v°/EPA
United States
Environmental Protection
Agency
Office of Health and
Environmental Assessment
Washington DC 20460
EPA/600/8-84/026B
April 1986
Review Draft
Research and Development
Health Assessment
Document for
Beryllium
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
(Do Not
Cite or Quote)
j
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(Do Not EPA-600/8-84-026B
Cite or Quote) April 1 986
Review Draft
Health Assessment Document
for
Beryllium
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.
Environmental Criteria and Assessment Office
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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DISCLAIMER
This report is an external draft for review purposes only and does not
constitute Agency policy. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
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PREFACE
The Office of Health and Environmental Assessment, in consultation with
other Agency and non-Agency scientists, has prepared this health assessment to
serve as a "source document" for Agency-wide use. Specifically, this document
was prepared at the request of the Office of Air Quality Planning and Standards.
In the development of this assessment document, the scientific literature
has been inventoried, key studies have been evaluated, and summary/conclusions
have been prepared such that the toxicity of beryllium is qualitatively and
where possible, quantitatively, identified. Observed effect levels and dose-
response relationships are discussed where appropriate in order to place
significant health responses in perspective with observed environmental levels.
in
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ABSTRACT
The chemical and geochemical properties of beryllium resemble those of
aluminum, zinc, and magnesium. This resemblance is primarily due to similar
ionic potentials which facilitate covalent bonding. The three most common forms
of beryllium in industrial emissions are the metal, the oxide, and the
hydroxide.
The main routes of beryllium intake for man and animals are inhalation and
ingestion. While the absorption of ingested beryllium is probably quite
insignificant, the chemical properties of beryllium are such that transformation
of soluble to insoluble forms of inhaled beryllium results in long retention
time in the lungs. The tissue distribution of absorbed beryllium is
characterized by main depositions in the skeleton where the biological half-time
is fairly long.
The lung is the critical organ of both acute and chronic non-carcinogenic
effects. However, unlike most other metals, the lung effects caused by chronic
exposure to beryllium may be combined with systemic effects, of which one common
factor may be hypersensitization. Certain beryllium compounds have been shown
to be carcinogenic in various experimental animals under differing routes of
exposure. Epidemiologic studies present equivocal conclusions on the
carcinogenicity of beryllium and beryllium compounds. A lifetime cancer risk
o
for continuous inhalation exposure at I jjg beryllium/in has been estimated.
IV
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TABLE OF CONTENTS
Page
LIST OF TABLES vi i i
LIST OF FIGURES x
1. INTRODUCTION 1-1
2. SUMMARY AND CONCLUSIONS 2-1
2.1 BACKGROUND INFORMATION 2-1
2.2 BERYLLIUM METABOLISM 2-1
2.3 BERYLLIUM TOXICOLOGY 2-2
2.3.1 Subcellular and Cellular Aspects of Beryllium
Toxicity 2-2
2.3.2 Pulmonary and Systemic Toxicity of Beryllium in
Man and Animals 2-3
2.3.3 Dermatological Effects of Beryllium Exposure 2-5
2.3.4 Teratogenic and Reproductive Effects of Beryllium
Exposure 2-5
2.4 MUTAGENIC EFFECTS OF BERYLLIUM EXPOSURE 2-5
2.5 CARCINOGENIC EFFECTS OF BERYLLIUM EXPOSURE 2-6
2.5.1 Animal Studies 2-6
2.5.2 Human Studies 2-6
2.5.3 Qualitative Carcinogenicity Conclusions 2-7
2.6 HUMAN HEALTH RISK ASSESSMENT OF BERYLLIUM 2-7
2.6.1 Exposure Aspects 2-7
2.6.2 Relevant Health Effects 2-7
2.6.3 Dose-Effect and Dose-Response Relationships of
Beryl 1 i urn 2-8
2.6.4 Populations at Risk 2-10
3. BERYLLIUM BACKGROUND INFORMATION 3-1
3.1 GEOCHEMICAL AND INDUSTRIAL BACKGROUND 3-1
3.1.1 Geochemistry of Beryllium 3-1
3.1.2 Production and Consumption of Beryllium Ore 3-2
3.1.3. Industrial Uses of Beryllium 3-3
3.2 CHEMICAL AND PHYSICAL PROPERTIES OF BERYLLIUM 3-4
3.3 SAMPLING AND ANALYSIS TECHNIQUES FOR BERYLLIUM 3-6
3.4 ATMOSPHERIC EMISSIONS, TRANSFORMATION, AND DEPOSITION 3-7
3.5 ENVIRONMENTAL CONCENTRATIONS OF BERYLLIUM 3-11
3.5.1 Ambient Air 3-11
3.5.2 Soils and Natural Waters 3-11
3.6 PATHWAYS TO HUMAN CONSUMPTION 3-13
4. BERYLLIUM METABOLISM IN MAN AND ANIMALS 4-1
4.1 ROUTES OF BERYLLIUM ABSORPTION 4-1
4.1.1 Beryllium Absorption by Inhalation 4-1
4.1.2 Gastrointestinal Absorption of Beryllium 4-3
4.1.3 Percutaneous Absorption of Beryllium 4-4
4.1.4 Transplacental Transfer of Beryllium 4-4
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TABLE OF CONTENTS (continued)
4.2 TRANSPORT AND DEPOSITION OF BERYLLIUM IN MAN AND
EXPERIMENTAL ANIMALS 4-4
4.3 EXCRETION OF BERYLLIUM IN MAN AND ANIMALS 4-5
5. BERYLLIUM TOXICOLOGY 5-1
5.1 ACUTE EFFECTS OF BERYLLIUM EXPOSURE IN MAN AND ANIMALS 5-1
5.1.1 Human Studies 5-1
5.1.2 Animal Studies 5-2
5.2 CHRONIC EFFECTS OF BERYLLIUM EXPOSURE IN MAN AND ANIMALS ... 5-2
5.2.1 Respiratory and Systemic Effects of Beryllium 5-2
5.2.1.1 Human Studies 5-2
5.2.1.2 Animal Studies 5-13
5.2.2 Teratogenic and Reproductive Effects of Beryllium .. 5-17
5.2.2.1 Human Studies 5-17
5.2.2.2 Animal Studies 5-17
6. MUTAGENIC EFFECTS OF BERYLLIUM 6-1
6.1 GENE MUTATIONS IN BACTERIA AND YEAST 6-1
6.1.1 Salmonella Assay 6-1
6.1.2 Host-Mediated Assay 6-1
6.1.3 Escherichia coli WP2 Assay 6-3
6.2 GENE MUTATIONS IN CULTURED MAMMALIAN CELLS 6-3
6.3 CHROMOSOMAL ABERRATIONS 6-5
6.4 SISTER CHROMATID EXCHANGES 6-5
6.5 OTHER TESTS OF GENOTOXIC POTENTIAL 6-7
6.5.1 The Rec Assay 6-7
6.5.2 PpJ Assay 6-7
6.5.3 Hepatocyte Primary Culture/DNA Repair Test 6-8
6.5.4 Beryllium-Induced DNA Cell Binding 6-8
6.5.5 Mitotic Recombination in Yeast 6-9
6.5.6 Biochemical Evidence of Genotoxicity 6-9
6.5.7 Mutagenicity Studies in Whole Animals 6-9
7. CARCINOGENIC EFFECTS OF BERYLLIUM 7-1
7.1 ANIMAL STUDIES 7-1
7.1.1 Inhalation Studies 7-1
7.1.2 Intratracheal Injection Studies 7-8
7.1.3 Intravenous Injection Studies 7-9
7.1.4 Intramedullary Injection Studies 7-16
7.1.5 Intracutaneous Injection Studies 7-16
7.1.6 The Percutaneous Route of Exposure 7-17
7.1.7 Dietary Route of Exposure 7-17
7.1.8 Tumor Type, Species Specificity, Carcinogenic
Forms, and Dose-Response 7-18
7.1.8.1 Tumor Type and Proof of Malignancy 7-18
7.1.8.2 Species Specificity and Immunobiology 7-19
7.1.8.3 Carcinogenic Forms and Dose-Response
Relationships 7-20
7.1.9 Summary of Animal Studies 7-21
vi
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TABLE OF CONTENTS (continued)
Page
7.2 EPIDEMIOLOGIC STUDIES 7-25
7.2.1 Bay!iss et al. (1971) 7-25
7.2.2 Bay!iss and Lainhart (1972, unpublished) 7-26
7.2.3 Bayliss and Wagoner (1977, unpublished) 7-27
7.2.4 Wagoner et al. (1980) 7-29
7.2.5 Infante et al. (1980) 7-37
7.2.6 Mancuso and El-Attar (1969) 7-41
7.2.7 Mancuso (1970) 7-41
7.2.8 Mancuso (1979) 7-43
7.2.9 Mancuso (1980) 7-46
7.2.10 Summary of Epidemiologic Studies 7-48
7.3 QUANTITATIVE ESTIMATION 7-49
7.3.1 Procedures for the Determination of Unit Risk 7-54
7.3.1.1 Low-Dose Extrapolation Model 7-54
7.3.1.2 Selection of Data 7-57
7.3.1.3 Calculation of Human Equivalent Dosages ... 7-57
7.3.1.3.1 Inhalation Exposure 7-58
7.3.1.3.1.1 Case 1 7-58
7.3.1.4 Calculation of the Unit Risk from Animal
Studies 7-60
7.3.1.4.1 Adjustments for Less Than Life
Span Duration of Experiment .... 7-60
7.3.1.5 Model for Estimation of Unit Risk Based
on Human Data 7-61
7.3.2 Estimation of the Carcinogenic Risk of Beryllium ... 7-62
7.3.2.1 Calculation of the Carcinogenic Potency
of Beryllium on the Basis of Animal Data .. 7-67
7.3.2.2 Calculation of the Carcinogenic Potency
of Beryllium on the Basis of Human Data ... 7-71
7.3.2.2.1 Information on Exposure Levels . 7-71
7.3.2.2.2 Information on Excess Risk 7-72
7.3.2.2.3 Risk Calculation on the Basis
of Human Data 7-73
7.3.2.3 Risk Due to Exposure to 1 pg/m3 of
Beryllium in Air 7-73
7.3.3 Comparison of Potency With Other Compounds 7-75
7.3.4 Summary of Quantitative Assessment 7-81
7.4 SUMMARY 7-82
7.4.1 Qualitative Summary 7-82
7.4.2 Quantitative Summary 7-84
7.5 CONCLUSIONS 7-89
8. REFERENCES 8-1
APPENDIX - Analysis of Incidence Data with Time-dependent
Dose Pattern A-l
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LIST OF TABLES
Number Page
3-1 Global Production and U.S. Consumption of Beryllium Ore 3-2
3-2 Industrial Uses of Beryllium Products 3-4
3-3 Physical Properties of Beryllium and Related Metals 3-5
3-4 Natural and Anthropogenic Emissions of Beryllium 3-8
3-5 Concentrations of Beryllium in Urban Atmospheres 3-12
3-6 Potential Human Consumption of Beryllium from Normal
Sources in a Typical Residential Environment 3-16
5-1 Beryl 1i urn Regi stry Cases, 1959 5-4
5-2 Time from Last Exposure to First Symptom in the BCR, 1959 ... 5-4
5-3 Changes of Latency from 1922 to Present in Occupational
Beryl!iosis Cases 5-7
5-4 Symptoms of Chronic Beryllium Disease 5-7
5-5 Signs of Chronic Beryllium Disease 5-8
5-6 Comparison of 1971 and 1974 Data of Workers Surveyed in
Beryllium Extraction and Processing Plants 5-10
5-7 Comparison of 1971 and 1974 Arterial Blood Gas Results 5-10
6-1 Mutagenicity Testing of Beryllium: Gene Mutations in
Bacteria and in Yeast 6-2
6-2 Mutagenicity Testing of Beryllium: Gene Mutations
in Mammalian Cells In Vitro 6-4
6-3 Mutagenicity Testing of Beryllium: Mammalian Iji Vitro
Cytogenetics Tests 6-6
7-1 Pulmonary Carcinoma from Inhalation Exposure to Beryllium ... 7-3
7-2 Pulmonary Carcinoma from Exposure to Beryllium Via
Intratracheal Instillation 7-5
7-3 Beryllium Alloys -- Lung Neoplasms 7-10
7-4 Lung Tumor Incidence in Rats Among BeO, As203 and Control
Groups 7-11
7-5 Histological Classification of Lung Tumors and Other
Pathological Changes 7-11
7-6 Osteogenic Sarcomas in Rabbits 7-13
7-7 Osteosarcoma from Beryl 1i urn 7-14
7-8 Carcinogenicity of Beryllium Compounds 7-22
7-9 Percentage Distribution of Beryllium-Exposed Workers and
of Age-Adjusted U.S. White Male Population by Cigarette
Smoki ng Status 7-31
7-10 Lung Cancer Mortality Ratios for Males, by Current Number
of Cigarettes Smoked per Day, from Prospective Studies 7-31
7-11 Observed and Expected Deaths Due to Lung Cancer According to
Duration of Employment and Time Since Onset of Employment
Among White Males Employed Sometime During January 1942
Through December 1967 in a Beryllium Production Facility
and Followed Through 1975 7-34
7-12 Industries in the Lorain Area 1942-1948 7-45
7-13 Comparison of Study Cohorts and Subcohorts of Two
Beryllium Companies 7-50
viii
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LIST OF TABLES (continued)
Number
7-14 Problems with Beryllium Cohort Studies 7-52
7-15 Beryllium Dose-Response Data from Ten Inhalation Studies on
Animals and the Corresponding Potency (Slope) Estimations ... 7-68
7-16 Upper-Bound Cancer Potency Estimates Calculated Under
Various Assumptions 7-74
7-17 Relative Carcinogenic Potencies Among 55 Chemicals
Evaluated by the Carcinogen Assessment Group as Suspect
Human Carcinogens 7-77
A-l Time-to-Death Data A-2
IX
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LIST OF FIGURES
Figure Page
3-1 Pathways of Environmental Beryllium Concentrations
Leading to Potential Human Exposure 3-14
5-1 Latency of Occupational Berylliosis According to Year of
Fi rst Exposure 5-6
7-1 Pulmonary Tumor Incidence in Female Rats, 1965-1967 7-6
7-2 Histogram Representing the Frequency Distribution of the
Potency Indices of 55 Suspect Carcinogens Evaluated by
the Carcinogen Assessment Group 7-76
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Dr. Carol Sakai
Reproductive Effects Assessment Group
U.S. Environmental Protection Agency
Washington, D.C.
Project Manager:
Ms. Donna J. Sivulka
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina
Special assistance to the project manager was provided by
Ms. Darcy Campbell.
The carcinogenicity chapter was reviewed by the Carcinogen Assessment Group
(CAG) of the U.S. Environmental Protection Agency. Participating members of
the CAG are:
Steven Bayard, Ph.D.
Robert P. Bellies, Ph.D
Herman J. Gibb, B.S., M.P.H.
Bernard H. Haberman, D.V.M., M.S.
Charalingayya B. Hiremath, Ph.D
James W. Holder, Ph.D
Aparna M. Koppikar, M.D., D.P.H., D.I.H.
Robert McGaughy, Ph.D.
Jean C. Parker, Ph.D
Charles H. Ris, M.S., P.E.
Dharm V. Singh, D.V.M., Ph.D.
The following individuals reviewed earlier drafts of this document and submitted
valuable comments:
Dr. Frank D'ltri
Michigan State University
East Lansing, Michigan
Dr. Philip Enterline
University of Pittsburgh
Pittsburgh, Pennsylvania
Dr. Jean French
Center for Disease Control
Atlanta, Georgia
Dr. Richard Henderson
Health Sciences Consultants
Osterville, Massachusetts
Dr. Marshall Johnson
Thomas Jefferson Medical College
Philadelphia, Pennsylvania
xi i
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AUTHORS AND REVIEWERS
The authors of this document are:
Mr. David L. Bayliss
Carcinogen Assessment Group
U.S. Environmental Protection Agency
Washington, D.C.
Dr. Chao W. Chen
Carcinogen Assessment Group
U.S. Environmental Protection Agency
Washington, D.C.
Dr. James C. Cogliano
Carcinogen Assessment Group
U.S. Environmental Protection Agency
Washington, D.C.
Dr. Margaret M. L. Chu
ICF-Clement
Arlington, Virginia
(formerly of the Carcinogen Assessment Group)
Dr. Robert Eli as
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina
Dr. David Jacobson-Kram
Reproductive Effects Assessment Group
U.S. Environmental Protection Agency
Washington, D.C.
Dr. Kantharajapura S. Lavappa
U.S. Food and Drug Administration
Washington, D.C.
(formerly of the Reproductive Effects Assessment Group)
Dr. William E. Pepelko
Carcinogen Assessment Group
U.S. Environmental Protection Agency
Washington, D.C.
Dr. Magnus Piscator
Karolinska Institute
Stockholm, Sweden
Dr. Andrew L. Reeves
Wayne State University
Detroit, Michigan
XI
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Dr. Magnus Piscator
Karolinska Institute
Stockholm, Sweden
Dr. Neil Roth
Roth and Associates
Rockville, Maryland
Dr. Flo Ryer
Exposure Assessment Group
U.S. Environmental Protection Agency
Washington, D.C.
Dr. Carl Shy
University of North Carolina
Chapel Hill, North Carolina
Dr. Vincent Simmon
Genex Corporation
Gaithersburg, Maryland
Dr. F. William Sunderman, Jr.
University of Connecticut
Farmington, Connecticut
Dr. J. Jaroslav Vostal
General Motors Research Laboratory
Warren, Michigan
Dr. John Wood
University of Minnesota
Navarre, Minnesota
In addition, there are several scientists who contributed valuable information
and/or constructive criticism to interim drafts of this report. Of specific
note are the contributions of: Jack Behm, Richard Chamber!in, Thomas J.
Concannon, John Copeland, Bernie Greenspan, Si Duk Lee, Brian MacMahon, Robert
J. McCunney, Ray Morrison, Om Mukheja, Chuck Nauman, Martin B. Powers, and Otto
Preuss.
Technical Assistance
Project management, editing, production, word processing, and workshop from
Northrop Services, Inc., under contract to the Environmental Criteria and
Assessment Office:
Ms. Barbara Best-Nichols
Mr. John Bennett
Ms. Linda Cooper
Dr. Susan Dakin
Ms. Anita Flintall
Ms. Kathryn Flynn
xi 1
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Ms. Miriam Gattis
Ms. Lorrie Godley
Ms. Tami Jones
Ms. Varetta Powell
Ms. Patricia Tierney
Ms. Jane Winn
Word processing and other technical assistance at the Office of Health and
Environmental Assessment:
Ms. Linda Bailey
Ms. Frances P. Bradow
Ms. Renee Cook
Mr. Doug Fennel!
Mr. Allen Hoyt
Ms. Barbara Kearney
Ms. Theresa Konova
Ms. Emily Lee
Ms. Marie Pfaff
Ms. Diane Ray
Ms. Judy Theisen
Ms. Donna Wicker
xiv
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1. INTRODUCTION
This report evaluates the effects of beryllium on human health, with
particular emphasis on those effects which are of most concern to the general
U.S. population. It is organized into chapters that present in a logical order
those aspects of beryllium that relate directly to the human health risk. The
chapters include: an executive summary (Chapter 2); background information on
the chemical and environmental aspects of beryllium, including levels of beryllium
in media with which U.S. populations may come into contact (Chapter 3); beryl-
lium metabolism, where absorption, biotransformation, tissue distribution, and
excretion of beryllium are discussed with reference to the element's toxicity
(Chapter 4); beryllium toxicology, where the various acute, subacute, and
chronic health effects of beryllium in man and animals are reviewed (Chapter 5);
beryllium mutagenesis, in which the ability of beryllium to cause gene mutations,
chromosomal aberrations, and sister-chromatid exchanges is discussed (Chapter 6);
and information on beryllium carcinogenesis, which includes a discussion of
selected dose-effect and dose-response relationships (Chapter 7).
This report is not intended to be an exhaustive review of all the beryllium
literature, but is focused instead upon those data thought to be most relevant
to human health risk assessment. Literature was collected and reviewed up to
April, 1985. In view of the fact that this document is to provide a basis for
making decisions regarding the regulation of beryllium as a hazardous air pollu-
tant under the pertinent sections of the Clean Air Act, particular emphasis is
placed on those health effects associated with exposure to airborne beryllium.
Health effects associated with the ingestion of beryllium or with exposure via
other routes are also discussed, providing a basis for possible use of this
document for multimedia risk assessment purposes. The background information
provided on sources, emissions, and ambient concentrations of beryllium in
various media is presented to provide a general perspective for viewing the
health-effects evaluations contained in later chapters of the document. More
detailed exposure assessments will be prepared separately for use in subsequent
EPA reports regarding regulatory decisions on beryllium.
1-1
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2. SUMMARY AND CONCLUSIONS
2.1 BACKGROUND INFORMATION
The industrial use of beryllium has increased tenfold in the last 40 years.
Despite this fact, increases in the environmental concentrations of beryllium
have not been detected. Atmospheric beryllium is primarily derived from the
combustion of coal.
Contamination of the environment occurs almost entirely by the deposition
of beryllium from the air. Beryllium from the atmosphere eventually reaches
the soil or sediments, where it is probably retained in the relatively insoluble
form of beryllium oxide. Since the time of the industrial revolution, it is
likely that no more than 0.1 |jg Be/g has been added to the surface of the soil,
which has a natural beryllium concentration of 0.6 pg/g. Distributed evenly
throughout the soil column, beryllium derived from the atmosphere could account
for not more than one percent of the total soil beryllium. Allowing for greater
mobility of atmospheric beryllium in soil than natural beryllium, it is possible
that 10 to 50 percent of the beryllium in plants and animals may be of anthro-
pogenic origin.
The typical American adult usually takes in 400 to 450 ng Be/day, of which
50 to 90 percent comes from food and beverages. Some of this beryllium found in
food may be derived from the atmosphere; however, aside from primary and secon-
dary occupational settings, air or dust has little impact on total human intake.
2.2 BERYLLIUM METABOLISM
Inhalation and ingestion are the main routes of beryllium intake for man
and animals. Percutaneous absorption is insignificant.
Due to the specific chemical properties of beryllium compounds, even
primarily soluble beryllium compounds are partly transformed to more insoluble
forms in the lungs. This can result in long retention times in the lungs
following exposure to all types of beryllium compounds. Like other particu-
lates, dose and particle size are critical factors that determine the deposi-
tion and clearance of inhaled beryllium particles. Of the deposited beryllium
that is absorbed, part will be rapidly excreted and part will be stored in bone.
Beryllium is also transferred to regional lymph nodes. Beryllium transferred
from the lungs to the gastrointestinal tract is mainly eliminated in the feces
with only a minor portion being absorbed.
2-1
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There are no quantitative data on absorption of beryllium from the gastro-
intestinal tract in humans, but several animal studies indicate that the absorp-
tion of ingested beryllium is less than one percent. The absorption of beryl-
lium through intact skin is very small, as beryllium is tightly bound in the
epidermis.
Absorbed beryllium will enter the blood, but there are no data on the
partitioning of beryllium between plasma and erythrocytes. In plasma, there
are limited data to suggest that, at normally occurring levels of beryllium,
the main binding is to various plasma proteins. In animal experiments, it has
been shown that large doses of injected beryllium are found in aggregates bound
to phosphate. The smaller the dose, the more beryllium will be in the diffusi-
ble form. The data are insufficient to permit an estimate of the levels of beryl-
lium normally occurring in blood or plasma.
Absorbed beryllium is deposited in the skeleton, with other organs con-
taining only very low levels. In the liver, beryllium seems to be preferen-
tially taken up by lysosomes. There are not enough data to permit any defini-
tive conclusions about the distribution and amounts of beryllium normally pre-
sent in the human body. However, total body burden is probably less than 50 pg.
Based on animal studies, beryllium appears to have a long biological half-
time, caused mainly by its retention in bone. The half-time in soft tissues is
relatively short.
Beryllium seems to be normally excreted in small amounts in urine, normal
levels probably being only a few nanograms per liter. Animal data indicate that
some excretion occurs by way of the gastrointestinal tract.
2.3 BERYLLIUM TOXICOLOGY
2.3.1 Subcellular and Cellular Aspects of Beryllium Toxicity
It is not well known in what form or through which mechanism beryllium is
bound to tissue. Beryllium can bind to lymphocyte membranes, which may explain
the sensitizing properties of the metal. A number of reports describe various
j_n vivo and jji vitro effects of beryllium compounds on enzymes, especially alka-
line phosphatase, to which beryllium can bind. Effects on protein and nucleic
acid metabolism have been shown in many experimental studies; however, the
doses in these studies have been large and parenterally administered. Because
such administrative routes have less practical application to humans, the
data from these studies have limited utility in advancing an understanding of
human effects, which are mainly on the lung. Beryllium particles retained in
2-2
-------
the lung are found in the macrophages, and the understanding of how these and
other pulmonary cells metabolize beryllium is probably of most relevance to the
understanding of chronic beryllium disease.
An important aspect of beryllium toxicology is that beryllium can cause
hypersensitivity which is essentially cell-mediated. There are species differ-
ences; humans and guinea pigs can be sensitized to beryllium, whereas the
present data indicate that no such mechanism exists for the rat. There are also
strain differences among guinea pigs indicating that a genetic component may be
operative. Patch tests have been used to detect beryllium hypersensitivity in
humans, but these tests are no longer used since they were shown to cause a
reactivation of latent beryllium disease. Presently, the lymphoblast trans-
formation test is regarded as the most useful test to detect hypersensitivity
to beryllium.
2.3.2 Pulmonary and Systemic Toxicity of Beryllium in Man and Animals
There are no data indicating that moderate beryllium exposure by oral
administration causes any local or systemic effects in humans or animals.
Respiratory effects, occasionally combined with systemic effects, constitute the
major health concern of beryllium exposure, with hypersensitization likely
playing an important role in the manifestation of the systemic effects.
Respiratory effects may occur as either a nonspecific acute disease or as a more
specific chronic beryllium disease.
The most acutely toxic beryllium compounds are probably beryllium oxides
fired at low temperatures, e.g. 500°C, and some salts, such as the fluoride and
the sulfate. The latter forms of beryllium are acidic, and part of the toxic
reactions caused by these compounds may be due to the acidity of the particles.
Acute effects have generally occurred at concentrations above 100 pg Be/m .
The main feature of such effects is a chemical pneumonitis which may lead to
pulmonary edema and even death. In animal experiments, concentrations of more
3
than 1 mg/m have generally been needed to produce acute effects, but effects
have been reported at lower levels of exposure. In most cases, the acute dis-
ease will regress, but it may take several weeks or months before recovery is
complete. If there is no further excessive exposure to beryllium, it is gen-
erally believed that acute disease will not lead to chronic beryllium disease.
The amount initially deposited during acute exposure and an individual's pre-
disposition are probably the main factors leading to later sequelae.
2-3
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Acute beryllium poisoning was quite common in the 1940s, but since the
present standards were established in 1949, the number of new cases reported has
been relatively small.
Chronic beryllium disease occurred as an epidemic in the 1940s, which led
to the establishment of the "Beryllium Case Registry" (BCR), a file for all
cases of acute and chronic beryllium disease. Chronic beryllium disease is
characterized by dyspnea, cough, and weight loss. It is sometimes associated
with systemic effects in the form of granulomas in the skin and muscles, as well
as effects on calcium metabolism. There are many similarities between chronic
beryllium disease and sarcoidosis, but in sarcoidosis the systemic effects are
much more prominent. In most cases of chronic beryllium disease, there are only
lung effects without systemic involvement. Pathologically, the disease is a
granulomatous interstitial pneumonitis in which eventually there may be
fibrosis, emphysema, and also cor pulmonale. Deaths from chronic beryllium
disease are often due to cor pulmonale. A long latency time is typical;
sometimes there may be more than 20 years between last exposure and the
diagnosis of the disease.
It has been very difficult to establish the levels of beryllium in air that
may cause the disease. One reason for this difficulty is that exposure data
have not always been obtainable. Another factor is that hypersensitization may
cause the occurrence of the disease in people with relatively low exposures,
whereas in nonsensitized people with much higher exposures there may be no
effects. Diagnosis of the disease is obtained by X-ray examinations, but lung
function tests of vital capacity may decrease before roentgenological changes
are seen. Hypersensitization can be detected by the lymphoblast transformation
test.
There are limited data on levels of beryllium found in lung tissue in cases
of acute and chronic beryllium disease, and these data do not allow for con-
clusions about dose-effect relationships.
New cases of chronic beryllium disease are still being reported due to the
fact that, in some instances, the standards have been exceeded. In industries
where the average exposure generally has been below 2 pg/m , there have been
very few new cases of chronic beryllium disease.
There have also been a large number of "neighborhood" cases of beryllium
disease. Neighborhood cases are those in which chronic beryllium disease occurs
in people living in the vicinity of beryllium-emitting plants. The air concen-
trations of beryllium in such areas at the time when the disease occurred have
2-4
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o
probably been around 0.1 ug/m , but considerable exposure via dust transferred
to homes on workclothes likely contributed to the occurrence of the disease. No
new "neighborhood" cases of beryllium disease have occurred since standards of
0.01 ug/m were set for the ambient air and the practice of washing workers'
clothes in the plants was initiated. Presently, ambient air levels are general-
's
ly below 1 ng/m .
2.3.3 Dermatological Effects of Beryllium Exposure
Contact dermatitis and some other dermatological effects of beryllium have
been documented in occupationally exposed persons, but there are no data indi-
cating that such reactions have occurred, or may occur, in the general popula-
tion.
2.3.4 Teratogenic and Reproductive Effects of Beryllium Exposure
Available information on the teratogenic or reproductive effects of beryl-
lium exposure is limited to three animal studies. The information from these
studies is not sufficient to determine whether beryllium compounds have the
potential to produce adverse reproductive or teratogenic effects. Further stu-
dies are needed in this area.
2.4 MUTAGENIC EFFECTS OF BERYLLIUM EXPOSURE
Beryllium has been tested for its ability to cause gene mutations in
Salmonella typhimurium, Escherichia coli, yeast, cultured human lymphocytes,
and Syrian hamster embryo cells; DMA damage in Escherichia coli, and unscheduled
DNA synthesis in rat hepatocytes.
Beryllium sulfate and beryllium chloride have been shown to be nonmutagenic
in all bacterial and yeast gene mutation assays. However, this may be due to
the fact that bacterial and yeast systems generally are not sensitive to metal
mutagens. In contrast, gene mutation studies in cultured mammalian cells,
Chinese hamster V79 cells, and Chinese hamster ovary (CHO) cells have yielded
positive mutagem'c responses of beryllium. Similarly, chromosomal aberration
and sister-chromatid exchange studies in cultured human lymphocytes and Syrian
hamster embryo cells have also resulted in positive mutagem'c responses of beryl-
lium. In DNA damage and repair assays, beryllium was negative in pol, rat hepa-
tocyte, and mitotic recombination assays, but was weakly positive in the rec
assay. Based on available information, beryllium appears to have the potential
to cause mutations.
2-5
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2.5 CARCINOGENIC EFFECTS OF BERYLLIUM EXPOSURE
2.5.1 Animal Studies
Experimental beryllium carcinogenesis has been induced by intravenous or
intramedullary injection of rabbits, by inhalation exposure or by intratracheal
injection of rats and monkeys, but not by oral ingestion in any animals
studied to date. Carcinogenic responses have been induced by a variety of
forms of beryllium including beryllium sulfate, phosphate, oxide, and beryl
ore. The carcinogenic evidence in mice (intravenously injected or exposed via
inhalation) and guinea pigs and hamsters (exposed via inhalation) is equivocal.
Osteosarcomas are the predominant types of tumors induced in rabbits.
These tumors are highly invasive, metastasize readily, and are judged to be
histologically similar to human osteosarcomas. In rats, pulmonary adenomas
and/or carcinomas of questionable malignancy have been obtained, although
pathological end points have not been well documented in many cases.
Although, individually, many of the reported animal studies have method-
ological and reporting limitations compared to current standards for bio-
assays, collectively the studies provide good evidence for carcinogenicity.
Responses have been noted in multiple species at multiple sites and, in some
cases, afford evidence of a dose response. On this basis, using EPA's Proposed
Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1984) to classify the
weight of evidence for carcinogenicity in experimental animals, there is
"sufficient" evidence to conclude that beryllium is carcinogenic in animals.
Since positive responses were seen for a variety of beryllium compounds, all
forms of beryllium are considered to be carcinogenic.
2.5.2 Human Studies
Epidemiologic studies provide equivocal conclusions on the carcinogenicity
of beryllium and beryllium compounds. Early epidemiologic studies of beryllium
exposed workers (see IARC, 1972, 1980; Bayliss et al., 1971; Bayliss and Lain-
hart, 1972) do not report positive evidence for increased cancer incidence.
However, recent studies do report a significantly increased risk of lung can-
cer in exposed workers. The absence of beryllium exposure levels and a demon-
strated concern about possible confounding factors within the workplace make
the reported positive correlations between beryllium exposure and increased
risk of cancer difficult to substantiate. This relegates the reported
2-6
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statistically significant increases of lung cancer to, at best, an elevated inci-
dence that is not statistically significant. Because of these limitations,
the EPA (U.S. EPA, 1984) considers the available epidemiologic evidence to be
"inadequate" to support or refute the existence of a carcinogenic hazard for
humans exposed to beryllium.
2.5.3 Qualitative Carcinogenicity Conclusions
Using the EPA weight-of-evidence criteria for evaluating both human and
animal evidence, beryllium is most appropriately classified in Group B2, indi-
cating that, on the strength of animal studies, beryllium should be considered
a probable human carcinogen. This category is reserved for chemicals having
"sufficient" evidence for Carcinogenicity in animal studies and "inadequate"
evidence in human studies. In this particular case, the animal evidence demon-
strates that all beryllium species should be regarded as probably being carcino-
genic for humans.
2.6 HUMAN HEALTH RISK ASSESSMENT OF BERYLLIUM
2.6.1 Exposure Aspects
In the general U.S. population, the dietary intake of beryllium is proba-
bly less than 1 ug a day, and due to its chemical properties, very little is
available in the gut for absorption. Approximately half of the absorbed beryl-
lium enters the skeleton.
For most people, the daily amount of beryllium inhaled is only a few nano-
grams. However, it is likely that much of this is retained in the lungs. The
available data indicate that the beryllium lung burden in the average adult
ranges from 1 to 10 ug. Since beryllium occurs in cigarettes, it is possible
that smokers will inhale and retain more beryllium than nonsmokers. Unfortunate-
ly, the data on beryllium concentrations in mainstream smoke are, at present,
uncertain.
2.6.2 Relevant Health Effects
Occupational exposure to various beryllium compounds has been associated
with acute respiratory disease and chronic beryllium disease (in the form of
granulomatous interstitial pneumonitis). Some systemic effects have also been
noted and a hypersensitization component probably plays a major role in the
2-7
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manifestation of these effects. In the past, chronic beryllium disease was
found in members of the general population living near beryllium-emitting
plants, but past exposures were relatively high compared to present levels of
beryllium in the ambient air. Contaminated workclothes brought home for
washing contributed to these exposures. No "neighborhood" cases of chronic
beryllium disease have been reported in the past several years.
Numerous animal studies have been performed to determine whether or not
beryllium and beryllium-containing substances are carcinogenic. Although some
of these studies have limitations, the overall evidence from animal studies
should be classified as "sufficient" using EPA's Proposed Guidelines for
Carcinogen Risk Assessment (U.S. EPA, 1984). The International Agency for
Research on Cancer (IARC) has also concluded that the evidence from animal
studies is "sufficient." Human studies on beryllium carcinogenicity have
deficiencies that limit any definitive conclusion that a true association
between beryllium exposure and cancer exists. Nevertheless, it is possible
that a portion of the excess cancer risks reported in these studies may, in
fact, be due to beryllium exposure. Although IARC concluded that beryllium
and its compounds should be classified as having "limited" human evidence of
carcinogenicity, the U.S. Environmental Protection Agency's Carcinogen Assess-
ment Group (CAG) has concluded that the human evidence is "inadequate."
2.6.3 Dose-Effect and Dose-Response Relationships of Beryllium
As previously stated, beryllium can act upon the lung in two ways, either
through a direct toxic effect on pulmonary tissue or through hypersensitization.
Even if reliable and detailed exposure data were available, it would still be
difficult to establish dose-effect and dose-response relationships due to this
hypersensitization factor. No adverse effects have been noted in industries
o
complying with the 2 ug/m standard; therefore, it appears that this level of
beryllium in air provides good protection with regard to respiratory effects.
It is unknown whether exposures to the maximum permissible peak standard (25
ug/m ) can cause delayed effects.
From available data, the CAG has estimated carcinogenic unit risks for in-
halation exposure to beryllium. The quantitative aspect of carcinogen risk
assessment is included here because it may be of use in setting regulatory pri-
orities and in evaluating the adequacy of technology-based controls and other
aspects of the regulatory decision-making process. However, the uncertainties
associated with estimated cancer risks to humans at low levels of exposure
2-8
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should be recognized. The linear extrapolation procedures used (see Section
7.3) provide a rough but plausible estimate of the upper limit of risk—that is,
it is not likely that the true risk would be much higher than the estimated
risk, but it could be considerably lower. The risk estimates presented below
should not be regarded, therefore, as accurate representations of true cancer
risks even when the exposures are accurately defined. The estimates presented
may, however, be factored into regulatory decisions to the extent that the con-
cept of upper-limit risks is found to be useful.
Both animal and human data are used to estimate the carcinogenic potency
of beryllium. Many of the animal inhalation studies conducted on beryllium are
not well documented, were conducted at single-dose levels and, in some cases,
did not utilize control groups. Despite individual deficiencies, data from ten
inhalation studies (eight studies of rats, one study of hamsters and one study
of monkeys) have been analyzed and show that potency estimates among several
studies using the same form of beryllium (beryllium sulfate) differed to only a
small degree, while different forms resulted in a much greater variation in
potency. The upper-bound potency estimates, calculated on the basis of animal
-33 3
data range from 2.9 x 10 /(ug/m ) to 4.3/(ug/m ), using a surface area correc-
tion. Among the four beryllium compounds examined in the ten studies, beryl
ore, which is the least soluble, is the least carcinogenically potent, while
beryllium sulfate, the most soluble of the compounds, is the most potent. The
estimated potency values for beryllium on the basis of animal studies, except
the potency value estimated with the Wagner et al., (1969) study on beryl ore,
are considerably greater than those estimated from human data.
Even though the epidemiologic studies have been judged to be qualitatively
inadequate to assess the potential of carcinogenicity for humans, these studies
can be analyzed to determine the largest plausible risk that is consistent with
the available epidemiologic data. This upper bound can be used both to esti-
mate human risk and to evaluate the reasonableness of estimates derived from
animal studies. Information from the epidemiologic study by Wagoner et al. ,
(1980) and the industrial hygiene reviews by NIOSH (1972) and Eisenbud and
Lisson (1983) have been used to estimate a plausible upper bound for incremen-
tal cancer risk associated with exposure to air contaminated with beryllium.
o
The upper-bound incremental lifetime cancer risk associated with 1 ug/m of
-3
beryllium in the air is estimated to be 2.4 x 10 . This estimate is based
upon occupational exposure to beryllium compounds thought to have a low degree
of solubility.
2-9
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Because the carcinogenic potencies of beryllium compounds derived from the
animal data are much greater than the estimate derived from the human data, the
animal values are judged to be less relevant to human environmental exposure
and the estimate based upon human data is recommended for use with caveat. If
the form of beryllium present contains more than a small fraction of the more
-3 3
soluble forms, then the human estimate (2.4 x 10 /ug/m ) may underestimate the
upper limit and consideration should be given to noting the animal based esti-
mates. The incremental upper limit risk of 2.4 x 10 /(ug/m ) places beryllium
in the lower part of the third quartile of 55 suspect carcinogens evaluated by
the CAG.
2.6.4 Populations at Risk
In terms of exposure, persons engaged in handling beryllium in occupa-
tional environments obviously comprise individuals at highest risk. With regard
to the population at large, there may be a small risk for people living near
beryllium-emitting industries. However, the risk for such individuals may not
be from ambient air levels of beryllium, but rather from beryllium-contaminated
dust within the household. There are no data that allow an estimate of the num-
ber of people that may be at such risk, but it is reasonable to assume that it
is a very small group. It should be noted that no new "neighborhood" cases of
beryllium disease have been reported since the 1940s.
2-10
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3. BERYLLIUM BACKGROUND INFORMATION
3.1 GEOCHEMICAL AND INDUSTRIAL BACKGROUND
3.1.1 Geochemistry of Beryllium
Average crustal rock contains about 2.8 ug Be/g (Mason, 1966), but beryl-
lium also occurs in more concentrated forms as a component of over forty
different minerals. Granites are enriched by 15 to 20 pg Be/g. It is likely
that most beryllium minerals were formed during the cooling of granitic magmas
(Beus, 1966). The element was excluded during the early cooling stages and
accumulated in the crystallization products formed during the final stages, com-
monly in association with quartz. The most highly enriched deposits of beryl-
lium are in pegmatitic intrusions.
Only two beryllium minerals are of current economic importance, beryl and
bertrandite. Beryl, an aluminosilicate (BeoA^SiVOg), is mined largely
in the USSR, Brazil, and the People's Republic of China; smaller
amounts are produced in several other countries (Table 3-1). Formed
by pegmatite processes, beryl is 5- to 11-percent beryllium oxide and, in its
purest gem-quality form, is treasured as the green or blue emerald. Until the
late 1960s, the common technique for separating beryl from associated rock was
to crush the rock and hand pick the mineral crystals. By 1969, mechanical flo-
tation separation techniques were developed, and a second mineral, bertrandite
[Be.Si?07(OH)p], became economically important (Anonymous, 1980). Bertrandite
occurs as very tiny silicate granules that have a beryllium oxide concentration
of less than one percent. The only active commercial deposit of bertrandite
in the United States is at Spor Mountain, Utah. This domestic source supplies
about 85 percent of the beryllium ore consumed in the United States, the rest
is imported, either as beryl or bertrandite, as listed in Table 3-1 (U.S.
Bureau of Mines, 1984).
Beryllium was discovered by Vauquelin in 1798. The element was isolated
in metallic form in 1828 by Woehler, and perhaps independently that same year
by Bussy (Beus, 1966). Beryllium is a light-grey, low-density metal with a
high melting point, exceptional resistance to corrosion, and the capacity to
absorb heat. In the United States, beryllium ore is processed at Delta, Utah
by Brush Wellman, Inc.
Although beryllium was isolated as a metal in 1828, it was not until the
1930s that beryllium-copper alloys came into widespread use. Deposits of
beryl known for gem production were the first to be exploited. In the USSR,
3-1
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TABLE 3-1. GLOBAL PRODUCTION AND U.S. CONSUMPTION OF BERYLLIUM ORE
(METRIC TONS)
Country
Argentina
Brazil
Madagascar
Mozambique
People's Republic of China (1)
Portugal
Rwanda
U.S.S.R.
United States (2)
Zimbabwe
Other Countries (3)
World production
U.S. consumption
(1) Estimated from U.S. imports.
(2) Includes bertrandite ore, calcul
1948
45
1617
8
73
(4)
9
40
(4)
82
--
257
2131
1787
ated as ec
1968
593
2078
--
95
(4)
128
149
1197
152
88
2088
6568
8384
juivalent
1980
31
550
10
20
580
19
108
1814
6756
9
--
9897
11YI
to beryl
1984
15
1252
10
15
239
18
36
1905
5469
50
--
9009
8166
containing
11% BeO.
(3) Includes Australia, French Morroco, India, South-West Africa, and Spain
in 1948, and Australia, India, Kenya, Malagasy Republic and Uganda in
1968. These countries are no longer a significant part of global beryl-
lium production.
(4) Data not available, not included in total.
(--) No production or less than 0.5 tons.
Source: U.S. Bureau of Mines (1950, 1970, 1984)
geochemical techniques for locating beryl deposits by chemical anomalies in
surrounding rock formations were used for some time, but had little success
(Goldschmidt and Peters, 1932).
3.1.2 Production and Consumption of Beryllium Ore
From the ore, beryllium is extracted as the hydroxide, from which all forms
of the metal and its alloys can be made. The most useful products are beryllium
metal, beryllium oxide, and beryllium-copper alloys. Its stiffness-to-weight
ratio and high thermal conductivity make beryllium metal useful in the aero-
space industry. In the electronics industry, beryllium oxide is used to dis-
sipate heat away from thermally sensitive components. Beryllium-copper alloys,
which provide a combination of strength, electrical conductivity, and resistance
3-2
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to stress relaxation, are used extensively for electrical/electronic switches,
sockets, and connectors. The alloys are also non-magnetic. Other beryllium
alloys are especially valuable for their resistance to oxidation or corrosion
and have been used in the production of dental prostheses (New!and, 1982).
From 1930 to 1969, deposits of beryl remained the sole source of beryllium.
The consumption of beryllium increased 600-percent between 1948 and 1968
(Table 3-1), a rate that was ten times that of any other common metal (Knapp,
1971). During this period, the nuclear power industry joined the aerospace
and electronics industries as a consumer of beryllium products (Anonymous, 1980).
Two countries, the USSR and the United States, became the primary consumers of
beryllium ore and producers of beryllium products.
After the production of bertrandite became economically feasible in 1969,
its production in the United States rose to the equivalent of about 6000 tons
of beryl by 1981. From the domestic production of 5469 equivalent tons of beryl
ore, the use of existing stocks, and the import of 1208 actual tons, the United
States produced about 107 tons of contained beryllium in 1984, of which about
18 tons were exported as finished or unfinished products.
3.1.3 Industrial Uses of Beryllium
About 10 percent of the domestic beryllium hydroxide is used in the
production of pure beryllium metal in sheet, rod, or wire form. Since 1979,
Brush Wellman, Inc. has been the only free-world producer of beryllium metal
(Anonymous, 1980). The metal is milled to desired specifications at the user
facility, producing beryllium dust and scrap in the vicinity of machine shops.
Because of the high cost of the metal, efficient recovery and recycling of the
metal are a high priority.
About 15 percent of the raw beryllium hydroxide is consumed in the produc-
tion of beryllium oxide (beryllia). It is used in the production of ceramics
that have excellent thermal conductivity, especially at high temperatures
(Table 3-2). These products make good electrical insulators and have a high
resistance to thermal shock. The high melting point permits the use of beryl-
lium oxide in rocket nozzles and thermocouple tubing.
The remaining 75 percent of beryllium hydroxide is used in the production
of alloys, primarily beryllium-copper alloys. As a general rule, two percent
beryllium in a copper alloy with a mixture of other metals can markedly increase
the strength, endurance, and hardness of the alloy. Most applications for
beryllium alloys are in the electronic field, although specialized uses such
3-3
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TABLE 3-2. INDUSTRIAL USES OF BERYLLIUM PRODUCTS
Beryllium Metal
Aircraft disc brakes
Navigational systems
X-ray transmission windows
Space vehicle optics and
instruments
Aircraft/satellite structures
Missile parts
Beryllium Oxide
High-technology ceramics
Electronic heat sinks
Electrical insulators
Microwave oven components
Gyroscopes
Beryllium Alloys
Springs
Electrical connectors and relays
Pivots, wheels and pinions
Plastic injection molds
Nuclear reactor neutron
reflectors
Fuel containers
Precision instruments
Rocket propel 1 ants
Heat shields
Mirrors
Nuclear weapons
Military vehicle armor
Rocket nozzles
Crucibles
Thermocouple tubing
Laser structural components
Precision instruments
Aircraft engine parts
Submarine cable housings
Non-sparking tools
as springs, wheels, and pinions serve an indispensable industrial function.
Kawecki-Berylco, Inc. at Reading, Pennsylvania and Brush Wellman at Elmore,
Ohio are the major producers of beryllium alloys in the United States.
3.2 CHEMICAL AND PHYSICAL PROPERTIES OF BERYLLIUM
The chemical and physical properties of beryllium resemble those of alumi-
num, zinc, and magnesium (Table 3-3). Chemical similarities are due primarily
3-4
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TABLE 3-3. PHYSICAL PROPERTIES OF BERYLLIUM AND RELATED METALS
Be Al Zn Mg
Metal
Atomic number
Atomic weight
Atomic radius
Valence 0
Ionic radius A
Density 25 °C
Melting point °C
Boiling point °C
Thermal conductivity 100°
Electrical resistivity
(u°nm • cm @ 20°C)
4
9.012
1.40
2+
.35
1.85
1283
2970
.401
4.31
13
26.98
1.82
3+
.51
2.7
660.4
2467
.573
2.65
30
65.38
1.53
2+
.74
7.14
419.58
907
1.12
5.916
12
24.31
1.72
2+
.66
1.74
648.8
1107
.376
4.45
Oxide
Formula BeO A190, ZnO MgO
Molecular weight 25.01 101796 81.37 40.31
Density 3.008 3.965 5.606 3.58
Melting point °C 2530 2072 1975 2852
Boiling point °C 3900 2980 — 3600
Thermal conductivity 725°C .111
(cal/sec • cm • °C/cm)
Hydroxide
Formula
Molecular weight
Density
Solubility moles/liter
Decomposes to oxide °C
Be(OH),
43. or
.
0.8 x 10"4
250-300
Al(OH),
78.00
2.42
300
Zn(OH)?
99.38^
3.053
125
Mg(OH)?
58.33^
2.36
350
to similar ionic potentials, which facilitate covalent bonding (Novoselova and
Batsanova, 1969).
The properties of beryllium are often considered in the context of the
three most common forms of potential industrial emissions: the metal, the
oxide and the hydroxide. In certain occupations, beryllium halides may also be
important, but these cases are too few to merit extended discussion.
Beryllium is extracted from ores as the hydroxide and shipped in this form
to commercial processing plants (Anonymous, 1980). The most common concentra-
tion process involves the leaching of 20-mesh particles with sulfuric acid
followed by hydroxylation with di-2-ethylhexylphosphate in kerosene. The
3-5
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beryllium hydroxide salt is then collected by filtration. The process recovers
about 80 percent of the beryllium found in low-grade bertrandite ore.
From beryl, beryllium may be extracted by the Sawyer-Kjellgren process;
the ore is melted at 1625°C and cooled quickly with water to form a beryllium
glass. The glass is dried and ground to 200-mesh powder, then leached with
sulfuric acid. Sodium hydroxide is used to convert the sulfate to beryllium
hydroxide. This process is also about 80-percent efficient but can not be used
to extract the small amounts of beryllium in bertrandite ore.
A third process, the Copaux-Kawecki process, uses sodium ferric fluoride
to extract beryllium from low-grade, fine-grained bertrandite ores at a 90-per-
cent efficiency. This process is no longer used in the United States or Europe,
due to its expense and the toxicity of beryllium fluoride. Indeed, the first
medical report of berylliosis in 1933 can be attributed to exposure to beryl-
lium fluoride at an extraction plant (Weber and Englehardt, 1933).
3.3 SAMPLING AND ANALYSIS TECHNIQUES FOR BERYLLIUM
Beryllium occurs in environmental samples at concentrations of about 0.01
o
to 0.1 ng/m in air, 0.05 to 0.1 ug/g in dust, 0.01 to 1.0 ng/g in surface
waters, 0.3 to 6.0 ug/g in soil, and 0.01 ug/g in biological materials. Some
plants, such as hickory, may accumulate beryllium as much as 1 |jg/g dry weight
(Newland, 1982). Two techniques, gas chromatography (GC) (Ross and Sievers,
1972) and atomic absorption spectroscopy (AAS) (Owens and Gladney, 1975),
appear to offer the best combination of sensitivity and sample handling
efficiency. However, colorimetry, fluorometry, and emission spectrometry are
also occasionally used.
Environmental samples analyzed by atomic absorption spectroscopy and gas
chromatography require pretreatment to remove interfering substances and in-
crease sensitivity. At high concentrations (500 ug/g), aluminum and silicon
interfere with beryllium analysis by AAS. Separation of these elements is
achieved by chelation and extraction with an organic solvent. The limit of de-
tection for the flame method of AAS is 2 to 10 ng/ml, and 0.1 ng/ml for the
flameless method. Air samples of a few cubic meters must be concentrated after
extraction to a liquid volume of less than 1 ml to enter the detection range.
o
The high-volume sampler, which collects in the range of 1.1 to 1.7 m /min, is
more desirable than either a low-volume sampler or a cascade impactor, which
3-6
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o
collect at 0.001 m /min. Normal concentrations of dust, water, and biological
materials are all at or below the detection limits of flameless AAS, so that
preconcentration by wet digestion is necessary.
Using gas chromatography, Ross and Sievers (1972) reported a detection
limit for beryllium in air of about 0.04 ng/m3, making this method marginally
acceptable for small sample sizes. Extensive chemical digestion and extraction
are required, however.
Standard reference materials are available for each method in the form of
fly ash, coal, orchard leaves, and bovine liver. Beryllium values for these
standard sources have been reported by Owens and Gladney (1975).
3.4 ATMOSPHERIC EMISSIONS, TRANSFORMATION, AND DEPOSITION
Although there is little evidence for significant emissions of beryllium
to the atmosphere during ore production, emissions could be significant without
existing regulations. The 20 percent of beryllium lost as waste during pro-
cessing (in the form of the hydroxide or the fluoride) could also represent an
environmental problem. Any potential effects from these sources of exposure
would be locally confined to the sole ore-processing plant in the United States,
operated by Brush Wellman at Delta, Utah.
Emission of beryllium from non-metallurgical processes (coal and fuel oil
combustion) accounts for 99 percent of U.S. emissions (Table 3-4). The average
concentration of beryllium in coal is between 1.8 and 2.2 ug/g. In 1984, the
United States burned 790 x 10 metric tons of coal. Had emission control mea-
sures for other pollutants not been used, 1300 tons of beryllium would have
been emitted, an amount that is far greater than the 0.3 tons lost during beryl-
lium ore processing. However, there is evidence that emission control measures
capture 70 to 90 percent of beryllium in the fly ash. The actual efficiency
of beryllium retention during coal combustion is a subject of controversy and
a source of confusion in several published reports. Phillips (1973) presented
data that suggested 86 percent of the beryllium in coal is released to the at-
mosphere. Gladney and Owens (1976) concluded that less than 4 percent escapes.
Henry (1979) suggested that less than 1 percent escapes, but could not account
for 35 percent of the beryllium in mass-balance estimates. The following cal-
culations may explain this descrepancy.
All three authors use a form of a mass-balance calculation in which the
concentration of beryllium in the coal and the fly ash is either measured or
assumed. Since beryllium output is presumed to be confined to captured fly
3-7
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TABLE 3-4. NATURAL AND ANTHROPOGENIC EMISSIONS OF BERYLLIUM
Natural
Windblown dust
Volcanic particles
Total
Anthropogenic
Coal combustion
Fuel oil
Beryllium ore processing
Total
Total U.S.
Production
(10b t/yr)
8.2
0.41
640
148
0.008b
Emission
Factor
(g/t)
0.6
0.6
0.28
0.048
37. 5b
Emission
(t/yr)
5
0.2
5.2
180
7.1
0.3
187.4
aUnits are in metric tons
The production of beryllium ore is expressed in equivalent tons of
beryl; the emission factor of 37.5 is hypothetical.
ash and emitted stack gases, that fraction of the coal input not found in the
fly ash is considered as emitted to the atmosphere. Neither Phillips (1973)
nor Gladney and Owens (1976) knew the actual mass of the ash produced. In
both cases, they reported ash content published elsewhere in the literature.
Phillips measured a beryllium content of the coal (2.5 pg/g) and of the ash
(5.0 pg/g), and assumed an ash content of 7 percent to calculate the emitted
fraction as:
2.5 ng/g -(Q.Q7) (5 Mg/g) = 0>86
2.5 |jg/g
Gladney and Owens (1976) assumed an ash content of 12 percent, which is
near the upper range of the 7 to 14 percent normally found in coal. They mea
sured a coal beryllium content of 1.89 and an ash beryllium content of 15.3
pg/g. The calculated percent loss would be:
1.89 pg/g - (0.12)(15.3 pg/g) = 0 0285
1.89 pg/g
3-8
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Both calculations are extremely sensitive to the assumed ash content of
coal. Using the range of 7 to 14 percent, the data of Phillips would show beryl-
lium losses of 72 to 86 percent, and the data of Gladney and Owens, 0 to 43 per-
cent. It is also possible that errors of analysis were made in measuring the
beryllium concentration of coal and ash. Coal and ash from the same plant that
Phillips investigated were reported by the Southwest Energy Study (1972) to con-
tain 0.43 and 7 |jg Be/g, respectively. However, these concentrations cannot be
considered typical because in the range of 7 to 14 percent ash, these data would
yield a percent beryllium loss of less than zero. If the average beryllium con-
tent of western coal (1 ug/g) is used with the Phillips data, the loss to the
atmosphere ranges from 30 to 65 percent.
Henry (1979) made similar measurements of coal and ash. Sixty-five per-
cent of the beryllium was accounted for in the ash. However, measurements
of beryllium at the precipitation outlet and in the stack did not account for
the remainder of the beryllium. In simulation runs, Yeh et al. (1976) found 77
percent retention of the beryllium in the slag and fly ash.
Although the data range from 0 to 86 percent, it seems reasonable to con-
clude that between 10 and 30 percent of the beryllium in coal is emitted to the
atmosphere during the coal combustion process. While not all coal burning fa-
cilities control emissions as well as power plants, the following calculation
is a conservative estimate of total beryllium emissions from coal in the United
States during 1984.
790 x 106 t coal/yr x 1.4 g Be/t coal x (0.1 to 0.3) = 220 + 110 t Be/yr
efficiency
Emissions from oil-burning facilities may be calculated from the average
beryllium concentrations of fuel oil (Anderson, 1973), an assumed loss of 40
Q
percent, and a consumption of 1.1 x 10 tons residual oil per year. From this
calculation, it appears that 7.1 tons of beryllium are emitted from this source.
Although no data exist, it is likely that less than 0.5 percent of the con-
tained beryllium is emitted during the post-ore production metallurgical pro-
cesses, adding a maximum of 0.12 tons/year to the atmosphere. Therefore, 187
tons/year would seem to be a reasonable estimate for anthropogenic beryllium
emissions from the United States. An estimate by Flinn and Reimers (1974) that
coal combustion accounts for 88 percent of the total beryllium emissions was
3-9
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probably conservative and could perhaps be revised upward to 95 percent or
higher.
Assuming a residence time of 10 days, an effective stratospheric volume
16 3
of 2.3 x 10 m , and stationary air mass above the United States, this amount
of beryllium could account for an average atmospheric concentration of 0.22
ng/m . Because of the dispersion caused by moving global air masses, the actual
air concentrations are about one-third this value.
Because most atmospheric beryllium is derived from coal combustion, it is
likely that its chemical form would be beryllium oxide. Conversion to ionized
salts is possible, but has not been reported. Gladney and Owens (1976) studied
the particle size distribution of stack emissions and reported that most beryl-
lium is found on particles smaller than 1 |jm. Particles of this size remain
aloft for about ten days.
Removal of beryllium from the atmosphere is by wet and dry deposition.
The rate of dry deposition of aerosol particles is a function of particle size,
windspeed, and surface roughness. The actual deposition rate for beryllium has
not been measured, but can be estimated by analogy to other elements. Davidson
et al. (1982) described the relationship between concentration of particles in
air, particle size, and surface roughness. For vegetation surfaces, a reason-
able deposition velocity would be 0.25 cm/sec. Assuming an average air concen-
tration of 0.1 ng Be/m in air, 0.002 ng of beryllium would be removed from the
atmosphere per square centimeter of actual surface area.
Kwapulinski and Pastuszka (1983) have determined that in Poland, emissions
of beryllium appear to be in balance with deposition. They applied the solution
of the Reynolds mass-balance model described by Astarita et al. (1979) to the
deposition of beryllium as a function of air concentration. The coefficient
of deposition, K-., was found to be constant during rainy periods and linearly
correlated with windspeed during dry periods. This report confirms that beryl-
lium is removed from the atmosphere by both wet and dry deposition in a manner
similar to metals on particles of comparable size distribution. Values for K-,
have not yet been measured in the United States. Because K-, varies regionally
with surface roughness and windspeed, calculations based on metals associated
with particles of comparable size are an acceptable substitution.
Concentrations of beryllium in precipitation have not been reported in the
United States. Assuming that half of the beryllium emitted into the atmosphere
3-10
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returns to earth as wet precipitation, the average concentration of beryllium
in rain or snow is expected to be 0.01 ng/g. This value is below the detection
limit for most analytical techniques. In a report from Australia, the actual
concentration of beryllium in rain was reported to average 0.07 ng/g (Meehan
and Smyth, 1967).
Beryllium oxide is very insoluble and would not be mobilized in soil or
surface water at normal environmental pH ranges of 4 to 8. If this is the
chemical form of beryllium at the time of deposition, the compound would not
move easily along grazing food chains, but would instead be confined to soil
and sediment. If, however, significant amounts of beryllium are converted to
chloride-, sulfate-, or nitrate-salts during atmospheric transport, solubility
upon deposition would be greatly enhanced and mobility within ecosystems could
be facilitated. Beryllium is classified as a fast-exchange metal, which means
that it could potentially interfere with the transport of nutritive metals,
such as calcium, into eukaryotic cells (Wood and Wang, 1983). There is a need
for research into the effects of pH on the mobility of beryllium in ecosystems
and its subsequent effects on plants and animals. Some of the toxic effects
of beryllium on natural populations of plants and animals are reviewed by
Brown (1979).
3.5 ENVIRONMENTAL CONCENTRATIONS OF BERYLLIUM
3.5.1 Ambient Air
Beryllium is measured at many of the stations in the SLAMS (State and
Local Air Monitoring Stations) and NAMS (National Air Monitoring Stations)
networks. The data are available from the SAROAD (Storage and Retrieval of
Aerometric Data) data base of the U.S. Environmental Protection Agency. The
3
detection limit for these analyses is 0.03 ng/m , and most annual averages are
3
at this concentration. Annual averages which exceeded 0.1 ng/m during 1977-81
are listed in Table 3-5. The highest 24-hour observation recorded was 1.78
3
ng/m in Atlanta, Georgia in 1977. At no sampling site did the 30-day average
concentration approach the 10 ng/m standard set by the U.S. Environmental
Protection Agency (Federal Register, 1973).
3.5.2 Soils and Natural Waters
Shack!ette et al. (1971) reported a geometric mean of 0.6 ug Be/g in soil
for 847 samples taken from sites distributed evenly across the United States.
Only 12 percent of the samples exceeded 1.5 ug/g. The soils were sampled at a
3-11
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TABLE 3-5. CONCENTRATIONS OF BERYLLIUM IN URBAN ATMOSPHERES'
Birmingham, AL
Douglas, AZ
Tucson, AZ
Ontario, CA
Hialeah, FL
Miami, FL
St. Petersburg, FL
Tampa, FL
Atlanta, GA
East Chicago, IN
Gary, IN
Hammond, IN
Indianapolis, IN
Des Moines, IA
Kansas City, KS
Ashland, KY
Baton Rouge, LA
Portland, ME
Baltimore, MD
Fall River, MA
New Bedford, MA
Flint, MI
Lansing, MI
Kansas City, MO
Omaha, NB
Camden Co. , NJ
Perth Amboy, NJ
Trenton, NJ
Albuquerque, NM
Niagara Falls, NY
Syracuse, NY
Cincinnati , OH
Cleveland, OH
Columbus, OH
Dayton, OH
Mansfield, OH
Portsmouth, OH
Steubenville, OH
Toledo, OH
Youngstown, OH
1977 1978
.11(20)
.11(20)
.12(13)
.11(23) .11(22)
.19(27) .13(24)
.11(18)
.15(25)
.14(28)
.16(23) .37(19)
.19(26)
.11(29)
.12(26)
.12(29)
.13(15)
.22(24)
.13(28)
.17(5)
.19(2)
.11(30)
.15(26)
.11(26)
.21(26)
.15(29)
.14(27)
.13(24)
.19(27)
1979 1980
.25(7)
.14(11)
.16(21)
.12(23)
•11(19)
.18(5)
.11(6)
.13(10)
.17(14)
.11(19)
.11(16)
.17(28)
.11(11)
.14(26) .18(10)
1981b
.11(7)
•22(1)
.11(7)
.11(6)
.13(4)
.22(6)
(continued on the following page)
3-12
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TABLE 3-5. (continued)
1977
1978
1979
1980
1981
Guayanilla Co.,
Baja Co., PR
Knoxville, TN
Nashville, TN
Dallas, TX
El Paso, TX
Houston, TX
Lubbock, TX
Pasadena, TX
Seattle, WA
Charleston, WV
Milwaukee, WI
PR
11(15)
11(29)
,14(25)
17(17)
,13(23)
,15(23)
.13(25)
.15(7)
.17(5) .16(5)
.13(11)
.40(2)
.17(13)
.11(7)
Values exceeding 0.1 ng/m are reported for the period 1977-81. Units are in
ng/m . Values in parentheses are the number of 24-hour observations used to
determine average annual concentrations.
Values not yet available.
depth of 20 cm. These results are lower than those of previous geochemical
surveys conducted by Vinogradov (1960), Hawkes and Webb (1962), and Mitchell
(1964), each of whom reported a mean of 6.0 [jg/g. The differences may be due
to limitations in analytical techniques. The 0.6 ug/g value is more consistent
with the average crustal value of 2.8 ug/g reported by Mason (1966).
Values for beryllium in surface waters range from 0.01 to 1.0 ng/g (Bowen,
1979). The lowest value (0.01 ng/g) was reported by Meehan and Smythe (1967)
in Australia. These concentrations are in the same range as the expected
concentration of beryllium in precipitation (0.01 ng/g) discussed above. The
beryllium concentration in seawater was reported to be 0.0005 ng/g by Merrill
et al. (1960) and 0.0056 ng/g by Bowen (1979). There are no available reports
of beryllium concentrations in groundwater.
3.6 PATHWAYS TO HUMAN CONSUMPTION
Humans may be exposed to beryllium through air, food, water, and dust
(Figure 3-1). In this section, beryllium concentrations are estimated for
typical environments not exposed to extraordinary sources of beryllium. These
values are combined with the consumption rates of air, food, water, and dust to
estimate the typical total daily intake of beryllium.
o
A likely average concentration of 0.08 ng Be/m in a residential environ-
ment can be projected from data collected from monitoring stations. Values are
3-13
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INDUSTRIAL
EMISSIONS
SURFACE AND
GROUND WATER
DRINKING
WATER
Figure 3-1. Pathways of environmental beryllium concentrations leading to potential human exposure.
3-14
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undoubtedly influenced by the distance and location of monitoring stations
from beryllium sources, and whether indoor or outdoor, filtered or unfiltered
air is sampled. Only limited data on the beryllium content of foods are avail-
able. Meehan and Smythe (1967) analyzed a few foods from Australia, and
reported values from 0.05 to 0.15 ng/g fresh weight. The reported values of
beryllium in drinking water range from 0.01 to 1.2 ng/g, with an average of 0.2
ng/g. There are no reports of beryllium in household dust, but if it is assumed
that such dust originates solely from the atmosphere having a beryllium
3
concentration of 0.1 ng/m , and that the air/dust ratio is 600, then household
dust would contain 60 ng Be/g.
The average American adult inhales 20 m of air/day, and consumes 1200 g
of food and 1500 g of water and beverages (Pennington, 1983). The daily con-
sumption of dust is not well established, but a conservative estimate of 0.02 g
is made here for the purpose of illustration. The typical American adult con-
sumes 423 ng/day of beryllium, most of which comes from food and beverages
(Table 3-6). It is apparent that air or dust derived from air has little
impact on the total intake of beryllium. This overall determination is
extremely sensitive to the average concentration of beryllium in food and
water, which accounts for 99.3 percent of total daily consumption of beryllium.
Variation in these numbers can be expected, depending on the types of food and
beverages consumed and the atmospheric contribution to the beryllium
concentrations of food and beverages.
Daily consumption from extraordinary sources, such as occupational expo-
sures or secondary occupational exposure e.g., a non-worker's exposure to a
worker's clothes, may increase the relative contribution of air and dust to
o
overall beryllium exposure. At 2 pg Be/m (the current occupational standard),
a worker's exposure for an 8-hour shift would increase to more that 13,000 ng/
day. Dust of beryllium metal or metal oxide consumed at a daily rate of 0.02 g
(including dust consumed during the working shift and dust carried home on the
clothing of the worker), could add 2,000,000 ng beryllium to the total daily
consumption. There is also the possibility that certain individuals might be
exposed to beryllium from implanted dental prostheses. Although the leaching
of nickel and chromium from alloys used in prostheses has been reported, no
studies on the leaching of beryllium are available.
Consumption of beryllium from cigarette smoking was discussed by Zorn and
Diem (1974). They found an average of 6,30 ng Be/cigarette and an average of 35
ng Be/cigarette in the inhaled smoke. Based on these findings, a person smoking
3-15
-------
a pack of twenty cigarettes per day would inhale about 700 ng of beryllium,
which is nearly twice the daily consumption from other sources. Unfortunately,
details in this study are lacking. The origin of the tobacco was not given,
and the relationship between the beryllium concentration of the tobacco and
the smoke was very weak.
TABLE 3-6. POTENTIAL HUMAN CONSUMPTION OF BERYLLIUM FROM
NORMAL SOURCES IN A TYPICAL RESIDENTIAL ENVIRONMENT
Air
Food
Water
Dust
Environmental
Concentration
0.08 ng/m3
0.1 ng/g
0.2 ng/g
60 ng/g
Total Daily
Human
Intake
20m3
1200g
1500g
0.02g
Consumption
1.6 ng/day
120
300
1.2
Percent of
Total Daily
Consumption
0.4
28.4
70.9
0.3
Total 422.8
3-16
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4. BERYLLIUM METABOLISM IN MAN AND ANIMALS
4.1 ROUTES OF BERYLLIUM ABSORPTION
4.1.1 Beryllium Absorption by Inhalation
There are no data on the absorption of inhaled beryllium in humans. How-
ever, it can be expected that the dose, size, and solubility of beryllium
particles will be important factors in determining the rates of absorption and
clearance.
Beryllium has been found in the lungs of persons without known occupational
exposure to the metal. Cholak (1959) analyzed 70 lungs from unexposed individ-
uals and reported an average concentration of 3.3 ug Be/kg dry weight (range:
0.1-19.8 ug/kg). Meehan and Smythe (1967) reported a mean beryllium level
of 1.3 ug/kg wet weight (range: 0.3-2.0 ug/kg) in four human lungs (a value
which corresponds to about 6 ug/kg dry weight). Sumino et al. (1975) analyzed
beryllium in the lungs of 12 Japanese subjects and found concentrations of up
to 30 ug/kg wet weight. It should be kept in mind that smoking habits were not
taken into account in any of these studies. In addition, it is difficult to
validate such data, as well as other data on beryllium in tissues or body
fluids, since no interlaboratory or quality control studies have been conducted,
and no reference samples for beryllium in tissues or body fluids are available.
The highest value recorded by Cholak (20 ug Be/kg dry weight) has been used to
denote an upper normal level of beryllium in human lung tissue (Hasan and
Kazemi, 1974).
Animal studies have shown that rats exposed to beryllium sulfate at an
o
average beryllium concentration of 35 ug/m for 7 hours a day, 5 days a week,
for 72 weeks, reached a plateau in lung beryllium concentrations of about 13.5
ug (in whole lungs) after 36 weeks of exposure. A plateau in the tracheobron-
chial lymph nodes was also reached at that time. After exposure was termi-
nated, pulmonary beryllium was initially eliminated with a half-time of two
weeks, followed by a much slower elimination rate (Reeves et al. , 1967; Reeves
and Vorwald, 1967).
In studies of the distribution of radioactive beryllium compounds adminis-
tered by intratracheal injection, Kuznetsov et al. (1974) reported a half-time
of 20 days in rats given a single injection of beryllium chloride, whereas Van
Cleave and Kaylor (1955) reported that beryllium citrate was rapidly eliminated
T
in rats. Longer observation periods in rats, however, suggest a half-time of
4-1
-------
about 325 days after inhalation of beryllium oxide (Sanders et al., 1975,
1978). Reanalysis of the latter data showed that there was an initial clear-
ance of 30 percent of the deposited beryllium at a half-time of 2.5 days, while
the rest was cleared much more slowly at a half-time of 833 days (Rhoads and
Sanders, 1985). About 25 percent of the beryllium cleared from the lungs
during the slow phase was translocated to regional lymph nodes (Sanders et al. ,
1978).
Hart et al. (1984) exposed 20 rats for one hour to beryllium oxide fired
at 560°C. The average concentration of beryllium was 447 ug/m , and 90 per-
cent of the particles had a mean diameter of 1 urn or less. The beryllium oxide
contained a trace of carrier-free Be. Four animals were killed at 2.5 hours
and at 2, 5, 12, and 21 days after exposure. Lungs were lavaged and the beryl-
lium content was determined in the lavage fluid and in the lung tissue. In the
lung tissue, about 200 ng of beryllium was found 2.5 hours after exposure. This
amount remained constant over the following weeks. In contrast, the amount of
beryllium in the lavage fluid decreased from 280 ng to 16 ng in three weeks.
The lavage fluid contained free alveolar cells (mainly macrophages).
It is not known in detail how beryllium is retained in the lungs. It is
likely that soluble beryllium compounds are transformed to insoluble complexes
with, for instance, phosphate, when the beryllium concentration reaches a cer-
tain level (Reeves and Vorwald, 1967). Beryllium particles in the insoluble
state are apt to be taken up by macrophages as demonstrated i_n vitro (Hart and
Pittman, 1980). At high i_n vitro and i_n vivo exposures, beryllium has been
shown to be very toxic to alveolar macrophages (Camner et al., 1974; Sanders
et al., 1975; Hart et al., 1984). Robinson et al. (1968) exposed two dogs for
20 minutes to a mixture of beryllium oxide, beryllium fluoride and beryllium
chloride (average concentration 115 mg/m ). The dogs were killed after three
years. The average beryllium concentration in the lungs was 3.9 and 5.5 mg/kg
wet weight. Beryllium deposits were seen in the interstitial tissue where they
were in the lysosomes of histiocytes.
Zorn et al. (1977) exposed rats and guinea pigs to beryllium sulfate
aerosol (with Be added as the chloride) for a period of three hours. Animals
(number not given) were killed at the end of 3 hours and then from 20 to 408
hours, thereafter. The total amount of beryllium inhaled was less than 3 mg
of which 10 ng was Be. At the end of the exposure, about 5 ng of the isotope
was retained and about 0.5 ng was found in excreta. Of the retained amount of
Be, about 67 percent was in the lungs and 15 percent was in the skeleton,
4-2
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indicating a rapid initial clearance. After 408 hours (17 days), about 80
percent of the total body burden of Be was in the skeleton and approximately
18 percent was in the lungs. Less than one percent of Be was in other organs.
During the first four days, Be was cleared from the lungs with a half-time of
about 24 hours. This was followed by a slower clearance with a half-time of
several weeks. Unfortunately, the lack of detailed information precludes a
thorough evaluation of this study.
4.1.2 Gastrointestinal Absorption of Beryllium
There are no data on the absorption of ingested beryllium compounds in
humans. Animal experiments, however, generally indicate that less than one per-
cent of ingested beryllium is absorbed (Hyslop et al. , 1943; Crowley, 1949;
Furchner et al., 1973). The latter two studies were done using tracer amounts
of 7Be.
Reeves (1965) gave two groups of rats, four in each group, beryllium sul-
fate in drinking water. The average daily intake was about 6.6 ug Be in one
group and 66.6 Be in the other. One rat in each group was killed after 6, 12,
18, and 24 weeks of exposure. Reeves found that 60 to 90 percent of the ingest-
ed beryllium was eliminated in the feces, indicating that an appreciable amount
was absorbed. However, the skeletal uptake of beryllium in both groups of rats
was nearly the same, averaging 1.49 ug in the low-dose group and 1.19 ng in the
high-dose group. This suggests either that gastrointestinal absorption was
much less in the high exposure group or that the uptake in bone was independent
of absorbed dose. If it is assumed that 50 percent of gastrointestinally
absorbed beryllium goes to the skeleton and that the biological half-time in
the skeleton is 100 to 1000 days, the daily absorbed amount would be less than
50 ng (or less than I percent of the low oral daily dose).
In reporting the study, Reeves (1965) concluded that due to the low
solubility of beryllium in intestinal fluid, it was precipitated as the phos-
phate and was not, therefore, available for absorption. Reeves surmised that
most of the beryllium found in the body was absorbed from the stomach.
In contrast to Reeves' study, Morgareidge et al. (1977, abstract) found
that uptake in bone was dose-dependent. They exposed rats orally to beryllium
as the sulfate at concentrations of 5, 50, and 500 mg/kg for up to two years.
Unfortunately, no quantitative data are given in the abstract of this study.
4-3
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4.1.3 Percutaneous Absorption of Beryllium
There are no data on skin absorption in humans. Tracer studies in rats
have shown that small amounts of beryllium may be absorbed from the tail
(Petzow and Zorn, 1974). Belman (1969) reported that ionic beryllium applied
to the skin will bind to epidermal constituents, mainly alkaline phosphatase.
However, the chemical properties of beryllium in any of its different forms
make it unlikely that significant absorption can occur through intact skin.
4.1.4 Transplacental Transfer of Beryllium
In a study by Bencko et al. (1979), the soluble salt of beryllium, BeCl2,
was evaluated for its ability to penetrate the placenta and reach the fetus of
mice. Radiolabeled BeCl2, injected into the caudal vein of 7 to 9 mice,
crossed the placenta and was deposited in various organs of the fetus (see
Chapter 5 for a detailed discussion of this study).
No other data are available on placental transfer of beryllium.
4.2 TRANSPORT AND DEPOSITION OF BERYLLIUM IN MAN AND EXPERIMENTAL ANIMALS
Ingestion studies on animals have shown that beryllium absorbed from the
gastrointestinal tract accumulates mainly in the skeleton. In soft tissues,
concentrations have mainly been found in the liver (Reeves, 1965; Mullen et
al., 1972). Similar results have been obtained in injection studies on animals
(Mullen et al., 1972; Hard et al., 1977). In the case of the injection studies,
the physiochemical state of the injected compound determines the main site of
deposition: soluble beryllium rapidly distributes to the skeleton, whereas col-
loidal forms go mainly to the liver (Klemperer et al., 1952). In rat blood,
large doses of injected beryllium tend to aggregate and bind to phosphate,
whereas small doses remain largely in a diffusible form (Vacher and Stoner,
1968a,b). At low doses of beryllium, the main binding in human blood was
reported to be the prealbumin and orglobulin fractions of plasma (Stiefel et
al., 1980). Recent data indicate that there is a binding site for beryllium in
the lymphocyte membrane (Skilleter and Price, 1984).
Witschi and Aldridge (1968) found that less than 10 percent of an intra-
venous dose of beryllium sulfate in rats was in the liver 24 hours after dosing
(dose range: 0.75-15 pg 7Be/kg b.w. ). In contrast, more than 25 percent was
found in the liver following the administration of doses of 63 HQ/kg D-w- or
higher. With increasing dose, comparatively more beryllium was located in the
nuclear fraction and less in the supernatant of subcellular fractions of rat
4-4
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liver. At the lowest dose (0.75 pg), the light mitochondria! fraction had the
highest amount of beryllium, and some evidence was presented for beryllium
being located in the lysosomes. Further evidence for a role of lysosomes in
the hepatic accumulation of beryllium was presented by Skilleter and Price
(1979).
There are few data on beryllium levels in humans. Analysis of tissues
from people occupationally exposed to beryllium showed that, generally, concen-
trations were highest in bone, liver, and kidney (Tepper et al., 1961). Meehan
and Smythe (1967) reported that in the brain, kidney, spleen, liver, muscle,
and heart, concentrations were generally less than I pg/kg wet weight. However,
in one bone sample the concentration was 2 pg/kg, and in five vertebrae the
mean was 3.6 pg/kg. The form in which beryllium is stored in bone is presently
unknown.
4.3 EXCRETION OF BERYLLIUM IN MAN AND ANIMALS
In rats given intravenous injections of tracer doses of Be, 15 percent of
the dose was excreted in urine by day 1 and 64 percent was excreted by day 64
(Crowley et al., 1949). In mice, monkeys, and dogs, urinary excretion was the
main route of beryllium elimination during the first days after parenteral
dosing (Furchner et al., 1973). These researchers found that only later did
elimination by the gastrointestinal tract equal that of urinary excretion. In
early studies, Scott et al. (1950) discovered that increasing the dose in
experimental animals resulted in lowering urinary excretion rates. Biliary
excretion seems to play only a minor role in total beryllium excretion (Cikrt
and Bencko, 1975).
With oral dosing, Reeves (1965) found that less than one percent of the
administered dose was excreted in urine of rats.
Quantitative data on the excretion of beryllium in humans are scarce. In
one study of persons not exposed to an occupational source of beryllium, very
small amounts (<0.1 pg Be/1), as measured by emission spectroscopy, were found
in the urine (Lieben et al., 1966). Much higher values (averages of 0.9 pg
Be/1) were reported in two other studies, one of 120 people from California
(Grewel and Kearns, 1977) and another of 20 individuals from Germany (Stiefel
et al., 1980). In the latter two studies, flameless atomic absorption spectros-
copy was used to measure the beryllium concentrations. Thus, the differences
observed between these two studies and that of Lieben et al. (1966) may have
been due to the different analytical methods used.
4-5
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Since human dietary intake of beryllium is low, and animal studies suggest
that gastrointestinal absorption would also be low, the total human body burden
of beryllium is likely to be such that only a few nanograms would be excreted
daily. Based on the limited data reported by Meehan and Smythe (1967), the
soft tissue burden of an adult is likely to be less than 20 pg and the skeletal
burden about 30 ng.
Presently, there are no estimates of the biological half-time of beryllium
in humans. However, in dogs, mice, rats, and monkeys, the long-term biological
half-times of beryllium after injection have been estimated at 1270, 1210, 890,
and 770 days, respectively (Furchner et al., 1973). Some circumstantial evi-
dence suggests that the half-time in human bone is likely to be many years.
4-6
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5. BERYLLIUM TOXICOLOGY
This chapter reviews the non-mutagenic and non-carcinogenic effects of
beryllium. Because of the volume of information available regarding the
mutagenic and carcinogenic effects of beryllium, these topics are dealt with
specifically in Chapters 6 and 7.
5.1 ACUTE EFFECTS OF BERYLLIUM EXPOSURE IN MAN AND ANIMALS
5.1.1 Human Studies
Acute lung disease from excessive exposure to beryllium compounds was first
reported in Europe during the 1930s. The first case in the United States was
reported in 1943 (Van Ordstrand et al., 1943). In the 1940s, many hundreds of
cases occurred, but with today's improved working conditions, acute beryllium
poisoning is rare.
Acute lung disease can be caused by inhalation of soluble beryllium com-
pounds, such as the fluoride with acidic pH or the low-fired beryllium oxide.
The reported symptoms have been nonspecific, with chemical pneumonitis as the
most severe manifestation (Freiman and Hardy, 1970; Reeves, 1979). In a study
of six fatal cases, Freiman and Hardy (1970) reported that death occurred
between 17 days and 10 weeks after exposure. Interstitial edema and cellular
infiltration dominated the histological tissue analyses. The beryllium con-
centrations in the lung ranged from 4 to 1800 pg/kg. It was not stated whether
the analyses were based on wet or dry weight.
In most cases of acute poisoning, recovery is slow, taking several weeks
or months (Reeves, 1979). In the U.S. Beryllium Case Registry (BCR), a file
on reported cases of acute and chronic beryllium disease, 215 cases of acute
poisoning were registered up to 1967 (Freiman and Hardy, 1970). Since 1967,
an additional nine cases have been reported (Eisenbud and Lisson, 1983).
The fact that there still is some occupational risk for acute beryllium
disease is shown by recent case reports by Hooper (1981) and Lockey and co-work-
ers (1983). Hooper describes a case of an 18-year-old sandblaster exposed to
grinding dyes containing a copper-beryllium alloy. The man developed acute
respiratory disease, which was diagnosed as interstitial pneumonitis by an open
lung biopsy performed six days after exposure. Beryllium concentrations in the
lung tissue were 28 pg/kg dry weight compared to a normal level of 20 ug/kg or
less. In the report by Lockey and co-workers, acute chemical pneumonitis in a
5-1
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dental laboratory technician was attributed to the casting and grinding of den-
tal bridges containing nickel-beryllium alloys.
Contact dermatitis caused by exposure of skin to soluble beryllium salts
has also been described (Van Ordstrand et al., 1945).
5.1.2 Animal Studies
Acute chemical pneumonitis has been produced in a variety of animals
exposed to beryllium as a sulfate or fluoride (Stokinger et al., 1950). Some
insoluble compounds, especially low-fired beryllium oxide, have also caused
acute effects in rats (Hall et al., 1950). The concentrations needed to cause
3
acute effects have generally been on the order of several mg/m .
Injection of beryllium compounds can cause acute liver damage (Cheng, 1956;
Aldridge et al., 1949).
5.2 CHRONIC EFFECTS OF BERYLLIUM EXPOSURE IN MAN AND ANIMALS
5.2.1 Respiratory and Systemic Effects of Beryllium
5.2.1.1 Human Studies. Hardy and Tabershaw (1946) were the first to report
chronic lung disease caused by beryllium. They presented data on 17 persons
employed in the fluorescent lamp manufacturing industry. The main symptoms
noted were dyspnea on exertion, cough, and weight loss. In most cases, the
symptoms first appeared months or even years after exposure. The patients
were generally younger than 30 years of age and the majority were women.
X-rays showed that an early sign of chronic beryllium poisoning was a fine
diffuse granularity in the lungs. In the second stage, a diffuse reticular
pattern was seen, while in the third stage, distinct nodules appeared. After
generally less than two years of illness, five deaths occurred among the 17
persons. Though disability persisted in most cases, some recovery was noted
in two cases. Postmortem examination of the lungs from one person showed a
granulomatous inflammation characterized by central and eccentrically located
giant cells of the foreign body type in the alveoli. Infiltration of plasma
cells and lymphocytes was also noted.
This pioneer study by Hardy and Tabershaw led to further occupational stud-
ies, which have been documented in papers by Hardy (1980) and Eisenbud (1982).
In addition, there have been reports on "neighborhood cases," i.e. beryllium
disease in persons living in the vicinity of beryllium-emitting plants. In
5-2
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these cases, exposure was not only to beryllium in ambient air, but also
to contaminated clothing brought into the house from occupationally exposed mem-
bers of the household (Eisenbud et al., 1949). At least three children, ages 7
to 14 years, were counted among such cases (Hall et al., 1959).
These and other findings led to the adoption of beryllium standards for
both the industrial and natural environments. A Threshold Limit Value (TLV) of
2 jjg/m was set as an average for an 8-hour occupational exposure; the maximum
permissible peak (not to exceed more than one 30-minute period) was set at 25
3 3
|jg/m . For the general environment, a level of 0.01 |jg/m was proposed. It
o
should be noted that the 2 |jg/m standard was not based on actual dose-response
relationships. As stated by Eisenbud (1982), the standard was based on the mo-
lar toxicity of beryllium in relation to some heavy metals such as lead and mer-
cury, which have TLVs around 100 pg/m .
While these proposed standards seemed to prevent acute poisoning, many new
cases of chronic beryllium disease appeared mainly as a result of heavy expo-
sures during the period from 1940 to 1946. This led to the foundation of the
Beryllium Case Registry (BCR) in 1952. The BCR was intended to serve as a file
for all cases of acute and chronic beryllium disease, from which information on
the development and clinical manifestations of beryllium disease could be ob-
tained. Since 1978, the BCR has been maintained by the National Institute for
Occupational Safety and Health.
Throughout the years, many scientific reports have relied on the information
found in the BCR. In 1959, Hall et al. presented data on 601 cases (Table 5-1).
The authors noted that most male cases were acute. However, in later reports
the number of cases of chronic disease increased and currently number more than
600. In contrast, only a few additional cases of acute disease have been report-
ed. It should be noted that 28 of the acute cases in Table 5-1 were also clas-
sified as chronic. Between 1966 and 1974, 74 new cases of beryllium disease were
reported to the BCR, of which 36 had been exposed after 1949 (Hasan and Kazemi,
1974).
Chronic beryllium disease often appears many years after exposure ends.
In more than 20 percent of the cases recorded in the BCR before 1959, the time
since last exposure was greater than 5 years, the maximum being 15 years (Table
5-2). There has been some overlap between acute and chronic disease, but
generally the disease has been registered as chronic if it has lasted more than
one year.
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TABLE 5-1. BERYLLIUM REGISTRY CASES, 1959
Acute
Chronic
Men
227
191
Women
20
191
Total
247 (39%)
382 (61%)
Dead
15 ( 6%)
121 (31%)
Source: Hall et al. (1959)
TABLE 5-2. TIME FROM LAST EXPOSURE TO FIRST SYMPTOM* IN THE BCR, 1959
Time
Less than 1 month
1 month to 1 year
1-5 years
5-10 years
More than 10 years
Cases of beryllium disease
126
27
89
56
12
310
%
41
9
29
18
4
^Maximum was 15 years.
Source: Hall et al. (1959)
The latest report contains 897 cases, 10 of which have been added since
1978 (Center for Disease Control, 1983). Eisenbud and Lisson (1983) reported
on 888 cases, but noted that they knew of 45 other chronic cases that had not
yet been included in the BCR. Therefore, the total number of cases of beryl-
lium disease in this country may exceed 900.
Of the 888 cases reported by Eisenbud and Lisson, 224 were classified as
acute. This number is smaller than the one given in Table 5-1, but as mentioned
earlier, 28 acute cases in that table were also classified as chronic. The
chronic cases were reported to be 622, leaving 42 cases unaccounted. Of the 622
cases, 557 occurred in individuals occupationally exposed to beryllium and 65
occurred among members of the general populace. Of the latter, 42 were attri-
buted to ambient air exposure and 23 to dust exposure in the home.
The majority of the occupational cases cited by Eisenbud and Lisson were
from the fluorescent lamp (319) or beryllium extraction (101) industries. In
5-4
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62 percent of the cases, dates for first exposure and onset of disease were
available. Figure 5-1 shows that up to 40 years may elapse between initial ex-
posure and onset of disease. There is some suggestion, however, that latency
times may be declining in recent years (Table 5-3). Eisenbud and Lisson urged
caution when interpreting these data, as a rough correspondence between the
maximum latency time and number of years elapsed since first exposure must exist.
It could be argued, for instance, that among the more recent members of the co-
hort, not enough time has passed for them to develop the disease. Hence, a per-
son exposed in the 1960s cannot have a latency time of more than 20 years.
Some of the common symptoms of chronic beryllium disease noted from the
BCR are shown in Table 5-4 (Hall et al., 1959). These symptoms confirm those
reported earlier by Hardy and Tabershaw (1946). Table 5-5 shows some of the
signs of chronic beryllium disease. The cardiovascular signs can be attribu-
ted to cor pulmonale, which is a sequela of the severe forms of chronic beryl-
lium disease. There are also signs that may be seen as pure systemic effects of
beryllium exposure.
An extensive description of chronic beryllium disease was presented by
Stoeckle et al. (1969). In their report, clinical findings and the results of
treatment were presented. In another paper by Freiman and Hardy (1970), the pul-
monary pathology was presented. Data were given for 60 patients with chronic
beryllium disease who had been investigated at the Massachusetts General
Hospital between 1944 and 1966. Patients came from different industries and
exposure levels were unknown. Consequently, the data cannot be used for dose-
response analyses. However, valuable information can be derived from the clini-
cal findings and the diagnostic problems noted during the examination of these
patients. In addition to the pulmonary effects, there was further evidence for
extrapulmonary signs of beryllium disease. In some patients, granulomas were
found in muscle or skin.
Some of the features of chronic beryllium disease are similar to those
seen in sarcoidosis. In the paper by Stoeckle et al., as well as in an earlier
paper by Israel and Sones (1959), the differentiation of these two diseases is
discussed. One distinguishing characteristic between the diseases is the con-
siderably greater systemic involvement in sarcoidosis, as noted in more than 80
percent of the sarcoidosis cases. X-rays of the lungs, however, may show very
similar pictures of the two conditions.
5-5
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en
i
cr>
50
40
S 30
O
UJ
20
10
I I I I
1 I I I
I I
• o
• o
:, •<,
•••
• EXPOSED TO BERYLLIUM PHOSPHORUS
O EXPOSED TO OTHER BERYLLIUM
COMPOUNDS
0
o
1932
1940
o
o
9
0
o o
O O
O
o o
0 8 8" °°
I 8 I I
o o
o „
1948 1956 1964
YEAR OF FIRST EXPOSURE
1972
1980
Figure 5-1. Latency of occupational berylliosis according to year of first exposure.
Source: Eisenbud and Lisson (1983).
-------
TABLE 5-3. CHANGES OF LATENCY FROM 1922 TO PRESENT IN
OCCUPATIONAL BERYLLIOSIS CASES
a
Period of First
Exposure
No. of Cases
Latency,in years
Mean Range
1922-1981
1922-1937
1938-1949
1950-1959
1960-1981
347
33
264
32
18
11
16
9.8
9.6
6.6
1-41
4-40
1-39
1-25
1-13
Cases were included only if both dates of first exposure and diagnosis of
first symptoms were known.
Source: Eisenbud and Lisson (1983)
TABLE 5-4. SYMPTOMS OF CHRONIC BERYLLIUM DISEASE
Symptom
Dyspnea
on exertion
at rest
Weight loss
> 10%
< 10%
Cough
nonproductive
productive
Fatigue
Chest pain
Anorexia
Weakness
Percent
69
17
46
15
45
33
34
31
26
17
Source: Hall et al . (1959)
5-7
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TABLE 5-5. SIGNS OF CHRONIC BERYLLIUM DISEASE9
Sign
Chest signs
Cyanosis
Clubbing
Hepatomegaly
Splenomegaly
Complications
Cardiac failure
Renal stone
Pneumothorax
Percent
43
42
31
5
3
17
10
12
aSigns attributable to cardiac failure are not included.
Source: Hall et al. (1959)
Among laboratory findings in cases of beryllium disease, hypercalcemia,
hypercalcuria, stone formation, and osteosclerosis have been noticed (Stoeckle
et al., 1969), as has hyperuricemia (Kelley et al., 1969).
In addition to studies based on the BCR, there have also been some studies
within industrial populations. Balmes and co-workers (1984) reported on four
cases of suspected chronic beryllium disease in a group of workers exposed to
beryllium released from melted scrap metals. Wagoner et al. (1980) conducted a
more extensive mortality study on a cohort of 3055 workers exposed to beryllium
in a plant in Pennsylvania. (See Section 7.2 for detailed discussion of lung
cancer within the cohort.) Among causes of death other than lung cancer, there
was a significant excess of heart disease (396 observed versus 349 expected) and
respiratory disease other than influenza and pneumonia (31 observed versus 18.7
expected). It is conceivable that some of the cardiac deaths were, in fact,
caused by cor pulmonale secondary to beryllium disease. There are no data to
indicate that beryllium exposure by inhalation has a direct effect on the
cardiovascular system.
5-8
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These data can be compared to a mortality study by Infante et al. (1980) on
421 white males listed in the BCR during the period of 1952 through 1975. Heart
disease was stated to be the cause of death in 31 of these cases (29.9 were
expected). Respiratory disease other than influenza and pneumonia was the
cause of death in 52 cases (only 1.6 were expected). Hb'gberg and Rajs (1980)
reported granulomatous myocarditis as the cause of death in two individuals
who were occupationally exposed to beryllium.
Results of studies on respiratory function have been presented by Andrews
et al. (1969), Kanarek et al. (1973), and Sprince et al. (1978). Andrews et al.
performed lung function tests (vital capacity and FEV-^ on 41 patients registered
in the BCR as having chronic beryllium disease. In only two patients were the
test results normal; 16 out of the 41 patients had airway obstruction.
The studies by Kanarek et al. (1973) and Sprince et al. (1978) were per-
formed on workers employed in beryllium extraction and processing plants. In
the first study, 214 employees were examined. They had been exposed for I to
14 years, and exposure had started after recommended occupational standards had
been set. It was known, however, that the recommended standards of 2 and 25
o
ng/m for 8-hour and short-term exposures, respectively, had been exceeded. In
some areas of the plants, peak exposures were above 1 mg/m . Lung function
tests including FVC, FEV-., and gas exchange were performed. Among the 31 sub-
jects with X-ray abnormalities of the lung, 11 had hypoxemia at rest, but these
subjects were also heavy smokers. In this study, there was no control group
and it is difficult, therefore, to establish whether smoking or beryllium caused
the effects. However, lung biopsies were performed in two subjects, and in one
of these cases a diffuse granulomatous reaction, typical of beryllium exposure,
was found. The beryllium content of the lung was elevated in both cases. It
is noteworthy that the case with the granulomatous reaction had a much lower
beryllium concentration in the lung than did the case without tissue changes.
A follow-up was made three years later on these workers (Sprince et al. ,
1978). Occupational exposure levels had been reduced due to engineering
3
changes, and peak concentrations were now less than 25 (jg/m . For some oper-
ations, peak concentrations were less than 2 ug/m . Workers who had partici-
pated in 1971 and had not changed smoking habits were studied (Table 5-6).
There were no major differences between the results from the two examinations,
but as seen in Table 5-7, there had been some improvement of hypoxemia as indi-
cated by the results of the Pan determinations. In the 13 persons who had
2
clearly demonstrated hypoxemia in 1971, there was a highly significant rise
5-9
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TABLE 5-6. COMPARISON OF 1971 AND 1974 DATA OF WORKERS SURVEYED IN BERYLLIUM
EXTRACTION AND PROCESSING PLANTS3
Workers
Smokers
Ex-smokers
Nonsmokers
Total
Year
1971
1974
1971
1974
1971
1974
1971
1974
No.
55
55
36
36
20
20
111
111
Age
(years)
40.9
43.9
43.3
46.3
43.4
46.4
42.1
45.1
Ciga-
rette-
Pack-
years
23
27
25
25
0
0
23.5
26.2
Length of
Employ-
ment
(years)
10.2
13.2
10.6
13.6
10.9
13.9
10.4
13.4
FEVX (%
predicted)
92.9
90.4
97.9
97.7
105.3
102.4
96.7
95.1
FVC (%
predicted)
96.6
95.2
97.8
101.2
98.6
102.5
97.3
98.5
PEFR (%
predicted)
96.9.
91. 3b
100.0
94. 8C
104.7
99.2
99.3.
93. 8d
FEV, = 1-sec forced expiratory volume; FVC = forced vital capacity; PEFR = peak
expiratory flow rate. Results are mean values.
bp < 0.02
cp = 0.02
dp < 0.01
Source: Sprince et al. (1978)
TABLE 5-7. COMPARISON OF 1971 AND 1974 ARTERIAL BLOOD GAS RESULTS3
Workers
Smokers
Ex-smokers
Nonsmokers
Total
Year
1971
1974
1971
1974
1971
1974
1971
1974
No.
55
55
36
36
20
20
111
111
Pao
(mm flg)
90.9.
96. lb
89.1,
95.7b
93.4
100. 2C
90.8.
96. 8b
Paco
(mm Hg)
38.0.
35. lb
37.9.
36. lb
38.0
36.3
38.0.
35. 7b
pH
7.42
7.42
7.42
7.42
7.43,
7.41b
7.43
7.42C
Pan = arterial Pn ; Parn = arterial P
• Uo U/N LUrt
bp< §.01 22
Cp< 0.05
Source: Sprince et al. (1978)
CO,
Results are mean values.
5-10
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in Pan by 1974 (average rise of 19mm Hg). Among the 98 workers who had a nor-
2
mal Pa,, in 1971, the average increase was 4.1 mm. Of the 31 subjects
who had X-ray abnormalities in 1971, 9 now showed normal X-ray readings.
These findings indicate that some minor effects might be reversible in beryl-
lium-exposed workers if exposure is reduced. A new follow-up was conducted
in 1977 and reported briefly (Sprince et a!., 1979). The improvement in Pan
2
remained, and there was a tendency towards normalization of lung X-rays.
It is obvious, however, that due to long latency times, longer follow-ups are
necessary before any final conclusions can be made with regard to prognosis.
In a recent British study, Cotes et al. (1983) presented data on workers
exposed to beryllium compounds, mainly beryllium oxide. The plant in which
these workers had been employed started operation in 1952. The first study of
these workers was made in 1963 when 130 men out of a group of 146, who had
worked for more than 6 months, were examined. Chest X-rays were taken, and in
all but one case, pulmonary function was measured by a set of respiratory func-
tion tests. Airborne beryllium had been measured during the years 1952 to
1960, but it was unclear whether any measurements had been made since 1960.
3
In a total of 3401 samples taken, only 20 exceeded the 25 ug/m limit and 318
3
exceeded the 2 ug/m limit. Concentrations were presented as geometric means,
3
and in both 1952 and 1960 these concentrations were never above 2 ug/m . Gener-
3
ally, concentrations were far below 1 ug/m . The 1963 study found six cases
of definite or suspected beryllium disease.
In a follow-up in 1973, 106 of the original 130 workers were examined. In
another follow-up in 1977, only 8 men from the 1973 group and one ex-employee
were examined, but to this new group were added 24 employees and 14 ex-employ-
ees employed since 1963. The same tests were performed on these subjects.
The follow-up studies did not find any new cases of beryllium disease. However,
after the 1977 study, two further cases were added. Both were men who had worked
since 1952. There were also two cases of acute beryllium pneumonitis, and these
two men were among a group of 17 who were deemed to have had the highest expo-
sures. Both of these cases were normal in the 1963 study.
After adjusting for age, smoking, and other factors, the respiratory
function tests showed that exposure was related only to vital capacity. In the
1963 study, a significant negative correlation between estimated total exposure
to beryllium and lung compliance was shown in a subgroup of 19 workers from the
5-11
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slip-casting bay. Comparison between data from 1963 and 1973 showed only
changes that could be ascribed to personal factors. The conclusion of the
authors was that respiratory function studies generally could not detect beryl-
lium disease before radiographic changes appeared. Decreases in lung function
were only observed in cases with clear X-ray changes. However, Preuss and
Oster (1980) have noted that changes in vital capacity may occur long before
X-ray changes appear.
As mentioned above, chronic beryllium disease differs from some other
occupational lung diseases in that it has a systemic component. The systemic
involvement suggests that there is also an immunological component to the
disease, and that hypersensitivity can explain some of the findings in chronic
beryllium disease.
In 1951, Curtis developed a patch test which was found to be positive for
most cases of dermatitis and skin granuloma caused by beryllium. In addition,
it was positive in many cases of lung disease caused by beryllium (Curtis,
1959; Nishimura, 1966). However, the patch test could also initiate the devel-
opment of skin reactions or pulmonary disease in people exposed to beryllium,
but who had not had previous symptoms of respiratory illness (Sneddon, 1955;
Stoeckle et al., 1969; Rees, 1979; Cotes et a!., 1983).
These early studies led to attempts to develop other tests suitable for
studying hypersensitivity to beryllium. Of these, the lymphocyte transformation
test has been the most useful (Deodhar et al., 1973; Williams and Williams,
1982a,b, 1983). This test gave a positive response in 16 patients with
established chronic beryllium disease, whereas it was negative in 10 subjects
with suspected disease. Only two positive responses were reported among 117
healthy beryllium workers (Williams and Williams, 1983). Similar results have
also been reported by Van Ordstrand (1984). It is not clear, however, if a posi-
tive test in an otherwise healthy worker really indicates that such an individual
is at a higher risk for getting pulmonary disease.
Rom et al. (1983) conducted a three-year prospective study to evaluate the
relationship between lymphocyte transformation and beryllium exposure. The aver-
age beryllium exposure levels ranged from 7.18 ug/m in 1979 to less than 1
ug/m from 1980 to 1982. Of 11 workers with a positive test in 1979, 8 were
negative in 1982. A possible reason for this change may have been the decrease
in exposure levels.
5-12
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In an area in Czechoslovakia where coal with a high beryllium content is
burned, Bencko et al. (1980) studied immunoglobulins and autoantibodies in
workers in a power plant and in people living in the vicinity of the plant. The
3
average concentration of beryllium in the town was estimated to be 80 ng/m ,
which is 8 times higher than the suggested standard for ambient air in the Unit-
ed States. In both the workers and general public, levels of immunoglobulins
IgG and IgA and concentrations of autoantibodies were elevated compared to a
control group not exposed to beryllium. The workers had higher exposure than
3
the town dwellers (up to 8 yg/m ), and they also had considerably higher levels
of IgM than either the town residents or the control group. Since many factors
can contribute to increases in immunoglobulin levels, the significance of these
findings is not clear.
5.2.1.2 Animal Studies. There have been a large number of animal studies on
the acute and chronic effects of beryllium exposure by air. Much of the early
work in the 1940s and 1950s has been described by Vorwald et al. (1966). A
large number of the rat studies were performed by Vorwald and co-workers, but
many were never fully reported. The main information source continues to be
the 1966 review by Vorwald et al.
In one study, rats were exposed to beryllium sulfate aerosol in concentra-
3
tions ranging from 2.8 to 194 ug/m of air. The exposures were usually given 7
3
hours a day, for 1 to 560 days. It was stated that exposure to 2.8 ug/m did
3
not produce any specific inflammatory abnormalities, whereas 21 ug/m caused
3
significant inflammatory changes in some long-surviving rats. At 42 ug/m ,
3
chronic pneumonitis was produced, while an exposure level of 194 ug/m caused
acute beryllium disease.
The main finding of this study was that the low-exposure group had a high
incidence of pulmonary cancer (13 of 21 rats). There has been some concern
about the validity of the low-exposure data, however (see Section 7.1.8.3). In
3
the group exposed to 42 ug/m , microscopic examination of lung tissue showed
alveolar changes with a large increase in the number of macrophages. With
longer exposure, diffuse pneumonitis and focal granulomatous lesions became
increasingly prominent, typically occurring in patches.
Schepers et al. (1957) exposed rats to beryllium sulfate at an average
3
concentration of beryllium of 35 ug/m . In one experiment, 115 animals were
exposed for six months; the number of controls was 139. In this study, 46
animals died during exposure and 17 were killed at the end of exposure.
Fifty-two rats were then transferred to normal air and observed for up to 18
5-13
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additional months. The cause of death during exposure was mainly pleural
pericarditis with a tendency to chronic pneumonitis. No bacteria were isolated,
but the authors concluded that the response was caused by infection, since
sulfathiazole had a beneficial effect. In further experiments, similar
exposures were given, but no rats died during exposure or up to nine months
afterward. Among the findings after six months of exposure were: adenomas;
foam-cell clusters; focal mural infiltration; lobular septal-cell proliferations;
peribronchial, alveolar-wall epithelialization, and granulomatosis.
In a study by Reeves et al. (1967), 150 rats (with an equal number of con-
trols) were exposed to beryllium sulfate at a mean concentration of 34 pg/m .
Exposure was for 72 weeks, 7 hours a day, 5 days a week. Control of the
exposure concentrations was poor (the standard deviation of the mean level was
3
24 ug/m ). Every month, three male and three female rats from the exposed and
control groups were killed. Among the findings were progressive increases in
lung weight in the exposed animals. At the end of the experiment, the lung
weights of exposed animals were, on an average, more than four times greater
than those of controls. Histological examination showed inflammatory and
proliferative changes. Also, clusters of macrophages in the alveolar spaces
were a common finding. Granulomatosis and fibrosis were only occasionally seen.
The proliferative changes ultimately led to the generation of tumors in all of
the exposed animals (43/43) (see Section 7.1.1).
Wagner et al. (1969) exposed two groups of 60 rats to the beryllium ores,
beryl and bertrandite, for up to 17 months at a concentration of 15 mg/m . This
3 3
dose corresponded to 210 (jg Be/m as bertrandite and 620 |jg Be/m as beryl.
Exposure was generally for 6 hours a day, 5 days a week. A very large incidence
of lung tumors was reported among rats exposed to beryl. Among the
non-malignant changes, clusters of dust-laden macrophages were seen. Granulomas
were seen in lungs from bertrandite-exposed rats.
Sanders et al. (1975) exposed rats to beryllium oxide particles calcined
at 1000°C. Single exposures to beryllium oxide were given through the nose
only. Exposure time ranged from 30 to 180 minutes, and concentrations of beryl-
3
lium were from 1 mg to 100 mg/m . The single exposures resulted in chronic
changes characterized by the appearance of foamy macrophages and some granulo-
matous lesions. A significant depression of alveolar clearance was also
observed.
5-14
-------
Other studies have examined the effects of beryllium exposure on monkeys
(Vorwald et al., 1966; Schepers, 1964; Wagner et al., 1969; Conradi et a!.,
1971), dogs (Conradi et al., 1971; Robinson et al. , 1968), guinea pigs
(Policard, 1950; Reeves et al., 1971, 1972) and hamsters (Wagner et al. , 1969).
Vorwald et al. (1966) exposed monkeys to intermittent daily administrations
3
of beryllium sulfate (average concentration of 35 ng/rn ) for several months.
Some monkeys were given intratracheal instillations of beryllium oxide. Both
routes of administration led to typical chronic beryllium disease with pneumo-
nitis and granulomatosis.
Schepers (1964) exposed three groups of monkeys, four in each group, to
aerosols of beryllium fluoride, beryllium sulfate, and beryllium phosphate in
3
concentrations of about 200 ug/m beryllium. In another experiment, two groups
of monkeys, four animals in each, were given higher concentrations of the
3
beryllium phosphate, containing about 1140 and 8380 ug Be/m , respectively.
Exposure was for 1 or 2 weeks in the animals exposed to the fluoride and sulfate,
and from 3 to 30 days in the groups exposed to the phosphate. After exposure
ceased, the animals were kept in normal air for different periods of time.
There were signs of initial general toxicity, in the form of anorexia, in
the exposed animals. Dyspnea, one of the typical signs of human chronic beryl-
lium disease, developed rapidly in the animals exposed to fluoride and to the
high beryllium phosphate concentrations. Mortality was 100 percent in the
animals exposed to the two highest beryllium phosphate concentrations. Exami-
nation of lungs from animals who either died during the experiment or were
killed showed pulmonary edema and congestion, mainly in the animals exposed to
beryllium fluoride or to the highest concentration of beryllium phosphate. Cor
pulmonale was also a common finding. The histological picture was similar to
that seen in other animals and humans. Notable were pigment-filled macrophages
and invasion of plasma cells in the alveoli.
Wagner et al. (1969) exposed 2 groups of 12 squirrel monkeys for 23 months
to beryl dust (620 ug Be/m ) and bertrandite dust (210 ug Be/m ). Exposure was
generally for six hours a day, five days a week. While both dusts caused macro-
phage clusters, no other marked changes were seen compared to the controls.
The effects of beryllium oxide calcined at 1400°C were studied by Conradi
et al. (1971). Five monkeys received inhalation exposures with concentrations
3
varying between 3.3 and 4.4 mg Be/m . Exposure was for 30 minutes at 3 monthly
intervals. After two years follow-up, histological examinations were negative
and no other differences were noted between controls and exposed animals.
5-15
-------
Conradi et al. (1971) studied six dogs exposed in the same way as the mon-
keys. No pathological changes were observed.
Robinson et al. (1968) exposed two dogs for 20 minutes to rocket exhaust
products containing mixtures of beryllium oxide, beryllium fluoride, and beryl-
o
lium chloride at average concentrations of 115 mg beryllium/m. The dogs were
observed for a period of three years and were then killed. Immediately after
exposure the dogs had some acute symptoms, but during the rest of the study
they remained clinically healthy. Histological examination of the lungs showed
small foci of granulomatous inflammation scattered throughout the lungs of both
dogs. Beryllium deposits were also found in the lungs. The average beryllium
content of the lungs of these dogs was 3.9 and 5.5 mg/kg wet weight.
Granulomatosis has also been shown in guinea pigs exposed to beryllium
oxide dust (Policard, 1950; Chiappino et al., 1969). In the guinea pig, it
is possible to produce beryllium sensitivity, and this is thought to have some
protective effect against the development of pulmonary disease (Reeves et al.,
1971; Reeves et al., 1972). Barna et al. (1981) studied two strains of guinea
pigs given intratracheal injections of 10 mg of beryllium oxide. All of the
animals in one strain developed granulomatous lung disease, whereas the animals
in the other strain did not, indicating genetic differences in beryllium
sensitivity. The latter animals also showed negative skin tests and lymphocyte
transformation tests, whereas positive reactions were seen in the group with the
lung reactions. Administration of the immunosuppressive drug prednisone had a
beneficial effect on the animals with lung disease. However, this effect lasted
only as long as treatment continued. Further studies by Barna et al. (1984a,b)
have confirmed these findings. Barna and co-workers observed that beryllium
exerted a more direct toxic effect on alveolar macrophages in nonsensitized
animals.
Wagner et al. (1969) exposed two groups of hamsters, 48 animals in each
group, for 17 months to beryl and bertrandite dust under the same exposure con-
ditions previously described above for rats and squirrel monkeys. After six
months of exposure, the bertrandite-exposed animals had a few granulomatous
lesions in the lungs, and in both groups there were some atypical cell prolifer-
ations.
It is noteworthy that rats, in the various studies showing differing degrees
of granulomatosis, have not developed beryllium hypersensitivity (Reeves, 1978).
5-16
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There have also been some experimental studies of chronic, oral beryllium
exposure. In some early studies (Guyatt et al., 1933; Jacobson, 1933; Kay and
Skill, 1934), rickets was produced in young animals by giving large doses of
beryllium carbonate (0.1-0.5 percent; 1000-5000 mg/kg food). This effect has
since been regarded as an indirect result of the binding of phosphate to beryl-
lium in the gut and, consequently, phosphorus depletion in the body.
Schroeder and Mitchener (1975a,b) gave rats and mice beryllium in drinking
water at a concentration of 5 mg/1 for the duration of their lifetimes. No con-
sistent differences were noticed between exposed animals and controls with regard
to weight or life span. In a two-year feeding study, Morgareidge et al. (1977,
abstract) fed rats dietary concentrations of 5, 50, and 500 mg Be/kg. The
highest dose level resulted in a slight decrease in weight. Specific details
about the results were not reported.
A large number of studies have been conducted on beryllium compounds injec-
ted into animals. Some of these are mentioned in Section 7.1 on experimental
carcinogenicity. Some of these studies have also been presented in earlier
documents on beryllium, especially with regard to the effect of beryllium on
enzymes (Drury et al., 1978). However, these injection studies are less rele-
vant than inhalation or ingestion studies for understanding the action of beryl-
lium in humans.
5.2.2 Teratogem'c and Reproductive Effects of Beryllium
5.2.2.1 Human Studies. There are no known studies on the possible teratogenic
and reproductive effects of beryllium in humans.
5.2.2.2 Animal Studies. Very few studies have investigated the teratogenic or
reproductive effects of beryllium in animals. Only three such studies exist:
one that evaluates the behavior of the offspring of mice exposed to beryllium
sulfate during pregnancy (Tsujii and Hoshishima, 1979), one that deals with
the ability of beryllium chloride to penetrate the placenta (Bencko et al., 1979),
and another concerned with the effects of beryllium chloride on developing chick
embryos (Puzanova et al., 1978).
Hoshishima et al. (1978) presented a brief abstract and, later, a more
extensive report (Tsujii and Hoshishima, 1979) on the effects of trace amounts
of beryllium injected into pregnant CFW strain mice. Six female mice were
exposed to 22 compounds of metals, including BeSO. (140 ng/mouse/day). The mice
received intraperitoneal injections (0.1 ml) 11 times during pregnancy. The
5-17
-------
injections were given once daily for three consecutive days and then every other
day for an additional eight treatments. The gestational days of treatment were
not reported. In this study, beryllium (140 ng/day or ~ 5 ug/kg/b.w.) produced
the following differences in the offspring of the metal-exposed dams as compared
to the offspring from a control group: delayed response in head turning in a
geotaxis test, acceleration in a straight-walking test, delayed (for a moment)
bar-holding response, and acceleration of bar holding (for 60 seconds).
In a study by Bencko et al. (1978), the soluble salt of beryllium, BeCl?,
was evaluated for its ability to penetrate the placenta and reach the fetus.
Radiolabelled BeCK was injected into the caudal vein of seven to nine ICR SPF
mice and was administered in three different time periods: (1) before copulation
(group A), (2) the 7th day of gestation (group B), and (3) the 14th day of gesta-
tion (group C). The animals were sacrificed on the 18th to 19th day of preg-
nancy and the radioactivity associated with the fetal and maternal compartments
was evaluated. In group C, higher levels of radioactivity were associated with
the fetuses than were associated with fetuses of other exposure periods (group
A, 0.0002 ug Be/g fetus; group B, 0.0002 ug Be/g fetus; and group C, 0.0013
ug Be/g fetus). The amount of radioactivity in the various organs of the
fetus was generally not influenced by beryllium exposure except in the spleen
and liver. The amount of Be penetrating the spleen was decreased, while in
the liver it was increased when Bed was given on the 14th day of pregnancy.
Puzanova et al. (1978) conducted studies on the effects of beryllium on the
development of chick embryos. BeCl? (300 to 0.00003 ug dissolved in 3 ul
twice-distilled water) was injected subgerminally into chick embryos (10 embryos
per dose) on the second day of embryogenesis. After a 24-hour incubation, the
eggs were opened and stained with 0.1 percent neutral red so that the distance
between the origin of the vitelline arteries and the caudal tip of the body
could be measured. In a second part of this experiment, the same doses of BeClp
were administered subgerminally to two-day-old embryos and intra-amniotically to
three- and four-day-old embryos. The surviving embryos were examined after the
6th day of incubation.
In the first part of the experiment, it was found that 300 ug BeClp killed
all of the embryos, whereas 0.3 ug was not lethal to any. Doses of 0.003 ug and
less had no observable effects on the development of the embryos. When the eggs
were treated on day two, the most common malformation was caudal regression, open
5-18
-------
abdominal cavity, and ectopia cordis. When administered on the fourth day, exe-
cephalia, mandibular malformation, and malformations described as the "strait-
jacket syndrome" were reported. It is not known, however, if these types of
teratogenic effects in chick embryos are reflective of effects that might occur
in humans. Additional studies would have to be done using mammals to determine
whether beryllium has teratogenic potential.
Considered collectively, current data are not sufficient to determine
whether beryllium compounds have the potential to produce adverse reproductive
or teratogenic effects. It should be noted that the studies discussed above
were not designed to specifically investigate the effects of beryllium compounds
on reproduction or the developing conceptus. Further studies in this area are
desirable.
5-19
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6. MUTAGENIC EFFECTS OF BERYLLIUM
Beryllium has been tested for its ability to cause genetic damage in both
prokaryotic and eukaryotic organisms. The prokaryotic studies include gene
mutations and DMA damage in bacteria. The eukaryotic studies include DNA damage
and gene mutations in yeast and cultured mammalian cells, and studies of
chromosomal aberrations and sister-chromatid exchanges in mammalian cells i_n
vitro. The available literature indicates that beryllium has the potential to
cause gene mutations, chromosomal aberrations, and sister-chromatid exchange in
cultured mammalian somatic cells.
6.1 GENE MUTATIONS IN BACTERIA AND YEAST
The studies on beryl 1iurn-induced gene mutations in bacteria and yeast are
summarized in Table 6-1.
6.1.1 Salmonella Assay
Beryllium has been tested for its ability to cause reverse mutations in
Salmonella typhimurium (Simmon, 1979a; Rosenkranz and Poirier, 1979).
Simmon (1979a) found that beryllium sulfate was not mutagenic in Salmonella
strains TA1535, TA1536, TA1537, TA98, and TA100. Agar-incorporation assay, with
and without S-9 metabolic activation, was employed. The highest concentration of
beryllium sulfate tested was 250 ug/plate (12.5 ug Be). No mutagenic response
was obtained in any of the above strains.
Beryllium sulfate was also not mutagenic in Salmonella typhimurium strains
TA1535 and TA1538, both in the presence and absence of the S-9 activation system
(Rosenkranz and Poirier, 1979). The two concentrations of the test compound used
were 25 ng/plate and 250 (jg/plate. No significant differences in the mutation
frequencies between the experimental and the control plates were noted.
6.1.2 Host-Mediated Assay
Negative mutagenic response of beryllium sulfate was obtained in the
host-mediated assay (Simmon et al., 1979). Several procedures were used. In
all procedures the tester strain was injected intraperitoneally and the beryl-
lium sulfate was given orally or by intramuscular injection. Four hours later,
the Salmonella or Saccharomyces tester strain was recovered from the peritoneal
6-1
-------
TABLE 6-1. MUTAGENICITY TESTING OF BERYLLIUM: GENE MUTATIONS IN BACTERIA AND IN YEAST
cr>
i
ro
Test System
Salmonel la
typhimurium
Salmonel la
typhimurium
Saccharomyces
cerevisiae
Salmonella
typhimurium
Escherichia
coli
Strain
TA1535
TA1536
TA1537
TA100
TA98
TA1530
TA1538
TA1535
D3
TA1535
TA1538
WP2
Concentration of S-9 Activation
Test Compounds as Be System
Maximum of ±
12.5 (jg/plate
Unknown Host-mediated
[Given either as assay in mice
i.m. injections
(25 mg/kg) or by
gavage (1200mg/kg
beryllium sulfate)]
1.25 ug/plate ±
12.5 ug/plate
0.9-90 (jg/plate
Results
Reported
negative
in al 1
strains
Reported
negative
in al 1
strains by
both routes
of exposure
Reported
negative
Reported
negative
Comments Reference
1. Only highest Simmon, 1979a
concentration
used.
Simmon et al . ,
1979
Rosenkranz and
Poirier, 1979
Ishizawa,
1979
-------
cavity and plated to determine the number of mutants (Salmonella) or recombi-
nants (Saccharomyces) and the number of recovered microorganisms. Simultaneous
experiments were conducted with control (untreated) mice. Using 25 mg/kg given
intramuscularly, beryllium sulfate was not mutagenic with tester strain TA1530
or TA1538. Using 1200 mg/kg given orally, beryllium sulfate was not mutagenic
in TA1535 and did not significantly increase the recombination frequency in
S. cerevisiae D3.
6.1.3 Escherichia coli WP2 Assay
A negative mutagenic response in the Escherichia coli WP2 system was obtained
with beryllium concentrations ranging from 0.1 to 10 (jmol/plate (10.5-105 ug
Be/plate) (Ishizawa, 1979). These results should not be taken as proof, however,
that beryllium is not mutagenic. The standard test system may be insensitive for
the detection of metal mutagens because of the large amount of magnesium salts,
citrate, and phosphate in the minimal medium (McCann et al., 1975). Bacteria
appear to be selective in which metal ions are internalized. More research is
needed to select a suitable strain of bacteria to detect metal-induced muta-
genesis in these prokaryotic systems.
6.2 GENE MUTATIONS IN CULTURED MAMMALIAN CELLS
The ability of various beryllium compounds to cause gene mutations in
cultured mammalian cells has been investigated by Miyaki et al. (1979) and Hsie
et al. (1979a,b) (Table 6-2).
Miyaki et al. (1979) demonstrated the induction of 8-azaguanine-resistant
mutants by beryllium chloride in the Chinese hamster V79 cells. Beryllium
chloride at concentrations of 2 and 3 mM (18 and 27 ug Be/ml, respectively)
induced 35.01 ± 1.4 and 36.5 ± 1.7 mutant colonies per 10 survivors. These
values were approximately six times higher than the control value of 5.8 ± 0.8
colonies per 10 survivors. The cell survival rates were 56.9 percent at 2 mM
concentration and 39.4 percent at 3 mM. Analysis of mutant colonies revealed
that they were deficient in the enzyme hypoxanthine guanine phosphoribosyl
transferase (HGPRT) activity indicating that the mutation had occurred at the
HGPRT locus.
Hsie et al. (1979a,b) also reported that beryllium sulfate induced 8-
azaguanine-resistant mutants in Chinese hamster ovary (CHO) cells. However,
6-3
-------
TABLE 6-2. MUTAGENICITY TESTING OF BERYLLIUM: GENE MUTATIONS IN MAMMALIAN CELLS IN VITRO
cr>
i
Test System
Chinese
hamster
Chinese
hamster
Concentration of
Strain Test Compounds as Be
V79 cells; 18 ug/ml
resistance 27 ug/ml
to 8-
azaguanine
CHO cells; Not stated
resistance
to 8-
azaguanine
S-9 Activation
System Results
None Reported
positive
6.0 to
6.3-fold
increase
± Reported
mutagenic
and weakly
mutagenic
Comments Reference
1. 99 percent Miyaki et al.,
pure. 1979
2. No dose
response.
1. No details. Hsie et al . ,
2. The authors 1979 a,b
noted variable
results with
noncarcinogens
such as calcium.
-------
they did not provide details about the concentrations of the test compound and
the number of mutants induced per 10 survivors.
These studies indicate that beryllium has the ability to cause gene
mutations in cultured mammalian cells.
6.3 CHROMOSOMAL ABERRATIONS
Beryllium sulfate was tested for its clastogenic potential in cultured
human lymphocytes and Syrian hamster embryo cells (Larramendy et a!., 1981)
(Table 6-3). Cultured human lymphocytes (24-hours old) were exposed to a single
concentration, 2.82 x 10 M (0.25 ug Be/ml), of beryllium sulfate, and chromosome
preparations were made 48 hours after the treatment. A minimum of 200 meta-
phases were scored for chromosomal aberrations. In cultures treated with
beryllium, there were 19 cells (9.5 percent) with chromosomal aberrations, or
0.10 ± 0.02 aberration per metaphase. In the nontreated control cells, only 3
cells (1.5 percent) had chromosomal aberrations. This sixfold increase in the
aberration frequency clearly indicates that beryllium sulfate is clastogenic in
cultured human lymphocytes. A beryllium concentration of 2.82 x 10 M was
selected because it induced a maximum number of sister-chromatid exchanges in
human lymphocytes in another experiment reported by the same authors (see
Section 6.4).
In the Syrian hamster embryo cells the results were even more dramatic.
This same concentration of beryllium sulfate induced aberrations in 38 out of
200 cells (19 percent) 24 hours after the treatment. The number of aberrations
per metaphase was 0.12 ± 0.03. In control cells, only 3 cells (1.5 percent) had
aberrations, or 0.01 ± 0.01 aberration per cell. In these studies, chromosomal
gaps were also considered as aberrations. Even if the gaps were not included as
true aberrations, the aberration frequency was still far above the control
level, indicating that beryllium sulfate has clastogenic potential in cultured
mammalian eel Is.
6.4 SISTER CHROMATID EXCHANGES
Larramendy et al. (1981) also studied the potential of beryllium to induce
sister chromatid exchanges (Table 6-3). Both cultured human lymphocytes and
Syrian hamster embryo cells were used in these studies.
After 24 hours of cultivation, lymphocytes were exposed to increasing con-
centrations of beryllium sulfate (0.05, 0.125, and 0.25 ug Be/ml) followed by 10
6-5
-------
TABLE 6-3. MUTAGENICITY TESTING OF BERYLLIUM: MAMMALIAN IN VITRO CYTOGENETICS TESTS
cr>
cr>
Test System
Chromosomal
aberrations
Chromosomal
aberrations
Sister
chromatid
exchanges
Sister
chromatid
exchanges
Concentration of
Strain Test Compounds as Be
Human
lymphocytes
Syrian
hamster
embryo
cells
Human
lymphocytes
Syrian
hamster
embryo
cells
0.25 (jg/ml
0.25 |jg/ml
0.05 ng/ml
0.125 ug/ml
0.25 ug/ml
0.05 ug/ml
0.125 ug/ml
0.25 ug/ml
S-9 Activation
System Results
Reported
positive
Reported
positive
Reported
positive
Reported
positive
Comments
1. 6x above
background level .
2. Primarily
breaks.
1. 12x above
background level.
2. Primarily
breaks and gaps.
1. Less than two-
fold increase.
2. Insufficient
evidence for a
positive conclu-
sion.
1. Less than two-
fold increase.
2. Insufficient
evidence for a
positive conclu-
sion.
Reference
Larramendy
et al . , 1981
Larramendy
et al. , 1981
Larramendy
et al. , 1981
Larramendy
et al. , 1981
-------
ug BrdUrd/ml medium. Cultures were incubated for an additional 48 hours and
chromosome preparations were made and stained for sister-chromatid exchange
analysis. At least 30 metaphases were scored for each concentration of the test
compound. The background sister-chromatid exchange level was 11.30 ± 0.60.
According to these investigators, there was a dose-dependent increase in sister-
chromatid exchanges, i.e. 17.75 ± 1.10, 18.15 ± 1.79, and 20.70 ± 1.01, respec-
tively, for the above concentrations.
In the Syrian hamster embryo cells, the same concentrations of beryllium
sulfate induced 16.75 ± 1.52, 18.40 ± 1.49, and 20.50 ± 0.98 sister-chromatid
exchanges. The background sister-chromatid exchange frequency was 11.55 ± 0.84.
The sister-chromatid exchange assay has been extensively used in mutagenicity
testing because of its sensitivity to many chemicals.
The authors stated that the results of the sister-chromatid exchange
studies in human lymphocytes and Syrian hamster embryo cells demonstrated a
dose-response relationship. However, in these studies, the increase was less
than twofold and fell within a plateau region. Thus, the dose-response rela-
tionship suggested by the authors may be somewhat tenuous. Further experimen-
tation to confirm the study results are advisable.
6.5 OTHER TESTS OF GENOTOXIC POTENTIAL
6.5.1 The Rec Assay
Kanematsu et al. (1980) found that beryllium sulfate was weakly mutagenic
in the rec assay. Bacillus subtil is strains H17 (rec+) and M75 (reef) were
streaked onto agar plates. An aqueous solution (0.05 ml) of 0.01 M (4.5 |jg
Be/plate) beryllium sulfate was added to a filter paper disk (10-mm diameter)
placed on the plates at the starting point of the streak. Plates were first
cold incubated (4°C) for 24 hours and then incubated at 37°C overnight.
Inhibition of growth due to DMA damage was measured in both the wild-type H17
(rec ) and the sensitive-type ( rec ) strains. The difference in growth
inhibition between the wild-type strain and the sensitive strain was 4 mm, which
was considered to indicate a weak mutagenic response. Similar results were also
obtained by Kada et al. (1980).
6.5.2 Pol Assay
Beryllium was tested for mutagenicity in the pol assay using Escherichia
coli (Rosenkranz and Poirier, 1979; Rosenkranz and Leifer, 1980). This assay
is based on the fact that cells deficient in DNA repair mechanisms are more
6-7
-------
sensitive than normal cells to the growth-inhibiting properties of mutagenic
agents. Escherichia coli strains pol A (normal) and pol A (DMA polymerase
I-deficient) were grown on agar plates, and filter disks impregnated with 250
(jg of beryllium sulfate were placed in the middle of each agar plate and incu-
bated at 37°C for 7 to 12 hours. Experiments were conducted both in the pre-
sence and absence of an S-9 activation system. There was no difference in the
diameter of the zones of growth in either strain. Positive and negative con-
trols were used for comparison. The shortcomings of this assay are that (1)
conclusions can be drawn only when measurable zones of growth inhibition occur;
(2) it is possible that the test chemical may not be able to penetrate the
test organisms; and (3) insufficient diffusion of chemicals from the disk can
occur because of low solubility or large molecular size.
6.5.3 Hepatocyte Primary Culture/DMA Repair Test
DNA damage and repair, as reflected by unscheduled DMA synthesis (incor-
poration of tritiated thymidine), was examined for beryllium sulfate by Williams
et al. (1982). Rat primary hepatocyte cultures were exposed to 0.1, 1, and
10 mg/ml of beryllium sulfate with 10 |jCi/ml of tritiated thymidine and incu-
bated for 18 to 20 hours. Following incubation, autoradiographs of cells were
prepared. A minimum of 20 nuclei was counted for each concentration and the
uptake of radioactive label was measured as grain counts in each nucleus.
The compound was considered positive when the nuclear grain count was five
grains per nucleus above the control value. The compound was considered
negative in the assay if the nuclear grain count was less than five at the
highest nontoxic dose. Cytotoxicity was determined by the morphology of the
cells. According to the authors, beryllium sulfate did not induce a statisti-
cally greater grain count at any of the concentrations. Benzo(a)pyrene was
employed as a positive compound.
6.5.4 Beryllium-Induced DNA Cell Binding
Kubinski et al. (1981) reported that beryllium induces DNA protein com-
plexes (adducts) that can be measured. Escherichia coli cells and Ehrlich
ascitis cells were exposed to radioactive DNA in the presence of 30 uM of
beryllium. Methyl methanesulfonate (MMS) was used as a positive control. The
negative control consisted of cells only and radioactive DNA. The radioactive
DNA bound to cell membrane proteins was measured, and, like MMS, beryllium
6-8
-------
induced positive results. However, the significance of beryllium-induced DNA
binding to cell membranes is not clear in terms of its ability to induce
mutations.
6.5.5 Mitotic Recombination In Yeast
Beryllium sulfate did not induce mitotic recombination in the yeast
Saccharomyces cerevisiae D^ (Simmon, 1979b). The S. cerevisiae strain Do is a
heterozygote with mutations in ade 2 and his 8 of chromosome XV. When grown on
a medium containing adenine, cells homozygous for the ade 2 mutation produce a
red pigment. These homozygous mutants can be generated from the heterozygotes
by mitotic recombination induced by mutagenic compounds. A single concentration
(0.5 percent) of beryllium induced 10 mutant colonies per 10 survivors, while
5
in the control the mutant frequency was 6 colonies per 10 . In the mitotic
recombination assay, there must be a threefold increase in the mutant frequency
of experimental over the control in order to be considered a positive mutagenic
response. The negative mutagenic response of beryllium may be due to an in-
ability of beryllium to penetrate yeast cells.
6.5.6 Biochemical Evidence of Genotoxicity
Several i_n vitro experiments of the genotoxic potential of beryllium have
been reported. In one study, j_n vitro exposure of rat liver cells to beryllium
resulted in its binding to phosphorylated non-histone proteins (Parker and
Stevens, 1979). Perry et al. (1982) found that exposure of cultured rat hepa-
tosomal cells to beryllium reduced the glucocorticoid induction of tryosine
transaminase activity. In a DNA fidelity assay, beryllium increased the mis-
incorporation of nucleotide bases in the daughter strand of DNA synthesized
i_n vitro from polynucleotide templates (Zakour et al., 1981). Beryllium has
also been investigated for its effects on the transcription of calf thymus DNA
and phage T, DNA by RNA polymerase (from E. coli) under controlled conditions.
Beryllium inhibited overall transcription but increased RNA chain initiation,
indicating the interaction of the metal with the DNA template (Niyogi et al.,
1981).
6.5.7 Mutagenicity Studies in Whole Animals
Information on the mutagenicity of beryllium compounds in whole animal
organisms, such as Drosophila and mammals, is not available in the literature.
6-9
-------
Such studies would be highly valuable for assessing the j_n vivo effects of beryl-
lium compounds, in particular to learn whether or not they induce mutations in
germ cells. Metals such as cadmium and methyl mercury have been implicated in
the induction of aneuploidy (numerical chromosomal aberrations) in female rodent
germ cells. Aneuploidy is generally induced as a result of malfunctioning of
the spindle apparatus. Such studies with beryllium compounds would yield
valuable information.
6-10
-------
7. CARCINOGENIC EFFECTS OF BERYLLIUM
The purpose of this section is to evaluate the carcinogenic potential of
beryllium, and on the assumption that beryllium is a human carcinogen, to esti-
mate its potency relative to other known carcinogens, as well as its impact on
human health.
The estimation of the carcinogenic potential of beryllium relies on animal
bioassays and epidemiological studies. However, studies on the mutagenicity,
DNA interaction, and metabolism of beryllium are also important for the quali-
tative and quantitative assessment of its carcinogenicity. Because the latter
are specifically dealt with elsewhere in this document, this section focuses on
animal and epidemiological studies as well as the dose-response (i.e. quantita-
tive) aspects of beryllium carcinogenicity. Summary and conclusions sections
highlight the most significant aspects of beryllium carcinogenicity.
7.1 ANIMAL STUDIES
Numerous animal studies have been performed to determine whether or not
beryllium and beryllium-containing substances are carcinogenic. In these
studies, metallic beryllium, salts of beryllium, and beryllium-containing
alloys and ores were administered by various routes. In the discussions that
follow, the studies are grouped according to the route of administration.
7.1.1 Inhalation Studies
The first report of pulmonary tumors after exposure to beryllium by
inhalation was made by Vorwald (1953). Four of 8 female rats exposed to
3
beryllium sulfate (BeSO.) aerosol (at 33 ug Be/m , 7 hrs/d, 5.5 d/wk) for one
year developed primary pulmonary adenocarcinomas. The rate was 80 percent
(4/5) for animals necropsied after 420 days of exposure. This study was pre-
sented in a paper read before a meeting of the American Cancer Society, but
was never published; an abstract of the presentation was printed two years
later (Vorwald et al., 1955).
Schepers et al. (1957) updated the Vorwald study to include 136 rats, 78
of which survived to planned necropsy. Tumors were counted after the animals
had been exposed for 6 months to beryllium sulfate aerosol followed by up to 18
7-1
-------
months in normal air. The total number of tumors (76) -- not the number of
tumor-bearing animals -- was counted. Eight histologic variants of neoplasms
were observed. Intrathoracic metastases were also noted, and transplantation
was successful in several cases.
During the late 1950s and early 1960s, both Schepers and Vorwald continued
their experiments. Unfortunately, because these studies were never published,
details are often lacking, although some of the results have been alluded to in
subsequent reviews (Schepers, 1961; Vorwald et al., 1966). It can be surmised
that Schepers observed 35 to 60 tumors in 170 rats (21-35%) exposed to beryllium
3
phosphate at a concentration of 32 to 35 ug Be/m , and 7 tumors in 40 animals
(17.5%) at 227 ug Be/m . After exposure to beryllium fluoride, he obtained a
tumor rate of 10 to 20 in 200 animals (5-10%) exposed to 9 ug Be/m3. With zinc
beryllium manganese silicate (ZnEeMnSiO,), a fluorescent phosphor in use at that
time, the tumor rate was 4 to 20 in 220 animals (2-9%) exposed to 0.85 to 1.25
3
mg Be/m (Table 7-1). No tumors were observed in similarly exposed rabbits or
guinea pigs.
In all but one of his inhalation experiments, Vorwald exposed rats to
beryllium sulfate aerosol at concentrations ranging from 2.8 to 180 ug Be/m at
exposure schedules of 3 to 24 months. In one experiment, beryllium oxide was
3
used at 9 mg/m (temperature of firing not given). Pulmonary lesions believed
to be adenocarcinomas were found in all groups at frequencies ranging from 20
to 100 percent. Weak correlations were observed between tumor rate and expo-
sure concentrations, and between tumor rate and exposure length (Table 7-2).
No metastases were observed, and serial homotransplants were unsuccessful.
Reeves et al. (1967) exposed 150 rats of both sexes, and an equal number
of controls, to beryllium sulfate aerosol at a mean concentration of 34.25 ±
3
23.66 ug Be/m for 35 hours a week. Sacrifices were conducted quarterly. The
first lung tumors were seen at 9 months, and by 13 months all 43 animals
necropsied had pulmonary adenocarcinomas. Similar results were reported by
Reeves and Deitch (1969) two years later for another animal group. In the
latter study, 225 female rats of various ages were exposed for 3 to 18 months
3
to 35.66 ± 13.77 ug Be/m (35 hrs/wk) (Figure 7-1). It was found that tumor
yield depended not on length of exposure but on age at exposure. Rats exposed
at an early age for only 3 months had essentially the same tumor frequency
(19/22; 86%) as rats exposed for the full 18 months (13/15; 86%), whereas rats
receiving the 3-month exposure later in life had substantially reduced tumor
7-2
-------
TABLE 7-1. PULMONARY CARCINOMA FROM INHALATION EXPOSURE TO BERYLLIUM
Atmospheric
concentration
Compound Species (jg/m3 as Be
BeS04 Rats 33-35
33-35
32-35
55
180
18
18
18
18
1.8-2.0
1.8-2.0
1.8-2.0
21-42
2.8
34
36
36
36
36
36
Monkeys 35-200
38.8
Weekly
exposure
time
(hours)
33-38
33-38
44
33-38
33-38
33-38
33-38
33-38
33-38
33-38
33-38
33-38
33-38
33-38
35
35
35
35
35
35
42
15
Duration
of
exposure
(months)
12-14
13-18
6-9
3-18
12
3-22
8-21
9-24
11-16
8-21
9-24
13-16
18
18
13
3
6
9
12
18
8
36+
Incidence
of
pulmonary
carcinoma
4 in 8
17 in 17
58 in 136
55 in 74
11 in 27
72 in 103
31 in 63
47 in 90
9 in 21
25 in 50
43 in 95
3 in 15
Almost all
13 in 21
43 in 43
19 in 22
33 in 33
15 in 15
21 in 21
13 in 15
0 in 4
8 in 11
Reference
Vorwald, 1953
Vorwald et al. , 1955
Schepers et al. , 1957
Vorwald, 1962
Vorwald, 1962
Vorwald, 1962
Vorwald, 1962
Vorwald, 1962
Vorwald, 1962
Vorwald, 1962
Vorwald, 1962
Vorwald, 1962
Vorwald et al. , 1966
Vorwald et al. , 1966
Reeves, 1967
Reeves and Deitch,
1969
Reeves and Deitch,
1969
Reeves and Deitch,
1969
Reeves and Deitch,
1969
Reeves and Deitch,
1969
Schepers, 1964
Vorwald, 1968
(continued on the following page)
7-3
-------
TABLE 7-1. (continued)
Compound
BeS04
BeHP04
BeF2
ZnBeMnSi03
Beryl ore
Betrandite
ore
Species
Guinea pigs
Rats
Monkeys
Rats
Monkeys
Rats
Rabbits
Guinea pigs
Rats
Hamsters
Monkeys
Rats
Hamsters
Monkeys
Weekly Duration
Atmospheric exposure of
concentration time exposure
ug/m3 as Be (hours) (months)
35
36
3.7-30.4
^15
32-35
227
200
1100
8300
9
180
700
700
700
620
620
620
210
210
210
NR
35
35
35
NR
NR
42
42
42
NR
42
NR
NR
NR
30
30
30
30
30
30
12
12
18-24
18-24
1-12
1-12
8
8
8
6-15
8
9
24
22
17+
17+
17+
17+
17+
17+
Incidence
of
pulmonary
carcinoma
0
2 in 20
0 in 58
0 in 110
35-60 in
170*
7 in 40*
0 in 4
1 in 4
0 in 4
10-12 in
200
0 in 4
4-20 in
220*
0
0
18 in 19
0 in 48
0 in 12
0 in 30-60
0 in 48
0 in 12
Reference
Schepers, 1961
Schepers, 1971
Reeves, 1972
Reeves, 1976
Schepers, 1961
Schepers, 1961
Schepers, 1964
Schepers, 1964
Schepers, 1964
Schepers, 1961
Schepers, 1964
Schepers, 1961
Schepers, 1961
Schepers, 1961
Wagner et al . , 1969
Wagner et al. , 1969
Wagner et al . , 1969
Wagner et al . , 1969
Wagner et al . , 1969
Wagner et al. , 1969
*Number of tumors per number of animals exposed.
NR: Not reported.
Source: Adapted from Reeves (1978)
7-4
-------
TABLE 7-2. PULMONARY CARCINOMA FROM EXPOSURE TO BERYLLIUM VIA INTRATRACHEAL INSTILLATION
I
en
Compound
ZnBeMnSi03
Be Stearate
Be(OH)
Be Metal
Be 0
Species
Rabbits, rats, and guinea pigs
Rabbits, rats, and guinea pigs
Rabbits, rats, and guinea pigs
Rabbits, rats, and guinea pigs
Rabbits, rats, and guinea pigs
Rats
Monkeys
Total
dose
(mg)
0.46
2.3-6.9
3.4
5.0
31
54
75
.338
18-90+
Incidence
of
pulmonary
carcinoma
0
0
0
0
0
0
0
1 in 4
3 in 20
Reference
Vorwald,
Vorwald,
Vorwald,
Vorwald,
Vorwald,
Vorwald,
Vorwald,
Vorwald,
Vorwald,
1950
1950
1950
1950
1950
1950
1950
1953
1968
Source: Adapted from Reeves (1978)
-------
I
cr>
AGE MO.
EXP. MRS.
M|A|M|J|J|A|S|O|N|D)J| FJM|A|M|J |J|A|S|O|N|D|J| F |M
2400 (CHAMBER TIMER!
| EXPOSURE TO 35y Be (as SO«)/m>
35 Hrs./Wk.
• ANIMAL LOST
A NO TUMOR
o SMALL TUMOR
O LARGE TUMOR
Figure 7*1. Pulmonary tumor incidence in female rats, 1965-1967.
Source: Reeves and Deitch (1969).
-------
counts (3-10/20-25; 15-40%). Generally, an incubation time of at least 9 months
after commencement of exposure was required to produce actual tumors. Epithe-
lial hyperplasia of the alveolar surfaces commenced after about 1 month,
progressed to metaplasia by 5 to 6 months, and to anaplasia by 7 to 8 months.
In guinea pigs, 18 months of exposure (35 hrs/wk) to three different concentra-
tions of beryllium sulfate (3.7 ± 1.5 ug Be/m3, 16.6 ± 8.7 ug Be/m3, and 30.4 ±
10.7 pg Be/m3) produced only alveolar hyperplasia/metaplasia (associated with
diffuse interstitial pneumonitis) in 23 of 144 animals. No tumors were seen.
The rate of hyperplasia/metaplasia in unexposed controls was 3/55 (Reeves et al.,
1971, 1972; Reeves and Krivanek, 1974). Schepers (1971) reported the occurrence
of lung tumors in 2 of 20 guinea pigs exposed to beryllium sulfate (at 36 ug
o
Be/m , 35 hrs/wk) for one year. While these results are suggestive of a positive
effect when compared to the very low background incidence of tumors in guinea
pigs, very little detail was given in the report to reach definitive conclusions.
Sanders et al. (1978) exposed female rats to submicron aerosols of medium-
fired (1000°C) beryllium oxide by the nose-only method for a single exposure
period of 30 to 180 minutes. Only 1 of 184 rats developed a lung tumor during
the two-year observation period. Alveolar deposition of beryllium ranged from
1 to 91 ug beryllium, with a lung clearance half-time of 325 days.
Wagner et al. (1969) exposed rats, hamsters, and squirrel monkeys to aero-
sols of beryl ore and bertrandite ore at what was then regarded as the "nuisance
2
limit" for all dusts (15 mg/m ). At this particle concentration, the beryllium
content of the aerosols was 620 and 210 ug Be/m for beryl and bertrandite,
respectively. Exposure was continued intermittently for 17 months. Of the 19
rats exposed to beryl dust, 18 had bronchiolar or alveolar cell tumors, 7 of
which were judged to be adenomas, 9 adenocarcinomas, and 2 epidermoid tumors.
Metastases were not observed, and transplants were not attempted. No indispu-
table tumors were found in either hamsters or squirrel monkeys exposed to beryl
dust, although atypical proliferations were seen in the hamsters which, accord-
ing to the authors, "could be considered alveolar cell tumors except for their
size." There were no indisputable tumors in any of the animals exposed to
bertrandite dust. However, granulomatous lesions were seen in each species and
"atypical proliferations" of the cells lining the respiratory bronchioles and
alveoli were seen in the rats and hamsters.
Schepers (1964) found that among 20 female rhesus monkeys exposed for
eight months by inhalation to beryllium sulfate (BeSO.), beryllium phosphate
(BeHPO,), or beryllium fluoride (BeFp) (concentrations ranging from 0.035 to
7-7
-------
8.3 mg Be/m ), only one animal had a small (3 mm) pulmonary neoplasm which
appeared to be an alveolar carcinoma. The animal was exposed to beryllium
3
phosphate at a concentration of 1.1 mg Be/m . The tumor was discovered on day
82 of exposure; however, its association with the beryllium exposure was
judged uncertain. Unfortunately, the eight-month exposure period used in the
study was probably insufficient to induce lung cancer in any of the monkeys.
Vorwald (1968) reported the outcome of a three-year chamber study on rhesus
monkeys intermittently inhaling beryllium sulfate aerosol, with exposures
3
averaging 15 hours a week, at a mean atmospheric concentration of 38.8 |jg Be/m .
Eight of 11 surviving monkeys had pulmonary tumors, with adenomatous patterns
predominating amid areas with epidermoid characteristics. Extensive metastases
to the mediastinal lymph nodes were seen, and in some animals there were
metastases to the bones, liver, and adrenals. No control animals were kept in
this experiment.
Dutra et al. (1951) exposed 5, 6, and 8 rabbits to beryllium oxide aerosol
(degree of firing unidentified) at 1, 6, and 30 mg Be/m , respectively, on a
25-hour-per-week schedule for 9 to 13 months. One rabbit in the group exposed
to 6 mg Be/m developed osteosarcoma of the pubic bone, with extension into the
contiguous musculature. Scattered tumors which were judged to be metastases of
the osteogenic sarcoma were seen in the lungs and spleen. The lungs also
exhibited extensive emphysema, interstitial fibrosis, and lymphocytic infil-
tration. Rabbits in the other groups remained free of malignancies.
7.1.2 Intratracheal Injection Studies
Intratracheal administration of beryllium compounds was used as a
substitute for inhalation in experiments by Vorwald (1953), Van Cleave and
Kaylor (1955), Spencer et al. (1965), Kuznetsov et al. (1974), Ishinishi et al.
(1980), and Groth et al. (1980). The fate and effects of beryllium compounds
deposited by intratracheal injection are not necessarily the same as those for
identical compounds deposited by inhalation. Intratracheal injection produces
an unnatural deposition pattern in the lungs and permits the entry of larger
particles that normally would be filtered out in the upper respiratory tract.
Dusts, therefore, frequently show longer pulmonary half-times after intra-
tracheal injection than after inhalation.
Vorwald (1953) found one lung tumor after intratracheal injection of 338 ug
beryllium (as beryllium oxide) and one "sarcoma" (site unidentified) after
7-8
-------
intratracheal injection of 33.8 ug beryllium (as sulfate). The induction of
lung cancer with intrathoracic metastases in rhesus monkeys following intra-
bronchial injection and/or bronchomural implantation of "pure" beryllium oxide
(firing temperature unknown) has been mentioned in a review, but without refer-
ence to any original publication (Vorwald et al., 1966).
Groth et al. (1980) intratracheally injected rats with dusts of beryllium metal,
passivated beryllium metal (with < 1% chromium), and various beryllium
alloys, as well as beryllium hydroxide. Lung tumors were observed after in-
jection of beryllium metal, passivated beryllium metal, and a beryllium-aluminum
alloy (containing 62% beryllium), but not after injection of other beryllium
alloys in which the beryllium concentration was less than four percent. The
injection of beryllium hydroxide into 25 rats yielded 13 cases of neoplasia, of
which six were judged to be adenomas and seven adenocarcinomas (Table 7-3). The
remaining animals had various degrees of metaplasia, which were regarded as
precancerous lesions. Several of the tumors were successfully transplanted.
The most detailed studies of intratracheal injections of beryllium were
reported by Spencer et al. (1965, 1968, 1972). High-fired (1600°C), medium-
fired (1100°C), and low-fired (500°C) specimens of beryllium oxide were injected
into rats. The rates of pulmonary adenocarcinomas were 3/28, 3/19, and 23/45
(11, 16, and 51%) in the three groups, respectively.
Ishinishi et al. (1980) intratracheally injected 30 rats with beryllium
oxide (calcined at 900°C) in 15 weekly doses of 1 mg each. Of 29 animals
examined 1.5 years later, seven (24%) had lung tumors, i.e. one squamous cell
carcinoma, one adenocarcinoma, four adenomas, and one malignant lymphoma. Of
the four adenomas, three had "strong histological architectures [of] suspected
malignancy" (Tables 7-4 and 7-5). The malignant lymphoma was found not only in
the lung, but also in the hilar lymph nodes and in the abdominal cavity, with
the primary site remaining undetermined. Six extrapulmonary lymphosarcomas,
fibrosarcomas, or other tumors were found in further injected animals but in
only one of the 16 control animals. The frequency of clearly malignant primary
pulmonary tumors in this experiment was 2/29, or seven percent.
7.1.3 Intravenous Injection Studies
In 1946, Gardner and Heslington, in a search to find the cause of an "unusual
incidence of pulmonary sarcoid" in the fluorescent light tube industry, inject-
ed zinc beryllium silicate (ZnBeSiQ-J into rabbits. They found osteosarcomas
7-9
-------
TABLE 7-3. BERYLLIUM ALLOYS—LUNG NEOPLASMS
Dose of
compound
Compounds (mg)
Be metal
Be metal
Passi vated
Passi vated
BeAl alloy
BeAl alloy
4% BeCu al
4% BeCu al
2.2% BeNi
2.2% BeNi
Be metal
Be metal
loy
loy
alloy
alloy
2.4% BeCuCo alloy
2.4% BeCuCo alloy
Saline
3D walim f
Cncham' c r\nt
2.5
0.5
2.5
0.5
2.5
0.5
2.5
0.5
2.5
0.5
2.5
0.5
-
^— 4-3-ilo«H -1- at
Dose of
Be
(mg)
2.
0.
2.
0.
1.
0.
0.
0.
0.
0.
0.
0.
-
- + 1 ti/Kn r\
5
5
5
5
55
3
1
02
056
Oil
06
012
•fr1 Krt 1 1 1 r-i
Total
no. rats
autopsied
16
21
26
20
24
21
28
24
28
27
33
30
39
/-i i-irtrt^T ^*-m f v*r\.
Autopsy intervals and lung
neoplasm frequencies (months)
1
0/5b
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
0/5
.
2-7
_
0/3
0/2
0/1
0/3
-
0/1
0/2
0/1
0/2
0/3
0/2
0/3
8-10
_
0/5
1/5
0/3
2/5
0/1
0/5
-
0/5
-
0/5
-
0/5
11-13
3/5
0/5
4/10
-
0/5
0/6
0/6
0/4
0/5
0/5
0/5
0/5
0/5
16-19
6/6
2/3
4/4
7/11
2/6
1/9
0/11
0/13
0/12
0/15
0/15
0/18
0/21
P value3
<0.0001
0.011
<0.0001
0.0001
0.043
0.30
•^ -1- ^»/-v 1 i i r\/-»
neoplasm frequency in the saline control group at the autopsy period of 16-19 months. Because of multiple com-
parisons with the control group, the individual P value must be 0.008 or less to be significant.
Number of rats with a lung neoplasm divided by total number of rats autopsied at the specified interval.
Source: Groth et al. (1980)
-------
TABLE 7-4. LUNG TUMOR INCIDENCE IN RATS AMONG BeO, As203 AND CONTROL GROUPS
Group
BeO (1 mg)*
As203 (1 mg)*
Control
Sex
M
M
M
Number of rats
surviving after
15 instillations
30/30
19/30
16
Average
545
546
398
Range
99-791
98-820
1-617
Malignant
tumor
2+(l)A
1
0
Benign
tumor
4
0
0
*Amount of one instillation Be or As.
AUnknown which is primary tumor or metastasis.
Source: Ishinishi et al. (1980)
TABLE 7-5. HISTOLOGICAL CLASSIFICATION OF LUNG TUMORS AND OTHER PATHOLOGICAL CHANGES
Group
BeO (1 mg as Be)
As203 (a mg as As)
Control
Sex
M
M
M
No. of
rats
29*
18*
16
Malignant
Squamous
cell
carcinoma
la
1
0
tumors (A)
Adeno-
carcinoma
lb
0
0
Benign tumors (B)
Malignant
lymphoma
(DC
0
0
Ade-
noma
4(3)A
0
0
All
tumors
(A + B)
[tumor
incidence
rats]
21.4%
5.6%
0
Squamous
cell
meta-
plasia
2
5
1
Osseous
metaplasia
1
2
0
Other
site
tumors
except
the lung
tumor
*l
3e
1
Coexistence of squamous cell carcinoma and adenocarcinoma.
Coexistence of adenocarcinoma and adenoma.
Malignant lymphoma in the left lobule of the lung, the lymphatic nodules in
the pulmonary hilus, and in the abdominal cavity.
Lymphosarcoma or fibrosarcomas (except one).
p
Mesothelioma in peritoneum, liver and mesentery.
*0ne rat was not histopathologically observed because of cannibalism.
AThree of four adenomas have strong histological architectures of suspected malignancy.
Source: Ishinishi et al. (1980)
-------
of the long bones in all seven animals which survived the treatment for seven
or more months. Because this was the first instance of experimental carcino-
genesis by an inorganic substance, it evoked great interest. Beryllium was
clearly implicated as the causative agent because zinc oxide, zinc silicate, or
silicic acid did not cause osteosarcomas in a second set of trials, whereas
beryllium oxide (firing temperature unknown) did. Guinea pigs and rats, when
similarly treated with both zinc beryllium silicate and beryllium oxide, failed
to respond. The dose of beryllium within the two compounds injected (beryllium
oxide and zinc beryllium silicate) was 360 and 60 mg, respectively, and was
given in 20 divided doses during a 6-week period.
This basic experiment was repeated many times by several investigators
(Tables 7-6 and 7-7). Cloudman et al. (1949) produced osteosarcomas in four out
of five rabbits receiving a total dose of 17 mg beryllium (as zinc beryllium
silicate). Mice were also injected with "some" tumors being produced (counts
not stated). In this experiment, "substantially 100 percent beryllium oxide by
spectrographic standards" (degree of firing not stated, total dose 1.54-390 mg
beryllium) produced no tumors. Nash (1950) produced five cases of osteosarcomas
in 28 rabbits injected with zinc beryllium silicate phosphor. The minimum
effective dose appeared to be 200 mg zinc beryllium silicate (12 mg beryllium).
Dutra and Largent (1950) produced osteosarcomas in rabbits with both zinc
beryllium silicate (2/3) and beryllium oxide (6/6), and reported a successful
transplant in the anterior chamber of the eye of a guinea pig. Barnes et al.
(1950) produced six cases of osteosarcomas among 17 rabbits injected with zinc
beryllium silicate and one case of osteosarcoma among 11 rabbits injected with
beryllium silicate. The tumors were multicentric in origin, and blood-borne
metastases were common. Hoagland et al. (1950) injected rabbits with two
samples of zinc beryllium silicate phosphor, containing 2.3 and 14 percent
beryllium oxide, and produced osteosarcomas in 3/6 and 3/4 rabbits,
respectively. With uncompounded BeO, the tumor rate was 1/8. The osteosarcomas
appeared to be highly invasive, but could not be transplanted. Beryllium
phosphate produced no tumors.
Araki et al. (1954) injected 35 rabbits with zinc beryllium manganese
silicate, zinc beryllium silicate, or beryllium phosphate. The rate of osteo-
sarcoma formation was 6/24, 2/7, and 2/4 in the three groups, respectively.
There were no tumors among three rabbits injected with beryllium oxide (firing
temperature unstated) or among two uninjected controls. There was also a
7-12
-------
TABLE 7-6. OSTEOGENIC SARCOMAS IN RABBITSC
Compound
ZnBeSi03
BeO
ZnBeSi03
ZnBeSi03
ZnMnBeSi03
ZnMnBeSi03
BeO
Be metal
ZnBeSi03
BeSi03
ZnBeSi03
BeO
ZnBeSi03
ZnBeSi03
BeO
Dose of
compound
(g)
i
i
UN
UN
0.45-0.85
0.2
UN
0.04
1-2.1
1-1.2
UN
UN
1
1
1
Be phosphate 0.103
BeO
BeO
ZnBeSi03
BeO
Totals for
0.22-0.4
0.42-0.6
0.02
Inhalation
6 mg Be/m3
Dose of
beryl lium
(mg)
UN
360
17
0.264
3.7-7.0
10-12.6
360
40
7.2-15
UN
64-90
360-700
12
12
360
UN
79-144
151-216
0.144
ZnBeSi03 + ZnMnBeSi03
Route No. of Incidence
of animals of
injection with tumors tumors
i. v.
i . v.
i. v.
i.v.(M)
i. v.
i. v.
i . v.
i . v.
i. v.
i. v.
i . v.
i. v.
i . v.
i . v.
i. v.
i . v.
IMD
IMD
IMD
i. v.
7
I
4
1
3
3
1
2
6
1
2
6
5
10
3
1
7
11
4
1
40
7/7 (100%)
UN
4/5 (80%)
UN
± 3/6 (50%)
> 3/4 (75%)
> 1/9 (11%)
2/5 (40%)
6/13 (46%)
1/8 (13%)
2/3 (67%)
6/6 (100%)
5/10 (50%)
10/13 (77%)
UN
UN
7/9 (78%)
11/11 (100%)
4/12 (33%)
> 1/6 (>17%)
40/61 (66%)
Incidence
of
metastases
3/7 (43%)
UN
3/4 (75%)
UN
5/7 (713)
UN
4/6 (67%)
None
2/2 (100%)
6/6 (100%)
>2/5 ( 40%)
UN
2/3 (66%)
UN
UN
UN
3/4 (75%)
1/1 (100%)
> 18/30 (60%)
Reference
Gardner and Heslington, 1946
Cloudman et al . , 1949
Hoagland et al. , 1950
Barnes et al. , 1950
Barnes et al. , 1950
Dutra and Largent, 1950
Janes et al. , 1954
Kelly et al., 1961
Komitowski, 1968
Vorwald, 1950
Yamaguchi, 1963
Tapp, 1969
Dutra et al . , 1951
UN = unknown; IMD = intramedullary; ZnBeSi03 = zinc beryllium silicate; (M) = mouse; ZnMnBeSi03 = zinc manganese
beryllium silicate; BeO = beryllium oxide.
Source: Groth (1980)
-------
TABLE 7-7. OSTEOSARCOMA FROM BERYLLIUM
I
I—1
-P*
Compound Species
ZnBeSi03 Rats
Guinea pigs
Mice
Rabbits
Splenectomized rabbits
ZnBe silicate Rabbits
(BeO - 2.3%)
ZnBe silicate Rabbits
(BeO = 14%)
Total
dose
(mg Be)
60
60
0.26
60
7.2
16
12+
64-90
12
12
3300
17
12
3-7
10-12
Incidence of
Mode
i .v.
i. v.
i . v.
i . v.
1 . V.
1 . V.
1 .V.
1 .V.
1 .V.
1 . V.
1 .V.
1 . V.
i . v.
i . v.
i . v.
of
in
in
in
in
in
in
administration
20
20
doses
doses
osteosarcoma
20-22 doses "
20
doses
6-10 doses
6-10 doses
repeated
in
in
in
in
in
in
in
in
17-25 doses
20
20
20
20
20
30
30
doses
doses
doses
doses
doses
doses
doses
7
4
2
5
2
5
10
II
4
7
3
3
0
0
some"
in
in
in
in
in
in
in
many
in
in
in
in
7
14
3
28
3
10
14
II
5
7
6
4
Reference
Gardner and
Heslington,
Gardner and
Heslington,
Cloudman et
1949
Gardner and
Heslington,
Barnes et al
Barnes et al
Nash, 1950
1946
1946
al
• i
1946
1950
1950
Dutra and Largent,
1950
Janes et al .
Kelly et al.
Higgins et al.
Cloudman et
Janes et al.
Hoagland et
1950
Hoagland et
1950
al
1
al
al
1954
1961
, 1964
. , 1949
1956
(continued on the following page)
-------
TABLE 7-7. (continued)
Total
dose
Compound Species (mg Be)
BeO Rats 360
Guinea pigs 360
Mice 0.55
en Rabbits 140
180
360
360-700
360
1
6
30
Be Phosphate Rabbits 130?
Incidence of
Mode of administration osteosarcoma
i.v. in 20 doses
i.v. in 20 doses
i.v. in 20-22 doses
i.v. in 20-22 doses
i.v. in 6-10 doses
i.v. in 1-30 doses
i.v. in 20-26 doses
i.v. in 20-22 doses
Inhalation, 25h/wk, 9-18 mo.
Inhalation, 25h/wk, 9-18 mo.
Inhalation, 25h/wk, 9-18 mo.
i.v. in 1-30 doses
0
0
0
0
1 in
1 in
6 in
1 in
0 in
1 in
0 in
0 in
11
8
6
7
5
6
8
5
Reference
Gardner and
Heslington, 1946
Gardner and
Heslington, 1946
Cloudman et al . ,
1949
Cloudman et al . ,
1949
Barnes et al . , 1950
Hoagland et al . ,
1950
Dutra and Largent,
1950
Gardner and
Heslington, 1946
Dutra et al. , 1951
Dutra et al . , 1951
Dutra et al . , 1951
Hoagland et al. ,
1950
Source: Adapted from Reeves (1978)
-------
primary thyroid tumor in the group injected with zinc beryllium manganese
silicate. Liver cirrhosis and splenic fibrosis were also observed. Transplant
experiments were all negative.
Several experiments reported from the Mayo Foundation confirmed the
carcinogenic effects of intravenous beryllium on bone (Janes et al. , 1954, 1956;
Kelly et al., 1961). Twenty-two of 31 rabbits receiving zinc beryllium silicate
(total dose 12 mg Be) developed osteosarcomas. New bone formation was observed
in the medullary cavities of the long bones before the malignant changes became
apparent. Of particular interest was the observation of splenic atrophy only in
those animals which developed bone tumors. Following spelenectomy, the inci-
dence of bone tumor or new bone formation in the medullary cavity was 100
percent, whereas the incidence of these developments in non-splenectomized
rabbits receiving identical doses of beryllium was only 50 percent. The results
suggest that a well-functioning spleen may serve as protection against beryllium
carcinogenesis in the rabbit. Tibia! chondrosarcomas were also produced, and
successful transplants to the anterior chambers of the eyes of rabbits were
performed (Higgins et al., 1964).
7.1.4 Intramedullary Injection Studies
Beryllium oxide or zinc beryllium silicate was directly introduced into the
medullary cavity of bones of rabbits by Yamaguchi (1963), Tapp (1969), and Fodor
(1977). Osteosarcomas, chondrosarcomas, and presarcomatous changes (irregular
bone formation) were observed. Twenty to 30 injections (20 mg beryllium oxide
per injection) gave the highest frequency of tumor formation. The tumors
developed directly from the medullary bone, and were sometimes preceded by
fibrosis. Tumors metastasized to the liver, kidney, lymph nodes, and particu-
larly the lung.
7.1.5 Intracutaneous Injection Studies
Neither the intracutaneous injection of beryllium sulfate, nor the acciden-
tal introduction of insoluble beryllium compounds (beryllium oxide, beryllium
phosphate, beryllium-containing fluorescent phosphors) into the skin have been
found to produce tumors (Van Ordstrand et al., 1945; Reeves and Krivanek, 1974).
The lesions that were produced were cutaneous granulomas, or, in the case of
extensive injury, necrotizing granulomatous ulcerations.
In the immunotoxicologic experiments of Reeves et al. (1971, 1972) beryl-
lium sulfate was administered intracutaneously in doses of 5 ug beryllium, but
7-16
-------
there was no evidence that measurable amounts of beryllium left the sites of
administration.
7.1.6 The Percutaneous Route of Exposure
No neoplasms have been observed following percutaneous administration of
beryllium compounds in any species. However, eczematous contact dermatitis has
been noted in humans who have worked with soluble compounds of beryllium (Van
Ordstrand et al. , 1945). Curtis (1951) studied the allergic etiology of these
reactions and developed a beryllium patch test. In 1955, Sneddon reported that
a patient with a positive beryllium patch test developed a sarcoid-like granu-
loma at the test site. Granulomatous ulcerations followed if insoluble beryllium
compounds became imbedded in the skin. Using pigs, Dutra et al. (1951) were
able to produce beryllium-induced cutaneous granulomas that resembled the human
lesions. There is no record that any of these lesions underwent malignant de-
generation. The fact that no neoplasms were observed could be explained by the
virtual impenetrability of intact skin by beryllium (see section 4.1.3).
7.1.7 Dietary Route of Exposure
No known neoplasms have been observed following beryllium exposure by the
dietary route in any species. Guyatt et al. (1933), Jacobson (1933), and Kay
and Skill (1934) produced rickets in young rats fed beryllium carbonate at 0.1
to 0.5 percent dietary level. This result is attributable to the precipitation
of beryllium phosphate in the intestine, leading to phosphate deprivation.
Using similar dietary concentrations of beryllium, Sols and Dierssen (1951)
observed a decrease in the intestinal absorption of glucose, which has been
attributed to the inhibition of alkaline phosphatase (Du Bois et al., 1949). At
intake levels of 5 to 500 ppm in the diet, no toxic effects of any kind were
found (Reeves, 1965; Schroeder and Mitchener, 1975a,b; Morgareidge et al.,
1977, abstract).
If insoluble beryllium dusts (beryllium, beryllium alloys, beryllium oxide,
beryllium phosphate, or beryllium ores) are ingested, the bulk of these sub-
stances will pass through the gastrointestinal tract unabsorbed. Depending
on the size of the particles, and, in the case of beryllium oxide, on the firing
temperature, a minor proportion of these dusts could become dissolved in gastric
juices, and traces of the resultant beryllium chloride could be absorbed from
the stomach. Upon entry into the intestine, any dissolved beryllium would become
precipitated again, mainly as beryllium phosphate (Reeves, 1965).
7-17
-------
In most mammalian species, alimentary absorption of soluble beryllium salts
[beryllium fluoride (BeF2), beryllium chloride (BeClJ, beryllium sulfate
(BeSO^), and beryllium nitrate (Be[N03]2) is minor. Researchers have observed
that 80 percent or more of an oral beryllium intake of 0.6 to 6.6 ug/day passes
unabsorbed through the gastrointestinal tract of rats (Reeves, 1965; Furchner et
al., 1973; Schroeder and Mitchner, 1975a,b). Upon entering the alkaline milieu
of the intestine, beryllium forms a precipitate that is excreted with the feces.
There is some evidence that increasing the intake concentration does not
increase the amount absorbed from the intestine, because the latter is governed
by the solubility of the intestinal precipitates rather than by the total amount
of beryllium present.
7.1.8 Tumor Type, Species Specificity, Carcinogenic Forms, and Dose-Response
7.1.8.1 Tumor Type and Proof of Malignancy. Pulmonary neoplasms found in rats
after beryllium exposure have been classified as adenocarcinomas, showing a
predominantly alveolar pattern. Reeves et al. (1967) distinguished four his-
tological variants, including focal columnar, focal squamous, focal vacuolar,
and focal mucigenous. Schepers et al. (1957) distinguished several more,
including some adenomas judged to be non-malignant. Wagner et al. (1969) and
Groth et al. (1980) found that about half of the tumors they produced with
beryllium were benign adenomas. The diagnosis of pathological lesions is
complicated, and requires special expertise. The histological differentiation
between adenomas and adenocarcinomas is not always well defined and may also
have species-related peculiarities, so that different conclusions on the same
specimen may sometimes be reached by pathologists. This is especially true when
pathologists have been trained in human rather than veterinary medicine. It is
also noteworthy that neoplasia in the lungs of rats was invariably associated
with the purulent lesions of chronic murine pneumonia, which itself was
exacerbated by inhalation of the acidic beryllium sulfate aerosol.
Metastases, as well as successful transplants, were claimed by Schepers et
al. (1957). In the rat experiments of Vorwald, neither was claimed, but later
reports have been ambiguous on these points (Vorwald et al., 1966; see also
Lesser, 1977). In the monkey experiments of Vorwald (1968), which lacked con-
trols, extensive metastases to the mediastinal lymph nodes and sometimes to the
bones, liver, and adrenals were reported. Groth et al. (1980) performed
successful transplants in experiments with intratracheal administration of
beryllium metal and beryllium alloy, but metastasis to the mediastinal lymph
node was observed in only one animal.
7-18
-------
The nature of the neoplasms produced by the intravenous or intramedullary
administration of beryllium in rabbits is much more certain. The osteosarcomal
or chondrosarcomal character of these neoplasms has not been challenged, and
metastases to all parts of the body have been observed. Transplant results have
been equivocal, however. Successful transplants to the anterior chamber of the
eye were reported by Dutra and Largent (1950) and Higgins et al. (1964), whereas
failure with transplants was expressly admitted by Hoagland et al. (1950) and
Araki et al. (1954). It is possible that the degree of malignancy of the bone
tumors depends on the type of compound used in the injection.
7.1.8.2 Species Specificity and Immunobiology. Pulmonary tumors were produced
after inhalation exposure and sometimes after intratracheal injection in rats
(Vorwald, 1953; Vorwald et al. , 1955; Schepers et al. , 1957; Schepers, 1961;
Vorwald et al., 1966; Reeves et al., 1967; Reeves and Deitch, 1969; Spencer et
al., 1965, 1968, 1972; Wagner et al., 1969; Groth et al. , 1980; Ishinishi et
al., 1980) and in monkeys (Schepers, 1964; Vorwald et al., 1966; Vorwald, 1968;
but see Wagner et al., 1969 for negative evidence). No pulmonary tumors were
produced in rabbits (Vorwald, 1950). The evidence for hamsters (Wagner et al.,
1969), and guinea pigs (Vorwald, 1950; Schepers, 1961, 1971; Reeves et al.,
1972), while generally negative, was suggestive of a positive effect in some
cases.
Bone tumors were produced by intravenous or intramedullary injection in
rabbits (Gardner and Heslington, 1946; Dutra and Largent, 1950; Barnes et al.,
1950; Hoagland et al., 1950; Araki et al. , 1954; Janes et al., 1954, 1956; Kelly
et al., 1961; Yamaguchi, 1963; Higgins et al., 1964; Tapp, 1969; Fodor, 1977).
The single report claiming osteosarcomas in mice (Cloudman et al., 1949) needs
confirmation, as does the report of osteosarcomas in rabbits after inhalation
exposure (Dutra et al., 1951). Bone tumors were not observed in rats or guinea
pigs.
It would appear from these data that (1) pulmonary tumors can be obtained
with beryllium in rats and in monkeys, possibly in hamsters and guinea pigs, but
not in rabbits, and (2) that bone tumors can be obtained with beryllium in rab-
bits and perhaps in mice, but not in rats or guinea pigs. The negative evidence
with guinea pigs involves both the intravenous injection (Gardner and Heslington,
1946; Vorwald, 1950) and inhalation (Schepers, 1961; Reeves et al., 1972) of
beryllium at levels that were definitely carcinogenic in rabbits and rats, re-
spectively. However, in the later inhalation studies of Schepers (1971) there
was suggestive evidence for the induction of lung cancer in guinea pigs.
7-19
-------
This apparent species specificity, which might operate with other types of
carcinogenesis as well (guinea pigs are generally regarded as poor models for
cancer induction), has remained largely unexplored. It is certainly noteworthy
that guinea pigs develop cutaneous hypersensitivity to beryllium, whereas rats
do not (Reeves, 1978). In rabbits, the spleen has been found to be involved in
the neoplastic response to intravenous beryllium. Gardner and Heslington (1946)
observed prompt splenic atrophy in beryllium-injected rabbits, while Janes et
al. (1954) found that splenic atrophy afflicted only those animals that devel-
oped the osteosarcomas. In later work, Janes et al. (1956) increased the yield
of osteosarcomas in beryl 1iunrinjected rabbits twofold by performing splenec-
tomy. These studies suggest that some form of cellular immunity, with immuno-
competent cells arising from the spleen, may be a factor in determining whether
beryllium is neoplastic. Various species, or perhaps individual members of a
species, may have resistance to berylliurn-induced cancer according to their im-
munocompetence.
7.1.8.3 Carcinogenic Forms and Dose-Response Relationships. There is insuffi-
cient evidence to implicate any specific chemical form of beryllium as the
exclusive carcinogenic entity. Ionic beryllium changes to beryllium hydroxide
upon inhalation, and both forms have caused pulmonary tumors in rats when in-
haled (ionic beryllium) or injected intratracheally (beryllium hydroxide) (Vor-
wald, 1953; Schepers et al. , 1957; Reeves et al., 1967; Groth et al. , 1980).
There is reason to believe that beryllium hydroxide particles can change to
beryllium oxide upon aging (Reeves, in press). Beryllium oxide, when directly
introduced into the lungs of rats, showed a remarkable pattern of carcinogeni-
city, clearly indicating that firing temperature had a definite influence on the
tumor yield and that only "low-fired" (500°C) beryllium oxide was highly
carcinogenic (Spencer et al., 1968, 1972). Sanders et al. (1978) observed only
one lung tumor among 184 rats exposed to "medium-fired" (1000°C) beryllium
oxide. Frequently, no tumors are obtained with beryllium oxide; however, in
early studies, the type of beryllium oxide to which the animals were exposed was
not generally identified (Cloudman et al., 1949; Dutra and Largent, 1950;
Hoagland et al., 1950; Araki et al., 1954; Vorwald et al., 1966).
Experiments attempting to establish a dose-response relationship with
intravenous beryllium are limited. Nash (1950) suggested 12 mg beryllium per
rabbit was the minimum effective total dose to produce osteosarcomas. In the
experiments of Hoagland et al. (1950), the frequency of osteosarcomas increased
from 50 to 75 percent as beryllium oxide content of a fluorescent phosphor was
7-20
-------
increased from 2.3 to 14 percent. Barnes et al. (1950) could increase the rate
of rabbit osteosarcomas from 4/14 (29%) to 2/3 (67%) by doubling the dose of
intravenous zinc beryllium silicate from 7.5 to 15 mg. However, in the
inhalation experiment of Dutra et al. (1951) and in the intramedullary
experiments of Yamaguchi (1963), no clear-cut relation between dose and tumor
yield was found.
Vorwald et al. (1966), citing results of their own unpublished studies,
claimed that "almost 100 percent of a large number of rats" developed lung
3
cancer after 18 months of exposure to 42 or 21 ug Be/m (as sulfate). After
3
exposure to 2.8 ug Be/m (as sulfate), their reported rate of lung cancer was
13/21 (62%). These figures came under considerable scrutiny during the beryl-
lium hearings at the Occupational Safety and Health Administration (Lesser,
1977). It was pointed out that these experiments were poorly controlled and
that the exposure data of 2.8 ug Be/m deserved no confidence. Wagner et al.
(1969) obtained pulmonary tumors in rats with beryl ore (beryllium content
4.14%) but not with bertrandite ore (beryllium content 1.4%). Similarly, Groth
et al. (1980) obtained pulmonary tumors with beryllium metal, beryllium hy-
droxide, and a beryllium-aluminum alloy, with beryllium content ranging from
62 to 100 percent. They obtained no tumors with other alloys, ranging in
beryllium content from 2.2 to 40 percent. Thus, the evidence points to the
existence of a definable dose-response relationship in experimental beryllium
carcinogenesis.
Reeves (1978) examined this relationship by the probit method. For the
induction of osteosarcomas in rabbits following intravenous injection of zinc
beryllium silicate, the median effective total dose per animal was 11.0 mg
beryllium. The dose-response curve intersected the 1 percent incidence level at
3.8 mg, the 0.1 percent incidence level at 2.7 mg, and the 0.01 percent inci-
dence level at 2.0 mg. For the induction of pulmonary carcinoma in rats after
inhalation of beryllium sulfate (a 35-hr/wk chamber exposure lasting 3 or more
3
months), the median effective concentration was 18.0 ug Be/m , and the curve
3
intersected the 1 percent incidence level at 12.0 ug Be/m , the 0.1 percent
incidence level at 10.5 ug Be/m , and the 0.01 percent incidence level at 9.0 ug
3
Be/m . Obviously, these estimates are subject to considerable uncertainty.
7.1.9 Summary of Animal Studies
The results of the studies that have been reviewed in this section are
summarized in Table 7-8.
7-21
-------
TABLE 7-8. CARCINOGENICITY OF BERYLLIUM COMPOUNDS
Year
1946
1949
1949
1950
1950
I960
1951
1953
1954
1954
1957
1961
1964
Species
Rabbit
Mouse
Rabbit
Rabbit
Rabbit
Rabbit
Rabbit
Rat
Rabbit
Rabbit
Rat
Rabbit
Rabbit
Compound
Zinc beryllium silicate
Zinc beryllium silicate
Zinc beryllium silicate
Zinc beryllium silicate
and beryllium metal
Zinc beryllium silicate
Beryllium oxide and
zinc beryllium silicate
Beryllium oxide
Beryllium sulfate
tetrahydrate
Beryl lium phosphate
beryllium oxide
Zinc beryllium silicate
Beryllium sulfate
tetrahydrate
Zinc beryllium silicate
Zinc beryllium silicate
Route of Administration
Intravenous
Intravenous
Intravenous
Intravenous
Intravenous
Intravenous
Inhalation
Inhalation
Intravenous
Intravenous
Inhalation
Intravenous
Intravenous
Tumor
Osteosarcoma
"Malignant bone
tumors"
Osteosarcoma
Osteosarcoma
Osteosarcoma
Osteosarcoma
Osteosarcoma
Lung cancer
(adeno and
squamous)
Osteosarcoma
Osteosarcoma
Lung cancer
(adeno and
squamous)
Osteosarcoma
Chondrosarcoma
Reference
Gardner and
Hesl ington
Cloudman et al .
Cloudman et al .
Barnes et al .
Hoagland et al .
Dutra and Largent
Dutra et al .
Vorwald
Araki et al .
Janes et al .
Schepers et al .
Kelly et al .
Higgins et al .
(continued on the following page)
-------
TABLE 7-8. (continued)
Year
1966
1966
1967
1968
1969
1969
1969
1969
1971
1975 a,b
1975
Species
Monkey
Monkey
Rat
Rabbit
Rat
Hamster
Monkey
Rabbit
Rat
Rat
Rat
Compound
Beryllium oxide
Beryllium sulfate
tetrahydrate
Beryllium sulfate
tetrahydrate
Beryllium oxide
Beryl ore
Bertrandite ore
Beryl ore
Bertrandite ore
Beryl ore
Bertrandite ore
Zinc beryllium silicate
Beryllium silicate
Beryllium oxide
Beryllium hydroxide
Beryllium sulfate
tetrahydrate
Beryllium fluoride
Beryllium chloride
Route of Administration
Intratracheal
instillation
Inhalation
Inhalation
Intravenous
Inhalation
Inhalation
Inhalation
Subperiosteal
injection
Intratracheal
Ingestion
Inhalation
Tumor
Pulmonary cancer
(anaplastic)
Pulmonary cancer
Lung-cancer
(alveolar-adeno Ca)
Osteosarcoma
Lung cancer (adeno)
No tumors
None
None
None
None
Osteosarcoma
Osteosarcoma
Osteosarcoma
Pulmonary tumors
7
No greater than
controls
Lung cancer
(adeno and squamous)
Reference
Vorwald et al .
Vorwald et al .
Reeves et al.
Komi tows ki
Wagner et al .
Wagner et al .
Wagner et al .
Tapp
Groth and Mackay
Schroeder and
Mitchener
Litvinov et al .
(continued on the following page)
-------
TABLE 7-8. (continued)
Year
1975
1977
1978
1980
1980
Species
Rabbit
Rat
Rat
Rat
Rat
Compound
Zinc beryllium silicate
Beryllium sulfate
tetrahydrate
Beryllium oxide
Beryllium metal
Beryllium alloy
Passivated beryllium metal
Beryllium hydroxide
Beryllium oxide
Route of Administration
Intramedul lary
Ingestion
Inhalation
Intratracheal
instillation
Intratracheal
instillation
Tumor
Osteosarcoma
?
Ho greater than
controls
Single lung cancer
(adeno)
Lung cancer (adeno
and squamous)
n
H
Lung cancer
(squamous, adeno,
lympho)
Reference
Mazabrau
Morgareidge et a
Sanders et al.
Groth et al .
Ishinishi et al.
Source: Adapted from Kuschner (1981)
-------
Tumors have been successfully induced by intravenous or intramedullary
injection of beryllium into rabbits and, possibly, mice, and by inhalation expo-
sure or intratracheal injection into rats, monkeys, and possibly guinea pigs.
Attempts to induce tumorigenesis by the dietary route have proven unsuccessful
in any species tested. This failure to induce tumors is probably attributable
to minimal absorption resulting from the precipitation of beryllium compounds in
the intestine. Guinea pigs and hamsters appear to have a low degree of suscep-
tibility to beryllium carcinogenesis. This species specificity appears to be
connected with immunocompetence.
In rabbits, osteosarcomas and chondrosarcomas have been obtained. The
tumors are highly invasive and metastasize readily, but transplant with variable
success. They have been judged to be histologically similar to corresponding
human tumors. In rats, pulmonary adenomas and/or adenocarcinomas of questionable
malignancy have been obtained. The tumors are less invasive, and their meta-
static and transplant potential are variable. They appear to be histologically
associated with the purulent lesions of chronic murine pneumonia.
There is some evidence that the carcinogenicity of beryllium oxides is
inversely related to their firing temperature, with only the "low-fired" (500°C)
variety presenting a substantial hazard. Limited dose-response evidence indi-
cates that approximately 2.0 mg beryllium (as beryllium oxide) is the minimum
intravenous dose for production of osteosarcomas in rabbits, and approximately
3
10 ng Be/m (as sulfate) is the minimum atmospheric concentration for the pro-
duction of adenocarcinomas in rats.
Although some studies involving beryllium clearly have limitations, the com-
bined data, using EPA's Proposed Guidelines for Carcinogen Risk Assessment (U.S.
EPA, 1984) to classify weight of evidence for carcinogenicity in experimental
animals, suggest there is "sufficient evidence" to conclude that beryllium and
beryllium compounds are carcinogenic in animals.
7.2 EPIDEMIC-LOGIC STUDIES
7.2.1 Bayliss et al. (1971)
The first in a series of government-sponsored studies of cancer in workers
exposed to beryllium was conducted by Bayliss et al. (1971). This cohort mor-
tality study consisted originally of 10,356 former and current employees of the
beryllium-processing industry (the Brush Beryllium Company of Ohio and
Kawecki-Berylco Industries of Pennsylvania.) Some 2153 workers were excluded
7-25
-------
because of insufficient data. Records consisted only of names of workers and
approximate years of employment of workers employed at the Brush Beryllium Com-
pany prior to 1942. Company employment records provided no additional informa-
tion despite an intensive search. These lists were prepared by a former Brush
Beryllium Company physician, now deceased. After further removal of 1130 females,
the cohort totaled 6818 males. In this group, 777 members died during the period
from January 1, 1942 to the cutoff date, December 31, 1967. This was less than
the 842.4 expected deaths based upon U.S. male death rates—a shortfall attri-
butable to the "healthy worker effect." No elevated risk of lung cancer (Inter-
national Classification of Diseases [ICD] 160-164) was evident overall (36
observed versus 34.06 expected). No significant excess risk of lung cancer was
found to exist in relation to length of employment, beginning date of employment,
or kind of employment (office versus production), nor were significant risks of
other forms of cancer evident from these data.
This study suffers from several deficiencies. Over 2000 individuals had to
be eliminated from the cohort because birth date, race, and sex were not avail-
able. The authors indicated that this reduction in the size of the study neces-
sitated the elimination of some 251 deaths, and represented a loss of over
20 percent of the cohort and 25 percent of the known deaths, a circumstance that
had the potential for introducing considerable bias into the results.
A second major problem with the study is the fact that the authors did not
analyze the data according to length of time since initial employment in the
industry. The lack of such an analysis meant that questions dealing with latency
could not be addressed.
A third deficiency is that the populations of several different plants were
combined into one cohort for the study. As a result, the study failed to
consider the many potential differences of exposure levels at different plants.
Individuals were studied in groups according to beginning date and duration of
employment, despite the fact that their exposure histories may have been totally
dissimilar.
For the above-cited reasons, this study is not adequate for the evaluation
of cancer mortality in beryllium-exposed workers.
7.2.2 Bayliss and Lainhart (1972, unpublished)
In an attempt to remedy the deficiencies of the 1971 study, Bayliss and
Lainhart (1972), in an unpublished report presented at the American Industrial
Hygiene Association meeting on May 18, 1972, narrowed the scope of the original
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study by focusing only on data from Kawecki-Berylco Industries (KBI) which had
seemingly complete employment records for two locations in Pennsylvania. This
change effectively reduced the size of the cohort to some 3795 white males while
retaining the same starting and cutoff dates as were used in the earlier study.
In the 1972 study, Bayliss and Lainhart found that 601 members of the cohort had
died, compared to 599.9 expected deaths based on period- and age-specific U.S.
white male death rates. Again, no significant excess of unusual mortality from
any cause was evident. For lung cancer (ICD 160-164) overall, 25 deaths were
observed versus 23.69 expected. Even when latency was considered, no
significant excess risk of lung cancer was apparent after a lapse of 15 years
from initial exposure, at which time 14 deaths were observed versus 13.28
expected. In addition, no significant risks were apparent in relation to
intensity of exposure, duration of exposure, or beginning date of employment.
The Bayliss and Lainhart (1972) study was criticized by Bayliss and Wagoner
(1977) in a third version of the study, which was submitted to the Occupational
Safety and Health Administration (OSHA) as part of the beryllium standards
development process. In this criticism, the 1972 study was said to have
multiple limitations, among which were the following: (1) the study included
clerical and administrative workers who presumably had not been exposed to
beryllium; (2) the data were obtained from industrial representatives, which
precluded an independent assessment of plant employment files to ensure that all
potentially exposed workers were included; and (3) the study did not assess
latency 20 or more years after initial employment, although it did examine
mortality after a 15-year lapse.
7.2.3 Bayliss and Wagoner (1977, unpublished)
In the third attempt to remedy the deficiencies of the two previous
studies, Bayliss and Wagoner (1977) reduced the size of the cohort to include
workers employed at only one plant site of the KBI. This particular plant site
in Pennsylvania was considered to be the best choice for a cohort mortality
study for the following reasons: (1) this plant had, according to the authors,
the most complete and detailed set of personnel records of any of the companies
and sites examined; (2) it had been in continuous operation producing beryllium
prior to 1940, thus, allowing an analysis of latent effects; and (3) it provided
a large group of employees from which valid inferences could be made. Other
plant sites were deficient in one or more of these respects. The cohort was
composed of 3070 white males who were followed until January 1, 1976. Vital
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status was unknown for only 80 members of the cohort (3%), and these individuals
were considered to be alive until the study's cutoff period. Altogether, 884
deaths were observed, compared to 829.41 expected (based on period- and age-spe-
cific U.S. white male death rates). A significant excess of lung cancer was
noted (ICD 162-163), with 46 cases observed versus 33.33 expected (p < 0.05).
A significant excess of heart disease was also noted (399 observed versus 335.15
expected, p < 0.05), as was a significant excess of nonmalignant respiratory
disease (32 observed versus 19.02 expected, p < 0.01). Irrespective of duration
of employment, a significant excess was noted in bronchogenic cancer following
a lapse of 25 or more years since initial employment.
In this study, the authors discussed for the first time the impact of ciga-
rette smoking as a possible confounding agent contributing to the excess risk of
lung cancer. An examination of the results of a cross-sectional health exam-
ination survey conducted at the plant by the U.S. Public Health Service (PHS)
in 1968 revealed some differences in the cigarette-smoking patterns of the
surveyed employees, compared to smoking patterns in the United States as a whole
(determined from a health interview survey conducted by the PHS from 1964 to
1965). A greater percentage of heavy smokers was indicated in the 1968 survey
as compared with national data (21.4 versus 15.3%). However, Wagoner et al.
(1980) later dismissed the results as a possible cause of the increased risk of
bronchogenic cancer and other diseases in the study cohort. Dismissing the role
of cigarette smoking as a contributing cause of the excess risk of lung cancer
may have been premature for several reasons. First, the smoking patterns of the
379 current employees surveyed in 1968 were probably not the same as those of
the entire cohort of 3795, which included both current and past workers employed
as early as 1942. Second, the first national reports of smoking as a cause of
lung cancer were published in 1964 and were accompanied by a great deal of media
attention. By 1968, intense media coverage dealing with the health consequences
of smoking probably produced a diminution of cigarette smoking among various
subgroups of the population in the 4-year interim period between surveys.
Furthermore, while the 1968 survey at the plant did speak of current
cigarette-smoking patterns, the issue of prior cigarette smoking was not
addressed, nor was the issue of pipe or cigar smoking. Additional criticisms of
the Bayliss and Wagoner (1977) study, as well as the final version of the study
(Wagoner et al., 1980), follow.
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7.2.4 Wagoner et al. (1980)
Wagoner et al. (1980) slightly reduced the cohort of Bayliss and Wagoner
(1977) to a smaller cohort mortality study of 3055 white males employed some
time between January 1, 1942 and December 31, 1967, in the same beryllium-
processing facility. This version of the study did not differ markedly from the
Bayliss and Wagoner (1977) study except in minor respects. Thirteen persons who
had been included in the earlier cohort were found to be salespersons who had
never appeared in the plant; thus, they were removed from the cohort. In
addition, three individuals who were nonwhite and therefore also ineligible for
inclusion were removed. One individual with a definite diagnosis of lung cancer
but questionable employment credentials was added. The results showed a
significantly high risk of lung cancer (47 observed versus 34.29 expected, p <
0.05) for those individuals followed until December 31, 1975. This excess
extended to members of the cohort followed for more than 24 years since initial
employment (20 observed versus 10.79 expected, p < 0.01). When the analysis was
confined to those whose initial employment occurred prior to 1950, but who were
followed for 15 years or more from date of initial employment, a significantly
high risk of lung cancer was apparent (34 observed versus 22.46 expected, p <
0.05). For those whose initial employment occurred after 1950, 4 deaths from
lung cancer were observed versus 2.4 expected. The authors concluded that this
excessive risk of lung cancer "could not be related to an effect of age, chance,
self-selection, study group selection, exposure to other agents in the study
facility, or place of residence."
This study has received severe criticism from several sources: an internal
Center for Disease Control (CDC) Review Committee appointed to investigate
defects in the study, several professional epidemiologists (MacMahon, 1977,
1978; Roth and Associates, 1983), and also one of the study's co-authors
(Bayliss, 1980). These researchers criticized Wagoner et al. for inadequately
discussing all qualifiers that might explain any of the significant findings of
the study.
The cohort studied by Wagoner et al. (1980) was composed of workers at the
facility who had been employed prior to December 31, 1967, based on the facili-
ty's employment records and the results of a 1968 cross-sectional medical survey
of the plant. The cohort excluded employees who were not directly engaged in
the extraction, processing, or fabrication of beryllium, or in on-site
administrative, maintenance, or support activities. The numbers of expected
deaths used in the study were based on U.S. white male death rates that had been
7-29
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generated by an analytic life table program designed by the National Institute
for Occupational Safety and Health (NIOSH). As a basis for these calculations,
the program used actual U.S. deaths recorded by cause, age, race, sex, and year
through 1967, together with census population data from 1941 to 1967. These
data were provided by the Bureau of the Census and the National Center for
Health Statistics. Unfortunately, at the time of this study and subsequent
studies on beryllium, cause of death information was not available from these
agencies on a year-to-year basis after 1967. As a result, the NIOSH life-table
program could not generate death rates during this period without certain
assumptions. In order to estimate expected deaths during the period from 1968
through 1975, death rates were assumed by the authors to be unchanged from those
generated by the NIOSH life-table program for the period from 1965 through 1967.
The result was that for causes of death with declining death rates, expected
deaths were overestimated, with a resultant underestimate of risk. Similarly,
for those causes with increasing death rates during the interval studied, ex-
pected deaths were underestimated, with a resultant upward risk bias, which
was the case for all of the lung cancer risk calculations made by the authors.
After this problem had been corrected by the inclusion of actual lung cancer
mortality data for the period in question, expected lung cancer deaths were
recomputed by Bayliss (1980) prior to the Wagoner et al. (1980) publication.
The result was an increase from 34.29 to 38.2 expected lung cancer deaths, or an
excess of 11 percent. This correction in itself was enough to eliminate the
statistical significance calculated by Wagoner et al. in their overall lung
cancer tabulation. With respect to latency, the risk of lung cancer remained
significant in the subgroup of the cohort that was observed for 25 years or more
after initial employment (20 observed versus 13.36 expected, p = 0.05). These
corrections have been confirmed by Richard Monson (MacMahon, 1977, 1978),
following a reanalysis of the NIOSH data tapes in an independent Monson
life-table program at Harvard University.
In attempting to assess the impact of cigarette smoking on the risk of
developing lung cancer in this cohort, Axel son's method (1978) was applied to
the meager cigarette smoking data that were available from Wagoner et al. (Table
7-9).
The problems with these data have been discussed in the earlier critique
of the Bayliss and Wagoner (1977, unpublished) paper. However, in the interest
of adjusting the expected lung cancer deaths by the contribution due to ciga-
rette smoking, one must first assume as valid the risks of lung cancer by level
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TABLE 7-9. PERCENTAGE DISTRIBUTION OF BERYLLIUM-EXPOSED WORKERS AND
OF AGE-ADJUSTED U.S. WHITE MALE POPULATION BY CIGARETTE SMOKING STATUS
Cigarette
Smoking Status
Never smoked
Former smokers
Current smokers
< 1 pack a day
> 1 pack a day
Beryllium Production
Workers (%)
27.2
22.4
50.4
29.0
21.4
U.S. Population3
(%)
24.7
20.5
54.7
39.4
15.3
National Center for Health Statistics, 1967.
Source: Wagoner et al. (1980)
of smoking that are given in the American Cancer Society's 25 State Study
(Hammond, 1966). These data are given in Table 7-10.
Next, a number of different assumptions about the data must be made in
order to produce a range of estimates that will presumably include the best
estimate of the contribution due to smoking. Four calculations were done based
on varying the assumptions as follows: for the first calculation, the former
smokers were grouped with the nonsmokers, and the lower risk ratios were used
(i.e., 4.62 and 14.69); second, the former smokers were again grouped with the
nonsmokers, but the higher risk ratios were used (i.e., 8.62 and 18.77); third,
the former smokers were grouped with the moderate smokers, and the lower risk
TABLE 7-10. LUNG CANCER MORTALITY RATIOS FOR MALES, BY CURRENT NUMBER
OF CIGARETTES SMOKED PER DAY, FROM PROSPECTIVE STUDIES
American Cancer Society
25-State Study
Nonsmokers
Moderate
Heavy
Cigarettes Smoked
per Day
0
1-9
10-19
20-39
40+
Mortality
Ratio
1.00
4.62
8.62
14.69
18.77
Source: Hammond (1966)
7-31
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ratios were used; and for the fourth calculation, the former smokers were
grouped with the moderate smokers, and the higher risk ratios were used. Using
this method, the increase in expected lung cancer deaths ranges from 4.1 to 9.8
percent. This procedure is described below.
Let I = the incidence in the comparison population (U.S. males),
IQ = the incidence in any nonsmoking population,
R-p R£, and R^ = the relative risks in nonsmokers, moderate smokers,
and heavy smokers, respectively, and
Pp p2, and p3 = the percentage of the population who are nonsmokers,
moderate smokers, and heavy smokers, respectively.
Then, the incidence of lung cancer in the comparison population is:
ig = (R! • P! • V - (R2 • P2 • y + (R3 • P3 • y
Similarly, if I = the incidence of lung cancer in the plant study population
and IQ, Rp R2, and R3 are the same as above, but p-^ p2, and p3 are the
percentages of the plant population who are nonsmokers, moderate smokers, and
heavy smokers, respectively, then the incidence of lung cancer in the plant or
study population is:
Jp = (R1 ' P! ' V +
-------
A number of assumptions must be made in order to apply this crude method
to adjust for the contribution to lung cancer due to cigarette smoking. These
are outlined below:
1. Smoking levels in Table 7-9 are similar to those of the entire cohort.
This is not necessarily true. Although most former employees began
work prior to 1950, a smaller proportion of those current workers in
1967 who participated in the smoking survey began work prior to 1950.
Smoking among blue-collar employees was thought to be greater in the
1940s.
2. Smoking levels at the plant in 1968 are similar to those of the
United States in 1964. The survey on smoking in the U.S. population
was completed in 1964 at about the same time as the release of the
report on smoking and health by the Surgeon General, while the survey
of the plant was completed in 1968. The ensuing national publicity
engendered by the Surgeon General's report helped to produce a
reduction in smoking levels in the U.S. population, and probably in
this plant, during the three-year period from 1964 to 1968.
Therefore, these levels are not strictly comparable because of a lack
of concurrence of the two events.
3. In each smoking category (heavy, moderate, and nonsmoking), the age
distributions are similar. This is not necessarily the case. It was
impossible to age-adjust the plant population in each smoking
category to the U.S. male population in the same smoking category
because of the lack of age-specific smoking data in each category of
both populations.
4. The assignment of persons into specific smoking categories by quan-
tity smoked assumes that such persons always belonged to the category
to which they were classified. This may not be the case in either
population. No time factor could be used to classify persons as to
the category of smoking to which they were assigned, since such
information was not available.
Unfortunately, these estimates are by necessity based on the only data availa-
ble to the U.S. Environmental Protection Agency's Carcinogen Assessment Group
(CAG). Table 7-11, which is adapted from the Wagoner et al. (1980) study, has
been corrected to eliminate the 11-percent underestimate of expected deaths
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TABLE 7-11. OBSERVED AND EXPECTED DEATHS DUE TO LUNG CANCER ACCORDING TO
DURATION OF EMPLOYMENT AND TIME SINCE ONSET OF EMPLOYMENT AMONG WHITE
MALES EMPLOYED SOMETIME DURING JANUARY 1942 THROUGH DECEMBER 1967 IN
A BERYLLIUM PRODUCTION FACILITY AND FOLLOWED THROUGH 1975 (REVISED)
Duration of employment (years) '
Interval Since Onset
of Employment (yrs)
< 15
15 - 24
> 25
Total
<
obs.
7
15
17
39
5 years
, vs. exp.
8.88
13.44
12.00
34.32
>
obs.
1
3
3
7
5 years
vs. exp.
1.76
3.15
2.67
7.58
obs.
8
18
20
46
Total
vs. exp.
10.64
16.59
14.67
41.90
Employment histories were ascertained only through 1967.
No comparison is statistically significant at p < 0.05; obs. = observed,
exp. = expected.
caused by the failure to use the appropriate lung cancer death rates in the com-
parison population and has been adjusted upward another 4.1 percent (minimum
effect) to account for the smoking contribution based on the information pro-
vided in Table 7-9. One ineligible lung cancer death has been removed from
the observed deaths.
Wagoner et al. found 875 deaths in their cohort. The vital status of
79 members of the cohort remained unknown as of December 31, 1975. The authors'
assumption was that these individuals would be counted as alive until the end
of the study, and that because of their added person-years, any finding of in-
creased cause-specific mortality would tend to be underestimated. Actually,
these 79 individuals represented only two percent of the total cohort, and any
additional person-years included from the time when they were last known to be
alive would have added little to the number of expected deaths. Furthermore,
given the intense scrutiny afforded this population in determining vital status
by both Wagoner and Mancuso in their own studies of the same workers, and con-
sidering the fact that these researchers shared information on newly found lung
cancer deaths, it is questionable whether any additional lung cancers would
have been found either in the 79 individuals with unknown vital status or in
the 15 known dead for whom causes of death were not known by the cutoff date of
the study. The latter number was reduced to ten in subsequent tabulations,
after information on causes of death was located for five individuals (Bayliss,
1980). None of these was lung cancer.
Additional factors that could have contributed to the finding of an excess
risk of lung cancer in Wagoner et al. (1980) are as follows:
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1) One lung cancer victim was added to the cohort based on a single 4 by
7 inch personnel card that listed the same day (June 1, 1945) as the "starting
date" and "release date" in the plant. In actuality, the individual, according
to company sources, never reported for work because a preemployment chest X-ray
revealed a lung abnormality. The company paid him for the time he was being
examined, which is why his name and social security number appeared on a social
security earnings report. Bayliss excluded him from his original cohort based
on the information on the same personnel record that said "did not pass chest
X-ray."
2) In a supplemental summation on the epidemiology of beryllium with
respect to the proposed occupational safety and health standard for exposure to
beryllium (January 13, 1978; prepared by Roth and submitted by Brush Wellman),
it is stated that 295 white males, who were employed at the Reading plant of
Kawecki-Berylco Industries (KBI) in jobs similar or identical to those of the
Wagoner et al. cohort, were not included in the study cohort. Of that group,
the report states that 199 employees had a known vital status: 181 were alive
and 18 were deceased by the close of the study period. Dr. Roth's post hearing
statement indicated that the inclusion of these additional employees would have
increased the cohort by about ten percent.
3) In researching the medical files of the 47 lung cancer victims, David
Bayliss, one of the co-authors, discovered that 23 files contained information
to the effect that the individuals in question were smokers. In addition, the
company from which the cohort was derived provided data indicating that 36 of
the 47 lung cancer victims (77%) smoked cigarettes. These data were based on a
company-sponsored survey by Hooper-Holmes and reported in a KBI interoffice
memorandum (Butler, 1977). Bayliss determined that of the 47 cases, a total of
42, or nearly 90 percent, smoked cigarettes, based on a combination of smoking
information gathered by the company and smoking information from the medical
files. If this information is accurate, it could indicate the presence of a
confounding effect due to cigarette smoking. Bayliss further established that
one of the remaining five cases died from another cause of death. This victim
actually died from a glioblastoma multiforme (astrocytoma) of the brain,
according to medical data. However, his death certificate incorrectly listed
lung cancer as an underlying cause of death. If the 47 cases are reduced to
46, then 91 percent smoked cigarettes.
4) An inadequate discussion was presented on the confounding effects of
exposure to potential carcinogens prior to and following employment in the
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beryllium industry. These factors are especially important since the authors
maintained that only short-term employees were affected. Evidence from employ-
ment records, medical files, questionnaires administered during the 1968 NIOSH-
sponsored medical survey of the plant, and death certificates indicated a
distinct possibility that these factors are significant in the cohort under
study (Bayliss, 1980).
Another problem with the Wagoner et al. (1980) study, as stated by the
authors, is that the expected deaths were overestimated by 19 percent because
of the use of death rates for white males in the United States as a whole,
rather than those for Berks County, Pennsylvania, where the plant was located.
This statement was based on a comparison by Mason and McKay (1973) of the 1950
to 1969 age-adjusted lung cancer death rate for white males in Berks County,
Pennsylvania, with that of the 1950 to 1969 age-adjusted lung cancer rate for
white males in the United States. This reference by Wagoner et al. to "lower"
Berks County rates as a justification for the position that the expected deaths
based on national rates are overestimated, has been criticized by Roth and
Associates (1983) as well as by Bayliss (1980). Bayliss cited the fact that the
periods of observation were different, i.e. the Mason data covered the period
from 1950 through 1969, while those of Wagoner et al. (1980) covered the period
from 1942 through 1975. Bayliss also pointed out that to derive reliable
county death rates from the existing data would be extremely difficult to do
with any confidence. Roth and Associates criticized the use of Berks County
rates as not being reflective of greatly elevated lung cancer death rates for
the City of Reading, which they maintained were 12 percent higher than the
national rates. According to Roth and Associates (1983), 46 percent of the
workers employed by the plant in 1968 resided within the city limits, whereas
only 34 percent of Berks County residents (1970) resided within the city.
Therefore, death rates calculated for Berks County should be weighted toward
the relatively higher City of Reading rates. This adjustment would have the
effect of generating comparison lung cancer rates that are perhaps greater than
U.S. rates and, consequently, would increase the number of estimated expected
deaths.
Wagoner et al. (1980) also claimed to have noted an unusual
histopathologic distribution of cell types in 27 of the 47 lung cancer deaths
for which pathologic specimens could be obtained. Adenocarcinomas were noted
in 8 of 25 individuals (32%) histologically confirmed to have died from
bronchogenic carcinoma (Smith and Suzuki, 1980). Wagoner et al. apparently
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disregarded the conclusion of Smith and Suzuki that "the prevalence of
histopathologic cell types of bronchogenic carcinomas among beryllium-exposed
workers could not be presently defined." Smith and Suzuki attributed their
conclusion to the fact that there was "an inadequate response rate for the
submission of pathology specimens for review," since tissue specimens were not
available for 20 (43%) of the total number of lung cancers. Wagoner et al. ,
however, citing data from earlier studies (Haenszel et al. , 1962; Axtell et
al. , 1976) to the effect that the frequency of adenocarcinomas in U.S. white
males was 15 or 16 percent, concluded that a significant "shift" of histologic
cell types was apparent in lung cancer deaths in beryllium workers. However,
an internal NIOSH memorandum (Smith, 1978) stated that more recent data by
Vincent et al. (1977) indicated that a shift in the prevalences of
histopathological cell types of lung cancer in the general population over time
has led to an increase in the prevalence of adenocarcinoma to 24 percent, and
therefore the prevalence of adenocarcinomas in the lung cancer deaths of
beryllium workers is not significantly different from that expected. Smith
suggested in his memorandum that any mention by Wagoner et al. of the
histopathological examination of lung tumor specimens that does not take into
consideration the unrepresentative nature of the specimens should be deleted
from the paper.
To summarize, it appears that the authors of the Wagoner et al. (1980)
study tended to exaggerate the risk of lung cancer in a population of workers
potentially exposed to beryllium, and underemphasized or did not discuss suffi-
ciently the shortcomings of the study. The net effect was to turn a
"nonsignificant association" of lung cancer with beryllium exposure into a
questionable "significant association." Despite the study's problems, there
still remains a possibility that the elevated risk of lung cancer reported
therein was due in part to beryllium exposure, and although the CAG considers
the study inadequate to assess the risk of lung cancer from exposure to
beryllium at this time, it recommends further refinement and follow-up of this
cohort to determine if the reported increase associated with lung cancer
becomes statistically significant.
7.2.5 Infante et al. (1980)
In a companion paper by Infante et al. (1980), which appeared in the same
journal as the Wagoner et al. (1980) study, lung cancer mortality was studied
by the retrospective cohort method in white males for whom data had been
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entered into the Beryllium Case Registry (BCR) with diagnoses of beryllium
disease. A person was judged to have beryllium disease and thus to be eligible
for inclusion into the BCR if three or more (two were mandatory) of the
following five criteria were met (Hasan and Kazemi, 1974).
Mandatory -- (1) Establishment of significant beryllium exposure based
on sound epidemiologic history.
(2) Objective evidence of lower respiratory tract disease and
a clinical course consistent with beryllium disease.
Mandatory -- (3) Chest X-ray films with radiologic evidence of intersti-
tial fibronodular disease.
(4) Evidence of restrictive or obstructive defect with
diminished carbon monoxide diffusing capacity by physiologic
studies of lung function.
(5) 1 - Pathologic changes consistent with beryllium disease
on examination of lung tissue.
2 - Presence of beryllium in lung tissue or thoracic
lymph nodes.
At the time of the studies, close to 900 individuals had been entered into
the BCR, based on evidence of nonmalignant respiratory disease objectively
determined by appropriate and established medical procedures (Mullan, 1983).
According to Mullan (1983), the criteria listed above are characterized by
high sensitivity but low specificity. Hence, while they are able to identify
cases of actual beryllium disease, they can also lead to the inclusion of non-
beryllium disease cases, in particular, cases of sarcoidosis.
Infante et al. (1980) eliminated from their cohort all nonwhite and female
subjects because of their lack of "statistical sensitivity." They also
eliminated all subjects who were deceased at the time of the BCR entry. The
authors maintained that this constraint was necessary in order to ensure that
no bias would result from the "selective referral of individuals with the
outcome still under investigation", i.e. individuals with lung cancer. The use
of the above procedure, however, raises the question that such a self-imposed
constraint may not have prevented the "selective referral" of lung cancer
victims prior to their deaths. This possible effect might have been eliminated
if the above-referenced limitation had been applied to such cases as well. Or,
alternatively, it should perhaps have been assumed that no potential bias
existed, and that all BCR cases added posthumously should have been retained.
Altogether, Infante et al. (1980) included in their study cohort only 421
members of the BCR, less than 50 percent of the total. Of these, vital status
could not be determined for 64 (15%), while 139 (33%) were found to have died
by December 31, 1975. In this latter group, the causes of death could not be
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ascertained for 15 individuals. These were placed in an "undetermined cause of
death" category. The authors ceased accumulating person-years on the group of
64 with unknown vital status at the time each was last known to be alive
instead of to the end of the study. This procedure served to slightly reduce
expected mortality in every cause category. This reduction was offset,
however, by the fact that no potential deaths that might have occurred up to
the cutoff date were included. With the intense scrutiny given the issue of
lung cancer and beryllium by Infante and the many research investigators who
have worked with the BCR since its inception (including Wagoner, Bayliss, and
Mancuso), it is questionable whether any of the 15 deaths from undetermined
causes, or any of the 64 cases with unknown vital status, were lung cancer
deaths. Hence, it is probable that the estimated lung cancer risk is somewhat
overestimated by this procedure.
Additionally, since the same National Institute for Occupational Safety
and Health (NIOSH) life-table program that was used to calculate lung cancer
deaths in the Wagoner et al. study was the method used to derive expected lung
cancer deaths in the Infante et al. study, it was subject to the same problems
as mentioned previously, i.e. an 11-percent deficit in the calculated expected
lung cancer deaths. If it is assumed that this distortion is of the same
magnitude as that described in the discussion of the Wagoner et al. (1980)
study, the SMR of the Infante et al. (1980) study would also be inflated by 11
percent.
As expected, Infante et al. (1980) found a significantly high excess risk
of "non-neoplastic" respiratory disease (52 observed deaths versus 3.17
expected). In terms of total cancer, 19 deaths were observed versus 12.41
expected. With respect to lung cancer, 6 deaths occurred more than 15 years
after the onset of beryllium exposure versus 2.81 expected (p < 0.05). If the
expected deaths are adjusted upwards by 11 percent to compensate for the
overestimate produced by the NIOSH life-table program, the results are 6 deaths
versus 3.12 expected (p > 0.05).
Infante et al. divided their cohort on the basis of "acute" versus
"chronic" beryllium disease. Subjects were considered "acute" if the BCR
records indicated a diagnosis of chemical bronchitis, pneumonitis, or other
acute respiratory illness at time of entry into the registry. Subjects were
called "chronic" if BCR records indicated a diagnosis of pulmonary fibrosis or
some recognized chronic lung condition at time of entry into the registry. All
other cases, if they could not be designated as chronic, were considered by
7-39
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Infante et al. to be acute if the onset of the disease occurred within one year
of initial exposure. These definitions should not be confused with the
medically accepted definitions of acute and chronic beryllium disease, in which
cases of beryllium disease lasting one year or less are termed "acute," while
those lasting longer than one year are termed "chronic." The authors found no
significant lung cancer, not even an excess in their "chronic" respiratory
disease group of 198 persons (1 observed death versus 1.38 expected). However,
in their "acute" respiratory disease group, they found 6 observed lung cancer
deaths versus 1.91 expected (p < 0.05), and in the interval of more than 15
years since initial onset of beryllium exposure, 5 observed lung cancer deaths
were found versus 1.56 expected (p < 0.05). These findings, however, suffer
from the same problems previously discussed regarding the NIOSH life-table
program and must therefore be regarded as questionable with respect to their
implications.
The possibility cannot be discounted that cigarette smoking may have con-
tributed to an excess risk in the Infante et al. (1980) study, despite the
authors' claim that cigarette smoking is unlikely to have played a role in the
marginally increased lung cancer risk they found. Although the criteria for
inclusion in the BCR have been undergoing revision to improve their sensitivity
and specificity since the Registry's inception in 1952, it is possible that, in
the early years of the Registry, the criteria could have allowed the inclusion
of individuals with respiratory disease either brought on or exacerbated by
cigarette smoking. Such individuals would then have been likely candidates for
selection into the BCR. Of the seven lung cancer cases discussed by Infante et
al. (1980), six were admitted to the hospitals for treatment before 1955, and
one was admitted in 1964. The ability to detect subtle radiographic changes
consistent with a diagnosis of beryllium disease was relatively undeveloped in
the early 1950s. Given current practices in the interpretation of X-rays and
pulmonary function data, such a misdiagnosis would be unlikely today.
Any one of the factors referred to above could have been of sufficient
magnitude to produce a significant excess lung cancer risk in the group under
study. The authors' treatment of these confounders serves to exaggerate this
risk without presenting any compensating negatives. It appears likely that
correcting or controlling the influence of two or more of these factors could
reduce the estimated risk calculated to nonsignificance. The findings of
Infante et al. (1980) are thus seen to be, at best, only suggestive of an
increased risk of lung cancer from exposure to beryllium.
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7.2.6 Mancuso and El-Attar (1969)
The first in a series of four epidemiologic studies of mortality in
workers exposed to beryllium was conducted by Mancuso and El-Attar (1969) on
the same study population used in the Bayliss and Wagoner studies. The names
and social security numbers of individuals who made up the cohort in the
Mancuso and El-Attar study, however, were derived from quarterly earnings
reports provided by the Social Security Administration. Quarterly earnings
reports on every employee of a given company covered by social security are
filed four times a year by all companies included under the Social Security
Act. These reports generally consist of lists of names, social security
numbers, dates of birth, and reported earnings during the quarters for which
filing is done. With respect to beryllium, Mancuso and El-Attar obtained
quarterly earnings reports for both companies studied by Bayliss et al. (1971)
and Wagoner et al. (1980), but limited their study to the period of employment
from 1937 to 1948. Altogether, they identified 3685 white males from two
beryllium plants. Only 729 white males were found to have died through the
year 1966. Included in this group were 31 lung cancers (ICD 162-163). The
authors contrasted internally generated age-, plant-, and period-specific death
rates by cause with internally generated age-specific death rates by cause from
an "industrial control." Unfortunately, because of the small numbers involved,
the authors did not include any employees aged 55 or over. The industrial
cohort used for purposes of comparison was not identified. The 729 deaths were
distributed into 160 narrow subcategories, based on four broad age groups, two
companies, four periods of time, and five broad death categories. Internal
death rates were computed in each subcategory. Because the numbers from which
these internal rates were derived are so small (in some instances nonexistent)
from one subcategory to another, the comparisons with 20 rates generated from
the industrial control are shaky at best and appear to vary considerably. No
trends are evident. No significance tests were done. The data are open to
interpretation. The authors themselves conclude, based on their analysis, that
their data are "severely limited" with respect to answering the question of
carcinogenic risk.
7.2.7 Mancuso (1970)
In a second study of the same cohort, Mancuso (1970) added duration of
employment as a variable, and divided the cohort into a 1937 to 1944 component
and a 1945 to 1948 component, by dates of initial employment. Both subgroups
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were followed until 1967, and internal death rates were computed based on a
technique the author termed "the generation cohort method." Each cohort was
classified into 10-year age groups, beginning with 1940. An average annual
mortality rate was calculated by age as of 1940. Age adjustment was done
through the direct method, using the 1950 standard million as a base population
(presumably the U.S. 1950 standard million, although the author does not
specifically identify his comparison population). Comparisons were internal by
gradient of exposure as defined by duration of employment and by evidence of
prior chemical respiratory disease.
A higher rate of lung cancer was noted by the author among workers whose
first employment occurred during the period 1937 to 1944 in age category 25 to
64, and who were employed for five or fewer quarters (99.9 per 100,000)
compared to those employed six quarters or longer (33.2 per 100,000) based on
16 and 4 lung cancers, respectively. In one company, the author also found a
higher rate of lung cancer among a group of workers with histories of chemical
respiratory illness than in those who did not have this condition. During the
1940 to 1948 period, 142 white males with respiratory illness were identified
in this plant. Out of a total of 35 deaths occurring in this group, 6 were due
to lung cancer. Based on these 6 lung cancers, an age-adjusted lung cancer
death rate of 284.3 per 100,000 was calculated, compared to an age-adjusted
rate of 77.7 per 100,000 (based on 9 lung cancer deaths) in the total cohort of
this company's workers employed from 1937 to 1948. These calculations were
confined to individuals who were in the 25 to 64 age group in the year 1940.
For some unknown reason, the author neglected to include the 15 to 24 age
group. Had he done so, the lung cancer death rate in individuals without prior
respiratory illness would have increased by the addition of two lung cancer
deaths, leaving the rate unchanged in those with respiratory illness and
narrowing the difference between the two rates. No significance tests were
done, and, as noted by the author, the observations were based upon small
numbers.
Although Mancuso (1970) found elevated risks in these groups, the results
are subject to considerable variability. Mancuso criticized his own study for
several alleged deficiencies. Some of these criticisms seem inappropriate,
while others appear valid for this study and also for later studies by Mancuso
on this same population. The deficiencies, according to Mancuso, consisted of
"the marked influence of labor turnover on duration of employment, perhaps
induced by the presence of respiratory disease; the inability to define the
specific populations by department, process, or by type or form of beryllium
7-42
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exposure; the presence of competing causes of death; and the shortness of the
period of observation." Other potential problems with these data, which were
not mentioned by the author, are a lack of consideration of the effects of
smoking and the effects of exposure to potential carcinogens in other jobs the
workers may have had before and after their exposure to beryllium, since the
suggested increase appeared only in "short-term employees." This is discussed
further in a later description of the study (Mancuso, 1979). The author's
conclusion that prior chemical respiratory illness influenced the subsequent
development of lung cancer among beryllium workers may be somewhat overstated,
in view of the many limitations of the study.
7.2.8 Mancuso (1979)
In a third update, Mancuso (1979) conducted a cohort mortality study in
which he divided the cohort into two subgroups, each consisting of former and
current employees of the two beryllium manufacturing companies. Employees were
included in the study if they had worked at any time during the period from
1942 to 1948. The original source documents, from which names and social
security numbers were derived to form the cohort, consisted of quarterly
earnings reports submitted to the Social Security Administration. The Ohio
cohort consisted of 1222 white males, of which 334 were deceased. The
Pennsylvania cohort consisted of 2044 white males, of which 787 were deceased.
A life-table analysis was performed by NIOSH, utilizing U.S. white male age-
and period-specific rates (5-year age groupings) to generate expected lung
cancer deaths (ICD 162, 163) through 1974 for the Ohio cohort, and through 1975
for the Pennsylvania cohort. An excess risk of lung cancer appeared in the
Ohio employees after a lapse of 15 years from the onset of employment (22
observed versus 9.9 expected, p < 0.01). The same was true for the
Pennsylvania employees (36 observed versus 22.0 expected, p < 0.01) following a
similar latent period. The author noted that this risk occurred to workers with
less than one year's duration of employment in the industry. No significant
excess risk was noted in workers of either plant who were employed for more
than five years in the industry. The author concluded on the basis of this
study and the Wagoner et al. (1980) study that "there is evidence that
beryllium causes cancer in man."
Several questions must be considered before these conclusions can be
accepted as valid. These data, although derived from social security quarterly
earnings reports and not from personnel records, are not independent of the
data set utilized in the Wagoner et al. (1980) study. Both sets of data were
7-43
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analyzed through the use of the NIOSH life-table program. The expected deaths
generated in both studies are subject to the same influences introduced by the
use of the same life-table program, and by the use of the same comparison rates
(U.S. white male lung cancer rates). In addition, the extensive cooperation
between Mancuso (at the University of Pittsburgh) and Wagoner (at NIOSH) in the
search for causes of death in the respective cohorts for study, contributed to
the inclusion of lung cancer deaths known to one but not the other in both
studies. As mentioned previously, because of the use of the NIOSH life tables
in the Mancuso study, the calculation of expected lung cancer deaths was on the
low side (approximately 11%) because of the same artifact involving the calcu-
lation of lung cancer rates for which the Wagoner et al. (1980) study was crit-
icized. Hence, these results should not be considered independent of the
results of the Wagoner study.
Another problem with this cohort is the use of social security quarterly
earnings reports to constitute a cohort of potentially exposed employees. These
files, for the most part, are limited with respect to the data available. Only
the full name, social security number, and amount paid into the system each
quarter of any given year are provided, and only for covered employees. An
examination of microfilm records of the reports maintained by the Social
Security Administration shows that there is no possibility of determining from
the reports what jobs these individuals performed for the companies, where
their job stations were located, whether their jobs were on or off the
premises, or whether they had actually been exposed to beryllium, or even
precisely when during the three-month period they actually started work. And,
of course, these records give no information on workers who were not covered by
the Act. Furthermore, in the period prior to 1942, the social security system
was in the process of being established, and tremendous logistic problems in
setting up the system were being encountered during this time. Because the
system was not fully functional until 1942, millions of employees throughout
the country did not get social security numbers until after that date. Large
numbers of employees refused to join the system because they considered it to
be "welfare," and many more simply reported their social security numbers
inaccurately if at all when applying for work. Thus, questions remain
concerning the validity of this cohort.
Another difficulty with the Mancuso (1979) study, as with his earlier
studies, is a lack of discussion of other exposures these workers may have
received. The author observed that the main effect (lung cancer) occurred in
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short-term employees more than 15 years after initial employment. These workers
had an opportunity to be exposed to other potential carcinogens at jobs they
may have held prior to or immediately following their short employment in the
beryllium industry. This is a distinct possibility because the beryllium-
manufacturing companies are located in or near heavily industrialized areas of
Ohio (Cleveland, Toledo) and Pennsylvania (Reading). Roth and Associates
(1983) report the presence of several industries in the Lorain, Ohio area in
the period from 1942 to 1948 that conceivably could have provided an oppor-
tunity for short-term employees to receive exposure to potential carcinogens
(Table 7-12).
TABLE 7-12. INDUSTRIES IN THE LORAIN AREA 1942-1948
Company Operations Approx. No. Employees
National Tube Foundry, rolling, extruding, 12,000
(now U.S. Steel) coke ovens
Thew Shovel Foundry, machining, fabricating 2000
Lorain Products Electrical conductors, 500
fabricating, nonferrous foundry
American Crucible Structural steel parts, machining, 200
fabricating, foundry
Iron Ore Ship Dock Unloading ore ?
Source: Roth and Associates (1983)
Another serious omission of the Mancuso (1979) study is the lack of a dis-
cussion of the effect of cigarette smoking on the target organ of interest,
i.e. the lung. With respect to the question of smoking, it would appear likely
that since there was considerable overlap between this study and the Wagoner
study, it is probable that most of the lung cancer victims in the Pennsylvania
cohort of the Mancuso study were smokers. Hence, it is possible that cigarette
smoking contributed to the increased risk of lung cancer in the Pennsylvania
cohort. No information was provided in the Ohio portion of the Mancuso study
regarding the smoking influence, an exposure of considerable importance in lung
cancer. The findings of significant excesses of lung cancer in both plants
must be seen as limited because of the inadequate consideration of the con-
founding effects of these two likely exposures, the problem with the NIOSH
7-45
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life-table programs, and the inadequate nature of social security quarterly
earnings reports in defining an occupationally exposed cohort for study.
7.2.9 Mancuso (1980)
In the fourth update to his study of workers potentially exposed to beryl-
lium in two beryllium-manufacturing facilities, Mancuso (1980) found statisti-
cally significant elevated risks of lung cancer in 3685 white males employed
during the period from 1937 to 1948 and followed until the end of 1976, when
contrasted with viscose rayon workers. The beryllium cohort, as mentioned
earlier, was derived from quarterly earnings reports filed with the Social
Security Administration by the two companies. The only new addition to this
latest update was the introduction of a new comparison population, that of
viscose rayon workers. The source or location of these workers, however, is
not mentioned by the author, who states that the "viscose rayon cohort" was
derived from one company's "complete" file of microfilmed employment data on
employees first hired during the period from 1938 to 1948 and followed until
1976 (a period which began one year later than that of the beryllium cohort).
The origin and description of this group of workers is inadequately discussed.
Lung cancer mortality experience in the beryllium cohort was contrasted
with that expected, based on rates specific to age and duration of employment
generated from the mortality experience of the viscose rayon worker cohort.
Rates were based either on the total group of employees in the viscose rayon
industry, or on employees with permanent assignments to only one department,
according to the author. Presumably, those who moved from one department to
another were excluded from the lung cancer death rate calculations in the
second method. No rationale is presented by the author to explain why
mortality in beryllium workers should be contrasted with expected deaths
derived in these two separate ways. However, the net result was two separate
sets of expected lung cancer rates that differed considerably from each other.
Mancuso observed 80 lung cancer deaths in his beryllium cohort of employees
from the two companies combined, as compared to 57.06 expected deaths based on
the former set of derived rates and 50.63 expected deaths based on the latter
subset of employees working their entire time in only one department. The
author did not compare his beryllium workers on the basis of time since onset
of employment, but did contrast them by duration of employment. He found a
statistically significant excess risk of lung cancer in employees who had been
employed for one year or less, and also in employees who had been employed for
7-46
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four or more years by the beryllium companies. No basis was given for choosing
four years of total employment as the point at which short-term workers should
be separated from long-term workers. In his earlier versions, the author
utilized different durations of employment, i.e. five quarters (1 1/4 years)
and five-year duration of employment categories.
An interesting omission from this study is any consideration of the
effects of latency according to duration of employment. It seems unusual that
a discussion of this topic was not included by Mancuso, since the major output
of the NIOSH life-table program, which was utilized by Mancuso, is a set of
tabulations by time since onset of employment. Lung cancers diagnosed within
ten years of initial exposure probably were not a consequence of that exposure.
Furthermore, the designation "duration of employment" is not necessarily
uninterrupted continuous employment. In reality, what is meant is "total
employment", that is periods of time when the employee was not exposed or not
actually working. Layoffs and terminations, sickness, vacations, and leaves of
absence between initial employment and final day of employment are not counted
by the NIOSH life-table program in the category "duration of employment."
Therefore, it is possible that included in the observed deaths are the deaths
of individuals who had worked only a few days for the companies and who died
from lung cancer 20 years later, as well as individuals who worked for the
companies for several years continuously, but who died within five years of
initial employment.
Additionally, the viscose rayon cohort appears to have been a somewhat
younger population by age at hire than was the beryllium cohort (47.2% in the
viscose rayon cohort were under age 25 when hired, compared to the beryllium
cohort in which 38.4% were under age 25 when hired). Whether or not the author
adjusted for age differences is questionable. Indeed, at the Peer Review
Workshop on the Health Assessment Update for Beryllium (February, 1984)
sponsored by the U.S. Environmental Protection Agency, an epidemiologist from
NIOSH, Dr. Jean French, expressed concern that the age adjustment in Mancuso1 s
comparison of expected mortality based on viscous rayon workers with that of
actual mortality from Mancuso's beryllium cohort was "inadequate." Dr. French
reported that NIOSH reanalyzed the data and found serious problems with
Mancuso's analysis. Efforts to resolve this issue have not been successful
through official NIOSH channels. Unsuccessful attempts to obtain the results
of the analysis from NIOSH have made it difficult to determine the magnitude of
impact of the required adjustment on risk estimates. Since the viscous rayon
7-47
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cohort was younger than the beryllium cohort, the net impact of an adjustment
would be to decrease the gap between observed lung cancer deaths based on the
beryllium cohort and expected deaths based on the viscous rayon cohort.
Another problem concerns the acquisition of cause-of-death data. Some
4.3 percent of the reported deceased members of the viscous rayon cohort
remained without a cause of death, compared to only 1.5 percent of the
beryllium cohort. This could potentially lead to a greater underestimate of
lung cancer in the viscous rayon cohort compared to the beryllium cohort if the
causes of death in these two groups were fairly evenly distributed.
As in the earlier studies by the same author, a further difficulty with
this study is its lack of discussion of the confounding effects of smoking and
its disregard of potential exposures received not only while working for the
beryllium companies, but also in jobs prior and subsequent to employment in the
beryllium industry. This represents a particular problem because a large
majority of this cohort worked for less than one year. Because the towns in
which the beryllium companies were located were considerably industrialized,
work in these industries could potentially have produced exposures to other
known or suspected carcinogens. As an example, one of the major employers in
the Lorain, Ohio area in the period from 1942 to 1948 was the National Tube
Company (now U.S. Steel), whose operations involved extensive exposure to coke
ovens. Nothing is revealed in the study of the origin or makeup of the viscous
rayon cohort. What is known about its location comes from the Wagoner et al.
(1980) study in which the authors stated that Mancuso's viscous rayon cohort
was located in the vicinity of the beryllium companies.
Furthermore, since both cohorts utilized the NIOSH life-table program,
both suffer from the previously discussed 11-percent underestimation of
expected lung cancer deaths.
In conclusion, despite the author's certainty regarding the existence of a
causal relationship between beryllium exposure and lung cancer, the evidence
presented in this study is not convincing because of the many limitations of
the study, as described above. Hence it would appear that the study is at best
only suggestive of an increased risk of lung cancer due to exposure to
beryllium.
7.2.10 Summary of Epidemiologic Studies
Although several studies claim a statistically significant excess risk of
lung cancer in individuals exposed to beryllium, all of the studies cited have
7-48
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deficiencies that limit any definitive conclusion that a true association
exists. Support for a finding of an excess risk of lung cancer in beryllium-
exposed persons consists of evidence from cohort mortality studies of two
companies (Table 7-13) and one cohort mortality study of cases admitted to the
Beryllium Case Registry. None of these studies can be said to be independent,
since all are studies of basically the same groups of workers. Extensive
cooperation existed between the authors of all of these studies, even to the
extent of running all cohorts through a NIOSH computer-based life-table program
known to produce an 11-percent underestimate of expected lung cancer deaths at
the time. This problem has since been remedied. Furthermore, the authors
could not adequately address the confounding effects of smoking or of exposures
received during prior and subsequent employment in other non-beryllium indus-
tries in the area known to produce potential carcinogens (especially in beryl-
lium workers with short-term employment). Problems in the design and conduct
of the studies further weaken the strength of the findings. There appeared to
be a tendency on the part of the authors to overemphasize the positive nature
of their results and minimize the contribution of qualifying factors. A list
of these problems is presented in Table 7-14. If the errors detailed in the
preceding paragraphs were corrected and proper consideration given to
addressing the problems described above, the finding of a significant excess
risk would probably no longer be apparent, although the possibility, neverthe-
less, remains that a portion of the remaining excess lung cancer risk may
be partially due to beryllium exposure. Thus, the CAG feels that the findings
of these studies must be considered to be at least suggestive. The Internation-
al Agency for Research on Cancer (IARC) has concluded that beryllium and its
compounds should be classified as "limited" with respect to the human epidemi-
ologic evidence of carcinogenicity. The CAG, however, regards the epidemiologic
evidence of beryllium carcinogenicity in beryllium-exposed workers as inadequate.
7.3 QUANTITATIVE ESTIMATION
This quantitative section deals with estimation of the unit risk for
beryllium as a potential carcinogen in air, and compares the potency of beryl-
lium to other carcinogens that have been evaluated by the CAG. The unit risk
for an air pollutant is defined as the incremental lifetime cancer risk to
7-49
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TABLE 7-13. COMPARISON OF STUDY COHORTS AND SUBCOHORTS OF TWO BERYLLIUM COMPANIES
i
en
O
Bayliss
(1971)
Bayliss
Lainhart
Bayliss
Wagoner
et al.
and
(1972)
and
(1977)
Company
where
employed
KBI, BRUSH
6818 males
KBI only
3795 white
males
KBI-Reading
Facility only
Period of
Source employment
Personnel 1942-1967
records
Same as 1942-1967
above
Same as 1942-1967
above
Comparison
population
U.S.
males
U.S. white
males
U.S. white
males
Termination
date of Chief lung ,
follow-up cancer results
1967 Total
36~70),
1967 Total
25~70),
Latency
14 (0),
1975 Total
46~70),
34.
23
15
13.
33
1 (E)
(E)
yrs +
3 (E)
(E)
Wagoner et al.
(1980)
3070 white
males
KBI-Reading
Facility only
3055 white
males
Same as
above
1942-1967
U.S. white
males
1975
(p < 0.05)
Latency 15 yrs +
37 (0), 24 (E)
(p < 0.05)
Total
47~70), 34.3 (E)
(p < 0.05)
Latency 15 yrs +
38 (0), 24.86 (E)
(p < 0.05)
Mancuso and
El -Attar (1969)
KBI, BRUSH
3685 white
males
Social 1937-1948
Security
Quarterly
Earnings
Reports
Industrial 1966
Control
(Unidentified)
Equivocal
(continued on the following page)
-------
TABLE 7-13. (continued)
en
Company
where
employed3
Mancuso (1970) KB I, BRUSH
3685 white
males
Mancuso (1979) KBI-2044
BRUSH- 1222
white males
Mancuso (1980) KBI
3685 white
males
Period of
Source employment
Social 1937-1944
Security and
Quarterly 1945-1948
Earnings
Reports
Same 1942-1948
Same 1937-1948
Comparison
population
Internal
Control
U.S. white
males
Viscous
rayon
workers
Termination
date of
follow-up
1966
BRUSH
1974
KBI
1975
1976
Chief lung .
cancer results
Duration of employment (rate)
> 1 1/4 yrs 33.2/1055
< 1 1/4 yrs 99.9/105
Prior respiratory disease only
with 284.3/105
without 77.7/105
Latency 15 yrs + only
Ohio - 22 (0), 9.9 (E)
(p < 0.01)
Pennsylvania - 36 (0), 22 (E)
(p < 0.01)
Mobility (deaths)
Among departments
80 (0), 57.1 (E)
(p < 0.01)
Remained in same department
80 (0), 50.6 (E)
(p < 0.01)
KBI = Kawecki-Berylco Industries (Pennsylvania).
BRUSH = Brush Beryllium Co. (Ohio).
(0) = observed
(E) = expected
-------
TABLE 7-14. PROBLEMS WITH BERYLLIUM COHORT STUDIES
Bayliss et al. (1971)
Bayliss and Lainhart (1972)
Bayliss and Wagoner (1977)
and
Wagoner et al. (1980)
Mancuso and El-Attar (1969)
Mancuso (1970)
Mancuso (1979)
Mancuso (1980)
A. Loss of 2000 individuals because of insufficient data.
B. No latency considerations.
C. Combined study populations of several plants from two
companies.
A. Includes clerical and administrative personnel with no
exposure.
B. No independent assessment plant employment files.
C. Latency after 20 years not assessed.
A. Cigarette smoking a possible confounder.
B. Underestimate of expected lung cancer deaths in comparison
population by 11 percent.
C. Inclusion of 1 lung cancer victim who did not fit
definition for inclusion.
D. Loss of 295 individuals from study cohort.
E. Exposure to potential carcinogens prior and post beryllium
employment.
A. Unidentified comparison population.
B. Internal rates based on small numbers.
C. Tremendous variability and impossible to test
significance.
D. No smoking consideration as possible confounder.
A. Internal rates based on small numbers.
B. Inappropriate comparison (age group 15-24 left out of
comparison).
C. No consideration of smoking as a possible confounder.
D. No consideration of latency.
E. Exposure to potential carcinogens prior and post beryllium
employment.
A. Underestimate of expected lung cancer deaths in comparison
population by 11 percent.
B. No consideration of smoking as a possible confounder.
C. Incomplete delineation of cohort from use of Social
Security Quarterly Earnings reports.
D. Exposure to potential carcinogens prior and post beryllium
employment.
A. No consideration of latent effects.
B. Probable lack of age adjustment.
C. No consideration of effects of smoking.
D. No description of origin or makeup of comparison cohort
except for age.
E. Underestimate of expected lung cancer deaths
in comparison population by 11 percent.
7-52
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•a
humans from daily exposure to a concentration of 1 ug/m of the pollutant in
air by inhalation.
The unit risk estimate for beryllium represents an extrapolation below the
dose range of experimental data. There is currently no solid scientific basis
for any mathematical extrapolation model that relates exposure to cancer risk
at the extremely low concentrations, including the unit concentration given
above, that must be dealt with in evaluating environmental hazards. For
practical reasons, the correspondingly low levels of risk cannot be measured
directly either by animal experiments or by epidemiologic studies. Low-dose
extrapolation must, therefore, be based on current understanding of the
mechanisms of carcinogenesis.
At the present time, the dominant view of the carcinogenic process
involves the concept that most cancer-causing agents also cause irreversible
damage to DNA. This position is based in part on the fact that a very large
proportion of agents that cause cancer are also mutagenic. There is reason to
expect that a quantal response characteristic of mutagenesis is associated with
a linear (at low doses) nonthreshold dose-response relationship. Indeed, there
is substantial evidence from mutagenicity studies with both ionizing radiation
and a wide variety of chemicals that this type of dose-response model is the
appropriate one to use. This is particularly true at the lower end of the
dose-response curve; at high doses, there can be an upward curvature, probably
reflecting the effects of multistage processes on the mutagenic response. The
linear (at low doses) nonthreshold 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). Some supporting evidence also exists from animal experiments (e.g. the
initiation stage of the two-stage carcinogenesis model in rat liver and mouse
skin).
Because its scientific basis, although limited, is the best of any of the
current mathematical extrapolation models, the nonthreshold model, which is
linear at low doses, has been adopted as the primary basis for risk extrapola-
tion to low levels of the dose-response relationship. The risk estimates made
with such a model should be regarded as conservative, representing a plausible
7-53
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upper limit for the risk, i.e. the true risk is not likely to be higher than
the estimate, but it could be lower.
For several reasons, the unit risk estimate based on animal bioassays is
only an approximate indication of the absolute risk in populations exposed to
known carcinogen concentrations. First, there are important species differ-
ences in uptake, metabolism, and organ distribution and elimination of carcin-
ogens, 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 as compared to animals on a
mg/surface area basis is virtually without experimental verification with
respect to the carcinogenic response. Finally, genetic constitution, diet,
living environment, activity patterns, and other cultural factors are quite
varied among different human populations.
The unit risk estimate can give a rough indication of the relative potency
of a given agent as compared with other carcinogens. Such estimates are, of
course, more reliable when the comparisons are based on studies in which the
test species, strain, sex, and routes of exposure are similar.
The quantitative aspect of carcinogen risk assessment is addressed here
because of its possible value in the regulatory decision-making process, for
example, in setting regulatory priorities, evaluating the adequacy of
technology-based controls, and so forth. However, the imprecision of presently
available technology for estimating cancer risks to humans at low levels of
exposure should be recognized. At best, the linear-extrapolation model used
here provides a rough but plausible estimate of the upper limit of risk—that
is, with this model it is not likely that true risk would be much more than the
estimated risk, but it could be considerably lower. The risk estimates
presented in subsequent sections should not be regarded, therefore, as accurate
representations of the true cancer risks, even when the exposures involved are
accurately defined. The estimates presented may, however, be factored into
regulatory decisions to the extent that the concept of upper-risk limits is
found to be useful.
7.3.1 Procedures for the Determination of Unit Risk
7.3.1.1 Low-Dose Extrapolation Model. Two dose-response models, which are
derivatives of the theory of multistage carcinogenesis, are used to calculate
the unit risk of beryllium on the basis of animal data. The selection of these
7-54
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two models is dictated by the nature of the data available for quantitative
risk assessment. The first model, a multistage model that allows for a
time-dependent dose pattern, was developed by Crump and Howe (1984), and uses
the theory of multistage carcinogenesis developed by Armitage and Doll (1961).
The Armitage-Doll multistage model assumes that a cell is capable of generating
a neoplasm when it has undergone k changes in a certain order. The rate, r- ,
j_ L 1
of the i change is assumed to be linearly related to D(t), the dose at age t,
i.e. r. = a. + b-D(t), where a. is the background rate, and b. is the propor-
tionality constant for the dose. It can be shown that the probability of can-
cer by age t is given by
P(t) = 1 - exp [-H(t)]
where
H(t) = J V uk... J U2 {[aj + b1D(u1)].
[(ak + bkD(U|<)]} dur..duk
is the cumulative incidence rate by time t.
When H(t) or the risk of cancer is small, P(t) is approximately equal to
H(t). When only one stage is dose-related, all proportionality constants are
zero except for the proportionality constant for the dose-related stage.
This model will be applied to the data in Reeves and Deitch (1969) where
the dose D(t) is constant for t in an interval [S-, , S?] and is zero elsewhere.
Under this particular exposure pattern and the assumption that only a single
stage is dose-related, the term H(t) can be written as the sum of two
components H-L(t) and H2(t) where H-^t) = a^ • a2 . . . ak t /k! represents the
background cumulative incidence and H2(t) is the incremental cumulative
incidence due to exposure. Three special cases of H? which are often used to
interpret a given set of data are given below.
0 t < s
H2(t) = l x (t - s/
kla-j^
(t - S) - (t -
7-55
-------
if the first stage is affected (r = 1),
0 t < s
1
H (t) = .) tk _ k-l[kt _ (k _ < <
k'a -1- 1-2
K'ak-l
sjj'^kt - (k-l)s2] - s^Ckt - (k-Ds^ s2 < t
if the penultimate stage is affected (r = k - 1), and
0 t < S;L
H,(t)= dbk<"ai> tk-sk Sl
-------
7.3.1.2 Selection of Data. For some chemicals, several studies in different
animal species, strains, and sexes, each run at several doses and different
routes of exposure, are available. A choice must be made as to which of the
data sets from several studies to use in the model. It may also be appropriate
to correct for metabolism differences between species and for absorption
factors via different routes of administration. The procedures used in
evaluating these data are consistent with the approach of making a maximum-
likely risk estimate. They are as follows:
1. The tumor incidence data are separated according to organ sites or
tumor types. The set of data (i.e. dose and tumor incidence) used in the model
is the set where the incidence is significantly higher statistically than the
control for at least one test dose level and/or where the tumor incidence rate
shows a statistically significant trend with respect to dose level. The data
set that gives the highest estimate of the lifetime carcinogenic risk, q£, is
selected in most cases. However, efforts are made to exclude data sets that
produce spuriously high risk estimates because of a small number of animals.
That is, if two sets of data show a similar dose-response relationship, and one
has a very small sample size, the set of data having the larger sample size is
selected for calculating the carcinogenic potency.
2. If there are two or more data sets of comparable size that are
identical with respect to species, strain, sex, and tumor sites, the geometric
mean of q£, estimated from each of these data sets, is used for risk
assessment. The geometric mean of numbers A-,, A^, ••-, A , is defined as
x ... x A
1/m
3. If two or more significant tumor sites are observed in the same
study, and if the data are available, the number of animals with at least one
of the specific tumor sites under consideration is used as incidence data in
the model .
7.3.1.3 Calculation of Human Equivalent Dosages. Following the suggestion of
Mantel and Schneiderman (1975), it is assumed that mg/surface area/day is an
equivalent dose between species unless adequate evidence is presented to the
contrary. Since, to a close approximation, the surface area is proportional to
the two-thirds power of the weight, as would be the case for a perfect sphere,
7-57
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the exposure in mg/day per two-thirds power of the weight is also considered to
be equivalent exposure. In an animal experiment, this equivalent dose is com-
puted 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 exposure is
2/3
Le x W
7.3.1.3.1 Inhalation Exposure. Often it is necessary to convert given expo-
sures into mg/day. 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 (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 absorp-
tion of poorly water-soluble gases is expected to be proportional to the meta-
bolic rate, which is proportional to the rate of oxygen consumption, itself a
function of surface area. Only the case of aerosols will be considered here.
7.3.1.3.1.1 Case 1. Agents that are in the form of aerosols can
reasonably be expected to be deposited proportionally to the breathing rate and
deposition fraction. In this case the dosage in mg/day may be expressed as
m = I x v x de
7-58
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3 3
where I = inhalation rate in m /day, v = mg/m of the agent in air, and de =
the deposition fraction.
If exposures are given in terms of ppm in air, the following calculation
may be used:
3
I ppm = 0.041/molecular weight (mg/m )
This relationship is based on sea level barometric pressure and a temperature
of 24°C. For other pressures and temperatures, an appropriate correction must
be made. Clearance rates may also influence dosage, but cross-species
comparisons are seldom available for making such adjustments.
The inhalation rates, I, for various species can be calculated from the
observations of the Federation of American Societies for Experimental Biology
(FASEB, 1974) that 25-g mice breathe 34.5 liters/day and 113-g rats breathe 105
liters/day. For mice and rats of other weights, W (in kilograms), the surface
3
area proportionality can be used to find breathing rates in m /day as follows:
For mice, I = 0.0345 (W/0.025)273 m3/day
For rats, I = 0.105 (W/0.113)273 m3/day
Respiratory values for most other laboratory species are also reported in FASEB
o
(1974). For humans, the value of 20 m /day* is adopted as a standard breathing
rate (International Commission on Radiological Protection, 1977). The
2/3
equivalent dose in mg/W for these agents can be derived from the air intake
data using an empirically derived factor for the air intake per kg per day, i =
I/W. These are tabulated as follows:
Species W i = I/W
Man
Rats
Mice
70
0.35
0.03
0.29
0.64
1.3
"From "Recommendation of the International Commisaion3on Radiological Protec-
tion,''page 9. The average breathing rate is 10 cm per 8-hour workday and
2 x 10 cm in 24 hours.
7-59
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2/3
Therefore, the equivalent exposure in mg/W is
d = _ = _ = jWvde = 1
w2/3 w2/3 w2/3
In the absence of experimental information or a sound theoretical argument
to the contrary, the fraction deposited, de, is assumed to be the same for all
species.
7.3.1.4 Calculation of the Unit Risk from Animal Studies. The risk associated
273
with d mg/kg /day is obtained from GLOBAL79, and for most cases of interest
to risk assessment, can be adequately approximated by P(d) = 1 - exp (-q*d). A
"unit risk" in units X is simply the risk corresponding to an exposure of X = 1.
2/3
This value is estimated by finding the number of mg/kg /day that corresponds
to one unit of X, and substituting this value into the above relationship.
3
Thus, for example, if X is in units of ug/m in the air, then for case 1, d =
1 /O _0 0/0 O
0.29 x 701/-3 x 10 mg/kg 7 /day, and for case 2, d = 1, when ug/nT is the unit
used to compute parameters in animal experiments.
Note that an equivalent method of calculating unit risk would be to use
3 for the animc
cient by an amount
mg/kg for the animal exposures, and then to increase the j polynomial coeffi-
(Wh/Wa)j/3 j = 1, 2, ..., k,
and to use mg/kg equivalents for the unit risk values.
7.3.1.4.1 Adjustments for Less Than Life Span Duration of Experiment. If the
duration of experiment L is less than the natural life span of the test animal
L, the slope q?, or more generally the exponent g(d), is increased by multiply-
3
ing by a factor (L/L ) . We assume that if the average dose d is continued,
the age-specific rate of cancer will continue to increase as a constant func-
tion of the background rate. The age-specific rates for humans increase at
least by the second power of the age and often by a considerably higher power,
as demonstrated by Doll (1971). Thus, it is expected that the cumulative tumor
rate would increase by at least the third power of age. Using this fact, it is
assumed that the slope q?, or more generally the exponent g(d), would also
increase by at least the third power of age. As a result, if the slope q^ [or
g(d)] is calculated at age L , it is expected that if the experiment had been
7-60
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continued for the full life span L at the given average exposure, the slope q?
3
[or g(d)] would have been increased by at least (L/Lg) .
This adjustment is conceptually consistent with the proportional hazard
model proposed by Cox (1972) and the time-to-tumor model considered by Daffer
et al. (1980), where the probability of cancer by age t and at dose d is given
by
P(d,t) = 1 - exp [-f(t) x g(d)]
7.3.1.5 Model for Estimation of Unit Risk Based on Human Data. If human epi-
demiologic studies and sufficiently valid exposure information are available
for a compound, they are always used in some way. If they show a carcinogenic
effect, the data are analyzed to give an estimate of the linear dependence of
cancer rates on lifetime average dose, which is equivalent to the factor B,,.
If they show no carcinogenic effect when positive animal evidence is available,
then it is assumed that a risk does exist, but it is smaller than could have
been observed in the epidemiologic study. An upper limit to the cancer inci-
dence is calculated, assuming hypothetically that the true incidence is below
the level of detection in the cohort studied, which is determined largely by
the cohort size. Whenever possible, human data are used in preference to
animal bioassay data.
Very little information exists that permits extrapolation from high-expo-
sure occupational studies to exposures at low environmental levels. However, if
a number of simplifying assumptions are made, it is possible to construct a
crude dose-response model whose parameters can be estimated using vital statis-
tics, epidemiologic studies, and estimates of worker exposures.
In human studies, the response is measured in terms of the relative risk
of the exposed cohort of individuals as compared with the control group. The
mathematical model employed for low-dose extrapolation assumes that for low
exposures the lifetime probability of death from cancer, PQ, may be represented
by the linear equation
PQ = A + BHx
where A is the lifetime probability in the absence of the agent, and x is the
average lifetime exposure to environmental levels in units such as ppm. The
factor BH is the increased probability of cancer associated with each unit
increase of x, the agent in air.
7-61
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If it is assumed that R, the relative risk of cancer for exposed workers
as compared to the general population, is independent of length of exposure or
age at exposure, and depends only upon average lifetime exposure, it follows
that
_ P . A + BH (xl + V
P
or
RPQ = A + BH (x1 + x2)
where x-. = lifetime average daily exposure to the agent for the general popula-
tion, x2 = lifetime average daily exposure to the agent in the occupational
setting, and PQ = lifetime probability of dying of cancer with no or negligible
exposure.
Substituting PQ = A + B,, (x-,) and rearranging gives
BH = P0 (R - D/x2
To use this model, estimates of R and x« must be obtained from epidemiologic
studies. The value PO is derived by means of the life- table methodology from
the age- and cause-specific death rates for the general population found in
U.S. vital statistics tables.
7.3.2 Estimation of the Carcinogenic Risk of Beryllium
In extrapolating from animal data, the equivalent human dose may be in-
fluenced by a variety of factors. An important variable for inhalation studies
is measurement (or estimation) of lung ventilation during exposure. In general,
differences in metabolic rate for animals of different sizes are adjusted by
variations in minute volume respiration rather than by lung volume per unit
body weight. It has been shown by McMahon et al. (1977), for example, that mi-
nute volume respiration varies with the 0.66 power of body weight. On this ba-
sis, it could be concluded that ventilation is almost perfectly adjusted for vari-
ations in metabolic rate, and if effective concentrations of a toxic chemical
7-62
-------
vary directly with metabolic rate, then equivalent concentrations could be con-
sidered the same in humans and experimental animals.
More commonly, however, dose conversions are carried out by using
estimated values for inspiratory volumes per unit time in combination with
metabolic rate conversion based on body weight to the two-thirds power. If the
generally accepted value of 20 m /day is used for humans, the human equivalent
concentration is decreased to slightly greater than one-third the value for
rats. This occurs primarily because the equivalent concentrations for rats are
based on respiratory levels measured for animals at rest. The human value,
however, represents a daily minute volume based on normal 24-hour activity
levels. While such a method of conversion is probably somewhat conservative,
it is not unreasonable, since rodent species normally sleep and therefore
respire less during the hours when exposure typically occurs.
The efficiency of deposition may also influence the equivalent human dose.
For small particles, such as those used in the beryllium inhalation studies,
the fraction deposited in the alveoli and smaller conducting airways would be
predicted to be somewhat less in rats than in humans (Raabe et al., 1977;
Lippman, 1977; Schlesinger, 1985). Within these studies, however, deposition
varied greatly within species due to breathing patterns and experimental
techniques. For most studies, the standard error of the means overlapped for
humans and rats exposed to comparable particle sizes. Furthermore, McMahon et
al. (1977) reported that for 0.75 pm diameter particles deposition percentages
were independent of species for animals ranging in size from mice to dogs.
Due to the variability in deposition efficiency, an adjustment in dose at
this time was not considered to be appropriate. Futhermore, even though
deposition may be slightly more efficient in humans, any small increase in the
human dose due to this factor is likely to be compensated for by the relatively
large estimate of human ventilation in comparison with laboratory species.
Retention of particles can be an important factor for determining dose to
the lung, since the degree of solubilization and absorption is related to
residence time. Rhoads and Sanders (1985) reported a clearance half-time for
beryllium in rats of 833 days. This is an exceptionally slow rate. Rats
normally clear even quite insoluble particles much more rapidly. Since 833
days exceeds the expected lifetime of the rat, it is doubtful that clearance
rate differences between rodents and humans will significantly influence
absorbed dose.
7-63
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In calculating exposure levels, a separation of total dose between the
fraction deposited in the tracheobronchial region and the alveolar region could
be considered. The Science Advisory Board suggested such an approach in
comments dated July 20, 1985. Such a separation would be of interest because
most human cases of lung cancer originate in the conducting airways. While
total deposition in this region is much less than in the alveoli, the surface
area is also less, so dose per unit of surface area may be as great or even
greater than in alveolar regions, especially at airway junctions where impac-
tion occurs.
Oberdoerster (personal communication) calculated an equivalent human
concentration in both alveolar and tracheobronchial regions using the data of
Reeves and Deitch (1969) as follows:
Ch = Cr (Ir/Ih) (Fr/Fl)
(Wr/Wh)2/3
where Ch - equivalent human concentration, Cr = exposure concentration for the
3
rat, I = the volume of air inspired per day (Ir = 0.223 m /day for rats and Ih
3
= 20 m /day for humans), W = body weight (Wr = 0.35 kg for rats and Wh = 70 kg
for humans), and F = the fraction of inhaled particles deposited in the respira-
tory tract. For the tracheobronchial region, Fr = 0.01 for rats and Fh = 0.02
for humans, and for the alveolar region, Fr = 0.1 for rats and Fh = 0.2 for
humans.
3
For a concentration of 35 (jg/m in the rat studies, the human equivalent
3
concentration was calculated to equal 6.7 M9/m i'n both the alveolar and the
tracheobronchial regions. The values were identical because the ratios of
relative deposition efficiency between rats and humans was considered to be the
same for both regions of the lungs.
This method did not take into account possible differential deposition at
airway junctions, which are considered likely areas for the origin of many human
lung cancers. This method also failed to account for differential absorption
efficiencies based on much more rapid clearance of deposited particles from the
conducting airways (less than one day) than from alveolar regions. Unfortu-
nately, little data are available to accurately estimate differential absorption
between alveoli and conducting airways.
7-64
-------
Human equivalent concentrations using Oberdoerster's calculations differ
slightly from those appearing in this document for two reasons: lung
deposition in humans was assumed to be twice that of the rat, and no adjustment
was made for less than 18-months exposure duration.
Finally, consideration should be given to the appropriateness of a surface
area versus a body weight correction of inhaled dose. Dose corrections compen-
sating for metabolic rate differences are largely based on the belief that a
smaller animal, with a correspondingly more rapid metabolic rate, will inactivate
or eliminate potentially harmful xenobiotics more rapidly.
Several lines of evidence indicate that beryllium may be sequestered in
the cells lining the alveoli and bronchioles and is inactivated or eliminated
slowly, if at all. For example, as mentioned earlier, beryllium oxide is
cleared very slowly. Rhoads and Sanders (1985) attributed this to low solubil-
ity, but even beryllium compounds, such as beryllium sulfate, which is con-
sidered to be quite soluble, are cleared slowly (Reeves and Vorwald, 1967).
Moreover, compounds such as titanium oxide, which are known to be highly insolu-
ble, are cleared with half times of only two to three months (Ferin and Leach,
1977). The very slow rate of clearance of beryllium suggests that most of it
enters the intracellular compartment following deposition. This possibility is
supported by studies of Wagner et al. (1969), in which it was shown that less
than one percent of the deposited dose was transferred to the liver, kidneys,
or bone. Since lung cancer was induced in this study, the solubilized beryl-
lium most likely remained in the lung cells rather than moving into the blood
with transport to other organs.
According to Vorwald et al. (1966), inhaled beryllium aerosols are
precipitated by lung fluids, but then hydrolysis results in a supply of
beryllium ions that enter the cell and react with macromolecules, possibly DNA
and RNA. Vorwald and Reeves (1959) found that 85 percent of subcellular
beryllium sedimented in the nuclear fraction. Any conclusions were limited,
since the actual localization of beryllium could not be shown by biochemical
means. Firket (1953), however, was able to identify beryllium histochemically
in the nucleolus, an organelle made up of macromolecules including RNA. If
beryllium reacts with macromolecules and no mechanism is available for elimina-
tion or deactivation, then toxic dose levels are not likely to correlate well
with metabolic rate.
7-65
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Although the data suggest that beryllium is bound intracellularly and is
eliminated very slowly, the evidence is not sufficiently conclusive to show
that a dose adjustment based on metabolic rate is incorrect. Moreover, Vorwald
and Reeves (1959) reported that clearance of beryllium was initially quite
rapid following cessation of exposure to beryllium sulfate, with the remainder
cleared at a much slower rate. If the slowly cleared fraction is bound to
macromolecules, then the size of this fraction would be limited by potential
reactive sites. Little is known of possible differences between humans and
laboratory animals in this respect.
The direct experimental evidence available to compare effective dose with
body size, or to determine if the rat is uniquely susceptible to the carcino-
genic effects of beryllium, is quite limited. While no definitive positive
results are available for hamsters, Wagner et al. (1969) reported atypical pro-
liferations in animals of this species exposed to beryl ore at beryllium levels
3
of 620 [jg/m , a dose producing tumors in 18 of 19 rats. The authors would have
considered these proliferations to be broncho-alveolar tumors except for their
size. It is quite possible that these proliferations would have progressed to
tumors if the hamsters had a longer life span. Other investigators, such as
Dontenwill et al. (1973), reported a progression of effects in hamsters' lungs
from hyperplasia through metaplasia, anaplasia, and leucoplakia, but not to
overt cancer, following exposure to a known carcinogen, cigarette smoke. They
also suggested that the life span of the hamster may be too short to allow full
development of lung cancer.
Although statistically significant positive responses were not seen in
guinea pigs, Schepers (1971) reported the occurrence of lung tumors in 2 of 20
animals exposed to beryllium sulfate and in 1 of 30 males and 1 of 20 females
exposed 12 months to beryllium oxide. Since lung tumors are extremely rare in
guinea pigs, this response is suggestive even if exposure conditions were not
well described and control values were not reported.
The only species other than rats in which a clear-cut response occurred
was the rhesus monkey. In these studies, reported by Vorwald et al. (1966) and
3
Vorwald (1968), the mean beryllium concentration was 38.8 ug/m . The monkeys
were exposed an average of 15 hours a week, compared with 30 to 35 hours a week
during most of the rat studies. If the exposure duration is adjusted to be com-
parable to rats, the monkeys could have been exposed to about 15 ug/m of beryl-
3
lium. Eight of 11 monkeys (76%) in this study developed tumors. At 35 ug/m ,
7-66
-------
the response in rats to soluble beryllium compounds was generally 90 percent or
o
more, while in one study conducted at 2.8 ug/m beryllium, 62 percent responded
positively. Based on this limited evidence, monkeys appear to be about as sen-
sitive as rats.
While data on hamsters, guinea pigs, and monkeys are individually weak,
taken collectively the data suggest that the rat is not uniquely sensitive to
beryllium. In fact, rhesus monkeys, much closer relatives of man, appear to be
as sensitive as rats. The very limited data for monkeys also indicate that,
since a comparable concentration results in a similar response to that of rats,
a surface area correction for dose remains plausible.
7.3.2.1 Calculation of the Carcinogenic Potency of Beryllium on the Basis of
Animal Data. Only the data from inhalation studies are used for risk assess-
ment because that route of administration is the exposure route of interest
to humans. Although there are many animal studies showing carcinogenic effects
of beryllium by inhalation, the data that can be used for estimating the car-
cinogenic risks associated with beryllium are very limited. In order to pro-
vide some comparison among species, potency values were estimated for guinea
pigs and rhesus monkeys, as well as for rats, even though the studies using the
former two species were poorly documented and, in the case of guinea pigs, only
suggestive of an effect. Except for Reeves and Deitch (1969), the studies were
conducted at single dose levels and/or did not include control groups. In Reeves
and Deitch (1969), animals were exposed to nine different dose patterns, varying
in the duration of exposure and the time at which exposure was begun and termi-
nated. The data from Reeves and Deitch (1969) and nine other studies that had
only single dose levels are used herein to calculate the carcinogenic potency
of beryllium. For the Reeves and Deitch data, the multistage model with time-
dependent dose patterns is used as the low-dose extrapolation model. The data
and the calculations are presented in the Appendix. For the studies with single
dose levels, the one-hit model, as described in section 7.3.1.1, is used as the
low-dose extrapolation model. The data for the nine studies with single dose
levels and potency estimates on the basis of all ten of the data sets are pre-
sented in Table 7-15. Both body weight and surface area corrections have been
used to arrive at an equivalent human dose.
In all of these calculations, the equivalent concentrations are arrived at
by the following procedure, using ventilatory values arrived at as described in
o
section 7.3.1.3.1.1. For an experimental exposure concentration of 1 ug/m ,
2
where 0.224 m /day is assumed to be the volumetric breathing rate for a rat
7-67
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TABLE 7-15. BERYLLIUM DOSE-RESPONSE FROM TEN INHALATION STUDIES ON ANIMALS AND THE CORRESPONDING
POTENCY (SLOPE) ESTIMATIONS
en
Co
Beryl 1 ium
Investigator compound
Mean beryllium
concentration
exposure pattern
Standardized
experimental
concentration
(ug/m3)
Pulmonary
tumor Surface
incidence area
rate correction
Human
equivalent
concentration
(ug/Be/m3)
Maximum
likelihood .
estimate slope
(ug/m3)-1
RATS
Vorwald BeSO.
(1953)
Schepers et al . BeSO.
(1957)
Schepers BeHPO.
(1961) 4
Schepers BeF?
(1961)
Vorwald BeSO.
et al.
(1966)
Reeves and BeSO.
Deitch
(1969)
33 ug/Be/m3
35 hr/wk for 13
months
33.5 ug/Be/m3
35 hr/wk for 7.5
months
227 ug/Be/m3
35 hr/wk for 6.5
months
9 ug/Be/m3
35 hr/wk for 10.5
months
2.8 |jg/Be/m3
35 hr/wk for 18
months
35.7 pg/Be/m3
35 hr/wk for 18
months
5.0
2.9
17.1
1.1
0.58
7.4
4/8 +
58/136 +
7/40 +
11/200 +
13/21 +
13/15 +
1.9
11.2
1.1
6.5
6.5
39.6
0.42
2.5
0.22
1.30
2.8
16.6
3.7 x 10"J
6.3 x 10 ^
5.0 x 10~i
8.6 x 10 L
3.0 x I0"i
5.0 x 10 J
1.4 x 10"i
2.4 x 10"^
4.3 x 10°,
7.4 x 10 i
7.1X10'1
1.2 x 10 x
(continued on the following page)
-------
TABLE 7-15. (continued)
i
en
Investigator
Wagner
et al.
(1969)
Reeves and
Dei ten
(1969)
Schepers
(1971)
Vorwald
(1968)
Mean beryl 1 ium
Beryllium concentration
compound exposure pattern
beryl ore 620 ug/Be/m
intermittently for
17 months
BeSO. 35.7 (jg/Be/m3
35 hr/week for
varying durations
BeSO. 36 ug/Be/m3
35 hr/wk for 12
months
BeSO.d 38.8 pg/Be/m3
15 hr/wk for
3 years
Standardized
experimental
concentration
(pg/ffl3)
585.6
GUINEA
5.1
RHESUS
0.69
Pulmonary
tumor Surface
incidence area
rate correction
9/19 +
PIGS
2/20 +
MONKEYS
8/11 +
Human
equivalent
concentration
(pg/Be/m3)
223.4
1306.4
1.7
8.8
0.36
1.04
Maximum
likelihood .
estimate slope
2.9 x 10~3
4.9 x 10 *
8.1 x 10~]
1.4 x 10 -"•
6.5 x IQ~1
1.2 x 10 *
3.6 x 10?
1.2 x 10U
Standardized experimental dose is calculated by d x (h/168) x (6/18) where d is the mean experimental concentration,
h is the number of hours exposed per week (168 hours), and L is the number of months exposed.
Estimated by assuming that the control response is zero.
cSee appendix for details.
A life span of 15 years is assumed.
-------
3
weighing 0.35 kg, and 20 m /day is assumed for a 70-kg man, the human equiva-
3
lent concentration (ug/m ) satisfies the equation
C = (0.244/20) m3/day x (70/0.35)2/3 kg
3
or C = 0.38 ug/m assuming a surface area correction. For potency estimates
not assuming a body weight correction, the human equivalent concentration
satisfies the equation
C = (0.224/20) m3/day x (70/0.35) kg
3 3
or C = 2.24 ug/m . Therefore, the human equivalent concentration in ug/m is
obtained by multiplying the experimental dose by either 0.38 if a surface area
correction is used, or 2.24 if corrected only for body weight.
A quantitative assessment of risk can also be carried out using guinea
pigs and rhesus monkeys. For a 466-g guinea pig with a reported daily breath-
3
ing volume of 0.23 m (Handbook of Biological Data, 1971), using a surface area
correction, the human equivalent concentration satisfies the equation
C = (0.23/20) m3/day x (70/0.466)2/3 kg = 0.32 ug/m3
If only a body weight correction is made, the human equivalent
concentration satisfies the equation
C = (0.23/20) m3/day x (70/0.466) kg = 1.73 ug/m3
For a 2.68-kg rhesus monkey with a reported daily breathing volume of 1.24
o
m /day (Handbook of Biological Data, 1971), using a surface area correction,
the equivalent concentration satisfies the equation
O O/O 3
C = (1.24/20) ni /day x (70/2.68r/J kg = 0.55 ug/ni
If only a body weight correction is made, the human equivalent concentration
satisfies the equation
C = (1.24/20) m3/day x (70/2.68) kg = 1.61 ug/m3
7-70
-------
The last column of Table 7-15 represents the carcinogenic potency of
beryllium as calculated from each of the inhalation studies. The maximum
-4
likelihood slope estimates range from 4.9 x 10 to 4.3. The magnitude of the
potency appears to depend upon the form of the beryllium used in the experi-
ment. Beryl ore is the least potent compound among the four compounds studied,
while beryllium sulfate (BeSO,) is the most potent. Using a surface area cor-
rection, four of the five rat studies on beryllium sulfate have potency values
that approximate 0.5/(|jg/m ). The carcinogenic potency of beryllium sulfate
3
calculated from the rhesus monkey study is 3.6/(ug/m ), which approximates the
largest value calculated using rats. Using guinea pigs, the potency is about
one order of magnitude less than that obtained from the rat studies in which
beryllium sulfate was used.
7.3.2.2 Calculation of the Carcinogenic Potency of Beryllium on the Basis of
Human Data. Given the need to estimate the cancer risk of beryllium and the
uncertainty inherent in the use of animal data, it is desirable to use the
available human data in some way to estimate the carcinogenic potency of
beryllium. Data from Wagoner et al. (1980) are considered appropriate for
this purpose. This study is selected because the cohort consisted of beryllium
workers employed prior to 1949, when controls on beryllium in the workplace be-
gan. The workers' exposures to beryllium before 1949 were very high. A 1947
study reviewed by NIOSH (1972) reported beryllium concentrations in a beryllium
extraction plant in Pennsylvania of up to 8840 ug/m . In more than 50 percent
of the determinations reviewed, beryllium concentrations were in excess of 100
3
ug/m . According to NIOSH (1972), the levels of environmental exposure to beryl-
lium in the workplace were markedly reduced after control measures were insti-
tuted in 1949. In one Ohio extraction plant, the beryllium exposure levels
were recorded at 2 ug/m or less during almost all of a seven-year period.
The information available about beryllium exposure levels in the workplace and
the excess cancer risk observed among workers employed in beryllium production
plants is summarized below.
7.3.2.2.1 Information on Exposure Levels. The beryllium plant studied by
Wagoner et al. (1980) was a major beryllium extraction, processing, and
fabrication facility located in Pennsylvania. The workplace concentrations of
beryllium in various beryllium production plants in Pennsylvania and Ohio were
found to be comparable (Eisenbud and Lisson, 1983). Based on the NIOSH (1972)
7-71
-------
report described previously, the lower-bound estimate of the median exposure
o
concentration exceeded 100 pg/m , since more than 50 percent of the
determinations exceeded that level. According to Eisenbud and Lisson (1983), it
o
is likely that this value (100 [jg/m ) is an underestimation of the actual median
exposure level in the workplace, and thus should be considered to be a
lower-bound estimate of median level. Eisenbud and Lisson (1983) stated
"...published studies of conditions in the Pennsylvania production plant indi-
cate that the levels of exposure prior to installation of dust controls were
comparable to conditions in the Ohio plants. Concentrations in excess of 1000
3
ug/m were commonly found in all three extraction plants during the late 1940s."
On the other hand, it is unlikely that the median level could greatly exceed
o
1000 |jg/m , since at that level almost all of the exposed workers developed
acute respiratory diseases (Eisenbud, 1955). Thus, it is reasonable to assume
3
that the median level of beryllium concentration did not exceed 1000 pg/m . In
the risk calculation, the median level of beryllium concentration is assumed to
3
range from 100 to 1000 (jg/m . This is the narrowest range for median exposure
that could be obtained on the basis of available information.
7.3.2.2.2 Information on Excess Risk. Wagoner et al. (1980) conducted a
cohort study of 3055 white males who were initially employed in a plant in
Pennsylvania from 1942 to 1967, and who were followed to December 30, 1975. Of
particular interest to the present risk assessment is a subcohort of workers who
were initially employed prior to 1950, and who were followed for at least 25
years from the date of initial employment. The elevation of lung cancer mor-
tality was originally shown by Wagoner et al. (1980) to be statistically signi-
ficant (p < 0.05). However, the significant elevation of lung cancer mortality
disappears after making an adjustment for differences in cigarette smoking
between cohort and control populations. For the subcohort of workers who were
followed at least 25 years since their initial employment, the smoking-adjusted
expected lung cancer deaths are found to range from 13.91 to 14.67, in compari-
son with the 20 observed lung cancer deaths. The relative risk estimates are
20/13.91 = 1.44 and 20/14.67 = 1.36, which are not statistically significant
(p > 0.05). Although the epidemiologic study did not show carcinogenic effects,
the data can be used to calculate an upper limit of lung cancer risk.
Assuming that the observed cases follow a Poisson distribution and the
expected value is constant, the 95 percent confidence limits for the two
relative risk estimates, 1.36 and 1.44, are respectively 1.98 and 2.09. The
7-72
-------
values 1.98 and 2.09 are used to estimate the lifetime lung cancer risk due to 1
3
ug/m of beryllium in air.
7.3.2.2.3 Risk Calculation on the Basis of Human Data. To calculate the
lifetime cancer risk on the basis of information described previously, the
median level of beryllium exposure must be converted to the "effective" dose,
through multiplying by a factor of (8/24) x (240/365) x (f/L), to reflect that
workers were exposed to beryllium 8 hours/day, 240 days/year, for f years out of
a period of L years at risk (i.e. from the onset of employment to the termina-
tion of follow-up). Two values of f/L are used in the calculation: f/L = 1
and f/L = 0.25. The use of f/L = 1 would avoid overestimating the risk (but
could underestimate the risk) if the observation by Reeves and Deitch (1969)--
that tumor yield depends not on length of exposure but on age at exposure—is
valid. Table 7-16 presents a range of cancer potency estimates calculated under
various assumptions about relative risk estimates and level of exposures. The
upper-bound estimate of the cancer risk associated with 1 yg/m of beryllium
-4 -3 -3
ranges from 1.6 x 10 to 7.2 x 10 , with a geometric mean of 2.4 x 10 .
q
7.3.2.3 Risk Due to Exposure to 1 ug/m of Beryllium in Air. The positive tu-
morigenic response in rhesus monkeys, along with suggestive responses in guinea
pigs and hamsters, indicates that the rat is not uniquely sensitive to the car-
cinogenic effects of beryllium. The responsiveness of the rhesus monkey, a
close relative of man, also suggests that it is unlikely that the humans would
be insensitive to beryllium under similar exposure conditions, despite the un-
certain response in the workplace environment. The most likely reason for the
large difference in potency estimates between animals and humans relates to the
form of beryllium present during exposure. All of the animal potency estimates
derived from exposure to beryllium sulfate were much greater than the estimates
derived from human exposures to forms of beryllium present in the workplace.
Beryllium phosphate was less potent but still gave a greater potency estimate
than that derived from human exposure. Only beryl ore resulted in a potency
estimate in the same range as those for humans.
Humans are generally exposed to different forms of beryllium than those
used in most of the animal inhalation experiments. In mining operations the
primary forms of beryllium present are beryl, which has a low potency in
animals, and bertrandite, which failed to induce tumors in animals despite
exposure to high concentrations. In the extraction process, the primary product
is beryllium oxide, which is then reduced to the metallic form. In operations
7-73
-------
TABLE 7-16. UPPER-BOUND CANCER POTENCY ESTIMATES
CALCULATED UNDER VARIOUS ASSUMPTIONS
Beryllium
concentration
in workplace
()jg/m3)
100
1,000
"Effective"
dose
f/L (pg/m3)
1 21.92
0.25 5.48
1 219.18
0.25 54.79
95 percent
upper-bound
estimate of
relative risk
1.98
2.09
1.98
2.09
1.98
2.09
1.98
2.09
Cancer potency
(pg/m3)-1
1.61 x 10"3
1.79 x 10"3
6.44 x 10"3
7.16 x 10"3
1.61 x 10"4
1.79 x 10"4
6.44 x 10"4
7.16 x 10"4
"Effective" dose is calculated by multiplying the beryllium concentration in
the workplace by the factor (8/24) x (240/365) x (f/L).
For a given "effective" dose d and a relative risk R, the carcinogenic potency
is calculated by the formula B = (R-l) x 0.036/d, where 0.036 is the estimated
lung cancer mortality rate in the U.S. population.
such as melting, pouring, or welding of beryllium, fumes consisting of fine
particles of beryllium oxide are produced by condensation from the vapor phase.
Other sources of workplace contamination result from metallic dusts generated
by a variety of operations such as crushing, grinding, or cutting of beryllium-
containing material. For further details regarding industrial processing of
beryllium, refer to Tepper et al. (1961). Beryllium is also found in the ambient
air as a trace metal component of fly ash emitted from coal-burning electric
power plants. While other forms of beryllium are undoubtedly present, those
described are expected to be present in greatest concentrations.
All of the above described forms of beryllium are likely to have a much
lower carcinogenic potency than beryllium fluoride or sulfate, based on differ-
ences in solubility. The beryllium ores have already been shown to be much
less potent than beryllium sulfate. When instilled intratracheally into rats,
beryllium oxide calcined at 1100°C or 1600°C is less soluble and much less po-
tent than beryllium oxide calcined at 500°C (Spencer et al., 1968). According
7-74
-------
to Tepper et al. (1961), temperatures during the formation of
beryllium oxide in the extraction process are near 1600°C, thus favoring the
formation of a relatively insoluble form. Beryllium is present in fly ash as a
trace metal (Fisher et al. , 1980). Since it is bound to silicates, its
bioavailability is quite low. Even very high concentrations of fly ash failed
to induce lung tumors in experimental animals (Wehner, 1981).
If one adopts the most conservative approach, the upper-bound potency
o
estimate of 4.3/(ug/m ) would be used to represent the carcinogenic potential
of beryllium. This potency is estimated on the basis of data observed in an
experiment in which the level of exposure was very similar to the occupational
exposure. Thus, the high potency estimate is not simply due to the use of a
particular extrapolation model. The use of such a potency estimate would over-
estimate the human risk and is not consistent with the human experience in the
beryllium industry. Therefore, the CAG recommends that the estimate of 2.4 x
-3 3
10 /(ug/m ) be used as the carcinogenic potency of beryllium. This value is
the geometric mean of eight potency estimates calculated on the basis of human
data under various assumptions. On this basis, the incremental risk associated
3 -3
with 1 ug/m of beryllium in air is estimated to be 2.4 x 10 . This estimate
could be considered to be an upper-bound estimate of the cancer risk because
low-dose linearity is assumed in the extrapolation and the 95 percent upper con-
fidence limits of the relative risks are used in the calculations.
7.3.3 Comparison of Potency With Other Compounds
One of the uses of quantitative potency estimates is to compare the rela-
tive potencies of carcinogens. Figure 7-2 is a histogram representing the
frequency distribution of potency indices for 55 suspect carcinogens evaluated
by the CAG. The actual data summarized by the histogram are presented in Table
7-17. The potency index used herein was derived from the carcinogenic potency
of the compound and is expressed in terms of (mmol/kg/day) . Where no human
data were available, animal oral studies were used in preference to animal
inhalation studies, since oral studies have constituted the majority of animal
studies.
To calculate the potency index, it is necessary to convert the potency
estimate 2.4 x 10 /(ug/m ) into 8.4/(mg/kg/day), a potency estimate in a
different dose unit. The new potency estimate, 8.4/(mg/kg/day), is obtained by
7-75
-------
20
4th QUART)LE | 3rd QUARTILE , 2nd QUARTILE, 1st QUARTILE
1 x 10+1
4 x 10+2
2x10+3
18
16
14
o
UJ
12
10
o
I
•:*:*:*:
•
S&&&
:•:•:*:•
tiffi
MW
16
K'X'KC
"&:•'
mm
mm
•
Sfey:
^^
^
•
0
I
LOG OF POTENCY INDEX
Figure 7-2. Histogram representing the frequency distribution of the potency
indices of 55 suspect carcinogens evaluated by the Carcinogen
Assessment Group.
7-76
-------
TABLE 7-17. RELATIVE CARCINOGENIC POTENCIES AMONG 55 CHEMICALS EVALUATED BY THE CARCINOGEN ASSESSMENT GROUP
AS SUSPECT HUMAN CARCINOGENS
Level
of evidence
Compound
Acrylonitrile
Aflatoxin B,
Aldrin
Allyl chloride
Arsenic
~-j
-ij B[a]P
— i
Benzene
Benzidene
Beryl 1 i urn
1,3-Butadiene
Cadmi urn
Carbon tetrachloride
Chlordane
Chlorinated ethanes
1,2-Dichloroethane
hexachloroethane
1,1,2, 2-Tetrachl oroethane
1,1,2-Trichloroethane
CAS Number
107-13-1
1162-65-8
309-00-2
107-05-1
7440-38-2
50-32-8
71-43-2
92-87-5
7440-41-7
106-99-0
7440-43-9
56-23-5
57-74-9
107-06-2
67-72-1
79-34-5
79-00-5
Humans
L
L
I
S
I
S
S
L
I
L
I
I
I
I
I
I
Animals
S
S
L
I
S
S
S
S
S
S
S
L
S
L
L
L
Grouping
based on
IARC
criteria
2A
2A
3
1
2B
1
1
2A
2B
2A
2B
3
2B
3
3
3
Slope6 ,
(mg/kg/day) i
0.24(W)
2900
11.4
1.19xlO"2
15(H)
11.5
2.9xlO~2(W)
234(W)
8.4(W)
1.8(1)
6.1(W)
1.30X10"1
1.61
9.1xlO~2
1.42x10 *
0.20 ,,
5.73x10 ^
Molecular
weight
53.1
312.3
369.4
76.5
149.8
252.3
78
184.2
9
54.1
112.4
153.8
409.8
98.9
236.7
167.9
133.4
Potency
i ndex
lxlO+1
9xlO+5
4xlO+3
9x10" l
2xlO+3
3xlO+3
2x10°
4xlO+4
8xlO+1
lxlO+2
7xlO+2
2xlO+1
7xlO+2
n
9xloo
3x10°
3x10 X
8xlOu
Order of
magnitude
(log,-
+1
+6
+4
0
+3
+3
+0
+5
+2
+2
+3
+1
+3
+1
0
+1
+1
(continued on the following page)
-------
TABLE 7-17. (continued)
Compound
Chloroform
Chromium VI
DDT
Dichlorobenzidine
1,1-Dichloroethylene
(Vinyl idene chloride)
Dichloromethane
(Methylene chloride)
Dieldrin
2 ,4-Di ni trotol uene
Diphenylhydrazine
Epichlorohydrin
Bis(2-chloroethyl)ether
Bis(chloromethyl )ether
Ethylene dibromide (EDB)
Ethylene oxide
Heptachlor
Hexachl orobenzene
Level
of evidence
CAS Number
67-66-3
7440-47-3
50-29-3
91-94-1
75-35-4
75-09-2
60-57-1
121-14-2
122-66-7
106-89-8
111-44-4
542-88-1
106-93-4
75-21-8
76-44-8
118-74-1
Humans
I
S
I
I
I
I
I
I
I
I
I
S
I
L
I
I
Animals
S
S
S
S
L
S
S
S
S
S
S
S
S
S
S
S
Grouping
based on
IARC
criteria
2B
1
2B
2B
3
2B
2B
2B
2B
2B
2B
1
2B
2A
2B
2B
Slopeb ,
(mg/ kg/day) i
8. Ixio"2
41(W)
0.34
1.69
1.16(1)
1.4xlO"2(I)
30.4
0.31
0.77
9.9xlO"3
1.14
9300(1)
41
S.SxlO^d)
3.37
1.67
Molecular
weight
119.4
100
354.5
253.1
97
84.9
380.9
182
180
92.5
143
115
187.9
44.1
373.3
284.4
Potency
index
lxlO+1
4xlO+3
lxlO+2
4xlO+2
lxlO+2
1x10°
lxlO+4
6X10+1
lxlO+2
9X10"1
2xlO+2
lxlO+6
8xlO+3
2xlO+1
lxlO+3
5xlO+2
Order of
magnitude
(log,Q
inde-X)
+1
+4
+2
+3
+2
0
+4
+2
+2
0
+2
+6
+4
+1
+3
+3
(continued on the following page)
-------
TABLE 7-17. (continued)
Compound
Hexachl orobutadiene
Hexachl orocyc 1 ohexane
technical grade
alpha isomer
beta isomer
gamma isomer
Hexachl orodibenzodi oxi n
Nickel refinery dust
Nickel subsulfide
Nitrosamines
Dimethylnitrosamine
Diethylnitrosamine
Dibutylnitrosamine
N-nitrosopyrrol idine
N-ni troso-N-ethy 1 urea
N-nitroso-N-methylurea
N-nitroso-diphenylamine
PCBs
Phenols
2,4,6-Trichlorophenol
Tetrachlorodibenzo-p-dioxin
(TCDD)
CAS Number
87-68-3
319-84-6
319-85-7
58-89-9
34465-46-8
0120-35-722
62-75-9
55-18-5
924-16-3
930-55-2
759-73-9
684-93-5
86-30-6
1336-36-3
88-06-2
1746-01-6
Level
of evidence
Humans
I
I
I
I
I
S
S
I
I
I
I
I
I
I
I
I
I
Animals
L
S
L
L
S
S
S
S
S
S
S
S
S
S
S
S
S
Grouping
based on
IARC
criteria
3
2B
3
3
2B
1
1
2B
2B
2B
2B
2B
2B
2B
2B
2B
2B
Slopeb ,
(mg/kg/day)
7.75xlO"2
4.75
11.12
1.84
1.33
6.2X10"1"3
1.05(W)
2.1(W)
25.9(not by q*)
43.5(not by q*)
5.43 i
2.13
32.9
302.6 ,
4.92x10 J
4.34
1.99xlO"2
. r
1.56x10 D
Molecular
weight
261
290.9
290.9
290.9
290.9
391
240.2
240.2
74.1
102.1
158.2
100.2
117.1
103.1
198
324
197.4
322
Potency
i ndex
2xlO+1
1x10*?.
3x107:
5x10 ,
4x10 L
2xlO+6
2.5xlotj
5.0x10 i
2x10^
4x10*,
9x10.,
2x10.,
4xl°Ii
3x10^
1X10°
lxlO+3
4x10°
. -7
5xlO+7
Order of
magnitude
(log,n
ind^X)
+1
+3
+3
+3
+3
+6
+2
+3
+3
+4
+3
+2
+4
+4
0
+3
+1
+8
(continued on the following page)
-------
TABLE 7-17. (continued)
--j
i
oo
o
Level
of evidence
Compound
Tetrachloroethylene
Toxaphene
Trichloroethylene
Vinyl chloride
CAS Number
127-18-4
8001-35-2
79-01-6
75-01-4
Humans
I
I
I
S
Animals
L
S
L/S
S
Grouping
based on
I ARC
criteria
3
2B
3/2B
1
Slope6 ,
(mg/kg/day)
5.1xlO~2
1.13
l.lxio"2
1.75xlO"2(I)
Molecular
weight
165.8
414
131.4
62.5
Potency
i ndex
8x10°
5xlO+2
1x10°
1x10°
Order of
magnitude
O°g10
inde-50
-n
+3
0
0
S = Sufficient evidence; L = Limited evidence; I = Inadequate evidence.
Animal slopes are 95% upper-limit slopes based on the linearized 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. Not all of the carcinogenic potencies presented in this table
represent the same degree of certainty. All are subject to change as new evidence becomes available. The slope value is an upper
bound in the sense that the true value (which is unknown) is not likely to exceed the upper bound and may be much lower, with a lower
bound approaching zero. Thus, the use of the slope estimate in risk evaluations requires an appreciation for the implication of the
upper bound concept as well as the "weight of evidence" for the likelihood that the substance is a human carcinogen.
cThe potency index is a rounded-off slope in (mmol/kg/day) and is calculated by multiplying the slopes in (m/kg/day) by
the molecular weight of the compound.
-------
dividing 2.4 x Id'3/(|jg/m3) by a factor of (1 ug/m3) x (20 m3/day)/70 kg = 2.86
~4
x 10 mg/kg/day, under the assumption that the volumetric air intake for a
3 +1
70-kg person is 20 m /day. The potency index for beryllium is 8 x 10 , calcu-
lated by multiplying the potency estimate, 8.4/(mg/kg/day), and the molecular
weight of beryllium (9). This calculation places the relative potency of beryl-
lium in the lower part of the third quartile of the 55 suspect carcinogens
evaluated by the CAG.
The ranking of relative potency indices is subject to the uncertainties
involved in comparing a number of potency estimates for different chemicals,
based on varying routes of exposure in different species, by means of data from
studies whose quality varies widely. All of the indices presented are based on
estimates of low-dose risk, using linear extrapolation from the observational
range. These indices may not be appropriate for the comparison of potencies if
linearity does not exist at the low-dose range, or if comparison is to be made
at the high-dose range. If the latter is the case, then an index other than
the one calculated above may be more appropriate.
7.3.4 Summary of Quantitative Assessment
Both animal and human data have been used to calculate the carcinogenic
potency of beryllium. Many of the animal studies conducted on beryllium are
not well documented, were conducted at single dose levels, and in some cases
did not utilize control groups. Nevertheless, because positive effects were
seen in multiple species, at multiple sites, and often at very low doses, these
studies collectively provide sufficient evidence for carcinogenicity. In the
present report, data from ten animal inhalation studies (using rats, guinea
pigs, or rhesus monkeys) have been used to calculate the upper bounds for the
potency of beryllium. Both surface area and body weight corrections were used
in these calculations. The maximum likelihood slope estimates, calculated on
-4
the basis of animal data, vary from 4.9 x 10 to 4.3, a range of four orders
of magnitude.
The magnitude of the potency appears to depend primarily on the beryllium
compound used in the experiment, although some variability in sensitivity among
species was also seen with guinea pigs responding to a lesser degree than rats
or monkeys. Among the beryllium compounds examined in the ten animal studies,
beryl ore is the least carcinogenically potent, while beryllium sulfate (BeSO.)
is the most potent. The potency is most likely related to solubility. Beryl
ore is less soluble than beryllium sulfate. Further support for the importance
of solubility is provided by intratracheal instillation studies of Spencer et
7-81
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al. (1968, 1972). Beryllium oxide calcined at 1100°C and 1600°C was much less
potent than the more soluble form of beryllium oxide which was calcined at
500°C. If one adopts the most conservative approach, the maximum potency
estimate, 4.3/(ug/m ), would be used to represent the carcinogenic potential of
beryllium. This potency is estimated on the basis of animal data (Vorwald et
al. , 1966) obtained in an experiment in which the level of exposure was very
similar to occupational exposure conditions. Thus, the high potency estimate
is not due to the use of a particular low-dose extrapolation model. Since most
beryllium compounds present in ambient air or the workplace environment are much
less soluble and thereby less potent than beryllium sulfate, the use of such a
potency estimate would clearly overestimate the human risk and would be incon-
sistent with the human experience in the beryllium industry.
Data from the epidemiologic study by Wagoner et al. (1980) and the indus-
trial hygiene reviews by NIOSH (1972) and Eisenbud and Lisson (1983) have been
used to calculate the cancer risk associated with exposure to air contaminated
with beryllium. Two upper-bound relative risk estimates, 1.98 and 2.09, have
been used by the CAG to calculate the carcinogenic potency of beryllium. In
recognition of the greater uncertainty associated with the exposure estimation,
four different "effective" levels of exposure that reflect various uncertain-
ties, along with two relative risk estimates, have been used in the present
calculations. As a result, eight potency estimates have been calculated, rang-
ing from 1.6 x 10 /(ug/m ) to 7.2 x 10 /(ug/m ), with the geometric mean of
-3 3
the eight estimates being 2.4 x 10 /(ug/m ). The incremental lifetime cancer
3
risk associated with 1 ug/m of beryllium in the air is thus estimated to be
-3
2.4 x 10 . This estimate could be considered an upper-bound estimate of the
cancer risk because low-dose linearity is assumed in the extrapolation and the
95 percent upper confidence limits of the relative risks are used in the cal-
culations. This calculation places the relative carcinogenic potency of beryl-
lium in the lower part of the third quartile of the 55 suspect carcinogens
evaluated by the CAG.
7.4 SUMMARY
7.4.1 Qualitative Summary
Experimental beryllium carcinogenesis has been induced by intravenous or
intramedullary injection of rabbits, and by inhalation exposure or intratracheal
instillation of rats and monkeys.
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Osteosarcomas were induced in rabbits by intravenous injection of zinc
beryllium silicate (9 studies), beryllium oxide (2 studies), metallic beryllium
(1 study) and by intramedullary injection of zinc beryllium silicate and
beryllium oxide (1 study each). Lung tumors were induced in rats by intratra-
cheal instillation of beryllium oxide (4 studies), beryllium hydroxide (2 stu-
dies), metallic beryllium (2 studies), beryl ore (1 study) and in monkeys by
beryllium oxide (1 study). Lung tumors were also induced in rats by inhalation
of beryllium sulfate (5 studies), beryllium phosphate, beryllium fluoride, and
beryl ore (1 study each), and in monkeys by beryllium sulfate (1 study). No
significant neoplastic responses were observed via the intracutaneous, per-
cutaneous, or dietary routes. This was considered to be due to low absorption
efficiency resulting from precipitation of beryllium compounds in the small
intestine.
The beryllium-induced osteosarcomas in rabbits were shown to be highly
invasive and to readily metastasize. They were judged to be histologically
indistinguishable from non-beryllium-induced human osteosarcomas, although the
sites may be different.
As noted above, positive carcinogenic responses in animals were obtained
in multiple species and through various routes of exposure. In studies using
either inhalation or the intravenous injection route, positive results were
obtained in multiple experiments. For several of the beryllium compounds
tested, such as beryllium sulfate, significant responses were obtained at low
dose levels. Based on the above findings, the overall evidence for
carcinogenicity of beryllium in animals is convincing despite the lack of con-
trols, the use of only one dose level, and the inadequate documentation of many
of the studies. According to EPA's criteria for evaluating the weight of evi-
dence for carcinogenicity (U.S. EPA, 1984), the evidence for carcinogenicity of
beryllium in animals is considered to be "sufficient".
Although several studies (Wagoner et. al., 1980; Mancuso, 1979; Manusco,
1980) claim a statistically significant excess risk of lung cancer in individ-
uals exposed to beryllium, all of the studies cited have deficiencies that
limit definitive conclusions regarding a true carcinogenic association. Sup-
port for finding an excess risk of lung cancer in beryllium-exposed persons
consists of evidence from cohort mortality studies of two beryllium production
facilities. None of these studies are independent as they are all based on
the same groups of workers. Extensive collaboration existed between the
authors of these studies. The expected lung cancer deaths used in all of these
7-83
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studies were based on a NIOSH computer-based life-table program known to pro-
duce an 11-percent underestimation of expected lung cancer deaths. Furthermore,
the studies did not adequately address the confounding effects of smoking or of
exposures received during prior or subsequent employment in other non-beryllium
industries in the area. Many of these industries were known to produce other
potential carcinogens. Problems in the design and conduct of the studies
further weaken the strength of the findings. After correcting the life-table
error and adjusting for some of the problems described above, the finding of a
significant excess risk is no longer apparent. While the possibility remains
that the portion of the reported excess lung cancer risk remaining in these
studies may, in fact, be due to beryllium exposure, the epidemiologic evidence
is, nevertheless, considered to be "inadequate" according to EPA's criteria for
evaluating the weight of evidence provided by epidemiologic data.
Limited testing has shown beryllium sulfate and beryllium chloride to be
nonmutagenic in bacterial and yeast gene mutation assays. In contrast, gene
mutation studies in cultured mammalian cells, Chinese hamster V79 cells, and
Chinese hamster ovary (CHO) cells have yielded positive mutagenic responses for
beryllium. Beryllium increased the infidelity of DMA and RNA polymerase in
prokaryotes. Chromosomal aberration and sister chromatid exchange studies in
cultured human lymphocytes and Syrian hamster embryo cells have also resulted
in positive mutagenic responses for beryllium. In DMA damage and repair
assays, beryllium is negative in the pol, rat hepatocyte, and mitotic
recombination assays but is weakly positive in the rec assay. Based on the
information available, beryllium appears to have the potential to cause
mutations.
Using the EPA criteria for evaluating the overall weight of evidence for
carcinogenicity in humans, beryllium is most appropriately classified as group
B2, a probable human carcinogen. This category is reserved for those chemicals
having sufficient evidence for carcinogenicity in animals but inadequate evi-
dence in humans.
7.4.2 Quantitative Summary
Both animal and human data are used to estimate the carcinogenic potency
of beryllium. Among the animal studies, only data from inhalation exposures
are used because the intravenous or intramedullary exposure routes are not
considered to be directly relatable to human exposures, and all dietary inges-
tion studies yielded negative results. Many of the animal inhalation studies
7-84
-------
for beryllium are not well documented, were conducted at single-dose levels, and,
in some cases, did not utilize control groups. Collectively, however, the stud-
ies provide a reliable basis for estimating potency (at least for beryllium sul-
fate), as exemplified by the consistency of response in rats and rhesus monkeys.
Data from ten studies (8 studies of rats, 1 study of guinea pigs, and 1 study
of monkeys) using beryllium sulfate, phosphate, fluoride and beryl ore have
been used to calculate the upper bounds for the carcinogenic potency of beryl-
lium. Both surface area and body weight corrections were used in the calcula-
tions. While some data suggest that body weight corrections may be more appro-
priate for calculating the potency of beryllium, the overall weight of evidence
supports the use of surface area corrections. The upper-bound potency estimates
calculated on the basis of the animal data, using only surface area corrections,
-33 3
vary from 2.9 x 10 /(ug/m ) to 4.37 (ug/m ), a range of over three orders of
magnitude. If potency estimates are based on only one compound, such as beryl-
lium sulfate, the variation is decreased to only one order of magnitude.
The magnitude of the potency estimates from animal data depends to a large
extent on the beryllium compound used in the experiment, although some variabil-
ity in sensitivity among species is also seen, with guinea pigs responding to
a lesser degree than rats or monkeys. Among the beryllium compounds examined
in the ten animal studies, beryl ore is the least carcinogenically potent, while
beryllium sulfate (BeSO.) is the most potent. The potency is most likely re-
lated to solubility. Beryl ore is less soluble than beryllium sulfate. Further
support for the importance of solubility is provided by the intratracheal in-
stillation studies of Spencer et al. (1968; 1972). Beryllium oxide calcined
at 1100°C or 1600°C was much less potent than the more soluble form of beryllium
oxide which was calcined at 500°C. If one adopts an approach which selects
data from the most sensitive experimental animal species and the most potent
compound as being representative of risk to humans, the maximum potency estimate,
4.3/((jg/m ), would be used to represent the carcinogenic potential of beryllium.
This potency is estimated on the basis of data from rats exposed by inhalation
(Vorwald et al., 1966). The level of beryllium exposure used by Vorwald and
co-workers is very similar to occupational exposure conditions, although the
form of beryllium used (BeSO.) is more soluble than forms likely to be present
in ambient air or occupational environments.
Information from the epidemiologic studies by Wagoner et al. (1980) and
the industrial hygiene reviews by NIOSH (1972) and Eisenbud and Lisson (1983)
7-85
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have been used to estimate the cancer risks associated with exposure to work-
place air contaminated with beryllium. Even though the epidemiologic evidence
does not demonstrate a causal association between beryllium and cancer, that
does not mean that no risk exists. The size of the study population, the back-
ground risk, and a variety of other factors limit the ability of a study to
detect small risks. Each study has a level of sensitivity, and the study popu-
lation may be too small to show a statistically significant association if the
true risk is below this level. An upper-bound risk estimate can be calculated
from an inconclusive, or even negative, study to describe the study's level of
sensitivity. Risk levels below that upper bound are completely compatible with
the study data. The upper bound may be thought of as indicating the largest
plausible risk that is consistent with the available data. Thus, the epidemi-
ologic studies can be used to estimate a plausible upper bound for the increased
cancer risk from human exposure to beryllium.
In the Wagoner et al. (1980) study, 20 lung cancer deaths were observed
in a cohort of workers followed for at least 25 years compared with 13.91 to
14.67 expected (p < 0.10). Using the revised estimates of relative risk from
this study, two upper-bound relative risk estimates, 1.98 and 2.09, have been
used by the CAG to calculate the carcinogenic potency of beryllium. In
recognition of the greater uncertainty associated with the exposure estimation,
four different "effective" levels of exposure that reflect various
uncertainties, along with the two relative risk estimates, have been used in
the present calculations. As a result, eight unit risk estimates have been
calculated, ranging from 1.6 x 10 /(|jg/m3) to 7.2 x 10 /(pg/in ), with the
-3 3
geometric mean of the eight estimates being 2.4 x 10 /(ug/m ). The
o
incremental lifetime cancer risk associated with 1 ug/m of beryllium in the
-3
air is thus estimated to be 2.4 x 10 . This estimate could be considered an
upper-bound estimate of cancer risk because low-dose linearity is assumed in
the extrapolation and the 95 percent upper confidence limits of the relative
risk are used in the calculations. The estimate 2.4 x 10 /(ug/m ) is about
three times greater than the previous unit risk estimate reported in the Review
Draft of Beryllium (December, 1984).
The reasons that the updated unit risk estimates are higher are as follows:
1. A statistical upper confidence limit for the relative risk, rather than a
point estimate, has been used in the calculation.
7-86
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2. The median concentration in the workplace is estimated to range from 100
to 1000 ppm, rather than from 160 to 1000 ppm (as was previously used).
In a 1947 study reported by NIOSH (1972), more than 50 percent of air con-
centrations in the workplace exceeded 100 ppm. If it is assumed, as was in
the earlier risk estimate, that the concentration measurements followed a
log-normal distribution, then a median value of 160 ppm could be calculated.
Since there are no data to substantiate (or to deny) a log-normal assumption,
100 ppm is used as the low median concentration in the workplace.
The discrepancy in potency estimates derived from rat versus human data is
not likely to be due to lower sensitivity in humans, since rhesus monkeys also
showed a high degree of responsiveness at beryllium concentrations not greatly
different from those found in the workplace environment. While a dose extra-
polation based upon body weight results in smaller differences in potency esti-
mates between animal and human data, the weight of evidence still favors a
dose extrapolation based upon surface area, despite some theoretical arguments
to the contrary. There is some indication that the percentage of inhaled
beryllium deposited in the human lung may be as much as twice that of the rat
lung. However, any adjustment for this possibility could not account for the
discrepancy between estimates from human and animal data, since such an adjust-
ment would increase the differences in potency estimates calculated from these
two data bases.
The greater potency values estimated from animal data are probably due to
the different forms of beryllium. In the epidemiology studies, humans were
generally exposed to relatively insoluble, and thereby less potent, compounds
than were used in most of the animal experiments. In the occupational environ-
ment upon which human potency estimates are based, beryllium oxide and beryllium
metal are most commonly present, while beryllium sulfate was used in most of the
animal experiments. When animals are exposed to a less soluble form of beryl-
lium, such as beryl ore, the potency estimates agree very closely with those
derived from human exposures. This can be seen by comparing the risk estimate
-3 3
based upon human data, 2.4 x 10 (pg/m ), with the risk estimate of 2.9 x
~3 3
10 ((jg/m ) derived from animal data in which exposures were to relatively
insoluble beryl ore.
A major uncertainty of the risk estimate based on human data comes from
the derivation of exposure levels in the workplace and the temporal effect of
the patterns of exposure. To account for these uncertainties, the "effective"
exposure level of beryllium is derived in several ways, and the geometric mean
7-87
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of different potency estimates thus calculated is used to represent the carcino-
genic potency of beryllium.
Another uncertainty concerns the use of potency values derived from ex-
posures in the workplace environment to estimate potency from exposure in
ambient air. The types of sources which emit beryllium to the ambient air are
limited. There is little evidence that ore production is a significant source
of beryllium emissions. Metallurgical processing is likewise considered an
insignificant source. As much as 95 percent of atmospheric beryllium emissions
are estimated to come from coal-fired electric power plants, with most of the
remainder resulting from fuel oil combustion (see Chapter 3). During coal com-
bustion beryllium is likely emitted as an insoluble oxide, generally as a trace
contaminant of fly ash particles which are even more insoluble. On this basis,
the potency of beryllium from this source would be expected to be quite low.
Beryllium emissions from fuel oil combustion are similarly likely to occur
primarily in the oxide form. Experimental evidence also indicates that beryl-
lium in fly ash has a low degree of potency, since even very high concentrations
of fly ash containing other known carcinogens have failed to induce cancer in
laboratory animals. On this basis, it is unlikely that values derived from
exposure in the workplace will significantly underestimate the potency of beryl-
lium in ambient air, unless soluble beryllium compounds such as fluoride, phos-
phate, or sulfate are known to be present.
Because of the apparently greater carcinogenic potency of the beryllium
compounds used in animal data than those reported from human data, the
estimates derived from animal data are judged to be less relevant to human
environmental exposure. Despite some uncertainties concerning exposure levels
in the, workplace and possible differences in the forms of beryllium found in
ambient air compared with the workplace environment, the CAG-revised relative
risks from the Wagoner et al. (1980) epidemiologic study were considered to be
the best choice for estimating the upper-bound incremental cancer risk for
inhalation exposure to mixtures of beryllium compounds likely to be present in
ambient air.
-3 3
The upper-bound incremental unit risk of 2.4 x 10 /(ug/m ) results in a
potency index of 8 x 10+1, which places beryllium in the third quartile of the
55 suspect carcinogens evaluated by the CAG. The low molecular weight of
beryllium is at least partially responsible for its relatively low potency
index.
7-88
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7.5 CONCLUSIONS
Using EPA's Proposed Guidelines for Carcinogen Risk Assessment (U.S. EPA,
1984) to classify the weight of evidence for carcinogenicity in experimental
animals, there is sufficient evidence to conclude that beryllium and beryllium
compounds are carcinogenic in animals. This evidence is based upon the induc-
tion of osteosarcomas and chondrosarcomas by intravenous and intramedullary
injection in rabbits and upon the induction of lung tumors in rats and monkeys
by inhalation and intratracheal instillation. Due to limitations in
methodology, the epidemiological evidence is considered to be "inadequate",
even though significant increases in lung cancer were seen in some epidemiology
studies of occupationally exposed persons.
_3 3
A potency of 2.4 x 10 /(ug/m ) was calculated from occupational studies
involving human exposure to relatively insoluble beryllium compounds commonly
present in the workplace.
The carcinogenic potency of inhaled beryllium derived from animal studies
depends on the form of beryllium, with more soluble forms being more potent. A
range of potencies calculated from the animal studies varied from a high of
3 33
4.3/(ug/m ) for the relatively soluble beryllium sulfate to 2.9 x 10 /(ug/m )
for the less soluble beryl ore. Another ore, bertrandite, which failed to
induce lung cancer in rats, would have yielded an even lower value if an upper-
bound potency estimate had been calculated. Because studies in which rhesus
monkeys were exposed to beryllium sulfate also yielded a potency estimate
similar to that of the rat, the CAG believes that humans would also be quite
sensitive to the more soluble forms of beryllium.
Recognizing that the carcinogenic potency of inhaled beryllium varies
according to the form of beryllium present, an upper-bound incremental lifetime
o
cancer risk for continuous inhalation exposure at 1 ug Be/m is estimated to be
-3
2.4 x 10 for general ambient conditions. This presumes that ambient air is
characterized by relatively insoluble forms such as beryllium oxide and
metallic beryllium. This means that the actual unit risk is not likely to be
higher, but could be lower, than 2.4 x 10~3. This also places beryllium in the
lower part of the third quartile of 55 suspect carcinogens evaluated by the
CAG. It should be cautioned, however, that if compounds such as beryllium
fluoride, phosphate, and sulfate are known to be present in other than a small
percentage of total beryllium in the ambient air, this potency estimate will
7-89
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likely underestimate the potential carcinogenic risk. Conversely, since beryl-
lium has not been shown to induce neoplasms via oral ingestion in any studies
to date, this potency estimate is likely to overestimate risk by this route.
7-90
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APPENDIX
ANALYSIS OF INCIDENCE DATA WITH TIME-DEPENDENT DOSE PATTERN
Table A-l presents time-to-death data with or without lung tumors. These
data are reconstructed from Figure 1 in Reeves and Deitch (1969), in which
study animals were exposed to beryllium by inhalation at a concentration of 35
ug/m , 35 hours/week, for specific durations during the 24-month observation
period.
The computer program ADOLL1-83, developed by Crump and Howe (1984), has
been used to fit these data. Models with one to seven stages, and with one of
the stages affected by the dose, have been calculated. The model with the
maximum likelihood has been selected as the best-fitting model. The identified
best-fitting model has six stages, with the fifth stage dose-affected. Using
this model, the maximum likelihood estimate of the slope (linear component),
under the assumption of constant exposure, is 0.81/(ug/m ). The 95 percent
o
upper confidence limit for the slope is 1.05/(ug/m ).
A-l
-------
TABLE A-l. TIME-TO-DEATH-DATA0
Exposure period
Time-to-death
1. Control
2. 14th - 19th
month
3. llth - 16th
month
4. 8th - 13th
month
5. 5th -10th
month
6. 2nd - 8th
month
7. 8th - 19th
month
8. 2nd - 13th
month
9. 2nd - 19th
19", 20 (2), 21 (6), 22 (8), 24 (8)
"(2), 15, 20(4), 20,
, 22~(5), 24~(3),
24
20"(2),
13" 14", 20(2),
24+(3)
, 22", 22(3), 24(9)
13",
, 20(3),
, 22(6), 23"(2), 24~(4),
, 22~(4), 23", 24(3)
16" 17", 18", 19~(4), 20"(2), 20 , 2l"(3), 21 (3), 22",
22 (6), 24
, 22(2),
, 17 19, 20(3),
24"(2), 24 (4)
14", 18",
16",
, 20(3),
, 22+(4), 24+(2)
, 20"(5), 20(3),
, 22
at+^n'and t"^n^indicate, respectively, the time-to-death with and without
lung tumor; n is the number of replications.
All animals were exposed to beryllium at a concentration of 35 pg/m , 35
hours/week.
A-2
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