 3°F
Flash point (tag closed-cup): -2°F
Autoignition temperature: 1031°F
Explosive limit with air at 28°C
lower: 7.3% by volume
upper: 16.0/6 by volume
3.3.10 Dielectric Constant
4.67 (at 16°C)
3.3.11 Thermodynamic Data
Latent heat of vaporization at 25°C: 6328 cal/mol
Latent heat of vaporization at boiling point: 6257 cal/mol
Latent heat of fusion: 1557 cal/mol
Specific Heat: 0.275 cal/g
Heat of combustion: 261.93 kcal/raol
Heat of polymerization: -18.0 kcal/mol
Heat of formation (liquid monomer): -6 kcal/mol
Heat of formation (gaseous monomer): 0.3 kcal/mol
Heat capacity at 25.15°C (liquid monomer): 26.7^5 cal/mol/degree
Heat capacity at 25.15°C (ideal gas): 16.04 cal/mol/degree
Critical parameters:
Temperature (T ): 222°C
O
Volume (V ): 2.19 cm3/mol
G
Pressure (P ): 51.3 atm
C*
3.3.12 Viscosity
0.3302 cP (centipoise) (at 20°C)
3-3
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3.3.13 Conversion Factors at 25°C and 760 mm pressure:
1 ppm E 3-97 rag/in^ (air)
3.4 STORAGE AND TRANSPORTATION OF THE MONOMER
Without added inhibitors, vinylidene chloride in the presence of air forms a
complex peroxide compound at temperatures as low as -UO°C. The peroxide is
violently explosive. Decomposition products of vinylidene chloride peroxides
are formaldehyde, phosgene, and hydrochloric acid. Since the peroxide is a
polymerization initiator, formation of insoluble polymer in stored vinylidene
chloride monomer may be an indication of peroxide formation. The peroxides are
adsorbed on the precipitated polymer. Any dry composition containing more than
about 15/6 peroxide detonates from a slight mechanical shock or from heat;
therefore, the separation of the polymer from the monomer by filtration,
evaporation, or drying may result in explosion.
Inhibitors are used to prevent formation of peroxides in the monomer. The
most common practice to inhibit peroxide formation is the addition of 200 ppm of
the monomethyl ether of hydroquinone (MEHQ). Other inhibitors include
alkylamines, phenols, and organic sulfur derivatives. Inhibited vinylidene
chloride is shipped under a nitrogen blanket to avoid contact with air and to
prevent the formation of peroxides. In the absence of water, light, and
excessive heat, inhibited vinylidene chloride under a blanket of nitrogen can be
stored indefinitely.
To retard polymerization, uninhibited vinylidene chloride should be kept
away from light and at a temperature below -10°C. Uninhibited vinylidene
chloride can be stored in mild steel, stainless steel, or nickel containers.
Contact with copper and aluminum should be avoided because the acetylinic
impurities in vinylidene chloride may form copper acetylides and aluminum
acetylides, and because aluminum reacts with vinylidene chloride to form
3-4
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aluminum chloroalkyls. Both of these classes of compounds are extremely reactive
and potentially hazardous.
3.5 CHARACTERISTICS OF THE COMMERCIAL PRODUCT
A typical analysis of commercial-grade vinylidene chloride monomer
(excluding inhibitors) is as follows: vinylidene chloride 99.856;
trans- 1 ,2-dichloroethylene, 900 ppm; vinyl chloride, 800 ppm; 1 , 1 , 1-trichloro-
ethane, 150 ppra; cis-1 ,2-dichloroethylene, 10 ppm; and 1 , 1-dichloroethane,
ethylene chloride, and trichloroethylene — each less than 10 ppm.
3.6 PURIFICATION OF THE MONOMER
Vinylidene chloride forms an azeotrope with 6% methanol. Distillation of
the azeotrope, followed by extraction of the methanol with water, is a method of
purification of vinylidene chloride.
3.7 CHEMICAL REACTIVITY
Vinylidene chloride, like other olefins, is expected to undergo addition
reactions. An example of this addition reaction with HC1 is as follows:
CH2=CC12 + HC1 - >• CH
This reaction is used commercially for the production of 1 , 1 , 1-trichloroethane
(methyl chloroform).
The addition reaction of vinylidene chloride with bromine is shown below:
CH2=CC12 + Br2 - »• CH2Br-CCl2Br
The reaction product from bromination of vinylidene chloride was used as a
confirmatory method for the identification and quantification of the parent
compound (Going and Spigarelli, 1977). Other reactions of vinylidene chloride
with thiolate (McKinney et al., 1959) and cysteinate (Francis and Leitch, 1957)
are also known.
In the presence of polymerization initiators, vinylidene chloride undergoes
self -polymerization to form homopolymers , or polymerizes with other compounds —
3-5
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namely, vinyl chloride, alkyl acrylates, and acrylonitrile—to yield copolymers.
Copolymers containing various amounts of vinylidene chloride are used as
packaging films, carpet backing materials, and modacrylic fibers. When compared
with that of other monomers, the reactivity of vinylidene chloride towards
polymerization is considered to be average.
3-6
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H. SAMPLING AND ANALYTICAL METHODS
Several methods are available for the measurement of vinylidene chloride in
air, water, soil and disposal site samples, and polymers, and as migrated monomer
into food-simulating solvents. The analysis of vinylidene chloride in air is
more frequently studied because atmospheric air is probably the most prevalent
medium of vinylidene chloride contamination. Because of its high volatility,
vinylidene chloride lost during its industrial production and processing
primarily enters the atmosphere. Moreover, vinylidene chloride originally
present in aqueous media is likely to contribute significantly to air contamina-
tion as a result of its high volatility from water.
The sampling and analysis of vinylidene chloride in different media are
discussed individually in the following sections.
4.1 AIR
4.1.1 Air Sampling
Three general methods have been used in the past for the collection of
vinylidene chloride in air samples: grab sampling, cold-trapping, and trapping
in sorbent.
Grab samples can be collected in vacuum bottles or in evacuated syringes
(Irish, 1967, cited in Hushon and Kornreich, 1978). The difficulties with this
method of collection are twofold. First, since it does not allow sample precon-
centration, the detection limit of the method is too high to permit detection of
most ambient air levels of vinylidene chloride. Second, the inherent limitation
of any grab sampling method is that samples collected by this method will not
permit the determination of time-weighted average concentrations.
The inability to collect samples representative, of time-weighted average
concentrations with the grab sampling method was overcome by the use of a
-------
personal sampler that used the critical orifice concept (Williams et al., 1976).
The sampler consisted of an evacuated container (<1 torr) equipped with a
critical orifice (2 to 5 ^m diameter). In such a sampler, the gas flow into the
container remains constant as long as a critical flow pattern exists. In order
for this to occur, the internal pressure of the container must remain less than
half the external atmospheric pressure during sampling. Thus, the length of
sampling time depends on both the size of the orifice and the volume of the
sample container. For a container of 100 ml volume equipped with a 2 (j.m orifice,
the critical flow will exist for 22 hours. The use of a critical orifice for time
averaged sampling has been used in source sampling for many years. The major
problem that occurs is blockage of the orifice by particulate matter.
In the cold-trap method, air containing vinylidene chloride is pumped
through a cold-trap maintained at a suitable temperature (Irish, 1967, cited in
Hushon and Kornreich, 1978). In order to avoid sample loss, the temperature of
the cold-trap must be maintained so that the trapped compound has negligible
vapor pressure under the applied pressure. The cold-trap method was used by
Singh et al. (198la,b) for the measurement of ambient air concentrations of
vinylidene chloride. In this method, sample preconcentration was conducted with
a 4-inch long stainless steel tubing packed with 100/120 mesh glass beads and
maintained at liquid Q temperature.
The collection of atmospheric vinylidene chloride by sorbent-trapping has
been used by several investigators. The advantage of the sorbent-trapping method
is that it permits collection of a large volume of air and it concentrates the
compound of interest in a small volume of the sorbent. Both liquid and solid
sorbents have been used. Gronsberg (1975) bubbled air through pyridine to
collect vinylidene chloride. Guillemin et al. (1979) suggested bubbling air
through an impinger containing chilled water for the collection of halogenated
-------
ethylenes; however, the method was not applied for sampling air and the
efficiency of collection was not established. The disadvantage of handling the
impingers in the field and transporting them to the laboratory renders this
method unattractive.
The trapping of vinylidene chloride in a solid sorbent is a more suitable
method for its collection from air samples. Although silica gel was used in the
past (Irish, 1967, cited in Hushon and Kornreich, 1978), sorption on activated
carbon has been used extensively in recent years for the collection of vinylidene
chloride in air. Many investigators (Russell, 1975; Severs and Skory, 1975;
Foerst, 1979) used this method for the monitoring of the higher levels of vinyli-
dene chloride present in workplace atmospheres. In only one investigation (Going
and Spigarelli, 1977) was this method utilized for monitoring ambient air levels
of vinylidene chloride.
The adsorption capacity of vinylidene chloride on activated carbon depends
on the characteristics of the carbon (source, particle size, nature of pretreat-
ment) and the amount used. Generally, for short-term sampling (less than 8
hours) sample tubes containing smaller amounts of carbon are used than for long-
term sampling (about 24 hours). For example, an increase in the amount of a
specific activated charcoal (PCS 12 x 30) from 150 mg to 600 mg allowed an
increase in collection time from 10 to 15 minutes to at least 75 minutes at a flow
rate of 1 liter/minute (Severs and Skory, 1975). The effect of adsorption
capacity on the nature of activated carbon was also demonstrated by these inves-
tigators. Segmentation of the carbon tubes into a front and back section is
usually employed for determination of the breakthrough limit during sample
collection. If the back section retains more than a certain predetermined
percentage of vinylidene chloride, it is taken as an indication that the break-
through limit has been exceeded.
4-3
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The sampling unit usually consists of the following components assembled in
the order given: probe, charcoal tube, critical orifice, and a battery-operated
pump. The tube containing the charcoal is held vertically at a height of 4 to 6
feet from the ground and air is drawn through it at a constant flow rate for a
specified length of time. At the end of sample collection period, the tube is
closed with caps and shipped to the laboratory for analysis.
For a known weight and nature of activated carbon, the breakthrough charac-
teristics during sample collection are dependent on: (1) concentration of
vinylidene chloride in air, (2) flow rate of air through the carbon bed, (3)
relative humidity of air, and (4) presence of other contaminants in the air. The
influence of the first three factors on the breakthrough volume has been
thoroughly studied by Foerst (1979). This investigator sampled vinylidene
chloride through a 100 mg front section and 50 mg back section of MSA-8 charcoal
tubes, and monitored the vinylidene chloride concentration by gas chromato-
graphy-flame ionizatLon detector (GC-FID). The results of his experiments
showing the dependence of breakthrough volume on the three parameters are given
in Table 4-1. It is evident from Table 4-1 that the flow rate and concentration
of vinylidene chloride have relatively less effect on both the breakthrough
volume and loading at breakthrough than do the changes in relative humidity.
The effect of loading on breakthrough volume of Carbosieve B was also
studied by Russell (1975). This investigator stated that, "the quantity of the
compound of interest collected affects the breakthrough volume very slightly. A
pollutant present at 20 ppm will break through at a slightly smaller volume than
when at 1 ppm." Relative humidity, however, has a more profound effect on the
breakthrough characteristics. A change in relative humidity from 17 to 95%
resulted in an almost 90% decrease in both the breakthrough volume and loading
capacity. It should be noted that the findings of Russell (1975) regarding the
-------
TABLE 4-1
Breakthrough Volume of Vinylidene Chloride as a Function
of Flow Rate, Concentration, and Relative Humidity3
Concentration Flow Rate Relative Humidty Breakthrough Loading at
(mg/m3) (I/rain) ($) Volume (1) Breakthrough
Effect of
13.5
13.4
Effect of
114
13.5
Effect of
114
114
Flow Rate
1.00
0.20
Concentration
1.00
1.00
Humidity
0.74
1.00
87
85
95
87
17
95
8.9
6.9
6.0
8.9
56.0
6.0
121
93
684
121
6375
684
aSource: Foerst, 1979
Volume at which the effluent from the charcoal tubes is equal to 5% of the
concentration being sampled.
4-5
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effect of relative humidity on breakthrough volume are consistent with those of
Foerst (1979) as shown in Table 4-1.
It is interesting to point out that the breakthrough studies done by Going
and Spigarelli (1977) employed air with a relative humidity of 39 to 42$ for
sampling vinylidene chloride through a 2 g bed of Fisher activated charcoal.
They concluded that the maximum loading before breakthrough occurs at approxi-
mately 2.5% of the weight of total charcoal bed and that, for vinylidene chloride
concentrations much lower than 10 ppm (as expected in ambient air), sampling can
be performed at 1 liter/minut'e for 24 hours without exceeding the breakthrough
characteristics. While this may be true at 39 to 42JS relative humidity, the
results of Foerst (1979) indicate that the volume and loading characteristics
will drastically change at considerably higher relative humidity. Although the
relative humidity during the collection of samples was not recorded by Going and
Spigarelli (1977), light rain was falling during the collection of some samples,
which indicates that the relative humidity during field sampling was much higher
than 39 to 42?. The field samples collected by Going and Spigarelli (1977) at
high relative humidity at a sampling rate of 1 liter/minute for 24 hours might
have exceeded the breakthrough characteristics; consequently, some of the
results reported by these investigators may be erroneous.
The possibility of using other sorbents for the preconcentration of vinyli-
dene chloride during atmospheric sample collection was studied by Pellizzari and
Bunch (1979). They evaluated three sorbents, namely, charcoal, XAD-2, and Tenax
GC for the evaluation. It was determined by these investigators that while
charcoal and XAD-2 may form traces of halogenated hydrocarbons by in situ reac-
tions of C12, olefins, and other pollutants present in the atmosphere, the
possibility of artifact formation was minimal with Tenax GC. Therefore, Tenax GC
sorbent was used by these investigators for the collection of vinylidene chloride
4-6
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and other volatile organics in the atmosphere. The performance characteristics
of Tenax GC as a sorbent for the collection of organics in ambient air were also
evaluated by Brown and Purnell (1979). It should be mentioned that although
Pellizzari and Bunch (1979) reported minimal artifact formation with Tenax GC,
Singh et al. (1979) observed "serious" artifact formation problems with this
adsorbent. In addition, Singh et al. (1979) encountered "serious difficulties"
in quantitatively adsorbing and desorbing a few specific species with this
sorbent.
4.1.2 Storage of Samples Collected in Solid Sorbent Tubes
The stability of vinylidene chloride collected in charcoal-packed tubes was
studied by a number of investigators (Severs and Skory, 1975; Going and
Spigarelli, 1977; Foerst, 1979). No loss of vinylidene chloride was detected
when the samples in charcoal-packed glass collecting tubes were stored in a
refrigerator (2 to 4°C) for 16 to 21 days (Going and Spigarelli, 1977; Foerst,
1979). Similarly, Tenax-GC cartridges stored in cooled culture tubes showed high
recoveries with halogenated aliphatic compounds (Pellizzari, 1982; Krost et al.,
1982).
4.1.3 Analytical Methods
Vinylidene chloride collected by the grab method can be analyzed by three
different methods: gas chromatography with various detectors, Infra-red (IR)
analysis, and Laser Stark Spectrometry.
In the combined gas chromatography-mass spectrometric (GS-MS) method
applied by Grimsrud and Rasmussen (1975), 20 ml samples were flushed onto a SCOT
OV-101 chromatographic column temperature-programmed from -60°C to 100°C. The
effluents from the GC were passed to a mass spectrometer operated in the single-
ion mode. The identity of vinylidene chloride was established on the basis of
chromatographic retention time and by monitoring ions of masses 61 and 96 in the
4-7
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mass spectrum. The detection limit of the method was 5 ppt; however, the
chromatographic conditions employed could not separate vinylidene chloride from
its isomers cis~ and trans-1,2-dichloroethylene.
A portable IR analyzer was used by Foerst (1979) for continuously monitoring
vinylidene chloride produced in a dynamic flow vapor generator. A Wilks Miran IA
IR analyzer operated in the absorbance mode at a wavelength of 9.1 ^m, with a
cell path length of 20.25 meters, and a slit width of 2 mm was used. The response
time for vinylidene chloride was M seconds. This method, however, is unsuitable
for monitoring vinylidene chloride in atmospheric air for two reasons. First,
the concentration of vinylidene chloride in atmospheric air (on the order of ppt)
is far below the detection limit of the IR analyzer. Second, some of the other
halohydrocarbons present in atmospheric air samples will produce interference in
the vinylidene chloride determinations.
Laser Stark Spectrometry with a 9.6 (Jim line from a C0? IR laser can be used
for the determination of vinylidene chloride; however, the detection limit of
this method with a 40 cm Stark cell is in the ppm range (Sweger and Travis, 1979).
A multipass Stark cell could result in a significant increase in vinylidene
chloride detection sensitivity but is not yet available. Other disadvantages of
this method include interferences from other halohydrocarbons such as Freons,
methyl chloride, methyl fluoride, and vinyl chloride (Sweger and Travis, 1979).
Both the IR and Laser Stark Spectrometry methods have the inherent
capability for continuous monitoring of vinylidene chloride levels in the work-
place where the concentration of vinylidene chloride is considerably higher than
that of atmospheric air and where few interfering substances may be present.
A modified commercial nitrogen oxide analyzer with an ethylene supply
system substituted for the ozone source may also be used for the monitoring of
compounds containing unsaturated double bonds (Hilborn et al., 1976). This
-------
instrument, which utilizes the principle of chemiluminescence, may be useful for
monitoring total unsaturated hydrocarbons in the atmosphere (including vinyli-
dene chloride), but is not suitable for monitoring individual unsaturated hydro-
carbons when they are present in a mixture. In addition to detecting olefinic
compounds, the instrument also responds to compounds containing sulfide and
amine groups (Hilborn et al., 1976).
In one of the more recent methods for determining vinylidene chloride in the
ambient air, Singh et al. (198la,b) collected the samples by cryogenic cooling
(see Section 4.1.1). With this method, the desorption of chemicals from the
cooling trap was accomplished by maintaining the trap at boiling water tempera-
ture and purging it with carrier gas. The desorbed vinylidene chloride was
analyzed by a long (33 foot) packed column and electron capture detector.
When vinylidene chloride was collected in an impinger containing pyridine,
a colorimetric method was used for its quantification (Gronsberg, 1975). The
pyridine solution containing vinylidene chloride was heated with NaOH in a sealed
container and then coupled with barbituric acid or CgH5NH2 in acetic acid to form
a cyanine dye. The dye color intensity was measured with a spectrophotometer.
Neither vinyl chloride nor acrylonitrile interfered with vinylidene chloride
determination. The detection limit of the method (10 mg/nr of air), however,
renders it unsuitable for monitoring vinylidene chloride in ambient air.
Vinylidene chloride collected by bubbling air through water in an impinger
can be analyzed by injecting the aqueous solution onto a steam-modified gas-solid
chromatograph (Guillemin et al., 1979). The details of this technique are given
in Subsection 4.2.2. A Spherosil XOA-400 column operated at an isothermal
temperature of 128°C with a mobile phase containing a mixture of 50 ml/minute N«
gas and 16 ml/minute steam has been successfully used for the separation and
quantification (by flame ionization detectors) of the haloethylenes including
4-9
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vinylidene chloride (Guillemin et al., 1979). By using a 200 |il aqueous solution
injection with this method, 20 ppb vinylidene chloride in water can easily be
detected.
Vinylidene chloride collected by adsorption on solid sorbents is analyzed
by a two-step method. The first step in the analysis is the desorption of
vinylidene chloride from the sorbent. The second step is the separation, identi-
fication, and quantification of the desorbed vinylidene chloride, usually by gas
chromatography employing a flame ionization detector.
Thermal elution and solvent extraction are two commonly used methods for the
desorption of vinylidene chloride from solid sorbents. The thermal desorption
technique was used by several authors (Pellizzari and Bunch, 1979; Bozzelli et
al., 1980). In one thermal desorption method, the sampling tube was reversed
(the end where air entered during sampling was attached to the injection port) to
allow backflushing of the sorbed compounds into the injection port of a GC. With
a 2 x 0.25 inch tube packed with Carbosieve B, Russell (1975) determined the
recovery of vinylidene chloride to be 100$ (+3% standard deviation) when the tube
was heated at 270°C for 5 minutes at a nitrogen flow of 20 ml/minute. When the
dimension of the collection tube was increased to 5.5 by 0.25 inches, however,
Severs and Skory (1975) demonstrated that 10 liters of N? gas were required to
pass through a heated (J»30°C) PCB 12 x 30 activated carbon collection tube to
desorb vinylidene chloride. The desorption efficiency under the above condi-
tions was determined to be 88$.
The sensitivity of the activated carbon adsorption and thermal desorption
technique is approximately 1 ppb for a 1-liter air sample using flame ionization
detection (Russell, 1975). The high temperature required for desorption,
however, may cause some organic compounds to chemically react on the catalytic
surface of the sorption tube, thereby altering their chemical composition. For
4-10
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example, methyl bromide appears to exchange a Br atom for a Cl atom (present as
an impurity in the adsorbent) during thermal desorption from Carbosieve B. Thus,
peaks from both methyl bromide and methyl chloride appear in the chromatogram
(Russell, 1975).
In some of the more recent methods that used Tenax GC as the sorbent, the
thermally desorbed vinylidene chloride was either collected in stainless steel
tubes under pressure (Bozzelli et al., 1980) or the desorbed gas purged with
helium was collected into a liquid nitrogen-cooled nickel capillary trap
(Pellizzari and Bunch, 1979). In both cases, the final separation and analysis
of vinylidene chloride was done by high resolution gas chromatography with flame
ionization detectors.
Desorption by solvent extraction has been used by a few investigators. In
this technique, the adsorbent is added to 1 to 10 ml CSp either at room tempera-
ture in a crimp-sealed vial (Foerst, 1979), or cooled in wet ice (Severs and
Skory, 1975), or in dry ice (Going and Spigarelli, 1977). The effect of CS2 both
at 30°C and at -78°C showed almost the same recovery for desorption times ranging
from 15 to 90 minutes. The CS- desorption efficiency was determined to be 1005&
by Severs and Skory (1975) and by Going and Spigarelli (1977). Foerst (1979),
however, reported that the desorption efficiency was dependent on loading level.
There was a trend towards lower desorption efficiencies at lower loadings. This
dependence of desorption efficiency on loading level is shown in Figure 4-1. The
stability of dilute vinylidene chloride solutions in CS? was studied by Going and
Spigarelli (1977). About 20% loss of vinylidene chloride was observed whether
the sample was stored at -18°C (freezer), 4°C, or 25°C for 7 days. The loss was
much less (about 6%) when the solution was stored for only 4 days at the same
three temperatures. Therefore, the desorbed vinylidene chloride in CS? should be
analyzed within 4 days, regardless of the temperature of storage.
-------
100'
P 90-S
z
LU
8 so
LU
i 70-
o 60-
UJ
o 50-
u.
S 40-
o 3Q i
20
co
LU
Q 10
TTT] — - 1 - 1 — r" I i i i 1 1
10 100
MEASURED SAMPLE SIZE (p. g)
i
i
rrq
1000
» 1 DAY STORAGE
= 7 DAYS STORAGE
Figure 4-1. Desorpcion Efficiency vs. Amount. Found by GC Analysis
(Foerst, 1979)
4-12
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The second step in the analysis of vinylidene chloride by the solvent
extraction method involves injection of the CS2 solution into a gas chromatograph
equipped with a flame ionization detector (FID). The choice of FID is based upon
its compatibility with CS2; that is, CS2 has very little response with FID. A
number of columns including 10$ TCEP, OV-225, 3% Dexsil, Tenax GC, Porapak N, and
Chromosorb 102 were tested (Foerst, 1979). None of these columns were able to
separate vinylidene chloride, vinyl chloride, and CS?. The most suitable column
was found to be Durapak OPN on Porasil C (Foerst, 1979; Going and Spigarelli,
1977). Limited success was attained with 20% DC200 (Severs and Skory, 1975), but
the separation of vinylidene chloride from CS2 solvent was less than ideal with
this packing material.
The confirmation for vinylidene chloride quantified by FID was made both by
mass spectrometry and by bromination of vinylidene chloride (Going and
Spigarelli, 1977). The bromination was performed by reacting vinylidene
chloride with a 500-fold molar excess of Br2 for 30 minutes. The excess Br2 was
removed by 0.5 M NaOH solution. The brominated vinylidene chloride was dried
over anhydrous NapSO^ and analyzed on a 1.5% OV-101 column equipped with an FID.
4.2 WATER
4.2.1 Water Sampling
Grab water samples should be collected in narrow-mouth, glass, screw-cap
bottles with Teflon-faced, silicone rubber, septa cap liners (Federal Register,
1979; Going and Spigarelli, 1977; Bellar and Lichtenberg, 1979;Bellar et al.,
1979). To avoid vinylidene chloride loss, the bottles should be filled to
overflow with water and should be sealed immediately without leaving any head-
space. If the sample contains free or combined chlorine, sodium thiosulfate (10
mg/40 ml for 5 ppm C12) should be added to the water at the time of sample
collection (Federal Register. 1979; Bellar et al., 1979). If left unneutralized,
4-13
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C12 will react with organics in water and will increase the levels of chlorinated
hydrocarbons (Bellar et al., 1974, 1979). The samples collected this way should
be shipped in ice and refrigerated during storage. A sample stored at 4°C was
found to be stable for at least 9 days (Going and Spigarelli, 1977) and samples
similarly stored for up to 27 days were stable (Bellar and Lichtenberg, 1981).
It was suggested that the analysis of the stored samples be performed within 14
days (Federal Register, 1979).
4.2.2 Analytical Methods
Vinylidene chloride in water samples has been analyzed by three different
techniques: direct head-space analysis, direct injection on a steam-modified
gas-solid chromatograph, and by the purge-trap technique.
The direct head-space analysis studied by Piet et al. (1978) has the advan-
tage that no preconcentration and prehandling of the samples are required; there-
fore, systematic error is reduced. The additional advantages of the method are
its good GC separability due to the absence of solvents and its low detection
limit. The method can be applied for tap water, ground water, and surface
waters. In this method, 100 ml N? is bubbled through 1 liter of water at 30°C and
the Np containing the head-space vinylidene chloride is trapped between two
columns of water in a special apparatus (Piet et al., 1978). Up to 500 |il of the
head-space gas could be injected into a gas chromatograph equipped with an
electron capture detector. The GC column used was a wide-bore glass capillary
coated with OV-225 and operated isothermally at 22°C. The detection limit for a
100 (il injection was determined to be 2 |jig/l.
Castello et al. (1982) also used the head-space technique for the determina-
tion of halocarbons in drinking water. In their technique, a 5 ml aliquot of
water was placed in a closed vial, the sample was thermostatically held at 30°C
for 1 hour in a water bath, and 200 \il of the head-space gas was injected into the
4-14
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GC column attached to an electron capture detector. The authors did not provide
the detection limit for vinylidene chloride by this method.
The steam-modified gas-solid chromatography technique, which utilizes a
composite of inert carrier gas and a controlled amount of steam as the mobile
phase, a porous packing material as the stationary phase, and a flame ionization
detector, appears to be a powerful tool for the analysis of aqueous samples
(Guillemin et al., 1979). For the analysis of aqueous samples of haloethylenes
including vinylidene chloride, a Spherosil XOA-MOO column operated isothermally
at 128°C and a mobile phase containing a mixture of 50 ml/minute N2 and 1^
ml/minute steam were sucessfully used. One advantage of this method is that it
allows for direct aqueous injections, thereby eliminating time-consuming and
loss-incurring pretreatment of samples. The other advantage of this technique
over the traditional GC technique is that large amounts of aqueous samples can be
injected onto the column without causing any trouble or artifact on the baseline
stability, even at maximum sensitivity of the detector amplifier (Guillemin et
al., 1979). By using a 200 jil injection with this method, 20 ppb vinylidene
chloride in aqueous samples can easily be detected. The method may not be
applicable to polluted water samples, however, because of GC separation problems
arising from co-contaminants and rapid deterioration of the GC column due to
sorption of impurities.
The purge-trap technique is the most widely applied method for the analysis
of vinylidene chloride in aqueous samples (Bellar et al., 1979; Bellar and
Lichtenberg, 1974, 1979; Going and Spigarelli, 1977; Dowty et al., 1975). This
method is applicable for vinylidene chloride analysis in a diversity of media
including drinking water, on one extreme, and in raw undiluted sewage on the
other (Bellar et al., 1979). This technique has been adopted as the recommended
method for the analysis of vinylidene chloride in water samples (Federal
4-15
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Register, 1979). In the purge-trap technique, the water sample is purged with an
inert gas, such as Np or He, at room temperature. The purged vinylidene chloride
is adsorbed on a trapping column. The trapped vinylidene chloride is thermally
desorbed and passes through an analytical column.
The optimum conditions for purging were determined to be either 38 ml/minute
for 10 minutes (Going and Spigarelli, 1977) or 40 ml/minute for 11 to 15 minutes
(Bellar and Lichtenberg, 1979). Increasing the purge time at the specified flow
rate of inert gas resulted in a decrease in vinylidene chloride recovery (Going
and Spigarelli, 1977). The purged vinylidene chloride was trapped in a Tenax GC
precolumn (Going and Spigarelli, 1977; Bellar et al., 1979). The thermal desorp-
tiori was performed in the backflush mode for 4 minutes at a temperature of 180°C
with an inert gas flow rate of 20-60 ml/minute (Bellar et al., 1979). The
average recovery of vinylidene chloride determined for the entire method by
multiple analyses over 21 days using repeated 5 ml aliquots of 2 [ig/1 aqueous
solution was determined to be Q8% by this purge-trap thermal desorption technique
(Bellar and Lichtenberg, 1979). The sensitivity of this technique is dependent
on the method of detection and the volume of water used for purging. However,
the method is very sensitive because the entire amount of purged vinylidene
chloride is used for a single analysis. A method detection limit (MDL) of 0.003
ug/1 was reported in EPA method 502.1 (Bellar and Lichtenberg, 1981).
Analytical columns packed with four kinds of materials~-0.2/& Carbowax 1500
on 80/100 mesh Carbopack-C (Bellar and Lichtenberg, 1979; Going and Spigarelli,
1977), 1% SP-1000 on 60/80 mesh Carbopack-B (Federal Register, 1979), n-octane on
100/120 mesh Porasil C (Federal Register, 1979), and 10% SF-96 and 1$ Igepal CO
880 capillary column (Dowty et al., 1975)—were found to be best suited for the
separation of vinylidene chloride from co-contaminants. Proper temperature pro-
gramming was found to be necessary for successful separation.
4-16
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Both flame ionization (Dowty et al., 1975; Going and Spigarelli, 1977) and
halogen specific (Bellar et al., 1979; Federal Register, 1979) detectors were
used for the quantification of vinylidene chloride. The flame ionization
detector is somewhat unsuitable, however, because the calibration procedure
needed with the purge-trap method requires the preparation of aqueous standards
by mixing reagent-free water with aliquots of standard solution in water-
miscible solvents, such as methanol. Consequently, the aqueous standards pre-
pared in this manner contain relatively large quantities of the miscible organic
solvent, relative to the compound of interest. While these organic solvents are
purged with relatively low efficiency, their relatively high concentration may
lead to significant interferences with the FID. Therefore, the halogen specific
detector is more suitable for the purge-trap technique.
The confirmation of vinylidene chloride quantified by GC-FID or GC-Hall
detector was made by the GC-MS technique (Bellar et al., 1979; Going and
Spigarelli, 1977; Dowty et al., 1975; Federal Register, 1979). Mass spectro-
metry, either in the specific ion mode (SIM) or in the mass scan mode, was used as
the confirmatory technique. The specific ion mode, however, showed better sensi-
tivity of detection (Bellar et al., 1979).
The purge-trap technique described in the preceding discussions, or
slightly modified methods, have been used by several investigators recently for
the determination of vinylidene chloride in aqueous samples (Pereira and Hughes,
1980); Otson et al., 1982a,b). The precision of the purge-trap method using
GC/MS also has been determined recently by Olynyk et al. (1981).
4.3 SOIL AND DISPOSAL SITE SAMPLES
4.3.1 Sampling
DeLeon et al. (1980) reported taking samples from 30-foot vertical borings
using the split-spoon method. The samples were placed in glass jars,
4-17
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sealed with Teflon-lined screw caps, and shipped in containers maintained at
temperatures between 6°C and 10°C. Upon arrival at the laboratory, the samples
were transferred to a freezer, where they were kept at -20°C until analyzed.
Speis (1980) collected sediment with a methanol rinsed stainless steel spatula in
40 ml vials sealed with teflon baked silcon septa. The vials were filled to
capacity to minimize headspace and stored up to 1 week at wet ice temperatures.
4.3.2 Analysis
DeLeon et al. (1980) solvent extracted the samples in sealed vials with
either n-hexane (for FID quantification) or ri-hexadecane (for MS confirmation)
by mixing them with a vortex for 30 seconds. Tribromomethane (bromoform) was
added as an internal standard for the samples analyzed by FID. The solvent
extracts were quanitified for vinylidene chloride by the GC-FID method and by GC
coupled with MS for confirmation. A temperature-programmed capillary column
coated with SE-52 was employed as the analytical column. This column (27 meters
long) was found to be suitable for the separation of vinylidene chloride from its
isomers cis- and trans-1,2-dichloroethylene. The recoveries of vinylidene
chloride by this method were determined at different levels of contamination. At
vinylidene chloride levels of 10 |ig/g, 100 ng/g, and 300 ng/g, the percent
recoveries were determined to be 110.5 + 3.5 (standard deviation), 86.9 + 8.3,
and 80.2 •+ 3.7, respectively. The detection limit of the method was determined
to be 10 iig/g.
Speis (1980) transferred a weighed portion of sediment into a Hypo vial,
sealed the vial, and injected internal standards. The vials were then placed in
a sand bath at 110°C and purged with an inert gas at 40 ml/min by means of a
*
sharpened stainless steel tube inserted through the septum to the bottom of the
vial. The outlet was passed through a water trap to a Tenax silica gel trap.
Desorption and analysis were virtually identical to EPA method 624. Detection
4-18
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limits were reported to be 5 Hg/kg and recoveries were 67% for a 10 jig spike, 90$
for a 20 \ig spike, 81.1$ for a HO jig spike and 84$ for an 80 (ig spike.
4.4 MONOMER CONTENT IN POLYMERS AND MONOMER MIGRATION INTO FOOD-SIMULATING
SOLVENTS
Saran film is a copolymer of vinyl chloride (15-20$) and vinylidene chloride
(80-85$). It is marketed primarily as household film (0.5 mil thickness) and as
industrial film (2.0 mil thickness). The monomers in saran films used for food
packaging applications have the potential for migration into foods. Therefore it
is important to determine the monomer content in the polymer and the extent of
the monomer's migration into food-simulating solvents.
4.4.1 Sample Collection
The saran films required for analysis of residual monomer or of its migra-
tion into food-simulating solvents can be obtained from the manufacturer or can
be purchased directly at retail stores.
4.4.2 Analysis
The analysis of saran films for the monomer concentration has been accomp-
lished by two methods. In one method (Birkel et al., 1977; Hollifield and
McNeal, 1978), the film was dissolved in tetrahydrofuran (THF) in a teflon-lined
screw cap glass bottle at 70°C. The dissolved polymer containing the monomer was
directly injected into a gas chromatograph equipped with an electron capture
detector for quantification. The analytical column used was packed either with
Chromosorb-102 (Birkel et al., 1977) or Chromosorb-104 (Hollifield and McNeal,
1978). When THF spiked with vinylidene chloride was used, this method yielded
recoveries of 96-102$ through the quantification steps (Birkel et al., 1977).
When a Chromosorb-104 column was used, the detection limit of the method was
determined to be about 1 ppm vinylidene chloride in the polymer (Hollifield and
McNeal, 1978). The confirmatory technique used with gas-solid chromatography-
4-19
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electron capture detectors (GSC-ECD) was GC-MS in the specific ion mode (SIM).
The disadvantage of this method is that the injections of polymer solutions leave
polymer residue in the glass liner of the injection port. If the injection port
liner is not cleaned frequently, the polymers may enter the column and alter its
performance.
This disadvantage in the analysis of vinylidene chloride monomer by solvent
dissolution of the polymer can be overcome by analyzing the monomer content of
the polymer by head-space technique. The additional advantage of the head-space
technique is that the method is free from solvent interference such as that
encountered with the solvent dissolution method. The head-space technique was
used by Going and Spigarelli (1977). In this method, the polymer was crimp-
sealed in a vial (teflon-lined cap) and the vial was heated. The optimum
conditions for heating were determined to be 100°C for 90 minutes. At a higher
temperature (150°C), vinylidene chloride was found to decompose; at lower
temperatures (50°C and 75°C), vinylidene chloride was not released from the
polymer. A 100 |il head-space gas was injected into a Durapak OPN on a 80/100 mesh
Porasil C GC column and the separated vinylidene chloride was quantified by FID.
This technique, however, has its own disadvantage. The calibration of the method
requires standard polymer samples that have known vinylidene chloride concentra-
tion. In the absence of such a standard, it becomes impossible to determine the
recovery of vinylidene chloride from the thermal release procedure used in the
head-space technique.
In order to determine the extent of the migration of vinylidene chloride,
the analysis of food-simulating solvents in contact with polymers was performed
by Hollifield and McNeal (1978). They used three food-simulating solvents—corn
oil, heptane, and water. Strips of saran wraps were placed in 400 ml food-
simulating solvents in a sealed can and stored at 49°C; this temperature is
4-20
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suggested in the Code of Federal Regulations (CFR, 1977, cited in Hollifield and
McNeal, 1978) as the most severe temperature condition to which the food
packaging material is expected to be subjected. After the desired storage time,
20 ml of the solvent was placed in screw cap bottles sealed with teflon-lined
septa. The bottles were heated to 90°C for 30 minutes or more and 1-2 ml of the
head-space gas was withdrawn for analysis. For canned water samples, the head-
space gas at 25°C was analyzed. The quantitative analysis was done by a GC with a
Chromosorb-104 column and an electron capture detector. A gas chromatograph
equipped with the same column and coupled with a mass spectrometer operated in
the selective ion mode was used as a confirmatory analysis. The recovery of
vinylidene chloride after spiking the migration system solution and analyses by
the head-space gas-solid chromatography technique was found to be quantitative
(95 to 1385&). The vinylidene chloride detection limit was determined to be 5-10
ppb in the food-simulating solvents (Hollifield and McNeal, 1978).
A similar head-space technique was employed by Gilbert et al. (1980) for the
determination of vinylidene chloride monomer in packaging films. In this method,
the films cut into narrow strips were put into hypovials and sealed with rubber
septa. The hypovials were heated to 120°C by an air-circulating fan oven for 30
minutes and 1 ml of the head-space gas was removed for analysis by GC with an
electron capture detector.
4.5 ANALYSIS OF FOODS AND OTHER BIOLOGICAL SAMPLES
The analysis of vinylidene chloride in food products in contact with poly-
vinylidene chloride wrappings was performed by Gilbert et al. (1980) by a head-
space method similar to that described for wrapping materials. For cooked meat
and cheese products, the samples were ground under liquid nitrogen to a fine
powder prior to their placements into hypovials. The hypovials were heated to
60°C in a waterbath for a minimum of 90 minutes prior to analysis.
4-21
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The analysis of vinylidene chloride in fish samples and in body tissues was
performed by the purge-trap method similar to that described for aqueous samples
(Lin et al., 1982; Easley et al. ,1981). Lin et al. (1982) used computerized
GC-MS for the determination of vinylidene chloride in fish, and Easley et al.
(1981) used a GC equipped with a Hall electrolytic conductivity detector for
vinylidene chloride determination in body tissues. The approximate limit of
detection for vinylidene chloride in spiked fish samples was determined to be 10
jig/kg by Easley et al. (1981). Lin et al. (1982) determined the absolute
detection limit of 50 jig/kg for the analysis of vinylidene chloride in body
tissues by their method.
Hiatt (1981, 1983) analyzed fish tissue for volatile compounds including
vinylidene chloride by vacuum distillation. Whole fish, stored in dry ice, were
homogenized in a food cutter with added liquid nitrogen to prevent loss of
volatiles. A 10 g fish sample in the sample flask was then heated to 50 °C at 360
torr while immersed in an ultrasonic cleaner bath. Distillation was continued
for 15 min.; the volatiles were trapped at liquid nitrogen temperature. The
contents of the trap were transferred to a DBS coated fused-silica capillary
column (FSCC) (30 m x 0.32 mm, 0.1 \M film thickness) at -99°C, which was then
programmed up to 180°C. Analysis was performed by mass spectrometry. Recovery
was reported to be 71* + 8/1 as opposed to 59 _+ 19/6 for purge and trap of a diluted
sample. FSCC chromatography gave better resolution than packed columns for late
eluting peaks.
4-22
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5. SOURCES IN THE ENVIRONMENT
The purpose of this document is to present available information relevant to
human health effects that could be caused by this substance.
Any information regarding sources, emissions, ambient air concentrations,
and public exposure has been included only to give the reader a preliminary
indication of the potential presence of this substace in the ambient air. While
the available information is presented as accurately as possible, it is acknow-
ledged to be limited and dependent in many instances on assumption rather than
specific data. This information is not intended, nor should it be used, to
support any conclusions regarding risks to public health.
If a review of the health information indicates that the Agency should
consider regulatory action for this substance, a considerable effort will be
undertaken to obtain appropriate information regarding sources, emissions, and
ambient air concentrations. Such data will provide additional information for
drawing regulatory conclusions regarding the extent and significance of public
exosure to this substance.
Vinylidene chloride is a man-made chemical. To date, there is no evidence
that any natural process produces this chemical. The sources of vinylidene
chloride in four different environmental media—air, water, soil, and foods—are
discussed below.
5.1 SOURCES OF AIR POLLUTION
The following operations contribute to the presence of vinylidene chloride
in the air:
(1) Manufacture of vinylidene chloride monomer,
(2) Manufacture of polymers containing polyvinylidene chloride,
5-1
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(3) Processing or fabrication of polyvinylidene homopolymers and
copolymers,
(4) Storage, handling, and transportation of the monomer,
(5) Chemical intermediate production, and
(6) Incineration of polymers containing polyvinylidene chloride.
5.1.1 Manufacture of Vinylidene Chloride Monomer
Vinylidene chloride is manufactured industrially either as a coproduct of
ethyl ene di chloride, produced from the chlorination of ethane or ethyl ene, or by
the dehydrochlorination of 1 , 1 ,2-trichloroethane. The chemical reactions for
the processes are the following:
CH_-CH3 + 3C12 - >• CH2=CC12 + 4HC1
CH2=CH2 + 2C12 - »• CH2=CC12 + 2HC1
CH2C1-CHC12 + NaOH - -»• CH2rCCl2 + NaCl + H20
The current domestic manufacturers of Vinylidene chloride monomer and their
estimated annual capacity are given in Table 5-1.
The Lake Charles facility of PPG Industries, which used 130 million pounds
of Vinylidene chloride annually for captive consumption in the manufacture of
1 , 1 , 1-trichloroethane, now produces 1 , 1 , 1-trichloroethane by a route that does
not utilize Vinylidene chloride (PPG Industries verbal communication, 1980).
The Lake Charles facility of PPG continues to produce Vinylidene chloride,
however, for sale in the merchant market.
It is reported that the Dow facility at Freeport produces about two-thirds
of its total annual capacity (Neufeld et al., 1977). Dow captively consumes
about 85$ of the total Vinylidene chloride it manufactures annually. The balance
is shipped to its other polymer-producing facilities or sold to the merchant
market .
5-2
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Vinylidene chloride is emitted to the air during the manufacture of the
monomer. The air emission factors, that is, the fraction of vinylidene chloride
lost to the air during its manufacture, can be estimated from material balance.
TABLE 5-1
Monomer Production Facilities in the United States and Their Capacities3
Estimated Capacity
Manufacturer Location (million Ib/yr)
PPG Industries Lake Charles, LA 78b
Dow Chemical Freeport, TX and
Plaquemine, LA 95-100
aSource: Neufeld et al., 1977
^Figure obtained from Anonymous, 1978
These air emission factors for vinylidene chloride manufacturing processes
are given by A.D. Little (1976, cited in Going and Spigarelli, 1977). Based on
these values and the estimated production (estimated as 80% of capacity) of
vinylidene chloride monomer, the annual emission rates derived are shown in Table
5-2.
The estimated emission of ^50,000 pounds/year is considerably lower than
the figure given by other authors (Hushon and Kornreich, 1978). The difference
is due mainly to PPG Industries' no longer producing 1,1,1-trichloroethane from
vinylidene chloride. However, PPG still produces vinylidene chloride for sale to
polymer producing facilities.
5.1.2 Manufacture of Polymers Containing Polyvinylidene Chloride
The two primary uses of vinylidene chloride are in the manufacture of
polymers and chemical intermediates. The breakdown of vinylidene chloride
consumption in different industrial uses is given in Table 5-3.
5-3
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TABLE 5-2
Air Emissions of Vinylidene Chloride During Monomer Manufacture
Producer
Location
Air Emission Factor
(emission in lb/100
Ib monomer produced)
Annual Emission
(thousands of Ib/yr)
PPG Industries
Dow Chemical
Lake Charles, LA
Freeport, TX and
Plaquemine, LA
0.10
0.118
62
384
5-U
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TABLE 5-3
Yearly Consumption of Vinylidene Chloride in Different Industries3
Amount Consumed
Industry (million Ib/yr) Percent of Total
Polymers
Domestic Use
Export
Chemical Intermediate
TOTAL
108-115
20
5
133-1^0
81*
15*
4*
100*
aSource: Neufeld et al., 1977
5-5
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It can be seen from Table 5-3 that except for a small application as a
chemical intermediate, most of the vinylidene chloride is consumed domestically
for the production of polymers. Because of its excellent fire and barrier
resistance properties, vinylidene chloride polymer has been used in the manufac-
ture of copolymers with other monomers. In general, copolymers that contain a
high percentage of vinylidene chloride (70-95$) are used for the barrier resis-
tance characteristic, and copolymers with a lower percentage of vinylidene
chloride (10-40$) are used for fire retardant properties. The three different
polymerization processes used industrially for the production of polymeric
materials and the uses of these polymers are shown in Table 5-4.
Emulsion latexes used as barrier coatings usually contain 70 to 95% vinyli-
dene chloride copolymerized with a variety of other monomers such as vinyl
chloride, acrylic acid, and acrylonitrile. These copolymers have a unique and
excellent barrier resistance to gases, water vapor, organic vapors, and odors.
The speciality latexes obtained by copolymerization of 10 to 40$ vinylidene
chloride and butadiene-styrene have excellent fire retardant properties and are
used as carpet backing materials.
The solid resins obtained by converting emulsion or suspension latexes to
the powdered resin may contain different amounts of vinylidene chloride. As in
the case of latexes, the characteristics of the copolymer are strongly influenced
by the vinylidene chloride content. Solid resins are used for coating cellophane
and extrusion into film or for manufacturing multilayer laminates.
Solution polymerization of 10 to 30$ vinylidene chloride with acrylonitrile
produces modacrylic fibers. The modacrylics are produced solely for the flame
retardant characteristics they impart to sleepwear fabric, drapery fabric, and
automobile upholstery.
5-6
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TABLE 5-M
Polymerization Processes, Products, and Their Applications'"
Process
Product
Application
Emulsion Polymerization
Suspension Polymerization
I Emulsion Latex
^Speciality Latex
Resin
Solution Polymerization.
Fiber -r
Barrier coating
Carpet backing
Barrier coating on
I multilayer laminate
/ Molded plastics
I Extruding films and
pipes
Modacrylic fibers
Source: Neufeld et al., 1977
5-7
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The major plant site for vinylidene chloride polymerization and the type of
polymer produced by these facilities are shown in Table 5-5.
The estimated annual emissions of vinylidene chloride from polymer
synthesis are given in Table 5-6.
5.1.3 Processing or Fabrication of Polymers
The fabrication processes include coating of paper, glassine, paper
products, cellophane, and plastic films. Fabrication processes also include
extrusion of films and monofilament fibers and molding operations.
The major polyvinylidene chloride latex users for miscellaneous fabrication
processes are given in Tables 5-7, 5-8, and 5-9.
The estimated annual emission rate of vinylidene chloride in the processing
of polyvinylidene chloride polymers is given in Table 5-10.
5.1.4 Storage, Handling, and Transportation of the Monomer
Vinylidene chloride monomer is shipped from the production sites to the user
site in bulk railroad tank cars or tank trucks. A small unspecified quantity is
shipped in drums (Neufeld et al., 1977). Approximately 90 million pounds of
vinylidene chloride is transported annually in various ways. Vinylidene
chloride emissions can be expected to occur during storage, transfer, and filling
operations. It has been estimated that of the total vinylidene chloride loss
during its manufacture, subsequent polymerization, and processing, 25% takes
place during storage, transfer, and handling and 75% takes place during
processing (Neufeld et al., 1977). Since only half of the total vinylidene
chloride manufactured is transported to other locations (the other half is
captively used), this half is solely responsible for losses related to storage,
transportation, and handling. The total vinylidene chloride loss during
manufacture, subsequent polymerization, and processing adds up to 1,160,000
5-8
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TABLE 5-5
Polymerization Sites and Type of Polymer Produced0
Manufacturer
Location
Polymer Type
Primary Usage
Dow Chemical
W.R. Grace
Morton Chemicals
A.E. Staley
Rohm and Haas
GAP
Midland, MI
Dalton, GA
Owensburg, KY
Ringwood, IL
Lemont, IL
Knoxville, TN
Chattanooga, TN
Reichhold
Chemicals
Cheswold, DE
National Starch Meridosia, IL
Eastman Kingsport, TN
Monsanto Decatur, AL
American Cyanamid Pensacola, FL
DuPont Circleville, OH
Suspension latex
Emulsion latex
Solid resin
Speciality latex
Emulsion latex
Speciality latex
Emulsion latex
Emulsion latex
Emulsion latex
Emulsion latex
Speciality latex
Emulsion latex
Speciality latex
Emulsion latex
Speciality latex
Modacrylics
Modacrylics
Modacrylics
Solid resin
Barrier coating
Barrier coating
Barrier coating
Carpet backing
Barrier coating
Carpet backing
Barrier coating
Barrier coating
Barrier coating
Barrier coating
Carpet backing
Barrier coating
Carpet backing
Barrier coating
Carpet backing
Fiber
Fiber
Fiber
Barrier coating
Source: Neufeld et al., 1977
5-9
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TABLE 5-6
Estimated Annual Emissions of Vinylidene Chloride from Polymer Synthesis'
Emission Factor
(lb/100 Ib vinylidene
Polymer chloride polymerized)
Barrier-coating latex 0.60
Latex for miscellaneous coatings 1
Synthetic fibers 1
Resin for cellophane coating 0.7
Extrusion resin (emulsion) 0.13
Extrusion resin (suspension) 0.26
TOTAL
aSource: A.D. Little, Inc., 1976
Annual Emissions
(thousands of Ib/yr
120
150
160
182
27
40
679
5-10
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TABLE 5-7
Major Polyvinylidene Chloride Processorsc
Company
Plant Location
Barrier-Coating on Paper and Glassine
Deerfield-Reed Corporation
American Bag and Paper
Consolidated Paper
Crown Zellerbach
Daniels
Diversa-Pax
Dixico
DuPont
Milprint
Philip Morris
Rexham
St. Regis
Thilmany
Chase Bag Company
Print Pak
Barrier-Coating on Paperboard
Gordon Carton
Green Bay Packaging
Interstate Folding Box
Michigan Carton Company
Olin Kraft
Zumbril
Barrier-Coating on Plastic
DuPont
Cryovac
Minnesota Mining and Manufacturing
Allied Chemical Corporation
Hercules
Milprint
Cryovac
Bemis
American Can Company
Standard Packaging
Sealed Air Corporation
Clifton, NJ
Philadelphia, PA
Wisconsin Falls, WI
Portland, OR
Rhinelander, WI
St. Petersburgh, FL
Dallas, TX
Circleville, OH
Milwaukee, WI
Nicholasville, KY
Memphis, TN
Rhinelander, WI
Kaukauna, WI
Hudson Falls, NY
Atlanta, GA
Baltimore, MD
Green Bay, WI
Middletown, OH
Battle Creek, MI
W. Monroe, LA
Cincinnati, OH
Circleville, OH
Simpsonville, SC
Irvington, NJ
Decatur, AL
Pittsville, PA
Convington, VA
Milwaukee, WI
Simpsonville, SC
New London, WI
Neenah, WI
Clifton, NJ
Fairlawn, NJ
Source: Neufeld et al., 1977
5-11
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TABLE 5-8
Manufacturers of Polyvinylidene Chloride-Coated Cellophane3
Manufacturer Share of Market Location
DuPont 40$ Richmond, VA
Clinton, IA
Tecumseh, KS
FMC 35$ Fredericksburg, VA
Olin 25% Pisgah Forrest, NC
Covington, VA
aSource: Neufeld et al., 1977; A.D. Little, Inc., 1976
5-12
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TABLE 5-9
Major Extruders of Polyvinylidene Chloride Film0
Manufacturer
Plant Location
Cryovac
Oscar Mayer
Dow Chemical
American Can Company
Union Carbide Corporation
Amtech, Inc.
Simpsonville, SC
Cedar Rapids, IA
Camarillo, CA
Iowa Park, TX
Madison, WI
Chicago, IL
Davenport, IA
Philadelphia, PA
Nashville, TN
Vernon, CA
Sherman, TX
Midland, MI
Cleveland, OH
Centerville, IA
Odenton, MO
Source: Neufeld et al., 1977; A.D. Little, Inc., 1976
5This plant extrudes monofilament, which is used primarily as filter cloth
in the chemical industry.
5-13
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TABLE 5-10
Estimated Emissions from Polyvinylidene Chloride Processingc
Process
Emission Factor
(lb/100 Ib
Polymer Used)
Annual Vinylidene
Chloride Emissions
(Ib/yr)
Coating cellophane
Coating plastics, paper
and glass ine
Extrusion
Miscellaneous coating
TOTAL
0.06
0.03
0.001
0.04
1,560
16,380
430
12,000
30,370
Source: A.D. Little, Inc., 1976
5-14
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pounds per year. Half of this figure has been used in the following calculation
to determine the losses during storage, transportation, and handling:
1,160,000 x 0.5 x 25% = x
x = 145,000 Ib/yr
This annual loss of 145,000 pounds during storage, handling, and transpor-
tation does not include any additional losses due to accidental spillage during
transportation.
5.1.5 Chemical Intermediate Production
The primary chemical intermediate that is manufactured from vinylidene
chloride is chloroacetyl chloride. Since PPG Industries, the sole manufacturer
of 1,1,1-trichloroethane from, vinylidene chloride, no longer uses this process
for 1,1,1-trichloroethane manufacture, no vinylidene chloride emissions can be
expected from this intermediate. Chloroacetyl chloride is captively used by Dow
Chemical Company and no losses of vinylidene chloride to the environment are
reported during its manufacture (Neufeld et al., 1977). The purified chloro-
acetyl chloride used as an intermediate for further chemical reaction is reported
to be free of vinylidene chloride contamination (Neufeld et al., 1977). Thus,
its usage cannot be a source of vinylidene chloride in air.
5.1.6 Incineration of Polymers Containing Polyvinylidene Chloride
Over 95% of vinylidene chloride polymers are used for packaging, in the
manufacture of textile fibers, or as a flame-retardant carpet backing (Neufeld et
al., 1977). All these consumable items are disposed of at the end of their
useful life. The ultimate disposal operation is either incineration or placement
in a solid waste landfill. If incineration is used as the disposal process, it
may contribute to small amounts of vinylidene chloride in air. The residual
monomer in the polymer may be released into the air during heating. The decom-
position of polymer to monomer is not likely to occur. The products of thermal
5-15
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degradation will depend primarily on the heating temperature. Thermal degrada-
tion of poly vinyl iclene chloride has been studied in detail by Wessling and
Edwards (1970). These investigators found that polyvinylidene chloride begins
to decompose at about 125°C., At very high temperatures, graphitization of
carbonaceous residue takes place. On pyrolysis, polyvinylidene chloride yields
70$ hydrogen chloride, 26% carbonaceous ash, and H% volatile hydrocarbons
consisting of benzene, chlorobenzene, and three dichlorobenzenes (O'Mara et al.f
1973). The thermal decomposition is also catalyzed by various metal salts. The
mechanism of thermal decomposition of polyvinylidene chloride was also studied
by Ballistreri et al. (1981). Currently an estimate of the amount of vinylidene
chloride released to the air from incineration is not available. However,
incineration Ls not expected to be a significant source of vinylidene chloride in
air.
5.2 SOURCES IN WATER
The only industrial operation that produces liquid effluents containing
vinylidene chloride monomer is reported to be the polymerization operation
(Neufeld et al., 1977). The two main sources of vinylidene chloride loss during
polymerization operations are waste polymer sludges arising from reactor
cleaning during normal operation or from products containing bad batches, and
wastewater from condensation of gases during stripping operations. Neufeld et
al. (1977) estimate that approximately ^100 pounds per year of vinylidene
chloride loss can be attributed to this source.
A small but unknown amount of vinylidene chloride may originate in water
from the cleaning of rugs backed with speciality latexes.
5.3 SOURCES IN SOIL
The disposal of consumer products that contain processed vinylidene
chloride polymers (1 to 3 ppm residual vinylidene chloride monomer) by municipal
5-16
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solid waste disposal operations may result in soil contamination. Neufeld et al.
(1977) estimate that the maximum potential quantity of vinylidene chloride
monomer in solid wastes would be 180 pounds per year.
5.4 SOURCES IN FOODS
The three potential sources of vinylidene chloride contamination in foods
are as follows: (1) migration of monomer from the polymeric wrapping materials to
foods, (2) contaminated drinking water, (3) edible aquatic foods that have
bioconcentrated vinylidene chloride from polluted water. All these are
secondary sources, however, whose primary sources (i.e., polymers and water)
have already been discussed.
5.5 SUMMARY OF ENVIRONMENTAL LOSSES
This section presents estimates of the amount of vinylidene chloride
monomer lost to the atmosphere, to water streams, or to soils. The losses are
summarized in Table 5-11.
5-17
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TABLE 5-11
Summary of Estimated Environmental Losses of Vinylidene Chloride
Vinylidene Chloride Contamination (Ib/yr)
Source
Monomer Synthesis
Polymer Synthesis
Polymer Fabrication
Air
446,000
679,000
30,400
Water
0
4100
0
Soil
0
0
0
Storage, Handling, and
Transportation 145,000 ' Oa 0
Chemical Intermediate
Production 00 0
Disposal of Polymers 0 0 180
TOTAL 1,300,400 4100 180
aSome water and soil contamination may arise from this source.
Incineration of polymers may contaminate air with an undeterminable amount.
5-18
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6. ENVIRONMENTAL FATE, TRANSPORT, AND DISTRIBUTION
6.1 ATMOSPHERIC FATE, TRANSPORT, AND DISTRIBUTION
6.1.1 Reaction with Atmospheric Radicals and Ozone
Very little information is available on this subject. Upon entering the
atmosphere, vinylidene chloride, like other chloro-olefin vapors, may interact
with 0», OH-, and R02" radicals, and with ozone already present in the
atmosphere. In addition, chloro-olefins in the atmosphere will generate
chlorine atoms, which may interact with the parent molecules. The gas phase
oxidation of halo-olefins at room temperature initiated by Cl atoms, 0[^P]
radicals, and 0., has been reviewed (Sanhueza et al., 1976; Heicklen et al.,
1975). In the presence of 02, the oxidation of vinylidene chloride by chlorine
atoms produced 98$ chloroacetyl chloride, and about 2% phosgene and CO as the
reaction products. The reaction of vinylidene chloride with 0[-*P] in the
presence of 0? produced CO, chloroacetyl chloride, polymer, and another
unidentified compound. The rate of 0[3P] attack on vinylidene chloride is the
same as the rate of 0[3P] attack on C^ (Sanhueza, 1976; Heicklen et al., 1975);
however, the relative reactivity of 0[3P] with vinylidene chloride (1.0) in the
gas phase at room temperature is higher than the reactivity of Cl atoms with
vinylidene chloride (0.72) under the same conditions (Heicklen et al., 1975).
Based on a reaction rate constant of 7.8 x 10~ 3 cm3 molecule" sec" (Graedel,
1978) for 0[3P] reaction with vinylidene chloride (same as C Hj, reaction rate)
o 4
and the concentration of 0[ P] in the ambient atmosphere as 5 x 10 molecules
cm"3 (Cupitt, 1980), the half-life for this reaction can be estimated to be
approximately 206 days.
In the absence of Op, 0[3p] forms the same reaction products it produces in
the presence of 0?; however, the quantam yield for carbon monoxide formation is
6-1
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reduced from 0.78 in the presence of 0~ to 0.35 in the absence of Op (Heicklen et
al., 1975).
The main products of 0 interaction with vinylidene chloride in the vapor
phase at 25°C are phosgene and formaldehyde (Sanhueza et al., 1976; Heicklen et
al., 1975; Brown et al., 1975). The formation of chloroacetyl chloride, CO, C0_,
HC1, and possibly water has also been reported (Hull et al., 1973). The yield of
phosgene is always either comparable to or greater than the yield of formic acid
(Heicklen et al., 1975). The 0^ reaction in the presence of 0~ is, however, too
slow to be important in the urban atmosphere (Sanhueza et al., 1976; Heicklen et
al., 1975). Based on a reaction rate constant of 4 x 10 cnr molecule" sec"
(Cupitt, 1980) and the concentration of ozone in the ambient atmosphere at 1 x
12 3
10 molecule em~J (Cupitt, 1980), the half-life for ozone reaction with
vinylidene chloride in the atmosphere can be calculated to be approximately 201
days.
The interaction of RO and OH radicals with vinylidene chloride was reported
by Brown et al. (1975). The formation of phosgene and formaldehyde was reported
with both EO and OH radicals. The rate constant for the oxidation with OH
12 ^ 11
radicals was reported to be ii x 10 cnr molecule" sec" (Cupitt, 1980). If
-6
the concentration of OH radicals in the ambient atmosphere is assumed to be 10
radicals cm"-' (Cupitt, 1980), the half-life for this reaction can be calculated
to be 2 days. The half-life for peroxy radicals reaction with vinylidene
chloride in the atmosphere has been reported to be about 22 years by Brown et al.
(1975).
It can be concluded from the above discussion that the most significant
oxidation reaction of vinylidene chloride in the ambient atmosphere is its
reaction with hydroxyl radicals. The half-life for this reaction has been
estimated to be about 2 days.
6-2
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6.1.2 Atmospheric Photochemical Reactions
Gay et al. (1976) studied the photoreaction of vinylidene chloride in air in
the presence of nitrogen dioxide with ultraviolet light. At a concentration of
4.85 ppm and in the presence of 2.26 ppm N02, vinylidene chloride was found to
decompose rapidly—8356 decomposition had taken place within 140 minutes. The
reaction products identified were HCOOH, HC1, CO, HCHO, 0 , COC12, chloroacetyl
chloride, formyl chloride, and nitric acid.
The photolysis of vinylidene chloride under simulated atmospheric
conditions was also studied by Billing et al. (1976). In the presence of 5 ppm NO
and at a relative humidity of 3555, 10 ppm vinylidene underwent photolysis at
wavelengths greater than 290 nm, and disappeared with a half-life of 2.1 hours.
Addition of cyclohexane was found to retard the photodecomposition rate of
vinylidene chloride. Although vinylidene chloride was not tested, reaction of a
closely related halo-olefin (trichloroethene) showed similar reactivity with
ozone and N02 as with NO.
The above experiment of Billing et al. (1976) was conducted at ultraviolet
light intensity of about 2.6 times that of natural sunlight at noon on a summer
day in Freeport, TX. Therefore, the estimated half-life of vinylidene chloride
under bright sunlight and in the presence of NO is approximately 5 to 12 hours
(Billing et al., 1976). In the absence of NO, the half-life for photodecom-
position of vinylidene chloride under bright sunlight may increase five-fold.
This estimate is based on the experimental half-life of a closely-related halo-
olefin (trichloroethene) in the presence and absence of NO as determined by
Billing et al. (1976). Therefore, it is estimated that vinylidene chloride will
photodecompose under bright sunlight with a half-life of one to three days.
Pearson and McConnell (1975), on the other hand, exposed quartz flasks containing
halogenated aliphatic compounds in air to incident radiations from the sun and
6-3
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estimated the tropospheric photolytic half-life of 56 days for vinylidene
chloride. Although the experiments of Pearson and McConnell (1975) were not
adequately controlled in terms of air composition, temperature, and light
intensity, it is difficult to explain the large discrepency in the photolytic
half-life of vinylidene chloride between this investigation and the work of
Billing et al. (1976). That the photolysis of vinylidene chloride in the
atmosphere is a possibility has also been indicated (but no quantitative rate
data given) by Cupitt (1980). In conclusion, it can be predicted that photolysis
of vinylidene chloride in the atmosphere may be competitive with its reaction
involving hydroxyl radicals. The half-life of vinylidene chloride in air under
atmospheric smog conditions (air containing NO , 0 , etc.) may be further reduced
X 3
due to its greater photochemical reactivity in the presence of NO and 0 .
x j
6.1.3 Atmospheric Physical Processes
Recently, the atmospheric fate of vinylidene chloride under physical and
chemical removal processes was studied by Cupitt (1980). The atmospheric half-
life of vinylidene chloride removal by rain droplets was estimated to be 110,000
years. The lifetime of vinylidene chloride removal by adsorption onto aerosol
particles was estimated to be 5.3 x 10 days. Therefore, the possibility of
vinylidene chloride removal by these two physical removal processes is remote„
6.2 AQUATIC FATE, TRANSPORT, AND BIOACCUMULATION
Very little experimental data pertaining to the various fate processes of
this chemical in aquatic media and its bioaccumulation potential in aquatic
organisms are available in the literature. In the following discussion the
experimental data whenever available have been used to predict the fate of
vinylidene chloride in aquatic media. In the absence of such data, the
prediction of the fate has been based on calculated or estimated data using
empirical or theoretical methods. Extreme caution should be exercised in
6-4
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interpreting the fate of a chemical based solely on calculated or estimated data.
This reservation concerning the estimated data is justified by the large
discrepencies observed in a few instances between the experimental and estimated
data where both data are available.
6.2.1 Fate and Transport in Water
The photolysis and hydrolysis of vinylidene chloride in natural aquatic
media are probably not significant processes (Mabey et al., 1981). No
experimental data on the possibility of oxidation of vinylidene chloride by
singlet oxygen (0P) and peroxy radicals present in aquatic media could be found.
However, based on the experimental data from closely related analogues (e.g.,
trichloroethene and tetrachloroethene), Callahan et al. (1979) concluded that
vinylidene chloride is "more amenable" to oxidation in aquatic media than both
trichloroethene and tetrachloroethene. From the calculated (based on
R — 1 1
structure/activity relationship) rate constant values of less than 10 M~ hr~
and 3 M~ hr~ (Mabey et al., 1981) for singlet oxygen and peroxy radical
reactions, respectively, with vinylidene chloride in aquatic media and the
-12 -9
estimated concentrations of 10 M and 10 ^ M for singlet oxygen and proxy
radicals in aquatic media (Mill and Mabey, 1980), the oxidation of vinylidene
chloride by either process can be calculated to be environmentally
insignificant.
The biodegradability of vinylidene chloride was studied by Tabak et al.
(1981) by the static-culture flask-screening procedure with settled domestic
wastewater as microbial inoculum. These authors reported a significant
degradation of vinylidene chloride with the unacclimated sludge. At 5 mg/1
initial concentration, 7856 of the compound biodegraded in 7 days of incubation at
25°C. The biodegradation was only 45? when the initial concentration was 10 mg/1
and the other conditions were the same. Similarly, it has been reported by
6-5
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Patterson and Kodukala (1981) that activated sludge treatment of a municipal
wastewater at an influent vinylidene chloride level of 0.04 mg/1 resulted in 9756
removal of the compound. It can be concluded from these experimental results
that vinylidene chloride may undergo biodegradation in ambient aquatic media.
However, until the role of biodegradation of this compound in natural aquatic
media is defined, it is not possible to predict the significance of this process
in determining its fate in aquatic media. It should be mentioned that on the
basis of limited experimental evidence on related chloroaliphatics, Callahan et
al. (1979) have concluded that vinylidene chloride probably biodegrades in
aquatic media at a slow rate.
The transport of vinylidene chloride from aquatic media to the atmosphere
through volatilization appears to be its primary transport process (Callahan et
al., 1979). The evaporation characteristics of vinylidene chloride in water were
studied by Dilling (1977). When a 1 mg/1 aqueous solution of 6.5 cm depth was
stirred at 200 rpm in still air (<0.2 mph air current) at 25°C, the half-life for
evaporation was found to be 27.2 minutes. The measured half-life for evaporation
of vinylidene chloride from dilute aqueous solution was reasonably close to the
calculated value of 20.1 minutes (Dilling, 1977) based on liquid and vapor-phase
mass transfer coefficients for exchange between the water body and the
atmosphere. However, this agreement is somewhat fortuitous since the calculated
value depends on the exchange constants, whereas the experimental values depend
on the stirring rate, air current, and other factors (Dilling, 1977).
The half-life for the evaporation of vinylidene chloride from pond, river,
and lake waters can also be calculated from the reaeration rate constant of this
compound. Assuming the reaeration rate ratios (K C/K °) of 0.601 (calculated
from diffusion coefficients) (Mabey et al., 1981) for vinylidene chloride, and
the values for oxygen reaeration rate constants of 0.19 day" , 0.96 day" , and
6-6
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0.24 day"1 for pond, river, and lake waters, respectively (Mabey et al., 1981),
the half-lives for evaporation can be calculated to be 6.1 days, 1.2 days, and
4.2 days from pond, river, and lake waters, respectively.
No specific information pertaining to the sorption of vinylidene chloride
onto sediments could be found. However, based on the experimental data from
related analogues (e.g., trichloroethene and tetrachloroethene), Callahan et al.
(1979) concluded that the sorption of vinylidene chloride onto sediments is
probably an insignificant process. The significance of sorption of this compound
onto sediments can also be predicted from the correlation equation of
Schwarzenbach and Westall (1981). Assuming the octanol/water partition
coefficient value of 69 for vinylidene chloride (Mabey et al., 1981), the log K
o c
value (K = sorption coefficent x 100 } sediments containing 0.5% organic
oc % organic carbon °
carbon can be calculated to be 1.81 from the equation of Scharzenbach and Westall
(1981). This log K value is somewhat lower than the experimental log K value
of 1.92 for benzene (Schwarzenbach and Westall, 1981). Therefore, the rate of
sorption of vinylidene chloride onto sediments is expected to be less than
benzene sorption onto sediments. In other words, the sorption of vinylidene
chloride onto sediments containing low organic carbon is not likely to be
significant but may increase as the organic carbon content in the sediment
increases.
It can be concluded from the above discussions that volatilization from
aquatic media is probably the most significant process for vinylidene chloride.
The role of biodegration in determining the fate of this compound in natural
aquatic media has not been definitely determined. All other aquatic processes
are probably insignificant in determining the fate of vinylidene chloride in
natural aquatic media.
6-7
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6,2.2 Bioaccumulation of Vinylidene Chloride in Aquatic Organisms
No experimental data are available for the bioaccumulation factor (BCF) for
vinylidene chloride in any kind of fish or other edible aquatic organisms. A
number of theoretical correlation equations are available that relate the BCF to
either the octanol-water partition coefficient or the water solubility of the
chemical. These equations are given below:
Log BCF = 0.76 log KOW - 0.23 (Veith et al., 1979)
Log BCF = 0.542 log KQW + 0.124 (Neely et al., 1974)
Log BCF = -0.508 log S + 3-41 (Chiou et al., 1977)
where K = partition coefficient of the chemical between octanol-water.
ow
and
S = water solubility of the chemical expressed in [imol/1.
The above equation of Veith et al. (1979) is applicable for the whole fish,
whereas the equations of Neely et al. (1974) and Chiou et al. (1977) are
applicable for fish muscle only.
If the values of log K and S for vinylidene chloride are assumed to be
1.48 (Tute, 1971) and 2.19 x 103 nmol/1 (Hu'shon and Kornreich, 1978),
respectively, the theoretical values for BCF can be calculated to be 7.8
(equation of Veith et al., 1979) for the whole fish and 8.5 (equation of Neely et
al., 1974) or 51 (equation of Chiou et al., 1977) for fish muscle. The
relatively low value for BCF indicates that vinylidene chloride will probably not
bioaccumulate in fish to any significant extent.
6.3 FATE, PERSISTENCE, AND TRANSPORT IN SOIL
No information pertaining specifically to the fate, persistence, and
transport of vinylidene chloride in soils could be found. However, the fate and
transport processes of this compound can be partially predicted from the
estimated log K value of 1.81 in soils containing 0.5? organic carbon. This
6-8
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relatively low log K value, coupled with a solubility of 2250 mg/1 and a vapor
pressure of 600 mm of mercury at 25 °C would indicate that both volatilization and
leaching may play significant roles in determining the fate of this chemical in
soils. In fact, the detection of this compound in several groundwaters (see
Section 7.2) is indicative of the leaching of vinylidene chloride from soils.
Unless more experimental or calculated data are available, no prediction
regarding the microbial degradability and chemical oxidation of this chemical in
soils can be made, although Kobayashi and Rittmann (1982) have reported the
biodegradation of vinylidene chloride by soil bacteria.
6-9
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7. ENVIRONMENTAL LEVELS AND EXPOSURE
When an environmental pollutant is suspected of being a potential health
hazard, it becomes necessary to determine the level of that pollutant in the
environment and its possible human intake from various environmental media. The
four environmental media of interest in this regard are air, water, soil, and
foods. The vinylidene chloride levels from each individual medium and the
possible human exposure therefrom are discussed in the following subsections.
The purpose of this document is to present available information relevant to
human health effects that could be caused by this substance. Any information
regarding sources, emissions, ambient air concentrations, and public exposure
has been included only to give the reader a preliminary indication of the poten-
tial presence of this substance in the ambient air. While the available informa-
tion is presented as accurately as possible, it is acknowledged to be limited and
dependent in many instances on assumption rather than specific data. This
information is not intended, nor should it be used, to support any conclusions
regarding risks to public health.
If a review of the health information indicates that the Agency should
consider regulatory action for this substance, a considerable effort will be
undertaken to obtain appropriate information regarding sources, emissions, and
ambient air concentrations. Such data will provide additional information for
drawing regulatory conclusions regarding the extent and significance of public
exposure to this substance.
7.1 AIR
7.1.1 Environmental Levels
The concentration of vinylidene chloride in air can be determined by moni-
toring its level in the atmosphere. In the absence of monitored data, the
7-1
-------
concentration can be theoretically estimated by dispersion modelling based on
the amount of vinylidene chloride losses in air from each plant. Such theore-
tical modelling, which is generally recognized to be accurate within a factor of
two in predicting the concentration of a pollutant in the vicinity of a plant,
has been used for estimating the population exposure to other atmospheric pollu-
tants, such as acrylonitrile (Suta, 1979). A vinylidene chloride model based on
analogy to 1,1,1-trichloroethane has been developed to estimate potential human
exposure (Wapora, 1982). Using dispersion modelling, Hushon and Kornreich
(1978) estimated the vinylidene chloride concentration levels at a single
distance from three vinylidene chloride monomer production sites in the United
States using atmospheric dispersion modeling. The 10-minute peak exposures of an
individual 500 m downwind from the three plants were estimated to be 0.87 ppm,
0.44 ppm, and 0.52 ppm for the Dow plant at Freeport, the Dow plant at
Plaquemine, and the PPG plant at Lake Charles, respectively. The corresponding
24-hour peak concentrations at the same three locations were estimated to be 0.52
ppm, 0.26 ppm, and 0.32 ppm. In order to estimate these values, it was assumed
that these plants have certain yearly emission rateis of vinylidene chloride
(Hushon and Kornreich, 1978), the wind speed was 6 m/s, the height of the plants
was 12.3 m, and vinylidene chloride monomer would be non-reactive in the
atmosphere. The last assumption may have lead to erroneous estimates of vinyli-
dene chloride concentration at longer distances. The half-life of vinylidene
chloride under simulated smog conditions was estimated to be 5 to 12 hours
(Dilling et al., 1976) and approximately 2 days under atomspheric hydroxyl reac-
tions (Cupitt, 1980). This relatively rapid atmospheric oxidation may not have a
significant effect on ambient air concentration at short distances from the
source, but may have a dramatic effect at longer distances. Thus, any dispersion
modelling for estimation of vinylidene chloride concentrations at various
7-2
-------
distances from the source should include the effect of disappearance of
vinylidene chloride due to atmospheric oxidation.
One of the earlier attempts to experimentally determine atmospheric levels
of halocarbons including vinylidene chloride was made by Grimsrud and Rasmussen
(1975) in rural Pullman, WA, during the period of December 1974 to February 1975.
They used a GC-MS method for the quantification of vinylidene chloride. Because
of the limitations of the analytical methodology (inadequate GC column),
however, they could not separate vinylidene chloride from its isomers cis- and
trans-1,2-dichloroethylene, and reported the combined concentration of the three
isomers to be <5 ppt.
The monitoring of vinylidene chloride near industrial sites was conducted
by Research Triangle Institute (Research Triangle Institute, 1977a,b, cited in
Hushon and Kornreich, 1978) during the period 1976 to 1977. Vinylidene chloride
concentrations ranging from 9 ppt to 249 ppt were detected near Dow plant sites,
one at Freeport, TX, and four at Plaquemine, LA. Seven other Dow sites at
Plaquemine, LA, showed no detectable trace of vinylidene chloride.
The more systematic environmental monitoring for vinylidene chloride near
industrial sites was performed by Going and Spigarelli (1977) during the period
of January 1977 to April 1977. These investigators selected sampling points near
six industrial plants representing manufacturers of vinylidene chloride monomers
and polymers and fabricators of the polymers. The analyses of the samples were
performed by gas chromatography-flame ionization detectors (GC-FID) and gas
chromatography-mass spectrometry (GC-MS).
The concentrations of vinylidene chloride in the ambient air throughout the
U.S. have been measured by several other investigators. The ambient atmospheric
levels of vinylidene chloride throughout the continental U.S. as determined by
these and other investigatory are shown in Table 7-1. It should be noted that
7-3
-------
TABLE 7-1
Vinylidene Chloride Concentrations in the Ambient Air Throughout the Continental U.S,
Location
Aldine, TX
Baton Rouge, LA
Bats to, NJ
Beaumont, TX
(grab sample)
Bridgeport , NJ
Bristol, PA
Camden, NJ
Chapel Hill, NC
(grab sample)
Charleston, WV
Denver, CO
Edison, NJ
Elizabeth, NJ
Freeport, TX
Sampling Mean Std.a
Date Cone. Dev.
(duration) (ppt) (ppt)
1977
(88 days)
1977
(78 days)
1979
(306 days)
1980 12
1977
( 1 hour )
1977
( 1 hour )
1979
(198 days)
1980 2
1977
(53 days)
1980
(10 days)
1976
(98 days)
1979
(347 days)
1976
36 62
ND 0
ND 0
, 000 NR
ND 0
ND 0
ND 0
,800 NR
ND 0
6.4 21
ND 0
ND 0
130 NR
Datab
Quality Reference
4
4
4
4
4
4
4
4
4
3
4
4
4
Pellizzari et
Pellizzari et
Bozzelli et al
Wallace, 1981
Pellizzari and
Pellizzari and
Bozzelli et al
Wallace, 1981
al., 1979
al., 1979
., 1980
Bunch, 1979
Bunch, 1979
., 1980
Pellizzari, 1978b
Singh et al . ,
Pellizzari et
Bozzelli et al
Pellizzari et
198la
al., 1979
., 1980
al., 1979
(2 hours)
7-4
-------
TABLE 7-1 (cont.)
Location
Front Royal, VA
Geismar, LA
(grab sample)
Houston, TX
Institute, WV
Sampling
Date
(duration)
1977
(29 days)
1977
1977
(1091 days)
1977
1977
Mean
Cone.
(ppt)
49
5
16
ND
ND
Std.a
Dev.
(ppt)
53
NR
15
0
0
Datab
Quality
4
4
3
4
4
Reference
Pellizzari,
Pellizzari,
Singh et al
Pellizzari
Pellizzari
1978b
1978a
., 198la
et al . ,
et al . ,
1979
1978b
Lake Charles, LA
Liberty Mound, OK
Marcus Hook, PA
Midland, MI
N. Philadelphia, PA
Newark, NJ
Nitro, WV
Plaquemine, LA
Riverside, CA
(1 day)
1977 6,700 73
(1 day)
1977 ND 0
(42 days)
1977 ND 0
(1 hour)
1977 6,100 6
(1 day)
1977 ND 0
(1 hour)
1979 ND 0
(342 days)
1977 ND 0
(51 days)
1977 1,100 69
(29 days)
1977 30 NR
1980 6.5 3
(10 hours)
2 Going and Spigarelli, 1977
4 Pellizzari, 1978b
4 Pellizzari and Bunch, 1979
2 Going and Spigarelli, 1977
4 Pellizzari and Bunch, 1979
4 Bozzelli et al., 1980
4 Pellizzari, 1978b
2 Going and Spigarelli, 1977
4 Pellizzari et al., 1979
3 Singh et al., 1981a
7-5
-------
TABLE 7-1 (cont.)
Location
Rutherford, NJ
S. Charleston, WV
S. Amboy, NJ
St. Louis, MO
St. Albans, WV
Tulsa, OK
Vera, OK
W. Belle, WV
Sampling Mean Std.a
Date Cone. Dev.
(duration) (ppt) (ppt)
1979 ND 0
(348 days)
1977 ND 0
(51 days)
1977 ND 0
(336 days)
1980 3-6 1.7
(9 days)
1977 ND 0
(28 days)
1977 ND 0
(72 days)
1977 ND 0
(3 hours)
1977 ND 0
(51 days)
Datab
Quality Reference
4
4
4
3
4
4
4
4
Bozzelli et al . , 1980
Pellizzari, 1978b
Bozzelli et al., 1980
Singh et al . , 198 1a
Pellizzari, 1978b
Pellizzari, 1978b
Pellizzari, 1978b
Pellizzari, 1978b
aStandard deviation
Data quality; 1: excellent, 2: good, 3: acceptable, 4: questionable
ND = Not Detected; NR = Not Reported
7-6
-------
the data presented in Table 7-1 represent vinylidene chloride levels in air
samples for various durations, and from different types of sites, namely,
rural/remote areas, urban/suburban areas, and source areas. An assessment of the
quality of data presented in Table 7-1 was made by Brodzinsky and Singh (1982) on
the basis of the error limits of the data. Some of the investigators did not
provide adequate data to calculate the error limit. In these cases, the quality
codes were assigned on the basis of expert judgement of Brodzinsky and Singh
(1982). The quality codes of 1, 2, 3, and 4 signify excellent, good, acceptable
and questionable data, respectively. The mean concentrations of vinylidene
chloride in the ambient air samples collected in 1979 from Los Angeles, CA,
Phoenix, AZ, and Oakland, CA, were measured to be 4.9 ppt, 29.8 ppt, and 12.6
ppt, respectively (Singh et al., 198lb). These values have not been presented in
Table 7-1 because no assessment of the quality of these data was made by
Brodzinsky and Singh (1982).
The mean ambient air concentrations of vinylidene chloride, the averaging
times (duration), the standard deviations, and the data qualities for all the
data categorized by the types of sites are given in Table 7-1. Data with
assessed qualities of excellent, good, and acceptable are presented in Table 7-2
in parentheses. Additionally, the median vinylidene chloride levels in air
samples from different site types for which the determined data have been
assessed to be acceptable or better also are shown in Table 7-2. It is obvious
from Table 7-2 that the median concentration of vinylidene chloride in U.S.
urban/suburban ambient air is approximately 5 ppt. However, this value is
subtantially higher (3600 ppt) for ambient air samples collected from vinylidene
chloride source areas.
7-7
-------
TABLE 7-2
Mean and Median Vinylidene Chloride Concentrations in U.S. Ambient Air
of Different Site Types3
Site Type
Grand totals
Rural/ remote
Urban/suburban
Source areas
No. of
Samples
767 (339)
2 (0)
665 (325)
100 (14)
Mean
Cone .
(ppt)
260 (170)
ND (0)
220 (8)
540 (3800)
Std.
Dev.
1500 (930)
0 (0)
1500 (14)
1700 (2800)
Median
Conc.c
(ppt)
5
0
5
3600
Data
Quality
3.5 (3)
4.0 (0)
3.5 (3)
3-7 (2)
a_ .
1091 days.
The values in parentheses refer only to data with quality of 3 or lower.
The median concentrations refer only to data with quality of 3 or lower.
7-8
-------
7.1.2 Exposure
The Office of Air Quality Planning and Standard (OAQPS), U.S. EPA, Research
Triangle Park, NC, has prepared a document estimating human exposure to vinyli-
dene chloride in the atmosphere around plants producing the monomer and the
polymer. The ranges of measured concentrations associated with the monomer and
•3 -3
polymer plants were 90-100 ng/nr and 25-50 ng/m , respectively. For a detailed
discussion, the readers are referred to the OAQPS document (Wapora, 1982).
Landau and Manos (1976) estimated the number of Americans who reside within 5
miles of 38 major plants in the United States that produce monomers and polymers
and fabricate polymers. The estimated values are given in Table 7-3. The values
are only population estimates and are not meant to indicate the absolute number
of people exposed to vinylidene chloride.
The size of the population residing near plant sites as given in Table 7-3
may have changed slightly due to shut down of a few plants or addition of new
plants and due to some population shifts. It should be noted that the number of
people likely to be exposed to vinylidene chloride is not shown in Table 7-3.
The estimation of these values would require knowledge of the chemical's
transport characteristics. Theoretically, dispersion modelling could provide an
estimate of vinylidene chloride concentrations at different distances from the
plant sites; however, such data are not presently available.
Experimental data could provide a solution to this problem. Going and
Spigarelli (1977) detected vinylidene chloride at a distance of 1.5 miles from a
vinylidene chloride monomer production facility. Their study was not designed to
provide vinylidene chloride levels at different distances from the source.
Therefore, the study of Going and Spigarelli (1977) cannot be used to estimate
vinylidene chloride exposure.
7-9
-------
TABLE 7-3
Estimated Population Residing Near Plant Producing or
Fabricating Monomers and Polymers of Vinylidene Chloride
(Landau and Manos, 1976)
Perimeter
(miles)
Producing or Process Plants
Monomer
Polymer
Fabrication
Total
0-1/2
1/2-1
1-3
3-5
TOTAL
315
1,035
17,356
70,230
88,936
11,114
34,091
221,966
337,547
604,718
37,310
100,974
1,064,994
1,676,463
2,879,741
48,739
136,100
1,304,316
2,084,240
3,573,395
7-10
-------
With the median ambient levels (averaged over 1 hour up to 1091 days) given
in Table 7-1, and assuming 20 m of air is inhaled per day by an individual, the
estimated daily vinylidene chloride intake from urban/suburban areas through
inhalation is approximately 0.4 \ig, Pellizzari et al. (1979) estimated the
daily average vinylidene chloride intake through inhalation of ambient air from
the Baton Rouge, Geisman, and Plaquemine, LA, area and the Houston, Deer Park,
and Pasadena, TX, area to be 0.7 i-ig and 1.6 ^.g, respectively. However, the daily
inhalation exposure may be as high as 0.3 rag near the immediate vicinity of
source areas if a median vinylidene chloride level of 3600 ppt (see Table 7-2) is
employed to calculate the exposure value.
7.2 WATER
7.2.1 Environmental Levels
The presence of vinylidene chloride in water samples was reported as early
as 1975. Monitoring investigations performed prior to or during 1976 have
reported the presence of vinylidene chloride in a wide range of water samples
ranging from industrial effluents to drinking waters. Some of the earlier
attempts at analysis, however, could not separate vinylidene chloride from its
isomers due to inadequate GC column selection. The presence of unseparated
vinylidene chloride and its isomers has been reported in effluents from the
textile industry, effluents from the latex industry, effluents from sewage
treatment plants, raw surface waters, finished drinking waters, and even in well
water (Schackelford and Keith, 1976).
The presence of vinylidene chloride alone, separated from its isomers, has
been reported four times in industrial effluents, two times in raw surface
waters, seven times in finished drinking water, and one time in well water
(Shackelford and Keith, 1976). No quantitative values for vinylidene chloride
concentrations are available from most of these earlier reports, however,
7-11
-------
because the vinylidene chloride concentrations were very low and mass spectro-
metry was used for its identification and not for quantification. The levels of
vinylidene chloride in industrial raw wastewaters and treated wastewaters have
been determined recently and are shown in Table 7-H and Table 7-5. These tables
also indicate the expected vinylidene chloride loading in surface waters due to
the discharge of the wastewaters into these water bodies. According to these
tables, nonferrous metals manufacturing industries are likely to contribute to
the maximum vinylidene chloride loading into the water bodies.
In a recent publication, Keith and Telliard (1979) reported the approach
used by the U.S. EPA in establishing a priority pollutant list for toxic
chemicals. Industrial effluents were screened by GC-MS for various pollutants,
including vinylidene chloride. Among the over 2,000 samples representing 17
different industrial categories that were analyzed up until August 1978, 1.1%
qualitatively showed the presence of vinylidene chloride.
The levels of vinylidene chloride in surface waters around a few industrial
sites were determined by Going and Spigarelli (1977). The samples were analyzed
by a combination of GC-FID and GC-MS. Table 7-6 lists the concentrations of
vinylidene chloride in these water samples.
The levels of vinylidene chloride in U.S. raw surface and ground waters used
for the abstraction of drinking waters and in potable drinking waters were
monitored as part of the National Organic Monitoring Survey (NOMS) (U.S. EPA,
1977) and National Organics Reconnaissance Survey (NORS) (Coleman et al., 1976).
The results of these two surveys were combined with four other surveys conducted
for the U.S. EPA (namely, surveys by Stanford Research Institute, Office of Toxic
Substances (OTS), Annapolis Field Study and U.S. EPA Region V Survey) by Coniglio
et al. (1980) to derive at statistics on the levels of volatile organics in raw
and finished waters in the U.S. None of the surface waters from the 105 cities
7-12
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(JO
TABLE 7-H
Industrial Occurrence of Vinylidene Chloride in Raw Wastewater'
,a,b
Industry
Auto and Other Laundries (c)
Coal Mining (d)
Aluminum Forming
Battery Manufacturing
Coil Coating
Metal Finishing (d)
Procelain Enameling
Nonferrous Metala Manufacturing
Organic Chemicals Manufacturing/
Plastics
Paint and Ink Formulation (c)
Soap and Detergent Manufacturing (c)
Steam Electric Power Plants (f )
Textile Mills (d)
Number
of
Samples
5
17
NA
27
30
95
1
66
NA
36
3
11
50
Number
of
Detections
3
3
ND
8
2
16
ND
9 (e)
22
.8
3
ND
1
Concentration, ug/1
Minimum
2.0
3
ND
ND
2
ND
NA
NA
11
Maximum
23
3
10
36
10,000
6,100
NA
620
25
<5
Mean
7.5
3
10
10
760
200
200
78
18
Loading,
kg/dg
Mean
0.001U
0.011
0.0008
0.0011
0.61
1.6
NA
0.00031
0.0016
<0.0035
Source: U.S. EPA, 1981
The pollutant was not detected during screening analyses for the following industries: Leather
Tanning and Finishing, Foundries, Explosives Manufacture, Gum and Wood Chemicals, Pharmaceutical
Manufacturing, Nonferrous Metals Manufacturing, Pulp and Paperboard Mills, Rubber Processing, Timber
Products Processing.
°Screening data
Screening and verification data
Detections >10 (tg/1
f
Verification data plus surveillance and analyses
gPollutant loadings determined by multiplying mean pollutant concentration by industry wastewater
discharges; where mean is not available one-half the reported maximum was utilized.
NA = Not Available; ND = Not Detected
-------
TABLE 7-5
Industrial Occurrence of Vinylidene Chloride in Treated Wastewater'
a,b
Industry
Auto and Other Laundries (a)
Coal Mining (b)
Coil Coating
Explosives Manufacture
Pharmaceutical Manufacturing
Nonferrous Metals Manufacturing
Organic Chemicals Manufacturing/
~j Plastics
i
^ Paint and Ink Formulations (a)
Soap and Detergent Manufacturing
Steam Electric Power Plants (d)
Number
of
Samples
1
51
5
NA
2
70
NA
24
NA
12
Number
of
Detections
ND
3
ND
NA
2
10 (c)
15
4
NA
1
Concentration, [ig/1
Minimum
3
NA
10
ND
NA
NA
NA
Maximum
3
NA
10
4,100
NA
44
NA
10
Mean
3
NA
10
120
6.8
19
NA
Loading,
kg/dg
Mean
0.0056
NA
0.0091
0.96
NA
0.000076
NA
0.015
Source: U.S. EPA, 1981
The pollutant was not detected during screening analyses for the following industries: Leather Tanning and
Finishing, Aluminum Forming, Battery Manufacturing, Foundries, Porcelain Enameling, Gum and Wood Chemicals,
Rubber Processing, Timber Products Processing.
°Screening data
Screening and verification data
Detections >10
Verification data plus surveillance and analyses
^Pollutant loading determined by multiplying mean pollutant concentration by industry wastewater discharges;
where mean is not available, one-half the reported maximum was utilized.
NA = Not Available; ND = Not Detected
-------
TABLE 7-6
Vinylidene Chloride Concentration in a Few Waters Near Industrial Sites'
Sample
Source
Mississippi
River
Industrial
Site
Dow Chemical ,
Plaquemine, LA
Industrial
Process
Monomer producer
Frequency
of
Detection
1/2
Concentration
High
(lig/D
0.2
Low
(ng/D
ND
PPG Canal
Ohio River
PPG Industries
Lake Charles,
LA
W.R. Grace,
Owensboro, KY
Monomer and 1/2
methyl chloroform
producer
Polymer producer 0/2
550
ND
ND
ND
Holston River
Tittabawasse
River
Eastman,
Kingsport, TN
Dow Chemical ,
Midland, MI
Modacrylic
producer
Polymer producer
and extruder
2/4
1/3
1 ND
<1 ND
Source: Going and Spigarelli, 1977
bThe samples were collected at different points upstream and downstream from
the discharge outfall.
°The first figure indicates the number of samples that showed presence of
compound and the second figure indicates the total number of samples analyzed,
This plant no longer uses vinylidene chloride to produce methyl chloroform.
ND = Not Detected
7-15
-------
monitored in this survey showed any detectable level of vinylidene chloride.
Only two finished waters abstracted from surface waters from 103 cities showed
the presence of this compound at concentrations of 0.2 jig/1 and 0.51 ng/1. Since
the compound was not present in the raw water, it is likely that the treatment
process is the source of vinylidene chloride in these treated waters. Going and
Spigarelli (1977) also monitored the treated surface waters from Cincinnati, OH,
Philadelphia, PA, and Lawrence, MA, for vinylidene chloride. Neither the pre-
chlorinated nor the post-chlorinated treated water from any of these cities
showed any detectable level of vinylidene chloride. Recently, Pellizzari et al.
(1979) reported the mean concentration of vinylidene chloride in the drinking
water from New Orleans and Baton Rouge, LA, areas to be 0.2 fig/1.
A survey of raw and treated groundwaters from 13 U.S. cities was also
conducted by Coniglio et al. (1980). Raw groundwaters from two cities both
showed detectable quantities of vinylidene chloride at a level of 0.5 (ig/1.
Vinylidene chloride was detected in treated groundwater from only one city at a
concentration of 0.2 \ig/l. Going and Spigarelli (1977) also detected 0.059 ng/1
and 0.045 jig/1 of vinylidene chloride in pre-chlorinated and post-chlorinated
treated groundwater, respectively, from Miami, FL. Eight state agencies (e.g.,
AL, FL, KY, ME, MA, NC, SC, and TN) also monitored the levels of dichloro-
ethylenes (three unseparated isomers) in their well water. Of the total of 781
samples tested, 23% showed detectable levels of dichloroethylenes with a maximum
level of 860 jig/1 (Coniglio et al., 1980). The levels of vinylidene chloride in
378 groundwater samples from urban, suburban, rural, and dump site areas in New
Jersey were monitored by Page (1981). Approximately 44$ of the groundwaters
showed detectable levels of vinylidene chloride. Although the highest concen-
tration of vinylidene chloride detected in a groundwater, probably from a dump
7-16
-------
site (author did not specify the sites) was 17.3 mg/1, the median concentration
of vinylidene chloride in all samples was below the detection limit (10 ^g/1).
The levels of vinylidene chloride in raw and treated (both ground and
surface waters) from 30 Canadian potable water treatment facilities serving
about 5.5 million consumers across Canada were monitored by Otson et al.
(1982a,b). Vinylidene chloride was not detected in any of the raw water samples,
and only one finished water sample collected during the summer months (Aug.-
Sept.) showed a mean concentration of less than 1 ng/1 and a maximum concentra-
tion of 20 p.g/1 for vinylidene chloride.
7.2.2 Exposure
It can be concluded from the discussions in Section 7.2.1 that about 3% of
the total drinking water supplies in the U.S. contain vinylidene chloride at an
estimated mean concentration of 0.3 Hg/1. Assuming that an individual consumes 2
liters of water per day, the daily exposure to vinylidene chloride for these
consumers (3% water supplies) would be approximately 0.6 \ig. For the majority of
the U.S. population, the daily exposure to vinylidene chloride from the consump-
tion of drinking water would be lower than 0.6 \ig. Therefore, the daily exposure
of vinylidene chloride to the general population in the U.S. from the consumption
of drinking water would be <0.6 p.g, although the maximum daily exposure in
certain communities could exceed 1 \±g (see Section 7.2.1).
7.3 SOIL
DeLeon et al. (1980) analyzed over 100 soil samples within and around a few
chemical waste disposal sites for 11 chlorinated hydrocarbons including vinyli-
dene chloride. The analytical method used was gas chromatography-electron cap-
ture detector (GC-ECD) for quantification and gas chromatography-mass spectro-
metry (GC-MS) for confirmation. One of the three samples collected from a
midwestern chemical disposal site (name not mentioned) showed 21.9 (ig/g (dry
7-17
-------
weight) of vinylidene chloride, while none was detected in the other two samples.
The detection limit of the method was given as 10 ng/g.
7.4 FOODS
Human exposure to vinylidene chloride from foods can occur in two ways:
from consumption of food contaminated by polyvinylidene wrappings, and from
consumption of edible aquatic foods that have bioconcentrated vinylidene
chloride from water. Vinylidene chloride content both in food-packaging
materials and in the foods themselves have been determined. The extent of
migration of residual vinylidene chloride from polyvinylidene packaging
materials into foods is customarily tested with food-simulating solvents rather
than with foods themselves (Hollifield and McNeal, 1978). The three food-
simulating solvents, which represented aqueous, oily, and fatty foods, were
water, corn oil, and heptane, respectively (Hollifield and McNeal, 1978).
The results of analysis of vinylidene chloride content in saran and meat
packaging films as determined by Going and Spigarelli (1977) are shown in Table
7-7.
Hollifield and McNeal (1978) analyzed five commercial food-packaging saran
films of 0.5 mil thickness and determined that the residual monomer concentration
varied between 1.6 |ig/g and 8.1 |ig/g.
The extent of migration of vinylidene chloride from saran films to food-
simulating solvents at 49°C is shown in Table 7-8.
It can be concluded from Table 7-8 that the migration of the residual
monomer from the 0.5 mil film was essentially complete in corn oil and heptane in
well under 24 hours. It leveled off at about 60$ in water after 24 hours.
It is difficult to estimate the extent of human exposure to vinylidene
chloride resulting from consumption of food contaminated by polyvinylidene
packaging materials. The exposure to vinylidene chloride from consuming
7-18
-------
TABLE 7-7
Analysis of Food-Packaging Films for Vinylidene Chloride
Concentration
Sample (HS/g)
Saran Wrap 41-58
Saran Wrap 4.9
Oscar Mayer Film A ND
Oscar Mayer Film B ND
Oscar Mayer Film C ND
aSource: Going and Spigarelli, 1977
This saran wrap, presumably produced in 1974, contained
higher amounts of vinylidene chloride
ND = Not Detected. The detection limit was 0.005 |ig/g.
7-19
-------
TABLE 7-8
Migration of Vinylidene Chloride from Saran Films to Heptane,
Corn Oil, and Water at 49°Ca
Film Thickness
Heptane
0.5 mil
Corn Oil
0.5 mil
Water
0.5 mil
Residue Monomer
Concentration Time of Contact
Hg/g (hours)
8.1 0.5
1.0
2.0
2.5
8.1 1
3
6
24
48
8.1 4
24
312
696
Concentration
Found in
Solvent (ppb)
34
37
41
44
18
34
40
39
41
26
27
24
24
Percent of
Total
Extracted
76%
88?
94?
106?
41?
76%
94?
94?
94?
59?
65?
59?
59?
Source: Hollifield and McNeal, 1978
7-20
-------
contaminated edible aquatic foods is equally difficult to estimate, even when the
bioaccumulation factor is available. To calculate body burden, a knowledge of
the concentration of vinylidene chloride in the water from which the aquatic
organism originated is necessary.
7-21
-------
8. BIOLOGICAL EFFECTS ON PLANTS AND MICROORGANISMS
The 96-hour EC™ (median.effective concentration) values for the freshwater
alga Selenastrum capricornutum and the marine alga Skeletonema costatum were
found to be greater than 798 or 712 mg vinylidene chloride/1, respectively (U.S.
EPA, 1978). These were the highest concentrations tested. The reported "no
effect concentration" was <80 mg/1 for Selenastrum capricornutum and 712 mg/1 for
Skeletonema costatum. The criteria for toxic effect in these bioassays were
reduction in cell number or chlorophyll a content in algae cultures grown for 96
hours.
No studies were found in the literature searched on the biological effects
of vinylidene chloride on microorganisms.
8-1
-------
9. BIOLOGICAL EFFECTS ON AQUATIC ORGANISMS
9.1 ACUTE TOXICITY
The acute toxicity of vinylidene chloride has been determined with several
species of freshwater and marine fish and invertebrates. Acute toxicity values
are presented in Table 9-1.
9.1.1 Freshwater Fish
The 96-hour LC - (95$ confidence interval) for bluegill sunfish, Lepomis
macrochirus, tested under static exposure conditions was 73.9 (56.8-90.7) mg/1
(U.S. EPA, 1978; Buccafusco et al., 1981). This value is the same as the 24-hour
LC n (Table 9-1), indicating that all mortalities during the test occurred within
50
the first day of exposure. The "no effect" concentration was 32.0 mg/1. Dawson
et al. (1977) reported a much higher 96-hour LC5Q for bluegill sunfish (220
mg/1). The chemical used was identified as "vinylidene chlorine" and presumable
was vinylidene chloride. This test was conducted under static exposure condi-
tions. Dill et al. (n.d., cited in U.S. EPA, 1979) determined the 96-hour LC50
for fathead minnows, Pimephales promelas, under static and flow-through exposure
conditions. The values were 169 mg/1 and 108 mg/1, respectively. The different
results indicate that the flow-through technique gave a higher estimate of the
acute toxicity of vinylidene chloride than did the static exposure technique.
9.1.2 Freshwater Invertebrates
The only freshwater invertebrate for which vinylidene chloride toxicity
data are available is the water flea, Daphnia magna. The 24-hour and 48-hour
static LC Q (95% confidence interval) values were 98 (71-130) and 79 (62-110)
mg/1, respectively (LeBlanc, 1980). The "no discernible effect" concentration
was <2.4 mg/1, which was the lowest concentration tested. In another study (Dill
9-1
-------
TABLE 9-1
Acute Toxicity Values for Marine and Freshwater Fish and Invertebrates Exposed to Vinylidene Chloride
Test Water LC50 (mg/l)a
Species Type Type 21-h 18-h 72-h
FISH
Bluegill Sunfish ST FW 73.9 73-9 73.9
(Lepomis macrochirus) (56.8-90.7) (56.8-90.7) (56.8-90.7)
ST FW
Fathead Minnows ST FW
(Pimephales promelaa)
ST FW
Sheepshead Minnow ST SW 219 219 219
(Cyprinodon variegatua) (198-338) (198-338) (198-338)
Tidewater Silversides ST SW
(Menidia beryllina)
INVERTEBRATES
Water Fleas ST FW — 11. 6b
(Daphnia magna)
Water Fleas ST FW 98 79
(Daphnia magna) (71-130) (62-110)
Mysid Shrimp ST SW >798 >798 >798
(Mysidopsis bahia)
96-h
73.9
220
169
108
219
(198-338)
250
__
221
(106-131)
No Effect
Concentration
(mg/1) References
32.0 U.S. EPA, 1978
Buccafusco
et al., 1981
Dawson et al . ,
1977
Dill et al.,
n.d.
Dill et al.,
n.d.
79.8 U.S. EPA, 1978
Heitmuller
et al., 1981
Dawson et al . ,
1977
Dill et al.,
n.d.
<2.1 LeBlanc, 1980
11.2 U.S. EPA, 1978
Numbers in parentheses represent the 95> confidence interval
Median effective concentration (EC,./,)
ST = static exposure; FT = flow-through exposure; FW = freshwater; SW = sea water
-------
et al., n.d., cited in U.S.EPA, 1979), the 48-hour static EC5Q (median effective
concentration) was 11.6 mg/1, which is much lower than the previously cited LC Q
values. The difference may be due to the different toxicity endpoints measured
(effective concentration vs. lethal concentration) or some other factor(s).
9.1 .3 Marine Fish
The 96-hour LC._0 (95? confidence interval) for sheepshead minnows,
t>u
Cyprinodon variegatus, tested under static exposure conditions, was 249
(198-338) mg/1 (U.S. EPA, 1978; Heitmuller et al. , 1981). As occurred with
bluegill sunfish, the 96-hour LC™ was the same as the 24-hour LC™ (Table 9-1).
The "no effect" concentration was 79.8 mg/1. The only other study with marine
fish was by Dawson et al. (1977), who reported a 96-hour LC,-0 value of 250 mg/1
for tidewater silversides, Menidia beryllina, tested under static exposure
conditions. This value is nearly identical to the 96-hour LC^_ for sheepshead
minnows.
9 .1 .4 Marine Invertebrates
The mysid shrimp, Mysidopsis bahia, is the only species of marine inverte-
brate that has been tested for vinylidene chloride toxicity. The 96-hour LC^Q
value (95% confidence interval) for this species was 224 (106-434) mg/1. The
LC^- value at 24, 48, and 72 hours could not be determined precisely, but was
greater than 798 mg/1 for each time period. The "no effect" concentration was
14.2 mg/1. The 96-hour LC,-,. value for mysid shrimp was similar to the 96-hour
LC^n values for sheepshead minnows and tidewater silversides.
9 .2 SUBACUTE TOXICITY
The only information regarding the subacute effects of vinylidene chloride
on aquatic organisms concerns one species of freshwater fish.
9-3
-------
Dill et al. (n.d., cited in U.S. EPA, 1979) determined the 13-day LC for
fathead minnows under flow-through conditions. This value, 29 mg/1, was
considerable lower than the equivalent 96-hour LC _ value (108 rag/1).
No adverse effects were observed in a fathead minnow embryo-larval test at
2.8 mg/1, which was the highest concentration tested (U.S. EPA, 1978). In this
test, fathead minnow eggs were exposed under flow-through conditions to a series
of vinylidene chloride concentrations through the hatching and early larval life
stages.
Most of the previously cited aquatic toxicity tests were conducted under
static exposure conditions. As far as can be determined, the LC^f. values
obtained from these tests were calculated on the basis of initial nominal concen-
trations, rather than actual measured concentrations.
Due to the high volatility of vinylidene chloride (Section 3), it is
probable that test organisms in static toxicity tests would be exposed to rapidly
decreasing concentrations of vinylidene chloride. This rapid loss may account
for the observations that the static LC Q values for bluegill sunfish and sheeps-
head minnow (U.S. EPA, 1978) did not decrease between 24 and 96 hours of exposure
and that the static 96-hour LC,-0 for fathead minnows was higher than the flow-
through 96-hour LC50 with the same species (Dill et al., cited in U.S. EPA,
1979). Although the static tests with bluegills and sheepshead minnows produced
apparent lethal thresholds by 24 hours of exposure, Dill et al. (n.d., cited in
U.S. EPA, 1979) showed that flow-through exposure with fathead minnows resulted
in sufficient additional mortality between 4 and 13 days of exposure to lower the
LC,-Q from 108 to 29 mg/1. Although static tests may provide some useful informa-
tion concerning the potential ecological effects of vinylidene chloride in spill
9-4
-------
situations, the flow-through results indicate that static tests may under esti-
mate the effects of acute and chronic exposure to constant vinylidene chloride
concentrations.
In summary, the reported acute LC^ or EC™ values for four fish species and
two invertebrate species ranged between 11.6 and 250 mg/1. The acute static "no
effect" concentrations reported in U.S. EPA (1978) decreased in this order:
sheepshead minnow (79.8 mg/1) > bluegill sunfish (32.0 mg/1) > mysid shrimp
(14.2) > Daphnia magna (>2.4 mg/1, the lowest concentration tested). However,
insufficient species have been tested to definitely establish whether or not
there may be significant differences in sensitivity to vinylidene chloride
between marine and freshwater organisms, or between fish and invertebrates. Of
the species tested, the most sensitive species appears to be Dapjinia magna, which
was adversely affected at 2.4 mg/1, the lowest concentration tested with that
species in the U.S. EPA (1978) study. This concentration is lower than the
concentration (2.8 mg/1) reported in the same study to cause no adverse effects
on fathead minnows in a flow-through embryo-larval test.
Additional flow-through chronic or subchronic testing with paphnia magna
and other freshwater and marine species would be required to estimate more
accurately the range of species sensitivity and to determine the maximum accep-
table concentrations of vinylidene chloride compatible with protection of
aquatic life.
9-5
-------
10. BIOLOGICAL EFFECTS
10.1 PHARMACOKINETICS
The available data characterize the disposition and metabolism of vinyli-
dene chloride in experimental animals when administered as a single dose or
exposure. The effects of age, sex, route, species and fasting on disposition and
metabolism are also characterized. Information on the disposition and metabo-
lism of vinylidene chloride during subchronic or chronic exposure, however, is
lacking.
10.1.1 Absorption and Distribution
Studies with experimental animals indicate that vinylidene chloride is
readily absorbed and rapidly distributed in the body. Systemic absorption after
ill
intragastric administration of C-vinylidene chloride to male or female rats
appears to be rapid and fairly complete based on the rapid appearance of labeled
vinylidene chloride in the expired air (McKenna et al., 1978b; Reichert et al.,
1979) and the extensive pulmonary and urinary excretion of radioactivity (Jones
and Hathway, 19?8a; McKenna et al., 19?8b; Reichert et al., 1979). Intraperi-
toneal administration also resulted in extensive pulmonary and urinary excretion
(Jones and Hathway, 1978a).
Anderson et al. (1979a) studied the rate of uptake of vinylidene chloride
vapor by fasted male rats. Fasting (for 18 hours) has been shown to deplete the
glutathione content of the liver, and to increase the sensitivity of rats to the
toxicity of vinylidene chloride; these observations are consistent with the role
of glutathione in the detoxification of vinylidene chloride (Section
10.1.2.2.1). Throughout Section 10.1, animals can be assumed to be fed unless
fasting is specified. Uptake was determined from disappearance of vinylidene
chloride from a closed chamber as a function of time, corrected for nonspecific
10-1
-------
loss. Uptake could be resolved into a rapid and a slow phase. The rapid phase
was riot affected by pretreatment of the rats with inhibitors of microsomal
metabolism and could therefore be separated from the slow phase, in which the
rate was markedly reduced by these inhibitors (the slow phase is discussed in
Section 10.1.2.1). The rapid phase was a first-order process with a rate
constant of 2.2 hr (half-life = 0.315 hr). The rate constant did not vary
significantly with initial concentration of vinylidene chloride. The magnitude
of the rapid component was proportional to the initial concentration of vinyli-
dene chloride and the weight of rats in the chamber. The concentration of
vinylidene chloride in the body as a function of concentration in the chamber at
equilibrium (whole body solubility coefficient) was 0.0163 mg/kg body weight/ppm
chamber, equivalent to a body/gas distribution coefficient of 4.04. The rapid
phase was essentially complete in 60 to 80 minutes. On the basis of these
characteristics, Andersen et al. (1979a) concluded that the rapid phase
represented whole body equilibration.
Jaeger et al. (1977a) investigated the distribution of radioactivity in
various tissues 30 minutes after cessation of a 2-hour exposure of fed and fasted
14
male rats to C-vinylidene chloride. Exposure occured in a closed chamber; the
initial concentration of vinylidene chloride was 2000 ppm. Although there was no
significant difference between fed and fasted rats in the overall rate of uptake
of vinylidene chloride, the tissues and serum of fasted rats contained more
radioactivity than those of fed rats. The highest concentration of radioactivity
was found in kidney, and the next highest in liver. Spleen contained an inter-
mediate level of radioactivity; heart and brain contained the least. In both fed
and fasted rats, most of the radioactivity in kidney was trichloracetic acid
(TCA)-soluble. Approximately one-third of the radioactivity in liver was
10-2
-------
TCA-precipitable, indicating that it was covalently bound to macromolecules.
Liver contained more TCA-precipitable radioactivity than did kidney.
McKenna et al. (19?8a) from the Dow Chemical Company investigated the fate
of "^C-vinylidene chloride in fed and fasted (deprived of food for 18 hours) male
rats 72 hours after a 6-hour inhalation exposure to 10 or 200 ppm. As presented
in Table 10-1, fasted rats had lower body burdens of C than did fed rats.
Although most of the body burdens had been excreted within 72 hours, a small but
significant amount remained in the carcasses. After the 200 ppm exposure, more
radioactivity was retained in the carcasses of fasted rats than in those of fed
rats. All of the radioactivity found in urine, feces, and tissues was nonvola-
tile and therefore was considered to represent nonvolatile metabolites of
vinylidene chloride. Seventy-two hours after exposure to either 10 or 200 ppm
vinylidene chloride, concentrations of radioactivity were highest in kidney and
liver and decreased in the following order: kidney > liver > lung > skin > plasma
> fat, muscle, and remaining carcass. At both exposure levels, concentrations of
radioactivity remaining in the tissues of fasted rats were greater than those in
the tissues of fed rats when the data were normalized to account for the lower
end-exposure body burdens of fasted rats.
In similar experiments with intragastric administration of 1 or 50 ing
ill
C-vinylidene chloride to fed and fasted male rats, McKenna et al. (1978b) found
at 72 hours after dosing that concentrations of radioactivity were highest in
liver and next highest in kidney. Levels of radioactivity in lung were riot as
high as noted in the inhalation experiment previously described (McKenna et al.,
1978a). Jones and Hathway (1978a) reported that the whole animal autoradiography
of young male rats after intragastric administration of C-vinylidene chloride
ill
revealed high concentrations of C in the kidneys and liver 30 minutes after
dosing, followed at 1 hour by a more general distribution of radioactivity
10-3
-------
Table 10-1
ili
End-Exposure Body Burdens and Disposition of C Activity in Rats 72 Hours
Following Exposure to 10 or 200 ppm of C-Vinylidene Chloride for 6 Hours (McKenna et al., 19?8a)
Fasted rats
10 ppm
Fed rats
Fasted rats
200 ppin
Fed rats
o
-tr
Body burden
Total milligram equivalents
of C-vinylidene
chloride/rat
Milligram equivalents of
C-vinylidene chloride/kg
Percentage body burden
0.589 * 0.19
2.30 -H 0.05
0.748 + 0.041
2.89 + 0.12
9.57 + 0.08
35.39 + 0.301
11.41 + 0.64
44.53 + 0.64
Expired vinylidene chloride
CO
Urine
Feces
Tissues and carcass
Skin
Cage wash
1.60 + 0.19
8.27 + 0.80
78.19 + 1.42
6.75 + 0.56
3.91 + 0.05
1.37 + 0.25
0.27 + 0.11
1.63 + 0.07
8.74 + 1.86
74.72 + 1.65
9.73 + 0.05
3.45 + 0,30
1.30 + 0.09
0.44 + 0.14
8.36 + 0.27
7.24 + 0.51
70.41 + 1.86
2.72 + 0.41
7.45 + 1.01
3.07 + 1.0
0.76 + 0.10b
4.17 + 0.62
8.22 + 0.54
74.66 + 2.62
6.39 + 1.50
4.26 + 0.09°
1.92 + 0.29
0.34 + 0.02
values are given as X- ± SE (n = four Per Sroup)'
Significantly different from fed animals of the same exposure group, p<0.05, Student's t test.
Significantly different from fed animals of the 10 ppm exposure group, p<0.05, Student's t test.
-------
throughout the soft tissues. According to the authors, liver and kidney retained
radioactivity longer than did other tissues.
10.1.2 Metabolism
The metabolism of vinylidene chloride by experimental animals has been
extensively studied. A metabolic scheme that integrates the data from several
laboratories is presented in Figure 10-1. In this scheme, vinylidene chloride is
metabolized to reactive intermediates, 1,1-dichloroethylene oxide, chloroacetyl
chloride, and monochloroacetic acid. These reactive intermediates are detoxi-
fied by conjugation with glutathione (GSH), ultimately leading to the formation
of mercapturic acids (derivatives of N-acetyl cysteine) or degradation to
various thioglycolic acids. A minor pathway for detoxification of monochloro-
acetic acid involves further oxidation to CO . 1,1-Dichloroethylene oxide,
chloroacetyl chloride, and monochloroacetic acid can react with (i.e., alkylate)
cellular macromolecules; this type of reaction could be involved in the produc-
tion of toxic effects.
From an analysis of the literature on the metabolism of chlorinated
ethylenes, Lowe et al. (1983) have concluded that the extent of metabolism of
these compounds generally decreases with increasing degree of chlorine substitu-
tion. Thus the extent of metabolism appears to be: vinyl chloride = vinylidene
chloride > trans or cis-dichloroethylene > trichloroethylene > tetrachloro-
ethylene. These conclusions were drawn from a comparison of the results of a
number of oral and inhalation studies, taking into account species and dose
differences.
10.1.2.1 Metabolism to Reactive Intermediates
Vinylidene chloride is thought to be metabolized by the microsomal mixed-
function oxidase system to an epoxide (oxirane), 1,1-dichloroethylene oxide
(Bonse and Henschler, 1976; Liebman and Ortiz, 1977; McKenna et al., 1977).
10-5
-------
H,C-CCL,—
vinyl..d*n«
chloride
Cl y-CO-CH-CH, -S-CS, -CO-CI
I
MH
I
Clu
S-glucachiouyl acecyl saiorid*
-01 y, -Glu
1 H-ac»cyiaeian
R' -OC-Ca-CH,-5-C'A,-CO-a
I
NH
L-3— ;y»ceinyl.
acacvl lerivaciva
HOOC-C2-CH.,-i-Ci,-COOH
K.jC-S-ai,-CO-NH-CH,-Ca,-OH
sachyXthio-acacyianiaoachanoI
* ->^ac
ci-ca,;o-MH-ca,-
-------
According to Bonse and Henschler (1976), 1,1-dichloroethylene oxide is extremely
unstable and could not be isolated during attempts at chemical synthesis,
although its expected rearrangement product, chloroacetyl chloride, was formed
after chemical oxidation of vinylidene chloride with m-chloroperbenzoic acid.
Metabolism of vinylidene chloride to this epoxide has not been directly demon-
strated, but rather is inferred by analogy with the metabolism of other chlori-
nated ethylenes (Leibman and Ortiz, 1977; Bonse and Henschler, 1976; Uehleke et
al., 1976) and from the observed metabolism of vinylidene chloride to monochloro-
acetic acid.
The metabolism of vinylidene chloride by hepatic cytochrome P—450 in micro-
somes from male Long-Evans rats was studied jLn vitro by Costa and Ivanetich
(1982) in an attempt to identify metabolites and detoxification pathways.
Vinylidene chloride was shown to be metabolized to dichloroacetaldehyde and to
monochloroacetic acid by hepatic microsomes, after binding to cytochrome P-450
in the presence of an NADPH-generating system. Certain forms of cytochrome P-450
appear to play minor roles in the metabolism of vinylidene chloride (such as the
phenobarbital-inducible form) while other forms may be more efficient.
Radioactively-labeled monochloroacetic acid has been identified in the
urine of rats after intragastric administration in corn oil of C-vinylidene
chloride (Jones and Hathway, 1978a), in rat livers perfused with C-vinylidene
chloride (Reichert and Bashti, 1976), and after incubation of 14C-vinylidene
chloride with 9000 x g supernatants from rat liver homogenates (Leibman and
Ortiz, 1977). Monochloroacetic acid is the expected product of rearrangement of
the epoxide to chloroacetyl chloride and subsequent hydrolysis (Bonse and
Henschler, 1976; Leibman and Ortiz, 1977). Alternatively, monochloroacetic acid
could result from metabolism of the epoxide by epoxide hydrase to the diol shown
10-7
-------
in Figure 10-1, followed by rearrangement to chloroacetyl chloride and
hydrolysis to monochloroacetic acid (Leibman and Ortiz, 1977).
The relative importance of the diol pathway is difficult to assess. Jones
and Hathway (1978b) suggested that conversion to the diol is not important
because C00, a possible degradation product, is found only in small amounts in
2. ~~
vivo. It is not known, however, whether the diol is metabolized to CO to a
L
significant extent. Leibman and Ortiz (1977) concluded that diol formation is
relatively unimportant in the metabolism of vinylidene chloride to monochloro-
acetic acid because, 1,1,l-trichloropropene-2,3-oxide and cyclohexene oxide
(inhibitors of epoxide hydrase) stimulated, rather than inhibited, the formation
of monochloroacetic acid in incubations of vinylidene chloride with 9000 x g
supernatants from rat liver homogenates. These two inhibitors react with gluta-
thione (Oesch and Daly, 1972). Thus the results of Leibman and Ortiz (1977)
could be explained by the depletion of glutathione, thereby resulting in the
accumulation of monochloroacetic acid. Furthermore, according to Oesch (1972),
there are two types of epoxide hydrase activity—one is tightly coupled with
mixed-function oxidase activity, whereas the other is not. The coupled form is
thought to be more important in detoxifying epoxides formed by mixed function
oxidases and is relatively resistant to inhibitors (Oesch, 1972).
Andersen et al. (1979a) investigated the metabolism of vinylidene chloride
by studing the rate of uptake of vinylidene chloride vapor by fasted male rats.
Uptake was determined from the disappearance of vinylidene chloride as a function
of time (usually plotted on linear coordinates) from a closed chamber, corrected
for nonspecific loss. The uptake of vinylidene chloride by fasted male rats was
biphasic; the initial rapid phase represented tissue equilibration (Section
10.1.1) and the slow phase represented metabolism. The slow phase of uptake was
relatively independent of concentration at higher exposure levels and dependent
10-8
-------
on concentration at lower exposures. A series of uptake experiments using
different initial concentrations of vinylidene chloride were performed. The
instantaneous rates of uptake were determined from tangents to the curves at 60
to 80 minutes of exposure, so that the contribution from the rapid phase was
negligible. Instantaneous rates plotted against actual chamber concentration
yielded a rectangular hyperbola typical of Michaelis-Menten kinetics, as would
be expected if the slow phase represented metabolism. V , the maximum velocity
at saturating exposure levels, was 132 ppm/kg/hr (equivalent to 15.87 mg of
vinylidene chloride metabolized/kg/hr). K , the exposure level that produced
half the maximum velocity, was 335 ppm (equivalent to a body burden of 5.43
mg/kg).
At an initial concentration of vinylidene chloride of 300 ppm in air (below
the K ), the rate constant of the slow phase was reduced 84, 92, and 65% by
pretreatment with pyrazole, carbon tetrachloride, and aminotriazole, respec-
tively, but was unaffected by pretreatment with SKF 525A or 2,3-epoxy-
propan-1-ol. These compounds, with the exception of 2,3-epoxypropan-l-ol, are
inhibitors of microsomal metabolism; all have been shown to affect the acute
toxicity of vinylidene chloride (Section 10.2) (Andersen et al., 1980). At high
initial concentrations of vinylidene chloride, the V was unaffected by
3 ' max J
pretreatment with phenobarbital or by using fed rather than fasted rats, and was
similar for immature and mature rats (Andersen et al., 1979a).
As determined by Andersen et al. (1979b), the acute toxicity of inhaled
vinylidene chloride was relatively independent of concentration and dependent on
duration of exposure at concentrations above 200 ppm (Section 10.2). In an
attempt to correlate metabolism with toxicity, Andersen et al. (1979a) calcu-
lated the two theoretical curves shown in Figure 10-2. The solid line is based
on the assumption that the product of exposure concentration times the duration
10-9
-------
5 —
oo
(N
4—
o
LO
H-
2 —
LT50(95%C. I.)
ppm X time = k.
1000
CONCENTRATION (ppm)
2000
Figure 10-2
Comparisons of Observed LT50 Data for Vinylidene Chloride
with Theoretical Curves Predicted for Two Different
Mechanisms of Toxicity. As indicated by the symbol in
upper right, data are given as LT50 and its 95% confidence
interval. (Andersen at al. , 1979a)
10-10
-------
of exposure required to produce a given effect is constant. The dashed line is
based on the assumption that the product of the rate of metabolism (at each
exposure concentration) times the duration of exposure required to produce a
given effect is constant. The experimentally determined LT50 (time required to
produce 50% mortality rate) of M.1 hours at a 200 ppm exposure concentration was
used to calculate the constant. The experimentally determined LT50 values
(Andersen et al., 1979b) fit the theoretical curve based on metabolism more
closely than they fit the theoretical curve based on exposure concentration,
suggesting that toxicity is a function of the amount of metabolite formed rather
than the concentration of vinylidene chloride (Andersen et al., 1979a).
Using an experimental protocol similar to that of Andersen et al. (1979a),
Filser and Bolt (1979) investigated the kinetics of metabolism of vinylidene
chloride in the male rat. Filser and Bolt (1979) focused on strict zero-order
and first-order kinetics, whereas Andersen et al. (1979a) focused on
Michaelis-Menten kinetics. Both groups of investigators, however, demonstrated
the saturable dose-dependent nature of vinylidene chloride metabolism. As
determined by Filser and Bolt (1979); the V „„ (velocity for zero-order metabo-
LuCiX
lism) was 100 jxraol/kg/hr (9.7 mg/kg/hr).
Reichert and Henschler (1978) reported that pretreatment of female rats
with an inducer of mixed-function oxidases, DDT, increased the uptake of vinyli-
dene chloride 3556, while direct addition of inhibitors (pyrazole and ethanol) of
mixed-function oxidases decreased the uptake of vinylidene chloride 35 to 405& in
isolated, perfused rat livers. Pretreatment with phenobarbital, or direct
addition of SKF 525A, 6-nitro-1,2,3-benzothiadiazole, and 5,6-dimethyl-1,2,3-
benzothiadiazole to the perfusate had little effect on uptake when low concentra-
tions of vinylidene chloride were used. The uptake of vinylidene chloride,
measured as the difference between prehepatic and posthepatic concentrations of
10-11
-------
vinylidene chloride under steady state conditions was taken to be equivalent to
metabolism. The authors stated that with a high concentration of vinylidene
chloride in the perfusate, pretreatment with phenobarbital elevated the uptake
of vinylidene chloride by approximately 30$. The results of Reichert and
Henschler (1978) for perfused livers of female rats are in general agreement with
the results of Andersen et al. (1979a) for intact fasted male rats except for the
stimulation of uptake (metabolism) by phenobarbital pretreatment noted by
Reichert and Henschler (1978). Pretreatment with ethanol for a 3 week period
enhanced the activity of rat liver drug-metabolizing enzymes six-fold in their
ability to convert vinylidene chloride (Sato et al., 1980). The authors
discussed the increased rate of vinylidene chloride metabolism and noted that
this may increase the toxicity of the compound if metabolites are the actual
causative agents.
A comparison of sex, age, and species differences in metabolism and toxicity
suggests that vinylidene chloride is metabolized to a toxic intermediate by
mixed-function oxidases. In general, raicrosomal oxidation of compounds was
found to be greater in male rats than in female rats (Kato, 1974). Male rats were
much more susceptible to the hepatotoxic effects of vinylidene chloride than were
female rats (Andersen and Jenkins, 1977). Microsomal oxidase activity reached a
maximum in the rat at 30 to 40 days of age (Kato et al., 1964), an age range which
corresponded to the size (100-150 g) of rats most susceptible to the toxicity of
vinylidene chloride in the report of Andersen and Jenkins (1977). All of the
studies reviewed in Section 10.1 of this report, however, were performed on
mature (180-350 g) rats and mature mice unless otherwise specified.
A greater percentage of an orally administered dose (50 mg/kg) of C-
vinylidene chloride was metabolized by mice than by rats, based on quantitation
of excreted radiolabeled metabolites and unchanged vinylidene chloride (Jones
10-12
-------
and Hathway, 1978b). Similarly, as presented in Table 10-2, mice metabolized
more vinylidene chloride per kg body weight than did rats after inhaling 10 ppm
14
C-vinylidene chloride in air for 6 hours (McKenna et al., 1977). The overall
pattern of excretion for mice and rats was similar. The concentration of
covalently bound radioactivity in liver and kidney was much higher in mice than
in rats, as shown in Table 10-3. Binding was measured as radioactivity that was
TCA-precipitable and 80% methanol-insoluble and thus represented radioactivity
covalently bound to protein and nucleic acid. As discussed in Section 10.4.1,
the 9000 x g supernatant from mouse liver was more active than the 9000 x g
supernatant from rat liver in metabolizing vinylidene chloride to mutagenic
substances. These observations of increased metabolism and covalent binding in
mice versus rats parallel the greater sensitivity of mice to the acute lethality,
hepatotoxicity, and renal toxicity of vinylidene chloride (Short et al.,
1977a,b). A brief review of the metabolism of vinylidene chloride by rats and
mice is presented by Cooper (1980).
Hypoxia (7% oxygen), which inhibits mixed-function oxidase activity,
decreased the hepatotoxicity of inhaled vinylidene chloride to fasted male rats
(Jaeger, 1978). Disulfuram, which has been reported to inhibit hepatic mixed-
function oxidases (Zemaitis and Green, 1976), protected male mice from the acute
lethal and hepatotoxic effects of inhaled vinylidene chloride (Short et al.,
1977a,b). Measured at 4 and 24 hours after intraperitoneal administration of
14
C-vinylidene chloride, covalent binding of radioactivity to protein in liver
and kidney was significantly reduced in mice fed disulfuram before and during
exposure (Short et al., 1977a,b). Additional studies dealing with the relation-
ship between the induction and inhibition of microsomal mixed function oxidases
and the toxicity of vinylidene chloride are discussed in Section 10.2.
10-13
-------
Table 10-2
14,
End-Exposure Body Burdens and Disposition of C-Activity in
Rats and Mice 72 Hours Following Inhalation Exposure to
10 ppm C-Vinylidene Chloride for 6 Hours3
Mice'
C
rag-Eq C-vinylidene chloride/kg
Percentage body burden
Source: McKenna et al., 1977
3X + SE, n = 4.
Rats
111
Body burden, rag-Eq C-vinylidene
chloride/kg
Total metabolized vinylidene chloride
5.30 ± 0.75
5.27 + 0.74
2.89 + 0.24
2.84 + 0.26
Expired vinylidene chloride
14
Expired CO
Urine
Feces
Carcass
Cage Wash
0.65 + 0.07
4.64 + 0.17
80.83 + 1.68
6.58 + 0.81
5.46 + 0.41
1.83 + 0.84
1.63 ± 0.14
8.74 + 3.72
74.72 + 2.30
9.73 ± 0.10
4.75 + 0.78
0.44 + 0.28
14,
Calculated from the total C-activity recovered (end-exposure body burden)
minus the C-vinylidene chloride exhaled from each rat
Mice were males of the Ha(ICR) strain.
eRats were males of the Sprague-Dawley strain.
10-14
-------
Table 10-3
ili
Covalently Bound C-Activity in Tissues 72 Hours
u Following Inhalation Exposure to 10 ppm
C-Vinylidene Chloride for 6 Hours (McKenna et al., 1977)
C-vinylidene chloride, [ig-Eq/g protein
(X + SE, n = U)
Liver Kidney
Mice 22.29 + 3-77 79.55+ 19.11
Rats 5.28 + 0.14 13.14 + 1.15
10-15
-------
The identification of methylthio-aeetylaminoethanol as a urinary metabolite
of vinylidene chloride suggested the alkylation of lipids by a reactive inter-
mediate (Reichert et al., 1979; Henschler and Hoos, 1981). The pathway of
formation of methylthio-aeetylaminoethanol has not yet been clarified. Reichert
et al. (1979) hypothesized that the first step could be the reaction of
chloroacetyl chloride with phosphatidyl ethanolamine (a constituent of lipid
membranes). This postulated pathway is illustrated in Figure 10-1.
10.1.2.2 Detoxification Pathways
10.1.2.2.1 Conjugation with Glutathione
Conjugation of vinylidene chloride or its metabolites with glutathione is
indicated because administration of C-vinylidene chloride (intragastrically or
by inhalation) to rats and mice produced several S-containing radioactive meta-
bolites. The major urinary metabolites of vinylidene chloride in rats have been
identified as thiodiglycolic acid (thiodiacetic acid) (Jones and Hathway,
1978a,b; Reichert et al., 1979; McKenna et al., 1977, 1978a,b) and mercapturic
acids: an N-acetyl-S-cysteinyl acetyl derivative shown in Figure 10-1 (Jones and
Hathway, 1978a,b), N-acetyl-S-(carboxymethyl)cysteine (Reichert et al., 1979),
and N-acetyl-S-(2-hydroxyethyl)cysteine (McKenna et al., 1977, 1978a,b). N-
acetyl-S-(2-hydroxyethyl)cysteine is not shown as part of the metabolic scheme
in Figure 10-1 because its .relationship to other metabolites of vinylidene
chloride is unclear. The major urinary metabolites of vinylidene chloride in
mice were dithioglycolic acid and an N-acetyl-S-cysteinyl acetyl derivative
shown in Figure 10-1 (Jones and Hathway, 1978b).
Vinylidene chloride itself does not appear to react with glutathione.
McKenna et al. (1977) stated that they were unable to demonstrate conjugation of
vinylidene chloride with glutathione either nonenzymatically or in the presence
of the soluble fraction (which contains glutathione S-transferases) of a rat
10-16
-------
liver homogenate. Conjugation with glutathione required the presence of a micro-
somal enzyme system, suggesting that vinylidene chloride was metabolized to a
reactive intermediate before conjugation with glutathione. Unfortunately, no
data or experimental details were presented.
Additional evidence that the S-containing metabolites (mercapturic and
thioglycolic acids) of vinylidene chloride arise from conjugation with gluta-
thione is as follows. The origin of the cysteine moiety in mercapturic acid
derivatives of many xenobiotics has been shown to be glutathione (Chasseaud,
1973). In y_ivo experiments with unlabeled vinylidene chloride, in which the
14
cysteine-cystine pools were labeled with C, resulted in the production of
labeled thiodiglycolic acid (Jones and Hathway, 1978a). Thus, at least part of
the carbon skeleton of thiodiglycolic acid must have been derived from cysteine.
Administration of vinylidene chloride to male or female rats in vivo, or
during perfusion of isolated rat livers, depleted the liver glutathione content
(Jaeger et al., 1974; Reichert et al., 1978; McKenna et al., 1977; McKenna,
1979). Depletion of glutathione was maximal at about 4 hours after oral adminis-
tration of vinylidene chloride to female rats and was dependent on the dose
administered (Reichert et al., 1978). Depletion of glutathione after inhalation
exposure of male rats was similarly dose dependent (McKenna et al., 1977;
McKenna, 1979).
Reichert et al. (1978) attempted to demonstrate a correlation between the
glutathione content of isolated, perfused livers from female rats and the rate of
metabolism of vinylidene chloride measured as uptake (see Section 10.1.2.1,
Reichert and Henschler, 1978). When the glutathione content was decreased 80% by
the prior addition of diethyl maleate to the perfusate, an 18% decrease in
vinylidene chloride metabolism was measured. A less pronounced decrease in
glutathione content, produced by prior fasting of the rats, was not associated
10-17
-------
with a decrease in vinylidene chloride metabolism; a slight increase (10$) was
observed; neither Ghange in metabolism was statistically significant. The
authors concluded that the glutathione content of liver becomes a limiting factor
in the metabolism of vinylidene chloride only when the glutathione content has
been severely depleted.
Evidence for the metabolic pathways shown in Figure 10-1 that involve
conjugation with glutathione has been obtained from the analysis of the urinary
111
metabolites resulting from the administration of C-labeled vinylidene
chloride, monochloroacetic acid, and other metabolic intermediates to rats and
mice. As shown in Table 10-4, the N-acetyl-S-cysteinyl acetyl derivative was
ill
detected only when rats were given C-vinylidene chloride and not when they were
given C-monochloroacetic acid. The N-acetyl-S-cysteinyl acetyl derivative
must therefore have come from conjugation of glutathione with a metabolite
arising prior to the formation of monochloroacetic acid (Jones and Hathway,
1978a).
ill ill
The administration of either C-vinylidene chloride or C-monochloroacetic
1U
acid gave rise to C-labeled S-(carboxymethyl)cysteine, N-acetyl-S-(carboxy
methyl)cysteine, thiodiglycolic acid, thioglycolic acid, and dithioglycolic acid
(Tables 10-4 and 10-5, Jones and Hathway, 1978a). These results suggest that
monochloroacetic acid is a key intermediate in the metabolism of vinylidene
chloride and the S-(carboxymethyl)glutathione can be metabolized to thioglycolic
acids or to a oiercapturic acid.
S-(CarboxymethylJcysteine was metabolized to thiodiglycolic acid and to COp
(Green and Hathway, 1977; Yllner, 1971; Jones and Hathway, 1978b). Because
labeled C0_ was detected only when the cysteine moiety of S-(carboxymethyl)-
cysteine was uniformly labeled with C (Jones and Hathway, 1978b) but not when
the carboxymethyl moiety was labeled (Yllner, 1971), C0? must have been produced
10-18
-------
Table 10-4
Relative Proportions of C Urinary Metabolites After Intragastric
Administration.jOf 350 mg/kg 1- C-Vinylidene Chloride or 50 mg/kg
C-Monochloroacetic Acid to Male Rats
(Adapted from Jones and Hathway, 1978a; Hathway, 1977*)
Vinylidene Chloride and
Chloroacetic Acid Metabolites
Thiodiglycolic acid
N-acetyl-S-cysteinyl-acetyl
derivative
Dithioglycolic acid
Thioglycolic acid
Chloroacetic acid
Urea
S- (Carboxymethyl )cysteine
N-acetyl-S-(carboxymethyl)cysteine
% of
Vinylidene
Chloride
37.0
48.0
5.0
3.0
3.0
0.5
0
—
Urinary Radioactivity
Chloroacetic
Acid
90.0
0
3.0
3.0
0
0.5
2.0
2.0*
10-19
-------
Table 10-5
Relative Proportions of C Excretory Products After Intragastric
Administration of 50 mg/kg of 1- -C-Vinylidene Chloride to
Male Rats or Mice (Jones and Hathway, 1978b)
C Excretory Products
C Expressed at Percent of Dose
Mice Rats
Unchanged vinylidene chloride
(pulmonary excretion)
Carbon dioxide (pulmonary
excretion)
Chloroacetic acid
Thiodiglycolic acid
Thioglycolic acid
Dithioglycolic acid
Thioglycolyloxalic acid
N-Acetyl-S-cysteinyl acetyl
(derivative)
N-Acetyl-S-(2-carboxymethyl)
cysteine
Urea
6
3
0
3
5
23
3
50
4
3
28
3.5
1
22
3
5
2
28
0
3.5
10-20
-------
from the decarboxylation of cysteine. ™C-Thiodiglycolic acid was converted to
thioglycolic acid, dithioglycolic acid, and thioglycolyloxalic acid, indicating
that these metabolites arise from B-thionase hydrolysis of thiodiglycolic acid
(Jones and Hathway, 19?8b), shown in Figure 10-1. As can be seen from the
relative proportions of thioglycolic acids in Table 10-5, 3-thionase conversion
occurred to a greater extent in mice than in rats (Jones and Hathway, 1978b).
Results of experiments with rats suggest that conjugation with glutathione
serves to detoxify reactive metabolites of vinylidene chloride. The hepato-
toxicity of vinylidene chloride _in vivo and in the isolated perfused liver was
greater if vinylidene chloride was administered when glutathione levels in the
liver had been diminished by fasting (Jaeger et al., 197^, 1975a; McKenna et al.,
1978a), diurnal variation (Jaeger et al., 1973a, 1975a), by pretreatment with
diethyl maleate (Jaeger et al., 1974, 1975a; Andersen et al., 1980), or by
pretreatment with thyroxine (Jaeger et al., 1977b). The degree to which
pretreatment with various epoxides or diethyl maleate exacerbated the acute
toxicity of vinylidene chloride was related to the degree to which these
compounds depleted glutathione (Andersen et al., 1980). Increasing the levels of
glutathione in the liver by chemical or surgical thyroidectomy protected against
the toxicity of vinylidene chloride (Jaeger et al., 1977b). Hypoxia, which
inhibited mixed- function oxidase activity, protected against the hepatotoxicity
of vinylidene chloride and concomitantly prevented depletion of liver gluta-
thione (Jaeger, 1978).
Additional evidence for the role of glutathione in detoxification can be
obtained from studies of covalent binding. Fasting and, hence, a low level of
ill
liver glutathione were associated with decreased total metabolism of C-vinyli-
dene chloride, increased covalent binding of radioactivity to liver macromole-
cules, and centrilobular hepatic necrosis in male rats (McKenna et al., 1978a,b).
10-21
-------
Data for intragastric and inhalation administration are shown in Tables 10-6 and
10-7, respectively. Binding was measured 72 hours after exposure, as radio-
activity that was TCA-precipitable and B0% methanol-insoluble, and thus repre-
sents radioactivity covalently bound to protein and nucleic acid. At the higher
exposure levels, fasted male rats had significantly greater concentrations of
bound radioactivity in their livers when the data were normalized to account for
differences in metabolism.
Jaeger et al. (1977a) studied the subcellular distribution of free and bound
radioactivity in livers from fed and fasted male rats exposed to C-vinylidene
chloride. The analyses were performed 30 minutes after the cessation of a 2-hour
inhalation exposure to vinyliciene chloride (initial concentration, 2000 ppm) in
a closed chamber. Significantly more radioactivity was found in all subcellular
fractions from fasted animals than was found in those from fed animals. In
livers from both fed and fasted rats, the radioactivity in the mitochondrial and
microsomal fractions was largely TCA-precipitable; radioactivity in the cyto-
plasmic fractions was largely TCA-soluble. Because substantial amounts of the
TCA-precipitable radioactivity of mitochondria and microsomes were soluble in
chloroform, the authors suggested that binding to lipid had occurred. As
discussed in Section 10.1.2.1, methylthio-acetylaminoethanol, a metabolite of
vinylidene chloride, is though to be a product of the alkylation of lipids by a
reactive intermediate of vinylidene chloride (Reichert et al., 1979; Henschler
and Hoos, 1981). The amounts (per mg protein) of radioactivity presumably
covalently bound to protein and nucleic acid (TCA-precipitable, chloroform-
insoluble material) and to lipids (TCA-precipitable, chloroform-soluble
material) were greater in mitochondrial and microsomal fractions from fasted
rats than in the corresponding fractions from fed rats. Similarly, fasted rats
10-22
-------
Table 10-6
14,
Metabolism of C-Vinylidene Chloride and Covalent Binding of C Activity
to Rat Hepatic Tissue after Intragastric Dose of C-Vinylidene Chloride3 (McKenna et al., 1978b)
ro
OJ
Dose n
1 mg/kg
Fed rats 4
Fasted rats 4
50 mg/kg
Fed rats 3
Fasted rats 3
A
Metabolized vinylidene
chloride (mg Eq of C-
vinylidene chloride/kg)
0.956 + 0.136°
0.924 + 0.032
39.08 + 3.58
31.86 ± 1.81
B
Covalently bound vinvlidene
chloride (^ig Eq of C-
vinylidene chloride/g of
liver protein) B/A
0.854 + 0.003 0.89 + 0.36
0.861 + 0.022 0.93 + 0.04
37.67 + 3.16 0.96 + 0.12
44.45 + 3.21 1.40 ± 0.08a
SA11 values represent the X + SE for the number of rats indicated in the table.
bCovalent binding data normalized to account for differences in metabolized vinylidene chloride.
Calculated from the total recovery of CO plus nonvolatile radioactivity from each animal.
Significant fed vs. fasted difference, p<0.05, Student's t test.
-------
Table 10-7
Metabolism of C-Viriylidene Chloride and Covalent Binding of C Activity to Rat Hepatic Tissue
after Inhalation Exposure to 10 or 200 ppm of C-Vinylidene Chloride (McKenna et al., 1978a)
Exposure con-
centration and
pre treatment
Body burden (mg of
C-vinylidene
chloride/kg)
Metabolized C-
vinylidene chloride
(mg Eq/kg)
Microgram equivalents of
C-vinylidene chloride
bound per gram of
liver protein
B/AC
o
1
ru
-tr
10 ppm
Fed
Fasted
200 ppm
Fed
Fasted
2.89 + o
2.30 + o
44.53 + 6
35.93 ± 0
.12b
.05
•05H
.30d
2.84 +
2.26 +
42.73 +
32.92 +
0.13°
0.06
3.18
0.32°
2
2
64
79
.49 +
.47 +
.18 +
.46 +
0.17
0.29
7.97
4.90
0
1
1
2
.88 +
.10 +
.49 +
.42 +
0.08
0.15
0.10 .
0.17d
Covalent binding data normalized to account for differences in metabolized vinylidene chloride.
All values represented the mean + SE for four rats.
Calculated from the total C activity recovered (end-exposure body burden) minus the C-vinylidene chloride
exhaled from each rat.
Significantly different from fed rats exposed to the same concentration of vinylidene chloride, p<0.05, Student's
t test.
-------
had greater amounts (per mg protein) of radioactivity bound to protein and
nucleic acid of the cytoplasmic fraction than did fed rats.
The relationship among glutathione depletion, total metabolism, and
covalent binding to macromolecules is not clear, as shown in Figure 10-3.
Immediately after a 6-hour inhalation exposure to C-vinylidene chloride, male
rats were sacrificed and hepatic glutathione and covalent binding of radio-
activity to protein and nucleic acids were measured. The total amount of vinyli-
dene chloride metabolized was apparently measured, as indicated in the legend to
Table 10-7. Glutathione depletion and metabolism of vinylidene chloride
displayed a similar, non-linear, dose dependence, whereas covalent binding
increased linearly with increased exposure concentrations (McKenna et al., 1977;
Dedrick, 1979; McKenna, 1979).
Suggestive evidence for an enhancement of hepatic lipid peroxidation _in
vitro after vinylidene chloride administration in vivo has been obtained in rats
under conditions designed to overwhelm the GSH conjugating capacity of the liver:
i.e., the rats were pretreated with phenobarbital to induce mixed-function
oxidases and were then treated with a very high dose of vinylidene chloride (500
mg/kg) (Siegers et al., 1982). This dose is higher than those used by other
investigators to produce hepatic damage in noninduced rats (Section 10.2.1). In
general, however, the hepatotoxic effects of vinylidene chloride are not thought
to be due to a lipoperoxidative mechanism of action (Section 10.2.1).
10.1.2.2.2 Minor Oxidative Pathway for Monochloroacetic Acid
Yllner (1971) demonstrated the oxidative degradation of C-monochloro-
acetic acid to glycolic acid, oxalic acid, and COp by mice after intraperitoneal
administration. S-(Carboxymethyl-1,2- Ocysteine was not metabolized to
appreciable amounts of labeled C02 anc* hence is not an intermediate in the
metabolism of monochloroacetic acid to COp (Yllner, 1971). Trace amounts of
10-25
-------
s
(N
CO
CM
100
3 2 2.5-,
ig uJ
S K
S O
cc
LU
2.0-
1.5-3
a
U
Q
1.0-
o
0-5—|
o
c
* 0
0
150
ppm 14C-VDC
200 250
(McKenna et al., 1977)
' I
) 50
I
100
1
150
' 1
200
1
250
EXPOSURE CONCENTRATION ( ppm)
(McKenna et_ a_l. , 1977, replotted by Dedrick, 1979)
Figure 10-3 Dose-Response Relationship for Hepatic Glutathione (GSH)
Levels, Total Metabolism of 1L+C-Vinylidene Chloride (VDC),
and Covalent Binding of Radioactivity to Hepatic
Macromolecules.
10-26
-------
14
labeled oxalic acid have been detected in experiments with C-monochloroacetic
acid in rats (Jones and Hathway, 1978a). Small amounts of labeled C0_ and urea
were identified as metabolites of 1 C-vinylidene chloride (see Table 10-5)
(Jones and Hathway, 1978b). Thus it appears that the metabolism of monochloro-
acetic acid to C0? is a minor pathway in the metabolism of vinylidene chloride.
10.1.3 Excretion
Vinylidene chloride and its metabolites are excreted fairly rapidly by
experimental animals. The influence of route of administration and size of dose
on the pattern of excretion of vinylidene chloride and its metabolites by male
rats is shown in Table 10-8 (Jones and Hathway, 19?8a). According to Jones and
Hathway (19?8a), f>Q% of the 0.5 mg/kg intraveous dose of C-vinylidene chloride
was expired unchanged within 5 minutes of injection; 80% was expired unchanged
within 1 hour. These results indicated an efficient arterial-alveolar transfer
of vinylidene chloride. With intragastric or intraperitoneal administration of
0.5 mg/kg of14C-vinylidene chloride, most of the radioactivity was excreted in
the urine within the first 2U hours, whereas with 350 mg/kg, most of the radio-
activity was expired as unchanged vinylidene chloride. The percentage of radio-
activity expired as C0? decreased with the higher dose of vinylidene chloride.
These changes in the pattern of excretion were attributed by Jones and Hathway
(1978a) to saturable drug metabolism and to the efficient transfer of vinylidene
chloride from systemic blood to the alveoli, leaving a relatively low concentra-
tion of vinylidene chloride available for metabolism in subsequent passes
through the liver.
Similar dose-related shifts in the relative proportion of radioactivity
excreted by various routes have been reported by Reichert et al. (1979) for
111
intragastric administration of C-vinylidene chloride (0.5, 5.0, and 50 mg/kg)
to female rats and by McKenna et al. (1978b) for intragastric administration of 1
10-27
-------
Table 10-8
11,,
Excretion of Radioactivity by Male Rats Given 0.5 rag/kg or 350 mg/kg C-Vinylidene Chloride Intragastrically,
Intravenously, or Intraperitoneally (Jones and Hathway, 1978a)
Radioactivity Excreted (Percent of Dose)a
Intragaatric
Size
of Time
Dose (h)
0.5 0-24
mg/kg
_ 24-48
0
r^o 48-72
oo
Total
150 0-24
mg/kg
24-48
48-72
Total
Exhaled
Vinylidene
Chloride
0.6+0.2
0.06
0.08
0.7+0.1
62.4+4.3
4.8+2.8
0.1
67.3+4.3
Air
Carbon
Dioxide
3.9+0.7
0.5+0.4
0.5+0.2
4.8+1.3
0.3
0.4
0.3
29.5+6.7
Intravenous Intraperitoneal
Exhaled Air Exhaled Air
Urine
71
5
3
80
17
10
1
1
.3+1
.2
.3+0.9
.6+1
.2+1
.6+4
.0+4
.9+1
.3+0
.7
.4
.4
.0
.0
.4
Vinylidene
Feces Chloride
5.1+0.7 80.0+4.0
2.7+0.9 0
0.6+0.2 0
8.3+0.1 80.0+4.0
0.4
0.5+0.3
0.4
Carbon Vinylidene
Dioxide Urine Feces Chloride
3.5+0.6 14.4+3.6 0.3 11.4+2.8
0 0.7+0.2 0.1 0.2
000 0.1
3.5+4.0 15.0+3.9 0.4 11.7+_2.8
90.5+2.9
0.6+0.3
0
91.1+3.2
Carbon
Dioxide
2.6+0.7
0.5+0.1
0.5+0.2
3.6+0.7
0.7+0.4
0.5+0.2
0.1
1.3+0.6
Urine
65.8+2.5
2.0+0.1
1.2+0.3
69.0+2.8
7.1+2.1
0.3
0.3
7.7+2.1
Feces
14.2+4
1.6+1
0.4
16.2+4
0.5+0
0.1
0.1
0.7+0
.4
.1
.5
.2
.3
Values shown are the Mean + Standard Deviation of those means (n=four per group).
-------
and 50 mg/kg C-vinylidene chloride to fed and fasted male rats. Fed and fasted
ili
male rats that inhaled 200 ppm C-vinylidene chloride exhaled a greater percen-
tage of their body burden as unchanged vinylidene chloride than did rats exposed
to 10 ppm, but this was the only significant dose-related change in excretion
(see Table 10-1) (McKenna et al., 1978a). After intragastric administration of
ill
50 mg/kg C-vinylidene chloride, fasted male rats exhaled a greater percentage
of the dose as unchanged vinylidene chloride and a lesser percentage in the urine
than did fed male rats (McKenna et al., 1978b). No such difference was apparent
with a dose of 1 mg/kg. These results indicate a reduced capacity for metabolism
of vinylidene chloride in fasted animals. Fed/fasted and species differences in
excretion that have already been noted in Section 10.1.2 will not be discussed
here.
Following intragastric administration of 350 mg/kg C-vinylidene chloride,
urinary excretion of radioactivity in intact male rats was approximately equal to
the sum of the separate urinary and biliary excretions in male rats with biliary
fistulae (Jones and Hathway, 19?8a). This finding suggests that the origin of
part of the urinary radioactivity was via the enterohepatic cycle.
Reported half lives of excretion for different nutritional states (fed
versus fasted) and dose levels are compiled in Table 10-9. The only difference
between fed and fasted rats was that fed rats excreted urinary metabolites more
rapidly during the first 48 hours after administration of 200 ppm than did fasted
rats (McKenna et al., 1978b). Changes in half-lives with increasing doses are
inconsistent. It is not known whether the inconsistencies could be due to normal
experimental variation, to an effect on more than one process, or to possible
toxic effects.
10.1.4. Summary of Pharmacokinetics. Vinylidene chloride is readily absorbed
by mammals following oral or inhalation exposure. Judging from excretion in the
10-29
-------
Table 10-9
Half-Lives of Excretion of C-Vinylidene Chloride, C0_, and
Radiolabeled Urinary Metabolites of C-Vinylidene Chloride
Dose
Excretion Route Amount
Pulmonary
Vinylidene intragastric 1 mg/kg
chloride 50 mg/kg
intragastric 0.5 mg/kg
5.0 mg/kg
50.0 mg/kg
O inhalation 10 ppm
^ 200 ppm
O
Carbon Dioxide intragastric 0.5 mg/kg
5.0 mg/kg
50.0 mg/kg
Urinary
Metabolites intragastric 1 mg/kg
50 mg/kg
intragastric 0.5 mg/kg
5.0 mg/kg
50.0 mg/kg
inhalation 10 ppm
200 ppm
200 ppm
Rates
Sex
male
male
female
female
female
male
male
female
female
female
male
male
female
female
female
male
male
male
Nutritional
Status
fed and fasted*
fed and fasted*
fed
fed
fed
fed and fasted*
fed and fasted*
fed
fed
fed
fed and fasted* .
fed and fasted*
fed
fed
fed
fed and fasted*
fed
fasted
Half-lives
Rapid
Phase
25 min
21 min
13 min
18 min
27 min
20 min
21 min
4 hr 30 min
4 hr 45 min
2 hr 15 min
6 hr
6 hr
4 hr 30 min
3 hr 1)5 min
5 hr 15 min
3.1 hr
4.5 hr
3.8 hr
Slow
Phase
117 min
66 min
381 min
217 min
133 min
35 hr
24 hr
20 hr 45 min
16.8 hr
16.8 hr
18 hr 30 min
14 hr
25 hr
19.3 hr
1 hr
23.9 hr
Reference
McKenna et al., 1978b
Reichert et al., 1979
McKenna et al., 1978a
Reichert et al., 1979
McKenna et al., 1978b
Reichert et al., 1979
McKenna et al., 1978a
fasted
-------
exhaled air and urine, most of an orally administered dose is absorbed through
the gastrointestinal tract. Data for retention (as a percent of the inhaled
concentration) during inhalation exposure were not encountered. Vinylidene
chloride is metabolized in the liver with a number of possible reactive inter-
mediates, including an epoxide, being formed. These reactive intermediates may
react with macromolecules, producing toxic effects, and are detoxified primarily
by conjugation with glutathione. Excretion of metabolites and parent compound
occurs primarily via the urine and the exhaled air, with greater percentages of
the dose being exhaled as unchanged vinylidene chloride at high doses/exposures.
Vinylidene chloride does not appear to be stored or accumulated in the tissues.
10.2 ACUTE, SUBACUTE, AND CHRONIC TOXICITY
10.2.1 Acute Exposure
As a class, the halogenated olefins and the chloroethylenes in particular
show many similarities in their biologic effects. Anesthesia, hepatotoxicity,
and nephrotoxicity are commonly measured indices of acute exposure in experi-
mental animals, although considerable differences exist in relative potency.
Factors that influence the toxicity of chloroethylenes include inherent chemical
reactivity, species, sex, diet, and exposure to exogenous chemicals that modify
drug-metabolizing enzyme activity. With the chloroethylenes (e.g., vinylidene
chloride, trichloroethylene, vinyl chloride, perchloroethylene), toxic effects
appear to be mediated by the metabolic formation of a critical intermediate,
which is probably an epoxide (Andersen and Jenkins, 1977; Andersen et al., 1979b;
Reynolds and Moslen, 1977; Jaeger, 1977).
Carpenter and coworkers (19*19) published the first report on the toxicity of
vinylidene chloride. They indicated that a single 4-hour inhalation exposure to
32,000 ppm was lethal to 2, 3, or 4 rats out of a group of 6 (exact number that
died was not specified) over a 14-day observation period. More subjective
10-31
-------
information on the acute inhalation toxicity of vinylidene chloride was
published in 1962 by Irish (1962) at the Dow Chemical Company. He reported that
exposures to 4000 ppm could rapidly produce stupor and unconsciousness, but noted
that complete recovery from the anesthetic effect was probable if duration of
exposure was brief. No-effect levels for experimental animals were estimated at
1000 ppm for up to 1 hour and 200 ppm for up to 8 hours. These values are in
reasonable agreement with the data of Siegel et al. (1971), indicating that the
4-hour LC50 for vinylidene chloride in rats is about 6350 ppm.
Over the past decade, several groups of investigators have explored the
biochemical mechanism of vinylidene chloride-induced hepatotoxicity in rats.
These studies were prompted by early observations that the toxicity of vinylidene
chloride was similar to that of carbon tetrachloride, a well documented hepato-
toxin (Jenkins et al., 1972). Initial studies involving the administration of
single oral doses (500 mg/kg) to rats established that vinylidene chloride
produced biochemical changes that were qualitatively similar to those produced
by carbon tetrachloride (Jenkins et al., 1972). These included depressed liver
glucose-6-phosphatase activity and increased activities of liver alkaline phos-
phatase and tyrosine transaminase, and of plasma alkaline phosphatase and
alanine aminotransferase. In addition, vinylidene chloride displayed greater
potency than did carbon tetrachloride in its effect on several of these bio-
chemical parameters. In contrast to carbon tetrachloride, however, the
biochemical alterations induced by vinylidene chloride were less pronounced in
female rats and were reduced by pretreatment of animals with phenobarbital, an
inducer of hepatic drug-metabolizing enzymes. On the other hand, Carlson and
Fuller (1972) demonstrated that enzyme inducers (phenobarbital and 3-methyl-
cholanthrene) as well as enzyme inhibitors (SKF 525A and Lilly 18947) increased
the lethality of vinylidene chloride by inhalation in rats, whereas the opposite
10-32
-------
effect was seen in rats receiving carbon tetrachloride. These results strongly
suggested a mechanism of toxic action for vinylidene chloride that differed from
that for carbon tetrachloride. Confirmation of this belief was provided by
Jaeger and coworkers (1973a,b), when they demonstrated that the hepatotoxic
effects of vinylidene chloride are not due to a lipoperoxidative mechanism of
action, as is the case with carbon tetrachloride.
Further studies on the hepatotoxicity of vinylidene chloride have focused
on the relationship of metabolism to acute toxicity, and the influence of nutri-
tional status, age, and sex on mortality. Jaeger and coworkers (1973a) observed
that the acute lethality of vinylidene chloride administered by inhalation in
male rats was greater during the period from 6:00 p.m. to 10:00 p.m. than during
the period 6:00 a.m. to 10:00 a.m. This pattern of sensitivity to vinylidene
chloride was correlated with the diurnal variation in hepatic glutathione
concentration, which is highest during the day and lowest during the night.
Thus, the hypothesis was offered that a glutathione-dependent pathway mediates
the detoxification of vinylidene chloride, a mechanism which is known to be
important in the detoxification of certain carcinogenic chemical intermediates
(e.g., epoxides) (Jaeger, 1979). The importance of adequate hepatic glutathione
concentrations in protecting against acute intoxication with vinylidene chloride
has subsequently been confirmed in studies using fasted animals that have reduced
hepatic glutathione levels (Jaeger et al., 1974; Andersen and Jenkins, 1977). In
male rats fasted for 18 hours, the 24-hour LC50 following a 4-hour inhalation
exposure to vinylidene chloride was 600 ppm, whereas in fed animals an estimated
LC50 of 15,000 ppm was obtained (Jaeger et al., 1974). The minimum lethal
concentration of vinylidene chloride was 200 ppm in fasted animals and 10,000 ppm
for fed animals. The functional state of the thyroid gland, which apparently
played a role in the regulation of glutathione levels in the liver, also
10-33
-------
influenced the hepatotoxicity of vinylidene chloride (Jaeger et al., 1977b;
Szabo et al., 1977). Chemical or surgical thyroidectomy was associated with an
increase in hepatic glutathione, and a concomitant decrease in the mortality and
hepatic necrosis caused by a 4-hour inhalation exposure of fasted male rats to
2000 ppm vinylidene chloride.
The studies of Jaeger (1977) and his coworkers (Jaeger et al., 1977a,b) led
to the hypothesis that the mechanism of toxicity for vinylidene chloride involved
damage to hepatic cellular mitochondria. This postulation was supported by
evidence showing biochemical alterations following exposure of fasted male rats
to vinylidene chloride (200-500 ppm for 1-24 hours); these alterations were
indicative of an inhibition of the tricarboxylic acid cycle. Among these changes
was a significant elevation of hepatic citric acid concentration in fasted (i.e.,
glutathione deficient) rats after 12 hours of exposure to 250 ppm vinylidene
chloride in air. Thus, the authors suggested that vinylidene chloride may induce
mitochondria-specific injury via the metabolic formation of monochloroacetic
acid, which may subsequently give rise to monochlorocitric acid.
Studies conducted by Reynolds et al. (1975) and Reynolds and Moslen (1977)
supported the theory that vinylidene chloride is a unique hepatotoxin in terms of
its rapid action and its effect on mitochondria. The acute hepatotoxicity of
chloroethylenes was shown to be, in decreasing order: vinylidene chloride >
trichloroethylene > vinyl chloride > perchloroethylene. Exposure of rats to
vinylidene chloride by inhalation (200 ppm, 4 hours) produced an abrupt hemorr-
hagic centrilobular necrosis. Parenchymal cell injury is characterized by
retracted cell borders with pericellular spaces forming that may contain red
blood cells and fibrin. Nuclear changes include the loss of perinucleolar
chromatin and the aggregation of chromatin along the nuclear perimeter against
the nuclear envelope. Within 2 hours after onset of exposure, swollen and
10-34
-------
ruptured mitochondria were observed in hepatic parenchymal cells, whereas the
rough and the smooth endoplasmic reticulum appeared normal. In contrast,
trichloroethylene, carbon tetrachloride, vinyl chloride, and perchloroethylene
all produced damage to the endoplasmic reticulum.
Reynolds et al. (1980) associated the biochemical changes in the liver, such
as sodium, potassium, calcium and glutathione (GSH) levels, with subsequent
histological changes in rats exposed to 200 ppm vinylidene chloride for 1 to 4
hours. By the end of the first hour of exposure, sorbital dehydrogenase (SDH)
activity was elevated and hepatic Na levels increased while GSH decreased. This
trend continued for the second hour of exposure. By the third and fourth hour
SDH, as well as serum alanine aminotransferase activity, and sodium and calcium
levels were greatly increased above controls. These increases remained high for
12 hours post-exposure. Histological injury included nuclear changes and
centrilobular necrosis. Ion changes were attributed to changes in the membrane
ion pumps, either directly or due to an adenosine triphosphate (ATP) deficiency.
Decreased levels of GSH were attributed to a conjugation reaction in the metabo-
lism of vinylidene chloride. Enzymatic activity increased during detoxification
(Reynolds et al., 1980).
Similarly, Chieco et al. (1982) combined histological and chemical analyses
to study the hepatotoxic effect of acute exposure to vinylidene chloride in rats.
Histochemical testing was conducted at 1, 2, 4, or 6 hours after oral doses of
50, 100, 150, or 200 mg vinylidene chloride. The degree of liver or hepato-
cellular damage was assessed by histology and by measurements of liver ion levels
(Na, Ca and K) and serum transaminase activity. Injury was noted in the form of
increased transaminase activity, decreased membrane adenosine triphosphatase
activity, decreased succinate dehydrogenase activity (on the inner mitrochon-
drial membrane) and corresponding changes in the plasma and mitochondrial
10-35
-------
membrane histology. The investigators (Chieco et al., 1982) concluded that
membranous organelles and membrane bound enzymes were the primary sites of hepa-
tocellular damage by vinylidene chloride. These changes in turn resulted in
secondary alterations in glutathione levels, cellular ion imbalances, and
cytoplasmic changes (Chieco et al., 1982).
Recently, vinylidene chloride has been shown to inhibit the activity of rat
liver microsomal calcium pumps in the presence of a NADPH-generating system. The
calcium pumps were not inhibited when vinylidene chloride was applied in vitro in
the absence of a NADPH-generating system (Moore, 1980; Ray and Moore, 1982).
Moore (1982) also reported inhibition of the liver endoplasmic reticulum calcium
pump activity by vinylidene chloride. The concomitant rise in liver calcium
levels occurred soon after vinylidene chloride administration and was attributed
to the inactivity of the calcium pumps. Calcium released from the endoplasmic
reticulum may serve as a trigger for the influx of extracellular calcium and,
ultimately, cytotoxicity (Moore, 1982).
Information regarding the acute toxicity of vinylidene chloride is not
restricted entirely to its effect on the liver. Jenkins and Andersen (1978)
recently reported a nephrotoxic action of vinylidene chloride following oral
administration to rats. Biochemical indices of kidney damage (plasma urea
nitrogen, plasma creatinine) were elevated in fasted male rats given a single
oral 400 rag/kg dose of vinylidene chloride (Table 10-10). Conversely, rats that
were not fasted were protected from the nephrotoxic effect. At doses below 400
mg/kg, no significant alterations were noted in plasma indicators of kidney
damage (Table 10-11). In addition, female rats were much less sensitive to the
effects of vinylidene chloride on the kidney. In both male and female rats,
however, histological evidence of renal damage was obtained at various times
following the administration of a single oral dose of 400 mg/kg vinylidene
10-36
-------
Table 10-10
Influence of 24-Hour Fasting on the Effect of Oral
Administration of Vinylidene Chloride (400 mg/kg)
in Corn Oil on Plasma Urea Nitrogen Concentration
in Male Rats (341 + 7 g)a
Status
Fasted
Fasted
Fed
Fed
Hours After
Challenge Challenge
Corn Oil 24
48
72
Vinylidene 24
chloride
48
72
Corn Oil 24
48
72
Vinylidene 24
chloride
48
72
Urea Nitrogen
(nig/ 100 ml)
21 ± 1b
20 + 1
22 + 1
51 + 16°
82 + 39°
50 + 3°
20 + 2
21 + 1
22 + 1
19 + 2
12±2d
15 + 1°
o
Source: Jenkins and Andersen, 1978
All data are expressed as mean + SE of groups of 3 to 6 rats.
Significantly higher (p<0.05) than fasted, corn oil-challenged controls
at the same time after challenge (method of analysis not mentioned).
Significantly lower (p<0.05) than fed, corn oil-challenged controls at
the same time after challenge.
10-37
-------
Table 10-11
Relationships of Plasma Indicators of Kidney Damage to Dose 24 Hours
After Oral Administration of Vinylidene Chloride to Male Rats
(289 + 9 g)a
Dose (rag/kg)
0
50
100
200
400
800
Urea Nitrogen
(mg/100 ml)
20 + 2b
23 ± 1
26 + 1
32 + 7
80 ± 1C
108 + 18°
Creatinine
(mg/100 ml)
0.76 + 0.06
0.61 + 0.11
0.62 + 0.06
0.80 + 0.06
2.33 + 0.05°
NDd
aSource: Jenkins and Andersen, 1978
All data are expressed as mean +_ SE of groups of two to six rats.
CSignificantly different from zero-dose control (p<0.05); however,
the method of analysis was not mentioned.
Not done
10-38
-------
chloride (Table 10-12). Since female rats showed the same, if not greater,
histologic damage to the kidney as did males, it was suggested that biochemical
parameters may not be sensitive indicators of kidney damage in females.
A single report has been published (Siletchnik and Carlson, 1974)
concerning the cardiac sensitizing effects of vinylidene chloride by acute
inhalation exposure in rats. Cardiac arrhythmias could not be produced by a
single 4 ng/kg injection of epinephrine to male rats; however, when rats inhaled
25,600 ppm vinylidene chloride for 80 minutes, doses of epinephrine as low as 0.5
jig/kg could elicit serious cardiac arrhythmias, which could be further enhanced
by pretreatment of rats with phenobarbital (50 mg/kg i.p. for 4 days).
Pulmonary damage has been observed in mice after either oral or intraperi-
toneal administration of vinylidene chloride (Forkert and Reynolds, 1982;
Krijgsheld et al. , 1983). At 6 hours after administration, a single oral dose of
100 mg/kg produced degeneration of the endoplasmic reticulum of the Clara cells
of the bronchiolar epithelium; a single oral dose of 200 mg/kg resulted in
necrosis of both ciliated and Clara cells, with exfoliation of the bronchiolar
epithelium (Forkert and Reynolds, 1982). Hypoxia (measured as a decrease in
oxygen partial pressure of arterial blood) was observed 24 hours after adminis-
tration of the higher dose, but the animals recovered and the bronchiolar epithe-
lium had regained a normal appearance by 7 days. Clinical chemistry indices of
liver damage (SGOT and SGPT levels) were greatly elevated even at the 100 mg/kg
dose, 24 hours after administration.
Twenty-four hours after intraperitoneal injection of mice with vinylidene
chloride at a dose of 125 mg/kg, microscopic examination of the lungs revealed
necrosis and sloughing of the Clara cells lining the bronchioles (Krygsheld et
al., 1983). Pulmonary cytochrome P-450 levels and related monoxygenase activi-
ties were decreased; the authors suggested that these decreases may have been a
10-39
-------
Table 10-12
Comparison of Prevalence of Histopathologic Effects of Oral Administration of
Vinylidene Chloride (400 mg/kg) in Male and Female Rat Kidneys (Jenkins and Andersen, 1978)
Time in
hours after
Vinylidene
Chloride
Treatment Sex
0
3 2
i
jr
O
4
8
24
48
72
M
F
M
F
M
F
M
F
M
F
M
F
M
F
Prevalence of Effect
Chronic Tubular
Normal Inflammation Pigment Dilitationc Necrosis Vacuolization6
6/8f 1/8
2/4 2/4
7/8
1/4 1/4
8/8
1/4
4/4
—
1/2
1/4
1/3
— —
— — __
—
1/8
—
1/8
3/4
—
3/4
• M «« B
4/4
1/2
3/4 1/4
2/3 2/3 1/3
2/4 — 3/4 1/4
2/3 3/3 1/3
3/4 3/4 4/4 1/4
-------
Table 10-12 (cont.)
Time in
hours after
Vinylidene
Chloride
Treatment
96
o 12°
i
4r
144
Prevalence of Effect
Sex Normal
M
F 1/4
M
F
M
F
Chronic
Inflammation3 Pigment
2/3
2/4
2/2
2/4
2/2
3/4
Dilitation0
1/2
1/4
1/2
1/4
1/2
4/4
Tubular
Necrosis Vacuolization
-
1/4 1/4
— —
1/4 1/4
— *. — —
— — ™ —
rocal collections of mononuclear cells were present.
^ew to several tubules contained blue-black amorphous material.
Q
Focally, the tubules were distended and lined by basophilic regenerated epithelium.
xhe tubular epithelium, chiefly proximal, showed eosinophilic coagulative necrosis with loss of cellular detail
and inflammatory cell infiltration.
Q
The lining epithelium of occasional tubules contained cytoplasmic vacuoles.
f
Number of tissues in which effect was seen per number of tissues examined.
-------
reflection of the destruction of the Clara cells, which are known to contain
relatively high levels of cytochrome P-450. The livers and kidneys of the
treated mice were relatively unaffected, as judged by microscopic appearance,
cytochrome P-450 content and monoxygenase activities.
10.2.1.1 Mechanisms of Toxicity
The acute toxicity of vinylidene chloride is altered by several factors in
addition to the effects on sensitivity produced by fasting. A series of time-
course and dose-response studies that explored mechanisms of toxicity for
vinylidene chloride have recently been published.
Chieco et al. (1981) examined the effect of the administration vehicle on
the toxicity and bioligical fate of vinylidene chloride in fasted and fed male
Sprague-Dawley rats. Vinylidene chloride was given at 200 mg/kg orally in corn
oil, mineral oil, or aqueous Tween-80 (0.5%; Sigma). Measurements of exhaled
vinylidene chloride (unchanged) were taken at 15 minute intervals for 5 hours
and rats were sacrificed at 6 hours for biochemical analyses as an assessment of
hepatic injury. The vehicle did not affect the overall amount of vinylidene
chloride exhaled, which ranged from 37 to 51% of the administered dose. The
nature of the administration vehicle did, however, alter the rate at which
vinylidene chloride was absorbed and exhaled. Aqueous Tween-80, which is readily
absorbed, allowed the vinylidene chloride to be readily absorbed and exhaled in a
shorter period of time. Corn oil was intermediate, while the poorly digested
and absorbed mineral oil prolonged absorption and exhalation times in fasted and
fed rats. Hepatic injury, measured as elevated glutamic oxalacetic transaminase
(GOT) and glutamic pyruvic transaminase (GPT) serum levels, was greatest in
fasted rats treated with vinylidene chloride in mineral oil or corn oil (up to
150-fold increase in GOT and GPT levels). Fasted rats treated with vinylidene
chloride in Tween-80 were moderately affected (15 to 18 times increase in GOT and
10-42
-------
GPT levels). In fed rats treated with vinylidene chloride in corn or mineral
oil, enzymatic activity was slightly elevated (2 to 5 times) above the enzymatic
activity in fed rats, while GOT was not different from control levels. Chieco et
al. (1981) in connection with results of this study suggested that decreased
hepatic injury in fed animals is due to the ability of these animals to detoxify
vinylidene chloride over a longer period of time than fasted animals.
Histologically, fasted rats fed vinylidene chloride in corn or mineral oil
showed massive hepatic necrosis, which was consistent with biochemical changes.
Only scattered necrotic hepatocytes were seen in fasted animals given vinylidene
chloride in aqueous Tween-80. Fasted animals given vinylidene chloride in corn
oil or mineral oil also had granular "heme" casts in Henle's loop of the kidney.
Concomitant high levels of free plasma hemoglobin and "pink urine" were noted in
these animals. No pathological abnormalities were observed in the heart, lungs,
spleen, adrenals, or duodenum in vinylidene chloride-treated animals (Chieco et
al., 1981).
Andersen and Jenkins (1977) observed that body size or the age of the animal
had a dramatic effect on the toxicity of vinylidene chloride when a single oral
dose was given to fasted male rats. Dose-response curves for vinylidene
chloride-induced mortality were constructed for animals of three different sizes
(Figure 10-4). Mortality among large animals (395 + 11 g) increased linearly
from 0 to 100? at doses between 800 and 2000 mg/kg; however, minimum lethal doses
were found to be as low as 50 mg/kg. In medium-sized rats (224 _+ 1 g), doses
between 50 and 800 mg/kg produced mortality which varied from 10 to 33%. The
most aberrant results were obtained in small rats (73 +• 1 g). Mortality
increased to 100? at a dose of 300 mg/kg, but then decreased with increases in
dose up to 800 mg/kg. The LD5Q values calculated from the data presented in
10-43
-------
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Figure 10-4 would appear to be widely variable as shown by dependence on body
size.
In an attempt to explain the effect of body size on acute mortality,
Andersen and Jenkins (1977) examined the relationship between hepatotoxicity
(indicated by plasma enzyme levels) and body size following the administration of
a. single oral 50 mg/kg dose of vinylidene chloride in corn oil. They found that
both mortality within the first 24 hours and plasma enzyme activities after 24
hours were greatest among rats weighing between 130 and 160 g. In animals of
this size, the estimated LD,_0 was less than 50 mg/kg, whereas in large rats, the
LD^0 would be 30 times greater. The unusual dose-mortality curve for immature
rats (see Figure 10-4) was partially explained by the fact that increases in
plasma transaminase activities paralleled mortality, and the retention of orally
administered vinylidene chloride reached a maximum at a total dose of 100 mg/kg
and then leveled off.
In comparison to fasted male rats, female animals were much less susceptible
to the effects of vinylidene chloride. Plasma transaminase levels were not
altered by a 50 mg/kg dose, regardless of body size. In female rats, the
threshold dose for expression of acute toxic effects (plasma transaminase eleva-
tion) was about 100 mg/kg. Based on their results and on analogy to other
halogenated hydrocarbons, Andersen and Jenkins (1977) postulated that vinylidene
chloride is metabolized by a saturable microsomal enzyme-mediated reaction to a
toxic intermediate that is probably an epoxide. A second enzyme-mediated
reaction that converts the toxic intermediate to a less toxic form was also
proposed. In young rats, this detoxification mechanism may be absent or present
at only low levels, thus accounting for increased susceptibility.
In subsequent studies, Andersen and coworkers (1978, 1979b) examined in
greater detail the relationship between vinylidene chloride metabolism and
10-45
-------
expression of toxic effects. Chemical modifiers of microsomal enzyme activity
were administered to fasted male rats followed by a single oral dose of vinyli-
dene chloride (Andersen et al., 1978). Phenobarbital pretreatment, which causes
microsomal enzyme induction, protected rats against the lethal effects of
vinylidene chloride. This protection by phenobarbital was opposite to that
observed by Carlson and Fuller (1972) following inhalation exposure of rats.
This protective action increased with increasing body size. Conversely, the
microsomal enzyme inhibitor SKF 525A greatly enhanced the lethality of vinyli-
dene chloride in large rats (261 + 2 g) but had little influence in immature rats
(88 + 2 g). In addition, pretreatment of rats with the metabolic inhibitors
pyrazole, aminotriazole, and carbon tetrachloride protected animals of all sizes
against the lethal action of vinylidene chloride. These results supported the
argument that two sequential enzyme-mediated reactions are involved in the
activation of vinylidene chloride. The first reaction, which is inhibited by
pyrazole, aminotriazole, and carbon tetrachloride, leads to formation of a toxic
intermediate. The second reaction, which is affected by phenobarbital and SKF
525A pretreatment, is a detoxification step that apparently exists at greater
levels in mature animals.
Subsequent studies by Andersen and coworkers (1979b) demonstrated that
mortality induced in rats by inhalation of vinylidene chloride failed to follow a
strict concentration x time relationship. Instead, mortality was more dependent
on time of exposure than on concentration once a threshold level (about 200 ppm)
had been reached (Figure 10-5). These data supported the involvement of a
saturable enzymatic reaction in the production of a metabolite that is respon-
sible for the expression of vinylidene chloride-induced toxicity. The authors
appropriately noted that, under conditions of exposure that produce enzyme
-------
3
I
O
CO
(N
4 HOUR EXPOSURES
n = 6/GROUP
250 500
CONCENTRATION (ppml
750
1000
Figure 10-5
Effect of Increasing Concentration of Vinylidene Chloride
on Mortality in Mature Male Rats (Anderson et_ al., 1978)
(Each point represents percentage mortality of a. group of
6 animals exposed for 4 hours.)
-------
saturation, misleading estimates of the LC5Q (inhalation) or LD^Q (oral and
parenteral) could result.
Studies by Short and coworkers (1977a,b) with rats and mice support the
conclusions reached by Andersen et al. (1978, 1979b). Non-fasted animals (groups
of 10) inhaled vinylidene chloride for 22 to 23 hours per day for up to 7 days.
Short et al. (1977a,b) found that male mice were more sensitive than were male
rats to lethal effects and hepatotoxic effects (measured by serum glutamic-
oxaloacetic transaminase and serum glutamic-pyruvic transaminase activities) of
vinylidene chloride (Table 10-13). Histopathologic examination revealed hepatic
and renal damage among male mice exposed to 15, 30, and 60 pptn vinylidene
chloride (1-5 days); hepatic damage only was seen in male rats exposed at 60 ppm
for 3 days. When mice were given disulfuram (0.10$ in feed 23 days before and
during exposure), or thiram (0.10$ in feed 3 days before and during exposure),
the acute lethality of vinylidene chloride was reduced. The authors observed
that these compounds are known to protect against drug-induced toxicity, and may
act by decreasing metabolic activation or increasing detoxification or both.
10.2.2 Subacute and Chronic Exposure
10.2.2.1 Inhalation Studies
Several groups of investigators have characterized the toxicity of vinyli-
dene chloride by repeated administration to experimental animals. Both inges-
tion and inhalation have been employed as routes of exposure. These studies
established that, in general, the target organs affected by chronic exposures
(i.e., liver and kidneys) are the same as those affected by acute administration
of vinylidene chloride.
The first published report regarding the chronic toxicity of vinylidene
chloride was a brief summary of inhalation studies conducted by the Dow Chemical
Company (Irish, 1962). Unspecified animals exposed to 100 ppm and 50 ppm vinyli-
10-48
-------
Table 10-13
Toxicity of 60 ppm Vinylidene Chloride in Male Mice and Rats
(Short et al., 1977b)
Days SCOT
Species Exposed (IU/1]
mouse 1 1946 +
2 751 ±
rat 1 74 +
2 263 +
\
270
150
6
33
SGPT
3045 + 209
1112 _+ 226
44 + 7
198 + 29
Ratio
Dead/Exposed
2/10
8/10
0/10
0/10
+ SE for 2 to 5 determinations
SCOT = Serum glutamic-oxaloacetic transaminase; SGPT = Serum glutamic-pyruvic
transaminase
10-49
-------
dene chloride (5 days per week, 8 hours per day for several months) developed
liver and kidney damage. Minimal lesions were also observed in the liver and
kidney of animals exposed at concentrations of 25 pptn.
Prendergast and coworkers (1967) published the first detailed account of
the chronic toxicity of vinylidene chloride. Groups of rats, rabbits, dogs, and
monkeys were exposed in one of two ways: 30 exposures, 8 hours per day, 5 days
o
per week to a concentration of 395 mg/nr (100 ppm) or 90 days of continuous
•a o o
exposure to a concentration of 189 mg/nr (48 ppm), 101 mg/nr (26 ppm), 61 mg/nr
(16 ppm), or 20 mg/m (5 ppm). The results of these studies are summarized in
Table 10-14. The most prominent effects observed included hepatic damage in
dogs, monkeys, and rats exposed to 189 mg/m ; this damage consisted of fatty
metamorphosis, focal necrosis, hemosiderin deposition, lymphocytic infiltration,
bile duct proliferation, fibrosis, and pseudo-lobule formation. Rats also
showed nuclear hypertrophy of the renal tubular epithelium when exposed to
vinylidene chloride at 189 mg/m .
Gage (1970) conducted limited studies in rats exposed to vinylidene
chloride by inhalation that support the previous observations of Prendergast and
coworkers (1967). Four male and 4 female rats received twenty 6-hour exposures
to vinylidene chloride at concentrations of 500 or 200 ppm. At the higher
concentration, retarded weight gain and nasal irritation were noted. Liver cell
degeneration was observed upon autopsy. Inhalation of 200 ppm vinylidene
chloride produced slight nasal irritation but no significant findings at
autopsy; however, the group size was very small.
Lee and coworkers (1977) exposed CD-1 mice (36 males and 36 females) to 55 ppm
of vinylidene chloride for 6 hours per day, 5 days per week, for up to 12 months.
Two male mice died on the 13th day of exposure, and revealed acute toxic hepa-
titis and tubular necrosis of the renal cortex. Hepatic hemangiosarcomas were
10-50
-------
Table 10-11
Effect on Experimental Animals of Long Term Inhalation of Vinylidene Chloride
(data from Prendergast et al., 196?)
Concentration
Schedule
Species
Mortality
Significant Findings
100 ppm
(395 + 32 mg/m3)
30 exposures,
8 hr/day,
5 days/ week
rat
guinea pig
rabbits
dog
monkey
0/15
0/15
0/3
0/2
0/3
None.
None.
Weight loss in treated animals.
None.
Weight loss in treated animals.
_, 48 ppm
-------
Table 10-14 (cont.)
o
!
U1
Concentration Schedule
26 ppm 90 days,
(101 + 4.4 rag/or*) 24 hr/day
16 ppm 90 days
(61 +5.7 mg/nr5) 24 hr/day
5 ppm 90 days
(20+2.1 mg/nr5) 24 hr/day
Control
Species
rat
guinea pig
rabbit
dog
monkey
rat
guinea pig
dog
monkey
rat
guinea pig
dog
monkey
rat
guinea pig
rabbit
dog
monkey
Mortality
0/15
3/15
0/3
0/2
2/3
0/15
3/15
0/2
0/9
2/45
2/45
0/6
1/21
7/304
2/314
2/48
0/34
1/57
Significant Findings
None.
Mortality occurred between
day 3 and day 5 of exposure.
Animals lost weight.
Animals lost weight.
Mortality occurred between
day 3 and day 6 of exposure.
Animals gained less weight
than controls.
Mortality occurred on day 3
and day 4.
None.
Animals lost weight.
Animals gained less
weight than controls.
None.
Animals lost weight.
None.
-------
observed in three exposed mice, and various hepatic lesions that included
enlarged and basophilic hepatocytes, enlarged nuclei with eosinophilic inclu-
sions, mitotic figures or polyploidy, microfoci of mononuclear cells, focal
degeneration, and necrosis were generally observed (specific incidences were not
given). Hepatic hemangiosarcomas were not observed in any of 72 control mice.
Bronchiolo-alveolar adenomas were observed in six exposed mice and one control
mouse.
Dow Chemical Company performed an inhalation toxicity study with vinylidene
chloride and interim results were published by Rampy and coworkers (1977). In a
90-day study, groups of 40 Sprague-Dawley rats (20 male and 20 female) were
exposed for 6 hours per day, 5 days per week, to vinylidene chloride at a
concentration of 25 or 75 ppm. Eight animals of each sex were sacrificed after
30 days, and the remainder killed after 90 days. Among animals exposed at both
concentrations, increased cytoplasmic vacuolation of hepatocytes was seen 30
days or longer after initial exposure. No other remarkable effects were attri-
buted to the vinylidene chloride exposure.
In another study, Rampy and coworkers (1977) exposed Sprague-Dawley rats
for 18 months (6 hours/day, 5 days/week) to vinylidene chloride at several
concentrations in air. For the first 5 weeks, rats (104 males and 104 females)
were exposed to levels of 10 or 40 ppm, after which the concentrations were
raised to 25 and 75 ppm, respectively, for the remainder of the 18-month exposure
period. Animals were maintained for an additional 6 months after termination of
exposure. Although male rats gained weight at a slightly slower rate than
controls, no clinical evidence of overt toxicity was seen during the study. Both
male and female rats sacrificed at an interim of 1 year, however, showed hepatic
lesions consisting of increased cytoplasmic vacuolation of hepatocytes. In
10-53
-------
addition, higher kidney weights were seen in female rats exposed at both
treatment levels of vinylidene chloride.
The final data of this 2-year inhalation study (interim results reported by
Rampy et al., 1977) were recently compiled and reported by McKenna et al.
(1982). Data were reported on hematologic parameters, urinalysis, clinical
chemistry, cytogenic changes in the bone marrow, body weight, major organ
weights, and histopathology following necropsy on all animals (either at interim
periods of 1, 6 , 12, or 18 months or at the termination of the experiment at 734
to 736 days). Statistical evaluations of data were made using analysis of
variance and Dunnett's test (body weight, hematology, urinalysis, clinical
chemistry, and organ weight data) or by the Fischer exact test (mortality rates,
gross and microscopic pathologies, and tumor incidence). The level of signifi-
cance was chosen as P<0.05.
Mortality figures for male rats exposed to vinylidene chloride at either
dose level did not reveal significant increases. Females exposed at 25 ppm
vinylidene chloride had increased mortality rates when compared to controls from
the 15th through 22nd months. Statistically significant increased mortality
rates in females exposed at 75 ppm vinylidene chloride were noted during months
15, 17, and 21 of the study. The earlier onset of mammary tumors and higher
incidences of pneumonia in treated groups may have contributed to these higher
mortality rates.
No consistent dose-related decrease in mean body weight for male rats
exposed to 25 or 75 ppm vinylidene chloride was observed. A general trend of
decreased body weight was noted in exposed males when compared to control males
but increased mean body weights were noted in the exposed groups sporadically
throughout the study. Generally, females exposed to either 25 or 75 ppm vinyli-
10-54
-------
dene chloride had higher mean body weights for the first 6 months but were
comparable to controls throughout the remainder of the study.
No significant dose-related effects in hematological, urinalysis, clinical
chemistry, or cytogenetic parameters were reported in any exposure group. The
only significant changes in organ weight were a decreased mean liver weight in
males exposed to 25 or 75 ppm vinylidene chloride at the 1-year interim sacrifice
and an increased mean kidney weight in both exposure groups of female rats at 1
year. Both organ weight changes were statistically significant when compared to
controls and considered to result from vinylidene chloride exposure (McKenna et
al., 1982).
Many gross and microscopic lesions were seen in control and vinylidene
chloride-exposed rats; most were spontaneously occurring, age-related changes
common to Sprague-Dawley rats. The incidence of lesions from chronic murine
pneumonia in exposed male and female rats was elevated, but lower levels in
controls were attributed to the physical separation of exposed and control groups
which deterred the spread of pneumonia. Chronic renal disease was the predomi-
nant cause of death in male rats of the study. Females had a high incidence of
subcutaneous tumors of the mammary gland region which was frequently the cause of
death. There was a statistically significant increase in the incidence of
hepatocellular fatty change in female rats exposed to 75 ppm during the 18 month
exposure period. These changes were reversed during the 6 month post-exposure
period, however. Females treated at 25 ppm showed a similar but non-significant
trend. This reversible and non-progressive liver change was noted in males at
the 6 and 12 months interim sacrifice but not at 18 months.
The incidence of pituitary adenomas was decreased in both dose groups of
male rats and the 25 ppm vinylidene chloride dose group of females. There were
fewer pancreatic islet cell adenomas and thyroid adenocarcinoma in male rats
10-55
-------
exposed to 75 ppm vinylidene chloride. Mammary adenocarcinomas were statis-
tically increased in female rats treated at 25 ppm vinylidene chloride.
Subcutaneous or mammary tumors were more prevalent in 75 ppm vinylidene chloride
treated females than in controls. The total number of rats with primary neo-
plasms was similar for both sexes at all dose groups, including controls. The
total number of rats with primary neoplasms was similar (ranging from 84 to 86)
for all 6 dose/sex groups. Summarizing the tumor incidence data, the authors
reported that none of the statistically significant differences were considered
to be direct effects of vinylidene chloride exposure.
10.2.2.2 Ingestion Studies
A single long-term study has been conducted with vinylidene chloride
administered in the drinking water of rats. This study was conducted by the Dow
Chemical Company for the Manufacturing Chemists' Association (Humiston et al.,
1978). Groups of 96 Sprague Dawley rats (48 males and 48 females) were exposed
for 2 years to vinylidene chloride incorporated into the drinking water at
nominal concentrations of 50, 100, and 200 ppm. These dose levels corresponded
to approximate daily intakes of vinylidene chloride in the range of 5-12, 8-20,
and 16-40 rag/kg at the 50, 100, and 200 ppm concentrations, respectively. In
comparison to control animals, vinylidene chloride-treated rats displayed no
significant or consistent differences in general appearance, body weight, food
consumption, water consumption, hematologic values, urinalysis, clinical
chemistry values, or organ weights. Gross and histopathologic examination of
tissues from treated rats, however, revealed a number of statistically signifi-
cant lesions. These are partially summarized in Table 10-15. The authors
considered the most important lesions to be the hepatocellular fatty change and
periportal hepatocellular hypertrophy which occurred in male rats at the 200 ppm
10-56
-------
Table 10-15
Pathologic Effects of Long-Term Ingestion of Vinylidene Chloride
Incorporated in the Drinking Water of Sprague-Dawley Rats
(data from Humiston et al., 1978)
Dose Level
50 ppm 100 ppm 200 ppm
Effect M F M F M F
Increased incidence of intra-abdominal fluid X
or blood in the abdominal cavity
Increased incidence in the total number of
rats with hepatocellular fatty change or
fatty degeneration XXX
Increased incidence of hepatocellular fatty
change with location in lobule not specified XXX
Increased incidence in periportal
hepatocellular fatty change X
Increased incidence of periportal
hepatocellular hypertrophy X XXX
Increased incidence of hepatic
centrilobular atrophy X
Increased incidence of mammary gland
fibroadenomas/adenofibromas X
M = male; F = female
10-57
-------
dose level and in females at all dose levels. The authors did not observe any
hepatocellular necrosis that could be considered treatment-related.
Results of this long-term, oral study with rats were subsequently published
in the open literature by Quast et al. (1983), along with results of a 97-day
oral study with dogs; the dog study was also conducted by the Dow Chemical
Company. Groups of four male and four female beagle dogs were administered
vinylidene chloride in doses of 0, 6.25, 12.5 or 25 mg/kg daily for 97 days. The
chemical or vehicle (peanut oil) was administered orally in a capsule once a day.
As compared with controls, the groups of treated dogs had no differences in
general appearance or demeanor, body weight, food consumption, hematologic and
clinical chemistry values, urinalysis, organ weights and gross and microscopic
appearance of the tissues.
10.2.3 Summary of Toxicity
The biologic activity of vinylidene chloride has been thoroughly studied in
experimental mammals; no information is available concerning the effects of
vinylidene chloride on domestic animals or wildlife.
The toxicity of vinylidene chloride varies with the age, sex, and species of
the animal exposed. In the most studied animal, rat, inhalation exposure to
32,000 to 6,350 ppm has proven to be fatal. In rats fasted prior to exposure, the
LC,-0 value was as low as 600 ppm. For oral adminstration of vinylidene chloride,
however, the determination of an LDj.,. value is difficult as a result of the
relatively flat dose mortality curve which possesses an extended plateau region.
The target organs affected by acute exposure to vinylidene chloride are the liver
and kidneys with evidence from studies of the liver to indicate that mitochondria
damage occurs. Both liver and kidney damage are also observed following
subchronic and chronic exposure to vinylidene chloride by either inhalation or
ingestion. Continuous inhalation exposure of rats to 5 ppm of vinylidene
10-58
-------
chloride has been shown to adversely affect body weight gain while ingestion of
vinylidene chloride by rats at 5 to 12 mg/kg/day produced fatty livers. A
no-observed effect level (NOEL) for inhalation exposure (<5 ppm) or ingestion (<5
mg/kg/day) has not been demonstrated.
10.3 TERATOGENICITY AND REPRODUCTIVE TOXICITY
Short et al. (1977c) performed an extensive investigation of the toxicity
during gestation of inhaled vinylidene chloride in mice and rats (approximately
20 animals in the exposed groups and 60 in the control groups). This study
examined toxicity to the dams, toxicity to the fetus, and teratogenic and
behavioral effects in the pup. In the initial part of the experiment, rats (18
to 20 per group) were exposed to 15, 57, 300, and 449 ppm vinylidene chloride,
and mice to 15, 30, 57, 144, and 300 ppm vinylidene chloride for 23 hours per day
from day 6 to 16 of gestation. In rats, appreciable deaths (over 25%} of the dams
occurred in the 300 to 449 ppm group, and maternal well being, as measured by
food consumption and weight gain, was adversely affected in the 15 ppm and above
groups. Similar results were observed in mice, with no pregnant mice surviving
at the 144 or 300 ppm levels, arid food consumption and weight gain being reduced
in all groups except the 15 ppm animals. Early resorptions were common in
exposed animals, with 100/& resorption in mice exposed to 30 and 57 ppm vinylidene
chloride (resorption in the 15 ppm groups was comparable to controls), and 49 and
64$ resorption in rats exposed to 57 and 449 ppm vinylidene chloride, respec-
tively. Dams that survived the exposure at other concentration levels had
resorption rates comparable to those of controls. There were no increases in
external gross abnormalitites noted in surviving pups in any of the exposed
groups of rats or mice; however, fetotoxicity was observed as soft tissue anoma-
lies in rats (none were observed in mice) and some skeletal ossificaton problems
in all groups of mice and rats. The authors concluded that these anomalies could
10-59
-------
not be evaluated in regard to teratogenic effects, since there were overt signs
of toxicity (reduced weight gain and food consumption) due to the treatment in
the dams. Abnormalities at a similar incidence to those observed in the treated
animals were also observed in a group of animals on a food-restricted diet.
The study was continued using only mice, with a group of 10 to 21* dams
exposed to a variety of concentrations of vinylidene chloride for different
periods of time during gestation (Table 10-16), in an attempt to alleviate
maternal toxicity as usually indicated by decreased maternal weight gain. By
shortening the exposure periods, the incidence of resorption was lessened;
however, treatment-related weight loss in the dams was still evident. It was
interesting to note that exposures starting on days 10 and 12 and ending on day
15 were associated with a higher resorption rate than that observed when expo-
sures were started on day 8 of gestation. This may have occurred because of some
adaptation of the animals as a result of the longer exposure prior to a critical
period during the latter part of gestation. Pups from vinylidene chloride-
exposed dams again had a variety of soft tissue and skeletal anomalies, but these
occurred only when maternal welfare had been adversely affected by the exposure
to vinylidene chloride. In addition, the behavioral studies demonstrated no
major adverse effect on pups exposed in utero to vinylidene chloride. These test
included: surface righting, pivoting, auditory startle, bar holding, righting
in air, visual placing, swimming ability, physical maturation, and activity
test. The authors concluded that vinylidene chloride was possibly a weak tera-
togen based on the increase in soft tissue anomalies although these anomalies
were not statistically significant. However, a conclusion of teratogenicity is
weakened by additional effects on the pups as a result of maternal toxicity at
nearly all concentrations of vinylidene chloride used.
10-60
-------
Table 10-16
Exposure Levels and Duration of Exposure to Vinylidene Chloride
During Gestation in Mice (Short et al.f 1977c)
Vinylidene
Chloride
ppm
54
74
54
41
54
54
112
81
56
1 12
81
56
112
81
56
112
81
56
nil
Days of Gestation
6 7 8 9 10 11 12 13 14 15
R _ -ic
8 ic
8 ic
in ic
i ••> 1 c
6__ __ Q
A Q
6 q
Q 1 p
9_____ ___.ip
9____ ____ip
ip 1C
1 p 1 c
1p ic
1C
IK
1C,
\-J~-
l^ai".ir*n of T?vnrtoiiv>o
16 17
.__ 17
________ 17
.____ _17
10-61
-------
Murray et al. (1979) exposed rabbits to vinylidene chloride by inhalation,
and rats by inhalation and by incorporating the compound into the drinking water
(Table 10-17). Exposure occurred during days 6-15 or 6-18 of gestation for rats
and rabbits, respectively. Inhalation exposure was for 7 hours/day to vinylidene
chloride which was 99 -5% pure and contained the polymerization inhibitor mono-
methylether of hydroquinone (MEHQ) at a level of 200 to 400 ppm. An exposure
level of 200 ppm was employed in the drinking water study using redistilled
vinylidene chloride containing only 1 to 5 ppm of residual MEHQ. On the termina-
tion of the observation period, on days 21 and 29 of gestation for rats and
rabbits, respectively, the dams were killed and examined for changes in liver
weight, and in non-pregnant animals for signs of conception. The fetuses were
measured, examined for external anomalies, and one-third of the animals were
dissected for soft-tissue alteration, while all fetuses were examined for
skeletal alterations.
In the inhalation study in rats, maternal weight gain was decreased in the
80 and 160 ppm groups during the exposure period and increased during the post-
exposure period, while no changes were observed in the 20 ppm groups or the
animals in the drinking water study. Food consumption followed similar trends.
Only in dams exposed to 160 ppm was there an increase in the liver to body weight
ratio, although the absolute liver weight was similar to control animals. Expo-
sure to vinylidene chloride did not affect the outcome of pregnancy as indicated
by number of implants, live fetuses, or resorption rates, nor were there changes
in fetal sex ratios or fetal body weights. There was a significant increase in
the crown-rump length in fetuses of rats receiving vinylidene chloride in the
drinking water. Although no increase in major malformations (taken individually
or collectively) was present, the fetuses of animals exposed in the 80 and 160
ppm groups showed an increased incidence of minor skeletal alterations (Table
10-62
-------
Table 10-17
Number of Animals and Exposure Levels Used to Study
the Teratogenicity of Vinylidene Chloride*
Route
inhalation
oral
Concentration
160
160
80
80
20
0
0
200
0
Species
rats
rabbits
rats
rabbits
rats
rats
rabbits
rats
rats
No. of Animals
30
18
30
22
44
20-47/group
16
26
24
"Source: Murray et al. (1979)
10-63
-------
10-18). The most common skeletal alteration was wavy ribs, which was observed to
be more severe at the higher exposure level. Wavy ribs and delayed ossification
were interpreted as feto- and embryotoxic manifestations of maternal toxicity at
the higher exposure levels. Rats receiving vinylidene chloride in the drinking
water were estimated (using data from metabolism studies) to have received the
equivalent of a 7-hour inhalation exposure to 120 ppm of vinylidene chloride. It
was speculated that a lack of toxic effects in the rats maintained on drinking
water containing 200 ppm vinylidene chloride as compared to the high dose inhala-
tion group may have resulted from diurnal variation in metabolism, although other
mechanisms are also possible.
In rabbits exposed to 160 ppm of vinylidene choride, there was a decrease in
body weight gain during exposure and an increase after termination of exposure.
Only dams exposed at 80 ppm had an increase in liver-to-body-weight-ratio. There
was also an increase in the resorption rate in the 160 ppm group, with resorption
associated with animals having the greatest weight loss. Similar to the study in
rats, exposure to vinylidene chloride produced no increase in major malforma-
tions, although there was an increase in minor skeletal alterations in the 160
ppm group (Table 10-19). Again, the fetal anomalies observed in rabbits were
attributed to maternal toxicity rather than to a teratogenic effect of vinylidene
chloride.
The effect of vinylidene chloride on reproduction and its teratogenic
potential when ingested in the drinking water was tested in a three generation
study in Sprague-Dawley rats (Nitschke et al., 1980; Nitschke et al., 1983). The
parental generation (f ), consisting of 10 male and 20 females in each of three
treatment groups, received 50, 100, or 200 ppm vinylidene chloride. No vinyli-
dene chloride was administered to a control group of 15 males and 30 females.
Equivalent doses for males ingesting 50, 100, or 200 ppm vinylidene chloride
10-64
-------
TABLE 10-18
Incidence of Fetal Alterations Among Rats Exposed to Vinylidene Chloride
By Inhalation or by Ingestion
Route of exposure15 (ppm vinylidene chloride)
External and skeletal
examination
Soft tissue examination
Bones of the skull
External examination
Multiple defects0
Omphalocele
Narrow head, point snout
Soft tissue examination
Diaphragmatic hernia
_» Ectopic ovaries (only)
o
I Skeletal examination
Si Missing one thoracic and
one lumbar vertebrae
Extra thoracic vertebrae
and pair of ribs
Vertebrae, delayed ossifica-
tion of centra of cervical
vertebrae
d
Wavy ribs
Type I1,
T
Type II1
Total
Skull, delayed ossification
Total malformed fetuses
0
470/40
162/40
308/39
1(1)
0
0
0
1(1)
0
0
34(17)
5(5)
4(4)
9(7)
42(17)
2(2)
20
462/40
158/40
304/39
0
0
0
0
0
0
0
58(19)
10(7)
3(2)
13(7)
36(18)
0
Inhalation
0
No. fetuses
230/20
77/20
153/20
No. fetuses
0
0
0
1(1)
0
0
0
24(14)
0
0
0
13(7)
1(1)
Drinking Water
80
examined/No.
292/27
103/27
189/26
0
litters examined
209/17
70/17
139/17
160
291/26
100/26
191/26
0
250/24
86/24
164/23
200
290/25
100/25
190/24
(litters) affected
0
1(1)
1(1)
0
0
0
0
47(17)
9(8)e
2(2)
11(9)
38(13)®
2(2)
1(1)
0
0
0
0
2(1)
1(1)
30(13)
2(1)
1(1)
3(1)
24(8)
4(2)
0
0
0
0
0
14(4)
0
107(20)e
9(5)
13(9)%
22(10)e
59(20)e
14(4)
0
0
0
0
0
0
0
46(16)
0
1(1)
1(1)
19(10)
0
0
0
0
0
0
0
0
72(18)
3(2)
0
3(2)
32(11)
0
aSource: Murray et al., 1979
bRats were exposed to 20, 80, or 160 ppm vinylidene chloride for 7 hours/day or were given drinking water containing 200 ppm of the compound from days
6 to 15 of gestation.
°Each of these fetuses had: short trunk, hypoplastic tail, ectopic ovaries, missing all lumbar and sacral vertebrae, and missing ribs.
^his alteration was considered to be a skeletal variant and was not included in the calculation of the total malformed fetuses.
eSignificantly different from control value by a modified Wilcoxon test, p<0.05
f
Type 1, gentle wave; Type II, callous or "U"-shaped bend in rib
-------
TABLE 10-19
Incidence of Fetal Malformation Among Litters of Rabbits
Exposed to Vinylidene Chloride3
Vinylidene Chloride (ppm)
80
0
160
External and skeletal
examination
Soft tissue examination
External examination
No malformation
observed
No. fetuses/No, litters examined
116/14 155/18 111/13 91/12
44/14 56/18 42/13 37/12
No. fetuses (litters) affected
Soft tissue examination
Dilated cerebral
ventricles
Thinning of ventri-
cular wall of heart
Skeletal examination
Missing ribs
Extra vertebrae
Hemivertebrae and
fused ribs
Total malformed fetuses
0
0
0
0
0
0
KD
0
0
1(1)
1(1)
3(3)
0
0
1(1)
KD
0
2(2)
0
KD
0
0
KD
2(2)
Source: Murray et al., 1979
DRabbits were exposed to 80 of 160 ppm Vinylidene chloride for 7 hr/day from
days 6 to 15 of gestation. No value differed significantly from the control
value by a modified Wilcoxon test, p<0.05.
10-66
-------
continuously in the drinking water were 6, 10, or 19 mg/kg/day, and 8, 13, or 26
mg/kg/day, respectively. Following 100 days of exposure to vinylidene chloride,
all groups of males and females (fQ) were mated (within dose groups), resulting
in the first filial (f.,.) generation. Due to the low fertility rate during this
initial breeding, the f rats were re-mated after a period of no less than 10
days after weaning of the f which produced the f1B offspring. The fQ genera-
tion rats were exposed to vinylidene chloride at the three respective doses for a
2-year toxicity study (Humiston et al., 1975). The f and f1B litters of all
dose groups were examined for reproductive indices (number of litter/number of
dams; survival of pups at 1, 7, 14, and 21 days). The animals to be raised as the
f1 generation adults were randomly selected from the f„ generation and continued
to be exposed to vinylidene chloride. All other f. and f-B rats were sacrificed
at 21-24 days of age for internal and external examinations.
At =110 days of age, the f adults were mated, producing the f2 progeny.
The f litters were examined similar to the previous litters, and randomly
selected males and females were maintained for f2 adults. The remaining f^
weanlings were terminated and examined for external and internal aberrations.
Adult f rats were mated at =110 days of age to produce the f^A gneration.
Survival of the f-,fl litters in all groups receiving vinylidene chloride was
J«
decreased so the f adults were re-mated after the f_A litters were weaned. To
determine if the decreased survival in the dose groups was due to prenatal or
postnatal exposure to vinylidene choride, one-third of the f_ litters born to
200 ppm vinylidene chloride-treated dams were exchanged with litters of
untreated dams. No dose-related decreased survival was noted in any groups of
the fog litter. At least 10 days after the f^g litters were weaned, the f2
parents were mated again to produce the f_c litters to determine survival rates
of this group. A selected number of male and female rats from each dose group of
10-67
-------
the f-,R litters were raised for 185-213 days as f~ adults. All remaining
weanling rats of the f^, f and f^ litters were sacrificed at 21-24 days of
age for external and internal examination (Nitschke et al., 1980).
The water containing the vinylidene chloride was available continuously
throughout this study to all treated rats. The first generation rats (f ) were
treated during their maturation, during mating periods, throughout gestation and
lactation for females, and were subsequently used in a 2-year toxicity study.
Pups were exposed prenatally and throughout their life until their sacrifice, or
longer if they were selected as breeders of that generation (Nitschke et al.,
1980).
The results of this study indicate few, if any, dose-related effects on
reproduction or the development of progeny in rats treated with vinylidene
chloride in the drinking water at the dose levels tested (Nitschke et al., 1980).
A slight decrease in the fertility (number of litters/number of mated dams) of
the f rats was noted in controls and the two highest dose groups (120 and 200
ppm) when compared to historical controls of Sprague-Dawley rats. Survival of f~
progeny was decreased in all treated groups but this response was not dose-
related since animals treated at 100 ppm vinylidene chloride showed the greatest
mortality, while groups treated at 50 and 200 ppm were similar. Decreased
survival during the lactation period in the f.,fl generation did appear dose-
jA
related, but survival in the f litters of dams given 100 and 200 ppm vinylidene
chloride was higher than controls. It was not possible to ascertain the cause,
whether it be prenatal or postnatal exposure to vinylidene chloride, of the
decreased survival in the f_. generation mice. No decrease in any group of the
jA
f.,B, including those cross-fostered (control gruop dams rearing 200 ppm progeny
and vice versa), was noted. The decreased survival of the f-. generation was
10-68
-------
negated since the similarly treated f generation showed no dose-related,
decreased survival.
Fetal survival, litter size, and growth rates of the neonates showed no
consistent dose-related effects for any generation during this study. At
necropsy, histopathological examination revealed hepatocellular fatty change and
pronounced hepatic lobular patterns in adult f rats treated with 100 or 200 ppm
vinylidene chloride. Fatty changes of the hepatocytes were also noted in adult
f females. Liver degeneration was noted in f adults treated with 100 or 200
ppm vinylidene chloride and at all dose levels in f_ adults. No dose-related
malformations or changes in organ weights were revealed after necropsy of wean-
lings in any dose group or generation (Nitschke et al., 1980).
In summary, the three generation study by Nitschke et al. (1980) indicated
that vinylidene chloride in drinking water of rats at 50, 100, or 200 ppm did not
adversely affect reproduction or neonatal development. Neonatal survival was
decreased in the f litters, but contradictory results were shown in the f-B and
Jr\ 3D
f litters. Histopathological examination revealed mild dose-related hepato-
JXj
toxic effects in adult rats treated with vinylidene chloride, but no dose-related
changes or malformations were seen in neonates. Reproductive capacities in
adults did not appear altered by vinylidene choride exposure (Nitschke et al.,
1980).
10.4 Mutagenicity
10.4.1. Mutagenicity in Bacteria
A variety of assay methods have been used to assess the mutagenic potential
of vinylidene chloride. These include the standard Salmonella typhimurium plate
incorporation assay of Ames, the liquid suspension assay, the host mediated
assay, as well as exposure of the bacteria to an atmosphere containing vinylidene
chloride. Due to the volatile nature of vinylidene chloride, the most commonly
10-69
-------
used assay method involves the exposure of the tester bacteria (in combination
with a mammalian metabolic activating system, if used) to a defined atmosphere of
vinylidene chloride in a desiccator. Following the exposure period, the bacteria
are incubated in petri dishes to allow the growth of mutant colonies.
Bartsch et al. (1975) exposed bacteria of S. typhimurium strains TA100 and
TA1530 to an atmosphere of 0.2, 2.0, or 20% vinylidene chloride (v/v) in air for
4 hours. The concentration of vinylidene chloride in the agar after 2 hours of
_ii _•?
exposure was shown by gas chromatography to be 3-3 10 , 3-3 x 10 , and 3-3 x
••)
10 M, respectively, with no further increases in the vinylidene chloride
concentration for up to 7 hours of exposure. In the presence of a metabolic
activation system prepared from the livers of mice pretreated with phenobarbital
(0.1/t in the drinking water for 7 days), both TA100 and TA1530 showed increases
in the number of revertant colonies. The maximum mutation rate occurred in TA100
with 2.0% vinylidene chloride ( = 11-fold); it was suggested that the higher
concentrations of vinylidene chloride caused inactivation of the activating
enzymes. Vinylidene chloride has recently been shown to inhibit the activity of
microsomal cytochrome P-H50 ir\ vitro (Poptawski-Tabarelli and Uehleke, 1982).
The same group of workers (Bartsch et al., 1975) have repeatedly demonstrated the
sensitivity of TA100 to the mutagenic effect of vinylidene chloride in a study
characterizing the stability of the metabolic activation system (Malaveille et
al., 1977). It was shown that these results were not due to the stabilizer
4-methoxyphenol present in the vinylidene chloride in these assays.
In more limited studies, other investigators have demonstrated the muta-
genic potential of vinylidene chloride following vapor phase exposure of S_.
typhimurium. In an investigation of suspected mutagenic compounds in drinking
water, Simmon (Simmon et al., 1977; Simmon, 1978) demonstrated a six-fold
increase (125 in controls to 650 in tested) in revertant colony number using
10-70
-------
tester strain TA100 in the presence of rat liver homogenate following exposure
for 9 hours to a 5% (v/v) atmosphere of vinylidene chloride. Also, Baden et al.
(1976) used a 3% atmosphere (exposure period of 8 hours) and Waskell (1978) used
a 5/6 atmosphere (exposure period of 4 hours) of vinyidene chloride as a positive
control in a study assessing the mutagenic potential of volatile compounds.
TA100 and TA98 showed a four-fold and 2.5-fold increase, respectively, compared
to controls in revertant colony number in the presence of a metabolic activation
system from Aroclor 1254-pretreated female BDV1 rats. In the absence of meta-
bolic activation, the number of revertants did not vary significantly from the
spontaneous controls.
The mutagenicity of vinylidene chloride (99.9? pure) has also been demon-
strated when the bacteria (E. coli or J3. typhimurium) were exposed to the
compound in sealed tubes in liquid media (liquid suspension assay). Greim et al.
(1975) used a strain of E_. coli K12 sensitive to back mutation (gal+, arg+, and
nad+) and one forward mutation system which leads to resistance to 5-methyl-DL-
tryptophan. Only the reverse mutation in the Arg+ strain showed an increased
number of revertant colonies (2.3-fold over control) following exposure of the
bacteria to 2.5 mM vinylidene chloride for 2 hours. A liver homogenate from
phenobarbital-pretreated mice was employed for metabolic activation. Baden and
coworkers (Baden et al., 1976, 1977, 1978) have used the liquid suspension assay
with S_. typhimurium to assess the mutagenicity of volatile anesthetics, and have
used vinylidene chloride as a positive control for these assays. Both tester
strain TA1535 and TA100 showed positive responses in the presence of a mammalian
metabolic activating system after a 1-hour exposure to vinylidene chloride at a
concentration that made the head space gas 3% vinylidene chloride.
An abstract (Cerna and Kypenova, 1977) reported vinylidene chloride to be
mutagenic in the host-mediated assay with J3. typhimurium strains TA1950, TA1951,
10-71
-------
and TA1952. Vinylidene chloride was administered to ICR mice at doses equal to
the LD,-Q and one-half the LD(-Q dose. There were fewer revertant colonies at the
higher exposure level. This assay has been demonstrated to have a poor correla-
tion with known genotoxic compounds (Simmon et al., 1979).
Many compounds (pro-mutagens) are inactive until metabolized by mammalian
enzyme systems to ultimate mutagens. Metabolism occurs in many cases via the
mixed-function oxidases associated with the microsomal fraction of a tissue
homogenate. Vinylidene chloride requires metabolic activation in order to
produce a mutagenic response in bacterial in vitro assays. In a single report in
which Vinylidene chloride was not mutagenic (using DNA repair-deficient 13.
subtilis and a comparison of zones of inhibition with the wild type and the
standard Ames plate incorporation assay), a metabolic activation system was not
employed (Laumbach et al.f 1977).
Livers from a variety of species have been used to metabolically activate
Vinylidene chloride. These include livers from mice, rats, and humans (Baden et
al., 1976; 1977). Of these species, the 9000 x g supernatant (S9) containing
microsomal and soluble enzymes from the livers of mice was most effective,
particularly when the enzyme systems were induced by pretreatment of the animals
with phenobarbital or Aroclor 125^. Liver biopsy samples from 4 humans were only
11, 16, 17, and 38$ as effective in activating Vinylidene chloride as was mouse
liver, as indicated by the relative numbers of revertant colonies in ,S.
typhimurium strains TA100 or TA1530 (Bartsch, 1976; Bartsch et al., 1979).
Bartsch et al. (1975) have demonstrated that S9 prepared from the liver, kidney,
or lung of OF-1 male mice was effective in activating Vinylidene chloride,
although the lung possessed only marginal activity (Table 10-20). The ability to
metabolically activate Vinylidene chloride may have wide tissue and species
10-72
-------
Table 10-20
Mouse Tissue Mediated Mutagenicity of Vinylidene Chloride in S. typhimurium
(modified from Bartsch et
Experiment
Number Species
1
2
3
4
S*
LO
6
7
8
9
10
11
12
OF-1 mouse/male
OF-1 mouse/male
OF-1 mouse/ male
OF-1 mouse/ male
OF-1 mouse/male
OF-1 mouse/ male
OF-1 mouse/ male
OF-1 mouse/ male
OF-1 mouse/ male
OF-1 mouse/ male
OF-1 mouse/ male
OF-1 mouse/male
Tissue
Pheno bar bi tone (9000 x g)
Pretreatment supernatant)3
Yes
Yes
No
No
Yes
Yes
No
No
Yes
Yes
No
No
liver
liver
liver
liver
kidney
kidney
kidney
kidney
lung
lung
lung
lung
al., 1975)
2% Vinylidene 20$ Vinylidene
Chloride in Air, Chloride in Air
his+ Revertant his* Revertants
Cofactors per plate0 per plate0
+ 500 + 23
23+10
+ 330 + 49
16 + 4
+ 147 + 15
31+7
+ 67 + 2
20 + 3
+ 34 + 4
5 + 4
+ 21+5
6 + 9
330 + 29
7 + 5
435 + 46
1 ± 3
173 + 5
17 + 2
125 + 5
16 + 1
48 + 5
10 + 1
37 + 3
14 + 8
Equivalent to 38 mg wet tissue per plate
NADP+ (2.0 (imol per plate) and glucose-6-phosphate (2.5 nmol per plate)
T^ean values +_ S.E. from 1-4 experiments, each using pooled tissue from 4 mice. The number of spontaneous mutations
per plate (49 + 2) has been subtracted from each value.
-------
distribution, but it is apparent that there is considerable variability in the
efficiency of activation by different S9 preparations.
There has been speculation as to the nature of the ultimate mutagen formed
during metabolic activation of vinylidene chloride. Barstch et al. (1975) have
suggested that an alkylating intermediate is formed, since mutations occur in jS.
typhimurium strain TA1530—which is reported by Ames et al. (1973) to be
specifically reverted by monofunctional alkylating agents. Nevertheless, an
alkylating compound was not identified in the trapping agent 4-(4f-nitrobenz)-
pyridine when a gas that contained vinylidene chloride was passed through a mouse
S9 activating system, even though this system provided activated metabolites
that mutated S. typhimurium strain TA100 (Barbin et al., 1978). It has also been
suggested that an unstable oxirane, possibly 1,1-dichloroethylene oxide, may be
formed during metabolism and that this metabolite plays a significant role in the
mutagenic activity of vinylidene chloride (Greim et al., 1975; Bonse et al.,
1975; Bartsch et al., 1979). Presently, however, there is little evidence
identifying the exact metabolic intermediate or intermediates that constitute
the ultimate mutagenic form of vinylidene chloride (see Section 10.1.2.1).
10.4.2 Mutagenicity in Plants and Yeast
The plant Tradescantia has been used as a detector of gaseous mutagens in
the laboratory and in tests conducted in the field. This assay system involves a
phenotypic change in flower color from blue to pink as a measure of mutagenic
pollutants in the atmosphere. The plants are highly sensitive and produce an
effect from contaminated ambient air. Collection and concentration of the
gaseous contaminants is not necessary. A mutation (or loss) of a dominant gene
(for blue color) results in the expression of recessive pink flower pigmentation.
In this assay system, vinylidene chloride exposure for 24 hours at 22 ppm was
sufficient to induce the mutagenic response. A maximum concentration at which no
10-74
-------
effects was observed after a 6-hour exposure was 1288 ppra (Van't Hof and
Schairer, 1982).
Bronzetti et al. (1981) reported that vinylidene chloride was mutagenic
with D7 yeast (Saccharomyces cerevisiae) only in the presence of a mammalian
activation system. When a mouse hepatic supernatant was included, vinylidene
chloride (above 20 mM) was effective in increasing point mutations and gene
conversions in a dose-related response. In an intrasanguineous host-mediated
assay, vinylidene chloride was mutagenic to yeast (injected into mice) which were
removed from the liver and kidneys after both acute (400 mg/kg by gavage to mice)
and subacute (100 mg/kg/day, 5 times/week for 23 administrations) vinylidene
chloride exposure.
10.4.3 Mutagenicity in Cultured Mammalian Cells
Drevon and Kuroki (1979) exposed V79 Chinese hamster cells in a desiccator
to an atmosphere of 2 or W% vinylidene chloride for 5 hours. Following expo-
sure, the cells were assayed for viability and mutations to 8-azaguanine, or
ouabain resistance. Dose-dependent toxicity was observed in cells exposed to
vinylidene chloride in the presence of a 15,000 x g supernatant from rat liver.
Cells exposed to vinylidene chloride in the presence of a 15,000 x g supernatant
from mouse liver or in the absence of a metabolic activating system showed no
apparent toxic effect. Both rats and mice were pretreated with 1.056 pheno-
barbital in drinking water for 7 days prior to sacrifice. There was no indica-
tion under any of the experimental conditions of an increase in 8-azaguanine or
ouabain resistance.
10.4.4 Mutagenicity In Vivo
Dominant lethal studies with vinylidene chloride have been performed in
male CD-1 mice (Anderson et al., 1977) and in CD rats (Short et al., 1977d). Male
mice (20 animals/group) were exposed to 10 and 30 ppm of vinylidene chloride for
10-75
-------
6 hours per day for 5 days. One group was exposed to 50 ppm for 6 hours per day
for 2 days; however, the poor survival of these animals precluded any assessment
of rautagenic damage. The male rats (11 animals) ware exposed to 55 ppm vinyli-
dene chloride for 6 hours per day, 5 days per week for 11 weeks. At the end of
these exposure periods, the animals were mated with nonexposed virgin females.
In neither rats nor mice did the treatment result in an excess of p re implantation
or postimplanatation losses. In the studies performed by Andersen et al.
(1977), a positive control of cyclophosphamide was included to assure the
sensitivity of this strain of mouse in the dominant lethal assay.
10.4.5 In Vivo DNA Repair
Reitz et al. (1980) used CD-1 male mice and Sprague-Dawley male rats to
study the effect of vinylidene chloride on DNA synthesis and repair in the liver
and kidneys. The mice were exposed at 10 ppm for 6 hours. Total DNA synthesis
•3
was measured by H-thymidine incorporation into DNA 48 hours after exposure. DNA
repair synthesis was measured immediately after exposure to vinylidene chloride
by H-thymidine incorporation into DNA in the presence of hydroxyurea. Hydroxy-
urea inhibits replicative DNA synthesis, but allows DNA repair synthesis to
occur. The ability of vinylidene chloride to alkylate DNA was also examined by
14
exposing the animals to C-vinylidene chloride followed by isolation and
analysis of the DNA from the liver and kidneys. Vinylidene chloride was most
efficient at alkylating the DNA in mouse kidney, with 30 alkylations/10 nucleo-
tides in animals exposed to 50 ppm vinylidene chloride and 11 alkylations/10
nucleotides in animals exposed to 10 ppm. In mouse liver, the values were 6.1
and 0.94 alkylations/10 nucleotides in the 50 and 10 ppm exposure groups,
respectively. In rats, the rate of alkylation was 2 and 0.87 alkylations/10
nucleotides in the kidney and liver, respectively. These alkylation rates were
considerably less than the 3000 to 4000 per 10 nucleotides observed in rats with
10-76
-------
the potent carcinogen dimethyInitrosamine (DMN). The elimination of alkylated-
nucleotides was rapid, with a biphasic elimination pattern. The first phase
occurred during the first 8 hours and the second phase continued for 192 hours.
The pattern of DNA repair synthesis was similar to that of alkylation. Some
repair synthesis was noted in both kidney and liver; however, only the synthesis
in the kidneys of mice exposed to the highest concentration was significantly
elevated over control levels. Although repair synthesis was increased only
marginally following vinylidene chloride treatment, total DNA synthesis was
increased markedly in the kidney of mice. This indicates that vinylidene
chloride caused cell damage and compensatory growth, but did not interact with
DNA directly and cause repair synthesis. The liver carcinogen DMN caused little
increase in total DNA synthesis, while dramatically increasing DNA repair
synthesis. The authors concluded that the kidney tumors in mice reported by
Maltoni et al. (1977) were not the direct result of a genetic effect of vinyli-
dene chloride, but may have been the result of an epigenetic effect following the
kidney toxicity.
10-77
-------
10.5 CARCINOGENICITY
10.5.1 Animal Studies
There have been a number of laboratory investigations of the carcinogenic
potential of vinylidene chloride (VDC). These studies have been performed
using rats, mice, and hamsters, with VDC administered by inhalation, gavage,
incorporation into drinking water, subcutaneous injection, and topical
applications. These results are summarized in Table 10-21, and have also been
summarized by Chu and Milman (1981). Of the studies performed, only the
results reported by Maltoni et al. (1977, 1980) indicated a positive
carcinogenic effect following VDC treatment.
Maltoni et al. (1980, 1977) exposed Sprague-Dawley rats, Swiss mice, and
Chinese hamsters to VDC (99.95% pure, Table 10-22) in an inhalation chamber
for 4 hours daily, 4 to 5 days a week for 12 months * The exposure
concentration used depended on the species' susceptibility to VDC's toxic
action; the highest tolerated dose in mice and rats was used as the maximum
concentration. The exposure level for hamsters was not selected on the basis
of achieving a maximum tolerated dose. Rats, initially 16 weeks old, were
exposed to VDC at 150, 100, 50, 25, and 10 ppm (Table 10-23), while mice,
initially 16 weeks or 9 weeks old, were chronically exposed to VDC at 25 and
10 ppm (Table 10-24), and hamsters, initially 28 weeks old, to a concentration
of VDC at 25 ppm (Table 10-25). In addition, rats, initially 9 weeks old, were
treated by gavage with 20, 10, 5, and 0.5 mg/kg/day of VDC dissolved in olive
oil (Table 10-26). Body weights were recorded every 2 weeks during treatment
and monthly thereafter. At the time of their 1980 report, the studies were
completed (137 weeks for the inhalation study in rats, 147 weeks for the
10-78
-------
TABLE 10-21. RESULTS OF CAPCINOGENICITY BIOASSAYS OF VINYLIDENE CHLORIDE
Species
Sprague-Dawley
rats
Swiss mice
Chinese hamsters
l— •
O
-------
TABLE 10-21. (continued)
H-1
O
1
00
O
Species
Fischer 344 rats
B6C3F1 mice
CD mice
CD rats
Ha:ICR Swiss
Ha:ICR Swiss
Sprague-Dawley
rats
Sprague-Dawley
rats
Dose
5 ml/kg of a 1000
or 200 ppm
solution
10 ml/kg of a
1000 or 200 ppm
solution
55 ppm, 5 days/
week 1, 3, or
6 months
55 ppm, 5 days/
week 1 , 3, 6, or
10 months
121 rag/mouse
2 rag/mouse
10, 25, 50, 100,
150 ppm
0.5, 5, 10, 20
mg/kg/day
Route of
administration
Gavage "> days/week
Gavage 5 days/week
Inhalation 6 hr/day
Inhalation 6 hr/day
Skin application,
3 times/week
Subcutaneous injection
once/week
Inhalation 4 to 5 days/
week
Gavage, 5 days/week
Total duration
of observation
103 weeks
103 weeks
13, 15, or 18
months
13, 15, 18, or 22
months
Lifetime
Lifetime
52 weeks
52-59 weeks
Findings
No statistically
significant increase
No statistically
significant increase
No statistically
significant increase
, No statistically
significant increase
No tumors
No tumors at site of
injection or in other
organs
No brain tumors
No brain tumors
Reference
NCI/NTP, 1981
NCI/NTP, 1981
Hong et al. , 1981
Hong et al. , 1981
Van Duuren et al. , 1980
Van Duuren et al. , 1980
Maltoni et. al. , 1982
Maltoni et al. , 1982
-------
TABLE 10-22. GAS CHROMATOGRAPHY ANALYSIS OF VINYLIDENE CHLORIDE
Compound Amount
Vinylidene chloride (1,1-Dichloroethylene) 999.5 g/kg
1,2-Dichloroethylene trans 0.4 g/kg
Acetone 0.1 g/kg
Methylene chloride 0.05 g/kg
Monochloroacetylene and Dichloroacetylene 0.02 g/kg
Paramethoxyphenol (as stabilizer) 200 ppm
Source: Maltoni et al., 1977
TABLE 10-23. EXPERIMENT DT401: EXPOSURE BY INHALATION TO VINYLIDENE
CHLORIDE (VDC) IN AIR AT 150, 100, 50, 25, 10 PPM,
4 HOURS DAILY, 4-5 DAYS WEEKLY, FOR 52 WEEKS
GROUP
NOS.
I
II
III
IV
V
VI
Total
(Sprague-Dawley
CONCENTRATION
200 (a) - 150 ppm
100 ppm
50 ppm
25 ppm
10 ppm
No treatment
Males
60
30
30
30
30
100
250
ANIMALS
rats, 16 weeks old at start)
Females
60
30
30
30
30
100
280
Total
120
60
60
60
60
200
560
(a) Two treatments only because of the high toxicity of this dose level.
Source: Maltoni et al.; 1980.
10-81
-------
TABLE 10-24. EXPOSURE BY INHALATION TO VINYLIDENE CHLORIDE (VDC) IN AIR
AT 200, 100, 50, 25, 10 PPM, 4 HOURS DAILY,
4-5 DAYS WEEKLY, FOR 52 WEEKS
RROIIP
NOS.
I
II
III
IV
IV bis (a)
V
VI
VII
Total
TRFATMFNT
Concentration
200 ppm
100 ppm
50 ppm
25 ppm
25 ppm
10 ppm
No treatment
(Controls) (b)
No treatment
(Controls) (c)
Length
2 days (d)
2 days (d)
1 week (d)
52 weeks
52 weeks
52 weeks
ANIMALS
Swiss mice 16 weeks old (groups I,
II, III, IV, V, VI) and 9 weeks old
(groups IV bis and VII)
Males
60
30
30
30
120
30
100
90
490
Females
60
30
30
30
120
30
100
90
490
Total
120
60
60
60
240
60
200
180
980
(a) The treatment started two weeks later than in other groups.
(b) Controls to the groups I, II, III, IV, V.
(c) Controls to the group IV bis.
(d) The treatment was interrupted because of the high toxic effects and high
mortality.
Source: Maltoni et al., 1980.
10-82
-------
TABLE 10-25. EXPERIMENT BT405: EXPOSURE BY INHALATION TO VINYLIDENE CHLORIDE
(VDC) IN AIR AT 25 PPM, 4 HOURS DAILY, 4-5 DAYS WEEKLY, FOR
52 WEEKS
GROUP
NOS. CONCENTRATION
I 25 ppm
II No treatment
(Controls)
Total
ANIMALS
(Chinese hamsters, 28 weeks old
Males
30
18
48
Females
30
17
47
at start)
Total
60
35
95
Source: Maltoni et al., 1980,
10-83
-------
TABLE 10-26. EXPERIMENT BT403: EXPOSURE BY INGESTION (STOMACH TUBE) TO
VINYLIDENE CHLORIDE IN OLIVE OIL AT 20, 10, 5 MG/KG BODY WEIGHT, ONCE DAILY
4-5 DAYS WEEKLY, FOR 52 WEEKS
GROUP
NOS.
I
II
III
IV
Total
(Sprague-Dawley
fONTFNTRATTO'M
20 mg/kg
10 mg/kg
5 mg/kg
None (olive oil alone)
(Controls)
Males
50
50
50
100
250
ANIMALS
rats, 9 weeks old at start)
Females
50
50
50
100
250
Total
100
100
100
200
500
EXPERIMENT BT404: EXPOSURE BY INGESTION (STOMACH TUBE) TO
VINYLIDENE CHLORIDE IN OLIVE OIL AT 0.5 MG/KG BODY WEIGHT, ONCE DAILY,
4-5 DAYS WEEKLY, FOR 52 WEEKS
GROUP
NOS.
I
II
Total
(Sprague-Dawley
rONPFMTRATTON
Males
0.5 mg/kg 50
None (olive oil 82
alone) (Controls)
132
ANIMALS
rats, 9 weeks old at start)
Females
50
77
127
Total
100
159
259
Source: Maltoni et al., 1980.
10-84
-------
ingestion study in rats, 121 weeks for the inhalation study in mice, and 157
weeks for the inhalation study in hamsters. Animals were allowed to survive
until spontaneous death. Each animal was necropsied, and tissues and organs,
as well as tumors and lesions, were examined histopathologically.
No treatment-related effect on body weights in rats was evident. Body
weight data for mice and hamsters were not reported, but no effect attribut-
able to treatment was noted.
There were no significant (P<0.05) differences in tumor development
between control and treated hamsters.
A number of neoplastic lesions were observed in control and treated rats,
with no treatment- or dose-related effect in evidence from either inhalation
exposure or gavage administration. The 1977 report by Maltoni et al.
presented interim (82 weeks) results showing an increased incidence of mammary
tumors in treated rats compared to controls in the inhalation study; however,
at that time, a clear dose-related effect was not evident, spontaneous mammary
tumor incidence in female controls was 32%, and histopathologic diagnosis of
the mammary tumors was ongoing. The final mammary tumor data for female rats
in this study, as described in the Maltoni et al. (1980) report and Table
10-27 herein, show statistically significant (P<0.05) increases in the total
number of tumor-bearing animals in the 10 ppm and 100 ppm groups compared to
controls, and in the number of animals with fibromas and fibroadenomas in each
treatment group compared to controls. However, there was no clear
dose-related increase in mammary tumor incidence, latency time for mammary
tumor formation was similar among all groups, there was a high (61%) incidence
of spontaneously formed mammary tumors in controls, and mammary carcinoma
10-85
-------
TABLE 10-27. EXPERIMENT BT401: EXPOSURE BY INHALATION TO VINYLIDENE CHLORIDE (VDC) IN AIR AT 150, 100, 50, 25, 10 PPM, 4 HOURS DAILY, 4-5 DAYS
FOR 52 WEEKS. RESULTS AFTER 137 WEEKS (END OF EXPERIMENT).
DISTRIBUTION OF THE DIFFERENT TYPES OF MAMMARY TUMORS
!
CO
MAMMARY TUMORS (b)
Histologically Examined
Histotype
ANIMALS
(Sprague-Dawley rats, 16
GROUP CONCEN- weeks old at start)
NOS.
I
II
III
IV
V
VI
TRATIONS
Sex
M
150 ppm F
M and F
M
100 ppm F
M and F
M
50 ppm F
M and F
M
25 ppm F
M and F
M
10 ppm F
M and F
No treat- M
ment F
(Controls) M and F
No. at
start
60
60
120
30
30
60
30
30
60
30
30
60
30
30
60
100
100
200
Corrected
number
(a)
60
60
120
30
30
60
30
30
60
28
30
58
29
30
59
87
99
186
To-
tal
No.
8
44
52
5
25*
30
1
23
30
4
21
25
3
28*
31
11
61
72
%
(c)
13.3
73.3
43.3
16.7
83.3
50.0
23.3
76.7
50.0
14.3
70.0
43.1
10.3
93.3
52.5
12.6
61.6
38.7
Average
latency
time
(weeks)
(d)
97+14
82+ 3
821 3
104+ 9
82+ 4
851 4
1061 5
791 4
86+ 4
103+10
861 4
881 4
81123
83+ 4
811 4
1151 6
871 2
911 3
No. of
tumors/
tumor-
hearing
animals
1.0
1.5
1.4
1.0
1.7
1.6
1.0
1.9
1.7
1.0
1.6
1.5
1.0
1.6
1.5
1.0
1.5
1.4
Fibromas and
fibroadenomas
To-
tal
No.
8
43
51
5
23
28
7
22
29
4
20
24
3
24
27
11
56
67
°f
fo
(e)
100.0
97.7
98.1
100.0
92.0
93.3
100.0
95.6
96.7
100.0
95.2
96.0
100.0
85.7
87.1
100.0
91.8
93.0
No.
6
38*
44
5
21*
26
7
21*
28
4
20*
24
3
24*
27
11
44
55
to
(f)
75.0
88.4
86.3
100.0
91.3
92.8
100.0
95.4
96.5
100.0
100.0
100.0
100.0
100.0
100.0
100.0
78.6
82.1
Average
latency
time
(weeks)
(d)
1091 8
83+ 3
861 3
1041 9
831 5
871 4
106+ 5
82+ 4
881 4
103110
87+ 4
90+ 4
81+23
851 4
851 4
115+ 6
881 3
93+ 3
No.
1
9
10
0
3
3
0
1
1
0
4
4
0
5
5
0
16
16
Carcinomas
%
(f)
12.5
20.9
19.6
.
13.0
10.7
4.5
3.4
.
20.0
16.7
.
20.8
18.5
28.6
23.9
Average
latency
time
(weeks)
(d)
26
78+ 8
73+ 8
.
102+10
102110
68
68
82+10
82+10
.
90+14
90114
951 5
951 5
Total
560
543
(a) Alive animals after 10 weeks, when the first tumor (a leukemia)
was observed.
(b) Two or more tumors of the same and/or different types (fibroadenomas,
carcinomas, sarcomas, carcinosarcomas) may be present in the same
animals. A carcinosarcoma was found in one male in the 150 ppm
group, and no animals were observed to have sarcomas.
(c) The percentages refer to the corrected numbers.
(d) Average age at the onset of the first mammary tumor per animal, detected
at the periodic control or at autopsy.
(e) The percentages refer to total numbers of animals bearing mammary
tumors.
(f) The percentages refer to total numbers of animals bearing mammary
tumors, histologically examined.
* Statistically significant increase compared to control by chi-square test
(P<0.05). Comparisons are made between numbers with tumors/corrected
numbers.
Source: Maltoni et al., 1980.
-------
incidence in treated groups was not significantly (P<0.05) different from and
was actually consistently less than that of controls. Hence, the evidence for
a carcinogenic effect of inhaled vinylidene chloride in female Sprague-Dawley
rats, as mammary tumors, in this study would appear to be inconclusive.
In male Swiss mice, kidney adenocarcinomas were observed following
inhalation exposure to VDC at 25 ppm (Table 10-28). In female Swiss mice,
mammary carcinoma incidence in both the 10 ppm and combined 25 ppm groups
compared to combined controls was significantly (P<0.01) increased, and a
small incidence of mammary carcinomas was evident in females exposed to VDC at
50, 100, or 200 ppm for 1 week or less (Table 10-28). The incidence of
pulmonary adenomas was significantly (P<0.01) increased in male and female
mice exposed to VDC at 10 and 25 ppm compared to controls (Table 10-28);
however, pulmonary carcinomas were not found in any of the mice.
Maltoni et al. (1980) concluded that the kidney tumors in male mice
developed in response to VDC treatment, particularly since no corresponding
spontaneous tumors were noted in the 190 control male mice. Maltoni (1977)
also concluded that the observed kidney tumors in Swiss mice were a
strain-specific phenomenon. It has been noted that male mice of several
strains are particularly sensitive to the toxic effects of VDC, and that a
direct relationship may exist between the degree of toxicity and the
carcinogenic effect of VDC (Maltoni et al. 1977; Maltoni 1977; Henck et al.
1980). These authors postulated that a metabolite is responsible for both
effects of VDC. Maltoni et al. (1977) noted that degeneration and necrotic
changes in kidneys, especially in the tubular region, in male Swiss mice which
died from exposure to 200 ppm VDC, 4 hours daily, for 2 days were observed as
10-87
-------
TABLE 10-28. EXPERIMENT BT402: EXPOSURE
BY INHALATION TO VINYLIDENE CHLORIDE (VDC) IN AIR AT 200, 100, 50, 25, 10 PPM, 4 HOURS DAILY, 4-5 DAYS
FOR 52 WEEKS. RESULTS AFTER 121 WEEKS (END OF EXPERIMENT).
DISTRIBUTION OF THE DIFFERENT TYPES OF MAMMARY TUMORS
1
ANIMALS WITH TUMORS
TREATMENT
GROUPS CONCEN-
NOS . TRATIONS LENGTH
I 200 ppm 2 days
II 100 ppm 2 days
III 50 ppm 1 week
M IV 25 ppm 52 weeks
O
oo
00
IV bis 25 ppm 52 weeks
V 10 ppm 52 weeks
No
VI treatment
(Controls)
No
VII treatment
(Controls)
ANIMALS (Swiss mice
16 weeks old
111,1V, V, VI)
old (Grs IV
at start)
Sex
M
F
M and F
M
F
M and F
M
F
M and F
M
F
M and F
M
F
M and F
M
F
M and F
M
F
M and F
M
F
M and F
(Grs I, II,
and 9 weeks
bis, VII)
No. at start
60
60
120
30
30
60
30
30
60
30
30
60
120
120
240
30
30
60
100
100
200
90
90
180
Kidney adenocarcinomas
Corrected
number
(a)
1
28
29
12
13
25
17
14
31
21
26
47
98
112
210
25
26
51
56
73
129
70
85
155
Average la-
tency time
No. % (weeks) (b)
0 -
0 -
0 -
0 -
0 -
0 -
1 5.9 64
0 - -
1 3.2 64
3C 14.3 71± 5
0 - -
3 6.4 71+ 5
256 25.5 75± 2
1 0.9 77
26 12.4 75± 2
0 -
0 -
0 -
0 - -
0 - -
0
0
0 - -
0
Corrected
number
(a)
6
53
59
21
28
49
27
28
55
29
30
59
117
118
235
30
30
60
92
97
189
80
88
168
Mammary Tumors
No.
0
1
1
0
3
3
0
2
2
°f
4f
4
1,
12f
13
Of
6f
6
1
2
3
0
1
1
Average la-
tency time
% (weeks )(b)
.
1.9
1.7
_
10.7
6.1
_
7.1
3.6
_
13.3
6.8
0.8
10.2
5.5
_
20.0
10.0
1.1
2.1
1.6
„
1. 1
0.6
.
87
87
_
46± 3
46± 5
-
39±13
39113
_
68+11
68+11
46
69+ 4
67± 4
_
63± 5
63+ 5
25
49+ 7
41± 9
_
83
83
A
Pulmonary adenomas"
Corrected
number
(a) No.
5
46
53
18
26
44
26
27
53
28
29
57
113
118
231
28
30
58
80
92
172
73
86
159
0
1
1
2
2
4
1
3
4
78
78
14
168
II8
27
II8
3g
14
3
4
1
3
2
5
Average la-
tency time
% (weeks) (b)
-
2.2
1.9
11.1
7.7
9.1
3.8
11.1
7.5
25.0
24.1
24.6
14.2
9.3
11.7
39.3
16.0
24.1
3.7
4.3
4.1
4.1
2.3
3.1
.
57
57
62+ 7
53+ 2 '
58+ 4 '
62
80+ 8 ,
75+ 7
73+ 6
85+ 6
30+ 4
77+ 3
78+ 6
77+ 3
71+ 5
68+ 4
70+ 4
66+ 7
56+ 4
60+ 4
56+11
75+12
64+ 8
(a) Alive animals when the first tumor was observed: kidney
adenocarcinoraa, 55 weeks; mammary tumor, 27 weeks; pulmonary
adenoma, 36 weeks. The percentages refer to the corrected
numbers.
(b) Average time from the start of the experiment to the detection (at
the periodic control or at autopsy).
(c) All mammary tumors in females were histologically diagnosed as
Carcinomas.
(d) Some pulmonary adenomas were cellular atypias.
(e) P < 0.01, combined 25 ppm (28/119) males vs. combined control males (0/196)
by chi-square test. Based on corrected numbers.
(f) P < 0.01 Combined control females (3/185) vs. 10 ppm females (6/30) and
vs. combined 25 ppm females (16/148). Based on corrected numbers.
(g) P < 0.01. Combined control males (6/153) vs. 10 ppm males (11/28) and vs.
combined 25 ppm males (29/294). Also, combined control females (6/178)
vs. 10 ppm females (3/30) and vs. combined 25 ppm females (18/147).
Source: Maltoni et al. (1980).
-------
a similar effect in the kidneys of mice which developed kidney adenocarcinomas
in the lifetime inhalation study.
The significant (P<0.01) increase in mammary carcinomas in treated female
Swiss mice would indicate evidence for the carcinogenicity of VDC in these
animals. However, Maltoni et al. (1980) concluded that a direct relationship
between induction of mammary tumors, as well as pulmonary adenomas, in mice
and vinylidene chloride exposure remains open and needs further clarification
because of reasons that include the following, as quoted from the Maltoni et
al. (1980) paper:
1) "There are some significant higher rates of mammary and pulmonary
tumors in VDC exposed groups when compared to the controls;"
2) "When the incidence of these tumors is adjusted for survival
rate, the relevance of the difference between treated and
control groups is reduced;"
3) "No dose-response relationship could be calculated either
during the total time of the experiment or in different
time intervals;" and
4) "Overall there was a clear fluctuation and imbalance of
this trend in the different groups."
The authors (1980) stated that survival of mice exposed to 10 and 25 ppm
VDC was higher than survival of the control groups. Numbers of mice surviving
10-89
-------
at 27, 36, and 55 weeks are given in Table 10-28, herein, and Maltoni et al.
(1977) observed an interim survival for female mice of: (1) 47% in the 25
ppm group (IV), 20% in the 10 ppm group (V), and 21% in the matched control
group (VI) when these groups were 98 weeks old, and (2) 40% in the 25 ppm
(Group IV bis) and 40% in the matched control group (VII) when these groups
were 91 weeks old. Maltoni et al. (1980) presented survival data and their
statistical analyses of pulmonary adenoma and mammary carcinoma data in mice
to support their conclusions quoted above. Their analyses include data
presented in Table 10-29 which were obtained from an appendix in the Maltoni
et al. (1980) report. The authors noted that "with one exception" slightly
higher mean survival times for the treatment groups were not significantly
(P < 0.05) different from those of their matched controls by a rank test of
Krauth. The significant (P < 0.05) differences shown in Table 10-29 for
survival include comparisons of Groups IV and V with Group VII, which was not
the matched control group for these two treatment groups, and Group IV bis
with Group IV, which were the two groups exposed to 25 ppm VDC; hence, the
authors (1980) indicated that "with one exception" significant differences in
mean survival were found only between groups which began their exposure at
different ages.
Statistically significant (P < 0.01) differences in tumor incidences
between control and treated mice shown in Table 10-28 were calculated using
the chi-square test by combining control and 25 ppm groups since, outside of
differences in age at the start of the study and the two week difference in
the starting times of the study (Table 10-24), similar tumor incidences for
the separate control and 25 ppm groups were found with the same protocol.
Maltoni et al. (1980) found statistically significant (P < 0.05) increases in
10-90
-------
TABLE 10-29. STATISTICAL ANALYSES OF SURVIVAL, MAMMARY CARCINOMA INCIDENCE
AND PULMONARY ADENOMA INCIDENCE FOR MALE AND FEMALE SWISS MICE IN A
CARCINOGENICITY STUDY OF VINYLIDENE CHLORIDE
(MALTONI ET AL. 1980)
Mean and Standard Deviation (in weeks) of lifetime
(Test of Krauth, one-sided)
Group
VII
VI
V
IV bis
IV
Tumor
N.
Group
VI
V
IV
VII
IV bis
Male
Animals Lifetime
at start Mean Stand. Dev.
90 70.7 C 22.58
100 75.4 C 22.08
30 83.7 x * 15.77
120 75.0 15.85
30 79.6 * 17.03
Female
Animals Lifetime
at start Mean Stand. Dev.
90 81.0 C 18.51
100 83.1 C 20.32
30 87.5 * 12.97
120 84.3 17.41
30 90.0 x * 18.40
incidence for MA and PA at the end of experiment; N.TU (respectively
MA, N.PA) is the number of animals with tumors (respectively MA, PA
(Exact Fisher Test, one-sided)
Male
Animals , ,
at start N.TU N.MA° N.PA
100 7 03
30 11 x 0 11 x
30 11 x 0 7 x
90 7 03
120 43 x 1 16 x
Tumor incidence for MA and PA at the end
N.PA) is the number of animals with MA
Group
VI
V
IV
VII
IV bis
Male
Animals
at start N.MA N.PA
100 0 3
30 0 11 x
30 0 7 x
90 03
120 1 16*
Female
Animals
at start N.TU N.MA N.PA
100 15 2 4
30 15 x 6 x 3
30 17 x 4 * 7 x
90 12 1 2
120 40 x 12 x 11 *
of experiment; N.MA (respectively
(respectively PA) (Logrank test)
Female
Animals
at start N.MA N.PA
100 2 4
30 6 x 3
30 4 7 *
90 1 2
120 12 * 11
VII - Matched control for Group IV bis, VI - Matched control for Groups V
and IV, V - 10 ppm VDC exposure, IV bis and IV - 25 ppm VDC exposure.
-i
"control
*P < 0.05
P < 0.01
N.TU -- Number of animals with tumors
p
N.MA -- Number of animals with mammary tumors
N.PA -- Number of animals with pulmonary tumors
10-91
-------
mammary carcinoma and pulmonary adenoma incidences in treated mice compared
to matched control mice by the Fisher exact test (Table 10-29); however,
their analysis of these data by the Log Rank test, to take into account
survival patterns, indicated a lower level of statistical significance for
these differences between control and treated mice. A dose-related increase
in tumor incidence in treated mice was not clearly apparent from the data in
Table 10-29-
In summary, the studies by Maltoni et al. (1977, 1980) show significant
(P<0.01) increases in the incidence of kidney adenocarcinomas in male Swiss
mice and mammary carcinomas in female Swiss mice chronically exposed to VDC.
However, the authors concluded that the relationship between VDC exposure and
mammary carcinoma induction in female mice remains open as discussed above.
There was a significant (P<0.05) increase in the incidence of fibromas and
fibroadenomas in each treated group of female Sprague-Dawley rats compared to
controls in the inhalation study; however, there were no significant (P<0.05)
increases in mammary carcinoma incidence between treated and control rats, and
there was no clear dose-response for induction of mammary tumor in treated rats.
A broader evaluation of the carcinogenicity of VDC by Maltoni et al.
(1977, 1980) might have been possible if exposure periods longer than 12
months had been used and if, at the beginning of treatment, younger animals,
such as weanlings, had been evaluated to cover the portion of their lifespans
during growth to adulthood. It does not appear that doses as high as those
maximally tolerated were used in the inhalation study in hamsters and the
gavage study in rats, in that neither toxicologic effects from VDC treatment
nor an attempt to select a maximally tolerated dose is indicated in the report
on these studies.
10-92
-------
Viola and Caputo (1977) exposed male and female Wistar strain rats
initially 2 months old in an inhalation chamber for 4 hours per day, 5 days
per week, to VDC at 200 ppm (99.8% pure) for 5 months, followed by an
additional 7 months of reduced exposure to VDC at 100 ppm to avoid toxicity.
All animals were observed until death (22 to 24 months). Thirty untreated
controls of each sex, 23 treated females, and 51 treated males were examined
for tumors. During the exposure period, a rapidly growing mass appeared in
the external ear duct of many of the animals, but on biopsy examination, only
signs of an inflammatory reaction were present with no indications of dermal
or epidermal neoplasia. Tumors of the abdominal cavity were present at the
same incidence in both experimental (23%) and control (25%) rats. Although
histology of the tumors was described, there was no mention of which organs,
if any, were routinely evaluated histologically for neoplastic or
pre-neoplastic changes. Furthermore, the 12-month exposure period was shorter
than potential lifetime exposures for laboratory rats. In a second study
using male and female Sprague-Dawley rats exposed to VDC at 100 and 75 ppm
(started in the summer of 1975) for an unspecified duration, there was again
no increased tumor incidence in the experimental animals as compared with the
controls. There were 30 rats in each control and 100 ppm group, and 21
females and 16 males in the 75 ppm group examined for tumors. At the time of
the report, only gross tumors were enumerated; results from microscopic
examination of the tissues from the Sprague-Dawley rats were to be reported
later.
Lee et al. (1978), in a study primarily concerned with chronic inhalation
exposure of CD-I mice and CD rats (Charles River), initially about 2 months
old, to vinyl chloride (99.8% pure), exposed a group of rats and mice (36
10-93
-------
males and 36 females) to a single 55 ppm concentration of VDC. Concurrent
control groups exposed to inhalation of air alone consisted of 36 males and 36
females. The exposure was for 6 hours daily, 5 days per week for 12 months,
at which time all surviving animals were terminated. Following sacrifice, the
brain, pituitary, thyroid, respiratory tract, alimentary canal, urogenital
organs, thyrous, heart, liver, pancreas, spleen, mesenteric lymph nodes, and
other organs with gross pathological lesions were histologically examined.
The incidence of tumors observed in both rats and mice is given in Table
10-30. There was no statistically significant (P<0.05, Fisher exact test)
increase in tumors at any of the sites examined as compared with control
animals. The short duration (12 months) of this study may have precluded
observing tumors that have a long latency period.
In a follow-up study, Lee and coworkers (Hong et al., 1981) exposed 8 to
12 CD-I mice of each sex and 4-16 CD rats of each sex, initially 2 months old,
to VDC vapors (99% pure) at a concentration of 55 ppm. The mice were exposed
6 hours/day, 5 days/week for a period of 1, 3, or 6 months (12 mice of each
sex were treated for 6 months), while the rats were exposed on the same
schedule for 1, 3, 6, or 10 months (16 rats of each sex were treated for 10
months). Concurrent controls exposed to inhalation of air alone consisted of
28 mice and 16 rats of each sex. All animals were observed for an additional
period of 12 months following exposure. Histologic examinations were
performed as described above in Lee et al. (1978). Focusing on males and
females, respectively, in the groups with the longest durations of exposure,
18 and 21% of control mice, 50 and 42% of treated mice, 38 and 44% of control
rats, and 79 and 56% of treated rats died before terminal sacrifice. Although
tumors were observed in some exposed and control animals, the incidence of
10-94
-------
TABLE 10-30. TUMOR INCIDENCE IN RATS AND MICE EXPOSED TO VINYLIDENE CHLORIDE
O
Species
CD-I mice
CD-I mice
CD-I mice
CD-I mice
CD-I mice
CD-I mice
CD rats
CD rats
Sex
M
F
M
F
M
F
M
F
Tumor type
Bronchioloalveolar adenoma
Bronchioloalveolar adenoma
Hemangiosarcoma of the liver
Hemangiosa rcoma of the liver
Heptoma
Heptoma
Hemangiosarcoma of any organ
except liver
Hemangiosarcoma of any organ
except liver
No. tumors/No, exposed
animals
(55 ppm vinylidene chloride)
6/35
0/35
2/35
1/35
2/35
1/35
2/36
0/35
No. tumors/No, control
animals
1/26
0/36
0/26
0/36
0/26
0/36
0/35
0/35
None of the tumor increases were statistically significant when compared to controls.
Source: Lee et al., 1978.
-------
these tumors was not significantly (P<0.05) increased over control levels
(Table 10-31). The small number of animals in each group weakens the ability
of this study to detect a tumorigenic response, and the exposure durations
were less than potential lifetime exposures. A broader evaluation could have
been made with additional exposure levels in each study.
Two studies have been performed for the Manufacturing Chemists
Association to assess the effects of chronic inhalation and ingestion (in
drinking water) of VDC. The studies were conducted in two phases, the first
for 90 days and the second for 2 years. Norris (1977) presented preliminary
results of these studies with a detailed final report of the drinking water
study presented by Humiston et al. (1978) and Quast et al. (1983). An
additional report of these two studies to the open literature was provided by
Rampy et al. (1977), and the final results of the inhalation study have been
presented by McKenna et al. (1982).
In the inhalation study (Rampy et al., 1977; McKenna et al., 1982),
Sprague-Dawley rats, with initial body weights of 250 to 300 g for males and
190 to 230 g for females, were exposed to VDC (S99% pure) for 6 hours per day,
5 days per week for a period of 18 months, and animals that survived the
treatment were observed for an additional 6 months. A total of 86 males and
86 females per group were used for each exposure group plus a concurrent
untreated control group. The animals were initially exposed to VDC at 10 or
40 ppm; however, after 5 weeks of exposure, an interim kill revealed no
effects of exposure, and the concentrations were raised to 25 and 75 ppm, with
these concentrations being used for the remainder of the experiment.
Analytical and nominal atmospheric concentrations of VDC in inhalation
10-96
-------
TABLE 10-31. TUMOR INCIDENCE IN RATS AND MICE EXPOSED TO VINYLIDENE CHLORIDE
Species
CD-I mice
CD-I mice
CD-I mice
CD-I mice
-------
chambers were equivalent. The overall evaluation of toxicity included
survival, body weights, organ weights, hematology, urinalysis, clinical
chemistry, cytogenetics, gross pathology, and histopathology.
There were no overt signs of toxicity shown by the overall evaluation in
the treated groups, and a significant (P<0.05) increase in mortality was
observed only in female rats exposed to 25 ppm during months 15 to 23 and 75
ppm at months 15, 17, and 21 (Tables 10-32 and 10-33). However, increases in
mortality in treated groups might have been influenced by histopathologically
diagnosed increases in chronic murine pneumonia incidence (number of rats with
pneumonia/cumulative number of animals examined) as follows: males - 0/86
control, 26/85 low dose, 24/86 high dose; females - 9/84 control, 21/86 low
dose, 22/84 high dose. Although control cages were in the inhalation chamber
room during exposures, control animals were not placed in the inhalation
chambers. Decreased body weights in both treated groups of male rats compared
to controls are indicated in Table 10-34, but the relationship to a direct
effect of VDC appears rather uncertain in that a consistent slight but
significant (P<0.05) decrease is evident only in the low-dose group of males,
no clear dose response is evident, and information on food consumption could
have shown whether this could have affected the body weight trends shown.
Body weights between control and treated female rats were similar
(Table 10-35).
Treatment-related induction pf non-neoplastic lesions was not apparent,
with the possible exception of ovarian cysts in high-dose females [6/84 in
controls; 8/86 in the low-dose group; 14/84, (P<0.05) in the high-dose group].
An increase in midzonal fatty changes in the livers of treated female rats was
10-98
-------
TABLE 10-32. VINYLIDENE CHLORIDE: A CHRONIC INHALATION TOXICITY
AND ONCOGENICITY STUDY IN RATS
CUMULATIVE PERCENT MORTALITY FOR MALE RATS
Exposure level
Months
on
Study
Number of rats
a
alive on day 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16.
17
18
19
20
21
22
23
24
25
Terminals Kill
30-Day Interim Kill
6-Month Interim Kill
12-Month Interim Kill
26 Weeks Cytogenetic
Killb
Total Rats in Study
Excludes those rats
b „
Control
number dead
(%
1
1
1
1
1
3
4
5
5
5
6
8
9
10
14
19
23
27
32
39
49
54
63
72
73
13
4
5
5
4
104
in the
dead)
86
(1)
(1)
(1)
(1)
(1)
(4)
(5)
(6)
(6)
(6)
(7)
(9)
(11)
(12)
(16)
(22)
(27)
(31)
(37)
(45)
(57)
(63)
(73)
(84)
(85)
interim kills
_T _JJ_J
25 ppm
number dead
(%
3
3
3
4
4
4
4
5
5
6
6
7
8
8
8
17
18
25
36
47
50
58
65
72
72
13
4
5
5
3
103
and
dead)
85
(4)
(4)
(4)
(5)
(5)
(5)
(5)
(6)
(6)
(7)
(7)
(8)
(9)
(9)
(9)
(20
(21)
(29)
(42)
(55)
(59)
(68)
(77)
(85)
(85)
c
75 ppm
number dead
1
1
2
3
3
4
4
5
5
7
8
8
9
10
12
12
16
27
37
47
56
66*
71
74
78
8
4
5
5
4
104
the cytogenetic
_*_L _^~j-_
_ 4- ^ -_ 1
(% dead)
86
(1)
(1)
(2)
(4)
(4)
(5)
(5)
(6)
(6)
(8)
(9)
(9)
(11)
(12)
(14)
(14)
(19)
(31)
(43)
(55)
(65)
(77)
(83)
(86)
(91)
kill.
i- _ .C _«-..J_-
Includes one rat designated for cytogenetics study but not used due to
death six weeks prior to cytogenetic kill.
* Statistically different from control data when analyzed using Fisher's
Exact Probability test, P<0.05.
Source: McKenna et al., 1982.
18-99
-------
TABLE 10-33. VINYLIDENE CHLORIDE: A CHRONIC INHALATION TOXICITY
AND ONCOGENICITY STUDY IN RATS
CUMULATIVE PERCENT MORTALITY FOR FEMALE RATS
Exposure level
Months
on
study
Number of rats
o
alive on day 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Terminal Kill
30-Day Interim Kill
6-Month Interim Kill
12-Month Interim Kill
26 Weeks Cytogenetic
KillD
Total Rats in Study
o
Excludes those rats
b T,
Control
number dead
(%
0
0
0
1
1
1
1
1
1
1
2
2
4
4
5
8
9
16
23
30
39
46
56
64
65
19
4
5
5
4
102
in the
1
dead)
84
(0)
(0)
(0)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(2)
(2)
(5)
(5)
(6)
(10)
(11)
(19)
(27)
(36)
(46)
(55)
(67)
(76)
(77)
interim kills
-» Til
25 ppm
number
dead
(% dead)
86
0
0
0
0
0
1
1
1
3
3
6
6
9
10
18*
19*
19*
29*
37*
49*
55*
59*
65
72
75
11
4
5
5
4
104
and the
(0)
(0)
(0)
(0)
(0)
(1)
(1)
(1)
(4)
(4)
(7)
(7)
(11)
(12)
(21)
(22)
(22)
(34)
(43)
(57)
(64)
(69)
(76)
(84)
(87)
0
0
0
0
0
1
1
1
1
1
1
5
6
7
13*
16
18*
20
29
41
51*
54
61
68
68
16
4
5
5
4
102
cytogenetic
75 ppm
number dead
(% dead)
84
(0)
(0)
(0)
(0)
(0)
(1)
(1)
(1)
(1)
(1)
(1)
(6)
(7)
(8)
(16)
(19)
(21)
(24)
(35)
(49)
(61)
(64)
(73)
(81)
(81)
kill.
Four rats per exposure level were added one month after start of study.
* Statistically different from control data when analyzed using Fisher's
Exact Probability test, P<0.05.
Source: McKenna et al., 1982.
10-100
-------
TABLE 10-34. VINYLIDENE CHLORIDE: A CHRONIC INHALATION TOXICITY
AND ONCOGENICITY STUDY IN RATS
MEAN BODY WEIGHT FOR MALE RATS
Study
Month
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Time
Day
0
8
13
20
26
39
52
79
113
140
174
201
209
212
219
233
260
287
321
348
375
409
436
463
497
524
551
578
612
646
677
704
Controls
275.82
319.74
346.77
378.09
399.47
428.59
448.09
489.09
518.47
536.55
561.78
579.24
572.32
601.29
565.01
579.07
598.12
603.05
615.80
639.17
637.45
638.81
638.46
631.71
659.41
627.18
606.18
609.37
607.78
597.50
574.96
587.27
15 ppm
276.05
305 . 84*
340 . 06*
363.06*
385 . 93*
412.48*
431.80*
468.71*
500.00*
512.86*
528.74*
528.15*
528.50*
563.12*
535.02*
550.81*
555.11*
569.36*
586.04*
593.14*
611.82*
613.47
623.26
618.00
614.94*
585 . 60*
596.84
575.20
582.11
569.04
554.65
549.69
75 ppm
282.56*
328 . 20*
353.56*
375.61
396.02
423.88
447.24
488.15
518.94
539.54
549.27
556.47*
552.79*
557.76*
558.60
559.31*
565.36*
572.19*
588.57*
586.36*
625.81
639.74
645.81
635.24
628.62*
618.39
583.75
585.84
563.10*
541.85
536.13
529.55
Significantly different from control mean, p <.05.
Source: McKenna et al., 1982.
10-101
-------
TABLE 10-35. VINYLIDENE CHLORIDE: A CHRONIC INHALATION TOXICITY
AND ONCOGENICITY STUDY IN RATS
MEAN BODY WEIGHT FOR FEMALE RATS
Study
Month
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Time
Day
0
8
13
20
26
39
52
79
113
140
174
201
209
212
219
233
260
287
321
348
375
409
436
463
497
524
551
578
612
646
677
704
Controls
210.24
230.20
238.48
252.87
259.52
269.89
278.78
294.14
311.28
322.03
332.67
336.18
337.11
332.63
331.73
338.73
339.60
343.67
356.89
367.94
376.74
379.60
386.38
390.53
406.30
396.26
395.10
414.86
443.06
412.23
420.33
427.00
25 ppm
212.58
221.38*
243 . 40*
246.59*
258.60
277.79*
280.84
301.51*
317.23
329.17
342 . 63*
331.11
334.58
335.27
335.80
338.93
348.01
362 . 06*
370 . 98*
377.14
375.25
386.23
391.36
397.31
411.39
419.26
429.48
405 . 68
411.72
435-19
460.71
462.67
75 ppm
203.22*
241.57*
247 . 40*
255.68
264.34
280.79*
289 . 26*
308.79*
325 . 10*
335.96*
342.12*
339.93
336.71
343.73*
340.29
340.23
348.26
356.57
368 . 90*
363.14
387.52
397.57*
402.62
397.10
419.64
426.13
421.21
413.13
448.65
457.27
469.91
438.62
Significantly different from control mean, p <.05.
Source: McKenna et al., 1982.
10-102
-------
evident [1/84 in controls; 6/86, (P>0.05) in the low-dose group; 8/84,
(P<0.05) in the high-dose group] which may be treatment-related. However,
these changes were mainly evident in females sacrificed at the end of exposure
at 8 months, and only 1 high-dose female had this midzonal fatty change in
liver during the 6-month post-exposure period. Furthermore, the total numbers
of females with any type of fatty change in liver were as follows: 15/84
controls, 13/86 low-dose rats, and 16/84 high-dose rats.
VDC exposure did not result in significant (P<0.05) increases in tumor
incidence in this study, except for the mammary tumor data discussed below.
Mammary tumor data are presented in Table 10-36 for comparison with mammary
tumor data on female Sprague-Dawley rats exposed to VDC in the inhalation
study by Maltoni et al. (1980; Table 10-27). The incidence of adenocarcinoma
without metastasis was significantly (P<0.05) increased in low-dose females
compared to controls; however, mammary adenocarcinoma incidence was not
significantly (P<0.05) increased in high-dose females, and adenocarcinoma
without metastasis was found in another control female, which causes the
adenocarcinoma incidence in low-dose females to lose significance (P>0.05).
The significant increase (P<0.05) in total mammary tumor incidence in
high-dose females compared to control females includes animals with both
benign and malignant tumors and according to the authors, total mammary tumor
incidence in the control group and in each treatment group is within the
historical control range for the Sprague-Dawley strain of rats at the
investigating laboratory. Thus, demonstration of an induction of mammary
tumor formation in female Sprague-Dawley rats under the conditions of the
study by McKenna et al. (1982) does not seem apparent. Overt toxicity of VDC
in Sprague-Dawley rats does not appear evident, and an attempt to use higher
10-103
-------
TABLE 10-36. VINYLIDENE CHLORIDE: A CHRONIC INHALATION TOXICITY AND ONCOGENICITY STUDY IN RATS
HISTOPATHOLOGIC DIAGNOSIS AND NUMBER OF TUMORS IN FEMALE RATS
Number of rats necropsied
during the time period
indicated
MAMMARY GLAND
Fib roadenoma/adeno fibroma
S-25
Fibroma
S-26
Adenocarcinoma with pulmonary
metastasis
S-40
Adenocarcinoma without metastasis
S-27
Leiomyosarcoma without metastasis
S-41
Carcinosarcoraa of the mammary
gland
S-43
Adenofibroma based on gross
examination only
S-44
Total number of animals with
a subcutaneous and/or
mammary gland tumor
S-02, S-05, S-25, S-26, S-27,
S-40, S-41, S-43, S-44
Number of rats with a malignant
tumor in mammary region or skin°
S-05, S-27, S-40, S-41, S-43
Control
25 ppm
75 ppm
Control
25 ppm
75 ppm
Control
25 ppm
75 ppm
Control
25 ppm
75 ppm
Control
25 ppm
75 ppra
Control
25 ppm
75 ppm
Control
25 ppm
75 ppm
Control
25 ppm
75 ppm
Control
25 ppm
75 ppm
Control
25 ppm
75 ppm .
0-6
Months
1
1
1
0
0
1/1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
7-12
Months
1
5
4
0
2/2
6/4
0
0
0
0
0
0
0
1/1
0
0
0
0
0
0
0
0
0
0
0
3
4
0
1
0
13-18
Months
14
23
15
17/10
40/20
17/14
0
0
0
0
0
0
0
2/2
2/2
0
0
0
0
0
0
0
0
0
10
20
14
0
2
2
19-24 Terminal
Months Kill
49
46
48
78/39
76/38
100/40
0
0
1/1
1/1
0
0
1/1
1/1
0
0
1/1
0
0
0
0
0
0
1/1
39
38
41
2
2
0
19
11
16
37/15
16/8
33/15
0
0
1/1
0
0
0
0
4/3
2/2
0
0
0
1/1
0
0
0
0
0
16
9
15
2
3
2
Cumulative
Results
85
86
85
U
132/64°
134/68^
157/74
0
g
2/2
l/lb
0
0
l/lb
8/7&'b
4/4b
0
1/1
0
l/lb
0
0
0
0 b
65
70
75a
4
8
4
Significantly different from control data when analyzed using Fisher's Exact Probability Test, P < 0.05.
Number of tumors/number of animals with tumors.
A subcutaneous fibroma was found in one female in the 75 ppm group, and a subcutaneous fibrosarcoma
without metastasis was observed in one female in the control group.
Source: McKenna et al., 1982.
10-104
-------
exposure levels in this study might have provided a broader evaluation for
carcinogenicity.
In the reports of Quast et al. (1983) and Humiston et al. (1978), male
and female Sprague-Dawley rats, initially 6 to 7 weeks old, were exposed to
VDC at 50, 100, and 200 ppm (99.5% pure) in drinking water for two years.
Because of the volatile nature of VDC, the water was made up at higher
concentrations, and the above figures reflect the average concentrations
during 24-hour periods. The actual VDC levels measured in the drinking water
were 68 ± 21, 99 ± 22, and 206 ± 33 ppm (mean ± S.D.). When taking into
account the water consumption of the rats, the time-weighted average dose was
equivalent to 7, 10, or 20, and 9, 14, or 30 mg/kg/day in males and females,
respectively. The VDC used in this study was distilled prior to making up the
test water in order to reduce to 1 to 5 ppm the concentration of the inhibitor
monomethyl ether of hydroquinone (this inhibitor would normally be at low
levels in copolymers used for food packaging applications). Each treatment
group consisted of 48 rats of each sex, and an untreated control group
consisted of 80 males and 80 females. Animals were evaluated for survival,
body weight, food and water consumption, hematology, clinical chemistry,
urinalysis, gross pathology, and histopathology. The animals were observed
until morbidity, or 24 months, at which time surviving animals were
sacrificed. The specific tissues examined are presented in Table 10-37. There
was no evidence of statistically significant (P<0.05) treatment-related
effects of VDC on the toxicologic endpoints evaluated in treated animals as
compared to controls. At least 50% of each group survived for approximately as
long as 20 months.
10-105
-------
TABLE 10-37.
REPRESENTATIVE TISSUE SPECIMENS OBTAINED AT NECROPSY
FROM ALL ANIMALS
esophagus
salivary glands
stomach
large intestine
pancreas
liver
kidneys
urinary bladder
prostate
accessory sex glands
epididymides
testes
ovaries
uterus
mammary tissue (females)
brain (cerebrum, cerebellum
with brain stem)
pituitary gland
spinal cord
peripheral nerve
trachea
lungs (bronchi)
nasal turbinates ,
sternum and sternal bone marrow
spleen
mediastinal lymphoid tissue
(thymus, mediastinal lymph nodes)
lymph nodes (mesenteric)
heart
aorta
skeletal muscle
adrenal glands
thyroid gland
parathyroid gland3
adipose tissue
skin
any gross lesion or mass
eyes
These tissues were evaluated histologically only to the extent that
they were included in the routine sections of adjacent larger organs.
Sternum and enclosed bone marrow were to be evaluated histologically
only if indicated by abnormal findings in the hematological studies.
p
Eyes were saved in formalin if the rat died or was culled from the
study. If the rat was from the terminal kill, a portion of these
were fixed in Zenker's fixative and the remainder in formalin. Only
selected animals had their eyes microscopically examined.
Source: Humiston et al., 1978
10-106
-------
A number of neoplastic lesions were observed in both control and experi-
mental animals. The total tumor incidence is given in Table 10-38. The tumor
frequency at specific sites, as reported by Quast et al. (1983), did not show
a treatment-related effect of VDC. The only statistically (P<0.05)
significant increase in a specific neoplasm was in female rats exposed to VDC
at 50 ppm. These animals had an increased incidence of mammary gland
fibroadenomas/adenofibromas (40/48 50 ppm females vs. 53/80 control females).
This tumor was not considered by the authors to be treatment-related, since
there was no dose relationship between tumor incidence, i.e., 36/48 100 ppm
females and 35/48 200 ppm females, and exposure to VDC. Also, the spontaneous
incidence of mammary tumors was high in this strain of rats, and the tumor
incidence observed in the 50 ppm females was within the limits for historical
controls at the testing laboratory. Four control, 1 low-dose, and 2 mid-dose
females had mammary carcinomas. No treatment-related effects of VDC on
non-neoplastic lesions were evident, except for minimal fatty change and
swelling in the livers of high-dose males and females in all treatment groups.
The dose of VDC ingested in the drinking water appeared low enough to produce
no overt toxic effects. The use of higher exposure levels might have provided
a stronger evaluation of the carcinogenic potential of VDC; however, the
authors indicated that 200 ppm, the maximum concentration of VDC in water used
in this study, was the highest concentration possible given the solubility of
VDC (2.25 g/Jl at 25°C) .
The National Cancer Institute/National Toxicology Program (NCI/NTP, 1982)
has prepared a report on a cancer bioassay of VDC (99% pure) performed on
Fischer 344 rats and B6C3F1 mice, initially 9 weeks old. Male and female rats
(50 animals of each sex) received VDC, dissolved in corn oil, by gavage at
10-107
-------
TABLE 10-38. TUMOR INCIDENCE FOLLOWING INGESTION OF VDC
Average number of
Total number of Total number of neoplasms/number
Concentration neoplasms rats in group of rats
UJ- VU\j
water (ppm)
0
50
100
200
Male
100
53
43
53
Female
187
132
120
124
Male
80
48
48
47
Female
80
48
48
48
Male
1.3
1.1
0.9
1.1
Female
2.3
2.8
2.5
2.6
Source: Humiston et al., 1978.
doses of 1 and 5 mg/kg, while male and female mice (50 animals of each sex)
received doses of 2 and 10 mg/kg. The animals were treated 5 days/week for a
total of 104 weeks. Animals were observed for gross signs of toxicity during
the exposure period, as indicated by food consumption patterns, body weight
gain, and mortality. The treated and control animals were killed after 104
weeks of exposure or when moribund, and the tissues indicated in Table 10-39
were examined histologically for both tumorigenic and non-tumorigenie pathology.
The survival (greater than 50% for the whole study for all groups) and
weight gain of rats were unaffected by treatment with VDC; however, 12 control
and 10 low-dose male animals were accidentally killed as a result of a 5-hour
exposure to 37°C on week 82 of the study. Including the male rats accidentally
killed, survival of rats at terminal sacrifice was as follows: 20/50 vehicle
control males, 24/50 low dose males, 37/50 high dose males, 27/50 vehicle
control females, 28/50 low dose females, and 29/50 high dose females. In
mice, only survival in the low-dose female group was adversely affected by
treatment. However, at least 64% of the mice in all groups survived the study
(33/50 vehicle control males, 35/50 low dose males, 36/50 high dose males,
10-108
-------
TABLE 10-39. TISSUES EXAMINED3 FOR HISTOLOGIC CHANGES IN THE NCI BIOASSAY
skin liver
lungs and bronchi pancreas
trachea stomach
bone and bone marrow small intestine
spleen large intestine
lymph nodes kidney
heart urinary bladder
salivary gland pituitary
adrenal mammary gland
thyroid prostate
parathyroid brain
seminal vesicles (male) uterus (female)
testis (male) ovary (female)
thymus larynx
esophagus
o
These tissues were examined in all animals, except where advanced autolysis
or cannibalism prevented meaningful evaluation.
Source: NCI/NTP, 1981.
40/50 vehicle control females, 32/50 low dose females, and 42/50 high dose
females). Body weight gain was slightly depressed in both dose groups of male
mice and in female mice of the low-dose group as compared to either the
corresponding high-dose or control animals (Table 10-40); however, a
dose-response was not evident, and body weight decreases were greater in
low-dose than in high-dose mice. Dose-related non-neoplastic lesions consisted
of liver necrosis in mice (male controls, 1/46, 2%; low-dose, 3/46, 7%;
high-dose, 7/49, 14%; female controls, 0/47, 0%; low-dose, 4/49, 8%;
high-dose, 1/49, 2%) and inflammation of the kidney in rats (male controls,
26/49, 53%; low-dose, 24/48, 50%; high-dose, 43/48, 90%; female controls,
3/49, 6%; low-dose, 6/49, 12%; high-dose, 9/49, 20%). It is noted in the NTP
(1982) report that chronic nephritis is a common lesion in aging rats. Other
histopathologic changes of a non-tumorigenic type were observed randomly in
control and treated animals, and were not considered treatment-related.
10-109
-------
TABLE 10-40.
MEAN BODY WEIGHT CHANGE (RELATIVE TO CONTROLS) OF MICE
ADMINISTERED VINYLIDENE CHLORIDE BY GAVAGE
Week No.
Mean body weight change
grams
Control Low dose High dose
Weight change rela-
tive to controls (a)
(percent)
Low dose High dose
Male
mice
Female
mice
0
1
20
40
60
80
100
0
1
20
40
60
80
100
28(b)
1
13
19
22
21
20
19(b>
2
9
12
17
19
24
24(b)
2
11
17
21
20
21
18
2
8
12
15
18
21
25(b)
2
13
19
23
22
21
18
3
9
13
18
14
24
+ 100
-15
-20
-5
-5
+5
0
-11
0
-12
-5
-13
+ 100
0
0
+5
+5
+5
+50
0
+8
+6
+35
0
(a)
Weight change relative to controls =
Weight change (dosed group) - Weight change (control group) x 100
Weight change (control group)
Initial weight
Source: NCI/NTP, 1981.
10-110
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In rats and mice, increased tumor incidences were observed in a number of
organs (Table 10-41). While unadjusted analyses of these data suggested that
some responses were marginally statistically significant at the P = .05 level,
such analyses do not take into account the multiple organs compared. As
indicated by NCI/NTP (1980) and discussed in greater detail by Gart et al.
(1979), it is more accurate to account for multiplicity of comparisons by the
Bonferroni correction when using the Fisher exact test, and to account for
differing patterns of mortality among the dose groups by time-adjusted
analyses. Making these corrections, the only statistically significant
(P<0.05) increased response was for lymphomas in the low-dose group female
mice compared to the matched controls using the Fisher exact test.
Furthermore, only lymphomas represent a statistical increase in malignant
tumors in Table 10-41. However, a similar increase in the high-dose group was
not noted, and the Cochran-Armitage test for linear trends was not significant.
Since the matched controls had a low incidence (4%) of lymphomas when compared
to the incidence (9.8%) in historical controls, this effect was not considered
to be treatment-related. Thus, the conclusion in the NTP (1981) report is
that VDC was not carcinogenic to F344 rats or B6C3F1 mice under the conditions
of this assay. Survival and body weight data suggest that higher doses of VDC
could have been given to rats and mice to more strongly challenge these
animals for carcinogenicity.
VDC was tested for its potential as a brain carcinogen on the basis that
t
vinyl chloride causes neuroblastomas in animal studies and is associated with
brain neoplasms in exposed humans (Maltoni et al., 1982). No increase in the
incidence of gliomas, meningiomas, or ependymomas was reported among Sprague-
Dawley rats exposed by inhalation to VDC at 10, 25, 50, 100, or 150 ppm for
10-111
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TABLE 10-41. TUMORS WITH INCREASED INCIDENCE IN RATS AND MICE, AS INDICATED
BY THE FISHER EXACT TEST OR THE COCHRAN-ARMITAGE TEST FOR
LINEAR TREND
Incidence
Species
rat
rat
rat
rat
rat
mice
(male)
(male)
(male)
(female)
(male)
(female)
Tumor
adrenal ,
pheochromocytomas
pancreatic islet-cell,
adenomas/carcinoma (a)
testes, interstitial-cell
pituitary, adenomas
subcutaneous, fibromas
lymphomas
Control
6/50
(P=0.
4/49
(P=0.
43/50
(P=0.
16/48
(P=0.
0/50
(P=0.
2/48
(12%)
01)*
(8%)
025)*
(86%)
013)*
(33%)
017)
(0%)
024)*
(4%)
Low
5/48
1/47
39/47
20/49
1/48
9/48
(P=0.
Dose
(10%)
(2%)
(83%)
(41%)
(2%)
(18%)
028)**
High
13/47
(P=0.
8/48
47/48
(P=0.
24/43
(P=0.
4/48
6/50
Dose
(28%)
045)**
(17%)
(98%)
034)**
(56%)
026)**
(8%)
(12%)
(a) All pancreatic tumors were carcinomas, except for adenomas in two
high-dose males. Carcinomas alone were not significant by the Cochran-
Armitage test.
* Significant for linear trend by Cochran-Armitage test (P < 0.05).
--''Significant by Fisher exact test (P < 0.05).
Source: NCI/NTP, 1982.
4 or 5 days weekly for 52 weeks. Male and female rats exposed by ingestion
(gavage) to 0.5, 5, 10, or 20 mg/kg of VDC for 5 days weekly for 52-59 weeks
did not show an increased incidence of brain tumors when compared to controls.
Ponomarkov and Tomatis (1980) assessed the carcinogenic potential of VDC
in BDIV rats exposed to the compound starting in utero and continuing to 120
weeks of age. Pregnant rats (24 animals) received a single 150 mg/kg dose of
VDC (99% pure) by gavage in corn oil on day 17 of gestation. Following birth,
10-112
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the pups (89 males and 90 females) received VDC by gavage at a dose of
50 rag/kg weekly for the duration of the study. The animals were killed at the
termination of the study or when moribund, and major organs and gross lesions
were examined histologically.
There was no treatment-related effect on the reproductive success of the
dams or on the survival or weight gain of the offspring of rats treated with
VDC. Non-tumorigenic lesions in the liver, consisting of degeneration of the
parenchymal cells, liver necrosis, and hemorrhage, were observed in treated
animals moribund after 80 weeks of treatment or killed at termination. In
cases of early death (30 weeks of treatment), lung and kidney congestion were
also observed in treated rats. The total tumor incidence in either the dams
or the offspring was not significantly increased by treatment (Table 10-42);
however, there was an increased incidence of meningiomas in male rats,
although this was also not significantly different from control levels.
Although slight differences in tumor incidence were observed following VDC
treatment, this study did not demonstrate a statistically significant effect
of VDC treatment on the induction of tumors in either the dams or their
offspring. Although liver lesions were seen, it appears that higher doses
could possibly have been used, since no effect was observed on survival and
body weight.
Skin application has been used to assay VDC for tumor initiation and
complete carcinogen action in lifetime studies using the two-stage
tuniorigenesis model in female Ha:ICR Swiss mice (Van Duuren et al., 1979). In
two-stage tumorigenesis, an initiator agent is applied in a single dose to the
skin of a mouse. The initiator does not produce tumors at the applied
10-113
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Table 10-42.
Tumor incidence in female BDIV rats treated with VDC on day 17 of pregnancy,
in their progeny treated weekly for life and controls (Ponomarkov and Tomatis, 1980)
Group
Females given VDC
Progeny treated weekly
with VDC
Males
Females
Females given olive oil
Progeny treated weekly
with olive oil
Males
Females
Effective Tumor
number of bearing
rats rats
23
81
90
1U
49
47
n
11
31
53
5
16
24
*
47.8
38.3
66.3
35.7
32.7
51.1
Number of
tumors
Total
14
35
64
7
16
29
per rat
0.6
0.4
0.8
0.5
0.3
0.6
Animals with
more than one
tumor
n J
3 13
4 4.9
11 13.8
2 14.3
-
5 10.6
-------
Table 10-42. (cont.)
Distribution of Tumors
oral
meninges cavity stomach liver
0
I—1
Ul
Group
Females given VDC
Progeny treated weelciy
with VDC
Males
Females
Females given olive oil
Progeny treated weekly
with olive oil
Males
Females
n > n
- 2
6 7.4 5
1
1
1 2.0 2
1
% n % n %
8.7 1 4.3
6.2 1 1.2 1 1.2
1.3 2 2.5 3 3.8
7.1 -
4.1 -
2.1 1 2.1 - -
soft
tissue
n I
-
9 11.1
7 8.8
1 7.1
4 8.2
mammary
gland
n %
8 34.8
1 1.2
39 48.8
4 28.6
. «.
22 46.8
ovary other
n J n
2 8.7 1b
12°
6 7.5 6d
- - 1e
- - 9f
3 6.4 2g
*
4.3
14.8
7.5
7.1
18.4
4.3
Liver
hyperpl .
nodules
%
2 8.7
2 2.5
6 7.5
-
_ _
-
The percentages and the number of tumors per rat are expressed in relation to the effective number of rats.
Survivors at the time the first tumors were observed.
°Urinary bladder papilloma; 1 lymphoma, 4 pituitary adenomas; 3 adrenal cortical adenomas; 1 spleen haemangioma; 1 lung sarcoma, pleomorphic; 1 skin
squamous cell carcinomas; 1 seminoma.
1 salivary gland carcinoma; 1 salivary gland adenoma; 1 lymphoma; 1 pituitary adenoma; 1 rectal adenomalous polyp; 1 uterine adenoma
eAdrenal cortical adenoma
1 osteosarcoma; 1 mediastinal sarcoma; 1 lung epidermoid carcinoma; 2 lymphomas; 1 spleen haemangioma; 2 pituitary adenomas; 1 adrenal cortical adenoma
g1 lymphoma; 1 uterine adenoma
-------
concentration, but predisposes the skin so that later repeated applications of
a promoter (an agent that by itself will not produce tumors) will cause the
formation of tumors. A complete carcinogen is one which, if applied in
sufficient concentrations, can produce tumors by itself. When VDC was applied
3 times each week at a dose of 121 mg/mouse to the shaved backs of 30 mice, no
tumors were observed; however, when a single dose of 121 mg/mouse of VDC was
applied to the skin of 30 mice, followed by repeated application of phorbol
myristate acetate (PMA) as the promoter, a significant increase (P<0.005) in
skin papillomas (8 mice with papillomas/9 total papillomas) was observed as
compared to controls. No skin papillomas were observed in 30 controls treated
with acetone, the dosing vehicle, and 100 untreated controls, whereas 9 mice
(10 total papillomas) of 120 mice given 0.0025 mg PMA and 6 mice (7 total
papillomas) of 90 mice given 0.005 mg PMA on the same schedule as that for
treated mice were found. Squamous cell carcinomas on the skin in the
initiation-promotion study were observed on one mouse in the VDC group, one
mouse in the low-dose PMA group, and 2 mice in the high-dose PMA group. A
positive control group of 30 mice in the initiation-promotion study given 0.02
mg/mouse of 7,12-dimethylbenz[a]anthracene as the initiating agent developed
papillomas in 29 mice (317 total papillomas) and local squamous cell
carcinomas in 14 mice. In the same study, VDC was also tested for complete
carcinogenic action in 30 female Swiss ICR/Ha mice by repeated subcutaneous
injection once a week at a dose of 2 mg/mouse. Following treatment for 548
days, no tumors were observed at the site of injection or at sites distant
from the site of injection. Although this study indicates that VDC is a tumor
initiator in mouse skin, it is not clear how this relates to the processes of
complete chemical carcinogenesis in other organs, or if tumor initiation as
observed here is a phenomenon solely restricted to the skin of mice. The
10-116
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relevance of positive results in this tumor initiation study with regard to
the assessment of human health effects is not clear, particularly since
complete carcinogenic activity could not be demonstrated. Maximally tolerated
doses, estimated from preliminary short-term tests, were used in the tests for
carcinogenicity performed by Van Duuren et al. (1979).
In summary, the evidence supporting the carcinogenicity of VDC is
limited. It has been shown that VDC is a mutagen in bacterial assay systems,
and Van Duuren et al. (1979) have demonstrated that VDC acts as a tumor
initiator in mouse skin; however, of the three animal species used to assess
the carcinogenicity of this compound-- rats, mice, and hamsters—only one
strain of mice developed a unique tumor type (kidney carcinomas) following
exposure to VDC. Maltoni (1977) and Norris (1982) suggested that the observed
increase in kidney tumors may be a species- and strain-specific effect, and
Maltoni et al. (1980) and Maltoni (1977) obtained experimental evidence for a
direct relationship between the sensitivity to acute toxic effects of VDC and
carcinogenic responses in the species and strains of rats and mice evaluated
for VDC carcinogenicity in their studies. Norris (1982) reviewed some of the
pharmacokinetic, toxicological, and carcinogenic data on the effects of VDC in
animals, and emphasized the unique susceptibility of Swiss mice to the toxic
and tumorigenic effects of this compound. A statistically significant
increase in mammary carcinomas was found in female Swiss mice by Maltoni et
al. (1982), but these investigators concluded that this evidence was not
conclusive due to reasons discussed in their report.
There have been a number of other carcinogenicity bioassays of VDC in
which no statistically significant increase in tumor incidence was observed
10-117
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(Table 10-21). From these studies, it could be concluded that VDC has not
been found to be carcinogenic in rats or hamsters, nor in mice when
administered by the oral or dermal route. The only published inhalation
studies in mice, except for the positive bioassay of Maltoni et al. (1977),
used either a shorter exposure period (Hong et al., 1981) or a shorter
observation period (Lee et al., 1978), although the level of exposure in both
studies was higher (55 ppm, 6 hours/day) than the high-dose group (25 ppm for
4 hours/day) used by Maltoni et al. (1977). Furthermore, higher doses
possibly could have been tested in several of the negative studies.
Nonetheless, in view of the present evidence for VDC carcinogenicity found in
one mouse strain in the inhalation study by Maltoni et al. (1980, 1977), the
available evidence regarding the carcinogenicity of VDC in animals is thus
seen to be limited and not sufficient for a firm conclusion on the potential
carcinogenicity of this compound in humans.
10.5.2 Epidemiologic Studies
Adequate data regarding the carcinogenic potential of VDC in humans are
lacking. One study, that of Ott et al. (1976) investigated 138 Dow Chemical
Company workers exposed primarily to VDC, and gave mortality data and the
results of health examinations. The authors noted that vinyl chloride is a
common contaminant of VDC monomer and that liquid VDC contained less than 0.2%
by weight of vinyl chloride in recent years prior to publication of their
study. In this study, time-weighted average (TWA) exposures were estimated
based on job descriptions and industrial hygiene surveys. Based on TWA
exposure estimates, each job initially fell into one of four categories: <10
ppm, 10 to 24 ppm, 25 to 49 ppm, and 50+ ppm. However, since operators in
10-118
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fiber production were the only workers with exposures above 25 ppm TWA, only
three concentration categories were used to calculate cumulative dose:
<10 ppm (5 ppm used for calculation); 10-24 ppm (17 ppm used for calculation);
^25 ppm (43 ppm used for calculation). Cumulative career exposures were
estimated by multiplying the TWA times the duration, in months, of potential
exposure (Table 10-43). As indicated in the table, the size of the population
having a lengthy duration of exposure or a long latency period since the
initial time of exposure was small. Moreover, it cannot be determined from
the data presented in the study report whether those individuals for whom the
greatest time had elapsed since initial exposure were also among the most
heavily exposed subjects. Thus, it is possible that for detection of
long-latency diseases such as cancer, the population examined in this study
may not be adequate.
Cohort mortality was compared with U.S. white male mortality for 1942,
1947, 1952, 1957, 1962, 1967, and 1971 by the indirect method. The most
recent health inventory for the cohort was compared with matched controls.
For the total cohort of 138 persons, 5 deaths were recorded. One death of an
individual with a 745 ppm cumulative dose was attributed to malignancy
(respiratory cancer); however, his smoking history was not known. The
expected respiratory cancer death rate was 0.3 for the total cohort; 0.2 for
the total cohort 15+ years after first exposure to VDC; and 0.2 for the cohort
with 500+ ppm months of exposure. An examination of company health inventory
records on this same cohort revealed no statistically significant (P<0.05)
clinical difference between the VDC-exposed group and matched (for age and
smoking) controls. Ott et al. (1976) mentioned that the cohort exposed to VDC
was also exposed to copolymers other than vinyl chloride, and that individuals
10-119
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TABLE 10-43. ESTIMATED CUMULATIVE DOSE, DURATION OF EXPOSURE AND DATE OF
FIRST EXPOSURE AMONG 138 INDIVIDUALS EXPOSED TO VINYLIDENE CHLORIDE
Exposure measures Total population
Estimated career dosage (TWA x months of exposure)
<500 ppm months 50
500-999 ppm months 28
1000-1999 ppm months 28
2000+ ppm months 32
Duration of exposure
<12 months 35
12-59 months 43
60-119 months 35
120+ months 25
Date of first exposure
1940-1949 9
1950-1959 74
1960-1969 55
Status as of January 1974.
Source: Ott et al., 1976.
in the matched control population might have been exposed to a number of other
chemicals.
10.5.3 Quantitative Estimation
This quantitative section deals with the unit risk for VDC in air, and
the potency of VDC relative to other carcinogens that the CAG has evaluated.
The unit risk estimate for an air pollutant is defined as the lifetime cancer
risk occurring in a hypothetical population in which all individuals are
exposed continuously from birth throughout their lifetimes to a concentration
3
of 1 |Jg/m of the agent in the air they breathe. Unit risk estimates are used
10-120
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for two purposes: 1) to compare the carcinogenic potency of several agents
with each other, and 2) to give a crude indication of the population risk
which might be associated with air or water exposure to these agents, if the
actual exposures are known.
10.5.3.1 Procedures for Determination of Unit Risk
The data used for the quantitative estimation of unit risk for VDC were
taken from a lifetime animal study. In animal studies it is assumed, unless
evidence exists to the contrary, that if a carcinogenic response occurred at
the dose levels used in the study, then responses would also occur at all
lower doses, at an incidence determined by an extrapolation model. However,
there is no solid scientific basis for any mathematical extrapolation model
that relates carcinogen exposure to cancer risks at the extremely low
concentrations that must be dealt with in evaluating environmental hazards.
For practical reasons, such low levels of risk cannot be measured directly
either by animal experiments or by epidemiologic studies. It is necessary,
therefore, to depend on current knowledge of the mechanisms of carcinogenesis
for guidance as to the correct risk model to use.
At the present time, the dominant view is that most cancer-causing
agents also cause irreversible damage to DNA. This position is reflected by
the fact that a very large proportion of agents that cause cancer are also
mutagenic. There is reason to expect that the quantal type of biological
response, which is characteristic of mutagenesis, is associated with a linear
non-threshold dose-response relationship. Indeed, there is substantial
evidence from mutagenicity studies with both ionizing radiation and a wide
10-121
-------
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 is also consistent with the
relatively few epidemiologic studies of cancer responses to specific agents
that contain enough information to make the evaluation 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).
There is also some evidence from animal experiments that is consistent with
the linear non-threshold model (e.g., the initiation stage of the two-stage
carcinogenesis model in rat liver and mouse skin).
Because its scientific basis, although limited, is the best of any of
the current mathematical extrapolation models, the linear non-threshold model
has been adopted as the primary basis for risk extrapolation to low levels of
the dose-response relationship. The risk estimates made with this model
should be regarded as conservative, representing the most 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 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 the 95% confidence limit
sense) at low extrapolated doses that is consistent with the data at all dose
levels of the experiment.
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10.5.3.2 Description of the Low-Dose Animal Extrapolation Model
Let P(d) represent the lifetime risk (probability) of cancer at dose d.
The multistage model has the form
where
q.S 0, i = 0, 1, 2, ..., k
Equivalently,
2 k
P (d) = 1 - exp [q..d + q~d + ... + q d )]
where
- P(0)
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, P (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,
P (d), are calculated by using the computer program GLOBAL 79, 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 q1.
Whenever q,>0, at low doses the extra risk P.(d) has approximately the form
Pf(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 Ln be the maximum value of the log-likelihood function.
The upper limit, q* is calculated by increasing q, to a value q* such that
10-123
-------
when the log-likelihood is remaximized subject to this fixed value q* for the
linear coefficient, the
satisfies the equation
linear coefficient, the resulting maximum value of the log-likelihood LI
2 (LQ - Lj) = 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,
P (d), is an improvement on the Crump et al. (1977) model. The upper
confidence limit for the extra risk calculated at low doses is always linear.
This is conceptually consistent with the linear non-threshold 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, P (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 ex-
periment, 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
h (X. - N.P.)2
y2 - j i 11
A ~ L N.P. (1-P.)
10-124
-------
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
2
fit is determined to be unacceptable 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 co-
efficients .
10.5.3.3 Calculation of Human Equivalent Dosages from Animal Data
Following the suggestion of Mantel and Schneiderman (1975), we assume that
mg/surface area/day is an equivalent dose between species. Since, to a close
approximation, the surface area is proportional to the 2/3 power of the
weight, as would be the case for a perfect sphere, the exposure in mg/day per
2/3 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
L = duration of experiment
1 = duration of exposure
m = average dose per day in mg during administration of the agent
(i.e., during 1 ), and
W = average weight of the experimental animal.
Then, the lifetime average exposure is
10-125
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d _ 1 x m
~ «
L x W
e
Inhalation
When exposure is via inhalation, the calculation 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 proportionally 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.
Case 1
Agents that are in the form of particulate matter or virtually completely
absorbed gases, such as sulfur dioxide, can reasonably be 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,
3 3
where I = inhalation rate per day in m , v = mg/m of the agent in air, and
r = the absorption fraction.
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The inhalation rates, I, for various species can be calculated from the
observations (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
3
rates in m /day, as follows:
For mice, I = 0.0345(W/0.025) ' m /day
2/3 3
For rats, I = 0.105 (W/0.113) ' m /day.
3
For humans, the values of 20 m /day* is adopted as a standard breathing rate
(1CRP, 1977).
2/3
The equivalent exposure in mg/W 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 70 0.29
Rats 0.35 0.64
Mice 0.03 1.3.
Therefore, for particulates or completely absorbed gases, the equivalent
2/3
exposure in mg/W is
m _ Ivr _ iWvr _ .yl/3
w2/3 w2/3 ~ w2/3 ~ 1W Vr
*From "Recommendation of the International Commission onJRadiological
Protection- p.~9. The average breathing rate is 10 cm per 8-hr, workday
and 2 x 20 cm in 24 hrs.
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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.
Case 2
The dose in mg/day of partially soluble vapors is 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 absorp-
tion coefficient, r, for the gas. Therefore, expressing the 02 consumption as
2/3
0 = k W , where k is a constant independent of species, it follows that
, 2/3
m = kw xvxr
or
m
,
= kvr
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
3
concentration in ppm or |Jg/m 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 or animals (Dripps et al. 1977). When the
animals are exposed via the oral route and human exposure is via inhalation or
vice versa, the assumption is made, unless there is pharmacokinetic evidence
to the contrary, that absorption is equal by either exposure route.
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10.5.3.4 Calculation of the Unit Risk from Animal Studies
2/3
The 95% upper limit risk associated with d mg/kg /day is obtained from
GLOBAL 79, 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
2/3
finding the number of mg/kg /day corresponding to one unit of X and substituting
this value into the above relationship. Thus, for example, if X is in units
3 1/3 3 2/3
of (Jg/m in the air, we have that for case 1, d = 0.29 x 70 x 10 mg/kg /day,
3
and for case 2, d = 1, when |Jg/ra 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:
- molecular weight (gas) mg/m3
-I ppffl — J. »jL X
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 jth polynomial coefficient by
(Wh/Wa)j/3 j = 1, 2, ..., k
and use mg/kg equivalents for the unit risk values.
10.5.3.5 Interpretation of Quantitative Estimates
For several reasons, the unit risk estimate based on animal bioassays is
only an approximate indication of the absolute risk in populations exposed to
10-129
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known carcinogen concentrations. First, there are important species
differences in uptake, metabolism, and organ distribution of carcinogens, as
well as species differences in target site susceptibility, immunological
responses, hormone function, dietary factors, and disease. Second, the
concept of equivalent doses for humans compared to animals on a tag/surface
area basis is virtually without experimental verification as far as
carcinogenic response is concerned. Finally, human populations are variable
with respect to genetic constitution and diet, living environment, activity
patterns, and other cultural factors.
The unit risk estimate can give a rough indication of the relative
potency of a given agent compared with other carcinogens. The comparative
potency of different agents is more reliable when the comparison is based on
studies in the same test species, strain, and sex, and by the same route of
exposure, preferably inhalation.
The quantitative aspect of carcinogen risk assessment is included here
because it may be of use in the regulatory decision-making process, e.g., in
setting regulatory priorities, evaluating the adequacy of technology-based
controls, etc. However, it should be recognized that with present technology,
only imprecise estimations are possible concerning cancer risks to humans at
low levels of exposure. At best, the linear extrapolation model used here
provides a rough but plausible estimate of the upper limit of risk, and while
the true risk is not likely to be more than the estimated risk, it could be
considerably lower. The risk estimates presented in subsequent sections
should not be regarded, therefore, as accurate representations of the true
cancer risks even when the exposures are accurately defined. The estimates
10-130
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presented may, however, be factored into regulatory decisions to the extent
that the concept of upper risk limits is found to be useful.
10.5.3.6 Alternative Methodological Approaches
The methods used by the CAG for quantitative assessment are consistently
conservative; that is, they tend toward high estimates of risk. The use of
the linear non-threshold extrapolation model tends to contribute to this con-
servatism. Other extrapolation models are available that would give lower
risk estimates. These alternative models have not been used by the CAG in the
following analysis because the limited available data show a positive response
at only one dose level. Thus only the background and linear parameters have
any meaning.
10.5.3.7 Estimation of Unit Risk Using the Maltoni Inhalation Study
The only animal study showing a significant increase in tumors is the
inhalation study of Maltoni et al. (1980), in which male Swiss mice developed
kidney adenocarcinomas. The long-term (52 weeks) exposure data from this
study are presented in Table 10-44. The two control groups were combined, as
well as the two groups treated at 25 ppm, since the responses within treatment
groups were not statistically different. Lacking information on early
mortality and scheduled sacrifice, the number surviving to the time of the
first kidney adenocarcinoma is used as the denominator.
Since VDC is only slightly soluble in water, it is considered a partially
soluble vapor in which the inhalation dose is proportional to 62 consumption.
10-131
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TABLE 10-44. DATA FROM MALTONI INHALATION STUDY ON MALE SWISS MICE
Dose ppm
daily for
12 months
0
0
10
25
25
Lifetime
continuous
equivalent
ppm
0
0
0.54
1.34
1.34
Number of
animals at
start
100
90
30
30
120
Kidney adenocarcinomas/
number surviving 55 weeks
from start
0/56*
0/70*
0/25
3/21(14.3%)**
25/98(25.5%)**
* Groups were combined since responses were not statistically different.
**These groups were combined, since responses using the same dose level were
not statistically different.
Furthermore, evidence by Dallas et al. (1983) indicates that the small un-
charged lipid-soluble molecule is easily absorbed across the lung membranes
into the systemic circulation, and that at low doses all of the chemical
presented to the animal will be retained until near-equilibrium is reached.
This behavior is considered similar to that of a water-insoluble anesthetic
gas. (As discussed in the methodology section on equivalent inhalation dose
(Case 2), exposure with these types of compounds to concentrations in ppm or
3
(Jg/m is considered equivalent between animals and humans) .
The lifetime continuous equivalent exposure is determined by dividing
total dose by total lifetime. In this experiment, inhalation exposure was 4
hours/day, 4-5 days/week for one year. On a continuous basis, this is
10 ppm x 4/24 x 4.5/7 x 1/2 = 0.54.
The calculation of the upper confidence level of risk by the multistage
model yields a slope factor of
10-132
-------
q* = 1.7 x 10 (ppm) .
In terms of risk, a lifetime exposure to VDC at 1 ppm corresponds to a
lifetime risk of induced cancer of
P = l-exp-(1.7 x 10"1) = 0.16.
3
To express the unit risk in terms of JJg/m , the following conversion is
used:
1 pg/m3 = l(pg/m3) x 10"3 (m3/l)/(l.2(g/l) x MW(VDC)/MW(air))
= 10~3/(1.2 x 97/28.8) jjg/g = 2.5 x 10~4 ppm.
For a lifetime continuous exposure to 1 |Jg/m3 of VDC, the corresponding
estimate is
-1 -4 -5
P = 1 - exp(-1.7 x 10 x 2.5 x 10 )= 4.2 x 10 .
10.5.3.8 Relative Potency
One of the uses of the concept of unit risk is to compare the relative
potency of carcinogens. To estimate the relative potency on a per mole basis,
the unit risk slope factor is multiplied by the molecular weight, and the
resulting number is expressed in terms of (mMol/kg/day) . This is called the
relative potency index.
Figure (10-6) is a histogram representing the frequency distribution of
potency indices of 53 chemicals evaluated by the CAG as suspect carcinogens.
The actual data summarized by the histogram are presented in Table (10-45).
10-133
-------
4th 3rd 2nd 1st
QUARTILElQUARTILElQUARTILEloUARTILE
2 4
LOG OF POTENCY INDEX
Figure 10-6. Histogram representing the frequency distribution of the potency
indices of 53 suspect carcinogens evaluated by the Carcinogen Assessment Group.
10-134
-------
TABLE 10-45. RELATIVE CARCINOGENIC POTENCIES AMONG 53 CHEMICALS EVALUATED
BY THE CARCINOGEN ASSESSMENT GROUP AS SUSPECT HUMAN CARCINOGENS ' '
Slope
Compounds (mg/kg/day)
Acrylonitrile
Aflatoxin B
Aldrin
Allyl Chloride
Arsenic
B[a]P
Benzene
Benzidine
Beryllium
Cadmium
Carbon Tetrachloride
Chlordane
Chlorinated Ethanes
1 ,2-dichloroethane
Hexachloroethane
1,1,2 , 2-tetrachloroethane
1,1, 1- trichloroethane
1 , 1 ,2-trichloroethane
Chloroform
Chromium
DDT
Dichlorobenzidine
1 , 1-dichloroethylene
0.24(W)
2924
11.4
1.19x10"
15 (H)
11.5
5.2xlO~2(W)
234(W)
4.86
6.65(W)
1.30X10"1
1.61
6.90x!0"2
1.42x!0"2
0.20
1.6xlO~3
5.73xlO~2
7xlO"2
41
8.42
1.69
1.47xlO"1(I)
Molecular
Weight
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
104
354.5
253.1
97
Potency
Index
lxlO+1
9xlO+5
4x1 0+3
9xlO-1
2xlO+3
3xlO+3
4x10°
4xlO+4
4xlO+1
7xlO+2
2xlO+1
7xlO+2
7x10°
3x10°
3xlO+1
2X10"1
8x10°
8x10°
4xlO+3
3xlO+3
4xlO+2
lxlO+1
Order of
Magnitude
Index
+1
+6
+4
0
+3
+3
+1
+5
+2
+3
+1
+3
+1
0
+ 1
-1
+1
+1
+4
+3
+3
+1
10-135
-------
TABLE 10-45. (continued)
Compounds
Dieldrin
Dinitrotoluene
Diphenylhydrazine
Epichlorohydrin
Bis (2-chloroethyl)ether
Bis (chloromethyl ) ether
Ethylene Dibromide (EDB)
Ethylene Oxide
Formaldehyde
Heptachlor
Hexachlorobenzene
Hexachlorobutadiene
Hexachlorocyclohexane
technical grade
alpha isomer
beta isomer
gamma isomer
Nickel
Nitrosamines
Dimethylnitrosamine
Diethylnitrosamine
Dibutylnitrosamine
N-nitrosopyrrolidine
N-nitroso-N-ethylurea
Slope
(mg/kg/day)
30.4
0.31
0.77
9.9x!0"3
1.14
9300(1)
8.51
0.63(1)
2.l4xlo"2(I)
3.37
1.67
7.75xlO~2
4.75
11.12
1.84
1.33
1.15CW)
25. 9 (not by q
43. 5 (not by q
5.43
2.13
32.9
10-136
Molecular
Weight
380.9
182
180
92.5
143
115
187.9
44.0
30
373.3
284.4
261
290.9
290.9
290.9
290.9
58.7
l) 74.1
}) 102.1
158.2
100.2
117.1
Potency
Index
lxlO+4
6xlO+1
lxlO+2
9X10"1
2xlO+2
lxlO+6
2xlO+3
3xlO+1
6X10"1
lxlO+3
5xlO+2
2xlO+1
lxlO+3
3xlO+3
5xlO+2
4xlO+2
7xlO+1
2xlO+3
4xlO+3
9xlO+2
2xlO+2
4xlO+3
Order of
Magnitude
(Iog10)
Index
+4
+2
+2
0
+2
+6
+3
+1
0
+3
+3
+1
+3
+3
+3
+3
+2
+3
+4
+3
+2
+4
-------
TABLE 10-45. (continued)
Compounds
N-nitroso-N-methylurea
N-nitroso-diphenylamine
PCBs
Phenols
2,4, 6-trichlorophenol
Tetrachlorodioxin
Tetrachloroethylene
Toxaphene
Trichloroethylene
Vinyl Chloride
Remarks:
1. Animal slopes are
Slope
(mg/kg/day)
302.6
4.92xlO~3
4.34
1.99x!0"2
4.25xl05
5.3lxlO~2
1.13
1.26x!0"2
1.75xlo"2(I)
95% upper-limit
Molecular
Weight
103.1
198
324
197.4
322
165.8
414
131.4
62.5
slopes based
Potency
Index
3xlO+4
1x10°
lxlO+3
4x10°
lxlO+8
9x10°
+2
5x10
2x10°
1x10°
Order of
Magnitude
lino
V -*- vo 1 f\ i
1 U )
Index
+4
0
+3
+1
+8
+1
+3
0
0
on the linearized
2.
3.
multistage model. They are calculated based on animal oral studies,
except for those indicated by I (animal inhalation), W (human
occupational exposure), and H (human drinking water exposure).
Human slopes are point estimates, based on the linear nonthreshold
model.
_ -i
The potency index is a rounded-off slope in (mMol/kg/day) and is
calculated by multiplying the slopes in (mg/kg/day) by the molecu-
lar weight of the compound.
Not all the carcinogenic potencies presented in this table represent
the same degree of certainty. All are subject to change as new
evidence becomes available.
10-137
-------
Where human data were available for a compound, they were used to calculate
the index. Where no human data were available, animal oral studies and animal
inhalation studies were used, in that order. Animal oral studies were
selected over animal inhalation studies because most of the chemicals have
been tested with animal oral studies, thus allowing potency comparisons by
route.
The potency index for VDC based on kidney adenocarcinomas in the Maltoni
(1980) inhalation biossay is 1.4 x 10 (mMol/kg/day) . This is derived as
-5 3 -1
follows: the slope estimate from the Maltoni study, 4.2 x 10 (pg/ffl ) > is
-1 3
first converted to units of (mg/kg/day) , assuming a breathing rate of 20 m
of air per day and a 70-kg person.
/ -, -i«~5 /• / ->3-l 1 day 1 ug
4.2 x 10 (|Jg/m) x •£ x ^- x 70 kg
20 m 10 mg
= 1.47 x 10"1 (mg/kg/day)"1.
Multiplying by the molecular weight of 97 gives a potency index of 1.4 x 10
Rounding off to the nearest order of magnitude gives a value of 10 , which is
the scale presented on the horizontal axis of Figure 10-1. The index of 1.4 x
10 lies at the bottom of the third quartile of the 53 suspect carcinogens.
Ranking of the relative potency indices is subject to the uncertainty of
comparing estimates of potency of differnt chemicals based on different routes
of exposure to different species using studies of different quality.
Furthermore, all the indices are based on estimates of low-dose risk using
linear extrapolation from the observational range. Thus, these indices are
not valide to compare potencies in the experimental or observational range if
linearity does not exist there.
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SUMMARY AND CONCLUSIONS
QUALITATIVE SUMMARY
The carcinogenicity of VDC was evaluated by inhalation exposure of both
sexes of Swiss mice and Sprague-Dawley rats to VDC concentrations as high as
those maximally tolerated (25 ppm for mice and 150 ppm for rats) for 12 months
followed by lifetime observation as well as in Chinese hamsters exposed to 25
ppm VDC (less than a maximally tolerated dose) for 12 months followed by
lifetime observation (Maltoni et al., 1980). A statistically significant
increase in kidney adenocarcinomas was found in male Swiss mice, and, although
a statistically significant increase in mammary carcinomas in treated female
Swiss mice was evident, the investigators concluded that a direct relationship
between this reponse in female mice and VDC treatment remains open, largely
due to stated results of their statistical analysis indicating a weaker
response when the data are adjusted for survival and lack of a dose-related
response over the course of the study. A carcinogenic effect of VDC in
Sprague-Dawley rats and Chinese hamsters was not apparent. The 12-month
exposure period used in this study was below lifetime exposures.
Additional inhalation exposure studies of VDC in animals have been done
(Table 10-21). Exposure of male and female Sprague-Dawley rats to 25 ppm and
75 ppm VDC for 18 months followed by 6 months of observation did not show a
carcinogenic effect (McKenna et al., 1982); however, the exposure levels used
did not appear to be overtly toxic, and use of additional higher exposure
levels might have provided a broader evaluation for carcinogenicity.
10-139
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No statistically significant increase in tumor formation in treated
animals was shown in any of the following separate studies of exposure to VDC:
(1) Male and female Wistar rats exposed to 200 ppm for 5 months and 100
ppm for 7 months followed by observation for an additional 12 months (Viola
and Caputo, 1977);
(2) MaLe and female Sprague-Dawley rats exposed to 75 ppm and 100 ppm
for an unspecified duration (Viola and Caputo, 1977);
(3) CD-I mice and CD rats exposed to 55 ppm and observed for a period of
12 months (Lee et al., 1978);
(4) CD-I mice exposed for 55 ppm for as long as 6 months and observed
for 12 additional months (Hong et al., 1981); and
(5) CD rats exposed to 55 ppm for as long as 10 months and observed for
an additional 12 months (Hong et al., 1981).
The known exposure periods of 12 months or less used in these studies were
shorter than potential lifetime exposure periods, and use of more than one
exposure level in the studies with CD-I mice and CD rats could have provided a
stronger evaluation of dose-response.
Several carcinogenicity studies in which VDC was administered orally to
experimental animals have been reported as negative. These studies include:
(1) Gavage administration of VDC in olive oil at doses as high as 20
mg/kg to male and female Sprague-Dawley rats for 12 months, followed by
lifetime observation (Maltoni et al., 1980);
10-140
-------
(2) Administration of VDC in drinking water at levels of maximum water
solubility (200 ppm) to male and female Sprague-Dawley rats for 2 years (Quast
et al., 1983; Humiston, et al., 1978).
(3) Gavage administration of VDC in corn oil to male and female Fischer
344 rats at 1 and 5 mg/kg and male and female B6CF1 mice at 2 and 10 mg/kg for
2 years (NCI/NTP, 1981);
(4) Gavage administration of 150 mg/kg of VDC in corn oil to pregnant
BDIV rats on day 17 of gestation, followed by weekly gavage doses of 50 mg/kg
of VDC to the pups for their lifetimes following birth (Ponomarkov and
Tomatis, 1980).
The 12-month exposure in Sprague-Dawley rats given VDC by gavage was
below the potential lifetime exposure, and a maximally tolerated dose does not
appear to have been selected. No clear effect on survival and body weight in
Fischer 344 and B6C3F1 mice given VDC in corn oil suggests that higher doses
could have been tested to challenge the animals more strongly for
carcinogenicity. A broader evaluation of VDC carcinogenicity in BDIV rats
might have been possible with the addition of more than the one dose level
used in the study, and with more than one treatment each week.
VDC was not carcinogenic in female ICR/Ha mice when applied to the skin
at 121 mg/mouse three times per week, or when injected subcutaneously at 2
mg/mouse once weekly at maximum tolerated doses in lifetime studies (Van
Duuren et al., 1980). When a single application of 121 mg/mouse of VDC was
followed by repeated application of the tumor-promoting agent phorbol
myristate acetate, skin papillomas resulted in ICR/Ha mice.
10-141
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One epidemiologic study on a population of 138 workers (Ott et al., 1976)
showed no carcinogenic effects attributable to VDC. At the time the study was
published in 1976, the dates of first exposures for 55 workers were between
1960 and 1969, thus indicating that nearly 40% of the workers had no more than
16 years latency since first exposure and that continued follow-up could
strengthen the evaluation for carcinogenicity.
Quantitative Summary
Only the Swiss mice inhalation study of Maltoni et al. (1980) provides
sufficient evidence for a quantitative cancer risk estimate for VDC. Based on
kidney adenocarcinomas in male mice, the 95% upper-limit unit risk estimate for
3
additional cancer from a lifetime of continuous exposure to l|Jg (VDC)/m (air)
is 4.2 x 10 . The relative potency of VDC, expressed in molar units, is 1.4
x 10 (mMol/kg/day) . Among 53 chemicals which the CAG has evaluated as
suspect carcinogens, VDC ranks at the bottom of the third quartile.
Conclusions
Evidence for the carcinogenicity of VDC in one strain of mice was found
in an inhalation study (Maltoni et al., 1980). Kidney adenocarcinomas were
diagnosed in treated male Swiss mice, and, although a statistically
significant excess of mammary carcinomas was evident in female Swiss mice, the
study investigators concluded that a direct correlation between this response
in female mice and VDC treatment could not be made. As discussed herein, VDC
has demonstrated mutagenicity in bacterial assay systems with metabolic activation
and can be metabolized to intermediates capable of reacting with cellular
10-142
-------
macromolecules. A 6-hour exposure of male CD-I mice and male Sprague-Dawley
rats to 10 or 50 ppm VDC was reported to produce minimal DNA alkylation and
DNA repair synthesis in liver and kidney, and increased DNA replication only
in mouse kidney.
Applying the International Agency for Cancer Research (IARC) approach for
classifying carcinogenic agents, this level of evidence can be considered to
be limited and not sufficient to make a firm conclusion regarding the
carcinogenicity of VDC in experimental animals. Applying IARC criteria for
evidence of human carcinogenicity, currently available data could also be
considered inadequate for making a judgment on the carcinogenicity of VDC in
humans. Based on the overall evidence, VDC would be, according to the IARC
method, a Group 3 chemical, by definition according to the IARC method, cannot
be classified as to its carcinogenicity to humans.
The kidney adenocarcinomas in male Swiss mice, however, provide data for
estimating an upper limit of potential human risk. This 95% upper-limit risk
-5 3
is 4.2 x 10 for a lifetime continuous exposure to l^g (VDC)/m air. Among
53 chemicals which the GAG has evaluated as suspect carcinogens, VDC would
rank at the bottom of the third quartile.
10-143
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