EPJ-560/2-76-D01
ENVIRONMENTAL
PROTECTION
DALLAS, TEXAS
LIBRARY
ASBESTOS:
a review ol selected literature
through 1973 relating to
environmental exposure and health
effects
January 1976
OFFICE OF TOXIG SUBSTANCES
ENVIRONMENTAL PROTECTION A6ENCY
WASHIN6TON, D.C. 20460
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EPA-560/2-76-001
ASBESTOS: A REVIEW OF SELECTED LITERATURE
THROUGH 1973 RELATING TO
ENVIRONMENTAL EXPOSURE AND HEALTH EFFECTS
ts
>.
v
*
Prepared by
Office of Toxic Substances
Environmental Protection Agency
Washington, D. C. 20460
January 1976
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NOTICE
This report has been reviewed by the
Office of Toxic Substances, EPA, and
approved for publication. Approval
does not signify that the contents
necessarily reflect the views and
policies of the Environmental Pro-
tection Agency, nor does mention of
trade names or commercial products
constitute endorsement or recommenda-
tion for use.
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PREFACE
Asbestos in air has been demonstrated to be a significant
threat to health in occupational and certain specific environ-
mental exposures. It has also been suggested to pose a threat to
health from more widespread environmental exposure due to presence
in air, water, soil, drugs, foods and beverages.
This report is an attempt to summarize and consolidate much
of the available information on asbestos throught 1973, prelimi-
nary to an environmental hazard assessment and to provide evalua-
tive comments where appropriate. Several more recent documents
have also been examined. This report was prepared in the early
stages of the development of the Office of Toxic Substances'
activities on asbestos. It should be considered primarily a
background document which is already somewhat out of date due to
the rapid advance of knowledge relating to asbestos over the past
two years. This report was written by Frank D. Kover, Office of
Toxic Substances.
The writer wishes to acknowledge the guidance provided by
Dr. Farley Fisher, Chief of the Early Warning Branch o'f the Office
of Toxic Substances. Appreciation is expressed for the informa-
tion, comments, suggestions, and technical reviews provided by:
Benigna Carroll, National Institute of Occupational Safety and
Health; Peter Bertozzi, Environmental Protection Agency - Water
Supply Research Laboratory; Robert Carton, EPA - Office of Toxic
Substances; Dr. I. E. Wallen, EPA - Office of Toxic Substances;
Philip M. Cook, EPA - National Water Quality Laboratory, Duluth;
John Cofrancesco, EPA - Water Supply Division; Lawrence Plumlee,
EPA - Medical Science Advisor; William Upholt, EPA - Senior
Science Advisor, Office of Water and Hazardous Materials Control;
William Switky, formerly with EPA - Office of Toxic Substances;
George W. Walsh, EPA - Emission Standards and Engineering Division;
Lawrence C. Gray, EPA - Office of Air, Land and Water Use; and
A.C. Trakowski, EPA - Office of Monitoring and Technical Support.
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TABLE OF CONTENTS
PREFACE i i
LIST OF FIGURES vi
LIST OF TABLES vi
INTRODUCTION AND SUMMARY 1
REVIEW OF SELECTED AVAILABLE INFORMATION
I. GENERAL INFORMATION 10
Structure and Properties 10
Chemical Composition, Physical Properties 15
Occurrence 20
Contaminants of Asbestos 20
Asbestos as a Contaminant 21
II. CHEMISTRY 24
III. PRODUCTION, IMPORTS, EXPORTS, CONSUMPTION 26
(Also See Appendix A)
Production Methods and Processes 26
(Also See Appendix B)
IV. USES (Also See Appendix C) 30
Major Categories by Type 30
Discontinued Uses 33
Possible Alternatives to Uses 33
V. CURRENT PRACTICES 35
VI. ENVIRONMENTAL DISPERSION POTENTIAL 37
Environmental Dispersion from Mining
Operations 38
Environmental Dispersion from Milling
Processes 39
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TABLE OF CONTENTS (cont.)
Environmental Dispersion from Manufacture
of Products Containing Asbestos 40
Environmental Dispersion from Transport
and Storage 42
Environmental Dispersion Potential from
Di sposal 43
Environmental Dispersion Potential from Use... 43
Envi ronmental Exposure Factors 46
VII. CONTROL TECHNOLOGY 50
General 50
Advantages & Disadvantages of Fabric
Filter Baghouses 51
Mining Controls 51
Asbestos Milling Process Controls 53
Manufacturing Emission Controls 56
Other 56
Sprayed Asbestos Fireproofing and Insulation.. 57
VIII. ANALYTICAL METHODS 58
Chrysotile 58
Amphiboles 60
Asbestos in Air 61
Asbestos in Water 64
IX. ENVIRONMENTAL EFFECTS 65
X. HUMAN EFFECTS 68
Asbestos is 68
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TABLE OF CONTENTS (cont.)
Lung Cancer 69
Mesothelial Tumors 71
Gastrointestinal Cancers 73
Pleural Calcification 74
"Asbestos Bodies" - Ferruginous Bodies 75
XI. TOXICITY - ANIMAL STUDIES 78
Experimental Asbestosis 78
Experimental Neoplasia 78
Studies Related to the Ingestion of Asbestos... 83
Other I_n Vivo Studies 87
III Vitro Studies 88
XII. CURRENT ENVIRONMENTAL REGULATIONS AND STANDARDS 90
Emission Standards 90
Eff1uent Standards 92
Other Regulations 92
APPENDIX A - Salient Statistics A-l
Asbestos Emissions Inventory A-7
APPENDIX B - Mines (Sites), Manufacturing \
Sites B-l
APPENDIX C - Uses; Products C-l
APPENDIX D - Research Recommendations D-l
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LIST OF FIGURES
FIGURE 1
FIGURE 2
FIGURE 3
FIGURE 4
FIGURE 5
TABLE 1
TABLE 2
TABLE 3
TABLE 4
TABLE 5
TABLE 6
TABLE 7
TABLE 8
Schematic Diagram of the Structure
of a Chrysotile Fiber 12
Schematic Diagram of the Structure
of an Amphibole Fiber 13
Dust Control for Percussion
Drill 54
Rotary Drill with Dust Control
System 54
Working Hypothesis of Trace Metals
in Chemical Carcinogenesis of
Asbestos Cancers 82
LIST OF TABLES
Chemical Composition of Common
Fibrous Silicate Minerals 16
Typical Physical Properties of
Chrysotile, Crocidolite, and
Asbestos 17
Physical, Chemical, and Mineralo-
gical Properties of Varieties of
Asbestos 18
Talc and its Associated Asbestos
Mineral s 23
Summary of All Brake and Clutch
Emissions 45
Possible Instrumentation for
Fiber Analysis and Constraints 59
Summary of Methods and Their
Application 63
Asbestos Fibers Found After
Intragastric Injection 84
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INTRODUCTION AND SUMMARY
Sources, Uses. Exposure
Asbestos is everywhere -- including homes, farms, factories,
automobiles, ships, trains, and airplanes. It has been estimated
to have over 3,000 uses, many of which cannot be satisfied by a
substitute. Well over 90% of all asbestos used is the mineral form
called chrysotile. Other varieties which include amosite, antho-
phyllite, crocidolite and tremolite are used in specialized
applications. The majority of end-product uses have been said to
effectively immobilize the fibers (estimates range from 85 - 92
percent), thus reducing potential exposures to the general popu-
lation. Specific individual exposure to asbestos is possible from
products which contain asbestos as a contaminant, such as talc,
food, beverages, and drug preparations. The mining, milling,
fabrication, and manufacture of asbestos create many point sources
for emissions and for potential water contamination. Many non-
point sources of environmental contamination are associated with
ultimate use and disposal of the variety of asbestos containing
products.
Human Data
Asbestosis, a fibrotic lung disease caused by inhalation of
asbestos particles, is largely confined to occupational exposure
although there is considerable individual variation in response.
Clinical manifestations can result from short, heavy exposures but
are usually associated with low to moderate exposures for 20 years
or more. All commercially used forms have been shown to produce
asbestosis. Indications are that good control practices in industry
can significantly reduce the risk and incidence of asbestosis.
An excess risk of lung cancer is associated with workers in
the asbestos industry. However, the available evidence suggests
that the risk of lung carcinoma and mesothelioma is small among
workers in chrysotile mines and mills. Some evidence exists to
show that amosite similarly involves a low risk for mine and mill
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workers. Crocidolite mining and mill workers are considered to
run a higher risk of contracting mesothelioma than amosite or
chrysotile workers. In some instances, communities in the neigh-
borhood of mines or other asbestos air pollution sources, have
suffered appreciable exposure to asbestos dust, and mesotheliomas
have been observed in these populations as well as those exposed
to dusty clothing at home (IARC, 1973).
These studies which indicate differences in pathogenicity
among types of asbestos should not be considered conclusive since
they often lack quantitative data on cumulative exposures, fiber
characteristics, the presence of other substances during exposure,
and other cofactors which may have been or are operative. The
complex exposure factors involved make it unwise to assign a
relative risk by type-of-asbestos to either asbestosis or neo-
plasia.
Industrial exposures can involve mixed types of asbestos.
The excess risk of lung cancer in industrial workers has usually
resulted from their past record of heavy exposures. Mesothelioma
has been observed more frequently in industrial asbestos workers
working with crocidolite than with amosite or chrysotile. Onset
of symptoms is usually 20 years or more after the first exposure
and can occur in the absence of other asbestos-related diseases.
Differences in risk among different segments of the asbestos
industry cannot be attributed to a single factor. The type
of fiber, past exposure levels, the form of dust produced by the
process, and the length of exposure, as well as other factors, may
be relevant. There is some indication that the risk of lung
carcinoma is related to asbestosis (IARC, 1973).
Cigarette smoking has been shown to enhance the risk of lung
carcinoma in asbestos workers to a much greater degree than in the
rest of the population (ESL, 1973).
Some direct and some indirect evidence shows that persons
other than those working directly with asbestos have been exposed
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to the material. Asbestos-like fibers have been observed in the
lungs of persons not occupational!,/ exposed. Populations in a few
geographic areas have been found with pleural plaques or pleural
calcification, considered by some as an indication of reaction to
asbestos exposure. Other investigators do not regard pleural
calcification as a reliable indication of exposure. Asbestos
fibers have been shown to be present in ambient air, and indi-
cations are that most human lungs contain thousands or millions of
fibers. In the majority of cases, in persons not occupationally
exposed, the numbers of fibers are relatively small. Chrysotile
fibers have been positively identified in human lung tissue.
However, other possible sources of airborne fibers such as man-
made fibers and plant fibers derived from the combustion of paper,
wood, and coal must be considered. Talc is another source of
asbestos fibers often used generously in contact with human skin
as a dusting powder. Talc has been shown to contain significant
amounts of tremolite as well as chrysotile and anthophyllite.
The discovery of "ferruginous bodies" similar to those found
in the lungs of asbestos workers, in a large portion of randomly
selected lung specimens from the general population has been taken
by some investigators as presumptive evidence that persons with no
occupational contact may have inhaled and retained asbestos. Some
inferences have been made by extrapolation of a few occupational
and para-occupational studies concerning the presence of these
bodies and the risk of mesothelioma. However, some occupational
populations for which exposure to asbestos greatly exceeds that of
the general public have shown inp_ increased risk of mesothelioma.
This variation in the relationship between asbestos and meso-
thelioma in the occupational setting makes extrapolation to the
environmental situation difficult.
The excess risk of gastrointestinal cancers and peritoneal
mesothelioma observed among asbestos workers has given rise to
suggestions that pulmonary clearance and subsequent swallowing of
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a large percentage of the inhaled asbestos fibers is the probable
mechanism involved.
There is presently little evidence to indicate that past
exposure of the general population to asbestos dust in the ambient
air or in beverages, drinking water, food, or pharmaceutical
preparations has increased the risk of cancer. However, the
asbestos contaminated talc which is used in rice processing has
been suspected as a factor in the high rate of gastrointestinal
cancers observed in Japanese men. Also, neighborhood exposures
have been shown to be associated with an increased occurrence of
mesotheliomas.
It has been definitely established that asbestos plays a
carcinogenic role (active and/or passive), and it must be assumed
that the initiation of malignancy after single, low level expo-
sures is possible, although improbable; and that with frequent or
chronic exposure and at low levels, the probability of malignancy
is increased. It must also be recognized that malignant trans-
formations associated with asbestos do not lead immediately to
cancer but may remain latent for a number of years (NIOSH, 1972).
The significance of the long period of latency between expo-
sure and the onset of asbestos cancer must not be underestimated
when interpreting current levels of risk.
Although epidemiological studies have presented the most
convincing evidence that asbestos is a hazard to working popula-
tions, demonstrating an increased risk to the general population
is much more difficult. Even if all factors were known which
could influence its evaluation, and a prospective study were
designed, any conclusions would be subject to doubt because many
variables could not be satisfactorily controlled. Extreme dif-
ficulties would be encountered in selecting the proper cohort and
assuming the rest of the population to be unexposed, or at least
to be exposed to a low, uniform level. The increasing use of
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asbestos, the differences in its composition, possible exposure in
various localities, and exposure to other carcinogens in the
environment would further obfuscate the issue. The possibility of
an unequivocal answer from epidemiological data alone would be
very remote. (Tabershaw, 1968)
Indications From Animal Data
Injections of asbestos into the pleura! cavity of laboratory
animals have demonstrated that all commercial forms of asbestos
can produce mesotheliomas. The role that oils, waxes, trace
metals or other coexisting substances play in the carcinogenic
response to asbestos remains unclear. Inhalation experiments on
rats and guinea pigs have demonstrated fibrotic lesions in lung
pleura similar to those found in man. Mesotheliomas and lung
carcinomas have also been produced in a small proportion of the
experimental rats after inhalational exposure. There are indica-
tions from several animal studies that both fiber size and diam-
eter are significant factors in the toxic effects of asbestos. The
view receiving current attention is that fibers < 5 microns in
length do not produce a carcinogenic effect. Several experimental
studies seem to bear this out.
Environmental Effects (other than occupational)
There is little evidence to indicate significant environ-
mental effects from asbestos exposure other than those to man in
para-occupational and neighborhood situations closely associated
with commercial operations and heavy exposures. Available data
indicate that exposure in the general environment is principally
to the small fibers (<5y). Currently (1973) some investigators
feel that the hazard associated with exposure to fibers less than
five microns in length is small.
Control Technology
The available control technologies appear capable of reducing
asbestos emissions in many situations. However, there remain some
aspects of the overall asbestos mining and processing operations
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which require new or continued development. These would include,
for example, controls for air emissions especially in milling, the
reduction of potential for water contamination associated with
tailing dumps and prevention of dispersal from waste disposal re-
lated to processing. Controlling the asbestos contamination of
water has received little or no attention until recently.
Analytical Methods and Environmental Monitoring
Much work is being done in this area, but even presently
acceptable techniques constantly require refinement in order to
improve precision and accuracy. Many methods are highly sophis-
ticated and tedious which limits their usefulness for routine
analysis. The development of analytical approaches and refine-
ments to describe asbestos exposures more completely should be
encouraged. Past analyses paralleled to present electron micro-
scopic or other analyses, could possibly lead to a useful, sta-
tistical correlation or index that would allow comparison with
data acquired in the past. Present procedures used for water
sample analysis have not been standardized.
Because the correlation of biological effects of asbestos
with its physicochemical characteristics has not been determined
with certainty, it appears that a prudent analytical approach
would involve providing chemical and physical characterizations of
asbestos as complete as present technology permits.
Asbestos emission and effluent data are only beginning to be
collected with appropriate regard for fiber characterization and
quantisation. The need for such data remains critical to a
realistic assessment of environmental exposures and associated
health and environmental effects.
Research Recommendations
Given the limited information available to assess the envi-
ronmental hazard of asbestos, and the economic importance of
asbestos, a recommendation totally prohibiting its use and pro-
duction is not justified.
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In light of the carcinogenic or co-carcinogenic character of
asbestos, prudence dictates that unnecessary exposure to the
material be avoided. From this review it is apparent that the
strict control of asbestos in Industrial and other occupational
settings and adjacent neighborhood environments is necessary. We
must not be premature in extrapolating the effects of heavy expo-
sures to minor and low-level exposures encountered in the general
environment. However, attention should be focused on products
with high potential for release of asbestos fibers.
Analytical methodology relates directly to capabilities
needed for monitoring of environmental samples including air,
water, and biota for asbestos. Many have pointed out the need for
research to improve the analytical methodology for asbestos. A
recent review of the Duluth, Minnesota, asbestos problem by the
Office of Technical Analysis in the Office of Enforcement and
General Counsel, EPA (January 1974), lists those methods used by
EPA contractors in analyzing samples collected in the course of
investigating the problem. The variety of techniques used illus-
trates the need for research and standardization of analytical
methods for asbestos. Standardization will allow better com-
parison of environmental data.
Much of the deficiency in asbestos health effects research
can be attributed to the long latent period before effects are
observed, thus leading to an untimely recognition of the problem.
Various international meetings of experts in this area have
resulted in guidelines and recommendations for research (see
Appendix D).
The almost universal occurrence of asbestos fibers in drinking
water has led to a recognition of the need for research on the
effects of asbestos which has been orally ingested. In November,
1973, a Conference on Biological Effects of Ingested Asbestos was
held. The proceedings are published in Environmental Health Per-
spectives, Volume 9, December, 1974. The closing paper discusses
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research needs attuned to present concerns about asbestos in the
environment (see appendix D). In 1965, the Geographical Pathology
Committee of the International Union Against Cancer published its
recommendation in regard to asbestos research problems in the
areas of epidemiological studies, pathology and experimental
pathology, and others relating to physics and chemistry (related
to air exposure). The committee met again in October, 1972, and
published further recommendations in 1973. Additional areas of
recommended research included morbid anatomy and histology,
clinical research, and experimental studies (see appendix D for
recommendations).
The Occupational Health Program of the USPHS in 1966 outlined
a recommended research program on the health effects of asbestos
(also contained in appendix D).
These documents concerning recommendations for future research
reflect the consensus of a large number of scientists engaged in
research or studies associated with asbestos problems as well as
the opinions of those responsible for protection of the public
health in regulatory capacities or affiliations. It is quite clear
that past research has not answered many important health effects
and environmental effects questions regarding asbestos. Speci-
fically, the etiological relationships between asbestos bodies and
lung tumors are presently poorly understood; the presence of
asbestos bodies in the lungs of the general population further
complicates the issue. Studies examining both inhalation and
ingestion routes are needed which more clearly define the impor-
tance of the nature, severity, and length of asbestos exposure in
the development of cancer. Experimental research with animals to
determine the mechanism of action is of fundamental importance.
The role that the fibrous character, type, size, and forms of
asbestos play in the induction of cancer, as well as the importance
of co-factors, will, when definitive answers become available,
afford a better understanding of the extent of the environmental
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hazard posed by asbestos. Definitive data from monitoring efforts
which describe environmental exposure to asbestos will also enhance
understanding of the problem. However, in all likelihood the
answers to these critical questions will not be known for several
years.
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!- GENERAL INFORMATION
Structure and Properties (Berger, 1963; Kirk-Othmer, 1967; Gaze,
1965; Hendry, 1965)
The word "asbestos" is a broad term referring to a number of
fibrous, mineral silicates that vary widely in their chemical
composition. Commercially important asbestos fibers consist of
two main groups. The largest of these by consumption (about 95%)
is chrysotile, with the amphi boles second. Both are fibrous
silicates, but they differ in geological origin, chemical com-
position, crystalline structure, fiber size, and in many other
characteristics. It must be kept in mind that the properties
shown by the asbestos varieties themselves (chemical structure,
thermal and acid behavior, cleavability, etc.) represent functions
of the geologic, geochemical, petrographic, and mineralogic
conditions that prevailed during their formation period; whereas
other characteristics, such as mechanical properties, are governed
by the fine fibrous structure.
The varieties of asbestos are subdivided into two main
groups. Their approximate formulae are presented below:
1. Serpentines - chrysotile
Z. Amphiboles - amosite
crocidolite
anthophyllite - (Mg,Fe)7Sig022(OH)2
tremolite - Ca2Mg5Sig022(OH)2
actinolite - Ca(Mg,Fe)5Sig022(OH)2
These compositions are theoretical and correspond only
approximately to the figures actually obtained by chemical analysis.
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Similar to all natural silicates, chrysotile and the amphi-
boles have silicon-oxygen tetrahedra as their basic structural
unit; the structural difference between the two classes is related
to the arrangement of the tetrahedral units. In chrysotiles, the
tetrahedral units form Si20c double layers, resulting in a laminar
structure. The amphiboles differ in that they combine to produce
Si.O,, double chains, producing a banded structure. The chryso-
tile layers are held together by layers of brucite [Mg(OH)2], and
the chains of amphiboles are held together by cation linkages.
The asbestoses can be considered a ternary system consisting of
SiCLj metal oxides, and water (Berger, 1963; Rubin and Maggiore,
1974).
Chrysotile fibers are not solid but hollow tubes formed from
layers that appear rolled-up (see figure 1). The silica layer has
a somewhat tighter spacing than is required for a good fit with
the brucite layer; as a result, the layers are contorted into
scrolls or tubes with the magnesium hydroxide layer on the outside.
The finest fibers (fibrils) range from 150 to 400 Angstroms in
diameter (Gaze, 1965). Fibrils can be considered to be the
fundamental form of chrysotile.
It is not generally possible to differentiate with certainty
between the various amphibole fibers by electron microscopy. The
chains or strips characteristic of amphiboles are loosely bonded
to each other along the edges and faces, so fibrous cleavages
readily occur (see figure 2). The smallest fibers of amphibole
asbestos (usually between 800 and 1000 Angstroms in diameter) are
more solid and coarser than are chrysotile fibrils (Gaze, 1965).
It is difficult to classify chrysotile within a particular
crystal system due to its capillary structure. The tubular
"fibrils" of the natural product are not precise capillaries. All
gradations are found from partial to full capillaries. The
crystalline types of amphibole fibers, on the other hand, can be
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r
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- 4 SILICON
40XYC,tN 1HYOROXYI
/CATION
- 40XVGf N
- 4 Sll « ON
- ! OXYt.lN
Fig. 2 Schematic diagram of the crystal structure of an amphibole
fibre, indicating the unit cell based on X7Sis022 (OH)2- The line
A-A represent the edge of the preferred cleavage plane along which
the fibres will split to form even smaller fibres.
Figure by permission of Dr. A.A. Hodgson
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classified since they are solid; amosite crocidolite and tremolite
belong to the monoclinic system,while anthophyllite belongs to
the orthorhombic system (Berger, 1963).
Commercial asbestos fibers are of various thicknesses and
consist of bundles of a great many fibers (up to thousands) lying
parallel to one another. The differences in the fineness of
commercial asbestos fibers depend on the degree of disintegration
(i.e. from processing in the mills). The average diameter for
commercial particles of chrysotile is 1 micron, of amphiboles,
about 3 microns. Comparison with other known fibers shows
asbestos fibers to be the finest known.
Inorganic Fibrous Materials (Berger. 1963)
Diameter of Fiber (y)
Chrysotile 0.02 to 0.04
(commercial 0.75 to 1.5)
Amphibole asbestoses 0.1 to 0.2
(commercial 1.5 to 4.0)
Glass Silk, glass fiber 1 to 5
Rock fibers 4 to 7
Slag fibers 3 to 5
Organic Fibrous Materials
Bast fibers (flax, hemp,
jute, ramie, etc.) 12 to 80
Cotton 10
Wool 20 to 28
Spider web 7
Human hair 40
Copperartificial silk
rayon, nylon 7 to 7.5
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Chemical Composition
The percentage composition of asbestos is presented in Table 1
However, it gives only a general guide to typical ranges of composi-
tion. Differences in values due to the various localities from
which specimens may come reflect the variations in impurities,
some of which are part of the crystal structure and others of
which are extraneous minerals.
The various "contaminants" which can occur as part of the
crystal structure of asbestos may be of great importance in regard
to the processing and use of asbestos products, as well as to
biological activity. An important undesirable contaminant is
magnetite, especially in regard to its uses for electrical pur-
poses. The iron oxides present, FeO and Fe^O.,, do not exert any
electrical disturbing actions. However, magnetite (Fe~0»), which
can be enveloped in granular form by the fibers, is both electri-
cally conductive and magnetic. Although most of the magnetite is
removed from the fibers during the milling operation (with fibers
from many sources), there can still be a considerable quantity
varying from 2 to 5 percent in the final products. As a result,
low-magnetite chrysotiles are acquiring greater importance for
electrical applications.
Physical Properties
Some properties of various asbestos minerals are summarized
in Tables 2 and 3.
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Table 2 (Gaze, 1965)
Typical Physical Properties of Chrysotile, Crocidolite end Amosite
Approximate
dimeter of
smallest fibers
Specific gravity
Average tensile
strength
Modulus of
elasticity
micron '
Ib./inch2
Ib./inch2
Chrysotile
white asbestos
0.01
2.55
350,000
23.5 x 106
Crocidoli te
blue asbestos
0.08
3.37
500,000
27.0 x 106
Amosite
0.1
3.45
175.000
23.5 x 106
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(EPA, 1973)
Table 3. PHYSICAL, CHEMICAL, AND MIIMERALOGICAL PROPERTIES OF VARIETIES OF ASBESTOS
Property
Chemical
formula
Essential
composition
Percentage
chemical
composition
5,0,
MgO
FeO
FejO,
Al;0j
H,0
CaO
Na,0
CaO and
Na,0
pH
Resistance to
acids
Veining
Co! Of
Texture
Luster
Hardn«>a
Flexibil'tv
Sp,ri.>ti. Illy
Teisii'
strer>gth,
!t)'in:
Fusion
point, *F
Spei'dc heat,
8ui/ll>°F
ChrylotlU
MgjS.jOjIOH),
Hydrous silicate
of magnesia
37. to 44.
39. to 44.
0.0 to 6.0
0 1 to 5.0
0.2 to 1.5
12.0 to 15.0
true* to 5.0
9 2 to 98
Poor
Cross and
slip fibers
Green, gray.
amber to
white
Soft to harsh,
also silky
Silky
2.5 to 40
High
Very good
824,000 max
2,770
0266
'tfsaayrs
NajFejSI.OjjIOH),
Silicate of sodium
and iron with
sorm vMter
49. to S3.
0. to 3.
13. to 20.
17. to 20.
2.5 to 4.5
4.0to 8.5
Good
Cross fiber
Blue
Soft to harsh
Silky to dull
4
Good
Fair
876,000 max.
2,180
0201
Amotlt*
(F«M8)TSi,0,,(OH],
Silicate of iron
and magnesium
higher iron then
anthophyllite
49. to 53.
1. to 7.
34. to 44
2. to 9.
2. to 5.
0.5 to 2.5
Cross fiber
Gray, yellow
to dark
brown
Coarse bu*
somewhat
pliable
Vitreous,
somewhat
pearly
5.5 to 60 .
Good
Fair
16.000 :o
90,000
2,550
0.133
Anthophylllw
ic»M8|,Si,0,,IOH),
Magnesium silicata
with iron
56. to 58.
28. to 34.
3. to 12.
0.5 to 1.5
1.0 to 6.0
Neutral
Slip, mass
fiber unonented
and interlacing
Ypllowish
brown, grayish
white
Harsh
Vitreous to
pearly
5 5 to 6.0
Poor
Poor
4,000
and less
2,675
0210
Trsmoitt*
CajMfcSI.OjjIOH),
Calcium and
magnesium silicate
with some water
51. to 62.
0. to 30.
1.5 to 5.0
1.0 to 4.0
0. to E.O
o tois
0. to 9
Good
Slip or
mass fiber
Gray-white,
greenish, yellowish,
bluish
Generally
harsh,
sometimes
soft
Silky
5.5
Poor
Poor
I.OOQto
8.CJO
2,400
0212
Actlnoiln
(CaMjFsLSiiOulOHl,
CBlcium-magnejium-iron
lil'uata; water up
to 5%
Good
Slip of
mass fiber
Greenish
Harsh
Silky
6±
Poor
Poor
1,000
and less
2,540
02)7
- 18 -
-------
Table 3. (continued) PHYSICAL, CHEMICAL, AND MINERALOGICAL PROPERTIES OF
VARIETIES OF ASBESTOS
Property
Electric
charge
Filtration
properties
Specittc
gravity
Cleavage
Optical
properties
Retiactive
index
Resistance to
destruction
byh«ai
Tempe rature
at ignition
loss.'F
Magnetite
content. %
Crys-Jl
stiuctute
Crystal
system
Mi-Teratojical
structure
Mineral
ssocwuon
Chrysotite
Positive
S'ow
2 4 to 2.6
010 perfect
Biaxial positive,
extinction
parallel
1 50 to 1.55
Good, brittle
at high
temperatures
1,800
00 to 50
Fibrous and
asbestiform
Monoclmic and
orthorhombic
In veins of
serpentine, etc.
In pltered
pendittte
adjacent to
serpentine
a^d limestone
neLf rcntsct
with basic
ignrous rocks
CroctdoliK
Negative
Fast
3.2 to 3.3
1 1 0 perfect
Biaxial ±,
extinction
inclined
1.7
pleochroic
Poor, fuses
1,200
3.0 to 5.9
Fibrous
Monocttnic
Fibrous in
iron stones
Iron rich
SlIlCIOUS
argidite
in queruose
schists
Amowte
Negative
Fast
3.1 to 3.25
1 1 0 perfect
Biaxial positive,
extinction
parallel
1.64+
Good, brittle
at high
temperatures
1,600 to 1,800
0
Prismatic,
lamellar to
fibrous
Monoclmic
Lamellar,
coarse to
fine fibrous
and asbestiform
In crystalline
schists, etc.
Anthophyllite
Negative
Medium
2.85 to 3.1
110 perfect
Biaxial positive,
extinction
parallel
1-61+
Very good
1,600
0
Prismatic,
lamellar to
fibrous
Orthorhombic
Lamellar,
fibrous
asbestiform
tn crystalline
schists and
grwtsses
Tremoiite
Negative
Medium
2.9 to 3.2
110 perfect
Biaxtal negative,
extinction
inclined
1.611
(
Fair to good
1,800
0
Long and thin
columnar to
fibrous
Monoclinic
Long, prismatic
and fibrous
aggregates
In Mg limestones
as alteration
product of
magnesian
rocks, metamorphic
and igneous
rocks
Actinotit.!
Negative
Medium
3.0 to 3.2
110 perfect
Biaxial negative,
extinction
inclined
1.63±
weakly pleochrotc
Long and thin
columnar to
fibrous
Monoclmic
Reticulated
long prismatic
crystal and
fibers
In limestones and
in crystalline
schists
"Working SCA'C of Harsnnss 1, vei y easily scratched by ftnoernail, and has greasy feel to the hand, 2, easily scratched by fingernail; 3, scratch try twass pin or
copper to-n, 4, ees.ly icfolch^d by knife, 5, scratch with difficulty with kntfe, 6, easily scratched by file, 7, little touched by file, but wilt scratch window glass
A!' hn-rf-r I*-?", 7 v 1! ic'etc'i \s ndc»w gff^s *
- 19 -
-------
Occurrence (Hendry, 1956)
Asbestos probably occurs in nearly every country in the
world. However, it is important to distinguish between occurrences
and commercial deposits.
Canada is the world's largest producer of chrysotile.
Approximately 93% of the world's total asbestos production can be
considered to be chrysotile (See Appendix A).
The United States has significant commercial chrysotile
deposits in Vermont, Arizona and California. Anthophyllite is
mined in North Carolina.
Contaminants of Asbestos
Trace Metals
The presence of nickel, chromium, manganese, and iron has
been determined in asbestos fibers (chrysotile, crocidolite,
amosite) by atomic absorption (AA) spectrometry. Chromium and
nickel have been found to be common impurities in natural and
processed fibers (Dixon et^ aJL , 1970; Cralley e_t aj_. » 1967; Roy-
Chowdhury et_ a_l_. , 1973).
Lockwood (1974) analyzed chrysotile asbestos fibers (natural
chemical state) by AA and found the following metals at microgram
levels in one gram samples: beryllium (6-8 yg), cadmium (3-5 yg),
chromium (202-771 yg), cobalt (40-78 yg), copper (9-13 yg),
manganese (325-651 yg), nickel (437-1187 yg) and thallium (40-71
Trace Organic Compounds
Some samples of asbestos have been shown to contain appreci-
able amounts of primary (natural) oils which may contain poly-
cyclic hydrocarbons such as benzo(a)pyrene (Harrington and Roe,
1965). Secondary oils may be present as a result of contamination
during processing and transport. Antioxidants, oils from poly-
olefin bags, and oils from jute bags have been found in commercial
- 20 -
-------
asbestos samples. Commins and Gibbs (1969) found 4,4'-bis-(2,6-
dltertiary butyl phenol) and 3,3',5,5'-tetratert1ary butyl dipheno-
quinone in chrysotile and crocidolite which were stored in poly-
ethylene bags. The quinone is apparently an oxidation product of
the phenol.
In a Japanese study of asbestos (amosite, chrysotile, crocid-
olite) for the presence of polynuclear aromatic hydrocarbons using
thin layer chromatography and fluorescence spectroscopy, all
samples were reported to contain pyrene, fluoranthenes, chrysenes,
benzo(a)pyrene, benzo(b) fluoranthene, benzo(k)fluoranthene,
perylenes, anthanthrene, and benzo- perylene. Amosite from Africa
also contained benzo(a)anthracene and coronene (Matsushita and
Arashiya, 1972). Details on experimental variables such as the
sample size and sample history (milled, natural, storage conditions)
were limited in the available account of this study so that the
significance of these results is difficult to evaluate.
Hilborne, e_t a_K, (1974) studied the organic content of the
U.I.C.C. reference samples of asbestos and found that they consist
largely of n-alkanes. "Evidence for the presence of potentially
carcinogenic polycyclic hydrocarbons was inconclusive due to the
fact that these compounds, if present, are found as traces in the
organic extract. In addition, the complexity of the chromatograms
from the oils made identification of polycyclics based solely on
retention times uncertain. However, it can be calculated that if
only 1% of the organic material is polycyclic aromatic hydrocar-
bons, then each gram of asbestos contains a maximum of 2-3 micro-
gram of polycyclic aromatic hydrocarbons."
Asbestos as a Contaminant
Asbestiform minerals are an ubiquitous impurity in many
deposits of commercially valuable, non-metallic minerals such as
talc and mica (Speil and Leineweber, 1969).
Anthophyllite and tremolite have been found to constitute
minor or major fractions of commercial talc (Schulz and Williams,
1942; Merliss, 1971; Blejer and Arlon, 1973; Kleinfeld et. al_., 1973),
- 21 -
-------
Chrysotile has also been found in talc, although amphiboles
are much more common. Of 22 cosmetic talcum products analyzed,
fiber contents ranged from 8 to 30 percent and included antho-
phyllite, tremolite, and chrysotile (Cralley et al., 1968).
Rohl and Langer (1974) have discussed the geological coex-
istence of talc and many hydrated magnesium silicate mineral
species, many of which are asbestos. Table 4 summarizes the
chemical, physical property information on talc and associated
asbestos minerals.
Asbestos minerals are also associated with metallic mineral
deposits such as taconite (iron ore).
- 22 -
-------
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- 23 -
-------
11. CHEMISTRY
Reactions. Involved in Uses
Treating chrysotile with soap forms a surface layer of mag-
nesium stearate (or oleate, etc.) to make the fiber water repel-
lent (U.S. Patent, 1937).
Other Reactions
A 0.5% suspension of chrysotile in water that is free of
carbon dioxide acts somewhat like magnesium hydroxide, giving a pH
of 10.33 (Pundsack, 1955). Acids readily attack chrysotile and
dissolve the magnesium, leaving mostly a silica structure (Badol-
let, 1948). Magnesium leaches from chrysotile fibers in aqueous
solutions with a pH reading under 10.8 (Nagy and Bates, 1952).
Chrysotile is the most susceptible of the asbestoses to acid
attack. It is almost completely destroyed when placed in IN HC1
for one hour at 95°C. Strong acids decompose chrysotile rapidly
removing all the MgO and 60% of the total weight. The remaining
residue consists of amorphous silica which retains a very fragile,
fibrous morphology (Speil and Leineweber, 1969).
In contrast, amphibole fibers are more resistant to acids.
Crocidolite, for example, in 4N hydrochloric acid at 100°C after
eight hours decomposes only by about nine percent (Speil and
Leineweber, 1969).
Chrysotile is decomposed by water. Soxhlet extraction (three
to four hours) results in a high concentration of magnesium in the
extract. The precipitation of amorphous magnesium silicate accom-
panies the loss of magnesium. Magnesium and silica are both
removed in amounts proportional to their representation in chry-
sotile after an initially rapid reaction. Whether removal of
silica is by solution or by formation of colloidal silica remains
to be determined. It is clear that chrysotile is slowly "soluble"
in water under conditions of continuous extraction (Speil and
Leineweber, 1969).
- 24 -
-------
With crocidolite, four percent of the silica and six percent
of the sodium are removed by Soxhlet extraction with water (Speil
and Leineweber, 1969).
Decomposition
In air at 600°C chrysotile partially degrades to olivine
(forsterite). At 650°C - 700°C chrysotile completely decomposes
to forsterite. At 750°C the formation of enstatite begins (Hargreaves
and Taylor, 1946). The probable reaction is: Mg3$i2(OH)4 heat >
Mg3SiO. + SiO, + 4^0, with SiCL present as amorphous silica
(Deere et^ a]_., 1966).
At the temperatures reached on brake linings (about 900°F),
thermal metamorphosis of asbestos to different minerals, forsterite
and enstatite, occurs. Less than one percent free fiber has been
found in the decomposition product, as compared to about 50% in
the lining (Lynch, 1968; Hickish and Knight, 1970).
- 25 -
-------
III. PRODUCTION, IMPORTS, EXPORTS, CONSUMPTION
The total apparent consumption of asbestos in the United
States for 1974 is reported to be 817,100 tons (CEH, 1975).
Total apparent consumption is arrived at by summing quantities
produced, adding imports, and subtracting exports. The average
apparent consumption for the last ten years is 791,100 tons. A
more detailed breakdown including market values is shown in the
tables presented in Appendix A.
Asbestos mines, processing plants, and sites are listed by
state in Appendix B.
Asbestos is mined domestically in four states, and approxi-
mately 90% of the asbestos consumed in the United States is
imported.
Production Methods and Processes
Mines, U.S. (May and Lewis, 1970) -- In Vermont, the fiber-bearing
rock is removed by open-pit methods. Similar methods are employed
in the Copperopolis district of California; but in the Coalinga
district, the highly sheared ore is simply "plowed" and allowed to
air dry; the coarse fraction is then screened out from the mill
feed.
In Arizona, a heading is driven into barren limestone beneath
the fiber zone, then blasted down and hand-cobbed.
In North Carolina, open pit methods are used.
Milling - Air Separation (Paddock et^ aJL, 1972) -- All but one of
the U.S. plants use a mechanical means to free the fibers and air
aspiration for removal from the ore. The incoming coarse ore is
typically crushed by a "jaw crusher" to a given size that depends
upon the particular mill. Oversized rock is separated by rotating
cylindrical trammel screens and crushed in a secondary crusher,
usually a cone type. The ore streams in most plants are then
conveyed to a dryer (rotary kiln in larger plants) where moisture
- 26 -
-------
in the ore (up to 30% by weight) is removed. The dried ore is
then stored. Large amounts are often held to allow for variations
in fiber demand and mine production over short periods of time.
The dried ore is conveyed to an additional crushing step and
then through a series of milling, shaking, and aspirating steps.
Milling is carried out by hammer mills or crushers which separate
the fibers from the rock and each other. Shaking is carried out
on progressively finer screens so that the smaller rocks and fiber
bundles fall through and larger rocks are retained for conveying
to tailing dumps or for further crushing. The freed fibers are
removed by air-flow through powerful suction hoods.
The separated fibers are caught in dry cyclones and conveyed
to grading screens. After grading (fiber length segregation), the
fibers are stored in bins by grade. Final operations consist of
removing the fibers from the storage bins, blending in a mixer to
produce the desired final grade, and bagging for shipment.
The dry cyclone control device depends upon centrifugal
force. The asbestos-laden air enters tangentially into a vertical
cylinder which has an inverted cone attached to its base. The air
or gas spirals downward toward the apex of the cone. Centrifugal
force moves the particles to the wall, and they fall into the cone
and through to a collecting hopper. The clean air escapes through
a centrally set tube which extends into the cylinder. Large
volumes of air, 30 to 25,000 cubic feet/minute, can be cleaned by
this device. Loadings must be high (lOg/ft) for good efficien-
cies. Particle size should be in the range of 5 to 200 microns.
Banks of cyclones operated in parallel are often used.
Wet Method -- The details of this process are proprietary. Only
one plant in the United States mills with a wet method. Its known
points are that ore from the mill's source is naturally loose with
little crushing required, and the product is available as loose
fiber or as compressed pellets of 1/4" to 1/2" diameter.
- 27 -
-------
Manufacture of Asbestos-Con tal ni ng Products (Paddock e_t a_K, 1972)
Processes common to the manufacture of all asbestos con-
taining products are receiving, handling, and storage of the
(bagged) asbestos fiber (removal from the bags, fluffing of
fibers, discarding of bags, etc. are also included). In the
manufacture of asbestos cement products the asbestos fiber is
mixed with the cement either wet or dry and comprises about 15%--
20% of the total material. The resulting mixture (if mixed with
ore) is generally metered in a flat layer onto an open surface
where the necessary water is applied by an overhead spray. The
resulting layer is then wound onto mandrels (for pipe) in a spiral
mat until the requisite thickness is achieved; or it is layed flat
into wall board, shingle, and other forms. A similar winding or
layering process may be used for wet-mixed products, or the mix-
ture may be cast.
Finishing processes of the dried products may include grind-
ing, drilling, sawing, and cutting.
Asbestos Vinyl and Asphalt Floor Tile (Paddock et_ al_., 1972) --
Asbestos, as used in these products, comprises 10 to 30% of the
total product weight. It is used because it improves strength and
stability without reducing flexibility or compressibility. The
fiber is added to hot vinyl or asphalt. Finishing processes
involve cutting the tiles to size and shredding wastes and trim-
mings for reuse. If the asbestos is in polyolefin bags, they can
be shredded and used as part of the material input.
Asbestos Friction Products (Paddock e_t aJL , 1972) -- Friction
products and gaskets using asbestos contain from 30% to 80%
asbestos in an organic binder. These products are made either by
mixing loose fiber with the binder or by impregnating matted or
woven textile asbestos with the binder. The latter is probably
more suitable for gaskets. Subsequent processes include molding
and curing. Finishing processes include shaping, cutting, and
sawing cured material.
- 28 -
-------
Asbestos Paper Products (Paddock ejt al_., 1972) -- Asbestos papers
are made by the same techniques as are standard wood-pulp papers,
but the fiber is 80% to 90% asbestos; usually china clay and
starch or sodium silicate are present as binders. (The slitting
process may be an emission source.)
Asbestos Textile Products (Paddock ejt al_., 1972) -- Chrysotile
can be incorporated into the full range of textile products (other
asbestos types cannot be woven). Long fibers are necessary for
spinning. To protect fiber length, the fiber is often obtained in
"crude" form as unopened, hand-cobbed, rock-free, fiber blocks or
bundles.
If the fibers are received in the crude form, they are opened
by knife-edge into small, fiber-like bundles. These are then
milled into extremely fine fibers for flexibility. The resultant
fibers are both more delicate and breakable and they are also more
floatable.
When the fibers have been adequately opened and fluffed, they
may be blended with up to 20% of a cellulosic fiber such as cot-
ton, the specific material depending upon the application of the
final product. Subsequent processes such as carding, lapping,
roving, spinning, weaving, and braiding are all performed on
equipment essentially the same as standard textile machinery. A
recent development in asbestos textile technology uses a thin
coating of a polymer on the asbestos yarn which increases effi-
ciency of the process and reduces fiber emissions.
- 29 -
-------
IV. USES
Asbestos has been referred to as "the mineral of a thousand
uses." This expression is entirely appropriate since asbestos is
a major constituent in a very wide variety of products. To a
large extent the different characteristics among the types of
fibers dictate their uses and applications (Hendry, 1965).
Major use categories based on amount of asbestos used include:
(1) asbestos cement products
(2) floor tile
(3) asbestos paper
(4) friction materials and gaskets
(5) paints, roof coatings, caulks, etc.
(6) asbestos textiles
(7) plastics
Significant minor uses include:
(1) sprayed insulation for fire proofing
(2) molded thermal insulation
(3) filter media
Although most of the asbestos used is chrysotile, it is
meaningful to look at the major uses for each type of asbestos.
(1) Tremolite and actinolite are utilized in the chemical
industry as filter mediums and as inexpensive fillers in
manufactured products. Tremolite is processed and repurified
(by acid treatment) for special uses in the filtration field.
(2) Anthophyllite, because of its low strength fibers, finds
limited usage in products which need reinforcement, such as
asbestos cement, floor tile, etc. However, it is finding
greater usage as filler material or as a partial replacement
- 30 -
-------
for higher strength chrysotile fibers. Anthophyllite is
used in the chemical industry as a filler in rubber and
plastics and in various adhesives and cements.
(3) Amosite has a more unique use in the insulation field in
the form of pipe and boiler coverings, bulkhead linings in
ships, and 85% magnesia insulation.
(4) Crocidolite is chiefly used in the manufacture of
asbestos cement products. In addition, this mineral is used
in the manufacture of acid-resistant filters, packings,
insulations, and certain types of lagging.
(5) Chrysotile
(a) The asbestos textile industry consumes long fibers
for the manufacture of safety clothing, curtains, lag-
ging cloth, woven brake linings, clutch facings, and
many other articles. These products serve both the
electrical insulation industry and the construction
industry. The chrysotile asbestos content of these
products can vary from 80 to 100 percent, (b) The
(b) The asbestos cement industry is the principal
consumer of chrysotile in terms of both tonnage and
dollars. Most countries of the world have one or more
asbestos cement operations contributing to the manu-
facture of pipes, flat and corrugated sheets, shingles,
etc. The asbestos cement manufacturing process combines
medium- long to medium-short fibers with cement, silica,
and water, thoroughly mixed to produce the maximum open
state of the fibers. The chrysotile fibers function as
tiny reinforcing rods in the finished product. Depending
on the product, the proportion by weight of asbestos to
cement may vary from 15 to 90%.
- 31 -
-------
(c) A wide variety of chrysotile grades is employed in
the manufacture of friction materials and packings.
Chrysotile is used for its heat stability. At the same
time, it also serves as a reinforcing agent, a filler,
an inhibitor of resin flow in the molding process, and
as a dispersing agent for the metal chips and other
particles formed. It is also used because it is less
abrasive than other heat stable fillers in the same low
price range.
Five major types of friction materials contain
chrysotile. They are woven, dry mix, sheeter, profile
calender, and extruded. The composition of friction
materials includes binder, metal chips, friction parti-
cles, chrysotile asbestos, filler, and solvent. The
asbestos content may vary from 30 to 80% of the total.
On the average 40-50% chrysotile is used. Disc brake
pads require less asbestos fiber than do conventional
drum brake linings.
Packings and gaskets used to reduce friction
between surfaces may contain 40 to 75% chrysotile.
This level of asbestos content is essential for the
strength, toughness, resiliency, durability, and heat
resistance required in the final product.
(«h) Paper products made from chrysotile include mill
board, roofing felts, pipe covering, fine quality
electrical papers, insulating papers, asbestos-latex
flooring felt, and many others. Asbestos papers are
necessary for the inorganic properties reflected in the
final product, such as heat resistence, chemical inert-
ness, and electrial and insulating properties. Asbestos
paper products may contain 30 to 90% asbestos.
- 32 -
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(e) Only very short chrysotile fibers are used in the
manufacture of floor tile. The fibers serve as filler
and reinforcement media. The typical floor tile formu-
lation contains from 10 to 30% chrysotile with either
vinyl resin or asphalt in combination with various other
fillers.
(f) The use of short chrysotile fibers in paint, roof
coatings, caulks, sealants, and joint fillers have
developed to a high degree in the U.S. and Canada.
Chrysotile in these uses serves the purpose of an
inexpensive filler, as well as a reinforcer.
(g) Very short grades of chrysotile are used in a wide
range of plastic products including cold-molded, thermo-
plastic, and thermosetting plastics. The chrysotile
imparts toughness, increases hardness, retards the
burning rate, and reduces molding costs by allowing more
control of the material under pressure.
(h) Miscellaneous uses include sprayed insulation,
asphalt paving, welding rod coatings, filter mediums,
chlorine cell diaphragms, acetylene cylinder packings,
and many others.
Discontinued Uses
Food, beverage, and drug processing filters are being replaced
with cellulose membrane filters.
Spraying-asbestos insulation and fireproofing are uses that
have been curtailed due to restrictions and outright banning by
some states and municipalities.
Possible Alternatives to Uses
Glass fibers have frequently been substituted for asbestos
fibers with some success where insulation properties are sought.
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For many products and uses, a suitable substitute doesn't
exist; for others, economics makes them impractical.
Possible alternatives for friction materials have been men-
tioned. A list of possible replacements, with significant remarks,
was presented by Hatch, 1970:
Glass Fiber - Low strength, relatively low melting point,
(520°C) severe frictional instability
Steel Wool - Low availability, high cost, low strength,
damage to drums
Mineral Wool - very low strength, brittle to the extent of
limiting mixing processes.
Carbon Fibers - very expensive.
Sintered Metals- probably the best possibility eventually, but
cost will always be relatively high.
Manufactured inorganic fibers of alumina and zirconia to
replace asbestos for some uses are currently under development by
Imperial Chemical Industries (trade mark - Saffil). These fibers
are being evaluated by ICI in a variety of potential applications
including high temperature furnace insulation; air, hot gas,
potable liquid and chemical filtration; and reinforcement for
friction materials such as brake linings. (Bate, 1973)
It is important that the potential hazard of proposed substi-
tutes be evaluated before large scale production and use begins.
Appendix C contains tables which list the variety of uses
and products associated with asbestos.
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V. CURRENT PRACTICES
Special Handling in Use-Bags (Paddock et al_., 1972) -- Several
types of bags for containing asbestos currently in use ere jute,
Kraft paper, and polyolefin. Emissions can occur as a result of
the tearing or breaking of weak bags, or leakage can occur through
seams or permeation. In addition, spillover from the bagging
process and fibers adhering to the bag surface can contribute to
emissions.
Methods for Transport and Storage (Paddock et_ al_., 1972) The
milling industry has been advocating bulk transportation in
sealed railroad cars with appropriate loading and unloading tech-
niques to minimize losses and, consequently, emissions. Such
handling, if properly done, could eliminate losses from bagging,
unbagging, and bag disposal. Until this method of handling is
generally adopted, bagging appears to be the best solution.
Disposal Method (Paddock e/t aj_., 1972) -- Tailing dumps are used
for wastes from mining of asbestos and both metallic and non-
metallic mining operations associated with asbestos deposits. For
example, the taconite beneficiation process leads to direct
discharge of asbestos waste which coexists with the taconite one.
Air-method and wet-method fibrous milling wastes are recov-
ered and usually sold for lower grade uses. Associated ore
wastes may go back to tailing dumps or to non-specific landfills
or dumps. Wet-method wastes may have a reduced emission potential,
but they possess greater potential for contamination of waterways.
Asbestos cement product waste from finishing processes
collected by a baghouse filter may be recovered for reuse.
Asbestos vinyl and asphalt floor tile wastage is reuseable
in the product.
More information is necessary on the disposal methods for
wastes associated with the processing of asbestos to produce
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friction, paper, and textile products. Effluent discharges
associated with asbesto containing product manufacture are
subject to Effluent Guidelines established by EPA (see Appendix
E).
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VI. ENVIRONMENTAL DISPERSION POTENTIAL
General
Asbestos fibers are easily dispersed in air as a result of
mining, milling, processing, and related activities. Contamin-
ation of waterways may similarly occur from such operations and
other related mining or milling processes. It has been estimated
that about 85% of the asbestos currently consumed is used in
applications where the fibers are "locked in" or tightly bound
and are therefore not able to become airborne to a significant
degree (Tabershaw, 1968).
The open-pit mining and milling of various other minerals
which may contain associated asbestos-bearing rock could result
in asbestos fiber emissions. An example is the taconite benefici-
ation process on western Lake Superior where amphibole fibers
coexist with taconite ore. Similar emissions can occur when
secondary blasting is done to reduce boulders to a size acceptable
for mill operations or to dislodge large rock disposits in open-
cast mining (EPA, 1973).
Harwood and Blaszak (1974) in a recent review for EPA char-
acterized the asbestos emissions from open sources including
asbestos mines, mills, and manufacturing waste piles. In their
recommendation they suggest that the fate of sub-micron aerosol
particles (like asbestos) has not been sufficiently studied and
that the possibility is very real that they remain suspended for
very long time periods and that they are continually increasing
in concentration. They also conclude that waste dumps associated
with manufacturing are a more important source of exposure since
they are usually located in populated areas. On the other hand,
asbestos mining operations which emit more fibers are regarded as
a less serious source of airborne exposure since in the U.S. they
are found in remote unpopulated areas.
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All of the processes associated with asbestos mining are
potential sources of air emissions while some permit dispersion to
water. Local meteorological conditions can significantly influ-
ence the degree of emission. For example, rain, sleet, and snow
are favorable conditions because they wet or cover exposed ore
deposits in addition to scavenging the atmosphere. Conversely,
strong winds that are capable of widely distributing existing
emissions, in addition to entraining loosely bound fibers from
exposed material, are an adverse condition. Also, the natural
phenomena of earth movement, temperature cycling, wind erosion,
and water erosion present opportunities for the dispersion of
asbestos in air and water media from virgin surface-ore deposits
(EPA, 1973).
Asbestos emission factors for all source categories based on
1968 data were developed for EPA by Davis ejt al_., 1970. See
appendix A (p. A-7).
Environmental Dispersion from Asbestos Mining Operations
Open-cast mining involves removing ore from shallow deposits
by earth-moving equipment. A shallow overburden containing low
concentrations of asbestos fibers must usually be removed initially.
Heavy emissions can occur from drilling, blasting, and overburden
and ore removal. In addition, surface ore transfer and the hand-
cobbing of ore can lead to significant emissions (Paddock et al.,
1972).
Open-pit mining is similar to open-cast operations except
that the work goes much deeper in order to follow fiber veins.
Blasting and ore removal occur primarily on the sides of the pit
along terraces which spiral down toward the bottom. Sources of
emission are essentially the same as for open-cast mining (Paddock
et al., 1972).
Underground mining involves following the veins of ore with
shafts, galleries, and drifts using blasting and earth moving.
Overburden removal is not necessary. The ore veins are not
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exposed to weathering, and many dusty operations take place
underground. Emissions from this type of mining are lower than
from surface techniques.
Open-pit mining, by the block-caving technique, significantly
reduces the required blasting and eliminates the need for removing
the overburden, thus reducing potential emissions. The volume of
rock to be mined is undercut, leaving solid support pillars to
hold up the main block. As the block caves in down the "chimney",
ore is removed from below; mill and mine tailings are replaced on
top to maintain the downward pressure on the block. This use of
tailings also reduces tailing-dump emissions and space require-
ments. This block-caving technique is said to reduce direct mining
emissions to a level comparable to "normal" underground mining
operations (Rezovsky, 1957).
Other aspects of mining operations may give rise to environ-
mental dispersion, such as the run-off entering waterways. Simi-
larly, naturally occuring, surface-exposed deposits can give rise
to dispersion from weathering or surface or ground water contact.
Wet methods used in mining operations to reduce emissions is a
mixed blessing, as the dispersion potential to waterways is
increased.
Environmental Dispersion From Asbestos Milling Processes
The milling of asbestos ore by a dry process requires an
extensive amount of handling and subdividing of the material in
both the damp and dry states. There are many potential sources of
asbestos emission at a milling facility. A primary source is the
effluent from ore dryers, where mechanical agitation and contact
with large volumes of air contribute to the potential for emissions.
Feed and discharge points on primary and secondary crushers may
give rise to emissions. Other sources at a milling facility
include the transfer of waste rock from the mill site, the packaging
and shipping operations, the grading processes, conveyor transfer
within the facility, and the dumping of mine ore onto a stockpile
or into receiving hoppers (EPA, 1973).
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Air aspiration systems used to accomplish fiber removal
require 7 to 10 tons of process-air for every ton of fiber pro-
duced. Such large volumes of air lead to significant potential
emissions. Davis, e_t a_L, (1970) estimated 64 pounds per ton as
the overall emission factor for asbestos milling based on a bag-
house efficiency of 99.5% and cyclone efficiency at 80%.
The greatest potential emissions arise from the cyclone
collector's exhaust. The series of process cyclones normally used
are of a relatively large diameter design in order to linrt damage
to the fiber. As a consequence, the overall efficiency of capture
is in the range of 90% and the fibers which escape are predomin-
antly the smaller, respirable, and wind transportable ones (Pad-
dock et al_.f 1972).
Wet-method milling is a proprietary method, and details of
the processes are not known. However, because of the nature of
the ore where this method is used, the emission potential from
transport and unloading could be substantial because much more of
the asbestos is free fiber at this stage. Drying of the fiber
should also have great emission potential because the fiber is
more free than with other ores. Wastes discarded to tailing dumps
may have low emission potential, but their water contamination
potential is high (Paddock e_t al_., 1972).
Environmental Dispersion Potential From Manufacture of Products
Containing Asbestos (Paddock et aj_., 1972)
Most of the well over 1,000 different asbestos products fall
into one of two categories: essentially free fiber throughout the
fabrication process and in the final product; or wetted or bound
into a matrix at an early stage of processing. These two cate-
gories effectively describe asbestos emission potential for the
manufacturing industry, and, to a certain extent, water pollution
potential. The asbestos product categories with largest volume are
the following:
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General Nearly all manufacturing and processing operations
involve the handling of dry, readily dispersible asbestos fibers
prior to thsir mixing and introduction into various product
formulations. These operations have in common a high potential
for abestos emissions.
Asbestos cement products Mil lowing (fluffing) of the fibers in
the dry state carries a high potential for emission. Dry-mixing
methods have a higher emission potential than have wet methods.
Finishing processes«on dried cement products have some emission
potential. Wet methods, of course, present the possibility of
water contamination with discharges from indiscriminate disposal.
Asbestos vinyl and asphalt floor tile (18 to 25% asbestos) In
this case emission potential is virtually nil once the fibers are
mixed with the hot vinyl or asphalt. The potential for emission
may be significant during those operations which introduce the
dry asbestos fibers into the formulation and during the mixing
process which follows. Emission from the finishing processes
should be negligible, since the cutting process does not disperse
fibers. Wastage and trimmings are readily reused by introducing
into the hot vinyl or asphalt.
Asbestos friction products The potential for emission arises
here principally from finishing processes and operations preceding
inclusion of the asbestos in a wet-processing mixture. Finishing
operations which generate dust include the use of band saws,
abrasive wheels, drills, cylindrical grinders, disc grinders, and
circular saws. For example, the drilling and grinding of brake
linings can result in the release of as much as 30% of the lining
materials as waste (Davis, et aj_., 1970).
Asbestos paper products Significant emission potential is
associated with the slitting process as well as the pre-wet-mix
handling operations.
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Asbestos Textile Products Milling associated with obtaining the
long fibers necessary for spinning has a high potential for emis-
sion of the smaller, respirable fibers. The resultant fibers
(opened and fluffed) are delicate and highly transportable by
wind.
Standard textile-type equipment and processes are used.
Large surface areas per unit volume of asbestos exist during the
entire processing procedure, creating a high emission potential.
The weaving operation potentially generates more dust than any
other textile operation. The separate large pieces of equipment
used are necessary for frequent access and are difficult to hood
for emission control (Paddock, e_t a^L, 1972).
Environmental Dispersion From Transport and Storage
Transporting the ore from the mine to the mill can result in
emissions. Typically, open trucks of 20 to 75 ton capacities are
used, although some 200 ton units are in use. Private mine-mill
roads are frequently paved with tailings which liberate fibers, to
the environment when trucks pass by. In this context, the use of
200 ton trucks is of mixed significance for emission levels during
transport. Larger truck capacities should reduce emissions from
the transporting of the ore with their larger volume-to-surface
ratio. Their size reduces the number of trips per unit of ore.
However, the road itself suffers more damage from each truck's
passing. The relative significance here is undetermined. Any
stored ores exposed to weathering can generate emissions and pose
a potential for water contamination (Paddock e_t aj_., 1972).
Asbestos mills store dried ore in large amounts and hold it
to allow for variations in fiber demand and mine production over
the short term, thus giving rise to potential emissions from the
requisite handling operations. Residual rock, which contains
small amounts of unremoved fiber and dust, is usually transported
to a tailing dump. With wet-method milling, it is suspected that
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there is a low emission potential from transport and storage,
since the material is wet (Paddock e_t al_., 1972).
Environmental Dispersion Potential From Disposal (Paddock, e_t
al_., 1972)
In mining operations, large quantities of asbestos ore are
sometimes rejected at the mine site because either the concentra-
tion or the form the ore is dispensed in renders recovery of the
asbestos uneconomical. In most surface mining operations it is
necessary to remove the overburden that contains small concentra-
tions of asbestos in order to expose asbestos ore deposits. The
taconite beneficiation process again illustrates the water con-
tamination possible with waste from other types of mining and
milling operations
Related to manufacturing is the disposal of bags which have
asbestos fibers clinging to them. Wastes from the finishing
processes of asbestos cement products, asbestos friction products,
and asbestos textile products are reuseable in some situations.
The manufacture of asbestos cement and asbestos paper produces a
mixture of asbestos fibers and water; this mixture poses a poten-
tial contamination for natural ground and surface waters or, if
contained and allowed to dry, may give rise to emissions. A lot
of asbestos wastes come from baghouse collections. The ultimate
disposal of asbestos wastes in open dumps can significantly raise
emission potential as well as contribute to water contamination.
Environmental Dispersion Potential From Use
Emissions of asbestos from sprayed asbestos fireproofing and
insulation arise from handling the dry mixture, the escape of
unwetted fiber and mixture, overspray and backsplash, and the
cleanup and disposal of wastes (Paddock ejt al_., 1972; Reitze et^
aj_., 1972). Regulations related to this problem are discussed
in a later section.
The construction industry, which utilizes many materials
containing asbestos, (wall board, insulation, etc.) can create
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many sources of asbestos emissions, if not controlled. A similar
situation for emission potential develops when buildings are
demolished. Wastes from demolition are frequently sources of
asbestos containing materials including materials such as pipe and
boiler thermal insulations, and bound materials such as asphalt-
asbestos floor tile, vinyl-asbestos flooring products, asbestos-
cement roofing and siding shingles, and acoustical ceiling tile
(EPA, 1973).
Return-air plenums and the interior surfaces of buildings
with asbestos fireproofing or insulation create a potential
exposure for occupants. This problem relates to the issue of
indoor air pollution (Castleman and Fritsch, 1973).
Asbestos friction products, such as brake linings and clutch
facings, emit fibers during vehicle operation. On the average
less than 1% of the 30-50% asbestos contained in brake linings
escapes into the atmosphere as free asbestos fiber. The remainder
is thermally decomposed to some other non-fibrous mineral form
(Lynch, 1968). A recent emissions test study by Jacko et al.
(1973) showed an average of 0.23% asbestos content (by weight) in
brake emissions indicating the remainder is converted to other
products. Brakes containing brass chips emitted 1/3 less asbestos
than those without. The calculated annual national emissions of
asbestos from brake and clutch use is 5,060 pounds. A summary of
estimated emissions is presented in Table 5 from Jacko et al.
(1973).
Davis e_t al_. (1970) estimated that 190 tons of asbestos was
emitted to the atmosphere in 1968 as a result of grinding and
fitting during installation of new brake linings.
Asbestos cement pipe has been suggested as a source of
contamination in drinking water where it is used to carry water
supplies. But, the contribution asbestos-cement pipes make to the
asbestos fiber content of tap water is uncertain (Kuschner
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Table 5.
Summary of All
(Ib. per year)
Brake and Clutch
(Jacko, et al.,
Emissions
1973)
Distribution
Number
of Vehicles
96.400.000
17.100,000
2,600,000
1,200000
li.fi 15 000
Totals
°o ol Total
Total
Asbestos
Emissions
60,400
32,300
16.300
32.900
16,300'
153.200
Dropout
49,470
28,420
14,330
28.920
14,330
135.4/0
(85 G)
Airborne
2,230
940
470
950
470
5060
(32)
Brake
Retention
8,700
2,940
1,500
3,030
1.500
17,670
(112)
Passenger Cars
Light Trucks
N'eduim Trucks
and Buses
Y',\n i Trucks
'Estimated i\|ual to medium truck", as wiriht", of Inction material used lor
-lyrics are aline >! equal Ini liile-. inotorcyc'o". trailers, and the like.
both cato-
Reprinted with permission, copyright © Society of Automotive
Engineers, Inc., 1973, all rights reserved.
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e_t al_. , 1974). Use of the product 1n sewage pipes has also been
suggested as contributing to asbestos contamination of waterways.
Asbestos-asphalt paving compounds which contain two to three
percent by weight asbestos may give rise to some asbestos fiber
emission as a result of abrasions to the pavement. This type of
paving has been used extensively in California. Rainfall could
wash abraded fibers into nearby ground and surface waters (EPA,
1973).
EM examination of the wastewater effluent from chlor-alkali
plants which use an asbestos diaphragm cell process showed 1.5 x
o
10 asbestos fibers/liter. The steam condensate from caustic
o
evaporation was also found to contain 2.0 x 10 fibers/liter
(Beaman e_t al_. , 1975).
Many consumer products contain asbestos, among them ironing
board covers, drapes, filtering and insulating materials.
Talc and talc products contain varying amounts of asbestos as
an impurity and have uses which may give rise to asbestos exposure.
Many food and drug products have been filtered through
asbestos pads; however, this practice is said to be declining
sharply.
Environmental Exposure Factors
Presence of asbestos or asbestiform fibers in the air and
waters of North America is widespread and appropriately considered
ubiquitous.
Asbestiform fibers can be released to the atmosphere directly
from fibrous silicate mineral outcroppings and indirectly from
soils or as a result of weathering processes. Asbestiform fibers
can also enter the atmosphere from mining and milling of asbestos,
talc, and other mining operations (e.g., taconite) as well as
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manufacture and use of asbestos containing products, building
demolition and solid waste disposal of many types (NAS, 1971).
Selikoff et aK (1972) measured mass concentrations of
chrysotile 1n ambient air at various sites in New York City
_Q
ranging from 10 to 60 x 10 g/cubic meter. Other urban areas
also showed chrysotile asbestos fibers in ambient air samples:
Philadelphia, Allegany, Pa. and Ridgewood, N.J.
Alcocer e_t aJL (1970) detected asbestos fibers in urban air
samples from New York, San Francisco, San Diego and Newark.
Water
Contamination of water supplies can result from improper
waste disposal of asbestos during mining, milling, manufacture of
asbestos containing products, or primary and secondary use. Other
mining and milling processes with coincident asbestos deposits may
also contribute. This contamination can be supplemented by atmos-
pheric asbestos dust settling or washing out by precipitation as
well as erosion of natural deposits. It is noteworthy that the
amphibole minerals are more plentiful and more widely distributed
than serpentine although chrysotile is the most extensively used
and has received the most attention to date (Nicholson, 1974).
Cunningham and Pontefract (1973) reported that Ottawa tap
water contains approximately 2 x 10 fibers/liter while Ottawa
river water concentrations ranged from 8.1 to 9.5 x 10 fibers/-
liter and melted snow contained 33.5 x 10 fibers/liter. Some
inferences about atmospheric asbestos contamination and dispersal
can be made from the snow figures and may indicate that asbestos
fibers serve as condensation nuclei.
A survey of municipal surface water supplies of 22 Ontario
(Canada) cities showed upon EM analysis that all contained asbes-
tos fibers ranging in concentration from 446,000 fibers/liter to
3,876,000 fibers/liter (Kay, 1974).
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Cooke, e_t al_. (1974) reported the detection of asbestiform
amphibole fibers in municipal water supplies taken from western
Lake Superior. (The asbestos contamination in this part of the
lake is the result of industrial effluent discharge of taconite
tailings.) Estimates from EM examination of 1973 Duluth water
supply samples ranged from 1 to 30 x 10 amphibole fibers/liter.
Amphibole fibers were also detected in water samples taken from
the Minnesota towns of Silver Bay, Beaver Bay, Two Harbors and
Cloquet.
Nicholson (1974) also analyzed samples from the Duluth water
supply system. He found amphibole fibers ranging from 20 x 10 to
75 x 10 fibers/liter. Nicholson also identified the fibers which
required the use of electron diffraction and electron microprobe
analytical techniques as well as transmission electron microscopy.
Approximately 50-60% of the fibers were in the cumnringtonUe-
grunerite series, 20% were in the actinolite-tremolite series and
about 5% were chemically identical to amosite.
A recent report by the Great Lakes Research Advisory Board
(1975) indicates that the background level of asbestos fiber
concentration in the water of the Great Lakes varies widely, but
averages from less than 1 to 10 million asbestos fibers per liter.
EM examination of water samples from various water sources
and municipal supplies in the U.S revealed the presence of asbes-
tiform fibers. Concentrations reported ranged 0.0048 to 6.42
yg/gallon (Kuschner et^ a_l_., 1974).
Food
FDA found asbestos fibers in salt recovered as a by-product
from chlorine production (chlor-alkali process employing asbestos
diaphragms) and intended for table salt use. Such use was approved
in 1974 by FDA but is expected to be revoked. The FDA analysis by
light microscopy revealed 225 asbestos fibers in 25 grams of the
by-product salt as compared to none in supermarket purchased salt.
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Further analysis by electron microscopy showed 16 million asbestos
fibers per gram of by-product salt and none in supermarket purchased
salt. The expected official regulation will have little Impact
since the by-product salt never reached the marketplace (Burros,
1975).
Transport Across Media
Dispersed asbestos fibers can be washed from the atmosphere
by precipitation and/or settle to the earth's surface and become
suspended in runoff water and contribute to the contamination of
ground and surface waters. Similarly, asbestos fibers may be
entrained in waterways as they traverse natural or man-made
deposits.
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VII. C.ONJROL. TECHNOLOGY
General
Dry cyclone devices, as previously mentioned, are commonly
used to control asbestos emissions from mining, milling, and many
other processing operations. Their collection efficiency is low
because many of the asbestos fibers are small (less than 1 micron
diameter) and have low specific gravities (approximately 2-3).
Twin cyclone collectors four feet in diameter have been found
to be the most efficient type for use in the Quebec area mines.
However, even their best performance is not satisfactory due to
their low efficiency on fine particles and fibers (Li, 1973). Dry
cyclones should be considered as precleaners to reduce fabric
filter loadings.
"Wet" collecting equipment such as wet cyclones or venturi
scrubbers are rarely used because resultant asbestos slurries tend
to clog pumps, drains, etc., and reuseable fibers are more diffi-
cult to reclaim. In connection with the use of a fabric filter,
clogging and blocking problems arise in the baghouse due to the
humidity created in wet collecting (Paddock et^ a]_., 1972).
Electrostatic precipitators have been tried and proven to be
inefficient collectors due to the resistivity characteristics of
most types of asbestos (Ibid).
Fabric filters have been found to be the most efficient type
of collector for controlling asbestos emissions and are currently
in wide use. These types of filters are often enclosed in moderate-
sized structures and referred to as a "baghouse".
Typically, tubular bags 5 to 18 inches in diameter and 2 to
30 feet long are suspended with open ends attached to an inlet
manifold at either the top or bottom of the housing, or both. The
lower manifold serves as a collector for dust. Entering air
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strikes a baffle plate which causes the larger particles to fall
into a hopper. The air then passes through the bags, leaving the
dust on the interior surface of the cloth. Cleaning is generally
done by shutting down and shaking the bags from the top. The
material used for filters depends upon the corrosiveness of the
gases, temperature, and humidity. The efficiency of a cloth
filter is largely dependent upon the accumulated layer of dust,
i.e., efficiency increases with high dust loadings.
Advantages of Fabric Filter Baghouses
One advantage of this control method is that further pro-
cessing of captured asbestos fibers for reuse is not required.
Collected materials may be returned directly to the process or
used in some other application such as friction material. Water
treatment and water handling are not required. Systems can be
sectionalized so that maintenance may be done on one section while
the others continue to operate. Baghouses are less costly to buy,
maintain, and operate than any other system with a comparable
collection efficiency. Baghouses can also control other dry
particulate emissions if necessary (Paddock ejt al_., 1972).
Disadvantages of Fabric Filter Baghouses
A large area per unit of gas flow is needed for installation.
Minor damage to a bag can cause significant loss in its cleaning
efficiency. The cleaning efficiency is variable, being lowest just
after bags are cleaned or when new bags are installed. Bag chang-
ing is expensiveboth in labor and materials. The baghouse
temperature must be kept above the dewpoint but below the limit of
bag tolerance which is sometimes a delicate procedure (Ibid).
The following sections briefly describe typical control
approaches. Particulate control efficiency estimates for various
segments of the asbestos industry are contained in Appendix A (p.
A-8).
Mining Controls
Overall emissions from asbestos mining facilities are not
stringently controlled at the present time. The lack of a higher
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degree of control is due to the fact that most operations are
completely exposed to the atmosphere, with the result that emis-
sions are diluted with ambient air over relatively large surface
areas, such as mining pits and roads (EPA, 1973). The block-
caving technique of open-pit mining can significantly reduce
asbestos emissions. The baghouse-collection technique has only
limited application in mining processes. Portable baghcuse
systems can be used to good effect during drilling operations
which occur prior to blasting. However, a wet drilling method
could be just as effective and cost less.
Blast emissions are impossible to collect but can be con-
trolled by employing a good blast technique and by calculating how
to produce minimum breakage of the rocks.
An effective technique has been developed for coal mining in
France which uses plastic capsules filled with water or water-
containing wetting agents to suppress dust from the blast; 20 to
80 percent reductions in emissions have been achieved. It may
have potential for application to asbestos mining but may present
a problem if present milling methods cannot remove the plastic
contamination from the ore (Grossmueck, 1968).
Dusts generated during ore transport are usually controlled
by covering the truck bodies with canvas.
Road surfaces covered with tailings can be wetted with water,
road oil, a 10 to 25% water solution of liquid sulfonate, or
emulsified asphalt. However, chemical dust suppressants on mine
roads over the ore body may cause unacceptable ore contamination.
In Canadian mines, wet drilling is not practical because of
the severe winter climate. One solution has been to use envelope-
type bag filters on percussion primary drills mounted on the frame
of the rig. The bags used are made of silicate-treated nylon
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acetate, which sheds dust easily and dries quickly if water is
accidentally drawn into the filter (see figure 3).
With larger rotary drills, the platform serves as the top oi
the dust hood. The sides of the hood are formed by rubber aprons,
the end apron being hinged to prevent cuttings from being dragged
back into the hole (see figure 4).
The ultimate disposal of mill tailings and overburden in the
Canadian mine operations is complicated by the close proximity of
towns to the mines. The disposal of tailings is further compli-
cated because they leave the mill in a very dry state. Recent
experiments involving the application of wetting agents at the
point where tailings are discharged have had an undetermined
degree of success, and further work is needed. Revegetating areas
of tailings is also being investigated by the Quebec Asbestos
Mining Association's research laboratory. One of the major diffi-
culties with this technique is the high alkalinity (pH 9) of
serpentine tailings. Grass has been grown on selected areas after
mixing with acidic tailings from a copper mine at a depth of 2
inches (Li, 1973).
The stabilization and revegetation of overburden waste areas
have not presented many difficulties, as the waste area's alluvial
sands and clays are usually neutral. Grasses and trees have been
successfully established on overburden waste (Li, 1973).
Asbestos Milling Process Controls
Ore stockpile emissions can be controlled by spraying with
water. However, the discharge of asbestos-containing water from
the facility also requires control (EPA, 1973).
In-plant transfer by conveyor should be fully enclosed to
prevent asbestos emissions from the material in transit and from
- 53 -
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- 54 -
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the emptied return side of the conveyor. Such control is cur-
rently applied only to a limited extent (Ibid).
Feed and discharge points for crushers can be fitted with
hoods ventilated to a gas cleaning device. A cyclone collector is
usually used. Cyclone exhaust may then be directed into a fabric
filter baghouse.
The cyclone collector has been the most widely applied type
of gas-cleaning device to control asbestos emissions from ore
dryers.
A baghouse filter which collects ore-dryer emissions requires
heat resistant materials, such as orlon or dacron, due to the high
temperatures (250°F) and humidity of the exhaust stream. Other
heat resistant materials used for the bags are fiberglass, teflon,
and Nomex. Also, insulation of the baghouse is necessary to avoid
condensation and resultant blockage (EPA, 1973).
Asbestos emissions from the beds of vibrating grading screens
are amenable to control by capture-hoods, exhausted to cyclone
collectors, and finally sent to a bag filter. Asbestos emissions
from bagging operations can be similarly controlled (EPA, 1973).
The control of emissions at mill tailings piles can be con-
trolled somewhat by maintaining a relatively flat disposal pile.
This is achieved by use of a mobile dumper at the end of the
conveyor belt that transports the wastes. As the disposal pro-
ceeds, the location of the dumper is periodically changed in order
to maintain the tailings pile as nearly level as possible and
thereby minimize emissions caused by moving the tailings with
earth-moving equipment. An inverted funnel mounted to the dumper
discharges the wastes close to the surface in order to lower
emissions at the point of deposition. However, a water or chem-
ical spray may be needed to eliminate visible emissions at the
point of discharge. Similarly, mixing the tailings with water
- 03 -
-------
prior to deposition is an effective technique for controlling
asbestos air emissions. However, the possibility of shifting the
problem from air to water media again presents itself (EPA, 1973).
The wet method of milling reduces emission potential; how-
ever, the drying process may have a greater emission potential
than conventional ore drying (Paddock ejt a_]_., 1972).
Manufacturing Emissions Control
Current control of mill-to-manufacturer handling and storage
emissions is effected by bagging the fiber in jute, kraft paper,
or polyolefin. Prior to introduction in the final product, the
asbestos fibers must be removed from their bags and fluffed to
loosen them from their packed condition. Enclosure of the total
process and baghouse filter collection is the usual control. A
dry cyclone for precleaning may be necessary if air fluffing is
used.
Other
The collection of emisssions from finishing processes asso-
ciated with asbestos cement products is best controlled by the
baghouse method.
In the asbestos vinyl and asphalt floor tile industry,
controls are applied at stages before the fibers are mixed with
the hot vinyl or asphalt. Baghouse filtering is applied to the
fluffing or blending processes. If polyolefin bags are reused in
the process, their emission potential is reduced.
It has been found that a thin coating of a polymer on the
asbestos yarn improves the processing efficiency and results in
about an 80% reduction in fiber emissions from successive pro-
cesses (Paddock et al., 1972).
- 56 -
-------
Sprayed Asbestos Fireproofing and Insulation
This use has been totally banned in some areas under regula-
tions of the Clean Air Act, which restricts spraying to materials
containing less than one percent asbestos. Alternative materials
have been found which are suitable and of negligible economic
impact. They include mineral wool, ceramic fibers, calcium
silicate, and vermiculite alumina.
- 57 -
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VIII. ANALYTICAL METHODS
Analysis for asbestos in environmental samples (air, water,
tissue, food, etc.) presents many problems. The development of
solutions to these problems will take a good deal of time. The
research community in this field is in its infancy and just
beginning to grow (Everett, 1974). Recognizing the probability
that new developments in this field will arise rather rapidly, the
discussion in this section is likely to quickly be outdated and is
therefore limited.
Langer (1974) has discussed the various approaches to asbes-
tos fiber identification and quantification and associated con-
straints. The range of media in which asbestos contamination is
sought can present sample preparation problems. Electron beam
instruments (electron microscopes) are superior for identification
purposes but, the area searched is generally small and may not be
representative of the total sample. Another difficulty is the
presence of other fibrous particles in the sample, especially in
water. In practice this means that in scanning one would have to
stop and perform electron area diffraction on each fiber for
identification. In addition, with amphibole fibers microchemical
analysis is always necessary. Electron beam instrument analysis
also requires a great deal of time which limits the number of
particles as well as the number of samples which may by analyzed.
A summary of limitations associated with various instruments used
for asbestos analysis is contained in Table 6.
Langer and Pooley (1973) have reviewed and summarized by
asbestos type the capabilities of electron beam instruments in
identifying asbestos fibers in tissues.
Chrysotile
Individual unit fibrils can be resolved with a transmission
electron microscope (TEM). Fibril morphology of chrysotile
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is so unique that the mineral species may be identified on this
basis alone. This unique morphology results in a characteristic
electron diffraction pattern which identifies the fiber as chrysotile.
Use of an electron microprobe analyzer for chemical identifi-
cation has had limited success, since chrysotile tends to degrade
both chemically and physically in vivo; the fibers tend to break
down into units of a size not easily resolved by the probe, and
chrysotile readily loses magnesium.
Amphi boles (amosite, anthophyllite, crocidolite, and tremolite)
The optical properties of these fibers may be ambiguous, as
they may have become altered in vivo or may be obscured by "asbes-
tos body" coatings. Generally, upon electron microscopic examin-
ation, these fibers appear straight and electron dense. Single
fibers tend to be similar and cannot easily be differentiated.
When many amphibole fibers are present, knowledge pertaining to
exposure may be the only key to identification. Each of the
fiber-types appears to possess a unique diameter distribution.
Anthophyllite fibers are significantly thicker than amosite
fibers, which in turn are significantly thicker than those of
crocidolite; tremolite fibers tend to be short and stubby.
However, most asbestos exposures are mixed, so the value of
morphological analysis for fiber identification is limited.
Electron diffraction patterns of amphiboles are also non-distinc-
tive; the pattern is unique for the group but not for the indi-
vidual mineral species.
Microchemical analysis probably provides the best means of
differentiating between amphibole fibers. The electron microprobe
analyzer is presently the most reliable instrument for the identi-
fication of amphibole fibers. The size limitation in using this
instrument (0.2 microns) allows only the largest fibers to be
analyzed without difficulty and with high confidence.
- 60 -
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Langer and Pooley (1973) recommended the following analytical
procedure for identifying single asbestos fibers in tissue:
"Tissue preparation: Use of the carbon extraction method is
recommended since it can be used on normal histologic prepar-
ations and the carbon substrate is stable under the electron
beam; the grids should be mounted on locator-type, copper
substrates to insure ease of particle location.
Light microscopy: This phase of examination should be used
only to check on the extraction preparation and the general
condition of the grids; areas which contain visible fibers
and amounts of relict tissue should be selected; areas which
appear to be void of fibers should be scanned as well.
Electron microscopy and selected area diffraction: Photo-
graphs of fibers should be taken as a basis for their mor-
phological identification; selected area diffraction patterns
are necessary on all electron-dense fibers to determine if
they are amphibole types; the locations of these fibers
should be noted for further microchemical analysis with the
probe.
Electron microprobe: Fibers on which diffraction and morpho-
logical studies have been completed can be located by means
of the locator grids and Microchemical analyses obtained."
Asbestos in Air -- (Langer et^ _al_., 1973; Lynch and Ayer, 1968;
Cralley, 1971) Light microscopy samples are collected on cellulose
membrane filters. Particles smaller than a nominal pore size are
retained. The samples are then mounted on standard microscope
slides, and a viscous solution of diethyl oxalate and dimethyl
phthalate is placed on the filter to make it transparent. This
preparation is stable for 28-30 days. After that, migration of
fibers and particles occurs, causing a loss in area! concentration.
The fibers on the filter surface are counted under phase-
contrast conditions at a magnification of 450X. The counting
field is delineated by a Porton reticle. Only fibers greater than
5 microns are counted. Any particle with an aspect ratio of three
or greater is considered a fiber (Edwards and Lynch, 1968).
- 61 -
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This method is used to determine the level of asbestos in
occupational environments so that compliance with the TLV and OSHA
standards can be checked.
The major deficiences of this method are that it doesn't
identify asbestos fibers and it is not capable of resolving
particles smaller than one micron. It is said to be only a
useful index of fiber concentration, since only a fraction of the
fibers seen with an electron microscope is observed.
Samples collected on membrane filters may be transferred
directly to coated grids for analysis under an electron microscope
(Keenan and Lynch, 1970).
X-ray diffraction is suitable for quantitatively determining
the amount of chrysotile, amosite, and crocidolite in bulk or
settled dust samples (Ibid). X-ray diffraction will identify the
presence of certain minerals except where there are strong inter-
ferences from associated materials. This method cannot distin-
guish between a fibrous mineral and the parent, non-fibrous
mineral with the same crystal structure, e.g. non-fibrous serpen-
tine and chrysotile. This method also appears to be somewhat
dependent on particle size and has a sensitivity which is not
generally low enough for airborne exposure samples.
Atomic absorption spectrometry has been used for the analysis
of certain metallic elements present in samples of airborne
asbestos fibers and also in bulk asbestos minerals. Magnesium in
airborne samples may be measured and used to indicate exposure if
only one compound carrying the element to be analyzed is in the
sample (Keenan and Lynch, 1970).
Neutron-activation analysis has been used to irradiate
samples for analyses using tracer techniques (Ibid).
The electron microprobe under ideal conditions is capable of
analyzing for all elements of atomic number 5 and greater and can
- 62 -
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be used to Identify metallic impurities located on the surface? of,
or incorporated within, the lattice of asbestos fibers (Keenan arid
Lynch, 1970). However its usefulness for routine analysis is
limited.
Emission spectroscopy is applicable only to bulk samples for
a determination of elemental composition. Table 7
summarizes some of the analytical methods used for asbestos (Keenan
and Lynch, 1970).
Table 7. Summary of Methods and Their Application
Mrlh.Kl
Appliiatiu
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Asbestos in Water -- For the most part, the methods mentioned
above have been adapted for the analysis of asbestos fibers in
water. Success has been very limited. In addition to the prob-
lems inherent in these methods, attempts to quantify and identify
asbestos fibers in water have been plagued by sampling difficul-
ties because fibers may settle out or adhere to the walls of the
sample container. Another problem is that these fibers may
change their physical or chemical characteristics over time while
immersed in water. In fact, it has been shown that if chrysotile
fibers are allowed to remain in water, much of their magnesium
leaches out and the central canal begins to fade (Cunningham and
Pontefract, 1973).
The method principally used for water analysis is light
microscopy for enumeration and detection at 450X. (Recently 1000X
has been used by EPA.) Electron beam instruments are also used
for identification and enumeration. Reproducibility of results
with both methods has frequently proven inadequate.
General Note
The development of a rapid method for the sampling and
analysis of asbestos in air, water, tissue, food, etc. has been
largely unsuccessful. All of the above methods which can identify
asbestos require sophisticated equipment and much time; from one
day to one week (depending on sample loading), to make a deter-
mination on one sample. The light microscopic technique, although
it lacks identification capabilities, is a faster method for the
enumeration of fibers greater than one micron and may give a
statistically useful index of asbestos fiber concentration.
In summary, the inadequacy of present analytical techniques
requires that activities to develop techniques which can identify
and enumerate asbestos fibers in environmental samples be given a
high priority.
- 64 -
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IX.
Chemical Stability In the Environment
Asbestos is considered to be indestructible, but changes in
physical and chemical properties have been produced by high heat,
chemicals, and body fluids (Tabershaw, 1968).
The brucite [Mg(OH)2] layer of chrysotile results in a reac-
tivity characteristic of magnesium hydroxide. Chrysotile is
slowly "soluble" in water, losing magnesium ions from its crystal
structure (Speil and Leineweber, 1969).
Biological Degradation
The in vivo alteration of chrysotile (by leaching of magne-
sium) to amorphous and crystalline silica has been observed
(Suzuki and Churg, 1969; Langer e_t al_. , 1973 cites six references)
Persistence
Mechanical degradation can lead to the release of fibers
where asbestos is subjected to weathering and physical forces and
where there are materials containing asbestiform minerals that are
not "locked in". There are no indications in the literature that
significant degradation of asbestos occurs in the environment.
Thus, it must be considered persistent. Asbestos is best thought
of as a fibrous particulate. If immobilized, the fibers present
less potential for dispersion throughout the environment.
Environmental Transport
The fineness of asbestiform mineral fibers makes them readily
transportable as particulates through air and water media. The
key factor again is whether the fibers are immobilized throughout
the operations related to mining, milling, use, disposal, etc.
- 65 -
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Bioaccumulation
Apparently, only partial clearance of asbestos from the lunqs
occurs, so Inhalational exposures are therefore cumulative. The
presence of asbestos in human lungs would seem to indicate this
(Selikoff et a1., 1972). Animal experimentation indicates that
the oral exposure route probably does not lead to absorption. No
study was found to indicate that asbestiform minerals can be
conveyed in a food chain.
Environmental Epidemiologic Studies - Asbestos and Mesothelioma
in Man
Wagner e_t aK (1960) reported 33 cases of mesothelioma in the
North Western Cape Province of South Africa. Several of these
cases had no known exposure to asbestos except that they lived in
the vicinity of the asbestos mines. The authors pointed out that
mesothelioma is rarely observed elsewhere in South Africa.
Newhouse and Thompson (1965) surveyed a series of 83 mesothelioma
patients from the London Hospital to determine possible exposure
to asbestos. They observed that occupational and domestic exposures
(living in the same house as an asbestos worker) gave rise to an
increased risk of mesothalioma. In addition their survey indicated
that neighborhood exposures may be important. Eleven of their
mesothelioma patients with no_ occupational or domestic exposures
lived within 1/2 mile of an asbestos factory.
Lieben and Pistawka (1967) studied 42 cases of mesothelioma
and observed that eight (8) had only been exposed to asbestos by
either living in the immediate neighborhood of asbestos plants
(within 1/2 to 1 1/2 mile radius) or being employed next to an
asbestos plant.
Others have also observed mesothelioma associated with
neighborhood exposure to asbestos (Borow e_t al_., 1967; Bohlig et
a]_., 1970; Ashcroft and Heppleston, 1967; Anspach, 1969; and
Solomon, 1969). Main et al. (1974) reviewed the literature from
- 66 -
-------
1964-1972 on mesothelioma associated with asbestos exposure and
found that 95 cases of neighborhood (environmental) exposure have
been reported.
A retrospective study of 150 cases in Hamburg (Main et al.,
1974) showed 20 cases associated with neighborhood (environmental)
exposure (within 1 km. around an asbestos plant) and 8 cases in
outlying areas. In a previous survey of Hamburg by this group
(Bohlig et^ aK» 1970), they pointed out that working conditions of
the asbestos factories in Hamburg were uncontrolled until the mid-
30's when indoor dust control was started but without any control
on exhausted air. Not until after World War II was the exhausted
air controlled for economic reasons (recovery for reuse). Of the
119 cases studied 43 were not associated with occupational or
domestic exposure to asbestos but were neighborhood exposures. In
their later study (Hain e_t aJL, 1974) which does overlao with the
previous one, they advise that neighborhood (environmental)
exposure requires precise definition and should not be referred to
as general urban exposure. Also, it is appropriate to note that
the latent period before onset of mesothelioma is long and exposures
likely occurred when asbestos plants practiced little or no
internal or external environmental control.
- 67 -
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X. HUMAN EFFECTS
General
The background document on asbestos for the hazardous pollut-
ants list in Section 112 of the Clean Air Act cites about 30
occupational studies. Nearly all the positive evidence linking
asbestos with human effects has come from such occupational
studies. Except for a few specific (neighborhood) environmental
exposures, these occupational studies concern workers engaged in
the mining and milling of asbestos, the manufacture of asbestos-
containing products, and the application and removal of asbestos-
containing insulation material.
The major deficiences in these studies is the lack of detailed
exposure histories in regard to (1) what other materials may have
been inhaled besides asbestos, (2) time-dose information, (3) size
distribution of fibers and (4) quantitative exposure estimates.
Asbestosis
Pulmonary asbestosis is a slowly progressive, diffuse, inter-
stitial fibrosis which may not be detectable by chest x-ray in the
early stages. Fibrosis and calcification of the pleura may also
have varying degrees of association. The main symptom is dyspnea.
Finger clubbing, cyanosis, and fine basal rales tend to develop a
long time after the onset of exposure. Severe fibrosis can ulti-
mately lead to death from cardiac failure (reviewed in Castleman
and Fritsch, 1973).
Asbestosis usually develops after long exposure to high
concentrations of asbestos dust. Thus, it is largely confined to
occupational exposures. The degree of risk varies directly with
the length of exposure and the concentration. Following continued
exposure to high concentrations, asbestosis may develop to clini-
cal stages in seven to nine years and may cause death as early as
- 68 -
-------
thirteen years from the onset of exposure. However, the usual
exposure period in workers before recognition of asbestosis is 20
to 40 years, with death following two to ten years later. Once
established, asbestosis progresses even after exposure has ceased.
Short, heavy exposures have lead to asbestosis. Dose vs. time
relationships for the onset of the disease have been difficult to
establish; however, the data available has been used to arrive at
a "threshold limit value" for occupational exposure which appears
to reduce the risk of asbestosis (ACGIH, 1971).
All varieties of asbestos can produce asbestosis. It is not
known whether one type is more fibrogenic than another (ESL, 1973).
Association With Neoplastic Disorders of the Hematopoietic System
Five cases of asbestosis associated with tumors of the hema-
topoietic system (in a series of 35 cases confirmed by autopsy)
have been reported. The disorders observed included two cases
with multiple myeloma, two with myeloproliferative disorders, and
one Waldenstrom's macroglobulinemia. The incidence of this associ-
ation is significantly higher than the overall incidence of such
disorders in the corresponding age group of patients without
asbestosis (Gerber, 1970).
Other Clinical Features
Physiological changes are observed consistent with a restric-
tive lung disorder manifested by decreased forced vital capacity,
diminished diffusion capacity, and decreased pulmonary compliance
(Kleinfeld, 1973).
The prevalance of pulmonary fibrosis in one study was 40% in
smokers and 24% in non-smokers. Age, sex, and the duration of
exposure did not account for this difference (Weiss, 1971).
Lung Cancer
Lung cancer is not an unusual complication of asbestosis. It
may appear unaccompanied by asbestosis but after asbestos exposure
(Athanassiadis and Sullivan, 1969).
- 69 -
-------
Kannerstein and Churg (1972), after a review of the literature
and their own studies, were not able to accept fibrogenesis as an
intermediate, essential, causal phase in inducing lung cancer
since a quantitative relationship between the severity of as-
bestosis and lung cancer was not evident. Increased incidence of
pulmonary carcinoma has not been observed in other fibrosing
pneumoconioses.
A relationship has been established between past occupational
exposure to asbestos and a higher than expected incidence (5X-7X)
of lung cancer (Kleinfeld, 1973; Wagner ejt al_., 1971).
Some studies demonstrate differences in the degree of risk
between different occupationally exposed groups; these are prob-
ably related to type and concentration of asbestos fiber; nature
of the work performed and other factors, such as smoking cigarettes
(Selikoff et al_., 1968).
Selikoff ejt al_., (1968) in a study comparing insulation
workers who smoked cigarettes to men who neither smoked nor worked
in the insulation industry, reported a mortality rate from lung
cancer 92 times greater in the former as compared to the latter.
Features peculiar to asbestos-related lung cancers are: (ESL,
1973)
a) all cell types that are histological indicators of malig-
nancy are observed;
b) 2/3 of the lung cancers are lower lobe types;
c) the cancers tend to be peripheral;
d) the pleura are often involved early;
e) bronchus tumors are infrequent.
In a study of textile workers by, Knox e_t al_. (1968), there
are indications that the incidence of lung cancer decreases with
progressively smaller total exposures to asbestos fibers. However,
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a true dose-response relationship was not established nor can one
be inferred.
One study of « population of asbestos textile workers luv,
shown that the occurrence of pulmonary cancer differs markedly
with total exposure. No increase in the incidence of bronchogenic
cancer in a group that had low to moderate exposure was observed,
whereas a heavily exposed group showed an eight-fold increase in
incidence of lung cancer (Newhouse, 1969).
Similarly, a recent study of mortality in chrysotile mines
and mills in Quebec showed only a small excess from lung cancer.
However, the "heavily exposed" workers had a rate of lung cancer
five times that of the "lightly exposed" workers (McDonald et al.,
1971).
Whether the carcinogenic role of asbestos is related to the
specific kind of fiber has not yet been determined. Only one
study exists that involves exposure to only one kind of fiber.
This study showed that exposure occurring during the mining of
anthophyllite in Finland was associated with a three-fold increase
in lung cancer deaths (Kiviluoto and Meurman, 1970). It should be
pointed out that this was a small study (eight cases) and observed
only short exposure times.
The data from one occupational study suggests a cocarci-
nogenic role for asbestos. In the study of insulation workers by
Selikoff e_t aJU (1968), not a single bronchogenic cancer was found
in an insulation worker who was a noncigarette smoker, even though
asbestos exposures were the same as for those who smoked and
developed lung cancer. The role of cofactors other than cigarette
smoking remains to be determined.
Mesothelial Tumors
Primary malignant tumors of the pleura, peritoneum, and
pericardium have been a matter for dispute until very recent
times. Investigators in many parts of the world have examined the
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distribution and the frequency of mesothelioma in populations
occupationally exposed to asbestos. These studies indicate that
there is a relationship between exposure to asbestos fiber and the
incidence of mesothelioma (Wright, 1969).
However, there still remains some controversy among patholo-
gists regarding diagnostic criteria. Histological aspects, as
well as the determination by autopsy, of whether the tumor is
primary or secondary, are the major points of difference (NAS,
1971). Many of the cases reported in the literature as being
related to asbestos are diagnosed on the basis of a biopsy alone,
so that under- or over-diagnosis of mesothelioma is possible
(Wright, 1969).
Approximately seven percent of deaths among asbestos workers
are caused by pleural and peritoneal mesothelioma (2/3 peritoneal
and 1/3 pleural). After diagnosis, the duration of life is only
infrequently longer than a year (ESL, 1973).
It has been suggested that inhaled asbestos fibers cleared
from the lung and swallowed migrate through the gastrointestinal
(GI) wall to the peritoneum. This may account for the association
of peritoneal mesotheliomas with inhalational exposure to asbestos.
It is estimated that only about 1% to 2% of the dust inhaled
during a lifetime is retained in the lungs. The remainder is
transported via the pulmonary clearance mechanism to the pharynx,
thus it is probable that the GI tract receives much of the inhaled
and subsequently ingested dust including fibers (Gross, et a!.,
1974).
The first cases reported in the literature were not taken
seriously until 1960, when Wagner reported 33 cases of pleural
mesothelioma discovered in the Northwest Cape of South Africa.
Seventeen of the cases were from occupational exposure; all but
two of the remaining had lived near the mines or had household
contacts (Wagner ejt aJL , 1960).
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No studies have been possible to determine if a specific kind
of fiber is involved in the relationship between asbestos and
mesothelioma. However, the Mviluoto and Meurman (1970) study has
been cited in this regard because not a single mesothelioma was
observed in a population of mine and mill workers exposed only to
anthophyllite. Caution has been urged, however, as the period
between exposure to asbestos and the appearance of mesothelioma is
often longer than 30 years (Wagner, 1965; Selikoff and Hammond,
1963).
All of the studies which indicate differences in pathogen-
icity among various types of fibers conspicuously lack quanti-
tative data on cumulative exposures, fiber characteristics, and
the presence of other substances and cofactors.
There has been some speculation where mesothelioma cannot be
related to occupational, para-occupational, or specific environ-
mental exposure to asbestos. Selikoff has pointed out that
asbestos is not the only substance shown to be associated with
mesothelioma; the disease has also been associated with silica and
polyurethane (in laboratory animals) (Selikoff and Hammond, 1968).
Gastrointestinal Cancers
A two to three-fold increase in the incidence of gastroin-
testinal-tract cancer (stomach, colon, esophagus, rectum) has been
observed among asbestos workers (ESL, 1973).
Since 1955 asbestos-like fibers have entered the water supply
of Duluth, Minnesota. Masson e_t al_. (1974) conducted a study of
the correlations to cancer mortality for Duluth from 1955-1969.
They found no carcinogenic effect apparent in the patterns of
cancer mortality among persons of all ages in Duluth for the 14
year period. An excess of cancers of the colon for 1965-1969 was
observed, but, the authors feel it was a chance observation since
the latest statistics on asbestos workers show cancer of the
esophagus and stomach in far greater excess than cancer of the
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colon. Masson, ejt al_. point out that their study cannot be con-
sidered conclusive since the period of observation is short
relative to the observed latent periods for occupationally induced
carcinogenesis from asbestos. A much longer follow-up is neces-
sary in the future to assess the cancer hazard related to asbestos
fibers in drinking water supplies.
Other Cancers
Asbestos has also been suggested as an etiologic factor in
ovarian cancer. Asbestos-related mesotheliomas have been observed
to resemble ovarian cancer in appearance (Graham and Graham,
1967). Keal (1960) was impressed by a higher incidence of ovarian
cancers in women suffering from pulmonary asbestosis as compared
to other women.
Generally, studies on other cancers and their association
with asbestos are inconclusive, due in part to insufficient data
concerning other substances and other factors associated with
exposure (NAS, 1971).
Pleural Calcification
Calcified pleura! plaques have been observed frequently in
workers exposed to asbestos (NAS, 1971). Pleural plaques are also
used by some investigators in diagnosing an asbestos-related
disease (ESL, 1973).
Pleural calcification has been reported to occur in varying
frequencies in different occupationally exposed groups. These
differences have not been explained (NAS, 1971; Kleinfeld, 1973).
In asbestos workers, calcified plaques rarely appear until 20
years after their first exposure and are not necessarily corre-
lated with fibres is (NAS, 1971).
Pleural plaques are often absent in persons with well-developed,
diffuse, pulmonary fibrosis resulting from asbestos exposure, and
they can be very extensive in persons with little or no diffuse
fibrosis (Wright, 1969).
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The finding of pleural calcification or pleura! plaques in
large segments of populations that are not directly exposed occupa-
tionally but live in or near regions where asbestos fibers are
produced and used has been reported as being common (Wright, 1969;
Kleinfeld, 1973; Kiviluoto, 1960).
No evidence exists to indicate that there is any relationship
between pleural plaques and the development of mesothelioma
(Wright, 1969; Kleinfeld, 1973).
The use of pleural plaques or pleural calcification as an
indicator of exposure to asbestos appears to have limited value
since factors other than asbestos can result in pleural calcifica-
tion and the asbsence of plaques in no way connotes a lack of
exposure.
"Asbestos Bodies" - Ferruginous bodies
The coated fibers characteristically observed in lung tissue
in cases of asbestosis were originally called "asbestosis bodies."
The designation was shortened when it was discovered that persons
without asbestosis had these bodies in their lungs. It was later
determined that the presence of these bodies is not always related
to asbestos exposure but may be due to other fibrous materials
which can produce bodies identical in appearance (Gross et al.,
1969). Gross and associates (1968(a)) suggested the term "fer-
ruginous bodies" (rust coloriron containing) for these structures
and felt that they should be called "asbestos bodies" only when
it is known with certainty, or could be presumed on the basis of
known exposure, that the central fiber of the body is in fact
asbestos.
The frequency of "bodies" occurring in the lungs of the
general public apparently depends upon the volume of lung tissue
examined and on the intensity of the search. Findings have ranged
from 25 to almost 100 percent frequency in the population studies
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which involve direct examination of long tissues or of the juices
pressed from such tissue (Thomson, 1965; Utidjian et aj_., 1968).
Attempts at identifying the core fibers have often been
unsuccessful because of inconclusive results (NAS, 1971).
The total amount of fibrous matter in the lung has recently
become the focus of attention; that is, coated and uncoated fibers
are enumerated and identification attempts made. A study of 3,000
consecutive autopsies in New York City showed that approximately
half (1449) had coated fibers in the lungs and that two-thirds of
these also had uncoated fibers present. One-quarter of the total
sample had no coated fibers in the lungs. Twenty-eight samples
from this same series were examined by electron microscopy and
were found to contain sublight microscopic chrysotile fibers
(Langer ejt al_., 1971).
It appears to be relatively well established that asbestos
fibers are present in many human lungs. However, it is noteworthy
that sources of airborne fibers exist other than asbestos. Some
vegetable fibers are probably derived from the burning of leaves
and from burning plant products such as paper, wood, and coal.
Man-made fibers (principally vitreous) have also been identified
in the sediment isolated from human lungs. Talc, mentioned
several times earlier in this report, may contain significant
amounts of asbestos fibers (NAS, 1971).
Information is limited concerning the increasing use of
asbestos and its correlation with increased numbers of lungs
containing fibers and ferruginous bodies. Reports in the lit-
erature include those of Selikoff and Hammond (1969) who compared
lung tissues obtained in 1934 with 1967 samples and found no
significant increase in the number of lungs containing ferruginous
bodies. However, Urn (1971) reported an increase in asbestos
bodies each succeeding decade in samples of lungs taken from
persons who died in London in 1936, 1946, 1956, and 1966.
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Davis and Gross (1973) have observed that many of the fibers
found in the lungs of adults are less than five microns lonq arid
about 101- can be identified «s rhrysottlo. Aftor study <>l In-
ruginous bodies in lungs not industrially exposed to asbestos
fibers, they concluded that ferruginous bodies do not qualify as
an index of asbestos air pollution for the following reasons:
"(1) Ferruginous bodies are not specific for asbestos.
(2) There is no quantitative relation between the number
of ferruginous bodies and the number of asbestos fibers
in a lung.
(3) The mobility of people in industrialized communities
precludes the likelihood that ferruginous bodies found
in a lung are nucleated by fibers inhaled in only one
community."
It is clear that further study of ferruginous bodies is
necessary in both qualitive and quantitative terms before any
meaningful interpretation of their significance can be made as to
health risk for persons other than those occupationally and para-
occupationally exposed.
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XI. TOXICITY - ANIMAL STUDIES
Presently, there are no satisfactory experimental models
which can duplicate the prolonged inhalation of asbestos by man.
Studies of routes other than inhalation are very limited. Most
studies involve inhalation or the intrapleural administration of
asbestos associated with asbestosis and/or neoplasia.
Experimental Asbestosis
Asbestosis (pulmonary fibrosis) has been produced in various
species including rats, guinea pigs, hamsters, rabbits, and
monkeys (Wagner, 1963). The fibrosis produced resembles early
asbestotic development in man. However, in order to produce
diffuse fibrosis, very high concentrations of asbestos dust and
long periods of exposure or observation were necessary. Studies
to determine correlations between asbestosis and fiber length have
been inconclusive (NAS, 1971).
Experimental Neoplasia
The following possible mechanisms for carcinogenesis have
been or are under consideration: (Harington e_t al_., 1967).
(1) That it is due entirely, or in part, to organic materials
associated with the fiber, either naturally or as a
result of contamination or treatment of the asbestos
during processing.
(2) That it is due to the presence of certain carcinogenic
metals or metal-complexes in asbestos from ores or from
mining, milling, processing, and shipping operations.
(3) That it is an "Oppenheimer effect," i.e., that cancer
arises as a result of prolonged residence in the tissues
of a chemically inert material which cannot be removed
or can only be slowly removed by phagocytosis.
(4) Related to (3) above is the size distribution of
fibers (length and diameter).
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(5) The type of asbestos may be relevant.
(6) The promoting or potentiation of other organic and
inorganic substances in the respiratory tract may be
enhanced.
Lung cancer has been produced in rats (sixteen out of seventy-
two) from inhalation exposure to chrysotile dust (86 mg/M,)
(Gross et a]_., 1967 (b)).
Other investigators (Stanton ejt al_., 1969) did not find a
carcinogenic response in the lung or pleura of rats exposed to
implanted wax pellets containing asbestos; nor was there a response
from artificially produced infarcts which allow accumulation of
asbestos fibers. However, sarcomas of the pleura and pericardium
developed in 74% of those rats in whom the pleura was covered with
an asbestos-impregnated, fibrous, glass coat.
Continuation of Stanton's work (Stanton and Wrench, 1972)
with amosite, chrysotile, and four different specimens of crocid-
olite applied via a fibrous glass vehicle to the pleura of rats
yielded high incidences of pleural mesotheliomas (ranging from 58
to 75%) two years later. (The sample size of the experimental rat
groups was 30.)
Mesothelioma has been reported in rats and hamsters that
received intrapleural injections of amosite, chrysotile, and
crocidolite (Smith et^ al_., 1965; Wagner, 1962; Wagner and Berry,
1969). However, the amounts introduced were very large, and
extrapolation of these results to human inhalation cannot be used
for drawing firm conclusions.
Malignant mesotheliomas were induced in the peritoneum of
rats by a single injection of chrysotile or crocidolite asbestos
fibers. Immediate toxicity manifested as acute peritonitis
producing approximately 40% mortality was noted in both groups
eight days after injection. In the first two or three days after
intraperitoneal injection, liver sections from the crocidolite
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group revealed clearly visible asbestos fibers surrounded by white
blood cells. Between ten and fourteen months after exposure, nine
of 45 rats developed peritoneal mesothelioma. In the chrysotile
group, eight of 33 rats developed peritoneal mesothelioma. Shin
and Firminger (1973) feel that the large numbers of asbestos
fibers in their experiments played an important role in producing
cytotoxic inflammatory reactions with subsequent fibrosis, which
may not be directly related to the development of mesothelioma.
They suggest that the initiation of mesothelioma may be associated
with a much smaller number of asbestos fibers without significant
inflammatory reaction at the site.
It has been suggested that natural oils, waxes, and contam-
inant oils from milling could contribute to the induction of
cancer (Harington and Roe, 1965). However, asbestos samples
prepared from the five UICC standards (amosite, Rhodesian and
Canadian chrysotile, crocidolite, and anthophyllite) from which
the oils were extracted gave very similar results to unextracted
fibers. In total, 58 out of 160 rats in the oil-extracted group
and 56 out of 160 in the unextracted group developed mesotheliomas
after intrapleural administration (Wagner, 1972).
Studies to ascertain the importance of fiber diameter, length,
and shape have been conducted. Timbrel 1 and Rendrall (1972)
ground UICC Canadian chrysotile to a fine powder; it produced
higher incidences of mesothelioma by intrapleural administration
in rats than did the standard. However, Stanton and Wrench (1972)
found fewer mesotheliomas with pulverized UICC crocidolite than
with the standard. It should be pointed out that these studies
are not strictly comparable because techniques of grinding may
differ; the asbestos type may be different; and other test param-
eters may have varied.
Chrysotile asbestos powder (50% suspension in normal saline)
was intraperitoneally injected into mice. A proliferative,
granulomatous, and invasive fibrosis was observed to be histologically
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similar to mesothelloma, although specific morpholoqlc evidence of
an actual malignancy was not obtained (Jagatlc et aj., 1967).
Evidence that variation in flbrogenlc and carcinogenic
response is correlated to asbestos fiber length has been inferred
by observations in hamsters. Intrapleural injections of 25 mg
samples of chrysotile suspended in saline were administered to
test groups of 50 hamsters maintained up to 700 days. Groups
injected with long fibers (5.3 to 38.9 microns) showed intra-
thoracic tumors with characteristics of pleura! mesotheliomas in
approximately one-fifth of the test group (ten animals). The
shorter fiber groups (0.37 to 0.86 microns) induced relatively
thin pleura! adhesions with no characteristics of mesothelioma
(Smith et a!., 1972).
Stanton (1974) and Gross (1974) have focussed attention on
fiber size as the the possible carcinogenic mechanism in asbestos
cancers as a result of the observed lack of effects in experi-
mental studies associated with "small" asbestos fibers i.e. fibers
<5y in length (Gross) and >3y diameter of various lengths or <3y
diameter and <20y length (Stanton). If these observations are
correct, the majority of asbestos fibers to which people in the
general environment are exposed would be "too small" or "too
large" to be considered potent carcinogens (Stanton, 1974). The
asbestos fibers present in drinking water and certain beverages
nearly all fall into the "toe small" catagory. Stanton (1974)
also raises the possibility that if fiber size is the important
carcinogenic factor then other fibers generally >5y length may
present a carcinogenic hazard.
_ 81 -
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r-. ,. , . - [RHONIHCX.I NIC (.AM.INOMA
?4 ii,,,-' ' ll'n,,,py,,.n. Troce n.PtoK N. , Cr '' ' ,]
"''P'""' 'VI' >»IO'» *",n'Mhl mrM'Ol'Mti uf HI' (liri'KAl Ml r,OTHI I IOM/\
/ liMirn'r '"-'iIwil- tirr* ,ut '
''' in t u'K) "^ t ,i* Mtj
,,,h;' ,. ^ , , (N .hi'. I'!' V1""'"'"' '". /".In''1
'"'" ' i'iilu(l,,ni , niiilriniilil \'H,t)
A.r (Viiulrn
^rnrVinq ^ ,'
C^l.^t^.,1 rr * /
*i"i'kri1 fojiH Mftohdlu liydronylnlf d
pftHfud1; fioncorrmogentc
Figure 5. Horking Hypothesis of Trace Metals in Chemical
Carcinogenesis in Asbestos Cancers
A mechanism was hypothesized by Dixon et_ a]_., (1970) which
involved the role of trace metals in chemical carcinogenesis
associated with asbestos cancers (see figure 5). The experimental
work relating to this hypothesis involved an in vitro procedure
where microsomal fractions of homogenates (from rat lungs) were
used to which were added increasing concentrations of metals
(associated with asbestos).
Results were that metals could stimulate or inhibit the
activity of BP hydroxylase depending on the relative concentration
of the metal added to the microsomal fraction.
All the metals do not show the same activity. Copper (Cu+2),
Magnesium (Mg+2), iron (Fe+2), zinc (Zn+2), nickel (Ni+2), and
cobalt (Co+2) stimulated BP hydroxylase enzyme activity signifi-
cantly at low concentrations as well as inhibited the enzyme at
higher concentration. Beryllium (Be+2), iron (Fe+3), and chromium
(Cr+6) significantly inhibited the enzyme. No effect was demon-
strated with arsenic (As+3), selenium (Se+4), and chromium (Cr+3).
Trace metals extracted from chrysotile asbestos, when added
to the enzyme reaction mixture, inhibited enzyme activity approxi-
mately 73%. The investigators feel that inhibition of BP hydrox-
ylase by the trace metals contained in chrysotile suggests that
chrysotile has the potential for interfering with the detoxication
of benzopyrene and could thereby contribute to carcinogenesis
(Dixon e_t a]_., 1970).
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Studies conducted by Roe e_t aK (1967) in mice showed the
development of pleural and peritoneal mesothelioma after subcu-
taneous injections of crocidolite, amosite, and chrysol.Mo,
indicating that asbestos fibers can migrate in tissue. These
studies are of otherwise limited significance in drawing con-
clusions regarding the pathogenicity of these fibers to man, in
whom subcutaneous exposure would be uncommon.
Studies Related to the Ingestion of Asbestos
In female rats that were fed chrysotile asbestos (six percent
in a synthetic diet), electron microscopy revealed asbestos
particles on many sites in the colonic epithelium and lamina
propria. These particles appeared to have migrated through the
mucus of the goblet cells into the cell itself and then to the
lamina propria. It was suggested by the researchers that this
observation may have significance in relation to carcinogenesis of
the gastrointestinal tract (Westlake et_ al_., 1965).
Chrysotile fibers injected into the stomachs of rats were
isolated two to four days later from the blood, spleen, liver,
kidney, omentum, muscle, lung, and brain. The highest levels were
found in the omentum. The investigators concluded that this was
evidence that the fibers crossed the GI wall. Tissues were
solubilized and samples prepared for observation with the electron
microscope. Unexpected high levels of asbestos, the source of
which could not be determined, were also found in the tissues of
the control rats (Cunningham and Pontefract, 1973). Table 8
summarizes these results.
Tritated chrysotile fibers intravenously injected into rats
are rapidly removed from the blood; most of them are deposited in
the tissues within six minutes, with the highest levels being
found in the lungs, liver, and spleen. But during the next 24
hours the levels in the lung tend to fall and the levels in the
liver, spleen, and muscle increase slightly (Ibid).
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Table 8. Asbestos Fibers Found After Intragastric
Injection (M1ll1ons/g)
Tissue
Blood
Spleen
Omentum
Heart
Brain
Lungs
Controls
0.00
2.33
2.46
2.09
0.05
1.06
Killed at
2 days
(9.4 billion
admin-
istered)
4.65"
4.11
2.74
0.31
1.80
Killed at
4 days
(94 billion
admin-
istered)
1.19
3.45
18.25
2.28
0.29-
1.74
P <0.05; - P < 0.01.
Neutron-activated asbestos intravenously injected into rats
on the fifteenth day of pregnancy resulted in considerable activ-
ity in the whole fetus and in fetal liver. The authors feel this
is another indication of the ability of asbestos fibers to cross
membranes (Ibid).
Pinocytosis (incorporation into a cell by invagination and
pinching off of a region of membrane) and physical piercing have
been suggested as mechanisms by which asbestos fibers could cross
the gastrointestinal wall (Cunningham and Pontefract, 1973).
As an adjunct to their studies, Cunningham and Pontefract (1973)
analyzed for asbestos content tissues from three humans who died
of natural causes. Levels of 0.378 million fibers per gram were
found in the brain, 0 - 0.253 in the spleen, and 0.773 - 0.915 in
the peritoneum.
Gross e_t aj_. (1974) reported on three independent investiga-
tions of the ability of ingested asbestos fibers to penetrate
gastrointestinal (GI) tissue in rats. All three concluded that
there was no evidence of tissue penetration or storage of ingested
asbestos mineral fibers. Separate studies were conducted with
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amosite, chrysotile, crocidolite and taconite tailings. Iho
animals in one of these studies were fed asbestos (chrysotile and
crocidolite groups 0.2 to 0.4% in butter) over much of their
lifetime and allowed to live to the age of reproduction. No
evidence of "carcinogenic" effect was observed. The very few
fibers (1-3) observed in tissue digest with the electron micro-
scope were attributed to contamination. The authors also pre-
sented the rationale that if transmigration of fibers through the
GI wall was a fact, one would expect more than one to three fibers
out of billions to accomplish the feat and this phenomenon to be
demonstrable in more than five out of 37 rats.
The results obtained in these studies contrast those of
Cunningham and Pontefract (1973) discussed above. It has been
suggested that experimental error and the technique (intragrastric
injection) used account for the contrasting observations.
The issue of GI transmigration of asbestos fibers is still
felt to be unresolved by some. Gross ejt al_ (1974) have pointed
out the differences from a histological standpoint between alveolar
membrane and GI mucosa to attain a proper perspective. The
alveolar membrane is largely composed of thin squamous cells,
whereas the intestinal mucosa is composed not only of mucin-
covered tall columnar epithelium but also by a substantial tunica
propria mucosae. The GI mucosa is thus a much more formidable
barrier against the intrusion of foreign particles than the
alveolar membrane. In addition, the presence of enlarged, dis-
colored satellite lymph nodes in coal and hard rock miners demon-
strates penetration of the alveolar membrane. However, no such
involvement of mesenteric lymph nodes has been described even
though these miners ingest (via pulmonary clearance) during their
lifetime many times the amount of dust retained and stored in
their lungs and satellite nodes.
Webster (1974) reported on crocidolite ingestion studies with
baboons. The baboons had eaten food and drunk water contaminated
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with asbestos for up to five years. No evidence was found of
peritoneal or gastrointestinal tumors. Only occasional asbestos
fibers were found in ashed tissue of the stomach ranging in size
from 0.5 to 1 micron which Webster feels probably came from iron
containing macrophages.
Pooley (1974) points out that in his attempts to find asbestos
fiber in 61 tissue one of the first things found was that angula-
tions in the GI tract can hold material up for an appreciable
period of time with an attendant high risk of sample contamina-
tion. In addition, the mucus on the gut wall can hold material
that might later be regarded as being within the specimen. Pooley
found no fibers in GI tissue specimens with the light microscope
and only 6 or 7 in a few animals by electron microscopy.
Davis e_t aJL (1974) studied the penetration of cells by
asbestos fibers in rats fed asbestos in butter ad libitum. Exam-
ination of the gut lining by electron microscopy showed no evidence
of penetration by asbestos fibers either through or between
epithelial cells.
In rats two to three days after intraperitoneal injections of
crocidolite, liver sections revealed clearly visible asbestos
fibers (Shin and Firminger, 1973).
Zaidi (1974) has commented on the choice of test animal for
asbestos ingestion studies. He indicates that the rat is not one
of the animals which should be used. Since its stomach is lined
with squamous epithelium and therefore does not simulate the human
stomach. Dogs and guinea pigs are suggested as the animals of
choice since they seem to be most similar to man as indicated by
experimental ulceration studies.
Radioactive tracer methods were used to study the distri-
bution of crocidolite between the upper and lower respiratory
tracts in rats after single, short inhalation exposures. With
the UICC (International Union Against Cancer) standard reference
- 86 -
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sample of crocidolite, it was found that 50 + 5% of the deposited
asbestos was in the lower respiratory tract after a simjlo short
59
exposure. Rats held for 30 days showed ' Fe activity 1n the feces
indicating about 73% excretion of the total deposition (Evans ejt
aJL , 1973).
In an incompletely described study (Smith ejt al_., 1965) using
45 hamsters maintained on a diet of one percent chrysotile or
amosite throughout life, no gastrointestinal tumors or gastric
carcinomas were observed. However, an anaplastic neoplasm in the
mesentery near the colon was observed, as well as occasional
gastric ulcers, one lymphoma that invaded the pancreas, and one
cholangiocarcinoma of the liver. The researchers did not comment
on the significance of these observations except to mention that
gastric ulcers, lymphomas, and cholangiocarcinomas have been
described as spontaneous lesions in hamsters by Fortner et a!.
(1961).
Other studies where animals have ingested asbestos are said
to have been conducted; however, their negative results have
inhibited publication. A Federal interagency effort to conduct
appropriate feeding studies was begun in 1974 under FDA leadership.
Other In Vivo Studies
A study by Jagatic et al_., (1967), involved intraperitoneal
injections of mice with chrysotile asbestos fibers in a 50%
solution of normal saline; the fibers had previously been treated
at very high temperatures (1000°C) for three hours. Within 24
hours, nine had died and all 50 mice injected showed severe signs
of toxicity. Within 36 hours, 26 mice were dead; at 48 hours, 30
mice were dead. The remaining 20 mice in the group showed a toxic
reaction for approximately four days and subsequently recovered.
A study by Hayashi (1974) using chrysotile heated to 650° to 800°C
and injected intraperitoneally in mice gave similar results with
death occuring in 48 hours.
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Analysis of heat-treated material similar to that used by
Jagatic e_t aJL (1967) was analyzed by x-ray diffraction and showed
the major constituent to be forsterite, Mg^SiCL. The minor
constituent was identified as a member of the pyroxene group,
enstatite [Mg(Si03)]. (Free crystalline silica was not detected.)
Chrysotile and serpentine are converted to olivine by heating.
This conversion occurs at around 750°C. The probable reaction is:
Mg3Si2(OH)4 heat 3 Mg2$i04 + Si02 + 4H20, with Si02 being present
as amorphous silica (Deere ert aj_. , 1966).
In Vitro Studies
In vitro effects of chrysotile, crocidolite, and amosite
asbestos on hamster peritoneal macrophages have been monitored by
estimating the release of acid phosphatase into the culture
medium, and by changes in the phospholipid composition on the
cells in addition to cell number and morphological examination.
Chrysotile was observed to be toxic to the cultures, while
crocidolite and amosite were relatively inert (Miller and Haring-
ton, 1972).
Chrysotile fibers have been observed to exert marked hemo-
lytic activity on suspensions of washed sheep erythrocytes,
whereas the amphiboles show only negligible hemolytic properties.
Chrysotile hemolytic properties (ability to cause destruction of
red blood cells) are dependent on the openess of the fibers (i.e.
the degree that fiber ends are split into many fibrils); hammer-
milled and air-jet-milled samples showed hemolytic activity while
none of the hand-cut, crude samples was active (Schnitzer and
Pundsack, 1970).
The hemolytic activity of chrysotile has been confirmed by
others (Harington et^ aJL, 1971). Other forms of asbestos were
observed to have varying hemolytic activities related to the
magnesium to silicon ratio of each form. Notably, amosite and
crocidolite were observed to be relatively inactive in this
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regard. Although hemolysis as such appears to have little or
nothing to do with pathogenesis, such an iri^ vitro, technique for
hemolysis is a simple and rapid way of studying the effects of
mineral dusts and fibers on a biological membrane.
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CURRENT ENVIRONMENTAL REGULATIONS AND STANDARDS
Emission Standards
Illinois -- The Illinois Pollution Control Board emission
standard initiated June 30, 1972, provides that "... a factory,
plant, or enterprise which engages in the processing or manu-
facturing of any asbestos-containing product shall discharge no
visible emission of particulate matter from such manufacturing or
processing into the ambient air and shall emit no concentrations
of asbestos fiber in excess of two fibers per cubic centimeter of
air."
The method of counting specified is the phase-contrast
optical technique routinely used for industrial hygiene measure-
ments.
National -- The national emission standard under Section 112 of
the Clean Air Act was published in the Federal Register, Volume
38, Number 66, pages 8821 - 8823 on April 6, 1973. This standard
relies on limitations on visible emissions with an option in some
cases to use designated control equipment, requirements that
specific procedures be followed and prohibitions on the use of
certain materials or of certain operations. EPA concluded that
satisfactory means of measuring asbestos emissions are unavailable
and the regulation indicates it is not practicable at this time to
establish allowable numerical concentration or mass emission
limits for asbestos. The standard applies to asbestos mills,
selected manufacturing operations, the use of spray-on asbestos
materials, demolition operations and the surfacing of roadways
with asbestos tailings. Amendments to the national emission
standard were published in the Federal Register, Volume 40, Number
199, pages 48292-48311 on October 14, 1975. They extend the scope
of the asbestos regulations to include shot-gun shell manufacturing
and asphalt plants. Among other changes disposal regulations were
ammended to include properly operated sanitary landfills as accept-
able disposal sites for asbestos-containing wastes.
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Asbestos Spray in Building Construetjon
The national emission standard prohibits visible emissions
from sprays containing more than one percent asbestos which are
used to insulate or fireproof equipment and machinery.
On April 13, 1970, New York City took the lead in the United
States and promulgated strong regulations controlling the applica-
tion and use of all sprayed fireproofing materials -- both asbestos
and non-asbestos-containing material (Ahmed e_t cfL, 1972). Chicago,
Boston, and Philadelphia have also established regulations regarding
spraying of asbestos-containing material (Ahmed ejt aJL» 1972).
On July 18, 1971, the Philadelphia Board of Health regulation
prohibiting the use of asbestos spray in building construction and
limiting the allowable quantity of asbestos fiber exposure became
effective. Included in the regulations are the following para-
graphs (Gorson and Lieberman, 1973):
"1. (a) No spray material containing asbestos as a component
part shall be applied in building construction, reconstruction, or
alteration within the City of Philadelphia."
"2. (b) No worker shall be exposed to the inhalation of
airborne asbestos fibers exceeding the following Threshold Limit
Value - asbestos (all types): five fibers (greater than five
microns in length) per milliliter of air."
"4. No building shall be occupied by the general public
whenever the concentration of airborne asbestos fibers exceeds the
maximum permissible concentration of 2.5 fibers (greater than five
microns in length) per milliliter of air averaged over any eight-
hour period."
The regulations also require air monitoring for asbestos
fibers in places of employment and buildings occupied by the
general public whenever the concentration of airborne asbestos
fibers is likely to exceed certain stated limits (Gorson and
Lieberman, 1973).
Chicago's ordinance prohibits the spraying of asbestos-
containing substances in or upon any building, structure, column,
frame, floor, ceiling, or other portion, part, or member thereof
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during Us construction, reconstruction, alteration, or repair
(Ahmed et ah, 1972).
The Boston buildings' commissioner recently Issued a direc-
tive stating that the spraying of asbestos is not an "acceptable
practice" and that building permits would not be granted unless
some other mode of applying asbestos is specified (Ibid).
State of Illinois regulations prohibited the spraying of
asbestos-containing material on March 31, 1972. Additional
regulations that became effective on April 14, 1972, provide
proper housekeeping procedures for the spraying of non-asbestos
products in all work performed in an area open to the atmosphere.
They further provide that the cutting, fitting, trimming, and
stripping of asbestos materials be conducted in properly enclosed
areas (Ibid).
Effluent Standards
National -- The national effluent guidelines and standards
for the asbestos manufacturing point source category under Section
304(b) of the Federal Water Pollution Control Act were promulgated
in two phases. Phase I applies to the following subcategories:
asbestos-cement pipe, asbestos cement sheet, asbestos paper (starch
binder), asbestos paper (elastomeric binder), asbestos millboard,
asbestos roofing and asbestos floor tile (published in the Federal
Register. Volume 39, Number 39, pages 7526-7533 on February 26,
1974). Phase II applies to the following subcategories: coating
or finishing of asbestos textiles, vapor absorption (removal of
volatilized organic matter from atmospheric emissions by means of
wet scrubbers) and wet dust collection (published in the Federal
Register, Volume 40, Number 6, pages 1874-1878, on January 9,
1975).
Other Regulations
The U.S. Occupational Safety and Health Administration
(OSHA) and the Bureau of Mines (BOM) enforce regulations which
protect workers who are exposed to asbestos in their place of
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employment (OSHA - 29 CFR 1910.93a; BOM - 30 CFR 55.5). On Octo-
ber 9, 1975, OSHA published proposed revisions to the regulations
on occupational exposure to asbestos (Federal Register, volume 40,
number 197, pages 47652-47666.) In general the proposed changes
are more stringent than existing regulations and would require
better environmental control (workroom) as well as revise and
update other required industrial hygiene controls and practices.
The regulations of these two Federal agencies when complied with
reduce the capacity of asbestos mines, mills and associated
industrial operations to become major sources of asbestos emis-
sions. The EPA National Emission Standard takes into account the
reduced pollution potential as a result of the above cited regu-
lations.
The Food and Drug Administration (FDA) enforces regulations
which limit the amount of asbestos that food, drug and cosmetics
products may contain. In some cases this relates to the use of
asbestos filters for preparation of these products (see Federal
Register, Volume 38, Number 188, Friday, September 28, 1973).
- 93 -
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Urn, C.H. (1971), "Study of the Secular Trend in Asbestos Bodies in
Lungs in London, 1936-1966," Brit. Med. J., 2, 248-251.
U.S. Patent 2,068,219, M.S. Badollet (to Johns-Manville Corp.),
Jan. 19, 1936.
Utidjlan, M.D., et^al_. (1968), "Ferruginous Bodies in Human
Lungs," Arch. Environ. Health, Chicago, 17, 327.
- 102 -
-------
Wagner, J.C. (1972), "The Significance of Asbestos in Tissue," in
Current Problems in the Epidemiology of Cancers and Lymphomas
Recent Results in Cancer Research, ed. by E. Grundtnan and H.
Tulinius, 39_, p. 37, Berlin, Springer-Verlag, (through IARC
Monographs on the Evaluation of the Carcinogenic Risk of
Chemicals to Man Vol. 2. 1973).
Wagner, J.C. (1962), "Experimental Production of Mesothelial
Tumours of the Pleura by Implantation of Dusts in Laboratory
Animals," Nature, 146, 180-181.
Wagner, J.C. (1963), "Asbestosis in Experimental Animals," Brit.
J. Ind. Med. 20. 1-12.
Wagner, J.C. and G. Berry (1969), "Mesotheliomas in Rats Following
Inoculation With Asbestos," Brit. J. Cancer, 23_, 567-581.
Wagner, J.C., et^ al_. (1971), "Epidemiology of Asbestos Cancers,"
Brit. Med. Bull., 27^ 71-76.
Wagner, J.C., and J.W. Skidimore (1965), "Asbestos Dust Deposition
and Retention in Rats," Ann. N.Y. Acad. Sci., 132, 77.
Wagner, J.C., et_ al_. (I960), "Diffuse Pleura! Mesotheliomas and
Asbestos Exposure in the Northwestern Cap Province,," Brit.
J. Ind. Med. 17. 260-71.
Webster, I. (1974), "The Ingestion of Asbestos Fibers," Environ-
mental Health Perspectives. 9^ 199-202.
Weiss, W. (1971), "Cigarette Smoking, Asbestos and Pulmonary
Fibrosis," Am. Rev, of Resp. Pis.. 104, 223-227.
Westlake, G.E., H.J. Spjut and M.N. Smith (1965), "Penetration of
Colonic Mucosa by Asbestos Particles: An Electron Micro-
scopic Study in Rats Fed Asbestos Dust," Lab. Invest., 14,
2029-33.
Zaidi, S.H. (1974), "Ingestion of Asbestos," Environmental Health
Perspectives, 9_, 239-240.
- 103 -
-------
A-1
Appendix A
Table I.S.ilicnt a.sbrslON M.itiilus
(CHfton, 7973)
( nit. d Sfat4-.s:
I'nulurtinn (xnJ*'s) _ _. . short Ions _
Vnhio thoijsund _
Exports and reexports (unmanufactured)
short tons. ,
KxporU and reexports of
(value)
Imports for consumption
Valim
Cun-Mimption, apparent '
World: Production- -
ashes to* products
.thousands _
(unmiiuufartunMl)
short tons. ,
. . .thousands.
.... .do . .
19S7
123,189
$11,102
47,718
$6,025
$23,767
645,112
$65,743
720 5X3
1U68
120,690
$10,408
$ 1^679
$24.527
737,90!)
$72,930
817,363
,315,301
1US9
125,936
36,173
$4,979
$28,183
694,558
$76,422
781,321
3,599,123
1970
125,314
$10,6!I6
46.5X5
$6,996
$25,391
649,402
$75,146
728,131
3,846,475
1971
130 882
$12,174
53,678
$31,419
681,367
$80,090
758,571
3,917,996
by quantity prcxluevfl, plua iroiiorts, minua exports.
TabJe %UJ. imports for consumption o( asbrvon (unmanu{acturnl),
by classt* and countries (C1 J f tOH , 1 973 )
Crude (inrlmlinjt Toxtlle filler All other Total
blue liber)
}e»r am conn short Value Short Value Short Value Short
tons (thousands) tons (thousands) tons (thousands) tons
1970
Clinada «<>
Finland. _ - - - -
(irrnii>ny. Went. .
Italy .. - -..-
Mejico.
;ito?.ambique
South Africa.
Keixihlii- of 23,788 4
S.iiithcrn Africa,
nee HO
UmN'il Kingdom. 90
Total 24,068 4
1971
It-ily 2
South Africa,
Republic of.. 23.188 4
Swaziland *. - - . - 160
Total 23,793 4
' Ij** th.in 'a unit.
' effective Jan. 1, 1971, formerly
Table 5. U.S. imports for
Grade
Chrysolite:
All other . .
Crocrlohtp (blue)
Total
$4 15,398 $5,657 597.832 $64,104 613,310
4,141 276 4,141
65 11 65
'Z ~3 2 1 4
100 20 100
70 8 70
132 10 132
231 16 231
200 101 200
,158 85 18 2,855 568 26,728
22 . .. .. .- 110
IS 211 36 5 1 306
1,488 43 2,512 70 4,000
,203 17,184 5,757 608,150 65,186 649,402
96 11,620 5,306 636,7X2 69,577 648,642
4,1X2 342 4,182
4 .. .. .. -- 2
18 8 40 3 58
43 .. -. 157 31 360
,104 1 (') 1,822 399 25,011
46 230 59 390
109 3 109
2,613 69 2,613
,293 11,639 5,314 645,935 70,483 681,367
Southern Africa, n.p.c.
consumption of asbestos from specified countries, by
(Short tons) (d iftOR ,
1970 1971
Value
(thoiuMnda)
$69,765
276
11
4
20
8
10
16
101
4.744
22
r>6
113
75,116
74,979
342
4
11
74
4 . 503
105
3
69
80,090
grades
1973)
Canada Southern Republic of Canada Republic of
Rhodc.sia South Africa South Africa
80 591 18H
15,398 . «.") 11,620
.. . 697,832 200 2.8=15 636,782
.S.936 02
.. .. 14, 2*1
613 310 200 26 728 648,642
1,655
1
1,822
6,953
14,580
25.011
-------
A-2
1,000
Net Imperil (imperil mlnui exports and r«-««porl»)
Sill Domestic production
1964 1966
1.Domestic consumption
1968 1970
ao*. (Clifton,
Table 6.Asbestos: World production, by country
(Short tons)
(Clifton, 19/3]
Country
19(19
1970
1971
North Arm-rim:
Canada (salw) "1,676
(IniU'd States (sold or used l»y producers)- _ |Ufi,
South America:
Argentina
Itntzil ".
Kun»|N*.
Hulgtiria
Finland
Kranri- '
1 1 "i 1 >
Portugal ._ _
If.S.S.U.'-
Yugoslavia-. ...
M oKairil*i<|Uf*_. ._ ., ,_
Ithodesin, Southern ' , .
South Africa, Republic of . ..
Swi7il»nd
United Aral) Hepublir
Apia:
China, People's Kppuhlic of *_ .
Iirui
la _ , _
Japan _
Kort'a, Kepuhhr of. _ ,
l'ltiti|'pini>s
Tiiiwitii
Tiirki-x . .
OrriHii.t. AiiHlrulia . -
Total
Kstim.ttt*. i' I'rHiminary. ' It
In addition to thi- cotinlrics lislftl, (
in. uliitilr tiifitrtuatit-M is tn.idco.u.tU* t.i i
Includes ji^ln-HtoH Hour.
Includes vt*rrnit'uhtf .
' 14
,1
r 15
.- 124,
. ' 1,060,
12
. , KH,
284
'43.
,. ' 175
'L'<\
10
23
. . . . «
.(
f,
- '
---- '3,f,99
f\IVl\.
S7fi
359
MM
100
1H7
550
Oil!)
2'J4
000
B34
Hfi.S
000
5HS
077
000
1)^7
7:t4
1*1 1
5ir,
' 50
;t<)f>
tJ'IH
!»24
ia»
/i-rhoHloviiki:!, N'ortl) Korea, un't Honiiinia
tttU*' rt'liMtitf c.HtiniuU") of output It-Vf
.H.
'(25
18
3
If)
130
1,175
13
XX
a in
36
190
z*
10
2:1
1
I
3
1
1
3,H4(>
al»o pr
].'ll 1
39
000
,307
,019
550
(i 14
2^:1
,000
,312
251
001}
,K22
,439
49 F>
,000
,247
K.|0
,451
,513
3117
.133
tt57
,()O.S
,475
,,(lllr,- i
1-^;
22,
:l.
' 15
131
«
1,270
17
,
KH
351
39
175
4 'JJ
12
" 24
* i
'£
' 1
« 1
3.947
U4t't*Mt.oH,
US
40
ooo
300
(100
r,.-ji>
692
2211
000
Oil
2.r,0
ODD
963
114
GOO
001)
92T»
\-u
000
:uto
Mil
900
000
99<>
lull
-------
A-3
PRICES (Clifton, 1973)
Prices for Biitish Columbia, Canada,
chiy.solilc asbestos have lemained un
changed since Januaiy I, I!)7I. Quotations,
f.o.l). Vancouvei, weic as follows.
British Columbia and Arizona asbestos le-
mained unchanged.
Prices fot Ari/ona chrysolile asbestos Grade Description Per short ton
have lemained uuchaiigcd since August 1,
1968. Quotations, f.o.b. Globe, weic as fol-
lows:
Quoted prices for Quebec asbestos weic
increased I lo 6 peicenl ellei live July
1971. The incieascs were not abnormal
an inflationary economy, but the piice
AAA ....... NnnferroUH
Grade
Group No.
AAA
Group No.
Group No.
Group No.
Group No.
,
2..
3,.
4..
5..
6. -
7 .
Di-scription
. .do ..
Nonferrous filtering
and spinning.
Nonferrous plaatic
and filtering.
Plastic and fdtcnnK-
Refuse or shorts. ..
.. do .
Per short
$1 410-1
7UO-
423-
400-
385-
65
ton
650
<)r,n
sno
70(1
500
4211
250
40
As of July 1, 1971, Vcimont chrysotilc
asbestos, f.o.b. Monisville, was priced as
follows:
AA ________ ...... do. .. .
A ..... ____ .. _ilo
AC ___ ..... _. AH!X'HU>« cem
filiur.
AK __________ Stimuli- fiber
rp _________ ..... do
AS ___________ ____ do
(,'an$877
697
AX
CY
AY.
do
do
do
24H
22H
22.1
ZOH
147
147
Private negotiated sales are the African
asbestos producers' modus operand!. As
this rules out maiket quotations, the fol-
lowing are averages, regaidless of giade, of
the values of South African imports calcu-
lated from U.S. Department cl Commerce
Data:
Grade
Description Per short ton
Group No. 4 Shinglf finer $220.00
Group No. 5 . 1'npor lilx>r 159.50-lK7.,r>0
GroupNn.fi.. Wiuti;, sturro i>r 116.00
plaster fiber.
Group No. 7.. Shorts and floats.. 43.50-97.00
Quotations for Canadian (Quebec) rbry-
sotile, f.o.b. mine, were as follows, as of
July 1, 1971:
Grade
Description
Per short ton
Group No. 1 . Crude Can $1,615
Group No 2.. do . S75
Group No. 3 . Spinning liber 412- 675
Group No. 4.- Shingle liber 227- 883
Group No. 5.. Paper libur 164- 195
Group No. 6.. Waste, stucco or 120
plaster.
Group No. 7__ Refuse or shorts 52- 100
Type
Per short ton
19(59 1970 1971 '
Amosite $15:! $lfiO $164
Crocidolite 189 196 212
Chrynotilt!.. 192 198 120
1 First 6-inonth data on exports. Department of
Mines, Johannesburg.
Figure 2, drawn from calculations on
pertinent data,-i depicts dramatically that
the increased demand and greater price in-
creases have gone to the asbestos used in
cement products (groups 5, 7).
^Asbestos. V. 53, No. 4, Ouober 1971, p 44.
4 Industrial Minerals (London). No. 28, January
I97U, pp. U-2'J.
-------
A-4
ASBESTOS - SALIENT STATISTICS
ASI3I SU>!",
214.1020 A
MAY 1974
1,000r
900 THOUSANDS OF SHORT TONS
800
700
600'
APPARENT CONSUMPTION
I
IMPORTS (O) i
200
DOMESTIC SALES
EXPORTS
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
(1) ADDITIONAL CATEGORY: PRODUCTION is included in the table. Data have not been available since 1957.
(2) Data for 1973 are preliminary.
(3) ASBESTOS are naturally occurring fibrous mineral silicates that are classified as serpentine or amphibole. Serpentine
(chrysotile) fibers are tubular with a large cross-section. Amphibole fibers (further subdivided by chemical structure as
anthophyllite, amosite, crocidolite, tremolite, and actimjlite) are solid and appear as narrow sheets of smaller cross-section.
-------
20 P
A-5
ASBESTOS - SALIENT STATISTICS
(Thousands of Short Tons)
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973)6,
H-M
LJW1VI C,\
PRODUCTION
19.2
22.4
15.3
3.9
7.6
13.6
14.4
25.1
37.2
42.9
41 4
51.7
53.9
58.0
45.8
44.8
41.6
43.0
»
-
3 1 IU
SALES
20.1
24.4
15.5
6.0
6.7
12.2
14.1
24.0
37.1
43.4
42.4
51.6
53.9
54.5
47.6
44.6
41.3
43.7
44.0
45.5
45.2
52.8
53.2
66.4
101 1
118.3
125.9
123.2
1207
1259
1253
1309
131 7
150*1
1 1 A 0
IMPORTS
246.6
419.2
419.2
440.3
383.0
374.4
455.7
594.8
6479
509.4
705.5
761.9
709.5
692.2
678.4
740.4
689.9
682.7
644.3
713.0
669.5
616.5
676.0
667.9
739.4
719.6
726.5
645.1
737.9
694.6
649.4
681.4
735.5
792 5
llfi-^
EXPORTS
4.5
4.8
0.8
0.4
0.5
8.6
11.0
2.7
9.2
20.0
20.9
16.5
10.7
3.1
1.9
2.8
3.0
2.9
3.0
4.5
5.5
3.8
2.9
10.0
27.1
43.1
47.0
47.7
41.2
36.2
46.6
53.7
586
664
£ i-'i
APPARENT
CONSUMPTION
262.2
438.7
433.9
445.9
389.2
378.0
458.7
616.2
675.7
532.7
727.0
797 0
752.6
743.6
724.1
782.2
728.3
723 5
685.3
754.0
709 2
665.5
726 2
724.2
813 3
" 794 7
805.4
720.6
817.4
784.3
728.1
758 6
808.6
a*w ' '
See MANUAL OF CURRENT INDICATORS for additional data.
PRODUCTION and SALES. Domestic production consists of chrysotile from mines in Arizona, California, and Vermont
and anthophyllite from mines in North Carolina. Production value was $10.7 million in 1970, $12.2 million in 1971,
S13.4 million in 1972, and $16.4 million in 1973. In 1972, California accounted for 69% of the total domestic
production (from 4 minesl, followed in order of production by Vermont (1 mine), Arizona (1 mine), and North
Carolina (2 minesK Since 1940, the number of mines operating domestically has varied from a low of 8 in 1946 and
1972 :o a hiah of 21 in 1954, with a mean number of 12 mines. Data for 1947, the last year in which a production
breakdown iv.is piven, were 24 5 thousand short tons of chrysotile and 0 7 thousand short tons of amphibole.
IMPORTS Date? represent shipments of unmanufactured asbestos. Principal imports are chrysotiie from Canadian mines
'.711.3 thousand short tons m 1972), amosite, crocidolite, and chrysotile from South Africa (7.1, 5.4, and 2.4 thousand
short tons, respectively, in 1972), and unmanufactured crudes, chiefly from Canada, Finland, and the Republic of South
Africa Imports of chrysotile that had been under the Rhodesian Sanctions were resumed in 1972
EXPORTS Data represent shipments of unmanufactured asbestos Data for 1940-1946 include material of domestic
origm of *oreign material that has been milled, blended, or otherwise processed in the United States. Beginning in
1947. data also include material that has been imported and subsequently exported without processing. India, Japan,
and South Korea have been major recipients of exports since 1965, of the total exports in 1972, these three countries
accounted for 44% (25 7 thousand short tons). Imports to South Vietnam have increased from 1.7 thousand short
tons in 1970 to 6.4 thousand short tons in 1972 (11% of the total).
-------
A-6
ASBESTOS - SALIENT STATISTICS
ASBESTOS
214 1020 C
MAY 1974
(7) APPARENT CONSUMPTION. Reported by the Bureau of Mines and based on asbestos sold or used by producers.
plus IMPORTS, minus EXPORTS. Chrysotile accounted for over 97% of the total apparent consumption in 1972 The
construction industry (e.g., asbestos cement for pipes and other building materials) is the chief domestic market for
asbestos, accounting for 42% of total consumption in 1972. Other end uses, and relative 1972 consumption, are: floor
tile-11%, friction products-10%, paper-9%, asphalt felts-6%, packing and gaskets-4%, msulation-2%, and textiles-1%
(The data for this consumption pattern are based on a revised form and from an expanded list of consumers, and
therefore are not comparable to previously issued data.) Since 1964. imports have accounted for 89-91% of total
domestic consumption (down from an earlier average of approximately 95%).
(8) Government stocks as of October 31, 1972, contained 58.6 thousand short tons of amosite, 12.2 thousand short tons
of specification grade chrysotile, and 254 thousand short tons of crocidolite.
(9) Because of its reported carcinogenic effect and its deleterious respiratory effects, environmental regulations have been
established for asbestos mining, milling, and manufacture by the following U.S. Government agencies: Bureau of
Mines, Environmental Protection Agency, Food and Drug Administration, and the Occupational Safety and Health
Administration. These regulations limit the incidence of fibers in ambient air (restrictions to be tightened further in
1976, if not earlier) and in water effluent; in addition, these regulations restrict the use of asbestos products in certain
areas and applications (e.g., fibers for general use, and filters in food and drug production). Although it is not yet
evident in the above statistics, these regulations will soon have an adverse effect on production and markets.
SOURCES' (A) MINERALS YEARBOOK, U.S Department of the Interior, Bureau of Mines (PRODUCTION, SALES, and
APPARENT CONSUMPTION data for 1940-1972, and IMPORTS and EXPORTS data for 1940-1971)
(8) MINERAL INDUSTRY SURVEYS, ASBESTOS, 1973 Annual, Preliminary, U.S. Department of the Interior,
Bureau of Mines (SALES datum for 1973).
(C) U.S. IMPORTS-GENERAL AND CONSUMPTION, FT 135, U.S. Department of Commerce, Bureau of the
Census (IMPORTS data for 1972 and 1973).
(D) U.S. EXPORTS, FT 410, U.S. Department of Commerce, Bureau of the Census (EXPORTS data for 1972
and 1973).
(E) Kirk-Othmer, Editors, ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY, Second Edition, Volume 2,
Interscience Publishers, New York, 1963, pp. 734-742 (information in footnote 3).
CHEMICAL ECONOMICS HANDBOOK (SRI) STANFORD RESEARCH INSTITUTE, MENUO PARK, CALIFORNIA
\^.'..*<^X
-------
SOURCE CATEGORY
A-7
ASBESTOS EMISSIONS
(Davis et al_., 1970)
1968
SOURCE GROUP
SHORT TONS
MINING AND
OTHER BASIC PROCESSING
REPROCESSING
CONSUMPTIVE USES
Mining and Milling
Friction Materials
Asbestos Cement Products
Textiles
Paper
Floor Tile
Miscellaneous
Construction
Brake Linings
Steel Fireproofing
Insulating Cement
INCINERATION OR OTHER
DISPOSAL
TOTAL
NA - Data not available
EMISSIONS BY REGION
PLANTS
Region No. 1
Region No. 2
Region No. 3
Region No. 4
1
5,610
678
312
205
18
15
100
28
61
190
15
25
291
NA
6,579
SHORT TONS
3570
20
2020
Regional distribution includes the source groups - Mining and
Milling (representing 85 percent of total emissions)
Undistributed 15 percent
969
-------
A-8
ASBESTOS EMISSIONS FACTORS
(Davis et al., 1970)
MINING AND OTHER PROCESSING
REPROCESSING
Friction Materials
Asbestos Cement Products
Textiles
Paper
Floor Tile
CONSUMPTIVE USES
Brake Linings
Steel Fireproofing
Insulating Cement
C
C
C
C
C
NC
NC
C
93 Ib/ton of asbestos produced
6 Ib/ton of asbestos processed
1 Ib/ton of asbestos processed
2 Ib/ton of asbestos processed
1 Ib/ton of asbestos processed
1 Ib/ton of asbestos processed
10 Ib/ton of asbestos processed
10 Ib/ton asbestos applied
25 Ib/ton asbestos applied
Asbestos emissions factors are based on particulate control indicated as
follows:
Mining and Other Processing - Eighty percent.
Friction Materials
Asbestos Cement Products
Textiles
Paper
Floor Tile
Insulating Cement
- Ninety five percent.
- Seventy five percent.
- Ninety five percent.
- Seventy five percent.
- Seventy five percent.
- Eighty nine percent.
C - Controlled
NC - Not Controlled
-------
B-l
Appendix B
ASBESTOS MINES IN THE UNITED STATES
(Davis, 1970)
ARIZONA
Asbestos Manufacturing Company
Jaquays Mining Corporation
Metate Asbestos Corporation
LOCATION
Gil a County
Gil a County
Gil a County
ASBESTOS TYPE
Chrysotile
Chrysotile
Chrysotile
CALIFORNIA
Atlas Minerals Corporation
Coalinga Asbestos Company [1]
Pacific Asbestos Corporation [2]
Union Carbide Corporation
Fresno County
Fresno County
Calaveras County
San Bern'to County
Chrysotile
Chrysotile
Chrysotile
Chrysotile
NORTH CAROLINA
Powhatan Mining Company
Powhatan Mining Company
Powhatan Mining Company
Yancey County
Jackson County
Transylvania County
Anthophyllite
Anthophyllite
Anthophyllite
VERMONT
GAF Corporation
Orleans County
Chrysotile
[1] - Owned by Johns-Manville Corporation
[2] - Acquired by H. K. Porter Company, Inc. during 1968.
-------
B-2
REPROCESSING PLANTS PRODUCING ASBESTOS FRICTION MATERIALS
(Davis, 1970)
i CALIFORNIA
H. Krasne Manufacturing Company
Silver Line Brake Lining Corporation
Lasco Brake Products Corporation, Ltd.
LOCATION
Los Angeles
Los Angeles
Oakland
CONNECTICUT
H. K. Porter Company, Inc.
Raybestos-Manhattan, Inc.
Middletown
Stratford
ILLINOIS
Gatke Corporation
Grizzly Brake Division of Mar Pro Inc.
The L. S. Miley Company
Johns-Manville Corporation
Chicago
Chicago
Chicago
Waukegan
IN 1JIAN A
Raybestos-Manhattan, Inc.
H.'K. Porter Company, Inc.
World Bestos Company
(sub. of Firestone Tire & Rubber Co.)
Crawfnrdsville
Huntington
New Castle
KENTUCKY
H. K. Porter Company, Inc.
Richmond
MASSACHUSETTS
Auto Friction
Lawrence
MICHIGAN
American Brakeblock - Division Air.bes Corp. Birmingham
American Brake Shoe Company Troy
-------
B-3
NEW JERSEY
Johns-Manville Corporation
Reddaway Manufacturing Company, Inc.
Raybestos-Manhattan, Inc.
H. K. Porter Company, Inc.
Manville
Newark
Passaic
Trenton
NEW YORK
Bendix Corporation
Troy
NORTH CAROLINA
Southern Friction Materials Company
Charlotte
OHIO
American brake tinoe
General Motors Corporation
Maremont Corporation
Cleveland
Dayton
Pauiding
PENNSYLVANIA
Raybestos-Manhattan, Inc.
H. K. Porter Company, Inc.
Manheim
Pittsburgh
TEXAS
Standco Brake Lining Company
Houston
.TENNESSEE
Bendix Corporation
Cleveland
VIRGINIA
American Brake Shoe
Winchester
(Thomas Register, Dec. , 1968 Ed. , Fortune-1966 Plant & Product
Directory of the 1000 Largest U.S. Industrial Corporations; U.S.
Department of Commerce.)
-------
B-4
REPROCESSING PLANTS PRODUCING ASBESTOS" CEMENT PRODUCTS
ALABAMA
U. S. Cast Iron Pipe Company
GAF Corporation
Cement Asbestos Products Company
LQCATKM
Anniston
Mobile
Woodward
CALIFORNIA
Southern Pipe & Casing Company
Johns-Manville Corporation
Johns-Manville Corporation
Certain-Teed Products Corporation
Certain-Teed Products Corporation
Johns-Manville Corporation
Azuza
Long Beach
Pittsburgh
Riverside
Santa Clara
Stockton
CONNECTICUT
Tile Roofing Company
Stratford
Uniroyal, Inc.
GAF Corporation
Hogansville
Port Went worth
ILLINOIS
Acme Asbestos Covering & Flooring Company Chicago
Asbestos & Magnesia Materials Company Chicago
Flintkote Company Chicago
Western Slate Company Elmhurst
Fel-Pro, Inc. Skokie
Johns-Manville Corporation Waukegan
INDIANA
U. S. Gypsum Company
East Chicago
-------
B-5
LOUISIANA
Johns-Manville Corporation
National Gypsum Company
Marraro
New Orleans
MASSACHUSETTS
Johr . -Manville Corporation
No. Billerica *
MICHIGAN
American Asbestos Products Company
Detroit
MINNESOTA
Mac Arthur Company
St. Paul
Certain-Teed Products Corporation
GAP Corporation
National Gypsum Company
St. Louis
St. Louis
St. Louis
NEW EAS3PSHIRE
Johns-Manville Corporation
Nashua
NEW JERSEY
Johns-Manville Corporation
National Gypsum Company
Philip Carey Manufacturing Company
GAP Corporation
U. S. Plywood-Champion Papers, Inc.
Manville
Millington
Perth Amboy
So. Bound Brook
South River
NEW YORK
Asbeka Fabricators Corporation
National Gypsum Company, Inc.
Flintkote Company
Brooklyn
Buffalo
White Plains
-------
B-6
NORTH CAROLINA
U.K. Porter Company, Inc. Charlotte
lohns-Manville Corporation Marshville
OHIO
Philip Carey Manufacturing Company Cincinnati
Seagrave Columbus
Flintkote Company Ravenna
PENNSYLVANIA
Certain-Teed Products Corporation Ambler
Nicolet Industries, Inc. Ambler
Supradur Manufacturing Company Windgap
(sub. of Seagrave)
TEXAS
Johns-Manville Corporation Dennison
Certain-Teed Products Corporation Hillsboro
rniiip ^diey ividiiuiauLUUiuy ouinpauy nuuacuu
'WISCONSIN
Wisconsin Gasket & Manufacturing Company Milwaukee
(Thomas Register, Dec., 1968 Ed.; Fortune-1966 Plant & Product
Directory of the 1000 Largest U. S. Industrial Corporations; U.S.
Department of Commerce.)
-------
B-7
REPROCESSING PLANTS USING ASBESTOS IN FLOOR TILE
CAIIFORNIA
GAP Corporation
Armstrong Cork Company
Flintkote Company
LOCATION
Long Beach
South Gate
Vernon
ILLINOIS
Flintkote Company
GAP Corporation
Armstrong Cork Company
Johns-Manville Corporation
Chicago
Joliet
Kankakee
Waukegan
LOUISIANA
Johns-Manviue uorporauon
Flintkote Company
New Orleans
MASACHUSETTS
Flintkote Company
Watertown
MISSISSIPPI
Armstrong Cork Company
Jackson
NEW JERSEY
Congoleum-Nairn, Inc.
Johns-Manville Corporation
American Builtrote Rubber Company, Inc
Kearny
Manville
Trenton
NEW YORK
GAP Corporation
Vails Gate
-------
3-8 I ,
OHIO
Johns-Manvllle Corporatton Chillicothe
PENNSYLVANIA
Armstrong Cork Company Lancaster
TEXAS
GAP Corporation Houston
(Thomas Register, Dec., 1968 Ed.; Fortune-1966 Plant & Product '"'";
Directory of the 1000 Largest U.S. Industrial Corporations; U.S. j
Department of Commerce.)
-------
OniCR ASBESTOS REPROCESSING PtANTS
ALABAMA
GAP Corporation
LOCATION
Mobile
COSH.
B
CALIF ORNIA
Hill Brothers Chemical Company
Fibreboard Paper Products Corporation
Johns-Manville Corporation
Fibreboard Paper Products Corporation
Scott Labs, Inc.
Sacomo Manufacturing Company
George Short Company
City of Industry
Emeryville C
Pittsburg B C
Redwood City B
Richmond C
San Francesco ABC
San Francisco C
The Verticel Company
Englewood
CONNECTICUT
Brosiies Industries, Inc.
Standard Washer & Material, Inc.
Auburn Manufacturing Company
Greenwich
Manchester
Middletown
C
C
DELAWARE
Haveg Industries, Inc.
Wilmington
GEORGIA
Terri-Cord Mills
Roberta
ILLINOIS
Unarco Industries, Inc.
Accurate Felt & Gasket Manufacturing Co.
Acme Asbestos Covering & Flooring Co.
Bloominyton
Chicago
Chicago
C
C
B
-------
B-10
Asbestos & Magnesia Materials Company
Asbestos Textile Company
Chambers Gasket & Manufacturing Company
Colonial XoloaUe Company
A. Daiggsr & Company
Fllpaco Industries, Inc.
Geraghty Gasket & Manufacturing Company
L. E. Harnisch & Company
John Herman Manufacturing Corporation
Industrial Hermetic Materials, Inc.
Kopel Filter Paper Company
Sail Mountain Company
Singer Safety Products, Inc.
Grant Wilson, Inc.
United Gasket Corporation
Industrial Gloves Company
GAP Corporation
F. D. Farnam Company
Luse-Stevenson Company
Blackhawk Gasket Corporation
Excelsior Leather Washer Mfg. Co.
Nicolet Industries, Inc.
Johns-Manville Corporation
Chicago
Chicago
Chicago
Chicago
Chicago
Chicago
Chicago
Chicago
Chicago
Chicago
Chicago
Chicago
Chicago
Chicago
Cicero
Danville
Joliet
Lyons
Melrose Park
Rockford
Rock ford
Union
Waukegan
A B
A
C
C
C
C
B C
A
C
C
C
A
A B
C
A
B
ABC
C
C
C
B C
LOUISIANA
Johns-Manville Corporation
MARYLAND
Congoleum-Nairn, Inc.
MASSACHUSETTS
Armstrong Cork Company
Peppsrell Braiding Company
Barwood Manufacturing Corporation
Asbestos Textile Company, Inc.
MICHIGAN
Detroit Gasket & Manufacturing Corr.pany
Great Lakes Filter Media Company
Walker Manufacturing Company
New Orleans
Cedarhurst
Braintree
East Pepperell
Everett
No. Brookfield
Detroit
Detroit
Jackson
B
B
C
A
C
A
B
C
-------
B-n
MISSOURI
GAP Corporation
Standard Asbestos Mfg. & Insulating Co.
General Gasket Corporation
Tallman-McCluskey Fabrics Company
(sub. of H. K. Porter Co. Inc.)
Kansas City
Kansas City
St. Louis
St. Louis
B
B C
C
A
NEW HAMPSHIRE
American Asbestos Textile Corporation Meredith
Johns-Manville Corporation Tilton
A
B C
NEW JERSEY
Howard Industries, Inc.
Asbesto Corporation
Kavon Filter Products Company
Tnnr.q Asbestos (iomoanv
GAF Corporation
Colurrbi": Filter Company
Celluio Company
Imperial Products Company
Ladden Asbestos Corp. of New Jersey
Smyth Rubber & Packing Company
Smith & Kanzler Corporation
Johns-Manville Corporation
Flaherty-Kennedy Filter Fabrics
Asbestos Products Mfg. Corp.
Asbestospray Corporation
Johns-Manville Corporation
Electrical Insulation Sales Company
Brassbestos Manufacturing Corporation
LaFavciite Rubber Manufacturing Co.
J. T. Baker Chemical Company
Minerals & Insulation Company, Inc.
Baldwin-Ehret-Hill, Inc.
Berkley Heights
Bloomfleld A
Cranford C
tost Kutnertorc. A B
Gloucester City B
Hawthorne C
Hoboken C
Hoboken
Irvington A B
Jersey City C
Linden B C
Manvilie B C
Maplevvood C
Newark C
Newark C
New Brunswick C
North Bergen C
Patterson
Patterson C
Phillipsburg
Rochelle Park C -
Trenton C
NEW YORK
Atlantic Asbestos Corporation
Able-Val Canvas & Rope Mfg. Co.
Acme Canvas & Rope Company
Eureka Packing Company
Smith Chemical & Color Company
Pronx
Brooklyn
Brooklyn
Brooklyn
Brooklyn
B C
A
A
A
-------
B-12
U. S. Indestructible Gasket Company
Armstrong Cork Company
National Filter Corporation
Asbestos Ltd.
Atlantic Asbestos Corporation
Scientific Filter & Machinery Company
Whittaker, Clark & Daniels, Inc.
Pam Narrow Fabrics Corporation
Garlock, Inc.
Gaddis Engineering Company
Brooklyn A C
Fulton B
Mt. Vernon C
New York City
New York City
New York City
New York City
Oceanside A
Palmyra A C
Port Washington B C
NORTH CAROLINA
Carolina Asbestos Company
Tar Heel Mica Company
Davidson
Plumtree
OHIO
G. P. Hall Company
Johns-Manville Corporation
The Blemker Company
Cincinnati Gasket Packing. & Mfg. Co.
Russel Gasket Company
Comoanv
Bodwell-Lemmon Company
Foseco Inc.
Russell Gasket Company
Nicolet Industries, Inc.
The Cellulo Company
Asbeka Fabricators Corporation
Akron
Avery
Cincinnati
Cincinnati
Cincinnati
Cincinnati
/"M eitrol anH
Cleveland
Cleveland
Cleveland
Hamilton
Sandusky
Willoughby
B
C
C
C
C
C
C
C
11
i i
PENNSYLVANIA
Keasbey & Mattison Company
Nicolet Industries, Inc.
GAF Corporation
Debco Products
Raybestos-Manhattan, Inc.
American Asbestos Textile Corporation
Nicolet Industries, Inc.
Atlas Asbestos Company
Greene Tweed & Company
Aljay Manufacturing Company
Ambler A C
Ambler C
Erie A C
Herminie B
Manheim A C
Norristcwn A.
Norristown
North Wales '. A
North Wales C
Philadelphia A
-------
B-13
Aru'hoi Pelrking Cornpa.iy
Aur>ten IlilJ Maaufacturinq Corrpiny
Burnswick Asbestos Company
Collins Packing Company
Delaware Asbestos & Rubber Company
Manufactured Rubber Products Company
Mercer Rubbe- Company, Inc.
Philadelphia Asbestos Corporation
George A. Rowley & Company, Inc.
Charles A. Wagner Company, Inc.
Armstrong Cork Company
Pittsburgh Corning Corporation
Westinghouse Electric Corporation
Refractory and Insulation Corporation
Quaker Safety Products & Mfg. Co.
Carlisle Corporation
C
Philndclphi i
Philadelphia
Pniladelphia
Philadelphia
Philadelphia
Philadelphia
Philadelphia
Philadelphia
Philadelphia
Pittsburgh
Pittsburgh
Pittsburgh
Port Kennedy
Quakerstown
Ridgway
A
A C
C
C
SOUTH CAROLINA
Pnrtpr rVirnnflpv , Tnr..
TEXAS
GAP Corporation Dallas
Johns-Manville Corporation Fort Worth
Philip Carey Manufacturing Company Houston
Standco Asbestos Textile Company Houston
B
B
A
A C
VIRGINIA
Capitol Asbestos Fabricators Corporation
Forcee Manufacturing Corporation
Alexandria
Tappahannock
WISCONSIN
Ametek/Plymouth Plastics Division
Sheboygan
CODE - A - Textiles
B - Paper
C - Miscellaneous
(Thomas Register, Dec., 1968 Ed.; Fortune-1966 Plant & Product Directory
of the 1000 Largest U.S. Industrial Corporations; U.S. Department of
Commerce.)
-------
Appendix C
Table 1 ASBESTOS USES (Sullivan and Athanassiadas, 1969)
Text ilos:
Varieties used: Chrysotile, crocidolitc, and in part
amosite
Yarns and Cords;
Processes: Weaving of yarns and cords
Braiding (interlacing)
Classification of chrysotile fabrics:
Quality Code Asbestos Content (%)
AAAA 75-79.9
AAA 80-84.9
AA 85-89.9
A 90-94.9
Underwriters 95-100
Commercial
Scaling and Packing Materials:
Packing (woven fabrics)
stuffing for boxes and sleeves
manhole rings, boiler covers
Flat Packing;
Gaskets, flanges (on pipes) and containers
1. Without metal: high pressure gasket sheets (rubber)
2. With metal: material for sealing cylinder heads and
exhausts in motors and combustion engines,
and for sealing compressors and turbines
Asbestos Boards and Papers;
Boards
Filtering and clarifying
Coverings, coatings, casings, and jacketings for all
kinds of surfaces
Manufacturing of welders' and melters1 shields
Slideways in the glass industry
Handles and fire-doors
Auto Parts
Safes
Protective walls
Curtains, etc.
(continued)
-------
C-2
ASBESTOS USES
'; Sheets
;,' Inner/outer linings of furnaces and heating vessels ,
drying ovens, incubators, heaters, climate-
V controlled spaces, etc.
Plates
\ Insulating buildings against vibrations (aluminum-
asbestos)
Solar-heat reflecting surfaces (70% of solar heat)
Special Asbestos Papers
?. Filters
-. Asbestos Cement (10 to 25% asbestos):
\ Slabs
j. Corrugated sheets
(s Pipes
r. Corrugated tiles for roofs in industry, agriculture, and
dwellings
* Planks for platforms in buildings under construction
>! Balcony canopies
:'' Rain 'gutters
; Interior walls
J, Ventilating shafts
;' Air conditioning assemblies
\ Pressure piping (for underground drinking water
distribution systems, fuel gas, and sewage)
Cooling towers (electricity-generating stations)
\' Thermal Insulants and Fire-Proofing :
v' Sprayed asbestos (insulant in both heating and
" refrigeration), sound absorbent (eliminates booming and
\, improves acoustical properties of walls and ceilings)
^ Magnesia asbestos (85% magnesia, 15% asbestos) as
|f thermal insulant for covering pipes
»" Friction Material;
«* Woven: Brake lining
|= Nonwoven: Clutch lining
; Transmission lining
(continued)
»
it
-------
C-3
ASBESTOS
Asbestos Plastics ;
Flooring tiles (asbestos-asphalt tiles and, increasingly,
asbestos-polymers o£ vinyl)
Pressed or molded (thermal insulation and in electrical
machinery)
Resinated asbestos felt (manufacturing of wings and firing
of missiles and expansion cones for nozzles of boost
motors). Other uses in aircraft industry: nozzles for
motor tubes, missile tailpipes,, and missile-heat barriers;
fuselages for guided missiles, fuel tanks for fighter
bombers, cabin floors, etc.
Radar (large molded reflectors and scanners)
Asbestos Acid-Resistant Compositions ;
Used mostly in chemical industry
-------
C-4
Tahlp 2
Ian'e
LIST OF MANUFACTURED ASBESTOS PRODUCTS (Hull Ivan and 1n/._v'
Athanassiadas, 1969)
Industry and Product Description
Quantity Measure
Miscellaneous Nonmetallic Mineral Products
Asbestos Products
Asbestos Friction Materials
Brake Linings
Woven, containing asbestos yarn,
tape, or cloth
Molded, including all nonwoven types
Clutch facing
Woven, containing asbestos yarn,
tape, or cloth
Molded, including all nonwoven types
Asbestos-Cement Shingles and Clapboard
Siding shingles and clapboard,
including accessories
Roofing shingles
Asphalt Floor Tile
Asphalt floor tile
Vinyl Asbestos Floor Tile
Vinyl asbestos floor tile
Asbestos Textiles and Other Asbestos-
Cement Products '*
Asbestos textiles
Yarn, cord,'and thread
Cloth
Other asbestos textiles, including
roving, lap, wick, rope, tape,
carded fibers, etc.
Asbestos-cement products
Flat sheets and wallboard, all
thicknesses converted to V basis
Corrugated sheets
Pipe, conduits, and ducts, including
pressure pipe
Linear feet
Cubic feet
Thousand pieces
Thousand pieces
Squares
Squares
t
Thousand square
yards
Thousand square
yards
Pounds
Pounds
Pounds
100 square feet
100 square feet
Short tons
(continued)
-------
C-5
1967 LIST OF MANUFACTURED ASBESTOS PRODUCTS
Industry and Product Description
Quantity Measure
Asbestos felts
Roofing-asphalt or tar saturated Short Tons
Other * Short Tons
Other asbestos and asbestos-cement
products, including millboard and
prefabricated housing components
Gaskets and Insulation
Gaskets, All Types
Gaskets (for sealing nonmoving parts)
Asbestos, asbestos-metallic, and
asbestos-rubber
Packing (except leather, rubber, and
metal) and Asbestos Insulations
Asbestos compressed sheet
Packing (for sealing moving parts)
Asbestos, asbestos-metallic, and
asbestos-rubber
Insulation materials containing
asbestos pipe insulation
Cellular and laminated
85 percent magnesia
Diatomaceous silica, calcium,
silicate, expanded silica, and
asbestos fiber
Other pipe insulation
Block insulation, including sheet
and lagging
85 percent magnesia
Diatomaceous silica, calcium
silicate, expanded silica, and
asbestos fiber
Other block insulation, including
celluar and laminated
All other asbestos insulation
Pounds
Thousand pounds
Linear feet
Linear feet
Linear feet
Linear feet
Thousand
board feet
Thousand
board feet
Thousand
board feet
-------
C - 6
TMI.'.K 3 A-ifi -ro-, A'Tijev,;n\- '
H.nr .!M>, '<,,
\ ,.in TliU'.id
1 . !i Pap' i ( pi.'in md r.in :i<: ' M '
sV, M.isi'ir-M pipe foU'iiMfi, Ili^'i t< u.pi ratine in-ul..i lu'^
bank- .'in: I')comoli\e i:i{:sriii!i (ni"ld'd in v.nio'i- typ'-)
t'iT'i'.nir.i fot i':icaM:iu; of nmtcr M'.ldrd conipu-i! i.iii nn .|"<|[a.
A :!"i'ili;~ mil ullifi pi;rpo~c~
.\ic!(!i d I iUi> hiuiii; and brake Anicnmbiii- lio.'ir- ;i:id inl.vi
l,!ii(k> -i' cp("~ (rn-'Mid fi)l'apo~.!..,;i
Ki'i:i!oi<'!!!'n' n;;i.!»iic< !' jlli r m ].1:H ic-
! loi'i'iii; I-'cttin a':d ^ciii) 'nr.
A-! i -lu~ i "iiH nt i;rcilurts 1'IaMt r and -tin co
l'.aii!~.'. . in. -!. c< and fillers Spi 'ivi'd a-bi'-to- (a''OU-'H.d.
Fil'iui; li>: a-)'r-tu< m:ittro<~ in- Iti-'ilaiuin of ('..'tc'if1- (Ion-
--,;!.it:.n hb(i)
I'.-'ti it! 'ii ..." \\-ill.~ and !]oo'-~ In foundation- (to re-i-i -b"< ';
Ir.-'il.'.Miri 1:1 1'iidi'icinmd con- I'atkni^: for c-xplo-i\'i-- ot ot'n
dim- i !ori-< fjbrr) '-ritciial-
'*V,tdd r.'f ai -, I'Tnd^e- and tit!:;i>n Filtr r fiiifi- an''; flln r p-id-
i " ' I'' 11 . , j .-bi'-[ o- Jibi r for ill! el - C 'oa I nr/ 1i '1 \\ i I. hni; i o' i-
MILl
I'1 tint- ia.se\\(i ]MMI'
| '!,[> ei! i i'l J ie^I ' >-)
\ ' i! ( - ! \ I
AJ>i -./in Y'lin
:>i 'K' !.!!".';
'<'.:( \:;u. \ 'i!\ i. -U'lii. lii'aiili'd a"d
'.Ii i
(;:.~kf:- ,i",d ^:a-kct cloth
'\ 'd, ; <: i,.I l:\!vni:w .ii'p:iia",i- I!O;K-
"!'..;.., i-i -i'\v!in: I hii'ad Hf" kins: foi it'.id lab
i ii'ii'u fi\".i!" wire covci'iim Kli'ctni' cable ovi'i"'!
'I v!>ri!i u.iv i.i:mi!r> Siurk ;ii'i>;~
F'lt.'r~ fur liair fi'ltinE JSicani II
-------
C - 7
Hi'i. t-
D'.j. ,. - JlMiisiiiu- lor i \( *t";>-
I'.'iu!.'',- !"" !:' '.' !ii:h' .1:1; Hl.inki t- i:i fl'i'Mn'v/' ; ui's
!<..;;- . ii'i 'i:.'vl!i ii"-' (in oxysc-n ALuib.icrs
T,,hu, ,a)
\--i:-L'- Rujrs
"!"' i i!1.'!1 t ;; .'ii^ Thc.uix- ^CL'nciy
1 1 >. >: ! !,.:..' .:; liii ,. ;n - I'oi taMo nui'n.li pK'UiK1 1 . > .:'. ?
M , .I,:; . i-nio-'-i^tn fn aemi-Mral trc.itnii M
i!. .n i :\ ' !'' \\t klin (.iwi gl ip5
\^'v -;,'- ' . . J \\iiirr0 in curniiiu- F.icintc fur clrver fell
" . ; : ' > i s
I1':. i'!u<: ''Vit i'.'c( 5, iii'i'N, etc ) Fiiff in "lu>t cullecto'.s
1 ',' !'! - >K i 'i: .I'HOMiiiiili'r! l'i'(Ur>ct(i! ^ for K:i> h:'ir- in bal'"":i
; 'i.'ii i'i-i !. ,11011 L'liiRE in motors
I.'.!:i:i^ !: l.ilnii.iUi'.KS. cooling l'!:i~i'.c-
.'!: l'l'''i '- llllil Olll'.T K'Olllb
L.'.ir.-i: of :.i.:'ji!.'ili;le f.iorbo!>.rd> 1'nddiiiS for l.u'.r.diy ;n (.--'. - urn
mniiirk'S
\Vi:mjiin<; oil tank- ;md oil hi" -
in euciuos
I'nibivlut0 uad .-hic)d> (\ ".'ir-r1 n,i
fircr:r>n)
-and h,ii;~ i for ;>ro;!; Proti.-clion of undcjr«:iouiS'l j '['
',lu ],!;" r i:,.ich!!'(>- Xnise insulation
P'ui'-li.'iL- in ] i1"!')- Pla-ticR
i* li.'it- '"or tonv i-\ nip IIT sili-- '
other artiile-
Ir.Milatiris; loco.-iiotrvf -t", :u i ;
at bend-. e!i
ln-ul.i!".'s; ,11 in.tinies \\ uidnm u>iN
\\ i.uii'.iii bus b.ir- In-iilaiiiii; nndi-r^roiiiid ;.ib'. -
Mr'.i laboratories n-c--, as insulation for fla-k-, l(--t ti.ln-, ii'loi!-: ::<
-i'"i]^ HI diffusing irnwials
In i:la iii'itiui.K'tui'C lor wrapping linos of forks to t.dx boti'f- fio:1:
In- ,l,.iing olecinc wins on jilan^s and -hips
IVickPeirllnij
A- p.U-KT.H
-------
C - 8
MnliMii |.;r;np liuotli-
Iji\ (;.. iniiiL machine-*
Hood- o! aniomobiit-
( h i !\, , i Ii'I ill V kllll-
\- I. ''.»,i i \\.iliiio.ini I Vilinn o\ i i IK jih ;- MII ' IK i -I u K-
( lc.. I'nr IMI pidtrdidil
'' A i- !! mi .UK! UK talhc i'.iddlt.- ID ula- null-
\\ . -li''i- 1:1 i Ii i fin il .ipparati;- T< ill -IHI Id- .11111 .-\<>\c pip< 11:1^-
i ' Hi I. I i !.'d dour- (iirlui" 'I
'I'M'!- In. (,.! and \\ood (MI, )
i', '' ;r ; id- .'.ml r.la'- Stu\ <> mat-
!'. ;:'. ~h. .iiliius (of far:uric*
! '!ii_''i.i ' : room-, etc )
i'.: i:i'i!i- !p,i,,,i'lr and fixi'il K.\lciio! -h^afhiim (l-.alf-l.nihM-
C'iTof 0
:.!i\-:v;.i -i.lins: 1'oil.il.lc hi'ililm!:-
I! '-.:!' -'il - o! -!!!.il! lunlilnis- Scimportahlc nidMnii inr'!\;!(>
booth-
! :' ; 'is' i i ivi on ;n-ul,t!('r \.if-
(fiuiu which vaj'oi' i i-c-)
M > .ii'ir.L' ' :' ic-! in-tuinic':ii- .mil Lisbor.tlory talili top.-
" i1. U'i'il.Iit- ( .il»lll''t- ,ill,| ji.lll"! h()\ \v.)]];
l'.-..!.i'"- !' 'WI-PII ;il,a-c- and Mi.-ci ll.mcini- u-c- i;1 i>li i ini'i!
''.': l' dl f'l ( t i'l- .'ij.p.U.llll-
!.lii'.ii M.im (a-ini;- >p.irk an'f-ic i.-
!..'..: i r"i lilc.irlniic a;id ollv-i li,icki,ri(n:nd- and cutout- fi.r
; .';'.- .ir,d \ at- window ili.-i l.iv-
!'!. i KI",I! or honiliproof tidaid
\:t ('" .nul o'luT pii'i- roM'ini:- Holier jacket-
V-iii-ii-f'dt niofmi; A-!n-'u- Imd'-iip roofinn
A-!H-','"'-" pi'oioc'.c'l meta! loofmc Ci.i-k' t-. plain and iiiot.ilhi'
\Yiik'm oil luirning: .ippiirntii« Tnlx- in I'.cctnr-il indii-t~v
\\ i-ippint 01 cdcctncal wire Wr.ippinsi o| hut .ur pipo-
f.minsi- of -;O\T- and lioatf'i'-
J.i'iirm- of'
F'lr.m. c.il)inei= Caniidi;( -
Sul.li'.-i--'h.'lmc-tb C'aijct-
AIKO ruunler- Radiator i-ov :;
iJruin por.trolk".? Oooko1-'
Electi :c ".jiplianic'S
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s:i'.;di' iio; -sift-'; to -hic'd lv>t
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wind. n:u-t be ,-ewcd
-------
For r.HTvmc o[ water, -r..\vacr\ ga> Cor.duit.i /or i In trie ,;^ii ,\/r-
ar.d -I'ocial liquids rIc.
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wartime buildup-
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fiifj ai^ ..(;
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Di^t on m:i'.vrli«. old \\irr Ivfp.^. Xii'.-o in-ula: inn
etc
Iii-i.! .::.ln for maint'iirnns: r\on
-------
Appendix D
RESEARCH RECOMMENDATIONS
(1) Working Group on Asbestos and Cancer (Report and Recommen-
dations) D-l
(2) Research on Health Effects of Asbestos D-10
(3) Report of the Advisory Committee on Asbestos Cancer to
the Director of the IARC (recommendations for further
research) D-l4
(4) Research Perspectives Concerning Asbestos Minerals and
Their Effects on Biological Systems D-18
-------
-^1
221
D-l
Working Group
on Asbestos and Cancer
Report and Recom***da**0*s °f I1" Working
GrouP Convened Under-thrXfofices of the Geographical
PMgyCownittee of the International Unwn Against Cancer
Dr. A. J. deVilliers (E) Director, Biological
Unit Occupational
Health Division
Ministry of Health
& Welfare, Ottawa
(P)
Contents
List of delegates
Terms of reference
Association of asbestos dust exposure and cancer
Recommendations on problems requiring epidemiologi-
cal study
1. Importance of fiber type
2. Relation to dust dosage
3. Effects of removal from dust
4. Further investigations of mesothelial tu-
mors
5. Population groups requiring study
6. Epidemiologies! methods and criteria of
disease
Recommendations relating to pathology and experi
mental pathology
1, Diagnosis of asbestosis
2. Diagnosis of mesothelial tumors
3. Contribution of experimental pathology
4. Proposal for reference panels
Recommendations relating to physics and chemistry
1. Proposal for establishing reference samples
of types of asbestos
2. Methods of identification of asbestos in
tissues
List of Delegates
Dr. R. Guy
Dr. N. \V. Hendry* (C)
Dr. D. Magner
(P)
Delegates:
Australia
Dr. J. McNulty* (E)
Canada
Dr P. Carrier (E)
Department of
Public Health,
57 Murray St,
Perth
Thetford Industrial
Clinic, Thetford
Mines, Quebec
Chief of Pathology,
Sacre-Coeur Hospital,
Montreal, Quebec
Canadian
Johns-Manville
Asbestos Ltd.,
Quebec
Director, Canadian
Tumor Registry,
Dept of Pathology,
University of Ottawa
Dr. J. C. McDonald (E) Department of
Epidemiology
and Health,
McGill University,
1033 Pine Ave, West
Montreal 2, PQ
National Cancer
Institute of Canada,
790 Bay St,
Toronto 2, Ontario
Head, Non Metallic?
Sub-Division, Dept of
Mines & Technical
Surveys, 40 Lydia St,
Ottawa 1, Ontario
Dr. A. J. Phillips
(E)
Dr. H. M. VYoodroofe (C)
Finland
Dr. R. Kiviluoto
Prof. L. Noro
France
Prof. P. Galy
~=S£CaSrii SMS? «£
:~^c^
torch. Pa 13213 (Dr. Mancuso). .
.^-SS^S&sftSft
F3 'rK^^S^b=y.i'' - "»
3BSS5i=Ha«===
I'r. H. Stewart).
Arch Em-iron Hcalth-Vol 11, August, 1963
(E) Tampere Central
Hospital, Tampere
(E) Director, Institute of
Occupational Health,
Haartmaninkatu 1,
Helsinki
(P) Faculte de Medecine,
Chaire de Physio-
pathologie, Des Voics
Respiratoires, Lyon,
16 rue Emile Zola,
Lyon, (Rhone)
-------
D-2
-y .-INI) C.l.\Cf-K
Ci.Tflll.'MV
IV. H b
(E)
Municipal Hospital,
Ludensclicid
l./Yii( Britain an
-------
D-3
ASBESTOS AND CANCER
223
j Dr. W. CHueper* (P)
Dr. C W. Muggins (C)
Dr. T. F. Mancuso (E)
Dr. B. Naylor
Dr. W. Payne
Dr. W. Pod
(P)
(E)
(P)
Chief, Environmental
Cancer Section,
National Cancer
Institute, Department
of Health, Education
and Welfare,
Public Health Service,
Bethesda, Md 20014
US Department of
the Interior
Bureau of Mines,
P.O. Box 217,
Norris, Tenn 37828
Department of
Occupational Health
Graduate School
of Public Health
University of Pittsburgh
Department of
Pathology, University
of Michigan,
Ann Arbor, Mich
National Cancer
Institute, Department
of Health, Education
and Welfare.
Bethesda, Md 20014
Department of
Occupational Health
Graduate School of
Public Health
University of
Pittsburgh
The Mount Sinai
Hospital,
1 E 100 St,
New York 10029
Johns Manville
Corporation,
22 E 40th St,
New York 10016 ^
National Cancer
Institute,
Department of Health,
Education and Welfare,
Bethesda, Md 20014
Terms of Reference
I. Epidemiology.
A. To investigate the incidence of mesothelial
Uimors of the pleura and peritoneum in groups
and/or regions where exposure to only one type
'{ asbestos fiber has occurred.
B. To investigate the risk of bronchial car-
cinoma in populations exposed to asbestos dusts
^vhere the incidence of asbestosis is known or
Mieved to be low.
C. To investigate the incidence of other
iimors.
Dr. I. Selikoff
Dr. Kl Smith *
Dr. H. L. Stewart
(E)
(E)
(P)
II. Pathology and Experimental Pathology.
A. Establish criteria for diagnosis of meso-
thelial tumors, assemble material to assist in
standardization of diagnosis, and form consulta-
tive panels.
B. Develop a standard of grading of fibrosis
of the lung due to asbestosis.
C. Develop a standard method of assessing
semi-quantitatively the amount of asbestos
fibers and/or bodies in sputum, fresh lungs, and
fixed tissue.
D. Collate work in various countries.
III. Physics and Chemistry.
A. Investigate the usefulness of providing in
one center a set of standards of the main types
of asbestos fibers and their extracted organic
matter for distribution to centers investigating
the biological, physical, and chemical properties
of this material; if it is regarded as useful and
practical suggest a center.
B. Suggest a minimum list of characteristics
by which differences between these samples
should be identified.
C. Suggest standard methods for identifica-
tion of types of asbestos in the lung in (a)
large samples, and (b) tissue sections.
The Association of Exposure
to Asbestos Dust and Cancer
The main types of asbestos of commercial
interest are amosite, anthophyllite, chrysotile,
crocidolite, and tremolite. There is evidence of
an association between exposure to asbestos and
malignant neoplasia. This has been established
mainly on information from Germany, Italy,
South Africa, the United Kingdom, and the
United States of America.
The types of tumors which have been shown
to "be associated with exposure to asbestos dust
are:
(1) carcinoma of the lung and
(2) diffuse mesothelioma of the pleura and
peritoneum.
There is some suggestion of an association
also with gastrointestinal carcinoma, and pos-
sible ovarian tumors.
The latent period between first exposure to
the dust and detection of the related tumors is
many years, usually 20 or more. Instances up
to 60 years have been reported. For this reason,
further cases of these associated tumors will be
expected to occur for many years to come, e\~en
if dust exposures are now greatly reduced.
Present evidence indicates that the associated
carcinomas of the lung are not limited to ex-
posure to any one type of asbestos fiber. Ho\v-
Arch En-iron HealthVol 11, August. 1965
-------
224 ASBESTOS'
D-4
ever, further investigations are urgently needed
to establi>h whether the degree of risk is im-
purtantly related to the type of fiber inhaled.
In the case of mesotheliomas, evidence from
several countries suggests that exposure to
crocidolite may be of particular importance, but
it cannot be concluded that only this type of fiber
is concerned with these tumors, and further
investigation of this problem is needed.
Certain types of asbestos fibers in the virgin
state have been found to contain oils, waxes,
and other organic matter. In addition, asbestos
fibers readily absorb hydrocarbons subsequent
to mining. Small or trace amounts of various
elements such as nickel and chromium are also
found associated with some types of fiber. The
possible role of such associated materials in the
development of tumors following exposure to
asbestos dust is not yet clear.
These findings, when considered in relation
to the great increase in the use of asbestos for
many purposes in all countries, suggest that a
more serious and widespread hazard from ex-
posure to asbestos dust may exist than is widely
appreciated.
Requiring* EpaiemiologteitSiady
1. That tkermffirtaiice ofj£et -type on the
risk of developing asbestosis, carcinoma of the
lung, and mesothelial and other tutnors be in-
vestigated.
International and intranational comparative
studies of mining and other populations exposed
to onl
Among the countries'* in which and between
which studies should, if possible, be made are
the following:
Australia Crocidolite
Canada Chrysotile
Cyprus Chrysotile
Finland Anthophyllite
Italy Chrysotile
South Africa Amosite
Chrysotilc
Crocidolite
United States Chrysotile
Tremolite
USSR Chrysotile
The studies of the effect of exposure to differ-
ent types of fiber within a country are likely
to be' of special value, but studies of groups
exposed to apparently similar fibers in different
parts of the same country are also likely to be
informative.
2. That the relationship of dust dosage (in-
cluding concentration and duration of ex-
A\D CAXCLR
fosttrc), and the fom/-«umi«nrawr f&ysical state
of i!u' dust to the incidence- of tisl'cstiws, <.«/-
c:noi;:a of the Itntij, incsothctioinas, uttrl other
cancers be studied.
Comparative studies in factory populations in
the asbestos textile and other manufacturing
processes using asbestos are likely to be useful,
especially when there are records of past duat
measurements. In any prospective studies of
ne\v entrants, the measurement of dust by a
standardized method should be regarded as an
essential part of the investigation.
3. That the effects of removal from further
exposure to asbestos dust be investigated.
It is important to establish the subsequent
morbidity and mortality from asbestosis, and
the mortality from cancers associated with ex-
posure to asbestos in population groups no
longer exposed to the dust
4. That further investigations be made of past
and all future cases of diffuse mesothelial
tumors of the pleura and peritoneum to es-
tablish any association with asbestos and other
factors.
These tumors should be diagnosed on the
criteria suggested by the Panel on Pathology
(see below) and reviewed by a panel of pa-
thologists with experience of these rare tumors.
The tumor and lungs should be investigated
for the presence of asbestos by physical and
chemical methods (see below).
5. That studies of morbidity and mortality
be extended to asbestos-exposed populations that
have not so far been widely investigated.
A. It is recommended that special attention
be directed to surveys in:
(o) the insulating industry, including that
in ships,
(b) the asbestos cement industry,
(c) the asbestos products industry, and
(d) other plants in which asbestos is regu-
larly used, such as certain paper, paint,
and plastic factories.
B. It is also recommended that, since inci-
dental exposure to asbestos dust may occur in
certain trades and occupations, attention be
directed to
(a) handling and transporting asbestos,
(b) the building industry,
(c) pipe fitting, and
(d) ship building and breaking.
C. It is recommended that surveys be made
to study environmental and community ex-
posures, including populations near mines am'
factories and elsewhere.
Arch Environ HealthVol 11, August, 1965
-------
-Scfc
ASBESTOS AND CANCER
225
D. It is recommended that general popula-
tion surveys be made nationally and interna-
tionally to establish by standardized methods, in
areas of presumed high and low exposure to
asbestos dust, the prevalence of asbestos bodies
and fibers.
E. It is recommended that surveys of asbes-
tosis in domestic and wild animals be extended
to areas of high and low exposure.
6. Epidemiological methods.
A. General:
(a) In addition to the usual information
about the individual collected in such surveys,
special attention should be directed to a detailed,
social (including smoking habits), occupational,
environmental, and medical history from early
childhood to elucidate any possible exposure to
or association with any type of asbestos or other
dusts. A study of the family unit or household
may be of interest in view of the occasional
reports of significant neighborhood and house-
hold exposures.
(b) In view of the association between ex-
posure to asbestos dust and pulmonary fibrosis
and its complications, it is important to obtain
as much information as possible about morbid-
ity and mortality from all causes with particular
attention to asbestosis, chronic bronchitis and
emphysema, bronchiectasis, diffuse interstitial
fibrosis, pneumonia, tuberculosis, cor pulmonale,
carcinoma of the lung, diffuse mesothelial
tumors of the pleura and peritoneum, gastro-
intestinal tumors, and ovarian tumors.
(c) The principal epidemiological surveys
likely to be used are (1) retrospective, (2) cross
sectional, and (3) prospective, or a combination
of these. In most of the surveys one or prefer-
ably more control groups will be needed. It is
strongly urged that early and full consultation
with statisticians be made at all stages from
planning to analysis of the findings.
B. Clinical Criteria:
The need to establish the minimal clinical
information to be obtained in surveys of workers
exposed to asbestos was agreed. A small panel
met informally after the main working party and
their recommendations are as follows:
(a) Symptoms: It was agreed that in all sur-
\eys the presence or absence of cough, sputum,
dyspnea, and chest pain should be recorded as
a minimum. This should be recorded using a
standardized questionnaire.
The British Medical Research Council Ques-
tionnaire on Respiratory Symptoms (I960),1
with the additional que.-tions relating to chest
pains in the WHO Questionnaire on Cardio-
Arch Enriron Heal III
vascular Disease (1962)- is suitable for this
purpose, and these questionnaires have been
widely used internationally for interview sur-
veys. The Cancer Society Questionnaire in the
Cancer Prevention Study has been widely ap-
plied in the United States. It contains questions
about a wide range of symptoms and diseases
and was designed for self-completion.
(b) Signs. It was agreed that when physical
examination was possible, the minimal observa-
tions should include the presence or absence of
dubbing of fingers, cyanosis, and basal rales in
the chest.
It was agreed that the measurement of sputum
volume (first hour on rising) and degree of
purulence recorded in a standard way (Miller)3
was useful in association with the questionnaires
for assessing the prevalence of bronchitis, and
this may be relevant to the disability caused by
asbestosis.
The epidemiological usefulness of examina-
tions of sputum for asbestos bodies and fibers
is at present uncertain, but needs investigation.
C. Classification of Chest Radiographs of As-
bestos-Exposed Individuals:
There is no international or national stand-
ardized classification of the radiological appear-
ances of asbestosis. It is recommended that a
scheme based if possible on an extension of the
International Labor Office (ILO) Classification
(1958)* be developed.
Possible means of doing this were presented
at the New York Academy of Sciences Con-
ference on the Biological Effects of Asbestos
(1965)s by Finnish, German, South African,
and British contributors. The aim should be
to specify separately and record semi-quantita-
tively the principal radiological features seen in
asbestos-exposed groups, but exposure to mixed
types of dust is not uncommon and the appear-
ances may, therefore, include those caused in
part by other pneumoconioses.
The classification should be purely descrip-
tive of the radiological features and not imply
pathological change or extent of disability. It
is probable that the type and severity of altera-
tions in radiological features such as pleural
plaques, etc, vary with the type of dust exposure
and other factors so that a classification based
on the principles in the ILO Classification for
Pneumoconiosis, in which there is a semi-quan-
titative assessment of several qualitatively dif-
ferent types of abnormality, may be expected
to be useful.
It is recommended that a working group be
set up to develop and test a new international
classification.
\-Vol 11, August, 1965
-------
D-6
226
D. Lung Function Assessment.
The preferred Hits of lung functions to be
used wi'l v.iry according to the type of survey
and the facilities available. A list of minimal and
additional tests likely to be of use is as follows:
minimalforced vital capacity (FVC) and
forced expiratory volume over 1 second
(FEVi.o); additional-transfer factor (diffus-
ing capacity) of lung for carbon monoxide
(single breath method), lung compliance, stand-
ard exercise test, peak expiratory flow, and air-
ways resistance.
Recommendations on Pathology
and Experimental Pathology
1. Diagnosis of asbestosis.
A. Macroscopic Examination:
(a) At necropsy the parietal pleura should
be stripped, if possible, with the thoracic
contents. It is desirable that at least one
lung be inflated with fixative and whole
lung sections be prepared.
(fe) It is recommended that special note be
made of the following:
(1) Pleura for thickening and plaques (de-
fined as localized areas of stiff horn-
like material).6 The site and size of
all pleural lesions should be recorded.
(2) Liuigs for the presence of interstitial
fibrosis, brorichiectasis, cystic change,
tuberculosis, pneumonic consolidation
and tumors. The site of any tumor
should be recorded as precisely as pos-
sible.
(5) Mediastinal tissws should be ex-
amined for evidence of neoplastic in-
filtration and for tuberculosis.
(4) Peritoneum, parietal and visceral fi-
brosis in the peritoneum such as
parietal plaques and "sugar-icing" of
the spleen should be recorded.
B. Microscopic Examination:
It is recommended that at least six sections
be examined from the lungs before the degree
of asbestosis is decided and these blocks should
be taken from specific sites and identified in
the following standard manner:
(a) apex of right upper lobe, pleural sur-
face;
(fc) right middle lobe, lateral pleural surface;
(cj right lower lobe, middle of, basal sur-
face;
(cf) left upper lobe, central section;
(c) lingula, central section; and
(f) left lower lobe, central basal section. In
addition, sections be taken from the
Arch Environ Health-
bruncht and per'tracheal and per'.bron-
chial lymph glands.
'.: is presumed that all examining pathologies
! take further sections of any suspicious or
'.ormal tissue.
C. Assessment of the Severity of Asbestosis:
The need to assess this in some standard \vav
\\as agreed. It was recommended that the as-
sessment should be based on the severity of
ir.rerstitial fibrosis and the amount of tissue
involved. The-proposed scheme is as follows:
EXTENT OF
LUSC
IWQIVEMENT
SI!*
HoJuu.
DEGREE OF
INTERSTITIAL
SlijlH
Mo.VW
S1i9h>
A category of minimal asbestosis is also pro-
posed to describe slight focal fibrosis in the
region of the respiratory bronchioles associated
with the presence of asbestos bodies; such
changes are commonly confined to sections taken
from the bases of the lower lobes.
This scheme puts more emphasis on the ex-
tent of the lesions than the degree of fibrosis
(which should be averaged for the six sections).
Thus, a lung with moderately extensive disease
but only slight severity of fibrosis is graded as
"moderate asbestosis." The use of an average
assessment of the six sections makes it impos-
sible to have a grading of slight involvement
and moderate or marked degree of fibrosis.
D. The Detection and Significance of Asbes-
tos Bodies and Fibers:
(a) Sputum. The presence of asbestos
bodies and fibers is an indication of
the exposure to asbestos dust and not
evidence of asbestosis. It is therefore sug-
gested that the bodies should be referred to as
"asbestos bodies" and not by the previously
used term "asbestosis bodies". Because of their
sporadic appearance and in the case of fiber?
their relation to recent dust exposure, the Group
were of the opinion that quantitative assess-
ment of bodies and fibers in sputum was not.
in the light of present knowledge, a very useful
procedure but might become more useful when
further investigated.
In sputum detection by direct examination
under a coverglass and the use of phase
contrast, oblique illumination or narrowed con-
denser diaphragms is proposed. If sputum con-
centration is used antiformin or Eusol treatment
is recommended. If this technique is used for
-Vol 11, August, 1965
-------
*J"»
D-7
ASHhSTOS AXD CAXCLK
227
;,tii;e-scale comparative cpidemiological surveys,
i!ie exact methoil sliould be standardized.
(b) Lungs. From fresh lungs, the highest
HiMtive results are obtained from smears from
the base of a lower lobe (of the thickness of a
hick blood smear as for malarial parasites),
air dried and mounted in balsam. A rough quan-
titative examination by low power magnification
is easy and practicable. For fixed lungs, the
linear technique is of limited value and un-
stained sections 30/i thick are recommended.
(r) For investigation of asbestos fibers in
lung sections, microincineration, acid treatment,
and examination by phasecontrast are suggested.
Morphologically the fibers appear as straight
rods of varying lengths and thickness, but with
longitudinal shredding and in the thicker fibers
smaller fibrils may be recognized. While there
are other structures described as pseudo-asbes-
tos bodies, or curious bodies, it was the view
of the Group that in practice, little difficulty is
found in distinguishing the genuine from the
others. These other types usually have a carbon-
black center, a shape which is other than linear,
but the body that can mimic an asbestos body
completely is the small one found in talcosis,
which may be tremolite, a form of asbestos.
E. Chemical Analysis of Lung Tissue.
Where possible, blocks of tissue from these six
areas chosen for histology should be taken and
the amount of collagen relative to total proteins
estimated by the standard hydroxyproline meth-
ods. The results of collagen estimations should
be expressed in absolute amounts and as per-
centages of defatted dried lung tissue.7
2. The diagnosis of diffuse mesothelial
tumors.
A. Macroscopic:
(a) The salient characteristic of the diffuse
mesothdioma is its predilection to spread
along the serosal membrane in which it
occurs. In the pleural cavity, the entire
surface may become replaced by a continuous
layer of tumor due to symphysis of the pleural
surfaces. This is uncommon in the peritoneum
vhere the surfaces often remain separate but
covered by isolated plaques and nodules or
iiffuse infiltration. Only those mesothelial
tumors in which serosal spread is unequivocal
-houKI be termed "diffuse"'. A few benign
iiffuse mesotheliomas have been described. Al-
most all diffuse mesothelial tumors show evi-
dence of malignancy by direct infiltration of
s'ljacent tissues and organs and metastases to
regional lymph nodes.
(b) The' differentiation from metastatic
tumor is the main problem in diagnosis and can
only be made with complete certainty by the
exclusion of all other sources of tumor at nec-
ropsy. Because of the tendency of the tumor to
surround and infiltrate subserosal organs, these
organs most commonly come under suspicion
as points of origin. The possibility that the pri-
mary growth may have been surgically removed
must be borne in mind.
B. Microscopic:
Diagnosis is possible because the growth
commonly shows histologic patterns which
are infrequent in other tumors and es-
pecially those which might metastasize to
serosal membranes. Particularly helpful is the
presence in some diffuse mesotheliomas of a
mixed structure of malignant elements of both
epithelial and mesenchymal character, or other
diverse combinations. Growths in which only
one type of cytoarchitecture is present may also
have a highly distinctive pattern. For example :
(a) a tubular or rubulo-papillary pattern in
which the tumor celts show marked uniformity
and are cubical or flattened;
(b) masses of collagen in which there
are either clef-like spaces lined or oc-
cupied by tumor cells, or fine hyaline
strands which form complex meshworks and
laminated bundles. Other examples of these
tumors may have an entirely non-specific struc-
ture presenting the appearance of a spindle cell
sarcoma or of an anaplastic tumor.
Because of the difficulty in clearly distinguish-
ing on histologic grounds alone, some of these
growths from metastatic tumors, cases diag-
nosed from biopsy material should be called
"probable mesotheliomas." In epidemiological
studies precise details of the pathological evi-
dence on which the diagnosis was based should
be stated.
C. Histochemistry:
(a) Most of the mucoid material within
mesotheliomas, although often intimately
associated with the surfaces of the tumor
cells, is extracellular. Intracellular or intra-
tubular mucin of an adenocarcinoma will
usually take mucicarmine or PAS stains. The
absence of these reactions in a tumor which
contains mucoid material can, when taken with
the other features, be useful additional evidence
for a mesothelial tumor.
(b) Hyaluronic acid is often present in meso-
thelial tumors. The demonstration of its re-
moval from the tissue sections by specific
hyaluronidase preparations is a useful histo-
Arch Em-iron HealthVol 11, Atigttst, 1965
-------
"~lift:
D-8
228
.1X0 C. IXLLlt
chemical tost, but since the acid is soluble in
water, the te:-t requires that the tissues be Fixed
in a special precipitating fixative, such as fonnol
alcohol acetic acid (Wagner et al, 1962).8 It
also appears likely that the quantitative measure-
ment of hynluronic acid in effusions, where
this polysaccharide has been isolated and
chemically characterized, may well become a re-
liable method for assisting in the diagnosis of
mesotheltoma, but it is emphasized that positive
results for both the histochemical and chemical
tests for hyaluronic acid are found in only a
proportion of cases of mesothelioma and they
should not be used as sole diagnostic criteria.
D. Exfoliative Cytology:
The contribution to the diagnosis of
diffuse malignant mesothelioma by exfolia-
tive cytology of serous fluids requires
that the exfoliated neoplastic mesothelial
cells sufficiently resemble exfoliated nonneo-
plastic mesothelial cells for them to be recog-
nized as having a mesothelial origin; they also
possess the generally accepted features of
malignancy. The latter are not often present so
a definite diagnosis of mesothelioma is then
difficult.
Usually mesothelioma cells, while atypical, do
not appear malignant but still show evidence of
mesothelial origin. From cytology of the serous
fluid it is possible to be strongly suspicious and
in a few cases confident of the diagnosis of
mesothelioma, but usually its presence can only
be reported as possible.
The diagnosis of malignant mesothelioma by
exfoliative cytology requires a familiarity with
the nonneoplastic mesothelial cell. Mesothelial
hyperplasia and hypertrophy can easily be mis-
taken for malignant mesothelioma and vice
versa. It may be imprudent to do more than
suggest malignant mesothelioma if there is not
good supporting clinical, radiological, or bio-
chemical evidence. The exfoliated malignant
mesothelioma cell must also be distinguished
from the adenocarcinoma cell, by far the com-
monest malignant cell recovered from serous
fluids. This cell is well described in standard
texts of exfoliative cytology.
E. The Use of Tissue-Culture in the Diag-
nosis:
The various manifestations of mesothe-
liomas in some cases cause difficulty in
distinguishing such tumors from bronchogenic
carcinoma, metastatic ovarian carcinoma, fi-
brosarcoma, etc. It is therefore recommended
that, where possible, biopsy specimens of pleural
Arch Environ Health
and peritoneal neoplasm-; be studied after *li(»rt-
term passage in vi\o and in \itru to determine
whether the rate of growth and/or morphology
after transplantation can provide useful critcri;t
for a differential diagnosis of mesotheliomas. Ti,
achieve this it is recommended that clinical
pathologists seeing these tumors cooperate with
workers in experimental carcinogenesis who are
using tissue-culture methods.
3. The contribution of experimental patlwl-
ogy-
It was agreed that various types of asbestos
induce in many species of animals lesions similar
to those seen in human cases of asbestosis, meso-
thelioma, and possible carcinoma of the lung,
but the need for more precisely planned experi-
ments was emphasized.
The desirability of using healthy animals of
known response to asbestos under quantitative
conditions of exposure by inhalation, feeding.
and parenteral injection at several sites was
agreed. Experiments in great variety are being
undertaken in many parts of the world, par-
ticularly in Canada, Great Britain, South Africa.
and the United States. The prospect of provid-
ing standardized samples of chrysotile, amosite,
crocidolite, tremolite, and anthophyllite asbestos
for experimental work was welcomed.
It was agreed that there was a need for im-
proving methods of identifying the type of as-
bestos in submicroscopic fibers in tissues.
Further studies of the rate of formation and
resistance to destruction of asbestos bodies in
different species of animals may be useful.
It is recommended that there be closer col-
laboration between clinical and experimental
pathologists and other scientists in the field of
experimental pathology, biochemistry, and bio-
physics, as applied to the problems of the
biological action of asbestos.
- 4. Proposal for pathology reference panels.
It is recommended that central consultation
and reference panels be set up on regional, na-
tional, and international levels. These panels
will:
A. Assist in establishing standards for path-
ological classification of asbestosis.
B. Serve as consultation centers for diagnosis
of mesotheliomas and other tumors associate-'
with exposure to asbestos.
C. Serve as general exchange of pathological
material related to asbestosis and its associated
tumors.
D. It is suggested that a comprehensive atlas
on the pathology of mesotheliomas should be
prepared.
l~ol 11, August, 1965
-------
D -9
ASBESTOS AND CAXCER
229
Recommendations Relating to
Physics and Chemistry
1. Reference samples of asbestos for cxfcrl-
-------
D-10
i Research
on Health Effects
of Asbestos
LEWIS J. CRALLEY, Ph.D.
W. CLARK COOPER, M.D.
WILLIAM S. LAINHART, M.D.
MURRAY C. BROWN, M.D.
A SBESTOS AS A CURIOUS MATERIAL was
»~\ known several centuries B.C., especially for
its ability to withstand flame. The physical and
chemical properties of asbestos together with its
fibrous structure made it a unique material with
a wide range of potential industrial applications.
It was not until the end of the last century, how-
ever, that it gained importance as an industrial
resource. The study of the use of asbestos in a
number of technological areas and its contribu-
tion to new products is the precursor of the spe-
cial science of industrial mineral fiber technology.
The recommendations in this report resulted from a
meeting sponsored by the Occupational Health Program,
of the Public Health Service's National Center for Urban
and Industrial Health, em December 7 and 8, 1966, under
the Chairmanship of Murray C. Brown, M.D. Copies of this
paper may be obtained from the Occupational Health Pro-
gram, National Center for Urban and Industrial Health,
USPHS, DHEW, Cincinnati, Ohio.
Lewis J. Cralley, PhJ). is Associate Chief, Occupational
Health Program, USPHG, Cincinnati; W. Clark Cooper,
M.D. is Professor in Residence, Occupational Health, Uni-
versity of California, Berkeley; William S. Lainhart, M.D.
is Assistant Chief, Field Studies, Occupational Health Pro-
gram, USPHG, Cincinnati; and Murray C. Brown, MJO.,
Chief, Occupational Health Program, USPHS, Cincinnati,
Ohio.
38
Asbestos is essential in today's industrial tech-
nology including national defense, aerospace, and
civilian consumer use.
Asbestos is a general term applied to a group
of fibrous crystalline hydrated silicate minerals.
Although a number of different types of asbestos
minerals exist, only four or five are of commer-
cial importance. Each differs somewhat from the
others in chemical composition, physical proper-
ties such as ability to withstand heat and chemical
erosion, crystalline structure, fiber dimension, and
degree of fiber harshness and brittleness.
The worldwide production of asbestos has
greatly expanded since the turn of the century,
the over-all consumption in this country leveling
off for the period 1958 to 1963 at around 750,000
short tons annually. Of this tonnage, approximate-
ly 93% was chrysotile, 3.5% crocidolite, 2.5%
amosite, and 1% anthophylite and tremolite.
Even though asbestos has been in industrial use
for well over 50 years, much is unknown regard-
ing its health effects and safe levels of exposure.
It has been known since the early nineteen
hundred's that excessive exposure to asbestos
gives rise to the disabling pulmonary disease
"asbestosis." More recently, evidence has been de-
veloped that the incidence of respiratory tract
and other malignancies in asbestos workers is ex-
cessive. A major problem in studying the health
effects of asbestos is the long latent period of 20
or more years from initial exposure to the onset
of disease. Also in the mid-nineteen thirties and
earlier, there was little dust control and the work-
ers were often exposed to massive levels of dust
from asbestos and other associated materials in
the manufacture of asbestos products. Thus, the
causative agents of the resultant disease are es-
sentially unknown. Included in these potential
sources of causative agents, either alone or in
combination, are asbestos fibers themselves, ma-
terials associated with the fibers in the ores such
as trace minerals and polycyclic aromatic oils, ma-
terials added during processing such as metals,
tars and pitches, and concomitant external ex-
posures to tobacco smoke or other air pollutants.
A salient point is that in subsequent years when
heavy dust exposures were reduced, disease also
diminished. This definitely indicates that with
sufficient knowledge of the agent (s) responsible
for the disease, along with dose-response data,
safe levels of exposure can be established.
Research to elucidate the importance of the as-
bestos minerals as hazards to health fall into two
broad categories: first, studies to provide answers
January 1968 Volume 10 No. 1
-------
0-11
Cralley et al.
j urtfviit questions involving public policy and
imtrol efforts; and second, long-term studies to
rovido more information as to the physical and
hemical factors of fibrous materials as related
o their interaction with animals and man so that
afe working and living environments can be as-
ured. Consider, for example, the program to
ivaluate reports of the presence, to some extent,
>f asbestos bodies in the lungs of a third or more
>f the American population.
Before public policy regarding the production
md use of asbestos can be stated and implement-
id, we need answers to many questions: do these
asbestos bodies truly represent responses to as-
bestos fibers, or are other fibers also involved?
Where do these fibers come from, and what is
their potential significance in terms of health? Is
there an increasing incidence of mesothelial tu-
mors in our population and is this in any way re-
lated to asbestos minerals? Do fibrous minerals
play a major or minor role in the causation of lung
cancer? Are certain forms of asbestos or other
fibers more important in these relationships, and
what co-factors are important?
These pressing questions cannot be definitively
answered on the basis of present data. A strong
supported long-term program is needed to pro-
vide the information regarding the pathogenesis
of asbestosis and the other effects that appear as-
sociated with the inhalation of asbestos dust.
More precise data on the physical and chemical
characterization of the asbestos minerals which
lead to their being inhaled and retained in the
body, in their carrying with them other chemicals,
in their migration, may open up unsuspected ave-
nues of biological research.
Objectives
Research directed to answering the following
questions is needed in order to safeguard the
workers' health, yet permit the benefit of asbestos
in today's industrial technology. The information
gained will also have direct application in further-
ing the safe use of the many new synthetic fibers
being introduced into industry as the result of the
rapidly expanding science of industrial fiber tech-
nology.
1. What is the nature and pattern of disease in
workers exposed to the different types of asbestos
fibers and how do they relate to the magnitude and
duration of exposure?
The answers to the above are basic to defining
related health problems and setting up research
on a rational basis for their solution. They should
provide data evidencing etiologic factors involved
and their interrelationship, the dose-response re-
lationship of the agent(s) to the disease, the cri-
teria for establishing safe levels of exposure, and
the basis for establishing medical and environ-
mimtnl surveillance wherever a.«beslos is encoun-
tered and handled. It will also provide useful in-
formation for evaluating possible risks from in-
haled fibers in those not occupationally exposed.
2. How are the diseases and other manifesta-
tions observed in workers exposed to asbestiform
fibers characterized clinically and pathologically,
and do they differ when exposure involves one
type of asbestos or another? -
Far more information is needed on the patho-
genesis of asbestos and on other responses to as-
bestos fibers in man. This information should be
based on careful serial studies and correlations of
clinical, physiologic, radiographic, and histologic
changes. Results of these studies would relate to
the prevention of asbestos-related disease and
would give useful information on the biologic re-
sponse to other respirable fibers. The findings
would supplement current criteria for diagnosis,
prognosis, and management of disease, continued
employability, fair adjudication of compensation
claims, and effective rehabilitation. They would
also provide information important in maintain-
ing surveillance programs for asbestos workers
and in improving control measures.
3. What are the factors in the pathogenesis of
the diseases associated with the inhalation of as-
bestos minerals and what are the primary etiologic
factors involved? Although in many instances it
is the predominant ingredient, generally and with
only few exceptions, asbestos is formulated with
other materials in the preparation of asbestos
products. Even in the mining and milling of as-
bestos, recent studies have shown that these op-
erations are associated with exposures to poten-
tially injurious agents (such as trace minerals of
nickel, cobalt, manganese, zirconium, and ti-
tanium), polycyclic aromatic compounds from
some ores, and metals abraded from processing
equipment due to the harshness of the fibers.
These same injurious agents may be carried in
degrees in the milled fiber and subsequently in
increased degrees as processing of the fiber con-
tinues.
In the past, studies related resulting diseases
to fiber exposure only. Thus, the etiologic agents
resulting in the diseases observed in past studies
are generally unknown. They may have been one
or more of the fibrous forms of asbestos, trace
minerals in the ore, polycyclic aromatic corn-
Journal of Occupational Medicine
39
-------
Kesearcn on AsOestos Effect*
D-12
pounds associated with the ore, additives in pro-
cessing (such as metals, coal tars and pitch),
smoking, other air pollutants, or some combina-
tion of these factors. A fresh look into both the
clinical and animal research of the past and a new
approach to current research to further define re-
lated agents in the light of our more recent in-
formation is indicated.
4. What chemical and physical characteristics
of asbestos fibers relate to their respirability, mo-
bility, clearance, and immobilization in the body
and how do the types of asbestos differ in these
respects?
Most of the research relating to the respira-
bility and retention, mobility, and clearance of
materials from the lungs has been done on par-
ticulates which have random movements since
they are generally spherical, fibers, however, hav-
ing a much greater length-to-diameter ratio, have
direction and orientation in their movement and
many behave quite differently than particulates.
Fibers that are harsh and rigid may have tissue
penetration potential. Through this mechanism
they may, as carriers, transport toxic agents to
other tissue sites and, thus, have a causal rela-
tionship heretofore not evident. The behavior of
fibers in lungs and other tissues must be under-
stood and related to the respective physical and
chemical characteristics of fibers so that patterns
of response can be described and predicted.
5. How can asbestos fibers in vivo and in vitro
be differentiated as to type and how can they be
distinguished from non-asbestos fibers?
Respirable fibers are ubiquitous. They may be
either natural or synthetic and from animal, vege-
table, or mineral origin. Modern technology is
introducing increasing numbers of synthetic fibers
into industrial use.
It has been known for some time that asbestos
fibers in the lungs give rise to asbestos bodies. Re-
cently, similar-type bodies have been found in the
lungs of a large percentage of individuals coming
to autopsy in general urban hospitals. This finding,
even though the number found in any individual
may be relatively small, has given concern as to
its significance as well as to the identification of
the causative fibers and their environmental
source. Methods must be developed for isolating,
identifying, and quantitating fibrous materials in
the lungs and other tissues and in the associated
ferruginous bodies.
6. What levels of exposure to the etiologic
.i;;ents associated with asbestos-related diseases
can be regarded as safe?
Defining safe exposure levels is the prime ob-
jective of the research. When safe levels are de-
termined, necessary measures can be taken to
keep exposures within the recommended limits.
7. How can exposures be prevented?
The aerodynamic properties of fibers will differ
depending upon the specific physical and chemi-
cal properties of the fibers. Their behavior in air
is much less understood than that of particulates
spherical in shape. Information on the behavior of
fibers is needed for the design of ventilation con-
trol equipment and the design of process equip-
ment to minimize the dispersion of fibers into the
air.
8. What environmental and medical surveil-
lance procedures are recommended where asbes-
tos fibers are encountered or handled?
Surveillance of the working population at risk
to detect early changes before damages to health
have occurred is an essential part of any occupa-
tional health program in industry. Environmental
monitoring of exposure levels as well as continu-
ing information on the health status of the work-
ing force is an important segment of a surveillance
program. The continued development and ex-
panded application of surveillance procedures will
assure the use of asbestos with minimum risk to
health.
Projects
The answers to the above questions can come
only from widely-based interrelated research di-
rected to the health response of the worker in his
specific environment. The research, although di-
rected specifically to the asbestos worker and his
environment, should result in findings applicable
in the understanding of a wide range of allied oc-
cupational diseases, especially those relating to
fiber exposures. This research on health effects of
asbestos should encompass, as a minimum,
projects as outlined below.
1. Epidemiology: (a) Longitudinal studies of
groups of workers in different employment cate-
gories with contrasting exposures to different
types of asbestos fibers by magnitude and dura-
tion, singly and in combination with other associ-
ated materials capable of producing injury or
eliciting a synergistic response to establish inter-
relationships between health patterns of the work-
ers and environmental exposures.
(b) Studies of the relation between exposure to
asbestos minerals and clinical symptoms, pulmo-
10
January 1968 Volume 10 No. 1
-------
D-13
Cralley et al.
nary changes domonstruble by pulmonary func-
tion and work tests, and chost rocnlgenographic
shadows suggestive of asbestosis.
(c) Studies of records of morbidity and mo-
rality patterns and trends in groups of workers
with contrasting exposures to asbestos and other
associated materials; also a search for common
genetic or hereditary patterns relating to the dis-
ease.
(d) Analysis of selected postmortem tissues of
workers with work histories in industries having
contrasting exposures to different types of asbes-
tos and other associated materials during and after
periods of massive dust exposure. Also, studies
must be conducted on workers in these categories
who died from an exposure-associated disease as
well as those who showed no obvious indication of
associated disease.
(e) Sputum study of asbestos workers to cor-
relate and quantitate magnitude and duration of
exposures with the occurrence of asbestos bodies.
(f) Study of contrasting population groups with
respect to geographical areas, air pollution, em-
ployment patterns, etc., for presence of pulmonary
ferruginous bodies ("asbestos bodies") to deter-
mine if these correlate with disease patterns ob-
served.
(g) Study of ecological factors that may have
a bearing on the disease or be interrelated with
causative agents, including community exposures.
2. Clinical and human pathology: (a) Compre-
hensive study of selected individuals with different
patterns and progression of disease with respect
to: (1) impaired pulmonary vascular circulation,
both by tests of function and by angiography; (2)
pleural thickening in relation to reduced function,
physical signs, altered roentgenographic patterns,
and pleural tumors; (3) impact of viral infections
on persons with asbestos exposures; (4) sites of
pulmonary fiber depositions and injury; (5) im-
munochemical changes; (6) the nature of the em-
physema so often associated with asbestosis; (7)
the role of chronic bronchitis and other causes of
pulmonary obstructive disease in altering the prog-
nosis of asbestosis; (8) correlation between roent-
genographic evidence of disease and the capacity
of the cardiopulmonary system to fulfill its re-
quired function,
(b) Establishment of a mesothelioma case reg-
istry, including uniform criteria for diagnosis and
epidemiologic follow-up of reported cases.
(c) Development of a uniform classification for
reading chest roentgenograms of persons oxposwl
to asbestos and other fibers; correlation of roont-
genologic patterns with clinical, physiologic, and
histologic changes.
(d) Study to detect individuals who may be
hyper susceptible, either on an acquired or a go-
netic basis.
3. Animal experimentation and tissue culture:
(a) Determination of respirability, sites of reten-
tion, mobility, penetration, and migration to other
tissue, and clearance of pulmonary fibers in rela-
tion to their chemical and physical properties.
(b) Study of mechanism of formation and
meaning of ferruginous bodies arising from re-
spired pulmonary fibers from different sources.
(c) Study of the chemical and physical char-
acteristics of various types of asbestos fibers, singly
and in combination with other associated injurious
materials and their capacity to give rise to differ-
ent forms of cancer; evaluate additive, enhancing,
or inhibiting action of fibers and carcinogens from
cigarette smoke and other sources.
(d) Study of potential of pulmonary fibers as
carriers of carcinogenic and other agents from
lungs to other tissue sites.
(e) Development of dose-response data as an
aid to developing safe exposure levels.
(f) Investigation into the effects of asbestos and
other fibers, and of associated injurious materials,
on cellular physiology, enzyme suppression, and
genetic pattern.
(g) Study of immunochemical changes, bio-
chemical tests, etc., that may further characterize
the exposure-response pattern and serve as pre-
dictive tests.
4. Chemical and physical characteristics: (a)
Study of the positive identification of individual
fibers, both in vivo and in vitro; the nature and
quantity of other contaminants such as minerals,
metals, and oils associated with the fibers includ-
ing mechanism of association.
(b) Study of solubility of fibers and associated
contaminants in tissue fluids particularly as related
to blood and urine levels of associated materials.
(c) Study of sources and identification of re-
spirable fibers responsible for ferruginous bodies
seen in lungs and general population of non-as-
bestos workers.
Lewis J. Cralley, Ph.D.
Occupational Health Program
U.S. Public Health Service
1014 Broadway
Cincinnati, Ohio 45202
Journal of Occupational Medicine
41
-------
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D-l|7
Report of the Advisory Committee on Asbestos Cancers
Mr ^ Morgan
Or. F O Poolcy
IV S Spi-il
Dr. V I inihrcll
Dr. R S. J du Toil
Mr. W II Walton
Atomic F.ncrRV Research Fstnhlishment, Health Physics ;iml Medic (I Division,
limit MR Wit. ll.iiwcll, Ditlcot, Mcrks. I upland, UK
rsily C'tillcgi; (if Smith Wales ;tnd Monmouthshire, Department of Mincnil
it.itmn, Newpnil Ut>,itl. C.utlilV, W.ilcs. UK
Uni
Jtilin
M.invillc KfM.',iuii .mil I li^'jn
CcnK'i, (irccnwootl IMa/.i,
ulo, USA
Mci! ,il Rcsc.iah C\nmt.il, I'neiimoconiosis Unit, LlamlnuRh Hospil.il, Penurth,
tiliin irB-in, W.ilcs. UK
OovurniiKnl Mining 1 njiinecr's Division, Department of Minos, PO l!ox 1 H2,
Joluiiincsl>uij'. South Alnca
Institute nt ()cciip,ition,il Medicine, Roxburgh Place, Edinburgh [ HP 9SU.
Scotlaiul. UK (Chairm.m)
-------
D-18
mental Health
Research Perspectives Concerning Asbestos Minerals
and Thair Effects on Biological Systems
by Arthur M. Langer*
The interaction of asbestos minerals with biological material* is under intensive investiga-
tion throughout the world today. Physical scientists should be responsible for the selection of
fibers, and their varietal types, for biological studies; they should characterize these experi-
mental materials physically and chemically to the level of sophistication which currently
exists in their fields; they should develop definitive assay methods to monitor changes in
such characteristics after biological residence; they should actively participate in the formula-
tion of theories or mechanisms of particle interaction in biological systems.
Physical scientists should begin the characterization of minerals in the environment and the
determination of ambient fiber levels in air and potable water supplies. Such characterization
of the environment requires standardized instrumentation and preparation techniques.
Acquisition of data in numbers large enough to achieve statistical significance requires the
development of automated counting strategies. Instrumentation and software have yet to be
developed. The training of physical scientists in environmental areas Is lagging behind current
national needs and must be accelerated.
Introduction
There is an urgent need for the physical scien-
tist to take a leading role in the field of par-
ticle-biological systems interaction. There are
many reasons for this: the physical scientist is
more familiar with asbestos complexity and its
behavior in a range of media; he has developed
techniques for sampling and analysis of fiber at
all levels of contamination; he has developed the
instrumentation for fiber characterization and
recognizes the statistical shortcomings in pre-
sent day quantitation; he recognizes the need for
precisely determining all of the chemical and
physical parameters of materials used ex-
perimentally. Most .important, interaction
mechanisms of particles in biological systems
may he clarified from the direction and perspec-
tive of thr particle-end of input. Conventionally,
most of the work in this field was directed
toward host or tissue response rather than the
Mount Sinai School of Medicine of The City University
c.f New York. Ni-\\ York, 1002!).
nature of the materials. In accordance with the
principle of biological interaction, it is im-
perative to have knowledge before disease
stigmata appear, in addition to final response.
Etiologic mechanisms may be established by
prediction of response based on particle proper-
ty.
What are the needs in this area that the
physical scientist might fulfill?
The Need to Define Asbestos
The term "asbestos" should be explicitly
defined to all experimental biologists concerned
with fiber effects. The term as presently used
refers to a group of flexible, silicate mineral
fibers which possess, more or less, physical and
chemical characteristics which render them
"useful" as insulators, filtering agents, etc.
Frequently, asbestos is explained as a "generic"
term which includes a specific number of
mineral entities. However, what is generally un-
known to the biological scientist is that asbestos
minerals themselves are not pure materials, but
g
I
ifl
£
member 1971
335
-------
D-19
>ce;r as mixture* of varying complex
jr;. otal-eheinical s\ .i;,>;r.5. For example, the
; unrral amosite is urv.u!l> a member of the
gruiu'riU'-annmingtn'-.i'.c' ?oiid solution series;
croo idol i (e is h n ember of the
gl;mn>phanf-ru>b«?cki;o .-cries; unthophyllite is
also a member of the k'r'.;r.-.'riie-cumminKtonite
scries with additional a'.uminum; both tremolite
and actinolite are c.'.llt-d separate asbestos
minerals, but actually tht'y are end-members of
the tremolite-actinolite solid solution series.
The aniphibole asbestos minerals are
themselves extremely complex and never occur
as chemically pure end-members. Manganese is
a frequent minor element occurrence. Also, a
number of other elements may be present in
these minerals in substantial amounts. The
asbestos minerals thus possess a range of
chemical compositions which gives rise to
differences in their physical properties. The
chemistry of asbestos mineral fibers should be
defined in mineral terms, so that similar non-
economically exploited fibers will not escape
notice as being potentially biologically active.
The term asbestos should remain, but an
awareness of its true mineral character should
be created. This will be particularly important
as mining and milling operations are examined
in regard to their silicate minerals and their
possible biological hazards. Asbestos names,
and their component mineral names, should
enter the biological literature. Future Lake
Superiors may be avoided.
Workers in biological fields should be aware
not only of the chemical nature of asbestos, but
of the relationship between chemical and
physical properties. That is, small changes in ca-
tion substitution, especially at specific struc-
tural sites, may greatly influence such proper-
ties as mineral cleavage or surface charge.
Those properties may have great biological
significance in terms of mechanisms of interac-
tion.
The Need to Determine Effects of Differing Media
on Asbestos Stability
Work should begin concerning the alteration
of asbestos fiber after residence in potable
water. This has recently arisen after study of
fibers in the sediments of Lake Superior. Fibers
observed in older sediments were not identical
with those in the freshly discharged ore tailings
found at Silver Hay. There are indications that
an ion-leaching process at the surface of the
asbestos fiber removed iron from the structure,
leaving an altered, highly reactive surface. If
these observations are correct, then less stable
asbestos mineral phases, especially chryaotile
and croddolite may alter considerably after
prolonged residence in natural lake waters. The
possible biological effects of ;mch altered fibers
should be investigated at this time.
The Need to Determine Biological Effects of
Different Forms of the Same Fiber
There is presently being mined a new type of
chrysotile deposit commonly referred to as the
Coalinga-type. In this occurrence, unlike vein
serpentine deposits, chrysotile occurs as mats of
individual fibrils in massive lenses. From the
end-products which use such material, the dusts
generated are far more fine-grained than one
normally encounters in those which are
mined from vein deposits. The number of fine
fibers and individual fibrils, smaller than 5 ^m
in length, are more numerous. Biological work-
ers guided by physical scientists should be
presently engaged in research defining the long-
term effects incumbent upon the inhalation of
such large numbers of small fibers. The effects
which should be studied include both lung scar-
ring and carcinogenic potentials.
The Need to Determine the Biological Effects of
Different Fibers on the Organism-Organ-Cellular
Levels
The physical scientist should work with ex-
perimental biologists in determining the effect
of fiber type, chemical range, size range, surface
area, surface charge, etc., on living systems.
These systems should be both in vivo and in
vitro models, and should include all possible in-
teraction effects. The thrust of the work should
be toward the prediction of interaction
phenomena based on particle property rather
than observation of results. A review of the
interaction of silica and other important sili-
cate minerals in living systems should be
implemented.
The Need to Know More About Ambient Levels of
Asbestos Contamination
The question arises concerning how extensive
asbestos contamination in the environment real-
336
Environmental Health Perspectives
-------
h :> M<'.'v information
ivj.v.'-.iing the ambient k
cuir.riurity air, in potable U.'.'L':
human tissues. More mii:-t bo '.-
MMITC-S of (lie asbestos filvr.
kinds and amounts. Data arc :
D-20
:s urgently needed
-;.^ nf chrysotile in
-applies, and in
arned about the
including their
i concerning
the clu-mistry and physical : - Berries of these
particles and whether or P.I-: they had un-
dergone any alteration in the environment. In
an ongoing study in our laboratory, we have
demonstrated the presence of chrysotile
asbestos within the Greenland ice cap. Ice dated
from these areas have yielded samples which go
back several centuries in time. Although we
know nothing of time changes as yet, we are af-
forded the opportunity to determine if the am-
bient backgrounds we now observe are the
products of natural degradation of rocks or are
the products of industrial usage in the twentieth
century.
Concerning potable water supplies, the last
major study concerning suspended mineral
phases in waters was carried out in the early
part of this century. This work was done by-
light microscopy and is at best, qualitative.
Earth scientists must redo a study of this kind
and on the sublight microscopic level. Ingestion
of small particles, those which may easily
migrate to other anatomical sites, may be of
greater biological importance.
The Need to Determine Tolerable Fiber Levels in
Biological Systems
Materials which are widely used in construc-
tion trades, pharmaceutical trades, etc., which
might contain asbestos as a natural contami-
nant, should be scrutinized by both the
biological and physical scientist. For example,
asbestos in talc varies from major contaminant
to a trace. No talc we have examined contains an
absolute zero level of fiber. If a biologically
acceptable level exists, it should be determined.
The Need to Standardize Instrumentation:
Collection and Identification of Fiber
The instrumental techniques required for the
collection and analysis of asbestos fiber in gas,
liquid, or solid media need to be standardized.
For example, the sampling of particulates from
air should be restricted to filtration, either
membrane or polycarbonate, rather than im-
pingement or irnpaction devices. Analytical
methods should include both light and electron
microscopy and their range of instrumental
techniques. More important, however, the ac-
cumulated data from all laboratories in the
United States should be sent to a central
governmental agency which \\ould be responsi-
ble for the appropriate collation and evaluation
of such information and its dissemination back
to the various laboratories and interested
governmental agencies. In order properly to
evaluate such information, standard samples
should be analyzed by a number of laboratories
for comparison purposes. A prerequisite for
such comparison is the implementation of stan-
dard sampling, preparation and analytical
techniques. This is of critical importance in the
areas of low-level fiber contamination.
The Need to Develop Expertise in More People
There is an urgent need for more laboratories
to expand the training of technical staff for the
areas of fiber analysis. The number of samples
which may be processed by a single laboratory is
extremely small, being limited by the re-
quirements of time, instrumentation, and the
number of individuals capable of doing the
analysis. Although the instrumentation
problem is readily soluble by monetary support,
the qualified people required for future work
should be trained immediately. These in-
dividuals are in short supply now and will be in
even shorter supply as facilities develop in the
future.
The Need for Automation
There is an urgent need at the present time
for an automated system to be developed for the
identification, characterization and enumera-
tion of asbestos fibers in various media. This
would increase the number of samples studied
and yield statistically acceptable confidence
levels in quantitative work. Instrumentation
has now evolved to the point where automation
is feasible; environmental problems have evolv-
ed to the point where quantitation is urgently
needed.
All of the above research must be carried out
by physical scientists working in the field of en-
vironmental medicine. There is a most urgent
need for the recruitment of such individuals into
this field. Most important, there exist today
December 1974
337
-------
D-21
\ IT;, few laboratories in the United States which Acknowledgement
(vn properly anals.-.,' materials for their
a,lKMos fiber content. Because, this field is so The author wishes to acknowledge support
M]Mdl>,.M«md.nK.thv>e laboratories, uickuiinn under a Career Scientist Award from thP
i^tiumental ami human resources, will quickly WEI-IS. ESI4S12 and under a Center Grunt
lie overwhelmed l.y such work. from the NIEHS " v,tnier uiant
Environmental Henlth Perspectives
-------
TECHNICAL REPORT DATA
(I'lcasr naN().
67m=Po"RT DATE
January 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Frank D. Kover
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Office of Toxic Substances
U.S. Environmental Protection Agency
Washington, D.C. 20460
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
IS. SUPPLEMENTARY NOTES
16. ABSTRACT
This report reviews much of the available information on asbestos through
1973 as well as some more recent documents relating to health effects
and environmental exposure. Current federal and state regulations on
asbestos emissions, effluents, and occupational exposure are cited.
Analytical methodology and control technology are reviewed. In addition, general
information on uses and mining, milling, and reprocessing industries is provided
along with consumption figures and emissions estimates associated with each
category. Gaps in the knowledge about asbestos (especially health effects) are
pointed out and research recommendations of various investigators and scientific
groups are compiled to indicate need for further research activities to allow
meaningful evaluation of the environmental hazard present by asbestos.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
asbestos-chrysotile, amosite, anthophyl-
lite, crocidolite, actinolite,
tremolite
mesothelioma (pleura!, peritoneal)
lung cancer
asbestosis
experimental neoplasia
18. DISTRIBUTION STATEMENT
Document is available to public through
the National Technical Information Service
Springfield, Virginia 22151
b.lDENTIFIERS/OPEN ENDEO TERMS
environmental exposure
health effects
uses
research recommenda-
tions
c. COSATI Field/Group
06/A,J,T
07/B
11/E
20/B
19. SECURITY CLASS (This Report)
Unclassified
20. SECURITY CLASS (Thispage)
Unclassified
21. NO. OF PAG1
22. PRICE
EI»A Form 2220-1 (9-73)
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